A force / torque sensor

Abstract

The application provides a force / torque sensor and relates to the technical field of sensors.The photoelectric integrated chip integrates a light emitting unit and a plurality of light detecting units on the same chip, eliminates the light path alignment requirement of discrete optical elements, and significantly improves the integration degree of the sensor; the load conversion element enhances the deformation difference caused by mechanical loads of different dimensions through the specific structure, and provides a physical basis for accurate decoupling of the mechanical loads; the signal processing module processes the electric signals based on a calibration decoupling model, and can accurately calculate the mechanical load components; so that the application realizes the high integration of the sensor structure while maintaining high measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more particularly to a force / torque sensor and a sensing method. Background Technology

[0002] Six-axis force / torque sensors are sensors capable of simultaneously measuring three-dimensional forces (Fx, Fy, Fz) and three-dimensional torques (Mx, My, Mz), and are widely used in robotics, medical devices, wearable devices, and other fields. While there are numerous existing technologies for six-axis force / torque sensors, several common problems remain. Resistive and capacitive sensors have mature manufacturing processes and wide measurement ranges, exhibiting strong engineering applicability under high stiffness, heavy loads, and long-term operation conditions. However, they are susceptible to electromagnetic interference and may experience creep, hysteresis, fatigue, or temperature drift during long-term use. In miniaturization scenarios, limitations in strain gauge size, patch space, small capacitance readout, and signal-to-noise ratio requirements significantly increase manufacturing difficulty and performance consistency. Magnetic sensors are still in a relatively early stage of development; external magnetic field interference, temperature drift, nonlinearity, and hysteresis control are also significant factors limiting their engineering applications.

[0003] Optical solutions offer advantages such as strong resistance to electromagnetic interference, good insulation, and suitability for long-distance signal transmission, demonstrating unique value in minimally invasive surgery and high electromagnetic noise environments. However, current mainstream optical solutions typically require strict optical path alignment, packaging stability, and dedicated demodulation equipment, resulting in higher device and system integration costs. Optical links also have high requirements for mechanical tolerances and long-term stability, making further miniaturization difficult and limiting their widespread application in robotic fingertips, flexible end effectors, and wearable haptic devices.

[0004] Furthermore, six-axis force / torque measurement inherently suffers from problems such as multi-channel coupling, nonlinearity, crosstalk, and complex calibration. Even in recent years, in the research of strain gauge and optical six-axis sensors, structural decoupling, low crosstalk, temperature drift compensation, and miniaturization remain the focus of continuous optimization, indicating that a universal solution that simultaneously achieves high integration, simple structure, miniaturization, and high-precision six-axis decoupling has not yet been formed. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is: how to provide a highly integrated and decoupling-accurate six-axis force / torque sensor to solve the problems of low integration, complex optical path alignment, difficulty in miniaturization and insufficient decoupling accuracy of existing six-axis force / torque sensors.

[0006] On one hand, the present invention provides a force / torque sensor, comprising: an optoelectronic integrated chip including at least one light-emitting unit and multiple light-detecting units; a load conversion element disposed on the surface of the optoelectronic integrated chip for receiving external mechanical loads and generating deformation, the structure of the load conversion element being configured to enhance the difference in deformation caused by mechanical loads of different dimensions; and a signal processing module communicatively connected to the light-detecting units; wherein the light-emitting unit is used to emit probe light to the load conversion element; the load conversion element is used to modulate the probe light through its deformation to generate an optical response change and obtain an optical modulation signal; the multiple light-detecting units are used to receive the optical modulation signal and convert the optical modulation signal into an electrical signal; and the signal processing module is used to receive the electrical signal and calculate the mechanical load components based on a pre-trained calibration decoupling model, the mechanical load components including three-dimensional forces Fx, Fy, Fz and three-dimensional torques Mx, My, Mz along the X-axis, Y-axis, and Z-axis.

[0007] Optionally, the load transfer element has an asymmetric structure.

[0008] Optionally, the load transfer element is an asymmetric elastomer or an asymmetric reflective layer.

[0009] Optionally, the asymmetric elastomer is one of the following: a flexible block structure with a preset tilt angle, an elastomer with microstructures on its surface, or an elastomer with asymmetric boundary conditions.

[0010] Optionally, the light-emitting unit and the light-detecting unit are isomorphic photodiode units.

[0011] Optionally, the isomorphic photodiode unit operates as a light-emitting unit under forward bias and as a photodetector unit under zero bias or reverse bias.

[0012] Optionally, the calibration decoupling model includes a machine learning model trained on the mapping relationship between electrical signals and mechanical load components.

