Multi-dimensional state linkage carbon dioxide laser output closed-loop control method and system

Abstract

The present application relates to the technical field of laser control, and discloses a multi-dimensional state linkage carbon dioxide laser output closed-loop control method and system, the method comprising: obtaining target output parameters and real-time attitude data of a light guide system; determining geometric transmission limiting parameters according to the attitude data, and calculating predicted beam characteristics in combination with a thermal effect mapping relationship; comparing the predicted beam characteristics with a safety threshold; if the threshold is not met, executing a first strategy to adjust the combination of peak power and duty cycle of a laser driving signal to improve the beam characteristics while maintaining constant target single-pulse energy; and if the threshold is met, executing a second strategy to perform energy compensation on the laser driving signal according to transmission loss. The present application solves the transmission limiting problem caused by changes in the attitude of the light guide arm and thermal lens effect through dynamic waveform reconstruction and linear compensation, ensuring the accuracy of the laser output energy and the safety of the system.

Description

Technical Field

[0001] This invention relates to the field of laser control technology, and in particular to a closed-loop control method and system for carbon dioxide laser output with multi-dimensional state linkage. Background Technology

[0002] Carbon dioxide lasers are widely used in dermatology and surgery due to their high absorption of water molecules at a wavelength of 10.6 micrometers. In clinical applications, to meet the flexibility requirements of surgical procedures, laser energy typically needs to be transmitted to the treatment end through a light guide arm system containing multiple mirrors and rotating joints. This complex mechanical transmission structure means that the final output quality of the laser beam depends not only on the excitation state of the laser itself but also on the real-time geometry of the light guide system.

[0003] In actual operation, as the laser output power increases, the thermal effects within the optical transmission channel gradually become apparent. Particularly when the laser beam passes through various reflectors and the output window, the absorption of energy by the optical components leads to uneven temperature distribution, resulting in a thermal lensing effect. This thermally induced change in refractive index alters the wavefront curvature of the beam, causing dynamic drift in the beam diameter and divergence angle. For fixed optical paths, this drift can usually be corrected using pre-set optical compensation elements.

[0004] The unique characteristic of the light guide arm system lies in the unsteady nature of its transmission path. During operation, doctors frequently change the extension length and bending angle of the light guide arm, meaning that the total optical path length of the laser beam and the incident cross-section of the beam at each joint are constantly changing. When the thermal lensing effect causes the beam diameter to increase, and the light guide arm happens to be in a state of large-angle bending or long-distance transmission, the edge of the beam is very likely to touch the physical aperture limitation inside the joint.

[0005] This mismatch between beam size and physical aperture triggers a series of chain reactions. First, the mechanical truncation of the beam edge directly results in energy reaching the affected area being lower than the set value, causing uncertainty in treatment effectiveness. Second, the truncated high-energy-density beam bombarding the inner wall of the light guide arm or the lens holder causes severe local temperature rise, even ablation of mechanical components, further deteriorating the transmission performance of the optical path. Existing control schemes are mostly limited to single-dimensional adjustment, such as linear power compensation based solely on the light output duration, or relying solely on passive heat dissipation to suppress thermal effects. These methods struggle to cope with the complex situation of simultaneous "thermal beam diffusion" and "light guide arm posture restriction," failing to maintain high-precision energy output while ensuring equipment safety. Therefore, a closed-loop control scheme is needed that can simultaneously sense the light guide posture and thermal state and actively adjust beam characteristics. Summary of the Invention

[0006] The present invention aims to solve the problems of transmission loss fluctuation caused by joint posture changes in existing carbon dioxide laser beam guide arm transmission systems, as well as beam quality degradation and physical aperture truncation caused by thermal lensing effect under high power.

[0007] To address the above problems, the present invention provides the following technical solution:

[0008] The first aspect of this invention provides a closed-loop control method for carbon dioxide laser output with multi-dimensional state linkage, the method comprising the following steps:

[0009] First, target output parameters containing the target single-pulse energy and real-time attitude data of the light guiding system are acquired. The attitude data reflects the spatial morphology of the light guiding transmission system and is directly related to the geometric constraints of the transmission distance and path.

[0010] Secondly, based on the attitude data, geometric transmission constraint parameters are determined, and combined with the target output parameters and thermal effect mapping relationship, the predicted beam characteristics of the laser beam at the location of the constraint parameters are calculated. This step aims to predict the specific state of the laser beam when it reaches a physically constrained location (such as an articulated aperture or lens edge) after transmission in a specific attitude under the current energy output setting.

[0011] Next, the predicted beam characteristics are compared with a safety threshold, and different control strategies are adopted based on the comparison results:

[0012] If the comparison result shows that the safety threshold is not met, the system is determined to be in a restricted transmission state, and the first strategy is executed: while keeping the target single pulse energy constant, the combination of peak power and duty cycle of the laser driving signal is adjusted. The core of this strategy is to improve the beam characteristics to meet the transmission requirements by changing the time-domain waveform of the pulse (e.g., increasing the peak power and compressing the pulse width) while maintaining the total energy constant, thereby reducing the average thermal load or changing the formation conditions of the thermal lens.

[0013] If the comparison result shows that the safety threshold is met, the system is determined to be in a safe transmission state, and the second strategy is executed: energy compensation is performed on the laser drive signal according to the transmission loss corresponding to the attitude data. This strategy mainly compensates for the linear attenuation caused by the number of mirrors and the air optical path, ensuring that the energy reaching the treatment end meets the set value.

[0014] In one possible implementation, the geometric transmission constraint parameter specifically refers to the minimum effective aperture. Determining this parameter involves forward kinematics calculations, i.e., determining the incident angle deviation of the beam at each reflecting node in the light guide system and calculating the projection distortion correction factor. Simultaneously, considering the influence of gravity on the robotic arm, the lateral offset is calculated using a polynomial fitting model based on the horizontal projection distance of each reflecting node relative to the base. Finally, by combining projection distortion, gravity offset, and physical aperture, the local effective aperture of each node is calculated, and the minimum value is taken as the transmission bottleneck of the entire system.

[0015] In one possible implementation, the predicted beam characteristic is specifically the beam radius. The calculation process utilizes a pre-defined thermal lensing effect model, which includes a linear regression function with average power as the independent variable, used to calculate the dynamic beam quality factor. Combined with the optical transmission distance calculated from attitude data, the beam radius at a specific location is accurately calculated based on the Gaussian beam propagation equation (using parameters such as laser wavelength and beam waist radius).

[0016] In one possible implementation, the safety threshold is set based on the geometric transmission limitation parameter. Specifically, the value of this limitation parameter is obtained and scaled using a preset safety factor (e.g., 1.5 to 2.0). This setting ensures that the beam energy concentration area is far from physical boundaries, preventing edge diffraction effects or thermal damage.

[0017] Furthermore, the specific logic for executing the first strategy includes reverse derivation and waveform reconstruction: Based on the safety threshold and the current transmission distance, the maximum allowable beam quality factor under the current geometric constraints is derived in reverse; then, the maximum allowable pulse duration is solved using a thermal lensing effect model that includes duty cycle and average power variables; finally, based on the principle of energy conservation, the corrected peak power is calculated by dividing the target single pulse energy by the maximum pulse duration and a driving signal is generated.

[0018] To address hardware physical limitations, the method also includes an adaptive adjustment step: A physical saturation power threshold, dynamically corrected based on the DC bus voltage and laser tube temperature, is obtained. If the calculated corrected peak power exceeds this threshold, the peak power is clamped to the physical limit, and the confined pulse duration is calculated accordingly. Simultaneously, to maintain thermal balance, the repetition frequency of the laser output is recalculated and reduced based on the confined pulse duration and the allowable beam quality factor, suppressing the thermal lensing effect by reducing the total heat input per unit time.

