Implementation and Calibration of the LS-DYNA PID Controller for Female Cervical Muscles
Conference contribution, 2018

Summary
A previously validated open-source head-neck model, VIVA Open HBM [1-3], was enhanced by the addition of muscle activation. The previous model contained 129 beam elements on both the left and right side of the neck. Each element had Hill 3 elements (*MAT_MUSCLE_156) [4,5] definitions for material model. However, these muscles were defined as passive muscles model without any active tensile forces.
The first goal of this study was to implement the LS-DYNA PID (Proportional Integral Derivative) feedback control mechanism [5,6] on Finite Element (FE) models of cervical muscles, using the enhancements introduced in LS-DYNA version 9.2 [5]. The second goal was to calibrate the PID control gains by conducting a parameter identification using LS-OPT [7] with published-volunteer data in rear impact collisions [8-9] being used as reference performance data.
To activate these muscles, the closed-loop control strategy (reflexive feedback control function) was applied. To develop this strategy, the LS-DYNA PID Control function (PIDCTL) which can be defined inside the *DEFINE_CURVE_FUNCTION keyword was utilized. The method of controlling muscles activation with reflexive feedback control was adopted from Östh, et.al [10] and Olafsdottir [11].
To mimic the human body’s vestibular system, the coordinates of two nodes (Head Center of Gravity node and T1 node) and a reference node were sampled at specific times reference and used to define the controller vector. An angle was calculated between these two vectors and the difference between this angle and a reference value was calculated. This error signal then was delayed, mimicking the human’s neural delay. To model this neural delay, the DELAY function inside *DEFINE_CURVE_FUNCTION was applied. The PID controllers were given the delayed-error signalfrom the previous calculation and used to compute a control signal with an objective of zero error.
A calibration study was conducted to identify reasonable gain values of the controller so that the head displacements of the model in X and Z direction match within ± 1 Standard Deviation (SD) head displacements of the volunteer data.
The simulation results show that the LS-DYNA PIDCTL and DELAY function were successfully utilized for controlling the model muscle’s activation and by using controller’s gain value from the calibration’s result, the model was able to capture the kinematics motion of the volunteer data within the defined-corridors

References
1.Östh, J., Vazquez, M. M., Svensson, M. Y., Linder, A., & Brolin, K. (2016). Development of a 50thpercentile female human body model. 2016 IRCOBI Conference Proceedings - International ResearchCouncil on the Biomechanics of Injury, 573–575.
2.Östh, J., Vazquez, M. M., Linder, A., Svensson, M. Y., & Brolin, K. (2017). The VIVA Open HBM FiniteElement 50th Percentile Female Occupant Model: Whole Body Model Development and KinematicValidation. 2017 IRCOBI Conference Proceedings - International Research Council on the Biomechanicsof Injury, 443-466.
3.Östh, J., Mendoza-Vazquez, M., Sato, F., Svensson, M. Y., Linder, A., & Brolin, K. (2017). A female head–neck model for rear impact simulations. Journal of Biomechanics, 51, 49–56.https://doi.org/10.1016/j.jbiomech.2016.11.066
4.Hill, A. V. (1938). The Heat of Shortening and the Dynamic Constants of Muscle. Proceedings of the RoyalSociety B: Biological Sciences, 126(843), 136–195. https://doi.org/10.1098/rspb.1938.0050
5.Livermore Software Technology Corporation. (2016). LS-DYNA Keyword User’s Manual, R9.0. LivermoreSoftware Technology Corporation (Vol. I).
6.Keisser, C., & Yeh, I. (2017). Control System in LS-DYNA. The 11th European LS-DYNA Conference2017.
7.Stander, N., Roux, W., Goel, T., Eggleston, T., & Craig, K. (2010). LS-OPT ® User’s Manual - A DesignOptimization and Probabilistic Analysis Tool.
8.Ono, K., Ejima, S., Suzuki, Y., Kaneoka, K., Fukushima, M., & Ujihashi, S. (2006). Prediction of NeckInjury Risk Based on the Analysis of Localized Cervical Vertebral Motion of Human Volunteers DuringLow-Speed Rear Impacts. IRCOBI Conference Proceedings, 103–113.
9.Sato, F., Nakajima, T., Ono, K., & Svensson, M. (2014). Dynamic Cervical Vertebral Motion of Femaleand Male Volunteers and Analysis of its Interaction with Head/Neck/Torso Behavior during Low-SpeedRear. IRCOBI Conference Proceedings, 227–249.
10.Östh, J., Brolin, K., & Happee, R. (2012). Active muscle response using feedback control of a finiteelement human arm model. Computer Methods in Biomechanics and Biomedical Engineering, 15(4), 347–361.https://doi.org/10.1080/10255842.2010.535523
11.Ólafsdóttir, J. M. (2017) Muscle Responses in Dynamic Events- Volunteer Experiments And NumericalModelling For The Advancement Of Human Body Models For Vehicle Safety Assessment, Ph.D ThesisIn Machine And Vehicle Systems, Chalmers University of Technology.

Acknowledgement:
This study was funded by the Swedish Governmental Agency for Innovation Systems (VINNOVA). The simulations were performed on resources at Chalmers Centre for Computational Science and Engineering (C3SE) provided by the Swedish National Infrastructure for Computing (SNIC) and carried out at Vehicle and Traffic Safety Research Centre at Chalmers (SAFER). The authors would like to thank the project members: Astrid Linder, Mats Svensson, Lotta Jacobson, Anders Kullgren and Anders Flögard.

cervical muscles

feedback control

human body model

PID control

finite element

Author

I Putu Alit Putra

Chalmers, Mechanics and Maritime Sciences, Vehicle Safety

Johan Iraeus

Chalmers, Mechanics and Maritime Sciences, Vehicle Safety

Robert Thomson

Chalmers, Mechanics and Maritime Sciences, Vehicle Safety

Nordic LS-DYNA User's Conference 2018
Gothenburg, Sweden,

Virtual Vehicle Safety Assessment Step 2: Open Source Human Body Models and Crash Testing (Viva II)

VINNOVA, 2017-01-01 -- 2019-06-30.

Subject Categories

Other Medical Engineering

Bioinformatics (Computational Biology)

Control Engineering

More information

Created

4/17/2019