CN114689097A

CN114689097A - Sensing part of ultrasonic rotary encoder

Info

Publication number: CN114689097A
Application number: CN202210275919.6A
Authority: CN
Inventors: 韩志乐; 简小华
Original assignee: Suzhou Institute of Biomedical Engineering and Technology of CAS
Current assignee: Suzhou Institute of Biomedical Engineering and Technology of CAS
Priority date: 2020-06-18
Filing date: 2020-06-18
Publication date: 2022-07-01
Anticipated expiration: 2040-06-18
Also published as: CN114689098A; CN111748770B; CN114689098B; CN114689097B; CN111748770A

Abstract

The invention relates to a sensing component of an ultrasonic rotary encoder, which comprises a stator, a rotor, an ultrasonic sensor and a plurality of grid bars, wherein the echo signals formed by the grid bars and the echo signals formed by the side wall of the stator have strong and weak differences, grids are formed between every two adjacent grid bars, the grids formed by the grids arranged in sequence form grids, the grids are provided with a plurality of groups and correspond to the ultrasonic sensor one by one, each group of grids are distributed side by side along the length direction of the stator, the angle deviation of 180 degrees/N is formed between every two adjacent groups of grids in sequence, N is the number of the grid bars, and the ultrasonic sensor is positioned in an ultrasonic echo detection area formed by the grids. According to the invention, more information can be obtained through the corresponding arrangement of the plurality of grids and the ultrasonic sensor, so that the rotation angle and the rotation speed of the stator can be accurately calculated by the ultrasonic rotary encoder, and the error of the grids on ultrasonic echo detection is greatly reduced.

Description

Sensing part of ultrasonic rotary encoder

This application is a divisional application of a grating formation process entitled ultrasonic rotary encoder, filed 18/6/2020 and having application number 2020105620646.

Technical Field

The invention belongs to the field of ultrasonic encoders, and particularly relates to a sensing part of an ultrasonic rotary encoder.

Background

At present, a rotary encoder is also called a shaft encoder, and is a device that mainly converts a rotational position or a rotational amount into an electronic signal, and is applicable to industrial control, robotics, a dedicated lens, and the like.

The rotary encoder is mainly divided into an absolute encoder and an incremental encoder, wherein the incremental encoder calculates the rotating speed and the relative position by using a pulse detection mode and can output information related to rotary motion; an absolute type encoder will output the absolute position of the rotating shaft, which can be considered as an angle sensor.

Moreover, the operation modes of the encoder are generally classified into mechanical type, optical type, electromagnetic type, induction type, capacitance type and the like, the sensors combine the detection element and the processing circuit together, the structure is large, the diameter is generally more than 15mm, and the sensors cannot be well applied to the fields with narrow structures.

Meanwhile, in an ultrasonic encoder, motion information of a rotating shaft is mainly acquired through the intensity of an echo of ultrasonic waves, the intensity of the echo is mainly determined by a grating, and the current grating is generally composed of a large number of parallel slits with equal width and spacing, and is generally an optical device called as a grating, which is divided into a reflection grating, a transmission grating and the like. The grating is generally a planar structure, and is usually formed by photolithography, laser cutting, etching, and other techniques, in which a plurality of parallel notches are engraved on the surface of a specific material, such as glass or metal, to form a light-transmitting grating and an inverse grating in a staggered arrangement.

However, because the grating has high precision requirement and small size, the difficulty of manufacturing the grating on the surface of the cylinder is high, and the grating is usually manufactured by a planar grating curling method, which is easy to introduce errors at the curled joint.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a brand new sensing part of the ultrasonic rotary encoder.

