Obstacle avoidance trajectory planning method for bridge crane

Abstract

The application discloses a kind of barrier avoidance trajectory planning methods for bridge crane, including: barrier avoidance trajectory planning methods for bridge crane, including independent trajectory planning, define trolley moving range within barrier point information, screen effective barrier point and solve barrier point peak value, consider barrier avoidance trolley start timing calculation, consider barrier avoidance rope drop segment timing calculation and the like steps, by setting barrier point information to define the barrier body in work area, simplify the setting operation of barrier body, and can conveniently carry out barrier avoidance judgment;By the trajectory execution strategy of bridge crane is decomposed into three parts, independent planning is carried out rope ascending segment trajectory, rope drop segment trajectory and trolley moving trajectory instruction, solve the current barrier avoidance trajectory planning method of bridge crane, need to be set in advance complex barrier body, leading to complex process;Or roughly adopt single trajectory execution strategy, leading to the problem of poor accuracy of barrier avoidance.

Description

Technical Field

[0001] This invention relates to the field of crane technology, specifically to an obstacle avoidance trajectory planning method for bridge cranes. Background Technology

[0002] Cranes are primarily used for lifting operations, an industrial process that transports machinery or other objects from one location to another. Most cranes, after the lifting device picks up the material, begin their vertical or combined vertical and horizontal working stroke. Upon reaching the destination, they unload the material and then travel empty back to the picking location, completing one work cycle. Currently, the design for obstacle avoidance during crane operation in China generally uses a PLC programmable controller combined with trolley and crane positioning devices. By using specific algorithms within the PLC programmable controller, the safe operating range of the crane's trolley and crane mechanisms is pre-programmed to achieve obstacle avoidance during crane operation. However, this approach results in high crane costs, requiring extensive and complex programming within the PLC programmable controller and cumbersome on-site installation of the trolley and crane positioning devices.

[0003] Some companies have developed control methods based on various algorithms to achieve obstacle avoidance, but these require complex obstacle settings in advance, leading to complicated processes; or they crudely adopt a single trajectory execution strategy, resulting in poor obstacle avoidance accuracy.

[0004] To address the aforementioned issues, the applicant, based on the current safety production situation, developed this obstacle avoidance trajectory method. Targeting the physical and control characteristics of the electromechanical equipment of the bridge crane, the method defines obstacles within the working area by setting obstacle point information. Furthermore, by decomposing the bridge crane's trajectory execution strategy into three parts, and employing a time prediction and comparison method to determine the timing of the starting trolley and the starting rope descent segment trajectory commands, obstacle avoidance is achieved, ensuring the safety of the bridge crane's automatic trajectory execution. Summary of the Invention

[0005] The purpose of this invention is to provide an obstacle avoidance trajectory planning method for bridge cranes, in order to solve the problems mentioned in the background art, which are that the current obstacle avoidance trajectory planning methods for bridge cranes require the pre-setting of complex obstacles, resulting in a complicated process; or that they crudely adopt a single trajectory execution strategy, resulting in poor obstacle avoidance accuracy.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for obstacle avoidance trajectory planning for bridge cranes, characterized by comprising the following steps: Step 1: Independent trajectory planning; specifically including: 1) Based on the starting position of the target trajectory End position and intermediate height information Independently plan the trajectory of the rope ascending segment, the trajectory of the rope descending segment, and the trolley movement trajectory; discretize each segment trajectory into several command points with equal time intervals, and arrange the command points in chronological order to form a trajectory command sequence; The specific forms of the starting and ending positions are as follows: ; ; In the formula, It is the starting position point. This is the starting position value of the trolley. This is the starting rope length position value. It is the termination point. It is the termination position value of the trolley. This is the position value of the termination rope length; 2) Construct the instruction sequence for the rope ascent segment; based on the known initial rope length position value. and intermediate height information The change in rope length during the ascending section was calculated. :

[0007] Obtain the change in rope length during the ascending section Then, by combining the upper limits of the lifting speed and acceleration, the command sequence for the rope ascent segment trajectory can be obtained. ; The specific form of the rope ascent trajectory instruction sequence is as follows:

