Temperature self-compensation Wheatstone bridge structure

Abstract

The invention discloses a temperature self-compensation Wheatstone bridge structure, and relates to the field of Wheatstone bridges, at least one group of sub-strain gauges which are separated from adjacent arms, are mutually compatible and are attached to the same area of the same elastic beam exist in a four-arm resistor of the Wheatstone bridge structure; the temperature resistance change trends of the compatible sub strain gauges tend to be the same; wherein each group of compatible two sub-strain gauges are closely attached to each other so that the two sub-strain gauges are located in the same area of the same elastic beam, so that the two closely attached sub-strain gauges generate homodromous temperature resistance variation, resistance temperature drift caused by local temperature difference of different arms is counteracted, and temperature self-compensation is realized. According to the invention, temperature compensation can be carried out on the local temperature difference of the force sensor, so that the measurement accuracy of the six-dimensional force sensor is improved.

Description

Technical Field

[0001] This invention relates to the field of force sensors, and in particular to a temperature-compensated Wheatstone bridge structure. Background Technology

[0002] A multidimensional force sensor is a force sensor capable of simultaneously measuring force and torque components in two or more directions. In a Cartesian coordinate system, force and torque can each be decomposed into three components. Therefore, the most complete form of multidimensional force is a six-dimensional force / torque sensor, which can simultaneously measure three force components and three torque components. Widely used multidimensional force sensors are of this type. Because six-dimensional force sensors can simultaneously detect three-dimensional force and three-dimensional torque in space, they can serve as fundamental components for precision assembly, precision operation, precision control, and human-machine interaction control. Simultaneously, six-dimensional force sensors are also essential for robots to perform contact-based tasks, such as space exploration technology, force control of space manipulators, industrial robots, and remote control operation of underwater robots, all of which require large-range, high-precision six-dimensional force sensors.

[0003] Because the resistance of the strain gauges used in six-dimensional force sensors changes with temperature, temperature compensation is required. This is typically achieved using the symmetrical cancellation principle of a Wheatstone bridge to compensate for temperature drift. However, a Wheatstone bridge can generally only compensate for strain gauges at the same temperature. This means that when temperature differences exist between the elastic beams (i.e., when the resistance of the arms in the same Wheatstone bridge is at different temperatures), the temperature compensation effect will be significantly reduced due to the different resistance changes of each arm. Furthermore, due to inherent factors of the six-dimensional force sensor itself or environmental factors, localized temperature differences often occur, meaning there are temperature differences between the various elastic beams, leading to inaccurate measurement results. Summary of the Invention

[0004] In view of the aforementioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a temperature self-compensating Wheatstone bridge structure, which aims to compensate for the local temperature differences of a six-dimensional force sensor in order to improve the measurement accuracy of the six-dimensional force sensor.

[0005] To achieve the above objectives, the present invention discloses a temperature-compensated Wheatstone bridge structure. In the four arms of the Wheatstone bridge structure, at least one group of sub-strain gauges is independently located in adjacent arms but mutually matched and attached to the same region of the same elastic beam. The temperature resistance change trends of the mutually matched sub-strain gauges tend to be the same. Specifically, the two matched sub-strain gauges in each group are attached adjacent to each other so that they are located in the same region of the same elastic beam, causing the two adjacent sub-strain gauges to exhibit the same temperature resistance change, thereby offsetting the resistance temperature drift caused by local temperature differences between different arms and achieving temperature self-compensation.

[0006] In one specific embodiment, the sub-strain gauges on each arm of the four-arm resistor are connected in series, and the four different arms are paired with each other and attached to the same area on the same elastic beam.

[0007] Optionally, two adjacent sub-strain gauges of adjacent arms are attached close together so that they are located in the same area of ​​the same elastic beam, thereby forming a first strain-sensitive unit. The first strain-sensitive unit leads out three terminals, including two connection terminals connected to the sub-strain gauges of the same arm and one output terminal.

