Robot Builders

Robotics Engineer Chris Schur has documented his research into mobile robot docking. The discussion includes beacon and sensor selection and usage, techniques for successfully navigating to a charging station, and ideas about the mechanical and electrical aspects of the docking connection itself. -more-

For mobile robotics, head gear in augmented reality (AR) applications or computer vision, it is essential to continuously estimate the egomotion and the structure of the environment. This paper presents the system developed in the SmartTracking project, which simultaneously integrates visual and inertial sensors in a combined estimation scheme. The sparse structure estimation is based on the detection of corner features in the environment. From a single known starting position, the system can move into an unknown environment. The vision and inertial data are fused, and the performance of both Unscented Kalman filter and Extended Kalman filter are compared for this task. The filters are designed to handle asynchronous input from visual and inertial sensors, which typically operate at different and possibly varying rates. Additionally, a bank of Extended Kalman filters, one per corner feature, is used to estimate the position and the quality of structure points and to include them into the structure estimation process. The system is demonstrated on a mobile robot executing known motions, such that the estimation of the egomotion in an unknown environment can be compared to ground truth.

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This paper is concerned with multi-user haptic simulation environments in which users can interact across an Ethernet-based Local Area Network (LAN) or a Metropolitan Area Network (MAN). Using network protocols such as the UDP and TCP/IP under normal network traffic conditions, the achievable real-time packet communication rate can be well below the 1 kHz update rate suggested in the literature for high fidelity haptic rendering. However by adopting a multi-rate control strategy, the local control loops can be executed at a much higher rate than that of the data packet transmission between the user workstations. Within such a framework, two control architectures, namely centralized and distributed are presented. Mathematical models of the controllers are developed and used in a comparative analysis of their stability and performance. The results of such analysis demonstrate that the distributed control architecture has greater stability margins and outperforms the centralized controller. It is also shown that the limited network packet transmission rate can degrade the haptic fidelity by introducing a viscous damping into the perceived impedance of the virtual object. Using the proposed models, this damping value is calculated and compensated by active control. Experiments conducted with a dual-user/dual-finger haptic platform confirm the analytical results.

A team of U.S. researchers has found a new and inexpensive way to create a nanowire coating for titanium surfaces used in bone implants. Their nanowire scaffolds can be used ‘to create more effective surfaces for hip replacement, dental reconstruction and vascular stenting.’ As said the lead researcher, ‘We can control the length, the height, the pore openings and the pore volumes within the nanowire scaffolds’ by varying the time, temperature and alkali concentration in the reaction,’ who added that the process was also extremely sustainable, requiring only that the device be rinsed in reusable water after the heating process. These nanowire scaffolds might also be used in hospitals or in meat-processing plants to kill bacteria. read story

This paper proposes a real-time, robust and effective tracking framework for visual servoing applications. The algorithm is based on the fusion of visual cues and on the estimation of a transformation (either a homography or a 3D pose). The parameters of this transformation are estimated using a non-linear minimization of a unique criterion that integrates information both on the texture and the edges of the tracked object. The proposed tracker is more robust and performs well in conditions where methods based on a single cue fail. The framework has been tested for 2D object motion estimation and pose computation. The method presented in this paper has been validated on several video sequences as well as in visual servoing experiments considering various objects. Results show the method to be robust to occlusions or textured backgrounds and suitable for visual servoing applications.

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I’m back again and, not surprisingly, the robots.net editor’s mailbox is overflowing. The Shadow Robot Company, Ltd. let us know that their famous Shadow Dextrous Hand will be at the upcoming WIRED NextFest 2007 to represent British robotics innovation. For details see their press release (PDF format). Michael Somby told about his Review of Robotics Software Platforms published over at LinuxDevices.net. It covers both closed/proprietary platforms like Microsoft and the more standard free/open platforms such as OROCOS, Player/Stage, OpenJAUS. Our Australian friend Murray Cox pointed out some interesting video of NASA’s Tetrahedral Robot Concept. A couple of users submitted links to these Engadget photos of iRobot’s totally redesigned Roomba 560 and Roomba 530. There’s also a new high-end model called the Roomba 570. Know any other robot news, gossip, or amazing facts we should report? Send ‘em our way please. -more-

This paper addresses problems of robot navigation with nonholonomic motion constraints and perceptual cues arising from onboard visual servoing in partially engineered environments. A general hybrid procedure is proposed that adapts to the constrained motion setting the standard feedback controller arising from a navigation function in the fully actuated case. This is accomplished by switching back and forth between moving “down” and “across” the associated gradient field toward the stable manifold it induces in the constrained dynamics. Guaranteed to avoid obstacles in all cases, conditions are provided under which the new procedure brings initial configurations to within an arbitrarily small neighborhood of the goal.

Simulation results are given for a sample of visual servoing problems with a few different perceptual models. The empirical effectiveness of the proposed algorithm is documented by reporting results of its application to outdoor autonomous visual registration experiments with the robot RHex guided by engineered beacons.

In this paper, an algorithm for autonomous stair climbing with a tracked vehicle is presented. The proposed method achieves robust performance under real-world conditions, without assuming prior knowledge of the stair geometry, the dynamics of the vehicle’s interaction with the stair surface, or lighting conditions. The approach relies on fast and accurate estimation of the robot’s heading and its position relative to the stair boundaries. An extended Kalman filter is used for quaternion-based attitude estimation, fusing rotational velocity measurements from a 3-axial gyroscope, and measurements of the stair edges acquired with an onboard camera. A two-tiered controller, comprised of a centering- and a heading-control module, utilizes the estimates to guide the robot rapidly, safely, and accurately upstairs. Both the theoretical analysis and implementation of the algorithm are presented in detail, and extensive experimental results demonstrating the algorithm’s performance are described.

In the neurological system of primates, changes in posture are detected by the central nervous system through a vestibular process. This process, located in the inner ear, coordinates several system outputs to maintain stable balance, visual gaze, and autonomic control in response to changes in posture. Consequently the vestibular data is merged to other sensing data like touch, vision, …. The visuo-inertial merging is crucial for several tasks like navigation, depth estimation, stabilization. This paper proposes a “primate-inspired” sensing hardware, based on a CMOS imaging and an artificial vestibular system. The whole sensor can be considered like a smart embedded sensor where one of the most original aspects of this approach is the use of a System On Chip implemented in a FPGA to manage the whole system. The sensing device is designed around a 4 million pixels CMOS imager and the artificial vestibular set is composed of three linear accelerometers and three gyroscopes. With its structure, the system provides a high degree of versatility and allows the implementation of parallel image and inertial processing algorithms. In order to illustrate the proposed approach, depth estimation with Kalman filtering implementation is carried out.

An international team of European researchers has implanted an artificial cerebellum — the portion of the brain that controls motor functions — inside a robotic system. This EU-funded project is dubbed SENSOPAC, an acronym for ‘SENSOrimotor structuring of perception and action for emerging cognition.’ One of the goals of this project is to design robots able to interact with humans in a natural way. This project, which should be completed at the end of 2009, also wants to produce robots which would act as home-helpers for disabled people, such as persons affected by neurological disorders, such as Parkinson’s disease. read story