1. Interaction based adaptive walking using a wearable exoskeleton Vijaykumar Rajasekaran, Joan Aranda and Alicia Casals Institute for Bioengineering of Catalonia and Universitat Politécnica de Catalunya, BarcelonaTech Barcelona, Spain
Assistive walking using exoskeletons constitutes a major step forward in rehabilitation. However, walking based on completely assisted robot therapies induces slacking and unassisted or passive robot strategies can even cause damage to the patient.
In this work joint stiffness is adjusted according to the user’s contribution to the movement (interaction with the orthosis) while maintaining the equilibrium. The interaction forces between patient and orthosis, measured using strain gauges, are used to determine the impedance to be exerted by the exoskeleton as a function. To decide the points of assistance and resistance to be perceived by the patient it is necessary to identify the evolution of the patient’s interaction forces. maintained constant.
Initialization of the algorithm:
Registering trajectory and interaction forces of the patient with stiffness (20).
Obtain the time intervals (positive/negative) interaction forces
Maximum interaction forces with a scaling factor (defined by a therapist) to define the lower and upper threshold of interaction forces.
The difference in the performed and reference trajectory is due to the joint stiffness variation. The position error is bounded within the limits because of the changes in joint stiffness and the error threshold limits. The measured interaction forces during the calibration phase were within the limits of -3Nm to 10Nm. With the given scaling factor (60%) the thresholds were defined as -1.8Nm and 6Nm.The interaction forces are bounded within the limits even in the influence of maximum stiffness. This behavior also depicts that the patient is not applying too much or too little force.
**This work has been developed in the framework of HYPER project (Hybrid Neuroprosthetic and Neurorobotics Devices for Functional Compensation and Rehabilitation of Motor Disorders).