Posture control method and posture control device

A posture control device that controls a posture of a processing unit that performs processing on an inner peripheral surface or an outer peripheral surface of a round pipe, the posture control device comprising:

• a plurality of distance measuring units that is included in the processing unit, and measures a gap distance between the processing unit and a process surface of the round pipe to be processed by the processing unit;
• a posture controlling unit that controls the posture of the processing unit relative to the process surface, based on measurement results of at least four given distance measuring units, among the distance measuring units, wherein the four given distance measuring units are arranged to face the process surface in a positional relationship of four apexes of a rectangle, and
• the posture controlling unit controls the posture of the processing unit in a rotational direction about a roll axis, based on a difference between a first total distance obtained by adding measurement distances measured by two distance measuring units located in one diagonal position among the four given distance measuring units, and a second total distance obtained by adding measurement distances measured by two distance measuring units located in another diagonal position;
• wherein the process surface that the distance measuring units face is divided into four virtual partitioned areas, based on a first virtual boundary line extended in a pipe axis direction of the process surface, and a second virtual boundary line extended in a perpendicular direction perpendicular to the first virtual boundary line,
• the four virtual partitioned areas are composed of a first virtual partitioned area, a second virtual partitioned area adjacent to the first virtual partitioned area in the pipe axis direction, a third virtual partitioned area adjacent to the first virtual partitioned area in the perpendicular direction, and a fourth virtual partitioned area adjacent to the second virtual partitioned area in the perpendicular direction and also adjacent to the third virtual partitioned area in the pipe axis direction,
• among the four given distance measuring units, a first distance measuring unit is made to face the first virtual partitioned area, a second distance measuring unit is made to face the second virtual partitioned area, a third distance measuring unit is made to face the third virtual partitioned area, and a fourth distance measuring unit is made to face the fourth virtual partitioned area, and the posture controlling unit controls the posture of the processing unit in the rotational direction about the roll axis, based on a difference between the first total distance obtained by adding the second measurement distance measured by the second distance measuring unit and the third measurement distance measured by the third distance measuring unit, and the second total distance obtained by adding the first measurement distance measured by the first distance measuring unit and the fourth measurement distance measured by the fourth distance measuring unit.