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How to Make a Robot – Lesson 1: Getting Started

1. An electronic gyroscope measures the rate of angular acceleration and provides a corresponding signal analog voltage serial communication I2C etc Integrating this value twice will give you an angle e Advantages no moving mechanical components e Disadvantages the sensor is always subjected to angular acceleration whereas a microcontroller cannot always take continuous input meaning values are lost leading to drift Encoders Optical encoders as explained above use mini infrared transmitter receiver pairs to signal when the infrared beam is broken by a spinning disk mounted to a rotating shaft The number of times the beam is broken corresponds to the total angle travelled by a wheel A mechanical encoder uses a very finely machined disk with enough holes to be able to read specific angles Mechanical encoders can therefore be used for both absolute and relative rotation e Advantages accurate e Disadvantages for optical encoders the angle is relative not absolute to the starting position Environmental Conditions Light Sensor a A light sensor can be used to measure the intensity of a light source be it natural or artificial Usually its resistance is proportional to the light intensity e Advantages usually very inexpensive and very useful e Disadvantages cannot discriminate the source or type of light Sound sensor A sound sensor is essentially a microphone that returns a voltage
2. For example a robot can tell you the precise angular or linear acceleration it 1s subjected to while most humans would only tell you I m turning or I m moving A human can tell you based on experience if they think an object will be hot or cold without actually touching it whereas a thermal camera can provide a 2D thermal image of whatever is in front of it Although humans have five main senses robots can have an almost infinite number of different sensors Which sensors do my robots need So what types of sensors are available and which ones does your robot need You need to first ask yourself what do I want or need the robot to measure and refer to the appropriate category below There is a good chance what you have in mind will not fall nicely into one of these categories so try to break it down into its basic elements Contact Push button Contact switch Switches buttons and contact sensors are used to detect physical contact between objects and are not just restricted to humans pushing buttons bumpers on a robot can be equipped with momentary push buttons and whiskers just like an animal can be used to sense multiple distances e Advantages very low cost easy to integrate reliable e Disadvantages single distance measurement Pressure sensor Unlike a push button which offers one of two possible readings ON or OFF a pressure sensor produces an output proportional to the
3. more complex but allows for higher gear downs in a more confined space as well as higher efficiency and worm which allows for very high gear ratio with just a single stage and also prevents the output shaft from moving if the motor s not powered Just like a DC motor a DC gear motor can also rotate CW and CCW If you need to know the number of rotations of the motor an encoder can be added to the shaft R C Servo Motors R C or hobby servo motors are types of actuators that rotate to a specific angular position and were Classically used in more expensive remote controlled vehicles for steering or controlling flight surfaces Now that they are used in a variety of applications the price of hobby servos has gone down significantly and the variety different sizes technologies and strength has increased The common factor to most servos is that the majority only rotate about 180 degrees A hobby servo motor actually includes a DC motor gearing electronics and a rotary potentiometer which in essence measures the angle The electronics and potentiometer work in unison to activate the motor and stop the output shaft at a specified angle These servos are generally have three wires ground voltage in and a control pulse The control pulse is usually generated with a servo motor controller A robot servo is a new type of servo that offers both continuous rotation and position feedback All servos can rotate CW and C
4. 13090 Battery Pack 0 026179 AH Calculate www RobotShop com Data Details e Total mass of robot 200 g should include everything motors frame batteries and all e Number of drive motors Two motors are required for skid steering e Radius of drive wheel from 0 5 to about 1 should be an appropriate size for a desktop robot e Velocity of robot 0 2 m s would be nice for a desktop robot e Maximum incline Climbing some books would be cool let us choose 30 degrees e Supply Voltage Uncertain at the moment so we choose the default 12 V e Desired Acceleration Not sure so choose default 0 2 m s e Desired operating time 30 minutes is reasonable between charges e Total efficiency Not sure so we choose default 65 Using 0 5 as the wheel radius we obtain 150 rpm 1 4 oz in When using 1 the calculator provides 75rpm 2 8 oz in Selecting the Motor Check Out The Comparison Tables gt 4 Thus the motors we are looking for must turn at approximately 150 rpm and provide roughly 1 4123 oz in of torque We can use the DC motor Comparison Table in order to find the appropriate motor There are many motors available that fit the Johnny Robot Track Kit The Solarbotics GM8 and GM9 feature 70 rpm 43 oz in and 66 rpm at 43 oz in respectively Both sell for 5 46 each All Tamiya gearbox ad motor combinations sell for approximately 11 and up and provide a wide range of torques and speeds Hitec continuous
5. AC motors are mainly used in industrial environments where very high torque is required or where the motors are connected to the mains wall outlet DC Motors gt DC motors come in a variety of shapes and sized although most are cylindrical They feature an output shaft which rotates at high speeds usually in the 5 000 to 10 000 rpm range Although DC motors rotate very quickly in general most are not strong low torque In order to reduce the speed and increase the torque a gear can be added To incorporate a motor into a robot you need to fix the body of the motor to the frame of the robot For this reason motors often feature mounting holes which are generally located on the face of the motor so they can be mounted perpendicularly to a surface DC motors can operate in clockwise CW and counter clockwise CCW rotation The angular motion of the turning shaft can be measured using encoders or potentiometers Geared DC Motors A DC gear motor is a DC motor combined with a gearbox that works to decrease the motor s speed and increase the torque For example if a DC motor rotates at 10 000 rpm and produces 0 001 Nem of torque adding a 256 1 two hundred and fifty six to one gear down would reduce the speed by a factor of 256 resulting in 10 OOOrpm 256 39 rpm and increase the torque by a factor of 256 0 001 x 256 0 256 Nem The most common types of gearing are spur the most common planetary
6. B and B If your battery came with a connector and your controller uses screw terminals you may be able to find a mating connector with pigtails wires which you can connect to the screw terminal If not you may need to find another way to connect the battery to the motor controller while still being able to unplug the battery and connect it to a charger It is possible that not all the electromechanical products you chose for your robot can operate at the same voltage and thus may require several batteries or voltage regulation circuits See bellow the usual voltage levels involved in common hobby robotics components e DC gear motors 3V to 24V e Standard Servo motors 4 8V to 6V e Specialty Servo motors 7 4V to 12V e Stepper motors 6V to 12V e Microcontrollers usually include voltage regulators 3V to 12V e Sensors 3 3V 5V and 12V e DC motor controllers 3V to 48V e Standard batteries are 3 7V 4 8V 6V 7 4V 9V 11 1V and 12V If you are making a robot with DC gear motors a microcontroller and maybe a servo or two it is easy to see how one battery may not be able to power everything directly We recommend nevertheless choosing a battery which can directly power as many devices as possible The battery with the greatest capacity should be associated with the drive motors For example if the motors you chose are rated a nominal 12V your main battery should also be 12V then you can use a regulator o power a
7. Motor Control Since standard hobbyist servo motors are meant to use specific voltages for peak efficiency most operate at 4 8V to 6V and their current consumption is similar the steps for the selection are somewhat simplified However you may find a servo motor that operates at 12V it is important to do additional research about a servo motor controller if your servo motor is not considered standard Also most hobby servo motors use the standard R C servo input three wires which are ground voltage and l Choose the control method Some servo motor controllers allow you to control the servo s position manually using a dial switch buttons while others communicate using UART serial commands or other means Determine the number of servos to be controlled Servo controllers can control many servos usually 8 16 32 64 and up You can certainly select a servo motor controller capable of controlling more servos than you will need 3 As with DC motor controllers the control method is an important consideration Stepper Motor Control Is the motor you selected unipolar or bipolar Choose a stepper motor eonivoller type accordingly though a growing number are able to control both types The number of leads is usually a dead give away of the motor type if the motor has 4 leads then it is bipolar should it have 6 or more leads then it is unipolar Choose the motor controller voltage range to match your
8. Tags Grand Tutorial Series Make a Robot Make a Robot RobotShop Blog Posts about Make a Robot RobotShop Blog Read more Remove preview Lesson 3 Making Sense of Actuators Now that we learned about robotics in general in Lesson 1 and decided on the robot to make in Lesson 2 we will now choose the actuators that will make the robot move What is an actuator An actuator can be defined as a device that converts energy in robotics that energy tends to be electrical into physical motion The vast majority of actuators produce either rotational or linear motion For instance a DC motor is therefore a type of actuator Choosing the right actuators for your robot requires an understanding of what actuators are available some imagination and a bit of math and physics Rotational Actuators As the name indicates this type of actuators transform electrical energy into a rotating motion There are two main mechanical parameters distinguishing them from one another 1 torque the force they can produce at a given distance usually expressed in Nem or Ozein and 2 the rotational speed usually measured in revolutions per minutes or rpm AC Motor AC alternating current is rarely used in mobile robots since most of them are powered with direct current DC coming from batteries Also since electronic components use DC it is more convenient to have the same type of power supply for the actuators as well
9. Tutorial e Robot Arm Torque Calculator Practical Example In lesson 1 we determined the objective of our project would be to get a better understanding of mobile robots while keeping the budget to about 200 to a maximum of 300 In lesson 2 we decided we wanted a small tank on tracks that could operate on top of a desk First let us determine the type of actuators that would be required by answering the five aforementioned questions 1 Is the actuator being used to move a wheeled robot Yes A DC gear motor is the suggested type of actuator and skid steering is appropriate for a tank which means that each track will need it s own motor 2 Is the motor being used to lift or turn a heavy weight No a desktop rover should not be heavy 3 Is the range of motion limited to 180 degrees No the wheels need to urn continuously 4 Does the angle need to be precise No our robot does not require positional feedback 5 Is the motion in a straight line No since we want the robot to turn and move in all directions Since rotating a wheel needs rotational motion we could quickly eliminate all linear actuators and choose a DC gear motor The next logical question was which one A search online shows that there are not too many track systems intended for small robots which in itself would restrict which motors we could consider The Currently Available Track Systems eee At 2 and 3 wide the Lynxmotion tracks are mor
10. do not like water also consider water falling on electronics when accessing the robot after a dive e Surpassing depths of 10m or more can require significant research and investment e Very limited robotic community to provide help e Limited wireless communication options Miscellaneous and hybrid combinations Your idea for a robot may not fall nicely into any of the above categories or may be comprised of several different functional sections Note again that this guide is intended for mobile robots as opposed to stationary or permanently fixed designs other than robotic arms and grippers It is wise to consider when building a hybrid design to use a modular design each functional part can be taken off and tested separately Miscellaneous designs can include hovercraft snake like designs turrets and more Advantages e Designed and built to meet specific needs e Multi tasking and can be comprised of modules e Can lead to increased functionality and versatility Disadvantages e Possible Increased complexity and cost e Often times parts must be custom designed and built Arms amp Grippers Although these do not fall under the category of mobile robotics the field of robotics essentially started with arms and end effectors devices that attach to the end of an arm such as grippers electromagnets etc Arms and grippers are the best way for a robot to interact with the environment it is exploring Simple robot arms can have j
11. it and although some sort of RFID option may be possible it would require quite a bit of research Therefore out of the options available the most appropriate sensors to allow a robot to follow a human may be ultrasonic or infrared distance sensor s a camera and GPS A camera may be used to pick up a specific pattern placed on the shirt of the individual to follow while GPS units mounted on the robot and on the human would help the robot find the human if she cannot be seen visually Distance sensors would ensure the robot does not get too close to the human Therefore when choosing sensors to help your robot follow a human the sensors listed above would be a good starting point pA I want my robot to stay within the boundaries of our lawn There is no neighbour s grass sensor available that we are aware of so you will need to devise another sensor based solution e Q Are you looking to detect measure distance to or contact with an object o Yes we are looking to detect a boundary e Q Are you looking to measure rotation o Not really e Q Are you looking to measure environmental conditions o Not really but we ll keep an open mind since the robot is outdoors e Q Are you looking to measure position orientation or angle o Not really Applicable categories therefore include measuring distance feel contact detect an object and perhaps environmental conditions Out of the list of sensors in this category we can
12. motor s nominal voltage Find out how much current per coilyour motor requires and find out how much current per coil the stepper motor controller can provide If you cannot find the current per coil most manufacturers list the coil impedance R Using Ohms Law V IR you can then calculate the current T As with DC motor controllers the control method is an important consideration Linear Actuator Control Linear actuators come in three main flavours regarding their control method DC R C or position feedback Most DC linear actuators use a geared DC motor so a DC motor controller is usually appropriate However some linear actuators take R C servo input so you would select a servo motor controller Should an R C controlled linear actuator operate at a higher voltage than the servo controller s range the actuator may include separate wires for the higher supply voltage required Other Actuators Many miscellaneous electromechanical devices such as muscle wire solenoids or even powerful lights need to be controlled using motor controllers Below are some questions to determine if your actuator might need a motor controller e Higher current requirements any device that requires over 0 1A usually needs its own controller e Higher voltage requirements if the actuator operates above the microcontroller s voltage usually 5V or 3 3V it usually cannot be directly connected to a microcontroller For more inform