[0008] Optionally, two non-adjacent sub-strain gauges of adjacent arms are attached close together so that they are located in the same area of ​​the same elastic beam, thereby forming a second strain-sensitive unit. The second strain-sensitive unit leads out four terminals, including two connection terminals connected to the sub-strain gauges of the same arm, an input terminal, and an output terminal.

[0009] Optionally, the output voltage of the Wheatstone bridge satisfies:

[0010]

[0011] ΔR ij =△R ij_D +ΔR ij_T

[0012] Among them, V out V is the output voltage of the Wheatstone bridge. ex R is the input voltage of the Wheatstone bridge. ij Let ΔR represent the resistance of each of the sub-strain gauges, i represent the arm numbers 1, 2, 3, and 4, respectively, with the arm numbers proceeding counterclockwise according to the bridge group, j represent the sub-strain gauge numbers 1 and 2, respectively, with the sub-strain gauge numbers proceeding counterclockwise according to the bridge group. ij For R ij The total change in resistance, ΔR ij_D For R ij The change in deformation resistance, ΔR ij_T For R ij The change in resistance due to temperature.

[0013] Optionally, the sub-strain gauge is a semiconductor strain gauge, the semiconductor strain gauge material including silicon and germanium, the semiconductor strain gauge improves the sensitivity to deformation sensing through its piezoresistive effect.

[0014] Optionally, each of the sub-strain gauges has the same initial resistance, and when two of the sub-strain gauges are at the same temperature, their resistance changes due to temperature are the same.

[0015] Optionally, the shape of the sub-strain gauge includes one of straight strip type and bent grid type, and the deformation direction of the adjacent sub-strain gauge is perpendicular to that of the strain gauge.

[0016] Optionally, the deformation trends of non-adjacent strain gauge groups within the Wheatstone bridge tend to be the same, while the deformation trends of adjacent strain gauge groups tend to be opposite.

[0017] Optionally, the Wheatstone bridge structure is applied to a six-dimensional force sensor, which is equipped with four elastic beams, and the elastic beams are attached with corresponding sub-strain gauges to form six bridge circuits.

[0018] Optionally, the Wheatstone bridge structure is applied to a six-dimensional force sensor, which is equipped with three elastic beams, and the elastic beams are attached with corresponding sub-strain gauges to form six bridge circuits.

[0019] The beneficial effects of this invention are as follows: 1. The Wheatstone bridge of this invention includes four arm strain gauge groups, each arm strain gauge group including two sub-strain gauges connected in series; the deformation resistance change trend of the sub-strain gauges in the same arm tends to be the same, and the temperature resistance change trend of two adjacent sub-strain gauges in adjacent arms tends to be the same. In this invention, each adjacent arm has one sub-strain gauge closely attached so that they are located in the same region of the same elastic beam, so that the two closely attached sub-strain gauges have the same temperature resistance change, thus canceling the resistance temperature drift caused by the local temperature difference between different arms, achieving temperature self-compensation. This invention uses such a structure to make the temperature resistance changes of the sub-strain gauges on each elastic beam cancel each other out, thereby reducing the influence of temperature on the measurement results and improving measurement accuracy. 2. This invention can not only perform temperature compensation for arm resistance at different temperatures, but also, because it combines the basic structure of a Wheatstone bridge, can perform temperature compensation for arm resistance at the same temperature, making temperature compensation more comprehensive.

[0020] In summary, this invention can compensate for local temperature differences in a six-dimensional force sensor, thereby improving the measurement accuracy of the six-dimensional force sensor. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a temperature-compensated Wheatstone bridge structure provided in the first specific embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of a temperature-compensated Wheatstone bridge structure provided in the second specific embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of a temperature-compensated Wheatstone bridge structure provided in the third specific embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the structure of the first strain-sensitive unit provided in a specific embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the structure of the first strain-sensitive unit provided in another specific embodiment of the present invention. Detailed Implementation

[0026] This invention discloses a temperature-compensated Wheatstone bridge structure. Those skilled in the art can refer to this document and appropriately modify the technical details to achieve the desired implementation. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The apparatus and application of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the apparatus and application described herein without departing from the content, spirit, and scope of this invention to implement and apply the technology of this invention.

