A shuttle system is a compact vehicle used in a storage area for the automatic operation of a warehouse. People usually talk about a channel storage or satellite vehicle storage system when pallets are used as load carriers. In a bin storage system, a shuttle system runs individually in each row of racks on rails and is able to change both levels and aisles depending on the version. In such as shuttle system, the horizontal and vertical transport is separated. By installing several shuttles in one aisle it is possible to considerably increase the storage and retrieval performance compared to a conventional storage and retrieval crane. Using these favourably priced and light stacker cranes allows an improved energy balance thanks to the smaller share of moving masses and thus makes the performance scalable, as shuttles can be employed more frequently in peak times.
Shuttle systems are suitable for being used for order consolidation buffers, order picking, sequencing and far more fields of application which have to face the new challenges of intralogistics. These challenges arise from the increasing number of small parts, multi-channeling and the increasingly volatile order picking.
An automated storage and retrieval crane is a machine for storing and retrieving loading units (cardboard boxes, containers or trays) in an automated small-parts warehouse. Conventional storage and retrieval cranes feature a column design and are able to serve a huge number of storage levels with one device. Although the performance of the devices is limited with an average of 75 (single-deep storage) and 150 double cycles per aisle (double-deep) depending on the warehouse characteristic, these devices, however, offer advantages in case of large storage volumes and small to medium throughput. Compared to a shuttle system the investment costs are low as well as the complexity of the plant control system.
With level-bound shuttle systems each level is served by an own shuttle. This allows storage and retrieval performances of 500 - 1000 double cycles per aisle. The shuttle vehicle runs on rails that are integrated into the racking construction. Storage and retrieval is ensured mostly by driving under and/or pulling the loading unit. As to the energy supply, the shuttle is either connected via a conductor line or features an integrated battery and is able to run autonomously within one channel. The advantage of level-bound shuttles is their high performance. However, this is in contrast to high investment costs. The cost-intensive racking system has to be equipped with a running rail per each racking level. Warehouse control is complex as many vehicles must be controlled separately. The capacity of a shuttle system, however, is restricted by the number and performance of the storage lifts that connect the single storage levels.
Multi-level shuttle systems combine the advantages of an automated storage and retrieval crane and a shuttle system and are located in the mean to high performance range. Compared to a level-bound shuttle a multi-level shuttle system running on rails and transporting cardboard boxes, containers or trays serves a certain number of levels simultaneously. For e.g. 5 levels served simultaneously only one rail is required that is integrated into the racking construction. By arranging several multi-level shuttle systems above each other it is possible to equip small-parts warehouses as high as you want. Compared to an automated storage and retrieval crane, the performance is increased considerably. These "hermaphrodites" featuring also high performances of around 500 double cycles are characterized by an interesting price-performance ratio due to the manageable complexity of the structural steel shelving, the machine itself and the storage strategies. In case of several shuttle systems arranged above each other the systems are linked by means of a vertical lifter and the loading units are stored and retrieved.
To reduce costs and to adapt the number of shuttle vehicles to the performance desired, shuttle systems are able to change level by means of warehouse lifts or vertical transporters - mostly at the front end of the aisle - to be able to serve several levels. The capacity of the shuttle system, however, is restricted by the number and performance of the storage lifts. The investment and complexity of the warehouse control systems is comparatively high because of the many interfaces at the vehicles and vertical lifters.
Autonomous transport vehicles are shuttle systems featuring an additional forklift chassis. Typical fields of application are small and medium sized distribution centers or production facilities. The routes are coordinated centrally by a computer via a navigation system and the shuttles can mutually recognize each other. Autonomous shuttles are mostly operated by means of capacitors or rechargeable battery packs. These systems are rather used in complex building structures and for medium performance ranges.