Combined three-dimensional force / torque sensor and miniature calibration system thereof

Abstract

A combined three-dimensional force / torque sensor. A plurality of discrete one-dimensional force sensors (11, 12, 13, 14) are used to measure force components, and a conduction flange (2) is used to transmit an external force. The combined design effectively reduces inter-dimensional coupling and has a simple structure. The lateral torque and the axial pressure are monitored in a differential form and a summation form, thereby effectively improving the sensitivity and measurement accuracy of the sensor. Further disclosed is a miniature calibration system established by using the combined three-dimensional force / torque sensor. The calibration system has a small size and a simple structure, is easy to assemble and convenient to carry and transfer, and is capable of on-site calibration.

Description

A combined three-dimensional force / torque sensor and its small calibration system Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a combined three-dimensional force / torque sensor and a small calibration system thereof. Background Art

[0002] In fields such as industrial robotics, aerospace, and aviation, tasks like lunar soil collection, industrial mining, and land monitoring are frequently performed, requiring equipment to perform drilling operations in complex environments. However, the operating environment, such as beneath the lunar soil, cannot be directly monitored visually. Therefore, measuring the directional resistance and lateral torque required to assess the operating status is crucial for closed-loop control of the system, providing critical data to prevent equipment damage.

[0003] However, the forces acting in the direction of exploration are significantly greater than those acting in the lateral direction, resulting in significant differences in the range requirements for axial pressure and lateral torque. Conventional multi-dimensional force / torque sensors have relatively high deployment costs and similar ranges in each dimension, limiting their performance in exploration missions. Most sensors also suffer from complex structures, significant inter-dimensional coupling interference, and low sensitivity. One-dimensional force sensor technology is relatively mature, offering advantages such as low cost, high sensitivity, and strong anti-interference capabilities. However, a single sensor cannot meet mission requirements. Furthermore, work sites often involve assembly and disassembly tasks, such as changing equipment, which can affect sensor accuracy. Calibration is required for high-precision missions, but traditional multi-dimensional force / torque calibration equipment is bulky and complex, making it difficult to carry to the site. Therefore, designing a three-dimensional force / torque sensor with large range differences, minimal inter-dimensional coupling, high sensitivity, and a simple structure, along with a dedicated small calibration system, is crucial for improving operational efficiency and equipment safety in exploration environments.

[0004] Summary of the Invention

[0005] To solve the above problems, the present invention discloses a combined three-dimensional force / torque sensor and a small calibration system thereof, which has the advantages of large difference in the range of each vector, small inter-dimensional coupling, high sensitivity and measurement accuracy, simple structure, and on-site calibration.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A combined three-dimensional force / torque sensor comprises a combined sensing area, a conductive flange, a top cover and a base;

[0008] The combined sensing area is used to monitor the force, and includes four one-dimensional force sensors of the same specification, which are arranged in a square shape, fixed to the base at the bottom and connected to the conductive flange at the top;

[0009] The one-dimensional force sensor adopts an S-type force sensor based on the resistance strain principle, and has a threaded hole for assembly on the surface in the force measurement direction;

[0010] The conductive flange is used to transmit external force to the combined sensing area, reduce inter-dimensional coupling, and connect the combined sensing area and the top cover;

[0011] The conductive flange is in the shape of a cross fan blade, with a cylindrical boss with a threaded hole in the center, and four blades with threaded holes extending outward at equal distances from the edge of the boss;

[0012] The cylindrical boss is connected to the top cover through threaded engagement;

[0013] The blade is connected to the one-dimensional force sensor through threaded connection;

[0014] The top cover is used to encapsulate the sensor and is in the shape of a cylindrical cup with an opening at the bottom. The center of the top cover has a cylindrical recess with a threaded hole for threaded engagement with the conductive flange. The side has four equally spaced rectangular notches for leading out the signal lines and power lines of each one-dimensional force sensor.

[0015] The base is used to fix the combined sensing area and the bottom surface of the packaged sensor. There are four groups of square-arranged fixing bosses on the upper surface of the base. The spacing between each group of fixing bosses is the same as the thickness of the one-dimensional force sensor, and there is an assembly threaded hole in the center of each group of fixing bosses for installing the one-dimensional force sensor.