[0008] In the formula, There are n time intervals. The rope speed command; 3) Construct the rope length variation of the rope descent section and the sequence of instructions for the rope descent segment :

[0009]

[0010] In the formula, It is m time intervals. The rope speed command; 4) Construct the change in the distance of the car and the sequence of instructions for the movement trajectory of the vehicle :

[0011]

[0012] In the formula, It is k time intervals. The vehicle speed command; Step 2: Define obstacle point information within the trolley's movement range; simplify the obstacle avoidance problem of the lifting device into a 2D traversal obstacle avoidance problem; describe the obstacle profile through several obstacle points, and represent the obstacle point information as follows: Each obstacle point consists of the car's position value and the rope length position value. The obstacle information is arranged in order of the car's position, and there are a total of n obstacle points; Step 3: Selecting valid obstacle points and solving for the peak value of obstacle points; specifically including: 1) Valid obstacle information filtering: Obstacles within the range of the target vehicle's starting and ending positions are defined as valid obstacles. Before trajectory execution begins, valid obstacle information is filtered based on the vehicle's starting and ending position values. The valid obstacle point information meets the following conditions:

[0013] In the formula, The position value of the car for the valid obstacle point item. The rope length position value of the valid obstacle point item, k is the starting index value of the valid obstacle point information, and m is the number of valid obstacle point information elements; 2) Solve for the peak value at the obstacle point The obstacle point with the shortest rope length (i.e., the highest height above the ground) in the valid obstacle point information is defined as the obstacle point peak value. If multiple obstacle point peak rope length values ​​are equal, the point closest to the starting position of the vehicle is taken as the obstacle point peak value. .

[0014] Preferably, the trolley speed must not exceed the upper speed and acceleration limits specified in the performance indicators of the bridge crane's rope control.

[0015] Preferably, after selecting the effective obstacle points and solving for the peak value of the obstacle points, the following steps are also required: Step 4: Calculate the starting timing of the obstacle avoidance vehicle, defining the sequence of vehicle speed commands. The start time for sending the vehicle speed is the vehicle's startup timing; after obtaining the obstacle peak, trajectory execution begins. At the start of the trajectory, the speed command for the rope ascent segment is executed first. At this time, the vehicle has not yet started. Then, the following method is used to analyze in real time whether the vehicle can be started: 1) Filter out obstacle information for the rope ascent section. The obstacle point information in the ascending phase meets the following conditions:

[0016] In the formula, The position value of the car for the effective obstacle point item in the ascending segment. The rope length position value for the effective ascending obstacle point item. This is the current real-time position value of the car. s is the current real-time rope length position value, s is the starting index value of the obstacle point information in the ascending section, and t is the number of obstacle point information elements in the ascending section. 2) Use a time prediction comparison method to determine whether to start the car. Assume the car starts from the current moment and executes the sequence of car movement trajectory instructions. Real-time calculation of the time from the current position of the vehicle to the position of the vehicle at each obstacle point in the ascent segment. And the time from the current rope length position to the rope length position at each obstacle point of the ascent segment. .

[0017] The car can be started if the following conditions are met: .

[0018] Preferably, after selecting the effective obstacle points and solving for the peak value of the obstacle points, the following steps are also required: Step 5: Calculate the timing of the rope descent segment considering obstacle avoidance; define the instruction sequence according to the rope descent segment trajectory. The start time for sending the vehicle's speed is the timing of the rope descent segment. Once the vehicle starts and has crossed the obstacle peak, the system analyzes in real time whether the rope descent segment trajectory command can be initiated based on the following obstacle avoidance strategy: 1) Filter out obstacle information for the rope descent section. The obstacle point information during the descent phase meets the following conditions:

[0019] In the formula, The position value of the car for the effective obstacle point sub-item during the descent segment. The rope length position value for the effective obstacle point item in the descent phase. This is the current real-time position value of the car. Here, u represents the currently obtained real-time rope length position value, v represents the starting index value of the obstacle point information in the descent segment, and v represents the number of obstacle point information elements in the descent segment. This condition indicates that, for each instruction moment, any sub-item of obstacle point information in the descent segment satisfies the following conditions: its trolley position value is within the range of the current real-time trolley starting position value and the target trolley ending position value, and its rope length position value is within the range of the current real-time rope length position value and the ending rope length position value.

