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Technical Paper

A Coordination Approach for DYC and Active Front Steering

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.
Technical Paper

Adaptive Control Strategies for a Switchable Damper Suspension System

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.
Technical Paper

An Experimental and Theoretical Study of a Switchable Damper

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.
Technical Paper

Development and Analysis of a Prototype Controllable Suspension

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.
Technical Paper

A Novel Hybrid Roll Control Strategy for Partially Loaded Tanker Trucks

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.
Technical Paper

IVMC: Intelligent Vehicle Motion Control

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.