13. or Bluetooth interfaces etc As a consequence of this incredible versatility microcontrollers can be found in everyday products Practically every home appliance or electronic device uses at least one often many microcontroller For instance TV sets washing machines remote controls telephones watches microwave ovens and now robots require these little devices to operate Unlike microprocessors e g the CPU in personal computers a microcontroller does not require peripherals such as external RAM or external storage devices to operate This means that although microcontrollers can be less powerful than their PC counterpart developing circuits and products based on microcontrollers is much simpler and less expensive since very few additional hardware components are required It is important to note that a microcontroller can output only a very small amount of electrical power through its pins this means that a generic microcontroller will likely not be able to power electrical motors solenoids large lights or any other large load directly Trying to do so may even cause physical damage to the controller What are the more specialized features in a microcontroller Special hardware built into the microcontrollers means these devices can do more than the usual digital I O basic computations basic mathematics and decision taking Many microcontrollers readily support the most popular communication protocols such as UART a k a serial
14. order to accommodate for all parts 4 Some modifications need to be done to the design in order to accommodate for all parts such as o Add more mounting holes for the battery pack o Add more mounting points for servos or other accessories o Refined the hole placement 5 The cardboard frame will be made by printing the design onto white cardboard or gluing a printed paper sheet onto cardboard cutting it bending it and using hot glue in order to reinforce the bends edges and surfaces 6 Wecompletely assembled the robot using the cardboard frame in order to make sure everything fits properly 7 We measure everything again and once we were absolutely sure about the design we had it professionally manufactured 8 Test fit each component in case modifications are require 9 The frame is made in one piece so no assembly is required 10 Assembled the robot incorporating lots of accessories O O O O For further information on learning how to make a robot please visit the RobotShop Seance Center Visit the RobotShop Community Forum in order to seek assistance in building robots showcase your projects or simply hang out with other fellow roboticists Tags Grand Tutorial Series How To Make a Robot Make a Robot RobotShop Blog Posts about Make a Robot RobotShop Blog Read more Remove preview Lesson 10 Programming is usually the final step involved in building a robot If you followed the lessons so far you
15. rotation servo and Futaba continuous rotation servos sell for 17 and 14 respectively In the end we opted to use a pair of Solarbotics GM9 in order to use skid drive mainly because of their low cost It is important to note that although the calculator specified we needed about 150rpm we chose the motor anyway knowing it would move at about half the original desired velocity The torque produced by this motor is significantly greater than what we needed which means it can carry additional weight or climb stepper angles For further information on learning how to make a robot please visit the RobotShop Learning Center Visit the RobotShop Community Forum in order to seek assistance in building robots showcase your projects or simply hang out with other fellow roboticists Tags Grand Tutorial Series How To Make a Robot Tutorial Tutorial RobotShop Blog Posts about Tutorial RobotShop Blog Read more Remove preview Lesson 4 What is a microcontroller You might be asking yourself what is a microcontroller and what does it do A microcontroller is a computing device capable of executing a program 1 e a sequence of instructions and is often referred to as the brain or control center in a robot since it is usually responsible for all computations decision making and communications In order to interact with the outside world a microcontroller possesses a series of pins electrical signal conne
16. see that the following may be useful e Contact Detecting collisions in order to avoid obstacles e Distance o Ultrasonic infrared and laser These will help the robot to avoid hitting objects and when several placed facing downwards will help the robot avoid falling into openings such as pools e Rotation o Encoders Encoders these will help position the robot in two dimensional space based on a starting position o Positioning GPS Ideal the robot could be instructed to remain within certain coordinates e Environmental conditions o Humidity sensor This is not an intuitive solution and was creatively used on the Lawnbott Spyder lawn mower to differentiate between grass and non humid surfaces such as concrete and pavement o Magnetic sensor Magnetic sensors are used both indoors and outdoors to mark boundaries The perimeter is marked with a strip of conductive wire and the robot is equipped with a few magnetic sensors e Attitude o IMU this may make the data obtained from the encoders more accurate especially if there are slopes or uneven terrain e Miscellaneous irrelevant Therefore if you want your robot to stay within the boundaries of your lawn the sensors listed above would be a very good start For further information on learning how to make a robot please visit the RobotShop Learning Center Visit the RobotShop Community Forum in order to seek assistance in building robots showcase your
17. to Not all microcontrollers will be picked up by the computer and you should read the getting started guide in the manual to know exactly what to do to have your computer recognize it and be able to communicate with it You often need to download drivers specific to each operating system to allow your computer to understand how to communicate with the microcontroller and or the USB to serial converter chip Step 3 Check product s user guide for sample code and communication method protocol Don t reinvent the wheel if you don t have to Most manufacturers provide some code or pseudo code explaining how to get their product working The sample code may not be in the programming language of your choice but don t despair do a search on the Internet to see if other people have created the necessary code e Check product manuals user guides e Check the manufacturer s forum e Check the internet for the product code e Read the manual to understand how to write the code Useful Tips 1 Create manageable chunks of functional code By creating segments of code specific to each product you gradually build up a library Develop a file system on your computer to easily look up the necessary code 2 Document everything within the code using comments Documenting everything 1s necessary in almost all jobs especially robotics As you become more and more advanced you may add comments to general sections of code though
18. 5V microcontroller Without going into details NIMH and LiPo are the top two choices for small to medium sized robots Choose NiMh for a cheaper price and LiPo for a lighter weight Warning Batteries are powerful devices and can easily burn your circuits if they are connected incorrectly Always triple check that the polarity is right and that you device can handle the energy provided by the battery If you are not sure don t guess Electricity is much faster than you by the time you realize something is wrong the magic blue smoke already escaped your device Connecting Motor controllers to Microcontroller A microcontroller can communicate with motor controllers in a variety of ways e Serial The controller has two pins labelled Rx receive and Tx transmit Connect the Rx pin of the motor controller to the microcontroller s Tx pin and vice versa e 2C The motor controller will have four pins SDA SCL V GND Your microcontroller will have the same four pins but not necessarily labelled simply connect them one to one e PWM The motor controller will have both a PWM input and a digital input for each motor Connect the PWM input pin of the motor controller to a PWM output pin on the microcontroller and connect each digital input pin of the motor controller to a digital output pin on the microcontroller e R C To connect a microcontroller to an R C motor controller you need to connect the signal pin to a digital pin on the mi
19. CW Industrial Servo Motors An industrial servo motor is controlled differently than a hobby servo motor and is more commonly found on very large machines An industrial servo motor is usually made up of a large AC sometimes three phase motor a gear down and an encoder which provides feedback about angular position and speed These motors are rarely used in mobile robots because of their weight size cost and complexity You might find an industrial servo in a more powerful industrial robotic arm or very large robotic vehicles Stepper Motors A stepper motor does exactly as its name implies it rotates in specified steps actually specific degrees The number of degrees the shaft rotates with each step step size varies based on several factors Most stepper motors do not include gearing so just like a DC motor the torque is often low Configured properly a stepper can rotate CW and CCW and can be moved to a desired angular position There are unipolar and bipolar stepper motor types One notable downside to stepper motors is that if the motor is not powered it s difficult to be certain of the motor s starting angle Adding gears to a stepper motor has the same effect as a adding gears to a DC motors it increases the torque and decreases the output angular speed Since the speed is reduced by the gear ratio the step size 1s also reduced by that same factor If the non geared down stepper motor had a step size of 1 2 de
20. X GND and V connections are required It is important to note that although several serial connections can be shared on the same RX and TX pins proper bus arbitration 1s required in order to prevent cross talk errors and madness in general If you have very few serial devices it is often simple to use a single serial port for each one of them Wheels to motors Ideally you would have chosen wheels or sprockets which are designed to fit the shaft of the motor you chose If not hopefully there is a hub which fits between the two If you find that the wheel and motor you have chosen are not compatible with one another and cannot find a suitable hub you may need to find another hub which connects to the wheel but has a smaller bore you would then drill out the hub s bore to the same diameter as the shaft Electrical components to frame You can mount electronics to a frame using a variety of methods Be sure that whatever means you use do not conduct electricity Common methods include hex spacers screws nuts double sided tape Velcro glue cable ties etc Practical Example 1 Settle on a construction material choice 2 Weare getting the following parts in order to measure and test fit them o 2x Gear motors with 90 degree shafts 1x Arduino Uno 1x Johnny Robot Standard GM Track Kit 2x Arduino Motor controller Shield 2x Mini Breadboard 3 We will try to stay close to a 6 sided box but may have had to make modifications in
21. al and Service Robots are more capable rugged and often more expensive than domestic robots and are ideally suited for professional and or commercial use Security and Surveillance Most mobile robots are used to venture into areas where humans either should not or cannot go Robots of various sizes either remote controlled semi autonomous or fully autonomous are an ideal choice for these tasks Practical Example We anticipate that most of you following this guide have the objective of building a robot for learning and knowledge but also for sheer fun though many will have a specific idea or project they want to materialize The last major consideration is budget It is difficult to know exactly what people have in mind when they build their first robot one might already want to build an autonomous snow removal robot while another simply wants to make an intelligent clock A simple programmable mobile robot might cost about 100 while a more complex can be several thousands of dollars In this exercise we have chosen to make a mobile platform in order to get an understanding of motors sensors microcontrollers and programming and to include a variety of sensors We ll keep the budget to about 200 to 300 since we want it to be fairly complete For further information on learning how to make a robot please visit the RobotShop Learning Center Visit the RobotShop Community Forum in order to seek assistance in building ro
22. alogue and Serial interfaces with many safety features RB Pol 16 1 5 6V 5A dual Low cost controller with serial interface RB Pol 22 6 16V 9A dual PWM interface RB Spa 397 5 16V 2A dual serial interface RB Ada 02 4 5 36V 0 6A dual Arduino shield with PWM interface RB Cri 15 6 58V 10A single PWM RB Cri 14 6 58V 10A single PWM and many more There are a variety of other motor controllers which meet the criteria above which would work as well In order to reduce this list cost and features would need to be considered For example there is no need to consider a high current 10A motor controller which is understandably more expensive than a 5A controller We can also eliminate all single motor controllers The one controller that stands out from the rest is RB Pol 16 because of its lower voltage range this means that should we decide to power the motor at 3V it would fall within this controller s voltage range The other controller of interest is RB Ada 02 because it is made specifically for the microcontroller we selected 1 e the Arduino Uno However the one downside to RB Ada Q2 is that no additional shields can be installed afterwards The Pololu dual motor controller was ultimately chosen because of its lower voltage range and price www RobotShop com For further information on learning how to make a robot please visit the RobotShop Learning Center Visit the RobotShop Community Forum in order to s
23. an provide depth information stereo vision Robots equipped with cameras can be some of the most capable and complex robots produced A camera combined with the right software can provide color and object recognition e Advantages can provide dept information and a good feedback about a robot s environment e Disadvantages complex to program and use the information Positioning An indoor localization system can use several beacons to triangulate the robot s position within a room while others use a camera and landmarks e Advantages excellent for absolute positioning e Disadvantages requires complex programming and the use of markers GPS A GPS uses the signals from several satellites orbiting the planet to help determine its geographic coordinates Regular GPS units can provide geographical positioning down to 5m of accuracy while more advanced systems involving data processing and error correction thanks to the use of other GPS units or IMUs can be accurate down to several cm e Advantages does not requires markers or other references e Disadvantages can only function outdoors Rotation Potentiometer A rotary potentiometer is essentially a voltage divider and provides an analog voltage corresponding to the angle the knob is rotated to e Advantages simple to use inexpensive reasonably accurate provides absolute readings e Disadvantages most are restricted to 300 degrees of rotation Gyroscope
