A method and system for detecting the height of a heavy object suspended by a crane hook

Abstract

The present invention discloses a method and system for detecting the height of a heavy object suspended by a crane hook. No additional sensors are required. The height of the heavy object can be obtained by using the existing electronic control system of the crane in combination with a height calculation algorithm. The height of the heavy object refers to the height after the sling and the heavy object are connected together, that is, the height from the bottom of the hook to the bottom of the heavy object. The electronic control system of the hoisting mechanism of the crane adopts a frequency converter for speed regulation. The frequency converter adopts a closed-loop vector control mode. The hoisting motor is equipped with an incremental encoder. The motor encoder signal is connected to the frequency converter encoder card.

Description

Technical Field

[0001] The present invention relates to the field of crane detection technology, and more particularly to a method and system for detecting the height of a heavy object suspended by a crane hook. Background Art

[0002] At present, with the development of intelligent and safe cranes, how to actively avoid obstacles (avoid hitting obstacles) when the hook suspends heavy objects during automatic operation is an inevitable topic for intelligent and safe cranes. To achieve active obstacle avoidance, the height of the suspended heavy object must be obtained first, so that the heavy object suspended by the hook can be controlled to rise to a suitable height and cross the obstacles raised on the ground, which can not only take into account efficiency but also achieve the purpose of safe operation. Usually, the weights suspended by the crane in the actual working process are of various sizes and shapes, and the slings or wire ropes used to connect the hook and the heavy objects are also of different lengths. For example, the bundled steel bars, bucket cars, steel coils and other objects suspended by tower cranes on the construction site are of various shapes and shapes. If sensors are used to detect the height between the bottom of the hook and the bottom of these heavy objects, the installation position of the sensor, the harsh on-site environment, the power supply method, the detection accuracy and the cost are all issues that need to be considered. The detection scheme is quite complicated to implement and the reliability is not high.

[0003] Therefore, how to improve the convenience and reliability of detecting the height of a heavy object suspended by a crane hook is an issue that technical personnel in this field urgently need to solve. Summary of the invention

[0004] In view of this, the present invention provides a method and system for detecting the height of a heavy object suspended by a crane hook. No additional sensors are required. The height of the heavy object can be obtained by using the existing electronic control system of the crane in combination with a height calculation algorithm. The height of the heavy object refers to the height after the sling and the heavy object are connected together, that is, the height from the bottom of the hook to the bottom of the heavy object. The electronic control system of the crane's hoisting mechanism adopts a frequency converter for speed regulation. The frequency converter adopts a closed-loop vector control mode. The hoisting motor is equipped with an incremental encoder. The motor encoder signal is connected to the frequency converter encoder card.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for detecting the height of a heavy object suspended by a crane hook comprises the following steps:

[0007] Step 1: The crane hook is suspended in the air. When the inverter of the crane hoisting mechanism electric control system controls the hook to rise to the lifting end limit of the hoisting mechanism and stops, the inverter clears the encoder value;

[0008] The hook is not hung with any slings or heavy objects. The inverter controls the hook to rise to the lifting end limit of the lifting mechanism and stops. The inverter clears the encoder value to 0.

[0009] Step 2: Collect the encoder value Encode1 when the inverter controls the hook to descend to the ground until the bottom of the hook just touches the ground;

[0010] The bottom of the hook just touches the ground and stops. Record the encoder code value Encode1 displayed on the inverter panel at this time.

[0011] Step 3: Collect the encoder value Encode2 when the inverter controls the hook to rise to the position of the set unit distance from the ground;

[0012] The inverter controls the hook to rise precisely to a position 1 meter above the ground. Record the encoder code value Encode2 displayed on the inverter panel at this time.

