Optimization method for warehouse-out and box turning of material frame in forklift intensive warehousing system

Abstract

The invention provides an optimization method for warehouse-out and turnover of material frames in a forklift intensive warehousing system, and belongs to the technical field of warehousing management systems.The optimization method comprises the steps that basic information of a material stacking area is collected, the retrieval sequence of the material frames is obtained, and the stockpiling state of the material stacking area is initialized; a heuristic method is adopted to determine the upper bound of a box turnover scheme and the box turnover frequency; determining a box turnover scheme and the lower bound of the box turnover times by adopting an estimation method of the lower bound of the box turnover times of the material frame; if the upper bound of the number of times of turnover is equal to the lower bound of the number of times of turnover, the box turnover scheme determined by the heuristic method is the optimal box turnover scheme, otherwise, the upper bound of the number of times of turnover is used as the initial optimal upper bound, the lower bound of the number of times of turnover is used as the initial optimal lower bound, and deepened iterative search is performed by adopting a branch and bound algorithm to obtain the optimal box turnover scheme. The invention provides an optimization method for warehouse-out and box turning of a material frame in a forklift intensive warehousing system, which can optimize a warehouse-out and box turning scheme and improve the warehouse-out efficiency of the intensive warehousing system.

Description

Technical Field

[0001] The present invention belongs to the technical field of warehouse management systems, and in particular relates to optimized management of warehouse outbound box turning operations, and specifically is an optimized method for warehouse outbound box turning operations in a forklift-intensive warehouse system. Background Art

[0002] The forklift-intensive storage system refers to a three-dimensional storage system formed by stacking material frames in the vertical and horizontal directions. The system uses forklifts to transfer material frames. In this system, the material frames are stacked tightly to increase the material frame capacity, but the dense stacking brings troubles to the retrieval operation (outbound) of the material frames. For example, when it is necessary to retrieve the material frames located in the inner stack from the densely stacked stacking area, due to the limitation of the forklift's operating range, it is necessary not only to turn over the blocked material frames in the vertical direction of the stack, but also to consider the turning over of the material frames in the blocked stacks on the surrounding outbound paths. The actual outbound process involves retrieving multiple material frames in a given order, which is a very complex combinatorial optimization problem, and its goal is to minimize the total number of material frame turns during the entire retrieval process.

[0003] When material frames are shipped out of the existing dense storage system, the material frame turning over is usually achieved using a simple random strategy or a nearby strategy. Due to the dense stacking of material frames in the stacking area, the number of box turning overs will increase significantly when the material frames are shipped out using a simple box turning strategy, which seriously restricts the improvement of the efficiency of the dense storage system. Summary of the invention

[0004] To solve the above problems, the purpose of the present invention is to provide an optimization method for material frame outbound box turning in a forklift dense storage system, which is used to optimize the outbound box turning plan and improve the outbound efficiency of the dense storage system.

[0005] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0006] A method for optimizing the outbound box turning of a material frame in a forklift-intensive storage system comprises the following steps:

[0007] S1. Collect basic information of the stockpiling area, obtain the retrieval order of the material frame and initialize the stockpiling state of the stockpiling area;

[0008] S2, using heuristic methods to determine the upper bound of the box turning scheme and the number of box turning times;

[0009] S3, using the estimation method of the lower limit of the number of times of box turning by the material frame to determine the lower limit of the number of times of box turning;

[0010] S4, if the upper limit of the number of box turning times is equal to the lower limit of the number of box turning times, the box turning plan determined in step S2 is the optimal box turning plan, and step S6 is executed; otherwise, step S5 is executed;

[0011] S5. Taking the upper bound of the number of box turning as the initial optimal upper bound and the lower bound of the number of box turning as the initial optimal lower bound, a branch and bound algorithm is used to perform a deepening iterative search to obtain the optimal box turning solution;

[0012] S6. Output material frame out of warehouse and box turning plan.

[0013] As a specific implementation of the present invention, initializing the stacking state of the stacking area in step S1 includes numbering the material frames and numbering the stacks. When numbering the material frames, the material frames that need to be shipped out are arranged in front of the material frames that are not shipped out, and the material frames that need to be shipped out are numbered in sequence from small to large according to the retrieval order.

