High-precision six-dimensional force sensor

Abstract

The utility model relates to high accuracy six -dimensional force sensor, including integration elastomer base body, strain detection part and self -adaptation overload protection part, the integration elastomer base body includes intermediate cylindrical loading seat and peripheral annular fixed block, the outside of intermediate cylindrical loading seat and the inside of peripheral annular fixed block are connected with multiple deformation beams between, the self -adaptation overload protection part includes radial force self -adaptation buffer unit and axial force protection unit, the utility model discloses radial overload, disc spring and annular buffer piece graded trigger, axial overload, buffer column double -deck structure, namely silica gel micro -pressure, polyurethane medium -voltage, top and bottom piece high -voltage limit, all avoid deformation beam measurement area, do not disturb normal deformation, can bear radial overload, axial overload, and deformation beam breakage rate effectively reduces, and the service life is prolonged.

Description

Technical Field

[0001] This utility model relates to the field of force sensing and detection technology, and in particular to a high-precision six-dimensional force sensor. Background Technology

[0002] The six-dimensional torque sensor is a core component for intelligent robots to achieve force perception and compliant control. Its performance directly determines the robot's ability to complete complex and precise tasks, and it is widely used in industries such as industry, medicine, and aerospace.

[0003] Currently, in addition to the problems of large inter-dimensional coupling and difficulty in balancing sensitivity and strength, six-dimensional force sensors at home and abroad also have significant shortcomings in mechanical overload protection design. Most existing sensors adopt a single elastic limit post or rigid block design. For example, a simple polyurethane column can only achieve passive protection of "contact protection". When a robot collides with a radial or axial impact, it can easily bypass the existing protective structure and directly damage the deformation beam. It can also easily introduce additional stress interference, resulting in a decrease in measurement accuracy. Utility Model Content

[0004] This invention addresses the shortcomings of existing technologies by providing a high-precision six-dimensional force sensor. The specific technical solution is as follows:

[0005] A high-precision six-dimensional force sensor includes an integrated elastomer matrix, a strain detection unit, and an adaptive overload protection unit. The integrated elastomer matrix includes a central cylindrical loading seat and an outer annular fixing block. Multiple deformation beams are connected between the outer side of the central cylindrical loading seat and the inner side of the outer annular fixing block. The adaptive overload protection unit includes a radial force adaptive buffer unit and an axial force protection unit. The radial force adaptive buffer unit includes a radial buffer element and an annular buffer element fixedly connected to the outer side of the central cylindrical loading seat. One end of the radial buffer element is connected to the annular buffer element, and the other end of the annular buffer element extends radially to the inner side of the outer annular fixing block. The axial force protection unit includes a top block fixedly connected to the top of the central cylindrical loading seat and a bottom block fixedly connected to the bottom of the annular buffer element. A buffer column extending vertically is connected between the top block and the bottom block.

[0006] Preferably, the annular buffer is made of polyetheretherketone (PEEK), the radial buffer includes a slide rod, the inner side of the outer annular fixing block is provided with a sliding hole adapted to the slide rod, one end of the slide rod is fixed to the annular buffer, and the other end is fitted with a disc spring and inserted into the sliding hole.

[0007] Preferably, the central axis of the buffer column is parallel to the vertical axis of the sensor. The buffer column adopts a double-layer vulcanized structure, including an outer layer and an inner layer. The inner layer is a high-elasticity silicone column, and the outer layer is a polyurethane material sleeve. The top end of the buffer column is fixedly connected to the bottom of the top block, and the bottom end of the buffer column is fixedly connected to the top of the bottom block.

[0008] Preferably, both the radial force adaptive buffer unit and the axial force protection unit are provided in multiple sets and distributed on the outer periphery of the intermediate cylindrical loading seat.

[0009] Preferably, the deformation beam has four beams evenly distributed at 90° circumference along the central cylindrical loading seat. The deformation beam has a first through hole in the vertical direction and a second through hole in the width direction. The centers of the two holes intersect at the axis of the deformation beam. The upper and lower surfaces of the deformation beam have patch planes. The strain detection part includes strain gauges bonded to the patch planes.

[0010] Preferably, the intermediate cylindrical loading seat has a central hole at its center, and a plurality of threaded holes are provided around the central hole.

[0011] Preferably, it also includes a signal processing component, which includes a built-in integrated digital circuit board fixed in the annular groove of the peripheral annular fixing block. The digital circuit board integrates a 32-bit ARM microprocessor, a 16-bit A / D converter, and an EtherCAT communication interface.

