Weighing scales – Structural installation – Geographic
Patent
1993-12-03
1996-12-17
Brown, Brian W.
Weighing scales
Structural installation
Geographic
177 1, 177 2513, G01G 1902
Patent
active
055856047
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of determining a load measurement value in dynamic weighing, wherein an object to be weighed passes, while in motion, over a weighing platform supported by load-sensing means which then generates a load-dependent weighing signal which rises from a basic level to a peak level to subsequently fall to the basic level, which corresponds to the object moving onto the weighing platform, being situated in its entirety on the weighing platform, and moving out from the weighing platform, said method comprising the step of determining an at least approximative signal peak value as representing the weighed load. The invention is especially applicable to dynamic weighing of vehicles travelling at a high speed, e.g., in traffic controls.
TECHNICAL BACKGROUND
When weighing a vehicle or other object moving over a weighing platform, it is extremely difficult to obtain reproducible and accurate measurement values. This difficulty is especially pronounced in traffic controls on roads with very high maximum speed limits, e.g., motorways and the like, and where different sorts of vehicles are to be found, ranging from light private cars to heavy lorries. Tests have shown that the analog weighing signal then becomes very irregular, involving sudden, strong signal variations conditioned, e.g., by vibrations of the wheels, movements of the wheel suspensions, stones or the like struck in the tire tread, and so forth.
OBJECTS OF THE INVENTION
One object of the present invention is to improve the above method to enable the load measurement value to be determined with improved accuracy and with a resolution reflecting the actual quality of the measuring operation.
Another object of the invention is to provide such a method, which also permits the velocity of the object passing over the weighing platform to be determined in an advantageous manner and without any special separate velocity-measuring equipment, as has previously been required.
A further object of the invention is to provide such a method, which also is well-suited for low-velocity weighing.
SUMMARY OF THE INVENTION
According to the invention, these objects are achieved by a method having the distinctive features recited in the appended claims.
Thus, the method according to the invention is essentially characterised by integrating the weighing signal, at least during a time interval about the point where the signal peak value is determined, in order to produce a summation result, said time interval being recorded as a measurement time factor M; calculating a form factor F for the weighing signal in the form of the ratio of the summation result, i.e., the integrated area under the weighing signal for said time interval, to a corresponding rectangular area that would be obtained in static weighing, i.e., the product of a peak value and said time interval; and determining the load measurement value as said at least approximative signal peak value with a resolution depending on the form factor F and the measurement time factor M. The latter is preferably done by taking into account a quality factor conditions. The better the quality factor is, the more figures can be included in the load measurement value, i.e., resolution can be increased.
The form factor F will be a measure of the quality of the obtained signal compared with the result of static weighing of the same mass. It will be appreciated that the form factor is affected by the signal course, regardless of whether the weighing takes place at high or low velocity, although the likelihood of signal disturbances naturally is much greater when the velocity is very high.
Given the above definition of the form factor (the inverted ratio may also be used), the form factor will at best be 1, and this number will decrease as the form factor deteriorates.
The measurement time factor M is a measure of the velocity of the object moving over the weighing platform. This factor will not, however, indicate the velocity with exactitude, since the length of the pressu
REFERENCES:
patent: 3446299 (1969-05-01), Leonowicz
patent: 5300736 (1994-04-01), Ehrhardt
Brown Brian W.
Frontec Lulea AB
Gibson Randy W.
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