Statistical compensation of load position on a platform scale

Details Statistical compensation of load position on a platform scale Statistical compensation of load position on a platform scale

1998-12-11

2001-07-10

Shah, Kamini (Department: 2857)

Data processing: measuring, calibrating, or testing

Measurement system

Statistical measurement

C702S173000, C702S174000, C073S862627, C177S025140, C177S201000

Reexamination Certificate

active

06260003

ABSTRACT:

RELATED APPLICATIONS
Not applicable.
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
MICROFICHE APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of multiple load cell vehicle scales. More particularly, the invention is concerned with using statistical analysis to derive load position correction factors for a scale having a plurality of load cells.
2. Description of the Prior Art
A typical platform scale includes a platform supported by a plurality of load cells that are coupled with a signal processor. The load cells produce load signals representative of the weight experienced by each load cell. The signal processor processes the load cell signals to produce weight signals representative of the total weight of a load on the platform. The weight signals are derived from a combination of the load signals from the load cells.
However, the weight signals are subject to error due to the position of the load on the platform. That is, the same load at different positions on the platform may produce different weight indications. This is known as load position error. Load position correction factors must be derived for use with each of the load signals in order to compensate for this error.
One prior art technique for load position compensation is to place a given load in turn over each load cell on the platform. At each position, load cell readings are taken. These readings are used in a set of simultaneous equations, one equation for each load cell and one unknown (the correction factor) for each load cell. Algebraic techniques are used to solve these equations for the correction factors. However, these techniques use only one set of readings for each load position over a given load cell and thereby, cannot compensate for cyclic or random errors.
SUMMARY OF THE INVENTION
The present invention solves the prior art problems discussed above and provides a distinct advance in the state of the art. In particular, the platform scale apparatus hereof derives load position correction factors using statistical techniques providing the ability to compensate for cyclic and random errors.
The preferred scale apparatus in accordance with the present invention includes a platform supported by a plurality of load cells coupled with a signal processor which is operable to receive load signals from the load cells and to produce weight signals derived from a combination of load signals representative of the weight of a load on a scale. The processor is operable to perform a statistical analysis of the load signals corresponding to a plurality of different positions of a given load on the platform to derive therefrom respective load position correction factors. These factors are used to compensate for load position error in deriving subsequent weight signals.
In preferred forms, the correction factors are derived from load signals corresponding to a load placed on the platform over each of the load cells a plurality of times. This compensates for cyclic and random errors. The preferred statistical analysis includes least squares analysis or successive approximation analysis. Other preferred aspects of the preferred embodiment are disclosed herein.


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