69 research outputs found
MPC/OC Code for: Learning with Muscles: Benefits for Data-Efficiency and Robustness in Anthropomorphic Tasks
No full textThis code allows you reproduce the optimal control and model predictive control results of the paper: "Learning with Muscles: Benefits for Data-Efficiency and Robustness in Anthropomorphic Tasks" by Isabell Wochner, Pierre Schumacher, Georg Martius, Dieter Büchler, Syn Schmitt and Daniel F.B. Haeufle. Always cite the paper together with this dataset because this dataset is not self-explanatory.Note: This code requires demoa version 2.2, which can be downloaded from https://doi.org/10.18419/DARUS-2550, DaRUS, V4
Replication Data for: A physiologically enhanced muscle spindle model: using a Hill-type model for extrafusal fibers as template for intrafusal fibers
No full textThis code/data allows you reproduce the results of the paper: "A physiologically enhanced muscle spindle model: using a Hill-type model for extrafusal fibers as template for intrafusal fibers" by P. F. S. Chacon, M. Hammer, I. Wochner, J. R. Walter and S. Schmitt. Always cite the paper together with this dataset because this dataset is not self-explanatory. More information about the dataset can be found here: README.md
The benefit of muscle-actuated systems : internal mechanics, optimization and learning
No full textWe are facing the challenge of an over-aging and overweight society. This leads to an increasing number of movement disorders and causes the loss of mobility and independence. To address this pressing issue, we need to develop new rehabilitation techniques and design innovative assistive devices. Achieving this goal requires a deeper understanding of the underlying mechanics that control muscle-actuated motion. However, despite extensive studies, the neural control of muscle-actuated motion remains poorly understood. While experiments are valuable and necessary tools to further our understanding, they are often limited by ethical and practical constraints. Therefore, simulating muscle-actuated motion has become increasingly important for testing hypotheses and bridge this knowledge gap. In silico, we can establish cause-effect relationships that are experimentally difficult or even impossible to measure. By changing morphological aspects of the underlying musculoskeletal structure or the neural control strategy itself, simulations are crucial in the quest for a deeper understanding of muscle-actuated motion. The insights gained from these simulations paves the way to develop new rehabilitation techniques, enhance pre-surgical planning, design better assistive devices and improve the performance of current robots.
The primary objective of this dissertation is to study the intricate interplay between musculoskeletal dynamics, neural controller and the environment. To achieve this goal, a simulation framework has been developed as part of this thesis, enabling the modeling and control of muscle-actuated motion using both model-based and learning-based methods. By utilizing this framework, musculoskeletal models of the arm, head-neck complex and a simplified whole-body model are investigated in conjunction with various concepts of motor control.
The main research questions of this thesis are therefore:
1. How does the neural control strategy select muscle activation patterns to generate the desired movement, and can we use this knowledge to design better assistive devices?
2. How does the musculoskeletal dynamics facilitate the neural control strategy in accomplishing this task of generating desired movements?
To address these research questions, this thesis comprises a total of five journal and conference articles. More specifically, contributions I-III of this thesis focus on addressing the first research question which aims to understand how voluntary and reflexive movements can be predicted.
First, we investigate various optimality principles using a musculoskeletal arm model to predict point-to-manifold reaching tasks. By using predictive simulations, we demonstrate how the arm would move towards a goal if, for example, our neural control strategy would minimize energy consumption. The main finding of this contribution shows that it is essential to include muscle dynamics and consider tasks with more openly defined targets to draw accurate conclusions about motor control. Through our analysis, we show that a combination of mechanical work, jerk and neuronal stimulation effort best predicts point-reaching when compared to human experiments.
Second, we propose a novel method to optimize the design of exoskeleton power units taking into account the load cycle of predicted human movements. To achieve this goal, we employ a forward dynamic simulation of a generic musculoskeletal arm model, which is first scaled to represent different individuals. Next, we predict individual human motions and employ the predicted human torques to scale the electrical power units employing a novel scalability model. By considering the individual user needs and task demands, our approach achieves a lighter and more efficient design. In conclusion, our framework demonstrates the potential to improve the design of individual assistive devices.
