Accomplishing task-invariant assembly strategies by means of an inherently accommodating robot arm

Despite the fact that the main advantage of robot manipulators was always meant to be their flexibility, they have not been applied widely to the assembly of industrial components in situations other than those where hard automation might be used. We identify the two main reasons for this as the 'fragility' of robot operation during tasks that involve contact, and the lack of an appropriate user interface. This thesis describes an attempt to address these problems.We survey the techniques that have been proposed to bring the performance of cur¬ rent industrial robot manipulators in line with expectations, and conclude that the main obstacle in realising a flexible assembly robot that exhibits robust and reliable behaviour is the problem of spatial uncertainty.Based on observations of the performance of position-controlled robot manipulators and what is involved during rigid-body part mating, we propose a model of assembly tasks that exploits the shape invariance of the part geometry across instances of a task. This allows us to escape from the problem of spatial uncertainty because we are 110 longer working in spatial terms. In addition, because the descriptions of assembly tasks that we derive are task-invariant, i.e. they are not dependent on part size or location, they lend themselves naturally to a task-level programming interface, thereby simplifying the process of programming an assembly robot.the process of programming an assembly robot. However, to test this approach empirically requires a manipulator that is able to control the force that it applies, as well as being sensitive to environmental constraints. The inertial properties of standard industrial manipulators preclude them from exhibiting this kind of behaviour. In order to solve this problem we designed and constructed a three degree of freedom, planar, direct-drive arm that is open-loop force-controllable (with respect to its end-point), and inherently accommodating during contact.In order to demonstrate the forgiving nature of operation of our robot arm we imple¬ mented a generic crank turning program that is independent of the geometry of the crank involved, i.e. no knowledge is required of the location or length of the crank. I11 order to demonstrate the viability of our proposed approach to assembly we pro¬ grammed our robot system to perform some representative tasks; the insertion of a peg into a hole, and the rotation of a block into a corner. These programs were tested on parts of various size and material, and in various locations in order to illustrate their invariant nature.We conclude that the problem of spatial uncertainty is in fact an artefact of the fact that current industrial manipulators are designed to be position controlled. The work described in this thesis shows that assembly robots, when appropriately designed, controlled and programmed, can be the reliable and flexible devices they were always meant to be

Reflexively stumbling towards sustainability : understanding social learning in regional governance networks

