View Single Post
  #10   Spotlight this post!  
Unread 27-05-2015, 22:34
GeeTwo's Avatar
GeeTwo GeeTwo is offline
Technical Director
AKA: Gus Michel II
FRC #3946 (Tiger Robotics)
Team Role: Mentor
 
Join Date: Jan 2014
Rookie Year: 2013
Location: Slidell, LA
Posts: 3,666
GeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond reputeGeeTwo has a reputation beyond repute
Re: about the torque calculation of a mecanum wheel

Quote:
Originally Posted by Ether View Post
But arguably, it also has consequences within the scope of the paper for its readers, who may assume the paper has been properly vetted and who may be misled/confused.
The likelihood of confusion deepens. With the exception of the last two rows, the results in table 1 are what is predicted with the improper wheel orientation shown in the force diagrams of figures 2 through 6. As shown, the wheel rotations indicated in the last two rows would not result in any rotation of the vehicle unless the center of gravity and geographic center were offset in the X direction. This is depicted in figure 6, but it is not clear from a casual reading of the text that this was a necessary condition to achieve the stated rotation.
At first glance (and for me, second and third), the translations reported in table 2 seem to be at odds with the results of table 1. In all 32 cases, wheels 1 (right rear) and 3 (left front) are rotated equally in the positive direction, and wheels 2 (right front) and 4 (left rear) are rotated by the same amount as each other, but less than the magnitude of rotation of wheels 1 and 3. Using the directions depicted in figure 5 (and not contradicted in figure 6), this would lead to a westerly (negative x) translation. All of the results in table 2 report a positive X offset, that is toward the east. The resolution of this inconsistency is in the final, parenthesized sentence at the end of the second paragraph of section 3.1:
Quote:
(The inclination angle α in the prototype is 135°.)
That is, that the wheels are installed in the standard mecanum configuration depicted in the graphics of figures 1-6, not the configuration shown in the force diagrams of figures 2-6.

At this point, I'll back away from this paper, rather than trying to figure out if the mistakes and inconsistencies are maintained or repaired in the analysis of table 3 and statement of conclusions.
__________________

If you can't find time to do it right, how are you going to find time to do it over?
If you don't pass it on, it never happened.
Robots are great, but inspiration is the reason we're here.
Friends don't let friends use master links.