[0016] Principle of achieving three-dimensional force / torque measurement:

[0017] Four one-dimensional force sensors are arranged in a square, and the measured forces are F1, F2, F3, and F4 respectively. F1 and F2 are on opposite sides, and F3 and F4 are on opposite sides. A pair of forces on opposite sides constitutes a couple. The difference between the two forces is multiplied by the lengths of the corresponding stress arms kx and ky to obtain the torque. The measurement of the moments Mx and My in the X and Y directions is completed by differential method, and the sum of the forces on the four sensors is the force Fz in the Z direction:

[0018] The small calibration system is specifically used to calibrate the axial pressure Fz and lateral moments Mx, My three-dimensional force / torque information of the combined large-range differential three-dimensional force / torque sensor, including the bottom bracket and the upper functional area;

[0019] The bottom bracket has three fixed legs and one longitudinally movable leg at the bottom, which is in contact with the ground and can be adjusted for stability;

[0020] The bottom bracket has five longitudinal movable columns on the upper part, and the front ends of the columns are provided with free movable feet for supporting the horizontal panel and adjusting the level;

[0021] The upper functional area includes a horizontal panel, a pair of Z-axis lifting platforms, an XY-axis two-dimensional displacement platform, and a calibration flange;

[0022] The horizontal panel is a square plate placed above the bottom bracket and has an array of threaded holes on its surface for assembling the various adjustment platforms;

[0023] The Z-axis lifting platform has a threaded hole at the bottom for connection with the horizontal panel, and a displacement slider on the side. The slider is equipped with a grooved fixed pulley for transmitting horizontal force to the vertical direction.

[0024] The Z-axis lifting platforms, a pair of two in total, are symmetrically placed in the centers of opposite sides of the horizontal panel, with the sliders facing the same side and the pulleys extending outward and beyond the horizontal plane;

[0025] The XY axis two-dimensional displacement platform is placed at the center of the horizontal panel, and the X axis direction is the same as the direction of the slider of the Z axis lifting platform;

[0026] The XY axis two-dimensional displacement platform has a threaded hole array on the top for connecting to the bottom of the three-dimensional force / torque sensor;

[0027] The calibration flange is cylindrical, and the bottom and top of the cylinder are both discs. The bottom disc has a threaded hole for connecting to the top of the three-dimensional force / torque sensor. Two annular grooves are opened on the cylinder, and the spacing between the annular grooves is fixed.

[0028] The principle of achieving three-dimensional force / torque calibration: the Z-axis pressure Fz is calibrated by directly stacking weights in the center of the force sensor; when calibrating the X- and Y-axis torques, the calibration flange is first installed on the upper part of the force sensor, and then a wire rope loop is used to transmit the force. The two rope loops are respectively wrapped around and embedded in the upper and lower grooves of the calibration flange for positioning, and then respectively placed in the grooves of the grooved fixed pulleys on the left and right Z-axis lifting platforms. Weights are hung at the ends of the rope loops, and the loading force is horizontally adjusted by adjusting the height of the slider of the Z-axis lifting platform, completing the loading of a pair of equal and opposite forces on the force sensor to form a couple, and the torque is the distance between the upper and lower grooves of the calibration flange; through installation and adjustment, the X-axis or Y-axis direction of the force sensor is made the same as the direction of the slider of the Z-axis lifting platform, thereby realizing the calibration of the X-axis torque Mx or Y-axis torque My of the force sensor.

[0029] The beneficial effects of the present invention are:

[0030] (1) The combined three-dimensional force / torque sensor and its small calibration system designed by the present invention use multiple discrete one-dimensional force sensors to measure component forces and transmit external forces through a conductive flange. The combined design effectively reduces inter-dimensional coupling and has a simple structure.

[0031] (2) The combined three-dimensional force / torque sensor and its small calibration system designed in the present invention respectively use differential and additive forms to monitor lateral torque and axial pressure, effectively improving the sensitivity and measurement accuracy of the sensor.

[0032] (3) The combined three-dimensional force / torque sensor and its small calibration system designed by the present invention have a small size, a simple structure, are easy to assemble, and are convenient to carry and transfer and to perform on-site calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a structural schematic diagram 1 of a combined three-dimensional force / torque sensor of the present invention.

[0034] FIG2 is a schematic diagram of a conductive flange of the present invention.

[0035] FIG3 is a diagram of the base of the present invention.

[0036] FIG. 4 is a diagram of the top cover of the present invention.

[0037] FIG5 is a diagram of the bottom bracket of the calibration platform of the present invention.

[0038] FIG6 is a diagram of the upper functional area of ​​the calibration platform of the present invention.

[0039] FIG. 7 is a diagram of a calibration flange according to the present invention.

