Contact persons

• Raphael Hoffmann, M.Sc.
• Chenglin Lyu, M.Sc.

Project description

Wearable lower-limb exoskeletons can assist patients with limited walking abilities, e.g., due to post-stroke hemiplegia, or even patients without the residual function of the lower-limb musculoskeletal system. The support is performed by providing additional torques to the subject’s joints. At MedIT we investigate novel drive concepts and different control approaches to make such systems more secure and user-friendly. For this purpose, we have developed two different lower limb exoskeletons. One exoskeleton is designed for hemiplegic patients with residual functions and the other one for patients without residual function, e.g., people with paraplegia.
Our L2Exo-SE achieves patient assistance through variable stiffness actuators (VSAs). These actuators are characterized by an elastic, adjustable coupling between the exoskeleton and the patient, thus ensuring a higher safety. Additionally, the elastic element functions as a torque sensor for the human-machine interaction torque by measuring the spring deflection using high precision encoders.
One crucial part in cooperatively assisting the patient’s rest motor function with these VSAs is to detect the patient’s intention to move. Our approach to addressing this challenge is based on the system theoretical knowledge. Using detailed mathematical models of the exoskeleton’s and patient’s dynamical behavior and the interaction torque measurement via the elastic actuator, we can estimate the patient’s movement in real-time. This approach is advantageous because the patient does not need to be equipped with additional sensors such as electrodes to measure muscle activity.
Having detailed knowledge about the patient’s movement intention is essential for implementing further control strategies. For example, it can be used to realize a behavior of the exoskeleton that is similar to an e-bike, where a specific assisting factor amplifies the subject’s torque. On the other hand, the information about the patient’s joint torque can also be used to quantify the strength and fatigue of the patient during rehabilitation training.
Our goal is to combine the concepts of variable stiffness actuators, patient-cooperative control, fatigue estimation, and gait stabilization to obtain an overall concept that safely and user-friendly assists patients and physiotherapists in rehabilitation training.

Student projects

In the exciting rehabilitation robotics and exoskeletons field, we are always happy to have enthusiastic students from electrical engineering or mechanical engineering courses. Methodically, the topics to be addressed are mainly in the following areas:

• Control Theory: Design and validation of different control concepts
• Electronics: Sensory design
• Mechanics: Construction and design

If you are interested in a specific topic and want to realize your own ideas, call or write an email to the supervisor. We are looking forward to hearing from you!