Optical focusing system driven by a stepper motor

Abstract

The application discloses a stepping motor driven optical focusing system and relates to the technical field of multi-axis synchronous motion control systems.The system comprises a driving parameter pre-configuration module, an adaptive tolerance management module and a synchronous closed-loop control module, two stepping motors are set with chopping currents based on a focusing distance, a maximum allowable speed and a load dynamic, and synchronous focusing is performed, the current flowing into the motor winding is accurately controlled based on the chopping current, it is ensured that the peak value always does not exceed the chopping current, the current tolerance threshold in the focusing process is dynamically corrected based on the running state parameters, the output state of the stepping motor in the focusing process is dynamically adjusted based on the winding current of the two stepping motors and the corrected current tolerance threshold, the dynamic adjustment of the output state of the stepping motor comprises output torque adjustment of the stepping motor and motor speed adjustment of the stepping motor, high-precision closed-loop synchronous control of the double motor is realized, and the focusing efficiency of the system is significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of multi-axis synchronous motion control system, and particularly to an optical focusing system driven by a stepping motor. BACKGROUND

[0002] The optical focusing system widely adopts a stepping motor as a driving source, and its core principle is to convert a received digital pulse signal into an accurate angular displacement or linear displacement by the motor, and then control a lens group or an imaging target surface to move with micron-level or even nanometer-level precision through a transmission mechanism (such as a ball screw). This driving mode realizes digital and automatic control of the focal length, has the advantages of accurate positioning, no cumulative error, fast response speed, and easy integration with a computer system, and is widely used in optical systems such as microscopes, endoscopes, industrial cameras, optical communication equipment, and automatic driving laser radars that require high-precision and automatic focusing. The introduction of a closed-loop stepping motor system further improves the anti-interference ability and positioning reliability of the system.

[0003] In the prior art, optical focusing driven by a stepping motor is achieved through a precise electrically controlled mechanical system: a controller generates a pulse sequence, a driver converts it into a phase sequence current required by the motor, and the stepping motor is driven to rotate accurately by a preset angle; the rotational movement of the motor is transmitted to a ball screw or a precision screw thread transmission mechanism through a shaft coupling, and is converted into linear motion; the linear displacement directly or through a flexible mechanism pushes a lens group or an image sensor, and the displacement amount is accurately controlled by controlling the total number of pulses to achieve focusing, while the pulse frequency controls the movement speed, thereby achieving fast, high-resolution, and automatic focus adjustment.

[0004] For example, the patent application No. CN103676710B discloses an optical remote sensor double-path focusing control system and a control method, which includes two motor driving units, two focal plane position remote sensing units, and a focal plane focusing control unit. The two motor driving units jointly drive the axial movement of an external focal plane structure assembly; the two focal plane position remote sensing units detect the actual distance of the axial movement of the focal plane structure assembly driven by the linear stepping motor and send a digital signal to the focal plane focusing control unit; and the focal plane focusing control unit sends a pulse driving signal to the two motor driving units respectively, judges the synchronization of the axial movement of the focal plane structure assembly driven by the two motor driving units, and corrects when the comparison result is different.

[0005] However, in the process of implementing the technical scheme of the present application, the present application finds that the above-mentioned technology at least has the following technical problems:

[0006] In the prior art, the lubrication state, wear degree and assembly precision of the guide rails and lead screws of the two linear stepper motors cannot be completely consistent, resulting in different load torques of the two motors. Under the same pulse driving, the motor with light load moves fast, and the motor with heavy load moves slow, thereby rapidly causing asynchronization and leading to low focusing efficiency. SUMMARY

[0007] The embodiment of the present application provides a stepper motor driven optical focusing system, and solves the problem of asynchronization and low focusing efficiency caused by the different load torques of two motors due to the different lubrication states, wear degrees and assembly precisions of guide rails and lead screws of the two linear stepper motors in the prior art. The embodiment of the present application realizes high-precision closed-loop synchronous control of the double motors and significantly improves the motion precision and focusing efficiency of the system.

[0008] The embodiment of the present application provides a stepper motor driven optical focusing system, and solves the problem of asynchronization and low focusing efficiency caused by the different load torques of two motors due to the different lubrication states, wear degrees and assembly precisions of guide rails and lead screws of the two linear stepper motors in the prior art. The embodiment of the present application realizes high-precision closed-loop synchronous control of the double motors and significantly improves the motion precision and focusing efficiency of the system.

