JPH0249542Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a detector for rotational displacement of a shaft, for example, a detector connected to a supporting shaft of a robot arm or a rotating shaft of a prime mover such as an engine. The rotation angle is detected, and this detection signal is used as a feedback signal or display in a control system for the rotation angle position and rotation speed of the object to be detected.

Prior Art This type of detector includes a rotary encoder, a resolver, 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.

That is, the resolver has first and second coils wound around poles in two orthogonal directions of the stator, respectively.
A third coil is wound around the rotor rotating inside the rotor, and the first and second coils are supplied with carrier waves Va, Vb, which have a phase difference of 90 degrees, Va=V ₂ sinωt Vb=V ₂ cosωt The magnetic flux corresponding to the carrier waves Va and Vb is radiated from each pole. Here,
V ₂ represents the amplitude of the carrier wave, and ω represents the angular frequency. Therefore, when this rotor is connected to the shaft to be measured and rotated, the proportion of the magnetic flux interlinking with the rotor among the respective radiated magnetic fluxes changes depending on the rotation angle θ, and as a result, the third A phase signal Vc Vc=K ₂ V ₂ cosωtsin θ +K ₂ V ₂ sinωtcosθ = K ₃ V ₂ sin(ωt+θ) is induced in the coil, the phase of which changes according to the rotation angle θ. Here, K ₂ and K ₃ represent proportionality coefficients. However, since resolvers use electromagnetic signal generation means as described above, they require coils and rotary transformers for extracting signals from the coils, which imposes restrictions on downsizing. The problem is that the moment of inertia is also larger than that of a rotary encoder. 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. Patent No.
There is one disclosed in No. 3306159. 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 stationary polarizing plate has its transmission axis shifted by 45 degrees from each other. 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, when the rotating polarizing plate is now rotated by an angle θ, the intersection angles between the rotating polarizing plate and the first to fourth stationary polarizing plates are θ, θ+45°, θ+90°, and θ+, respectively.
135°, and as a result, each transmittance is
Corresponding to cos2θ, -sinθ, -cos2θ, and sin2θ, corresponding output forces are generated in each light receiving section. However, the above transmittance is always greater than 0, so if the above transmittance is expressed strictly, the intersection angle is 90
In the case of 3 degrees, it is the sum of the orthogonal transmittance and the above-mentioned transmittance, and each light receiving section also includes a DC component corresponding to the orthogonal transmittance.

Next, the carrier wave sinωt,
cosωt, −sinωt, and −cosωt are multiplied and then added. Therefore, the DC component mentioned above is canceled by this addition, and the added output is sin(ωt +
2θ).

However, in this case, it is necessary to accurately arrange the first to fourth polarizing plates so that their transmission axes are shifted by 45 degrees. ,
It is unavoidable that adjustment techniques require skill and a great deal of work time.

The present invention is intended to solve the problem of having to adjust the position of a large number of polarizing plates when arranging them.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention reduces the position adjustment of the transmission axis of the polarizing plate to two locations, and shifts the transmission axis by 45 degrees to create polarized light from two large and small plates. A first plate body in which the plates are overlapped to form an overlapping part and a non-overlapping part, and a first plate body with the transmission axis shifted by 45 degrees from each other.
a second plate body to which a second polarizing plate is fixed and disposed opposite the non-overlapping portion of the first plate body; and a second plate body arranged to face the non-overlapping portion of the first plate body and the second plate A first light source and a light-receiving section, which are arranged to face each other across the first and second polarizing plates of the body, and an overlapping portion of the second light source and light-receiving section and the first plate body. A third light source and a light receiving section, which are arranged to face each other, and a fourth light source and a light receiving section, and a sine wave lighting having a phase difference of 90 degrees between the first and second light sources. a lighting control unit that sends out signals and sends a constant DC lighting signal to the third and fourth light sources, and a sine signal having a phase difference of 90 degrees between the outputs of the third and fourth light receiving units, respectively. This is a photoelectric displacement detector comprising a modulating section that performs modulation by multiplying by a wave-like carrier, and an arithmetic section that has an adding/subtracting circuit that calculates the difference between the output of the modulating section and the output of the first and second light receiving sections.

