Why do we trust established search engines?
The answer is simple: because we trust well-known brands more than others. Researchers from Penn State University (PSU) have integrated Google results pages into pages looking like coming from other search engines, such as Yahoo!, MSN Live Search or an in-house PSU search application. Then they asked a panel of students to judge which search engine offered the most relevant results. The testers found that the results from Yahoo! or Google were the best — even if they were exactly the same than the ones offered by the two other tools. The researchers conclude that branding matters — even when searching. read story
Homography-based 2D Visual Tracking and Servoing
The objective of this paper is to propose a new homography-based approach to image-based visual tracking and servoing. The visual tracking algorithm proposed in the paper is based on a new efficient second-order minimization method. Theoretical analysis and comparative experiments with other tracking approaches show that the proposed method has a higher convergence rate than standard first-order minimization techniques. Therefore, it is well adapted to real-time robotic applications. The output of the visual tracking is a homography linking the current and the reference image of a planar target. Using the homography, a task function isomorphic to the camera pose has been designed. A new image-based control law is proposed which does not need any measure of the 3D structure of the observed target (e.g. the normal to the plane). The theoretical proof of the existence of the isomorphism between the task function and the camera pose and the theoretical proof of the stability of the control law are provided. The experimental results, obtained with a 6 d.o.f. robot, show the advantages of the proposed method with respect to the existing approaches.
Adaptive Dynamic Walking of a Quadruped Robot on Natural Ground Based on Biological Concepts
The paper reports on a project to make a quadruped robot walk with medium forward speed on irregular terrain in an outdoor environment using a neural system model. The necessary conditions for stable dynamic walking on irregular terrain in general are proposed, and the neural system is designed by comparing biological concepts with those necessary conditions described in physical terms. A PD-controller is used at joints to construct a virtual spring—damper system as the visco-elasticity model of a muscle. The neural system model consists of a CPG (central pattern generator), responses and reflexes. A response directly and quickly modulates the CPG phase, and a reflex directly generates joint torque. The state of the virtual spring—damper system is switched, based on the CPG phase. In order to make a self-contained quadruped (called Tekken2) walk on natural ground, several new reflexes and responses are developed in addition to those developed in previous studies. A flexor reflex prevents a leg from stumbling on small bumps and pebbles. A sideways stepping reflex stabilizes rolling motion on a sideways inclined slope. A corrective stepping reflex/response prevents the robot from falling down in the case of loss of ground contact. A crossed flexor reflex helps a swinging leg keep enough clearance between the toe and the ground. The effectiveness of the proposed neural system model control and especially the newly developed reflexes and responses are validated by indoor and outdoor experiments using Tekken2. A CPG receives sensory feedback as a result of motions induced by reflexes, and changes the period of its own active phase. Since a CPG has the ability of mutual entrainment with pitching motion of legs and rolling motion of the body in addition, the consistency between motion of a leg temporally modified by a reflex and motions of the other legs is maintained autonomously. It is shown that CPGs can be the center of sensorimotor coordination, and that the neural system model simply defining the relationships between CPGs, sensory input, reflexes and mechanical system works very well even in complicated tasks such as adaptive dynamic walking on unstructured natural ground.
Image-based Visual Servoing of a Gough–Stewart Parallel Manipulator using Leg Observations
In this paper, a tight coupling between computer vision and parallel robotics is exhibited through the projective line geometry. Indeed, contrary to the usual methodology where the robot is modeled independently from the control law that will be implemented, the proposed method takes into account, from the early modeling stage, the fact that vision will be used for control. Hence, kinematic modeling and projective geometry are fused into a control-devoted projective kinematic model. Thus, starting from a vision-based kinematic modeling of a Gough—Stewart manipulator, a visual servoing scheme is presented, where the image projection (edges) of the non-rigidly linked legs are servoed, rather than the end-effector pose or the leg directions.
