| Unmanned aerial vehicles(UAV)have been widely used in military and civil fields because of their high efficiency and convenience.Sensorless control technology can not only reduce the cost and enhance the reliability,but also improve the driving performance of permanent magnet synchronous motor(PMSM)used in UAV.Although sliding mode observer method is an effective sensorless control technology,this method can cause problems such as chattering and phase lag.In this thesis,PMSM used in UAV power system was employed to study the sliding mode observer method that was based on flux linkage observation.Firstly,based on the mathematical model of motor and propeller load,the principle of variable structure control with sliding mode was analyzed.According to the secondorder state equation of PMSM in static coordinate system,the traditional sliding mode observer was constructed to observe the counter potential.To realize sensorless control of UAV power system,rotor position was extracted from inverse potential by arctangent function.MATLAB/Simulink software was also used to verify the control effect of propeller-loaded running,and the simulation results proved the correct of the established model.Then,a sliding mode observer based on flux linkage observation was studied to solve the problem of inverse potential observation in traditional sliding mode observer.The fourth order state equation of the motor was constructed by selecting current and flux as state variables,and the current error was chosen as sliding mode surface.The sliding mode observer was constructed to realize the observation of flux,and the stability of the observer was testified according to Lyapunov theorem.Based on the observation value of flux linkage,the rotor position was calculated using phase-locked loop,which avoids the introduction of arctangent function and differential operation and improves the accuracy of position estimation.Since the slide-mode control signal was filtered by the flux equation,the use of low-pass filter was avoided and the obtained position signal was smoother,without problems including amplitude attenuation and phase lag.The sliding mode observer was based on the fourth-order state equation of the motor,in which the resistance,inductance and speed have some influence on the observation results.This thesis analyzed the influence of stator resistance,inductance and rotation speed on the observation effect of the observer.According to the observation error expression of the observer and the phase relation between the current and the flux,the amplitude and phase relation between the observed value and the actual value under the influence of parameter error were obtained.Besides,the starting strategy of the motor was designed,and the simulation result of the observed value under the influence of error was given.Finally,a sensorless control experiment platform was built based on E5000-M10 UAV power system motor and completed the system hardware design and software compilation.Theoretical analysis and simulation results were simultaneously conducted.The experimental results verified the position estimation effect of the observer in UAVs,and the experimental results of parameter error were consistent with the theoretical analysis. |
