Laser external light path shaping method and system based on PLC servo control

Abstract

The application provides a laser external light path shaping method and system based on PLC servo control, and relates to the technical field of laser external light path shaping. The method comprises the following steps: generating a multi-axis interpolation track based on the actual position, actual angle, actual light beam parameter and target light beam parameter of an optical element; driving a servo motor according to the multi-axis interpolation track to drive the optical element to adjust; collecting the actual position, actual angle and actual light beam parameter of the optical element in real time; obtaining a current error value according to the actual light beam parameter and the target light beam parameter; calculating a correction parameter based on the current error value; and driving the servo motor according to the correction parameter to drive the optical element to fine tune. The laser external light path shaping method and system based on PLC servo control solve the technical problem that the existing laser external light path shaping control system in the related art is difficult to meet the high-reliability, high-dynamic, easy-maintenance industrial application requirements of the light beam shaping system of high-end laser printing equipment.

Description

Technical Field

[0001] This invention relates to the field of laser external optical path shaping technology, specifically to a laser external optical path shaping method and system based on PLC servo control. Background Technology

[0002] Laser beam shaping technology is a crucial step in laser processing equipment (especially laser printing equipment). Its core objective is to transform the original Gaussian distributed laser beam into a beam with a specific spatial intensity distribution (such as a ring-shaped beam) to meet different process requirements. An advanced beam shaping scheme utilizes the diffraction properties of light, employing polarizing gratings and diffractive optical elements (DOEs). By designing micro / nano structures on the DOE surface, the amplitude, phase, and polarization parameters of the incident beam are precisely controlled, splitting a single beam into multiple beams and achieving complex beam distribution shaping. Compared to traditional refractive beam shaping devices (such as lens groups and prisms), this DOE scheme offers significant advantages such as small size, light weight, high integration, high shaping accuracy, and the ability to achieve complex beam distributions.

[0003] In practical engineering applications, to achieve precise and dynamic adjustment of beam parameters, it is usually necessary to drive optical elements to adjust their position or angle. A common driving solution uses a servo motor as the load actuator, and a host computer, in conjunction with a motion control card, sends commands to the servo driver to drive the optical element's movement. Some systems also introduce sensor closed-loop feedback to improve adjustment accuracy. Simultaneously, some solutions also attempt to use real-time buses such as EtherCAT (Ethernet Automation Technology) and ProfiNET (Process Field Network) for communication, aiming to achieve better multi-axis synchronization performance; under ideal conditions, synchronization errors can be controlled at the microsecond level.

[0004] However, the aforementioned laser external optical path shaping control system based on a host computer and motion control card still suffers from the following technical shortcomings in practical industrial applications. First, the system lacks stability. This type of system is highly dependent on the host computer's operating system. Issues such as process scheduling, memory management, interrupt response mechanisms, and potential system crashes, virus intrusions, and software conflicts can all lead to delays or loss of control commands. In complex industrial environments with electromagnetic interference and temperature and humidity variations, the failure rate of the host computer during continuous operation is significantly higher than that of a programmable logic controller (PLC), making it difficult to meet the demands of long-term, uninterrupted production for laser printing equipment. Second, real-time performance is limited. The closed-loop control cycle of ordinary motion control cards is typically 1 to 10 milliseconds, making it difficult to achieve sub-millisecond dynamic response requirements. When rapid and accurate compensation for beam drift or high-speed dynamic shaping switching is needed, the lag effect of the control system directly affects the shaping effect. Furthermore, multi-axis synchronization performance heavily depends on the processing performance of the host computer and the bus load status. When the host computer performs other background tasks or network load fluctuates, the synchronization accuracy between servo axes will significantly decrease, leading to optical path alignment deviations. Secondly, existing PC-based solutions lack the hardware redundancy design, fault self-diagnosis functions, and safety interlocking mechanisms that are mature applications in industrial automation. Finally, implementing existing solutions usually requires mastering specific motion control software secondary development capabilities, and field maintenance personnel must have advanced software programming and debugging skills. Once a fault occurs, troubleshooting often relies on original equipment manufacturer (OEM) technical support or senior motion control engineers, making it impossible for ordinary electrical maintenance personnel to quickly locate and repair the problem, resulting in long equipment downtime and high labor maintenance costs.

