Modeling, simulation, and experimental validation of electro-hydraulic power steering system in multi-axle vehicles

Abstract

An accurate electro-hydraulic power steering system (EHPSS) model is essential to analyze dynamic steering performance and advanced nonlinear control. The main obstacle to establish an accurate model is the complex structure, including steering mechanism, valve controlled dual hydraulic-actuator, and heavy duty tires. This paper constructs a suitable model incorporating these parts, based on a Lagrange equation describing the steering trapezoid mechanism and dual cylinder hydraulic dynamics, regarding steering resisting moment as an external load. A simplified tire model is used to represent the tire basic steering load characteristics. Due to the complexity of the kinematic relationship in the model, several expressions are fitted using back propagation neural networks to significantly reduce calculation difficulty. Experimental measurements and simulation using Matlab/Simulink and experiment are realized for the case of in situ steering, and the results validate the proposed model accuracy. Thus, the proposed model is suitable to analyze the system and design advanced controllers.

Frequency domain modeling, analysis and verification of electro-hydraulic servo steering system for heavy vehicles

“…EHSSS consists of two parts, the mechanical system and the hydraulic system, as shown in Figure 1. 15 The mechanical system is composed of trapezoidal mechanism (including left and right steering knuckle arms, tie rod and axle) and left and right tires. The hydraulic system is composed of servo solenoid valve, double power cylinders, angle sensor and other components.…”

“…The mechanical structure diagram of steering axle is shown in Figure 2. 15 Set the angle of the right tire around the king pin as β , and the left side as α . Taking the right angle as the independent variable, the relationship between the angles of the left and right tires can be obtained by the kinematic relationship, as shown in equation (1)…”

“…The modeling process of the the dynamic model of EHSSS has been described in detail in the previous paper, 15 and the specific derivation process is shown in Appendix 2. This paper focuses on establishing the frequency domain model based on EHSSS dynamics model.…”

“…The hydraulic model transfer function can be obtained by the transfer function of the cylinder flow and pressure (15) and the transfer function of the valve flow equation (18), that is, the relationship between the load pressure and the right angle…”

“…In addition, according to the Lagrange dynamic equation, Du et al 15 established a nonlinear time domain model of EHSSS, including steering mechanism and hydraulic system, which provides a good reference for modeling and analysis of EHSSS. But his research merely analyzes the tracking problem of steering signal in time domain, and does not include the frequency response analysis.…”