Full-plane six-dimensional force sensor based on thin film sputtering technology

Abstract

The invention discloses a full-plane six-dimensional force sensor based on a thin film sputtering technology. The full-plane six-dimensional force sensor is used for synchronously measuring three-dimensional orthogonal force and torque. The sensor comprises a force transmission table, an elastic body, a base, a strain gauge and the like, wherein the elastic body adopts a composite structure of an inner-layer cross beam and an outer-layer honeycomb-like parallel beam. The innovation lies in that all strain sensitive areas of the elastomer are flat planes with upper and lower surfaces to form a full-plane design, so that the requirement of a thin film sputtering process on the flatness of a substrate is met. 24 strain gauges are sputtered on an upper plane and a lower plane to form 6 groups of Wheatstone bridges, so that six-dimensional force signal detection is realized. According to the full-plane structure, the problem that a strain gauge in a traditional sensor needs to be pasted on a narrow side face or edge is avoided, full-automatic surface mounting can be achieved, the long-term stability, temperature adaptability and measurement consistency of the sensor are remarkably improved, and the sensor is suitable for high-precision force measurement in the fields of industrial robots, aerospace and the like.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a planar six-dimensional force sensor based on thin-film sputtering technology. Background Technology

[0002] Multidimensional force / torque sensors, as core components for sensing mechanical interactions, can simultaneously detect all or part of the combined information of three orthogonal force components (Fx, Fy, Fz) and three orthogonal torque components (Mx, My, Mz). This precise multidimensional force sensing capability is key to achieving adaptive and refined interaction between high-end intelligent systems and complex environments. For example, in the field of industrial robotics, it enables robots to perform compliant operations such as precision assembly and force-controlled grinding; in the aerospace field, it is an important tool for wind tunnel experiments and structural fatigue testing of aircraft; and in medical engineering and the automotive industry, it is also widely used in surgical force feedback and component mechanical performance testing. Currently, the elastic body structure design of most multidimensional force sensors is derived from the classic and technologically mature crossbeam structure or its variants (such as parallel beams, vertical beams, etc.). Its working principle is as follows: when the elastic body senses an external force, it will generate concentrated stress in a specific area. The stress signal is converted into a resistance change by a strain gauge group attached to the area. Then, the Wheatstone bridge circuit outputs an electrical signal that is linearly related to the force / torque components. Finally, the measurement values ​​of each dimension are obtained through a decoupling algorithm.

[0003] However, the installation and fixing process of strain gauges has always been a key constraint in the technological development of this field. For a long time, traditional strain gauge bonding technology (i.e., manual bonding using organic or epoxy resin adhesives) has dominated the industry. While this method is flexible and low-cost, its inherent technical limitations are becoming increasingly apparent.

[0004] First, there is a problem of adhesive layer performance degradation: after the adhesive has cured, its polymer chain segments may continue to volatilize or combine with water molecules in the environment to produce a hygroscopic effect, which causes the adhesive layer to expand or shrink in volume and redistribute internal stress, thereby causing a decrease in strain transfer efficiency and an increase in zero-point drift, which seriously affects the long-term measurement stability and reliability of the sensor.

[0005] Secondly, poor temperature adaptability: there is a mismatch in the coefficient of thermal expansion between the adhesive and the elastomer material (usually alloy steel or aluminum alloy). In a wide temperature field, especially in alternating temperature environments, this mismatch introduces significant additional thermal stress, generating a huge thermal output signal, which seriously interferes with the measurement accuracy of the real mechanical signal and limits the application of the sensor in harsh working conditions.

[0006] Secondly, there are challenges in process consistency and repeatability: the manual bonding process is highly dependent on the operator's experience, and the thickness, uniformity, and curing pressure of the adhesive layer are difficult to control precisely, easily introducing human error. This directly leads to large performance variations among sensor products in the same batch, making it difficult to guarantee product qualification rate and consistency, and also creating obstacles for the mass production and large-scale application of sensors.

