JPH0635986B2 - 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 The present invention is a speed detector that obtains a voltage signal corresponding to a speed from a resolver output by a PLL circuit. The frequency difference signal between the output of the excitation oscillator of the resolver and the output of the voltage controlled oscillator of the PLL circuit is output as a resolver output. By using it as a phase comparison reference with, it is possible to detect speed with excellent detection accuracy and responsiveness.

C. 2. Description of the Related Art Resolvers are widely used as sensors for detecting 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
By the combination of (Phase Locked Loop) circuit,
Some obtain a voltage signal proportional to speed. This conventional device is shown in FIG.

In Figure 2, the axis of rotation of the resolver 1 is directly coupled to the rotating shaft of the rotating body 2, the stator winding resolver 1 sinusoidal signal sin .omega _{c t} and different cosine wave phase by 90 degrees to the excitation oscillator 3 signal cos .omega _{c t} is applied as excitation voltage.
In response to this excitation voltage, the output of the resolver 1 has a rotor 2
Of the cosine wave (or sine wave) signal cos (ω _c −ω _r ) t, which is the difference between the angular frequency ω _r and the excitation voltage angular frequency ω _c .

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 the DC signal V _d by the low pass filter 4 _3. is a voltage controlled oscillator 4 ₂
And the bias component V _dr 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 cutoff frequency of the low pass filter 4 _3. However, the frequency ω _c −
As ω _r increases, the ratio of ω _r to the frequency ω _c decreases 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 includes a resolver coupled to a rotating body and excited by an excitation oscillator, and a low-pass filter using an output of the resolver as a phase comparator input. PL that obtains a voltage signal corresponding to the rotation speed at the output of PL
An L circuit and an arithmetic circuit that uses a signal that becomes a frequency difference between the output of the excitation oscillator and the output of the voltage controlled oscillator of the PLL circuit as a comparison reference of the phase comparator, while increasing the excitation frequency of the resolver. The oscillation frequency range of the voltage-controlled oscillator of the PLL circuit is made narrow to match the range of the rotating body.

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 _{x t} and it differs cosine wave signal phase by 90 degrees to cos .omega _{x t} to the output of the voltage controlled oscillator 4 _2, the two signals from the excitation oscillator 3 sinusoidal signal sin .omega _{c t,} multiplied by the multiplier 6 _{1 and} 6 ₂ of the cosine wave signal cos .omega _{c t} and each arithmetic circuit adds the outputs of both the multipliers 6 _and 62 in the adder 7 by the lies in that the configuration of the comparison input of the phase comparator 4 _1.

In such a configuration, the angular frequency ω _c of the excitation oscillator 3,
When the rotational angular frequency ω _r of the rotating body 2 is set, the output of the resolver 1 becomes the angular frequency ω _c −ω _r . On the other hand, the voltage controlled oscillator 4
Located ₂ of the angular frequency omega _x, the output _{V x} from the adder 7 is a frequency difference _{sinω x t · sinω c t +} cosω x t · cosω c t = cos
(Ω _c −ω _x ) t. If the output V _d of the low-pass filter 4 ₃ and the output angular frequency ω _x of the voltage controlled oscillator 4 ₂ have a proportional constant k, that is, ω _x = k · V _d , the adder 7 The output V _x becomes V _x = cos (ω _c −k · V _d ) t, V _d = ω _r / k in the locked state in the PLL circuit 4, and the output V _d proportional to the rotation speed and thus V _N are obtained. be able to.

Here, it should be noted that the oscillation angular frequency omega _x of the voltage controlled oscillator 4 ₂ becomes a narrow range to match the angular frequency omega _r of the rotary member 2, the control voltage V _d to be the output of the low pass filter 4 ₂ The linearity within the range is good against changes, and the detection accuracy is high.

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 the delay is small, good response In addition, the ripple of the detected speed voltage V _N also becomes small.

Further, since the frequency component of the excitation oscillator 3 is included in the output of the adder 7 and canceled by the phase comparison of the PLL circuit, it is not necessary to increase the frequency accuracy.

G. EFFECTS OF THE INVENTION As described above, according to the present invention, the difference between the frequency of the excitation oscillator of the resolver and the frequency of the voltage control oscillator is used as the phase comparison reference. There is an effect that the detection accuracy can be improved by narrowing the frequency range of 1 and the frequency accuracy of the excitation oscillator need not be increased, and the cost can be reduced.

[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, 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 circuit using an output of the resolver as a phase comparator input to obtain a voltage signal corresponding to a rotating speed of the rotating body at an output of a low-pass filter. A speed detector for a rotating body, comprising: an arithmetic circuit that uses a signal that is a frequency difference between the output of the excitation oscillator and the output of the voltage controlled oscillator of the PLL circuit as a comparison reference of the phase comparator. .