Research Of The Hydraulic System Power Optimized Matching And Control Technique In Construction Machinery

The hydraulic system power optimized matching control technique is one of the important core techniques of modern construction machinery. It makes an indivisible organism of the modern hydraulic control theories, automatic control theories, computer technique and engine technique etc. The application of the hydraulic system power optimized matching control technique in construction machinery greatly improves some performance of the machine, such as working efficiency, energy conservation effects etc, increases the machine adaptability of various working conditions and working environment, makes the machine's operation, usage and maintenance more human, and promotes the machine's automation and intelligence level. In this article, the research is carried out on the application of the hydraulic system power optimized matching control technique in the concrete pump truck. The concrete machineries are used as a sort of construction equipments for continuously transporting the concrete, therefore the working efficiency and Economic parameter of which are one of the main performance of the whole truck. Both can make the output of engine and hydraulic system a fine matching and are very important in satisfying the customers'needs to use the truck in various working conditions: low speed, high speed, high pressure, low pressure etc. Therefore it is very meaningful to carry out a research on the concrete machinery's power control optimized technique. Meanwhile, since the hydraulic technique and control technique share so many common points, it is easy to expand the technique application and make it applicable in various construction machineries. Among the traditional designs, in the matters of hydraulic system power matching, the influence of various kinds of factor have to be taken into account, such as working conditions, impact loads, engine speed, construction of hydraulic system etc. therefore, it is hard to achieve the optimized matching of engine power output and hydraulic system in every kind of working condition and engine speed so that the machine's working efficiency becomes low, system has great caloricty and the oil consumption becomes high. This study brings advanced hydroelectric control theory, automation control technique and mechatroics technique into the design of concrete pump truck, and realizes optimized matching of the hydraulic system power. In order to realize optimized matching at different engine speed, first we should realize open loop control of the engine output through controller, speed sensor. Each kind of accelerator position has a corresponding work mode. When engine speed output is fixed, the controller will store target engine speed in each work mode. As we know, according to engine's performance data, when the exportation of hydraulic system changes, the engine speed would change correspondingly. Meanwhile the signal of engine speed will be input to the controller, after comparing with target speed, controller will adjust the output according to the deviation, automatically changes the exportation power of hydraulic system, and therefore, the engine speed would be around the target speed. We can make machine work at max power and best energy point through changing setting of target speed. When user pursues max power, the machine will work at max power point. When we expect the machine to work at the lowest energy consumption and the most economical point at definite working capacity, we can make the machine work at minimal energy point. This study uses close-loop hydraulic system, the advantage of which is the flexible switch. In the design we use hydroelectric proportion technique. When controller outputs the signal, importation electric current of relief valve is changed, therefore exportation pressure changes, the pressure functions directly at the reversal valve of main pump, the exportation displacement of main pump is in proportion to the hydraulic control reversal valve's importation pressure, and main pump's displacement will change accordingly. The concrete machines usually work at the environment of high temperature, high vibration and high particulate, the function and power supply of controller will to a large extent change with working environment. This study researches onclose-loop control system regarding engine speed as the input variable and control object, the characteristic of hardware directly affects the stability and reliability of the whole system. On the condition that the cost increase is not so evident, and the control function is ensured, this study adopts PLC technique that have already been used extensively in the construction machinery. This technique has the advantage of low price, easy programming, convenience maintenance, high reliability etc. As the PLC programmable controller with multi-output module especially designed for the construction machinery control system appears in the market, PLC becomes more and more convenient and practical. Modern PLC not only has the function of controlling various switch measure signal, but also has very strong ability of dealing analog quantity signal of mathematics calculate, data processing, motion control, and PID calculate etc. This study aims to realize close-loop control of engine speed through controller that controls the hydraulic pump's exportation displacement and through the inspection of the engine speed and finally realizes the control of the hydraulic variable pump's output power. Since the system has serious nonlinear and time behavior, it is hard to find out the accurate mathematics model through the method of automatic control theories. Meanwhile, the system still exist serious hysterics. In order to improve the system function and dynamic response speed, in this study we use the PID calculate way( Proportional-Integral-Derivative). Through collection of signals from the actual exportation of machine's speed and accelerator position potentiometer, according to the signals of speed and accelerator position potentiometer the CPU computes engine target speed, and then computes the difference of speed. The PID regulation in essence is the calculation according to the importation worth, by proportion, integral and differential calculus's function. And according to calculate way, PWM pulse signal which has certain occupy-empty is output, control iron electromagnetism's exportation moving is controlled. Proportional magnetic valve correspondingly outputs a pressure value, thus changing exportation displacement of hydraulicvariable capacity pump. PID regulate method is simple, parameter is easy to adjust and abundant experience is accumulated in the long-term application. Furthermore the software system is flexible, PID algorithm would be perfect through revision, and anticipant result which modern control theories analysis cannot achieve will be attained. This study is in essence about hydroelectric proportion speed control system. The system's static characteristic and dynamic characteristics relates to the PLC system's characteristic, but also relates to response characteristic of the hydroelectric proportioning valve, oil pump etc. Therefore, in order to analyze the system's static characteristic and dynamic characteristics, we establish the transfer function of the system. Based on this, the system is analyzed. In this study the optimized matching control technique of construction machinery hydraulic system power adopts a whole mode control system. We can adjust accelerator stepless within a certain range, setting output mode stepless, moreover the output displacement stepless velocity modulation, and could stepless match with exportation mode. Compared w ith the traditional limited mode, the control range and convenience are greatly increased. The application of research achievement in our concrete pump truck, increases its working efficiency, decreases energy consumption, lifts the automatic level and makes usage convenient. Therefore it makes our concrete pump truck much more competitive.