Dynamic focusing optics and methods for laser shock peening

Abstract

The application discloses a dynamic focusing optical device and method for laser shock peening. The device comprises a coaxial and adjustable interval lens group, a distance sensing module, a displacement driving unit, a displacement sensor and a control module. The control module calculates the target equivalent focal length according to the axial distance, solves the displacement control quantity in combination with the lens group equivalent focal length model, and makes the laser focal point keep in the preset working distance according to the sensor feedback closed loop control. In the method, the weighted square sum of the interval change amount of the adjacent lenses is taken as the target, the optimal adjustment amount is solved under the constraints of the focal length error and the stroke, and the multi-lens collaborative focusing is realized. The application can adapt to the complex curved surface change, has fast response, stable optical axis, high precision, and guarantees the energy density consistency of the laser shock peening.

Description

Technical Field

[0001] This invention relates to the fields of laser shock strengthening and intelligent manufacturing technology, and more specifically to a dynamic focusing optical device and method for laser shock strengthening. Background Technology

[0002] Laser shock peening is an advanced surface strengthening technology that uses high-energy pulsed lasers to induce plasma shock waves on the material surface, thereby introducing high-amplitude residual compressive stress and improving the microstructure. Compared with traditional shot peening, laser shock peening has advantages such as high impact pressure, large strengthening depth, good controllability, and high processing precision. It has been widely used in aerospace, energy equipment, and high-end manufacturing fields, and is especially suitable for improving the fatigue life of complex structural components, complex curved surface components, and critical load-bearing parts.

[0003] In practical engineering applications, many key components (such as aero-engine blades, fuselage panels, integral structural parts, and complex curved surface components) are characterized by large curvature variations, complex geometric shapes, and variable spatial attitudes. When performing laser shock peening on such complex components, the laser beam typically needs to scan a large area along the component surface. The actual working distance between the laser processing head and the workpiece surface changes continuously with the surface morphology. When the distance between the laser focal point and the workpiece surface is large, the laser energy density on the workpiece surface will change, leading to fluctuations in impact pressure, which in turn affects the uniformity of residual compressive stress distribution and the consistency of the strengthening effect.

[0004] In existing technologies, to improve the quality of laser shock peening of curved structures, some studies compensate for the effects of curvature changes by adjusting laser energy parameters or optimizing the scanning path. For example, invention patent CN109136526B proposes a laser shock peening method for curved structures, which achieves a relatively uniform strengthening effect by fitting a mathematical model of the curved surface and setting different laser energy distributions in different regions. However, this method mainly relies on mathematical modeling of the workpiece surface and preset process parameters, and its laser focusing system still adopts a fixed focal length optical structure. When the workpiece surface has a complex morphology or is subject to processing deformation, it is still difficult to ensure that the laser focus remains stably in the ideal position.

[0005] Invention patent CN220902166U discloses a focusing lens position adjustment structure and a laser shock blasting device for sheet metal. This device adjusts the laser focal point by changing the position of the focusing lens through a mechanical adjustment mechanism to adapt to different processing conditions. While this solution achieves laser focal length adjustment to a certain extent, its lens adjustment structure mainly relies on mechanical transmission mechanisms such as lead screws or sliders to achieve overall displacement. This results in a large structural size and high moment of inertia, making it difficult to achieve rapid response and high-precision dynamic adjustment. Furthermore, this type of mechanism is difficult to design compactly, hindering its integration with laser shock blasting heads or multi-degree-of-freedom motion platforms, and limiting its adaptability in strengthening complex curved surfaces or spatial components.

