High-torsion rigid joint torque sensor
By adopting thin-wall strain beam and Wheatston bridge structure in the torque sensor, combined with the design of annular groove and flange, the problems of insufficient rigidity and great crosstalk influence of existing torque sensors are solved, and high torsional rigidity and high precision torque are achieved Sensor, suitable for collaborative robots.
Patent Information
- Application Number
- CN202411876422.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-07-23
- Filing Date
- 2024-12-19
- Publication Date
- 2025-02-11
AI Technical Summary
The existing torque sensors have insufficient structural rigidity and great crosstalk impact, resulting in long stability time for collaborative robots during precise positioning, large reading errors, and lack of redundancy in single-channel design.
A high torsion rigid joint torque sensor is designed, using thin-walled strain beams and Wheatston bridge structures, which enhances torsional rigidity through a combination of annular grooves and flanges, and reduces crosstalk influence through a dual-channel structure and symmetrical circuit design.
The torsional rigidity and measurement accuracy of the torque sensor are improved, the stability time of the collaborative robot at the target position is shortened, reading errors are reduced, and redundant protection is achieved through a dual-channel design.
Smart Images
Figure CN119413340A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of torque sensors, and in particular relates to a high torsional rigidity joint torque sensor. Background Art
[0002] When a collaborative robot is operating, the rigidity of each component is inconsistent, and the rigidity of the collaborative robot is generally determined by the weakest rigid component. Rigidity has a relatively large impact on the performance of the collaborative robot. During the operation of the collaborative robot, due to the constant presence of inertia, the end effector will swing when it stops. A stabilization time is required to allow the end effector to accurately position at the target position. The stabilization time is related to the rigidity. Under the same control parameters, the better the rigidity, the shorter the stabilization time, and the worse the rigidity, the longer the stabilization time. It can be seen that collaborative robots have a demand for high rigidity. At the same time, torque sensors need to be installed to ensure safety. At this time, torque sensors become an important component for collaborative robots to improve rigidity.
[0003] Most of the existing torque sensors are beam structures, with as few as 2-4 strain beams and as many as 8 strain beams or even more. Most torque sensors use metal strain gauges, which are pasted to the same side of the strain beams. Whether the existing torque sensors have 2 strain beams, 4 strain beams or 8 strain beams, their rigidity has certain disadvantages. The rigidity of torque sensors with fewer strain beams will be worse, and the rigidity of torque sensors with more strain beams will be slightly better, but overall the deformation is a bit large, which affects the rigidity of the collaborative robot to a certain extent. If the rigidity problem is to be solved, it is necessary to design from a structural perspective.
[0004] In addition, the existing torque sensors generally paste the metal strain gauges on the same side of the strain beam, which causes crosstalk when reading torque, resulting in large errors in the torque sensor readings. The strain gauges currently used are generally metal strain gauges, and are fixed to the strain beam of the torque sensor elastic body by pasting. The pasting accuracy and consistency cannot be guaranteed, which will amplify the impact of crosstalk to a certain extent. In addition, the existing torque sensors are single-channel designs with no redundancy. If a single channel is damaged, there is no spare channel available. 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 torsional rigidity joint torque sensor.
[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:
[0007] A high torsional rigidity 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 a front side and a back side opposite to the front side, and an annular groove is arranged on the back side or the front side of the torque sensor flange; the portion of the torque sensor flange located outside the annular groove forms an outer flange, and the portion of the torque sensor flange located inside the annular groove forms an inner flange, and the groove bottom of the annular groove forms a thin-walled strain beam; at least one strain gauge group is arranged on the thin-walled strain beam, and each of the strain gauge groups comprises four front strain gauge pairs arranged at equal intervals along the circumferential direction on the front side or the back side of the thin-walled strain beam, and each of the front strain gauge pairs comprises a first strain gauge and a second strain gauge; the four first strain gauges and the four second strain gauges of each strain gauge group are connected through the PCB circuit board to form a Wheatstone bridge structure.
