Speed control device, automatic navigation system and method of controlling speed

1. A speed control device configured to control a speed of a marine vessel so that the speed automatically follows a speed setting set by a user, comprising:

processing circuitry configured

to set a target speed that is a target of the speed of the marine vessel to follow, for every unit time, according to the speed setting, to change the target speed based on a given rate of change;

to decrease the rate of change by adjusting the rate of change at multiple stages, when the target speed approaches the speed setting;

to calculate a base throttle opening related to a throttle opening control of an engine provided to the marine vessel, based on the target speed; and

to output the base throttle opening to a control device of the engine as a throttle opening for control, such that the processing circuitry outputs a given lower limit of the throttle opening to the control device of the engine as the throttle opening for control when the base throttle opening is below the given lower limit of the throttle opening, with the given lower limit being based on a dead zone during which the speed of the marine vessel remains unchanged in response to a change in the throttle opening received by the control device of the engine.

2. The speed control device of claim 1 , wherein the rate of change in the target speed is acquired based on a given speed change parameter, the speed change parameter including the unit time and a reference amount of change in the target speed for every unit time.

3. The speed control device of claim 2 , wherein the processing circuitry adjusts the rate of change to two different values based on the setting of the reference amount of change.

4. The speed control device of claim 1 , wherein the processing circuitry is further configured

to set a first rate of change, a second rate of change smaller than the first rate of change, and a change speed at which the first rate of change is switched to the second rate of change, based on a given speed change parameter, and

while the speed setting is above the speed of the marine vessel

to output the first rate of change when the target speed is below the change speed, and

to output the second rate of change when the target speed is above the change speed, and

while the speed setting is below the speed of the marine vessel,

to output the first rate of change when the target speed is above the change speed, and

to output the second rate of change when the target speed is below the change speed.

5. The speed control device of claim 1 , wherein the processing circuitry is further configured

to acquire an actual speed that is a current speed of the marine vessel;

to store the speed setting as a turning start speed; and

to output a turning speed setting that is the speed setting during a turning of the marine vessel,

wherein, while the marine vessel is turning, the processing circuitry sets the actual speed as the speed setting, when a turning angle of the marine vessel from a start of the turning is within a given angle range.

6. The speed control device of claim 1 , wherein the processing circuitry is further configured

to acquire an actual speed that is a current speed of the marine vessel; and

to control the speed of the marine vessel based on the target speed and the actual speed so that the speed follows the target speed.

7. An automatic navigation system, comprising:

the speed control device of claim 1 ; and

a navigation device configured to display information related to navigation.

8. A method of controlling a speed, comprising:

setting a target speed that is a target of a speed of a marine vessel to follow for every unit time, according to a speed setting set by a user in order to make the speed of the marine vessel follow the target speed by the control to change the target speed based on a given rate of change;

adjusting the rate of change at multiple stages when the set target speed approaches the speed setting to decrease the rate of change;

calculating a base throttle opening related to a throttle opening control of an engine provided to the marine vessel, based on the target speed; and

outputting the base throttle opening to a control device of the engine as a throttle opening for control, such that a given lower limit of the throttle opening is output to the control device of the engine as the throttle opening for control when the base throttle opening is below the given lower limit of the throttle opening, with the given lower limit being based on a dead zone during which the speed of the marine vessel remains unchanged in response to a change in the throttle opening received by the control device of the engine.

9. The speed control device of claim 2 , wherein the processing circuitry is further configured

to set a first rate of change, a second rate of change smaller than the first rate of change, and a change speed at which the first rate of change is switched to the second rate of change, based on a given speed change parameter, and

while the speed setting is above the speed of the marine vessel

to output the first rate of change when the target speed is below the change speed, and

to output the second rate of change when the target speed is above the change speed, and

while the speed setting is below the speed of the marine vessel,

to output the first rate of change when the target speed is above the change speed, and

to output the second rate of change when the target speed is below the change speed.

10. The speed control device of claim 3 , wherein the processing circuitry is further configured

to set a first rate of change, a second rate of change smaller than the first rate of change, and a change speed at which the first rate of change is switched to the second rate of change, based on a given speed change parameter, and

while the speed setting is above the speed of the marine vessel

to output the first rate of change when the target speed is below the change speed, and

to output the second rate of change when the target speed is above the change speed, and

while the speed setting is below the speed of the marine vessel,

to output the first rate of change when the target speed is above the change speed, and

to output the second rate of change when the target speed is below the change speed.

11. The speed control device of claim 2 , wherein the processing circuitry is further configured

to acquire an actual speed that is a current speed of the marine vessel;

to store the speed setting as a turning start speed; and

to output a turning speed setting that is the speed setting during a turning of the marine vessel,

wherein, while the marine vessel is turning, the processing circuitry sets the actual speed as the speed setting, when a turning angle of the marine vessel from a start of the turning is within a given angle range.

12. A non-transitory computer-readable recording medium storing a program causing a processor of a hull control device to execute processing, the processor configured to control operation of the device, the processing comprising:

setting a target speed that is a target of a speed of a marine vessel to follow for every unit time, according to a speed setting set by a user in order to make the speed of the marine vessel follow the target speed by the control to change the target speed based on a given rate of change;

adjusting the rate of change at multiple stages when the set target speed approaches the speed setting to decrease the rate of change;

calculating a base throttle opening related to a throttle opening control of an engine provided to the marine vessel, based on the target speed; and

outputting the base throttle opening to a control device of the engine as a throttle opening for control, such that a given lower limit of the throttle opening is output to the control device of the engine as the throttle opening for control when the base throttle opening is below the given lower limit of the throttle opening, with the given lower limit being based on a dead zone during which the speed of the marine vessel remains unchanged in response to a change in the throttle opening received by the control device of the engine.