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Subject: 
"Servo" Driver for NQC
Newsgroups: 
lugnet.robotics
Date: 
Sun, 27 Jan 2002 15:06:28 GMT
Viewed: 
582 times
  
Hi All,

I've got a bit of a problem! Whenever I do a cartesian (or other) robot
model, I typically (in NQC) will program a "driver" which can spin the
motors with the rotation sensors to any position and delecerate to finely
reach the destination. However, I've not been able to do this ever very
smoothly.

Has anyone done something similar?

I'm changing a variable in the main task (like, xPos or yPos or similar),
and the "servo" task will note the difference between it's actual position
and the desired position. It'll spin the motor in the direction it should
go, and when it gets within a certain number of counts on the rotation
sensor, jumps to a slow speed by pulsing the motor (on, wait 1, off, wait
1).

Is this the right newsgroup to be asking? I'm not sure, maybe I should try
one of the NQC ones.

Anyway, I'm just anxious to see if anyone else has ever done something
similar, because with a robot I'm working on for an upcoming competition,
the method of control I just mentioned is far too "jumpy" and causes my
robot to vibrate, shake, and spring all over.

Thanks in advance,

    Iain



Message has 3 Replies:
  Re: "Servo" Driver for NQC
 
(...) This is absolutely the right group! If you do searches on 'skipped counts' or similar wording you will find lots of posts on the rotation sensor missing counts at low speeds. And if you want to get to the bottom line quickly, check this (...) (22 years ago, 27-Jan-02, to lugnet.robotics)
  Re: "Servo" Driver for NQC
 
Rebel Transcanner wrote: > (...) I take it you are really doing on...float...on...float cycles with your motor instead of using "off", which actually performs active braking (on/off cycles are almost guaranteed to give serious mechanical jitters). (...) (22 years ago, 29-Jan-02, to lugnet.robotics)
  Re: "Servo" Driver for NQC
 
(...) Well I haven't seen your version of the Project-X design, but I'll assume it's similar (albeit vastly inferior) to the one I'm entering. I'm assuming that for the sake of speed, you are keeping moving mass to a minimum and hence, not loading (...) (22 years ago, 30-Jan-02, to lugnet.robotics)

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