Improvement of the Cheetah Locomotion Control

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1 Improvement of the Cheetah Locomotion Control Master Project - Midterm Presentation 3 rd November 2009 Student : Supervisor : Alexander Sproewitz Professor : Auke Jan Ijspeert

2 Presentation of the Cheetah

3 Presentation of the Cheetah Light weighted, biollogically inspired small quadruped robot

4 Presentation of the Cheetah Light weighted, biollogically inspired small quadruped robot Pantograph, compliant legs

5 Presentation of the Cheetah Light weighted, biollogically inspired small quadruped robot Pantograph, compliant legs Leg design and proportions chosen from characteristic values for Mammals.

6 Goals of the project

7 Goals of the project Improve the locomotion control in term of efficiency, Robustness and controllability

8 Goals of the project Improve the locomotion control in term of efficiency, Robustness and controllability Model mechanic improvement, and measure their effect on the locomotion behavior : New foot design Adding a scapula joint Adding a spinal coord Test different leg segmentation and connections...

9 Table of contents

10 Table of contents Locomotion Behavior in Nature

11 Table of contents Locomotion Behavior in Nature Timeline of the project

12 Table of contents Locomotion Behavior in Nature Timeline of the project Work done Update of the webots model

13 Table of contents Locomotion Behavior in Nature Timeline of the project Work done Update of the webots model Work to be done CPG design Spinal Coord Compliant Foot

14 Three Self-Stabilization Principles [Seyfarth03] Swing Leg Retraction: a simple control model for stable running, André Seyfarth and Hartmut Geyer, Journal of experimental Zoology 206: (2003) [Daley09] The Role of Intrinsic muscle mechanics in the neuromuscular control of stable running in the guinea fowl, Journal of Physiology (2009) pp Video Extract : Youtube

15 Three Self-Stabilization Principles Self-Stabilization Passive capacity to stabilize in open loop process (no sensory feed back as a response to internal or external disturbance) [Seyfarth03] Swing Leg Retraction: a simple control model for stable running, André Seyfarth and Hartmut Geyer, Journal of experimental Zoology 206: (2003) [Daley09] The Role of Intrinsic muscle mechanics in the neuromuscular control of stable running in the guinea fowl, Journal of Physiology (2009) pp Video Extract : Youtube

16 Three Self-Stabilization Principles Self-Stabilization Passive capacity to stabilize in open loop process (no sensory feed back as a response to internal or external disturbance) Leg Stiffening [Seyfarth03] Swing Leg Retraction: a simple control model for stable running, André Seyfarth and Hartmut Geyer, Journal of experimental Zoology 206: (2003) [Daley09] The Role of Intrinsic muscle mechanics in the neuromuscular control of stable running in the guinea fowl, Journal of Physiology (2009) pp Video Extract : Youtube

17 Three Self-Stabilization Principles Self-Stabilization Passive capacity to stabilize in open loop process (no sensory feed back as a response to internal or external disturbance) Leg Stiffening Leg Retraction [Seyfarth03] [Seyfarth03] Swing Leg Retraction: a simple control model for stable running, André Seyfarth and Hartmut Geyer, Journal of experimental Zoology 206: (2003) [Daley09] The Role of Intrinsic muscle mechanics in the neuromuscular control of stable running in the guinea fowl, Journal of Physiology (2009) pp Video Extract : Youtube

Three Self-Stabilization Principles Self-Stabilization Passive capacity to stabilize in open loop process (no sensory feed back as a response to

control model for stable running, André Seyfarth and Hartmut Geyer, Journal of experimental Zoology 206:2547-2555 (2003) [Daley09] The Role of

18 Three Self-Stabilization Principles Self-Stabilization Passive capacity to stabilize in open loop process (no sensory feed back as a response to internal or external disturbance) Leg Stiffening Leg Retraction [Seyfarth03] Leg Extension [Daley09] [Seyfarth03] Swing Leg Retraction: a simple control model for stable running, André Seyfarth and Hartmut Geyer, Journal of experimental Zoology 206: (2003) [Daley09] The Role of Intrinsic muscle mechanics in the neuromuscular control of stable running in the guinea fowl, Journal of Physiology (2009) pp Video Extract : Youtube

19 Other locomotion blueprints [Fisher06] The Tri Segmented Limbs of Therian Mammals: Kinematics, Dynamics, and Self-Stabilization-A Review, Martin S. Fisher and Reinhard Blickhan, Journal of experimental Zoology 305A: (2006) Video Extract : Youtube & BBC

20 Other locomotion blueprints Wrist linkage and compliance [Fisher06] The Tri Segmented Limbs of Therian Mammals: Kinematics, Dynamics, and Self-Stabilization-A Review, Martin S. Fisher and Reinhard Blickhan, Journal of experimental Zoology 305A: (2006) Video Extract : Youtube & BBC

[Fisher06] [Fisher06] The Tri Segmented Limbs of Therian Mammals: Kinematics, Dynamics, and

