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This thesis focuses on modelling of passive hydraulic automotive dampers for use in computationally-fast vehicle-dynamic simulation. An extended version of the Duym and Reybrouck 1998 physical model is examined to enable work with high frequency input displacements. This computationally-expensive model is verified with real damper data under both isothermal and variable temperature regular, and random (Pave) input displacement conditions. Initially the extension includes just additional input kinematics to account for inertial effects, with an imposed temperature profile. Subsequently a heat generation model is developed to include appropriate energy losses. When the heat generation model is coupled to the damper model, naturally-generated transient-temperature operation of the damper can be accounted for.

Vehicle suspension systems, as one kind of typical non-linear systems, play a crucial role in riding comfort, safety handling, and road damage minimization in modern vehicles. Three contributions have been made in this thesis in response to the problems raised from vehicle non-linear and uncertain properties. A novel framework of type-2 fuzzy control system for vehicle active suspensions has been constructed with emphasizes on its mathematical vehicle modelling and control.

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The benefits of vehicles with semi-active suspension systems have been widely accepted, mainly for improvement in ride and handling, over the passive system. However, the durability of the suspension components resulting from this implementation received very little attention. Therefore, this research aims to examine the effect of employing a selection of semi-active control strategies on the components' durability. To achieve this early in the design cycle, accurate representations of the load histories must be generated as these histories are the prerequisite in predicting fatigue life. This requires an alternative modelling and simulation approach capable of combining the complexity of vehicle suspensions with semi-active controller models, and at the same time capable of maintaining accurate dynamic responses. In realizing this objective, a multi-body cosimulation approach has been proposed to predict these loads. Initially, efforts are centred on verifying the proposed method against conventional modelling and simulation techniques. This is followed by the evaluating the responses of vehicle suspension models of different complexities fitted with a selection of semi-active control strategies when subjected to transient and random road inputs. In an attempt to demonstrate the flexibility of MBS cosimulation, a magnetorheological damper model derived from experimental data is introduced,in which its dynamic characteristics and dynamic response are examined. It is concluded that the proposed method is capable of producing reasonably accurate load histories but at the expense of increasing solution time. Evaluation of the durability of a lower suspension arm of a multi-purpose passenger vehicle suggested that the two state semi-active strategies with skyhook damping control produced shorter fatigue life than from the conventional passives suspension systems.

This research focuses on the integration of roll moment distribution control and variable torque distribution control to improve vehicle handling and dynamics. A survey of the literature determines the current state of the art and directs the research toward undeveloped areas. The work is carried out with the racing environment in mind. The most promising control systems prove to be roll moment distribution and variable torque distribution. The control objectives are to both improve the driveability of the vehicle and ensure the stability. The driveability is measured by the ability to track a linear reference yaw rate. This aims to linearise the yaw rate response to the steering input and gives the driver predictable handling. Vehicle stability is determined by the sideslip behaviour of the vehicle, where the controllers aim to minimise the sideslip. The testing is achieved by computer simulation. An eight degree of freedom nonlinear vehicle model is developed to model the University of Leeds Formula Racing Car. Initially independent controllers are developed for both roll moment distribution and variable torque distribution to control the driveability and stability individually. The independent controllers are able to enhance the vehicle behaviour with respect to each of these goals. However, the roll moment distribution is more suited to the stability control while the variable torque distribution achieves the yaw rate tracking more effectively. The independent controllers are combined to determine any interactions between them before a final integrated control strategy is developed. This integrated control strategy integrates the variable torque distribution driveability control and the roll moment distribution stability control to give a complete vehicle control strategy. The integrated controller shows improved yaw rate tracking as well as the ability to stabilise the vehicle at limit handling.

A vehicle active suspension system, in comparison with its counterparts, plays a crucial role in adequately guarantee the stability of the vehicle and improve the suspension performances. With a full understanding of the state of the art in vehicle control systems, this thesis identifies key issues in robust control design for active suspension systems with uncertainty, contributes to enhance the suspension performances via handling tradeoffs between ride comfort, road holding and suspension deflection. Priority of this thesis is to emphasize the contributions in handing actuator-related challenges and suspension model parameter uncertainty. The challenges in suspension actuators are identified as time-varying actuator delay and actuator faults. Time-varying delay and its effects in suspension actuators are targeted and analyzed. By removing the assumptions from the state of the art methods, state-feedback and output-feedback controller design methods are proposed to design less conservative state-feedback and output-feedback controller existence conditions. It overcomes the challenges brought by generalized timevarying actuator delay. On the other hand, a novel fault-tolerant controller design algorithm is developed for active suspension systems with uncertainty of actuator faults. A continuous-time homogeneous Markov process is presented for modeling the actuator failure process. The fault-tolerant H∞ controller is designed to guarantee asymptotic the stability, H∞ performance, and the constrained performance with existing possible actuator failures. It is evident that vehicle model parameter uncertainty is a vital factor affecting the performances of suspension control system. Consequently, this thesis presents two robust control solutions to overcome suspension control challenges with nonlinear constraints. A novel fuzzy control design algorithm is presented for active suspension systems with uncertainty. By using the sector nonlinearity method, Takagi-Sugeno (T-S) fuzzy systems are used to model the system. Based on Lyapunov stability theory, a new reliable fuzzy controller is designed to improve suspension performances. A novel adaptive sliding mode controller design approach is also developed for nonlinear uncertain vehicle active suspension systems. An adaptive sliding mode controller is designed to guarantee the stability and improve the suspension performances. In conclusion, novel control design algorithms are proposed for active suspension systems with uncertainty in order to guarantee and improve the suspension performance. Simulation results and comparison with the state of the art methods are provided to evaluate the effectiveness of the research contributions. The thesis shows insights into practical solutions to vehicle active suspension systems, it is expected that these algorithms will have significant potential in industrial applications and electric vehicles industry.