Strain type force sensor with self-calibration function

Abstract

The invention discloses a strain type force sensor with a self-calibration function, which comprises an upper cantilever beam and a lower cantilever beam, and is characterized in that the rigidity of the upper cantilever beam is greater than that of the lower cantilever beam; the fixed end of the lower cantilever beam is fixedly connected with the fixed end of the upper cantilever beam, and a pushing calibration mechanism is arranged between the movable end of the lower cantilever beam and the movable end of the upper cantilever beam; in a measurement mode, the pushing calibration mechanism is in a retraction state, and the upper cantilever beam and the lower cantilever beam are attached to each other so that the upper cantilever beam and the lower cantilever beam deform synchronously; in a calibration mode, calculating a target movement stroke of the free end of the lower cantilever beam and a target movement stroke of the pushing calibration mechanism according to a theoretical calibration force value; and the pushing calibration mechanism is ejected to the target moving stroke so as to drive the free end of the lower cantilever beam to move. Standard force loading is simulated through the internal pushing mechanism, external equipment is not needed, calibration can be completed in situ on the sensor, on-site real-time calibration is achieved, and the device is suitable for high-precision and unattended industrial scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of strain type force sensors, and in particular to a strain type force sensor with a self-calibration function. Background Art

[0002] Strain-gauge force sensors, due to their simple structure, high measurement accuracy, and excellent reliability, are widely used in industrial force measurement, automated control, robotic tactile sensing, and other fields. Their core principle is to utilize the deformation of an elastic body (such as a cantilever beam) under load, causing the resistance of the strain gauge attached to its surface to change. This resistance is converted into a voltage signal through a bridge circuit. However, the measurement accuracy of strain-gauge sensors is easily affected by factors such as ambient temperature, material creep, and zero-point drift caused by long-term use. Therefore, regular calibration is required to ensure measurement accuracy.

[0003] Traditional calibration methods typically rely on external standard force sources (such as weights or calibration machines) to apply a known force value for calibration. However, this method requires regular disassembly and downtime. The strain gauge force sensor must first be removed from the equipment, calibrated using an external standard force source, and then reinstalled. This calibration operation is cumbersome and time-consuming, making it difficult to achieve real-time on-site calibration and unsuitable for high-precision, unattended industrial measurement scenarios. In addition, the traditional method of relying on an external standard force source for calibration requires frequent disassembly and installation of the sensor, which can easily introduce additional friction or structural errors to the sensor, affecting its long-term stability. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies in the prior art and to provide a strain gauge force sensor with a self-calibration function.

[0005] The objective of the present invention is achieved through the following technical solutions: a strain gauge force sensor with a self-calibration function, comprising an upper cantilever beam and a lower cantilever beam, the stiffness of the upper cantilever beam being greater than that of the lower cantilever beam; the fixed end of the lower cantilever beam is fixedly connected to the fixed end of the upper cantilever beam, and a push calibration mechanism is provided between the movable end of the lower cantilever beam and the movable end of the upper cantilever beam; a strain gauge is installed on the lower cantilever beam; in the measurement mode, the push calibration mechanism is in a retracted state, the upper cantilever beam and the lower cantilever beam are fitted to make the upper cantilever beam and the lower cantilever beam deform synchronously; in the calibration mode, a theoretical calibration force value is determined, and the target moving stroke of the free end of the lower cantilever beam and the target moving stroke of the push calibration mechanism are calculated according to the theoretical calibration force value; the push calibration mechanism is pushed out to the target moving stroke to drive the free end of the lower cantilever beam to move, and the output value of the strain gauge force sensor is collected, and the target moving stroke of the free end of the lower cantilever beam and the output value curve of the strain gauge force sensor are fitted.

[0006] Preferably, when calculating the target moving stroke of the free end of the lower cantilever beam and the target moving stroke of the pushing calibration mechanism, the calibration force value allocated to the free end of the lower cantilever beam is determined according to the stiffness ratio between the upper cantilever beam and the lower cantilever beam, and the target moving stroke of the free end of the lower cantilever beam and the target moving stroke of the pushing calibration mechanism are calculated according to the calibration force value allocated to the free end of the lower cantilever beam.

