System Design and Project Plan
Contents
1. Measurement Unit angular rate sensors that knowledge of M 75 Interfacing Design provide angular position technology for the control system F6 1 Research Determine possible Knowledge of M 25 PC components of unit technology E e N Work Breakdown Structure Fall 2009 continued F7 0 Parts Selection Make final decisions on Order parts needed parts to be used and documentation of C H M 10 PC all purchases torque requirements technology F7 2 Axle and Wheel Choose materials that Design details Assembly will hold specified C M gt 1 PC weights F7 3 Gearing and Chains Choose gears and chains Design details according to ratio and C M gt 2 PC torque requirements F7 4 Microcontroller Find board that is Knowledge of sufficient for all technology components Choose size and power Knowledge of deliverability determined technology by motor requirements Analyze entire design to Test dimensions test for functionality power requirements torque requirements data analysis System Design and Breakdown of design and Report visual aided Project Plan build process with presentation detailed scheduling Write detailed report regarding the ideas mentioned above Present ideas to faculty PowerPoint CHM 05 Pc F10 0 Final Design Finalize the design and Report visual aided no more changes can be presentation made past this point F10 1 Report Write detailed report Report regarding the ide2. 25 Chai gt wen pP OCKE FOP Zen 17 95 each electricscooterparts com 10 4 2009 for main shaft 2 Sprockets for motor shaft 2 10 3 2009 25 Chain With Master Link 2 8 40 each 10 3 2009 Dual Axis Gyro 14 95 10 3 2009 Samples de freescale com 10 1 2009 1073 2008 Microprocessor Accelerometers 2 Fall 2009 Casey Christensen Harrison Cobb Misael Marriaga BOMSS Network Diagram Spring 2010 Casey Christensen Harrison Cobb Misael Marriaga ans 17 Appendices Appendix A Mechanical Drawings NOTE The Dimensions that were chosen for the technical drawings are specific to this design only The limits on size were dependent on the battery size motor footprint estimated circuit board size wheel diameter and foot platform area The dimensions are subject to change but as drawn all components will fit within the frame with no complications 19 Appendix B Requirements Specification Document Balancing Omni directional Multi Surface Skateboard BOMSS Requirements Specification Harrison Cobb Misael Marriaga Casey Christensen Overview Riding a skateboard can be difficult and discouraging to learn We plan to create a device that has an easy learning curve allowing beginners to quickly enjoy being able to ride a skateboard It will also have a compact design that allows it to be easily maneuvered in an urban environment The BOMSS will be
3. Balancing Omni directional Multi Surface Skateboard BOMSS System Design and Project Plan October 13 2009 Casey Christensen Harrison Cobb Misael Marriaga Table of Contents SA 2 3 SYSTEM OVEIVIEW RM nn 3 Block District 5 Functional DECOMPOSITION of Blocks u 6 Project Plan alal 8 Organization Management sin aida 9 Work Breakdown Structure Fall 2009 asien 10 Work Breakdown Structure Spring 2010 8 12 Estimated Costs andBudgeting india o 13 Gantt Chart Fall 2009 ni O NA a 14 Gantt Spring 2010 nd an 15 Network Diagram Fall 20090000 le 16 Network Diagrami Springe 2010 Sa 17 Appendiees a 18 Appendix A Mechanical Drawings eu 19 Appendix B Requirements Specification Document ss 23 Appendix Data Sheets Cost Estimates is 29 System Design Background Riding a skateboard can be difficult and discouraging to learn We will create a device that will allow beginners to quickly enjoy being able to ride a skateboard It will also have a compact design that allows it to be easily maneuvered in an urban environment The BOMSS will be a skateboard style self balancing vehicle Basic design consists of a platform for the rider to stand on with two independently operated wheels fastened centrally to the underside The operatio
4. The chosen power source will be a 24V rechargeable battery with a capacity rating of at least 12 Ah Options include SLA NiMH and NiCd Motor Controller This unit will accept the signals from the microprocessor and control both the speed and direction of each independent motor Left and Right Motors Motors selected are 350 watt motors Each motor is independently controlled by the microprocessor via the programmed motor controller Based on inputs from the accelerometers and angular rate sensors the controller will drive the motors appropriately to maintain balance as well as produce motion Battery Level Display The battery level display is an LED voltage display typically used in remote controlled aircraft This will provide the user with instant information on the state of charge of the battery On Off switches There are two individual On Off switches both of which engage disconnect power from the battery Note that neither switch will provide any function to the BOMSS unless the aforementioned anti theft key is securely in place The first switch is a main power push button switch that when engaged will allow the BOMSS to be powered and ready for a rider However it does not allow for any unauthorized motion or balancing at this point as the second switch also needs to be engaged for full operation The second switch is a safety switch that is activated by a specified weight depressing the foot platforms Without this second sw
