WO2021133185A1

WO2021133185A1 - Torque sensor

Info

Publication number: WO2021133185A1
Application number: PCT/RU2019/001000
Authority: WO
Inventors: Андрей Владимирович НОВИКОВ; Владимир Николаевич ГЕРАСИМОВ; Роман Александрович ГОРБАЧЕВ; Никита Евгеньевич ШВИНДТ; Владимир Иванович НОВИКОВ; Андрей Евгеньевич ЕФРЕМЕНКО; Дмитрий Леонидович ШИШКОВ; Михаил Нилович ЗАРИПОВ; Филипп Александрович КОЗИН; Алексей Михайлович СТАРОСТЕНКО
Original assignee: Общество С Ограниченной Ответственностью "Нейроассистивные Технологии"
Priority date: 2019-12-23
Filing date: 2019-12-23
Publication date: 2021-07-01

Abstract

The invention relates to robotics, in particular to devices for measuring torque, and even more particularly to torque sensors that can be used in various fields of technology including robotics. A torque sensor (1) comprises a body (2), a plurality of resistive strain gauges (11) and a signal recording and processing module (3) for recording and processing signals from the resistive strain gauges (11). The body (2) comprises a rim (8) and a hub (9) positioned concentrically with the rim (8), and also a plurality of ribs connecting the rim (8) and the hub (9). The ribs include rigid ribs (10.1) and flexible ribs (10.2), wherein two flexible ribs (10.2) are positioned between two adjacent rigid ribs (10.1). The resistive strain gauges (11) are positioned on the lateral sides of the flexible ribs (10.2) facing each other. The technical result is that of increasing the accuracy and stability of measurement of torque magnitude, reducing the mass and dimensions of a device, and increasing resistance to transverse deformations.

Description

TORQUE SENSOR

The invention relates to devices for measuring torque, in particular, to torque sensors that can be used in various fields of technology, including robotics.

DE102013013634 describes a torque measuring device comprising a first tubular torsional deformation body having two end fixing devices, a second torsion deformation body having two end fixing devices coaxially located in said first torsion deformation body. The second torsion deformation body is directly or indirectly connected by its two end portions with the two end portions of the first tubular body. To measure the moment, the device contains a first torsion bar and a second torsion bar.

The presence of torsion bars significantly complicates the design of the known device for measuring torque and increases its mass and dimensions, which is critical for use in robotics, in particular, in robotic manipulators.

US Pat. No. 7,424,829 discloses a torque sensor whose sensing elements provide a bipolar-type output signal, thereby reducing the effect of shaft eccentricity on the output signal. In the torque sensor, the first and second rotary shafts are located on a common axis, and these rotary shafts are connected by means of a torsion bar to detect the torque transmitted between the rotary shafts. The sensor is provided with means for generating a magnetic field in the radial direction, centered on the axis, means for changing the magnetic field for changing the direction and magnitude of the magnetic flux coming from the means for generating along the center line in accordance with the relative rotation between the rotating shafts, and a magnetic sensor for detecting magnetic flux. The magnetic sensor generates an output signal whose polarity changes depending on the direction of the detected magnetic flux, and the magnitude changes depending on the size of the detected magnetic flux.

Other known magnetic torque sensors are those described in US Pat. Nos. US8418570, US9234811, etc.

A common disadvantage of these sensors is that the magnetic sensor is susceptible to interference from external devices (for example, electric motors), which affects the accuracy and stability of measurements. In addition, the design of the sensor itself is quite complex, which is due to the use of magnetic sensors.

Article Jong-In Kim, Hyeong-Seok Jeon, Yong-Jun Jeong and Yong-Jae Kim. HIGH STIFFNESS CAPACITIVE TYPE TORQUE SENSOR WITH FLEXURE STRUCTURE FOR COOPERATIVE INDUSTRIAL ROBOTS. 201714th International Conference on Ubiquitous Robots and Ambient Intelligence (URAI). June 28 - July 1, 2017 describes a torque sensor for robotic manipulators with capacitive sensing elements. The sensor is made highly sensitive and rigid, consists of inner and outer rings, and flexible ribs of complex shape, which provide deflection to increase sensitivity and maintain rigidity between the inlet and outlet. Containers are used as sensing elements, one plate of which is placed on one edge, and the second - on a counter-opposing second edge. Symmetrically placed four double rigid ribs can compensate for torque and absorb unwanted off-axis moments.

