Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2001-01-02
2001-11-13
Wolfe, Willis R. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C123S406160, C701S111000
Reexamination Certificate
active
06317681
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method for monitoring the operation of a sensor in an internal combustion engine and an electronic controller monitoring the operation of a sensor.
The growing dependency on fundamental functions in motor vehicles—such as ignition, injection, and knock control—by electronic control systems is placing extremely stringent requirements on their reliability. Furthermore, reliable electronic control systems demand reversionary running programs for fault situations. Self-diagnosis is thus one of the basic functions in modern microprocessor-controlled systems. The objects of self-diagnosis in such control systems are to identify faults and to evaluate them diagnostically, to protect endangered components by suitable reversionary running programs, to provide any substitute parameters required for reversionary running, and to transmit a fault message to the driver.
Under normal operation, sensors derive measurement values from the sensor signals in an evaluation circuit. For example, sensors can derive measurement values of the voltage or current levels. The current levels are proportional to the sensor signal. The evaluation circuit checks these measured values for plausibility by comparing them with plausibility limit values. Depending on the nature of the sensor, a malfunction of the sensor is diagnosed if the plausibility limit value is infringed in either direction over a number of measurement cycles.
For knock control, such a method is known from Published, Non-Prosecuted Patent Application DE 41 26 961 A1, corresponding to U.S. Pat. No. 5,121,729. In order to suppress knocking in an internal combustion engine, a measured value is produced in an evaluation circuit from the sensor signals from a knock sensor, cyclically synchronized with time intervals. The time intervals are defined by the engine cycles of the internal combustion engine.
This measured value is then compared with a fixed plausibility limit value. If the measured value remains below the plausibility limit value throughout a predetermined number of engine cycles in this case, a malfunction of the knock sensor is diagnosed and the ignition is delayed in order to suppress the knocking.
However, in methods such as this, fault identification is feasible only if the measured value in the event of a fault is outside a plausibility range that is governed by the correctly operating sensor.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for monitoring a sensor in an internal combustion engine by evaluating a distribution about the comparison value of the measured values versus the respective amplitudes.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for monitoring the operation of a sensor in an internal combustion engine. The first step is forming measured values from sensor signals in an evaluation circuit. The next step is associating each measured value with a respective amplitude. The next step is calculating a comparison value from a previously formed measured value. The next step is evaluating a distribution about the comparison value of the measured values versus the respective amplitudes.
In accordance with a further object of the invention, the method includes calculating the comparison value as a sliding average from previous measured values.
In accordance with a further object of the invention, the method includes defining an amplitude window that includes the comparison value, incrementing a value of an error counter whenever a measured value is within the amplitude window, resetting the value of the error counter when the measured value is outside this amplitude window, and diagnosing a malfunction of the sensor when the value of the error counter exceeds a predetermined counter threshold value.
In accordance with a further object of the invention, the amplitude window has a bandwidth and the bandwidth of the amplitude window is a function of the amplitude distribution that occurs in a fault of the sensor.
In accordance with a further object of the invention, the amplitude window has a bandwidth, and the bandwidth of the amplitude window is a function of an engine speed of the internal combustion engine.
In accordance with a further version of the invention, the method includes calculating absolute difference values between the measured values and the comparison values. The next step is accumulating the absolute difference values with an accumulator. At the same time, the method includes the step of incrementing a value of a signal counter for each new a measured value. The method then resets the value of the accumulator and the value of the signal counter when the accumulated difference value exceeds a predetermined reset value. The method diagnoses a malfunction of the sensor when the value of the signal counter exceeds a predetermined diagnosis threshold value.
In accordance with a further object of the invention, the reset value is a function of the amplitude distribution of electronic noise that occurs in the evaluation circuit in a fault.
In accordance with a further object of the invention, the reset value is a function of an engine speed of the internal combustion engine.
In accordance with a further object of the invention, the method includes transmitting a fault message to a driver and initiating reversionary running of the internal combustion engine, when a malfunction of the sensor is diagnosed.
It is a further object of the invention to provide an electronic controller accomplishing the method that works in conjuction with an internal combustion engine producing sensor signals and having an actuator for. The electronic controller includes a sensor connected to an internal combustion engine. The sensor measures the sensor signals. The electronic controller also includes an evaluation circuit connected to the sensor. The evaluation circuit diagnoses the sensors in accordance with the method. A control circuit connects to the evaluation circuit and the actuator. The control circuit initiates reversionary running of the internal combustion engine. The electronic controller also includes a warning light connected to the evaluation circuit and displays a fault message to a driver in the event of a matching diagnosis of a malfunction of the sensors.
The invention is therefore based on the problem of developing a method that allows the malfunctioning of a sensor in an internal combustion engine to be detected correctly even when the measured values are within the plausibility range of the sensor in the event of a fault.
In the event of a fault, the measured values are governed by the electronic noise in the evaluation circuit. The amplitude distribution of the electronic noise is in this case very narrow, because the electronic noise has a coherent origin. In comparison, the measured values when the sensor is operating correctly, particularly in the case of sensors with a wide output signal dynamic range have a considerably wider amplitude distribution. Examples of sensors with wide output signal dynamic range include knock sensors, air mass flow meters, and magnetic position sensors for valve operation. If the distribution of electronic noise is used to monitor the operation of the sensors, the amplitude level of the measured values is no longer relevant, so that reliable fault identification is ensured even if the amplitudes of the measured values in the event of a fault are roughly within their range of normal operation.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for monitoring the operation of sensors in an internal combustion engine, and an electronic controller operating in accordance with this method, the scope of the invention is nevertheless not intended to be limited to the details shown, because various modifications and structural changes may be made therein without
Amtmann Markus
Bolz Stephan
Elliott Mark
Fischer Gerhard
Haug Thomas
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
Wolfe Willis R.
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