[0027] The applicant's research revealed that the resistance of the strain gauges used in force sensors and six-dimensional force sensors changes with temperature, necessitating temperature compensation. This is typically achieved using the symmetrical cancellation principle of a Wheatstone bridge to compensate for temperature drift. However, Wheatstone bridges generally only provide temperature compensation for strain gauges at the same temperature. This means that when temperature differences exist between the elastic beams (i.e., when the resistance of each arm in the same Wheatstone bridge is at a different temperature), the varying resistance changes of each arm significantly reduce the effectiveness of temperature compensation. Furthermore, due to inherent characteristics of six-dimensional force sensors or environmental factors, localized temperature differences often occur between the elastic beams, leading to inaccurate measurement results.

[0028] Therefore, embodiments of the present invention provide a temperature-compensated Wheatstone bridge structure. In the four arms of the Wheatstone bridge structure, at least one group of sub-strain gauges is independently located in adjacent arms but mutually matched and attached to the same region on the same elastic beam. The temperature resistance change trends of the mutually matched sub-strain gauges tend to be the same. Each group of matched sub-strain gauges is attached adjacent to each other so that they are located in the same region of the same elastic beam, causing the two adjacent sub-strain gauges to exhibit the same temperature resistance change, thereby offsetting the resistance temperature drift caused by local temperature differences in different arms and achieving temperature self-compensation.

[0029] In typical applications, temperature compensation can be directly applied to all four arms. This embodiment uses temperature compensation for all four arms for illustration. In practical applications, compensation can be applied to specific local areas. This embodiment does not constitute a limitation on the scope of local area protection, and in practical applications, it is not necessarily necessary to compensate all four arms.

[0030] In this embodiment, the sub-strain gauges on each arm of the four-arm resistor are connected in series, and the four different arms are paired with each other and attached to the same area on the same elastic beam.

[0031] like Figure 1 and Figure 2 As shown, the Wheatstone bridge structure includes: a Wheatstone bridge consisting of four arm strain gauge groups 1 attached to an elastic beam of an elastic body; each arm strain gauge group 1 includes two sub-strain gauges 2 connected in series; the deformation resistance change trend of the sub-strain gauges 2 in the same arm tends to be the same, and each sub-strain gauge 2 is paired with one in each adjacent arm so that the temperature resistance change trend of the two paired sub-strain gauges tends to be the same; wherein, the two paired sub-strain gauges 2 in each group are attached close to each other so that they are located in the same area of ​​the same elastic beam, so that the two adjacent sub-strain gauges 2 have the same temperature resistance change, thereby offsetting the resistance temperature drift caused by the local temperature difference of different arms and realizing temperature self-compensation.

[0032] It should be noted that each sub-strainer 2 is matched and matched only once to ensure that their respective resistance temperature drifts correspond one-to-one and cancel each other out.

[0033] In a first specific embodiment, two adjacent sub-strain gauges 2 of adjacent arms are closely attached so that they are located in the same area of ​​the same elastic beam, thereby forming a first strain-sensitive unit 101. The first strain-sensitive unit 101 has three terminals, including two connection terminals connected to the sub-strain gauges 2 of the same arm and one output terminal. This embodiment is, for example... Figure 1 As shown, Figure 1 The dashed box in the middle represents the first strain-sensitive element 101, which is formed by adjacent bonding. That is, R... 12 and R 21 Adjacent to each other, they form a first strain-sensitive element 101, R 22 and R 31 Adjacent to each other, they form a first strain-sensitive element 101, R 32 and R 41 Adjacent to each other, they form a first strain-sensitive element 101, R 42 and R 11 The adjacent elements form a first strain-sensitive unit 101.

