Article: Meller MA, Bryant M, Garcia E; (2014) “Reconsidering the McKibben Muscle: Energetics, operating fluid, and bladder material”, Journal of Intelligent Material Systems and Structures, 25 (18): 2276-2293
Abstract: In spite of extensive modeling and characterization efforts, little is known about the energetics of McKibben muscle actuators. This article experimentally investigates the effectiveness of traditional McKibben muscles at converting fluid energy delivered to the actuator to mechanical output work over full actuation cycles. Once these efficiency metrics are established, a comparison of the efficiencies of traditional pneumatic fluidic artificial muscles and hydraulic fluidic artificial muscles is presented. Two new hydraulic oil compatible bladder materials are testedan elastomeric Viton bladder and an inelastic low-density polyethylene bladder. The performance of these muscle variants is compared by measuring blocked force and free contraction as a function of pressure, hysteresis, and energy efficiencies. The measurement of fluid volume delivered to the fluidic artificial muscles over their actuation ranges is shown to be useful for evaluating the accuracy of existing cylindrical volume models. Models of the energy conversion efficiency are developed and compared to the experimental data. The results show that using an inelastic bladder significantly improves the efficiency, force capacity, and contraction range of McKibben muscles; however, it also increases the actuator’s hysteretic behavior. Powering the muscles hydraulically and operating at higher pressures improves the efficiency as well.
Funding Acknowledgement: Defense Advanced Research Projects Agency (DARPA) [W31P4Q-13-1-0012]
Funding Text: This work was supported by the Defense Advanced Research Projects Agency (DARPA) through the Maximum Mobility and Manipulation (M3) Program under the direction of Dr Gill Pratt (grant number W31P4Q-13-1-0012). Funding for Matthew Bryant was provided by the Intelligence Community (IC) Postdoctoral Research Fellowship Program under the direction of Dr Jim Beckwith.