[0005] In summary, solving the above problems usually requires the additional development of a large number of low-level drivers, logic judgments, and security protection programs, which not only prolongs the equipment development cycle but also significantly increases the overall cost of software and hardware. Existing PC-based laser external beam shaping control systems have obvious shortcomings in terms of stability, real-time performance, engineering integration, and maintainability, making it difficult to meet the industrial-grade application requirements of high-end laser printing equipment for high reliability, high dynamism, and easy maintenance of beam shaping systems.

[0006] Therefore, existing technologies need further development. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a laser external optical path shaping method and system based on PLC servo control, so as to solve the technical problem that the existing laser external optical path shaping control system in related technologies is difficult to meet the industrial application requirements of high reliability, high dynamics and easy maintenance of beam shaping system in high-end laser printing equipment.

[0008] To achieve the above technical objectives, the present invention adopts the following technical solution: A laser external optical path shaping method based on PLC servo control is provided, comprising: generating a multi-axis interpolation trajectory based on the actual position, actual angle, actual beam parameters, and target beam parameters of the optical element; a servo driver driving a servo motor according to the multi-axis interpolation trajectory to adjust the optical element; real-time acquisition of the actual position, actual angle, and actual beam parameters of the optical element; obtaining the current error value based on the actual beam parameters and the target beam parameters; calculating correction parameters based on the current error value, wherein the method for calculating the correction parameters includes using adaptive PID control to calculate the adaptive PID output; using feedforward compensation to calculate the feedforward compensation amount; superimposing the adaptive PID output and the feedforward compensation amount to obtain the correction parameters; and the servo driver driving a servo motor according to the correction parameters to fine-tune the optical element.

[0009] Furthermore, the method also includes: repeatedly calculating the error value and fine-tuning the relational elements based on the error value until the error value is less than a preset threshold.

[0010] Furthermore, the methods for calculating the adaptive PID output in adaptive PID control include:

[0011] ,

[0012] ,

[0013] ,

[0014] Where e(k) is the current error value, |e| max α is the maximum permissible error value, β is the proportional adaptive coefficient, γ is the differential adaptive coefficient, and γ is the integral adaptive coefficient.

[0015] Furthermore, the methods for calculating the feedforward compensation amount include: , where K f Δr / Δt is the feedforward gain, and Δr / Δt is the rate of change of the setpoint.

[0016] Furthermore, the preset threshold is a position error of less than ±0.01mm; or, a beam parameter error of less than a preset allowable value.

[0017] Furthermore, the target beam parameters include spot size, optical axis position, wavefront, spot diameter, and spot uniformity.

[0018] Furthermore, the method also includes outputting the generated multi-axis interpolation trajectory to the servo driver via a high-speed pulse or real-time bus.

[0019] Furthermore, the real-time bus is an EtherCAT bus or a ProfiNET bus; the multi-axis synchronization error of the real-time bus is less than 1 microsecond.

[0020] A laser external optical path shaping system based on PLC servo control is also provided. This system includes: a multi-axis interpolation trajectory generation unit, used to generate a multi-axis interpolation trajectory based on the actual position, actual angle, actual beam parameters, and target beam parameters of the optical element; a drive unit, used by a servo driver to drive a servo motor according to the multi-axis interpolation trajectory to adjust the optical element; a real-time acquisition unit, used to acquire the actual position, actual angle, and actual beam parameters of the optical element in real time; an error calculation unit, used to obtain the current error value based on the actual beam parameters and the target beam parameters; a correction unit, used to calculate correction parameters based on the current error value, wherein the method for calculating the correction parameters includes using adaptive PID control to calculate the adaptive PID output; using feedforward compensation to calculate the feedforward compensation amount; and superimposing the adaptive PID output and the feedforward compensation amount to obtain the correction parameters; and an adjustment unit, used by a servo driver to drive a servo motor according to the correction parameters to fine-tune the optical element.

[0021] A computer-readable storage medium is also provided, on which computer-readable instructions are stored. When executed by a processor, the computer-readable instructions implement the various steps of the laser external optical path shaping method based on PLC servo control or the laser external optical path shaping system based on PLC servo control as described above.