[0019] In one possible implementation, when executing the second strategy, the total number of mirrors and the total optical path length of the beam are determined based on attitude data. The total optical transmission efficiency is calculated by combining the single-mirror reflectivity and the air medium attenuation coefficient. The compensated target energy is obtained by dividing the target single-pulse energy by this efficiency, and the pulse width is adjusted while maintaining the reference peak power. At the same time, the maximum duty cycle of the adjusted pulse width is checked.

[0020] In addition, the method also involves nonlinear linearization processing and real-time impedance fine-tuning: On the one hand, characteristic curve tables containing the mapping relationship between driving commands and measured power are retrieved, and linear interpolation is used to eliminate the nonlinear gain of the laser; on the other hand, radio frequency voltage and current are collected during the laser ignition stabilization stage, the deviation rate between the real-time load impedance and the optimal matching impedance is calculated, and the power loss is estimated accordingly and the pulse width is extended within the current pulse for compensation.

[0021] The second aspect of the present invention provides a multi-dimensional state linkage closed-loop control system for carbon dioxide laser output, the system comprising a main control unit, a laser emission unit, a light guide transmission unit, a cooling circulation unit, and a human-machine interaction unit.

[0022] The human-computer interaction unit is connected to the main control unit and is used to receive target output parameters input by the user, which include at least the target single pulse energy.

[0023] The light guiding and transmission unit is composed of multiple hollow reflective joints connected in series, with an angle encoder integrated at the rotation axis of each reflective joint. The angle encoder measures the relative rotation angle of the joint in real time and sends this as the attitude data of the light guiding system to the main control unit.

[0024] The laser emitting unit includes a laser tube and a driving power supply. The driving power supply applies excitation to the laser tube according to the driving control signal sent by the main control unit, thereby generating laser output.

[0025] The main control unit includes a processor and a memory, and communicates with each unit via a data bus. The processor is configured to execute the control logic described in the first aspect above: determine geometric constraints based on attitude data, predict beam characteristics by combining thermal effect mapping, and select either a waveform reconstruction strategy (first strategy) or a linear loss compensation strategy (second strategy) based on the comparison results, thereby generating the final drive control signal.

[0026] In summary, the present invention has at least one of the following beneficial technical effects:

[0027] 1. This invention resolves the coupling contradiction between attitude and thermal effects. Unlike traditional compensation methods that only address a single variable, this invention can simultaneously handle the geometric transmission limitations caused by changes in the light guide arm's attitude and the thermal lensing effect caused by high power. By distinguishing between constrained and safe states, two distinct strategies—waveform reconstruction and linear compensation—are employed respectively, maximizing the output target energy while ensuring throughput.

[0028] 2. This invention improves the system's safety and lifespan. By accurately calculating the minimum effective aperture and setting a safety threshold, it prevents the laser beam edge from bombarding the inner wall of the light guide arm or the lens holder, thus preventing device damage due to overheating. Simultaneously, the introduction of a physical saturation power threshold protects the drive power supply and laser tube from operating under overload conditions.

[0029] 3. This invention ensures consistency in clinical treatment. Through nonlinear linearization processing, transmission loss compensation, and impedance mismatch compensation, it ensures that the actual laser energy reaching the patient is highly consistent with the target energy set by the doctor, and is not affected by the extension length of the light guide arm, bending angle, or thermal state of the equipment.

[0030] 4. This invention achieves optimal output under physical limits. By actively reducing the repetition frequency when hardware capabilities reach a bottleneck (such as peak power saturation), the single-pulse energy and beam quality are achieved. This is of great significance in clinical applications for ensuring the therapeutic effect of a single pulse. Attached Figure Description

[0031] Figure 1 This is a structural block diagram of a multi-dimensional state-linked closed-loop control system for carbon dioxide laser output according to an embodiment of the present invention;

[0032] Figure 2 This is a flowchart illustrating a multi-dimensional state-linked closed-loop control method for carbon dioxide laser output according to an embodiment of the present invention.

[0033] Figure 3 This is a flowchart of the kinematic attitude calculation and geometric bottleneck extraction of the light guide transmission unit in one embodiment of the present invention;

[0034] Figure 4 This is a flowchart of beam radius prediction and transmission status verification in one embodiment of the present invention;

[0035] Figure 5 This is a flowchart of an equal-energy waveform reconstruction strategy under constrained transmission conditions in one embodiment of the present invention;

[0036] Figure 6 This is a flowchart of adaptive boundary control under physical power limits in one embodiment of the present invention;

[0037] Figure 7 This is a flowchart of linear power compensation under secure transmission state in one embodiment of the present invention;

[0038] Figure 8 This is a flowchart of real-time feedback fine-tuning based on gas impedance characteristics in one embodiment of the present invention;

[0039] Figure 9 This is a comparison chart of the single-pulse energy stability of the traditional control method and the control method of the present invention under continuous working conditions;

[0040] Figure 10 A comparison chart showing the changing trend of the beam radius at the geometric bottleneck during the extension of the light guide arm.

[0041] Among them, 100 is the main control unit; 200 is the laser emitting unit; 201 is the laser tube; 202 is the driving power supply; 203 is the sampling circuit; 300 is the light guiding and transmission unit; 301 is the reflection joint; 302 is the angle encoder; 400 is the cooling circulation unit; and 500 is the human-machine interaction unit. Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, and to make the above-mentioned objectives, features and advantages of the embodiments of this application more apparent and understandable, the technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0043] See attached document Figure 1 , Figure 1 This is a structural block diagram of a multi-dimensional state-linked closed-loop control system for carbon dioxide laser output according to an embodiment of the present invention. The present invention provides a multi-dimensional state-linked closed-loop control system for carbon dioxide laser output, the system including a main control unit 100, a laser emitting unit 200, a light guiding and transmission unit 300, a cooling circulation unit 400, and a human-machine interaction unit 500.

[0044] The main control unit 100 includes a microprocessor, a memory, and an input / output interface. The memory stores the computer program for executing the closed-loop control logic, a laser power characteristic curve table, and a transmission efficiency lookup table. The main control unit 100 establishes communication connections with the laser emitting unit 200, the light guiding and transmission unit 300, and the cooling circulation unit 400 via a data bus, respectively, sending control commands and receiving status feedback data.

[0045] The laser emitting unit 200 includes a laser tube 201, a driving power supply 202, and a sampling circuit 203. The input terminal of the driving power supply 202 is connected to the control signal output terminal of the main control unit 100, and the output terminal is connected to the excitation electrode of the laser tube 201. The driving power supply 202 applies high-voltage excitation to the laser tube 201 according to the pulse width modulation signal and current setting signal sent by the main control unit 100. The sampling circuit 203 is connected in series in the power supply circuit of the laser tube 201, and acquires the holding voltage signal and circuit current signal across the laser tube 201 in real time at a sampling rate of not less than 1MHz. The sampling circuit 203 converts the acquired analog electrical signals into digital signals and transmits them to the main control unit 100.

[0046] The light guiding and transmission unit 300 is composed of multiple hollow reflective joints 301 connected in series, with reflective mirrors installed inside each reflective joint 301. An angle encoder 302 is integrated at the rotation axis of a selected reflective joint 301. The angle encoder 302 measures the relative rotation angle of the reflective joint 301 in real time and sends the angle position data to the main control unit 100.

[0047] The cooling circulation unit 400 includes a circulation pump and a fluid sensor. The fluid sensor monitors the coolant flow rate and temperature and feeds the monitoring data back to the main control unit 100. The circulation pump drive motor is connected to the main control unit 100, and the main control unit 100 adjusts the circulation pump speed and frequency.

[0048] The human-machine interface unit 500 is connected to the main control unit 100, receives treatment parameters input by the user, including target energy density, pulse duration and repetition frequency, and displays the system working status and alarm information.

