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KDC Arm Project

KDC Arm Project. John Kua Kathryn Rivard Benjamin Stephens Katie Strausser. Outline. Overview Mechanical Design & Fabrication Electrical & Software Simulation & Control Demo Future Work. Overview. Goal : Design and control a novel dynamically balancing manipulator

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KDC Arm Project

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  1. KDC Arm Project John Kua Kathryn Rivard Benjamin Stephens Katie Strausser

  2. Outline • Overview • Mechanical Design & Fabrication • Electrical & Software • Simulation & Control • Demo • Future Work

  3. Overview • Goal: Design and control a novel dynamically balancing manipulator • Motivation: Assistive robot manipulator to be mounted on friendly household Segway robot • Typical Task: Pick up objects from cupboard, open doors, take out the garbage

  4. Mechanical • Started with dynamic analysis to decide system specifications and parameters

  5. Mechanical • Designed mechanism in Solidworks CAD • Easy to use aluminum extrusions • Single linear actuator moves counterweight to balance arm • Ball bearings support screw drive assembly

  6. Electrical • Sensors • Joint encoder (500 CPR) • Screw encoder (2048 CPR) • Accelerometer (3-axis) • Rate gyro (2-axis) • Limit switches (SPST) • Motor control • Serial commands • 24V/10A max • Gripper control • Standard servo PWM • Microcontroller • ARM7TDMI-S • 60 MHz

  7. Software • Microcontroller • 100 Hz main loop • Motor control input/output • Servo control • Data logging to serial port • 50 kHz sensor polling • 500 Hz servo PWM output • PC Side • Controller (100Hz) • Data logging to file PC RS-232 Microcontroller TTL Serial TTL PWM TTL / Analog Motor Controller Sensors Gripper Servo

  8. Software • Kalman Filter • Estimated states – tilt and gyro bias • Sensor inputs at two speeds • 2 kHz rate gyro • 50 Hz accelerometer • Gyro primary sensor • Drifting bias • Accelerometer to estimate bias • Noisy, captures more than pure rotation

  9. Software – Kalman Filter • Process update (2 kHz) • Measurement update (50 Hz)

  10. Software – Kalman Filter

  11. Software – Kalman Filter

  12. Simulation & Control • Problem: Move counterweight to balance arm independent of gripper weight • KeyIdea: Counterweight moves slowly -- must plan ahead! • Solution: • Plan a trajectory from an initial state to the arm set point • Use acceleration to determine the counterweight set point.

  13. Simulation Results

  14. Experimental Results

  15. DEMO!

  16. Future Work • More sophisticated control: Input shaping, MPC, etc. • Optimize counterweight mass/travel • Shoulder joint actuation • Joint shape iteration (yoking joint) • Increase robustness for object balance • Interface to Segway

  17. Effect of a yoke: Balanced torques

  18. The End • Special thanks to Garth Zeglin for helping us design the arm.

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