A Soft Barometric Tactile Sensor to Simultaneously Localize Contact and Estimate Normal Force With Validation to Detect Slip in a Robotic Gripper

Abstract

Soft tactile sensing technologies provide the potential to endow a sense of touch to robots for grasping and manipulating objects. During the execution of such tasks, having accurate knowledge on the contact location and quantitative forces in broad exerted force ranges is key. For industrial adoption such sensor needs to be low-cost, robust with limited or no calibration procedures and easy to manufacture. In this work we present a microelectromechanical (MEMS) based barometric sensor array covered with an elastomer layer, with the sensor signals being interpreted in real-time on the basis of a parameterized Gaussian type of distribution. The contact location is determined by finding in real-time the corresponding parameters of the Gaussian distribution that on its turn is used for normal contact force estimation. Results show accuracies in terms of localization of 0.5 mm and normal force errors of 10 % in force ranges up to 25 N and 15 % in high force ranges of 25 -50 N. The proposed soft tactile sensor has furthermore been validated to provide the ability to detect slip when gripping various objects.

BaroTac: Barometric Three-Axis Tactile Sensor with Slip Detection Capability

“…For instance, when handling fragile or vulnerable objects with a minimum force so as not to damage them, they are very likely to miss the grasped object, leading to the failure of the task. Adopting a tactile sensor is one attempt to handle this issue due to its functionalities in localizing the contact force [ 4 , 5 , 6 ], measuring multi-axial forces [ 7 , 8 , 9 ], and detecting dynamic events between end-effectors and grasped objects [ 10 , 11 , 12 ]. Among the various functionalities, tactile sensors capable of measuring forces in multi-axis and detecting slip can highly improve performance accuracy and grasping stability [ 13 , 14 ].…”

“…Tactile sensors for robotic applications have been achieved with many sensing methodologies such as piezo-resistive [ 21 , 22 ], piezo-capacitive [ 12 , 23 ], piezo-electric [ 8 , 24 ], magnetic [ 6 , 9 ], optical [ 17 , 25 ], and barometric [ 4 , 15 , 26 , 27 , 28 , 29 , 30 ]. Among various types of sensors, barometric sensors have been utilized as tactile sensors due to their several advantages.…”

“…Among various types of sensors, barometric sensors have been utilized as tactile sensors due to their several advantages. They are inexpensive, robust, small in size, easy to customize, and simple to use [ 4 , 15 , 26 , 27 , 28 , 29 , 30 ]. A barometric pressure sensor chip (BPSC) has an analog-to-digital (A2D) conversion board embedded inside so that it does not require additional circuits or filtering processes.…”

“…Howe et al adopted BPSC as a tactile sensor by casting soft material on the top to measure normal force [ 26 ]. Koiva et al arrayed multiple BPSCs for localizing contact force, and Clercq et al detected dynamic events based on localized force [ 4 , 27 ]. By wiring BPSCs with flexible and stretchable wire, Jentoft et al were able to attach the sensing system to curved surfaces [ 28 ].…”

“…However, this optical-type sensor requires a large volume for embedding the camera inside the sensor, and there is still a problem in decoupling the type of stimuli when complex stimuli are given simultaneously. Another method is to continuously observe the center of pressure (CoP) with arrayed sensors in high resolution [ 4 , 6 ]. If the sensor is able to localize force, it can track the CoP and observe the movement of the contacted objects.…”