[0022] Beneficial effects:

[0023] The laser external beam shaping method based on PLC servo control of this invention dynamically adjusts parameters according to real-time errors through adaptive PID control, correcting deviations after they occur. Simultaneously, it combines feedforward compensation to pre-calculate compensation based on the rate of change of setpoints, predicting and offsetting system inertia and transmission lag. The combined output of these two methods allows feedforward compensation to offset most of the foreseeable lag effects, while adaptive PID then finely corrects the remaining errors. This achieves both sub-millisecond dynamic response and micron-level steady-state accuracy on a PLC industrial controller with limited computing power. Furthermore, leveraging the inherent high anti-interference capability, hardware redundancy, fault self-diagnosis, and safety interlocking characteristics of PLCs, the method significantly improves system stability and engineering adaptability, reduces maintenance costs, and solves the technical problem that existing laser external beam shaping control systems cannot meet the high reliability, high dynamics, and easy maintenance requirements of high-end laser printing equipment for beam shaping systems in industrial applications. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the laser external optical path shaping method based on PLC servo control used in an embodiment of the present invention.

[0025] Figure 2 This is a block diagram of the laser external optical path shaping system based on PLC servo control used in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the adaptive PID and feedforward control process used in the embodiments of the present invention;

[0027] Figure 4 This is a schematic diagram of the control loop principle of the laser external optical path shaping system based on PLC servo control used in an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the structure of a laser external optical path shaping system based on PLC servo control provided in an embodiment of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0030] According to an embodiment of the present invention, a laser external optical path shaping method based on PLC servo control is provided. Please refer to [link to relevant documentation]. Figures 1 to 5 ,include:

[0031] S100 generates a multi-axis interpolation trajectory based on the actual position, actual angle, actual beam parameters, and target beam parameters of the optical elements;

[0032] In practice, the target beam parameters include spot size, optical axis position, wavefront, spot diameter, and spot uniformity.

[0033] In this embodiment, the programmable logic controller (PLC) first acquires the current actual position and angle of the optical element through sensors, as well as the actual beam parameters fed back by the CCD camera and laser power meter. Simultaneously, the host computer or HMI (human-machine interface) sends the target beam parameters to the PLC. Based on the initial deviation between the actual and target parameters, and combined with a preset kinematic model, the PLC generates a multi-axis interpolation trajectory, including the linear motion trajectory of the lens along the optical axis and the rotational angle trajectory of the reflector.

[0034] Specifically, the optical elements include, but are not limited to, adjustable lenses and mirrors; the current actual position accuracy of the optical elements is 0.001 mm, and the actual angle accuracy is 0.001°.

[0035] In some embodiments, the actual beam parameters include the beam diameter and beam uniformity.

[0036] The S200 servo driver drives the servo motor according to the multi-axis interpolation trajectory to adjust the optical element;

[0037] In practice, the generated multi-axis interpolation trajectory is output to the servo driver via a high-speed pulse or real-time bus.

[0038] Preferably, the real-time bus is an EtherCAT bus or a ProfiNET bus; the multi-axis synchronization error of the real-time bus is less than 1 microsecond.

[0039] In this embodiment, the servo driver parses the trajectory commands received from the EtherCAT bus and converts the weak electrical commands into strong electrical signals through the internal power module, driving the rotary servo motor to operate. The rotary servo motor converts the rotational motion into linear motion through a ball screw, causing the lens to translate along the optical axis; at the same time, another servo motor directly drives the reflector to rotate, adjusting the beam angle.

[0040] Specifically, the servo motor has a built-in 17-bit BISS encoder (i.e., a bidirectional synchronous serial interface encoder) that provides real-time feedback of the motor position to the driver, forming a closed loop of speed and position at the motor level, which initially suppresses transmission errors.

[0041] S300 acquires the actual position, actual angle, and actual beam parameters of the optical element in real time;

[0042] In this embodiment, an external precision sensor directly measures the actual position of the lens, and a laser interferometer measures the actual angle of the reflector. Simultaneously, a CCD / CMOS camera captures the light spot image via an image acquisition card, and the actual light spot diameter and uniformity are analyzed. A laser power meter (accuracy ±0.1%) acquires the beam power in real time, and a wavefront sensor acquires wavefront distortion data. These sensors transmit analog signals (4-20mA) or digital signals to the PLC in real time via an EtherCAT bus. The PLC first performs a first-order low-pass filter on the feedback signal to filter high-frequency noise and stores the filtered valid data in a designated register.

