CN108363085B - Cable crane anti-collision early warning method based on GPS/RFID combined positioning - Google Patents

Abstract

A cable crane anti-collision early warning method based on GPS/RFID combined positioning comprises the following steps: step 1: presetting safety distance thresholds D1 and D2 corresponding to the second-level early warning level and the third-level early warning level in a computer simulation analysis program; step 2: according to the parameters of the construction equipment: the method comprises the following steps of calculating early warning distances d1 and d2 at secondary and tertiary early warning levels by parameters such as cable machine running speed v1, braking acceleration a1, tower crane running speed v2, braking acceleration a2, field measuring and calculating equipment reaction lag time t1, operator reaction time t2, cable machine lifting rope length l, positioning signal processing and simulation analysis program calculation time t3 and the like; and step 3: the positioning signal processing program optimizes the RFID measured value according to the GPS monitoring signal of the GPS/RFID combined positioning device and determines the accurate equipment distance; and 4, step 4: and monitoring the distance of the equipment in real time, dynamically simulating and calculating in real time to judge the motion condition of the equipment and whether the equipment is within each early warning distance, and sending out a necessary early warning instruction. The anti-collision early warning method provided by the invention can realize effective early warning of collision in the operation of the cable crane tower crane, and greatly avoid equipment collision accidents.

Description

A kind of anti-collision early warning method for cable crane tower crane based on GPS/RFID combined positioning

technical field

The invention relates to the field of collision early warning of water conservancy and hydropower construction machinery, in particular to an anti-collision early warning method for cable cranes and tower cranes based on GPS/RFID combined positioning.

Background technique

In the process of water conservancy and hydropower construction, large construction equipment such as tower cranes and cable cranes are generally used. They have the characteristics of wide coverage and flexible operation. However, these equipments are usually staggered in space, and the work area is easy to use. Overlapping occurs, especially in weather conditions with low visibility at night, rainy days, and haze days. The equipment operator is affected by factors such as distance, angle, on-site light, and personnel fatigue. It is difficult to accurately estimate the possible collision between equipment. distance, which can easily cause collisions between construction equipment. In order to prevent the occurrence of equipment collision accidents, it is necessary to take anti-collision measures for construction equipment to effectively control the safe operation of construction equipment.

The traditional method of anti-collision early warning is human observation and control. This method is more likely to cause equipment collision due to human negligence due to the poor sight of the observer and the untimely response of the operator. With the development of technology, some methods use ultrasonic echo ranging technology to measure the distance between moving objects and surrounding obstacles. First, the transmitter transmits signal waves, and then uses the receiver to receive the target transmitted waves to detect whether there is a collision. Or other moving objects and their distances, if the detected distance is less than the preset safe distance, it will alarm, but this technology is only suitable for equipment that is located on the same plane and has no rotational motion; in addition to ultrasonic technology, there are also construction equipment. Placed in the same coordinate system, GPS positioning technology is used to obtain the distance between each sports equipment and other sports equipment or obstacles. Although this technology makes up for the shortcomings of ultrasonic technology, GPS satellite signals are easily interfered by weather, environment, etc., and GPS devices on field equipment are also easily blocked, resulting in weak or no signal, which will lead to inaccurate positioning or even failure.

Therefore, it is of great significance to further study the anti-collision early warning method, solve the problem of inaccurate positioning and apply computer simulation technology to realize the anti-collision early warning of the operation of the cable crane tower crane.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of poor equipment positioning signal, insufficient positioning accuracy and imperfect collision warning system in the existing anti-collision early warning methods, the present invention proposes a GPS/ Anti-collision early warning method for cable crane tower crane based on RFID combined positioning.

The technical scheme adopted in the present invention is:

An anti-collision early warning method for a cable crane tower crane based on GPS/RFID combined positioning, comprising the following steps:

Step 1: preset safety distance thresholds D ₁ , D ₂ corresponding to the second-level warning level and the third-level warning level in the computer simulation analysis program;

Step 2: According to the equipment parameters used in the actual construction: cable crane running speed v ₁ , braking acceleration a ₁ , tower crane running speed v ₂ , braking acceleration a ₂ , the length l of the cable crane hoisting rope is measured on site, the equipment response delay time t ₁ , the operator response time t ₂ , the positioning signal processing and simulation analysis program calculates the time t ₃ parameter, and calculates the early warning distances d ₁ and d ₂ under the second-level warning level and the third-level warning level;

Step 3: Initialize the positioning system, and the positioning signal processing program optimizes the RFID observation value and determines the final observation distance according to the GPS signal strength of the GPS/RFID combined positioning device;

Step 4: Real-time uninterrupted monitoring of the equipment distance, dynamic simulation and real-time calculation to determine the movement of the equipment and whether it is within each early warning distance, and issue corresponding early warning instructions.

