Robotic fingertip flexible self-resetting tactile sensing unit

Abstract

The application provides a robot fingertip flexible self-resetting tactile sensing unit, comprising a flexible contact cap and a mounting base, and further comprising: a composite elastic self-resetting mechanism arranged between the flexible contact cap and the mounting base, comprising a corrugated elastic fine adjustment unit and a super-elastic main reset unit; and a multi-dimensional magnetic sensing module; the application adopts a left-handed inner spiral elastomer and a right-handed outer spiral elastomer as the main reset elements in a coaxial nested mode, uses the super-elastic reversible phase change of a nickel-titanium shape memory alloy to realize zero hysteresis energy storage and release, and the axial restoring forces of the two are superimposed on each other and the torsional moments are offset, so that the upper structure is driven to accurately return to the initial zero position along a uniquely determined path; meanwhile, the corrugated elastic fine adjustment unit with lower overall stiffness provides micro-compliance through macro-thin-wall bending, absorbs lateral force disturbance and automatically compensates for assembly gaps, and forms a hierarchical cooperation with the super-elastic main reset unit, so that the fingertip flexible contact characteristics are retained and the reset accuracy is further improved.

Description

Technical Field

[0001] This invention relates to a flexible self-resetting tactile sensing unit for robot fingertips, belonging to the field of robot tactile sensing technology. Background Technology

[0002] Tactile perception is the core foundation for robots to achieve precise grasping, dexterous operation and safe human-robot interaction. The multi-dimensional force tactile sensing unit integrated into the robot's fingertips must have both flexible compliance and reliable self-resetting characteristics to accurately measure normal contact force and tangential friction force, and ensure the consistency of measurement signals and the effectiveness of decoupling models under long-term operation. Currently, non-contact magnetic tactile sensors based on permanent magnets and magnetic sensors have become the mainstream development direction due to their high sensitivity, good dynamic response, and ease of multidimensional decoupling. However, the self-resetting function of existing flexible magnetic tactile sensing units relies entirely on the elastic deformation recovery of flexible polymer materials such as silicone and rubber. The elastic recovery of polymer materials is essentially a viscoelastic behavior. During deformation, the frictional energy dissipation and irreversible slippage between molecular chains inevitably produce recovery hysteresis and residual deformation, resulting in zero-point drift with each loading and unloading. After cyclic loading, the accumulation of residual deformation causes the multidimensional force decoupling matrix to gradually fail. At the same time, long-term use of polymer materials will result in permanent deformation and aging, causing the sensor sensitivity to decrease year by year, requiring frequent calibration or even replacement. In addition, the complex deformation field inside the elastomer will cause the permanent magnet reset trajectory to be non-unique, exacerbating the coupling of signals on each axis. Existing improvement methods, such as replacing with high-hardness elastomers, applying mechanical preload, or digital compensation algorithms, have not broken away from the fundamental framework of relying on polymer viscoelastic reset. They can only delay the problem but cannot eliminate the root cause of drift and hysteresis from a physical perspective. To address the aforementioned technical challenges, a flexible self-resetting tactile sensing unit for robot fingertips is proposed. Summary of the Invention

[0003] In view of this, the present invention provides a flexible self-resetting tactile sensing unit for robot fingertips to solve or alleviate the technical problems existing in the prior art, and at least provides a beneficial alternative.

[0004] The technical solution of this invention is implemented as follows: a robot fingertip flexible self-resetting tactile sensing unit, including a flexible contact cap and a mounting base, further comprising: A composite elastic self-resetting mechanism is disposed between the flexible contact cap and the mounting base, including a corrugated elastic fine-tuning unit and a super-elastic main reset unit; The corrugated elastic fine-tuning unit is a rotary housing with corrugated sidewalls. The upper end of the rotary housing is fixedly connected to the flexible contact cap, and the lower end of the rotary housing is fixedly connected to a mounting bracket. The superelastic main reset unit includes a coaxially nested outer spiral elastomer and an inner spiral elastomer. The top ends of the outer spiral elastomer and the inner spiral elastomer are connected to the mounting bracket, and the bottom ends of the outer spiral elastomer and the inner spiral elastomer are connected to the mounting base. The multidimensional magnetic sensing module includes a permanent magnet mounted on the mounting frame and a triaxial magnetic sensor group mounted on the mounting base and located below the permanent magnet. A flexible encapsulation layer is wrapped around the composite elastic self-resetting mechanism and the multidimensional magnetic sensing module, and the bottom of the flexible encapsulation layer is fixedly connected to the mounting base.

