sách điều khiển tự động Control

1 Phase I - Control FundamentalRMT Sales Training - 05 /98 Level 1 Fundamentals Training Fundamentals Training Level 1 - ControlRMT Training - 05 /98 2 Topics: Slide No: • Process Control Terminology 3 - 10 • Control Principles 11 - 18 • Basic Control Loop 19 - 23 • Advance Control Loop 24 - 31 • Control Algorithm 32 - 46 • Control System 47 - 54 • Exercise 55 - 59 Contents Contents Level 1 - ControlRMT Training - 05 /98 3 Any operation or sequence of operations involving a change in the substance being treated. Examples: A change of energy state - hot to cold, liquid to gas A change of composition - a chemical reaction A change of dimension - grinding coal Process Control Terminology Process Control Terminology What is a PROCESS ? What is a PROCESS ? Types of PROCESS VARIABLE: Types of PROCESS VARIABLE: Pressure Specific Gravity of liquid Flow Density Level Mass Temperature Conductivity Liquid Interface Composition Moles Level 1 - ControlRMT Training - 05 /98 4 A combination of instruments or functions that are interconnected to measure and control a process variable with feedback. Process Control Terminology Process Control Terminology What is a CLOSED LOOP ? What is a CLOSED LOOP ? PROCESS input output A A System System with with Feedbac Feedbac k k FINALCONTROL ELEMENT MEASUREMENT CONTROLLER Level 1 - ControlRMT Training - 05 /98 5 • A device that registers a non-electrical parameter (eg. process variable) and outputs a corresponding useable electrical signal. – Pressure to Capacitance – Pressure to Resistance or mV – Temperature to Resistance – Temperature to mV • Example: – Capacitance pressure sensor module – Piezo-resistive pressure sensor module – RTD – Thermocouple Process Control Terminology Process Control Terminology What is a TRANSDUCER What is a TRANSDUCER Level 1 - ControlRMT Training - 05 /98 6 • A device that will translate the transducers interpretation of the measured variable into a standard transmission signal. – 3 - 15 psi pneumatic signal – 4-20 mA dc electrical signal – 1-5 V dc electrical signal Process Control Terminology Process Control Terminology What is a TRANSMITTER What is a TRANSMITTER Level 1 - ControlRMT Training - 05 /98 7 • Lower installation cost – simple, twisted pair wiring • Better noise immunity – current vs. voltage • Insensitive to wire resistance – current vs. voltage • Better suited for hazardous locations – intrinsic safety Process Control Terminology Process Control Terminology ADVANTAGE OF 4-20mA CURRENT SIGNAL ADVANTAGE OF 4-20mA CURRENT SIGNAL Level 1 - ControlRMT Training - 05 /98 8 • Used to keep a process variable at a desired value (set point). – Closed loop vs. Open loop control • Difference: Open loop control has no feedback – Control Modes • ON/OFF (Binary) • Proportional (P) • Proportional-plus-Integral (PI) • Proportional-plus-Integral-plus-Derivative (PID) Process Control Terminology Process Control Terminology What is a CONTROLLER ? What is a CONTROLLER ? Level 1 - ControlRMT Training - 05 /98 9 Process Control Terminology Process Control Terminology What is a SIGNAL ? What is a SIGNAL ? • An event that conveys data from one point to another. What is an INDICATOR ? What is an INDICATOR ? • An instrument which visually shows the value of the variable. What is a RECORDER ? What is a RECORDER ? • An instrument that makes and displays a continuous graphic, acoustic or magnetic record of a measured variable. What is a DCS ? What is a DCS ? • Distributed Control System consisting of functional integrated subsystems. The subsystems are connected by a communication linkage (eg) data bus,data highway. Level 1 - ControlRMT Training - 05 /98 1 0 Process Control Terminology Process Control Terminology • The last control element in the process control loop that manipulates the process variable. – Control Valves » modulates flow rate » operated by actuator – Louvers and Dampers » operated by pneumatic actuators – Variable Speed Drives » operated by electronic control signals ♦ 4 - 20 mA What is a FINAL CONTROL ELEMENT? What is a FINAL CONTROL ELEMENT? [...]