Apparatus for measuring the velocity of a moving body

• US 5,224,075 A
• Filed: 11/21/1991
• Issued: 06/29/1993
• Est. Priority Date: 03/26/1990
• Status: Expired due to Term

• Current Assignee: Furuno Electric Co, Ltd
• Original Assignee: Furuno Electric Co, Ltd
• Inventors: Aoyama, Shigeru, Ishihara, Shinji, Iino, Hiroshi
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US07/775,986
• Time in Patent Office: 586 Days
• Field of Search: 367/89, 367/90, 367/91
• US Class Current: 367/91
• CPC Class Codes: G01S 15/60 wherein the transmitter and receiver are mounted on the moving object, e.g. for determining ground speed, drift angle, ground track
• CPC Class Codes: G01S 15/86 Combinations of sonar systems with lidar systems; Combinations of sonar systems with systems not using wave reflection
• CPC Class Codes: G01S 15/87 Combinations of sonar systems

Abstract

A system measures the velocity of a moving body such as a ship and a water body. The system uses a first apparatus which measures the speed of a moving body by detecting a phase difference between a reference signal and echo signals resulting from a transmitted ultrasonic signal, implementing a Fourier transformation on the phase difference data obtained, computing the speed of the ship with respect to the water based on the Fourier spectrum data, and, computing the velocity of a water current based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water obtained. The system also uses a second apparatus which measures the speed of a moving body by detecting the period for each pulse in received echo signals, obtaining a Doppler shift frequency from an inverse value of the period obtained, computing the speed of the ship with respect to the water based on the Doppler shift frequency, and computing the velocity of the water current at a depth at which the echo signals are generated based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water obtained. The system also includes a switch to select either the first apparatus for measuring the speed of a moving body or the second apparatus for measuring the speed of a moving body.

Claims

1. An apparatus for measuring a speed of a ship with respect to the ground and a speed of the ship with respect to water and determining a velocity of a water current comprising:

speed means for measuring a position of at least two points on the Earth and a time required to travel between the two points and for obtaining the speed of the ship with respect to the ground based on the measured positions and time;

transmitting means for transmitting ultrasonic signals into the water;

phase difference detecting means for detecting a phase difference between a reference signal and received echo signals generated at a depth;

Fourier means for implementing a Fourier transformation signals resulting from on the phase difference data obtained by said phase difference detecting means and for computing the speed of a ship with respect to the water at the depth based on Fourier spectrum data obtained from the Fourier transformation; and

velocity means for computing the velocity of the water current at the depth based on the speed of a ship with respect to the ground and the speed of the ship with respect to the water.

2. An apparatus for measuring a speed of a ship with respect to the ground and a speed of the ship with respect to water and determining a velocity of a water current based on the speeds of the ship comprising:

speed means for measuring a position of at least two points on the Earth and a time required to travel between the two points and for obtaining the speed of the ship with respect to the ground based on the measured positions and time;

transmitting means for transmitting ultrasonic signals into the water;

phase difference detecting means for detecting a phase difference between a reference signal and received echo signals generated at a plurality of depths;

Fourier means for implementing Fourier transformations on signals resulting from the phase difference data obtained by said phase difference detecting means and for computing the speed of a ship with respect to the water at the plurality of the depths based on Fourier spectra data obtained from the Fourier transformation; and

velocity means for computing the velocity of water currents at the plurality of the depths based on the speed of the ship with respect to the ground and the speeds of the ship with respect to the water at the plurality of depths.

3. An apparatus for measuring a Doppler frequency shift comprising:

period detecting means for detecting a period for each pulse in the echo signals during a given measurement time;

period judging means for determining whether the period detected by said period detecting means is in a normal period range;

average period computing means for computing an average period from a plurality of periods which are judged as normal by said period judging means; and

inverse means for obtaining a Doppler shift frequency from an inverse value of the average period obtained by said average period computing means.

