High-precision joint torque sensor

Abstract

The invention discloses a high-precision joint torque sensor, which comprises a torque sensor flange and a PCB 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 invention, 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 invention belongs to the field of torque sensors, and in particular relates to a high-precision joint torque sensor. Background Art

[0002] Torque sensors are usually used in the joints of collaborative robots to read the torque output of each joint. This can improve safety performance and can also be used in control algorithms to accurately control the speed of each joint of the collaborative robot to achieve better performance. Collaborative robots usually use safety as one of their performance indicators. Ways to achieve safety include installing torque sensors to read the torque value of each joint to improve safety performance, and to achieve the function of dragging the end of the collaborative robot. As a sensor that can read torque, the torque sensor is installed at the output end of each joint of the collaborative robot and has a compact structure.

[0003] Existing torque sensors generally stick metal strain gauges to the same side of the strain beam to achieve the function of reading torque. However, there is the influence of crosstalk, which causes large errors in the torque sensor readings. Therefore, reducing crosstalk has become an indicator for improving the performance of torque sensors. The smaller the crosstalk effect, the better the performance of the torque sensor, and the corresponding precision and accuracy are also higher.

[0004] The structure of the existing torque sensor determines that the impact of crosstalk cannot be reduced. The only way to ensure that the crosstalk is controlled within a certain range is to ensure the consistency of the torque sensor elastic body. If the structure is optimized, the impact of crosstalk can be reduced. The strain gauges currently used are metal strain gauges, and they are pasted to the strain beam of the torque sensor elastic body. The pasting accuracy and consistency cannot be guaranteed, which will amplify the impact of crosstalk to a certain extent. If the strain gauge is optimized, the impact of crosstalk can be reduced. In addition, the existing torque sensor is a single-channel design with no redundancy. If a single channel is damaged, there is no backup channel to use. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a high-precision joint torque sensor.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A high-precision joint torque sensor 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 strain beam group connecting the outer flange and the inner flange; the outer flange is annular, the inner flange is arranged inside the outer flange and coaxially with the outer flange, an annular hollow is formed between the outer flange and the inner flange, and each of the strain beam groups comprises four strain beams arranged in the annular hollow at equal intervals along the circumferential direction; the outer flange, the inner flange and the strain beam respectively comprise a front face and a back face opposite to the front face, a first strain gauge and a second strain gauge are respectively arranged on the front face or the back face of each of the strain beams, and the first strain gauge and the second strain gauge on the four strain beams of each of the strain beam groups are connected through the PCB circuit board to form a Wheatstone bridge structure.

[0008] Further, each of the strain beam groups comprises a first strain beam, a second strain beam, a third strain beam and a fourth strain beam which are arranged in the annular hollow in sequence and at equal intervals along the circumferential direction, a first end of a first strain gauge of the first strain beam is electrically connected to a first end of a first strain gauge of the fourth strain beam, a second end of the first strain gauge of the fourth strain beam is electrically connected to a second end of a second strain gauge of the fourth strain beam, and a first end of the second strain gauge of the fourth strain beam is electrically connected to a 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 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, and 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.

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

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

[0012] Furthermore, the PCB circuit board is annular, and the PCB circuit board is fixed to the front side of the inner flange by using insulating adhesive; a grounding hole is provided on the PCB circuit board, and a grounding threaded hole is provided at a position corresponding to the grounding hole on the front side of the inner flange, and a grounding screw is passed through the grounding hole, and the grounding screw is screwed and fixed in the grounding threaded hole, thereby realizing electrical connection between the grounding hole and the grounding threaded hole;

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

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

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

[0016] Furthermore, 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 the area where the strain amount of the strain beam is the largest, and the area where the strain amount of the strain beam is the largest is determined by the simulation results of finite element simulation software.

[0017] Furthermore, the outer flange, the inner flange and each strain beam are formed as a whole by integrally molding with rigid 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 along the circumferential direction, and a convex ring is arranged on the back side 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 along the circumferential direction.

