Torque sensor integrated on harmonic reducer in situ, calibration device and method

Abstract

The invention belongs to the technical field of sensors, and provides a torque sensor integrated on a harmonic reducer in situ, a calibration device and a calibration method. The torque sensor is integrated on the harmonic reducer flexible gear and comprises a plurality of measurement sensitive grids which are connected in series to form a loop. A plurality of groups of measuring structures are arranged in a redundant manner in the circumferential direction, so that not only can the accuracy and sensitivity of measurement be improved, but also the reliability of measurement can be improved, and when one group breaks down, the redundant measuring structures can be used for measurement. The torque sensor calibration device comprises a robot joint, a standard torque sensor and a loading device. The calibration process is carried out on the robot joint, and the influence caused by installation of the torque sensor is avoided. Meanwhile, according to the calibration method, interference signals in the in-situ measurement process are combined with the position information of the wave generator, and the precision of the in-situ integrated torque sensor is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a torque sensor in-situ integrated on a harmonic reducer, a calibration device and a method. Background Art

[0002] Accurately acquiring joint torque information is crucial for collaborative robots. This information not only provides real-time information on the forces acting between the robot and its environment, ensuring safety during collaboration and interaction between the robot and humans, but also enables advanced motion control and the completion of tasks requiring greater force. This capability is crucial for the adaptability and flexibility of collaborative robots, particularly for tasks operating in complex environments.

[0003] CN105422792A proposes directly attaching strain gauges to the harmonic reducer in a robot joint, and detecting the deformation of the flexspline in the harmonic reducer to obtain the joint's output torque information. This method does not affect the robot's joint stiffness and does not require changes to the robot's overall structure, making it an ideal technical choice. However, during the measurement process, the flexspline is also subject to deformation interference caused by the periodic squeezing action of the wave generator, making it difficult to accurately extract the target torque signal.

[0004] This paper proposes a torque sensor integrated in situ on a harmonic reducer, thereby eliminating the effects of interference signals on torque measurement. To further improve the sensor's measurement accuracy, a torque sensor calibration device integrated in situ on the harmonic reducer is proposed, eliminating the effects of sensor installation. Furthermore, this paper proposes a calibration method that combines interference signals with the position of the wave generator, effectively improving the measurement accuracy of the in-situ integrated torque sensor and having important implications for torque measurement in robot joints. Summary of the Invention

[0005] To address the interference caused by the wave generator during the measurement process of an in-situ integrated torque sensor, this invention proposes a torque sensor, calibration device, and method integrated in-situ on a harmonic reducer. These methods effectively improve the accuracy of in-situ measurements and are widely applicable in the field of robotics. Furthermore, redundantly arranging multiple sets of strain gauge torque measurement structures in the circumferential direction not only enhances measurement accuracy and sensitivity, but also improves measurement reliability. If one set fails, measurement can be continued using the remaining sets.

[0006] The technical solution of the present invention is as follows: the torque sensor 1 in situ integrated on the harmonic reducer includes a strain-type torque measurement structure 1-1, an insulating film 1-2 and a protective film 1-3; the harmonic reducer 2 includes a rigid wheel 2-1, a flexible wheel 2-2 and a wave generator 2-3; the strain-type torque measurement structure 1-1 includes a measurement sensitive grid 3, a connecting grid 4, a lead 5 and a pad 6; a plurality of measurement sensitive grids 3 are connected in series through the connecting grid 4 and are evenly distributed around the circumference of the flange groove 10 of the flexible wheel 2-2 to form a continuous bending structure; the pad 6 is located at the end of the strain-type torque measurement structure 1-1; one end of the lead 5 is bonded to the pad by an adhesive. 6 is connected, and the other end extends outward; the insulating film 1-2 is a circular ring structure, arranged between the strain type torque measurement structure 1-1 and the flange groove 10 of the flexible wheel 2-2, and the insulating film 1-2, the strain type torque measurement structure 1-1, and the flange groove 10 of the flexible wheel 2-2 are cocentric; the measuring sensitive grid 3, the connecting grid 4 and the pad 6 in the strain type torque measurement structure 1-1 are prepared by one method selected from magnetron sputtering, vacuum evaporation, screen printing, and plasma enhanced chemical vapor deposition; the protective film 1-3 is a circular ring structure, arranged on the strain type torque measurement structure 1-1, and hollowed out at the position of the pad 6.

