Methods to improve motion servo control accuracy of pneumatic cylinders - review and prospect

Low-cost, non-polluting pneumatic technology is one of the most important engineering technologies. However, the application of pneumatic servo system is limited by the low control accuracy due to the nonlinear factors such as pneumatic actuator friction and compressibility of working medium. Many researchers have been exploring the reasons for this and have taken some targeted measures. Through extensive literature research, this paper summarises these methods into four categories: high-precision friction modelling and compensation, advanced control strategies, improved system stiffness and improved friction characteristics. In addition, the paper offers a new idea that removes the uncertain part of friction that is harmful to the control system and retains the damping part that is beneficial to the control system. For example, it can be considered to introduce a deterministic damping coefficient after removing the friction to enhance the stability of the system, and thus improve the control accuracy of the pneumatic system.