To enable robots to grasp unknown objects, we have developed a new type of fingertip-mounted sensor that can detect distance, material type, and interior structure without making contact with the object to be grasped. Due to its working principle, the sensor is named as Dual-Modal and Dual Sensing Mechanisms (DMDSM) pretouch sensor. To enable the wide deployment of the DMDSM sensor, we need to scan a large number of common household items using the sensor to establish an object/material database. Here we report our progress in designing an automatic object scanning system and the sensor calibration algorithm with the new sensor. The object scanning system is constructed by a refitted 3D printer with a motorized turntable mounted on its printing stage. The extruder of the 3D printer is replaced by the sensor to perform 3D translation. The turntable rotates the object of interest to allow a full-body scan. A prototype of the scanning system has been built, and a new calibration algorithm has been developed to estimate the parameters of both the sensor and the scanning system. The system design and ranging accuracy have been verified by physical experiments, and the collected data from seven types of common household objects have shown promising prospects of using DMDSM sensors in grasping.
