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Proceedings in Manufacturing Systems, Volume 6, Issue 1, 2011 ISSN 2067-9238 KNOWLEDGE BASED ENGINEERING – AN APPROACH VIA AUTOMATED DESIGN OF STORAGE/RETRIEVAL SYSTEMS Christian LANDSCHUETZER 1,* , Dirk JODIN 2 , Andreas WOLFSCHLUCKNER 3 1) DI Dr. techn., workgroup leader, TU Graz, Institute for Logistics Engineering ITL, Graz, Austria 2) Prof. Dr.-Ing. habil., head of ITL, TU Graz, Institute for Logistics Engineering ITL, Graz, Austria 3) DI, PhD candidate, TU Graz, Institute for Logistics Engineering ITL, Graz, Austria Abstract: Expanding markets and flexible commercial structures (e-commerce) generate various logistic demands and force manufacturers to offer diverse material handling equipment. To fulfill this demands specially the design process must be straight forwarded to minimize developing time, as most of the whole costs to produce a new product are settled here. Automated storage/retrieval systems (AS/RS) are back- bones of many distribution centers and widespread. As they have lots of common attributes and nearly equal characteristics, they are predestinated for knowledge based techniques. The paper now describes knowledge based engineering in general and its additional value and focuses on a practical design of an AS/RS. The main describing equations are derived and the realization in ProEngineer is presented. Key words: KBE, knowledge based engineering, CAD, CAE, PLM, logistics, logistics engineering, AS/RS, material handling equipment, automated generation 1. INTRODUCTION, MOTIVATION, THE FIELD OF MATERIAL HANDLING DESIGN 1 Nowadays social consumerism demands new and up- dated products, shorter product life cycles and increasing variety. Production systems therefore have to be custom- ized, following those trends, and must handle frequent product changes, multiple variations and must bear the cost pressure. For supporting Material Flow Systems this means high flexibility, adaptability and high efficiency. Hence the design process of such systems and basic ma- chinery has to be innovative, cost efficient and fast, in- volving new technologies to develop new solutions. At the Institute of Logistics Engineering the design experts team is focussing and implementing a promising pretty new approach via Knowledge-Based-Engineering (KBE). The typical use case within classic design is adapted for further fields of appliance. Material Handling System design and layouting is often not more than ap- plication of predefined rules for design, calculation schemes and standards. Their integration into the engi- neering process brings reduction of costly tasks and minimizes the risk of failures. Designing a Material Han- dling System means applying rules, schemas and stan- dards beside taking the engineers capabilities concerning creativity and experience into account. Dimensioning of ails, shelves, storage buffers and standard techniques are only a few good working examples. Applying KBE prin- * Corresponding author: TU Graz, Institute of Logistics Engineering ITL, Graz Austria Tel +43 (316) 873 7325 Fax +43 (316) 873 107325 E-mail: [email protected] (C. Landschuetzer), [email protected] (A. Wolfschluckner), Web: www.itl.tugraz.at ciples here leads towards Knowledge Based Planning (KBP). Within this article the specific realization of a KBE approach for developing AS/RS is shown as well as common use cases and methods are described. KBE opens wide ranging advantages for Material Handling Design which is described here, with details of the design process and its influencing factors. Further research topics are settled at the Institute of Logistics Engineering, dealing with KBE and design process optimization for different Material Handling Equipment such as Autonomous Guided Vehicles (AGV), Rope Drums of Cranes and more. 2. KNOWLEDGE BASED TECHNOLOGIES FOR DESIGN PURPOSES Before focusing on KBE theory and extended use it’s adequate to describe the main achievements and actual state of art by KBE in engineering business. To keep business successful many major companies are investing in the use of KBE as a powerful factor of success as can be seen from historical development. Global emerging markets with global resources – specially engineering capacities – force manufacturers of nearly all branches to reduce their production costs. Keeping business local is therefore not the best choice to keep up with low wages as paid in some Asia regions. On another side advance in engineering is what differs European sites from many others but is only possible with highly qualified employees who are loyal to their company. These and many other challenges in engineer- ing business lead to some new approaches in engineering such as Knowledge Based Engineering (KBE) to ensure local business and to keep advance into one’s own com- pany.