[0013] Optionally, the machine learning model is one of a multilayer perceptron model, a convolutional neural network model, a Transformer model, or an ensemble learning model.

[0014] On the other hand, the present invention provides a six-axis force / torque sensing method based on optoelectronic chips and optical modulation, applied to the six-axis force / torque sensor as described above, comprising the following steps: S1, emitting probe light to a load conversion element through the light-emitting unit of the optoelectronic integrated chip; S2, the load conversion element modulates its own deformation caused by external mechanical load into an optical response change of the probe light, thereby obtaining an optical modulation signal; S3, multiple optical detection units receive the optical modulation signal and convert the optical modulation signal into an electrical signal; S4, receiving the electrical signal through a signal processing module and calculating the mechanical load components based on a pre-trained calibration decoupling model, wherein the mechanical load components include three-dimensional forces Fx, Fy, Fz and three-dimensional torques Mx, My, Mz along the X-axis, Y-axis and Z-axis.

[0015] Optionally, the calibration decoupling model is established through the following steps: applying a known mechanical load component to a sensing system equipped with a load conversion element and an optoelectronic integrated chip to generate an electrical signal; acquiring the electrical signal; using the electrical signal as input and the known mechanical load component as output, training a machine learning model to obtain the calibration decoupling model.

[0016] The implementation of this invention offers the following advantages: The optoelectronic integrated chip integrates a light-emitting unit and multiple photodetector units onto the same chip, eliminating the need for optical path alignment of discrete optical components and significantly improving the sensor's integration density. The load conversion element modulates the probe light according to the deformation differences to generate optical response changes, thereby converting mechanical loads of different dimensions into different optical modulation signals. The photodetector units receive and convert the optical modulation signals into electrical signals. The signal processing module processes the electrical signals based on a calibration decoupling model, accurately calculating the mechanical load components. Through the synergistic effect of these technical features, this invention achieves a high degree of sensor integration while maintaining high measurement accuracy, thus realizing a synergistic optimization of high integration density and high decoupling accuracy. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of a force / torque sensor in one embodiment.

[0018] Figure 2 The following is a process for preparing the tilted elastomer in one embodiment.

[0019] Figure 3 This is a structural configuration of a GaN optoelectronic device in one embodiment.

[0020] Figure 4 In one embodiment, the sensing mechanism of the force / torque sensor under different force and torque loading conditions is described.

[0021] Figure 5 This is a schematic diagram of an experimental setup for six-axis force / torque measurement in one embodiment.

[0022] Figure 6 This is a schematic diagram illustrating the output optical power of an integrated LED under different driving currents in one embodiment.

[0023] Figure 7 In one embodiment, the IV curves of the integrated PD under different LED drive currents are shown.

[0024] Figure 8 This is a schematic diagram of the electroluminescence (EL) spectrum of an on-chip LED and the absorption spectrum of a PD in one embodiment.

[0025] Figure 9 In one embodiment, the force / torque sensor exerts a force F in the x-axis direction. x A comparison chart of predicted and actual values.

[0026] Figure 10 In one embodiment, the force / torque sensor exerts a force F in the y-axis direction. y A comparison chart of predicted and actual values.

[0027] Figure 11 In one embodiment, the force / torque sensor exerts a force F in the z-axis direction. z A comparison chart of predicted and actual values.

[0028] Figure 12 In one embodiment, the force / torque sensor measures the torque M about the x-axis. x A comparison chart of predicted and actual values.

[0029] Figure 13 This is a comparison chart of the predicted and actual values ​​of the torque Mᵧ around the y-axis by the force / torque sensor in one embodiment.

[0030] Figure 14 In one embodiment, the force / torque sensor measures the torque M about the z-axis. z A comparison chart of predicted and actual values.

