MEMS six-dimensional force sensor based on polar plate distance change measurement

Abstract

The invention discloses an MEMS six-dimensional force sensor based on polar plate distance change measurement, and the sensor comprises a central stress rigid platform, and four sides of the central stress rigid platform are each provided with two vertical moving polar plates and a transverse moving polar plate; a fixed outer shell is arranged on the outer side of the center stress rigid body platform, insulating vertical bearing plates are arranged at the positions, corresponding to the vertical movable polar plates, of the fixed outer shell, vertical fixed polar plates are carried on the insulating vertical bearing plates, the vertical fixed polar plates and the vertical movable polar plates are opposite to form a vertical measuring capacitor, and the area of the vertical fixed polar plates is smaller than that of the vertical movable polar plates. When the vertical movable polar plate moves in the measurement movement range, the vertical fixed polar plate is always completely opposite to the vertical movable polar plate; insulation transverse bearing plates are arranged at the positions, corresponding to the transverse moving polar plates, of the fixed outer shell, transverse fixed polar plates are carried on the insulation transverse bearing plates and are opposite to the transverse moving polar plates to form a transverse measuring capacitor, and the transverse fixed polar plates and the vertical top polar plates are similar. According to the invention, inter-dimensional coupling can be reduced, so that the measurement result is more accurate.

Description

Technical Field

[0001] The invention relates to the field of force sensors, and in particular to a MEMS six-dimensional force sensor based on measuring the distance change of pole plates. Background Art

[0002] A multi-dimensional force sensor refers to a force sensor that can simultaneously measure force and torque components in more than two directions. In the Cartesian coordinate system, force and torque can be decomposed into three components each. Therefore, the most complete form of multi-dimensional force is a six-dimensional force / torque sensor, that is, a sensor that can simultaneously measure three force components and three torque components. The widely used multi-dimensional force sensor is this type of sensor. The six-dimensional force sensor can be used as a basic component for precision assembly, precision operation, precision control, and human-computer interaction control because it can simultaneously detect three-dimensional forces and three-dimensional torques in space. At the same time, the six-dimensional force sensor is also a guarantee for robots to complete contact operations. For example, space detection technology, space manipulator force control, industrial robots, and underwater robot remote control operations all require a large range of high-precision six-dimensional force sensors.

[0003] MEMS, or Micro-Electro-Mechanical Systems, is a micro system that integrates micro sensors, actuators, and signal processing and control circuits. It usually uses advanced semiconductor manufacturing technology to integrate micromechanical structures, micro sensors, micro actuators, and signal processing and control circuits on one or more chips to form a complete micro system. MEMS technology is applied to six-dimensional force sensors, and MEMS six-dimensional force sensors are available. At the same time, MEMS six-dimensional force sensors have the advantages of miniaturization, high precision, and high stability due to the characteristics of MEMS, and are often used in the field of robotics. Capacitive MEMS six-dimensional force sensors are a more common type of MEMS six-dimensional force sensors. The working principle of capacitive MEMS six-dimensional force sensors is mainly based on the capacitive effect. When an external force or torque acts on the sensor, the elastic body inside it will undergo a slight deformation, resulting in a change in the distance or area between the capacitor plates, which in turn causes a change in the capacitance value. This capacitance change can be converted and amplified by the circuit to output an electrical signal proportional to the external force or torque. With the introduction of MEMS technology, the microstructure inside the sensor can achieve high-precision measurement and fast response. However, when the capacitive MEMS six-dimensional force sensor measures the force or torque of a certain dimension, the plates of the inductive capacitors corresponding to other dimensions will also produce changes in relative area, thus generating output, and the inter-dimensional coupling is large, affecting the measurement accuracy. Summary of the invention

[0004] In view of some of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a MEMS six-dimensional force sensor based on the measurement of the distance change of the plates, aiming to reduce the inter-dimensional coupling through the structure to make the measurement result more accurate.

