Friction compensation control of a feed drive system operated in a vacuum

Abstract

In a feed drive system, friction is a typical nonlinear component that increases the complexity of the dynamic behavior. A feed drive system equipped with rolling contact components, such as ball screws and linear motion guides, undergoes complicated friction behavior. In this regard, various techniques have been proposed to decrease the effect of friction and thus achieve the precise control of the feed drive system. Friction compensation control is a widely used technique that cancels out the friction force by applying an additional driving force that corresponds to the friction estimated by a friction model. A variety of friction models have been proposed to estimate the friction force accurately for friction compensation control. However, conventional friction models have focused on estimating the friction force of a feed drive system operating in atmospheric pressure although air pressure affects the friction characteristics. The accuracy of the conventional friction models might decrease for a feed drive system operated in a vacuum. This paper presents a friction compensation controller on the basis of a new friction model that considers the effect of the vacuum pressure on friction. A vacuum chamber that can control the vacuum pressure and a vacuum-compatible feed drive system are constructed to measure the friction force at various vacuum pressures. The relationship between the friction characteristics and the vacuum pressure is investigated on the basis of the experimental results and applied to the friction model. A friction compensation controller based on the friction model and Kalman filter is designed and evaluated experimentally.