[0049] See attached document Figure 2 , Figure 2 This is a flowchart illustrating a multi-dimensional state-linked closed-loop control method for carbon dioxide laser output according to an embodiment of the present invention. The present invention provides a multi-dimensional state-linked closed-loop control method for carbon dioxide laser output, comprising the following steps:

[0050] S100, the main control unit 100 obtains the target output energy, pulse width and repetition frequency parameters set by the user through the human-machine interaction unit 500, and generates the initial laser drive command according to the power characteristic curve table in the memory;

[0051] S200, during the preprocessing time slot before laser light emission, the main control unit 100 reads the angle data of each angle encoder 302 in the light guide transmission unit 300, performs kinematic forward solution calculation based on the angle data, determines the incident angle deviation at each reflection joint 301, and calculates the minimum effective light transmission aperture under the current light guide arm posture.

[0052] S300, the main control unit 100 calls the thermal lensing effect model based on the user-defined average power parameters, calculates the predicted value of the beam radius at the position of the minimum effective aperture of the laser beam, and compares and verifies the predicted value of the beam radius with the minimum effective aperture.

[0053] S400 When the predicted beam radius is greater than or equal to the minimum effective aperture safety threshold, the main control unit 100 determines that it is in a restricted transmission state and executes a waveform reconstruction strategy. It calculates the corrected duty cycle and peak power, and reduces the duty cycle and increases the peak power while keeping the single pulse energy constant, until the predicted beam radius meets the safety threshold requirements.

[0054] S500, the main control unit 100 performs a physical limit check on the corrected peak power calculated in step S400. If the corrected peak power does not exceed the rated maximum power of the drive power supply 202, the drive power supply 202 is controlled to output according to the corrected parameters. If the corrected peak power exceeds the rated maximum power, the peak power is clamped to the rated maximum power, and the pulse width is limited according to the safety priority principle.

[0055] S600, when the predicted beam radius is less than the minimum effective aperture safety threshold, the main control unit 100 determines that it is in a safe transmission state, calculates the transmission loss coefficient based on the angle data, and performs linear compensation on the output power of the drive power supply 202.

[0056] S700 During the laser pulse output, the main control unit 100 obtains the impedance characteristics of the laser tube 201 in real time through the sampling circuit 203, calculates the deviation value between the real-time impedance and the reference impedance, and if the deviation value exceeds the preset range, the pulse width is truncated or extended for fine adjustment within the current pulse cycle.

[0057] The following provides a detailed description of each step of the method of the present invention.

[0058] In step S100, the main control unit 100 performs system initialization and control parameter mapping processing. This step converts user-level clinical treatment parameters into low-level hardware-level drive signals, establishing a deterministic relationship between energy commands and the physical output of the laser. Specifically, step S100 further includes the following steps:

[0059] S101, the main control unit 100 receives setting parameters from the human-machine interface unit 500 via a communication interface. The setting parameters include the target single-pulse energy. Pulse duration and pulse repetition frequency .

[0060] The main control unit 100 verifies the validity of the received settings, and the verification logic is based on a pre-stored database of the laser's safe operating range. This database pre-sets the physical limit thresholds of the laser tube 201, including the maximum permissible duty cycle. (Typically, this value is between 40% and 60%, depending on the heat dissipation structure of the laser tube) and minimum excitation pulse width. (Depending on the ignition time of gas ionization, it is typically 5 μs to 10 μs).

[0061] If the duty cycle or pulse width calculated from the set parameters exceeds the aforementioned physical limit threshold, the main control unit 100 will truncate the parameters to the maximum safe value or send a parameter error flag to the human-machine interaction unit 500. The specific protocol implementation and data packet parsing methods of the communication interface are well-known to those skilled in the art and will not be elaborated upon here.

[0062] S102, the main control unit 100 calculates the theoretically required peak power based on the verified setting parameters. Since the output energy of a carbon dioxide laser in pulsed operation mode is mainly determined by the integral of the peak power and duration within the pulse, under the ideal rectangular wave approximation, the theoretical peak power... The calculation satisfies the following relationship:

[0063] ;

[0064] in, The target single-pulse energy set by the user, in joules (J). The pulse duration set by the user, in seconds (s); The theoretical peak power required to meet energy targets, measured in watts (W). These are only theoretical calculations and do not yet include the effects of photoelectric conversion efficiency and heat loss. They need to be corrected through subsequent mapping steps.

[0065] S103, the main control unit 100 calculates the theoretical peak power. The laser power characteristic curve table is retrieved from the memory to determine the corresponding drive control quantity.

[0066] Carbon dioxide laser tubes exhibit typical nonlinear photoelectric response characteristics, including a ignition threshold voltage and a power saturation region. Directly calculating the driving voltage using linear formulas can lead to no light emission in the low-power range or excessive energy deviation in the high-power range. Therefore, this embodiment employs a lookup table (LUT) technique to linearize this nonlinear characteristic.

[0067] This lookup table is constructed based on the factory calibration data of the laser emitting unit 200 or the data from the last self-calibration. During calibration, the system scans the drive range in fixed steps (e.g., 1% duty cycle or 0.1V voltage) and records the optical output power measured by a power meter, thereby generating N sets of data pairs. The mapping table. Among them... Indicates the first Each quantization level represents a drive command value (corresponding to the digital value of the PWM duty cycle or current setting voltage). Indicates the value of the driving instruction The measured laser output power under the action, The index value ranges from 1 to N. The value of N is usually between 100 and 1024 to balance storage space and lookup accuracy; in this embodiment, N is preferably 256.

[0068] The main control unit 100 searches the lookup table for a match. The adjacent data nodes of the condition are used, and a linear interpolation algorithm is employed to calculate the accurate initial drive command value. The calculation formula is as follows:

[0069] ;

[0070] in, The calculated initial drive instruction value; and These are the values ​​of two adjacent driver instruction nodes in the lookup table; and Corresponding to and The power rating.

[0071] Through the above interpolation calculation, the main control unit 100 can eliminate the influence of the nonlinear gain characteristics of the laser tube 201 on the output accuracy, ensuring that the set energy value is accurately responded to at the physical output end. The drive command value here is specifically reflected in the duty cycle value of the pulse width modulation (PWM) signal controlling the laser drive power supply 202, and the digital-to-analog converter (DAC) voltage value controlling the current amplitude.

[0072] S104, the main control unit 100 will calculate the initial drive command value The signals are converted into specific electrical control words and written into the microprocessor's PWM compare register and DAC output data register, respectively, to generate the initial laser drive instruction. This initial laser drive instruction is in a pending state, waiting for the optical path state verification results in subsequent steps to determine whether to output directly or enter the waveform reconstruction process.

[0073] See attached document Figure 3In step S200, the main control unit 100 performs kinematic attitude calculation and geometric bottleneck extraction of the light guide transmission unit 300. The light guide transmission unit 300 typically employs a cantilever structure with multiple joints connected in series. Under gravity, its distal joints undergo elastic deformation, causing the optical path center to deviate from the mechanical aperture center. Furthermore, assembly errors during joint rotation accumulate, preventing the light beam from consistently propagating along the mechanical axis center during transmission. This step calculates the actual light beam's transmission capacity at each joint by establishing a kinematic model and an error compensation model. Specifically, step S200 further includes the following steps:

[0074] S201, the main control unit 100 synchronously reads the values ​​from the angle encoders 302 installed at each joint of the light guide transmission unit 300 via a serial bus. The angle encoders 302 are absolute encoders, preferably with a resolution of 16 to 20 bits, corresponding to an angular resolution of 0.005 degrees to 0.0003 degrees, to meet the requirements of precise optical path tracking. The main control unit 100 collects the rotation angle data of each joint. ,in This represents the number of degrees of freedom of the light guide arm, typically taken as 7. Indicates the first The rotation angle of each joint relative to the previous stage link.

