## Re: [SeattleRobotics] 2-wheel balancing

Expand Messages
• Isn t what you are describing a rate gyro? The fundamental problem with this scheme is the drift associated with both accelerometers - Since the two unit are
Message 1 of 8 , Jul 7, 2002
• 0 Attachment
Isn't what you are describing a rate gyro? The fundamental problem
with this scheme is the drift associated with both accelerometers -
Since the two unit are independent, their drift will look like a low
level acceleration or rotation. This scheme does have the advantage
that is combines the rate gyro and the tilt sensors using cheap linear
accelerometers. However, I don't think the rate gyros are that
expensive and are probably a lot more sensitive and have less drift
since they are machined on one piece of silicon or piezo ceramic
(depending upon unit). I suspect that combining a rate gyro with a
tilt accelerometer would work best if I could just figure out the
math.

Anyway, do make a base and try to get your scheme to work. It would
be a cool, simple, unit for hobbyists to replicate for their own
balancing robots.

----- Original Message -----
From: "Mike Jones" <michaelj@...>

> A couple of days ago there was a discusion about how to use
> accelerameters to help a 2 wheeled robot keep its balance.
> The hard part seemed to be getting rid of the acceleration
> caused by the robot's motion so that you could have a good
> reference to a true vertical.
>
> Just a moment ago a small LED (I'm not confident enough for
> it to be a lightbulb ;) ) lit up over my head!
>
> What if you mount 2 accelerameters equidistant from the
> center of rotation but on opposite sides of the line of
> rotation (like counter weights) such that the axises being
> measured were parallel and pointing horizontally directly
> ahead when the robot is in a vertical position (or pointing
> in a vertical position, either way should work). Any
> acceleration induced by the robot's forward motion would be
> equal and in the same direction for both sensors but any
• ... Actually there isn t any gyro in this at all. The only sensors would be accelerometers. ... I plan to try to get a base up for experimenting. I have a
Message 2 of 8 , Jul 8, 2002
• 0 Attachment
> Isn't what you are describing a rate gyro?

Actually there isn't any gyro in this at all. The only
sensors would be accelerometers.

>The
> fundamental problem with this scheme is the drift
> associated with both accelerometers - Since the two unit
> are independent, their drift will look like a low level
> acceleration or rotation. This scheme does have the
> advantage that is combines the rate gyro and the tilt
> sensors using cheap linear accelerometers. However, I
> don't think the rate gyros are that expensive and are
> probably a lot more sensitive and have less drift since
> they are machined on one piece of silicon or piezo ceramic
> (depending upon unit). I suspect that combining a rate
> gyro with a tilt accelerometer would work best if I could
> just figure out the math.
>
> Anyway, do make a base and try to get your scheme to work.
> It would be a cool, simple, unit for hobbyists to
> replicate for their own balancing robots.

I plan to try to get a base up for experimenting. I have a
couple of accelerometers on order.

Mike
>
> ----- Original Message -----
> From: "Mike Jones" <michaelj@...>
>
>
> > A couple of days ago there was a discusion about how to
> > use accelerameters to help a 2 wheeled robot keep its
> > balance. The hard part seemed to be getting rid of the
> > acceleration caused by the robot's motion so that you
> > could have a good reference to a true vertical.
> >
> > Just a moment ago a small LED (I'm not confident enough
> > for it to be a lightbulb ;) ) lit up over my head!
> >
> > What if you mount 2 accelerameters equidistant from the
> > center of rotation but on opposite sides of the line of
> > rotation (like counter weights) such that the axises
> > being measured were parallel and pointing horizontally
> > directly ahead when the robot is in a vertical position
> > (or pointing in a vertical position, either way should
> > work). Any acceleration induced by the robot's forward
> > motion would be equal and in the same direction for both
> sensors but any
>
>
>
>
> Visit the SRS Website at http://www.seattlerobotics.org
>
> To unsubscribe from this group, send an email to:
> SeattleRobotics-unsubscribe@yahoogroups.com
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
Your message has been successfully submitted and would be delivered to recipients shortly.