[0013] Step 4: Calculate the code value of the unit distance of the hook rise according to the encoder value Encode1 and the encoder value Encode2;

[0014] At this point, the code value for each meter the hook rises can be obtained, expressed as a variable PPM. The calculation formula for PPM is as follows:

[0015] PPM=|Encode2-Encode1|

[0016] The value of PPM is a positive value. Take the absolute value in the calculation formula and fill the value of PPM into the corresponding parameter of the inverter;

[0017] Step 5: Collect the load torque value LoadTorque1 when the inverter controls the hook to rise at a preset speed when it is suspended in the air;

[0018] The inverter controls the hook to rise at a steady speed of 10HZ. Record the load torque value LoadTorque1 displayed on the inverter panel at steady speed, and fill this value into the inverter parameters.

[0019] Step 6: When the hook is hanging a heavy object, the inverter controls the hook to rise at a preset speed, and collects the load torque value LoadTorque2 when the heavy object is completely off the ground according to the load torque value LoadTorque1, as well as the encoder code value Encode3;

[0020] Control the hook to move to the top of the weight, fix the weight with one end of the sling or wire rope, and then hang the other end of the sling or wire rope on the hook; after hanging, the inverter controls the hook to rise at a speed of 10HZ. During the hook rising process, the inverter will detect the change of load torque in real time until the weight is completely lifted off the ground by the hook. The load torque will no longer increase and the load torque value will become LoadTorque2;

[0021] If the load torque value LoadTorque2 does not change for 0.5 seconds, it can be judged that the weight has completely left the ground, and the inverter will record the encoder code value Encode3 at this moment;

[0022] Step 7: Calculate the height of the weight suspended by the hook, that is, the height from the bottom of the hook to the bottom of the weight, according to the code value of the unit distance of the hook rise, the encoder code value Encode1 and the encoder code value Encode3;

[0023] According to the PPM obtained in S4 and Encode1 obtained in S2, calculate the height H between the bottom of the hook and the bottom of the weight. The calculation formula is as follows:

[0024] H = |Encode3-Encode1| / PPM.

[0025] Preferably, in step 1, the frequency converter controls the hoisting motor to rotate forward, and the hoisting motor drives the hook to rise to the rising end limit through the drum, wire rope, and pulley. After receiving the rising end limit signal, the frequency converter controls the motor to stop. At this time, the frequency converter clears the encoder value fed back by the encoder to 0, and the position with the code value of 0 is used as the position reference point of the hook;

[0026] The inverter clears the code value fed back by the encoder to 0, which means that when the hook is at the rising end limit, the inverter will receive the switch signal of the rising end limit. The limit switch signal is connected to the digital input terminal signal of the inverter. After receiving the signal, the inverter clears the code value of the encoder to 0.

[0027] Preferably, in step 2, the frequency converter controls the hook to descend to the ground until the bottom of the hook just touches the ground. Stopping means that the driver operates the lifting handle and gives the frequency converter a reverse command, and then the frequency converter controls the hook to descend. When it descends close to the ground, the driver can give the frequency converter a forward or reverse command through the lifting handle to adjust it until the bottom of the hook just touches the ground. At this time, the ground cannot have any supporting force on the hook.

[0028] Preferably, in step 3, the unit distance is 1 meter, and the method in which the frequency converter controls the hook to rise precisely to a position 1 meter from the ground means that the frequency converter controls the hook to rise until the height between the bottom of the hook and the ground is exactly 1 meter.

[0029] Preferably, in step 5, the inverter controls the motor in a closed-loop vector control mode, and the load torque is an important calculation variable for the inverter to control the motor operation. The load torque is a characteristic value that characterizes the weight of the load carried by the motor. The heavier the weight of the weight carried by the motor, the greater the load torque, and the lighter the weight of the weight, the smaller the load torque; the load torque value LoadTorque1 characterizes the load weight of the motor with an empty hook, and is a calibration value of the empty hook load weight.

[0030] Preferably, in step 6, the specific method of fixing the heavy object with one end of the sling or wire rope and then hanging the other end of the sling or wire rope on the hook is:

[0031] When the two ends of a sling or wire rope are hung on a heavy object and a hook respectively, a certain length of surplus is left on the sling or wire rope for the convenience of hooking. After the two ends are hung, the sling or wire rope with a certain length of surplus is hung down.