[0009] The one or more technical solutions provided in the embodiment of the present application have at least the following technical effects or advantages:

[0010] 1. Through the triple adaptive closed-loop control mechanism, the dual-motor achieves ultra-high precision synchronization and anti-interference ability in complex working conditions. First, the current demand is calculated based on load inertia and motion planning, and then the dynamic safety factor is used to compensate for the performance degradation caused by long travel, high frequency operation and motor temperature rise, providing the optimal power reference for the system. On this basis, real-time tolerance management dynamically adjusts the tightness of the synchronization criterion according to the focusing stage, running speed and acceleration, balancing the robustness of the starting stage and the accuracy of the stable running. Finally, the millisecond torque and speed coordination through the double closed loop composed of current feedback and position feedback real-time offset the load imbalance and external disturbances, thus fundamentally eliminating the out-of-sync phenomenon and ensuring the high precision, high reliability and high energy efficiency of the optical focusing system throughout its life cycle.

[0011] 2. The peak torque required for the focusing process is set by theoretical calculation, and a dynamic safety factor based on historical operation data is innovatively introduced. This enables the system to overcome the conservative mode of traditional fixed safety factor, and to achieve a current limit that matches the current task difficulty and the system state, ensuring that the motor has sufficient but not excessive torque output in any working condition, fundamentally preventing out-of-sync and locked-rotor, and significantly reducing system energy consumption and heating by avoiding long-term overdrive, thus simultaneously improving focusing reliability, accuracy and equipment life.

[0012] 3. By real-time monitoring of key operating state parameters such as focusing pulse number, pulse frequency and acceleration, and based on multi-threshold comparison and dynamic algorithm, the current tolerance threshold is adaptively modified, so that the system tolerance ability is no longer a fixed value, but can flexibly change with the operating state: in the starting, braking stage or high-speed high-acceleration conditions, the tolerance is intelligently relaxed to prevent false alarms caused by normal inertia impact or vibration; in the stable running stage, the tight tolerance is maintained to maintain high synchronization accuracy. This achieves an optimal balance between false trigger rate and detection sensitivity, greatly enhancing the stability and adaptability of the system in complex application scenarios.

[0013] 4. By constructing a dual-loop synchronization control architecture combining current loop and position loop, the load imbalance is quickly identified by real-time monitoring of the current deviation of the dual-motor, and the output torque of the two motors is immediately balanced by adjusting the chopping current in the opposite direction, thus compensating for the mechanical load difference from the root. At the same time, the synchronization error is monitored by high-precision position feedback, and a compensation speed command is generated to accelerate the lagging motor and maintain the speed of the leading motor, achieving position correction and forming a forced and high-response synchronization locking effect, ensuring ultra-high synchronization accuracy, dynamic response speed and running stability of the dual-motor in various complex working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1This is a schematic diagram of the structure of a stepper motor driven optical focusing system provided in an embodiment of this application;

[0015] Figure 2 This is a schematic diagram of a coil drive for a stepper motor provided in an embodiment of this application. Detailed Implementation

[0016] This application provides a stepper motor-driven optical focusing system, solving the problem in existing technologies where the lubrication, wear, and assembly precision of the guide rails and lead screws of two linear stepper motors are not perfectly identical, leading to different load torques between the two motors. Under the same pulse drive, the lighter-loaded motor moves faster, while the heavier-loaded motor moves slower, quickly creating asynchrony and resulting in low focusing efficiency. The overall approach is as follows:

[0017] By dynamically setting differentiated chopping currents (i.e., peak current limits of motor windings) for two stepper motors based on real-time focusing distance, speed, and load conditions, and using this current value as the core for synchronization control, the system dynamically corrects the current tolerance threshold based on operating status parameters. By monitoring the comparison between the motor winding current and the corrected threshold in real time, the system dynamically adjusts the output torque and speed of each motor, thereby ensuring that the two motors can maintain precise synchronization and efficient focusing even under uneven load conditions.

[0018] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0019] like Figure 1 The diagram shows a schematic of a stepper motor-driven optical focusing system provided in this embodiment of the application. The stepper motor-driven optical focusing system includes: a drive parameter pre-configuration module, an adaptive tolerance management module, and a synchronous closed-loop control module. The drive parameter pre-configuration module dynamically sets the chopping current of the two stepper motors based on the focusing distance, maximum allowable speed, and load, and performs synchronous focusing. The chopping current is the peak current set for the motor windings in the stepper motor driver using chopping control technology. The current flowing into the motor windings is precisely controlled based on the chopping current to ensure that its peak value never exceeds the chopping current. The adaptive tolerance management module dynamically corrects the current tolerance threshold during the focusing process based on operating state parameters, achieving intelligent adaptation of the tolerance threshold and preventing system misjudgment and oscillation. The synchronous closed-loop control module dynamically adjusts the output state of the stepper motors during focusing based on the winding currents of the two stepper motors and the corrected current tolerance threshold. Dynamic adjustment of the stepper motor output state includes adjusting the output torque and speed of the stepper motors, achieving real-time closed-loop synchronous control of force and position, fundamentally suppressing step loss.