[0007] Preferably, the pushing calibration mechanism includes a first mounting cavity arranged at the free end of the upper cantilever beam and a second mounting cavity arranged at the free end of the lower cantilever beam, a pushing device is arranged in the first mounting cavity, a rotating shaft is arranged in the second mounting cavity, a fixed push rod is arranged on the pushing device, a movable push rod is connected to the fixed push rod, one end of the movable push rod is hinged to one end of the fixed push rod, and the other end of the movable push rod is provided with a groove matching the rotating shaft.

[0008] Preferably, the mating groove is a "U"-shaped groove, the groove width of the mating groove is the same as the diameter of the rotating shaft, and the mating groove is provided with an arc surface adapted to the rotating shaft; when the push calibration mechanism drives the free end of the lower cantilever beam to move, the arc surface in the mating groove fits with the rotating shaft.

[0009] As a preference, the target moving stroke of the free end of the lower cantilever beam is The calculation formula is as follows: ; Where, E 2 is the elastic modulus of the lower cantilever beam, L 2 is the length of the lower cantilever beam, K 1 is the length of the upper cantilever beam, K 2 is the length of the lower cantilever beam, I 2 is the section moment of inertia of the lower cantilever beam, F ext is the theoretical calibration force value; Target moving stroke of the push calibration mechanism x The calculation formula is as follows: ; Where, L 0 is the length of the push rod.

[0010] Preferably, the pushing device is a linear motor.

[0011] Preferably, the ratio of the upper cantilever beam stiffness to the lower cantilever beam stiffness is greater than 10.

[0012] Preferably, a deformation cavity is provided in the middle of the lower cantilever, and two strain gauges are respectively provided on the upper and lower surfaces of the deformation cavity, and the four strain gauges constitute a strain gauge bridge.

[0013] Preferably, a locking mechanism is provided between the free end of the upper cantilever beam and the free end of the lower cantilever beam; when the strain gauge force sensor is in the measurement mode, the free end of the upper cantilever beam and the free end of the lower cantilever beam are locked by the locking mechanism.

[0014] Preferably, the locking mechanism includes a guide seat arranged at the upper end of the lower cantilever beam, a movable locking rod is slidably connected to the guide seat, and a spring is arranged between the movable locking rod and the guide seat; one end of the movable locking rod is an insertion end, and a card slot corresponding to the insertion end of the movable locking rod is provided on the inner wall of the first mounting cavity; the other end of the movable locking rod is provided with a first inclined surface; the movable push rod is provided with an inclined block corresponding to the movable locking rod, and the inclined block is provided with a second inclined surface matching the first inclined surface; when the strain type force sensor is in the measuring mode, the second push rod moves to the pushing position, at this time the second inclined surface on the inclined block contacts the first inclined surface on the movable locking rod, and the movable locking rod is inserted into the card slot under the pushing action of the inclined block.

[0015] The beneficial effects of the present invention are: 1. During the calibration process, the target movement stroke of the lower cantilever beam is precisely controlled by the push calibration mechanism. Combined with the theoretical calibration force value calculated by material mechanics theory, high-precision calibration force loading can be achieved. By fitting the stroke-output value curve, errors such as temperature drift and zero point offset can be effectively corrected to ensure that the measurement accuracy after calibration meets high-precision industrial requirements.

[0016] 2. Traditional force sensor calibration relies on external force sources such as weights and calibration machines, and the sensor needs to be disassembled. The present invention simulates standard force loading through an internal pushing mechanism, does not require external equipment, and can complete calibration in situ. This solves the pain points of traditional methods of "dependence on external force sources and the need for disassembly and shutdown", realizes on-site real-time calibration, and is suitable for high-precision, unattended industrial scenarios.

