| 1. |
- Putra, I Putu Alit, 1992, et al.
(author)
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Finite element human body models with active reflexive muscles suitable for sex based whiplash injury prediction
- 2022
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In: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 10
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Journal article (peer-reviewed)abstract
- Previous research has not produced a satisfactory resource to study reflexive muscle activity for investigating potentially injurious whiplash motions. Various experimental and computational studies are available, but none provided a comprehensive biomechanical representation of human response during rear impacts. Three objectives were addressed in the current study to develop female and male finite element human body models with active reflexive neck muscles: 1) eliminate the buckling in the lower cervical spine of the model observed in earlier active muscle controller implementations, 2) evaluate and quantify the influence of the individual features of muscle activity, and 3) evaluate and select the best model configuration that can be used for whiplash injury predictions. The current study used an open-source finite element model of the human body for injury assessment representing an average 50th percentile female anthropometry, together with the derivative 50th percentile male morphed model. Based on the head-neck kinematics and CORelation and Analyis (CORA) tool for evaluation, models with active muscle controller and parallel damping elements showed improved head-neck kinematics agreement with the volunteers over the passive models. It was concluded that this model configuration would be the most suitable for gender-based whiplash injury prediction when different impact severities are to be studied.
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| 2. |
- Putra, I Putu Alit, 1992, et al.
(author)
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Implementation and Calibration of Active Reflexive Cervical Muscles on Female Head-Neck Model
- 2019
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Conference paper (other academic/artistic)abstract
- Problem outline ViVA OpenHBM is an open source human body model that represents the 50th percentile female population for assessing whiplash protection systems in car. ViVA OpenHBM was developed with intention to fill the gap of current available HBMs which excluded the average female size although injury statistics since 1960s have shown that females have three times higher risk to sustain whiplash injury compared to males. In this study, the current model is being enhanced by implementing active muscles as previous studies have shown that cervical muscles could alter the head and neck kinematics of the occupant during low-speed rear- crashes. Study objectives The first goal of this study was to implement a Proportional Integral Derivative (PID) feedback control mechanism adding to the Finite Element models of cervical muscles. The second goal was to calibrate the PID control gains by conducting an optimization-based parameter identification with publishedvolunteer data and to analyze the effects of three calibration objectives to the head and cervical kinematics of the model. Methodology The VIVA OpenHBM head-neck model, previously validated to PMHS data, was used. To represent the 34 cervical muscles, 129 beam elements with Hill-type material models were implemented. A closedloop control strategy was applied to activate these muscles mimicking the human body’s vestibular system. Calibration studies of head and cervical spine kinematics were conducted by comparing the model against published-volunteer responses to identify reasonable gain values for the controller. Three different calibrations were conducted with three different objectives: head kinematics in linear and angular direction, head and cervical spine kinematics in angular direction, and head and cervical spine kinematics in linear and angular direction. Results and Conclusion The simulation results show that the reflexive feedback control was numerically stable and able to control model muscle’s activation. Gain values of the implemented muscle control strategies were able to be identified from calibration simulations. Muscle activation changed the head kinematics by reducing peak linear and angular displacements, as compared to the model without muscle activation. The agreement of specific kinematic variables such as head kinematic and cervical spine angular displacement was dependent on the controller calibration objectives. Best agreement of head kinematics was observed in the model that calibrated against only volunteer head kinematics. However, in the vertical and angular direction there was a discrepancy of head response caused by anteriorposterior buckling of the cervical spine. In the model that was calibrated against head and cervical spine in angular direction, less contraction of cervical muscles was observed. As the result, good agreement was obtained in the cervical spine angular kinematics but not in the head kinematics. The best agreement was obtained by the model that calibrated against both linear and angular displacement of volunteer head and cervical spine kinematics although reduced the agreement of head kinematics compared to the model that was calibrated against only volunteer head kinematics. This was because of different calibration objectives that opposing each other.
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| 3. |
- Putra, I Putu Alit, 1992, et al.
