On 12 June 2018 at 12:17, andy pugh <bodge...@gmail.com> wrote:
> As far as I can see so far the resolver module will have to infer the
> position read from the position.txt file by being netted to the
> joint.N.pos-fb (or pos-cmd) HAL pin. Unless there is a better way?
This turns out to be interesting. It takes a few hundred servo cycles for the
joint.0.pos-fb pin to become non-zero, whereupon it takes the resolver
feedback value, and then a bit later the value from the position file
is added.
position.txt =
-72.37295348494777159
-326.96276413789018989
0.00000000000000000
0.00000000000000000
0.00000000000000000
0.00000000000000000
0.00000000000000000
0.00000000000000000
0.00000000000000000
Resolver position = -0.08153193 (dithers in the hundreds of nanometers)
In dmesg I get:
[ 4403.473613] hm2: Current resolver.0.pos-fb = -0x1.4DD68989EB852P-4 cycle 352
...
[ 4403.494611] hm2: Current resolver.0.pos-fb = -0x1.21D177B3C4665P+6 cycle 373
Luckily Python can help:
>>> float.fromhex("-0x1.4DD68989EB852P-4")
-0.08150342680048198
>>> float.fromhex("-0x1.21D163027A665P+6")
-72.45447925445622
A further wrinkle is that the home offsets play in to this, at least
when initially homing to set things up. index-homing zeros the
position at the resolver zero-angle. But then calls this the
home-offset number.
I was wondering why I could not make the numbers add up.
I think that to make this work I need:
HOME_OFFSET = 0
HOME_POS = -2
MAX_LIMIT = -2
Or something similar to make axis absolute zero correspond to resolver
zero. As things stand the position jumps by exactly 1.000 every time I
press the "Home" button.
--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916
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