[0020] 2) Use a time prediction comparison method to determine whether to initiate the rope descent trajectory command. Assuming the rope descent trajectory command is initiated from the current moment, execute the rope descent trajectory command sequence. Real-time calculation of the time from the current position of the vehicle to the position of the vehicle at each obstacle point in the descent segment. And the time from the current rope length position to the rope length position at each obstacle point in the descent. , If the following conditions are met, it indicates that the rope descent trajectory command can be initiated: .

[0021] Compared with the prior art, the beneficial effects of the present invention are: This obstacle avoidance trajectory planning method for bridge cranes includes steps such as independent trajectory planning, defining obstacle point information within the trolley's movement range, filtering effective obstacle points and solving for obstacle point peak values, calculating the trolley start timing considering obstacle avoidance, and calculating the rope descent timing considering obstacle avoidance. By defining obstacles within the working area through setting obstacle point information, the method simplifies obstacle setting operations and facilitates obstacle avoidance judgment. By decomposing the bridge crane trajectory execution strategy into three parts—the rope ascent trajectory, the rope descent trajectory, and the trolley movement trajectory command—it independently plans these three parts. A time prediction comparison method is used to determine the timing of the trolley start and the rope descent trajectory start commands, thereby achieving obstacle avoidance and ensuring the safety of the bridge crane's automatic trajectory execution. This method solves the problems of current obstacle avoidance trajectory planning methods for bridge cranes, which require complex obstacle setting in advance, leading to complicated processes, or crudely employ a single trajectory execution strategy, resulting in poor obstacle avoidance accuracy. Attached Figure Description

[0022] Figure 1 This is a flowchart of an obstacle avoidance trajectory planning method for a bridge crane according to the present invention. Figure 2 This is a schematic diagram of a bridge crane structure; Figure 3 This is a schematic diagram of independent trajectory planning in this invention; Figure 4 This is a schematic diagram of the obstacle points.

[0023] In the picture: 1. Trolley; 2. Rope; 3. Lifting device. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figure 1 The present invention provides a technical solution: an obstacle avoidance trajectory planning method for a bridge crane, comprising the following steps: independent trajectory planning, defining obstacle point information within the trolley's movement range, filtering effective obstacle points and solving for the peak value of obstacle points, calculating the trolley's start-up timing considering obstacle avoidance, and calculating the timing of the rope descent segment considering obstacle avoidance.

[0026] The first step, independent trajectory planning, please refer to [link / reference]. Figure 2 A bridge crane can be simplified to consist of the following main structures: trolley, ropes, and lifting gear. (Based on the starting position of the target trajectory.) End position and intermediate height information Independently plan the trajectory for the rope ascent segment, the rope descent segment, and the trolley movement trajectory. The specific starting position, ending position, and intermediate height are as follows: Figure 3 As shown in the diagram. Specifically, we discretize each segmented trajectory into several segments spaced at equal time intervals. The command points are arranged in chronological order to form a trajectory command sequence.

[0027] The specific forms of the starting and ending positions are as follows: (1) (2) In the formula, It is the starting position point. This is the starting position value of the trolley. This is the starting rope length position value. Similarly... It is the termination point. It is the termination position value of the trolley. It is the position value of the termination rope length. Construct the instruction sequence for the rope ascent segment. Based on the known initial rope length and position values... and intermediate height information We can calculate the change in rope length during the ascending section. : (3) Obtain the change in rope length during the ascending section Then, by combining the upper limits of the lifting speed and acceleration, the command sequence for the rope ascent segment trajectory can be obtained. The upper limits for lifting speed and acceleration are performance indicators of the rope control system for bridge cranes. The specific form of the rope ascending segment trajectory command sequence is as follows: (4) In the formula, There are n time intervals. The rope speed command.

[0028] Similarly, construct the rope length variation of the rope descent section. and the sequence of instructions for the rope descent segment : (5) (6) In the formula, It is m time intervals. The rope speed command.

