Safe activation of free-drive mode of robot arm

A robot controller for controlling a robotic arm, the robot controller for switching the robotic arm between a first mode of operation and a free-drive mode of operation, where the robot controller is configured to perform operations comprising:

• keeping the robotic arm in a posture that is static when only gravity acts on the robotic arm;
• and
• allowing a change in the posture of the robot arm when an external force different from gravity is applied to the robotic arm;
• wherein the free-drive mode of operation is activatable in response to a free-drive activation signal at the robot controller;
• wherein, in response to the free-drive activation signal, the robotic controller is configured to perform operations comprising:
• monitoring a value of at least one parameter of at least one sensor associated with a joint of the robotic arm, the monitoring being performed in an activation sequence period of time, and
• comparing the value to at least one threshold value;
• and
• wherein the robot controller is configured to switch the robotic arm to the free-drive mode of operation when the value of the at least one parameter does not exceed the at least one threshold value within the activation sequence period of time.