Soft-Material-Based Highly Reliable Tri-Axis Tactile Thin-Film Sensors for Robotic Manipulation Tasks

Tactile sensing is essential for intelligent robot control such as for dexterous manipulation tasks. To provide reliable sensors that can withstand industrial applications, we have developed a soft and thin-film tactile sensor capable of detecting tri-axis force components including normal and shear forces. The thickness of the sensor is 5.5 mm, and the sensor can be easily attached on an end-effector. Two layers of capacitive-sensing-electrode arrays sandwiching an elastomer layer of 2-mm spatial resolution are embedded in soft material, and output signals are distributed. To measure the external force vector, center-of-distributed-signal calculation was conducted. Our sensor exhibited linear behavior within 0.1 to 10 N for normal force and 0.1 to 4 N for shear force. With high reliability, sensor sensitivity did not change over ±10.0% even after one million repetitive keystroke cycles and one million repetitive shear-movement cycles. To determine the sensor’s effectiveness for manipulation tasks, a grasping-force control experiment was conducted using sensor signal feedback, and multiple local-shear-force vectors were successfully calculated using area-divided methods.