[0017] 3. The calibration method of traditional strain-type force sensors is prone to introducing additional friction or structural errors (such as installation gaps, changes in stress distribution, etc.) due to frequent disassembly and installation. The self-calibration process of the present invention does not require disassembly of the sensor, so that the connection relationship and structural state of the upper and lower cantilever beams remain stable, fundamentally reducing the interference of external operations on the sensor and significantly improving the measurement stability during long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the strain type force sensor in Example 1 of the present invention.

[0019] Figure 2 4 is a cross-sectional view of the strain gauge force sensor in Example 1 of the present invention.

[0020] Figure 3This is a structural diagram of the push calibration mechanism in Example 1 of the present invention.

[0021] Figure 4 This is a schematic diagram of the push calibration mechanism when calibrating the strain gauge force sensor.

[0022] Figure 5 4 is a cross-sectional view of the strain-type force sensor in Example 2 of the present invention.

[0023] Figure 6 for Figure 5 Enlarged view of part A in the middle.

[0024] In the figure: 1. Upper cantilever beam, 2. Lower cantilever beam, 3. Deformation cavity, 4. Strain gauge, 5. First mounting cavity, 6. Second mounting cavity, 7. Pushing device, 8. Moving push rod, 9. Rotating shaft, 10. Fixed push rod, 11. Matching groove, 12. Bevel block, 13. Guide seat, 14. Movable locking rod, 15. Spring limit ring, 16. Spring, 17. Slot. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0026] It should be understood by those skilled in the art that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0027] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0028] Example 1: like Figures 1 to 4As shown, a strain gauge force sensor with self-calibration function includes an upper cantilever beam 1 and a lower cantilever beam 2. The upper cantilever beam 1 has a greater stiffness than the lower cantilever beam 2. The fixed end of the lower cantilever beam 2 is fixedly connected to the fixed end of the upper cantilever beam 1, and a push calibration mechanism is provided between the movable end of the lower cantilever beam 2 and the movable end of the upper cantilever beam 1. A strain gauge 4 is mounted on the lower cantilever beam 2. In measurement mode, the push calibration mechanism is retracted, and the upper cantilever beam 1 and the lower cantilever beam 2 are aligned to achieve synchronous deformation of the upper and lower cantilever beams 1 and 2. In calibration mode, a theoretical calibration force value is determined, and a target travel of the free end of the lower cantilever beam 2 and a target travel of the push calibration mechanism are calculated based on the theoretical calibration force value. The push calibration mechanism is pushed out to the target travel to drive the free end of the lower cantilever beam 2 to move, and the output value of the strain gauge force sensor is collected, and a curve of the target travel of the free end of the lower cantilever beam 2 and the output value of the strain gauge force sensor is fitted.

[0029] In the present invention, the stiffness of the upper cantilever beam 1 is greater than that of the lower cantilever beam 2. The upper cantilever beam 1 deforms less when subjected to external force, while the lower cantilever beam 2 deforms more when subjected to external force.

[0030] In the measurement mode, an external force acts on the free end of the upper cantilever beam 1. Since the upper cantilever beam 1 and the lower cantilever beam 2 are tightly fitted together, the upper cantilever beam 1 and the lower cantilever beam 2 form a whole. The upper cantilever beam 1 transfers the force to the lower cantilever beam 2, so that the upper cantilever beam 1 and the lower cantilever beam 2 maintain synchronous deformation. The overall deformation (strain) of the upper cantilever beam 1 and the lower cantilever beam 2 is proportional to the external force, and the external force is calculated by measuring the deformation.

