A tower crane safety data monitoring method based on virtual sensing

Abstract

The application provides a tower crane safety data monitoring method based on virtual sensing, comprising: collecting data of a hoisting frequency converter, an amplitude-changing frequency converter, a programmable logic controller (PLC), a gyroscope and a magnetometer module of a tower crane, and collecting the data to an industrial computer through a 485 bus, and calculating a hook height, a hoisting load, a trolley amplitude, a large arm rotation angle of the tower crane in real time, and presenting the parameters to a tower crane operator through a display screen. The method does not need to wire and install external sensors, and only needs to collect and calculate data of the frequency converter and the PLC in the tower crane control system, and data of the gyroscope and the magnetometer module built in the safety monitoring system, so that the hook height, the hoisting load, the trolley amplitude, the large arm rotation angle, a position limiter state and other operating state parameters of the tower crane can be calculated in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of crane safety monitoring, and in particular to a tower crane safety monitoring system based on virtual sensing. Background Art

[0002] Existing tower crane safety monitoring systems still rely on external sensors to calculate operating parameters such as hook height, load, trolley amplitude, and boom slew angle. The load is often measured using a pin-type stress and strain sensor mounted on the fixed pulley, while hook height, trolley amplitude, and slew angle are often measured using encoders and potentiometers installed on the motor shaft or drum. This method is not only costly, but also susceptible to damage from prolonged exposure to wind and sun, and it also increases the strain on the tower crane's wiring. Therefore, developing a sensor-free tower crane safety monitoring system has become a pressing technical challenge for the industry. Summary of the Invention

[0003] Purpose of the Invention: This invention aims to reduce the hardware and installation costs of tower crane safety monitoring, reduce wiring pressure on the tower crane, improve the cab environment, and extend the service life of the tower crane safety monitoring system. By collecting data from the inverter and PLC in the tower crane control system, as well as the built-in gyroscope and magnetometer modules, the tower crane operating status parameters are presented to the tower crane operator in real time.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A virtual sensing-based tower crane safety data monitoring method collects data from the tower crane's hoisting inverter, luffing inverter, PLC (Programmable Logic Controller), built-in gyroscope, and magnetometer modules. The data is aggregated to an industrial computer via a 485 bus, and the crane's hook height, hoisting load, trolley amplitude, boom slewing angle, and other values ​​are calculated in real time. The data is then presented to the operator via a display screen.

[0006] The hook height, H, is calculated using the absolute encoder read from the hoist inverter. To prevent the hook from slipping, the hoist system uses closed-loop vector control, which uses a built-in motor encoder. The motor encoder value read from the hoist inverter consists of a high-order bit, h, and a low-order bit, l. The high-order bit represents the integer value of the current encoder revolution, while the low-order bit represents the current revolution scale value (a single revolution contains 1024 scales). Therefore, the current total number of encoder revolutions, S, is:

[0007]

[0008] When the hook touches the ground, the encoder circle value in the lifting inverter is calibrated to 0, and the height value H of the hook is:

[0009]

[0010] D q is the diameter of the hoisting mechanism drum, i q Reduction ratio of the lifting mechanism reducer

[0011] The hoisting load Z is determined by the output frequency f of the lifting inverter. q , output current a, output power p q , the output torque T is calculated. The calculation formula is:

[0012] Z=G(f q ,a,p q ,T)

[0013] G is the corresponding relationship model.

[0014] The trolley amplitude F is determined by the amplitude converter output frequency f b The calculation formula is:

[0015]

[0016] Where H(f b ,β) is the speed of the variable amplitude motor calculated by the frequency and load rate measured by the variable amplitude inverter, ∫ is the integral symbol, d is the differential operator, t is the time, D b is the diameter of the drum of the luffing mechanism, i b The formula for defining the reduction ratio load rate of the luffing mechanism reducer is as follows:

[0017] β=p b / P b

[0018] Where p b The output power of the variable amplitude inverter is P b Rated power of luffing motor;

[0019] The boom rotation angle is calculated by the built-in gyroscope magnetometer module after data fusion. The magnetometer is easily affected by the soft and hard magnetic interference on the tower crane. It is only necessary to measure the angle value of the tower crane in the static state of rotation and obtain the rotation angle u1 in the initial state through Kalman filtering. Since the tower crane has a slow rotation speed, the gyroscope is used to calculate its rotation angular velocity ω. The angle J obtained by fusion is:

[0020] J=u1+ω Δt t1

[0021] Where t1 is the gyroscope sampling interval, ωΔt is the average angular velocity of the current sampling interval.

[0022] The built-in gyroscope and magnetometer module is characterized in that the gyroscope / magnetometer is built into an industrial computer. The industrial computer is fixedly installed in the tower crane cab. During installation, the gyroscope and magnetometer modules are installed in a direction parallel to the boom tip. In this way, the direction angle measured by the gyroscope and magnetometer modules is the tower crane boom rotation direction angle.