[0007] The number of the strain gauge torque measurement structures 1-1 of the torque sensor is a multiple of 2, and the output is amplified by a Wheatstone half-bridge circuit or a full-bridge circuit in different configurations.

[0008] The strain-type torque measuring structures 1 - 1 of the torque sensor are arranged in one or two circles in the circumferential direction of the flange groove 10 of the flexspline 2 - 2 , and the strain-type torque measuring structures 1 - 1 arranged in each circle are at the same radial position.

[0009] The strain-type torque measurement structure 1-1 of the torque sensor has a thickness of 200-800 nm, a length of the measurement sensitive grid 3 of 1-5 mm, and a width of 10-500 μm.

[0010] The torque sensor calibration device integrated in situ on the harmonic reducer includes a robot joint 7, a standard torque sensor 8 and a loading device 9; the harmonic reducer 2 is installed on the robot joint 7; the output of the robot joint 7 is connected to one end of the standard torque sensor 8, and the other end of the standard torque sensor 8 is connected to the loading device 9.

[0011] The loading device 9 is a magnetic powder brake, a torque motor or a connecting rod.

[0012] The calibration method of the torque sensor integrated in situ on the harmonic reducer includes the following steps:

[0013] Step 1: Calibrate using only robot joint 7;

[0014] Step 1.1: Move the wave generator 2-3 to the absolute zero position of the motor end of the robot joint 7 and adjust the output signal of the torque sensor 1 integrated in the harmonic reducer to zero. Then rotate the wave generator 2-3 point by point with a step size of 3°, stop at each point for 10s until it reaches the 360° position; record the angle of the wave generator 2-3 and the output voltage of the torque sensor 1 integrated in the harmonic reducer respectively, and use the angle theta of the wave generator 2-3 as the output voltage. wg 1 The horizontal axis is the output voltage U0 of the torque sensor 1 integrated in the harmonic reducer. 1 is the vertical axis, fitting the relationship between the two;

[0015] Step 1.2: Repeat step 1.1, and rotate wave generator 2-3 to 720° and 1080° respectively, until the output end of robot joint 7 rotates a full circle and wave generator 2-3 rotates to 36000°; respectively fit the output voltage U0 of torque sensor 1 integrated in situ on the harmonic reducer in different angle ranges. i With wave generator 2-3 angle theta wg i , i=2, 3, ..., 100;

[0016] Step 2: Connect the output of the robot joint 7 to one end of the standard torque sensor 8, and connect the other end of the standard torque sensor 8 to the loading device 9 for calibration;

[0017] Step 2.1: Move the wave generator 2-3 to the absolute zero position of the motor end of the robot joint 7 and adjust the output signal of the torque sensor 1 to zero. Then lock the wave generator 2-3 and control the loading device 9 to apply m equally spaced, step-by-step loads to the calibration device until the torque sensor 1 reaches its full range and then gradually unloads. Stop at each point for 10 seconds; record the output voltage U of the torque sensor 1 in the forward and reverse strokes respectively. 00 The torque T of the standard torque sensor 8 is used as the horizontal coordinate, and the output voltage U of the torque sensor 1 is used as the horizontal coordinate. 00 As the vertical coordinate, the corresponding linear relationship U is obtained by least square fitting. 00 =A1T+B1;

[0018] Step 2.2: Repeat step 2.1 and rotate wave generator 2-3 to 30°, 60°, 90°, 120°, and 150° positions in turn to obtain two calibration lines U 030 =A2T+B2、U 060 =A3T+B3、U 090 =A4T+B4、U 0120 =A5T+B5、U 0150=A6T+B6; then the six fitting lines are averaged to obtain the final fitting line U=AT+B, where U is the output voltage of the torque sensor, A=(A1+A2+A3+A4+A5+A6) / 6, and B=(B1+B2+B3+B4+B5+B6) / 6;

[0019] Step 2.3: The measured torque information is: T = [(U-U0 i )-B] / A.

