1. Stumpy An autonomous bipedal robot Michael Cowling | Andrew Jeffs | Nathan Kaesler Supervisors: Dr Frank Wornle | Mr George Osborne School of Mechanical Engineering Mechatronics Honours Project 2005

2. History of bipedal walking robots 1968~1969: first functional robot: WL-3 Current: fully functioning humanoids such as Honda ASIMO and Sony QRIO Applications Prosthetics for the disabled Entertainment Human assistance Background Mechanical Engineering 2 Sony 2005 Honda 2005 “Bipedal walking robots” www.humanoid.rise.waseda.ac.jp “Multifunctional Above-knee Prosthesis” www.humanoid.rise.waseda.ac.jp

3. Motivation University of Adelaide designed pneumatic muscles Stimulate robotics research at the University Mechanical Engineering 3

4. Seminar Outline Project aims Control techniques Traditional method: biomechanical Contemporary method: gait synthesis Passive dynamic design concept Design process Passive biped for downhill walking Pneumatic muscle actuated biped Results and future directions Mechanical Engineering 4

5. Aims Design and build a unactuated biped Extend design to incorporate muscle actuation Make self-contained Extension goal: incorporate standing still, stopping and starting Mechanical Engineering 5

6. Design Methodologies Two main design methods Biomechanical control Traditional control method Robust and versatile ‘Robotic’ looking gait Difficult and expensive to implement Unnecessarily complex Inefficient and heavy Control based on gait synthesis “Asimo X2 at Robodex 2003” http://www.plyojump.com/asimo.html Mechanical Engineering 6

7. Control by Gait Synthesis Simulate natural kinematics of walking Begins with essentials of walking Actuate only when required Relatively new approach McGeer 1990, Wisse 2004 Inherent sequential design Suited to muscle actuation Simple control required Very efficient Collins et al 2005 Mechanical Engineering 7

8. Control by Gait Synthesis Passive dynamic concept Gravitational power only Perfect starting point Natural looking gait Simple and light Leads to human-like behaviour Only dynamically stable Collins et al 2005 Mechanical Engineering 8

9. Preliminary Design Gait synthesis approach chosen Simplifications to human physiology Fewer degrees of freedom Minimal actuators Simplest walker concept Natural starting point Prototypes for feasibility ‘Mancano’ promising ‘Legoman’ unsuccessful “Simplest Walker” http://mms.tudelft.nl/dbl/research/biped ‘Mancano’ ‘Legoman’ Mechanical Engineering 9

10. Design of Stumpy Extremely difficult task Discrete events and varying configuration Non-linear and naturally unstable dynamics Complex mathematical model Empirical results required Design based on McGeer’s kneed walking model Unactuated kneed biped Made goals achievable McGeer 1990 Mechanical Engineering 10

11. Mechanical Design Simple mechanical layout Four legs in pairs Pinned knee joints Curved feet Consideration for tuning and actuation Limb lengths Weight distribution Muscle mounting Foot position and radius Mechanical Engineering 11 Muscle clamp Mass Clamp R

12. Final Design Mechanical Engineering 12

13. Testing and Results Many variables Limb lengths Foot radius Mass distribution Ramp angle Starting conditions Success! Mechanical Engineering 13

14. Testing and Results Poor repeatability Knee bounce main failure mechanism Knee damping ineffective Latch required Very promising for next design stage Mechanical Engineering 14

15. Biped Actuation Passive biped has limited functionality Only walks downhill Cannot start, stop or stand still Actuation can overcome these Modify passive biped Add actuation Add associated power and control Mechanical Engineering 15

16. Muscle Actuation Pneumatic muscle operation Mains air or bottled CO 2 supply (~2 bar) Power required for switching Preserves passive dynamic action Other benefits Simple construction Light and powerful Low cost Efficient Gas supply Power Bladder Mechanical Engineering Valve assembly 16

17. Mechanics Various muscle configurations possible Actuate knees only Actuate hips, and use knee latches Actuate all joints, with either 1 or 2 muscles on each Five muscles used Antagonistic hip arrangement Only two actuators required Simple lever arm attachment Muscle-spring system for knees 1 2 3 4 5 Outer leg lever arm Inner leg lever arm Mechanical Engineering 17

18. Electronics and Control Motorola 9S12C32 microcontroller on-board H-Bridge muscle switching On/off muscle sequencing Real-time tuning via PC On-board user controls Foot switch cycle initialisation Li-ion batteries for power and electronics Micro H-Bridge Mechanical Engineering 18

19. Final design Mechanical Engineering 19

20. Results Stumpy walks successfully with some assistance Mechanical Engineering 20

21. Achievements Stumpy walked passively Actuated walking successful Will improve with fine tuning Self-contained, but with mobile gas supply Mechanical Engineering 21

22. Future Directions Standing still, starting and stopping Turning Incorporating upper body More degrees of freedom Two legs Active ankles Mechanical Engineering 22

23. Conclusion Gait synthesis instead of biomechanical control Two prototypes built Passive biped Stumpy based on existing design Walked successfully Muscle actuation added to Stumpy Powered biped walked with some assistance Mechanical Engineering 23

24. Acknowledgements Supervisors Dr Frank Wornle and Mr George Osborne Mechanical engineering workshop staff Electronics and instrumentation staff Mechanical Engineering 24

25. Questions Mechanical Engineering 25