[0029] Similarly, construct the distance change of the car and the sequence of instructions for the movement trajectory of the vehicle : (7) (8) In the formula, It is k time intervals. The trolley speed command. It is important to note that the trolley speed command planning needs to consider the upper limits of trolley speed and acceleration, as well as anti-sway strategies. The upper limits of trolley speed and acceleration are performance indicators of the bridge crane's cable control. The anti-sway strategy is not the focus of this article and will not be discussed in detail.

[0030] Define obstacle information within the trolley's movement range. Obstacle avoidance for bridge cranes differs from typical 2D and 3D mobile robot obstacle avoidance problems; it is a traversal obstacle avoidance problem. Because the bridge crane's spreader is controlled by rope connections, obstacle avoidance during movement must consider not only the interference between the spreader and the obstacle, but also the interference between the rope and the obstacle. Furthermore, since the obstacles faced by bridge cranes during actual operation are mostly regular cuboid structures, and the crane stops moving once aligned with a specific container bay, the spreader's obstacle avoidance problem can be viewed as a 2D traversal obstacle avoidance problem.

[0031] To further simplify, we describe the obstacle profile using several obstacle points, and the obstacle point information is represented as follows: Each obstacle point consists of the car's position value and the rope length position value. The obstacle information is arranged in order of the car's position, with a total of n obstacles. The specific representation of the obstacle points is as follows: Figure 4 As shown.

[0032] Filter valid obstacle points and solve for the peak value of obstacle points.

[0033] Valid obstacle point information filtering. The valid obstacle points refer to obstacles within the range of the target vehicle's starting and ending positions.

[0034] Before the trajectory execution begins, valid obstacle point information is filtered out based on the vehicle's starting and ending position values. The valid obstacle point information meets the following conditions: (9) In the formula, The position value of the car for the valid obstacle point item. Here, k represents the rope length position value of a valid obstacle point sub-item, k is the starting index value of the valid obstacle point information, and m is the number of valid obstacle point information elements. This condition indicates that for any obstacle point information sub-item, it satisfies the condition that it falls within the range of the target vehicle's starting position value and the vehicle's ending position value.

[0035] Solving for the peak value of the obstacle point The peak value of an obstacle point is defined as the obstacle point with the shortest rope length and the highest height above the ground among the valid obstacle point information. If multiple obstacle point peak rope length values ​​are identical, the point closest to the starting position of the vehicle is taken as the peak value of the obstacle point. .

[0036] The calculation of the vehicle's start-up timing is considered, and this start-up timing is based on the vehicle's speed command sequence. The start time for sending the vehicle speed data.

[0037] After obtaining the peak value of the obstacle point, trajectory execution begins. Initially, the speed command for the rope ascent phase is executed, but the vehicle is not yet started. Then, based on a carefully designed obstacle avoidance strategy for the ascent phase, real-time analysis is performed to determine whether the vehicle can be started. The specific obstacle avoidance strategy for the ascent phase is as follows: a) Filter out obstacle information for the rope ascent section The obstacle point information during the ascent phase meets the following conditions: (10) In the formula, The position value of the car for the effective obstacle point item in the ascending segment. This refers to the rope length position value of the effective obstacle point item during the ascent phase. This is the current real-time position value of the car. Here, s represents the currently obtained real-time rope length position value, t represents the starting index value of the obstacle point information in the ascending segment, and t represents the number of obstacle point information elements in the ascending segment. This condition indicates that, for each instruction moment, any sub-item of the obstacle point information in the ascending segment satisfies the following conditions: its trolley position value is within the range of the current real-time trolley starting position value and the peak obstacle point trolley position value, and its rope length position value is within the range of the current real-time rope length position value and the peak obstacle point rope length position value.

[0038] b) A time-prediction comparison method is used to determine whether to start the vehicle. The specific strategy is to assume the vehicle will start from the current moment and execute the vehicle's movement trajectory command sequence. Real-time calculation of the time from the current position of the vehicle to the position of the vehicle at each obstacle point in the ascent segment. And the time from the current rope length position to the rope length position at each obstacle point of the ascent segment. .