... Basic Control Loop 2 2 Level Control Loop (Inflow) I/P LIC • Level Loop Issues: – Control At Inflow or Outflow – Non-Self Regulating LT RMT Training - 05 /98 Level 1 - Control Basic Control Loop 2 3 Level Control Loop (Outflow) LIC I/P LT RMT Training - 05 /98 Level 1 - Control Advance Control Loop 2 4 What is CASCADE CONTROL ? Consist of one controller (primary, or master) controlling the variable that... the wild flow transmitter and the flow controller set point Flow B is controlled in a preset ratio to flow A Multi-Variable Control Controlled flow, B Wild flow, A Ratio Output = A x ratio relay SP Remote set controller Output RMT Training - 05 /98 Controlled flow, B Wild flow, A SP Ratio controller Output Level 1 - Control Advance Control Loop 3 0 Example of RATIO CONTROL Pickling Process Acid supply... feedback control Multi-Variable Control Steam Feedwater FT FT Flow controller PV O/P LT Boiler SP RMT Training - 05 /98 Level indicating controller SP Feed forward Level 1 - Control Advance Control Loop Implementing Feedforward Control RMT Training - 05 /98 2 8 Level 1 - Control Advance Control Loop 2 9 What is RATIO CONTROL ? An uncontrolled flow determines a second flow so that a desired ratio is... second controller (secondary, or slave) controlling another variable that can cause fluctuations in the first variable The primary controller positions the set point of the secondary, and it, in turn, manipulates the control valve r1 Primary controller FBC c1 RMT Training - 05 /98 r2 Secondary controller FBC c2 Multi-Variable Control m Disturbance Secondary Process Primary Process Level 1 - Control. .. Advance Control Loop 2 5 Example of CASCADE CONTROL The temperature of the liquid in the vessel is controlled by regulating the steam pressure in the jacket around the vessel Temperature transmitter IN Temperature controller Measurement Output Measurement Jacket OUT Valve SINGLE-LOOP CONTROL RMT Training - 05 /98 Pressure transmitter Pressure controller Steam Cascade Control Loop Level 1 - Control. .. Control Advance Control Loop Implementing Cascade Control RMT Training - 05 /98 2 6 Level 1 - Control Advance Control Loop 2 7 What is FEED FORWARD CONTROL ? Applies to a system in which a balance between supply and demand is achieved by measuring both demand potential and demand load and using this data to govern supply It gives a smoother and stable control than feedback control Multi-Variable Control Steam... Fieldbus Control System RMT Training - 05 /98 Level 1 - Control Basic Control Loop 1 9 Pressure Control Loop I/P PIC • Pressure Loop Issues: – May be a Fast Process » Liquid » Small Volume – May Require Fast Equipment PT RMT Training - 05 /98 Level 1 - Control Basic Control Loop 2 0 Temperature Control Loop • Temperature Loop Issues: Fluid response slowly to change in input heat – Requires advanced control. .. Alarm Control Indicate Light Point (Test Connection) Record Transmit Valve, Damper, Louver Level 1 - Control Control Principle 1 7 Signal Types (ISA) Connection to Process, Instrument Supply, or Direct Mechanical Link Pneumatic Signal Electric Signal RMT Training - 05 /98 Level 1 - Control Control Principle Controller Types 1 8 • Pneumatic • Analog • Digital – Single Loop Controllers – Distributed Control. .. a result of abnormal operating conditions Multi-Variable Control O/P PIC PV RMT Training - 05 /98 Low select O/P RS Speed PIC Control O/P PV Pump Level 1 - Control Control Algorithm 3 2 • On/Off • Multi-step • Proportional • Integral • Derivative RMT Training - 05 /98 Level 1 - Control Control Algorithm 3 3 On-Off Control It is a two-position control, merely a switch arranged to be off (or on as required)... Alarm control Measured variable differential Controller output Time RMT Training - 05 /98 Level 1 - Control Control Algorithm 3 4 Multi-Step Action Input A controller action that may initiate more than two positioning of the control valve with respect to the respective predetermined input values 8 5 8 0 7 5 Valve position Time 4 3 2 1 Multi-step action RMT Training - 05 /98 Time Level 1 - Control Control . (PID) Process Control Terminology Process Control Terminology What is a CONTROLLER ? What is a CONTROLLER ? Level 1 - ControlRMT Training - 05 /98 9 Process Control Terminology Process Control Terminology What. electronic control signals ♦ 4 - 20 mA What is a FINAL CONTROL ELEMENT? What is a FINAL CONTROL ELEMENT? Level 1 - ControlRMT Training - 05 /98 1 1 Control Principle Control Principle Level 1 - ControlRMT. (ISA) Control Principle Control Principle Level 1 - ControlRMT Training - 05 /98 1 8 Control Principle Control Principle • Pneumatic • Analog • Digital – Single Loop Controllers – Distributed Control