Optical mechanical multi-axis torque sensor

Abstract

The invention discloses an optical mechanical multi-axis torque sensor which comprises a probe, a concentric-square-shaped nanometer light beam cavity, an optical crystal microcavity and a supporting suspension beam arm. Through cooperative use of the optical crystal microcavity and the concentric-square-shaped nanometer light beam cavity, linear relations between wavelengths in different axial directions and force and torque are established, so that corresponding force and torque are measured, and torque measurement on three axes is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of torque measurement, and more specifically, relates to an optical mechanical multi-axis torque sensor. Background Art

[0002] The three-axis torque sensor is a device used to measure the torque magnitude of an object in three-dimensional space. It can detect torque in three directions at the same time, namely the 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 torque in a single direction, while three-axis torque sensors can measure torque in three directions at the same time, greatly improving the accuracy and efficiency of measurement. Its working principle is mainly to measure the deformation of an object when it is subjected to external force, and then convert these deformations into electrical signals, and then process them through circuits to finally obtain the magnitude of the torque. The main components of the three-axis torque sensor include sensitive elements, conversion elements and processing circuits. The sensitive element is the part that directly contacts the object being measured, and it can convert the deformation of the object into a physical quantity that can be measured. The conversion element converts the physical quantity converted by the sensitive element into an electrical signal. The processing circuit processes the electrical signal and finally obtains the magnitude of the torque. The technical difficulty of the three-axis torque sensor lies mainly 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 a certain 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 sensors use 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 sensors are very suitable for applications requiring precise torque measurement and have demonstrated excellent performance in modern industrial applications. Summary of the invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and to provide an optomechanical multi-axis torque sensor that directly measures torque through the change in the resonant wavelength of an optical crystal microcavity or a circular nanobeam cavity.

[0005] To achieve the above-mentioned purpose of the invention, the present invention provides an optomechanical multi-axis torque sensor, characterized in that it comprises: a probe, a return-shaped nano-beam cavity, an optical crystal micro-cavity and a supporting cantilever arm;

[0006] The probe shown is directly fixed on the ring-shaped nanobeam cavity and is located at the center of one side of the ring-shaped nanobeam cavity to sense the external torque;

[0007] The circular nanobeam cavity comprises two layers of circular nanobeam cavity walls with the same structure, wherein the upper layer is a movable circular nanobeam cavity wall and the lower layer is a fixed circular nanobeam cavity; the movable circular nanobeam cavity wall is supported and fixed by a supporting cantilever arm, so that there is a gap between the upper and lower layers of the circular nanobeam cavity walls, thereby forming a circular nanobeam cavity;

[0008] The optical crystal microcavity includes four groups, which are installed on both sides of two sides parallel to the probe and are symmetrical with the central axis of the circular nanobeam cavity; each group of optical crystal microcavity includes a movable optical crystal and a fixed optical crystal, wherein the movable optical crystal is connected to the circular nanobeam cavity, the fixed optical crystal is placed next to the movable optical crystal, and there is a gap between the two groups of optical crystals;

[0009] The supporting cantilever arm is installed at the center of two sides parallel to the two sides of the probe, and is used to realize the displacement of the movable circular nano-beam cavity wall on the X, Y and Z axes.

[0010] The object of the invention of the present invention is achieved in this way:

[0011] The present invention discloses an optomechanical multi-axis torque sensor, comprising: a probe, a circular nano-beam cavity, an optical crystal micro-cavity and a supporting cantilever arm; by using the optical crystal micro-cavity and the circular nano-beam cavity in coordination, a linear relationship between wavelengths and force and torque in different axial directions is established, thereby measuring the corresponding force and torque, and realizing torque measurement on three axes.

