Trajectory generation and control of a knee exoskeleton based on dynamic movement primitives for sit-to-stand assistance. (2nd July 2016)

• Record Type: Journal Article
• Authors: Kamali, Kaveh; Akbari, Ali Akbar; Akbarzadeh, Alireza
• Is Part Of: Advanced robotics. Volume 30:Number 13(2016)
• Page Start: 846
• Page End: 860
• Publication Date: 2016-07-02
• Subjects: Exoskeleton -- dynamic movement primitives -- assistive control -- sit-to-stand; Robotics -- Periodicals; Robotics -- Japan -- Periodicals; Robotics; Japan; Periodicals; 629.89205
• DOI: 10.1080/01691864.2016.1154800
• Languages: English
• ISSNs: 0169-1864

Abstract

Abstract: This paper presents a novel control approach for a knee exoskeleton to assist individuals with lower extremity weakness during sit-to-stand motion. The proposed method consists of a trajectory generator and an impedance controller. The trajectory generator uses a library of sample trajectories as the training data and the initial joint angles as the input to predict the user's intended sit-to-stand trajectory. Utilizing the dynamic movement primitives theory, the trajectory generator represents the predicted trajectory in a time-normalized and rather a flexible framework. The impedance controller is then employed to provide assistance by guiding the knee joint to move along the predicted trajectory. Moreover, the human-exoskeleton interaction force is used as the feedback for on-line adaptation of the trajectory speed. The proposed control strategy was tested on a healthy adult who wore the knee exoskeleton on his leg. The subject was asked to perform a number of sit-to-stand movements from different sitting positions. Next, the measured data and the inverse dynamic model of the human-exoskeleton system are used to calculate the knee power and torque profiles. The results reveal that average muscle activity decreases when the subject is assisted by the exoskeleton. Abstract :