Rotation control device of working machine

Abstract

To automatically prevent a reverse movement by inhibiting an excessive increase in an output torque of an electric motor. A means () calculates a target value for a rotation speed based on a command from a system (), a means () calculates a deviation between a detection value from a rotation speed sensor () and the target value, a means () calculates a first target torque in a direction that the deviation will be eliminated, and a means () calculates, based on a command from the system (), a second target torque in the same direction as the target value. A means () calculates a variation in a rotation angle of an electric motor () in a first range, and a means () calculates the same variation in a second range. A means () calculates, based on the variations from the means (), a third target torque in a direction that the rotation angle will return to a rotation angle before a predetermined time (t), and a means () limits the first target torque to one of the second and third target torques, said one target torque being in the same direction as the first target torque and being greater in absolute value. Substantially an entirety of the first range specifies a range for the variation in one direction, a remaining small range specifies a range for the variation in the other direction, substantially an entirety of the second range specifies a range for the variation in the other direction, and a remaining small range specifies a range for the variation in the one direction.