JP2009300222A - Device for detecting abnormal condition in angular displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for detecting abnormal conditions in an angular displacement sensor capable of detecting abnormal conditions with improved accuracy. <P>SOLUTION: A controlling circuit 2 as the device for detecting the abnormal conditions in an angular displacement finds phase contrast between a sine-phase and a cosine-phase based on sine-signals and cosine-signals output from a resolver 1 and compares it with a threshold to determine presence of the abnormal conditions in the resolver 1. An effect of a temperature change is eliminated by taking phase contrast, so that there is no need to take margin in the threshold. Accordingly, by comparing phase contrast with the threshold, abnormal conditions detection in the resolver 1 can be performed with improved accuracy. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for detecting an abnormality in an output signal of an angular displacement sensor.

A resolver, which is one of angular displacement sensors, is used, for example, as a torque sensor for a power steering device of an automobile (see, for example, Patent Document 1). From a one-phase input / two-phase output type resolver, a two-phase signal of a sin signal and a cos signal is output under a one-phase (sin) excitation input. The sum of squares of these two-phase signals should be a constant regardless of the electrical angle according to the theorem of sin ² θ + cos ² θ = 1. Therefore, it is possible to detect an abnormality of the resolver by monitoring whether or not the sum of squares is within a range in which an allowable error is taken into consideration for the constant (see, for example, Patent Document 2).

JP 2004-309165 A (page 3) JP 2007-292697 A (second page)

The resolver has a temperature characteristic in which the amplitude of the output signal changes with temperature. Therefore, the value of the sum of squares also varies with temperature. When the operating temperature range is wide as in an automobile, it is necessary to set a wide range of values that are determined to be normal in consideration of the operating temperature range and temperature characteristics when detecting the abnormality of the resolver. However, as a result of setting with such a margin, there is a case where a true abnormality cannot be distinguished from a fluctuation due to temperature characteristics, and there is a problem that the accuracy of abnormality detection deteriorates.
In view of such a conventional problem, an object of the present invention is to provide an abnormality detection device for an angular displacement sensor that can accurately detect an abnormality.

  The abnormality detection device for an angular displacement sensor according to the present invention obtains a mutual phase difference between a sin phase phase and a cos phase based on a sin signal and a cos signal output from the angular displacement sensor, and compares this with a threshold value. The presence or absence of abnormality of the angular displacement sensor is determined.

  In the abnormality detection device for an angular displacement sensor configured as described above, the sin phase phase and the cos phase phase change due to a temperature change, but the rate of change is smaller than the amplitude and the direction of change is the same. Therefore, by taking the phase difference, the influence of the temperature change is canceled out. If the influence of the temperature change is eliminated, it is not necessary to allow a margin for the threshold value. Therefore, the abnormality of the angular displacement sensor can be accurately detected by comparing the phase difference with a strict threshold value.

In the abnormality detection apparatus, at least three sampling points are set for each of the sin signal and the cos signal, the sin component and the cos component of each signal are obtained, and the sin phase phase and the cos phase are determined based on these components. The phase may be obtained.
In this case, if there are three sampling points, an abnormality of the angular displacement sensor can be detected, so the calculation burden on the abnormality detection device is light.

  According to the abnormality detection device for an angular displacement sensor of the present invention, the influence of the temperature change is eliminated by taking the phase difference, so that it is not necessary to allow a margin for the threshold value. Therefore, the abnormality of the angular displacement sensor can be detected with high accuracy by comparing the phase difference with a strict threshold value.

  FIG. 1 is a circuit diagram showing an equivalent circuit of a resolver 1 as an angular displacement sensor, and a control circuit 2 that is a rotation angle detection device connected to the resolver 1 and also an abnormality detection device according to an embodiment of the present invention. It is. The control circuit 2 is mainly a microcomputer and also includes an A / D converter. The resolver 1 includes a rotor 11 that rotates together with a rotation angle detection target (not shown), an input-side stator 12 that is supplied with excitation input, and an output-side output that outputs two-phase signals of sin and cos. And a stator 13. The control circuit 2 obtains tan θ (θ is a rotation angle) from the two-phase signal, and obtains the rotation angle θ by its arctangent.

Here, when the excitation signal is sin ωt (ω: angular frequency, t: time), the two-phase signal output from the stator 13 is
sin signal: sin (ωt + α) · sinθ. . . (1)
cos signal: sin (ωt + β) · cos θ. . . (2)
It becomes. Here, α is a sin phase (sin phase phase), β is a cos phase (cos phase phase), and θ is a rotation angle of the rotor 11. Both the sin phase and the cos phase change in the same direction in the same direction depending on the temperature. Therefore, it can be said that the phase difference between the two phases is constant regardless of the temperature.

  On the other hand, as a typical cause of abnormality, there is a short circuit between the lines in the stator, and the signal line of the excitation signal and the signal line of the sin signal are electrically connected to each other via a resistor as shown by the dotted line in FIG. Suppose that a failure occurs. Here, FIG. 2 is a graph that displays the excitation signal (upper) and the sin signal (middle) and the cosine signal (lower) based on the excitation signal side by side when the horizontal axis is time and the vertical axis is voltage. It is. Regarding the sin signal, a broken line indicates a normal state, and a solid line indicates a failure state. Here, the rotor 11 is assumed to be stopped.

