Autopilot for AGVs

The primary aim of material logistics is to optimize processes, reduce costs and ensure smooth workflows. Transparency plays a decisive role in being able to manage and control transportation processes efficiently and flexibly. This requires a solution that seamlessly combines all aspects of material logistics. In order to achieve the highest possible productivity and avoid bottlenecks, information flows accompanying the material must be ensured. This was the challenge faced by the specialist for drive and control technology, KEB Automation, when it came to intralogistics in the electronics plant.

At the production plant in Barntrup, the company wanted to automate all non-value-adding warehouse processes as far as possible. The reason for this was the move into a new production hall, where detailed planning was possible right down to the production areas. From the outset, the aim was to replace the use of forklift trucks in the production area with a driverless transport system.

Warehouse control and pallet tracking using RFID technology

"On the routes in the production area, the identification and tracking of all pallets is to be ensured fully automatically using RFID labels," says Viktor Derksen, Head of Industrial Engineering at KEB. The labels have a unique handling unit number (HU), which gives the load carriers their identity in SAP EWM. By additionally printing the number as a barcode and plain text, it is irrelevant by whom, where and in what way a pallet is identified. A transport order therefore always refers to an HU, even between storage locations across systems, executed by the AGV or by conventional industrial trucks.

At the automated warehouse, the picked pallets are prepared for the AGV using conveyor technology. From this starting point, they are transported to all the electronics production halls. Depending on the destination, the route includes several individual sections and intermediate buffers. The individual transport orders are carried out not only by AGVs, but also by manually operated industrial trucks and stationary conveyor technology. In this mixed operation, the exact tracking of the pallets and the precise control of their movements pose challenges that are to be overcome by using RFID technology.

To determine the route, the AGV always requires instructions or position information. "This is quite straightforward for a simple pallet transport from one workstation to another," says Phillip Hannesen, Digital Transformation Manager Production at KEB in Barntrup. "It becomes problematic in zones where several pallets are temporarily stored, which are later picked up by another vehicle and taken to another location. If the load carriers are mixed, a consistent HU-to-place assignment is no longer guaranteed, which is why road users must always be able to identify the loaded pallet."

To ensure reliable identification of the load, it is important that this can take place regardless of the orientation and positioning of the pallet. The UHF RFID system from Turck provides a solution for all installation situations in the application and achieves a read rate of almost 100 %.

Pallet detection at the transfer station

At a transfer point for forklifts and AGVs, the presence of the pallets is checked at defined storage locations. The Q5X laser distance sensor from Turck's opto partner Banner Engineering is used for this. 20 Q5X sensors with a range of 5 m are used to detect 20 pallets. The Q5X sensors, which are mounted at a height of 3 m, determine whether there are pallets at the transfer point that can be transported away. As soon as the distance sensor has detected the presence of a pallet, a travel order is generated for the AGV. This picks up the pallet, drives through the RFID gate and finally receives the HU information from SAP EWM. Before a transport order is generated, the system checks whether the destination is occupied. Before the Q5X sensors were used, the AGV first had to drive to the destination to determine this. In this case, it waited in front of the blocked storage location until an employee cleared it. Today, the vehicle receives information in advance as to whether the destination is occupied and only starts the journey if it is free.

Antennas connected to the UHF RFID reader are attached to both sides of a hall door. They ensure reliable detection of the RFID labels on the pallets. As the AGV approaches the door, it sends a signal to the Q300 via the network to start the scanning process.

Efficient identification even in the near field

Two production halls are connected via a bridge with stationary pallet conveyor technology, which was also equipped with RFID technology. In contrast to the application at the hall gate, where RFID labels have to be detected over long distances, the challenge in this application is to only read RFID labels in the immediate vicinity, i.e. at a distance of up to around 10 cm. This is achieved with near-field antennas that are positioned to the left and right of the pallet conveyor system.

At the transfer points, the conveyor system communicates with the AGV to ensure a smooth transfer process. When the pallet is set down, the AGV sends a request to the middleware to identify the pallet via the Q300 reader's near-field antennas. This information is returned to the middleware, which determines the warehouse tasks for this pallet from the SAP EWM data.

The Q5X laser distance sensors mounted at a height of 3 m determine whether pallets are present at the transfer point. © Turck

The RFID solution offers KEB the advantage of end-to-end transparency. It is possible to see where a pallet is located at any time. In some situations, it is possible to automate the acknowledgement of EWM warehouse tasks using RFID. This is supplemented by the manual operation of mobile devices. "Turck's solution provides us with the transparency we wanted without time-consuming manual effort," says Derksen. "The RFID tags are recorded fully automatically and warehouse tasks from SAP Extended Warehouse Management are completed or processed at the same time."

Agile warehouse management allows controlled chaos

Another advantage of the RFID solution is that it allows mixed traffic in the production hall. This means that both AGVs and employees with pallet trucks or forklift trucks can load and unload in the staging area at the same time. Separate storage location management is not necessary, as each pallet can be identified at each fork. "By using this RFID solution, we can deliberately allow a certain degree of chaos at this point to enable efficient work. As soon as a pallet leaves the area, it is automatically recognized which pallet it is and where it has to be transported to," says Hannesen, who also emphasizes the good cooperation with Turck: "Turck's service and the short communication channels enable efficient cooperation, we are happy to rely on this trusting and well-established partnership."

Due to the successful use of the AGVs with Turck's RFID technology, additional expansions are planned. Waste disposal has also been successfully integrated into the system: Bins in which used cardboard is collected are picked up by the AGV. It is planned that these containers will be transferred directly to a new waste compactor, which would mean fully automatic disposal. In addition, the laser distance sensors are to be equipped with IO-Link modules from Turck in the future, which will take over control tasks independently by using the Turck Argee logic software.

Phil Whorton, responsible for customer-specific system solutions at Turck's Application Service Center