4. An apparatus for measuring a speed of a ship by detecting a Doppler shift frequency generated with ultrasonic echo signals propagating in the water comprising:

period detecting means for detecting a period for each pulse in the echo signals during a given measurement time;

period judging means for determining whether the period detected by said period detecting means is in a normal period range;

average period computing means for computing an average period from a plurality of periods which are judged as normal by said period judging means;

inverse means for obtaining a Doppler shift frequency from an inverse value of the average period obtained by said average period computing means; and

speed computing means for computing the speed of the ship based on the obtained Doppler shift frequency.

5. The apparatus as claimed in claim 4 wherein said speed computing means computes the speed of the ship with respect to water.

6. The apparatus as claimed in claim 4 wherein said speed computing means computes the speed of the ship with respect to a seabed.

7. An apparatus for determining a velocity of a water current by detecting a Doppler shift frequency generated with ultrasonic echo signals propagating in the water comprising:

period detecting means for detecting a period for each pulse in received echo signals generated at a seabed and in water during a given measurement time;

period judging means for determining whether a period detected by said period detecting means is in a normal period range;

average period computing means for computing an average period from a plurality of periods which are judged as normal by said period judging means;

inverse means for obtaining a Doppler shift frequency from an inverse value of the average period obtained by said average period computing means;

speed computing means for computing a speed of a ship with respect to the seabed and the speed of the ship with respect to the water based on the obtained Doppler shift frequency; and

water current velocity computing means for computing the velocity of the water current at a depth at which the echo signals are generated based on the speed of the ship with respect to the seabed and the speed of the ship with respect to the water.

8. The apparatus as claimed in claim 7 wherein said water current velocity computing means computes speeds of water currents at a plurality of depths.

9. An apparatus for measuring a speed of a ship with respect to the ground and the speed of the ship with respect to water and determines a velocity of a water current on the speeds of the ship comprising:

speed means for measuring a position of at least two points on the Earth and a time required to travel between the two points and for obtaining the speed of a ship with respect to the ground based on the measured positions and time;

period detecting means for detecting a period for each pulse in received echo signals generated in the water during a given measurement time;

period judging means for determining whether a period detected by said period detecting means is in a normal period range;

average period computing means for computing an average period from a plurality of periods which are judged as normal by said period judging means;

inverse means for obtaining a Doppler shift frequency from an inverse value of the average period obtained by said average period computing means;

speed computing means for computing the speed of the ship with respect to the water based on the obtained Doppler shift frequency; and

water current velocity computing means for computing the velocity of the water current at the a depth at which the echo signals are generated based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water.

10. The apparatus as claimed in claim 9 wherein said water current velocity computing means computes speeds of water currents at a plurality of depths.

11. A system for determining a velocity of a water current by detecting a Doppler shift frequency generated with ultrasonic echo signals propagating in water comprising:

a first apparatus for measuring the speed of a moving body;

said first apparatus including,

phase difference detecting means for detecting a phase difference between a reference signal and received echo signals generated at a seabed and in the water,

first computing means for implementing Fourier transformations on signals resulting from the phase difference data obtained by said phase difference detecting means and for computing speed of a ship with respect to the seabed and the speed of the ship with respect to the water based on Fourier spectrum data obtained from the Fourier transformation, and

second computing means for determining the velocity of a water current at a depth at which the ultrasonic echo signals are generated based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water;

a second apparatus for measuring the speed of a moving body;

said second apparatus including,

period detecting means for detecting a period for each pulse in received echo signal generated at the seabed and in the water during a given measurement time,

period judging means for determining whether a period detected by said period detecting means is in a normal period range,

average period computing means for computing an average period from a plurality of periods which are judged as normal by said period judging means,

inverse means for obtaining a Doppler shift frequency from an inverse value of the average period obtained by said average period computing means,

speed computing means for computing the speed of the ship with respect to the ground and the speed of the ship with respect to the water based on the obtained Doppler shift frequency, and

water current velocity computing means for computing the velocity of the water current at the depth at which the echo signals are generated based on the speed of the ship with respect to the water obtained from said speed computing means; and

switching means for selecting said first apparatus for measuring the speed of a moving body or said second apparatus for measuring the speed of a moving body.