Effect When the first and second plates generate a relative rotational displacement θ, the polarizing plate of the non-polymerized portion of the first plate and the first and second polarizing plates of the second plate The intersection angle with each transmission axis is shifted by θ, and as a result, the transmittance α ₁ and α ₂ of each light changes as follows.

α ₁ = (H ₀ − H ₉₀ ) cos ² θ + H ₉₀ = K ₁ cos2θ + K ₂ ... α ₂ = (H ₀ − H ₉₀ ) cos ² (θ + 45°) + H ₉₀ = K ₁ cos2 (θ + 45°) + K ₂ = −K ₁ sin2θ＋K ₂ ... Here, H ₀ : Parallel transmittance H ₉₀ : Orthogonal transmittance K ₁ = (1/2) (H ₀ −H ₉₀ ) K ₂ = (1/2) (H ₀ −H ₉₀ ) At this time, the transmittance α ₃ of the overlapping part of the first plate
is constant regardless of the rotational displacement θ of the second plate, and is as follows.

α ₃ = (H ₀ − H ₉₀ ) cos ² 45° + H ₉₀ = K ₂ ... Therefore, the non-polymerized portion of the first plate and the first and second polarizing plates of the second plate are The amount of light from the light sources placed on one side is determined by their respective transmittances α ₁ and α ₂
The amount of light from the light source placed on one side across the overlapping portion is multiplied by 3 and is multiplied by ₃ to reach the first and second light receiving sections placed on the other side. The light reaches the light receiving section located at the

Now, the third and fourth light sources are constant, the first and second light sources are
The light source is a periodic signal in the form of a sine wave whose phase is shifted by 90 degrees from each other, for example, a lighting signal consisting of a sine wave, B
The amount of light emitted is controlled by (Asinωt1) and B(Acosωt+1), and the amount of light C ₁ , C ₂ , C ₃ ,
Emit C ₄ .

C ₁ = E (Dsinωt+1) C ₂ = E (Dcosωt+1) ... C ₃ = C ₄ = E Here, A, B, D, and E are proportional coefficients. These C ₁ , C ₂ , C ₃ , and C ₄ are When passing through the first and second plates, the transmittances α ₁ , α ₂ , α ₃ , α _{3 are multiplied by 3} , respectively, and reach the corresponding first to fourth light receiving sections, where the light beams correspond to the amount of light received. It is converted into electrical signals e ₁ to e ₄ . In other words, e ₁ =K ₃ sinωtcos2θ+K ₄ cos2θ +K ₅ sinωt+K ₆ e ₂ = −K ₃ cosωtsin2θ−K ₄ sin2θ +K ₅ cosωt+K ₆ e=K ₆ e ₄ = K ₆ ...Here, the conversion coefficient between the light amount and electrical signal is set as β, K ₃ = DEK ₁ β K ₄ = EK ₁ β K ₅ = DEK ₂ β K ₆ = EK ₂ β Subsequently, the outputs e ₃ and e ₄ of the third and fourth light receiving sections are modulated. A sinusoidal carrier introduced into the section and out of phase with each other by 90 degrees, for example, a sine wave (1+Dsinωt), (-
1+Dcosωt), and the following two modulated outputs e ₃ ′ and e ₄ ′ are formed.

e ₃ ′=K ₅ sinωt+K ₆ e ₄ ′=K ₅ cosωt+K ₆ ...Then, the outputs e ₁ and e ₂ of the first and second light receiving sections and the modulation signals e ₃ ′ and e ₄ ′ are sent to the calculation section. is introduced, added and subtracted, and converted into an output e ₀ having a phase shift corresponding to the relative rotational displacement θ of the first and second plates as follows.

e ₀ = (e ₁ + e ₂ ) − (e ₃ ′ + e ₄ ′) = K ₃ sin (ωt − 2θ) + K ₅ (cos2θ − sin2θ) ... Here, the lighting frequency (ω / 2π) is It is selected to be sufficiently high compared to the displacement speed dθ/dt, and the second term in the above equation is removed by passing the output e ₀ through a high-pass filter.

