Cylinder servo motor with built-in control device

An operation command for constructing compensation data is generated in a control device, and measurement data obtained from an external length measuring device is input to an input unit. The measurement data is compared with an estimated position in a control device of a cylinder servo motor, and errors between them is stored in a compensation memory. In addition, in normal operation, the external length measuring device is removed. A movement command is input to the input unit and compensated using the error stored in the compensation memory, so that the estimated error is deleted in the normal operation.