Proximity and Contact Sensor for Human Cooperative Robot by Combining Time-of-Flight and Self-Capacitance Sensors

In recent years, human cooperative robots (HCRs) have attracted considerable attention. HCRs should be equipped with proximity and contact sensors to ensure human safety. This study combines time-of-flight (ToF) and self-capacitance sensors to obtain proximity and contact sensors for HCRs. ToF sensor can determine the distance between an object and sensor in the proximity range; however, the detection accuracy decreases in a close range. The self-capacitance proximity sensor can detect objects before and during contact; it has high sensitivity in close range. For proximity measurements with high sensitivity and wide range, it is possible to combine the ToF and self-capacitance sensors. We modularized one sensor and connected the other sensor module using a serial bus; the sensor covered the entire HCR surface to ensure human safety. In this sensor, it is possible to obtain efficient measurements for distance ranging 300-0 mm. The prototype 24 pieces of sensor modules were established on the robot arm and these sensor modules detected the object's position without establishing any contact and detected the human touch. Additionally, the robot arm was controlled in real time based on the sensor information. We believe the proposed sensor system can be employed as a proximity and contact sensor for HCRs.