By the way, when the light quantities C ₁ to _{C 4} of the first to fourth light sources change, the light receiving section outputs e ₁ to e ₄ also change correspondingly. If there is a possibility that a change in light intensity may occur in this way, compare one or both of the third and fourth light receiving section outputs e ₃ and e ₄ with a fixed preset value, and calculate the change from that set value. It detects the presence or absence of a change in light intensity based on the presence or absence of deviation, and detects the amount of change in light intensity based on the size of deviation, and also determines the magnitude of the lighting signal sent from the lighting control unit to the light source so that the deviation becomes zero. A light amount correction section that changes the amount of light may be provided within the lighting control section.

Furthermore, by comparing e ₃ and e ₄ in this light amount correction section, it is possible to monitor whether or not a characteristic change has occurred between the third and fourth light sources and the light receiving section.

EXAMPLE Hereinafter, as an example, a first plate body is formed by overlapping two large and small polarizing discs, and a second plate body is formed by arranging two polarizing plates in parallel. The present invention will be explained in detail.

In FIGS. 1 and 2 showing the mechanical parts of the embodiment,
Reference numeral 1 denotes a rotatably supported shaft, and on the shaft 1 there is provided a large-diameter polarizing disc 11 and a small-diameter polarizing disc 12, which are superimposed concentrically with their transmission axes shifted by 45 degrees. One plate body 10 is integrally fixed.

A second plate is located opposite to a non-overlapping portion consisting only of the large-diameter polarizing disc 11 located on the outer circumferential side of the first plate.
A plate body 40 is disposed, and the second plate body 40 includes first and second polarizing plates 4 whose transmission axes are shifted by 45 degrees from each other.
1 and 42 are fixed. And the first one,
The first and second light sources 2 are placed facing each other with the second polarizing plates 41 and 42 and the non-overlapping portion of the first plate body 10 in between.
1 and 22, and first and second light receiving sections 31 and 32 (however, 32 is not shown) are provided.

In addition, third and fourth light sources 23 and 24 and a third,
Fourth light receiving sections 33 and 34 are arranged.

Therefore, in this mechanism part, when the large and small diameter polarizing disks 11 and 12 are superposed, the transmission axis is assembled and adjusted to 45 degrees, and the first and second plates in the second plate are assembled and adjusted.
There are only two adjustment operations: shifting the transmission axes of the second polarizing plates 41 and 42 by 45 degrees and assembling and adjusting them.

Next, FIG. 3 shows the first to fourth light sources 21 to 2.
a lighting control section that controls the amount of light emitted by the first to fourth lights;
This is an embodiment of a calculation unit that calculates the rotational displacement of the first plate body 10 by calculating the outputs of the fourth light receiving units 31 to 34, and the calculation units 1 to 3 with the same numbers as in FIGS. The fourth light sources 21 to 24 and the light receiving sections 31 to 34 are the first,
This is the same as Figure 2.

In this case, the lighting control section 50 controls the third and fourth lights.
A constant DC lighting signal is sent to the light sources 23 and 24, and a periodic lighting signal is made of a sine wave signal having a phase difference of 90 degrees between the first and second light sources 21 and 22.
B(Asinωt+l) and B(Acosωt+1) are sent out, respectively, and the light amounts C ₁ to _{C 4} shown in the above formula are emitted.

Further, the calculation unit 60 modulates the outputs of the third and fourth light receiving units with sine wave carriers (1+Dsinωt) and (1+Dcosωt), respectively, which are sent from the carrier oscillator 66 and have a phase difference of 90 degrees. the first and second modulating sections 61 and 62, the difference between the output of the first light receiving section 31 and the first modulating section 61, the output of the second light receiving section 32 and the second modulating section 62
It consists of first and second adder/subtractor circuits 63, 64 which respectively calculate the output difference of , and a third adder/subtractor 65 which calculates the sum of the outputs of both adder/subtractor circuits 63, 64.

