RESUMO
Currently, 3D reconstruction methods in structured light are generally implemented in a pre-calibrated area. To realize a full-field reconstruction, the calibration plate can be moved to multiple positions in a time-consuming manner, or the whole field can be calibrated with the help of a large calibration plate, which is more costly. In this paper, we address this problem by proposing a method for obtaining a global phase-angle model under a locally calibrated region, and based on this relationship, we investigate and analyze the reconstruction inside and outside of the calibrated zone. The results show that the method can reconstruct the object outside of the calibration zone completely, and can keep the planarity error around 0.1 mm and the sphericity error below 0.06 mm. The method only requires local calibration of the projected fringes at the two calibration positions to realize the 3D reconstruction of the full-field, which makes the method more advantageous.
RESUMO
A uniaxial micro-electro-mechanical systems (MEMS) micro-vibration mirror can be used to construct a new type of fringe projection profilometry (FPP) system. In FPP system calibration, some pixels may be calibrated worse than other pixels due to various error sources, which will affect the final reconstruction accuracy. In addition, there are some difficulties in calibrating the MEMS-based system because a projector using the uniaxial vibration mirror does not have focusing optics and can only project unidirectional fringes. In this paper, we developed an FPP system using a uniaxial MEMS micro-vibration mirror. To solve the calibration problems, we propose a calibration model suitable for the MEMS-based system and a pixel refinement method. These pixels with relatively large calibration errors are called outlier-pixels, which will significantly increase the error of the following 3D mapping. Therefore, the pixel refinement method classifies all pixels based on a frequency distribution histogram of calibration errors during calibration and prevents outlier-pixels from participating in the following 3D mapping. The experimental results show that the proposed method can improve the accuracy of 3D reconstruction, and the feasibility of the self-developed system is verified.
RESUMO
Bionics is the inspiration resource of state-of-the-art science and technology. The chameleon can capture prey at great distances with the assistance of its highly stretchable and ballistic tongue. Inspired by this biological structure, here we demonstrate the fabrication of flexible electromagnetic manipulators. The as-prepared flexible electromagnetic manipulator can reach a maximum velocity of 8.1 m s-1and acceleration of 627 m s-2at an applied voltage of 360 V. The working mechanism of this flexible electromagnetic manipulator has been studied based on Maxwell and Abaqus simulations. Diverse parameters, including the lengths of the magnetic tube (the cylindrical magnet) and the whole manipulator and the applied voltage values, have been considered to tune the ejecting performance of the manipulator. Furthermore, flexible electromagnetic manipulators can be upgraded to capture various objects by attaching a mechanical force triggered gripper to their top pads. With this design, the velocity of the gripper can be significantly improved (the maximum is 8.1 m s-1, whereas soft grippers in previous research do not have the characteristic of fast movement), thus making it possible to get objects without approaching them; in other words, we can catch objects even though they are far away from us, which provides the possibility of long-distance capture. We believe this kind of bio-inspired fabrication is a powerful strategy to design and synthesize flexible even stretchable manipulators, extending the boundaries of conventional manipulators for soft robots.
