A closed-loop velocity-position cascade control system for a profiling float is investigated, simulated, and tested. In the dynamic model, drag experienced by the plant is linearized to facilitate Laplace Transform, and transfer function is computed. A discrete-time PID controller with low-pass signal filter is integrated into the model in the Laplace domain, and resulting Root Locus computed. For a tested set of control gains the Root Locus predicts an over damped response to step input. Simulink simulation of the non-linear plant, and subsequent testing in the MBARI Test Tank showed the plant exhibited slight oscillation when given a step input. The cascaded strategy was successful in depth control within +/0.2 dbar, but is energetically expensive. For long term float deployments, a more efficient strategy of achieving neutral buoyancy is needed.
[1]
L. Moskowitz,et al.
Estimates of the Power Spectrums for Fully Developed Seas for Wind Speeds of 20 to 40 Knots
,
1964
.
[2]
Thomas S. Bianchi,et al.
The changing carbon cycle of the coastal ocean
,
2013,
Nature.
[3]
Trevor Platt,et al.
Primary productivity of planet earth: biological determinants and physical constraints in terrestrial and aquatic habitats
,
2001
.
[4]
E. D’Asaro.
Performance of Autonomous Lagrangian Floats
,
2003
.
[5]
Nicolas Gruber,et al.
Observing Biogeochemical Cycles at Global Scales With Profiling Floats and Gliders Prospects for a Global Array
,
2009
.