[0005] To achieve the above-mentioned purpose, the present invention discloses a MEMS six-axis force sensor based on the measurement of electrode plate distance change, the MEMS six-axis force sensor comprising: a central force-bearing rigid body platform, the four sides of the central force-bearing rigid body platform are each provided with two vertical moving electrodes and one lateral moving electrode plate; a fixed outer shell is arranged on the outer side of the central force-bearing rigid body platform, an insulating vertical bearing plate is arranged on the fixed outer shell at a position corresponding to each of the vertical moving electrodes, a vertical fixed electrode plate is carried on the insulating vertical bearing plate and is opposite to the vertical moving electrode plate to form a vertical measurement capacitor, the vertical fixed electrode plate The area of ​​the vertical moving electrode plate is smaller than that of the vertical moving electrode plate, and when the vertical moving electrode plate moves within the measurement range, the vertical fixed electrode plate always remains completely opposite to the vertical moving electrode plate; an insulating horizontal bearing plate is arranged on the fixed outer shell at a position corresponding to each of the traverse moving electrode plates, and a traverse fixed electrode plate is carried on the insulating traverse bearing plate to form a traverse measuring capacitor relative to the traverse moving electrode plate, and the area of ​​the traverse fixed electrode plate is smaller than that of the traverse moving electrode plate, and when the traverse moving electrode plate moves within the measurement range, the traverse fixed electrode plate always remains completely opposite to the traverse moving electrode plate;

[0006] When the MEMS six-dimensional force sensor measures the force or torque in a certain dimension, the central force-bearing rigid platform is subjected to the force or torque in this dimension, so that the force or torque in this dimension corresponds to the movement of the moving electrode plate of the measuring capacitor relative to the fixed electrode plate, and the relative distance thereof changes, and thus the capacitance thereof changes accordingly; the moving electrode plates of the measuring capacitors in some other dimensions move in a direction perpendicular to the direction of the fixed electrode plate, and their relative distances remain unchanged, and during the rotation, the fixed electrode plate always remains completely opposite to the moving electrode plate, and their relative areas remain unchanged, and thus the capacitance remains unchanged.

[0007] Optionally, a first angle sensor is arranged on the central force-bearing rigid body platform, and a second angle sensor is arranged on the fixed outer shell, and the first angle sensor and the second angle sensor are respectively used to collect the inclination angles of the central force-bearing rigid body platform and the fixed outer shell, so as to obtain the first rotation angle of each vertical moving pole plate relative to its corresponding vertical fixed pole plate, and the second rotation angle of each transverse moving pole plate relative to its corresponding transverse fixed pole plate; the first rotation angle is used to solve the relative area between the vertical moving pole plate and its corresponding vertical fixed pole plate; the second rotation angle is used to solve the relative area between the transverse moving pole plate and its corresponding transverse fixed pole plate.

[0008] Optionally, the fixed outer shell is arranged around the central force-bearing rigid platform, and a cavity is arranged between the fixed outer shell and the central force-bearing rigid platform.

[0009] Optionally, a first connection port is provided on the central force-bearing rigid platform, and the first connection port is used to connect to the measuring end; a second connection port is provided on the fixed outer shell, and the second connection port is used to connect to the fixed end.

[0010] Optionally, the outer shell is further provided with an opening, and a sealing cover is provided on the opening, and the sealing cover is used to package the MEMS six-dimensional force sensor.

[0011] Optionally, the fixed outer shell and the central force-bearing rigid platform are prepared separately, and the central force-bearing rigid platform is prepared by photolithography.

[0012] Optionally, the force dimension and torque dimension of the MEMS six-dimensional force sensor are calibrated differently.

