How do PLCs coordinate robot motion in a manufacturing cell?

• A. PLCs control lighting only
• B. PLCs replace robot controllers entirely
• C. PLCs only monitor temperature
• D. PLCs manage sequencing, interlocking, I/O control, safety monitoring, and exchange commands/status with the robot controller

Answer: (D)

In a manufacturing cell, the PLC acts as the central coordinator that drives the overall flow of automation. It handles sequencing—deciding the order of operations and when each device should act—while also enforcing interlocks to prevent unsafe or premature actions. Through its I/O control, the PLC reads sensors (part present, gate status, etc.) and drives actuators (conveyors, grippers, alarms), keeping the whole line in sync. Safety monitoring is a key role, too, with monitoring of emergency stops and safety interlocks to ensure the system can halt safely if needed. Crucially, the PLC exchanges commands and status with the robot controller, so the robot knows when to move or wait and can report back its state. The robot controller handles the precise motion paths, but the PLC provides the overarching flow, gating, and synchronization across the cell, coordinating multiple devices and ensuring safe, coherent operation.