| With the dramatically development of vehicle electronic control technology, steer-by-Wire technology as a new-type electronic control technology which adapts to the method of controlling by signal instead of by mechanical connection between steering wheel and vehicle wheel, is increasingly being progressed and applied in vehicle. In this paper, the author designed a fully new type of tractor hydraulic steering by-Wire system based on the combination between the advantages of steer-by-Wire technology and full hydraulic steering technology. The system not only simplified steering system structure, but possessed strong power-output of hydraulic system, which resulted in more accurate, stable and flexible steering operation.Hydraulic steering by-Wire system was supposed to possess not only better steering characteristics of the traditional steering system but capability of accurately steering under the driver's operation, furthermore, stress state and movement of vehicle wheels and total vehicle, i.e. road feeling, as a feedback should be transmitted to driver in this system.This article conducted the following research based on study of road feeling and characteristics of hydraulic steering by-Wire system:Firstly, the mechanical designs of hydraulic steering by-Wire system were conducted, which incorporated steering wheel model, steering model and ECU model of road feeling system, especially choose and matching of hardware of steering model, and introduce system structure and operating principle by combination of design regulation.Secondly, based on the steering cylinder piston rod force and the tractor speed, road feeling characteristics of hydraulic steering by-Wire system were analyzed. By comparing and concluding the common road feeling characteristics curves, the typical road feeling characteristics were introduced, furthermore, the relationships among steering road feeling, steering cylinder pressure and vehicle velocity, the specific procedures included:(1)obtain the relations between different velocity and the maximum force of steering cylinder piston rod by tractor full-test, (2)obtain the maximum road feeling value under the condition of relative velocity by computing and empirical analysis, afterwards fit relationships between the gradient of characteristic curve and vehicle velocity, (3) finally plot typical three-dimensional curve of road feeling characteristics. The results show that, the designed characteristics of road feeling could coordinate contradiction between portability and road feeling of steering system.Thirdly, road feeling control strategy of hydraulic steering by-Wire system was analyzed and researched in this section and a new double-closed loop road feeling control system was purposed. By analyzing the current control algorithm advantages, PID control algorithm was chose to apply in this control system. After then, the double-closed loop system was established based on the operating principle of hydraulic steering by-Wire system, and analysis of simulation of road feeling control system were conducted. The results show that, PID controller has better adaptability for road control system, the designed system has better following performance and stability, and could also control road feeling system of tractor effectively.Finally, the author finished the design of hydraulic steering by-Wire system, established test bench of total system and achieved acquisition and calibration of sensor signal and simulation of road feeling on bench. Results show that, this hydraulic steering by-Wire system could effectively achieve feedback function of road feeling. |
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