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Page 1: KNOWLEDGE BASED ENGINEERING – AN APPROACH VIA …

Proceedings in Manufacturing Systems, Volume 6, Issue 1, 2011

ISSN 2067-9238

KNOWLEDGE BASED ENGINEERING – AN APPROACH VIA AUTOMATED DESIGN OF STORAGE/RETRIEV AL SYSTEMS

Christian LANDSCHUETZER 1,*, Dirk JODIN 2, Andreas WOLFSCHLUCKNER 3

1) DI Dr. techn., workgroup leader, TU Graz, Institute for Logistics Engineering ITL, Graz, Austria

2) Prof. Dr.-Ing. habil., head of ITL, TU Graz, Institute for Logistics Engineering ITL, Graz, Austria 3) DI, PhD candidate, TU Graz, Institute for Logistics Engineering ITL, Graz, Austria

Abstract: Expanding markets and flexible commercial structures (e-commerce) generate various logistic demands and force manufacturers to offer diverse material handling equipment. To fulfill this demands specially the design process must be straight forwarded to minimize developing time, as most of the whole costs to produce a new product are settled here. Automated storage/retrieval systems (AS/RS) are back-bones of many distribution centers and widespread. As they have lots of common attributes and nearly equal characteristics, they are predestinated for knowledge based techniques. The paper now describes knowledge based engineering in general and its additional value and focuses on a practical design of an AS/RS. The main describing equations are derived and the realization in ProEngineer is presented. Key words: KBE, knowledge based engineering, CAD, CAE, PLM, logistics, logistics engineering, AS/RS,

material handling equipment, automated generation 1. INTRODUCTION, MOTIVATION, THE FIELD

OF MATERIAL HANDLING DESIGN 1

Nowadays social consumerism demands new and up-dated products, shorter product life cycles and increasing variety. Production systems therefore have to be custom-ized, following those trends, and must handle frequent product changes, multiple variations and must bear the cost pressure. For supporting Material Flow Systems this means high flexibility, adaptability and high efficiency. Hence the design process of such systems and basic ma-chinery has to be innovative, cost efficient and fast, in-volving new technologies to develop new solutions.

At the Institute of Logistics Engineering the design experts team is focussing and implementing a promising pretty new approach via Knowledge-Based-Engineering (KBE). The typical use case within classic design is adapted for further fields of appliance. Material Handling System design and layouting is often not more than ap-plication of predefined rules for design, calculation schemes and standards. Their integration into the engi-neering process brings reduction of costly tasks and minimizes the risk of failures. Designing a Material Han-dling System means applying rules, schemas and stan-dards beside taking the engineers capabilities concerning creativity and experience into account. Dimensioning of ails, shelves, storage buffers and standard techniques are only a few good working examples. Applying KBE prin-

* Corresponding author: TU Graz, Institute of Logistics Engineering ITL, Graz Austria Tel +43 (316) 873 7325 Fax +43 (316) 873 107325 E-mail: [email protected] (C. Landschuetzer), [email protected] (A. Wolfschluckner), Web: www.itl.tugraz.at

ciples here leads towards Knowledge Based Planning (KBP).

Within this article the specific realization of a KBE approach for developing AS/RS is shown as well as common use cases and methods are described. KBE opens wide ranging advantages for Material Handling Design which is described here, with details of the design process and its influencing factors.

Further research topics are settled at the Institute of Logistics Engineering, dealing with KBE and design process optimization for different Material Handling Equipment such as Autonomous Guided Vehicles (AGV), Rope Drums of Cranes and more.

2. KNOWLEDGE BASED TECHNOLOGIES FOR

DESIGN PURPOSES

Before focusing on KBE theory and extended use it’s adequate to describe the main achievements and actual state of art by KBE in engineering business. To keep business successful many major companies are investing in the use of KBE as a powerful factor of success as can be seen from historical development.

Global emerging markets with global resources – specially engineering capacities – force manufacturers of nearly all branches to reduce their production costs. Keeping business local is therefore not the best choice to keep up with low wages as paid in some Asia regions. On another side advance in engineering is what differs European sites from many others but is only possible with highly qualified employees who are loyal to their company. These and many other challenges in engineer-ing business lead to some new approaches in engineering such as Knowledge Based Engineering (KBE) to ensure local business and to keep advance into one’s own com-pany.

