Title page for ETD etd-05212009-143624


Type of Document Dissertation
Author Dippold, Amanda
Author's Email Address ayoung83@vt.edu
URN etd-05212009-143624
Title Vision-Based Obstacle Avoidance for Multiple Vehicles Performing Time-Critical Missions
Degree PhD
Department Aerospace and Ocean Engineering
Advisory Committee
Advisor Name Title
Hovakimyan, Naira Committee Chair
Woolsey, Craig A. Committee Co-Chair
Farhood, Mazen Committee Member
Hall, Christopher D. Committee Member
Keywords
  • Path generation
  • path following
  • obstacle avoidance
  • path deformation
  • vision-based estimation
  • visual sensors
  • coordinated control
  • time-critical missions
Date of Defense 2009-05-05
Availability unrestricted
Abstract
This dissertation discusses vision-based static obstacle avoidance for a fleet of

nonholonomic robots tasked to arrive at a final destination simultaneously. Path generation

for each vehicle is computed using a single polynomial function that incorporates the vehicle

constraints on velocity and acceleration and satisfies boundary conditions by construction.

Furthermore, the arrival criterion and a preliminary obstacle avoidance scheme is incorporated

into the path generation. Each robot is equipped with an inertial measurement unit

that provides measurements of the vehicle’s position and velocity, and a monocular camera

that detects obstacles. The obstacle avoidance algorithm deforms the vehicle’s original path

around at most one obstacle per vehicle in a direction that minimizes an obstacle avoidance

potential function. Deconfliction of the vehicles during obstacle avoidance is achieved by

imposing a separation condition at the path generation level. Two estimation schemes are

applied to estimate the unknown obstacle parameters. The first is an existing method known

in the literature as Identifier-Based Observer and the second is a recently-developed fast estimator.

It is shown that the performance of the fast estimator and its effect on the obstacle

avoidance algorithm can be arbitrarily improved by the appropriate choice of parameters as

compared to the Identifier-Based Observer method. Coordination in time of all vehicles is

completed in an outer loop which adjusts the desired velocity profile of each vehicle in order

to meet the simultaneous arrival constraints. Simulation results illustrate the theoretical

findings.

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