Intelligent logistics four-way shuttle robot technology and application!


Release time:

Jul 08,2022

Intelligent logistics four-way shuttle robot technology and application!

Foreword

 
The narrow definition of four-way shuttle robot refers to a storage robot that can shuttle in four directions (front, back, left, right) in the plane, which is mainly different from the traditional two-way shuttle (forward and backward). Compared with AGV, although the shuttle robot needs to run on the track, the speed of the car will be faster and the positioning will be more accurate, which is far beyond the AGV system.
 
Classification of 1. four-way shuttle robot
 
The four-way shuttle robot is mainly divided into two types: the material box shuttle and the pallet shuttle according to the different types of units it handles. These two versions each have different characteristics.
 
For pallet type four-way shuttle robot, it is mainly used for pallet access operation. Compared with AS/RS, it has the advantages of more flexible storage and higher flexibility, can adapt to any complex warehouse structure, can increase or reduce the number of trolleys according to the demand of entering and leaving the warehouse, and can realize high-density storage, etc. However, its disadvantage is that it increases the cost of shelves, thus forming a phenomenon of mutual advantages in practical application. That is, in most cases, AS/RS shows a greater cost advantage, but in some extreme cases, a four-way shuttle is more appropriate. If the warehouse is not high, the shape of the warehouse is irregular, the frequency of entering and leaving the warehouse is not high, or the frequency of entering and leaving the warehouse is too high, the four-way shuttle can give full play to its advantages.
 
The bin type four-way shuttle robot is a robot for bin access. Corresponding technologies include Miniload and multi-layer shuttles. Miniload is an AS/RS system dedicated to bin access. Compared with tray type AS/RS, the Miniload is lighter and faster, but the height is generally not very high, and the load is generally less than 50kg. Multi-layer shuttle is a reciprocating access device running in the shelf. Compared with Miniload, it is faster and more flexible. Therefore, when higher access speed is required, multi-layer shuttle has Miniload incomparable advantages and is widely used in goods-to-people picking systems. Box-type four-way shuttle robot is a more flexible product, similar to the pallet-type four-way car, it has a wide range of adaptability, can be applied to a variety of warehouse types, can also be flexible by increasing or decreasing the number of cars to match the actual needs. Especially in the goods-to-people picking system, because the car can change floors through the hoist, in fact, it can run flexibly in a 3-dimensional space. Therefore, foreign countries call it 3D Satellite shuttl car more vividly, which is incomparable between Miniload and multi-layer shuttle cars.
 
The four-way shuttle robot is a revolutionary technology in the logistics and warehousing system. Although its application history is not long, it has attracted widespread attention in the industry and is considered to be an important part of the future intelligent logistics system. In this paper, the technical characteristics and application scope of the four-way shuttle robot are discussed in detail.
 
Key points of 2. technology
 
2.1 working principle
 
The four-way shuttle generally has two sets of wheel trains, one of which is responsible for walking in the X direction and the other for walking in the Y direction. The trolley runs on the track and encounters a turn, which is done by replacing the gear train. Thus, the orientation of the cargo unit is constant throughout the operating time.
 
If the car to change the layer, most of it is done by the hoist outside the roadway. After the car automatically drives into the hoist, the hoist is lifted to the required floor to complete the floor change. In practical application, there are two operation modes of the hoist: operation with car and operation without car. When working without a car, the hoist only lifts the cargo unit. When working with a car, the car and the cargo enter the hoist at the same time for each operation. At this time, there is no need to change the floor hoist. Obviously, when lifting without a car, each floor needs a cargo transfer workstation, which is not a small cost, and the system will be much simpler when working with a car, and the end of each floor will be much simpler, but the efficiency will also be much lower. This is to be noted.
 
The biggest feature of the four-way shuttle car is that each car can reach every warehouse location. Therefore, theoretically speaking, if there is no requirement for the ability to enter and leave the warehouse, one car can complete the entry and exit operations of the entire warehouse. This has a great advantage for systems with low access frequency.
 
As a system, the four-way shuttle needs to form a complete system with shelves (tracks), hoists, conveying systems, communication systems, and charging systems to work. Of course, software systems related to management, monitoring, scheduling and control It is also essential.
 
2.2 common technical characteristics
 
In the form of four-way shuttle robot, whether it is pallet type or box type, its technology has some common characteristics, such as shelves, tracks, positioning, communication, power supply, maintenance and so on.
 
