Method for calculating size and angle of moving container on roller transmission line by using light curtain
By installing a light curtain on the drum transmission line, the size and angle of the cargo box are detected, the problems of change in the attitude and size of the cargo box on the transmission line are solved, and the accurate detection and processing of the cargo box size and angle are achieved.
Patent Information
- Application Number
- CN202510268586.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-07
- Publication Date
- 2025-06-06
AI Technical Summary
The cargo boxes on the transmission line are easily rotated or deformed during the transportation process, resulting in their posture and size that cannot meet the requirements of subsequent processes. There is a lack of a simple and reliable method to detect and process the size and inclination angle of the moving cargo boxes.
By installing a light curtain on the drum transmission line, the light curtain emitting end and the receiving end are installed on the upper and lower sides of the drum respectively. The light beads on the light curtain are numbered in sequence to obtain the distance data between adjacent light beads, and the size and angle data of the cargo box are calculated.
Accurate detection of the size and angle of the cargo box on the transmission line is achieved, the problem of affecting the calculation results due to changes in transmission speed is avoided, and the accuracy and efficiency of detection are improved.
Smart Images
Figure CN120101640A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of logistics transmission, and in particular to a method for calculating the size and angle of a moving cargo box on a roller transmission line by using a light curtain. Background Art
[0002] For the cargo boxes on the conveyor line, they are prone to rotation or deformation during the transportation process due to some reasons, resulting in their posture and size not meeting the requirements of subsequent processes. Therefore, a simple and reliable method is needed to detect the size and tilt angle of the moving cargo boxes, and the cargo boxes can be further processed based on the detection results. Summary of the invention
[0003] In response to the above-mentioned problems, the present invention provides a method for calculating the size and angle of a moving cargo box on a roller transmission line by using a light curtain.
[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions:
[0005] A method for calculating the size and angle of a moving cargo box on a roller conveyor line using a light curtain, comprising:
[0006] 1) Install the transmitting end and receiving end of the light curtain on the upper and lower sides of the roller transmission line respectively, and make several light beams emitted by the transmitting end of the light curtain pass through the gap between the rollers to reach the receiving end of the light curtain;
[0007] 2) Number the light beads on the light curtain in order and obtain the distance data between adjacent light beads;
[0008] 3) Calculate the size and angle data of the cargo box based on the distance data between adjacent light beads, the light bead number detected during the process from the beginning to the end of the cargo box blocking the light curtain, and the corresponding time.
[0009] Furthermore, the cargo box is a rectangular or square cargo box.
[0010] Furthermore, in step 1), the transmitting end of the light curtain is located on the upper side of the roller transmission line, the receiving end of the light curtain is located on the lower side of the roller transmission line, and the setting height of the transmitting end on the upper side of the roller transmission line should be higher than the maximum height of the cargo box on the roller transmission line;
[0011] Alternatively, the transmitting end of the light curtain is located at the lower side of the roller conveyor line, the receiving end of the light curtain is located at the upper side of the roller conveyor line, and the setting height of the receiving end on the upper side of the roller conveyor line should be higher than the maximum height of the cargo box on the roller conveyor line.
[0012] As a possible implementation, further, in step 2), the light beads on the light curtain are numbered one by one in order from left to right.
[0013] Furthermore, in step 3), the light bead numbers and corresponding times detected in the process from the beginning of the cargo box blocking the light curtain to the end of the blocking of the light curtain include: the starting light bead number (i.e., the first light bead number blocked when the cargo box initially blocks the light curtain), the ending light bead number (i.e., the last light bead number blocked when the cargo box ends blocking the light curtain), the minimum light bead number (i.e., the minimum light bead number detected in the process from the beginning of the cargo box blocking the light curtain to the end of the blocking of the light curtain), the maximum light bead number (i.e., the maximum light bead number detected in the process from the beginning of the cargo box blocking the light curtain to the end of the blocking of the light curtain), as well as the blocking start time (i.e., the time corresponding to the start of the cargo box blocking the light curtain), the time corresponding to the blocking of the minimum light bead number, and the time corresponding to the blocking of the maximum light bead number.
