Watercraft and method of controlling watercraft

Abstract

A watercraft includes a first steering actuator to swing a first nozzle deflector to change a first direction of water jetted from the first nozzle deflector, and a second steering actuator to swing a second nozzle deflector to change a second direction of water jetted from the second nozzle deflector. A controller is configured or programmed to control the first steering actuator such that the first direction is inclined leftward with respect to a center of gravity of the watercraft, and also control the second steering actuator such that the second direction is inclined rightward with respect to the center of gravity of the watercraft when it is determined that a watercraft body is intended to move straight forward based on steering information.

What is claimed is: 
     
         1 . A watercraft to be propelled by a jet of water, the watercraft comprising:
 a watercraft body;   a first jet propulsion device attached to a port side of a rear portion of the watercraft body, and including a first nozzle deflector to jet water and be swingable right and left;   a second jet propulsion device attached to a starboard side of the rear portion of the watercraft body and symmetrical to the first jet propulsion device with respect to a back-and-forth direction of the watercraft body, the second jet propulsion device including a second nozzle deflector to jet water and be swingable right and left;   a first actuator to swing the first nozzle deflector to change a first direction of the water jetted from the first nozzle deflector;   a second actuator to swing the second nozzle deflector to change a second direction of the water jetted from the second nozzle deflector;   a steering sensor to detect steering information regarding steering of the watercraft body; and   a controller configured or programmed to control the first actuator such that the first direction is inclined leftward with respect to a center of gravity of the watercraft and also to control the second actuator such that the second direction is inclined rightward with respect to the center of gravity of the watercraft when it is determined that the watercraft body is intended to move straight forward based on the steering information.   
     
     
         2 . The watercraft according to  claim 1 , wherein the controller is configured or programmed to set the first direction and the second direction such that a rotational moment acting about the center of gravity is closer to zero. 
     
     
         3 . The watercraft according to  claim 1 , wherein the controller is configured or programmed to set the first direction and the second direction such that an axial direction of the first nozzle deflector and an axial direction of the second nozzle deflector are oriented toward the center of gravity in a plan view of the watercraft. 
     
     
         4 . The watercraft according to  claim 1 , wherein the controller is configured or programmed to set the first direction and the second direction such that an angle between each of the first direction and the second direction and the back-and-forth direction is reduced as the center of gravity is located farther forward on the watercraft. 
     
     
         5 . The watercraft according to  claim 1 , further comprising:
 a steering on the watercraft body and operable by an operator of the watercraft to change a steering angle of the watercraft; wherein   the steering sensor is operable to detect an angle of a steering operation by the steering; and   the controller is configured or programmed to determine that the watercraft body is intended to move straight forward when the angle of steering operation falls within an absolute angular range from 0° to a predetermined threshold.   
     
     
         6 . The watercraft according to  claim 1 , further comprising:
 an angular sensor to detect a pitch angle of the watercraft body; wherein   the controller is configured or programmed to obtain a location of the center of gravity based on the pitch angle of the watercraft body.   
     
     
         7 . The watercraft according to  claim 1 , further comprising:
 a ballast water amount sensor to detect an amount of ballast water in a ballast water tank on or in the watercraft body; wherein   the controller is configured or programmed to obtain a location of the center of gravity based on the amount of ballast water.   
     
     
         8 . The watercraft according to  claim 7 , wherein the controller is configured or programmed to obtain the location of the center of gravity based on the amount of ballast water and a location of the ballast water tank. 
     
     
         9 . The watercraft according to  claim 1 , further comprising:
 a number-of-people-on-board detector to detect a number of people on board the watercraft body; wherein   the controller is configured or programmed to obtain a location of the center of gravity based on the number of people on board the watercraft body.   
     
     
         10 . The watercraft according to  claim 1 , further comprising:
 a location-of-people-on-board detector to detect locations of people on board the watercraft body; wherein   the controller is configured or programmed to obtain a location of the center of gravity based on the locations of people on board the watercraft body.   
     
