Colin Bell

Autonomous Maintenance for Through-Life Engineering

This chapter looks at the overall theme of automating maintenance practices with a particular focus upon the application of robotics within this field. Covering the current state of the art in automating maintenance processes this chapter also looks at the current challenges to moving beyond simple inspection and diagnosis to the design and construction of fully automated platforms for undertaking maintenance. This includes methodologies for capturing and classifying maintenance task processes so that they can be automated in some way and how to link this task classification with some level of automation. The chapter ends with a discussion on how the design process can be adapted to aid automated maintenance, self-healing and no fault found applications.

Concepts of Self-Repairing Systems

Systems fail. Period. No matter how much planning and fault analysis is performed, it is impossible to create a perfectly reliable machine. The existing approach to improving reliability invariably involves advances in fault prediction and detection to include specific mechanisms to overcome a particular failure or mitigate its effect. While this has gone a long way in increasing the operational life of a machine, the overall complexity of systems has improved sharply, and it is becoming more and more difficult to predict and account for all possible failure modes. What is discussed here is a possible shift in approach from specific repair strategies to autonomous self-repair. Rather than focusing on mitigating or reducing the probability of failure, the focus is instead on what can be done to correct a failure that will invariably occur at some point during operation. By taking this approach, it is not just expected failure that can be designed for, unexpected failure modes are also inherently compensated for, extending the potential life of a system and reducing the need for through-life servicing.

Tribological optimization of a toroidal-type continuously variable transmission

Continuously variable transmissions (CVTs) are mechanical devices that allow a continuous variation of the output velocity by adjusting its internal geometrical configuration. Through the use of an epicyclic gear set, a CVT can deliver an infinite number of transmission ratios, allowing the vehicles engine to operate within a higher efficiency envelope for longer periods of time. This offers several advantages over traditional transmissions such as better fuel efficiency, quieter operation, and a lower mass. Current efforts to reduce the vehicles’ fuel consumption in order to protect the environment and save fuel have seen a recent revival in CVT research, especially in the automotive industry. This article documents a successfully implemented search algorithm for the dimensional optimization of a novel CVT design in order to determine the maximum theoretical efficiency of the device. In addition to showing an economical and simple method of calculating contact losses, this method of optimization also proved to be a powerful tool that can be used to select the dimensions of the transmission to fulfil any desired characteristics.

Multi-criteria optimisation of a continuously variable transmission

Manufacturing companies face tough competition across global markets with continuous demands to decrease product-development-cycle time whilst lowering costs without compromising quality. This paper presents a method of improving the efficiency of one aspect of the development cycle: functional optimisation. This optimisation technique is based around a modified genetic algorithm. This is used to develop a set of dimensions that fulfil stated, functional targets relating to the performance of a continuously variable transmission. These targets are prioritised based on an adapted Pugh’s decision matrix for a number of different applications to automatically obtain weighted targets. Additionally, it is shown that for this particular problem, stochastic restarting of the genetic algorithm can lead to superior results without affecting computational time. This paper demonstrates that the methodology discussed can be successfully applied to a number of multi-objective problems in order to quickly yield the most favourable set of dimensions.

Self-repairing design process applied to a 4-bar linkage mechanism

Despite significant advances in modelling and design, mechanical systems almost inevitably fail at some point during their operative life. This can be due to a pre-existing design flaw, which is usually overcome in a revision, or more commonly due to some unexpected damage during operation. To overcome a failure during operation, a new method in designing machines or systems is proposed that creates a result, that is, resilient to both expected and unexpected failure. By shifting the focus from a detailed assessment of the underlying cause of failure to how that failure will manifest, a system becomes inherently resilient against a wide range of failure modes. The proposed process involves five steps: cause, detection, diagnosis, confirmation and correction. This is demonstrated with an application to a generic 4 bar linkage mechanism. Through this process, the system is able to return to a near perfect state even after a permanent deformation occurs in the mechanism. These results show the potential that this self-repairing design process has applications including robotics, manufacturing and other systems.

Design for Zero-Maintenance

This chapter looks at the concept of zero-maintenance, in particular how it relates to design. It begins by defining what constitutes zero-maintenance, presenting current research on the themes of autonomous maintenance and self-healing and repair. A wider context of how zero-maintenance affects through-life engineering services is also discussed with a focus on the no-fault found phenomenon. Case studies are then presented for design strategies in self-healing electronics and no-fault found and the failure of design. Finally, a design for zero-maintenance process is outlined and discussed.

Concept design optimisation for Continuously Variable Transmissions

The intense competition on the global markets faced by manufacturing companies is reflected by critical issues like decreasing the product-development-cycle, lowering costs and increasing quality. This can be viewed as a multi-criteria decision-making problem set within the space of engineering-characteristics for the designed system. In this paper one aspect of a design method: Quality Function Deployment (QFD) is used to assess different design concepts for transmission systems and explore the relationship between the most important features for the system definition in specific applications. Various concepts are assessed, whilst dimensions of individual components of a novel CVT are optimised to meet the derived requirements.

Zero-maintenance of electronic systems: Perspectives, challenges, and opportunities

Self-engineering systems that are capable of repairing themselves in-situ without the need for human decision (or intervention) could be used to achieve zero-maintenance. This philosophy is synonymous to the way in which the human body heals and repairs itself up to a point. This article synthesises issues related to an emerging area of self-healing technologies that links software and hardware mitigations strategies. Efforts are concentrated on built-in detection, masking and active mitigation that comprises self-recovery or self-repair capability, and has a focus on system resilience and recovering from fault events. Design techniques are critically reviewed to clarify the role of fault coverage, resource allocation and fault awareness, set in the context of existing and emerging printable/nanoscale manufacturing processes. The qualitative analysis presents new opportunities to form a view on the research required for a successful integration of zero-maintenance. Finally, the potential cost benefits and future trends are enumerated.