High-precision joint torque sensor

Abstract

The utility model discloses a high-precision joint torque sensor, which comprises a torque sensor flange and a PCB (printed circuit board) arranged on the torque sensor flange, and is characterized in that the torque sensor flange comprises an outer flange, an inner flange and at least one strain beam group connected with the outer flange and the inner flange; an annular hollow part is formed between the outer flange and the inner flange; each strain beam group comprises four strain beams which are arranged in the annular hollow part at equal intervals along the circumferential direction; a first strain gauge and a second strain gauge are arranged on the front face or the back face of each strain beam, and the first strain gauges and the second strain gauges on the four strain beams of each strain beam set are connected through a PCB to form a Wheatstone bridge structure. According to the utility model, the strain gauges are connected to form the Wheatstone bridge, and the torque measurement can be completed only through one AD sampling, so that the measurement is more convenient.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of moment sensor, especially relates to a high-precision joint moment sensor. BACKGROUND

[0002] The moment sensor is usually applied to the joint of the collaborative robot, reads the torsion output by each joint, and can improve the safety performance through the mode, and can be used on the control algorithm to accurately control the speed of each joint of the collaborative robot to realize better performance. The collaborative robot usually takes safety as one of its performance indexes, and the safety is realized by adding the moment sensor to read the value of the torsion of each joint to improve the safety performance, and the function of dragging the end of the collaborative robot is realized. The moment sensor is installed at the output end of each joint of the collaborative robot and has the characteristics of compact structure.

[0003] The existing moment sensor generally pastes the metal strain gauge on the same side of the strain beam to realize the function of reading the torsion, but the crosstalk exists, which causes a large error in the reading of the moment sensor, so reducing the crosstalk becomes an index for improving the performance of the moment sensor, the smaller the influence of the crosstalk, the better the performance of the moment sensor, and the higher the corresponding precision and accuracy.

[0004] The structure of the existing moment sensor determines that the influence of the crosstalk cannot be reduced, and only the consistency of the elastic body of the moment sensor can be ensured within a certain range, and the influence of the crosstalk can be reduced by optimizing the structure. The strain gauge used at present is a metal strain gauge, which is pasted on the strain beam of the elastic body of the moment sensor, and the pasting accuracy and consistency cannot be guaranteed, which will amplify the influence of the crosstalk to a certain extent, and the influence of the crosstalk can be reduced by optimizing the strain gauge. In addition, the existing moment sensor is designed as a single channel without redundancy, and when the single channel is damaged, there is no standby channel to use. UTILITY MODEL CONTENTS

[0005] In view of the above technical problems of the prior art, the utility model solves the technical problems by providing a high-precision joint moment sensor.

[0006] To solve the above technical problems, the utility model provides the following technical scheme:

[0007] The application discloses a high-precision joint torque sensor, which comprises a torque sensor flange and a PCB circuit board arranged on the torque sensor flange, wherein the torque sensor flange comprises an outer flange, an inner flange and at least one set of strain beam groups connecting the outer flange and the inner flange; the outer flange is annular, the inner flange is arranged inside the outer flange and coaxially arranged with the outer flange, and a ring-shaped hollow is formed between the outer flange and the inner flange; each strain beam group comprises four strain beams arranged equidistantly in the circumferential direction inside the ring-shaped hollow; the outer flange, the inner flange and the strain beams each comprise a front surface and a back surface opposite to the front surface; the first strain gauge and the second strain gauge are arranged on the front surface or the back surface of each strain beam respectively; and the first strain gauges and the second strain gauges on the four strain beams of each strain beam group are connected to form a Wheatstone bridge structure through the PCB circuit board.

[0008] Further, each strain beam group comprises a first strain beam, a second strain beam, a third strain beam and a fourth strain beam arranged equidistantly in the circumferential direction inside the ring-shaped hollow in sequence; the first end of the first strain gauge of the first strain beam is electrically connected with the first end of the first strain gauge of the fourth strain beam; the second end of the first strain gauge of the fourth strain beam is electrically connected with the second end of the second strain gauge of the fourth strain beam; the first end of the second strain gauge of the fourth strain beam is electrically connected with the first end of the second strain gauge of the third strain beam.

[0009] The second end of the first strain gauge of the first strain beam is electrically connected with the second end of the second strain gauge of the first strain beam; the first end of the second strain gauge of the first strain beam is electrically connected with the first end of the second strain gauge of the second strain beam; the second end of the second strain gauge of the second strain beam is electrically connected with the second end of the first strain gauge of the second strain beam; the first end of the first strain gauge of the second strain beam is electrically connected with the first end of the first strain gauge of the third strain beam; and the second end of the first strain gauge of the third strain beam is electrically connected with the second end of the second strain gauge of the third strain beam.