5. a skateboard style self balancing vehicle Basic design consists of a platform for the rider to stand on with two independently operated wheels fastened centrally to the underside The operational components will be contained in water and vibration resistant compartments with easy accessibility to the user clear of any interference and protected from collisions with foreign objects The BOMSS will be a desirable alternative to traditional styles of transportation Operation Before operation of the BOMSS a push button switch for the main power Figure 1 must be ON for operation This will be incorporated into the vehicle s platform and easily accessible to the riders foot Until the power switch is ON the vehicle will remain powerless Figure 1 I A B Figure 1 Position A shows the ON position of the switch Position B shows the OFF orientation of the push button switch For ease and safety the OFF position of the switch was oriented in the compressed position so only one motion would be required to initiate power shutdown The BOMSS will then provide a safe mounting technique for the user The start up sequence consists of two stages both dependent on the other 1 The BOMSS will mechanically sense the weight of a rider on the platform who must weigh no less than 20kg 44165 f 4 2 The platform must be brought level with the ground Once both criteria are met the BOMSS will immediat
6. as C1 H Mb 0 5 PC mentioned above F10 2 Present ideas to faculty Documentation Continue to log all work Sufficient into laboratory books documentation to CHM 17 PC Notebooks depict project progress Project Oversee project progress Smoothly operating Management and keep the project on project C 17 Class Literature course PC SolidWorks AutoCAD MultiSim Work Breakdown Structure Spring 2010 Deliverables Duration People Resources Checkpoints Ww 7 V verify they work C H M 10 ne Equipment Se Compile Circuitry Create and test circuitry Finished main circuitry RSS test data board oscilloscopes S1 3 Board Etching Design and order circuit Professionally made ln H Outsourcing boards circuit board S1 4 Sensors Build circuits and verify Proper sensor readings en that sensors operate test data 2 board according to ca oscilloscope specifications Power Supply Mount battery to Adequate power supply structure and attach to 2 Oscilloscope circuitry Microprocessor Build circuitry and verify Working device test correct operation of data device 51 7 Motors Connect motors to Functional motors test power and verify correct data Power supply operation and oscilloscope functionality S1 8 Gears and chains Attach gears and chains Smooth operation test and verify correct data operation Wheels Attach wheels to Attached wheel to structure and verify shaft free movement Powe
7. ed as an input in its controls algorithm The vehicle will be maneuverable in the forward and aft direction as well as steering left and right Angular position and angular rate will be monitored by the accelerometers and angular rate sensors gyros These sensors will send a signal to the microcontroller that runs controls algorithm based on the equations of motion of the skateboard rider system Once the velocity of the skateboard necessary to maintain the level platform is calculated by the microcontroller it will send a signal that will adjust the power delivered to the motors to achieve such velocity Safety features will include a minimum rider weight and an anti theft key Before power is delivered to the system the rider must insert a removable anti theft key and then fully depress a mechanical weight sensor Power is provided by a rechargeable on board battery 1 For further detail describing the operation refer to the requirement specifications document located in Appendix B Deliverables for this project will include the self balancing skateboard capable of a runtime of approximate 1 hour anti tamper key user s manual and all relative schematics analysis drawings and documentation showing test results Block Diagram Balaneing Omni directional Multi Surface Skateboard Casey Christensen Harrison Cobb Misael Marriaga Functional Decomposition of Blocks Physical Input Parameters These parameters inc
