Design Criteria for Multi-Axis Closed Loop Computer Numerical Control Systems

Automatic machine tools have traditionally been controlled by hard-wired numerical controllers (NC). Recently, systems have been introduced which use a general purpose mini-computer (CNC). Some of these computer systems generate position references and close the position control loops of the machine tool’s feed axes using software, while others retain these functions in hardware. If the software approach is used, the dynamic performance of the system may be degraded. This paper investigates the constraints necessary to avoid severe performance degradation.