JPS59116048A - Speed detection system of electric motor - Google Patents

Abstract

PURPOSE:To enable speed detection by using the output of a resolver by processing each of the sine wave voltage output and cosine wave voltage output of the resolver via a differentiating circuit, multiplier, a difference circuit, and a low pass filter. CONSTITUTION:The sine wave voltage ea and cosine wave voltage eb outputted from a resolver are differentiated respectively in differentiating circuits 104a, 104b, to outputs eat, ebt. The differentiated outputs eat, ebt are multiplied by the voltages eb, ea in multipliers 104c, 104d to outputs Ea, Eb. The difference Er between the outputs Ea and EB is determined by an adder 104, and an output Er is obtd. When the difference output Er is passed through a low pass filter 104f, it is cut of the high frequency component sin<2>wt and a DC component is obtd.; therefore, an actual speed voltage TSA is outputted and is fed to an arithmetic circuit. The speed detection is thus made possible by using the output of the resolver.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric motor speed detection method that can detect the rotational speed of an electric motor based on the output direction of a resolver.

In order to control the speed of an electric motor, it is necessary to detect the rotational speed of the electric motor. Generally, a tachometer generator is used to detect the rotational speed of an electric motor, but since the tachometer generator is a type of generator, it is composed of worn parts such as brushes, and as it ages, it generates noise due to sparks, etc. There is a drawback that it does. A method of detecting speed using an optical encoder is also known, but it is not reliable enough because it uses components that change over time, such as photodiodes.

For this reason, there has been a desire for a speed detection method that can provide sufficient reliability even against changes over time.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a speed detection method for an electric motor that can detect the speed using the output of a highly reliable resolver used as a position detector.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a configuration diagram of the resolver, and FIG. 2 is its output waveform diagram.

In the figure, 102 is a resolver connected to the shaft of the electric motor, and detects the position of the field pole of the electric motor. This resolver includes a rotor 102a, a four-rotor winding 102b, and two stator windings 10 arranged with a phase of 90° to each other.
2c, 102d and sin wt carrier (for example, 3
Carrier wave generation circuit 102 that generates kHz or 6KH2)
It has e. Now, assuming that the rotor 102a is at the angle θ, the stator windings 1o2c, 102! c.
The voltage generated from l to the following equation is e a == sir
+θ sinwt (1) eb=aysθ
sin w t (21 is output; that is, as shown in FIG. 2, a rein wave voltage ea and a cosine wave voltage eb are output from the resolver 102 according to the position θ of the field pole of the motor.

Then, the sine wave voltage ea and the cosine wave voltage eb are 5i
In nWi, the synchronous rectification deviation is sinθ, Q)Sθ in Figure 2.
An output is obtained, and from this output, for example, the position of the field pole of a synchronous motor can be obtained.

In the present invention, the speed is detected in the following manner using the sine wave voltage ea and cosine wave voltage eb from the resolver 102 with R1 and ff formed in this manner.

■ Differentiate the sine wave voltage ea and the cosine wave voltage eb. Therefore, the differential outputs eat and ebt are as follows.

dθ 6Hi=-(0)Sθru sinwt-1-sinθ・w
−cxysw t (3) t dθ e b j = −(−s+nθ sInwt+”θ,
W-coswt (4)i ■Next, the differential output eat and the cosine wave voltage eb are connected to the differential output ebt and the sine voltage! fea to obtain the respective busyness calculation outputs Ea and Eb.

Ea = eat X eb dθ = (---θ・sin W t −1−sinθ・W
-coswt) -cmθ・t sin w t
(5) Eb = et)t Xea − (east θ, −5oθ), sinwt+−θ−W, c
oswt).

t sin θ-sin W t (6) (2) Next, obtain the difference Er between the multiplication outputs Ea and Eb.

Er=Ea-Eb--'! −” −5ih2wt (sln2θ0cL
)s2θ)t −”! −sin2wt
'Force i ■When the difference Er is passed through a filter, sir+2
Since the wt term has a constant value, (the method is dθ
(8) Er - old K dθ υ, since the center shows the time differentiation of the rotation angle, that is, the speed, the actual speed voltage TSA is dθ
(9) TSA= , , i( , and from the resolver outputs ea and eb, the actual speed voltage TS
A is obtained.

Next, a configuration for realizing the present invention will be described using a synchronous motor as an example of the motor.