[0075] S202, the main control unit 100 is based on the collected angle data. Using the pre-stored link geometry parameters, a kinematic model is established using the improved Denavit-Hartenberg (DH) parameter method. Forward kinematics calculations are performed to determine the spatial position and attitude matrix of each reflective joint 301 in the base coordinate system. For the first... Transformation matrix of each joint Its calculation follows the general homogeneous transformation formula:

[0076] ;

[0077] in, For joint variables; The link twist angle; The length of the link; This refers to the link offset. The above parameters... , and All of these are known constants determined by the mechanical design drawings of the light guide arm and are stored in the system's non-volatile memory.

[0078] Through multiplication The main control unit 100 obtained the first The spatial coordinate vector of the center of each mirror and normal vector .

[0079] S203, the main control unit 100 calculates the actual incident angle of the laser beam on each reflector based on the spatial orientation of each reflector, and determines the deviation of the incident angle. Due to machining tolerances and bearing clearances, the normal of the reflector often cannot be kept on the ideal angle bisector.

[0080] The main control unit 100 first calculates the... Beam direction vector within the connecting rod Subsequently, the beam vector was calculated using the dot product formula. With the Normal vectors of the reflectors The angle between :

[0081] ;

[0082] Then calculate the incident angle deviation. :

[0083] ;

[0084] in, The preset ideal angle of incidence (45 degrees). When As the size increases, the projection of the circular light spot onto the mirror surface will be elongated into an ellipse, resulting in a reduction in the effective reflective area.

[0085] S204, Main control unit 100 based on incident angle deviation Given the physical aperture of each joint, calculate the minimum effective aperture in the current posture. The effective aperture refers to the maximum theoretical radius that allows the light beam to pass through without loss, after deducting the beam center offset and projection distortion.

[0086] For the Each joint has a local effective light-transmitting aperture. The calculation formula is as follows:

[0087] ;

[0088] in, For the first The physical and mechanical aperture radius of each joint is typically taken as 8mm to 12mm. For projection correction items; This represents the lateral offset caused by gravity and tolerances.

[0089] Since the gravitational sag of the light guide arm has a non-linear relationship with its horizontal extension length, this embodiment uses a quadratic polynomial fitting model to calculate this offset:

[0090] ;

[0091] in, For the first The horizontal projection distance of each joint relative to the base is determined by the coordinate vector in step S202. Calculation yields ( ); Static assembly error constant (unit: mm); It is the linear deformation coefficient; This is the second-order bending moment coefficient. , , This value was obtained by performing a full-stroke scan calibration of the light guide arm using a position-sensitive detector during the manufacturing process. The typical value range is: ∈[0.1,0.5], ∈[10 -4 10 -3 ], ∈[10 -6 10 -5 ].

[0092] The main control unit 100 iterates through the local effective light-transmitting apertures of all joints, and extracts the minimum value in the entire optical path by comparison, which is taken as the minimum effective light-transmitting aperture of the system. .

[0093] Should The value represents the geometric boundary that restricts beam transmission in the optical path under the current orientation of the light guide arm. This value will be passed as a key parameter to the subsequent thermal lensing effect verification step. The specific calibration method of the DH parameter and the basic mathematical principles of matrix operations are well-known techniques in the field of robot kinematics, and will not be elaborated here.

[0094] See attached document Figure 4 In step S300, the main control unit 100 calls the thermal lensing effect model based on the user-defined average power parameters to calculate the predicted beam radius at the position of the minimum effective aperture, and compares and verifies the predicted beam radius with the minimum effective aperture. This step aims to establish a quantitative correlation between laser thermal load and beam transmission quality, predict the degree of beam divergence angle degradation under high-power operation, and thus prevent the beam edge from bombarding the inner wall of the light guide arm, causing overheating or damage. In specific implementation, step S300 further includes the following steps:

[0095] S301, the main control unit 100 calculates the average thermal load power under the current operating condition based on the setting parameters obtained in step S100. Although the laser operates in a pulsed manner, the thermal lensing effect is a thermal effect generated by the accumulation of thermal relaxation time of the laser gain medium (such as carbon dioxide gas). Its response speed is much slower than the single-pulse time scale, so it mainly depends on the average power rather than the peak power.

[0096] The main control unit 100 calculates the average power using the following formula. :

[0097] ;

[0098] in, The energy is a single pulse (J). The repetition frequency (Hz). This average power. It will be used as an input variable for the thermal lensing effect model.

[0099] S302, the main control unit 100 calls the preset thermal lensing effect model to calculate the beam quality factor M under the current thermal load. 2 During stimulated emission (SEE) in a carbon dioxide laser tube, the gas temperature at the center of the discharge region is higher than that at the edges, resulting in a radial gradient distribution of gas density and refractive index. This refractive index gradient is optically equivalent to a diverging lens (negative lens), increasing the far-field divergence angle of the laser beam. As the injected power increases, this lensing effect intensifies, leading to an increase in the beam quality factor M. 2 The numerical value increases (i.e., the beam quality deteriorates).

[0100] This embodiment uses a linear regression model to characterize this power dependence:

[0101] ;

[0102] in, This is the inherent beam quality factor of the laser in the cold state or at low power (reference state). For radio frequency excited diffuse-cooled carbon dioxide lasers, its typical value ranges from 1.1 to 1.2. This is the thermal degradation coefficient, in W. -1 .parameter and The system constants are obtained by fitting measured data from a laser beam analyzer at different power levels (e.g., from 10W to maximum power, in 10W increments) during the system's factory calibration phase, and are stored in the controller's non-volatile memory area. The typical value range is 0.002 to 0.01W. -1 It depends on the heat dissipation structure design of the laser tube.

[0103] Using this model, the main control unit 100 can obtain the corrected dynamic beam quality factor. .

[0104] S303, the main control unit 100 calculates the optical path length of the laser beam from the laser output window to the joint position where the minimum effective aperture is determined in step S200, and predicts the beam radius at that position based on the Gaussian beam propagation theory.

[0105] First, the main control unit 100, based on the kinematic calculation results in step S200, accumulates the values ​​from the root of the light guide arm to the... The transmission distance is obtained by calculating the lengths of each link segment in each joint (i.e., the joint identified as the bottleneck). :

[0106] ;

[0107] in, The fixed optical path from the laser tube outlet to the light guide arm inlet is determined by the mechanical structure design drawings; For the light guide arm The geometric length of the connecting rod segment.

[0108] Subsequently, using M 2 The modified Gaussian beam propagation equation calculates the transmission distance as follows: Predicted beam radius at location :

[0109] ;

[0110] in, The laser beam waist radius refers to the spot radius (1 / e) at the laser output coupler or at the beam waist position after beam expansion. 2 (At the intensity point), where the system constants are known; The wavelength is 10.6 μm in this embodiment; Pi is the mathematical constant. This formula shows that, under far-field propagation conditions, the beam radius... With transmission distance and beam quality factor M 2 They are approximately linearly positively correlated.

[0111] S304, the main control unit 100 constructs safety verification logic, and calculates the beam radius prediction value. The minimum effective aperture calculated in step S200 Compare them.

[0112] To ensure that laser energy is concentrated in the center of the light guide channel without heating the mechanical structure, a safety margin must be reserved. The main control unit 100 defines the minimum effective aperture safety threshold. :

[0113] ;

[0114] in, This is a safety factor. The value of this factor is determined based on the energy distribution characteristics of the Gaussian beam. Because the Gaussian beam has a radius... The energy density at that point drops to 1 / e of the peak value. 2 (Approximately 13.5%), while within a radius of 1.5 The energy density has dropped to approximately 1.1%. To cut off over 99% of the energy and avoid diffraction ring effects and internal wall temperature rise, The preferred value range is 1.5 to 2.0.

[0115] The main control unit 100 performs the following logical judgment:

[0116] like If the current state is determined to be a restricted transmission state, it means that under the current power and light guide arm posture, there is a risk that the edge of the beam will touch the inner wall of the machine, and the system will enter step S400 to perform waveform reconstruction.

