JPS61256221A - Resolver excitation circuit - Google Patents

Abstract

PURPOSE:To enable the removal of a speed ripple due to residual voltage, by providing a differentiation filter circuit for removing the component due to the residual voltage. CONSTITUTION:A differentiation filter circuit 6 is inserted into the rear stage of a resolver 5 which comprises an excitation circuit 1, a low pass filter 2, a waveform shaping circuit 3 and an R/D converter 4 to remove the speed ripple generated as overlapped with a residual voltage component. So to speak, the fundamental wave component of K1.sin(omega+omegaM)t and the residual voltage component of K2.omegasinomegaMt are passed through omega+omegaM and omegaM is cut with the differentiation filter circuit 6. According to this system, the cut-off frequency and the filter order of the differentiation filter circuit 6 are determined by the passage area of omega+omegaM of the fundamental wave component an the attenua tion ratio of the residual voltage component omegaM when the residual voltage component ratio K2.omega/K1 is known previously. Thus, the speed ripple due to the residual voltage can be removed with a simple circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an excitation circuit for an l/solver of a speed and position detector.

[Conventional technology]

Mechanical non-contact type position detectors such as precision resolvers can detect speed by differentiating position, and have recently been used as servo detectors. Furthermore, the number of uses for this purpose is increasing, requiring high accuracy as detectors for machine tools and drive control. Among the uses of machine tools, it is particularly required for precision processing machines to reduce not only the speed ripple at low speeds of the speed detector itself but also the speed ripples at medium and high speeds.

However, as is well known, the resolver has a phase error caused by the resolver itself as a speed detection error factor. This is caused by the processing accuracy, winding method, tooth profile, material, etc. of the resolver body. On the other hand, in a circuit that excites a resolver, for example, in a two-phase excitation-one-phase input/output method, excitation waveform distortion, voltage balance, and phase difference may occur. In order to improve this error, various proposals have been made in the past. One of the causes of this speed error is due to residual voltage existing in the resolver.

Figure 7 shows an example of a model where residual voltage occurs in the resolver stator (two poles, two-phase excitation on the stator side, detection winding on the rotor side, the old coil and D3 have the same winding direction (solid line), and the coils D2 and D4 The winding direction (dotted line) is the same).

Now, since residual magnetism has occurred in the stator, the gap magnetic flux density Bg(θ) is calculated as Bg(θ) = Bgm sinθ(B
gm: Gap maximum magnetic flux density, θ: Stator lot number
, angle from S11 to rotor throw 7, SR1), t, Fig. 7 (1) each '+ Ile OL,
[12, 03, D4 interlinking magnetic fluxes are respectively Φ1. Φ
2. Φ3. Assuming Φ4, Φ+=fBg(θ) 11 sentences l1r11dθ= Bgm
s sentence' r e f s1nθ-dO However, sentence:
Taro length, r: Rotor diameter, ψ = 2π15 Similarly, θ44ψ Φ2 = -Bgm *1m rf 5ino-dθ
θ+29 θ◆39.

Φ3=Bgm@MarJ s+ne*dθO◆ψ O.

Φ4 ==Bgm *la rf 5ino-dθθ
6ψ The total flux linkage of the detection coil is Φ■=ΣΦn=Φl+Φ2+Φ3+Φ4ml = BgmeJl” reV* cosθ=n
acos θ (n= Bgms, Q*
r@V.

■=Constant) Now, the rotors R1, R2,..., R5 are θ=ωn-t(
θ: rotational angular velocity), the detection coil terminal voltage Vθ1 is dΦV61=-he − t=NFI*n・ωhφ sinωMt=2・0M 6 sinωMt However, NR: Number of turns of the detection winding It is expressed as This occurs as a residual voltage, which increases in proportion to the rotational speed. Although not shown in the figure, the excitation voltage Vα=Vo@sinωt, Vμ=Vooc in the excitation phase
When osωt is applied, the detected voltage Vθ2 is Va2 = K3e 5in (ωt + θ), and 3: proportionality constant θ = ωi ◆t, then it is expressed as Va2 = K3 # 5in (ω + ωn)t, so the residual magnetic flux Vaz described above By adding
When the rotors R1 to R5 are rotating at ωH, the detected voltage Ve is 3115 in (ω + ωn) to Va = 2 @ (
1) When this voltage, which is M ・sinωMk, is passed through the speed detection circuit shown in Figure 9 (R/D conversion means resolver/digital conversion), the speed ωre' becomes, as shown in Figure 8. As such, velocity ripple occurs. The speed ripple percentage (peak-to-peak) is 2■/(
1-m'), the larger the rotor angular velocity ωh is, the larger it becomes. For example, in applications where speed errors at medium and high speeds are averse, removal of this error is absolutely necessary.

