Solar Power

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The above video is from [1].

In our lab we are interested in several outdoor environmental monitoring problems, where we would like to be able to embed a robot in the environment for a long time. However, the robots are currently limited by their battery capacity, so that none can currently operate for more than a few hours, unless we can charge the battery somehow on the field. The most practical way to do this is through the use of built-in photovoltaic panels.

On the left is Clearpath Husky A200, and on the right is Oceanscience Q-Boat 1800D.  Both are shown with dual Solartec 20 watt panels.

These solar panels provide some interesting path planning problems. Fundamentally we would like to travel in the sun rather than the shade, if possible, but if the shortest path is in the shade it might not be worthwhile to deviate. We need an accurate solar map of the environment, as well as an accurate sense of the energy required to drive along a given path.

In our work so far we have focused on accomplishing this mapping using only GPS information and measurements of solar intensity on the panels. This allows us to add the system to any field robot, even a very minimal field robot, without requiring expensive additional sensors.

The McNamara Alumni Center is one of our favored test environments

In [JFR 2013] we demonstrated the feasibility of solar aware path planning, and demonstrated a basic Gaussian Process regression approach to construct the solar map. This method works well in the short term but it doesn't have a good way to account for the predictable movement of the sun.

Map constructed using Gaussian Process regression

In [IJRR 2013] we were operating on a lake, so we used raytracing to determine the positions of shadow casting objects, and then used the estimated positions of these objects to obtain a solar map for any time of day. We took advantage of the fact that these objects were most likely to appear on the shoreline. This gave us a good time varying map on the lake.

On Lake Como we can approximate all shadow-casting objects as occurring right along the lake boundary. Estimated solar map for 07:42 CST on September 16th, 2012

In [IROS 2013] we extended our approach for when we had no prior information on the positions of the shadow casting objects. We learned the positions of these objects by clustering together shade measurement rays that passed close to each other. This allowed us to obtain a good time varying map even when the object positions were completely unconstrained.

Estimated minimum heights at Alumni Center Estimated probability of sun at Alumni Center

For more information on the uses of this work, see Carp Tracking.

Related Publications

2016
7P. A. Plonski, J. Vander Hook, C. Peng, N. Noori, V. Isler
Environment Exploration in Sensing Automation for Habitat Monitoring
IEEE Transactions on Automation Science and Engineering, PP(99): 1-14, 2016.
6Patrick A. Plonski, Joshua Vander Hook, Volkan Isler
Environment and Solar Map Construction for Solar-Powered Mobile Systems
IEEE Trans. Robotics, 32(1): 70--82, 2016.
2014
5P. A. Plonski, V. Isler
A Competitive Online Algorithm for Exploring a Solar Map
In Proc. International Conference on Robotics and Automation, 2014.
pdf,.bib
4 Patrick A Plonski, Joshua Vander Hook, Volkan Isler
Environment and Solar Map Construction for Solar-Powered Mobile Systems
Technical Report, Department of Computer Science, University of Minnesota, 2014.
pdf,.bib
2013
3 Patrick A Plonski, Pratap Tokekar, Volkan Isler
Energy-Efficient Path Planning for Solar-Powered Mobile Robots
Journal of Field Robotics, 2013.
pdf,.bib
2 Narges Noori, Patrick Plonski, Alessandro Renzaglia, Pratap Tokekar, Joshua Vander Hook, Volkan Isler
Long-Term Search Through Energy Efficiency and Harvesting
Technical Report, Department of Computer Science, University of Minnesota, 2013.
pdf,.bib
2012
1 Patrick A. Plonski, Pratap Tokekar, Volkan Isler
Energy-Efficient Path Planning for Solar-Powered Mobile Robots
In The 12th International Symposium on Experimental Robotics, 2012.
pdf,.bib