[0031] In calibration mode, without external forces acting, the push calibration mechanism directly applies force to the free end of the lower cantilever beam 2, driving the free end of the lower cantilever beam 2 downward, causing the lower cantilever beam 2 to deform. Due to the greater stiffness of the upper cantilever beam 1 (the ratio of the stiffness of the upper cantilever beam 1 to the stiffness of the lower cantilever beam 2 is greater than 10), deformation is not easy to occur. By rationally allocating the stiffness ratio between the upper cantilever beam 1 and the lower cantilever beam 2, the deformation of the upper cantilever beam 1 can be ignored. This design ensures that during the push calibration process, the upper cantilever beam 1 hardly deforms due to its high stiffness, while the push force mainly acts on the lower cantilever beam 2 with lower stiffness, so that the deformation of the lower cantilever beam 2 can be precisely controlled by the push calibration mechanism. By recording the travel of the free end of the lower cantilever beam 2 and the corresponding sensor output value and fitting the data, the sensor can be calibrated.

[0032] In the calibration mode, since the material parameters such as stiffness, elastic modulus, and length of the upper cantilever beam 1 and the lower cantilever beam 2 are known, after determining the theoretical calibration force value applied to the strain-type force sensor, the target moving stroke required for the free end of the lower cantilever beam 2 can be reversed based on the theoretical calibration force value. After calculating the target moving stroke of the free end of the lower cantilever beam 2, the target moving stroke of the pushing calibration mechanism (i.e., the length that the pushing calibration mechanism needs to be ejected) is calculated based on the structural characteristics of the pushing calibration mechanism. The target moving stroke of the pushing calibration mechanism corresponds one-to-one to the target moving stroke of the free end of the lower cantilever beam 2.

[0033] The push calibration mechanism pushes out according to the target travel, pushing the free end of the lower cantilever beam 2 (at this point, the upper cantilever beam 1 hardly deforms due to its high stiffness and can be considered a rigid member), causing the lower cantilever beam 2 to deform according to the theoretical calibration force value. The voltage signal output by the strain gauge 4 is collected and the sensor output value is obtained. A curve "target travel (corresponding to the theoretical calibration force value) and sensor output value" is fitted to establish a correspondence between the known theoretical calibration force value and the actual output value of the strain gauge force sensor. The calibration coefficient is calculated, completing the calibration. The calibration coefficient is the ratio of the strain gauge force sensor output value to the theoretical calibration force value.

[0034] like Figure 3 As shown, the push calibration mechanism includes a first mounting cavity 5 provided at the free end of the upper cantilever beam 1 and a second mounting cavity 6 provided at the free end of the lower cantilever beam 2. A push device 7 is provided in the first mounting cavity 5, and a rotating shaft 9 is provided in the second mounting cavity 6. A fixed push rod 10 is provided on the push device 7, and a movable push rod 8 is connected to the fixed push rod 10. One end of the movable push rod 8 is hinged to one end of the fixed push rod 10, and the other end of the movable push rod 8 is provided with a groove 11 that matches the rotating shaft 9. Among them, the matching groove 11 is a "U"-shaped groove, the groove width of the matching groove 11 is the same as the diameter of the rotating shaft 9, and the matching groove 11 is provided with an arc surface that matches the rotating shaft 9; when the push calibration mechanism drives the free end of the lower cantilever beam 2 to move, the arc surface in the matching groove 11 fits with the rotating shaft 9.

[0035] In the measurement mode, the fixed push rod 10 retracts to its initial position, at which point the fixed push rod 10 and the movable push rod 8 are exactly aligned. When the thrust device 7 drives the fixed push rod 10 to extend, the fixed push rod 10 maintains its original position during the extension process, and the movable push rod 8 drives the free end of the lower cantilever beam 2 to move during the extension process.

[0036] The first mounting cavity 5 (at the free end of the upper cantilever beam 1) and the second mounting cavity 6 (at the free end of the lower cantilever beam 2) provide internal mounting space for components such as the push mechanism 7 and the rotating shaft 9, allowing the push calibration mechanism to be fully integrated within the upper and lower cantilever structures. This design prevents interference from external protruding components on the overall sensor structure and ensures that in measurement mode (when the push mechanism is retracted), the upper and lower cantilever beams 2 fit tightly together without any additional gaps or obstructions, ensuring consistent, synchronized deformation of the two beams and maintaining the original measurement accuracy in measurement mode.