[0020] The present invention's beneficial effects include: The torque sensor, calibration device, and method proposed for in-situ integration with a harmonic reducer eliminate the impact of external sensor elastomers on robot joint performance. Furthermore, by arranging the torque sensor's strain gauge torque measurement structure along the circumference of the flexspline and integrating interference signals from the measurement process with the position of the wave generator, interference from the wave generator's extrusion on the measurement can be effectively suppressed, significantly improving the accuracy of in-situ torque measurement on the harmonic reducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the torque sensor structure integrated in situ on the harmonic reducer, where the number of strain gauge torque measurement structures is 4, arranged in one circle;

[0022] Figure 2 for Figure 1 The schematic diagram of the Wheatstone bridge circuit to which the torque sensor is connected is shown;

[0023] Figure 3 Schematic diagram of the torque sensor structure integrated in situ on the harmonic reducer, where the number of strain gauge torque measurement structures is 4, arranged in 2 circles;

[0024] Figure 4 for Figure 3 The schematic diagram of the Wheatstone bridge circuit to which the torque sensor is connected is shown;

[0025] Figure 5 Schematic diagram of the torque sensor structure integrated in situ on the harmonic reducer, where the number of strain gauge torque measurement structures is 6 and arranged in 2 circles;

[0026] Figure 6 for Figure 5 Schematic diagram of the Wheatstone bridge circuit connected to the torque measurement structure shown;

[0027] Figure 7 It is the structural diagram of the harmonic reducer;

[0028] Figure 8 Schematic diagram of the torque sensor structure integrated in situ on the harmonic reducer;

[0029] Figure 9 Schematic diagram of the torque sensor calibration device integrated in situ on the harmonic reducer.

[0030] In the figure, 1 is a torque sensor, 1-1 is a strain-type torque measurement structure, 1-2 is an insulating film, 1-3 is a protective film, 2 is a harmonic reducer, 2-1 is a rigid wheel, 2-2 is a flexible wheel, 2-3 is a wave generator, 3 is a measurement sensitive grid, 4 is a connecting grid, 5 is a lead, 6 is a pad, 7 is a robot joint, 8 is a standard torque sensor, 9 is a loading device, and 10 is a flange groove. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The present invention proposes a torque sensor integrated in situ on a harmonic reducer. By arranging multiple measurement sensitive grids on the circumference of the flexible pulley of the harmonic reducer and connecting the multiple measurement sensitive grids in series to form a loop, the influence of interference signals on torque measurement is eliminated. In order to further improve the measurement accuracy of the sensor, a torque sensor calibration device integrated in situ on a harmonic reducer is proposed, which includes a robot joint, a standard torque sensor and a loading device. The calibration process can be carried out in an on-machine state, avoiding the influence of sensor installation. At the same time, the present invention proposes a calibration method that combines the interference signal with the position of the wave generator, which can effectively improve the measurement accuracy of the in-situ integrated torque sensor and is of great significance for the torque measurement of robot joints.

[0033] The torque sensor 1 integrated in situ on the harmonic reducer includes a strain-type torque measurement structure 1-1, an insulating film 1-2, and a protective film 1-3; the harmonic reducer 2 includes a rigid wheel 2-1, a flexible wheel 2-2, and a wave generator 2-3; the strain-type torque measurement structure 1-1 includes a measurement sensitive grid 3, a connecting grid 4, a lead 5, and a pad 6; a plurality of measurement sensitive grids 3 are connected in series through the connecting grid 4 and evenly distributed around the circumference of the flange groove 10 of the flexible wheel 2-2, forming a continuous bending structure; the pad 6 is located at the end of the strain-type torque measurement structure 1-1; one end of the lead 5 is connected to the pad 6 by an adhesive. The other end extends outward; the insulating film 1-2 is a circular ring structure, arranged between the strain type torque measurement structure 1-1 and the flange groove 10 of the flexible wheel 2-2, and the insulating film 1-2, the strain type torque measurement structure 1-1, and the flange groove 10 of the flexible wheel 2-2 are cocentric; the measurement sensitive grid 3, the connecting grid 4 and the pad 6 in the strain type torque measurement structure 1-1 are prepared by one method including magnetron sputtering, vacuum evaporation, screen printing, and plasma enhanced chemical vapor deposition; the protective film 1-3 is a circular ring structure, arranged on the strain type torque measurement structure 1-1, and hollowed out at the position of the pad 6.

