Hostname: page-component-78c5997874-t5tsf Total loading time: 0 Render date: 2024-11-05T05:01:46.623Z Has data issue: false hasContentIssue false
  • English
  • Français

Empowering lower limbs exoskeletons: state-of-the-art

Published online by Cambridge University Press:  15 August 2018

Slavka Viteckova Open the ORCID record for Slavka Viteckova [Opens in a new window] ,
Patrik Kutilek ,
Gérard de Boisboissel ,
Radim Krupicka ,
Alena Galajdova ,
Jan Kauler ,
Lenka Lhotska  and
Zoltan Szabo
Slavka Viteckova*
Affiliation:
Faculty of Biomedical Engineering, Czech Technical University in Prague, Prague, Czechia
Patrik Kutilek
Affiliation:
Faculty of Biomedical Engineering, Czech Technical University in Prague, Prague, Czechia
Gérard de Boisboissel
Affiliation:
Saint-Cyr Military Academy Research Center, Guyer, France
Radim Krupicka
Affiliation:
Faculty of Biomedical Engineering, Czech Technical University in Prague, Prague, Czechia
Alena Galajdova
Affiliation:
Faculty of Mechanical Engineering, The Technical University of Košice, Košice, Slovakia
Jan Kauler
Affiliation:
Faculty of Biomedical Engineering, Czech Technical University in Prague, Prague, Czechia
Lenka Lhotska
Affiliation:
Faculty of Biomedical Engineering, Czech Technical University in Prague, Prague, Czechia
Zoltan Szabo
Affiliation:
Faculty of Biomedical Engineering, Czech Technical University in Prague, Prague, Czechia
*
*Corresponding author. E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Summary

Given the advanced breakthroughs in the field of supportive robotic technologies, interest in the integration of the human body and a robot into a single system has rapidly increased. The aim of this work is to provide an overview of empowering lower limbs exoskeletons. Along with lower exoskeleton limbs, their unique design concepts, operator–exoskeleton interactions and control strategies are described. Although many problems have been solved in recent development, many challenges remain. Especially in the context of infantry soldiers, fire fighters and rescuers, the challenges of empowering exoskeletons are discussed, and improvements are outlined and described. This study is not only a summary of the current state, but also points to weaknesses of empowering lower limbs exoskeletons and outlines possible improvements.

Keywords

AugmentationEmpoweringExoskeletonLower limbsWearable robot
Type
Articles
Information
Robotica , Volume 36 , Issue 11 , November 2018 , pp. 1743 - 1756
Copyright
Copyright © Cambridge University Press 2018 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1. Viteckova, S., Kutilek, P. and Jirina, M., “Wearable lower limb robotics: A review,” Biocybernetics Biomed. Eng. 33 (2), 96–105 (2013).Google Scholar
2. ReWalk Robotics, Inc., “Rewalk 6.0–home,” Web Page (http://rewalk.com/), Accessed: Feb. 2017.Google Scholar
3. Kwa, H. K., Noorden, J., Missel, M., Craig, T., Pratt, J. and Neuhaus, P., “Development of the IHMC Mobility Assist Exoskeleton,” Proceedings of the IEEE International Conference on Robotics and Automation ICRA'09 (May 2009) pp. 2556–2562.Google Scholar
4. Rex Bionics, “Rex bionics,” Web Page (www.rexbionics.com), Accessed: Feb. 2017.Google Scholar
5. Kim, J.-H., Han, J. W., Kim, D. Y. and Baek, Y. S., “Design of a walking assistance lower limb exoskeleton for paraplegic patients and hardware validation using cop,” Int. J. Adv. Robotic Syst. 10 (2012). doi: 10.5772/55336Google Scholar
