Research On Direct Torque Control Strategy Of Electric Main Rotor For Helicopter

The main rotor of helicopter is directly driven by motor,which has the advantages of low noise,high reliability,high efficiency and simple operation.The permanent magnet synchronous motor is applied to the main rotor drive control of helicopters.According to the characteristics of the controlled object,direct torque control is adopted and the traditional direct torque control strategy is studied and improved according to the control requirements to obtain more excellent control effect.The research contents of this article are as follows:First,the aerodynamic modeling of the main rotor of the sample helicopter is performed to calculate the required power of the main rotor.The optimal speed of the main rotor is determined without reducing the flight performance of the helicopter,and according to the analysis of the main rotor electric drive system,the permanent magnet synchronous motor is selected as the drive,and the control characteristics of the rotor electric drive system are described as a whole..Secondly,In the main rotor electric drive,the output speed of the motor is required to be constant.in view of the problems existing in DTC,such as uneven selection of basic voltage space vector,large torque ripple,and variable switching frequency of inverter.Under the condition of sudden load change,the output speed and torque will change.the method of space vector pulse width modulation(SVPWM)is proposed on the premise of retaining the basic advantages of traditional DTC,then the SVPWM module is designed.The SVPWM-DTC simulation model of PMSM is built in Simulink.The simulation results show that the improved control strategy can greatly reduce the ropple of flux and torque in DTC control.The speed error of motor output is reduced.Thirdly,The main rotor electric drive control system requires fast dynamic response and strong anti-interference ability,the digital implementation of DTC Algorithm of PMSM has the disadvantage of one-beat delay.Therefore,the deadbeat predictive control algorithm is applied to the control of PMSM,and a method of deadbeat flux and torque predictive is proposed.In view of the poor tracking effect of the open-loop current observer,a zero order holder is added to form the closed-loop stator current observer,The stator flux observer of voltage current combination model is designed to improve the accuracy of flux observation.Simulation results show that combining the deadbeat control algorithm with space-based modulation can improve the control performance of the main rotor electric drive system greatly,reduce system jitter,enhance the antiinterference ability of the system,and improve the dynamic response performance of the system.Finally,It is necessary to study the speed loop controller according to the poor anti disturbance ability of the electric drive speed control of the main rotor and the influence of unstable air flow.Aiming at the shortcomings of speed overshoot and poor antiinterference performance caused by PI controller in deadbeat direct torque control strategy,Direct error calculation is used to linearize the ADRC and redesign the speed controller.The simulation results show that ADRC can reduce the system speed overshoot,improve the system anti-interference,and improve the robustness to the change of motor parameters,which verifies the effectiveness of the theoretical design.