Navigation planning system and navigation planning method

1 . A navigation planning system, comprising:

a processing circuitry configured to:

acquire a planned route for a movable body on a water;

acquire movable body information including a position, a moving direction, and a speed of the movable body;

acquire obstacle information including a position, a moving direction, and a speed of an obstacle located in a surrounding area of the movable body;

generate a plurality of potential evasion routes, different from the planned route, each comprising a starting point located on the planned route and a return point located on the planned route;

select an evasion route from among the plurality of potential evasion routes;

calculate a collision risk indicating a risk level of collision between the movable body and the obstacle based on the movable body information and obstacle information;

obtain a maximum evasion route collision risk when the movable body travels on the evasion route, and a maximum planned route collision risk when the movable body travels on the planned route;

compare the maximum evasion route collision risk with the maximum planned route collision risk; and

output a navigation route change signal to cause the movable body to change the planned route to the evasion route when the maximum evasion route collision risk is less than the maximum planned route collision risk,

wherein the processing circuitry further configured to:

calculate a planned route distance travelled by the movable body for a predetermined time on the planned route and an evasion route distance travelled by the movable body for a predetermined time on the evasion route respectively;

determine whether to output the navigation route change signal based on the maximum evasion route collision risk and the maximum planned route collision risk, and the planned route distance and the evasion route distance; and

output the navigation route change signal when one of a difference between the evasion route distance and the planned route distance is within a predetermined value, and a distance ratio between the evasion route distance and the planned route distance is equal to or less than a predetermined value.

2 . The navigation planning system according to claim 1 , wherein:

the processing circuitry is further configured to set the evasion route different from the planned route for a part of or an entire unnavigated route of the planned route when the risk evaluator determines a necessity of the evasion route.

3 . The navigation planning system according to claim 1 , wherein the starting point is a future position of the movable body calculated from a current navigational position of the movable body moving along the planned route.

4 . The navigation planning system according to claim 1 , wherein the processing circuitry further configured to:

calculate the maximum evasion route collision risk when the movable body travels along the evasion route from the starting point to the return point; and

select the potential evasion route, as the evasion route, having the maximum evasion route collision risk that is minimum among the plurality of potential evasion routes.

5 . The navigation planning system according to claim 1 , wherein the evasion starting point is a current navigational position of the movable body moving along the planned route.

6 . A navigation planning method, comprising:

acquiring a planned route for a movable body on a water;

acquiring movable body information including a position, a moving direction, and a speed of the movable body;

acquiring obstacle information including a position, a moving direction, and a speed of an obstacle located in a surrounding area of the movable body;

generating a plurality of potential evasion routes, different from the planned route, each comprising a starting point located on the planned route and a return point located on the planned route;

selecting an evasion route from among the plurality of potential evasion routes;

calculating a collision risk indicating a risk level of collision between the movable body and the obstacle based on the movable body information and obstacle information;

obtaining a maximum evasion route collision risk when the movable body travels on the evasion route and a maximum planned route collision risk when the movable body travels on the planned route, calculated by the collision risk calculator respectively;

comparing the maximum evasion route collision risk with the maximum planned route collision risk;

outputting a navigation route change signal to cause the movable body to change the planned route to the evasion route when the maximum evasion route collision risk is less than the maximum planned route collision risk;

calculating a planned route distance travelled by the movable body for a predetermined time on the planned route and an evasion route distance travelled by the movable body for a predetermined time on the evasion route respectively;

determining whether to output the navigation route change signal based on the maximum evasion route collision risk and the maximum planned route collision risk, and the planned route distance and the evasion route distance; and

outputting the navigation route change signal when one of a difference between the evasion route distance and the planned route distance is within a predetermined value, and a distance ratio between the evasion route distance and the planned route distance is equal to or less than a predetermined value.

7 . The navigation planning method according to claim 6 , further comprising:

calculating the maximum collision risk when the movable body travel along the evasion route from the evasion starting point to the return point; and

selecting the potential evasion route, as the evasion route, having the maximum collision risk minimum among the plurality of potential evasion routes.

8 . The navigation planning system according to claim 1 , wherein the processing circuitry further configured to:

output the navigation route change signal when a difference between the maximum planned route collision risk and the maximum evasion route collision risk is greater than a predetermined value; and

determine whether to output the navigation route change signal based on the difference between the evasion route distance and the planned route distance when the difference between the maximum planned route collision risk and the maximum evasion route collision risk is within the predetermined value.

9 . The navigation planning system according to claim 1 , wherein the processing circuitry further configured to:

calculate a congestion risk indicating a degree of approaching a plurality of obstacles simultaneously based on each of the collision risk between the movable body and the obstacle;

obtain a maximum evasion route congestion risk when the movable body travels on the evasion route and a maximum planned route congestion risk when the movable body travels on the planned route, calculated by the congestion risk calculator respectively;

compare the maximum evasion route congestion risk with the maximum planned route congestion risk; and

output the navigation route change signal when the maximum evasion route collision risk is less than the maximum planned route collision risk, and the maximum evasion route congestion risk is less than the maximum planned route congestion risk.

10 . The navigation planning system according to claim 9 , wherein the processing circuitry further configured to:

calculate the congestion risk of the planned route based on a logical sum of a plurality of collision risks.

11 . The navigation planning system according to claim 9 , wherein the processing circuitry further configured to:

calculate the congestion risk based on the collision risks including the maximum collision risk among the plurality of collision risks.

12 . The navigation planning system according to claim 9 , wherein the processing circuitry further configured to:

the congestion risk calculator further configured to calculate the congestion risk based on the collision risks including a second large collision risk among the plurality of collision risks excluding the maximum collision risk.

13 . The navigation planning method according to claim 7 , further comprising:

calculating a congestion risk indicating a degree of approaching a plurality of obstacles simultaneously based on each of the collision risk between the movable body and the obstacle;

obtaining a maximum evasion route congestion risk when the movable body travels on the evasion route and a maximum planned route congestion risk when the movable body travels on the planned route, calculated by the congestion risk calculator respectively;

comparing the maximum evasion route congestion risk with the maximum planned route congestion risk; and

outputting the navigation route change signal when the maximum evasion route collision risk is less than the maximum planned route collision risk, and the maximum evasion route congestion risk is less than the maximum planned route congestion risk.