FIG. 5 is a schematic diagram of one embodiment of the present invention, and in the figure, 1
01 is a rotating field type synchronous motor, 102 is the above-mentioned resolver, and 105 is a synchronous rectifier circuit, which synchronously rectifies the sine wave voltage ea and the cosine voltage eb, respectively.
It outputs nθ, low θ (Fig. 2). Reference numeral 104 denotes a speed detection circuit to be described later, which outputs an actual speed voltage TSA from a sine wave voltage ea and a cosine wave voltage eb. 1
05 is an arithmetic circuit that calculates the difference (hereinafter referred to as speed error) ER between the speed command voltage VCMD commanded from a speed command circuit (not shown) and the actual speed m pressure TSA, and 106 is a speed 1 difference Wa.
Increase the armature current swing by +1 fji
An error amplifier that outputs Is, 107 and 108 are multiplication circuits, and the difference between the error amplifier output and the output of the synchronous rectifier circuit 103 is θ.
, sin θ, and outputs two-phase current commands I, a (2 l5 - (2) θ) and I, b (2 lS - 5 In θ), respectively. 109 is a 2-phase to 3-phase conversion circuit for converting a 2-phase signal into 6-phase signals, and has a circuit configuration as shown in FIG. That is, the 2-phase to 3-phase i conversion circuit includes two operational amplifiers OAI and OA2, and a resistor of 10Ω to R4.
And we are looking at the resistance l of Ω at 578 and the resistance R6 of Ω at 5. Now, by determining the values of each resistor R, ~R6 as described above and connecting them as shown, the terminals Tu, Tv
, Tw, respectively. These Iu, Iv, and Iw have a phase difference of 2π/3 from each other, and an induced electromotive force E.

The 6-phase current command is in the same phase as the current command.

110U, 110V, and 110W are arithmetic circuits provided for each phase, respectively, and command currents Iu, Iv, and Iw.
and the actual phase currents Iau, Iav, and Iaw; 111 is an arithmetic circuit that adds Iav and Iaw and outputs the in-phase phase current Iau; 112V;
112W are the phase currents Iav and I of the ■ phase and W phase, respectively.
Galvanometer to detect aw, 113U, 113V, 11
3W is a current amplifier provided for each phase and amplifies the current difference between each phase, 114 is a pulse width modulation circuit, 115 is an inverter controlled by the output signal of the pulse width modulation circuit, 116 is a 6-phase AC power supply, 117 is a known rectifier circuit that rectifies three-phase alternating current into direct current, and includes a diode group 117a and a capacitor 117b.

Next, the operation shown in FIG. 6 will be described in the case where the speed command increases while the synchronous motor 101 is rotating at a certain speed.

In order to rotate the synchronous motor at a desired rotational speed Vc,
A speed command voltage VCMD having a predetermined analog value is input to an addition terminal of the arithmetic circuit 105 .

On the other hand, since the synchronous motor 101 is rotating at the actual speed Va ((Vc), the speed detection circuit 104 outputs an actual speed voltage TEA proportional to the actual speed Va, and this actual speed voltage T
SA is input to the subtraction terminal of the arithmetic circuit. Therefore, the arithmetic circuit calculates the speed error E, which is the difference between the commanded speed Vc and the actual speed VaO.
R is calculated and inputted to the error amplifier 106. The error amplifier 106d performs proportional-integral calculation as shown in the following equation.

Note that the calculation result Is of Equation 90 corresponds to the amplitude of the m-mode current. That is, when the load fluctuates or the speed command changes, the speed error ER (=Vc-Va) increases, and the armature current amplitude Is also increases accordingly. As Is becomes larger, a larger torque is generated, and this torque brings the actual speed of the electric motor to the commanded speed.

On the other hand, since the two-phase sine wave sin θ and cosine wave ■θ indicating the position (angle θ) of the field pole of the synchronous motor 101 are obtained by the resolver 102 and the synchronous rectifier circuit 103, the multiplier circuits 107 and 108 respectively I, a (=I
s-sθ), II b (=I B -5usθ
) output is obtained.

Next, the 2-phase to 3-phase conversion circuit 109 performs the calculation shown in equation C0) and outputs the current commands Iu, Iv, and Iw for each phase. Note that these Iu, Iv, and Iw are five-phase current commands that are in phase with the induced electromotive force Eo of the synchronous motor 101.

Thereafter, the three-phase current commands Iu, Iv, Iw are converted into actual phase currents Iau, Iav by the calculation circuits 110U, 110V, 110W.

The difference between Iaw and Iaw is taken, and the three-phase AC signals iu, iv, iw, which are the differences, are then sent to current amplifiers 113U, 11
3V.

The signal is amplified at 113W and input to the pulse width modulation circuit 114.

The pulse width modulation circuit 114 compares the amplitudes of the sawtooth wave signal 8TS and the three-phase alternating current signals iu, iv, iw, and applies the pulse width modulated three-phase current command to each power transistor Q, ~, which constitutes the inverter 115. It is input to the base of Q6, controls on/off of each of the power transistors Q1 to Q6, and supplies three-phase current to the synchronous motor 101.

