Dynamic pneumatic actuator model for a model-based torque controller

The modeling of pneumatic actuators, also known as artificial muscles, has been the main focus in several research papers in the past [1, 2, 3, 4, 5]. At the Center for Intelligent Systems (CIS) at Vanderbilt University, we have been using pneumatic actuators for our Intelligent Soft Arm Control (ISAC, Figure 1). For the position control of a joint, driven by two artificial muscles, a physical actuator model was designed and used as the basis for a subsidiary torque control. It is known that such actuators contain a high nonlinearity including a hysteresis. Experiments show that the static hysteresis is less important than the dynamic one. In similar models, damping properties of the muscles have not been considered. This research paper focuses on the modification of a physical static model and the extension with a dynamic part. The quality of the model was verified by implementing it as a torque controller and running experiments on a testbed.