[0020] likeFigure 2 As shown, the coil driving schematic provided by the embodiment of the application, the stepping motor power driving circuit adopts the chopping control MOSFET working mode, the chopping control is a kind of constant current driving technology, the current peak value in motor winding is limited by fast switching (chopping) MOSFET, so that it is stabilized in the chopping current value, ensure that the motor can obtain strong, stable torque under different rotating speeds, and the core device is N-MOSFET tube (N-channel metal oxide semiconductor field effect transistor), as an electronic switch, its conduction and turn-off are controlled by control signal, it is the ideal choice for driving large current load.The phase sequence signal (such as A, B, C, D) of logic level is generated by control board such as MCU, the signal is amplified by current through buffer, and the amplified signal is used to drive the source of N-MOSFET, so as to control the power-on and power-off of motor winding.The focusing motor adopts single four-beat working mode, which is the most basic driving mode of stepping motor, only one phase winding is powered each time, and the step angle of the motor is: 1.8°, the rotor rotates 1.8 degrees for each pulse received by the motor, if forward rotation, the focusing motor is powered in sequence according to A-B-C-D-A……, if reverse rotation, the motor is controlled according to D-C-B-A-D timing sequence, which lays a solid hardware foundation for the fast, smooth and high-precision synchronous movement of the whole system.

[0021] In the embodiment, the chopper control technology makes the driver a constant current source, which can work efficiently even when the power supply voltage is high, and the motor can quickly obtain the required current to achieve high-speed operation, while avoiding winding overheating through chopper, and the system has high overall efficiency, low energy consumption and small heat; compared with simple voltage drive, constant current chopper drive can ensure that the motor provides continuous and smooth torque in a wide speed range, prevents torque attenuation caused by speed increase, and ensures the strength and reliability of the focusing action; MOSFET has the advantage of extremely fast switching speed, can accurately and correctly execute every pulse instruction issued by the microcontroller, and realizes millisecond-level response of motor start-stop, acceleration and deceleration, which is the basis for realizing high-precision position control; single four-beat control timing is the simplest step motor driving method, with clear logic and easy implementation by microcontroller, which reduces the complexity of software and hardware; the use of buffer chip isolates the fragile logic circuit of MCU and the large current and high voltage of the motor driving part, and protects the core control board from interference and damage. The application builds a set of high-precision and high-reliability double-step motor synchronous focusing solution through the cooperative work of three core modules of driving parameter pre-configuration, adaptive tolerance management and synchronous closed-loop control. Through the pre-configuration module based on load and motion curve, the system provides the optimal initial current setting, ensuring the efficiency and rationality of power output; through the adaptive tolerance management module integrating multiple environmental parameters, the current tolerance threshold is intelligently and dynamically adjusted, greatly enhancing the adaptability of the system in complex working conditions and effectively preventing misjudgment and system shock; finally, through the millisecond-level real-time monitoring of motor winding current and position deviation, reverse adjustment of torque and speed fine-tuning by the synchronous closed-loop control module, the risk of out-of-step caused by uneven load of double motors is eliminated, thereby fundamentally realizing the accurate synchronization of double motors from torque to position. The system not only significantly improves the precision, speed and smoothness of optical focusing, but also greatly prolongs the service life of the motor and mechanical structure through intelligent overload and overheating prevention mechanism, and has excellent comprehensive performance and reliability.

