JP2005147729A - Rotational angle detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotational angle detector using a resolver capable of detecting the rotational angle precisely. <P>SOLUTION: At the time when the resolver 3 is stopping, the variable frequency excitation signal output circuit 13 outputs excitation signal f(t) of continuously varying frequency, the signal selection circuit 14 selects either one of f(t)sinθ, or f(t)cosθ, the variable gain amplifier 16 amplifies the signal selected by the signal selection circuit 14, the adder 17 adds the output signal of the variable gain amplifier 16 and the excitation signal f(t), the minimum value detector circuit 18 detects the time point when the amplitude of the output signal of the adder 17 is minimum, the delay time calculation circuit 19 calculates the delay time τ from the frequency F<SB>0</SB>of the excitation signal f(t) at the time point when the amplitude of the output signal is minimum, and the angle correction circuit 20 calculates the correction detection rotation angle ϕc based on the delay tim τ, when the resolver 3 is rotating. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rotation angle detection device using a resolver.

  In a conventional rotation angle detection device using a resolver, a signal delay due to the wire length between the resolver and the resolver-digital conversion circuit (hereinafter referred to as an R / D conversion circuit), or a signal delay in the R / D conversion circuit occurs. In this case, there is a temporal difference between the actual angle indicated by the rotator to be actually detected and the detected rotation angle (angle conversion result), and the influence becomes more remarkable as the rotation speed increases. Is used for controlling the synchronous motor, there is a problem that the output torque of the synchronous motor is reduced.

  Therefore, in the prior art, as shown in Patent Document 1, for example, in a resolver circuit with one-phase excitation and two-phase output, the output signal on one side is phase-shifted by π / 2 with respect to the excitation signal by the phase shift circuit, and the other output The detected rotation angle is obtained by canceling the lag component from the two signals obtained by adding and subtracting with the signal.

JP-A-9-126809

  However, in such a rotation angle detection device, since a phase shift circuit is required, a time delay due to the phase shift potentially occurs, which hinders improvement in the accuracy of the detected rotation angle and the absolute amount of the phase shift. Affects the angle conversion accuracy, so that it is necessary to improve the absolute accuracy and temperature characteristics of the phase shift circuit, resulting in an increase in circuit scale and cost.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a rotation angle detection device that can accurately detect a rotation angle.

  In order to achieve this object, in the present invention, when the resolver is stopped, the frequency of the excitation signal is continuously changed, and the phase difference between the excitation signal and the signal output from the resolver becomes 180 °. A delay time is calculated from the frequency of the excitation signal, and the detected rotation angle is corrected based on the delay time when the resolver rotates.

  In the rotation angle detection device according to the present invention, the detected rotation angle is corrected based on the delay time, and therefore the rotation angle can be detected with high accuracy.

(First embodiment)
FIG. 1 is a view showing a rotation angle detection device according to the present invention. As shown in the figure, when the resolver 3 is rotating, an excitation signal f (t) having a predetermined frequency is applied to the resolver 3 from the variable frequency excitation signal output circuit 13, and the resolver 3 is rotated by the rotation angle ( Two output signals (AC signals) f (t) sinθ and f (t) cosθ that are amplitude-modulated according to the shaft angle) θ are output. The filter circuit 9 removes disturbance factors such as motor operating noise from the output signals f (t) sinθ and f (t) cosθ. The differentials 22 and 23 remove common noise from the output signals f (t) sinθ and f (t) cosθ. The sinφ / cosφ generation circuit 24 generates sinφ and cosφ based on the detected rotation angle φ from the UP / DOWN counter 6 (described later). The product-sum operation circuit 25 calculates f (t) (sinθcosφ−cosθsinφ) = f (t) sin (θ−φ). The synchronous detection circuit 21 obtains the deviation sin (θ−φ) by synchronously detecting the signal f (t) sin (θ−φ) with the excitation signal f (t) from the variable frequency excitation signal output circuit 13. The compensator 7 sets the UP / DOWN counter 6 to UP / DOWN so that the deviation sin (θ−φ) becomes zero, so that φ = θ, and the UP / DOWN counter 6 outputs the detected rotation angle φ. The angle correction circuit 20 corrects the detected rotation angle φ based on the delay time τ (described later) to obtain the corrected detected rotation angle φc. The correction detection rotation angle φc is read by the CPU 8 and used for synchronous motor control and the like.