[0010] Further, in one strain beam group, one of the strain beams is used as a positive strain beam, the strain beam opposite to the positive strain beam is used as a grounding strain beam, the remaining two strain beams in the strain beam group are used as an output positive end strain beam and an output negative end strain beam respectively; the second end of the first strain gauge of the positive strain beam is used as a voltage input end of the Wheatstone bridge structure and is used for connecting a positive voltage supply end; the second end of the first strain gauge of the grounding strain beam is used as a grounding end of the Wheatstone bridge structure and is used for grounding; the second end of the first strain gauge of the output positive end strain beam is used as an output positive end of the Wheatstone bridge structure and is used for connecting a positive end of a measuring device; and the second end of the first strain gauge of the output negative end strain beam is used as an output negative end of the Wheatstone bridge structure and is used for connecting a negative end of the measuring device.

[0011] Further, the first and second strain gauges are arranged on the front surface of the thin-walled strain beam, and a third strain gauge is arranged on the back surface of each strain beam at a position corresponding to the first strain gauge, and a fourth strain gauge is arranged on the back surface of each strain beam at a position corresponding to the second strain gauge, each third strain gauge is connected in parallel with the first strain gauge at the corresponding position, and each fourth strain gauge is connected in parallel with the second strain gauge at the corresponding position.

[0012] Further, the PCB circuit board is annular, and the PCB circuit board is fixed to the front surface of the inner flange by insulating adhesive; the PCB circuit board is provided with a grounding hole, the front surface of the inner flange is provided with a grounding threaded hole at a position corresponding to the grounding hole, a grounding screw rod is arranged in the grounding hole, and the grounding screw rod is screwed and fixed in the grounding threaded hole, so as to realize electrical connection between the grounding hole and the grounding threaded hole.

[0013] The PCB circuit board is provided with a notch at a position corresponding to each first and second strain gauge on the strain beam, the notch exposes the first and second strain gauges, a first pad and a second pad are arranged on one side of the notch at a position corresponding to the first strain gauge, and a third pad and a fourth pad are arranged on one side of the notch at a position corresponding to the second strain gauge; the first end of each first and third strain gauge is connected to the first pad at the corresponding position by a wire, and the second end is connected to the second pad at the corresponding position by a wire; the first end of each second and fourth strain gauge is connected to the third pad at the corresponding position by a wire, and the second end is connected to the fourth pad at the corresponding position by a wire.

[0014] Further, the first and second strain gauges are both silicon strain gauges, and the silicon strain gauges are fixedly arranged on the strain beam by a glass micro-fusion sintering process.

[0015] Further, the axis of each strain beam passes through the center of the inner flange, and the first and second strain gauges of each strain beam are symmetrically arranged along the axis of the strain beam.

[0016] Further, the angle between the axis of the first strain gauge and the axis of the second strain gauge is 90°, and the first and second strain gauges are arranged in a region with the largest strain of the strain beam, and the region with the largest strain of the strain beam is determined by the simulation result of the finite element simulation software.

[0017] Further, the outer flange, the inner flange and the strain beams are integrally formed by using a steel material; the inner flange is provided with a through hole in the middle, a plurality of inner flange threaded holes are arranged on the periphery of the through hole in the circumferential direction, and a convex ring is arranged on the back surface of the inner flange at the periphery of the plurality of inner flange threaded holes; and a plurality of outer flange threaded holes are arranged on the outer flange in the circumferential direction.

[0018] Further, the torque sensor comprises two strain beam groups, namely a first strain beam group and a second strain beam group, and the angle between the axis of each strain beam in the first strain beam group and the axis of the adjacent strain beam in the second strain beam group is 45°.

[0019] In the utility model, the strain gauges are connected to form a Wheatstone bridge, and the torque measurement can be completed by using one AD sampling, and the measurement is more convenient; the symmetry of the overall circuit structure is realized through the special bridge connection mode, and the crosstalk of the circuit is smaller. The strain gauges are arranged on the front and back surfaces of the strain beam, and the influence of external force in other directions except the torque direction can be basically eliminated, and the measurement precision of the torque value is greatly improved. The strain gauges are arranged in the area with the maximum strain of the strain beam through simulation, the first strain gauge and the second strain gauge are symmetrically arranged along the axis of the strain beam, the angle between the axis of the first strain gauge and the axis of the second strain gauge is 90°, and the precision of the tested torque can be further improved. The strain gauges use silicon strain gauges, and are fixed through a glass micro-melting sintering process, and compared with metal strain gauges, the sensitivity and anti-interference performance can be improved; the eight strain beams are used to form a double channel, and the redundant design can be realized, and normal work can be ensured when a channel fails. BRIEF DESCRIPTION OF DRAWINGS

[0020] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application, and the illustrative embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0021] Figure 1 It is a structure schematic view of the torque sensor flange in the high-precision joint torque sensor embodiment of the utility model.

