When the semi-finished parts are delivered to the plant, the pallets are first automatically picked up via a scanner portal. The plant's internal SAP system assigns the goods a storage location in a fully automated high-bay warehouse (HBW). Shortly before assembly, the required parts are retrieved from the high-bay warehouse and made available to production in a highly dynamic buffer system. The automated Caesar 2F platform trucks, which weigh 470 kilograms and are 1,423 millimetres long, pick up the tray stacks with the semi-finished parts from a stationary conveyor system and transport them to the required transfer stations in the production line - just in time. On their way, the vehicles equipped with a double belt conveyor collect empty containers and take them independently to a central empties station.

Successive expansion of the system
The system was initially installed with three Caesar 500 2GF-0.4 Mr automated guided vehicles (AGVs). In the following years, the system was successively expanded in several stages. Thanks to the modular structure of MLR's own LogOS control software, the new vehicles and new driving courses could be quickly integrated into the system. Today, vehicles with new vehicle technology run in parallel with older vehicles in one system.

Innovative energy management
While the older vehicles still run on NiCad batteries, the newer vehicles are equipped with maintenance-free and fast-charging LiFePo4 batteries. This enables short intermediate charges. The shortest breaks in driving are used for charging - so the vehicles can remain in use around the clock. To protect the sensitive components being transported from electrostatic charges, the entire production area is located on an antistatic ESD floor.

Each of the vehicles, which travel at speeds of up to 1.6 meters per second, is fully equipped with all safety devices - one laser scanner at the front and one at the rear. The detection field in front of the laser scanner is divided into the warning area and the stop area. If the AGV approaches an obstacle, the vehicle is reduced from maximum speed to creep speed of around 0.3 meters per second in the warning area. If the scanner detects a person in the stop zone, the vehicle is brought to an immediate standstill. In addition to the protection provided by the laser scanners, bumpers with contact strips are fitted around the vehicle, which immediately trigger an emergency stop in the event of contact with an obstacle.

LogOS control and management software responds
MLR's own LogOS control and management software coordinates and controls the AGVs and manages the transport orders. It optimizes the journeys of the entire fleet. The software plans the fastest route for each vehicle and finds alternative routes if other vehicles cross or an obstacle arises. If new driving orders are added, LogOS reacts and adjusts the route accordingly. Where possible, jobs are combined and processed in parallel. For example, LogOS ensures that a vehicle always sets off with two containers and, after dropping them off, collects trays that are already waiting on its way back. This reduces empty runs. A visualization can be called up via a monitor, allowing the employees on site to quickly gain an overview of the entire system. The approximately 500-metre-long route is displayed on a map; the current location and status of the vehicles are shown. The corresponding job can be called up for each vehicle. Battery status or faults can be read off. An extended statistics function also provides continuous data on the system and the individual vehicles. This allows the routes and working times per vehicle to be evaluated, and the driving time, fault times and proportion of empty runs to be monitored. Communication between the master computer and the vehicles takes place via WLAN. The vehicles can also be maintained remotely via remote access. Navigation takes place anywhere in the room. Regular referencing within the route takes place via magnets embedded in the floor.

Continuous optimization
A key success factor of the system was the close cooperation between Continental and MLR in optimizing the driving logic. In several optimization loops, the utilization of the vehicles was continuously improved and thus the system performance increased. This made it possible to avoid new investments; the added value of the automated guided vehicle system for the Frankfurt plant was significantly increased overall. Currently, seven AGVs form the final link in a fully automated material supply chain that ensures the supply of the assembly lines with the A-parts valve intake, ECU and engine. Assembly takes place around the clock in up to 21 shifts per week.