CN115451082A

CN115451082A - Harmonic reducer, method for measuring torque in harmonic reducer and robot

Info

Publication number: CN115451082A
Application number: CN202211275424.XA
Authority: CN
Inventors: 安然; 彭俊才; 宋庭科; 王世全
Original assignee: Feixi Technology Co ltd; Flexiv Robotics Ltd
Current assignee: Feixi Technology Co ltd; Flexiv Robotics Ltd
Priority date: 2022-10-18
Filing date: 2022-10-18
Publication date: 2022-12-09

Abstract

The invention relates to a harmonic reducer, a method for measuring torque in the harmonic reducer and a robot. This harmonic speed reducer ware includes: a wave generator; a rigid wheel provided with internal teeth; a flexspline disposed between the wave generator and the rigid gear and configured to intermesh with the internal teeth of the rigid gear; a plurality of sets of torque sensors, wherein each of the plurality of sets of torque sensors includes a plurality of strain gauges, each of the plurality of sets of torque sensors is for measuring torque transmitted by the harmonic reducer during rotation of the flexspline, wherein signals measured by each of the plurality of sets of torque sensors include an amount of torque ripple, and the plurality of sets of torque sensors are arranged crosswise; and a processor configured to calculate a true torque delivered by the harmonic reducer from the signals measured by the plurality of sets of torque sensors, wherein the true torque does not include an amount of torque ripple.

Description

Harmonic reducer, method for measuring torque in harmonic reducer and robot

Technical Field

The present invention relates generally to the field of harmonic reducers and, in particular, to a harmonic reducer, a method of measuring torque in a harmonic reducer, and a robot.

Background

In recent years, robot technology has been developed at a high speed, and is widely used in industrial production. A harmonic reducer is generally used in a robot as a speed reducing mechanism for reducing a rotating speed and increasing a torque, so as to adjust a moving speed and an output torque of a connecting arm of the robot, and realize harmonic speed reduction transmission. Harmonic reducers are generally composed of a rigid gear with internal teeth, a flexible gear, and a wave generator that deforms the flexible gear in the radial direction. As the wave generator rotates, the flexible gear undergoes a controlled elastic deformation whereby the teeth of the flexible gear mesh with the internal teeth of the rigid gear to transmit motion and force.

At present, in a joint between connecting arms of a robot, in order to measure an output torque of a harmonic reducer, it is considered to connect the harmonic reducer in series with an elastic element, and to measure the output torque by arranging a torque sensor on the elastic element. However, this increases the number of parts, and therefore is disadvantageous in terms of miniaturization of the robot joint and cost reduction.

In addition, in other solutions, it is also contemplated to achieve the purpose of measuring the output torque by arranging a torque sensor (e.g., a strain gauge) inside the harmonic reducer (e.g., on the flexspline). However, since the strain gauges are usually discretely arranged inside the harmonic reducer, the strain of each strain gauge and thus the measured strain value are not completely uniform, and then the torque value converted from the strain value may fluctuate, thereby affecting the measurement accuracy of the output torque.

Disclosure of Invention

Accordingly, the present invention has been made to overcome one or more of the above-mentioned disadvantages, and provides a harmonic reducer, a method of measuring torque in the harmonic reducer, and a robot, which are capable of effectively eliminating the influence of the amount of torque fluctuation in a signal measured by a torque sensor, thereby being capable of accurately measuring a true torque in the harmonic reducer.

Specifically, an aspect of the present invention provides a harmonic reducer including: a wave generator; a rigid wheel provided with internal teeth; a flexspline disposed between the wave generator and the rigid gear and configured to intermesh with the internal teeth of the rigid gear; a plurality of sets of torque sensors, wherein each of the plurality of sets of torque sensors includes a plurality of strain gauges, each of the plurality of sets of torque sensors is for measuring torque transmitted by the harmonic reducer during rotation of the flexspline, wherein signals measured by each of the plurality of sets of torque sensors include an amount of torque ripple, and the plurality of sets of torque sensors are arranged crosswise; and a processor configured to calculate a true torque delivered by the harmonic reducer from the signals measured by the plurality of sets of torque sensors, wherein the true torque does not include an amount of torque ripple.

In one embodiment, the plurality of sets of torque sensors includes a first set of torque sensors including four strain gauges and a second set of torque sensors including four strain gauges, the strain gauges of the first set of torque sensors being arranged across the strain gauges of the second set of torque sensors at 45 ° intervals from each other.

In one embodiment, the harmonic reducer further comprises an angle measuring device configured to measure an angle of the wave generator relative to the flexspline during rotation of the flexspline.