1) shelf and track
Compared with the traditional three-dimensional storage system, the shelf is the biggest change of the shuttle system. All the paths that the car passes through need to be paved with tracks, special transfer plates at turning points, and charging points for each car. This is the characteristic of the four-way shuttle car and the main reason for the increase in cost. Relatively speaking, the processing accuracy and installation accuracy of the shuttle system for the shelves are higher than those of the traditional shelves, which will increase the cost of processing and installation. At present, there are not many domestic enterprises that can produce shuttle shelves. Especially for the box type shuttle truck shelves, the requirements are more stringent.
 
2) Positioning
The positioning of the shuttle car generally uses bar code and photoelectric switch positioning. Positioning accuracy requirements within 3mm. Simpler than an AGV, the shuttle runs on a fixed track and does not require a navigation system.
 
3) Communication
How to achieve communication in dense shelves requires experience and skills. What kind of antenna and communication technology to choose is very important to the stability of the project.
 
4) Power supply
Generally, the capacitor lithium battery is used, and the capacitor must ensure that one charge can complete the farthest operation, which will make a big difference to the configuration of the car. The longer the path, the larger the capacitor required. The battery can only be used as an auxiliary power supply to avoid power failure or low voltage in the middle of the car.
 
5) Control
The majority of European shuttle car control using PLC, but this higher cost. In Japan, the use of a dedicated integrated circuit board for control can greatly reduce the cost of the product. There are also two options for domestic equipment.
 
6) Dispatching system
For a four-way shuttle car, there are often multiple cars working at the same time in a working area. How to improve the overall efficiency of the system requires the car to be scheduled. The contents of scheduling include: vehicle condition identification, vehicle selection, route planning and so on. The more cars, the more important and difficult the scheduling.
 
7) Maintenance
Relatively speaking, due to the large size of the pallet shuttle, the wider roadway, and the higher floor height, theoretically, personnel can enter the interior of the shelf for operation. However, the material box shuttle is not the case. Therefore, on the one hand, try to avoid entering the shelf, on the other hand, consider the possibility of entering the shelf in the design, which is an important difference.
 
2.3 non-generic technical characteristics
 
1) Tray type four-way shuttle
 
① Transfer
For pallet shuttle, the cargo unit transported is a pallet, and the weight generally reaches 500~1000kg. Therefore, the transfer device of the trolley can neither use forks nor chains, but directly drive into the shelf and place the pallet on the shelf track, which is the characteristic of the pallet shuttle. This approach can easily achieve dense storage, but it will reduce the efficiency of operations and increase shelf costs.
 
② Hoist
The hoist is responsible for the cargo pallets in and out of the warehouse and is the key auxiliary equipment of the four-way shuttle system. The pallet type hoist can not only lift the pallet, but also lift the shuttle car, and the two can be shared.
 
③ Velocity and acceleration
The speed of the no-load shuttle can reach more than 4 m/s, the load is generally 3 m/s, and the acceleration is generally 0.5m/s2. But for different requirements, can also be changed.
 
2) Box type four-way shuttle
 
① Transfer
In contrast, the box shuttle is much more flexible. This is mainly after the unit becomes smaller and lighter, there can be a variety of ways to carry out the transfer. The simplest way is to use a fork. In order to improve the storage density, you can use the double depth of the fork, sometimes in order to adapt to different width of the carton, the fork can also change the width. The fork is the most important part of the shuttle. Forks developed by professional companies in Europe are sometimes sold for more than 100000 yuan.
 
② Hoist
There are two typical structures, with car hoist and without car hoist. The belt hoist is mainly used for the floor change of the shuttle car. Sometimes, in order to simplify the system, it can also be used to carry the car every time, but the operation efficiency will decrease. The hoist without a car has a greater lifting capacity, and sometimes a double-station hoist can be used, with a lifting capacity of more than 200 times per hour or even higher.
 
③ Velocity and acceleration
In order to improve the operation efficiency, the speed of the trolley will be as high as 5 m/s, because the clamping device is used, the acceleration of the trolley can reach 2m/s2, which greatly improves the operation efficiency of the trolley. For the hoist, the lifting speed will generally reach more than 4 m/s to match the efficiency of the entire system.
 
3. application field exploration
 
3.1 tray type
 
The main application of the pallet-type four-way shuttle is in dense storage, especially the cold chain logistics system. In the cold chain system, especially the cold chain system of -18 ℃ and below, the four-way shuttle car is used for storage, which can greatly improve the space utilization rate, and can greatly improve the environment of the operation area, which is more comfortable for the operators.
 
There are many technologies for intensive storage. For AS/RS systems, the use of dual-deep cargo spaces is a very effective and practical approach. For shuttle boards and child-mother vehicles, the efficiency of intensive storage is also very high. The four-way shuttle is similar, but the four-way shuttle is more flexible, flexible and adaptable, which is its main feature.
 