[0008] Further, each of the strain gauge groups respectively includes a first front strain gauge pair, a second front strain gauge pair, a third front strain gauge pair and a fourth front strain gauge pair which are arranged on the thin-walled strain beam in sequence and at equal intervals along the circumferential direction, a first end of the first strain gauge of the first front strain gauge pair is electrically connected to a first end of the first strain gauge of the fourth front strain gauge pair, a second end of the first strain gauge of the fourth front strain gauge pair is electrically connected to a second end of the second strain gauge of the fourth front strain gauge pair, and a first end of the second strain gauge of the fourth front strain gauge pair is electrically connected to a first end of the second strain gauge of the third front strain gauge pair;
[0009] The second end of the first strain gauge of the first front strain gauge pair is electrically connected to the second end of the second strain gauge of the first front strain gauge pair, the first end of the second strain gauge of the first front strain gauge pair is electrically connected to the first end of the second strain gauge of the second front strain gauge pair, the second end of the second strain gauge of the second front strain gauge pair is electrically connected to the second end of the first strain gauge of the second front strain gauge pair, the first end of the first strain gauge of the second front strain gauge pair is electrically connected to the first end of the first strain gauge of the third front strain gauge pair, and the second end of the first strain gauge of the third front strain gauge pair is electrically connected to the second end of the second strain gauge of the third front strain gauge pair.
[0010] Furthermore, in the strain gauge group, one of the positive strain gauge pairs is used as the positive strain gauge pair, and the positive strain gauge pair opposite to the positive strain gauge pair is the grounding strain gauge pair, and the remaining two positive strain gauge pairs in the strain gauge group are respectively an output positive end strain gauge pair and an output negative end strain gauge pair, the second end of the first strain gauge of the positive strain gauge pair is used as the voltage input end of the Wheatstone bridge structure for connecting the positive end of the power supply voltage, the second end of the first strain gauge of the grounding strain gauge pair 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 gauge pair is used as the output positive end of the Wheatstone bridge structure for connecting the positive end of the measuring device, and the second end of the first strain gauge of the output negative end strain gauge pair is used as the output negative end of the Wheatstone bridge structure for connecting the negative end of the measuring device.
[0011] Furthermore, the four front strain gauge pairs are arranged on the front side of the thin-walled strain beam, and the strain gauge group also includes four back strain gauge pairs arranged on the back side of the thin-walled strain beam, and the back strain gauge pairs correspond to the front strain gauge pairs one by one; each of the back strain gauge pairs respectively includes a third strain gauge and a fourth strain gauge, the third strain gauge is arranged opposite to the first strain gauge of the corresponding front strain gauge pair, and the fourth strain gauge is arranged opposite to the second strain gauge of the corresponding front strain gauge pair; a first strain gauge wiring hole is respectively arranged on one side of each of the third strain gauges, and a second strain gauge wiring hole is respectively arranged on one side of each of the fourth strain gauges; 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] A notch is respectively provided at a position corresponding to each pair of front strain gauges on the PCB circuit board, and the notch exposes the third strain gauge and the fourth 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 thin-walled strain beam by using a glass micro-melting sintering process.
[0015] Furthermore, the first strain gauge and the second strain gauge of each front strain gauge pair are symmetrically arranged, and the symmetry axis of the first strain gauge and the second strain gauge passes through the center of the inner flange; the angle between the axis of the first strain gauge and the axis of the second strain gauge and the symmetry axis is 45°.
[0016] Furthermore, the thickness of the thin-walled strain beam is determined by simulation software according to the strain size requirement of the torque sensor; the first strain gauge and the second strain gauge are arranged in the area where the strain of the thin-walled strain beam is the largest, and the area where the strain of the thin-walled strain beam is the largest is determined by the simulation results of finite element simulation software.
[0017] Furthermore, the torque sensor flange is made of rigid material; a through hole is arranged in the middle of the inner flange, a plurality of inner flange threaded holes are arranged around the through hole in a circumferential direction, a convex ring is arranged on the back 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 a circumferential direction.
[0018] Furthermore, the torque sensor includes two strain gauge groups, namely a first strain gauge group and a second strain gauge group, and the spacing between each front strain gauge pair in the first strain gauge group and the adjacent front strain gauge pair in the second strain gauge group is equal.
