Optomechanical multi-axis torque sensor

Abstract

The application discloses an optical mechanical multi-axis torque sensor, comprising a probe, a back-shaped nanometer light beam cavity, an optical crystal microcavity and a supporting suspension beam arm; through cooperation of the optical crystal microcavity and the back-shaped nanometer light beam cavity, linear relations of wavelengths and forces and torques in different axial directions are established, so that the corresponding forces and torques are measured, and torque measurement on three axes is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of torque measurement, more specifically, to a kind of optomechanical multi-axis torque sensor. BACKGROUND

[0002] Three-axis torque sensor is a device used to measure the torque of an object in three-dimensional space. It can detect the torque in three directions, namely X-axis, Y-axis and Z-axis. This sensor is widely used in robotics, aerospace, automotive industry, biomechanics and other fields. Traditional torque sensors can only measure the torque in a single direction, while three-axis torque sensors can measure the torque in three directions simultaneously, greatly improving the accuracy and efficiency of measurement. Its working principle is mainly through measuring the deformation of the object when subjected to external force, then converting these deformations into electrical signals, and finally obtaining the size of torque through circuit processing. The main components of three-axis torque sensor include sensitive element, conversion element and processing circuit. The sensitive element is the part that directly contacts the measured object, which can convert the deformation of the object into physical quantities that can be measured. The conversion element converts the physical quantities obtained by the sensitive element into electrical signals. The processing circuit processes the electrical signals and finally obtains the size of torque. The technical difficulties of three-axis torque sensor mainly lie in how to accurately measure the torque in three directions and how to process and analyze these data. At present, this problem has been solved to some extent, but there are still some challenges, such as how to improve the sensitivity and stability of the sensor, how to reduce the size and weight of the sensor, etc.

[0003] Optomechanical torque sensor uses advanced optical technology to measure torque by analyzing the phase change of light. This change is captured by a photodetector and converted into an electrical signal, which is then analyzed by a data processing system to obtain the torque value. Due to its high sensitivity and accuracy, nanobeam cavity torque sensor is very suitable for occasions that require precise torque measurement, and it has shown excellent performance in modern industrial applications. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide an optomechanical multi-axis torque sensor that directly measures torque through the resonance wavelength change of optical crystal microcavity or back-type nanobeam cavity.

[0005] To achieve the above-mentioned purpose of the application, an optomechanical multi-axis torque sensor is provided, characterized in that it comprises a probe, a back-type nanobeam cavity, an optical crystal microcavity and a support cantilever arm.

[0006] The probe is directly fixed on the back-type nanobeam cavity and located at the center of one side of the back-type nanobeam cavity, for sensing external torque.

[0007] The back-shaped nanometer light beam cavity comprises two layers of back-shaped nanometer light beam cavity walls with the same structure, wherein the upper layer is a movable back-shaped nanometer light beam cavity wall, and the lower layer is a fixed back-shaped nanometer light beam cavity; the movable back-shaped nanometer light beam cavity wall is supported and fixed by a support cantilever arm, so that a gap exists between the two layers of back-shaped nanometer light beam cavity walls, thereby forming the back-shaped nanometer light beam cavity;

[0008] The optical crystal microcavity comprises four groups, which are installed on both sides of the two edges parallel to the probe and are in a symmetrical state with the central axis of the back-shaped nanometer light beam cavity; each group of optical crystal microcavities comprises a movable optical crystal and a fixed optical crystal, wherein the movable optical crystal is connected to the back-shaped nanometer light beam cavity, and the fixed optical crystal is placed beside the movable optical crystal, and a gap exists between the two groups of optical crystals;

[0009] The support cantilever arm is installed at the center of the two edges parallel to the probe, and is used to realize the displacement of the movable back-shaped nanometer light beam cavity wall in the X, Y and Z three axes.

