(Georgia Institute of Technology, 2012-12-18)
Szwaykowska, Klementyna; Zhang, Fumin
This paper establishes the method of controlled Lagrangian particle tracking (CLPT) to analyse the
offsets between physical positions of marine robots in the ocean and simulated positions of controlled
particles in an ocean model. The offset, which we term the CLPT error, demonstrates distinguished
characteristics not previously seen in drifters and floats that cannot be actively controlled. The CLPT
error growth over time is exponential until it reaches a turning point that only depends on the resolution
of the ocean model. After this turning point, the error growth slows down significantly to polynomial
functions of time. In the ideal case, a theoretical upper threshold on exponential growth of CLPT
error can be derived. These characteristics are proved theoretically, verified via simulation, and justified
with ocean experimental data. The method of CLPT may be applied to improve the accuracy of ocean
circulation models and the performance of navigation algorithms for marine robots.
(Georgia Institute of Technology, 2011)
Wu, Wencen; Zhang, Fumin
We design a switching strategy for a group of
robots to search for a local minimum of an unknown noisy
scalar field. Starting with individual exploration, the robots
switch to cooperative exploration only when they are not able
to locate the field minimum based on the information collected
individually. In order to test and demonstrate the switching
strategy in real-world environment, we implement the switching
strategy on a multi-robot test-bed. The behaviors of a group of
robots are compared when different parameters for exploration
are adopted. Especially, we observe the effect of memory lengths
on the switching behaviors as predicted by theoretical results.
The experimental results also justify the effects of different
formation sizes and noise attenuation levels on the performance
of the cooperative H∞ filter that are utilized in the cooperative
exploration phase.
(Georgia Institute of Technology, 2011)
Zhang, Shaowei; Yu, Jiancheng; Zhang, Aiqun; Zhang, Fumin
Underwater Gliders have found broad applications
in ocean sampling. In this paper, the nonlinear dynamic
model of the glider developed by the Shenyang Institute of
Automation, Chinese Academy of Sciences, is established. Based
on this model, we solve for the parameters that characterize
steady state spiraling motions of the glider. A set of nonlinear
equations are simplified so that a recursive algorithm can be
used to find the solutions.