24. and physics and arts aesthetics and users are free to use their imagination Amusing others with your creations especially if they are user friendly and interactive helps others to become interested in the field Competitions amp Contests Competitions give the project design guidelines and a due date They also put your robot against others in the same class and test your design and construction skills Although many competitions are specifically for students elementary to university there also exist open competitions where adults and professionals alike can compete Autonomous life form ff ne een are natural creators and innovators The next great innovation will be to develop a fully autonomous life form that rivals or surpasses ourselves in ability and perhaps creativity This goal is still being accomplished in small steps by individuals research organizations and professionals Domestic or Professional tasks a Domestic robots help liberate people from unpleasant or dangerous tasks and give them more liberty and security Professional and Service Robots are used in a variety of applications at work in public in hazardous environments in locations such as deep sea battlefields and space just to name a few In addition to the service areas such as cleaning surveillance inspection and maintenance we utilize these robots where manual task execution 1s dangerous impossible or unacceptable Profession
25. are equipped with buttons or simple contacts placed in strategic locations for example on a front bumper to determine if it has come into contact with an object Robot pets may have contact or force sensors placed in their head feet and back but if you try to touch an area where there is no sensor the robot has no way of knowing it has been touched and will not react As research into humanoid robots continues perhaps an electromechanical skin will be developed What can robots sense that humans can t Although a robot cannot tell you if a substance tastes good or if an odour smells bad the steps involved in analyzing the chemical composition can give it far more information than a normal human could about its properties A robot equipped with a carbon monoxide sensor would be able to detect carbon monoxide gas which is otherwise colorless odorless to humans A robot would also be able to tell you the Ph level of a substance to determine if it is acidic or basic and much much more Humans use a pair of eyes to get a very good sense of depth though for many accurately gauging distance is not easy A human might tell you the tree looks to be about 50 feet away but a robot equipped with the right distance sensors can tell you the tree is 43 1 feet away Additionally robots can not only sense but give accurate values of a variety of environmental factors that humans are otherwise unaware of or incapable of sensing
26. as you start you should add a comment to almost every line 3 Save different versions of the code do not always overwrite the same file if you find one day that your 200 lines of code do not compile you won t be stuck going through it line by line instead you can revert to a previously saved and functional version and add modify it as needed Code does not take up much space o a hard drive so you should not feel pressured to only save a few copies 4 Raise the robot off the table or floor when debugging so its wheels legs tracks don t accidentally launch it off the edge and have the power switch close by in case the robot tries to destroy itself An example of this is if you try to send a servo motor to a 400us signal when it only accepts a 500 corresponding to 0 degrees to 2500us corresponding to 180 degrees signal The servo would try to move to a location which it cannot physically go to 9 degrees and ultimately burn out 5 If code does something that does not seem to be working correctly after a few seconds turn off the power it s highly unlikely the problem will fix itself and in the meantime you may be destroying part of the mechanics 6 Subroutines may be a bit difficult to understand at first but they greatly simplify your code If a segment of code is repeated many times within the code it is a good candidate to be replaced with a subroutine Practical Example We have chosen an Ard
27. ate readings and should therefore not be used for critical applications Magnetometers Magnetic sensors or magnetometers can be used to detect magnets and magnetic fields This is useful to know the position of magnets e Advantages can detect ferromagnetic metals e Disadvantages some times the sensors can be damaged by strong magnets Attitude roll pitch and heading Compass A digital compass is able to use the earth s magnetic field to determine its orientation with respect to the magnetic poles Tilt compensated compasses account for the fact that the robot may not be perfectly horizontal e Advantages provides absolute navigation e Disadvantages greater accuracy increases the price Gyroscope Electronic gyroscopes are able to provide the angle of the tilt in one or more axes Mechanical tilt sensors usually determine if a robot has been tilted past a certain value by using mercury in a glas capsule or a conductive ball e Advantages electronic tilt sensors have a higher accuracy than mechanical ones e Disadvantages can be expensive Accelerometers Accelerometers measure the linear acceleration This allows to measure the gravitational acceleration or any other accelerations the robot is subject to This can be a good option to approximate distance travelled if your robot cannot use the surrounding environment as a reference Accelerometers can measure accelerations along one two or three axis A
28. ation regarding actuator control and communications method please visit the RobotShop Learning Center Practical Example In the previous lesson we had chosen the Solarbotics GM9 gear motors Below are this motor s specifications Gear Ratio 143 1 Unloaded RPM 3V 40 Unloaded RPM 6V 78 Unloaded Current 3V 50mA Unloaded Current 6V 52mA Stall Current 3V 400mA Stall Current 6V 700mA Stall Torque 3V 44 441n oz Stall Torque 6V 76 381n oz Applying the steps l The nominal voltage is 3V or 6V 2 There is no mention of continuous current though the stall torque at both voltages is provided 400mA and 700mA If we take 25 of these values the continuous current can be approximated at 100mA to 175mA To be safe we can take the larger value We have chosen a microcontroller that has many different pins including serial PWM analog and digital Our little rover will be using two identical motors so we can use a dual motor controller Given the above criteria we are looking for a motor controller with the following specifications Voltage range can accommodate a 3V to 6V motor Continuous current at least 350mA per channel low power category Communication method is PWM I2C or analog or several of these Dual motor control is preferred By Looking at the Brushed DC Motor Controllers Comparison Table imperial version several motor controllers fit the criteria RB Dim 19 6 18V 5A dual An
29. bots showcase your projects or simply hang out with other fellow roboticists Tags Grand Tutorial Series Make a Robot RobotShop Tutorial Tutorial RobotShop Blog Posts about Tutorial RobotShop Blog Read more Remove preview Lesson 2 Lessons Menu e Lesson Getting Started e Lesson 2 Choosing a Robotic Platform e Lesson 3 Making Sense of Actuators e Lesson 4 Understanding Microcontrollers e Lesson 5 Choosing a Motor Controller e Lesson 6 Controlling your Robot e Lesson 7 Using Sensors e Lesson 8 Getting the Right Tools e Lesson 9 Assembling a Robot e Lesson 10 Programming a Robot Following the first lesson you now have a basic understanding of what a robot is and what current robots normally do Now it is time to decide on the type if robot you are going to build A custom robot design often starts with a vision of what the robot will look like and what it will do The types of robots possible are unlimited though the more popular are e Land wheeled tracked and legged robots e Aerial planes helicopters and blimp e Aquatic boats submarines and swimming robots e Misc and mixed robots e Stationary robot arms and manipulators This lesson is intended to help you decide what type of robot to build to best suite your mission Since you have brainstormed on what tasks or functions you want it to accomplish after lesson 1 you can now choose the type of
30. cally to the internet and data received via the internet is then sent wirelessly to the robot Advantages e Robot can be controlled trough the Internet from anywhere in the world e The robot is not limited to an operating time since it could use Power over Ethernet PoE e Using Internet Protocol IP can simplify and improve the communication scheme e Same advantages as with direct wired computer control Disadvantages e Programming involved is more complex e The tether can get caught or snagged and potentially cut e Distance is limited by the length of the tether e Dragging a long tether adds friction and can slow or even stop the robot from moving Wireless Infrared Infrared transmitters and receivers cut the cables connecting the robot to the operator This is usually a milestone for beginners Infrared control requires line of sight in order to function the receiver must be able to see the transmitter at all times in order to receive data Infrared remote controls such as universal remote controls for televisions are used to send commands to an infrared receiver connected to a microcontroller which then interprets these signals and controls the robot s actions Advantages e Low cost e Simple TV remote controls can be used as controllers Disadvantages e Needs to be line of sight e Distance is limited Radio Frequency RF Commercially available Remote Control R C units use s
31. ck in causing it to surface If you want to be able to send and or receive commands from your robot you will need to determine its level of autonomy and if you want it to be tethered wireless or fully autonomous Tethered Direct Wired Control The easiest way to control a vehicle is with a handheld controller physically connected to the vehicle using a cable e a tether Toggle switches knobs levers joysticks and buttons on this controller allow the user to control the vehicle without the need to incorporate complex electronics In this situation the motors and a power source can be connected directly with a switch in order to control its forward backwards rotation Such vehicles usually have no intelligence and are considered to be more remote controlled machines than robots Advantages e The robot is not limited to an operating time since it can be connected directly to the mains e There is no worry about loss of signal e Minimal electronics and minimal complexity e The robot itself can be light weight or have added payload capacity e The robot can be physically retrieved if something goes wrong very important for underwater robots Disadvantages e The tether can get caught or snagged and potentially cut e Distance is limited by the length of the tether e Dragging a long tether adds friction and can slow or even stop the robot from moving Wired Computer Control The next step is to incorporate a mic
32. control and two PWM pins for speed control this will be explained in more detail in Lesson 5 The robot will also transmit and receive data so it will need to support the UART a k a serial or RS232 communication protocol in our case We would also like the option of adding other sensors and devices in the future so analogue pins and many extra digital pins would be appropriate The upcoming RobotShop Microcontroller comparison table allows us to compare the main features of one microcontroller with another The Pololu and Arduino microcontrollers seemed to conform best to the above criteria In order to select a specific microcontroller from these two manufacturers each was researched in order to determine the amount of available material code user community Google hits and more www RobotShop com The Arduino Duemilanove recently replaced by the Arduino Uno was ultimately chosen based on price vs features and because of the concept of shields separate accessory boards you plug and stack onto the microcontroller which add specific functionality Also Arduino is rather popular there are many sample projects and its community is very active B For further information on learning how to make a robot please visit the RobotShop Learning Center Visit the RobotShop Community Forum in order to seek assistance in building robots showcase your projects or simply hang out with other fellow roboticists Tags Arduino Tuto
33. controllers specifically for use with Java e NET C Microsoft s proprietary language used to develop applications in Visual Studio Examples include Netduino FEZ Rhino and others e Processing Arduino a variant of C that includes some simplifications in order to make the programming for easier e Python one of the most popular scripting languages It is very simple to learn and can be used to put programs together very fast and efficiently In lesson 4 you chose a microcontroller based on the features you needed number of I O user community special features etc Often times a microcontroller is intended to be programmed in a specific language For example e Arduino microcontrollers use Arduino software and are re programmed in Processing e Basic Stamp microcontrollers use PBasic e Basic Atom microcontrollers use Basic Micro e Javelin Stamp from Parallax is programmed in Java If you have chosen a hobbyist microcontroller from a known or popular manufacturer there is likely a large book available so you can learn to program in their chosen programming language If you instead chose a microcontroller from a smaller lesser known manufacturer e g since it had many features which you thought would be useful for your project it s important to see what language the controller is intended to be programmed in C in many cases and what development tools are there available usually from the chip manufacturer Gett
34. crocontroller Regardless of the communication method the motor controller s logic and the microcontroller need to share the same ground reference this is achieved by connecting the GND pins together and the same logic high level this can be achieved by using the same V pin to power both devices A logic level shifter is required 1f the devices don t share the same logic levels 3 3V and 5V for instance Connecting Sensors to a Microcontroller Sensors can be interfaced with microcontrollers in a similar way than motor controllers Sensors can use the following types of communication e Digital The sensor has a digital signal pin that connects directly to a digital microcontroller pin A simple switch can be regarded as a digital sensor e Analogue Analogue sensors produce an analogue voltage signal that needs to be read by an analogue pin If your microcontroller does not have analog pins you will need a separate analog to digital circuit ADC Also some sensors some with the required power supply circuit and usually have three pins V GND and Signal If a sensor is a simple variable resistor for instance it will require you to create a voltage divider in order to read the resulting variable voltage e Serial or I2C the same communication principles explained for motor controllers apply here Communication device to microcontroller Most communication devices e g XBee Bluetooth use serial communication so the same RX T
35. ctions that can be turned HIGH 1 ON or LOW 0 OFF through programming instructions These pins can also be used to read electrical signals coming form sensors or other devices and tell whether they are HIGH or LOW Microcontroller Male pins Most modern microcontrollers can also measure analogue voltage signals i e signals that can have a full range of values instead of just two well defined states through the use of an Analogue to Digital Converter ADC By using the ADC a microcontroller can assign a numerical value to an analogue voltage that 1s neither HIGH nor LOW What can a microcontroller do Although microcontrollers can seem rather limited at first glance many complex actions can be achieved by setting the pins HIGH and LOW in a clever way Nevertheless creating very complex algorithms such as advanced vision processing and intelligent behaviours or very large programs may be simply impossible for a microcontroller due to its inherent resource and speed limitations For instance in order to blink a light one could program a repeating sequence where the microcontrollers turns a pin HIGH waits for a moment turns it LOW waits for another moment and starts again A light connected to the pin in question would then blink indefinitely In a similar way microcontrollers can be used to control other electrical devices such as actuators when connected to motor controllers storage devices such as SD cards WiFi
