JPS60107521A - Rotary sensor - Google Patents

Abstract

PURPOSE:To detect a count error by guiding light from a light emitting element to two photodetecting elements intermittently through a rotary disk, and counting it by a counter. CONSTITUTION:Photocurrents of the 1st photodetecting element 11 of a front photodetection side unit and the 2nd photodetecting element 12 of a rear photodetection side unit are amplified by amplifiers 13 and 14 and shaped into pulse trains of 0 and 1. Outputs (a) and (b) of the amplifiers 13 and 14 are inputted to two input terminals of an exclusive OR gate 15 and ORed exclusively to input an absolute differential value output (c) to the clock input of the counter 16. Then, the least significant digit LSB (0 in this case) and the pulse train (a) are ORed (e) exclusively by an exclusive OR gate 17 for count error detection. The exclusive OR output (e) is 0 when the outputs (a) and (d) are equal and 1 when not. When the LSB output (d) is an error pulse, the outputs (d) and (a) are different, so an error signal appears at the output (e).

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field The present invention relates to a rotation sensor for detecting the position and speed of a rotating body or other moving body.

Linear motion can be converted to rotation by using gears. The rotational speed and rotational speed of the rotating body can be measured by an encoder. Encoder speed, linear motion, rotational motion speed, and displacement can be measured.

A device that measures the displacement of rotational motion, including an encoder, is referred to here as a rotation sensor.

As the rotation sensor, a potentiometer or the like may be used when the amount of rotation is limited.

Some measure the rotational speed using twisted magnetism.

This connects a disk and a rotating measurement object, attaches a permanent magnet to the disk, and places a Hall element near the disk.
A search coil or the like is provided. Hall voltage and electromotive force are generated by the approach and separation of permanent magnets, so the rotation speed can be determined by calculating this.

In addition to these, there are also mechanical rotation sensors that combine a large number of gears.

However, the most accurate and quickest rotation sensor is one that uses light.

(B) Prior Art A rotation sensor using light consists of (1) a light emitting element, (2) a light receiving element, and (3) a rotating disk having a number of openings provided at regular intervals on a circumferential surface. A light-emitting element and a light-receiving element are placed so as to face each other on both sides of the disk, so that light from the light-emitting element enters the light-receiving element through the opening. Since the light is blocked by the non-apertured portion of the disk, the output of the light receiving element is 0 at this time. When the aperture, the light emitting element, and the light receiving element are lined up on a line, the output of the light receiving element is 1.

A pulse corresponding to passage through the aperture is generated at the output of the light receiving element. Therefore, by counting the number of pulses, it is possible to know the number of apertures that cross the optical axis connecting the light emitting element and the light receiving element. In this way, the displacement and speed of the rotating body can be calculated.

A light emitting diode, a laser diode, etc. can be used as the light emitting element. As the light receiving element, a suitable photoelectric conversion element such as a photodiode, a photocell, or a phototube can be used.

Still, a photoelectric switch (on the transmitting side) that is also integrated with a driving circuit including a light emitting element, and a photoelectric switch (on the receiving side) that is also integrated with an amplifier circuit that includes a light receiving element are sometimes provided on both sides of the disk.

Such rotation sensors have the disadvantage that they cannot detect counting errors.

The pulse signals obtained by the light receiving element are counted using a counter, but sometimes there is a possibility that a counting error may occur. Furthermore, noise may cause erroneous counting.

The secondary ffi rotation sensor does not have a count error detection function, so even if there is a count error, it cannot be detected.

(1) Structure of the Invention The present invention uses two light-receiving elements provided at positions that are not in the same phase with respect to the opening of the rotating disk.

If necessary, use two light emitting elements.

The signal received by the photodetector is composed of two pulses with different phases (
Since this is the ig sequence, the direction of rotation of the rotating disk can be determined.

A differential absolute value waveform is created from two sets of received signals with different phases, and this is calculated using Katank.

Kakunta's least significant bit (LSB: LeastSign)
ificant Bit), the output value changes every time the pulse of the differential absolute value waveform rises (or falls).

The differential absolute value waveform generates short pulses at the rising and falling edges of the received signal, and since these are put into the kakunta, the LSB rises and falls in synchronization with the rising (or falling) of the received signal ( or falling).

Therefore, the received signal and the LSB output should always be equal. If the two match, there is a high count error, and if the two do not match, a count error has occurred.

