An aerodynamic housing for a stream-lined grating reader head and a method of designing the same

Abstract

This invention discloses an aerodynamic housing for a streamlined grating readhead and its design method, belonging to the field of precision equipment measurement technology. It solves the problem that existing grating readhead designs do not consider aerodynamic performance, making it difficult to meet the stable flight measurement requirements of grating readheads under complex stress conditions. The method includes: S1, initializing a parameterized model of the aerodynamic housing of the grating readhead, and generating multiple sets of design parameter combinations for the aerodynamic housing based on the parameterized model; S2, performing transient flow field calculations on each set of design parameter combinations to obtain the transient parameters of the corresponding design parameter combinations; S3, constructing a predictive surrogate model using multiple sets of design parameter combinations as input and the transient parameters of the multiple sets of design parameter combinations as output; S4, solving the predictive surrogate model using a genetic algorithm to obtain a Pareto solution set, and determining the final shape parameters of the aerodynamic housing based on the Pareto solution set. This invention is used for the housing design of grating readheads.

Description

Technical Field

[0001] This invention relates to a pneumatic housing for a streamlined grating reading head and its design method, belonging to the field of precision equipment measurement technology. Background Technology

[0002] High-precision displacement measurement is a core technology for high-end equipment such as lithography machines and ultra-precision machine tools, and its performance directly affects the positioning accuracy and processing quality of these high-end equipment. In recent years, as semiconductor manufacturing has developed towards smaller linewidths (such as below 28nm), the requirements for the movement speed and accuracy of ultra-precision workpiece stages have increased significantly, requiring grating measurement systems to still achieve nanometer-level resolution (within ±1nm) under high-speed (0.5m / s~10m / s) conditions.

[0003] Currently, as a key component of the measurement system, the aerodynamic performance of the grating readhead is crucial to the measurement stability under high-speed motion. Traditional grating readheads mostly adopt rectangular or cylindrical shells. Such designs are prone to airflow separation, wake vortex and pressure pulsation in high-speed motion (>1m / s), leading to the following problems: (1) Vibration caused by turbulence will couple to the optical system, generating aerodynamic noise interference and reducing the signal-to-noise ratio. For example, under high-speed conditions, when the speed is >1m / s, the turbulent kinetic energy of the traditional rectangular / cylindrical shell increases by more than 40%, resulting in a 6dB decrease in the signal-to-noise ratio. (2) Airflow vibration will cause the angle θ between the indicator grating and the scale grating to change, making the interference fringe displacement Δx nonlinear with θ, causing displacement measurement error and resulting in a decrease in dynamic accuracy. (3) High resistance increases the load on the drive system, and frictional heat affects the thermal stability of optical components, increases the temperature non-uniformity in the grating reading slit, causes fluctuations in the refractive index of the medium, and thus leads to optical interference measurement error.

[0004] Existing grating readhead designs primarily consider structural installation and component layout, neglecting aerodynamic performance optimization. Readhead aerodynamic designs reliant on designer experience are ill-suited to meet the stable flight measurement requirements of grating readheads under complex stress conditions. Summary of the Invention

[0005] This invention provides an aerodynamic housing for a streamlined grating readhead and its design method, which can solve the problem that the shape design of existing grating readheads does not fully consider the optimization of aerodynamic performance and is difficult to meet the requirements of stable flight measurement of grating readheads under complex stress conditions.

[0006] On one hand, the present invention provides a pneumatic housing design method for a streamlined grating reading head, the method comprising:

[0007] S1. Initialize the parametric model of the pneumatic housing of the grating reading head, and generate multiple sets of design parameter combinations for the pneumatic housing based on the parametric model; the pneumatic housing is a spindle-shaped streamline.

[0008] S2. Perform transient flow field calculations for each set of design parameters to obtain the transient parameters for the corresponding design parameter combination;

[0009] S3. Using multiple sets of design parameter combinations as input and the transient parameters of multiple sets of design parameter combinations as output, construct a predictive surrogate model;

[0010] S4. Solve the predictive surrogate model using a genetic algorithm to obtain a Pareto solution set, and determine the final shape parameters of the aerodynamic shell based on the Pareto solution set.

