Data processing: structural design – modeling – simulation – and em – Simulating nonelectrical device or system – Mechanical
Reexamination Certificate
1999-10-18
2001-09-04
Teska, Kevin J. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Simulating nonelectrical device or system
Mechanical
C703S002000, C318S561000, C318S568220, C366S078000, C700S031000, C700S032000, C701S097000
Reexamination Certificate
active
06285972
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to computer modeling of a system, machine or process. More particularly, the present invention relates to generating an improved nonlinear system model, such as a neural network, as well as using a nonlinear system model or the improved nonlinear system model to generate drive signals as input to a vibration system.
Vibration systems that are capable of simulating loads and/or motions applied to test specimens are generally known. Vibration systems are widely used for performance evaluation, durability tests, and various other purposes as they are highly effective in the development of products. For instance, it is quite common in the development of automobiles, motorcycles, or the like, to subject the vehicle or a substructure thereof to a laboratory environment that simulates operating conditions such as a road or test track. Physical simulation in the laboratory involves a well-known method of data acquisition and analysis in order to develop drive signals that can be applied to the vibration system to reproduce the operating environment. This method includes instrumenting the vehicle with transducers “remote” to the physical inputs of the operating environment. Common remote transducers include, but are not limited to, strain gauges, accelerometers, and displacement sensors, which implicitly define the operating environment of interest. The vehicle is then driven in the same operating environment, while remote transducer responses (internal loads and/or motions) are recorded. During simulation with the vehicle mounted to the vibration system, actuators of the vibration system are driven so as to reproduce the recorded remote transducer responses on the vehicle in the laboratory.
However, before simulated testing can occur, the relationship between the input drive signals to the vibration system and the responses of the remote transducers must be characterized or modeled in the laboratory. This procedure is referred to as “system identification” and involves obtaining a respective linear model or transfer function of the complete physical system (e.g. vibration system, test specimen, and remote transducers) hereinafter referred to as the “physical system” and calculating an inverse system linear model or transfer function of the same. The inverse linear system model or transfer function is then used iteratively to obtain suitable drive signals for the vibration system to obtain substantially the same response from the remote transducers on the test specimen in the laboratory situation as was found in the operating environment.
As those skilled in the art would appreciate, this process of obtaining suitable drive signals is not altered when the remote transducers are not physically remote from the test system inputs (e.g. the case where “remote” transducers are the feedback variables, such as force or motion, of the vibration system controller).
Although the above-described method for modeling and obtaining drive signals for a vibration system has enjoyed substantial success, there is a continuing need to improve such systems. In particular, there is a need to improve the system model and/or the process for obtaining the drive signals. Current techniques for obtaining the drive signals subject the test specimen to loads and displacements during the iterative process to ascertain the drive signals. These initial loads and displacements can damage the test specimen before the intended testing occurs. Accordingly, a method and system that reduces application of “non-testing” loads and displacements in developing drive signals would be desirable.
SUMMARY OF THE INVENTION
A method and system for generating an improved nonlinear system model includes generating a linear system model and using a response therefrom to generate the nonlinear system model. In one embodiment, the method includes applying an original system input to the system and obtaining a first system output from the system; generating a linear system model; applying an alternative input to the linear system model and obtaining a linear system output from the linear system model; applying the alternative input to the system and obtaining a second system output, and generating a nonlinear system model using the alternative input, the linear system output from the linear system model and the second output from the system.
A method and system for generating drive signals for a test system uses the improved nonlinear system model or a conventional nonlinear system model. In a first exemplary embodiment, the method includes applying a drive signal to the system; obtaining a response of the system to the drive signal; generating an inverse nonlinear system model using the drive signal and the response; and calculating a final drive signal using a selected response and the inverse nonlinear system model.
In a second embodiment for generating drive signals, the method includes applying a drive signal to the system; obtaining a response of the system to the drive signal; generating a nonlinear system model using the drive signal and the response; generating an inverse linear system model; calculating a test drive signal using a selected response and the inverse linear system model; applying the test drive signal to the nonlinear system model; obtaining an actual response of the nonlinear system model to the test drive signal; calculating an error as a function of the actual response and the selected response; and if the error exceeds a selected threshold, obtaining a new drive signal using the linear system model and repeating the above-described steps where the test drive signal comprises the new drive signal until the error is less than or equal to the selected threshold.
REFERENCES:
patent: 3855841 (1974-12-01), Hunter
patent: 4061017 (1977-12-01), Sloane et al.
patent: 4480480 (1984-11-01), Scott et al.
patent: 4513622 (1985-04-01), Uretsky
patent: 4537076 (1985-08-01), Lax et al.
patent: 4885692 (1989-12-01), Kurihara et al.
patent: 4916632 (1990-04-01), Doi et al.
patent: 4989158 (1991-01-01), Sloane
patent: 5175678 (1992-12-01), Frerichs et al.
patent: 5209661 (1993-05-01), Hildreth et al.
patent: 5311421 (1994-05-01), Nomura et al.
patent: 5339016 (1994-08-01), Thoen
patent: 5353207 (1994-10-01), Keeler et al.
patent: 5377307 (1994-12-01), Hoskins et al.
patent: 5568404 (1996-10-01), Strumolo
patent: 5572440 (1996-11-01), Harashima
patent: 5598076 (1997-01-01), Neubauer et al.
patent: 5598329 (1997-01-01), Niemann
patent: 5649063 (1997-07-01), Bose
patent: 5677609 (1997-10-01), Khan et al.
patent: 5729463 (1998-03-01), Koenig et al.
patent: 5901072 (1999-05-01), Shimmell
patent: 5908122 (1999-06-01), Robinett et al.
patent: 5914830 (1999-06-01), Kadlec et al.
patent: 5949989 (1999-09-01), Falkowski et al.
patent: WO 85/03547 (1985-08-01), None
patent: WO 97/42553 (1997-11-01), None
B.W. Cryer et al., “A Road Simulation System for Heavy Duty Vehicles”, Society of Automotive Engineers, Automotive Engineering Congress and Exposition, Detroit, Michigan, Feb. 23-17, 1976, pp. 1-13.
MTS Brochure, “Explaining the Six Steps of Remote Parameter Control™”, MTS Systems Corporation, May 1996, pp. 1-11.
J.B. Craig, “ITFC—How it works and where to use it”, Carl Schenck AG, Sep. 1979, pp. 1-61.
Wolpert et al., “Multiple paired forward and inverse models for motor control”, Neutral Networks, vol. 11, No. 7/08 , Oct. 1, 1998, pp. 1317-1329.
Jürgen Petersen et al., SAE Technical Paper Series—The Conception, Description, and Applications of a New Vehicle Endurance Test System at AUDI NS, International Congress and Exposition, Detroit, Michigan Feb. 22-26, 1982, pp. 1-13.
Ian Cook, “Appendix A—User Presentations: How to Get a Drive File—Jaguar Cars”, RPC User Group, 8th RPC User Group Meeting, Nov. 9-10, 1988, Eindhoven, the Netherlands, pp. 1-51.
Schenck Brochure: “ITFC Computer Control—the modern approach to Automated-Muliple-Input Simulation Testing” Carl Schenck AG, prior to Jan. 22, 1998.
Phil Grote and Glen Grenier, “Taking the Test Track to the Lab” Automotive Engineers
Broda Samuel
Koehler S.
MTS Systems Corporation
Teska Kevin J.
Westman Champlin & Kelly P.A.
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