[0006] Furthermore, invention patent CN113319425B discloses a multi-axis laser scanning optical system, which includes a dynamic focusing module, a beam parallel translation module, a two-dimensional scanning module, and a focusing module, enabling multi-directional control of the laser beam. The dynamic focusing module employs multiple lenses arranged sequentially along the optical axis, adjusting the lens spacing to change the beam diameter and the Z-axis position of the focal point to meet the needs of general laser processing such as laser drilling, cutting, and etching. However, this patent primarily relies on optical path geometry to adjust the focal position and beam attitude, without disclosing the real-time distance sensing, target equivalent focal length calculation, multi-lens collaborative optimization control, and closed-loop feedback control technology for lens displacement in addressing the dynamic defocusing problem of complex curved surfaces during laser shock reinforcement.

[0007] While existing technologies have made some progress in energy control and path planning for laser shock peening, they generally lack a dynamic focusing technique that can sense changes in the workpiece surface position in real time during processing and simultaneously adjust the laser focusing state. Especially in the laser shock peening of complex curved components, it is difficult to keep the laser focus position consistently within the preset working distance range, which can easily cause energy density fluctuations, thus affecting the stability and consistency of the strengthening effect.

[0008] Therefore, there is an urgent need for a dynamic focusing optical device and method suitable for laser shock strengthening of complex curved components. By sensing the processing distance in real time and dynamically adjusting the laser focal length, precise and stable dynamic focusing is achieved, solving the problems of focal drift and energy density fluctuation caused by changes in the workpiece surface, thereby improving the consistency of energy density and processing stability in the laser shock strengthening process of complex structural components. Summary of the Invention

[0009] In view of the above problems, the present invention is proposed to provide a dynamic focusing optical device for laser shock enhancement that overcomes or at least partially solves the above problems, comprising:

[0010] A lens group consists of n lenses arranged coaxially along the optical axis, where n ≥ 2, and the spacing between adjacent lenses is adjustable. The distance sensing module is used to acquire axial distance information between the point to be laser-strengthened and the dynamic focusing optical device; A displacement driving unit is used to drive the lenses in the lens group to generate axial displacement along the optical axis. A displacement sensor is used to acquire the actual displacement of the lens along the optical axis. The control module is electrically connected to the distance sensing module, the displacement sensor, and the displacement driving unit, respectively. The control module is used to calculate the target equivalent focal length based on the axial distance information, solve the lens displacement control amount based on the target equivalent focal length and the equivalent focal length model of the lens group, and perform closed-loop control of the displacement driving unit based on the lens displacement control amount and the actual displacement fed back by the displacement sensor, so as to keep the laser focus position within a preset working distance range.

[0011] Preferably, it further includes a displacement amplification system, which is disposed between the displacement driving unit and the lens, and is used to amplify the displacement generated by the displacement driving unit and output it to the lens; The displacement sensor is positioned between the fixed end and the output end of the displacement amplification system to directly obtain the displacement of the output end of the displacement amplification system as the actual displacement of the lens.

[0012] Preferably, the distance sensing module includes a binocular camera, the center of which is on the same horizontal plane as the center of the dynamic focusing optical device, and the left and right binocular cameras are symmetrically mounted on both sides of the dynamic focusing optical device via slide rails.

[0013] Preferably, the displacement driving unit includes a micro actuator; for the same lens, at least two sets of the displacement driving units are provided and arranged symmetrically along the circumference of the lens to drive the lens to achieve axial translation in a symmetrical force application manner.

[0014] Preferably, it further includes an elastic return mechanism, which is disposed between the displacement driving unit and the lens mount to cooperate with the displacement driving unit to realize bidirectional displacement adjustment of the lens.

[0015] Preferably, the lens group consists of three lenses—a first lens, a second lens, and a third lens—arranged sequentially along the optical axis, wherein the first lens is a plano-convex lens, the second lens is a plano-concave lens, and the third lens is a plano-convex lens.

[0016] Preferably, an annular spacer is provided between adjacent lenses, and the outer edge of the annular spacer is fixed to the inner wall of the lens support structure to define the initial distance between adjacent lenses.

[0017] Preferably, the displacement sensor is any one of a capacitive displacement sensor, a grating displacement sensor, a magnetic grating displacement sensor, or a displacement sensor based on flexible beam strain measurement.