[0011] Optionally, the multiple sets of design parameter combinations for generating the aerodynamic shell based on the parameterized model in step S1 specifically include:

[0012] Based on the parameterized model, the streamlined profile of the aerodynamic shell is generated using the non-uniform rational B-spline curve method.

[0013] Based on the streamlined profile, multiple sets of design parameter combinations for the aerodynamic shell are generated using the Latin hypercube sampling method.

[0014] Optionally, S2 specifically includes:

[0015] For each combination of design parameters, perform mesh deformation to obtain the deformed mesh for the corresponding combination of design parameters;

[0016] Transient flow field calculations are performed on the deformed mesh for each set of design parameter combinations to obtain the transient parameters for the corresponding design parameter combinations.

[0017] Optionally, the transient parameters include aerodynamic drag coefficient, turbulent kinetic energy, and dynamic attitude angle offset;

[0018] The objective function of the predictive agent model is to minimize the transient parameters; the optimization constraint is that the size of the reading head does not exceed the installation size of the grating ruler box.

[0019] Optionally, the genetic algorithm is an improved non-dominated sorting genetic algorithm.

[0020] Optionally, after S4, the method further includes:

[0021] The pneumatic housing is manufactured according to the final shape parameters, and multiple grooves are machined on the outer surface of the pneumatic housing; each groove extends in a direction perpendicular to the airflow direction;

[0022] Multiple grooves are arranged along the airflow direction.

[0023] Optionally, the depth of the trench is 10μm to 50μm; the width of the trench is 20μm to 100μm.

[0024] Optionally, after manufacturing the pneumatic housing according to the final shape parameters, the method further includes:

[0025] Guide vanes are embedded on both sides of the end of the aerodynamic housing.

[0026] Optionally, the angle between the directional guide vane and the aerodynamic housing is adjustable.

[0027] On the other hand, the present invention provides a pneumatic housing for a streamlined grating reading head, wherein the pneumatic housing is designed using any of the above-described pneumatic housing design methods for streamlined grating reading heads.

[0028] The beneficial effects that this invention can produce include:

[0029] The aerodynamic housing design method for a streamlined grating reading head provided by this invention adopts a streamlined profile as the design concept. By taking multiple sets of design parameters of the aerodynamic housing as input and the transient parameters of the multiple sets of design parameters as output, a predictive surrogate model is constructed to determine the final shape parameters of the aerodynamic housing. This method fully considers the influence of aerodynamic performance on the shape design of the reading head, significantly reduces air resistance, suppresses turbulence generation, optimizes and stabilizes the reading optical path, and improves the measurement stability and accuracy under high-speed motion.

[0030] The aerodynamic housing design method for a streamlined grating reading head provided by this invention significantly reduces aerodynamic drag and turbulence intensity through streamlined contour optimization and surface microgroove design; it enhances the aerodynamic stability of the reading head under various operating conditions by designing directional guide vanes; this design method combines computational fluid dynamics simulation optimization and advanced manufacturing processes, exhibiting high engineering applicability. This invention possesses advantages such as excellent aerodynamic performance, structural stability, and strong engineering applicability, making it suitable for high-speed nanometer displacement measurement systems in high-end equipment such as lithography machines and ultra-precision machine tools. Attached Figure Description

[0031] Figure 1 A flowchart illustrating the pneumatic housing design method for a streamlined grating reading head provided in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the three-dimensional geometric shape model of the grating reading head provided in an embodiment of the present invention;

[0033] Figure 3 A schematic diagram of the parameterized model of the grating reading head provided in an embodiment of the present invention;

[0034] Figure 4A schematic diagram illustrating the generation of design parameter combinations using the Latin hypercube sampling method provided in this embodiment of the invention;

[0035] Figure 5 This is a schematic diagram of dynamic mesh deformation based on radial basis functions provided in an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of a predictive agent model of a reverse neural network provided in an embodiment of the present invention;

[0037] Figure 7 This is a schematic diagram illustrating the determination of final shape parameters from the Pareto solution set provided in an embodiment of the present invention.