[0022] Figure 2 It is a top view of the torque sensor flange.

[0023] Figure 3 It is a structure schematic view of the torque sensor flange in the high-precision joint torque sensor embodiment of the utility model. Figure 2

[0024] It is an enlarged view of A in the high-precision joint torque sensor embodiment of the utility model. Figure 4 Figure 2 It is a structure schematic view of the torque sensor flange in the high-precision joint torque sensor embodiment of the utility model.

[0025] Figure 5 It is a structure schematic view of the torque sensor flange in the high-precision joint torque sensor embodiment of the utility model. Figure 4

[0026] It is a circuit diagram of the Wheatstone bridge structure formed by connecting the first strain gauge and the second strain gauge of the first strain beam group. Figure 6

[0027] It is a circuit diagram of the Wheatstone bridge structure formed by connecting the first strain gauge and the second strain gauge of the first strain beam group.​Figure 7 A circuit diagram of a Wheatstone bridge structure formed by connecting the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge of the first strain beam group.

[0028] Figure 8 A circuit diagram of a Wheatstone bridge structure formed by connecting the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge of the second strain beam group.

[0029] The description of the drawings is as follows:

[0030] Torque sensor flange-100; outer flange-110; outer flange threaded hole-111; inner flange-120; through hole-121; inner flange threaded hole-122; inner flange disc pin hole-123; wire passing barrel threaded hole-124; grounding threaded hole-125; convex ring-126;

[0031] First strain beam-131, 135; second strain beam-132, 136; third strain beam-133, 137; fourth strain beam-134, 138; first strain gauge-141; second strain gauge-142; third strain gauge-143; fourth strain gauge-144; annular hollow-150;

[0032] PCB circuit board-200; first pad-201; second pad-202; third pad-203; fourth pad-204; grounding hole-210; notch-220. DETAILED DESCRIPTION

[0033] The embodiments of the present application are described below through specific specific examples, and the drawings provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and the following examples and features in the examples can be combined with each other without conflict.

[0034] Please refer to Figure 1 , Figure 2 and Figure 3 , the embodiment of the present application includes torque sensor flange 100 and PCB circuit board 200 arranged on torque sensor flange 100, the torque sensor flange 100 includes outer flange 110, inner flange 120 and at least one strain beam group connecting the outer flange 110 and the inner flange 120. The outer flange 110, the inner flange 120 and each strain beam are integrally formed by using a high hardness and high elongation steel material (such as stainless steel material) as a whole. The structure composed of the outer flange 110, the inner flange 120 and the strain beam can be called an elastic body. The outer flange 110, the inner flange 120 and the strain beam respectively include a front surface and a back surface opposite to the front surface.

[0035] The middle part of the inner flange 120 is provided with a through hole 121, and the periphery of the through hole 121 is provided with a plurality of inner flange threaded holes 122 in the circumferential direction. The periphery of the through hole 121 is generally also provided with a wire passing barrel threaded hole 124 and an inner flange disc pin hole 123. The back surface of the inner flange 120 is provided with a convex ring 126 corresponding to the periphery of the plurality of inner flange threaded holes 122; and the outer flange 110 is provided with a plurality of outer flange threaded holes 111 in the circumferential direction. The inner flange threaded holes 122 and the outer flange threaded holes 111 are used to connect different joints, the wire passing barrel threaded hole 124 is used to connect a wire passing barrel to facilitate wiring through the wire passing barrel (not shown in the figure), and the inner flange disc pin hole 123 is used to connect a load block through a pin (not shown in the figure), and the shear force transmitted through the pin can increase the transmitted torque.

[0036] The outer flange 110 is annular, the inner flange 120 is arranged inside the outer flange 110 and coaxially arranged with the outer flange 110. An annular hollow 150 is formed between the outer flange 110 and the inner flange 120. Each of the strain beam groups includes four strain beams arranged equidistantly in the circumferential direction inside the annular hollow 150. The thickness of the strain beam is smaller than the thickness of the outer flange 110, and the thickness of the strain beam is generally determined by simulation software according to the strain size requirement of the torque sensor. The front surface of the outer flange 110, the front surface of the inner flange 120 and the front surface of each strain beam are in the same plane. In this embodiment, two strain beam groups are arranged, which are a first strain beam group and a second strain beam group. Of course, in other embodiments, one strain beam group, three strain beam groups or more strain beam groups can also be arranged.