[0007] To overcome the drawbacks of traditional bonding techniques, thin-film sputtering technology is considered a promising alternative. This technology employs physical vapor deposition (PVD) to directly sputter and pattern strain-sensitive materials (such as constantan and nickel-chromium) onto the surface of an elastomer that has undergone precise pretreatment (such as cleaning, activation, and masking) in a vacuum environment, forming a thin-film strain resistor bonded to the substrate at the atomic / molecular level. This "dry" process fundamentally eliminates the problems associated with adhesive layers, and is expected to produce strain-sensitive units with higher precision, better stability, and stronger environmental adaptability. However, successfully applying thin-film sputtering technology to crossbeam-type multidimensional force sensors and achieving high-performance, low-inter-coupling interference measurements still faces a series of unresolved technical challenges, including sensor structure optimization, strain zone layout, and sputtering process parameter matching. This is precisely the core focus of this invention. Summary of the Invention

[0008] To address the aforementioned issues, this invention discloses a fully planar six-dimensional force sensor based on thin-film sputtering technology, which has advantages such as high sensitivity and low inter-dimensional coupling, and is suitable for multi-dimensional force measurement in fields such as aerospace and industrial robotics.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A planar six-dimensional force sensor based on thin-film sputtering technology includes a force transmission platform, an elastic body, a base, a top cover, a bottom cover, and strain gauges. The elastic body comprises a central platform, an inner cross beam, an outer honeycomb-like parallel beam, a floating beam, and a square corner.

[0011] The force transmission platform is a rectangular parallelepiped with a square cross-section; four threaded holes are machined on each of the upper and lower surfaces of the force transmission platform, which are used to connect with the top cover and the cross beam respectively.

[0012] The elastomer includes a central platform, an inner crossbeam, an outer honeycomb-like parallel beam, a floating beam, and a square corner. The central platform is located at the center of the inner crossbeam and has a rectangular columnar structure with a square cross-section. The central platform has four through holes; during assembly, four bolts are inserted from the bottom surface of the central platform upwards to engage with the threaded holes on the lower surface of the force transmission platform, thereby fixing the force transmission platform above the central platform of the elastomer. External loads are applied to the upper surface of the force transmission platform via the top cover and transmitted to the central platform through the force transmission platform. The four sides of the central platform are connected to the inner crossbeam. The inner crossbeam consists of four rectangular crossbeams, each beam connected at one end to… The central platform is connected to the floating beam at one end. The floating beam is located around the cross beam and consists of four rectangular thin-walled beams arranged in a square structure. The center of the inner side of the floating beam is connected to the cross beam, and the center of the outer side is connected to the outer layer of imitation honeycomb parallel beams. Both ends are connected to the square corners. The outer layer of imitation honeycomb parallel beams consists of two convex thin-walled beams with rectangular cross-sections. One end of each beam is connected to the floating beam, and the other end is connected to the square corner. There are eight square corners in total. They are rectangular columnar structures with square cross-sections and are located at both ends of the floating beams and one end of the imitation honeycomb parallel beams. Each square corner has a connecting hole for connecting to the central boss of the base.

[0013] During sensor assembly, the force transmission table is connected to the elastic body via a threaded connection; the square corner connection hole of the elastic body is connected to the threaded connection on the central boss of the base; the top cover is connected to the force transmission table via a threaded connection; and the bottom cover is connected to the base via a mounting hole.

[0014] The measurement principle of the all-planar six-dimensional force sensor is as follows: 24 strain gauges are sputtered onto an elastic body, forming 6 sets of Wheatstone bridges: 4 sets on the inner crossbeam and 2 sets on the outer honeycomb-like parallel beam. All strain gauges are sputtered in the upper and lower planes of the elastic body. Specifically, in the outer honeycomb-like parallel beam, 4 strain gauges are sputtered at the center of the upper and lower surfaces parallel to the X-axis, forming a bridge circuit for measuring the force Fx in the X direction; 4 strain gauges are sputtered at the center of the upper and lower surfaces parallel to the Y-axis, forming a bridge circuit for measuring the force Fy in the Y direction; and 4 strain gauges are sputtered on the upper and lower surfaces of the two main beams parallel to the X-axis near the central axis of the central platform in the inner crossbeam, forming a bridge circuit for measuring the force Fz in the Z direction. Bridge circuits: Four strain gauges are sputtered on the upper and lower surfaces of the two main beams parallel to the Y-axis in the cross beam near the side edge of the central platform to form a bridge circuit for measuring the torque Mz in the Z direction; four strain gauges are sputtered on the upper and lower surfaces of the two main beams parallel to the Y-axis in the cross beam away from the central axis of the central platform to form a bridge circuit for measuring the torque Mx in the X direction; four strain gauges are sputtered on the upper and lower surfaces of the two main beams parallel to the X-axis in the cross beam away from the central axis of the central platform to form a bridge circuit for measuring the torque My in the Y direction.

