Research On Control Strategy Of Lifting System Of Vending Machine

With the development of intelligence,vending machines began to be popularized in China.This paper studies the lifting system of a new vending machine.Due to the design of the internal structure of the vending machine and the higher requirements of the internal manipulator of the lifting system for position control compared with other vending machines,it is necessary to design a higher performance control strategy for the lifting system to meet the requirements of no position overshoot,smaller error,faster speed,weaker vibration and lower cost.Based on the comprehensive analysis of the specific requirements of the lifting system,the DC motor is used as the driving motor of the vending machine lifting system,which saves the cost compared with other motors.For the DC motor position control system of the lifting system,it should not only meet the requirements of no position overshoot,but also have accurate and fast dynamic response.The traditional three closed-loop DC motor control system sacrifices the dynamic performance of the system in order to meet the requirement of no position overshoot.In order to improve the accuracy and speed of the control system,a differential negative feedback is added on the basis of the traditional three closed-loop system.By predicting the position change trend,the overshoot is restrained,the speed of the system dynamic response is guaranteed,and the anti load disturbance ability is improved.Under the differential negative feedback without overshoot,the feedforward compensation link is introduced to further obtain higher tracking performance and accuracy.Through simulation analysis,it is proved that the strategy meets the characteristics of no overshoot,fast response,anti load disturbance and high-performance tracking,and can improve the performance of the lifting and receiving device of the vending machine.In order to reduce the impact of sudden change in acceleration during the operation of the lifting system on the machine,resulting in jitter and speed overshoot,affecting the accuracy of movement.S-type acceleration and deceleration control is designed during the movement of the lifting system to design smooth and accurate speed planning for the lifting motor.Based on the S-shaped speed curve of the lifting system and combined with the operation of the lifting system,the optimal time planning problem of the S-shaped speed curve of the lifting system is transformed into a nonlinear programming problem.Through the analysis of the solution results,the S-shaped speed curve is divided into three types,and the S-shaped speed curve planning algorithm is formed.In the simulation,the effectiveness of the planning is verified,and the position output of the S-curve is taken as the position given.Combined with the DC motor control simulation of feedforward plus differential negative feedback,it is proved that the S-type acceleration and deceleration control can suppress the sudden change of acceleration,and the performance of the system tracking S-type acceleration and deceleration can improve the accuracy of the system and reduce the mechanical impact and vibration.Finally,experiments show that this control strategy can meet the requirements of no position overshoot,smaller error,faster speed,weaker vibration and lower cost.It meets the requirements of the lifting system of the vending machine.