[0018] Furthermore, the torque sensor includes 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 present invention, by connecting strain gauges to form a Wheatstone bridge, only one AD sampling is needed to complete the measurement of torque, which makes the measurement more convenient; the symmetry of the overall circuit structure is achieved through a special bridge connection method, which makes the circuit crosstalk smaller. By arranging strain gauges on the front and back sides of the strain beam, the influence of external forces in directions other than the torque direction can be basically eliminated, greatly improving the measurement accuracy of the torque value. Through simulation, each strain gauge is set in the area where the strain of the strain beam is the largest, and the first strain gauge and the second strain gauge are symmetrically arranged along the axis of the strain beam, and the angle between the axis of the first strain gauge and the axis of the second strain gauge is 90°, which can further improve the accuracy of the torque test. The strain gauge uses a silicon strain gauge and is fixed by a glass micro-melting sintering process. Compared with metal strain gauges, it can improve sensitivity and anti-interference performance; using eight strain beams to form a dual channel can achieve a redundant design, and normal operation can still be ensured when one channel fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0021] Figure 1 Schematic diagram of the structure of the torque sensor flange in one embodiment of the high-precision joint torque sensor of the present invention.

[0022] Figure 2 Top view of the torque sensor flange.

[0023] Figure 3 for Figure 2 Schematic diagram of the structure of the torque sensor flange after the PCB circuit board is installed.

[0024] Figure 4 for Figure 2 Enlarged view of point A in the middle.

[0025] Figure 5 For the general Figure 4 A schematic diagram of a combined structure of the first strain gauge and the second strain gauge when the opening is arranged inward.

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

[0027] 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 accompanying drawings in the specification are 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 pin hole-123; threaded hole for wire barrel-124; grounding threaded hole-125; convex ring-126;

[0031] First strain beams 131, 135; second strain beams 132, 136; third strain beams 133, 137; fourth strain beams 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 solder pad-201; second solder pad-202; third solder pad-203; fourth solder pad-204; grounding hole-210; notch-220. DETAILED DESCRIPTION

[0033] The following describes the implementation methods of the present invention through specific examples. The illustrations provided in the following embodiments are only used to schematically illustrate the basic concept of the present invention. The following embodiments and features in the embodiments may be combined with each other without conflict.

[0034] See also Figure 1 , Figure 2 and Figure 3 An embodiment of the high-precision joint torque sensor of the present invention includes a torque sensor flange 100 and a PCB circuit board 200 arranged on the torque sensor flange 100, wherein the torque sensor flange 100 includes an outer flange 110, an inner flange 120 and at least one set of strain beams 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 of a rigid material with high hardness and high elongation (such as stainless steel material). The structure composed of the outer flange 110, the inner flange 120 and the strain beam can be called an elastomer. The outer flange 110, the inner flange 120 and the strain beam respectively include a front side and a back side opposite to the front side.

[0035] A through hole 121 is provided in the middle of the inner flange 120, and a plurality of inner flange threaded holes 122 are provided on the periphery of the through hole 121 along the circumferential direction. A threaded hole 124 for passing a wire barrel and an inner flange pin hole 123 are generally provided on the periphery of the through hole 121. A convex ring 126 is provided on the back of the inner flange 120 corresponding to the periphery of the plurality of inner flange threaded holes 122; and a plurality of outer flange threaded holes 111 are provided on the outer flange 110 along the circumferential direction. The inner flange threaded holes 122 and the outer flange threaded holes 111 are used to connect different joints, the threaded hole 124 for passing a wire barrel is used to connect a wire barrel, so as to facilitate routing through the wire barrel (not shown in the figure), and the inner flange pin hole 123 is used to connect a load block through a pin (not shown in the figure), and the shear force transmitted by the pin can improve the transmission torque.

