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Persisting concerns regarding ride comfort, directional stability and more recently road damage have caused the manufacturers of commercial vehicles to consider controllable suspension systems. An electronically controllable adaptive suspension that comprises a variable spring rate system, switchable damping and load levelling is proposed as a cost-effective solution. This paper describes the aforementioned system and provides an outline of the design scheme for a prototype system; practical issues such as system configuration/detail, control system requirements, etc., are discussed. The system is evaluated analytically and both ride and handling modes are examined. In conclusion, performance capabilities are defined and cost-benefit issues addressed.

In this paper, a hybrid roll control system, including passive and active roll control units, is designed to improve the roll dynamics of tanker vehicles and to reduce the lateral shifts of the liquid cargo due to lateral accelerations. The passive control system consists of radial partitions installed inside the vehicle container. These partitions rotate in phase with the liquid cargo as one unit about the longitudinal axis of the container in response to the induced momentum forces due to the lateral acceleration excitation. Torsion dampers are fixed between the partitions and the container's front and rear walls to reduce the oscillating motion of the liquid cargo. While the passive partition dampers control the dynamics of the liquid cargo inside the container, the dampers of the vehicle suspension are switchable, generating anti-roll damping moments based on the lateral acceleration level and the container filling ratio.

The detailed, dynamic properties of dampers are known to influence substantially some of the subtle - and yet nevertheless hugely important - refinement aspects or ride and handling. Despite this, most of the current work on damping characterization relies on steady-state properties and transient aspects are left largely to subjective in-car assessments by test drivers. The paper describes research work aimed at improving our understanding of the transient properties of dampers through mathematical modeling and then attempting to link these properties to detailed aspects of the vehicle ride and handling. Further experimental work is planned to follow later. From a moderately complex mathematical model of a damper, an attempt is made to identify (a) those transient characteristics which are important in influencing the vehicle responses perceived by test drivers, and (b) which design features of the damper control those characteristics.

Integrating chassis control systems can lead to improvements in the safety, efficiency of action and overall production of a modern car. The sharing of information between chassis sub-systems allows the controller to take the optimum course of action since it has more than one option to affect the dynamics of a vehicle. This paper investigates the principle of coordination of chassis subsystems by selecting active steering and yaw stability control. A controller that coordinates the action of active front steering(AFS) and direct yaw moment control(DYC) is proposed. Preliminary results for the coordinated controller using limit handling tests suggest that such an integrated approach can lead to overall improvements in vehicle dynamic response.

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.

The development of Integrated Chassis controllers has followed two main approaches. The pragmatic approach is to integrate existing chassis subsystems (e.g. DYC, ABS, TCS, ARC) with heuristic control laws. The more theoretical approach is to calculate control actions by solving a model of the vehicle dynamics. There is a dearth of literature that investigates the interface between these two strategies. This interface can give vehicle manufacturers ownership of the core vehicle motion control algorithm and allow them to select chassis controllers from a range of component suppliers. IVMC aims to give a global design methodology for Intelligent Vehicle Motion Control that interfaces a theoretical, generic controller with existing chassis subsystems. The interface takes the generic actuation forces and distributes them to the braking and steering chassis subsystems, DYC and active steering.

Previous work to examine the performance of a variety of control strategies for a switchable damper suspension system is extended to include an adaptive suspension. The aim of this adaptation algorithm is to maintain optimal performance over the wide range of input conditions typically encountered by a vehicle. The adaptive control loop is based on a gain scheduling approach and two strategies are examined both theoretically and experimentally using a quarter vehicle test rig. For the first strategy, the gains are selected on the basis of root mean square (r.m.s.) wheel acceleration measurements whereas in the second approach the r.m.s. value of suspension working space is used. A composite input is used consisting of sections of a road input disturbance of differing levels of magnitude in order to test the control systems' abilities to identify and adapt efficiently as the severity of the road input changes.

It is now widely accepted that electronically controlled suspension systems can offer substantial improvements over passive designs. However, much of the published work is based on idealised, theoretical calculations and practical developments have indicated that component limitations play a major part in governing the potential benefits available. In this work, the detailed response characteristics of a three-state switchable damper are first measured on a laboratory rig. The switching dynamics between states are characterised for both bump and rebound behaviour. Then, the performance of this damper in combination with a self levelling, hydro-pneumatic suspension is examined both theoretically and experimentally using a quarter vehicle rig. The issue of compensating for component limitations in the control system design is examined and shown to be an important feature in extracting the best ride performance from switchable damper systems.

In this paper, the effect of the dynamic interaction between tractor and semitrailer on the ride behaviour of heavy good vehicles is investigated. A multi-body model is constructed for a 4-axle tractor-semitrailer vehicle with flexible frames and excited by random road irregularities. The modal parameters of the connected frames are calculated using the FEM (Finite Element Method), as an integrated free vibrating structure, and incorporated with the equations of motion of the whole vehicle which are generated using the Lagrange energy approach. Frequency response analysis is carried out for random road excitations to evaluate the vehicle ride dynamics. In order to give a broad overview of the vehicle ride quality, different loading conditions are considered in the computer simulation. The results showed that the acceleration levels of vehicle components are significantly increased when the effect of an empty semitrailer is considered within the vehicle model.

There have been numerous studies of various forms of active suspensions over the past three decades. Most of published literature has reported theoretical studies and outlined the potential advantages in both vehicle ride and handling of such systems over their passive equivalents. One of the systems, which have been shown to have considerable practical potential is a limited bandwidth active scheme based on hydro-pneumatic components. However, in order to exploit the full potential of this arrangement, the control law should include two features; (a) the ability to exploit the wheel-base preview effect in which information at the front suspension of the vehicle is used to improve performance at the rear and (b) the ability to adapt on gain scheduling approach to a variety of different operating conditions. Both features are investigated in the paper using a four degree of freedom model and practical performance benefits are quantified.

This paper describes the analysis and design of a hydropneumatic limited bandwidth active suspension system. The design is based on hydropneumatic suspension components taken from an existing European saloon. Mathematical modeling based on the well-known quarter car model is used to compare the performance of the proposed suspension with both the baseline passive system and an idealised fully active system. Practical features, such as actuator time delays and self-levelling controllers, are included in the model of fully active suspension system, and of the limited bandwidth suspension respectively. The controller design for the proposed suspension is based on limited state feedback, and the Nelder-Mead simplex algorithm was used to calculate the gains to optimise the performance index. Overall, the performance of the proposed system appears to be nearly as good as that of the idealised fully active system.

Torsional motion of a truck driveline system is coupled with other motions of its components. In this paper, a comprehensive model of the truck driveline and body for vibration analysis was developed. Coupling of the torsional vibration of the truck driveline system with the body fore-aft and vertical vibrations was investigated. A mathematical model, including the torsional vibration of the driveline system and the whole body vibrations of the truck, was constructed. The driveline system was modelled as a set of inertia discs linked together by massless springs and the tyre was represented as having massless circumferential band which is elastically connected to the carcass with the bands being subject to longitudinal forces at the road surface. System behaviour at steady and transient runs was developed.