A segmented frequency conversion galvanizing crane control method

Abstract

The present invention discloses a segmented variable frequency galvanizing crane control method, which solves the problem of contactless soft start and soft stop of the crane, and the crane can realize self-positioning and positioning. The method can maximize the operation efficiency of the crane while taking into account stability. The method adopts multi-stage variable frequency speed regulation to control the crane, establishes a mathematical model of the crane, determines the galvanizing process control method through fuzzy control method, and calculates the speed switching point. Compared with other variable frequency control crane methods, the crane operation can eliminate swinging, be more stable, and have higher efficiency. Using an object-oriented approach, multiple position points between the galvanizing processes are optimized for different components of the tower and the on-site environment, that is, the position points of different galvanized materials are different, and the position points are bound to the components respectively. Image processing, limit switches and other methods are used to realize the self-correction function of the crane error.

Description

Technical Field

[0001] The invention relates to the field of hot-dip galvanizing production of iron towers, and in particular to a segmented variable frequency galvanizing crane control method in the galvanizing production process. Background Art

[0002] With the rapid growth of the national economy and the continuous improvement of people's living standards, the demand for electricity for production and life has increased significantly, and the construction of power grids has also developed rapidly, which ultimately increased the demand for iron tower products. Since iron towers work in an external environment for a long time, such as humidity, high temperature, high salt and other harsh climates, they are very easy to corrode. Galvanizing is a common steel anti-corrosion technology. Among them, hot-dip galvanizing is one of the most commonly used galvanizing technologies in the industry.

[0003] The steel tower is mainly composed of angle steel, tower foot, plate and other parts. The galvanizing process of these parts is mostly realized by manual handheld remote control equipment to control the crane. Since the crane hangs a lot of galvanized materials during galvanizing, the crane has large inertia, and the manual control of the crane is unstable and inefficient during the galvanizing process. In addition, the long-term manual control of the crane has high labor intensity, and the quality of galvanizing is greatly affected by the workers' proficiency. Therefore, improving the automation level of crane control is the key to solving the above problems. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a segmented frequency conversion galvanizing crane control method, which utilizes segmented frequency conversion to control the crane to reduce the labor intensity of workers, achieve precise control of the crane, and ensure the efficiency, stability and safety of galvanizing.

[0005] In order to solve the technical problem, the technical solution adopted by the present invention is: a segmented variable frequency galvanizing crane control method, comprising the following steps: S01), installing an encoder, a proximity switch, and a limit switch on the crane, the encoder is installed on both sides of the crane, and is used to count the number of high-speed pulses during the operation of the crane to achieve self-positioning of the crane, and the proximity switch is installed at each process node of the galvanizing process to detect and transmit position signals; the limit switch is installed at both ends of the crane hook hoist and the horizontal stroke of the crane. When the encoder fails or other reasons cause the hook position to be wrong or the crane cannot stop, the limit switch plays a protective role and sends a signal to the crane at the same time, the crane stops and triggers an audible and visual alarm; the encoder, the proximity switch, and the limit switch are all connected to the PLC controller, the PLC controller is connected to the frequency converter, and the frequency converter adjusts the output of different power supply frequencies according to different control signals to control the crane motor to output different speeds; S02), the crane is controlled to be unloaded to the origin position by a handheld device. Since the positions of each process node of the galvanizing process are fixed, the crane obtains and records the position information when it passes through the proximity switches at the above positions in sequence; S03), the protection To ensure that the crane takes into account both stability and efficiency during operation, the crane is set to three operating speeds: fast, medium and slow, corresponding to three frequencies respectively, and the speeds of the three frequencies are obtained; S04) Establish a mathematical model of the motion of the crane's pendulum, and use fuzzy control rules to analyze and determine the speed control method of the crane's pendulum in the galvanizing process, that is, determine the acceleration and deceleration points of the three operating speeds; S05) Take an object-oriented approach, and analyze and calculate the positions of the acceleration and deceleration points of the mathematical model according to the situation that different parts of the tower have different heights, control the crane movement, and judge whether the hook is To meet the stability requirements, the time compensation δ is introduced, and the time compensation δ is adjusted according to the swing of the hook. The movement time of the crane in each stage is extended or shortened according to the time compensation δ to achieve the purpose of eliminating the swing. After determining the position, the virtual point is bound to the material and the virtual point is recorded; S06) The crane hook adopts two-stage speed switching in the pickling tank, zinc tank and cooling tank. Under the premise of ensuring the process, the speed acceleration and deceleration points are as close to the pool surface as possible, and the PLC controls the hoist speed switching; S07) After all points are confirmed, the crane is controlled to return to the origin and wait for the galvanizing operation to start.

