To detect the rotational position of a rotating shaft having a rotation stroke of 360° or larger only by using signals from a sensor for detecting the presence or absence of a dog.

When an origin sensor 16c has detected a dog 20c and neither an OT+sensor 16a nor an OT-sensor 16b has detected a dog 20a or a dog 20b, it is determined that a processing head 13 is at an origin position. When the origin sensor 16c has detected the dog 20c, the OT-sensor 16b has not detected the dog 20b, and the OT+sensor 16a has detected the dog 20a, it is determined that the processing head 13 has been rotated by +360°. When the origin sensor 16c has detected the dog 20c, the OT+sensor 16a has not detected the dog 20a, and the OT-sensor 16b has detected the dog 20b, it is determined that the processing head 13 has been rotated by -360°.

COPYRIGHT: (C)2011,JPO&INPIT