Prepared by: Chris Hall Dept. of Electrical and Computer Engineering Utah State University

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Pneumatic Artificial Muscle (PAM) Prepared by: Chris Hall Dept. of Electrical and Computer Engineering Utah State University E: chris.hall@aggiemail.usu.edu ; T: (435)770-2951; F: (435)797-3054 (ECE Dept.) 3/11/2010

2. Outline • Reference list • To probe further • Major applications • Basic working principle illustrated • A typical sample configuration in application (application notes) • Major specifications • Limitations • And many more relevant issues in applications (such as, how to choose, cost information, where to buy etc.) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference list • http://mech.vub.ac.be/multibody/topics/pam.htm • http://en.wikipedia.org/wiki/Pneumatic_artificial_muscles • http://en.allexperts.com/e/p/pn/pneumatic_artificial_muscles.htm ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. Reference list • http://www.springerlink.com/content/v0637k213535313p/ • http://bdml.stanford.edu/twiki/pub/HSR/HumanSafeRobot/ChouHannaford96.pdf • http://www.shadowrobot.com/ ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. To explore further (survival pointers of web references etc) • http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.89.6717&rep=rep1&type=pdf • http://www.ece.clemson.edu/crb/octor/publications.htm • http://lucy.vub.ac.be/ • http://www.computer.org/portal/web/csdl/doi/10.1109/SICE.2006.315536 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Major applications • PAMs are used to mirror the relationship in biological muscle systems • Great for walking robot applications: • High torque/weight and power/weight ratios • Muscles’ natural compliance • The actuator can be positioned at the joint without complex gearing mechanisms • Adaptable passive behaviour suited for energy storage • Shock absorbance during impact ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Major applications • Robotic exoskeleton to assist people’s legs during rehabilitation (University of Michigan) • (http://engineeringtv.com/blogs/etv/archive/2007/08/13/episode-62-artificial-muscles.aspx) http://www.kines.umich.edu/research/ccb/hnl.html http://www.kines.umich.edu/research/ccb/hnl.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Major applications • Useful for interactions with humans or for delicate operations • When a force is exerted on a PAM it “gives in”, without increasing the force in the actuation • Applications requiring no stiction and an immediate response • Applications requiring a flexible actuator • High power-to-weight ratio 400:1, whereas DC motors/pneumatic cylinders have a ratio of 16:1 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Basic Working Principle • Pneumatic artificial muscles are contractile devices operated by pressurized air. • When inflated, they bulge, shorten and thereby generate a contraction force. http://mech.vub.ac.be/multibody/topics/pam.htm http://en.wikipedia.org/wiki/Pneumatic_artificial_muscles ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Basic Working Principle • The force depends on the applied pressure and on the muscle’s length, ranging from an extremely high value at maximum length, i.e. zero contraction, to zero at minimum length or maximum contraction. http://lucy.vub.ac.be/gendes/actuators/muscles.htm ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Basic Working Principle • retraction strength is limited by the sum total strength of individual fibers in the woven shell. • exertion distance is limited by weave tightness • a very loose weave allows greater bulging, which further twists individual fibers in the weave. http://lucy.vub.ac.be/gendes/actuators/muscles.htm ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. Basic Working Principle • Because of the one-way force a paired or antagonistic set-up is needed in order to generate a restoring force or movement. http://lucy.vub.ac.be/gendes/actuators/muscles.htm ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Basic Working Principle • Very lightweight, just a thin membrane • Can be directly connected to the structure they power • Cheap to replace a defective muscle, just replace membrane • Easy to replace broken parts ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Sample Configuration • Pneumatic artificial muscles only generate force when they shorten. To have a bi-directional working joint one has to couple two muscles antagonistically. At each joint the muscles are attached in a leverage mechanism by pulling rods. The points of attachment are essential in the design since they determine torque characteristics. http://www.memagazine.org/backissues/membersonly/may98/features/anatomy/anatomy.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. Major Specifications • Braid diameter • Length stretched • Air fitting • Weave tightness • Pull at a given pressure/load (can get curves) • Cost ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. Limitations • Force exerted is dependent on the state of inflation as well as the pressure • PAMs are a nonlinear system which is difficult to model and therefore difficult to control precisely • A PAM that uses long tubes must have a control system that can deal with a delay between the movement control signal and the effective muscle action, because gas is compressible. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Limitations • Requires electric valves and compressed air generator, which are neither light nor small. • Surface fibers must stay evenly distributed and undisturbed across the internal bladder • If a gap is created by externally pushing an object into the loose weave, this gap allows nonuniform swelling of the internal bladder, which may inflate through the gap and rupture the internal bladder. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. Videos of PAMs • http://www.shadowrobot.com/airmuscles/videos.shtml • http://engineeringtv.com/blogs/etv/archive/2007/08/13/episode-62-artificial-muscles.aspx • http://lucy.vub.ac.be/gendes/actuators/hopper.avi • http://www.ece.clemson.edu/crb/octor/multimedia.htm • http://umich.edu/news/index.html?Vid/bionicboot ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Cost Information/Where to Buy • Shadow Robot inventory (http://www.shadowrobot.com/shop.shtml) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. Current Research and Development • Vrije Universiteit Brussel • University of Michigan • DAG Technology, Malaysia • Northern Malaysia University College of Engineering • Waseda University, Tokyo, Japan • Department of Biomedical Engineering, University of Malaya, Kuala Lumpur, Malaysia • Clemson University ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators