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Jafari, Hedyeh
Publications (6 of 6) Show all publications
Jafari, H. (2020). On mimicking human balance with brain-inspired modeling and control. (Licentiate dissertation). Luleå University of Technology
Open this publication in new window or tab >>On mimicking human balance with brain-inspired modeling and control
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Luleå University of Technology, 2020
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Robotics Control Engineering
Research subject
Control Engineering
Identifiers
urn:nbn:se:ltu:diva-77546 (URN)978-91-7790-522-6 (ISBN)978-91-7790-523-3 (ISBN)
Presentation
2020-03-18, A1547, Luleå, 10:30 (English)
Opponent
Available from: 2020-01-29 Created: 2020-01-29 Last updated: 2020-02-17Bibliographically approved
Jafari, H., Pauelsen, M., Röijezon, U., Nyberg, L., Nikolakopoulos, G. & Gustafsson, T. (2019). A novel data driven model of ageing postural control. In: : . Paper presented at EU Falls Festival.
Open this publication in new window or tab >>A novel data driven model of ageing postural control
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2019 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Background

Postural control is a complex system. Based on sensorimotor integration, the central nervous system (CNS) maintains balance by sending suitable motor commands to the muscles. Physiological decline due to ageing, affects balance performance through failing postural control – and in turn affects falls self-efficacy and activity participation. Understanding how the CNS adapts to these changes and predicts the appropriate motor commands to stabilize the body, has been a challenge for postural control research the latest years.

Aims

To understand and model the performance of the central nervous system as the controller of the human body.

Methods

Modelling was based on postural control data from 45 older adults (70 years and older). Ankle, knee and hip joint kinematics were measured during quiet stance using a motion capture system. Principal component analysis was used in order to reduce the measured multidimensional kinematics from a set of correlated discrete time series to a set of principal components. The outcome was utilized to predict the motor commands. The adaptive behaviour of the CNS was modelled by recurrent neural network including the efference copy for rapid predictions. The data from joint kinematics and electromyography (EMG) signals of the lower limb muscles were measured and separated into training and test data sets.

Results

The model can predict postural motor commands with very high accuracy regardless of a large physiological variability or balancing strategies. This model has three characteristics: a) presents an adaptive scheme to individual variability, 2) showcases the existence of an efference copy, and 3) is human experimental data driven.

Conclusion

The model can adapt to physical body characteristics and individual differences in balancing behaviour, while successfully predict motor commands. It should therefore be utilised in the continued pursuit of a better understanding of ageing postural control.

National Category
Physiotherapy Robotics
Research subject
Physiotherapy; Robotics and Artificial Intelligence
Identifiers
urn:nbn:se:ltu:diva-76838 (URN)
Conference
EU Falls Festival
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2019-11-25
Jafari, H., Nikolakopoulos, G. & Gustafsson, T. (2019). Replicating human brain mechanisms towards balancing. In: : . Paper presented at 17th European Control Conference (ECC)-Naples June 25-28, 2019..
Open this publication in new window or tab >>Replicating human brain mechanisms towards balancing
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Understanding the performance of the human brain to stabilize the body remains an open fundamental research question. In this article, we study the hypothesis of internal model of the Central Nervous System (CNS) by a novel proposed architecture based on a recurrent neural network. The overall objective of the article and the main contribution stems from demonstrating the capability of replicating the balancing mechanisms of the brain by training the proposed bio-inspired network architecture with human balancing data and in the sequel applying the resulting control structure for controlling a single link inverted pendulum. Towards this direction, the body kinetics and kinematics measurements of forty-five subjects during upright stance trails were collected and utilized for training the proposed neural network. The efficacy of the proposed scheme will be proven through multiple simulation results with a single link inverted pendulum, where it will be demonstrated that the brain-inspired control scheme achieves a proper balance.

Keywords
Internal model, recurrent neural network, human motor control, postural control
National Category
Engineering and Technology Control Engineering Robotics
Identifiers
urn:nbn:se:ltu:diva-73248 (URN)
Conference
17th European Control Conference (ECC)-Naples June 25-28, 2019.
Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2020-01-29
Pauelsen, M., Jafari, H., Vikman, I., Nyberg, L. & Röijezon, U. (2019). Using the frequency power spectrum to learn more about aging postural control and fall-related concerns. In: : . Paper presented at EU Falls Festival.
Open this publication in new window or tab >>Using the frequency power spectrum to learn more about aging postural control and fall-related concerns
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2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Backgound:

Posturography is widely used to describe and analyze human postural control. The traditional features of the center of pressure (CoP) trajectory during open eyes quiet standing tests have been used to show the association between declined sensorimotor systems and the variation in fall-related concerns (FrC), but seem to be too crude to separate each sensorimotor system’s contribution. Therefore, research has moved towards analysing the frequency domain of the CoP trajectory.

