Deadline Interrupt Controller for Autonomous System Safety
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Solution Overview
Problem
Autonomous systems face challenges in ensuring timely processing of interrupt requests, which can lead to safety issues due to the potential for interrupt handlers to take too long or fail to clear requests, especially when operating at lower safety integrity levels like ASIL-B, potentially violating higher safety standards such as ASIL-D.
Innovation Solution
The implementation of a deadline interrupt controller that sets a time limit for handling interrupt requests, using a timer component to detect when the predetermined time has elapsed and reporting to an event handler to take corrective actions, ensuring that interrupt requests are processed within the specified timeframe and maintaining the desired safety integrity level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an operating system handles interrupt requests without time limits, then flexibility and ease of operation are improved, but safety and reliability deteriorate due to potential delays or failures in processing
Solution Approach 1:
The patent applies preliminary action by pre-configuring time limits for interrupt request processing before the operating system handles interrupts. The system establishes maximum execution time thresholds in advance, and the hardware monitor automatically enforces these limits during runtime, preventing safety issues without requiring the OS to implement complex safety logic.
Solution Approach 2:
The patent introduces a hardware-based time limit monitor as an intermediary between the operating system and interrupt request processing. This mediator component independently tracks execution time and automatically intervenes when limits are exceeded, allowing the OS to operate flexibly while ensuring safety through hardware enforcement.
2Reliability
If time limits are enforced for interrupt request handling, then safety and reliability are improved, but system complexity increases due to additional monitoring mechanisms
Solution Approach 1:
The patent replaces complex software-based safety monitoring with a hardware time limit monitor that automatically tracks execution time and enforces limits. This substitution reduces the complexity burden on the software system while maintaining reliable safety enforcement through dedicated hardware circuitry.
Solution Approach 2:
The hardware time limit monitor operates autonomously, self-managing the tracking and enforcement of time limits without requiring complex external control. The system configures limits once and the monitor independently manages enforcement, reducing overall system complexity.
3Reliability
If interrupt handlers are allowed to execute without time constraints, then processing completeness may be achieved, but response time and productivity worsen due to potential delays in critical operations
Solution Approach 1:
The patent applies dynamics by making the interrupt handling process adaptive through time-based constraints. The system dynamically monitors execution progress against predetermined limits, allowing handlers to complete necessary operations while automatically interrupting excessive executions, thus balancing completeness with response time requirements.
4Device complexity
If lower safety integrity level components are used, then device complexity and cost are reduced, but the ability to meet higher safety standards deteriorates
Solution Approach 1:
The patent applies segmentation by separating safety-critical functions from the main operating system. The hardware time limit monitor handles safety enforcement independently, allowing the OS to remain relatively simple while the dedicated safety mechanism ensures compliance with higher integrity standards through isolated, specialized circuitry.
Data Source
AI summary
In various examples, a timer component that generates an event when an interrupt request has not yet been cleared within at least a predetermined amount of time.