This paper gives a review of the application of linear optimal control theory to the design of control laws for an actively suspended vehicle. Both common descriptions of the road surface input, which assume that it can be modelled either as integrated while noise or altered white noise, are considered. Particular attention is paid to the problem of accounting in the control law for (a) the cross–correlation between left and right tracks and (b) correlation arising from the fact that the rear wheel is a delayed version of the front. Both the cases of full and limited state feedback are considered. It is shown that a control law with practical potential can be derived which uses limited slate feedback hereby avoiding the need to measure the ground input states and which accounts for cross–correlation and time delay features mentioned above.

The powertrain is at the heart of vehicle design; the engine – whether it is a conventional, hybrid or electric design – provides the motive power, which is then managed and controlled through the transmission and final drive components. The overall powertrain system therefore defines the dynamic performance and character of the vehicle. The design of the powertrain has conventionally been tackled by analyzing each of the subsystems individually and the individual components, for example, engine, transmission and driveline have received considerable attention in textbooks over the past decades. The key theme of this book is to take a systems approach – to look at the integration of the components so that the whole powertrain system meets the demands of overall energy efficiency and good drivability.

Hybrid Electric Vehicles HIGHLIGHTS  PROCESS AND TECHNOLOGY STATUS – A hybrid electrical vehicle (HEV) is a vehicle equipped with either an internal combustion engine (ICE) and an electrical motor powered by electrical batteries. In 1997, Toyota sold in Japan the first modern hybrid electric car, the Toyota Prius. Today’s HEVs are an emerging technology in the automotive market, with manufacturers designing and producing hybrid systems for passenger cars, light-duty vehicles, heavy duty vehicles, and even locomotives. The improved efficiency of HEVs over conventional (i.e. non-hybrid) vehicle is achieved by operating a smaller (more efficient) ICE within a narrower, more efficient operational speed/power band and using an electric engine and electrical storage (i.e. the battery) to balance the performance energy requirements. In general, in the current-generation HEVs, the combustion engine provides the main power during long-distance drive while the electrical motor can either complement the ICE or power the vehicle in electric-only mode (as long as energy is available from the battery) during the urban service, where the ICE is less efficient. The battery charge is provided by regenerative braking and excess energy from the ICE (stored when the vehicle has lower power requirements). There are however different grades of hybridization and many configurations of hybrid vehicles, including micro, mild, full hybrids, with different role for the electric motor. Currently, only hybrids combining a petrol or diesel combustion engine with an electric motor are commercially available. Improving battery capacity and technology may enable longer electric drive range and reduce the need for the ICE contribution. New-generation HEVs include batteries rechargeable from the grid (known as plug-in hybrid electrical vehicles, PHEVs, see also ETSAP TB05).

Hybrid Electric Vehicles HIGHLIGHTS  PROCESS AND TECHNOLOGY STATUS – A hybrid electrical vehicle (HEV) is a vehicle equipped with either an internal combustion engine (ICE) and an electrical motor powered by electrical batteries. In 1997, Toyota sold in Japan the first modern hybrid electric car, the Toyota Prius. Today’s HEVs are an emerging technology in the automotive market, with manufacturers designing and producing hybrid systems for passenger cars, light-duty vehicles, heavy duty vehicles, and even locomotives. The improved efficiency of HEVs over conventional (i.e. non-hybrid) vehicle is achieved by operating a smaller (more efficient) ICE within a narrower, more efficient operational speed/power band and using an electric engine and electrical storage (i.e. the battery) to balance the performance energy requirements. In general, in the current-generation HEVs, the combustion engine provides the main power during long-distance drive while the electrical motor can either complement the ICE or power the vehicle in electric-only mode (as long as energy is available from the battery) during the urban service, where the ICE is less efficient. The battery charge is provided by regenerative braking and excess energy from the ICE (stored when the vehicle has lower power requirements). There are however different grades of hybridization and many configurations of hybrid vehicles, including micro, mild, full hybrids, with different role for the electric motor. Currently, only hybrids combining a petrol or diesel combustion engine with an electric motor are commercially available. Improving battery capacity and technology may enable longer electric drive range and reduce the need for the ICE contribution. New-generation HEVs include batteries rechargeable from the grid (known as plug-in hybrid electrical vehicles, PHEVs, see also ETSAP TB05).