The known sensor makes it possible to measure moments of large magnitude, however, to ensure high measurement accuracy, it will be necessary to use an appropriate highly sensitive circuit for processing signals from capacitive sensors, which is susceptible to interference from devices in which this sensor can be used. In addition, the regulation of the sensitivity (accuracy) of the sensor measurements cannot be carried out by simply replacing the sensitive elements, if such regulation is at all possible in this sensor.

RF patent RU108139 discloses a torque sensor, which is a disc-shaped aluminum alloy flange containing an outer rim to which an external load moment is applied, an inner rim fixed on the output shaft of a motor or gearbox, and four radial elements (spokes) connecting the inner and outer rims. The radial elements are the main elastic elements with eight strain gauges fixed on them, located in the places where the through grooves are cut, which play the role of auxiliary elastic elements. The torque sensor also includes spacers installed between the inner rims of the flange and the spokes. A printed circuit board with an electrical circuit that measures torque is attached to the face of the flange. By changing the design of the spokes (cutting grooves in the spokes and installing spacers), it is possible to adjust the accuracy of the sensor, the maximum permissible torque on the hinge.

The use of four radial elements with strain gages placed on them requires, on the one hand, sufficient flexibility of these elements so that it is generally possible to determine the moment (for which they even make grooves in them), and on the other hand, stiffness to ensure the rigidity of the entire sensor structure. In addition, such a design of radial elements leads to the fact that the sensor is susceptible to bending, and this will lead to errors in the measurement of the moment.

Another torque meter is described in RF patent RU2326357. It includes an elastic element placed in the power transmission channel and deformable under the action of the measured torque, and means for registering the torque from the deformation of the elastic element. The elastic element comprises a first fixable part (input part) fixed on the base of the rotary drive, a second fixable part (output part) fixed on a fixed part of the rotary drive, and a deformable part located between the first fixed part and the second fixed part. The deformable portion is provided with eight slotted portions, and the joints of the slotted portions alternately consist of a torque element for receiving a torque applied to the elastic element and a load element independently of the torque element to support the load of the elastic element. The technical result consists in the possibility of registering only the torque, excluding the influence of various extraneous loads. However, this torque meter is characterized by low accuracy, which is determined, first of all, by the locations of the torque registration means on the torque elements. At the same time, the authors of this meter note that the means for registering the torque can be mounted even in a section different from the torque element, or only on one of the torque elements.

Thus, there is a problem of creating such a torque transducer, which provides high measurement accuracy, while being compact and simple in design, and also not subject to interference from external magnetic fields.

The technical result of the claimed invention is to improve the accuracy and stability of measuring the magnitude of the torque, reduce the weight and dimensions of the device, increase the resistance to lateral deformations.

The problem is solved, and the claimed technical result is achieved in a torque sensor, which contains a housing, a plurality of strain gages and a signal registration and processing module for registering and processing signals from strain gages. The housing includes a rim and hub concentric with the rim, as well as a plurality of ribs connecting the rim and hub. The ribs include rigid ribs and flexible ribs, with two flexible ribs interposed between two adjacent rigid ribs. Strain gages are located on the lateral sides of the flexible ribs facing each other.

According to the invention, strain gauges are placed on the lateral sides of the flexible ribs, i. E. in places of maximum deformation of the side ribs, which are concentrators of deformation stresses, and not on the outer sides, as in the known analogs. In this case, the strain gages are placed on the side faces facing each other, which makes it possible to significantly increase the accuracy, since when deformation occurs, some ribs will shrink or bend towards the strain gage installed on it, and the opposite ribs will stretch or bend away from the strain gage installed on it. Together with this, the use of strain gages as a sensitive element allowed to make a simple, compact and reliable design of the entire device, providing accurate torque measurement and at the same time not being subject to external interference, for example, from an electric motor.

The problem is solved, and the claimed technical result is also achieved in preferred embodiments of the invention, according to one of which the torque sensor additionally contains an insulating gasket between the flange and the printed circuit board of the signal registration and processing module to provide electrical isolation between the specified components of the device.

The signal registration and processing module may contain a printed signal amplifier and an analog-to-digital converter installed on the board for performing at least primary processing of the received signal, such as amplifying, digitizing and filtering the signal. In this case, it is preferable to implement the module for recording and processing a signal according to a ratiometric circuit in order to reduce the requirements for a power source.

