A systems engineering approach to product modularity

Product modularity has been successfully adopted in a number of specific industries, such as computer technology and software development where it provides a number of advantages over monolithic product architectures. This paper presents initial findings from research at a range of companies within the UK where modularity is being applied or considered to address increasing product complexity and the growing need for the symbiosis of mechanical, electrical, electronic, optical, and software technologies in a wider range of manufactured products to meet discerning market requirements. The research identifies a need to address the current application of modularity within industry at three levels; a systems engineering based framework; a methodology for product modularisation; and the underlying process of modular product development. Concluding remarks highlight the issues drawn from the research and opportunities for addressing these issues

Modularisation as a means of product and process integration

Investigative work carried out to determine a strategy to address modularity as a facilitator for integration of design with manufacture. Modularisation is considered in conjunction with a large car manufacturer, a company that produce geophysical measuring systems for down hole drilling, and a company that produce electronic scanners for the pre press printing industry. Generic factors are being determined. These factors touch upon the benefits to product and process integration and also areas in which modularisation enables effective product customisation in meeting market needs. The aim, is to pool and document experience that can then be analysed and presented in a more accessible form by providing guidelines / checklists, evaluation tools and a product strategy based on derivatives

Holonic product design: a process for modular product realisation

This paper introduces a fresh perspective on product modularisation and proposes a process for modular product realisation called Holonic Product Design. The holon has recently been adopted from Arthur Koestler’s work to represent subsystem entities within manufacturing systems and the enterprise chain. In addition, it has been embraced as a philosophy for change that attempts to fashion modern manufacturing businesses and manufacturing activity. This paper demonstrates the holon as being equally valid as an approach to product development. Through research at a number of UK companies Holonic Product Design (HPD) is developed and presented as a structured approach to product realisation. Addressing a total view through systems engineering, HPD provides an accessible and customisable modular product development workbook. The efficacy of the new approach is demonstrated through the initial results from a HPD case study. Further work remains in refining the integration of HPD elements and thoroughly testing the approach through a full new product development process

The use of a kinematic contraint map to prepare the structure for a dimensional variation analysis model

Dimensional variation analysis (DVA) models are widely used in the automotive industry to predict how minor variations in the size, shape and location of the component parts are likely to propagate throughout a body structure, suspension, engine or transmission system and how this will affect the overall assembly, operation and performance. This paper is one of in series of four papers that describe how different techniques can be utilised to aid the creation and application of DVA models. This paper explains the development and use of the kinematic constraint map (KCM) method to prepare, in advance, the most appropriate structure for a DVA model. The KCM method provides a concise and comprehensive graphical method that, in one document, can identify all the physical constraints that govern the location and (where applicable) the motion of each component within a complete mechanical system. Once complete, the KCM for a mechanical system contains sufficient information to fully define the structure of the subsequent DVA model. The other three papers cover the use of virtual fixtures, jigs and gauges to achieve the necessary component location and the required variation measurements; the use of two stage DVA models to simulate interdependence between different model configurations and the use of 3D plots to display large numbers of DVA results as a single 3D shape

The use of a two stage dimensional variation analysis model to simulate the action of a hydraulic tappet adjustor in a car engine valve train system

Dimensional variation analysis (DVA) models have been used in the manufacturing industry for over 20 years to predict how minor variations in the size, shape and location of the components parts is likely to propagate throughout and affect the overall dimensions, operation and performance of a complete mechanical system. This paper is one of in series of four papers that describe how different techniques can be utilised to aid the creation and application of DVA models. This paper explains the development and use of a two stage DVA model to simulate the action of a hydraulic tappet adjuster and dimensional interdependence that exists between the adjustment of a hydraulic tappet and the actuation (opening & closing) of the cylinder valve. The three other papers cover the use of kinematic constraint maps to prepare the structure of a DVA model; the use of virtual fixtures, jigs and gauges to achieve the necessary component location and the required variation measurements, and the use of 3D plots to display large numbers of DVA results as a single 3D shape. A hydraulic tappet adjustor performs two functions; it is part of the valve train system that actuates (opens & closes) the cylinder valve and it also self adjusts to take up any free play in the valve train system. These two functions, tappet adjustment and valve actuation, are separate operations that occur at different times during the valve train operating cycle and so need to be modelled as different configurations in a DVA model. In a conventional multiple configuration DVA model, each configuration has to be fully constrained and mathematically closed independently of any other model configuration. This requirement makes it difficult to include the interdependence between tappet adjustment and valve actuation. The two stage approach overcomes this limitation by allowing the output variation from the tappet setting configuration to be carried over into the valve actuation configuration and can thereby fully account for the interdependence between the two operation

A method of visualising the 3D dimensional variation behaviour of kinematic systems