[0022] Further, the step of setting the chopping current of the two stepping motors based on the focusing distance, the maximum allowable speed and the load dynamics and synchronously focusing includes: obtaining a focusing motion curve based on the focusing distance and the maximum allowable speed, the focusing motion curve containing real-time speed and real-time acceleration in the focusing process, the focusing motion curve being generated directly by a system controller such as an MCU by inputting the focusing distance and the maximum allowable speed and through a built-in algorithm; extracting a maximum acceleration value and a corresponding speed value from the focusing motion curve; obtaining a maximum inertia torque based on the product of the total rotational inertia and the maximum acceleration value, the total rotational inertia being the sum of the rotational inertia of the entire mechanical system, including the motor rotor, the lead screw, the coupling and the load "focal plane assembly" moved to the motor shaft, and being directly obtained from historical focusing data, the maximum inertia torque being the torque required to overcome the inertia of the system; obtaining a load torque based on the lead screw pitch, the predefined mechanical efficiency and the axial force of the focal plane assembly, TL=(F*P) / (2*π*η), wherein TL is the load torque, which is the torque required to maintain the uniform motion of the load, F is the axial force of the focal plane assembly, P is the lead screw pitch, i.e., the moving lead of the focal plane assembly, and η is the mechanical efficiency, which can be obtained from the product technical manual, the axial force of the focal plane assembly including static friction, dynamic friction and gravity component, wherein the static friction is the maximum friction that needs to be overcome when the focal plane assembly starts from a stationary state, the dynamic friction is the friction that needs to be overcome when the focal plane assembly moves uniformly on the guide rail, and the gravity component is the component of the gravity of the focal plane assembly in the moving direction when there is an inclination in the installation direction of the focusing mechanism; obtaining a peak torque by summing the maximum inertia torque and the load torque, the peak torque being the sum of the torque required to be provided by the motor shaft when starting at the maximum acceleration while also overcoming the external load; and obtaining the chopping current of the two stepping motors based on the peak torque, the predefined torque constant of the stepping motor obtained from the torque-current curve in the motor manual and the safety factor.

[0023] The safety factor is a dynamic value based on historical operation state parameters, the historical operation state parameters include an estimated total pulse number, a historical focusing cycle start-stop frequency and a motor winding resistance, the estimated total pulse number is an arithmetic mean value calculated by a plurality of actual pulse numbers corresponding to the same target focusing distance based on historical focusing data; the correction method of the safety factor includes: step one: judging whether the estimated total pulse number exceeds a preset pulse number safety threshold, if yes, recording the difference between the pulse number safety threshold and the estimated total pulse number as a deviation pulse number, obtaining a first safety factor adjustment value based on the product of the deviation pulse number and a preset pulse number correction factor, and dynamically correcting the safety factor based on the first safety factor adjustment value, otherwise, directly entering step two; step two: judging whether the historical focusing cycle start-stop frequency exceeds a preset start-stop frequency threshold, if yes, recording the difference between the historical focusing cycle start-stop frequency and the start-stop frequency threshold as a deviation start-stop frequency, obtaining a second safety factor adjustment value based on the product of the deviation start-stop frequency and a preset frequency correction factor, and dynamically correcting the safety factor based on the second safety factor adjustment value, otherwise, directly entering step three; step three: comparing the difference between the motor winding resistance and a reference resistance value with the reference resistance value to obtain a resistance change rate, obtaining the resistance change rate based on the motor winding resistance and a preset reference resistance value, judging whether the resistance change rate exceeds a preset resistance change threshold, if yes, recording the difference between the resistance change rate and the resistance change threshold as a deviation resistance change rate, obtaining a third safety factor adjustment value based on the product of the deviation resistance change rate and a preset resistance correction factor, and dynamically correcting the safety factor based on the third safety factor adjustment value, if not, no additional processing is performed.

[0024] The drive parameter pre-configuration module further includes a current conversion unit configured to convert the chopping current into a corresponding analog voltage signal, and output the analog voltage signal to the chopping current setting pin of the two motor drivers, so as to limit the peak value of the motor winding current within the range defined by the chopping current.

[0025] In the embodiment, the historical focusing cycle start-stop frequency is obtained by internal statistics of the motion controller; the motor winding resistance can be measured by the driver. In the process of dynamically correcting the safety factor based on the safety factor adjustment value, the safety factor adjustment value is added to the current safety factor to obtain the corrected safety factor. The application converts the traditional fixed safety factor into a dynamic variable that can intelligently predict and actively respond to various potential risks by comprehensively evaluating three key parameters: stroke load (estimated total pulse number), work intensity (historical start-stop frequency), and motor state (winding resistance temperature rise). Not only can it reserve torque margin in advance for harsh working conditions such as long stroke and high frequency start-stop, effectively preventing stall and step loss, but also can automatically compensate for output torque attenuation according to real-time temperature changes of the motor, thereby minimizing unnecessary energy waste and heating loss while absolutely ensuring system reliability and focusing accuracy. It realizes the optimal balance between safety, efficiency and equipment life, representing a major progress from static empirical design to dynamic intelligent adaptive control of optical focusing systems.

