Abstract: Software reuse technology can efficiently and cost-effectively construct embedded CNC systems to meet current manufacturing needs. This paper analyzes the characteristics of embedded CNC systems, proposes a component model for embedded CNC systems, and provides a detailed description. Keywords: Embedded CNC system; Component; Software reuse The characteristics of modern CNC systems—high speed, intelligence, networking, integration, and openness—make microcontroller-based CNC systems no longer suitable for the development and demands of modern CNC. PC-based CNC systems, due to their structural and performance versatility, do not offer significant advantages in modern CNC applications. On the other hand, with the development of microelectronics technology, the reliability and application level of microprocessors, as the hardware carrier of embedded systems, are increasing. They integrate more and more components, have more and more powerful functions, and not only consume less power but also integrate more and more with analog circuits. The gap between embedded microprocessors and PC systems is narrowing, and their application advantages are increasing in some situations. Meanwhile, the compact structure, high reliability, integration, and real-time performance of embedded microprocessors and embedded systems, their adaptability to harsh working environments, unified programming interfaces, and powerful network communication capabilities all well meet the needs of modern CNC. Embedded software is the soul of an embedded system, responsible for the allocation, scheduling, and control of all its resources. The development of embedded systems hinges on the development of embedded software. However, the inherent shortcomings of lifecycle-based software development technologies have long plagued embedded software developers, such as long overall development cycles, low modularity, poor reusability, poor portability, and high maintenance costs. Therefore, shortening software development cycles, reducing development and maintenance costs, and improving software quality are urgent requirements for embedded software developers and are also essential for embedded software to adapt to the rapid development of embedded technology and the rapid expansion of its application areas. Software reuse is an effective method to improve software quality and development efficiency and is one of the current hot topics in software development research. Software reuse mainly involves component-based development (CBD) or component-based software engineering (CBSE). It is a new paradigm of software development, which is the process of constructing application software systems efficiently and with high quality by reusing one or more software components from a component library under the support of a certain component model and through combination. This paper proposes a component model adapted to the characteristics of embedded CNC systems. 1. Basic Concepts of Components OO technology improves the way of understanding things on the basis of "data + algorithm". The concept of objects conforms to people's habits of understanding the world, while the idea of ​​components focuses more on the consideration of software production, that is, components can be incorporated into new systems as parts in the software production of application domains and reused. Therefore, components are the continuation and extension of OO thinking, and the perspective of understanding things rises from the individual object itself to the role of the individual in the group. Components have the following basic attributes: 1) Components are independently configurable units, so components must be self-contained. 2) Components emphasize separation from the environment and other components, so the implementation of components is strictly encapsulated, and the outside world has no opportunity or need to know the internal implementation details of the component. 3) Components can be used in combination in appropriate environments, so components need to provide clear interface specifications and can interact with the environment. 4) Components should not be persistent, that is, components do not have individual unique attributes. It is understood that components should not be distinguished from their own copies. In any environment, there is at most one copy of a specific component. Theoretically, the debate on component models has never stopped. Representative theoretical models include: (1) 3C model The 3C model is a component model that is widely recognized in academia and has a guiding role. This model describes components from three different aspects: concept, content and context. u Concept is an abstract description of "what the component does". The function of the component can be understood through the concept. The concept includes two parts: interface specification and semantic description; u Content is the specific implementation of the concept, which describes how the component completes the function described by the concept; u Context is the relationship between the component and the surrounding environment at the concept level and the content level. Context describes the application environment of the component and provides guidance for the selection and adaptive modification of the component. (2) REBOOT model (faceted model) The REBOOT model is a faceted classification and retrieval model based on existing software components. It describes the attributes of software components from various angles, that is, faces. (3) The Bluebird Model: The Bluebird Project of Peking University defines the component model from three perspectives (form, hierarchy, and representation) and nine aspects. (1) Concept: An abstract description of the component's function. (2) Operation Specification: Used to refer to the services that the component provides to the outside world and can be requested. (3) Interface: Provides a description of the component's external behavior. (4) Type: Used to define "what values ​​can be used as operation parameters". (5) Implementation: This is the specific implementation part of the component, which is the system that actually completes the requested service. (6) Component Composition: Components are composed of components to form a system. (7) Component Properties: Indicate the form, hierarchy, and representation of the component. (8) Component Annotation: Describes other properties related to the component library. (9) Component Context: Describes the software and hardware usage environment and implementation dependencies of the component. The Bluebird component model is more concerned with the understandability, encapsulation, and interrelationships of components. It separates service providers and their service requesters by providing clear external interfaces to components. It is more concerned with the interaction between components and their users, especially the parts that are meaningful to component users. Currently, mature component model implementation technologies applied in general-purpose computer system environments include Microsoft's Component Object Model (COM), the Common Object Request Broker Architecture (CORBA) proposed by the Object Management Group (OMG), and Sun Microsystems' EJB (Enterprise JavaBeans) component technology. Each technology has different advantages and is suitable for applications of different scales and types in general-purpose computer system environments. 