Subject:
|
Re: COG shifter off topic
|
Newsgroups:
|
lugnet.robotics
|
Date:
|
Thu, 15 May 2003 18:33:51 GMT
|
Viewed:
|
998 times
|
| |
|
|
In lugnet.robotics, Øyvind Steinnes writes:
> Can anybody explain to me what a "Centroid" is?
> I know what a COG is, here in this groups it means a robot that moves the
> center of gravity to hold the balance when walking (?).
Centroid and COG (center of gravity) are at the same location if you're
considering an object of uniform density. This is usually the case so the
two terms get used often to describe the same thing, and their definitions
become the same.
However, if the object is not uniform (such as a "COG walker"- contains
plastic and metal) then the COG wouldn't necessarily coincide with the
centroid (1).
The center of gravity (COG) is the point at which all gravitational forces
balance (i.e. there is zero moment). Therefore if you could theoretically
hold at object at its COG (with a frictionless pinned connection), it
wouldn't rotate when subject to gravity.
I believe the proper definition of a centroid is the geometric center of an
object. To find this, you'd pretend all parts of your complex object were of
the same density. The centroid depends on volumes rather than masses (and if
2D, it would depend on areas). You find the centroid the same way you find
the center of gravity, but use volumes (or areas for 2D) instead of mass.
-TJ
NOTES:
1. If by chance the metal parts were "perfectly centered" in the plastic
parts, the total COG might just be the same as the centroid.
2. I think I'm right in stating the above :-) In my job as a structural
engineer, the two terms "centroid" and "COG" are used rather loosely.
|
|
Message is in Reply To:
 | | Re: COG shifter off topic
|
| Can anybody explain to me what a "Centroid" is? I know what a COG is, here in this groups it means a robot that moves the center of gravity to hold the balance when walking (?). "Tony Burton" <lego-robotics@crynwr.com> wrote in message (...) (21 years ago, 15-May-03, to lugnet.robotics)
|
4 Messages in This Thread:
  
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