In one embodiment, the processor calculates the true torque according to the following equation:

wherein, tau _o Is the true torque, τ, transmitted by the harmonic reducer ₁ Is formed by the firstTorque value, τ, measured by a group torque sensor ₂ Is the torque value measured by the second set of torque sensors, and θ is the angle of the wave generator relative to the flexspline.

In one embodiment, the angle measuring device comprises a first angle sensor configured to measure an angle of the wave generator relative to the rigid spline during rotation of the flex spline, and a second angle sensor configured to measure an angle of the flex spline relative to the rigid spline during rotation of the flex spline, thereby measuring an angle of the wave generator relative to the flex spline during rotation of the flex spline.

In one embodiment, the plurality of sets of torque sensors includes a first set of torque sensors including four strain gauges, a second set of torque sensors including four strain gauges, and a third set of torque sensors including four strain gauges, the strain gauges of the first set of torque sensors, the strain gauges of the second set of torque sensors, and the strain gauges of the third set of torque sensors being arranged crosswise with a mutual spacing of 30 °, wherein each strain gauge of the second set of torque sensors is advanced by 30 ° compared to an adjacent strain gauge of the first set of torque sensors, and each strain gauge of the third set of torque sensors is retarded by 30 ° compared to an adjacent strain gauge of the first set of torque sensors.

τ _o ＝τ ₅ +τ ₆ -τ ₄

wherein, tau _o Is the true torque, τ, transmitted by the harmonic reducer ₄ Is the torque value, τ, measured by said first set of torque sensors ₅ Is the torque value, τ, measured by said second set of torque sensors ₆ Is the torque value, τ, measured by said third set of torque sensors _o Is the output of a harmonic reducerThe value of the torque.

wherein, tau _o Is the true torque, τ, transmitted by the harmonic reducer ₄ Is the torque value, τ, measured by said first set of torque sensors _5′ Is the torque value, τ, measured by said second set of torque sensors _6′ Is a torque value measured by the third set of torque sensors, Δ α is an angular offset between the second set of torque sensors and the first set of torque sensors, and Δ β is an angular offset between the third set of torque sensors and the first set of torque sensors.

In one embodiment, each of the plurality of sets of torque sensors is disposed on the flexspline and is arranged about an axis of the flexspline.

In one embodiment, the flexspline comprises: a body portion; a toothed portion provided at one end of the body portion and configured to be capable of intermeshing with the internal teeth of the rigid gear; and a flange extending radially outward from an end of the body portion opposite the toothed portion. The plurality of sets of torque sensors are disposed on at least one of an inner side of the flexspline, an outer side of the body portion, a side of the flange facing the toothed portion, and a side of the flange facing away from the toothed portion.

In one embodiment, the wave generator, the rigid wheel, and the flexible wheel are coaxially arranged.

In one embodiment, the strain gauge is made of polyvinylidene fluoride, or a material suitable for hall sensors, capacitive sensors.

In one embodiment, the strain gage is made by screen printing.

In one embodiment, the harmonic reducer further comprises a kalman filter.

Another aspect of the invention provides a method of measuring torque in a harmonic reducer. The harmonic speed reducer includes: a wave generator; a rigid wheel provided with internal teeth; a flexspline disposed between the wave generator and the rigid gear and configured to intermesh with the internal teeth of the rigid gear; a plurality of sets of torque sensors, wherein each set of the plurality of sets of torque sensors comprises a plurality of strain gauges, the plurality of sets of torque sensors being arranged in a cross; and a processor. The method comprises the following steps: measuring, by each of the plurality of sets of torque sensors, a torque transmitted by the harmonic reducer during rotation of the flexspline, wherein a signal measured by each of the plurality of sets of torque sensors includes an amount of torque ripple; and calculating, by the processor, a true torque delivered by the harmonic reducer as a function of the signals measured by the plurality of sets of torque sensors, wherein the true torque does not include an amount of torque ripple.

A further aspect of the invention provides a robot comprising a plurality of link arms, any two adjacent link arms being pivotably connected by a robot joint, wherein the robot joint comprises any one of the harmonic reducers as described above.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation of the invention.

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is an axial cross-sectional schematic view of a harmonic reducer according to an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of a robot joint equipped with a harmonic reducer according to an embodiment of the present invention.

FIG. 3 is a schematic perspective view of a flexspline of a harmonic reducer according to one embodiment of the present invention.

FIG. 4 is a schematic diagram of an arrangement pattern of two sets of torque sensors according to an embodiment of the invention.

FIG. 5 is a flow chart of a method of measuring true torque in a harmonic reducer according to one embodiment of the present invention.

FIG. 6 is a schematic diagram of a layout pattern of three sets of torque sensors according to another embodiment of the present invention.

Fig. 7 is a schematic structural diagram of a robot according to an embodiment of the present invention.