21 Other locomotion blueprints Wrist linkage and compliance Use More Sagital bending of Spine than proximal articulation in assymetrical running gait. [Fisher06] [Fisher06] The Tri Segmented Limbs of Therian Mammals: Kinematics, Dynamics, and Self-Stabilization-A Review, Martin S. Fisher and Reinhard Blickhan, Journal of experimental Zoology 305A: (2006) Video Extract : Youtube & BBC

22 Timeline Model Update Fix Webots Model Prepare optimization framework Design of the control Foot trajectory definition Gait Optimization New Foot Testing Mechanical Improvement New Scapula Joint Sipnal Cord

23 Timeline Model Update Fix Webots Model Prepare optimization framework Design of the control Foot trajectory definition Gait Optimization New Foot Testing Mechanical Improvement New Scapula Joint Sipnal Cord

24 Modelisation of the Knee Actuator Motor

25 Modelisation of the Knee Actuator Assymetrical mechanism Motor

26 Modelisation of the Knee Actuator Assymetrical mechanism Motor Implementation cannot be easily done with Webots Servo Node

27 Modelisation of the Knee Actuator Assymetrical mechanism Motor Implementation cannot be easily done with Webots Servo Node Make a complete Model of the Mechanism (with different state for the motor and the limb)

28 Modelisation of the Knee τ pert U mot + K I R+L.p τ mot + + τ ch 1 (J eq).p 2 Θ mot µred η red Θ out Ω mot K e.p

29 Modelisation of the Knee 1) Get the value Δx t from webots τ pert U mot + K I R+L.p τ mot + + τ ch 1 (J eq).p 2 Θ mot µred η red Θ out Ω mot K e.p

30 Modelisation of the Knee 1) Get the value Δx t from webots 2) Compute the cable tension, using a rigid or spring cable Fc τ pert U mot + K I R+L.p τ mot + + τ ch 1 (J eq).p 2 Θ mot µred η red Θ out Ω mot K e.p

31 Modelisation of the Knee 1) Get the value Δx t from webots 2) Compute the cable tension, using a rigid or spring cable Fc 3) Update the value α t+1 knowing α t and τc with the servo model. τ pert U mot + K I R+L.p τ mot + + τ ch 1 (J eq).p 2 Θ mot µred η red Θ out Ω mot K e.p

32 Modelisation of the Knee 1) Get the value Δx t from webots 2) Compute the cable tension, using a rigid or spring cable Fc 3) Update the value α t+1 knowing α t and τc with the servo model. 4) Send to Webots the value Fc + Fspring as command U mot + Ω mot K I R+L.p τ mot + + τ pert τ ch K e.p 1 (J eq).p 2 Θ mot µred η red Θ out

33 Implementation in Webots Use a Spring and damping system (rigid cable still too unstable) Use Runge Kunta 4 rather than Euler method for inner state update.

34 Design of the CPG (not yet implemented)

35 Design of the CPG (not yet implemented) Use the Central Pattern Generator of Ludovic Righetti.

36 Design of the CPG (not yet implemented) Use the Central Pattern Generator of Ludovic Righetti. Transform its output to generate a foot trajectory.

37 Design of the CPG (not yet implemented) Use the Central Pattern Generator of Ludovic Righetti. Transform its output to generate a foot trajectory. Think rather in term of behavior, than geometry

38 Design of the CPG (not yet implemented) Use the Central Pattern Generator of Ludovic Righetti. Transform its output to generate a foot trajectory. Think rather in term of behavior, than geometry Conserve the attraction property of the limit cycle.

39 Design of the CPG (not yet implemented) Use the Central Pattern Generator of Ludovic Righetti. Transform its output to generate a foot trajectory. Think rather in term of behavior, than geometry Conserve the attraction property of the limit cycle. Use Inverse Kinematics to generate command of the Servos

40 Foot improvement (not yet implemented)

41 Foot improvement (not yet implemented) Reason : Increase foot clearence

42 Foot improvement (not yet implemented) Reason : Increase foot clearence Additional energy storage until toe off

43 Foot improvement (not yet implemented) Reason : Increase foot clearence Additional energy storage until toe off Make the distal segment follow the two parralel link segment

44 Foot improvement (not yet implemented) Reason : Increase foot clearence Additional energy storage until toe off Make the distal segment follow the two parralel link segment Use a virtual spring

45 Adding a spinal coord (not yet implemented) Increase further the step length for running gaits Spinal coord bending is equivalent of : translate horizontally the Hip Joint. Increase the amplitude of the Hip Joint Spinal coord can be reduce to a linear actuator

46 Questions?

Passive compliant quadruped robot using central pattern generators for locomotion control

Passive compliant quadruped robot using central pattern generators for locomotion control Simon Rutishauser, Alexander Spröwitz, Ludovic Righetti and Auke Jan Ijspeert Biologically Inspired Robotics Group,