Patent ID: 8482242

Claim:
A rotary drive device comprising: a servo motor; a reduction gear; a current control unit configured to supply current to the servo motor according to a current reference value; a controller configured to output an angle reference value of a rotation shaft of the reduction gear; a first angle-detecting unit configured to detect the rotation angle of the rotation shaft of the servo motor and output a first rotation angle that can be obtained by dividing the detection result by the reduction ratio of the reduction gear; a second angle-detecting unit configured to detect the rotation angle of the rotation shaft of the reduction gear and output the detection result as a second rotation angle; a torque calculation unit configured to calculate the torque acting on the rotation shaft of the reduction gear by multiplying the angle difference between the first rotation angle and the second rotation angle by the torsional stiffness of the reduction gear; an angle-control unit configured to generate a torque reference value needed to bring the second rotation angle close to the angle reference value according to the difference between the angle reference value and the second rotation angle; and a torque control unit configured to generate the current reference value needed to bring the torque close to the torque reference value according to the difference between the torque reference value and the torque.