In a particular version of the torque sensor, it contains four rigid ribs and, therefore, eight flexible ribs and eight strain gages. In this case, it is preferable that the first four strain gages, located opposite each other in the direction of the axis, form the first bridge circuit, and the second four strain gauges form the second bridge circuit, and both bridge circuits are connected to the signal registration and processing module. The claimed sensor may contain an additional eight strain gages, each of which is located next to the corresponding strain gage of the specified first four and second four strain gages and forms a double strain gage, and all together - four bridge circuits connected to the signal registration and processing module.

It is also preferable that the angle between adjacent flexible ribs is more than 90 °, which makes it possible to increase the area of the strain gauges (and, therefore, to increase their sensitivity) and the convenience of their installation.

Further, the invention and some possible variants of its implementation are explained in more detail with reference to the figures, which show: in fig. 1 is a general view of the claimed torque sensor; in fig. 2 - partially disassembled torque sensor; in fig. 3 is a top view of the first version of the torque sensor; in fig. 4 - a variant of the circuit for measuring signals from strain gages according to the first variant of the torque sensor (Fig. 5a); in fig. 5a - a version of the torque sensor with one strain gauge on the edge; in fig. 5b - version of the torque sensor with two strain gauges on the edge; in fig. 6 - a variant of the circuit for measuring signals from strain gages according to the second variant of the torque sensor (Fig. 5b).

In the figures, reference numerals indicate:

1 - torque sensor;

2 - case;

3 - signal registration and processing module;

4 - printed circuit board;

5 - amplifier;

6 - analog-to-digital converter;

7 - insulating gasket;

8 - rim;

8.1, 8.2 - rim mounting holes;

9 - hub;

9.1 - hub mounting hole;

9.2 - hub groove;

10.1 - rigid rib;

10.2 - flexible rib;

11 - strain gauge.

R 1 ... R8, R'1 ... R'8 - strain gauges on versions of the torque sensor (Fig. 5a, 5b) and circuits for measuring signals from strain gauges (Fig. 4, 6);

+ U, -U - supply voltage on the circuits for measuring signals from strain gages. FIG. 1 is a general view of a torque sensor 1 according to the present invention. The sensor 1 is made in the form of a disk, which simplifies its use and ensures its compactness.

The sensor 1 consists of a housing 2, which is a measuring element of the claimed device and contains sensitive elements for these purposes, and a signal registration and processing module 3 containing a printed circuit board 4, on which elements for processing signals coming from the sensitive elements are located (Fig. 2). These elements of signal processing can be, in particular, a signal amplifier 5 and an analog-to-digital converter 6 (ADC) (Fig. 4, 6), for example, with a capacity of 24 bits. The signal amplifier 5 and the ADC 6 can be made as a single device as a part of the signal registration and processing module 3, for example, in the form of an ADC with a built-in amplifier, or they can be separate signal processing elements, as shown in FIG. 4, 6.

The body 2 is made in the form of a disk and in fact determines the geometric dimensions of the sensor 1; its thickness can be from 7 to 25 mm. The body 2 can be made, for example, by means of milling technology from aluminum, or aluminum-magnesium alloys, or duralumin, or steels and alloys based on them.

The printed circuit board 4 is preferably made in the form of a fiberglass ring, on top of which a copper layer is applied in the range from 18 to 75 microns. Signal processing elements are mounted on a printed circuit board 4 by means of surface mounting technology.

An insulating gasket 7 can be additionally placed between the housing 2 and the printed circuit board 4 to ensure the required dielectric gap between the indicated elements of the sensor 1. The insulating gasket 7 is made of fiberglass, getinax, transformer paper, plastic, and other suitable material by means of milling, mechanical or laser engraving, another suitable way. The thickness of the insulating strip 7 is selected on the basis of the need to set a seat for it and preferably varies in the range from 0.2 to 1.5 mm. The housing 2 consists of a rim 8, a hub 9 concentrically located in it, and a plurality of ribs that connect the rim 8 and the hub 9 and on some of which the sensing elements are located (Fig. 3). In the rim 8, fastening holes 8.1, 8.2 of the rim (Fig. 2, 3) can be made for ease of installation, for example, on the stator of an electric motor or other device, and in the hub 9 - fastening holes 9.1 of the hub for ease of installation, for example, on reducer. The hub 9 can also be provided with a groove 9.2 of the hub (Fig. 2) for mounting a bearing therein.

The plurality of these ribs includes rigid ribs 10.1 and flexible ribs 10.2. In this case, it is preferable that between two adjacent rigid ribs 10.1 are placed two flexible ribs 10.2, and the number of rigid ribs 10.1 is four (therefore, the number of flexible ribs 10.2 is eight), as shown in the figures.

