Precise Control Of Sprayer Pressure Under Strong Load Disturbances

In recent years,the scale of the coating equipment market continues to increase,highpressure airless sprayer also penetrated into the major manufacturing sectors,the rapid growth of market demand.However,some of the products developed independently since the introduction of high pressure airless sprayer equipment in China in the last century have minor defects in pressure control,and most of the domestic high-end sprayer market is occupied by imported products,and sprayer pressure control technology is in urgent need of localisation.Domestic products use the traditional double closed-loop motor control strategy,it is difficult to cope with the inherent mechanical characteristics of the sprayer caused by the cycle of changing load characteristics,resulting in large output pressure pulsation,the spraying effect is not ideal.The design of high-pressure airless sprayer control system,accurate control of sprayer output pressure has important practical significance for China’s coating equipment market.In this paper,a high pressure airless sprayer driven by a permanent magnet synchronous motor(PMSM)is used as the research object.Based on the study of the control scheme of the permanent magnet synchronous motor and the mechanical load characteristics of the sprayer,a three-closed-loop vector control strategy for pressure,speed and current with a high-resolution Hall position information estimation algorithm is proposed.This improves the accuracy of the static pressure control of the sprayer and reduces the power consumption of the control system.Firstly,a detailed analysis of the control scheme of the PM synchronous motor of the sprayer is carried out,a mathematical model of the PM synchronous motor in different coordinate systems is established and the vector control is determined by comparison.Secondly,a sine wave control strategy based on a high-resolution position estimation algorithm with Hall position sensors is designed and simulated to verify its feasibility by optimising for the conventional low-resolution rotor position information.The mechanical structure and load characteristics of the sprayer are analysed,its kinematic equations and the mathematical model of flow pulsation are established,and the reasons for the existence of periodic pressure pulsation in the sprayer are explained.Finally,a negative pressure feedback control loop for the sprayer is designed to collect the output pressure of the sprayer in real time.The hardware circuitry and software algorithms of the sprayer control system are then designed to propose an accurate control strategy for sprayer pressure based on a triple closed-loop control method for pressure,speed and current,and a bench and sprayer prototype experimental platform is built.The experimental results verify the feasibility of the triple closed-loop vector control algorithm for high-resolution rotor position estimation and demonstrate that the algorithm designed in this paper can effectively improve the pressure control effect of the high-pressure airless sprayer and reduce output pressure errors and control system losses compared to conventional control methods.