Current sustainability challenges are regarded as very complex and even wicked in that they are contested and ambiguous with respect to their underlying knowledge, values and causes, as well as with respect to the pathways that might help in addressing them. In order to meaningfully engage with such challenges, a so-called transition perspective is increasingly advocated in both science and society. Transition here is seen as a delicate composition of entangled non-linear processes of social change by which a societal system is structurally transformed towards a state that is deemed more desirable, here more sustainable, than the current one. A transition perspective suggests that, rather than optimizing existing systems, practices and routines (continue doing the things we do, but only better), there seems to be a need to radically reconsider the assumptions and values upon which these systems have been build (doing better things altogether). A transition perspective implies new ways of ‘doing’ policy, new behaviour, new relationship building (trust) and new ways of knowledge creation and learning. Here a shift from ‘governmentality’ to reflexive governance and a shift from individual learning, personal development and competition to joint learning, community building and solidarity, is emphasized. These proposed new ways and shifts call for the active seeking or inviting of pluralism in situations where old routines no longer suffice in light of complex sustainability challenges. Governance networks are networks where many actors are involved, such as municipalities, entrepreneurs, educational institutes, NGO’s, citizens and other actors. These networks have a relatively stable character and provide so-called discursive spaces where analyses, diagnoses, and solutions can be debated, negotiated and, under certain circumstance, even be co-created. . Within such networks there is a high degree of interaction and interdependency. Reflexive governance networks can help communities respond to complex problems, when they aim to co-create new knowledge, new relations and new policy. For this, a process of collaborative learning is seen as core to the transition process. The concept of social learning is promising in this context, because it takes the diversity of actors, knowledge, perspectives, languages and interests, as a starting point for the creation of new-shared knowledge. The concept of social learning has also been developed to understand processes of social transformation as learning processes. Through this lens, social learning can be seen as a double-edged process: where individual learning and interactive learning take place simultaneously in a process of social change with effects on wider social-ecological systems. As there are many different definitions and approaches of social learning social learning is defined in this thesis as ‘an interactive and dynamic process in a multi-actor setting where knowledge is exchanged and where actors learn through dialogue and the co-creation of new knowledge through on-going interaction’. In this sense, a social learning process can contribute to system innovation by providing a collective knowledge basis for action. Assumed in this thesis is that through social learning effective use of the diversity of actors can be made, by looking at possible root causes and possible solutions for complex and wicked problems. However, although social learning provides a powerful theoretical, in practice it faces some challenges, in part due to the diversity of actors. This thesis represents a journey to better understand these challenges in the context of localised and/or regional development in which multiple stakeholder jointly seek to become more sustainable in one way or another. The overarching research question is: What fosters social learning processes in regional governance networks for sustainability transitions? By applying a constructivist actionable methodological approach and using a mix of methods (e.g. retrospective analysis, reflexive monitoring, semi-structured surveys , open interviews and learning histories), the research was able to reveal that in the hybrid and discursive space where actors interact, they may encounter lack of trust, and/or a lack of commitment and/or lack of willingness to reframe underlying assumptions about both the root causes and possible solutions to sustainability challenges. When this happens, the social learning process can come to a hold, which is also referred to as lock-in. The interactions become less open, or even stop and become hostile, as if the discursive space becomes a battleground. This moment can be regarded as a significant moment or a tipping point, from where the social learning process can revitalise and start up again, or where the network starts to fall apart (a make-or-break moment). When governance networks are self-governing in social learning, they can manage the lock-in situation by becoming reflexive. Reflexivity is an expansive way of learning, by making underlying assumptions and frames explicit and reorienting them by asking: are we doing the right things or should we do something completely different? Reflexivity has the power to change perceptions and intentions - in order to do better things. When the networks are facilitated networks, which is often the case, they might need some skilled facilitation from change agents in order to become reflexive. Other actors or objects can behave as change agents or boundary spanners, between the different perceptions, interests and cultures contributing to the governance networks. The interventions from the change agents support the reflexivity of the actors and the network. The actors become able and willing to reorient their current values, knowledge, roles and actions. When these so-called ‘reflexive turns’ take place, an increase in trust, commitment and reframing can be seen as emergent properties of social learning. These properties are interrelated; changes in one property will likely induce changes in the others. For example, when trust increases, also the commitment seems to grow and vice versa. When these dynamics take place during the social learning process, indicators of effective learning are the changes in knowledge, relations (including roles), values and assumption, and, indeed, actions (including decisions). These changes are seen to contribute to sustainability transitions in regional development, such as the creation of local food initiatives, local energy cooperatives and new participative policy on these issues. Four studies were carried out in this thesis. They will be described here in brief. Study 1. Action research in a regional development setting: students as boundary workers in a learning multi-actor network. The aim of this first study (Chapter 2) is to investigate whether regional development can be supported with action-oriented research. The sub question is to find out more about the role of boundary spanners in this process. The hypothesis is that action oriented research might foster social learning and the co-creation of knowledge, for regional development. The area under research is the Western Quarter region in the province of Groningen, where issues about maintaining the landscape and economic vitality of the region bring many actors together in new regional networks. Methods used are an action oriented research approach, and a retrospective analysis of the first year of this process. The action-oriented approach is expected to contribute to better interactions, better collaboration and more shifting roles in order to bring about more valuable and legitimate impact of research. The retrospective analysis supported the understanding of the dynamics in the process, and proceeded insights in the changing roles of all actors and especially the roles of boundary spanners in this. It is found that boundary spanners are valuable and necessary for action-oriented research, because they provide bridges between divergent values, languages, interests, and viewpoints of the actors engaged. Boundary spanners seemingly create opportunities for building new relations between different actors. This in turn seems to stimulate the interactive character of social learning and to support the expansion of new shared knowledge, which is needed for regional and sustainable development. Study 2. Social learning in regional innovation networks: trust, commitment and reframing as emergent properties of interaction. The second study (Chapter 3) is a deeper reflection on the social learning process that took place in the first study. There were some interesting changes in behaviours of actors that could be interpreted as dynamics in trust, commitment and reframing. The research question therefore was: what is the role of trust, commitment and reframing in social learning dynamics in multi-actor innovation networks? The sub question here was whether trust, commitment and reframing are interrelated. Main methods used were; a retrospective analysis and an ex-post analysis. The retrospective analysis delivered a learning history of the network’s social learning dynamics, the interactions between the actors at significant moments and the behaviours of the actors according to trust, commitment and reframing. Findings are, that in social learning processes trust, commitment and reframing can be regarded as emergent and interrelated properties of social learning. In these dynamics, the fostering of the social learning process seems important. These findings have been integrated in a hypothetical framework, which is grounded theoretically in grounded theory and empirically in the case study. Study 3. Strengthening ecological mindfulness through hybrid learning in vital coalitions. In this third study (Chapter 4) the concept of reflexivity within a Dutch Policy Framework on Biodiversity is explored. Child city, a day care system, explores the possibilities of developing ecological mindfulness for young children, by offering them challenging playgrounds in natural environments. A small and active hybrid actor network of board members, nursery teachers and NGO-actors, was closely followed during one year through reflexive monitoring, and interviews, to see what kind of learning took place among the stakeholders and what kind of involvement in social learning and decision making took place. The main conclusion of this study is that understanding the social learning dynamics enhances the anticipation of tipping points as significant moments where the social learning needs to be fostered. In this study change agents are important at these moments because they are able to foster reflexivity using specific interventions. The increase of trust, commitment and reframing is seen as the effect of these interventions. Study 4. Reframing the future: the role of reflexivity in governance networks in sustainability transitions. Study 4 (in chapter 5) is oriented on the relation between social learning dynamics and outcomes and a better understanding of the role of reflexivity in governance networks. The sub-question here is: which actors and roles can foster the effectiveness of social learning processes in regional transitions? The Dutch national ‘Duurzaam Door’ (Moving Sustainably Forward) Policy Programme regards these regional sustainability networks on circular energy, food and economy as generative governance arrangements where new knowledge, actions and relations can co-evolve towards sustainability transitions. In order to understand the dynamics of social learning, three Dutch regional networks have been monitored on emergent properties of social learning between the years 2014 and 2016. Methods used were surveys, reflexive monitoring in action (RMA) workshops and learning histories with key actors. The focus in this study is particularly on the interrelated role of trust, commitment, reframing and reflexivity. Reflexivity and reflexive turns of the network are found to be a critical property at lock-in moments that can make or break the process of social learning. The study shows that change agents can support and facilitate reflexivity which in turn can lead to an increase of trust, commitment and reframing, and, ultimately, improved social learning in regional governance networks. All studies in this thesis point to the role of reflexivity in social learning dynamics, and the relation with emergent properties such as trust, commitment and reframing. Moreover, the role of change agents in lock-in situations seems to be important for the occurrence of reflexive turns, which foster the effectivity and outcomes social learning process towards new knowledge, relations and actions (including decisions) in governance networks. These types of change and agency are expected to contribute to sustainability transitions at the regional level considering energy, economy and food systems. The theoretical contribution of this thesis in the field of social learning can be seen as supplying the ongoing debate with deeper insights about the dynamics of social learning, the role of reflexivity, trust, commitment and reframing; and the possible interventions in them. The empirical contribution of this thesis is the increased effectivity of social learning processes in different Dutch regions, and the tangible outcomes in new relations, knowledge and actions.</p

