Velocity Sensorless Estimation Of Stepper Motor Base On Robust Filter

The two-phase hybrid stepper motor and micro-step drive system are low-cost position control actuators in digital control system.In the system composed of bus,encoder is often used to detect the velocity of the stepper drive system.Because of the defects of the encoder,the research on the velocity estimation technology of stepper without sensor has practical significance.The scheme of using Extended Kalman Filter(EKF)as observer is the mainstream of stepper sensorless system.However,stepper motor has the characteristics of strong nonlinearity,inductance and other parameters changing dramatically,so it needs robust filter scheme.In this paper,aiming at the subdivided drive system of stepper motor,a set of velocity estimation scheme using the Extended H_∞Filter(EHF)as an observer is proposed to enhance the robustness of the system parameters.This paper is divided into three parts:Firstly,the mathematical model of two-phase hybrid stepping motor and its micro-step drive system is established.The simplest model and non-linear model based on magnetic network are derived,and the origin and expression of non-linear phase inductance of motor are emphasized.Combined with the current vector,the simplest model of stepper motor is derived,which regards the inductance nonlinearity as the parameter uncertainty,and the energy boundedness of the uncertainty is analyzed.Then,starting from the linear Kalman filter and the H_∞filter,the expressions of EKF and EHF as the observers of the stepper motor drive system are derived,and we compare the differences between EKF and EHF in the nonlinear system,then the conclusion that EHF is more suitable for the stepper system and the expression of the key parameters are obtained.Finally,in the simulation part,the stepper motor and its micro-step drive system are constructed under the MATLAB/Simulink,and we compare the performance and robustness of the velocity estimation module based on EKF and EHF.In the experiment part,on the platform of STF series open-loop stepping motor driver from MOONS’,with CANopen bus,the EHF observer is used to estimate the velocity of stepper motor on the PC,which proves the feasibility of the scheme.