[0043] Preferably, the external precision sensor is a grating ruler with a resolution of 0.001 mm.

[0044] S400 obtains the current error value based on the actual beam parameters and the target beam parameters;

[0045] In this embodiment, the PLC reads the actual spot diameter and the target spot diameter from the register and calculates the error value e = actual spot diameter - target spot diameter.

[0046] Specifically, the actual spot diameter is 5.02 mm, and the target spot diameter is 5.00 mm, so e = 5.02 - 5.00 = +0.02 mm.

[0047] Furthermore, the errors of parameters such as spot uniformity and optical axis position are calculated similarly.

[0048] S500 calculates correction parameters based on the current error value. The method for calculating the correction parameters includes: calculating the adaptive PID output using adaptive PID control; calculating the feedforward compensation amount using feedforward compensation; and superimposing the adaptive PID output and the feedforward compensation amount to obtain the correction parameters.

[0049] It should be noted that the proportional (P), integral (I), and derivative (D) parameters of traditional PID control are fixed values, making it difficult to adapt to scenarios with dynamically changing system errors. This is especially true when errors change abruptly or when there is lag due to mechanical inertia, which can easily lead to problems such as slow response and large overshoot. This embodiment employs error-driven adaptive PID control, dynamically adjusting the P / I / D parameters according to the real-time error magnitude to achieve adaptive parameter matching.

[0050] Specifically, see Figure 3 Let the current control error be e(k), and the maximum permissible error be |e|. max Based on the basic PID parameter K p ,K i ,K d Based on this, adaptive coefficients α, β, and γ are introduced to update parameters in real time. The methods for calculating the adaptive PID output in adaptive PID control include:

[0051] ,

[0052] ,

[0053] ,

[0054] Where e(k) is the current error value, |e| max α is the maximum permissible error value, β is the proportional adaptive coefficient, β is the differential adaptive coefficient, and γ is the integral adaptive coefficient.

[0055] In this embodiment, the adaptive coefficients α, β, and γ are not fixed constants, but rather adjustment factors that are pre-tuned and dynamically coordinated according to the system characteristics and error state. Specifically, the values ​​of α, β, and γ are closely related to the system's mechanical inertia, transmission stiffness, and the response characteristics of the optical components. After obtaining the transfer function model of the controlled object through system identification experiments, the initial values ​​of these three coefficients are determined by combining engineering tuning experience.

[0056] The method for obtaining α (proportional coefficient adaptive gain) includes: α is used to accelerate the system response when there is a large error, and its value range is usually 0.3 to 0.8.

[0057] Specifically, in the system step response experiment, the output overshoot and rise time are observed;

[0058] If the current error suddenly increases from zero to more than 80% of the maximum permissible error, and the system rise time is greater than 1.2 times the expected threshold, then increase the value of α (e.g., from 0.5 to 0.6) to enhance the proportional effect under large errors.

[0059] If the overshoot exceeds 20% of the target value, the α value should be appropriately reduced to avoid oscillation.

[0060] In this embodiment, α=0.6 is taken on the lens translation axis (with a large load inertia), and α=0.4 is taken on the mirror rotation axis (with a small load inertia) to achieve axis type adaptation.

[0061] Furthermore, the method for obtaining β (adaptive attenuation factor of integral coefficient) includes: β is used to weaken the integral effect under large errors, preventing system overshoot and oscillation caused by integral saturation. Its value range is usually 0.2 to 0.5.

[0062] Specifically, observe the rate of accumulation of the integral term: if, during a large error step response, the integral term exceeds 60% of the output limit before the error decays to near zero, then increase the β value (e.g., from 0.3 to 0.45) to more aggressively suppress integral saturation.

[0063] Conversely, if the system has persistent small steady-state errors (residual steady-state errors), the value of β should be appropriately reduced to ensure the residual elimination capability of the integral action.

[0064] Preferably, in this embodiment, β = 0.4.

[0065] Furthermore, the methods for obtaining γ (adaptive gain factor of differential coefficient) include: γ is used to enhance the differential action when there is a large error, suppress system oscillation in advance, and achieve the prediction effect of "braking before deviation". Its value range is usually 0.3 to 0.6.

