JP3309027B2 - Reluctant resolver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reluctance resolver used for detecting the position and speed of a servomotor of a machine tool.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view showing an example of a conventional reluctance resolver, FIG. 5 is a block diagram showing an example of an electric circuit of the reluctance resolver of FIG. 4, and FIG. 6 is a timing chart thereof. . 4, 5, and 6
, The timing generator 4 generates a clock signal CLK and a hold signal HD which are two synchronized signals. The excitation signal generator 5 generates an excitation signal Ve which is a sine wave signal synchronized with the clock signal CLK. The excitation signal Ve is current-amplified by the differential amplifier 17 to become an excitation voltage Vep. As shown in FIG. 4, on the inner periphery of the stator 3, four exciting salient poles A to D made of a magnetic material such as a silicon steel plate and arranged at equal intervals of 90 ° are provided. Exciting salient poles A and C, and exciting salient poles B and D
However, each is 180 ° out of phase. Excitation salient pole pair A
And C are wound with a winding Lf and a winding Lh, respectively, and the exciting salient pole pairs B and D are wound with a winding Lg and a winding Li, respectively. The ends of the exciting salient poles A to D face inward, and the rotor 2 is arranged via a gap in a space surrounded by the ends. The rotor 2 is made of a cylindrical magnetic body eccentric with respect to the rotation shaft 1. When the rotor 2 rotates due to this eccentric shape, the air gap between the rotor 2 and the end of each of the exciting salient poles A to D changes in accordance with the rotation angle θ.
With a phase difference of ゜, 90 ゜, 180 ゜, 270 変 化, an inductance change corresponding to a trigonometric function for one cycle per rotation of the rotor 2 is caused in each of the windings Lf to Li.

As shown in FIG. 5, one end of a connection end of windings Lf to Li is connected to an output of a differential amplifier 17 and an inverting input terminal.
The other ends are connected to the current detection resistors 21 to 24, respectively. The windings Lf to Li convert a change in inductance due to the rotation of the rotor 2 into a change in current, and the current detection resistors 21 to 24 convert the change in current into a change in voltage. The output voltage Vf generated at the current detection resistors 21 to 24
Vi is input to the differential amplifiers 6 and 7, respectively. That is, the output voltage Vf is applied to the inverting input terminal of the differential amplifier 6,
An output voltage Vh is input to the non-inverting input terminal, and an A-phase signal Va whose amplitude is modulated in a sinusoidal manner by the rotation angle θ of the rotor 2 is output from the output terminal of the differential amplifier 6. The output voltage Vg is applied to the inverting input terminal of the differential amplifier 7.
However, the output voltage Vi is input to the non-inverting input terminal, and the output terminal of the differential amplifier 7 outputs a B-phase signal Vb whose amplitude is modulated in a sinusoidal manner by the rotation angle θ of the rotor 2. As shown by the arrow in FIG. 4, when the rotor 2 rotates clockwise, the phase of the B-phase signal is 9 times higher than that of the A-phase signal.
The amplitude changes by 0 °. This is shown in FIG.
Vb. The output signals Vf to Vi are amplified by the differential amplifiers 6 and 7 and input to the sample-and-hold circuits 8 and 9 as the A-phase signal Va and the B-phase signal Vb as described above. The sample and hold circuits 8 and 9 sample the input signal when the hold signal HD is at "L" level, and hold the sampled signal when it is at "H" level. The A / D converters 10, 11 are:
At the rising edge of the hold signal HD, sample and
The analog signals output from the hold circuits 8 and 9 are converted into digital signals A and B. The interpolation circuit 12 calculates and outputs the target angle θ by taking the arc tangent of the result of dividing the digital signals A and B. Va and Vb of such a reluctance resolver are represented by equations. now,
The impedances Xf to Xi of Lf to Li are represented by the DC resistance r of the winding and the change L of the inductance caused by the rotation of the rotor 2.
Xf = r + jω · (Lo + L · cos (θ)) ··· Equation 1 Xg = r + jω · (Lo + L · cos (θ + 90 °)) ··· Equation 2 Xh = r + jω · (Lo + L) Cos (θ + 180 °)) Formula 3 Xi = r + jω (Lo + Lcos (θ + 270 °)) Formula 4 Assuming that the resistance values of the current detection resistors 21 to 24 are R, the output signals Vf to Vi are as follows: Vf = Vep · R / (R + Xf) Equation 5 Vg = Vep · R / (R + Xg) Equation 6 Vh = Vep · R / (R + Xh) Equation 7 Vi = Vep · R / (R + Xi) Equation 8 Substituting Equations 1 to 4 into Equations 5 to 8 and rearranging, Vf = Vep · R · (R + r−jω (Lo + L · cos (θ))) / ((R + r) ² + ω ² (Lo + L · cos (θ)) ² ) ・ ・ ・ Equation 9 Vg = Vep · R · (R + r−jω (Lo + L · cos (θ + 90 °))) / ((R + r) ² + ω ² (Lo + L · cos (θ + 90 °)) ² ) 10 Vh = Vep · R · (R + r−jω (Lo + L · cos (θ + 180 °))) / ((R + r) ² + ω ² (Lo + L · cos (θ + 180 °)) ² ) Equation 11 Vi = Vep · R · (R + r-jω ( Lo + L · cos (θ + 270 °))) / ((R + r) 2 + ω 2 (Lo + L · cos (θ + 270 °)) ²⁾ formula 12 here, Lo >> L by Lo ≒ Lo + L・ Cos (θ) ・ ・ ・ Equation 13 ≒ Lo + L ・ cos (θ + 90１３) ・ ・ ・ Equation 14 ≒ Lo + L ・ cos (θ + 180 ゜) ・ ・ ・ Equation 15 I do. On the other hand, Va and Vb are as follows: Va = Vh−Vf Expression 17 Vb = Vi−Vg Expression 18 Therefore, Expressions 13 to 16 are substituted into the denominator side of Expressions 9 to 12, and are substituted into Expressions Substituting into 17, 18 and rearranging, Va = 2 · Vep · R · jω · L · cos (θ) / ((R + r) ² + ω ² · Lo ² ) Equation 19 Vb = 2 · Vep · R · jω · L · cos (θ + 90 °) / ((R + r) 2 + ω 2 · Lo 2) the equation 20. From Expressions 19 and 20, it can be seen that the amplitudes of Va and Vb depend on the DC resistance r of the winding.

