A Nonlinear Model Predictive Controller (NMPC) for trajectory tracking of surface vessels is presented. NMPC calculates the future control inputs based on the present state variables by optimizing a cost function. The fact that cost function incorporates input constraints as well as state errors in determining the control inputs is exploited. This method can be applied to all systems with input saturation. NMPC formulation and derivation of input constraints are presented. Here the controller is designed based on a 3 DOF nonlinear dynamic model of the vessel. The performance of the controller is demonstrated by simulations. A constant speed sine trajectory is defined as desired path and the simulation results for input saturation case show the control inputs (propeller speed and rudder angle of the vessel) remain within the saturation limits in extreme maneuvers, the vessel recovers from saturation, and the vessels follows the trajectory very closely when the inputs are not saturated.

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The dynamic characteristics of a tire are studied by simulating its rolling over a cleat and observing the effect on in-plane rigid belt vibration modes. Three modeling approaches are used to understand various tire design parameters affecting the tire dynamics relevant for vehicle ride performance. First, a simplified three-degree-of-freedom rigid ring model is used for fundamental understanding of these modes. Next, a detailed finite element model accounting for component compliances is used for studying the sensitivity of the modes to most common design parameter variations employed in tire development. Finally, to study these tire design changes in operation, vehicle simulations using CarSim and FTire models are performed. FTire model parameters corresponding to tire design parameters are adjusted accordingly. Observations are reported of the effects of tire design parameters on cleat responses and on correlation of results between finite element and FTire models.

The goal of this study is two fold, one is to introduce a novel double damper based semi active suspension design and the other is to demonstrate the application of dynamic tire model in development of suspension controllers. In this study, a novel double damper suspension is introduced to show that a simple design modification of suspension can further improve the performance of the semi active suspension. A dynamic tire model was developed using a rigid ring tire and a tandem elliptical cam design for the enveloping model. A Lyapunov based adaptive ride control algorithm using a quarter car vehicle model with single damper and double damper suspension is developed. An ideal Skyhook-Groundhook 2DOF suspension is used as the reference model. The tire model and active suspension controller are then integrated with a full vehicle model to perform ride analysis. Using RMS acceleration of sprung mass vertical, roll and pitch motions as ride performance metrics, ride performance of no control, fully active control of single damper suspension and semi active control of double damper suspension are performed. The simulation results demonstrated that the importance of considering tire enveloping and dynamic effects and the emulation of novel semi active suspension system as active suspension without bottoming of suspension or deterioration of road holding properties. This behavior results in reduced power consumption, complexity and cost while the system performs like a fully active suspension system.

The objective of this study is to understand the influence of high frequency tire vibrations induced due to road disturbances and brake torque cycling due to anti-lock braking system (ABS) on braking performance. Under these conditions, transient dynamics of the tire play a crucial role in the generation of braking force. To implement this, a dynamic tire model was developed using a rigid ring tire and a tandem elliptical cam design for the enveloping model. This tire model is validated using experimental data obtained from high-speed cleat tests on a fixed axle. The validated tire model is then integrated with a quarter vehicle and a commercial grade rule-based ABS model to evaluate braking performance with and without a road cleat, which can provide a high frequency disturbance. Simulation results show that the presence of a 1 cm cleat causes large variations in wheel slip, consequently increasing the braking distance. The developed tool will help both tire and vehicle manufactures for quick and early evaluation of braking performance without computationally intensive finite element analysis (FEA) tools.