[0014] As a specific implementation of the present invention, step S2 includes:

[0015] S21, determine whether the outbound task is completed, if yes, execute step S27, otherwise execute step S22;

[0016] S22, taking the material frame with the smallest number in the current material stacking area as the target material frame, called the first target material frame, and judging whether there is a blocking material frame in the first target material frame. If not, the first target material frame can be directly shipped out without turning over the box, and directly executing step S23; otherwise, executing step S24;

[0017] S23, completing the outbound operation of the first target material frame, updating the stockpiling status of the stockpiling area, and returning to step S21;

[0018] S24, determining the priority number of each stack in the current stockpiling area, the box frame to be turned over, the optional placement stack, the G-type optional placement stack and the B-type optional placement stack;

[0019] The specific determination rules are as follows:

[0020] Stack priority number: If the stack is not empty and the number of the smallest frame in the stack is less than or equal to M, the number of the smallest frame in the stack is used as the stack priority number of the stack, otherwise the stack priority number of the stack is M+1; M is the total number of frames that need to be shipped out;

[0021] Box material frame to be turned over: Select the blocked material frames from all the blocked material frames of the first target material frame one by one as the box material frame to be turned over in the order from the outside to the inside of the stacking area and from the top to the bottom of the stack;

[0022] Optional drop-in stack: a stack that is outside the stack where the first target material frame and its blocking material frame are located and whose height does not reach the height limit and can be directly placed by a forklift;

[0023] G-type optional placement stacks and B-type optional placement stacks: The optional placement stack with a stack priority number of M+1 or the optional placement stack with a stack priority number greater than the number of the box material frame to be turned over is a G-type optional placement stack, and the remaining optional placement stacks are B-type optional placement stacks;

[0024] S25: Perform a box turning operation according to a box turning operation location stack selection rule, the specific rules are:

[0025] When the G-type optional placement stack and the B-type optional placement stack coexist, the G-type optional placement stack shall be selected as the final placement stack;

[0026] When there are at least two G-class optional placement stacks, if the box material frame to be turned over needs to be removed from the warehouse, the G-class optional placement stack with the smallest stack priority number will be used as the final placement stack, otherwise, stacks will be selected from the G-class optional placement stacks in the internal stack, the G-class optional placement stacks in the corner stack, and other G-class optional placement stacks in descending order of priority as the final placement stack; when there are at least two G-class optional placement stacks in the same priority level, for the G-class optional placement stacks in the internal stack and the G-class optional placement stacks in the corner stack, the stack with the smallest stack number will be selected as the final placement stack, and for other G-class optional placement stacks, the stack with the largest stack priority number will be selected as the final placement stack;

[0027] When selecting the final landing stack from the Class B optional landing stacks, if the number of empty storage spaces of the Class B optional landing stack with the largest stack priority number is equal to 1, then the stack with the second largest stack priority number in the Class B optional landing stacks is preferentially selected as the final landing stack; if the number of empty storage spaces of the Class B optional landing stack with the largest stack priority number is greater than 1, then the Class B optional landing stack with the largest stack priority number is selected as the final landing stack.

[0028] S26: Obtain the box turning path and update the stockpiling status of the stacking area, and return to step S22;

[0029] S27: Output the total number of box turning times and the box turning path.

[0030] As a specific implementation of the present invention, step S3 includes:

[0031] S31, calculating the number n of blocking material frames in the material stacking area in the initial state, and setting the number of box turning times LB = n;

[0032] The rules for determining a blocked material frame are as follows: the material frame that needs to be shipped out is the target material frame, called the second target material frame, and the blocked material frames in the same stack of the second target material frame are marked; after all the blocked material frames in the same stack of the second target material frame are marked, the marked material frames in the entire stacking area are the first blocked material frames;

[0033] S32, taking the material frame with the smallest number in the current material stacking area and that needs to be shipped out as the target material frame, called the third target material frame, and determining whether the third target material frame is in the internal stack, if so, executing step S33, otherwise, executing step S35;

[0034] S33 determines whether there is an operation of removing the blocked material frame from the material stacking area in order to search for other material frames before searching for the third target material frame, if yes, then terminate, otherwise, execute step S34;

[0035] S34, determining the non-same-stack blocked material frames of the third target material frame, the material frames in the non-same-stack blocked material frames of the third target material frame that are not marked as once blocked material frames are newly added blocked material frames, counting the number i of newly added blocked material frames, and updating the number of box turning times LB=LB+i;

[0036] S35, if the stack priority numbers of all optional placement stacks are less than M, the maximum value of the stack priority numbers in all optional placement stacks is used as a threshold, and the material frame with a number greater than the threshold in the blocking material frame of the third target material frame is a secondary blocking material frame, otherwise there is no secondary blocking material frame, the number j of secondary blocking material frames is counted, and the number of box turning times LB=LB+j is updated;

[0037] S36, remove the third target material frame and its blocking material frame from the stacking area, update the status of the stacking area, and terminate if all the material frames that need to be shipped out of the stacking area are removed, and output the total number of box turning times; otherwise, repeat steps S32-S36.

