Soft Sensitive Skin for Safety Control of a Nursing Robot Using Proximity and Tactile Sensors

This article presents a novel robot skin that integrates both proximity and tactile sensors in a nursing robot to maximize the safety of patient transfer tasks. Two types of sensors are mounted on a honeycomb substrate made of flexible photosensitive resin. The proximity sensor consists of several distance sensor arrays, each with 16 laser sensors connected to a microprocessor via an inter-integrated circuit bus. The sensor array is made of a flexible printed circuit, and the distance between the robotic arm and object is measured based on the time-of-flight principle. The tactile sensor consists of multiple 125 mm $\times125$ mm pressure sensor patches, each integrating 64 piezoresistive pressure sensors. This article presents the design and manufacture of the sensitive skin and proposes the safety control strategies of a nursing robotic arm using sensor information. In particular, by employing proximity sensors to detect approaching objects, the robotic arm can avoid high-speed collisions. The posture of the arm can be adjusted by using the tactile sensors to prevent the patient from slipping off and failure of the robotic arm. Preliminary experiments were conducted using the proposed sensitive skin and our nursing robot. The results are presented to demonstrate the accuracy of the sensor data and feasibility of the safety control strategies.