JPH07198418A - Signal processing circuit - Google Patents

Abstract

PURPOSE:To provide a signal processing circuit having the excellent temperature characteristic with less effects of the dispersion of parts and the offset voltage of an operational amplifier in the signal processing circuits of the sensors in various kinds of sensors. CONSTITUTION:Two kinds of inputted detected signals are subtracted in a subtracting means 21. The subtracted signals are rectified in first and second switching means 23 and 24. Thus, the subtractions with small errors can be performed, the effect of the offset voltage of an operational amplifier becomes small and the highly accurate signal processing circuit is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor signal processing circuit for various sensors.

[0002]

2. Description of the Related Art A case in which a torque sensor is used as a typical example of various sensors will be described below.

FIG. 7 is a sectional view of the torque sensor, and FIG.
It is a circuit diagram of a sensor sensing means by a torque sensor. In FIG. 7, 1 is a shaft 2a, 2b that is rotatably supported.
Is on the surface of the shaft 1 45 ° to the longitudinal direction of the shaft 1, −45
Amorphous metal ribbons 3a and 3b made of amorphous material having magnetostriction and provided with a plurality of slits in the direction of 0 ° are wound on the outer sides of the amorphous metal ribbons 2a and 2b via a bobbin (not shown). It is an excitation / detection coil that is rotated and excited to detect.

In FIG. 8, 4a and 4b are resistors, 5 is an AC power source, and an AC bridge is constituted by the elements 3a, 3b, 4a and 4b.

With respect to the torque sensor configured as described above, the following operation will be described. Axis 1 rotates and Axis 1
A strain is generated in the amorphous metal thin bodies 2a and 2b adhered on the upper side, and a change in the permeability of the strain is detected as a change in the inductance of the excitation / detection coils 3a and 3b that are detected by excitation, and the sensor sensing means. More two types of sensing signals are output.

The signal processing circuit of this torque sensor will be described below. FIG. 9 is a block diagram of a conventional signal processing circuit, and FIG. 10 is this circuit diagram. In FIG.
Reference numerals 11 and 12 are first and second rectifying means, 13 is subtracting means, and 14 is smoothing means. In FIG. 10, 11 is the first
With the rectifying means of, two operational amplifiers 11a and 11b, two diodes 11c and 11d, and three resistance elements 11e,
The second rectifying means 12 is composed of 11f and 11g and a capacitor 11h. Reference numeral 13 is a subtraction means, which is an operational amplifier 13a and four resistance elements 13b, 1
It is composed of 3c, 13d and 13e. Reference numeral 14 denotes a smoothing means, which is an operational amplifier 14a and capacitors 14b and 3
It is composed of one resistance element 14c, 14d, 14e.

The operation of the conventional signal processing circuit configured as described above will be described below. FIG. 11 is a signal waveform diagram at each point.

First, from the sensor sensing means, as shown in FIG.
Sensing signals A and B as shown in (b) are input to the first and second rectifying means 11 and 12, respectively, to perform full-wave rectification.
1 (c), (d) rectified signals A, B subtraction means 13
Output to.

Next, the subtracting means 13 inputs the rectified signals A and B shown in FIGS. 11 (c) and 11 (d) outputted from the first and second rectified means 11 and 12, and outputs from the rectified signal B. The subtraction signal shown in FIG. 11E obtained by subtracting the rectified signal A is output to the smoothing means 14.

Next, the smoothing means 14 receives the subtraction signal shown in FIG. 11 (e) output from the subtracting means 13 and smoothes it to obtain the sensor signal shown in FIG. 11 (f).

[0011]

However, in the above-mentioned conventional configuration, the two kinds of sensing signals A and B output from the sensor output sensing means are the first and second rectifying means 11 and 12.
After being subjected to full-wave rectification by the subtraction means 13, the subtraction means 13 performs the subtraction processing, that is, before the subtraction means 13, the first and second
If the respective rectification means 11 and 12 are included, there is variation in each element, the peak values of the outputs of the first and second rectification means 11 and 12 are different, and the operational amplifier 11 used in each means.
The offset voltages of a, 11b, 12a, 12b, 13a, and 14a are added to the respective signals, and the sensor signals which are the output values of the signal processing circuit are significantly different.

An object of the present invention is to solve the above problems, and an object thereof is to provide a signal processing circuit which is less affected by variations in parts and offset voltage of an operational amplifier and which is excellent in temperature characteristics.

