A thin film torque sensor integrated in situ on a harmonic reducer and its preparation method

Abstract

The present invention belongs to the field of robot joint torque measurement and proposes a thin film torque sensor integrated in situ on a harmonic reducer and a preparation method thereof. The thin film torque sensor is integrated in situ on the surface of the flexspline flange groove or the inner plane of the flange in the harmonic reducer. The thin film torque sensor includes an intermediate transition layer film, an insulating film, a torque sensitive unit and a protective film from bottom to top. A signal processing unit of the thin film torque sensor is provided on one side of the flexspline flange groove. The torsional deformation information measured by the torque sensitive unit is superimposed through a Wheatstone bridge circuit and output to the signal processing unit in the form of an electrical signal. The thin film torque sensor of the present invention can effectively eliminate the interference generated by the rotation of the process wave generator during the in-situ measurement of the output torque of the harmonic reducer and obtain accurate output torque information. The surface of the thin film sensor obtained by the preparation method of the present invention is dense and pore-free.

Description

Technical Field

[0001] The present invention relates to the field of robot joint torque measurement, and in particular to a thin film torque sensor in-situ integrated on a harmonic reducer and a preparation method thereof. Background Art

[0002] Robots, with their lightweight and flexible features, are widely used in the automotive, medical, and electronics sectors. However, in complex and ever-changing application scenarios, robot collisions are inevitable, posing significant safety risks to the production process. Therefore, to ensure the safety of humans, robots, and even the surrounding environment during operation, joint torque information combined with the robot's dynamics model is often used to determine whether the robot has collided with the external environment. Appropriate protective measures are then implemented, ensuring efficient collaboration while ensuring the safety of both humans and robots.

[0003] At present, the measurement of the output torque of robot joints is mostly achieved by adding a joint torque sensor to the output end of the harmonic reducer, such as CN202110124625.9. This method not only introduces additional flexible units, but also increases the complexity of the joint structure, significantly reducing the stiffness and movement accuracy of the joint. In addition, in CN109139856A, researchers proposed to place strain gauges directly on the surface of the flexible wheel of the harmonic reducer, and obtain the output torque of the robot joint by measuring the force and deformation of the flexible wheel. However, the torque signal measured by this method will be affected by the signal generated by the rotation of the wave generator in the harmonic reducer, making it difficult to obtain accurate torque information.

[0004] In response to the above problems, the present invention designs a thin-film torque sensor integrated in situ on the harmonic reducer. It adopts a contact measurement method and utilizes circumferentially evenly arranged torque-sensitive units to measure the torsional deformation of multiple points on the groove surface of the flexspline flange or the inner plane of the flange to obtain the joint output torque information. This not only significantly eliminates the influence of the wave generator rotation on the torque measurement results, but also does not change the original performance of the robot joint, and accurately measures the robot joint output torque. Summary of the Invention

[0005] In order to accurately measure the output torque of robot joints, the present invention proposes a thin-film torque sensor integrated in situ on a harmonic reducer, which effectively eliminates the interference caused by the rotation of the wave generator during the torque measurement process and does not change the original stiffness of the robot. It has important application prospects in the field of robot joint torque measurement.

[0006] The technical solution of the present invention is: a thin film torque sensor integrated in situ on a harmonic reducer, the thin film torque sensor is in situ integrated on the flange groove 1-1 surface or the flange inner side 1-2 plane of the flexible wheel 1 in the harmonic reducer; the thin film torque sensor includes an intermediate transition layer film 9, an insulating film 2, a torque sensitive unit 3 and a protective film 4; the intermediate transition layer film 9 is in situ grown on the flange groove 1-1 surface or the flange inner side 1-2 plane of the flexible wheel 1; the insulating film 2 is prepared on the intermediate transition layer film 9; the torque sensitive unit 3 is deposited on the surface of the insulating film 2; and the protective film 4 covers the torque sensitive unit surface 3.

