Development of an Indoor Multirotor Testbed for Experimentation on Autonomous Guidance Strategies

Despite the vast popularity of rotary wing unmanned aerial vehicles and research centres that develop their guidance software, there are only a limited number of references that provide an exhaustive description of a step-by-step procedure to build-up a multirotor testbed. In response to such need, the first part of this thesis aims to describe, in detail, the complete procedure to establish and operate an autonomous multirotor unmanned aerial vehicle indoor experimental platform to test and validate guidance, navigation and control strategies. Both hardware and software aspects of the testbed are described to offer a complete understanding of the different aspects. The second part of this thesis focuses on two benchmarks multirotor guidance, navigation and control problems. Initially, the guidance law for an accurate landing manoeuvre is studied. Multirotor usually have a flight time limited to a few minutes. Autonomous landing and docking to a charging station could extend the mission duration of these vehicles. Subsequently, the guidance strategy for the formation flight between two multirotors is considered. In this case, the fundamental goal is an accurate autonomous alignment between two vehicles, each of them behaving as a target and chaser simultaneously. In the last part of this thesis, the problem of minimum energy manoeuvres is tackled. Again, in this case, the motive is to address the limitation in multirotor flight duration. The fundamental objective of this guidance, navigation and control strategy is to determine and implement, in real-time, the minimum energy control histories that transfer the multirotor from its initial point to a given final point. As opposed to conventional guidance strategies, mostly based on proportional-integral-derivative laws, a minimum energy controller allows the vehicle to execute the manoeuvre with a minimum electrical power expenditure

A high-level architecture for believable social agents

The creation of virtual humans capable of behaving and interacting realistically with each other requires the development of autonomous believable social agents. Standard goal-oriented approaches are not well suited to it because they don't take into account important characteristics identified by the social sciences. This paper tackles the issue of a general social reasoning mechanism, discussing its basic functional requirements using a sociological perspective, and proposing a high-level architecture based on Roles, Norms, Values and Type

Working memory training in older adults: Bayesian evidence supporting the absence of transfer

The question of whether working memory training leads to generalized improvements in untrained cognitive abilities is a longstanding and heatedly debated one. Previous research provides mostly ambiguous evidence regarding the presence or absence of transfer effects in older adults. Thus, to draw decisive conclusions regarding the effectiveness of working memory training interventions, methodologically sound studies with larger sample sizes are needed. In this study, we investigated whether or not a computer-based working memory training intervention induced near and far transfer in a large sample of 142 healthy older adults (65-80 years). Therefore, we randomly assigned participants to either the experimental group, which completed 25 sessions of adaptive, process-based working memory training, or to the active, adaptive visual search control group. Bayesian linear mixed-effects models were used to estimate performance improvements on the level of abilities, using multiple indicator tasks for near (working memory) and far transfer (fluid intelligence, shifting, and inhibition). Our data provided consistent evidence supporting the absence of near transfer to untrained working memory tasks and the absence of far transfer effects to all of the assessed abilities. Our results suggest that working memory training is not an effective way to improve general cognitive functioning in old age

Imaging haemodynamic changes related to seizures: comparison of EEG-based general linear model, independent component analysis of fMRI and intracranial EEG

Background: Simultaneous EEG-fMRI can reveal haemodynamic changes associated with epileptic activity which may contribute to understanding seizure onset and propagation. Methods: Nine of 83 patients with focal epilepsy undergoing pre-surgical evaluation had seizures during EEG-fMRI and analysed using three approaches, two based on the general linear model (GLM) and one using independent component analysis (ICA): 1. EEGs were divided into up to three phases: early ictal EEG change, clinical seizure onset and late ictal EEG change and convolved with a canonical haemodynamic response function (HRF) (canonical GLM analysis). 2. Seizures lasting three scans or longer were additionally modelled using a Fourier basis set across the entire event (Fourier GLM analysis). 3. Independent component analysis (ICA) was applied to the fMRI data to identify ictal BOLD patterns without EEG. The results were compared with intracranial EEG. Results: The canonical GLM analysis revealed significant BOLD signal changes associated with seizures on EEG in 7/9 patients, concordant with the seizure onset zone in 4/7. The Fourier GLM analysis revealed changes in BOLD signal corresponding with the results of the canonical analysis in two patients. ICA revealed components spatially concordant with the seizure onset zone in all patients (8/9 confirmed by intracranial EEG). Conclusion: Ictal EEG-fMRI visualises plausible seizure related haemodynamic changes. The GLM approach to analysing EEG-fMRI data reveals localised BOLD changes concordant with the ictal onset zone when scalp EEG reflects seizure onset. ICA provides additional information when scalp EEG does not accurately reflect seizures and may give insight into ictal haemodynamics