[0036] The outer flange 110 is annular, and 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, and each of the strain beam groups includes four strain beams arranged in the annular hollow 150 at equal intervals along the circumferential direction. The thickness of the strain beam is less 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 requirements of the torque sensor. The front of the outer flange 110, the front of the inner flange 120 and the front of each strain beam are all on the same plane. In this embodiment, there are two strain beam groups, namely the first strain beam group and the 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 set.

[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 which are arranged in the annular hollow 150 at equal intervals in the circumferential direction, 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 which are arranged in the annular hollow 150 at equal intervals in the circumferential direction. The above eight strain beams are arranged in the annular hollow 150 at equal intervals, 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, a first strain gauge 141 and a second strain gauge 142 are respectively arranged on the front side of each strain beam. When the first strain gauge 141 and the second strain gauge 142 are arranged only on one side of the strain beam, they are generally arranged on the front side 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 side of the strain beam. The first strain gauge 141 and the second strain gauge 142 are generally arranged in the area where the strain amount of the strain beam is the largest, and the area where the strain amount of the strain beam is the largest is determined by the simulation results of the finite element simulation software. The axis of each strain beam passes through the center of the inner flange 120, and the first strain gauge 141 and the second strain gauge 142 of each strain beam are symmetrically arranged along the axis of the strain beam. The axis of the first strain gauge 141 forms a certain angle with the axis of the second strain gauge 142. 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°, and the accuracy of the torque test is the highest at this time.

[0039] See also Figure 4 The "figure eight" structure formed by the combination of the first strain gauge 141 and the second strain gauge 142 can be opened outward. Figure 5 The "figure eight" structure formed by the combination of the first strain gauge 141 and the second strain gauge 142 can also be opened inward, 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 gauges 141 and the second strain gauges 142 (eight strain gauges in total) on the four strain beams of each strain beam group are connected through the PCB circuit board 200 to form a Wheatstone bridge structure, 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] Please refer to the circuit structure formed after connection Figure 6 , wherein P1-1 represents the first strain gauge 141 of the first strain beam 131, and 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, and 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, and 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. 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, 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, 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 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] By adopting the above connection method, no matter from which strain beam the first strain gauge 141 and the second strain gauge 142 connection end are viewed, the actual setting positions of the two strain gauges in the circuit are completely symmetrical, thereby achieving symmetry and making the circuit crosstalk smaller. If the first strain gauge 141 and the second strain gauge 142 of each strain beam are connected in the same order for bridge formation, such a symmetrical effect cannot be achieved. In addition, by adopting the above connection method, any one of the strain beams in the strain beam group can be used as the positive strain beam without limiting the strain beam at a specific position as the positive strain beam. At this time, the strain beam opposite to the positive strain beam is the grounded strain beam, and the remaining two strain beams in the strain beam group are the output positive end strain beam and the output negative end strain beam, respectively. The second end of the first strain gauge 141 of the positive strain beam (i.e., the connecting end of the first strain gauge 141 and the second strain gauge 142) is used as the voltage input end of the Wheatstone bridge structure to connect the positive end of the power supply voltage (i.e., the VCC end); the second end of the first strain gauge 141 of the grounded strain beam is used as the grounding end of the Wheatstone bridge structure for grounding (i.e., the GND end); the second end of the first strain gauge 141 of the output positive end strain beam is used as the output positive end of the Wheatstone bridge structure to connect the positive end of the measuring device; and the second end of the first strain gauge 141 of the output negative end strain beam is used as the output negative end of the Wheatstone bridge structure to connect the negative end of the measuring device.

[0043] In this embodiment, the first strain beam 131 is used as the positive strain beam, that is, the second end of the first strain gauge 141 of the first strain beam 131 is used as the 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 the 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 the 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 the output positive end of the Wheatstone bridge structure. Of course, due to the symmetry of the circuit structure in this embodiment, the second strain beam 132 can also be used as the positive strain beam, that is, the second end of the first strain gauge 141 of the second strain beam 132 is used as the 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 the 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 the 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 the output positive end of the Wheatstone bridge structure; in this case, the arrangement positions of the strain gauges in the circuit are still completely symmetrical.

