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Patent Analysis of

PHOTOELECTRIC ANGULAR POSITION SENSOR

Updated Time 15 March 2019

Patent Registration Data

Publication Number

GB1523679A

Application Number

GB1976050676

Application Date

06 December 1976

Publication Date

06 September 1978

Current Assignee

SLADKOV G V,GUMEN V F KALININSKAYA T V LOPAREV R N

Original Assignee (Applicant)

SLADKOV G V,GUMEN V F KALININSKAYA T V LOPAREV R N

International Classification

G01D5/26,G01D5/30

Cooperative Classification

G01D5/30

Inventor

Abstract

1523679 Detecting angular position V F GUMEN T V KALININSKAYA R N LOPAREN and G V SLADKOV 6 Dec 1976 50676/76 Heading G1A In a photo-electric angular position sensor for a stepping motor, a mirror pyramid 8 is positioned on top of the motor's shaft 3. As the shaft rotates the pyramid reflects light from a source 5 as shown via one of a series of mirrors 10 so as to scan across a series of ends of light guides 12. Each guide leads to a photo-electric receiver 14. The pulse outputs of the photo-electric receivers (which represent the positions passed) may be given a direction or sign by processing them, Fig. 4 (not shown) with the pulse signal outputs of a corresponding set of photo-electric receivers 24 forming a corresponding optical system 15, 19, 22. A condenser lens 25, Fig. 3 (not shown) may be placed between the emitting end of each light guide and its corresponding photo-electric receiver.

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Claims

**WARNING** start of CLMS field may overlap end of DESC **.

of the photoelectric sensor to a power supply unit 32 (Figure 4).

The disclosed photoelectric position sensor of a stepping motor operates as follows.

The luminous flux from the filament lamp 5 (Figure 1) is formed into a light beam 7 by the focusing lens 6 of the light source 4 and the beam is directed upon the mirror pyramid 8 secured on the shaft 3 of the stepping motor. Depending on the angular position of the pyramid 8, the light beam 7 reflected therefrom falls upon a respective mirror 10 of the faceted reflector 9. The light beam 7 is reflected from the reflector and illuminates a respective light guide 12, thus actuating the associated photoelectric receiver 14.

When the shaft 3 turns to the next position, the light beam 7 is reflected from the pyramid 8 and the same mirror 10 and falls upon the light guide 12 next adjacent in the direction of rotation and is sensed by the respective photoelectric receiver 14. The information from this receiver 14 is fed to the rectangular pulse shaper 27 (Figure 4) as a photo-current pulse indicating the position has been passed.

When the shaft 3 (Figure 1) has turned through a number of positions equal to the number of the light guides 12, the light beam 7 is transferred to the next mirror 10 in the rotation direction. And, finally, when the shaft 3 has turned through a number of positions equal to the product of the number of light guides 10 and the number of facets of the reflector 9, that is the number of mirrors 10, the light beam 7 is transferred to the next face of the mirror pyramid 8 in the direction of rotation.

The product of the number of faces of the mirror pyramid 8 multiplied by the number of facets of the reflector 9 and by the number of light guides 12 corresponds to the number of identifiable angular positions of the shaft 3 for one revolution of the stepping motor.

In this case the same components of the photoelectric sensor are employed several times to obtain information on the positions passed, which ensures small dimensions of the sensor while retaining a high resolution.

In order to determine the direction of rotation of the shaft 3 of the stepping motor, an electric signal is taken from the photoelectric receiver 24, which is phase-shifted with respect to the signal from the photoelectric receiver 14. The manner in which the light beam 18 is treated to reach the photoelectric receiver 24 is analogous to that of the light beam 7 to the photoreceiver 14.

For clarity it is pointed out that the term "mirror pyramid" is used herein to denote a reflector having a plurality of reflective surfaces of which the median normals are equispaced about and equally inclined to an axis, while the term "faceted reflector" is used to denote any arrangement providing a plurality of reflective surfaces equiangularly spaced about a common axis and arranged to direct received light towards a common position.

WHAT WE CLAIM IS

1. A photoelectric angular position sensor comprising a stationary source of a light beam, a mirror pyramid as herein defined secured on a rotatable shaft of which the position is to be sensed and placed in the path of the light beam from said source, a faceted reflector as herein defined placed in the path of the light beam reflected from a respective face of the mirror pyramid during rotation of the shaft, a plurality of light guides, the number of which is determined by the ratio between the number of positions required to be identified in revolution of the shaft and the product of the number of faces of the mirror pyramid multiplied by the number of facets of the reflector, one end of each said light guide being placed in the path of the light beam reflected from a respective facet of the mirror reflector, and a respective photoelectric receiver being located to receive light emerging from the other end of each of said light guides.

