The Digital Electro-hydraulic Proportional System Used In The Distribution Of The Auto Brake Pressure

With the development of auto industry, people's requisition forcomfortableness, security , dependability of the automobile is higher and higher.Among them, the applying the brake of the automobile has got more and moreconcerns as one of the main performance of the automobile. But at present , forassemble ordinary automobile of brake, it is unavoidable for the wheel to slipextremely to embrace when applying the brake. Theory and practice prove atstraight road , if the front wheel is embraced and extremely slipped and movedfirst , the automobile is apt to lose the ability of changing direction; Rear wheelembrace very much extremely apt to appear the side slip first, cause the vehicle tolose stationarity. It is only in front and rear axle embrace at the same timeextremely it tow slippery situation avoid not turning to not working and back shaftside slip. Only the front and rear axle embrace at the same time could the front andrear wheel brake make power assign according to I line rule, the relation of I lineABS is with its such advantages as remarkable improvement of efficiencyand steady driving performance, etc. to being popularized rapidly in theautomobile. But in the previous one applies the brake, ABS system has not beenmediated to applying the brake of the vehicle, so in order to make vehicledistribute the power on the intelligent reasonable regulation according to a ideal Iline rule, the subject utilize electric liquid proportion control technology axle makepower go on automatically to automobile, and make power digital electric liquidproportion assign system , making automobile can distribute the power accordingto ideal distribution curve.This subject adopts the pulse width digital high-speed switch valve and formsthe proportion of digital electric liquid control system. Because the valve structureof proportion of the electric liquid is complicated, require the liquid have goodpurity, price comparatively high, and professional maintenance, bad adaptability topoor vehicle working environment, so there is certain restriction in applying it toengineering vehicles. Digital electro-hydraulic proportion control system has manymerits such as excellent repetitiveness, small, cheap, simple structure, goodflexibility to pollution, convenient interface with computer, etc., so there are wideapplication prospects of it. The high-speed switch valve works on two states: onand off. Ordinary spiral shell pipeline can control it, so the expensive proportionelectro-magnet such as the proportion valve can be saved.The control principle of the whole system is: the sensor gather the pressuresignal and give it to the control module, after computer operation in the controlmodule, produce the PWM signal in need corresponding to the law, export afterthe power amplification circuit on the automatically controlled module isamplified, drive the high-speed switch to work.. When the high-speed switch valveis powered, the controlling cavity connects the oil source and the oil enterer thecontrolled cavity, so the controlling cavity is rising. But when the high-speedswitch valve is out of power, the controlled cavity connect the oil tank, and the oilis flow outwards, the pressure of the controlled cavity is reducing. When inputcontinuous PWM signals, we can see the average cavity pressure will round acertain invariable value. While when the width of the PWM signal pulse changed,the cavity pressure will be changed too. So we can control the automotivefront-rear shaft's brake force distribution device by tuning up the width of thePWM signal that drives the high-speed switch valve.This text divides seven chapters altogether.Chapter one analyzed the current research situation and development trendthat the domestic and international automobile, have carried on comparativeanalysis in assembling the automobile of the ordinary brake and automobile of theequipment ABS system. Brief to introduce the concept of electric liquid proportioncontrol, prove its research meaning and explain what this text want to study.Chapter two analyze automobile when applying the brake strength situationand make power assign the law at first. To have regular ratio front and rear brakemake to apply the brake department's characteristic has gone on research power.Have recommended the composition of the proportion of digital electric liquid andbasic principle. Regard this as the theoretical foundation of the control system ofthis text.Chapter three carried on research to the high-speed switch valve. Itsummarizes various kinds of the method to control the valve and productionmethod of the signal of the PWM pulse width, and then make a analyze accordingto PWM pulse width signal. Through the above, it can know that it is feasible tomake the high-speed switch valve as the executive body of this system.Chapter four make a characteristic study about the high-speed switch valveand he influence of it to the system. The main research contents include thefollowing several respect. In the study of characteristic of the component, it has setup the mathematics model of the valve core movement of high-speed switch atfirst, and has analyzed the switch characteristic mechanism of the high-speedswitch valve. In systematic research, focus on studying the impact on hydraulicpressure system of the high-speed switch valve, have analyzed mainly thehigh-speed switch valve controls the jar characteristic of the hydraulic pressure.Through modeling and emulation in system, it made a reliable basis to considerhydraulic pressure systematic influence of dynamic characteristic in the study ofcontrol logic design research.Chapter five confirmed the design plan of hardware of the automaticallycontrolled unit in order to meet the demand of the location of each worker of thehydraulic pressure system, and make the exhaustive narration about each hardwareact. The hardware circuit is put up according to circuit principle picture, includingsignal amplify circuit, power vary voltage circuit and ADC0809 circuit boardcircuit, and write the software procedure, from the whole structure of the softwaresystem to the concrete flow chart of the important module, have carried ondetailed analysis and explanation.Have fully considered the dependability and stability of the system inautomobile reality in the design of the automatically controlled module. In order toreach the goal of the above, adopt the design methods of level and module at thetime of the design, make function thinning and reduce the complexity designed.The level is designed and used in the systematic hardware level design. Themodule is designed and used in the software design of the system, and it debugsconvenient advantages.Chapter six is the test of the control system. Through the test we can knowthe device has realized the main function, and has realized the ideal I line rule. In...