PlatinumZealot wrote: ↑
Sun Nov 06, 2022 2:59 pm
Hoffman900 wrote: ↑
Wed Oct 26, 2022 9:52 pm
dans79 wrote: ↑
Wed Oct 26, 2022 9:49 pm
I just worked on a project where I used a Savitzky–Golay filter
to get smoothed velocity and acceleration data from positional data with some noise in it. It worked exceptionally well!
I’m not sure what the camshaft measuring software uses, but this is an issue when measuring camshaft data. You really need a linear encoder and measurements of multiple points / degree to get anything super useful for Velocity / Acceleration / Jerk plots. Hand measured plots at one degree increments is useless.
A quick and dirty way use to use a polynomial smoothing function in excel. It helps get a sense of the shape of the curve, but useless in terms of absolute values.
The question is.. are the camshaft lobes designed on polynomial curves (whether multiple joined poly-curves) or trial and error?
Use to be polynomials, now it's B-Splines, polynomials, and a few other curve methods etc. I think most of the commercial cam lobe designers are still using Blair's program: http://www.profblairandassociates.com/G ... esign.html
, some are using housemade (Jones), other's Lotus, and others Andrews Products.
Harold Brookshire (General Kinetics, Reed Cams, Comp Cams (first designer), Ultradyne, Lunati, Arrington (NASCAR)) back in the 1970s and 1980s use to use a time share computer and brute force his way with polynomials. A few old cam designers use to joke that Cosworth didn't know how to design cams, they were just a base circle and a nose radius with a straight line. I've never looked at them on a Camshaft Analyzer to know, but a bunch of people made careers or became notable fixing their cams.
A strong suit of a graphical design is you can control the acceleration curve at the valve and it integrates back through the valvetrain to a lobe shape.
As for constraints, it's "it depends". It use to be trail and error but now Spintrons allow designers to get very close and then a firing engine gets them that last little bit, usually on the exhaust side with a pushrod engine due to the amount of deflection.