Research And Realization Of Control Algorithm For Electronic Controlled Hydraulic Power Steering System

The production of engineering machinery towards to large scale, microminiaturization, multi-purpose, customization and automated development, as well as the working field becomes more and more difficulty and vile, which asks steering unit up to a higher level. Traditional full hydraulic steering system needs to layout the steering wheel in the bottom of the steering, where the space is actually very small, which increases the difficulty of maintenance for steering system.Aiming at the difficulties and problems of steering system of construction machinery, a new steering system based on Steering-By-Wire Technology was proposed. Comparing with the full hydraulic steering system, it cancelled the rigid link between steering wheel and the vehicles wheel; using a small fluid to control a big one, which through employing high-speed switching valve to control flow-enlarging valve; it adopted PIDNNs as system control algorithm; it selected DSP2812as the main controlling chip and combined with the technology of sensor, which through gathering vehicle speed and steering wheel angular speed to determine the switch and PWM of high speed switch valve group. Its goal was to realize a new electronic controlled hydraulic power steering system which was suitable for construction machinery. Safety, fast, speediness, accuracy, comfort, digitalization and simple structure should be characteristic of the new ECHPS system.It presented some aspects of the new system in terms of composition, operational principles and control strategies. There was a calculation for the whole system based on a actual vehicle. Through analyzing the driving characteristics of construction machinery, it introduced a comprehensive idea which determined the pulse duty cycle of the high speed switching valve according to vehicle speed and steering wheel speed, which had been graphical and formulaic.In order to satisfy the steering characteristics had been deduced above, it selected PIDNNs as control algorithm for the system. The structure as well as deducing process of the algorithm had been given. It designed the flow charts for algorithm and compiled charts into the source code, which had been proved in the following simulation experiment. It completed the software design of control system of the whole system and gave the key points, flow chart and source code for each sub-module.The hardware circuit of the control system had been presented. It introduced the hardware structures and functions of DSP2812and designed minimum hardware system attaching schematic diagrams for that chip. Moreover, it finished the work of power drive circuit board exhibited schematic diagrams, key points and experiences while designing the board.There was a joint simulation experiment of the system that used the software of MatLAB and AMEsim, which was compared with the existing full hydraulic steering bench. The results proved that the new ECHPS system had excellent stability, follow-up characteristic and relatively quick response speed. The system with PIDNNs was three times the response speed of that without it. Through doing a comparative experiment between simulation model and existing full hydraulic steering bench, it indicated that simulation model consistent somewhat with test bench.It worked out an experiment producing PWM signal. It revealed that the compilation of the system software was correct, which could produce PWM signal with any pulse width duty factor and insert the dead time; it could change the pulse width duty factor according to the input signal. Control strategies had been achieved basically.