36. cts which were based on existing mass produced products such as bottles cardboard boxes Tupperware etc This is essentially re purposing a product and has the potential to either save you a lot of time and money or create added hassle and headache The amazing RoboBrrdto the left is a very good example of how to repurpose materials and make a very capable robot out of them Basic construction material Some of the most basic construction materials can be used to make excellent frames One of cheapest and most readily available materials is cardboard which you can often find for free and can be easily cut bent glued and layered Example You can create a reinforced cardboard box which looks a lot nicer and is more proportional in size to your robot You can then spread epoxy or glue to make it more durable and then paint it Flat structural material One of the most common ways to make a frame is to use a standard material such as a Sheet of wood plastic or metal and add holes for connecting all the actuators and electronics A durable piece of wood tends to be fairly thick and heavy whereas a thin sheet of metal may be too flexible Example A flat 1 piece of dense wood can be easily cut with a saw drilled without fear of shattering painted sanded and more You can connect devices to both sides for example connect the motors and caster wheels to the bottom and the electronics and battery to the top and the wood will
37. e intended for medium sized robots so we l omit them The price does fall within the budget though The Vex Tank Tread Kit is definitely a good option but it would restrict us to one specific motor The Tamiya Track and Wheel Set is definitely a good option and would limit our choices to Tamiya motors and gearboxes This would also be within the budget There are several Johnny Robot Track Kits one for a Hitec continuous rotation servo which is essentially a gear motor in a servo s body another for a Futaba continuous rotation servo one for Tamiya motors and another for Pololu or Solarbotics motors This is definitely a good option and also within our budget Mainly because of aesthetic and motor compatibility reasons we are going to stick with this choice There is always the option of hacking a toy such as an R C tank and convert it into a robot This option would also give us compatible motors however the objective is to design our own robot and not hack another product Computing the motor requirements The next step is to fill out the DC Drive Motor Selector Tool using approximate values INPUT Total mass of robot Number of dnve motors Radius of drive wheel Viaximum incline Supply voltage Desired acceleration Desired operatina time Total efficiency OUTPUT per drive motor ey TEET Angular Velocity 150 46 rev min Torque 1 4123 ozf in Total Power 0 15708 Maximum current 0 0
38. e robot is being used on and cause the tracks to wear e Not many different tracks are available robot is usually constructed around the tracks e Drive sprocket might significantly limit the number of motors that can be used e Increased mechanical complexity idler placement and number of links and connections Legs we tt Sar Fiat iy An increasing number of robots use legs for mobility Legs are often preferred for robots that must navigate on very uneven terrain Most amateur robots are designed with six legs which allow the robot to be statically balanced balanced at all times on 3 legs robots with fewer legs are harder to balance The latter require dynamic stability meaning that if the robot stops moving mid stride it might fall over Researchers have experimented with monopod one legged hopping designs though bipeds two legs quadrupeds four legs andhexapods six legs are the most popular Advantages e Closer to organic or natural motion e Can potentially overcome large obstacles and navigate very rough terrain Disadvantages e Increased mechanical electronic and coding complexity not the easiest way to get into robotics e Lower battery size despite increased power demands e Higher cost to build Air A AUAV Autonomous Unmanned Aerial Vehicle is very appealing and is entirely within the capability of many robot enthusiasts However the advantages of building an autonomous
39. e serial pin it will be sent in the correct order Putting all the code together makes the robot move forward and sweep the servo while reading distance values You can see the full robot and the user manual VJ Hirsch Computer Math Instructor Van Nuys High School 6536 Cedros Avenue Van Nuys CA 91411 vxh16221 lausd net 818 778 6800
40. earchers and developers have resorted to alternatives to biological senses What can humans sense that robots can t Robots can see but have a hard time understanding what they are looking at Using a camera a robot may be able to pick up an image made up of millions of pixels but without significant programming it would not know what any of those pixels meant Distance sensors would indicate the distance to an object but would not stop a robot from bumping into it Researchers and companies are experimenting with a variety of different approaches to permit a robot to not only see but understand what it is looking at It may be a long time before a robot is able to differentiate between objects placed before it on a table especially if they do not appear to be exactly the same as what is in its database of objects Robots have a really hard time tasting and smelling A human may be able to tell you this tastes sweet or this smells bad whereas a robot would need to analyze the chemical composition and then look up the substance in a database to determine if humans have marked the taste as being sweet or the smell as being bad There has not been much demand for a robot that can taste or smell so not much effort has been put into creating the appropriate sensors Humans have nerve endings throughout their skin and as such we know when we have touched an object or when something has touched us Robots
41. echanics an actuator that produces linear motion may be used to rotate an object and vice versa like on a car s windshield wiper 1 Is the actuator being used to move a wheeled robot Drive motors must move the weight of the entire robot and will most likely require a gear down Most robots use skid steering while cars or trucks tend to use rack and pinion steering If you choose skid steering DC gear motors are the ideal choice for robots with wheels or tracks as they provide continuous rotation and can have optional position feedback using optical encoders and are very easy to program and use If you want to use rack and pinion you will need one drive motor DC gear is also suggested and one motor to steer the front wheels For stirring since the rotation required is restricted to a specific angle an R C servo would be the logical choice 2 Is the motor being used to lift or turn a heavy weight Lifting a weight requires significantly more power than moving a weight on a flat surface Speed must be sacrificed in order to gain torque and it is best to use a gearbox with a high gear ratio and powerful DC motor or a DC linear actuator Consider using system either with worm gears or clamps that prevents the mass from falling in case of a power loss 3 Is the range of motion limited to 180 degrees If the range is limited to 180 degrees and the torque required is not significant an R C servo motor is ideal Servo m
42. eek assistance in building robots showcase your projects or simply hang out with other fellow roboticists Tags actuator Grand Tutorial Series How To Motor Controllers Motor Controllers RobotShop Blog Posts about Motor Controllers RobotShop Blog Read more Remove preview Lesson 6 Lessons Menu e Lesson Getting Started e Lesson 2 Choosing a Robotic Platform e Lesson 3 Making Sense of Actuators e Lesson 4 Understanding Microcontrollers e Lesson 5 Choosing a Motor Controller e Lesson 6 Controlling your Robot e Lesson 7 Using Sensors e Lesson 8 Getting the Right Tools e Lesson 9 Assembling a Robot e Lesson 10 Programming a Robot The definition we have chosen for a robot requires the device to obtain data about its environment make a decision and then take action accordingly This does not exclude the option of a robot being semi autonomous having aspects which are controlled by a human and others which it does on its own A good example of this is a sophisticated underwater robot a human controls the basic movements of the robot while an on board processor measures and reacts to underwater currents in order to keep the robot in the same position without drifting A camera onboard the robot sends video back to the human while onboard sensors may track the water temperature pressure and more If the robot loses communication with the surface an autonomous program may ki
43. efore it is built Autodesk 123D is another free 3D CAD Computer Aided Design software aimed at hobbyists While it shares many of the same features as Google Sketchup it has some interesting features such as solid based part design assemblies parametrized transforms and other functionalities that are usually seen in higher end CAD programs o Programming softwareY our first programming software should correspond to whichever microcontroller you selected If you chose an Arduino microcontroller you should choose the Arduino software if you chose a Basic Stamp from Parallax you should choose PBasic and so forth In order to use a variety of microcontrollers you may want to learn a more fundamental programming language such as BASIC or C o Schematics and PCBsThere are many free programs available on the market and CadSoft s EAGLE is one of the more popular It includes an extensive library of parts and helps you convert your schematic to a PCB Ultimate o CADSolidWorks is the CAD program of choice for many when doing mechanical design but it is certainly not the only one available Whet working at this level i e using programs worth several thousands of dollars you should have a good idea of your needs in order to choose the right tool Unigraphics Catia ProE etc CAMIf you are using a CNC machine you will need a proper 3D CAD program such as ProE AutoCAD SolidWorks or other similar program In order to convert your CAD mod
44. el to useable code to send to the CNC machine you need a CAM program Often you can purchase a CAM program specifically for the CAD software you selected or find a third party supplier Raw Materials Essential Thin sheet metalThis material can be cut easily with scissors and can be bent and shaped as needed to form the frame or other components of your robot without necessarily having to do machining CardboardThe right cardboard thick but can still be cut using hand tools can easily be used to make a frame or prototype Even basic glue can be used to hold cardboard together Thin plasticPolypropylene PVC about 1 16 thick can be scored or sawed to create a more rigid and longer lasting frame for your robot Thin woodWood is a great material to work with if you have the means It can be screwed glued sanded finished and more ME O f Intermediate PolymorphPolymorph allows you to create plastic parts without the hassle of having to create custom moulds Sheet metallf you have thicker metal cutting sheers sheet metal makes an excellent building material for a robot frame because of its durability flexibility and resistance to rust Plastic sheetsPlastic sheets are fairly rigid and resist deformation If you are cautious and slow when cutting or drilling most plastics the results can look professional Practical Examples Essential Workshop Ard e Ard e the Arduino based robot is an example of what you c
45. esson 7 Using Sensors e Lesson 8 Getting the Right Tools e Lesson 9 Assembling a Robot e Lesson 10 Programming a Robot Now that you have chosen all the basic building blocks used to make a robot the next step is to design and build a structure or frame which keeps them all together and gives your robot a distinct look and shape Making the Frame There is no ideal way to create a frame since there is almost always a trade off to be made You may want a lightweight frame but it may need to use expensive materials or end up too fragile You may want a robust or large chassis but realize it will be expensive heavy or hard to produce Your ideal frame may be complex and take too much time to design and create when a simple frame may have been just as good There 1s also rarely ever an ideal shape but some designs can certainly look more elegant in their simplicity while others can attract attention because of their complexity Materials There are many materials you can use to create a frame As you use more and more materials to build not only robots but other devices you will get a better feeling as to which is most appropriate for a given project The list of suggested building materials below include only the more common ones and once you have tried a few feel free to experiment with ones not on the list or merge some together Use existing commercial products WY ou have likely seen school proje
46. force that is being applied to it e Advantages allows gauging how much force is being applied e Disadvantages can be imprecise and are more difficult to use than simple switches Distance Ultrasonic range finders use acoustics to measure the time between when a signal 1s sent versus when its echo is received back Ultrasonic range finders can measure a range of distances but are used specifically in air and are affected by the reflectivity of different materials e Advantages medium range several meters measurement e Disadvantages surfaces and environmental factors can affect the readings Infrared Infrared light which as we saw is used in communication can also be used to measure distance Some infrared sensors measure one specific distance while others provide an output proportional to the distance to an object e Advantages low cost fairly reliable and accurate e Disadvantages closer range than ultrasonic Laser Lasers are used when high accuracy or long distances or both are required when measuring the range to an object Scanning laser rangefinders use spinning lasers to get a two dimensional scan of the distances to objects e Advantages very accurate very long range e Disadvantages much costlier than regular infrared or ultrasonic sensors Encoders Optical encoders use mini infrared transmitter receiver pairs and send signals when the infrared beam is broken by a specifically designed sp
47. ge is usually determined by the choice of wireless router GPRS Cellular Another wireless technology that was originally developed for human to human communication the cell phone is now being used to control robots Since cellular frequencies are regulated incorporating a cellular module on a robot usually requires added patience for programming as well as an understanding of the cellular network system and the regulations Advantages e Robot can be controlled anywhere it has a cellular signal e Direct satellite connection is possible Disadvantages e Setup and configuration can be complex NOT for beginners e Each network has its own requirements restrictions e Cellular service is not free usually the more data you transmit receive the more money you will need to pay e System is not yet well setup for robotics use Autonomous The next step is to use the microcontroller in your robot to its full potential and program it to react to input from its sensors Autonomous control can come in various forms pre programmed with no feedback from the environment limited sensor feedback and finally complex sensor feedback True autonomous control involves a variety of sensors and code to allow the robot to determine by itself the best action to be taken in any given situation The most complex methods of control currently implemented on autonomous robots are visual and auditory commands For visual control a robot loo