6. Zhang, C., Liu, G., Li, C., Zhao, J., Yu, H. and Zhu, Y., “Development of a lower limb rehabilitation exoskeleton based on real-time gait detection and gait tracking,” Adv. Mech. Eng. 8 (1), 1687814015627982 (2016).Google Scholar
7. Aguilar-Sierra, H., Yu, W., Salazar, S. and Lopez, R., “Design and control of hybrid actuation lower limb exoskeleton,” Adv. Mech. Eng. 7 (6), 1687814015590988 (2015).Google Scholar
8. Dollar, A. M. and Herr, H., “Lower extremity exoskeletons and active orthoses: Challenges and state-of-the-art,” IEEE Trans. Robot. 24, 144–158 (Feb. 2008).Google Scholar
9. Boynton, A. C., Crowell, H. P. III, and U. S. A. R. Laboratory, “A human factors evaluation of exoskeleton boot interface sole thickness,” ARL-TR-3812. Technical report (2006). https://www.arl.army.mil/arlreports/2006/technical-report.cfm?id=1188.Google Scholar
10. Schiffman, J. M., Gregorczyk, K. N., Bensel, C. K., Hasselquist, L. and Obusek, J. P., “The effects of a lower body exoskeleton load carriage assistive device on limits of stability and postural sway,” Ergonomics 51 (10), 1515–1529 (2008). PMID: 18803092.Google Scholar
11. Gregorczyk, K. N., Hasselquist, L., Schiffman, J. M., Bensel, C. K., Obusek, J. P. and Gutekunst, D. J., “Effects of a lower-body exoskeleton device on metabolic cost and gait biomechanics during load carriage,” Ergonomics 53 (10), 1263–1275 (2010). PMID: 20865609.Google Scholar
12. de Boisboissel, G., “Le Soldat Augmenté (The Enhanced Soldier),” Défense & Sécurité Internationale 45th Off-Line Review (2015) p. 56.Google Scholar
13. Séchaud, P., “Le Soldat Augmenté (The Enhanced Soldier),” Défense & sScurité Internationale 45th Off-Line Review (2015) p. 52.Google Scholar
14. Dollar, A. M. and Herr, H. M., “Design of a Quasi-Passive Knee Exoskeleton to Assist Running,” Proceedings of the Intelligent Robots and Systems, IEEE (2008) pp. 747–754.Google Scholar
15. Díaz, I., Gil, J. J. and Sánchez, E., “Lower-limb robotic rehabilitation: Literature review and challenges,” J. Robot. 2011 (2011). doi: 10.1155/2011/759764Google Scholar
16. Mohammed, S., Amirat, Y. and Rifai, H., “Lower-limb movement assistance through wearable robots: State of the art and challenges,” Adv. Robot. 26 (1–2), 1–22 (2012).Google Scholar
17. Chen, G., Chan, C. K., Guo, Z. and Yu, H., “A review of lower extremity assistive robotic exoskeletons in rehabilitation therapy,” Crit. Rev. &trade Biomed. Eng. 41 (4–5), 343–363 (2013).Google Scholar
18. Huo, W., Mohammed, S., Moreno, J. C. and Amirat, Y., “Lower limb wearable robots for assistance and rehabilitation: A state of the art,” IEEE Syst. J. 10, 1068–1081 (Sept 2016).Google Scholar
19. Chen, B., Ma, H., Qin, L.-Y., Gao, F., Chan, K.-M., Law, S.-W., Qin, L. and Liao, W.-H., “Recent developments and challenges of lower extremity exoskeletons,” J. Orthopaedic Transl. 5 (Supplement C), 26–37 (2016). Special Issue: Orthopaedic Biomaterials and Devices.Google Scholar
20. Young, A. J. and Ferris, D. P., “State of the art and future directions for lower limb robotic exoskeletons,” IEEE Trans. Neural Syst. Rehabil. Eng. 25, 171–182 (Feb. 2017).Google Scholar
21. Yang, C.-J., Zhang, J.-F., Chen, Y., Dong, Y.-M. and Zhang, Y., “A review of exoskeleton-type systems and their key technologies,” Proc. Inst. Mech. Eng., Part C: J. Mech. Eng. Sci. 222 (8), 1599–1612 (2008).Google Scholar
22. Lee, H., Kim, W., Han, J. and Han, C., “The technical trend of the exoskeleton robot system for human power assistance,” Int. J. Precis. Eng. Manuf. 13, 1491–1497 (Aug. 2012).Google Scholar
