Plotting velocity of a piston

Hi everyone,

At the moment I'm trying to use MATLAB to plot velocity of a piston for an engineering report but I'm having trouble with my values. I have an equation for the velocity as a function of the angle of the crankshaft from vertical, and this is my code so far:

>> x=0:360; %0-360 deg rotation
>> b=asind(.0405*sin(x)/.13); the angle I need in my equatin, based on x
>> y=29.688*(sin(0+b))/(sin(90-b)); the equation of velocity of the piston

So for each value of x I have a value for b, but y only comes up with one value, rather than 361. I've been going through help files in MATLAB but to no avail. Can anyone guide me?

Thanks,

Mike

Answer 1

[Matt Fig]

You probably wanted element-by-element division rather than array division...

y=29.688*(sin(0+b))./(sin(90-b));  % Note ./ rather than /

[Mike]

Thanks heaps mate: I'm still new at using it, and that gets me everytime!

Answer 2

[Walter Roberson]

sin() operates on radians, but you are feeding it degrees. sind() is the degree equivalent.

[Mike]

Thanks for clarifying that Walter, I saw sind in the help file and was wondering what it represented :)