Brushless DC Motor Drive System Based On EtherCAT Bus

With the wider application of brushless DC motors,people are increasingly demanding the performance of brushless DC motors.The traditional bus type brushless DC motor drive systems are usually based on RS485 bus communication and with Hall position sensor,driving the motor through square wave voltage.The control method is simple,workable and the cost of hardware is low,but it requires the back EMF of brushless DC motor is ideal trapezoidal wave.However,the back EMF of brushless DC motor is difficult to be ideal trapezoid wave in the actual manufacturing,and the methods such as skewing stator slots and skewing rotor poles are used to reduce cogging torque make the back EMF wave close to the sine wave,causing motor driven by the square wave exist torque ripple and commutation noise in working process.At the same time,RS485 bus has the disadvantages of low utilization of bus and bad real-time performance,especially when the number of control units in industrial applications is large,the real time of communication is more unable to guarantee.EtherCAT bus communication can effectively improve the real time and reliability of brushless DC motor drive systems.These drive systems show excellent performance in motor control,such as low noise,small torque ripple,accurate positioning,speed stability and so on.Therefore,designing a reliable brushless DC motor drive system with EtherCAT communication interface is of great significance.Aiming at the design of Brushless DC motor drive system,this paper has carried out the following research:Firstly,designing the overall scheme of EtherCAT brushless DC motor drive system including the selection of EtherCAT slave controller LAN9252 chip and microprocessor STM32F103VET6 chip.Secondly,derivating the mathematical model and establishing vector control system of brushless DC motor with sine wave back EMF.At the same time,researching the principles of field oriented control(FOC)and space vector voltage modulation(SVPWM)and their applications in motor control.Thirdly,using Altium Designer 10 to design the hardware circuit,including drive and inverter circuit,current detection circuit,USB to the serial port circuit,PDI interface circuit between the EtherCAT slave controller and microprocessor,physical communication port circuit,slave station information interface circuit and so on.In addition,designing the software of drive system,including the PDI interface and CoE object dictionary,XML files,the motor control algorithm which bases on the principle of magnetic field oriented control and SVPWM,host computer debug software,these software realize the speed and position control of motor.Finally,building a simple lifting device to test the performance of the drive system,including network communication reliability tests of single and multiple units,the tests of speed,location accuracy,control signal and phase current when different power motors are running under no load and load.The tests result show that the brushless DC motor drive system in this paper can meet the design requirements.