[0023] Because direct communication is established with the PLC, the limiter status value can be obtained by reading the value in the corresponding register, eliminating the need to connect wires to read each limiter. The limiter status value includes the lifting height limit, lifting weight limit, trolley amplitude limit, rotation angle limit, and torque limit. The limit signals of these lifting height limit, lifting weight limit, trolley amplitude limit, rotation angle limit, and torque limit are used as inputs to the PLC for its logical operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0025] Figure 1 It is a structural diagram of the security monitoring system of the present invention.

[0026] Figure 2 Schematic diagram of Kalman filter results.

[0027] Figure 3 It is the model training flow chart. DETAILED DESCRIPTION

[0028] like Figure 1 As shown, data is collected from the tower crane's lifting inverter (2), amplitude inverter (3), PLC (4), built-in gyroscope and magnetometer module (5), and the data is aggregated to the industrial computer (1) through the 485 bus. The hook height, lifting load, trolley amplitude, boom rotation angle and other values ​​of the tower crane are calculated in real time and presented to the tower crane operator through the display screen (6).

[0029] The hook height H is calculated using the absolute encoder read from the hoist inverter. To prevent the hook from slipping, the hoist system uses closed-loop vector control, which means it has its own motor encoder. The motor encoder value read from the inverter consists of a high-order bit (h) and a low-order bit (l). The high-order bit represents the integer value of the current encoder revolution, while the low-order bit represents the current revolution scale value (a single revolution contains 1024 scales). Therefore, the current total number of encoder revolutions, S, is:

[0030]

[0031] When the hook touches the ground, the encoder circle value in the inverter is calibrated to 0, and the height value H of the hook is:

[0032]

[0033] D q is the diameter of the hoisting mechanism drum, i q Reduction ratio of the lifting mechanism reducer

[0034] The hoisting load Z is determined by the output frequency f of the lifting inverter. q , output current a, output power p q , the output torque T is calculated. The calculation formula is:

[0035] Z=G(f q ,a,p q ,T)

[0036] G is the corresponding relationship model.

[0037] Table 1

[0038]

[0039] Table 1 shows the lifting inverter data when hoisting standard weights of 420kg, 800kg, and 2000kg. After analysis, it can be seen that under the same load and different gear steady-speed operation conditions, as the frequency increases (that is, the gear increases), the motor torque increases; at the same frequency, as the load increases, the motor output torque also increases. The lifting mechanism is driven by a motor, and the mathematical model of the three-phase asynchronous motor is a high-order nonlinear differential equation with multi-variable coupling, so it is very difficult to establish an equation for the load and the inverter parameters. Here, the support vector machine (SVM) in the machine learning algorithm is borrowed to establish the load prediction model G. Data-based machine learning is to derive rules that cannot be obtained through principle analysis from observed sample data, and use it to predict test data. The input for model training is the measured multiple sets of inverter output frequencies f q , output current a, output power p q , output torque T; the output is the corresponding lifting load. The model training flow chart is as follows Figure 3 shown.

[0040] The trolley amplitude F is determined by the amplitude converter output frequency f b The calculation formula is:

[0041]

[0042] H(f b,β) is the speed value of the variable amplitude motor calculated based on the frequency and load rate measured by the variable amplitude inverter, ∫ is the integral symbol, d is the differential operator, t is the time, D b is the diameter of the drum of the luffing mechanism, i b The formula for defining the reduction ratio load rate of the luffing mechanism reducer is as follows:

[0043] β=p b / P b

[0044] Where p b The output power of the variable amplitude inverter is P b Rated power of luffing motor;

[0045] H(f b ,β) is the variable amplitude motor speed value calculated by the frequency and load rate measured by the inverter, and the amplitude value F is calculated by integration. The speed formula of the three-phase asynchronous motor is:

[0046]

[0047] Where s is the slip rate, n' is the synchronous speed of the motor, n is the measured speed, p is the number of motor pole pairs, and the frequency f is set by the inverter, with the number of pole pairs p being a fixed value. Therefore, determining the motor speed only requires determining the slip. Empirical analysis shows that the factors determining the slip s are the frequency f and the load factor β. Therefore, by measuring the motor speed under different loads and frequencies, the equation for the relationship between slip and frequency and load factor is determined. Some of the measured data is shown in Table 2:

[0048] Table 2

[0049]

[0050] The multiple linear regression model of slip rate s is established by using the data in the table, and the following is obtained:

[0051] s=M(f,β)

[0052] then Finally, the trolley amplitude F is obtained by integrating the speed. The arm rotation angle is calculated by the built-in gyroscope magnetometer module after data fusion. The magnetometer is easily affected by the soft magnetic and hard magnetic interference on the tower crane. It is only necessary to measure the angle value of the tower crane in the static state of rotation and obtain the rotation angle u1 in the initial state through Kalman filtering, as shown in the figure below: Figure 2 As shown in the figure, since the tower crane has a slow rotation speed, a gyroscope is used to calculate its rotation angular velocity ω, and the angle J obtained by fusion is:

[0053] J=u1+ω Δt t1

[0054] Where t1 is the gyroscope sampling interval, ω Δt is the average angular velocity of the current sampling interval.