[0031] In the picture: 1. Protective layer; 2. Load conversion element; 3. Light emission unit; 4. Photodetector unit; 5. Signal processing module; 6. Mold; 7. Molding material; 8. Pad; 9. Distributed Bragg reflector layer; 10. Silicon dioxide insulating layer; 11. Electrode; 12. Transparent conductive layer; 13. p-type gallium nitride layer; 14. Multi-quantum well active region; 15. n-type gallium nitride layer; 16. Sapphire substrate; 17. Digital pressure gauge; 18. Six-axis force / torque sensor; 19. Adjustable angle platform; 20. Knob. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0033] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0034] In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0035] Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0036] Example 1 In this embodiment, as Figure 1 and Figure 3 The force / torque sensor shown includes: An optoelectronic integrated chip, comprising at least one light-emitting unit and multiple light-detecting units; A load conversion element, disposed on the surface of an optoelectronic integrated chip, is used to receive external mechanical loads and generate deformation. The structure of the load conversion element is configured to enhance the difference in deformation caused by mechanical loads of different dimensions. The signal processing module is connected to the optical detection unit via communication. The light-emitting unit is used to emit probe light to the load conversion element; The load conversion element is used to modulate the probe light through its deformation to generate a change in optical response and obtain an optically modulated signal; Multiple optical detection units are used to receive optical modulation signals and convert them into electrical signals; The signal processing module is used to receive electrical signals and calculate six-dimensional mechanical load components based on a pre-trained calibrated decoupling model. The mechanical load components include three-dimensional forces Fx, Fy, and Fz along the X, Y, and Z axes and three-dimensional torques Mx, My, and Mz.

[0037] In this embodiment, as Figure 1 As shown, the six-axis force / torque sensor comprises, from top to bottom, a protective layer, a load conversion element, an optoelectronic integrated chip, and a signal processing module. The top protective layer stably transmits external mechanical loads (including force and torque) to the load conversion element, which converts the external force / torque into an optically modulated signal. The optoelectronic integrated chip serves as an on-chip light source and detection component, working in conjunction with the load conversion element to convert force / torque signals into electrical signals. The bottom signal processing module performs current reading, feature extraction, model inference, and wired or wireless result output.

[0038] In this embodiment, the load conversion element has an asymmetric structure. The asymmetric structure of the load conversion element can enhance the difference in deformation caused by mechanical loads of different dimensions, thereby improving the consistency of mechanical loads applied to the optoelectronic integrated chip.

[0039] In one possible embodiment, the load transfer element is an asymmetric elastomer or an asymmetric reflective layer.

[0040] Optionally, the asymmetric elastomer is one of the following: a flexible block structure with a preset tilt angle, an elastomer with microstructures on its surface, or an elastomer with asymmetric boundary conditions.

[0041] In this embodiment, the asymmetric elastomer can be a cube, cuboid, frustum, spherical cap, or other deformable geometry; the material of the asymmetric elastomer can be Ecoflex (EEcoflex series soft silicone), PDMS (Polydimethylsiloxane), silicone rubber, polyurethane elastomer, hydrogel, or other transparent / semi-transparent elastic materials. The above materials, shapes, and tilt angles can be adjusted according to the target range, sensitivity, and packaging size.

[0042] In this embodiment, the light-emitting unit of the optoelectronic integrated chip is an LED, and the light-detecting unit is a PD (Photodiode).

[0043] In this embodiment, after the probe light emitted by the light-emitting unit enters the load conversion element, it undergoes reflection, refraction, or total internal reflection between the interfaces of the load conversion element, the optoelectronic integrated chip, air, and the protective layer, and then returns to multiple light detection units, ultimately causing a change in the light intensity received by the corresponding PD.

[0044] In this embodiment, the working principle of the six-axis force / torque sensor is as follows: Figure 4 As shown: In the initial state, due to the preset tilt angle at the bottom of the asymmetric elastomer, the symmetry of the probe light propagation is broken, and the light signals received by PDs located at different positions are different when no external force / torque is applied. Specifically, as follows (the coordinate definitions below are only for illustrating this embodiment): Perpendicular to Figure 4 The plane shown points outwards as the positive X-axis, horizontally to the right as the positive Y-axis, and vertically upwards as the positive Z-axis. The chip surface is the XY plane. The tilt angle of the asymmetric elastomer can be equivalent to rotating the XY plane clockwise around the X-axis by approximately 10°, causing the photodiodes (PDs) on different sides to generate different initial photocurrents. When an external force or torque is applied, the asymmetric elastomer deforms, altering the refraction, reflection, and coupling of light signals into different PDs. After absorbing the probe light, the PD generates a corresponding current signal, thus completing the physical parameter conversion from force / torque to light to electricity. In the figure, n1 represents the refractive index of the sapphire substrate; n2 represents the equivalent refractive index of the elastomer in its initial state; and n3 represents the equivalent refractive index of the elastomer after deformation under force. and These represent the critical angles when light rays are incident from a medium with a refractive index of n1 onto the interface of an elastic body, respectively, in the initial state and under stress.

[0045] In this embodiment, the specific testing device for the six-axis force / torque sensor is as follows: Figure 5 As shown, the top features a digital pressure gauge, and the six-axis force / torque sensor is placed on an adjustable angle platform. The platform can be adjusted in angle and translation via a knob at the bottom.