[0037] The fixed push rod 10 and the movable push rod 8 are connected by a hinge, which converts the linear motion of the jacking device 7 (such as the extension and retraction of the jacking device 7) into a directional thrust of the movable push rod 8 on the lower cantilever beam 2. The hinged structure can eliminate the lateral force that may occur during the jacking process. The movable push rod 8 cooperates with the rotating shaft 9 through the matching groove 11. This design ensures that the direction of the jacking force always passes through the axis of the rotating shaft 9, ensuring the consistency of the force application position. The groove at the end of the movable push rod 8 forms a stable contact pair with the rotating shaft 9 of the lower cantilever beam 2. This matching method can not only ensure the effective jacking of the lower cantilever beam 2 by the movable push rod 8 (that is, the rotating shaft 9 is limited by the groove to avoid slipping), but also directly convert the "target moving stroke" of the jacking device 7 into the displacement of the free end of the lower cantilever beam 2 through the movement of the movable push rod 8. The hinged structure of the movable push rod 8 and the fixed push rod 10 can rotate flexibly as the relative angle of the upper and lower cantilever beams 2 changes. The cooperation between the groove at the end of the movable push rod 8 and the rotating shaft 9 also allows small angle adaptive adjustment; this structural design completely eliminates the structural interference caused by the relative movement of the two beams, ensuring that the pushing process is smooth and without jamming, and ensuring the reliability of the calibration operation.

[0038] When calculating the target moving stroke of the free end of the lower cantilever beam 2 and the target moving stroke of the push calibration mechanism, the calibration force value allocated to the free end of the lower cantilever beam 2 is determined based on the stiffness ratio between the upper cantilever beam 1 and the lower cantilever beam 2, and the target moving stroke of the free end of the lower cantilever beam 2 and the target moving stroke of the push calibration mechanism are calculated based on the calibration force value allocated to the free end of the lower cantilever beam 2.

[0039] The free end stiffness k of the cantilever beam represents the force required to produce unit deflection, and its calculation formula is as follows: .

[0040] Where, E is the elastic modulus, L is the length of the cantilever beam, I is the section moment of inertia of the cantilever beam.

[0041] The stiffness of the upper cantilever beam and the lower cantilever beam are defined as k 1. k 2. When the theoretical calibration force value When acting on the free end of the upper cantilever beam, the force F2 distributed to the free end of the lower cantilever beam is: .

[0042] Target moving stroke of the free end of the lower cantilever beam The calculation formula is as follows: ; Where, E 2 is the elastic modulus of the lower cantilever beam, L 2 is the length of the lower cantilever beam, k 1 is the length of the upper cantilever beam, K 2 is the length of the lower cantilever beam, I 2 is the section moment of inertia of the lower cantilever beam, F ext is the theoretical calibration force value.

[0043] refer to Figure 4 , in calculating the target moving stroke of the push calibration mechanism x When calculating the target moving stroke of the push calibration mechanism, x Target moving stroke with the free end of the lower cantilever beam The difference △ x ,△ x The calculation method is as follows: ; Where, L 0 is the length of the push rod, b is the vertical projection length of the push rod, is the maximum rotation angle of the end section of the free end of the cantilever beam, The calculation formula is as follows: .

[0044] Target moving stroke of the push calibration mechanism x The calculation formula is as follows: .

[0045] In this application, the pushing device is a linear motor.

[0046] The ratio of the stiffness of the upper cantilever beam 1 to the stiffness of the lower cantilever beam 2 is greater than 10. The larger the ratio of the stiffness of the upper cantilever beam 1 to the stiffness of the lower cantilever beam 2, the smaller the deformation of the upper cantilever beam 1 in the calibration mode, and the smaller the impact on the calibration accuracy.

[0047] A deformation cavity 3 is provided in the middle of the lower cantilever. Two strain gauges 4 are provided on the upper and lower surfaces of the deformation cavity 3 respectively. The four strain gauges 4 constitute a strain gauge bridge.

