Mitsubishi Electric 4F-FS001-W200 Instruction Manual page 66

8 Using the Force Sense Function (Programming)
8.1.2.3 Stiffness Coefficient
Stiffness control/limited 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.
When 0.0 is set with the stiffness coefficient, the reaction force is not generated in the case of the position is
changed by external force.
When the limited stiffness control, the robot is controlled within the specified reaction force that is set with limit
value.
8.1.2.4 Damping Coefficient
Vibrations that occur when applying positional offsets with force sense control (stiffness control, limited 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.)
8-54 Force Sense Control
5 mm