A laser directed energy deposition powder feed delay prediction compensation method and system

Abstract

The application discloses a laser directional energy deposition powder feeding delay prediction compensation method and system, and belongs to the technical field of metal additive manufacturing. The method comprises the following steps: according to the powder feeder output powder mass flow at the effective powder feeding delay time before the target time and an effective powder mass flow prediction model, a target effective powder mass flow prediction value is calculated and determined; a deviation between the target powder mass flow and the effective powder mass flow prediction value is calculated as an effective powder feeding deviation; according to the effective powder feeding deviation, a powder feeding compensation amount is determined, and a powder feeder control instruction is determined; the target time is subtracted by the effective powder feeding delay to obtain a powder feeding control instruction triggering time; and the powder feeder is controlled through the powder feeder control instruction at the powder feeding control instruction triggering time, so that the molten pool powder feeding consistency and the forming quality stability in the deposition process are ensured, and the technical problem that the actual powder mass flow received by the molten pool cannot be synchronized with the process demand due to the powder feeding delay is solved.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, and in particular to a method and system for predicting and compensating delays in laser-directed energy deposition powder feeding. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Laser Directed Energy Deposition (LDED) is an advanced additive manufacturing technology that uses a high-energy laser beam as a heat source to continuously transport metal powder to the laser action area and simultaneously melt and deposit it, thereby achieving near-net-shape forming of complex metal components.

[0004] In the process of laser directional energy deposition, the powder feeding stability of the powder feeding system directly affects the molten pool size, deposition height, dilution rate, and final forming quality.

[0005] In current laser-directed energy deposition processes, powder feeding control typically focuses on the output flow rate of the powder feeder, neglecting the time delay and dynamic losses during powder transport. This results in the powder feeding adjustment failing to synchronize with the actual powder supply demand of the molten pool. When the scanning speed, laser power, or deposition path changes, the actual powder mass flow rate received by the molten pool consistently lags behind the process requirements, leading to problems such as molten pool size fluctuations, inconsistent deposition heights, and localized over-melting or under-melting. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a method and system for predicting and compensating powder feeding delay in laser directional energy deposition, enabling real-time prediction, advance compensation, and adaptive control of the powder feeding process, thereby improving the consistency of powder supply to the molten pool and the stability of the forming quality during deposition.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, a method for predicting and compensating for delay in powder delivery during laser-directed energy deposition is proposed, including: Obtain the target powder mass flow rate required for the molten pool at the target time and the powder feeder output powder mass flow rate at the effective powder feeding delay time before the target time; Based on the powder mass flow rate output by the powder feeder at the effective powder feeding delay time before the target time and the effective powder mass flow rate prediction model, the predicted value of the effective powder mass flow rate at the target time is calculated and determined; wherein, the effective powder mass flow rate prediction model is the relationship model between the effective powder mass flow rate of the molten pool and the powder mass flow rate output by the powder feeder when considering the effective powder feeding delay. The deviation between the target powder mass flow rate required by the molten pool at the target time and the predicted effective powder mass flow rate at the target time is calculated as the effective powder supply deviation. The powder supply compensation amount is calculated and determined based on the effective powder supply deviation. Determine the control command for the powder feeder based on the powder feeding compensation amount; Subtract the effective toner delivery delay from the target time to obtain the toner delivery control command trigger time. When the powder feeding control command is triggered, the powder feeder is controlled by the powder feeder control command.

[0008] Furthermore, the effective powder feeding delay includes the powder feeder response delay, the powder transport delay in the powder conveying pipe, and the flight delay experienced by the powder from leaving the nozzle to entering the molten pool.

[0009] Furthermore, the effective powder mass flow rate prediction model is as follows: time t The actual effective powder mass flow rate received by the molten pool is equal to the time... t Effective powder delivery and delay t e The powder mass flow rate output by the powder feeder multiplied by the time. t Effective powder delivery and delay t e The overall transport efficiency of powder from the powder feeder to the molten pool area at any given time.

[0010] Furthermore, the process of determining the powder feeder control command based on the powder feeding compensation amount includes: Obtain the current mass flow rate output by the powder feeder; Add the current powder feeder output mass flow rate to the powder feed compensation amount to obtain the compensated target powder feed mass flow rate; The target speed of the powder feeder is determined based on the corresponding relationship between the compensated target powder mass flow rate and the powder feeder speed and the powder output mass flow rate. Based on the target rotation speed of the powder feeder, generate control commands for the powder feeder.

[0011] Furthermore, the effective powder mass flow rate actually received by the molten pool at the target time is obtained; The effective powder supply error is calculated and determined based on the actual effective powder mass flow rate received by the molten pool at the target time and the target powder mass flow rate. The effective powder mass flow rate prediction model is corrected based on the effective powder supply error.

[0012] Further modifications to the effective powder mass flow rate prediction model include: Corrections to overall transport efficiency and to effective powder delivery delay.

[0013] Secondly, a laser-directed energy deposition powder delivery delay prediction and compensation system is proposed, including: The mass flow rate acquisition unit is used to acquire the target powder mass flow rate required by the molten pool at the target time and the powder feeder output powder mass flow rate during the effective powder feeding delay time before the target time. The mass flow prediction unit is used to calculate and determine the predicted value of the effective powder mass flow at the target time based on the powder mass flow rate output by the powder feeder at the effective powder feeding delay time before the target time and the effective powder mass flow prediction model. The effective powder mass flow prediction model is a model of the relationship between the effective powder mass flow rate of the molten pool and the powder mass flow rate output by the powder feeder when considering the effective powder feeding delay. The effective powder supply deviation calculation unit is used to calculate the deviation between the target powder mass flow rate required by the molten pool at the target time and the predicted value of the effective powder mass flow rate at the target time, which is used as the effective powder supply deviation. The powder delivery compensation unit is used to calculate and determine the powder delivery compensation amount based on the effective powder delivery deviation. The powder feeder control command determination unit is used to determine the powder feeder control command based on the powder feeding compensation amount. The instruction triggering time determination unit is used to subtract the effective toner delivery delay from the target time to obtain the toner delivery control instruction triggering time. The instruction control unit is used to control the powder feeder via the powder feeder control instruction when the powder feeding control instruction is triggered.

