A Programmable Logic Controller is the workhorse of factory automation: a hardened controller that reads inputs, runs a fixed-cycle program, and drives outputs with guaranteed timing. PLCs are valued for deterministic real-time control, safety certification, ruggedization and decade-plus availability.
Where a PLC struggles is everything beyond control: vision, machine learning, modern connectivity and open tooling. That's the gap a Raspberry Pi node fills — beside the PLC, not in its safety path.