A strain gauge force sensor with self-calibration function

Abstract

This invention discloses a strain gauge force sensor with self-calibration function, comprising an upper cantilever beam and a lower cantilever beam, wherein the stiffness 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 to the fixed end of the upper cantilever beam, and a pushing calibration mechanism is provided between the movable end of the lower cantilever beam and the movable end of the upper cantilever beam; in measurement mode, the pushing calibration mechanism is in a retracted state, and the upper and lower cantilever beams are in contact to allow them to deform synchronously; in calibration mode, the target travel distance of the free end of the lower cantilever beam and the target travel distance of the pushing calibration mechanism are calculated based on the theoretical calibration force value; the pushing calibration mechanism extends to the target travel distance to drive the free end of the lower cantilever beam to move. This invention simulates standard force loading through an internal pushing mechanism, eliminating the need for external equipment, and can complete calibration in situ, achieving real-time on-site calibration, suitable for high-precision, unattended industrial scenarios.

Description

Technical Field

[0001] This invention relates to the field of strain gauge force sensor technology, and in particular to a strain gauge force sensor with self-calibration function. Background Technology

[0002] Strain gauge force sensors are widely used in industrial force measurement, automation control, and robotic tactile sensing due to their simple structure, high measurement accuracy, and good reliability. Their core principle is based on the deformation of an elastic body (such as a cantilever beam) under stress, causing a change in the resistance of a strain gauge attached to its surface. This change is converted into a voltage signal output through a Wheatstone 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 necessary to ensure measurement accuracy.

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

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a strain gauge force sensor with self-calibration function.

[0005] The objective of this invention is achieved through the following technical solution: a strain gauge force sensor with self-calibration function, comprising an upper cantilever beam and a lower cantilever beam, wherein the stiffness 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 to the fixed end of the upper cantilever beam, and a jacking calibration mechanism is provided between the movable end of the lower cantilever beam and the movable end of the upper cantilever beam; strain gauges are installed on the lower cantilever beam; in measurement mode, the jacking calibration mechanism is in a retracted state, and the upper and lower cantilever beams are in contact to allow them to deform synchronously; in 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 jacking calibration mechanism are calculated based on the theoretical calibration force value; the jacking 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 gauge force sensor is collected, fitting the target movement stroke of the free end of the lower cantilever beam and the output value curve of the strain gauge force sensor.

[0006] Preferably, when calculating the target travel distance of the free end of the lower cantilever beam and the target travel distance of the jacking 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 and lower cantilever beams, and the target travel distance of the free end of the lower cantilever beam and the target travel distance of the jacking calibration mechanism are calculated based on the calibration force value allocated to the free end of the lower cantilever beam.

[0007] Preferably, the jacking calibration mechanism includes a first mounting cavity disposed at the free end of the upper cantilever beam and a second mounting cavity disposed at the free end of the lower cantilever beam. A jacking device is disposed in the first mounting cavity, and a rotating shaft is disposed in the second mounting cavity. A fixed push rod is disposed on the jacking device, and 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 that cooperates with the rotating shaft.

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

[0009] Preferably, the target travel distance of the free end of the lower cantilever beam is... The calculation formula is as follows:

[0010] ;

[0011] In the formula, E 2 represents the elastic modulus of the lower cantilever beam. L 2 represents the length of the lower cantilever beam. K 1 represents the length of the upper cantilever beam. K 2 represents the length of the lower cantilever beam. I 2 represents the moment of inertia of the lower cantilever beam section. F ext For theoretical calibration force values;

[0012] Target travel distance of the pusher calibration mechanism x The calculation formula is as follows:

[0013] ;

[0014] In the formula, L 0 represents the length of the moving push rod.

[0015] Preferably, the pushing device is a linear motor.

[0016] Preferably, the ratio of the stiffness of the upper cantilever beam to the stiffness of the lower cantilever beam is greater than 10.

[0017] 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 form a strain gauge bridge.

[0018] Preferably, a locking mechanism is provided between the free ends of the upper and lower cantilever beams; when the strain gauge force sensor is in measurement mode, the locking mechanism locks the free ends of the upper and lower cantilever beams together.

