JPS6157810A - Photoelectric displacement detector - Google Patents

Abstract

PURPOSE:To detect the relative rotational displacement between the 1st and the 2nd plate bodies by placing two polarizing plates of the 2nd plate body oppsite nonoverlap parts of two polarizing plates of the 1st plate body, and variation in the quantity of transmitted light between them and the quantity of transmitted light at the overlap part of the 1st plate body into electric signals and processing them. CONSTITUTION:A plate body 10 having a large-diameter polarizing disk 11 and a small-diameter polarizing disk 12 overlapping with each other concentrically while axes of transmission have a 45 deg. shift is fixed integrally on a shaft 1 which is supported rotatably. A plate body 40 is arranged facing nonoverlap parts composed of only a disk 11 and polarizing plates 41 and 42 are fixed to the plate body 40 so that axes of transmission shift by 45 deg. from each other. Light sources 21 and 23 and photodetection parts 31 and 32 are arranged opposite each other across the polarizing plates 41 and 42 and nonoverlap parts of the plate body 10, and a light source 23 and a photodetection part 33 are arranged opposite each other across the overlap part of the disks 11 and 12. The light source 21-23 are connected in series and turned on by a turn-on control part 50. An arithmetic part 60 processes photodetection outputs of the photodetection parts 31- 33 to detect the relative rotational displacement between the plate bodies 10 and 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a detector for rotational displacement of a shaft.
For example, it is connected to the support shaft of a robot arm or the rotating shaft of a prime mover such as an engine to detect its rotation angle, and this detection signal is fed back to the control system for the rotation angular position and rotation speed of the detection target. Used for signals and their displays.

2. Description of the Related Art Detectors of this type include rotary encoders, resolvers, and the like. Among them, resolvers have a relatively simple structure despite having high resolution, and have the characteristic that angular information can be extracted for each period of the carrier wave.

In other words, in the resolver, first and second coils are wound around the poles of the stator in two orthogonal directions, and a third coil is wound around the rotor rotating inside the resolver. are carrier waves \“a, \”1] that are 90 degrees in phase with each other,
V a = V 2 sin ω + V l] = V,,, cos ω1 Here, \72: Carrier wave amplitude ω: Carrier wave angular velocity is supplied to radiate magnetic flux corresponding to carrier waves \7a, \゛1〕 This is how it was done. Therefore, when this rotor is connected to the shaft to be measured and rotated, the proportion of the magnetic flux that interlinks with the rotor among the respective radiated magnetic fluxes changes depending on the rotation angle θ, and as a result, the proportion of the magnetic flux that interlinks with the rotor changes depending on the rotation angle θ. is a phase signal V c whose phase changes depending on the rotation angle θ.

Vc = K 2 V 2 cos ωt s i n θ 2 V 2 sin ω t co s θ ” K 3 V 2 sin (ωt + θ) Here, K2, K3: Proportionality coefficients will be induced. However, the resolver is electromagnetic as described in 1. Since it uses a conventional signal generation means, it requires a coil and a low retransformer for taking out the signal from the coil, which imposes restrictions on miniaturization, and the moment of inertia of the rotor is also lower than that of a rotary encoder. It has problems such as being large and large.

Furthermore, in order to obtain a predetermined magnetic flux distribution during manufacture, strict precision is required in the shape and position of the coil, resulting in a problem of high cost.

This drawback of the resolver is due to the use of electromagnetic signal generation means, and a possible solution to this problem is to use photoelectric signal generation means.

Examples of this type include, for example, U.S. Pat.
There is one disclosed in No. 159. In this system, four stationary polarizing plates, numbered 1 to 4, are arranged to face a portion of the polarizing plate fixed to the rotating shaft, and each of the stationary polarizing plates has its transmission axis shifted by 45 degrees from each other. Then, a light source and a light receiving section are arranged facing each other on the outside of each of the stationary polarizing plates and the rotating polarizing plate.

