Pressure Ulcer Breakout Time Estimation Model for the Wearable Robot Use

• Published in: International journal of precision engineering and manufacturing Vol. 25; no. 11; pp. 2353 - 2363
• Main Authors: Lee, Chang-Hwan, Gwak, Kwan-Woong
• Format: Journal Article
• Language: English
• Published: Seoul Korean Society for Precision Engineering 01.11.2024
• Subjects: Engineering; Industrial and Production Engineering; Materials Science; Regular Paper; Shear stress; Wearable robot; Skin injury; Robot safety; Pressure ulcer breakout time estimation model; Pressure
• ISSN: 2234-7593; 2005-4602
• DOI: 10.1007/s12541-024-01061-0

Pressure ulcer (PU) is the representative skin injury and is a major limiting factor in the long-term use of the wearable robots. For the sake of the health of the wearable robot user and to improve the usability of the wearable robot, we developed a pressure ulcer breakout time estimation model (PUBTEM). The model estimates the possible breakout time of PU at the skin beneath the cuff of the wearable robot, hence, it can be used as a guide for the design, control, and operational strategy of wearable robot. To develop the model, PU breakout mechanisms were analyzed extensively in the biomechanical perspective. From the analysis, skin pressure, skin shear stress and compressive stress in muscle tissue were identified as major factors causing PU and their relationships with time were collected. However, the skin shear stress and compressive stress are either difficult or impossible to measure in the environment where the wearable robot is used. Hence, we converted those two factors into the pressure—a easily measureable quantity—by applying the FEM analysis of the human musculoskeletal model and the relationship with friction coefficient. Through this conversion process, the relationship of all three factors with PU breakout time could be modeled with respect to a single variable, the skin pressure. Finally, the most conservative relationship that has fastest PU occurrence time was established as the PUBTEM. The model was validated with the human subject experiments approved by the IRB.