23. Anam, K. and Al-Jumaily, A. A., “Active exoskeleton control systems: State of the art,” Procedia Eng. 41 (Supplement C), 988–994 (2012). International Symposium on Robotics and Intelligent Sensors 2012 (IRIS 2012).Google Scholar
24. Kazerooni, H., The Berkeley Lower Extremity Exoskeleton (Springer, Berlin, Heidelberg, 2006).Google Scholar
25. Accoto, D., Sergi, F., Tagliamonte, N. L., Carpino, G., Sudano, A. and Guglielmelli, E., “Robomorphism: A nonanthropomorphic wearable robot,” IEEE Robot. Autom. Mag. 21, 45–55 (Dec. 2014).Google Scholar
26. Colombo, G., Wirz, M. and Dietz, V., “Driven gait orthosis for improvement of locomotor training in paraplegic patients,” Spinal Cord 39, 252 EP– (06 2001).Google Scholar
27. Hidler, J. M. and Wall, A. E., “Alterations in muscle activation patterns during robotic-assisted walking,” Clin. Biomech. 20, 184–193 (2017/12/16 2005).Google Scholar
28. Veale, A. J. and Xie, S. Q., “Towards compliant and wearable robotic orthoses: A review of current and emerging actuator technologies,” Med. Eng. Phys. 38 (4), 317–325 (2016).Google Scholar
29. Walsh, C. J., Endo, K. and Herr, H., “A quasi-passive leg exoskeleton for load-carrying augmentation,” I. J. Humanoid Robot. 4 (3), 487–506 (2007).Google Scholar
30. Shamaei, K., Cenciarini, M., Adams, A. A., Gregorczyk, K. N., Schiffman, J. M. and Dollar, A. M., “Design and evaluation of a quasi-passive knee exoskeleton for investigation of motor adaptation in lower extremity joints,” IEEE Trans. Biomed. Eng. 61, 1809–1821 (Jun. 2014).Google Scholar
31. van Dijk, W., van der Kooij, H. and Hekman, E., “A Passive Exoskeleton with Artificial Tendons: Design and Experimental Evaluation,” Proceedings of the IEEE International Conference on Rehabilitation Robotics (Jun. 2011) pp. 1–6.Google Scholar
32. Australian Government, Department of Defence Science and Technology, “Flexible skeleton takes the weight off,” Web Page (https://www.dst.defence.gov.au/news/2015/07/31/flexible-skeleton-takes-weight), Accessed: Dec. 2017.Google Scholar
33. Mooney, L. M., Rouse, E. J. and Herr, H. M., “Autonomous exoskeleton reduces metabolic cost of human walking during load carriage,” J. NeuroEng. Rehabil. 11, 80 (May 2014).Google Scholar
34. Rosen, J. and Perry, J. C., “Upper limb powered exoskeleton,” Int. J. Humanoid Robot. 04 (03), 529–548 (2007).Google Scholar
35. Kim, W., Lee, S., Kang, M., Han, J. and Han, C., “Energy-Efficient Gait Pattern Generation of the Powered Robotic Exoskeleton Using DME,” Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (Oct. 2010) pp. 2475–2480.Google Scholar
36. Yamamoto, K., Hyodo, K., Ishii, M. and Matsuo, T., “Development of power assisting suit for assisting nurse labor,” JSME Int. J. Series C 45, 703–711 (2004).Google Scholar
37. Yan, T., Cempini, M., Oddo, C. M. and Vitiello, N., “Review of assistive strategies in powered lower-limb orthoses and exoskeletons,” Robot. Auton. Syst. 64, 120–136 (2015).Google Scholar
38. Marchal-Crespo, L. and Reinkensmeyer, D. J., “Review of control strategies for robotic movement training after neurologic injury,” J. NeuroEng. Rehabil. 6, 20–20 (2009).Google Scholar
39. Tucker, M. R., Olivier, J., Pagel, A., Bleuler, H., Bouri, M., Lambercy, O., Millán, J. d. R., Riener, R., Vallery, H. and Gassert, R., “Control strategies for active lower extremity prosthetics and orthotics: A review,” J. NeuroEng. Rehabil. 12, 1 (Jan. 2015).Google Scholar
