Machine Control Verification Using Declarative Safety Logic
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Solution Overview
Problem
Current control systems for machines, particularly in industrial automation and medical contexts, face challenges in ensuring safety due to complex programming and the difficulty in verifying the absence of safety-critical conditions, leading to potential physical damage and uncertainty in covering all relevant situations.
Innovation Solution
A computer-implemented method using a declarative programming paradigm to separate data processing and control programming, where data manipulation is performed in a data processing unit and control logic is executed in a control processing unit, with explicit conditions monitored to ensure safety and prevent violations, such as using a finite state machine or behavior tree structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If formal verification is used to ensure safety, then safety reliability is improved, but device complexity and programming difficulty increase
Solution Approach 1:
The control program is segmented into two distinct parts: a data processing unit that manipulates process data according to the control program, and a verification unit that independently verifies the data against safety specifications. This segmentation allows formal verification to be applied only to the verification unit and safety-critical data paths, rather than the entire control system, thereby reducing overall programming complexity while maintaining safety reliability.
Solution Approach 2:
A separate verification unit is introduced as an intermediary component between the data processing unit and the control system. This verification unit acts as a mediator that checks whether the processed data satisfies safety specifications before the data is used for control actions. The intermediary approach isolates the complex verification logic from the main control program, making the system more manageable while ensuring safety.
2Reliability
If test cases are written to probe functionality, then safety coverage is improved, but time and effort for testing increase
Solution Approach 1:
The verification unit performs automatic self-verification of the control program's output data against the safety specifications. Instead of requiring external test cases to probe functionality, the system continuously self-checks whether the processed data satisfies the safety conditions. This automated self-service approach provides comprehensive safety coverage without requiring manual test case development and execution for each scenario.
Solution Approach 2:
The verification process operates continuously alongside the data processing operations, rather than as separate discrete test cases. The verification unit continuously monitors and verifies the control data as it is generated, providing ongoing safety assurance throughout system operation. This continuous verification eliminates the need for separate testing phases and provides constant safety coverage.
3Reliability
If assert statements are added to check assumptions, then safety verification is improved, but device complexity increases
Solution Approach 1:
The verification logic is extracted from the control program and placed into a separate verification unit. Instead of embedding assert statements throughout the control code, all safety verification is taken out and centralized in the dedicated verification unit. This extraction reduces code complexity in the control program while maintaining comprehensive safety verification capabilities in the separate unit.
Data Source
AI summary
Computer-implemented method and control apparatus for controlling a machine by executing program steps which verifiably execute predefined control tasks is provided, including manipulating data based on input data received from the machine and resulting in reference data by data programming steps structured according to a declarative programming paradigm in a data processing unit, and performing control program steps verifying the reference data with respect to explicit conditions, without any further manipulation of the reference data in the control program steps in a control processing unit, and providing instructions resulting from the performed control program steps to the machine for execution of the instructions by the machine.