Obstacle detection device, obstacle detection method, and obstacle detection computer program product
An obstacle detection device is configured to evaluate a ghost likelihood of a detection point to be high when a movement pattern of the detection point does not match a movement pattern of a detection point when a received carrier wave is a reflected wave from an obstacle, when the movement pattern of the detection point matches a movement pattern when the detection point is a ghost, when a characteristic of a strength or a degree of steepness of the carrier wave matches a characteristic of a strength or a degree of steepness when the detection point is a ghost, or when another detection point that has a direction and a speed correlated with a direction and a speed of the detection point and is different from the detection point, is present.
1. An obstacle detection device configured to control transmitter-receivers that are configured to be mounted on a vehicle, the obstacle detection device comprising:
a memory; and
a hardware processor coupled to the memory,
the hardware processor being configured to:
cause first transmitter-receivers to successively transmit carrier waves, based on a transmission order;
successively identify, when the first transmitter-receivers receive carrier waves, a detection point indicating coordinates of an obstacle, based on time differences between transmission of the carrier waves and reception of the carrier waves by the transmitter-receivers, and
evaluate a ghost likelihood indicating a likelihood that the identified detection point is a ghost that is generated due to reception of a carrier wave transmitted from another vehicle different from the vehicle, wherein
the hardware processor is configured to identify a movement amount and a moving direction of the identified detection point, and
the hardware processor is further configured to:
estimate a moving speed of the identified detection point; and
evaluate the ghost likelihood of the identified detection point to be high in a case in which another detection point that is in a substantially same direction as the identified detection point and moves at a speed substantially two times the moving speed of the identified detection point in the substantially same direction as the identified detection point, is present.
2. The obstacle detection device according to claim 1 , wherein
the hardware processor is further configured to evaluate the ghost likelihood of the identified detection point to be high in any of a case in which a movement pattern indicated by a movement amount and a moving direction of the another detection point generated when causing the first transmitter-receivers to successively transmit the carrier waves does not match a movement pattern indicated by the movement amount and the moving direction of the identified detection point, and a case in which a movement pattern indicated by a movement amount and a moving direction of a detection point generated when second transmitter-receivers of another vehicle successively perform transmission matches the movement pattern indicated by the movement amount and the moving direction of the identified detection point.
3. The obstacle detection device according to claim 1 , wherein
the hardware processor is further configured to analyze a reception waveform indicating a temporal change of a strength of the carrier waves received by the first transmitter-receivers, and extract a peak waveform corresponding to the identified detection point in the reception waveform to calculate a peak strength of the peak waveform or a degree of steepness of the peak waveform, and
the hardware processor is further configured to evaluate the ghost likelihood of the detection point to be high in a case in which the peak strength is larger than a strength that is expected in a case in which the carrier waves travel back and forth a distance to the identified detection point, or a case in which the degree of steepness of the peak waveform is larger than a degree of steepness that is expected when dispersion is caused by reflection.
4. The obstacle detection device according to claim 1 , wherein
the hardware processor is further configured to compare the ghost likelihood with a ghost likelihood threshold, and
the hardware processor is further configured to, when evaluating that the ghost likelihood is larger than the ghost likelihood threshold, change a transmission interval of the carrier waves.
5. The obstacle detection device according to claim 4 , wherein the hardware processor is further configured to change the transmission interval of the carrier waves in accordance with a distance to the identified detection point, and the transmission interval at a time when the distance is shorter is smaller than the transmission interval at a time when the distance is longer.
6. The obstacle detection device according to claim 4 , wherein the ghost likelihood is evaluated or the ghost likelihood threshold is set in accordance with a distance between the vehicle and the identified detection point, and the transmission interval of the carrier waves is made easier to change as the distance is shorter.
7. The obstacle detection device according to claim 4 , wherein
the ghost likelihood is evaluated or the ghost likelihood threshold is set in accordance with a vehicle speed indicating a speed at which the vehicle travels, and
the transmission interval of the carrier waves is made easier to change as the vehicle speed is higher.
8. The obstacle detection device according to claim 4 , wherein
the hardware processor is further configured to calculate a collision margin time until the identified detection point meets the vehicle, and
the hardware processor is further configured to change the transmission interval when the collision margin time is smaller than a collision margin time threshold.
9. The obstacle detection device according to claim 4 , wherein the hardware processor is further configured to change the transmission interval when a distance to the identified detection point in a vehicle width direction tends to reduce.
10. The obstacle detection device according to claim 4 , wherein
the hardware processor is further configured to evaluate an adverse effect caused by changing the transmission interval of the carrier waves,
the hardware processor is further configured to evaluate the adverse effect based on at least one of conditions that a direction of the identified detection point is same as a traveling direction of the vehicle, that a distance to the identified detection point tends to reduce, that a speed reduction of the identified detection point is large, that the distance to the identified detection point is small, and that a traveling speed of the vehicle is high, and
the ghost likelihood is evaluated or the ghost likelihood threshold is set in accordance with the evaluated adverse effect or increase or decrease of the adverse effect.
11. The obstacle detection device according to claim 1 , wherein
the hardware processor is further configured to determine a necessity of emergency braking in accordance with a possibility that the identified detection point meets the vehicle, and
the hardware processor is further configured to exclude, from a determination target, a detection point having the ghost likelihood higher than a threshold.
12. The obstacle detection device according to claim 1 , wherein
the hardware processor is further configured to evaluate the ghost likelihood of the identified detection point to be high in a case of at least one of:
a movement pattern of the identified detection point not matching a movement pattern of the another detection point in a case in which the received carrier waves are reflected waves from the obstacle;
the movement pattern of the identified detection point matching a movement pattern in a case in which the identified detection point is the ghost;
a characteristic of a strength or a degree of steepness of the received carrier waves matching a characteristic of a strength or a degree of steepness in a case in which the detection point is the ghost; and
the another detection point being different from the identified detection point and having a direction and a speed correlated with the moving direction and the moving speed of the identified detection point, is present.
13. An obstacle detection method performed by an obstacle detection device configured to control transmitter-receivers that are configured to be mounted on a vehicle, the obstacle detection method comprising:
causing first transmitter-receivers to successively transmit carrier waves, based on a transmission order;
successively identifying, when the first transmitter-receivers receive carrier waves, a detection point indicating coordinates of an obstacle based on a time difference between transmission of the carrier waves and reception of the carrier waves by the first transmitter-receiver,
evaluating a ghost likelihood indicating a likelihood that the detection point identified at the identifying is a ghost that is generated due to reception of a carrier wave transmitted from another vehicle different from the vehicle; and
estimating a moving speed of the detection point, wherein
in the identifying, a movement amount and a moving direction of the detection point are identified, and
in the evaluating, the ghost likelihood of the detection point is evaluated to be high in a case in which another detection point that is in a substantially same direction as the detection point and moves at a speed substantially two times the moving speed of the identified detection point in the substantially same direction as the identified detection point, is present.
14. The obstacle detection method according to claim 13 , wherein
in the evaluating, the ghost likelihood of the identified detection point is evaluated to be high in a case of at least one of:
a movement pattern of the identified detection point not matching a movement pattern of the another detection point in a case in which the received carrier waves are reflected waves from the obstacle;
the movement pattern of the identified detection point matching a movement pattern in a case in which the identified detection point is the ghost;
a characteristic of a strength or a degree of steepness of the received carrier waves matching a characteristic of a strength or a degree of steepness in a case in which the detection point is the ghost; and
the another detection point being different from the identified detection point and having a direction and a speed correlated with the moving direction and the moving speed of the identified detection point, is present.