[0014] Thirdly, a computer device is proposed, the device comprising: A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements a laser-directed energy deposition powder delivery delay prediction and compensation method proposed in the first aspect.

[0015] Fourthly, a computer-readable storage medium is proposed, wherein the computer-readable storage medium stores a computer program adapted to be loaded by a processor and executed by a processor to provide a laser-directed energy deposition powder delivery delay prediction and compensation method proposed in the first aspect.

[0016] Fifthly, a computer program product is proposed, which includes a computer program that, when executed by a processor, implements a laser-directed energy deposition powder delivery delay prediction and compensation method proposed in the first aspect.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention proposes a method and system for predicting and compensating powder delivery delay in laser-directed energy deposition (EDD). The method fully considers the effective powder delivery delay when controlling the powder feeder. First, using an effective powder mass flow rate prediction model, the effective powder mass flow rate at the target time is predicted based on the powder feeder output powder mass flow rate at the effective powder delivery delay time before the target time. Then, based on the predicted effective powder mass flow rate at the target time and the target powder mass flow rate required by the molten pool at the target time, the effective powder supply deviation is calculated and determined. The powder delivery compensation amount is then calculated based on the effective powder supply deviation, and finally, the powder feeder control command is determined. Next, the effective powder delivery delay is subtracted from the target time to obtain the powder delivery control command trigger time. Finally, at the powder delivery control command trigger time, the powder feeder is controlled by the powder feeder control command, ensuring that the powder accurately enters the molten pool at the target time after the effective powder delivery delay. This achieves time synchronization between the molten pool powder supply process and the deposition process requirements, ensuring that the actual effective powder mass flow rate received by the molten pool at the target time remains consistent with the process requirements.

[0018] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0020] Figure 1 This is a flowchart of a laser-directed energy deposition powder delivery delay prediction and compensation method proposed in an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0025] Laser Directed Energy Deposition (LDED) is an advanced additive manufacturing technology that uses a high-energy laser beam as a heat source to continuously deliver metal powder to the laser's action area and simultaneously melt and deposit it, achieving near-net-shape forming of complex metal components. Due to its advantages such as high material utilization, high forming efficiency, and the ability to manufacture and repair large and complex components, it is widely used in aerospace, energy equipment, mold manufacturing, and high-end equipment remanufacturing.

[0026] In laser-directed energy deposition (LDED), the powder feeding system plays a crucial role in the stable delivery of metal powder. Its stability directly affects the molten pool size, deposition height, dilution rate, and final forming quality. Therefore, powder feeding control has always been one of the key technologies in the control of the LDED process.

[0027] Currently, most laser directional energy deposition (DED) equipment uses a powder feeder speed control method, which adjusts the powder output flow rate by changing the speed of the powder feeder motor to achieve powder feeding control under different process parameters. However, this control method usually assumes that the powder feeder output flow rate can act on the molten pool in real time, while ignoring the significant dynamic transport characteristics of the powder feeding system itself.

[0028] In reality, from the moment the control system issues the powder feeding adjustment command until the powder actually enters the laser molten pool and participates in deposition, it needs to go through multiple processes in sequence, including powder feeder response, powder release, powder conveying pipe transport, carrier gas carrying, powder beam convergence, and powder melting. Each stage has varying degrees of dynamic delay, causing the powder feeding system to exhibit significant large inertia, long time lag, and nonlinear characteristics. When the scanning speed, laser power, or deposition path changes during the deposition process, the actual powder mass flow rate received by the molten pool cannot respond synchronously to the control command, but always lags behind the process requirements.

[0029] For example, at path corners, sudden speed changes, or start / stop positions, when the robot's movement speed decreases, the amount of powder required for deposition per unit length should decrease accordingly. However, due to the powder feeding delay, changes in the powder feeder output cannot be transmitted to the molten pool in a timely manner, causing the molten pool to maintain a high powder supply for a period of time. This results in problems such as local accumulation, increased molten pool size, and deposition height exceeding tolerance. Similarly, when the scanning speed increases, defects such as insufficient powder supply, under-melting, and forming interruption are more likely to occur.

[0030] Existing technologies also improve powder feeding stability by optimizing the powder feeder structure, increasing the motor response speed, or using traditional PID control methods. However, all of these methods take the output flow of the powder feeder as the control object and do not consider the time delay and dynamic loss in the powder transportation process. As a result, the powder feeding adjustment is always a post-feedback control, making it difficult to achieve real-time synchronization between the powder feeding process and the deposition process.

