Dual Time Base Verification for Networked Machine Control
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Solution Overview
Problem
The migration of control programs to external computing units in controllable machines, such as AGVs and robots, complicates the provision of a reliable time base, as these units often lack the necessary independent timers, posing risks due to potential malfunctions or manipulation.
Innovation Solution
Implement a method using two independent time bases, where the first time base is provided by an internal clock of the external processing unit and the second time base is derived from a network component via the IEEE 1588 interface of the PTP network protocol, with time telegrams broadcasted at fixed intervals and checked for accuracy using the Christians algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If control programs are migrated to external computing units, then productivity and flexibility are improved, but reliability of time base deteriorates due to lack of independent timers
Solution Approach 1:
The patent introduces a time base verification unit as an intermediary component between the control program and the time base source. This unit independently verifies the time base provided by the external computing unit, ensuring reliability even when the external unit lacks independent timers. The verification unit acts as a mediator that checks time consistency without interfering with the external computing unit's operation.
Solution Approach 2:
The system implements feedback mechanisms where the time base verification unit continuously monitors and verifies the time base against expected values and time intervals. When discrepancies are detected, the system can trigger safety responses or corrective actions, ensuring that time base reliability is maintained through continuous feedback validation.
2Reliability
If two independent time bases are implemented, then reliability is improved through independent verification, but device complexity increases
Solution Approach 1:
Instead of requiring two completely independent time base sources, the patent creates a verification copy of the time base values and compares them against expected time intervals and previously recorded values. This copying approach provides independent verification without duplicating the entire time base generation system, thereby reducing complexity while maintaining reliability.
Solution Approach 2:
The time base verification unit performs self-verification by comparing received time base values against internally maintained time interval expectations and previously recorded values. This self-service mechanism eliminates the need for complex external synchronization systems, as the verification is performed autonomously within the control unit.
3Reliability
If time base verification is performed continuously, then reliability is improved through error detection, but use of energy increases
Solution Approach 1:
The time base verification is performed periodically at specific intervals rather than continuously. The verification unit checks time base values at defined time points and compares them against expected time intervals, reducing processing load and energy consumption while maintaining adequate time base accuracy for safety-critical operations.
Solution Approach 2:
The verification process performs partial validation by checking only critical time base parameters and comparing against pre-calculated expected values. This selective verification approach provides sufficient reliability for safety functions without the full computational overhead of complete continuous verification, optimizing the balance between reliability and energy consumption.
Data Source
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AI summary
The invention relates to a method for providing a reliable time base for a control program (211, 212) for operating a controllable machine (100), which includes an internal control unit (110) for controlling the machine (100), wherein the control program (211, 212) is executed on an external computing unit (200) which is connected to the internal control unit (110) via a communication link of a communication network (150) for transmitting information for controlling the machine (100). In the method, the control program (211, 212) is provided with a first time base (ZB1) from an internal clock (220) of the external computing unit (200) and a second time base (ZB2), which is independent of the first time base (ZB1), from an internal clock (231, 320) of a network component (230, 300) of the communication network (150).