Speed Sensorless Control Of Induction Motor Based On SMO And MRAS In Electric Vehicles

Under the energy crisis and environmental pollution background,as an efficient,energy saving,environmental protection and new tape vehicle.Electric vehicle has been paid to more and more attentions.Academic research is also gradually in depth.Motor is an important part of electric vehicle power mechanism,the performance of the motor and its control system plays an important role in performance of the whole vehicle.Due to its simple and reliable structure,low cost of manufacture and maintenance,and wide range of speed regulation,induction motor(IM)plays a leading role in the market of electric vehicles.The vector control technology makes IM to be comparable to the performance of the direct current motor,vector control induction drive system is still widely used in the mainstream speed control scheme.For the consideration of the performance and the technical difficulty,most of the current electric vehicles are equipped with rotating transformer for detecting motor speed.However,the speed sensorless control technology is still one of the important technical requirements of electric vehicle drive system.On the one hand,the speed sensorless control can be used as an alternative to the abnormal speed detection,and increase the redundancy of the system to improve the reliability of the vehicle.On the other hand,with the improvement of the performance of the speed sensorless,it is possible to completely avoid the installation of the rotating transformer,improve the reliability of the drive system and reduce the cost of the controller.This paper focuses on the rotor field oriented vector control technology study.Firstly,the direct field oriented and indirect field oriented vector control of two typical schemes are discussed.The dependence of performance of direct field orientation vector control system on rotor flux and the parameter sensitivity to rotor time constant of indirect field orientation is analyzed.Secondly,the paper puts forward on the advantages,disadvantages and applicability of the direct calculation method,the model reference adaptive system(MRAS),the sliding mode observer(SMO)and the adaptive observer method.In practical application,usually used in combination to achieve better effect.Finally,this paper presents a sensorless vector control algorithm for IM based on sliding mode adaptive hybrid observer.an intermediate current variable is defined to simplify the Γ-type representation of IM,and design a SMO with the quantity as state variable.From the equations about theflux and current,the state equations about the equivalent control components of the SMO are derived.Further,using the state equation as adjustable mode and the actual values obtained in SMO as the reference mode,a MRAS is designed to estimate the IM speed.At the same time,the paper comprises the direct calculation of the speed from the equivalent control components of SMO into the speed adaptation mechanism of MRAS through feed-forward operation.As a result,not only the convergence rate and the dynamic performance are improved,but also the disadvantage of the parameter sensitivity of the direct calculation is overcome.As shown by the simulation and experiments,the speed observation scheme,proposed in this paper,exhibits better stable and dynamic performance and parameter robustness.