[0031] To ensure that the actual effective powder mass flow rate received by the molten pool remains consistent with the process requirements, and to improve the consistency of powder supply and the stability of the forming quality during deposition, this invention proposes a laser-directed energy deposition powder delivery delay prediction and compensation method, such as... Figure 1 As shown, it includes: Obtain the target powder mass flow rate required for the molten pool at the target time and the powder feeder output powder mass flow rate at the effective powder feeding delay time before the target time; Based on the powder mass flow rate output by the powder feeder at the effective powder feeding delay time before the target time and the effective powder mass flow rate prediction model, the predicted value of the effective powder mass flow rate at the target time is calculated and determined; wherein, the effective powder mass flow rate prediction model is the relationship model between the effective powder mass flow rate of the molten pool and the powder mass flow rate output by the powder feeder when considering the effective powder feeding delay. The deviation between the target powder mass flow rate required by the molten pool at the target time and the predicted effective powder mass flow rate at the target time is calculated as the effective powder supply deviation. The powder supply compensation amount is calculated and determined based on the effective powder supply deviation. Determine the control command for the powder feeder based on the powder feeding compensation amount; Subtract the effective toner delivery delay from the target time to obtain the toner delivery control command trigger time. When the powder feeding control command is triggered, the powder feeder is controlled by the powder feeder control command.

[0032] This invention proposes a method for predicting and compensating powder delivery delay in laser-directed energy deposition. When controlling the powder feeder, the method fully considers the effective powder delivery delay. First, an effective powder mass flow rate prediction model is used to predict the effective powder mass flow rate at the target time. Then, based on the predicted effective powder mass flow rate at the target time and the target powder mass flow rate required by the molten pool at the target time, the effective powder delivery deviation is calculated and determined. The powder delivery compensation amount is then calculated based on the effective powder delivery deviation, and finally, the powder feeder control command is determined. Next, the effective powder delivery delay is subtracted from the target time to obtain the trigger time of the powder delivery control command. Finally, at the trigger time of the powder delivery control command, the powder feeder is controlled by the powder feeder control command, ensuring that the powder accurately enters the molten pool at the target time after the effective powder delivery delay. This achieves time synchronization between the molten pool powder delivery process and the deposition process requirements, ensuring that the actual effective powder mass flow rate received by the molten pool at the target time remains consistent with the process requirements.

[0033] In some embodiments, the effective powder mass flow rate prediction model is specifically as follows: time t The actual effective powder mass flow rate received by the molten pool is equal to the time... t Effective powder delivery and delay t e The powder mass flow rate output by the powder feeder multiplied by the time. t Effective powder delivery and delay t e The overall transport efficiency of powder from the powder feeder to the molten pool area at specific times; where, at specific times t Effective powder delivery and delay t e The effective powder feeding delay τe and the overall transport efficiency of powder output from the powder feeder to the molten pool area are determined by the effective powder feeding delay τe at time t. t e The operating status parameters, equipment structural parameters, and deposition process parameters of the powder feeding system are calculated and determined.

[0034] Traditional powder feeding control theory typically assumes that the output flow rate of the powder feeder is the actual powder supply during the deposition process, thus the controlled object only includes the powder feeder motor and the powder feeder output. However, this invention argues that the true controlled object of the powder feeding system should be the dynamic movement of the powder throughout the entire transport chain. Therefore, this invention proposes the Dynamic Powder Transport Theory (DPTT). This theory posits that after metal powder is output from the powder feeder, it does not immediately participate in deposition but undergoes a continuous transport process within the powder feeding system. After experiencing multiple dynamic stages, the powder finally enters the molten pool to participate in deposition, and each stage collectively determines the final powder supply state. The entire powder transport process includes five continuous stages, including: Phase 1: Powder Release Phase The powder undergoes bridging, particle loosening, and continuous release processes inside the powder feeder. Its output flow rate is influenced by the powder feeder structure, motor response, and powder flow characteristics.

[0035] This stage determines the initial mass flow rate of the powder leaving the powder feeder.

[0036] Second stage: Powder transport stage After being released, the powder enters the powder conveying pipe under the action of the carrier gas and completes the gas-solid two-phase transport along the powder conveying pipe.

[0037] This stage determines the following factors during the powder conveying process: conveying speed, conveying time, pipe wall collision, flow fluctuation, and particle dispersion.

[0038] This stage is also the main source of delayed powder delivery.

[0039] Phase 3: Particle Reconstruction Phase After leaving the nozzle, the powder forms a three-dimensional powder bundle, which converges, diffuses, and spatially reconstructs under the combined action of the protective airflow and the carrier gas.

[0040] The geometry of the powder beam directly affects the density distribution of the powder entering the laser-acting zone.

[0041] Fourth stage: Laser coupling stage After the powder enters the laser-acting region, it couples with the laser energy, and the particles begin to absorb heat, melt, and change velocity. This stage determines the effective proportion of powder that can actually enter the molten pool and participate in deposition.

[0042] Fifth stage: Molten pool absorption stage Molten particles enter the molten pool and participate in the increase of the molten pool mass, forming actual deposited material.

[0043] The final material input received by the molten pool is formed.

[0044] In this embodiment of the invention, the "powder flow rate" and the "powder feeder speed" are no longer directly controlled. Instead, the continuous powder flow is discretized into powder transport units with timestamps, quality, speed and expected arrival time. The controller performs prediction, scheduling and compensation for each powder transport unit.

[0045] The powder transport unit (PTU) is not an actual physical particle cluster, but rather the smallest control unit after the continuous powder feed stream is discretized by the control system based on a fixed sampling period or sliding time window.

[0046] Each PTU corresponds to a set of powder output within a time window, and it has an independent transport state in the entire powder feeding system.

[0047] The control system performs state prediction, delay calculation, transport compensation, and feedback correction for each PTU, thereby realizing digital modeling and predictive control of the continuous powder feeding process.

