The Mitsubishi General AC Servo MELSERVO-J4 series has higher performance and more powerful functions than the previous MELSERVO-J3 series. The rotary servo motor corresponding to the MELSERVO-J4 uses a 22-bit (4194304 pulses/rev) high-resolution absolute position encoder. In addition, the speed response is as high as 2.5 KHz. Therefore, compared with the MELSERVO-J3, it is possible to perform higher speed and higher precision control. J4 series servo has three control modes: position control, speed control and torque control. Among them, the position control mode can correspond to 4Mpps high-speed command pulse input, and position/speed switching control, speed/torque switching can also be selected. Control and torque/position switching control. Therefore, this servo can be used not only for high-precision positioning and smoothing speed control of machine tools and general industrial machinery, but also for line control and tension control, etc., and has a wide range of applications.