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Abstract-We describe an autonomous robotic system capable of navigating through an office environment, opening doors along the way, and plugging itself into electrical outlets to recharge as needed. We demonstrate through extensive experimentation that our robot executes these tasks reliably, without requiring any modification to the environment. We present robust detection algorithms for doors, door handles, and electrical plugs and sockets, combining vision and laser sensors. We show how to overcome the unavoidable shortcoming of perception by integrating compliant control into manipulation motions. We present a visual-differencing approach to highprecision plug-insertion that avoids the need for high-precision hand-eye calibration.

This paper presents the software framework established to facilitate cloud-hosted robot simulation. The framework addresses the challenges associated with conducting a task-oriented and real-time robot competition, the Defense Advanced Research Projects Agency (DARPA) Virtual Robotics Challenge (VRC), designed to mimic reality. The core of the framework is the Gazebo simulator, a platform to simulate robots, objects, and environments, as well as the enhancements made for the VRC to maintain a high fidelity simulation using a high degree of freedom and multisensor robot. The other major component used is the CloudSim tool, designed to enhance the automation of robotics simulation using existing cloud technologies. The results from the VRC and a discussion are also detailed in this work. Note to Practitioners-Advances in robot simulation, cloud hosted infrastructure, and web technology have made it possible to accurately and efficiently simulate complex robots and environments on remote servers while providing realistic data streams for human-in-the-loop robot control. This paper presents the software and hardware frameworks established to facilitate cloud-hosted robot simulation, and addresses the challenges associated with conducting a task-oriented robot competition designed to mimic reality. The competition that spurred this innovation was the VRC, a precursor to the DARPA Robotics Challenge, in which teams from around the world utilized custom human-robot interfaces and control code to solve disaster response-related tasks in simulation. Winners of the VRC received both funding and access to Atlas, a humanoid robot developed by Boston Dynamics. The Gazebo simulator, an open source and high fidelity robot simulator, was improved upon to met the needs of the VRC competition. Additionally, CloudSim was created to act as an interface between users and the cloud-hosted simulations.

Abstract. Open Dynamics Engine (ODE) is the most popular rigidbody dynamics implementation for robotics simulation applications. While using it to simulate common robotic scenarios like mobile robot locomotion and simple grasping, we have identified the following shortcomings each of which adversely affect robot simulation: lack of computational efficiency, poor support for practical joint-dampening, inadequate solver robustness, and friction approximation via linearization. In this paper we describe extensions to ODE that address each of these problems. Because some of these objectives lie in opposition to others-e.g., speed versus verisimilitude-we have carried out experiments in order to identify the trade-offs involved in selecting from our extensions. Results from both elementary physics and robotic task-based scenarios show that speed improvements can be gained along with useful joint-dampening. If one is willing to accept an execution time cost, we are able to represent the full-friction cone, while simultaneously guaranteeing a solution from our numerical solver.

In current practice, unsteady flow simulations for turbomachinery are performed using a dual-time-stepping scheme. This work is motivated by the need to solve the timeaccurate Navier-Stokes equations with greatly decreased computational cost. The purpose of this paper is to investigate the introduction of an initial ADI step, guaranteeing second order accuracy in time, followed by a small number of cycles of the dual-time-stepping scheme augmented by multigrid. The O ∆t 2 accuracy in time should be retained without the need for large numbers of inner iterations required for convergence of typical iterative methods. The details of this new scheme are presented in this paper while examples are given to demonstrate the second order accuracy and the convergence properties of the scheme.