[0018] Preferably, the control module is used to solve for the lens displacement control quantity by taking the minimum weighted sum of squares of the changes in the spacing between adjacent lenses as the objective function and taking the error of the target equivalent focal length not exceeding a preset threshold as the constraint condition.

[0019] Based on the unified inventive concept, this invention also discloses a dynamic focusing method for laser shock enhancement, applied to the aforementioned dynamic focusing optical device, comprising the following steps: S1. During the laser shock strengthening process, the axial distance information between the point to be laser shock strengthened and the dynamic focusing optical device is acquired in real time. S2. Calculate the target equivalent focal length based on the axial distance information; S3. Solve for the lens displacement control amount based on the target equivalent focal length and equivalent focal length model; S4. Send a displacement command according to the lens displacement control amount to drive the lens to generate axial displacement; S5. The actual displacement of the lens along the optical axis is acquired in real time, and closed-loop control is performed based on the deviation between the actual displacement and the lens displacement control amount, so that the actual displacement of the lens reaches the lens displacement control amount, thereby achieving dynamic focusing.

[0020] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following: (1) By adjusting the axial displacement of multiple lenses by a small amount, the focal length can be changed, avoiding the large inertia caused by the overall movement, so that the dynamic focusing process has the characteristic of rapid response. (2) By integrating multiple lenses coaxially and arranging the displacement drive module and lens support structure in an integrated manner, a compact optical focusing structure is formed, which is beneficial to reduce the size of the device and improve the system integration. (3) By placing the displacement sensor between the fixed end and the output end of the displacement amplification system, the actual displacement of the lens can be directly obtained and closed-loop control can be implemented, which can effectively compensate for the hysteresis and nonlinearity of the amplification mechanism and improve the focusing accuracy and repeatability. (4) By using the symmetrical collaborative driving and differential suppression strategy of multiple sets of displacement driving units, the lens eccentricity and tilt are reduced, and the optical axis stability is improved; (5) It can adaptively match the changes in part shape caused by the processing, reduce the influence of clamping method and processing deformation on the laser shock strengthening effect, and is suitable for laser shock strengthening processing conditions with high requirements for focus stability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a dynamic focusing optical device for laser shock enhancement provided in an embodiment of the present invention; Figure 2 This is a flowchart of a dynamic focusing optics method for laser shock enhancement provided in an embodiment of the present invention; Among them, 1. workpiece; 2. lens support structure; 3. annular spacer; 4. first displacement drive unit; 5. micro driver; 6. displacement amplification system; 7. displacement sensor; 8. binocular camera; 9. first lens; 10. second lens; 11. third lens; 12. second displacement drive unit; 13. third displacement drive unit. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention discloses a dynamic focusing optical device for laser shock enhancement, comprising: A lens group consists of n lenses arranged coaxially along the optical axis, where n ≥ 2, and the spacing between adjacent lenses is adjustable. The distance sensing module is used to acquire axial distance information between the point to be laser-strengthened and the dynamic focusing optical device; A displacement driving unit is used to drive the lenses in the lens group to generate axial displacement along the optical axis. A displacement sensor is used to acquire the actual displacement of the lens along the optical axis. The control module is electrically connected to the distance sensing module, the displacement sensor, and the displacement driving unit, respectively. The control module is used to calculate the target equivalent focal length based on the axial distance information, solve the lens displacement control amount based on the target equivalent focal length and the equivalent focal length model of the lens group, and perform closed-loop control of the displacement driving unit based on the lens displacement control amount and the actual displacement fed back by the displacement sensor, so as to keep the laser focus position within a preset working distance range.

[0025] Specifically, such as Figure 1 As shown, the device includes a lens group, a displacement driving unit, a displacement sensor, a distance sensing module, and a control module.

