Application examples of AC servo

In addition to the characteristics explained in the previous section, using a servo motor with a servo amplifier realizes the positioning control which is not provided by other speed variators.

The following shows application examples of a servo motor, based on the servo-specific positioning

control and the characteristics.

1) Machinery that needs positioning control When used with a controller that is exclusively used for positioning control, AC servo system becomes capable of providing highly accurate positioning.
For example, in general Mitsubishi AC servo system, the motor shaft can be divided into 4000 to 262144 for positioning purposes. This is enough to provide positioning control of 1 m, if the motor is driving a machine of 24 to 8m/min.

2) Machinery that needs a wide speed control range AC servo system can be used for applications that need highly accurate speed-variable control, such as production line control. This is because the AC servo's speed control range is 1:1000 to 5000, and its speed fluctuation ratio is 0.01% or less, and also because AC servo motors can rotate with constant output torque, which is a feature not provided by other speed-variable motors.

3) Frequent positioning operation AC servo system can provide up to 300% of the rated torque, allowing rapid acceleration and deceleration. More precisely, with a motor alone, AC servo system takes just several 10ms to accelerate the speed from 0 to the rated speed. Also, it can respond to more than 100 times of positioning commands in one minute. For positioning control, refer to (1). Having no mechanical contacts is another advantage of AC servo system compared to other positioning systems (e.g. clutches, brakes, DC motors). With no mechanical contacts, the maintenance is not required and the operation is not affected by ambient temperature as much as the other positioning systems.

4) Torque control There are models that feature torque control in addition to speed and position controls. Such models can be used for tension control purposes (e.g. winding and unwinding machines).