JP2006029889A - Rotation speed detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation speed detection device stably detecting the rotational speed down to very low speed by correcting the frequency characteristics of the output signal from the signal generation means with a simple and economical constitution. <P>SOLUTION: The rotational speed detection device for detecting the number of rotations using the output signal of the signal generation means which is provided with the rotational speed detection device for outputting the signal proportional to the number of rotations while synchronizing to the rotation of the rotor. The output signal of the signal generator 1 which varies corresponding to the frequency is inputted over the speed range to be detected by the rotor. The signal correction circuit 2 for correcting the amplitude of the output signal of the signal generator 1 by the input/output gain characteristics for correcting the output signal of the signal generator 1 so as to fall into the prescribed range is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rotational speed detection device that detects the rotational speed by detecting the rotational speed of a rotating body.

  The means for detecting the rotational speed by detecting the rotational speed of the rotating body has been conventionally used in a system that moves by wheels of a railway vehicle or the like. In general, a signal generator is used as a means for detecting the number of rotations of the rotating body. However, particularly in a railway vehicle, a speed generator that does not require a power source is widely used as a signal generator. Here, the speed generator has the same structure as a general AC generator, and is usually mounted on the axle end and is proportional to the rotation speed of the wheel by driving the rotor by the rotation of the wheel. The frequency alternating current is output from the stator.

However, the amplitude of the output voltage of the speed generator is structurally dependent on the number of revolutions. When the number of revolutions is small, the amplitude of the output voltage is small, and when the number of revolutions is large, the amplitude of the output voltage is large. It has the characteristic of becoming saturated when it reaches a certain size.
FIG. 9 shows a schematic diagram of the output voltage characteristics of the speed generator, where the horizontal axis represents the frequency f proportional to the rotational speed, and the vertical axis represents the amplitude V _pp of the output voltage.
As described above, since the output voltage of the speed generator has frequency characteristics, there is a problem that the amplitude V _{pp of the} output voltage becomes small at low speed and the rotational speed cannot be detected accurately.

As a method for solving this problem, there is a conventional technique described in Patent Document 1 described later.
FIG. 10 is a block diagram of the speed detection method described in FIG. In FIG. 10, AC signals E _sg1 and E _sg2 are output from a speed generator (not shown) through a low-pass filter for removing high-frequency noise, and then converted into digital signals by an A / D converter. A sine wave signal converted into a value. These sine wave signals E _sg1 and E _sg2 are signals that are 90 ° out of phase with each other. For simplicity, E _sg1 is a sine wave and E _sg2 is a cosine wave.

The sine wave signals E _sg1 and E _sg2 and the sine wave signals E _R1 and E _R2 generated by the function generator 105 are input to the multipliers 101a and 101b, and the multiplier 101a calculates the product of E _sg1 and E _R1. the product of the _{E sg2} and _{E R2} are respectively calculated by the multiplier 101b. These calculation results are entered in the code shown in the adder 102, the difference therebetween is calculated as the phase difference detection output e _V.
That is, the multipliers 101a and 101b and the adder 102 constitute phase difference detection means.

Here, when the sine wave signal E _sg1 = sin α, it can be expressed as E _sg2 = cos α from the phase relationship between E _sg1 and E _sg2 .
On the other hand, assuming that the sine wave signal output from the function generator 105 is E _r1 = cos β and E _r2 = sin β, the calculation results by the multipliers 101a and 101b are expressed by Equations 1 and 2.

Therefore, the output e _V from the adder 102 is expressed by Equation 3, and the phase α of the input signals (sinusoidal signals E _sg1 , E _sg2 ) and the phase β of the output signal (E _r1 , E _r2 ) of the function generator 105. And a phase difference Δθ = α−β.

From Equation 3, when the phase difference Δθ = 0, e _V = 0. Therefore, if the phase β of the output signal of the function generator 105 is controlled so that e _V = 0, the output signal of the function generator 105 Can be synchronized with the output signal of the speed generator.
Therefore, instead of the output signal of the speed generator, the output signal of the function generator 105 can be used as a frequency signal proportional to the rotational speed of the rotating body. This control uses a so-called PLL (phase locked loop) principle.
With such a configuration, an accurate sine wave signal synchronized with the output signal of the speed generator is obtained from the function generator 105. By using this signal as the rotation angle information, it is possible to detect the rotational speed at a low speed and more Accurate rotation speed detection is possible.