In order to solve the technical problems, the invention adopts the following technical scheme:

a sensing component of an ultrasonic rotary encoder is used for obtaining detection information and comprises a stator with a circular and straight tube-shaped cross section, a rotor arranged in the stator in a way of freely rotating around the central line direction of the stator, an ultrasonic sensor fixedly arranged at the end part of the rotor extending into the stator, and a plurality of grid bars uniformly distributed around the circumferential direction of the stator, wherein the echo signals formed by the grating bars and the echo signals formed by the side wall of the stator have different intensity, and grids are formed between every two adjacent grid bars, the grids arranged in sequence form grids, the grids are provided with a plurality of groups, the ultrasonic sensors are in one-to-one correspondence, each group of grids are distributed side by side along the length direction of the stator, 180 DEG/N angular deviation is formed between every two adjacent groups of grids in sequence, N is the number of grid bars, and the ultrasonic sensors are located in an ultrasonic echo detection area formed by the grids.

Preferably, the echo signals formed by the grating strips are stronger than the echo signals formed by the stator side walls.

Furthermore, the stator is made of plastic or rubber, and the grid bars are made of metal coatings or metal pieces.

According to a specific implementation and preferred aspect of the invention, the stator is formed with a plurality of elongated slots, each elongated slot is a circular arc segment centered at the center of the stator, and each elongated slot extends in the length direction along the stator, wherein the grid bars are in one-to-one correspondence with the elongated slots, and the grid bars are disposed in the elongated slots.

Preferably, the elongate slot is located on the outer wall surface of the stator.

Preferably, the groove depth of each long-shaped groove is equal, and the distance between the groove bottom surface and the corresponding inner wall of the stator is 1/6-1/2 of the wall thickness of the stator.

Preferably, the grid bars are metal coatings formed in the long grooves through spraying, evaporation or sputtering, and the thickness of the metal coatings is equal to the depth of the corresponding long grooves.

According to a further embodied and preferred aspect of the invention, the rotor is the shaft to be tested and has a diameter greater than or equal to 0.3 mm; the inner diameter of the stator is more than or equal to 0.4mm, and the outer diameter of the stator is more than or equal to 0.5 mm.

According to still another embodiment and preferred aspect of the present invention, a mounting groove extending along a length direction thereof is formed at an end of the rotor, and the plurality of ultrasonic sensors are arranged side by side in the mounting groove.

In addition, each of the gratings and one of the ultrasonic sensors constitute a set of information acquisition units, and the ultrasonic rotary encoder further includes an information acquisition unit having a single grating bar, wherein an angular deviation of 180 °/N is also formed between the single grating bar and the grating of the adjacent grating, and N is the number of grating bars. Under the action of a single grid bar, each motion period can be easily seen, so that the ultrasonic rotary encoder can make accurate judgment conveniently.

Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages:

according to the invention, more information can be acquired through the corresponding arrangement of the plurality of grids and the ultrasonic sensor, so that the rotating angle and the rotating speed of the stator can be accurately calculated by the ultrasonic rotary encoder, and the error of the grids on ultrasonic echo detection is greatly reduced.

Drawings

FIG. 1 is a schematic structural view (partially in section) of an ultrasonic rotary encoder of the present invention;

fig. 2a, 2b, 2c and 2d are corresponding schematic views of the state in step 1);

FIGS. 3a and 3b are schematic views of the corresponding states in step 2);

FIGS. 4a and 4b are schematic views of the corresponding states in step 3);

FIGS. 5a and 5b are schematic views of the corresponding states in step 4);

FIG. 6 is a schematic view of the structure of an ultrasonic rotary encoder of the present invention (absolute type encoder);

wherein: 1. a sensor component; 10. a stator; 11. a rotor; 110. mounting grooves; 12. an ultrasonic sensor; 13. grid bars; 2. a rotation transmission member; 20. a rotating part; 21. an information transmission unit; 3. a signal processing section; 4. an inner support member; 5. a separation sleeve; 6. a layer of material; 7. coating; s, a grid area; f. a non-grid area; c. a long-shaped groove; q, an information acquisition unit.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise explicitly specified or limited, a first feature "on" or "under" a second feature may be directly contacted with the first and second features, or indirectly contacted with the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

As shown in fig. 1, the ultrasonic rotary encoder disclosed in the present embodiment includes a sensor unit 1, a rotary transmission unit 2 (which may be a slip ring, a rotary transformer, a rotary capacitor, a rotary fiber coupler, etc.), and a signal processing unit 3, wherein the rotary transmission unit 2 includes a rotary part 20 for driving a detected shaft to rotate around its axis direction, and an information transmission part 21 communicating with the sensor unit 1 and the signal processing unit 3, detection information obtained by the sensor unit 1 is transmitted to the signal processing unit 3 by the information transmission part 21, and the signal processing unit 3 performs signal analysis to obtain measurement information.