[0013] Beneficial effects of the present invention: 1. The insulating vertical bearing plate of the present invention carries a vertical fixed electrode and a vertical moving electrode to form a vertical measuring capacitor, the area of ​​the vertical fixed electrode is smaller than the area of ​​the vertical moving electrode, and when the vertical moving electrode moves within the measuring range, the vertical fixed electrode always remains completely opposite to the vertical moving electrode; the insulating horizontal bearing plate carries a horizontal fixed electrode and a horizontal moving electrode to form a horizontal measuring capacitor, the area of ​​the horizontal fixed electrode is smaller than the area of ​​the horizontal moving electrode, and when the horizontal moving electrode moves within the measuring range, the horizontal fixed electrode always remains completely opposite to the horizontal moving electrode. The present invention uses such a structure to ensure that when the moving electrode moves, the relative area of ​​the induction capacitor will not change in most cases, and then the capacitance of the induction capacitor is only affected by the relative distance in most cases, so that the force or torque corresponding to the measuring dimension has an output, and the output of other capacitors remains zero, reducing the coupling between dimensions and making the measurement result more reliable. 2. The present invention also arranges a first angle sensor on the central force-bearing rigid platform, and a second angle sensor on the fixed outer shell. The two angle sensors can be used to obtain the deflection angle of the moving electrode relative to the fixed electrode, and the correct relative area of ​​the electrodes can be obtained in the torque dimension measurement, and then correction can be made. This can also reduce inter-dimensional coupling and increase the accuracy of the measurement results.

[0014] In summary, the present invention can reduce inter-dimensional coupling and make the measurement result more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a MEMS six-dimensional force sensor based on plate distance change measurement provided by a specific embodiment of the present invention;

[0016] Figure 2It is a schematic diagram of a top view of a central force-bearing rigid platform provided by a specific embodiment of the present invention;

[0017] Figure 3 is a schematic diagram of a top view of a fixed outer shell provided by a specific embodiment of the present invention;

[0018] Figure 4 It is a structural schematic diagram of a moving electrode plate and a fixed electrode plate of an induction capacitor provided by a specific embodiment of the present invention;

[0019] Figure 5 It is a schematic diagram of the inductive capacitance annotation of a MEMS six-dimensional force sensor provided by a specific embodiment of the present invention;

[0020] Figure 6 It is a schematic diagram of solving the tilted relative area between the plates of a MEMS six-dimensional force sensor provided by a specific embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention discloses a MEMS six-dimensional force sensor based on the measurement of the change in the distance between the plates. Those skilled in the art can refer to the content of this article and appropriately improve the technical details for implementation. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all deemed to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0022] The applicant has found that when the capacitive MEMS six-dimensional force sensor measures the force or torque of a certain dimension, the plates of the inductive capacitors corresponding to other dimensions will also change in relative area, thus generating output, with large coupling, which affects the measurement accuracy. In order to ensure the accuracy of the output measurement results, decoupling is required, but some decoupling algorithms are complex and need to be adjusted according to the actual structure, which is time-consuming and labor-intensive.

[0023] Therefore, the embodiment of the present invention provides a MEMS six-dimensional force sensor based on the measurement of the distance change of the electrode plates, such as Figure 1 , Figure 2 , Figure 3 as well as Figure 4As shown, the MEMS six-dimensional force sensor includes: a central force-bearing rigid platform 101, and two vertical moving plates 102 and a horizontal moving plate 103 are arranged on the four sides of the central force-bearing rigid platform 101; a fixed outer shell 104 is arranged on the outer side of the central force-bearing rigid platform 101, and an insulating vertical bearing plate 105 is arranged on the fixed outer shell 104 at a position corresponding to each vertical moving plate 102, and a vertical fixed plate 106 is carried on the insulating vertical bearing plate 105 to form a vertical measuring capacitor relative to the vertical moving plate 102, and the area of ​​the vertical fixed plate 106 is smaller than the area of ​​the vertical moving plate 102 , and when the vertical moving electrode plate 102 moves within the measuring range of motion, the vertical fixed electrode plate 106 always remains completely opposite to the vertical moving electrode plate 102; an insulating horizontal bearing plate 107 is arranged on the fixed outer shell 104 at a position corresponding to each lateral moving electrode plate 103, and a horizontal fixed electrode plate 108 is carried on the insulating horizontal bearing plate 107 to form a horizontal measuring capacitor relative to the lateral moving electrode plate 103, the area of ​​the horizontal fixed electrode plate 108 is smaller than the area of ​​the lateral moving electrode plate 103, and when the lateral moving electrode plate 103 moves within the measuring range of motion, the horizontal fixed electrode plate 108 always remains completely opposite to the lateral moving electrode plate 103.

