Research Of High Reliability BLDC Control Algorithm Using Auxiliary Sensorless Operation Method

Hydraulic pump which is responsible for providing sufficient fluid pressure and flow,plays an important role in hydraulic servo systems.Electric hydraulic pumps consist electric motor and oil pump.In our company,most electric hydraulic pumps utilize brushed DC motors,which are simple in structure and control scheme.However,due to the wear of commuters,the reliability is reduced.In contrast,Brushless DC motors are used more and more widely for their high reliability and high performance.In the dissertation,a control scheme which is mixed up of sensorless control algorithm and resolver based commutation algorithm is proposed to enhance system reliability,Reduce system reliability and make the system unstable.Brushless DC motor is widely applied in practice since its simple structure,excellent performance and good control effect.In this scheme,the motor is operated with resolver commutation,in case of resolver failure,the sensorless control is activated to continue the operation.A hardware platform is built to demonstrate the mixed control scheme.First,the basic working principal of BLDC motor is introduced,including 3-phase bridge,back-EMF generation and BEMF zero-crossing sensorless control method.An Matlab/Simulink model based on BLDC running theory is built,and a simulation of back-EMF zero-crossing detection sensorless algorithm is performed.Then the design procedure of BLDC motor controller is discussed.The controller is capable of driving 3k W BLDC motor.At last,Both BEMF zero-crossing sensorless control algorithm and resolver commutation algorithm are implemented by FPGA,and the resolver fault-detection method is experimented.The result shows that in the case of resolver fail,the motor will continue to operate under sensorless control algorithm.