In FIG. 10, 103 is a digital filter, and outputs a phase angle (signal proportional to the integrated travel distance) based on the output e _V of the adder 102. A coefficient unit 104 multiplies the output signal of the digital filter 103 by a coefficient to calculate the rotation angle of the rotating body, and this rotation angle corresponds to β.

Japanese Patent Laid-Open No. 11-4588 (paragraphs [0017] to [0023], FIG. 7)

According to the above-described prior art of Patent Document 1, the frequency characteristics of the output signal of the speed generator can be corrected to detect the rotational speed at a low speed and more accurate rotational speed detection. There is.
(1) If the phase difference between the two sine wave signals output from the speed generator is not 90 °, the rotational speed cannot be accurately detected. In particular, it is difficult to apply in the railway vehicle field using a speed generator in which the phase difference between two signals is as wide as 60 to 120 °.
(2) When the sine wave signal of one speed generator becomes abnormal, the correct rotation speed cannot be detected.
(3) Since the output signal of the speed generator is digitized by the A / D converter and the phase locked loop is configured using the function generator, the circuit configuration becomes complicated and expensive.

  Therefore, the problem to be solved by the present invention is that the rotation speed can be detected stably up to the extremely low speed range by correcting the frequency characteristics of the output signal of the signal generator such as the speed generator with a simple and inexpensive configuration. It is to provide a speed detection device.

In order to solve the above problems, the invention described in claim 1 is provided with signal generating means for outputting a signal having a frequency proportional to the number of rotations in synchronization with the rotation of the rotating body, and an output signal of the signal generating means. In the rotational speed detection device that detects the rotational speed of the rotating body using
An output signal of the signal generating means whose amplitude changes according to the frequency is input, and the signal is generated by an input / output gain characteristic such that the amplitude of the output signal of the signal generating means falls within a predetermined range over the speed range to be detected by the rotating body. The signal correcting means for correcting the output signal of the means is provided.

  According to a second aspect of the present invention, in the first aspect, the signal correction means corrects the output signal by input / output gain characteristics such that the amplitude of the output signal of the signal generation means becomes a substantially constant value.

  According to a third aspect of the present invention, in the first or second aspect, the signal correction unit has a predetermined gain in the extremely low speed range with respect to the output signal of the signal generation unit corresponding to the outside of the speed range to be detected by the rotating body. It has an input / output gain characteristic which becomes a characteristic and becomes an integral characteristic in a high speed range.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, when the amplitude of the output signal of the signal generating means varies between the minimum value and the maximum value, the amplitude is minimized. The gain of the signal correction means is set with priority given to the extremely low speed, and the output signal of the signal correction means is clamped as necessary at the high speed at which the amplitude is maximized.

According to the present invention, it is possible to correct the frequency characteristics of the output signal of a signal generator such as a speed generator with a relatively simple configuration. As a result, the rotational speed of the rotating body can be stably detected up to an extremely low speed range. A possible low-cost rotation speed detection device can be realized.
In particular, since it does not depend on the principle of detecting the rotational speed using two sine wave signals as in the prior art, it is most suitable for detecting the vehicle speed in the railway vehicle field, for example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a first embodiment of the present invention corresponding to claims 1 to 3.
In FIG. 1, a signal generator 1 is for generating a signal having a frequency proportional to the number of rotations of a rotating body, and is, for example, a speed generator or the like installed at an axle end of a railway vehicle or the like. The frequency signal output from the signal generator 1 is corrected by a signal correction circuit 2 described later, input to the waveform shaping circuit 3, and converted into a square wave signal. The speed calculation circuit 4 is configured to calculate the rotation speed of the rotating body by counting the input signals.

Here, when a speed generator is used as the signal generator 1, for example, the output signal has the frequency characteristics as shown in FIG. 9, so that the output of the signal generator 1 in the extremely low speed range. The amplitude of the signal becomes very small, and there is a possibility that correct rotation speed calculation cannot be performed.
For this reason, in this embodiment, the frequency characteristic of the output signal of the signal generator 1 is corrected by the signal correction circuit 2 having a predetermined input / output gain characteristic.

