Research And Realization Of Hydraulic Steering By-Wire System Road Sense Based On Fuzzy Pid Control

According to the practical application of existing agricultural vehicles, this paper combined the advantages of steering by wire and full hydraulic steering technology, and designed a hydraulic steering by-wire system, which contained rational space layout and simple structure. In addition, the paper studied the control strategies of road sense. The hydraulic steering by-wire system consists of steering wheel module, ECU module and steering module. Comparing with the full hydraulic steering system, the hydraulic steering by-wire system cancelled the rigid link between steering wheel and the vehicles wheel; it adopted fuzzy PID as control strategy as road sense feedback control; the system used DSP2812as the main chip of ECU and combined the technology of sensors, which determined PWM of the motor control voltage by collecting the signal value of oil pressure sensor and steering wheel torque sensor to achieve the feedback control of road sense. Based on the characteristics of hydraulic steering by-wire system, the paper has done the following work.Frist, the paper analyzed the advantages and disadvantages of the existing full hydraulic steering system, and proposed the design principles of hydraulic steering by-wire system which used in agricultural vehicles. The steering wheel module, steering module and the ECU module of this system were designed, and also the composition of the three parts and the system’s working principles were presented in detail. The paper put emphasis on the closed-loop control of front wheel angle and road sense motor feedback.Second, the common simulated control strategies of road sense were analyed, and the dynamic modeling method was selected. Furthermore, the paper analyzed the steering theoretical of wheeled vehicles and established the mathematical model of back to the positive torque and the model and the motor. Later, the paper designed the details of fuzzy PID controller, whose input was the error of the desired motor torque and the actual motor torque, and then determined its membership functions and control rules.Third, the paper completed the electronic control parts of hydraulic steering by-wire system road sense feedback control, including the circuit design and software design of the control system based on TMS320F2812. The circuit design implemented the signal conditioning of sensors and actuators, and was matched with the power distribution and the interface module of power supply of the TMS320F2812. The design of software achieved the functions of the sensor signal acquisition and PWM signal transmitter by using A/D acquisition and PWM signal transmitter modules in TMS320F2812. The fuzzy PID control algorithm used in the main program for signal processing, and the software realized closed-loop control of the system.Finally, based on the data of the JS-504tractor, a tractor model was built in the MATLAB/SimMechanics, and the performance of hydraulic steering by-wire system was simulated. The results showed that fuzzy PID control strategy of this system achieved a good road sense closed-loop control, and the ideal characteristics of road sense can be achieved. The paper also raised the design of hydraulic steering by-wire system bench, which was based on the hydraulic experimental platform, motors and various sensors. As a result, the road sense feedback control system was completed. The bench initially realized hydraulic steering by-wire system road sense based on fuzzy PID control, and obtained the relevant data and graphics signals to verify the correctness of the design.