一階保持器FOH

一階保持器是一種按照線(xiàn)性規(guī)律外推的保持器

一階保持器的單位脈沖響應(yīng)可以分解為若干階躍函數(shù)和斜坡函數(shù)之和

其單位脈沖響應(yīng)的拉普拉斯變換可以表示為

s = tf('s');

T = 2 ;%? 采樣周期T=2s

G = T*(1+T*s)*((1-exp(-T*s))/(T*s))^2 ;

bode(G)

w = 0:0.001:500;

T = 0.1;

G = T*(1+1j*T*w).*(sin(w*T/2)./(T*w/2)).^2.*exp(-1j*w*T);

plot(w,abs(G))

title("FOH的相頻特性")

xlabel('w/(rad/s)')

ylabel('|G(jw)|')

figure

plot(w,angle(G))

title("FOH的幅頻特性")

xlabel('w/(rad/s)')

ylabel('\angleG(jw)')

w = logspace(1,3,1000);

T = 0.1;

G = T*(1+1j*T*w).*(sin(w*T/2)./(T*w/2)).^2.*exp(-1j*w*T);

plot(w,[abs(G);angle(G)])

axis([0 1000 -5 5])

title('the Frequency Characteriistic of FOH')

xlabel('w (rad/s)')

ylabel('Amplitude-Phase-frequency characteristic')?

w = logspace(1,3,1000);

T = 0.1; %sample time

G = T*(1+1j*T*w).*((1-exp(-1j*w*T))./(1j*T*w)).^2;

figure % new figure

[hAx,hLine1,hLine2] = plotyy(w,abs(G),w,angle(G));

title('the Frequency Characteriistic of FOH')

xlabel('w (rad/s)')

ylabel(hAx(1),'Amplitude-frequency characteristic') % left y-axis?

ylabel(hAx(2),'Phase-frequency characteristic') % right y-axis

與ZOH的幅頻特性相比，F(xiàn)OH的幅頻特性的幅值較大，高頻分量較大，相位滯后比ZOH更大，對(duì)系統(tǒng)穩(wěn)定性不利

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