Rigid ribs 10.1 serve to stiffen the structure of the sensor 1, as well as to reduce the influence of lateral forces applied to the body 2.

Flexible ribs 10.2 are designed to relieve longitudinal stresses and are concentrators of deformation stresses. In places of their maximum deformation, sensitive elements are placed, for which strain gauges 11 have been chosen. Flexible ribs 10.2, preferably, have some inclination with respect to rigid ribs 10.1, so that the angle between two adjacent flexible ribs 10.2 is more than 90 °, which makes it possible to displace the area of concentration of deformations and to improve the convenience of mounting strain gages 11.

Strain gages 11 change their own resistance in accordance with their deformation. They are well known to a person skilled in the art and can be made on any available basis, including paper, fabric, glass fabric, and other materials. The sensitive material of the strain gauge 11 can be a metal or a semiconductor.

Strain gages 11 can be attached to the facing each other lateral sides of adjacent flexible ribs 10.2 by means of adhesive technology or any other suitable technology. As mentioned above, the signal registration and processing module 3 contains printed circuit elements installed on the printed circuit board 4 for processing signals coming from the sensing elements, in particular, strain gages 11. It is preferable if the leads of the strain gages 11 are mounted on the printed circuit board 4.

The signal registration and processing module 3 may additionally include a switch for connecting the strain gauges 11 through it to the signal processing elements, in particular, to the signal amplifier 5 and the ADC 6, and not directly.

It is preferable if the signal registration and processing module 3 is made according to the ratiometric scheme. This solution allows you to reduce the requirements for the power source for the primary converter. The main feature of the ratiometric signal, which is formed at the output, is the dependence of its value on the supply voltage.

In the first, basic embodiment of the claimed detector 1, one strain gauge 11 is mounted on each flexible rib 10.2, as shown in FIG. 3 and FIG. 5a. In particular, when using in the detector 1 eight strain gauges 11, designated for ease of understanding of the subsequent description as Rl, R2, .. R8, the first four strain gauges Rl, R2, R3 and R4, located opposite each other in the direction of the axis, are combined into a bridge scheme. The second bridge circuit is formed by the remaining four second strain gages R5, R6, R7 and R8, located on the perpendicular axis. Both of these bridge circuits are connected to the signal processing elements as shown in FIG. four.

To increase the resistance of the detector 1 to temperature extremes, as well as to reduce distortions at the beginning of the scale of measurements of the moment arising from longitudinal bending deformations, additional eight strain gauges 11 can be used, indicated in Fig. 5b and 6 as Rl ', R2', .. R8, each of the strain gages Ri 'is placed next to the corresponding strain gauge Ri on the same flexible rib 10.2 (Fig. 5b), thus forming a double strain gauge including two sensitive elements. In this case, all strain gages 11 form four bridge circuits, which are connected to the signal processing elements as shown in FIG. 6. The advantage of the claimed torque sensor is the absence of a torsion bar, resistance to alternating and constant magnetic fields, which can be created by an electric motor. With eight double strain gages, the resistance to lateral deformations and the measurement accuracy are increased.

Claims

CLAIM

1. A torque sensor comprising: a housing including a rim, a hub arranged concentrically with the rim, and a plurality of ribs connecting the rim and the hub, the ribs including rigid ribs and flexible ribs, so that two flexible ribs are placed between two adjacent rigid ribs, a plurality of strain gages located on the side faces facing each other of adjacent flexible ribs, and a signal registration and processing module for registering and processing signals from the strain gages.

2. The torque sensor according to claim 1, further comprising an insulating gasket between the flange and the printed circuit board of the signal registration and processing module.

3. The torque sensor according to claim 1, wherein the signal recording and processing module comprises a signal amplifier and an ADC.

4. The torque sensor according to claim 1, in which the signal registration and processing module is made according to the ratiometric scheme.

5. The torque sensor according to claim 1, comprising four rigid ribs.

6. The torque sensor according to claim 5, containing eight strain gages, and the first four strain gages form the first bridge circuit, and the second four strain gauges form the second bridge circuit connected to the signal registration and processing module.

7. The torque sensor according to claim 6, containing an additional eight strain gages, each of which is located next to the corresponding strain gage from the specified first four and second four strain gages, forming a double strain gage, and all together - four bridge circuits connected to the signal registration and processing module.

8. The torque sensor of claim 5, wherein the angle between adjacent flexible ribs is greater than 90 °.