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AssigneeDelco Electronics Corporation
InventorsBrian K. Good, Mark R. Keyse
Estimating the term…
In accordance with the teachings of the present invention, an adaptive threshold circuit is provided which develops a series of square-wave voltage pulses from an alternating differential voltage that is produced in response to the rotation of a wheel. The adaptive threshold circuit includes an input circuit for providing an input voltage in response to the alternating differential voltage. A first voltage comparator compares the input voltage with an adaptive analog threshold voltage and produces an output in response thereto which causes a rising edge of the square-wave voltage pulse. A second voltage comparator compares a selected portion of the input voltage with the adaptive analog threshold voltage and produces an output in response thereto. The adaptive threshold circuit further includes a binary counter having a reset input for receiving the first voltage comparator output and an enable input for receiving the second voltage comparator output and provides a plurality of binary outputs. The second voltage comparator output thereby enables the counter so as to detect a peak input voltage. A digital-to-analog converter receives the binary outputs from the binary counter and generates the adaptive analog threshold voltage as a function of a selected percent of peak voltage.
An adaptive threshold circuit for developing a series of square-wave voltage pulses from an alternating differential voltage that is produced by a sensor in response to the rotation of a wheel, comprising:
An apparatus for developing a series of square-wave voltage pulses that are developed during rotation of a rotatable wheel comprising:
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
With an adaptive threshold: generated by feedback
For measuring angular speed: by measuring frequency of generated current or voltage
Pulse technique
Measuring linear or angular speed, acceleration, deceleration, or shock
Term ended 22 Feb 2014 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
1. Technical Field
This invention relates generally to an adaptive threshold circuit and, more particularly, to an adaptive threshold circuit for use with a magnetic or variable reluctance sensor that produces an alternating differential voltage in response to rotation of a wheel.
2. Discussion
Other objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description and upon reference to the drawings in which:
FIG. 1 is a block diagram which illustrates a variable reluctance sensor interface module for interfacing a variable reluctance sensor with a processing module in accordance with the present invention;
FIGS. 2A and 2B are circuit diagrams which when taken together illustrate the variable reluctance sensor interface module as shown in FIG. 1;
Referring now to FIGS. 1, 2A and 2B, a variable reluctance sensor interface module 25 is shown therein for interfacing a variable reluctance sensor 15 with a processing module (not shown). The variable reluctance sensor interface module 25 is adapted to be used in a vehicle (not shown), such as an automobile. More particularly, this invention will be described for use in sensing rotational wheel speed for systems such as anti-lock braking systems. However, it is to be understood that the use of this invention is not restricted to automobiles and anti-lock braking systems, but could have other uses such as determining engine crankshaft position and speed for a distributorless ignition system (DIS).
With particular reference to FIG. 1, a rotatable wheel 10 is shown which may be driven in conjunction with a wheel/tire assembly found on a vehicle such as an automobile. The wheel 10 has a plurality of slots 12 that are preferably evenly spaced from each other about the outer periphery of the wheel 10. In a distributorless ignition system (DIS) application for a spark ignited internal combustion engine, an additional slot may be employed for purposes of synchronizing the distributorless ignition system in a manner known to those skilled in the art.
A variable reluctance magnetic pick-up or magnetic sensor 15 is disposed adjacent to the outer periphery of wheel 10. The magnetic sensor 15 includes a magnetic pick-up made up of a permanent magnet 14 which has a core formed of magnetic material and a pick-up coil 16 that is wound on the permanent magnet 14. The magnetic sensor 15 has a first sensor output line 18 connected to one side of pick-up coil 16 and a second sensor output line 20 connected to the other side of pick-up coil 16.