Electric motor breaking

I have a robot design that needs to climb a hill. Part way I up I want to stop it to take some observations. Problem I am coming into is that when I
disengage drive power the motors start to freewheel and the robot rolls backwards.
Without putting in a dedicated break is there any way to do a motor break?
Thanks, David
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 20 Jul 2003 21:18:21 -0400, David Shoemaker wrote:

You could apply just enough power to your motors to counteract gravity and hold them stationary. You'd need a way to sense wheel rotation, but you might already have that if you have motor shaft encoders installed.
Cheers, -Brian
--
Brian Dean, snipped-for-privacy@bdmicro.com
BDMICRO - Maker of the MAVRIC ATmega128 Dev Board
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That would waste an awful lot of energy, and maybe even damage the motors, if you stopped for a while. My suggestion? Two words: worm gears.
Tom
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
My main problem with the active breaking systems people are suggesting (which all sound like good ideas) is that this is a solar powered unit. As such I don't really have a lot of spare power and when I am stopped I would rather be using the juice to recharge my storage cells then using it running the motors.
David

the
Light
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Didn't see what other people are suggesting, but are worm drive motors an option?
Mike

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yup,
Just implement a servo loop.
Mike

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
David Shoemaker wrote:

if it is a rather light-weight robot, one solution may be to glue (or screw into a mounting hole) a plastic or wood post by the post coming out of the motor. then you could attatch a sort of triangle that is rounded on one side to the post.
with this in place, the motor should be able to turn only one direction. might pose a problem backing up though :).
just a thought
--
C.M. Hobbs [KD5RYO]
http://www.destroyallmachines.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
why dont you use stepper motors then naturally break due to the way they work
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I would try to short-circuit the motoros' wireings: any movement of the shaft would generate a current that would in turn generate a magnetic field in the motor trying to compensate for the movement. At least in theory. Worth a try...
Andras Tantos

I
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yes, I have used the 'short circuit' technique before and it works. Most full-bridge drivers have the ability to act as a break by shorting the motor. The only problem is that ultimately there are some losses in the system and so the EMF generated by the motor isn't enough to overcome a large force, but you should be ok on a slope. Regards,
Geoffrey.

to
when
break?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Back emf is a good thing - easy to implement and we use in our robot as well, although we are talking little here - 2.5Kg mass and we dont go up hills.

to
when
break?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.