Motion compensation system for under water sonar systems

Abstract

An underwater buoyancy apparatus for compensating for wave induced vertical and/or horizontal motion, particularly in sonar devices deployed from nautical platform. The underwater buoyancy apparatus is slidably connected along a tether between a nautical platform and an underwater sonar device. The underwater buoyancy apparatus contains a volume of air and/or water which can be changed to thereby alter the underwater buoyancy apparatus's depth in a body of water, in response to vertical and/or horizontal motion the nautical platform.

1 . A nautical system comprising; 
 a) a nautical platform adapted for positioning on or within a body of water;    b) an underwater buoyancy apparatus connected to the nautical platform via at least one tether, which underwater buoyancy apparatus comprises:    a housing defining an inner buoyancy chamber, which buoyancy chamber is capable of containing a volume of air and/or water, and wherein the housing comprises at least one air valve capable of allowing air into and/or out of the inner buoyancy chamber and at least one flood port capable of allowing water into and/or out of the inner buoyancy chamber;    c) an underwater sonar device connected to the underwater buoyancy apparatus via at least one tether, such that a distance between the underwater buoyancy apparatus and the sonar device is adjustable, which sonar device is capable of transmitting and/or receiving acoustic sonar signals; and    d) a control arrangement for controlling the at least one valve and/or the at least one flood port of the underwater buoyancy apparatus.    
     
     
         2 . The nautical system of  claim 1  wherein the at least one tether is sufficiently slack between the nautical platform and the underwater buoyancy apparatus such that a horizontal and/or vertical motion of the nautical platform does not impart a substantial vertical or horizontal force to the underwater buoyancy apparatus.  
     
     
         3 . The nautical system of  claim 1  wherein the underwater buoyancy apparatus is slidably connected along at least one tether between the nautical platform and the sonar device.  
     
     
         4 . The nautical system of  claim 1  wherein the at least one tether between the nautical platform and the underwater buoyancy apparatus is continuous with the at least one tether between the underwater buoyancy apparatus and the underwater sonar device.  
     
     
         5 . The nautical system of  claim 1  wherein the at least one tether between the nautical platform and the underwater buoyancy apparatus is not continuous with the at least one tether between the underwater buoyancy apparatus and the underwater sonar device.  
     
     
         6 . The nautical system of  claim 1  wherein the underwater buoyancy apparatus comprises an air controller for the at least one air valve for controlling a flow of air into and/or out of the inner buoyancy chamber.  
     
     
         7 . The nautical system of  claim 1  wherein the underwater buoyancy apparatus comprises a water controller for the at least one flood port for controlling a flow of water into and/or out of the inner buoyancy chamber.  
     
     
         8 . The nautical system of  claim 1  wherein the at least one air valve comprises a vent valve capable of expelling air from the buoyancy chamber.  
     
     
         9 . The nautical system of  claim 1  wherein the at least one air valve comprises a blow valve capable of injecting air into the buoyancy chamber.  
     
     
         10 . The nautical system of  claim 9  further comprising an air source.  
     
     
         11 . The nautical system of  claim 1  wherein the control arrangement comprises a depth control system comprising: 
 a) an underwater buoyancy apparatus depth sensor for sensing the depth of the underwater buoyancy apparatus and an underwater sonar device depth sensor for sensing the depth of the underwater sonar device and which underwater buoyancy apparatus depth sensor and sonar device depth sensor are each capable of sending a data signal to a depth control processor, which data signal provides depth and/or position data of the underwater buoyancy apparatus and the underwater sonar device, respectively, to a depth control processor; and    b) a depth control processor capable of sending and receiving data signals and/or action signals to and from the underwater buoyancy apparatus depth sensor, the sonar device depth sensor, the at least one air valve, and/or the at least one flood port, and which depth control processor is further capable of controlling the at least one air valve and/or the at least one flood port.    
     
     
         12 . The nautical system of  claim 11  which further comprises at least one tether connection sensor capable of sensing a break in a tether connection between the nautical platform and the sonar device.  
     
     
         13 . The nautical system of  claim 11  which further comprises an underwater buoyancy apparatus vertical velocity sensor far sensing the vertical velocity of the underwater buoyancy apparatus, which underwater buoyancy apparatus vertical velocity sensor is capable of sending a data signal to the depth control processor, which data signal provides vertical velocity data of the underwater buoyancy apparatus to the depth control processor.  
     
