Ronald J. Anderson

Handling Characteristics of Car-Trailer Systems; A State-of-the-Art Survey

SUMMARY Work relevant to the state of the art as regards passenger cars towing trailers is referenced and reviewed. Not only included is the very limited amount of work specifically dealing with passenger cars towing trailers, but also reviewed is the much larger body of work having a bearing on car-trailer systems. Topics included are aerodynamic forces, tire forces, the compliance concept, relevant work on vehicles without trailers, vehicles with trailers, and the role of the driver. The types of stability problems exhibited by car-trailer systems are discussed. The state of the art as regards ability to predict vehicle response to specific steering inputs is shown to be fairly advanced. Recent significant advances include the appearance of experimental data useful for validating theoretical models. However, the state of the art as regards definition of what constitute desirable handling characteristics is still at a primitive stage, largely because of a lack of understanding of the roles played by driv...

A general vector-network formulation for dynamic systems with kinematic constraints

Abstract The vector-network method is a simple, systematic procedure for formulating the equations of motion of dynamic mechanical systems. The method serves as a basis for “self-formulating” computer programs, useful in computer-aided design, which simulate system response, given only the system description as input. The method in this paper includes kinematic constraints and is a significant extension to earlier formulation techniques, which are seen to be special cases of this method. A computer program, RESTRI, has been developed for two- and three dimensional constrained systems; a flowchart and computer example are included. A similarity is observed between the vector-network equations of motion and those obtained by Chace for the DRAM program.

Optimal control of an active anti roll suspension for an off-road utility vehicle using interconnected hydragas suspension units

SUMMARY This paper presents the results of a simulation study on a full car nonlinear multibody model of the IAVSD litis benchmark equipped with an active interconnected hydragas suspension aimed to reduce vehicle body roll. Models for vehicle and suspension units are briefly presented. For the design of a linear optimal controller the highly nonlinear equations of motion must be linearized; a numerical linearization technique is outlined. Simulation results show the potential and limitations of an active suspension device employing hydragas suspension units.

Experimental Testing and Mathematical Modeling of the Interconnected Hydragas Suspension System

The Moulton Hydragas suspension system improves small car ride quality by interconnecting the front and rear wheel on each side of the vehicle via a hydraulic fluid pipe between the front and rear dampers. A Hydragas system from a Rover Group MGF sports car was statically and dynamically tested to generate stiffness and damping coefficient matrices. The goal was to develop the simplest possible model of the system for use in ride quality studies. A linear model showed reasonable accuracy over restricted frequency ranges. A second model used bilinear spring and damping constants, and was more accurate for predicting force at both the front and rear units for frequencies from 1 to 8 Hz. The Hydragas system static stiffness parameters, when used in the model, caused peak force underprediction in the jounce direction. The bilinear model required increased jounce stiffness to account for hysteresis in the rubber elements of the system, and dynamic fluid flow phenomena.

Preview control algorithms for the active suspension of an off-road vehicle

SUMMARY The potential performance improvement using preview control for active vehicle suspension was first recognized in the late nineteen sixties. All work done since that time has been based on optimal control theory using simple vehicle models. In this article, the performance of quarter vehicle preview controllers when applied to a real off-road vehicle is simulated using both two degree of freedom quarter and ten degree of freedom full vehicle models. The results, which are compared with non-preview active and conventional passive suspensions, confirm that preview control reduces vertical acceleration of the body centre of gravity, which results in improved ride quality. Further, reductions in pitch and roll motion result from smaller vertical displacements of the vehicle quarters. Coupling between quarters, through the vehicle body, appears to have a smoothing effect on the control. As an alternative to optimal control theory based controllers, a simple ad hoc preview controller based on isolating ...

Characteristics of Guided-Steering Railway Trucks

SUMMARY The dynamic characteristics of guided-steering railway trucks are described both in a general sense and in terms of a specific design. Stability margins and curving performance have been predicted and are compared for both conventional and steered vehicles. It is shown that guided-steering trucks exhibit modes of instability which, although surmountable by proper design, are not found in conventional trucks. In particular, a low conicity, divergent, leading truck instability is described together with a companion high conicity, divergent trailing truck instability. Curving and dynamic performance for steered vehicles is shown to have the potential of being far superior to that of comparable conventional vehicles. Factors influencing the design of steered rail vehicles are presented and discussed.

The vector-network method for the modelling of mechanical systems

This paper presents an extension of the vector-network approach to the problem of motion prediction. The entire procedure is a basic application of concepts of graph theory in which laws of vector dynamics have been combined. A comprehensive mathematical model for the systematic formulation of the equations of motion of dynamic three-dimensional constrained multi-body systems is derived. The method embodies simultaneously the three-dimensional inertial equations associated with each rigid body and the kinematic constraints into a symmetrical format yielding the differential equations governing the response of the system. The modelling technique is thoroughly described in this work and its validity is impartially established.

Computerized generation of motion equations using variational graph-theoretic methods

Severe tolerances on mechanical components have created increasingly stringent demands on the quality of new mechanical designs. The mathematical models used to simulate the various types of mechanical systems these days need to incorporate an optimization algorithm capable of minimizing the number of matrix multiplications when deriving symbolically the equations of motion. The method is based on a simplistic topological approach which is incorporated into an efficient variational graph-theoretic process used to solve these non-linear problems. The system is represented by a linear graph, in which nodes represent reference frames on rigid bodies, and edges represent components that connect these frames. By selecting a proper spanning tree for the graph, the analyst can choose the set of coordinates appearing in the final system of equation. The procedure casts, simultaneously, the Lagranges equations of motion and the kinematic constraints into a symmetrical format which yields a symbolic solution. The algorithm serves as a basis for a computer program which generates the equations of motion in symbolic form, and provides the time varying response of the system. The effectiveness of this approach is demonstrated in the analysis of a spatial four-bar mechanism and an articulated semi-trailer vehicle.

DYNAMICS OF UNSYMMETRIC SUSPENSION TRUCKS WITH SEMIACTIVE CONTROL

SUMMARY This paper presents dynamic characteristics of unsymmetric suspension trucks with semi-active control to achieve compatibility between high speed stability and curving performance. According to the direction of vehicle motion, the primary longitudinal stiffness is switched so that the interwheelset structure is asymmetric fore-and-aft. Unsteady state curving behavior of the proposed unsymmetric trucks during curve entry is calculated using full car body models with non-linear wheel profiles. These calculation results are compared with experiments. In Japan, the Central Japan Railway Company made and tested trial bogies. Experimental measurements show the lateral forces acting on wheels in curve negotiation are dramatically reduced. Consequently, from botii meoretical predictions and experiments, it was verified that the proposed truck is a realistic way to solve the incompatibility between steering ability and high speed operation.

LOW CONICITY INSTABILITIES IN FORCED-STEERING RAILWAY VEHICLES

SUMMARY The dynamic stability of forced-steering rail vehicles is considered through the use of three models having three, eight, and seventeen degrees-of-freedom respectively. It is shown that, at low values of conicity, these trucks may experience instabilities which are not found in conventional rail vehicles. The simpler of these models of varying complexity is used to establish an understanding of the basic phenomenon. The more detailed models are included to give realistic results which show the potential magnitude of the problem.