[0026] Further, the step of dynamically correcting the current tolerance threshold in the focusing process based on the operating state parameter comprises: the operating state parameter comprises pulse frequency, acceleration and focusing pulse number; comparing the focusing pulse number with preset first pulse threshold and second pulse threshold, and outputting first basic tolerance threshold according to the comparison result: if the focusing pulse number is less than or equal to the first pulse threshold, the difference between the first pulse threshold and the focusing pulse number is recorded as the first deviation pulse number, the ratio of the first deviation pulse number to the first pulse threshold is calculated, and the ratio is added to the unit value to obtain the pulse adjustment multiple, and the product of the pulse adjustment multiple and the current tolerance threshold is recorded as the first basic tolerance threshold; if the focusing pulse number is greater than the first pulse threshold and less than the second pulse threshold, the current tolerance threshold is recorded as the first basic tolerance threshold; if the focusing pulse number is greater than or equal to the second pulse threshold, the difference between the focusing pulse number and the second pulse threshold is recorded as the second deviation pulse number, the ratio of the second deviation pulse number to the second pulse threshold is calculated, and the unit value is subtracted from the ratio to obtain the pulse adjustment multiple, and the product of the pulse adjustment multiple and the current tolerance threshold is recorded as the first basic tolerance threshold; comparing the real-time pulse frequency with the preset frequency threshold, and outputting a frequency correction coefficient according to the comparison result: if the real-time pulse frequency is less than or equal to the frequency threshold, the frequency correction coefficient is set to 1; if the real-time pulse frequency is greater than the frequency threshold, the difference between the real-time pulse frequency and the frequency threshold is recorded as the deviation pulse frequency value, and the ratio of the deviation pulse frequency value to the frequency threshold is recorded as the frequency correction coefficient; comparing the absolute value of the real-time acceleration value with the preset acceleration threshold, and outputting an acceleration correction coefficient according to the comparison result: if the absolute value of the real-time acceleration value is less than or equal to the acceleration threshold, the acceleration correction coefficient is set to 1; if the absolute value of the real-time acceleration value is greater than the acceleration threshold, the difference between the real-time acceleration value and the acceleration threshold is recorded as the deviation acceleration value, and the ratio of the deviation acceleration value to the acceleration threshold is recorded as the acceleration correction coefficient; correcting the current tolerance threshold according to the first basic tolerance threshold, the frequency correction coefficient and the acceleration correction coefficient.

[0027] In the process of correcting the current tolerance threshold according to the first basic tolerance threshold, the frequency correction coefficient and the acceleration correction coefficient, the first basic tolerance threshold, the frequency correction coefficient and the acceleration correction coefficient are multiplied to obtain the corrected current tolerance threshold.

[0028] In the embodiment, the interval judgment is performed by setting a double pulse threshold value, the fine and adaptive management of the whole focusing process (start, stable operation, braking) is realized, the focusing process is divided into three typical stages of start / brake zone, stable operation zone and overstroke zone, and the current tolerance threshold value is dynamically adjusted according to different stages: the tolerance is automatically relaxed in the start and brake stages (when the pulse number is small), so as to avoid false alarm of the system due to mechanical inertia or disturbance; the reference tolerance is maintained in the stable operation stage, so as to ensure the synchronization accuracy; the tolerance is tightened again when approaching the end of the stroke (when the pulse number is too large), so as to play a dual role of preventing overstroke and protecting the equipment; in the pulse frequency dimension, the system will enlarge the tolerance threshold value in proportion when running at high speed. Because the ripple of the chopper current of the driver and the back electromotive force of the winding will increase when the motor is in high speed state, the noise of the current feedback signal is more significant, and relaxing the tolerance can effectively filter high-frequency electrical noise, avoid unnecessary adjustment interference and system oscillation in the high-speed stable operation stage, and ensure the stability of the control loop; in the real-time acceleration dimension, the system will intelligently relax the tolerance in proportion under high acceleration conditions. High acceleration means that the motor needs to output a huge inertial torque to overcome the system inertia, which will cause significant current fluctuation. Relaxing the tolerance allows greater current deviation, which can effectively distinguish between "normal large load impact" and "abnormal locked rotor or out-of-step", and fundamentally prevent false alarm and false adjustment of the system in the most error-prone stage of acceleration and deceleration. The ideal tolerance value which can accurately reflect the current actual working condition is obtained by multiplying the correction coefficients of the three dimensions with the basic tolerance. It can quickly respond in the case of load mutation leading to out-of-step, and can maintain stability in the case of high speed and high acceleration, avoid over-adjustment, improve the synchronization accuracy of the double motor, and significantly enhance the adaptability, stability and reliability of the system.

