Control method for package loading speed on sorting loop line

Abstract

The present invention discloses a method for controlling the speed of packages on a sorting loop line. After successful vehicle assignment, the method controls the speed and timing of the packages being loaded onto the line. This method not only achieves the initial sorting function but also meets the stability and center positioning requirements for the loading of packages of various sizes onto the line. This effectively reduces the probability of slippage and loss, and improves the sorting efficiency of the sorting machine. When a package is delivered to the synchronous loading section, the light curtain assembly is triggered to measure the length of the package along the running direction, the width perpendicular to the running direction, and the offset between the center of the package and the center of the conveyor belt of the synchronous loading section. The PLC attempts to assign an empty sorting cart to the package. If the assignment is successful, the package will begin accelerating and be loaded onto the sorting cart. Synchronization with the cart is achieved by adjusting the acceleration time. The package is obliquely introduced from the loading section into the sorting loop line and stops at the geometric center of the sorting cart. If the assignment is unsuccessful, the package will remain in the synchronous section.

Description

Technical Field

[0001] The present invention relates to a method for dynamically adjusting and controlling the online speed of packages used in initial sorting of a sorting system, and belongs to the field of logistics and warehousing. Background Art

[0002] Currently, in the field of logistics and warehousing, automation and intelligent control technologies are developing rapidly. With the continuous increase in industrial and commercial land and labor costs, intensive cross-belt sorting systems have higher operating efficiency because they can fully utilize space efficiency and correspondingly reduce labor requirements.

[0003] The cross-belt sorting loop disclosed in the prior art has parcels of varying sizes. When feeding the sorting cart, due to the error between the front-end conveying speed and the timing of the sorting cart's arrival, it is usually difficult to accurately position the parcel at the geometric center of the cart's conveying surface, i.e., there is a certain offset. Adding to the parcel volume factor, there are significant differences in the offset state of the cart. When accelerating, large parcels tend to slide sideways or even fall off the cart. This type of lost parcel problem often occurs at current logistics operations, causing significant trouble for the overall sorting work.

[0004] In view of this, this patent application is hereby filed. Summary of the Invention

[0005] The control method for the speed of packages on a sorting loop line described in the present invention aims to solve the problems existing in the above-mentioned prior art and proposes a method for controlling the mutual speed and the timing of loading the package after the vehicle is successfully assigned, so as to achieve effective control of the accuracy of package introduction and positioning on the vehicle, thereby meeting the stability and center positioning requirements of packages of various volumes on the line on the basis of realizing the initial sorting function, effectively reducing the probability of slippage and loss of packages, and improving the sorting efficiency of the sorting machine.

[0006] To achieve the above design objectives, the present application describes a method for controlling the speed of parcels on a sorting loop line. When a parcel is conveyed to the synchronous uploading section, a light curtain assembly is triggered. The light curtain assembly measures the length of the parcel along the running direction, Parcel_L; the width of the parcel perpendicular to the running direction, Parcel_W; and the offset between the center of the parcel and the center of the conveyor belt in the synchronous uploading section.

[0007] Assume that the running speed of the sorting loop is Vst and the pitch between two adjacent trolleys is W_car, then the pitch time of each trolley is Tp = W_car / Vst;

[0008] The uniform speed of the uploading section is V252. To ensure that the process of the parcel being introduced from this section to the sorting cart is smooth and does not deflect, the component of V252 in the running direction of the sorting line should be consistent with the running speed Vst of the sorting line, that is, V252 = Vst / cosα, where α is the angle between the two.

[0009] The time Tload required for the package to be imported from the upload section to the geometric center of the sorting cart is satisfied.

[0010] Tload=(L_B2+0.5*L_car / sinα+offset / tanα-0.5*Parcel_L) / V252

[0011] =(L_B2+0.5*L_car / sinα+offset / tanα-0.5*Parcel_L)*cosα / Vst;

[0012] Based on the time Tload, the PLC attempts to assign an empty sorting cart to the package. If the assignment is successful, the package will begin to accelerate and be introduced online to the sorting cart, achieving synchronization with the cart by adjusting the acceleration time. The package will be diagonally introduced into the sorting loop from the upload segment and stop at the geometric center of the sorting cart. If the assignment is unsuccessful, the package will remain in the synchronization segment.

