Tracking Performances of Cascade and Sliding Mode Controllers with Application to a XY Milling Table

Design and implementation of robust tracking controllers for linear feed drive high speed machine tools are the primary objectives of this work. Cutting forces and friction forces limit tracking accuracy and their influences are minimised through robust controller design. This paper discusses the design and tracking performances of a traditional cascade and a sliding mode controller for a X-Y milling table. Circular tests are performed at selected tracking speeds and circle radii for tracking performance analysis. The tracking error for cascade P/PI controller is proportional to the reference tracking speed and is inversely proportional to the velocity gain value of the position loop controller. Speed and acceleration feedforward further reduce this tracking error. Quadrant glitches, a product of nonlinear friction at the points of velocity reversal, are observed. Sliding mode controller exhibits better tracking accuracy and dynamic stiffness and yields a significant reduction of the quadrant glitches.