Soft robotics shows considerable promise for various underwater applications. Soft grippers as end-effectors are particularly useful for compliant and robust grasping compared to rigid mechanisms. In this work, we describe the design, fabrication and operation of a soft robotic hand driven by water hydraulics for underwater grasping. The proposed design has, in addition to the five fingers of a human hand, an extra soft thumb arranged symmetrically in an active soft palm. The soft fingers are designed with four chambers to enable bidirectional bending and deflection motions. We propose a novel elastic fiber reinforced structure to enhance and constrain the flexion movements of three palm actuators. The versatility of the underwater robotic hand is evaluated by implementing the human grasping gestures of the Feix taxonomy. Furthermore, we present a low-cost one-camera-multiple-mirrors imaging approach for capturing the grasps from multiple viewpoints simultaneously.

The depth of focus (DOF) of a lens is a crucial parameter in glasses-free 3D displays that affects the viewing distance range. Here we proposed a vector light field display based on intertwined flat lens for extended viewing distance. The gray-scale diffractive lens (GDL) is designed and fabricated with extended DOF for red (658 nm), green (532 nm), and blue (450 nm) colors. By integrating the intertwined GDLs with a liquid crystal display, four views form a smooth horizontal parallax with a cross talk below 26% over a viewing distance from 24 to 90 cm. The enhancement of the DOF is 1.8 × 1 0 4 -fold. The light efficiency of the pixelated GDL reaches 82%. The proposed vector light field 3D display has the advantages of a thin form factor, high efficiency, high color fidelity, and large viewing distance. The potential applications include portable electronics, 3D TVs, and tabletop displays.

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This paper presents a method to solve the kinematics of a rigid-flexible and variable-diameter continuous manipulator. The multi-segment underwater manipulator is driven by McKibben water hydraulic artificial muscle (WHAM). Considering the effect of elasticity and friction, we optimized the static mathematical model of WHAM. The kinematic model of the manipulator with load is established based on the hypothesis of piecewise constant curvature (PCC). We developed an optimization algorithm to calculate the length of the WHAMs according to the principle of minimum strain energy and obtain the configuration space parameters of the kinematic model. Based on the infinitesimal method, the homogeneous transformation matrices of the variable-diameter bending sections are computed, and the terminal position and attitude are obtained. In this paper, we studied the working space of the manipulator by quantitative analysis of the impact factors including pressure and load. A deep neural network (DNN) with six hidden layers is designed to solve inverse kinematics. The forward kinematic results are used to train and test the DNN, and the correlation coefficient between the output and target samples reaches 0.945. We carried out an underwater experiment and verified the effectiveness of the kinematic modeling and solution method.

Two techniques for pincushion correction are evaluated based on their effect on calculation of the image geometry and 3D positions of object points. Images of a uniform wire mesh and a calibration phantom containing lead beads in its surface were acquired on the image intensifier TV systems in our catheterization labs. The radial mapping functions relating points in the original images and in the corrected images were determined using the mesh image. The undistorted mesh model was also used to determine and correct the distortions locally, i.e., for each square region between the mesh points. Thus, two corrected images were obtained. Images of the calibration phantom before and after correction were analyzed to determine the 3D position of the lead beads and the imaging geometry, using a calibration algorithm and the enhanced Metz-Fencil technique. In comparing the 3D positions calculated from the radially corrected and locally corrected images, the calculated 3D positions using the calibration technique vary by less than 0.6 mm in the x and y direction and less than 5.0 mm in the z direction. The uncorrected data yields differences of over 1 cm in the z direction. The 3D positions calculated using the enhanced Metz-Fendil technique appear to be more accurate when pincushion correction is applied.