[0048] Since the metal powder undergoes multiple dynamic stages after being output from the powder feeder, each stage is influenced by the combined effects of equipment structural parameters, process parameters, and operating status. Therefore, to accurately predict the effective powder mass flow rate at a target moment, it is necessary to collect real-time operating status parameters, equipment structural parameters, and deposition process parameters, including the powder feeder rotation speed, during the laser directional energy deposition process. n Set the powder delivery quality flow rate Q s Carrier gas flow rate Q c Protective airflow Q p Nozzle defocus heightH Powder conveying pipe length L Inner diameter of powder conveying pipe D Average particle size of powder d 50 Powder density r Scanning speed at the target time V and laser power P Parameters such as feeder speed, carrier gas flow rate, powder conveying pipe length, powder conveying pipe inner diameter, average powder particle size, and powder density mainly affect the powder's movement time within the conveying system and are used to calculate the effective powder delivery delay. Carrier gas flow rate, protective gas flow rate, nozzle defocusing height, powder particle size, and powder density are used to calculate the overall conveying efficiency. The scanning speed and laser power at the target time are used to calculate the target powder delivery mass flow rate, and the feeder speed is used to determine the feeder's output mass flow rate, providing a reference for subsequent compensation time calculations.

[0049] To avoid the problem of asynchronous sampling from data from different sources, this invention uses a unified control period to synchronously collect all parameters and constructs a feature vector of the impact of powder delivery delay based on the timestamp: X=[ n , Q s , Q c , Q p , H , L , D , d 50 , r , V , P ]; The feature vector affecting powder delivery delay is used as input to the powder delivery delay prediction model and is updated in real time throughout the deposition process.

[0050] The embodiments of the present invention also establish a Dynamic Powder Transport Model (DPTM) to describe the dynamic transport behavior of metal powder from the powder feeder to the laser molten pool throughout the entire process, and to predict the effective powder delivery delay based on the powder transport state.

[0051] In existing laser-directed energy deposition (LDED) processes, the powder mass flow rate output from the powder feeder is typically used as the control object, assuming that the powder output from the feeder can act on the molten pool in real time. However, in actual deposition, after the powder is output from the feeder, it needs to go through five consecutive dynamic stages: powder release, powder transport, powder beam reconfiguration, laser coupling, and molten pool absorption. In each transport stage, the powder is affected by the combined effects of equipment structural parameters, process parameters, and operating conditions, resulting not only in transport time delays but also, due to factors such as particle collisions, carrier gas disturbances, powder beam diffusion, and particle scattering, some powder cannot ultimately enter the molten pool to participate in deposition. Therefore, there is a significant dynamic time lag and mass loss relationship between the powder mass flow rate output from the powder feeder and the effective powder mass flow rate actually obtained by the molten pool.

[0052] To accurately describe the mapping relationship between the powder feeder output and the actual powder supply to the molten pool, this invention defines the powder mass flow rate output by the powder feeder as: Q s ( t The effective powder mass flow rate is defined as the actual powder mass flow rate that enters the molten pool and participates in the deposition process per unit time. Q e ( t ).

[0053] Because there is a time delay in the powder transport process, therefore at any given moment t The effective powder actually obtained from the molten pool does not originate from time. t The output of the toner feeder is not derived from the effective toner feeding delay. t e The output of the powder feeder at that time.

[0054] Meanwhile, to describe the effective transport capacity of powder from the powder feeder to the molten pool, a comprehensive transport efficiency is introduced. theT ( t - t e ), defined as follows: theT ( t - t e ) (1); In the formula, Q e ( t (time) t The actual effective powder mass flow rate received by the molten pool; Q s ( t - t e (time) t Effective powder delivery and delay t e The powder mass flow rate output by the powder feeder at all times; theT ( t - t e (time) t Effective powder delivery and delay t e The overall transport efficiency of powder from the powder feeder to the molten pool area at any given time.

[0055] To characterize the overall transport capacity of powder from the powder feeder to the molten pool under different operating conditions, this invention first establishes an overall transport efficiency model through pre-calibration experiments. Based on the time... t Effective powder delivery and delay t e Carrier gas flow rate acquired at all times Q c Protective airflow Q p Nozzle defocus height H Average particle size of powder d 50 and powder density r Parameters, calculate time t Effective powder delivery and delay t e Overall transport efficiency at any given moment: theT ( t - t e )= F ( Q c , Q p , H , d 50 , r (2); In the formula, A comprehensive transport efficiency calibration model can be established through experimental fitting, response surface analysis, or machine learning.

[0056] Based on the above definition, the dynamic relationship between the effective powder mass flow rate of the molten pool and the powder mass flow rate output by the powder feeder can be obtained, i.e., the effective powder mass flow rate prediction model. Specifically, this effective powder mass flow rate prediction model is as follows: At time... t The actual effective powder mass flow rate received by the molten pool is equal to the time... t Effective powder delivery and delay t e Powder mass flow rate output by the constant powder feeder Q s (t - t e Multiply by time t Effective powder delivery and delay t e The overall transport efficiency of powder from the powder feeder to the molten pool area at any given time theT ( t - t e The formula for the effective powder mass flow rate prediction model is as follows: Q e ( t )= Q s ( t - t e ) theT ( t - t e (3); This model shows that the actual effective powder mass flow rate obtained by the molten pool is determined by two factors: firstly, the output state of the powder feeder after considering the powder feeding delay; and secondly, the effective transport ratio during the powder transport process. Therefore, compared with the existing method of directly using the powder feeder output flow rate as the actual powder supply, this invention can more accurately describe the true powder supply state during laser directional energy deposition.

[0057] In some embodiments, effective powder delivery delay t e Including powder feeder response delay t r Delay in powder transport within the powder conveying pipe t t and the flight delay experienced by the powder from leaving the nozzle to entering the molten pool t f .