[0005] More preferably, the longitudinal section of the sidewall of the rotating shell has continuous peaks and troughs extending in a closed circumferential direction, the wall thickness of the rotating shell is 0.1mm-0.5mm, and the rotating shell is made of liquid crystal polymer.

[0006] More preferably, the inner helical elastomer is left-handed and the outer helical elastomer is right-handed, and both the outer and inner helical elastomers are wound from nickel-titanium shape memory alloy wires.

[0007] Further preferably, the mounting bracket also includes a preload adjustment assembly, which includes a guide post and a locking nut. The guide post is fixedly connected to the top of the mounting base. The mounting bracket has a through hole at its center, through which the guide post passes. The locking nut is threaded onto one side of the through hole of the guide post.

[0008] More preferably, the permanent magnet is annular and axially magnetized; the triaxial magnetic sensor group consists of four triaxial Hall sensors symmetrically distributed in a cross shape, the center lines of the triaxial Hall sensors forming a square, and the center of the square coinciding with the axis of the permanent magnet.

[0009] More preferably, one side of both the mounting bracket and the mounting base is fixedly connected with a limiting member, which is four sets of ring-shaped limiting blocks, with four limiting blocks in each set.

[0010] More preferably, the flexible contact cap is made of medical-grade silicone, and the outer surface of the flexible contact cap is provided with microstructure textures to increase the coefficient of friction.

[0011] More preferably, the flexible encapsulation layer is integrally cast from silicone rubber, and the flexible encapsulation layer is sealed to the mounting base.

[0012] Further preferably, it also includes a signal processing module, which is electrically connected to four triaxial Hall sensors. The signal processing module stores a six-dimensional force-magnetic field mapping model that has been established in advance through calibration experiments, which is used to calculate the normal force, tangential force and torque in real time.

[0013] More preferably, the overall stiffness of the corrugated elastic fine-tuning unit is less than the overall stiffness of the hyperelastic main reset unit.

[0014] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: This invention employs coaxially nested left-handed inner helical elastomers and right-handed outer helical elastomers as the main reset elements. It utilizes the hyperelastic reversible phase transition of nickel-titanium shape memory alloys to achieve zero-hysteresis energy storage and release. Furthermore, the axial restoring forces of both elements are superimposed, and their torsional moments cancel each other out, driving the upper structure to precisely return to its initial zero position along a uniquely determined path. This eliminates restoring hysteresis and residual deformation at the source, ensuring the long-term effectiveness of the multidimensional force decoupling matrix. Simultaneously, a corrugated elastic fine-tuning unit with lower overall stiffness provides microscopic compliance through macroscopic thin-wall bending, absorbing lateral force disturbances and automatically compensating for assembly gaps. This forms a hierarchical synergy with the hyperelastic main reset unit, further improving reset accuracy while retaining the fingertip flexible contact characteristics. In addition, the continuously adjustable preload design can adapt to different ranges and sensitivity requirements. Four sets of ring-shaped limiting components provide all-around overload protection, and the flexible encapsulation layer only serves an environmental protection function and does not participate in the reset process, further improving the long-term stability and service life of the sensing unit and significantly reducing subsequent calibration and maintenance costs. This invention is suitable for various complex application scenarios such as precision grasping in industrial robots and safe human-machine interaction.

[0015] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a structural diagram of the present invention; Figure 2 This is a structural diagram of the flexible contact cap in this invention; Figure 3This is an exploded structural diagram of the present invention; Figure 4 This is a bottom view of the mounting bracket in this invention; Figure 5 This is a cross-sectional view of the present invention; Figure 6 This is a structural diagram of the mounting base in this invention.