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12 C. Landschuetzer, D. Jodin and A. Wolfschluckner

Fig. 1. Product cost related to the design process

2.1. Design work

Focusing later on the main benefits of KBE [2] in diferent areas it is first to outline engineering deToday’s developing process is multidisciplinary with many different CAx tools and special methods, where data preprocessing is often more timethe analyzing process itself. The engineer is therefore confronted with an increasing number of refrom different fields of mechanical engineering. spread suppliers’ product information has multiple fomats and is often more than pure geometry. Constantly changing technologies force engineers to readjust their work flow to new methods. So the main challenge and question is how to become better products in shorter time with lower resources.

The very best actual answer is KBE with credo: Data must become information.possible, to automate engineering processes (not onlCAD donkeywork) and to arrange engineering work as a flow driven process with dependency relations and dnamic evolving, advance is guaranteed, as the main costs are determined by concept design but really ariseduction as incurred costs (Fig. 1 [7]). According to only 25 % of the complete design knowledge for efficient product development and production has to feed a KBE system by determining nearly 75 % of all costs acceptable relation between effort and benefit.now a tool in use to generate much more different prouct configurations during an early stage of development brings optimized costs and functions of products.

KBE tries to collect all information available in the product lifecycle to make it reusable. Itable to merge capabilities of conventional Knowledge Based Systems with those of Computer Aidedand Engineering. Hence it has to be a blend of artificial intelligence, CAD, mechanical engineering knowand software engineering in its most sophisticated occurence. As a young discipline with still developing and refining methods its most dramatic impact would be the automated generation of a KBE application basing on general knowledge, collected in various knowledge maagement systems, closing the gap between knowlmanagement and engineering.

2.2. Design work – historic development

Having such sublime goals in focus than described above, it is necessary to describe the actual stage and the historical development of KBE techniques

C. Landschuetzer, D. Jodin and A. Wolfschluckner / Proceedings in Manufacturing Systems, Vol. 6, Iss

Product cost related to the design process [7].

Focusing later on the main benefits of KBE [2] in dif-ferent areas it is first to outline engineering design work.

developing process is multidisciplinary with many different CAx tools and special methods, where

time-consuming than The engineer is therefore

confronted with an increasing number of requirements from different fields of mechanical engineering. Wide-

product information has multiple for-mats and is often more than pure geometry. Constantly changing technologies force engineers to readjust their

the main challenge and better products in shorter time

The very best actual answer is KBE with its main t become information. If it becomes

possible, to automate engineering processes (not only CAD donkeywork) and to arrange engineering work as a flow driven process with dependency relations and dy-namic evolving, advance is guaranteed, as the main costs

really arise in pro-According to Fig. 1

only 25 % of the complete design knowledge for efficient product development and production has to feed a KBE system by determining nearly 75 % of all costs – a pretty

tion between effort and benefit. Having to generate much more different prod-

early stage of development costs and functions of products.

KBE tries to collect all information available in the product lifecycle to make it reusable. It is a technology able to merge capabilities of conventional Knowledge

Computer Aided Design . Hence it has to be a blend of artificial

AD, mechanical engineering know-how ost sophisticated occur-

rence. As a young discipline with still developing and refining methods its most dramatic impact would be the automated generation of a KBE application basing on general knowledge, collected in various knowledge man-

losing the gap between knowledge

historic development

Having such sublime goals in focus than described necessary to describe the actual stage and the

historical development of KBE techniques [1].

Fig. 2. Historical development

As with first 2D-CAD-systems engineering work got

more effective, first systems where introduced in the 1970s in form of selection criteria for geometry reprduction like nowadays common used Also within those static approaches to technical drawing (as 2D-CAD can be seen) easy calculation procedures where integrated into the CAD environment i.e. for caculating shaft diameters from simple stress calculations and more. A major step was the next evolution which can be seen in parametric modeling. element and part libraries for often used standard parts the parametric system enables and assembly changes by simple modification of ulying dimensions and design variables (but it must be said that those simple sounding procedure is one of the major challenges in the design process model non corrupt during the change processes, which can be launched by different users).ogy complements the parametric approach by providing macro-like commands for widely used design operations.