  Further, when the correction mechanism control circuit 10 detects that the power is supplied to the R / D conversion circuit 26 when the resolver 3 is stopped, that is, when the rotation angle θ is constant, the excitation frequency instruction circuit 12 is instructed to continuously change the excitation frequency instruction to the variable frequency excitation signal output circuit 13, and the variable frequency excitation signal output circuit 13 outputs the excitation signal f (t) whose frequency continuously changes. However, in this embodiment, since the circuit is digitized and it is difficult to completely change the excitation frequency continuously, it is actually configured to create a pseudo continuous change state in a very small step. ing. Further, in this embodiment, the excitation signal f (t) output from the variable frequency excitation signal output circuit 13 can be implemented with an arbitrary waveform. / N In order to detect well, the most suitable sine wave is used.

  In this case, an excitation signal f (t) whose frequency continuously changes is input to the resolver 3, and output signals f (t) sinθ and f (t) that are amplitude-modulated according to the rotation angle θ from the resolver 3. cosθ is output. Note that since the rotation angle θ is constant, the sin θ and cos θ of the output signals f (t) sinθ and f (t) cosθ are also constant.

  The signal selection circuit 14 outputs the output signals f (t) sinθ, f so that the amplitude is as large as possible and the same phase as the excitation signal f (t) is obtained from the output signals f (t) sinθ, f (t) cosθ. (t) Either one of cosθ is selected, and the polarity of the selected output signals f (t) sinθ and f (t) cosθ is reversed as necessary. Specifically, the output signals f (t) sinθ and f (t) cosθ are selected as shown in Table 1 according to the value of the detected rotation angle φ before correction. That is, when the detected rotation angle φ is 45 to 135 °, the signal selection instruction circuit 14a switches the switches 14b and 14d to select the output signal f (t) sinθ, and the detected rotation angle φ is 135 to 225 °. Sometimes, the signal selection instruction circuit 14a switches the switches 14b and 14d to select the output signal f (t) cosθ (−f (t) cosθ) whose polarity is inverted by the polarity inversion circuit 14c, and the detected rotation angle φ is 225. When it is ˜315 °, the signal selection instruction circuit 14a switches the switches 14b and 14d to select and detect the output signal f (t) sinθ (−f (t) sinθ) whose polarity is inverted by the polarity inversion circuit 14c. When the rotation angle φ is 315 to 45 °, the signal selection instruction circuit 14a switches the switches 14b and 14d to select the output signal f (t) cos θ.

利得指示回路１５は、回転角θがどの値であっても信号選択回路１４によって選択された信号が一定の振幅となるように、補正前の検出回転角φを用いて必要な利得を求め、利得指示回路１５は可変利得アンプ１６を制御し、可変利得アンプ１６は信号選択回路１４によって選択された信号を増幅する。これらは、後述する加算器１７の出力信号の振幅変化をＳ／Ｎ良く検知するために実施するものであるので、システムに求められる精度に応じて、本回路ブロックは省略してもかまわない。ここで得られる可変利得アンプ１６の出力信号の振幅は、励磁信号ｆ(ｔ)の振幅に等しくなるように構成する。

The gain instruction circuit 15 obtains a necessary gain by using the detected rotation angle φ before correction so that the signal selected by the signal selection circuit 14 has a constant amplitude regardless of the rotation angle θ. The gain instruction circuit 15 controls the variable gain amplifier 16, and the variable gain amplifier 16 amplifies the signal selected by the signal selection circuit 14. These steps are performed in order to detect the amplitude change of the output signal of the adder 17 to be described later with good S / N. Therefore, this circuit block may be omitted depending on the accuracy required for the system. The amplitude of the output signal of the variable gain amplifier 16 obtained here is configured to be equal to the amplitude of the excitation signal f (t).

