JPH09292407A - Angular acceleration detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angular acceleration detector which capable of obtaining superior S/N signal by using the diffraction interference figures of light by a three-grating-optical system. SOLUTION: The rotating duck of a three-grating reflex rotary encoder is formed of the first rotating disc 1 on a circumferential surface close to a rotation axis 5, the second rotating disc 2 on a circumferential surface farther from the first one and second rotating disc supporting parts 4 to support the both in between them. A light source 13 produces light, and the light beams through the openings of a grating 10 are reflected at gratings 6 and 7 on each of the disks 1 and 2, respectively. Then angular acceleration is obtained from the phase difference of the light beams received at each of the light-receiving elements 111 , 112 , 121 and 122 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular acceleration detector for detecting the angular acceleration of a rotating body such as a motor.

[0002]

2. Description of the Related Art Conventionally, as such means, for example, Japanese Patent Application Laid-Open No. 6-337212, an integrated detection device of velocity and angular acceleration is known. Regarding this conventional example, FIG. 6 (a) is a side view of the configuration, and FIG. 6 (b) is a plan view for explaining the lattice. The angular acceleration detector is composed of light emitting diodes 71, 8
1. The semiconductor position detectors 72 and 82, the rigid disk 50 having the first slit row 51 and the elastic disk 60 having the second slit row 61 have a relative azimuth angle between their lattices. Is configured. The first slit row 51 is composed of a radial grid with a constant pitch, and when angular acceleration occurs on the rotating shaft 56, a relative positional change in the rotational direction occurs between the rigid disk 50 and the elastic disk 60, and the first slit row 51 And the second slit row 61
The crossing position of changes. The angular acceleration is detected by detecting the change in the crossing position with the semiconductor position detectors 72 and 82.

[0003]

However, the detection method according to the conventional example has a tendency to cause deterioration of the detection signal due to the diffraction interference phenomenon of light. This will be described with reference to the lattice diagram of FIG. That is, the detection sensitivity s of the angular acceleration signal in the conventional example is shown by the following (Formula 1). s = r / tan δ ………………………………………… (1) However, r is the distance from the slit intersection position to the center of the disk δ is the intersection angle. In order to realize a small-sized and highly sensitive angular acceleration detector, it is necessary to use a thin grating and reduce the intersection angle δ. To use a thin grating, it is necessary to reduce the grating pitch and receive light that has passed through many gratings so that the level of the detection signal does not decrease. Therefore, there is a problem that a signal with good S / N cannot be obtained.

Further, in order to prevent contact between both discs due to vibration or shock, the gap between the rigid disc and the elastic disc cannot be made very small, which causes a diffraction phenomenon of light and gives a good S / N signal. There was a problem of not having. put it here,
An object of the present invention is to provide an angular acceleration detector that can obtain a signal with a good S / N by utilizing a diffraction interference image of light by a three-grating optical system.

[0005]

In order to solve this problem, the present invention applies the principle of the three-grating reflection type using the diffraction phenomenon of light, not the linear type, but adopts this as a rotary encoder. , A rigid disk and an elastic disk are arranged on the same plane, a plurality of three gratings are respectively arranged, and means for detecting a phase shift between the rigid disk and the elastic disk by receiving reflected light is provided. Angle detection with high S / N, high reliability of angular acceleration detection signal, and high sensitivity even if the gap between the rotating disk and the sensor scale surface on which the light receiving element is arranged is wide It is configured to be a container.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention includes a diffused light source for emitting diffused light, and a radial light source grating for limiting light from the diffused light source to generate a radial line light source. A first rotating disk coaxially fixed to a rotating body, a main grating arranged on the first rotating disk at equal intervals in a radial pattern, and a plurality of receiving the reflected light reflected by the main grating. And a second main grating, which is coaxial with the first rotating disk and is provided on the same plane as the first rotating disk at equal intervals in a radial pattern.
A plurality of rotating discs, elastic supporting means for supporting the second rotating disc on the first rotating disc, and a plurality of index gratings are arranged on the sensor scale, respectively. The first index grating and the second index grating that receive reflected light that has been reflected and reached from the main grating and the second main grating of each of the two rotating disks, and the reflection that has passed through the first index grating. This is an angular acceleration detector characterized by comprising a plurality of light receiving elements for receiving light and converting it into an electric signal. With this, an angular acceleration detector using a diffraction interference image of light can be obtained. Has the effect of.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention.
FIG. 2 is a perspective view for explaining the state / positional relationship of each grating, FIG. 2 is a block diagram showing the circuit configuration of the phase detection circuit in the first embodiment of the present invention, and FIG. 3 is an output waveform of the phase detection circuit of FIG. FIG. In FIG. 1, 1 is a first rotating disk, 2 is a second rotating disk, 3 is a sensor scale,
_{4a, 4b} ... are second rotary disk support parts [collectively referred to as second rotary disk support parts 4], 5 is a rotary shaft, 6 is a first main grid, 7 is a second main grid, and 8 is a first Index grid, 9 is the second index grid, 10 is the light source grid, and 11
12 is a light receiving element, 13 is a light source, 14 and 15 are DC constant voltage power supplies, and 16 to 19 are negative feedback resistors.

