servo motor boebot going in circles as battery flattens
Archiver
Posts: 46,084
Hi
I'm using two modified servo motors to drive a small boebot type
rover.
The problem I have is that even though I've calibrated them so it
goes straight when suppied by a dc power adaptor, the calibration
varies at diffent voltages (i.e. as the batteries flatten the curve
changes and it starts to go in circles).
I was going to use some sort of switch to figure out when each wheel
had gone around once, and build some code to adjust speed/keep it
straight.
Has anyone already written PBASIC code to do this. I'd like to aviod
re-inventing the wheel.
Also, what is the best way of doing the physical sensing ? I was
thinking of just putting a 'lump' on the inside of the wheel that
depresses a little contact switch mounted on the body to register
the rotation, or is there a more sensible way of doing it?
Alternatively am I just missing something in my servo calibration or
powering approach?
All suggestions greatfully received!
kc
I'm using two modified servo motors to drive a small boebot type
rover.
The problem I have is that even though I've calibrated them so it
goes straight when suppied by a dc power adaptor, the calibration
varies at diffent voltages (i.e. as the batteries flatten the curve
changes and it starts to go in circles).
I was going to use some sort of switch to figure out when each wheel
had gone around once, and build some code to adjust speed/keep it
straight.
Has anyone already written PBASIC code to do this. I'd like to aviod
re-inventing the wheel.
Also, what is the best way of doing the physical sensing ? I was
thinking of just putting a 'lump' on the inside of the wheel that
depresses a little contact switch mounted on the body to register
the rotation, or is there a more sensible way of doing it?
Alternatively am I just missing something in my servo calibration or
powering approach?
All suggestions greatfully received!
kc
Comments
Try this thread:
http://groups.yahoo.com/group/basicstamps/message/24922
David H Lawrence
Simple Multi-tasking, Co-Processors, Compilers, and Virtual Controls
mailto:david@r...
http://www.rhombus-tek.com
Original Message
From: "carruthers_kim" <kim_carruthers@h...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, March 16, 2003 11:04 PM
Subject: [noparse][[/noparse]basicstamps] servo motor boebot going in circles as battery
flattens
> Hi
> I'm using two modified servo motors to drive a small boebot type
> rover.
>
> The problem I have is that even though I've calibrated them so it
> goes straight when suppied by a dc power adaptor, the calibration
> varies at diffent voltages (i.e. as the batteries flatten the curve
> changes and it starts to go in circles).
>
> I was going to use some sort of switch to figure out when each wheel
> had gone around once, and build some code to adjust speed/keep it
> straight.
>
> Has anyone already written PBASIC code to do this. I'd like to aviod
> re-inventing the wheel.
>
> Also, what is the best way of doing the physical sensing ? I was
> thinking of just putting a 'lump' on the inside of the wheel that
> depresses a little contact switch mounted on the body to register
> the rotation, or is there a more sensible way of doing it?
>
> Alternatively am I just missing something in my servo calibration or
> powering approach?
>
> All suggestions greatfully received!
>
> kc
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.462 / Virus Database: 261 - Release Date: 3/13/03
You can certainly use a closed-loop system to control
the motor speed, but you may want to regulate the
battery voltage. Using a closed-loop system involves
much code (like what to do at very low speeds when
signal pulses become far apart) and would probably be
most effective with an optical system (break-beam
system or reflective). But you may also want to try a
modular DC/DC converter for power. I had a similar
problem with a small bot due to gearbox efficiencies.
When the batteries were low, the motor with the higher
load would run slower. So to run the 5V motors
equally, I used a 12V, 3AH Gel battery and a 25 Watt
DC/DC converter rated at 12V in and 5V @ 5A out to
provide a regulated 5V from my fluctuating 12V source.
It cost $9.00 and solved all of my problems. The
converter would work down to 7 volts, but I recharged
at 10 to aviod damage. Just a thought.
DrDiode
--- carruthers_kim <kim_carruthers@h...> wrote:
> Hi
> I'm using two modified servo motors to drive a small
> boebot type
> rover.
>
> The problem I have is that even though I've
> calibrated them so it
> goes straight when suppied by a dc power adaptor,
> the calibration
> varies at diffent voltages (i.e. as the batteries
> flatten the curve
> changes and it starts to go in circles).
>
> I was going to use some sort of switch to figure out
> when each wheel
> had gone around once, and build some code to adjust
> speed/keep it
> straight.
>
> Has anyone already written PBASIC code to do this.
> I'd like to aviod
> re-inventing the wheel.
>
> Also, what is the best way of doing the physical
> sensing ? I was
> thinking of just putting a 'lump' on the inside of
> the wheel that
> depresses a little contact switch mounted on the
> body to register
> the rotation, or is there a more sensible way of
> doing it?
>
> Alternatively am I just missing something in my
> servo calibration or
> powering approach?
>
> All suggestions greatfully received!
>
> kc
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed.
> Text in the Subject and Body of the message will be
> ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
__________________________________________________
Do you Yahoo!?
Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop!
http://platinum.yahoo.com