Data processing: measuring – calibrating – or testing – Testing system – Of mechanical system
Reexamination Certificate
1999-02-22
2001-10-16
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Testing system
Of mechanical system
C073S023310
Reexamination Certificate
active
06304829
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to vehicle test fixtures which simulate vibrational effects of road conditions and, more specifically, to a method for determining accurate test control input signals for such a fixture suitable for testing a vehicle exhaust system.
BACKGROUND ART
Generally, a vehicle exhaust system must perform several demanding and diverse requirements, i.e., attenuating engine noise while porting and reducing emission levels of engine exhaust gas to the atmosphere. In addition, legislative action in combination with typical market driven design concerns have made the need for durable exhaust systems greater than ever before.
Thus, the need for determining exhaust system durability in a cost effective manner has generated demand for a system capable of verifying complete system performance prior to integration with a vehicle. Due to reduced product cycle time, physical testing of system level hardware and durability has been used to validate computer aided engineering (CAD) analysis. However, the methods of determining durability to date have not proven reliable. Thus, physical test fixtures are typically used in an attempt to simulate actual road conditions for measuring system durability.
However, the problem with using physical test fixtures is that reliability of the test results is directly related to the realism with which the input control signals/boundary conditions simulate actual road conditions. While the structural materials of the exhaust system have generally linear responses, other factors such as exhaust hanger isolations, are nonlinear or not well defined but will greatly influence the exhaust system dynamic loads, accelerations, and displacements. As a result, a need exists for a method which can accurately define these control signals and boundary conditions for application to a test fixture.
DISCLOSURE OF THE INVENTION
It is, therefore, an object of the present invention to provide a method and system for defining engine hot exhaust thermal profiles, engine attachment control boundary conditions, and vehicle frame control signals for input to an exhaust system laboratory test fixture which will accurately reproduce real world dynamic load conditions on the tested exhaust system.
In accordance with this and other objects, the present invention provides a method and system for generating engine attachment control boundary conditions and corresponding actuator control signals for an exhaust system laboratory test fixture in which actual acceleration road load data is initially collected for both a vehicle frame at each of the locations where the exhaust system attaches to the vehicle frame, and relative displacement or acceleration data for a vehicle powertrain relative to the vehicle frame, after which a remote parameter control processor is programmed to obtain vehicle coordinates for positioning of test fixture accelerometer locations by identifying the vehicle coordinates that define the locations and directions on the vehicle frame at which the actual acceleration road load data was collected. A rigid body analysis is performed by applying the actual acceleration road load data and the identified vehicle coordinates in a statistical multiple linear regression analysis to define a rigid body that fits the road load acceleration data at the vehicle coordinates. The fit of the defined rigid body can be verified. Then, boundary conditions on the test fixture are determined by selecting a set of accelerometer locations and directions which best define and fit the defined rigid body. Determination of the boundary conditions includes determining the number of degrees of freedom (DOF) from 1 to 6 needed to control the powertrain and chassis. The actuator control signals are determined based on the determined boundary conditions in combination with a first control model arranged to control frame motion relative to a test floor, and a second control model arranged to control powertrain motion relative to the frame and/or chassis exhaust components if the test fixture is to be operated in a powertrain frame attached mode.
Thus, the present invention provides a method for defining engine attachment control boundary conditions for an exhaust system laboratory test fixture which will reproduce the dynamic behavior of the vehicle powertrain during operation in conjunction with reproducing the dynamic behavior of the vehicle frame during operation in the area where the exhaust system is attached to the vehicle frame.
The above object and other objects, features and advantages of the present invention are more readily understood from a review of the attached drawings and the accompanying specification and claims.
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Team Corporation Web page published Bulletins, “Automotive Vibration Test System”; Engine Simulation Systems; “Four Poster Test Systems”; “The CUBE 6 Degrees of Control”; “Team Corporation Introduces the CUBE™ Six Degree of Control™ Vibration Test System”; and “Team Delivers Flexible ‘Four Post’ Test System”; May 20, 1998, 9 pp.
IATO Paper Techniques for Laboratory Durability Testing of Exhaust Systems (Steven R. Haeg, P.E.) Published 11/97 (SAE Indonesia).
Alanoly James
Elsenety Nabih Wassef
Fricke David M.
Olson David W.
Page Arthur J.
Drouillard Jerome R.
Ford Global Technologies Inc.
Hang Dinh
Hoff Marc S.
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