L [ a f ( t ) ] = a F ( s ) L[af(t)]=aF(s) L[af(t)]=aF(s)
线性定理-叠加性
L ( f 1 ( t ) ± f 2 ( t ) ) = F 1 ( s ) ± F 2 ( s ) L(f_1(t)\pm f_2(t))=F_1(s)\pm F_2(s) L(f1(t)±f2(t))=F1(s)±F2(s)
微分定理-一阶导
L [ d f ( t ) d t ] = s F ( s ) − f ( 0 ) L[\frac{df(t)}{dt}]=sF(s)-f(0) L[dtdf(t)]=sF(s)−f(0)
微分定理-二阶导
L [ d 2 f ( t ) d t 2 ] = s 2 F ( s ) − s f ( 0 ) − f ′ ( 0 ) L[\frac{d^2f(t)}{dt^2}]=s^2F(s)-sf(0)-f'(0) L[dt2d2f(t)]=s2F(s)−sf(0)−f′(0)
微分定理-n阶导
L [ d n f ( t ) d t n ] = s n F ( s ) − ∑ k = 1 n s n − k f k − 1 ( 0 ) L[\frac{d^n f(t)}{dt^n}]=s^nF(s)-\sum_{k=1}^{n}s^{n-k}f^{k-1}(0) L[dtndnf(t)]=snF(s)−∑k=1nsn−kfk−1(0)
微分定理
L [ t f ( t ) ] = − d d s F ( s ) L[tf(t)]=-\frac{d}{ds}F(s) L[tf(t)]=−dsdF(s)
积分定理-一阶导
L [ ∫ f ( t ) d t ] = F ( s ) s + [ ∫ f ( t ) d t ] t = 0 s L[\int f(t)dt]=\frac{F(s)}{s}+\frac{[\int f(t)dt]_{t=0}}{s} L[∫f(t)dt]=sF(s)+s[∫f(t)dt]t=0
积分定理-二阶导
L [ ∬ f ( t ) ( d t ) 2 ] = F ( s ) s 2 + [ ∫ f ( t ) d t ] t = 0 s 2 + [ ∬ f ( t ) ( d t ) 2 ] t = 0 s L[\iint f(t)(dt)^2]=\frac{F(s)}{s^2}+\frac{[\int f(t)dt]_{t=0}}{s^2}+\frac{[\iint f(t)(dt)^2]_{t=0}}{s} L[∬f(t)(dt)2]=s2F(s)+s2[∫f(t)dt]t=0+s[∬f(t)(dt)2]t=0
积分定理-n阶导
L [ ∫ … ∫ ⏞ n f ( t ) ( d t ) n ] = F ( s ) s n + ∑ k = 1 n [ ∫ … ∫ ⏞ k f ( t ) ( d t ) k ] t = 0 s n − k + 1 L[\overbrace{\int \dotso \int}^{n}f(t)(dt)^n]=\frac{F(s)}{s^n}+\sum_{k=1}^n\frac{[\overbrace{\int \dotso \int}^{k}f(t)(dt)^k]_{t=0}}{s^{n-k+1}} L[∫…∫nf(t)(dt)n]=snF(s)+∑k=1nsn−k+1[∫…∫kf(t)(dt)k]t=0
延迟定理
L [ f ( t − T ) 1 ( t − T ) ] = e − T s F ( s ) L[f(t-T)1(t-T)]=e^{-Ts}F(s) L[f(t−T)1(t−T)]=e−TsF(s)
衰减定理
L [ f ( t ) e − a t ] = F ( s + a ) L[f(t)e^{-at}]=F(s+a) L[f(t)e−at]=F(s+a)
终值定理
lim t → ∞ f ( t ) = lim s → 0 s F ( s ) \lim\limits_{t \to \infty}f(t)=\lim\limits_{s \to 0}sF(s) t→∞limf(t)=s→0limsF(s)
初值定理
lim t → 0 f ( t ) = lim s → ∞ s F ( s ) \lim\limits_{t \to 0}f(t)=\lim\limits_{s \to \infty}sF(s) t→0limf(t)=s→∞limsF(s)
卷积定理
L [ ∫ 0 t f 1 ( t − τ ) f 2 ( τ ) d τ ] = F 1 ( s ) F 2 ( s ) L[\int_{0}^{t}f_1(t-\tau)f_2(\tau)d\tau]=F_1(s)F_2(s) L[∫0tf1(t−τ)f2(τ)dτ]=F1(s)F2(s)
尺度定理
L [ f ( a t ) ] = 1 ∣ a ∣ f ( s a ) L[f(at)]=\frac{1}{\vert a\vert}f(\frac{s}{a}) L[f(at)]=∣a∣1f(as)
常用函数的变换
时间函数
变换后
时间函数
变换后
δ ( t ) \delta(t) δ(t)
1
1 − e − a t 1-e^{-at} 1−e−at
a s ( s + a ) \frac{a}{s(s+a)} s(s+a)a
δ T ( t ) = ∑ n = 0 ∞ δ ( t − n T ) \delta_T(t)=\sum_{n=0}^\infty\delta(t-nT) δT(t)=∑n=0∞δ(t−nT)
1 1 − e − T s \frac{1}{1-e^{-Ts}} 1−e−Ts1
e − a t − e − b t e^{-at}-e^{-bt} e−at−e−bt
b − a ( s + a ) ( s + b ) \frac{b-a}{(s+a)(s+b)} (s+a)(s+b)b−a
1 ( t ) 1(t) 1(t)
1 s \frac{1}{s} s1
sin ω t \sin \omega t sinωt
ω s 2 + ω 2 \frac{\omega}{s^2+\omega^2} s2+ω2ω
t t t
1 s 2 \frac{1}{s^2} s21
cos ω t \cos \omega t cosωt
s s 2 + ω 2 \frac{s}{s^2+\omega^2} s2+ω2s
t 2 2 \frac{t^2}{2} 2t2
1 s 3 \frac{1}{s^3} s31
e − a t sin ω t e^{-at}\sin \omega t e−atsinωt
ω ( s + a ) 2 + ω 2 \frac{\omega}{(s+a)^2+\omega^2} (s+a)2+ω2ω
t n n \frac{t^n}{n} ntn
1 s n + 1 \frac{1}{s^{n+1}} sn+11
e − a t cos ω t e^{-at}\cos \omega t e−atcosωt
s + a ( s + a ) 2 + ω 2 \frac{s+a}{(s+a)^2+\omega^2} (s+a)2+ω2s+a
e − a t e^{-at} e−at
1 s + a \frac{1}{s+a} s+a1
a t / T a^{t/T} at/T
1 s − ( 1 / t ) ln a \frac{1}{s-(1/t)\ln a} s−(1/t)lna1