     
         14 . The nautical system of  claim 11  which further comprises an underwater buoyancy apparatus vertical acceleration sensor for sensing the vertical acceleration of the underwater buoyancy apparatus, which underwater buoyancy apparatus vertical acceleration sensor is capable of sending a data signal to the depth control processor, which data signal provides vertical acceleration data of the underwater buoyancy apparatus to the depth control processor.  
     
     
         15 . The nautical system of  claim 1  which further comprises a locking sheave system through which the at least one tether is routed, which locking sheave system is positioned between the nautical platform and the underwater buoyancy apparatus, which locking sheave system is capable of locking to and unlocking from the at least one tether at adjustable positions along the at least one tether to thereby maintain a substantially fixed distance between the sonar device and the underwater buoyancy apparatus, and/or adjust the distance between the underwater buoyancy apparatus and the sonar device.  
     
     
         16 . An underwater buoyancy apparatus comprising a housing defining an inner buoyancy chamber, which buoyancy chamber is capable of containing a volume of air and/or water, and wherein the housing comprises at least one air valve capable of allowing air into and/or out of the inner buoyancy chamber and at least one food port capable of allowing water into and/or out of the inner buoyancy chamber; which underwater buoyancy apparatus further comprises at least one tether for connecting the underwater buoyancy apparatus to a nautical platform; and which underwater buoyancy apparatus further comprises at least one tether for connecting the underwater buoyancy apparatus to an underwater sonar device such that a distance between the underwater buoyancy apparatus and the underwater sonar device is adjustable.  
     
     
         17 . The underwater buoyancy apparatus of  claim 16  wherein the control arrangement comprises a depth control system comprising: 
 a) an underwater buoyancy apparatus depth sensor for sensing the depth of the underwater buoyancy apparatus is capable of sending a data signal to a depth control processor, which data signal provides depth and/or position data of the underwater buoyancy apparatus to a depth control processor; and    b) a depth control processor capable of sending and receiving data signals and/or action signals to and from the underwater buoyancy apparatus depth sensor, the at least one air valve, and/or the at least one flood port, and which depth control processor is further capable of controlling the at least one air valve and/or the at least one flood port.    
     
     
         18 . The underwater buoyancy apparatus of  claim 17  further comprising an underwater buoyancy apparatus vertical velocity sensor for sensing the vertical velocity of the underwater buoyancy apparatus, which underwater buoyancy apparatus vertical velocity sensor is capable of sending a data signal to the depth control processor, which data signal provides vertical velocity data of the underwater buoyancy apparatus to the depth control processor.  
     
     
         19 . The underwater buoyancy apparatus of  claim 17  further comprising an underwater buoyancy apparatus vertical acceleration sensor for sensing the vertical acceleration of the underwater buoyancy apparatus, which underwater buoyancy apparatus vertical acceleration sensor is capable of sending the data signal to a depth control processor, which data signal provides vertical acceleration data of the underwater buoyancy apparatus to the depth control processor.  
     
     
         20 . The underwater buoyancy apparatus of  claim 16  which further comprises a locking sheave system through which the at least one tether is routed, which locking sheave system is capable of locking to and unlocking from the at least one tether at adjustable positions along the at least one tether.  
     
     
         21 . A method for adjusting the position of an underwater sonar device which comprises: 
 I) deploying a nautical system into a body of water, which nautical system comprises: 
 a) a nautical platform adapted for positioning on or within a body of water;  
 b) an underwater buoyancy apparatus connected to the nautical platform via at least one tether, which underwater buoyancy apparatus comprises:  
 a housing defining an inner buoyancy chamber, which buoyancy chamber is capable of containing a volume of air and/or water, and wherein the housing comprises at least one air valve capable of allowing air into and/or out of the inner buoyancy chamber and at least one flood port capable of allowing water into and/or out of the inner buoyancy chamber;  
 c) an underwater sonar device connected to the underwater buoyancy apparatus via at least one tether, such that a distance between the underwater buoyancy apparatus and the sonar device is adjustable, which sonar device is capable of transmitting and/or receiving acoustic sonar signals; and  
 d) a control arrangement for controlling the at least one valve and/or the at least one flood port of the underwater buoyancy apparatus;  
   II) accepting sufficient amounts of air and/or water into the inner buoyancy chamber such that underwater buoyancy apparatus maintains a substantially fixed depth within the body of water; and    III) controllably adjusting the depth of the underwater buoyancy apparatus to thereby compensate for the effects of movement of the nautical platform on the underwater sonar device by conducting at least one of steps (i) and (ii): 
 i) lowering the underwater buoyancy apparatus within the body of water, by releasing air from within the buoyancy chamber via the at least one air valve, and taking water into the buoyancy chamber via the at least one flood port; and/or  
 ii) raising the underwater buoyancy apparatus within the body of water, by taking air into the buoyancy chamber via the at least one air valve, and releasing water from within the buoyancy chamber via the at least one flood port.  
   