48. grees and you add a gear down of 55 1 the new step size would be 1 2 55 0 0218 degrees Linear Actuators A linear actuator produces linear motion motion along one straight line and have three main distinguishing mechanical characteristics the minimum and maximum distance the rod can move a k a the stroke in mm or inches their force in Kg or lbs and their speed in m s or inch s DC Linear Actuator A DC linear actuator is often made up of a DC motor connected to a lead screw As the motor turns so does the lead screw A traveller on the lead screw is forced either towards or away from the motor essentially converting the rotating motion to a linear motion Some DC linear actuators incorporate a linear potentiometer which provides linear position feedback In order to stop the actuator from destroying itself many manufacturers include limit switches at either end which cuts power to the actuator when pressed DC linear actuators come in a wide variety of sizes strokes and forces Solenoids Solenoids are composed of a coil wound around a mobile core When the coil is energized the core is pushed away from the magnetic field and produces a motion in a single direction Multiple coils or some mechanical arrangements would be required in order to provide a motion in two directions A solenoid s stroke is usually very small but their speed is very fast The strength depends mainly on the coil size and the curre
49. hardware side microcontroller developments boards add convenience and are easier to use Over time These boards usually break out all the useful pins of the microcontroller and make them easy to access for quick circuit prototyping They also provide convenient USB power and programming interfaces that plug right into any modern computer For those unfamiliar with the term a Development Board is a circuit board that provides a microcontroller chip with all the required supporting electronics such as voltage regulator oscillators current limiting resistors and USB plugs required to operate If you are not planning to design your own support circuit buying a development board is preferable to simply getting a single microcontroller chip Note Robot programming is covered in greater depth in Lesson 10 Why not use a standard computer It is apparent that a microcontroller is very similar to a PC CPU or microprocessor and that a development board is akin to a Computer motherboard If this is the case why not simply use a full computer to control a robot Microcontroller r P eee Pat oties am As a matter of fact in more advanced robots especially those that involve complex computing and vision algorithms the microcontroller is often replaced or supplemented with a standard computer A desktop computer includes a motherboard a processor a main storage device such as a hard drive video processing on board or ex
50. have chosen the actuators electronics sensors and more and have assembled the robot so it hopefully looks something like what you had initially set out to build Without programming though the robot is a very nice looking and expensive paperweight It would take much more than one lesson to teach you how to program a robot so instead this lesson will help you with how to get started and where and what to learn The practical example will use Processing a popular hobbyist programming language intended to be used with the Arduino microcontroller chosen in previous lessons We will also assume that you will be programming a microcontroller rather than software for a full fledged computer What Language to Choose 4 There are many programming languages which can be used to program microcontrollers the most common of which are e Assembly its just one step away from machine code and as such it is very tedious to use Assembly should only be used when you need absolute instruction level control of your code e Basic one of the first widely used programming languages it is still used by some microcontrollers Basic Micro BasicX Parallax for educational robots e C C one of the most popular languages C provides high level functionality while keeping a good low level control e Java it is more modern than C and provides lots of safety features to the detriment of low level control Some manufacturers like Parallax make micro
51. how fast the motor should turn Thus the microcontroller and the motor controller have to work together in order to make the motors move appropriately Usually the microcontroller can instruct the motor controller on how to power the motors via a standard and simple communication method such as UART a k a serial or PWM Also some motor controllers can be manually controlled by an analogue voltage usually created with a potentiometer The physical size and weight of a motor controller can vary significantly from a device smaller than the tip of your finger used to control a mini sumo robot to a large controller weighing several Kg The weight and size of a motor controller usually has a minimal impact on the robot until you get into small robotics or unmanned aerial vehicles The size of a motor controller is usually related to the maximum current it can provide Larger current also means having to use larger diameter wires the smaller the gauge number the larger the diameter Motor Controller Types Since there are several types of actuators as discussed in lesson 3 there are several types of motor controllers e Brushed DC motor controllers used with brushed DC DC gear motors and many linear actuators e Brushless DC motor controllers used with brushless DC motors e Servo Motor Controllers used for hobby servo motors e Stepper Motor Controllers used with unipolar or bipolar stepper motors depending on their kind Choo
52. http www robotshop com blog en how to make a robot lesson 1 3707 e enera on How to Make a Robot Lesson 1 Getting Started RobotShop Blog Lessons Menu Lesson 1 Getting Started Lesson 2 Choosing a Robotic Platform Lesson 3 Making Sense of Actuators Lesson 4 Understanding Microcontrollers Lesson 5 Choosing a Motor Controller Lesson 6 Controlling your Robot Lesson 7 Using Sensors Lesson 8 Getting the Right Tools Lesson 9 Assembling a Robot Lesson 10 Programming a Robot Getting Started Welcome al Read more Remove preview How to Make a Robot Lesson 1 Getting Started Posted on August 4 2010 by Coleman Benson amp filed under How To Make a Robot Tutorials z YS z p F P A O pya 5 A S oO o 0 2 Q ra 5 F o o amp Er E gt J g ROBOTSHOP GRAND TUTORIAL Lessons Menu e Lesson Getting Started e Lesson 2 Choosing a Robotic Platform e Lesson 3 Making Sense of Actuators e Lesson 4 Understanding Microcontrollers e Lesson 5 Choosing a Motor Controller e Lesson 6 Controlling your Robot e Lesson 7 Using Sensors e Lesson 8 Getting the Right Tools e Lesson 9 Assembling a Robot e Lesson 10 Programming a Robot Getting Started Welcome to the first installment of the Grand RobotShop Tutorial a series of 10 lessons that will teach you how to make your own robot This tutorial is a
53. i Hakan apnicathon Gay Lie Baar a7 Being afraid of programming microcontrollers is getting old fashioned Unlike the old days where making a light blink took advanced knowledge of the microcontroller and several dozen lines of code not to mention parallel or serial cables connected to huge development board programing a microcontroller is very simple thanks to modern Integrated Development Environments IDE that use up to date languages fully featured libraries that readily cover all of the most common and not so common action and several ready made code examples to get beginners started Now a days microcontrollers can be programmed in various high level languages including C C C Processing a variation of C Java Python Net and Basic Of course it is always possible to program them in Assembler but this privilege is reserved for more advanced users with very special requirements and a hint of masochism In this sense anyone should be able to find a programming language that best suit their taste and previous programming experience IDEs are becoming even simpler as manufacturers create graphical programming environments Sequences which used to require several lines of code are reduced to an image which can be connected to other images to form code For example one image might represent controlling a motor and the user need only place it where he she wants it and specify the direction and rpm On the
54. icrocontroller has a large supporting community or has been successfully used in a similar or even the same situation could simplify your design phase considerably This way you could benefit from other user s experience and among hobbyists It is common for robot builders to share results code pictures videos and detail successes and even failures All this available material and the possibility of receiving advice from more experienced users can prove very valuable 2 Does it have any special features the robot requires As popular as a microcontroller might be t must be able to perform all the special actions required for your robot to functions properly Some features are common to all microcontrollers e g having digital inputs and outputs being able to perform simple mathematical operations comparing values and taking decisions while others need specific hardware e g ADC PWM and communication protocol support Also memory and speed requirements as well as pin count should be taken into consideration 3 Are the accessories I need available for a particular microcontroller If your robot has special requirements or there is a particular accessory or component that is crucial for your design choosing a compatible microcontroller is obviously very important Although most sensors and accessories can be interfaced directly with many microcontrollers some accessories are meant to interface with a specific microcontroller and even
55. imed at anybody willing to get started in robotics and have a basic understanding of terms such as voltage current motor and sensors Although this might seem pretty basic even people with previous robot building experience might find useful information regarding the general method of building a robot What is a robot There are many definitions of robot and no real consensus has been attained so far We loosely define a robot as follows Robot An electromechanical device which is capable of reacting in some way to its environment and take autonomous decisions or actions in order to achieve a specific task This means that a toaster a lamp or a car would not be considered as robots since they have no way of perceiving their environment On the other hand a vacuum cleaner that can navigate around a room or a solar panel that seeks the sun can be considered as a robotic system It is also important to note that the robots featured in Robot Wars for instance or any solely remote controlled device would not fall under this definition and would be closer to a more complex remote controlled car Although this definition is quite general it might need to evolve in the future in order to keep up with the latest advancement in the field In order to get a sens of how robotics is rapidly growing we suggest you take a look at the RobotShop History of Robotics Let s get started This series of tutorials is
56. ing Started The first program you will likely write is Hello World referred to as such for historic reasons This is one of the simplest programs that can be made in a computer and is intended to print a line of text e g Hello World on the computer monitor or LCD screen In the case of a microcontroller another very basic program you can do that has an effect on the outside world rather than just on board computations is toggling an IO pin Connecting an LED to and I O pin then setting the I O pin to ON and OFF will make the LED blink Although the simple act of turning on an LED may seem basic the function can allow for some complex programs you can use it to light up multi segment LEDs to display text and numbers operate relays servos and more Step 1 Ensure you have all components needed to program the microcontroller Not all microcontrollers come with everything you need to program them and most microcontrollers need to be connected to a computer via USB plug If your microcontroller does not have a USB or DB9 connector then you will need a separate USB to serial adapter and wire it correctly Fortunately many hobbyist microcontrollers are programmable either via an RS 232 port or by USB and include the USB connector on board which is used not only for two way communication but also to power the microcontroller board Step 2 Connect the microcontroller to the computer and verify which COM port it is connected
57. inning disk mounted to a rotating shaft The number of times the beam is broken corresponds to the total angle travelled by a wheel Knowing the radius of the wheel you can determine the total distance travelled by that wheel Two encoders give you a relative distance in two dimensions e Advantages assuming there is no slip the displacement is absolute Often comes installed on the rear shaft of a motor e Disadvantages additional programming required more accurate optical encoders can be 50 each Linear Potentiometer resistive band A linear potentiometer is able to measure the absolute position of an object A resistive band changes resistance depending on where a force is applied e Advantages position is absolute A resistive band requires pressure to be applied at a given position e Disadvantages range is very small Stretch and Bend Sensors A stretch sensor is made up of a material whose resistance changes according to how much it has been stretched A bend sensor is usually a sandwich of materials where the resistance of one of the layers changes according to how much it has been bent These can be used to determine a small angle or rotation for example how much a finger has been bent e Advantages useful where an axis of rotation is internal or inaccessible e Disadvantages not very accurate and only small angles can be measured Stereo Camera System Just like human eyes two cameras placed a distance apart c
58. intended to guide you through the steps of building a complete mobile robot There are 10 lessons that will be released in the following 10 weeks Each lesson guides you through one step of making a general purpose mobile robot This will enable you to build your very own mobile robot in order to perform a task of your choice Each lesson will be illustrated with an example from RobotShop experience in producing the RobotShop Rover The lessons are intended to be read one after the other and build upon the information gained STEP 1 The first step is to determine what your robot should do i e what is its purpose in life Robots can be used in almost any situation and are primarily intended to help humans in some way If you are unsure of what you want your robot to do or simply want to concentrate your efforts on specific tasks here are some ideas Knowledge amp Learning In order to build increasingly complex robots most professionals and hobbyists use knowledge they have acquired when building previous robots Instead of building one robot you can learn how to use individual components with the objective of building your own knowledge library to use to undertake a larger more complex design in the future Amusement amp Companionship Building a robot is in and of itself is fun and exciting Robotics incorporates aspects of many disciplines including engineering mechanical electrical computer sciences mathematics
