Transcript Presentation - University of Adelaide

Mechatronics Honours Project 2005
School of Mechanical Engineering
Stumpy
An autonomous bipedal robot
Michael Cowling | Andrew Jeffs | Nathan Kaesler
Supervisors: Dr Frank Wornle | Mr George Osborne
2
Background
Mechanical Engineering
• History of bipedal walking robots
• 1968~1969: first functional robot: WL-3
• Current: fully functioning humanoids
such as Honda ASIMO and Sony QRIO
• Applications
“Bipedal walking robots”
www.humanoid.rise.waseda.ac.jp
• Prosthetics for the disabled
• Entertainment
• Human assistance
“Multifunctional
Sony 2005
Above-knee
Honda
2005
Prosthesis”
www.humanoid.rise.waseda.ac.jp
3
Motivation
Mechanical Engineering
• University of Adelaide designed
pneumatic muscles
• Stimulate robotics research at the University
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
5
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Aims
Mechanical Engineering
Design and build a unactuated biped
Extend design to incorporate muscle actuation
Make self-contained
Extension goal: incorporate standing still,
stopping and starting
6
Design Methodologies
Mechanical Engineering
• 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
“Asimo X2 at Robodex 2003”
http://www.plyojump.com/asimo.html
• Control based on gait synthesis
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
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Inherent sequential design
Suited to muscle actuation
Simple control required
Very efficient
Collins et al 2005
Mechanical Engineering
8
Control by Gait Synthesis
Mechanical Engineering
• Passive dynamic concept
• Gravitational power only
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Perfect starting point
Natural looking gait
Simple and light
Leads to human-like
behaviour
• Only dynamically stable
Collins et al 2005
Collins et al 2005
9
Preliminary Design
Mechanical Engineering
• 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
‘Mancano’
“Simplest
Walker”
‘Legoman’
http://mms.tudelft.nl/dbl/research/biped
10
Design of Stumpy
Mechanical Engineering
• 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
11
Mechanical Design
Mechanical Engineering
• Simple mechanical layout
• Four legs in pairs
• Pinned knee joints
• Curved feet
• Consideration for tuning
and actuation
Muscle
clamp
• Limb lengths
• Weight distribution
• Muscle mounting
• Foot position and radius
Mass
Clamp
12
Final Design
Mechanical Engineering
13
Testing and Results
• Many variables
• Limb lengths
• Foot radius
• Mass distribution
• Ramp angle
• Starting conditions
• Success!
Mechanical Engineering
14
Testing and Results
• Poor repeatability
• Knee bounce main
failure mechanism
• Knee damping
ineffective
• Latch required
• Very promising for
next design stage
Mechanical Engineering
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
16
Muscle Actuation
Mechanical Engineering
• Pneumatic muscle operation
• Mains air or bottled CO2 supply (~2 bar)
• Power required for switching
• Preserves passive dynamic action
• Other benefits
• Simple construction
• Light and powerful
Valve assembly
Gas supply
• Low cost
• Efficient
Power
Bladder
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Mechanics
Mechanical Engineering
• 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
Inner leg
lever arm
• Only two actuators required
• Simple lever arm attachment
• Muscle-spring system
for knees
2
1
3
4
5
Outer leg
lever arm
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Electronics and Control
Mechanical Engineering
• Motorola 9S12C32 microcontroller on-board
• H-Bridge muscle switching
• On/off muscle sequencing
• Real-time tuning via PC
Micro
• On-board user controls
• Foot switch cycle initialisation
H-Bridge
• Li-ion batteries for power and electronics
19
Final design
Mechanical Engineering
20
Results
Mechanical Engineering
• Stumpy walks successfully with some assistance
21
Achievements
• Stumpy walked passively
• Actuated walking successful
• Will improve with fine tuning
• Self-contained, but with mobile gas supply
Mechanical Engineering
22
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Future Directions
Standing still, starting and stopping
Turning
Incorporating upper body
More degrees of freedom
• Two legs
• Active ankles
Mechanical Engineering
23
Conclusion
Mechanical Engineering
• 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
24
Acknowledgements
• Supervisors
• Dr Frank Wornle and Mr George Osborne
• Mechanical engineering workshop staff
• Electronics and instrumentation staff
Mechanical Engineering
25
Questions
Mechanical Engineering