[0015] The beneficial effects of this invention are:

[0016] (1) Achieving an innovative all-planar elastomer structure: This invention proposes an all-planar configuration design for the first time, in which all strain-sensitive areas are located on the upper and lower flat surfaces of the elastomer, completely changing the limitation of traditional six-dimensional force sensors where strain gauges must be arranged on narrow sides, edges, or non-flat areas. This design provides a structural basis for the introduction of thin-film sputtering technology and is the key to achieving high consistency and automated patching.

[0017] (2) Achieving deep integration of full-planar structure and thin-film sputtering process: The full-planar configuration of the elastomer fully meets the stringent requirements of the sputtering process for substrate flatness, enabling the "attachment" process of strain gauges to achieve fully automated sputtering molding. This not only avoids the random errors caused by manual pasting in narrow spaces, but also fundamentally solves the problems of aging, temperature drift and poor consistency of traditional adhesives, significantly improving the long-term reliability and temperature adaptability of the sensor.

[0018] (3) High-performance measurement was achieved through composite structure and planar layout optimization: The sensor adopts a composite structure of inner cross beam and outer honeycomb parallel beam, combined with full-plane strain gauge layout, which not only effectively concentrates the stress in the sensitive area and improves the measurement sensitivity, but also significantly reduces the coupling interference between the six-dimensional force / torque signals through structural optimization, thereby achieving high-precision and low-coupling measurement performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the elastomer structure of the present invention.

[0020] Figure 2 This is a schematic diagram of the force transmission table of the present invention.

[0021] Figure 3 This is a schematic diagram of the base structure of the present invention.

[0022] Figure 4 This is an assembly diagram of the present invention. Figure 1 .

[0023] Figure 5 This is an assembly diagram of the present invention. Figure 2 .

[0024] Figure 6 This is a schematic diagram showing the location of the strain gauge patch in this invention.

[0025] Figure 7 This is a schematic diagram of the six bridge circuits in this invention.

[0026] List of identifiers in attached diagrams:

[0027] 10. Elastomer, 11. Central platform, 12. Inner cross beam, 13. Outer honeycomb parallel beam, 14. Floating beam, 15. Square corner, 16. Strain gauge, 20. Force transmission platform, 50. Top cover, 51. Base, 52. Bottom cover, 53. Central boss. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0029] The present invention discloses a planar six-dimensional force sensor based on thin-film sputtering technology, comprising an elastic body 10, a force transmission platform 20, a top cover 50, a base 51, a bottom cover 52, and a strain gauge 16. To better describe the specific implementation, a spatial Cartesian coordinate system is established as shown in the figure, including three directions: X, Y, and Z.

[0030] like Figure 1 As shown, the elastic body 10 includes a central platform 11, an inner cross beam 12, an outer honeycomb-like parallel beam 13, a floating beam 14, and a square corner 15. The central platform 11 is located at the center of the inner cross beam 12, and has a rectangular column structure with a square cross section. The central platform 11 has four through holes. During assembly, four bolts are inserted from the bottom surface of the central platform 11 upwards and engage with the threaded holes on the lower surface of the force transmission platform 20, thereby fixing the force transmission platform 20 above the central platform 11 of the elastic body 10. The four sides of the central platform 11 are respectively connected to the inner cross beam 12. The inner cross beam 12 is composed of four rectangular cross beams, each beam connecting one end to the central platform 11 and the other end to... The floating beam 14 is located around the cross beam 12. It consists of four thin-walled beams with rectangular cross sections, forming a square structure. The center of its inner side is connected to the cross beam 12, and the center of its outer side is connected to the outer layer of the honeycomb parallel beam 13. Both ends are connected to the square corners 15. The outer layer of the honeycomb parallel beam 13 consists of two convex thin-walled beams with rectangular cross sections. One end of each beam is connected to the floating beam 14, and the other end is connected to the square corner 15. There are eight square corners in total. They are rectangular columnar structures with square cross sections, and are respectively located at both ends of the floating beam 14 and one end of the honeycomb parallel beam. Each square corner 15 is provided with a connecting hole for connecting to the central boss 53 of the base 51.