[0046] In this embodiment, the critical angle of the load conversion element at the substrate interface The relationship between light intensity and light intensity can be expressed by the following geometrical optical relationship: Formula (1); As the effective refractive index increases, Increase.

[0047] According to formula (1), the following situations will occur depending on the preset tilt angle of the asymmetric elastic body: 1) When a normal force F is applied zWhen the asymmetric elastomer is compressed mainly along the thickness direction, the density of the asymmetric elastomer increases, which in turn increases the effective refractive index of the asymmetric elastomer.

[0048] 2) When a lateral force F is applied x or F y When the asymmetric elastic body undergoes shear deformation, the shear deformation on both sides of the asymmetric elastic body is inconsistent due to the presence of a preset tilt angle, resulting in different magnitudes of increase in effective refractive index on both sides of the force direction.

[0049] 3) When a torque M is applied x M y When the asymmetric elastic body bends around the corresponding axis, due to the existence of the preset tilt angle, the bending deformation on both sides of the asymmetric elastic body is inconsistent, resulting in an increase in the effective refractive index on one side and a decrease on the other side.

[0050] 4) When a torque Mz is applied, the effective refractive index in the four PD regions changes differently due to the presence of the preset tilt angle of the asymmetric elastomer.

[0051] When an external force or torque is applied to an asymmetric elastic body, the asymmetric elastic body undergoes changes in its optical response. Specifically, the shape, contact state, local strain distribution, equivalent refractive index, and preset tilt angle of the asymmetric elastic body change, thereby altering the propagation path, reflection ratio, and intensity distribution of the probe light returning to each photodiode (PD) within the asymmetric elastic body and at its interfaces. Different external forces or torques, after passing through the asymmetric elastic body, cause deformations of different directions and components, ultimately generating unique optical modulation signals. These optical modulation signals produce different photocurrent response modes on multiple PD channels, thus forming electrical signals that can be used for decoupling in the calibration decoupling model.

[0052] In this embodiment, the preset tilt angle of the asymmetric elastomer refers to the fact that the asymmetric elastomer can be installed at any preset tilt angle relative to the surface of the optoelectronic integrated chip. The preset tilt angle can be a single-axis tilt, a dual-axis tilt, or an equivalent tilt formed by asymmetric boundary conditions; the purpose of all is to enhance the distinguishability of different force / torque components in multiple optoelectronic channels.

[0053] In this embodiment, the signal processing module is a PCB (Printed Circuit Board) integrating a microcontroller. The calibration decoupling model includes a machine learning model trained on the mapping relationship between electrical signals and mechanical load components.

[0054] Optionally, the machine learning model is one of a multilayer perceptron model, a convolutional neural network model, a Transformer model, or an ensemble learning model.

[0055] In this embodiment, the machine learning model adopts a Multi-Head MLP (Multi-Head Multi-Layer Perceptron) regression model. The machine learning model takes multi-channel photocurrent as input and a three-dimensional force F along the X-axis, Y-axis, and Z-axis as input. x F y F z and three-dimensional torque M x M y M z The output dataset is used for training to achieve decoupling of electrical signals.

[0056] In this embodiment, the trained machine learning model is deployed on a microcontroller, embedded processor, or host computer that communicates with the signal processing module on a PCB board, thereby enabling real-time prediction of mechanical loads.

[0057] Example 2 Based on Embodiment 1, this embodiment provides an optional solution for the specific structure of the load conversion unit.

[0058] In this embodiment, the asymmetric elastomer is a flexible block structure with a preset tilt angle to enhance the sensitivity to torque components, especially bending moment components about the transverse or longitudinal axis.

[0059] In this embodiment, the preparation process of the asymmetric structural elastomer is as follows: Figure 2 As shown, the molding material is poured into a mold with a 10° tilt at the bottom, thoroughly mixed, and vacuumed to remove air bubbles. After curing for about 30 minutes, it is demolded to obtain an asymmetric elastomer with a preset tilt angle.

[0060] In this embodiment, the molding material is Ecoflex, and Ecoflex components A and B are mixed in a mass ratio of 1:1.

[0061] When external forces or torques are applied to an asymmetric elastic body, the shape, contact state, local strain distribution, equivalent refractive index, and critical interface angle of the asymmetric elastic body change, thereby altering the propagation path, reflection ratio, and intensity distribution of light returning to each photocurrent distribution (PD) within the elastic body and at the interface. Loads of different directions and components will generate different photocurrent response modes on multiple PD channels, thus forming an optical fingerprint for six-axis decoupling.

