JP2004117312A - Sensor abnormality detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor of a potentiometer type for accurately detecting a short circuit between a sensor output line and a sensor supply power line. <P>SOLUTION: This detecting method comprises comparing the voltage of the sensor output line with that of the sensor supply power line and determining the short circuit between the sensor output line and the sensor supply power line unless the voltage of the sensor output line is lower by a fixed value or greater than the voltage of the sensor supply power line. Thus, in a system using the sensor of the potentiometer type, the operable region of the sensor is reduced so that the short circuit between the sensor output line and the sensor supply power line is accurately detected through upper/lower limit error determination from the voltage of the sensor output line, avoiding the limitation of the operation range of a control part using the sensor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sensor abnormality detection method. In particular, the present invention relates to a sensor that receives power supply and outputs a voltage, and particularly relates to a sensor abnormality detection method that detects a short circuit between a sensor output line and a sensor supply power line.
[0002]
[Prior art]
In order to improve the accuracy of the throttle sensor and stabilize the operation of the electronically controlled throttle device, the following document discloses that the operation range of the brush on the resistor is more than half of the operating range of the brush on the resistor corresponding to the minimum opening to the maximum opening of the throttle valve. It is described that the brush and the resistor are arranged such that a small continuous range including the minimum opening degree is present on a line connecting the throttle valve shaft and the rotation shaft of the motor or an extension of this line. Have been.
[0003]
[Patent Document 1]
JP-A-2002-89292
[Problems to be solved by the invention]
The abnormality determination threshold value in the upper / lower limit check is generally determined by a voltage range corresponding to an actual operation range of the object to be measured by the sensor. That is, when the sensor output voltage exceeds the voltage range of the actual operation range, it is determined to be abnormal. Here, considering the case where the sensor output line and the supply power supply line are short-circuited (hereinafter referred to as sensor output / power supply short-circuit), the sensor output voltage and the sensor supply power supply voltage are equal, and the sensor supply power supply voltage when there is no short-circuit Go down. As a result, the upper threshold value set in the upper / lower limit check may not be exceeded. In this case, even if the output line and the power supply line are short-circuited, the upper and lower limit check cannot detect an abnormality, and the sensor output value is regarded as a large value. When the sensor has a double system configuration, the output value of the abnormal sensor becomes large as compared with another normal sensor output voltage, and the above-mentioned correlation abnormality is detected. However, in that case, it cannot be determined which sensor is abnormal.
[0005]
When the sensor output line is short-circuited with the sensor power supply line, there is a method to limit the actual operating range of the object to be measured by the sensor in order to reliably detect the abnormality by the upper and lower limit check. Since the actual operating range is set so as to make maximum use of the effective range of the sensor, it is often impossible to actually adopt the actual operating range.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, the present invention uses a deviation between a sensor supply voltage and a sensor output voltage. When the sensor output line and the sensor power supply line are short-circuited, there is basically no deviation between the two voltages. However, in order to compare the two voltages, A / D conversion is usually performed using an A / D converter, but a certain degree of deviation may occur strictly due to errors included in the A / D conversion. . In the following, an error accompanying the A / D conversion is referred to as a sensor A / D error.
[0007]
According to the present invention, when the absolute value of the deviation of the A / D conversion value of the voltage between the sensor output line and the sensor supply power line is smaller than the sensor A / D error, the sensor output line and the sensor supply power line are short-circuited. It is determined that there is. Since the A / D error is small in many cases, this determination method can be applied over the entire actual operating range of the sensor measurement target.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventors have studied various types of sensors this time. As a sensor that outputs a voltage, there is a potentiometer type sensor. In this type of sensor, when power is supplied to the sensor, a signal level corresponding to a characteristic of an object to be sensed by the sensor is generated as a voltage. For example, in a sensor that detects the rotational angle position of a control device, a contact that rotates in conjunction with the rotation of the control device rotates while contacting a resistor on an arc, and applies a DC voltage to both ends of the resistor. When the voltage indicated by the contact indicates a value corresponding to the rotation angle, the contact voltage is measured, and the rotation angle of the control device is detected.
[0009]
Representative examples of such a sensor self-diagnosis include an upper / lower limit check and a correlation check. In the upper and lower limit check, an upper limit and a lower limit voltage value of the output voltage in the actual operation range of the sensor are determined, and when the sensor output value exceeds the upper limit or falls below the lower limit, it is determined that the sensor is abnormal. The causes of detection of sensor abnormality include abnormality of the sensing object and abnormality of the sensor itself, as well as failure of the connection line between the sensor and the processing device or microcomputer that detects the sensor abnormality, that is, disconnection or other signal. Short to the level.
[0010]
Another correlation check is a method used in the case of a multi-system sensor, and is determined to be abnormal when the absolute value of a deviation between two or more sensor output values is larger than a threshold value. However, in this case, which of the two sensors compared is abnormal cannot be determined by itself.