[0040] List of Figure Symbols:

[0041] 1. Combined sensing area, 2. Conductive flange, 3. Top cover, 4. Base, 5. Bottom bracket, 6. Horizontal panel, 7. Z-axis lifting platform, 8. XY-axis two-dimensional displacement platform, 9. Calibration flange, 11-14. One-dimensional force sensor, 21. Cylindrical boss, 22. Blade, 31. Fixed boss, 32. Assembly threaded hole, 41. Cylindrical recess, 42. Rectangular notch, 51. Fixed foot, 52. Adjustment foot, 53. Movable column, 54. Movable foot, 71. Displacement slider, 72. Grooved fixed pulley, 91. Threaded hole, 92, 93. Circular groove. DETAILED DESCRIPTION

[0042] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0043] The present invention proposes a combined three-dimensional force / torque sensor and a small calibration system thereof, as shown in FIG1 . To facilitate the description of directions, a spatial Cartesian coordinate system is established as shown in FIG1 . The combined three-dimensional force / torque sensor monitors the Z-axis pressure and the X- and Y-axis torques. The combined three-dimensional force / torque sensor includes a combined sensing area 1, a conductive flange 2, a top cover 3, and a base 4.

[0044] The combined sensing area 1 is used to monitor the force, and includes four one-dimensional force sensors of the same specifications. The one-dimensional force sensors 11 to 14 are arranged in a square, fixed to the base 4 at the bottom, and connected to the conductive flange 2 at the top;

[0045] The one-dimensional force sensors 11 to 14 are S-type force sensors based on the resistance strain principle, with assembly threads on the force measurement direction surface, and output analog voltage signals, the voltage magnitude of which is linearly positively correlated with the magnitude of the force;

[0046] As shown in FIG2 , the conductive flange 2 is used to transmit external force to the combined sensing area 1 , reduce inter-dimensional coupling, and connect the combined sensing area 1 and the top cover 4 ;

[0047] The conductive flange 2 is in the shape of a cross fan blade, with a cylindrical boss 21 with a threaded hole in the center, and four blades 22 with threaded holes extending outward at equal distances from the edge of the boss;

[0048] The cylindrical boss 21 is connected to the top cover 4 through threaded engagement;

[0049] The blade 22 is connected to the one-dimensional force sensors 11 to 14 through threaded connection;

[0050] As shown in FIG3 , the base 3 is used to fix the combined sensing area 1 and the bottom surface of the packaged sensors 11 to 14. The upper surface of the base has four groups of square-arranged fixing bosses 31. The spacing between each group of bosses is the same as the thickness of the one-dimensional force sensor, and each group of bosses has a mounting threaded hole 32 in the center.

[0051] As shown in FIG4 , the top cover 4 is used to encapsulate the sensors 11 to 14 and is in the shape of a cylindrical cup with an opening at the bottom. The center of the top cover has a cylindrical recess 41 with a threaded hole for threaded engagement with the conductive flange. Four equidistant rectangular notches 42 are provided on the side to lead out the signal and power lines of each 1D force sensor.

[0052] The combined three-dimensional force / torque sensor implements the principle of three-dimensional force / torque measurement. The one-dimensional force sensors 11 to 14 are arranged in a square. The measured forces are F1, F2, F3, and F4, respectively. F1 and F2 are on opposite sides, and F3 and F4 are on opposite sides. A pair of forces on opposite sides constitutes a couple. The difference between the two forces is multiplied by the lengths kx and ky of the corresponding stress arms to obtain the torque. Thus, the measurement of the moments Mx and My in the X and Y directions is completed by differential means. The sum of the forces acting on the four sensors is the force Fz in the Z direction:

[0053] The small calibration system is specifically used to calibrate the axial pressure Fz and lateral moments Mx, My of the combined large-range differential three-dimensional force / torque sensor, and includes a bottom bracket 5 and an upper functional area;

[0054] As shown in FIG5 , the bottom bracket 5 has three fixed legs 51 and one longitudinal adjustment leg 52 at the bottom, which are in contact with the ground and can be adjusted for stability. The top bracket has five longitudinal movable columns 53, and the front ends of the columns are provided with free movable legs 54 for supporting the horizontal panel and adjusting the level.

[0055] As shown in Figure 6, the upper functional area includes a horizontal panel 6, a pair of Z-axis lifting platforms 7, an XY-axis two-dimensional displacement platform 8, and a calibration flange 9. The three-dimensional force / torque sensor formed by the combined sensing area 1, the conductive flange 2, the top cover 3, and the base 4 is placed between the calibration flange 9 and the XY-axis two-dimensional displacement platform 8.