[0031] like Figure 2 As shown, the force transmission platform 20 is a square cross-section column structure; its upper and lower surfaces are respectively provided with four threaded holes, which are used to achieve threaded connection with the upper surface of the center platform 11 of the elastic body 10 and the lower surface of the top cover 50.

[0032] like Figure 4As shown, the force transmission platform 20 is fixed to the center platform 11 of the elastic body 10 by a threaded connection; the square corner 15 of the elastic body 10 is also connected to the central boss 53 of the base 51 by a thread; the top cover 50 is connected to the force transmission platform 20 by a thread; and the bottom cover 52 is connected to the base 51 by a mounting hole.

[0033] The materials used in the processing of the elastomer 10, force transmission platform 20, top cover 50, base 51 and bottom cover 52 involved in this invention can be flexibly selected according to actual performance requirements, and the types of materials should not constitute a limitation on the scope of protection of this invention.

[0034] Figure 6 The arrangement of the 24 strain gauges (numbered R1 to R24) of this invention is shown. This invention exemplifies a fully planar six-dimensional force sensor based on thin-film sputtering technology. All strain gauges are sputtered in both the upper and lower planes of the elastic body, specifically 24 strain gauges in total, forming 6 sets of Wheatstone bridges: 4 sets on the inner crossbeam and 2 sets on the outer honeycomb-like parallel beam. The specific sputtering positions are as follows:

[0035] R1 and R7 are located on the central axis of the upper and lower surfaces of the inner cross beam near the center platform section in the positive Y direction;

[0036] R2 and R8 are located on the central axis of the upper and lower surfaces of the inner cross beam near the center platform section in the negative Y direction;

[0037] R3 and R9 are located at the midline of the upper and lower surfaces of the far center platform section of the inner cross beam in the negative X direction;

[0038] R5 and R11 are located at the midline of the upper and lower surfaces of the far center platform section of the inner cross beam in the positive X direction;

[0039] R4 and R10 are located at the midline of the upper and lower surfaces of the far center platform segment of the inner cross beam in the positive Y direction;

[0040] R6 and R12 are located at the midline of the upper and lower surfaces of the far center platform section of the inner cross beam in the negative Y direction;

[0041] R13 and R14 are located at the center of the upper and lower surfaces of the outer layer of the pseudo-honeycomb parallel beam in the negative X direction;

[0042] R17 and R18 are located at the center of the upper and lower surfaces of the outer layer of the pseudo-honeycomb parallel beam in the positive X direction;

[0043] R19 and R20 are located at the center of the upper and lower surfaces of the outer layer of the pseudo-honeycomb parallel beam in the negative Y direction;

[0044] R15 and R16 are located at the center of the upper and lower surfaces of the outer layer of the pseudo-honeycomb parallel beam in the positive Y direction;

[0045] R23 and R24 are located at the upper and lower surface edges of the inner cross beam near the center platform section in the positive X direction;

[0046] R21 and R22 are located at the upper and lower surface edges of the inner cross beam near the center platform section in the negative X direction.

[0047] Figure 7 The diagram shows six Wheatstone bridges composed of strain gauges with six channels. Strain gauges R13, R14, R17, and R18 form a Wheatstone bridge to measure the force Fx in the X direction; strain gauges R15, R16, R19, and R20 form a Wheatstone bridge to measure the force Fy in the Y direction; strain gauges R1, R2, R7, and R8 form a Wheatstone bridge to measure the force Fz in the Z direction; strain gauges R4, R6, R10, and R12 form a Wheatstone bridge to measure the torque Mx in the X direction; strain gauges R3, R5, R9, and R11 form a Wheatstone bridge to measure the torque My in the Y direction; and strain gauges R21, R22, R23, and R24 form a Wheatstone bridge to measure the torque Mz in the Z direction.

[0048] The measurement principle of the six-dimensional force sensor is as follows: An input force / torque in one dimension acts on the force transmission platform-elastic body structure through the top cover, causing deformation of the elastic body. This results in a change in the resistance of the strain gauge at the corresponding position, which in turn changes the output voltage of the corresponding bridge circuit. Simultaneously, due to the structural design, the output voltages in other dimensions do not change significantly, effectively reducing inter-dimensional coupling interference and thus improving the sensor's measurement accuracy. Therefore, during use, only the voltage changes of all six channels need to be measured to obtain the force / torque values ​​for each dimension. Let R0 represent the zero-position resistance value of the strain gauge, ΔRFx, ΔRFy, ΔRFz, ΔRMx, ΔRMy, and ΔRMz represent the changes in strain gauge resistance under the action of Fx, Fy, Fz, Mx, My, and Mz, respectively, and E represent the bridge excitation voltage. The changes in the output voltage of each channel are then expressed as follows:

[0049] .

