Analysis, Design, Control and Experimental Research on Novel Unrestrained Defecation-Assisting Nursing Bed

As population aging intensifies, older adults who are bedridden or have limited mobility often experience strong restraint and poor comfort during defecation nursing; therefore, an unrestrained defecation-assisting device is urgently required. This study aims to design a novel unrestrained defecation-assisting posture transformation mechanism and defecation-receiving protective cover mechanism to improve the defecation experience of older adults. Firstly, a posture adjustment mechanism composed of a translation module and a back-elevation, leg-flexion, and leg-abduction module is proposed. The degrees of freedom of the system are calculated to ensure proper and coordinated motion. Furthermore, the human body slip displacement during the posture transformation process is analyzed. Secondly, a defecation-assisting coordinated docking mechanism is developed. Inspired by the pangolin model, a protective cover mechanism is designed. Through kinematic and workspace analyses, the driving lengths of the four-section keel are determined as 34 mm, 19 mm, 38 mm, and 40 mm, respectively. Thirdly, the control system for the entire nursing device is established, the control method of human body translation motion based on visual sensing is analyzed, and the control method of the protective cover mechanism based on the fuzzy adaptive control algorithm is conducted. Lastly, experiments are conducted and the results show that the motion error of the translation module is ≤7.6 mm. The posture transformation mechanism demonstrates excellent operational performance, the back-slip compensation effect is significant, the working trajectory of the mechanism meets human body requirements, and the protective cover accurately conforms to the human body with a reasonable contact pressure distribution. The results indicate that the proposed device effectively alleviates the sense of restraint associated with a conventional wearable excretion-care device, and provides a feasible solution for the application of intelligent nursing device.