     
         11 . The watercraft according to  claim 6 , further comprising:
 a storage to store an initial location of the center of gravity; and   a velocity-related information detector to detect information related to a velocity of the watercraft; wherein   the controller is configured or programmed to use the initial location of the center of gravity without using the location of the center of gravity obtained based on the pitch angle when a difference between the pitch angle obtained from the detected velocity and the pitch angle detected by the angular sensor is greater than or equal to a predetermined amount.   
     
     
         12 . The watercraft according to  claim 11 , further comprising:
 a throttle to regulate a thrust generated by each of the first jet propulsion device and the second jet propulsion device; wherein   the velocity-related information detector includes an opening degree sensor to detect an opening degree of the throttle; and   the controller is configured or programmed to obtain the velocity based on the opening degree of the throttle.   
     
     
         13 . The watercraft according to  claim 11 , wherein
 the first jet propulsion device includes a first drive source;   the second jet propulsion device includes a second drive source;   the velocity-related information detector includes a rotational speed sensor to detect a rotational speed of the first drive source or the second drive source; and   the controller is configured or programmed to obtain the velocity based on the rotational speed of the first drive source or the second drive source.   
     
     
         14 . The watercraft according to  claim 1 , wherein
 the controller is configured or programmed to obtain a target steering angle based on the steering information;   when the target steering angle is an angle to the port side, the controller is configured or programmed to drive only the second nozzle deflector and not the first nozzle deflector within an absolute angular range from 0° to a predetermined threshold; and   when the target steering angle is an angle to the starboard side, the controller is configured or programmed to drive only the first nozzle deflector and not the second nozzle deflector within the absolute angular range of steering operation from 0° to the predetermined threshold.   
     
     
         15 . The watercraft according to  claim 1 , further comprising:
 a throttle to switch between forward movement and rearward movement by each of the first and second jet propulsion devices; and   a position-of-throttle detector to detect a position of the throttle; wherein   the controller is configured or programmed to control the first actuator such that the first direction is inclined leftward and also control the second actuator such that the second direction is inclined rightward when it is determined that the watercraft body is intended to move straight rearward based on the position of the throttle and the steering information.   
     
     
         16 . A method of controlling a watercraft including a watercraft body, a first jet propulsion device attached to a port side of a rear portion of the watercraft body and including a first nozzle deflector to jet water and swingable right and left, a second jet propulsion device attached to a starboard side of the rear portion of the watercraft body symmetrically to the first jet propulsion device with respect to a back-and-forth direction of the watercraft body and including a second nozzle deflector to jet water and swingable right and left, a first actuator to swing the first nozzle deflector to change a first direction of the water jetted from the first nozzle deflector, and a second actuator to swing the second nozzle deflector to change a second direction of the water jetted from the second nozzle deflector, the method comprising:
 detecting when the watercraft body is intended to move straight forward based on information regarding steering of the watercraft body; and   controlling the first actuator such that the first direction is inclined leftward with respect to a center of gravity of the watercraft, and also controlling the second actuator such that the second direction is inclined rightward with respect to the center of gravity of the watercraft when it is detected that the watercraft body is intended to move straight forward.   
     
     
         17 . A watercraft comprising:
 a watercraft body; and   a first propulsion device attached to a port side of the watercraft body to generate a thrust by jetting water therefrom;   a second propulsion device attached to a starboard side of the watercraft body symmetrically to the first propulsion device with respect to a back-and-forth direction of the watercraft body to generate a thrust by jetting water therefrom;   a direction changer to change a first direction of the water jetted from the first propulsion device and a second direction of the water jetted from the second propulsion device;   a steering sensor to detect steering information regarding steering of the watercraft body; and   a controller configured or programmed to control the direction changer to incline the first direction leftward with respect to a center of gravity of the watercraft and incline the second direction rightward with respect to the center of gravity of the watercraft when it is determined that the watercraft body is intended to move straight forward based on the steering information.