The third contribution focuses on predicting reflexive movements in response to sudden perturbations of the head-neck complex. To achieve this, we conducted experiments in which volunteers were placed on a table while supporting their heads with a trapdoor. This trapdoor was then suddenly released leading to a downward movement of the head until the reflexive reaction of the muscles stops the head from falling. We analyzed the results of these experiments, presenting characteristic parameters and highlighting differences between separate age and gender groups. Using this data, we also set up benchmark validations for a musculoskeletal head-neck model, including reflex control strategies. Our main findings are that there are large individual differences in reflexive responses between participants and that the perturbation direction significantly affects the reflexive response. Furthermore, we show that this data can be used as a benchmark test to validate musculoskeletal models and different muscle control strategies.
While the first three contributions focus on the research question (1), contributions IV-V focus on (2) whether and how the musculoskeletal dynamics facilitate the learning and control task of various movements. We utilize a recently introduced information-theoretic approach called control effort to quantify the minimally required information to perform specific movements. By applying this concept, we can for example quantify how much biological muscles reduce the neuronal information load compared to technical DC-motors. We present a novel optimization algorithm to find this control effort and apply it to point-reaching and walking tasks. The main finding of this contribution is that the musculoskeletal dynamics reduce the control effort required for these movements compared to torque-driven systems.
Finally, we hypothesize that the highly nonlinear muscle dynamics not only facilitate the control task but also provide inherent stability that is beneficial for learning from scratch. To test this, we employed various learning strategies for multiple anthropomorphic tasks, including point-reaching, ball-hitting, hopping, and squatting. The results of this investigation demonstrate that using muscle-like actuators improves the data-efficiency of the learning tasks. Additionally, including the muscle dynamics improves the robustness towards hyperparameters and allows for a better generalization towards unknown and unlearned perturbations.
In summary, this thesis enhances existing methods to control and learn muscle-actuated motion, quantifies the control effort needed to perform certain movements and demonstrates that the inherent stability of the muscle dynamics facilitates the learning task. The models, control strategies, and experimental data presented in this work aid researchers in science and industry to improve their predictions in various fields such as neuroscience, ergonomics, rehabilitation, passive safety systems, and robotics. This allows us to reverse-engineer how we as humans control movement, uncovering the complex relationship between musculoskeletal dynamics and neural controller
Effect of a gluten and milk protein free diet on gastrointestinal symptoms in children with Autism Spectrum Disorder: A systematic review
No full textAbstract
Title: Effect of a gluten and milk protein free diet on gastrointestinal symptoms in
children with Autism Spectrum Disorder: A systematic review
Author: Isabell Stahlén and Mikaela Thelander
Supervisor: Andrea Mikkelsen
Examiner: Frode Slinde
Programme: Programme in dietetics, 180/240 ECTS
Type of paper: Bachelor’s thesis in clinical nutrition, 15 higher education credits
Date: April 5th, 2017
Background: Autism spectrum disorders (ASD) is a collective term for neurodevelopmental
disorders which leads to a reduced or different way of perceive, process and understand
information. Hypotheses suggest that peptides originated from gluten and casein may have an
impact on behaviors typical of ASD, as well as an impact on gastrointestinal (GI) symptoms
which are frequent in children with ASD.
Objective: The aim of this study was to review and summarize the scientific evidence for the
effect of a diet free from gluten and milk proteins on GI symptoms in children with ASD.
Search strategy: Systematic literature searches were conducted during January 2017 in the
databases PubMed and Scopus. Keywords used were ”autism”, ”autism spectrum disorders”,
”gastrointestinal”, ”gluten”, ”casein”, ”free”, ”child, ”children”, ”wheat” and ”dairy” (free
text) and ”autism spectrum disorder”, ”diet, gluten-free” and ”milk proteins” (MeSH).
Selection criteria: Inclusion criteria were RCT and cross-over studies, interventions
consisting of a diet free from gluten and milk proteins, GI symptoms as outcome measures,
human studies in children (0-17 years) diagnosed with ASD and articles written in Swedish or
English.
Data collection and analysis: A total of three articles were audited using the template “Mall
för kvalitetsgranskning av randomiserade studier” by Statens Beredning för Medicinsk och
Social Utvärdering. Total strength of evidence was assessed using the audit model “Underlag
för sammanvägd bedömning enligt GRADE” by University of Gothenburg.
Main results: None of the studies showed any difference in GI symptoms between
intervention and control group. One study showed a significant difference in GI symptoms in
the intervention group.
Conclusions: The studies show a moderate strength of evidence (+++) that a diet free from
gluten and milk proteins has no effect on GI symptoms in children with ASD.
