Industrial Controller Scheduling With Deadline-Based Function Block Clusters
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Solution Overview
Problem
Conventional scheduling methods for cyclic control applications in industrial automation systems are inflexible and prone to violations of real-time constraints, leading to cycle overruns and alarms, especially in large projects with diverse timing demands.
Innovation Solution
A method that clusters function blocks based on sampling times and creates organization blocks with associated deadline values, allowing for dynamic scheduling that prioritizes execution based on the earliest deadline, using techniques like K-means clustering and logical function block creation to manage dependencies and interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sequential execution of organization blocks is used, then simplicity of scheduling is improved, but real-time constraint compliance deteriorates
Solution Approach 1:
The patent implements dynamic scheduling by continuously monitoring the dynamic buffer (which stores function blocks to be executed) and adjusting the execution sequence based on real-time conditions. The cyclic organization block executes function blocks from the dynamic buffer rather than following a fixed sequential order, allowing the system to adapt to changing real-time requirements and prevent cycle overruns.
2Speed
If priority-based preemptive scheduling is used, then high priority task execution is improved, but low priority task deadline compliance deteriorates
Solution Approach 1:
The patent employs feedback mechanisms by monitoring the execution status and timing of all function blocks through the dynamic buffer. The system continuously checks whether low priority tasks are at risk of missing their deadlines and adjusts the scheduling accordingly, ensuring that even low priority tasks meet their deadline requirements while still allowing high priority tasks to execute with appropriate speed.
3Adaptability or versatility
If more function blocks are added to handle large projects, then functionality is improved, but scheduling flexibility deteriorates
Solution Approach 1:
The patent segments the large number of function blocks into organized clusters within the dynamic buffer, grouping them by their execution requirements and timing characteristics. This segmentation allows the system to handle large projects with many function blocks while maintaining scheduling flexibility, as the cyclic organization block can selectively execute functions from different segments based on real-time needs without being overwhelmed by the total number of functions.
Data Source
AI summary
A method for scheduling cyclic control applications on a controller includes defining a plurality of function block clusters by clustering a plurality of function blocks of the cyclic control applications based on a sampling time of each function block, creating a plurality of organization blocks from the plurality of function block clusters, each organization block comprising at least one function block from a function block cluster and an organization block record including a sampling time value and next deadline time value associated with the corresponding organization block, and scheduling the plurality of organization blocks for execution on the controller, based on either a sampling time value and/or the next deadline time value, where a sampling time value of an organization block is based at least one sampling time of at least one function block of the corresponding organization block.