In the above step 1, the simulation analysis program is based on the Vaga Prime software platform and C++ language programming, which can realize the dynamic simulation of 3D animation, calculate the relative positional relationship between the cable crane and the tower crane in real time, judge the operation status and output the early warning command, and carry out in this program. Before the dynamic simulation, first use CATIA software to establish the 3D model of the construction environment and the cable crane and tower crane, then use 3D Max software to import the 3D model and render the construction environment and construction machinery model to increase its immersion, and then use the rendered model. Import the Lynx graphical interface provided by Vaga Prime, and finally import the positioning signal to drive the three-dimensional model of the cable crane and tower crane through the plug-in developed by programming to realize dynamic simulation and real-time calculation and analysis;

In the above step 1, the safety distance thresholds D ₁ and D ₂ corresponding to the second-level warning level and the third-level warning level divide the distance between the centers of the two devices into three areas: the safe operation area, the operation interference area and the operation collision area. ; The three-dimensional space where the equipment center distance is greater than D1 is the safe operation area, the three _- dimensional space where the equipment center distance is between D1 and D2 is the operation interference area, and the _{three -} dimensional space where the equipment center distance is less _than D2 is the operation collision area.

In the above step 2, each parameter calculates the warning distances d ₁ and d ₂ under the second-level warning level and the third-level warning level, which are composed as follows:

The expression of the warning distance under the second warning level is:

The expression of the warning distance under the third warning level is:

① The plus sign of ± in equations (1) and (2) corresponds to the two devices running in the opposite direction, and the minus sign corresponds to the two devices running in the same direction or chasing. When the chased device is stationary, take v ₂ =0;

② In formulas (1) and (2), S ₁ is the distance that the hook is displaced by the swing of the cable when the equipment is braked. The linearization equation expression of the swing of the cable is approximated as:

From this, the expression of the rope swing angle θ can be obtained as:

Then S ₁ can be obtained by S ₁ =l·tanθ;

③ In formulas (1) and (2), S ₂ is the distance that the rope swings and the hook is displaced by wind pressure, which is related to the wind speed, wind direction, hoisting weight, etc. The distance is generally not less than 2m, and gusts above level 6 should stop at high places hoisting work;

④ In formulas (1) and (2), S ₃ is the RFID and GPS signal processing and computer software analysis and calculation time t ₃ The expression of the moving distance of the equipment is:

S ₃ =(v ₁ ×t ₃ )±(v ₂ ×t ₃ ) (5).

In the above-mentioned step 3, the positioning signal processing program is based on the Matlab software platform and C++ language programming, which can realize the reading of the positioning signals input by the GPS and RFID receivers into the computer and filter the abnormal signals. designated location;

In the above step 3, the RFID positioning uses the signal strength (RSSI) algorithm to measure the distance. In the path loss model of RFID signal transmission, p is the reference energy transmitted, d is the signal transmission distance, and s(d, p) is the received signal in each model. Signal strength, ξ ₁ is a model parameter, then the received signal strength can be expressed as:

In formula (6), d ₀ is the reference distance, which is usually taken as 1m, and ξ ₁ is the path attenuation factor. In the ideal free transmission space, ξ ₁ =2, in the actual transmission environment, its value is usually between 2 and 5 . The observation distance d between the RFID reader and the tag can be obtained from the above formula:

After the RFID positioning distance is measured, the GPS observation distance is weighted according to the ratio of the number of the two signals for joint positioning. In the GPS/RFID combined positioning system, the positioning accuracy is represented by the GDOP value, and the GDOP value varies with the GPS observation satellites. / The number of signals increases and decreases monotonically. When the RFID observation value increases, the GDOP value will also decrease. However, when the RFID observation value is too large, the impact on the GDOP value is no longer significant, and the computer calculation process is more complicated. Therefore, it is necessary to measure the RFID observation value. For optimization, the principles are as follows:

①When the number of visible satellites in the GPS system is N≥4, select a single RFID observation value according to the criterion of the smallest contribution value of the positioning error;

② When the number of visible satellites in the GPS system is 0≤N<4, 4-N RFID observations are preferred.

