The increasing occurrence of interdiscipli nary product development has removed many traditional constraints and given the designer a much wider freedom of choice of means of satisfying any given statement of requirements. Schemebuilder, a comprehensive , intelligent knowledge-based design package, aims to support the designer in the conceptual through embodiment stages of design, providing guidance on the range of options available. In the field of energetic systems, bond graph methodology, possessing as it does a common structure and clear causal rules across engineering domains, forms an admirable basis for Schemebuilder development. This paper describes how the conceptual scheme generation process may be assisted and structured by the use of function-mean s trees developed by the application of bond graph-inspired rules.

The software package Dymola, which implements the new, vendor-independent standard modelling language Modelica, exemplifies the emerging generation of object-oriented modelling and simulation tools. This paper shows how, in addition to its simulation capabilities, it may be used as an embodiment design tool, to automatically size a design assembled from a library of generic parametric components. The example used is a miniature model aircraft diesel engine. To this end, the component classes contain extra algebraic equations for calculating the overload factor (or its reciprocal, the safety factor) for all the different failure modes, such as buckling or tensile yield. Thus, the simulation results contain the maximum overload or the minimum safety factor for each failure mode, along with the critical instant and the device state at which it occurs. The Dymola “Initial Conditions Calculation” function, controlled by a simple software script, may then be used to perform automatic component sizing. Each component is minimised in mass, subject to a chosen safety factor against failure, over a given operating cycle. Whilst the example is in the realm of mechanical design, it must be emphasised that the approach is equally applicable to the electrical or mechatronic domains, indeed to any design problem requiring numerical constraint satisfaction

The issue of complexity in modeling and simulation arises from the desire to understand fully the behaviour of physical systems at the time design and acquisition decisions are being taken. This avoids the need for extensive experimentation, testing and product development, increasing confidence and reducing time to market. The article describes the development of causally consistent models of different complexity and shows how they may be applied to the simulation and animation of an electrical drive system. Functional objects have a physical form which may be modelled as a three dimensional solid object having sets of functional axes that define the spatial positioning of component interaction. Object interaction is not limited to energetic interaction but may be in relation to any aspect of its context. The object may interact with respect to mass, reliability, failure modes, cost, etc., which may be included in economic and environmental aspects of the models