[0117] like If the current state is determined to be a safe transmission state, it indicates that the optical path is unobstructed, and the system enters step S600 to perform conventional linear compensation.

[0118] See attached document Figure 5 In step S400, the main control unit 100 performs equal-energy waveform reconstruction under the restricted transmission state. When step S300 determines that the beam is in a "restricted transmission state," it indicates that the current average heat load has caused excessive thermal lensing, causing the beam divergence angle to exceed the tolerance range of the guide arm's geometric bottleneck. This step, based on the principle of laser energy conservation and the thermal relaxation characteristics of gas, reduces heat accumulation in the laser gain medium while maintaining constant single-pulse energy by adjusting the duty cycle and peak power of the laser driving signal, thereby suppressing the thermal lensing effect. In specific implementation, step S400 further includes the following steps:

[0119] S401, the main control unit 100, based on the minimum effective light transmission aperture determined in step S200, Inversely derive the maximum allowable beam quality factor at the current transmission distance. .

[0120] To ensure the beam can pass through the joint identified as a bottleneck without damage, the physical radius of the beam at that location... It must be less than the safety threshold determined in step S300. .

[0121] The main control unit 100 calculates the upper limit of beam quality degradation that the system can tolerate based on the inverse operation of the Gaussian beam propagation equation. :

[0122] ;

[0123] in, This is a safety threshold; The waist radius; For transmission distance; Where λ is the laser wavelength. This formula defines the critical boundary value of the beam quality factor under the current geometric constraints. If the actual beam quality factor is lower than this value, the beam can safely pass through.

[0124] S402, the main control unit 100, based on the maximum permissible beam quality factor... By combining a thermal lensing effect model that includes duty cycle correction, the maximum allowable pulse duration is calculated. .

[0125] For radio frequency excited diffuse-cooled carbon dioxide lasers, the intensity of the thermal lensing effect depends not only on the average power but also closely on the pulse duty cycle. A wider pulse leads to a higher temperature rise in the discharge region gas within a single cycle and a shorter cooling time, thus exacerbating the formation of the radial refractive index gradient. Therefore, by compressing the pulse width (i.e., reducing the duty cycle) and utilizing the gas's thermal relaxation time for cooling, beam quality can be effectively improved. The modified thermal lensing model is expressed as:

[0126] ;

[0127] Will and Substituting into the above formula, we obtain information about the pulse width. Functional relationship:

[0128] ;

[0129] in, Average power thermal distortion coefficient (unit: W) -1 ), This is the duty cycle thermal distortion coefficient (dimensionless). and These are inherent parameters of the system, with a typical value range of [value range missing]. ∈[0.002,0.005], ∈[0.1,0.5].

[0130] The main control unit 100 calculates to satisfy Maximum allowable pulse width under conditions :

[0131] ;

[0132] If the calculation result Smaller than the minimum physical ignition pulse width of the laser If the waveform reconstruction alone fails to meet the transmission requirements (usually 5μs), the system will automatically switch to frequency reduction protection logic.

[0133] S403, the main control unit 100 calculates the pulse width compression to the principle of equal energy reconfiguration. Peak power required for reconstruction .

[0134] To ensure that the interaction effects between the laser and biological tissue (such as ablation depth and thermal damage range) remain unchanged, the single-pulse energy must be guaranteed. It remains constant before and after the reconstruction.

[0135] According to the energy integral formula New peak power The calculation is as follows:

[0136] ;

[0137] This step, by shortening the pulse duration and simultaneously increasing the instantaneous power density, achieves the goal of maintaining therapeutic energy output while reducing the thermal lensing effect.

[0138] S404, main control unit 100 pairs of reconfiguration peak power Perform hardware capability boundary verification and generate the final driver instructions.

[0139] The main control unit 100 reads the preset maximum peak power threshold of the laser from the memory. This threshold is determined by the rated current capacity of the laser power supply and the saturation characteristics of the RF power amplifier.

[0140] like The waveform reconstruction scheme was deemed feasible. The main control unit 100 then applied the new pulse width... and new peak power The signals are converted into corresponding PWM control signals and RF power supply voltage adjustment signals to update the laser emission parameters.

[0141] like The system determines that the required peak power exceeds the hardware limit. At this point, the main control unit 100 clamps the peak power to... And set the pulse width according to the principle of constant energy. Because the pulse width at this time Greater than the ideal pulse width This prevents the beam quality factor from being reduced to a certain level. The main control unit 100 will then automatically reduce the repetition frequency. The thermal lensing effect is further suppressed by reducing the total heat input per unit time until the safe transmission conditions are met.

[0142] For the specific circuit implementation of PWM signal generation and RF power supply voltage regulation, those skilled in the art can refer to existing laser drive control technology for implementation, and will not be elaborated here.

[0143] See attached document Figure 6 In step S500, the main control unit 100 performs adaptive boundary control under physical power limits. This step aims to address the problem that the theoretical reconstruction parameters calculated in step S400 may exceed the physical limits of the laser hardware. By establishing a judgment logic for the saturated and unsaturated regions, the system automatically switches to a "power clamping-frequency compensation" control mode when the hardware capability reaches saturation, ensuring that the device operates within safe physical boundaries under any operating condition. In specific implementation, step S500 further includes the following steps:

[0144] S501, the main control unit 100 reads the hardware status parameters of the laser driver power supply and determines the physical saturation power threshold under the current environment. The physical saturation power threshold refers to the maximum instantaneous power that a laser can output without glow discharge instability, damage to the RF amplifier, or gain saturation. DC bus voltage and the current temperature of the laser tube These are jointly determined dynamic variables. Since the output power of the RF power supply decreases as the supply voltage drops, and the quantum efficiency of the laser gain medium decreases as temperature increases, the main control unit 100 needs to correct the rated power in real time. The main control unit 100 obtains this value through a lookup table or a pre-stored polynomial function.

[0145] ;

[0146] in, Rated peak power; Rated voltage; For reference temperature; and These are the derating factors for voltage and temperature, respectively. The value range is typically from 0.01 to 0.05V. -1 , The value range is typically from 0.005 to 0.02℃. -1 These two coefficients were determined during the product development phase by testing the slope of the curve showing the change in laser output power with voltage and temperature under constant temperature and humidity conditions and a programmable power supply.

[0147] Through real-time calculation The system can prevent hardware damage caused by forced overclocking output when the power grid fluctuates or the heat dissipation is poor.

[0148] S502, the main control unit 100 reconstructs the theoretical peak power calculated in step S400. With physical saturation power threshold The comparison is performed, and the system operating state is divided into "non-saturated modulation region" and "saturated clamping region" based on the comparison results.

[0149] like The system is determined to be in the non-saturated modulation region. At this point, the hardware has sufficient margin to execute the waveform reconstruction planned in step S400. The main control unit 100 directly locks the output parameters: ultimately executing the peak power... Final execution pulse width Ultimately, the execution frequency remains unchanged as set by the user.

[0150] S503, if The system is determined to be in the saturation clamping region. This means that in order to meet the geometric passability requirements (i.e., to obtain a sufficiently small beam radius), the instantaneous power required according to step S400 exceeds the hardware supply capacity. At this point, the system cannot meet the beam quality requirements by simply compressing the pulse width. The main control unit 100 executes a power clamping strategy, forcibly limiting the final peak power to the physical limit:

[0151] ;

[0152] Based on the principle of constant energy of a single pulse ( To ensure the treatment dose remains unchanged, the main control unit 100 must extend the pulse duration. The limited pulse width at clamping power must be recalculated. :

[0153] ;

[0154] because This will inevitably lead to According to the thermal lensing model in step S400, increasing the pulse width will lead to increased thermal distortion within a single pulse, resulting in a decrease in the beam quality factor M. 2 Exceeding the allowed limit again .

