Kazem Alemzadeh

A Systems Approach Towards Reliability-Centred Maintenance (RCM) of Wind Turbines☆

Abstract Wind turbines are a proven source of clean energy with wind power energy harvesting technologies supplying about 3% of global electricity consumption. However there is an increasing demand on maintenance and operational improvements since turbines have been plagued with downtime problems of major components e.g. gearboxes and generators, especially with offshore turbines which are difficult to access. Reliability Centric Maintenance (RCM) is a way of capturing the potential causes of downtime and poor performance by preventing failures and having a proactive approach to operations and maintenance (O&M). However, for a large fleet of turbines, adopting the RCM approach becomes difficult due to the complexities that arise as a result of the interactions between individual elements that make up the system in the product lifecycle. This paper discusses how a systems thinking approach can be used to identify the relevant aspects and possible interactions between the RCM approach and wind turbine gearboxes and also how the gaps that exist within the system can be closed so as to add value to business. The outcome of the paper is a proposal for applying a systems approach to wind turbine gearbox operation and maintenance, optimising the asset value adding contribution at minimal total cost to the operator.

The chewing robot: A new biologically-inspired way to evaluate dental restorative materials

This paper presents a novel in vitro dental wear simulator based on 6-6 parallel kinematics to replicate mechanical wear formation on dental materials and components, such as individual teeth, crowns or bridges. The human mandible, guided by a range of passive structures moves with up to six degrees of freedom (DOF). Currently available wear simulators lack the ability to perform these complex chewing movements. In addition simulators are unable to replicate the normal range of chewing forces as they have no control system able to mimic the natural muscle function controlled by the human central nervous system. Such discrepancies between true in vivo and simulated in vitro movements will influence the outcome and reliability of wear studies using such approaches. This paper summarizes the development of a new dynamic jaw simulator based on the kinematics of the human jaw.

Prototyping Artificial Jaws for the Bristol Dento-Munch Robo-Simulator; `A parallel robot to test dental components and materials'

This paper presents the robot periphery for the robotic dental testing simulator based on a parallel robot (i.e. stewart platform) to simulate the wear of materials on dental components, such as individual teeth, crowns or a full set of teeth. Current chewing simulators move in only 1 or 2 degrees of freedom (DOF) and therefore lack accuracy. The Bristol simulator has been developed to replicate accurate human chewing patterns in 6-DOF. This paper describes the artificial jaws and compliance module of the robot. The jaws have been reverse engineered and represent a human-like mandible and maxilla with artificial teeth. Each clinically fabricated tooth consists of a crown and glass ceramic roots which are connected using resin cement. Correct occlusion of the artificial jaws assembly was assessed by a dental teaching simulator. A compliance module had to be built between the lower jaw and the robot platform to sustain the fluctuating forces that occur during normal chewing in the occlusal contact areas, where these high bite forces are major causes of dental component failure. A strain gauge force transducer has been integrated into the machined lower jaw, underneath the second molars, to measure axial biting forces applied to the posterior teeth.

Improved visualisation of the design space using nested performance charts

Abstract Performance charts are an important visual means by which designers explore the design space and optimise the performance of products and systems. Traditional performance charts are usually limited to one or two design variables. However, many design problems have more than two important design variables. This paper presents a new concept of performance chart that can plot the performance of a product or system as a function of more than two design variables. The paper illustrates the new type of chart with the example of the design optimisation of a large mechanical structure that has four design variables.

A 3-dimensional vision system for dental applications

There is an increasing demand for techniques that make use of 3-dimensional measurement in the field of dental research. This paper utilized a new 3-dimensional vision system for tooth surface information reconstruction. The system is based on a computational framework for constructing point cloud using digital fringe projection patterns. Surface information extracted from the point cloud can be used in various dental applications, for example, extracting characteristic features, building up a filling model for tooth restoration and determining molar movement during headgear treatment.

A team based CAD project utilising the latest CAD technique and web-based technologies

This paper describes a newly created third-year CAD project in the Department of Mechanical Engineering at Bristol University which brings together the most current CAD practices and web-based technologies to provide a stimulating and dynamic learning environment for the students. The project involves the design of a machine that sorts chips of different materials. The main objective is to provide a complete and up-to-date CAD experience for the students. The CAD project provides the opportunity for students to practise geometric modelling, mechanism design, assembly modelling, product visualisation (simulation and animation) and product customisation in an active learning environment. It also teaches the students parametric modelling and how quickly and efficiently to build, visualise and animate a CAD model of a proposed design, with further customisation using CAD principles.

