With more axles for multi-axle vehicles, conventional steering trapeziums are unable to let every tire fit Ackermann\nsteering which cause tire wear increasingly more serious. To alleviate this problem, an original mechanic-hydraulic servo\nsteering system with a controllable tie rod is designed. By controlling the angle of one wheel and the length of tie rod,\nboth wheels can be controlled as per default trajectory which implemented Ackermann steering. This article utilized\nmechanic-hydraulic servo feedback to design a mechanic-hydraulic servo valve which controlled the tie rod accurately. It\nensured dynamic characteristics of steering wheels and driving force. To understand inherent characteristics of system,\nthe mathematical model was established. The transfer function was derived, and this high-order system was reduced by\nRouth approximation. Analyzed natural frequency and the main parameter (the gain coefficient of displacement) which\ninfluences the dynamic characteristics had been found out. Analysis shows that the lower the gain coefficient, the higher\nthe speed of response. Moreover, the accurate simulation model of servo system is built on AMESim. Contrasting five\ngroups of simulation results, it is obtained that the influence rule of the gain coefficient is consistent with theoretical\nanalysis. This research provides a useful reference for future nonlinear control.
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