[0037] The first strain beam group includes a first strain beam 131, a second strain beam 132, a third strain beam 133 and a fourth strain beam 134 arranged equidistantly in the circumferential direction inside the annular hollow 150 in sequence, and the second strain beam group includes a first strain beam 135, a second strain beam 136, a third strain beam 137 and a fourth strain beam 138 arranged equidistantly in the circumferential direction inside the annular hollow 150 in sequence. The above eight strain beams are arranged equidistantly inside the annular hollow 150, that is, the angle between the axis of each strain beam in the first strain beam group and the axis of the adjacent strain beam in the second strain beam group is 45°.

[0038] In this embodiment, the front surface of each of the strain beams is respectively provided with a first strain gauge 141 and a second strain gauge 142. When the first strain gauge 141 and the second strain gauge 142 are arranged on only one surface of the strain beam, they are generally arranged on the front surface of the strain beam. Of course, in other embodiments, the first strain gauge 141 and the second strain gauge 142 can also be arranged on the back surface of the strain beam. The first strain gauge 141 and the second strain gauge 142 are generally arranged in the region with the largest strain of the strain beam, which is determined by the simulation results of the finite element simulation software. The axis of each of the strain beams passes through the center of the inner flange 120, and the first strain gauge 141 and the second strain gauge 142 of each of the strain beams are symmetrically arranged along the axis of the strain beam. The axis of the first strain gauge 141 and the axis of the second strain gauge 142 form a certain angle, and in this embodiment, the angle between the axis of the first strain gauge 141 and the axis of the second strain gauge 142 is 90°, at which the accuracy of testing the torsion force is the highest.

[0039] Please refer to Figure 4 , the "figure-eight" structure formed by the combination of the first strain gauge 141 and the second strain gauge 142 can have an outward opening. Please refer to Figure 5 , the "figure-eight" structure formed by the combination of the first strain gauge 141 and the second strain gauge 142 can also have an inward opening, as long as the angle between the axis of the first strain gauge 141 and the axis of the second strain gauge 142 is 90°.

[0040] The first strain gauge 141 and the second strain gauge 142 on the four strain beams of each strain beam group (a total of eight strain gauges) are connected to form a Wheatstone bridge structure through the PCB circuit board 200, and the Wheatstone bridge structure of each strain beam group forms a data acquisition channel. For example, in the first strain beam group, the first end of the first strain gauge 141 of the first strain beam 131 is electrically connected to the first end of the first strain gauge 141 of the fourth strain beam 134, the second end of the first strain gauge 141 of the fourth strain beam 134 is electrically connected to the second end of the second strain gauge 142 of the fourth strain beam 134, and the first end of the second strain gauge 142 of the fourth strain beam 134 is electrically connected to the first end of the second strain gauge 142 of the third strain beam 133. The second end of the first strain gauge 141 of the first strain beam 131 is electrically connected to the second end of the second strain gauge 142 of the first strain beam 131, the first end of the second strain gauge 142 of the first strain beam 131 is electrically connected to the first end of the second strain gauge 142 of the second strain beam 132, the second end of the second strain gauge 142 of the second strain beam 132 is electrically connected to the second end of the first strain gauge 141 of the second strain beam 132, the first end of the first strain gauge 141 of the second strain beam 132 is electrically connected to the first end of the first strain gauge 141 of the third strain beam 133, and the second end of the first strain gauge 141 of the third strain beam 133 is electrically connected to the second end of the second strain gauge 142 of the third strain beam 133.

[0041] The circuit structure formed after connection can be seen from Figure 6 , wherein P1-1 represents the first strain gauge 141 of the first strain beam 131, P2-1 represents the second strain gauge 142 of the first strain beam 131; P3-1 represents the first strain gauge 141 of the second strain beam 132, P4-1 represents the second strain gauge 142 of the second strain beam 132; P5-1 represents the first strain gauge 141 of the third strain beam 133, P6-1 represents the second strain gauge 142 of the third strain beam 133; P7-1 represents the first strain gauge 141 of the fourth strain beam 134, and P8-1 represents the second strain gauge 142 of the fourth strain beam 134. The point A in the circuit is the connection end of the first strain gauge 141 and the second strain gauge 142 of the first strain beam 131, the point F in the circuit is the connection end of the first strain gauge 141 and the second strain gauge 142 of the second strain beam 132, the point H in the circuit is the connection end of the first strain gauge 141 and the second strain gauge 142 of the third strain beam 133, and the point C in the circuit is the connection end of the first strain gauge 141 and the second strain gauge 142 of the fourth strain beam 134.

