JPH0635985B2 - Rotor speed detector - Google Patents

Description

Detailed Description of the Invention A. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed detector for a rotating body using a resolver.

B. SUMMARY OF THE INVENTION According to the present invention, in a speed detector that obtains a voltage signal corresponding to speed from a resolver output by a PLL circuit, the difference between the frequency close to the excitation frequency of the resolver and the output frequency of a voltage controlled oscillator of the PLL circuit is calculated. By using it as a reference for phase comparison with the resolver output, speed detection with good detection accuracy and excellent responsiveness can be performed.

C. 2. Description of the Related Art Resolvers are widely used as sensors for detecting the speed and position of rotating bodies such as rotating machines because they are robust, have excellent environmental resistance, and are economical.

As a speed detector using a resolver, a resolver and a PLL
(Phase locked loop) circuit combination,
Some obtain a voltage signal proportional to speed. This conventional device is shown in FIG.

In FIG. 2, the rotary shaft of the resolver 1 is directly connected to the rotary shaft of the rotating body 2, and the stator winding of the resolver 1 has a sinusoidal wave signal sinω _ct from the excitation oscillator 3 and a cosine wave signal having a 90 ° phase difference. cosω _ct is applied as the excitation voltage. For this excitation voltage, the output of the resolver 1 is the cosine wave (or sine wave) signal cos (ω _c −ω _r ) t which is the difference between the angular frequency ω _r of the rotor 2 and the excitation voltage angular frequency ω _c. Is taken out.

The output signal of the resolver 1 is phase-compared with the output signal of the voltage controlled oscillator 4 ₂ in the phase comparison circuit 4 ₁ of the PLL circuit 4, and this phase difference detection output is converted into a DC signal Vd by the low pass filter 4 _3. Voltage controlled oscillator 4 ₂
Of the bias frequency Vdr
Is subtracted and taken out as the speed detection signal V _N.

D. Problems to be Solved by the Invention In a conventional speed detector, in order to improve the response of speed detection, the frequency ω _c of the excitation voltage of the resolver 1 is increased and the output angular frequency ω _c − of the resolver 1 is increased. increasing the omega _r, it may be reduce its delay by increasing the cut-off frequency of the low pass filter 4 _3. However, the frequency ω _c −
When ω _r becomes large, the ratio of ω _r to the frequency ω _c becomes small and the detection accuracy deteriorates. On the other hand, if the frequency ω _c is reduced to improve the detection accuracy, the speed detection response becomes poor.

As described above, in the related art, the detection accuracy and the response are in a contradictory relationship, and both characteristics cannot be satisfied.

E. Means and Actions for Solving Problems The present invention has been made in view of the above problems, and a resolver coupled with a rotating body and excited by an excitation oscillator, and an output of this resolver as a phase comparator input. A PLL circuit that obtains a voltage signal corresponding to the rotation speed of the rotating body at the output of the low-pass filter, a sine wave oscillator that obtains a frequency output close to the frequency of the excitation oscillator, and the output of this oscillator and the voltage-controlled oscillator of the PLL circuit. And an arithmetic circuit that uses a signal having a frequency difference from the output of the phase comparator as a comparison reference of the phase comparator, and the oscillation frequency range of the voltage controlled oscillator of the PLL circuit is close to the range of the rotating body while increasing the excitation frequency of the resolver. Make it narrow.

F. Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention. Portions figure differs from FIG. 2, to obtain a sine wave signal sin .omega _xt and the cosine wave signal cos .omega _xt it different in phase by 90 degrees to the output of the voltage controlled oscillator 4 _2, sine the two signals from the sine wave oscillator 5 wave signal sin .omega _dt, multiplied by the multiplier 6 _{1 and} 6 ₂ of the cosine wave signal cos .omega _dt and each arithmetic circuit, the phase comparison circuit 4 outputs of both multipliers 6 _and 62 are added by the adder 7 _The point is that it is configured as a comparison input of ₁ . Here, the oscillation angular frequency ω _d of the sine wave oscillator 5 is set to a value slightly higher than the angular frequency ω _c of the excitation oscillator 3.

In such a configuration, the angular frequency ω _d of the sine wave oscillator 5 is
If There the _{ω d = ω c + ω e} , the output of the adder 7 is a frequency difference _{sinω xt · sinω dt + cosω xt} · cosω dt = cos (ω d -ω x) t. Therefore, the phase comparison in the phase comparison circuit 4 ₁ is performed by using the output cos (ω _c −ω _r ) t of the resolver 1 and the adder 7
Will be to detect the phase difference between the output _{cos (ω d -ω x) t} , the oscillation angular frequency omega _x of the voltage controlled oscillator 4 ₂ ω _r -
The operating range may be a narrow range from the minimum to the maximum of ω _e . For example, if ω _e = 2 | ω _r | max, then ω _x max =
3 | ω _r | max may be set.

That is, the operating range of the voltage controlled oscillator 4 ₂ becomes a narrow range of about several times the operating range of the rotary body 4, good linearity within the range in response to a change in the control voltage Vd to be output of the low pass filter 4 ₂ , The detection accuracy becomes higher.

Accordingly, the oscillation angular frequency omega _c of the excitation oscillator 3 can be set high without being bound by the accuracy, resulting in a higher cut-off frequency of the low-pass filter 4 ₂ reduced the delay, the better the response However, the ripple of the detected speed voltage V _N also becomes small.

G. As described above, according to the present invention, since the phase comparison reference is the difference between the frequency close to the excitation frequency of the resolver and the frequency of the voltage controlled oscillator, voltage control is performed while increasing the excitation frequency and increasing the responsiveness. This has the effect of narrowing the frequency range of the oscillator and improving the detection accuracy.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a conventional circuit diagram. 1 ... Resolver, 2 ... Rotating body, 3 ... Excitation oscillator, 4
...... PLL circuit, 5 …… Sine wave oscillator, 6 ₁ , 6 ₂ ……
Multiplier, 7 ... Adder.

Claims (1)

[Claims] 1. A resolver coupled to a rotating body and excited by an exciting oscillator, and a PLL for obtaining a voltage signal corresponding to a rotating speed of the rotating body at an output of a low-pass filter using an output of the resolver as a phase comparator input. Circuit, a sine wave oscillator that obtains a frequency output close to the frequency of the excitation oscillator, and a signal that is a frequency difference between the output of this oscillator and the output of the voltage controlled oscillator of the PLL circuit is used as the comparison reference of the phase comparator. A speed detector for a rotating body, comprising: an arithmetic circuit.