2. A photoelectric angular position sensor in accordance with claim 1, wherein a respective condenser lens is placed in the path of each light beam between the end of the light guide which faces the photoelectric receiver and the photoelectric receiver itself.

3. A photoelectric angular position sensor substantially as herein described with reference to Figures 1 and 2 and 4 of the accompanying drawings.

4. A modification of the photoelectric angular position sensor claimed in claim 3, substantially as herein described with reference to Figure 3 of the accompanying drawings.

5. A photoelectric angular position sensor in accordance with any one of the preceding claims when used to sense the angular position of the shaft of a stepping motor.

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Claim Tree

  • 1
    1. A photoelectric angular position sensor comprising
    • a stationary source of a light beam, a mirror pyramid as herein defined secured on a rotatable shaft of which the position is to be sensed and placed in the path of the light beam from said source, a faceted reflector as herein defined placed in the path of the light beam reflected from a respective face of the mirror pyramid during rotation of the shaft, a plurality of light guides, the number of which is determined by the ratio between the number of positions required to be identified in revolution of the shaft and the product of the number of faces of the mirror pyramid multiplied by the number of facets of the reflector, one end of each said light guide being placed in the path of the light beam reflected from a respective facet of the mirror reflector, and a respective photoelectric receiver being located to receive light emerging from the other end of each of said light guides.
    • 2. A photoelectric angular position sensor in accordance with claim 1, wherein
      • a respective condenser lens is placed in the path of each light beam between the end of the light guide which faces the photoelectric receiver and the photoelectric receiver itself.
    • 5. A photoelectric angular position sensor in accordance with any one of the preceding claims when used to sense the angular position of the shaft of a stepping motor.
  • 3
    3. A photoelectric angular position sensor substantially as herein described with reference to Figures 1 and 2 and 4 of the accompanying drawings.
    • 4. A modification of the photoelectric angular position sensor claimed in claim 3, substantially as herein described with reference to Figure 3 of the accompanying drawings.
See all 2 independent claims

Description

(54) IMPROVED PHOTOELECTRIC ANGULAR POSITION SENSOR

(71) We, VALERY FEDOROVICH GUMEN, of Kirovsky prospekt, 27, kv. 112, Leningrad, USSR., and TATYANA VASILIEVNA KALININ SKAYA, of prospekt Metallistov, 21, korpus 2, kv. 98. Leningrad, USSR., and ROBERT

NIKOLAEVICH LOPAREV, of Torzhkovskaya ulitsa, 16, kv. 38, Leningrad, USSR., and

GERMAN VLADIMIROVICH SLADKOV, of ulitsa

B.Podyache-skaya, 23, kv. 12, Leningrad, USSR., all citizens of the Union of Socialist

Republics., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to a photoelectric angular position sensor which may be used to sense the angular position of the shaft of a stepping motor. The positional information thus obtained may be used for the processing of control pulses fed to the stepping motor.

In order to improve the efficiency, response and accuracy of a stepping motor, such as is employed in coordinate plotters, programmed machines, sensitometric and other follow-up instrumental systems, as well as various mechanisms featuring digital control systems, it is required that the operational speed of the stepping motor shall be increased and this involves the installation of a sensor on the shaft to provide for the position sensing of the stepping motor.

Stepping motors find extensive applications in modern practice and the design of the stepping motor position sensors should be uncomplicated and reliable. Besides, the present tendency to reduce the separation of the discrete motor positions (the length of the steps) calls for sensors of high resolution without, however, producing an excessive moment of inertia on the shaft of the motor.

It is an object of this invention to provide a photoelectric angular position sensor suitable for use with a stepping motor, which possesses high resolution and in which a small increase in moment of inertia is produced by the sensor components on the shaft of the stepping motor.

According to the present invention there is provided a photoelectric angular position sensor comprising a stationary source of a light beam, a mirror pyramid as herein defined secured on a rotatable shaft of which the position is to be sensed and placed in the path ofthe light beam from said source, a faceted reflector as herein defined placed in the path of the light beam reflected from a respective face of the mirror pyramid during rotation of the shaft, a plurality of light guides, the number of which is determined by the ratio between the number of positions required to be identified in revolution of the shaft and the product of the number of faces of the mirror pyramid multiplied by the number of facets of the reflector, one end of each said light guide being placed in the path of the light beam reflected from a respective facet of the mirror reflector, and a respective photoelectric receiver being located to receive light emerging from the other end of each of said light guides.

