Watercraft propulsion system, and watercraft

Abstract

A watercraft propulsion system includes first and second propulsion devices attachable to a hull asymmetrically with respect to an anteroposterior center line of the hull, a lateral movement command generator to generate a first lateral movement command and a second lateral movement command to laterally move the hull rightward and leftward, and a controller. The controller includes a memory to store first and second lateral movement thrust ratios indicating ratios between a forward propulsive force and a reverse propulsive force in a first lateral movement control and a second lateral movement control. When one of the first and second lateral movement thrust ratios is set in a calibration mode, the controller is configured or programmed to set an initial value of the other of the first and second lateral movement thrust ratios to an inverse of the one of the first and second lateral movement thrust ratios.

What is claimed is: 
     
         1 . A watercraft propulsion system comprising:
 a first propulsion device attachable to a hull;   a second propulsion device attachable to the hull asymmetrically to the first propulsion device with respect to an anteroposterior center line of the hull;   a lateral movement command generator to generate a first lateral movement command to laterally move the hull in one of a rightward direction and a leftward direction, and to generate a second lateral movement command to laterally move the hull in the other of the rightward direction and the leftward direction; and   a controller configured or programmed to perform a first lateral movement control in response to the first lateral movement command to cause one of the first propulsion device and the second propulsion device to generate a reverse propulsive force and cause the other of the first propulsion device and the second propulsion device to generate a forward propulsive force, and to perform a second lateral movement control in response to the second lateral movement command to cause the one of the first propulsion device and the second propulsion device to generate a forward propulsive force and cause the other of the first propulsion device and the second propulsion device to generate a reverse propulsive force; wherein   the controller includes a memory to store a first lateral movement thrust ratio indicating a ratio between the forward propulsive force and the reverse propulsive force in the first lateral movement control and a second lateral movement thrust ratio indicating a ratio between the forward propulsive force and the reverse propulsive force in the second lateral movement control, and is configured or programmed to set the forward propulsive force and the reverse propulsive force to be generated in the first lateral movement control according to the first lateral movement thrust ratio stored in the memory, and to set the forward propulsive force and the reverse propulsive force to be generated in the second lateral movement control according to the second lateral movement thrust ratio stored in the memory;   the controller is configured or programmed to set the first lateral movement thrust ratio and the second lateral movement thrust ratio in a calibration mode and, when one of the first lateral movement thrust ratio and the second lateral movement thrust ratio is set in the calibration mode, to set an initial value of the other of the first lateral movement thrust ratio and the second lateral movement thrust ratio to an inverse of the one lateral movement thrust ratio.   
     
     
         2 . The watercraft propulsion system according to  claim 1 , wherein the first propulsion device is an engine propulsion device, and the second propulsion device is an electric propulsion device. 
     
     
         3 . The watercraft propulsion system according to  claim 1 , wherein the first propulsion device is located on the center line, and the second propulsion device is offset from the center line. 
     
     
         4 . The watercraft propulsion system according to  claim 3 , wherein the first propulsion device and the second propulsion device are attachable to a stern of the hull. 
     
     
         5 . The watercraft propulsion system according to  claim 1 , wherein
 the first propulsion device includes a propeller rotation axis lower than a keel of the hull; and   the second propulsion device includes a propeller rotation axis higher than the keel of the hull.   
     
     
         6 . A watercraft propulsion system comprising:
 a first propulsion device attachable to a hull;   a second propulsion device attachable to the hull asymmetrically to the first propulsion device with respect to an anteroposterior center line of the hull;   a lateral movement command generator to generate a first lateral movement command to laterally move the hull in one of a rightward direction and a leftward direction, and to generate a second lateral movement command to laterally move the hull in the other of the rightward direction and the leftward direction; and   a controller configured or programmed to perform a first lateral movement control in response to the first lateral movement command to cause one of the first propulsion device and the second propulsion device to generate a reverse propulsive force and cause the other of the first propulsion device and the second propulsion device to generate a forward propulsive force, and to perform a second lateral movement control in response to the second lateral movement command to cause the one of the first propulsion device and the second propulsion device to generate a forward propulsive force and cause the other of the first propulsion device and the second propulsion device to generate a reverse propulsive force; wherein   a magnitude relationship between the forward propulsive force and the reverse propulsive force in the first lateral movement control and a magnitude relationship between the forward propulsive force and the reverse propulsive force in the second lateral movement control are reversed from each other.   
     
     
         7 . A watercraft comprising:
 a hull; and   the watercraft propulsion system according to  claim 1  attached to the hull.   
     
     
         8 . A watercraft comprising:
 a hull; and   the watercraft propulsion system according to claim  6  attached to the hull.