[0038] As a specific implementation of the present invention, step S5 includes:

[0039] S51: Determine whether the outbound task is completed; if so, execute step S58; otherwise, execute step S52;

[0040] S52, determining a target material frame in the current stockpiling state of the stockpiling area, called the fourth target material frame, and judging whether there is a blocking material frame in the fourth target material frame; if there is, executing step S53, otherwise executing step S54;

[0041] S53, completing the search operation of the fourth target material frame, updating the stockpiling state of the stockpiling area, and returning to step S51;

[0042] S54, branching: according to the stocking state corresponding to the current node, determine the fourth target material frame and its blocking material frame and the optional drop stack, and turn the material frame to be turned over to each optional drop stack to form a new stocking state as a new branch;

[0043] S55, pruning: the branch set with a depth of k in the search tree of the branch and bound algorithm represents the branch node set obtained after the material frame in the stockpile area has been turned over k times from the initial state. For each new branch state generated in step S54, the total number of box turning times of the branch state is solved using the estimation method of the lower bound of the number of box turning times of the material frame as the lower bound estimation. If the sum of the lower bound estimation of a branch state and the search depth k is greater than the current optimal lower bound, the branch node is pruned in this round;

[0044] S56, update bounds: for a branch in the search tree, if the sum of the lower bound estimate of the branch state and the search depth k is equal to the current optimal lower bound minus 1, then use a heuristic method to solve the total number of box flips of the branch state as the upper bound estimate. If the sum of the upper bound estimate of the branch state and the search depth k is less than the current optimal upper bound, then update the current optimal upper bound, and the optimal upper bound is updated to the sum of the upper bound estimate of the branch state and the search depth k. If the optimal upper bound is equal to the optimal lower bound, execute step S58, otherwise execute step S57;

[0045] S57, select branch: select the branch node with the smallest lower bound estimate from all the next-layer branch nodes that have not been pruned or traversed by the current node as the new current node; when all branches in the next layer are pruned or traversed, mark the current node as traversed, and use a deep search method to search for the branch node with the smallest lower bound estimate layer by layer as the new current node; if the new current node is a leaf node, the branch route to the leaf node is the optimal solution and execute step S58; when the new current node is not a leaf node, repeat steps S51-S57 until backtracking to the root node. After backtracking to the root node, the optimal lower bound value is increased by 1, and it is determined whether the current optimal lower bound is equal to the current optimal upper bound. If so, execute step S58, otherwise, return to step S51 to start a new round of search;

[0046] S58. The iterative deepening search ends and the optimal solution is returned.

[0047] Beneficial effects:

[0048] The present invention provides an optimization method for material frame outbound box turning in a forklift intensive storage system, which can optimize the outbound box turning plan and improve the outbound efficiency of the intensive storage system.

[0049] The present invention uses a fast-solving heuristic method and an estimation method for the lower bound of the number of times the material frame turns over boxes to quickly determine whether the optimal solution is found. Compared with the branch and bound algorithm, the solution process using these two methods is simpler and helps save time. At the same time, even if the above two methods do not find the optimal solution, they provide the branch and bound algorithm with an initial optimal upper bound and an optimal lower bound, which improves the computational efficiency of the branch and bound algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below.

[0051] Figure 1 is a flow chart of Embodiment 1 of the present invention;

[0052] Figure 2 This is a schematic diagram of the stockpiling state of a stockpiling area in one embodiment of the present invention;

[0053] Figure 3 It is a schematic diagram of the stockpiling state of the stockpiling area in another embodiment of the present invention. DETAILED DESCRIPTION

[0054] The present invention will be further described in detail below in conjunction with the embodiments and drawings.

[0055] In the present invention, Figure 2 As shown, the stacks in the stacking area are arranged in rows and columns, and the top view is a rectangle; the corner stacks refer to the stacks located at the four corners of the rectangular frame of the stacking area; the external stacks refer to the stacks located on the quadrilateral formed by connecting the four corner stacks end to end, that is, the outermost stacks of the entire stacking area (the corner stacks belong to the external stacks); the internal stacks refer to the stacks located in the circle surrounded by all the external stacks.