It is advisable that the photoelectric sensor shall comprise a respective condensor lens placed in the path of each light beam between the end of the light guide which face the photoelectric receiver and the photoelectric receiver itself.

The photoelectric angular position sensor to be described possesses high resolution, small dimensions and a low moment of inertia produced by the mirror pyramid on the shaft of the stepping motor. This is achieved because the mirror pyramid employed in the sensor has only a small number of faces. Such a pyramid is not large and adds a minimum moment of inertia to the shaft of which the position is sensed. In this case higher resolution of the sensor is attained not by increasing the number of faces of the mirror pyramid, but by the use of structural elements, specifically the faceted reflector and light guides placed in the casing and producing no additional moment of inertia on the shaft of the stepping motor.

With such a design the sensor realizes the principle of multiple employment of the same components of the sensor in one revolution of the shaft.

A specific embodiment of the invention as applied to sensing the angular position of the shaft of a stepping motor will now be described in greater detail with reference to the accompanying drawings, in which:

Figure 1 shows a partly sectional side view of a sensor frame, facets of the reflector and a longitudinal section view of the light source of a photoelectric position sensor for a stepping motor, which is secured on the casing of a stepping motor;

Figure 2 shows a partly sectional plan view of the sensor frame and the facets of the mirror reflector of the photoelectric sensor shown in Figure 1;

Figure 3 shows a sectional view of a mounting member with a light guide, a condenser and a photoelectric receiver as used in the photoelectric position sensor secured therein; and

Figure 4 shows a block diagram of electrical circuitry for the described photoelectric sensor and a conversion circuit for the electrical signals taken from its receivers.

The photoelectric angular position sensor for a stepping motor which is shown in

Figures 1 and 2, comprises a frame 1 (Figure 1) secured on the casing 2 of a stepping motor (the figure shows its shaft only). The frame 1 carries a light source 4 including a filament lamp 5 and a focusing lens 6 forming a light beam 7. A mirror pyramid 8 is placed in the path of the beam 7 and is rigidly secured on the shaft 3 of the stepping motor.

A faceted reflector 9 is provided in this embodiment of the sensor by a group of separate mirrors 10 each of which forms one of the facets of the reflector and which are located in the path of the light beam 7 reflected from the faces of the mirror pyramid 8. Each mirror 10 (Figure 2) is secured to the frame 1 by means of a respective adjusting screw 11.

The photoelectric sensor further comprises a group of light guides 12, made in this embodiment as fibre optics light guides, the number of which is dependent upon the ratio between the number of discrete positions to be identified in one revolution of the stepping motor and the product of the number of faces of the mirror pyramid 8 multiplied by the number of facets of the mirror reflector 9, that is in this embodiment by the number of mirrors 10. The light guides 12 are secured to the frame 1 by means of a mount 13 preferably made of a dielectric material and each has a first end positioned to receive the light beam 7 (Figure 1) reflected from each facet, that is each mirror 10, of the faceted reflector 9.A photoelectric receiver 14 is also secured in the mount 13 and, in the present embodiment, is formed by a photodiode located in the immediate vicinity of the other end of the light guide 12.

In order to make the photoelectric sensor sensitive to the direction of rotation of the shaft 3 of the stepping motor, the sensor may be additionally provided with a second light source 15 comprising a filament lamp 16 and a focusing lens 17 arranged to form a light beam 18 and to direct it on to the mirror pyramid 8. A faceted reflector 19 analogous to the reflector 9 is placed in the path of the light beam 18 reflected from the faces of the mirror pyramid 8. The mirrors 20 (Figure 2) of the reflector 19 are secured to the frame 1 by means of screws 21 and shifted by a quarter of the distance representing one step of the stepping motor with respect to the mirrors 10 of the reflector 9.

Light guides 22 equal in number to the light guides 12 are placed in the path of the light beam 18 (Figure 1) reflected from the mirror plates 20 (Figure 2) of the reflector 19.

Each light guide 22 is secured to the frame 1 by means of a mount 23, wherein there is also secured a photoelectric receiver 24 (Figure 1) similar to the photoelectric receiver 14.

A second embodiment of a photoelectric position sensor of a stepping motor, analogous to the one described above, is illustrated by Figure 3. In this embodiment the light beam 7 emerging from the ends of the light guide 12 facing the photoelectric receiver 14 is concentrated upon the photoelectric receiver through a condenser which is conveniently a focusing lens 25 placed in the gap between the end of the light guide 12 and the photoelectric receiver 24. In the illustrated embodiment the lens 25 is secured in the mount 13 by means of a bushing 26, the photoelectric receiver 14 being also secured in the mount.