[0042] With the above connection mode, no matter from which connection end of the first strain gauge 141 and the second strain gauge 142 of the strain beam, the actual setting positions of the two strain gauges in the circuit are completely symmetrical, thereby realizing the symmetry and making the crosstalk of the circuit smaller. If the first strain gauge 141 and the second strain gauge 142 of each strain beam are connected in the same order to form a bridge, the symmetrical effect cannot be achieved. In addition, with the above connection mode, any strain beam in the strain beam group can be used as a positive strain beam without limiting a strain beam at a specific position as the positive strain beam. At this time, the strain beam opposite to the positive strain beam is a ground strain beam, and the remaining two strain beams in the strain beam group are an output positive end strain beam and an output negative end strain beam respectively. The second end of the first strain gauge 141 of the positive strain beam (i.e. the connection end of the first strain gauge 141 and the second strain gauge 142) is used as a voltage input end of the Wheatstone bridge structure for connecting a power supply voltage positive end (i.e. a VCC end), the second end of the first strain gauge 141 of the ground strain beam is used as a ground end of the Wheatstone bridge structure for grounding (i.e. a GND end), the second end of the first strain gauge 141 of the output positive end strain beam is used as an output positive end of the Wheatstone bridge structure for connecting a measurement device positive end, and the second end of the first strain gauge 141 of the output negative end strain beam is used as an output negative end of the Wheatstone bridge structure for connecting a measurement device negative end.

[0043] In the embodiment, the first strain beam 131 is used as the positive strain beam, i.e. the second end of the first strain gauge 141 of the first strain beam 131 is used as a voltage input end of the Wheatstone bridge structure, the second end of the first strain gauge 141 of the second strain beam 132 is used as an output negative end of the Wheatstone bridge structure, the second end of the first strain gauge 141 of the third strain beam 133 is used as a ground end of the Wheatstone bridge structure, and the second end of the first strain gauge 141 of the fourth strain beam 134 is used as an output positive end of the Wheatstone bridge structure. Of course, due to the symmetry of the circuit structure in the embodiment, the second strain beam 132 can also be used as the positive strain beam, i.e. the second end of the first strain gauge 141 of the second strain beam 132 is used as a voltage input end of the Wheatstone bridge structure, the second end of the first strain gauge 141 of the third strain beam 133 is used as an output negative end of the Wheatstone bridge structure, the second end of the first strain gauge 141 of the fourth strain beam 134 is used as a ground end of the Wheatstone bridge structure, and the second end of the first strain gauge 141 of the first strain beam 131 is used as an output positive end of the Wheatstone bridge structure; at this time, the setting positions of the strain gauges in the circuit are still completely symmetrical.

[0044] In order to better reduce the crosstalk, a third strain gauge 143 is arranged at the position corresponding to the first strain gauge 141 on the back of each strain beam, and a fourth strain gauge 144 is arranged at the position corresponding to the second strain gauge 142. That is, the third strain gauge 143 and the fourth strain gauge 144 of the strain beam are also symmetrically arranged along the axis of the strain beam in the region with the maximum strain of the strain beam, and the angle between the axis of the third strain gauge 143 and the axis of the fourth strain gauge 144 is also 90°. Each third strain gauge 143 is connected in parallel with the first strain gauge 141 at the corresponding position, and each fourth strain gauge 144 is connected in parallel with the second strain gauge 142 at the corresponding position. In the embodiment, the first strain gauge 141, the second strain gauge 142, the third strain gauge 143 and the fourth strain gauge 144 are all silicon strain gauges, which can be fixed on the strain beam by using a glass micro-fusion sintering process. Compared with the bonding method of metal strain gauges, the use of silicon strain gauges and the sintering process can improve the sensitivity and anti-interference performance.

[0045] After the third strain gauge 143 and the fourth strain gauge 144 are arranged on the back of each strain beam, the connection of the circuit structure formed will be described below. Figure 7 In the formula, P1-2 represents the third strain gauge 143 of the first strain beam 131, P2-2 represents the fourth strain gauge 144 of the first strain beam 131; P3-2 represents the third strain gauge 143 of the second strain beam 132, P4-2 represents the fourth strain gauge 144 of the second strain beam 132; P5-2 represents the third strain gauge 143 of the third strain beam 133, P6-2 represents the fourth strain gauge 144 of the third strain beam 133; P7-2 represents the third strain gauge 143 of the fourth strain beam 134, and P8-2 represents the fourth strain gauge 144 of the fourth strain beam 134. At this time, the first strain gauge 141 and the third strain gauge 143 at the corresponding position become an integral strain gauge, and the second strain gauge 142 and the fourth strain gauge 144 at the corresponding position become an integral strain gauge, and the working principle of the circuit remains unchanged.

