Task-Based OPC UA Access for Automation Information Models
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Solution Overview
Problem
Existing automation systems face challenges with high hardware resource demands and complexity due to large information models containing numerous data objects, particularly in embedded computers with real-time requirements, and the integration of field devices via fieldbuses, leading to increased load and configuration complexity.
Innovation Solution
The system generates data objects on the server dynamically based on the specific technical task, using OPC UA services and methods, allowing clients to access only the necessary functions and parameters, reducing the need for a complete information model and hardware resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a complete information model with all data objects is provided in the server, then the client can access all functions and parameters of the automation device, but hardware resource requirements and system complexity increase significantly
Solution Approach 1:
The complete information model is segmented into multiple data object sets, where each set corresponds to a specific technical task. Instead of loading all data objects simultaneously, the system divides them into manageable segments that can be selectively loaded based on the current task requirements, reducing memory usage and improving system responsiveness.
Solution Approach 2:
The information model transitions from a static complete model to a dynamic task-based model. Data objects are dynamically loaded into memory only when needed for a specific technical task, and unloaded when no longer required. This dynamic approach allows the system to adapt its resource consumption to actual operational needs rather than always maintaining the complete model in memory.
2Adaptability or versatility
If all data objects are loaded into memory, then complete access is enabled, but memory consumption and processing load increase
Solution Approach 1:
Instead of loading the complete information model into memory (excessive action), the system loads only the subset of data objects required for the current technical task (partial action). This selective loading approach ensures that memory resources are utilized efficiently, allocating space only to the necessary data structures rather than maintaining the entire model in memory simultaneously.
3Adaptability or versatility
If the information model contains all functions and parameters, then comprehensive access is possible, but configuration and maintenance become more complex
Solution Approach 1:
The configuration process is segmented by technical tasks rather than requiring configuration of the entire information model. Each technical task has its own associated data objects that can be independently configured, validated, and maintained. This segmentation reduces the complexity of configuration activities and makes it easier to identify and fix issues without affecting the entire system.
4Loss of information
If a meshed network structure is used for data objects, then real-world relationships are better represented, but the number of data objects and processing requirements increase
Solution Approach 1:
The meshed network of data objects is segmented by technical tasks, where only the relevant subset of data objects and their relationships are loaded into memory for each task. This allows the system to maintain the comprehensive meshed structure on disk for accurate relationship representation, while only activating the necessary portions during operation, thus balancing information completeness with resource efficiency.
Data Source
AI summary
An automation system of a machine or an installation includes an automation device that is accessed by a client via a server. Address information for access operations is provided by the server in an address space in the form of data objects that are organized in the form of nodes of a meshed network in an information model of the server. Depending on a technical task to be performed, the client, by calling a functionality offered by the server, generates data objects on the server that allow the client to perform the access operations to the automation device and/or to at least one field device networked with the server via a fieldbus that are necessary to achieve the technical task.