GoFa Singularity

jakobhoerbst

hi, 

I have encountered a problem with the GoFa (CRB15000). When I linearly traverse a path from a point (with y=0) below the home position to a point (with y=0) above the home position, the robot jumps into an error "near singularity".

The robot should not get into a wrist singularity because axis 4 and 6 of the GoFa are not aligned even with axis 5 = 0? With SingArea I can't solve the problem either, but if I use ConfL \Off the movement works. Why is that so? 

CONST robtarget below:=[[570,0,550],[0.707106792,0,0.707106771,0],[0,0,0,1],[9E+09,9E+09,9E+09,9E+09,9E+09,9E+09]];

CONST robtarget above:=[[570,0,1050],[0.707106786,0,0.707106776,0],[0,0,0,0],[9E+09,9E+09,9E+09,9E+09,9E+09,9E+09]];

xerim

Does it have to be a linear movement? Try MoveJ, or change the position of the joints in the starting position

jakobhoerbst

Not for this application, I'm really more concerned with why GoFa has a problem here in the first place. That should not be the case.

(Background story: I'm currently working on controlling GoFa with EGM via a HoloLens2 and run into the problem with a hand singularity. So I'm currently looking for the causes or ways to improve that. In the process, I came across this problem.)

ABB_YuMiGuide

The simple answer to your question as to why this problem is occuring with GoFa, it is simply because of the different geometry of the robot. By moving from below to above or vice versa, the robot passes through a point of singularity where joint 4, 5 and 6 are aligned. When you attempt to move between 2 points with a wrong arm configuration, this singularity will occur, infact this can occur with any robot, not just GoFa, the only solution is to change the trajectory and reteach the position. As to why the singularity does not show up when ConfL is off is because the robot is free to change greatly the arm configuration not resulting in a singluarity