40. Kazerooni, H., Racine, J. L., Huang, L. and Steger, R., “On the Control of the Berkeley Lower Extremity Exoskeleton (BLEEX),” Proceedings of the IEEE International Conference on Robotics and Automation (Apr. 2005) pp. 4353–4360.Google Scholar
41. Swift, T. A., Strausser, K. A., Zoss, A. B. and Kazerooni, H., “Control and Experimental Results for Post Stroke Gait Rehabilitation with a Prototype Mobile Medical Exoskeleton,” Proceedings of the ASME 2010 Dynamic Systems and Control Conference, vol. 1 (2010) pp. 405–411.Google Scholar
42. Kutilek, P., Mares, J., Hybl, J., Socha, V., Schlenker, J. and Stefek, A., “Myoelectric arm using artificial neural networks to reduce cognitive load of the user,” Neural Comput. Appl. 28 (2), 419–427 (2017).Google Scholar
43. Rosen, J., Fuchs, M. B. and Arcan, M., “Performances of hill-type and neural network muscle models—toward a myosignal-based exoskeleton,” Comput. Biomed. Res. 32, 415–439 (Oct. 1999).Google Scholar
44. Fontana, M., Vertechy, R., Marcheschi, S., Salsedo, F. and Bergamasco, M., “The body extender: A full-body exoskeleton for the transport and handling of heavy loads,” IEEE Robot. Autom. Mag. 21, 34–44 (Dec. 2014).Google Scholar
45. Chen, F., Yu, Y., Ge, Y., Sun, J. and Deng, X., “WPAL for Enhancing Human Strength and Endurance during Walking,” Proceedings of the International Conference on Information Acquisition ICIA'07 (Jul. 2007) pp. 487–491.Google Scholar
46. Peternel, L., Noda, T., Petrič, T., Ude, A., Morimoto, J. and Babič, J., “Adaptive control of exoskeleton robots for periodic assistive behaviours based on EMG feedback minimisation,” PLOS ONE 11, 1–26 (02 2016).Google Scholar
47. Zadeh, L., “Fuzzy sets,” Inform. Control 8 (3), 338–353 (1965).Google Scholar
48. Kong, K. and Jeon, D., “Design and control of an exoskeleton for the elderly and patients,” IEEE/ASME Trans. Mechatron. 11, 428–432 (Aug. 2006).Google Scholar
49. Skoda, D., Kutilek, P., Socha, V., Schlenker, J., Stefek, A. and Kalina, J., “The Estimation of the Joint Angles of Upper Limb During Walking Using Fuzzy Logic System and Relation Maps,” Proceedings of the 2015 IEEE 13th International Symposium on Applied Machine Intelligence and Informatics (SAMI) (Jan. 2015) pp. 267–272.Google Scholar
50. Yin, Y. H., Fan, Y. J. and Xu, L. D., “Emg and epp-integrated human–machine interface between the paralyzed and rehabilitation exoskeleton,” IEEE Trans. Inform. Technol. Biomed. 16, 542–549 (Jul. 2012).Google Scholar
51. Kutilek, P. and Farkasova, B., “Prediction of lower extremities' movement by angle-angle diagrams and neural networks,” Acta Bioeng. Biomech. 13 (2), 57–65 (2011).Google Scholar
52. Yeh, T.-J., Wu, M.-J., Lu, T.-J., Wu, F.-K. and Huang, C.-R., “Control of mckibben pneumatic muscles for a power-assist, lower-limb orthosis,” Mechatronics 20 (6), 686–697 (2010).Google Scholar
53. Pratt, J., Krupp, B., Morse, C. and Collins, S., “The Roboknee: An Exoskeleton for Enhancing Strength and Endurance During Walking,” Proceedings of the IEEE International Conference on Robotics and Automation ICRA'04, vol. 3 (Apr. 2004) pp. 2430–2435.Google Scholar
54. B-TEMIA Inc., “K-srd sup TM dermoskeleton sup TM,” Web Page (http://military.b-temia.com/k-srd-dermoskeleton), Accessed: Jan. 2017.Google Scholar
55. Ste-Croix, C., Tack, D., Boucher, D., Ruel, F., Pageau, G. and Bedard, S., “Experimental evaluation of the dermoskeleton concept: Addressing the soldiers overload challenge,” Proceedings of the Human Factors and Ergonomics Society Annual Meeting 56 (1), 2393–2396 (2012).Google Scholar