[0019] In the present invention, the thin-walled strain beam is a thin ring, which can fill the gap between the outer flange and the inner flange, so that the thin-walled strain beam, the outer flange and the inner flange form a whole without being hollowed out, thereby strengthening the torsional rigidity. At the same time, by controlling the thickness of the thin-walled strain beam, the deformation amount can be used to squeeze the strain gauge, that is, the rigidity is improved and the reading accuracy is guaranteed. By connecting the strain gauges to form a Wheatstone bridge, only one AD sampling is needed to complete the torque measurement, which is more convenient; the symmetry of the overall circuit structure is achieved through a special bridge connection method, so that the crosstalk of the circuit is smaller. By setting strain gauges on the front and back of the thin-walled strain beam respectively, the influence of external forces in other directions other than the torque direction can be basically eliminated, and the measurement accuracy of the torque value can be greatly improved. By simulating, each strain gauge is set in the area where the strain amount of the thin-walled strain beam is the largest, and the first strain gauge and the second strain gauge are set symmetrically, which can further improve the accuracy of the test torque. The strain gauge uses a silicon strain gauge and is fixed by a glass micro-melting sintering process, which can improve the sensitivity and anti-interference performance compared with the metal strain gauge. 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 This is a schematic structural diagram of the torque sensor flange in an embodiment of the high torsional rigidity 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 positive strain gauge pair of the first strain gauge group.
[0027] Figure 7 A circuit diagram of a Wheatstone bridge structure formed by connecting the front strain gauge pair and the back strain gauge pair of the first strain gauge group.
[0028] Figure 8 A circuit diagram of a Wheatstone bridge structure formed by connecting the front strain gauge pair and the back strain gauge pair of the second strain gauge 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] The first front strain gauge pair - 131, 135; the second front strain gauge pair - 132, 136; the third front strain gauge pair - 133, 137; the fourth front strain gauge pair - 134, 138; the first strain gauge - 141; the second strain gauge - 142; the third strain gauge - 143; the fourth strain gauge - 144; the annular groove - 150; the thin-walled strain beam - 160; the first strain gauge routing hole - 161; the second strain gauge routing hole - 162; the first back strain gauge pair - 171, 175; the second back strain gauge pair - 172, 176; the third back strain gauge pair - 173, 177; the fourth back strain gauge pair - 174, 178;
[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 torsional rigidity 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. The torque sensor flange 100 includes a front side and a back side opposite to the front side. The torque sensor flange 100 is provided with an annular groove 150, and the annular groove 150 is generally arranged on the back side of the torque sensor flange 100. Of course, the annular groove 150 can also be arranged on the front side of the torque sensor flange 100. The portion of the torque sensor flange 100 located outside the annular groove 150 forms an outer flange 110, and the portion of the torque sensor flange 100 located inside the annular groove 150 forms an inner flange 120. The bottom of the annular groove 120 forms a thin-walled strain beam 160; the thickness of the thin-walled strain beam 160 (i.e., the residual thickness of the annular groove 150) is generally determined by simulation software according to the strain size requirements of the torque sensor. The torque sensor flange 100 is made of a rigid material with high hardness and high elongation (such as stainless steel). The structure composed of the outer flange 110 , the inner flange 120 and the thin-walled strain beam 160 may be referred to as an elastic body.
[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] In this embodiment, two strain gauge groups are arranged on the thin-walled strain beam 160, namely, the first strain gauge group and the second strain gauge group. Of course, in other embodiments, one strain gauge group, three strain gauge groups or more strain gauge groups may also be arranged. Each of the strain gauge groups includes four front strain gauge pairs arranged at equal intervals along the circumferential direction on the front side of the thin-walled strain beam 160. When the front strain gauge pair is arranged on only one side of the thin-walled strain beam 160, it is generally arranged on the front side of the thin-walled strain beam 160. Of course, in other embodiments, the four front strain gauge pairs may also be arranged on the back side of the thin-walled strain beam 160. Each of the front strain gauge pairs includes a first strain gauge 141 and a second strain gauge 142. The first strain gauge 141 and the second strain gauge 142 are generally arranged in the area where the strain of the thin-walled strain beam 160 is the largest. The area where the strain of the thin-walled strain beam 160 is the largest can be determined by the simulation results of the finite element simulation software. According to the simulation results, the area with the largest strain of the thin-walled strain beam 160 is an annular area. Therefore, when setting the front strain gauge pairs, it is only necessary to ensure the relative positions between the front strain gauge pairs.