The adder 17 adds the output signal of the variable gain amplifier 16 and the excitation signal f (t). At this time, the phase difference between the output signal of the variable gain amplifier 16 and the excitation signal f (t) is substantially determined by the delay time of the filter circuit 9. Therefore, when the frequency of the excitation signal f (t) is continuously changed as described above, the frequency F ₀ in which the delay time and the half cycle (180 °) of the excitation signal f (t) coincide with each other. The phase difference between the two becomes 180 °, and the output of the adder 17 becomes zero. Specifically, assuming that the frequency of the excitation signal f (t) when the amplitude of the output of the adder 17 is minimum is F ₀ , the delay time τ (correction constant) can be obtained by the following equation. .

τ = (1/2) × (1 / F ₀ ) (1)
Note that the output of the adder 17 may not become zero due to circuit variations in practice, but in this case as well, the output of the adder 17 is minimized at the frequency F ₀ and is compared with the previous and subsequent frequencies. If it is detected that the amplitude becomes relatively small, the frequency F ₀ can be specified. This indicates that high accuracy is not required for the gain of the circuit that determines the amplitude, and this is one of the advantages of the present invention. 2 ((a) is a graph showing a change in frequency of the excitation signal f (t), (b) is a graph showing a waveform of the excitation signal f (t), etc.), the output signal of the variable gain amplifier 16 is shown. An example is shown in which the amplitude and the amplitude of the excitation signal f (t) do not match.

  The minimum value detection circuit 18 detects the time point (timing) when the amplitude of the addition signal that is the output signal of the adder 17 becomes minimum. This is realized by detecting the amplitude of the output signal of the adder 17 at each frequency change step of the excitation signal f (t) and detecting the point at which the change in the amplitude of the output signal of the adder 17 turns from decreasing to increasing. can do.

The delay time calculation circuit 19 calculates the delay time τ from the frequency F ₀ of the excitation signal f (t) at the time when the amplitude of the output signal of the adder 17 becomes the minimum, according to the above equation (1).

  Based on the delay time τ, the angle correction circuit 20 uses the detected rotation angle φ before correction and the rotation number per unit time of the resolver 3 obtained from the change rate of the detected rotation angle φ to calculate the corrected detection rotation angle φc. calculate. Specifically, if the rotational speed per unit time of the resolver 3 is R, the sampling interval of the detected rotational angle φ is Δt, and the rotational speed of the resolver 3 between the sampling intervals Δt is ΔR, the corrected detected rotational angle. φc can be obtained by the following equation.

R = ΔR / Δt (2)
φc = φ + 360 ° × τ ÷ (1 / R) (3)
The variable frequency excitation signal output circuit 13 constitutes excitation signal output means for outputting an excitation signal to the resolver 3. Further, an AC signal corresponding to the rotation angle output from the resolver is input by the sinφ / cosφ generation circuit 24, the product-sum operation circuit 25, the synchronous detection circuit 21, the compensator 7, and the UP / DOWN counter 6 to detect the rotation angle. Rotation angle detection means for detecting The variable frequency excitation signal output circuit 13 constitutes frequency modulation excitation signal output means for outputting an excitation signal whose frequency continuously changes to the resolver when the resolver is stopped. In addition, the signal selection circuit 14, the variable gain amplifier 16, the adder 17, the minimum value detection circuit 18, and the delay time calculation circuit 19 input an excitation signal input from the frequency modulation excitation signal output means to the resolver and a signal output from the resolver. The delay time detecting means for detecting the delay time from the excitation signal input from the frequency modulation excitation signal output means to the resolver at the time when the phase difference between the first and second signals becomes 180 °. The adder 17 constitutes addition signal detection means for detecting an addition signal obtained by adding the excitation signal input from the frequency modulation excitation signal output means to the resolver and the signal corresponding to the signal output from the resolver. . Further, the minimum value detecting circuit 18 constitutes a minimum value detecting means for detecting a time point when the amplitude of the added signal detected by the added signal detecting means is minimized. Further, the angle correction circuit 20 constitutes correction means for correcting the detected rotation angle detected by the rotation angle detection means based on the delay time detected by the delay time detection means when the resolver rotates.