[0007] The torque sensitive unit 3 includes a measurement sensitive grid 5, a horizontal grid 6, a lead 7 and a pad 8; each measurement sensitive grid 5 is connected by the horizontal grid 6 to form a loop, which is evenly distributed at the same radial position in the circumferential direction of the surface of the insulating film 2; the pad 8 is located outside the coverage of the protective film 4; the pad 8 is located at both ends of the torque sensitive unit 3.

[0008] The torque information measured by the torque sensing unit 3 is output in the form of an electrical signal after being amplified by a Wheatstone bridge circuit.

[0009] The angle between the arrangement direction of the measuring sensitive grid 5 and the axial direction of the flange groove 1 - 1 or the inner side 1 - 2 of the flange is ±45°.

[0010] The insulating film 2 is made of one or more inorganic materials and organic materials.

[0011] The material of the torque sensitive unit 3 is one or more of alloy material, semiconductor material, and pure metal material.

[0012] The material of the protective film 4 is one or more of inorganic materials and organic materials.

[0013] The intermediate transition layer film 9, the insulating film 2, the torque sensitive unit 3 and the protective film 4 are all prepared by physical vapor deposition or chemical vapor deposition process.

[0014] A signal processing unit 10 of a thin film torque sensor is provided on one side of the flange groove 1 - 1 of the flexspline 1 .

[0015] After being processed by the signal processing unit 10 , the torque sensing unit 3 can also obtain the angle change of the input end of the harmonic reducer during the working process in real time.

[0016] A method for preparing a thin film torque sensor integrated in situ on a harmonic reducer comprises the following steps:

[0017] Step 1: Polish the area to be coated on the flexible wheel 1 and clean it with acetone and anhydrous ethanol;

[0018] Step 2: Depositing an insulating film 2 on the surface of the flexible spline 1 treated in step 1;

[0019] Step 3: Using a metal mask, a torque sensitive unit 3 structure is prepared on the surface of the insulating film 2 prepared in step 2 by magnetron sputtering;

[0020] Step 4: Cover the pad 8 of the torque sensitive unit 3 and deposit a protective film 4 on the torque sensitive unit 3;

[0021] Step 5: Use conductive silver paste to connect the exposed pad 8 of the torque sensitive unit 3 to the lead 7, and then use organic silicone to potting.

[0022] The insulating film 2 is made of SiO2 or Parylene with a thickness of 3-5 μm; the torque sensitive unit 3 is 0.6-1.2 μm thick; the protective film 4 is made of the same material as the insulating film 2 with a thickness of 500-1000 nm.

[0023] When the material used for the insulating film 2 and the protective film 4 is SiO2, SiO2 is deposited by plasma-enhanced chemical vapor deposition; SiH4 and N2O are used as reaction gases, the deposition temperature is 100-300°C, the radio frequency power is 15-75W, and the working pressure is 20-60Pa; when the material used for the insulating film 2 and the protective film 4 is Parylene, the background vacuum is 2.5-7.5mTorr, the Parylene powder sublimes at 120-180°C, and the temperature of the cracking process is 650-700°C.

[0024] The torque sensitive unit 3 was prepared by DC magnetron sputtering process, with a background vacuum of 5.0×10 -3 Pa, sputtering power 150-200W, sputtering gas pressure 0.5-0.8Pa, NiCr alloy as target material, and argon gas with a volume percentage purity of not less than 99.99% as medium.

[0025] The lead 7 is a flexible circuit board with a thickness between 0.1-0.3 mm. A connecting wire is provided on the flexible circuit board. One end of the connecting wire is connected to the pad 8 to connect the torque sensitive unit 3 into a Wheatstone bridge circuit, and the other end outputs the signal of the torque sensitive unit 3 to the signal processing unit 10.