[0010] The application aims to achieve the following purposes:

[0011] The optical mechanical multi-axis torque sensor comprises a probe, a back-shaped nanometer light beam cavity, an optical crystal microcavity and a support cantilever arm; by cooperation of the optical crystal microcavity and the back-shaped nanometer light beam cavity, a linear relationship between wavelength and force and torque in different axes is established, so that the corresponding force and torque are measured, and torque measurement in three axes is realized.

[0012] Meanwhile, the optical mechanical multi-axis torque sensor has the following beneficial effects:

[0013] (1) The torque measurement of the optical mechanical multi-axis torque sensor adopts a direct measurement method, has fewer error terms and is more accurate;

[0014] (2) Compared with the traditional torque sensor, the optical mechanical multi-axis torque sensor is much smaller in size and is more easily used in various small fields;

[0015] (3) The optical mechanical multi-axis torque sensor can measure torque in three axes through the optical crystal microcavity and the back-shaped nanometer light beam cavity;

[0016] (4) The back-shaped nanometer light beam cavity can work normally in harsh environments such as high temperature and high pressure, and will not lose accuracy due to environmental changes, and is suitable for multiple fields from automobile manufacturing to aerospace and mechanical processing, and especially performs well in high-precision equipment testing. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structure diagram of the optical mechanical multi-axis torque sensor, wherein (a) is a top view, and (b) is a left view;

[0018] Figure 2 is a schematic diagram of a mirror surface pattern;

[0019] Figure 3 is a schematic diagram of an optical crystal;

[0020] Figure 4 is a schematic diagram of the displacement of the horizontal direction of the nano-optical cavity cantilever when the probe is subjected to X-axis torque;

[0021] Figure 5 is a schematic diagram of the displacement of the vertical direction of the nano-optical cavity cantilever when the probe is subjected to Y-axis torque;

[0022] Figure 6 is a schematic diagram of the displacement of the movable back-type nano-beam cavity wall when the probe is subjected to Z-axis torque. DETAILED DESCRIPTION

[0023] The specific embodiments of the present application will be described below with reference to the accompanying drawings so that those skilled in the art can better understand the present application. It should be particularly noted that in the following description, when detailed descriptions of known functions and designs may obscure the main content of the present application, these descriptions will be omitted here.

[0024] EMBODIMENT

[0025] Figure 1 is a structural diagram of an optical mechanical multi-axis torque sensor according to the present application.

[0026] In the present embodiment, as shown in Figure 1 , the optical mechanical multi-axis torque sensor according to the present application comprises a probe, a back-type nano-beam cavity, an optical crystal microcavity, and a support cantilever arm.

[0027] As shown in Figure 1 (a), the probe a is directly fixed on the back-type nano-beam cavity and located at the center of one side of the back-type nano-beam cavity, for sensing external torque; in the present embodiment, the probe a is arranged on the b1 side of the back-type nano-beam cavity;

[0028] As shown in Figure 1 (b), the back-type nano-beam cavity comprises two layers of back-type nano-beam cavity walls with the same structure, wherein the upper layer is a movable back-type nano-beam cavity wall and the lower layer is a fixed back-type nano-beam cavity wall; the movable back-type nano-beam cavity wall is supported and fixed by the support cantilever arm, so that there is a gap between the two layers of back-type nano-beam cavity walls, thereby forming the back-type nano-beam cavity;

[0029] In the embodiment, the two edge arms of the U-shaped nanobeam cavity in the horizontal direction are denoted as nanooptical cavity cantilever arms b1 and b2, and the two edges in the vertical direction are denoted as nanooptical cavity cantilever arms b3 and b4; the mirror pattern is arranged at the center of each edge, the mirror patterns are of the same shape, and are in a symmetrical state along the central axis of the U-shaped nanobeam cavity wall;

[0030] As shown in Figure 2 , the hole shape of the mirror pattern gradually evolves from a circular shape to an elliptical shape, the spacing between adjacent two holes is the same, each hole on the mirror pattern is similar to a gap, and a series of holes with a length of n m from both ends to the inside are collectively referred to as outer holes, and the outer holes form a group of mirrors; a series of holes with a length of n c from the center point to both ends are collectively referred to as inner holes, and the inner holes form an optical cavity supporting an optical mode.

