digital computer process control lecture 1 · jie yu digital computer process control 10 what you...

Jie Yu Digital Computer Process Control 1

Dr. Jie Yu

Department of Chemical Engineering

McMaster University

Digital Computer Process Control

Lecture 1


Course Outline

Introduction

Section I: Dynamic Models – Continuous Systems

Fundamental models

Linearization

Transfer-function representation

State-space representation

Conversion between transfer-function and state-space models

Section II: Dynamic Models – Discrete Systems

Model discretization

Z-transforms

Pulse transfer function

Conversion between transfer-function and state-space models

Dynamic Responses


Course Outline

Section III: Systems Identification

Least-square formulation and solution to first-order models

First-order plus dead-time model

General ARMA models

Model Diagnostics

Input test signal and data pre-processing

Section IV: Closed-Loop Analysis – Continuous Systems

Closed-loop transfer function

Stability analysis

Controller design using direct synthesis

Section V: Closed-Loop Analysis – Discrete Systems

Closed-loop transfer function of sampled-data systems

Stability analysis


Course Outline

Section VI: Digital Control Design

Discretization of continuous-time control laws

Direct Approach

Section VII: Model Predictive Control

Unconstrained MPC – SISO systems

Unconstrained MPC – MIMO systems

Closed-loop properties

Constrained MPC

MPC implementation issues


What is control system?

Controlled Variable Feedback

Set-point

Manipulated Variable


Controller sensor pump patient

Set-point

What is control system?

Controlled Variable - Blood Glucose

Manipulated Variable - Insulin Injection


What is digital control?

Process parameters and variables sampled at discrete time instants

Discrete sample systems

Controller sees output responses only at discrete sample points

However, the process being controlled may still be in continuous operation

Control law computed discretely by digital computer

Distributed computer control network used in a plant


Digital Computer Control Diagram


Pros/Cons of Digital Computer Control

Pros

Easy data acquisition

High speed computation

Data storage and retrieval

Flexible calculation of control law

Cons

Potential failure of control systems due to computer malfunction

Inability for handle unexpected operation event

Security issue on process control computer network may cause plant operation upset or even serious incident

Software cost for control systems


What you are expected to learn?

How to discretize continuous-time control law?

How to analyze closed-loop control systems?

What is the effect of sampling time on closed-loop stability?

How to design discrete-time control law?

Regulatory control

Model predictive control

How to run discrete control law on continuous systems?

How to achieve desirable closed-loop behavior?


Major Steps of Control System Design


Remarks on Digital Control Design

Identification of discrete-time dynamic models from plant data

Digital signal processing and analysis

Control design strategy specifically for discrete-time system

Simulation of digital control system

Matlab

Simulink

Performance analysis of digital control system


Process Control Basics

Specific control objectives

Increase product throughput

Increase yield of higher valued products

Reduce energy consumption

Reduce environmental pollution

Improve product quality

Improve process safety

Extend equipment life

Improved economic profit

Reduce work labor


Process Control Basics

Controlled Variable (CV)

- Variables used to quantify control objectives such as product quality and profit

Manipulated Variable (MV)

- Variables being adjusted dynamically to keep the controlled variables at set-points

Disturbance Variable (DV)

- Variables that can cause controlled variables to deviate from set-points

Plant Controller CV MV

DV


Feedback Control

Feedback – Boiler Level

DV – Steam Flow

MV – Feedwater Flow


Feedforward Control

Feedforward – Steam Flow

MV – Feedwater Flow


Feedforward-feedback Control


Key Items to Control Design

Closed-loop Stability

Bounded Inputs Bounded Outputs

Controller Performance

Setpoint Tracking

Disturbance Rejection

Process Output Variability

Valve Moves

System Robustness

Model Uncertainty

Operation Condition Change

digital computer process control lecture 1 · jie yu digital computer process control 10 what you...

Documents