Multidimensional Tactile Sensor with a Thin Compound Eye-Inspired Imaging System

Abstract

Artificial tactile sensing for robots is a counterpart to the human sense of touch, serving as a feedback interface for sensing and interacting with the environment. A vision-based tactile sensor has emerged as a novel and advantageous branch of artificial tactile sensors. Compared with conventional tactile sensors, vision-based tactile sensors possess stronger potential thanks to acquiring multimodal contact information in much higher spatial resolution, although they typically suffer from bulky size and fabrication challenges. In this article, we report a thin vision-based tactile sensor that draws inspiration from natural compound eye structures and demonstrate its capability of sensing three-dimensional (3D) force. The sensor is composed of an array of vision units, an elastic touching interface, and a supporting structure with illumination. Experiments validated the sensor's advantages, including competitive spatial resolution of deformation as high as 1016 dpi on a 5 • 8 mm 2 sensing area, superior accuracy of 3D force measurement at levels of 0.018 N for tangential force and 0.213 N (0.108 N at the center region) for normal force, and real-time processing at 30 Hz, while achieving a thin size of 5 mm. We further demonstrate the sensor capability in sensing 3D force and slip occurrence in real grasping experiments. This device paves the way for robotic applications that require rich tactile information with miniaturized sensor structure.

A Tactile Sensing Concept for 3D Displacement and 3D Force Measurement using Light Angle and Intensity Sensing

“…In contrast, Zhang et al proposed a miniature thin optical vision-based tactile sensor based on a bionic compound eye structure. The sensor has a height of 5 mm and has 3D force sensing with contact geometry perception [28]. This is one of the first tactile sensors at this scale which retains the advantages inherited from vision-based tactile sensors.…”

“…3) that can estimate 3D point displacements and 3D point forces by interpreting the measured angle and intensity of light (i.e., the light vector) arriving at an optical sensor; thus, we named it the LiVec sensor. Compared with other existing optical-based tactile sensors [9], [23], [27], [28], the LiVec sensor has a simple structure consisting of a soft deformable skin, LEDs, and a light angle and intensity sensor. All the sensing elements are combined onto a singular printed circuit board (PCB), giving it the potential for substantial volume reduction compared to other existing tactile sensors [7] [10], [21], [25], [29]- [31] [32] and significantly reducing the complexity of the manufacturing process.…”

DenseTact: Optical Tactile Sensor for Dense Shape Reconstruction

“…Marker-based approaches seen in most tactile sensors are hard to deal with the aliasing problem with large deformation. One other approach such as the use of a randomly colored pattern [20] enables intrinsic features to follow, but it is only applicable for sensors with planar surfaces, and the RGB channel can make interference with the pattern itself. Furthermore, the pattern requires to have a unique pattern to avoid the aliasing problem and maintain a balanced density between the pattern and background to extract the feature from the surface deformation.…”

Large field of view 3D detection with a bionic curved compound-eye camera

“…Trueeb et al [15] introduced another sensor, utilizing a multi-camera setup, featuring a large contact surface and a slim profile. Zhang et al [10] presented a sensor that employed a novel compound eye imaging system comprised of an array of pinholes on a single complementary metal oxide semiconductor (CMOS) sensor, reducing the thickness to just 5 mm. Chen et al [16] optimized the sensor by utilizing a microlens arraybased vision system, maintaining the same slim profile while capturing clearer images.…”

“…To address this problem, researchers have begun to explore the use of compound-eye imaging systems [9]. Inspired by the eyes of certain insects, these systems consist of vision units, each capturing a partial view of the visual field [10]. This design allows for a wide field of view and large area tactile perception while maintaining a compact form factor.…”