59. ks to a human or an object in order to get its commands Getting a robot to turn to the left by showing a piece of paper with arrow pointing left 1s a lot harder to accomplish than one might initially suspect An auditory command such as turn left also requires quite a bit of programming Programming a variety of complex commands like get me a drink from the fridge or get my shoes they re near the front door is no longer fantasy but requires a very high level of programming and a lot of time Advantages e This is real robotics e Tasks can be as simple as blinking a light based on one sensor readings to landing a spacecraft on a distant planet Disadvantages e It s only as good as the programmer if it s doing something you don t want it to do the only option you have is to check your code modify it and upload the changes to the robot Practical Example For our project the goal is to create an autonomous rover capable of making a decision based on external input from sensors Should the robot misbehave it will be physically close and shutting it off will not be an issue However having the option of semi autonomous wireless control to allow us the option of making a remote controlled vehicle is also attractive We will not have the need for tethered control The microcontroller chosen in the previous lesson uses what are called shields which are essentially ad on boards specific to the Ard
60. ly can give the robot significant mobility advantages A common misconception about building a wheeled robot is that large low cost DC motors can propel a medium sized robot As we will see later in this series there 1s a lot more involved than just a motor Advantages e Usually low cost compared to other methods e Simple design and construction e Abundance of choice e Six wheels or more rival a track system e Excellent choice for beginners Disadvantages e May lose traction slip e Small contact area only a small rectangle or line underneath each wheel is in contact with the ground Tracked Robots Tracks or treads are what tanks use Although tracks do not provide added force torque they do reduce slip and more evenly distribute the weight of the robot making them useful for loose surfaces such as sand and gravel Also a track system with some flexibility can better conform to a bumpy surface Finally most people tend to agree that tank tracks add an aggressive look to the robot as well Advantages e Constant contact with the ground prevents slipping that might occur with wheels e Evenly distributed weight helps your robot tackle a variety of surfaces e Can be used to significantly increase a robot s ground clearance without incorporating a larger drive wheel Disadvantages e When turning there is a sideways force that acts on the ground this can cause PAE Pre AD ds i damage to the surface th
61. mall microcontrollers in the transmitter and receiver to send receive and interpret data sent via radio frequency RF The receiver box has a PCB printed circuit board which comprises the receiving unit and a small servo motor controller RF communication requires either a transmitter matched paired with a receiver or a transceiver which can both send and receive data RF does not require line of sight and can also offer significant range transmission distance Standard radio frequency devices can allow for data transfer between devices as far away as several kilometres and there is seemingly no limit to the range for more professional RF units XBee and Zigbee modules use RF for communication but allow the user to vary many of the communication parameters involved These modules have a specific footprint layout and are only produced by certain companies Their main advantage is that they provide a very robust easy to set up link and take care of all of the communication protocol details Many robot builders choose to make semi autonomous robots with RF capability since it allows the robot to be as autonomous as possible provide feedback to a user and still give the user some control over some of its functions should the need arise Advantages e Considerable distances possible e Setup can be straightforward e Omni directional impeded but not entirely blocked by walls and obstructions Disadvantages e Very low data rate simple com
62. mands only e Pay attention to the transmission frequencies they can be shared Bluetooth Bluetooth is a form of RF and follows specific protocols for sending and receiving data Normal Bluetooth range is often limited to about 10m though it does have the advantage of allowing users to control their robot via Bluetooth enabled devices such as cell phones PDAs and laptops though custom programming may be required to create an interface Just like RF Bluetooth offers two way communication Advantages e Controllable from any Bluetooth enabled device usually additional programming is necessary such as a Smartphone laptop desktop etc e Higher data rates possible e Omnidirectional does not need line of sight and can travel a little through walls Disadvantages e Devices need to be paired e Distance is usually about 10m without obstructions WiFi WiFi is now an option for robots being able to control a robot wirelessly via the internet presents some significant advantages and some drawbacks to wireless control In order to set up a WiFi robot you need a wireless router connected to the internet and a WiFi unit on the robot itself For the robot you can also use a device that is TCP IP enabled with a wireless router Advantages e Controllable from anywhere in the world so long as it is within range of a wireless router e High data rates possible Disadvantages e Added programming required e Maximum ran
63. material Remember measure twice and cut once 8 Test fit each component before assembling the frame in case modifications are require 9 Go crazy and assemble your frame using hot glue screws nails Duck tape or whatever other binding technique you choose for your robot 10 Fit all the components onto the frame and voila you have just created a robot from scratch NO Assembling the Robot Components Step 10 from the list above deserves to be elaborated upon In previous lessons you had chosen the electrical components and actuators Now your need to get them all working together For the following section we will use generic cable colors and terminal names that only cover the common case As always the datasheet and manuals are you bests friends when understanding how robotic equipment works Connecting Motors to Motor Controllers A DC gear motor or DC linear actuator will likely have two wires red and black Connect the red wire to the M terminal on the DC motor controller and the black to M Reversing the wires will only cause the motor to spin in the opposite direction A servo motor there are are three wires one black GND red 4 8 to 6V and yellow position signal A servo motor controller has pins matching these wires so the servo can be plugged directly to it Connecting Batteries to a Motor Controller or a Microcontroller Most motor controllers have two screw terminals for the battery leads labelled
64. mediate The Intermediate electronics lab builds upon the essential lab by adding the following Adjustable temperature soldering stationA basic soldering iron can only take you so far A variable temperature soldering iron with interchangeable tips will allow you to be more precise and decrease the risk of burning or melting components Brass sponge for solderIn combination with the more traditional wet sponge to wipe away excess solder a brass sponge can help clean the soldering iron tip without cooling it down allowing you to spring back into action quicker and solder like a ninja Variable power supply instead of wall adapter Having a powerful and reliable power source is very important when developing complex circuits and robots A variable power supply allows you to test various voltages and currents without the hassle of needing several types of batteries and power adaptors Ultimate o QscilloscopeAn oscilloscope is very useful when dealing with analogue circuits or periodic signals o Logic AnalyserA logic analyzer is like a digital eye when working with digital signals It allows you to see and store the data produced by a microcontroller and makes it simpler to debug digital circuits Miscellaneous ma O j lt er A Essential o 22 gauge hook up wireThe most common wire diameter gauge used in robotics is 22 0 0254 or 0 64 mm Although there are advantages to multi strand wires single
65. nd can give you a list of other tools which they have found useful The Essential setup is intended for first time robot builders who foresee building a few inexpensive robots for fun or have a single project in mind It is the least expensive setup at less than 100 but don t be fooled by the price tag In the right hands a workshop such as this can be used to create professional robots too The Intermediate setup is intended for builders who are not quite professional but are willing to invest a bit more in tools and equipment in order to ease fabrication assembly testing and troubleshooting The Ultimate setup is intended for users who plan to make many advanced robots and prototypes using a variety of parts and materials This type of builder wants the finished prototype to look as professional as possible and may even want to produce some small production runs of the finished design This is the type of setup would likely find at a small robotics company We cannot cover all the tools required at this level but can give some general suggestions As always it is very important to have the right tool for the right task and only you know your needs best Below you will find the various tools and materials suggestions for your workshop classified by level and type Mechanical Tools O ov le Essential Small screwdriver setThese small screwdrivers are necessary when working with electronics Don t force them too much th
66. nsors can be used on an autonomous lawn mower to detect wire embedded into a lawn e Advantages usually inexpensive e Disadvantages usually need to be relatively close to the object and sadly cannot detect non magnetic metals Vibration Vibration sensors detect the vibration of an object by using piezoelectric or other technologies RFID Radio Frequency Identification devices use active powered or passive non powered RFID tags usually the size and shape of a credit card small flat disc or addition to a key chain other shapes are possible as well When the RFID tag comes within a specific distance of the RFID reader a signal with the tag s ID is produced e Advantages RFID tags are usually very low cost and can be individually identified e Disadvantages not useful for measuring distance only if a tag is within range Practical Examples 1 I want my robot to follow a person More info on the robot featured in the video There is no person following sensor available yet so you would need to see which categories above may apply and which don t need to be considered e Q Are you looking to detect measure distance to or contact with an object o Immediately the answer should be yes and this first category of sensors will likely give the best results e Q Are you looking to measure rotation o Perhaps but you really don t need to know 1f the robot is rotated that s a different aspect entirel
67. nt going trough it This type of actuator is commonly used in valves or latching systems and there is usually no position feedback it s either fully retracted or fully extended Muscle wire Muscle wire is a special type of wire that will contract when an electric current traverses it Once the current is gone and the wire cools down it returns to its original length This type of actuator is not very strong fast or provides a long stroke Nevertheless it is very convenient when working with very small parts or in a very confined space Pneumatic and Hydraulic A oad Pneumatic and hydraulic actuators use air or a liquid e g water or oil respectively in order to produce a linear motion These types of actuators can have very long strokes high force and high speed In order to be operated they require the use of a fluid compressor which makes them more difficult to operate than regular electrical actuators Because of they high force speed and generally large size they are mainly used in industrial environments Choosing an Actuator To help you with the selection of an actuator for a specific task we have developed the following questions to guide you in the right direction It is important to note that there are always new and innovative technologies being brought to market and nothing is set in stone Also note that an single actuator may perform very different task in different contexts For instance with additional m
68. or RS232 SPI and C This feature is incredibly useful when communicating with other devices such as computers advanced sensors or other microcontrollers Although it is possible to manually implement these protocols it is always nice to have dedicated hardware built in that takes care of the details It allows the microcontroller to focus on other tasks and allows fora cleaner program Analogue to digital converters ADC are used to translate analogue voltage signals to a digital number proportional to the magnitude of the voltage this number can then be used in the microcontroller program In order to output an intermediate amount of power different from HIGH and LOW some microcontrollers are able to use pulse width modulation PWM For example this method makes it possible to smoothly dim an LED Finally some microcontrollers integrate a voltage regulator in their development boards This is rather convenient since it allows the microcontroller to be powered by a wide range of voltages that do not require you to provide the exact operating voltage required This also allows it to readily power sensors and other accessories without requiring an external regulated power source Analogue or Digital Below you can find two examples that illustrate when to use a digital or analogue pin Arduino um Digital A digital signal is used in order to assess the binary state of a switch As illustrated below on the left side of the solderle
69. otors are offered in a variety of different torques and sizes and provide angular position feedback most use a potentiometer and some specialized ones use optical encoders R C servos are used more and more to create small walking robots 4 Does the angle need to be very precise Stepper motors and geared stepper motors coupled with a stepper motor controller can offer very precise angular motion They are sometimes preferred to servo motors because they offer continuous rotation However some high end digital servo motors use optical encoders and can offer very high precision 5 Is the motion in a straight line Linear actuators are best for moving objects and positioning them along a straight line They come in a variety of sizes and configurations Muscle wire should be considered only if your motion requires very little force For very fast motion consider pneumatics or solenoids and for very high forces consider DC linear actuators up to about 500 pounds and then hydraulics Tools In order to compute the strength or torque and speed required for your application many rather complex computations are required involving the physics of the machine to be created In order to simplify the design process we have put together a few tools that can help you out e DC Drive Motor Selector useful for robots with wheels or tracks Also consult the Drive Motor Sizing Tutorial for further details e Robot Leg Torque
70. ough their size makes them more fragile Regular screwdriver setAll workshops need a multi tool or tool set which includes flat Phillips and other screwdriver heads Needle nose pliersA set of needle nose pliers is incredibly useful when working with small components and parts and is a very inexpensive addition to your toolbox These are different from regular pliers because they come to a point which can get into small areas Wire strippers cuttersIf you are planning to cut any wires a wire stripper will save you considerable time and effort A wire stripper when used properly will only remove a cable insulation and will not produce any kinks or damage the conductors The other alternative to a wire stripper is a pair of scissors though the end result can be messy Scissors ruler pen marker pencil exacto knife or other handheld cutting tool These are essentials in any office TOJ Intermediate Rotary Tool Dremel for example Rotary tools have proven to be incredibly versatile and can replace most of the conventional power tools provided the work that needs to be done is at a small scale They can cut drill sand engrave polish etc DrillA drill is very useful especially when creating larger holes or using stronger thicker materials If you are prepared to make the investment a drill press allows you to reliably create perfectly perpendicular holes O Ae 9 7 aw ae SawA saw of some type is beneficial at this