In this rotation angle detection device, when power is turned on to the R / D conversion circuit 26 while the resolver 3 is stopped, the variable frequency excitation signal output circuit 13 causes the excitation signal f whose frequency continuously changes. (t) is output, so that the signal selection circuit 14 has as large an amplitude as possible and the same phase as the excitation signal f (t) from the output signals f (t) sinθ and f (t) cosθ of the resolver 3. In addition, one of the output signals f (t) sinθ and f (t) cosθ is selected, and the polarity of the selected output signals f (t) sinθ and f (t) cosθ is reversed as necessary. Next, the variable gain amplifier 16 amplifies the signal selected by the signal selection circuit 14 and makes the amplitude of the output signal of the variable gain amplifier 16 equal to the amplitude of the excitation signal f (t). Next, the adder 17 adds the output signal of the variable gain amplifier 16 and the excitation signal f (t), and the minimum value detection circuit 18 detects the point in time when the amplitude of the output signal of the adder 17 is minimized, The delay time calculation circuit 19 calculates the delay time τ from the frequency F ₀ of the excitation signal f (t) at the time when the amplitude of the output signal of the adder 17 becomes the minimum.

  On the other hand, when the resolver 3 is rotating, an excitation signal f (t) having a predetermined frequency is applied to the resolver 3 from the variable frequency excitation signal output circuit 13, and the product-sum operation circuit 25 outputs the output signal f (t) of the resolver 3. ) f (t) sin (θ−φ) is calculated from sinθ and f (t) cosθ and the output signals sinφ and cosφ of the sinφ · cosφ generating circuit 24. Next, the synchronous detection circuit 21 obtains the deviation sin (θ−φ) by synchronously detecting the signal f (t) sin (θ−φ), and the compensator 7 determines that the deviation sin (θ−φ) is zero. The UP / DOWN counter 6 is UP / DOWN so that the UP / DOWN counter 6 outputs the detected rotation angle φ. Next, the angle correction circuit 20 corrects the detected rotation angle φ based on the delay time τ to obtain a corrected detected rotation angle φc.

  In such a rotation angle detection device, the detected rotation angle φ is corrected based on the delay time τ to obtain the corrected detection rotation angle φc, so that the rotation angle can be detected with high accuracy. As a result, it is possible to prevent a decrease in torque due to the above and to adjust the delay time for each system to be applied. Therefore, the versatility of the device is increased, and the design cost and the maintenance cost can be reduced. In addition, since the delay time τ can be calculated from the relative magnitude relationship of the signal amplitude, the requirement for the accuracy of the circuit is relatively relaxed, and the accuracy can be improved by adding a minimum number of circuits.

(Second Embodiment)
FIG. 3 is a diagram showing another rotation angle detection device according to the present invention. As shown in the figure, the synchronous detection circuits 31 and 32 of the R / D conversion circuit 37 are the excitation signals f (t) from the variable frequency excitation signal output circuit 13 and the output signals f (t) of the differentials 22 and 23. Sine signal sinθ and cosine signal cosθ are obtained by synchronously detecting sinθ and f (t) cosθ. The product-sum operation circuit 33 calculates sinθcosφ−cosθsinφ = sin (θ−φ) from the sine signal sinθ, the cosine signal cosθ, and the output signals sinφ and cosφ of the sinφ / cosφ generation circuit 24. The subtractor 34 detects the difference between the output signal of the variable gain amplifier 16 and the excitation signal f (t), and the maximum value detection circuit 35 maximizes the amplitude of the difference signal that is the output signal of the subtractor 34. Detect time. This is realized by detecting the amplitude of the output signal of the subtractor 34 at each frequency change step of the excitation signal f (t) and detecting the point at which the change in the amplitude of the output signal of the subtractor 34 turns from increasing to decreasing. can do. The delay time calculation circuit 36 calculates the delay time τ from the frequency F ₀ of the excitation signal f (t) at the time when the amplitude of the difference signal that is the output signal of the subtractor 34 becomes maximum. Other configurations are the same as those of the rotation angle detection device shown in FIG.