[0044] In order to better reduce crosstalk, a third strain gauge 143 is generally provided at the position corresponding to the first strain gauge 141 on the back of each strain beam, and a fourth strain gauge 144 is provided 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 area where the strain amount of the strain beam is the largest, and the axis of the third strain gauge 143 and the axis of the fourth strain gauge 144 are also 90°. Each of the third strain gauges 143 is connected in parallel with the first strain gauge 141 at the corresponding position, and each of the fourth strain gauges 144 is connected in parallel with the second strain gauge 142 at the corresponding position. In this 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 using a glass micro-melting sintering process. The strain gauge adopts a silicon strain gauge and is fixed on the strain beam through a sintering process, which can improve the sensitivity and anti-interference performance compared with the bonding method of metal strain gauges.

[0045] After the third strain gauge 143 and the fourth strain gauge 144 are arranged on the back of each strain beam, the circuit structure formed after the connection is shown in FIG. Figure 7 , wherein 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, it is equivalent to turning the first strain gauge 141 and the third strain gauge 143 at the corresponding position into an integral strain gauge, turning the second strain gauge 142 and the fourth strain gauge 144 at the corresponding position into an integral strain gauge, and the working principle of the circuit remains unchanged.

[0046] Similarly, in the second strain beam group, the first strain gauge 141, the second strain gauge 142, the third strain gauge 143 and the fourth strain gauge 144 on the four strain beams, a total of sixteen strain gauges (eight strain gauges if only the first strain gauge 141 and the second strain gauge 142 are provided) will also be connected through the PCB circuit board 200 to form a Wheatstone bridge structure, and the connection method is the same as that of the first strain beam group. Figure 8, is a circuit diagram formed by 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 4; R5-1 represents the first strain gauge 141 of the third strain beam 137, and 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, and 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, and 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, and R8-2 represents the fourth strain gauge 144 of the fourth strain beam 138.

[0047] Please continue reading Figure 3 The PCB circuit board 200 is annular, and the PCB circuit board 200 is fixed to the front of the inner flange 120 by using insulating adhesive. A grounding hole 210 is provided on the PCB circuit board 200, and a grounding threaded hole 125 is provided at a position corresponding to the grounding hole 210 on the front of the inner flange 120. A grounding screw (not shown in the figure) is passed through the grounding hole 210, and the grounding screw is screwed and fixed in the grounding threaded hole 125, thereby realizing electrical connection between the grounding hole 210 and the grounding threaded hole 125, so that the PCB circuit board 200 can be grounded 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 the first strain gauge 141 and the second strain gauge 142 on each strain beam, and the notch 220 exposes the first strain gauge 141 and the second strain gauge 142, so as to facilitate the lead connection of the first strain gauge 141 and the second strain gauge 142 with the pads (i.e., the first pad 201, the second pad 202, the third pad 203 and the fourth pad 204). The first pad 201 and the second pad 202 are provided at the position corresponding to the first strain gauge 141 on one side of the notch 220, and the third pad 203 and the fourth pad 204 are provided at the position corresponding to the second strain gauge 142. The first end of each of the first strain gauge 141 and the third strain gauge 143 is connected to the first pad 201 at the corresponding position through a wire, and the second end is connected to the second pad 202 at the corresponding position through a wire, so as to realize the parallel connection of the first strain gauge 141 and the third strain gauge 143 at the corresponding position. The first end of each of the second strain gauge 142 and the fourth strain gauge 144 is connected to the third pad 203 at the corresponding position through a wire, and the second end is connected to the fourth pad 204 at the corresponding position through a wire, so as to realize the parallel connection of the second strain gauge 142 and the fourth strain gauge 144 at the corresponding position. Of course, the PCB circuit board 200 is also provided with printed wires connecting the various pads to realize Figure 7 and Figure 8 The circuit structure shown.