[0013] Furthermore, the parcel width Parcel_W = (Parcel_max_point - Parcel_min_point) * (beam spacing G); the offset between the parcel center and the belt center offset = (Parcel_max_point + Parcel_min_point) / 2 - belt_center_point; the parcel length Parcel_L = T1 * V1, the time it takes for the parcel to pass through the light curtain is T1, and the speed at which the parcel passes through the light curtain is the fixed value V1 initially set by the system.

[0014] Furthermore, an array of position sensors is equidistantly arranged on the sorting loop. When the sorting trolley runs at a constant speed along the loop, a pulse signal is generated each time it passes a position sensor. The sorting machine main control PLC collects the synchronous pulse signal and distributes it to the induction station PLC of the bidirectional induction device to serve as the position and time control reference signal for the package induction online.

[0015] Furthermore, the process of the package being imported from the uploading section to the sorting cart is uniform, and the synchronization section is set to have two high and low running speeds VL and VH, where VL is the speed of the package when passing through the light curtain assembly, and VH is consistent with V252; the minimum and maximum values of the variable speed running time of the package in the synchronization section are Tmin=TL_H+(LB_1-SL_H) / VH; Tmax=TL_H+(LB_1-SL_H) / VL; the acceleration time point Tb is between the above maximum and minimum values, and the package executes the "non-stop" control mode, that is, the package will experience VL uniform speed running, VL acceleration to VH and VH uniform speed running in the synchronization section, with a total running time of Tadj_ns; the acceleration delay time Tb of the package in the synchronization section 251 is [N*Tp+(offset / sinα+ΔL) / Vst–Ta-TL_H-(LB_1-SL_H) / VH] / [1-VL / VH].

[0016] Furthermore, when the package passes the light curtain assembly from the tail, if it is determined that there is no sorting trolley that can complete the speed control within a reasonable time, the package will brake immediately until a sorting trolley that meets the time range requirements is found again at a certain synchronization pulse moment; the package needs to go through two stages from starting to acceleration, from 0 to VH, and VH constant speed operation after the tail of the package passes the dividing line between the upload segment and the synchronization segment. The required time Tadj_s is calculated as follows: Tadj_s = T0_H + (LB_1–S0_H-SL_0) / VH = VH / a + (LB_1–VH 2 / 2a-VL 2 / 2a) / VH; acceleration delay time wrapped in the synchronization segment Tc=(N+1)*Tp+(offset / sinα+ΔL) / Vst-Tadj_s-Tload.

[0017] In summary, the control method for the speed of packages on the sorting loop line described in this application has the advantages of being able to comprehensively and accurately calculate the acceleration time period allocation and loading timing required for the introduction of the package on the line based on multiple factors such as the conveying speed before the package is put on the line, the location and size of the package, thereby achieving the control effect of the geometric center of the package on the vehicle, fundamentally solving the occurrence of sliding and lost items, and maximizing the sorting efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will now be further described with reference to the following drawings.

[0019] Figure 1 This is a calculation diagram of the control method applied to the speed of packages on the sorting loop line;

[0020] Figure 2This is the principle diagram of the PLC system regulating the belt conveyor speed;

[0021] Figure 3 It is a structural diagram of a bidirectional introduction device;

[0022] Figure 4 This is a schematic diagram of the light curtain assembly. DETAILED DESCRIPTION

[0023] To further illustrate the technical means employed by this application to achieve the intended design objectives, the following preferred embodiments are presented in conjunction with the accompanying drawings. Specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways than those described herein, and those skilled in the art may make similar designs without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0024] Example 1, as Figures 1 to 4 As shown, the present application proposes a method for controlling the speed of parcels on a cross-belt sorter, wherein a bidirectional introduction device is connected between the introduction ends of the sorting loops 6 on both sides.

