Boots – shoes – and leggings
Patent
1989-04-07
1991-04-09
Dixon, Joseph L.
Boots, shoes, and leggings
36442602, 36472419, G06F 1531, H03F 126, G06G 700
Patent
active
050070070
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to apparatus for converting a measurement signal V.sub.R(i), which is disturbed at least occasionally by a disturbance function into an undisturbed signal V.sub.R(o) by the use of a filter having variable filter parameters.
When the speed of a vehicle wheel, is measured for the purpose of brake-pressure control (ABS), for example, there is frequently impressed on the measurement signal V.sub.R(i) a disturbance signal of one or more specific frequencies which can distort the signals to be evaluated (e.g., the wheel-speed signal itself or its derivatives).
It is known quite generally that disturbance signals can be eliminated by filtering. However, the frequencies of the disturbances often are not known and, moreover, such frequencies are variable as a function of the given influences. So-called adaptive digital filters therefore lend themselves to such filtering; however, they must be adjusted so that only the disturbance signal is filtered out.
SUMMARY OF THE INVENTION
The present invention provides apparatus which determines the filter parameters for the disturbance signal, during periods in which the disturbance signal is available or represented separately, and, through a comparison, determines whether the newly determined parameters produce better filtering than the previously set parameters. If the new parameters would provide better filtering, the apparatus transfers these parameters to the actual filter (the first adaptive digital filter). Two so-called "adaptive ladder filters" are preferably used in this system.
When the ladder-filter parameters have been adapted to a disturbance signal, the desired signal (input signal minus disturbance signal) appears at the output of the filter. To make certain that the input signal contains no desired signal during the parameter determination, the disturbance signal is isolated from the input signal only at given times. For example, after a pressure reduction in a wheel brake cylinder in an antilock braking system, the wheel speed often shows oscillations which are also known as "axle oscillations". To filter these axle oscillations out of the wheel signal, the second adaptive ladder filter is switched to its adaptation mode when the wheel, after the pressure reduction, has again entered the stable region of the wheel-slip curve. The adaptation is discontinued, at the latest, when a pressure-buildup pulse occurs. After this adaptation, the new filter parameters are transferred to the first adaptive filter, which continuously filters the wheel signal V.sub.R. If the new parameters would provide better filtering, the apparatus.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention and to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a preferred embodiment of the invention.
FIG. 2, comprised of FIGS. 2a and 2b, are signal diagrams illustrating the operation of the apparatus of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 illustrates apparatus for adaptive filtering of the disturbed signal V.sub.R. V.sub.R(i) is the unfiltered wheel speed, and V.sub.R(o) the filtered wheel speed.
Inserted in the signal path between the terminals 1 and 2 is a first adaptive ladder filter 3. However, the wheel-speed signal V.sub.R(i) is also fed to a high-pass filter 4, which is followed by a second adaptive ladder filter 5. A microprocessor 6 is provided for controlling the filters 3 and 5. Moreover, a further high-pass filter 7 is provided to which the filtered signal V.sub.R(o) is fed. The outputs of the filters 5 and 7 are connected to a comparator in the microprocessor 6.
The adaptive filters 3 and 5 are controlled by a microprocessor with respect to their function. The microprocessor determines when the adaptation in the adaptive ladder filter 5 is to start and when it is to stop. The microprocessor further determines whether the new parameters are to be tr
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1980 IEEE Int'l Symposium on Circuits & Systems Proceedings, vol. 3, IEEE, (US), McColl et al.
Principals and Applications of Adaptive Filters-pp. 1143-1157.
IEEE Transactions on Power Apparatus and Systems, vol. PAS-104, No. 13, Dec. 1985, pp. 3341-3342.
Kost Friedrich
van Zanten Anton
Dixon Joseph L.
Robert & Bosch GmbH
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