At the very end there is one last system which is staic, passive and non-reactive as well as all tioned above. These approachesnamed as augmented CAD – feed the feature technology with easy calculation and validation results from CADintern computing, provided by captured knowledge from simple and easy design work. It is quasi an expert system of best practice within the CAD environment, supporting the design engineer with suggestions for his work. This approach can also be seen in some CAE tools for simultion content management and template based simulation scripts, trying to guarantee proofed procprocessing, solving and postuser’s possibilities to a necessary minimum. according to the authors view –level of KBE complexity fulfilling Material Handling Systems Design as in chapters

2.3. KBE systems – an overview

As seen from the historical development there are KBE systems integrated within CAD environment on the one hand (“augmented CAD”) from aerospace and automotive industrysystems (realized via object oriented special software tools) on the other hand. This section

Iss. 1, 2011 / 11−18

development of CAD and KBE.

systems engineering work got more effective, first systems where introduced in the 1970s in form of selection criteria for geometry repro-duction like nowadays common used copy/paste (Fig. 2). Also within those static approaches to technical drawing

CAD can be seen) easy calculation procedures where integrated into the CAD environment i.e. for cal-culating shaft diameters from simple stress calculations

the next evolution which can be seen in parametric modeling. Instead of storing large element and part libraries for often used standard parts

ric system enables − until now − geometry and assembly changes by simple modification of under-

ing dimensions and design variables (but it must be said that those simple sounding procedure is one of the major challenges in the design process – holding the model non corrupt during the change processes, which can be launched by different users). The feature technol-ogy complements the parametric approach by providing

like commands for widely used design operations. At the very end there is one last system which is stat-

as well as all systems men-approaches for KBE – sometimes

feed the feature technology with easy calculation and validation results from CAD-intern computing, provided by captured knowledge from simple and easy design work. It is quasi an expert system

st practice within the CAD environment, supporting the design engineer with suggestions for his work. This approach can also be seen in some CAE tools for simula-tion content management and template based simulation scripts, trying to guarantee proofed processes for pre-processing, solving and post-processing isolating the

possibilities to a necessary minimum. This is – – the affordable and useful

level of KBE complexity fulfilling Material Handling 3 and 4.

an overview

As seen from the historical development there are KBE systems integrated within CAD environment on the

(“augmented CAD”) and as an actual trend from aerospace and automotive industry “full KBE”

tems (realized via object oriented special software tools) on the other hand. This section here now tries to

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C. Landschuetzer, D. Jodin and A. Wolfschluckner / Proceedings in Manufacturing Systems, Vol. 6, Iss. 1, 2011 / 11−18 13

differ between them by only introducing the methodolo-gy behind full KBE in form of MOKA [3, 4] and not focusing on software details. There are attempts to stand-ardize KBE development via the creation of a common language, following the trend that CAD becomes more knowledge based with convergence of KBE and Product Lifecycle Management PLM [6]. Problems resulting from data conversion between CAD and CAE, producing large efforts as described in [12] by introducing a com-mon data model, are not taken into concern here.

Augmented CAD systems with KBE are found in many different CAD environments and have different scopes of operation [5]. Well known commercial prod-ucts are Knowledge Ware within CATIA and Knowledge Fusion within NX [2]. But all approaches together have some common characteristics:

• No full generative modeling and therefore manual adjusting effort.

• No exploitation outside their KBE language and therefore not web-based frameworks.

• Lots of editing effort and “unfriendly” scripting lan-guages.

• They only do better donkeywork and are non-reactive to new technologies.

But beside all those factors of limitation it’s always a decision with consideration of intellectual and monetary effort, which features are must haves and which are addi-tional. An investment into a full KBE system is nowa-days only seen in automotive and aeronautic sectors [8] with their fast innovation times as subsumed in the fol-lowing statements [2]:

“Jaguar cars reduced the design time for an inner bonnet from 8 weeks to 20 minutes.”

“British Aerospace reduced the design time of a wing box from 8000 hours to 10 hours.”

Full KBE systems are object oriented highly advanced generic and super ordinated software programs which apply captured knowledge to design processes by using different visualization tools [1]. The systems must drive the way of design automatically by using various valida-tion rules and should not criticize pre-generated results leading towards engineering process automation. Object oriented KBE now means inheritance from classes of objects and customization of very unified models, fol-lowing the classical tree structure (Bill of material - BOM). Depending on the state of detail regeneration must not follow every modification (i.e. FEM meshes must not regenerate during design work). To visualize dependency relationships the hierarchical tree is used (comparable to BOM) with its physical properties via objects and sub objects. Design modeling uses feature based solid modeling engines with different stages of detail and various representation methods (detailed prop-erties automatically derive with evolving design process, i.e. step by step consideration of sizing, manufacturing and refining, using various levels of representation). Beside those design modeling steps there are tasks of optimization, documentation and presentation to handle. At the optimization tasks different environments of CAE must seamlessly integrate into a unified model with au-tomated data flow to manage releases and store configu-rations.

