Coded data generation or conversion – Converter compensation
Reexamination Certificate
2001-03-29
2002-10-08
Jeanpierre, Peguy (Department: 2819)
Coded data generation or conversion
Converter compensation
C341S120000
Reexamination Certificate
active
06462683
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a circuit configuration and a method for setting the switching points of a decision maker which is actuated by an analog input signal.
Sensors are used in a known manner to detect the movement or the position or orientation state of rotating parts. Examples of this include crankshaft, cam shaft, transmission and ABS sensors in automobiles. Hall sensors are preferably used as sensors and monitor a change in a magnetic field. To this end, for example, a permanent magnet is fitted to a stationary part, in order to produce a magnetic field. The magnetic field is then modulated by a gear wheel mounted on the rotating part or by some other ferromagnetic transmitter, depending on the position or orientation. The Hall sensor is in this case preferably located between the permanent magnet and the gear wheel or transmitter, and can thus detect fluctuations in the magnetic field. If, for example, a tooth of the gear wheel is located in the magnetic field, then a “high” output signal is supplied, while a gap between the teeth results in a “low” output signal. In this way, the signal emitted from the Hall sensor can be used to deduce the instantaneous orientation or position of a rotating part.
The signal supplied from a sensor is influenced substantially by the operating conditions in which the sensor is used. These operating conditions include unavoidable incalculable factors, such as the operating temperature or the size of the air gap etc. Despite the fluctuations caused by the operating conditions, the sensor should supply an output signal that is as well defined as possible. Therefore, the output signal should have a well-defined profile irrespective of fluctuations caused by the operating conditions. The reason for this is now described. If, for example, a sensor configuration supplies a sinusoidal signal, then a system controlled by the sensor configuration can maintain a well-defined response when the system switching processes, which depend on the output signal from the sensor, are carried out at the zero crossings of the signals. Specifically, the zero crossings are independent of the respective signal amplitude and, furthermore, have a high edge gradient.
If the output signal from the sensor has other signal forms, a switching point other than the zero crossing or signal mid-point may, of course, also be advantageous.
When evaluating the output signal of a sensor for switching a system which is controlled by this sensor, a switching point should therefore be maintained irrespective of the signal amplitude of the output signal from the sensor, and this applies even to very slow signals. In detail, VDI Reports 1287, 1996, pages 583 to 611, titled “Eine neue Generation von “Hall-Effekt”-Zahnradsensoren: Vorteile durch die Verbindung von BIMOS-Technologie und neuen Verpackungsrezepten” [A new Generation of “Hall Effect” Gearwheel Sensors: Advantages Resulting From the Use of BIMOS Technology and New Packaging Forms] describes a sensor configuration in which the amplitude of the output signal from the sensor is initially normalized, possibly with the aid of an analog/digital converter. The signal peak values are detected with the aid of two further analog/digital converters and digital/analog converters. This is used to derive and define a switching threshold. In the end, this allows a system response to be achieved which is essentially independent of temperature fluctuations and the width of the air gap. However, the complexity required for the sensor configuration is relatively high, since gain matching and numerous analog/digital converters are required.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a circuit configuration and a method for setting the switching points of a decision maker which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type, which is actuated by an analog input signal, in which configuration and method switching processes can be set reliably and with high accuracy at selected points of an input signal, with little complexity.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration for correcting an analog input signal having a DC element, an AC element, and upper and lower signal peaks whose ratio to one another is fixed but variable. The analog input signal being corrected by compensation for the DC element. The circuit configuration contains a decision maker receiving the input signal and a calibration device. The calibration device includes an analog/digital converter actuated by the input signal and is connected to the decision maker. Peak-value detectors are provided for determining the upper and lower signal peaks of the input signal, the peak-value detectors are disposed downstream from the analog/digital converter. A controllable reference unit is provided for generating a reference value. A computation unit for determining a mean value from at least one signal minimum and at least one signal maximum is disposed downstream from the peak-value detectors. The mean value is either an arithmetic mean of the upper and lower signal peaks or mean weighted using the fixed but variable ratio. A comparison unit for determining a signal position of the input signal by comparing the reference value with the mean value determined by the computation unit is provided. The comparison unit is connected to the computation unit and to the controllable reference unit. A first regulating unit has an input connected to the comparison unit and an output linked to the decision maker. The first regulating unit compensates for the DC element in the input signal if an unbalanced signal position is detected by the comparison unit, with the compensation being carried out by subtraction of a value which is determined from an output of the comparison unit from the input signal. A second regulating unit has an input connected to the comparison unit and an output connected to the controllable reference unit. The second regulating unit readjusts the reference value in an opposite sense to an output signal from the comparison unit, in which case a difference between the mean value and the reference value is used to form a new reference value. A device for scaling the mean value is disposed between the computation unit and the comparison unit or an output side of the comparison unit.
The circuit configuration according to the invention for setting the switching points of a decision maker which is actuated by an analog input signal, independently of any DC element which is included in the input signal and together with upper and lower signal peaks, contains a control device having peak-value detectors. The peak-value detectors are actuated by the input signal, for determining the upper and lower signal peaks of the input signal. Furthermore, the control device has a controllable reference unit for providing a reference value, a computation unit connected downstream from the reference unit and the peak-value detectors for determining the mid-value from at least one upper and one lower signal peak, and a comparison unit for determining the signal position of the input signal by comparison of the reference value with the mid-value determined by the computation unit. Finally, a first regulating unit is provided whose input side is connected downstream from the comparison unit and whose output side is linked to the decision maker, in order to compensate for the DC element in the input signal by a compensation signal when a DC element is detected by the comparison unit.
A second regulating unit, whose input side is connected downstream from the comparison unit and whose output side is connected to the reference unit, is preferably also provided, for readjusting the reference value in the opposite sense.
The circuit configuration according to the invention allows the DC element contained in an analog input signal, independently of an AC element, to be determine
Jeanpierre Peguy
Lauture Joseph J
Mayback Gregory L.
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