As the input / output gain characteristics of the signal correction circuit 2, for example, as shown in FIG. 2B, the amplitude of the output signal after correction falls within an allowable range set in the speed range to be detected. Then, the gain characteristic is increased, and gain characteristics are set such that the gain decreases and converges to a constant value as the frequency increases.
In FIGS. 2B and 2C, the gain characteristics are shown such that the amplitude of the output signal after the correction by the signal correction circuit 2 becomes a constant value for the sake of simplicity, but in the speed range to be detected. The gain characteristics may be set so as to be within the set allowable amplitude range.

  Further, as shown in FIG. 3, the input / output gain characteristics of the signal correction circuit 2 become constant gain characteristics in the extremely low speed range outside the speed detection range (range A in FIG. 3B), and the rotational speed detection is performed. In the high speed range outside the range (range B in FIG. 3B), it may be configured to have integral characteristics. In this way, unnecessary signals can be attenuated and more stable rotation speed can be detected.

For example, the signal correction circuit 2 capable of approximately realizing the input / output gain characteristics shown in FIG. 3B includes the circuit configuration of the first embodiment shown in FIG. The circuit of Figure 4 is configured by one operational amplifier _{Q 1,} three resistors _{R 1,} R 2, _{R 3} and two capacitors _C 1, _{C 2.}
Here, the transfer characteristic of the circuit shown in FIG. 4 is obtained. 4, the signal correction circuit Z ₁ impedance between the input terminal 2a and the inverting input terminal of the operational amplifier to Q _{1 2,} impedance Z ₂ between the output terminal 2b of the inverting input terminal and the signal correction circuit 2 Then, the transfer function is expressed by Equation 4. From FIG. 4, Z ₁ is expressed by Equation 5.

Z ₂ in Equation 4 is the combined impedance of the capacitor C ₁ , the series circuit of the resistor R ₂ and the capacitor C ₂ , and the parallel circuit of the resistor R ₃ . Assuming that the admittance of the capacitor C ₁ is Y _2a , the admittance of the series circuit of the resistor R ₂ and the capacitor C ₂ is Y _2b , and the admittance of the resistor R ₃ is Y _2c , the combined admittance Y ₂ of the parallel circuit is given by Equation 6. expressed.

Therefore, the impedance _{Z 2} becomes Equation 7.

  Substituting Equations 5 and 7 into Equation 4 gives Equation 8.

  When Formula 8 is transformed to obtain Formula 9, and part of Formula 9 is placed as Formula 10, Formula 11 is obtained.

Therefore, the transfer characteristic of Formula 11 is as shown in FIG.
Here, since Expression 12 holds, Expressions 13 to 15 are obtained by Expressions 10 to 12.

  Equation 16 is obtained from Equation 13 and Equation 15, and Equation 17 is obtained from Equation 14 to Equation 16.

Therefore, from Equations 15 to 17, T _{1 to} T ₃ and the low-frequency gain shown in FIG. 5 are set, and if any one of the circuit constants is set, the remaining circuit constants are unambiguous. Can be determined. Therefore, it can be seen that the gain characteristic shown in FIG. 5 can be realized by the circuit configuration shown in FIG. 4, and the gain characteristic shown in FIG.

Next, FIG. 6 shows a second embodiment of the signal correction circuit. Like this signal correction circuit 2A, a resistor R ₁ having the same circuit constant as that of the feedback loop side is provided between _one terminal 2a ₂ of the input terminals 2a ₁ and 2a ₂ and the non-inverting input terminal of the operational amplifier Q ₁ and the ground. '~ R ₃ ' and capacitors C ₁ ', C ₂ ' are connected, and the input part of the operational amplifier Q _{1 is used} as a differential input of the output signal of the signal generator 1, so that it is common to the output part of the signal generator 1. Even when mode noise is superimposed, it is possible to make it less susceptible to the influence.

FIG. 7 shows a second embodiment of the present invention corresponding to the fourth aspect.
In this embodiment, as shown in FIG. 7 (a), the upper limit voltage clamping circuit with inverting amplifier 5 is connected to the output side of the operational amplifier to Q ₁ in the signal correction circuit 2A, the output signal V _out is 1 The signal is input to the waveform shaping circuit 3. Note that the inverting amplifier 5, an operational amplifier Q _2, a resistor R ₄ connected to its inverting input terminal, composed of a Zener diode ZD _1, a series circuit of ZD ₂ and its parallel resistor R ₅ Prefecture in the feedback loop and is one in which the output voltage _{V out} over a predetermined range of input voltage _{V in} the positive and negative by the zener voltage _{V LM1, V LM2} of the Zener diode _ZD 1, ZD ₂ as is well known is limited (FIG. 7 (b) reference).

