Jawaharlal Nehru Technological University Hyderabad B.Tech III Year PROCESS DYNAMICS AND CONTROL Previous Question Paper (February - 2022 - R18)

A process control system is an integrated arrangement of hardware and software components designed to maintain a process variable at a desired setpoint by automatically adjusting the input to the process. It involves measuring the output, comparing it to the target value, and applying corrective action through a controller.

The primary objectives of process control are:

• Safety: Ensuring the process operates within safe limits to prevent accidents or equipment damage.
• Product Quality: Maintaining consistent product specifications by minimizing deviations from the setpoint.
• Economic Efficiency: Reducing waste, energy consumption, and raw material usage.
• Environmental Compliance: Ensuring emissions and effluents remain within legal regulatory limits.

The functions include:

• Measurement: Sensing the process variable using transmitters.
• Comparison: Evaluating the error between the measured value and the setpoint.
• Decision-making: Calculating the appropriate corrective action based on control algorithms like PID.
• Implementation: Adjusting the final control element, such as a control valve, to influence the process.

The fundamental difference lies in the nature of the input and the intended response of the system.

In a self-regulation system, the process inherently possesses the ability to reach a new steady state following a disturbance without external intervention, though a controller is added to force the variable back to the original setpoint. In a servo system, the system is specifically designed to minimize the error between a rapidly changing reference input and the actual output, requiring high-bandwidth components to ensure the output accurately follows the command signal.