[0026] The device is installed between the laser beam output port of the laser shock peening equipment and workpiece 1, with one end connected to the laser beam output port and the other end facing the surface of workpiece 1. The lens assembly consists of... n ( The lens group consists of lenses arranged coaxially along the optical axis. The lens materials and coatings meet the requirements of the laser wavelength and power density used in laser shock peening. Each lens is coaxially mounted within the lens support structure 2, with the optical axes coinciding, and the spacing between adjacent lenses is adjustable. The equivalent focal length of the lens group is... f Spacing between adjacent lenses d There is a functional relationship .

[0027] The distance sensing module is used to acquire the axial distance L between the point to be laser-strengthened and the device in real time.

[0028] Displacement driving units (such as the first displacement driving unit 4, the second displacement driving unit 12, and the third displacement driving unit 13) are set up corresponding to each lens to receive instructions from the control module and drive the corresponding lens to generate axial displacement along the optical axis.

[0029] Displacement sensor 7 is set up corresponding to each lens to obtain the actual displacement of the corresponding lens along the optical axis and send the actual displacement as a feedback signal to the control module.

[0030] The control module, as the core of the control system, is electrically connected to the distance sensing module, displacement sensor, and displacement drive unit. During the machining process, the control module receives real-time axial distance information. Information, based on the preset ideal working distance Calculate the required target equivalent focal length Then, the control module uses the internally stored equivalent focal length model. Solving for the desired result The required target displacement of each lens is determined, and displacement commands are sent to the displacement drive unit. During lens movement, the control module continuously receives actual displacement feedback from displacement sensor 7, and precisely adjusts the action of the displacement drive unit through a closed-loop control algorithm (such as PID control) until the lens reaches the target position. Through this closed-loop dynamic focusing process, the laser focus is stabilized in real time and precisely within the preset working distance range, ensuring the consistency of laser shock enhancement energy density.

[0031] In one embodiment, a displacement amplification system is further included, which is disposed between the displacement driving unit and the lens, and is used to amplify the displacement generated by the displacement driving unit and output it to the lens; The displacement sensor is positioned between the fixed end and the output end of the displacement amplification system to directly obtain the displacement of the output end of the displacement amplification system as the actual displacement of the lens.

[0032] Specifically, this embodiment also includes a displacement amplification system 6. For example... Figure 1 As shown, the lens support structure 2 has several radial mounting holes arranged circumferentially, and a displacement driving unit 4 is embedded in each radial mounting hole. The displacement driving unit 4 includes a micro-driver 5 and a displacement amplification system 6, which is disposed between the micro-driver 5 and the lens. The telescopic end of the micro-driver 5 (such as a piezoelectric ceramic driver) is connected to the input end of the displacement amplification system 6, and the output end of the displacement amplification system 6 abuts against or connects to the outer edge annular groove or lens mount of the lens. This structure amplifies the minute displacement of the micro-driver to obtain a lens travel that meets the focusing requirements, causing the lens to produce axial translational displacement along the optical axis.

[0033] Furthermore, the displacement sensor 7 is specifically positioned between the fixed end and the output end of the displacement amplification system 6. Its fixed end is installed on the fixed reference part of the displacement amplification system 6, while its measuring end corresponds to the moving part of the output end of the displacement amplification system 6. This arrangement allows the displacement sensor to directly measure the amplified actual displacement acting on the lens, thereby avoiding errors such as hysteresis and flexible deformation that might be introduced by only measuring the driver stroke. This significantly improves the accuracy of displacement measurement and the precision of closed-loop control.

[0034] In one embodiment, the distance sensing module includes a binocular camera, the center of which is on the same horizontal plane as the center of the dynamic focusing optical device, and the left and right binocular cameras are symmetrically mounted on both sides of the dynamic focusing optical device via slide rails.

