The design and experimental research of an open architecture soft-CNC system based on RTX and an IPC

Abstract

The concept of open architectures has been discussed extensively for many years. Software-oriented Computer Numerical Control (soft-CNC) is considered as one of the ideal solutions for open architecture CNC (OACNC). In recent years, this has become the mainstream direction for open CNC systems by employing a personal computer (PC) as the hardware platform and a real-time operating system as the software platform. However, existing CNC systems are limited in expansibility, portability, modularity, networking, and openness. In order to overcome these problems and in accordance with the characteristics and requirements of an OACNC system, a novel numerical control kernel (NCK) based on the real-time extension (RTX) and an industrial personal computer (IPC) is proposed. The implementation of the NCK is a difficult task, especially when real-time performance is desired. To compensate for the lack of real-time features in Windows NT, RTX provides a real-time software environment to implement the time-critical operations of a CNC system on an IPC by modifying the hardware abstraction layer (HAL). The proposed soft-CNC system consists of four components: the human machine interface (HMI), shared memory, the real-time subsystem (RTSS), and the device layer. This work first presents the hierarchical system architecture for developing an open architecture soft-CNC system and then describes the choices for the hardware and software platform of the soft-CNC system. Furthermore, this paper focuses on the software design and implementation of the soft-CNC system; thus, the software tasks, data flow, and the communication mechanisms are studied in detail. Finally, experiments are conducted to validate the real-time performance, the schedulability and the functions of the proposed soft-CNC system, thus verifying its feasibility.