[0025] The bidirectional introduction device has two sets of parallelly arranged first conveying components 13 and second conveying components 14 , and a code reading device 15 is arranged vertically above the first conveying components 13 and the second conveying components 14 .

[0026] A first introduction section 21 and a second introduction section 22 with opposite conveying directions are connected to both sides of the first conveying component 13, and a third introduction section 16 and a fourth introduction section 20 with opposite conveying directions are connected to both sides of the second conveying component 14; the first introduction section 21 and the third introduction section 16 are connected to the first encoding section 17, which is connected from one side and guides the package into the sorting loop 6; the second introduction section 22 and the fourth introduction section 20 are connected to the second encoding section 23, which is connected from the other side and guides the package into the sorting loop 6.

[0027] The first introduction section 21 , the second introduction section 22 , the third introduction section 16 and the fourth introduction section 20 may adopt the same driving and conveying structure, such as a synchronous belt conveyor.

[0028] In order to improve the posture control during the package induction and transportation process and prevent excessive deflection or overturning, the connection end of the synchronous belt conveyor is connected obliquely to the connection direction of the synchronous belt.

[0029] Specifically, the first introduction section 21, the second introduction section 22, the third introduction section 16 and the fourth introduction section 20 are all obliquely connected to the first encoding section 17 and the second encoding section 23;

[0030] The first encoding section 17 and the second encoding section 23 are both connected to the sorting loop line 6 at an angle.

[0031] The package is scanned and identified on the first conveyor assembly 13 or the second conveyor assembly 14. The barcode reader 15 records the package's barcode information and uploads it to the host system, which then provides feedback on the designated slot. The first conveyor assembly 13 or the second conveyor assembly 14 automatically selects the delivery direction. If the delivery direction indicates the first inlet section 21 or the third inlet section 16, the package is directed to the sorting loop 6 via the first encoding section 17. If the delivery direction indicates the second inlet section 22 or the fourth inlet section 20, the package is directed to the sorting loop 6 via the second encoding section 23.

[0032] The first encoding section 17 and the second encoding section 23 have the same structural design. The second encoding section 23 is connected to the synchronous uploading section 25, which is connected to the sorting loop 6. A light curtain assembly 24 is vertically positioned between the second encoding section 23 and the synchronous uploading section 25. The first encoding section 17 is connected to the second synchronous uploading section 19, which is connected to the sorting loop 6. A second light curtain assembly 18 is vertically positioned between the first encoding section 17 and the second synchronous uploading section 19. The synchronous uploading sections 25 and 19, as well as the light curtain assembly 24 and 18, are all structurally identical and symmetrically positioned.

[0033] Taking the synchronous uploading section 25 as an example, it includes a synchronous section 251 and an uploading section 252 connected in sequence. The synchronous section 251 can adopt a full belt conveyor, and the uploading section 252 can adopt a narrow belt conveyor.

[0034] Furthermore, the uploading section 252 of the synchronous uploading section 25 is connected to the sorting loop line 6 at an angle.

[0035] The control method for the speed of the packages on the sorting loop line described in the present application is to trigger the light curtain assembly 24 when the package is transported from the second encoding section 23 to the synchronous uploading section 25. The light curtain assembly 24 includes a group of package size detection light curtains 241 arranged at equal intervals on the top and height limiting photoelectric screens 242 symmetrically arranged on both sides.

[0036] The height-limiting photoelectric device 242 is used to check whether the package is too high. If it is too high, the height-limiting photoelectric device 242 will be triggered, and the second encoding section 23 and the synchronous uploading section 25 will simultaneously perform a reversal action to unload the package to the end of the second encoding section 23 and hand it over to human intervention.

[0037] The package size detection light curtain 241 is used to measure the length of the package in the running direction, the width perpendicular to the running direction, and the specific position of the package entering the synchronous uploading section 25.