The first rotary disk 1 is rigidly fixed to a rotary shaft 5 which rotates integrally with the rotary body, and the second rotary disk 2 is rotated by the second rotary disk support 4 with respect to the first rotary disk 1. It is fixedly attached so as to have elasticity in the direction. The first and second rotating disks 1 and 2 are soda-lime glass sheets formed of the same member and capable of transmitting light, and are formed of a so-called ordinary rotary encoder disk material. A member having a larger elastic coefficient than that of the first and second rotating discs 1 and 2 is applied to the second rotating disc support portion 4, and various constants such as the number, length, width and thickness thereof are preset. . The light source 13 and the light source grid 10 constitute a radial linear light source.

In addition, each grating has a pattern of chrome or the like deposited on the disk by several thousand Å to improve light reflection, and the first main grating 6 and the second main grating 7 are evenly spaced from each other. Are equal, and the first index grating 8 and the second index grating 9 are arranged corresponding to the first main grating 6 and the second main grating 7, respectively. The light from the light source 13 passes through the light source grating 10 on the sensor scale 3 and illuminates the first main grating 6 and the second main grating 7 radially formed on the first rotating disk 1 and the second rotating disk 2.

That is, the first main grating 6 and the second main grating 7 have a repeating slit pattern of a reflective portion and a non-reflective portion. The light reflected by the first main grating 6 irradiates the light receiving elements 11 ₁ and 11 ₂ through the first index gratings 8 ₁ and 8 ₂ formed on the sensor scale 3, respectively. The light reflected by the second main grating 7 irradiates the light receiving elements 12 ₁ and 12 ₂ through the first index gratings 9 ₁ and 9 ₂ formed on the sensor scale 3, respectively.

Detection signals from the respective light receiving elements 11 and 12 are input to the phase difference detection circuit. Between the first index gratings 8 ₁ and 8 _{2 and} between 9 ₁ and 9 ₂ are formed so as to obtain signals having an electrical angle of 90 degrees relative to the positional displacement of the rotating body. Index grid 8
_{Between 1} and 9 ₂ is formed so that a signal in phase with respect to the position displacement can be obtained when the angular acceleration is zero.

When the angular acceleration α is generated in the rotating body, the following (2) is generated between the first rotating disk 1 and the second rotating disk 2.
The relative angular displacement φ _m shown in (Equation) occurs. φ _m = {j / K} × α …………………………………… (2 formula) where K is the spring constant of the second rotary disk support 4 and j is the second rotary disk. 2. Moment of inertia Next, an example of the circuit configuration of the phase detection circuit is shown in a block diagram in FIG. The detection signals are photoelectrically converted by the light receiving elements 11 and 12, and converted into voltage signals by using the operational amplifiers 21 to 24.

Outputs V _i1 , V _i2 , V of the operational amplifiers 21 to 24 when the rotating body rotates and the angular acceleration α is generated in the rotating body.
_i3 and V _i4 are respectively expressed by (3 expression) to (6 expression). V _i1 = sin (θ _e ) ………………………………………… (3 formulas) V _i2 = cos (θ _e ) …………………………………… …… (Equation 4) V _i3 = sin (θ _e −φ _e ) ………………………………………… (Equation 5) V _i4 = cos (θ _e −φ _e ) …… …………………………………… (Equation 6) However, θ _e = 2 × 2πN _s × θ _m …………………………………… (Equation 7) φ _e = 2 × 2πN _s × φ _m = 2 × {2πN _s × (j / K)} × α (Equation 8) θ _m is the angular displacement of the first rotating disk 1 with respect to the sensor scale 3. N _s is the number of slits in the first rotating disk 1 or the second rotating disk 2 [the number of slits in both is the same]

