Download - Locomotion Exploiting Body Dynamics
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Locomotion Exploiting Body Dynamics
- Semester Project -
Student: Matteo de GiacomiSupervisor: Jonas Buchli
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INTRODUCTION
- Purpose of the project- The Puppy II robot- The CPG- Turning
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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
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Puppy II
4 hip motors 1 spring per knee
(passive dynamics) Sensors (inertia,
touch, tortion, IR) Parameters:
Amplitude Frequency Center of rotation
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CPG
Fully connected system
Matrix describing a galloping in this system:
FL FR
RL RR
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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.
CPG
Turn
Actuate
basic rythm
feedback
Complete behaviour
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Turning – Setpoint control
Idea: modify the basic position of each leg with a small value
FL FR
RL RR
+Δs
- Δs
+ Δs
- Δs
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Turning – Amplitude Control
Idea: Increase the amplitude of movement of two ipsilateral legs and decrease the amplitude of their two opposites.
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PERFORMED TESTS
- Introduction- Straight Locomotion- Setpoint Control- Amplitude Control
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General Framework
Variables influencing PuppyII‘s behaviour: Amplitude Frequency Centers of oscillation
Centers of rotation have been fixed: PuppyII tilted 15° to the front
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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
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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
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Videos: Straight Locomotion
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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
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Tests on turning behaviour (2) Example of circle estimation on tracked
trajectory
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Video: Turning
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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
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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!
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CONCLUSION
- Discussion- Further works
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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?
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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?
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THE END
Thank you!Any Question?