JP6732238B2 - Method and apparatus for converting analog signals to digital signals - Google Patents

Description

The present invention relates to a two-phase excitation two-phase output and phase modulation type rotation detector, and more particularly to a method and apparatus for converting an analog signal related to rotation detection into a digital signal.

A technique is known in which a digital conversion method is made redundant when a signal from a rotation detector is processed and an angle is output. An example of such a technique is disclosed in Patent Document 1, for example.

Japanese Patent Laid-Open No. 11-118521

However, the conventional technique has a problem that an accurate angle cannot be continuously output when a failure occurs in a part of the circuit. For example, in the configuration of Patent Document 1, since two detection signals are added and used, it is difficult to output an accurate angle when a failure occurs in any one of them.

The present invention has been made to solve such a problem, and it is an object of the present invention to provide a signal conversion method and device capable of continuing output of an accurate angle even if a part of the failure occurs. To aim.

A method according to the present invention is a method for converting an analog signal relating to rotation detection of a two-phase excitation two-phase output and a phase modulation method into a digital signal,
Generating a main system digital signal based on the first phase analog signal and the second phase analog signal;
Generating a first backup system digital signal based on the first phase analog signal;
Generating a second backup digital signal based on the second phase analog signal;
Outputting a final digital signal based on the main digital signal, the first digital backup signal and the second digital backup signal.
In a particular aspect, the final digital signal is selected from the main system digital signal, the first backup system digital signal and the second backup system digital signal by the principle of majority.
In certain aspects,
The step of generating the main digital signal is realized using negative feedback control,
The negative feedback control is
Multiplying each of the first-phase and second-phase analog signals by each of the signals representing the sine and cosine of the main system digital signal to generate a first intermediate signal and a second intermediate signal;
Modifying the main system digital signal so that the difference signal between the first intermediate signal and the second intermediate signal becomes 0 or approaches 0.
In certain aspects,
The first backup system digital signal is a signal representing the phase difference between the first phase analog signal and the first phase excitation signal,
The second backup system digital signal is a signal representing the phase difference between the second phase analog signal and the second phase excitation signal.
Further, the device according to the present invention is
A main system signal processing unit for generating the main system digital signal;
A backup system signal processing unit for generating the first backup system digital signal and the second backup system digital signal is provided, and an analog signal is converted into a digital signal by executing the above method.

According to the present invention, the main system signal processing section and the two backup system signal processing sections are used when the analog signal related to the rotation detection is converted into a digital signal, and the main system signal processing section is a two-phase analog signal. An accurate angle output is obtained by using the signal as a double redundant signal, and the backup system signal processing unit simply obtains each angle output based on the analog signal of each phase, and outputs these three angle outputs. Since the final angle signal is output based on this, even if a failure occurs in part, it is possible to continue outputting the accurate angle. Therefore, it is possible to contribute to improving the reliability of the system that handles the rotation detector.

It is a figure which shows the example of a structure containing the digital conversion part which concerns on Embodiment 1 of this invention. It is a figure showing the state where the analog signal of the 2nd phase was lost. It is a figure which shows the state which the analog signal of the 1st phase was lost. It is a figure which shows the state when a failure generate|occur|produces in the main system signal processing part.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Embodiment 1.
FIG. 1 shows an example of a configuration including a digital conversion unit 30 according to the first embodiment of the present invention. Digital converter 30 is a device that converts an analog signal into a digital signal by performing the methods described herein. The digital conversion unit 30 is provided so as to be connected to the rotation detector 10. The rotation detector 10 is a two-phase excitation two-phase output and phase modulation type rotation detector, and the digital conversion unit 30 converts an analog signal related to rotation detection of the rotation detector 10 into a digital signal.

An excitation circuit 20 is connected to the rotation detector 10. The excitation circuit 20 generates two orthogonal excitation signals and supplies them to the rotation detector 10. The two-phase excitation signal is represented as, for example, a first-phase excitation signal E·cosωt and a second-phase excitation signal E·sinωt.