[0019] Preferably, the locking mechanism includes a guide seat disposed at the upper end of the lower cantilever beam, a movable locking rod slidably connected to the guide seat, and a spring disposed between the movable locking rod and the guide seat; one end of the movable locking rod is an insertion end, and a groove corresponding to the insertion end of the movable locking rod is disposed 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 that cooperates with the first inclined surface; when the strain gauge force sensor is in the measurement mode, the second push rod moves to the push position, at which 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 groove under the push action of the inclined block.

[0020] The beneficial effects of this invention are:

[0021] 1. In the calibration process, the target movement stroke of the lower cantilever beam is precisely controlled by the top-pushing calibration mechanism. Combined with the theoretical calibration force value calculated by the 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, ensuring that the measurement accuracy after calibration meets the high-precision industrial requirements.

[0022] 2. Traditional force sensor calibration relies on external force sources such as weights and calibration machines, and requires disassembling the sensor. This invention simulates standard force loading through an internal pushing mechanism, eliminating the need for external equipment and enabling calibration to be completed in situ. This solves the pain point of traditional methods that "rely on external force sources and require disassembly and shutdown," achieving real-time on-site calibration and making it suitable for high-precision, unattended industrial scenarios.

[0023] 3. Traditional calibration methods for strain gauge force sensors are 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 this invention does not require disassembly of the sensor, which keeps the connection relationship and structural state of the upper and lower cantilever beams stable, fundamentally reducing the interference of external operation on the sensor and significantly improving the measurement stability during long-term use. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the strain gauge force sensor in Embodiment 1 of the present invention.

[0025] Figure 2 This is a cross-sectional view of the strain gauge force sensor in Embodiment 1 of the present invention.

[0026] Figure 3 This is a schematic diagram of the top-pushing calibration mechanism in Embodiment 1 of the present invention.

[0027] Figure 4 This is a schematic diagram of the top-push calibration mechanism during the calibration of a strain gauge force sensor.

[0028] Figure 5 This is a cross-sectional view of the strain gauge force sensor in Embodiment 2 of the present invention.

[0029] Figure 6 for Figure 5 Enlarged view of section A.

[0030] In the diagram: 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. Fitting groove, 12. Inclined block, 13. Guide seat, 14. Movable locking rod, 15. Spring limiting ring, 16. Spring, 17. Slot. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0032] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0033] 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.

[0034] Example 1:

[0035] 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, wherein the stiffness of the upper cantilever beam 1 is greater than that of 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; strain gauges 4 are installed on the lower cantilever beam 2. In measurement mode, the push-calibration mechanism is in a retracted state, and the upper cantilever beam 1 and the lower cantilever beam 2 are in contact to allow the upper cantilever beam 1 and the lower cantilever beam 2 to deform synchronously; in calibration mode, the theoretical calibration force value is determined, and the target movement stroke of the free end of the lower cantilever beam 2 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 2 to move, and the output value of the strain gauge force sensor is collected, and the target movement stroke of the free end of the lower cantilever beam 2 and the output value curve of the strain gauge force sensor are fitted.

[0036] In this 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.

[0037] In the measurement mode, the 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 closely fitted together, they form a whole. The upper cantilever beam 1 transmits 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. The external force is calculated by measuring the deformation.

[0038] In calibration mode, without external force, the jacking calibration mechanism directly applies force to the free end of the lower cantilever beam 2, driving it downwards and causing deformation. Because the upper cantilever beam 1 has higher stiffness (the ratio of stiffness of upper cantilever beam 1 to lower cantilever beam 2 is greater than 10), it is less prone to deformation. By rationally distributing the stiffness ratio of upper cantilever beam 1 and lower cantilever beam 2, the deformation of upper cantilever beam 1 can be ignored. This design ensures that during the jacking calibration process, upper cantilever beam 1, due to its high stiffness, hardly deforms, while the jacking force mainly acts on the lower cantilever beam 2, which has lower stiffness. This allows the deformation of lower cantilever beam 2 to be precisely controlled by the jacking calibration mechanism. By recording the travel distance of the free end of lower cantilever beam 2 and the corresponding sensor output values, and fitting the data, sensor calibration is achieved.

[0039] In 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 gauge force sensor, the target movement stroke required at the free end of the lower cantilever beam 2 can be deduced from the theoretical calibration force value. After calculating the target movement stroke at the free end of the lower cantilever beam 2, the target movement stroke of the jacking calibration mechanism (i.e., the length that the jacking calibration mechanism needs to push out) is calculated based on the structural characteristics of the jacking calibration mechanism itself. The target movement stroke of the jacking calibration mechanism corresponds one-to-one with the target movement stroke at the free end of the lower cantilever beam 2.

