Step detection device and step detection method

1. A step detection device comprising:

a distance sensor which is mounted on a vehicle and detects a distance and a direction to a road surface around the vehicle;

a step determination position circuit which sets a first step determination position on the road surface, the first step determination position being away from the distance sensor in a first predetermined direction by a first predetermined distance and extending in a direction orthogonal to the first predetermined direction, and which sets a second step determination position on the road surface, the second step determination position being away from the distance sensor in a second predetermined direction different from the first predetermined direction by a second predetermined distance and extending in a direction orthogonal to the second predetermined direction;

a road surface height calculation circuit which calculates a height change of the road surface at the first step determination position and a height change of the road surface at the second step determination position, based on the distance and the direction to the road surface detected by the distance sensor; and

a step detection circuit which detects a step on the road surface based on one of the first step determination position and the second step determination position, a gradient of the height change of the road surface at the one being larger than a gradient of the height change of the road surface at the other.

2. The step detection device according to claim 1 , wherein

if the gradient of the height change of the road surface at one of the first step determination position and the second step determination position is larger than or equal to a threshold, the step detection circuit detects the step on the road surface based on the height change of the road surface at the one, the gradient of the height change of the road surface at the one being larger than or equal to the threshold.

3. The step detection device according to claim 1 , further comprising a step existing area estimation circuit which estimates a step existing area in which the step exists at the first step determination position, wherein

the step determination position circuit sets the second step determination position passing through the step existing area.

4. The step detection device according to claim 3 , wherein

the step existing area estimation circuit estimates the step existing area based on the height change of the road surface at the first step determination position.

5. The step detection device according to claim 3 , wherein

the step detection circuit repeatedly detects the step on the road surface at predetermined intervals, and

the step existing area estimation circuit estimates the step existing area based on a position of the step which was previously detected.

6. The step detection device according to claim 3 , wherein

the step determination position circuit sets a plurality of the first step determination positions,

the step detection circuit tries to detect the step on the road surface for every first step determination position, and

the step existing area estimation circuit estimates the step existing area based on a position of the step which was successfully detected.

7. The step detection device according to claim 3 , further comprising:

a map acquisition circuit which acquires map information on surroundings of the vehicle; and

a self-position estimation circuit which estimates a position of the vehicle on a map, wherein

the step existing area estimation circuit estimates the step existing area based on the estimated position of the vehicle on the map.

8. The step detection device according to claim 1 , wherein

if the gradient of the height change of the road surface at the first step determination position is larger than or equal to a threshold, the road surface height calculation circuit does not calculate the height change of the road surface at the second step determination position, and the step detection circuit detects the step on the road surface based on the height change of the road surface at the first step determination position.

9. A step detection method comprising:

detecting a distance and a direction to a road surface around a vehicle using a distance sensor mounted on the vehicle;

setting a first step determination position on the road surface, the first step determination position being away from the distance sensor in a first predetermined direction by a first predetermined distance and extending in a direction orthogonal to the first predetermined direction;

setting a second step determination position on the road surface, the second step determination position being away from the distance sensor in a second predetermined direction different from the first predetermined direction by a second predetermined distance and extending in a direction orthogonal to the second predetermined direction;

calculating a height change of the road surface at the first step determination position and a height change of the road surface at the second step determination position, based on the distance and the direction to the road surface detected by the distance sensor; and

detecting a step on the road surface based on one of the first step determination position and the second step determination position, a gradient of the height change of the road surface at the one being larger than a gradient of the height change of the road surface at the other.