[0011]
Hereinafter, a sensor abnormality detection method according to the present invention will be described in detail with reference to the illustrated embodiments.
[0012]
In the following, a sensor of the type that detects the rotational angle position of the control element will be described as an example, but the present invention is not limited to this type of sensor.
[0013]
FIG. 1 shows an embodiment of the structure of the sensor. This sensor includes a rotating shaft 20 to which the contact 15 is fixed, and rotates in conjunction with the rotating shaft 20. Further, the sensor includes a fixed resistor 50, and the contact 15 rotates in conjunction with the rotating shaft 20 while contacting the fixed resistor 50. The fixed resistor 50 has a uniform resistance, and a constant voltage (V0) is applied to both ends thereof. A parallel fixed resistor 60 different from the fixed resistor 50 is included. The contact 15 is always in contact with the fixed resistor 50 at a contact point 51, and is always in contact with the parallel fixed resistor 60 at a contact point 61. As a method therefor, for example, when the parallel fixed resistor 60 is arranged so as to form a concentric circle in a shape similar to the fixed resistor 50 and the contact 15 rotates in conjunction with the rotation shaft 20. The contact 15 is configured to always contact the fixed resistor 50 and the parallel fixed resistor 60 together with the contact points 51 and 61. A material having a high conductivity between the contact points 51 and 61 and the resistance of the parallel fixed resistor 60 is high enough to be regarded as zero.
[0014]
Here, if the potential difference between the end point P1 of the fixed resistor 50 and the one end Q of the parallel fixed resistor 60 is measured, the potential difference changes in conjunction with the rotation operation of the rotating shaft 20. The reason is that since the parallel fixed resistor 60 has zero resistance, the potential Q between the position Q and the contact points 61 and 51 is equal, and the potential difference between the position P1 and the position Q is in contact with the position P1. This is because there is a potential difference between the points 51.
[0015]
When the fixed resistor 50 has a uniform resistance distribution and a voltage of V0 is applied between the positions P1 and P2, the distance between P1 and P2 of the fixed resistor 50 is L, P1 and the contact point 51 Is the distance of l, the voltage V measured at the position Q is approximately (l / L) × V0. This 1 is proportional to the rotation angle of the contact 15, and the rotation angle is equal to the rotation angle of the rotation shaft 20. When the rotation angle of the rotation shaft 20 is θ, the voltage V measured at the position Q is V = (θ / θmax) × V0
Therefore, the rotation angle θ is obtained as (V / V0) × θmax. Here, θmax is the rotation angle from P1 to P2.
[0016]
FIG. 2 shows FIG. 1 as an electric circuit. However, some parts have been added. The fixed resistor 50 is represented as a single variable resistor VR in FIG. The contact point 51 corresponds to the arrow in contact with VR in FIG. The portion from the contact point 51 to the position P1 in FIG. 1 corresponds to Ra in FIG. 2, and the portion from the position P2 to the contact point 51 corresponds to Rb in FIG. Further, the total resistance of the variable resistor VR in which A corresponds to P1 and B corresponds to P2 is Ra + Rb. A protection resistor Rs is inserted between the sensor power supply V0 and the variable resistor VR. This is provided to prevent an excessive current from flowing from the sensor power supply when the point B is short-circuited to the ground, and to protect the internal circuit when the point B is short-circuited to a high voltage.
[0017]
FIG. 3 is a graph showing a sensor output value and a measured value of the sensor supply power supply voltage when the sensor output line and the sensor supply power supply line are short-circuited. In FIG. 3, the sensor output voltage over the actual operating range of the sensor in a normal state is indicated by a sensor output value 430. V0 characteristic 1 and V0 characteristic 2 indicate the sensor supply power supply voltage when the sensor output line and the sensor supply power supply line are short-circuited. The difference between the two is due to the difference in the value of the protection resistance Rs and the like. In the section A, the V0 characteristic 2 at the time of short-circuit is lower than the upper limit voltage Vmax, and no abnormality is detected in the upper / lower limit check. As the protection resistance Rs is smaller, the characteristic line at the time of short-circuiting moves higher, and the area corresponding to the section A can be reduced and further eliminated. However, when the value of the protection resistor Rs decreases, the current flowing through the protection resistor Rs when the sensor power supply line is short-circuited to ground or high voltage increases, and heat generation of the circuit element accelerates. If the temperature of the circuit element rises due to heat generation, the element is destroyed or the output is restricted or the output is stopped due to the protection function, and the parts are destroyed or malfunction occurs. Further, when the protection resistance value increases, the sensor output voltage when the sensor power supply line and the sensor output line are short-circuited decreases, and the area of section A in FIG. 3 expands. In the section A, no abnormality is detected in the upper / lower limit check. Therefore, referring to the value, the voltage Ver when the angular position is the minimum is recognized as the position of Per, and therefore, the angular position is determined to be the large position Qer. Since this causes a large error, it is necessary to take measures such as narrowing the actual operation range and eliminating the section A.