[0055] In the aforementioned slew angle calculation model, the tower crane boom rotates with wind direction under wind load, meaning the boom's slew angle also changes even when the slew frequency converter is not operating. Therefore, the slew angle is calculated using data fusion from the gyroscope and magnetometer modules.

[0056] In a specific implementation, the present application provides a computer storage medium and a corresponding data processing unit, wherein the computer storage medium is capable of storing a computer program that, when executed by the data processing unit, executes the invention of a tower crane safety data monitoring method based on virtual sensing provided by the present invention and some or all of the steps in each embodiment. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0057] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present invention can be implemented by means of computer programs and their corresponding general hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, in essence or in other words, the part that contributes to the prior art, can be embodied in the form of a computer program, i.e., a software product. The computer program software product can be stored in a storage medium and includes several instructions for enabling a device including a data processing unit (which can be a personal computer, a server, a single-chip microcomputer, a MUU, or a network device, etc.) to execute the methods described in various embodiments of the present invention or certain parts of the embodiments.

[0058] The present invention provides a method for monitoring tower crane safety data based on virtual sensing. There are numerous methods and approaches for implementing this technical solution. The above is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A tower crane safety data monitoring method based on virtual sensing, characterized in that: include: Data is collected from the tower crane's hoisting inverter, luffing inverter, programmable logic controller (PLC), gyroscope, and magnetometer modules, and aggregated to the industrial computer via the 485 bus. The crane's hook height, lifting load, trolley amplitude, and boom slewing angle are calculated in real time and presented to the crane operator via a display screen. The trolley amplitude F is determined by the amplitude converter output frequency f b The calculation formula is: Where H(f b ,β) is the speed of the variable amplitude motor calculated by the frequency and load rate measured by the variable amplitude inverter, ∫ is the integral symbol, d is the differential operator, t is the time, D b is the diameter of the drum of the luffing mechanism, i b is the reduction ratio of the luffing mechanism reducer; The load factor calculation formula is as follows: β=p b / P b where p b is the output power of the variable amplitude inverter, P b is the rated power of the variable amplitude motor.

2. The method according to claim 1, characterized in that The hook height H is calculated by the absolute value encoder read in the lifting inverter: the lifting system adopts closed-loop vector control to prevent the hook from slipping, that is, it has its own motor encoder; The motor encoder value read from the hoisting inverter is the high bit h and the low bit l, where the high bit represents the integer value of the current encoder number of revolutions and the low bit represents the current circle scale value. The current total number of encoder revolutions S is: When the hook touches the ground, the encoder circle value in the lifting inverter is calibrated to 0, and the height value H of the hook is: Among them D q is the diameter of the hoisting mechanism drum, i q Reduction ratio of the lifting mechanism reducer.

3. The method according to claim 2, characterized in that The hoisting load Z is determined by the output frequency f of the lifting frequency converter. q , output current a, output power p q , the output torque T is calculated, and the calculation formula is: Z=G(f q ,a,p q ,T) Where G is the corresponding relationship model.

4. The method according to claim 3, characterized in that The boom rotation angle is calculated by data fusion of the gyroscope and magnetometer modules. The magnetometer is easily affected by soft and hard magnetic interference on the tower crane. It is only necessary to measure the angle value of the tower crane in the static state of the rotation motion, and obtain the rotation angle u1 in the initial state through Kalman filtering. Since the tower crane has a slow rotation speed, the gyroscope is used to calculate the tower crane's rotation angular velocity ω. The fused angle J is: J=u1+ω Δt t1 Where t1 is the gyroscope sampling interval, ω Δt is the average angular velocity of the current sampling interval.

5. The method according to claim 4, characterized in that The gyroscope and magnetometer modules are built into an industrial computer; the industrial computer is fixedly installed in the tower crane cab. During installation, ensure that the installation direction of the gyroscope and magnetometer modules is parallel to the direction of the boom tip, so that the direction angle measured by the gyroscope and magnetometer modules is the rotation direction angle of the tower crane boom.

6. The method according to claim 5, characterized in that By reading the value in the register, the limiter status value can be obtained without wiring each limiter for reading; the limiter status value includes lifting height limit, lifting weight limit, trolley amplitude limit, rotation angle limit, and torque limit. The limit signals of the lifting height limit, lifting weight limit, trolley amplitude limit, rotation angle limit, and torque limit are used as input quantities of the PLC for the logical operation of the PLC.

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