Sensor Module Combining Time-of-Flight With Self-Capacitance Proximity and Tactile Sensors for Robot

Human collaborative robots (HCRs) are a useful future workforce because they can operate alongside people. Proximity and tactile sensing are important for HCRs to ensure safety. In this study, we propose a combined sensor module for HCRs using time-of-flight (ToF) as well as self-capacitance proximity and tactile sensors. The distance to an object in a noncontact range can be detected by a ToF sensor; however, the detection accuracy and the X-Y measurement range are lower for short ranges, with the Z axis as the measurement plane direction. The self-capacitance proximity and tactile sensors can detect objects and contact conditions in short ranges. For high-sensitivity proximity and contact measurements over a large distance, two of the aforementioned sensors can be combined. Prototypes of the sensor modules were prepared, and sixteen modules were mounted on a robot arm to detect the position and distance of an object at 300 mm or less, along with the pressure and position upon contact. In addition, the robot arm was controlled using information obtained from the sensors. The proposed sensor modules can thus be employed for proximity and tactile sensing in HCRs.

I. Introduction

Human collaborative robots (HCRs) can be operated without safety fences in the same space alongside humans. HCRs can be placed in small spaces and work efficiently; hence, they are expected to assist with labor shortage. These robots must comply with specific requirements and guidelines according to ISO/TS 15066. Sensors are important for meeting this standard and safe operation of HCRs in collaboration with humans. Thus, many types of robot sensors have been proposed [1]–[20]. This study aims to detect the environment around a robot to ensure the safety of human workers. To this end, proximity and tactile sensors are developed and mounted on the HCR surface, as shown in Fig. 1. These sensors measure the contact state in addition to the proximity of the robot to other workers in the vicinity. The HCR with such sensing capabilities can avoid collisions with humans, and the HCR can be operated even when there is direct contact with a worker. Thus, the safety and workability of HCR can be improved. Fig. 1.

Illustration of the sensing mechanism used this study. The combined sensor module is mounted on the surface of a robot arm and can detect objects both with and without contact. In addition, the robot arm can be controlled using the data obtained by the sensors.