[0155] S504, the main control unit 100 performs frequency compensation calculations in the saturation clamping region. When the thermal effect within a single pulse (determined by the pulse width) is limited by hardware power and cannot be further reduced, the system instead reduces the pulse repetition frequency. This reduces the total heat input per unit time, thereby reducing the contribution of average power to the thermal lensing effect.

[0156] The main control unit 100 is based on the thermal lens model containing frequency variables established in step S400, and... Given the target value, solve for the corrected repetition frequency. .

[0157] Will and target Substituting into the aforementioned thermal lens model, solve... :

[0158] ;

[0159] in, The maximum allowable beam quality calculated in step S401; As a reference beam quality; The average power thermal distortion coefficient; This is the duty cycle thermal distortion coefficient. This formula shows that, within the pulse width... When locked, reduce the frequency This can linearly reduce the beam quality factor. This will bring it back to the safe threshold. Within.

[0160] S505, the main control unit 100 calculates the correction frequency. Perform minimum effective truncation verification. Since laser scanning treatment typically requires a high overlap of the laser spot on the tissue, excessively low repetition frequencies can lead to discontinuities in the scanning pattern, affecting treatment uniformity or cutting smoothness. The system has a preset minimum operating frequency threshold. This threshold is determined by the motion speed of the scanning galvanometer. and spot diameter A decision usually needs to meet certain conditions. In this embodiment, it is set to 50Hz.

[0161] The main control unit 100 performs the following judgment:

[0162] like Then the final execution frequency will be set to and in accordance with , , Generate laser control commands.

[0163] like If the current operating condition is determined to be unable to maintain the minimum effective treatment under the premise of meeting safe transmission requirements, the main control unit 100 will trigger a "path blockage alarm", immediately stop laser output, and send a prompt message to the user interface that "the posture of the light guide arm is limited and cannot be compensated".

[0164] The parameter storage, comparison operations, and logical judgments involved in the above steps are all implemented by the microprocessor (MCU) or field-programmable gate array (FPGA) in the main control unit by executing the pre-compiled firmware program. Its hardware circuit structure is a well-known technology in the field of embedded control and will not be described in detail here.

[0165] See attached document Figure 7 In step S600, the main control unit 100 performs linear power compensation under safe transmission conditions. When step S300 determines that the beam is in a "safe transmission state," it indicates the current predicted beam radius value. Less than the safety threshold This means that there is no thermal risk of edge diffraction or inner wall bombardment during beam propagation within the beam guide arm. In this state, the beam quality factor M... 2 Within the system's permissible baseline range, there is no need to suppress the thermal lensing effect by compressing the pulse width. Therefore, this step employs a control strategy of fixed peak power and adjusted pulse width, compensating only for the inherent optical losses of the light guide system to ensure that the actual laser energy reaching the treatment target point matches the user-set preset energy. Consistent. In the specific implementation process, step S600 further includes the following steps:

[0166] S601, the main control unit 100 calculates the total optical transmission efficiency of the current transmission path based on the structural parameters of the light guide arm. .

[0167] When a laser beam is transmitted within a light guide arm, its energy loss mainly comes from two aspects: first, the reflection loss caused by absorption and scattering of the joint reflector; and second, the absorption attenuation of the laser during long-distance transmission in the air medium.

[0168] The main control unit 100 calculates the total transmission efficiency using the following formula:

[0169] ;

[0170] in, This refers to the reflectivity of a single mirror. For the gold-plated silicon mirror or dielectric copper mirror used in this embodiment, this parameter is determined by the optical coating process, and is typically at a wavelength of 10.6 μm. ∈[0.985,0.995]. N is the total number of reflectors in the optical path. This number is determined by the degree of freedom configuration of the light guide arm. In the 7-joint light guide arm described in this embodiment, the light beam must pass through 7 reflective surfaces in sequence before it can be led out, so N=7. The air attenuation coefficient for laser light (unit: m) -1 This coefficient is affected by ambient humidity and carbon dioxide concentration, and its typical value range is 1×10⁻⁶. -4 Up to 3×10 -4 m -1 . The current total optical path length is calculated in step S303.

[0171] S602, the main control unit 100 calculates the compensated target output energy according to the principle of energy conservation. .

[0172] To compensate for energy loss during transmission, the energy at the laser output port (i.e., the coupling point before entering the light guide arm) must be higher than the target energy set by the user. The main control unit 100 performs the following calculations:

[0173] ;

[0174] A linear scalar compensation strategy is used here. Unlike the waveform reconstruction in step S400, since we are currently in a safe transmission state, the system assumes that the slight increase in thermal lensing effect brought about by the increased pulse energy is insufficient to affect the beam radius. Touching the safety threshold Therefore, there is no need to limit the peak power; only the total energy needs to be corrected.

[0175] S603, the main control unit 100 will compensate the target output energy Converted into specific pulse width control parameters.

[0176] In the PWM control mode of an RF-excited carbon dioxide laser, when the peak power of the drive signal... When kept constant, the single-pulse energy is linearly proportional to the pulse width. The main control unit 100 calculates the compensated pulse width. :

[0177] ;

[0178] in, This is the system's preset reference peak power. The system defaults to this value when the S400 waveform reconstruction logic is not triggered. This is equal to the laser's rated optimal operating power (typically 80%–90% of maximum power) to ensure output mode stability. This step compensates for losses along the transmission path by generating more photons through extended laser pumping time.

[0179] S604, main control unit 100 pairs of compensated pulse widths Perform a maximum duty cycle safety check.

[0180] Although the optical path is currently in a safe state, it is necessary to prevent overcompensation from causing the duty cycle to exceed the linear operating range or thermal load limit of the RF power supply. The main control unit 100 calculates the current compensation duty cycle. :

[0181] ;

[0182] like Then the main control unit 100 directly uses The final execution pulse width is used to generate the PWM drive signal. Among them, The maximum allowable duty cycle threshold for the laser is determined by the heat dissipation capability of the RF power amplifier and the switching characteristics of the MOSFET, with a typical value of 40% to 50%.

[0183] like This indicates that the required compensation energy is too large, exceeding the linear operating range of the hardware. At this point, the main control unit 100 clamps the pulse width to... At this point, the system sacrifices some energy compensation accuracy to prioritize equipment safety and simultaneously records a "low optical transmission efficiency" status code in the system log, prompting maintenance personnel to check for contamination or oxidation of the light guide arm lenses.

[0184] For the specific connection methods of the PWM signal generator and laser driver circuit, those skilled in the art can refer to the relevant circuit design manuals for implementation, and will not be elaborated here.

[0185] See attached document Figure 8 In step S700, the main control unit 100 performs real-time feedback fine-tuning based on gas impedance characteristics. This step aims to address the deviation between the actual output energy and the theoretically calculated value caused by gas aging, accumulated thermal lensing effects, or power supply fluctuations during actual laser operation. The core load of an RF-excited carbon dioxide laser is a mixed gas (typically CO2:N2:He) filling the discharge tube. The equivalent impedance of this mixed gas dynamically changes with the discharge state, gas temperature, and degree of aging. Since the impedance matching network of the RF power supply is usually a fixed-parameter network designed for a specific impedance value, impedance mismatch occurs when the load impedance drifts, causing some RF energy to be reflected back to the power supply, thereby reducing the pump power of the actual injected gas.

[0186] The system utilizes high-speed sampling data within a single pulse cycle to calculate the instantaneous gas impedance deviation and dynamically corrects the pulse width before the current pulse ends. In specific implementation, step S700 further includes the following steps:

[0187] S701, the main control unit 100 performs synchronous sampling of voltage and current during the ignition stage of laser pulse excitation.

[0188] After the main control unit 100 sends a PWM start-up signal, the system enters the sampling window period. Because the RF power supply experiences transient oscillations at the start-up moment, and the establishment of glow discharge through gas breakdown requires a certain time (typically 1μs to 3μs), in order to obtain impedance data that accurately reflects the plasma state, the sampling time... Set between 2μs and 5μs after the rising edge of the PWM signal.