[0034] The strain gauge torque measurement structure 1-1 of the torque sensor in-situ integrated on the harmonic reducer is a multiple of 2, and the output is amplified by a Wheatstone half-bridge circuit or a full-bridge circuit in different configurations.

[0035] The strain type torque measurement structure 1-1 of the torque sensor in-situ integrated on the harmonic reducer is arranged in one or two circles in the circumferential direction of the flange groove 10 of the flexible wheel 2-2, and the strain type torque measurement structure 1-1 arranged in each circle is at the same radial position.

[0036] The strain-type torque measurement structure 1-1 of the torque sensor in-situ integrated on the harmonic reducer has a thickness of 200-800 nm, a measurement sensitive grid 3 has a length of 1-5 mm, and a width of 10-500 μm.

[0037] The torque sensor calibration device integrated in situ on the harmonic reducer includes a robot joint 7, a standard torque sensor 8 and a loading device 9; the harmonic reducer 2 integrated with the torque sensor 1 is installed on the robot joint 7; the output of the robot joint 7 is connected to one end of the standard torque sensor 8, and the other end of the standard torque sensor 8 is connected to the loading device 9.

[0038] The loading device 9 is a magnetic powder brake, a torque motor or a connecting rod; for the magnetic powder brake or the torque motor, the loading size is controlled by adjusting the controller voltage or current; for the connecting rod, the load size is adjusted by changing the mass of the weight at the end of the connecting rod.

[0039] The calibration method of the torque sensor integrated in situ on the harmonic reducer includes the following steps:

[0040] Step 1: Calibrate using only robot joint 7;

[0041] Step 1.1: Move the wave generator 2-3 to the absolute zero position of the motor end of the robot joint 7 and adjust the output signal of the torque sensor 1 integrated in the harmonic reducer to zero. Then rotate the wave generator 2-3 point by point with a step size of 3°, stop at each point for 10s until it reaches the 360° position; record the angle of the wave generator 2-3 and the output voltage of the torque sensor 1 integrated in the harmonic reducer respectively, and use the angle theta of the wave generator 2-3 as the output voltage. wg 1 The horizontal axis is the output voltage U0 of the torque sensor 1 integrated in the harmonic reducer. 1 As the vertical coordinate, the relationship between the two is fitted by the second-order Fourier series: U0 1 =-1.12+14.56cos(0.04theta wg 1 )+4.02sin(0.04theta wg 1)-1.21cos(0.08theta wg 1 )+

[0042] 0.87sin(0.08theta wg 1 )

[0043] Step 1.2: Repeat step 1.1, and rotate wave generator 2-3 to 720° and 1080° respectively, until the output end of robot joint 7 rotates a full circle and wave generator 2-3 rotates to 36000°; respectively fit the output voltage U0 of torque sensor 1 integrated in situ on the harmonic reducer within different angle ranges. i With wave generator 2-3 angle theta wg i , i=2,3,...,100: U0 2 =-1.11+14.66cos(0.04theta wg 2 )+3.92sin(0.04theta wg 2 )-1.27cos(0.08theta wg 2 )+0.85sin(0.08theta wg 2 ), U0 3 =-1.10+14.61cos(0.04theta wg 3 )+3.99sin(0.04theta wg 3 )--1.20cos(0.08theta wg 3 )+0.89sin(0.08theta wg 3 ),..., U0 100 =-1.11+14.68cos(0.04theta wg 100 )+3.99sin(0.04theta wg 100 )-1.29cos(0.08theta wg 100 )+0.77sin(0.08theta wg 100 ); Through this step, the peak-to-peak value of the interference signal during the measurement process was reduced from 13.32mV to 1.91mV.