[0037] The first strain gauge 141 and the second strain gauge 142 of each of the front strain gauge pairs are symmetrically arranged, and the symmetry axes of the first strain gauge 141 and the second strain gauge 142 pass through the center of the inner flange 120. The axis of the first strain gauge 141 and the axis of the second strain gauge 142 form a certain angle. In this embodiment, the angles between the axis of the first strain gauge 141 and the axis of the second strain gauge 142 and the symmetry axis are both 45°. That is, 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.
[0038] 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 5The "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°.
[0039] Each of the strain gauge groups includes a first front strain gauge pair, a second front strain gauge pair, a third front strain gauge pair, and a fourth front strain gauge pair, which are arranged on the thin-walled strain beam 160 at equal intervals in the circumferential direction. In this embodiment, the first strain gauge group includes a first front strain gauge pair 131, a second front strain gauge pair 132, a third front strain gauge pair 133, and a fourth front strain gauge pair 134, which are arranged on the front of the thin-walled strain beam 160 at equal intervals in the circumferential direction, and the second strain gauge group includes a first front strain gauge pair 135, a second front strain gauge pair 136, a third front strain gauge pair 137, and a fourth front strain gauge pair 138, which are arranged on the front of the thin-walled strain beam 160 at equal intervals in the circumferential direction. The eight front strain gauge pairs are arranged at equal intervals on the thin-walled strain beam 160, that is, the angle between the symmetry axis of the first strain gauge 141 and the second strain gauge 142 in each front strain gauge pair in the first strain gauge group and the symmetry axis of the first strain gauge 141 and the second strain gauge 142 in the adjacent front strain gauge pair in the second strain gauge group is 45°. For example, the angle between the symmetry axis of the first strain gauge 141 and the second strain gauge 142 in the first front strain gauge pair 131 and the symmetry axis of the first strain gauge 141 and the second strain gauge 142 in the first front strain gauge pair 135 is 45°.
[0040] The first strain gauge 141 and the second strain gauge 142 (eight strain gauges in total) on the four front strain gauge pairs of each strain gauge group are connected through the PCB circuit board 200 to form a Wheatstone bridge structure, and the Wheatstone bridge structure of each strain gauge group forms a data acquisition channel. For example, in the first strain gauge group, the first end of the first strain gauge 141 of the first front strain gauge pair 131 is electrically connected to the first end of the first strain gauge 141 of the fourth front strain gauge pair 134, the second end of the first strain gauge 141 of the fourth front strain gauge pair 134 is electrically connected to the second end of the second strain gauge 142 of the fourth front strain gauge pair 134, and the first end of the second strain gauge 142 of the fourth front strain gauge pair 134 is electrically connected to the first end of the second strain gauge 142 of the third front strain gauge pair 133. The second end of the first strain gauge 141 of the first front strain gauge pair 131 is electrically connected to the second end of the second strain gauge 142 of the first front strain gauge pair 131, the first end of the second strain gauge 142 of the first front strain gauge pair 131 is electrically connected to the first end of the second strain gauge 142 of the second front strain gauge pair 132, the second end of the second strain gauge 142 of the second front strain gauge pair 132 is electrically connected to the second end of the first strain gauge 141 of the second front strain gauge pair 132, the first end of the first strain gauge 141 of the second front strain gauge pair 132 is electrically connected to the first end of the first strain gauge 141 of the third front strain gauge pair 133, and the second end of the first strain gauge 141 of the third front strain gauge pair 133 is electrically connected to the second end of the second strain gauge 142 of the third front strain gauge pair 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 front strain gauge pair 131, and P2-1 represents the second strain gauge 142 of the first front strain gauge pair 131; P3-1 represents the first strain gauge 141 of the second front strain gauge pair 132, and P4-1 represents the second strain gauge 142 of the second front strain gauge pair 132; P5-1 represents the first strain gauge 141 of the third front strain gauge pair 133, and P6-1 represents the second strain gauge 142 of the third front strain gauge pair 133; P7-1 represents the first strain gauge 141 of the fourth front strain gauge pair 134, and P8-1 represents the second strain gauge 142 of the fourth front strain gauge pair 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 front strain gauge pair 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 front strain gauge pair 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 front strain gauge pair 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 front strain gauge pair 134.
