Robuste Zwei-Freiheitsgrade Linear Quadratisch Gaußsche Positions-regelung für den Vorderachsaktuator eines Steer-by-Wire Systems

Abstract

The Steer-by-Wire (SbW) system is a key technology for highly automated driving. For automated lateral vehicle guidance, the precise position control of the SbW Front Axle Actuator is an essential prerequisite. This contribution presents the modeling, control design, nominal performance, and stability analysis as well as the robustness analysis of the position control for the SbW Front Axle Actuator. Based on a nonlinear model of the plant a simplified linear system model is derived. This model yields the basis for the design of a Two-Degrees of Freedom Linear Quadratic Gaussian Control (2DOF LQG control), which allows an independent design of the command and the disturbance response. Besides an evaluation of the nominal control behavior, μ-analysis is applied to assess the robustness of performance and stability. Finally, real vehicle tests for different driving maneuvers are presented to verify simulation results.

Development and Analysis of a Detail Model for Steer-by-Wire Systems

“…The feedback actuator is also called SFU motor and is used to generate a desired steering feel for the driver. Both the steering wheel and the SFU motor are connected by a torsion bar [6]. The torsion bar is modeled by the stiffness c TB and the damping constant b TB (see Fig.…”

“…The frequency response can be used to show the influence of a variation of individual parameters on the characteristics of the SRU. For example, the first eigenfrequency at about 150 rad/s (24 Hz) corresponding to the most dominant eigenvalue pair can be determined very well by the equation ω 0 ≈ c res J res (6) with…”

“…Since the viscoelastic wheel attachments usually have a much lower stiffness than the remaining viscoelastic elements of the SRU (c RW ≪ c MR ), the dominant behavior of the SRU is thus determined by the parameters of the viscoelastic wheel attachments according to (6) to (10). Therefore, a better model of the SRU with two degrees of freedom can be developed based on the results of the model analysis from chapter 3.2 by a physically motivated order reduction which reproduces this dominant characteristic of a real SRU.…”