Deep Space Formation Flying Spacecraft Path Planning
Efficient algorithms for collision-free energy sub-optimal path planning for formations of spacecraft flying in deep space are presented. The idea is to introduce a set of way-points through which the spacecraft are required to pass, combined with parameterizations of the trajectories which are energy-optimal for each spacecraft. The resulting constrained optimization problem is formulated as a quasi-quadratic parameter optimization problem in terms of the way-points parameters. The mathematical structure of the problem is further exploited to develop gradient-based algorithms in which the gradients are computed analytically. The collision avoidance constraints are approximated such that closed form solutions are generated. This combination results in fast and robust numerical algorithms which work very well for scenarios involving a large number of spacecraft (e.g. 20).
People as an AI computing tool
The tagging phenomenon started about 3 years ago, with people putting labels on their posts in their blogs or on their pictures or videos. Now, a researcher from the University of Southern California (USC) has discovered the newest AI computing tool: people. Computer scientist Kristina Lerman thinks that ’she has found a new source of artificial intelligence computing power to solve difficult IT problems of information classification, reliability, and meaning.’ For example, ‘by extracting the tags that Flickr users had described the images with, and applyng a mathematical technique called the “Expectation-maximization (EM) algorithm,’ she found it’s possible to quite accurately separate pictures of insects from pictures of cars returned by the “beetle” search. So can we expect better search tools in the future? Time will tell.
Constraint-based Task Specification and Estimation for Sensor-Based Robot Systems in the Presence of Geometric Uncertainty
This paper introduces a systematic constraint-based approach to specify complex tasks of general sensor-based robot systems consisting of rigid links and joints. The approach integrates both instantaneous task specification and estimation of geometric uncertainty in a unified framework. Major components are the use of feature coordinates, defined with respect to object and feature frames, which facilitate the task specification, and the introduction of uncertainty coordinates to model geometric uncertainty. While the focus of the paper is on task specification, an existing velocity- based control scheme is reformulated in terms of these feature and uncertainty coordinates. This control scheme compensates for the effect of time varying uncertainty coordinates. Constraint weighting results in an invariant robot behavior in case of conflicting constraints with heterogeneous units. The approach applies to a large variety of robot systems (mobile robots, multiple robot systems, dynamic human-robot interaction, etc.), various sensor systems, and different robot tasks. Ample simulation and experimental results are presented.
Acting Robotic Desk Lamp
Guy Hoffman of MIT’s Robotic Life Research group is merging robots and the art of acting by animating a robotic desk lamp named AUR with a little inspiration from a 5-axis robot arm. AUR’s debut is a play at MIT’s Dramashop, touted as the first step in an effort towards a fully autonomous robotic actor. Video shows the lamp following a human’s lighting needs in a dimly lit room.
Manipulation of Convex Objects via Two-agent Point-contact Push
This paper explores a sensorless manipulation method for orienting and translating convex objects in the plane. The manipulation task is performed by a two-agent point-contact push. During the manipulation, each agent makes a point contact with the object, and both agents push together along a straight-line. One advantage of the two-agent point-contact push over the physical fence based push is that the two-agent point-contact push can manipulate non-polygonal parts, and reduce the position and orientation uncertainties simultaneously. First, two manipulation primitives are identified, equilibrium and non-equilibrium pushes, and the motion of the object characterized under these two pushing actions. Then, a controllability analysis is conducted for this class of manipulation using the theory of positive bases. After the analysis, the planning problem is studied in the framework of a switched system, and an analytical solution to the planning problem is developed. Finally, manipulation examples and experiments are provided to demonstrate the proposed manipulation method.
An Introduction to Inertial and Visual Sensing
In this paper we present a tutorial introduction to two important senses for biological and robotic systems — inertial and visual perception. We discuss the fundamentals of these two sensing modalities from a biological and an engineering perspective. Digital camera chips and micro-machined accelerometers and gyroscopes are now commodities, and when combined with today’s available computing can provide robust estimates of self-motion as well 3D scene structure, without external infrastructure. We discuss the complementarity of these sensors, describe some fundamental approaches to fusing their outputs and survey the field.