With such a circuit configuration, for example, the output signal of the signal generator 1 varies among individuals due to the mounting accuracy of the signal generator 1 and the like, and as shown in FIG. In addition, when the output signal of the signal generator 1 varies within the range from the maximum value to the minimum value, the gain of the signal correction circuit 2A is set in preference to the extremely low speed at which the amplitude is minimum, and the output in the vicinity of the maximum amplitude at high speed the voltage increases, if necessary, by clamping the output signal by the clamping circuit in the inverting amplifier 5, is possible to prevent latch-up of the operational amplifier to Q ₁ in the signal correction circuit 2A it can. The clamp voltage can be set to an arbitrary value by setting the Zener voltages V _LM1 and V _LM2 .
According to this embodiment, even when the amplitude of the output signal changes for each individual due to the mounting accuracy of the signal generator 1, etc., it can be used with the same circuit constant, and extra work such as gain adjustment is required. Can be omitted.

  7A shows an example in which the inverting amplifier 5 with the upper / lower limit voltage clamp circuit is connected to the output side of the signal correction circuit 2A of FIG. 6, the inverting amplifier 5 is the signal correction circuit of FIG. 2 is also applicable.

1 is a block diagram showing a first embodiment of the present invention. It is a figure which shows the output signal of the signal generator in FIG. 1, the gain characteristic of a signal correction circuit, and an output signal. It is a figure which shows the other example of the output signal of the signal generator in FIG. 1, the gain characteristic of a signal correction circuit, and an output signal. FIG. 4 is a configuration diagram illustrating a first embodiment of a signal correction circuit that approximately realizes the input / output gain characteristics of FIG. 3. FIG. 5 is a diagram illustrating input / output gain characteristics of a signal correction circuit having the circuit configuration of FIG. 4. FIG. 4 is a configuration diagram illustrating a second embodiment of a signal correction circuit that approximately realizes the input / output gain characteristics of FIG. 3. FIG. 7 is a circuit configuration diagram (FIG. 7A) showing a main part of the second embodiment of the present invention and a characteristic diagram of a clamp circuit in the inverting amplifier (FIG. 7B). It is a figure which shows the output signal of a signal generator in case there exists dispersion | variation between individuals. It is a schematic diagram which shows the output voltage characteristic of a speed generator. It is a block diagram which shows the prior art described in patent document 1. FIG.

Explanation of symbols

1: signal generators 2, 2A: signal correction circuits 2a, 2a ₁ , 2a ₂ : input terminal 2b: output terminal 3: waveform shaping circuit 4: speed calculation circuit 5: inverting amplifiers Q ₁ and Q with upper and lower limit voltage clamp circuits ₂ : operational amplifiers R _{1 to} R ₅ , R ₁ ′ to R ₃ ′: resistors C ₁ , C ₂ , C ₁ ′, C ₂ ′: capacitors ZD ₁ , ZD ₂ : Zener diodes

Claims (4)

In a rotation speed detection device comprising signal generation means for outputting a signal having a frequency proportional to the rotation speed in synchronization with rotation of the rotation body, and detecting the rotation speed of the rotation body using an output signal of the signal generation means ,
Input / output gain characteristics such that the output signal of the signal generating means whose amplitude changes according to the frequency is input, and the amplitude of the output signal of the signal generating means falls within a predetermined range over the speed range to be detected by the rotating body A rotation speed detecting device comprising signal correcting means for correcting the output signal of the signal generating means. The rotational speed detection device according to claim 1,
The rotation speed detection device according to claim 1, wherein the signal correction means corrects the output signal by an input / output gain characteristic such that an amplitude of an output signal of the signal generation means becomes a substantially constant value. In the rotation speed detection device according to claim 1 or 2,
The signal correction means has an input / output gain characteristic that has a predetermined gain characteristic in an extremely low speed region and an integral characteristic in a high speed region with respect to an output signal of the signal generating means corresponding to a speed range outside the speed range to be detected by the rotating body. A rotational speed detection device comprising: In the rotation speed detection device according to any one of claims 1 to 3,
When the amplitude of the output signal of the signal generating means varies between the minimum value and the maximum value, the gain at the extremely low speed at which the amplitude is minimized is preferentially set in the signal correcting means, and A rotational speed detection device that clamps the output signal of the signal correction means as necessary at high speed when the amplitude is maximized.

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