The electro-hydraulic servo steering system is one of the core components of a heavy vehicle, and frequency response characteristics of this system are essential to guarantee the vehicle flexibility. However, it is difficult to establish frequency domain model directly for the frequency response characteristics analysis due to the strong nonlinearity of steering trapezoidal mechanism and hydraulic power system in electro-hydraulic servo steering system. This paper proposes a simplified linearization analysis method for the electro-hydraulic servo steering system. By variable substitution defining the load flow and load pressure, and linear fit between double tire angles and cylinder displacement, the original model is simplified to a frequency domain model. Based on this model, the essential frequency response characteristics and the effects of key parameters to electro-hydraulic servo steering system can be obtained. Through the sweep frequency response analysis, the linearized frequency domain model is compared with the nonlinear time domain model and the actual test system, respectively. As shown in Bode plots, the amplitude-frequency phase-frequency characteristic curves of models match well, which verifies linearization analysis method and linear frequency domain model. The key parameters affecting the system frequency domain characteristics are the valve flow gain, the area of cylinder rodless and rod chamber, and the linearization coefficient between the left and right tire angles and so on. The electro-hydraulic servo steering system bandwidth is only 7.38 rad/s (1.17 Hz). This research is helpful for the design and optimization of heavy vehicle dynamic steering system.

中文翻译：

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重型车辆电液伺服转向系统频域建模、分析与验证

电液伺服转向系统是重型车辆的核心部件之一，该系统的频率响应特性对于保证车辆的灵活性至关重要。然而，由于电液伺服转向系统中转向梯形机构和液压动力系统的非线性强，很难直接建立频域模型进行频率响应特性分析。本文提出了一种电液伺服转向系统的简化线性化分析方法。通过变量代换定义载荷流量和载荷压力，以及双轮胎角度和气缸位移之间的线性拟合，将原始模型简化为频域模型。基于这个模型，可以获得电液伺服转向系统的基本频率响应特性和关键参数的影响。通过扫频响应分析，将线性化频域模型分别与非线性时域模型和实际测试系统进行比较。如波特图所示，模型的幅频相频特性曲线匹配良好，验证了线性化分析方法和线性频域模型。影响系统频域特性的关键参数有气门流量增益、气缸无杆和有杆室的面积、左右轮胎角之间的线性化系数等。电液伺服转向系统带宽仅为 7.38 rad/s (1.17 Hz)。