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将功率谱离散化,并在离散点上建立对应的频谱值,然后通过FFT逆变换即得- % 频域离散点采样
- %nextpow2() 取最接近的较大2次幂
- clear;
- clc;
- Av=[1.2107,1.0181,0.6816,0.5376,0.2095,0.0339];
- Aa=[3.3634,1.2107,0.4128,0.3027,0.0762,0.0339];
- Ws=[0.6046,0.9308,0.8520,1.1312,0.8209,0.4380];
- Wc=[0.8245,0.8245,0.8245,0.8245,0.8245,0.8245];
- k=0.25;
- rand('state',0);
- %yl=1.524;yu=304.8;
- yl=0.5;yu=50;
- pr1={'V='};
- in1=inputdlg(pr1,'线路参数模拟信息',1,{'100'});
- V=str2num(in1{1});
- pr2={'选择路面等级i=','输入不平顺种类(1-高低不平顺,2-方向不平顺,3-水平及轨距不平顺j='};
- in2=inputdlg(pr2,'线路参数模拟信息',1,{'6','1'});
- i=str2num(in2{1});
- j=str2num(in2{2});
- v=V/3.6;
- switch j
- case 1
- s=@(f)(k*Av(i)*Wc(i)^2./((f.*2*pi/v).^2.*((f*2*pi/v).^2+Wc(i)^2)))/v;%%s=k*Av(i)*Wc(i)^2/(w^2*(w^2+Wc(i)^2));
- case 2
- s=@(f)(k*Aa(i)*Wc(i)^2./((f*2*pi/v).^2.*((f*2*pi/v).^2+Wc(i)^2)))/v;
- case 3
- s=@(f)(4*k*Av(i)*Wc(i)^2./((f*2*pi/v).^2+Ws(i)^2)./((f*2*pi/v).^2+Wc(i)^2))/v;
- end
- fu=v/yl;fl=v/yu;
- co=1;%判断点的个数和Nr/2的关系
- while(co>0)
- Ts=inputdlg('模拟时间Ts=','模拟的时间长度',1,{'10'});
- Ts=str2num(Ts{1});
- dt=0.0001;
- N=Ts/dt;
- Nr=2^(nextpow2(N));
- Xm=zeros(1,Nr/2+1);
- df=1/(Nr*dt);
- n0=ceil(fl/df);
- nf=ceil(fu/df);
- if nf<=Nr/2
- S=feval(s,(n0+1:nf)*df);
- Xm(n0+1:nf)=Nr*sqrt(S*df);
- break;
- % N0+1~N0+Nf数值非零,其余为零。
- end
- end
- n=nf-n0;
- q=2*pi*rand(1,Nr/2+1);
- X=Xm.*q;
- temp=fliplr(X);
- X=[X,temp(2:end)];
- x=ifft(X,Nr);
- t=(1:Nr)*dt;
- %%-->频域法模拟结果
- figure(1);
- subplot(2,1,1);
- plot(t,x);
- grid on;
- Fs=1/dt;
- fn=(1:Nr/2)/Nr*Fs;
- Xnn=fft(x,Nr);
- Xn=Xnn(1:Nr/2);
- Sn=(abs(Xn)*2/Nr).^2;
- figure(1);
- subplot(2,1,2);
- loglog(fn,Sn,'* g',fn,s(fn),'r');
- legend('模拟值','解析值');
- xlim([0,100]);
- ylim([1e-8,1]);
复制代码 时域信号。 |
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模拟出的时域信号,并由模拟的信号求功率谱并和解析值对比
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