Universal Robots Singularities
Considering the robot’s work-space, besides having a reach of 1300 mm it is important to take into account the occurrence of singularities. ISO-10218 defines a singularity as a ”condition caused by the collinear alignment of two or more robot axes resulting in unpredictable robot motion and velocities”, and should, therefore be avoided. There are three types of singularities: wrist, shoulder and elbow singularities:
- Wrist singularities: Happen when the axes of joints 4 and 6 become parallel, and can cause these joints to spin 180 degrees instantaneously. In the UR robots, this corresponds to θ5=0°, θ5=±180° or θ5=±360°;
- Elbow singularities: Happen when the axes of joints 2, 3 and 4 are co-planar, causing the elbowto lock in position. In the UR robots, this corresponds to θ3= 0°;
- Shoulder singularities: Happen when the intersection point of the axes of joints 5 and 6 aligns with the plane passing through the axes of joints 1 and 2, causing joints 1 and 4 to spin 180 degrees instantaneously.
Video link: Visual representation in Polyscope.