[0032] Preferably, in step 6, during the hook rising process, since the sling or wire rope is initially hanging down, the sling or wire rope will first be gradually straightened by the hook, and the load torque of the inverter at this time is LoadTorque1 in S5. The weight will not be lifted off the ground until the sling or wire rope is straightened and tightened, and the load torque of the inverter will increase rapidly during the process of the weight being lifted off the ground. The load torque will no longer increase until the weight is completely lifted off the ground by the hook, and the load torque value becomes LoadTorque2.

[0033] Preferably, in step 6, the load torque will no longer increase. Maintaining a stable value means that after the weight leaves the ground, the ground no longer has any supporting force on the weight, and the load torque will no longer change. This stable value is greater than the load torque value LoadTorque1, and after 0.5 seconds, the inverter records the encoder code value at this time, that is, the value of Encode3.

[0034] A system for detecting the height of a heavy object suspended by a crane hook, comprising a lifting mechanism electric control system and a detection mechanism;

[0035] The electric control system of the lifting mechanism includes a lifting motor and a frequency converter; the frequency converter controls the lifting motor to drive the hook up or down; the encoder of the frequency converter records the encoder value and load torque value, and transmits them to the detection mechanism;

[0036] The detection mechanism calculates the height of the hook hanging the weight according to the encoder value and the load torque value.

[0037] Through the above technical scheme, it can be known that compared with the prior art, the present invention discloses a method and system for detecting the height of a heavy object suspended by a crane hook. The height of the heavy object can be obtained by using the existing electronic control system of the crane in combination with the height calculation algorithm. The encoder code value when the hook is suspended in the air, just touching the ground, and rising to a unit height is collected by the frequency converter of the electronic control system of the crane hoisting mechanism, and the code value of the calculated hook rising unit distance is collected. Then, by collecting the load torque of the steady rise of the hook when the hook is suspended in the air, and the load torque value and encoder code value when the heavy object is suspended until the heavy object just leaves the ground, the height of the heavy object suspended by the hook is obtained according to the code value of the unit distance of the hook rise and the encoder code value when the heavy object is suspended. The load torque value is used to determine whether the hook or the heavy object is completely lifted. After the heavy object is hung on the hook, the sling or wire rope is hanging down and will not be in a tensioned state. Only when the heavy object is lifted off the ground by the hook through the sling or wire rope and the sling or wire rope is in a fully tensioned state can the true height between the bottom of the hook and the bottom of the heavy object be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0039] Figure 1 The accompanying drawing is a schematic diagram of hook data calibration provided by the present invention;

[0040] Figure 2 The accompanying drawing is a schematic diagram of the heavy object lifting process provided by the present invention;

[0041] Figure 3 The accompanying drawing is a schematic diagram of the change of load torque during the lifting process of a heavy object provided by the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] A method for detecting the height of a heavy object suspended by a crane hook provided in an embodiment of the present invention comprises:

[0044] Figure 1The main purpose is to calibrate the hook 1 during the debugging phase. The hook data calibration includes four steps, namely S1, S2, S3, and S4. These four steps should be performed in sequence.

[0045] S1 is to find a fixed height on the crane as the reference point for the position of hook 1. Since cranes are equipped with a limit switch at the end of the rise to prevent dangerous accidents, hook 1 will automatically stop when it receives the action signal of the limit switch during the rising operation, so it is most appropriate to use the limit position at the end of the rise as the reference point. The inverter controls the hook to rise L1 to the limit position at the end of the rise, and the inverter will receive the limit signal at the end of the rise. At this time, the code value fed back by the encoder is cleared to 0, and the code value of 0 is used as the reference point for the position of hook 1.

