Scanning path planning method for uniform laser ablation of hemispherical resonator

Abstract

A scanning path planning method for uniform laser ablation of a hemispherical resonator comprises the steps that the radius of the surface to be machined of the hemispherical resonator is measured, the azimuth angle change of each traversal point is calculated to ensure that the linear velocity of laser ablation is consistent, and then uniform ablation is achieved. And planning an ablation scanning path. Through the scanning path, uniform deposition of laser energy of each traversal point is realized, the effect of uniform laser ablation is achieved, and the problem of frequency splitting caused by non-uniformity of circumferential quality of the hemispherical harmonic oscillator is solved. The invention also relates to a method for controlling the two rotating platforms in the latitude and longitude directions of the hemispherical harmonic oscillator to move synergistically to ensure that each point on the surface is ablated by laser according to a preset path and speed. The laser ablation precision and efficiency are improved, the operation difficulty and complexity are reduced, a new efficient solution is provided for uniform laser ablation of the hemispherical harmonic oscillator, and the laser ablation device has wide application prospects.

Description

Technical Field

[0001] The invention relates to the field of optical element processing, in particular to a path planning method for laser uniform ablation of a spherical optical element. Background Art

[0002] The hemispherical resonant gyroscope is known as "the most ideal device for inertial navigation systems of various types of vehicles in the 21st century, and its development will bring about revolutionary and subversive changes in the field of inertial navigation". The hemispherical resonant gyroscope is a new type of solid-state gyroscope with high precision, high reliability and long life. It is a kind of Columbia vibrating gyroscope that uses the radial vibration standing wave precession effect of the lip of the hemispherical shell to sense the rotation of the base. It has high measurement accuracy, super stability and reliability, good shock and vibration resistance and temperature performance, and also has unique shutdown and radiation resistance. In particular, the expected life is up to 15 years. It is a key component of the inertial measurement unit and attitude stabilization control of satellites or spacecraft. It has unique advantages and broad prospects in the field of space applications.

[0003] The hemispherical resonator is the core component of the hemispherical resonator gyroscope. The basic structure is a hemispherical shell, which is usually made of high-quality materials (such as fused quartz) to ensure its high stability and high precision. Fused quartz is a hard and brittle material. It is very easy to produce surface defects and sub-surface defects during the traditional grinding process, which seriously affects the measurement accuracy and service life of the gyroscope. Laser ablation uses the high energy density of the laser beam to instantly heat the surface of the material to an extremely high temperature, so that the surface layer of the material is vaporized or sputtered to achieve the purpose of removing the material. Because it does not require direct contact with the surface of the material, it avoids the damage to the material by the cutting force and compressive stress in mechanical processing, and has unique advantages in the flexible processing of fused quartz. However, in the process of laser point-by-point ablation on the surface of the hemispherical resonator, compared with plane processing, it is very easy to cause circumferential inhomogeneity of the hemispherical resonator, that is, the mass and stiffness distribution of the hemispherical resonator in the circumferential direction is uneven, thereby introducing additional vibration modes. Different vibration modes have different frequencies, which will lead to frequency splitting. The existence of frequency difference will affect the accuracy and stability of the hemispherical resonator, especially in high-precision applications. In order to give full play to the advantages of laser ablation processing, ensuring that the same mass is removed along the spherical ablation path is an urgent problem to be solved. Summary of the invention

[0004] The present invention provides a scanning path planning method for uniform laser ablation of a hemispherical resonator, which realizes uniform deposition of laser energy on a spherical optical element during laser ablation and solves the problem of frequency splitting caused by circumferential quality non-uniformity introduced during the process of removing surface / sub-surface defects.

[0005] The technical solution of the present invention is as follows:

[0006] A scanning path planning method for uniform hemispherical resonator laser ablation is characterized in that it comprises the following steps:

[0007] Step 1) measuring the radius R of the surface to be processed of the hemispherical resonator;

[0008] Step 2) Calculate each traversal point P of the hemispherical resonator surface to be processed i Azimuth change To ensure the consistency of the line speed during laser ablation, thus achieving uniform ablation, the formula is as follows:

[0009]

[0010] Where n depends on the spot diameter and the overlap rate of the ablation path, and m is any adjacent traversal point P. i-1 and P i The chords between them are of equal length, θ i For point P i The polar angle of

[0011] Step 3) Calculate the angular velocity of the hemispherical resonator in the latitude direction and the angular velocity V in the longitude direction θ The formula is as follows:

[0012]

[0013] V θ =Δθ / dt=(π / 2-arcsinα) / ndt

[0014] Where dt is the adjacent point P i-1 Move to P i The time interval dt satisfies dt=m / V laser , V laser Constant laser ablation speed, α is the polar angle corresponding to the connection point between the central rod of the hemispherical resonator and the ablation surface;

[0015] Step 4) Control the coordinated movement of the two rotating platforms in the longitude and latitude directions of the hemispherical resonator to ensure that each point on the surface of the hemispherical resonator is ablated by the laser according to a predetermined path and speed.

