Automatic centering method of bridge crane with self-compensation function

Abstract

The invention discloses a bridge crane automatic centering method with a self-compensation function. The method comprises the steps that whether a lifting rope is in a straightened state or not is judged through a tension sensor; if the lifting rope is in the unstraightened state, the winding drum is controlled to rotate until the lifting rope is in the straightened state; if the lifting rope is in the straightened state, the real-time rope length of the lifting rope is obtained through an encoder; the centering benchmark is calculated according to the real-time rope length, the centering benchmark at different heights is compensated, and the cable-stayed angle of the lifting rope is obtained; calculating the offset of the lifting rope according to the diagonal angle of the lifting rope; and the large and small vehicles are operated for centering according to the lifting rope offset. Thus, the accurate relative position offset of the trolley and the hoisting load is obtained through the sensor and a designed centering compensation algorithm, then accurate automatic centering operation is achieved through the motion control system based on the PLC, accurate automatic centering of the bridge crane can be rapidly achieved in a short time, and the safety problem caused by inclined pulling and inclined hoisting is effectively avoided.

Description

Technical Field

[0001] The present application relates to the field of automation technology, and in particular to an automatic centering method for a bridge crane with a self-compensation function. Background Art

[0002] Bridge cranes are important equipment for mechanization and automation of production processes in modern industrial production and lifting. They are widely used in industrial and mining enterprises, steel and chemical industries, railway transportation, ports and terminals, and logistics turnover. The safety of their use has always been a matter of great concern to users and R&D personnel. Before the bridge crane is hoisted, the tilting and slanting of the lifting rope will bring more serious hazards. On the one hand, the force on the lifting rope increases during slanting, which may cause overload and even the accident of the lifting rope being broken. On the other hand, the horizontal component of force generated during slanting will cause the heavy object to swing toward the vertical center at the moment it leaves the ground or the carrier, and collide with the hanging personnel, surrounding workers or other objects, causing accidents. Therefore, when the bridge crane is hoisting, the lifting rope must pass through the center of gravity of the hoisted object and remain vertical.

[0003] Slanting refers to the situation that when the weight is on the ground, the center of gravity of the weight does not coincide with the median perpendicular line of the rope. If the weight is lifted at this moment, a large initial slanting angle will be generated, which may cause a safety accident. The principle of using a cable displacement sensor to measure the slanting angle of the rope is to fix the cable of the cable displacement sensor on the rope. When the rope swings, the cable will stretch or shrink. By measuring the vertical distance from the cable displacement sensor to the fixed point of the rope, the slanting angle of the rope can be calculated.

[0004] At present, the main method to solve the problem is to use the operator's human eyes to repeatedly adjust the crane, but the adjustment efficiency and automation level are low. Some companies have now taken measures to prevent cranes from tilting. To address this problem, the current solution is to monitor the tilt angle between the hook and the lifting center during lifting. When the tilt angle exceeds a given threshold, an audible and visual alarm is activated to stop lifting. Therefore, accurate measurement of the tilt angle is particularly important. Commonly used tilt angle measurement methods include: (1) detecting the tilt angle of the lifting rope based on an electronic angle sensor; (2) detecting the tilt angle of the lifting rope based on encoders on both directions of the trolley; (3) using machine vision technology to collect rope length images and analyze the tilt angle of the lifting rope; collecting hook images, and calculating the position of the hook center and the angle from the lifting center after image processing. Summary of the invention

[0005] The embodiment of the present application provides an automatic centering method for a bridge crane with a self-compensation function, which can quickly realize accurate automatic centering of the bridge crane in a short time and effectively avoid safety problems caused by crooked or slanted lifting.

