Quote:
Originally Posted by Ether
Paul Copioli wrote:
I am curious as to why you are proposing this equation based method when the filter based method posted from post #18 in this thread:http://www.chiefdelphi.com/forums/sh...motion+profile
The filter method is so much more real time friendly and flexible as you can determine the motion acceleration type just by manipulating the filter lengths. Hi Paul,
Thanks for that link. Since that thread is closed, I invite interested parties to respond here if they wish.
Please note that I am not advocating any particular method. I'd simply like to discuss the pros and cons.
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It's worth pointing out that the equation-based method is also real-time safe (deterministic runtime and does not allocate), although a microcontroller without an FPU would not be able to run it as quickly as a cascade of Boxcar filters.
The main advantage of polynomial-based motion profiling techniques is that you have a bit more flexibility in the constraints you can obey. For example, you could easily accommodate asymmetric forwards and backwards velocity/acceleration limits. It is also easy to change your constraints on the fly - as often as each control cycle. Doing this (for higher order constraints...velocity is easy) with FIR filters requires resizing the number of filter taps and pre-loading the new filter with the right initial conditions.
One other reason to favor the polynomial method is that relatively few high school students have had any exposure to linear filtering, but if they have taken a physics class they will know (and be able to apply) basic kinematics equations.
In general, though, either method works fine, and the filtering approach will be faster if you can get away with no asymmetries and constant constraints on higher order derivatives.