Three‐dimensional localization of thin‐walled sheet metal parts for robotic assembly

This article presents a technical demonstration of a system for determining the three‐dimensional spatial location of complexly shaped, thin‐walled sheet metal parts grasped by robots during assembly. For successful part assembly, the precise location of grasped parts (essential for successful mating of parts) must be achieved. A localization system is implemented to determine the accurate position and orientation of a sheet metal part that has been picked up by a robot from an arbitrary location. The proposed localization system employs a novel sensing method, utilizing laser‐based proximity and edge detectors, to extract the part feature data in real time. These geometrical feature data are incorporated into an existing localization algorithm, which is based on the singular value decomposition formulation of the part localization problem. The sensing method is particularly effective in measuring 3‐D feature geometry (i.e., thin edges) of sheet metal parts. An experimental single‐robot test bed has been developed to demonstrate the feasibility of the part localization concept for a single sheet metal part. The experimental results obtained from the test bed demonstrate that the system can be effectively used for the localization of thin‐walled sheet metal parts. © 2002 Wiley Periodicals, Inc.     

Three‐dimensional map building for mobile robot navigation environments using a self‐organizing neural network

In recent years, mobile robots have been required to become more and more autonomous in such a way that they are able to sense and recognize the three‐dimensional space in which they live or work. In this paper, we deal with such an environment map building problem from three‐dimensional sensing data for mobile robot navigation. In particular, the problem to be dealt with is how to extract and model obstacles which are not represented on the map but exist in the real environment, so that the map can be newly updated using the modeled obstacle information. To achieve this, we propose a three‐dimensional map building method, which is based on a self‐organizing neural network technique called “growing neural gas network.” Using the obstacle data acquired from the 3D data acquisition process of an active laser range finder, learning of the neural network is performed to generate a graphical structure that reflects the topology of the input space. For evaluation of the proposed method, a series of simulations and experiments are performed to build 3D maps of some given environments surrounding the robot. The usefulness and robustness of the proposed method are investigated and discussed in detail. © 2004 Wiley Periodicals, Inc.     

Three‐dimensional moiré display

In this paper, we present an autostereoscopic 3D display based on the moiré effect. The left and right images are built of the moiré patterns. When observed from a proper location, these moiré images can be perceived stereoscopically without special eyeglasses. The principle is confirmed by preliminary experiments.     

Three‐dimensional printing technologies for terahertz applications: A review

Three‐dimensional (3D) printing technologies enables fast prototyping of complex 3D objects with ever improving printing qualities. To date, 3D printing has been found useful in areas such as manufacturing, industrial design, aerospace, dental and medical industries, and many others. In this article, we review recent advances of 3D printing technologies for terahertz (THz) applications. Different 3D printing technologies and printable materials are first discussed and compared. 3D‐printed THz components and devices, which are categorized as waveguides/fibers, antennas, and quasi‐optical components, are further demonstrated. It is found that the performances and functionalities of 3D‐printed THz devices have been greatly enhanced, while the operating frequencies have been increased from the lower end of THz range to over 1 THz region. With further development of novel materials and printing techniques, it is believed that 3D printing technologies will play an important role in the realization of THz components for efficient control and manipulation of THz waves.     

Three‐dimensional analysis of a driver‐passenger vehicle interface

This article presents a method of analyzing how drivers' anthropometric data are best accommodated by a specific driver‐vehicle interface. Three‐dimensional (3‐D) manikins with 18 links were developed using anthropometric data for the U.S. 95th percentile male and 5th percentile female. In addition, an adjustable seating buck was constructed to control 7 package variables. After the manikins were positioned in each driving environment, 3‐D Cartesian coordinates for the manikins' articulations were determined using a coordinate measuring machine. The data were then converted into joint angles to suggest suitable driving environments that consider appropriate driving postures. © 2004 Wiley Periodicals, Inc. Hum Factors Man 14: 269–284, 2004.     

Terrain‐inclination‐based Three‐dimensional Localization for Mobile Robots in Outdoor Environments

A new terrain‐inclination‐based localization technique is proposed in this paper to enable a robot to identify its three‐dimensional location relative to measurable terrain inclinations. Given a topographical map and a planned path, a robot‐terrain‐inclination model (RTI model) is extracted along the path on the terrain upon which the robot is operating. A particle filter is then used to fuse the measurement data with the robot motion based on the extracted RTI model for either a three‐wheeled or a four‐wheeled mobile robot. Experiments were carried out in four outdoor scenarios: one short path with different initial conditions and map resolution, another short path with different surface roughness and sensor accuracy, and two long paths with different types of rigid terrains and multiple loops. Experimental results show that the proposed method could achieve good localization performance on inclined outdoor terrains.     

