10.7 Freedrive Mode
Recovery mode: When the robot arm is in violation of one of the other modes (i.e. Normal or
Reduced mode) and a Stop Category 0 has occurred,
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the robot arm will start up in Recovery
mode. This mode allows the robot to move slowly back to the allowed area using MoveTab
or Freedrive. It is not possible to run programs for the robot in this mode.
WARNING:
Note that limits for joint position, TCP position and TCP orientation
are disabled in Recovery mode, so take caution when moving the
robot arm back within the limits.
The subtabs of the Safety Configuration screen enable the user to define separate sets
of safety limits for Normal and Reduced mode. For the tool and joints, Reduced mode limits
regarding speed and momentum are required to be more restrictive than their Normal mode
counterparts.
When a safety limit from the active limit set is violated, the robot arm performs a Stop Category
0. If an active safety limit, such as a joint position limit or a safety boundary, is violated already
when the robot arm is powered on, it starts up in Recovery mode. This makes it possible to move
the robot arm back within the safety limits. While in Recovery mode, the movement of the robot
arm is limited by a fixed limit set that is not customizable by the user. For details about Recovery
mode limits, see the Hardware Installation Manual.
10.7 Freedrive Mode
When in Freedrive mode (see 13.1.5) and the movement of the robot arm comes close to certain
limits, the user will feel a repelling force. This force is generated for limits on the position,
orientation and speed of the robot TCP and the position and speed of the joints.
The purpose of this repelling force is to inform the user that the current position or speed is
close to a limit and to prevent the robot from violating that limit. However, if enough force
is applied by the user to the robot arm, the limit can be violated. The magnitude of the force
increases as the robot arm comes closer to the limit.
10.7.1 Backdrive
In Freedrive mode, the robot joints can be moved with relatively little force because the brakes
are released. During initialization of the robot arm, minor vibrations may be observed when the
robot brakes are released. In some situations, such as when the robot is close to collision, these
tremors are undesirable and the Backdrive feature can be used to forcefully move specific joints
to a desired position without releasing all brakes in the robot arm.
To enable Backdrive:
1. Press ON to enable power for the joints. The robot state is set to “Idle”. Do not release the
brakes (i.e. do not press START).
2. Press and hold the Freedrive button. The robot state changes to “Backdrive”.
3. Brakes will only be released in the joints to which significant pressure is applied, as long
as the Freedrive button is engaged/pressed. While using Backdrive, the robot feels heavy to
move around.
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According to IEC 60204-1, see Glossary for more details.
Version 3.11
Copyright © 2009–2019 by Universal Robots A/S. All rights reserved.
II-7 e-Series
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