Boots – shoes – and leggings
Patent
1995-04-13
1998-06-16
Elmore, Reba I.
Boots, shoes, and leggings
364159, 381 71, 381 94, G05B 1302
Patent
active
057681244
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an adaptive control system and method for reducing undesired primary signals generated by a primary source of signals.
The basic principle of adaptive control is to produce a cancelling signal which interferes destructively with the primary signals in order to reduce them. The degree of success in cancelling the primary signals is measured to adapt the cancelling signal to increase the reduction of the undesired primary signals.
This idea is thus applicable to any signal such as electrical signals within an electrical circuit in which undesired noise is produced. One particular area which uses such adaptive control is in the reduction of unwanted acoustic vibrations in a region.
It is to be understood that the term "acoustic vibration" applies to any acoustic vibration including sound and mechanical vibration.
There has been much work performed in this area with a view to providing a control system which can adapt quickly to changes in amplitude and frequency of vibrations from a source. Such systems are generally considered in "Adaptive Signal Processing", by B. Widrow and S. D. Stearns. One such system is disclosed in WO88/02912 the content of which is hereby incorporated by reference. In this document a controller is disclosed which is implemented as a digital adaptive finite impulse response (FIR) filter. In order for the filter to be adapted the filter coefficients must be modified based on the degree of success in cancelling the undesired vibrations. For the control system disclosed in this document there are a large number of error signals, drive signals and reference signals and there are therefore a large number of calculations which must be performed. In the arrangement disclosed in WO88/02912 the coefficients are updated adaptively using an algorithm. In practice, there is a possibility that the adaptive control system will become unstable and it can possibly even contribute to the noise which it is supposed to be trying to cancel out.
It is therefore an object of the present invention to provide an adaptive control system which can detect erroneous or faulty operation of the system and can provide an indication of a fault which can be used to shut the system down.
The present invention provides an adaptive control system for reducing undesired signals comprising secondary means to provide at least one secondary signal for interference with said undesired signals; residual means to provide at least one residual signal indicative of the interference between said undesired and secondary signals; adaption means operative to adjust said at least one secondary signal using said at least one residual signal to reduce said at least one residual signal; and adaption fault detection means to detect erroneous or faulty operation of the system and provide an indication of a fault.
Preferably the adaption means comprises adaptive response filter means having filter coefficients and adapted to adjust said at least one secondary signal using said filter coefficients.
In one embodiment the system includes shut-down means to shut down the operation of the adaptive control system when the adaption fault detection means indicates a fault. Preferably in such an embodiment restart means are included which are adapted to restart the adaptive control system following a shut-down and wherein said shut-down means is adapted to disable said restart means after a predetermined number of shut-downs in a period of time to prevent restart.
In one embodiment the adaptive fault detection means comprises test means to periodically increase or decrease at least one secondary signal by a predetermined amount; and monitoring means to monitor said at least one residual signal and indicate a fault if during an increase or decrease in at least one said secondary signal there is no increase by a predetermined amount in at least one said residual signal.
In embodiments of the present invention the test means can be adapted to periodically increase or decrease the filter coefficients by a predetermined
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Transactions of the Society of Instrument Technology, "Automatic Optimization", by P.E. W. Grensted et al., Sep. 1961, pp. 203-212.
Journal of the Acoustical Society of America, "Use of ramdon noise for on-line transducer modeling in an adaptive active attenuation system", by L.J. Ericksson and M.C. Allie, Feb. 1989, vol. 85, No. pp. 797-802.
Bowles C. L.
Hutchins S. M.
McDonald A. M.
Stothers I.
Dolan Robert J.
Elmore Reba I.
Lotus Cars Limited
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