To understand KBE functionality the development process and major steps for the KBE development is described here, following the Methodology and tools Oriented to KBE Applications – MOKA [3, 4, 11] (used for development of the commercial software PCPACK [13] and used by Airbus and Fokker; with aerospace industry as one of KBE key user [9]) is described here.

MOKA is a standardized method from the late 1990s to reduce lead times and costs of KBE development. It provides a methodology to provide a consistent way of developing and maintaining KBE systems [2]. It is struc-tured in six phases: • Identify: defining scope and purpose of KBE with

assessing the technical feasibility. • Justify: assesses the risk, estimates resources and

costs and develops business cases. • Capture: means knowledge acquisition from experts

to create an informal model as a structured represen-tation of forms. This informal model can be used to create a knowledge management (KM) and splits up into an informal product model (representing the product structure with constraints) and an informal process model which captures design engineers activ-ities and all rules of each stage.

• Formalize: uses the informal model from the captur-ing process. To build the formal model it’s necessary to use a graphical, object oriented representation of engineering knowledge one level above application code, written in the modeling language i.e. MML the MOKA Modeling Language. The formal product model specifies the knowledge items from informal model with different views focusing on structure, function, behaviour, technology and geometric repre-sentation. The design process model is the process flow of the KBE system taking into account the con-straints, the operating system and the types of special-ists involved in the process.

• Package: means generating, testing and debugging code of the formal models.

• Activate: means distribution of the KBE system to end-users and training. Having all those features in mind it’s next, to merge

all general tasks to specific Material Handling Design.

2.4. KBE for Material Handling Equipment

Some general demands of KBE for SMEs (as most manufacturers of material handling equipment do not have as much engineering stuff than automotive or aero-space companies they are therefore typical SMEs) as a first approach are described in [10] using geometry based design rules and constraints and no evolution.

What KBE means within Material Handling Equip-ment Design (MHED) is best shown in Fig. 3. Specifying input parameters in form of rules and constraints classes for KBE in MHED. Some fuzzy criteria such as shape design, leading to customer acceptance or not, and sys-tem integration are relevant as well as the “harder” facts concerning manufacturing and costs, which can be for-mulated within rules much more easy. As every MHE is determined by the demands of throughput (in tons or pieces per hour) it is necessary, to define throughput as the major input parameter. All other classes derive direct-

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14 C. Landschuetzer, D. Jodin and A. Wolfschluckner

ly therefrom as especially all rules and constraints for design and engineering/sizing. Therein standards have to be considered as well as know- how of employees for i.e. variant management using carry-overcosts and stock for production. Taking all those input together leads to a KBE system of whatever enviroment, containing a set of rules and constraints settled around the BOM and its underlying product structure.

Key feature is the reliable function otomated design, providing the designer with additional information for geometry design. There he gets infomation about minimal sizes resulting from stress calcultions, information about useable space and interface connections all from as less as possible input parameters (throughput, storage capacity…). Having in mind, that this approach is settled around augmented systems it’s not the main objective, to get fully automaed design with generative modeling. Also the knowledge reuse is limited, as many of the rules have to be written in CAD scripting language without export functions!

Altogether leads to major improvements in the design workflow for MHE and last but not least to better proucts with less development effort and better ness So manufacturers are able to fulfill customer dmands much more easy and to react faster on new trends, offering tailored products. Higher innovation is guarateed, as the design engineer is unburdened from daily

Fig. 3. KBE for material handling equipment

C. Landschuetzer, D. Jodin and A. Wolfschluckner / Proceedings in Manufacturing Systems, Vol. 6, Iss

ly therefrom as especially all rules and constraints for design and engineering/sizing. Therein standards have to

how of employees for i.e. over-parts to reduce

costs and stock for production. Taking all those input together leads to a KBE system of whatever environ-ment, containing a set of rules and constraints settled around the BOM and its underlying product structure.

