In practice,if you chose a small sampling period, then any of these will work. For the 2 other approx, it only works in one direction. Tustin is the only method that guaranty that a stable continuous system is mapped to a stable discrete system. Amongst the possibilities, here are a few approximations s=tf('s') į=(1-0.2*s)/(1+5*s)^2 % Transfert function but can work with any linear time invariant systemįd=c2d(F,Ts,'zoh') % discrete equivalentįigure step(F,'r',Fd,'b') grid on legend('Continuous','Discrete') Īpproximation are often used if you designed a continuous controller and you want to implement it. If a system is associated to a zero order hold, then it is possible to compute a z transform of the assembly (system+zoh). First, you need to specify if you are looking for an exact transformation or an approximation.
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