Control apparatus for small boat

1. An apparatus for controlling a small boat having a hull, at least one outboard motor driven by an internal combustion engine and adapted to be mounted on a stern of the hull, and an actuator adapted to open/close a throttle valve of the engine for regulating speed of the engine, comprising:

an acceleration sensor installed on the boat to generate an output indicative of acceleration acting on the boat in a direction of gravity axis;

a correction amount calculator that calculates a correction amount of the engine speed for said at least one outboard motor based on the output of the acceleration sensor so as to change behavior of the boat such that the boat moves toward a corrected navigation direction; and

an actuator controller that controls operation of the actuator based on the calculated correction amount;

wherein the correction amount calculator calculates the correction amount of the engine speed such that a speed of the boat increases when the acceleration in the direction of gravity axis increases.

2. The apparatus according to claim 1 , wherein values of the correction amount of the engine speed are predetermined and set beforehand with respect to the output of the acceleration sensor.

3. The apparatus according to claim 1 , wherein the number of the outboard motors mounted on the stern of the hull is two or more and including:

a declinometer that produces an output indicative of a direction of navigation of the boat;

the acceleration sensor output is indicative of angular acceleration about the gravity axis; and

the correction amount calculator calculates correction amounts of the engine speeds for the outboard motors so as to correct the behavior of the boat such that the boat moves toward the corrected navigation direction based on angular acceleration about the gravity axis detected by the acceleration sensor.

4. The apparatus according to claim 3 , wherein the correction amount calculator calculates a difference between a desired navigation direction and a detected navigation direction determined from the output of the declinometer and calculates the correction amounts of the engine speeds for the outboard motors so as to correct the calculated difference based on the output of the acceleration sensor.

5. The apparatus according to claim 3 , wherein values of the correction amounts of the engine speeds are predetermined and set beforehand with respect to the difference between the desired and detected navigation directions.

6. A method of controlling a small boat having a hull, at least one outboard motor driven by an internal combustion engine and adapted to be mounted on a stern of the hull, and an actuator adapted to open/close a throttle valve of the engine for regulating speed of the engine, comprising the steps of:

detecting acceleration acting on the boat in a direction of gravity axis;

calculating a correction amount of the engine speed for said at least one outboard motor based on the detected acceleration so as to change behavior of the boat such that the boat moves toward a corrected navigation direction; and

controlling operation of the actuator based on the calculated correction amount;

wherein the step of correction amount calculation calculates the correction amount of the engine speed such that a speed of the boat increases when the acceleration in the gravity axis increases.

7. The method according to claim 6 , wherein values of the correction amount of the engine speed are predetermined and set beforehand with respect to the output of the acceleration sensor.

8. The method according to claim 6 , wherein the number of the outboard motors mounted on the stern of the hull is two or more and including the step of:

detecting a direction of navigation of the boat;

the acceleration sensor output is indicative of angular acceleration about the gravity axis; and

the step of correction amount calculation involves calculating correction amounts of the engine speeds for the outboard motors so as to correct the behavior of the boat such that the boat moves toward the corrected navigation direction based on detected angular acceleration about the gravity axis.

9. The method according to claim 8 , wherein the step of correction amount calculation involves calculating a difference between a desired navigation direction and the detected navigation direction of the boat and by calculating the correction amounts of the engine speeds for the outboard motors so as to correct the calculated difference based on the detected angular acceleration.

10. The method according to claim 8 , wherein values of the correction amounts of the engine speeds are predetermined and set beforehand with respect to the difference between the desired and detected navigation directions.