Key feature is the reliable function of the partly au-, providing the designer with additional

information for geometry design. There he gets infor-mation about minimal sizes resulting from stress calcula-tions, information about useable space and interface

ess as possible input parameters ). Having in mind, that

this approach is settled around augmented CAD KBE systems it’s not the main objective, to get fully automat-

Also the knowledge s limited, as many of the rules have to be written

in CAD scripting language without export functions! Altogether leads to major improvements in the design

workflow for MHE and last but not least to better prod-better cost aware-

So manufacturers are able to fulfill customer de-mands much more easy and to react faster on new trends, offering tailored products. Higher innovation is guaran-

unburdened from daily

donkeywork in his CAD environment and can focus on creative design approaches. Taking total cost of owneship into account, the investment for building up the KBE system will return soon (see

3. KBE OF AN AS/RS

Storage and retrieval systems are the meaning of design and engineering approach. The rate of really new designs is very low. The main engneering task is adapting existing solutions to new prolems. For storage and retrieval devices, this means an adjustment with respect to the geometric and drive dmensions. This leads to an augmented CADproach demonstrated in Fig. 4.

The user has not to be an especially skilled engineer (certainly the deeper sense of KBE). The only user task is to input the customer requests intool for engineering calculations with implemented dsign rules is evaluating all geometric parameters to maage the parametric CAD assembly. At this stage it is necessary to establish more parameters, relations and conditions in the CAD – system, to handle the automatic generation of the AS/RS model. Now suitable templates are used for creating result data required for manufactuing. But the results are not only for also valuable for visualization,tinuative analysis like FEM

KBE for material handling equipment – demands, features, benefits

Iss. 1, 2011 / 11−18

environment and can focus on Taking total cost of owner-

ship into account, the investment for building up the (see Eq. (1) in chapter 2.4).

Storage and retrieval systems are typical for MHE in the meaning of design and engineering approach. The rate of really new designs is very low. The main engi-neering task is adapting existing solutions to new prob-lems. For storage and retrieval devices, this means an

t to the geometric and drive di-mensions. This leads to an augmented CAD KBE ap-

4. not to be an especially skilled engineer

certainly the deeper sense of KBE). The only user task is to input the customer requests into KBE Software. Now a tool for engineering calculations with implemented de-sign rules is evaluating all geometric parameters to man-age the parametric CAD assembly. At this stage it is necessary to establish more parameters, relations and

system, to handle the automatic generation of the AS/RS model. Now suitable templates are used for creating result data required for manufactur-ing. But the results are not only for production. They are also valuable for visualization, layout planning and con-

or multi-body simulations.

benefits.

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C. Landschuetzer, D. Jodin and A. Wolfschluckner / Proceedings in Manufacturing Systems, Vol. 6, Iss. 1, 2011 / 11−18 15

Fig. 4. Sequence of events diagram for an AS/RS KBE SW.

At this point it should be noted that iterations for finding a final solution are essential (e.g. mass properties). 3.1. Dimensioning an AS/RS

The core of the software is the dimensioning unit. All the engineering know-how concerning dimensioning the components of an AS/RS is implemented in this program describing classes of rules (Fig. 3). Three calculating procedures following the input data for length, height, etc. are accomplished in this software:

• Evaluating the drive power (traction drive, lift drive) and whether or not anti-oscillating drive is necessary (depending mainly from mast height) using FEM 9.311 guidelines [14].

• Sizing of the machine elements (geared belts, bear-ings, gear boxes, screws …) using manufacturers’ in-structions and engineer standards.

• Dimensioning of beams, sheet metals, shafts, welding seams, …( e.g. using DIN 743 – strength analysis of fatigue and static failure with consideration of notch effects, influence of size and surface hardening [15]).

To perform this calculations the knowledge of internal forces for static and dynamic conditions of the compo-nents is needful. In Fig. 6, the procedure for gathering the free body diagram for the main components is shown (dynamic conditions; two drive directions – black and blue variables). Starting with the whole AS/AR the com-ponents are cut free step by step considering gravity-, load- and mass forces. Different load cases must be con-

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sidered. These cases are combinations of direction of acceleration, load height and several ways to control the drives (e.g. anti-oscillating drive yes/no). In Fig. 6, this process is performed for the load handling device, the lift belt and the running gear. Of course this approach has to be refined until the free body diagram of every machine element is achieved.

With the internal forces the stress resultants in the components can be evaluated and accordingly the main dimensions which control the CAD model. 3.2. Integration of Dimensioning into CAD

For implementing the data calculated by the dimen-sioning software into CAD, a capable interface is impor-tant.