In the above, when the shaft 1 is rotationally displaced by θ, the first plate 10 is also rotated integrally by θ,
The intersection angles of the transmission axes of the first and second polarizing plates 41 and 42 and the non-overlapping portion of the polarizing plate 11 are θ and (θ
+45°), and its transmittance α ₁ and α ₂ are as above,
It changes according to the rotational displacement θ as shown in the equation.

On the other hand, the transmittance of the overlapping portion of the first plate 10 is constant regardless of the rotational displacement θ of the shaft 1, and is expressed by the above equation.

Therefore, the constant amount of light emitted from the first to fourth light sources 21 to 24 is multiplied by α ₁ to _{α 3} and reaches the corresponding light receiving sections 31 to 34, respectively.
34 generates electric signals e ₁ to _{e 4} shown in the above equations corresponding to the amount of light received.

Then, the outputs of the third and fourth light receiving sections 33 and 34
e ₃ and e ₄ are modulated by the first and second modulation sections 61 and 62, respectively, and the modulated outputs e ₃ ',
e ₄ ′, and the modulated outputs e ₃ ′ and e ₄ ′ are added as subtraction signals to the corresponding first and second adding/subtracting circuits 63 and 64, respectively, and the first,
Difference from the output of the second light receiving section (e ₁ − e ₃ ′), (e ₂ − e ₄ ′)
is calculated, and then the sum of both signals is calculated in the third addition/subtraction circuit 65 to form an output e ₀ corresponding to the rotational displacement of the first plate 10 shown in the above equation.

In addition, 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.
The same effect can be obtained by using these and optical fibers.

Further, the order of calculations performed by the calculation section 60 on the outputs of the light receiving sections is not limited to the above embodiment, and may be any order as long as it satisfies the above calculation formula.

Further, in the above embodiment, each light receiving section is made to face the first to fourth light sources, but if _the first and second light sources and each common light receiving part are made to face _{each other} , )
It is also possible to generate the output directly.

Further, in the above embodiment, the first plate 10 is fixed to the shaft 1 and rotated, but the first and second polarizing plates of the second plate 40 are shaped like donuts. The same effect can be achieved by providing the discs on different radii and fixing them to a shaft for rotational displacement.

Effects of the invention As described above, the present invention provides a first polarizing plate having a polymerized portion and a non-polymerized portion of two polarizing plates.
The two polarizing plates of the second plate are opposed to the non-overlapping portion of the first plate, and the 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. processing to form an output corresponding to the rotational displacement of the first and second plates, the transmission axes of the polarizing plates only need to be adjusted for the two pairs of polarizing plates.
Overall assembly and procurement is simplified and work efficiency is improved.

[Brief explanation of the drawing]

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. 10...first plate body, 40...second plate body, 2
0... Light source, 30... Light receiving section, 60... Calculating section,
50...Lighting control section.

Claims (1)

[Scope of utility model registration request] The first one consists of overlapping two large and small polarizing plates with their transmission axes shifted by 45 degrees to form an overlapping part and a non-overlapping part.
a second plate body, to which first and second polarizing plates are fixed with their transmission axes shifted by 45 degrees from each other, and which is disposed facing the non-overlapping portion of the first plate body; , a non-polymerized portion of the first plate and a first portion of the second plate,
A first light source and a light-receiving section are arranged to face each other with a second polarizing plate in between, and a second light source and a light-receiving part are arranged to face each other with an overlapping portion of the first plate in between. a third light source and a light receiving section arranged as
and transmits a sinusoidal lighting signal having a phase difference of 90 degrees to the fourth light source, the light receiving unit, and the first and second light sources, respectively, and lights the third and fourth light sources with a constant DC current. a lighting control unit that sends out signals, a modulation unit that modulates the third and fourth light receiving unit outputs by multiplying them by sinusoidal carriers having a phase difference of 90 degrees, and the modulation unit output and the first light receiving unit; , and an arithmetic unit having an addition/subtraction circuit that calculates the difference between the outputs of the second light receiving unit.