[0024] When the MEMS six-dimensional force sensor measures force or torque in a certain dimension, the central force-bearing rigid platform 101 is subjected to the force or torque in that dimension, causing the moving electrode plate of the measuring capacitor corresponding to the force or torque in that dimension to move relative to the fixed electrode plate, and their relative distance changes, thereby changing their capacitance accordingly; the moving electrode plates of some other dimension measuring capacitors move in a direction perpendicular to the direction of the fixed electrode plate, and their relative distance remains unchanged. During the rotation, the fixed electrode plate always remains completely opposite to the moving electrode plate, and their relative area remains unchanged, thereby changing their capacitance.

[0025] It should be noted that in a general six-dimensional force sensor, when measuring the force or torque of a certain dimension, the plates of the inductive capacitors corresponding to other dimensions will also produce changes in relative area, and then the capacitance will also change to produce output. However, the inductive capacitors corresponding to these other dimensions are not used to measure the force or torque of this dimension, and inter-dimensional coupling will occur at this time. In the embodiment of the present invention, the area of ​​the fixed electrode plate is set to be smaller than that of the moving electrode plate, and then the fixed electrode plate is restricted to always be opposite to the moving electrode plate within the range, so that in most measurement situations, the relative area of ​​the inductive capacitor will not change, and other capacitors except the measurement dimension will not produce output because the relative area and relative distance do not change, thereby avoiding inter-dimensional coupling and improving measurement accuracy.

[0026] In another specific embodiment, the area of ​​the moving electrode plate is set smaller than that of the fixed electrode plate, and when the moving electrode plate moves within the measuring range of motion, the fixed electrode plate always remains completely opposite to the moving electrode plate. In this embodiment, the fixed electrode plate is directly prepared, and the moving electrode plate is mounted on an insulating carrier plate.

[0027] In this specific embodiment, the central force-bearing rigid platform 101 is connected to the fixed outer shell 104 through a sensitive layer, and the sensitive layer deforms after the central force-bearing rigid body is subjected to force. The two sides of the sensitive layer are a moving electrode plate and a fixed electrode plate.

[0028] In this specific embodiment, a first angle sensor is arranged on the central force-bearing rigid platform 101, and a second angle sensor is arranged on the fixed outer shell 104. The first angle sensor and the second angle sensor are respectively used to collect the inclination angles on the central force-bearing rigid platform 101 and the fixed outer shell 104, so as to obtain the first rotation angle of each vertical moving pole plate 102 relative to its corresponding vertical fixed pole plate 106, and the second rotation angle of each transverse moving pole plate 103 relative to its corresponding transverse fixed pole plate 108; the first rotation angle is used to solve the relative area between the vertical moving pole plate 102 and its corresponding vertical fixed pole plate 106; the second rotation angle is used to solve the relative area between the transverse moving pole plate 103 and its corresponding transverse fixed pole plate 108.

[0029] Furthermore, the inclination angles of the central force-bearing rigid platform 101 and the fixed outer shell 104 collected by the first angle sensor and the second angle sensor are calculated to obtain the first rotation angle of each vertical pole plate 102 relative to its corresponding vertical pole plate 106, and the second rotation angle of each transverse pole plate 103 relative to its corresponding transverse pole plate 108.

[0030] It should be noted that, although the embodiments of the present invention can ensure that the relative area of ​​the plates remains unchanged when measuring the force dimension by making the areas of the moving and fixed plates different, when measuring the torque dimension, because it is a torsion, the plates will inevitably be no longer parallel and tilted, and the relative area will change at this time. The embodiments of the present invention can solve the relative area by setting an angle sensor, and then correct it to ensure that the inductive capacitor output that does not belong to the measurement dimension is zero force data.