[0062] In one possible embodiment, the load conversion unit may also be a vertically mounted cubic or flat-topped flexible layer. In this embodiment, the load conversion unit can also map different mechanical loads into different electrical signals through deformation, achieving the distinction between normal mechanical loads and some radial mechanical loads, but not for the two orthogonal radial force components (F...x and F y ) and corresponding bending moment components (M) x and M y Their ability to distinguish is relatively weak.

[0063] It should be noted that asymmetric elastomers are not limited to generating optical response changes solely through deformation; other alternative methods that map mechanical loads into optical response changes should also be within the scope of this invention. These include, but are not limited to, the following forms: ①Asymmetric elastomers are capacitive, meaning that asymmetric elastomers convert mechanical loads into changes in the spacing / area of ​​capacitor plates, thereby mapping different mechanical loads into corresponding changes in optical response.

[0064] ② The asymmetric elastic body is magnetic, that is, a magnet is embedded in the asymmetric elastic body, and a Hall sensor detects the change in magnetic field, thereby mapping different mechanical loads to corresponding changes in optical response.

[0065] ③ The asymmetric elastomer is a piezoresistive type, that is, a strain gauge is printed / embedded on the surface of the asymmetric elastomer. Mechanical loads will change the resistance of the asymmetric elastomer, thereby mapping different mechanical loads to corresponding optical response changes.

[0066] Example 3 This embodiment provides an optional solution for the specific structure of a monolithic integrated chip, based on the above embodiments.

[0067] In this embodiment, the monolithic integrated chip includes a light-emitting unit and a photodetector (PD) disposed around the light-emitting unit.

[0068] In this embodiment, the light-emitting unit is an LED.

[0069] In this embodiment, the light-emitting unit and the light-detecting unit are made of the same material.

[0070] Optionally, both the light-emitting unit and the photodetector unit adopt GaN, InGaN / GaN multiple quantum wells, AlGaN / GaN, or other GaN-based material systems.

[0071] In a preferred embodiment, the light-emitting unit and the light-detecting unit also adopt the same structure, that is, the light-emitting unit and the light-detecting unit adopt the same or substantially the same semiconductor diode unit structure.

[0072] Optionally, both the light-emitting unit and the photodetector unit can be GaN-based pn diode structures, LED structures, or diode units with the same epitaxial layer, ohmic electrode, and transparent electrode layout. Devices with the above structures can operate as light-emitting units under forward bias and as photodetector units under zero bias, reverse bias, or photocurrent readout modes.

[0073] In one specific embodiment, the light-emitting unit and the photodetector unit are isomorphic diode units fabricated based on the same InGaN / GaN multi-quantum-well epitaxial structure.

[0074] In this embodiment, the diode unit serves as a light-emitting unit under forward bias and as a photodetector unit under zero bias, reverse bias, or illumination readout modes. Since the electroluminescence spectrum and photoresponse spectrum of the multi-quantum-well structure partially overlap, it eliminates the need for heterogeneous light sources and detector units. Light emission and detection functions can be achieved using the same material system, the same epitaxial platform, and the same or essentially the same device fabrication process. Therefore, this invention integrates the light-emitting unit and the photodetector unit isomorphically (same structure) and homogeneously (same material) into a single integrated chip. It does not simply connect the light-emitting unit and the photodetector unit in parallel, but rather utilizes the dual-functionality of the GaN-based standard diode structure under different bias states, allowing the same type of device unit to function as both a light-emitting unit and a photodetector unit, thereby achieving integrated light emission, detection, and subsequent photoelectric response processing.

[0075] In this embodiment, the light-emitting unit and the photodetector unit are made of the same material or have the same structure. They can be fabricated using the same material system, the same epitaxial platform, and the same or similar process flow, avoiding the process complexity caused by heterogeneous material bonding, heterogeneous device transfer, external light source coupling, or complex packaging alignment. Simultaneously, since the emission spectrum and the detection response spectrum originate from the same or similar material system, they have a natural spectral matching relationship, which is beneficial for improving on-chip optical coupling efficiency, device consistency, and array integration. This reduces the complexity of the material system and process flow, lowers the risk of spectral mismatch between devices, and improves manufacturing consistency, interchangeability, and batch processing stability during array expansion.

[0076] In one possible embodiment, the light-emitting unit and the photodetector unit may also employ different material systems. For example, the light-emitting unit may be a GaN-based LED or a Si-based photodiode, while the photodetector unit may be a GaAs detector, a CdS / CdSe photosensitive device, or a combination of organic photodetectors.

