Research On Improved Predictive Control Of Permanent Magnet Linear Synchronous Motor

Permanent magnet linear synchronous motor（PMLSM）is widely used in CNC machine tools,precision machining,robotics,rail transportation and other industries because of its advantages of high-precision control,large thrust and fast response.In the PMLSM servo control system,the quality of current loop is the key to determine the performance of the whole PMLSM control system.Compared with other traditional control methods,model predictive current control（MPCC）algorithm has better dynamic and static performance,can realize multivariable control and is easy to deal with nonlinear constraints.It is more suitable for high-precision occasions.However,MPCC itself also has some problems,such as low prediction accuracy,too large current ripple and too dependent on PMLSM model parameters.In order to solve these problems of MPCC,this thesis improves the traditional MPCC and three vector MPCC is designed.On this basis,fast vector selection low switching frequency three vector MPCC and robust MPCC are proposed respectively.Firstly,the basic structure and working principle of PMLSM are described,and the mathematical model of PMLSM is established.The principle of PMLSM vector control is described,and the PMLSM vector control system is established.The principle of voltage space vector pulse width modulation technology used in vector control is introduced,and the type of voltage vector and the relationship between switching state and voltage vector are explained.Then,the principles of PMLSM traditional MPCC and three vector MPCC are described.Aiming at the problem that the amplitude and range of the selected voltage vector are fixed in the traditional MPCC of PMLSM,a three vector MPCC is proposed,which increases the number of selected vectors in a sampling period to three,synthesizes the three vectors and selects the optinal vetor,so that the selected vector can have any amplitude and range.The simulation results show that the proposed control method reduces the current ripple and thrust ripple,reduces the current harmonic content,and improves the steady-state performance of the system.Finally,in view of the fact that PMLSM three vector MPCC still has slow vector selection,too high switching frequency and vulnerable to parameter changes,the three vector MPCC is improved in two aspects.Firstly,a fast vector selection low switching frequency three vector MPCC is proposed to change the way of selecting effective vector and zero vector.The simulation results show that the proposed control method further reduces the current ripple and thrust tipple,reduces the switching frequency and has higher steady-state performance.Then a robust three vector MPCC is proposed,the steady-state current error and current oscillation caused by the change of motor parameters are analyzed,and the current tracking formula is derived to solve the problem of parameter disturbance.The simulation results show that the proposed control method effectively eliminates the current static error,improves the current tracking performance of the system and enhances the robustness of the system.