[0058] To achieve effective prediction of powder delivery delay, this invention establishes a powder delivery delay decomposition model based on the powder transport process. The entire process from powder output from the powder feeder to entering the molten pool is divided into three continuous stages: (1) Powder feeder response stage.

[0059] The powder feeder response delay is defined as the time difference between the control system issuing the powder feeding adjustment command and the powder feeder output mass flow rate reaching the target steady state. Its calculation formula is: t r= t s- t c (4); in, t c To control the timing of command issuance, t s The moment when the output mass flow rate of the powder feeder first enters the preset stable error range (e.g., ±5%) and remains stable. The powder feeder response delay is mainly affected by the response speed of the powder feeder motor, the structure of the powder feeding mechanism, and the powder flow performance.

[0060] Furthermore, to reflect the variation of the powder feeder response time under different operating conditions, this invention establishes a powder feeder response delay model: t r= f r ( n ,△ n , d 50 , r (5); in, f r ( ) is the response delay model established through the powder feeding calibration experiment, used to predict the response delay of the powder feeder based on the current operating status of the powder feeder; Δn is the amount of speed adjustment of the powder feeder in this operation.

[0061] (2) Powder conveying stage.

[0062] This stage represents the time it takes for the powder to travel along the powder conveying pipe to the nozzle outlet under the action of the carrier gas. The powder transport velocity is affected by the carrier gas flow rate, powder particle size, powder density, and the structural parameters of the powder conveying pipe; therefore, the powder transport delay in the powder conveying pipe is also a factor. t t Represented as: (6); In the formula: L This refers to the length of the powder conveying pipe; v p The average transport velocity of the powder within the powder conveying pipe is given by time. t and time t The average of all transport speeds within the previously set time period is used to determine the speed.

[0063] (3) Powder free flight stage.

[0064] This stage represents the time it takes for the powder to travel from the nozzle to the laser-affected area and into the molten pool under the influence of the carrier gas and protective gas. Specifically, it includes the flight delay from the powder leaving the nozzle to entering the molten pool. t f Represented as: (7); In the formula: H The effective flight distance from the nozzle exit to the surface of the molten pool; v f The average velocity of the powder during free flight is given by time. t and time t The average velocity of all free-flying powders within the previously set time period was calculated to determine the value.

[0065] Therefore, the combined effective powder feeding delay between the powder output from the powder feeder and the effective reception of the molten pool is... t e for: t e = t r+ t t+ t f (8); The above-mentioned delay decomposition model can transform the powder delivery delay, which cannot be directly measured, into multiple stage delays with clear physical meanings. Combined with the obtained powder delivery delay influence characteristic parameters, the dynamic prediction of effective powder delivery delay can be achieved.

[0066] To achieve the digital representation and dynamic prediction of the dynamic powder delivery model (DPTM), this invention discretizes the continuous powder delivery process into multiple powder transport units (PTUs). A PTU is not a new model independent of the dynamic powder delivery model, but rather the smallest computational unit within it, used to describe the transport state of the continuous powder flow over different time periods. By independently predicting the state of each powder transport unit, dynamic calculations of powder arrival time, overall transport efficiency, and effective powder supply status can be achieved within the dynamic powder delivery model.

[0067] The control system performs timing statistics on all powder conveying units based on their conveying status and calculates the effective powder delivery delay under the current operating conditions. t e Overall transport efficiency ηT and predicted effective powder mass flow rate Q e ( t This allows for the solution of the dynamic transport model for powder delivery, providing a predictive basis for subsequent advance compensation control of powder delivery.

[0068] In some embodiments, the target time is obtained based on robot motion trajectory planning data and current deposition process parameters. t dTarget powder mass flow rate required for the molten pool Q d ( t d ), representing the target time. t d Theoretical demand for powder mass flow rate in molten pool, target time t d Target powder mass flow rate required for the molten pool Q d ( t d ) Calculated according to equation (9): Q d ( t d )= kρBhV (9); In the formula, Q d ( t d ) is the target time t d Target powder mass flow rate (g / s) required for the molten pool; B For the target time t d Target deposition channel width (mm); h For the target time t d The target deposition layer thickness (mm); V For the target time t d The robot scanning speed (mm / s); r Density of the deposited material (g / mm²) 3 ); k This is a powder utilization correction factor used to account for scattering losses and deposition efficiency.

[0069] In some embodiments, formula (2) and effective powder delivery delay τ are used. e The calculation formula is based on the effective powder delivery delay time before the target time (i.e., t d - t e The operating parameters of the powder feeding system are obtained at a given time, and the overall transport efficiency at that time is calculated. ( t d - t e ) and effective powder delivery delay te Furthermore, based on the powder feeder output powder mass flow rate during the effective powder feeding delay time before the target time... Q s ( t d - t e and overall transportation efficiency ( t d - t e The effective powder mass flow rate actually obtained by the molten pool at the target time is predicted and defined as the predicted value of the effective powder mass flow rate at the target time. Q e ( t d Among them, the comprehensive transport efficiency corresponding to the effective powder delivery delay time before the target time. ( t d - t e )for: ( t d - t e )= F ( Q c , Q p , H , d 50 , r (10); In the formula, Q c , Q p , H , d 50 , r All are valid powder delivery delay times t before the target time. d -τ e The parameters obtained.

[0070] Predicted effective powder mass flow rate at target time Q e ( t d )for: Q e ( t d )= Q s ( t d - t e ) ( t d - t e (11); To evaluate the deviation between the current powder supply status and the target powder supply demand, this invention defines an effective powder supply deviation Δ. Q ( t d ): △ Q ( t d )= Q d ( t d )- Q e ( t d (12); When: △ Q ( t d When ) > 0, it means that the predicted effective powder supply is lower than the target demand, and the powder supply needs to be increased; When: △ Q ( t d When ) < 0, it means that the predicted effective powder supply is higher than the target demand, and the powder supply needs to be reduced.

