JPS58195156A - Detection circuit for speed signal - Google Patents

Abstract

PURPOSE:To obtain a speed signal with small ripple without spoiling responsiveness in not only a high frequency region but a low frequency region as well, by using a pulse detecting circuit in the high frequency region and utilizing a differential detection circuit in the low frequency region. CONSTITUTION:A positive signal of a sinusoidal waveform is inputted to an input terminal 1 and is converted to a pulse waveform with a pulse converting circuit and is made into the DC voltage proportional to the density of a pulse train by an LPF3. On the other hand, a differentiator 4 differentiates the position signal and the differentiated signal is subjected to full wave rectification in an absolute value circuit 5. The peak value thereof is held in a peak holding circuit 6. A signal changeover circuit 7 changes over and selects the signal from a pulse detection circuit B when the frequency of the position signal is higher than a reference frequency and the signal from a differential detection circuit C when said signal is lower than said frequency and outputs the same to an output terminal 8. The pulse detection circuit is used in the high frequency region and the differential detection circuit in the low frequency region in the above-mentioned way, whereby the speed signal is obtained with small ripple without spoiling the responsiveness over the entire frequency range.

Description

Detailed Description of the Invention The present invention detects the moving speed of a moving platform such as a carriage in various terminal devices based on the frequency of a position signal that periodically changes in response to the displacement of the moving platform. The present invention relates to a speed signal detection circuit.

Conventionally, a pulse detection circuit that uses pulse conversion has been used as a circuit that detects a speed signal proportional to the frequency of a sinusoidal or triangular position signal that changes periodically in response to the displacement of the moving platform. be.

The detection principle of this circuit is, as shown in Figure 1, a sine wave or triangular wave position signal obtained from a position detection circuit that detects the position of the moving platform [Figure 1 (a) shows the case of a sine wave. ] is used as a trigger to generate a pulse with a constant pulse width as shown in Figure (b), and by utilizing the fact that the pulse density is proportional to the frequency of the position signal, the generated pulse train is filtered through a low-pass filter. The aim is to obtain the velocity signal shown in FIG. 10(c), which is expressed by the amplitude of the direct current.

However, with this circuit, when the frequency of the position signal is relatively high, a speed signal with small ripples can be obtained as shown in Figure 1, but when the frequency is low, a speed signal with small ripples can be obtained as shown in Figure 2. Ripple becomes larger.

In order to reduce this ripple, it is necessary to increase the time constant of the low-pass filter, but in this case, the response of the speed signal to frequency changes will be significantly poor due to the phase delay in the low-pass filter. Become.

Therefore, in this detection circuit, 1. If the responsiveness of the speed signal is to be suppressed within an allowable range, there is a drawback that an increase in ripple in the low frequency region cannot be avoided.

The present invention has been made in view of the above, and its purpose is to use a pulse detection circuit in the high frequency region and a differential detection circuit in the low frequency region, so that the frequency range from the low frequency region to the high frequency region can be changed. It is an object of the present invention to provide a speed detection circuit capable of obtaining a speed signal with small ripples and good responsiveness over the entire range. □ Hereinafter, implementation of the present invention:- will be explained. First, the sinusoidal position signal is expressed as x = A sin 2tc f
t (A: amplitude, f: frequency), the differential signal is dx/dt= 2 g f A cos2 n
f t , and its amplitude 2πfA is proportional to the frequency f. Therefore, if a signal corresponding to the amplitude 2πfA is detected, a signal proportional to the frequency, that is, proportional to the speed can be obtained.

Specifically, the 38th! ! As shown in I (b), the peak value of the differential signal is ±2π[A, so the differential signal is passed through an absolute value circuit and subjected to full-wave rectification as shown in (c) of the same figure, and its peak value is If it is held as shown in FIG. 4(d), a DC speed signal having a value of 2πfA can be obtained. Note that it is also possible to directly hold only the positive peak value of the differential signal without using the absolute value circuit, but in that case, the period of updating of the held value is doubled.