[0077] In another possible embodiment, the light-emitting unit and the photodetector unit can also have different structures, that is, the light-emitting unit and the photodetector unit can adopt different device structures, different epitaxial systems, or different process modules. For example, the light-emitting unit can be an on-chip LED or a separate photodiode, and the photodetector unit can be a photoresistor, a CMOS image sensor, or other heterogeneous detection structure combination.

[0078] In another possible embodiment, the monolithic integrated optical chip may also employ a structure of multiple light-emitting units in conjunction with one photodetector unit, or multiple light-emitting units in conjunction with multiple photodetector units. In this embodiment, the light-emitting units and photodetector units can be arranged in a ring, cross, rectangle, array, or surround pattern. Furthermore, the light-emitting units and photodetector units can be formed by replicating identical or substantially identical isomorphic diode units.

[0079] Example 4 This embodiment provides a verification embodiment based on the above embodiments.

[0080] In this embodiment, the load conversion element is a flexible block structure with a preset tilt angle, which is equivalent to rotating the XY plane clockwise about the X-axis by approximately 10°. It should be noted that 10° is an exemplary tilt angle used in this embodiment, not the only optimal value, and is not intended to limit the scope of protection of this application. The preset tilt angle is mainly used to break the structural symmetry of the load conversion element, causing different deformations and photoelectric responses to forces and torques in different directions. If the tilt angle is too small, the structure is nearly symmetrical, and the signal difference may not be significant; if the tilt angle is too large, it may cause local stress concentration, reduced range, or increased nonlinear response. Therefore, the specific tilt angle can be selected based on the size of the elastomer, the material, the load range, and the packaging space.

[0081] In this embodiment, when α = 10°, the six-axis predicted R... 2 All values ​​are greater than 0.94, indicating that this angle can achieve six-axis force / torque sensing.

[0082] In this embodiment, the load transfer element is made of Ecoflex material.

[0083] In this embodiment, a central LED and four surrounding PDs are integrated on a single integrated optical chip, and the light-emitting unit and the light-detecting unit are made of the same material and have the same structure. They are all isomorphic diode units formed based on the same InGaN / GaN multi-quantum-well epitaxial structure.

[0084] In this embodiment, Figure 3 The structure shown is a cross-sectional view of a homogeneous photodiode unit. This structure as a whole can function as both a light-emitting unit and a photodetector unit; it is not a single layer that constitutes either a light-emitting or photodetector unit. Multiple independent homogeneous photodiode units are disposed on the optoelectronic integrated chip. Some of these units function as light-emitting units under forward bias, while others function as photodetectors under zero bias or reverse bias.

[0085] When operating as a light-emitting unit, a forward driving current is applied between the p-type and n-type pads. Electrons and holes are injected into the multi-quantum-well active region through the n-type GaN layer and p-type GaN layer, respectively, and radiative recombination occurs within the multi-quantum-well active region to generate probe light. A portion of the upward-propagating light is reflected by the distributed Bragg reflector layer towards the sapphire substrate. The probe light exits through the sapphire substrate and enters the load conversion element.

[0086] When operating as a photodetector unit, the probe light, modulated by the load conversion element, is incident from one side of the sapphire substrate and absorbed by the multi-quantum-well active region and its adjacent semiconductor layer, generating photogenerated electron-hole pairs. Under zero-bias or reverse-bias conditions, the photogenerated carriers are collected and form a photocurrent, thereby converting the optical modulation signal into an electrical signal.

[0087] Specifically, such as Figure 3 As shown, the isomorphic photodiode unit includes pads 8, a distributed Bragg reflector layer 9, a silicon dioxide insulating layer 10, electrodes 11, a transparent conductive layer 12, a p-type gallium nitride layer 13, a multi-quantum-well active region 14, an n-type gallium nitride layer 15, and a sapphire substrate 16. The pads 8 include p-type pads and n-type pads, and the electrodes 11 include p-type electrodes and n-type electrodes electrically connected to the p-type semiconductor region and the n-type semiconductor region, respectively.

[0088] The sapphire substrate 16 supports the epitaxial structure and serves as the exit or entrance window for the probe light; the n-type gallium nitride layer 15 and the p-type gallium nitride layer 13 are used for electron and hole transport, respectively; the multi-quantum-well active region 14 is used for radiative recombination of electrons and holes in the light-emitting mode and for absorbing incident light and generating photogenerated carriers in the photodetector mode; the transparent conductive layer 12 is used to improve the current spread uniformity of the p-type region; the silicon dioxide insulating layer 10 is used to achieve electrical isolation, passivation, or limit the current injection region; the distributed Bragg reflector layer 9 is used to reflect light propagating upwards towards the device, directing it toward the sapphire substrate 16 to improve the coupling efficiency of the probe light to the load conversion element.