[0044] Step 2: Connect the output of the robot joint 7 to one end of the standard torque sensor 8, and connect the other end of the standard torque sensor 8 to the loading device 9 for calibration;

[0045] Step 2.1: Move the wave generator 2-3 to the absolute zero position of the motor end of the robot joint 7 and adjust the output signal of the torque sensor 1 integrated in situ on the harmonic reducer to zero. Then lock the wave generator 2-3 and control the loading device 9 to apply four equally spaced, step-by-step loads to the calibration device until the full scale of the torque sensor 1 integrated in situ on the harmonic reducer reaches 20 N·m. Then gradually unload the load and stop at each point for 10 seconds; record the output voltage U of the torque sensor 1 integrated in situ on the harmonic reducer under forward and reverse travel respectively. 00 The torque T of the standard torque sensor 8 is used as the horizontal coordinate, and the output voltage U of the torque sensor 1 is used as the horizontal coordinate. 00 As the vertical coordinate, the corresponding linear relationship U is obtained by least square fitting. 00 =5.28T-3.77;

[0046] Step 2.2: Repeat step 2.1 and rotate wave generator 2-3 to 30°, 60°, 90°, 120°, and 150° positions in turn to obtain two calibration lines U 030 =5.30T-3.91, U 060 =5.29T-3.31, U 090 =5.32T-3.62, U 0120 =5.23T-3.96, U 0150 =5.09T-4.15; then the six fitting lines are averaged to obtain the final fitting line U=AT+B, where U is the output voltage of the torque sensor, A=(A1+A2+A3+A4+A5+A6) / 6, and B=(B1+B2+B3+B4+B5+B6) / 6;

[0047] Step 2.3: The measured torque information is: T = [(U-U0 i )-3.79] / 5.25.

Claims

1. A torque sensor integrated in-situ on a harmonic reducer, characterized in that: The torque sensor (1) integrated in situ on the harmonic reducer comprises a strain-type torque measurement structure (1-1), an insulating film (1-2) and a protective film (1-3); the harmonic reducer (2) comprises a rigid wheel (2-1), a flexible wheel (2-2) and a wave generator (2-3); The strain-type torque measurement structure (1-1) comprises a measurement sensitive grid (3), a connection grid (4), a lead wire (5) and a pad (6); a plurality of measurement sensitive grids (3) are connected in series via the connection grid (4) and evenly spread over the circumference of the flange groove (10) of the flexible wheel (2-2) to form a continuous bending structure; the pad (6) is located at the end of the strain-type torque measurement structure (1-1); one end of the lead wire (5) is connected to the pad (6) via an adhesive, and the other end extends outward; The insulating film (1-2) is a circular ring structure, which is arranged between the strain-type torque measurement structure (1-1) and the flange groove (10) of the flexible wheel (2-2), and the insulating film (1-2), the strain-type torque measurement structure (1-1) and the flange groove (10) of the flexible wheel (2-2) are co-centered. The measuring sensitive grid (3), the connecting grid (4) and the pad (6) in the strain-type torque measuring structure (1-1) are prepared by a method selected from the group consisting of magnetron sputtering, vacuum evaporation, screen printing and plasma enhanced chemical vapor deposition; The protective film (1-3) is a circular ring structure, which is arranged on the strain-type torque measurement structure (1-1) and is hollowed out at the position of the welding pad (6).

2. The torque sensor integrated in-situ on the harmonic reducer according to claim 1, characterized in that: The number of strain-type torque measurement structures (1-1) of the torque sensor (1) integrated in situ on the harmonic reducer is a multiple of 2, and the output is amplified by a Wheatstone half-bridge circuit or a full-bridge circuit in different configurations.