[0035] Specifically, such as Figure 1As shown, the distance sensing module includes a binocular camera 8 and an auxiliary illumination source (not shown in the figure). The center of the binocular camera 8 is on the same horizontal plane as the center of the dynamic focusing optics. The left and right cameras are symmetrically mounted on both sides of the dynamic focusing optics via sliding rails. This symmetrical layout and coplanar design helps improve the reliability and accuracy of distance measurement. The auxiliary illumination source surrounds the binocular camera and its position is adjustable to improve imaging quality under complex surface conditions. The binocular camera 8 obtains intrinsic parameters, extrinsic parameters, and baseline parameters through calibration. During processing, it outputs the depth information from the point to be processed to the reference plane of the device in real time, and calculates the axial distance L between the point to be processed and the dynamic focusing optics based on the device's structural parameters.

[0036] In one embodiment, the displacement driving unit includes a micro actuator; for the same lens, at least two sets of the displacement driving units are provided and arranged symmetrically along the circumference of the lens to drive the lens to achieve axial translation in a symmetrical force application manner.

[0037] Specifically, to suppress lens eccentricity and tilt during dynamic focusing, at least two sets of displacement driving units (such as the first displacement driving unit 4) consisting of a micro-actuator 5 and a displacement amplification system 6 are provided for the same lens (e.g., the first lens 9). These two sets of units are arranged symmetrically along the circumference of the lens, for example, installed at 180° or equiangularly symmetrically opposite each other at the outer edge of the lens. The control module coordinates the control of these two sets of units to drive the lens with symmetrical driving force, ensuring its smooth translation in the optical axis direction, thereby maintaining extremely high optical axis stability.

[0038] In one embodiment, an elastic return mechanism is further included, which is disposed between the displacement driving unit and the lens mount to cooperate with the displacement driving unit to realize bidirectional displacement adjustment of the lens.

[0039] Specifically, this embodiment also includes an elastic return mechanism (not shown in the figure). The elastic return mechanism is located between the output end of the displacement drive unit and the lens mount, and can be, for example, a spring or sheet structure. When the micro-actuator 5 is de-energized or retracted, the elastic return mechanism provides a return force, pushing the lens to move in the opposite direction. This allows the lens to achieve controllable displacement in both the extension and retraction directions, realizing true bidirectional displacement adjustment to meet different needs of increasing or decreasing focal length.

[0040] In one embodiment, the lens group consists of three lenses—a first lens, a second lens, and a third lens—arranged sequentially along the optical axis. The first lens is a plano-convex lens, the second lens is a plano-concave lens, and the third lens is a plano-convex lens.

[0041] Specifically, this embodiment provides a preferred three-lens group scheme. For example... Figure 1As shown, the number of lenses in the lens group n =3, with lenses arranged sequentially along the optical axis as follows: first lens 9, second lens 10, and third lens 11. Lens 9 is a plano-convex lens, lens 10 is a plano-concave lens, and lens 11 is a plano-convex lens, forming a convex-concave-convex arrangement. The optical parameters of each lens are known. The equivalent focal length of the lens group is... Spacing with adjacent lenses and mapping relationship It can be derived using the Gaussian formula for thick lenses and pre-stored in the control module for subsequent optimization solutions.

[0042] In one embodiment, an annular spacer is provided between adjacent lenses, the outer edge of which is fixed to the inner wall of the lens support structure to define the initial distance between adjacent lenses.

[0043] Specifically, such as Figure 1 As shown, an annular spacer 3 is provided between two adjacent lenses. The outer edge of the annular spacer 3 is fixed to the inner wall of the lens support structure 2, which is used to limit the initial distance between adjacent lenses and provide an assembly positioning reference. Let the first... The axial position of the sheet lens is The distance between adjacent lenses is The equivalent focal length of the lens group satisfies The above functional relationship can be calculated using the lens focal length formula and stored in the control module for solution.

[0044] In one embodiment, the displacement sensor is any one of a capacitive displacement sensor, a grating displacement sensor, a magnetic grating displacement sensor, or a displacement sensor based on flexible beam strain measurement.