[0006] In order to achieve the above object, the technical solution of the embodiment of the present invention is:

[0007] In a first aspect, an embodiment of the present invention provides an automatic centering method for a bridge crane with a self-compensation function, comprising:

[0008] The tension sensor is used to determine whether the suspension rope is in a stretched state; if the suspension rope is not in a stretched state, the reel is controlled to rotate until the suspension rope is in the stretched state;

[0009] If the suspension rope is in a straight state, the real-time rope length of the suspension rope is obtained through an encoder; the centering reference is calculated according to the real-time rope length, and the centering reference at different heights is compensated to obtain the inclined angle of the suspension rope;

[0010] Calculating the deflection of the suspension rope according to the suspension rope inclined angle;

[0011] The large and small carriages are operated for centering according to the offset of the lifting rope.

[0012] In some possible implementations, if the suspension rope is in an unstraightened state, the control drum is rotated until the suspension rope is in the straightened state, including: if the suspension rope is in the unstraightened state, the measured oblique angle of the suspension rope is greater than the theoretical oblique angle, and the real-time rope length is greater than the theoretical rope length, then the control drum is rotated until the suspension rope is in the straightened state.

[0013] In some possible implementations, the calculating of the centering reference according to the real-time rope length and compensating the centering reference at different heights to obtain the rope oblique angle includes: determining the rope oblique angle according to the centering reference, which is expressed by the following formula: q = tan -1 (2H / (WD)),

[0014] Among them, H is the lifting height; W is the distance between the two ends of the rope, which is proportional to the lifting height, that is, W=kH, k is the proportional constant; D is the diameter of the movable pulley; L is the rope length; q is the inclined angle of the rope; n is the vertical displacement from the wire displacement sensor to the fixed end of the rope; m is the wire length of the wire displacement sensor, m=n / tana.

[0015] In some possible implementations, the calculation of the rope offset according to the rope oblique angle includes: taking points A and B as the installation positions of the wire displacement sensor; point O is the intersection of the mounting frame, point C is the center position of the rope, point D is the position where the rope is in a "skewed" position, H and W are respectively the distances between the wire displacement sensors A and B and the origin of the coordinate system, and the values ​​are obtained by measurement; AC and BC are respectively based on the length of the wire in the centered state and obtained by calculation; AD and BD are respectively the length of the wire in the "skewed" state, which are measured by the wire displacement sensor; w and h are respectively the offsets in the directions of the large and small vehicles; w and h are obtained according to the cosine theorem, and are respectively expressed as:

[0016]

[0017]

[0018]

[0019] f=e+d-90°,

[0020] w=BD*sin(f),

[0021] h=AD*sin(b),

[0022] Among them, a is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the movement direction of the trolley, d is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the movement direction of the trolley, e is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the wire BD, f is the oblique angle in the trolley direction, and b is the oblique angle in the trolley direction.

[0023] In some possible implementations, operating the large and small vehicles for centering according to the suspension rope offset includes:

[0024] The displacement of the car to be corrected is x, and the speed of the car is v c , rope length l, rope retraction speed v l ; To ensure that the trolley moving speed matches the rope recovery speed during the centering process, x and l must satisfy: l = x / cosθ,

[0025] Differentiate both sides of the above equation with respect to time t to obtain: l =v x / cosθ, where θ is the inclined angle of the trolley direction;

[0026] The control strategy for automatic centering of anti-skewed and slanted cranes is to pre-straighten the ropes using the data from the tension sensor, and then make position corrections based on the slant angle as the centering criterion. During the correction process, the moving speeds of the trolleys and the rope retracting speeds are constrained.

[0027] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0028] The automatic centering method of a bridge crane with a self-compensation function of the present invention determines whether the suspension rope is in a straight state through a tension sensor; if the suspension rope is in a straight state, the real-time rope length of the suspension rope is obtained through an encoder; the centering reference is calculated according to the real-time rope length, and the centering reference at different heights is compensated to obtain the inclined angle of the suspension rope; the suspension rope offset is calculated according to the inclined angle of the suspension rope; and the large and small vehicles are operated for centering according to the deviation of the suspension rope. In this way, the accurate relative position offset of the trolley and the hoisting weight is obtained through the sensor and the designed centering compensation algorithm, and then the accurate automatic centering operation is realized through the motion control system based on PLC, which can quickly realize the accurate automatic centering of the bridge crane in a short time, and effectively avoid the safety problems caused by crooked and slanted lifting. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention, the accompanying drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0030] Figure 1 A schematic flow chart of an embodiment of an automatic centering method for a bridge crane with a self-compensation function provided for the implementation of the present invention;

[0031] Figure 2 This is a schematic diagram of a suspension rope not being stretched straight in an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of centering error provided for the implementation of the present invention;

[0033] Figure 4 A schematic diagram of the angle of the suspension rope provided for the implementation of the present invention;

[0034] Figure 5 The measurement principle diagram of the wire displacement sensor provided for the implementation of the present invention;

[0035] Figure 6 The automatic centering speed constraint principle diagram provided for the implementation of the present invention;

[0036] Figure 7 This is a schematic diagram of the installation of an automatic centering sensor in an embodiment of the present invention;

[0037] Figure 8 Schematic diagram of the automatic centering process in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] In the relevant description of this embodiment, the terms "including, containing, having" and the like are open terms and are generally understood as including but not limited to; the term "at least one" is generally understood as one or more, where "plurality" refers to two or more; the term "at least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items.

[0040] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0041] Those skilled in the art will appreciate that the numerical ranges in the embodiments of the present application are to be construed as also specifically disclosing each intermediate value between the upper and lower limits of the scope. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded in the scope.

[0042] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0043] Based on this, an embodiment of the present invention provides an automatic centering method for a bridge crane with a self-compensation function, which can quickly realize accurate automatic centering of the bridge crane in a short time and effectively avoid safety problems caused by crooked and slanted lifting.

[0044] Figure 1 A schematic diagram of an embodiment of a method for automatically centering a bridge crane with a self-compensation function provided by the present invention is shown in FIG. Figure 1 As shown, the above method may include:

[0045] S101, judging whether the suspension rope is in a stretched state by means of a tension sensor; if the suspension rope is in an unstretched state, controlling the reel to rotate until the suspension rope is in the stretched state.

[0046] It should be noted that if the suspension rope is not straightened before automatic centering, the measured inclined angle β 测 Greater than β理 , the measured rope length l 测 Greater than l 理 At this time, directly performing automatic centering will result in the inability to accurately measure the actual deviation angle of the suspension rope, so the centering function cannot be achieved. For details, see Figure 2 As shown, Figure 2 It is a schematic diagram of the suspension rope not being stretched straight in an embodiment of the present invention.

[0047] In order to avoid the phenomenon of centering error caused by the rope not being straightened before automatic centering, a method of using a tension sensor to detect the rope tension and then determine whether the rope is in a straight state is proposed. When the rope is in a straight state, the tension it is subjected to should be greater than a certain value. Since this value is in a range of variation, a fixed value can be assigned based on experience. Therefore, before the trolley performs position correction, the drum is controlled to rotate until the rope is in a straight state.

[0048] S102, if the suspension rope is in a straight state, the real-time rope length of the suspension rope is obtained through an encoder; the centering reference is calculated according to the real-time rope length, and the centering reference at different heights is compensated to obtain the inclined angle of the suspension rope.

[0049] The real-time rope length is obtained through the encoder, and the centering reference is calculated based on the real-time rope length. Figure 3 As shown, Figure 3 A schematic diagram of the centering error provided by an embodiment of the present invention. Since one end of the suspension rope is fixed, the angle of the suspension rope is different under different rope lengths, resulting in different measurement values ​​of the wire displacement sensor when the suspension rope is in the centering state at different heights, which results in different centering benchmarks at different heights, so it is necessary to compensate for the centering benchmarks at different heights.

[0050] See also Figure 4 As shown, Figure 4 A schematic diagram of the angle of the suspension rope provided in an embodiment of the present invention. Figure 4 The angle a can be obtained as:

[0051] q=tan -1 (2H / (WD)),

[0052] Among them, H is the lifting height; W is the distance between the two ends of the lifting rope, which is proportional to the lifting height, that is, W=kH, k is the proportional constant; D is the diameter of the movable pulley; L is the rope length; q is the inclined angle of the lifting rope; n is the vertical displacement from the wire displacement sensor to the fixed end of the lifting rope; m is the wire length of the wire displacement sensor.

[0053] Among them, the wire length w of the wire displacement sensor is expressed as:

[0054] m=n / tana.

[0055] S103, calculating the deviation of the suspension rope according to the suspension rope oblique angle.

[0056] Specifically, Figure 5 As shown, Figure 5 This is the measurement principle diagram of the cable displacement sensor. Points A and B are the installation positions of the cable displacement sensor; point O is the intersection of the mounting frame, which is also the origin of the coordinate system; point C is the center position of the suspension rope, and point D is the "tilted" position of the suspension rope. H and W are the distances between the cable displacement sensors A and B and the origin of the coordinate system, respectively. The values ​​can be known through measurement; AC and BC are the lengths of the cable in the center state, which are the reference and can be obtained through calculation; AD and BD are the lengths of the cable in the "tilted" state, respectively, which can be measured by the cable displacement sensor; w and h are the offsets in the direction of the large and small vehicles, respectively; w and h can be calculated according to the cosine theorem, that is:

[0057]

[0058]

[0059]

[0060] f=e+d-90°,

[0061] w = BD*sin(f).

[0062] Similarly, it can be determined that:

[0063] h=AD*sin(b).

[0064] Among them, a is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the movement direction of the trolley, d is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the movement direction of the trolley, e is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the wire BD, f is the oblique angle in the trolley direction, and b is the oblique angle in the trolley direction.

[0065] S104, operating the large and small vehicles for centering according to the offset of the lifting rope.

[0066] According to the offset of the trolley and the crane calculated in the previous step, the offset is reduced by running the trolley and the crane. In the process of automatic centering, the trolley movement and the rope retraction are required to be carried out simultaneously, so the trolley speed and the rope retraction speed need to be constrained to avoid the phenomenon that the rope is retracted too quickly, causing the weight to be lifted off the ground and swing during the centering process, or the rope is retracted too slowly, causing the rope to not be straightened, which increases the offset measurement error and affects the centering effect. In the process of rope retraction, the centering reference is continuously adjusted according to the change of rope length.

[0067] See also Figure 6 As shown, Figure 6The schematic diagram of the automatic centering speed constraint provided by the embodiment of the present invention, the displacement x of the trolley to be corrected, the speed v of the trolley x , rope length l, rope retraction speed v l To ensure that the trolley moving speed matches the rope recovery speed during the centering process, x and l must satisfy: l = x / cosθ, where θ is the trolley direction oblique angle;

[0068] Differentiate both sides of the above equation with respect to time t to obtain: l =v x / cosθ.

[0069] The control strategy for automatic centering of anti-skewed and slanted cranes is to first pre-straighten the rope using the data from the tension sensor, and then make position corrections based on the slant angle as the centering criterion. During the correction process, the moving speeds of the trolleys and the rope retracting speeds are constrained.

[0070] The automatic centering method of the bridge crane with self-compensation function of the present invention uses a tension sensor to detect the tension of the suspension rope and then judge whether the suspension rope is in a straight state. When the suspension rope is not in a straight state, the drum is controlled to rotate until the suspension rope is in a straight state; the real-time rope length is obtained through an encoder, and the centering reference is calculated according to the rope length and the centering reference at different heights is compensated; the displacement of the suspension rope is measured by a wire displacement sensor; and the large and small vehicles are operated for centering according to the measured displacement. In this way, the accurate relative position offset of the trolley and the hoisting weight is obtained through the sensor and the designed centering compensation algorithm, and then the precise automatic centering operation is realized through the motion control system based on PLC.

