US Patent 7471056 Control device

A control device includes a first switch (400) by which an input signal to a motor speed control loop (910) is selected from a signal of a position control loop (300) and a signal of the speed control loop (200), and a switch controller (500) that controls switching of the first switch (400), so that the first switch (400) can switch between a quadruple loop (a current control loop, the motor speed control loop, the speed control loop (200) and the position control loop (300)) with the speed control loop (200) embedded therein, and a triple loop (the current control loop, the motor speed control loop and the position control loop (300)) without the speed control loop (200), corresponding to a transient state and a steady state.