The sensor component 1 comprises a stator 10 with a circular and straight-tube-shaped cross section, a rotor 11 arranged inside the stator 10 in a freely rotating mode around the center line direction of the stator 10, an ultrasonic sensor 12 fixedly arranged at the end part of the rotor 11, wherein the end part of the stator 10 extends into the rotor 11, and a plurality of grid strips 13 uniformly distributed around the circumference of the stator 10, echo signals formed by the grid strips 13 are stronger than echo signals formed by the side wall of the stator, grids are formed between two adjacent grid strips 13, grids are formed by the grids arranged in sequence, and the ultrasonic sensor 13 is positioned in an ultrasonic echo detection area formed by the grids.

In this example, the stator 10 is a plastic part and the grid bars 13 are metal parts.

Specifically, the rotor is a detected shaft, and the diameter of the rotor is greater than or equal to 0.3 mm; the inner diameter of the stator is more than or equal to 0.4mm, and the outer diameter of the stator is more than or equal to 0.5 mm.

In this example, the outer diameter of the stator 10 is 1.0mm, the inner diameter of the stator is 0.8 to 0.9mm, and the outer diameter of the rotor 11 is 0.6 mm.

Specifically, the grid forming process comprises the following steps:

referring to fig. 2a to 2d (wherein fig. 2a is a front view, fig. 2b is a right view; fig. 2c is a front view, fig. 2d is a right view), 1), the stator 10 is supported on the inner wall by the inner supporting member 4 in a fixed shape, then the stator 10 is sleeved with the separating sleeve 5 which divides the stator 10 into the grid area s and the non-grid area f, and then the stator 10 in the grid area s is coated with the material layer 6 which is easy to be peeled off from the surface of the stator;

2) a plurality of elongated grooves c (shown in fig. 3a, which is a front view) are formed on the wall surface of the stator 10 and are recessed inward from the surface of the material layer 6, wherein the cross section of each elongated groove c is the same, each elongated groove c is an arc segment (shown in fig. 3b, which is a right view from the middle of the elongated groove) with the center of the stator as a center, the plurality of elongated grooves are uniformly distributed around the circumference of the stator, and each elongated groove extends along the length direction;

3) forming a coating 7 with a uniform thickness on the groove surface of the elongated groove c and the surface of the material layer 6 not forming the elongated groove (see fig. 4a and 4b, wherein fig. 4a is a front view, and fig. 4b is a right view from the middle of the elongated groove), wherein the echo signal formed by the coating 7 is stronger than the echo signal formed by the side wall of the stator 10;

4) and stripping off the material layer 6 (shown in a combined view of fig. 5a and 5b, wherein fig. 5a is a front view, and fig. 5b is a right view from the middle of the elongated slot) with the coating 7 formed on the surface from the surface of the stator 10, and drawing out the inner supporting member 4 from the inside of the stator 10, wherein the coating formed in each elongated slot c is a grid strip 13, a grid is formed between every two adjacent grid strips 13, and a plurality of grids arranged in sequence form the grid.

To further facilitate the above-described grid formation, the following measures are also adopted in this example.

In step 1), the material layer is a glue layer capable of dissolving in water, so that once the grid is formed, the whole stator is placed in water, and the material layer on the surface of the stator is quickly removed by the dissolution of the material layer.

Of course, the material layer can be peeled off conveniently by adopting a water-insoluble glue layer and a corresponding means of heating (or irradiating to degum the glue layer), parylene film layer and external force peeling.

