Design Methods for Systems Integration

Finally, in the last section the two methods will be compared and a combined application of the two methodologies will be presented. 1.

Introduction The term system is used in daily life with a variety of meanings. Society, companies, our body are all examples of systems. A clear definition of a system was provided by Wilson [1]. He defined a systems starting from the definition of the dictionary: "a system is a structured set of objects and/or attribute together with the relationships between them", and then, basing on Iceland's classification, he organizes them as follows: I.

Natural systems it. Designed systems ii. Human activity systems 'v. Social and cultural systems For the aim of this paper we will focus on the designed systems, which are defined by Wilson adapting Iceland's definition as "both physical (tools, bridges, automated complexes) and abstract (mathematics, language, philosophy)" [1].

The interrelationships occurring in a physical system usually have the purpose of carrying out a function. According to Pall et al, a function is an "input/output relationship of a system whose purpose is to perform a task" [2].In order to accomplish their task, among the functions there is a flow of energy, material or signals. A representation of the concept of system is depicted in Fig. 1.

Fig. 1. Representation of a system and its functions and relations 3 2. Brief Overview of Integrated systems When we focus on systems such as automobiles, trains, buildings, aircrafts and so on. We realize that the structure presented in the previous section is too simple to describe such a complex artifacts.

If we consider an automobile we can notice that there are several components with different functions and interconnections between each other.The power is generated in the engine and is transferred to the wheels wrought the transmission system. This example shows how inside a system several systems can coexist. Therefore, we can conceptualize those systems as sub-systems of the main system and the relations among them as sub-functions (Fig. 2).

A formal definition for this structure is given by the notion of product architecture introduced by Statesman et al in [3]: "Product architecture in formal terms is defined as how distinct physical modules of a product technically interact in order to obtain a functioning of the whole". Fig. . Representation of a system with its sub-systems and relations 4 3. Overall Picture of Design Process for Systems Integration In order to successfully design and enhance complex systems it is vital to adopt a systematic approach. Systems Engineering Standards can be used as an effective guideline during the design process.

Among the various systems engineering standards, Ella-632 is proposed as a suitable and effective procedure for systems design. Moreover, as stated by Yon et al [4], Ella-632 "defines tasks which are required for doing systems engineering" and the relationships among them.Fig. 3 depicts requirements' interconnections. Fig. 3.

System Design Process of Ella-632 [4] Once the requirements are defined, the design of the components of the artifacts can begin. In the following section two design methodologies applicable for this purpose will be discussed. 4. Design Methods 4. 1 Product Life Cycle Design Method The methodology based on product life cycle (PL) aims to understand the actual need of certain components at each stage during the life of the product.

The methods evolve through three tasks: creation of customer groups, categorize components, understanding components combination. For a more practical understanding, the method will be presented in parallel with a case study of a litigator with a rotary harrow (Fig. 4) as proposed by Auricle [5]. 5 Fig.

4. Cultivator with rotary harrow [5] 4. 1. 1 Task 1: creation of customer groups An effective approach to discern which components are relevant and which can be dismissed, is to divide customers into groups and distinguish which types of application of process the product is applied [5].

Driving the attention on the cultivator case, not all of the customers will apply the cultivator in the same environment. Say for example that some of them, due to different conditions of ground, do not need to grab (phase x) and harrow it (phase y), whereas other customer do. It is straight forward to divide those customers into two groups, customer group 1 and customer group 2, as shown in Fig. 5.

Fig. 5. Customer Group specific PL [5] 4. 1 . 2 Task 2: categorize components A further analysis allows dividing components into two categories: mandatory components and optional components (Fig.

) [5]. Mandatory components are components which without them the product cannot achieve the function it was designed for, whereas the latter are only related to the application intended by the customer [5]. 6 Fig. 6.

Types of physical components [5] 4. 1 . 3 Task 3: understanding components combination A deeper investigation on the components can provide more detailed information about possible combinations, variations (Fig. 6) and interactions between them. As noticed by Auricle [5], "components show decisive dependencies among each other".In other words, it is fundamental to determine whether components entail other sub- components or if components are mutually exclusive.

To illustrate this it is useful to base on the matrix depicted in Fig. 7. When used, it is filled up with Is if the variations are combinable or with So if they are mutually exclusive. Component 1 Component 1 Component 2 Component Component n Component NT 2 Van Component NT Fig.

7. Interdependencies and combination rules matrix Referring to the cultivator, if variant 1 of the rotary harrow is chosen, then variant 1 of threatening mounting is required.Likewise, variant 1 of the three-point mounting causes no restriction in choosing from all the variants of the under frame (Fig. 8) [5]. This allows the company to ease components combination of the same product or of products belonging to the same family.