[0045] Specifically, this embodiment lists the optional types of displacement sensor 7. The displacement sensor 7 can be a capacitive displacement sensor, measuring displacement using changes in capacitance; it can also be a grating or magnetic grating displacement sensor, acquiring displacement by reading grating scale markings; or it can be a strain gauge displacement sensor, measuring strain using strain gauges attached to the key flexible beam of the displacement amplification system 6 and calculating the output displacement after calibration. All of these sensors can provide high-precision displacement feedback signals.

[0046] In one embodiment, the control module is used to solve for the lens displacement control quantity by taking the minimum weighted sum of squares of the changes in the spacing between adjacent lenses as the objective function and taking the error of the target equivalent focal length not exceeding a preset threshold as the constraint condition.

[0047] Specifically, the control module constructs the solution process as an optimization problem. Let the distance vector between adjacent lenses in the current period be... objective function Designed as the weighted sum of squares of the changes in the spacing between adjacent lenses, i.e. ,in These are the weighting coefficients for adjusting each lens. The constraints include: 1) Focal length error constraint To ensure focusing accuracy, among other things, The equivalent focal length function of the lens group. ; Indicates the error threshold; 2) Travel constraints To ensure mechanical safety.

[0048] By minimizing the solution to this optimization problem, we can find the most balanced solution that minimizes the movement of each lens while ensuring focusing accuracy, thereby reducing energy consumption, improving response speed, and minimizing disturbance to the optical axis.

[0049] Based on the same inventive concept, the present invention also discloses a dynamic focusing method using any of the above-described device embodiments, comprising the following steps: S1. During the laser shock strengthening process, the axial distance information between the point to be laser shock strengthened and the dynamic focusing optical device is acquired in real time. S2. Calculate the target equivalent focal length based on the axial distance information; S3. Solve for the lens displacement control amount based on the target equivalent focal length and equivalent focal length model; S4. Send a displacement command according to the lens displacement control amount to drive the lens to generate axial displacement; S5. The actual displacement of the lens along the optical axis is acquired in real time, and closed-loop control is performed based on the deviation between the actual displacement and the lens displacement control amount, so that the actual displacement of the lens reaches the lens displacement control amount, thereby achieving dynamic focusing.

[0050] Specifically, this method cyclically performs the following steps during laser shock peening: The control module is electrically connected to the distance sensing module, displacement sensor, and displacement drive unit, and is used to: receive distance... Information; calculate the equivalent focal length of the target; construct and solve the optimization problem to obtain the change in the distance between adjacent lenses; further decompose to obtain the target displacement of each lens; implement closed-loop control on the displacement driving unit to keep the laser focus position dynamically within the preset working distance range.

[0051] In this embodiment, a dynamic focusing optical device is applied to the laser shock strengthening process. The workpiece 1 to be laser shock strengthened is a metal part with a certain curvature change. During this process, a pulsed laser acts on the workpiece surface under the adjustment of the dynamic focusing optical device. The laser-induced shock wave forms a residual compressive stress field and gradient structure on the workpiece surface, thereby improving the strength and fatigue resistance of the part. The number of lenses in the lens group is... A first lens 9, a second lens 10, and a third lens 11 are arranged sequentially along the optical axis, wherein the first lens 9 is a plano-convex lens, the second lens 10 is a plano-concave lens, and the third lens 11 is a plano-convex lens. The optical parameters of each lens are known parameters, and they are respectively connected to the corresponding displacement driving unit to realize the controllable axial displacement of the lens along the optical axis.

[0052] In the lens group, the thicknesses of the first plano-convex lens, the second plano-concave lens, and the third plano-convex lens are respectively... and The focal lengths of the lenses are respectively and The radii of curvature of the sphere are respectively The air gap between the lenses is and The refractive index of the lenses is According to Gaussian formula for the focal length of a thick lens, the focal length of a single thick lens satisfies... The equivalent focal length of the two lenses is obtained by combining the focal lengths of the first and second lenses. satisfy Use the same method to and The total focal length is obtained by combining the results. satisfy This allows us to obtain the mapping relationship between the equivalent focal length of the lens group and the spacing between adjacent lenses. .

