怎樣做一個最好的double pendulum混沌擺?

What do you mean "the best" is?

It is best to do a simulation by altering the lengths and masses of the bobs of a double pendulumn, and observe how it responds. The following web-page provides a good animation:

http://www.myphysicslab.com/dbl_pendulum.html

By checking the box marked "show controls" at the bottom of the graph, you could change the masses and lengths of the pendulumn. By suitably adjusting these parameters and observing how the pendulumn swings, you could be able to find the "best" combination of masses and lengths.