[0026] Beneficial effects of the present invention: The present invention proposes a thin film torque sensor that is in-situ integrated on a harmonic reducer. The flexible wheel of the harmonic reducer is used as an elastic body, and a thin film torque sensor that can measure the load deformation at multiple points within the entire circumference is directly integrated on the groove surface of the flexible wheel flange or the inner plane of the flange. This not only ensures the original output performance of the robot joint, but also introduces the function of real-time measurement of the joint output torque. It can also significantly eliminate the influence of the rotation of the wave generator during the transmission process of the harmonic reducer on the torque measurement, thereby realizing accurate measurement of the joint output torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The schematic diagram of the structure of a thin film torque sensor integrated in situ on a harmonic reducer;

[0028] Figure 2 Schematic diagram of the structure of the torque sensitive unit in the thin film torque sensor;

[0029] Figure 3 Shown Figure 2 The schematic diagram of the Wheatstone bridge circuit connected to the torque sensitive unit in the thin film torque sensor shown;

[0030] Figure 4 This is a structural diagram of the harmonic reducer flexspline;

[0031] Figure 5 is a cross-sectional view of a thin film torque sensor according to the present invention;

[0032] Figure 6 Comparison of test results between the sensor of the present invention and the strain gauge arranged at a single position;

[0033] Figure 7 Schematic diagram of the lead structure.

[0034] In the figure: 1 is a flexible pulley, 1-1 is a flange groove, 1-2 is the inner side of the flange, 2 is an insulating film, 3 is a torque sensitive unit, 4 is a protective film, 5 is a measurement sensitive grid, 6 is a horizontal grid, 7 is a lead, 8 is a pad, 9 is an intermediate transition layer film, and 10 is a signal processing unit. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] like Figure 1 As shown, a thin film torque sensor is integrated in situ on a harmonic reducer. The thin film torque sensor is integrated in situ on the surface of the flange groove 1-1 or the plane 1-2 inside the flange of the flexspline 1 in the harmonic reducer. The specific structure of the flexspline of the harmonic reducer is shown in FIG. Figure 4 shown.

[0037] The thin film torque sensor comprises an intermediate transition layer film 9, an insulating film 2, a torque sensitive unit 3 and a protective film 4. Figure 5 As shown; the intermediate transition layer film 9 is in-situ grown on the surface of the flange groove 1-1 of the flexible wheel 1 or the plane of the inner side 1-2 of the flange; the insulating film 2 is prepared on the intermediate transition layer film 9; the torque sensitive unit 3 is deposited on the surface of the insulating film 2; and the protective film 4 covers the surface of the torque sensitive unit 3.

[0038] The torque-sensing unit 3 is a structure capable of measuring torsional deformation across the entire circumference of the flexspline flange groove surface. By measuring strain changes at each point along the entire circumference and amplifying them through a Wheatstone bridge circuit, the torque-sensing unit 3 effectively eliminates interference signals generated by the periodic rotation of the harmonic reducer's process wave generator. The torque-sensing unit 3 comprises a measurement-sensitive grid 5, a horizontal grid 6, leads 7, and pads 8. Each measurement-sensitive grid 5 is connected by the horizontal grid 6 to form a circuit, evenly distributed across the surface of the flexspline 1 flange groove 1-1 or the surface of the insulating film 2 at the same radial position along the circumference of the flange inner surface 1-2. One end of the lead 7 is connected to the pad 8, connecting the measurement-sensitive grids 5 to form a Wheatstone bridge circuit output. The pads 8 are exposed outside the protective film 4.

[0039] The angle between the arrangement direction of the measuring sensitive grid 5 in the torque sensitive unit 3 and the axial direction of the flange groove 1 - 1 or the flange inner side 1 - 2 where the measuring sensitive grid 5 is located is ±45°.

[0040] The material of the torque sensing unit 3 is composed of one or more alloy materials, semiconductor materials or pure metal materials. Among them, alloy materials include NiCr, CuNi, PdCr; semiconductor materials include AlN, TaN; pure metal materials include Au, Pt.

[0041] The insulating film 2 is made of one or more inorganic or organic materials. The organic materials include one or more combinations of Parylene or polyimide, and the inorganic materials include one or more combinations of Al2O3, SiO2 or Si3N4, which play the role of insulation and deformation transmission.

[0042] The protective film 4 is made of one or more inorganic or organic materials. The organic material includes one or more combinations of Parylene or polyimide, while the inorganic material includes one or more combinations of Al2O3, SiO2, or Si3N4. This protects the torque sensing unit 3 and insulating film 2 from oxidation and failure during operation, thereby improving the reliability of the thin-film torque sensor.

