Research On Active Disturbance Rejection Control Strategy Of Direct-drive Pmsm Traction Machine During Zero-speed And Low-speed Mode

Permanent magnet synchronous motor(PMSM)has been widely used as traction machine in direct-drive elevator due to its advantages of high efficiency,high power density and small volume,etc.The zero-speed mode during start-up and the low-speed operation are two important parts in the research of controlling elevator.Firstly,to ensure the riding comfort of passengers during start-up,the active disturbance rejection control(ADRC)can be adopted to track and compensate the “total disturbance” of the system,including the load torque,the current error and so on.By eliminating the disturbance in advance,the sliding distance of the lift car can be reduced to ensure the riding comfort.Secondly,to improve the stationarity of the system during the low-speed operation,a smooth tracking regulator of the rotor position can be established based on the time optimization theory.This regulator will make the step-like signal of the position smoother,thus the speed information by differential calculating will be fast during transient state and continuous during steady state.Using the speed as the feedback of the system,better performance will be obtained during low speed mode.This thesis focuses on the ADRC based zero-speed during start-up and time optimization based low-speed operation for the direct-drive traction system.To begin with,the mathematical model of the traction system is established considering the time delay of the electromagnetic brake and the friction model.By analyzing the nonlinear braking force during the brake is releasing,the deterioration of the riding comfort is explained.Simulations are carried out to verify the influence of the time-delay of the brake and the unknown external disturbance.On the basis of above,the main factors of the sliding during start-up is confirmed,which can be solved by adopting ADRC strategy to suppress the large sliding distance.Firstly,the “total disturbance” is estimated and compensated by the extend state observer(ESO),thus the system is simplified as a first-order integral system,which is easier to be controlled.Several parameters in the observer are discussed.In order to select optimal values,analysis of stability and dynamic performance has been made.Furthermore,as the traction machine will “slide back” to the opposite direction after sliding,the principle of ADRC is analyzed to find the reason of “sliding back”,which leads to the conclusion that the ESO will eliminate the static error.As a result,integral link in the speed regulator is not needed.By adopting the nonlinear error feedback controlled in the speed loop,smaller sliding distance and speed can be obtained.After that,the control strategy for low-speed operation is proposed.By adopting the time optimal theory,a smooth tracking regulator is established to regulate the origin step-like position signal more continuous.As a result,the speed which is calculated by differentiation will be more accurate without high-frequency noise.The expression of the optimal control synthesis(OCS)function is deduced under the condition of discretization.Applying the chirp signal in simulation platform,the parameters in the OCS function is analyzed to obtain the optimal performance of the regulator.Finally,based on the theoretical analysis,the simulation with Matlab/Simulink was given to verify the proposed methods.And the effectiveness of the proposed ADRC strategies is tested at an 11.7k W PMSM drive experimental platform with an ARM chip.