[0013]

In order to achieve this object, the signal processing circuit of the present invention comprises a sensor output sensing means for outputting two kinds of sensing signals according to the output of the sensor, and a sensor output sensing means of the sensor output sensing means. Subtracting means for subtracting two kinds of sensing signals and outputting a subtracting signal, one subtracting signal of the subtracting means is input to the first switch means, and the other subtracting signal is input to the second switch means via the inverting means. In addition, the first switch means and the second switch means are alternately turned on / off in response to a control signal for switch control to output a combined switch signal.

Further, it has a construction in which capacitors are respectively connected between the subtracting means and the first switching means and between the inverting means and the second switching means.

Further, a sensor output sensing means for outputting two kinds of sensing signals according to the output of the sensor, and a sensing signal of the sensor output sensing means and a sensing signal for the first switch according to the control signal of the switch control means. Means and the second switch means are alternately input, the switch signals output from the first and second switch means are input to the subtraction means, and the subtracted subtraction signal is output.

[0016]

With this configuration, since the two sensing signals are directly subtracted, it is possible to perform the subtraction with a small error, and the influence of the offset voltage of the operational amplifier is reduced by the AC coupling by the capacitor, thereby enabling the highly accurate signal processing. Become.

Further, since the two sensing signals are switched by the switch and subtracted, the signal path between the sensor output sensing means and the subtracting means is shortened, and subtraction with a small error is possible, so that highly accurate signal processing is possible. Become.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. Here, the same components as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 1 is a block diagram of a signal processing circuit of the present invention, and FIG. 2 is this circuit diagram.

In FIG. 1, 21 is a subtracting means, 22 is an inverting means, 23 is a first switch means, 24 is a second switch means, 25 is a switch control means for controlling the first and second switch means, 26 is a smoothing means.

In FIG. 2, reference numeral 21 is a subtraction means, which is an operational amplifier 21a and four resistance elements 21b, 21c, 21d,
21e. Reference numeral 22 denotes an inverting means, which is composed of an operational amplifier 22a and three resistance elements 22b, 22c, 22d. Reference numeral 23 is a first switch means, which is composed of an analog switch, and similarly is a second switch means 2
4 is also configured. Reference numeral 25 is a switch control means, which includes two operational amplifiers 25a and 25b and six resistance elements 25c,
25d, 25e, 25f, 25g, 25h, an operational amplifier 25i, a capacitor 25j, and three resistance elements 25.
The phase shifter is composed of k, 25l, and 25m.
Reference numeral 26 is a smoothing means, which includes an operational amplifier 26a and a capacitor
b and three resistance elements 26c, 26d and 26e. 27 and 28 are DC cut capacitors.

The operation of the signal processing circuit configured as described above will be described. FIG. 3 is a signal waveform diagram at each point.

First, from the sensor sensing means, as shown in FIG.
The subtraction means 21 inputs the sensing signals A and B having the signal waveform shown in (b) and subtracts the sensing signal A from the sensing signal B, and the subtraction signal of the signal waveform of FIG. It outputs to the first switch means 23.

Next, the inverting means 22 inputs the subtraction signal output from the subtracting means 21, inverts it, and outputs the inverted signal having the signal waveform of FIG. 3D to the second switch means 24.

Next, the first switch means 23 and the subtraction signal output from the subtraction means 21 and the switch control means 25.
The control signal A output from the above is input and the switch signal A having the signal waveform of FIG.

Next, the second switch means is the inverting means 22.
The inversion signal output from the switch control unit 25 and the control signal B output from the switch control unit 25 are input, and the switch operation is performed.
The switch signal B having the signal waveform of (f) is smoothed by the smoothing means 26.
Output to.

Next, the smoothing means 26 has the switch signals A and B output from the first and second switch means 23 and 24.
A composite switch signal obtained by combining is input and smoothed to obtain a sensor signal.

Another embodiment of the present invention will be described below with reference to the drawings. Here, the same components as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 4 is a block diagram of the signal processing circuit of the present invention, and FIG. 5 is this circuit diagram.

In FIG. 4, 31 is a first switch means, 32 is a second switch means, 33 is a switch control means, 34 is a subtraction means, and 35 is a smoothing means.