In the above, light from the light source passes through the rotating polarizing plate, and then passes through each of the first to fourth stationary polarizing plates to reach each light receiving part, but at this time, each light receiving part The amount of light that reaches this value varies depending on the intersection angle of the transmission axes of the rotating polarizing plate and each of the first to fourth stationary polarizing plates. That is, the transmittance of light changes corresponding to a cosine function of the angle of intersection. Therefore, now, when the rotating polarizing plate rotates by the angle θ, the angles between the rotating polarizing plate and the first to fourth stationary polarizing plates are as follows.
θ, θ+45°, θ+90°, and θ+135°, respectively, and as a result, the respective transmittances are cos 2θ,
-5in2θ, -cos 2θ, 5in2θ,
Each light receiving section also generates corresponding outputs. However, the above transmittance is always greater than O. Therefore, to express the above transmittance strictly, when the intersection angle is 90 degrees, it is the sum of the orthogonal transmittance and the above transmittance. The part also includes a DC component corresponding to the orthogonal transmittance.

Next, each light receiving unit output has a carrier wave sinω1, CO2
O3, -5inω1, -cosω1 are multiplied and then added. Therefore, the above-mentioned DC component is canceled by this addition, and the added output becomes 5 inches (ωt+2θ) whose phase changes in accordance with the angle multiplied by the rotation angle θ of the rotating polarizing plate.

However, in this case, it is necessary to arrange the first to fourth polarizing plates so that their transmission axes are shifted by 45 degrees at positive values, but this requires skill in assembling and adjusting the detector. It is unavoidable that it requires a lot of time and a lot of work time.

Problems to be Solved by the Invention The present invention attempts to solve the problem of having to adjust the position of a large number of polarizing plates when arranging them.

In order to solve the above problem, the present invention reduces the position adjustment of the transmission axis of the polarizing plate to two places, and shifts the transmission axis by 15 degrees. A first plate body having a polymerized part and a non-polymerized part made by polymerizing two large and small polarizing plates, and a first plate body and a second plate body which are disposed opposite to the polymerized part and whose transmission axes are shifted by 45 degrees.
a second plate body having a polarizing plate, the second plate body (or the first plate body) being integrally connected to the first plate body, and the first and second polarizing plates of the second plate body or facing thereto; a first and second light receiving section disposed facing either side of the non-polymerized portion; a third light receiving portion disposed facing the overlapping portion; one or more light sources disposed opposite each of the light receiving sections with a plate in between, a lighting control section that sends a constant lighting signal to the light sources, and outputs of the first to third light receiving sections. , and forms an output corresponding to the relative rotational displacement of the first and second plates.

Effect When the first and second plates produce a relative rotational displacement θ, the polarizing plate of the non-overlapping portion of the first plate and the first and second transmission axes of the second plate The intersection angles of the two are shifted by θ, and as a result, the respective light transmittances a1 and α2 change as follows.

α+= (HO-H90)c032θ+H90”Ktc
os2θ+2 ・・・■ α2” (Ho-H90) CO32(θ+45°)+H
9° = 1cO82 (θ+45°) 102 = -Ksi 2 θ 102 ・ ・ ・ ・■Here, I(.: Parallel transmittance H90: Orthogonal transmittance, = (1, / 2) (Ho-H9,) K 2 = (1/2) (H, -890) At this time, the first
The transmittance α3 of the overlapping portion of the plates is constant regardless of the rotational displacement θ of the second plate, and is as follows.

α3= (Ho−H9o) cos245°+I(90
2.2...■ Therefore, the amount of light from the light source placed on one side with the non-polymerized portion of the first plate and the first and second polarizing plates of the second plate in between is , the transmittance of each is multiplied by α1.02 and reaches the light receiving part placed on the other side, and the amount of light from the light source placed on one side with the overlapped part is multiplied by a certain transmittance α3 and reaches the other side. The light reaches the light receiving section located on the side.

As a result, if the amount of light emitted is now set as C, and the conversion coefficient between the light amount of the light receiving section and the electric signal is set as β, the following outputs e1 to e3 are obtained from the first to third light receiving sections. Each occurs.

e, -a, Cβ=　K　　3(!O32θ10K.

e2−α2Cβ= −K 3sin2θ, ■
e3−α3Cβ=K.

