CN104865848A - Dynamic object generation system for aviation spectral camera - Google Patents

Abstract

The invention relates to a dynamic target generating system of an aerial spectrum camera, which belongs to the technical field of photoelectric detection. The purpose of the present invention is to provide a kind of aerial film that can ensure the target film to rotate at low speed and high speed and high precision at a constant speed (speed range 7mm/s~51mm/s) and move at a uniform speed, more realistically and reliably simulating the relative movement of the aircraft and the ground scene. Spectral camera dynamic target generation system. The invention is composed of a host computer, a cRIO system, a servo motor and a servo driver, a servo motor reducer, an encoder, a voltage stabilizing module, a target film, a mechanical mounting frame and a box body, and a main control system. The invention is a dynamic target generating system with low price, flexibility and convenience, and high control precision. The system structure is modular, easy to assemble and disassemble. The invention is a dynamic target generation system, which simplifies the control of the rotation speed of the dynamic target through a mechanical turntable, and can accurately control the speed of the target film, and is suitable for the imaging detection of the aerial spectrum camera used in the current high-altitude and high-speed environment.

Description

Dynamic Target Generating System for Aeronautical Spectrum Camera

technical field

The invention belongs to the technical field of photoelectric detection.

Background technique

Spectral imaging technology is widely used in military reconnaissance, resource inspection, agriculture and forestry, hydrological and geological exploration, environmental monitoring, disaster investigation, surveying and mapping and other fields. The imaging performance of aerial spectral cameras directly determines the results of aerial earth observation, which requires us to test the performance indicators of spectral cameras in the process of development, use and maintenance. The direct detection method is to install the spectral camera on the aircraft or other aircraft for flight test, through a large number of flight tests, adjust the equipment status, and evaluate the imaging performance of the equipment. However, the flight test requires a lot of manpower, material and financial resources, and it needs to fly many times to complete the detection task, which consumes a lot of resources. Therefore, if the various technical indicators of the aeronautical spectrum camera can be fully tested and correctly evaluated in the ground laboratory, reliable basic data will be provided for the field test flight test, thereby greatly reducing the number of test flights using actual flight tests to detect it , not only saves a lot of manpower, material resources and funds, but also shortens the development cycle and improves the quality of development.

At present, the research units of domestic aerial camera testing equipment mainly include Changchun Institute of Optics and Mechanics of Chinese Academy of Sciences, a certain military industry enterprise, Harbin Institute of Technology, Changchun University of Science and Technology and other scientific research institutions. The dynamic target simulation system researched by the Changchun Institute of Optics and Mechanics, Chinese Academy of Sciences, drives the target graphics to move regularly through the turntable, and the dynamic target graphics are made into the graph line of the discrimination rate board, simulating the dynamic imaging of the ground at infinity, and determining the dynamic imaging resolution of the camera The aviation CCD camera performance testing equipment developed by an ordnance enterprise, the CCD image plane of the camera to be tested is coplanar with the intersection of the optical axes of three parallel light tubes with fixed angle intervals, and the resolution plate is controlled according to the speed-to-height ratio of the aircraft. Running speed, the camera is imaged through a collimated light tube, and the resolution of the camera under different field of view angles is interpreted and tested; the aerial camera performance testing equipment developed by Harbin Institute of Technology simulates the yaw motion and roll motion of the aircraft at high altitude, and the resolution The board moves in a straight line at different speeds to simulate the relative movement between the aircraft and the ground scene, and the performance of the aerial camera is tested by evaluating the quality of the photos taken by the camera; the aerial camera ground scene simulation system developed by Changchun University of Science and Technology uses film to simulate the ground scene, and the torque The motor drives the film to rotate, and the aerial camera under test is placed on the other side of the collimator to take pictures of the film rotating at a constant speed, and then evaluate the quality of the captured images and give the evaluation results.

