Analysis of Nonlinear Control Systems

The development of chassis control schemes has been a major area of study for automotive control engineers over the past 30 years. The volume of published literature is large, exceeding 1000 papers. Of this literature, there are 250 examining yaw and sideslip control. Here is a comprehensive review of this field of study to identify the current state of the art and research in yaw rate and sideslip control. The survey shows that there is still a significant research effort needed to address the subjective performance of handling systems, and more research is needed to develop schemes that integrate systems to achieve high-level performance objectives.

A review of yaw rate and sideslip controllers for passenger vehicles

The application of multi-disciplinary automotive technologies to hybrid vehicles has resulted in the integration of alternative propulsion sources and drive-by-wire components for enhanced ground vehicle performance, fuel economy, and occupant safety. The integration of steer-by-wire systems in vehicles facilitates autonomous and semi-autonomous operations, better lateral vehicle behavior, an adjustable steering "feel," and elimination of problems arising due to potential engine cycling. In this paper, a continuous time-varying tracking controller is designed for the vehicle's position/orientation using a simplified vehicle description and reference model for tracking. The tracking error is globally, exponentially forced to a neighborhood of about zero by transforming the system into a flat input-state system and then fusing a filtered tracking error transformation with the dynamic oscillator design. Mathematical models are presented for a steer-by-wire rack and pinion unit, vehicle chassis, and tire/road interface dynamics. Representative numerical results are discussed to demonstrate the vehicle's transient response for a prescribed trajectory profile.

A trajectory tracking steer-by-wire control system for ground vehicles

The historical developments in the discipline of engineering dynamics are briefly reviewed, with attention paid to the formulation and solution of the dynamic behaviour of multi-body systems. It is shown that the dynamic characteristics of practical multi-body systems are dependent upon the interactions of many physical phenomena that can induce, restrain or constrain motion of parts. The long process of understanding and formulating the physics of multi-body motions, in some cases with pioneering contributions centuries old, together with continual refinements in numerical techniques and enhanced computing power has resulted in the solution of quite complex and practical engi- neering problems. Linking the historical developments to the fundamental physical phenomena and their interactions, the paper presents solutions to two complex multi-body dynamic problems. The practical implications of the approach in design of these systems are highlighted.

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Multi-body dynamics: Historical evolution and application:

For the on-centre handling behaviour of vehicles the steering system is absolutely important. To investigate the interaction of the vehicle and steering system a validated, especially tailored simulation model was developed. Some meaningful vehicle and steering system parameters are altered to show the influence on steering wheel torque, steering feel and understeer. The results underline the importance of an accurate steering system model. Identified measures to improve the centre feel and steering response were a stiffer torsion bar, a higher cornering stiffness or a lower overall steering ratio. The steering response, however, suffers when the centre feel is improved by a higher trail. The steering rack friction reduces mainly the steering response while the steering column friction decreases the centre feel whereas a stiffer torsion bar lessens the understeer tendency.

Interaction of vehicle and steering system regarding on-centre handling

Modeling, Characterization and Simulation of Automobile Power Steering Systems for the Prediction of On-Center Handling

In this paper, the authors present four wheel automobile model and a multi-loop quasi-liner driver mode. The models were used to evaluate conventional front wheel steering and four wheel steering systems for their behavior during cross wind disturbances and collision avoidance maneuvers.

Nonlinear analysis of closed loop driver/automobile performance with four wheel steering control

An investigation of the vertical dynamics of a tractor semi-trailer traversing a random road profile was conducted. This paper presents the development of a 14 degree-of-freedom (DOF), dynamic ride model of a tractor semi-trailer. It is based on work previously conducted by Vaduri and Law [1] and Law et al [2]. The DOFs include: (a) vertical displacements of each of the five axles, the tractor frame, the engine on its mounts, the cab on its suspension, and the driver's seat; (b) pitch displacements of the trailer with respect to the tractor, the cab, and the rigid tractor frame; and, (c) the first bending or beaming modes of the tractor and trailer frames. The model also incorporates suspension friction, and tire non-uniformities. The simulation of the model is conducted using MATLAB software. Further, the model is used to examine the effects on ride and pavement loading of wide-base and conventional tires, suspension friction, tractor and trailer beaming, and statistical variations in parameters such as tire pressure, axle suspension stiffness, etc.

Ride Dynamics and Pavement Loading of Tractor Semi-Trailers on Randomly Rough Roads

Understanding the effects of tire and vehicle properties on the rollover propensity of tractor semi-trailer trucks is essential. The major objective of the project described by this paper was to develop a simplified computational tool that can be used to understand and predict the effects of various tire characteristics and truck design parameters on rollover under steady cornering and non-tripped conditions. In particular, this tool may be used to help understand the basic me hanisms governing rollover propensity of trucks equipped with New Generation Wide Single tires as contrasted with conventional tires. Effects of tire flexibility, roll-compliant suspensions, fifth -wheel lash and nonlinear suspension characteristics are included in the model and are presented below. Design parameter data used as input to the model were obtained from Michelin Americas Research and Development Corporation. Results have shown that changing from dual tires to New Generation Wide Single tires increases the rollover threshold by approximately 3%.

E. H. Law

Papers

Modeling, Characterization and Simulation of Automobile Power Steering Systems for the Prediction of On-Center Handling

Nonlinear analysis of closed loop driver/automobile performance with four wheel steering control

Ride Dynamics and Pavement Loading of Tractor Semi-Trailers on Randomly Rough Roads

Effects of Tire and Vehicle Design Characteristics on Rollover of Tractor Semi-Trailers

An Investigation of the Pulse Steer Method for Determining Automobile Handling Qualities