armax相关的frequency response和impulse

sky______sky

现在我需要做一个4个输入一个输出的armax和arm模型，定阶的时候有疑惑，
frequency response和step response一点都看不懂，求教高人帮忙分析一下，
z=iddata(delta,[Ay,Vx,phip,psip],0.002)
ge=spa(z)
bode(ge)
step(z)

Ts=0.002
z1=iddata(delta,Vx,Ts)
z2=iddata(delta,Vx)
z2=iddata(delta,Vx,0.002)
z3=iddata(delta,phip,Ts)
z4=iddata(delta,psip,Ts)
NN=struc(1:5,1:5,1:5)
ze1=detrend(z1)
zv1=z1
v1=arxstruc(ze1,zv1,NN)
nn1=selstruc(v1,0)
ze2=detrend(z2)
zv2=z2;
v2=arxstruc(ze2,zv2,NN)
nn2=selstruc(v2,0)
ze3=detrend(z3)
zv3=z3;
v3=arxstruc(ze3,zv3,NN)
nn3=selstruc(v3,0)
ze4=detrend(z4)
zv4=z4;
v4=arxstruc(ze4,zv4,NN)
nn4=selstruc(v4,0)
z=iddata(delta,[Ay,Vx,phip,psip],0.002)
m_armax=armax(z,'na',5,'nb',[nn1(2) nn2(2) nn3(2) nn4(2)],'nc',0,'nk',[nn1(3),nn2(3),nn3(3),nn4(3)])
zpplot(m_armax,3)
impulse(z,'sd',3,'fill')

sky______sky

好像我做的用system identification 工具箱里面的quick start就能做，可是我分析不了

sky______sky

有没有人知道啊