Dead Zone Compensation Method by Mass Flow Rate Twin Drive System for a Pneumatic Driving System

Abstract

Pneumatic cylinders have advantages of light weight, low heat generation, and low cost, making them potentially suit- able for coarse motion stages in large positioning systems. However, the high-precision and high-speed positioning with the pneumatic driving system has many challenges. One challenge is the dead zone, which is one of the nonlinear characteristics. The conventional dead zone compensation method using the inverse model of the valve cannot cope with the dead zone variation caused by temperature and pressure fluctuation. Furthermore, the effect of nonlinearity is strong at small flow rates near the dead zone, making flow control difficult. To solve these problems, we proposed a twin-drive system using two valves, which can control the sum and difference of mass flow rates (total flow rate and leakage). By setting the leakage of the mass flow rate, the system can be driven at an operating point with high linearity, which enables precise flow control. The interference between the two valves was decoupled by the Hadamard matrix. The experimental results show that the mass flow rate difference follows the reference value without being affected by the dead zone compared to the conventional method.