[0038] The measurement principle is to select detection photoelectric light curtains with different specifications and models with intervals ranging from 10mm to 50mm according to the measurement accuracy requirements. The width of the package can be calculated by detecting the number of times the package blocks the light beam, and the length of the package can be calculated by the time the package blocks the light beam and the package conveying speed. The relative position of the package perpendicular to the two sides of the synchronous uploading section 25 is calculated by the deviation between the center point of the light curtain detection area and the center position in the width direction of the package.

[0039] Define the following parameters accordingly:

[0040] Parcel length Parcel_L;

[0041] Parcel width Parcel_W;

[0042] Beam spacing G (system initial setting);

[0043] The offset between the package center and the conveyor belt center of the synchronous uploading section 25;

[0044] Conveyor belt center point belt_center_point (system initial setting);

[0045] After the package passes through the light curtain, the maximum beam value Parcel_max_point is measured;

[0046] Parcel_max_point is the minimum beam value measured after the package passes through the light curtain;

[0047] When a package passes through the package size detection light curtain 241, the PLC collects the starting value LSCR_FIRST_BLOCK_POINT and the end value LSCR_LAST_BLOCK_POINT of the light beam blocked by the light curtain in real time through the serial port or industrial Ethernet communication. The sampling interval is approximately 10-30ms depending on the different models of the light curtain.

[0048] When the parcel passes through the light curtain, the PLC compares the starting and ending values of the light beam collected each time with the values collected last time, and finally calculates the maximum beam point Parcel_max_point and the minimum beam point Parcel_min_point of the parcel collected by the light curtain after the parcel passes through the light curtain;

[0049] Parcel width Parcel_W = (Parcel_max_point - Parcel_min_point) * (beam spacing G);

[0050] Parcel center and belt center offset = (Parcel_max_point + Parcel_min_point) / 2 - belt_center_point;

[0051] The timer starts when the package enters the light curtain detection area and ends when the tail of the package leaves the light curtain. The time it takes for the package to pass through the light curtain is T1. The speed of the package passing through the light curtain is the fixed value V1 initially set by the system. Therefore, the package length Parcel_L = T1*V1;

[0052] Based on the measured parameters, the PLC attempts to assign the parcel to an available sorting cart. If the assignment is successful, the parcel accelerates and is introduced to the sorting cart, achieving synchronization with the cart by adjusting the acceleration time. If the assignment is unsuccessful, the parcel remains in synchronization segment 251. Specifically, before the parcel enters the sorting loop 6 from the second encoding segment 23, it waits in synchronization segment 251 for an available sorting cart to be assigned. The parcel is synchronized with the sorting cart by adjusting the acceleration time of synchronization segment 251 and the upload segment 252, or by delaying the start. When the cart arrives, the upload segment 252 conveys at the same speed as the sorting cart. The parcel is then diagonally introduced into the sorting loop 6 by the upload segment 252 and stops at the geometric center of the sorting cart.

[0053] An array of position sensors is evenly spaced along the sorting loop 6. Each time the sorting cart passes a position sensor while running at a constant speed along the loop, a pulse signal (called a synchronization signal) is generated. The sorting machine master control PLC collects this synchronization pulse signal and distributes it to the induction station PLC of the bidirectional induction device, which serves as a reference signal for position and timing control of parcel induction.

[0054] Assume that the running speed of sorting loop 6 is Vst and the pitch between two adjacent trolleys is W_car, then the pitch time of each trolley is Tp=W_car / Vst;

[0055] The uniform running speed of the uploading section 252 is V252. To ensure that the process of the package from this section to the uploading line to the sorting trolley is smooth and does not deflect, the component of V252 in the running direction of the sorting loop should be consistent with the running speed Vst of the sorting loop 6, that is, V252 = Vst / cosα, where α is the angle between the two.

