Contemporary time-stepping methods used in the dynamic simulation of rigid bodies suffer from problems in accuracy, performance, and robustness. Significant allowances for tuning, coupled with careful implementation of a broad phase collision detection scheme is required to make dynamic simulation useful for practical applications. A recently developed formulation method is presented herein that is more robust, and not dependent on broad-phase collision detection or system tuning for its behavior. Several uncomplicated benchmark examples are presented to give an analysis and make a comparison of the new Polyhedral Exact Geometry time-stepping method with the well-known Stewart-Trinkle time-stepping method. The behavior and performance for the two methods are discussed. This includes specific cases where contemporary time-steppers fail, and how they are ameliorated by the new method presented here. The goal of this work is to complete the groundwork for further research into high performance simulation.

This paper presents a methodology for treating energy consistency when considering multiple simultaneous impacts and contacts with friction in the simulation of systems of multiple interconnected bodies. Hard impact and contact is considered where deformation of the impacting surfaces is negligible. The proposed approach uses a discrete algebraic model of impact in conjunction with moment and tangential co-efficients of restitution (CORs) to develop a general impact law for determining post-impact velocities. This process depends on impulse-momentum theory, complementarity conditions, a principle of maximum dissipation, and the determination of contact forces. The proposed methodology also uses an energy-modifying COR to directly control the system's energy. The approach is illustrated on a bicycle-like structure.

This paper presents a method for determining impact forces associated with an abrupt velocity change when a free-flying body comes into contact with another body. Hard impact is considered where deformation of the impacting surfaces is negligible. The proposed approach uses a discrete algebraic model of impact in conjunction with moment and tangential coefficients of restitution (CORs) to develop a general impact law for determining post-impact velocities. This process depends on impulse-momentum theory, complementarity conditions, a principle of maximum dissipation, and the determination of impact and contact forces as well as post-impact accelerations. The proposed methodology also uses an energy-modifying COR to directly control the system's energy profile over time. The approach is illustrated on a planar bicycle-like structure.

Teleoperated robots generally receive high level commands from a remote system, while accomplishing motion control through conventional means. We present a teleoperated system that removes the entire motion control structure from the robot, in order to preserve the availability of crucial onboard resources. The operation of state feedback control is performed by a system remote from the robot. We have designed a computerized motion planning and control system for Mobile Emulab, and in this article, discuss the implementation of trajectory tracking control. A component of the Emulab network testbed, Mobile Emulab is used for wireless network experiments requiring mobility; and is publicly available to remote researchers via the Internet. Medium scale wheeled mobile robot couriers are used to move wireless antennas within a semi-controlled environment. Experimenters use a Web-based GUI to specify desired paths and configurations for multiple robots. State feedback is provided by an overhead camera based visual localization system. Kinematic control is used to generate velocity commands, which are sent to robots over a computer network. Data availability is restricted to a low sampling frequency. There is significant noise, loss, and phase lag present in the robot localization data, which our research overcomes to provide an autonomous trajectory tracking mobile robot control system.

Abstract — Simulation has been the dominant research methodology in wireless and sensor networking. When mobility is added, real-world experimentation is especially rare. However, it is becoming clear that simulation models do not sufficiently capture radio and sensor irregularity in a complex, real-world environment, especially indoors. Unfortunately, the high labor and equipment costs of truly mobile experimental infrastructure present high barriers to such experimentation. We describe our experience in creating a testbed to lower those barriers. We have extended the Emulab network testbed software to provide the first remotely-accessible mobile wireless and sensor testbed. Robots carry motes and single board computers through a fixed indoor field of sensor-equipped motes, all running the user’s selected software. In real-time, interactively or driven by a script, remote users can position the robots, control all the computers and network interfaces, run arbitrary programs, and log data. Our mobile testbed provides simple path planning, a vision-based tracking system accurate to 1 cm, live maps, and webcams. Precise positioning and automation allow quick and painless evaluation of location and mobility effects on wireless protocols, location algorithms, and sensor-driven applications. The system is robust enough that it is deployed for public use. We present the design and implementation of our mobile testbed, evaluate key aspects of its performance, and describe a few experiments demonstrating its generality and power. I.

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No abstract available.