Thereafter, similar control is performed and finally the synchronous motor 101
will rotate at the commanded speed.

FIG. 5 is a block diagram of the speed detection circuit 104 having the configuration shown in FIG.
2), the twin wave voltage ea and the cosine wave voltage eb of equations (1) and (2) are differentiated to produce differential outputs eat and ebt of equations (3) and (4), respectively. The differential constant is determined so that the frequency gain exhibits linear characteristics in the motor speed range (sin θ frequency range). 104c and 104d are multiplication circuits, each of which is composed of an analog multiplier, and differentiating circuits 104a and 104d.
The outputs eat and ebt of 04b are multiplied by the dyne wave voltage ea and the cosine wave voltage eb to obtain the multiplication output Ea of equations (5) and (6).

The one that emits Eb, 104e, is an adder circuit, and the multiplier outputs Ea, Eb (7) of the multiplier circuits 104C and 104d.
The circuit 104f that outputs the difference Er is a low-pass filter that cuts the high frequency component of the output Br of the adder circuit 104e and outputs the actual speed voltage TSA.

Next, to explain the operation of the configuration shown in FIG.
The sine wave tortoise pressure ea and cosine wave voltage eb outputted from 02 are differentiated by differentiating circuits 104a and 104b, respectively, and become differential outputs eat and ebt of equations (3) and (4). , then each differential output eat, ebt is the multiplication circuit 1
04c and 104d, they are multiplied by the cosine wave voltage eb and the sine wave voltage ea, respectively, resulting in multiplication outputs Ea and Eb shown in equations (5) and (6). Furthermore, each multiplication output Ea,
The difference Er is taken from Eb by the addition circuit 104e, and the (
The difference output Er of the method is obtained. When this differential output Er passes through the low-pass filter 104f, the high frequency component of sin2wt is cut and a DC component is obtained, so that the actual speed voltage T
SA is output and sent to arithmetic circuit 105 in FIG.

In the above description, a synchronous motor was used as an example, but the present invention can also be applied to other AC motors and even DC motors.

As explained above, according to the present invention, there is provided a differentiating circuit that differentiates each of the sine wave voltage output and the cosine wave voltage output of the resolver, and the differentiated sine wave voltage and the cosine wave voltage. Equipped with a multiplier circuit that multiplies a cosine wave voltage and the sine wave voltage, a difference circuit that obtains a difference between the outputs of each of the multiplier circuits, and a low-pass filter that cuts high frequency components of the output of the difference circuit, Since the actual speed voltage is obtained from the output of the low-pass filter, the speed can be detected from the output of the resolver, and there is no need to use a tacho generator or optical encoder, which deteriorates over time and is not reliable. This can greatly contribute to improving the reliability of electric motors and making them maintenance-free.

Further, the speed detection output can be obtained in an analog manner without momentary interruption, and a highly accurate actual speed voltage that is no different from a speed signal from a conventional tacho generator can be obtained. Furthermore, when applied to a synchronous electric machine, the sir+θ, O)Sθ multiplied signal and actual speed signal indicating the position of the field pole can be obtained from one resolver, and there is no need to provide a separate position detector. play.

Although the present invention has been described with reference to one embodiment, various modifications can be made within the scope of the present invention, and these are not excluded from the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a resolver used in the present invention, FIG. 2 is an output waveform diagram of the configuration shown in FIG. 1, FIG. 6 is a block diagram of an embodiment for realizing the present invention, and FIG. FIG. 5 is a diagram showing the configuration of the main parts of the configuration, and FIG. 5 is a diagram showing the configuration of the speed detection circuit of the configuration shown in FIG. In the figure, 101... electric motor, 102... resolver, 1
02a-rotor, 102b--rotor winding, 102c
. 102d...Stator winding, 104...Speed detection circuit, 104a, 104b--Differential circuit, 104c,
104d...Multiplication circuit, 104e...Addition circuit, 1
04 f...Low pass filter 0 Patent applicant: Fanuc Co., Ltd. agent Patent attorney: Tsuji ff [2 others]

Claims (1)

[Claims] a resolver having a rotor and a stator that rotate together with an electric motor; a differentiating circuit that differentiates each of a sine wave voltage output and a cosine wave voltage output of the resolver; A multiplication circuit that multiplies the differentiated cosine wave voltage and the sine wave voltage, a difference circuit that obtains a difference between the outputs of each of the multiplication circuits, and a low-pass filter that cuts high frequency components of the output of the difference circuit. 9. A speed detection method for an electric motor, characterized in that an actual speed voltage is obtained from the output of the low-pass filter.