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Re: [SeattleRobotics] 2-wheel balancing

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  • Larry Barello
    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
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      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
    • Mike Jones
      ... 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
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        > 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
        >
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