These detection signals V _i1 , V _i2 , V _i3 and V _i4
Is calculated by the multipliers 31 to 34 and the adders / subtractors 25 and 26 as follows.
The calculation shown in (Expression 10) and (Expression 10) is performed, and the adder / subtractor 25, 26
Signals of sin (φ _e ) and cos (φ _e ) are obtained at the outputs of the above. V _O1 = V _i1 × V _i4 −V _i2 × V _i3 = sin (φ _e ) ……………………………………………… (Formula 9) V _O2 = V _i2 × V _i4 + V _i1 × V _i3 = cos (φ _e ) ………………………………………… (10 formulas)

By configuring this detection system so that the phase signal φ _e can be detected in a range sufficiently smaller than π / 2, the output V _O1 of the adder / subtractor 25 (shown by the V ₁ output signal in FIG. 2) is subjected to angular acceleration. It can be a detection signal. That is, FIG. 3 (a) shows an analog detection voltage waveform diagram of angular acceleration, and FIG. 3 (b) shows a range used as the angular acceleration detection voltage waveform (0 → 421, 0 → 422). Further, when the present detection system is configured so that the phase signal φ _e can be sufficiently larger than π / 2, the outputs V _O1 and V _O2 of the adder / subtractors 25 and 26 are converted into rectangular waves using a comparator, A digital angular acceleration detection signal can be obtained by the digitizing circuit 40 (the details of the circuit are shown in FIG. 4A) that counts the edge portion of the rectangular wave.

FIG. 4 is a detailed explanatory diagram of the digitizing circuit. 4 (a) is a block diagram showing the internal circuit configuration, FIG. 4 (b) is an angular acceleration analog signal waveform diagram, FIG. 4 (c) is a waveform shaping circuit output waveform diagram, and FIG. 4 (d) is edge detection & FIG. 4 (e) is a diagram showing a signal obtained by monitoring the digitized signal by the D / A converter 41, the edge detection waveform diagram of the direction discriminating means.

FIG. 5 is a diagram showing respective signal waveforms from when the rotating shaft reaches a constant speed to when the rotating shaft decelerates and stops. FIG. 5 (a) shows an angular velocity signal waveform, which starts rotation (time t ₁ ), gradually increases the speed (t ₁ → t ₄ ), reaches a constant speed (time t ₄ ), and continues it for a certain period, optimum deceleration begins at time t _5, is an explanatory view was stopped at t _8. 5 (b) is a diagram of the angular acceleration signal waveform, FIG. 5 (c) is a detailed diagram of the rising and falling of the waveform of the angular acceleration signal of FIG. 5 (b), and FIG. 5 (d) is an adder / subtractor (25 in FIG. 2). , 26) output signal waveform diagram, FIG. 5 (e) is the edge detection signal waveform diagram after waveform shaping of FIG. 5 (d), FIG.
(f) is the angular acceleration direction discrimination output signal waveform diagram of FIG. 5 (c), and FIG. 5 (g) is the signal waveform diagram of the angular acceleration digitized signal of FIG. 5 (c) monitored by a D / A converter. . Note that t ₂ , t ₃ , t
₆ and t ₇ are the times shown in the figure. It can be seen that the slit pitch of each slit may be reduced to increase the detection sensitivity.

(Embodiment 2) Further, according to the present invention, although not shown, the first disk-shaped rotating disk 1 fixed near the rotating shaft 5 in FIG. 1 and the first main grating 6 are flush with each other. A second rotating disc 2 formed above the rotating shaft 5 and a support means 4 (4 _a, 4 _b ...) For the second rotating disc 2 between the first rotating disc 1 and the second rotating disc 2.
As the first elastic disk 1 and the second elastic disk with the third elastic member.
Support part that fills the gap of the rotating disk 2 [no gap]
The first rotating disk 1, the third elastic member, and the third
The elastic member and the second rotating disk 2 may be fixed or welded with an adhesive. At this time, the materials of the first rotary disc 1, the second rotary disc 2, and the elastic member can be freely selected. That is, in the second embodiment,
As a means for fixing the support member 4 for supporting the second rotary disk 2 to the first rotary disk 1, the elastic coefficient of the two rotary disks is between the first rotary disk 1 and the second rotary disk 2. Between two rotating discs 1 and 2 are filled with different concentric circumferential zones, and angular acceleration is detected by integrally fixing the first rotating disc 1, the circumferential zone, and the second rotating disc 2 together. It is a vessel.