[0056] In the present invention, a blocking material frame refers to a material frame that prevents a forklift from contacting a target material frame. The blocking material frames are divided into two categories, namely, same-stack blocking material frames and non-same-stack blocking material frames, wherein the same-stack blocking material frame refers to a blocking material frame that is located in the same stack as the target material frame, that is, a material frame that is located directly above the target material frame, and a non-same-stack blocking material frame refers to a blocking material frame that is located outside the stack where the target material frame is located. For example, taking the stack where the target material frame is located as the central stack, the stack that the central stack passes through along a straight line to the outside of the stacking area is the blocking stack, and the material frame in the blocking stack that prevents the forklift from contacting the target material frame is a non-same-stack blocking material frame. It should be noted that for an ordinary forklift, it is necessary to move the blocking stack The target material frame can be moved only after all the material frames in the stack have been turned over. At this time, all the material frames in the blocking stack are blocking material frames, but for the reach forklift, it can fork (place) materials in the length direction of at most two material frames. Therefore, it does not need to turn over all the material frames in the blocking stack. Therefore, the material frames with lower layers than the target material frames in the blocking stack adjacent to the target material frame do not need to be turned over. At this time, the blocking material frames are: the material frames with greater than or equal to the target material frames in the blocking stack adjacent to the target material frame, and all the material frames in the blocking stack that are not adjacent to the target material frame.

[0057] Example 1

[0058] A method for optimizing the outbound box turning of a material frame in a forklift-intensive storage system comprises the following steps:

[0059] S1: Collect the basic information of the stacking area, obtain the retrieval order of the bins, and initialize the stacking status of the stacking area.

[0060] In this step, the retrieval order is the outbound order of the bins. Initializing the stacking status of the stacking area includes numbering all stacks and numbering all bins (the number of each bin is P ij ), and obtaining the bay numbers of each bin (the bay number refers to the row number (bay number), column number (bay column number), and layer number (bay layer number) where the bin is located). When numbering the bins, arrange the bins that need to be outbound in front of the bins that do not need to be outbound, and the bins that need to be outbound need to be numbered in ascending order according to the sequence of the retrieval order. Other bins (bins that do not go outbound) can be numbered randomly, but the numbers are all greater than the bins that need to be outbound. For example, assume that the total number of bins in all stacks is N, and the total number of bins that need to be outbound is M (M ≤ N). Then, the bins numbered from 1 to M need to be outbound, and the bin numbered i (i < M) is outbound earlier than the bin numbered i + 1. The bins numbered from M + 1 to N do not need to be outbound;

[0061] S2: Use a heuristic method for fast solution to solve the upper bound UB0 of the repositioning plan and the number of repositioning times, and let the current optimal upper bound best_ub = UB0;

[0062] This step includes performing retrieval operations on each bin to be outbound in sequence according to the retrieval order until the retrieval operation of the last bin to be outbound is completed, and counting the number of repositioning times in the retrieval operation; specifically, this step includes the following steps:

[0063] S21: Determine whether the outbound task is completed. If so, execute step S27; otherwise, execute step S22;

[0064] S22: Take the bin with the smallest number in the current stacking status of the stacking area as the target bin, called the first target bin, and determine whether there is a blocking bin for the first target bin. If not, it can be directly outbound without repositioning operation, and directly execute step S23. If so, execute step S24; The first target bin in the internal stack can move linearly in multiple directions to the outside of the stacking area. In this embodiment, the path with the least total number of blocking bins of the first target bin is used as the repositioning path to reduce the number of repositioning times.

[0065] S23: Complete the outbound operation of the first target bin, update the stacking status of the stacking area, and return to step S21;

[0066] S24: Determine the priority sequence Q of each stack i in the current stacking status of the stacking area, the bins to be repositioned, the optional stacking locations, the G - type optional stacking locations, and the B - type optional stacking locations;

[0067] The specific determination rules are as follows:

[0068] Stack priority number Q i : For an empty stack, its stack priority number is M+1; for a non-empty stack, when the number of the smallest frame in the stack is less than or equal to M, the number of the smallest frame in the stack is used as the priority number of the stack, otherwise the stack priority number of the stack is M+1;