[0042] By adopting the above connection method, no matter from which connection end of the first strain gauge 141 and the second strain gauge 142 of the positive strain gauge pair is viewed, the actual setting positions of the two strain gauges in the circuit are completely symmetrical, thereby achieving symmetry and reducing the crosstalk of the circuit. If the first strain gauge 141 and the second strain gauge 142 of each positive strain gauge pair 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 positive strain gauge pairs in the strain gauge group can be used as the positive strain gauge pair, without limiting the positive strain gauge pair at a specific position as the positive strain gauge pair. At this time, the positive strain gauge pair opposite to the positive strain gauge pair is a grounding strain gauge pair, and the remaining two positive strain gauge pairs in the strain gauge group are respectively an output positive end strain gauge pair and an output negative end strain gauge pair. The second end of the first strain gauge 141 of the positive strain gauge pair (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, generally connected to a +5V voltage), the second end of the first strain gauge 141 of the grounding strain gauge pair 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 gauge pair 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 gauge pair 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 front strain gauge pair 131 is used as the positive strain gauge pair, that is, the second end of the first strain gauge 141 of the first front strain gauge pair 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 front strain gauge pair 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 front strain gauge pair 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 front strain gauge pair 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 front strain gauge pair 132 can also be used as the positive strain gauge pair, that is, the second end of the first strain gauge 141 of the second front strain gauge pair 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 front strain gauge pair 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 front strain gauge pair 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 front strain gauge pair 131 is used as the 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 crosstalk, the strain gauge group may further include four back strain gauge pairs arranged on the back of the thin-walled strain beam, and the back strain gauge pairs correspond to the front strain gauge pairs one by one. In this embodiment, back strain gauge pairs 171, back strain gauge pairs 172, back strain gauge pairs 173, back strain gauge pairs 174, back strain gauge pairs 175, back strain gauge pairs 176, back strain gauge pairs 177, and back strain gauge pairs 178 are provided. Among them, the back strain gauge pair 171 corresponds to the front strain gauge pair 131, the back strain gauge pair 172 corresponds to the front strain gauge pair 132, the back strain gauge pair 173 corresponds to the front strain gauge pair 133, the back strain gauge pair 174 corresponds to the front strain gauge pair 134, the back strain gauge pair 175 corresponds to the front strain gauge pair 135, the back strain gauge pair 176 corresponds to the front strain gauge pair 136, the back strain gauge pair 177 corresponds to the front strain gauge pair 137, and the back strain gauge pair 178 corresponds to the front strain gauge pair 138.
[0045] Each of the back strain gauge pairs includes a third strain gauge 143 and a fourth strain gauge 144, respectively. The third strain gauge 143 is arranged opposite to the first strain gauge 141 of the corresponding front strain gauge pair, and the fourth strain gauge 144 is arranged opposite to the second strain gauge 142 of the corresponding front strain gauge pair. That is, the third strain gauge 143 and the fourth strain gauge 144 of the back strain gauge pair are also symmetrically arranged along the symmetry axis passing through the center of the inner flange 120 in the area where the strain of the thin-walled strain beam 160 is the largest, and the angle between the axis of the third strain gauge 143 and the axis of the fourth strain gauge 144 is also 90°.
[0046] 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. A first strain gauge wiring hole 161 is provided on one side of each of the third strain gauges 143, and a second strain gauge wiring hole 162 is provided on one side of each of the fourth strain gauges 144 to facilitate wiring. 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 thin-walled strain beam 160 using a glass micro-melting sintering process. The strain gauge uses a silicon strain gauge and is fixed on the thin-walled strain beam 160 through a sintering process, which can improve sensitivity and anti-interference performance compared to the bonding method of metal strain gauges.