Characterisation of the structure and self-assembly of a small cyclic peptide: an analysis using NMR spectroscopy, diffusion and heteronuclear relaxation measurements

Pseudodesmin A, a member of the viscosin group, is a cyclic lipodepsipeptide (CLP) consisting out of an oligopeptide that is cyclised through a lactone bond between its C-terminal carboxyl group and the hydroxyl group of a threonine side chain and a 3-hydroxydecanoic acid moiety bonded to the N-terminal end of the peptide. It is found to self-assemble in apolar organic solvents, which is reminiscent of its expected ability of forming ion pores in cellular membranes. The goal of this dissertation is to investigate the self-assembly in organic solvents and the structure of the assemblies formed mainly by translational diffusion and heteronuclear relaxation NMR measurements. After covering some theory and background concerning diffusion, translational diffusion NMR, NMR relaxation, and CLPs, the elucidation of the pseudodesmin A conformation – by both X-ray diffraction and NMR – will be discussed. Next, the self-assembly is studied by translational diffusion measurements at different concentrations in chloroform and acetonitrile/chloroform mixtures. Using these results, a model is proposed for the supramolecular assembly that explains the selective self-assembly in non-polar environment, the limitless nature of the assembly and the biological function of the ion pore. This model, confirmed by the detection of intermolecular rOe contacts, encompasses a side by side aggregation of the amphipathic monomer alpha-helical units followed by a stacking of these aggregates – along a direction closely parallel to the alpha-helix – to cylindrically shaped structures. Heteronuclear 13C-alpha relaxation is then used to gain more insight in the organisation of the supramolecular structure and to confirm some aspects of the proposed model. The dependence of the 13C-alpha R1 and R2 relaxation rate constants on the 13C-1H bond vector orientation within a molecular structure is used to obtain information concerning the rotational diffusion properties of the assembly and the orientation of the monomer within the supramolecular assembly. This is used to acquire the shape and average dimensions of the supramolecular assembly, which confirm the model of cylindrical assemblies that grow in only one dimension, nearly parallel with the helix structure. Finally, a theoretical simulation is performed to assess the impact of the self-association equilibria on the relaxation rate constants

Physical models for the motility of malaria parasites

The malaria disease is transmitted by a unicellular parasite that heavily relies on motility throughout its life cycle. We present different modelling approaches to the migration of the most motile form of the malaria parasite, the sporozoite, which is injected into the host skin by a mosquito. Their bent, elongated geometry shapes their trajectories. We first develop a geometrical model for the migration of a single sporozoite in the presence of obstacles. This enables us to trace the complex trajectories observed in vivo back to the structural features of both parasite and environment. Our second model shows that sporozoites can collectively organise in stable whirl-like structures, as observed experimentally in the salivary glands of malaria-infected mosquitos. Thirdly, we adopt a microscopic viewpoint linking the experimentally observed adhesion dynamics of gliding sporozoites with the presence of translational and rotational stochastic friction. Finally, we connect the propulsion system of sporozoites with mechanical cell deformations. Analysing experimental time series of sporozoite speed and curvature we can quantitatively distinguish the components of the gliding machinery. Overall, our physical models explain many essential features of gliding sporozoites and provide predictions that motivate novel experiments