[0004]

In such a reluctance resolver, when the ambient temperature rises, each winding Lf-L
Since the DC resistance r of i increases and the exciting current decreases,
The amplitude of the detection signal decreases. As a result, there is a problem that the resolution for detecting the rotation angle is reduced. Conversely, when the ambient temperature decreases, the DC resistance value of the winding decreases, and the amplitude of the detection signal increases. Thereby, the A / D converter 1
There is a problem that the input range exceeds the input range of 0 and 11 and an error occurs in the detection of the rotation angle. As described above, in the related art, since the amplitude of the detection signal changes due to a change in the ambient temperature, a stable and reliable rotation angle cannot be detected. Further, as shown in FIGS. 4 and 5, the conventional reluctance resolver is connected to an electric circuit at a total of five points including the output of the differential amplifier 17 and the four input terminals of the differential amplifiers 6 and 7. . Also, four current detecting resistors are used. As described above, since the number of lines connecting the resolver portion and the electric circuit portion and the number of current detection resistors are large, there has been a problem that the device becomes complicated and the cost of parts and assembly increases. The present invention has been made to solve such a problem, and eliminates the temperature dependency of the amplitude of a detection signal, enables stable and reliable rotation position detection, and has a resolver portion and an electric circuit portion. It is an object of the present invention to realize an inexpensive reluctance resolver in which the number of lines connecting electronic devices and the number of electronic components are reduced and the apparatus is simplified.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a reluctance resolver used for detecting the position and speed of a servomotor or the like of a machine tool. Is 0 ゜, 9
In a resolver having four sets of windings that periodically change with a phase difference of 0 °, 180 °, and 270 °, a first phase in which windings of the inductance change of 0 ° and 180 ° are connected in series. A winding, a second phase winding in which windings having a change in inductance of 90 ° and 270 ° are connected in series, and the first phase winding and the second phase winding connected in parallel;
A constant current exciting means for supplying an exciting current to both ends thereof and keeping the exciting current constant with respect to a change in ambient temperature, and an offset serving as a reference for calculating a rotation angle of the rotor based on an output voltage of the constant current exciting means. Offset voltage generating means for generating a voltage, and calculating a rotation angle of the rotor based on a difference between the voltage output from each of the series connection points in the first phase winding and the second phase winding and the offset voltage. And an interpolating means.

[0006]