The rotation detector 10 phase-modulates the input excitation signal, and outputs an analog signal having a phase corresponding to the rotation angle θ with respect to the excitation signal. For example, when the first-phase excitation signal E·cosωt and the second-phase excitation signal E·sinωt are input, the first-phase analog signal K·E·cos(ωt−θ) and the second-phase analog signal K·E·sin(ωt−θ) is output. However, K is a transformation ratio.

The digital conversion unit 30 is configured as a triple system including a main system signal processing unit 40, a backup system signal processing unit 50, and a backup system signal processing unit 60. The operation when all of these processing units are normal will be described below.

The main system signal processing unit 40 is a main system digital signal representing an angle based on the first-phase analog signal K·E·cos(ωt−θ) and the second-phase analog signal K·E·sin(ωt−θ). Generate the signal φ _M.

The generation of the main system digital signal φ _M is realized by using negative feedback control. In the negative feedback control, the feedback signal is multiplied with the analog signal to generate the intermediate signal. In this embodiment, a two-phase feedback signal is generated as a signal representing the sine and cosine of the result obtained by subtracting the main digital signal φ _M from the reference signal ωt output from the counter. In other words, the feedback signal is represented as a feedback signal representative of the cosine of the feedback signal sin (ωt-φ _M) and the main system digital signal phi _M representing the sine of the main system digital signal _{φ M cos (ωt-φ M} ).

The feedback signal sin(ωt−φ _M ) representing sine is multiplied by the first phase analog signal K·E·cos(ωt−θ), and as a result of the multiplication, the first intermediate signal K·E·cos(ωt−). θ)·sin(ωt−φ _M ) is generated. Similarly, the feedback signal cos(ωt−φ _M ) representing the cosine is multiplied by the analog signal K·E·sin(ωt−θ) of the second phase, and the result of the multiplication is the second intermediate signal K·E·sin. (Ωt−θ)·cos(ωt−φ _M ) is generated.

In the negative feedback control, the difference ε between the first intermediate signal and the second intermediate signal (that is, the difference between the multiplication outputs) is defined as a control deviation, and the predetermined control is performed so that the control deviation becomes 0 or approaches 0. The law modifies the main system digital signal φ _M. This difference ε is expressed as follows.
ε = K · E · cos ( ωt-θ) · sin (ωt-φ M)
-K · E · sin (ωt- θ) · cos (ωt-φ M)
= K · E · sin (θ -φ M) ... ( Equation 1)
From this equation, when the negative feedback control system becomes epsilon = 0 functioning properly, K · E · sin (θ -φ M) = 0 becomes, that is, phi _M = theta. In this way, the main system signal processing unit 40 converts the analog signal from the rotation detector 10 into a digital angle output, and generates a main system digital signal φ _M.

The backup system signal processing unit 50 generates a first backup system digital signal φ _C based on the first phase analog signal K·E·cos(ωt−θ). In this embodiment, the first backup system digital signal φ _C is a signal representing the phase difference between the first-phase analog signal K·E·cos(ωt−θ) and the first-phase excitation signal E·cosωt. Is generated. When the backup system signal processing unit 50 to function properly, the first backup system digital signal phi _C becomes ωt- (ωt-θ) = θ . In this way, the backup system signal processing unit 50 converts the analog signal from the rotation detector 10 into a digital angle output, and generates the first backup system digital signal φ _C.

Similarly, the backup system signal processing unit 60 generates the second backup system digital signal φ _S based on the second phase analog signal K·E·sin(ωt−θ). In the present embodiment, the second backup system digital signal φ _S is a signal representing the phase difference between the second phase analog signal K·E·sin(ωt−θ) and the second phase excitation signal E·sin ωt. Is generated. When the backup signal processing section 60 functions normally, the second backup digital signal φ _S becomes ωt−(ωt−θ)=θ. In this way, the backup system signal processing unit 60 converts the analog signal from the rotation detector 10 into a digital angle output, and generates the second backup system digital signal φ _S.