[0034] The specific first strain-sensitive unit 101 can be as follows: Figure 4 and Figure 5 As shown, Figure 4 and Figure 5 The first strain-sensitive unit 101 is composed of strain gauges 2 of different shapes, each of which has three terminals. Figure 4 and Figure 5 The yellow area in the middle represents the wiring terminals.

[0035] In a second specific embodiment, two non-adjacent sub-strain gauges 2 of adjacent arms are closely attached so that they are located in the same area of ​​the same elastic beam, thereby forming a second strain-sensitive unit 201. The second strain-sensitive unit 102 has four terminals, including two connection terminals connected to the sub-strain gauges 2 of the same arm, one input terminal, and one output terminal. This embodiment is an example of... Figure 2 As shown, Figure 2 The dashed box in the middle represents the second strain-sensitive element 102, which is formed by adjacent bonding. That is, R... 11 and R 22 A second strain-sensitive element 102 is formed by closely attaching the elements to each other. 12 and R 41 A second strain-sensitive element 201, R, is formed by closely attaching to each other. 21 and R 32 A second strain-sensitive element 201, R, is formed by closely attaching to each other. 31 and R 41 Two first strain-sensitive units 201 are attached adjacent to each other.

[0036] In the third specific embodiment, any two sub-strain gauges 2 from different arms in adjacent arms can form a strain-sensitive unit. For example... Figure 3 As shown, Figure 3 There are four third strain-sensitive units 301, one of which consists of adjacent sub-strain gauges 2, and the other three consist of non-adjacent sub-strain gauges 2.

[0037] It should be noted that any one of the sub-strain gauges 2 in one arm of the strain gauge group 1 can form a strain-sensitive unit with any one of the sub-strain gauges 2 in the other arm of the strain gauge group 1. The two sub-strain gauges 2 of the strain-sensitive unit are attached adjacent to each other so that they are located in the same region of the same elastic beam. This is to ensure that the changes in resistance caused by temperature are matched.

[0038] In one specific embodiment, such as Figure 1 As shown, the output voltage of the Wheatstone bridge satisfies:

[0039]

[0040] ΔR ij =ΔR ij_D +ΔR ij_T

[0041] Among them, V out V is the output voltage of the Wheatstone bridge. ex R is the input voltage of the Wheatstone bridge. ijLet represent the resistance of each sub-strain gauge 2, and let i represent the arm numbers 1, 2, 3, and 4, respectively. The arm numbers are arranged counterclockwise according to the bridge group. Figure 1 As shown, j represents sub-strain gauge 2, numbered 1 and 2 respectively. The sub-strain gauge 2 is numbered counterclockwise according to the bridge group, as shown below. Figure 1 As shown, ΔR ij For R ij The total change in resistance, ΔR ij_D For R ij The change in deformation resistance, ΔR ij_T For R ij The change in resistance due to temperature.

[0042] It is worth mentioning that ΔR ij <<R ij .

[0043] Furthermore, the initial resistance values ​​of each sub-strain gauge 2 are the same, i.e., R 11 =R 12 =R 21 =R 22 =R 31 =R 32 =R 41 =R 42 Therefore, at the same temperature, the change in its temperature resistance is also the same, so we have ΔR 12_T =ΔR 21_T ΔR 22_T =ΔR 31_t ΔR 32_T =ΔR 41_T and ΔR 42_T =ΔR 11_T This ensures that the output voltage of the Wheatstone bridge satisfies:

[0044] This formula shows that the embodiments of the present invention can offset the resistance temperature drift caused by the local temperature difference of different arms, realize temperature self-compensation, and improve measurement accuracy.

[0045] In this specific embodiment, the sub-strain gauge 2 is a semiconductor strain gauge. The semiconductor strain gauge material includes silicon and germanium. The semiconductor strain gauge improves the sensitivity to deformation sensing through its piezoresistive effect.