12. An apparatus for measuring a speed of a ship with respect to water and the speed of the ship with respect to ground and determines a velocity of water current based on the speeds of the ship comprising:

navigational means for measuring the speed of the ship with respect to the ground using navigational data;

transmitting means for transmitting ultrasonic signals into the water;

phase difference detecting means for detecting a phase difference between a reference signal and received echo signals generated at a depth;

Fourier means for implementing a Fourier transformation on signals resulting from the phase difference data obtained by said phase difference detecting means and for computing the speed of a ship with respect to the water at the depth based on Fourier spectra data obtained from the Fourier transformation; and

velocity means for computing the velocity of the water at the depth based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water.

13. The apparatus as claimed in claim 12 wherein said navigational means is a Global Positioning System Receiver.

14. An apparatus for measuring a speed of a ship with respect to water and the speed of the ship with respect to the ground and determining a velocity of a water current based on the speeds of the ship comprising:

speed means for measuring the speed of the ship with respect to the ground;

transmitting means for transmitting ultrasonic signals into the water;

period detecting means for detecting a period for each pulse in received echo signals generated at the water during a given measurement time;

period judging means for determining whether a period detected by said period detecting means is in a normal period range;

average period computing means for computing an average period from a plurality of periods which are judged as normal by said period judging means;

inverse means for obtaining a Doppler shift frequency from an inverse value of the average period obtained by said average period computing means;

speed computing means for computing the speed of the ship with respect to the water based on the obtained Doppler shift frequency; and

water current velocity computing means for computing the velocity of the water current at the depth at which the echo signals are generated based on the speed of the ship with respect to the water.

15. The apparatus as claimed in claim 14 wherein said speed means is a Global Positioning System Receiver.

16. A system for measuring a speed of a ship with respect to water and the speed of the ship with respect to the ground and determining a velocity of a water current based on the speeds of the ship comprising:

a first apparatus for measuring the speed of a moving body;

said first apparatus including,

speed means for measuring the speed of the ship with respect to the ground,

transmitting means for transmitting ultrasonic signals into the water,

phase difference detecting means for detecting a phase difference between a reference signal and received echo signals generated at a depth,

first computing means for implementing a Fourier transformation on the phase difference data obtained by said phase difference detecting means and for computing the speed of the ship with respect to the water at the depth based on the Fourier spectrum data obtained from the Fourier transformation, and

second computing means for computing the velocity of a water current at a depth at which the ultrasonic echo signals are generated based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water obtained from said first computing means;

a second apparatus for measuring the speed of a moving body;

said second apparatus including,

period detecting means for detecting a period for each pulse in received echo signal generated in the water during a given measurement time,

period judging means for determining whether a period detected by said period detecting means is in a normal period range,

average period computing means for computing an average period from a plurality of periods which are judged as normal by said period judging means,

inverse means for obtaining a Doppler shift frequency from an inverse value of the average period obtained by said average period computing means,

speed computing means for computing the speed of the ship with respect to the water based on the obtained Doppler shift frequency, and

water current velocity computing means for computing the velocity of the water current at the depth at which the echo signals are generated based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water obtained from said speed computing means; and

switching means for selecting first apparatus for measuring the speed of a moving body or said second apparatus for measuring the speed of a moving body.

17. The apparatus as claimed in claim 16 wherein said speed means is a Global Positioning System Receiver.

18. The apparatus as claimed in claim 16 wherein said speed means measures a position of at least two points on the Earth and a time required to travel between the two points and obtains the speed of the ship with respect to the ground based on the measured positions and time.

19. A method for measuring a speed of a ship with respect to the ground and a speed of the ship with respect to water and determining a velocity of a water current comprising the steps of:

(a) measuring a position of at least two points on the Earth and a time required to travel between the two points and for obtaining the speed of the ship with respect to the ground based on the measured positions and time;

(b) transmitting ultrasonic signals into the water;

(c) detecting a phase difference between a reference signal and received echo signals generated at a depth;

(d) implementing a Fourier transformation on signals resulting from the phase difference data obtained by said step (c) and computing the speed of a ship with respect to the water at the depth based on Fourier spectrum data obtained from the Fourier transformation; and

(e) computing the velocity of the water current at the depth based on the speed of a ship with respect to the ground and the speed of the ship with respect to the water.

