How do I animate a block (say an image) to vibrate at a particular frequency?

I want to show how a spring vibrates at its natural frequency. Without using any other models (quarter car or other response based models), I want to show the animation of a spring at a particular frequency, just as a vertical motion. Can I use MATLAB to do this?

For example, assume a car has a front natural frequency of 1.5 Hz and a rear natural frequency of 1.7 Hz. I want to show two springs going up and down at these frequencies so that the user gets an idea of the system. Please let me know if I can write a code for this.

Answer 1

[Jan]

Yes, you can write code for it. Do you want to obtain the vibration trajectories by a simulation or do you just want an animation?

[Harikrishna Devarajan]

I just want to show the simulation as an up-down movement. Basically, it is to show to the user that the front and rear resonate at different frequencies and the way they resonate. I don't require the trajectories at this stage. Thanks.

[Harikrishna Devarajan]

And I want the frequency to be a user input. The animation should change the way it vibrates accordingly. Where should I start and what command (s) should I use?

Thanks in advance.

[Jan]

Compute the positions for a time vector in the wanted resolution. Most likely some simple sin() commands will do this.

Open a figure, then an axes. Create the graphical objects you want in 2D or 3D, e.g. by surf, line, cyclinder etc. Then write a loop and modify the 'XData', 'YData', 'ZData' properties of the created object accoring to the calculated positions.

Search in teh net for examples: Look for "Matlab animation".

[Harikrishna Devarajan]

Hi!

I now have a code to generate a helical coil spring.

time = 0:pi/50:25*pi;   % Time array
radius = 2;             % Radius of the coil spring
height = 2;             % Height of the coil spring
x = sin(time) * radius; % Compute x and y
y = cos(time) * radius;
z = height/(2*pi) * time;   %Compute z which will be used later to animate
plot3(x,y,z);

And the plot looks like this:

Let's assume an amplitude of 1, with the frequency at say 1.5 Hz.

To compute the positions of the time vector and to continuously update and redraw the plot, I have written a small piece of code.

h = plot3(x,y,z);
while 1
     t=0; 
     for t= 0:1000
         zadd = sind(1.5*2*pi*t);
         znew = z + zadd;
         set(h,'ZData',znew)
         t = t + 1;
         drawnow
         pause(0.1);    
      end
 end

I am able to animate the graph, but I am not sure about the following.

1. Is it vibrating at the right frequency?

2. Have I factored in the resolution here? (I wrote the code based on a few help files)

3. Can I stretch/compress the spring a bit instead of bouncing it up and down?

I would love to hear your views on this. Thanks.