The Wave Glider is made by Liquid Robotics. It consists of a surface float 208 cm x 60 cm and a submerged glider 191 cm long with 6 wings having a wing span of 107 cm. The float and glider are connected by a 7-meter tether. The surface float is subjected to wave motion, while the glider is below much of the wave action. The wings are pivoted. When the float rises, the tether pulls the wings into a positive angle of attack. When the wings are pulled upward, the glider moves forward. The tether has some thickness, but it appears to be flexible and can only exert tension between the float and glider. When the glider descends into the trough of a wave, I am guessing that the tether slackens and springs force the wings into a negative angle of attack so that they move forward as the glider descends due to gravity.
Googling the company name brings up some web pages that I explored briefly. There is also literature in the trade journals. There are basically two types of autonomous gliders. One type takes long dives by adjusting trim surfaces, deflating a bladder and/or shifting a weight (possibly the battery) and then reverses these adjustments to take a long climb to the surface. At the surface it dumps data and receives instructions via satellite. The data are gathered at various depths by on-board sensors. Navigation, communication, and measurement electronics is powered by a battery that cannot be recharged during most missions.
The Liquid Robotics Wave Glider, on the other hand, has solar photovoltaic panels on the surface float that are used for battery charging, onboard electronics, and payloads. The surface float and glider have rudders at their aft ends for steering. Station keeping can be maintained within a 40 m radius in moderate sea states and currents. There is a GPS receiver and a heading sensor. Navigation accuracy is a 3 m radius. A mission can last as long as a year.
The ocean is a vast expanse, and manned vessels are too expensive for observation and data collection. These gliders perform many tasks more efficiently and at much lower cost than manned vessels. Some jobs, like inspecting underwater pipelines, cannot be performed by gliders. Many powered autonomous underwater vehicles have been developed to carry sonars and video cameras on these missions.
Comments