117 research outputs found
The Portfolio Choice in Emergent Markets a Rational or a Behavioral Decision: a Cognitive Answer
The purpose of this study is to explore the relationship between the rational and the behavioral portfolio theories, two theories that describes the decision making process on the domain of portfolio choice, under investors' perception. This will offer a more realistic answer that describes the investors' decision on term of portfolio choice. Our sample contains 30 Tunisian investors who trade at the Tunisian stock exchange (BVMT). We introduce an approach based on cognitive mapping with a series of interviews. We combine both concepts that belong to the mean-variance and the behavioral approach and we explore the interactions between them. We introduce some new notions such as the zone of communication between the two cited theories and the variables of connection. We demonstrate that investors use the mean-variance theory of portfolio choice but they are affected by their cognitive biases and emotions when making their portfolio choice decision. Keywords: Mean-variance portfolio Choice, Behavioral Portfolio Choice, cognitive maps, areas of communication, concepts of connection
TEAM: a parameter-free algorithm to teach collaborative robots motions from user demonstrations
Learning from demonstrations (LfD) enables humans to easily teach
collaborative robots (cobots) new motions that can be generalized to new task
configurations without retraining. However, state-of-the-art LfD methods
require manually tuning intrinsic parameters and have rarely been used in
industrial contexts without experts. We propose a parameter-free LfD method
based on probabilistic movement primitives, where parameters are determined
using Jensen-Shannon divergence and Bayesian optimization, and users do not
have to perform manual parameter tuning. The cobot's precision in reproducing
learned motions, and its ease of teaching and use by non-expert users are
evaluated in two field tests. In the first field test, the cobot works on
elevator door maintenance. In the second test, three factory workers teach the
cobot tasks useful for their daily workflow. Errors between the cobot and
target joint angles are insignificant -- at worst 0.28 deg -- and the motion is
accurately reproduced -- GMCC score of 1. Questionnaires completed by the
workers highlighted the method's ease of use and the accuracy of the reproduced
motion. Public implementation of our method and datasets are made available
online.Comment: 8 pages, 4 figures, accepted to ICINCO202
Parallel robotics, from research to industry
New trends and impact of parallel robotics and machinery in industry
Are Functional Measures Sufficient to Capture Acceptance? A Qualitative Study on Lower Limb Exoskeleton Use for Older People
Lower limb exoskeletons (LLE) are robotic devices developed to assist walk. In the field of healthcare, this technology has been available for almost a decade, yet it still faces important acceptance issues. While LLE were first developed for patients with spinal cord injuries, we expect their use to expand to everyday settings to benefit other populations, namely that of older people with reduced mobility (RM). We propose a qualitative approach to unearth key psychosocial themes on the acceptance of LLE in daily living for older people. The study analyses perceptions of older people with RM, as well as their entourage, including informal and professional caregivers. Using a grounded theory approach we analysed 12 semi-structured interviews with older people with RM; 2 focus groups with informal caregivers, and 2 focus groups with professional caregivers. LLE were introduced to participants through photo-elicitation. Older people with RM believed that LLE would increase their autonomy. They also perceived that using LLE would make them feel less of a burden for their entourage. Beyond these expected benefits, results captured participants' ambivalence, dependent on their experiences of the ageing process and perceptions on the human-machine interaction. Informal caregivers highlighted that LLE could provide important relief related to the burden of care. Nonetheless, professional caregivers raised the fear of LLE leading to dehumanization of care. While each group had specific concerns on how LLE use would impact their lives, psychosocial considerations played a key role in LLE acceptance
Profibus PC based motion control with application to a new 5 axes parallel kinematics
Generally the classical control architecture used to carry out a robot position control is based on a classical industrial motion planner that needs encoders cabling and analog cabling to insure the regulation loop. This work proposes a Profibus PC based control architecture that has a double-originality. The first originality concerns the hardware architecture and the second concerns the software flexibility that allows easiness in implementation, either modification, for controlling parallel robots. The hardware architecture is based upon so-called “intelligent” digital drives and the whole fieldbus hardware
Maximizing Performance with Minimal Resources for Real-Time Transition Detection
Assistive devices, such as exoskeletons and prostheses, have revolutionized
the field of rehabilitation and mobility assistance. Efficiently detecting
transitions between different activities, such as walking, stair ascending and
descending, and sitting, is crucial for ensuring adaptive control and enhancing
user experience. We here present an approach for real-time transition
detection, aimed at optimizing the processing-time performance. By establishing
activity-specific threshold values through trained machine learning models, we
effectively distinguish motion patterns and we identify transition moments
between locomotion modes. This threshold-based method improves real-time
embedded processing time performance by up to 11 times compared to machine
learning approaches. The efficacy of the developed finite-state machine is
validated using data collected from three different measurement systems.
Moreover, experiments with healthy participants were conducted on an active
pelvis orthosis to validate the robustness and reliability of our approach. The
proposed algorithm achieved high accuracy in detecting transitions between
activities. These promising results show the robustness and reliability of the
method, reinforcing its potential for integration into practical applications.Comment: Submitted for a conference. 7 pages including references, 8 figures,
3 table
ExoRecovery: Push Recovery with a Lower-Limb Exoskeleton based on Stepping Strategy
Balance loss is a significant challenge in lower-limb exoskeleton
applications, as it can lead to potential falls, thereby impacting user safety
and confidence. We introduce a control framework for omnidirectional recovery
step planning by online optimization of step duration and position in response
to external forces. We map the step duration and position to a human-like foot
trajectory, which is then translated into joint trajectories using inverse
kinematics. These trajectories are executed via an impedance controller,
promoting cooperation between the exoskeleton and the user.
Moreover, our framework is based on the concept of the divergent component of
motion, also known as the Extrapolated Center of Mass, which has been
established as a consistent dynamic for describing human movement. This
real-time online optimization framework enhances the adaptability of
exoskeleton users under unforeseen forces thereby improving the overall user
stability and safety. To validate the effectiveness of our approach,
simulations, and experiments were conducted. Our push recovery experiments
employing the exoskeleton in zero-torque mode (without assistance) exhibit an
alignment with the exoskeleton's recovery assistance mode, that shows the
consistency of the control framework with human intention. To the best of our
knowledge, this is the first cooperative push recovery framework for the
lower-limb human exoskeleton that relies on the simultaneous adaptation of
intra-stride parameters in both frontal and sagittal directions. The proposed
control scheme has been validated with human subject experiments.Comment: Submitted for a conference. 8 pages including references, 8 figure
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