[0056] The horizontal panel 6 is a square plate placed above the bottom bracket, with an array of threaded holes on its surface for assembling the various adjustment platforms;

[0057] The Z-axis lifting platform 7 has a threaded hole at the bottom for connecting to the horizontal panel 6, and a displacement slider 71 on the side. A grooved fixed pulley 72 is placed on the slider to transmit horizontal force to the vertical direction;

[0058] The Z-axis lifting platforms 7, a pair of two in total, are symmetrically arranged at the centers of opposite sides of the horizontal panel 6, with the sliders 71 facing the same side and the pulleys 72 extending outward and beyond the horizontal plane;

[0059] The XY-axis two-dimensional displacement platform 8 is placed at the center of the horizontal panel 6, with the X-axis direction oriented in the same direction as the displacement slider 71 of the Z-axis lifting platform 7, and has an array of threaded holes on the top for connecting to the bottom of the three-dimensional force / torque sensor;

[0060] The calibration flange 9 is cylindrical, with the bottom and top of the cylinder being discs. The bottom disc has a threaded hole 91 for connecting to the top of the three-dimensional force / torque sensor. The cylinder has two upper and lower annular grooves 92 and 93, and the spacing between the annular grooves is fixed.

[0061] The principle of achieving three-dimensional force / torque calibration: the Z-axis pressure Fz is calibrated by directly stacking weights in the center of the three-dimensional force / torque sensor; when calibrating the X and Y axis torques, first install the calibration flange 9 on the upper part of the three-dimensional force / torque sensor, and then use a wire rope loop to transmit the force. The two rope loops surround and embed the upper annular groove 92 and the lower annular groove 93 of the calibration flange for positioning, and then respectively place them in the grooves of the grooved fixed pulleys 72 on the left and right Z-axis lifting platforms 7, hang weights at the end of the rope loop, and then adjust the Z-axis lifting platform to The height of the displacement slider 71 of 7 makes the loading force in a horizontal state, completing the loading of a pair of forces of equal magnitude and opposite direction on the three-dimensional force / torque sensor to form a couple, and the torque is the distance between the upper and lower grooves 92 and 93 of the calibration flange; by installation adjustment, the X-axis or Y-axis direction of the three-dimensional force / torque sensor is made to be the same as the direction of the slider 71 of the Z-axis lifting platform 7, so as to realize the calibration of the X-axis torque Mx or the Y-axis torque My. The complete calibration process is to first read the voltage zero position of the one-dimensional force sensor 11~14 in the no-load state, U0=[U 10 U 20 U 30 U 40 ]

[0062] Let the output voltage matrix of each one-dimensional unit be U, and the difference from zero be U', U=[U1 U2 U3 U4] U'=[U1'U2'U3'U4']=U-U0

[0063] Then, calculate the effective voltage information in each direction,

[0064] Finally, the final force in each direction is obtained by linear decoupling. The parameter h is the interdimensional coupling coefficient, such as h zx It represents the voltage coupling coefficient of the X-axis to the Z-axis, and so on.

[0065] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A combined three-dimensional force / torque sensor, characterized in that: It comprises a combined sensing area (1), a conductive flange (2), a top cover (3) and a base (4); The combined sensing area (1) is used to monitor force, and includes four one-dimensional force sensors of the same specification. The one-dimensional force sensors (11-14) are arranged in a square, fixed to the base (4) at the bottom, and connected to the conductive flange (2) at the top; The one-dimensional force sensor (11-14) is an S-type force sensor based on the resistance strain principle, with a mounting thread on the surface in the force measurement direction, and outputs an analog voltage signal, the voltage being linearly positively correlated with the force. The conductive flange (2) is used to conduct external force to the combined sensing area (1), reduce inter-dimensional coupling, and connect the combined sensing area (1) and the top cover (4); The conductive flange (2) is in the shape of a cross fan blade, with a cylindrical boss (21) with a threaded hole in the center, and four blades (22) with threaded holes extending outward at equal distances from the edge of the boss; The cylindrical boss (21) is connected to the top cover (4) through threaded engagement; The blade (22) is connected to the one-dimensional force sensor (11-14) through threaded engagement; The base (3) is used to fix the combined sensing area (1) and the bottom surface of the packaged sensor (11-14), and the upper surface of the base has four groups of square-arranged fixing bosses (31), the spacing between each group of bosses is the same as the thickness of the one-dimensional force sensor, and the center of each group of bosses has an assembly threaded hole (32); The top cover (4) is used to encapsulate the sensors (11-14) and is in the shape of a cylindrical cup with an opening at the bottom. The center of the top cover has a cylindrical recess (41) with a threaded hole for threaded engagement with the conductive flange. The side surface has four equidistant rectangular notches (42) for leading out signal lines and power lines of each one-dimensional force sensor.