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

[0050] See also Figures 1 to 8 , assuming that the joint of the collaborative robot includes a first joint and a second joint, when in use, the output end of the first joint of the collaborative robot is connected to the outer flange 110, and fastened through the outer flange threaded hole 111, the input end of the second joint of the collaborative robot is connected to the inner flange 120, and fastened through the inner flange threaded hole 122, and the load block is connected to the inner flange pin hole 123 through a pin, and the pin can increase the transmission torque of the inner flange 120. When the first joint and the second joint move relative to each other, each strain beam will deform, and when deformed, the silicon strain gauge will be stretched or squeezed to generate voltage and converted into torque value; taking the eight strain beams and two channels of this embodiment as an example, the silicon strain gauge is divided into two groups, that is, the silicon strain gauge of each strain beam group is a group, so that the torque reading of the two channels can be formed. In normal use, only the first channel formed by the silicon strain gauge of the first strain beam group can be used, and the second channel formed by the silicon strain gauge of the second strain beam group is used as a backup, which can be used when the first channel fails.

[0051] by Figure 7 Take the circuit in as an example, when measuring torque, Figure 7Point A of the circuit is connected to the power supply voltage VCC, and point H of the circuit is grounded; point C of the circuit is connected to the positive terminal of the measuring device, and point F of the circuit is connected to the negative terminal of the measuring device. Assume that the resistance of each silicon strain gauge is R and the strain factor is Ks; take the application of clockwise torque as an example, assuming that the strain of each silicon strain gauge is ΔL and the resistance change is ΔR, then the resistance of P1_1, P1_2, P3_1, P3_2, P5_1, P5_2, P7_1 and P7_2 increases to (R+ΔR), and the resistance of P2_1, P2_2, P4_1, P4_2, P6_1, P6_2, P8_1 and P8_2 decreases to (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 express Figure 6 The resistance between point A and point B, and so on for the rest.

[0055] ΔR=Ks×ΔL×R

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

[0057] =ΔR / R×Vcc

[0058] =Ks×ΔL×Vcc

[0059] Where V represents the measurement voltage of the measuring device; V IN+ Represents the voltage at point C; V IN- Indicates the voltage at point F. When a torque other than the torque direction is applied, V remains almost unchanged. Therefore, through this bridge construction method, the torque can be measured by only one AD sampling without measuring the deformation of each strain gauge; and the crosstalk caused by forces in directions other than the torsion direction can be reduced, thereby effectively measuring the torque.

[0060] The existing torque sensor has insufficient anti-crosstalk performance, and the torque value read is easily affected by the bending moment, axial force, and radial force, so it is not very accurate. This embodiment aims to solve the crosstalk problem, reduce the impact of crosstalk on accuracy, and thus improve accuracy; it has the following main advantages:

[0061] (1) By connecting strain gauges to form a Wheatstone bridge, torque measurement can be completed using only one AD sampling, making measurement more convenient.

[0062] (2) The symmetry of the overall circuit structure is achieved through a special bridge connection method, which reduces the crosstalk of the circuit.

[0063] (3) Through simulation, each strain gauge is set in the area where the strain of the strain beam is the largest, and 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°, which can further improve the accuracy of the torque test.

[0064] (4) The strain gauge uses a silicon strain gauge and is fixed by a glass micro-melting sintering process, which can improve sensitivity and anti-interference performance.

[0065] (5) By arranging strain gauges on the front and back sides of the strain beam, the influence of external forces in directions other than the torque direction can be basically eliminated.

[0066] (6) Using eight strain beams to form dual channels can achieve redundant design and ensure normal operation when one channel fails.

