View Single Post
  #34   Spotlight this post!  
Unread 14-12-2011, 15:09
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,120
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: 2 motor drive VS 4 motor drive


For students interested in the math, attached are the equations of motion1 and plots2 of distance, velocity, and acceleration vs time, for the 2 and the 4 CIM vehicles, at 73% and 100% drivetrain efficiency, assuming:
- assume constant 12V supply to the motors (not a good assumption, agreed)

- "speed loss constant" 100% (e.g. vehicle top speed corresponds to motor free speed. may not be a good assumption)

- motive force varies linearly with vehicle speed

- wheels are not traction limited
With the given assumptions, the equations of motion can be solved analytically to obtain a closed-form solution (no need for numerical integration).

1 http://maxima.sourceforge.net/

2 units converted to feet for plotting

Attached Thumbnails
Click image for larger version

Name:	robot equations of motion.gif
Views:	23
Size:	14.2 KB
ID:	11196  Click image for larger version

Name:	2 vs 4 CIM 73.gif
Views:	22
Size:	9.1 KB
ID:	11197  Click image for larger version

Name:	2 vs 4 CIM 100.gif
Views:	19
Size:	8.6 KB
ID:	11198  
Attached Files
File Type: txt F & S.txt (364 Bytes, 6 views)

Last edited by Ether : 14-12-2011 at 15:26. Reason: added footnotes