Which of the following are common standard control modes for a plant control system?

The correct answer is based on the common standard control modes used in process control systems. Proportional, Integral, and Derivative (often collectively referred to as PID control) are foundational strategies employed to regulate a process variable.

Proportional control adjusts the output proportionally to the error, which is the difference between a setpoint and a measured value. This helps maintain the process variable close to the desired level. Integral control addresses accumulated past errors, integrating the error over time to eliminate steady-state errors, while derivative control anticipates future errors based on the rate of change, improving response time and stability. When used together in a PID controller, these elements enable precise and stable control of dynamic systems, making them a widely accepted standard in industrial applications.

The other options involve different types of control strategies or operational modes. Open loop and closed loop systems describe system architecture, while feedback and feedforward refer to how information is used within those systems. Manual, automatic, and semi-automatic describe the mode of operation of operators with respect to the systems rather than the control approach itself. Therefore, while all these concepts are relevant to control systems, only the PID control modes directly constitute standard control modes in the context of process control.