     
     
         22 . The method of  claim 21  wherein the control arrangement comprises a depth control system comprising: 
 a) an underwater buoyancy apparatus depth sensor for sensing the depth of the underwater buoyancy apparatus and an underwater sonar device depth sensor for sensing the depth of the underwater sonar device and which underwater buoyancy apparatus depth sensor and sonar device depth sensor are each capable of sending a data signal to a depth control processor, which data signal provides depth and/or position data of the underwater buoyancy apparatus and the underwater sonar device, respectively, to a depth control processor; and    b) a depth control processor capable of sending and receiving data signals and/or action signals to and from the underwater buoyancy apparatus depth sensor, the sonar device depth sensor, the at least one air valve, and/or the at least one flood port, and which depth control processor is further capable of controlling the at least one air valve and/or the at least one flood port;    wherein the underwater buoyancy apparatus depth sensor sends a depth data signal to the depth control processor, which depth control processor receives the depth data signal and sends an action signal, in response to the depth data signal, to the at least one air valve and/or the at least one flood port to thereby adjust the depth of the underwater buoyancy apparatus according to step (III).    
     
     
         23 . The method of  claim 22  wherein the nautical system further comprises an underwater buoyancy apparatus vertical velocity sensor for sensing the vertical velocity of the underwater buoyancy apparatus, which underwater buoyancy apparatus vertical velocity sensor is capable of sending a data signal to the depth control processor, which data signal provides vertical velocity data of the underwater buoyancy apparatus to the depth control processor, and which depth control processor receives the vertical velocity data signal and sends a command signal, in response to the vertical velocity data signal, to the at least one air valve and/or the at least one flood port to thereby adjust the depth of the underwater buoyancy apparatus according to step (III).  
     
     
         24 . The method of  claim 22  wherein the nautical system further comprises an underwater buoyancy apparatus vertical acceleration sensor for sensing the vertical acceleration of the underwater buoyancy apparatus, which underwater buoyancy apparatus vertical acceleration sensor is capable of sending a data signal to the depth control processor, which data signal provides vertical acceleration data of the underwater buoyancy apparatus to the depth control processor, which depth control processor receives the vertical acceleration data signal and sends a command signal, in response to the vertical acceleration data signal, to the at least one air valve and/or the at least one flood port to thereby adjust the depth of the underwater buoyancy apparatus according to step (III).  
     
     
         25 . The method of  claim 22  which further comprises a locking sheave system through which the at least one tether is routed, which locking sheave system is positioned between the nautical platform and the underwater buoyancy apparatus, which locking sheave system is capable of locking to and unlocking from the at least one tether at adjustable positions along the at least one tether to thereby maintain a substantially fixed distance between the sonar device and the underwater buoyancy apparatus, and/or adjust the distance between the underwater buoyancy apparatus and the sonar device; wherein the locking sheave system locks and/or unlocks in response to a signal from the depth control processor to thereby adjust the depth of the underwater buoyancy apparatus according to step (III).  
     
     
         26 . The method of  claim 22  which comprises the steps of: selecting an ordered depth of the underwater buoyancy apparatus; determining a control depth zone adjacent to the ordered depth, sending a depth signal from the underwater buoyancy apparatus depth sensor to the depth control processor, determining a depth error if the underwater buoyancy apparatus reaches a depth within the body of water which depth is outside the control depth zone.  
     
     
         27 . The method of  claim 26  further comprising the steps of: sending a command signal, in response to the depth error signal, from the depth control processor to the at least one air valve and/or the at least one flood port, to thereby adjust the depth of the sonar device according to step (III) such that the underwater buoyancy apparatus within the body of water maintains a depth within the control depth zone.  
     
