Modeling and compensation control of asymmetric hysteresis in a pneumatic artificial muscle

Pneumatic artificial muscle is a novel compliance actuator, and it has many excellent actuator characteristics, such as high power density, safety, and compliance. However, it also has strong nonlinear and asymmetric hysteresis, which makes the accurate trajectory control for a pneumatic artificial muscle very difficult. In this article, the pressure/length hysteresis of a pneumatic artificial muscle was analyzed via an isotonic test. And then, it was described using extended unparallel Prandtl–Ishlinskii model, and the model parameters were identified by an adaptive weight particle swarm optimization with a mutation portion algorithm. For the comparison, the classical Prandtl–Ishlinskii was also considered, and its parameters were identified by least square method. Based on the hysteresis model built by extended unparallel Prandtl–Ishlinskii model, an integral inverse compensator was proposed, and then a proportional–integral–derivative controller with the integral inverse compensator (integral inverse-proportional–integral–derivative) was designed. The simulations and experiments validated that the integral inverse-proportional–integral–derivative controller has good dynamic performance. Compared with conventional proportional–integral–derivative controller without a hysteresis compensator, the control precision of integral inverse-proportional–integral–derivative controller is improved by 43.86%.