Road surface condition estimation device

Patent metadata

Field	Value
Publication number	US-10597009-B2
Application number	US-201615770517-A
Country	US
Kind code	B2
Filing date	Sep 23, 2016
Priority date	Oct 27, 2015
Publication date	Mar 24, 2020
Grant date	Mar 24, 2020

Abstract

A road surface condition estimation device extracts a detection signal of a vibration power generation element during a ground contact section to detect a road surface condition. A threshold used for determination of the ground contact section is variable according to a traveling speed of a vehicle. As a result, even if a pulse level of an output voltage of the vibration power generation element changes according to the traveling speed of the vehicle, the threshold corresponding to the change can be set. The ground contact section is determined with the use of the above thresholds, thereby being capable of performing the determination with high accuracy. Therefore, the road surface condition can be detected with high accuracy based on the ground contact section determined with high accuracy.

First claim

What is claimed is:

1. A road surface condition estimation device provided in a vehicle, comprising:
a tire side device that includes
a vibration detection unit which is attached to a rear surface of a tread of a tire provided in the vehicle and which outputs a detection signal corresponding to a magnitude of vibration of the tire,
a signal processing unit having
a section identification unit which identifies a ground contact section in which a portion of the tread corresponding to a placement location of the vibration detection unit contacts the road during one rotation of the tire, and
a level calculation unit which calculates a level of a high frequency component of the detection signal in the ground contact section, and

a transmitter which transmits a calculation result of the level of the high frequency component as road surface condition data representing a road surface condition; and

a vehicle side device that includes
a receiver that receives the road surface condition data transmitted from the transmitter, and
a road surface condition estimation unit that estimates a road surface condition of a traveling road surface of the tire based on the road surface condition data, wherein

the section identification unit includes
a threshold setting unit that sets, according to a traveling speed of the vehicle, a first threshold and a second threshold for comparison with a pulse level of a pulse waveform indicated by the detection signal, the second threshold being smaller than the first threshold, and
a section extraction unit that extracts a period between a ground contact start time to a ground contact end time as a ground contact section, the ground contact start time being defined as a next maximum value of the pulse waveform indicated by the detection signal after the pulse waveform becomes larger than the first threshold, and the ground contact end time being defined as a next minimum value of the pulse waveform after the pulse waveform becomes smaller than the second threshold.

2. The road surface condition estimation device according to claim 1 , wherein
the section identification unit includes a peak value detection unit that detects a maximum value and a minimum value of the pulse waveform as values corresponding to the traveling speed of the vehicle, and that stores the maximum value and the minimum value of a previous rotation of the tire as a previous first peak value and a previous second peak value, respectively, and
the threshold setting unit
changes the first threshold to a value larger than that of the previous one rotation if the maximum value during the current rotation of the tire is larger than the first peak value, and changes the first threshold to a value smaller than that of the previous one rotation if the maximum value during the current rotation of the tire is smaller than the first peak value, and
changes the second threshold to a value smaller than that of the previous one rotation if the minimum value during the current rotation of the tire is smaller than the second peak value, and changes the second threshold to a value larger than that of the previous one rotation if the minimum value during the current rotation of the tire is larger than the second peak value.

3. The road surface condition estimation device according to claim 2 , wherein
the threshold setting unit changes the first threshold to a value larger than that of the previous one rotation and changes the second threshold to a value smaller than that of the previous one rotation only if the maximum value during the current rotation of the tire is larger than the first peak value while the minimum value during the current rotation of the tire is smaller than the second peak value, and
the threshold setting unit changes the first threshold to a value smaller than that of the previous one rotation and changes the second threshold to a value larger than that during the previous one rotation only if the maximum value during the current rotation of the tire is smaller than the first peak value while the minimum value during the current rotation of the tire is larger than the second peak value.

4. The road surface condition estimation device according to claim 1 , wherein
the section identification unit includes a pulse interval detection unit that detects a maximum value and a minimum value of the pulse waveform as values corresponding to the traveling speed of the vehicle, sets a time interval between reaching the maximum value and reaching the minimum value during one rotation of the tire as a ground contact pulse interval, and stores the ground contact pulse interval of previous one rotation of the tire, and
the threshold setting unit
changes the first threshold to a value larger than that of the previous one rotation and changes the second threshold to a value smaller than that of the previous one rotation if the ground contact pulse interval during the current rotation of the tire is shorter than the ground contact pulse interval of the previous one rotation, and
changes the first threshold to a value smaller than that of the previous one rotation and changes the second threshold to a value larger than that of the previous one rotation if the ground contact pulse interval during the current rotation of the tire is longer than the ground contact pulse interval of the previous one rotation.

5. The road surface condition estimation device according to claim 2 , wherein
the section identification unit includes a pulse interval detection unit that detects a maximum value and a minimum value of the pulse waveform as values corresponding to the traveling speed of the vehicle, sets a time interval between reaching the maximum value and reaching the minimum value during one rotation of the tire as a ground contact pulse interval, and stores the ground contact pulse interval of previous one rotation of the tire,
the threshold setting unit changes the first threshold to a value larger than that of the previous one rotation and changes the second threshold to a value smaller than that of the previous one rotation only if the maximum value during the current rotation of the tire is larger than the first peak value, the minimum value during the current rotation of the tire is smaller than the second peak value, and the ground contact pulse interval during the current rotation of the tire is shorter than the ground contact pulse interval of the previous one rotation, and
the threshold setting unit changes the first threshold to a value smaller than that of the previous one rotation and changes the second threshold to a value larger than that of the previous one rotation only if the maximum value during the current rotation of the tire is smaller than the first peak value, the minimum value during the current rotation of the tire is larger than the second peak value, and the ground contact pulse interval during the current rotation of the tire is longer than the ground contact pulse interval of the previous one rotation.

6. The road surface condition estimation device according to claim 1 , wherein
the section identification unit includes a centrifugal force detection unit that detects a centrifugal force of the tire acting on the tire side device as a value corresponding to the traveling speed of the vehicle,
the threshold setting unit changes the first threshold to a value larger than that of a previous one rotation of the tire and changes the second threshold to a value smaller than that of the previous one rotation if the centrifugal force during the current rotation of the tire is larger than the centrifugal force during the rotation of the tire of the previous one rotation, and
the threshold setting unit changes the first threshold to a value smaller than that of the previous one rotati

Assignees

• Denso Corp

Inventors

• Suzuki Youichirou
• Takaoka Akira
• Sekizawa Takatoshi

Classifications

• B60W2050/0055

  High-pass filters · CPC title

• B60T8/1763

  responsive to the coefficient of friction between the wheels and the ground surface (B60T8/1764 takes precedence) · CPC title

• B60W2422/70

  on the wheel or the tyre · CPC title

• B60T8/171

  Detecting parameters used in the regulation; Measuring values used in the regulation · CPC title

• B60W2420/90

  Single sensor for two or more measurements · CPC title