[0067] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high-precision joint torque sensor, characterized in that: The invention 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 strain beam group connecting the outer flange and the inner flange; the outer flange is annular, the inner flange is arranged inside the outer flange and coaxially with the outer flange, an annular hollow is formed between the outer flange and the inner flange, and each of the strain beam groups comprises four strain beams arranged in the annular hollow at equal intervals along the circumferential direction; the outer flange, the inner flange and the strain beams respectively comprise a front face and a back face opposite to the front face, a first strain gauge and a second strain gauge are respectively arranged on the front face or the back face of each of the strain beams, and the first strain gauge and the second strain gauge on the four strain beams of each of the strain beam groups are connected through the PCB circuit board to form a Wheatstone bridge structure.

2. The high-precision joint torque sensor according to claim 1, characterized in that: Each of the strain beam groups comprises a first strain beam, a second strain beam, a third strain beam and a fourth strain beam which are arranged in the annular hollow in sequence and at equal intervals along the circumferential direction, a first end of a first strain gauge of the first strain beam is electrically connected to a first end of a first strain gauge of the fourth strain beam, a second end of the first strain gauge of the fourth strain beam is electrically connected to a second end of a second strain gauge of the fourth strain beam, and a first end of the second strain gauge of the fourth strain beam is electrically connected to a first end of a 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, and 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. The high-precision joint torque sensor according to claim 2, characterized in that: In one of the strain beam groups, one of the strain beams is used as the positive strain beam, and the strain beam opposite to the positive strain beam is the grounded strain beam. The remaining two strain beams in the strain beam group are respectively an output positive end strain beam and an output negative end strain beam. The second end of the first strain gauge of the positive strain beam is used as the voltage input end of the Wheatstone bridge structure to connect the positive end of the power supply voltage, the second end of the first strain gauge of the grounded strain beam is used as the grounding end of the Wheatstone bridge structure for grounding, the second end of the first strain gauge of the output positive end strain beam is used as the output positive end of the Wheatstone bridge structure to connect the positive end of the measuring device, and the second end of the first strain gauge of the output negative end strain beam is used as the output negative end of the Wheatstone bridge structure to connect the negative end of the measuring device.

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

5. The high-precision joint torque sensor according to claim 4, characterized in that: The PCB circuit board is annular, and the PCB circuit board is fixed to the front side of the inner flange by using insulating adhesive; a grounding hole is provided on the PCB circuit board, and a grounding threaded hole is provided at a position corresponding to the grounding hole on the front side of the inner flange, a grounding screw is passed through the grounding hole, and the grounding screw is screwed and fixed in the grounding threaded hole, thereby realizing electrical connection between the grounding hole and the grounding threaded hole; The PCB circuit board is respectively provided with a notch at a position corresponding to the first strain gauge and the second strain gauge on each strain beam, and the notch exposes the first strain gauge and the second strain gauge; a first pad and a second pad are provided at a position corresponding to the first strain gauge on one side of the notch, and a third pad and a fourth pad are provided at a position corresponding to the second strain gauge; a first end of each of the first strain gauge and the third strain gauge is connected to the first pad at the corresponding position through a wire, and a second end is connected to the second pad at the corresponding position through a wire; a first end of each of the second strain gauge and the fourth strain gauge is connected to the third pad at the corresponding position through a wire, and a second end is connected to the fourth pad at the corresponding position through a wire.

6. The 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 using a glass micro-melting sintering process.

7. The high-precision joint torque sensor according to 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. The high-precision joint torque sensor according to claim 7, characterized in that: The included angle between the axis of the first strain gauge and the axis of the second strain gauge is 90 degrees, and the first strain gauge and the second strain gauge are arranged in the area where the strain amount of the strain beam is the largest. The area where the strain amount of the strain beam is the largest is determined by the simulation results of finite element simulation software.

9. The 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 of rigid material; a through hole is provided in the middle of the inner flange, a plurality of inner flange threaded holes are provided on the periphery of the through hole along the circumferential direction, and a convex ring is provided on the back side of the inner flange corresponding to the periphery of the plurality of inner flange threaded holes; a plurality of outer flange threaded holes are provided on the outer flange along the circumferential direction.

10. The 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. The included 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°.

Images