[0039] The car can be started if the following conditions are met: (11) This condition means that if the time taken for the car to reach the position of each obstacle on the ascending section from the current position is greater than the time taken to reach the position of the rope length at each obstacle on the ascending section, then a collision will not occur.

[0040] The timing calculation for the rope descent segment, considering obstacle avoidance, is as follows. The timing of the rope descent segment refers to the timing according to the sequence of rope descent trajectory instructions. The start time for sending the vehicle speed data.

[0041] Once the vehicle starts and has crossed the peak of the obstacle, the system analyzes in real time whether to initiate the rope descent trajectory command based on a carefully designed obstacle avoidance strategy for the descent phase. The specific obstacle avoidance strategy for the descent phase is as follows: a) Filter out obstacle information for the rope descent section The obstacle point information during the descent phase meets the following conditions: (12) In the formula, The position value of the car for the effective obstacle point sub-item during the descent segment. The rope length position value for the effective obstacle point item in the descent phase. This is the current real-time position value of the car. Here, u represents the currently obtained real-time rope length position value, v represents the starting index value of the obstacle point information in the descent segment, and v represents the number of obstacle point information elements in the descent segment. This condition indicates that, for each instruction moment, any sub-item of obstacle point information in the descent segment satisfies the following conditions: its trolley position value is within the range of the current real-time trolley starting position value and the target trolley ending position value, and its rope length position value is within the range of the current real-time rope length position value and the ending rope length position value.

[0042] B) Use a time-prediction comparison method to determine whether to initiate the rope descent trajectory command. Specifically, assume the rope descent trajectory command will be initiated from the current moment and execute the rope descent trajectory command sequence. Real-time calculation of the time from the current position of the vehicle to the position of the vehicle at each obstacle point in the descent segment. And the time from the current rope length position to the rope length position at each obstacle point in the descent. .

[0043] If the following conditions are met, it indicates that the rope descent trajectory command can be initiated: (13) This condition means that if the time taken for the car to reach the obstacle points of each descent segment from its current position is less than the time taken to reach the rope length position at each obstacle point, a collision will not occur.

[0044] In summary, the obstacle avoidance trajectory planning method for bridge cranes proposed in this solution has a significantly simpler and more efficient anti-collision trajectory strategy compared to existing methods, greatly improving the safety of automated operations.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for obstacle avoidance trajectory planning for bridge cranes, characterized in that, Includes the following steps: Step 1: Independent trajectory planning; specifically including: 1) Based on the starting position of the target trajectory End position and intermediate height information Independently plan the trajectory of the rope ascending segment, the trajectory of the rope descending segment, and the trolley movement trajectory; discretize each segment trajectory into several command points with equal time intervals, and arrange the command points in chronological order to form a trajectory command sequence; The specific forms of the starting and ending positions are as follows: In the formula, It is the starting position point. This is the starting position value of the trolley. This is the starting rope length position value. It is the termination point. It is the termination position value of the trolley. This is the position value of the termination rope length; 2) Construct the instruction sequence for the rope ascent segment; based on the known initial rope length position value. and intermediate height information The change in rope length during the ascending section was calculated. : Obtain the change in rope length during the ascending section Then, by combining the upper limits of the lifting speed and acceleration, the command sequence for the rope ascent segment trajectory can be obtained. ; The specific form of the rope ascent trajectory instruction sequence is as follows: (4) In the formula, There are n time intervals. The rope speed command; 3) Construct the rope length variation of the rope descent section and the sequence of instructions for the rope descent segment : In the formula, It is m time intervals. The rope speed command; 4) Construct the change in the distance of the car and the sequence of instructions for the movement trajectory of the vehicle : In the formula, It is k time intervals. The vehicle speed command; Step 2: Define obstacle point information within the trolley's movement range; simplify the obstacle avoidance problem of the lifting device into a 2D traversal obstacle avoidance problem; describe the obstacle profile through several obstacle points, and represent the obstacle point information as follows: Each obstacle point consists of the car's position value and the rope length position value. The obstacle information is arranged in order of the car's position, and there are a total of n obstacle points; Step 3: Selecting valid obstacle points and solving for the peak value of obstacle points; specifically including: 1) Valid obstacle information filtering: Obstacles within the range of the target vehicle's starting and ending positions are defined as valid obstacles. Before trajectory execution begins, valid obstacle information is filtered based on the vehicle's starting and ending position values. The valid obstacle point information meets the following conditions: (9) In the formula, The position value of the car for the valid obstacle point item. The rope length position value of the valid obstacle point item, k is the starting index value of the valid obstacle point information, and m is the number of valid obstacle point information elements; 2) Solve for the peak value at the obstacle point The obstacle point with the shortest rope length and the highest height from the ground in the valid obstacle point information is defined as the obstacle point peak value. If there are multiple obstacle point peak rope length values ​​that are the same, the point closest to the starting position of the trolley is taken as the obstacle point peak value H.

