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Abstract-Monitoring of environmental phenomena with embedded networked sensing confronts the challenges of both unpredictable variability in the spatial distribution of phenomena, coupled with demands for a high spatial sampling rate in three dimensions. For example, low distortion mapping of critical solar radiation properties in forest environments may require two-dimensional spatial sampling rates of greater than 10 samples/m 2 over transects exceeding 1000 m 2 . Clearly, adequate sampling coverage of such a transect requires an impractically large number of sensing nodes. A new approach, Networked Infomechanical System (NIMS), has been introduced to combine autonomous-articulated and static sensor nodes enabling sufficient spatiotemporal sampling density over large transects to meet a general set of environmental mapping demands. This paper describes our work on a critical parts of NIMS, the Task Allocation module. We present our methodologies and the two basic greedy Task Allocation policies -based on time of the task arrival (Time policy) and distance from the robot to the task (Distance policy). We present results from NIMS deployed in a forest reserve and from a lab testbed. The results show that both policies are adequate for the task of spatiotemporal sampling, but also complement each other. Finally, we suggest the future direction of research that would both help us better quantify the performance of our system and create more complex policies combining time, distance, information gain, etc.

A perturbation analysis of nonlinear wheel shimmy in aircraft landing gear is presented for nonlinear models that include terms due to coulomb friction between the oleo struts and freeplay in the torque links. The method of multiple timescales is used to obtain general expressions for the limit-cycle amplitude and the frequency that are functions of ground speed. The analysis shows that stable or unstable limit cycles can exist for taxi speeds above or below a critical value with stability of the limit cycles being determined by the sign of a computed coef cient. When only coulomb friction is present, an unstable limit cycle exists. When only freeplay is present, a stable limit cycle exists. When both coulomb friction and freeplay are present, it is shown that stable and unstable limit cycles and a turning point can exist depending on the system parameter values. The solution method is applied to a simple shimmy model, and results from the perturbation analysis are shown to be in good agreement with those obtained by direct numerical integration of the nonlinear shimmy equations. Nomenclaturevectors of nonlinear terms f cf = vector of coulomb friction terms f fp = vector of nonlinear stiffness terms including freeplay effects f .n/ j ; f .n/ k = Fourier coef cient vectors i = imaginary unit, p ¡1 K; N K = stiffness matrices K .0/ = ² 0 -order term in expansion for K K .1/ = ² 1 -order term in expansion for K M; N M = mass matrices q = vector of state variables q m = coordinate vector in expansion for q V = system parameter (ground speed) V i = i th-order term in expansion for V V 0 = critical value of V ®= complex coef cient = complex coef cient°= complex coef cient ± = complex coef cient ² = small parameter ¿ = independent variable time ¿ m = multiple timescales à = phase ! = frequency, dependent on amplitude A ! 0 = eigenvalue for V 0 and det L 0

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