     
         28 . The method of  claim 26  wherein the depth error value is calculated by the formula:  
           DE=f   A   A+f   V   V+f   D ( D   O   −D   S )+ f   Q   Q    wherein:    DE is a calculated depth error;    A is a sensed vertical acceleration of the underwater buoyancy apparatus;    V is a sensed vertical velocity of the underwater buoyancy apparatus,    D O  is an ordered depth of the underwater buoyancy apparatus;    D S  is a sensed depth of the underwater buoyancy apparatus, as sensed by the underwater buoyancy apparatus depth sensor;    Q is a damping factor, said damping factor being determined to provide a time delay between the depth signal exceeding a depth control band and the generation of a command signal;    f A  is an empirically determined control response factor, said factor determined such that a sensed vertical acceleration (A) results in a calculated depth error;    f V  is an empirically determined control response factors, said factor determined such that a sensed vertical velocity (V) results in a calculated depth error;    f D  is an empirically determined control response factors, said factor determined such that a difference between sensed depth (D S ) and ordered depth (D O ) results in a calculated depth error; and    f Q  is an empirically determined control response factor, said factor determined such that a damping factor (Q) results in a calculated depth error.    
     
     
         29 . The method of  claim 21  wherein: 
 the nautical system comprises group of sensors that sense the depth, vertical velocity, and vertical acceleration of the underwater buoyancy apparatus;    step (II) comprises selecting a desired underwater buoyancy apparatus operating depth;    step (III) comprises determining a control function for slowing an error response to minimize depth oscillations; and    step (III) comprises an algorithm for calculating a depth error signal;    whereby the depth error signal is applied to the control valves in a manner such that water is forced out of or flooded into the underwater buoyancy apparatus to maintain its depth within a controlled depth band.    
     
     
         30 . The method of  claim 21  wherein the at least one air valve comprises at least one vent valve capable of releasing air from within the buoyancy chamber to thereby lower the underwater buoyancy apparatus within the body of water, and/or at least one blow valve capable taking air into the buoyancy chamber via an air source to thereby raise the underwater buoyancy apparatus within the body of water.  
     
     
         31 . A method for the emergency recovery of an underwater buoyancy apparatus and a sonar device which arc part of a nautical system, the method comprising; 
 I) deploying a nautical system into a body of water, which nautical system comprises: 
 a) a nautical platform adapted for positioning on or within a body of water;  
 b) an underwater buoyancy apparatus connected to the nautical platform via at least one tether, which underwater buoyancy apparatus comprises:  
 a housing defining an inner buoyancy chamber, which buoyancy chamber is capable of containing a volume of air and/or water, and wherein the housing comprises at least one air valve capable of allowing air into and/or out of the inner buoyancy chamber and at least one flood port capable of allowing water into and/or out of the inner buoyancy chamber;  
 c) an underwater sonar device connected to the underwater buoyancy apparatus via at least one tether, such that a distance between the underwater buoyancy apparatus and the sonar device is adjustable, which sonar device is capable of transmitting and/or receiving acoustic sonar signals; and  
 d) a control arrangement for controlling the at least one valve and/or the at least one flood port of the underwater buoyancy apparatus; and  
 e) a tether connection sensor capable of sensing a loss of tether continuity between the nautical platform and the sonar device; and  
 f) a depth control system comprising: 
 i) an underwater buoyancy apparatus depth sensor for sensing the depth of the underwater buoyancy apparatus and an underwater sonar device depth sensor for sensing the depth of the underwater sonar device and which underwater buoyancy apparatus depth sensor and sonar device depth sensor are each capable of sending a data signal to a depth control processor, which data signal provides depth and/or position data of the underwater buoyancy apparatus and the underwater sonar device, respectively, to a depth control processor; and  
 ii) a depth control processor capable of sending and receiving data signals and/or action signals to and from the underwater buoyancy apparatus depth sensor, the sonar device depth sensor, the at least one air valve, and/or the at least one flood port, and which depth control processor is further capable of controlling the at least one air valve and/or the at least one flood port; and  
 
 g) a locking sheave system through which the at least one tether is routed, which locking sheave system is positioned between the nautical platform and the underwater buoyancy apparatus, which locking sheave system is capable of locking to and unlocking from the at least one tether at adjustable positions along the at least one tether to thereby maintain a substantially fixed distance between the sonar device and the underwater buoyancy apparatus, and/or adjust the distance between the underwater buoyancy apparatus and the sonar device;  
   II) generating a first command signal from the depth control system, in response to a loss of tether continuity signal from the tether connection sensor, such that the locking sheave system locks;    III) generating a second command signal from the depth control system, thereby directing the opening of the at least one air valve of the underwater buoyancy apparatus in response to a loss of tether continuity signal; and    IV) controllably forcing air into the underwater buoyancy apparatus such that underwater buoyancy apparatus is raised to the surface of the body of water in response to the loss of tether continuity signal.