2. The obstacle avoidance trajectory planning method for a bridge crane according to claim 1, characterized in that, The speed of the trolley must not exceed the upper speed and acceleration limits specified in the performance indicators of the bridge crane's rope control.

3. The obstacle avoidance trajectory planning method for a bridge crane according to claim 2, characterized in that, After identifying the valid obstacle points and calculating their peak values, the following steps are required: Step 4: Calculate the starting timing of the obstacle avoidance vehicle, defining the sequence of vehicle speed commands. The start time for sending the vehicle speed is the vehicle's startup timing; after obtaining the obstacle peak, trajectory execution begins. At the start of the trajectory, the speed command for the rope ascent segment is executed first. At this time, the vehicle has not yet started. Then, the following method is used to analyze in real time whether the vehicle can be started: 1) Filter out obstacle information for the rope ascent section. The obstacle point information in the ascending phase meets the following conditions: (10) In the formula, The position value of the car for the effective obstacle point item in the ascending segment. This refers to the rope length position value of the effective obstacle point item during the ascent phase. This is the current real-time position value of the car. s is the current real-time rope length position value, t is the starting index value of the obstacle point information in the ascending section, and t is the number of elements of the obstacle point information in the ascending section. 2) Use a time prediction comparison method to determine whether to start the car. Assume the car starts from the current moment and executes the sequence of car movement trajectory instructions. Real-time calculation of the time from the current position of the vehicle to the position of the vehicle at each obstacle point in the ascent segment. And the time from the current rope length position to the rope length position at each obstacle point of the ascent segment. ; The car can be started if the following conditions are met: (11)。 4. The obstacle avoidance trajectory planning method for a bridge crane according to claim 1, characterized in that, After identifying the valid obstacle points and calculating their peak values, the following steps are required: Step 5: Calculate the timing of the rope descent segment considering obstacle avoidance; define the instruction sequence according to the rope descent segment trajectory. The start time for sending the vehicle's speed is the timing of the rope descent segment. Once the vehicle starts and has crossed the obstacle peak, the system analyzes in real time whether the rope descent segment trajectory command can be initiated based on the following obstacle avoidance strategy: 1) Filter out obstacle information for the rope descent section. The obstacle point information during the descent phase meets the following conditions: (12) In the formula, The position value of the car for the effective obstacle point sub-item during the descent segment. The rope length position value for the effective obstacle point item in the descent phase. This is the current real-time position value of the car. The current real-time rope length position value is denoted by u, the starting index value of the obstacle point information in the descent segment is denoted by v, and the number of obstacle point information elements in the descent segment is denoted by v. This condition means that for each instruction moment, any sub-item of obstacle point information in the descent segment satisfies the following conditions: its trolley position value is within the range of the current real-time trolley starting position value and the target trolley ending position value, and its rope length position value is within the range of the current real-time rope length position value and the ending rope length position value. 2) Use a time prediction comparison method to determine whether to initiate the rope descent trajectory command. Assuming the rope descent trajectory command is initiated from the current moment, execute the rope descent trajectory command sequence. Real-time calculation of the time from the current position of the vehicle to the position of the vehicle at each obstacle point in the descent segment. And the time from the current rope length position to the rope length position at each obstacle point in the descent. , If the following conditions are met, it indicates that the rope descent trajectory command can be initiated: (13)。

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