This thesis investigates the principle of integration of vehicle dynamics control systems by proposing a novel control architecture to integrate the brake-based electronic stability control (ESC), active front steering (AFS), normal suspension force control (NFC) and variable torque distribution (VTD). A nonlinear 14 degree of freedom passive vehicle dynamics model was developed in Matlab/Simulink and validated against commercially available vehicle dynamics software CarSim. Dynamics of the four active vehicle control systems were developed. Fuzzy logic and PID control strategies were employed considering their robustness and effectiveness in controlling nonlinear systems. Effectiveness of active systems in extending the vehicle operating range against the passive ones was investigated. From the research, it was observed that AFS is effective in improving the stability at lower lateral acceleration (latac) region with less interference to the longitudinal vehicle dynamics. But its ability diminishes at higher latac regions due to tyre lateral force saturation. Both ESC and VTD are found to be effective in stabilising the vehicle over the entire operating region. But the intrusive nature of ESC promotes VTD as a preferred stability control mechanism at the medium latac range. But ESC stands out in improving stability at limits where safety is of paramount importance. NFC is observed to improve the ability to generate the tyre forces across the entire operating range. Based on this analysis, a novel rule based integrated chassis control (ICC) strategy is proposed. It uses a latac based stability criterion to assign the authority to control the stability and ensures the smooth transition of the control authority amongst the three systems, AFS, VTD and ESC respectively. The ICC also optimises the utilisation of NFC to improve the vehicle handling performance further, across the entire operating regions. The results of the simulation are found to prove that the integrated control strategy improves vehicle stability across the entire vehicle operating region.

Chassis control systems have evolved dramatically over the past two decades and their impacts on vehicle dynamics can be usefully separated into the three directions, i.e. lateral, longitudinal and vertical directions. Accordingly, the state survey of chassis control systems can be reviewed in following sub-system areas, i.e. steering, driveline/braking and suspension. The developments within each of these areas have progressed at different rates and each has had different impacts on improving vehicle behavior in relation to safety, ride, handling dynamics or economy. However, the biggest challenge is in the whole chassis integration of these sub-systems to avoid their interventions and thus to improve overall vehicle dynamics performance. Hence, a hot research topic, named integrated vehicle dynamics control (IVDC) or integrated chassis control, arose. Based on the published literatures in the recent twenty years, this paper presents a comprehensive state of the art survey on IVDC. First, the roadmap and methodologies of IVDC are reviewed, and then the control strategies of coordination between the subsystems are summarized. At present, integration technique between steering and braking/traction has been most concerned, and is being researched and developed intensively both in academic and industrial aspects. It can be expected that once X-by-Wire technology and actuator hardware are further developed, more potential benefits of IVDC can be obtained.

In this paper, an integrated controller for a full-vehicle active suspension system is designed to simultaneously improve vehicle ride comfort and steady-state handling performance. First, the suspension and handling sub-system models and the nonlinear relationship between tyre normal load and lateral force are described. Next, the link between suspension model and steady-state handling characteristics is analysed. Then, based on the analysis, an H,, controller is designed for the suspension sub-system to achieve integrated ride comfort and handling performance control. Finally, the controller is verified through computer simulations in frequency- and time-domains.

In this paper, a full-vehicle active suspension system is designed to simultaneously improve vehicle ride comfort and steady-state handling performance. First, a linear suspension model of a vehicle and a nonlinear handling model are described. Next, the link between the suspension model and vehicle steady-state handling characteristics is analysed. Then, an H-infinity controller for the suspension is designed to achieve integrated ride-comfort and handling control. Finally, the controller is verified by computer simulations.

This paper proposes an advanced control strategy to improve vehicle handling and directional stability by integrating either Active Front Steering (AFS) or Active Rear Steering (ARS) with Variable Torque Distribution (VTD) control. Both AFS and ARS serve as the steerability controller and are designed to achieve the improved yaw rate tracking in low to mid-range lateral acceleration using Sliding Mode Control (SMC); while VTD is used as the stability controller and employs differential driving torque between left and right wheels on the same axle to produce a relatively large stabilizing yaw moment when the vehicle states (sideslip angle and its angular velocity) exceed the reference stable region defined in the phase plane. Based on these stand-alone subsystems, an integrated control scheme which coordinates the control actions of both AFS/ARS and VTD is proposed. The functional difference between AFS and ARS when integrated with VTD is explained physically. The effect of the integrated control system on the vehicle handling characteristics and directional stability is studied through an open loop computer simulation of an eight degrees of freedom nonlinear vehicle model. Simulation results confirm the effectiveness of the proposed control system and the overall improvements in vehicle handling and directional stability.

In this work, the active front steering control is studied using linear three degrees of freedom handling model incorporating the driver's operation model and vehicle suspension derivatives. The active steering control strategy is based on the optimal control theory. In this design, the active front steering angle is determined based on minimizing all model state variables and full state feedback gains. The results are generated when the model is excited by random wind excitation, which was modeled as quasi-static approach with statistical properties taken from previous work, and presented in frequency domain as power spectral density as well as root mean square values in tables. Significant improvements are achieved for the vehicle handling characteristics using active front steering control in comparison with active four wheel steering and conventional two wheel steering.