[0189] The voltage transformer and Hall current sensor located in the output stage of the RF power amplifier respectively acquire the instantaneous value of the RF voltage. and instantaneous value of radio frequency current To satisfy the Nyquist sampling theorem and ensure measurement accuracy, the sampling frequency is set to at least 2.5 times the RF carrier frequency, or a detector circuit is used to extract the envelope and then perform low-frequency sampling.

[0190] S702, the main control unit 100 calculates the real-time gas impedance under the current operating conditions. and with the pre-stored reference impedance By comparing the results, the impedance deviation rate can be obtained. .

[0191] The main control unit 100 first calculates the equivalent load impedance magnitude based on the sampled values:

[0192] ;

[0193] Subsequently, the main control unit 100 retrieves the "Power-Impedance Characteristic Curve Table" from the memory. This curve table was obtained during the product's factory calibration phase through tests using a standard dummy load and a power meter. The table records the power output at different setpoints under standard gas pressure and temperature. The corresponding optimal matching impedance value The gas discharge of carbon dioxide lasers exhibits typical negative impedance characteristics, meaning that as the injected power increases, the gas ionization degree and electron density increase, leading to a nonlinear decreasing trend in the equivalent impedance.

[0194] Impedance deviation rate The calculation is as follows:

[0195] ;

[0196] like This indicates that the gas impedance is too high, which physically corresponds to insufficient discharge current or excessively high gas temperature leading to a shortened mean free path of electrons; if This indicates that the gas impedance is too low, which physically corresponds to overcurrent or a tendency for local arc discharge.

[0197] S703, Main Control Unit 100 based on impedance deviation rate The predicted deviation coefficient of the actual output power is calculated using the impedance-efficiency coupling model. .

[0198] When the load impedance Offset from the center frequency impedance of the matching network At this time, reflected waves will be generated on the radio frequency transmission line, causing the voltage standing wave ratio to increase, and the actual effective power coupled into the laser tube will decrease. The power loss will be less than the output power of the power supply. The main control unit 100 uses the following linearization model to estimate this power loss:

[0199] ;

[0200] in, This is the impedance-power coupling coefficient (dimensionless). This coefficient reflects the sensitivity of the RF matching network to impedance mismatch and is mainly determined by the quality factor (Q value) of the matching network. In this embodiment, through experimental determination, when the impedance deviation is within ±20%, The value ranges from 0.5 to 0.8. This formula shows that regardless of whether the impedance is too large or too small, any mismatch will lead to a decrease in the actual coupling efficiency. Less than 1.

[0201] S704, the main control unit 100 calculates the deviation coefficient. It corrects the remaining pulse width in real time within the current pulse period.

[0202] To ensure single-pulse energy Strictly equal to the target value, the main control unit 100 needs to adjust the pulse duration to compensate for power loss. Let the original pulse width be... Corrected pulse width The calculation is as follows:

[0203] ;

[0204] This calculation process is executed by a Field Programmable Gate Array (FPGA) within the main control unit. The FPGA then processes the calculation results... The value of the compare register of the counter in the PWM generation module is dynamically modified, thereby delaying the falling edge of the currently output PWM signal and realizing real-time stretching of the pulse width.

[0205] S705, main control unit 100, corrected pulse width Perform a security boundary check.

[0206] To prevent damage to the RF amplifier caused by excessively large calculated pulse widths due to serious hardware issues such as sensor malfunctions or gas leaks, the system has a maximum permissible correction range. In this embodiment, Set to original pulse width 20%.

[0207] The main control unit 100 performs the following judgment:

[0208] like Then the modified pulse width will be executed. This enables closed-loop energy correction.

[0209] like If the laser is found to be in an abnormal state, the main control unit 100 will forcibly truncate the current pulse, stop the subsequent pulse delivery, and report a fault code of "laser cavity impedance mismatch".

[0210] Through the above steps, the system achieves closed-loop control within the pulse, effectively eliminating the impact of gas density changes caused by the thermal lensing effect on the stability of single-pulse energy. For the logic implementation of the voltage and current sampling circuit and the FPGA, those skilled in the art can refer to relevant embedded hardware design specifications; further details are omitted here.

[0211] To verify the effectiveness and technical advantages of the multi-dimensional state-linked closed-loop control system for carbon dioxide laser output proposed in this invention, a comparative experiment was conducted in a controlled laboratory environment. The experiment selected a traditional open-loop control method (setting only the power, without considering the beam guide arm attitude and thermal lensing effect) as a control group, and compared it with the multi-dimensional linkage closed-loop control method described in this invention.

[0212] 1) Energy stability test under long-term operation

[0213] The experimental conditions were set as follows: target single pulse energy 100mJ, repetition frequency 200Hz (average power 20W), and continuous light emission time 60 seconds. The sampling rate was set to 10Hz.

[0214] See attached document Figure 9 , Figure 9 This is a comparison chart of the single-pulse energy stability of the traditional control method and the control method of the present invention under continuous working conditions.

[0215] The horizontal axis in the graph represents the running time (seconds), and the vertical axis represents the percentage deviation (%) of the measured single-pulse energy from the set value.

[0216] The dashed line (curve A) represents the measured data of the traditional open-loop control method. It can be seen that as the running time increases, the energy exhibits a significant nonlinear decay trend due to impedance mismatch caused by heat accumulation inside the laser tube, accompanied by large random fluctuations (caused by gas discharge instability), with the energy dropping by more than 12% at the end of 60 seconds.

[0217] The solid line (curve B) represents the measured data using the control method of this invention. Thanks to the real-time feedback fine-tuning mechanism based on gas impedance characteristics in step S700, the system can sense impedance changes in real time and dynamically stretch the pulse width. Test data shows that although there is a small amount of physical quantization noise, the overall energy deviation remains stable within ±1.5%, and no thermal decay phenomenon occurs.

[0218] 2) Test on the impact of changes in the light guide transmission path on beam quality and safety

[0219] The experiment simulated the process of the light guide arm gradually extending from a folded state (short optical path) to its maximum working radius (long optical path) during clinical operation. A minimum effective aperture safety threshold was set. It is 3.5mm.

[0220] See attached document Figure 10 , Figure 10 This is a comparison chart showing the changing trend of the beam radius at the geometric bottleneck during the extension of the light guide arm.

[0221] The horizontal axis in the figure represents the optical path length (mm), and the vertical axis represents the measured value of the beam radius (mm).

[0222] The dashed line (curve C) represents the traditional control method. Because it doesn't consider the coupling effect of thermal lensing and transmission distance, the spot radius increases approximately linearly with increasing optical path length. When the optical path exceeds 1200mm, the measurement data points cross the safety threshold line (short black horizontal line), entering an uncontrollable area, posing a significant risk of bombardment of the inner wall.

[0223] The solid line (curve D) represents the control method of this invention. Under safe transmission conditions with short optical paths (0–1200 mm), its performance is consistent with traditional methods; when the main control unit predicts that the spot radius is close to... At approximately 1200mm, the waveform reconstruction strategy in step S400 is triggered. As shown in the figure, curve D exhibits a clear clamping characteristic in the latter half. Although there are slight ripples caused by the control algorithm adjustment, they are always limited below the safety threshold, ensuring the safety of the optical path throughout the entire journey.

[0224] In summary, by combining kinematic attitude calculation, thermal lensing effect model and real-time impedance feedback, this invention significantly solves the problems of energy thermal attenuation and overheating of the light guide arm in traditional carbon dioxide laser medical devices, and achieves accurate and safe output under all working conditions.