[0014] Furthermore, the calculation method of the cargo box size data in step 3) is as follows:
[0015] First, determine t 1 ,t 2 The size of 1 =t min -t b , t 2 =t max -t b , t b Indicates the start time of the light curtain blocking of the cargo box, t min Indicates the time corresponding to the blocking of the smallest light bead number during the transportation of the cargo box; t max Indicates the time corresponding to the blockage of the largest light bead number during the transportation of the cargo box;
[0016] When t 1 ≥t 2 When a and b are the lengths of the two adjacent sides of the cargo box, where a represents t b ~t max In this time period, the four sides of the cargo box can block the side A'-B corresponding to the starting light bead number and the maximum light bead number. max '; b represents the length of the side A'-B in the cargo box max 'The length of the adjacent side; L1 = |B max -A|×d,L2=|B max -C|×d, where A is the starting bead number, B max is the maximum light bead number, C is the end light bead number, and d is the distance between adjacent light beads;
[0017] In the above formula, in Among them, B 2 Indicates t max The smallest light bead number among the light beads blocked at any moment;
[0018] When t 1 <t 2 When a and b represent the lengths of the two adjacent sides of the cargo box, respectively, where a represents t b ~t min In this time period, the four sides of the cargo box can block the side A'-B corresponding to the starting light bead number and the minimum light bead number. min '; b represents the length of the side A'-B in the cargo box min 'The length of the adjacent side; L4 = |AB min |×d,L5=|CB min |×d, where A is the starting bead number, B min is the minimum light bead number, C is the end light bead number, and d is the distance between adjacent light beads;
[0019] In the above formula, in Among them, B 1 Indicates t min The maximum light bead number among the light beads blocked at that moment.
[0020] Furthermore, the calculation method of the cargo box angle data in step 3) is as follows:
[0021] When t 1 ≥t 2 When , the cargo box tilt angle θ is calculated as follows:
[0022] When the length and width of the cargo box are not equal, and the correct cargo box posture is that the short side is parallel to the light curtain; if a≤b, then θ=∠α; if a>b, then θ=90-∠α;
[0023] When the length and width of the cargo box are not equal, and the correct cargo box posture is that the long side is parallel to the light curtain; if a≤b, then θ=90-∠α; if a>b, then θ=∠α;
[0024] When the length and width of the cargo box are equal; if ∠α≤45°, then θ=∠α; if ∠α>45°, then θ=90-∠α;
[0025] When t 1 <t 2 When , the cargo box tilt angle θ is calculated as follows:
[0026] When the length and width of the cargo box are not equal, and the correct cargo box posture is that the short side is parallel to the light curtain; if a≤b, then θ=∠β; if a>b, then θ=90-∠β;
[0027] When the length and width of the cargo box are not equal, and the correct cargo box posture is that the long side is parallel to the light curtain; if a≤b, then θ=90-∠β; if a>b, then θ=∠β;
[0028] When the length and width of the cargo box are equal; if ∠β≤45°, then θ=∠β; if ∠β>45°, then θ=90-∠β.
[0029] The beneficial effects of the present invention are as follows:
[0030] The main part of the present invention is a light curtain, which has the characteristics of simple structure, low cost and easy operation. When measuring the size and tilt angle of the cargo box on the transmission line, there is no need to stop the cargo box from moving forward, so the efficiency of cargo box transmission will not be reduced. In addition, the calculation method of the cargo box size and angle is independent of the transmission speed, avoiding the influence of the change of the transmission speed of the roller transmission line on the calculation result, making the calculation result more accurate.
[0031] The present invention uses the data obtained by the light curtain to calculate the size and angle of the moving cargo box on the roller transmission line. It can be applied to some scenarios where it is inconvenient to identify the size and angle of the cargo box through visual images, such as: cargo box size and angle detection on the irradiation conveyor line (the image acquisition camera is easily damaged in the irradiation environment). BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0033] Figure 1 It is a schematic diagram of the arrangement of the light curtain in the present invention;
[0034] Figure 2 t 1 ≥t 2 Schematic diagram of the cargo box posture in the case;
[0035] Figure 3 t 1 <t 2 Schematic diagram of the cargo box posture in the case.