[0066] Specifically, observe the rate of change of error and the degree of system oscillation: if the system exhibits significant oscillation after a large error step (the error fluctuates repeatedly around the target value more than 3 times), then increase the value of γ (e.g., adjust it from 0.4 to 0.55) to enhance the damping effect;

[0067] If the differential term is too sensitive, causing the system to overreact to high-frequency noise (manifested as frequent jitter of the actuator), then the value of γ should be appropriately reduced.

[0068] Preferably, in this embodiment, γ = 0.5.

[0069] It should be noted that during system operation, the PLC also records the error convergence curve for each iteration and uses a self-learning strategy to periodically fine-tune α, β, and γ offline: if the system consistently exhibits a slow rise time within a large error range during multiple iterations, the PLC prompts the operator via the HMI to appropriately increase α; if the system oscillates repeatedly around the target value, it prompts to appropriately increase γ; if a stable positive / negative deviation persists after convergence, it prompts to appropriately decrease β (restoring integral action). This self-diagnostic prompting function ensures the system's long-term adaptability under different operating conditions. It should also be noted that when the error is large, the proportional coefficient K is increased. p To accelerate the response speed, the integral coefficient K should be appropriately reduced. i 'Avoid integral saturation while increasing the differential coefficient K' d 'Suppress oscillations in advance; when the error is small, dynamically adjust parameters to enhance system stability and eliminate steady-state error.'

[0070] It is understandable that, given the common mechanical inertia and transmission lag issues in the system, relying solely on the ex-post error correction of adaptive PID control is insufficient to completely solve the response delay problem. Therefore, this embodiment introduces feedforward control to achieve advance compensation. By predicting the system's lag trend, compensation is added in advance to offset the adverse effects of lag.

[0071] In practice, the design of feedforward control is centered on the rate of change of the setpoint. The setpoint is set to r, and the rate of change of the setpoint is Δr / Δt. A feedforward gain K is introduced. f Wherein, the feedforward gain K f Tuning is based on the magnitude of system inertia.

[0072] Specifically, the setpoint r is not a fixed constant, but a time-varying target that changes dynamically with the laser printing process stages (such as fill scanning, contour scanning, and jump switching). In dynamic beam shaping scenarios, the setpoint r is a trajectory curve that changes over time, rather than a single static point.

[0073] Furthermore, in this embodiment, the feedforward gain K f The K value is obtained through a combination of theoretical calculation and experimental tuning. First, the equivalent transfer function model of the controlled object (including the servo motor, ball screw, and lens slide) is obtained through system identification experiments. Based on this model, the initial theoretical feedforward gain of the feedforward compensation stage is calculated. Specifically, in speed closed-loop control mode, the ratio of the steady-state speed error to the commanded speed is recorded when the motor is running at different constant speed commands. The average value of multiple sets of data is taken as K. fThe theoretical benchmark value is used. However, due to factors such as ball screw backlash (approximately 0.003 mm), nonlinear friction, and load inertia fluctuations in actual mechanical transmission systems, the theoretical calculation value cannot fully compensate for the actual lag. Therefore, fine-tuning on-site is required based on the theoretical value.

[0074] It should be noted that during the tuning process, K is first set... f Setting K to 0 enables the system to operate solely based on adaptive PID feedback control. The PLC reads the actual lens position from the grating ruler feedback, plots the position response curve as the setpoint changes stepwise, and records the steady-state following error (i.e., the difference between the commanded position and the actual position). Subsequently, K is gradually increased... f The value (step size 0.05) is incremented, and the same step test with the same set value is repeated after each increment to observe the trend of the following error. When the following error increases with K... f When K increases and continues to decrease, continue increasing K. f When the following error decreases to its minimum and then begins to increase in the opposite direction, or when the system exhibits slight oscillations, K will be adjusted. f The price retraces to the previous level; that level is the optimal K. f Value. In this embodiment, K is determined via the above-described adjustment process on the lens translation axis. f =0.15; For the rotating axis of the reflector with a small load inertia, K is tuned to obtain... f =0.08. Two different shaft types K f The difference in the values ​​fully reflects the design principle of precisely matching the feedforward gain with the system inertia: a large inertia axis requires a larger feedforward gain to overcome inertial lag, while a small inertia axis requires a smaller gain to avoid overcompensation.

