Research On Methods Of Improving The Control Precision Of Electric Dynamometer Systems

An electrical dynamometer is a group of motors which provide load in the test of power machines.The existence of friction,disturbance torque and velocity disturbance,reduces the control accuracy of the electrical dynamometer system.In order to improve the control accuracy of the electrical dynamometer system,it is necessary to compensate the friction torque,disturbance torque and speed disturbance effectively.In this regard,the main contents of this paper are as follows:1.The electrical dynamometer system is abstracted and simplified,and the modelling and dynamics analysis of the electrical dynamometer system are completed.In addition,the disturbance sources of the electrical dynamometer system,and the adverse effects of friction on the electrical dynamometer are analyzed.2.The PID speed control experiments of the electrical dynamometer are completed.The results show that the friction torque,disturbance torque and speed disturbance of the electrical dynamometer lead to a wide range of torque fluctuations and low speed accuracy.3.Aiming at the problem of low accuracy of the conventional parameter identification method of LuGre friction model,a new parameter identification method of LuGre model and the total moment of inertia,is proposed in this paper.The improved Quantum-behaved Particle Swarm Optimization(QPSO)algorithm is adopted to improve the accuracy and efficiency of parameter identification.4.After identifying the parameters of LuGre model and the total moment of inertia,based on the LuGre model and the proposed standardized nonlinear PID(SNPID),a friction compensation program of the electrical dynamometer system is designed and simulated.The speed error is reduced after the friction compensation.SNPID is a new type of PID,which has the advantages of fast response,small overshoot and better dynamic performance.At the same time,the static error of step response of SNPID is low,which can improve the accuracy of electrical dynamometer system.5.In order to solve the problem of speed disturbance and torque disturbance,three kinds of disturbance torque compensation schemes and a weighted compensation strategy of speed disturbance are proposed.The weighted compensation strategy is combined with the three kinds of disturbance torque compensation methods,respectively.The conventional PID,SNPID and model predictive control(MPC)are used as controllers,respectively,the Kalman filter is used as the state observer,and the state variables are the spindle angle,angular velocity and disturbance torque of the electrical dynamometer system.With the disturbance compensation scheme of PID control adopted,after the disturbance compensation,the fluctuation range of torque is significantly reduced.With the disturbance compensation scheme of SNPID control,the system regulation time is shorter and the response is faster.The fluctuation range of measuring torque in SNPID and MPC control scheme is smaller than that in PID control scheme.In the three disturbance compensation schemes,after the disturbance torque compensation,the speed error and the torque fluctuation range are reduced,so the accuracy of the electrical dynamometer system is improved.Comparing among the three schemes,the SNPID control scheme proposed in this paper is optimal.