[0036] The numbers in the attached drawings are: 1-transmitting end of the light curtain; 2-cargo box; 3-roller transmission line; 4-receiving end of the light curtain. DETAILED DESCRIPTION
[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0038] This embodiment provides a method for calculating the size and angle of a moving cargo box on a roller transmission line by using a light curtain, wherein the cargo box is a rectangular or square cargo box, and the method specifically includes:
[0039] 1) Install the transmitting end and receiving end of the light curtain on the upper and lower sides of the roller transmission line respectively, and make several light beams emitted by the transmitting end of the light curtain pass through the gap between the rollers to reach the receiving end of the light curtain. Among them, the transmitting end of the light curtain can be located on the upper side of the roller transmission line, and the receiving end of the light curtain is located on the lower side of the roller transmission line. The setting height of the transmitting end on the upper side of the roller transmission line should be higher than the maximum height of the cargo box on the roller transmission line;
[0040] Alternatively, the transmitting end of the light curtain is located at the lower side of the roller conveyor line, the receiving end of the light curtain is located at the upper side of the roller conveyor line, and the setting height of the receiving end on the upper side of the roller conveyor line should be higher than the maximum height of the cargo box on the roller conveyor line.
[0041] In this embodiment, the transmitting end of the light curtain can be located on the upper side of the roller transmission line, and the receiving end of the light curtain is located on the lower side of the roller transmission line (such as the attached Figure 1 shown).
[0042] 2) The light beads on the light curtain are numbered in sequence, and the distance data between adjacent light beads are obtained; in this embodiment, the distance between any adjacent light beads on the light curtain is known and constant, and the light beads are numbered one by one in sequence from left to right.
[0043] 3) Calculate the size and angle data of the cargo box based on the distance data between adjacent light beads, the light bead number detected during the process from the beginning to the end of the cargo box blocking the light curtain, and the corresponding time.
[0044] Among them, the light bead numbers and corresponding times detected in the process of the cargo box starting to block the light curtain and ending to block the light curtain include: the starting light bead number (i.e. the first light bead number blocked when the cargo box starts to block the light curtain), the ending light bead number (i.e. the last light bead number blocked when the cargo box ends to block the light curtain), the minimum light bead number (i.e. the minimum light bead number detected in the process of the cargo box starting to block the light curtain and ending to block the light curtain), the maximum light bead number (i.e. the maximum light bead number detected in the process of the cargo box starting to block the light curtain and ending to block the light curtain), as well as the blocking start time (i.e. the time corresponding to the start of the cargo box blocking the light curtain), the time corresponding to the blocking of the minimum light bead number, and the time corresponding to the blocking of the maximum light bead number.
[0045] The calculation method of the cargo box size data in step 3) is as follows:
[0046] First, determine t 1 ,t 2 The size of 1 =t min -t b , t 2 =t max -t b , t b Indicates the start time of the light curtain blocking of the cargo box, t min Indicates the time corresponding to the blocking of the smallest light bead number during the transportation of the cargo box; t max Indicates the time corresponding to the blockage of the largest light bead number during the transportation of the cargo box;
[0047] See attached Figure 2 As shown, when t 1 ≥t 2 When a and b are the lengths of the two adjacent sides of the cargo box, where a represents t b ~t max In this time period, the four sides of the cargo box can block the side A'-B corresponding to the starting light bead number and the maximum light bead number. max '; b represents the length of the side A'-B in the cargo box max 'The length of the adjacent side; L1 = |B max -A|×d,L2=|B max -C|×d, where A is the starting bead number, B max is the maximum light bead number, C is the end light bead number, and d is the distance between adjacent light beads;
[0048] In the above formula, in Among them, B 2 Indicates t max The smallest light bead number among the light beads blocked at any moment;
[0049] See attached Figure 3 As shown, when t 1 <t 2 When a and b represent the lengths of the two adjacent sides of the cargo box, respectively, where a represents t b ~t min In this time period, the four sides of the cargo box can block the side A'-B corresponding to the starting light bead number and the minimum light bead number. min '; b represents the length of the side A'-B in the cargo box min 'The length of the adjacent side; L4 = |AB min |×d,L5=|CB min |×d, where A is the starting bead number, B min is the minimum light bead number, C is the end light bead number, and d is the distance between adjacent light beads;
[0050] In the above formula, in Among them, B 1 Indicates t min The maximum light bead number among the light beads blocked at that moment.