In this way, the main system digital signal φ _M , the first backup system digital signal φ _C , and the second backup system digital signal φ _S are generated as triple redundant system angle outputs. The digital conversion unit 30 outputs a final digital output signal (final digital signal φ) based on these three digital signals φ _M , φ _C , and φ _S. For this purpose, the digital conversion unit 30 may include an output determination processing unit (not shown).

The final digital signal φ may be determined or calculated by any algorithm or calculation formula, but is selected from the three digital signals φ _M , φ _C , φ _S by the principle of majority voting, for example. The method of realizing the principle of majority decision can be designed arbitrarily. For example, when two or more of the three digital signals φ _M , φ _C , and φ _S show the same value, the value is selected. The final digital signal φ is output and this is output. Alternatively, the difference is calculated for each of two sets (three possible sets are possible) of the three digital signals φ _M , φ _C , and φ _S , and based on the set that minimizes the absolute value of the difference. The final digital signal φ may be determined or calculated (for example, by averaging two values included in the set).

Next, the operation when a failure occurs in a part of the configuration will be described.
FIG. 2 shows a state where the second-phase analog signal K·E·sin(ωt−θ) is lost. In this case, the difference ε that is the control deviation is as follows.
ε=K·E·cos(ωt−θ)·sin(ωt−φ _M )−0·cos(ωt−φ _M ).
=(1/2)·K·E·{sin(θ−φ _M )+sin(2ωt−θ−φ _M )}
…(Equation 2)
Even in such a case, the main-system signal processing unit 40 can be configured to output φ _M normally or almost normally. Here, the meaning of the term “almost normal” can be appropriately defined or interpreted by those skilled in the art according to the embodiment, but for example, the magnitude of the deviation (difference) from the normal value of φ _M is It can be said that the output of the final digital signal φ is not affected. Alternatively, it can be said that the influence of the deviation of φ _{M on} the final digital signal φ remains within the allowable range as the output of the digital conversion unit 30. Although the specific configuration of the main system signal processing unit 40 can be arbitrarily designed, an example is shown below.

If ε=0 in the above equation 2, it can be approximated as φ _M ≈ θ+sin(2ωt−2θ). sin(2ωt−θ−φ _M ) is usually a frequency component approximately twice the excitation frequency. However, if the frequency characteristic of the negative feedback control system is appropriately configured with respect to the excitation frequency, the double frequency component can be obtained. It can be attenuated or eliminated. In this case, φ _M =θ, or φ _M becomes a signal that vibrates slightly around θ. That is, the digital conversion by the main system signal processing unit 40 can be normally performed, or at least can be continued normally with an error.

In the case of FIG. 2, φ _S cannot be digitally converted, but φ _C can be converted as in the normal case without being affected by the failure. Therefore, since two of the three digital signals φ _M , φ _C , and φ _S (φ _M and φ _{C in} this case) are output normally or almost normally, the final digital signal φ is also determined and output. , Can be done normally or almost normally. As described above, as a specific method of determining the final digital signal φ, for example, the principle of majority voting can be used.

Although FIG. 2 shows a state where the second-phase analog signal K·E·sin(ωt−θ) is lost, the second-phase analog signal K·E·sin(ωt−θ) is normal. The same applies to the case where the feedback signal cos(ωt−φ _M ) representing the cosine is lost.

FIG. 3 shows a state in which the first-phase analog signal K·E·cos(ωt−θ) is lost. In this case, the difference ε that is the control deviation is as follows.
ε = 0 · sin (ωt- φ M) -K · E · sin (ωt-θ) · cos (ωt-φ M)
=(1/2)*K*E*{sin([theta]-[phi] _M )-sin(2[omega]t-[theta]-[phi] _M )}
…(Equation 3)
Even in such a case, the main-system signal processing unit 40 can be configured to output φ _M normally or almost normally. The specific configuration can be designed arbitrarily, but an example is shown below.