[0046] Similarly, in the second strain beam group, the sixteen strain gauges (eight strain gauges if only the first strain gauge 141 and the second strain gauge 142 are arranged) on the four strain beams, i.e., the first strain gauge 141, the second strain gauge 142, the third strain gauge 143 and the fourth strain gauge 144, also form a Wheatstone bridge structure through the PCB circuit board 200, and the connection mode is the same as that of the first strain beam group. Please refer to Figure 8The circuit diagram formed after connecting the first strain gauge 141, the second strain gauge 142, the third strain gauge 143 and the fourth strain gauge 144 of the second strain beam group. Among them, R1-1 represents the first strain gauge 141 of the first strain beam 135, R1-2 represents the third strain gauge 143 of the first strain beam 135; R2-1 represents the second strain gauge 142 of the first strain beam 135; R2-2 represents the fourth strain gauge 144 of the first strain beam 135; R3-1 represents the first strain gauge 141 of the second strain beam 136, R3-2 represents the third strain gauge 143 of the second strain beam 136; R4-1 represents the second strain gauge 142 of the second strain beam 136, R4-2 represents the fourth strain gauge 144 of the second strain beam 136; R5-1 represents the first strain gauge 141 of the third strain beam 137, R5-2 represents the third strain gauge 143 of the third strain beam 137; R6-1 represents the second strain gauge 142 of the third strain beam 137, R6-2 represents the fourth strain gauge 144 of the third strain beam 137; R7-1 represents the first strain gauge 141 of the fourth strain beam 138, R7-2 represents the third strain gauge 143 of the fourth strain beam 138; R8-1 represents the second strain gauge 142 of the fourth strain beam 138, R8-2 represents the fourth strain gauge 144 of the fourth strain beam 138.

[0047] Please continue to see Figure 3 The PCB circuit board 200 is annular, and the PCB circuit board 200 is fixed on the front surface of the inner flange 120 by insulating adhesive. The PCB circuit board 200 is provided with a grounding hole 210, and the front surface of the inner flange 120 is provided with a grounding threaded hole 125 corresponding to the position of the grounding hole 210. A grounding screw (not shown in the figure) is arranged in the grounding hole 210 and is screwed and fixed in the grounding threaded hole 125, so as to realize the electrical connection between the grounding hole 210 and the grounding threaded hole 125, so that the PCB circuit board 200 can realize grounding through the grounding hole 210 and the grounding screw.

[0048] The PCB circuit board 200 is provided with a notch 220 at the position corresponding to each of the first strain gauges 141 and the second strain gauges 142 on the strain beam, the notch 220 exposes the first strain gauges 141 and the second strain gauges 142 to facilitate the lead connection of the first strain gauges 141 and the second strain gauges 142 with the pads (i.e. the first pad 201, the second pad 202, the third pad 203 and the fourth pad 204). One side of the notch 220 is provided with the first pad 201 and the second pad 202 at the position corresponding to the first strain gauges 141, and is provided with the third pad 203 and the fourth pad 204 at the position corresponding to the second strain gauges 142. The first end of each of the first strain gauges 141 and the third strain gauges 143 is connected with the first pad 201 at the corresponding position through a lead, and the second end is connected with the second pad 202 at the corresponding position through a lead, so as to realize the parallel connection of the first strain gauges 141 and the third strain gauges 143 at the corresponding position. The first end of each of the second strain gauges 142 and the fourth strain gauges 144 is connected with the third pad 203 at the corresponding position through a lead, and the second end is connected with the fourth pad 204 at the corresponding position through a lead, so as to realize the parallel connection of the second strain gauges 142 and the fourth strain gauges 144 at the corresponding position. Of course, the PCB circuit board 200 is also provided with printed leads connecting the various pads to realize the circuit structure as shown in Figure 7 and Figure 8 .

[0049] The working principle of the embodiment is as follows:

[0050] Please refer to Figures 1 to 8 , assuming that the joints of the collaborative robot include a first joint and a second joint, in use, the output end of the first joint of the collaborative robot is connected with the outer flange 110, fastened through the outer flange threaded hole 111, the input end of the second joint of the collaborative robot is connected with the inner flange 120, fastened through the inner flange threaded hole 122, and the load block is connected in the inner flange disc pin hole 123 through the pin, and the pin can improve the transmission torque of the inner flange 120. When the relative movement occurs between the first joint and the second joint, each strain beam will be deformed, and when deformed, the silicon strain gauges will be stretched or pressed to generate voltage and convert into torque values; taking the two channels of the eight strain beams in the embodiment as an example, the silicon strain gauges are divided into two groups, i.e. the silicon strain gauges of each strain beam group form a group, so as to form two channels of torque reading, in normal use, only the first channel formed by the silicon strain gauges of the first strain beam group can be used, and the second channel formed by the silicon strain gauges of the second strain beam group is used as a backup, which can be used when the first channel fails.

