Underwater vehicle with sonar array

Abstract

An underwater vehicle including an axi-symmetric framing system rotatable about a centerline to define a shell of revolution having a uniformly-convex outer boundary. A narrow-beam sonar array is mounted on the axi-symmetric framing system, and includes a multitude of simultaneously-fireable and/or asynchronously-fireable transducers distributed substantially evenly over a 4π-steradian viewing angle. The present invention provides the necessary configuration for a vehicle wherein an internal algorithm can compare a “new” geometry to an “old” geometry collected earlier to construct a best fit of the new world map with the old world map and locate the vehicle within the context of the new world map. This then provides a completely independent mechanism for correction of the gradual drift in x and y that is not dependent on any form of external navigation aid.

We claim: 
     
       1. An underwater vehicle for operating in an underwater environment, said underwater vehicle comprising:
 a source of power; 
 an axi-symmetric framing system rotatable about a centerline to define a shell of revolution having a uniformly-convex outer boundary; 
 a narrow-beam sonar array connected to said source of power and mounted on said axi-symmetric framing system, said narrow-beam sonar array having a first and third plurality of transducers distributed substantially evenly over along said outer boundary within a first plane, a second and fourth plurality of transducers distributed substantially evenly over along said outer boundary within a second plane, and a plurality of lateral imaging transducers orientated to project within a third plane that is orthogonal to said first and second planes; 
 a plurality of digital signal processors connected to said narrow-beam sonar array; and 
 a plurality of bidirectional circumferential thrusters connected to said source of power and mounted, to said axi-symmetric framing system, said plurality of bidirectional circumferential thrusters being oriented to selectively cause rotation of said axi-symmetric framing system and propulsion of said vehicle within said underwater environment, said plurality of circumferential thrusters positioned within said shell of revolution; 
 wherein each transducer of said plurality of transducers each of said transducers is configured to project a beam having a width of no more than about two degrees or less radially outwardly along an associated beam path, and the angle of separation between beam paths transducers is at least greater than about ten degrees. 
 
     
     
       2. The underwater vehicle of  claim 1  wherein each of said transducers comprises projector and a corresponding hydrophone, each of said hydrophones is operative to receive a reflected signal originating from its corresponding projector to (a) determine, said transducers configured to communicate said signals to said plurality of digital signal processors for use by a main processor bank in (a) determining the position of said underwater vehicle within said underwater environment; (b) map mapping said underwater environment; and/or or (c) move moving said underwater vehicle within said underwater environment. 
     
     
       3. The underwater vehicle of  claim 1  further comprising at least one vertical thruster mounted to said axi-symmetric framing system and positioned within said shell of revolution. 
     
     
       4. The underwater vehicle of  claim 1  further comprising at least one flotation panel mounted to said axi-symmetric framing system. 
     
     
       5. The underwater vehicle of  claim 1  wherein said plurality first and second pluralities of transducers further comprises: comprise a plurality of obstacle avoidance transducers; and wherein said third and fourth pluralities of transducers further comprise a plurality of fine imaging transducers. 
     
     
       6. The underwater vehicle of  claim 5  wherein said plurality of digital signal processors further comprises:
 a first digital signal processor stack connected to said plurality of obstacle avoidance transducers; and 
 a second digital signal processor stack connected to said plurality of fine imaging transducers. 
 
     
     
       7. The underwater vehicle of  claim 1  further comprising a main processor bank contained within a pressure housing mounted to said axi-symmetric framing system. 
     
     
       8. The underwater vehicle of  claim 7  further comprising a motor control system contained within a pressure housing and electrically connected to said main processor bank, said motor control system operative to actuate said circumferential thrusters. 
     
     
       9. The underwater vehicle of  claim 7  further comprising a Doppler velocity log electrically connected to said main processor bank. 
     
     
       10. The underwater vehicle of  claim 7  further comprising an inertial measurement unit contained within a pressure housing and electrically connected to said main processor bank. 
     
     
       11. The underwater vehicle of  claim 7  further comprising:
 a variable buoyancy system contained Within a pressure housing and electrically connected to said main processor bank; 
 a ballast chamber connected to said variable buoyancy system; and 
 at least one gas supply tank in fluid communication with said ballast chamber. 
 
     
     
       12. The underwater vehicle of  claim 1  wherein said plurality of circumferential thrusters comprises:
 a first pair of circumferential thrusters mounted to said axi-symmetric framing system at positions distal from said centerline and orientated to provide thrust in a first direction perpendicular to said centerline; and 
 a second pair of circumferential thrusters mounted to said axi-symmetric framing system at positions distal from the centerline and orientated to provide thrust in a second direction perpendicular to said centerline, wherein said second direction is coplanar with and orthogonal to said first direction. 
 
     
     
       13. The underwater vehicle of  claim 7  further comprising a processor-readable medium electrically connected to said main processor bank, said processor-readable medium comprising a set of computer readable instructions for estimating a trajectory of the vehicle, the set of instructions comprising:
 constructing a 3D compact map data structure representative of the surrounding environment within said processor-readable medium; 
 initialing a set of particles within said processor-readable medium, each particle of the set having an associated pose; 
 predicting a new pose for each particle of the set of particles using dead reckoning navigation; 
 taking real range measurements of the vehicle environment; 
 assigning a weight to each particle of the set of particles by comparing the real range measurements to simulated range measurements derived by ray-tracing with the particle pose and map, wherein the weight for a particle having a pose and map consistent with real range measurements is high and the weight for a particle having pose and map that are inconsistent with real range measurements is low; 
 resampling the set of particles according to the assigned weights, wherein particles with low weights are likely to be discarded and particles with high weights are likely to be duplicated; 
 updating said 3D compact map data structure based on the real range measurements; and 
 generating a position estimate of the vehicle within the vehicle environment from the set of particles.