The design of a SbW (Steer-by-Wire) system a generic controller structure is proposed with bidirectional position feedback. The design goal for SbW here is to match the dynamics of an (electric/hydraulic power) steering system which may be subdivided into a manual and an assistance steering part. For matching the manual steering part a generic linear controller structure and for matching the assistance steering part a nonlinear unilateral controller structure are suggested. The primary scope of SbW control design is to copy the properties of a conventional steering system. This means that the intervening dynamics w.r.t. position and forces between the steering wheel and the front wheel in both directions is equivalent to the conventional steering system dynamics. Hence, the two basic requirements to be satisfied designing the SbW control system are (1) equivalence and (2) robust stability of the entire system including SbW, the driver impedance, and the vehicle impedance. Due to varying operating conditions and varying biomechanics of the driver the vehicle and the driver impedances have to be considered uncertain within certain bounds. A SbW-system consists of: a) driver, b) actuated steering wheel (SWA), c) controller, d) front wheel actuator and e) vehicle. Assuming the driver and vehicle impedances to be strictly passive (but otherwise arbitrary) a necessary and sufficient condition for robust stability of the whole system (comprising driver, environment and manual steering part of SbW) is established by applying a criterion based on the structured singular value. The task of the SbW-controller is to provide the right torque set points for both the steering wheel actuator and the front wheel actuator. It turns out that the controller structure introduced has more degrees of freedom than actually necessary. Therefore, only position sensors, but no force and torque sensors are assumed for the SbW system. The controller design problem is formulated as a system dynamics equivalence problem, either based on a physical or an identified model, and is solved exactly. This result is then adapted according to practical considerations. For robustness and stability analysis of the linear part of the steer-by-wire system passivity theory is applied and performance is evaluated by Bode magnitude plots and a H infinity performance criterion. Nonlinear simulations at various operating conditions (vehicle speed, road/tire contact) with a high fidelity vehicle dynamics model demonstrate the robustness of the whole system.
How to make steer-by-wire feel like power steering
Wie kann man bei der elektronischen Fahrzeuglenkung (steer-by-wire) das Gefühl einer Servolenkung nachahmen?
2002
6 Seiten, 5 Bilder, 4 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
How to Make Steer-By-Wire Feel Like Power Steering
Deutsches Zentrum für Luft- und Raumfahrt (DLR) | 2002
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