In step 2), the machining is mechanical machining or laser machining, but it should be reminded that the groove depth of each long-shaped groove is equal, and the distance between the groove bottom and the corresponding inner wall of the stator is 3/5 of the stator wall thickness.

Preferably, in step 3), the stator is kept spinning down, and the coating layer is formed on the outer circumference of the stator by spraying, evaporation, or sputtering. In this way, it is ensured that each grating strip is formed with equal thickness, and thus each grating strip provides equal echo intensity.

In this example, the metal material is an acoustic reflective material, such as one of stainless steel, gold, aluminum, and the like, and is formed in the elongated groove on the outer periphery of the stator by vapor deposition.

As shown in fig. 6, a mounting groove 110 extending along the longitudinal direction of the rotor 11 is formed at the end of the rotor, a plurality of ultrasonic sensors 12 are arranged in the mounting groove 110 side by side, the grids correspond to the ultrasonic sensors 12 one by one, and the formed ultrasonic echo detection regions are distributed side by side along the longitudinal direction of the stator 10, an angular deviation of 180 °/N is formed between every two adjacent sets of grids, and N is the number of grid bars. Through the corresponding setting of a plurality of grids and ultrasonic sensor to can acquire more information, thereby make the turned angle and the slew velocity of the accurate calculation stator of supersound rotary encoder.

Each of the gratings and one ultrasonic sensor 13 constitute a group of information acquisition units q, and the ultrasonic rotary encoder further includes an information acquisition unit q having a single grating bar, wherein an angular deviation of 180 °/N is also formed between the single grating bar 13 and the grating of the adjacent grating, and N is the number of grating bars. Under the action of a single grid bar, each motion period can be easily seen, so that the ultrasonic rotary encoder can make accurate judgment conveniently.

Therefore, in this example, there are three groups of information obtaining units q, namely 3-bit gray code, i.e. absolute type encoder.

Also, the number of gray-coded bits can be increased by increasing the number of scale lines and the number of ultrasonic sensors, thereby increasing the resolution of the encoder.

In addition, taking an ultrasonic probe with a center frequency of 50MHz as an example, the transverse resolution of the ultrasonic probe is about 200um, and the size of the resolution determines that the minimum scale interval of the grating bars on the stator cannot be smaller than the transverse resolution of the ultrasonic probe, so that the required strong and weak signals can be acquired.

Assuming a lateral resolution of λ, the angular resolution of the encoder is up to 360 °/λ. We can improve the accuracy of the encoder by increasing the number of sensors.

In summary, in the embodiment, the sensor is designed by using the intensity of the reflected echoes of different reflectors when the ultrasonic waves encounter, and the rotation speed and the position of the rotating object are measured by using the principle of rotation coding.

Meanwhile, the ultrahigh frequency miniature ultrasonic sensor can be used for designing the structure of the encoder to be used for measuring the rotating speed and the position of a detected shaft with the diameter of more than 0.3mm, so that the ultrahigh frequency miniature ultrasonic sensor can be applied to the field of high-precision detection, such as in-vivo interventional medical imaging equipment, can effectively correct image distortion (NURD) and the like caused by rotational distortion, ensures the accuracy of images and has very good advantages.

The detection process of this embodiment is as follows:

(1) replacing the rotor with the detected shaft, forming a mounting groove at the end part of the rotor, and correspondingly distributing the ultrasonic sensors in the mounting groove and correspondingly positioning the ultrasonic sensors in an ultrasonic echo detection area formed by a plurality of grid bars;

(2) starting the rotary transmission component and the ultrasonic sensor, and acquiring signals of ultrasonic echoes under the synchronous rotation of a detected shaft and the ultrasonic sensor, wherein when the transmitting surface of the ultrasonic sensor is parallel to the tangent line of each grating strip, the reflected echo intensity is maximum Amax, when the transmitting surface of the ultrasonic sensor is over against the middle position of two adjacent grating strips, the reflected echo intensity is minimum Amin, and when the transmitting surface of the ultrasonic sensor is at other positions, the reflected echo intensity is between Amax and Amin;

(3) the ultrasonic sensor transmits the collected reflected echo intensity to the signal processing part, the signal processing part analyzes and images data, and the rotating speed and the rotating angle of the detected shaft can be calculated according to imaging information.