Aim:

To explore the frequency domain of CoP trajectory signals in an effort to learn more about ageing postural control and how it mediates and is mediated by FrC 

Method:

We recruited 45 people aged 70 or more. To measure body sway during quiet stance, we registered CoP trajectories using a force plate. A power spectral density analysis was performed on the CoP signal of all participants, from which we then extracted features: peak power, mean power, 50% power and 80% power. Principal component analysis, orthogonal projection to latent structures (OPLS), and OPLS-discriminant analysis were used to explore patterns of explanation of the features by a wide range of sensorimotor variables and FrC measured on the participants. A PLS-tree was used for the initial grouping.

Results:

The PLS-tree gave 2 groups. Group 2 had significantly more FrC, lower morale, larger errors in knee proprioception, slower reaction times, and weaker lower limb strength. They also had lower frequencies at all four features (significant at all but peak power).

Conclusions:

Under the assumption that the vision feedback loop generates more power in the lower frequencies of quiet stance sway, one explanation of the findings could be that once an individual starts experiencing postural control decline, vision gets weighed heavier in the integration process. More research is needed to find the most accurate ways to investigate postural control changes.

National Category
Physiotherapy
Research subject
Physiotherapy
Identifiers
urn:nbn:se:ltu:diva-76837 (URN)
Conference
EU Falls Festival
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2019-11-25
Jafari, H., Pauelsen, M., Röijezon, U., Nyberg, L., Nikolakopoulos, G. & Gustafsson, T. (2018). On Internal Modeling of the Upright Postural Control in Elderly. In: : . Paper presented at 2018 IEEE International Conference on Robotics and Biomimetics (IEEE ROBIO 2018), December 12-15, 2018, Kuala Lumpur, Malaysia..
Open this publication in new window or tab >>On Internal Modeling of the Upright Postural Control in Elderly
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2018 (English)Conference paper, Published paper (Refereed)
National Category
Control Engineering Physiotherapy
Research subject
Control Engineering; Physiotherapy
Identifiers
urn:nbn:se:ltu:diva-72472 (URN)
Conference
2018 IEEE International Conference on Robotics and Biomimetics (IEEE ROBIO 2018), December 12-15, 2018, Kuala Lumpur, Malaysia.
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2020-01-29
Jafari, H., Castaño Arranz, M., Gustafsson, T. & Nikolakopoulos, G. (2017). On Control Structure Design for a Walking Beam Furnace. In: 2017 25th Mediterranean Conference on Control and Automation, MED 2017: . Paper presented at 25th Mediterranean Conference on Control and Automation, MED 2017, University of Malta, Valletta, Malta, 3-6 July 2017 (pp. 1355-1360). Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), Article ID 7984307.
Open this publication in new window or tab >>On Control Structure Design for a Walking Beam Furnace
2017 (English)In: 2017 25th Mediterranean Conference on Control and Automation, MED 2017, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1355-1360, article id 7984307Conference paper, Published paper (Refereed)
Abstract [en]

The aim of this article is to introduce a novel sparse controller design for the temperature control of an experimental walking beam furnace in steel industry. Adequate tracking of temperature references is essential for the quality of the heated slabs. However, the design of the temperature control is hindered by the multivariable (non-square) dynamic behavior of the furnace. These dynamics include significant loop interactions and time delays. Furthermore, a novel data-driven model, based on real life experimental data that relies on a subspace state representation in a closed loop approach is introduced. In the sequel, the derived model is utilized to investigate the controller's structure. By applying the relative gain array approach a decentralized feedback controller is designed. However, in spite of the optimal and sparse design of the controller, there exists interaction between loops. By analyzing the interaction between the inputs-outputs with the Σ2 Gramian-based interaction methodology, a decoupled multi-variable controller is implied. The simulation result, based on the experimental modeling of the furnace, shows that the controller can successfully decrease the interaction between the loops and track the reference temperature set-points.

Place, publisher, year, edition, pages
Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017
Series
Mediterranean Conference on Control and Automation, ISSN 2325-369X
Keywords
Control Structure Design, Interaction Measures, Decentralized Control, Walking Beam Furnace
National Category
Control Engineering
Research subject
Control Engineering
Identifiers
urn:nbn:se:ltu:diva-63041 (URN)10.1109/MED.2017.7984307 (DOI)000426926300222 ()2-s2.0-85027842203 (Scopus ID)978-1-5090-4533-4 (ISBN)
Conference
25th Mediterranean Conference on Control and Automation, MED 2017, University of Malta, Valletta, Malta, 3-6 July 2017
Projects
Integrated Process Control based on Distributed In-Situ Sensors into Raw Material and Energy Feedstock, DISIRE
Funder
EU, Horizon 2020, 636834
Available from: 2017-04-17 Created: 2017-04-17 Last updated: 2018-05-29Bibliographically approved
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