The above detection equipment mainly provides resolution detection or dynamic imaging detection functions for early film cameras or CCD cameras, and mainly tests optical cameras in the visible light segment. For the aerial spectral camera in the visible light to infrared spectrum, the imaging target and optical system of the original detection equipment cannot meet the imaging detection requirements of the spectral camera.

For the aerial spectral cameras currently used in high-altitude and high-speed environments, the imaging detection equipment needs to simulate the flight altitude from a few thousand meters in the low altitude to 30 kilometers in the adjacent space, and the simulated flight speed from low subsonic speed to Mach 3 supersonic speed. The simulated flight platform The range of pitch angle and roll angle is -15°～+15°, the spectral range of the tested camera is 400nm～2500nm, and the field of view reaches more than 30°. In order to meet the above requirements, the developed system includes a high-temperature and high-speed airflow generation device for simulating aerothermal and aerodynamic environments, a swing platform for simulating flight attitude, a dynamic target generation device for simulating ground movement scenes, an optical system for simulating infinite imaging and corresponding auxiliary equipment.

Among them, the dynamic target generating device mainly cooperates with the collimator to simulate the ground environment when the aircraft is flying. Its main function is to drive the target film to move according to the speed parameters given by the main control platform, and at the same time adjust the brightness of the light source to simulate the brightness of the ground environment. Since the occurrence of dynamic targets directly affects the subsequent imaging performance evaluation of aerial cameras, it is critical to precisely control the rotation rate of the film.

The existing domestic dynamic target generating devices such as the Changchun Institute of Optics and Mechanics of the Chinese Academy of Sciences, an ordnance enterprise, and Harbin Institute of Technology all control the speed of the dynamic target through a mechanical turntable. The processing cost is high and it is not easy to move and carry. The aerial camera ground scene simulation system developed by Changchun University of Science and Technology uses a torque motor to control its speed. Although it is flexible and convenient, it cannot achieve good results when the control accuracy is convenient.

Contents of the invention

The purpose of the present invention is to provide a device that can ensure the target film to rotate at a low speed and high speed and high precision at a constant speed (speed range 7 mm/s ~51 mm/s) and move at a uniform speed, and more realistically and reliably simulate the relative motion of the aircraft and the ground scene. Dynamic target generation system for aerial spectrum camera.

The present invention is composed of a host computer, a cRIO system, a servo motor and a servo driver, a servo motor reducer, an encoder, a voltage stabilizing module, a target film, a mechanical mounting frame and a box, and a main control system;

The main control system is the LabVIEW man-machine interface software program, which is installed in the host computer;

The upper computer is connected to the controller of the cRIO system through Ethernet and a network cable, the chassis is plugged into the controller, the power supply is connected to 220V voltage, and the power output terminal 24V+ is connected to the controller terminal V1 and the voltage regulator module through wires. Input+, power supply terminal 24V-connected to terminal C of the controller and input- of the voltage stabilizing module through wires, output + of the voltage stabilizing module is connected to pin 1 of the terminal X1 of the servo driver and the red line of the encoder, The digital board and the analog board are inserted into the slots of the chassis, respectively inserted into slot 1 and slot 2. The 0 pin of the analog board is connected to the 21 pin of the terminal X1 of the servo drive through a wire, and the output of the encoder The blue line is connected to the 14 pins of the digital board. The servo drive terminal X2 is connected to the servo motor through a standard socket. The servo drive terminal U, V, W is connected to the servo motor through a standard socket. The servo drive terminal L1 and L1C, L2 and L2C are connected by wires, L1 and L2 are connected to 220V voltage through the power cord, the rotating shaft of the servo motor is connected to the reducer, and the servo motor is locked on the reducer by an external hexagonal wrench, and the rotating shaft of the reducer is connected Go to the bottom of the film drum fixed on the mechanical mounting frame, fix it with screws, above the mechanical mounting frame, the target film is wound on the film drum, adjust the film pressing device, tighten the film, fix the encoder on the mechanical mounting frame, and encode Install the upper coupling on the rotating shaft, and the coupling is close to the film, so that the film rotates to drive the encoder to rotate, the output of the voltage regulator module -, the 1 pin of the analog board (COM connection port), and the 1 pin of the digital board (COM connection port), the 8 pins, 9 pins and 14 pins of the servo drive terminal X1 are all connected to 0V;