[0071] Figure 7 is a schematic diagram of the installation of the automatic centering sensor in an embodiment of the present invention, Figure 8 The automatic centering process in the embodiment of the present invention is a schematic diagram. Through the accurate automatic centering method of the bridge crane with self-compensation function of the present invention, the accurate automatic centering of the bridge crane can be quickly achieved in a short time, effectively avoiding the safety problems caused by crooked and slanted lifting.

[0072] In some embodiments, the above alignment method can also be used to perform an alignment test through the following process:

[0073] 1) Perform an alignment test on the trolley. The premise is to keep the trolley and the load in a centered state, that is, the trolley and the load are in the same plane and perpendicular to the ground, and the deflection angle is 0. At this time, change the initial position of the trolley to make it tilted and slanted with the load, and press the "Auto Centering" button on the control handle to start the automatic centering program. The experiment selected four different pre-centering deviations and corresponding deflection angles, and measured and recorded the centering deviations and corresponding centering deflection angles of the trolleys and loads after the automatic centering and manual centering experiments, as well as the time it took to complete the centering process. The recorded data is then processed to find out the improvement in centering accuracy and efficiency of automatic centering compared to manual centering. If the improvement effect exceeds 40%, it is qualified, otherwise it is considered unqualified;

[0074] 2) Perform an alignment test on the trolley. The premise is to keep the trolley and the load in a centered state, that is, the trolley and the load are in the same plane and perpendicular to the ground, and the deflection angle is 0. At this time, change the initial position of the trolley to make it tilted and tilted with the load, and press the "Auto Centering" button on the control handle to start the automatic centering program. The experiment selected four different pre-centering deviations and corresponding deflection angles, and measured and recorded the centering deviations and corresponding centering deflection angles of the trolleys and loads after the automatic centering and manual centering experiments, as well as the time it took to complete the centering process. The recorded data is then processed to find out the improvement in centering accuracy and efficiency of automatic centering compared to manual centering. If the improvement effect exceeds 40%, it is qualified, otherwise it is considered unqualified;

[0075] 3) Perform alignment tests on the large and small vehicles at the same time, change the initial positions of the large and small vehicles so that they are tilted and slanted with the load, and press the "Auto Centering" button on the control handle to start the automatic centering program. The experiment selected four different groups of pre-centering deviations and corresponding deflection angles, measured and recorded the centering deviations and corresponding centering deflection angles of the large and small vehicles after the automatic centering and manual centering experiments, as well as the time it took to complete the centering process. The recorded data is then processed to find out the improvement in centering accuracy and efficiency of automatic centering compared to manual centering. If the improvement exceeds 40%, it is qualified, otherwise it is considered unqualified;

[0076] The test results of the above test process are shown in Tables 1 to 6 below:

[0077] Table 1 shows the trolley alignment test

[0078]

[0079] Among them, east and north are defined as positive directions (+), and west and south are defined as negative directions (-);

[0080] Table 2 is the data processing of the trolley direction alignment test

[0081]

[0082] The calculation method for the indicator improvement effect in the definition table is (manual centering result - automatic centering result) / manual centering result, which represents the percentage of improvement in accuracy and efficiency of automatic centering compared with manual centering.

[0083] Table 3 shows the trolley alignment test

[0084]

[0085] Table 4 shows the data processing of the truck centering test.

[0086] Parameters Manual centering Automatic centering Index improvement effect (%) Average value of deflection angle after centering 0.292° 0.114° 60.96 Average deviation after centering 3.125cm 1.225cm 60.80 Average alignment time 33.56s 13.698s 59.18

[0087] Table 5 shows the simultaneous alignment test of large and small vehicles

[0088]

[0089] Table 6 shows the data processing of the simultaneous centering test of large and small vehicles.