[0069] Box material frame to be turned over: among all the blocked material frames of the first target material frame, the blocked material frames are selected one by one as the box material frame to be turned over in the order from the outside to the inside of the stacking area and from the top to the bottom of the stack. For example, when the stack where the first target material frame is located is an outer stack, the box material frame to be turned over is the blocked material frame at the top of the stack where the first target material frame is located, that is, the highest blocked material frame in the same stack; when the stack where the first target material frame is located is an inner stack, and there are blocked material frames on one side that are not in the same stack and the number is 0, the box material frame to be turned over is the blocked material frame at the top of the stack where the first target material frame is located; when the stack where the first target material frame is located is an inner stack, but the surrounding stacks are all non-empty stacks and there are blocked material frames that are not in the same stack on the outbound path, the box material frame to be turned over is the top material frame in the first blocked stack from the outside to the inside on the outbound path;

[0070] Optional drop-in stack: a stack that is located outside the stack where the first target material frame and its corresponding blocking material frame are located and whose height does not reach the height limit and on which the forklift can directly complete the fork placement operation (i.e., a stack that does not reach the height limit and can directly perform the fork placement operation except the stack where the first target material frame is located and the stack on the case turning path that blocks the first target material frame from leaving the warehouse);

[0071] G-type optional placement stack and B-type optional placement stack: In the optional placement stack, the stack priority number is Q i =M+1 or the stack whose stack priority number is higher than the number of the box material frame to be turned over is a G-type optional placement stack, and the rest are B-type optional placement stacks.

[0072] S25: Perform a box turning operation according to a box turning operation location stack selection rule, the specific rules are:

[0073] If there are optional placement stacks of category G and optional placement stacks of category B, the final placement stack will be selected from the optional placement stack of category G first. If there is no optional placement stack of category G, the final placement stack will be selected from the optional placement stack of category B.

[0074] When there are at least two G-class optional landing stacks to choose from, if the box material frame to be turned over needs to be removed from the warehouse, the final landing stack is the stack with the smallest stack priority number in the G-class optional landing stacks; if the box material frame to be turned over does not need to be removed from the warehouse, the final landing stack is selected from the G-class optional landing stacks in the internal stack, the G-class optional landing stacks in the corner stack, and other G-class optional landing stacks in descending order of priority. When there are two or more optional G-class optional landing stacks in the same priority level, for the G-class optional landing stacks in the internal stack and the G-class optional landing stacks in the corner stack, the stack with the smallest stack number is selected as the final landing stack, and for other G-class optional landing stacks, the stack with the largest stack priority number is selected as the final landing stack;

[0075] When selecting the final landing stack from the B-type optional landing stacks, if the stack with the largest stack priority number has only one empty storage slot, the final landing stack will be the stack with the second largest stack priority number among the B-type optional landing stacks; if the stack with the largest stack priority number has more than 1 empty storage slot, the final landing stack will be the stack with the largest stack priority number among the B-type optional landing stacks.

[0076] S26: Obtain the box turning path and update the stockpiling status of the stacking area, and return to step S22;

[0077] S27: Output the total number of box turning times and the box turning path, and the heuristic solution process ends.

[0078] S3: Using the estimation method of the lower bound of the number of box turning times of the material frame to solve the box turning scheme and the lower bound of the number of box turning times LB0, and setting the current optimal lower bound best_lb = LB0, including the following steps:

[0079] S31, calculate the number n of blocking material frames in the material stacking area in the initial state, and set the lower bound LB = n;

[0080] The rules for determining a blocked material frame are as follows: the material frame that needs to be shipped out is the target material frame, called the second target material frame, and the blocked material frames in the same stack of the second target material frame are marked; after all the blocked material frames in the same stack of the second target material frame are marked, the marked material frames in the entire stacking area are the first blocked material frames;

[0081] S32, taking the material frame with the smallest number in the current material stacking area and that needs to be shipped out as the target material frame, called the third target material frame, and determining whether the third target material frame is in the internal stack, if so, executing step S33, otherwise, executing step S35;

[0082] S33 determines whether there is an operation of removing the blocked material frame from the material stacking area in order to search for other material frames before searching for the third target material frame, if yes, then terminate, otherwise, execute step S34;

[0083] S34, determining the non-same-stack blocked material frames of the third target material frame, the material frames in the non-same-stack blocked material frames of the third target material frame that are not marked as once blocked material frames are newly added blocked material frames, counting the number i of newly added blocked material frames, and updating the number of box turning times LB=LB+i;

[0084] S35, if the stack priority numbers of all optional placement stacks are less than M, the maximum value of the stack priority numbers in all optional placement stacks is used as a threshold, and the material frame with a number greater than the threshold in the blocking material frame of the third target material frame is a secondary blocking material frame, otherwise there is no secondary blocking material frame, the number j of secondary blocking material frames is counted, and the number of box turning times LB=LB+j is updated;

[0085] S36, remove the third target material frame and its blocking material frame from the stacking area, update the status of the stacking area, and terminate if all the material frames that need to be shipped out of the stacking area are removed, and output the total number of box turning times; otherwise, repeat steps S32-S36.