[0048] The present invention has the following advantages: the calibration of traditional force sensors relies on external force sources such as weights and calibration machines, and the sensor needs to be disassembled; the present invention simulates standard force loading through an internal pushing mechanism, does not require external equipment, and can complete calibration in situ on the sensor, solving the pain points of the traditional method of "relying on external force sources and requiring disassembly and shutdown", realizing on-site real-time calibration, and is suitable for high-precision, unattended industrial scenarios. The calibration method of traditional strain-type force sensors is prone to introducing additional friction or structural errors (such as installation gaps, stress distribution changes, etc.) due to frequent disassembly and installation. The self-calibration process of the present invention does not require the disassembly of the sensor, so that the connection relationship and structural state of the upper and lower cantilever beams 2 remain stable, fundamentally reducing the interference of external operations on the sensor, and significantly improving the measurement stability in long-term use. During the calibration process of the present invention, the target moving stroke of the lower cantilever beam 2 is precisely controlled by the pushing calibration mechanism, and the theoretical calibration force value calculated by the material mechanics theory can achieve high-precision calibration force loading; by fitting the stroke-output value curve, errors such as temperature drift and zero point offset can be effectively corrected to ensure that the measurement accuracy after calibration meets high-precision industrial requirements.

[0049] Example 2: like Figures 5 and 6 As shown, the difference between Example 2 and Example 1 is that: in Example 2, a locking mechanism is provided between the free end of the upper cantilever beam 1 and the free end of the lower cantilever beam 2; when the strain type force sensor is in the measurement mode, the free end of the upper cantilever beam 1 and the free end of the lower cantilever beam 2 are locked by the locking mechanism.

[0050] The locking mechanism includes a guide seat 13 mounted at the upper end of the lower cantilever beam 2, with a movable locking rod 14 slidably connected to the guide seat 13. The guide seat 13 is provided with a transverse guide hole, into which the movable locking rod 14 slides. A spring 16 is interposed between the movable locking rod 14 and the guide seat 13; the movable locking rod 14 is provided with a retaining ring for the spring 16, with one end of the spring 16 in contact with the retaining ring. One end of the movable locking rod 14 is an insertion end, and a slot 17 corresponding to the insertion end of the movable locking rod 14 is provided on the inner wall of the first mounting cavity 5; the other end of the movable locking rod 14 is provided with a first inclined surface; the movable push rod 8 is provided with an inclined block 12 corresponding to the movable locking rod 14, and the inclined block 12 is provided with a second inclined surface matching the first inclined surface; when the strain type force sensor is in the measuring mode, the second push rod moves to the pushing position, at this time the second inclined surface on the inclined block 12 contacts the first inclined surface on the movable locking rod 14, and the movable locking rod 14 is inserted into the slot 17 under the pushing action of the inclined block 12.

[0051] In the measurement mode, if the upper cantilever beam 1 and the lower cantilever beam 2 are not tightly fitted (there is a gap between them or they are relatively loose), this will cause the upper cantilever beam 1 and the lower cantilever beam 2 to be unable to deform synchronously. When an external force acts, the upper cantilever beam 1 will first deform slightly to fill the gap, and then drive the lower cantilever beam 2 to deform, causing the deformation of the lower cantilever beam 2 to lag behind the actual force. At this time, the strain value collected by the strain gauge 4 cannot correspond to the external force value in real time and accurately. Especially in dynamic force measurement scenarios (such as alternating force and instantaneous impact force), the hysteresis effect will significantly amplify the measurement deviation.

