Research On Key Technologies Of Large Telescope Control Based On Segmented Permanent Magnet Synchronous Motor

The photoelectric telescope is an important modern equipment for observing space targets.It needs to work together in many fields such as optics,machinery,and electricity.With the development of astronomical observation technology,the index of observation of space targets is getting higher and higher,and the tracking performance of the photoelectric telescope directly affects the final imaging quality of the measured target.This requires that the tracking accuracy of the telescope servo tracking system continues to improve,even to the arc-second level.For large telescopes,in order to increase light collection capacity and resolution,the larger the aperture of the telescope,the better.However,the increase in aperture will directly lead to a sharp increase in the volume and weight of the telescope.Therefore,the selection of the telescope drive motor is very important and needs to be considered from many aspects of electrical parameters,mechanical parameters,processing,maintenance and so on.Compared with brushed DC torque motors,permanent magnet synchronous torque motors have higher power density and smaller size and become the mainstream motors driven by large telescopes.However,telescopes with a diameter of more than 4 meters put forward higher requirements on the motor,regardless of processing,transportation,maintenance and other aspects,the permanent magnet synchronous torque motor segment processing is an important solution to solve the problem of super high torque output.The segmented permanent magnet synchronous motor belongs to the category of permanent magnet synchronous motor,and it can draw on the rotating permanent magnet synchronous motor in the control principle.At present,there are already many giant telescopes in foreign countries using such segmented motors,and only two scientific research institutions in China are researching and developing telescopes based on segmented permanent magnet synchronous motors.Therefore,this subject is of great significance to the engineering research of segmented motors.The driving scheme of multiple segmented permanent magnet synchronous motors is an important guarantee for the smooth operation of the telescope.This paper introduces a driving scheme and has been successfully applied to the driving system of large telescopes.This scheme is composed of the main controller and six torque controllers.The main controller and torque controller are composed of DSP,FPGA and peripheral circuits.The power drive part adopts Mitsubishi's Intelligent Power Module(IPM),which has overcurrent,overvoltage,undervoltage and overtemperature detection Features.Through practical application to the telescope control system,the feasibility of the driving scheme and the reliability and high-precision real-time requirements of the hardware system are verified.On the basis of this hardware system,the frequency sweep test is performed on the telescope control system,the frequency sweep signal covers a wide range of telescope operating frequencies,and the frequency characteristic test is performed using the spectrum analysis method.The frequency characteristic test obtains the first-order and second-order resonance frequencies as the main reference basis for the design of the speed loop and position loop controller.For the design of telescope servo control systems,the proportional integral derivative(PID)controller is the most widely used control method.Based on the telescope servo system of segmented permanent magnet synchronous motor,this paper designs a multi-loop PID controller from the perspective of engineering application.Analyze and design in the order of current loop,speed loop and position loop.In order to improve the dynamic performance of the telescope servo system,a model predictive control algorithm is used to design the speed loop controller.The basic principle of Model Predictive Control(MPC)is introduced in detail,which has the advantages of multi-step prediction,feedback correction,and optimized output.Based on the telescope control system model,a multi-step prediction model is established,and an optimal value function is designed.Through simulation and experiment,the model predicts that the speed controller has better dynamic performance.Due to the particularity of the segmented permanent magnet synchronous motor,the motor not only contains cogging torque,but also introduces side end torque disturbance.This paper introduces and analyzes the cogging effect and the edge effect respectively,and summarizes that both effects cause periodic torque ripple.The methods of torque ripple suppression are divided into motor body optimization design and control algorithm design,and a brief review of the current research status.In this paper,a model predictive iterative learning controller is proposed,which iteratively compensates for periodic torque pulsation,and is experimentally verified on the platform of the servo control system of the spindle of the large-diameter telescope.The comparison of the peak-to-peak velocity and the analysis of the disturbance spectrum verify the effectiveness of the proposed algorithm and improve the tracking accuracy of the telescope control system.The dead zone effect and magnetic flux harmonics of high-power drivers are the main factors that cause current harmonics.This article analyzes the magnetic flux harmonics and the dead zone effect in detail,and summarizes the main order of the current harmonics.Fractional order control(FOC)is a control algorithm that is worthy of study in recent years.Based on the definition and theory of fractional calculus,this paper proposes a fractional resonant controller,which is combined with an integral model predictive current controller to form a composite control.Device.Experimental results show that compared with traditional control strategies,the proposed composite controller not only improves the current dynamic performance,but also effectively suppresses current harmonics,so that both current steady-state performance and speed steady-state performance are improved.