[0018] Reference numerals: 11. Flexible contact cap; 12. Mounting base; 13. Flexible encapsulation layer; 14. Signal processing module; 15. Triaxial Hall sensor; 16. Limiting component; 17. Outer helical elastomer; 18. Inner helical elastomer; 19. Guide post; 21. Mounting bracket; 22. Locking nut; 23. Rotating housing; 24. Permanent magnet. Detailed Implementation

[0019] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0020] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] like Figure 1-6 As shown, this embodiment of the invention provides a flexible self-resetting tactile sensing unit for robot fingertips, which relates to the specific application of the flexible self-resetting tactile sensing unit for robot fingertips in the field of 3C electronics manufacturing, especially suitable for the precision gripping, handling and assembly process of ultra-thin tempered glass cover plates for mobile phones with a thickness of 0.3mm-0.5mm; the flexible magnetic tactile sensors used in the prior art for this scenario generally have a recovery hysteresis of 3%-8% due to their reliance on the viscoelastic reset of polymer materials, and the zero-point drift reaches 4%FS after every 500 cycles of loading, requiring daily manual calibration, which seriously affects the continuous production efficiency of the production line; at the same time, lateral force disturbances can easily cause the permanent magnet 24 to deviate from its reset trajectory, resulting in a tangential force decoupling error of more than ±0.05N, causing the glass edge to chip or break, making it difficult to improve the yield rate. It is composed of a flexible contact cap 11, a mounting base 12, a composite elastic self-resetting mechanism, a multi-dimensional magnetic sensing module, a flexible encapsulation layer 13, a pre-tightening force adjustment component, an overload protection limit structure and a signal processing module 14.