[0050] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A planar six-dimensional force sensor based on thin-film sputtering technology, characterized in that: It includes a force transmission platform, an elastic body, a base, a top cover, a bottom cover, and strain gauges. The elastic body includes a central platform, an inner cross beam, an outer honeycomb-like parallel beam, a floating beam, and a square corner. The force transmission platform is a rectangular parallelepiped with a square cross-section; there are four threaded holes on each of the upper and lower surfaces of the force transmission platform, which are used to connect with the top cover and the elastic body respectively. The elastomer includes a central platform, an inner crossbeam, an outer honeycomb-like parallel beam, a floating beam, and a square corner. The central platform is located at the center of the inner crossbeam and has a rectangular columnar structure with a square cross-section. The central platform has four through holes; during assembly, four bolts are inserted from the bottom surface of the central platform upwards to engage with the threaded holes on the lower surface of the force transmission platform, thereby fixing the force transmission platform above the central platform of the elastomer. External loads are applied to the upper surface of the force transmission platform via the top cover and transmitted to the central platform through the force transmission platform. The four sides of the central platform are connected to the inner crossbeam. The inner crossbeam consists of four rectangular crossbeams, each beam connected at one end to… The central platform is connected to the floating beam at one end. The floating beam is located around the cross beam and consists of four rectangular thin-walled beams arranged in a square structure. The center of the inner side of the floating beam is connected to the cross beam, and the center of the outer side is connected to the outer layer of imitation honeycomb parallel beams. Both ends are connected to the square corners. The outer layer of imitation honeycomb parallel beams consists of two convex thin-walled beams with rectangular cross-sections. Each beam is connected to the floating beam at one end and to the square corner at the other end. There are eight square corners in total. They are rectangular columnar structures with square cross-sections and are located at both ends of the floating beams and one end of the imitation honeycomb parallel beams. Each square corner has a connecting hole for connecting to the central boss of the base. During sensor assembly, the force transmission platform is connected to the elastomer via threaded connections; the square corner connection hole of the elastomer is connected to the threaded connection on the central boss of the base; the top cover is connected to the force transmission platform via threaded connections; the bottom cover is connected to the base via mounting holes; 24 strain gauges are sputtered onto the elastomer, forming 6 sets of Wheatstone bridges: 4 sets on the inner crossbeam and 2 sets on the outer simulated honeycomb parallel beam; all strain gauges are sputtered in the upper and lower planes of the elastomer. Specifically, 4 strain gauges are sputtered at the center of the upper and lower surfaces parallel to the X-axis in the outer simulated honeycomb parallel beam, forming a bridge circuit for measuring the force Fx in the X direction; 4 strain gauges are sputtered at the center of the upper and lower surfaces parallel to the Y-axis in the outer simulated honeycomb parallel beam, forming a bridge circuit for measuring the force Fy in the Y direction. The bridge circuit consists of four strain gauges sputtered on the upper and lower surfaces of the two main beams parallel to the X-axis in the inner cross beam, near the central axis of the central platform, forming a bridge circuit for measuring the force Fz in the Z direction; four strain gauges sputtered on the upper and lower surfaces of the two main beams parallel to the Y-axis in the cross beam, near the side edges of the central platform, forming a bridge circuit for measuring the torque Mz in the Z direction; four strain gauges sputtered on the upper and lower surfaces of the two main beams parallel to the Y-axis in the cross beam, away from the central axis of the central platform, forming a bridge circuit for measuring the torque Mx in the X direction; and four strain gauges sputtered on the upper and lower surfaces of the two main beams parallel to the X-axis in the cross beam, away from the central axis of the central platform, forming a bridge circuit for measuring the torque My in the Y direction.

2. The measurement principle of a fully planar six-dimensional force sensor based on thin-film sputtering technology according to claim 1, characterized in that: When a force / torque in a certain dimension is applied to the sensor, the elastic body structure deforms, and the resistance of the strain gauge at the corresponding position changes, causing the output voltage of the corresponding bridge to change. The value of the force / torque in that dimension can be obtained by measuring the change in voltage.

Images