  Then, the sinφ / cosφ generation circuit 24, the synchronous detection circuits 31, 32, the product-sum calculation circuit 33, the compensator 7, and the UP / DOWN counter 6 input and detects an AC signal corresponding to the rotation angle output from the resolver. A rotation angle detecting means for detecting the rotation angle is configured. Further, the signal selection circuit 14, the variable gain amplifier 16, the subtractor 34, the maximum value detection circuit 35, and the delay time calculation circuit 36, an excitation signal input from the frequency modulation excitation signal output means to the resolver and a signal output from the resolver. The delay time detecting means for detecting the delay time from the excitation signal inputted from the frequency modulation excitation signal output means to the resolver at the time when the phase difference with respect to 180 ° becomes 180 °. Further, the subtractor 34 constitutes difference signal detection means for detecting a difference signal corresponding to the difference between the excitation signal input from the frequency modulation excitation signal output means to the resolver and the signal corresponding to the signal output from the resolver. ing. Further, the maximum value detecting circuit 35 constitutes a maximum value detecting means for detecting a time point when the amplitude of the difference signal detected by the difference signal detecting means becomes maximum.

In this rotation angle detection device, when the resolver 3 is rotating, an excitation signal f (t) having a predetermined frequency is applied to the resolver 3 from the variable frequency excitation signal output circuit 13, and the synchronous detection circuits 31, 32 are The output signals f (t) sinθ and f (t) cosθ of the resolver 3 are synchronously detected to obtain the sine signal sinθ and cosine signal cosθ, and the product-sum operation circuit 33 generates the sine signal sinθ, cosine signal cosθ, and sinφ · cosφ. The deviation sin (θ−φ) is calculated from the output signals sinφ and cosφ of the circuit 24. Next, the compensator 7 UP / DOWN the UP / DOWN counter 6 so that the deviation sin (θ−φ) becomes zero. The subtractor 34 detects the difference between the output signal of the variable gain amplifier 16 and the excitation signal f (t), and the maximum value detection circuit 35 detects the time point when the amplitude of the output signal of the subtractor 34 becomes maximum. The delay time calculation circuit 36 calculates the delay time τ from the frequency F ₀ of the excitation signal f (t) at the time when the amplitude of the output signal of the subtractor 34 becomes maximum. Other operations are the same as those of the rotation angle detecting device shown in FIG.

  It should be noted that the actual resolver 3 is configured so that one rotation is equally divided into a plurality of electrical rotations, or the detected rotation angle φ is converted into an encoder equivalent pulse. Although often used, there is no influence on the essence of the present invention, so the description is omitted.

  Further, in the above-described embodiment, the signal selection circuit 14 makes the amplitude as large as possible from the output signals f (t) sinθ and f (t) cosθ and obtains the same phase as the excitation signal f (t). While one of the output signals f (t) sinθ and f (t) cosθ is selected, the polarity of the selected output signals f (t) sinθ and f (t) cosθ is inverted as necessary. From the output signals f (t) sinθ and f (t) cosθ, the signal selection circuit makes the output signals f (t) sinθ and f (t (t) so that the amplitude is as large as possible and is in phase opposite to the excitation signal f (t). ) Cos θ may be selected and the polarity of the selected output signals f (t) sin θ and f (t) cos θ may be reversed as necessary. In this case, when the excitation signal f (t) and the output signal of the signal selection circuit are added by the adder, the point at which the output signal of the adder becomes maximum is detected by the maximum value detection circuit, while the excitation is detected by the subtractor. When the difference between the signal f (t) and the output signal of the signal selection circuit is detected, the time point at which the output signal of the subtractor becomes minimum is detected by the minimum value detection circuit.

  As described above, in the case of detecting the addition signal obtained by adding the excitation signal and the signal corresponding to the signal output from the resolver by the addition signal detecting means, the excitation signal and the signal corresponding to the signal output from the resolver are obtained. When the phase is the same, the minimum value detection means detects when the amplitude of the addition signal is minimum, and when the excitation signal and the signal corresponding to the signal output from the resolver are in opposite phases, the addition is performed by the maximum value detection means. The point in time when the amplitude of the signal becomes maximum is detected. On the other hand, when the difference signal detecting means detects a difference signal according to the difference between the excitation signal and the signal according to the signal output from the resolver, the excitation signal and the signal according to the signal output from the resolver are When the phase is the same, the point at which the amplitude of the difference signal becomes maximum is detected by the maximum value detection means. When the excitation signal and the signal corresponding to the signal output from the resolver are in opposite phases, the difference is detected by the minimum value detection means. The point in time when the amplitude of the signal is minimized is detected.

