CNC open architectures
Most computer numerical control (CNC) systems are closed for users. Engineers typically can only program the machine, nothing more. Even if it has a so-called programming interface (including 3D visualization and process simulation, pre-defined milling/turning cycles, or even a small CAD/CAM system), it cannot be freely modified by the user.
Open architecture control systems, however developers understand them, are a noticeable trend of modern control systems technology. “Open” is a very fashionable way to describe today’s control systems.
Many efforts are underway to make control system architectures more open. It helps to define the degree of openness of the proposed control system.
Evaluate CNC openness
A variety of open-architecture control systems can be found on the Internet. These include OSACA (Open System Architecture for Controls within Automation Systems), OMAC (Open Modular Architecture Controllers), NGC (Next Generation Controller project, National Center for Manufacturing Sciences), and OSEC (Open System Environment for Controller) control architectures, as well as others.
But what defines CNC openness? Can the degree of control system openness be measured?
A means for rating the openness of major control system attributes is provided in Chi Yonglin’s paper, “An evaluation space for open architecture controllers” ( International Journal of Advanced Manufacturing Technology , 2005).
Rating categories include applicable control system domain (0 rating means that the controller has been designed as special equipment; a 10 rating means it can be used for all domains of the manufacturing industry), as well as extensibility and scalability (0: traditional closed architecture, 10: a full open architecture whose topology can change depending on the application.)
Similar measurements can be made for other aspects of openness, such as modularized structure, standardized interface, function and performance requirements and more.
Once the relative “openness” of a system is ascertained, however, the truest measure comes when putting the technology into action within a production environment.
Project OCEAN (Open modular Control system for linEAr motioN drive) is a research grant of the Polish Ministry of Science processed by the research team of the Centre of Mechatronics, Szczecin University of Technology.
Nearly seven years of research includes:
Modeling of milling machine construction;
Development of many control algorithms, including robust two degree of freedom, fuzzy-logic, neural networks, predictive and hybrid control;
Laser 3D vibration monitoring; and
Modeling of the feed drives of CNC machines.
Project OCEAN is among four ongoing mechatronics projects undertaken by an interdisciplinary team at University Centre of Mechatronics, Szczecin University of Technology. The team includes five professors, six doctors, four Ph.D. students, and OCEAN project director professor Stefan Domek, with the faculty of Electrical Engineering.
| Intelligent CNC machines will diagnose themselves.
Source: K. Pietrusewicz and Control Engineering
Self diagnostics for machine tools
OCEAN’s main goal is to introduce an open interface to develop diagnostic functions of the milling machine, test it, and introduce it to users. It includes:
Motion control advanced algorithms;
Different interpolation algorithms, including NURBS (Non Uniform Rational Basis or Bezier Spline), mathematical representations of 3D geometries;
Flexible human-machine interface (HMI);
Options to extend system kernel functions;
Interface for the new flexible programming language; and
Interface for the new active control system of the motion components.
Next, the project will develop:
Full temperature model of the milling machine structure;
Intelligent, self-diagnostics tools; and
Noise and vibration control (active chatter suppression system of the tool-milling machine system is at the final stage of development).
University Centre of Mechatronics is seeking new partners for the next steps of the system; present cooperation is provided by Bernecker & Rainer, a Technology Provider and Integrator Member of OMAC. Project OCEAN is scheduled to be completed in 2010. Two more projects connected with the concept of intelligent CNC machines also will begin this year.
Open CNC architectures
The use of open architecture CNC is gaining importance as a promising industrial automation technology. It allows integration of equipment, a friendly interface for configuration, and improved machine tool communication. Benefits of using an open architecture when developing new CNC includes lower-cost electronics and higher-performance computers.
Several types of open architectures are being developed in the USA, Europe, and Asia. All use a standard PC computer for control.
OSACA is used mostly in the software area. It first appeared in Europe with the Esprit III Project 6379 program, one of the largest projects involving standards for OAC (Open Architecture Control), including network connections and applications, defining an independent hardware with modular design, and allowing addition or removal of numeric control, robot control, PLCs, and other controllers.
OMAC is primarily for industrial applications. OMAC began in December 1994 with the publication of “Requirements of Open, Modular Architecture Controllers for Applications in the Automotive Industry” by Chrysler, Ford, and General Motors. This document served as a guide for North American automotive manufacturers’ use of controllers.
OSEC architecture is used for automation in many industrial areas to control manufacturing equipment, improve its performance, and facilitate its maintenance.
HOAM-CNC (Hierarchical Open Architecture Multi-processor) system is for hardware (including new sensors and special modules).
