[PD] controlling a robot arm

me.grimm megrimm at gmail.com
Tue Nov 29 20:35:44 CET 2016


hi rolf,

>> i guess it comes from the motor's constantly trying to keep there
position against the gravity pulling on the arm.

yeah we believe thats whats is going on. not sure how to filter. going to
work on it this weekend. encoders as sending false positives. either we
filter (somehow) in hardware or directly in software (somehow)... but will
need time with it to troubleshoot.

>> The stand-alone feature made the use of standard Firmata impossible

got it.. thanks for your setup details!

m


On Tue, Nov 29, 2016 at 3:00 AM, <rolfm at dds.nl> wrote:

> hi,
>
> no experience with a robot-arm,
>
> but we are controlling up to 8 motors (servo or PWM),
> with Arduino Uno with SD-shield, and a PD front-end.
>
> The PD front-end can play and record scores.
> The manipulation of the motors is done with potmeters.
>
> In our situation the potmeters are read by the Arduino,
> the values are then sent to the PD front-end.
>
> In principle one could use direct input from a joystick, or a wiimote, or..
>
> The installations are able to run stand-alone;
> the Arduino program then uses a recorded score, stored on the SD.
>
> The stand-alone feature made the use of standard Firmata impossible.
>
> For a short period we tried to create an extended version, but gave up on
> it.
> Bottlenecks: the combination with the reading of the SD, and the max
> datarate for the serial port (115200) which forced us to make our own
> minimized message system.
>
>
> Re the noise of the servo's: i guess it comes from the motor's constantly
> trying to keep there position against the gravity pulling on the arm.
> How do you imagine to filter that?
>
> rolf
>
>


-- 
____________________
m.e.grimm, m.f.a, ed.m.
syracuse u., tc3
megrimm.net
____________________
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