[0038] Figure 8 This is a schematic diagram of the groove structure on the surface of the pneumatic housing provided in an embodiment of the present invention;

[0039] Figure 9 A schematic diagram of a grating reading head structure with directional airflow vanes provided in an embodiment of the present invention.

[0040] Figure label:

[0041] 11. Grating readout head; 12. Aerodynamic housing; 13. Groove; 14. Directional guide vane. Detailed Implementation

[0042] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0043] This invention provides a pneumatic housing design method for a streamlined grating reading head, such as... Figure 1 As shown, the method includes:

[0044] S1. Initialize the parametric model of the pneumatic housing 12 of the grating reading head 11, and generate multiple sets of design parameter combinations for the pneumatic housing 12 based on the parametric model; the pneumatic housing 12 is a spindle streamline shape.

[0045] In this invention, the pneumatic housing 12 of the grating reading head 11 adopts a spindle-shaped streamlined design with an aspect ratio of 3:1 to 5:1. The middle of the grating reading head 11 is arched to accommodate the reading chip, circuit and core components, and the two ends gradually taper into a cone shape, drawing inspiration from the shape design of underwater vehicles. The symmetrical design at both ends is used to reduce airflow separation and wake drag during the reciprocating motion measurement of the reading head.

[0046] In the design process of the pneumatic housing 12 of the grating reading head 11, based on the functional constraints and installation space limitations of the grating reading head 11, a streamlined parametric model is constructed, and the radius of curvature of the front ellipsoid is defined ( ), aspect ratio ( ), tail fin retraction angle ( Key geometric parameters such as these are used as variables for the optimized design of the aerodynamic shell 12.

[0047] refer to Figure 3 As shown, a parametric model of the pneumatic housing 12 of the grating reading head 11 is constructed. The pneumatic housing 12 adopts a spindle-shaped streamlined design with an initial aspect ratio of... Set to 4:1, the radius of curvature at the front end and the radius of curvature of the rear end All are 10mm, contraction angle It is 15°.

[0048] S1 generates multiple sets of design parameter combinations for the aerodynamic shell 12 based on the parametric model. Specifically, this includes: first, generating the streamlined profile of the aerodynamic shell 12 using the non-uniform rational B-spline curve method based on the parametric model; and then generating multiple sets of design parameter combinations for the aerodynamic shell 12 using the Latin hypercube sampling method based on the streamlined profile.

[0049] Specifically, non-uniform rational B-spline (NURBS) curves are used to generate the streamlined profile of the aerodynamic housing 12, ensuring smooth surface transitions to reduce airflow separation. The design takes into account the mounting space for the readout chip and core components, with a moderate arch in the middle and symmetrical tapering at both ends.

[0050] refer to Figure 4 As shown, 200 sets of design parameter combinations were generated using the Latin Hypercube Sampling (LHS) method, covering... (6mm~10mm) (10°~20°) The optimization space of (1~5).

[0051] S2. Perform transient flow field calculations for each set of design parameter combinations to obtain the transient parameters for the corresponding design parameter combinations.

[0052] Specifically, it includes:

[0053] (1) Perform mesh deformation on each set of design parameters to obtain the deformed mesh of the corresponding design parameter combination.

[0054] Using mesh generation software and radial basis function interpolation techniques, mesh deformation of the geometry of the grating reading head 11 in parameter space is achieved (see...). Figure 5The total number of meshes is 5 million, and the boundary layer mesh thickness is 0.01 mm.

[0055] (2) Perform transient flow field calculations on the deformed mesh for each set of design parameters to obtain the transient parameters for the corresponding design parameter combination. The transient parameters include aerodynamic drag coefficient, turbulent kinetic energy, and dynamic attitude angle offset.

[0056] In this invention, fluid dynamics simulation calculations are performed using fluid dynamics calculation software, and transient flow field calculations are performed using unsteady Navier-Stokes equations and a k-ε turbulence model. The inlet velocity boundary condition is set to 0.5 m / s to 5 m / s (covering the typical operating range of the reading head), the outlet pressure is atmospheric pressure, and no-slip boundary conditions are used on the wall.

