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从稳态误差入手(steady state Error)
误差 Error
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E\left( s \right) =R\left( s \right) -X\left( s \right) =R\left( s \right) -E\left( s \right) \cdot KG\left( s \right) \Rightarrow E\left( s \right) \left( 1+KG\left( s \right) \right) =R\left( s \right) \Rightarrow E\left( s \right) =\frac{1}{1+KG\left( s \right)}R\left( s \right) =R\left( s \right) \frac{1}{1+K\frac{N\left( s \right)}{D\left( s \right)}}=\frac{1}{s}\frac{1}{1+K\frac{N\left( s \right)}{D\left( s \right)}}
E(s)=R(s)?X(s)=R(s)?E(s)?KG(s)?E(s)(1+KG(s))=R(s)?E(s)=1+KG(s)1?R(s)=R(s)1+KD(s)N(s)?1?=s1?1+KD(s)N(s)?1?
单位阶跃unit step
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R\left( s \right) =\frac{1}{s}
R(s)=s1?
稳态误差Steady State Error
——FVT终值定理
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ess=\underset{t\rightarrow \infty}{\lim}e\left( t \right) =\underset{s\rightarrow o}{\lim}sE\left( s \right) =\underset{s\rightarrow o}{\lim}s\cdot \frac{1}{s}\frac{1}{1+K\frac{N\left( s \right)}{D\left( s \right)}}=\frac{1}{1+K\frac{N\left( 0 \right)}{D\left( 0 \right)}}=\frac{D\left( 0 \right)}{D\left( 0 \right) +KN\left( 0 \right)}
ess=t→∞lim?e(t)=s→olim?sE(s)=s→olim?s?s1?1+KD(s)N(s)?1?=1+KD(0)N(0)?1?=D(0)+KN(0)D(0)?