The early warning commands that can be issued in step 4 are divided into three levels. The first level corresponds to the distance between the cable crane and the tower crane greater than d ₁ , and the running distance between the two equipment is relatively safe. The green light is used to indicate that the mechanical operator can work normally; the second level corresponds to the cable crane and the tower crane. The distance between the crane and the tower crane is relatively close between d ₁ and d ₂ , and the yellow light is accompanied by a rapid sound to remind the operator to be ready to take braking measures at any time; the third-level command corresponds to the distance between the cable crane and the tower crane. When it is less than d ₂ , it is very close, and the red light flashes and cooperates with a sharp sound to warn the mechanical operator that he must immediately take braking measures to stop the movement of the equipment.

The present invention is an anti-collision early warning method for cable cranes and tower cranes based on GPS/RFID combined positioning, and the beneficial effects are as follows:

1: In view of the shortcomings of GPS positioning errors that are easily affected by the number of satellites and signal strength, and even unable to complete the positioning in severe cases, the combination of radio frequency identification RFID positioning technology and GPS positioning technology is selected, and RFID signals are preferred to improve the accuracy of combined positioning; Partition the space around the equipment, establish collision models under different relative motion conditions, use computer simulation technology to conduct 3D visual simulation simulation and real-time monitoring of equipment operating conditions, and calculate and determine the equipment movement conditions and whether it is within each early warning distance. The three-level early warning command is issued to remind the equipment operator, which effectively avoids the occurrence of collision accidents when the equipment is running.

2: By providing an anti-collision early warning method in the present invention, an effective early warning of collisions during the operation of the cable crane and tower crane can be realized, and the occurrence of equipment collision accidents can be greatly avoided.

Description of drawings

Below in conjunction with accompanying drawing and embodiment, the present invention will be further described:

FIG. 1 is a schematic diagram of a control flow of the present invention.

FIG. 2 is a working principle diagram of the GPS/RFID combined positioning system of the present invention.

Fig. 3 (a) is a schematic diagram of the software real-time simulation equipment motion state diagram of the present invention (the cable machine and the tower crane move toward each other).

Fig. 3(b) is a schematic diagram of the software real-time simulation equipment motion state diagram of the present invention (the cable machine and the tower crane are chasing motion).

Fig. 3 (c) is a schematic diagram of a software real-time simulation equipment motion state diagram of the present invention (a tower crane and a tower crane move toward each other).

Detailed ways

The principle of the invention is: during the operation of the cable crane tower crane, the GPS and the RFID device are used to observe and the RFID signal is selected by the positioning signal processing program, and then the relative distance of the equipment is obtained through the weighted calculation of the number ratio of the two signals, followed by computer simulation. The dynamic simulation and real-time calculation of the simulation software monitor the running status of the equipment. The relative distance of the equipment is beyond the second _- level early warning distance d1. When entering the second-level warning distance d ₁ and the third-level warning distance d ₂ , the early warning system will issue a second-level warning command, using a yellow light and a rapid sound to remind the operator that he needs to be ready to take braking measures at any time. Less than the third-level warning distance d ₂ , the early-warning system issues a third-level warning command, using red lights flashing and a sharp sound to warn the mechanical operator that he must immediately take braking measures to stop the equipment from moving.

The embodiments of the present invention will be further described below with reference to the accompanying drawings.

As shown in Fig. 1, Fig. 2, Fig. 3(a)-Fig. 3(c), a kind of anti-collision early warning method of cable crane tower crane based on GPS/RFID combined positioning shown in the present invention, its specific process is shown in Fig. 1 As shown in Fig. 1, the third-level warning threshold parameters are preset in the computer simulation analysis program; then, the second-level and third-level warning levels are calculated according to the equipment parameters used in actual construction and the parameters used to calculate the warning distance measured on site. During the operation of the equipment, the positioning signal processing program optimizes the RFID observation value and determines the final observation distance through the GPS signal strength of the GPS/RFID combined positioning device; finally, the entire anti-collision early warning system continuously performs dynamic simulation simulation and real-time monitoring. Calculate the distance of the equipment, judge the movement of the equipment and whether it is within each warning distance, and issue the corresponding warning instructions.

Example 1:

In this example, referring to the construction equipment configuration and parameters of a large-scale hydropower project in China, the specific steps of the anti-collision early warning method for cable cranes and tower cranes based on GPS/RFID combined positioning are as follows:

Step 1: Set the safety distance thresholds D ₁ and D ₂ corresponding to the second-level warning level and the third-level warning level in the computer simulation analysis program. _In this example, D1 is set to 30m and _D2 is set to 10m.