[0051] The calculation method of the cargo box angle data in step 3) is as follows:
[0052] See attached Figure 2 As shown, when t 1 ≥t 2 When , the cargo box tilt angle θ is calculated as follows:
[0053] When the length and width of the cargo box are not equal, and the correct cargo box posture is that the short side is parallel to the light curtain; if a≤b, then θ=∠α; if a>b, then θ=90-∠α;
[0054] When the length and width of the cargo box are not equal, and the correct cargo box posture is that the long side is parallel to the light curtain; if a≤b, then θ=90-∠α; if a>b, then θ=∠α;
[0055] When the length and width of the cargo box are equal; if ∠α≤45°, then θ=∠α; if ∠α>45°, then θ=90-∠α.
[0056] See attached Figure 3 As shown, when t 1 <t 2 When , the cargo box tilt angle θ is calculated as follows:
[0057] When the length and width of the cargo box are not equal, and the correct cargo box posture is that the short side is parallel to the light curtain; if a≤b, then θ=∠β; if a>b, then θ=90-∠β;
[0058] When the length and width of the cargo box are not equal, and the correct cargo box posture is that the long side is parallel to the light curtain; if a≤b, then θ=90-∠β; if a>b, then θ=∠β;
[0059] When the length and width of the cargo box are equal; if ∠β≤45°, then θ=∠β; if ∠β>45°, then θ=90-∠β.
[0060] From the above, it can be seen that in the present invention, the size and angle of the cargo box are mainly calculated by the light bead numbering and the spacing between adjacent light beads, and are independent of the transmission speed of the roller transmission line, thus avoiding the influence of the change of the transmission speed of the roller transmission line on the calculation result and making the calculation result more accurate.
[0061] Example 1
[0062] This embodiment describes the derivation process of using light curtains to calculate the size and angle of moving cargo boxes on a roller conveyor line, as follows:
[0063] The transmitting end and receiving end of the light curtain are respectively installed on the upper and lower sides of the roller transmission line, so that several light beams emitted by the transmitting end of the light curtain pass through the gap between the rollers to reach the receiving end of the light curtain. The light curtain has N light beads numbered from 1 to N. The distance between any adjacent light beads is known and constant. The linear size of the obstruction can be calculated based on the number of blocked light beads. When the light curtain is working, it continuously sends the data it detects to the external controller, and the external controller can receive the data generated by the light curtain in real time. The data generated by the light curtain includes: the number of the starting light bead in the blocked light beads, the number of the ending light bead, the maximum light bead number, the minimum light bead number, as well as the start time of the blockage, the time corresponding to the blockage of the minimum light bead number, and the time corresponding to the blockage of the maximum light bead number.
[0064] When the moving cargo box triggers the light curtain, from a bird's-eye view, the cargo box and the light curtain have an intersection point, and the first blocked light bead is recorded as A. When the cargo box leaves the light curtain, the cargo box and the light curtain have the last intersection point, and the last blocked light bead is recorded as C. During the period when the cargo box blocks the light curtain, the light bead at the minimum limit position of the intersection point between the cargo box and the light curtain is recorded as B. min 、Get detected B min The time taken t 1 (t 1 =t min -t b , t b Indicates the start time of the light curtain blocking of the cargo box, t min Indicates the time corresponding to the minimum light bead number being blocked during the transportation of the cargo box), and min The corresponding other intersection point B 1 (t minThe maximum light bead number among the light beads blocked at the moment); record the light bead number B at the maximum limit position of the intersection of the cargo box and the light curtain max 、Get detected B max The time taken t 2 (t 2 =t max -t b , t b Indicates the start time of the light curtain blocking of the cargo box, t max Indicates the time corresponding to the maximum light bead number being blocked during the transportation of the cargo box) and the time corresponding to the maximum light bead number being blocked during the transportation of the cargo box max The corresponding other intersection point B 2 (B 2 Indicates t max The smallest light bead number among the light beads blocked at that moment).
