Mitsubishi CR750 Series Instruction Manual page 53

8.1.2.3 Stiffness Coefficient
Stiffness control softness is specified with the stiffness coefficient. The stiffness coefficient is the equivalent of
spring constant, and the greater the value, the harder the control.
<Correlation between teaching position and reaction force>
If stiffness control mode is selected, when an external force acts on the arm tip, resulting in displacement
between the teach position and actual position, the robot moves to a position at which the reaction force
corresponding to the "displacement" and "stiffness coefficient" can be obtained.
In the following image, stiffness control is performed only for the tool Z-axis. By setting 0.5 [N/mm] for the
Z-direction stiffness coefficient, and the teaching position at 5 mm below the contact surface, force F produced
on the contact surface is calculated as follows.
Actual position
(contact position)
Position command
(teaching position)
F = 0.5 [N/mm] × 5 [mm] = 2.5 [N]
The smaller the stiffness coefficient, the smaller the reaction force, helping to deal with greater displacements.
8.1.2.4 Damping Coefficient
Vibrations that occur when applying positional offsets with force sense control (stiffness control or force control)
are adjusted with the damping coefficient. The greater the value, the greater the effect in suppressing vibrations,
however, positional offsetting is delayed with sudden changes in force, resulting in a greater force applied the
moment contact is made with the workpiece.
If required, damping coefficient adjustments should be made after force sense control gain adjustment is
complete. (Vibrations also occur if the force sense control gain is too great.)
8 Using the Force Sense Function (Programming)
5 mm
Force Sense Control 8-43