Reference numerals:

100. harmonic reducer

102. Wave generator

104. Rigid wheel

106. Flexible gear

108. Transmission input shaft

110. Stator

112. Rotor

114. Transmission output shaft

116. Output member

118. First reading head

120. First magnetic disk

122. Second reading head

124. Second magnetic disk

202. Body part

204. Toothed part

206. Flange

208. Strain gauge

300. Robot

301. Connecting arm

302. Robot joint

303. Robot gripping jaw

Regions A1, A2, A3, A4

S100-S200 steps

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, embodiments accompanying 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, as those skilled in the art will recognize without departing from the spirit and scope of the present invention.

It should be understood that although the terms "first," "second," etc. may be used herein to describe various elements, these elements are not intended to denote any order, quantity, or importance, but rather are used to distinguish one element from another. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. The word "comprising" or "comprises", and the like, means that the element or item preceding the word comprises the element or item listed after the word and its equivalent, but does not exclude other elements or items.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

Referring now to FIG. 1, a harmonic reducer 100 in accordance with an embodiment of the present invention will be described. FIG. 1 is an axial cross-sectional schematic view of a harmonic reducer 100 according to an embodiment of the present invention.

In fig. 1, there is provided a harmonic reducer 100, the harmonic reducer 100 comprising: a wave generator 102, such as a cam; a rigid wheel 104 provided with internal teeth; and a flexspline 106 provided between the wave generator 102 and the rigid spline 104 and configured to be capable of intermeshing with the internal teeth of the rigid spline 104. Further, the wave generator 102, the rigid spline 104, and the flexible spline 106 may be arranged substantially coaxially.

Referring to fig. 2, fig. 2 is a schematic structural diagram of a robot joint equipped with a harmonic reducer 100 according to an embodiment of the present invention. For example, in a robot joint equipped with the harmonic reducer 100, in order to realize, for example, reduction transmission, the wave generator 102 of the harmonic reducer 100 is usually connected to one end of a transmission input shaft 108, and a motor is attached to the other end of the transmission input shaft 108. In the example shown in fig. 2, the motor comprises a stator 110 and a rotor 112, and the stator 110 may be fixed to the housing of the robot joint by any suitable means. On the other hand, the flexspline 106 of the harmonic reducer 100 is connected to one end of a transmission output shaft 114, and an output member 116 of the robot joint, such as an end effector, for example, may be mounted on the other end of the transmission output shaft 114. Furthermore, the rigid wheel 104 of the harmonic reducer 100 may also be secured to the housing of the robot joint by any suitable means.

When used as a reducer, the wave generator 102 is typically active, the rigid gear 104 is fixed, and the compliant gear 106 outputs. Of course, it should be appreciated that in some embodiments, the flexible wheel 106 may be used to secure and the rigid wheel 104 used for output.

Specifically, during operation of the reduction gear using the harmonic reducer 100, the wave generator 102 rotates with the rotor 112 of the electric motor via the transmission input shaft 108, and the flexspline 106 periodically radially deforms during rotation with the wave generator 102, whereby the teeth of the flexspline 106 mesh with the corresponding teeth on the rigid spline 104, thereby transmitting torque. Further, the rotational speed of the transmission output shaft 114 is reduced by the harmonic reducer 100, so that a reduction transmission can be achieved.

Referring now to FIG. 3, a flexible spline 106 in accordance with one embodiment of the present invention will be described. Fig. 3 is a schematic perspective view of the flexspline 106 of the harmonic reducer 100 in accordance with an embodiment of the present invention.

In fig. 3, the flexspline 106 according to an embodiment of the present invention includes: a body portion 202; a toothed portion 204 provided at one end of the body portion 202 and configured to be capable of intermeshing with the internal teeth of the rigid gear 104; and a flange 206 extending radially outward from an end of the body portion 202 opposite the toothed portion 204. As shown in fig. 3, the flexspline 106 itself is of a cylindrical structure and is thin-walled, thereby being capable of elastic deformation. As mentioned above, during operation of the harmonic reducer 100, the flexspline 106 is able to undergo periodic radial deformation under the action of the wave generator 102.

Further, in an embodiment of the present invention, the harmonic reducer 100 further includes: a plurality of sets of torque sensors, wherein each of the plurality of sets of torque sensors comprises a plurality of strain gauges, each of the plurality of sets of torque sensors is for measuring torque transmitted by the harmonic reducer 100 during rotation of the flexspline 106, wherein signals measured by each of the plurality of sets of torque sensors include an amount of torque ripple, and the plurality of sets of torque sensors are arranged crosswise; and a processor (not shown) configured to calculate a true torque delivered by the harmonic reducer from the signals measured by the plurality of sets of torque sensors, wherein the true torque does not include an amount of torque ripple.

