Design of a self-positioning cleaning nursing bed toilet with a robotic hand based on infrared thermal imaging

This study develops a novel nursing bed toilet system integrated with a soft robotic hand and an infra-red array camera sensor to assist older adults' post-defaecation hygiene, while reducing caregiver workload and enhancing patient comfort and dignity.

The novel nursing bed toilet was designed through an integrated mechanical, control, and sensing framework. The system comprises a robot arm, a Soft Robotic hand, and an infra-red array sensor. The soft robotic hand integrates three units: an ultrasonic vibration cleaning, a water spray and a tendon-driven actuation mechanism for post-defaecation perianal hygiene. To clean the buttocks, it is necessary to know the position of the anus. Therefore, the sensing system was developed to determine the position of the anus using a thermal infra-red sensor. Due to the sensitivity of the area, a heating circuit was created to simulate the human anus temperature for system validation. The anus temperature was measured in 17 male participants using a digital thermometer. The average temperature was 37.1 °C. Experimental evaluations included static and dynamic positioning tests using a plastic buttock model with a heating circuit simulating the human anus, supporting the reliability of thermal-based detection.

Experimental evaluation of the toilet achieved high accuracy in anus positioning with a maximum error of 5 mm and a stable dynamic response, demonstrating reliable localisation performance.

This work presents the first full implementation of a toilet. It enables autonomous perianal hygiene for patients in nursing beds, reducing caregiver burden while preserving patient comfort and dignity.