[0006] Furthermore, ignoring factors including wind force, resistance, and friction, the mathematical model of the pendulum is obtained after simplifying the scene:

[0007]

[0008]

[0009] Where l is the length of the steel cable, M is the weight of the crane, m is the weight of the galvanized material, θ is the hook swing angle, Indicates the hook speed, represents the hook angular acceleration, x represents the travel displacement, represents the linear acceleration of the vehicle, g represents the acceleration due to gravity, and F(t) represents the input force;

[0010] Since the driving crane uses a frequency converter, the input of the mathematical model is the driving acceleration a. The scene is simplified and the maximum swing angle of the pendulum is stipulated to be no more than 5°. After modification, the mathematical equation of angular velocity and horizontal acceleration is obtained:

[0011]

[0012] Initial conditions t=0,θ=0, The solution is:

[0013]

[0014]

[0015]

[0016] It can be seen that the swing of the hook changes periodically with time, and the swing amplitude and speed are proportional to the acceleration a of the vehicle. By adjusting the acceleration, the entire running time of the trolley can be shortened and the purpose of eliminating the swing can be achieved.

[0017] Furthermore, the position compensation amount Е is determined by the camera at the origin and the limit switch at the origin. Each time the crane passes the origin limit switch, the PLC dynamically modifies the parameters of each coordinate of the process according to the position compensation amount E; the camera at the origin generates a driving image at the origin and sends it to the background. The background calculates the height difference of the hoists on both sides of the crane and notifies the PLC controller. The PLC controller controls the hook to rise or fall to achieve height compensation; the limit switch at the origin is used for horizontal error compensation and correction. The relative distances of all points are determined. After reaching the origin limit switch, the error compensation is obtained by comparing the existing coordinates with the original coordinates. All coordinates of the process are corrected by this error.

[0018] Furthermore, the frequencies corresponding to the three operating speeds of fast, medium and slow are 80 Hz, 50 Hz and 20 Hz respectively.

[0019] Furthermore, when the hook swing exceeds the threshold, the speed switching point is modified. While ensuring stability, the speed switching point is continuously optimized to minimize the objective function T, where T is the entire time the trolley is running. Finally, the speed switching point position parameters are bound to the material.

[0020] Beneficial effects of the present invention: The segmented variable frequency galvanizing crane control method described in the present invention solves the problem of contactless soft start and soft stop control of the crane, and the crane can realize self-positioning and positioning. The method maximizes the operation efficiency of the crane while taking into account stability. The method uses multi-stage variable frequency speed regulation to control the crane, establishes a mathematical model of the crane, determines the galvanizing process control method through a fuzzy control method, and calculates the speed switching point. Compared with other variable frequency control crane methods, the crane operation can eliminate swings, be more stable, and have higher efficiency. Using an object-oriented approach, multiple position points between the galvanizing processes are optimized for different components of the tower and the on-site environment, that is, the position points of different galvanized materials are different, and the position points are bound to the components respectively. Image processing, limit switches and other methods are used to achieve the self-correction function of the crane error. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the architecture diagram of the galvanizing automation control system;

[0022] Figure 2 It is a driving motion model;

[0023] Figure 3 This is the hot dip galvanizing process flow chart;