[0046] It should be noted that the sub-strain gauge 2 in the embodiments of the present invention includes, but is not limited to, semiconductor strain gauges and foil metal strain gauges.

[0047] Since semiconductor strain gauges are more sensitive to temperature, the embodiments of the present invention have a more significant temperature compensation effect on them.

[0048] In this specific embodiment, the initial resistance of each sub-strain gauge 2 is the same, and when the two sub-strain gauges 2 are at the same temperature, the amount of resistance change caused by temperature is the same.

[0049] It should be noted that, given the same initial resistance value for the sub-strain gauge 2, the temperature resistance changes cancel each other out best.

[0050] In this specific embodiment, the shape of the sub-strain gauge 2 includes one of straight strip type and bent grid type, and the deformation direction of the adjacent sub-strain gauge 2 is perpendicular to that of the sub-strain gauge 2.

[0051] It should be noted that the straight bar structure is simpler and easier to fabricate; the bent gate structure can achieve a higher sensitive gate resistance through bending, which can meet the requirements of higher precision.

[0052] It's worth noting that when the two strain gauges are perpendicular, one measures deformation in a specific direction, while the other shows no reaction to deformation; however, the deformation caused by temperature is consistent. In this case, one strain gauge X is used to measure deformation (arm A), and another strain gauge Y is combined with the other arm (arm B) to counteract the deformation caused by temperature in arm A. At the same time, on the other arm, strain gauge Y can also be used to measure deformation, while strain gauge X is used to counteract the deformation caused by temperature in arm B.

[0053] In this specific embodiment, the deformation trends of non-adjacent strain gauge groups 1 within the Wheatstone bridge tend to be the same, while the deformation trends of adjacent strain gauge groups 1 tend to be opposite. Based on this, the output voltage of the Wheatstone bridge will be relatively large and have good linearity.

[0054] In this specific embodiment, the Wheatstone bridge structure is applied to a six-dimensional force sensor. The six-dimensional force sensor is equipped with four elastic beams, and corresponding sub-strain gauges 2 are attached to the elastic beams to form six bridge circuits.

[0055] It should be noted that the four elastic beams of this six-dimensional force sensor are fitted with 24 strain gauges to form six full bridges to measure forces or moments in six dimensions.

[0056] In another specific embodiment, the Wheatstone bridge structure is applied to a six-dimensional force sensor. The six-dimensional force sensor is equipped with three elastic beams, and corresponding sub-strain gauges 2 are attached to the elastic beams to form six bridge circuits.

[0057] It should be noted that the six-dimensional force sensor consists of three elastic beams, each with four faces forming six bridge paths; strain gauges are attached to the opposite face of each beam to form bridges, and each beam has two bridge paths.

[0058] It is worth mentioning that, in principle, the deformation directions of the corresponding sub-strain gauges 2 in adjacent arms of the Wheatstone bridge of the six-dimensional force sensor should be opposite, and there is no need for them to have an absolute correlation with the coordinate axes of the spatial system.

[0059] The Wheatstone bridge of this invention includes four arm strain gauge groups 1, each arm strain gauge group 1 including two sub-strain gauges 2 connected in series; the deformation resistance change trend of the sub-strain gauges 2 in the same arm tends to be the same, and the temperature resistance change trend of two adjacent sub-strain gauges 2 in adjacent arms tends to be the same. In this embodiment, one sub-strain gauge 2 in each adjacent arm is closely attached so that they are located in the same region of the same elastic beam, so that the two closely attached sub-strain gauges 2 have the same temperature resistance change, thus canceling the resistance temperature drift caused by the local temperature difference between different arms, achieving temperature self-compensation. This structure of the present invention enables the temperature resistance changes of the sub-strain gauges 2 on each elastic beam to cancel each other out, thereby reducing the influence of temperature on the measurement results and improving measurement accuracy.