[0071] Furthermore, based on the effective powder supply deviation △ Q ( t d and overall transportation efficiency ( t d - t e ), calculate and determine the powder delivery compensation amount △ Q s ( t d ): (13); In the formula, △ Q s ( t d ) represents the powder feeding compensation amount, indicating the powder mass flow rate that needs to be compensated at the output of the powder feeder.

[0072] In some embodiments, the process of determining the powder feeder control command based on the powder feeding compensation amount includes: Obtain the current mass flow rate output by the powder feeder; The current output mass flow rate of the powder feeder is added to the powder feeding compensation amount to obtain the compensated target powder feeding mass flow rate. The calculation formula for the compensated target powder feeding mass flow rate is as follows: (14); In the formula, The target powder delivery quality flow rate after compensation; Set the feed quality flow rate for the target time.

[0073] Based on the compensated target powder mass flow rate and the correspondence between the powder feeder speed and the powder mass flow rate, the target speed of the powder feeder is determined. The calculation formula for the target speed of the powder feeder is as follows: (15); In the formula, Indicates the rotational speed of the powder feeder; This represents the relationship between the speed of the powder feeder and the mass flow rate of the powder.

[0074] Based on the target rotation speed of the powder feeder, generate control commands for the powder feeder.

[0075] During laser-directed energy deposition (LDED), the robot scanning speed, deposition path, and laser power vary depending on the processing position, resulting in different material requirements per unit length for different regions. When the scanning speed decreases, the amount of powder required for the molten pool per unit time decreases; conversely, when the scanning speed increases, the amount of powder required increases. Therefore, the powder feeding system needs to adjust the powder feeding rate in advance based on future process requirements.

[0076] However, due to the effective powder delivery delay τe from the powder feeder to the molten pool, if the control system adjusts the powder delivery rate after detecting a process change, the actual powder will continue to be delivered in the state before the adjustment, resulting in a lag in the powder supply response of the molten pool. Therefore, this invention compensates for the powder delivery control command based on the predicted effective powder delivery delay, ensuring that the powder enters the laser molten pool at the target time after the transport delay, thus achieving synchronous matching between the effective powder supply state of the molten pool and the deposition process requirements.

[0077] Since the effects of powder feeding adjustment can only be applied to the molten pool after an effective powder feeding delay, the powder feeding control command cannot be executed directly at the target time, but needs to be triggered in advance.

[0078] Define the target time as t d The powder feeding control command is triggered at the following time. t c for: t c= t d- t e (16); When the system runs to the time t c At that time, the controller adjusts the powder feeder output in advance so that the powder passes through... t e After time transport, at the target time t d The powder is fed into the molten pool region to achieve time synchronization between the powder supply process and the deposition process requirements, so that the effective powder mass flow rate actually received by the molten pool at the target time is consistent with the process requirements.

[0079] Using the above method, this step transforms traditional hysteresis feedback regulation into predictive compensation control oriented towards future states by utilizing the effective powder delivery delay prediction results. During robot speed changes, path corners, start and stop positions, and complex trajectory deposition processes, the control system can adjust the powder delivery state in advance, ensuring that the actual effective powder mass flow rate obtained by the molten pool remains consistent with the target requirement, reducing forming defects such as local accumulation, undermelting, and dimensional fluctuations caused by powder delivery delay.

[0080] In some embodiments, the effective powder mass flow rate actually received by the molten pool at the target time is obtained; The effective powder supply error is calculated and determined based on the actual effective powder mass flow rate received by the molten pool at the target time and the target powder mass flow rate. The effective powder mass flow rate prediction model is corrected based on the effective powder supply error.

[0081] According to the embodiment of the present invention, the effective powder mass flow rate prediction model is corrected online based on the information of the molten pool state change during laser directional energy deposition, so as to realize the adaptive update of effective powder delivery delay and comprehensive transport efficiency and improve the accuracy of powder delivery prediction compensation.

[0082] During actual deposition, the powder feeding system's operation is affected by factors such as batch-to-batch differences in powder, variations in powder flowability, changes in the internal state of the powder feeding pipe, fluctuations in carrier gas flow rate, and changes in environmental factors. These factors cause dynamic changes in the response time and transport efficiency during powder transport. Therefore, even if a fixed powder feeding delay parameter is used for control, prediction errors will still occur, and the stability of the molten pool powder supply under complex operating conditions cannot be guaranteed.

[0083] To address the aforementioned issues, this invention utilizes online molten pool detection information as feedback input to perform real-time correction of key parameters in the dynamic powder conveying model.

[0084] Specifically, during the laser-directed energy deposition process, the characteristic parameters of the molten pool state, including the molten pool length, molten pool width, molten pool area, molten pool brightness, and deposition channel geometry, are acquired in real time through coaxial vision sensors, molten pool image acquisition devices, or other online detection equipment.

[0085] Based on the molten pool state parameters, establish molten pool state characteristic quantities. M ( ): M ( )={ W ( ), A ( ), H ( ), I ( )}; In the formula, W ( ) is the target time The width of the molten pool; A ( ) is the target time The area of ​​the molten pool; H ( ) is the target time The amount of change in sedimentary height, I ( ) is the target time The characteristics of the molten pool light intensity.

[0086] The effective powder mass flow rate actually received by the molten pool at the target time is determined by the changes in the molten pool width, molten pool area and deposition height at the target time. The change in deposition height is the difference between the deposition height at the target time and the deposition height at the time before the target time.

