Curved Surface Objects Research Articles

A Cross-Line Structured Light Scanning System Based on a Measuring Arm

The measurement system proposed in this paper, using a measuring arm and line structured light, has a wide range of applications. To improve the scanning efficiency, the system outlined in this paper uses two single-line structured lights to form crosshair structured light, which we combine with a measuring arm to form a comprehensive scanning measurement system. The calibration method of Zhengyou Zhang and a calibration board are used to complete parameter calibration of the sensors and cameras, as well as hand–eye calibration of the measuring arm. For complex curved-surface objects, this system extracts the cross-line structured light optical center location, which suffers from ambiguity. Therefore, we introduce the use of periodic control of the two line structured light sources in order to resolve the light extraction polysemy. Our experimental results indicate that the proposed system can effectively satisfy the function of crosshair structured light scanning of large, complex surfaces.

Optimal Task-Space Tracking With Minimum Manipulator Reconfiguration

An optimal solution to the task-space tracking problem using a non-redundant manipulator is proposed. This is a recurring occurrence in automated manufacturing settings, e.g. welding, deburring, painting, or quality control inspections. Given a pre-defined path for the end-effector to follow, there may not exist a joint-space continuous solution for task-space tracking when the non-linear manipulator kinematics and collision avoidance with obstacles in the workcell are considered. This introduces undesirable manipulator reconfigurations where the end-effector is required to deviate temporarily from the pre-defined path. The unwanted motion results in pausing task-space tracking, often incurring not only ineffective time and energy demands but potentially compromising the quality of the task at hand due to the additional discontinuities. An algorithm is proposed that provides a globally optimal perspective to the choice of suitable joint-space connected segments so that the minimum number of manipulator reconfigurations during task-space tracking is guaranteed. By carefully selecting the inverse kinematic solutions, all sequences ensuring minimum reconfigurability are proven collected by Dynamic Programming. Moreover, a faster greedy strategy is suggested to increase the computational efficiency of the tracker whilst still preserving global optimality and completeness. The effectiveness of the proposed algorithm is validated against traditional sampling-based solvers in simulation and illustrated on challenging real-world tracking experimentation with a Universal Robotics manipulator and a curved-surface object, depicted also in an accompanying video. An open-source implementation has also been provided for the benefit of the robotics community.

Detection and filling of pseudo-hole in complex curved surface objects

The detection and filling of pseudo-hole in complex curved surfaces is always a hot and difficult problem in computer vision field. Aiming at the defect that the traditional method can only detect the small curvature of the pseudo-hole region, this paper proposes a new method to improve the pseudo-hole detection. Firstly, the hole can be classified by the projection method, it is divided into simple holes and complex holes, and then, the method of filling the simple hole is described. For complex holes, it is divided into a number of simple holes, and then filling every simple holes, to complete the filling of a complex pseudo-hole, finally map the results of filling the simple hole back to the object hole area.

Detection and filling of pseudo-hole in complex curved surface objects

The detection and filling of pseudo-hole in complex curved surfaces is always a hot and difficult problem in computer vision field. Aiming at the defect that the traditional method can only detect the small curvature of the pseudo-hole region, this paper proposes a new method to improve the pseudo-hole detection. Firstly, the hole can be classified by the projection method, it is divided into simple holes and complex holes, and then, the method of filling the simple hole is described. For complex holes, it is divided into a number of simple holes, and then filling every simple holes, to complete the filling of a complex pseudo-hole, finally map the results of filling the simple hole back to the object hole area.

Fast Bi-dimensional empirical mode decomposition as an image enhancement technique for fruit defect detection

Image enhancement is critical to detection of fruit defects by imaging techniques. Vignetting and noise are major image artifacts, which can seriously affect image segmentation results, especially in inspecting the curved-surface objects like fruit. It is common to use a calibration object or a mathematic model to reduce the vignetting effect in defect detection, but the approach is often cumbersome, inflexible, and difficult to achieve desired results. In this study, a new image enhancement method based on bi-dimensional empirical mode decomposition (BEMD) of images was proposed to isolate and subsequently remove the effects of vignetting and noise by means of selective image reconstruction. The new BEMD method, along with three other BEMD methods, was first tested on decomposing a synthetic image with artificially added vignetting and noise. The BEMD was found to be the most efficient for image decomposition in terms of computation time, and also give high-quality reconstructed images. Experiments were further conducted by applying the BEMD to the direct and amplitude component images of apple samples with subsurface bruising and surface defects, which were acquired by using a structured-illumination reflectance imaging (SIRI) system. BEMD effectively reduced the image vignetting and greatly enhanced the defect features of the apples, based on both visual inspection and quantitative evaluation. BEMD offers an effective tool for enhancing SIRI images, and it is also promising for image enhancement with other imaging modalities for fruit defect detection.