3. The torque sensor in-situ integrated on the harmonic reducer according to claim 1 or 2, characterized in that: The strain-type torque measurement structure (1-1) of the torque sensor (1) integrated in situ on the harmonic reducer is arranged in one or two circles in the circumferential direction of the flange groove (10) of the flexible wheel (2-2), and the strain-type torque measurement structure (1-1) arranged in each circle is located at the same radial position.

4. The torque sensor in-situ integrated on the harmonic reducer according to claim 1, characterized in that: The strain-type torque measurement structure (1-1) of the torque sensor has a thickness of 200-800 nm, and a measurement sensitive grid (3) has a length of 1-5 mm and a width of 10-500 μm.

5. A torque sensor calibration device integrated in situ on a harmonic reducer, characterized in that: Used for calibrating the torque sensor integrated in situ on the harmonic reducer as described in any one of claims 1 to 4; the calibration device comprises a robot joint (7), a standard torque sensor (8) and a loading device (9); the harmonic reducer (2) is installed on the robot joint (7); the output of the robot joint (7) is connected to one end of the standard torque sensor (8), and the other end of the standard torque sensor (8) is connected to the loading device (9).

6. The torque sensor calibration device in-situ integrated on the harmonic reducer according to claim 5, characterized in that: The loading device (9) is a magnetic powder brake, a torque motor or a connecting rod.

7. A method for calibrating a torque sensor integrated in-situ on a harmonic reducer, characterized in that: The steps include: Step 1: Calibrate using only the robot joints (7); Step 1.1: Move the wave generator (2-3) to the absolute zero position of the motor end of the robot joint (7) and adjust the output signal of the torque sensor (1) integrated in the harmonic reducer to zero. Then, rotate the wave generator (2-3) point by point with a step length of 3° and stop at each point for 10 seconds until the 360° position is reached. Record the angle of the wave generator (2-3) and the output voltage of the torque sensor (1) integrated in the harmonic reducer respectively, and use the angle theta of the wave generator (2-3) as the output voltage. wg 1 The horizontal axis is the output voltage U0 of the torque sensor (1) integrated in situ on the harmonic reducer. 1 is the ordinate, fitting the relationship between the two; Step 1.2: Repeat step 1.1, and turn the wave generator (2-3) to the positions of 720° and 1080° in turn, until the wave generator (2-3) turns to the position of 36000°; respectively fit the output voltage U0 of the torque sensor (1) integrated in situ on the harmonic reducer within different angle ranges. i Angle theta with wave generator (2-3) wg i , i=2, 3, ..., 100; Step 2: Connect the output of the robot joint (7) to one end of the standard torque sensor (8), and connect the other end of the standard torque sensor (8) to the loading device (9) for calibration; Step 2.1: Move the wave generator (2-3) to the absolute zero position of the motor end of the robot joint (7) and adjust the output signal of the torque sensor (1) integrated in situ on the harmonic reducer to zero, then lock the wave generator (2-3), control the loading device (9) to apply m equally spaced and step-increasing loads to the calibration device until the torque sensor (1) integrated in situ on the harmonic reducer reaches the full scale, and then gradually unload, stopping at each point position for 10 seconds; Record the output voltage U of the forward and reverse travel torque sensor (1) respectively 00 The torque T of the standard torque sensor (8) is taken as the horizontal coordinate, and the output voltage U of the torque sensor (1) is taken as the horizontal coordinate. 00 As the ordinate, the corresponding linear relationship U is obtained by least squares fitting. 00 =A1T+B1; Step 2.2: Repeat step 2.1, and turn the wave generator (2-3) to 30°, 60°, 90°, 120°, and 150° positions in turn to obtain two calibration lines U 030 =A2T+B2、U 060 =A3T+B3、U 090 =A4T+B4、U 0120 =A5T+B5、U 0150 =A6T+B6; then the 6 fitting lines are averaged to obtain the final fitting line U=AT+B, where U is the output voltage of the torque sensor, A=(A1+A2+A3+A4+A5+A6) / 6, B=(B1+B2+B3+B4+B5+B6) / 6; Step 2.3: The measured torque information is: T = [(U-U0 i )-B] / A.

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