8. ely power the onboard motors and maintain a level plane which is how the rider manipulates movement Upon leaning in either the forward or backward direction the skateboard will roll in the direction of tilt In this manner the skateboard can be moved in a straight path Upon putting pressure on the toes or heels the rider can alter the motion of the skateboard in the left or right direction When the user is ready to get off the vehicle he she will come to a complete stop before depressing the push button switch which will turn the main circuit board OFF causing a complete power down As an added safety feature removing weight from the platform will shut down power to the motors To re power the vehicle remount and bring the platform level As a precaution against theft or unauthorized use a removable anti tamper key will be included This key must be inserted into its appropriate slot for the BOMSS to operate Without this key there is no way to operate the BOMSS Deliverables User s manual Self balancing skateboard with anti tamper key CAD drawings electronic schematics 3D views and analyses Code and flowcharts Report of testing Final report Cl E a a Technical Requirements 1 The BOMSS will maintain a maximum speed of no less than 4 m s 13 ft s and no more than 10m s 33 ft s for safety concerns 2 The BOMSS will be powered for a runtime of no less than 60 minutes at 30 maximum speed 3 A turning radi
9. ideas for the Specifications the project will project in written accomplish in detail document Overall System Design overall project in Brainstorming ideas Design detail produce working design Mechanical and Calculating equations of Equations of motion Power Analysis motion stress analysis finite element and power requirements analysis Electrical Power Analysis EOM Calculate EOM of the Calculations and an en M C gt Textbooks system derivation F3 2 Stress Analysis Finite element analysis of Data from analysis M axles and frame we F3 3 Torque Calculate torque Calculations and Requirements requirements from EOM derivation F3 4 Power Deliverability Determine power using Calculations Task electrical analysis Structure Design Design the dimensions Design details and materials for housing knowledge of technology CAD Task Activity Description F1 0 drawings Dimensions of Frame Ensure dimensions are CAD drawings realistic C1MzHs Materials for Choose lightweight Design details Construction strong and durable materials Power Supply Battery circuit providing Design details Design inputs to limiters and knowledge of circuitry technology F5 1 Switches Choose switch that is Design details easily depressed knowledge of technology Voltage Regulator Research options Design details ES 3 Low Battery LED Research Options Knowledge of H C Display technology Inertial Accelerometer and Design details
10. itch in place if the main power button were engaged and the platform were inadvertently brought level without a user being onboard the BOMSS would begin its balancing operations and could become unsafe This safety concern required the addition of this second weight sensor switch Project Plan Organization and Management Casey Christensen Casey is a senior level mechanical engineering student and was selected as the team lead for this project He is responsible for determining mechanical dimensions and materials used in construction as well as performing finite element analysis of stresses and deformations to eliminate the possibility of a stress related failure of the frame or any other mechanical element Also alongside Misael he will be formulating the equations of motion that will ultimately be used to control the BOMSS Casey will work with Misael to select an appropriate gear ratio so as to insure little or no undue stress on any particular component Casey will provide CAD drawings and schematic specification sheets Throughout the entire project Casey will be responsible for ensuring that the project is moving at an appropriate rate and that is stays on course Harrison Cobb Harrison is a senior level computer engineering student with a 70 30 split between electrical engineering and computer science respectively He is the sole computer engineer on the project and is responsible for selecting and programming the microproces
11. lude the actual mass of the skateboard and its calculated rotational inertia as well as average estimates of the riders mass rotational inertia and height Equations of Motion Provided with physical input parameters these equations will be integrated as part of the controls algorithm into the software that enables the board to maintain a level plane Balance Sensors These sensors include an accelerometer and an angular rate sensor gyroscope The accelerometers will provide the microcontroller with readings of the component of gravity perpendicular to the skateboard with the purpose of calculating the board s angular position The angular rate sensors will provide readings on the angular velocity of the skateboard to the microcontroller which will calculate the direction in which the skateboard is tilting These calculations will be used to determine the proper adjustments of the motors to keep the skateboard on a level plane The accelerometer will require a supply of no less than 2 2 V and no more than 3 6 V The output signal will be no less than 289 5 mV g and no more than 326 5 mV g The accelerometer reads 4 g The angular rate sensors will require a supply of no less than 0 3 V and more than 6 0 V It will have a typical sensitivity of 2 0mV s Turn Sensors These sensors include an accelerometer and an angular rate sensor gyroscope These sensors will perform in the same way as the balance sensors but with the purpose of se
