Development Of Low-power Frequency Converter Under Pulse-type Load

When the motor load periodically fluctuates between no-load and on-load,a pulse-type load is formed.In a sports device such as a treadmill,the load torque generated by a person when walking or running is a pulse-type load torque that changes periodically.It is mainly described according to the three parameters of the load torque cycle,amplitude and duty cycle.When the motor is running normally,the pulse-type load will have repeated loading and unloading effects,which will affect the output performance of the controller.In the design,it is expected that the motor speed adjustment can be changed slowly,so that the human body feels minimal,and comfort control is achieved.Aiming at the motion device with pulse-type load torque characteristics,an AC motor-driven electric treadmill is taken as an example,and a closed-loop variable-frequency speed regulation technology with constant voltage frequency ratio control is selected.A self-tuning fuzzy PID algorithm is used.Using STM32F103ZET6 microcontroller,a dedicated AC speed controller suitable for pulse-type load was developed.Through the online modification of PID parameters to meet the different requirements of the load parameters on the control parameters,to achieve the comfort control of the motor speed.Through the speed regulation performance test,under different types of pulse loads,the motor speed overshoot is within 3%,which meets the comfort requirements of the treadmill.The pulse-type load dedicated AC speed controller developed in this paper can control the motor speed comfortably,it has a high cost performance and certain application prospects.At the same time,the controller adopts corresponding measures for the abnormal operation of the motor in the software and hardware design.These protective measures ensure the safety of users.