JPH11118520A - Digital angle conversation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable resolver/digital(R/D) conversion by software, remarkably simplify hardware, and realize cost reduction by calculating a digital angle by operating the two-phase outputs of a resolver output after A/D conversion by Fourier transformation. SOLUTION: Out of two-phase resolver outputs which are outputted from a resolver by using a single phase exciting signal sin ωt and have a phase difference of 90 deg. (have a phase of constant frequency component), a sin signal (sinθ.sinωt) and a cos signal (cosθ.sinωt) are Fourier-transformed by using a specified Fourier transformation formula, and a digital angle θis obtained. Thereby an R/D converter is not necessary to be used, so that the whole constitution is simplified, cost reduction is enabled, and reliability and convenience are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital angle conversion method, and more particularly to a method of calculating a phase of a constant frequency component in a resolver output waveform using a Fourier transform method without using a conventional resolver / digital converter. The present invention relates to a novel improvement for calculating a digital angle using software.

[0002]

2. Description of the Related Art As a conventional digital angle conversion method of this type, for example, a tracking method shown in FIG. 4 is often used. That is, what is indicated by reference numeral 1 in FIG. 4 is a resolver which is excited by the excitation signal E · sin ωt. And the output signal KEsin ωt · sin
(Θ-φ) where θ is the resolver rotation angle and φ is the output counter value) is synchronously rectified by the synchronous rectifier 3 to which the excitation signal E · sin ωt is input. The output signal KE sin (θ−φ) obtained from the synchronous rectifier 3 is input to the counter 5 as a pulse output 4 a via the voltage controlled oscillator 4, and the output counter value φ as a digital angle output is obtained from the counter 5. . This output counter value φ is fed back to form a feedback loop. Therefore, the output signal KE sin (θ−
φ), the speed signal 6 can be obtained, and the position signal 7 can be obtained from the output counter value φ from the counter 5.

[0003]

The conventional digital angle conversion method has the following problems because it is configured as described above. That is, in the above-described circuit configuration, since a part of each component has a complicated analog configuration, it is difficult to simplify the entire configuration, and the cost is reduced, the reliability is improved,
Convenience was difficult to achieve.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In particular, a conventional resolver / digital conversion is performed by calculating the phase of a constant frequency component in a resolver output waveform using a Fourier transform method. It is an object of the present invention to provide a digital angle conversion method in which a digital angle is calculated using software without using a device.

[0005]

A digital angle conversion method according to the present invention converts a two-phase resolver output having a 90-degree phase difference obtained from a one-phase excitation two-phase output resolver into a digital angle signal. In the digital angle conversion method, after A / D conversion of the resolver output,
In this method, the digital angle is calculated by calculating the phase of a constant frequency component included in the waveform of the resolver output by a Fourier transform method using a CPU.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a digital angle conversion method according to the present invention will be described below with reference to the drawings. Since the resolver itself has the same configuration as the well-known one-phase excitation two-phase output type shown in FIG. 4, its illustration is omitted here. First, using the one-phase excitation signal sin ωt, the two-phase signals output from the above-mentioned resolver are different from each other by 90 degrees.
Resolver output of phase (has phase of constant frequency component)
Of the sin signal (sin θ · sin ωt) and the cos signal (cos
θ · sin ωt) is subjected to Fourier transform using the following Fourier transform equation, whereby a digital angle θ is obtained.

[0007]

(Equation 1)

Next, a specific form for calculating the digital angle θ by the above-described Fourier transform will be described.
First, a two-phase sin signal (S-sin) and cos signal (S-cos) and an excitation signal (sin ωt) from a well-known A / D converter (not shown) shown in FIG. 1 are sent to a CPU (not shown). Ingest,
Multiply the read sin signal S-sin by sin ωt (SA
1) Also, multiply the sin signal by cos ωt (SB1).
SA1 and SB1 are repeated for the number of samples (n), and the results are added as follows. SA1 = S-sin (1) × S-BAS (1) +... + S-sin
(n) × S-BAS (n) SB1 = S-sin (1) × C-BAS (1) +... + S-sin
(n) × C-BAS (n) Next, similarly to the above, CA2 and CB2 are obtained by multiplying the cos signal by sin ωt and cos ωt. CA2 = S-cos (1) ×
S-BAS (1) + ... + S-cos (n) * S-BAS1 (n) CB2 = S-cos (1) * C-BAS (1) + ... + S-cos
(n) × C-BAS1 (n) Next, | sin θ | and | cos θ | are obtained from the above results by the following equations (2) and (3).

[0009]

(Equation 2)

The aforementioned | sin θ | and | cos θ |
x = │sin θ│ / │cos θ│ when n θ│> │cos θ│
X = │cos θ│ when │sin θ│ ≦ │cos θ│
/ │sin θ│, and θ △ corresponding to x is obtained from the tan ^-1 x table shown in FIG. 3 (0 ° to 45 °).
Therefore, the polarities of S-sin and S-cos and | sin θ |> |
By performing quadrant determination as shown in FIG. 2 from cos θ |, position data P corresponding to one revolution of the resolver can be obtained. Therefore, as described above, the digital angle of the resolver can be calculated by calculating the phase of the constant frequency component included in the waveform of the resolver output.

[0011]

Since the digital angle conversion method according to the present invention is configured as described above, the following effects can be obtained. That is, since the two-phase output of the resolver output after the A / D conversion is calculated by the Fourier transform method to calculate the digital angle, resolver / digital conversion (R / D conversion) is possible by software of the CPU.
Since a conventional R / D converter is not required, hardware can be greatly simplified and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing a resolver output in a digital angle conversion method according to the present invention.

FIG. 2 is a waveform chart showing a state of digital angle output.

FIG. 3 is a waveform chart showing an angle conversion table.

FIG. 4 is a block diagram showing a conventional tracking R / D converter.

[Explanation of symbols]

 θ Digital angle

Claims (1)

[Claims] 1. A digital angle conversion method for converting a two-phase resolver output having a 90-degree phase difference obtained from a one-phase excitation two-phase output resolver into a digital angle (θ). After / D conversion
A digital angle conversion method, wherein the digital angle (θ) is calculated by calculating the phase of a constant frequency component contained in the waveform of the resolver output by a Fourier transform method using a CPU.