[0022] A composite elastic self-resetting mechanism is disposed between the flexible contact cap 11 and the mounting base 12, including a corrugated elastic fine-tuning unit and a super-elastic main reset unit; the corrugated elastic fine-tuning unit is a rotating shell 23 with corrugated sidewalls, the upper end of the rotating shell 23 is bonded and fixed to the flexible contact cap 11, and the lower end of the rotating shell 23 is fixed to the mounting frame 21 by laser welding; the super-elastic main reset unit includes a coaxially nested outer spiral elastomer 17 and an inner spiral elastomer 18, the top ends of the outer spiral elastomer 17 and the inner spiral elastomer 18 are fixed to the mounting frame 21 by spot welding, and the bottom ends of the outer spiral elastomer 17 and the inner spiral elastomer 18 are fixed to the mounting base 12 by spot welding; The flexible contact cap 11 is made of medical-grade silicone, and its outer surface has microstructure textures to increase the coefficient of friction. The flexible contact cap 11 directly contacts external objects; its flexible material ensures conformity during contact, preventing damage to the grasped object. The microstructure textures on its outer surface enhance friction during grasping, preventing the object from slipping. The flexible contact cap 11 only serves as a force transmission and contact interface and does not participate in the self-resetting process. The longitudinal section of the sidewall of the rotating housing 23 has continuous peaks and troughs extending circumferentially. The wall thickness of the rotating housing 23 is 0.1mm-0.5mm, and the rotating housing 23 is made of liquid crystal polymer. The overall stiffness of the corrugated elastic fine-tuning unit is less than that of the superelastic main reset unit; the rotating shell 23 provides initial microscopic compliance through the elastic bending deformation of its thin-walled structure, which can absorb the small disturbances caused by the lateral force component, and automatically eliminate the assembly gaps between the components. During unloading, the elastic bending potential energy accumulated by the rotating shell 23 can provide auxiliary restoring force, further improving the reset accuracy; the mounting bracket 21 has a through hole in the center, and the permanent magnet 24 is embedded in the annular groove inside the mounting bracket 21 through an interference fit. The permanent magnet 24 is annular and axially magnetized; the mounting bracket 21 serves as an intermediate connecting component, On the one hand, it transmits the external force received by the flexible contact cap 11 to the superelastic main reset unit; on the other hand, it provides a stable mounting carrier for the permanent magnet 24, ensuring that the permanent magnet 24 can synchronously generate displacement and rotation with the upper structure. The outer helical elastomer 17 is right-handed, and the inner helical elastomer 18 is left-handed. Both the outer helical elastomer 17 and the inner helical elastomer 18 are wound from nickel-titanium shape memory alloy wire. The outer helical elastomer 17 and the inner helical elastomer 18 together constitute the superelastic main reset unit, utilizing the superelastic reversible phase transition characteristics of nickel-titanium shape memory alloy to achieve energy storage and release. The combination of left-handed and right-handed design ensures that both can deform under stress. The generated torsional moments cancel each other out, while the axial restoring forces are superimposed, which can drive the upper structure to accurately return to the initial zero position along a uniquely determined path, eliminating the restoring hysteresis and residual deformation from the root. In this embodiment, two coaxially nested helical elastomers are used as the superelastic main reset unit. In other embodiments, a single helical elastomer or three or more coaxially nested helical elastomers can also be used according to actual needs, as long as sufficient restoring force can be provided and the reset accuracy can be guaranteed. In addition to liquid crystal polymer, the rotating shell 23 can also be made of other materials with high elastic modulus and low hysteresis characteristics, such as high elasticity stainless steel. The preload adjustment assembly includes a guide post 19 and a locking nut 22. The guide post 19 is fixedly connected to the top of the mounting base 12 and passes through a through hole in the center of the mounting bracket 21. The locking nut 22 is threaded onto one side of the through hole of the guide post 19, and the diameter of the through hole is larger than the outer diameter of the guide post 19. The guide post 19 provides radial guidance for the movement of the mounting bracket 21, preventing the mounting bracket 21 from swaying during movement. By rotating the locking nut 22, the outer helical elastomer 17 and the inner helical elastomer 18 can be compressed simultaneously to achieve continuous adjustment of the preload, thereby eliminating the initial assembly gap and allowing adjustment of the measurement range and sensitivity of the sensing unit according to different application scenarios. The multidimensional magnetic sensing module includes four triaxial Hall sensors 15 symmetrically distributed in a cross shape. The triaxial Hall sensors 15 are fixedly mounted on the upper surface of the mounting base 12 and located directly below the permanent magnet 24. The centers of the three-axis Hall sensors 15 are connected to form a square, and the center of the square coincides with the axis of the permanent magnet 24. When the permanent magnet 24 moves with the mounting frame 21, it will cause changes in the distribution of the magnetic field in the surrounding