Cross-coupled Control Of Direct Drive X-y Table Based On Position Compensation

Nowadays, CNC technology is widely used to improve manufacturing capacity and the level. It is important way to accelerate economic development, enhance the comprehensive national strength and the national status that developed countries vigorously develop with numerical control technology as the core of the advanced manufacturing technology. There are the vital role and representation to improve the machining accuracy, performance and precise contour tracking control of CNC in X-Y table. With the growing of high accuracy complex surface parts processing requirements, contour precision has become an important precision index in CNC system.To weaken the influences of nonlinear system dynamic, uncertainties, and complex contour error model of curve trajectory for direct drive numerical control X-Y table servo system driven by Permanent Magnet Linear Synchronous Motors (PMLSM), the real-time contour error mode is established and a method of Cross-Coupled-Control(CCC) combined with Position Error Compensator(PEC) is used to reduce contour error. Rather than focusing only on contour error reduction, the approach can reduce position error. And the PDFF control is used to design the single axle speed controller, indirect to reduce the contour error.Firstly, the development, application, construction and work principles of direct drive X-Y table were introduced in this paper. Mathematical models of single axis permanent magnet synchronous linear motor (PMLSM) and X-Y table were established. According to the characters of X-Y table, the factors that affect the contour precision were analyzed. Direct drive technology eliminates the middle transmission parts and has the merits of large thrust, low friction, high dynamic stiffness and high positioning precision. However, X-Y table is sensitive to the uncertainties and nonlinear factors that its servo performance decreased, so it is necessary to design servo controllers to improve the robustness and contour precision.Secondly, based on describing the concept of X-Y table contour error, contour error model of the linear path, the circular path and the free-form path were calculated. Several methods of improving contour precision were summarized. Then the single axis speed controller and the position controller are designed respectively. Single axis controllers emphasizes on reducing the contour error through reducing single axis position errors. Then simulate and analysis the result.Finally, the article used a structure of modified CCC and designed the CCC. Simultaneously the position error compensator is used. It is calculated easily by the real-time contour error, current federate command and tracking dynamics of each axis. Rather than focusing only on contour error reduction, the approach can reduce position error.Yokogawa LM110 permanent magnet linear synchronous motor X-Y table is considered as the controlled object, and used the Matlab7.0 to simulate and analysis the result. The simulation result indicated that the PDFF controller improved the single-axis precision effectively. The structure of the Cross-Coupled-Controller and the position error compensator can enhance the robustness and the contour precision of X-Y table effectively.