56. Mooney, L. M. and Herr, H. M., “Biomechanical walking mechanisms underlying the metabolic reduction caused by an autonomous exoskeleton,” J. NeuroEng. Rehabil. 13, 4 (2016).Google Scholar
57. Mosher, R. S., “Handyman to hardiman,” Tech. Rep., Soc. Autom. Eng. Int. (SAE), 1967.Google Scholar
58. Fick, B. R. and Makinson, J. B., “Hardiman i prototype for machine augmentation of human strength and endurance,” Tech. Rep., GENERAL ELECTRIC CO SCHENECTADY NY SPECIALTY MATERIALS HANDLING PRODUCTS OPERATION, 1971.Google Scholar
59. Moore, J. A., “Pitman: A powered exoskeleton suit for the infantryman,” Tech. Rep., Los Alamos Nat. Lab., Los Alamos, NM, Tech. Rep. LA-10761-MS, 1986.Google Scholar
60. Rosheim, M. E., “Man-Amplifying Exoskeleton,” In: Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (Chun, W. H. and Wolfe, W. J., eds.), vol. 1195 (SPIE Press, Washington, USA, Mar. 1990) pp. 402–411.Google Scholar
61. Kazerooni, H., Steger, R. and Huang, L., “Hybrid control of the Berkeley lower extremity exoskeleton (BLEEX),” Int. J. Robot. Res. 25 (5–6), 561–573 (2006).Google Scholar
62. Zoss, A., Kazerooni, H. and Chu, A., “Biomechanical design of the Berkeley lower extremity exoskeleton (BLEEX),” IEEE/ASME Trans. Mechatron. 11, 128–138 (Apr. 2006).Google Scholar
63. Robotics, B., “Berkeley robotics & human engineering laboratory, exohiker™,” Web Page (http://bleex.me.berkeley.edu/research/exoskeleton/exohiker/), Accessed: Jul. 2018.Google Scholar
64. Robotics, B., “Berkeley robotics & human engineering laboratory, exoclimber™,” Web Page (http://bleex.me.berkeley.edu/research/exoskeleton/exoclimber/), Accessed: Jun. 2018.Google Scholar
65. Lockheed, M., “Hulc® with lift assist device” Web page (http://www.lockheedmartin.com).Google Scholar
66. Robotics, B., “Berkeley robotics & human engineering laboratory, bleex,” Web Page (http://bleex.me.berkeley.edu/research/exoskeleton/bleex), Accessed: Jul. 2018.Google Scholar
67. Robotics, B., “Berkeley robotics & human engineering laboratory, hulc™,” Web Page (http://bleex.me.berkeley.edu/research/exoskeleton/hulc), Accessed: Jul. 2018.Google Scholar
68. RB3D, “Exoskeletons hercule,” Web Page (http://www.rb3d.com/en/exo), Accessed: Jan 2017.Google Scholar
69. Yoshimitsu, T. and Yamamoto, K., “Development of a Power Assist Suit for Nursing Work,” SICE 2004 Annual Conference, vol. 1 (Aug. 2004) pp. 577–580.Google Scholar
70. Walsh, C. J., Pasch, K. and Herr, H., “An Autonomous, Underactuated Exoskeleton for Load-Carrying Augmentation,” Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (Oct. 2006) pp. 1410–1415.Google Scholar
71. Walsh, C., Paluska, D., Pasch, K., Grand, W., Valiente, A. and Herr, H., “Development of a Lightweight, Underactuated Exoskeleton for Load-Carrying Augmentation,” Proceedings IEEE International Conference on Robotics and Automation ICRA2006 (May 2006) pp. 3485–3491.Google Scholar
72. Kim, W.-S., Lee, S.-H., Lee, H.-D., Yu, S.-N., Han, J.-S. and Han, C.-S., “Development of the Heavy Load Transferring Task Oriented Exoskeleton Adapted by Lower Extremity Using Qausi—Active Joints,” Proceedings of the ICCAS-SICE (Aug. 2009) pp. 1353–1358.Google Scholar
73. Toyama, S. and Yamamoto, G., “Development of Wearable-Agri-Robot—Mechanism for Agricultural Work,” Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems IROS2009 (Oct. 2009) pp. 5801–5806.Google Scholar