[0089] When the isomorphic photodiode unit operates as a light-emitting unit, a forward bias is applied to the device through the pad 8 and the electrode 11. Electrons and holes are injected into the multi-quantum-well active region 14 and undergo radiative recombination to generate probe light. The generated probe light is reflected by the distributed Bragg reflector layer 9 and mainly emitted from one side of the sapphire substrate 16 into the load conversion element.

[0090] When the isomorphic photodiode unit operates as a photodetector unit, the probe light modulated by the load conversion element is incident from one side of the sapphire substrate 16, generating photogenerated carriers in the multi-quantum-well active region 14 and its adjacent semiconductor layer. The photogenerated carriers are collected by the electrode 11 to form a photocurrent, which is then transmitted to the signal processing module through the pad 8.

[0091] In this embodiment, as Figure 3 As shown, the electrode 11 that is in direct contact with the n-type gallium nitride layer 15 is an n-type electrode, and the electrode that is in contact with the transparent conductive layer 12 disposed on the p-type gallium nitride layer 13 is a p-type electrode; the pad 8 that is in direct contact with the n-type electrode is an n-type pad, and the pad that is in direct contact with the p-type electrode is a p-type pad.

[0092] In this embodiment, the photoelectric performance of the monolithic integrated optical chip is as follows: Figures 6-9 As shown.

[0093] Specifically, the IV curve of the LED at the center of a monolithic integrated optical chip is as follows: Figure 6 As shown, its turn-on voltage is approximately 3 V, and it can output high optical power at a drive current of 100 mA.

[0094] The IV characteristics of integrated PD, such as Figure 7 As shown, different curves correspond to the operating states of the PD under different LED driving currents; under no-light conditions, the PD dark current can reach 10. -9 A-level.

[0095] Figure 8 The absorption spectrum of the PD and the electroluminescence spectrum of the LED are presented, showing significant overlap between the two in the 375-410 nm range. These results demonstrate that the multi-quantum-well structure can simultaneously support both emission and detection functions.

[0096] In this embodiment, a pre-trained Multi-Head MLP (Multi-Head Multi-Layer Perceptron) regression model is used to decouple the photoelectric signals output by the six-axis force / torque sensor, thereby obtaining the force F along the three directions of the spatial coordinate system. x 、Fᵧ、F z and the torque M about the three coordinate axes x 、Mᵧ、M z The mechanical load applied by a standard loading device or a standard six-axis force / torque sensor is used as the true value, and the mechanical load output by the calibrated decoupling model is used as the predicted value, with a determination coefficient R0. 2 Evaluate the consistency between predicted and actual values.

[0097] like Figure 9 As shown, in F x Within a measurement range of approximately -150 mN to 150 mN, F x The predicted values ​​and the actual values ​​show good agreement, with a coefficient of determination R0. 2 It is 0.955.

[0098] like Figure 10 As shown, within the measurement range of approximately -150 mN to 150 mN, the predicted value of Fᵧ shows good agreement with the actual value, and the coefficient of determination R0 is high. 2 It is 0.983.

[0099] like Figure 11 As shown, in F z Within a measurement range of approximately -1000 mN to 0 mN, F z The predicted values ​​and the actual values ​​show good agreement, with a coefficient of determination R0. 2 It is 0.995.

[0100] like Figure 12 As shown, in M x Within a measurement range of approximately -0.75 N·mm to 0.75 N·mm, M x The predicted values ​​and the actual values ​​show good agreement, with a coefficient of determination R0. 2 It is 0.994.

[0101] like Figure 13 As shown, within the measurement range of Mᵧ from approximately -0.75 N·mm to 0.75 N·mm, the predicted value of Mᵧ shows good agreement with the actual value, and the coefficient of determination R0 is high. 2 It is 0.948.

[0102] like Figure 14 As shown, in M z Within a measurement range of approximately -0.15 N·mm to 0.15 N·mm, M z The predicted values ​​and the actual values ​​show good agreement, with a coefficient of determination R0. 2 It is 0.992.

[0103] The determination coefficients R of the above six force / torque components 2 All values ​​are greater than 0.94, indicating that the asymmetric load conversion element can generate differentiated multi-channel photoelectric responses to mechanical loads of different dimensions. The calibration decoupling model can effectively estimate the six-axis force / torque components within the calibration range of this embodiment. Under the pre-tilted structure and the test conditions of this embodiment, the resolution of small torque components can reach the order of 0.01 N·mm.

