Title: Simultaneous stiffness and position control of the pneumatic artificial muscle actuation system

Authors: Tad A. Driver; Xiangrong Shen

Addresses: Department of Mechanical Engineering, The University of Alabama, 290 Hardaway Hall, Box 870276, Tuscaloosa, AL 35487-0276, USA ' Department of Mechanical Engineering, The University of Alabama, 290 Hardaway Hall, Box 870276, Tuscaloosa, AL 35487-0276, USA

Abstract: Variable-stiffness actuators are highly useful in various robotic applications, especially those involving human-machine interaction and energy storage and reuse. To obtain such actuators, the pneumatic artificial muscle (PAM) is a very promising candidate, leveraging its multiple advantages such as simple structure, low weight, and controllable stiffness. This paper presents a new robust control methodology, with the purpose of enabling the simultaneous and independent control of position and stiffness of PAM actuation systems. As the basis of this controller, a two-input-two-output dynamic model is established, which incorporates the major non-linearities in the system. Subsequently, the multi-input-multi-output (MIMO) sliding mode control approach is applied, with the purpose of providing a good control performance in the presence of model uncertainties and disturbances. The controller is implemented on an experimental setup, and the effectiveness of the proposed controller is validated via experimental tracking performances of both the system position and stiffness.

Keywords: pneumatic artificial muscles; PAMs; variable stiffness actuators; sliding mode control; SMC; MIMO control; human-machine interaction; HMI; energy reuse; energy storage; model uncertainties; tracking control; robot control.

DOI: 10.1504/IJAAC.2013.057372

International Journal of Automation and Control, 2013 Vol.7 No.4, pp.271 - 287

Received: 21 Sep 2012
Accepted: 02 Aug 2013
Published online: 12 Jul 2014 *

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