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Locomotion Exploiting Body Dynamics

Locomotion Exploiting Body Dynamics. - Semester Project - Student: Matteo de Giacomi Supervisor: Jonas Buchli. INTRODUCTION. - Purpose of the project - The Puppy II robot - The CPG - Turning. Project objectives.

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Locomotion Exploiting Body Dynamics

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  1. Locomotion Exploiting Body Dynamics - Semester Project - Student: Matteo de Giacomi Supervisor: Jonas Buchli

  2. INTRODUCTION - Purpose of the project - The Puppy II robot - The CPG - Turning

  3. Project objectives • Develop a stable and controllable galloping gait for a quadruped robot endowed with passive dynamics • Use of a CPG based on Hopf oscillators

  4. Puppy II • 4 hip motors • 1 spring per knee (passive dynamics) • Sensors (inertia, touch, tortion, IR) • Parameters: • Amplitude • Frequency • Center of rotation

  5. CPG • Fully connected system • Matrix describing a galloping in this system: FL FR RL RR

  6. Turning • CPG: generates the basic galloping gait • Turn: modifies the basic rythm so that the robot can turn • Actuate:“translates“ the obtained values in values consistent with the robot architecture. Actuate Complete behaviour Turn feedback basic rythm CPG

  7. Turning – Setpoint control • Idea: modify the basic position of each leg with a small value +Δs FL FR - Δs + Δs RL RR - Δs

  8. Turning – Amplitude Control • Idea: Increase the amplitude of movement of two ipsilateral legs and decrease the amplitude of their two opposites.

  9. PERFORMED TESTS Introduction Straight Locomotion Setpoint Control Amplitude Control

  10. General Framework • Variables influencing PuppyII‘s behaviour: • Amplitude • Frequency • Centers of oscillation • Centers of rotation have been fixed: PuppyII tilted 15° to the front

  11. Test 1: Straight Locomotion (1) • Measure of linear speed depending on Amplitude and Frequency • 1 measure: space covered over 5 sec • 5 measures per test

  12. Test 1: Straight Locomotion (2) • Under certain limits in amplitude and frequency, locomotion is stable • Amplitude seems a good way to control the robot‘s speed

  13. Videos: Straight Locomotion

  14. Tests on Turning Behaviour (1) • Fixed camera 2.45m over the robot • Robot equipped with a red led on its back • Robot behaviour filmed for various parameters • Tracking of the robot (red spot) • Circle estimation in Matlab Estimation of the turning radius of the robot depending on the used parameters

  15. Tests on turning behaviour (2) • Example of circle estimation on tracked trajectory

  16. Video: Turning

  17. Test 2: Setpoint Control • At almost every speed (amplitude) it‘s possible to obtain a good turning behaviour with a good variety of turning radius

  18. Test 3: Amplitude Control • At high speed (amplitudes) the turning radius doesn‘t seem to be affected by the used parameter • At low speeds some localized peaks emerge: the robot CAN‘T turn there!

  19. CONCLUSION Discussion Further works

  20. Discussion • Amplitude is a good way to control the robot‘s speed in a range of values contrained by the enviroment and by the robot itself. • Setpoint control is a good way to precisely control the turning radius of the robot • Amplitude control permits large turns at high speeds. At low speed shows a strange behaviour. Feature of the used springs?

  21. Further Works • Feedback can improve the gait? • Embed the turning part in the oscillators themself may be useful? • We fixed some parameters (frequency and setpoints). What happens if we change them?

  22. THE END Thank you! Any Question?

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