Search Results

An accurate bushing model is vital for vehicle dynamic simulation regarding fatigue life prediction. This paper introduces the Advanced Bushing Model (ABM) that was developed in MATLAB® environment, which gives high precision and fast simulation. The ABM is a time-domain model targeting for vehicle durability simulation. It dynamically captures bushing nonlinearities that occur on stiffness, damping and hysteresis, through a time-history-based fitting technique, compensated with frequency dependency functionality. Among the simulated and test-collected bushing loads, good correlations have been achieved for elastomer bushings and hydraulic engine mounts and validated with a random excitation signal. This ABM model has been integrated into a virtual shaker table (from a parallel project) as the engine mount model to simulate the mount load, and has shown acceptable prediction on fatigue damage.

The focus of this paper is the development and modelling of a reverse-poppet valve train assembly, placing a major emphasis on the optimization routine used to develop a short-duration camshaft profile. A user-programmable script, known as the penalty function, was written to assign weighted numeric values to certain parameters associated with the valve lift profile and its derivatives. These design parameters include maximum acceleration, peak lift, area under the lift curve and minimization of jerk. Optimization tools built into Matlab were then used to generate a profile which minimizes the overall ‘penalty’ associated with each parameter as it deviates from a user-defined ideal. A commercially available multi-body dynamics software package was used to evaluate the dynamic performance of the valve train incorporating the generated cam profile. A flexible-body spring element provided insight into spring surge and coil contact.

In this study the capabilities of a semi-active suspension and an active roll suspension are evaluated for comparison with a passive suspension. The vehicle used is a utility truck modeled as a multi-body system in ADAMS/Car while the ECU (electronic control unit) is built in Matlab/Simulink. Cosimulation is used in linking the vehicle model with the controller by exchanging the input and output values of each sub-system with one another. For the simulation models considered, results indicate that for a fish-hook cornering maneuver the semi-active suspension is limited in increasing vehicle performance while the active roll suspension significantly improves it. Further analysis is needed to confirm these findings.

The paper describes a study conducted by the University of Windsor Vehicle Dynamics and Control Research Group into the stability of coupled vehicles, e.g., truck-trailer combinations. Several instabilities associated with truck-trailer combinations have been well documented, and have been predicted using mathematical models. Despite having relatively low complexity the classic truck-trailer model, a simple two body, three degree of freedom, linear model has been used extensively in coupled vehicle stability analyses. The aim of the presented work was to extend the conventional coupled vehicle analysis with a set of more elaborate mathematical models evaluating various vehicle configurations. Using in-house multibody dynamics software the linearized equations of motion of three dimensional models were automatically generated for various coupled vehicle configurations with general and military applications. Stability analyses were conducted over a range of expected operating speeds.

Though the purpose of a vehicle's suspension is multi-faceted and complex, the fundamentals may be simply stated: the suspension exists to provide the occupants with a tolerable ride, while simultaneously ensuring that the tires maintain good contact with the ground. At the root of the familiar ride/handling compromise, is the problem that tuning efforts which improve either grip or handling are generally to the detriment of the other. This study seeks to set forth a clear means for examining the familiar ride/handing compromise, by first exploring the key ideas of these terms, and then by describing the development of content-rich metrics to permit a direct optimization strategy. For simplicity, the optimization problem was examined in a unilateral manner, where heave (vertical; z-axis) behaviour is examined in isolation, though the methods described herein may be extended to pitch and roll behaviour as well.

The paper describes a closed-loop vehicle simulation environment developed to support a virtual vehicle design and testing methodology, proposed for the University of Windsor Formula SAE team. Virtual prototyping and testing were achieved through co-simulation of Matlab/Simulink® and Carsim®. The development of the required hybrid-control driver and vehicle models are described. The proposed models were validated with in vehicle test data. The proposed methods have shown to be effective and robust in predicting driver response, while controlling the vehicle within the developed simulation environment.

The paper describes a ‘virtual motorsports’ event developed by the University of Windsor Vehicle Dynamics and Control Research Group. The event was a competitive project-based component of a Vehicle Dynamics course offered by the University's Department of Mechanical, Automotive, & Materials Engineering. The simulated race was developed to provide fourth year automotive engineering students with design and race experience, similar to that found in Formula SAE®or SAE Baja®, but within the confines of a single academic semester. The project, named ‘Formula463’, was conducted entirely within a virtual environment, and encompassed design, testing, and racing of hi-fidelity virtual vehicle models. The efficacy of the Formula463 program to provide students with a design experience using model based simulation tools and methods has been shown over the past two years. All of the software has been released under a General Public License and is freely available on the authors website.

A vehicle undergoing longitudinal or lateral accelerations experiences load transfer, dynamically changing the normal load carried by each tire. Conventional braking systems are designed only to work adequately over a large range of conditions, but often ignore the dynamic state of the tire's normal load. Fortunately, new developments in braking system hardware give designers more control over the application of braking pressures. By identifying the tires that carry increased normal load, and biasing the braking system toward those tires, total braking force can be increased. The purpose of this research is to investigate advantages of open-loop load transfer based active brake pressure distribution. By estimating the tractive ability of the tires as a function of measurable vehicle conditions, brake pressure can be applied in proportions appropriate for the current dynamic state of the vehicle, referred to as Active Brake Proportioning (ABP).

This paper proposes and evaluates the use of a robust variable torque distribution (VTD) yaw moment control for an all wheel drive (AWD) hybrid vehicle prototype currently under development. The proposed VTD controller was used to improve the linearity of vehicle response to driver input through the modulation of front-to-rear torque distribution and a corrective torque differential between the left and right rear wheels. The development of a non-linear vehicle model and a reference model tracking sliding mode based control are discussed. The efficacy of the proposed control system was demonstrated through the use of numerical simulations using the developed non-linear vehicle model. The simulation results presented indicate the effectiveness of the proposed system and the potential restrictions to such a system including tire saturation and drivetrain component limitations.

As a part of any vehicle suspension design, the location of the roll centre should be determined. The location of the roll centre is a property of the suspension geometry that influences vehicle handling behaviour. Typically, the roll centre is located by application of a complex set of formulae that are derived for each particular type of suspension (short-long arm, strut, etc.). This paper presents an alternate method of roll centre analysis, based on a multibody dynamics approach. The method is applicable to any independent suspension that can be modeled using standard multibody constraints. The results show that the roll centres can be located through an eigenvector solution. Relatively little modification of the method is required to find pitch centre locations, and it simultaneously provides additional information regarding suspension kinematics. The process is demonstrated with an example.

The purpose of this study is to determine the feasibility of simulating an active suspension using cosimulation. The vehicle used is a utility truck created in ADAMS/View while the E.C.U. (electronic control unit) is implemented in Simulink for both a fully-active and semi-active controller. The LQR (Linear Quadratic Regulator) is used for the fully-active system while the semi-active system uses a switching law adopted from Karnopp et al. {1}. Nonlinear and linear vehicle models are compared and the influence of suspension bushings is examined. All simulations undertaken are geared towards evaluating the ride capabilities of such systems.