Step 2: According to the actual equipment parameters used: cable crane running speed v ₁ , braking acceleration a ₁ ; tower crane running speed v ₂ , braking acceleration a ₂ , on-site measurement of cable crane sling length l, equipment response delay time t ₁ The operator's response time t ₂ , the positioning signal processing and the simulation analysis program analyze the calculation time t ₃ and other parameters, and calculate the early warning distances d ₁ and d ₂ under the second-level and third-level warning levels. In this example, the running speed of the translational cable crane is 3m/s, the braking acceleration is 1.5m/s ² , the speed of the MD220 fixed tower crane is 1m/s, the braking acceleration is 0.5m/s ² , and the length of the cable crane rope is 12m, equipment response delay, operator response time and signal processing and computer program analysis and calculation time are all 1s. According to the aforementioned formula, d ₂ =30m and d ₁ =50m are calculated.

Step 3: Initialize the positioning system. The positioning signal processing program optimizes the RFID observation value and determines the final observation distance according to the GPS signal strength of the GPS/RFID combined positioning device. The working principle and process of the GPS/RFID combined positioning system are shown in Figure 2. In this example, there are 4 GPS satellite signals that can be observed, and according to the aforementioned optimization principle, it is necessary to select one RFID measurement value to minimize the error of the combined GPS/RFID positioning. The RFID tag distance is calculated by the aforementioned signal strength RSSI algorithm and model, and then the Kalman filter is used to obtain the optimal error model of the combined positioning, and an RFID measurement value that makes the combined positioning error is selected, and weighted to calculate the accurate equipment relative. distance.

Step 4: Real-time uninterrupted monitoring of the equipment distance, dynamic simulation and real-time calculation to determine the movement of the equipment and whether it is within each early warning distance, and issue corresponding early warning instructions. In this example, the hook of the translation cable crane and the rotating boom of the MD2200 tower crane are basically at the same height, and move horizontally to the tower crane at a speed of 3m/s from a far place, and the rotating boom of the MD2200 tower crane moves at a speed of 1m/s The rotation speed moves in the direction of the hook of the cable machine. As shown in Fig. 3(a), the relative movement of the tower crane cable crane is shown in the figure, the letters A and B in the figure represent the successive positions of the cable crane hanging tank, the arrows represent the moving direction of the cable crane hanging tank, and a and b represent the tower crane rotation. The successive positions of the boom, the arrow indicates the rotation direction of the tower crane rotating boom, the shaded part indicates the sweeping range of the rotating boom), when the cable crane hook and the tower crane rotating boom move to a horizontal distance of 50m (d ₁ ) At the same time, the system sends out a second-level early warning command, accompanied by a yellow light and a prompt sound, the cable crane and the tower crane simultaneously carry out a second-level early warning, and are ready to take braking measures at any time. After 5 seconds, when the horizontal distance between the hook of the cable crane and the rotating jib of the tower crane is 30m (d ₂ ), the system will issue a three-level warning command, accompanied by a red light and a sharp sound, and the cable crane and the tower crane will be at the same time. A three-level warning is carried out, and the operator immediately takes braking measures to stop the movement of the equipment. In this example, due to mechanical and human response delays and inertia, the cable crane hook and the tower crane rotating jib still move a certain distance, and the distance between them in the horizontal direction is about 10m (D ₂ ) when they finally stop moving.

The parameters in the above-mentioned specific embodiments, especially the numerical parameters, are only further examples to illustrate the present invention, and do not limit its scope. Those skilled in the art to which the present invention belongs can be within the scope of the technical idea of the present invention. Various modifications, additions or substitutions to the specific embodiments described are within the protection scope of the present invention. Matters not covered in the present invention belong to the common knowledge of those skilled in the art.

