A Study on the Control of a Sensorless Pneumatic Joint Using Predictive Control Method

In high voltage substations, motors and sensors of a manipulator are susceptible to strong electromagnetic interference (EMI) and cannot work normally. The pneumatic motor can be a good method to overcome this problem. We present a novel five degree-of-freedom (DOF) manipulator design which is driven by pneumatic motors with no angle sensors. This design is simple but effective, and it can make the manipulator possess the potential to withstand the ultra-high voltage. It is also insensitive to EMI in high voltage substation due to its sensorless structure. The dynamic model of the wrist joint is established, and the state space equation, in which the pressure loss is contained, is proposed. The experiments are performed under different air pressures to validate the accuracy of the angle prediction model. A closed-loop control method, in which the angle prediction model is used as a feedback signal, is developed for this sensorless wrist joint. Finally, the rotation experiments were applied to test the validity of this control method, and the results showed that this method can improve the controllability of this type of wrist joint.