Crossing singularities with a six-axis industrial robot arm

Unlike other six-axis industrial robot arms, the Meca500 can cross singularities in order to (1) simplify robot jogging and (2) allow larger Cartesian moves.

SIngularities are often said to be the boundaries of the robot workspace, but that is an oversimplification. The Cartesian workspace of a typical six-axis robot arm is a set of eight subsets of end-effector poses. In each subset, all poses are accessible with one of the eight possible robot configurations (flip/no-flip, elbow-up/elbow-down, front/back). Most poses in the Cartesian workspace are present in only a few of these eight subsets.

When you are jogging in Cartesian mode a typical six-axis industrial robot, its end-effector is confined to ONLY one of these eight subsets. But as we already mentioned, there are many other poses outside of this subset that are accessibly only with a different robot configuration. To reach them, you need to switch to joint mode, jog roughly to the desired pose, and then switch back to Cartesian mode in order to fine tune the desired pose.

These eight subsets of poses are not separated by impenetrable boundaries, but by regions that are of lower dimension. Think of two circular skating rinks connected by a very narrow passage. Obviously, you can't make pirouettes in that passage, but if you plan correctly your path, you can skate from one extremity of the whole complex to the other without even slowing down.

Thus, by being able to cross singularities, you can carefully plan your end-effector paths and then be able to make longer linear moves or make larger angular displacements. We're essentially providing an opening for you to explore, like the trunk pass-through in the backseat of some cars...

[wlysam]

A longer version of this video would have been great 👍

[Matt-]

I have a question about the trajectory/rotation planning. How does one plan a trajectory in xyz and also incorporate speed and acceleration? (A series of points in space along a designated path). I can understand how to calculate a series of points xyz but how does one incorporate acceleration? (Trapezoidal). And how do you drive the motors at that specified speed?

[DUIofPhysics]

Is this a new firmware update? I remember trying one of these robots a year back and had a lot of issues with singularities.