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Routh-Wurwitz 穩定判據

Routh-Hurwitz 穩定判據

系統穩定性概念

A stable system should exhibit a bounded output if the corresponding input is bounded.

The closed-loop system transfer function is written as:

T(s)=p(s)q(s)=Mi=1(s+zi)sNQk=1(s+σk)Rm=1[s2+2αms+(α2m+ω2m)]
q(s)=0 is the characteristic equation whose roots are the poles of the closed-loop system. The output response for an impulse function input(When N = 0) is then:
y
(t)=k=1QAkeαkt+m=1RBm(1ωmeαmtsin(ωmt+θm))

So, to obtain a bounded response, the poles of the closed-loop system must be in the left-hand portion of the s-plane

A necessary and sufficient condition for a feedback system to be stable is that all the poles of the system transfer function have negative real parts.

判斷系統穩定性的三種方法:

  • the s-plane approach;
  • the frequency plane (jω) approach;
  • the time domain approach;

Routh-Hurwitz 穩定判據

特徵方程:

Δ(s)=q(s)=ansn+an1sn1+s+a1s+a0=0
上式可以寫成:
an(sr1)(sr2)(srn)=0
其中:r1,r2,rn<0

又可以寫成:

(s)=ansnan(r1+r2++rn)sn1+an(r1r2+r1r3+r2r3+)sn2an(r1r2r3+r1r2r4+
)sn3+
+an(1)nr1r2r4rn=0

由上式可得系統穩定的必要條件是特徵方程多項式的係數同號且不為0,有係數0時可能為臨界穩定狀態。
snsn1sn2sn3s