FIG. 1 is a schematic perspective view of the rotation sensor of the present invention.

A light emitting side unit 1 and a light receiving side unit 2 are installed facing each other. In both cases, two units are provided adjacent to each other. One unit contains a light emitting element, a light emitting element driving circuit, a light receiving element, a received signal amplifier, etc.

Between the light-emitting unit 1 and the light-receiving unit 2, a rotating disk 3 is provided. I'm in touch.

A large number of openings 5 are bored at symmetrical positions on the circumference of the rotating disk 3. Light is transmitted from the light emitting unit 1 to the light receiving unit 2 through the opening 5 . The light blocking portion 6 other than the opening 5 blocks this light. An opening 5 and a light shielding part 6 appear alternately on the optical axis connecting the light emitting element and the light receiving element.

The central angle α for each opening and the central angle β for each light shielding portion with respect to the center of the rotating disk 3 are all equal. The distribution number n of the openings 5 on the circumference may be 1 or more, but is usually about several tens to several hundreds.

(α1β)n2360°0) It is. The larger n is, the higher the accuracy is.

Among the light-receiving side units 2, the one located at the front with respect to the rotational direction of the rotary disk 3 is designated as a, and the one located at the rear is designated as b.

As shown in FIG. 2, the time taken to cross the opening 5 and the light shielding part 6 differs depending on a and b. The front light receiving element (a) is the first
The light-receiving element, the rear light-receiving element (b) is called a second light-receiving element.

The opening 5 of the rotating disk 3 moves from the first light receiving element towards the second light receiving element. When the light receiving element is in the position corresponding to the opening 1 part 5, the light from the light emitting unit 1 reaches.
A photocurrent flows. When this is appropriately amplified, a pulse signal train is obtained which takes two values, 1' and 0', corresponding to the presence or absence of photocurrent.

Since the positions of the two light receiving elements are different, the pulse signal trains have different phases.

FIG. 4 shows pulse waveform diagrams at each portion.

(a) Irj:, front light receiving unit) first light receiving element 1 of a
1 is an example of a received signal. (b) illustrates the received signal of the second light receiving element 12 of the rear light receiving unit) b.

Although they are the same pulse train, b is delayed.

The delay time is also ``.

Front and rear light receiving unit) Let the interval between a and b be d. Rotating circle'#
The distance from the center axis of i, 3 to the center point of the opening 5 is R1
Let the angular velocity of the rotating disk 3 be Ω.

d=RΩυ (2) is given by d and R are constant.

The angular velocity Ω( is inversely proportional to the delay time υ. The delay time υ is not constant.

However, the signal from the first light receiving element 11 and the signal from the second light receiving element 12
The delay of the signal is constant from the perspective of phase.

The length during which the pulse value is "1" is called the on-time).
n, '0 long off time) is Tf, it is given by α=ΩTn (3) β=ΩTf t4+. One period To of the pulse train is To = Tn
+Tf (5) Defined as: The ratio of delay time υ to To is given by: This is a constant value.

Strictly speaking, the distance d between the front and rear light receiving units a and b is:
It means the arc length along the circular arc about the center of the rotational main shaft 4.

If υ/T o is (integer) or (integer + A), the rotation direction of the 1st edition circle A-3 cannot be determined by the pulse trains (a) and (b).

However, when υ/To is not, two pulse trains (a
) and (b), the rotation direction can be determined.

There are known rotational direction detection circuits.

As shown in FIGS. 4(a) and 4(b), the direction in which the pulse train a precedes b is referred to as the forward direction, and the direction in which the pulse train precedes a is referred to as the reverse direction.

Differentiate the pulse train and set it as Δb. Invert the pulse train 6) and take the differential of this to obtain Δstone.

The product of these and pulse train a is calculated.

The forward direction signal El and the backward direction signal E2 are given by E1=a·Δb(7) E2=a·Δb(8). If it is El-1 or E2-0, it is rotating in the forward direction. If it is El-0 or E2-1, they are rotating in opposite directions.

Now, an object of the present invention is to provide a count error detection circuit.

FIG. 3 shows an example of a count error detection circuit.

The photocurrent of the first light receiving element 11 of the front light receiving side unit a and the second light receiving element 12 of the rear light receiving side unit b is transmitted to the amplifier 13.14.
and is shaped into a pulse train of 0'' and "1".As mentioned above, in the case of forward transmission, the pulse train a
is faster.

