In a paper published at the previous ICBGM conference, it was argued that having knowledge of the internal

dynamics within the passenger's body could be attributed to their perception of ride comfort. Using the

biomechanical model developed for this purpose, a novel, quantitative ride comfort metric is devised. Then

the passenger model is exposed to the disturbance vibration coming in from a generic vehicle. A bond-

graph representation of a full-car model is developed and the complete system, including the passenger, the

seat, and the vehicle body as well as wheels and unsprung masses, is simulated. The nonlinear system of

equations is linearized and an observer-based state-variable-feedback controller is designed. It is shown

that with 3 sensors collocated with 3 actuators for seat control positioned at the rest locations on the seat,

ride comfort can be improved significantly while maintaining little power consumption.

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.

Rear-wheel steering (RWS) as we know it today is an idea that has been around for decades. Almost all literature discusses the technology though the conventional use, where the rear steers opposite the front at low speeds and in phase at high speeds. The work in this dissertation explores additional uses and benefits for using RWS.

The first idea explores decoupling yaw motion and lateral motion in order to allow the vehicle to behave with much more freedom than its front steering only counterpart. The handling characteristics are then controlled by a novel model reference concept, a virtual wheel base.

The second use explores how rear-wheel steering can enhance safety features in the vehicle. Rear-wheel steering is coupled with antilock braking and electronic stability control. These concepts show promising results and improvements to the vehicle.

The application of Inertial Force Actuators (IFAs) to vehicle dynamics is investigated. Theseare modeled as translational motors with a small proof mass attached such that forces applied by the actuator to the vehicle result in motion of the proof mass in inertial space. IFAs are shown to provide specific benefits compared to traditional active suspensions, which exhibit deleterious effects on secondary vehicle signals while pursuing their primary objectives. Since IFAs can be high power and generate high force magnitudes, and are constrained only by their internal stroke and force limits, their application is well suited for zero-mean band-limited white noise inputs such as from a vehicle roadway. The suspension control problem is studied with the incorporation of IFAs in cooperation with traditional actuators in order to meet the vehicle objectives hierarchy. Modern and classical control theory investigate the application of IFAs to control various vehicle output signals. High order vehicle simulation models are generated, and used to validate the controlled system.