Buoyancy engine is a device which changes net buoyancy of an underwater vehicle by attracting and conclusions. expelling water. Underwater gliders equipped with
buoyancy engines can be driven by net buoyancy forces to travel in the vertical plane. Existing underwater gliders,
such as Seaglider, Spray and SLOCUM are configured with single buoyancy engine and a longitudinally mass with nose, tail and fixed wings. Assuming that the hull,
shifting device by which pitch angle are varied by moving nose and tail are all symmetrical with respect to the
their center of gravity. The buoyancy engine on Seaglider horizontal plane of the hull and the wings are flat. The
and Spray include a high-pressure reciprocating pump and body of the glider considered in this paper is 2m in length
an external bladder [1,2]. For SLOCUM Battery, buoyancy and 0.22m in diameter. The total mass of glider is divided
engine is a piston driven by a motor. Modeling and control into the stationary mass ms and the variable mass mv.
of ocean gliders driven by buoyancy engines and The body coordinate is fixed on the center of stationary
mass-shifting device can be found