[0024] Figure 4 This is a schematic diagram of segmented frequency conversion control. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] This embodiment discloses a segmented variable frequency galvanizing crane control method, which is based on a galvanizing automation control system. Figure 1 As shown, the galvanizing automation control system includes a PLC controller, a frequency converter, a touch screen, a handheld device, a limit switch, a sensor, a proximity switch and an encoder. The PLC controller is used to receive and send signals, perform data calculation and analysis, and the frequency converter is connected to the PLC controller. The frequency converter outputs different power frequencies according to different control signals to control the output of different speeds of the single machine. The encoder and the proximity switch belong to the positioning module. The encoder is located on both sides of the crane and is used to count the number of high-speed pulses during the operation of the crane to realize the self-positioning function of the crane. The proximity switch is arranged at each link of pickling, pickling inspection, galvanizing and cooling to transmit position signals to the PLC controller. The touch screen is a display module, which is connected to the PLC controller to display various state parameters of the crane in real time during the galvanizing process. The handheld device is wirelessly connected to the PLC controller to control the travel of the crane.

[0028] The method described in this embodiment comprises the following steps:

[0029] S01) Install encoders, proximity switches and limit switches on the crane. Specifically, the encoders are installed on both sides of the crane, the proximity switches are installed at each process node of the galvanizing process, and the limit switches are installed at both ends of the crane hook hoist and the crane horizontal travel.

[0030] S02), control the unloaded crane to the origin position through the handheld device. Since the positions of each process node of the galvanizing process are fixed, the position information is obtained and recorded when the crane passes the proximity switch at the above position in sequence. Figure 3 As shown, the handheld device is used to control the vehicle to pass through the pickling, pickling inspection, galvanizing, cooling, and storage positions in sequence, and after receiving the signal from the proximity switch, the position information is recorded on the touch screen.

[0031] S03) To ensure that the vehicle is stable and efficient during operation, three operating speeds, fast, medium and slow, are set for the vehicle, which correspond to three frequencies of 80 Hz, 50 Hz and 20 Hz respectively, and the speeds of the three frequencies are obtained.

[0032] S04) Establishing a mathematical model of the motion of the crane, and using fuzzy control rule analysis to determine the speed control method of the crane in the galvanizing process.

[0033] During the galvanizing process, the crane accelerates and decelerates, and the hook will swing. In order to ensure the safety and efficiency of the galvanizing operation, it is hoped that the speed can be increased as much as possible while ensuring the stability of the hook. Ideally, the hook stops swinging when the crane reaches the predetermined process position. The mathematical model of the crane is established without considering air resistance and ground track friction. The simple mathematical model of the crane is as follows:

[0034]

[0035]

[0036] Where l is the length of the steel cable, M is the weight of the crane, m is the weight of the galvanized material, θ is the swing angle of the hook, x is the displacement, g is the acceleration of gravity, and F(t) is the input force.

[0037] Since the driving crane uses a frequency converter, the input of the mathematical model is the driving acceleration a. The scene is simplified and the maximum swing angle of the pendulum is stipulated to be no more than 5°. After modification, the mathematical equation of angular velocity and horizontal acceleration is obtained:

[0038]

[0039] Initial conditions t=0,θ=0, The solution is:

[0040]

[0041]

[0042]

[0043] It can be seen that the swing of the hook changes periodically over time, and the swing amplitude and speed are proportional to the acceleration a of the vehicle. Reasonable adjustment of the acceleration can make the entire time of the trolley running as short as possible and achieve the purpose of eliminating the swing.

[0044] S05) adopts an object-oriented approach, and for the situation where different parts of the tower (angle steel, tower foot, plate) have different pendulum heights l, the acceleration and deceleration point positions are obtained respectively according to the mathematical model, the driving movement is controlled, and it is judged whether the hook meets the stability requirements. Since the mathematical model ignores the air resistance and the friction between the rail and the ground, it is necessary to calculate and introduce the time compensation amount δ, and adjust the corrected time compensation amount δ according to the swing of the hook. According to the time compensation amount δ, the driving movement time in each stage is extended or shortened to achieve the purpose of eliminating the swing. After determining the position, the virtual point is bound to the material, and the virtual point is recorded on the touch screen.

