Slides - Automatica - Università degli Studi di Padova

Analisi (3/4): Sistemi non autonomi e a tempo discreto
Sistema a regime
Funzioni di trasferimento
Trasformata Zeta
Analogie e differenze tra modelli
a tempo continuo e discreto
4 CHAPTER 1. INTRODUCTION
noise
Actuators
external disturbances
Clock
System Sensors
D/A Computer A/D
Controller
operator input
76 CHAPTER 3. EXAMPLES
Figure 1.3: Components of a computer-controlled system. The upper dashed box represents
the process dynamics, which include the sensors and actuatorsProcessor in addition load to the dynamical
system being controlled. Noise and external disturbances can perturb the dynamics −1 of the
process. The controller is shown in the lower dashed box. It consists of a filter and analog-todigital
(A/D) and digital-to-analog (D/A) converters, as well as MaxClients a computer that implements
the control algorithm. A system clock controls Idlethe
operation of the controller, synchronizing
the A/D, D/A and computing processes. The operator input is also fed to the computer Control as an
external incoming input.
requests
KeepAlive
accept
Wait Busy
queue
−1
outgoing
Memory usage
A modern data controller senses the operation of a system, compares it against the
desired behavior, computes corrective actions based on a model of the system’s
Client Servers
response to external inputs and actuates the system to effect the desired change.
This basic Figure feedback 3.11: Feedback loop ofcontrol sensing, of acomputation web server. Connection and actuation requests arrive is theoncentral an inputcon queue,
cept in control. where theyThe are sent keytoissues a serverinprocess. designing A finitecontrol state machine logickeeps are track ensuring of the that state of the the
dynamics individual of the closed server processes loop system and responds are stable to requests. (bounded A control disturbances algorithmgive canbounded modify the
errors) and server’s thatoperation they have by controlling additional parameters desired behavior that affect its (good behavior, disturbance such as theattenua maximum
number of requests that can be serviced at a single time (MaxClients) or the amount of
tion, fast responsiveness to changes in operating point, etc). These properties are
time that a connection can remain idle before it is dropped (KeepAlive).
established using a variety of modeling and analysis techniques that capture the
essential dynamics of the system and permit the exploration of possible behaviors
Filter
noise
Process
Output
Ref