In an embodiment of the present invention, each of the plurality of sets of torque sensors may be disposed on the flexspline 106 and arranged around an axis of the flexspline 106. Thus, the sets of torque sensors, and thus the strain gauges, are located on the same plane relative to the axis of the flexspline 106. Specifically, as shown in connection with fig. 3, the plurality of sets of torque sensors and thus the plurality of strain gauges 208 may be disposed, for example, in at least one of a region A1 of an inner side of the flexspline 106, a region A2 of an outer side of the body portion 202, a region A3 of a side of the flange 206 facing the toothed portion 204, and a region A4 of a side of the flange 206 facing away from the toothed portion 204.

Hereinafter, for convenience of explanation, the plurality of torque sensors are further described as being disposed in the area A3 of the flange 206 on the side facing the toothed portion 204, but the present invention is not limited thereto.

Referring now to FIG. 4, an arrangement pattern of two sets of torque sensors according to an embodiment of the invention will be described.

In one embodiment of the present invention, the plurality of sets of torque sensors includes a first set of torque sensors including four strain gauges and a second set of torque sensors including four strain gauges, the strain gauges of the first set of torque sensors being arranged crosswise with respect to the strain gauges of the second set of torque sensors at 45 ° intervals from each other.

Specifically, as shown in fig. 4, in a region A3 of a side of the flange 206 facing the toothed portion 204, eight strain gauges 208 are uniformly and annularly arranged with respect to the axis of the flexspline 106, that is, each strain gauge 208 has an equal radial distance with respect to the axis of the flexspline 106, and adjacent strain gauges 208 are staggered by 45 ° with respect to the axis of the flexspline 106. The eight strain gauges 208 are divided into two groups, i.e., a first group of torque sensors and a second group of torque sensors, and thus the first group of torque sensors and the second group of torque sensors are arranged crosswise. For example, referring to fig. 4, the strain gauge 208 immediately above in the drawing is first, and the number is counted sequentially in the clockwise direction. Then, the first set of torque sensors may include the first, third, fifth, and seventh of the eight strain gages 208, and the second set of torque sensors may include the second, fourth, sixth, and eighth of the eight strain gages 208. Thus, each set of torque sensors includes four strain gauges 208. Further, the four strain gauges 208 included in each set of torque sensors form a Wheatstone bridge (Wheatstone bridge) to form a sensing circuit to measure the torque transmitted by the harmonic reducer 100 during rotation of the flexspline 106.

Further, in some embodiments, the strain gage 208 may be, for example, a Rosette type strain gage. As described above, by adopting eight strain gauges and arranging them symmetrically, as described below, the influence of the amount of torque fluctuation in the signal measured by the torque sensor can be effectively eliminated, so that the measurement sensitivity and, therefore, the accuracy of measurement can be effectively improved. Further, the strain gauge 208 may be made of polyvinylidene fluoride (PVDF), for example, or may be made of other materials suitable for hall sensors and capacitive sensors. In addition, the strain gauge 208 may be manufactured by, for example, screen printing and then mounted on the harmonic reducer 100. Alternatively, the strain gage 208 may also be formed directly to the harmonic reducer 100 by screen printing.

Referring again to fig. 2, further, in some embodiments, the harmonic reducer 100 may further include an angle measurement device configured to measure an angle θ of the wave generator 102 relative to the flexspline 106 during rotation of the flexspline 106.

Further, the angle measuring device may, for example, include a first angle sensor configured to measure an angle of the wave generator 102 relative to the rigid block 104 (or a housing or other component fixedly connected to the rigid block 104) during rotation of the flexspline 106, and a second angle sensor configured to measure an angle of the flexspline 106 relative to the rigid block 104 (or a housing or other component fixedly connected to the rigid block 104) during rotation of the flexspline 106, thereby measuring an angle θ of the wave generator 102 relative to the flexspline 106 during rotation of the flexspline 106.

Specifically, in the example shown in fig. 2, the first angle sensor comprises a first reading head 118 and a first magnetic disk 120, the first reading head 118 being arranged on a housing fixedly connected to the rigid wheel 104, the first magnetic disk 120 being arranged on the wave generator 102. Furthermore, the second angle sensor comprises a second read head 122 and a second magnetic disk 124, the second read head 122 being arranged on a housing fixedly connected to the rigid wheel 104, the second magnetic disk 124 being arranged on the flexspline 106. As shown in conjunction with fig. 3, the second magnetic disk 124 can be arranged, for example, in a region A4 of the flange 206 on the side facing away from the toothed section 204. Thus, during rotation of the flexspline 106, the processor can acquire angular data of the flexspline 106 and the wave generator 102, respectively, relative to the housing via the first read head 118 and the second read head 122, and thus can acquire the angle θ of the wave generator 102 relative to the flexspline 106.

