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During the first half of the last century, many navigation locks have been built
throughout the Netherlands. In the coming decades, approximately fifty navigation
locks have to be thoroughly renovated or replaced. Historically, locks have been
built using an Engineer-to-Order production strategy. This has resulted in a large
variety of lock designs, which is considered to be inefficient from the viewpoint
of design, construction, and maintenance. Therefore, Rijkswaterstaat (RWS), the
executive branch of the Dutch Ministry of Infrastructure and Water Management, is
developing a modularization and standardization strategy for locks. By doing so, RWS
aims to increase the efficiency of the replacement task and simultaneously increase
lock reliability and availability (RA), decrease life-cycle-costs (LCC), and decrease
uncertainty in construction costs and time.
This thesis contributes to the objectives of RWS by exploring methods for designing
a lock product platform. Product platforms are commonly used as part of Make-to-
Order and Configure-to-Order production strategies. Such a platform forms the basis
for the development of customized products from (semi-) standardized component
modules to meet specific customer needs.
It is proposed to create a lock product platform composed of fully-, semi-, and
non-standardized component modules. The platform distinguishes between basic
modules and optional modules. Basic modules are groups of components that are
always present in any lock. Optional modules are groups of components that are only
occasionally present in a lock. RWS can use this platform for the efficient development
of (semi)-standardized locks that meet location specific requirements and constraints.
The first part of this thesis explores the feasibility of the lock product platform
proposition given the existing design variety within the current lock portfolio of RWS.
The extent of the design variety is studied using a characteristic matrix, mapping locks
to lock characteristics, and a similarity matrix, showing the similarity between locks
based on the characteristics they possess. Clustering the similarity matrix reveals the
existence of seven groups of locks that share the same characteristics.
Subsequently, the commonality among the seven groups is investigated using the
dependency structure matrix (DSM) method. A DSM is an N × N matrix showing
dependencies, such as energy or information transfer, between N components. By
analyzing the network of dependencies between components one can find component
modules that have many internal dependencies, but relatively few external dependencies.
What is more, engineering systems typically contain component modules that have
many dependencies across the whole system, which are so-called ‘busses’. This thesis
presents a novel DSM clustering algorithm to efficiently find the bus and non-bus
component modules within the network of component dependencies.
Multiple DSMs have been made for representative locks from the different groups,
using available engineering data and expertise about the as-built locks. Subsequently,
a so-called DSM is obtained by summing the DSMs of the individual locks. The
clustering results are used to determine how best to modularize the locks and to
determine which modules are basic modules and which are optional modules.
By projecting (qualitative) RA and LCC data onto the DSM, the modules that
have a significant impact on RA and LCC of the whole lock portfolio are identified.
These modules are primary candidates for standardization in the lock product platform.
The second part of this thesis focuses on methods for creating function- and designspecifications
for the identified lock platform modules. Rijkswaterstaat outsources the
design and construction of locks. To ensure that future locks will meet the predefined
standards and interfaces dictated by the lock platform, detailed specifications need to
be created for each of the component modules. The consistency of such specifications is
essential to ensure the compatibility of the different modules and to prevent costly and
lengthy design iterations. The thesis presents a novel systems engineering language
for writing function and design specifications.
One of the key concepts of the language is a prescribed grammar for goal-functions,
which describe the functional purpose of components with respect to each other, and for
transformation-functions, which describe the internal workings of a component. This
concept has been developed further into the Elephant Specification Language (ESL),
which allows for the creation of function and design specifications in terms of needs,
requirements, and constraints at multiple granularity levels, following the systems
engineering V-model. The system decomposition tree forms the central structure of an
ESL specification. The needs, requirements, and constraints are specified within the
body of component definitions. ESL has a fixed syntax and semantics and supports
the formal derivation of dependencies between components, needs, requirements,
constraints, variables, and combinations thereof throughout the branches and layers of
the system decomposition tree.
The future locks have to meet additional function and design requirements compared
to existing locks. What is more, RA data of existing locks may not be representative
for future locks due to advancements in technology. Therefore, the thesis presents a
method to identify critical components with respect to RA based on the network of
dependencies between components derived from the specification. Critical components
require extra attention during design and construction.
A case study on the Princess Marijkesluizen renovation project shows that ESL
can be effectively used to create structured system specifications. By clustering and
visualizing dependencies between components, between functions, and combinations
thereof in a multi-domain-matrix (MDM), one can gain insight in the lock architecture,
in the lock function chains, and determine which parts of the lock architecture and
function chains are affected by the renovation.