Modern control design

Modern control design

1. Control

   • Act of producing a desired result
     • Artificial Processes
       • Automatic (f.e TV) or caused by human being (car driver)
     • Natural Processes
       • Natural environment: composition, temperature and pressure
   • Study
     • Control System
       • TYPES
         • depending upon the physical arrangement of its components
           • Open- loop control system
             • Control system is applied without the knowledge of the plant output
               • Successful only if the controller has a pretty good prior knowledge of the behavior of the plant (control input and plant output)
           • Closed - loop system
             • Control system in which the control input is a function of the plant's output
               • The controller is constantly in touch with the actual output
                 • Mechanism in which the actual info is conveyed to the controlled: FEEDBACK CONTROL SYSTEM
                   • Input to the controller: Error signal (could be different in other systems).
                     • Desired output is a constant: the resulting controller is called a regulator; if the desired output change with time the controller is called tracking system
                     • The principal tasks is make the error signal = to zero as quickly as possible
                   • Most common closed loop systems
           • Hybrid of open and closed- loop system
             • FEEDFORWARD CONTROL SYSTEM:
               • To counteract the effect of noise or reduce a known undesirable behavior of the plant
               • Incorporates some a priori knowledge of the plant's behavior
         • Physical nature of the laws obeyed by the system
           • DETERMINISTIC: when inicial conditions and the input are specified and can predict the state at a later time
             • CHAOTIC SYSTEM: when a small change in the initial conditions produces an arbitrary large change in the system's state at a later time (double pendulum)
           • STOCHASTIC / PROBABILISTIC: has no laws governing it so it its imposible to determine the system's state at later tima
         • Mathematical nature of the governing differential equations
           • depending upon what aspects of its behavior we are interested in
             • Linear or nonlinear
             • Partial differential equations: DISTRIBUTED PARAMETER SYSTEM
               • Continuos system / analog
             • Ordinary differential equations: LUMPED PARAMETER SYSTEM
               • Discrete system / digital
       • COMPONENTS
         • System to be controlled (PLANT)
         • System which excercises control over the plant (CONTROLLER)
           • Supply a signal to the plant : CONTROL INPUT
             • Physical processes
           • Produce a desire response from the plant: OUTPUT FROM THE PLANT
             • Anything that can be directly measured

2. Programming techniques

   • MATLAB
   • SIMULINK
     • Tool for modeling control systems and simulating their time response to specified inputs