Improved single- and multi-contact life-time testing of dental restorative materials using key characteristics of the human masticatory system and a force/position-controlled robotic dental wear simulator

This paper presents a new in vitro wear simulator based on spatial parallel kinematics and a biologically inspired implicit force/position hybrid controller to replicate chewing movements and dental wear formations on dental components, such as crowns, bridges or a full set of teeth. The human mandible, guided by passive structures such as posterior teeth and the two temporomandibular joints, moves with up to 6 degrees of freedom (DOF) in Cartesian space. The currently available wear simulators lack the ability to perform these chewing movements. In many cases, their lack of sufficient DOF enables them only to replicate the sliding motion of a single occlusal contact point by neglecting rotational movements and the motion along one Cartesian axis. The motion and forces of more than one occlusal contact points cannot accurately be replicated by these instruments. Furthermore, the majority of wear simulators are unable to control simultaneously the main wear-affecting parameters, considering abrasive mechanical wear, which are the occlusal sliding motion and bite forces in the constraint contact phase of the human chewing cycle. It has been shown that such discrepancies between the true in vivo and the simulated in vitro condition influence the outcome and the quality of wear studies. This can be improved by implementing biological features of the human masticatory system such as tooth compliance realized through the passive action of the periodontal ligament and active bite force control realized though the central nervous system using feedback from periodontal preceptors. The simulator described in this paper can be used for single- and multi-occlusal contact testing due to its kinematics and ability to exactly replicate human translational and rotational mandibular movements with up to 6 DOF without neglecting movements along or around the three Cartesian axes. Recorded human mandibular motion and occlusal force data are the reference inputs of the simulator. Experimental studies of wear using this simulator demonstrate that integrating the biological feature of combined force/position hybrid control in dental material testing improves the linearity and reduces the variability of results. In addition, it has been shown that present biaxially operated dental wear simulators are likely to provide misleading results in comparative in vitro/in vivo one-contact studies due to neglecting the occlusal sliding motion in one plane which could introduce an error of up to 49% since occlusal sliding motion D and volumetric wear loss V(loss) are proportional.

A Team-Based CAM Project Utilising the Latest CAD/CAM and Web-Based Technologies in the Concurrent Engineering Environment

This paper describes the computer-aided manufacture (CAM) part of newly created third-year computer-aided design/computer-aided manufacture (CAD/CAM) project in the Department of Mechanical Engineering at the University of Bristol, which brings together the most current CAD/CAM practices, web-based technologies and shop-floor practices, to provide a stimulating and dynamic learning environment for the students. The project involves the design and manufacture of a crest as a feature for a chip/material-sorting machine in a concurrent learning environment. The main objective is complete product development, from design to manufacture (i.e. the product cycle), using the latest CAD/CAM technologies for the students. Students carry out product development assessment and make suitable adjustments to the design once the problems with engineering curves are identified. They especially practise the design for manufacture (DFM) technique to ensure any part designed on the CAD/CAM system can actually be machined with available machines, tools and fixtures. They also learn how to animate the machining processes of their final product as a part of product visualisation practice. In generative machining (GM), students learn the CAD/CAM approach to computer numerical control (CNC) programming, where a tool-path is generated automatically. GM also teaches the students how quickly and efficiently a design can be customised, updated and manufactured automatically when a feature of the proposed design is modified using CAD/CAM and CNC machine tools principles.

A Framework for Optimizing Product Performance Through Using Field Experience of In-Service Products to Improve the Design and Manufacture Stages of the Product Lifecycle

For many component sub-systems which make up the individual elements of a larger product system, the optimization of their performance in the system becomes more difficult through design modifications and/or manufacturing process improvements alone. The authors argue this can be improved if adequate field performance data has been fed back to the early stages of the product lifecycle. This paper presents a framework for an inclusive lifecycle approach to optimizing product performance through the effective use of field experience and knowledge to improve the design and manufacturing of sub-systems. The problem is presented alongside a taxonomic and captious review of literature of relevant subject areas, followed by a case study using wind turbine sub-system components as a basis to support the investigation. A framework is then developed through the combination of systems thinking and continuous improvement tools, applied to the conventional product lifecycle. The findings of the investigation indicate that sub-system performance can be improved through the accumulation of knowledge fed back to the design and manufacture stages of the product lifecycle using information from in-service product performance. The approach would be useful to practitioners and academics with an interest in applying an inclusive and holistic approach to product lifecycle management. This framework is particularly useful for companies that produce and/or operate systems whose sub-systems are manufactured by different suppliers.

Capturing motions and forces of the human masticatory system to replicate chewing and to perform dental wear experiments

One way to evaluate the life-time performance of dental restorative materials is to use in vitro dental wear simulators, which generate accelerated artificial dental wear on dental restorative components outside of the human oral environment. However, the work of several researchers has questioned the reliability of these in vitro results as a consequence of significant result variations produced by different types of dental wear simulators testing identical dental specimens. Natural six degree of freedom (DOF) mandibular movements and other characteristics of the human masticatory system are not replicated by any of these available simulators. A simulator replicating and controlling 6 DOF mandibular movements and occlusal bite forces improves this situation. This paper presents a method by which accurate jaw motion data can be obtained using a conventional 6 DOF motion capturing system and a method of measuring occlusal bite forces. The data obtained have subsequently been used as input signals for a new 6 DOF dental wear simulator capable of generating single and multi-contact wear formations in dental wear studies.