Force Control+Multipath issues
/ Most recent by David_Gouffe
We are using our UR10 (Holding a grinder/sander with a Robotiq 2f Gripper) for basic deburr, grinding, sanding, and polishing operations.
The robot seems to have a very difficult time determining a path to take. We are essentially sanding in a square pattern. (Sanding a flat surface on a square with a cut out interior. Think of it as a large flat picture frame around 2ft by 3ft.)
Before starting to program; I release the brakes on the robot, move the tooling all around the part, and touch every angle I need to get to, and follow the general path I know I want the arm to make and confirm that I am able to touch all of the product with the sander without being close to a bind. sometimes, even when everything appears good. I can make the movements that the robot needs to make, manually. But then when I go to program the robot I am constantly (8/10 times) told that it is 'unable to calculate a path' when I am able to manipulate the arm into the position and path manually. Sometimes; when a path does work, its very inefficient. I have to run at a very slow speed to prevent it from 'snapping' into a bind. The positioning of the arm during the path seems to be what cause most binds and calculation errors. Sometimes I feel that there is a better\more efficient positioning available that is further from the binding positions.
When I program a path using the move command and waypoints, I can choose my own robot positioning...and it goes to the same arm positions every time.
Unfortunately; when im using the force control UR, I am limited to the multipath command. When I program movements using the 'multipath' commands, the arm positioning is determined by the program, instead of by me. I can have the arm facing the direction I want it to start and end, and then when I press play, the arm will choose its own position and path dependent only on tool position and not on any elbows or bends.
Not only does the arm take an unintended path, but if I add or even slightly edit any of the points in my multipath, it can have a huge impact on arm placement before and after the point I have edited. Evades and movements I have programmed in, that worked for the position the arm WAS in, will no longer work, causing the robot to crash during an improper evade.