About Singular Point Passage Function - Mitsubishi Electric CR750-Q Instruction Manual

5.20 About singular point passage function

(1) Overview of the function
Mitsubishi's robots calculate linear interpolation movement and store teaching positions as position data in
the XYZ coordinates system. In the case of a vertical 6-axis robot, for example, the position data is
expressed using coordinate values of the robot's X, Y, Z, A, B and C axes, but the robot can be in several
different postures even if the position data is the same. For this reason, the robot's position can be selected
among the possible options using the coordinate values and the structure flag (a flag indicating the posture).
However, there can be an infinite number of combinations of angles that a particular joint axis can take.
Even if the structure flag is used, at the positions where this flag is switched, it may not be possible to oper-
ate the robot with the desired position and posture (for example, in the case of a vertical 6-axis robot, axes
J4 and J6 are not uniquely determined when axis J5 is 0 degree). Such positions are called singular points,
and they cannot be reached through XYZ jog and linear interpolation-based operation. To avoid this problem
in the past, the operation layout had to be designed such that no singular points would exist in the working
area, or the robot had to be operated using joint interpolation if it could not avoid passing a singular point.
The singular point passage function allows a robot to pass singular points through XYZ jog and linear inter-
polation, which helps increasing the degree of freedom for the layout design by enlarging the working area
by linear interpolation.
*Positions of singular points that can be passed
The positions of singular points that the singular point passage function allows the robot to pass are as fol-
lows.
In the case of vertical 6-axis robots
<1> Positions where axis J5 = 0 degree
In these positions, the structure flag
switches between NonFlip and Flip.
In the case of vertical 5-axis robots
<2> Positions where the center of axis J5 coincides with the
In these positions, the structure flag switches between Right
and Left.
<1> Positions where the center of mechanical interface coincides with the rotation
axis of axis J1
In these positions, the structure flag switches between Right and Left.
rotation axis of axis J1
About singular point passage function 5-509
5Functions set with parameters