The gripper event tool allows monitoring the sensors in the gripper for bumps to the gripper. The action produced can detect bumps to the gripper that activates the accelerometer inside the gripper or the pressure sensors at the tip of the robot's fingers depending on the settings given.

The Event drop-down allows selection of the type of event that this action will detect. The Acceleration sliders allow selection of the accelerometer threshold to use if detecting accleration at the gripper. This value sets the magnitude of the bump that will be considered as an event. The higher the value the more insensitive the action will be to bumps. However, if this value is set too low, minor vibrations by the robot while moving will also register as a bump to the gripper.

Similarly, the Slip slider sets the sensitivity to slip events. Slip events occur when the robot's gripper have closed on an object and that object is slipping out of the gripper. These events allow the robot to detect slips and, hopefully, respond appropriately. The slip slider sets a value where the higher the value the more insensitive to slippage between the fingers.

Gripper events are designed to be used in conjunction with other actions in RCommander by adding another outcome to other actions. In the above screenshot we have a gripper action with the three usual outcomes: aborted, preempted, and succeeded. We then add event detector by selecting the gripper action (highlighted in blue), clicking Gripper Event, then clicking Add.

After adding, the original gripper action turns yellow with an added outcome that says detected event. Double-clicking on this yellow node will show you the original gripper action allowing you to make changes (if needed) similar to the nodes produced by the state machine tool. Connect another node to the detected event outcome to respond to detected events.

The gripper event action is not restricted to just encapsulating the gripper action. In fact, it will work on virtually any other action in RCommander including things such as sleep actions.