[0012] The beneficial effects of this utility model are:

[0013] Under radial overload, the disc spring and the ring buffer trigger in stages; under axial overload, the buffer column has a double-layer structure, namely silicone micro-pressure, polyurethane medium pressure, and top and bottom high-pressure limit, all of which avoid the deformation beam measurement area and do not interfere with normal deformation. It can withstand radial and axial overloads, effectively reducing the deformation beam fracture rate and extending its service life. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0015] Figure 2 This is a schematic diagram of the buffer column in this utility model.

[0016] Reference numerals: 1. Central cylindrical loading seat; 100. Center hole; 101. Threaded hole; 2. Annular buffer; 3. Deformation beam; 31. First through hole; 32. Second through hole; 4. Outer annular fixing block; 5. Strain gauge; 6. Disc spring; 7. Sliding hole; 8. Sliding rod; 9. Top block; 11. Buffer column; 111. Outer layer; 112. Inner layer; 12. Bottom block. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0018] Example

[0019] Please refer to Figures 1-2 The high-precision six-dimensional force sensor adopts an integrated processing technology to reduce assembly errors and inter-dimensional coupling, while providing a carrier for strain detection and overload protection. The overall structure can be made of 40CrNiMoA alloy steel (tensile strength ≥1000MPa, yield strength ≥800MPa, elastic modulus 206GPa, ensuring high strength and high elastic recovery), and is integrally formed through five-axis linkage processing. The overall structure is "intermediate loading - peripheral fixing - deformation beam 3 connection", including the central cylindrical loading seat 1, the peripheral annular fixing block 4 and four deformation beams 3, which are adapted to the lightweight requirements of robot end effectors.

[0020] The intermediate cylindrical loading seat 1 is cylindrical, with the top used to connect the robot's end effector or the load being measured; a central hole 100 is opened in the center for passing through cables or positioning pins; four threaded holes 101 (M8-M12) are evenly opened around the central hole 100 in the circumferential direction, and the load and the loading seat are rigidly connected by high-strength bolts; an arc-shaped groove is machined on the outside of the loading seat for installing the annular buffer 2.

[0021] The outer ring-shaped fixing block 4 is ring-shaped and is used to fix the sensor to the robot base or worktable; four sliding holes 7 are machined circumferentially on the inner side of the fixing block for installing the sliding rod 8 of the radial buffer; an annular groove is opened on the top or side of the fixing block for embedding the digital circuit board of the signal processing component; eight mounting holes are evenly opened on the outer side of the fixing block to fix the sensor as a whole by bolts.

[0022] Among them, 34 deformation beams 3 are evenly distributed at 90° circumference along the middle loading seat (connecting the outer side of the loading seat and the inner side of the fixing block); a first through hole 31 is opened vertically along the deformation beam 3, and a second through hole 32 is opened along the width direction. The centers of the two holes intersect at the axis of the deformation beam 3. The through hole design can change the stress distribution of the deformation beam 3, so that the stress is concentrated on the patch plane (reducing interdimensional coupling, coupling error ≤0.8%); patch planes are machined on both the upper and lower surfaces of the deformation beam 3 for precise bonding of strain gauges 5; limiting bosses are machined on both sides of the deformation beam 3 as secondary protective contacts in case of radial overload.

[0023] The strain detection unit uses strain gauges 5 to form a Wheatstone bridge, which converts the minute deformation of the deformed beam 3 into an electrical signal to achieve high-precision measurement of six-dimensional force. The strain gauges 5 are BX120-3AA type metal foil strain gauges, and the upper and lower surfaces of each deformed beam 3 are precisely positioned along the patch plane. The strain gauges 5 are bonded with CY-121 type strain adhesive and coated with a 0.1mm thick silicone rubber moisture-proof layer after curing.

[0024] Multiple strain gauges (5) are arranged into multiple Wheatstone bridges according to the principle of "independent dimensions and mutual compensation," some of which are used to detect the axial force (F) along the X / Y / Z axes. x / Fᵧ / F_z), partly used to detect torque (M) about three axes. x / Mᵧ / M_z); for example, the force F in the X-axis direction. x When in operation, only the two sets of bridge output signals correspond to the X-axis direction, and the changes of other bridge signals are ≤0.5%, effectively reducing interdimensional coupling (overall coupling error ≤0.8%, while traditional sensors exceed 5%).

[0025] Specifically, the conductors of strain gauge 5 (0.08mm diameter copper core PTFE insulated wires) converge through the center hole 100 of the intermediate loading seat and connect to the digital circuit board of the signal processing component. The conductors are protected by 111 polyimide tubes to prevent signal interference and mechanical damage.