[0043] The intermediate transition layer film 9, the insulating film 2, the torque sensitive unit 3 and the protective film 4 of the thin film torque sensor are all prepared by physical vapor deposition or chemical vapor deposition process.

[0044] A signal processing unit 10 of a thin film torque sensor is provided on one side of the flange groove 1 - 1 of the flexspline 1 .

[0045] The torque sensing unit 3 can also obtain the angle change of the input end of the harmonic reducer during the working process in real time after being processed by the signal processing unit 10 of the sensor.

[0046] like Figure 6 As shown, when the load torque information output by the harmonic reducer is measured only by a single-position strain gauge, it is greatly affected by the rotation of the wave generator. When no load torque is applied and only the wave generator rotates periodically, the measured signal fluctuates within the range of ±19.34mV (after calibration, the measured signal corresponds to ±9.68N·m load torque), which cannot reflect the actual load information. However, when measured by a thin-film torque sensor integrated in situ on the harmonic reducer of the present invention, the influence of the wave generator rotation on the in-situ torque measurement result can be significantly eliminated, and the signal amplitude is reduced to ±0.58mV (after calibration, the measured signal corresponds to ±0.22N·m load torque), and there is no obvious signal fluctuation.

[0047] A method for preparing a thin film sensor for measuring torque of a harmonic reducer, wherein the thin film sensor includes an insulating film 2, a torque sensitive unit 3, a protective film 4, and a lead 7. The thin film sensor is prepared on a flexible pulley 1 and includes the following steps:

[0048] Step 1: Polish the area to be coated on the flexible wheel 1 and clean it with acetone and anhydrous ethanol;

[0049] Step 2: Depositing an insulating film 2 on the surface of the flexible spline 1 after the treatment in step 1. When the insulating film 2 is made of SiO2, the SiO2 is deposited by plasma-enhanced chemical vapor deposition, with SiH4 and N2O as reaction gases, a deposition temperature of 150°C, a radio frequency power of 55W, and an operating pressure of 20Pa. When the insulating film 2 is made of Parylene, the background vacuum is 7.5mTorr, the Parylene powder is sublimated at 150°C, the temperature of the cracking process is 675°C, and the thickness of the deposited insulating film 2 is 3μm.

[0050] Step 3: Using a metal mask, a torque sensitive unit 3 structure is prepared on the surface of the insulating film 2 prepared in step 2 by magnetron sputtering. The DC magnetron sputtering process is used, and the background vacuum degree is 5.0×10 -3 Pa, sputtering power 150W, sputtering pressure 0.7Pa, using NiCr alloy as target material, using argon gas with a volume percentage purity of not less than 99.99% as medium, the thickness of the deposited torque sensitive unit 3 is 0.8μm;

[0051] Step 4: Block the pad 8 of the torque sensitive unit 3 and deposit a protective film 4 on the torque sensitive unit 3. When the material of the protective film 4 is SiO2, SiO2 is deposited by plasma enhanced chemical vapor deposition, with SiH4 and N2O as reaction gases, a deposition temperature of 150°C, a radio frequency power of 55W, and an operating pressure of 20Pa. When the material of the protective film 4 is Parylene, the background vacuum is 7.5mTorr, the Parylene powder is sublimated at 150°C, the temperature of the cracking process is 675°C, and the thickness of the deposited protective film 4 is 500nm.

[0052] Step 5: Select a lead wire 7 with a thickness of 0.3 mm, use conductive silver paste to connect the exposed pad 8 of the torque sensitive unit 3 to the connecting wire, and use organic silicone to potting, and connect the torque sensitive unit 3 to form a Wheatstone bridge circuit through the connecting wire.

