Kinematic Sensitivity Analysis of the Suspension Characteristics for the Initial Design of Four-Wheel Drive and Four-Wheel Steered Vehicles 2020-01-0990

A procedure for the initial design of a suspension concept with four independently driven and steered wheels is developed, whereby, steering angles above conventional values are considered. To fully exploit the potential of such vehicles, an autonomous closed-loop setup with integrated motion control is utilized. The goal is to obtain statements for an optimal suspension design and parametrization maintaining a general approach, while underlying black-box control and the vehicle configuration remains exchangeable. The investigation of the influence of the chassis parameters, with crucial impact on energy consumption, comfort and driving dynamics, namely camber, caster, scrub radius and the steering axis inclination (SAI) depending on a varying caster angle and SAI in relation to the steering angle will be focused. For this sensitivity analysis, an explicit behavioral-oriented model of the suspension is created. This behavior is evaluated with the resulting driving dynamics, specified as the control error, comfort, regarding maximum acceleration on the passengers, and energy demand of the actuators. Scenarios presented are the ISO double lane change and driving a circle while accelerating. The results show clearly that the dependency of the vehicle behavior and the interaction of chassis and controller results in a dominant influence on the driving dynamics, while comfort only improves relatively. Potentials arise during dynamic maneuvers, while stationary driving is mostly influenced by the controller. With the presented design algorithm, different parametrizations obtained with additional maneuvers followed by a cross evaluation result in simulation determined near optimal suspension taking advantage of the exceptional suspension concept.