Thesis Defense - Alihan Kuru (MSME)

Alihan Kuru – M.Sc. Mechanical Engineering

Assist. Prof. Özkan Bebek – Advisor

Date: 06.07.2022

Time: 11.00

Location: AB1 412

“Design and Development of Torsion Spring Based Series Elastic Actuator with Nested

Encoders for Wearable Exoskeleton Robot”

Assist. Prof. Özkan Bebek, Özyeğin University

Assist. Prof. Altuğ Melik Başol, Özyeğin University

Associate Professor Nezih Topaloglu, , Yeditepe University

Abstract:

This thesis proposes a series elastic actuator design to power an assistive exoskeleton for the paraplegic or stroke patient whom incapable to walk or provide any motion in the lower extremity portion of the body. Commonly, active exoskeleton robots are powered with rigid actuators which do not provide torque controllability physiological compliance, and physical elasticity with the patient.

Physical elasticity in the actuator can be used to compensate for the environmental external forces during the motion of the exoskeleton. Therefore, controlling the torque generated at the joints of the exoskeleton would provide safer human-robot interaction. Series elastic actuators are able to provide advanced control and high fidelity control with the elastic element located

between the motor and the mechanical output of the series elastic actuator. The main goal of this thesis is to develop a series elastic actuator for a powered exoskeleton to provide torque measurement and control during locomotion and optimize the elastic element of the actuator for high fidelity control.

To provide torque controllability a custom torsional spring has been produced and placed at the output side of the series elastic actuator. Especially developed SEA modules are designed to be modular, lightweight, and have a high torque-to-mass ratio. In addition, measurement of the angular displacement of the elastic element is challenging in terms of mechanical design. To circumvent this design problem, a double shaft mechanism was proposed. In this mechanism, the first shaft, which connects the spring and the spring encoder, goes through the second shaft, which is connected to the motor and the motor encoder. This way both encoders are placed on the same side of the SEA. In addition to design, results of the cascaded PID controller with a disturbance observer (DoB) applied on the actuator are presented.

Bio:

Alihan Kuru is a member of OzU Robotics Lab. He received his bachelor’s degree at Özyeğin University Mechanical Engineering Department in 2014. He voluntarily joined OzU Rover Team during his sophomore year and worked for 2 years in the mechanical division in his junior year working as an undergraduate research student for 3 months at Özyeğin University Robotics Laboratory, under the supervision of Asst. Prof. Özkan Bebek. After receiving his BSc degree in 2019, he started his master’s studies in the same department and institution. He worked both as a research assistant and teaching assistant in Özyeğin University Robotics Laboratory, under the supervision of Asst. Prof. Özkan Bebek.