Further, it should be appreciated that although in the example of fig. 2, the first disk 120 and the second disk 124 are both disposed on a housing, the first disk 120 and the second disk 124 may also be disposed directly on the rigid wheel 104.

Furthermore, it should be appreciated that although in the example of fig. 2 the angle measurement device comprises two angle sensors, the angle measurement device may also comprise only one angle sensor. For example, in this angle sensor, a read head and a magnetic disk are provided on the wave generator 102 and the flexspline 106, respectively.

Furthermore, in some embodiments, the harmonic reducer 100 may further include a kalman filter for eliminating high frequency measurement signal components to further improve measurement accuracy.

Referring now to FIG. 5, FIG. 5 is a flow chart of a method of measuring true torque in a harmonic reducer according to one embodiment of the present invention. As shown, another aspect of the present invention provides a method of measuring torque in a harmonic reducer. As described above, the harmonic reducer may include, for example: a wave generator; a rigid wheel provided with internal teeth; a flexspline disposed between the wave generator and the rigid gear and configured to intermesh with the internal teeth of the rigid gear; a plurality of sets of torque sensors, wherein each set of the plurality of sets of torque sensors comprises a plurality of strain gauges, the plurality of sets of torque sensors being arranged crosswise; and a processor.

The method may comprise the steps of:

s100, measuring the torque transmitted by the harmonic reducer in the rotation process of the flexible gear through each group of the plurality of groups of torque sensors, wherein the signal measured by each group of the plurality of groups of torque sensors comprises a torque fluctuation amount; and

s200, calculating real torque transmitted by the harmonic reducer according to signals measured by the plurality of groups of torque sensors through the processor, wherein the real torque does not contain torque fluctuation quantity.

Hereinafter, referring to fig. 4, the strain gauge 208 directly above in the drawing is first, and the number is counted in the clockwise direction. The first set of torque sensors includes the second, fourth, sixth, and eighth of the eight strain gages 208, and the second set of torque sensors includes the first, third, fifth, and seventh of the eight strain gages 208. Thus, each set of torque sensors includes four strain gauges 208. This is exemplified below, but the present invention is not limited thereto.

The four strain gauges 208 included in each set of torque sensors thus constitute a wheatstone bridge, forming a detection circuit to measure the torque transmitted by the harmonic reducer during rotation of the flexspline.

As described above, the torque fluctuation amount included in the signals measured by the first and second sets of torque sensors is related to the angle θ of the wave generator with respect to the flexspline, as shown in the following equation (1),

τ _r ＝τ _pr sin (2 θ) formula (1)

Wherein, tau _r Is the torque fluctuation quantity, tau, contained in the signal measured by the first set of torque sensors (or the second set of torque sensors) _pr Is a torque fluctuation peak in the torque fluctuation amount.

As described above, since the strain gauges in the first group of torque sensors and the strain gauges in the second group of torque sensors are arranged crosswise with a mutual interval of 45 °, there is a phase difference in the torque values measured by the strain gauges in the two groups of torque sensors. Assuming that the second set of torque sensors is delayed 45 from the first set of torque sensors, the torque values measured by the first and second sets of torque sensors are shown in equations (2) and (3) below,

τ ₁ ＝τ _o +τ _r ＝τ _o +τ _pr sin (2 θ) formula (2)

τ ₂ ＝τ _o +τ _r-45° ＝τ _o +τ _pr ·sin(2(θ-45°))＝τ _o +τ _pr Cos (2. Theta.) formula (3)

Wherein, tau ₁ Is the torque value, τ, measured by said first set of torque sensors ₂ Is the torque value, τ, measured by said second set of torque sensors _o Is the output torque value of the harmonic reducer.

Note that θ here is a relative angle between the wave generator and the flexspline, taking the position of any one of the strain gauges in the first set of torque sensors as a reference point on the flexspline and a point on the major axis of the elliptical wave generator as a reference point. If other points on the wave generator and the flexible gear are selected as reference points in practical application, the calculation formula is adjusted correspondingly, but the principle is not changed, and the principle and spirit of the application can still be applied.

Thereafter, the processor calculates a true torque transmitted by the harmonic reducer based on the torque values measured by the first and second sets of torque sensors, wherein the true torque can contain no torque ripple. More specifically, the above formulae (2) and (3) can be represented by the following formula (4) for τ _o And (4) performing calculation.

Therefore, the output torque value of the harmonic reducer may be as shown in the following equation (5).

Further, the method may further comprise the steps of: the high frequency measurement signal component is eliminated by using a kalman filter, thereby correcting errors and further improving measurement accuracy.

