[Alan Anderson]

Originally Posted by Ether

Is it my imagination, or are both Figure 2 and Figure 4 in the following link incorrect:

http://www.scipub.org/fulltext/ajas/ajas351831-1835.pdf

Figure 4 is definitely wrong. I think that robot would have real difficulty going straight.

Figure 2 might be wrong, or it might just be a bottom view. Since it's showing the force vectors, it actually makes sense to be showing the spot where the wheels contact the floor.