In FIG. 5, reference numeral 31 denotes a first switch means, which is composed of a multiplexer, and similarly a second switch means 32. A switch control unit 33 includes an operational amplifier 33a and two resistors 33b and 33.
It is composed of c. 34 is a subtraction means, which is an operational amplifier 34a and four resistance elements 34b, 34c, 34d, 34.
e. Reference numeral 35 is a smoothing means, which is composed of an operational amplifier 35a, three resistance elements 35b, 35c, 35d, and a capacitor 35e.

The operation of the signal processing circuit of the present invention constructed as above will be described. FIG. 6 is a signal waveform diagram during each operation.

First, the first and second switch means 31, 3
2 inputs the sensing signals A and B from the sensor sensing means shown in FIGS. 6A and 6B and the control signal from the switch control means 33, and switches the sensing signals A and B according to the control signals.
The switch signals A and B shown in FIGS. 6C and 6D are output to the subtracting means 34.

Next, the subtraction means 34 inputs the switch signals A and B shown in FIGS. 6C and 6D from the first and second switch means 31 and 32, and the switch signal B to the switch signal A. Is subtracted, and the subtraction signal shown in FIG.

Next, the smoothing means 35 inputs the subtraction signal output from the subtraction means 34, smoothes it, and outputs the sensor signal shown in FIG. 6 (f).

In the present embodiment, the sensor output sensing means has been described as a torque sensor which changes according to a change in torque. However, the sensor output sensing means is not limited to a torque sensor, but outputs two types of sensor signals such as an acceleration sensor and a yaw rate sensor. Anything can be applied.

[0035]

As described above, the signal processing circuit of the present invention is
A sensor output sensing unit that outputs two types of sensing signals according to the output of the sensor, a subtraction unit that subtracts the two types of sensing signals of the sensor output sensing unit and outputs a subtraction signal, and one subtraction signal of the subtraction unit The first subtraction signal is input to the first switch device, the other subtraction signal is input to the second switch device through the inverting device, and the first switch device and the second switch device are alternately switched according to the control signal for switch control. A configuration is provided to output a combined switch signal by turning on / off, and capacitors are respectively provided between the subtracting means and the first switching means and between the inverting means and the second switching means, and the signals are AC-coupled. By performing the processing, it is possible to realize an excellent signal processing circuit capable of performing subtraction with a small error and reducing the influence of the offset voltage of the operational amplifier.

Further, the signal processing circuit of the present invention comprises a sensor output sensing means for outputting two types of sensing signals according to the output of the sensor, and a switch control means for sensing signals A and B of the sensor output sensing means. The switch signals A and B output from the first and second switch means are alternately input to the first switch means and the second switch means in accordance with the control signal of 1. By providing the configuration for outputting the subtraction signal, the signal path between the sensor sensing means and the subtraction means can be shortened, so that a highly accurate signal processing circuit capable of subtraction with a small error can be realized.

[Brief description of drawings]

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

[Figure 2] Circuit diagram

[Fig. 3] Same signal waveform diagram

FIG. 4 is a block diagram of a signal processing circuit according to another embodiment of the present invention.

[Figure 5] Circuit diagram

FIG. 6 is a waveform diagram of the same signal.

FIG. 7 is a sectional view of a torque sensor used in a conventional signal processing circuit.

FIG. 8 is a circuit diagram of a torque sensor for explaining the conventional input part.

FIG. 9 is a block diagram of a conventional signal processing circuit.

FIG. 10 is a circuit diagram of the same.

FIG. 11 is a waveform diagram of the same signal.

[Explanation of symbols]

 21 subtraction means 22 inversion means 23 first switch means 24 second switch means 25 switch control means 26 smoothing means

Claims (3)

[Claims] 1. A sensor output sensing means for outputting two types of sensing signals according to the output of the sensor, a subtracting means for subtracting the two types of sensing signals of the sensor output sensing means, and a signal of one of the subtracting means. Is input to the first switch means, the other signal is input to the second switch means via the inverting means, and the first switch means and the second switch means are connected in accordance with a control signal for switch control. A signal processing circuit, which alternately turns on and off and outputs a combined switch signal. 2. A signal processing circuit according to claim 1, wherein capacitors are respectively connected between the subtracting means and the first switch means and between the inverting means and the second switch means. 3. A sensor output sensing means for outputting two kinds of sensing signals according to the output of the sensor, and a sensing signal of the sensor output sensing means for the first switch means and a first switch means according to the control signal of the switch control means. A signal processing circuit comprising: subtraction means for alternately inputting to the second switch means and inputting and subtracting the switch signals output from the first and second switch means to the subtraction means.