In other application areas, there are many four-way shuttle car, such as the use of four-way shuttle car system as the delivery of temporary storage is a good application, can greatly save space, and can achieve automated operations. In addition, the use of four-way shuttle cars instead of conveying systems to complete long-distance conveying should be an option, but there are not many applications in this area.
 
In general, the application of tray-type four-way shuttles is also limited, mainly due to cost performance. As storage, AS/RS is more popular, and the shuttle board is more economical when automation is relatively low. However, the four-way shuttle is, after all, a highly flexible technology, and its application will have greater room for development in the future.
 
3.2 cartridge type
 
Compared with the limited application of the tray type four-way shuttle, the application of the four-way shuttle is very extensive. On the one hand, it is related to its flexibility and flexibility, and more importantly, the development of e-commerce has promoted the rapid development of zero picking. The high efficiency of the four-way shuttle is one of the important reasons for its popularity. Its main applications are outlined below.
 
1) "delivery to man" storage system
The earliest application of the four-way shuttle is its application in the goods-to-people picking system. Compared with the multi-layer shuttle, the four-way shuttle is not only efficient, but also highly flexible, making its application more extensive. However, with the continuous improvement of the ability to enter and exit the warehouse, when the ability of the car becomes a bottleneck, the price advantage of the multi-storey shuttle car will be more obvious.
 
2) Collection and queuing
Like the pallet four-way truck, the magazine four-way shuttle is often used for collecting goods and queuing during the delivery process. The difference between it and the pallet is that the material box can be directly connected to the telescopic belt conveyor, thus completing the loading work more directly. In the case of multiple shipping destinations, the shuttle car can also play the role of queuing, solving the previous problem of loading sequence.
 
3) Other
Box-type four-way shuttle car, the application is very broad. At present, the applications include all kinds of large-scale storage systems (especially in the case of large storage capacity and low frequency of access and storage), such as libraries and archives. In addition, in other aspects of logistics, such as the production of the line side of the library, sorting systems have application prospects.
 
4. development trend
 
The four-way shuttle is undoubtedly a landmark technology. Its application is still in its infancy and there is still much room for future development. Technically speaking, there are mainly the following aspects:
 
1) More flexible
Flexibility is one of the basic directions of logistics technology development, and the application of AGV fully illustrates this point. From the current application of the four-way shuttle, there is still room for further flexibility. For example, the four-way shuttle car that can lift itself and the four-way shuttle car that can walk on the ground are two meaningful research topics. The technology of integrating AGV, hoist and shuttle car into one, these technologies have already had some research results.
 
2) More intelligent
When the four-way shuttle car is used for zero picking, the scheduling of the car has a great influence on the efficiency. The bigger the system, the more intelligent the effect can be reflected. Such as a variety of route optimization and queuing, the efficiency of the system will have a great impact. In addition, the real-time monitoring of the running state of the car has a great impact on the normal operation of the system. All of these jobs need to be improved in the future.
 
3) Higher cost performance
The stability of the four-way shuttle is the key to ensure the normal and efficient operation of the system. From the current application point of view, there is still to be further improved. Compared with AGV(kiva) and multi-layer shuttle, the cost of the four-way shuttle is much higher because of its complex structure. How to continuously optimize, reduce costs, and improve cost performance is helpful for market acceptance.
 
4) Standardization and serialization
At present, it is mainly based on standard size shuttle cars, and there will be some changes in the future.
 
5) Tray type four-way shuttle
It is mainly suitable for 1200 × 1000 standard pallets with a carrying capacity of 1000kg. The future serialization will be considered from two aspects of pallet size and carrying capacity. If the load will have 500/750/1000/1250 several levels to meet the different needs of the market. In terms of size, there will be more series combinations.
 
6) Box type four-way shuttle
It is mainly suitable for 600 × 400 standard boxes with a carrying capacity of 50kg. The future system mainly seeks serialization from the aspects of size and fork type to meet the market demand.
 

Standardization and serialization are the only way for product development, but because each shuttle car has to undergo rigorous testing before leaving the factory, and each model of new car has to undergo rigorous finalization testing, these tasks will bring challenges to serialization. From experience, because of the need to build a test bench for each new product, the test of new products is not only time-consuming and labor-consuming, but also affects production capacity.

 

---- Good article, worth sharing----

Author: Beijing Wuqiang Intelligent Technology Co., Ltd. Yin Junqi

Source: Lifting and Transport Machinery, No. 20, 2020.

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