(SEM VIII) THEORY EXAMINATION 2024-25 COMPUTERIZED PROCESS CONTROL

SECTION A – Short Answers (2 Marks Each) – Paragraph Style

a) Mention two economic benefits of using computers in process control.

Using computers in process control provides significant economic benefits by improving efficiency and reducing operational costs. Computers help optimize processes, which minimizes raw material wastage and energy consumption. They also reduce the need for manual supervision, thereby lowering labor costs while maintaining consistent product quality.

b) What is a real-time operating system (RTOS)? Why is it used?

A real-time operating system is an operating system designed to process data and respond to events within a fixed and predictable time constraint. It is used in process control applications because timely response is critical for safety, accuracy, and stability of industrial operations such as chemical plants, power systems, and manufacturing processes.

c) List any two standard industrial communication protocols.

Industrial communication protocols are used to enable data exchange between control devices. Two commonly used protocols are Modbus and PROFIBUS, which support reliable and real-time communication in industrial automation environments.

d) Explain pulse and analog interfaces in brief.

Pulse interfaces transmit information in the form of digital pulses and are commonly used for counting or speed measurement applications. Analog interfaces transmit continuous signals such as voltage or current, which represent physical parameters like temperature, pressure, or flow rate in process control systems.

e) What is the difference between physical and control models?

A physical model represents a process based on physical laws such as mass balance, energy balance, and fluid dynamics, while a control model is a simplified mathematical representation designed specifically for controller design and analysis. Control models focus on input-output relationships rather than detailed physical behavior.

f) Define model validation in process modeling.

Model validation is the process of verifying whether a developed mathematical model accurately represents the real industrial process. It involves comparing model predictions with actual plant data to ensure reliability before using the model for control or optimization.

g) What is cascade control? Where is it commonly used?

Cascade control is a control strategy in which one controller’s output acts as the set point for another controller. It is commonly used in temperature, flow, and pressure control systems where faster disturbance rejection is required.

h) State one application each of inferential and intelligent control.

Inferential control is applied in processes where direct measurement is difficult, such as estimating product composition in chemical reactors. Intelligent control is used in complex systems like adaptive furnace control or robotics where learning and decision-making capabilities are required.

i) Write a short note on electric oven temperature control.

Electric oven temperature control uses sensors to measure internal temperature and a controller to regulate heating elements. A computerized control system ensures uniform temperature distribution and maintains the desired set point by adjusting power input automatically.

j) Mention any two key challenges in computer-aided power generation control.

Two major challenges in computer-aided power generation control are maintaining system stability during load variations and ensuring reliable real-time communication between control units and power equipment.

SECTION B – Descriptive Answers (10 Marks Each) – Paragraph Style

a) Describe the architecture of hierarchical computer-aided process control systems.

Hierarchical computer-aided process control systems are structured in multiple levels to manage industrial processes efficiently. The lowest level consists of sensors and actuators that interact directly with the process. The next level includes controllers such as PLCs and DCS units responsible for real-time control. Above this lies the supervisory level, which handles monitoring, data acquisition, and optimization. The highest level involves enterprise management systems for production planning and decision-making. This hierarchical structure improves reliability, flexibility, and scalability.

b) Describe the structure of an industrial communication network and its importance.

An industrial communication network consists of field devices, controllers, communication media, and supervisory systems interconnected through standardized protocols. It enables real-time data exchange, coordination between machines, and centralized monitoring. Such networks are essential for maintaining synchronization, improving productivity, and ensuring safe and efficient plant operation.

c) Discuss the step-by-step modeling procedure for process control.

The modeling procedure begins with defining system objectives and identifying relevant variables. This is followed by developing mathematical equations based on physical laws or empirical data. Assumptions are then made to simplify the model. The model is simulated, validated using real process data, and refined until acceptable accuracy is achieved for control design.

d) Elaborate on predictive control and its advantages.

Predictive control uses a dynamic process model to predict future outputs and determine optimal control actions. It anticipates disturbances and constraints, allowing better control performance. Advantages include improved stability, better handling of multivariable systems, and enhanced process efficiency.

e) Describe the computerized temperature control system of an electric oven.

A computerized temperature control system for an electric oven includes temperature sensors, a controller, power control elements, and a user interface. The controller continuously compares measured temperature with the desired set point and adjusts heating power accordingly. This ensures accurate temperature regulation, energy efficiency, and consistent cooking or heating results.

SECTION C – Long Answers (10 Marks Each)

a) Explain the classification of computer-aided process control systems.

Computer-aided process control systems can be classified into supervisory control systems, direct digital control systems, distributed control systems, and hierarchical control systems. Supervisory systems monitor and optimize processes, while direct digital control replaces analog controllers with digital ones. Distributed systems improve reliability by distributing control functions, and hierarchical systems integrate control with management and planning functions.

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b) Discuss the economics and advantages of using computer-aided process control in industries.

Computer-aided process control improves economic performance by reducing production costs, improving product quality, and increasing plant efficiency. It minimizes downtime, enhances safety, and allows optimal utilization of resources. Automation also enables consistent operation and faster decision-making, resulting in higher profitability.