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Subject: 
Re: moving in a straight line with two motors?
Newsgroups: 
lugnet.robotics
Date: 
Fri, 13 Nov 1998 16:19:21 GMT
Original-From: 
John Scott Kjellman <jkjellman@ameritech.netAVOIDSPAM>
Viewed: 
2297 times
  
Tim,

Instead of using the differential for angle sensors, why not use it to
allow a single motor to drive both wheels?  Then a single angle sensor
coupled with a motor could drive the steering mechanism.  This setup
would be very similar to a radio controlled car.

Just a thought.

KJohn

Tim Rueger wrote:

Hi,

One of the first things I ran into when making a mobile 'bot using one
motor for each of two drive wheels was the mismatch in their speed.
Needless to say, it's a nice way to make curved path.  Not what I want.

So I've got one of those nifty angle sensors.  I'd like to use it for
feedback from the wheels to tell a motor to slow down when it gets too
far ahead of the other one.  An obvious thing to do is to use two
angle sensors and subtract them, but I'd like to do it with one sensor,
given there are only 3 sensor inputs.

A simple mechanical way to do this is to use a differential gear,
driving it backwards.  One input gets the rotation of one wheel, and
the other input gets an inverted rotation of the other wheel.  With
equal wheel rotations, there is no movement of the differential
housing.

Unfortunately, gear slop keeps this from working well for me.  Any
suggestions?

Thanks,
-Tim

--
Tim and/or Shelley Rueger - rueger "at" io.com
WWW page: http://www.io.com/~rueger/



Message has 2 Replies:
  Re: moving in a straight line with two motors?
 
(...) At one point, in the distant past, I saw plans for a gear box that used either 2 or 3 differentials, I do not remember which. 2 motors were used, 1 to drive both axles, one for steering. axle1 == motor1 + motor2 axle2 == motor1 - motor2 With (...) (26 years ago, 13-Nov-98, to lugnet.robotics)
  Re: moving in a straight line with two motors?
 
(...) The problem with this is that you now have a car-style turning radius (determined by front wheel deflection and traction) instead of a tank-style turning radius (essentially zero). Daniel "Dan'l" Miller Senior, School of Aeronautics and (...) (26 years ago, 13-Nov-98, to lugnet.robotics)

Message is in Reply To:
  moving in a straight line with two motors?
 
Hi, One of the first things I ran into when making a mobile 'bot using one motor for each of two drive wheels was the mismatch in their speed. Needless to say, it's a nice way to make curved path. Not what I want. So I've got one of those nifty (...) (26 years ago, 13-Nov-98, to lugnet.robotics)

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