2. Embedded CNC System Analysis As an organic whole oriented towards control applications, the implementation of a CNC system's control functions is composed of numerous hardware and software components arranged according to certain rules, such as topological relationships, synchronization relationships, and communication protocols. Although embedded CNC systems have requirements for diverse hardware platform choices and hard real-time operating system requirements, they, like traditional CNC systems, have the following functions: Human-Machine Interface Input: Inputting the CNC system's machining program segments, tool offsets, tool radii, control parameters, zero-point coordinates, compensation data, etc. Decoding: For input program segments containing part contour information (start point, end point, straight line, arc, or curve required machining speed) and M, S, T auxiliary information (tool change, gear shift, coolant switch, etc.), the computer uses a decoding program to translate the machining program into a language that the computer can recognize. The input program segment undergoes syntax checking, and feed coordinates that do not meet the machining accuracy range are rounded off. Tool Compensation Preprocessing: Tool compensation preprocessing generally includes tool radius compensation and tool offset coordinate conversion to obtain the tool center trajectory and to adjust the machining speed for acceleration and deceleration. This makes the machine tool run more smoothly and reduces operational shock. Interpolation: Based on the given curve type (such as straight line, arc, or higher-order curve), start point, end point, and speed, data points are densified between the start and end points. Motion Control: The position feed pulses or feed speed commands sent by the computer are transformed and amplified into the rotation of the servo motor, and speed and position control is performed based on signals from photoelectric encoders or gratings. Information Processing: Acquires and analyzes sensor signals from CNC machine tools, such as those related to tool stress, vibration, measurement, and oil temperature, and identifies potential machine tool errors, faults, and related patterns. Switching I/O: Responsible for I/O responses related to switching quantities. Management and Scheduling: Responsible for the coordination of various functional modules. Auxiliary Functions: Fieldbus interface, Ethernet interface, etc. See Figure 1. [align=center] Figure 1 Embedded CNC System Structure[/align] 3. Embedded CNC System Component Model CNC system components are prefabricated and reusable software parts, functional encapsulations for implementing domain applications. Based on the level of abstraction of CNC domain knowledge and the needs of logical division, component elements of different granularities can be generated. Components define their system functions and information transmission to the outside world through interfaces, providing explicit specifications for component services. The component interface represents all interactions between the component and the environment, and is the only interaction path. Beyond this, the environment should not make any other assumptions about the component unrelated to the interface. A CNC system is essentially an information processing system; the flow of information is the CNC machining process. Information generated by one component triggers the next. Machining information streams, automatically generated by CAD/CAM or manually input, are sent to the CNC device. The CNC device decodes and converts this information stream into information processing content for each component. After internal processing, it outputs corresponding position signals to the servo system. These signals, driven by motors and ball screws, move the worktable or tool according to set requirements. Simultaneously, it integrates auxiliary functions and on-site switch inputs, and monitors and protects the CNC system's operation. Continuous control of the CNC system encompasses both the information flow between components and numerous discrete behaviors, such as responses to manual mode, emergencies, and faults; handling different machining modes like rapid traverse, roughing, and finishing; and switching between different control modes like position control and speed control. Therefore, these components will have different states at different stages of the CNC program's execution. Thus, the state transitions must be reflected in the component model. Furthermore, considering that embedded CNC systems operate in real-time and are resource-constrained, embedded components must not only provide sufficient functionality but also meet system time and memory limitations. Moreover, compared to traditional software development, embedded system software components are closely linked to hardware; software errors can lead to physical system failures. Therefore, embedded components must possess high reliability—requiring users to perform version testing is too costly. We call these performance metrics of embedded components the Quality of Service (QoS) attributes. QoS attributes are an important basis for users to select suitable embedded components. This is also a key feature that distinguishes embedded components from general-purpose components. In summary, the component model design is shown in Figure 2. [align=center] Figure 2 Embedded CNC System Component Model[/align] In the figure, the upper left corner represents the component's interface. A component can support multiple different interfaces, which describe the services provided by the component and the required environmental services, reflecting the interaction between the component and the environment. The upper center uses a finite state machine with outputs to describe the component's behavior. After receiving external event messages, the component performs state transitions internally based on its current state, achieving real-time response to CNC system events. The upper right corner displays the component's attributes, including functional attributes such as description, constraints, configuration, and Quality of Service (QoS) attributes. This model can describe not only general atomic and composite components but also active object-based component systems. An active object-based component system is a collection of components and sub-component systems with certain functional and task relationships. It organizes closely related components that are frequently reused to achieve common CNC functions into a component system, serving as another basic unit for component library storage. Unlike general atomic and composite components, active object-based component systems are coarse-grained components. Each active object component is physically no smaller than a scheduling task (thread) in the CNC system. It integrates functionally or periodically related components into an active object task. Each task performs a specific function, and tasks can be nested, meaning a task can contain one or more subordinate tasks. A series of related task object components form a certain type of CNC system. Active object-based component systems support fine-grained component integration in the construction of active object components, thus easily achieving higher levels of CNC openness and more choices. On the other hand, component-based system integration of CNC systems based on active objects is beneficial for improving the granularity of reuse and the reuse of related components, thereby reducing system complexity and the difficulty of system integration. 4. Conclusion In the software development of embedded CNC systems, utilizing software reuse technology, especially component reuse, can not only meet the requirements of modularity, scalability, and integrability of embedded CNC systems, but also shorten the development cycle and improve the reliability of CNC systems. This paper, through the study of component characteristics in the field of embedded CNC systems, proposes a component model for embedded CNC systems, and has initially established a theoretical framework for embedded CNC systems. However, much work remains to be done in both theory and practice, and further research is needed. References 1. 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