Direct Inverse Hysteresis Compensation of a Pneumatic Artificial Muscles Actuated Delta Mechanism

Pneumatic artificial muscle (PAM) is a popular bionic actuator featuring flexible actuation. However, the inherent hysteresis of PAM reduces its tracking accuracy. This paper proposed a feedforward-feedback composite control method to compensate for the hysteresis nonlinearity of the PAM in a 2 degrees-of-freedom (DOF) Delta mechanism. Direct inverse modeling approach was utilized to obtain the inverse hysteresis model of the PAM directly from the measurement without inversion calculation. Subsequently, the inverse hysteresis model was cascaded in the feedforward loop to attenuate the PAM's hysteresis. Further, PID feedback control was also integrated to account for the unmodeled dynamics and the modeling uncertainties of the inverse hysteresis model. Experimental results showed that most of the angular tracking error could be reduced to the range of ± 0.5 °, which indicated that the proposed feedforward-feedback composite control method could effectively compensate the hysteresis of the PAM.