74. Marcheschi, S., Salsedo, F., Fontana, M. and Bergamasco, M., “Body Extender: Whole Body Exoskeleton for Human Power Augmentation,” Proceedings of the IEEE International Conference on Robotics and Automation (May 2011) pp. 611–616.Google Scholar
75. Lim, D., Kim, W., Lee, H., Kim, H., Shin, K., Park, T., Lee, J. and Han, C., “Development of a Lower Extremity Exoskeleton Robot with a Quasi-Anthropomorphic Design Approach for Load Carriage,” Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems IROS (Sep. 2015) pp. 5345–5350.Google Scholar
76. Zoss, A., Kazerooni, H. and Chu, A., “On the Mechanical Design of the Berkeley Lower Extremity Exoskeleton (BLEEX),” Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (Aug. 2005) pp. 3465–3472.Google Scholar
77. Wang, L., Bao, S. and Wang, K., “Experimentation Research on Lower-Limb Power Assisted Robot,” Proceedings of the 8th World Congress on Intelligent Control and Automation WCICA (Jul. 2010) pp. 1462–1467.Google Scholar
78. Miao, Y., Gao, F. and Pan, D., “Mechanical design of a hybrid leg exoskeleton to augment load-carrying for walking,” Int. J. Adv. Robot. Syst. 10 (11), 395 (2013).Google Scholar
79. Yali, H. and Xingsong, W., “Kinematics Analysis of Lower Extremity Exoskeleton,” Proceedings of the Control and Decision Conference CCDC2008, Chinese (2008) pp. 2837–2842.Google Scholar
80. Zhao, Y., Xu, C., Luo, Y. and Wang, Y., “Design, Modeling and Simulation of the Human Lower Extremity Exoskeleton,” Proceedings of the Control and Decision Conference (2008) pp. 3335–3339.Google Scholar
81. Activelink, “Powerloader light “pll”,” Web Page (http://activelink.co.jp), Accessed: Feb. 2017.Google Scholar
82. Jacobsen, S. C., Olivier, M., Smith, F. M., Knutti, D. F., Johnson, R. T., Colvin, G. E. and Scroggin, W. B., “Research robots for applications in artificial intelligence, teleoperation and entertainment,” Int. J. Robot. Res. 23 (4–5), 319–330 (2004).Google Scholar
83. Sarcos Corp., “Raytheon,” Web Page (http://www.raytheon.com), Accessed: Mar. 2017.Google Scholar
84. Sarcos Corp., “Sarcos product fact sheets,” Web Page (https://www.sarcos.com), Accessed: Jun. 2018.Google Scholar
85. Cyberdyne, “Other hal®series,” Web Page (https://www.cyberdyne.jp/english/), Accessed: Jan. 2017.Google Scholar
86. Mitsubishi, “Mhi develops power assist suit (pas) for nuclear disaster response,” Web Page (http://www.mhi-global.com), Accessed: Jan. 2017.Google Scholar
87. Rasouli, M. and Phee, L. S. J., “Energy sources and their development for application in medical devices,” Expert Rev. Med. Devices 7 (5), 693–709 (2010).Google Scholar
88. Wei, C. and Jing, X., “A comprehensive review on vibration energy harvesting: Modelling and realization,” Renewable Sustainable Energy Rev. 74 (Supplement C), 1–18 (2017).Google Scholar
89. Ruiz-Muñoz, M. and Cuesta-Vargas, A. I., “Electromyography and sonomyography analysis of the tibialis anterior: A cross sectional study,” J. Foot Ankle Res. 7, 11–11 (2014).Google Scholar
90. Chen, X., Zheng, Y.-P., Guo, J.-Y. and Shi, J., “Sonomyography (SMG) control for powered prosthetic hand: A study with normal subjects,” Ultrasound Med. Biol. 36, 1076–1088 (2017/12/16 2010).Google Scholar
91. Champion, R., Drones et killer robots : Faut-il les interdire ? (French) (Presses Universitaires de Rennes, Rennes, France, 2015), p. 16.Google Scholar
92. Asbeck, A. T., De Rossi, S., Galiana, I., Ding, Y. and Walsh, C. J., “Stronger, smarter, softer: Next-generation wearable robots,” IEEE Robot. Autom. Mag. 21 (4), 22–33 (2014).Google Scholar