(author)
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Optimization of Female Head–Neck Model with Active Reflexive Cervical Muscles in Low Severity Rear Impact Collisions
- 2021
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In: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 1573-9686 .- 0090-6964. ; 49:1, s. 115-128
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Journal article (peer-reviewed)abstract
- ViVA Open Human Body Model (HBM) is an open-source human body model that was developed to fill the gap of currently available models that lacked the average female size. In this study, the head–neck model of ViVA OpenHBM was further developed by adding active muscle controllers for the cervical muscles to represent the human neck muscle reflex system as studies have shown that cervical muscles influence head–neck kinematics during impacts. The muscle controller was calibrated by conducting optimizationbased parameter identification of published-volunteer data. The effects of different calibration objectives to head–neck kinematics were analyzed and compared. In general, a model with active neck muscles improved the head–neck kinematics agreement with volunteer responses. The current study highlights the importance of including active muscle response to mimic the volunteer’s kinematics. A simple PD controller has found to be able to represent the behavior of the neck muscle reflex system. The optimum gains that defined the muscle controllers in the present study were able to be identified using optimizations. The present study provides a basis for describing an active muscle controller that can be used in future studies to investigate whiplash injuries in rear impacts.
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| 4. |
- Fries, Johan, et al.
(author)
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Key parameters for droplet evaporation and mixing at the cloud edge
- 2021
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In: Quarterly Journal of the Royal Meteorological Society. - : Wiley. - 0035-9009 .- 1477-870X. ; 147:737, s. 2160-2172
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Journal article (peer-reviewed)abstract
- The distribution of liquid water in ice-free clouds determines their radiative properties, a significant source of uncertainty in weather and climate models. Evaporation and turbulent mixing cause a cloud to display large variations in droplet number density, but quite small variations in droplet size (Beals et al., Science, 2015, vol. 350, pp. 87-90). However, direct numerical simulations of the joint effect of evaporation and mixing near the cloud edge predict quite different behaviours, and how to reconcile these results with the experimental findings remains an open question. To infer the history of mixing and evaporation from observational snapshots of droplets in clouds is challenging, because clouds are transient systems. We formulated a statistical model that provides a reliable description of the evaporation-mixing process as seen in direct numerical simulations and allows us to infer important aspects of the history of observed droplet populations, highlighting the key mechanisms at work and explaining the differences between observations and simulations.
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| 5. |
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| 6. |
- Fries, Johan, et al.
(author)
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Lagrangian Supersaturation Fluctuations at the Cloud Edge
- 2023
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In: Physical Review Letters. - : American Physical Society (APS). - 1079-7114 .- 0031-9007. ; 131:25
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Journal article (peer-reviewed)abstract
- Evaporation of cloud droplets accelerates when turbulence mixes dry air into the cloud, affecting droplet-size distributions in atmospheric clouds, combustion sprays, and jets of exhaled droplets. The challenge is to model local correlations between droplet numbers, sizes, and supersaturation, which determine supersaturation fluctuations along droplet paths (Lagrangian fluctuations). We derived a statistical model that accounts for these correlations. Its predictions are in quantitative agreement with results of direct numerical simulations, and explain the key mechanisms at play.
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| 7. |
- Hallin, Karl, 1977, et al.
(author)
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Modelling Information for Mechatronic Products
- 2003
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In: Proceedings of ICED 03. ; :1331, s. 11-
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Journal article (peer-reviewed)abstract
- In mechatronic product development, there is a lack of a common understanding among different engineering domains, regarding the design. One step in improving this situation is to develop information models capable of representing both hardware and software elements. The objective of this paper is to investigate the Chromosome Model’s ability with respect to the mechatronic product and also to suggest an information model which implements its principles. The approach takes its point of departure on a theoretical level by analysing theories from mechanical and software engineering. Further, software concepts of relevance are incorporated into the Chromosome Model. The result, referred to as a meta model, is then transformed to an information model by utilising STEP AP214. Both the meta model and the information model are validated with an industrial example. The conclusions drawn from the work are that the Chromosome Model can be used as a meta model for mechatronic products and that STEP AP214 can be deployed within the scope of the meta model. The resulting information model captures the functional, causal and spatial relationships of a mechatronic product.
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| 8. |
- Kohn Rådberg, Kamilla, 1967, et al.
(author)
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From CDIO to challenge-based learning experiences – expanding student learning as well as societal impact?
