Study On Control Techniques Of5DOF Magnetic Levitated Planar Motor

The two-dimensional positioning device with high speed and high accuracy is needed in many modern high technology manufacturing fields, such as IC manufacturing, micro mechanical assembly, cell operation, ultra-precision measurement and microsurgery. However the traditional cascaded2dimensional positioning device has its intrinsic drawbacks:the positioning accuracy is low, response speed is slow and the manufacturing cost is high. Therefore the Magnetic Levitated Planar Motor (MLPM) is considered to be an effective way to achieve high speed and high accuracy positioning. Compared with the conventional two-dimensional positioning devices, the planar motor possesses many advantages such as direct driving, low friction (no friction), no backlash and high precision, thus it can work with not only high speed, but also high precision.In this dissertation, a new design of multi-degree of freedoms magnetic levitated planar motor is proposed. We focus on the levitation control technique and planar positioning control technique. The key techniques of the MLPM control system, such as modeling technique, coupling analysis, robust control strategy, controller development and etc are studied deeply. And the main research contents and achievements are shown as follows:The mechanical platform of MLPM based on the attractive direct current principle is designed. In the planar motor mechanical design, it consists a stator and a mover. In the stator, there are4U-shape electro-magnets which are installed vertically and8I-shape electro-magnets which are installed horizontally. The attractive magnetic forces from vertical and horizontal directions will drive the mover to be levitated in space and positioning in the plane. The MLPM has following characters:the efficiency of the electro-magnets is increased since the attractive direct current forces are applied in the design; the coupling effect of the magnetic forces are avoided in the structure since the mover is driven by vertical magnetic forces and horizontal forces independently; the heat dissipation problem is avoided since there is no coil or permanent arrays in the mover.The integrated control system framework based on PC is proposed. In the control system, the hardwares of the control system consist of a PC, input&output card based on PCI bus and an analog linear power amplifier board. The software platform of the control system is Windows XP which is installed with multi-tasks real-time software:RTX. On this software platform, the minimal hard real-time period can be0.1ms. The real time control and measurement program for the MLPM is also developed on the software platform. This program can synchronously feedback the sensor data of the system, control the planar motor, and display the sensor data on the screen of the control PC. The control results of the experiments show that the integrated control system is practical and reliable, it is suitable for the real-time control&measurement of the MLPM.For the MLPM, control technique is key for the system. In order to improve the levitation performance of the MLPM, the modeling method of the magnetic force is studied, and designed a nonlinear robust controller for the suspending problem of the MLPM. In the nonlinear robust controller which is robust against parameter perturbation, the Global Sliding Mode Control (GSMC) algorithm combined with feedback linearization technique are employed. Experiment and simulation results show that compared with classic PID, the proposed nonlinear robust controller provides better transient response performance and better robustness against the nonlinear parameter perturbation and will stabilize the MLPM in the levitated direction with large parameter uncertainty in the system.In order to achieve the decoupling control for the MLPM in the vertical direction, we establish the3DOF rigid body dynamic model for the magnetic suspension; then the robust decoupling controller is designed to manipulate the mover to rotate along its axis or move along z axis independently. The proposed controller applies fuzzy sliding mode control algorithm to eliminate the effect of parameter uncertainty in the system model, moreover it will estimate the uncertainty of the system in control procedure, with the estimated uncertainty the sliding mode control output will be softened and the chattering phenomenon will be eliminated. Meanwhile, the extended state observer is employed in the controller to observe the external disturbance and improve the robustness against external disturbance. Experimental results show that the proposed controller can achieve the decoupling control in the3DOF of the MLPM while it is robust against internal parameter uncertainty and external disturbance.The control technique for planar positioning of the MLPM is studied. First, the planar rigid body dynamic model of the MLPM mover is established; second, in order to reduce the inputs of the MLPM planar drive, a simplified control scheme is proposed. In the proposed control scheme, the electro-magnets in the negative direction of the X/Y axises are energized with constant direct current to provide negative magnetic drive force while the electro-magnets in the positive direction of the X/Y axises are used as the control inputs; then,3DOF decoupling robust controller are designed. The controller applies fuzzy sliding mode control algorithm combining extended state observer. with the proposed controller, the MLPM could achieve2DOF planar positioning. Planar positioning experimental results show that the MLPM proposed in this thesis is capable of generating translation of2mm in the X and Y axes.To sum up, the magnetic levitation planar motor experimental platform, integrated control scheme, the proposed scheme to simplify the control input of the system and the design of nonlinear decoupling controller discussed in this paper can realize5DOF control of the magnetic levitation planar motor, and make the motor realize precision plane positioning in direct drive. For the further development of high precision large stroke plane positioning device, this paper has certain theoretical meaning and practical value.