Resolver-to-Digital Conversion Based On Modified Angle Tracking Observer

With global climate change and fossil energy security drawing ever more public attention,electric vehicles,as an alternative to fuel vehicles,are increasingly favored by governments and car manufacturers.Due to the high power density and good speed regulation performance,permanent magnet synchronous motors are widely used in power drive systems for electric vehicles.Modern motor control systems require precise rotor position to implement motor control algorithms.Among the commonly used position sensors,the resolver has strong anti-interference ability,and is suitable for harsh environment,hence the best choice for electric vehicles.The signals output by the resolver cannot be directly utilized by motor controller unless they are processed by resolver-to-digital conversion.The existing resolver-todigital conversion generally adopts the phase-locked-loop-based conventional type-II angle tracking observer.Aiming at the problem that the conventional type-II angle tracking observer incurs a steady-state error in the measured rotor position when the motor accelerates,this paper proposes two modified angle tracking observers to improve the accuracy of resolver-to-digital conversion.The first modified angle tracking observer utilizes the idea of feedforward compensation.The output signals of the resolver are used to calculate the motor's speed and thus compensate for the speed measured by the angle tracking observer.The second uses the measured speed to obtain a signal proportional to the motor's acceleration and thus compensate for the position error.It can be theoretically proved that both modified angle tracking observers can eliminate the rotor position steady-state error caused by motor acceleration.In addition,according to analysis of the effect of varying parameters on the two modified angle tracking observers' bandwidths,this paper summarizes practical tuning guidelines for both of them respectively.On permanent magnet synchronous motor position measurement experimental platform with a resolver installed,motor acceleration experiments are conducted to compare the conventional type-II angle tracking observer and either of the modified angle tracking observers regarding their performance.According to experimental results,either modified angle tracking observer is able to eliminate the steady-state position error and accurately track the rotor position of an accelerating motor.