[0031] The optical crystal microcavity includes four groups, which are installed on both sides of the two edges parallel to the probe and in a symmetrical state with the central axis of the U-shaped nanobeam cavity; each group of optical crystal microcavities includes a movable optical crystal and a fixed optical crystal, and taking any one group as an example, the movable optical crystal is denoted as c1, and the fixed optical crystal is denoted as c2; the movable optical crystal c1 is connected to the U-shaped nanobeam cavity, and the fixed optical crystal c2 is placed beside the movable optical crystal c1, and there is a gap between the two groups of optical crystals.

[0032] In the embodiment, the movable optical crystal and the fixed optical crystal have the same structure, as shown in Figure 3 , each group of optical crystals is composed of two groups of arrayed photonic crystal holes f1 and air grooves f2 located therebetween, the photonic crystal holes f1 are arranged in a regular hexagonal honeycomb shape, as shown in f3 in the figure, and finally form an optical crystal.

[0033] The support cantilever is installed at the center of both sides of the two edges parallel to the probe, and is used to realize the displacement of the movable U-shaped nanobeam cavity wall in the X, Y and Z three axes.

[0034] When the optical mechanical multi-axis torque sensor measures torque, as shown in Figure 4As shown, when the probe is subjected to X-axis torque, the horizontal nano-optical cavity cantilevers b1 and b2 undergo out-of-plane displacement relative to the plane. This displacement alters the gap between the movable loop-shaped nano-beam cavity wall and the fixed loop-shaped nano-beam cavity wall, thus affecting the resonant wavelength of the movable loop-shaped nano-beam cavity wall. When the gap width between the nano-optical cavity cantilever b1 and the underlying fixed loop-shaped nano-beam cavity wall increases, the gap width between the nano-optical cavity cantilever b2 and the underlying fixed loop-shaped nano-beam cavity wall decreases, forming a differential structure. Compared to the non-differential structure, its measurement sensitivity is nearly doubled. The fixed loop-shaped nano-beam cavity wall only guides the input and output light. The corresponding force and torque are measured through the linear relationship between wavelength and force and torque.

[0035] When the probe is subjected to Y-axis torque, such as Figure 5 As shown, the vertical nano-optical cavity cantilevers b3 and b4 undergo out-of-plane displacement relative to the plane. This displacement alters the gap between the movable loop-shaped nano-beam cavity wall and the fixed loop-shaped nano-beam cavity wall, thus affecting the resonant wavelength of the movable loop-shaped nano-beam cavity wall. When the gap width between the nano-optical cavity cantilevers b3 and the underlying fixed loop-shaped nano-beam cavity wall increases, the gap width between the nano-optical cavity cantilevers b4 and the fixed loop-shaped nano-beam cavity wall decreases, forming a differential structure. Compared to the non-differential structure, its measurement sensitivity is nearly doubled. The fixed loop-shaped nano-beam cavity wall only guides the input and output light. The corresponding force and torque are measured through the linear relationship between wavelength and force and torque.

[0036] When the probe is subjected to Z-axis torque, such as Figure 6 As shown, the probe, carrying the movable loop-shaped nanobeam cavity wall, undergoes a deflection displacement within the paper plane, thereby altering the air gap gap in the optical crystal within the optical crystal microcavity. Based on its differential structure, if the movable optical crystal in the optical crystal microcavity approaches the fixed optical crystal, the movable optical crystal will move away from the fixed optical crystal. Compared to the non-differential structure, its measurement sensitivity is nearly doubled. The corresponding force and torque are then measured through the linear relationship between wavelength and force and torque.

