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Open AccessArticle

Knee Impedance Modulation to Control an Active Orthosis Using Insole Sensors

Postgraduate Program in Electrical Engineering, Federal University of Espirito Santo, Vitoria 29075-910, Brazil
Biomedical Engineering Research Group GIIB, Universidad Politécnica Salesiana, Cuenca 010105, Ecuador
Center of Medical Biophysics, University of Oriente, Santiago de Cuba 90500, Cuba
Postgraduate Program in Biotechnology, Universidade Federal do Espirito Santo, Vitoria 29043-900, Brazil
Authors to whom correspondence should be addressed.
Current address: Av. Fernando Ferrari, 514, Goiabeiras, Vitória CEP 29075-910, Brazil.
Sensors 2017, 17(12), 2751;
Received: 10 October 2017 / Revised: 19 November 2017 / Accepted: 22 November 2017 / Published: 28 November 2017
(This article belongs to the Special Issue Assistance Robotics and Biosensors)
Robotic devices for rehabilitation and gait assistance have greatly advanced with the objective of improving both the mobility and quality of life of people with motion impairments. To encourage active participation of the user, the use of admittance control strategy is one of the most appropriate approaches, which requires methods for online adjustment of impedance components. Such approach is cited by the literature as a challenge to guaranteeing a suitable dynamic performance. This work proposes a method for online knee impedance modulation, which generates variable gains through the gait cycle according to the users’ anthropometric data and gait sub-phases recognized with footswitch signals. This approach was evaluated in an active knee orthosis with three variable gain patterns to obtain a suitable condition to implement a stance controller: two different gain patterns to support the knee in stance phase, and a third pattern for gait without knee support. The knee angle and torque were measured during the experimental protocol to compare both temporospatial parameters and kinematics data with other studies of gait with knee exoskeletons. The users rated scores related to their satisfaction with both the device and controller through QUEST questionnaires. Experimental results showed that the admittance controller proposed here offered knee support in 50% of the gait cycle, and the walking speed was not significantly different between the three gain patterns (p = 0.067). A positive effect of the controller on users regarding safety during gait was found with a score of 4 in a scale of 5. Therefore, the approach demonstrates good performance to adjust impedance components providing knee support in stance phase. View Full-Text
Keywords: active knee orthosis; admitance control; footswitch; gait cycle; knee impedance active knee orthosis; admitance control; footswitch; gait cycle; knee impedance
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Villa-Parra, A.C.; Delisle-Rodriguez, D.; Souza Lima, J.; Frizera-Neto, A.; Bastos, T. Knee Impedance Modulation to Control an Active Orthosis Using Insole Sensors. Sensors 2017, 17, 2751.

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