Watercraft propulsion system and watercraft

Abstract

A watercraft propulsion system includes a propulsion unit to apply a propulsive force to a hull, and a controller configured or programmed to control the propulsion unit in response to a lateral movement command to cause the hull to move in a zig-zag pattern in a direction indicated by the lateral movement command between two parallel reference lines extending laterally of the hull and spaced apart from each other anteroposteriorly of the hull while maintaining an azimuth of the hull. The propulsion unit may include a bow thruster at the bow of the hull to generate a propulsive force laterally of the hull, a propulsion device on the hull to generate a propulsive force anteroposteriorly of the hull, and a steering to change the course of the hull.

What is claimed is: 
     
         1 . A watercraft propulsion system comprising:
 a bow thruster at a bow of a hull to generate a propulsive force laterally of the hull;   a propulsion device on the hull to generate a propulsive force anteroposteriorly of the hull;   a steering to change a course of the hull; and   a controller configured or programmed, in response to a lateral movement command, to set two parallel reference lines extending laterally of the hull and spaced a distance apart from each other anteroposteriorly of the hull, and to control the bow thruster, the propulsion device, and the steering to cause the hull to move in a zig-zag pattern in a direction indicated by the lateral movement command between the two reference lines while maintaining an azimuth of the hull.   
     
     
         2 . The watercraft propulsion system according to  claim 1 , wherein the zig-zag pattern of the hull includes a first movement which is a diagonal movement including a lateral movement component indicated by the lateral movement command and one of forward and rearward movement components, and a second movement including the other of the forward and rearward movement components, the first movement and the second movement being each carried out at least once. 
     
     
         3 . The watercraft propulsion system according to  claim 1 , wherein the controller is configured or programmed to control the bow thruster, the propulsion device, and the steering to cause the hull to alternately repeat a first movement and a second movement between the two reference lines, the first movement being a diagonally forward movement including a lateral movement component indicated by the lateral movement command, the second movement being a diagonally rearward movement including a lateral movement component indicated by the lateral movement command. 
     
     
         4 . The watercraft propulsion system according to  claim 2 , wherein the controller is configured or programmed to perform an azimuth holding control operation to maintain the azimuth of the hull during a switching period in which switching between the first movement and the second movement occurs. 
     
     
         5 . The watercraft propulsion system according to  claim 1 , wherein the two reference lines are located forward and rearward, respectively, of a gravity center of the hull. 
     
     
         6 . The watercraft propulsion system according to  claim 1 , wherein the two reference lines are both located forward or rearward of a gravity center of the hull. 
     
     
         7 . The watercraft propulsion system according to  claim 1 , wherein the propulsion device includes only one single propulsion device on a stern of the hull, or a plurality of propulsion devices on the stern of the hull and steerable at a same steering angle. 
     
     
         8 . The watercraft propulsion system according to  claim 1 , further comprising a lateral movement operator operable by a user to input the lateral movement command to the controller. 
     
     
         9 . The watercraft propulsion system according to  claim 8 , wherein the controller is configured or programmed to control the bow thruster, the propulsion device, and the steering to change a propulsive force to be generated in a lateral direction indicated by the lateral movement command according to an operation amount of the lateral movement operator. 
     
     
         10 . The watercraft propulsion system according to  claim 8 , wherein the controller is configured or programmed to change the distance between the two reference lines according to an operation amount of the lateral movement operator. 
     
     
         11 . The watercraft propulsion system according to  claim 8 , wherein the controller is configured or programmed to control the bow thruster, the propulsion device, and the steering so as to prioritize the maintaining of the azimuth of the hull over the lateral movement at a beginning of an operation of the lateral movement operator. 
     
     
         12 . The watercraft propulsion system according to  claim 1 , wherein the lateral movement command is generated by performing a position/azimuth holding control operation to maintain the azimuth and a position of the hull. 
     
     
         13 . The watercraft propulsion system according to  claim 1 , wherein the bow thruster is fixed to the hull in an unsteerable manner. 
     
     
         14 . A watercraft comprising:
 a hull; and   the watercraft propulsion system according to  claim 1 .   
     
     
         15 . A watercraft propulsion system comprising:
 a propulsion unit to apply a propulsive force to a hull; and   a controller configured or programmed to control the propulsion unit in response to a lateral movement command to cause the hull to move in a zig-zag pattern in a direction indicated by the lateral movement command between two parallel reference lines extending laterally of the hull and spaced apart from each other anteroposteriorly of the hull while maintaining an azimuth of the hull.   
     
     
         16 . A watercraft comprising:
 a hull; and   the watercraft propulsion system according to claim  15 .