Parametric Effect on Surface Finish of Three-Dimensional Printed Object

The ability to use different parameters and finishing techniques in fused deposition modelling (FDM) depends largely on part geometries, materials, printing processes like Z-resolution and post processing to some extent. Low quality poor surface finish due to layer ovality, improper Z-resolution parameter selection and fill of the empty shell in three-dimensional (3D) printing, results unexpected texture and appearance. An investigation is carried out on the effects of Z-resolution (0.15 mm to 0.40 mm) and Fill parameters on flat and curved surface objects manufactured using the FDM process. Moreover, post surface treatment was performed using acetone. It was found that average surface roughness increases with increasing Z-resolution. Solid Fill can create a smoother surface as oppose to Sparse Fill. Surface roughness improves significantly after post treatment with organic solvent acetone.

用于机器视觉测量曲面照明的LED阵列优化算法设计

用于机器视觉测量曲面照明的LED阵列优化算法设计

Remote Measurement Method of Surface Compliance Distribution for a Curved Surface Object

Remote Measurement Method of Surface Compliance Distribution for a Curved Surface Object

レーザプラズマ式３Ｄディスプレイにおける点列を用いた物体表現

This research proposes a method of representing objects for a 3D display device that uses a pulse laser and generates plasma luminous bodies in arbitrary positions in midair. By using a xyz-scanner, the device controls the position of plasma luminous bodies that appear and disappear one by one in 1 kHz. The device can display an object in one stroke in midair. We propose our method of representing primitive objects— polygons, polyhedrons and curved surface objects— in consideration of hardware limitations and human visual characteristics, and evaluate the objects in experiments. As a result, polygons can be represented visually, effectively reducing the scanner burden by smoothing accelerations at corners and increasing the plasma density; polyhedron faces are best drawn one by one; and when curved surface objects are drawn using spiral, we can stably perceive them.

로봇 손에 의한 자유곡면 물체의 파지 및 조작에 관한 운동학

로봇 손에 의한 자유곡면 물체의 파지 및 조작에 관한 운동학

Computing the perspective projection aspect graph of solids of revolution

An algorithm for computing the aspect graph for a class of curved-surface objects based on an exact parcellation of 3-D viewpoint space is presented. The object class considered is solids of revolution. A detailed analysis of the visual events for this object class is given, as well as an algorithm for constructing the aspect graph. Numerical search techniques, based on a geometric interpretation of the visual events, have been devised to determine those visual event surfaces that cannot be calculated directly. The worst-case complexity of the number of cells in the parcellation of 3-D viewpoint space, and, hence, the number of nodes in the aspect graph, is O(N/sup 4/), where N is the degree of a polynomial that defines the object shape. A summary of the results for 20 different object descriptions is presented, along with a detailed example for a flower vase. >

Computing the orthographic projection aspect graph of solids of revolution

Several researchers have recently addressed the problem of computing the aspect graph of an object by deriving the exact partition of viewpoint space from the object's geometry. Algorithms have been developed to handle general polyhedral objects, with viewpoint space modeled as either the Gaussian sphere or as 3-D space. This paper presents the first algorithm to handle a defined class of curved-surface objects. The algorithm automatically computes the partition of the Guassian sphere, and thereby the aspect graph, for solids of revolution defined as Right, Circular, Straight, Homogeneous Generalized Cylinders.

An adaptive subdivision method for surface-fitting from sampled data

A method is developed for surface-fitting from sampled data. Surface-fitting is the process of constructing a compact representation to model the surface of an object based on a fairly large number of given data points. In our case, the data is obtained from a real object using an automatic three-dimensional digitizing system. The method is based on an adaptive subdivision approach, a technique previously used for the design and display of free-form curved surface objects. Our approach begins with a rough approximating surface and progressively refines it in successive steps in regions where the data is poorly approximated. The method has been implemented using a parametric piecewise bicubic Bernstein-Bézier surface possessing G 1 geometric continuity. An advantage of this approach is that the refinement is essentially local reducing the computational requirements which permits the processing of large databases. Furthermore, the method is simple in concept, yet realizes efficient data compression. Some experimental results are given which show that the representation constructed by this method is faithful to the original database.

Understanding objects with curved surfaces from a single perspective view of boundaries

Given a single image of a scene containing a perspective view of three-dimensional objects, we would like a computer vision system to be able to perceive the objects in it. This paper describes an efficient way of labeling a line-drawing image and shows how to utilize the line-labeling and junction-labeling information to group together faces of the same object volume and predict the simplest arrangement and types of the hidden vertices caused by the overlapping of objects. This scheme is valid for both planar and curved-surface objects. In addition, it can handle some instances of multi-type vertices.

A system for interactive modeling of physical curved surface objects

It is often important to obtain descriptions of existing objects for computer graphics data bases. A system to aid interactive modeling (in three dimensions) of a physical object is described. The system allows a user to fit a bi-cubic parametric spline surface to an object by superimposing stereoscopic views of the computer surface with stereoscopic television views of the object. A 3-D joystick is used to manipulate surface control points while the user views the computed surface as isoparametric contours. A raster scan display polarization stereoscope is used. The left eye and right eye surface views are computed using a unique display processor designed and constructed for the evaluation of raster scan graphics techniques. The display processor consists of multiple non-pipelined concurrently operating microprogrammed modules. The computation of the two reasonably complex images (>500 vectors each) takes less than 33 msec allowing real time display at standard television rates.