Next, with reference to fig. 6, a layout pattern of three sets of torque sensors according to another embodiment of the present invention will be described. As shown, in this embodiment, twelve strain gauges 208 are uniformly and annularly arranged with respect to the axis of the flexspline 106 on a region A3 of the side of the flange 206 facing the toothed portion 204, i.e., each strain gauge 208 is at an equal radial distance with respect to the axis of the flexspline 106, and adjacent strain gauges 208 are offset by 30 ° with respect to the axis of the flexspline 106. The twelve strain gauges 208 are divided into three groups, i.e., a first group of torque sensors, a second group of torque sensors, and a third group of torque sensors, and the three groups of torque sensors are arranged crosswise with a mutual spacing of 30 °. For example, referring to fig. 6, the strain gauge 208 immediately above in the drawing is first, and the number is counted sequentially in the clockwise direction. Then, the first set of torque sensors may include the third, sixth, ninth, and twelfth of the twelve strain gauges 208, the second set of torque sensors may include the second, fifth, eighth, and eleventh of the twelve strain gauges 208, and the third set of torque sensors may include the first, fourth, seventh, and tenth of the twelve strain gauges 208. Thus, each set of torque sensors includes four strain gauges 208. Further, each strain gage of the second set of torque sensors is advanced by 30 ° compared to the adjacent strain gage of the first set of torque sensors, and each strain gage of the third set of torque sensors is retarded by 30 ° compared to the adjacent strain gage of the first set of torque sensors.

Further, the four strain gauges 208 included in each set of torque sensors form a wheatstone bridge to form a sensing circuit to measure the torque transmitted by the harmonic reducer 100 during rotation of the flexspline 106.

Likewise, the strain gage 208 may be, for example, a Rosette-type strain gage. As described above, by adopting twelve strain gauges and arranging them centrosymmetrically, the influence of the torque fluctuation amount in the signal measured by the torque sensor can be effectively eliminated, so that the measurement sensitivity and thus the measurement accuracy can be effectively improved. Further, the strain gauge 208 may also be made of polyvinylidene fluoride (PVDF), for example, or may be made of other materials suitable for hall sensors and capacitive sensors. Further, the strain gauge 208 may be formed by screen printing, for example, and then mounted on the harmonic reducer 100. Alternatively, the strain gage 208 may also be formed directly on the harmonic reducer 100 by screen printing.

Similarly, the torque ripple amounts contained in the signals measured by the first, second, and third sets of torque sensors are related to the angle θ of the wave generator relative to the flexspline, as shown in equation (1) above,

τ _r ＝τ _pr sin (2 θ) formula (1)

Wherein, tau _r Is the torque fluctuation quantity, tau, contained in the signal measured by the first set of torque sensors (or the second set of torque sensors or the third set of torque sensors) _pr Is a torque fluctuation peak in the torque fluctuation amount.

As described above, since the three sets of torque sensors are arranged crosswise with a mutual interval of 30 °, there is a phase difference in the torque values measured by the strain gauges in the three sets of torque sensors. The torque values measured by the first set of torque sensors, the second set of torque sensors, and the third set of torque sensors are respectively expressed by the following equations (6), (7), and (8),

τ ₄ ＝τ _o +τ _r ＝τ _o +τ _pr sin (2 θ) formula (6)

Wherein, tau ₄ Is the torque value, τ, measured by said first set of torque sensors ₅ Is the torque value, τ, measured by said second set of torque sensors ₆ Is the torque value, τ, measured by said third set of torque sensors _o Is the output torque value of the harmonic reducer.

Thereafter, the processor calculates a true torque transmitted by the harmonic reducer from torque values measured by the first, second, and third sets of torque sensors, wherein the true torque can include no torque ripple amount. More specifically, the above formulae (6), (7) and (8) can be expressed by the following formula (9) with respect to τ _o And (6) performing calculation.

τ _o ＝τ ₅ +τ ₆ -τ ₄ Formula (9)

Further, in this embodiment, a case where there is a positional error between the three sets of torque sensors is considered. That is, it is assumed that there are angular deviations Δ α and Δ β from the first set of torque sensors, respectively, after the second and third sets of torque sensors are arranged. Therefore, the second set of torque sensors is advanced (30 ° + Δ α) and the third set of torque sensors is retarded (30 ° + Δ β) from the first set of torque sensors, and the torque values measured by the second and third sets of torque sensors are as shown in equations (10) and (11) below, respectively,

τ _5′ ＝τ _o +τ _r+30° ＝τ _o +τ _pr sin (2 (. Theta. - (30. DELTA.)))))) (10)

Wherein, tau _5′ Is the torque value, τ, measured by said second set of torque sensors _6′ Is the torque value measured by the third set of torque sensors.

By the above-mentioned formulae (6), (10) and (11), τ can be measured by the following formula (12) _o And (6) performing calculation.

Further, in this embodiment, it is also possible to eliminate the high-frequency measurement signal component by using the kalman filter, thereby correcting the error and further improving the measurement accuracy.