[0026] The adaptive overload protection section consists of a radial force adaptive buffer unit and an axial force protection unit, which realizes graded protection of "micro overload buffer - medium overload enhancement - large overload rigid limit" without interfering with normal measurement. The radial force adaptive buffer unit (protects X / Y axis radial force) and the annular buffer 2 are made of polyetheretherketone (PEEK) material and are annular (the inner diameter is adapted to the annular groove of the intermediate loading seat, and the outer diameter extends to the inner side of the outer fixing block). It can be embedded into the annular groove of the intermediate loading seat through interference fit and move radially synchronously with the loading seat.

[0027] Four sets of radial buffers are evenly distributed around the annular buffer 2. Each set includes a slide rod 8 and a disc spring 6. One end of the slide rod 8 is fixed to the annular buffer 2 by a thread, and the other end is fitted with a disc spring 6 and then inserted into the sliding hole 7 of the outer fixing block.

[0028] When the radial force of the X / Y axis is less than 120% of the rated load, the disc spring 6 only produces slight deformation, the annular buffer 2 does not contact the limiting boss of the deformation beam 3, no additional stress is introduced, and it does not interfere with normal measurement.

[0029] When 120%≤radial force≤150% of rated load, the compression of disc spring 6 increases to 0.5-1mm, and the annular buffer 2 moves radially with slide bar 8, gradually fitting the limiting bosses on both sides of deformation beam 3, and buffering overload through the elastic force of disc spring 6 (impact force attenuation 40%).

[0030] When the radial force is greater than 150% of the rated load, the disc spring 6 is fully compressed (compression amount 5mm), the annular buffer 2 is fully fitted with the limiting boss, and the rigid support of PEEK material restricts the deformation beam 3 from further deformation, preventing the deformation beam 3 from exceeding the yield limit (the fracture rate drops from 20% to below 0.5%).

[0031] The axial force protection unit (protecting the Z-axis axial force) includes a top block 9 and a bottom block, both made of 40Cr material. The top block 9 is fixed to the bottom of the intermediate loading seat by bolts (coaxial with the loading seat), and the bottom block is fixed to the top of the outer ring fixing block 4 by bolts (aligned vertically with the top block 9). Both are machined with stepped surfaces (for positioning the buffer column 11).

[0032] The buffer column 11 adopts a double-layer vulcanized structure (the outer layer 111 and the inner layer 112 are vulcanized in one piece without adhesive gaps). The outer layer 111 is a polyurethane material sleeve, and the inner layer 112 is a high-elasticity silicone column. The top of the buffer column 11 is fixed to the step surface of the top block 9 by interference fit, and the bottom is fixed to the step surface of the bottom block. The four sets of buffer columns 11 are evenly distributed in the circumference (staggered from the position of the deformation beam 3).

[0033] When the Z-axis axial force is less than 130% of the rated load, only the inner layer 112 silicone pillars are slightly compressed. The low stiffness of the silicone avoids interfering with the normal deformation of the deformation beam 3 (measurement error change ≤ 0.2%).

[0034] When 130%≤axial force≤160% of rated load, the inner 112 silicone column is fully compressed (compression amount 5mm), and the outer 111 polyurethane begins to bear force. The high stiffness of polyurethane enhances the buffering force (impact force is reduced by 60%).

[0035] When the axial force is greater than 160% of the rated load, the buffer column 11 is fully compressed, and the top block 9 is in direct contact with the bottom block (rigid limit), which limits the axial deformation of the deformation beam 3 to ≤0.2mm, ensuring that the deformation beam 3 does not exceed the yield limit (elastic recovery rate 100%).

[0036] The signal processing component converts the weak signal output by strain gauge 5 into a standard digital signal, enabling real-time, interference-resistant transmission. The digital circuit board uses FR-4 epoxy resin copper-clad board (size adapted to the annular groove of the peripheral fixing block), integrating core components. It employs a 32-bit ARM microprocessor (model STM32H743, main frequency 480MHz, supporting floating-point operations) for bridge signal acquisition and compensation algorithms (temperature compensation, nonlinear compensation, inter-dimensional decoupling); a 16-bit A / D converter (model AD7799, sampling rate 1kHz) converts the mV-level differential pressure signal output by the Wheatstone bridge into a digital signal; an EtherCAT communication interface (supporting 100Mbps rate, transmission delay ≤1ms) is also compatible with an RS485 interface (backup), allowing direct connection to industrial Ethernet or robot control systems.