[0012] At the same time, the optical mechanical multi-axis torque sensor of the present invention also has the following beneficial effects:

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

[0014] (2) Compared with the traditional torque sensor, the optical mechanical multi-axis torque sensor of the present invention is much smaller in size and is easier to be used in various micro fields;

[0015] (3) The present invention can measure torque on three axes through optical crystal microcavity and return nanobeam cavity;

[0016] (4) The circular nano-beam cavity of the present invention can work normally in harsh environments such as high temperature and high pressure, and will not lose accuracy due to environmental changes. It is suitable for many fields ranging from automobile manufacturing to aerospace and mechanical processing, and performs particularly well in equipment testing with high precision requirements. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0022] Figure 6 It is a schematic diagram of the displacement of the movable circular nanobeam cavity wall when the probe is subjected to Z-axis torque. DETAILED DESCRIPTION

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

[0024] Example

[0025] Figure 1 This is a structural diagram of an optomechanical multi-axis torque sensor of the present invention.

[0026] In this embodiment, if Figure 1 As shown, the optical mechanical multi-axis torque sensor of the present invention comprises: a probe, a circular nano-beam cavity, an optical crystal micro-cavity and a supporting cantilever arm;

[0027] like Figure 1 As shown in (a), the probe a is directly fixed on the ring-shaped nanobeam cavity and is located in the center of one side of the ring-shaped nanobeam cavity to sense the external torque; in this embodiment, the probe a is set on the side of the ring-shaped nanobeam cavity b1;

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

[0029] In this embodiment, the two side arms of the circular nano-beam cavity in the horizontal direction are recorded as nano-optical cavity cantilevers b1 and b2, and the two sides in the vertical direction are recorded as nano-optical cavity cantilevers b3 and b4; a mirror pattern is set in the center of each side, and the mirror patterns have the same shape and are symmetrical along the central axis of the wall of the circular nano-beam cavity;

[0030] like Figure 2 As shown in the figure, the shape of the holes in the mirror pattern gradually changes from a circle to an ellipse. The spacing between two adjacent holes is the same. Each hole on the mirror pattern is similar to a gap, and the length from the two ends to the inside is n. m The series of holes are collectively called external holes, which form a group of reflectors; the length from the center point to both ends is n c The series of holes are collectively called inner holes, which form an optical cavity that supports the optical mode.

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

[0032] In this embodiment, the movable optical crystal and the fixed optical crystal have the same structure. Figure 3 As shown, each group of optical crystals consists of two groups of arrayed photonic crystal holes f1 and air slots f2 located between them. The photonic crystal holes f1 are arranged in a regular hexagonal honeycomb shape, such as f3 in the figure, to finally form an optical crystal.

[0033] The supporting cantilever arm is installed at the center of both sides of the two sides parallel to the probe, and is used to realize the displacement of the movable circular nano-beam cavity wall on the X, Y and Z axes.

[0034] When the optomechanical multi-axis torque sensor is measuring torque, Figure 4As shown in the figure, when the probe is subjected to the X-axis torque, the horizontal nano-optical cavity cantilever b1 and b2 will be displaced out of the plane relative to the plane, and the displacement causes the gap between the movable return-type nano-beam cavity wall and the fixed return-type nano-beam cavity wall to change, thereby affecting the resonance wavelength of the movable return-type nano-beam cavity wall. When the gap width between the nano-optical cavity cantilever b1 and the bottom fixed return-type nano-beam cavity wall increases, the gap width between the nano-optical cavity cantilever b2 and the bottom fixed return-type nano-beam cavity wall will decrease, forming a differential structure, and its measurement sensitivity is nearly doubled compared with the non-differential structure. The fixed return-type nano-beam cavity wall only guides the input and output light. The corresponding force and torque are measured through the linear relationship between wavelength, force and torque.

[0035] When the probe is subjected to Y-axis torque, such as Figure 5 As shown in the figure, the vertical nano-optical cavity cantilevers b3 and b4 will have an out-of-plane displacement relative to the plane, and the displacement will cause the gap between the movable return-type nano-beam cavity wall and the fixed return-type nano-beam cavity wall to change, thereby affecting the resonance wavelength of the movable return-type nano-beam cavity wall. When the gap width between the nano-optical cavity cantilever b3 and the bottom fixed return-type nano-beam cavity wall increases, the gap width between the nano-optical cavity cantilever b4 and the fixed return-type nano-beam cavity wall will decrease, forming a differential structure, and its measurement sensitivity is nearly doubled compared with the non-differential structure. The fixed return-type 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 a Z-axis torque, such as Figure 6 As shown in the figure, the probe brings the movable circular nanobeam cavity wall to deflect in the paper plane, so that the gap of the air slot in the optical crystal in the optical crystal microcavity changes. Based on its differential structure, if the active optical crystal in the optical crystal microcavity is close to the fixed optical crystal, the active optical crystal in the optical crystal microcavity will be far away from the fixed optical crystal. Compared with the non-differential structure, its measurement sensitivity is nearly doubled. Through the linear relationship between wavelength and force and torque, the corresponding force and torque can be measured.