The outputs a and b of the amplifiers 13 and 14 are input to two exclusive OR gates 15. This is to calculate an exclusive OR; if the two manpowers are the same, the output C will be 0, and if they are different, the output C will be 1.

c = a-b + a-100 (9). A and b are the same pulse train, with only a delay time υ. The output of exclusive OR C is 1 only by υ from the rise and fall of the -a pulse, and is 0 otherwise.
It is. FIG. 4(c) shows the pulse waveform of pressure C.

Pulse waveform CU, 1 for each falling - L, falling of a pulse
Therefore, it can also be tentatively called a differential absolute value output. It can be said to be an exclusive OR output.

The differential absolute value output C has twice the frequency of the a and b pulse trains.

The output c is input to the tally clock input CK of the counter 16.

Since the number of pulse trains is calculated using a counter, conventional rotation sensors also use counters.

Counter 16 may be a one-way counter.

However, when it is necessary to integrate the number of revolutions and calculate rotational displacement, and when there is a possibility of forward and reverse rotation, it is better to use an up-down force tank.

Switching of the up-down instruction input terminal is performed by the forward/reverse direction signals E1 and E2 mentioned above.

If the counter 16 is an n-bit counter, the output will be 01, o2., On from the least significant bit. This can also be inserted into a decoder/driver circuit to directly display the rotational speed. It is also possible to convert it into a D/A and use it as a control signal for some related device.

Since the differential absolute value output C is input to the clock input CK of the counter, at the rising edge of the output C, the lowest bit 01
changes. ol becomes half the frequency of the output C.

When the least significant bit OI rises, the value of the second significant bit 02 changes. In this way, when the output of the (n71)-order bit rises, the value of the 1-order bit changes.

If there is no count error, the value of 01 will always change when the differential absolute value output C rises. OI may not change when output C rises.

Also, 01 may change even though the output C does not rise. Noise is introduced and this causes the OI to change.

This is a counting error.

In addition to this, an error may also occur due to a double shift in the counter from 01 to 02.0 or from -1 to On. However, the possibility that a counting error will occur in such a counter is low.

The present invention does not address such counting errors.

The present invention deals with a count error between the differential absolute value output C and the OI of the counter.

In FIG. 4, the amplified pulse train (a) of the first light receiving element 11 is assumed to be 30.31, . . . . Second light receiving element 1
The amplified pulse train (b) of 2 is assumed to be 40.41, . The differential absolute value output (c) is 50.51.

The output C is input to a counter, and the output of the least significant bit o1 is set as d. Since this changes at the rising edge of C, in FIGS. 4(c) and 4(d), a normal pulse 61 that rises at 51 and falls at 52 in FIG. 4(c) appears at the 01 output d.

52,. 53, pulse 62 also appears as a normal pulse.

The counter malfunctions and there is no pulse change at C.
Assume that an error pulse 63 occurs in the d output due to noise or the like.

Conversely, even though there is a pulse of 56.57 at C, the d output does not respond to it, and 65, which should be a pulse (indicated by a broken line), may be missed at QV.

Assume that there is no pulse at C, and the counter is activated due to noise or the like. Assume that this is not reset immediately, but is reset by the next C pulse 60. Then, an error pulse 67 appears at the d output.

Now, in order to detect a count error, the least significant bit LS
The exclusive OR e of the output d of B (here U, OI) and the pulse train a is calculated.

Output efi of exclusive or gate 17 =
It is represented by a-d + a-d ilol. This is 0 if a and d are equal, and 1 if they are different.

Kattank's lowest pitch) LSB output output pressure normal pulse 61
．． When generating 62.64.66, a and d are equal, so the e output is O.

When generating the LSB output pressure error pulse 63, since d and a are different, an error signal 70 is generated at the e output.

When the LSB output pressure leaks and the pulse 65 is not generated, an error signal 71 having a length equal to the a pulse 33 is generated because a and dll'i are different.

When the LSB output output pressure is counted and the d pulse 67 is generated, since a and d continue to be inconsistent, the e output becomes 1 continuously (rising edge of 72).

FIG. 5 shows another example of the error detection circuit.

This method uses pulse trains a and b to calculate the differential of pulse train a, and further calculates the absolute value of the differential. In the example shown in Figure 3, I used Exclussidaor Gate 15, but I made a few changes here.

The pulse trains θ and b are input to a differential amplifier 18 with three-state output. Since its output C' is given by c' = a-b (II), it is the differential of pulse a.

