The Simulation Research Of Digital Electro-hydraulic Proportional Control For Loader Working Device

With the development of science technique, people are putting forward higher requirement for construction machine. Meanwhile, following up the gain ground and application of micro-electronics, information technique and computer, there is a breakthrough improvement in this field. In order to reform the maneuverability of the loader working device and to improve the level of automation, the high-speed switch valve was used as pilot valve to make up of a new type digital electro-hydraulic proportional directional valve with multiple-unit valve in this article, which accomplishes the simulation research of the working device for loader.The loader has been developed quickly in recent years, especially at the end of last century, it was impelled by the progress of communication technique. The computer administrant system which based on micro-electronics technique, assistant manipulate system of manipulator, computer dominate system of diesel engine, computer supervise system, the electronic switch system of automatic gearlever and the aptitude system of network are came into use of many fields of loader widely, these fields include design, handle, supervise, production and maintenance, which make the loader perfect, at the same time, the efficiency of production is improved sharply, the same as the automatism level .The composing of working device, the principle of hydraulic pressure system, the method of automation and the mode of work are introduced in this topic. Based the characteristic of frame work, analyze the kinematics of working device firstly, and then set up the kinematics mode and the formula of athwart answer.This topic has a brief summarize on the elementary concept and history of electro-hydraulic proportional control system, besides, the digital electro-hydraulic proportional control system which use high-speed switch valve as pilot valve and the PWM control method of pilot valve were introduced particularly. The control signal of high-speed switch valve is a PWM signal that produced by the data of computer , which drive high-speed to work after magnified by power amplifier, and it's control arithmetic was stored in the computer as a program. The press of multiple-unit valve control cavity was manipulated by high-speed switch valve, and the difference which produced by press is the impetus that drive the core of multiple-unit valve to move, this movement of core resulted in the switch and the variety of flux of the multiple-unit valve, thus control the displacement of loader working device cylinder piston. This is the control principle of digital electro-hydraulic proportional system. According to this principle, the math mode of the working device piston which controlled by valve and the transfer function between the ration that occupies space and the displacement of cylinder were set up. Besides, this topic has carried on the stable analysis to the system, which has provided the theory basis for this simulation of control system.The PID algorithm that used in this article is the universal applied algorithm in industry control, which to design the position controller of loader working device. This article introduces the principle of PID algorithm, elaborates the realized principle of computer of position type PID and increase type PID algorithm. Based on MAYLAB/SIMULINK, the simulation mode of the loader working device hydraulic system was established, following to the analysis of the simulation result and the continual adjustment of the parameter of PID controller, the controller parameter was determined finally, which carried out the design of position controller of the loader working device.There is still some over modulation on the PID position controller which can not reach the requirement of the control system. The PID and PI are compared in this topic in order to inspect the influence of KD, and the compare between PID and PD is used to inspect the influence of KI, all these compares indicated that incomplete differential PID algorithm is better than ordinary PID. The position controller are redesigned based on incomplete differential PID algorithm, and the compare result indicated that the ameliorate incomplete differential PID algorithm improve the result remarkably.The position controller of loader working device that design on incomplete differential PID algorithm has simple structure, the timeliness,static and dynamic characteristic of the system are all improved.