[0104] Example 5 Based on the above embodiments, this embodiment provides a six-axis force / torque sensing method based on optoelectronic chips and optical modulation.

[0105] In this embodiment, the six-axis force / torque sensing method based on photoelectric chip and optical modulation is applied to the six-axis force / torque sensor as described above, and includes the following steps: S1. The probe light is emitted from the light-emitting unit of the optoelectronic integrated chip to the load conversion element; S2. The load conversion element modulates the deformation of itself caused by the external mechanical load into a change in the optical response of the probe light, thus obtaining an optical modulation signal; S3. Multiple optical detection units receive optical modulation signals and convert them into electrical signals; S4. Receive electrical signals through the signal processing module and calculate the mechanical load components based on the pre-trained calibration decoupling model. The mechanical load components include three-dimensional forces Fx, Fy, Fz and three-dimensional torques Mx, My, Mz along the X-axis, Y-axis and Z-axis.

[0106] In this embodiment, the calibration decoupling model is established through the following steps: A known mechanical load component is applied to a sensing system equipped with a load conversion element and an optoelectronic integrated chip to generate an electrical signal; Acquire electrical signals; Using electrical signals as input and known mechanical load components as output, a machine learning model is trained to obtain a calibrated decoupling model.

[0107] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A force / torque sensor, characterized in that, include: An optoelectronic integrated chip includes a light-emitting unit and a light-detecting unit, wherein the light-emitting unit and the light-detecting unit are made of the same material; A load conversion element is disposed on the surface of the optoelectronic integrated chip to receive external mechanical loads and generate deformation; The signal processing module is communicatively connected to the optical detection unit; The light-emitting unit is used to emit probe light to the load conversion element; The load conversion element is configured to enhance the difference in deformation caused by mechanical loads of different dimensions, and modulate the probe light according to the difference in deformation to generate an optical response change, thereby converting the mechanical loads of different dimensions into different optical modulation signals. The optical detection unit is used to receive the optical modulation signal and convert the optical modulation signal into an electrical signal; The signal processing module is used to receive the electrical signal and calculate the mechanical load components based on the pre-trained calibration decoupling model. The mechanical load components include three-dimensional force and three-dimensional torque along the coordinate axes of the spatial coordinate system, respectively.

2. The force / torque sensor according to claim 1, characterized in that, The load conversion element has an asymmetric structure.

3. The force / torque sensor according to claim 2, characterized in that, The load conversion element is an asymmetric elastomer or an asymmetric reflective layer.

4. The force / torque sensor according to claim 2, characterized in that, The asymmetric elastomer is one of the following: a flexible block structure with a preset tilt angle, an elastomer with microstructures on its surface, or an elastomer with asymmetric boundary conditions.

5. The force / torque sensor according to claim 1, characterized in that, The light-emitting unit and the light-detecting unit are isomorphic photodiode units.

6. The force / torque sensor according to claim 5, characterized in that, The isomorphic photodiode unit functions as a light-emitting unit under forward bias and as a light-detecting unit under zero bias or reverse bias.

7. The force / torque sensor according to claim 1, characterized in that, The calibration decoupling model includes a machine learning model trained on the mapping relationship between the electrical signal and the mechanical load component.

8. The force / torque sensor according to claim 7, characterized in that, The machine learning model is one of the following: multilayer perceptron model, convolutional neural network model, Transformer model, or ensemble learning model.

9. A six-axis force / torque sensing method based on a photoelectric chip and optical modulation, applied to the force / torque sensor as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. The probe light is emitted from the light-emitting unit of the optoelectronic integrated chip to the load conversion element; S2. The load conversion element modulates its own deformation caused by the external mechanical load into an optical response change of the probe light, thereby obtaining an optical modulation signal; S3. The optical detection unit receives the optical modulation signal and converts the optical modulation signal into an electrical signal; S4. The electrical signal is received by the signal processing module, and the mechanical load components are calculated based on the pre-trained calibration decoupling model. The mechanical load components include three-dimensional force and three-dimensional torque along the coordinate axes of the spatial coordinate system.

10. The six-axis force / torque sensing method according to claim 9, characterized in that, The calibration decoupling model is established through the following steps: A known mechanical load component is applied to a sensing system equipped with the load conversion element and the optoelectronic integrated chip to generate the electrical signal; Acquire the electrical signal; Using the electrical signal as input and the known mechanical load components as output, a machine learning model is trained to obtain the calibration decoupling model.

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