Claims

1. A thin film torque sensor integrated in situ on a harmonic reducer, characterized in that: A thin film torque sensor is in-situ integrated on the surface of the flange groove (1-1) or the plane of the inner side (1-2) of the flange of a flexwheel (1) in a harmonic reducer; the thin film torque sensor comprises an intermediate transition layer film (9), an insulating film (2), a torque sensitive unit (3) and a protective film (4); the intermediate transition layer film (9) is in-situ grown on the surface of the flange groove (1-1) or the plane of the inner side (1-2) of the flange of the flexwheel (1); the insulating film (2) is prepared on the intermediate transition layer film (9); the torque sensitive unit (3) is deposited on the surface of the insulating film (2); and the protective film (4) covers the surface of the torque sensitive unit (3); The torque sensitive unit (3) comprises a measuring sensitive grid (5), a horizontal grid (6), a lead (7) and a pad (8); the measuring sensitive grids (5) are connected to each other via the horizontal grid (6) to form a loop, and are evenly distributed at positions of the same circumferential radius on the surface of the insulating film (2); the pad (8) is located outside the coverage of the protective film (4); the pad (8) is located at both ends of the torque sensitive unit (3); The angle between the arrangement direction of the measuring sensitive grid (5) and the axial direction of the surface of the flange groove (1-1) or the plane of the flange inner side (1-2) is ±45°.

2. The thin film torque sensor in-situ integrated on a harmonic reducer according to claim 1, characterized in that: The torque sensitive unit (3) amplifies the output through Wheatstone bridge circuits in different configurations.

3. A thin film torque sensor in-situ integrated on a harmonic reducer according to claim 1 or 2, characterized in that: A signal processing unit (10) of a thin film torque sensor is provided on one side of the flange groove (1-1) of the flexible wheel (1); after being processed by the signal processing unit (10), the torque sensitive unit (3) obtains the angle change of the input end of the harmonic reducer in real time during the working process.

4. A method for preparing a thin film torque sensor in-situ integrated on a harmonic reducer according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: polishing the area to be coated on the flexible wheel (1) and cleaning it with acetone and anhydrous ethanol; Step 2: depositing an insulating film (2) on the surface of the flexible spline (1) treated in step 1; Step 3: using a metal mask, a torque sensitive unit (3) structure is prepared on the surface of the insulating film (2) prepared in step 2 by a magnetron sputtering method; Step 4: shielding the position of the pad (8) of the torque sensitive unit (3), and depositing a protective film (4) on the torque sensitive unit (3); Step 5: Connect the exposed pad (8) of the torque sensitive unit (3) to the lead (7) using conductive silver paste, and then seal it with organic silicone.

5. The preparation method according to claim 4, characterized in that The insulating film (2) is made of SiO2 or Parylene with a thickness of 3-5 μm; the torque sensitive unit (3) has a thickness of 0.6-1.2 μm; the protective film (4) is made of the same material as the insulating film (2) with a thickness of 500-1000 nm.

6. The preparation method according to claim 4 or 5, characterized in that When the insulating film (2) and the protective film (4) are made of SiO2, SiO2 is deposited by a plasma enhanced chemical vapor deposition method; SiH4 and N2O are used as reaction gases, the deposition temperature is 100-300°C, the radio frequency power is 15-75W, and the working pressure is 20-60Pa; when the insulating film (2) and the protective film (4) are made of Parylene, the background vacuum is 2.5-7.5mTorr, the Parylene powder is sublimated at 120-180°C, and the temperature of the cracking process is 650-700°C.

7. The preparation method according to claim 4 or 5, characterized in that The torque sensitive unit (3) was prepared by DC magnetron sputtering process, with a background vacuum of 5.0×10 -3 Pa, sputtering power 150-200W, sputtering gas pressure 0.5-0.8Pa, NiCr alloy as target material, and argon gas with a volume percentage purity of not less than 99.99% as the medium.

8. The preparation method according to claim 4, characterized in that The lead (7) is a flexible circuit board with a thickness between 0.1 and 0.3 mm. A connecting wire is provided on the flexible circuit board. One end of the connecting wire is connected to the pad (8) to connect the torque sensitive unit (3) into a Wheatstone bridge circuit, and the other end outputs the signal of the torque sensitive unit (3) to the signal processing unit (10).

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