According to the present invention, since the winding is excited with a constant current by the constant current exciting means, a change in the amplitude of the detection signal is eliminated, and a stable and reliable rotation position can be detected. Since the windings 180 ° out of phase are connected in series for excitation and detection, the number of lines and electronic components connecting the resolver and the electric circuit are reduced, and the apparatus is simplified and inexpensive. Can be.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of the reluctance resolver of the present invention, FIG. 2 is a block diagram showing an example of an electric circuit thereof, and FIG. 3 is a timing chart thereof. In FIGS. 1, 2, and 3, the same components as those in FIGS. 4, 5, and 6 are denoted by the same reference numerals. 1, 2, and 3, the shapes of the stator 3 and the rotor 2, changes in inductance brought to the windings La to Ld by the rotation of the rotor 2, the excitation signal generator 5, and the differential amplifiers 6 and 7.
Subsequent steps are the same as in the conventional example, but differ in the method of connecting the windings, the number of lines connected to the electric circuit, the method of canceling the offset voltage, and the method of controlling the excitation voltage. 1, 2 and 3, a stator 3 has four sets of windings whose inductance periodically changes with a phase difference of 0 °, 90 °, 180 °, and 270 ° according to the rotation of the rotor 2. La to Ld are wound. And the phase of the change in inductance is 0
゜ and 180 ° windings La and Lc are connected in series to form a first phase winding. Further, the windings Lb and Ld having phases of change of inductance of 90 ° and 270 ° are connected in series to form a second phase winding. The first phase winding and the second phase winding are connected in parallel. One end of the parallel connection is connected to the output of the differential amplifier 17, and the other end is connected to the ground resistor 14. Further, a series connection point NAC between the winding La and the winding Lc in the first phase winding is connected to the inverting input terminal of the differential amplifier 6 in series connection between the winding Lb and the winding Ld in the second phase winding. The point NBD is input to each of the inverting input terminals of the differential amplifier 7. As shown in FIG. 2, the number of connection lines to the electric circuit is four, one less than the conventional one shown in FIG. 2, one side of the resistor 15 is connected to the output of the differential amplifier 17, and the other side is connected to the resistor 16 and the non-inverting input terminals of the differential amplifiers 6 and 7. Resistor 1
6 is connected to the grounding resistor 14 and the inverting input terminal of the differential amplifier 17. The number of resistors is three, one less than the conventional one shown in FIG. In addition, the grounding resistor 14
Indicates that the temperature characteristics are good (specifically, the temperature change of the resistance value is small), and that the resistance values of the resistors 15 and 16 have the same relative accuracy (specifically, the temperature characteristics and the resistance value are equal). And

With this configuration, all the current flowing through the winding flows through the grounding resistor 14, so that the voltage Ven generated at the grounding resistor 14 is negatively fed back to the exciting voltage Vep to excite the exciting voltage Vep. Since the exciting current proportional to the voltage Ve can always flow, the temperature dependency of the amplitude of the detection signal can be eliminated. More specifically,
If the DC resistance of the winding increases due to an increase in the ambient temperature, the current flowing through the grounding resistor 14 decreases and the voltage Ven increases.
Decrease. As a result, the potential of the inverting input terminal of the differential amplifier 17 connected to the ground resistor 14 also decreases. Then, the differential input voltage of the differential amplifier 17 increases and the excitation voltage Vep increases, so that the current flowing through the winding increases. Conversely, when the ambient temperature decreases and the DC resistance of the winding decreases, the voltage Ven increases, the excitation voltage Vep decreases, and the current flowing through the winding decreases. With the above operation, the current flowing through the winding is not affected by the ambient temperature. Therefore, the grounding resistor 14 and the differential amplifier 17 constitute the constant current exciting means of the present invention. Next, the voltage Vofs at the connection point between the resistor 15 and the resistor 16 is the voltage Vac at the connection point NAC between the winding La and the winding Lc and the voltage Vac at the connection point NBD between the winding Lb and the winding Ld. This is an offset voltage of the voltage Vbd.
This is shown as Vofs in FIG. Therefore,
The resistor 15 and the resistor 16 constitute the offset voltage generating means of the present invention. Also, the voltage Va of the series connection point NAC
The voltage cb and the voltage Vbd at the series connection point NBD are voltages whose amplitudes are modulated in a sine wave shape based on the inductance changes of the winding La and the winding Lc and the winding Lb and the winding Ld accompanying the rotation of the rotor 2. . This situation is shown in FIG.
bd. In the differential amplifier 6, the voltage Vac at the connection point NAC is subtracted from the offset voltage Vofs, amplification is performed around the midpoint potential of the input range of the A / D converter 10, and the amplification is performed by the sample-and-hold circuit 8. Is entered. The output signal of the differential amplifier 6 is an A-phase signal V whose amplitude is modulated in a sinusoidal manner by the rotation angle of the rotor 2.
a. Similarly, in the differential amplifier 7, the voltage Vbd of the connection point NBD is calculated from the offset voltage Vofs.
Is amplified, the signal is amplified around the midpoint potential of the input range of the A / D converter 11, and is input to the sample-and-hold circuit 9. The output signal of the differential amplifier 7 is a B-phase signal Vb whose amplitude is modulated in a sinusoidal manner by the rotation angle of the rotor 2, but when the rotor 2 rotates clockwise, the output signal is smaller than the A-phase signal. The phase advances by 90 ° and the amplitude changes. As described above, the amplitude of the output signals Va and Vb of the differential amplifiers 6 and 7 is the offset voltage Vofs.
The reference is set so as not to exceed the input range of 0 and 11, and is a reference voltage for calculating the rotation angle of the rotor. As a result, it is possible to eliminate an error in rotation angle detection that occurs when the input signals to the A / D converters 10 and 11 exceed the input range. A described above
The phase and B phase signals Va and Vb are supplied to sample and hold circuits 8 and 9, A / D converters 10 and 11, and an interpolation circuit 12.
Is converted into the target rotation angle θ in the same manner as in the prior art, and is output from the interpolation circuit 12. Va and Vb of such a reluctance resolver are represented by equations. Similarly to the conventional example, when the impedances Xa to Xd of La to Ld are shown as a DC resistance r of the winding and a change L of the inductance due to the rotation of the rotor 2 and an inductance Lo that does not change, Xa = r + jω · (Lo + L · cos (θ)) Expression 21 Xb = r + jω · (Lo + L · cos (θ + 90 °)) Expression 22 Xc = r + jω · (Lo + L · cos (θ + 180 °)) Expression 23 Xd = r + jω · ( Lo + L · cos (θ + 270 °)) Expression 24 Assuming that the current flowing through the grounding resistor 14 is I, the current flowing through the windings La to Ld has the same resistance and the same value of Xa + Xc and Xb + Xd according to the relations of Expressions 21 to 24. And I / 2. Then, Vac and Vbd are as follows: Vac = I / 2 · Xc + Ven (Equation 25) Vbd = I / 2 · Xd + Ven (Equation 26) In addition, Vep, Vofs, Va, and Vb are as follows: Vep = I / 2 · (Xa + Xc) + Ven Equation 27 Vofs = (Vep + Ven) / 2 Equation 28 Va = Vofs−Vac Equation 29 Vb = Vofs−Vbd: Equation 30 Equations 21 to 30 are rearranged. Va = I / 2 · jω · L · cos (θ) Equation 31 Vb = I / 2 · jω · L Cos (θ + 90 °) Expression 32 Equations 31 and 32 show that the amplitudes of Va and Vb do not depend on the DC resistance r of the winding.