If the position signal is an ideal triangular wave, the differential value will be the velocity. However, in the part with a negative slope, the polarity of the differential value is also reversed by 1', so through the absolute value circuit -c, Eo@r,
=@-・'jln+;l, u->-r, o4. You don't need peak hole white clay.
A differentiator is used for the differential operation described above, but in order to prevent amplification of high frequency noise, the differentiator is provided with an integral characteristic in the high frequency region, and the differential characteristic is limited only to the low frequency region.

Therefore, the linearity of the frequency of the speed signal obtained by the differential detection circuit using a differentiator is compensated only in the low frequency region as shown in FIG. On the other hand, the speed signal obtained by the pulse detection circuit described above has good linearity and small ripples in the high frequency region, however,
As mentioned above, in the low frequency region, if you try to ensure responsiveness, the ripple will increase.

Therefore, in the present invention, by using a pulse detection circuit in the high frequency region and a differential detection circuit in the low frequency region, a speed signal with good linearity and small ripples can be obtained over a wide frequency (velocity) region. be able to be detected.

FIG. 5 shows an embodiment of the speed signal detection circuit of the present invention. 1 is an input terminal into which a sinusoidal position signal is input, 2 is a pulse conversion circuit which receives the position signal and generates a pulse with a constant pulse width, and 3 is a pulse train whose density is proportional to the density of the pulse train from the pulse conversion circuit 2. This is a low-pass filter for obtaining a DC voltage, and these pulse converting circuits 2 and low-pass filters 3 constitute a pulse detection circuit B. 4 is a differentiator that differentiates the position signal; 5
6 is an absolute value circuit that performs full-wave rectification of the differential output, and 6 is a peak value circuit that holds the peak value of the output of the absolute value circuit 5.
It is a hold circuit, and these differentiator 4, absolute value circuit 5,
and the differential detection circuit C by the peak hold circuit 6.
is configured.

7 is a signal switching circuit that switches between the output of the pulse detection circuit B and the output of the differential detection circuit C, and when the frequency of the position signal applied to the input terminal 1 is higher than the reference frequency, The speed signal from the pulse detection circuit B is switched and selected, and if the speed signal is low, the speed signal from the differential detection circuit C is switched and outputted to the output terminal 8. In addition, when a triangular wave-like potential signal is applied to the input terminal l,
Peak hold circuit 6 is not necessary.

As explained above, the present invention uses a pulse detection circuit in the high frequency region and a differential detection circuit in the low frequency region, and therefore responds not only in the high frequency region but also in the low frequency region. Since it is possible to obtain speed signals with small ripples without compromising performance, it is possible to detect speed signals with good responsiveness and small ripples over a wide range of speeds, thereby significantly improving the characteristics of the control system. It has the characteristic that it is possible.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram to explain the operation of the pulse detection circuit in the high frequency range, Figure 2 is a waveform diagram to explain the operation of the same detection circuit in the low frequency range, and Figure 3 is a waveform diagram to explain the operation of the differential detection circuit. 4 is a characteristic diagram of directivity of the speed signal obtained by the pulse detection circuit and the differential detection circuit, and FIG. 5 is a circuit diagram of an embodiment of the speed signal detection circuit of the present invention. . □l""D',・B・
... Pulse detection circuit, C... Differential detection circuit, ■...
Input terminal, 2... Pulse conversion circuit, 3... Low pass filter, 4... Differentiator, 5... Absolute value circuit, 6
...Peak hold circuit, 7...Signal switching circuit,
8...Output terminal.

Claims (1)

[Claims] (1) Using a position detector that generates a periodic sine wave or triangular wave position signal in response to the displacement of the movable base, the moving speed of the movable base is detected based on the frequency of the position signal. The circuit includes a pulse detection circuit that converts the position signal into a pulse signal with a constant pulse width and detects a speed signal by utilizing the fact that the pulse density is proportional to frequency, and a pulse detection circuit that differentiates the position signal and detects the speed signal. and a differential detection circuit that detects a speed signal by utilizing the fact that the amplitude of the differential signal is proportional to the frequency. A speed signal detection circuit characterized by using a detection circuit.