In recent years, with the rapid development of e-commerce, express delivery industry, major e-commerce, express delivery enterprise logistics warehousing and distribution centers on the intelligent transport sorting equipment performance requirements are also more and more high. In order to solve the application problems of different scenarios such as small soft package sorting, large heavy-duty sorting, the balance wheel sorter as a logistics warehousing and distribution centers commonly used sorting equipment, its technology continues to iterative development, the successive emergence of a different structure of the balance wheel sorter, its performance continues to improve, in order to meet the fast-changing market demand, and improve the timeliness of logistics and distribution.
According to the different sorting efficiency, the development of the balance wheel sorter can be divided into three stages: low-speed, medium-speed and high-speed. Low-speed stage of the jacking type and pneumatic type pendulum sorter, sorting efficiency ≤ 2000pcs / h; medium-speed stage of the electric type and power ball type pendulum sorter, sorting efficiency ≤ 4000pcs / h. With the continuous improvement of the market demand, the performance of the logistics equipment is also increasing, accelerating the pendulum sorter into the high-speed stage.
The structure of the new balance wheel sorter is mainly composed of three main parts: conveying unit, transmission unit and steering unit, which adopts standard modular design, can be easily and quickly disassembled from top to bottom, which is convenient for on-site maintenance; independent modularization unit, simple structure, easy to expand the layout according to the application scenario, which brings more possibilities for system deployment. The product is driven by servo motors for soft steering, fast response, and stable operation under heavy load; through servo steering process control and steering angle control, it effectively reduces the impact of the sorting steering while realizing multi-angle and bi-directional sorting, which makes the trajectory of items sorting smoother and ensures the smoothness of the sorting; at the same time, it adopts dual-speed mode control and small-pitch precision control to ensure that the items’ distance will not change when high-speed sorting. change during high-speed sorting to improve sorting efficiency.
Efficient Sortation Control Technology
Improving the sorting efficiency of the pendulum sorter can be realized by increasing the running speed, narrowing the item gap, and improving the response speed of the steering action. Under the premise of high speed and high efficiency, how to ensure that the servo drive on the equipment steering structure impact is small, smooth operation? How to ensure flexible sorting of items to reduce the impact? Sorting control technology is particularly important.
Overview of the electrical control process
The electrical control of the pendulum sorter can be used as a separate control unit to control its conveyor sorting individually. After the front-end merging and pulling distance, the articles are arranged into the front-end conveyor line of the sorter according to a certain spacing. The code reader reads the barcode information of the articles and interacts with the WCS/WMS system to obtain the sorting destination of the articles. The conveyed items trigger the photoelectricity, the main control PLC gives the sorting action signal and destination direction signal, the first module pendulum wheel turns to the specified angle, the servo motor stops the steering action, and the pendulum wheel stays in this position. After a certain interval of time, the other module balance wheel will turn to the position successively to realize the sorting of goods.
As we all know, the sorting efficiency of the pendulum sorter is directly proportional to its running speed and inversely proportional to the item pitch (the sum of item length and item gap). Obviously, the length of the item is determined, in order to improve the sorting efficiency, can increase the operating speed of the equipment and reduce the item gap.
Speed control
When the items are conveyed straight, the running speed of the balance wheel is the same as that of the front and rear conveyors, but when the items are sorted, the speed of the balance wheel will be less than the speed of the straight conveyor, and the gap between the sorted items and the back of the straight items will gradually become smaller and smaller, thus affecting the conveying and sorting of the items in the subsequent period. Therefore, it is necessary to improve the running speed of the pendulum sorting, to ensure that the straight-line speed of the sorted items and the conveyor speed is the same. This requires the pendulum sorter has a double speed – the regular state of the straight-line speed and sorting speed, and the two speed modes can be quickly switched to ensure that the item gap will not change.
Item spacing control
Another way to improve sorting efficiency is to reduce the item gap, the pendulum adopts modular design, multi-group steering drive module, in order to ensure high speed and high efficiency sorting, the length of the pendulum module is generally <250mm. the length of each pendulum module should be less than the item gap, to ensure that the pendulum module steering will not affect the adjacent items of conveyor sorting. This requires that the balance wheel can complete the quick steering of 45° limit position in the adjacent article gap space, and the steering space of the limit position is 250-300mm. considering that the position of the article will be shifted after passing through different conveying and sorting equipments, which will cause the gap of the adjacent articles to become smaller, it is conventional to set the minimum gap of the adjacent articles to be 350mm, which can ensure the normal sorting efficiency and reduce the sorting return caused by too small gap of articles. Too small and caused by the sorting backflow.
Servo steering action control
The current balance wheel sorter mostly uses 400W servo motor, equipped with a certain speed ratio reducer, as the steering unit drive. In 150ms to complete the limit position switching, the servo steering requirements are very high. It is necessary to accelerate to the rated speed of the servo motor of 3,000rpm, steer evenly and then decelerate, with the same time for acceleration and deceleration, and ensure smooth steering action by reducing the rigidity of the servo motor. In addition, the steering acceleration of the servo motor is very large, and its impact is also very large. It is necessary to gradually increase/decrease the value of the steering acceleration of the servo motor in the starting/stopping phase of the servo motor, so as to make the motor’s rotational speed curve become smoother, and the servo motor’s rigidity can be reduced by adjusting the servo driver’s gain parameter, so as to reduce the sorting steering impact, and to ensure the steering action is smooth.
Multi-angle steering control
In order to ensure that the items are completely sorted, large-angle steering can be set to sort, but it may cause sudden change of direction and tumbling damage when sorting the items, which can be controlled by the steering angle, each balance wheel module is set to a different sorting angle, and the angle is gradually increasing, such as 30 °, 35 °, 45 °, 50 °, 60°, so that the items are smoothly steered to realize the flexible sorting of the items.
