Contour following control of two-axis servomechanism using CMAC and ILC

In addition to positioning control, contour following control is also an important application of two-axis servomechanisms such as X-Y tables. Therefore, the reduction of contour following error so as to improve contour following accuracy is one of the important research topics for two-axis servomechanisms. Generally, the assessment of contour following accuracy is based on two error indices - tracking error and contour error. Although the reduction of tracking error can lead to the improvement of contour following accuracy, many previous studies suggest that contour error is a more crucial indicator than tracking error in contour following applications. As a result, this paper aims at developing a control scheme for contour error reduction so as to improve contour following accuracy. The proposed control scheme consists of a PI type feedback controller, a Cerebellar Model Articulation Control (CMAC) algorithm and an Iterative learning Control (ILC) scheme. In particular, the CMAC is combined with the ILC to compensate for the adverse effects due to external disturbance and nonlinear phenomenon. Experimental results verify the effectiveness of the proposed contour following control scheme.