Research On Application Of Direct Torque Control In Automobile SbW System

The steer-by-wire system is a new type of steering control system that removes the linkage structure in the traditional system and increases the flexibility of the steering system.The steering execution motor is the key to the realization of the steering system,and its performance will directly affect the driving experience.This system selects a permanent magnet synchronous motor with small torque ripple as the steering execution motor of the steer-by-wire system,and selects a direct torque control algorithm with faster torque response for research.The main contents of the subject are as follows:(1)Analyze the car-by-wire steering system,and study the dynamics of the steering-by-wire system and the control algorithm of the motor system.The main content includes the introduction of the dynamic model of the steer-by-wire system and the disturbance of the system,which provides an application background for the subsequent permanent magnet synchronous motor torque ripple problem.(2)Research on direct torque control.The structural classification of permanent magnet synchronous motors and their models in different coordinate systems are given.The principle of direct torque control is mainly analyzed,and in order to improve the load capacity of the system,the maximum torque current ratio control is proposed.Then introduced the realization process of the motor model in Simulink,and verified the feasibility of the model through simulation experiments.Selecting the flux linkage amplitude and power factor as the control performance indicators,the simulation results verify the performance of the direct torque control method using the maximum torque current ratio control is very superior.(3)In-depth study of model predictive direct torque control.The motor model is discretized by Euler’s method,and different flux pulsation weight coefficients are applied to the prediction model according to the actual control effect.In order to avoid the influence of the selection of the weight coefficient on the system performance,a new value function containing only the error term of the stator flux prediction value is constructed,so that the weight coefficient can be eliminated.The flux amplitude pulsation,torque amplitude pulsation and inverter switching frequency are selected as the evaluation function.The simulation results show that the model predictive torque control has excellent control performance.(4)In-depth study of model predictive control combined with dual vector modulation technology.First of all,according to the characteristics of large torque ripple combined with dual vector control,re-optimization is carried out,and two dual vector calculation methods are proposed.And for the torque error and stator flux error combined with fuzzy control strategy for intelligent adjustment,in order to provide better control effect.The simulation results prove that the performance of dual vector model predictive torque control is better than traditional model predictive torque control.(5)Build an experimental platform for the steer-by-wire system.Three methods of traditional direct torque control,model-predicted direct torque control and dual-vector model-predicted direct torque control are realized by writing software programs,and they are verified by experiments.