space. The four three-axis Hall sensors 15 can collect the changes in magnetic field intensity in three-dimensional directions in real time, and improve the measurement accuracy through differential measurement, providing raw data for the calculation of six-dimensional force. The four three-axis Hall sensors 15 respectively collect the three-dimensional magnetic field components generated by the permanent magnet 24 at four different positions. When the permanent magnet 24 undergoes normal displacement, tangential displacement or torsion, the magnetic field signals of the four sensors will produce differential changes. The signal processing module 14 performs differential calculation and decoupling processing on the 12 raw signals of the four sensors through a pre-calibrated six-dimensional force and magnetic field mapping model, and finally obtains the normal force applied to the fingertip, the tangential force in two orthogonal directions, and the torque in three directions. The overload protection limiting structure consists of limiting elements 16, which are fixedly connected to the lower end face of the mounting bracket 21 and the upper end face of the mounting base 12. Each limiting element 16 comprises four sets of annularly distributed limiting blocks, with four blocks in each set. The four sets of limiting elements 16 are evenly distributed along the circumference. When the external force exceeds the rated range of the sensing unit, the limiting blocks on the mounting bracket 21 will contact the corresponding limiting blocks on the mounting base 12, limiting further displacement of the mounting bracket 21. This prevents damage to the outer spiral elastomer 17 and the inner spiral elastomer 18 due to excessive deformation, achieving comprehensive overload protection. Simultaneously, the limiting elements 16 provide limiting for the outer spiral elastomer 17 and the inner spiral elastomer 18. The flexible encapsulation layer 13 is composed of… The silicone rubber is integrally cast and molded, encapsulating the composite elastic self-resetting mechanism and the multi-dimensional magnetic sensing module. The bottom of the flexible encapsulation layer 13 is bonded and fixed to the mounting base 12 to achieve a sealed connection. The upper end face of the flexible encapsulation layer 13 is flush with the lower end face of the flexible contact cap 11 and bonded together. The flexible encapsulation layer 13 can prevent dust, moisture and other external pollutants from entering the sensing unit, ensuring the normal operation of the internal electronic components and mechanical structure. The flexible encapsulation layer 13 only serves the purpose of environmental protection and conforming to the shape, and does not provide any self-resetting force. The signal processing module 14 is installed in the internal cavity of the mounting base 12 and is electrically connected to four triaxial Hall sensors 15 through wires. The signal processing module 14 contains internal storage. It stores a six-dimensional force-magnetic field mapping model pre-established through calibration experiments. The six-dimensional force-magnetic field mapping model is established in the form of a linear decoupling matrix, and its establishment process is as follows: First, the sensing unit is fixed on the six-dimensional force calibration platform, and normal forces Fx, Fy, and Fz of known magnitude and torques Mx, My, and Mz in three directions are applied sequentially, covering the full range of the sensing unit; at each calibration load point, 12 raw magnetic field signals output by four triaxial Hall sensors 15 are simultaneously acquired, and zero-point calibration and filtering are performed on each signal to obtain the magnetic field feature vector under the corresponding load; the linear mapping relationship between the magnetic field feature vector and the six-dimensional force load is fitted by the least squares method to construct a 6×12-dimensional decoupling matrix. The matrix is ​​a six-dimensional force-magnetic field mapping model. In practical work, the signal processing module 14 substitutes the 12 magnetic field signals collected in real time into the decoupling matrix and obtains the six-dimensional force information applied to the fingertip through matrix operations. For small-range, high-precision application scenarios, a quadratic correction term can be superimposed on the above linear model to compensate for the nonlinear error of the magnetic field distribution and further improve the calculation accuracy. The signal processing module 14 receives the electrical signals output by four triaxial Hall sensors 15. After filtering, amplification and other preprocessing, it calls the pre-stored six-dimensional force-magnetic field mapping model to calculate the normal force, the tangential force in two orthogonal directions and the torque in three directions applied to the fingertip in real time, and outputs the calculation results to the robot control system. This embodiment completely decouples the flexible contact function from the self-resetting function. The flexible contact cap 11 and the flexible encapsulation layer 13 only provide contact compliance and environmental protection. All reset forces are provided by a non-viscoelastic composite elastic self-resetting mechanism, which fundamentally avoids the zero-point drift and residual deformation problems caused by the viscoelasticity of polymer materials. At the same time, through the stiffness hierarchy design, small lateral disturbances are preferentially absorbed by the low-stiffness corrugated elastic fine-tuning unit, while the main reset action with large displacement is completed by the high-stiffness hyperelastic main reset unit, thus achieving a unity of flexible compliance and precise reset.

