Internal state detector and vehicle
A detector that detects an internal state of a plate-shaped object including a fiber-reinforced resin. The detector includes an exciter that applies, to a surface of the object, ultrasonic vibrations of Lamb waves, in a selected frequency range where only a zero-order fundamental wave symmetric mode and a zero-order fundamental wave asymmetric mode of the Lamb waves appear, a vibration detector that detects the applied ultrasonic vibrations propagating in the object, and an internal state estimation calculator that estimates the internal state of the object, by obtaining a propagation time of the ultrasonic vibrations propagating in the object corresponding to each frequency of the Lamb waves, based on the detection result of the vibration detector, estimating the internal state based on a delay time of the propagation time relative to a reference propagation time of the object for each frequency in the selected frequency range, and outputting the estimated internal state.
1. An internal state detector that detects an internal state of an object, the object being of a plate shape and including a fiber-reinforced resin, the internal state detector comprising:
an exciter that applies, to a surface of the object, ultrasonic vibrations of Lamb waves, including the ultrasonic vibrations in a selected frequency range where only a zero-order fundamental wave symmetric mode and a zero-order fundamental wave asymmetric mode of the Lamb waves appear, the selected frequency range including a plurality of frequencies;
a vibration detector that detects the ultrasonic vibrations of the Lamb waves applied by the exciter to the object and propagating in the object; and
an internal state estimation calculator that estimates the internal state of the object, based on a detection result of the vibration detector, the internal state estimation calculator being configured to
obtain a propagation time of the ultrasonic vibrations propagating in the object corresponding to each frequency of the Lamb waves, based on the detection result of the vibration detector obtained responsive to the vibration application by the exciter,
estimate the internal state of the object, based on a delay time of the propagation time relative to a reference propagation time of the object for each of the plurality of frequencies in the selected frequency range, and
output the estimated internal state, wherein
the internal state estimation calculator is configured to estimate the internal state of the object, based on a maximum time difference in delay time of the propagation time for the plurality of frequencies in the selected frequency range.
2. The internal state detector according to claim 1 , wherein
the vibration detector includes a plurality of vibration detectors, and
the internal state estimation calculator obtains the propagation time of the ultrasonic vibrations propagating in the object from an output value of each of the plurality of vibration detectors.
3. The internal state detector according to claim 1 , further comprising:
a memory that stores reference propagation times of the object corresponding to a plurality of frequencies in the selected frequency range, wherein
the internal state estimation calculator estimates the internal state of the object, based on one of the stored reference propagation times of the object corresponding to each of at least one frequency in the frequency range and based on the propagation time corresponding to a frequency equal to said each frequency.
4. The internal state detector according to claim 1 , wherein
the ultrasonic vibrations applied by the exciter to the object have a frequency that increases or decreases with time.
5. The internal state detector according to claim 1 , wherein
each of the exciter and the vibration detector is a film-shaped piezoelectric element.
6. The internal state detector according to claim 1 , wherein
the object is formed of a woven fiber-reinforced resin material.
7. A vehicle using a plate member including a fiber-reinforced resin, the vehicle comprising:
the internal state detector according to claim 1 , wherein
the internal state detector is configured to detect an internal state of the plate member.