SPS
Also: Speicherprogrammierbare Steuerung, SPS-Steuerung, PLC, Programmable Logic Controller, speicherprogrammierbare Steuerungen
AI-generated
A Programmable Logic Controller (PLC) is an industrial computer that controls and monitors machines and systems in intralogistics through freely programmable logic. It forms the lowest automation level and communicates with sensors, actuators, and higher-level control systems.
Key facts
- A PLC processes sensor signals and controls actuators in real time with deterministic cycle times in the millisecond range.
- In intralogistics, the PLC forms the lowest automation level, below the Material Flow Controller and the WMS.
- Safety functions such as emergency stops are frequently implemented in a dedicated Safety PLC in accordance with IEC 62061 or EN ISO 13849.
- The question of who owns the PLC source code must be clarified contractually and has a direct impact on maintenance and expansion costs.
What is a PLC?
A Programmable Logic Controller (PLC) is a hardened industrial computer developed specifically for use in production and warehouse environments. Unlike a PC, it cyclically processes input signals from sensors and switches and calculates output signals for actuators such as motors, valves, or signal lights. The control program is stored in non-volatile memory and is retained even after a power failure. PLC systems are designed for high availability, noise immunity, and deterministic real-time behavior — properties that are indispensable in around-the-clock warehouse operations.
How does a PLC work in intralogistics?
In automated warehouses, a PLC typically controls individual system sections: conveyor lines, storage and retrieval machines, sorters, or lift tables. It continuously reads light barriers, barcode scanners, and weight sensors and responds to changes in status within milliseconds. Higher-level systems such as a Material Flow Controller (MFC) or a Warehouse Management System issue orders to the PLC and receive feedback on completed actions. Communication today is usually handled via fieldbuses such as PROFIBUS or real-time Ethernet protocols such as PROFINET and EtherNet/IP.
In practice, the following points are relevant for warehouse operations:
- A PLC handles safety functions for emergency stops and safety guards, often in a separate Safety PLC.
- Fault messages are forwarded directly to operator panels or higher-level SCADA systems, speeding up on-site diagnosis.
- Typical cycle times are in the single-digit millisecond range, which is sufficient for most conveyor technology applications.
What matters when making a selection?
Which PLC platform is suitable for a system depends on several factors. The availability of spare parts and qualified service personnel plays at least as important a role in the long term as the purchase price. Systems frequently run for ten to twenty years, so manufacturer support should be assured over this period. The openness of interfaces is also relevant: modern PLC platforms support OPC-UA as a standardized communication protocol, which simplifies integration into IT systems. If a system integrator configures the controls, you should specify in the contract who owns the source code of the PLC program — this is not uniformly regulated in the industry and can become a significant issue in the event of service requirements.
Related terms
- AGV
AGV (Automated Guided Vehicle) refers to driverless transport vehicles that automatically move goods in warehouses and production environments. They follow predefined or sensor-controlled routes without a human driver.
- AMR
AMR (Autonomous Mobile Robot) is a driverless, self-navigating transport robot that moves goods within a warehouse without any fixed installed infrastructure. It orientates itself independently using sensors and digital maps, and dynamically avoids obstacles.
- Abnahmeprozess (FAT/SAT)
The acceptance process (FAT/SAT) comprises two consecutive test phases used to verify that intralogistics systems comply with contractual requirements before commissioning.
- Aktuator
An actuator is a technical component that converts electrical, pneumatic, or hydraulic control signals into mechanical movement or force. In intralogistics, actuators control conveyor belts, diverters, grippers, and lifting elements in automated systems.
- Automatiklager
An automated warehouse is a fully or partially automated storage system in which the receipt, retrieval, transport and management of storage units are carried out without manual intervention, using conveyor technology, storage and retrieval machines, and a higher-level control software.
- Automations-Panel
An automation panel is an industrial-grade operator panel that serves as an HMI interface between operating personnel and automated systems in intralogistics. It enables manual control, monitoring, and parameterization of conveyor, storage, and picking systems directly on-site.
- Automatisierung
Automation refers to the use of technologies and systems to execute processes fully or partially without human intervention. In intralogistics, the spectrum ranges from simple conveyor systems to fully automated high-bay warehouses with autonomous vehicles.
- BDE-System
A BDE system (operational data collection system) captures machine and manual process data in real time directly at the source – such as at machines, conveyor systems, or workstations.
- Bedienerterminals mit Touch
Touch operator terminals are stationary or mobile input devices that use a touchscreen to enable direct interaction with warehouse management and control systems.