[0040] The jacking calibration mechanism pushes out according to the target stroke, causing the free end of the lower cantilever beam 2 to move (at this time, the upper cantilever beam 1, due to its high stiffness, hardly deforms and can be regarded as a rigid component), causing the lower cantilever beam 2 to produce a deformation corresponding to the theoretical calibration force value; the voltage signal output by the strain gauge 4 is collected and the sensor output value is obtained, and the curve of "target movement stroke (corresponding to theoretical calibration force value) and sensor output value" is fitted to establish the correspondence between the known theoretical calibration force value and the actual output value of the strain gauge force sensor, and the calibration coefficient is calculated, thus completing the calibration. The calibration coefficient is the ratio of the strain gauge force sensor output value to the theoretical calibration force value.

[0041] like Figure 3 As shown, the jacking calibration mechanism includes a first mounting cavity 5 located at the free end of the upper cantilever beam 1 and a second mounting cavity 6 located at the free end of the lower cantilever beam 2. A jacking device 7 is installed in the first mounting cavity 5, and a rotating shaft 9 is installed in the second mounting cavity 6. A fixed push rod 10 is mounted on the jacking 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 has a groove 11 that mates with the rotating shaft 9. The groove 11 is a U-shaped groove, and its width is the same as the diameter of the rotating shaft 9. The groove 11 has an arc surface that matches the rotating shaft 9. When the jacking calibration mechanism drives the free end of the lower cantilever beam 2 to move, the arc surface in the groove 11 fits against the rotating shaft 9.

[0042] In 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 on the same straight line. When the jacking device 7 drives the fixed push rod 10 to extend, the fixed push rod 10 maintains its direction throughout the extension process. During the extension process, the fixed push rod 10 drives the free end of the lower cantilever beam 2 to move through the movable push rod 8.

[0043] The first mounting cavity 5 (the free end of the upper cantilever beam 1) and the second mounting cavity 6 (the free end of the lower cantilever beam 2) provide built-in mounting space for components such as the jacking device 7 and the rotating shaft 9, allowing the jacking calibration mechanism to be fully integrated into the structure of the upper and lower cantilever beams. This design avoids interference from external protruding components on the overall structure of the sensor, ensuring that in measurement mode (when the jacking mechanism is retracted), the upper and lower cantilever beams 2 can fit tightly without any additional gaps or obstructions, guaranteeing the consistency of synchronous deformation of the two beams, thereby maintaining the original measurement accuracy in measurement mode.

[0044] The fixed push rod 10 and the movable push rod 8 are connected by a hinge, converting 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 hinge 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 mating 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 cooperation method can not only ensure the effective jacking of the lower cantilever beam 2 by the movable push rod 8 (i.e., the rotating shaft 9 is limited by the groove to avoid slippage), but also directly convert the "target movement 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 hinge structure of the moving 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 groove at the end of the moving push rod 8 and the cooperation with the rotating shaft 9 also allow for small adaptive angle adjustments. This structural design completely eliminates structural interference caused by the relative movement of the two beams, ensuring a smooth and uninterrupted jacking process and guaranteeing the reliability of the calibration operation.

[0045] When calculating the target travel distance of the free end of the lower cantilever beam 2 and the target travel distance of the jacking calibration mechanism, the calibration force value distributed 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. The target travel distance of the free end of the lower cantilever beam 2 and the target travel distance of the jacking calibration mechanism are then calculated based on the calibration force value distributed to the free end of the lower cantilever beam 2.

[0046] Wherein, the free end stiffness k of the cantilever beam represents the force required to produce a unit deflection, and its calculation formula is as follows:

[0047] .

[0048] In the formula, E For elastic modulus, L The length of the cantilever beam. I Let be the moment of inertia of the cantilever beam section.

[0049] Define the stiffnesses of the upper and lower cantilever beams as follows: k 1. k 2. When the theoretical calibration force value When acting on the free end of the upper cantilever beam, the magnitude of the force F2 distributed at the free end of the lower cantilever beam is:

[0050] .

[0051] Target movement distance at the free end of the lower cantilever beam The calculation formula is as follows:

[0052] ;

[0053] In the formula, E 2 represents the elastic modulus of the lower cantilever beam. L 2 represents the length of the lower cantilever beam. k 1 represents the length of the upper cantilever beam. K 2 represents the length of the lower cantilever beam. I 2 represents the moment of inertia of the lower cantilever beam section. F ext This is to calibrate the theoretical force value.