Operation process:

The main control system of the upper computer sets a line speed to the set value input terminal of the PID control algorithm. Since the input and output of the PID are analog voltages, the set line speed is converted into the voltage value that needs to be set corresponding to the rotation of the servo motor. The relationship between speed and analog voltage is obtained by the following method:

The output of the upper computer evenly increases the analog voltage output to the servo motor to make it rotate at a uniform acceleration with constant acceleration. The linear velocity of this process is collected through the encoder, and the data comparison relationship between the analog output voltage and the linear velocity of the target film is obtained. Then use the MATLAB software to fit the line speed-voltage relationship; through fitting, the relationship between the analog voltage and the line speed of the film drum is obtained as:

U=0.2033v+0.0462

U: Analog voltage

v: film linear velocity

The encoder is a photoelectric encoder, and the method for the encoder to collect real-time linear velocity is:

When the film drum drives the target film to rotate, it also drives the encoder shaft to rotate, so the linear speed of the film drum is the same as that of the encoder shaft, and the output of the encoder is a square wave pulse. The linear speed of the target film is calculated as follows:

f: square wave pulse frequency

m: encoder resolution

r: Encoder coupling shaft radius

v: Target film linear velocity

The input of the PID control algorithm is the analog voltage. Set the cRIO system supporting software of the upper computer to output the analog voltage through the 0 pin of the analog board, and transmit the analog voltage signal to the 21 pin of the terminal X1 of the servo drive through the wire. The servo driver controls the servo motor to rotate at the set line speed. At this time, because there is no PID closed-loop control, the error is relatively large, and then the real-time line speed is collected by the encoder, and the line speed is converted into an analog voltage. The real-time analog voltage The value is used as the variable input of the PID control algorithm, and the control variable is adjusted through the feedback value to realize precise control of the motor speed;

The above PID control algorithm is composed of proportional unit P, integral unit I and differential unit D. The relationship between the error e (t) between the input controller input and the set value and the output u (t) is as follows:

Among them, KP is the proportional coefficient; TI is the integral time constant; TD is the differential time constant;

When the computer processes the algorithm, the analog quantity cannot be directly processed, and a digital PID controller is used for calculation, so the above formula must be discretized and replaced by variables:

In the formula, k is the sampling number, and T is the sampling period. The shorter T is, the higher the system accuracy is, but the amount of calculation also increases accordingly;

Let kT simplify to k, get:

   

Since the control of the scene film rotation speed requires the increment of the control amount, and it is only related to the value of the last k feedbacks, the incremental PID control algorithm is selected in the speed measurement and control system, and it is recursively obtained from the above formula:

Subtract the two formulas to get:

  

In the above formula, ;

It can be seen from the above formula that if the values of the three parameters K _P , T _I , and T _D are input, only the feedback value and the set value obtained in the previous three times can be used to control the output volume with the incremental PID control algorithm. Calculation.

The invention is a dynamic target generating system with low price, flexibility and convenience, and high control precision. The system structure is modular, easy to assemble and disassemble. The invention is a dynamic target generation system, which simplifies the control of the rotation speed of the dynamic target through a mechanical turntable, and can accurately control the speed of the target film, and is suitable for the imaging detection of the aerial spectrum camera used in the current high-altitude and high-speed environment.

Description of drawings

Fig. 1 is a control flowchart of the present invention;

Fig. 2 is a hardware connection diagram of the present invention;

Fig. 3 is a comparison diagram of control flow and hardware connection of the present invention;

Fig. 4 is a control process block diagram of the present invention;

Fig. 5 is a flow chart of the control program of the present invention;

Fig. 6 is linear velocity and analog voltage fitting curve;

Fig. 7 is the data acquisition diagram of setting speed and real-time speed;

Figure 8 is the servo motor drives the target film to rotate, the encoder collects the real-time linear velocity, the encoder outputs a square wave pulse, and the collected pulse diagram;

Figure 9 is a diagram of the collected real-time line speed and the set line speed.