If ε=0 in Equation 3 above, φ _M ≈ θ−sin(2ωt−2θ) can be approximated, and sin(2ωt−θ−φ _M ) is attenuated or removed by the same idea as in FIG. Therefore, the digital conversion by the main system signal processing unit 40 is normally or almost normally performed. Further, in the case of FIG. 3, φ _C cannot be digitally converted, but φ _S can be converted as in the normal case without being affected by the failure. Therefore, since two of the three digital signals φ _M , φ _C , and φ _S (φ _M and φ _{S in} this case) are output normally or almost normally, the final digital signal is output as in the case of FIG. The signal φ can be determined and output normally or almost normally.

Although FIG. 3 shows a state where the first-phase analog signal K·E·cos(ωt−θ) is lost, the first-phase analog signal K·E·cos(ωt−θ) is normal. The same applies to the case where the feedback signal sin(ωt−φ _M ) representing the sine is lost.

FIG. 4 shows a state in which a failure has occurred in the main system signal processing unit 40. The example of FIG. 4 is in a state in which the difference ε that is the control deviation is lost. In this state, the main system signal processing unit 40 cannot perform digital conversion, and φ _M is not normally output. In addition, not only when the difference ε is lost, but when a situation occurs in which the negative feedback does not function, φ _M is not normally output, and the same result is obtained.

However, in this case, the backup system signal processing unit 50 and the backup system signal processing unit 60 operate normally, so that the digital conversion functions for two systems of the triple output. That is, since two of the three digital signals φ _M , φ _C , and φ _S (φ _C and φ _{S in} this case) are output normally, the final digital signal φ is also determined and output normally. It is possible. As described above, as a specific method of determining the final digital signal φ, for example, the principle of majority voting can be used.

As described above, according to the digital conversion unit 30 of the present invention, the main system signal processing unit 40, the backup system signal processing unit 50, and the backup system when converting the analog signal related to the rotation detection into the digital signal. Using the system signal processing unit 60, the main system signal processing unit 40 uses a two-phase analog signal as a dual redundant signal to obtain an accurate angle output, and the backup system signal processing unit 50 uses the first phase. Angle signal is simply obtained on the basis of the analog signal of, the backup system signal processing unit 60 simply obtains the angle output based on the analog signal of the second phase, and the final angle is obtained on the basis of these three angle outputs. Since the signal is output, it is possible to continue outputting an accurate angle even if a part of the failure occurs. Therefore, it is possible to contribute to improving the reliability of the system that handles the rotation detector.

30 digital conversion unit (device for converting analog signal to digital signal), 40 main system signal processing unit, 50, 60 backup system signal processing unit, φ _M main system digital signal, φ _C first backup system digital signal, φ _S Second backup digital signal.

Claims (5)

A method for converting an analog signal related to rotation detection of a two-phase excitation two-phase output and a phase modulation method into a digital signal,
Generating a main system digital signal based on the first phase analog signal and the second phase analog signal;
Generating a first backup system digital signal based on the first phase analog signal;
Generating a second backup digital signal based on the second phase analog signal;
Outputting a final digital signal based on the main digital signal, the first backup digital signal and the second backup digital signal. The method according to claim 1, wherein the final digital signal is selected from among the main digital signal, the first backup digital signal and the second backup digital signal by the principle of majority. The step of generating the main digital signal is realized using negative feedback control,
The negative feedback control is
Multiplying each of the first-phase and second-phase analog signals by each of the signals representing the sine and cosine of the main digital signal to generate a first intermediate signal and a second intermediate signal, respectively.
3. The method according to claim 1 or 2, further comprising the step of modifying the main system digital signal so that a difference signal between the first intermediate signal and the second intermediate signal becomes or approaches 0. The first backup system digital signal is a signal representing a phase difference between the first phase analog signal and the first phase excitation signal,
The method according to claim 1, wherein the second backup system digital signal is a signal representing a phase difference between the second-phase analog signal and the second-phase excitation signal. A main system signal processing unit for generating the main system digital signal;
An analog signal is obtained by performing the method according to any one of claims 1 to 4, further comprising a backup system signal processing unit that generates the first backup system digital signal and the second backup system digital signal. A device that converts digital signals.

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