At present, the output from the dimensional variation of an assembly is often in the form of a statistical process control chart or histogram. Such output, while informative, is not particularly suited to the evaluation of dimensional variation behaviour in complex kinematic assembly systems. This paper presents a graphical method of visualising the 3D dimensional variation behaviour of any chosen point feature in a kinematic assembly system by the use of 3D bounding surfaces. The bounding surfaces describe a volume such that there is a known probability that the chosen point is contained within the volume. The bounding surfaces and the volume they describe visualise the dimensional variation behaviour of the chosen point feature as it traverses one or more of the kinematic assembly system's movement ranges. This paper demonstrates that the visualisation allows the dimensional variation behaviour of the chosen point to be presented in a compact and readily comprehensible manner that enables evaluation of the analysis output within the context of the original simulation model geometry. An example of the method applied to a simple kinematic system is also shown

The use of virtual fixtures, jigs and gauges in dimensional variation analysis simulation models.

This paper describes the use and deployment of, virtual fixtures, jigs and gauges to locate, align and measure features in simulation models used in the dimensional variation analysis (DVA) of assembly systems. The particular example chosen in this paper is a McPherson strut suspension. The correct use of virtual fixtures, jigs and gauges can significantly improve the accuracy and realism of the simulation model and thus the DVA output. In kinematic assembly systems, the use of virtual fixture, jigs and gauges is often essential to produce a working simulation model

Implications of the End-of-Life Vehicles Directive on the vehicle recovery sector

To cope with the environmental effects of 9 million tonnes of vehicles that reach the end of their useful lives each year in Europe, the EC have created the End-of-Life Vehicles (ELVs) Directive. Two of the most radical measures included in the Directive are to provide free takeback to last owners and to achieve targeted levels for the recycling and recovery of material by set dates. This paper aims to provide a basis for future research by evaluating the potential direction of the recovery industry. This is achieved firstly by assessing the origins of the directive and previous research surrounding the subject. The paper then describes the current recovery infrastructure and practices in the UK, highlighting all the stakeholders involved in the recovery industry. This paper also highlights the issues related to the provision of takeback and the attainment of targets through two stages, namely the implementation and management of takeback, and the use of new technology to achieve the recovery targets. The paper concludes by identifying key aims for future research to support the objectives of the implemented legislation and the financial stability of all stakeholders

A new friction model in hybrid pump-controlled asymmetric (single-rod) cylinder drive system

Hybrid pump-controlled asymmetric cylinder drive systems are implemented for energy saving purposes in applications that do not require fast responses. Under low-velocity and low-pressure conditions, the friction influence in the hybrid pump-controlled system is evident. Researchers have developed various models to describe friction. These friction models are implemented based on the relative motion of the contact surfaces, and they can be categorized into static friction and dynamic friction models. For example, dynamic friction models are suitable for simulating the friction in hydraulic cylinder seals under lubrication conditions. Among the dynamic models, the LuGre model can capture almost all static and dynamic friction behaviors at the macroscopic level; for example, stiction, the Stribeck effect, and hysteresis. Thus, the LuGre model is suitable for describing the friction in hydraulic cylinders. Because the friction force in the hydraulic cylinder is mainly from the cylinder seal and seal deformation occurs under pressure due to its flexibility, the friction in a hybrid pump-controlled hydraulic system is affected by the relative motion of the contact surfaces. Therefore, to investigate factors that affect the friction other than the relative motion of the contact surfaces, the friction behaviors of a hybrid pump-controlled hydraulic system are studied. Pressure difference and acceleration terms are introduced in the LuGre friction model, and the simulated friction results of the updated LuGre model are compared with the measured experimental results to validate the new friction model

Modelling and energy efficiency analysis of a hybrid pump-controlled asymmetric (single-rod) cylinder drive system

A conventional valve-controlled cylinder drive system is not energy efficient, and a pump-controlled cylinder system can be unstable in some particular conditions. For drive systems not requiring fast response, a hybrid pump-controlled system, that combines the advantages of both valve and pump-controlled systems, is proposed. As nonlinear behaviours are inevitable in most asymmetric cylinder drive systems, the hybrid pump-controlled system also suffers from such problems, and extra nonlinear behaviours are identified, for example, stall when the cylinder change its direction of motion. A simulation model of the hybrid pump-controlled asymmetric cylinder drive system is developed and used to investigate the system’s simulation behaviours which are analysed and compared with the experimental test results. The energy efficiency of the hybrid pump-controlled system is compared with a comparable valve-controlled hydraulic system with the same hydraulic cylinder sizing. The outcome is to demonstrate the advantage of the hybrid pump-controlled system in energy-saving aspect, and the efficiency of the hybrid system is up to five times more than a conventional hydraulic system. Suggestions are given to improve the performance and stability of the hybrid pump-controlled system. </div