Safety Controller Time Partitioning for Jitter Reduction
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Solution Overview
Problem
Existing safety controllers in service robots and transportation equipment face challenges in executing tasks in a constant cycle due to time partitioning, leading to jitter, delayed task execution, dependence on non-safety-related tasks, and inefficient processor usage, which complicates software development and reduces system effectiveness.
Innovation Solution
A safety controller that schedules safety-related and non-safety-related tasks using a system program to allocate execution time in constant cycles, storing end information for task completion and releasing resources to maintain task independence, ensuring tasks are executed within designated cycles without unnecessary processor allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time partitioning is used to separate safety-related tasks from non-safety-related tasks, then task independence and safety are improved, but jitter occurs and constant cycle execution cannot be guaranteed
Solution Approach 1:
The system divides time into distinct partitions: safety-related time partitions exclusively for safety tasks and non-safety-related time partitions for other tasks. This segmentation ensures that safety tasks are not interrupted by non-safety tasks, eliminating jitter while maintaining task independence through clear temporal boundaries.
2Ease of manufacture
If time partitioning is used to reduce software development cost by excluding normal control program from safety-related system, then development cost is reduced, but safety control task execution is delayed or missed
Solution Approach 1:
The system activates the safety control task in advance within the safety-related time partition before the partition switches to non-safety-related tasks. This preliminary activation ensures that the safety control task begins execution at the correct timing and completes within the allocated time, preventing delays or missed executions while maintaining cost efficiency.
3Productivity
If execution time is allocated to tasks in constant cycle, then processor utilization is improved, but task completion cannot be guaranteed when processing exceeds allocated time
Solution Approach 1:
The system uses periodic time partitions that repeatedly switch between safety-related and non-safety-related allocations. Each safety-related time partition provides a guaranteed execution window for safety tasks, ensuring completion within the periodic cycle. This periodic structure maintains high processor utilization while guaranteeing task completion through enforced temporal boundaries.
Data Source
AI summary
The present invention relates to time partitioning to enable execution of tasks in a constant cycle while guaranteeing dependence of a safety-related system. A safety controller includes a processor and a system program for controlling allocation of an execution time of the processor to tasks. The processor executes the system program to schedule tasks in accordance with scheduling information indicating, in a constant cycle, a period of one of a safety-related TP to which a safety-related task belongs and a non-safety-related TP to which a non-safety-related task belongs. In a task of a TP in the constant cycle, the processor stores the end information upon completion of processing in the task and brings the task into a ready state. In the scheduling, when the end information is stored, the processor inhibits allocation of the execution time even when the task in the TP in the constant cycle is in the ready state, and deletes the end information during a period between an end of the period of the TP in the constant cycle and a start of a period in a next cycle of the TP.