[0045] S06) The crane hook adopts two-stage speed switching in the pickling tank, zinc tank and cooling tank. Under the premise of ensuring the process, the speed switching point is as close to the tank surface as possible, and the PLC controls the hoist speed switching.

[0046] S07) After all points are confirmed, click the touch screen return to origin button to control the crane to return to the origin and wait for the galvanizing operation to start. One-click crane starts working. First, hang the hook full of materials, select the corresponding mode on the touch screen, and the materials hung by the crane are pickled, pickled and inspected, galvanized, cooled, and stored one by one. The crane moves between the two galvanizing links. The encoder on the crane feeds back data in real time. The PLC determines the position relationship between the current position and the previously set multiple points, and performs segmented frequency conversion to control the crane speed, which not only ensures the galvanizing efficiency of the crane, but also avoids overshoot and excessive swing of the hook.

[0047] Furthermore, the positive position compensation E is determined by the camera at the origin and the limit switch at the origin. Each time the crane passes the origin, the parameters of each coordinate of the process are dynamically modified according to the position compensation E. The specific method is as follows: the camera at the origin generates a driving image at the origin and sends it to the background. The background calculates the height difference of the hoists on both sides of the crane and notifies the PLC controller. The PLC controller controls the hook to rise or fall to achieve height compensation; the limit switch at the origin is used for horizontal error compensation correction. The relative distances of all points are determined. After reaching the limit switch at the origin, the error compensation is obtained by comparing the existing coordinates with the original coordinates. All coordinates of the process are corrected by this error.

[0048] like Figure 4 As shown, according to the driving kinematics formula:

[0049]

[0050] v(t)=v(t 0 )+at,

[0051] 2a(s(t)-s(t 0 ))=v 2 (t)-v 2 (t 0 ),

[0052] Calculate the speed switching points 1, 2, 3, 4, and 5 for different galvanized materials. Then the crane hangs one of the materials, angle steel, tower foot, and plate, and automatically controls the crane to simulate the galvanizing process, such as Figure 4 As shown, it is determined whether the swing of the hook exceeds the threshold. If it exceeds the threshold, the time compensation amount δ is introduced, and the speed switching points 1, 2, 3, 4, and 5 are modified. While ensuring stability, the speed switching points are continuously optimized to minimize the objective function T=t1+t2+t3+t4+t5+t6+t7. Finally, the speed switching point position parameters are bound to the material.

[0053] The present invention realizes the automation of galvanizing based on PLC-controlled crane. PLC obtains position data by interacting with sensors to realize the positioning of the crane, establishes a mathematical model of the crane by simplifying environmental factors, determines the control mode of multiple switching speed points for every two processes by fuzzy algorithm, calculates the speed switching point position according to the kinematic formula, and realizes the switching of different speeds by PLC under the premise of ensuring stability. The hook error compensation is automatically realized by image processing, and the periodic crane motion error compensation function is realized by limit switch. Compared with other control algorithms, the equipment and algorithm adopted by this patent are less complex and more suitable for engineering applications. The use of the patented segmented frequency conversion control crane not only reduces the labor intensity of workers, but also realizes the precise control of the crane, ensuring the efficiency, stability and safety of galvanizing.