20. A method for measuring a Doppler frequency shift comprising the steps of:

(a) detecting a period for each pulse in the echo signals during a given measurement time;

(b) determining whether the period detected by said step (a) is in a normal period range;

(c) computing an average period from a plurality of periods which are judged as normal by said step (b); and

(d) obtaining a Doppler shift frequency from an inverse value of the average period obtained by said step (c).

21. A method for determining a velocity of a water current by detecting a Doppler shift frequency generated with ultrasonic echo signals propagating in the water comprising the steps of:

(a) detecting a period for each pulse in received echo signals generated at a seabed and in water during a given measurement time;

(b) determining whether a period detected by said step (a) is in a normal period range;

(c) computing an average period from a plurality of periods which are judged as normal by said step (b);

(d) obtaining a Doppler shift frequency from an inverse value of the average period obtained by said step (c);

(e) computing a speed of a ship with respect to the seabed and the speed of the ship with respect to the water based on the obtained Doppler shift frequency; and

(f) computing the velocity of the water current at a depth at which the echo signals are generated based on the speed of the ship with respect to the seabed and the speed of the ship with respect to the water.

22. A method for measuring a speed of a ship with respect to water and the speed of the ship with respect to ground and determines a velocity of a water current based on the speeds of the ship comprising the steps of:

(a) measuring the speed of the ship with respect to the ground using navigational data;

(b) transmitting ultrasonic signals into the water;

(c) detecting a phase difference between a reference signal and received echo signals generated at a depth;

(d) implementing a Fourier transformation on signals resulting from the phase difference data obtained by said step (c) and computing the speed of a ship with respect to the water at the depth based on Fourier spectra data obtained from the Fourier transformation; and

(e) computing the velocity of the water at the depth based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water.

23. The method as claimed in claim 22 wherein said step (a) measures the speed of the ship with respect to the ground using a Global Positioning System Receiver.

24. An apparatus for measuring a velocity of a moving body which measures a speed of a ship with respect to water by detecting a Doppler frequency shift contained in an ultrasonic echo signal propagating through the water comprising:

phase difference detecting means for detecting a phase difference between reference signals and a received echo signal, said phase difference being an angle;

transforming means for transforming the phase difference to a first signal and a second signal, said first signal being a value equal to a cosine of said phase difference, said second signal being a value equal to a sine of said phase difference;

multiplying means for multiplying said first and second signals by a Hanning window to produce third and fourth signals, respectively;

Fourier means for implementing a Fourier transformation on said third and fourth signals to obtain a Fourier spectrum;

first means for applying a frequency interpolation on the Fourier spectrum to obtain a Doppler frequency shift; and

speed means for computing the speed of the ship with respect to the water based on the Doppler frequency shift.

25. The apparatus for measuring the velocity of a moving body as claimed in claim 24 wherein said phase difference detecting means detects a phase difference between an echo signal and a reference clock signal.

26. An apparatus for measuring a speed of a moving body which measures a speed of a ship with respect to ground by detecting a Doppler frequency shift contained in an ultrasonic echo signal propagating through water comprising:

phase difference detecting means for detecting a phase difference between reference signals and a received echo signal, said phase difference being an angle;

transforming means for transforming the phase difference to a first signal and a second signal, said first signal being a value equal to a cosine of said phase difference, said second signal being a value equal to a sine of said phase difference;

multiplying means for multiplying said first and second signals by a Hanning window to produce third and fourth signals, respectively;

Fourier means for implementing a Fourier transformation on said third and fourth signals to obtain a Fourier spectrum;

first means for applying a frequency interpolation on the Fourier spectrum to obtain a Doppler frequency shift; and

speed means for computing the speed of the ship with respect to the ground based on the Doppler frequency shift.

27. An apparatus for measuring a speed of a moving body which measures a velocity of a water current by detecting a Doppler frequency shift contained in ultrasonic echo signals propagating through the water comprising:

phase difference detecting means for detecting a first phase difference between a reference signal and echo signals generated at a seabed and for detecting a second phase difference between a reference signal and echo signals generated at a certain depth;

arithmetic means for computing a difference between said first and second phase difference;

transforming means for transforming said difference first and second signals, said first signal being a value equal to a cosine of said difference, said second signal being a value equal to a sine of said difference;

multiplying means for multiplying said first and second signals by a Hanning window to produce third and fourth signals, respectively;

Fourier means for implementing Fourier transformations on said third and fourth signals to obtain a Fourier spectrum;

first means for applying a frequency interpolation on the Fourier spectrum to obtain a Doppler frequency shift; and

speed means for computing the velocity of the water current based on the Doppler frequency shift.

