Speed sensor fault detection system and method
First Claim
1. A method for detecting and reacting to "dropped pulse type" faults in the output signals from speed sensor assemblies (10) in a control system including a control unit (ECU) for processing input signals according to either a non-fault sensed set of predetermined logic rules and a separate fault sensed (fail safe, fail soft) set of predetermined logic rules and a speed sensor assembly of the type comprising a rotor (12) rotatably associated with the monitored rotatable member (14) and a relatively fixed sensor member (16), said sensor assembly providing an output signal (20, 22, 24, 26) comprising a plurality of pulses having a frequency indicative of the rotational speed (S) of said rotor, the rotational speed determined as a function of the number (N) of said pulses over a period of time, said method characterized by:
- selecting the period of time such that if the actual value of (N-1) is sensed as equalizing (N-2) or less, then a determined absolute value of the rate of change in S will be greater than a reference value equal to at least a largest expected deceleration rate of the monitored object;
determining a value indicative of the rate of change with respect to time in S;
comparing the absolute value of said value indicative of in the rate of change in S to said reference value (REF); and
if the absolute value of the value indicative of the rate of change of S is greater than said reference value, causing said control unit to process input signals according to said fault sensed set of predetermined logic rules.
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Accused Products
Abstract
The control method/system for sensing "tooth or pulse drop-out" type faults in the output signals from a rotational speed sensor assembly (10) of the type utilizing a rotor (12) and a relatively fixed sensor (16) to provide an output comprising a plurality of pulses having a frequency indicative of the rotational speed of the rotor is provided.
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Citations
7 Claims
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1. A method for detecting and reacting to "dropped pulse type" faults in the output signals from speed sensor assemblies (10) in a control system including a control unit (ECU) for processing input signals according to either a non-fault sensed set of predetermined logic rules and a separate fault sensed (fail safe, fail soft) set of predetermined logic rules and a speed sensor assembly of the type comprising a rotor (12) rotatably associated with the monitored rotatable member (14) and a relatively fixed sensor member (16), said sensor assembly providing an output signal (20, 22, 24, 26) comprising a plurality of pulses having a frequency indicative of the rotational speed (S) of said rotor, the rotational speed determined as a function of the number (N) of said pulses over a period of time, said method characterized by:
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selecting the period of time such that if the actual value of (N-1) is sensed as equalizing (N-2) or less, then a determined absolute value of the rate of change in S will be greater than a reference value equal to at least a largest expected deceleration rate of the monitored object; determining a value indicative of the rate of change with respect to time in S; comparing the absolute value of said value indicative of in the rate of change in S to said reference value (REF); and if the absolute value of the value indicative of the rate of change of S is greater than said reference value, causing said control unit to process input signals according to said fault sensed set of predetermined logic rules. - View Dependent Claims (2, 3, 4)
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5. A control system for detecting and responding to "dropped tooth type" faults in the output signals from tooth rotor type speed sensor assemblies, said control system including a control unit (ECU) for processing input signals according to either a non-fault sensed set of predetermined logic rules and a separate fault sensed (fail safe, fail soft) set of predetermined logic rules and a speed sensor assembly (10) of the type comprising a tooth rotor (12) rotatably associated with the monitored rotatable member (14) and a relatively fixed sensor member (16), said sensor assembly providing an output signal (20, 22, 24, 26) comprising a plurality of pulses having a frequency indicative of the rotational speed of said rotor, the rotational speed determined as a function of the number (N) of said tooth pulses sensed in a time period, said system characterized by:
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means for setting the time period such that if the actual value of (N-1) is sensed as equaling (N-2) or less, then a determined absolute value of the rate of change in S will be greater than a reference value equal to at least a largest expected deceleration rate of the monitored object; means for determining a value indicative of the rate of change with respect to time in S; means for comparing the absolute value of said value indicative of the rate of change in S to said reference value (REF) and if the absolute value of the value indicative of the rate of change of S is greater than said reference value, causing said control unit to process said input signals according to said fault sensed set of predetermined logic rules. - View Dependent Claims (6, 7)
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Specification