[0037] In the above, when the probe is displaced by x s The change in the gap between each air slot remains x. s Considering that the displacement of the movable part in this optomechanical multi-axis torque sensor also includes the displacement x generated under the action of laser, n And its own thermal Brownian noise x th Therefore, the total displacement is:

[0038] x = x s +x th +x a

[0039] Since the air slot gap length L and the internal laser wavelength satisfy:

[0040] λn=2L

[0041] where n is the effective refractive index of the medium in the cavity

[0042] Combining the two equations, the relationship between the total displacement and the wavelength can be obtained:

[0043] λn=2(L+x)

[0044] Based on this principle, the size of the external force or torque can be determined by measuring the size of the wavelength change. In addition, the multi-axis torque sensor of the present application also has a differential structure, and compared with the non-differential structure, the measurement sensitivity is improved by nearly one time.

[0045] In the present embodiment, the movable back-type nanobeam cavity wall and the fixed back-type nanobeam cavity wall can be manufactured in a 400 nm thick SiN layer above a 500 μm silicon layer. The fixed back-type nanobeam cavity wall only guides the input and output light. The movement of the movable back-type nanobeam cavity wall can be induced by various physical measurements, and the resonance wavelength is affected by the mechanical movement of the movable component.

[0046] The optical crystal microcavity is manufactured by removing the SiO2 in the middle region of the middle SiO2 layer of the SOI substrate through the photolithography technology. The silicon micromechanical resonator structure is manufactured on the top layer of silicon of the rectangular SOI substrate through the micro-nano processing process, while the bottom layer of silicon remains unchanged; the SiO2 in the middle region of the middle SiO2 layer of the SOI substrate is removed through the photolithography technology.

[0047] Although the above describes the illustrative specific embodiments of the present application in order to facilitate the understanding of the present application by those skilled in the art, it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present application defined and determined by the appended claims, all the inventions utilizing the concept of the present application are included in the protection.

Claims

1. An optomechanical multi-axis torque sensor, characterized in that, include: Probes, loop-shaped nanobeam cavities, optical crystal microcavities, and supporting cantilever arms; The probe shown is directly fixed to the loop-shaped nanobeam cavity and located in the center of one side of the loop-shaped nanobeam cavity to sense external torque. The loop-shaped nanobeam cavity includes two identical loop-shaped nanobeam cavity walls, wherein the upper layer is a movable loop-shaped nanobeam cavity wall and the lower layer is a fixed loop-shaped nanobeam cavity; the movable loop-shaped nanobeam cavity wall is supported and fixed by a supporting cantilever arm, so that there is a gap between the upper and lower loop-shaped nanobeam cavity walls, thereby forming a loop-shaped nanobeam cavity. The optical crystal microcavities comprise four sets, mounted on both sides of the two sides parallel to the probe, and symmetrical with the central axis of the loop-shaped nanobeam cavity; each set of optical crystal microcavities includes a movable optical crystal and a fixed optical crystal, wherein the movable optical crystal is connected to the loop-shaped nanobeam cavity, the fixed optical crystal is placed next to the movable optical crystal, and there is a gap between the two sets of optical crystals. The supporting cantilever arm is installed at the center of both sides parallel to the two sides of the probe, and is used to realize the displacement of the movable loop-shaped nanobeam cavity wall on the X, Y, and Z axes.

2. The optomechanical multi-axis torque sensor according to claim 1, characterized in that, The active optical crystal and the fixed optical crystal have the same structure. The optical crystal consists of two sets of arrayed photonic crystal holes and an air slot between them. The photonic crystal holes are arranged in a regular hexagonal honeycomb pattern to form a photonic crystal.

3. The optomechanical multi-axis torque sensor according to claim 1, characterized in that, The center of each of the four sides of the cavity wall of the loop-shaped nanobeam is provided with a mirror pattern. The mirror patterns are identical in shape and are symmetrical along the central axis of the cavity wall of the loop-shaped nanobeam.

4. The optomechanical multi-axis torque sensor according to claim 3, characterized in that, The shape of the holes in the mirror pattern gradually evolves from circular to elliptical, with the same spacing between adjacent holes. Each hole in the mirror pattern is similar to a gap, with a length of n from both ends inward. m A series of holes are collectively called external holes, which form a set of reflecting mirrors; the length from the center point to both ends is n. c A series of holes are collectively referred to as internal holes, which form an optical cavity that supports optical modes.

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