Error Analysis And Accuracy Compensation For High-Speed High-Precision Motion Platform

With the development of modern mechanical and electrical systems,such as mi-croelectronics manufacturing equipment,numerical control machine tools and optical detection systems,high-speed linear motion is usually needed to improve production ef-ficiency.At the same time,as the society enters the era of micro-nanotechnology,these devices and systems need to have micro or nano-level motion positioning accuracy.Therefore,the high-speed and high-precision motion platform equipped with advanced control system has become the foundation of high-end equipment manufacturing indus-try in China,and plays a decisive role in its development.The contradiction between high-speed and high-precision of motion platform is the key problem in the research and development of high-speed and high-precision motion platform.It is of great signifi-cance to study and solve the problem of high-precision positioning of motion platform in high-speed motion for the autonomy and industrialization of high-end manufacturing equipment in China.Due to the limitations of the existing manufacturing conditions and control sys-tems,there are some error factors in the high-speed and high-precision motion platform,which makes the accuracy of motion positioning decline and limits the performance of the motion platform.Aiming at the geometric errors and the errors caused by non-linear forces of two common driving platforms in high-speed and high-precision motion plat-forms(i.e.indirect driving platforms powered by ball screw and rotary motor and direct driving platforms powered by linear motor),error analysis and precision compensation methods are studied in this paper.The sources and characteristics of these errors are an-alyzed in detail.The problems such as the increase of positioning errors,the decrease of positioning accuracy and the decrease of repetitive positioning accuracy caused by errors are expounded.Aiming at these errors,the corresponding control algorithm is studied and designed to compensate the positioning accuracy of the platform.The ex-perimental results show that the developed high-speed and high-precision motion plat-form can achieve high-precision positioning under high-speed motion.The main work and research contents of this paper are as follows:1.Aiming at the different mechanism characteristics of two common high-speed and high-precision motion platforms,indirect drive platform and direct drive platform,are designed and physical platforms are built.The indirect driving platform takes the rotary motor as the output power source and connects with the ball screw through the coupling.The rotation of the ball screw drives the movement of the table.The direct drive platform is powered by linear motor,and the intermediate connection mechanism is omitted.The worktable is fixed on its primary level,thus directly driving the move-ment of the worktable.2.Aiming at the problem of geometric errors easily existing in high-speed and high-precision motion platform,the geometric errors of direct-drive platform are mea-sured and analyzed by using laser interferometer measurement system.Based on the measured data,the geometric error interpolation calculation model is established.Ge-ometric error is compensated by error compensation system.The experimental results show that the positioning error before compensation exceeds ± 15?m,while after com-pensation,the positioning error decreases to no more than ±4?m,the bidirectional po-sitioning accuracy increases from A =42.188?m to A =9.413?m,and the bidirectional repetitive positioning accuracy increases from R =13.823?m to R =8.893?m.The experimental data show that the compensation system and compensation method can effectively improve the positioning accuracy of the system.3.According to the characteristics of high-speed and high-precision indirect drive platform,the dynamic model of the platform is established,including permanent magnet AC synchronous servo motor,ball screw force transmission mechanism and dynamic friction model.An adaptive robust control algorithm based on non-linear friction com-pensation is proposed.The tracking experiments of common point-to-point trajectories(including high-speed and low-speed)and sinusoidal trajectories are carried out.Ex-periments show that the algorithm can effectively compensate for the errors caused by non-linear friction at a speed of 1.26m/s(the maximum theoretical speed of physical platform is 1.5m/s),and make the positioning accuracy of the platform reach micron level.4.The high-speed and high-precision direct drive platform driven by linear motor is studied,and the mathematical model of linear motor in d-q coordinate system is estab-lished.The special end effect of linear motor is analyzed,and the model of linear motor considering the end effect is given.Based on the analysis of traditional vector control al-gorithm and direct torque control algorithm,an adaptive robust position/thrust tracking control algorithm based on end effect compensation is proposed,and the correspond-ing controller is designed.Because it combines the wide speed range and continuity of vector control with the fast torque response characteristics of direct torque control,this method has the characteristics of fast response and smooth control.Through simulation analysis and experimental comparison,this method can compensate the non-linear force positioning error caused by the end effect of linear motor.5.Based on the analysis and modeling of non-linear electromagnetic force,fric-tion force,positioning force and geometric error,an adaptive robust control algorithm based on the comprehensive compensation of non-linear force error and geometric er-ror is proposed,and the algorithm verification experiment is carried out on the direct drive platform.Due to the limit of travel(330 mm in the whole journey)and phys-ical(theoretical maximum speed is 1.2m/s,acceleration is 11.25m/s2),the maximum speed selected in the experiment is lm/s,and the maximum acceleration is 10m/s2.The experimental results show that the proposed algorithm can significantly improve the geometric positioning accuracy of the system.The bidirectional positioning accuracy is raised to A =2.936?m,the bidirectional repetitive positioning accuracy is raised to R =2.211?m,and the positioning error range is reduced to(-1)um-1.5?m.The reso-lution of grating-scale feedback encoder is basically 1 ?m,which achieves high-speed and high-precision positioning effect.