[0075] In some embodiments, in advanced servo drives with self-tuning capabilities, intelligent optimization algorithms can also be used to automatically obtain K. f Specifically, the servo driver incorporates a particle swarm optimization (PSO) algorithm, with the objective function being the minimization of the root mean square value of the following error, within K... f The optimal solution is automatically searched within the preset search interval [0, 0.5]. However, this method involves a large amount of computation and relies on the computing power of the driver itself, so it is not the preferred method in this embodiment. This embodiment preferably adopts the experimental tuning method because it does not require additional algorithm development, the tuning process is intuitive, and the results are reliable. Ordinary electrical engineers can complete the single-axis K-axis tuning within 30 minutes through the HMI monitoring interface. f The tuning significantly reduces the difficulty of on-site commissioning and maintenance costs, aligning with the engineering usability goals pursued in this application. K obtained using the above method... f The value remains constant during system operation, combined with the feedforward calculation formula u, which is based on the rate of change of the set value. ff = K f× (Δr / Δt) achieves stable and precise compensation for system inertia and transmission lag.

[0076] Furthermore, the method for calculating the feedforward compensation amount includes:

[0077] ,

[0078] Among them, K f Δr / Δt is the feedforward gain, and Δr / Δt is the rate of change of the setpoint.

[0079] Furthermore, the total system control output is the sum of the adaptive PID control output and the feedforward compensation, i.e., u(k) = u pid_adaptive (k)+u ff (k) achieves an organic combination of ex-post correction and ex-ante compensation, where u pid_adaptive (k) represents the total control output calculated by the adaptive PID controller at the k-th sampling time. It is obtained by superimposing the dynamically adjusted proportional coefficient Kp', integral coefficient Ki', and derivative coefficient Kd' after calculating the current and historical errors respectively.

[0080] It should be noted that when using adaptive PID control alone, although it can dynamically adjust parameters according to real-time error and correct deviations after they occur, the control action always lags behind the occurrence of the error. For high-speed dynamic switching (such as the spot diameter changing at a rate of 10 mm / s) or lag caused by mechanical inertia that are common in laser external optical path shaping, the system will inevitably have a response delay, resulting in increased overshoot and extended settling time, making it difficult to meet the sub-millisecond dynamic response requirements.

[0081] In practice, if only adaptive PID is used, the PID output is 0.02488mm, while the actual required lens movement distance is 1.52488mm. The PID needs to go through multiple iterations to gradually approach the target, and the overall response time will be extended to more than 100ms, and oscillation is likely to occur.

[0082] Furthermore, if feedforward compensation is used alone, although the compensation amount of 1.5mm can be calculated in advance based on the rate of change of the set value to quickly offset most of the foreseeable hysteresis effects, feedforward control is an open-loop compensation and cannot eliminate the residual steady error caused by model inaccuracy or external disturbances. Under simple feedforward control, the final error of the spot diameter may be stable above ±0.02mm, which cannot meet the accuracy requirement of ±0.005mm.

[0083] Therefore, this embodiment combines adaptive PID and feedforward compensation in its output. The feedforward compensation outputs a dominant control quantity of 1.5mm in advance, driving the motor to respond almost synchronously to the target change, thus offsetting most of the lag effects in advance. The adaptive PID then only needs to output a fine correction quantity of 0.02488mm to perform post-processing calibration for residual steady-state errors that the feedforward cannot eliminate. With the combined effect of the two, the system achieves a spot diameter change from 5.00mm to 5.01mm in the first adjustment cycle, and converges to 5.002mm after the second iteration, with a total adjustment time of only 20ms, achieving both sub-millisecond dynamic response and micron-level steady-state accuracy. This enables the PLC-based external beam shaping system to surpass the traditional PC + motion control card solution in terms of dynamic response speed, solving the technical problem that existing laser external beam shaping control systems cannot meet the high reliability, high dynamics, and easy maintenance requirements of high-end laser printing equipment for industrial applications of beam shaping systems.

[0084] The servo driver in S600 drives the servo motor according to the correction parameters to fine-tune the optical element.

[0085] In practice, the PLC sends the calibration parameters to the servo driver via the EtherCAT bus. The driver then drives the servo motor to make micron-level fine adjustments to the lens position or the reflector angle based on these parameters.

[0086] S700 repeatedly calculates the error value and fine-tunes the relational element based on the error value until the error value is less than a preset threshold.

[0087] Preferably, the preset threshold is a position error of less than ±0.01mm; or, the beam parameter error is less than a preset allowable value.