Each architecture has integrated equipment from several manufacturers and the overall goal is to lower cost and not sacrifice performance.
For more information, read this article online at www.controleng.com/archive .
Control Engineering articles:
CNC Programming (STEP-NC data model) www.controleng.com/article/CA6339744.html
OMAC: Open technologies, sharing best practices help integrate discrete, process manufacturing
Other Control Engineering articles on open CNC
System integrators with related expertise
CNC vendors mentioned at Control Engineering Online.
CNC Control Systems search in the Control Engineering buyer’s guide at www.cesuppliersearch.com.
Companies in the OMAC Users Group work together to:
Derive common solutions for technical and non-technical issues in the development, implementation, and commercialization of open, modular architecture control (OMAC) technologies;
Promote OMAC development among control technology providers and OMAC adoption among end users, OEMs, and system integrators;
Act as a repository for OMAC requirements and operating experience from users, software developers, hardware builders, and OEMs in manufacturing applications;
Facilitate accelerated development and convergence of industry- and government-developed technology guidelines to one set that satisfies common use requirements; and
Collaborate with user groups for development of common international technology guidelines.
Packaging Machinery, Manufacturing Infrastructure, and Machine Tool are three OMAC working groups. They produce consensus guidelines to improve flexibility, improve capability, and reduce system integration costs.
OMAC has about 500 member representatives from end-user companies, OEMs, technology providers, and integrator companies. Members include companies interested in developing and implementing open control technologies for manufacturing applications.
OSACA (Open System Architecture for Controls within Automation Systems) phase II project 9115 was created to manage these modules, and establish modular software systems, communication interfaces, as well as operations and open database systems for new functions and for use in new digital equipment. This project began in 1992 in research institutes of Germany, Spain, France, Italy, and Switzerland. OSACA architecture allows assembly of the machine tool control with a user interface, without need to review the whole software. The platform is composed of hardware and program groups (operating system, communication system) that offer a uniform service for the functional unit (FU) control.
Three main platforms of the OSACA architecture are:
Communication System: Hardware and software are defined independently of the information exchange interface among modules of the controller application. The OSACA communication system allows transparent information exchange between client and server applications;
Reference Architecture: Determines the control FU and specifies the external interface. This is done to enable use and integration of external units through internal data in a defined way. FU examples are HMI, interlock logical control, and axes movement control. For each identified FU, an external module is defined using an object-oriented communication for data interfacing with application modules. The interface of writing and reading data access is located in the architecture-oriented object, and this access is available with use of a communication-oriented object;
System Configuration: Allows a controller dynamic configuration through a combination of different application modules. This determines a specific topology of a given functionality and the synchronization among distributed processes.
The OSACA system platform diagram shows how a configuration request generated by a microcomputer is sent to the system. The reconfiguration uses an FU, which works based on object-oriented programs and a class library, with variables and internal data. The OSACA application protocol uses a client/server base mounted on the object orientation principle.
All FU functionality will have external access, and it is configurable by the communication platform. From the customer’s viewpoint, the server can be accessed through shipping and reception of system communication messages.
Six Japan-based companies (Toshiba Machine Co., Toyoda Machine Works Ltd., Yamazaki Mazak Co., IBM Japan Ltd., Mitsubishi Electric Co., and SML Corp.) formed a group with the objective to develop a platform of open architecture for numeric control equipment. OSEC Architecture (Open System Environment for Controller) group seeks to create an open architecture based on a standard personal microcomputer PC to control manufacturing equipment, to improve its performance, and to facilitate its maintenance.
The personal microcomputer can control equipment and act as an information base system for factory operation. Equipment using this architecture can serve as an acquisition and logistics support system based on computer – CALS (Computer-aided Acquisition and Logistic Support).
There are research centers working on this open architecture concept, such as the enhanced machine controller project – EMC (Enhanced Machine Controller).
HOAM-CNC (Hierarchical Open Architecture Multi-processor – CNC) covers mainly machine hardware, offering two buses, a CNC control bus and another bus to allow introduction of new components.
The related graphic illustrates HOAM-CNC using a microcomputer. The standard main ISA bus deals with the monitor activities, data processing, adaptive control and HMI. The CNC bus controls the position and speed each axis in real time with a dedicated processor.
The system allows the addition of several processing modules in the primary bus and the interaction of control axes in the secondary bus.
For more information, visit:
www.ncms.org National Center for Manufacturing Sciences
www.we.ps.pl Szczecin University of Technology
|Krzysztof Pietrusewicz, Ph.D., Control Engineering Poland , teaches at the Szczecin University of Technology, Institute of Control Engineering, University Centre of Mechatronics. Reach him firstname.lastname@example.org .|