[0054] refer to Figure 4 In calculating the target movement distance of the top-pushing calibration mechanism x First, calculate the target movement distance of the jacking calibration mechanism. x Target movement distance at the free end of the lower cantilever beam The difference △ x , △ x The calculation method is as follows:

[0055] ;

[0056] In the formula, L 0 represents the length of the movable push rod. b The vertical projection length of the moving push rod. The maximum rotation angle of the end section at the free end of the cantilever beam. The calculation formula is as follows:

[0057] .

[0058] Target travel distance of the pusher calibration mechanism x The calculation formula is as follows:

[0059] .

[0060] In this application, the jacking device is a linear motor.

[0061] 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 during calibration mode, and the smaller the impact on calibration accuracy.

[0062] A deformation cavity 3 is provided in the middle of the lower cantilever. Two strain gauges 4 are respectively provided on the upper and lower surfaces of the deformation cavity 3. The four strain gauges 4 form a strain gauge bridge.

[0063] This invention offers the following advantages: Traditional force sensor calibration relies on external force sources such as weights and calibration machines, and requires sensor disassembly. This invention, through an internal pushing mechanism simulating standard force loading, eliminates the need for external equipment and allows calibration to be completed in situ, solving the pain points of traditional methods that "rely on external force sources and require disassembly and shutdown." It enables real-time on-site calibration, suitable for high-precision, unattended industrial scenarios. Traditional strain gauge force sensor calibration methods, due to frequent disassembly and reassembly, are prone to introducing additional friction or structural errors (such as installation gaps, stress distribution changes, etc.). The self-calibration process of this invention eliminates the need for sensor disassembly, maintaining the stable connection relationship and structural state of the upper and lower cantilever beams 2, fundamentally reducing external interference to the sensor and significantly improving measurement stability during long-term use. During calibration, the target movement of the lower cantilever beam 2 is precisely controlled by the pushing 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, ensuring that the measurement accuracy after calibration meets the requirements of high-precision industrial applications.

[0064] Example 2:

[0065] like Figures 5 to 6 As shown, the difference between Embodiment 2 and Embodiment 1 is that in Embodiment 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 gauge force sensor is in measurement mode, the locking mechanism locks the free end of the upper cantilever beam 1 and the free end of the lower cantilever beam 2.

[0066] The locking mechanism includes a guide seat 13 located 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 has a transverse guide hole, in which the movable locking rod 14 is slidably connected. A spring 16 is provided between the movable locking rod 14 and the guide seat 13; a spring 16 limiting ring is provided on the movable locking rod 14, with one end of the spring 16 contacting the spring 16 limiting ring. One end of the movable locking rod 14 is an insertion end, and the inner wall of the first mounting cavity 5 is provided with a slot 17 corresponding to the insertion end of the movable locking rod 14; 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 that cooperates with the first inclined surface; when the strain gauge force sensor is in the measurement mode, the second push rod moves to the push position, at which 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.

[0067] In measurement mode, if the upper cantilever beam 1 and the lower cantilever beam 2 are not tightly fitted (there is a gap or relative looseness between them), it will cause the upper cantilever beam 1 and the lower cantilever beam 2 to not deform synchronously. When an external force is applied, the upper cantilever beam 1 will first undergo a small deformation to fill the gap, and then the lower cantilever beam 2 will deform. This will cause 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.

[0068] In this invention, during 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 higher stiffness than the lower cantilever beam 2, and their fixed ends are already connected, the locking mechanism ensures that the upper and lower cantilever beams 2 are tightly joined together, eliminating the problem of misfitting. With no relative displacement space between their free ends, it ensures that when an external force is applied to the upper cantilever beam 1, the upper and lower cantilever beams 2 bend and deform completely synchronously. 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 accurately reflects the overall stress state (rather than local deformation). This eliminates measurement deviations caused by misfitting the upper and lower cantilever beams 2 at the structural level, improving the basic measurement accuracy of the force sensor.