Detailed ways

The system of the present invention includes a host computer, a cRIO system, a servo motor and a servo driver, a servo motor reducer, an encoder, a voltage stabilization module, a single-ended signal to differential signal chip, a target film, a mechanical mounting frame and a box, and a LabVIEW man-machine Interface software program;

The cRIO system is a compact real-time control platform cRIO of National Instruments, including a controller (cRIO 9024), a chassis (cRIO 9113), a power supply (NI PS-15), a digital board (NI 9401), an analog board (NI 9263);

The servo motor is MiG 40ST, and the servo driver is Maxsine-EP3;

The encoder is NOC-S5000-2MHC;

The servo reducer is produced by Shanghai Zongheng Precision Machinery Co., Ltd., with a reduction ratio of 1:320;

The voltage regulator module model is LM2576-12;

Among them, the servo motor, servo motor reducer, encoder and target film are installed at the corresponding positions of the mechanical mounting frame, the servo motor is connected to the servo motor reducer, the body is placed inside the mechanical box, the reducer shaft is connected to the film drum, and the film drum is placed Above the mechanical installation frame, it drives the target film to rotate. The servo motor is connected to the servo motor driver, and its speed is controlled by the servo motor driver. The driving voltage of the servo motor driver is provided by the voltage stabilization module. 15), the power supply not only supplies power to the cRIO system, but also supplies power to the servo motor driver and encoder through the voltage stabilization module. The cRIO power supply (NI PS-15) can be connected to the household 220v voltage, and the X1 port of the driver is connected to the cRIO analog board (NI 9263), to precisely control the motor speed, the FPGA module of cRIO itself can realize millisecond-level real-time control, and combine it with the PID control algorithm. According to the overall structure of the digital closed-loop speed regulation system, it is formed in the gray prediction theory On the basis of the new error sequence, the corrected PID parameter expression is derived, and then the output prediction is filtered to eliminate the shortage of high predicted value, and the control amount is adjusted through the feedback value to achieve precise control of the motor speed, and at the same time improve the motor speed. The robustness of the speed control and the error caused by the inaccurate model can achieve precise control of the uniform motion of the target film. The output of the encoder is connected to the digital board (NI 9401) to collect the current speed data. The digital board of the cRIO system and The analog board is inserted into the corresponding slot of the chassis (cRIO 9113), and the cRIO controller (cRIO 9024) communicates with the host computer through the Ethernet port. The encoder, voltage regulator module, cRIO system and servo motor driver need to be in the circuit Need to share a place. The main control system of the upper computer adopts LabVIEW software programming, which can give full play to the computer's ability, and make full use of the hierarchical and modular characteristics of LabVIEW software for software design, process and calculate the speed data collected by the digital board, and use PID control Algorithm to achieve the purpose of precisely controlling the target film speed.