[0065] The controller is based on A and B 1 , B 2 , C, B min , B max Six position data and t 1 With t 2 The size relationship is used to construct the geometric relationship. The construction method is as follows:
[0066] Judgment B min , B max The order of acquisition:
[0067] If t 1 ≥t 2 , then construct ΔA'B 2 'B max ' and ΔC'CB max ';
[0068] If t 1 <t 2 , then construct ΔA'B 1 'B min ' and ΔC'CB min ';
[0069] Based on the constructed geometric relationships, the dimensions and angles of the cargo box are solved.
[0070] If t 1 ≥t 2 , then the following analysis process is available (see Appendix Figure 2 shown):
[0071] In ΔA'B 2 'B max 'The length can be calculated in |A'O|:
[0072]
[0073] Then in ΔA'OB max ', we can get ∠A'B max 'O and a size of the cargo box | A'B max '|:
[0074]
[0075] In ΔC'CB max 'Another dimension of the box can be calculated |B max 'C|:
[0076]
[0077] If t 1 <t 2 , then the following analysis process is available (see Appendix Figure 3 shown):
[0078] In ΔA'B 1 'B min 'The length can be calculated in |A'O|:
[0079]
[0080] Then in ΔA'OB min ', we can get ∠A'B min 'O and a size of the cargo box | A'B min '|:
[0081]
[0082] In ΔC'CB min 'Another dimension of the box can be calculated |B min 'C|:
[0083]
[0084] The lengths of the two adjacent sides of the cargo box have been calculated to be |A'B m '|、|B m 'C|, where B m 'For B min ' or B max '. In ∠A'B m 'O(B m 'For B max ' or B min '), according to the correct posture of the cargo box, the inclination angle θ of the cargo box is calculated; the calculation method of the inclination angle θ of the cargo box is as follows (see Appendix Figures 2-3 shown):
[0085] When the length and width of the cargo box are not equal, and the correct cargo box posture is: the short side is parallel to the light curtain;
[0086] If |A'B m '|≤|B m 'C|, then θ=∠A'B m 'O;
[0087] If |A'B m '|>|B m 'C|, then θ=90-∠A'B m 'O.
[0088] When the length and width of the cargo box are not equal, and the correct cargo box posture is: the long side is parallel to the light curtain;
[0089] If |A'B m '|≤|B m 'C|, then θ=90-∠A'B m 'O;
[0090] If |A'B m '|>|B m 'C|, then θ=∠A'B m 'O.
[0091] When the length and width of the cargo box are equal;
[0092] If ∠A'B m 'O≤45°, then θ=∠A'B m 'O;
[0093] If ∠A'B m 'O>45°, then θ=90°-∠A'B m 'O;
[0094] Above B m 'At the same time, B min ' or both B max '.
[0095] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for calculating the size and angle of moving cargo boxes on a roller transmission line using a light curtain, characterized in that: include: 1) Install the transmitting end and receiving end of the light curtain on the upper and lower sides of the roller transmission line respectively, and make several light beams emitted by the transmitting end of the light curtain pass through the gap between the rollers to reach the receiving end of the light curtain; 2) Number the light beads on the light curtain in order and obtain the distance data between adjacent light beads; 3) Calculate the size and angle data of the cargo box based on the distance data between adjacent light beads, the light bead numbers detected during the process from the beginning to the end of the cargo box blocking the light curtain, and the corresponding time.
2. The method for calculating the size and angle of moving cargo boxes on a roller transmission line using a light curtain according to claim 1, characterized in that: The cargo box is a rectangular or square cargo box.