[0069] When the jacking calibration mechanism moves to the retracted state (measurement mode), the moving push rod 8 drives the inclined block 12 to move. The second inclined surface on the inclined block 12 fits against the first inclined surface of the movable locking rod 14. The guiding effect of the inclined surface converts the movement of the moving push rod 8 into the axial movement of the movable locking rod 14, allowing the movable locking rod 14 to overcome the spring force of the spring 16 and insert 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 are just fitted together, the fixed push rod 10 on the jacking device 7 continues to retract a certain distance. Through this distance of movement, the movable locking rod 14 is pushed into the slot 17.

[0070] When switching from measurement mode to calibration mode, the jacking calibration mechanism pushes out, and the moving 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 exits the slot 17 under the action of the spring 16. The free ends of the upper and lower cantilever beams 2 are released from the locking state, and the jacking device 7 can drive the lower cantilever beam 2 to deform independently. In this process, the fixed push rod 10 pushes out a certain distance until the end of the moving push rod 8 with the mating groove 11 just abuts the rotating shaft 9. During this movement, the movable locking rod 14 completely exits from the slot 17. The jacking device 7 will drive the free end of the lower cantilever beam 2 to move in the subsequent pushing process. The entire process of switching from measurement mode to calibration mode follows the logic of "first releasing the locking state, then driving the free end of the lower cantilever beam 2 to move".

[0071] The locking mechanism in this invention does not require an additional drive device to control locking and unlocking. It achieves the switching of the locking state solely through the action of the push calibration mechanism itself, which simplifies the control system and reduces the failure rate.

[0072] It is worth mentioning that, in calibration mode, the target movement distance of the top-push calibration mechanism is... x The stroke begins when one end of the push rod 8 just touches the rotating shaft 9.

[0073] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A strain gauge force sensor with self-calibration function, characterized in that, It includes an upper cantilever beam and a lower cantilever beam, with the upper cantilever beam having a higher 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 jacking calibration mechanism is provided between the movable end of the lower cantilever beam and the movable end of the upper cantilever beam; strain gauges are installed on the lower cantilever beam. The jacking calibration mechanism includes a first mounting cavity at the free end of the upper cantilever beam and a second mounting cavity at the free end of the lower cantilever beam. A jacking device is located in the first mounting cavity, and a rotating shaft is located in the second mounting cavity. A fixed push rod is mounted on the jacking device, and 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 has a groove that mates with the rotating shaft. The mate groove is a U-shaped groove, and its width is the same as the diameter of the rotating shaft. The mate groove has an arc surface that matches the rotating shaft. When the jacking calibration mechanism drives the free end of the lower cantilever beam to move, the arc surface in the mate groove fits against the rotating shaft. In measurement mode, the jacking calibration mechanism is in a retracted state, and the upper cantilever beam and the lower cantilever beam are in contact to make the upper and lower cantilever beams deform synchronously; in calibration mode, the 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 jacking calibration mechanism are calculated based on the theoretical calibration force value. The jacking calibration mechanism pushes out to the target movement stroke to drive the free end of the lower cantilever beam to move, and collects the output value of the strain gauge force sensor, fitting the target movement stroke of the free end of the lower cantilever beam and the output value curve of the strain gauge force sensor.

2. A strain gauge force sensor with self-calibration function according to claim 1, characterized in that, When calculating the target travel distance of the free end of the lower cantilever beam and the target travel distance of the jacking 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 and lower cantilever beams. The target travel distance of the free end of the lower cantilever beam and the target travel distance of the jacking calibration mechanism are then calculated using the calibration force value allocated to the free end of the lower cantilever beam.

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

4. A strain gauge force sensor with self-calibration function according to claim 1, characterized in that, The pushing device is a linear motor.

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

6. A 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. The four strain gauges form a strain gauge bridge.

7. A strain gauge force sensor with self-calibration function according to claim 1, characterized in that, A locking mechanism is provided between the free ends of the upper and lower cantilever beams; when the strain gauge force sensor is in measurement mode, the locking mechanism locks the free ends of the upper and lower cantilever beams together.

8. A strain gauge force sensor with self-calibration function according to claim 7, characterized in that, The locking mechanism includes a guide seat located at the upper end of the lower cantilever beam, a movable locking rod slidably connected to the guide seat, and a spring between the movable locking rod and the guide seat. One end of the movable locking rod is an insertion end, and a groove 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 moving push rod is provided with an inclined block corresponding to the movable locking rod, and a second inclined surface that cooperates with the first inclined surface is provided on the inclined block. When the strain gauge force sensor is in measurement 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 groove under the pushing action of the inclined block.

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