[0047] After the third strain gauge 143 and the fourth strain gauge 144 are arranged on the back of the thin-walled strain beam 160, the circuit structure formed after the connection is as shown in FIG. Figure 7, where P1-2 represents the third strain gauge 143 of the first back strain gauge pair 171, P2-2 represents the fourth strain gauge 144 of the first back strain gauge pair 171; P3-2 represents the third strain gauge 143 of the second back strain gauge pair 172, P4-2 represents the fourth strain gauge 144 of the second back strain gauge pair 172; P5-2 represents the third strain gauge 143 of the third back strain gauge pair 173, P6-2 represents the fourth strain gauge 144 of the third back strain gauge pair 173; P7-2 represents the third strain gauge 143 of the fourth back strain gauge pair 174, and P8-2 represents the fourth strain gauge 144 of the fourth back strain gauge pair 174. 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, and 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.
[0048] Similarly, in the second strain gauge group, the first strain gauge 141 and the second strain gauge 142 of the four front strain gauge pairs and the third strain gauge 143 and the fourth strain gauge 144 of the four back strain gauge pairs, a total of sixteen strain gauges (eight strain gauges if only the front strain gauge pairs 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 gauge group. Figure 8 , is a circuit diagram formed by connecting four first strain gauges 141, four second strain gauges 142, four third strain gauges 143 and four fourth strain gauges 144 of the second strain gauge group. Among them, R1-1 represents the first strain gauge 141 of the first front strain gauge pair 135, R1-2 represents the third strain gauge 143 of the first front strain gauge pair 135; R2-1 represents the second strain gauge 142 of the first front strain gauge pair 135; R2-2 represents the fourth strain gauge 144 of the first front strain gauge pair 135; R3-1 represents the first strain gauge 141 of the second front strain gauge pair 136, R3-2 represents the third strain gauge 143 of the second front strain gauge pair 136; R4-1 represents the second strain gauge 142 of the second front strain gauge pair 136, R4-2 represents the fourth strain gauge 144 of the second front strain gauge pair 136 4; R5-1 represents the first strain gauge 141 of the third front strain gauge pair 137, and R5-2 represents the third strain gauge 143 of the third front strain gauge pair 137; R6-1 represents the second strain gauge 142 of the third front strain gauge pair 137, and R6-2 represents the fourth strain gauge 144 of the third front strain gauge pair 137; R7-1 represents the first strain gauge 141 of the fourth front strain gauge pair 138, and R7-2 represents the third strain gauge 143 of the fourth front strain gauge pair 138; R8-1 represents the second strain gauge 142 of the fourth front strain gauge pair 138, and R8-2 represents the fourth strain gauge 144 of the fourth front strain gauge pair 138.
[0049] 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.
[0050] The PCB circuit board 200 is provided with a notch 220 at a position corresponding to each front strain gauge pair, and the notch 220 exposes the first strain gauge 141 and the second strain gauge 142 of the front strain gauge pair, so as to facilitate the connection of the first strain gauge 141 and the second strain gauge 142 with the pads through leads. The pads include a first pad 201 and a second pad 202 provided at a position corresponding to the first strain gauge 141 on one side of the notch 220, and a third pad 203 and a fourth pad 204 provided at a position corresponding to the second strain gauge 142.
[0051] 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; wherein the wire connecting the first end and the second end of the third strain gauge 143 passes through the first strain gauge wiring hole 161 and is connected to the first pad 201 and the second pad 202. 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; wherein the wire connecting the first end and the second end of the fourth strain gauge 144 passes through the second strain gauge wiring hole 162 and is connected to the third pad 203 and the fourth pad 204. 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.
[0052] The working principle of this embodiment is as follows:
[0053] 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, the thin-walled strain beam 160 will deform, and when deformed, the silicon strain gauge will be stretched or squeezed to generate voltage and converted into torque value; taking the two strain gauge groups of this embodiment as an example, the two strain gauge groups can form two-channel torque reading, and only the first channel formed by the silicon strain gauge of the first strain gauge group can be used in normal use, and the second channel formed by the silicon strain gauge of the second strain gauge group is used as a backup, which can be used when the first channel fails.
