Usability optimization of the interface parameter shape for pronation and supination movements with an interaction-based arm assistance system

• Applicant: Professor Dr.-Ing. Thomas Maier
• Subject Area: Human Factors, Ergonomics, Human-Machine Systems
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 430136438

During surgery, surgeons often find themselves in uncomfortable static arm and upper body postures, resulting in high stresses on the upper extremities. This can lead to fatigue and reduction in effectiveness in the form of increased error rates during procedures. These deficits need to be investigated and improved holistically. An arm assistance system can counteract these deficits. The surgical arm assistance system supports the users by adaptively transferring a support force to the forearm in static and dynamic arm postures and movements. To date, studies have been conducted on the usability of the functional principle, the support area, and the adaptive arm support force, as well as the shape, surface material, and padding material of the forearm support. Upper extremity relief and improvement in precision and comfort have been demonstrated. This research project builds on this by focusing on the investigation of the interface parameter shape with a focus on pronation and supination movements in an interaction-based arm assistance system in dynamic operating scenarios. The human-machine interface (HMI) shape of the forearm support is provided with a rotational degree of freedom around the longitudinal axis of the forearm to obtain the maximum range of motion of the forearm during pronation and supination. In this project, the parameters segmentation of the shape and resistance torque of a rotationally mounted shape are investigated in a novel way. The HMI shape as a conical anthropomorphic negative U-shape in each case is constructed gender-specifically for the critical percentiles. Due to the different changes in the rotation angles of the forearm during pronation and supination along its longitudinal axis, the HMI shape is segmented along this axis to compensate for the change in skin motion and tension in the different areas (from proximal to distal). Based on this, the resistance torque of the rotational degree of freedom around the longitudinal axis of the forearm is varied and investigated. The resistance torque corresponds to the torque amplitude of the rotational bearing of the form in Newton meters. The usability parameters effectiveness (precision, maximum rotation angle during forearm rotation), efficiency (time for task execution, surface pressure between forearm support resp. shape and forearm) as well as satisfaction (survey) are collected and evaluated. The result of the research project is a general statement on the segmentation of the shape and the resistance torque of a rotationally mounted shape with optimal usability for the users.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Peter Schmid