On the other hand, the causes of this residual voltage can be divided into internal factors, which are mainly caused by the stator core material (magnetic permeability, magnetization directionality) inside the resolver, gaps, eccentricity, and orthogonality, and external factors, which are direct causes. External factors include l) residual magnetism that occurs when a DC component is added to either the α phase or β phase and the stator core is DC magnetized, and 2) residual magnetism that occurs when a DC stationary magnetic field is applied around the resolver stator. is possible. Regarding 1), FIG. 10 shows the change in residual voltage when DC current is applied only to the α phase of the resolver. This is an experiment to see how much DC voltage is applied to the resolver to generate residual voltage.

In general, when the excitation circuit and power supply shown in Fig. 11 are used when turning on and off the control power supply equipped with an excitation amplifier, the cause of DC component being added to the excitation phase is 1.12.
One example of this is that a DC voltage as shown in the figure is applied to the Resol 8 excitation phase at the time of turning on and off, resulting in the generation of residual voltage. Even if a residual voltage occurs, it is possible to demagnetize it using a commercially available demagnetizer, but it is quite troublesome to do so when the motor is equipped with a resolver, and it also requires the control panel to be turned on and off. It is not practical to demagnetize each time.

An object of the present invention is to provide a resolver excitation circuit that eliminates speed ripples caused by residual voltage.

[Means for solving problems]

The resolver excitation circuit of the present invention is characterized in that it includes a differential filter circuit that passes only the phase detection voltage and removes components due to residual voltage.

This eliminates the need for measures such as changing the material of the resolver, and it becomes possible to eliminate speed ripples due to the influence of residual voltage with a simple circuit.

Another resolver excitation circuit of the present invention uses a resolver excitation amplifier as a demagnetizing device, and applies a demagnetizing current to the resolver before applying the normal excitation voltage after power is turned on to demagnetize the residual voltage of the resolver. It is characterized by being equipped with a demagnetizing circuit.

As a result, residual voltage can basically be removed from the resolver, and the effects of turning on and turning off the power can be removed.

Another resolver excitation circuit of the present invention includes a differential filter circuit that passes only the phase detection voltage and removes components due to residual voltage, and also uses a resolver excitation amplifier as a demagnetizing device to reduce the normal excitation voltage after power is turned on. The present invention is characterized in that it includes a demagnetizing circuit that applies a demagnetizing current to the resolver and demagnetizes the residual voltage of the resolver before applying the voltage.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a resolver excitation circuit according to the present invention.

In this embodiment, a differential filter circuit 6 is inserted after the resolver 5 of a conventional circuit consisting of an excitation circuit 1, a low-pass filter 2, a waveform shaping circuit 3, and an R/D converter 4, so that residual voltage components are superimposed. This is to remove the speed ripple that would otherwise have occurred.

Since the fundamental wave component is +-3in(ω+ωn)t and the residual voltage component is 2eωsinωst, ω+ωH is passed and ωh is cut by the differential filter circuit 6.

In this method, the residual voltage component ratio is set in advance by 2・ω/K+
If it is known, the cutoff frequency and filter order of the differential filter circuit 6 are determined by the passband of ω+ωi of the fundamental wave component and the attenuation ratio of the residual voltage component ω1.

FIG. 2 shows the speed ripple (p-p) with respect to the rotational speed, comparing the present embodiment and the conventional example (the resolver has multiple poles, and the order of the differential filter circuit 6 is 2nd order).

FIG. 3 is a block diagram of an embodiment of a resolver excitation circuit which also serves as a demagnetization circuit.

The principle of this circuit is that the resolver excitation frequency is generally 1 to 5.
K) Iz is often used, the resolver excitation input impedance seen from the excitation side is large, and the excitation current is much smaller than the instantaneous current of the excitation amplifier. voltage excitation),
Therefore, the excitation frequency is made lower than the normal excitation frequency,
Reduce the excitation input impedance and increase the excitation current.

On the other hand, in order to remove residual magnetism in the stator, it is possible to finally demagnetize the residual magnetism by applying a sufficient magnetomotive force around the stator as shown in FIG. This method is generally known as a method for demagnetizing residual magnetism. By adding a current waveform that makes this residual magnetism zero to the excitation winding of the resolver, it is possible to eliminate the residual magnetism of the resolver.

Tables containing α-phase and β-phase excitation patterns are stored in the ROM 13 and ROM 13A, respectively. The I10 port 18 receives the output of the CPU II and outputs a constant voltage a in the initial and normal excitation state, and a voltage a of 0 during demagnetization, and the level converter 19 converts these outputs a into low level and high level outputs, respectively. Convert to a′. Inverter 21 inverts output a' of level converter 19. The analog feet 201 and 203 are turned on when the output a' of the level converter 19 is at a low level, that is, at the initial time and in the normal excitation state, and the analog switch 202 is turned on during the demagnetization operation. Capacitor C1 is charged and discharged via resistor R1, and the signal at point b is supplied as reference voltage d to D/A converters 14 and 14A via resistor R2, analog switch 202, and resistor R3+Rii. The reference voltage generation circuit 17 also supplies the reference voltage C to the D/A converter 14 and i4A. Counter 12 counts the output of CPU II and RO
Generates an address to access M13.13A. Each excitation amplifier 15.15A is connected to a D/A converter 14.1.
The output of 4A is amplified and an α-phase excitation current Iα and a β-phase excitation current ■β are caused to flow through the resolver 16.