The increasing occurrence of interdisciplinary product development has removed many traditional constraints and given the designer a much wider freedom of choice of means of satisfying any given statement of requirements. Schemebuilder, a comprehensive, intelligent knowledge-based design package, aims to support the designer in the conceptual through embodiment stages of design, providing guidance on the range of options available. In the field of energetic systems, bond graph methodology, possessing as it does a common structure and clear causal rules across engineering domains, forms an admirable basis for Schemebuilder development. This paper describes how the conceptual scheme synthesis may be assisted and structured by the use of function-means trees developed by the application of bond graph-inspired rules. INHALTSANGABE:Das zunehmende Auftreten von interdisziplinaren Produktentwicklungen hat viele traditionelle Zwänge unnötig gemacht und den Designer einen viel größeren Freiraum in der Auswahl, den Mitteln und der Zufriedenstellung der gegebenen Bedürfnisse gegeben. "Schemebuilder" ist ein umfassendes, intelligentes Entwicklerpaket, welches darauf abzelt, den Entwickler durch die begriffliche Verkörperung der Phasen der Entwicklung zu unterstützen, wobei Möglichkeiten zur Auswahl zur Verfügung gestellt werden. Das Gebiet der energetischen System und der "Bond"-Graphiken, gekennzeichnet von gebräuchlichen Strukturen und klaren kausalen Regeln die durchweg in den Ingenieurwissenschaften vorkommen, bildet eine bemerkenswerte Basis für die Entwicklung mit "Schemebuilder". Dieses Script beschriebt wie die begriffliche Planungssynthese unterstützt und strukturiert werden kann, durch den Gebrauch Struktogrammen, welche durch die Anwendung von "Bond-Graph-Techniken entwickelt werden. INTRODUCTION Much interdisciplinary design is still carried out by individuals or groups who have been trained in a single engineering discipline with limited knowledge or experience of other fields. The most common approach towards achieving a truly interdisciplinary basis to product development has been to assemble design teams consisting of various technology specialists together with generalist mechatronic engineers in order to encourage communication and co-operation within the team. Recent advances in computer-aided design and the potential infusion of AI outgrowths like functional reasoning, constraint processing and planning into traditional CAD, suggest an alternative to the above approach. A computer system may support and guide the designer through the range of technological options available, with the aid of appropriate tools to process design data at the proper level of abstraction, through concept generation, means selection and matching, simulation, optimisation and visualisation. No such comprehensive system presently exists; the Schemebuilder project is aimed at creating one. THE SCHEMEBUILDER PROJECT It is intended that Schemebuilder be a kind of "design workbench" where designers are guided through the range of technological options available, aided by the provision of tools for rapidly accessing relevant information. It has therefore a role as both facilitator for the creation of models of the system to be designed and advice giver on the range of appropriate means. A fundamental feature is its ability simultaneously to generate and explore many alternative conceptual schemes with an appropriate allocation of function between appropriate forms of mechanical, electrical, electronic and software elements The main areas of computer support tackled by Schemebuilder are : • assisting in the identification of appropriate working principles and technologies • providing advice and browsing facilities on available technologies • synthesizing alternative functional schemes in appropriate technologies • producing system models for dynamic simulation • supporting embedded software design and development • monitoring system integrity, checking for continuity and matching • producing 3D layouts in the form of realistically sized 'solid sketches' • designing and modelling of casings and support structures It must be emphasised that the philosophy underlying our development work is a move from the classical expert systems approach of automated design to one embracing a more co-operative relationship between man and machine as underlined by the work of Fischer (Fischer 1990) and described by Oh (Oh 1993) and builds on the early work of Sharpe (Sharpe 1978) on Bond Graph Synthesis, which is reflected in the work of others (Ulrich and Seering 1989; Finger and Rinderle 1989; Malmqvist 1994). We believe that a more appropriate approach to computer-based design tools is for the computer to provide decision support and allow the human designer to apply the judgement. Figure 1: Diagram of Schembuilder and relation to the Design Process. A design develops generally by a set of iterative processes between problem analysis, conceptual design and embodiment design, in which decisions are tested and modified as part of the process. Schemebuilder covers the whole process from problem analysis through to embodiment design, providing an environment in which competing alternative components or sub-systems can be matched to functional requirements, compared on a wide range of criteria and be tested by means of simulation. The facilities are integrated by sharing a single set of data, employing cross-disciplinary component descriptions, of which the energetic parts are in the form of bond graphs (Sharpe and Bracewell 1993; Oh et al. 1994). FACILITIES FOR QUALITATIVE SYNTHESIS OF SCHEMES FROM FIRST PRINCIPLES Our definition of a scheme follows that in (French 1985), namely an "outline of a solution to a design problem, carried to a point where the means of performing each major function has been fixed, as have the spatial and structural relationships of the principal components. A scheme should be sufficiently worked out in detail for it to be possible to supply approximate costs, weights, and overall dimensions, and the feasibility should have been assured as far as circumstances allow. A scheme should be relatively explicit about special features or components but need not go into much detail...." The Schemebuilder software described previously is being further developed so that schemes may be developed using a function-means tree approach guided by sets of design and working principles. This allows for the progressive refinement and development of a design from abstractly expressed required functions to their eventual physical embodiment. Backed by an Assumption Truth Maintenance System, it is also possible for the tree structure to maintain the development of the alternative schemes. SCHEME GENERATION FROM FIRST PRINCIPLES It is often desirable to develop a conceptual design from first principles, exploring the myriad of alternative schemes in the process before choosing the best alternatives to pursue in detail. Such a process will begin with some expression of need, combining normal language and related numerical information. Employing techniques from AI like natural language processing and information retrieval in the implementation of dictionaries and thesauruses, it is possible, by means of prompts and iteration, to help the designer establish the design context and desired function. This is similar to the generation of the context diagram and event list of the Yourdon Structured Method, a popular technique used in systems analysis and design, particularly in the software field (Yourdon 1989). Furthermore, a software thesaurus may be used to search a dictionary of working principles, by matching words appearing in the functional aspect of the expression of need with key words describing the application of a principle. Having chosen one or more likely working principles it is necessary to determine possible means of achieving all their required functions. This is done by searching the component library (Oh 1994) for available means of achieving each function in turn, for example, a gyrator between DC electrical and mechanical rotational domains will search for an electric motor means. Alternatively, if no satisfactory means can be found for a particular function, it may be decomposed according to the set of rules derived from Bond Graph reasoning listed below, followed by a means search on the sub-functions thus generated. FUNCTION-MEANS DEVELOPMENT The example of a system for the operation of the control surfaces of an aircraft is shown in figure 2. This begins with a statement of the required function and its context Figure 2 also shows further development of the function-means tree from this single functional requirement and the searching of the function data space. The use of bond graph reasoning, provides a unique set of rules for the decomposition of energetic systems. These rules are based on the facts that only like energy ports may be connected to each other, that the causality of the energy co-variables must be correctly propagated and that there are a limited set of primary functions that may be used, such as the transformer (TF), gyrator (GY), resistor (R), compliant and inertial energy stores (C and I), parallel and series junctions (0 and 1) and sources of flow and effort (SF and SE). Each has a clear set of rules governing its function and how it may be decomposed, whilst still performing the same overall primary function (Sharpe 1978). Thus a TF, may be replaced by two TFs in series or any number of TFs in series or two or any even number of GYs in series. However a GY, due to its reversal of causality, may only be replaced by an odd number of GYs, in series with any number of TFs. This ability to split a function and introduce an intermediate energy domain allows the coupling of domains that are not normally possible. For example it is not possible directly to transfer energy between the electrical domain and the hydrosta

