Wave Glider: How it works
Each Wave Glider is comprised of a surfboard-like float that contains all the instrumentation needed for scientific experiments, plus the intelligence needed to keep the vessel on course or to maneuver it in a different direction. Two solar panels keep seven lithium-ion batteries charged in sequence, so that the topside instruments can be provided with six amps of continuous, 12-volt power.
But the craft doesn’t need power to move. Seven meters below the surface, a submersible craft is towed with the float. As waves lift the craft up, fins on the submarine direct the water behind the vessel, somewhat the way fins on an airplane provide lift. When the Wave Glider comes back down a wave, the fins are pushed to rotate in the opposite direction as the sub sinks. So the robot gets propulsion thrust almost constantly with no outside power needed, other than to move the rudder for steering. In the open ocean with more wave action, a Wave Glider can make about 1.5 knots. Closer to shore it slows to about 1 knot, but can almost always maintain speed, 24 hours per day.
Two payload bays store electronic gear for each mission in dry boxes designed to keep out corrosive sea water. Each box can hold about 25 pounds of gear. Onboard navigation is handled by a simple 8-bit processor that knows about 20 commands, mostly for turning or otherwise navigating the ship remotely. Commands can be sent to a Wave Glider through an Iridium Communications satellite modem. And the vessel keeps track of its position on a GPS receiver, which can track and navigate through up to 255 preprogrammed waypoints for long journeys, self correcting to keep a true course.
The mission sensors are driven by an ARM processor running an embedded version of Linux. Most of the time, the processor payloads are given their own Iridium Satellite modem so that some people on land can manage the sensors while others can concentrate on driving the boat, and the two systems don’t compete for limited bandwidth.
John Breeden II directs the GCN Lab. Follow him on Twitter: @GCNLabGuys.