[0088] In this embodiment, the PLC sends the correction command to the servo driver again, driving the motor to fine-tune the position / angle of the optical element; the cycle of "feedback acquisition → error calculation → correction command" is repeated until the error value is less than the preset threshold (e.g., <±0.01mm), and the system enters a stable state.

[0089] This embodiment also provides a laser external optical path shaping system based on PLC servo control. The system includes: a multi-axis interpolation trajectory generation unit, used to generate a multi-axis interpolation trajectory based on the actual position, actual angle, actual beam parameters, and target beam parameters of the optical element; a driving unit, used by a servo driver to drive a servo motor according to the multi-axis interpolation trajectory to adjust the optical element; a real-time acquisition unit, used to acquire the actual position, actual angle, and actual beam parameters of the optical element in real time; an error calculation unit, used to obtain a current error value based on the actual beam parameters and the target beam parameters; a correction unit, used to calculate correction parameters based on the current error value, wherein the method for calculating the correction parameters includes using adaptive PID control to calculate the adaptive PID output; using feedforward compensation to calculate the feedforward compensation amount; and superimposing the adaptive PID output and the feedforward compensation amount to obtain the correction parameters; and an adjustment unit, used by the servo driver to drive the servo motor according to the correction parameters to fine-tune the optical element.

[0090] With the above configuration, the laser external beam shaping method based on PLC servo control of this invention dynamically adjusts parameters according to real-time errors through adaptive PID control, correcting deviations that have already occurred. Simultaneously, it combines feedforward compensation to pre-calculate compensation based on the rate of change of the set value, predicting and offsetting system inertia and transmission lag. The combined output of these two methods allows feedforward compensation to offset most of the foreseeable lag effects, while adaptive PID then finely corrects the remaining errors. This achieves both sub-millisecond dynamic response and micron-level steady-state accuracy on a PLC industrial controller with limited computing power. Furthermore, leveraging the inherent high anti-interference capability, hardware redundancy, fault self-diagnosis, and safety interlocking characteristics of PLCs, the system stability and engineering adaptability are significantly improved, maintenance costs are reduced, and the technical problem of existing laser external beam shaping control systems failing to meet the high reliability, high dynamics, and easy maintenance requirements of high-end laser printing equipment for beam shaping systems in industrial applications is solved.

[0091] Example 1: See Figures 4 to 5 This embodiment takes the external optical path shaping system of a laser printing equipment as an example to explain in detail the laser external optical path shaping method based on PLC servo control.

[0092] Specifically, the external optical path shaping system of the laser printing equipment includes:

[0093] Instruction parsing and power amplification module: After receiving the instruction sent by the host computer, the PLC sends the instruction to the servo driver through bus communication (EtherCAT or ProfiNET). After receiving the instruction from the PLC, the servo driver parses the target position / speed and converts the weak current instruction into a strong current signal (such as three-phase AC) through the internal power module to drive the servo motor to run.

[0094] Rotary servo motor: Converts rotary motion into linear motion via ball screw (e.g., to move the lens along the optical axis), or directly drives the reflector to rotate (to adjust the beam angle).

[0095] Built-in encoder feedback module: The servo motor has a built-in absolute encoder or incremental encoder (such as a 17-bit BISS encoder with a resolution of 0.001mm) to collect the actual position / speed of the motor in real time and feed it back to the driver to form a "small closed loop" (speed loop + position loop) at the motor level, which initially suppresses errors.

[0096] External precision sensors: These directly acquire the actual position of the optical components and feed it back to the PLC, avoiding positioning deviations caused by mechanical transmission errors. These sensors include laser interferometers, optical grating rulers, etc.; the actual position includes the precise coordinates of the lens, the actual angle of the reflector, etc.; and transmission errors include lead screw backlash, etc.

[0097] Spot parameters: CCD / CMOS camera captures spot images, and the data is transmitted to PLC or host computer through image acquisition card to analyze spot diameter, optical axis center coordinates, spot uniformity, etc.

[0098] Beam power / wavefront: The laser power meter acquires the beam power in real time (feedback accuracy ±0.1%), and the wavefront sensor acquires the wavefront distortion data, transmitting the analog signal (4-20mA) or digital signal to the PLC.