[0056] At the same time, the component of V252 in the direction perpendicular to the running of the sorting loop line 6 should be consistent with the running speed of the sorting trolley belt "welcoming" the package;

[0057] The time Tload required for the package to be imported from the upload section 252 to the geometric center of the sorting cart is:

[0058] Tload=(L_B2+0.5*L_car / sinα+offset / tanα-0.5*Parcel_L) / V252

[0059] =(L_B2+0.5*L_car / sinα+offset / tanα-0.5*Parcel_L)*cosα / Vst;

[0060] It can be seen from the above formula that the time value Tload is related to parameters such as the longitudinal centerline length of the uploading section 252, the length of the sorting trolley, the angle α between the uploading section 252 and the sorting loop, the deviation between the package center and the light curtain center, the package length, and the running speed of the sorting loop.

[0061] Wherein, L_B1 is the length of the synchronization segment 251;

[0062] L_B2 is the length of the centerline of the upload segment 252;

[0063] L_B3 is the projection distance from the boundary between the center line of the uploading section 252 and the sorting trolley to the geometric center point of the trolley where the package is uploaded in the direction of package movement;

[0064] L1 is the distance from the sorting cart’s successful allocation to its operation until the package is loaded onto the cart’s geometric center point;

[0065] L2 is the distance from the tail of the package leaving the measuring light curtain to the geometric center point of the package being loaded onto the trolley;

[0066] Since the process of the package being introduced from the uploading section 252 to the sorting cart is uniform, during its operation on the synchronization section 251 (i.e., from the time the package leaves the light curtain assembly 24 at its tail end to the time it passes through the dividing line between the uploading section 252 and the synchronization section 251 and completely enters the uploading section 252), it can be divided into two control modes: non-stop and pause.

[0067] For the synchronization section 251, it is set to have two speeds, VL and VH, where VL is the speed of the package when it passes through the light curtain assembly 24, and VH is consistent with V252 to ensure that the package can smoothly pass the boundary between the upload section 252 and the synchronization section 251;

[0068] Set the belt acceleration and deceleration to a. The time and distance required for the package to decelerate from VL to 0, accelerate from VL to VH, and accelerate from 0 to VH are:

[0069] TL_0=VL / a, TL_0 is the braking time from VL to 0;

[0070] SL_0=VL 2 / 2a, SL_0 is the braking distance from VL to 0;

[0071] TL_H=(VH-VL) / a, TL_H is the acceleration time required for the speed to accelerate from VL to VH;

[0072] SL_H=(VH 2 -VL 2 ) / 2a, SL_H is the acceleration distance required to accelerate the speed from VL to VH;

[0073] T0_H=VH / a, T0_H is the acceleration time required for the speed to accelerate from 0 to VH;

[0074] S0_H=VH 2 / 2a, S0_H is the acceleration distance required to accelerate the speed from 0 to VH;

[0075] When a package passes the light curtain assembly 24 from the rear, the time difference Ta between this moment and the last synchronization pulse signal can be obtained by the timer. At this moment, it is judged whether there is a sorting trolley that meets the online import conditions (large enough) and can complete the speed control within the following reasonable time (no faults, no packages currently occupied, etc.). The judgment process is as follows:

[0076] There are two possible time points for the package to accelerate from VL to VH in the synchronization segment 251: the earliest and the latest. The earliest time point is the moment when the tail of the package leaves the light curtain assembly 24, and the latest acceleration position is the position equal to SL_H from the boundary between the upload segment 252 and the synchronization segment 251. That is, the package is guaranteed to have completed the acceleration process when it runs to the upload segment 252. Therefore, the running time of the package in the second synchronization segment 251 has two possible values: the minimum and the maximum:

[0077] Tmin=TL_H+(LB_1-SL_H) / VH;

[0078] Tmax=TL_H+(LB_1-SL_H) / VL;

[0079] If the acceleration time point Tb (starting from the time when the tail of the package leaves the light curtain assembly 24) is between the two, the package will execute the following "non-stop" control mode, that is, the package will experience three stages of VL uniform speed operation, acceleration from VL to VH, and VH uniform speed operation on the synchronization segment 251, with a total operation time of Tadj_ns:

