Author name cluster

Chris Prahacs

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

7 papers

1 author row

IROS Conference 2012 Conference Paper

Multi-domain monitoring of marine environments using a heterogeneous robot team

Florian Shkurti
Anqi Xu 0003
Malika Meghjani
Juan Camilo Gamboa Higuera
Yogesh A. Girdhar
Philippe Giguère
Bir Bikram Dey
Jimmy Li 0001

In this paper we describe a heterogeneous multi-robot system for assisting scientists in environmental monitoring tasks, such as the inspection of marine ecosystems. This team of robots is comprised of a fixed-wing aerial vehicle, an autonomous airboat, and an agile legged underwater robot. These robots interact with off-site scientists and operate in a hierarchical structure to autonomously collect visual footage of interesting underwater regions, from multiple scales and mediums. We discuss organizational and scheduling complexities associated with multi-robot experiments in a field robotics setting. We also present results from our field trials, where we demonstrated the use of this heterogeneous robot team to achieve multi-domain monitoring of coral reefs, based on real-time interaction with a remotely-located marine biologist.

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IROS Conference 2008 Conference Paper

Enabling autonomous capabilities in underwater robotics

Junaed Sattar
Gregory Dudek
Olivia Chiu
Ioannis M. Rekleitis
Philippe Giguère
Alec Mills
Nicolas Plamondon
Chris Prahacs

Underwater operations present unique challenges and opportunities for robotic applications. These can be attributed in part to limited sensing capabilities, and to locomotion behaviours requiring control schemes adapted to specific tasks or changes in the environment. From enhancing teleoperation procedures, to providing high-level instruction, all the way to fully autonomous operations, enabling autonomous capabilities is fundamental for the successful deployment of underwater robots. This paper presents an overview of the approaches used during underwater sea trials in the coral reefs of Barbados, for two amphibious mobile robots and a set of underwater sensor nodes. We present control mechanisms used for maintaining a preset trajectory during enhanced teleoperations and discuss their experimental results. This is followed by a discussion on amphibious data gathering experiments conducted on the beach. We then present a tetherless underwater communication approach based on pure vision for high-level control of an underwater vehicle. Finally the construction details together with preliminary results from a set of distributed underwater sensor nodes are outlined.

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IROS Conference 2006 Conference Paper

Characterization and Modeling of Rotational Responses for an Oscillating Foil Underwater Robot

Philippe Giguère
Chris Prahacs
Gregory Dudek

In order to better understand the behavior of the underwater robot developed at our laboratory, a simple but relatively good model of the underwater behavior of the robot had to be developed. In order to be useful for model-based control techniques onboard the robot, the model had to have low computing requirements, yet be complex enough to capture the transient response of the robot. To achieve this, a system identification approach was taken by first capturing the robot response to various inputs, and then matching them to a simple model

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IROS Conference 2005 Conference Paper

A visual servoing system for an aquatic swimming robot

Junaed Sattar
Philippe Giguère
Gregory Dudek
Chris Prahacs

This paper describes a visual servoing system for an underwater legged robotic system named AQUA and initial experiments with the system performed in the open sea. A large class of significant applications can be leveraged by allowing such a robot to follow a diver or some other moving target. The robot uses a suite of sensing technologies, primarily based on computer vision, to allow it to navigate in shallow-water environments. The visual servoing system described here allows the robot to track and follow a given target underwater. The servo package is made up of two distinct parts: a tracker and a feedback controller. The system has been evaluated in the sea water and under natural lighting conditions. The servo system has been tested underwater, and with minor modifications, the system can be used while the robot is walking on the ground as well.

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IROS Conference 2005 Conference Paper

A visually guided swimming robot

Gregory Dudek
Michael Jenkin
Chris Prahacs
Andrew Hogue
Junaed Sattar
Philippe Giguère
Andrew German
Hui Liu

We describe recent results obtained with AQUA, a mobile robot capable of swimming, walking and amphibious operation. Designed to rely primarily on visual sensors, the AQUA robot uses vision to navigate underwater using servo-based guidance, and also to obtain high-resolution range scans of its local environment. This paper describes some of the pragmatic and logistic obstacles encountered, and provides an overview of some of the basic capabilities of the vehicle and its associated sensors. Moreover, this paper presents the first ever amphibious transition from walking to swimming.

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IROS Conference 2004 Conference Paper

AQUA: an aquatic walking robot

Christina Georgiades
Andrew German
Andrew Hogue
Hui Liu
Chris Prahacs
Arlene Ripsman
Robert Sim
Luz Abril Torres-Méndez

This paper describes an underwater walking robotic system being developed under the name AQUA, the goals of the AQUA project, the overall hardware and software design, the basic hardware and sensor packages that have been developed, and some initial experiments. The robot is based on the RHex hexapod robot and uses a suite of sensing technologies, primarily based on computer vision and INS, to allow it to navigate and map clear shallow-water environments. The sensor-based navigation and mapping algorithms are based on the use of both artificial floating visual and acoustic landmarks as well as on naturally occurring underwater landmarks and trinocular stereo.

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ICRA Conference 2003 Conference Paper

Towards a dynamic actuator model for a hexapod robot

Dave McMordie
Chris Prahacs
Martin Buehler

We describe a model predicting the output torque of the battery-amplifier-actuator-gear combination used on the hexapod robot RHex, based on requested PWM (pulse width modulation) duty cycle to the amplifier, battery voltage, and motor speed. The model is broken into independent components, each experimentally validated: power source (battery), motor amplifier, motor and (planetary) gear. The resulting aggregate model shows <6% full scale RMS error in predicting output torque in the first quadrant of operation (positive torques). Understanding the key ingredients and the attainable accuracies of torque production models in our commonly used battery-amplifier-actuator-gear combinations is critical for mobile robots, in order to minimize sensing, and thus space, size, weight, power consumption, failure rate, and cost of mobile robots.

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