[0099] Feedback signal processing module: The PLC performs filtering processing on the acquired position signal and optical parameter signal (such as first-order low-pass filtering to filter high-frequency noise), extracts the valid data and stores it in the designated register.

[0100] This embodiment also provides a computer-readable storage medium storing computer-readable instructions. When executed by a processor, the computer-readable instructions implement the various steps of the laser external optical path shaping method based on PLC servo control or the laser external optical path shaping system based on PLC servo control as described in any of the preceding embodiments.

[0101] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0102] Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments, and will not be repeated here.

[0103] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0104] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0105] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A laser external optical path shaping method based on PLC servo control, characterized in that, include: Multi-axis interpolation trajectory is generated based on the actual position, actual angle, actual beam parameters of optical elements and target beam parameters. The servo driver drives the servo motor according to the multi-axis interpolation trajectory, thereby adjusting the optical element; Real-time acquisition of the actual position, actual angle, and actual beam parameters of the optical element; The current error value is obtained based on the actual beam parameters and the target beam parameters; The correction parameter is calculated based on the current error value. The method for calculating the correction parameter includes: calculating the adaptive PID output using adaptive PID control; calculating the feedforward compensation amount using feedforward compensation; and superimposing the adaptive PID output and the feedforward compensation amount to obtain the correction parameter. The servo driver drives the servo motor according to the correction parameters to drive the optical element for fine adjustment.

2. The laser external optical path shaping method based on PLC servo control according to claim 1, characterized in that, The method further includes: repeatedly calculating the error value and fine-tuning the relational element based on the error value until the error value is less than a preset threshold.

3. The laser external optical path shaping method based on PLC servo control according to claim 1, characterized in that, The method for calculating the adaptive PID output in adaptive PID control includes: ； ； ， Where e(k) is the current error value, |e| max α is the maximum permissible error value, β is the proportional adaptive coefficient, β is the integral adaptive coefficient, and γ is the differential adaptive coefficient.

4. The laser external optical path shaping method based on PLC servo control according to claim 1, characterized in that, The method for calculating the feedforward compensation amount includes: ， Among them, K f Δr / Δt is the feedforward gain, and Δr / Δt is the rate of change of the setpoint.

5. The laser external optical path shaping method based on PLC servo control according to claim 1, characterized in that, The preset threshold is a position error of less than ±0.01mm; or a beam parameter error of less than a preset allowable value.

6. The laser external optical path shaping method based on PLC servo control according to claim 1, characterized in that, The target beam parameters include spot size, optical axis position, wavefront, spot diameter, and spot uniformity.

7. The laser external optical path shaping method based on PLC servo control according to claim 1, characterized in that, The method also includes outputting the generated multi-axis interpolation trajectory to the servo driver via a high-speed pulse or real-time bus.

8. The laser external optical path shaping method based on PLC servo control according to claim 7, characterized in that, The real-time bus is an EtherCAT bus or a ProfiNET bus; the multi-axis synchronization error of the real-time bus is less than 1 microsecond.

9. A laser external optical path shaping system based on PLC servo control, characterized in that, The PLC servo-controlled laser external optical path shaping system includes: A multi-axis interpolation trajectory generation unit is used to generate a multi-axis interpolation trajectory based on the actual position, actual angle, actual beam parameters and target beam parameters of the optical element. A drive unit is provided, which is used by the servo driver to drive the servo motor according to the multi-axis interpolation trajectory, so as to drive the optical element to make adjustments; A real-time acquisition unit is used to acquire the actual position, actual angle, and actual beam parameters of the optical element in real time. An error calculation unit is used to obtain the current error value based on the actual beam parameters and the target beam parameters; The correction unit is used to calculate correction parameters based on the current error value. The method for calculating the correction parameters includes calculating the adaptive PID output using adaptive PID control; calculating the feedforward compensation amount using feedforward compensation; and superimposing the adaptive PID output and the feedforward compensation amount to obtain the correction parameters. An adjustment unit is provided, wherein the servo driver drives the servo motor according to the correction parameters to fine-tune the optical element.

10. A computer-readable storage medium storing computer-readable instructions thereon, characterized in that, When the computer-readable instructions are executed by the processor, they implement each step of the laser external optical path shaping method based on PLC servo control as described in any one of claims 1-8, or the laser external optical path shaping system based on PLC servo control as described in claim 9.

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