2. The combined three-dimensional force / torque sensor according to claim 1, characterized in that: Its working principle is as follows: one-dimensional force sensors (11-14) are arranged in a square, and the measured forces are F1, F2, F3, and F4 respectively, where F1 and F2 are on opposite sides, and F3 and F4 are on opposite sides. A pair of forces on opposite sides constitutes a couple, and the difference between the two forces is multiplied by the lengths of the corresponding stress arms kx and ky to obtain the torque, thereby completing the measurement of the moments Mx and My in the X and Y directions using a differential method, and the sum of the forces on the four sensors is the force Fz in the Z direction:

3. A small calibration system constructed using the combined three-dimensional force / torque sensor according to claim 1, characterized in that: It includes a bottom bracket (5) and an upper functional area; The bottom bracket (5) has three fixed feet (51) and one longitudinal adjustment foot (52) at the bottom, which are in contact with the ground and can be adjusted for stability. The top bracket has five longitudinal movable columns (53), and the front ends of the columns are covered with free movable feet (54) for supporting the horizontal panel and adjusting the level. The upper functional area includes a horizontal panel (6), a pair of Z-axis lifting platforms (7), an XY-axis two-dimensional displacement platform (8), and a calibration flange (9). A three-dimensional force / torque sensor formed by assembling the combined sensing area (1), the conductive flange (2), the top cover (3), and the base (4) is placed between the calibration flange (9) and the XY-axis two-dimensional displacement platform (8); The horizontal panel (6) is a square plate placed above the bottom bracket, and has an array of threaded holes on its surface for assembling the various adjustment platforms; The Z-axis lifting platform (7) has a threaded hole at the bottom for connecting to the horizontal panel (6), and a displacement slider (71) on the side. A grooved fixed pulley (72) is placed on the slider for transmitting horizontal force to the vertical direction; The Z-axis lifting platforms (7), a pair of two in total, are symmetrically arranged at the centers of opposite sides of the horizontal panel (6), with the sliders (71) facing the same side and the pulleys (72) extending outward and beyond the horizontal plane; The XY axis two-dimensional displacement platform (8) is placed at the center of the horizontal panel (6), with the X axis direction oriented in the same direction as the displacement slider (71) of the Z axis lifting platform (7), and has a threaded hole array on the top for connecting to the bottom of the three-dimensional force / torque sensor; The calibration flange (9) is cylindrical, and the bottom and top of the cylinder are both discs. The bottom disc is provided with a threaded hole (91) for connecting with the top of the three-dimensional force / torque sensor. The cylinder is provided with two upper and lower annular grooves (92, 93), and the spacing between the annular grooves is fixed.

4. The small calibration system according to claim 3, characterized in that: The principle of achieving three-dimensional force / torque calibration is as follows: the Z-axis pressure Fz is calibrated by directly stacking weights at the center of the three-dimensional force / torque sensor; when calibrating the X-axis and Y-axis torques, a calibration flange (9) is first installed on the upper part of the three-dimensional force / torque sensor, and then a wire rope loop is used to transmit force. Two rope loops are respectively surrounded and embedded in the upper annular groove (92) and the lower annular groove (93) of the calibration flange for positioning, and then respectively placed in the grooves of the grooved fixed pulleys (72) on the left and right Z-axis lifting platforms (7), and weights are hung at the ends of the rope loops. Then, by adjusting the Z-axis lifting platform, the Z-axis lifting platform is adjusted. The height of the displacement slider (71) of (7) makes the loading force in a horizontal state, completing the loading of a pair of forces of equal magnitude and opposite direction on the three-dimensional force / torque sensor to form a couple, and the torque is the spacing between the upper and lower grooves (92, 93) of the calibration flange; by installation adjustment, the X-axis or Y-axis direction of the three-dimensional force / torque sensor is made the same as the direction of the slider (71) of the Z-axis lifting platform 7, realizing the calibration of the X-axis torque Mx or the Y-axis torque My. The complete calibration process is to first read the voltage zero position of the one-dimensional force sensor (11-14) in the no-load state, U0=[U 10 U 20 U 30 U 40 ] Let the output voltage matrix of each one-dimensional unit be U, and the difference from zero be U', U=[U1 U2 U3 U4] U'=[U1'U2'U3'U4']=U-U0 Then, calculate the effective voltage information in each direction, Finally, the final force in each direction is obtained by linear decoupling. The parameter h is the interdimensional coupling coefficient, such as h zx It represents the voltage coupling coefficient of X-axis to Z-axis, and so on;

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