Here, K3 =, Cβ, = 2Cβ Below, these outputs e1 to e3 are introduced into the calculation section, and first, the calculation of (el-e3)+(e2-e3) is performed in the adder/subtraction circuit, 4 is removed from the constant term in el182. These differences are then sent to a modulation circuit and modulated by a 90 degree phase periodic signal, sinωtScosωt.Then, each modulation signal is added in an adder/subtractor circuit, and the first and second Relative rotational displacement θ of the plate of
Output e with a phase shift corresponding to . is formed.

eo” (el-e3)S!nωt +(e2- e3
)cosωt=K3sin(ω1.-2θ)
■・In addition, the calculation in the calculation section is performed first by e.
After modulating l, e2e3, addition and subtraction are performed in exactly the same way.

Embodiment In FIGS. 1 and 2 showing the mechanical part of the embodiment, 1 is a rotatably supported shaft, and the shaft 1"2 has a large diameter polarizing disc 11 and a small diameter polarizing disc 12. A first plate body 10 is integrally fixed to the first plate body 10, which is made by concentrically overlapping the two plates with their transmission axes shifted by 45 degrees.

Large-diameter polarizing disc located on the outer peripheral side of the first plate] 1
A second plate body 40 is disposed to face the non-overlapping portion consisting of a non-polymerized portion, and the second plate body 40 has first and second polarizing plates 41 and 42 whose transmission axes are shifted by 45 degrees from each other. is fixed. Then, the first and second polarizing plates 41 and 42 are placed facing each other with the non-overlapping portion of the first plate 10 interposed therebetween. Second
A light source 21.22 and first and second light receiving sections 31.32 (32 is not shown) are provided.

Also, large diameter and small diameter polarizing discs 11 located on the inner peripheral side of the first plate body 10. ．． A third light source 23 and a third light receiving section 33 are disposed facing each other with the overlapping portion of the light source 12 interposed therebetween.

Therefore, in this mechanism, the polarizing disk 1 of large and small diameters
During the polymerization of 1.12, the transmission axis is assembled and adjusted to 45 degrees, and the first and second polarizing plates 4.1 are attached to the second plate body.
, 42 are assembled and adjusted by shifting their transmission axes by 45 degrees.

Next, FIG. 3 shows a lighting control unit that controls the amount of light emitted from the first to third light sources, and a rotation of the first plate 10 by calculating the outputs of the first to third light receiving units. This is an example of a calculation unit that calculates displacement, and the first to third light sources 21 to 23 and light receiving units 31 to 33, which are given the same numbers as in Figures 1 and 2, are the same as in Figures 1 and 2. be.

In this case, a lighting control section 50 consisting of a constant current generator is used.
The output ends of are connected in series with the first to third light sources 21 to 23, and the first to third light sources 21 to 23 always emit a constant amount of light.

The calculation unit 60 also operates first and second addition/subtraction circuits 61 and 62 that calculate the difference between the output els e2 of the first and second light receiving units 31 and 32 and the output e3 of the third light receiving unit 33, respectively. ,
The first and second modulators 63 and 64 multiply the output of the adding/subtracting circuit 61°62 by the carrier sinωt and eO3ωt sent from the carrier oscillator 66, and the third modulator calculates the sum of the outputs of the respective modulators 63°64. (in addition) power circuit 65.

In the above, when the shaft 1 is rotationally displaced by θ, the first plate body 10 is also rotated integrally by θ, and the non-overlapping portions of the first and second polarizing plates 41 and 42 and the polarizing plate 11 are The intersecting angles of the transmission axes with .theta. and (.theta.+45.degree.) are respectively .theta. and (.theta.+45.degree.), and the transmittances .alpha.l and .alpha.2 change according to the rotational displacement .theta., as in equations (1) and (2) above.

On the other hand, the transmittance of the overlapping portion of the first plate body 10 is constant regardless of the rotational displacement θ of the shaft 1, and is equal to 1 as shown in equation 0 above.

That is, the first, second, and third light sources 21.22.2
The constant amount of light emitted from 3 is al, α2, α, respectively.
The light is multiplied by three and reaches each of the corresponding light receiving sections 31 to 33, and the light receiving sections 31 to 33 generate electrical signals e1-.e shown in equation 0 above corresponding to the amount of light received.