[0029] Further, the step of dynamically adjusting the output state of the stepping motor in the focusing process based on the winding current of the two stepping motors and the corrected current tolerance threshold value comprises: monitoring and obtaining the real-time current feedback value of the winding of the two stepping motors in real time; the absolute difference value of the real-time current feedback value of the winding of the two stepping motors is recorded as the deviation current value, whether the deviation current value exceeds the current tolerance threshold value is judged, if yes, it is judged that the two motor loads are uneven and there is a risk of out-of-step, and the torque adjustment process is started; if not, no additional processing is performed.

[0030] The torque adjustment process is: comparing the current feedback values of the two stepper motors, and recording the stepper motor with the smaller current feedback value as the low-load motor and the stepper motor with the larger current feedback value as the high-load motor; obtaining a current adjustment value based on the deviation current value and a preset current adjustment ratio, and performing reverse collaborative adjustment on the output torques of the two motors, specifically: reducing the chopping current set value of the low-load motor, while increasing the chopping current set value of the high-load motor, and the increase / decrease amplitude is the current adjustment value; iteratively executing the above steps until the deviation current value is less than or equal to the current tolerance threshold.

[0031] The synchronous closed-loop control module is also used to dynamically adjust the motor speed according to the positions of the two stepper motors, and the specific steps include: obtaining the position feedback values of the two stepper motors in real time, and calculating the actual position deviation value; comparing the actual position deviation value with a preset synchronization tolerance threshold, if the actual position deviation value exceeds the synchronization tolerance threshold, starting the speed adjustment process, otherwise no additional processing is performed.

[0032] The speed adjustment process specifically includes: according to the positive and negative of the actual position deviation value, marking the two stepper motors as leading motor and lagging motor; generating a speed adjustment amount according to the actual position deviation value, specifically including: multiplying the actual position deviation value by a preset first speed proportional coefficient to obtain a proportional adjustment component; multiplying the cumulative sum of the historical actual position deviation with a preset integral coefficient to obtain an integral adjustment component; comparing the difference between the actual position deviation value and the actual position deviation value of the last period with the control period time interval, and then multiplying it with a preset differential coefficient to obtain a differential adjustment component; coupling the proportional adjustment component, the integral adjustment component and the differential adjustment component, the coupling processing is the sum, to obtain the speed adjustment amount; taking the sum of the basic speed instruction value and the speed adjustment amount as the speed instruction value of the lagging motor, maintaining the speed instruction value of the leading motor, until the actual position deviation value does not exceed the synchronization tolerance threshold, and outputting the adjusted speed instruction value to the corresponding motor driver.

[0033] In the embodiment, the application is executed in a fixed control cycle time interval, which is a fixed value preset by the system, the calculation of the integral adjustment component depends on the historical deviation accumulation value with the control cycle time interval as the time reference, and the calculation of the differential adjustment component depends on the difference between the current cycle deviation absolute value and the last cycle deviation absolute value, and is multiplied by the reciprocal of the control cycle time interval. The application can intelligently compare the current double-motor winding current difference with the tolerance threshold optimized by multiple parameters in real time, so as to accurately identify the torque imbalance trend caused by uneven load in milliseconds; once the risk is detected, the torque adjustment process is started immediately, the reverse cooperative strategy of reducing the current of the low-load motor and increasing the current of the high-load motor is adopted, the output torque of the double motor is actively and compulsorily balanced, the torque difference causing the step-out is eliminated from the root, and the step-out risk is killed in the embryonic state. The system calculates the position deviation and generates accurate speed compensation in real time through independent position loop monitoring, and accelerates the lag motor, so as to realize accurate closed-loop correction from the position deviation to the speed instruction. The double and parallel adjustment of torque and speed not only eliminates the step-out cause, but also compensates the small position error, so as to ensure that the double motor can maintain high synchronization accuracy and motion stability under any complex load and dynamic working condition, and finally comprehensively improves the response speed, positioning accuracy and long-term operation reliability of the optical focusing system.

[0034] Those skilled in the art will appreciate that embodiments of the application can be supplied as a method, a system, or a computer program product. Accordingly, the application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the application can be embodied in the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk memory, CD-ROM, optical memory, etc.) having computer usable program code embodied therein.

[0035] The application is described with reference to flowcharts and / or block diagrams of the system, device (system), and computer program product according to the embodiments of the application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The function specified in one flow or multiple flows and / or blocks Figure 1 The function specified in one flow or multiple flows and / or blocks

[0036] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the Figure 1 function specified in the flow or flows and / or blocks Figure 1 of the block or blocks.

