Electromechanical Coupling System Controller Design Based On Explicit Model Prediction

Model Predictive Control(MPC)is one of the most effective methods to deal with the optimal control problem of multi-constraints system,which has become a hot topic.For the control of mechanical and electrical systems with nonlinear,high sampling frequency and strong coupling,there are still problems in MPC.the amount of online operations is too large,which can't be applied to systems with high sampling frequency.However,Explicit model predictive control(EMPC)addresses the problem of removing one of the main drawbacks of model MPC,namely,its on-line high complex computations.Firstly,the EMPC controller is designed for the DC servo system,which combines the state vector with the constraint conditions.The state partition of the controlled object is divided,and then the mapping relation between the state partition and the control vector is established to form the off-line calculation,which provides support for the online lookup table.The developed control strategy is verified by numerical simulation subsequently.Secondly,the model of the three-phase induction motor is built.The two controllers are designed subsequently by Direct torque control(DTC)and EMPC.The DTC control strategy utilizes a two-position hysteresis control of the torque and flux linkages to set the switch position combination table.During the operation of the system,according to the position of the stator flux linkage at this moment,the voltage vector suitable for the next moment is selected to achieve direct torque control.The EMPC control algorithm uses a three-phase asynchronous motor and a two-phase converter as a whole model to establish a state space expression.The state vector is given by the motor model,and the voltage vector is used as a control quantity,motor torque and stator flux as the model output.The feasible region is calculated based on the state vector and the constraint conditions,and then the result proves the feasibility of EMPC in high-speed sampling systems.Finally,the aforementioned control strategies are analyze and compared from the aspects of modeling methods,the output performance,etc.It is concluded that the EMPC method is simple and easy to implement,and the DTC algorithm can suppress the problem of torque ripple.The proposed methods can elegantly deal with constraints of the system on one hand,and predict and optimize its further behavior on the other hand.Therefore,the research work in this paper has great significance on the model predictive control,which is extended to the field of multi-phase motors.