Actuator and robot arm apparatus

A robot arm apparatus, comprising:

• an arm unit that includes a plurality of links that are Pined by one or a plurality of joint units;
• and
• a driving control unit configured to control drive of an actuator that is provided in at least one of the plurality of joint units based on a state of the joint unit,
• wherein the actuator includes:
• a reduction gear that is configured to:
• reduce, by a reduction ratio, a rotational velocity of an input shaft joined to a rotary shaft of a motor, and
• transmit the reduced rotational velocity to an output shaft,
• a first absolute angle encoder that is configured to detect a first rotational angle of the input shaft;
• a second absolute angle encoder configured to detect a second rotational angle of the output shaft;
• and
• at least one processor configured to compute a third rotational angle of the output shaft based on the detected first rotational angle and the detected second rotational angle.

A medical robot arm apparatus, comprising:

• an imaging device configured to monitor a surgical affected part of a body;
• a base unit;
• and
• an arm unit with a first end of the arm unit coupled to the imaging device and a second end of the arm unit coupled to the base unit,
• wherein the arm unit includes a plurality of joint portions and a plurality of links that are between the first end and the second end,
• wherein each of the plurality of joint portions includes at least an actuator,
• wherein the actuator includes:
• a reduction gear that is configured to:
• reduce, by a reduction ratio, a rotational velocity of an input shaft joined to a rotary shaft of a motor, and
• transmit the reduced rotational velocity to an output shaft,
• a first absolute angle encoder that is configured to detect a first rotational angle of the input shaft, and
• a second absolute encoder that is configured to detect a second rotational angle of the output shaft based on the detected first rotational angle.