Improvements on the Dynamical Behavior of a HiL-Steering System Test Bench

Abstract

Shorter available development times and fewer available vehicle prototypes have increased the subsystem-based investigation on test rigs within the automotive development process. Steering systems exhibit a direct interface to the driver, therefore, posing high requirements to the control performance of a test bench, especially for the perception of steering feel. This work proposes three approaches to improve the force control performance of permanent magnet linear motors incorporated on a steering test bench. The first method improves control accuracy when a harmonic force signal is introduced into the steering system by adjusting the reference force signal based on the identified peak values of the measured and reference forces. The second method allows the inclusion of the actuator’s inertia and the occurring ratios between steering wheel angle and rack displacement into the control scheme to reduce performance deterioration due to inertia. The third approach considers delay time in the actuator control and estimates its future position for delay compensation. A validation of the proposed methods is conducted, displaying an improvement for all three applications. The proposed methods extend the applicability of a steering test bench within the automotive development process by enabling more accurate and reproductible control performance.

An Objective Evaluation Approach for Safety-Relevant Steering Feedback on a Test Bench

“…The steering system and steering column are mounted like within the real vehicle to incorporate the gimbal error caused by the universal joints between the SWA and the steering gear. Additional information on the test bench can be found in [15][16][17]. An axle-parallel EPS, meaning that the servo force is provided by an electric motor mounted parallel to the steering rack axis, is utilized for steering feedback evaluations.…”

“…Reported evaluations of steering feedback on a steering system test bench focused on the usage of a sine-sweep rack force excitation signal to stimulate the steering system [4,10,15]. An FFT [13] analysis is then incorporated to receive the magnitude of the transfer function from the measured steering rack force 𝐹 , to the steering wheel torque 𝑀 , according to…”

“…This raises the question of how adequately and accurately this method is able to estimate the relevant feedback performance of a steering system and how they can be adapted or expanded. Reported evaluations of steering feedback on a steering system test bench focused on the usage of a sine-sweep rack force excitation signal to stimulate the steering system [4,10,15]. An FFT [13] analysis is then incorporated to receive the magnitude of the transfer function from the measured steering rack force F Meas,RRA to the steering wheel torque M Meas,SWA according to…”