Tugboat with a capsizing and sinking prevention system

Abstract

A tugboat for assisting a marine vessel to maneuver. The tugboat boat comprises an engine driving one or more propulsors with a controllable direction of thrust, a towing line for establishing a pulling connection between an assisted vessel and the tugboat, a first sensor arrangement configured for sensing the size and direction of the pulling force that the towing line exerts on the tugboat, a second sensor arrangement configured for sensing the orientation of the tugboat, a controller in receipt of a signal from the first sensor arrangement and in receipt of a signal from the second sensor arrangement. The controller is informed of the size and direction of thrust generated by the one or more propulsors, and the controller is configured to determine if a safety threshold is exceeded on the basis of: sensed size and direction of thrust, sensed size and direction of the pulling force, and sensed orientation of the tugboat.

What is claimed is: 
     
         1 . A tugboat for assisting a marine vessel to maneuver, said tugboat comprising:
 an engine driving one or more propulsors, the one or more propulsors having a controllable direction of thrust;   a towing line for establishing a pulling connection between the marine vessel and the tugboat;   a first sensor arrangement configured for sensing the size and direction of a pulling force that the towing line exerts on the tugboat;   a second sensor arrangement configured for sensing an orientation of the tugboat;   a third sensor arrangement configured for sensing a size and direction of thrust generated by the one or more propulsors; and   a controller configured to receive a signal from said first sensor arrangement and a signal from said second sensor arrangement;   said controller being configured to determine the size and direction of the thrust generated by said one or more propulsors, and   said controller being configured to determine if a first safety threshold, associated with said tugboat, is exceeded on the basis of:
 the sensed size and direction of thrust generated by said one or more propulsors; 
 the sensed size and direction of the pulling force; and 
 the sensed orientation of the tugboat. 
   
     
     
         2 . A tugboat according to  claim 1 , wherein said controller is configured to at least one of:
 reduce the size; or   change the direction;   of the thrust of the one or more propulsors, when the controller has determined that the tugboat has exceeded said first safety threshold.   
     
     
         3 . A tugboat according to  claim 1 , wherein said tugboat is provided with an arrangement for disconnecting the tugboat from said towing line in response to a command from said controller. 
     
     
         4 . A tugboat according to  claim 3 , wherein said controller is configured to cause severing of said towing line when the controller has determined that the tugboat has exceeded a second safety threshold that is higher than said first safety threshold. 
     
     
         5 . A tugboat according to  claim 1 , wherein said first safety threshold corresponds to at least one of:
 a risk of said tugboat capsizing; or   a risk of said tugboat sinking.   
     
     
         6 . A tugboat according to  claim 1 , wherein said controller is configured to determine that said tugboat is at risk of capsizing or sinking on the basis of a computer model that simulates the behavior of said tugboat. 
     
     
         7 . A tugboat according to  claim 1 , wherein said controller is provided with a mathematical model of said tugboat. 
     
     
         8 . A method of operating a tugboat, said method comprising:
 sensing a size and direction of a thrust created by one or more propulsors of said tugboat,   determining a size and direction of a pulling force applied to said tugboat by a towing line,   determining an orientation of said tugboat, and   determining if a combination of the size and direction of thrust from the one or more propulsors, the size and direction of the pulling force, and the orientation of said tugboat exceeds a safety threshold associated with said tugboat.   
     
     
         9 . A method according to  claim 8 , further comprising adjusting at least one of:
 the size; or   direction;   of said thrust, in order to prevent said tugboat from exceeding the safety threshold.   
     
     
         10 . A method according to  claim 8 , further comprising severing the towline when the safety threshold is exceeded. 
     
     
         11 . A tugboat according to  claim 3 , wherein the arrangement comprises a device for severing said towing line.