[0037] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the Figure 1 function specified in the flow or flows and / or blocks Figure 1 of the block or blocks.

[0038] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to encompass within their scope all such variations and modifications as are included within the scope of the application.

[0039] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A stepper motor driven optical focusing system, characterized in that, It includes a drive parameter pre-configuration module, an adaptive tolerance management module, and a synchronous closed-loop control module: The drive parameter pre-configuration module is used to dynamically set the chopping current of two stepper motors based on the focusing distance, maximum allowable speed and load, and to perform synchronous focusing. The chopping current is the peak current set for the motor windings in the stepper motor driver through chopping control technology. The current flowing into the motor windings is precisely controlled based on the chopping current to ensure that its peak value never exceeds the chopping current. The steps of dynamically setting the chopping current of the two stepper motors based on the focusing distance, maximum permissible speed, and load, and performing synchronous focusing, include: The focusing motion curve is obtained based on the focusing distance and the maximum permissible speed. The focusing motion curve includes the real-time speed and real-time acceleration during the focusing process. Extract the maximum acceleration value and its corresponding velocity value from the focusing motion curve; The maximum inertial torque is obtained based on the total moment of inertia and the maximum acceleration value; The load torque is obtained based on the lead screw pitch, the predefined mechanical efficiency, and the axial resultant force of the focal plane assembly, wherein the axial resultant force of the focal plane assembly includes static friction, dynamic friction, and a gravitational component. The peak torque is obtained by summing the maximum inertial torque and the load torque; The chopping current of the two stepper motors is obtained based on the peak torque, the predefined torque constant of the stepper motor, and the safety factor. The drive parameter pre-configuration module also includes a current conversion unit, which converts the chopper current into a corresponding analog voltage signal and outputs the analog voltage signal to the chopper current setting pins of the two motor drivers to limit the peak value of the motor winding current to the range defined by the chopper current. The safety factor is a dynamic value obtained by dynamically correcting historical operating status parameters. The historical operating status parameters include the estimated total number of pulses, the historical focusing cycle start and stop frequency, and the motor winding resistance. The estimated total number of pulses is the arithmetic mean of multiple actual pulses corresponding to the same target focusing distance in the historical focusing data of the stepper motor. The method for correcting the safety factor includes: Step 1: Determine whether the estimated total number of pulses exceeds the preset pulse number safety threshold. If so, record the difference between the pulse number safety threshold and the estimated total number of pulses as the deviation pulse number. Based on the deviation pulse number and the preset pulse number correction factor, obtain the first safety factor adjustment value, and dynamically correct the safety factor based on the first safety factor adjustment value. Otherwise, proceed directly to Step 2. Step 2: Determine whether the historical focus cycle start-stop frequency exceeds the preset start-stop frequency threshold. If so, record the difference between the historical focus cycle start-stop frequency and the start-stop frequency threshold as the deviation start-stop frequency. Based on the deviation start-stop frequency and the preset frequency correction factor, obtain the second safety factor adjustment value, and dynamically correct the safety factor based on the second safety factor adjustment value. Otherwise, proceed directly to Step 3. Step 3: Based on the motor winding resistance and the preset reference resistance value, obtain the resistance change rate, determine whether the resistance change rate exceeds the preset resistance change threshold. If so, record the difference between the resistance change rate and the resistance change threshold as the deviation resistance change rate. Based on the deviation resistance change rate and the preset resistance correction factor, obtain the third safety factor adjustment value, and dynamically correct the safety factor based on the third safety factor adjustment value. Otherwise, no additional processing is performed. The adaptive tolerance management module is used to dynamically correct the current tolerance threshold during the focusing process based on the operating status parameters. The step of dynamically correcting the current tolerance threshold during focusing based on operating status parameters includes: The operating status parameters include pulse frequency, acceleration, and number of focusing pulses, wherein the acceleration is the acceleration value in the focusing motion curve; The number of focusing pulses is compared with the preset first pulse threshold and second pulse threshold, and the first basic tolerance threshold is output based on the comparison result: If the focusing pulse value is less than or equal to the first pulse threshold, the difference between the first pulse threshold and the focusing pulse value is recorded as the first deviation pulse number. The ratio of the first deviation pulse number to the first pulse threshold is calculated, and the ratio is added to the unit value to obtain the pulse adjustment multiple. The product of the pulse adjustment multiple and the current current tolerance threshold is recorded as the first basic tolerance threshold. If the focusing pulse value is greater than the first pulse threshold and less than the second pulse threshold, then the current current tolerance threshold is recorded as the first basic tolerance threshold. If the focusing pulse value is greater