Breve guida per l'esame orale Azionamenti e controllo dei sistemi meccanici

1

| Contents

Feedforward Control

Feedforward control depends on the value for and the system plant. for this case the

x

ref

loop its not closed, the force wont depend on the system state and therefore there is not

a forcefield introduce to the system, there is not steady state error introduce asweel and

because of that the feedforward control cant change the poles of the system resulting in

the incapacity to change the stability of the system.

Feedforward Control

For the case of the Feedback control it will also depend on the value of xref and the system

plant but in this case the loop is close and the force will depend on the system state thus

there is a force field introduce to the system. in this case also since the loop is closed we

will introduce the concept of steady state error which is basically xref -x. depending on

the type of controller that we use the forcefield will have and impact in the stifnnes coef

or the damp coefficient in any case the feedback will be able to change the poles of the

system resulting in the capability to change the stability.

clear comparison

No closed loop no FF no pole change

→ →

Feedforward:

loop FF pole change

→ →

Feedback:

Stability Analysis

Stability is the capability of the system to comeback to their particular position after a

disturbance.

Lyapunov Theorem

Lyapunov analyise stability of an equilibium point without solving the system equations.

→ →

Bounded for all time Stable No coments on Non linear

→ →

Bounded for all time and converge to zero Locally Asymptotic Stable

Stable non linear → →

Unbounded for some time unstable Unstable Non Linear 2

| Contents

Conservative Forcefield

Non Conservative Forcefield

Laplace Domain

It is the integral transforms that converts time domain in to complex frequency domain

it is used to pass from linear equations to algebraic equations. it exist only if the function

is continuous and exponential.

Properties are: linearity, derivation, integration, time shift and convolution.

The important functions are:

Represent the sudden aplication of a signal, it is used to model inputs that switch

Step:

on at specific times.

represent instantaneuos input with finit area and zero duration. used to study

Impulse:

isntant conditions and define initial conditions.

IVT: FVT:

Block diagram

Block diagrams are used to separate the system in Sensor, Actuators, Controllers and the

Plant. allow to clearly see the feedback loops. Allows the derivation of the TF and the

analysis of the stability and performance.

Close Loop: Open Loop:

Bode diagram

it is used represent the modulus and the phase of