Keywords: Autism spectrum disorders, gluten, casein, milk proteins, gastrointestinal symptomsSammanfattning
Titel: Effekt av gluten- och mjölkproteinfri kost på gastrointestinala symtom hos
barn med autismspektrumtillstånd: En systematisk översiktsartikel
Författare: Isabell Stahlén och Mikaela Thelander
Handledare: Andrea Mikkelsen
Examinator: Frode Slinde
Linje: Dietistprogrammet, 180/240 hp
Typ av arbete: Självständigt arbete i klinisk nutrition, 15 hp
Datum: 2017-04-05
Bakgrund: Autismspektrumtillstånd (ASD) är ett samlat begrepp för flera neurologiska
funktionsnedsättningar vilket leder till ett nedsatt eller annorlunda sätt att ta in, bearbeta och
förstå information. Hypoteser antyder att peptider från gluten och kasein skulle kunna ha en
påverkan på beteenden typiska vid ASD, samt en påverkan på gastrointestinala (GI) symtom
vilket är frekvent förekommande hos barn med ASD.
Syfte: Syftet med denna systematiska översiktsartikel var att granska och sammanställa det
vetenskapliga underlaget för effekten av gluten- och mjölkproteinfri (GMF) kost på GIsymtom
hos barn med ASD.
Sökväg: Systematiska litteratursökningar genomfördes under januari 2017 i databaserna
PubMed och Scopus. Sökord som användes var ”autism”, ”autism spectrum disorders”,
”gastrointestinal”, ”gluten”, ”casein”, ”free”, ”child, ”children”, ”wheat” och ”dairy” (fritext)
samt ”autism spectrum disorder”, ”diet, gluten-free” och ”milk proteins” (MeSH).
Urvalskriterier: Inklusionskriterier var RCT- och cross over-studier, GMF-kost som
intervention, utfallsmått GI-symtom, humanstudier på barn (0-17 år) med diagnos ASD samt
artiklar skrivna på svenska eller engelska.
Datainsamling och analys: Totalt tre artiklar granskades med hjälp av ”Mall för
kvalitetsgranskning av randomiserade studier” utformad av Statens Beredning för Medicinsk
och Social Utvärdering. Sammanvägd evidensstyrka bedömdes med hjälp av
granskningsmallen ”Underlag för sammanvägd bedömning enligt GRADE” utformad av
Göteborgs Universitet.
Resultat: I samtliga studier kunde ingen skillnad i GI-symtom påvisas mellan interventionsoch
kontrollgrupp. En studie påvisade en signifikant skillnad i GI-symtom inom
interventionsgrupp.
Slutsats: Studierna visar måttlig evidensstyrka (+++) för att en GMF-kost saknar effekt på GIsymtom
hos barn med ASD.
Nyckelord: Autismspektrumtillstånd, gluten, kasein, mjölkprotein, gastrointestinala symto
The man, the myth, the legend – he who everyone has heard, but no one knows about : A discourse analysis of Johnny Bode´s memory
No full textAuthor: Isabell Sandahl Title: The man, the myth, the legend – he who everyone has heard, but no one knows about Under title: A discourse analysis of Johnny Bode´s memory Pages: 30 Key Words: Johnny Bode, Discourse analysis, Johnny Bode Appreciation Society Johnny Bode (1912 – 1983) was a Swedish singer and composer who lived a very scandalous life, where norm breaking, and crime played a big part. Bodes biggest scandal took place during the second world war, when he traveled to Norway, during the occupation, and worked for the Nazi regime. Since Bode was a public person and a man who constantly drew a lot of attention to him, the media often wrote about him during his career. However, after his stay in Norway, Bode became pariah in Sweden and the writing about him ceased. About 30 years later, Bode died almost totally forgotten. There are several biographies about Johnny Bode´s life and there is one research report that goes through his life. Something that does not exist however is an overview about what was being said about him during different periods of time. The purpose with this essay is to go through what was has been said about Bode between 1983 – 1987, and between 2009 – 2023, while then compare these periods. This will be done by discourse theory and discourse analysis. Since discourse theory is a very wide theory, a discussion about how discourse should be defined in this essay, will also take place. The material that is used in this essay are mainly articles from various newspapers in Sweden, as well as the Johnny Bode Appreciation Society and the book Swedish swindlers and cheaters (Svenska svindlare och fuskare) written by Fredrik Kullberg. The results shows that the parts of Bode´s life that where presented between 1983 – 1987 were the fact that he was a forgotten celebrity, his stay in Norway and his LP disc The brothel mother´s songs (Bordellmammas visor), while the parts of Bode´s life that where presented between 2009 – 2023 was mainly his scandalous life story and his title as the Father of the Genitalia rock
Author Correction: Automation of surgical skill assessment using a three-stage machine learning algorithm.