[0057] By monitoring the aerodynamic drag coefficient Turbulent kinetic energy and dynamic attitude angle offset To evaluate aerodynamic performance, including dynamic attitude angle offset. The expression is as follows:

[0058] ;

[0059] In the formula, and These are the longitudinal force and the lateral force under the action of airflow, respectively.

[0060] S3. Using multiple sets of design parameter combinations as input and the transient parameters of multiple sets of design parameter combinations as output, construct a predictive surrogate model.

[0061] The unsteady flow field and aerodynamic performance of the grating reading head 11 are calculated using the Navier-Stokes equations and the k-ε turbulence model. These results are used as evaluation results for the optimized configuration. To improve the efficiency of the optimization design, computational fluid dynamics simulation results are used as optimization design samples. A predictive surrogate model is constructed by combining neural networks to achieve rapid prediction of the flow field and aerodynamic performance.

[0062] refer to Figure 6 As shown, 200 sets of design parameter combinations and their transient parameters are used as training data to construct a predictive surrogate model based on a backpropagation neural network (BP). Specifically, the design parameter combinations of the pneumatic housing 12 of the grating reading head 11 are used as input, and the corresponding transient parameters are used as output to construct a fast predictive surrogate model.

[0063] S4. Solve the predictive surrogate model using a genetic algorithm to obtain the Pareto solution set, and determine the final shape parameters of the aerodynamic shell 12 based on the Pareto solution set.

[0064] In this invention, the genetic algorithm is an improved non-dominated sorting genetic algorithm. The objective function of the prediction surrogate model is to minimize the transient parameters; the optimization constraint is that the size of the reading head does not exceed the installation size of the grating ruler box.

[0065] This invention combines an improved NSGA-II multi-objective optimization algorithm to minimize the aerodynamic drag coefficient ( With the objectives of suppressing turbulent kinetic energy and reducing dynamic attitude deviation, a Pareto solution set is generated to achieve a balance between aerodynamic performance and structural stability. The optimization constraint is that the size of the reading head does not exceed the internal installation dimensions of the grating ruler box. The weight allocation for multi-objective optimization is: aerodynamic drag coefficient... Weight 0.4, turbulent kinetic energy Weight 0.3, dynamic attitude angle offset With a weight of 0.3, the objective function is:

[0066] objective function .

[0067] refer to Figure 7 As shown, in the Pareto solution set obtained by solving, a suitable combination of parameters is selected as the final shape parameters according to the geometric shape requirements of the grating reading head 11, the component installation space, etc.

[0068] Following S4, the method further includes:

[0069] The pneumatic housing 12 is manufactured according to the final shape parameters, and multiple grooves 13 are machined on the outer surface of the pneumatic housing 12; each groove 13 extends in a direction perpendicular to the airflow direction;

[0070] In this invention, multiple grooves 13 are arranged along the airflow direction.

[0071] The depth of the trench 13 can be set to 10μm~50μm; the width of the trench 13 can be set to 20μm~100μm.

[0072] The aerodynamic housing 12 of the grating reading head 11 is designed with longitudinal grooves 13 on its surface, with uniformly distributed spacing, similar to an eddy current generator on the surface of an aircraft, to delay boundary layer separation and reduce aerodynamic drag.

[0073] In practical applications, the surface grooves 13 can be processed using laser etching technology. The laser power is set to 50W, the processing depth is controlled at 30μm, the width is 50μm, and the spacing between adjacent grooves 13 is 100μm.

[0074] refer to Figure 8 As shown, the grooves 13 are uniformly arranged along the airflow direction (longitudinal direction), similar to the vortex generator on the surface of an aircraft, which can effectively delay boundary layer separation and further reduce aerodynamic drag.

[0075] After fabricating the pneumatic housing 12 according to the final shape parameters, the method further includes:

[0076] A guide vane 14 is embedded on both sides of the end of the aerodynamic housing 12.

[0077] Furthermore, the angle between the directional guide vane 14 and the aerodynamic shell 12 is adjustable.