[0046] S2 is to get the encoder code value Encode1 when the bottom of hook 1 touches the ground. The inverter controls the hook to descend to the ground until the bottom of the hook just touches the ground and stops. Record the encoder code value Encode1 displayed on the inverter panel at this time. Encode1 is an important data for subsequent calibration and calculation of the height of the heavy object.

[0047] S3 is to get the code value for every rise of the hook L2 = 1 meter. The inverter controls the hook to rise until the bottom of the hook is exactly 1 meter above the ground. This can be measured with a ruler. Record the encoder code value Encode2 displayed on the inverter panel at this time. The code value for every rise of the hook 1 by 1 meter can be calculated through Encode2 and Encode1 recorded in step S2. This code value is represented by the variable PPM. The calculation formula of PPM is as follows:

[0048] PPM=|Encode2-Encode1|

[0049] The value of PPM is a positive value. Take the absolute value in the calculation formula and fill the value of PPM into the corresponding parameter of the inverter. PPM is an important data for calculating the height of heavy objects in the subsequent steps.

[0050] S4 is to obtain the load torque value LoadTorque1 when the empty hook rises at 10HZ. The inverter controls the hook to rise at a steady speed of 10HZ, records the load torque value LoadTorque1 displayed on the inverter panel at steady speed, and fills this value into the inverter parameters. LoadTorque1 is a judgment value used to determine whether the sling or wire rope 2 has been straightened. When the inverter detects that the load torque value LoadTorque2 is greater than LoadTorque1 during the process of lifting the heavy object off the ground, it is considered that the wire rope has been tensioned, that is, straightened.

[0051] After the above data calibration is completed, the height of the heavy object suspended by the hook can be detected in real time during the actual lifting operation of the crane.

[0052] Figure 2 It is a schematic diagram of the process of crane lifting heavy objects from the ground during actual lifting operations. Figure 3 This is a schematic diagram of the load torque changes during the lifting process. Figure 2 and Figure 3 The moment when the weight leaves the ground can be obtained, and then the height from the bottom of the hook to the bottom of the weight can be calculated, including three steps S5, S6 and S7.

[0053] S5: Control the hook 1 to move to the vicinity of the top of the weight, fix the weight with one end of the sling or wire rope 2, and then hang the other end of the sling or wire rope 2 on the hook 1. For the convenience of hooking, the sling or wire rope 2 has a certain length of surplus, and after both ends are hung, the sling or wire rope 2 with a certain length of surplus is hung down, and the hook height is H1.

[0054] S6: After hanging, the inverter controls the hook 1 to rise steadily at a speed of 10HZ. The hook speed and load torque values ​​change with time as shown in the following figure. Figure 3 As shown, Figure 3 The middle line a represents the hook speed, and the curve b represents the load torque. The acceleration of hook 1 from 0HZ to 10HZ corresponds to Figure 3 The time period 0-t1 should be short enough, generally about 0.4 seconds. During the rising process of hook 1, since the sling or wire rope 2 is initially hanging down, the sling or wire rope 2 will first be gradually straightened by hook 1 to a height of H2. This process corresponds to Figure 3 During the period of 0-t2, the load torque value of the inverter during this period is LoadTorque1. The weight will not be lifted off the ground until the sling or wire rope 2 is straightened and tightened. During the process of the weight being lifted off the ground, the load torque of the inverter will increase rapidly from LoadTorque1 until the weight is completely lifted off the ground by hook 1. The load torque will no longer increase and the load torque value will become LoadTorque2. This process corresponds to Figure 3 The period of time t2-t3.

[0055] S7: If the load torque value LoadTorque2 in S6 does not change for 0.5 seconds, it can be judged that the weight has completely left the ground. This process corresponds to Figure 3 The inverter will record the encoder code value Encode3 at this moment. According to the PPM obtained in S2 and Encode2 obtained in S4, the height H3 between the bottom of the hook and the bottom of the weight can be calculated. The calculation formula is as follows:

[0056] H3=|Encode3-Encode1| / PPM

[0057] In the actual operation of the crane, when lifting different heavy objects, LoadTorque2 will be different depending on the weight of the heavy objects, but once the same heavy object is lifted, the load torque is a stable value.