Claims (1)

1. A cable crane anti-collision early warning method based on GPS/RFID combined positioning is characterized by comprising the following steps:

step 1: presetting a safety distance threshold D corresponding to a second-level early warning level and a third-level early warning level in a computer simulation analysis program₁，D₂；

And 2, step: according to the equipment parameters used in actual construction: running speed v of cable crane₁Acceleration of braking a₁Running speed v of tower crane₂Acceleration of braking a₂On-site measuring and calculating the length l of the lifting rope of the cable crane and the reaction delay time t of the equipment₁Operator reaction time t₂Time t is calculated by positioning signal processing and simulation analysis program₃Isoparametric, calculating the early warning distance d under the second-level early warning level and the third-level early warning level₁And d₂；

In the step 2, various parameters calculate the early warning distance d under the second-level early warning level and the third-level early warning level₁And d₂The composition is as follows:

the expression of the early warning distance at the secondary early warning level is as follows:

the expression of the early warning distance at the third-level early warning level is as follows:

the method comprises the following steps: in the formulas (1) and (2), plus signs of +/-correspond to the opposite operation of the two devices, minus signs correspond to the same direction of the two devices or the pursuit operation of the two devices, and v is taken when the pursued devices are static₂＝0；

Secondly, the step of: s in the formulae (1) and (2)₁For the distance that the lifting hook displaces due to the swing of the cable when the equipment is braked, the linear equation expression of the swing of the cable is approximately as follows:

from this, the expression for the cable swing angle θ can be found as:

then S₁Can pass through S₁L · tan θ;

③: s in the formulae (1) and (2)₂The distance for forcing the mooring rope to swing the lifting hook to move is related to wind speed, wind direction, lifting weight and the like, the distance is not less than 2m, and the high-altitude lifting operation should be stopped by gusts of wind above 6 levels;

fourthly, the method comprises the following steps: s in the formulae (1) and (2)₃Calculating time t for positioning signal processing and analog analysis₃The expression of the movement distance of the internal equipment is as follows:

S₃＝(v₁×t₃)±(v₂×t₃) (5)；

and step 3: initializing a positioning system, preferably selecting an RFID observation value and determining a final accurate positioning distance by a positioning signal processing program according to the GPS signal intensity of the GPS/RFID combined positioning device;

in the step 3, the distance is measured and calculated by adopting a signal strength (RSSI) algorithm in the RFID positioning, in a path loss model of RFID signal transmission, p is transmitted reference energy, d is a signal transmission distance s (d, p) is received signal strength and xi in each model₁For the model parameters, the received signal strength can be expressed as:

formula (A), (B) and6) in d₀For reference distances, typically taken as 1m, ξ₁In ideal free transmission space, xi, as path attenuation factor₁2, in the actual transmission environment, the value is between 2 and 5; the observation distance d between the RFID card reader and the label can be obtained by the following formula:

after the RFID positioning distance is measured, the RFID positioning distance and the GPS observation distance are weighted and calculated according to the proportion of the signal quantity of the RFID positioning distance and the GPS observation distance to be used for joint positioning, in a GPS/RFID combined positioning system, the positioning precision is represented by a GDOP value, the GDOP value is monotonically decreased along with the increase of the signal quantity of a GPS observation satellite, when the RFID observation value is increased, the GDOP value is also reduced, but when the RFID observation value is too much, the influence on the GDOP value is not obvious any more, and the calculation process of a computer is more complicated, so the RFID observation value is preferably selected as follows:

firstly, when the number N of visible satellites of the GPS system is more than or equal to 4, selecting a single RFID observation value according to the criterion of minimum positioning error contribution value;

secondly, when the number of visible satellites of the GPS system is not less than 0 and N is less than 4, selecting 4-N RFID observation values;

and 4, step 4: continuously monitoring the distance of the equipment in real time, dynamically simulating and calculating in real time to judge the motion condition of the equipment and whether the equipment is within each early warning distance, and sending out corresponding early warning instructions;

in the step 1, the simulation analysis program is based on a Vaga Prime software platform and C + + language programming, dynamic simulation of three-dimensional animation can be realized, the relative position relationship of a cable crane and a tower crane is calculated in real time, the operation state of the cable crane and the tower crane is judged, an early warning instruction is output, before the program is dynamically simulated, a three-dimensional model of a construction environment, the cable crane and the tower crane is established by CATIA software, 3D Max software is used for introducing the three-dimensional model and rendering the construction environment and a construction mechanical model, the immersion feeling of the three-dimensional model is increased, the rendered model is introduced into a Lynx graphical interface provided by Vaga Prime, and finally a positioning signal is introduced through a plug-in developed by programming to drive the cable crane and the tower crane three-dimensional model to realize dynamic simulation and real-time calculation analysis;

in step 3, the positioning signal processing program is based on a Matlab software platform and C + + language programming, and can realize reading positioning signals input into a computer by a GPS and an RFID receiver, filtering abnormal signals, preferably calculating more accurate positioning signals and then outputting the more accurate positioning signals to a specified position of the computer.

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