[0225] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A closed-loop control method for carbon dioxide laser output with multi-dimensional state linkage, characterized in that, Includes the following steps: Acquire target output parameters containing the target single-pulse energy and real-time attitude data of the light guiding system; Based on the attitude data, the geometric transmission constraint parameters are determined, and combined with the target output parameters and thermal effect mapping relationship, the predicted beam characteristics of the laser beam transmitted to the position of the constraint parameters are calculated. The predicted beam characteristics are compared with a safety threshold: If the safety threshold is not met, the first strategy is executed: while keeping the target single pulse energy constant, the combination of peak power and duty cycle of the laser driving signal is adjusted to improve beam characteristics; The execution of the first strategy specifically includes: Based on the aforementioned safety threshold and the current optical transmission distance, the maximum allowable beam quality factor under the current geometric constraints is derived in reverse. Based on the maximum allowable beam quality factor, the maximum allowable pulse duration is solved using a thermal lensing effect model that includes duty cycle and average power variables; Based on the principle of energy conservation, the target single pulse energy is divided by the maximum allowable pulse duration to calculate the corrected peak power and generate a driving signal. If the safety threshold is met, the second strategy is executed: energy compensation is performed on the laser driving signal based on the transmission loss corresponding to the attitude data; The execution of the second strategy specifically includes: The total number of mirrors through which the light beam passes and the total optical path length are determined based on the attitude data. The total optical transmission efficiency is calculated by combining the preset single-mirror reflectivity and air medium attenuation coefficient. The compensated target energy is obtained by dividing the target single-pulse energy by the total optical transmission efficiency. While maintaining the peak power as a reference value, the compensation pulse width corresponding to the compensation target energy is calculated, and the maximum duty cycle of the compensation pulse width is checked.

2. The multi-dimensional state-linked closed-loop control method for carbon dioxide laser output according to claim 1, characterized in that, The geometric transmission limiting parameter is the minimum effective light-transmitting aperture; the steps for determining the geometric transmission limiting parameter specifically include: Based on the attitude data, forward kinematics calculations are performed to determine the incident angle deviation of the light beam at each reflection node of the light guide system. Calculate the projection distortion correction factor based on the incident angle deviation. Based on the horizontal projection distance of each reflection node relative to the base, the lateral offset caused by gravity is calculated using a polynomial fitting model. By combining the projection distortion correction factor, lateral offset, and physical aperture, the local effective aperture of each reflection node is calculated, and the minimum value among them is determined as the minimum effective light-transmitting aperture.

3. The multi-dimensional state-linked closed-loop control method for carbon dioxide laser output according to claim 1, characterized in that, The predicted beam characteristic is the beam radius; the steps for calculating the predicted beam characteristic specifically include: Calculate the average power based on the target single-pulse energy and repetition frequency in the target output parameters; The preset thermal lensing effect model is invoked, which contains a linear regression function with average power as the independent variable, to calculate the dynamic beam quality factor. The optical transmission distance is obtained by summing the lengths of each link segment based on the attitude data. Based on the Gaussian beam propagation equation, the beam radius at the specified location is calculated using the dynamic beam quality factor, laser wavelength, beam waist radius, and optical transmission distance.

4. The multi-dimensional state-linked closed-loop control method for carbon dioxide laser output according to claim 1, characterized in that, The security threshold is set based on the geometric transmission limitation parameters; the method further includes a security threshold setting step: Obtain the value of the geometric transmission restriction parameter; The value is scaled by a preset safety factor, which ranges from 1.5 to 2.0, to ensure that the energy density at the beam edge is lower than a predetermined value. The scaled value is used as the security threshold.

5. The multi-dimensional state-linked closed-loop control method for carbon dioxide laser output according to claim 1, characterized in that, The execution of the first strategy also includes an adaptive adjustment step based on physical boundaries: The current physical saturation power threshold of the laser driver source is obtained, which is dynamically corrected based on the real-time collected DC bus voltage and laser tube temperature. If the corrected peak power is greater than the physical saturation power threshold, the following operation is performed: The peak power is clamped to the physical saturation power threshold. The duration of the restricted pulse is calculated based on the physical saturation power threshold and the target single pulse energy. Based on the restricted pulse duration and the maximum allowable beam quality factor, the repetition frequency of the laser output is recalculated and reduced to suppress the thermal lensing effect by reducing the total heat input.

6. The multi-dimensional state-linked closed-loop control method for carbon dioxide laser output according to claim 1, characterized in that, After obtaining the target output parameters, the process also includes a nonlinear linearization step: The theoretical peak power is calculated based on the target single pulse energy and the preset pulse duration; Retrieve a pre-stored laser power characteristic curve table, which contains multiple sets of mapping relationships between drive command values ​​and measured power values; Find two nodes adjacent to the theoretical peak power and use a linear interpolation algorithm to calculate the initial drive command value to eliminate the influence of the laser's nonlinear gain.

7. The multi-dimensional state-linked closed-loop control method for carbon dioxide laser output according to claim 1, characterized in that, The method also includes a real-time fine-tuning step based on impedance feedback: During the ignition and stabilization phase of the laser output pulse, radio frequency voltage and radio frequency current signals are acquired simultaneously. Calculate the real-time load impedance and its deviation rate from the optimal matching impedance; The actual power loss is estimated based on the deviation rate and the preset coupling coefficient; Before the current pulse ends, the pulse width is extended according to the actual power loss to compensate for the energy loss caused by impedance mismatch.

8. A multi-dimensional state-linked closed-loop control system for carbon dioxide laser output, used to execute the multi-dimensional state-linked closed-loop control method for carbon dioxide laser output as described in any one of claims 1-7, characterized in that, The system includes a main control unit, a laser emission unit, a light guide transmission unit, a cooling circulation unit, and a human-machine interaction unit; The human-computer interaction unit is connected to the main control unit and is used to receive target output parameters input by the user. The target output parameters include at least the target single pulse energy. The light guiding transmission unit is composed of multiple hollow reflective joints connected in series, and an angle encoder is integrated at the rotation axis of the reflective joint; the angle encoder is used to measure the relative rotation angle of the reflective joint in real time and send it to the main control unit as the attitude data of the light guiding system. The laser emitting unit includes a laser tube and a driving power supply; the input terminal of the driving power supply is connected to the main control unit, and the output terminal is connected to the laser tube; the driving power supply applies excitation to the laser tube according to the driving control signal sent by the main control unit. The main control unit includes a processor and a memory. The main control unit establishes communication connections with the laser emitting unit and the light guiding transmission unit via a data bus. The processor is configured to perform the following operations to generate the drive control signal: Based on the attitude data, the geometric transmission constraint parameters are determined, and combined with the target output parameters and thermal effect mapping relationship, the predicted beam characteristics of the laser beam transmitted to the position of the constraint parameters are calculated. The predicted beam characteristics are compared with a safety threshold; If the safety threshold is not met, the first strategy is executed: while keeping the target single pulse energy constant, the combination of peak power and duty cycle of the drive control signal sent to the drive power supply is adjusted to improve beam characteristics; The execution of the first strategy specifically includes: Based on the aforementioned safety threshold and the current optical transmission distance, the maximum allowable beam quality factor under the current geometric constraints is derived in reverse. Based on the maximum allowable beam quality factor, the maximum allowable pulse duration is solved using a thermal lensing effect model that includes duty cycle and average power variables; Based on the principle of energy conservation, the target single pulse energy is divided by the maximum allowable pulse duration to calculate the corrected peak power and generate a driving signal. If the safety threshold is met, the second strategy is executed: based on the transmission loss corresponding to the attitude data, energy compensation is performed on the drive control signal sent to the drive power supply; The execution of the second strategy specifically includes: The total number of mirrors through which the light beam passes and the total optical path length are determined based on the attitude data. The total optical transmission efficiency is calculated by combining the preset single-mirror reflectivity and air medium attenuation coefficient. The compensated target energy is obtained by dividing the target single-pulse energy by the total optical transmission efficiency. While maintaining the peak power as a reference value, the compensation pulse width corresponding to the compensation target energy is calculated, and the maximum duty cycle of the compensation pulse width is checked.

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