[0086] S4: If best_ub=best_lb, the heuristic solution is the optimal solution, and step S6 is executed; otherwise, step S5 is executed;

[0087] S5: Use the branch and bound algorithm to perform a deepening iterative search and obtain the theoretical optimal solution to the problem;

[0088] S51: Determine whether the outbound task is completed; if so, execute step S58; otherwise, execute step S52;

[0089] S52, determining a target material frame in the current stockpiling state of the stockpiling area, called the fourth target material frame, and judging whether there is a blocking material frame in the fourth target material frame; if there is, executing step S53, otherwise executing step S54;

[0090] S53, completing the search operation of the fourth target material frame, updating the stockpiling state of the stockpiling area, and returning to step S51;

[0091] S54, branching: according to the stocking state corresponding to the current node, determine the fourth target material frame and its blocking material frame and the optional drop stack, and turn the material frame to be turned over to each optional drop stack to form a new stocking state as a new branch;

[0092] S55: Pruning: The branch set with a depth of k in the search tree of the branch and bound algorithm represents the branch node set obtained after the material frame in the stacking area is turned over k times from the initial state. Each new branch state generated in step S54 The total number of box flipping times for the branch state is solved using the lower bound estimation method of the number of box flipping times for the material frame as the lower bound estimation If the lower bound estimate of a branch state The sum of the search depth k is greater than the current optimal lower bound best_lb, that is, , then the branch node is pruned in this round;

[0093] S56: Update Bounds: For a branch in the search tree, if the lower bound estimate of the branch state The sum of the search depth k is equal to the current optimal lower bound best_lb minus 1, that is, When , use the heuristic method to solve the total number of box flips in the branch state as the upper bound estimate If the upper bound of the branch state is The sum of the search depth k is less than the current optimal upper bound best_ub, that is, When , the current optimal upper bound will be updated If best_ub=best_lb, execute step S58, otherwise execute step S57;

[0094] S57: Select branch: Select the branch node with the smallest lower bound estimate from all the next-layer branch nodes that have not been pruned or traversed by the current node as the new current node. When all branches of the next layer are pruned or traversed, the current node is marked as traversed, and a deep search is used to find the branch node with the smallest lower bound estimate layer by layer as the new current node. If the new current node is a leaf node, that is, the required outbound material frames have all been outbound, then the branch route that reaches the leaf node is the optimal solution and step S58 is executed. When the new current node is not a leaf node, repeat steps S51-S57 until backtracking to the root node. After backtracking to the root node, the optimal lower bound value is incremented by 1 (best_lb=best_lb+1), and it is determined whether the current optimal lower bound best_lb is equal to the current optimal upper bound best_ub. If so, step S58 is executed, otherwise, return to step S51 to start a new round of search;

[0095] S58: The iterative deepening search ends and the optimal solution is returned.

[0096] S6: Output a set of material frame outbound box turning solutions under the layout, and the program ends.

[0097] The following will explain it with a specific example. The initial stockpiling state of the stockpiling area is as follows: Figure 3 As shown, material frames No. 1 to 20 need to be shipped out in sequence.

[0098] After calculation, the box turning scheme obtained by heuristic method is as follows:

[0099] Table 1. Box turning scheme obtained by heuristic method

[0100] Serial number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Material frame number 4 45 13 28 25 36 29 25 38 11 30 30 16 26 24 33 39 18 28 45 Stack number before turning over the box 14 14 11 2 15 15 4 14 14 6 6 11 8 8 7 7 13 13 1 1 Stack number after turning over the box 4 1 5 1 14 2 15 3 3 13 11 3 10 15 8 8 8 12 5 5

[0101] The lower bound of the number of box turning times is determined to be 14 times by using the estimation method of the lower bound of the number of box turning times of the material frame. Therefore, the branch and bound algorithm is used to perform in-depth iterative search to obtain the optimal box turning solution. The results are shown in Table 2.