In conclusion, PL design method, basing on a picture of how the product will be applied and the functions it will be asked to carry out over its life. This allows the company to manufacture and assemble products without creating an excess of components unneeded by different customer groups.Furthermore, when less components are embodied in a product, the overall probability of the system to break decreases. This results in an increased product's life. Furthermore, this method has significant consequences also on the supply chain of the industry in which it is applied. Indeed, manufacturing and assembly plants can be structured according to serve certain customer 7 groups, leading to inventory reduction and logistics optimization because each plant r production center does not need to handle unnecessary components.

Fig. 8.Interdependencies and combination rules of product components [5] 4. 2 Affordable Based Design Method Before going through the methodology it is useful to define what affordable means.

This word was first introduced by the psychologist J. J. Gibson (1979). He referred to all relationships between the environment and an actor. In engineering a definition of affordable was given in 2008 by Maier and Fidel [6].

They defined affordable as "a relationship between two systems in which a potential behavior can occur that would to be possible with either system in isolation".An example is provided by the helmet which affords protection to motorcyclist while he is riding. Tailoring the definition to the scope of designing products, we come across two types of affordable: ; artifact-user performances (ALGA), which describes relations between artifact and user; ; artifact-artifact affordable (AAA), which describes relations between two artifacts. 4.

2. 1 Affordable Based Design Process Like most of design procedures, the affordable-based design process is triggered by a market need.The process proposed by Maier and Fidel [6] goes through six tasks ND it is depicted in Fig. 9 page 9. 4.

2. 2 Affordable Structure Matrices One fundamental tool used in this method is the Affordable Structure Matrix (SAM). It is essentially a variation of the House of Quality. SAM allows to create relations between components of the system and its performances. An example applied to a case study of a vacuum cleaner carried out by Maier and Fidel [6] is shown in Fig. 10 page 11.

The matrix is divided horizontally between ALGA and AAA.Since the purpose of this paper is to introduce methods to design integrated systems, the main focus on the section of the matrix which contains the interrelations among the AAAs and the physical components. This will allow: ; to compare system requirements information with physical structure at the conceptual stage [6]; ; to find out weaknesses of the structure and components; ; to work on weaknesses and enhance the whole artifact. 8 Analyzing the SAM from the "roof" on the top side, we will find the interconnections between physical components.The purpose of the information contained in the roof, is to provide directions to designers when applying changes to the system. Illustrating this, we can refer to Fig.

0 and infer that the belt and brash are in relation. Therefore, a decision to replace the belt with one of a different kind, or to change the transmission technology, should take into account the consequences it will have on the brash. If we drive our attention to the roof on the left side, we can notice that it highlights the relationships among performances.This can be a powerful tool if used attentively.

In fact, it is possible that the changes applied to improve one affordable may bring positive consequences to other performances at the same time. Fig. 9. Overview of the affordable-based design process [6] For the vacuum cleaner example, if we improve the AAA named "loss of calculability by blocked air flow path", we are likely to improve also the "overheating" AAA allowing the air to 9 flow through the system cooling it down. Although, particular attention must be paid in order to avoid a win-lose situation [6].

The inner matrix gathers the type of relationships that exist among components and performances (+ helpful, - harmful, empty for no relations), while the rows on the bottom contains the total of helpful and harmful relationships for each component. If the difference between the two indicators is a negative number, it means that some hangers are needed for those components. Perhaps the most important section of SAM, it is the section on the right side (Fig. 10 page 11). It gathers the sums of helpful and harmful relations caused by the components to each affordable.

Performances in SAM are chosen to focus on what we want the interactions of components to do (AAA +) and what we do not want them to do (AAA-). As a matter of fact, a product needs a variety of components to achieve the overall function it is designed for. Nevertheless, when interacting among each other the components can affect in a negative way mom technical performances. Taking the affordable of overheating as an example from Fig. 10 page 11, we can see that the cell with the red background contains a negative difference.

This means that harmful relationships of the components with this affordable are more than the helpful ones.For example, canister, belt, brush, part behind canister, motor and impeller tend to overheat the system. Thus, these components should be the starting point for redesign. To remedy the situation either new parts can be added [6] or removed. Alternatively a new technology could be used to ameliorate the system. In the final analysis, affordable based design method is an effective approach to systematically analyze products as systems and to provide a picture of how the interrelations occurring among components affect the performances to the users and to the system itself.

Moreover, it helps designers question and work on the fulfillment of the overall functions of the system beyond its mere operation. The information that is obtainable by using this method is relevant for the awareness and the understanding of the overall performances that the systems should fulfill to satisfy customers' needs and integration of components. This is vital for a company to avoid failures, such as product remunerating or recall. 10 Fig. 10.

Affordable structure matrix for a vacuum cleaner [6] 5.Conclusion A fundamental condition for a successful product development is to make decisions and changes in the early stages of the design process. In this paper a brief overview of the concept of system and integrated system has been presented along with two design methods to serve the purpose stated above. Making comparison between the two methods, they show one strength in common: even if with a different approach, they aim to lengthen the life of the product. The PL method allows removing unnecessary components (bottom of Sect. 4.

1 . 1).