No full text‘Falling heads’ : investigating reflexive responses to head-neck perturbations
No full textBackground: Reflexive responses to head-neck perturbations affect the injury risk in many different situations ranging from sports-related impact to car accident scenarios. Although several experiments have been conducted to investigate these head-neck responses to various perturbations, it is still unclear why and how individuals react differently and what the implications of these different responses across subjects on the potential injuries might be. Therefore, we see a need for both experimental data and biophysically valid computational Human Body Models with bio-inspired muscle control strategies to understand individual reflex responses better.
Methods: To address this issue, we conducted perturbation experiments of the head-neck complex and used this data to examine control strategies in a simulation model. In the experiments, which we call ’falling heads’ experiments, volunteers were placed in a supine and a prone position on a table with an additional trapdoor supporting the head. This trapdoor was suddenly released, leading to a free-fall movement of the head until reflexive responses of muscles stopped the downwards movement.
Results: We analysed the kinematic, neuronal and dynamic responses for all individuals and show their differences for separate age and sex groups. We show that these results can be used to validate two simple reflex controllers which are able to predict human biophysical movement and modulate the response necessary to represent a large variability of participants.
Conclusions: We present characteristic parameters such as joint stiffness, peak accelerations and latency times. Based on this data, we show that there is a large difference in the individual reflexive responses between participants. Furthermore, we show that the perturbation direction (supine vs. prone) significantly influences the measured kinematic quantities. Finally, ’falling heads’ experiments data are provided open-source to be used as a benchmark test to compare different muscle control strategies and to validate existing active Human Body Models directly.Projekt DEALHorizon 2020Deutsche Forschungsgemeinschaf
State of the art in technology-supported resilience training for military professionals
No full textCertain professions carry a risk of experiencing traumatic events and sometimes developing Posttraumatic Stress Disorder (PTSD). Researchers have been working on strategies to prevent professionals in those fields from developing PTSD. Recently, there has been a focus on applying technology that supports these preventive strategies, especially in a military context. This chapter provides an overview of the state of the art in technology-supported resilience training for military professionals, which has considerable common ground with the interdisciplinary field of human computer confluence (HCC). The effectiveness of these technologies and the resilience strategies they support are reviewed through the literature
Design and Scaling of Exoskeleton Power Units Considering Load Cycles of Humans
No full textExoskeletons are powerful tools for aiding humans with pathological conditions, in dangerous environments or in manually exhausting tasks. Typically, they are designed for specific maximum scenarios without taking into account the diversity of tasks and the individuality of the user. To address this discrepancy, a framework was developed for personalizing an exoskeleton by scaling the components, especially the electrical machine, based on different simulated human muscle forces. The main idea was to scale a numerical arm model based on body mass and height to predict different movements representing both manual labor and daily activities. The predicted torques necessary to produce these movements were then used to generate a load/performance cycle for the power unit design. Considering these torques, main operation points of this load cycle were defined and a reference power unit was scaled and optimized. Therefore, a scalability model for an electrical machine is introduced. This individual adaptation and scaling of the power unit for different users leads to a better performance and a lighter design
Robert Reinert’s Opium. Interrogating a film print
No full textIn the framework of her master thesis, the author examined and documented a uniquely tinted and toned nitrate print of the early color film Opium (Robert Reinert, 1918/1919), and considered ethical, theoretical and practical aspects of today’s film restoration practice. This paper presents some crucial results of the research and documentation process underlying the work. The study begins with a reflection upon concepts and notions commonly used in analogue and digital approaches to film preservation and restoration. It then explains the ongoing relevance of the vocabulary and collaborative practice of the so-called Scuola Bolognese. In the second section, these ideas and concepts are applied to a case study of Robert Reinert’s Opium while offering insight into the fascinating engagement with film and non-film material and with the question of what film scholars and archivists can learn from a film (print)’s material history
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