12. n push button switch to the ON position and mount the platform Bringing the base level to the floor immediately initiates the self balancing algorithms The vehicle is now operational and will react to all movements To move forwards or backwards lean body in the desired direction of travel To arrest motion return to level plane Turning requires pressure with either the heels or toes depending on the desired direction ofturn To stop turn eliminate edge pressure 7 4 Dismount by depressing the OFF button on the base This completely removes power Also the skateboard has a safety feature that immediately halts power to the motors if a loss of weight on the platform is sensed this is useful in the event that the rider falls from the board Storage 1 Set main power push button switch to OFF 2 Store in a cool dry place 3 Battery maintenance is supplied in the user s manual Appendix C Data Sheets Cost Estimates
13. nal components will be contained in water and vibration resistant compartments where they will be protected from collisions with foreign objects These compartments and the components they contain will be easily accessible to the user while remaining hidden within the structure as to not interfere with the user s ability to effectively operate the vehicle The BOMSS will be an enjoyable recreation vehicle for users of nearly any age that are looking for a unique and inventive new way to spend their time lts maneuverability and ability to operate efficiently in many different environments will make it stand apart from other similar recreation and transportation vehicles System Overview The design is a two wheeled self balancing vehicle that provides a dynamic turning radius meaning that the turning radius is proportional to the velocity of the vehicle with a near zero turning radius at no forward motion If the vehicle for example it traveling at a rate of 4 m s the turning radius will be much greater and therefore more stable than if the vehicle were traveling at a rate of 0 5 m s where the radius would be significantly decreased This will make the vehicle useful and easy to maneuver an urban environment The Balancing directional Multi Surface Skateboard BOMSS will utilize accelerometers and gyroscopes to sense the angular position of the skateboard with respect to the horizontal plane This information will then be us
14. nsing the angular position and angular velocity of the skateboard about an axis perpendicular to the axle of the wheels and on the horizontal plane The turn sensors will provide the acquired information to the microcontroller which will send a signal to adjust the motors to turn The sensors will be the same as the ones used for balance though properly arranged to sense turning Software The software is the electrical manifestation of the equations of motion Using the derived equations along with the collected sensor values the software will calculate the duty cycles needed for the microprocessor to precisely control the motors for maintaining a level platform as well as maneuvering the skateboard Microprocessor This unit will compile the sensor information and communicate with programmed software Once the sensor information is collected the derived equations of motion can be applied through software to calculate the necessary duty cycle which controls each wheel s motion independently microprocessor may require up to four 4 A D Analog to Digital ports for sensor input and will require multiple ports for output to the motor controller A PR Voltage Regulator The voltage regulator contains hardware to supply various voltages necessary to run the 1 balance and turn sensors 2 microprocessor 3 motor controller and 4 possibly each motor Preliminary voltages required may include 5V 12V and 24 Power Source
15. r mounting to be stable no binding functional equipment component Programming Write code for Operational code test microprocessor and data PC evaluation download code to the board device Presentation project s status presentation ou System Integration Compile all individual Assemble product test components to build the data C H M 3 Work shop prototype Description PC evaluation board Power equipment 2 y Work Breakdown Structure Spring 2010 Cont System Testing Test the prototype per Test data PC evaluation specifications C H M 3 board requirements document oscilloscope Finalize Prototype Verify correct operation Working prototype and prepare for final PC evaluation demonstration ES board oscilloscope 7 0 Final Project Present the prototype Report visual aids C H M 0 5 PC resentation prototype C1 0 Documentation Continue logging all Sufficient research and work done documentation to C H M 15 PC Notebooks depict project progress C2 0 Project Oversee project Smoothly operating Management progress and keep the project C 16 Class project on course Literature Estimated Costs and Budgeting Items Costs Possible Vendor Date of Cost Cost Estimate Main Drive Wheels 2 front wheels 2 520 00 Bike City Searcy AR 10 3 2009 Lexan Sheeting 12 54 39 sq ft 10 9 2009 Center axle 12 51 10 3 2009 Bar stock for safety wheels 54 54 10 3 2009