[0037] In the above, when the probe is displaced x s , the change in the gap between each air slot is still x s , considering that the displacement of the movable part in the optomechanical multi-axis torque sensor also includes the displacement x generated by the laser n , and its own thermal Brownian noise x th , so the total displacement is:

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

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

[0040] λn=2L

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

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

[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 invention also has a differential structure, and its measurement sensitivity is nearly doubled compared with a non-differential structure.

[0045] In this embodiment, the movable and fixed nanobeam cavity walls can be fabricated in a 400nm thick SiN layer above a 500μm silicon layer. The fixed nanobeam cavity wall only guides the input and output light. The movement of the movable nanobeam cavity wall can be induced by various physical measurements, and its resonant wavelength is affected by the mechanical movement of the movable part.

[0046] Optical crystal microcavity is made by removing SiO2 in the middle area of ​​the middle SiO2 layer of SOI substrate through photolithography. Silicon micromechanical oscillator structure is made on the top silicon of rectangular SOI substrate through micro-nano processing technology, while the bottom silicon remains unchanged; SiO2 in the middle area is removed by photolithography on the middle SiO2 layer of SOI substrate.

[0047] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. An optomechanical multi-axis torque sensor, characterized in that: include: Probe, circular nanobeam cavity, optical crystal microcavity and supporting cantilever arm; The probe shown is directly fixed on the ring-shaped nanobeam cavity and is located at the center of one side of the ring-shaped nanobeam cavity to sense the external torque; The circular nanobeam cavity comprises two layers of circular nanobeam cavity walls with the same structure, wherein the upper layer is a movable circular nanobeam cavity wall and the lower layer is a fixed circular nanobeam cavity; the movable circular nanobeam cavity wall is supported and fixed by a supporting cantilever arm, so that there is a gap between the upper and lower layers of the circular nanobeam cavity walls, thereby forming a circular nanobeam cavity; The optical crystal microcavity includes four groups, which are installed on both sides of two sides parallel to the probe and are symmetrical with the central axis of the circular nanobeam cavity; each group of optical crystal microcavity includes a movable optical crystal and a fixed optical crystal, wherein the movable optical crystal is connected to the circular nanobeam cavity, the fixed optical crystal is placed next to the movable optical crystal, and there is a gap between the two groups of optical crystals; The supporting cantilever arm is installed at the center of two sides parallel to the two sides of the probe, and is used to realize the displacement of the movable circular nano-beam cavity wall on the X, Y and Z axes.

2. The optomechanical multi-axis torque sensor according to claim 1, characterized in that: The movable optical crystal has the same structure as the fixed optical crystal. The optical crystal consists of two groups of array-arranged photonic crystal holes and air slots located between them. The photonic crystal holes are arranged in a regular hexagonal honeycomb to form a photonic crystal.

3. The optomechanical multi-axis torque sensor according to claim 1, characterized in that: Mirror patterns are arranged in the center of the four sides of the circular nano-beam cavity wall. The mirror patterns have the same shape and are symmetrical along the central axis of the circular nano-beam cavity wall.

4. The optomechanical multi-axis torque sensor according to claim 3, characterized in that: The hole shape of the mirror pattern gradually changes from a circle to an ellipse, and the spacing between two adjacent holes is the same. Each hole on the mirror pattern is similar to a gap, and the length from the two ends to the inside is n m The series of holes are collectively called external holes, which form a group of reflectors; the length from the center point to both ends is n c The series of holes are collectively called inner holes, which form an optical cavity that supports the optical mode.

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