[0054] by Figure 7 Take the circuit in as an example, when measuring torque, Figure 7 Point 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:
[0055] R A_B =R B_C =R F_G =R G_H =(R+ΔR) / 2
[0056] R A_E =R E_F =R C_D＝ R D_H =(R-ΔR) / 2
[0057] In the formula, R A_B express Figure 6 The resistance between point A and point B, and so on for the rest.
[0058] ΔR=Ks×ΔL×R
[0059] V=V IN+ -V IN-
[0060] =ΔR / R×Vcc
[0061] =Ks×ΔL×Vcc
[0062] 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.
[0063] 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:
[0064] (1) The thin-walled strain beam 160 is a relatively thin circular ring. Compared with a torque sensor with multiple strain beams distributed therein, the present embodiment fills the gap between the outer flange 110 and the inner flange 120 completely. There is no need to limit the width and number of the thin-walled strain beam 160, so that the thin-walled strain beam 160, the outer flange 110, and the inner flange 120 form a whole without being hollowed out, thereby enhancing the torsional rigidity. At the same time, by controlling the thickness of the thin-walled strain beam 160, the deformation amount can be used to squeeze the strain gauge, thereby improving the rigidity and ensuring the reading accuracy.
[0065] (2) By connecting the strain gauges to form a Wheatstone bridge, the torque measurement can be completed using only one AD sampling, which makes the measurement more convenient.
[0066] (3) The symmetry of the overall circuit structure is achieved through a special bridge connection method, which reduces the crosstalk of the circuit.
[0067] (4) Through simulation, each strain gauge is arranged in the area where the strain of the thin-walled strain beam 160 is the largest, and the first strain gauge 141 and the second strain gauge 142 are symmetrically arranged at an angle of 90°, which can further improve the accuracy of the torque test.
[0068] (5) 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.
[0069] (6) By arranging strain gauges on the front and back sides of the thin-walled strain beam 160 , the influence of external forces in directions other than the torque direction can be substantially eliminated.
[0070] (7) The dual-channel structure can achieve redundant design and ensure normal operation when one channel fails.
[0071] 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 torsional rigidity joint torque sensor, characterized in that: It comprises a torque sensor flange and a PCB circuit board arranged on the torque sensor flange, wherein the torque sensor flange comprises a front side and a back side opposite to the front side, and an annular groove is arranged on the back side or the front side of the torque sensor flange; the portion of the torque sensor flange located outside the annular groove forms an outer flange, and the portion of the torque sensor flange located inside the annular groove forms an inner flange, and the groove bottom of the annular groove forms a thin-walled strain beam; at least one strain gauge group is arranged on the thin-walled strain beam, and each of the strain gauge groups comprises four front strain gauge pairs arranged at equal intervals along the circumferential direction on the front side or the back side of the thin-walled strain beam, and each of the front strain gauge pairs comprises a first strain gauge and a second strain gauge; the four first strain gauges and the four second strain gauges of each strain gauge group are connected through the PCB circuit board to form a Wheatstone bridge structure.
2. The high torsional rigidity joint torque sensor according to claim 1, characterized in that: Each of the strain gauge groups comprises a first front strain gauge pair, a second front strain gauge pair, a third front strain gauge pair and a fourth front strain gauge pair which are arranged on the thin-walled strain beam in sequence and at equal intervals along the circumferential direction, wherein a first end of a first strain gauge of the first front strain gauge pair is electrically connected to a first end of a first strain gauge of the fourth front strain gauge pair, a second end of a first strain gauge of the fourth front strain gauge pair is electrically connected to a second end of a second strain gauge of the fourth front strain gauge pair, and a first end of the second strain gauge of the fourth front strain gauge pair is electrically connected to a first end of a second strain gauge of the third front strain gauge pair; The second end of the first strain gauge of the first front strain gauge pair is electrically connected to the second end of the second strain gauge of the first front strain gauge pair, the first end of the second strain gauge of the first front strain gauge pair is electrically connected to the first end of the second strain gauge of the second front strain gauge pair, the second end of the second strain gauge of the second front strain gauge pair is electrically connected to the second end of the first strain gauge of the second front strain gauge pair, the first end of the first strain gauge of the second front strain gauge pair is electrically connected to the first end of the first strain gauge of the third front strain gauge pair, and the second end of the first strain gauge of the third front strain gauge pair is electrically connected to the second end of the second strain gauge of the third front strain gauge pair.
