Therefore, Dr. Kim Ingraham and Prof. Elliot Rouse at the University of Michigan as well as Prof. David Remy from the Institute for Nonlinear Mechanics and researcher at the cluster of excellence SimTech at the University of Stuttgart are focusing on subjective feedback instead of physiological measurements. They consider the users as the main focus of their research and give them the opportunity to directly change the setting parameters and to take into account preferences that are otherwise difficult to identify or measure. In this way, users can decide quickly and independently, which properties - such as comfort, performance, and stability - are most important for them and choose the setting accordingly, without the need for an expert to readjust. “The users’ ability to decide for themselves how it feels to be supported by an exoskeleton, will increase user satisfaction in the future and thus the acceptance of these devices,” says Kim Ingraham, “because no matter how helpful an exoskeleton might be: “If it’s not comfortable, people won’t wear it.”
In order to test the feasibility of the concept, the research team equipped users with ankle exoskeletons and a touchscreen and had them walk on a treadmill. The participants of the study were able to select different points on the touchscreen to change the behavior of the exoskeleton. Without knowing it, they were selecting the exoskeleton’s torque and timing values. These two parameters control what the support feels like.
from left: Dr. Kim Ingraham, Prof. David Remy und Prof. Elliot Rouse
© Privat, University of Stuttgart / Uli Regenscheit, UM Robotics/Megan Ocelnik
Reliable data for individual adjustment
“Although we changed the mapping between the points on the touchscreen and the parameters with each repetition of the experiment, the participants always found their way back to their preferred, individual settings,” says David Remy. “This shows how important individual adjustments are and that users can provide us with very reliable data for this purpose.” The researchers were also surprised at how quickly the users were finding their preferred settings: Even people who had no previous experience with an exoskeleton managed to do so in an average of one minute and 45 seconds - without knowing which parameters they were setting. In addition, preferences changed in the course of the experiment: Users who already have experience with an exoskeleton prefer a significantly higher level of support than users who wear an exoskeleton for the first time.
The researchers want to fundamentally explore how user preferences can be included in the control of exoskeletons. In the next step, they want to find out why users prefer what they prefer, how these preferences affect their energy consumption, muscle activity, and physiology, and how a preference-based control could be automatically implemented in practice.
The collaboration between the University of Michigan and the University of Stuttgart was funded by the Carl Zeiss Foundation within the GSO/CZS return program for scientists, which the foundation established in cooperation with the German Scholar Organization. The program supports universities in filling professorships with German scientists from abroad.