[0087] In some embodiments, the effective powder supply error is determined by calculating the following formula: (17); In the formula, The effective powder supply error at the target time. For the target time t d The target powder mass flow rate required for the molten pool; Q e ( t d ) represents the predicted effective powder mass flow rate at the target time.

[0088] when: >0 indicates that the actual powder obtained by the molten pool is insufficient, and the effective powder supply needs to be increased; when: <0 indicates that the molten pool actually receives too much powder, and the effective powder supply needs to be reduced.

[0089] In some embodiments, the modification of the effective powder mass flow rate prediction model includes: Corrections to overall transport efficiency and to effective powder delivery delay.

[0090] The process of correcting overall transport efficiency includes: Define the overall transport efficiency correction Δ : △ = k 1 (18); In the formula, k 1 represents the model correction coefficient.

[0091] The corrected overall transport efficiency is expressed as: : (19); In the formula, This is the initial overall transportation efficiency calculated based on the current operating parameters.

[0092] Meanwhile, to further improve the accuracy of powder feeding delay prediction, this invention utilizes changes in the molten pool state as a feedback indicator of the actual powder feeding response. During the deposition process, a molten pool visual inspection module acquires state parameters in real time, such as molten pool width, molten pool area, molten pool brightness, and changes in deposition height. When any of the above state parameters exceeds a preset change threshold for multiple consecutive sampling periods, it is considered that the current powder feeding adjustment has had a real impact on the molten pool, and this moment is defined as the time when the molten pool state first meets the response condition. t resp and at that moment t resp With the time when the powder feeding control command is issued t c The time difference between them is defined as the actual powder delivery response delay. t a : t a = t resp - t c (20); Furthermore, the actual powder delivery response delay is calculated. t a The effective powder delivery delay calculated by the model t e The difference, as a powder delivery delay error Eτ : E τ = t a - t e (twenty one); Based on powder delivery delay error E τ For effective powder delivery delay t e Make corrections to obtain the corrected effective toner delivery delay. : (twenty two); In the formula, k 2 is the delay correction factor.

[0093] After the above online correction, the updated comprehensive transport efficiency and effective powder delivery delay are re-input into the effective powder mass flow rate prediction model to re-predict the command trigger time and powder delivery control command for the next control cycle.

[0094] Furthermore, to improve the model's adaptability under different depositional conditions, this invention employs a continuous iterative correction method, ensuring that the model parameters are continuously updated throughout the depositional process. That is: { ηT,τ e} k+1 =F({ theT , t e} k , E Q , E τ ) (twenty three); In the formula, k For the current control cycle, k +1 indicates the next control cycle. F Functions for updating model parameters.

[0095] Through the above method, this step realizes the online correction of the powder feeding dynamic transport model based on molten pool state feedback, so that the effective powder feeding delay prediction results can adapt to different powder states, different process parameters and different equipment operating states, thereby improving the accuracy and stability of powder feeding prediction compensation control.

[0096] Finally, through closed-loop correction between the effective powder mass flow rate prediction model and the molten pool feedback, the powder feeding system is transformed from fixed parameter control to dynamic adaptive control, thereby achieving precise regulation of the effective powder supply state during laser directional energy deposition.

[0097] This invention proposes a method for predicting and compensating powder delivery delay in laser-directed energy deposition (EDD). Based on the Dynamic Powder Transport Model (DPTM), and with effective powder delivery delay prediction as its core, the method dynamically models the entire process of powder delivery from the feeder to the molten pool. It predicts the effective powder delivery delay in real time and issues advance powder delivery adjustment commands based on the prediction results, ensuring that the actual effective powder mass flow rate received by the molten pool at the target time matches the process requirements. Simultaneously, by incorporating molten pool status feedback, the method performs online correction of the dynamic powder transport model, continuously improving the accuracy of powder delivery delay prediction and achieving integrated closed-loop control of powder delivery prediction, advance compensation, and feedback correction.

[0098] This invention also proposes a laser-directed energy deposition powder delivery delay prediction and compensation system, comprising: The mass flow rate acquisition unit is used to acquire the target powder mass flow rate required by the molten pool at the target time and the powder feeder output powder mass flow rate during the effective powder feeding delay time before the target time. The mass flow prediction unit is used to calculate and determine the predicted value of the effective powder mass flow at the target time based on the powder mass flow rate output by the powder feeder at the effective powder feeding delay time before the target time and the effective powder mass flow prediction model. The effective powder mass flow prediction model is a model of the relationship between the effective powder mass flow rate of the molten pool and the powder mass flow rate output by the powder feeder when considering the effective powder feeding delay. The effective powder supply deviation calculation unit is used to calculate the deviation between the target powder mass flow rate required by the molten pool at the target time and the predicted value of the effective powder mass flow rate at the target time, which is used as the effective powder supply deviation. The powder delivery compensation unit is used to calculate and determine the powder delivery compensation amount based on the effective powder delivery deviation. The powder feeder control command determination unit is used to determine the powder feeder control command based on the powder feeding compensation amount. The instruction triggering time determination unit is used to subtract the effective toner delivery delay from the target time to obtain the toner delivery control instruction triggering time. The instruction control unit is used to control the powder feeder via the powder feeder control instruction when the powder feeding control instruction is triggered.

[0099] It should be noted that the laser-directed energy deposition powder feeding delay prediction and compensation system provided in the above embodiments is only illustrated by the division of the above functional modules when controlling the powder feeder. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the equipment can be divided into different functional modules to complete all or part of the functions described above. In addition, the laser-directed energy deposition powder feeding delay prediction and compensation system and the laser-directed energy deposition powder feeding delay prediction and compensation method embodiment belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0100] The present invention also discloses a computer device, the device comprising: A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements a laser-directed energy deposition powder delivery delay prediction and compensation method disclosed in the embodiments of the present invention.