than or equal to the second pulse threshold, the difference between the focusing pulse value and the second pulse threshold is recorded as the second deviation pulse number. The ratio of the second deviation pulse number to the second pulse threshold is calculated, and the unit value is subtracted from the ratio to obtain the pulse adjustment multiple. The product of the pulse adjustment multiple and the current current tolerance threshold is recorded as the first basic tolerance threshold. The real-time pulse frequency is compared with a preset frequency threshold, and a frequency correction coefficient is output based on the comparison result. If the real-time pulse frequency is less than or equal to the frequency threshold, then the frequency correction coefficient is set to 1; If the real-time pulse frequency is greater than the frequency threshold, the difference between the real-time pulse frequency and the frequency threshold is recorded as the deviation pulse frequency value, and the ratio of the deviation pulse frequency value to the frequency threshold is recorded as the frequency correction coefficient. The absolute value of the real-time acceleration is compared with a preset acceleration threshold, and an acceleration correction coefficient is output based on the comparison result. If the absolute value of the real-time acceleration is less than or equal to the acceleration threshold, then the acceleration correction factor is set to 1. If the absolute value of the real-time acceleration value is greater than the acceleration threshold, the difference between the real-time acceleration value and the acceleration threshold is recorded as the deviation acceleration value, and the ratio of the deviation acceleration value to the acceleration threshold is recorded as the acceleration correction coefficient. The current tolerance threshold is corrected based on the first basic tolerance threshold, the frequency correction factor, and the acceleration correction factor; The process of correcting the current tolerance threshold based on the first basic tolerance threshold, the frequency correction coefficient, and the acceleration correction coefficient is as follows: the first basic tolerance threshold frequency, the correction coefficient, and the acceleration correction coefficient are multiplied to obtain the corrected current tolerance threshold. The synchronous closed-loop control module is used to dynamically adjust the output state of the stepper motors during focusing based on the winding current of the two stepper motors and the corrected current tolerance threshold. The dynamic adjustment of the output state of the stepper motors includes the adjustment of the output torque of the stepper motors and the adjustment of the motor speed of the stepper motors. The steps for dynamically adjusting the output state of the stepper motors during focusing based on the winding currents of the two stepper motors and the corrected current tolerance threshold include: Real-time monitoring and acquisition of real-time current feedback values ​​of the two stepper motor windings; The absolute difference between the real-time current feedback values ​​of the two stepper motor windings is recorded as the deviation current value. It is determined whether the deviation current value exceeds the current tolerance threshold. If so, the torque adjustment process is started. Otherwise, no further processing will be performed; The torque adjustment process is as follows: The two stepper motors are compared based on the current feedback value, and the stepper motor with the smaller current feedback value is marked as the low-load motor, while the stepper motor with the larger current feedback value is marked as the high-load motor. The current adjustment value is obtained based on the deviation current value and the preset current adjustment ratio, and the output torque of the two motors is adjusted in reverse coordination, specifically as follows: Decrease the chopper current setting value for the low-load motor, and increase the chopper current setting value for the high-load motor, with the increase or decrease amount being the current adjustment value; The above steps are repeated iteratively until the deviation current value is less than or equal to the current tolerance threshold. The synchronous closed-loop control module is also used to dynamically adjust the motor speed according to the positions of the two stepper motors, and the specific steps include: The position feedback values ​​of the two stepper motors are acquired in real time, and their actual position deviation values ​​are calculated. The actual position deviation value is compared with the preset synchronization tolerance threshold. If the actual position deviation value exceeds the synchronization tolerance threshold, the speed adjustment process is started; otherwise, no additional processing is performed. The speed adjustment process specifically includes: The two stepper motors are labeled as the leading motor and the lagging motor, respectively, based on the sign of their actual position deviation values. The speed adjustment is generated based on the actual position deviation value. The specific steps include: The actual position deviation value is multiplied by the preset first speed proportional coefficient to obtain the proportional adjustment component; The integral adjustment component is obtained by multiplying the sum of the historical actual position deviations by the preset integral coefficient. The difference between the actual position deviation value and the actual position deviation value of the previous cycle is compared with the control cycle time interval, and then multiplied by the preset differential coefficient to obtain the differential adjustment component. The speed regulation quantity is obtained by coupling the proportional control component, the integral control component, and the derivative control component. The sum of the basic speed command value and the speed adjustment amount is used as the speed command value of the lagging motor, and the speed command value of the leading motor is maintained until the actual position deviation value does not exceed the synchronization tolerance threshold.

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