[0060] The embodiments of the present invention can not only perform temperature compensation for arm resistance at different temperatures, but also perform temperature compensation for arm resistance at the same temperature because it also has the basic structure of a Wheatstone bridge, making the temperature compensation more comprehensive.

[0061] In summary, the embodiments of the present invention can perform temperature compensation for local temperature differences in a six-dimensional force sensor, thereby improving the measurement accuracy of the six-dimensional force sensor.

[0062] Furthermore, it is worth mentioning that, in cases such as Figure 1 The diagram contains four dashed frames. In practical applications, only one of these dashed frames is designed for compensation. For example, R22 and R31 are applied to the same area on the elastomer for temperature compensation.

[0063] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0064] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A temperature-compensated Wheatstone bridge structure, characterized in that, In the four-arm resistors of the Wheatstone bridge structure, at least one group of sub-strain gauges is independent of adjacent arms but matched with each other and attached to the same region of the same elastic beam; the temperature resistance change trends of the matched sub-strain gauges tend to be the same; wherein, the two matched sub-strain gauges in each group are attached close to each other so that they are located in the same region of the same elastic beam, so that the two closely attached sub-strain gauges have the same temperature resistance change, thereby offsetting the resistance temperature drift caused by the local temperature difference of different arms and realizing temperature self-compensation.

2. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, The sub-strain gauges on each arm of the four-arm resistor are connected in series, and the four different arms are paired with each other and attached to the same area on the same elastic beam.

3. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, Two adjacent sub-strain gauges of adjacent arms are attached close together so that they are located in the same area of ​​the same elastic beam, thereby forming a first strain-sensitive unit. The first strain-sensitive unit leads out three terminals, including two connection terminals connected to the sub-strain gauges of the same arm and one output terminal.

4. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, Two non-adjacent sub-strain gauges of adjacent arms are attached close together so that they are located in the same area of ​​the same elastic beam, thereby forming a second strain-sensitive unit. The second strain-sensitive unit leads out four terminals, including two connection terminals connected to the sub-strain gauges of the same arm, one input terminal, and one output terminal.

5. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, The output voltage of the Wheatstone bridge satisfies: ΔR iij =ΔR ij_D +ΔR ij_T Among them, V out V is the output voltage of the Wheatstone bridge. ex R is the input voltage of the Wheatstone bridge. ij Let ΔR represent the resistance of each of the sub-strain gauges, i represent the arm numbers 1, 2, 3, and 4, respectively, with the arm numbers proceeding counterclockwise according to the bridge group, j represent the sub-strain gauge numbers 1 and 2, respectively, with the sub-strain gauge numbers proceeding counterclockwise according to the bridge group. ij For R ij The total change in resistance, ΔR ij_D For R ij The change in deformation resistance, ΔR ij_T For R ij The change in resistance due to temperature.

6. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, The sub-strain gauge is a semiconductor strain gauge, and the semiconductor strain gauge material includes silicon and germanium. The semiconductor strain gauge improves the sensitivity to deformation sensing through its piezoresistive effect.

7. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, Each of the sub-strain gauges has the same initial resistance, and when two of the sub-strain gauges are at the same temperature, their resistance changes due to temperature are the same.

8. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, The shape of the sub-strain gauge includes one of straight strip type and bent grid type, and the deformation direction of the adjacent sub-strain gauge is perpendicular to that of the strain gauge.

9. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, The deformation trends of non-adjacent strain gauge groups within the Wheatstone bridge tend to be the same, while the deformation trends of adjacent strain gauge groups tend to be opposite.

10. The temperature-compensated Wheatstone bridge structure according to claim 1, characterized in that, The Wheatstone bridge structure is used in a six-dimensional force sensor, which is equipped with four or three elastic beams, and the elastic beams are attached with corresponding sub-strain gauges to form six bridge circuits.

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