16. sor developing and building circuit boards and determining appropriate motors and battery Also he will be working with Casey and Misael in the general construction of the project Harrison will provide circuit simulations and a professionally etched circuit board Misael Marriaga Misael is a senior level mechanical engineering student He is responsible for selecting accelerometers and angular rate sensors gyros He is also developing the equations of motion necessary for control and he will perform finite element analysis of stresses and deformations to eliminate the possibility of a stress related failure of the frame or any other related mechanical element Misael will develop the control system algorithms that will be used and programmed into the microcontroller by Harrison He will also work with Casey to select an appropriate gear and chain ratio and help build the frame The tasks listed above for each engineer are not all inclusive All members are versatile enough to assist each other in their respective responsibilities therefore the above task schedule is subject to change All members are responsible constant documentation of all work completed as well as gathering and presenting their information and progress in the group s bi weekly presentation of an A3 status report 9 Work Breakdown Structure Fall 2009 Deliverables Duration People Resources Checkpoints weeks Requirements Document stating what General
17. um speed the BOMSS will be mounted then proven to travel a measured distance in a given amount of time A stopwatch will provide an adequate amount of accuracy The distance will be forty 40 meters on a flat asphalt or concrete surface Time to travel this distance must be between four 4 and ten 10 seconds s Turning Radius Test To test turning radius only a maximum turning radius will be required The skateboard will be placed inside a taped off square of one 1 meter by one 1 meter and then mounted A satisfactory test will be if the skateboard can be maneuvered a full 360 without leaving the taped square Draft User s Manual Initial setup di Connect the battery To connect a battery insert the battery into the appropriate tray in the vehicle and attach the positive and negative leads to their respective cables NOTE Use caution when connecting the batteries to the circuitry in the vehicle Reversing the positive and negative leads can cause damage to the batteries and circuit boards Charging the battery will require a battery charger not supplied for the chosen battery Batteries should be charged for the first time according to the battery maintenance sheet provided and then as necessary following first use Operation 1 3 Ensure the anti tamper key is in place as the vehicle will not be operational until this is inserted into the appropriate slot Set the BOMSS mai
18. us of no greater than 1mx1m 3ftx3ft at zero forward motion 4 The BOMSS will have a low battery indicator light cutoff voltage to be determined 5 The BOMSS will be capable of carrying a 91kg 200lbs adult over dense materials such as pavement and concrete on both a flat and inclined plane 6 The BOMSS will weigh no more than 23kg 51 Ibs Testing Plan To ensure proper operation the following tests will be conducted Run Time Test To test run time the BOMSS will be required to maintain operation for a total time of approximately sixty 60 minutes The rider will weigh between 91 and 100 kg 200 220lbs and will be required to maneuver a predetermined course refer to Figure 2 around the Harding University campus containing level planes inclines and declines over a multitude of surfaces Riding times can be discontinuous but a total time of sixty 60 minutes must be summed at an average of 30 of the maximum speed before the battery is recharged Figure 2 Figure 2 The course the BOMSS will be required to navigate during the test period is indicated in red The starting and ending place is the Pryor England Science Center highlighted in yellow The BOMSS will complete the course at least once to demonstrate its ability to operate in varying surfaces Care was taken in determining the course as to not encounter any dangerous traffic or intersections and place the tester in harm Minimum Speed Test To test the maxim
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