  In addition, in the equations (2) and (3), the unit matching is not mentioned, but it goes without saying that it is necessary to multiply by a coefficient according to the design of the unit system of the applied system. .

  In the above-described embodiment, a correction circuit configuration is added to the conventional R / D conversion circuit. However, since the added circuit configuration is relatively easy to make into an IC, the conventional R / D conversion is performed. It is possible to incorporate a part of the circuit in an R / D conversion IC that is integrated into an IC, and in this way, there is an effect that the accuracy can be improved as the unit hardly increases in circuit scale.

  Furthermore, in the above-described embodiment, the correction of the detected rotation angle φ is performed by the external circuit of the CPU 8. However, the CPU 8 performs some of the above-described operations such as generation of correction execution timing and correction calculation. May be.

  In the above-described embodiment, the delay time τ is detected when the power is turned on. However, since the present invention can detect the delay time τ when the resolver 3 is stopped, However, the delay time τ may be detected when it is detected that the resolver 3 is not rotating from the detected rotation angle φ. Further, when the temperature change of the environment where the system to be applied is placed is large and the temperature coefficient of the filter circuit 9 cannot be ignored in terms of accuracy, the operation for obtaining the delay time τ is performed a plurality of times during one power-on. You may implement.

It is a figure which shows the rotation angle detection apparatus which concerns on this invention. (a) is a graph which shows the change of the frequency of the excitation signal f (t), (b) is a graph which shows waveforms, such as the excitation signal f (t). It is a figure which shows the other rotation angle detection apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Resolver 6 ... UP / DOWN counter 7 ... Compensator 13 ... Variable frequency excitation signal output circuit 14 ... Signal selection circuit 16 ... Variable gain amplifier 17 ... Adder 18 ... Minimum value detection circuit 19 ... Delay time calculation circuit 20 ... Angle Correction circuit 21 ... Synchronous detection circuit 24 ... sinφ / cosφ generation circuit 25 ... Product-sum operation circuit 31 ... Synchronous detection circuit 32 ... Synchronous detection circuit 33 ... Product-sum operation circuit 34 ... Subtractor 35 ... Maximum value detection circuit 36 ... Delay time Calculation circuit

Claims (4)

In a rotation angle detection device comprising excitation signal output means for outputting an excitation signal to a resolver, and rotation angle detection means for detecting a detected rotation angle by inputting an AC signal corresponding to the rotation angle output from the resolver,
A frequency modulation excitation signal output means for outputting an excitation signal whose frequency continuously changes to the resolver when the resolver is stopped;
Input from the frequency modulation excitation signal output means to the resolver when the phase difference between the excitation signal input from the frequency modulation excitation signal output means to the resolver and the signal output from the resolver reaches 180 °. A delay time detecting means for detecting a delay time from the excitation signal,
And a correction means for correcting the detected rotation angle detected by the rotation angle detection means based on the delay time detected by the delay time detection means when the resolver rotates. Angle detection device.   The delay time detection means detects an addition signal obtained by adding an excitation signal input from the frequency modulation excitation signal output means to the resolver and a signal corresponding to the signal output from the resolver; and 2. A minimum value detecting means for detecting a time point when the amplitude of the added signal detected by the addition signal detecting means becomes minimum, or a maximum value detecting means for detecting a time point when the amplitude becomes maximum. The rotation angle detection device according to 1.   The delay time detecting means detects a difference signal corresponding to a difference between an excitation signal input from the frequency modulation excitation signal output means to the resolver and a signal corresponding to the signal output from the resolver. And a maximum value detecting means for detecting a time point when the amplitude of the difference signal detected by the difference signal detecting means becomes maximum or a minimum value detecting means for detecting a time point when the amplitude becomes minimum. The rotation angle detection device according to claim 1. When the frequency of the excitation signal when the amplitude of the addition signal or the difference signal is minimum or maximum is F ₀ ,
τ = (1/2) × (1 / F ₀ )
4. The rotation angle detection device according to claim 2, wherein the delay time τ is detected based on the rotation time τ.

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