Thin film type torque sensor integrated on harmonic reducer in situ and preparation method of thin film type torque sensor

Abstract

The invention belongs to the field of robot joint torque measurement, and provides a thin film type torque sensor integrated on a harmonic reducer in situ and a preparation method thereof, and the thin film type torque sensor is integrated on the surface of a flexible gear flange groove or the inner side plane of a flange in the harmonic reducer in situ. The film type torque sensor comprises a middle transition layer film, an insulating film, a torque sensing unit and a protective film from bottom to top. And a signal processing unit of the film type torque sensor is arranged on one side of the groove of the flexible gear flange. Torsional deformation information measured by the torque sensing unit is superposed through the Wheatstone bridge circuit and then is output to the signal processing unit in the form of an electric signal. The thin film type torque sensor can effectively eliminate interference generated by rotation of the wave generator in the process of in-situ measurement of the output torque of the harmonic reducer, and accurate output torque information is obtained. The surface of the thin film sensor obtained by the preparation method is compact and non-porous.

Description

Technical Field

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

[0002] Robots have been widely used in the automotive, medical, and electronic fields due to their light weight and high flexibility. However, when facing complex and changing application scenarios, robot collisions are inevitable, which poses a huge safety hazard to the production process. Therefore, in order to ensure the safety of humans, robots, and even the surrounding environment during work, the torque information of each joint is usually used in combination with the robot dynamics model to determine whether the robot collides with the external environment, and then take corresponding protective measures to ensure the safety of humans and robots while working efficiently.

[0003] At present, the measurement of robot joint output torque 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, which significantly reduces the stiffness and motion accuracy of the joint. In addition, in CN109139856A, researchers proposed to arrange 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 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, and it is difficult to obtain accurate torque information.

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

[0005] In order to accurately measure the output torque of the robot joint, the present invention proposes a thin film torque sensor integrated in situ on the harmonic reducer, which can effectively eliminate the interference caused by the rotation of the wave generator during the torque measurement process and will 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, wherein the thin film torque sensor is integrated in situ 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 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 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; the protective film 4 covers the torque sensitive unit surface 3.

[0007] The torque sensitive unit 3 includes a measuring sensitive gate 5, a horizontal gate 6, a lead 7 and a pad 8; each measuring sensitive gate 5 is connected by the horizontal gate 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 disposed 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 of 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 wheel 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 a magnetron sputtering method;

[0020] Step 4: shielding the pad 8 position of the torque sensitive unit 3 and depositing 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 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, Parylene powder sublimates 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, and the background vacuum degree was 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 invention: The invention proposes a thin film torque sensor integrated in situ on a harmonic reducer, which uses the flexible wheel of the harmonic reducer as an elastic body, and directly integrates a thin film torque sensor capable of measuring load deformation at multiple points within the entire circumference 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, and can 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 It is a schematic diagram of the structure of a thin film torque sensor integrated in situ on a harmonic reducer;

[0028] Figure 2 It is a 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 It is a structural schematic diagram of the flexible wheel of the harmonic reducer;

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

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

[0033] Figure 7 This is a schematic diagram of the lead structure.

[0034] In the figure: 1 is a flexible wheel, 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 in conjunction with the accompanying drawings and specific implementation schemes.

[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 flexible wheel 1 in the harmonic reducer. The specific structure of the flexible wheel of the harmonic reducer is as follows Figure 4 shown.

[0037] The thin film torque sensor comprises an intermediate transition layer thin 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 sensitive unit 3 is a structure that can measure the torsional deformation within the entire circumference of the surface of the flexwheel flange groove. The torque sensitive unit 3 measures the strain changes at each point within the entire circumference and amplifies them through the Wheatstone bridge circuit, which can effectively eliminate the interference signal generated by the periodic rotation of the harmonic reducer transmission process wave generator. The torque sensitive unit 3 includes a measuring sensitive grid 5, a horizontal grid 6, a lead 7 and a pad 8. Each measuring sensitive grid 5 is connected to form a loop through the horizontal grid 6, and is evenly distributed on the surface of the flexwheel 1 flange groove 1-1 or the surface of the insulating film 2 corresponding to the same radial position in the circumferential direction of the inner side 1-2 of the flange. One end of the lead 7 is connected to the pad 8, which is used to connect the measuring sensitive grid 5 to form a Wheatstone bridge circuit output. The position of the pad 8 is 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 inner side 1 - 2 of the flange is ±45°.

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

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

[0042] The protective film 4 material is composed of one or more inorganic materials or organic materials. The organic material includes one or more combinations of Parylene or polyimide, and the inorganic material includes one or more combinations of Al2O3, SiO2 or Si3N4, which prevents the torque sensitive unit 3 and the insulating film 2 from oxidation and failure during the working process, 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 arranged 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 affected by the periodic rotation of the wave generator, 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 rotation of the wave generator on the in-situ measurement result of the torque can be significantly eliminated, and the amplitude of the signal can be 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 comprises an insulating film 2, a torque sensitive unit 3, a protective film 4 and a lead 7, and is prepared on a flexible wheel 1, comprising the following steps:

[0048] Step 1: polish the area to be coated of 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 wheel 1 after being processed in step 1. When the insulating film 2 is made of 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 a working pressure of 20Pa. When the insulating film 2 is made of Parylene, the background vacuum is 7.5mTorr, 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, NiCr alloy as target material, 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: shield the pad 8 position 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 a working pressure of 20Pa; when the material of the protective film 4 is Parylene, the background vacuum is 7.5mTorr, Parylene powder sublimates 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 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 a flange groove (1-1) or the plane of the inner side (1-2) of a 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 (3) of the torque sensitive unit.

2. A thin film torque sensor integrated in-situ on a harmonic reducer according to claim 1, characterized in that: 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, which is evenly distributed at the same circumferential radial position on the surface of the insulating film (2); the pad (8) is located at a position outside the coverage of the protective film (4); and the pad (8) is located at both ends of the torque sensitive unit (3).

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

4. A thin film torque sensor integrated in-situ on a harmonic reducer according to claim 2 or 3, characterized in that: 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 inner side (1-2) of the flange is ±45°.

5. A thin film torque sensor integrated in-situ on a harmonic reducer according to claim 2 or 3, 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) acquires the angle change of the input end of the harmonic reducer in real time during the working process.

6. A method for preparing a thin film torque sensor in-situ integrated on a harmonic reducer as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: polishing the area to be coated of 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 wheel (1) treated in step 1; Step 3: using a metal mask to prepare a torque sensitive unit (3) structure on the surface of the insulating film (2) prepared in step 2 by a magnetron sputtering method; Step 4: shielding the pad (8) position of the torque sensitive unit (3), and depositing a protective film (4) on the torque sensitive unit (3); Step 5: Use conductive silver paste to connect the exposed pad (8) of the torque sensitive unit (3) to the lead (7), and use organic silicone to potting.

7. The preparation method according to claim 6, 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) 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.

8. The preparation method according to claim 6 or 7, characterized in that: When the material used for the insulating film (2) and the protective film (4) is SiO2, a plasma enhanced chemical vapor deposition method is used to deposit SiO2; 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 is sublimated at 120-180°C, and the temperature of the cracking process is 650-700°C.

9. The preparation method according to claim 6 or 7, 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 medium.

10. The preparation method according to claim 6, characterized in that: The lead wire (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. The other end of the connecting wire outputs the signal of the torque sensitive unit (3) to the signal processing unit (10).

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