- 2020
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In: European Journal of Engineering Education. - : Informa UK Limited. - 0304-3797 .- 1469-5898. ; 45:1, s. 22-37
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Journal article (peer-reviewed)abstract
- Challenge-based learning (CBL) is a multidisciplinary approach that encourages students to work actively with peers, teachers and stakeholders in society to identify complex challenges, formulate relevant questions and take action for sustainable development. In this paper, it is argued that CBL can be viewed as an evolution of the Conceive, Design, Implement, Operate concept, expanding as well as deepening the learning experience. The study reported on investigates the multiple aims of a particular CBL environment (the Challenge Lab at Chalmers University of Technology), which are to combine significant student learning and societal transformation. The results show that the students perceive that they have developed deep skills in problem formulation and sustainable development, as well as working across disciplines and with different stakeholders. Moreover, the study shows that although few student projects reach implementation stage, there is a potential for societal impact both during and after the Challenge Lab learning experience.
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| 9. |
- Putra, I Putu Alit, 1992, et al.
(author)
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Comparison of control strategies for the cervical muscles of an average female head-neck finite element model
- 2019
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In: Traffic Injury Prevention. - : Taylor & Francis. - 1538-9588 .- 1538-957X. ; 20:S2, s. S116-S122
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Journal article (peer-reviewed)abstract
- Objective: ViVA OpenHBM is the first open source Human Body Model (HBM) for crash safety assessment. It represents an average size (50th percentile) female and was created to assess whiplash protection systems in a car. To increase the biofidelity of the current model, further enhancements are being made by implementing muscle reflex response capabilities as cervical muscles alter the head and neck kinematics of the occupant during low-speed rear crashes. The objective of this study was to assess how different neck muscle activation control strategies affect head-neck kinematics in low speed rear impacts.Methods: The VIVA OpenHBM head-neck model, previously validated to PMHS data, was used for this study. To represent the 34 cervical muscles, 129 beam elements with Hill-type material models were used. Two different muscle activation control strategies were implemented: a control strategy to mimic neural feedback from the vestibular system and a control strategy to represent displacement feedback from muscle spindles. To identify control gain values for these controller strategies, parameter calibrations were conducted using optimization. The objective of these optimizations was to match the head linear and angular displacements measured in volunteer tests.Results: Muscle activation changed the head kinematics by reducing the peak linear displacements, as compared to the model without muscle activation. For the muscle activation model mimicking the human vestibular system, a good agreement was observed for the horizontal head translation. However, in the vertical direction there was a discrepancy of head kinematic response caused by buckling of the cervical spine. In the model with a control strategy that represents muscle spindle feedback, improvements in translational head kinematics were observed and less cervical spine buckling was observed. Although, the overall kinematic responses were better in the first strategy.Conclusions: Both muscle control strategies improved the head kinematics compared to the passive model and comparable to the volunteer kinematics responses with overall better agreement achieved by the model with active muscles mimicking the human vestibular system.
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| 10. |
- Putra, I Putu Alit, 1992, et al.
(author)
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COMPARISON OF HEAD-NECK KINEMATICS BETWEEN ISOLATED FINITE ELEMENT (FE) HEAD-NECK MODEL AND FULL-BODY MODEL IN LOW SEVERITY REAR-END IMPACT
- 2023
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In: 27th ESV Conference Proceedings. - : National Highway Traffic Safety Administration.
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Conference paper (peer-reviewed)abstract
- The objective of the present study was to analyze whether the kinematics of an isolated head-neck model can replicate those observed on a whole body model in order to reduce simulation time in development or optimization tasks. Previous studies have shown how muscle controllers improved head-neck kinematics responses over a passive neck muscle implementation. These studies used volunteer T1 displacement time histories prescribed on the model T1 as the loading input to develop the neck controller characteristics. It was not clear whether the implementation of a controller based on volunteer kinematics with an isolated head-neck model was directly transferable to a full-body model. The current study shows that the head-neck model produced almost identical responses as the full body model for the first 200ms of the event for most kinematic variables. The head rotational displacement corresponded well during the first 150ms. The isolated head-neck model predicted more displacement and rotations than when mounted on a full-body model. The current simplification of a head-neck model still produced reasonable kinematic responses during the critical time period to assess soft tissue neck injuries, making it suitable for developing and tuning neck muscle controllers.
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