Furthermore, in other embodiments of the present invention, the harmonic reducer may further include a circuit board to which the plurality of sets of torque sensors may be electrically connected. The circuit board is for example arranged on a side of the flexspline facing away from the toothed portion, fixedly connected to the flexspline, for example by bolting or gluing, and thereby rotatable in response to rotation of the flexspline. Further, on the circuit board, a processor for calculating the true torque, a memory for recording data relating to the output torque, and the like may also be mounted.

In addition, the invention provides a robot joint and a robot in another aspect. Referring now to fig. 7, a robot joint and a robot according to an embodiment of the present invention will be described. As shown, the robot 300 may include a plurality of connecting arms 301, any two adjacent connecting arms 301 being pivotably connected by respective robot joints 302, and these joints 302 may employ harmonic reducers as described above. The robot 300 further comprises robot jaws 303, one end of the robot jaws 303 being connected to the respective connecting arm 301, and at the other end of the robot jaws 303 one or more gripping means are provided. Thus, the robot 300 may be used to grab or capture an item. It should be understood by those of ordinary skill in the art that the configuration shown in fig. 7 is merely an exemplary embodiment of the robot 300. In other embodiments, the robot 300 may include more or fewer components, such as additional connecting arms and end effectors. Some components (e.g., two or more connecting arms) may be combined, and different or additional types of components than depicted may be employed. For example, the robot may also include I/O devices, network access devices, communication buses, processors, memory, actuators, and sensors to enable control of the system. For example, the robot 300 may include a processor and a memory storing instructions that, when executed by the processor, cause the processor to implement a control system. The memory may also store instructions that, when executed by the processor, cause the processor to activate or deactivate the robot gripper 303 in order to capture or release an item to be gripped.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "transverse," "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, but are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and are not to be construed as limiting 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 implicitly indicating 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 unless specifically defined 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 according to specific situations by those of ordinary skill in the art.

All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A harmonic reducer, comprising:

a wave generator;

a rigid wheel provided with internal teeth;

a flexible gear provided between the wave generator and the rigid gear and configured to be capable of intermeshing with the internal teeth of the rigid gear;

a plurality of sets of torque sensors, wherein each of the plurality of sets of torque sensors includes a plurality of strain gauges, each of the plurality of sets of torque sensors is for measuring torque transmitted by the harmonic reducer during rotation of the flexspline, wherein signals measured by each of the plurality of sets of torque sensors include an amount of torque ripple, and the plurality of sets of torque sensors are arranged crosswise; and

a processor configured to calculate a true torque transmitted by the harmonic reducer from signals measured by the plurality of sets of torque sensors, wherein the true torque does not include an amount of torque ripple.

2. The harmonic reducer of claim 1 wherein the plurality of sets of torque sensors includes a first set of torque sensors including four strain gauges and a second set of torque sensors including four strain gauges, the strain gauges of the first set of torque sensors being arranged crosswise with respect to the strain gauges of the second set of torque sensors at 45 ° intervals from each other.

3. The harmonic reducer of claim 2 further comprising:

an angle measurement device configured to measure an angle of the wave generator relative to the flex spline during rotation of the flex spline.

4. The harmonic reducer of claim 3 wherein the processor calculates the true torque according to:

wherein, tau _o Is the true torque, τ, transmitted by the harmonic reducer ₁ Is the torque value, τ, measured by said first set of torque sensors ₂ Is the torque value measured by the second set of torque sensors, and θ is the angle of the wave generator relative to the flexspline.

5. The harmonic reducer of claim 3, wherein the angle measurement device comprises a first angle sensor configured to measure an angle of the wave generator relative to the rigid gear during rotation of the flex spline and a second angle sensor configured to measure an angle of the flex spline relative to the rigid gear during rotation of the flex spline, thereby measuring an angle of the wave generator relative to the flex spline during rotation of the flex spline.

6. The harmonic reducer of claim 1 wherein the plurality of sets of torque sensors includes a first set of torque sensors including four strain gages, a second set of torque sensors including four strain gages, and a third set of torque sensors including four strain gages, the strain gages in the first set of torque sensors, the strain gages in the second set of torque sensors, and the strain gages in the third set of torque sensors being arranged crosswise spaced 30 ° apart from one another, wherein each strain gage in the second set of torque sensors is advanced 30 ° compared to a strain gage in an adjacent first set of torque sensors, and each strain gage in the third set of torque sensors is retarded 30 ° compared to a strain gage in an adjacent first set of torque sensors.