This is input into the absolute value circuit 19.

The output C is c = l c’l (12) It is. This is equivalent to the waveform in FIG. 4(C).

In reality, the differential amplifier 18 with three-state output is difficult to manufacture.

Therefore, in order to obtain the differential waveform C', without using the b pulse at all, a differentiating circuit consisting of a capacitor and a resistor is used.
The differential C' may also be created from the pulse.

Instead, by using two digital converters,
It is also possible to AND the output of this.

After all, the differential absolute value output C can be said to be the differential absolute value with respect to pulse train a, but when there is a pulse train a and a pulse train delayed from this, C can be said to be the exclusive OR output of a and b. most appropriate.

If the time variable is t and the pulse train change is expressed as 'a (t), then b (t) -a (t-u) (13)c = a-
It can be written as b + a-b (14).

(1) Effects According to the present invention, counting errors can be detected by using a rotation sensor.

(E) Can be used in general rotation sensors that measure the rotational displacement and rotational speed of rotating bodies.

In this example, two light emitting elements and two light receiving elements are used. There must be two light receiving elements.

However, as long as the light from the light-emitting element' spreads out, only one light-emitting element may be used. This is because light can be projected to both light receiving elements.

The two light receiving elements do not have to be adjacent to each other. You can be far away. It is sufficient that the delay υ/To expressed by equation (6) is not (integer)X(', 4).

Further, the light emitting element and the light receiving element do not necessarily need to be present in the light emitting side and light receiving side units 1.2.

Only the end surfaces of the optical fibers may be opposed to each other, and a light emitting element and a light receiving element may be arranged at the other end of the optical fiber.

(Force) Reflection type sensor In the sensor described above, openings and light shielding parts are provided alternately on a rotating disk, and light emitting and light receiving elements are provided on both sides of the rotating disk. It can be tentatively called a transmission type sensor.

Furthermore, the present invention can also be applied to reflective sensors.

A rotating disk is provided with reflective parts like a mirror surface and non-reflective parts like a black body alternately. The light-emitting element and the light-receiving element are arranged on the same side of the rotating disk, and the angle of the light-emitting element and the light-receiving element are adjusted with respect to the disk so that the incident light and the reflected light correspond to each element.

In the present invention, there are two light-receiving elements, and the light-emitting element may be arranged so that the light from the light-emitting element intermittently reaches the light-receiving element via a rotating disk.

(g) Case in which rotation can be performed in reverse order In this example, it is assumed that of the pulse trains a and b, a takes precedence. When the rotating disk rotates in the opposite direction, the pulse train may take the lead.

In this case, it is preferable to use an up-down kakunta as the kakunta 16.

Furthermore, it is necessary to calculate the exclusive OR of the least significant bit LSB and the pulse train. This can be configured by using the forward direction signal E1 and reverse direction signal E2 mentioned earlier and using some gate elements to switch between the LSB output d and the pulse trains A and A.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of a rotation sensor of the present invention. FIG. 2 is a schematic front view showing an example of the positional relationship between the opening of the rotating disc, the light shielding part, and the front and rear light receiving units (a) and (b). FIG. 3 is a side view of the count error detection circuit of the light receiving unit. FIG. 4 is a pulse waveform diagram at each part of the cacunto error detection circuit of the receiving side unit. FIG. 5 is a circuit diagram showing another example of the cacundo error detection circuit. 1 Light-emitting side unit 2 , , , , , , Light-receiving side unit 3 , times
Rotating circular plate 4 Rotating main shaft 5... Opening part 6 - Light shielding part 11... First light receiving element 12 Second light receiving element 13.14 Amplifier 15 Exclusive or gate 16 Calculator 11... Exclusive OR gate 18. -Differential amplifier 19...Absolute value circuits 30-72. pulse

Claims (1)

[Claims] a light-emitting element, a rotating disk that transmits or reflects light from the light-emitting element at a repetition frequency proportional to the rotation, and two light-receiving elements provided at positions with different phases to detect the transmitted light or reflected light; A circuit that calculates the exclusive OR C of the amplified outputs a and b of the two light receiving elements, a kakunta that calculates the exclusive OR C, a symbol that precedes the light receiving element outputs a and b, and the lowest part of the kakunta. A rotation sensor characterized by comprising a circuit that calculates an exclusive OR with an output d of LSB.