[0102] Table 2 Box flipping solutions obtained by branch and bound algorithm

[0103] Serial number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Material frame number 4 45 13 28 25 36 29 38 11 30 16 26 24 33 39 18 Stack number before turning over the box 14 14 11 2 15 15 4 14 6 6 8 8 7 7 13 13 Stack number after turning over the box 1 9 5 9 2 2 15 3 3 15 1 6 14 2 8 2

[0104] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for optimizing the box turning over when the material frame is out of the warehouse in a forklift-intensive storage system, characterized in that: The steps include: S1. Collect basic information of the stockpiling area, obtain the retrieval order of the material frame and initialize the stockpiling state of the stockpiling area; S2, using heuristic methods to determine the upper bound of the box turning scheme and the number of box turning times; S3, using the estimation method of the lower limit of the number of times of box turning by the material frame to determine the lower limit of the number of times of box turning; S4, if the upper limit of the number of box turning times is equal to the lower limit of the number of box turning times, the box turning scheme determined in step S2 is the optimal box turning scheme, and step S6 is executed; otherwise, step S5 is executed; S5, taking the upper bound of the number of box turning as the initial optimal upper bound, taking the lower bound of the number of box turning as the initial optimal lower bound, and using a branch and bound algorithm to perform a deepening iterative search to obtain an optimal box turning solution; S6. Output material frame out of warehouse and box turning plan.

2. The method for optimizing the material frame outbound box turning in a forklift intensive storage system according to claim 1, characterized in that: The initialization of the stacking state of the stacking area in step S1 includes numbering the material frames and the stacks. When numbering the material frames, the material frames that need to be shipped out are numbered in ascending order according to the search sequence, and the material frames that need to be shipped out are arranged in front of the material frames that do not need to be shipped out.

3. The method for optimizing the material frame outbound box turning in a forklift intensive storage system according to claim 2, characterized in that: Step S2 includes: S21, determine whether the outbound task is completed, if yes, execute step S27, otherwise execute step S22; S22, taking the material frame with the smallest number in the current material stacking area as the target material frame, called the first target material frame, and judging whether there is a blocking material frame in the first target material frame, if not, executing step S23, otherwise executing step S24; S23, completing the outbound operation of the first target material frame, updating the stockpiling status of the stockpiling area, and returning to step S21; S24, determining the priority number of each stack in the current stockpiling area, the box frame to be turned over, the optional stack, the G-type optional stack and the B-type optional stack; The specific determination rules are as follows: Stack priority number: If the stack is not empty and the number of the smallest frame in the stack is less than or equal to M, the number of the smallest frame in the stack is used as the stack priority number of the stack, otherwise the stack priority number of the stack is M+1; M is the total number of frames that need to be shipped out; Box material frames to be turned over: blocking material frames are selected one by one from all blocking material frames of the first target material frame in the order from the outside to the inside of the stacking area and from the top to the bottom of the stack as the box material frames to be turned over; Optional drop-in stack: a stack that is located outside the stack where the first target material frame and its blocking material frame are located and whose height does not reach the height limit and on which a forklift can directly complete the fork placement operation; G-type optional placement stacks and B-type optional placement stacks: the optional placement stack with a stack priority number of M+1 or the optional placement stack with a stack priority number greater than the number of the box material frame to be turned over is a G-type optional placement stack, and the remaining optional placement stacks are B-type optional placement stacks; S25: Perform a box turning operation according to a box turning operation location stack selection rule, the specific rules are: When the G-type optional placement stack and the B-type optional placement stack coexist, the G-type optional placement stack is preferentially selected as the final placement stack; When there are at least two of the G-type optional placement stacks, if the box material frame to be turned over needs to be removed from the warehouse, the G-type optional placement stack with the smallest stack priority number is used as the final placement stack, otherwise, a stack is selected from the G-type optional placement stack in the internal stack, the G-type optional placement stack in the corner stack, and other G-type optional placement stacks in descending order of priority as the final placement stack; when there are at least two of the G-type optional placement stacks in the same priority level, for the G-type optional placement stack in the internal stack and the G-type optional placement stack in the corner stack, the stack with the smallest stack number is selected as the final placement stack, and for the other G-type optional placement stacks, the stack with the largest stack priority number is selected as the final placement stack; When selecting the final landing stack from the Class B optional landing stacks, if the number of empty storage spaces of the Class B optional landing stack with the largest stack priority number is equal to 1, then the stack with the second largest stack priority number in the Class B optional landing stacks is preferentially selected as the final landing stack; if the number of empty storage spaces of the Class B optional landing stack with the largest stack priority number is greater than 1, then the Class B optional landing stack with the largest stack priority number is selected as the final landing stack. S26: Obtain the box turning path and update the stockpiling status of the stacking area, and return to step S22; S27: Output the total number of box turning times and the box turning path, and the heuristic solution process ends.

