Research of Control of Two-Degree-of-Freedom Pneumatic Trajectory Tracking System

Pneumatic servo actuators have the benefits of lowcost, cleanliness and a high power-to-weight ratio. However they have poor accuracy and low inherent frequency according to the compressibility of the working media, air, and the large static and Coulomb friction. This paper presents a control strategy for two-degree-of-freedom pneumatic trajectory tracking system. For each single axis, disturbance observer is designed for the sake of robustness, and zero phase error tracking controller (ZPETC), which increases closed-loop band width up to 100 rad/s, is designed according to identified model of closed loop. In order to improve the profile trajectory error, a compensator is used to generate compensating feed forward signal to each single axis controller. Experiments were conducted and an error within plusmn0.8 mm has been achieved.