Oscillatory servo-valve monitor
First Claim
1. An apparatus for monitoring a servo-control system to detect oscillations in an error signal, comprising:
- a first detection path receiving the error signal for detecting oscillations of said error signal within a first frequency range; and
a second detection path receiving the error signal for detecting oscillations of said error signal within a second frequency range;
said first detection path comprising;
(a) means for periodically accumulating a first count signal at a first rate while amplitude of said error signal is outside a first amplitude window; and
(b) means for periodically de-accumulating said first count signal at a second rate while amplitude of said error signal is within said first amplitude window, wherein said first rate is greater than said second rate.
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Abstract
An oscillatory servo-valve fault monitor is provided for identifying faults attributable to servo-control system components. In particular, both low frequency and high frequency (oscillatory) fault responses are identified. Such oscillatory fault responses are distinguished from normal position control adjustments and transient responses. As the reaction to a fault condition is to shut down the faulty actuator and corresponding servo-control, such capability avoids inadvertent shut-downs. Independent detection paths are provided for sensing low frequency responses and high frequency responses. Each path includes a respective window comparator and up-down counter. For a given path, the window comparator defines two thresholds--in effect, a window. If the monitored signal amplitude is outside the window, then a counter or count signal is incremented. If the signal amplitude is within the window, then the counter or count signal is decremented. The time constant for counting up is less than that for counting down, so that more up counts would occur in a given time period, than would down counts for the same period. As a result, faults causing an oscillatory amplitude beyond the thresholds of the window comparator are quickly identified. If the count signals (or the count in either of the up-down counters) exceed a respective value, then the monitor indicates that a fault condition is present.
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Citations
15 Claims
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1. An apparatus for monitoring a servo-control system to detect oscillations in an error signal, comprising:
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a first detection path receiving the error signal for detecting oscillations of said error signal within a first frequency range; and a second detection path receiving the error signal for detecting oscillations of said error signal within a second frequency range; said first detection path comprising; (a) means for periodically accumulating a first count signal at a first rate while amplitude of said error signal is outside a first amplitude window; and (b) means for periodically de-accumulating said first count signal at a second rate while amplitude of said error signal is within said first amplitude window, wherein said first rate is greater than said second rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for monitoring a servo-control system having an inner feedback loop for controlling a servo-valve and an outer feedback loop for controlling an actuator, the inner loop generating a servo-valve feedback signal, the outer loop generating an actuator position feedback signal, the apparatus detecting oscillations in a servo-valve error signal, the apparatus comprising:
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means for generating the servo-valve error signal from said servo-valve feedback signal and said actuator position feedback signal; a first detection path receiving the servo-valve error signal for detecting oscillations of said servo-valve error signal within a first frequency range; and a second detection path receiving the servo-valve error signal for detecting oscillations of said servo-valve error signal within a second frequency range; said first detection path comprising; (a) means for periodically accumulating a first count signal at a first rate while amplitude of said servo-valve error signal is outside a first amplitude window; and (b) means for periodically de-accumulating said first count signal at a second rate while amplitude of said servo-valve error signal is within said first amplitude window, wherein said first rate is greater than said second rate. - View Dependent Claims (11, 12, 13)
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14. A method for monitoring a servo-control system to detect oscillations in an error signal, comprising the steps of:
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receiving the error signal at a first detection path for detecting oscillation amplitudes of said error signal within a first amplitude window; within said first detection path, periodically accumulating a first count signal at a first rate while amplitude of said error signal is outside said first amplitude window; within said first detection path, periodically de-accumulating said first count signal at a second rate while amplitude of said error signal is within said first amplitude window, wherein said first rate is greater than said second rate; receiving the error signal at a second detection path for detecting oscillations of said error signal within a second frequency range; within said second detection path, periodically accumulating a second count signal at a third rate while amplitude of said error signal is outside a second amplitude window; and within said second detection path, periodically de-accumulating said second count signal at a fourth rate while amplitude of said error signal is within said second amplitude window, wherein said third rate is greater than said fourth rate; and identifying a fault when said first count signal reaches a first value or said second count signal reaches a second value. - View Dependent Claims (15)
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Specification