[0054] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A segmented frequency conversion galvanizing crane control method, characterized in that: The following steps are involved: S01) Install encoders, proximity switches and limit switches on the crane. Encoders are installed on both sides of the crane to count the number of high-speed pulses during the operation of the crane and realize self-positioning of the crane. Proximity switches are installed at various process nodes of the galvanizing process to detect and transmit position signals. Limit switches are installed at both ends of the crane hook hoist and the horizontal travel of the crane. When the encoder fails or other reasons cause the hook position to be wrong or the crane cannot stop, the limit switch plays a protective role and sends a signal to the crane to stop and trigger an audible and visual alarm. Encoders, proximity switches and limit switches are all connected to the PLC controller, which is connected to the frequency converter. The frequency converter adjusts the output of different power supply frequencies according to different control signals to control the crane motor to output different speeds. S02) Control the crane to the origin position with no load through a handheld device. Since the positions of various process nodes of the galvanizing process are fixed, the crane obtains and records the position information when it passes through the proximity switches at the above positions in turn. S03) Ensure that the crane is stable and efficient during operation, and the crane is set to be fast. , medium speed and slow speed, which correspond to three frequencies respectively, and obtain the speeds of the three frequencies; S04), establish a mathematical model of the motion of the crane's pendulum, and use fuzzy control rule analysis to determine the speed control method of the crane's pendulum in the galvanizing process, that is, determine the acceleration and deceleration points of the three operating speeds; S05), adopt an object-oriented approach, aiming at the situation where different parts of the tower have different heights, analyze and calculate the position of the speed acceleration and deceleration points of the mathematical model, control the movement of the crane, judge whether the hook meets the stability requirements, introduce the time compensation amount δ, adjust the corrected time compensation amount δ according to the swing of the hook, and extend or shorten the movement time of the crane in each stage according to the time compensation amount δ to achieve the purpose of eliminating the swing. After determining the position, bind the virtual point to the material and record the virtual point; S06), the crane hook adopts two-stage speed switching in the pickling tank, zinc tank and cooling tank. Under the premise of ensuring the process, the speed acceleration and deceleration points are as close to the pool surface as possible, and the PLC controls the hoist speed switching; S07), after all points are confirmed, control the crane to return to the origin and wait for the galvanizing operation to start.

2. The segmented frequency conversion galvanizing crane control method according to claim 1 is characterized in that: Ignoring factors including wind force, resistance, and friction, the mathematical model of the crane pendulum is obtained after simplifying the scene: Where l is the length of the steel cable, M is the weight of the crane, m is the weight of the galvanized material, θ is the swing angle of the hook, x is the displacement, g is the acceleration of gravity, and F(t) is the input force. Since the driving crane uses a frequency converter, the input of the mathematical model is the driving acceleration a. The scene is simplified and the maximum swing angle of the pendulum is stipulated to be no more than 5°. After modification, the mathematical equation of angular velocity and horizontal acceleration is obtained: Initial conditions t = 0, θ = 0, The solution is: It can be seen that the swing of the hook changes periodically with time, and the swing amplitude and speed are proportional to the acceleration a of the vehicle. By adjusting the acceleration, the entire running time of the trolley can be shortened and the purpose of eliminating the swing can be achieved.

3. The segmented frequency conversion galvanizing crane control method according to claim 1 is characterized in that: The position compensation E is determined by the camera at the origin and the limit switch at the origin. Each time the crane passes the origin limit switch, the PLC dynamically modifies the parameters of each coordinate of the process according to the position compensation E. The camera at the origin generates a driving image at the origin and sends it to the background. The background calculates the height difference of the hoists on both sides of the crane and notifies the PLC controller. The PLC controller controls the hook to rise or fall to achieve height compensation. The limit switch at the origin is used for horizontal error compensation and correction. The relative distances of all points are determined. After reaching the origin limit switch, the error compensation is obtained by comparing the existing coordinates with the original coordinates. All coordinates of the process are corrected through this error.

4. The segmented frequency conversion galvanizing crane control method according to claim 1 is characterized in that: The frequencies corresponding to the three operating speeds, fast, medium and slow, are 80Hz, 50Hz and 20Hz respectively.

5. The segmented frequency conversion galvanizing crane control method according to claim 2 is characterized in that: When the hook swing exceeds the threshold, the speed switching point is modified according to the time compensation δ. While ensuring stability, the speed switching point is continuously optimized to minimize the objective function T, where T is the entire time the trolley is running. Finally, the speed switching point position parameters are bound to the material.

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