[0009]

As described above, according to the reluctance resolver of the present invention, the current flowing through the winding is detected by the grounding resistor, negative feedback is applied to the constant current exciting means, and the current flowing through the winding is affected by the temperature. As a result, the temperature dependence of the change in the amplitude of the detection signal can be eliminated. Also,
The number of lines connecting the resolver part and the electric circuit part was reduced from five to four, and the number of resistors was also reduced from four to three.
As described above, stable and reliable rotation position detection is enabled, and a simplified and inexpensive reluctance resolver can be realized. Here, the reluctance resolver that detects the rotational position has been described, but the reluctance resolver that detects the linear position can be similarly configured.
Needless to say, the same effect can be obtained. When the rotor 2 is rotating, the output of the A / D converter A
By calculating the amplitudes of the phase and B-phase signals and controlling the excitation voltage so that the amplitudes are constant, the excitation current can be kept constant, and the same effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a reluctance resolver of the present invention.

FIG. 2 is a block diagram showing an example of an electric circuit of the reluctance resolver of the present invention.

FIG. 3 is a timing chart of FIG.

FIG. 4 is a diagram illustrating an example of a conventional reluctance resolver.

FIG. 5 is a block diagram showing an example of an electric circuit of a conventional reluctance resolver.

FIG. 6 is a timing chart of FIG.

[Explanation of symbols]

1 rotating shaft, 2 rotors, 3 stators, 4 timing generators, 5 excitation signal generators, 6, 7 differential amplifiers,
8,9 Sample and hold circuit, 10,11
A / D converter, 12 interpolation circuit, 14 ground resistor,
15, 16 resistor, 17 differential amplifier, A, B, C,
D excitation salient pole, La, Lb, Lc, Ld, Lf, Lg, L
h, Li winding.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01D 5/00-5/62 G01B ⁷ /00-7/34

Claims (1)

(57) [Claims] 1. A resolver having four sets of windings whose inductance periodically changes with a phase difference of 0 °, 90 °, 180 °, and 270 ° according to rotation of a rotor, A first phase winding in which windings having phases of 0 ° and 180 ° are connected in series; a second phase winding in which windings having phases of change in inductance of 90 ° and 270 ° are connected in series; A phase winding and the second phase winding connected in parallel, an exciting current flowing through both ends thereof, and a constant current exciting means for keeping the exciting current constant with respect to a change in ambient temperature; and Offset voltage generating means for generating an offset voltage serving as a reference for calculating the rotation angle of the rotor based on the output voltage; and voltages output from respective series connection points in the first phase winding and the second phase winding. And said off Reluctance resolver comprising: the interpolation means for calculating a rotation angle of the rotor based on the difference between Tsu G Voltage, the.