[0080] Tadj_ns=Tb+TL_H+(LB_1-SL_H–Tb*VL) / VH, and Tmin≤Tadj_ns≤Tmax;

[0081] If the above calculation conditions and results are met, there must be a sorting trolley whose time from the current moment to the point of convergence with the package center is between Tload+Tmin and Tload+Tmax. Therefore, by adjusting the acceleration delay time Tb of the package in the synchronization segment 251, the time from the tail of the package leaving the light curtain assembly 24 to the point of convergence with the package center to the geometric center of the sorting trolley can be satisfied, which is equal to the time required for the sorting trolley to run from the current moment to the point of convergence with the package center. In other words, the following conditions are met:

[0082] Tload+Tmin≤N*Tp+(offset / sinα+ΔL) / Vst-Ta≤Tload+Tmax

[0083] Where Tp is the pitch time of each trolley, Vst is the running speed of the sorting loop, ΔL is the set value of the relative position of the position sensor that generates the pulse synchronization signal. Generally, (-1)*W_car≤ΔL≤W_car, W_car is the distance between two adjacent trolleys;

[0084] The acceleration delay time Tb wrapped in the synchronization segment 251 can be derived from the above formula through loop judgment:

[0085] Tb+TL_H+(LB_1-SL_H–Tb*VL) / VH=N*Tp+(offset / sinα+ΔL) / Vst–Ta;

[0086] Tb=[N*Tp+(offset / sinα+ΔL) / Vst–Ta-TL_H-(LB_1-SL_H) / VH] / [1-VL / VH]

[0087] When the package passes the light curtain assembly 24 from the rear, if it is determined that there is no sorting trolley that completes the speed control within a reasonable time, the package will brake immediately until a sorting trolley that meets the time range requirements is found again at a certain synchronous pulse moment. This is the "stop" control mode:

[0088] In the "stop" mode, the acceleration delay time Tc of the synchronization segment 251 also needs to be calculated, but this is a delay relative to the synchronization pulse time.

[0089] From the start to the acceleration, the package tail passes through the boundary between the upload segment 252 and the synchronization segment 251 and needs to go through two stages: acceleration from 0 to VH and constant speed operation at VH. The required time Tadj_s is calculated as follows:

[0090] Tadj_s=T0_H+(LB_1–S0_H-SL_0) / VH

[0091] =VH / a+(LB_1–VH 2 / 2a-VL 2 / 2a) / VH;

[0092] The time it takes for a sorting vehicle that meets the conditions to run from the current moment to the meeting point with the parcel center is:

[0093] N*Tp+(offset / sinα+ΔL) / Vst≤Tadj_s+Tload≤(N+1)*Tp+(offset / sinα+ΔL) / Vst;

[0094] Through loop judgment, the corresponding N can be calculated (N is the Nth trolley running in the opposite direction of the sorting machine starting from the center point where the package meets the sorting trolley), and thus the acceleration delay Tc can be calculated:

[0095] Tc=(N+1)*Tp+(offset / sinα+ΔL) / Vst-Tadj_s-Tload.

[0096] The above is the acceleration time and speed control process under two different control modes.

[0097] When the tail of the package leaves the dividing line between the upload segment 252 and the synchronization segment 251, the speed of the synchronization segment 251 can be reduced to VL, so that subsequent packages can continue to enter the synchronization segment 251 to start a new package upload speed control process.

[0098] The embodiments described above, in conjunction with the accompanying drawings, are merely preferred solutions for achieving the objectives of the present invention. Those skilled in the art will readily be able to derive alternative structures consistent with the design concepts of the present invention based on these insights. Other structural features derived from these alternatives are also intended to fall within the scope of the present invention.