[0052] In the present invention, in the measurement mode, the movable locking rod 14 is inserted into the slot 17 by the push of the inclined block 12, locking the free ends of the upper cantilever beam 1 and the lower cantilever beam 2. Since the upper cantilever beam 1 has a greater rigidity than the lower cantilever beam 2 and the fixed ends of the two cantilever beams are connected, the locking mechanism locks the free ends of the two cantilever beams, allowing the upper and lower cantilever beams 2 to be tightly combined together, eliminating the problem of the upper and lower cantilever beams 2 not fitting together. There is no relative displacement space between the free ends of the two, ensuring that when an external force is applied to the upper cantilever beam 1, the upper and lower cantilever beams 2 are completely synchronously bent and deformed. This synchronous deformation avoids relative slippage or force lag between the upper and lower cantilever beams 2 due to gaps or looseness, ensuring that the strain gauge 4 on the lower cantilever beam 2 can accurately reflect the overall force state (rather than local deformation), eliminating the measurement deviation caused by the matching error between the upper and lower cantilever beams 2 at the structural level, and improving the basic measurement accuracy of the force sensor.

[0053] When the push calibration mechanism moves to the retracted state (measurement mode), the dynamic push rod 8 drives the inclined block 12 to move, and the second inclined surface on the inclined block 12 is aligned with the first inclined surface of the movable locking rod 14. The guiding effect of the inclined surface converts the movement of the dynamic push rod 8 into axial movement of the movable locking rod 14, so that the movable locking rod 14 overcomes the elastic force of the spring 16 and inserts into the slot 17, completing the automatic locking between the free ends of the upper cantilever beam 1 and the lower cantilever beam 2. It is worth mentioning that when the upper cantilever beam 1 and the lower cantilever beam 2 just fit together, the fixed push rod 10 on the push device 7 continues to retract a certain distance, and through the movement of this distance, the movable locking rod 14 is pushed into the slot 17.

[0054] When switching from measurement mode to calibration mode, the push calibration mechanism is pushed out, and the dynamic push rod 8 drives the inclined block 12 to move in the opposite direction. The pushing force of the inclined block 12 on the movable locking rod 14 disappears, and the movable locking rod 14 automatically withdraws from the slot 17 under the elastic force of the spring 16. The free ends of the upper and lower cantilever beams 2 are unlocked, and the push device 7 can independently drive the deformation of the lower cantilever beam 2. During this process, the fixed push rod 10 first pushes out a certain distance until the end of the dynamic push rod 8 with the matching groove 11 just contacts the rotating shaft 9. During this movement, the movable locking rod 14 completely withdraws from the slot 17. The push device 7 will then drive the free end of the lower cantilever beam 2 to move during the subsequent push-out process. The entire process of switching from measurement mode to calibration mode is carried out according to the logic of "first releasing the locking state, then driving the free end of the lower cantilever beam 2 to move."

[0055] The locking mechanism in the present invention does not require an additional driving device to control locking and unlocking, and the switching of the locking state is achieved only through the self-action of the pushing calibration mechanism, which simplifies the control system and reduces the failure rate.

[0056] It is worth mentioning that in the calibration mode, the target moving stroke of the push calibration mechanism is x The starting point of the stroke is when one end of the movable push rod 8 just touches the rotating shaft 9.

[0057] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A strain gauge force sensor with self-calibration function, characterized in that: The cantilever comprises an upper cantilever beam and a lower cantilever beam, wherein the upper cantilever beam has a greater stiffness than the lower cantilever beam; the fixed end of the lower cantilever beam is fixedly connected to the fixed end of the upper cantilever beam, and a push calibration mechanism is provided between the movable end of the lower cantilever beam and the movable end of the upper cantilever beam; a strain gauge is installed on the lower cantilever beam; In the measurement mode, the push calibration mechanism is in a retracted state, and the upper cantilever beam and the lower cantilever beam are in contact with each other so that the upper cantilever beam and the lower cantilever beam deform synchronously. In the calibration mode, a theoretical calibration force value is determined, and the target movement stroke of the free end of the lower cantilever beam and the target movement stroke of the push calibration mechanism are calculated based on the theoretical calibration force value. The push calibration mechanism is pushed out to the target movement stroke to drive the free end of the lower cantilever beam to move, and the output value of the strain force sensor is collected, and the target movement stroke of the free end of the lower cantilever beam and the output value curve of the strain force sensor are fitted.