4. The method for optimizing the material frame outbound box turning in a forklift intensive storage system according to claim 3, characterized in that: Step S3 includes: S31, calculating the number n of blocking material frames in the material stacking area in the initial state, and setting the number of box turning times LB = n; The rules for determining a blocked material frame are as follows: the material frame that needs to be shipped out is the target material frame, called the second target material frame, and the blocked material frames in the same stack of the second target material frame are marked; after all the blocked material frames in the same stack of the second target material frame are marked, the marked material frames in the entire stacking area are the blocked material frames; S32, taking the material frame with the smallest number in the current material stacking area and that needs to be shipped out as the target material frame, called the third target material frame, and determining whether the third target material frame is in the internal stack, if so, executing step S33, otherwise, executing step S35; S33 determines whether there is an operation of removing the blocking material frame from the stacking area in order to search for other material frames before searching for the third target material frame, if yes, then terminate, otherwise, execute step S34; S34, determining the non-same-stack blocking material frames of the third target material frame, the material frames in the non-same-stack blocking material frames of the third target material frame that are not marked as the first blocking material frames are newly added blocking material frames, counting the number i of the newly added blocking material frames, and updating the box turning times LB=LB+i; S35, if the stack priority numbers of all optional placement stacks are less than M, the maximum value of the stack priority numbers in all optional placement stacks is used as a threshold, and the material frame with a number greater than the threshold in the blocking material frame of the third target material frame is a secondary blocking material frame, otherwise there is no secondary blocking material frame, and the number j of the secondary blocking material frames is counted, and the number of box turning times LB=LB+j is updated; S36, remove the third target material frame and its blocking material frame from the stacking area, update the status of the stacking area, and terminate if all the material frames that need to be shipped out of the stacking area are removed, and output the total number of box turning times; otherwise, repeat steps S32-S36.

5. The method for optimizing the material frame outbound box turning in a forklift intensive storage system according to claim 2, characterized in that: Step S5 includes: S51: Determine whether the outbound task is completed; if so, execute step S58; otherwise, execute step S52; S52, determining a target material frame in the current material stacking area under the stacking state, called the fourth target material frame, and judging whether there is a blocking material frame in the fourth target material frame; if there is, executing step S53, otherwise executing step S54; S53, completing the search operation of the fourth target material frame, updating the stockpiling state of the stockpiling area, and returning to step S51; S54, branching: according to the stocking state corresponding to the current node, determining the fourth target material frame and its blocking material frame and optional drop-in stack, and turning the material frame to be turned over to each optional drop-in stack to form a new stocking state as a new branch; S55, pruning: the branch set with a depth of k in the search tree of the branch and bound algorithm represents the branch node set obtained after the material frame in the stockpile area has been turned over k times from the initial state. For each new branch state generated in step S54, the total number of box turning times of the branch state is solved using the estimation method of the lower bound of the number of box turning times of the material frame as the lower bound estimation. If the sum of the lower bound estimation of a branch state and the search depth k is greater than the current optimal lower bound, the branch node is pruned in this round; S56, update the limit: for a branch in the search tree, if the sum of the lower bound estimate of the branch state and the search depth k is equal to the current optimal lower bound minus 1, then use the heuristic method to solve the total number of box flipping times of the branch state as the upper bound estimate, if the sum of the upper bound estimate of the branch state and the search depth k is less than the current optimal upper bound, then update the current optimal upper bound, and the optimal upper bound is updated to the sum of the upper bound estimate of the branch state and the search depth k. If the optimal upper bound is equal to the optimal lower bound, execute step S58, otherwise execute step S57; S57, select branch: select the branch node with the smallest lower bound estimate from all the next-layer branch nodes that have not been pruned or traversed by the current node as the new current node; when all branches in the next layer are pruned or traversed, mark the current node as traversed, and use a deep search method to search for the branch node with the smallest lower bound estimate layer by layer as the new current node; if the new current node is a leaf node, the branch route to the leaf node is the optimal solution and execute step S58; when the new current node is not a leaf node, repeat steps S51-S57 until backtracking to the root node. After backtracking to the root node, the optimal lower bound value is increased by 1, and it is determined whether the current optimal lower bound is equal to the current optimal upper bound. If so, execute step S58, otherwise, return to step S51 to start a new round of search; S58. The iterative deepening search ends and the optimal solution is returned.

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