[0051] Taking the circuit in Figure 7 as an example, when measuring torque, the Figure 7The point A of the middle circuit is connected with the supply voltage VCC, the point H of the circuit is grounded, the point C of the circuit is connected with the positive terminal of the measuring device, and the point F of the circuit is connected with the negative terminal of the measuring device. Assuming that the resistance of each silicon strain gauge is R and the strain coefficient is Ks, taking the case of applying a clockwise torque as an example, assuming that the strain of each silicon strain gauge is ΔL and the resistance change is ΔR, the resistance of P1_1, P1_2, P3_1, P3_2, P5_1, P5_2, P7_1 and P7_2 is increased by (R+ΔR), and the resistance of P2_1, P2_2, P4_1, P4_2, P6_1, P6_2, P8_1 and P8_2 is decreased by (R-ΔR). At this time:

[0052] R A_B = R B_C = R F_G = R G_H = (R+ΔR) / 2

[0053] R A_E = R E_F = R C_D＝ R D_H = (R-ΔR) / 2

[0054] In the formula, R A_B represents Figure 6 the resistance between the points A and B, and the rest are similar.

[0055] ΔR=Ks×ΔL×R

[0056] V=V IN+ -V IN-

[0057] =ΔR / R×Vcc

[0058] =Ks×ΔL×Vcc

[0059] In the formula, V represents the measurement voltage of the measuring device; V IN+ represents the voltage of the point C; and V IN- represents the voltage of the point F. When a moment other than the torque direction is applied, V is almost unchanged. Therefore, by this bridge building mode, the measurement of the torque can be completed by only one AD sampling without measuring the deformation of each strain gauge, and the crosstalk generated by the force in the direction other than the torque direction can be reduced, so that the torque size can be effectively measured.

[0060] The existing torque sensor has poor anti-crosstalk performance, and the reading of the torque value is easily affected by the bending moment, axial force and radial force, so that the torque value is not very accurate. The embodiment aims to solve the crosstalk problem, so that the influence of the crosstalk on the accuracy is small, thereby improving the accuracy. The embodiment has the following advantages:

[0061] (1) by connecting the strain gauge to form a Wheatstone bridge, only one AD sampling is needed to complete the torque measurement, and the measurement is more convenient.

[0062] (2) the symmetry of the overall circuit structure is realized through a special bridge connection mode, so that the crosstalk of the circuit is smaller.

[0063] (3) through simulation, each strain gauge is arranged in the area with the maximum strain of the strain beam, the first strain gauge 141 and the second strain gauge 142 are symmetrically arranged along the axis of the strain beam, and the angle between the axis of the first strain gauge 141 and the axis of the second strain gauge 142 is 90°, so that the precision of the test torque can be further improved.

[0064] (4) the strain gauge uses a silicon strain gauge, and is fixed by a glass micro-fusion sintering process, so that the sensitivity and anti-interference performance can be improved.

[0065] (5) by arranging the strain gauges on the front and back surfaces of the strain beam, the influence of external force in other directions except the torque direction can be basically eliminated.

[0066] (6) the eight strain gauges are used to form a double-channel to realize a redundant design, so that the normal work can be ensured when a channel fails.

[0067] The above embodiments only express the preferred embodiments of the utility model, and the description is more specific and detailed, but it cannot be understood as the limitation of the scope of the utility model patent. It should be pointed out that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the utility model, and these belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent should be subject to the appended claims.

Claims

1. A high-precision joint torque sensor, characterized by: The torque sensor flange and the PCB circuit board arranged on the torque sensor flange, the torque sensor flange comprises an outer flange, an inner flange and at least one set of strain beam groups connecting the outer flange and the inner flange; the outer flange is annular, the inner flange is arranged inside the outer flange and coaxially arranged with the outer flange, and a ring-shaped hollow is formed between the outer flange and the inner flange; each strain beam group comprises four strain beams arranged equidistantly in the circumferential direction inside the ring-shaped hollow; the outer flange, the inner flange and the strain beams each comprise a front surface and a back surface opposite to the front surface; each strain beam is provided with a first strain gauge and a second strain gauge on the front surface or the back surface; the first strain gauges and the second strain gauges on the four strain beams of each strain beam group are connected to form a Wheatstone bridge structure through the PCB circuit board.