71. ould do achieve with a simple workshop including only essential tools Intermediate Workshop POLYRO POLYRO 1s a very advanced robot that can be built with an intermediate workshop It has most of the features professional robotic platforms used in research laboratories have Although it has many complex parts mostly all of them can be put made using simple hand tools For the standard practical example included at the bottom of every lesson only an intermediate level lab would be needed to put the robot together We will go into more detail in the following lesson Ultimate Workshop BaR2D2 The BaR2D2 is a good example of what can be achieved with such an advanced robotic workshop It has many intricate custom machined parts and requires good tooling abilities For further information on learning how to make a robot please visit the RobotShop Learning Center Visit the RobotShop Community Forum in order to seek assistance in building robots showcase your projects or simply hang out with other fellow roboticists Tags Grand Tutorial Series Tutorial Tutorial RobotShop Blog Posts about Tutorial RobotShop Blog Read more Remove preview Lesson 9 Lessons Menu e Lesson Getting Started e Lesson 2 Choosing a Robotic Platform e Lesson 3 Making Sense of Actuators e Lesson 4 Understanding Microcontrollers e Lesson 5 Choosing a Motor Controller e Lesson 6 Controlling your Robot e L
72. out 20 to 25 of the stall current All DC motor controllers provide a maximum current rating be certain this rating is about double that of the motor s continuous operating current Note that when a motor needs to produce more torque for example going up an incline it requires more current Choosing a motor controller with built in over current and thermal protection is a very good choice The Control method is another important consideration Control methods include analogue voltage PC PWM R C UART a k a serial If you are using a microcontroller check to see which pin types you have available and which motors are viable for you to choose If your microcontroller has serial communication pins you can choose a serial motor controller for PWM you will likely need one PWM channel per motor The final consideration is a practical one Single vs dual double motor controller A dual DC motor controller can control the speed and direction of two DC motors independently and often saves you money and time The motors do not need to be identical though for a mobile robot the drive motors should be identical in most cases You need to choose the dual motor controller based on the more powerful DC motor Note that dual motor controllers tend to have only one power input so if you want to control one motor at 6V and the other at 12V it will not be possible Note that the current rating provided is almost always per channel Servo
73. pos 1 variable pos goes from 0 degrees to 180 degrees in steps of 1 degree myservo write pos tell servo to go to position in variable pos delay 15 waits 15ms for the servo to reach the position j for pos 180 pos gt 1 pos 1 variable pos goes from 180 degrees to 0 degrees myservo write pos tell servo to go to position in variable pos delay 15 waits 15ms at each degree j Motor Controller Here is where it gets a bit harder since no sample code is available specifically for the Arduino The controller is connected to the Tx serial pin of the Arduino and waits for a specific start byte before taking any action The manual does indicate the communication protocol required a string with specific structure e 0x80 start byte e 0x00 specific to this motor controller if it receives anything else it will not take action e motor and direction motor one or two and direction explained in the manual e motor speed hexadecimal from 0 to 127 In order to do this we create a character with each of these as bytes within the character unsigned char buff 6 buff 0 0x80 start byte specific to Pololu motor controller buff 1 0 Device type byte specific to this Pololu controller buff 2 1 Motor number and direction byte motor one 00 01 buff 3 127 Motor speed 0 to 128 ex 100 is 64 in hex Serial write buff Therefore when this is sent via th
74. projects or simply hang out with other fellow roboticists Tags Grand Tutorial Series Tutorial Tutorial RobotShop Blog Posts about Tutorial RobotShop Blog Read more Remove preview Lesson 8 Lessons Menu e Lesson Getting Started e Lesson 2 Choosing a Robotic Platform e Lesson 3 Making Sense of Actuators e Lesson 4 Understanding Microcontrollers e Lesson 5 Choosing a Motor Controller e Lesson 6 Controlling your Robot e Lesson 7 Using Sensors e Lesson 8 Getting the Right Tools e Lesson 9 Assembling a Robot e Lesson 10 Programming a Robot At this stage you should have all the main components for your robot including actuators motor controllers a microcontroller sensors and communication systems Image credit zatalian You are now approaching the integration stage where you will put all these parts together in what will likely be a custom robotic frame For this you will need to get your workshop laboratory bat cave ready with the appropriate tools Robotics Workshop We have set up three possible robotic oriented labs scenarios Choosing which parts to add to your lab depends on how many robots you plan to make and how involved in robotics you would like to get We have outlined three broad categories for labs but don t assume the three labs are exclusive in the real world you will undoubtedly find robot builders who have tools from more than one section a
75. proportional to the ambient noise level More complex boards can use the data from a microphone for speech recognition e Advantages inexpensive reliable e Disadvantages more meaningful information requires complex programming Thermal Sensors Thermal sensors can be used to measure the temperature where it 1s on a particular component or the ambient temperature e Advantages they can be very accurate e Disadvantages more complex and accurate sensors can be more difficult to use Thermal Camera Infrared or thermal imaging allows you to get a complete 2D thermal image of whatever is in front of the camera This way it is possible to determine the temperature of an object e Advantages differentiate objects from the background based on their thermal signature e Disadvantages expensive Humidity Humidity sensors detect the percentage of water in the air and are often paired with temperature sensors Pressure Sensor A pressure sensor which can also be a barometric sensor can be used to measure atmospheric pressure and give an idea of the altitude of a UAV Gas sensors Specialized gas sensors can be used to detect the presence and concentration of a variety of different gases However only specialized robotic applications tend to need gas sensors e Advantages These are the only sensors which can be used to accurately detect gas e Disadvantages inexpensive sensors may give false positives or somewhat inaccur
76. provide out of the box functionally or sample code What does the future hold As the price of computers has gone down and advances in technology make them smaller and more energy efficient single board computer have emerged as an attractive option for robots These single board computers are essentially computers you may have used about 5 years ago and incorporate many devices into one board so you cannot swap anything out They can run a complete operating system Windows and Linux are most common and can connect to external devices such as USB peripherals LCDs etc Unlike their ancestors these single board computers tend to be much more power efficient Practical Example In order to choose a microcontroller we compiled a list of features criteria we wanted 1 The microcontroller s cost must be low while including a development board below 50 It must be easy to use and well supported It is also important to have lots of documentation readily available It should be programmed in C or a C based language It must be popular and have an active user community 5 Since the robot will be used as a general purpose platform the microcontroller should be very feature rich in order to allow for broad experimentation In this sense it should have several analogue and digital pins as well as an integrated voltage regulator a a Since our robot will use two motors the microcontroller will need two digital pins for direction
77. rable plastic parts Normally plastic parts require high temperatures and molds making them off limits to most hobbyists Example You can combine different shapes cylinders flat sheets etc to form complex plastic structures which look production You can also experiment with basic molding the Polymorph robotic arm is a good example of what you can achieve with this material Putting the Robot Together Given the selection of materials and methods how do you get started Follow the steps below to create an aesthetic simple and structurally sound smaller sized robot frame 7 Ps A B ole ios cor Settle on a construction material choice Get all the parts that you robot will require electrical and mechanical and measure them If you don t have all your parts on hand you can refer to the dimensions provided by manufacturer s 3 Brainstorm and sketch a few different designs for the frame Don t go into too much detail 4 Once you settle on a design make sure the structure is sound and that the components would be well supported 5 Draw each part of your robot in paper or cardboard at 1 1 scale real size You can also draw them using CAD software and print them out 6 Test your design in CAD and in real life with your paper prototype by test fitting each part and connections 7 Measure everything again and once you are absolutely sure your design is correct start cutting the frame into the actual
78. rials Grand Tutorial Series How To Microcontroller Microcontroller RobotShop Blog Posts about Microcontroller RobotShop Blog Read more Remove preview Lesson 5 Lessons Menu e Lesson Getting Started e Lesson 2 Choosing a Robotic Platform e Lesson 3 Making Sense of Actuators e Lesson 4 Understanding Microcontrollers e Lesson 5 Choosing a Motor Controller e Lesson 6 Controlling your Robot e Lesson 7 Using Sensors e Lesson 8 Getting the Right Tools e Lesson 9 Assembling a Robot e Lesson 10 Programming a Robot Now that the general shape the actuators or motors and the brain for the robot have been chosen it is time to make things move The first question many beginners have when building their first robot is how do I control the motors After a bit of research the word motor controller comes up a lot What is a motor controller and why do I need it A motor controller is an electronic device usually comes in the shape of a bare circuit board without enclosure that acts as an intermediate device between a microcontroller a power supply or batteries and the motors Although the microcontroller the robot s brain decides the speed and direction of the motors it cannot drive them directly because of its very limited power current and voltage output The motor controller on the other hand can provide the current at the required voltage but cannot decide
79. robot that will best suite your needs Below you will find a description of all the major robot types Land Land based robots especially the wheeled ones are the most popular mobile robots among beginners as they usually require the least investment while providing significant exposure to robotics On the other hand the most complex type of robots is the humanoid akin to a human as it requires many degrees of freedom and synchronizing the motion of many motors and uses many sensors Wheeled Robots Wheels are by far the most popular method of providing mobility to a robot and are used to propel many different sized robots and robotic platforms Wheels can be just about any size from a few centimetres up to 30 cm and more Tabletop robots tend to have the smallest wheels usually less than 5 cm in diameter Robots can have just about any number of wheels although 3 and 4 are the most common Normally a three wheeled robot uses two wheels and a caster at one end More complex two wheeled robots may use gyroscopic stabilization It is rare that a wheeled robot use anything but skid steering like that of a tank Rack and pinion steering such as that found on a car requires too many parts and its complexity and cost outweigh most of its advantages Four and six wheeled robots have the advantage of using multiple drive motors one connected to each wheel which reduces slip Also omni directional wheels or mecanum wheels used proper
80. rocontroller into the vehicle but continue to use a tether Connecting the microcontroller to one of your computer s I O ports e g a USB port allows you to control its actions using a keyboard or keypad joystick or other peripheral device Adding a microcontroller to a project also may require you to program how the robot reacts to the input Instead of using a laptop or desktop computer netbooks are often a desirable choice because of their low price small size and low weight Advantages e Same advantages as with direct wired control e More complex behaviours can be programmed or mapped to single buttons or commands e Larger controller choice mouse keyboard joystick etc e Added onboard intelligence means it can interface with sensors and make certain decisions on its own Disadvantages e Cost is higher than a purely tethered robot because of the added electronics e Same disadvantages as with direct wired control Ethernet A variation on computer control would be to use an Ethernet interface A robot that is physically connected to a router so it could be controlled via the Internet is also possible though not very practical for mobile robots Setting up a robot that can communicate using the internet can be fairly complex and more often than not a WiFi wireless internet connection is preferable A wired and wireless combination is also an option where there is a transceiver transmit and receive connected physi
81. sing a Motor Controller Motor controllers can only be chosen after you have selected your motors actuators Also the current a motor draws is related to the torque it can provide a small DC motor will not consume much current but cannot provide much torque whereas a large motor can provide higher torque but will require a higher current to do so DC Motor Control The first consideration is the motor s nominal voltage DC motor controllers tend to offer a voltage range For example if your motor operates at 3V nominal you should not select a motor controller that can only control a motor between 6V and 9V This will help you cross off some motor controllers from the list Once you have found a range of controllers that can power the motor with the appropriate voltage the next consideration is the continuous currentthe controller will need to supply You need to find a motor controller that will provide current equal to or above the motor s continuous current consumption under load Should you choose a 5A motor controller for a 3A motor the motors will only take as much current as they require On the other hand a 5A motors is likely to burn a 3A motor controller Many motor manufacturers provide a DC motor s stall current which does not give you a clear idea of the motor controller you will need If you cannot find the motor s continuous operating current a simple rule of thumb is to estimate the motor s continuous current at ab
82. ss breadboard a momentary switch or push button closes a circuit when pressed and allows current to flow a pull up resister is also shown A digital pin connected through a green wire in the picture to this circuit would return either LOW or O meaning that the voltage at the pin is in the LOW range OV in this case or a HIGH meaning the button is pressed and the voltage is at the HIGH range 5V in this case 2 Analogue A variable resistor or potentiometer as shown towards the right side of the board below is used to provide an analogue electrical signal proportional to a rotation e g the volume knob on a stereo As illustrated below when a potentiometer is connected to a 5V supply and the shaft is turned the output will vary between 0 and 5V proportionally to the angle of rotation The ADC on a microcontroller interprets the voltage and converts it to a numeric value For example a 10 bit ADC converts OV to the value 0 2 5V to 512 and 5V to 1023 Therefore if you suspect the device you plan to connect will provide a value that is proportional to something else for example temperature force position it will likely need an analogue pin CUES SC COVER ET VECO OEC S ee ereeeeeeneeeeee ee A a A S A wii i www RobotGhop com ee Seepeteces What about programming dwrvakpar au age an ae cd aubhaadar d h E M d Beatum d Auta ht ke Fi antecent F kN ia Cenn pn