[0023] The assembly steps of this embodiment are as follows: First, the guide post 19, the triaxial Hall sensor 15, and the limiting member 16 are fixed on the mounting base 12; then, the bottom ends of the outer helical elastomer 17 and the inner helical elastomer 18 are welded to the mounting base 12; next, the permanent magnet 24 is inserted into the annular groove inside the mounting frame 21 through an interference fit, the mounting frame 21 is fitted onto the guide post 19, and the top ends of the two helical elastomers are spot welded to the mounting frame 21; then, the locking nut 22 is installed and adjusted to a suitable preload; then, the rotating housing 23 is welded to the mounting frame 21, and the flexible contact cap 11 is bonded to the upper end of the rotating housing 23; finally, silicone rubber is poured into the exterior of the internal mechanism to form a flexible encapsulation layer 13, and the signal processing module 14 is installed inside the mounting base 12.

[0024] The specific structure and parameter configuration of each component in this embodiment are as follows: Flexible contact cap 11: Made of medical-grade silicone with a Shore hardness of 30A, it is integrally molded into a cylindrical shape with a diameter of 8mm and a height of 3mm. Its outer surface is laser-engraved with a diamond-shaped microstructure texture with a depth of 0.05mm and a spacing of 0.1mm, which increases the coefficient of friction of the contact surface to 0.85. The edges of the contact cap are rounded with an R0.5mm corner to avoid scratching the surface of the glass cover during gripping. Flexible contact cap 11 only undertakes the functions of force transmission and contact interface, and does not participate in the self-resetting process. Corrugated elastic fine-tuning unit: The rotating housing 23 is injection molded from liquid crystal polymer LCP-E471i with a wall thickness of 0.2mm; its sidewall longitudinal section has three continuous peaks and two continuous troughs extending in a closed circumferential direction, with a peak height of 1.2mm and a trough depth of 0.8mm; the overall stiffness of the rotating housing 23 is 0.05N / μm, which can absorb lateral force disturbances within a range of ±0.3mm and automatically compensate for component assembly gaps of ±0.1mm; the upper end of the rotating housing 23 is bonded to the flexible contact cap 11 with medical-grade silicone, and the lower end is fixed to the mounting bracket 21 by laser welding; The superelastic main reset unit includes a coaxially nested outer helical elastomer 17 and an inner helical elastomer 18, both of which are wound from nickel-titanium shape memory alloy wire with an atomic ratio of 55.8 at%, and the wire diameter is 0.3 mm. The outer helical elastomer 17 has a right-handed structure, an inner diameter of 6 mm, an outer diameter of 8 mm, and 8 effective turns. The inner helical elastomer 18 has a left-handed structure, an inner diameter of 3 mm, an outer diameter of 5 mm, and 8 effective turns. After being coaxially nested, the total axial stiffness is 0.2 N / μm, and the torsional torque mutual cancellation rate is ≥99.5%. The top ends of the outer helical elastomer 17 and the inner helical elastomer 18 are fixed to the mounting bracket 21 by spot welding, and the bottom ends are fixed to the mounting base 12 by spot welding. Multidimensional magnetic sensing module: The permanent magnet 24 is an N52 neodymium iron boron ring magnet with an outer diameter of 4mm, an inner diameter of 2mm, and a height of 1.5mm. It adopts axial magnetization and the magnetic field strength at the center of the surface is 120mT. The permanent magnet 24 is embedded in the annular groove inside the mounting bracket 21 through interference fit. The triaxial magnetic sensor group consists of four triaxial Hall sensors 15 symmetrically distributed in a cross shape, using MLX90393 chips. The center line of the four sensors forms a square with a side length of 3mm, and the center of the square coincides with the axis of the permanent magnet 24. The sampling frequency of the triaxial Hall sensor 15 is set to 1kHz. The signal processing module 14 has a built-in 16-bit high-precision ADC with a calculation delay of ≤1ms. It internally stores a six-dimensional force and magnetic field mapping model pre-established through a six-dimensional force calibration platform. Preload adjustment assembly: includes guide post 19 and locking nut 22. Guide post 19 is fixedly connected to the top center of mounting base 12. The center of mounting bracket 21 has a through hole with a diameter larger than the outer diameter of guide post 19. Guide post 19 passes through the through hole. Locking nut 22 is threaded onto the upper end of guide post 19. In this embodiment, the preload of the superelastic main reset unit is adjusted to 2N by rotating locking nut 22 to eliminate the initial assembly gap and stabilize the initial zero point of the sensing unit. Limiting component 16: It is fixedly connected to the lower end face of the mounting bracket 21 and the upper end face of the mounting base 12 respectively. It consists of four sets of evenly distributed ring-shaped limiting blocks, with four limiting blocks in each set. In this embodiment, the initial gap between the upper and lower limiting blocks is set to 0.8mm, which corresponds to the maximum normal vector distance of the sensing unit being 5N, the maximum tangential vector distance being 2N, and the overload protection triggering force being 5.5N. Flexible encapsulation layer 13: Made of silicone rubber with a Shore hardness of 40A, integrally cast in a vacuum environment, with a thickness of 0.5mm; its bottom is bonded and fixed to the mounting base 12 with UV adhesive to achieve a sealed connection, and its upper end face is flush with the lower end face of the flexible contact cap 11 and bonded together; the flexible encapsulation layer 13 has a protection level of IP65, which can adapt to the dust and small amount of cutting fluid environment of 3C electronic production line, and only serves the purpose of environmental protection and flexible shape, without providing any self-resetting and restoring force.

[0025] The production line installation and integration method of this embodiment is as follows: Two of the above-mentioned sensing units are installed in pairs at the ends of the two parallel grippers of the ABBIRB1200 industrial robot. The mounting base 12 is fixed in the mounting holes of the gripper finger seats by four M2.5 countersunk screws. The top of the flexible contact cap 11 protrudes 0.3mm from the gripper gripping surface to ensure that the sensing unit contacts the glass cover surface first during the gripping process. The signal processing module 14 of the two sensing units establishes a communication connection with the robot controller through the CAN bus to transmit the calculated six-dimensional force data in real time.

