Motion profile generator.

[richard]

henrik
did you ever get this working ?
I have been messing with this for years and think I have finally worked it out . my solution is in C code but the idea is probably fairly portable if your interested

[HenrikOlsson]

Hi Richard,
I have been working on it on and off but have yet to actually try it on real hardware. It's been over 6 months since I last looked at the code but the way I left it was that it figured out when it needed to start decelerating (which could be up to VMax past the ideal position) and then recalculating the needed deceleration value each tick untill ending up at the target. Basically this aproach WILL cause the decleration to be "steeper" than the acceleration which I know I said I don't want but in reallity I don't Think it'll matter that much, I mean, in simulation where a "move" is 100 "ticks" in total it looks "brutal" but in reallity I don't Think it'll be that bad.

I have NO idea why you write in C (just kidding) but I'd love to see your code, thanks for offering!

/Henrik.

[richard]

my basic premise is that the input to the pid filter is velocity error (not position error) . the required velocity (setpoint) is found from a lookup tables who's in put is based on position . The move routine has 5 possible modes 4 is start a new move , 3 accelerate ,2 steady speed (cruise) ,1 decelerate, 0 in position , -1 stalled (failure).
The lookup table was developed by - getting motor running at various velocities and throwing the brakes on (l393d style) and measuring the number of ticks travelled till at rest ,
I plotted these in a spread sheet (the motor I'm using is a 171:1 gear motor 564 ticks per rev, target vel is 32 rpm ) interestingly the pos vs vel curve is ver nearly parabolic.
the clever bit is using two lookup tables "the multi_map function" to interpolate the best velocity for the current position using only 9 entries in each table

[richard]

some debug runs