Three‐dimensional nonlinear H∞ guidance law

This paper proposes a novel three‐dimensional missile guidance law design based on nonlinear H_∞ control. The complete nonlinear kinematics of pursuit–evasion motion is considered in the three‐dimensional spherical co‐ordinates system; neither linearization nor small angle assumption is made here. The nonlinear H_∞ guidance law is expressed in a simple form by solving the associated Hamilton–Jacobi partial differential inequality analytically. Unlike adaptive guidance laws, the implement of the proposed robust H_∞ guidance law does not require the information of target acceleration, while ensuring acceptable interceptive performance for arbitrary target with finite acceleration. The resulting pursuit–evasion trajectories for both the H_∞‐guided missile and the worst‐case target are determined in closed form, and the performance robustness against variations in target acceleration, in engagement condition, and in control loop gain, is verified by numerical simulations. Copyright © 2001 John Wiley & Sons, Ltd.     

Three‐dimensional printed wideband,dual‐cavity Ku‐band antenna

A novel three‐dimensional (3D) printed, wideband, and low cost bull's eye antenna is proposed and designed for Ku‐band applications. The proposed antenna covers entire Ku‐band satellite communication bands starting from 10.5 GHz to 14.5 GHz. The antenna structure consists of dual‐cavity radiating aperture surrounded by a circular groove. With the addition of cavity and corrugation, the antenna gain is increased more than 6 dB. The antenna is fabricated using 3D printing technology and conductive painting. Measurement results indicate that the antenna has 72% fractional bandwidth from 8 GHz to 17 GHz. Measured antenna peak gain is 13.5 dBi at 13 GHz and no less than 11.5 dBi throughout the entire Ku band.     

Three‐dimensional reconstruction of underwater objects using wide‐aperture imaging SONAR

The estimation of the geometric structure of objects located underwater underpins a plethora of applications such as mapping shipwrecks for archaeology, monitoring the health of coral reefs, detecting faults in offshore oil rigs and pipelines, detection and identification of potential threats on the seabed, etc. Acoustic imaging is the most popular choice for underwater sensing. Underwater exploratory vehicles typically employ wide‐aperture Sound Navigation and Ranging (SONAR) imaging sensors. Although their wide aperture enables scouring large volumes of water ahead of them for obstacles, the resulting images produced are blurry due to integration over the aperture. Performing three‐dimensional (3D) reconstruction from this blurry data is notoriously difficult. This challenging inverse problem is further exacerbated by the presence of speckle noise and reverberations. The state‐of‐the‐art methods in 3D reconstruction from sonar either require bulky and expensive matrix‐arrays of sonar sensors or additional narrow‐aperture sensors. Due to its low footprint, the latter induces gaps between reconstructed scans. Avoiding such gaps requires slow and cumbersome scanning by the vehicles that carry the scanners. In this paper, we present two reconstruction methods enabling on‐site 3D reconstruction from imaging sonars of any aperture. The first of these presents an elegant linear formulation of the problem, as a blind deconvolution with a spatially varying kernel. The second method is a simple algorithmic approach for approximate reconstruction, using a nonlinear formulation. We demonstrate that our simple approximation algorithms perform 3D reconstruction directly from the data recorded by wide‐aperture systems, thus eliminating the need for multiple sensors to be mounted on underwater vehicles for this purpose. Additionally, we observe that the wide aperture may be exploited to improve the coverage of the reconstructed samples (on the scanned object's surface). We demonstrate the efficacy of our algorithms on simulated as well as real data acquired using two sensors, and we compare our work to the state of the art in sonar reconstruction. Finally, we show the employability of our reconstruction methods on field data gathered by an autonomous underwater vehicle.     

Adaptive Robust Three‐dimensional Trajectory Tracking for Actively Articulated Tracked Vehicles*

A new approach is proposed for an adaptive robust three‐dimensional (3D) trajectory‐tracking controller design. The controller is modeled for actively articulated tracked vehicles (AATVs). These vehicles have active sub‐tracks, called flippers, linked to the ends of the main tracks, to extend the locomotion capabilities in hazardous environments, such as rescue scenarios. The proposed controller adapts the flippers configuration and simultaneously generates the track velocities, to allow the vehicle to autonomously follow a given feasible 3D path. The approach develops both a direct and differential kinematic model of the AATV for traversal task execution correlating the robot body motion to the flippers motion. The benefit of this approach is to allow the controller to flexibly manage all the degrees of freedom of the AATV as well as the steering. The differential kinematic model integrates a differential drive robot model, compensating the slippage between the vehicle tracks and the traversed terrain. The underlying feedback control law dynamically accounts for the kinematic singularities of the mechanical vehicle structure. The designed controller integrates a strategy selector too, which has the role of locally modifying the rail path of the flipper end points. This serves to reduce both the effort of the flipper servo motors and the traction force on the robot body, recognizing when the robot is moving on a horizontal plane surface. Several experiments have been performed, in both virtual and real scenarios, to validate the designed trajectory‐tracking controller, while the AATV negotiates rubble, stairs, and complex terrain surfaces. Results are compared with both the performance of an alternative control strategy and the ability of skilled human operators, manually controlling the actively articulated components of the robot.     