  The sin signal and the cos signal are out of phase with respect to the excitation signal. The control circuit 2 sets the sampling points of the sin signal to AD_s [0], AD_s [1], AD_s [2], AD_s [3], and sets the sampling points of the cos signal to AD_c [0], AD_c [1], AD_c. [2] and AD_c [3]. Next, the control circuit 2 performs the following calculation.

From the above equations (3) and (4), the sin phase (sin phase phase) θ _sin is
θ _sin = tan ⁻¹ (b _sin / a _sin ). . . (5)
It becomes. Similarly, the control circuit 2 performs the following calculation.

From the above equations (6) and (7), the cos phase (cos phase phase) θ _cos is
θ _cos = tan ⁻¹ (b _cos / a _cos ). . . (8)
It becomes. Therefore, the phase difference θ is
θ = θ _sin −θ _cos . . . (9)
Can be obtained as Therefore, the control circuit 2, if the phase difference theta is within a predetermined threshold theta _th, determines resolver no abnormality, the resolver if it exceeds the threshold abnormalities, and. The phase difference θ is hardly affected by the temperature change, so that the abnormality can be detected with high accuracy.

  FIG. 3 is a graph showing an example of a phase and a phase difference in a state where the signal line of the excitation signal and the signal line of the sin signal are electrically connected to each other via a resistor. In the figure, the normal cos phase is a constant phase (about 150 degrees), but the abnormal sin phase has an arcuate shape that reverses at an electrical angle of 180 degrees as shown. Accordingly, the phase difference becomes a bow having a larger curvature. If this phase difference is within the threshold value based on the normal phase difference, the resolver is not abnormal, and if it exceeds the threshold value, the resolver is abnormal. It should be noted that, at 0, 90, 180, and 270 degrees, the accuracy of calculation decreases and the value becomes discontinuous. Therefore, these angles and the vicinity thereof are avoided, and comparison with threshold values is performed in other angle regions. It is necessary.

  As described above, in the control circuit 2 as the resolver abnormality detection device according to the present embodiment, the sin phase phase and the cos phase phase change due to a temperature change, but the rate of change is small compared to the amplitude, and the change is The direction is the same. Therefore, by taking the phase difference, the influence of the temperature change is canceled out. If the influence of the temperature change is eliminated, it is not necessary to allow a margin for the threshold value. Therefore, the abnormality of the resolver 1 can be detected with high accuracy by comparing the phase difference with a strict threshold value. In the case of a resolver used as a torque sensor of a power steering device, the detection capability of a short circuit via a resistance of a sensor harness, which has been difficult in the past, is greatly improved by improving the accuracy of abnormality detection.

  In the above embodiment, four sampling points are provided. However, if there are at least three sampling points, the phase can be calculated. That is, the control circuit 2 sets at least three sampling points for the sin signal and the cos signal, obtains the sin component and the cos component of each signal, and calculates the sin phase phase and the cos phase phase based on these components. You may make it ask. In this way, if there are at least three sampling points, the abnormality of the resolver 1 can be detected, so that the calculation burden on the control circuit 2 is light.

  In the above embodiment, the excitation signal signal line and the sin signal signal line are electrically connected to each other via a resistor. However, the excitation signal signal line and the cos signal signal line are connected to each other. Even in the state where they are electrically connected to each other via a resistor, the abnormality detection by the control circuit 2 can be similarly performed.

  The resolver abnormality detection device (control circuit 2) as described above can be applied to resolvers with various shaft angle multipliers, and is not limited to resolvers, and can output various signals of sin θ and cos θ according to angular displacement. It is applicable to an angular displacement sensor (for example, MR sensor).

It is a circuit diagram which shows the equivalent circuit of the resolver as an angular displacement sensor, and the control circuit which is a rotation angle detection apparatus connected to the resolver and is also an abnormality detection apparatus according to an embodiment of the present invention. It is a graph which displays side by side the excitation signal when the horizontal axis is time and the vertical axis is voltage, and the sin signal and cos signal based on the excitation signal. It is a graph which shows an example of a phase and a phase difference in the state where the signal line of the excitation signal and the signal line of the sin signal were electrically connected to each other via a resistor.

Explanation of symbols

1 Resolver (angular displacement sensor)
2 Control circuit (Abnormality detection device)

Claims (2)

  Based on the sin signal and cos signal output from the angular displacement sensor, a mutual phase difference between the sin phase phase and the cos phase phase is obtained and compared with a threshold value to determine whether the angular displacement sensor is abnormal. An abnormality detection device for an angular displacement sensor, characterized by:   The angle according to claim 1, wherein at least three sampling points are set for each of the sin signal and the cos signal, a sin component and a cos component of each signal are obtained, and a sin phase phase and a cos phase phase are obtained based on these components. Displacement sensor abnormality detection device.

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