2. A high-precision joint torque sensor according to claim 1, characterized in that: Each strain beam group comprises a first strain beam, a second strain beam, a third strain beam and a fourth strain beam arranged equidistantly in the circumferential direction inside the ring-shaped hollow; the first end of the first strain gauge of the first strain beam is electrically connected to the first end of the first strain gauge of the fourth strain beam; the second end of the first strain gauge of the fourth strain beam is electrically connected to the second end of the second strain gauge of the fourth strain beam; the first end of the second strain gauge of the fourth strain beam is electrically connected to the first end of the second strain gauge of the third strain beam; The second end of the first strain gauge of the first strain beam is electrically connected to the second end of the second strain gauge of the first strain beam; the first end of the second strain gauge of the first strain beam is electrically connected to the first end of the second strain gauge of the second strain beam; the second end of the second strain gauge of the second strain beam is electrically connected to the second end of the first strain gauge of the second strain beam; the first end of the first strain gauge of the second strain beam is electrically connected to the first end of the first strain gauge of the third strain beam; the second end of the first strain gauge of the third strain beam is electrically connected to the second end of the second strain gauge of the third strain beam.

3. A high precision joint torque sensor as claimed in claim 2, characterized in that: In one strain beam group, one of the strain beams is used as a positive strain beam, the strain beam opposite to the positive strain beam is a ground strain beam, the remaining two strain beams in the strain beam group are output positive and negative strain beams respectively; the second end of the first strain gauge of the positive strain beam is used as a voltage input end of the Wheatstone bridge structure for connecting a positive voltage supply; the second end of the first strain gauge of the ground strain beam is used as a ground end of the Wheatstone bridge structure for grounding; the second end of the first strain gauge of the output positive strain beam is used as an output positive end of the Wheatstone bridge structure for connecting a positive end of a measuring device; the second end of the first strain gauge of the output negative strain beam is used as an output negative end of the Wheatstone bridge structure for connecting a negative end of the measuring device.

4. A high precision joint torque sensor as claimed in claim 3, characterized in that: The first strain gauges and the second strain gauges are arranged on the front surface of the thin-walled strain beam; each strain beam is provided with a third strain gauge at a position corresponding to the first strain gauge on the back surface and a fourth strain gauge at a position corresponding to the second strain gauge; each third strain gauge is connected in parallel with the first strain gauge at the corresponding position; each fourth strain gauge is connected in parallel with the second strain gauge at the corresponding position.

5. A high precision joint torque sensor as claimed in claim 4, characterized in that: The PCB circuit board is annular, and is fixed on the front surface of the inner flange by insulating adhesive; a grounding hole is arranged on the PCB circuit board, a grounding threaded hole is arranged on the front surface of the inner flange at a position corresponding to the grounding hole, a grounding screw rod is arranged in the grounding hole, and the grounding screw rod is screwed and fixed in the grounding threaded hole, so that the grounding hole and the grounding threaded hole are electrically connected. The PCB circuit board is provided with a notch at a position corresponding to each first strain gauge and second strain gauge on the strain beam, the notch exposes the first strain gauge and the second strain gauge, a first pad and a second pad are arranged on one side of the notch at a position corresponding to the first strain gauge, and a third pad and a fourth pad are arranged at a position corresponding to the second strain gauge; the first end of each first strain gauge and third strain gauge is connected to the first pad at the corresponding position by a wire, and the second end is connected to the second pad at the corresponding position by a wire; the first end of each second strain gauge and fourth strain gauge is connected to the third pad at the corresponding position by a wire, and the second end is connected to the fourth pad at the corresponding position by a wire.

6. A high-precision joint torque sensor according to any one of claims 1 to 5, characterized in that: The first strain gauge and the second strain gauge are both silicon strain gauges, and the silicon strain gauges are fixedly arranged on the strain beam by a glass micro-melting sintering process.

7. A high precision joint torque sensor as claimed in claim 6, characterized in that: The axis of each strain beam passes through the center of the inner flange, and the first strain gauge and the second strain gauge of each strain beam are symmetrically arranged along the axis of the strain beam.

8. A high precision joint torque sensor as claimed in claim 7, characterized in that: The angle between the axis of the first strain gauge and the axis of the second strain gauge is 90°, and the first strain gauge and the second strain gauge are arranged in a region with the maximum strain of the strain beam, and the region with the maximum strain of the strain beam is determined by the simulation result of the finite element simulation software.

9. A high-precision joint torque sensor according to any one of claims 1 to 5, characterized in that: The outer flange, the inner flange and each strain beam are integrally formed by using a steel material; a through hole is arranged in the middle of the inner flange, a plurality of inner flange threaded holes are arranged on the periphery of the through hole in the circumferential direction, and a convex ring is arranged on the back surface of the inner flange corresponding to the periphery of the plurality of inner flange threaded holes; a plurality of outer flange threaded holes are arranged on the outer flange in the circumferential direction.

10. A high-precision joint torque sensor according to any one of claims 1 to 5, characterized in that: The torque sensor comprises two strain beam groups, namely a first strain beam group and a second strain beam group, and the angle between the axis of each strain beam in the first strain beam group and the axis of the adjacent strain beam in the second strain beam group is 45°.

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