With increased pressures coming from global competition and requirements for greater innovation in product development, designers are hard pressed to deliver designs of higher quality and variety using a repertoire of technological options from different disciplines. This interdisciplinary product development approach has not only removed many of the traditional constraints to design but has now given designers a much wider freedom of choice as to the best solution to a design problem. The focus of this paper is a knowledge-based design environment called Schemebuilder, which is a comprehensive and integrated suite of software tools aimed at supporting the designer in the rapid development of product design models in the conceptual, through embodiment stages of design. Illustrated is the use of the software tools in the qualitative generation of alternative schemes, by application of stored working and decomposition principles in the development of a function-means tree-like information structure. With mechatronic product development as the main theme, this paper describes a closely integrated methodology that incorporates a bond graph approach to continuous-time energetic systems and high-level Petri nets for the rigorous description of discrete-time information systems. Additionally, a technique is suggested for the decomposition of free format statements of need into the rigorously defined design context and required functions, which form the starting point of the function-means development process.

This paper describes a package of software tools supporting the conceptual and embodiment stages of mechatronic and mechanical systems design. This is currently under development at Lancaster Engineering Design Centre (EDC) under the general title "Schemebuilder". Extensive use is being made of bond graph and parametric techniques, to allow rapid creation and assessment of competing alternative designs. With an intuitive graphical interface and hypertext linking of information, Schemebuilder is intended for designers of all levels of experience. Engineering design may be thought of as the process of conversion of a need - expressed as an abstract concept in terms of general functionality - into a product fulfilling that need. The design process may be structured by decomposing the high level functional requirements specification into a nested hierarchy of functions from which potential solution schemes may be developed( 1). Matching between individual elements is then achieved through the provision of appropriate interfaces. Key features of mechatronic design are the need to achieve high levels of integration and to optimise the overall design by 'transferring complexity' between the mechanical, electrical, electronic and software elements forming the complete system. However, the expansion of the

Exploitation of the bond graph methodology's unified modelling approach over many energy domains has enabled a comprehensive, generic, computer-aided conceptual design tool (Schemebuilder) to be developed. This paper describes how bond graph fragments representing individual components are assembled into complete system models from which steady state performance and dynamic simulations may be computed. It is concluded that the bond graph methodology provides an excellent basis for the concurrent conceptual design of interdisciplinary products through to the generation of a “rapid prototype”

The dynamic performance of robots and manipulators are greatly influenced by the actuator characteristics used to actuate the joints of these mechanisms. The servo actuator characteristics are governed by the force/torque generation process, the energy conversion process and the type of control system used. Research into the dynamics of bilateral servo control systems for use in force-reflecting master-slave manipulators has led to the identification of energy covariables associated with `non-contact' inertial tasks and `in-contact' compliant tasks. The use of covariant control based on these energy covariables provide an fundamental basis to synthesize efficient control systems. It can be used around an actuator to reduce the anomalies arising from torque generation and varying load dynamics. The authors describe experimental work which has demonstrated the unique properties of covariant control applied to manipulators

A cell disrupter has been developed which can measure the forces required to disrupt both eukaryotic and prokaryotic cells. It operates a continuous process and will disrupt both large and small volumes. Shear forces are set up when a suspension under laminar flow conditions is released under high pressure through a short orifice. If the applied pressure is altered, the shear forces are simultaneously changed so that the amount of cell disruption can be compared under different known and repeatable conditions. The disrupter is now manufactured and supplied by Stansted Fluid Power Limited, Stansted, England. Phase-contrast microscopy has shown that the disrupter will break a variety of organisms including Chlorella, Aspergillus fumigatis, Fusarium sp., Saccharomyces cerevisiae, Escherichia coli, Lactobacillus casei, Bacillus subtilis, Clostridium perfringens, Streptococcus faecalis, Streptococcus zooepidermicus and Staphylococcus aureus. The cells are not all broken at one pressure but a certain pressure must be applied before disruption starts which will then increase rapidly as the applied pressure is increased. The applied pressure required to disrupt half the population in a culture is different from one species to another, rods being disrupted more easily than spheres. The case of disruption seems to be related to the shape and chemical composition of the cell wall. Furthermore, the disrupting process, in an unsynchronized culture is not random and may be related to the statistical size distribution of the cells.