This circuit uses analog switches 201, 202, and 203 to switch the resolver excitation voltage level between demagnetization operation and normal excitation operation, and excitation frequency switching is performed using the excitation pattern of ROM 13.13A. .

Basically, it is also possible to switch the excitation voltage level and excitation frequency using only ROM+, 3, and 13A.

FIG. 4 is a time chart of the resolver excitation circuit of FIG. 3.

When the power is turned on, the CPU II is in the reset state.

In the interval of 0th order T2, the CPU II outputs from the I10 port 18, and when one of these outputs accesses the table value containing the demagnetization excitation pattern in the ROM 13.13A, The D/A converter 14.14A outputs a frequency lower than the resolver excitation frequency. At this time, the analog switch 20+ connected to both ends of the capacitor C1 becomes an orb/, and the signal at point b has a small voltage as shown in the figure. , D/A converter 14
．． The reference voltage is 14A, and in the lightest case, a demagnetizing current larger than the excitation current flows through Iα and β. After this current flows, a normal excitation current flows in the section T3, and the control operation begins.

In this way, for example, even if a residual voltage is generated when the control power supply is cut off, it is demagnetized within this T2 period, so there is no residual magnetism during subsequent control, and no speed ripple occurs. A DC stationary magnetic field is generated around the stator, and residual magnetism is generated after it is removed, but even in this case, it is possible to demagnetize and eliminate this residual magnetism by turning the control power back on.

FIGS. 6(1) and 6(2) are diagrams showing examples of the demagnetizing effect of this embodiment.

In this example, a DC voltage was applied to the α phase to generate a residual voltage on a trial basis, and the speed ripple was monitored at this time.The demagnetizing current was 120mA, the normal excitation current was 25A, and the speed N = 200OR/ It was conducted under the conditions of M.

When the magnetizing current was 12t)+wA or more, some residual voltage remained, but when the magnetizing current was 120 mA or less, the residual voltage value was close to zero.

〔Effect of the invention〕

As explained above, by incorporating a differential filter circuit into the detection circuit, the present invention eliminates the need for measures such as changing the material of the resolver, and makes it possible to eliminate speed ripples caused by the influence of residual voltage with a simple circuit. By inserting a demagnetizing circuit, it is basically possible to remove residual voltage from the resolver, and it becomes possible to remove residual voltage when the power is turned on and off.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the resolver excitation circuit according to the present invention, FIG. 2 is a diagram showing the speed ripple in the embodiment of FIG. 1 in comparison with the conventional one, and FIG. A block diagram of the embodiment, FIG. 4 is a time chart of the embodiment of FIG. 3, FIG. 5 is a diagram showing the demagnetization operation of the embodiment of FIG. 3, and FIG. 6 is a diagram of demagnetization of the embodiment of FIG. 3. Figure 7 is a diagram showing an example of the effect, Figure 7 is a diagram showing an example of a model in which residual voltage occurs in the resolver stator, Figure 8 is a diagram showing speed ripple, Figure 9 is a circuit diagram of a conventional speed detection circuit, and the first θ The figure shows the change in residual voltage when DC current is applied only to the alpha phase of the resolver, and Figure 11 is a circuit diagram of a conventional resolver excitation circuit.
FIG. 12 is a diagram showing how residual voltage is generated when DC voltage is turned on and off in the circuit shown in FIG. 11. 1: Excitation circuit, 2: Low-pass filter, 3: Waveform shaping circuit, 4: R/D converter, 5.113: Resolver, 1t: CPU, 12 counters, 13.13
A: ROM, 14, 14A: D/A converter, 15.15A, excitation amplifier. 17: Reference voltage generation circuit, 18: I10 port, 13 two-level converter, 201.2
02,203: Analog switch, 21: Inverter. Patent Applicant Anno Co., Ltd.] 1 Electrical Manufacturing Agent Tadashi Wakabayashi Fig. 1 Fig. 2rIII Fig. 3 Fig. 4 Fig. 1θ Proceedings Amendment (self-motivated) June 1985 Today

Claims (1)

[Claims] 1. A resolver excitation circuit characterized by comprising a differential filter circuit that passes only a phase detection voltage and removes components due to residual voltage. 2. The resolver excitation amplifier is used as a demagnetizing device, and a demagnetizing circuit is provided to apply a demagnetizing current to the resolver and demagnetize the residual voltage of the resolver before applying the normal excitation voltage after turning on the power. Characteristic resolver excitation circuit. 3. Equipped with a differential filter circuit that allows only the phase detection voltage to pass and removes components due to residual voltage, and uses a resolver excitation amplifier as a demagnetizing device to detect the demagnetizing current before applying the normal excitation voltage after the power is turned on. What is claimed is: 1. A resolver excitation circuit comprising: a demagnetizing circuit that energizes the resolver and demagnetizes the residual voltage of the resolver.