In this special case using Mathcad (www.ptc.com) and Pro/Engineer (www.ptc.com) a data interchange is possible in the way of applying analysis features in Pro/E

to parts using particular declarations of the variable names in Mathcad whose numerical values are a result of the dimensioning process. So it is possibly to use the Mathcad Parameters in the parametric environment of Pro/Engineer and establish a connection between dimen-sioning Software and skeleton dimensions in CAD. The Mathcad Parameters are also applicable in parametric relations for achieving geometric constraints. Figure 5 is showing some of the main parameters (d1, d2, d3…) for managing the AS/RS assembly. Under the rules of Top-Down design the following information (parameter) flow underlies the CAD Model:

• Parameters from Dimensioning SW. • Skeleton/Relations. • Dimensions / Geometric Constraints. • AS/RS Assembly. • AS/RS Parts.

Fig. 5. Main control dimensions of the assembly.

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Fig. 6. Internal forces in an AS/RS.

Fig. 7. KBE process for an AS/RS.

4. SPECIFIC SCENARIO

Going through the AS/RS-KBE process step by step using a specific scenario will show how the AS/RS model works. A main element for demonstrating the model features is the BOM (Bill of Materials) which is the central unit in Fig. 7, which shows the KBE process. Starting with the users input and the dimensioning step the assembly control structure is illustrated. A system of relations and skeleton guarantees the independency of the AS/RS parts and subassemblies. That means changing on

parts dimensions or replace a part have no effect on other components. But higher ranked control mechanisms ensure a consistent Model without failure (Top-Down method).

In Fig. 7, the skeleton for the running gear consisting of curves, planes, axis and reference points is reflected. Skeletons are very useful for transferring e.g. geometric shapes to parts. Other control mechanisms are mathe-matical relations. For e.g. the relations for the running wheel are considering two different designs depend from

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wheel diameter by using an if-condition. Higher level relations are also used for replacing or supressing com-ponents. That means parameters evaluated from the di-mensioning software are allowed to changing the struc-ture of the BOM.

So parametric tools in CAD like skeletons, relations and family tables in combinations with some sort of dimensioning software is a proper way for realizing a AS/RS Model with KBE features.

The real challenge is to find a proper degree of auto-mation for the KBE-Model. It is not always the best way to create a fully parameterized assembly. Addicted from time to create a KBE model (tK), the time to create a conventional CAD assembly (tC) and the number of re-quired design variants (nV) a simple relation can be ex-pressed:

C

KV t

tn ≤ . (1)

Considering this constraint it is sometimes an appro-

priate solution automating only parts of a model. Expert knowledge is not only necessary for building the model but also to decide about wise adoption of KBE tools.

The developed AS/RS model can be implemented into an all-embracing KBE and KBP tool for logistic system planning. Such a system is able to choose aisle widths, number of shelves, shelf size and the number of AS/RS units with a few input parameters like type, quan-tity and throughput of the stored wares in the right way. The Institute of Logistics Engineering is doing basically new research on KBE based planning tools for ware-houses. 5. SUMMARY AND OUTLOOK

The article describes the use of KBE systems for en-gineering work in Material Handling Equipment Design. By giving an overview of KBE state of the art it focuses on an augmented CAD KBE system for Material Handling Equipment to hold balance between effort and benefit. Applying all general rules and demands de-scribed leads to a specific use case of KBE for automated design of automated storage and retrieval systems, pro-viding the design engineer with major sizing dimensions for critical parts, defining available spaces and specifying interface connections.

This leads towards shorter development cycles and tailored products, to fulfil customer’s ambitious demands fast, cost effective and reliable within constantly chang-ing environments. Beside shortening development times dramatically it brings reliability to engineering work by standardized application of predefined and validated processes. KBE unburdens the design engineer from daily donkeywork in CAD and converting procedures for CAE, generating the necessary freedom for invention and innovation.

One major challenge of future work with KBE within Material Handling Equipment Design is to make static captured knowledge within CAD systems and specific CAD assemblies reusable by feeding general knowledge systems and generating interconnections between the sometimes differing disciplines CAD vs. KM.

At the Institute of Logistics Engineering at Graz Uni-versity of Technology we have a unique combination of design experts (very experienced in CAD and CAE with FEM and MBS) with planning and material flow layout-ing experts who are consequently bringing forward new technologies such as KBE in the Material Handling Equipment Design business, not forgetting the all deter-mining demands from logistic material flow. This com-bined field of engineering is enhancing constantly here, applying the knowledge and developing new methods for further engineering work for Material Handling Equip-ment. Altogether leads towards Knowledge Based Plan-ning, enlarging KBE to the general material flow are to fulfil the demands of tomorrow’s logistic business!

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