Hessinger, Markus ; Buchta, Arthur ; Christmann, Eike ; Werthschützky, Roland ; Kupnik, Mario (2017)
User interaction torque monitoring of a 7-DOF upper-limb exoskeleton with IMU-based motion input.
Annual Meeting of the German Society of Biomedical Engineering and Joint Conference in Medical Physics. Dresden, Germany (10.09.2017-13.09.2017)
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Kurzbeschreibung (Abstract)

Assistive robots, such as upper-limb exoskeletons, require sophisticated online trajectory planning to ensure user safety during operation. In order to recognize the user intention, system integrated sensors are necessary to measure the interaction with the robotic device. In this work, the concept of a remotely controlled exoskeleton using an inertia measurement unit (IMU) motion capturing system is introduced, where the interaction between the human arm and the exoskeleton is measured with structurally integrated torque sensors. The motion capture system consists of four IMUs, placed on the torso, upper- and lower arm, and the hand of the operator, who performs the arm motion for the exoskeleton worn by the user. The upper-limb exoskeleton consist of a seven actuated joints, where each joint axis is collinear to their respective joint axis of the human arm. First, the joint angles of the motion capture system and exoskeleton are calibrated. The coordinate system alignment of the IMUs is based on a gravity-vector and omega calibration. For the exoskeleton, mechanical stops at the maximal joint angles define the zero positions. Once both systems are synchronized, the operator is able to remotely control the joint angles of the exoskeleton. The motion capture system detects movements of the arm with 100 Hz sample rate and a RMSE smaller than two degrees for static positioning and five degrees for dynamic movements to determine joint angles of the human arm during activities of daily living. The user interaction torque is derived from the measured torque and the dynamic properties of the exoskeleton. The overall goal of this work is to assist joint motion and monitor joint torques of a patient during continuous passive motion therapy, where a therapist teaches online movements with the IMU motion capture system.

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