As shown in the hardware connection, the main control system is installed on the upper computer, and the upper computer is connected to the controller of the cRIO system through Ethernet and a network cable. The wire is connected to the controller terminal V1 and the input + of the voltage stabilization module (LM2576-12), the power supply terminal 24V- is connected to the terminal C of the controller and the input − of the voltage stabilization module through wires, and the output of the voltage stabilization module is + Connect to the 1 pin of the servo drive terminal X1 and the red line of the encoder. The digital board and the analog board are inserted into the slots of the chassis, respectively inserted into the 1 slot and the 2 slot, and the 0 pin of the analog board ( AO0 wiring port) is connected to the 21 pins of the servo drive terminal X1 through wires, the output of the encoder is connected to the 14 pins of the digital board (DIO0 wiring port) with a blue line, and the servo drive terminal X2 is connected to the servo motor It is connected through a standard socket, the connecting terminals U, V, W of the servo drive are connected with the servo motor through a standard socket, the connecting terminals L1 and L1C of the servo drive, L2 and L2C are connected through wires, and L1 and L2 are connected to 220V voltage through the power line. The rotating shaft of the servo motor is connected to the reducer, and the servo motor is locked on the reducer by an external hexagonal wrench. The rotating shaft of the reducer is connected to the bottom of the film drum fixed on the mechanical mounting frame and fixed by screws. Above the mechanical mounting frame, The target film is wound on the film drum, the film pressing device is adjusted, the film is tightened, the encoder is fixed on the mechanical mounting frame, the shaft of the encoder is installed with a coupling, and the coupling is tightly attached to the film, so that the rotation of the film drives the rotation of the encoder , the output of the voltage regulator module -, 1 pin of the analog board (COM connection port), 1 pin of the digital board (COM connection port), 8 pins, 9 pins, 14 pins of the servo drive terminal X1 Pins are connected to 0V.

Operation process and realization principle:

Set a line speed (speed range 7 mm/s ~51mm/s) to the set value input terminal of the PID control algorithm through the main control system of the host computer. Since the input and output of the PID are analog voltages, we need to set the line speed The speed is converted into the voltage value that needs to be set corresponding to the rotation of the servo motor. The relationship between the linear speed and the analog voltage is obtained by the following method:

Output 0.01v from the host computer to uniformly increase the analog voltage output to the servo motor to make it rotate at a uniform acceleration with constant acceleration, and collect the linear speed of this process through the encoder (the model is specifically introduced in the content of the patent invention), which is obtained Simulate the relationship between the output voltage and the linear velocity of the target film, and then use the MATLAB software to fit the linear velocity-voltage relationship. Through fitting, the relationship between the analog voltage and the linear velocity of the film drum is obtained as:

U=0.2033v+0.0462

U: Analog voltage

v: film linear velocity

The encoder is a photoelectric encoder, and the method for the encoder to collect real-time linear velocity is:

When the film drum drives the target film to rotate, it also drives the encoder shaft to rotate, so the linear velocity of the film drum (target film) is the same as that of the encoder shaft, and the output of the encoder is a square wave pulse. Calculate the linear velocity of the target film as follows:

f: square wave pulse frequency

m: encoder resolution

r: Encoder coupling shaft radius

v: Target film linear velocity

The input of the PID control algorithm is the analog voltage. Set the cRIO system supporting software of the upper computer to output the analog voltage through the 0 pin (AO0 terminal) of the analog board, and transmit the analog voltage signal to the terminal X1 of the servo drive through the wire 21 pins, the servo driver controls the servo motor to rotate at the set line speed. At this time, because the PID closed-loop control is not formed, the error is relatively large, and then the real-time line speed is collected by the encoder, and the line speed is converted into an analog voltage. The real-time analog voltage value is input as the change amount of the PID control algorithm, and the control amount is adjusted through the feedback amount to realize precise control of the motor speed.

The above PID (proportion, integration, differentiation) control algorithm consists of a proportional unit (P), an integral unit (I) and a differential unit (D). The relationship between its input e (t) (the error between the controller input and the set value) and output u (t) is as follows:

Among them, KP is the proportional coefficient; TI is the integral time constant; TD is the differential time constant;

When the computer processes the algorithm, the analog quantity cannot be directly processed, and a digital PID controller is used for calculation, so the above formula must be discretized and replaced by variables:

In the formula, k is the sampling number, and T is the sampling period. The shorter T is, the higher the system accuracy is, but the amount of calculation increases accordingly.

For the convenience of writing, let kT be simplified into k, and get:

     

Since the control of the scene film rotation speed requires the increment of the control amount, and it is only related to the value of the last k feedbacks, the incremental PID control algorithm is selected in the speed measurement and control system, and it is recursively obtained from the above formula:

Subtract the two formulas to get:

In the above formula, .

