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 ofnonholonomic 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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