Reverse pneumatic artificial muscles (rPAMs): Modeling, integration, and control

• Published in: PloS one Vol. 13; no. 10; p. e0204637
• Main Authors: Skorina, Erik H., Luo, Ming, Oo, Wut Yee, Tao, Weijia, Chen, Fuchen, Youssefian, Sina, Rahbar, Nima, Onal, Cagdas D.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12.10.2018; Public Library of Science (PLoS)
• Subjects: Actuators; Air flow; Analysis; Artificial muscles; Biology and Life Sciences; Civil engineering; Computer Simulation; Computer-Aided Design - instrumentation; Control theory; Control valves; Engineering and Technology; Equipment Design - instrumentation; Feedforward control; International conferences; Kinematics; Mathematical analysis; Mathematical models; Mechanical engineering; Medicine and Health Sciences; Model accuracy; Models, Biological; Motion control; Muscle, Skeletal - physiology; Muscles; Orthotic Devices; Performance enhancement; Physical Sciences; Pressure; Robotics; Robots; Rubber; Silicone rubber; Silicones; Sliding mode control; Software; Solenoid valves; Static models; Test methods; Trajectory control; Valves; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0204637

Despite offering many advantages over traditional rigid actuators, soft pneumatic actuators suffer from a lack of comprehensive, computationally efficient models and precise embedded control schemes without bulky flow-control valves and extensive computer hardware. In this article, we consider an inexpensive and reliable soft linear actuator, called the reverse pneumatic artificial muscle (rPAM), which consists of silicone rubber that is radially constrained by symmetrical double-helix threading. We describe analytical and numerical static models of this actuator, and compare their performance against experimental results. To study the application of rPAMs to operate underlying kinematic linkage skeletons, we consider a single degree-of-freedom revolute joint that is driven antagonistically by two of these actuators. An analytical model is then derived, and its accuracy in predicting the static joint angle as a function of input pressures is presented. Using this analytical model, we perform dynamic characterization of this system. Finally, we propose a sliding-mode controller, and a sliding mode controller augmented by a feed-forward term to modulate miniature solenoid valves that control air flow to each actuator. Experiments show that both controllers function well, while the feed-forward term improves the performance of the controller following dynamic trajectories.