3. The method for calculating the size and angle of moving cargo boxes on a roller transmission line using a light curtain according to claim 1, characterized in that: In step 1), the transmitting end of the light curtain is located on the upper side of the roller transmission line, the receiving end of the light curtain is located on the lower side of the roller transmission line, and the setting height of the transmitting end on the upper side of the roller transmission line should be higher than the maximum height of the cargo box on the roller transmission line; Alternatively, the transmitting end of the light curtain is located at the lower side of the roller conveyor line, the receiving end of the light curtain is located at the upper side of the roller conveyor line, and the setting height of the receiving end on the upper side of the roller conveyor line should be higher than the maximum height of the cargo box on the roller conveyor line.
4. The method for calculating the size and angle of moving cargo boxes on a roller transmission line using a light curtain according to claim 1, characterized in that: In step 2), the light beads on the light curtain are numbered one by one from left to right.
5. The method for calculating the size and angle of moving cargo boxes on a roller transmission line using a light curtain according to claim 4, characterized in that: In step 3), the light bead numbers and corresponding times detected during the process from the beginning of the cargo box blocking to the end of the light curtain blocking include: the starting light bead number, the ending light bead number, the minimum light bead number, the maximum light bead number, as well as the blocking start time, the time corresponding to the blocking of the minimum light bead number, and the time corresponding to the blocking of the maximum light bead number.
6. The method for calculating the size and angle of moving cargo boxes on a roller transmission line using a light curtain according to claim 5, characterized in that: The calculation method of the cargo box size data in step 3) is as follows: First, determine the size of t1 and t2; where t1 = t min -t b , t2=t max -t b , t b Indicates the start time of the light curtain blocking of the cargo box, t min Indicates the time corresponding to the blocking of the smallest light bead number during the transportation of the cargo box; t max Indicates the time corresponding to the blockage of the largest light bead number during the transportation of the cargo box; When t1≥t2, then a and b are the lengths of the two adjacent sides of the cargo box, where a represents t b ~t max In this time period, the four sides of the cargo box can block the side A'-B corresponding to the starting light bead number and the maximum light bead number. max '; b represents the length of the side A'-B in the cargo box max 'The length of the adjacent side; L1 = |B max -A|×d,L2=|B max -C|×d, where A is the starting bead number, B max is the maximum light bead number, C is the end light bead number, and d is the distance between adjacent light beads; In the above formula, in Where B2 represents t max The smallest light bead number among the light beads blocked at any moment; When t1 < t2, then a and b respectively represent the lengths of two adjacent sides of the cargo box, where a represents the length of the side that can block the side A'-B corresponding to the starting bead number and the minimum bead number during the time period from t b to t min among the four sides of the cargo box; b represents the length of the adjacent side of the side A'-B in the cargo box; L4 = |A - B min '| × d, L5 = |C - B min '| × d, where A is the starting bead number, B min is the minimum bead number, C is the ending bead number, and d is the distance between adjacent beads; In the above formula, in Where B1 represents t min The maximum light bead number among the light beads blocked at that moment.
7. The method for calculating the size and angle of moving cargo boxes on a roller transmission line using a light curtain according to claim 6, characterized in that: The calculation method of the cargo box angle data in step 3) is as follows: When t1 ≥ t2, the calculation method of the cargo box tilt angle θ is as follows: When the length and width of the cargo box are not equal, and the correct cargo box posture is that the short side is parallel to the light curtain; if a≤b, then θ=∠α; if a>b, then θ=90-∠α; When the length and width of the cargo box are not equal, and the correct cargo box posture is that the long side is parallel to the light curtain; if a≤b, then θ=90-∠α; if α>b, then θ=∠α; When the length and width of the cargo box are equal; if ∠α≤45°, then θ=∠α; if ∠α>45°, then θ=90-∠α; When t1<t2, the calculation method of the cargo box tilt angle θ is as follows: When the length and width of the cargo box are not equal, and the correct cargo box posture is that the short side is parallel to the light curtain; if a≤b, then θ=∠β; if a>b, then θ=90-∠β; When the length and width of the cargo box are not equal, and the correct cargo box posture is that the long side is parallel to the light curtain; if a≤b, then θ=90-∠β; if a>b, then θ=∠β; When the length and width of the cargo box are equal; if ∠β≤45°, then θ=∠β; if ∠β>45°, then θ=90-∠β.