A multivariable centralized controller design methodology for a Steer-by-Wire system

Implementation and testing of different control strategies on a steer-by-wire research platform

“…This calls for a fast and precise position control. Just like with many other applications, a linear control approach, as provided by [2], [8] and [10], shows a good tracking behavior of the proposed control systems, however, their performance is negatively affected by parameter variations, changes in road conditions, impact of external disturbances or dominating nonlinear system behavior when operating outside of the linearly described system range. [4] and [1] on the other hand developed a nonlinear control approach.…”

“…It's natural to think that the target dynamics should match the real dynamics acting on the steering wheel when a conventional steering system is used, therefore many researchers make use of the vehicle's dynamics and kinematics to estimate the forces acting on the vehicle and its steering system and use this information to generate a target for the haptic feedback at the driver's input, i.e. the steering feel at the steering wheel, as done in [2], [9] and [10]. Another common approach is to identify the parameters that characterize the steering feel based on objective measurements of the steering system and to so define a target steering torque for the SbW system for different driving situations.…”

“…As in [1], [2] and [4]- [12], the main actor in the feedback actuator is represented by an electric motor. The majority of the motors used in industry are brushless DC motors that show the effect of cogging and ripple.…”

“…A lot of work has therefore been done on the question of how the haptic feedback should be generated and what dependencies it should show. The most common approach is to use an electrical motor connected to the steering wheel and generate a defined torque that simulates a realistic driver experience such as in [1], [2] and [4]- [11]. In [4] an adaptive control approach that combines the control of the steering gear and the feedback actuator is presented, assuming the target dynamics and torque for the driver feedback exists and is known, [5] on the other hand tries to address the question of how the target dynamics can be described mathematically for the use in a control system.…”

“…Due to their importance for the proper functioning and safety of the complete SbW system, several angular sensors are mounted (absolute and relative angle sensors) and available on the feedback actuator to ensure the systems redundancy. In [2], [4], [8], [10] and [12] the steering feel, independent from how it's calculated or defined, is a target value and becomes a controlled variable requiring a closed-loop control system and therefore also a torque sensor. On the other hand [11] reached good results without implementing any control algorithms.…”