Research On The Remote Brake System Of Off-road Vehicle Based On Quantitative Feedback Theory

Since the new century,the development of construction vehicles entering a new period,changes in operating conditions requires vehicles have higher off-road performance, better reliability and security. Because its good passing ability in complex road,off-road vehicles become a very important vehicle in the field of modern construction machinery.Braking performance is a very important indicator to measure the quality of vehicles,and good braking performance is an important guarantee for safe driving.In China earlier engineering machinery vehicle's braking system is mainly used pneumatic braking system or air-over-hydraulic brake system,and the studies of hydraulic-style off-road vehicles was relatively small.In recent years,with the development of hydraulic brake system and control technique,full hydraulic brake system is widely used in the field of construction machinery,there are many advantages of the brake system,such as high brake pressure,produce large brake torque,brake sensitive and easy to achieve electronic control.Hydraulic system is a nonlinear time-varying system which itself and the parameters change.The nonlinear of system including the nonlinear of valve hole flow equation,the difference between forward and backward characteristics of the movement of the asymmetric piston cylinder,the friction nonlinear of mechanical structure and other factors;the uncertainty of parameters including the wear of hydraulic components,fluid bulk modulus,external load and other factors.So how to determine the mathematical model of the hydraulic system and control it to achieve a better performance become an urgent problem for researchers in recent years.Therefore,with the funding of national"863"Nature Fund,he author studies about a new complex terrain-oriented environment travelling mechanism,which articulated body with two degrees of freedom.This two degree-of-freedom off-road vehicle has many advantages,such as outstanding terrain adaptiveness,high maneuverability,strong obstacle crossing and so on.Based on the mechanical structure,researchers do some corresponding technical design and improvement,introduces the wireless remote control technology and the electro-hydraulic proportional control technology,and make it become a remote control vehicle,let control officers to complete a variety of control actions outside the cab.In this paper has designed an off-road vehicle remote control system and carried on walks and the performance experiment.The experiment proved that remote control systems can complete off-road vehicle's pilotless function.Based on the analysis the author get the mathematical model of off-road vehicle hydraulic brake system,carried on the simulation and obtained hydraulic system's performance curve in the AMESim software.A new control theory--Quantitative feedback theory(QFT) be proposed for the nonlinear of the system.Quantitative feedback theory was gradually accepted and applied by many researchers because It can ensure the system has good stability and robust performance.Adding the controller G and the Pre-filter F,that desgin by QFT theory,in the system can make the whole closed-loop system be stable,and has the corresponding request robust performance.In this paper,the author design a controller by QFT,and greated a control model of the braking system in Simulink,then based on the S-Function function of AMESim to achieve co-simulation with AEMSim and Simulink.With the unique advantages of the two softwares in the field of hydraulic and control,Co-simulation can be closer to the actual system and precise achieve the target of control.After the confirmation,compared the QFT controller with the traditional PID controller,the QFT system has the quicker speed of response,and has the low amplitude error,and the system can faster stable arrive at the control objective.So using the QFT to design a controller is more sophisticated than use traditional methods.