i need to filter this ode45 sine wave becomes a smooth one...

Question

Amirul Akil 2015-4-4

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https://ww2.mathworks.cn/matlabcentral/answers/196123-i-need-to-filter-this-ode45-sine-wave-becomes-a-smooth-one

评论： Amirul Akil 2015-4-5

i used this line of code, and i implement Lowpass FIR filter, but maybe the code i used is wrong somewhere. can anybody help me fixed this

error popped is 'Index exceeds Matrix dimension' and 'Error using forced (line 2),Not enough input arguments.'

these are the codes

EDITOR: function dxdt = forced(t,x) dxdt_1 = x(2); dxdt_2 = -100*x(2)-250000*x(1)+ ((25000)*((0.00002)*sin(2.6735*t))^3); dxdt = [dxdt_1;dxdt_2];

COMMAND WINDOW: tspan=[0:0.1:20]; initial_x=0; initial_dxdt=0; [t,x]=ode45(@forced,tspan,[initial_x initial_dxdt]); figure plot(t,x(:,1)); grid on %UNTIL HERE IT WORKS FINE

fHandle=@forced; Fs=20; fc=3; t=linspace(0,0.1,Fs); Wn=(2/Fs)*fc; b=fir1(20,Wn,'low',kaiser(21,3)); fvtool(b,1,'Fs',Fs)

z=filter(b,1,fHandle());

plot(t(1:100),fHandle()(1:100)) hold on plot(t(1:100,z(1:100)) xlabel('Time(s)') ylabel('Amplitude') legend('Original Signal','Filtered Data') %the error appear here...

any suggestion or helps, much thanks.

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Answer 1

Mahdiyar 2015-4-4

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Hi Akil

I think you need this, of Course I am not sure about the technical point of view

Function:

function dxdt = forced(t,x)
dxdt_1 = x(2);
dxdt_2 = -100*x(2)-250000*x(1)+ ((25000)*((0.00002)*sin(2.6735*t)).^3);
dxdt = [dxdt_1; dxdt_2];

Command Windows

clear
clc
tspan=[0:0.1:20];
initial_x=0; initial_dxdt=0;
[t,x]=ode45(@forced,tspan,[initial_x initial_dxdt]);
figure 
plot(t,x(:,1));
grid on
fHandle=forced(t,x); 
Fs=20; 
fc=3; 
t=0:0.1:Fs; 
Wn=(2/Fs)*fc;
b=fir1(20,Wn,'low',kaiser(21,3));
fvtool(b,1,'Fs',Fs)
z=filter(b,1,fHandle);
plot(t(1:100),fHandle(1:100))
hold on 
plot(t(1:100),z(1:100)) 
xlabel('Time(s)') 
ylabel('Amplitude') 
legend('Original Signal','Filtered Data')