Three‐dimensional pixel configurations for optical outcoupling of OLED displays—optical simulation

Because of considerations on image quality and fabrication/integration compatibility, current active‐matrix OLED displays (AMOLEDs) hardly adopt any effective light outcoupling techniques/structures, and it remains an unsolved critical technical issue. Recently, through optical simulation, we proposed a three‐dimensional (3D) pixel configuration as a potential and promising way to boost light outcoupling of OLED display pixels. By extending the bottom reflective electrode to bank slope of the pixel definition layer (PDL) and selectively filling the bank opening (concave area) with high‐index filler to form the optically reflective concave structure, it is possible to give several‐fold light extraction enhancement. In this paper, we further extend the simulation work by evaluating effects of more realistic graded bank slopes vs straight bank slope, less challenging nonpatterned (blanket) high‐index filler vs patterned filler, and real OLED layer stacks and properties. The optical simulation clearly reveals that light extraction enhancement can be mostly kept with more realistic graded bank profiles and even less ideal (but also less challenging) nonpatterned filler can provide substantial extraction enhancement. The graded bank structure also provides beneficial effects on viewing characteristics.     

Three‐dimensional interaction and autostereoscopic display system using gesture recognition

We propose a 3D interaction and autostereoscopic display system that use gesture recognition, which can manipulate virtual objects in the scene directly by hand gestures and can display objects in 3D stereoscopy. The system consists of a gesture recognition and manipulation part as well as an autostereoscopic display as an interactive display part. To manipulate the 3D virtual scene, a gesture recognition algorithm is proposed, which use spatial‐temporal sequences of feature vectors to match predefined gestures. To get smooth 3D visualization, we utilize the programmable graphics pipeline in graphic processing unit to accelerate data processing. We develop a prototype system for 3D virtual exhibition. The prototype system reaches frame rates of 60 fps and operates efficiently with a mean recognition accuracy of 90%.     

Planar Segment Based Three‐dimensional Point Cloud Registration in Outdoor Environments

We present an odometry‐free three‐dimensional (3D) point cloud registration strategy for outdoor environments based on area attributed planar patches. The approach is split into three steps. The first step is to segment each point cloud into planar segments, utilizing a cached‐octree region growing algorithm, which does not require the 2.5D image‐like structure of organized point clouds. The second step is to calculate the area of each segment based on small local faces inspired by the idea of surface integrals. The third step is to find segment correspondences between overlapping point clouds using a search algorithm, and compute the transformation from determined correspondences. The transformation is searched globally so as to maximize a spherical correlation‐like metric by enumerating solutions derived from potential segment correspondences. The novelty of this step is that only the area and plane parameters of each segment are employed, and no prior pose estimation from other sensors is required. Four datasets have been used to evaluate the proposed approach, three of which are publicly available and one that stems from our custom‐built platform. Based on these datasets, the following evaluations have been done: segmentation speed benchmarking, segment area calculation accuracy and speed benchmarking, processing data acquired by scanners with different fields of view, comparison with the iterative closest point algorithm, robustness with respect to occlusions and partial observations, and registration accuracy compared to ground truth. Experimental results confirm that the approach offers an alternative to state‐of‐the‐art algorithms in plane‐rich environments.     

Three‐dimensional thinning algorithms on graphics processing units and multicore CPUs

Three‐dimensional curve skeletons are a very compact representation of three‐dimensional objects with many uses and applications in fields such as computer graphics, computer vision, and medical imaging. An important problem is that the calculation of the skeleton is a very time‐consuming process. Thinning is a widely used technique for calculating the curve skeleton because of the properties it ensures and the ease of implementation. In this paper, we present parallel versions of a thinning algorithm for efficient implementation in both graphics processing units and multicore CPUs. The parallel programming models used in our implementations are Compute Unified Device Architecture (CUDA) and Open Computing Language (OpenCL). The speedup achieved with the optimized parallel algorithms for the graphics processing unit achieves 106.24x against the CPU single‐process version and more than 19x over the CPU multithreaded version. Copyright © 2011 John Wiley & Sons, Ltd.     