[0058] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0059] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting the height of a heavy object suspended by a crane hook, characterized in that: The following steps are involved: Step 1: The crane hook is suspended in the air. When the inverter of the crane hoisting mechanism electric control system controls the hook to rise to the lifting end limit of the hoisting mechanism and stops, the inverter clears the encoder value; Step 2: Collect the encoder value Encode1 when the inverter controls the hook to descend to the ground until the bottom of the hook just touches the ground; Step 3: Collect the encoder value Encode2 when the inverter controls the hook to rise to the position of the set unit distance from the ground; Step 4: Calculate the code value of the unit distance of the hook rise according to the encoder value Encode1 and the encoder value Encode2; Step 5: Collect the load torque value LoadTorque1 when the inverter controls the hook to rise at a preset speed when it is suspended in the air; Step 6: When the hook is hanging a heavy object, the inverter controls the hook to rise at a preset speed, and collects the load torque value LoadTorque2 when the heavy object is completely off the ground according to the load torque value LoadTorque1, as well as the encoder code value Encode3; Step 7: Calculate the height of the weight suspended by the hook according to the code value of the unit distance of the hook rise, the encoder code value Encode1 and the encoder code value Encode3; The calculation formula for the code value of the unit distance of the hook rise in step 4 is: PPM= |Encode2- Encode1|; The calculation formula for the height of the weight suspended by the hook in step 7 is: H=|Encode3- Encode1| / PPM PPM is the code value of the unit distance of the hook rise.

2. A method for detecting the height of a heavy object suspended by a crane hook according to claim 1, characterized in that: In step 1, the inverter controls the lifting motor to rotate forward, and controls the lifting motor to stop after receiving the rising end limit signal. The inverter clears the encoder value fed back by the encoder to 0, and the current position is used as the position reference point of the hook; the rising end limit is connected to the digital input terminal of the inverter, and the limit switch signal is sent to the inverter.

3. A method for detecting the height of a heavy object suspended by a crane hook according to claim 1, characterized in that: In step 2, the inverter is given a reverse command by operating the lifting handle, and then the inverter controls the hook to descend. The inverter is given a forward or reverse command through the lifting handle until the bottom of the hook just touches the ground. At this time, there is no supporting force on the hook from the ground.

4. A method for detecting the height of a heavy object suspended by a crane hook according to claim 1, characterized in that: In step 5, the frequency converter controls the motor to adopt a closed-loop vector control mode, and collects a load torque value LoadTorque1, where the load torque value LoadTorque1 represents the load weight when the motor drives the suspended hook.

5. A method for detecting the height of a heavy object suspended by a crane hook according to claim 1, characterized in that: In step 6, the two ends of the sling or wire rope are hung on the weight and the hook respectively, and the sling or wire rope is in a hanging state. The inverter controls the hook to rise at a preset speed, and the sling or wire rope is gradually straightened by the hook. The load torque value of the inverter gradually increases until the sling or wire rope is straightened and tensioned, and the weight is lifted off the ground by the hook, and the load torque value will no longer increase.

6. A method for detecting the height of a heavy object suspended by a crane hook according to claim 1, characterized in that: In step 6, if the load torque value LoadTorque2 is greater than the load torque value LoadTorque1 and remains stable for 0.5 seconds, the encoder code value Encode3 is recorded.

7. A detection system for the method for detecting the height of a heavy object suspended by a crane hook according to any one of claims 1 to 6, characterized in that: Including lifting mechanism electric control system and detection mechanism; The electric control system of the lifting mechanism includes a lifting motor and a frequency converter; the frequency converter controls the lifting motor to drive the hook up or down; the encoder of the frequency converter records the encoder value and load torque value, and transmits them to the detection mechanism; The detection mechanism calculates the height of the hook hanging the weight according to the encoder value and the load torque value.

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