Robot arm and unmanned aerial vehicle equipped with the robot arm

A robot arm mountable on an unmanned aerial vehicle comprising a plurality of rotary wings, the robot arm comprising:

• an arm unit comprising a plurality of joints;
• arm controlling means for controlling driving of the joints;
• and
• a displacement detector capable of detecting a change of a position of the arm unit and an inclination of the arm unit,
• wherein two of the plurality of joints swingable in directions orthogonal to each other are regarded as a pair of the joints, and the plurality of joints comprise
• three pairs of the joints, and
• one joint, among the joints, that is located further at a side of a base end of the arm unit than the three pairs of the joints and that is rotatable in a circumferential direction, and
• wherein when the displacement detector has detected a position error that is an unexpected change of the position of the arm unit or an unexpected inclination of the arm unit, the arm unit controlling means is configured to cause the joints to absorb the position error so as to prevent the position error from being transmitted to a leading end of the arm unit.