Safety Controller Partition Scheduler Abnormality Response
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Solution Overview
Problem
Existing safety controllers in service robots and transportation equipment face delays in responding to abnormalities, inefficiencies in task scheduling due to prioritization and periodicity constraints, and issues with data sharing between time partitions, leading to potential system failures.
Innovation Solution
A safety controller with a partition scheduler that dynamically allocates execution time to safety monitoring, normal control, and safety control programs, allowing for rapid switching between time partitions based on detected abnormalities and prioritization, while ensuring data sharing integrity through partitioned shared memory access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If time partitioning is used to separate safety-related applications from non-safety-related applications, then software development cost is reduced, but response time to abnormalities is delayed
Solution Approach 1:
The partition scheduler dynamically switches between normal control mode and safety control mode based on abnormality detection. When an abnormality is detected in the current time partition, the scheduler immediately activates the safety control program in the next time partition, enabling rapid response while maintaining the cost benefits of time partitioning.
Solution Approach 2:
The safety control program is pre-configured and ready to execute in designated time partitions. When an abnormality is detected, the system has already prepared the safety control logic and data structures in advance, allowing immediate execution without delay for program loading or initialization.
2Loss of time
If partition scheduling is executed first and task scheduling is then executed emphasizing time constraints, then time constraints are satisfied, but flexibility in designing task priorities is impaired
Solution Approach 1:
The scheduling system is segmented into two independent layers: partition scheduling that manages time allocation for safety and normal control programs, and task scheduling that manages priority-based execution within each partition. This segmentation allows each layer to optimize for its specific requirements without compromising the other.
Solution Approach 2:
Different scheduling strategies are applied to different partitions based on their specific requirements. Safety control partitions use strict time-based scheduling to ensure deterministic response, while normal control partitions use priority-based scheduling to accommodate varying task importance. This local optimization resolves the contradiction between time constraints and priority flexibility.
Data Source
AI summary
Upon occurrence of an abnormality, a safety control can be executed more rapidly. An OS partially includes a partition scheduler that selects and decides a time partition to be subsequently scheduled according to a scheduling pattern including TP1 in which an execution time is allocated to a safety monitoring program, TP2 in which the execution time is allocated to a normal control program, and TP3 in which the execution time is allocated to a safety control program. A processor executes the OS to cause the partition scheduler to periodically operate. The partition scheduler is activated upon detection of an abnormality by one of the safety monitoring program executed in TP1 and the normal control program executed in TP2, and switches the time partition from TP1 or TP2 to TP3.