[0053] Before laser shock peening begins, a mapping relationship between the focal position / optimal energy density and the equivalent focal length is established using a standard planar target or a calibrated workpiece. The control module stores the mapping model. or its inverse mapping ,in A calibrated value indicating the axial position of the focus relative to the device or related to the working distance.

[0054] Set travel constraints for the displacement sensors, zero out each displacement sensor, and set the constraint range for the spacing between adjacent lenses. And the allowable displacement range of each lens; establish the safe travel range of the actuator movement.

[0055] Combination Figure 2As shown, in a preferred embodiment, during the laser shock peening process, the workpiece to be processed is divided into sections, and the following steps are performed cyclically on each section: S1: During laser shock peening, the distance sensing module acquires the axial distance information between the current point to be strengthened and the dynamic focusing optics in real time, and transmits the axial distance information to the control module. The axial distance information reflects the real-time spatial relationship between the dynamic focusing optics and the point to be strengthened, and is used to characterize the working distance deviation caused by workpiece deformation during the strengthening process.

[0056] S2: Let the preset working distance be... This results in a distance deviation. The control module calculates the equivalent focal length of the target required to keep the focus within the preset working distance range based on the calibration mapping relationship. ,in .

[0057] S3: The control module calls the equivalent focal length model. The solution process is then constructed as an optimization problem. Let the adjacent spacing vector of the current period be... Construct an objective function that minimizes the change in the distance between adjacent lenses, i.e. ,in The weights of each lens are used to reflect the adjustment priority of different lenses. An error threshold is set within this. ,satisfy The displacement of the drive is set to meet the safe travel range, i.e. This optimization problem can be solved using iterative methods such as nonlinear least squares or sequential quadratic programming, or by offline table lookup and online minimum cost selection. The solution yields the change in adjacent spacing.

[0058] S4: Based on the distance relationship between the three lenses ,Will Decomposed into axial displacement commands for each lens To obtain a unique solution for moving each lens, we can fix one lens m as a reference and let... And based on this, the rest can be obtained recursively. Then, the target displacement of each lens is sent to the corresponding displacement driving unit.

[0059] S5: The displacement drive unit drives the lens to generate axial displacement under the action of the displacement amplification system (the displacement amplification system is a preferred method, not mandatory; if the stroke of the selected micro-actuator can directly meet the displacement required for lens adjustment, the displacement amplification system can be omitted, and the output end of the displacement drive unit can be directly connected to or against the lens). The displacement sensor measures the displacement of the output end of the amplification mechanism (the actual displacement of the lens) in real time and feeds it back to the control module. The control module uses a PID control algorithm to make the actual displacement of each lens accurately track the target value. For two symmetrical drive units of the same lens, the control module adopts cooperative control, using the average value of the displacements of the two sensors as the axial displacement feedback of the lens and comparing it with the target, using the difference between the displacements of the two sensors as the tilt index and controlling it to approach zero, thereby realizing lens translational focusing and suppressing tilt eccentricity.

[0060] The above steps S1–S5 are executed cyclically during laser shock peening until the processing of each area of ​​the workpiece is completed. Through this method, the dynamic focusing optics can dynamically adjust the laser focal point position without overall movement throughout the laser shock peening process. This effectively adapts to changes in the workpiece shape during processing, ensuring the consistency of laser energy density within different parts, thereby improving the stability of the laser shock peening effect.