Meanwhile, in order to further improve the resolution of the encoder, in the step (1), three groups of information acquisition units can be arranged side by side to form a three-bit gray code, and of course, a plurality of groups of multi-bit gray codes arranged side by side can be used for detection, so that the motion data of the detected shaft can be more accurately obtained.

The present invention has been described in detail in order to enable those skilled in the art to understand the invention and to practice it, and it is not intended to limit the scope of the invention, and all equivalent changes and modifications made according to the spirit of the present invention should be covered by the present invention.

Claims

1. A sensing part of an ultrasonic rotary encoder for obtaining detection information, characterized in that: the sensing component comprises a stator with a circular and straight pipe-shaped section, a rotor arranged in the stator in a way of freely rotating around the central line direction of the stator, an ultrasonic sensor fixedly arranged at the end part of the rotor extending into the stator, and a plurality of grid bars uniformly distributed around the circumferential direction of the stator, wherein the echo signals formed by the grating bars and the echo signals formed by the side wall of the stator have different intensity, and grids are formed between every two adjacent grid bars, the grids arranged in sequence form grids, the grids are provided with a plurality of groups, and the ultrasonic sensors are in one-to-one correspondence, each group of grids are distributed side by side along the length direction of the stator, an angle deviation of 180 degrees/N is formed between every two adjacent groups of grids in sequence, N is the number of grid strips, and the ultrasonic sensors are positioned in an ultrasonic echo detection area formed by the grids.

2. The sensing component of an ultrasonic rotary encoder according to claim 1, wherein: echo signals formed by the grid bars are stronger than echo signals formed by the side wall of the stator.

3. The sensing component of an ultrasonic rotary encoder according to claim 2, wherein: the stator is made of plastic or rubber, and the grid bars are made of metal coatings or metal pieces.

4. A sensing member of an ultrasonic rotary encoder according to claim 1, characterized in that: the stator is provided with a plurality of long grooves, each long groove takes the center of the stator as an arc section of a circle center, and each long groove extends along the stator in the length direction, wherein the grid bars correspond to the long grooves one to one, and the grid bars are arranged in the long grooves.

5. The sensing component of an ultrasonic rotary encoder according to claim 4, wherein: the elongated slot is located on an outer wall surface of the stator.

6. The sensing component of an ultrasonic rotary encoder according to claim 5, wherein: the groove depth of each long-shaped groove is equal, and the distance between the groove bottom surface and the corresponding inner wall of the stator is 1/6-1/2 of the wall thickness of the stator.

7. The sensing component of an ultrasonic rotary encoder according to claim 6, wherein: the grid bars are metal coatings formed in the long grooves through spraying, evaporation or sputtering, and the formed thickness of the grid bars is equal to the depth of the corresponding long grooves.

8. The sensing component of an ultrasonic rotary encoder according to claim 1, wherein: the rotor is a detected shaft, and the diameter of the rotor is greater than or equal to 0.3 mm; the inner diameter of the stator is more than or equal to 0.4mm, and the outer diameter of the stator is more than or equal to 0.5 mm.

9. The sensing component of an ultrasonic rotary encoder according to claim 1, wherein: an installation groove extending along the length direction of the rotor is formed at the end part of the rotor, and the plurality of ultrasonic sensors are arranged in the installation groove side by side.

10. The sensing component of an ultrasonic rotary encoder according to claim 1, wherein: each of the gratings and one of the ultrasonic sensors constitute a group of information acquisition units, and the ultrasonic rotary encoder further includes an information acquisition unit having a single grating strip, wherein an angular deviation of 180 °/N is also formed between the single grating strip and the grating of the adjacent grating, and N is the number of grating strips.