Healthy cognition in old age: effects of an engaged lifestyle and cognitive training

Healthy cognitive functioning is a key aspect of successful aging and a crucial component of the well-being of older adults. On the group level, crystallized abilities (e.g., factual knowledge) remain relatively stable until old age, fluid cognitive abilities (e.g., working memory), however, decline gradually across the lifespan. Therefore, and in light of the projected demographic changes, the identification of modifiable lifestyle factors and the development of interventions that promote successful cognitive aging have become increasingly important. Thus, the main question of this thesis was if an engaged lifestyle and cognitive training interventions have a positive impact on cognitive ability, cognitive plasticity, and functional ability in everyday life in older adults. In Article 1, we found a positive association between measures of an engaged lifestyle and functional ability everyday life, which was mediated through cognitive ability. In Article 2 cognitive training studies in older adults were reviewed with regards to training, transfer and maintenance effects, as well as training-related structural and functional brain changes. In Article 3, we found evidence supporting the absence of generalization effects to untrained cognitive abilities after an intensive cognitive training intervention. In Article 4, we found that baseline cognitive performance predicted change in training performance, confirming the magnification account of cognitive change. Intakte kognitive Fähigkeiten sind ein grundlegender Aspekt des erfolgreichen Alterns und ein wesentlicher Bestandteil des Wohlbefindens älterer Menschen. Auf Gruppenebene zeigt sich, dass kristalline Fähigkeiten (z. B. Faktenwissen) bis ins hohe Alter stabil bleiben, während fluide Fähigkeiten (z. B. Arbeitsgedächtnis) sukzessive über die Lebensspanne abnehmen. Deshalb, und in Anbetracht der vorhergesagten demographischen Veränderungen, ist die Identifikation modifizierbarer Lifestyle-Faktoren und die Entwicklung von Interventionen die das erfolgreiche kognitive Altern fördern von grösster Bedeutung. Diese Arbeit ging der Frage nach, ob ein aktiver Lebensstil und kognitive Trainingsinterventionen einen positiven Effekt auf die kognitiven Fähigkeiten, die kognitive Plastizität und die funktionelle Fähigkeit im Alltag älterer Menschen haben. In Artikel 1 konnte ein positiver Zusammenhang zwischen einem aktiven Lebensstil und funktioneller Fähigkeit gezeigt werden, welcher durch die kognitive Fähigkeit mediiert wird. In Artikel 2 wurden kognitive Trainingsstudien mit älteren Menschen hinsichtlich ihrer Wirksamkeit evaluiert. In Artikel 3 konnte Evidenz für die Abwesenheit von Generalsierungseffekten zu untrainerten kognitiven Fähigkeiten nach einer Trainingsintervention gefunden werden. In Artikel 4 konnte gezeigt werden, dass die kognitive Leistung zur Baseline die Trainingsperformanz vorhersagt

Altered brain connectivity in sudden unexpected death in epilepsy (SUDEP) revealed using resting-state fMRI.

The circumstances surrounding SUDEP suggest autonomic or respiratory collapse, implying central failure of regulation or recovery. Characterisation of the communication among brain areas mediating such processes may shed light on mechanisms and noninvasively indicate risk. We used rs-fMRI to examine network properties among brain structures in people with epilepsy who suffered SUDEP (n = 8) over an 8-year follow-up period, compared with matched high- and low-risk subjects (n = 16/group) who did not suffer SUDEP during that period, and a group of healthy controls (n = 16). Network analysis was employed to explore connectivity within a 'regulatory-subnetwork' of brain regions involved in autonomic and respiratory regulation, and over the whole-brain. Modularity, the extent of network organization into separate modules, was significantly reduced in the regulatory-subnetwork, and the whole-brain, in SUDEP and high-risk. Increased participation, a local measure of inter-modular belonging, was evident in SUDEP and high-risk groups, particularly among thalamic structures. The medial prefrontal thalamus was increased in SUDEP compared with all other control groups, including high-risk. Patterns of hub topology were similar in SUDEP and high-risk, but were more extensive in low-risk patients, who displayed greater hub prevalence and a radical reorganization of hubs in the subnetwork. SUDEP is associated with reduced functional organization among cortical and sub-cortical brain regions mediating autonomic and respiratory regulation. Living high-risk subjects demonstrated similar patterns, suggesting such network measures may provide prospective risk-indicating value, though a crucial difference between SUDEP and high-risk was altered connectivity of the medial thalamus in SUDEP, which was also elevated compared with all sub-groups. Disturbed thalamic connectivity may reflect a potential non-invasive marker of elevated SUDEP risk