[0026] The specific working process of this embodiment is as follows: Approach and contact detection phase: The robot drives the gripper to move towards the glass cover to be gripped at a speed of 50 mm / s. When the flexible contact cap 11 contacts the glass surface, the corrugated elastic micro-adjustment unit with low stiffness first undergoes elastic bending deformation to absorb the contact impact energy. When the normal force calculated by the signal processing module 14 reaches 0.05 N, it immediately sends a contact detection signal to the robot controller. The robot then reduces the closing speed of the gripper to 5 mm / s to avoid the impact causing the glass to shatter. In the closed-loop control stage of gripping force: the gripper continues to close slowly, and the external force is transmitted to the mounting frame 21 through the rotating housing 23, which drives the superelastic main reset unit to generate axial compression deformation. The permanent magnet 24 moves downward along the guide column 19 with the mounting frame 21, causing changes in the magnetic field distribution in the surrounding space. Four triaxial Hall sensors 15 collect the three-dimensional magnetic field intensity changes in real time and transmit them to the signal processing module 14. The signal processing module 14 calls the pre-stored six-dimensional force and magnetic field mapping model to calculate the normal force currently applied to the fingertip in real time. When the normal force reaches the preset 0.8N, the robot controller immediately stops the gripper's closing action and maintains the gripping force for subsequent handling operations. Disturbance compensation stage during handling: During the handling of the glass cover, if the glass cover tends to slide laterally due to robot movement vibration or inertia, when the tangential force exceeds 0.1N, the signal processing module 14 will feed back the real-time calculated tangential force data to the robot controller. The controller will automatically fine-tune the clamping force of the gripper to 1.0N to prevent the glass cover from slipping. Placement and precise reset stage: After the robot precisely places the glass cover plate into the positioning fixture, the grippers open, and the external force applied to the flexible contact cap 11 is removed; at this time, the outer spiral elastomer 17 and the inner spiral elastomer 18 release the hyperelastic energy stored during deformation, and their axial restoring forces are superimposed, while their torsional torques cancel each other out, driving the mounting bracket 21 to return to the initial zero position along the guide post 19 vertically upward along a uniquely determined path; simultaneously, the corrugated elastic fine-tuning unit releases elastic bending potential energy, providing auxiliary restoring force and eliminating residual assembly gaps; the entire reset process takes ≤5ms, and the reset position accuracy is ≤±1μm; Overload protection phase: If the gripper closes excessively due to robot motion error or fixture positioning deviation, when the normal force applied to the fingertip reaches 5.5N, the limiting block on the lower end face of the mounting bracket 21 contacts the corresponding limiting block on the upper end face of the mounting base 12, limiting the further displacement of the mounting bracket 21 and preventing the nickel-titanium shape memory alloy helical elastomer from plastic damage due to excessive deformation; at the same time, the signal processing module 14 sends an emergency stop signal to the robot controller to protect the glass cover and sensing unit from damage.

[0027] After continuous operation testing on the production line, the sensing unit provided in this embodiment has the following excellent performance: recovery hysteresis rate ≤0.3%, far lower than the 8%-12% of existing silicone reset sensors; after 1 million cycles of loading, zero-point drift ≤0.15%FS, requiring no manual calibration in the middle; six-dimensional force decoupling accuracy reaches normal force ±0.02N, tangential force ±0.01N, and torque ±0.005N・m; glass cover plate gripping success rate ≥99.9%, and breakage rate reduced from 0.8% of the original technology to 0.02%; mean time between failures ≥15,000 hours, and subsequent maintenance costs reduced by 85%.

[0028] It should be noted that the parameter configuration of this embodiment can be adaptively adjusted according to glass cover plates of different thicknesses: for ultra-thin glass with a thickness of 0.3mm, the preload of the super-elastic main reset unit can be reduced to 1.5N, and the maximum normal vector distance can be adjusted to 4N; for glass cover plates with a thickness of 1.0mm, the diameter of the nickel-titanium shape memory alloy wire can be increased to 0.4mm, and the maximum normal vector distance can be increased to 8N; the technical solution of this embodiment is also applicable to application scenarios with extremely high requirements for contact force control precision, such as semiconductor wafer handling, precision ceramic component assembly, and optical lens assembly.

[0029] In one embodiment, the material of the rotating housing 23 is replaced by liquid crystal polymer with high-elasticity stainless steel to improve its fatigue strength and impact resistance, making it suitable for high-frequency, high-load precision gripping scenarios of industrial robots, while maintaining the original microscopic compliance and gap compensation functions.

[0030] In one embodiment, four triaxial Hall sensors 15 are replaced with six triaxial magnetic sensors, which are symmetrically distributed in a regular hexagon on the upper surface of the mounting base 12. This increases the number of sampling points for magnetic field measurement, improves the analytical accuracy of the spatial magnetic field distribution, and further reduces the coupling error of the six-dimensional force calculation.