[0031] like Figure 6 As shown, Figure 6 In the equation, θ is the angle between the plates, which is obtained by two angle sensors. Then S y =S d ×cosθ,S y is the relative area, S d is the fixed plate area.

[0032] In this specific embodiment, the fixed outer shell 104 is disposed around the central force-bearing rigid platform 101 , and a cavity is disposed between the fixed outer shell 104 and the central force-bearing rigid platform 101 .

[0033] It should be noted that the cavity can reduce weight, improve sensitivity and reduce interference.

[0034] In this specific embodiment, a first connection port is provided on the central force-bearing rigid platform 101, and the first connection port is used to connect to the measuring end; a second connection port is provided on the fixed outer shell 104, and the second connection port is used to connect to the fixed end.

[0035] In this specific embodiment, the outer shell is further provided with an opening, on which a sealing cover is arranged, and the sealing cover is used to package the MEMS six-dimensional force sensor.

[0036] In this specific embodiment, the fixed outer shell 104 and the central force-bearing rigid platform 101 are prepared separately, and the central force-bearing rigid platform 101 is prepared by photolithography.

[0037] In this specific embodiment, the force dimension and torque dimension of the MEMS six-dimensional force sensor are calibrated differently.

[0038] It should be noted that because the number of inductive capacitors corresponding to forces or torques of different dimensions is different, and the relative area of ​​the inductive capacitor will also change during torque measurement, different calibrations must be used to ensure the reliability and accuracy of the results.

[0039] In this specific embodiment, Figure 5 As shown, there are 12 inductive capacitors including C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, and C12. The force in the X-axis direction is measured by C1, C2, C5, and C6, the force in the Y-axis direction is measured by C3, C4, C7, and C8, and the force in the Z-axis direction is measured by C9, C10, C11, and C12; the moment in the X-axis direction is measured by C3, C4, C7, C8, C9, and C11, the moment in the Y-axis direction is measured by C1, C2, C5, C6, C10, and C12, and the moment in the Z-axis direction is measured by C1, C2, C3, C4, C5, C6, C7, and C8.

[0040] The insulating vertical bearing plate 105 of the embodiment of the present invention carries a vertical fixed electrode plate 106 which is opposite to the vertical moving electrode plate 102 to form a vertical measuring capacitor. The area of ​​the vertical fixed electrode plate 106 is smaller than the area of ​​the vertical moving electrode plate 102. When the vertical moving electrode plate 102 moves within the measuring range of motion, the vertical fixed electrode plate 106 always remains completely opposite to the vertical moving electrode plate 102. The insulating horizontal bearing plate 107 carries a horizontal fixed electrode plate 108 which is opposite to the horizontal moving electrode plate 103 to form a horizontal measuring capacitor. The area of ​​the horizontal fixed electrode plate 108 is smaller than the area of ​​the horizontal moving electrode plate 103. When the horizontal moving electrode plate 103 moves within the measuring range of motion, the horizontal fixed electrode plate 108 always remains completely opposite to the horizontal moving electrode plate 103. The embodiment of the present invention ensures through such a structure that when the moving electrode plate moves, the relative area of ​​the induction capacitor will not change in most cases, so that the capacitance of the induction capacitor is only affected by the relative distance in most cases, so that only the induction capacitor corresponding to the force or torque of the measurement dimension has an output, and the output of other capacitors remains zero, thereby reducing inter-dimensional coupling and making the measurement result more reliable.

[0041] The embodiment of the present invention further provides a first angle sensor on the central force-bearing rigid platform 101, and a second angle sensor on the fixed outer shell 104. The two angle sensors can obtain the deflection angle of the moving electrode plate relative to the fixed electrode plate, obtain the correct relative area of ​​the electrode plates in the moment dimension measurement, and then make corrections, which can also reduce the inter-dimensional coupling and increase the accuracy of the measurement results.

[0042] In summary, the embodiments of the present invention can reduce inter-dimensional coupling, making the measurement result more accurate.

