Medical robotic system and control method thereof

A position detection apparatus comprising:

• a frame configured to be coupled to a trocar, the frame including a first subframe disposed in a first direction, and a second subframe disposed in a second direction, contacting the first subframe;
• a sensing unit comprising a first photodiode array mounted in the first subframe and a second photodiode array mounted in the second subframe;
• a light-emitting unit comprising a first light-emitting unit mounted in a third subframe facing the first subframe to emit light to the first photodiode array and a second light-emitting unit mounted in a fourth subframe facing the second subframe to emit light to the second photodiode array;
• a coordinate detection unit to detect an X-coordinate of an instrument inserted into the trocar based on output values of the first photodiode array and a Y-coordinate of the instrument inserted into the trocar based on output values of the second photodiode array;
• and
• a transmission unit to transmit the detected coordinate information.