[0061] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0062] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dynamic focusing optical device for laser shock enhancement, characterized in that, include: A lens group consists of n lenses arranged coaxially along the optical axis, where n ≥ 2, and the spacing between adjacent lenses is adjustable. The distance sensing module is used to acquire axial distance information between the point to be laser-strengthened and the dynamic focusing optical device; A displacement driving unit is used to drive the lenses in the lens group to generate axial displacement along the optical axis. A displacement sensor is used to acquire the actual displacement of the lens along the optical axis. The control module is electrically connected to the distance sensing module, the displacement sensor, and the displacement driving unit, respectively. The control module is used to calculate the target equivalent focal length based on the axial distance information, solve the lens displacement control amount based on the target equivalent focal length and the equivalent focal length model of the lens group, and perform closed-loop control of the displacement driving unit based on the lens displacement control amount and the actual displacement fed back by the displacement sensor, so as to keep the laser focus position within a preset working distance range.

2. The dynamic focusing optical device for laser shock enhancement according to claim 1, characterized in that, It also includes a displacement amplification system, which is disposed between the displacement driving unit and the lens, and is used to amplify the displacement generated by the displacement driving unit and output it to the lens; The displacement sensor is positioned between the fixed end and the output end of the displacement amplification system to directly obtain the displacement of the output end of the displacement amplification system as the actual displacement of the lens.

3. The dynamic focusing optical device for laser shock enhancement according to claim 1, characterized in that, The distance sensing module includes a binocular camera, the center of which is on the same horizontal plane as the center of the dynamic focusing optical device, and the left and right binocular cameras are symmetrically mounted on both sides of the dynamic focusing optical device via sliding rails.

4. The dynamic focusing optical device for laser shock enhancement according to claim 1, characterized in that, The displacement driving unit includes a miniature actuator; for the same lens, at least two sets of the displacement driving units are provided and arranged symmetrically along the circumference of the lens to drive the lens to achieve axial translation in a symmetrical force application manner.

5. The dynamic focusing optical device for laser shock enhancement according to claim 1, characterized in that, It also includes an elastic return mechanism, which is disposed between the displacement driving unit and the lens mount to cooperate with the displacement driving unit to realize bidirectional displacement adjustment of the lens.

6. The dynamic focusing optical device for laser shock enhancement according to claim 1, characterized in that, The lens group consists of three lenses arranged sequentially along the optical axis: a first lens, a second lens, and a third lens. The first lens is a plano-convex lens, the second lens is a plano-concave lens, and the third lens is a plano-convex lens.

7. The dynamic focusing optical device for laser shock enhancement according to claim 1, characterized in that, An annular spacer is provided between adjacent lenses. The outer edge of the annular spacer is fixed to the inner wall of the lens support structure to define the initial distance between adjacent lenses.

8. The dynamic focusing optical device for laser shock enhancement according to claim 1, characterized in that, The displacement sensor is any one of a capacitive displacement sensor, a grating displacement sensor, a magnetic grating displacement sensor, or a displacement sensor based on flexible beam strain measurement.

9. The dynamic focusing optical device for laser shock enhancement according to claim 1, characterized in that, The control module is used to solve for the lens displacement control quantity by taking the minimum weighted sum of squares of the changes in the spacing between adjacent lenses as the objective function and taking the error of the target equivalent focal length not exceeding a preset threshold as the constraint condition.

10. A dynamic focusing method for laser shock peening, employing the dynamic focusing optical device according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. During the laser shock strengthening process, the axial distance information between the point to be laser shock strengthened and the dynamic focusing optical device is acquired in real time. S2. Calculate the target equivalent focal length based on the axial distance information; S3. Solve for the lens displacement control amount based on the target equivalent focal length and equivalent focal length model; S4. Send a displacement command according to the lens displacement control amount to drive the lens to generate axial displacement; S5. The actual displacement of the lens along the optical axis is acquired in real time, and closed-loop control is performed based on the deviation between the actual displacement and the lens displacement control amount, so that the actual displacement of the lens reaches the lens displacement control amount, thereby achieving dynamic focusing.

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