3. The high torsional rigidity joint torque sensor according to claim 2, characterized in that: In the strain gauge group, one of the positive strain gauge pairs is used as the positive strain gauge pair, and the positive strain gauge pair opposite to the positive strain gauge pair is the grounding strain gauge pair. The remaining two positive strain gauge pairs in the strain gauge group are respectively an output positive end strain gauge pair and an output negative end strain gauge pair. The second end of the first strain gauge of the positive strain gauge pair is used as the voltage input end of the Wheatstone bridge structure for connecting the positive end of the power supply voltage, the second end of the first strain gauge of the grounding strain gauge pair 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 gauge pair is used as the output positive end of the Wheatstone bridge structure for connecting the positive end of the measuring device, and the second end of the first strain gauge of the output negative end strain gauge pair is used as the output negative end of the Wheatstone bridge structure for connecting the negative end of the measuring device.
4. The high torsional rigidity joint torque sensor according to claim 3, characterized in that: The four front strain gauge pairs are arranged on the front side of the thin-walled strain beam, and the strain gauge group also includes four back strain gauge pairs arranged on the back side of the thin-walled strain beam, and the back strain gauge pairs correspond to the front strain gauge pairs one by one; each of the back strain gauge pairs respectively includes a third strain gauge and a fourth strain gauge, the third strain gauge is arranged opposite to the first strain gauge of the corresponding front strain gauge pair, and the fourth strain gauge is arranged opposite to the second strain gauge of the corresponding front strain gauge pair; a first strain gauge wiring hole is respectively arranged on one side of each of the third strain gauges, and a second strain gauge wiring hole is respectively arranged on one side of each of the fourth strain gauges; 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 torsional rigidity 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; A notch is respectively provided at a position corresponding to each pair of front strain gauges on the PCB circuit board, wherein the notch exposes the first strain gauge and the second strain gauge, and a first soldering pad and a second soldering pad are provided at a position corresponding to the first strain gauge on one side of the notch, and a third soldering pad and a fourth soldering 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 soldering pad at the corresponding position through a wire, and a second end is connected to the second soldering 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 soldering pad at the corresponding position through a wire, and a second end is connected to the fourth soldering pad at the corresponding position through a wire.
6. The high torsional rigidity 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 thin-walled strain beam by using a glass micro-melting sintering process.
7. The high torsional rigidity joint torque sensor according to claim 6, characterized in that: The first strain gauge and the second strain gauge of each front strain gauge pair are symmetrically arranged, and the symmetry axis of the first strain gauge and the second strain gauge passes through the center of the inner flange; the angle between the axis of the first strain gauge and the axis of the second strain gauge and the symmetry axis is 45°.
8. The high torsional rigidity joint torque sensor according to claim 7, characterized in that: The thickness of the thin-walled strain beam is determined by simulation software according to the strain size requirement of the torque sensor; the first strain gauge and the second strain gauge are arranged in the area where the strain of the thin-walled strain beam is the largest, and the area where the strain of the thin-walled strain beam is the largest is determined by the simulation results of finite element simulation software.
9. The high torsional rigidity joint torque sensor according to any one of claims 1 to 5, characterized in that: The torque sensor flange is made of 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 in a circumferential direction, 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 in a circumferential direction.
10. The high torsional rigidity joint torque sensor according to any one of claims 1 to 5, characterized in that: The torque sensor comprises two strain gauge groups, namely a first strain gauge group and a second strain gauge group. The spacing between each front strain gauge pair in the first strain gauge group and the adjacent front strain gauge pair in the second strain gauge group is equal.