UC Davis

With the rise of autonomous vehicles, ride comfort is becoming ever more important for vehicle manufacturers as a design criterion. Studies on the currently established metrics for ride comfort indicate that they are often discrepant, and their predicted zones of comfort do not overlap. It is hypothesized that the perception of ride comfort for a vehicle passenger is correlated with their body’s internal dynamic response to the disturbance vibrations coming in from the vehicle. To test this hypothesis, it is essential to develop a biomechanical model of a vehicle passenger.The passenger body’s internal mechanical structure is primarily the human spine which has an inherent geometric curvature. Therefore, in order to adequately predict the propagation of disturbance vibration into the passenger body, the biomechanical model should account for curved motion. A 25-DOF, lumped parameter, nonlinear biomechanical model of the upper body is proposed and validated against experimental literature. The model tracks curved trajectories and enables smooth posture prediction. A full car model is developed, and its seat track velocities become input to the passenger model. A non-dimensional, novel ride comfort cost function is devised according to the energy associated with the important internal displacements of the body. The nonlinear model is linearized around its equilibrium position and a linear, observer-based, state-variable feedback control strategy is proposed. In normal ride conditions, the controller reduces the cost function by more than 50% without excessive consumption of power. Actuation takes place through the seats and is therefore cost effective as compared to manipulation of the entire suspension system.