Subject-exoskeleton contact model calibration leads to accurate interaction force predictions

Knowledge of human–exoskeleton interaction forces is crucial to assess user comfort and effectiveness of the interaction. The subject-exoskeleton collaborative movement and its interaction forces can be predicted in silico using computational modeling techniques. We developed an optimal control framework that consisted of three phases. First, the foot-ground (Phase A) and the subject-exoskeleton (Phase B) contact models were calibrated using three experimental sit-to-stand trials. Then, the collaborative movement and the subject-exoskeleton interaction forces, of six different sit-to-stand trials were predicted (Phase C). The results show that the contact models were able to reproduce experimental kinematics of calibration trials (mean root mean square differences - RMSD - coordinates = 1.1° and velocities = 6.8°/s), ground reaction forces (mean RMSD= 22.9 N), as well as the interaction forces at the pelvis, thigh, and shank (mean RMSD = 5.4 N). Phase C could predict the collaborative movements of prediction trials (mean RMSD coordinates = 3.5° and velocities = 15.0°/s), and their subject-exoskeleton interaction forces (mean RMSD = 13.1° N). In conclusion, this optimal control framework could be used while designing exoskeletons to have in silico knowledge of new optimal movements and their interaction forces.Postprint (author's final draft

Recent Advances in Motion Analysis

The advances in the technology and methodology for human movement capture and analysis over the last decade have been remarkable. Besides acknowledged approaches for kinematic, dynamic, and electromyographic (EMG) analysis carried out in the laboratory, more recently developed devices, such as wearables, inertial measurement units, ambient sensors, and cameras or depth sensors, have been adopted on a wide scale. Furthermore, computational intelligence (CI) methods, such as artificial neural networks, have recently emerged as promising tools for the development and application of intelligent systems in motion analysis. Thus, the synergy of classic instrumentation and novel smart devices and techniques has created unique capabilities in the continuous monitoring of motor behaviors in different fields, such as clinics, sports, and ergonomics. However, real-time sensing, signal processing, human activity recognition, and characterization and interpretation of motion metrics and behaviors from sensor data still representing a challenging problem not only in laboratories but also at home and in the community. This book addresses open research issues related to the improvement of classic approaches and the development of novel technologies and techniques in the domain of motion analysis in all the various fields of application

Estratègies de control d'un exosquelet en el procés d'aixecar-se

L’ús d’exosquelets per a la rehabilitació de persones amb trastorns motrius greus ha demostrat que pot contribuir en la millora de la seva mobilitat o la seva autonomia en el desenvolupament de les tasques bàsiques de la vida diària. L’acció d’aixecar-se des d’una posició asseguda és una activitat bàsica del dia a dia que sol fer-se sense pensar, però comporta certa dificultat a persones amb parèsia o paràlisi de les extremitats inferiors. Una anàlisi més detallada dels factors que intervenen en el moviment mostra que no es pot tractar com un simple procediment de variació de posició, sinó que hi ha més variables a tenir en compte, com forces, parells i/o velocitats. En aquest projecte es desenvolupa una aplicació d’assistència al moviment d’aixecar-se d’una cadira utilitzant un exosquelet robòtic i proposant un nou sistema de control basat en la definició de diverses fases durant la transició del moviment, en funció de les característiques cinemàtiques de cada instant. La combinació de diverses estratègies de control i un algoritme que gestiona en temps real les transicions entre les fases permeten realitzar aquesta acció de manera més natural i cooperant amb l’usuari. El sistema de control proposat s’ha provat amb un exosquelet robòtic real i els resultats experimentals validen la teoria proposada i serviran de base per futurs treballs d’ampliació