Measuring and testing – Tire – tread or roadway
Reexamination Certificate
1999-03-08
2001-02-27
Oen, William (Department: 2855)
Measuring and testing
Tire, tread or roadway
Reexamination Certificate
active
06192745
ABSTRACT:
FIELD OF THE INVENTION
The invention is an improved system and method for simulating the interaction of a motor vehicle and a road surface, and specifically, pertains to a system and method of using computer models of a vehicle's wheels and tires to evaluate vehicle performance in relation to a computer model of a roadway.
BACKGROUND
Systems for the simulation of vehicle operation are well known. Among these systems are vehicle operating simulators, which can be operated by a driver manipulating conventional controls and producing visual, aural and tactile feedback, such as those taught by Briggs, et al, in U.S. Pat. No. 4,952,152 and DeGroat, et al, U.S. Pat. No. 5,277,584.
Systems for the analysis of the forces imposed on a motor vehicle during operation are also well known. Using traditional finite element analysis (FEA) techniques, it is possible to construct so-called FEA models of vehicles and their component parts utilizing a computer, and further, to use the computer to simulate forces acting upon the vehicle computer model to determine and predict stress, strain, durability and fatigue of vehicle components.
Our own finite element model builder system is an example of the current state of the art in the creation of finite element models using finite element analysis. With these systems, the structure of a motor vehicle body, chassis, drive train, suspension and other component parts can be created as a computer model. Manipulation of this model can then be performed in a variety of ways to assist the vehicle designer. The model can be viewed on a typical video display device, which allows the designer and engineer to rotate the view of the model, manipulate the components of the model and test the results of said manipulation or modification of the model.
Our software also interfaces with a wide variety of other computer programs, for example, computer programs which assist in the designing of production tools.
It is also known to utilize FEA models in a dynamic simulation environment. For example, a motor vehicle suspension model can be subjected to a repetitive computer-simulated force comparable to that force imposed on an actual motor vehicle suspension, e.g., the vehicle's encounter with a roadway pothole. By repeating this simulation, repetitive stresses on suspension components can be effectively evaluated, without the need to actually subject the physical component to the physical roadway conditions, in a much shorter time at less expense than that required by actual operation of a vehicle in the proving ground environment.
An underlying problem with prior simulation methods and systems is the imprecision of the inherent estimations which are required to run the simulations. For example, in prior art “pothole” simulations, the systems assumed that the forces transmitted by the impact of the motor vehicle tire with a pothole would result in an isolated vertical force being applied to the vehicle's suspension and body. In reality, the pothole also results in a rearward force on the vehicle's suspension when the vehicle tire strikes the vertical surface of the pothole as the vehicle travels forward. Further, prior simulation techniques largely ignored the size, shape, mass, geometry and dynamics of the wheel/tire combination, and treated forces applied to the motor vehicle suspension and vehicle body as essentially point source forces at particular points in the vehicle suspension. Such assumptions have been shown to provide largely inaccurate simulation data.
The present invention allows for the modeling and simulation of all vehicle components in the proving ground environment. Previous systems have been limited to the simulation of various vehicle sub-systems, but not the vehicle as a whole. The present invention also provides better consistency between successive tests and better consistency within specific model configurations. By providing an accurate model of both the vehicle and the road surface, any change in the individual model elements (e.g., the tire model) will isolate the effects of substitution of different elements under consideration, provided all other vehicle components and models remain unchanged.
SUMMARY OF THE INVENTION
Utilizing the system and method of the present invention, a computer-based model of a motor vehicle is created. Thereafter, additional computer models of various vehicle components, including the suspension, wheels and tires are created. Finally, a computer model of a typical test roadway surface is created. Once all required computer models have been generated, the vehicular components are combined into a virtual vehicle for computer analysis. The virtual vehicle is placed on a virtual roadway derived from the roadway model, digitized from the proving ground test track surface profile for example, and the elements of the vehicle and roadway are manipulated by computer analysis software which simulates the interaction between the virtual vehicle and the virtual roadway under various conditions of vehicle load, highway speed and maneuvering of the virtual vehicle in relation to the virtual highway. The stresses due to the forces imposed on the virtual vehicle during this analysis may be collected and analyzed by, among other means, computer-based fatigue analysis techniques. The data so obtained and analyzed can be displayed in the form of raw data, or in the form of graphic computer models which isolate and identify data of interest to vehicle designers and engineers, such as areas of high stress or low durability. The data may also be used to calculate and plot suspension parameters over the duration of the simulated interaction between the virtual vehicle and the virtual roadway. Such suspension parameters are valuable to suspension designers, development engineers, etc. in evaluating the effects of camber or toe change, caster, steer axis inclination, vehicle roll center, roll stiffness, anti-dive and anti-lift characteristics, and may be used to modify the vehicle suspension to achieve desired handling characteristics.
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Body-Structure Durability Analysis, Automotive Engineering, Jul. 1995, pp. 23-27.
Palmer Timothy J.
Tang Yue-Li A.
Engineering Technology Associates, Inc.
Harness & Dickey & Pierce P.L.C.
Oen William
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