[0043] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0044] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A MEMS six-dimensional force sensor based on plate distance change measurement, characterized in that: The MEMS six-dimensional force sensor includes: a central force-bearing rigid body platform, wherein the four sides of the central force-bearing rigid body platform are each provided with two vertical moving electrodes and one transverse moving electrode plate; a fixed outer shell is provided on the outer side of the central force-bearing rigid body platform, and an insulating vertical bearing plate is provided on the fixed outer shell at a position corresponding to each of the vertical moving electrodes, and a vertical fixed electrode plate is carried on the insulating vertical bearing plate to form a vertical measuring capacitor relative to the vertical moving electrode plate, and the area of ​​the vertical fixed electrode plate is smaller than the area of ​​the vertical moving electrode plate, and when the vertical moving electrode plate moves within the measurement range, the vertical fixed electrode plate always remains completely opposite to the vertical moving electrode plate; an insulating transverse bearing plate is provided on the fixed outer shell at a position corresponding to each of the transverse moving electrodes, and a transverse fixed electrode plate is carried on the insulating transverse bearing plate to form a transverse measuring capacitor relative to the transverse moving electrode plate, and the area of ​​the transverse fixed electrode plate is smaller than the area of ​​the transverse moving electrode plate, and when the transverse moving electrode plate moves within the measurement range, the transverse fixed electrode plate always remains completely opposite to the transverse moving electrode plate; When the MEMS six-dimensional force sensor measures the force or torque in a certain dimension, the central force-bearing rigid platform is subjected to the force or torque in this dimension, so that the force or torque in this dimension corresponds to the movement of the moving electrode plate of the measuring capacitor relative to the fixed electrode plate, and the relative distance thereof changes, and thus the capacitance thereof changes accordingly; the moving electrode plates of the measuring capacitors in some other dimensions move in a direction perpendicular to the direction of the fixed electrode plate, and their relative distances remain unchanged, and during the rotation, the fixed electrode plate always remains completely opposite to the moving electrode plate, and their relative areas remain unchanged, and thus the capacitance remains unchanged.

2. The MEMS six-dimensional force sensor based on plate distance change measurement according to claim 1, characterized in that: A first angle sensor is arranged on the central force-bearing rigid platform, and a second angle sensor is arranged on the fixed outer shell. The first angle sensor and the second angle sensor are used to collect the tilt angles of the central force-bearing rigid platform and the fixed outer shell, respectively, so as to obtain the first rotation angle of each of the vertical moving pole plates relative to the corresponding vertical fixed pole plates, and the second rotation angle of each of the horizontal moving pole plates relative to the corresponding horizontal fixed pole plates; The first rotation angle is used to solve the relative area between the vertically movable pole plate and its corresponding vertically movable pole plate; the second rotation angle is used to solve the relative area between the horizontally movable pole plate and its corresponding horizontally movable pole plate.

3. The MEMS six-dimensional force sensor based on plate distance change measurement according to claim 1, characterized in that: The fixed outer shell is arranged around the central force-bearing rigid platform, and a cavity is arranged between the fixed outer shell and the central force-bearing rigid platform.

4. The MEMS six-dimensional force sensor based on plate distance change measurement according to claim 1, characterized in that: A first connection port is arranged on the central force-bearing rigid platform, and the first connection port is used to connect the measuring end; a second connection port is arranged on the fixed outer shell, and the second connection port is used to connect the fixed end.

5. The MEMS six-dimensional force sensor based on plate distance change measurement according to claim 1, characterized in that: The outer shell is also provided with an opening, and a sealing cover is arranged on the opening, and the sealing cover is used to package the MEMS six-dimensional force sensor.

6. The MEMS six-dimensional force sensor based on plate distance change measurement according to claim 1, characterized in that: The fixed outer shell and the central force-bearing rigid platform are prepared separately, and the central force-bearing rigid platform is prepared by photolithography.

7. The MEMS six-dimensional force sensor based on plate distance change measurement according to claim 1, characterized in that: The force dimension and torque dimension of the MEMS six-dimensional force sensor are calibrated differently.

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