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Locomotion Exploiting Body Dynamics

This project focuses on developing a stable and controllable galloping gait for the quadruped robot Puppy II, which utilizes Central Pattern Generators (CPGs) based on Hopf oscillators. The project aims to analyze and optimize locomotion by adjusting parameters such as amplitude and frequency, utilizing sensors for feedback, and implementing setpoint control. Through various tests, stability and speed control through amplitude variation were observed, alongside the exploration of turning behaviors. The findings suggest potential improvements and future works on enhancing gait precision and adaptability.

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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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