2. The strain gauge force sensor with self-calibration function according to claim 1, characterized in that: When calculating the target moving stroke of the free end of the lower cantilever beam and the target moving stroke of the push calibration mechanism, the calibration force value allocated to the free end of the lower cantilever beam is determined based on the stiffness ratio between the upper cantilever beam and the lower cantilever beam, and the target moving stroke of the free end of the lower cantilever beam and the target moving stroke of the push calibration mechanism are calculated based on the calibration force value allocated to the free end of the lower cantilever beam.

3. The strain gauge force sensor with self-calibration function according to claim 1, characterized in that: The pushing calibration mechanism includes a first mounting cavity arranged at the free end of the upper cantilever beam and a second mounting cavity arranged at the free end of the lower cantilever beam. A pushing device is arranged in the first mounting cavity, a rotating shaft is arranged in the second mounting cavity, a fixed push rod is arranged on the pushing device, a movable push rod is connected to the fixed push rod, one end of the movable push rod is hinged to one end of the fixed push rod, and the other end of the movable push rod is provided with a groove matching the rotating shaft.

4. The strain gauge force sensor with self-calibration function according to claim 3, characterized in that: The mating groove is a "U"-shaped groove, the groove width of the mating groove is the same as the diameter of the rotating shaft, and the mating groove is provided with an arc surface adapted to the rotating shaft; when the push calibration mechanism drives the free end of the lower cantilever beam to move, the arc surface in the mating groove fits with the rotating shaft.

5. The strain gauge force sensor with self-calibration function according to claim 3, characterized in that: Target moving stroke of the free end of the lower cantilever beam The calculation formula is as follows: ； Where, E 2 is the elastic modulus of the lower cantilever beam, L 2 is the length of the lower cantilever beam, k 1 is the length of the upper cantilever beam, K 2 is the length of the lower cantilever beam, I 2 is the section moment of inertia of the lower cantilever beam, F ext is the theoretical calibration force value; Target moving stroke of the push calibration mechanism x The calculation formula is as follows: ； Where, L 0 is the length of the push rod.

6. The strain gauge force sensor with self-calibration function according to claim 3, characterized in that: The pushing device is a linear motor.

7. The strain gauge force sensor with self-calibration function according to claim 1, characterized in that: The ratio of the upper cantilever beam stiffness to the lower cantilever beam stiffness is greater than 10.

8. The strain gauge force sensor with self-calibration function according to claim 1, characterized in that: A deformation cavity is provided in the middle of the lower cantilever, and two strain gauges are respectively provided on the upper and lower surfaces of the deformation cavity, and the four strain gauges constitute a strain gauge bridge.

9. The strain gauge force sensor with self-calibration function according to claim 3, characterized in that: A locking mechanism is provided between the free end of the upper cantilever beam and the free end of the lower cantilever beam; when the strain gauge force sensor is in the measurement mode, the free end of the upper cantilever beam and the free end of the lower cantilever beam are locked by the locking mechanism.

10. The strain gauge force sensor with self-calibration function according to claim 9, characterized in that: The locking mechanism includes a guide seat arranged at the upper end of the lower cantilever beam, a movable locking rod is slidably connected to the guide seat, and a spring is arranged between the movable locking rod and the guide seat; one end of the movable locking rod is an insertion end, and a card slot corresponding to the insertion end of the movable locking rod is provided on the inner wall of the first mounting cavity; the other end of the movable locking rod is provided with a first inclined surface; the movable push rod is provided with an inclined block corresponding to the movable locking rod, and the inclined block is provided with a second inclined surface matching the first inclined surface; when the strain type force sensor is in the measuring mode, the second push rod moves to the pushing position, at this time the second inclined surface on the inclined block contacts the first inclined surface on the movable locking rod, and the movable locking rod is inserted into the card slot under the pushing action of the inclined block.

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