It can be seen from the above formula that if the values of the three parameters K _P , T _I , and T _D are input, the incremental PID control algorithm can be used to control the output Quantities are calculated, which can make the response time of the system faster.

In the main control program, by setting a given line speed, through the line speed-voltage relational expression, it is converted into an analog voltage output to the given amount of the PID control algorithm, and at the same time, the line speed of the current target film collected by the encoder is output to the The variation of the PID control algorithm, and the output of the PID is sent to the analog board of the cRIO system to control the speed of the servo motor. By selecting appropriate KP, TI and TD parameters, the speed accuracy can be controlled to within 0.8%, so that the subsequent aerial camera imaging performance can be better evaluated.

Example:

First calculate the relationship between the analog output voltage and the linear velocity of the film drum: output 0.01v through the host computer to uniformly increase the analog voltage output to the servo motor to make it rotate at a uniform acceleration with constant acceleration, and collect the linear velocity of this process through the encoder, that is, Figure out the data comparison relationship between the analog output voltage and the linear velocity of the target film. Since the voltage ranges from 0v to 10v and the number of data points is 1000, the following table only lists 50 sets of data:

Then use MATLAB software to fit the line speed-voltage relationship. Through fitting, the relationship between the analog voltage and the linear velocity of the film drum is obtained as:

U=0.2038v+0.0462

U: Analog voltage

v: film linear velocity

Set a line speed of 9 mm/s to the set input terminal of the PID control algorithm through the main control system of the host computer, and use the above formula for the relationship between the analog voltage and the line speed of the film drum to calculate the set amount input of the PID control algorithm as 1.8804v.

The servo motor drives the target film to rotate, the encoder collects the real-time linear velocity, and the output of the encoder is a square wave pulse, and the collected pulse is shown in Figure 8.

The output of the encoder is connected to the 14-pin (DIO0 wiring port) of the digital board by the blue line, and the frequencies of the latest three square wave pulses read in the host computer are 793Hz, 786Hz, and 798Hz, respectively, according to the formula:

f: square wave pulse frequency

m: Encoder resolution is 5000

r: Encoder coupling shaft radius is 9mm

v: Target film linear velocity

The last three real-time linear velocities of the target film are 8.969mm/s, 8.889mm/s, and 9.025mm/s, respectively, according to the relationship between the analog voltage and the linear velocity of the film drum

U=0.2033v+0.0462

It is obtained that the last three changes in the PID control algorithm are 1.8696v, 1.8833v, 1.8810v, and then through the PID control algorithm

Among them, T is the sampling period, which is the reciprocal of the sampling frequency. If the sampling frequency in the host computer is set to 1000, then T is 0.001s. The appropriate KP is set to 0.900, TI is 0.110 and TD is 0.001 through the host computer, and the PID output is obtained. The control voltage is 0.082v.

The collected real-time linear velocity and the set linear velocity are shown in Figure 9.

Claims (1)

