title: Investigation into strain propagation to determine preserve regions for compliant mechanisms

authors: Venter, Christoff

subjects: compliant mechanisms

abstract: This thesis aims to improve the theoretical modelling of compliant mechanisms. The
conclusions drawn from this work will help designers understand sources of error associated
with strain propagation when designing with lumped compliance. Compliant mechanisms
have increased in popularity as they allow for designs that feature lower part counts,
increased precision and reduced manufacturing costs. Although using theoretical models
to design compliant mechanisms is a useful tool, there is an assumption that only the
nodes in a compliant mechanism undergo strain. This is not the case. There is strain
occurring outside of the node in a region called the preserve region. The preserve region’s
impact on the theory is greatly under-explored in the literature.
The preserve region’s size, shape, and impact were found and quantified for a range
of critical node types. This was done through the use of FEA software by altering the
model of a simple, compliant mechanism. The size of the preserve region changed based
on the thickness and the fillet used, with an increase of thickness from 4mm to 8mm,
causing the radius of the arc that encompasses the preserve region to grow from 8.5mm to
13mm. The shape was also found to be an ellipse, irrespective of the node’s geometry. The
preserve region’s impact on the theoretical models was also quantified. It was found that
the thickness has the most drastic effect on the compliance values of the node, increasing
the error from 20.53% to 102.18% when the thickness was increased from 4mm to 8mm.
This work shows the importance of considering the preserve region when creating
theoretical models of compliant mechanisms. When properly considered, this research
shows that the error between the theoretical and the FEA values can be greatly reduced.

text: Investigation into strain propagation to determine preserve regions for compliant mechanisms This thesis aims to improve the theoretical modelling of compliant mechanisms. The
conclusions drawn from this work will help designers understand sources of error associated
with strain propagation when designing with lumped compliance. Compliant mechanisms
have increased in popularity as they allow for designs that feature lower part counts,
increased precision and reduced manufacturing costs. Although using theoretical models
to design compliant mechanisms is a useful tool, there is an assumption that only the
nodes in a compliant mechanism undergo strain. This is not the case. There is strain
occurring outside of the node in a region called the preserve region. The preserve region’s
impact on the theory is greatly under-explored in the literature.
The preserve region’s size, shape, and impact were found and quantified for a range
of critical node types. This was done through the use of FEA software by altering the
model of a simple, compliant mechanism. The size of the preserve region changed based
on the thickness and the fillet used, with an increase of thickness from 4mm to 8mm,
causing the radius of the arc that encompasses the preserve region to grow from 8.5mm to
13mm. The shape was also found to be an ellipse, irrespective of the node’s geometry. The
preserve region’s impact on the theoretical models was also quantified. It was found that
the thickness has the most drastic effect on the compliance values of the node, increasing
the error from 20.53% to 102.18% when the thickness was increased from 4mm to 8mm.
This work shows the importance of considering the preserve region when creating
theoretical models of compliant mechanisms. When properly considered, this research
shows that the error between the theoretical and the FEA values can be greatly reduced.

year: 2024

title: Compositional supervisor synthesis with state merging and transition removal

authors: Mohajerani, Sahar

abstract: This working paper proposes a framework to obtain memory-efficient supervisors for large discrete event systems, which are least restrictive, controllable, and nonblocking. The approach combines compositional synthesis and state-based abstraction with transition removal to mitigate the state-space explosion problem and reduce the memory requirements. Hiding and nondeterminism after abstraction are also supported. To ensure least restrictiveness after transition removal, the synthesised supervisor has the form of cascaded maps representing the safe states. These maps have lower space complexity than previous automata-based supervisors. The algorithm has been implemented in the DES software tool Supremica and applied to compute supervisors for several large industrial models. The results show that supervisor maps can be computed efficiently and in many cases require less memory than automata-based supervisors.

text: Compositional supervisor synthesis with state merging and transition removal This working paper proposes a framework to obtain memory-efficient supervisors for large discrete event systems, which are least restrictive, controllable, and nonblocking. The approach combines compositional synthesis and state-based abstraction with transition removal to mitigate the state-space explosion problem and reduce the memory requirements. Hiding and nondeterminism after abstraction are also supported. To ensure least restrictiveness after transition removal, the synthesised supervisor has the form of cascaded maps representing the safe states. These maps have lower space complexity than previous automata-based supervisors. The algorithm has been implemented in the DES software tool Supremica and applied to compute supervisors for several large industrial models. The results show that supervisor maps can be computed efficiently and in many cases require less memory than automata-based supervisors.

year: 2016

title: Kei moenga - Tārā i te ārero. Lest it be severed from the tongue

authors: Bailey, Iraia Thompson

subjects: te reo Māori

abstract: Tūwharetoa are a distinctive tribal group who are located within the central North Island. With a proud and celebrated history, Tūwharetoa evolved through out time to become a complex and unique tribe, containing a number of sub tribes, each with its own authority, structure and land holdings. However, like all Māori, Tūwharetoa were greatly affected by the impact of European colonisation. In particular the unique language and customs of Tūwharetoa where savaged by the policy of assimilation and the introduction of a new language and its cultural beliefs. Presently the traditional language of Tūwharetoa is in a perilous state, and regardless of the many Māori language initiatives that have been established over the past few decades, the special language of Tūwharetoa is declining. This thesis is concerned with understanding the reasons why the traditional language of Tūwharetoa finds itself in this position, while also assessing the initatives implemented by Tūwharetoa to rectify this situation. Furthermore this study will look to create a possible pathway forward for Tūwharetoa to support the regeneration and revitalisation of the language. Ultimately this thesis will propose a framework bedded within language planning theory, supported by a kaupapa Māori research methodology and founded within the beliefs of Tūwharetoa, to see the return of te reo Māori as the main form of communication for the people of Tūwharetoa, and as a clear marker of our identity and uniqueness.

text: Kei moenga - Tārā i te ārero. Lest it be severed from the tongue Tūwharetoa are a distinctive tribal group who are located within the central North Island. With a proud and celebrated history, Tūwharetoa evolved through out time to become a complex and unique tribe, containing a number of sub tribes, each with its own authority, structure and land holdings. However, like all Māori, Tūwharetoa were greatly affected by the impact of European colonisation. In particular the unique language and customs of Tūwharetoa where savaged by the policy of assimilation and the introduction of a new language and its cultural beliefs. Presently the traditional language of Tūwharetoa is in a perilous state, and regardless of the many Māori language initiatives that have been established over the past few decades, the special language of Tūwharetoa is declining. This thesis is concerned with understanding the reasons why the traditional language of Tūwharetoa finds itself in this position, while also assessing the initatives implemented by Tūwharetoa to rectify this situation. Furthermore this study will look to create a possible pathway forward for Tūwharetoa to support the regeneration and revitalisation of the language. Ultimately this thesis will propose a framework bedded within language planning theory, supported by a kaupapa Māori research methodology and founded within the beliefs of Tūwharetoa, to see the return of te reo Māori as the main form of communication for the people of Tūwharetoa, and as a clear marker of our identity and uniqueness.

year: 2013