[0037] It may also include a temperature sensor (model LM35) for real-time monitoring of the sensor's operating temperature (-20~80℃) and temperature drift compensation via a microprocessor.

[0038] The digital circuit board is coated with a waterproof layer, and the edges of the circuit board are fixed to the annular groove of the outer fixing block by potting compound (polyurethane material), achieving triple protection of waterproof, vibration-proof and heat conduction.

[0039] In summary, the load of this application is transmitted to the deformation beam 3 through the intermediate cylindrical loading seat 1. The X / Y / Z axial forces and moments cause the deformation beam 3 to undergo slight deformation, which in turn causes changes in the resistance of the surface strain gauges 5. The Wheatstone bridge composed of strain gauges 5 converts the resistance change into a mV-level differential pressure signal, which is then converted into a digital signal by a 16-bit A / D converter. A 32-bit ARM microprocessor executes a compensation algorithm (eliminating temperature, nonlinearity, and coupling errors). When the radial / axial force exceeds the rated load, the overload protection system is activated in stages (buffering-reinforcement-limiting) to limit the deformation of the deformation beam 3 within a safe range. When the limit is not exceeded, the protective structure does not interfere, ensuring measurement accuracy. The processed digital signal is transmitted to the robot controller in real time through the EtherCAT interface, providing data support for compliant control (such as assembly force feedback and surgical force control).

[0040] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A high-precision six-dimensional force sensor, characterized in that, It includes an integrated elastomer matrix, a strain detection unit and an adaptive overload protection unit. The integrated elastomer matrix includes a central cylindrical loading seat (1) and an outer annular fixing block (4). Multiple deformation beams (3) are connected between the outer side of the central cylindrical loading seat (1) and the inner side of the outer annular fixing block (4). The adaptive overload protection unit includes a radial force adaptive buffer unit and an axial force protection unit. The radial force adaptive buffer unit includes a radial buffer and an annular buffer (2) fixedly connected to the outside of the intermediate cylindrical loading seat (1). One end of the radial buffer is connected to the annular buffer (2), and the other end of the annular buffer (2) extends radially to the inner side of the outer annular fixing block (4). The axial force protection unit includes a top block (9) fixedly connected to the top of the intermediate cylindrical loading seat (1) and a bottom block (12) fixedly connected to the bottom of the annular buffer (2). A buffer column (11) extending vertically is connected between the top block (9) and the bottom block (12).

2. The high-precision six-dimensional force sensor according to claim 1, characterized in that: The annular buffer (2) is made of polyetheretherketone material. The radial buffer includes a slide rod (8). The inner side of the outer annular fixing block (4) is provided with a sliding hole (7) that is compatible with the slide rod (8). One end of the slide rod (8) is fixed to the annular buffer (2), and the other end is fitted with a disc spring (6) and inserted into the sliding hole (7).

3. The high-precision six-dimensional force sensor according to claim 2, characterized in that: The central axis of the buffer column (11) is parallel to the vertical direction of the sensor. The buffer column (11) adopts a double-layer vulcanized structure, including an outer layer (111) and an inner layer (112). The inner layer (112) is a high-elasticity silicone column, and the outer layer (111) is a polyurethane material sleeve. The top of the buffer column (11) is fixedly connected to the bottom of the top block (9), and the bottom of the buffer column (11) is fixedly connected to the top of the bottom block (12).

4. The high-precision six-dimensional force sensor according to claim 1, characterized in that: Both the radial force adaptive buffer unit and the axial force protection unit are provided in multiple sets and distributed on the outer periphery of the intermediate cylindrical loading seat (1).

5. The high-precision six-dimensional force sensor according to claim 1, characterized in that: The deformation beam (3) has four beams and is evenly distributed 90° around the central cylindrical loading seat (1). The deformation beam (3) has a first through hole (31) in the vertical direction and a second through hole (32) in the width direction. The centers of the two holes intersect at the axis of the deformation beam (3). The upper and lower surfaces of the deformation beam (3) have patch planes. The strain detection part includes strain gauges (5) bonded to the patch planes.

6. The high-precision six-dimensional force sensor according to claim 1, characterized in that: The intermediate cylindrical loading seat (1) has a central hole (100) at its center, and a plurality of threaded holes (101) are provided around the central hole (100).

7. The high-precision six-dimensional force sensor according to claim 1, characterized in that: It also includes a signal processing component, which includes a built-in integrated digital circuit board fixed in the annular groove of the peripheral annular fixing block (4). The digital circuit board integrates a 32-bit ARM microprocessor, a 16-bit A / D converter and an EtherCAT communication interface.

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