As can be seen from the above description, the present invention is
The three-grating system is adopted in which the light emitted from the light source is sent to the light-receiving element as a detection signal through three gratings: a light source grating, a main grating, and an index grating. For the basic principle of the 3-grid system, see SPIE [Society of Photo
-Optical Instrumentation Engineers] Vol.136 Ist Eu
ropean Congress Optics Appli-ed to Metorogy (1977)
Shown in p325-p332. As a rotary encoder using a three-grating system, there is Japanese Patent Application No. 7-289756 (submitted date: November 8, 1995) proposed by the present applicant. In the three-grating system, the grating pitch can be reduced even under the condition that the gap between the gratings is wide. Further, when a reflection type optical system is formed in which the distance between the main grating and the light source grating is equal to the distance between the main grating and the index grating, the deterioration of the detection signal due to the gap variation between the gratings is small. To have.

[0020]

As is apparent from the description of the anomaly, the present invention configures the optical system using the principle of the three-grating system, and can reduce the grating pitch of each grating, resulting in small size and high sensitivity. This has the effect of realizing a high angular acceleration detector. In addition, the gap between the rotating disk and the sensor scale can be increased, and the deterioration of the detection signal due to the gap variation between the gratings is small, so that it is possible to realize an angular acceleration detector that is strong against vibration and impact. You can

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention and explaining a state / positional relationship of respective lattices thereof.

FIG. 2 is a block diagram showing a circuit configuration example of a phase detection circuit that processes a detected phase signal according to the first embodiment of the present invention.

FIG. 3 shows a phase detection signal according to the first embodiment of the present invention, (a) is an analog signal waveform diagram thereof, and (b) is a partial detailed explanatory diagram of (a).

FIG. 4 is a detailed explanatory diagram of a digitizing circuit, (a) is a block diagram showing an internal circuit configuration, (b) is an angular acceleration analog signal waveform diagram, and (c) is a waveform shaping circuit output waveform diagram. (d) is the edge detection waveform diagram of the edge detection & direction discrimination means. (e) is the signal waveform diagram of the digitized signal monitored by the D / A converter.

[Fig. 5] Fig. 5 shows various signal waveforms from when the rotating shaft reaches a constant speed to when it decelerates to stop. (A) is an angular velocity signal waveform diagram (b) is an angular acceleration signal waveform diagram (c) Details of rising and falling of the angular acceleration signal waveform in (b) (d) is the angular acceleration analog signal waveform in (c) (e) is the edge detection signal in (d) (f) is in (c) Angular acceleration direction discrimination output signal waveform diagram (g) Signal waveform diagram of angular acceleration digitized signal of (c) monitored by D / A converter

FIG. 6 shows a configuration of a conventional example, (a) is a circuit configuration diagram thereof, and (b) is a lattice plane explanatory diagram thereof.

FIG. 7 is a diagram illustrating a change in the intersection position of the first slit row and the second slit row in the conventional example.

[Explanation of symbols]

1 1st rotating disk 2 2nd rotating disk 3 Sensor scale 4 _, 4 _a, 4 _b 2nd rotating disk support part 5 Rotating shaft 6 1st main grating 7 2nd main grating 8, 8 ₁ , 8 ₂ 1st index grating 9, 9 ₁ , 9 ₂ 2nd index grating 10 Light source grating 11 ₁ , 11 ₂ , 12 ₁ , 12 ₂ Light receiving element 13 Light source 14,15 DC constant voltage source 16,17,18,19 Negative feedback resistor 30 Phase detection circuit 40 Digitizing circuit 40a Wave shaping circuit 40b Edge detection & direction discrimination (means) 40c Up / down counter 41 D / A converter 50 Rigid disk (conventional example) 51 1st slit row (conventional example) 56 Rotation axis (conventional example) 60 Elastic disk (conventional example) 61 Second slit row (conventional example) 71,81 Light emitting diode (conventional example) 72,82 Semiconductor position detector (conventional example) α Angular acceleration r Distance from intersection of slit to disk center ( Conventional example) δ Intersection angle (conventional example)

Claims (1)

[Claims] 1. A diffused light source for emitting diffused light, a radial light source grating for limiting light from the diffused light source to generate a radial linear light source, and a first rotating disk fixed coaxially to a rotating body. And a plurality of index gratings that are arranged on the first rotating disk in a radial pattern at equal intervals, and a plurality of index gratings that receive reflected light reflected by the main grating. A second rotating disk having the same number of radial second main gratings arranged on the same plane as the rotating disk at equal intervals, and an elastic body supporting means for supporting the second rotating disk on the first rotating disk. A plurality of index gratings are arranged on the sensor scale, respectively, and are reflected from the main grating and the second main grating of the first rotating disk and the second rotating disk, respectively. A first index grating and a second index grating for respectively receiving reflected light, and a plurality of light receiving elements for receiving the reflected light transmitted through the first index grating and converting the reflected light into an electric signal. Angular acceleration detector.