Standby redundant control using Erlang/OTP and JADE for a manufacturing cell.

[摘要] ENGLISH ABSTRACT: In past decades, the manufacturing sector has been characterised by intensecompetition resulting from globalisation and shifting customer requirements. Thishas led to the pursuit of approaches and paradigms that better handle therequirements of modern manufacturers. This pursuit has culminated in the recentfocus on the Industry 4.0 and Industrial Internet of Things (IIoT) paradigms.The future manufacturing systems envisioned by these paradigms are increasinglycomplex. The reliability or availability of complex systems is a concern sincecomplexity increases the likelihood of unexpected failure modes. Holonic systemsshow great promise for managing this complexity, but they may contain holonsthat represent single points of failure. The availability of these holons can beimproved through standby redundancy.This dissertation evaluates the hypothesis that Erlang/OTP provides an effectiveplatform for implementing standby redundancy in a distributed holonicmanufacturing cell. Erlang is a functional programming language designed for thedevelopment of fault-tolerant soft real-time control systems. The Open TelecomPlatform (OTP) is a set of Erlang libraries that simplifies the development of largecomplex systems. OTP is such a central feature of Erlang that they are typicallyreferred to collectively, as Erlang/OTP.Erlang/OTP's standby redundancy effectiveness is evaluated in two stages. First, itis evaluated through the implementation of standby redundancy for a monolithicstation controller, the performance of which is benchmarked against the claims ofan existing commercial solution. This implementation is representative of standbyredundancy for singular resource holons. The evaluation shows that theErlang/OTP implementation can handle the same failure modes as the commercialsolution and achieves a similar changeover time. Furthermore, it shows thatErlang/OTP is suitable for implementing standby redundancy at a software levelfor embedded devices that do not provide such mechanisms at a hardware level.Next, Erlang/OTP's effectiveness for standby redundancy in a distributed holoniccell controller is evaluated through a case study comparison of an Erlang/OTPimplementation and a Java Agent Development (JADE) frameworkimplementation. JADE is a popular Multi-Agent System framework and has inmany respects become the de facto standard for holonic control implementationsin academic research. The two implementations are compared using a set ofquantitative and qualitative criteria. The comparison demonstrates that theErlang/OTP implementation outperforms the JADE implementation for all thestandby-redundant performance metrics. This is attributed to the centrality offault-tolerance in Erlang and OTP. The comparison suggests that moredevelopment effort may be required for a standby-redundant Erlang/OTP holonicimplementation, since Erlang/OTP does not contain the same degree ofsupporting communication and protocol infrastructure as an establishedframework like JADE. However, Erlang/OTP's superior performance outweighs thisshortcoming and the comparison concludes that Erlang/OTP provides a betterplatform for implementing standby redundancy than JADE.The findings of both evaluations confirm that Erlang/OTP provides an effectiveplatform for implementing standby redundancy in a distributed holonic controllerfor a manufacturing cell. Using Erlang/OTP, the ability to combine standbyredundancy and holonic control has the potential to improve controller availabilityfor the complex distributed systems envisioned by Industry 4.0 and IIoT.

[发布机构] Stellenbosch University