Claims

1. A method for controlling the speed of packages on a sorting line, characterized by: When the parcel is delivered to the synchronous uploading section, the light curtain assembly is triggered. The light curtain assembly measures the parcel's length along the running direction (Parcel_L), its width perpendicular to the running direction (Parcel_W), and the offset between the parcel center and the center of the conveyor belt in the synchronous uploading section (Offset). Assume that the running speed of the sorting loop is Vst and the pitch between two adjacent trolleys is W_car, then the pitch time of each trolley is Tp = W_car / Vst; The uniform speed of the uploading section is V252. To ensure that the process of the parcel being introduced from this section to the sorting cart is smooth and does not deflect, the component of V252 in the running direction of the sorting line should be consistent with the running speed Vst of the sorting line, that is, V252 = Vst / cosα, where α is the angle between the two. The time Tload required for the package to be imported from the upload section to the geometric center of the sorting cart is satisfied. Tload =(L_B2 +0.5*L_car / sinα +offset / tanα-0.5* Parcel_L) / V252 = (L_B2 +0.5*L_car / sinα +offset / tanα-0.5* Parcel_L)* cosα / Vst; Based on the time Tload, the PLC attempts to assign an empty sorting cart to the package. If the assignment is successful, the package will begin accelerating and be introduced to the sorting cart. The acceleration time is adjusted to achieve synchronization with the cart. The package is then diagonally introduced into the sorting loop from the upload segment and stops at the geometric center of the sorting cart. If the assignment is unsuccessful, the package will remain in the synchronization segment. An array of position sensors are set at equal distances on the sorting loop. When the sorting trolley runs at a constant speed along the loop, a pulse signal is generated every time it passes a position sensor. The sorter master control PLC collects the pulse signal and distributes it to the induction station PLC of the bidirectional induction device to serve as the reference signal for position and time control of the package induction line; The process of the package being introduced from the uploading section to the sorting cart is uniform. At the same time, the synchronization section is set with two speeds, VL and VH, where VL is the speed when the package passes through the light curtain assembly, and VH is consistent with V252. The minimum and maximum values of the variable speed running time wrapped in the synchronization segment are, Tmin= TL_H + (LB_1 - SL_H) / VH; Tmax= TL_H + (LB_1 - SL_H) / VL; When the acceleration time point Tb is between the maximum and minimum values, the package executes the "non-stop" control mode. That is, the package will experience three stages in the synchronization segment: VL uniform speed operation, acceleration from VL to VH, and VH uniform speed operation. The total operation time is Tadj_ns; The acceleration delay time Tb wrapped in the synchronization segment = [N*Tp +(offset / sinα + ΔL) / Vst –Ta- TL_H- (LB_1 - SL_H) / VH] / [1- VL / VH].

2. The method for controlling the speed of packages on a sorting line according to claim 1, characterized in that: Parcel width Parcel_W = (Parcel_max_point-Parcel_min_point)*(beam spacing G); The offset between the parcel center and the belt center is offset = (Parcel_max_point+Parcel_min_point) / 2 -belt_center_point; Parcel length Parcel_L = T1*V1, the time it takes for the parcel to pass through the light curtain is T1, and the speed at which the parcel passes through the light curtain is the fixed value V1 initially set by the system.

3. The method for controlling the speed of packages on a sorting line according to claim 1, characterized in that: When a package passes through the light curtain assembly from the rear, if it is determined that there is no sorting trolley that can complete the speed control within a reasonable time, the package will brake immediately until a sorting trolley that meets the time range requirements is found again at a certain synchronous pulse moment; From the start to the acceleration, the package tail passes through the boundary between the upload segment and the synchronization segment. It needs to go through two stages: acceleration from 0 to VH, and constant speed operation of VH. The time required is calculated as follows: Tadj_s= T0_H + (LB_1 – S0_H - SL_0) / VH <h2 style=";text-align:left;direction:ltr">= VH / a + (LB_1 – VH<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> / 2a - VL<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> / 2a) / VH; The acceleration delay time wrapped in the synchronization segment is Tc=(N+1)*Tp + (offset / sinα + ΔL) / Vst - Tadj_s -Tload.

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