1.2 Software tools for analysis and design of control systems Terminology. Formulation of the control problem... 11

Transcription

1 Contents 1 Introduction Theimportanceofcontrol Software tools for analysis and design of control systems Ashorthistoryofcontrol Introduction to feedback control Introduction Terminology. Formulation of the control problem Solutionstothecontrolproblem Introduction Control using a constant control signal Control using error-based control signal (feedback control) Examples of control systems. Documentation with P&I diagramandblockdiagram Functionblocksinthecontrolloop Controllerfunctions Introduction Tuningthenominalcontrolsignal

2 2 Finn Haugen: PID Control On/off controller Overview:ThePIDcontroller Pcontroller PIcontroller PIDcontroller Positive or negative controller gain? Practical problems: Control kicks, windup, and noise Reducing P- and D-kick caused by setpoint changes Integratorantiwind-up Measurement noise. Signal variance Performanceindexofcontrolsystems Selecting P, PI, PD, or PID? Reduction of control error by process changes Controlloopstability Control equipment Processcontrollers PLCsandsimilarequipment SCADAsystemsandDSCsystems SCADAsystems DCS Embedded controllers in motors etc Experimental tuning of PID controllers Introduction... 89

3 Finn Haugen: PID Control Acriterionforcontrollertuning TheP-I-Dmethod Ziegler-Nichols closedloopmethod Åstrøm-Hägglund s On/off method Ziegler-Nichols openloopmethod Ziegler-Nichols open loop method used experimentally Ziegler-Nichols open loop method with transfer functionmodels Consequences of adjusting controller parameters Introduction Increasing K p Reducing T i Increasing T d Auto-tuning PIDtuningwhenprocessdynamicsvaries Introduction GainschedulingPIDcontroller Adjusting PID parameters from process model Adaptivecontroller Discrete-time PID controller Introduction Computerbasedcontrolloop Development of discrete-time PID control function PID control function on absolute form

4 4 Finn Haugen: PID Control Incremental PID control function How the sampling interval influences loop stability and tuning Analysis of feedback control systems Introduction Aboutusingsimulators Setpoint tracking and disturbance compensation Introduction Analysis based on differential equation models Transfer function based analysis of setpoint tracking anddisturbancecompensation Frequency response analysis of setpoint tracking and disturbancecompensation Stabilityanalysisoffeedbacksystems Introduction Reviewofstabilityproperties Nyquist sstabilitycriterion Stability analysis in a Bode diagram Stabilitymarginsandrobustness Transfer function based PID tuning Introduction Controller tuning from specified characteristic polynomial Introduction Tuning a controller for an integrator process Tuning a controller for a firstorderprocess...201

5 Finn Haugen: PID Control Controller design using the direct method Dead-time compensator (Smith predictor) Skogestad smethod Introduction Skogestad stuningformulas Skogestad s method with faster disturbance compensation Skogestad s method for processes without time delay Controllerswithtwodegreesoffreedom Frequency response based PID tuning Introduction Useful facts about frequency response of a control loop Frequency response of the loop transfer function Frequency response of PID and PI controller Ziegler-Nichols frequencyresponsemethod Introduction Tuningprocedure Comparing PID and PI tuning in frequency domain Frequency response based adjustment of PID parameters Introduction Adjusting K p Adjusting T i Adjusting T d Summary...243

6 6 Finn Haugen: PID Control 9 Various control methods and control structures Feedforwardcontrol Introduction Designing feedforward control from differential equationmodels Designing feedforward control from transfer function models Cascadecontrol Ratio control and quality and product flow control Ratiocontrol Quality and production rate control Split-rangecontrol Control of product flow and mass balance in a plant Multivariablecontrol Introduction Single loop control with PID controllers Single loop PID control combined with decoupling Model-basedpredictivecontrol A Codes and symbols used in Process & Instrumentation Diagrams 279 A.1 Letter codes A.2 InstrumentationsymbolsusedinP&IDs B The Laplace transform 285 B.1 PropertiesoftheLaplacetransform B.2 Transformpairs...286