I/O Channel Write Access Control for Race-Free Process Automation
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Solution Overview
Problem
In process automation facilities, multiple writer user accounts accessing shared output channels can lead to conflicting or unpredictable control signals, causing actuators to behave erratically and negatively impacting process control loops, due to the risk of conflicting commands and race conditions.
Innovation Solution
Implementing a system that limits write access to a single active writer user account at a time, using a writer semaphore to determine availability and providing access to a reader account if the writer account is unavailable, ensuring that only one client can write to an output channel, thereby preventing conflicts and race conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple writer user accounts are permitted to access shared output channels simultaneously, then system versatility and accessibility are improved, but reliability deteriorates due to conflicting commands and race conditions causing erratic actuator behavior
Solution Approach 1:
The patent introduces a writer account availability determination mechanism as an intermediary between multiple writer user accounts and shared output channels. This mediator checks whether a writer account is currently available before granting access, preventing simultaneous writes from multiple accounts. The intermediary resolves the contradiction by enabling versatile access while maintaining reliability through coordinated control.
2Reliability
If write access is limited to a single writer user account at a time, then reliability is improved by preventing conflicting commands, but device complexity increases due to access control mechanisms and availability determination
Solution Approach 1:
The system implements self-service through automatic availability determination and account management. When a writer account becomes unavailable, the system automatically denies access to subsequent requests and can provide alternative reader accounts. This self-managing approach maintains reliability while minimizing the complexity burden on operators, as the system handles access control autonomously.
3Reliability
If a writer account is denied to a client, then reliability is maintained by preventing race conditions, but productivity decreases due to access denial and potential process delays
Solution Approach 1:
The system employs periodic availability checking and account release mechanisms. When a writer account is released after use, the system periodically checks for waiting requests and grants access in a controlled sequence. This periodic action maintains reliability by ensuring only one writer at a time while improving productivity compared to indefinite blocking, as the system actively manages account availability and quickly transitions to the next waiting writer when appropriate.
Data Source
AI summary
Implementations are described herein for determining whether to allow a cross-platform process automation client to write to an I/O channel controlled by a cross-platform process automation server. In various implementations, the cross-platform process automation client transmits a request to access a writer account of the cross-platform process automation server to the cross-platform process automation server, to write to the I/O channel. In response to receiving the request to access the writer account, the cross-platform process automation server determines whether the writer account is available. If the writer account is determined as being unavailable (e.g., currently being used by another cross-platform process automation client), the cross-platform process automation server can deny the request from the cross-platform process automation client to access the writer account, and/or provide the cross-platform process automation client access to a reader account.