[0016] Go further, click P i The polar angle, that is, the range of angle changes in the longitude direction

[0017] Furthermore, any adjacent traversal point P i-1 and P i The chord length between them is m = P i-1 P i >P i-1 B=R / n.

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] 1) By calculating the azimuth change of each traversal point Pi Ensure the consistency of line speed during laser ablation, thereby achieving uniform ablation, avoiding the problem of uneven line speed that may occur in traditional scanning path planning, and significantly improving ablation quality and efficiency.

[0020] 2) Dynamic angular velocity planning can adjust the ablation path and speed in real time according to the shape of the hemispherical resonator and the requirements of laser ablation, ensuring that each point can be laser ablated according to the predetermined path and speed.

[0021] 3) By controlling the coordinated movement of the two rotating platforms in the longitude and latitude directions of the hemispherical resonator, precise control of the laser ablation path is achieved.

[0022] 4) During the laser ablation process for removing surface / subsurface defects, it is possible to ensure uniform deposition of laser energy at each point and achieve uniform laser ablation, thereby avoiding the frequency splitting problem caused by the circumferential mass non-uniformity of the hemispherical resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a planning flow chart of Example 1 of the scanning path planning method for uniform laser ablation of a hemispherical resonator according to the present invention;

[0024] Figure 2 It is an analysis diagram of the ablation process of Example 1 of the scanning path planning method for uniform hemispherical resonator laser ablation of the present invention.

[0025] Figure 3 It is a schematic diagram of the scanning path of Example 1 of the scanning path planning method for uniform hemispherical resonator laser ablation of the present invention.

[0026] Figure 4 It is a morphology diagram of different sub-surface depths of Example 1 of the scanning path planning method for uniform hemispherical resonator laser ablation of the present invention. Specific implementation methods

[0028] The present invention is described in detail below, but the protection scope of the present invention shall not be limited thereto.

[0029] A scanning path planning method for uniform laser ablation of a hemispherical resonator, wherein the processing object is a formed hemispherical resonator element, comprises the following steps:

[0030] (1) Measuring the surface to be processed: Using a three-dimensional coordinate measuring machine to measure the size of the hemispherical resonator to be processed, that is, the radius R of the hemispherical resonator to be processed;

[0031] (2) Calculate the azimuth change of each traversal point on the surface to be processed by the hemispherical resonator To ensure the consistency of line speed during laser ablation, thus achieving uniform ablation.

[0032] Specifically include:

[0033] Any point P on the surface to be processed by the hemispherical resonator is expressed in the spherical coordinate system as Among them, r is the radial distance from point P to the center of the sphere, θ is the polar angle of point P (that is, the angle with the z-axis), is the azimuth of point P (i.e. the angle between its projection on the xy plane and the x-axis).

[0034] Two adjacent traversal points P i-1 and P i : Point Move to within time dt In order to ensure the linear velocity of laser ablation is consistent, it is necessary to ensure that the chord length between any adjacent traversal points is equal, denoted as m. The chord length m is the distance between two traversal points P. i-1 and P i The length of the straight line segment.

[0035] Let Zp be a point passing through P i-1 The center of the plane tangent to the sphere is A, which passes through point P. i And the center of the plane tangent to the sphere, according to the radius R of the hemispherical resonator, the following relationship is obtained:

[0036] AP i =R×sinθ i , that is, point P i The distance to the center A of its cross section

[0037] AB=Z p P i-1 =R×sinθ i-1 , that is, point P i-1 The distance to the center Zp of its cross section.

[0038] The longitudinal distance P between two adjacent traversal points i-1 B = R / n (n depends on the spot diameter and the ablation path overlap rate), that is, Thus, any traversal point P can be obtained i The polar angle changes

[0039] Among them, the angle variation range θ in the longitude direction i ∈(0,π / 2-arcsinα), α is the polar angle corresponding to the connection point between the central rod of the hemispherical resonator and the ablation surface;

[0040] Chord length m = P i-1 P i >Pi-1 B=R / n, where n is the spot diameter and the ablation path overlap ratio.

[0041] Step 3) Calculate the angular velocity of movement in the longitude and latitude directions, and control the laser ablation speed through the coordinated movement in the longitude and latitude directions during the hemispherical resonator laser ablation process.