[0031] In one embodiment, a single nickel-titanium shape memory alloy wire is continuously wound to form a double-layer coaxial helical structure, replacing the independent outer helical elastomer 17 and inner helical elastomer 18, reducing the number of parts and assembly steps, while retaining the core reset characteristics of superimposed axial restoring force and offset torsional torque.

[0032] In one embodiment, a temperature sensor is added to the upper surface of the mounting base 12 and electrically connected to the signal processing module 14. The signal processing module 14 has a built-in temperature compensation algorithm to correct the influence of ambient temperature changes on the superelastic properties of the nickel-titanium shape memory alloy and the output characteristics of the Hall sensor in real time, thereby expanding the operating temperature range of the sensing unit.

[0033] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flexible self-resetting tactile sensing unit for robot fingertips, comprising a flexible contact cap (11) and a mounting base (12), characterized in that, Also includes: A composite elastic self-resetting mechanism is provided between the flexible contact cap (11) and the mounting base (12), including a corrugated elastic fine-tuning unit and a super-elastic main reset unit; The corrugated elastic fine-tuning unit is a rotating housing (23) with corrugated sidewalls. The upper end of the rotating housing (23) is fixedly connected to the flexible contact cap (11), and the lower end of the rotating housing (23) is fixedly connected to the mounting bracket (21). The superelastic main reset unit includes a coaxially nested outer spiral elastomer (17) and an inner spiral elastomer (18). The top ends of the outer spiral elastomer (17) and the inner spiral elastomer (18) are connected to the mounting bracket (21), and the bottom ends of the outer spiral elastomer (17) and the inner spiral elastomer (18) are connected to the mounting base (12). The multidimensional magnetic sensing module includes a permanent magnet (24) mounted on the mounting frame (21) and a triaxial magnetic sensor group mounted on the mounting base (12) and located below the permanent magnet (24); A flexible encapsulation layer (13) is wrapped around the composite elastic self-resetting mechanism and the multidimensional magnetic sensing module. The bottom of the flexible encapsulation layer (13) is fixedly connected to the mounting base (12).

2. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: The sidewall longitudinal section of the rotating shell (23) has continuous peaks and troughs extending in a closed circumferential direction. The wall thickness of the rotating shell (23) is 0.1mm-0.5mm. The rotating shell (23) is made of liquid crystal polymer.

3. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: The inner helical elastomer (18) is left-handed, and the outer helical elastomer (17) is right-handed. Both the outer helical elastomer (17) and the inner helical elastomer (18) are wound from nickel-titanium shape memory alloy wire.

4. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: It also includes a preload adjustment assembly, which includes a guide post (19) and a locking nut (22). The guide post (19) is fixedly connected to the top of the mounting base (12). The mounting bracket (21) has a through hole in the center. The guide post (19) passes through the through hole. The locking nut (22) is threaded onto one side of the through hole of the guide post (19).

5. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: The permanent magnet (24) is ring-shaped and axially magnetized; the triaxial magnetic sensor group consists of four triaxial Hall sensors (15) symmetrically distributed in a cross shape, and the center line of the triaxial Hall sensors (15) forms a square, the center of the square coincides with the axis of the permanent magnet (24).

6. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: Both the mounting bracket (21) and the mounting base (12) are fixedly connected to one side of a limiting member (16). The limiting member (16) consists of four sets of ring-shaped limiting blocks, with four limiting blocks in each set.

7. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: The flexible contact cap (11) is made of medical-grade silicone, and the outer surface of the flexible contact cap (11) is provided with microstructure textures to increase the coefficient of friction.

8. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: The flexible encapsulation layer (13) is integrally cast from silicone rubber, and the flexible encapsulation layer (13) is sealed to the mounting base (12).

9. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: It also includes a signal processing module (14), which is electrically connected to four triaxial Hall sensors (15). The signal processing module (14) stores a six-dimensional force and magnetic field mapping model that has been established in advance through calibration experiments, which is used to calculate the normal force, tangential force and torque in real time.

10. The robot fingertip flexible self-resetting tactile sensing unit according to claim 1, characterized in that: The overall stiffness of the corrugated elastic fine-tuning unit is less than that of the hyperelastic main reset unit.

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