The Routing Protocol for Low power and Lossy Networks (RPL) is the IETF standard for IPv6 routing in low-power wireless sensor networks. It is a distance vector routing protocol that builds a Destination Oriented Directed Acyclic Graph (DODAG) rooted towards one sink (the DAG root), using an objective function and a set of metrics/constraints to compute the best path. In this paper, we propose a routing metric which minimizes the delay towards the DAG root, assuming that nodes run with very low duty cycles (e.g., under 1%) at the MAC layer. We evaluate the proposed routing metric with the Contiki operating system and compare its performance with that of the Expected Transmission Count (ETX) metric. Moreover, we propose some extensions to the ContikiMAC radio duty cycling protocol to support different sleeping periods of the nodes.

In specific virtual reality applications that require high accuracy it may be advisable to replace the built-in tracking system of the HMD with a third party solution. The purpose of this research work is to evaluate the accuracy of the built-in tracking system of the Oculus Rift S Head Mounted Display (HMD) in room scale environments against a motion capture system. In particular, an experimental evaluation of the Oculus Rift S inside-out tracking technology was carried out, compared to the performance of an outside-in tracking method based on the OptiTrack motion capture system. In order to track the pose of the HMD using the motion capture system the Oculus Rift S was instrumented with passive retro-reflective markers and calibrated. Experiments have been performed on a dataset of multiple paths including simple motions as well as more complex paths. Each recorded path contained simultaneous changes in both position and orientation of the HMD. Our results indicate that in room-scale environments the average translation error for the Oculus Rift S tracking system is about $$1.83$$1.83 cm, and the average rotation error is about $$0.77^\circ$$0 . 77 ∘ , which is 2 orders of magnitude higher than the performance that can be achieved using a motion capture system.

Next best view (NBV) planning is a central task for automated three-dimensional (3-D) reconstruction in robotics. The most expensive phase of NBV computation is the view simulation step, where the information gain of a large number of candidate sensor poses are estimated. Usually, information gain is related to the visibility of unknown space from the simulated viewpoint. A well-established technique is to adopt a volumetric representation of the environment and to compute the NBV from ray casting by maximizing the number of unknown visible voxels. This letter explores a novel approach for NBV planning based on surfel representation of the environment. Surfels are oriented surface elements, such as circular disks, without explicit connectivity. A new kind of surfel is introduced to represent the frontier between empty and unknown space. Surfels are extracted during 3-D reconstruction, with minimal overhead, from a KinectFusion volumetric representation. Surfel rendering is used to generate images from each simulated sensor pose. Experiments in a real robot setup are reported. The proposed approach achieves better performance than volumetric algorithms based on ray casting implemented on graphics processing unit (GPU), with comparable results in terms of reconstruction quality. Moreover, surfel-based NBV planning can be applied in larger environments as a volumetric representation is limited by GPU memory.

This paper presents a mobile manipulation platform designed for autonomous depalletizing tasks. The proposed solution integrates machine vision, control and mechanical components to increase flexibility and ease of deployment in industrial environments such as warehouses. A collaborative robot mounted on a mobile base is proposed, equipped with a simple manipulation tool and a 3D in-hand vision system that detects parcel boxes on a pallet, and that pulls them one by one on the mobile base for transportation. The robot setup allows to avoid the cumbersome implementation of pick-and-place operations, since it does not require lifting the boxes. The 3D vision system is used to provide an initial estimation of the pose of the boxes on the top layer of the pallet, and to accurately detect the separation between the boxes for manipulation. Force measurement provided by the robot together with admittance control are exploited to verify the correct execution of the manipulation task. The proposed system was implemented and tested in a simplified laboratory scenario and the results of experimental trials are reported.

This work presents an approach for part-based grasp planning in point clouds. A complete pipeline is proposed that allows a robot manipulator equipped with a range camera to perform object detection, categorization, segmentation into meaningful parts, and part-based semantic grasping. A supervised image-space technique is adopted for point cloud segmentation based on projective analysis. Projective analysis generates a set of 2D projections from the input object point cloud, labels each object projection by transferring knowledge from existing labeled images, and then fuses the labels by back-projection on the object point cloud. We introduce an algorithm for point cloud categorization based on 2D projections. We also propose a viewpoint aware algorithm that filters 2D projections according to the scanning path of the robot. Object categorization and segmentation experiments were carried out with both synthetic and real datasets. Results indicate that the proposed approach performs better than a CNN-based method for a training set of limited size. Finally, we show part-based grasping tasks in a real robotic setup.

This work presents a 3D vision system for automatic detection of cardboard parcel boxes of known size, located on the top layer of a pallet of known height. An industrial Time-of-Flight (ToF) sensor is adopted that can operate in different illumination conditions thanks to the use of an infrared light source. The perception system is intended for application in industrial warehousing for end-of-line operations, like robot depalletizing. The proposed method does not assume any predefined layout of parcels and, therefore, it can work even with an incomplete layer of misaligned cardboard boxes. The developed solution first extracts all possible object hypotheses, then an optimization problem is solved, based on a genetic algorithm, to exclude conflicts. Experiments have been performed on a real dataset including complex configurations of tightly packed parcels.