[0101] The present invention also discloses a computer-readable storage medium storing a computer program adapted for loading and execution by a processor of a laser-directed energy deposition powder delivery delay prediction and compensation method disclosed in the embodiments of the present invention.

[0102] The present invention also discloses a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements a laser-directed energy deposition powder delivery delay prediction and compensation method disclosed in the embodiments of the present invention.

[0103] The method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor. The software modules can reside in readily available storage media in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory, and the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method. To avoid repetition, detailed descriptions are omitted here.

[0104] Those skilled in the art will recognize that the units and algorithm steps described in conjunction with the embodiments herein can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0105] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for predicting and compensating delay in powder delivery during laser-directed energy deposition, characterized in that, include: Obtain the target powder mass flow rate required for the molten pool at the target time and the powder feeder output powder mass flow rate at the effective powder feeding delay time before the target time; Based on the powder mass flow rate output by the powder feeder at the effective powder feeding delay time before the target time and the effective powder mass flow rate prediction model, the predicted value of the effective powder mass flow rate at the target time is calculated and determined; wherein, the effective powder mass flow rate prediction model is specifically: time t The actual effective powder mass flow rate received by the molten pool is equal to the time... t Effective powder delivery and delay τ e The powder mass flow rate output by the powder feeder multiplied by the time. t Effective powder delivery delay in advance τ e The overall transport efficiency of powder from the powder feeder to the molten pool area at any given time ηT ( t - τ e ); ηT ( t - τ e According to time t Effective powder delivery and delay τ e Carrier gas flow rate acquired at all times Q c Protective airflow Q p Nozzle defocus height H Average particle size of powder d 50 and powder density ρ Calculation determined: ηT ( t - τ e )= F （ Q c ， Q p ， H ， d 50 ， ρ ）； In the formula, A comprehensive transport efficiency calibration model can be established through experimental fitting, response surface analysis, or machine learning. The deviation between the target powder mass flow rate required by the molten pool at the target time and the predicted effective powder mass flow rate at the target time is calculated as the effective powder supply deviation. The powder supply compensation amount is calculated and determined based on the effective powder supply deviation. Based on the powder feeding compensation amount, the powder feeder control command is determined. The process of determining the powder feeder control command based on the powder feeding compensation amount includes: obtaining the current output mass flow rate of the powder feeder. Add the current powder feeder output mass flow rate to the powder feed compensation amount to obtain the compensated target powder feed mass flow rate; The target speed of the powder feeder is determined based on the corresponding relationship between the compensated target powder mass flow rate and the powder feeder speed and the powder output mass flow rate. Based on the target rotation speed of the powder feeder, generate control commands for the powder feeder; Subtract the effective powder feeding delay from the target time to obtain the powder feeding control command trigger time. The effective powder feeding delay includes the powder feeder response delay, the powder transport delay in the powder conveying pipe, and the flight delay experienced by the powder from leaving the nozzle to entering the molten pool. When the powder feeding control command is triggered, the powder feeder is controlled by the powder feeder control command.

2. The laser-directed energy deposition powder delivery delay prediction and compensation method as described in claim 1, characterized in that, Obtain the actual effective powder mass flow rate received by the molten pool at the target time; The effective powder supply error is calculated and determined based on the actual effective powder mass flow rate received by the molten pool at the target time and the target powder mass flow rate. The effective powder mass flow rate prediction model is corrected based on the effective powder supply error.

3. The laser-directed energy deposition powder delivery delay prediction and compensation method as described in claim 2, characterized in that, The modifications made to the effective powder mass flow rate prediction model include: Corrections to overall transport efficiency and to effective powder delivery delay.

4. A laser-directed energy deposition powder delivery delay prediction and compensation system, used to implement the laser-directed energy deposition powder delivery delay prediction and compensation method according to any one of claims 1-3, characterized in that, include: The mass flow rate acquisition unit is used to acquire the target powder mass flow rate required by the molten pool at the target time and the powder feeder output powder mass flow rate during the effective powder feeding delay time before the target time. The mass flow prediction unit is used to calculate and determine the predicted value of the effective powder mass flow at the target time based on the powder mass flow rate output by the powder feeder at the effective powder feeding delay time before the target time and the effective powder mass flow prediction model. The effective powder mass flow prediction model is a model of the relationship between the effective powder mass flow rate of the molten pool and the powder mass flow rate output by the powder feeder when considering the effective powder feeding delay. The effective powder supply deviation calculation unit is used to calculate the deviation between the target powder mass flow rate required by the molten pool at the target time and the predicted value of the effective powder mass flow rate at the target time, which is used as the effective powder supply deviation. The powder delivery compensation unit is used to calculate and determine the powder delivery compensation amount based on the effective powder delivery deviation. The powder feeder control command determination unit is used to determine the powder feeder control command based on the powder feeding compensation amount. The instruction triggering time determination unit is used to subtract the effective toner delivery delay from the target time to obtain the toner delivery control instruction triggering time. The instruction control unit is used to control the powder feeder via the powder feeder control instruction when the powder feeding control instruction is triggered.

5. An electronic device, characterized in that, The device includes: A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements the laser-directed energy deposition powder delivery delay prediction and compensation method according to any one of claims 1-3.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program adapted to be loaded by a processor and executed by a processor to predict and compensate for the delay in laser-directed energy deposition powder delivery as described in any one of claims 1-3.

7. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements a laser-directed energy deposition powder delivery delay prediction and compensation method as described in any one of claims 1-3.

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