Authors

Jianping Lin, Nikhil V. Divekar, Ge Lv, Robert D. Gregg

Abstract

Task-invariant control methods for powered exoskeletons provide flexibility in assisting humans across multiple activities and environments. Energy shaping control serves this purpose by altering the human body’s dynamic characteristics in closed loop. Our previous work on potential energy shaping alters the gravitational vector to reduce the user’s perceived gravity, but this method cannot provide velocity-dependent assistance. The interconnection and damping assignment passivity-based control (IDA-PBC) method provides more freedom to shape a dynamical system’s energy through the interconnection structure of a port-controlled Hamiltonian system model. This paper derives a novel energetic control strategy based on IDA-PBC for a backdrivable knee-ankle exoskeleton. The control law provides torques that depend on various basis functions related to gravitational and gyroscopic terms. We optimize a set of constant weighting parameters for these basis functions to obtain a control law that produces ablebodied joint torques during walking on multiple ground slopes. We perform experiments with an able-bodied human subject wearing a knee-ankle exoskeleton to demonstrate reduced activation in certain lower-limb muscles.

Citation

BibTeX

@inproceedings{Lin_2021,
  title={{Optimal Task-Invariant Energetic Control for a Knee-Ankle Exoskeleton}},
  DOI={10.23919/acc50511.2021.9483212},
  booktitle={{2021 American Control Conference (ACC)}},
  publisher={IEEE},
  author={Lin, Jianping and Divekar, Nikhil V. and Lv, Ge and Gregg, Robert D.},
  year={2021},
  pages={5029--5034}
}

Download the bib file

References

  • Blankenstein, G., Ortega, R. & Van Der Schaft, A. J. The matching conditions of controlled Lagrangians and IDA-passivity based control. International Journal of Control 75, 645–665 (2002) – 10.1080/00207170210135939
  • Ortega, R., van der Schaft, A., Maschke, B. & Escobar, G. Interconnection and damping assignment passivity-based control of port-controlled Hamiltonian systems. Automatica 38, 585–596 (2002) – 10.1016/s0005-1098(01)00278-3
  • de-León-Gómez, Ví., Santibañez, V. & Sandoval, J. Interconnection and damping assignment passivity-based control for a compass-like biped robot. International Journal of Advanced Robotic Systems 14, 172988141771659 (2017) – 10.1177/1729881417716593
  • Embry, K. R., Villarreal, D. J., Macaluso, R. L. & Gregg, R. D. Modeling the Kinematics of Human Locomotion Over Continuously Varying Speeds and Inclines. IEEE Trans. Neural Syst. Rehabil. Eng. 26, 2342–2350 (2018) – 10.1109/tnsre.2018.2879570
  • Mooney, L. M., Rouse, E. J. & Herr, H. M. Autonomous exoskeleton reduces metabolic cost of human walking during load carriage. J NeuroEngineering Rehabil 11, (2014) – 10.1186/1743-0003-11-80
  • Wang, J. et al. Comfort-Centered Design of a Lightweight and Backdrivable Knee Exoskeleton. IEEE Robot. Autom. Lett. 3, 4265–4272 (2018) – 10.1109/lra.2018.2864352
  • Ortega, R., Loría, A., Nicklasson, P. J. & Sira-Ramírez, H. Passivity-Based Control of Euler-Lagrange Systems. Communications and Control Engineering (Springer London, 1998). doi:10.1007/978-1-4471-3603-3 – 10.1007/978-1-4471-3603-3
  • khalil, Nonlinear Systems (2002)
  • Murray, R. M., Li, Z. & Sastry, S. S. A Mathematical Introduction to Robotic Manipulation. (CRC Press, 2017). doi:10.1201/9781315136370 – 10.1201/9781315136370
  • Zhu, H. et al. Design and validation of a torque dense, highly backdrivable powered knee-ankle orthosis. 2017 IEEE International Conference on Robotics and Automation (ICRA) 504–510 (2017) doi:10.1109/icra.2017.7989063 – 10.1109/icra.2017.7989063
  • Bloch, A. M., Leonard, N. E. & Marsden, J. E. Stabilization of mechanical systems using controlled Lagrangians. Proceedings of the 36th IEEE Conference on Decision and Control vol. 3 2356–2361 – 10.1109/cdc.1997.657135
  • Lv, G. & Gregg, R. D. Underactuated Potential Energy Shaping With Contact Constraints: Application to a Powered Knee-Ankle Orthosis. IEEE Trans. Contr. Syst. Technol. 26, 181–193 (2018) – 10.1109/tcst.2016.2646319
  • Divekar, N. V., Lin, J., Nesler, C., Borboa, S. & Gregg, R. D. A Potential Energy Shaping Controller with Ground Reaction Force Feedback for a Multi-Activity Knee-Ankle Exoskeleton. 2020 8th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob) 997–1003 (2020) doi:10.1109/biorob49111.2020.9224341 – 10.1109/biorob49111.2020.9224341
  • Lv, G., Zhu, H. & Gregg, R. D. On the Design and Control of Highly Backdrivable Lower-Limb Exoskeletons: A Discussion of Past and Ongoing Work. IEEE Control Syst. 38, 88–113 (2018) – 10.1109/mcs.2018.2866605
  • Lin, J., Divekar, N., Lv, G. & Gregg, R. D. Energy Shaping Control with Virtual Spring and Damper for Powered Exoskeletons. 2019 IEEE 58th Conference on Decision and Control (CDC) 3039–3045 (2019) doi:10.1109/cdc40024.2019.9029624 – 10.1109/cdc40024.2019.9029624
  • Lin, J., Lv, G. & Gregg, R. D. Contact-Invariant Total Energy Shaping Control for Powered Exoskeletons. 2019 American Control Conference (ACC) 664–670 (2019) doi:10.23919/acc.2019.8815003 – 10.23919/acc.2019.8815003
  • Harib, O. et al. Feedback Control of an Exoskeleton for Paraplegics: Toward Robustly Stable, Hands-Free Dynamic Walking. IEEE Control Syst. 38, 61–87 (2018) – 10.1109/mcs.2018.2866604
  • Yan, T., Cempini, M., Oddo, C. M. & Vitiello, N. Review of assistive strategies in powered lower-limb orthoses and exoskeletons. Robotics and Autonomous Systems 64, 120–136 (2015) – 10.1016/j.robot.2014.09.032
  • Colgate, J. E. & Schenkel, G. G. Passivity of a class of sampled-data systems: Application to haptic interfaces. J. Robotic Syst. 14, 37–47 (1997) – 10.1002/(sici)1097-4563(199701)14:1<37::aid-rob4>3.0.co;2-v
  • yang, Electromyographic amplitude normalization methods: improving their sensitivity as diagnostic tools in gait analysis. Arch Phys Med Rehabil (1984)
  • Pickle, N. T., Grabowski, A. M., Auyang, A. G. & Silverman, A. K. The functional roles of muscles during sloped walking. Journal of Biomechanics 49, 3244–3251 (2016) – 10.1016/j.jbiomech.2016.08.004