Grasping With the SoftPad, a Soft Sensorized Surface for Exploiting Environmental Constraints With Rigid Grippers

A common trend in robotic manipulation is to build compliant hands that can exploit environmental constraints to perform robust grasps. However, in large-scale industrial applications, end-effectors are mostly rigid. How can we exploit environmental constraints using rigid industrial grippers? We propose to add compliance to the environment, thanks to a soft modular pneumatic surface: the SoftPad. Pressure sensors connected to its modules allow to estimate the object pose and center of mass and to detect the contact between the gripper and the SoftPad during a grasping task. A new grasp strategy that exploits such information for top-grasping objects, without using cameras or force sensors, is presented. It has been tested with objects having a wide range of sizes, shapes, and weights. The SoftPad design can easily be adapted to the set of objects that are used in a certain application.