7. The harmonic reducer of claim 6 wherein the processor calculates the true torque according to:

τ _o ＝τ ₅ +τ ₆ -τ ₄

wherein, tau _o Is the true torque, τ, transmitted by said harmonic reducer ₄ Is made of said first set of torquesTorque value, tau, measured by a sensor ₅ Is the torque value, τ, measured by said second set of torque sensors ₆ Is the torque value, τ, measured by said third set of torque sensors _o Is the output torque value of the harmonic reducer.

8. The harmonic reducer of claim 6 wherein the processor calculates the true torque according to:

or

Wherein, tau _o Is the true torque, τ, transmitted by said harmonic reducer ₄ Is the torque value, τ, measured by said first set of torque sensors _5′ Is the torque value, τ, measured by said second set of torque sensors _6′ Is a torque value measured by the third set of torque sensors, Δ α is an angular offset between the second set of torque sensors and the first set of torque sensors, and Δ β is an angular offset between the third set of torque sensors and the first set of torque sensors.

9. The harmonic reducer of claim 1 wherein each of the plurality of sets of torque sensors is disposed on the flexspline and arranged about an axis of the flexspline.

10. The harmonic reducer of claim 9 wherein the flexspline comprises:

a body portion;

a toothed portion provided at one end of the body portion and configured to be capable of intermeshing with the internal teeth of the rigid gear; and

a flange extending radially outward from an end of the body portion opposite the toothed portion,

wherein the plurality of sets of torque sensors are disposed on at least one of an inner side of the flexspline, an outer side of the body portion, a side of the flange facing the toothed portion, and a side of the flange facing away from the toothed portion.

11. A method of measuring torque in a harmonic reducer, the harmonic reducer comprising:

a wave generator;

a rigid wheel provided with internal teeth;

a plurality of sets of torque sensors, wherein each set of the plurality of sets of torque sensors comprises a plurality of strain gauges, the plurality of sets of torque sensors being arranged crosswise; and

a processor for processing the received data, wherein the processor is used for processing the received data,

the method comprises the following steps:

measuring, by each of the plurality of sets of torque sensors, a torque transmitted by the harmonic reducer during rotation of the flexspline, wherein a signal measured by each of the plurality of sets of torque sensors includes an amount of torque ripple; and

calculating, by the processor, a true torque delivered by the harmonic reducer from the signals measured by the plurality of sets of torque sensors, wherein the true torque does not include an amount of torque ripple.

12. The method of claim 11, wherein the plurality of sets of torque sensors includes a first set of torque sensors including four strain gauges and a second set of torque sensors including four strain gauges, the strain gauges in the first set of torque sensors being arranged crosswise with respect to the strain gauges in the second set of torque sensors at 45 ° intervals from each other.

13. The method of claim 12, wherein the harmonic reducer further comprises:

14. The method of claim 13, wherein the processor calculates the true torque according to:

wherein, tau _o Is the true torque, τ, transmitted by said harmonic reducer ₁ Is the torque value, τ, measured by said first set of torque sensors ₂ Is the torque value measured by the second set of torque sensors, and θ is the angle of the wave generator relative to the flexspline.

15. The method of claim 13, wherein the angle measurement device comprises a first angle sensor configured to measure an angle of the wave generator relative to the rigid gear during rotation of the flex spline and a second angle sensor configured to measure an angle of the flex spline relative to the rigid gear during rotation of the flex spline, thereby measuring an angle of the wave generator relative to the flex spline during rotation of the flex spline.

16. The method of claim 11, wherein the plurality of sets of torque sensors includes a first set of torque sensors including four strain gauges, a second set of torque sensors including four strain gauges, and a third set of torque sensors including four strain gauges, the strain gauges in the first set of torque sensors, the strain gauges in the second set of torque sensors, and the strain gauges in the third set of torque sensors being arranged crosswise spaced 30 ° apart from one another, wherein each strain gauge in the second set of torque sensors is advanced 30 ° compared to a strain gauge in an adjacent first set of torque sensors, and each strain gauge in the third set of torque sensors is retarded 30 ° compared to a strain gauge in an adjacent first set of torque sensors.

17. The method of claim 16, wherein the processor calculates the true torque according to:

τ _o ＝τ ₅ +τ ₆ -τ ₄

wherein, tau _o Is the true torque, τ, transmitted by the harmonic reducer ₄ Is the torque value, τ, measured by said first set of torque sensors ₅ Is the torque value, τ, measured by said second set of torque sensors ₆ Is the torque value, τ, measured by said third set of torque sensors _o Is the output torque value of the harmonic reducer.

18. The method of claim 16, wherein the processor calculates the true torque according to:

or

19. The method of claim 11, wherein each of the plurality of sets of torque sensors is disposed on the flexspline and is arranged about an axis of the flexspline.

20. A robot comprising a plurality of link arms, any two adjacent link arms being pivotably connected by a robot joint, wherein the robot joint comprises a harmonic reducer according to any of claims 1 to 10.