Wirelessly Actuated Snake Prototype

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Snake Robot @ CEC

Snake Robot @ CEC

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  • 1. WIRELESSLY ACTUATED SNAKE PROTOTYPE (WASP) Presented By, George Rahul Paul Meenu Saji Titto Thomas Tony Mohan Varghese Vidya Sekhar
  • 2. Snake Robots: What & Why ?• Snake Robot -Multiple actuated joints implying multiple degrees of freedom.• superior ability to flex, reach, and approach a huge volume in its workspace with infinite number of configurations.• Hyper redundant robots.• Advantages of Serpentine Motion: • Stability, Terrainability, Traction • Redundancy, Modular structure.• Applications • Rescue and Military Operation • Exploration, Inspection • Medical • Hazardous Environment
  • 3. In Scope•To create a control • Generate angles for •Parameter Sensing •Proof of Concept / signal format for all servos using Design •Signal Processing of communication algorithms environmental data •To Demonstrate•Generate signals as •To Pass them in Horizontal •Video of the scene per user’s instructions proper format to Movement•ZigBee motors • Basic vertical Communication movementWIRELESS ON FIELD ENVIRONMENTAL PROTOTYPE ICONTROL MOVEMENT ANALYSIS
  • 4. Functional Description • Control of Robot • Reception and Display of sensor parameters & Video PC • Provide a user interface for controlling the motion • Link between Modules on PC and Robot side Wireless • Highly secure one-to-one communication • Sensors for environmental sensing • Motion execution using motors. Snake Robot • Onboard microcontroller for master control.
  • 5. Block Diagram SENSORS WIRELESS WIRELESS CAMERA CAMERA RECEIVER SERVO MAIN TRANSMITTER RECEIVER MOTOR CONTROLLER PC GUI IN BATTERY VB SNAKE ROBOT ON FIELD PC SIDE
  • 6. Block Diagram of Mechanical SubsystemMechanical Subsystem
  • 7. Development Process Link Structure in WASP Orthogonal Joint – WASP Mechanical by DOWLING Structure
  • 8. Mechanical specification SPECIFICATIONS DETAILS Material Used Light weight, Low cost Aluminum alloy Number of links 8 Size of link(mm) 130x62x77 Weight of link(Kg) 0.28 Motion Range of joint(deg) [-90,+90] Actuators Servo motor, (Vigor – 6Kg cm Stall Torque) Sensors Temperature Sensor ( LM35 ) Light sensor (LDR)
  • 9. MOTION CONTROL MOTIONCONTROL UNIT PWM SERVO MOTOR (MCU) Block Diagram – Motion Subsystem Motion Subsystem
  • 10. PWM SIGNAL SERVO ANGLEPositions ofServo withrespect toPWM width
  • 11. Motion Subsystem • Head is controlled to trace a desired path • Head performs a new set of actions at a time, previous set of actions is propagated to next link • Speed at which one link performs the previously executed actions of head must be modulated.
  • 12. OBSERVER BASED CONTROL SCHEMEMappings for Control : =C(*-)=(1/s)K(s)(*-) (s)=C(s)( *-) *= sin(+(i-1))+ 
  • 13. CIRCUIT SUBSYSTEMCircuit subsystem includes following selection processes:•Microcontroller Selection•Wireless interface Selection•Sensor Selection
  • 14. MICROCONTROLLER SELECTION Various Alternatives • Separate Servo Controllers • PIC with PWM ModulesDSPIC33FJ256GP710 was chosen owing to the following specialties:•Multiple PWM modules to control 16 servo motors with single chip•High speed data processing•ADC module for sensor data•Simpler Circuit and Less cost of production