[0018]
In contrast, in the present invention, the sensor output value 430 is compared with the sensor supply power supply voltage V0, and when the absolute value of the difference is smaller than the sensor A / D error equivalent value, or when the sensor output value 430 is higher, Judge as sensor output / power supply short. Thus, the presence or absence of a sensor / power supply short can be determined in the entire area of the actual operation range shown in FIG. 3, and the threshold value of the upper / lower range check can be set to Vmax in FIG. 3, so that the entire area of the actual operation range is used. It becomes possible.
[0019]
As a result of the above, even if the area that does not cause an error in the upper and lower limit error check of the sensor output value includes the sensor output level when the sensor output and the power supply are short-circuited, as shown in FIG. The short circuit can be detected, and the actual operation range can be used including that area. FIG. 4 is a part of FIG. When the position of the sensing object is between Qer and max, the sensor output level is in a region indicated by X in FIG. 4, but this overlaps with the range of the sensor output level in the case of the sensor output / power short-circuit. However, when it is determined by the method of the present invention that there is no sensor output / power short-circuit, the position of the sensing object can be determined to any position between Qer and max in FIG. It is possible to eliminate the case of power supply short. A specific example of this effect will be described below. In many cases, the operation range of the object sensed by the sensor is a case where the rotation angle is approximately 90 °. Therefore, the usable range of the sensor operation range is a range obtained by adding a margin to 90 °. When the sensor use range is reduced in order to enable short-circuit determination based on the voltage characteristics at the time of short-circuit depending on the sensor processing circuit, the original operation range close to 90 ° should be included as the sensor use range. In some cases, it becomes impossible to reduce the sensor use range, which is a problem in such a case.
[0020]
Next, consider a case where the sensor is configured as a double system, and a short circuit between the sensor supply power supply line and the sensor output line occurs in one of the sensors. In such a case, the angle position indicated by the short-circuited sensor indicates a large angle, but the angle position indicated by a normal sensor indicates a small angle position. As described above, when a dual system is used, a correlation check can be performed. In such a case, a correlation error is detected because the difference between the output voltages of the two sensors is large. When a correlation error is detected, it is known that at least one sensor is abnormal, but it is not possible to specify which sensor is abnormal. In such a case, it is possible to use a relatively safer sensor value as a fail-safe operation, or to use a method using neither of the both sensor values. There is no guarantee that a sensor will be selected.
[0021]
On the other hand, if the short detection method between the sensor power supply line and the sensor output line is used based on the difference between the sensor power supply voltage and the sensor output voltage, which of the dual sensors is abnormal. Since it is possible to determine whether or not there is, even if a correlation error is detected, it is possible to select and use a sensor value of a sensor that is not abnormal.
[0022]
【The invention's effect】
According to the present invention, since the sensor output line voltage when the sensor output line and the sensor supply power supply line are short-circuited is lower than the upper threshold value for detecting the upper and lower limit abnormality of the sensor output value, the problem that the error is not determined is caused. On the other hand, even if the sensor output value shows a large value, a method for reliably detecting that the sensor output line and the sensor supply power supply line have short-circuited can be realized, and the above problem can be solved.
[0023]
Further, in order to solve the above problem, it is possible to avoid reducing the sensor use area, and the resolution of the sensor output value is not reduced.
[Brief description of the drawings]
FIG. 1 shows a basic configuration in a first embodiment.
FIG. 2 is an equivalent circuit showing an operation in the first embodiment.
FIG. 3 is a sensor characteristic diagram in the first embodiment.
FIG. 4 is a second sensor characteristic diagram in the first embodiment.
[Explanation of symbols]
Reference numeral 10: processing device, 15: contact, 20: rotating shaft, 30: rotor, 50: fixed resistor, 51, 61: contact point, 60: parallel fixed resistor, 100: sensor, 430: sensor output value.

Claims (3)

When the sensor indicating the control element characteristic value receives the sensor power supply and generates a sensor output, and the absolute value of the deviation between the sensor power supply voltage and the sensor output voltage is smaller than a predetermined value, or the sensor output voltage is A sensor abnormality detection method that detects a sensor abnormality when the voltage is higher than the sensor supply power supply voltage. A sensor processing apparatus for processing an output signal value of a sensor indicating a control element characteristic value, comprising the method of claim 1. In a sensor processing device that processes an output signal value of a sensor indicating a control element characteristic value, when a region where it is determined that the sensor is not abnormal based on the sensor output value is short-circuited between the sensor output signal line and the sensor supply power line. The sensor processing device including the method according to claim 1, wherein the sensor output signal line voltage region is included.

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