[0042] The details are as follows:

[0043] point Move to within the time interval dt To maintain a constant ablation speed Vlaser, the time interval dt satisfies the following conditions:

[0044] dt=m / V laser

[0045] Calculate the latitude direction (i.e. Angular velocity of movement in the direction The formula is as follows:

[0046]

[0047] Calculate the angular velocity V in the longitude direction θ , the formula is as follows:

[0048] V θ =Δθ / dt=(π / 2-arcsinα) / ndt

[0049] Step 4) Control the coordinated movement of the two rotating platforms in the longitude and latitude directions of the hemispherical resonator to ensure that each point on the surface of the hemispherical resonator is ablated by the laser according to a predetermined path and speed.

[0050] Specifically include:

[0051] The surface of the hemispherical resonator determines the position of each point by longitude and latitude, that is, the azimuth angle change of each point on the surface of the hemispherical resonator to be processed With the change of polar angle θ i ,During the laser ablation process, the rotation in these two directions needs to be ,precisely controlled to ensure that the laser beam can evenly cover the entire ,surface to be processed.

[0052] According to the requirements of ablation depth and the properties of the material, the output power of the laser is adjusted to achieve the best ablation effect. Adjusting the duty cycle changes the average power and energy intensity of the laser beam, thereby affecting the ablation effect.

[0053] Based on established The laser ablation paths are calculated by LabVIEW program based on the relationship and laser parameter settings. These paths can cover the entire surface to be processed and ensure uniform deposition of laser energy.

[0054] Example 1

[0055] A scanning path planning method for uniform laser ablation of a hemispherical resonator, wherein the processing object is a formed hemispherical resonator element, and the method comprises the following steps:

[0056] (1) Measuring the surface to be processed: Using a three-coordinate measuring machine to measure the size of the hemispherical resonator to be measured, the radius of the outer surface of the hemispherical resonator to be processed is 15 mm;

[0057] (2) Analysis of azimuth changes of all traversed points on the outer surface of the hemisphere: Figure 2 As shown, any point on the inner and outer surfaces of the hemispherical resonator Move to within time dt Let m = P i-1 P i =150 / 50000mm, m depends on the equivalent laser processing speed of 25.5mm / s, then AP i =R×sinθ i =15sinθ i , AB=Z p P i-1 =R×sinθ i-1 =15sinθ i-1 , P i-1 B = R / n = 15 / 50000mm (n = 50000, depending on the spot diameter of 100μm and the ablation path overlap rate of 85%), Thus, the polar angle change of any traversal point is obtained

[0058] (3) Analysis of the velocity of the hemispherical resonator in the longitude and latitude directions: Point The linear velocity of the coordinated motion in the longitude and latitude directions is equivalent to the laser ablation velocity V laser =25.5mm / s, then dt=m / V laser , and thus calculate the latitude direction movement speed The velocity V in the longitude direction θ =Δθ / dt=(π / 2-arcsinα) / ndt=0.2269rad / s;

[0059] (4) Planning the ablation scanning path: The LabVIEW program written independently is used to control the coordinated movement of the rotating platform in the longitude and latitude directions of the hemispherical resonator. i and , ablation depth of 20μm, set the output power of CO2 laser to 40W, pulse width to 60μs and duty cycle to 10%, and plan the laser ablation path, such as Figure 3 As shown; the experimental results show that ( Figure 4 As shown in Figure 3, after laser uniform ablation of 20 μm, the subsurface defects of the hemispherical resonator were effectively removed.

Claims

1. A scanning path planning method for uniform hemispherical resonator laser ablation, characterized in that: The following steps are involved: Step 1) measuring the radius R of the surface to be processed of the hemispherical resonator; Step 2) Calculate each traversal point P of the hemispherical resonator surface to be processed i Azimuth change To ensure the consistency of the line speed during laser ablation, thus achieving uniform ablation, the formula is as follows: Where n depends on the spot diameter and the overlap rate of the ablation path, and m is any adjacent traversal point P. i-1 and P i The chords between them are of equal length, θ i Point P i The polar angle of Step 3) Calculate the angular velocity of the hemispherical resonator in the latitude direction and the angular velocity V in the longitude direction θ The formula is as follows: V θ =Δθ / dt=(π / 2-arcsinα) / ndt Where dt is the adjacent point P i-1 Move to P i The time interval dt satisfies dt=m / V laser , V laser Constant laser ablation speed, α is the polar angle corresponding to the connection point between the central rod of the hemispherical resonator and the ablation surface; Step 4) Control the coordinated movement of the two rotating platforms in the longitude and latitude directions of the hemispherical resonator to ensure that each point on the surface of the hemispherical resonator is ablated by the laser according to a predetermined path and speed.

2. The scanning path planning method for hemispherical resonator laser uniform ablation according to claim 1, characterized in that: Point P i The polar angle, that is, the range of angle changes in the longitude direction 3. The scanning path planning method for hemispherical resonator laser uniform ablation according to claim 1, characterized in that: Any adjacent traversal point P i-1 and P i The chord length between them is m = P i-1 P i >P i-1 B=R / n.

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