Then, in the first and second addition circuits 61 and 62,
The difference between the first and second light receiving section output else2 and the third light receiving section output e3 is calculated, and then the difference is converted into a 90 degree phase sine wave in the first and second modulators 63 and 64. After being balanced modulated by , the third adding/subtracting circuit 65 adds the output e shown in the above equation 0. is formed.

In the above embodiment, the light source and the light receiving section are exemplified using a direct light emitting element and a light receiving element, but the same effect can be obtained by using these and an optical fiber.

Furthermore, the order of calculations performed by the calculation unit 60 on the outputs of the respective light receiving units is not limited to the above embodiment, and may satisfy the calculation formula 0, for example, modulate el and e2 with a periodic signal with a 90 degree phase. The same effect can be obtained by adding the sum of the 90-degree phase periodic signals, and then modulating e3 with a signal that is the sum of periodic signals of 90 degrees phase, and subtracting the modulated signal from the added signal.

Moreover, although the above-mentioned embodiment illustrated the case where the first to third different light sources were made to face each light receiving section, the same effect can be obtained even if a single light source is made to face each light receiving section.

Furthermore, the order of calculations performed by the calculation unit 60 on the outputs of each light-receiving unit is not limited to the example described in 1. The same effect can be obtained by modulating the sum signal and subtracting the modulated signal from the sum signal.

Moreover, although the above-mentioned embodiment illustrated the case where the first to third different light sources were made to face each light receiving section, the same effect can be obtained even if a single light source is made to face each light receiving section.

Further, in the above embodiment, the case where the first plate body 10 is fixed to the shaft 1 and rotated is illustrated, but the second plate body 4
1st of 0. The same effect can be obtained even if the second polarizing plate is shaped like a donut, is provided on different radii of the disk, and is fixed to a shaft for rotational displacement.

The effects of the invention are as described above, and the present invention provides that the non-polymerized portion of the first plate has a polymerized portion of two polarizing plates and a non-polymerized portion of the second plate. Two polarizing plates are placed facing each other, and changes in the amount of transmitted light between them and the amount of transmitted light at the overlapping portion of the first plate are converted into electrical signals and processed, corresponding to the rotational displacement of the first and second plates. Therefore, the transmission axis of the polarizing plate only needs to be adjusted for two pairs of polarizing plates.
Overall assembly and procurement is simplified and work efficiency is improved.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the mechanism section of the present invention, FIG. 2 is a left side view of FIG. 1, and FIG. 3 is a block diagram showing an embodiment of the lighting control section and calculation section of the present invention. It is.

Claims (1)

[Claims] 1. A first plate member having a polymerized portion and a non-polymerized portion, which are formed by polymerizing two polarizing plates with their transmission axes shifted by 45 degrees; , a second plate body having first and second polarizing plates whose transmission axes are shifted by 45 degrees; and a second plate body which is integrally coupled with either the first or second plate body, and which transmits the first and second polarized light. a first and second light receiving section disposed facing either one side of the plate or the non-overlapping portion facing it; a third light receiving section disposed opposite the overlapping portion; - One or more light sources integrally coupled with the third light receiving section and disposed facing each of the light receiving sections with the first and second plates in between, and a constant light source for the light source. a lighting control section that sends out a lighting signal; and a calculation section that calculates the outputs of the first to third light receiving sections to form an output that corresponds to the relative rotational displacement of the first and second plates. However, it is a photoelectric displacement detector. 2. The arithmetic unit includes a modulation circuit that modulates the outputs of the first and third light receiving sections and the outputs of the second and third light receiving sections, respectively, using periodic signals with a 90 degree phase, and a modulation circuit that modulates the outputs of the first and third light receiving sections and the outputs of the second and third light receiving sections, respectively, and The photoelectric displacement detection according to claim 1, which is an adjustment circuit that calculates the difference in the modulation signal of the output of the light receiving section and the sum of the difference of the modulation signal of the output of the second and third light receiving sections. vessel. 3. The calculation unit calculates the difference between the first and third light receiving unit outputs and the second
, an adding/subtracting circuit that calculates the difference between the outputs of the third light-receiving section, a modulating circuit that modulates each difference with a 90-degree phase synchronous signal, and an adding/subtracting circuit that calculates the sum of each of the modulated signals. A photoelectric displacement detector according to claim 1.