[0078] refer to Figure 9 As shown, the present invention manufactures and installs directional guide vanes 14 at the aerodynamic shell 12 at both ends, analogous to the vortex generator of an aircraft wing, for directional adjustment of the near-wall flow field characteristics and enhancement of the longitudinal flight reading stability of the reading head. The directional guide vanes 14, symmetrically embedded on the surface of the aerodynamic shell 12, have adjustable deflection angles, which can enhance the longitudinal stability of the reading head during high-speed motion.

[0079] In practical applications, the directional guide vanes 14 can be integrated into the aerodynamic housing and distributed at both ends.

[0080] refer to Figure 2 As shown, based on the unoptimized geometry of the grating readhead 11, this invention designs a streamlined aerodynamic housing 12 to enclose the photoelectric chip and its fixing device, thus avoiding large-area flow separation. The optimized grating readhead 11 is then mounted on a high-speed displacement test bench for actual measurement under high-speed motion conditions.

[0081] Another embodiment of the present invention provides a pneumatic housing for a streamlined grating reading head, wherein the pneumatic housing is designed using any of the above-described pneumatic housing design methods for streamlined grating reading heads.

[0082] The above descriptions are merely a few embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of the present invention using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A pneumatic housing design method for a streamlined grating reading head, characterized in that, The method includes: S1. Initialize the parametric model of the pneumatic housing of the grating reading head, and generate multiple sets of design parameter combinations for the pneumatic housing based on the parametric model; the pneumatic housing is a spindle-shaped streamline. S2. Perform transient flow field calculations for each set of design parameters to obtain the transient parameters for the corresponding design parameter combination; S3. Using multiple sets of design parameter combinations as input and the transient parameters of multiple sets of design parameter combinations as output, construct a predictive surrogate model; S4. Solve the predictive surrogate model using a genetic algorithm to obtain a Pareto solution set, and determine the final shape parameters of the aerodynamic shell based on the Pareto solution set.

2. The method according to claim 1, characterized in that, The multiple sets of design parameter combinations for generating the aerodynamic shell based on the parameterized model in S1 specifically include: Based on the parameterized model, the streamlined profile of the aerodynamic shell is generated using the non-uniform rational B-spline curve method. Based on the streamlined profile, multiple sets of design parameter combinations for the aerodynamic shell are generated using the Latin hypercube sampling method.

3. The method according to claim 1, characterized in that, S2 specifically includes: For each combination of design parameters, perform mesh deformation to obtain the deformed mesh for the corresponding combination of design parameters; Transient flow field calculations are performed on the deformed mesh for each set of design parameter combinations to obtain the transient parameters for the corresponding design parameter combinations.

4. The method according to claim 1, characterized in that, The transient parameters include aerodynamic drag coefficient, turbulent kinetic energy, and dynamic attitude angle offset. The objective function of the predictive agent model is to minimize the transient parameters; the optimization constraint is that the size of the reading head does not exceed the installation size of the grating ruler box.

5. The method according to claim 1, characterized in that, The genetic algorithm described is an improved non-dominated sorting genetic algorithm.

6. The method according to claim 1, characterized in that, Following S4, the method further includes: The pneumatic housing is manufactured according to the final shape parameters, and multiple grooves are machined on the outer surface of the pneumatic housing; each groove extends in a direction perpendicular to the airflow direction; Multiple grooves are arranged along the airflow direction.

7. The method according to claim 6, characterized in that, The depth of the trench is 10μm to 50μm; the width of the trench is 20μm. ~100μm.

8. The method according to claim 6, characterized in that, After manufacturing the pneumatic housing according to the final shape parameters, the method further includes: Guide vanes are embedded on both sides of the end of the aerodynamic housing.

9. The method according to claim 8, characterized in that, The angle between the directional airflow vane and the aerodynamic outer shell is adjustable.

10. A pneumatic housing for a streamlined grating reading head, characterized in that, The pneumatic housing is designed using the pneumatic housing design method of the streamlined grating reading head according to any one of claims 1 to 9.

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