Underwater Vehicle Bouyancy System

Abstract

A multiple stage buoyancy changing system, or variable buoyancy device, for an underwater vehicle. The multiple stage buoyancy changing system comprises: a pressure hull containing a flexibly-sized internal fluid reservoir; a flexibly-sized external fluid reservoir attached to the pressure hull and connected to the internal reservoir; a system of devices and channels configured to move fluid between the internal fluid reservoir and the external fluid reservoir to change a displaced volume of the vehicle. Each stage of the variable buoyancy device can be optimized for maximum energy efficiency while changing the vehicle's displaced volume within an ambient pressure range. A control system for the variable buoyancy device engages different stages depending on ambient external pressure such that maximum energy efficiency is achieved over a large range of pressures/depths.

1 . A multiple stage buoyancy changing system for an underwater vehicle, the multiple stage buoyancy changing system comprising:
 a pressure hull containing a flexibly-sized internal fluid reservoir;   a flexibly-sized external reservoir connected to the pressure hull; and   a system of devices and channels that connect and move fluid between the internal fluid reservoir and external fluid reservoir to change a displaced volume of the underwater vehicle.   
     
     
         2 . The multiple stage buoyancy changing system of  claim 1 , wherein there are enough stages to operate over any range of water depth or pressure that the pressure hull can withstand. 
     
     
         3 . The multiple stage buoyancy changing system of  claim 1 , wherein there are enough stages to minimize the energy used to change a buoyancy of the vehicle any range of water depth or pressure that the pressure hull can withstand. 
     
     
         4 . The multiple stage buoyancy changing system of  claim 3 , wherein each stage is optimized to operate for a particular range of pressure output. 
     
     
         5 . The multiple stage buoyancy changing system of  claim 1 , wherein the system of devices and channels comprises at least one motor, at least one gear train, at least one coupling, at least one pump, and at least one valve. 
     
     
         6 . The multiple stage buoyancy changing system of  claim 1 , further comprising a control system that uses sensors to determine if a change in displaced volume is necessary. 
     
     
         7 . The multiple stage buoyancy changing system of  claim 1 , wherein the underwater vehicle has a front and a rear, and is configured to shift its center of buoyancy and center of mass toward the front or the rear while decreasing and increasing its buoyancy, respectfully. 
     
     
         8 . The multiple stage buoyancy changing system of  claim 1 , wherein the stages of the system are controlled by electronics and/or software that can detect and use external pressure measurements in a decision process. 
     
     
         9 . The multiple stage buoyancy changing system of  claim 1 , wherein one of the channels comprises an electronically controlled valve that can be selectively opened to allow fluid to pass from the external fluid reservoir to the internal fluid reservoir under the influence of only external pressure. 
     
     
         10 . The multiple stage buoyancy changing system of  claim 4 , further comprising a continuous variable transmission that can electronically adapt to a torque-speed curve to obtain an optimal pumping rate for changing displaced volume.