Distributed stereo vision‐based 6D localization and mapping for multi‐robot teams

Joint simultaneous localization and mapping (SLAM) constitutes the basis for cooperative action in multi‐robot teams. We designed a stereo vision‐based 6D SLAM system combining local and global methods to benefit from their particular advantages: (1) Decoupled local reference filters on each robot for real‐time, long‐term stable state estimation required for stabilization, control and fast obstacle avoidance; (2) Online graph optimization with a novel graph topology and intra‐ as well as inter‐robot loop closures through an improved submap matching method to provide global multi‐robot pose and map estimates; (3) Distribution of the processing of high‐frequency and high‐bandwidth measurements enabling the exchange of aggregated and thus compacted map data. As a result, we gain robustness with respect to communication losses between robots. We evaluated our improved map matcher on simulated and real‐world datasets and present our full system in five real‐world multi‐robot experiments in areas of up 3,000 m² (bounding box), including visual robot detections and submap matches as loop‐closure constraints. Further, we demonstrate its application to autonomous multi‐robot exploration in a challenging rough‐terrain environment at a Moon‐analogue site located on a volcano.     

Three‐dimensional cylindrical design multiple‐input‐multiple‐output/diversity antenna with high isolation for wireless communication applications

In this article, a three‐port nonplanar multiple‐input‐multiple‐output/diversity antenna with very high isolation between the radiating elements is presented. To realize diversity from the proposed three‐dimensional (3‐D) antenna configuration, three monopole radiating elements are arranged at an angle of 120°. The isolation between the radiators is enhanced by using a multilayered cylindrical decoupling structure and defected ground structure (DGS). The DGS reduces the coupling due to surface waves while the cylindrical decoupling structure reduces the coupling due to space waves. The proposed antenna offers consistent pervasive connectivity in the wireless communication environment due to its 3‐D geometry with multiple radiating elements and good diversity performance. The prototype is fabricated and measured result shows that more than 42 dB isolation is obtained at the center frequency 1.45 GHz. An increment of 1.2 dBi in the antenna gain is also achieved by using DGS and decoupling structure arrangement. The proposed antenna can be easily placed inside the cylindrical housing or it can be integrated with the existing electronics chip, thus nullifying the requirement for dedicated location in the system.     

Natural terrain classification using three‐dimensional ladar data for ground robot mobility

In recent years, much progress has been made in outdoor autonomous navigation. However, safe navigation is still a daunting challenge in terrain containing vegetation. In this paper, we focus on the segmentation of ladar data into three classes using local threedimensional point cloud statistics. The classes are: “scatter” to represent porous volumes such as grass and tree canopy; “linear” to capture thin objects like wires or tree branches, and finally “surface” to capture solid objects like ground surface, rocks, or large trunks. We present the details of the proposed method, and the modifications we made to implement it on‐board an autonomous ground vehicle for real‐time data processing. Finally,we present results produced from different stationary laser sensors and from field tests using an unmanned ground vehicle. © 2006 Wiley Periodicals, Inc.     

Three‐dimensional impact angle‐constrained adaptive guidance law considering autopilot lag and input saturation

This work investigates three‐dimensional accurate guidance problem in the presence of impact angle constraint, input saturation, autopilot lag, and external disturbance, and presents a robust adaptive guidance method for maneuvering targets. More specifically, based on integral Lyapunov control algorithm, a robust guidance law, which can drive both terminal line‐of‐sight angle error and its rate to a small region around zero, while resisting the terrible influence caused by external disturbance, is proposed in this work. To deal with input saturation, guidance command is separated into two parts: real input and saturation error, and an adaptive control technique is employed to compensate the influence resulting from external disturbance and saturation error. Moreover, regarding autopilot lag as a first‐order dynamics, a backstepping designed controller with an adaptive term is proposed. Numerical simulations are carried out and their results demonstrate the proposed properties.     

Three‐dimensional lenticular display synthetic image rendering based on light field acquisition

Crosstalk is a critical defect affecting image quality in multiview lenticular 3D displays. Existing optimization methods require tedious computations and device‐specific optical measurements, and results are often suboptimal. We propose a new method, on the basis of light field acquisition and optimization, for crosstalk reduction in super multiview displays. Theory and algorithms were developed, and experimental validation results showed superior performance.     

Three‐dimensional PIC/MC simulations of the sustain discharge pulse in an ACPDP

Abstract— The strong discharge pulse between coplanar electrodes in an ACPDP cell is investigated using fully kinetic 3‐D simulations. Key phases in the discharge development are identified and thoroughly illustrated with an extensive set of plots. The main effort is focused on the study of the anode charging wave and striations formed above the dielectric surface in the anode area. To elucidate these physical phenomena, we perform a number of specially designed numerical experiments.