Research On The Control System Of Stepper Motor In Automatic Handheld Syringe

With the progress of science and technology,automatic equipment is more and more applied to industry and agricultural fields.Hand-held electric syringe will take place of manual syringe in the field of medical equipment for livestock.Stepper motor is suitable for automatic syringe as a electric actuator,because it has high operation precision,no accumulative error in normal operation,small volume,light weight and it can be conveniently controlled.But stepper motor has problems of over shooting,stepping out under the conventional open loop control strategy,what's more,full closed loop stepper motor with high-precision significantly increase the size and weight of the system.So choosing the right motor control strategy is vital for the design of hand-held electric syringe.This article is aimed to design a suitable stepper motor control system with higher accuracy compared to open loop control strategy,smaller size and lighter weight compared to full closed loop,so that it can fit high accuracy handheld devices.In order to find a suitable stepper motor control strategy,I read a lot of literature information from domestic and foreign database,and learnt more about classes and control strategies of the stepper motors.Then chose hybrid stepping motor control system based on current closed loop as research object in this thesis.Based on internal structure and mathematic model of stepper motor,thesis analyzed the reasons of low frequency oscillation and drawback of dynamic performance.Considered the way to optimize the low frequency oscillation and dynamic performance of stepper motor in the H bridge drive circuit.Then come up with the method two ways to achieve the goal,including current subdivision drive to optimize low frequency oscillation and alternate current damping to improve the dynamic performance.In order to verify the effect of the optimization mentioned in previous paragraph,this thesis designed a stepper motor drive control system with hardware and software based on AVR32 Single Chip Microcomputer,and realized current subdivision and the alternate current damping arithmetic.Finally,experiment tests were carried to verify the effectiveness of the design in this thesis based on the control system designed before.And the results showed that the new control system truly optimized the low frequency oscillation and improved the dynamic performance of stepper motors,which prove the optimization is feasible.