83. stage to cut thicker materials or make long straight cuts You can use a hand saw although you may need to finish the edges a bandsaw table saw etc ViseAs your work become more complex you will need to hold materials and parts firmly in place while you work on them A vise is essential for this and allows to go further in terms of precision and quality wy g Ultimate Tabletop CNC millA tabletop CNC machine allows you to precisely machine plastics metals and other materials and creates three dimensional intricate shapes Tabletop latheA manual tabletop lathe allows you to create your own hubs shafts spacers adapters and wheels out of various materials A CNC lathe tends to be overkill since most builders only need to change the diameter rather than create complex shapes Vacuum Forming Machine Vacuum forming machines are used to create complex plastic shells that are moulded to your exact specifications Metal BendersWhen making robotic frames or enclosures out of sheet metal or metal extrusions using a metal bender essential in order to obtain precise and repeatable bends Other Specialized toolsAt this stage you will be very aware of your machnining needs and will probably require more specialized tools such as metal nibblers welding machines 3D printers etc Electrical Tools O e i SsSsential BreadboardThis has nothing to do with slicing bread These boards are used to easily create prototype circui
84. still remain intact and solid Laser cut bent plastic or metal If you are at the stage where you are prepared to have a frame outsourced the best options are still to have the part precision cut using a laser or water jet Having a company produce a custom part is ideal only if you are confident in all your dimensions since mistakes can be quite costly Companies which offer computer controlled cutting services many also offer a variety of other services including bending and painting 3D printing 3D printing a frame is rarely ever the most structurally sound solution because it is built up in layers but this process can produce very intricate and complex shapes which would not be possible or very difficult by other means A single 3D printed part can contain all the necessary mounting points for all electrical and mechanical components while saving considerable weight As 3D printing becomes more popular the price of producing parts will also go down A very prominent advantage of 3D printing is not only that your design is easy to reproduce it is also easy to share For instance you can click on the turtle shell example on the left and get all the design instruction and CAD files Polymoph Polymorph is really in a class on its own at room temperature Polymorph is a hard plastic but when heated in hot water for instance it becomes malleable and can be shaped into intricate parts which then cools and solidifies into du
85. strand solid core allows you to easily plug them into pin headers and breadboards o Third handWhen soldering having a helping hand that is impervious to heat is extremely useful A third had is an incredibly helpful tool since it holds the PCB and components in place while you solder o Hot glue gunA hot glue gun is incredibly useful no matter what your level of expertise and will only set you back a few dollars The glue which comes out of a hot glue gun sets rapidly and provides a good bond Unlike normal glue this glue is three dimensional which means you can use it as a spacer glue filler bridge etc o TapeThe most popular types of tape used in robotics are duct and electrical Electrical tape is best suited for electrical components since it does not conduct while duct tape is best for structural elements Intermediate o Thicker wireAs you build larger robots DC motors will require higher current and therefore larger diameter wires The lower the gauge the thicker the wire and the more current it can handle o Vernier calliperIn addition to a regular ruler a vernier allows you to more precisely measure parts as well as diameters both inside and outside Software e Essential o CADE Google SketchUpis a free program which can be used to create your robot in 3D to the proper scale complete with texture This can help you ensure that parts are not overlapping check dimensions for holes and change the design b
86. ternal RAM and of course peripherals such as monitor keyboard mouse etc This type of system is usually more expensive physically larger more power hungry The main differences are highlighted in the table below Microcontroller Personal Computer Example Atmega328 Intel Pentium Core 2 Duo RAM IKB 4000000KB 4GB Storage 15KB 15000000KB 1000GB Power 0 1W 600W Voltage 12 12 Input OutputPins USB RS232 Wireless Bluetooth RF Bluetooth Video None 1000000KB 1GB Price 4 to 300 400 to 2000 Internet WiF1 or Ethernet WiFi or Ethernet Available as optional additions on many microcontrollers Choosing the right Microcontroller Unless you are into BEAM robotics or plan to control your custom robot using a tether or an R C system which based on our definition from Lesson would not be considered a robot you will need a microcontroller for any robotic project For a beginner choosing the right microcontroller may seem like a daunting task especially considering the range of products specifications and potential applications There are many different microcontrollers available on the market Arduino BasicATOM BasicX POB Technology Pololu Parallax and more When considering the right microcontroller ask yourself the following questions 1 Which microcontroller is the most popular for my application Of course making robots or electronic projects in general is not a popularity contest but the fact that a m
87. three axis accelerometer can be used also to measure the orientation a e Advantages they do not require any external reference or marker to function and can provide absolute orientation with respect to gravity or relative orientation e Disadvantages they only approximate the traveled distance and cannot precisely determine it IMU s An Inertial Measurement Unit combines a multi axis accelerometer with a multi axis gyroscope and sometimes a multi axis magnetometer in order to more accurately measure roll e Advantages it is a very reliable way of measuring the robots attitude without using external references besides the earth s magnetic field e Disadvantages can be very expensive and is complex to use Miscellaneous Current and Voltage Sensors Current and voltage sensors do exactly as their name describes they measure the current and or voltage of a specific electric circuit This can be very useful for gauging how much longer your robot will operate measure the voltage from the battery or if your motors are working too hard measure the current e Advantages they do exactly what they are intended to do e Disadvantages can disturb the voltage or current they are measuring Sometimes they require the circuit being measured to be modified Magnetic Sensors Magnetic sensors or magnetometers detect magnetic objects and can either require contact with the object or be relatively close to an object Such se
88. ts without having to solder This is good in the event that you have not fully developed your soldering skills or want to quickly put together prototypes and test ideas without having to solder a new circuit each time O O O Jumper wiresThese wires fit perfectly from hole to hole on a solderless breadboard and not only look pretty but also prevent clutter Breadboard power supply When experimenting with electronics it is very important to have a reliable and easy to use power source A breadboard power supply is the least expensive power supply offering these features Soldering tool kitAn inexpensive soldering iron kit has all the basic components needed to help you learn how to solder and make simple circuits MultimeterA multimeter is used to measure voltage resistance current check continuity of connections and more If you know you will be building several robots and working with electronics it is wise to invest in a higher quality multimeter Wall adapterStandard voltages used in robotics include 3 3V 5V 6V 9V 12V 18V and 24V 6V is a good place to start since it is often the minimum voltage for DC gear motors and microcontrollers and is also the maximum voltage for servo motors A wall adapter can also be a good replacement for batteries since they can be very expensive in the long run A wall adapter can allow you to use your project without interruption whereas even rechargeable batteries need to be recharged Inter
89. uino s pin layout There are many shields including ones that allow for Ethernet Xbee or Bluetooth communication There is even a shield that allows for GPRS i e cellular communications The basic robot will therefore have no additional modules though it is important to note that it does have wireless communication capability D For further information on learning how to make a robot please visit the RobotShop Learning Center Visit the RobotShop Community Forum in order to seek assistance in building robots showcase your projects or simply hang out with other fellow roboticists Tags Grand Tutorial Series How To Make a Robot Make a Robot RobotShop Blog Posts about Make a Robot RobotShop Blog Read more Remove preview Lesson 7 Lessons Menu e Lesson Getting Started e Lesson 2 Choosing a Robotic Platform e Lesson 3 Making Sense of Actuators e Lesson 4 Understanding Microcontrollers e Lesson 5 Choosing a Motor Controller e Lesson 6 Controlling your Robot e Lesson 7 Using Sensors e Lesson 8 Getting the Right Tools e Lesson 9 Assembling a Robot e Lesson 10 Programming a Robot Unlike humans robots are not limited to just sight sound touch smell and taste Robots use a variety of different electromechanical sensors to explore and understand their environment and themselves Emulating a living creature s senses is currently very difficult so res
90. uino microcontroller to be the brain of our robot To get started we can take a look at the Arduino 5 Minute Tutorials These tutorials will help you use and understand the basic functionality of the Arduino programming language Once you have finished these tutorials take a look at the example below For the robot we have made we will create code to have it move around left right forward reverse move the two servos pan tilt and communicate with the distance sensor We chose Arduino because of the large user community abundance of sample code and ease of integration with other products Distance sensor Fortunately in the Arduino code there is an example for getting values from an analog sensor For this we go to File gt Examples gt Analog gt AnalogInOutSerial so we can see the values Pan Tilt Again we are fortunate to have sample code to operate servos from an Arduino File gt Examples gt Servo gt Sweep Note that text after two slashes are comments and not part of the compiled code include lt Servo h gt This loads the servo script allowing you to use specific functions below Servo myservo create servo object to control a servo int pos 0 variable to store the servo position void setup required in all Arduino code myservo attach 9 attaches the servo on pin 9 to the servo object j void loop required in all Arduino code for pos 0 pos lt 180
91. unmanned aerial vehicles especially if you are a beginner have yet to outweigh the risks When considering an aerial vehicle most hobbyists still use existing commercial remote controlled aircraft On the professional side aircraft such as the US military Predator were initially semi autonomous though in recent years Predator aircraft have flown missions autonomously Advantages e Remote controlled aircraft have been in existence for decades so there is a large community at least for the mechanics e Excellent for surveillance Disadvantages e The entire investment can be lost in one crash e Limited robotic community to provide help for autonomous control Water An increasing number of hobbyists institutions and companies are developing unmanned underwater vehicles There are many obstacles yet to overcome to make underwater robots attractive to the wider robotic community though in recent years several companies have commercialized pool cleaning robots Underwater vehicles can use ballast compressed air and flooded compartments thrusters tail and fins or even wings to submerge Other aquatic robots such as pool cleaners are useful commercial products Advantages e Most of our planet is water so there is a lot to explore and discover e Design is almost guaranteed to be unique e Can be used and or tested in a pool Disadvantages e Robot can be lost many ways sinking leaking entangled e Most electronic parts
92. ust one motion while more complex arms can have a dozen or more unique degrees of freedom Advantages Very simple to very complex design possibilities Easy to make a 3 or 4 degree of freedom robot arm two joints and turning base Disadvantages Stationary unless mounted on a mobile platform Cost to build is proportional to lifting capability Practical Example In our case we have opted for building a robot that will provide the maximum exposure to robotics A programmable tracked platform that can accommodate a variety of sensors and gripper sees ideal in this case specially since we consider tank tracks are far cooler than wheels In order to keep the costs down we opted to build a small desktop robot that will be able to roam indoors and on tabletops We also have taken into consideration the fact that there are not many tracks available and to keep things simple we ll only consider a single drive sprocket and single idler sprocket system this should not be a problem since the robot will be very light weight The preliminary CAD below summarized the features describes so far Next we will be choosing the right actuators e g motors for your robot For further information on learning how to make a robot please visit the RobotShop Learning Center Visit the RobotShop Community Forum in order to seek assistance in building robots showcase your projects or simply hang out with other fellow roboticists
93. y or if the human is rotated with respect to the robot e Q Are you looking to measure environmental conditions o Notreally You might consider tracking a human based on their thermal signature but differentiating between humans and animals or even a microwave would be difficult e Q Are you looking to measure position orientation or angle o GPS is the first sensor which immediately stands out Having gone through the main categories we should be considering sensors related to distance contact and detection and also considering GPS Taking a closer look at the types of sensors in this category e Contact irrelevant since the robot will be following the human at a distance e Distance o Ultrasonic infrared and laser measuring the distance is useful when combined with other sensors o Camera This may be the best option and we will look into it o Stretch This would require the human to be physically connected to the robot which is something we do not want e Rotation irrelevant e Positioning o GPS placing a GPS unit on both the robot and the human would allow the robot to easily follow the human within a certain radius e Environmental conditions irrelevant e Attitude o Accelerometer not very useful since it does not give the robot an idea of where the human is o IMU not very useful since it does not give the robot an idea of where the human iS e Miscellaneous o RFID An RFID reader can locate a tag placed around

How to Make a Robot – Lesson 1: Getting Started

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How to Make a Robot &ndash; Lesson 1: Getting Started

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How to Make a Robot – Lesson 1: Getting Started