Feedback Control of Injection Rate of the Injection Molding Machine Based on PID Improved by Unsaturated Integral

An Yang,Hongwei Zhou,Jianping Cai,Tianlong Han,Congrong Zhao,Weigang Guo

doi:10.1155/2021/9960021

Abstract

In conventional proportional–integral–derivative (PID) control, the integral term occupies a significant amount of controller memory, which prolongs the calculation time. The integral term easily leads to overshooting and oscillation, while the derivative term reduces the controller's anti-interference ability. In view of these problems, a PID expression with a recurrence relationship was derived, and the integral and differential terms of the conventional PID model were improved using an unsaturated integral and passivation differential to achieve a good control effect. Then, the improved PID was applied to the injection speed control of an injection molding machine, which is usually controlled using conventional PID control that featured difficulty in mathematical modeling, a nonlinear relationship between the input and the output, and high system complexity. Taking an injection molding machine as the control object, the transfer function of the injection system was constructed. Then, the improved PID was simulated using Matlab/Simulink. Lastly, the improved PID was verified using experiments. The simulation and the experimental results showed that the control model had a rapid response, no overshoot, and a high precision.

Highlights

To make the parameters in the controlled object behave in an ideal way, it is necessary to use corresponding control methods, such as feedforward control [1], proportionalintegral-derivative (PID) control [2, 3], robust control [4, 5], adaptive control [6, 7], and compound control [8, 9]
In conventional PID control, the integral term occupies excessive memory for the controller, which results in a series of problems, such as overshoot and oscillation being caused by the integral term, as well as the decrease in the anti-interference ability of the controller caused by the differential term
Traditional PID control is still the most commonly used control strategy in actual production for injection speed control. erefore, this paper studies the highorder system model of injection speed, based on the analysis of the shortcomings of traditional PID controllers: slow response speed, large overshoot, poor robustness, and weak anti-interference ability. rough the modification of the integration and differentiation term of traditional PID, the improved PID has the advantages of rapid response, strong anti-interference ability, small overshoot, and good robustness

Summary

Introduction

To make the parameters in the controlled object behave in an ideal way, it is necessary to use corresponding control methods, such as feedforward control [1], proportionalintegral-derivative (PID) control [2, 3], robust control [4, 5], adaptive control [6, 7], and compound control [8, 9]. Feedforward control is a type of openloop control It uses a hysteresis model, which is easy to implement and does not require a sensor. PID control technology is advanced, and it does not require an accurate model of a controlled object It features easy parameter tuning, a simple algorithm, and good stability. Erefore, this paper studies the highorder system model of injection speed, based on the analysis of the shortcomings of traditional PID controllers: slow response speed, large overshoot, poor robustness, and weak anti-interference ability. Rough the modification of the integration and differentiation term of traditional PID, the improved PID has the advantages of rapid response, strong anti-interference ability, small overshoot, and good robustness Traditional PID control is still the most commonly used control strategy in actual production for injection speed control. erefore, this paper studies the highorder system model of injection speed, based on the analysis of the shortcomings of traditional PID controllers: slow response speed, large overshoot, poor robustness, and weak anti-interference ability. rough the modification of the integration and differentiation term of traditional PID, the improved PID has the advantages of rapid response, strong anti-interference ability, small overshoot, and good robustness

The Problem of Injection Speed Control of Injection Molding Machine

Improvement of the PID Controller

Mathematical Model of the Injection System of the Injection Molding Machine

Conclusions