1. An aerial spectrum camera dynamic target generating system is characterized in that: it is composed of host computer, cRIO system, servo motor and servo driver, servo motor reducer, encoder, voltage stabilizing module, target film, mechanical mounting frame and box body and main control system; The main control system is the LabVIEW man-machine interface software program, which is installed in the host computer; The upper computer is connected to the controller of the cRIO system through Ethernet and a network cable, the chassis is plugged into the controller, the power supply is connected to 220V voltage, and the power output terminal 24V+ is connected to the controller terminal V1 and the voltage regulator module through wires. Input+, power supply terminal 24V-connected to terminal C of the controller and input- of the voltage stabilizing module through wires, output + of the voltage stabilizing module is connected to pin 1 of the terminal X1 of the servo driver and the red line of the encoder, The digital board and the analog board are inserted into the slots of the chassis, respectively inserted into slot 1 and slot 2. The 0 pin of the analog board is connected to the 21 pin of the terminal X1 of the servo drive through a wire, and the output of the encoder The blue line is connected to the 14 pins of the digital board. The servo drive terminal X2 is connected to the servo motor through a standard socket. The servo drive terminal U, V, W is connected to the servo motor through a standard socket. The servo drive terminal L1 and L1C, L2 and L2C are connected by wires, L1 and L2 are connected to 220V voltage through the power cord, the rotating shaft of the servo motor is connected to the reducer, and the servo motor is locked on the reducer by an external hexagonal wrench, and the rotating shaft of the reducer is connected Go to the bottom of the film drum fixed on the mechanical mounting frame, fix it with screws, above the mechanical mounting frame, the target film is wound on the film drum, adjust the film pressing device, tighten the film, fix the encoder on the mechanical mounting frame, and encode Install the upper coupling on the rotating shaft, and the coupling is close to the film, so that the film rotates to drive the encoder to rotate, the output of the voltage regulator module -, the 1 pin of the analog board (COM connection port), and the 1 pin of the digital board (COM connection port), the 8 pins, 9 pins and 14 pins of the servo drive terminal X1 are all connected to 0V; Operation process: The main control system of the upper computer sets a line speed to the set value input terminal of the PID control algorithm. Since the input and output of the PID are analog voltages, the set line speed is converted into the voltage value that needs to be set corresponding to the rotation of the servo motor. The relationship between speed and analog voltage is obtained by the following method: The output of the upper computer evenly increases the analog voltage output to the servo motor to make it rotate at a uniform acceleration with constant acceleration. The linear velocity of this process is collected through the encoder, and the data comparison relationship between the analog output voltage and the linear velocity of the target film is obtained. Then use the MATLAB software to fit the line speed-voltage relationship; through fitting, the relationship between the analog voltage and the line speed of the film drum is obtained as: U=0.2033v+0.0462 U: Analog voltage v: film linear velocity The encoder is a photoelectric encoder, and the method for the encoder to collect real-time linear velocity is: When the film drum drives the target film to rotate, it also drives the encoder shaft to rotate, so the linear speed of the film drum is the same as that of the encoder shaft, and the output of the encoder is a square wave pulse. The linear speed of the target film is calculated as follows: f: square wave pulse frequency m: encoder resolution r: Encoder coupling shaft radius v: Target film linear velocity The input of the PID control algorithm is the analog voltage. Set the cRIO system supporting software of the upper computer to output the analog voltage through the 0 pin of the analog board, and transmit the analog voltage signal to the 21 pin of the terminal X1 of the servo drive through the wire. The servo driver controls the servo motor to rotate at the set line speed. At this time, because there is no PID closed-loop control, the error is relatively large, and then the real-time line speed is collected by the encoder, and the line speed is converted into an analog voltage. The real-time analog voltage The value is used as the variable input of the PID control algorithm, and the control variable is adjusted through the feedback value to realize precise control of the motor speed; The above PID control algorithm is composed of proportional unit P, integral unit I and differential unit D. The relationship between the error e (t) between the input controller input and the set value and the output u (t) is as follows: Among them, KP is the proportional coefficient; TI is the integral time constant; TD is the differential time constant; When the computer processes the algorithm, the analog quantity cannot be directly processed, and a digital PID controller is used for calculation, so the above formula must be discretized and replaced by variables: In the formula, k is the sampling number, and T is the sampling period. The shorter T is, the higher the system accuracy is, but the amount of calculation also increases accordingly; Let kT simplify to k, get:     Since the control of the scene film rotation speed requires the increment of the control amount, and it is only related to the value of the last k feedbacks, the incremental PID control algorithm is selected in the speed measurement and control system, and it is recursively obtained from the above formula: Subtract the two formulas to get:    In the above formula, ; It can be seen from the above formula that if the values of the three parameters K _P , T _I , and T _D are input, only the feedback value and the set value obtained in the previous three times can be used to control the output volume with the incremental PID control algorithm. Calculation.