In the operation of the above described photoelectric sensor the photoelectric receiver 14, the output signal of which is almost sinusoidal, is conveniently connected to a rectangular pulse shaper 27 (Figure 4). A sequence of rectangular pulses, which corresponds to the number of past positions of the stepping motor, is thus produced at the output 28 of the pulse shaper 27.

In order to determine the direction of rotation of the shaft 3 (Figure 1) of the stepping motor, the photoelectric receiver 24 is in operation also connected to a rectangular pulse shaper 29 (Figure 4), which in turn is connected to the input of a phasesensitive converter 30 of which the other input is joined to the output 28 of the pulse shaper 27. A voltage of alternating polarity which depends on the direction of rotation of the shaft 3 (Figure 1) of the stepping motor, is produced at an output 31 of the phasesensitive converter 30.

The lamps 5 and 16 of the light sources 4 and 15 respectively are connected in operation of the photoelectric sensor to a power supply unit 32 (Figure 4).

The disclosed photoelectric position sensor of a stepping motor operates as follows.

The luminous flux from the filament lamp 5 (Figure 1) is formed into a light beam 7 by the focusing lens 6 of the light source 4 and the beam is directed upon the mirror pyramid 8 secured on the shaft 3 of the stepping motor. Depending on the angular position of the pyramid 8, the light beam 7 reflected therefrom falls upon a respective mirror 10 of the faceted reflector 9. The light beam 7 is reflected from the reflector and illuminates a respective light guide 12, thus actuating the associated photoelectric receiver 14.

When the shaft 3 turns to the next position, the light beam 7 is reflected from the pyramid 8 and the same mirror 10 and falls upon the light guide 12 next adjacent in the direction of rotation and is sensed by the respective photoelectric receiver 14. The information from this receiver 14 is fed to the rectangular pulse shaper 27 (Figure 4) as a photo-current pulse indicating the position has been passed.

When the shaft 3 (Figure 1) has turned through a number of positions equal to the number of the light guides 12, the light beam 7 is transferred to the next mirror 10 in the rotation direction. And, finally, when the shaft 3 has turned through a number of positions equal to the product of the number of light guides 10 and the number of facets of the reflector 9, that is the number of mirrors 10, the light beam 7 is transferred to the next face of the mirror pyramid 8 in the direction of rotation.

The product of the number of faces of the mirror pyramid 8 multiplied by the number of facets of the reflector 9 and by the number of light guides 12 corresponds to the number of identifiable angular positions of the shaft 3 for one revolution of the stepping motor.

In this case the same components of the photoelectric sensor are employed several times to obtain information on the positions passed, which ensures small dimensions of the sensor while retaining a high resolution.

In order to determine the direction of rotation of the shaft 3 of the stepping motor, an electric signal is taken from the photoelectric receiver 24, which is phase-shifted with respect to the signal from the photoelectric receiver 14. The manner in which the light beam 18 is treated to reach the photoelectric receiver 24 is analogous to that of the light beam 7 to the photoreceiver 14.

For clarity it is pointed out that the term "mirror pyramid" is used herein to denote a reflector having a plurality of reflective surfaces of which the median normals are equispaced about and equally inclined to an axis, while the term "faceted reflector" is used to denote any arrangement providing a plurality of reflective surfaces equiangularly spaced about a common axis and arranged to direct received light towards a common position.

WHAT WE CLAIM IS

1. A photoelectric angular position sensor comprising a stationary source of a light beam, a mirror pyramid as herein defined secured on a rotatable shaft of which the position is to be sensed and placed in the path of the light beam from said source, a faceted reflector as herein defined placed in the path of the light beam reflected from a respective face of the mirror pyramid during rotation of the shaft, a plurality of light guides, the number of which is determined by the ratio between the number of positions required to be identified in revolution of the shaft and the product of the number of faces of the mirror pyramid multiplied by the number of facets of the reflector, one end of each said light guide being placed in the path of the light beam reflected from a respective facet of the mirror reflector, and a respective photoelectric receiver being located to receive light emerging from the other end of each of said light guides.

2. A photoelectric angular position sensor in accordance with claim 1, wherein a respective condenser lens is placed in the path of each light beam between the end of the light guide which faces the photoelectric receiver and the photoelectric receiver itself.

3. A photoelectric angular position sensor substantially as herein described with reference to Figures 1 and 2 and 4 of the accompanying drawings.

4. A modification of the photoelectric angular position sensor claimed in claim 3, substantially as herein described with reference to Figure 3 of the accompanying drawings.

5. A photoelectric angular position sensor in accordance with any one of the preceding claims when used to sense the angular position of the shaft of a stepping motor.

**WARNING** end of DESC field may overlap start of CLMS **.

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