[0090]

[0091]

[0092] The automatic centering method of a bridge crane with a self-compensation function of the present invention determines whether the suspension rope is in a straight state through a tension sensor; if the suspension rope is in a straight state, the real-time rope length of the suspension rope is obtained through an encoder; the centering reference is calculated according to the real-time rope length, and the centering reference at different heights is compensated to obtain the inclined angle of the suspension rope; the suspension rope offset is calculated according to the inclined angle of the suspension rope; and the large and small vehicles are operated for centering according to the deviation of the suspension rope. In this way, the accurate relative position offset of the trolley and the hoisting weight is obtained through the sensor and the designed centering compensation algorithm, and then the accurate automatic centering operation is realized through the motion control system based on PLC, which can quickly realize the accurate automatic centering of the bridge crane in a short time, and effectively avoid the safety problems caused by crooked and slanted lifting.

[0093] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0094] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A method for automatic centering of a bridge crane with a self-compensation function, characterized in that: The method comprises: The tension sensor is used to determine whether the suspension rope is in a stretched state; if the suspension rope is not in a stretched state, the reel is controlled to rotate until the suspension rope is in the stretched state; If the suspension rope is in a straight state, the real-time rope length of the suspension rope is obtained through an encoder; the centering reference is calculated according to the real-time rope length, and the centering reference at different heights is compensated to obtain the inclined angle of the suspension rope; Calculating the deflection of the suspension rope according to the suspension rope inclined angle; The large and small carriages are operated for centering according to the offset of the lifting rope.

2. The method according to claim 1, characterized in that: If the suspension rope is in an unstretched state, the reel is controlled to rotate until the suspension rope is in the stretched state, comprising: If the suspension rope is in the unstretched state, the measured suspension rope oblique angle is greater than the theoretical oblique angle, and the real-time rope length is greater than the theoretical rope length, the control drum is rotated until the suspension rope is in the stretched state.

3. The method according to claim 1, characterized in that The calculating of the centering reference according to the real-time rope length and compensating the centering reference at different heights to obtain the inclined angle of the suspension rope include: According to the centering reference, the inclined angle of the suspension rope is determined and expressed by the following formula: q−tan -1 (2H / (WD)), Among them, H is the lifting height; W is the distance between the two ends of the rope, which is proportional to the lifting height, that is, W=kH, k is the proportional constant; D is the diameter of the movable pulley; q is the inclined angle of the rope; L is the rope length; n is the vertical displacement from the wire displacement sensor to the fixed end of the rope; m is the wire length of the wire displacement sensor, m=n / tana.

4. The method according to claim 3, characterized in that: The calculating the suspension rope offset according to the suspension rope oblique pulling angle comprises: Points A and B are the installation positions of the cable displacement sensor; point O is the intersection of the mounting frame, point C is the center position of the lifting rope, and point D is the "skewed" position of the lifting rope. H and W are the distances between the cable displacement sensors A and B and the origin of the coordinate system, respectively, and the values ​​are obtained through measurement; AC and BC are based on the cable lengths in the centering state, respectively, and are obtained through calculation; AD and BD are the cable lengths in the "skewed" state, respectively, and are measured by the cable displacement sensor; w and h are the offsets in the directions of the large and small vehicles, respectively; According to the cosine theorem, w and h are expressed as: f=e+d-90°, w=BD*sin(f), h=AD*sin(b), Among them, a is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the movement direction of the trolley, d is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the movement direction of the trolley, e is the angle between the line connecting the installation positions of the two wire-type displacement sensors and the wire BD, f is the oblique angle in the trolley direction, and b is the oblique angle in the trolley direction.

5. The method according to claim 4, characterized in that The large and small carriages are operated to align according to the said lifting rope offset, including: The displacement of the car to be corrected is x, and the speed of the car is v x , rope length l, rope retraction speed v l ; To ensure that the trolley moving speed matches the rope recovery speed during the centering process, x and l must satisfy: l = x / cosθ, Differentiate both sides of the above equation with respect to time t to obtain: l =v x / cosθ, where θ is the inclined angle of the trolley direction; The control strategy for automatic centering of anti-skewed and slanted cranes is to pre-straighten the ropes using the data from the tension sensor, and then make position corrections based on the slant angle as the centering criterion. During the correction process, the moving speeds of the trolleys and the rope retracting speeds are constrained.

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