  • 15. DSPIC33FJ256GP710Operating voltage : 3.3VDigital I/O Pins : 85 programmable pinsCore Size : 16bitClock Speed : 10MHzPWM channels : 816 bit timer : 9Operating Temperature : -40˚C to 85˚CExternal interrupts : 5On-chip 2.5v voltage regulatorLow power consumption
  • 16. SERVO MOTOR SELECTIONVIGOR VTS- 08A was selected owing to following reasons•Fairly high stall torque of 6kg-cm•Compatible Operating voltage range: 4.8V-6V16 servo motors are used to implement serpentine motion•8 for vertical motion•8 for horizontal motion
  • 17. 7414 ICOutput from PWM port is incompatible for input to servo motor.7414 IC is hence used•Converts output from a PWM port voltage level to 5v•Operating Voltage: 5V•Three 7414IC used for 16 servo motors
  • 18. WIRELESS INTERFACE SELECTIONVarious alternatives :•IR Transmitters and Receivers•xBee•Bluetooth•Wi-Fi•Cell PhonexBee was chosen owing to following reasons•Very Low Power requirement•Wider Range• Ease of use• High baud rate•Fast response
  • 19. SENSOR SELECTIONTemperature Sensor Selected- LM35•Calibrated directly in ° Celsius (Centigrade)• Rated for full −55° to +150°C range• Operates from 4 to 30 volts
  • 20. Light Sensor Selected- LDR•Resistance variation with incident light intensity•Compact and low cost• LDR used in voltage divider configuration•If R1 is the photoresistor, V increases withlight intensity.•If R2 is thephotoresistor, V decreases with lightintensity.
  • 21. • (Vm)3.3 • (Vs)4.8- V/ 6V/ 1.0A – (Im)250 1.2A(Is) mA dsPIC Servo Zigbee Sensors • LM35 : 4V-• (Vz)2.8V 20V/10mA(It) – 3.4V/ • LDR : 45mA(Iz) (Vl)5V/150m A(I L) POWER SUBSYSTEM
  • 22. Total current requirement of power subsystem : ( Im+Iz+IL+It+Is )=4560mAMaximum voltage of power subsystem : 5VMaximum input to 7805 ( to get 5V) : 7.4VTotal Power Consumption = 7.4V * 4560mAH=33750mWAverage lifetime of the battery ( Full charge) = 30 minutesTotal Power required = 33750 * 0.5h = 16.872 Wh--If battery of 7.4V taken ,Then its current rating should be = 16.872Wh / 7.4V = 2- 2.25 AhPOWER MODEL OF SNAKE ROBOT
  • 23. Li-Po Lead Acid NiMH Li-ion Ni-Cd Alkaline BATTERY SELECTIONLiPo Battery – 7.4V/2200mAh selected
  • 24. BATTERYMONITORINGSYSTEM
  • 25. ON-BOARD POWER SUPPLY CIRCUITRY
  • 26. SOFTWARE SUBSYSTEM• UI software with coded commands that tells the robot what tasks to perform and control its actions.• low level control realization.• Visual Basic platform.• Identifies the COM Port to which xBee is connected and it does the low level controlling needed for snake motion.• Then by clicking the connect button connect to the particular communication port selected.• Individual control buttons : STOP, FORWARD, RIGHT and LEFT, PAUSE
  • 27. Flow chart of communication
  • 28. VB FLOWCHART
  • 29. - Using VB platform FRONT END GUI – A screen shot
  • 30. Final Specifications: Weight : 2.5Kg Length : 1m Speed : 0.25m/s On battery lifetime : 15min Battery charging time : 3Hr Range : Indoor - 20m, Outdoor – 70mResult and Conclusion
  • 31. • Various Gaits : Additional work in steering and gait transitions is necessary for more general locomotion.• Mechanism : an easier-to-disassemble joint structure with a rapid mechanical and electric connection, light weight materials such as polymers etc.• Power: Power efficient working system with long term battery life.• Sensing: use of sensors in achieving an autonomous locomotion and terrain adaptability.• Electronics: SMT miniaturization of circuits• Learning: Learning the environment , introducing a memory and adaptability. FUTURE SCOPES
  • 32. Lateral Undulation – A video
  • 33. Thank You