text: In many robotic domains such as flexible automated manufacturing or personal assistance, a fundamental perception task is that of identifying and localizing objects whose 3D models are known. Canonical approaches to this problem include discriminative methods that find correspondences between feature descriptors computed over the model and observed data. While these methods have been employed successfully, they can be unreliable when the feature descriptors fail to capture variations in observed data; a classic cause being occlusion. As a step towards deliberative reasoning, we present PERCH: PErception via SeaRCH, an algorithm that seeks to find the best explanation of the observed sensor data by hypothesizing possible scenes in a generative fashion. Our contributions are: i) formulating the multi-object recognition and localization task as an optimization problem over the space of hypothesized scenes, ii) exploiting structure in the optimization to cast it as a combinatorial search problem on what we call the Monotone Scene Generation Tree, and iii) leveraging parallelization and recent advances in multi-heuristic search in making combinatorial search tractable. We prove that our system can guaranteedly produce the best explanation of the scene under the chosen cost function, and validate our claims on real world RGB-D test data. Our experimental results show that we can identify and localize objects under heavy occlusion--cases where state-of-the-art methods struggle.
  @cite_26: 
  @cite_29: We propose a novel method to estimate a unique and repeatable reference frame in the context of 3D object recognition from a single viewpoint based on global descriptors. We show that the ability of defining a robust reference frame on both model and scene views allows creating descriptive global representations of the object view, with the beneficial effect of enhancing the spatial descriptiveness of the feature and its ability to recognize objects by means of a simple nearest neighbor classifier computed on the descriptor space. Moreover, the definition of repeatable directions can be deployed to efficiently retrieve the 6DOF pose of the objects in a scene. We experimentally demonstrate the effectiveness of the proposed method on a dataset including 23 scenes acquired with the Microsoft Kinect sensor and 25 full-3D models by comparing the proposed approach with state-of-the-art global descriptors. A substantial improvement is presented regarding accuracy in recognition and 6DOF pose estimation, as well as in terms of computational performance.
  @cite_17: 
  @cite_6: This paper focuses on developing a fast and accurate 3D feature for use in object recognition and pose estimation for rigid objects. More specifically, given a set of CAD models of different objects representing our knoweledge of the world - obtained using high-precission scanners that deliver accurate and noiseless data - our goal is to identify and estimate their pose in a real scene obtained by a depth sensor like the Microsoft Kinect. Borrowing ideas from the Viewpoint Feature Histogram (VFH) due to its computational efficiency and recognition performance, we describe the Clustered Viewpoint Feature Histogram (CVFH) and the cameras roll histogram together with our recognition framework to show that it can be effectively used to recognize objects and 6DOF pose in real environments dealing with partial occlusion, noise and different sensors atributes for training and recognition data. We show that CVFH out-performs VFH and present recognition results using the Microsoft Kinect Sensor on an object set of 44 objects.
  @cite_23: We present the Viewpoint Feature Histogram (VFH), a descriptor for 3D point cloud data that encodes geometry and viewpoint. We demonstrate experimentally on a set of 60 objects captured with stereo cameras that VFH can be used as a distinctive signature, allowing simultaneous recognition of the object and its pose. The pose is accurate enough for robot manipulation, and the computational cost is low enough for real time operation. VFH was designed to be robust to large surface noise and missing depth information in order to work reliably on stereo data.
  @cite_25: We propose a framework for automatic modeling, detection, and tracking of 3D objects with a Kinect. The detection part is mainly based on the recent template-based LINEMOD approach [1] for object detection. We show how to build the templates automatically from 3D models, and how to estimate the 6 degrees-of-freedom pose accurately and in real-time. The pose estimation and the color information allow us to check the detection hypotheses and improves the correct detection rate by 13 with respect to the original LINEMOD. These many improvements make our framework suitable for object manipulation in Robotics applications. Moreover we propose a new dataset made of 15 registered, 1100+ frame video sequences of 15 various objects for the evaluation of future competing methods.
  @cite_11: In this article we describe an object perception system for autonomous robots performing everyday manipulation tasks in kitchen environments. The perception system gains its strengths by exploiting that the robots are to perform the same kinds of tasks with the same objects over and over again. It does so by learning the object representations necessary for the recognition and reconstruction in the context of pick-and-place tasks. The system employs a library of specialized perception routines that solve different, well-defined perceptual sub-tasks and can be combined into composite perceptual activities including the construction of an object model database, multimodal object classification, and object model reconstruction for grasping. We evaluate the effectiveness of our methods, and give examples of application scenarios using our personal robotic assistants acting in a human living environment.
summary: The second, recognition systems employ a single-shot process for identifying object type and pose jointly. Global feature descriptors encode the notion of an object and capture shape and viewpoint information jointly in the descriptor. These approaches employ a training phase to build a library of global descriptors corresponding to different observed instances (e.g., each object viewed from different viewpoints) and attempt to match the descriptor computed at observation time to the closest one in the library. Additionally, global methods unlike the local ones, require points in the observed scene to be segmented into different clusters, so that descriptors can be computed on each object cluster separately. Some of the global recognition systems include Viewpoint Feature Histogram (VFH) @cite_23 , Clustered Viewpoint Feature Histogram (CVFH) @cite_6 , OUR-CVFH @cite_29 , Ensemble of Shape Functions (ESF) @cite_26 , and Global Radius-based Surface Descriptors (GRSD) @cite_11 . Other approaches to estimating object pose include local voting schemes @cite_17 or template matching @cite_25 to first detect objects, and then using global descriptor matching or ICP for pose refinement.