28. An apparatus for measuring a speed of a moving body which measures a velocity of a water current flow by detecting a Doppler frequency shift contained in ultrasonic echo signals propagating through the water comprising:

phase difference detecting means for detecting a first phase difference between a reference signal and echo signals generated at a seabed and for detecting a second phase difference between a reference signal and echo signals generated at a certain depth;

transforming means for transforming said first and second phase differences into first, second, third, and fourth signals, said first signal being a value equal to a cosine of said first phase difference, said second signal being a value equal to a sine of said first phase difference, said third signal being a value equal to a cosine of said second phase difference, said fourth signal being a value equal to a sine of said second phase difference;

multiplying means for multiplying said first, second, third, and fourth signals by a Hanning window to produce a first, second, third, and fourth product;

Fourier means for implementing Fourier transformations on said first, second, third, and fourth products to obtain Fourier spectra;

first means for applying a frequency interpolation on the Fourier spectra to obtain Doppler frequency shifts;

speed means for computing the speed of a ship with respect to ground and the speed of the ship with respect to the water based on the resultant Doppler frequency shifts; and

velocity means for computing the velocity of the water current based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water.

29. An apparatus for measuring a speed of a moving body which measures a velocity of water current flows by detecting Doppler frequency shifts contained in ultrasonic echo signals propagating through the water comprising:

phase difference detecting means for respectively detecting a first phase difference between a reference signal and echo signals generated at a seabed and a second phase difference between the reference signal and echo signals generated at a plurality of depths;

difference means for computing a difference between said first and second phase differences;

transforming means for transforming said difference into first and second signals, said first signal being a value equal to a cosine of said difference, said second signal being a value equal to a sine of said difference;

multiplying means for multiplying said first and second signals by a Hanning window to produce third and fourth signals, respectively;

Fourier means for implementing Fourier transformations on said third and fourth signals to obtain Fourier spectra;

first means for applying a frequency interpolation on the Fourier spectra to obtain Doppler frequency shifts; and

speed means for computing the velocity of the water current flowing at a plurality of depths based on the Doppler frequency shifts.

30. The apparatus for measuring the speed of a moving body as claimed in claim 29 wherein said reference signal is a reference clock signal.

31. An apparatus for measuring a speed of a ship with respect to ground and a speed of the ship with respect to water and determining a velocity of a water current comprising:

speed means for measuring a position of at least two points on Earth and a time required to travel between the two points and for obtaining the speed of the ship with respect to the ground based on the measured positions and time;

transmitting means for transmitting ultrasonic signals into the water;

receiving means for receiving echo signals generated at a depth;

Fourier means for implementing a Fourier transformation on signals resulting from the received echo signals and for computing the speed of a ship with respect to the water at the depth based on the Fourier spectrum data obtained from the Fourier transformation; and

velocity means for computing the velocity of the water current at the depth based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water.

32. An apparatus for measuring a speed of a ship with respect to ground and a speed of the ship with respect to water and determining a velocity of a water current comprising:

speed means for measuring a position of at least two points on Earth and a time required to travel between the two points and for obtaining the speed of the ship with respect to the ground based on the measured positions and time;

transmitting means for transmitting ultrasonic signals into the water;

receiving means for receiving echo signals generated at a depth;

multiplying means for multiplying signals resulting from the echo signals by a Hanning window to produce product signals;

Fourier means for implementing a Fourier transformation on said product signals to obtain a Fourier spectrum;

first means for applying a frequency interpolation on the Fourier spectrum to obtain a Doppler frequency;

speed means for computing the speed of the ship with respect to the water based on the Doppler frequency; and

velocity means for computing the velocity of the water current at the depth based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water.

33. An apparatus for measuring a speed of a ship with respect to ground and a speed of the ship with respect to water and determining a velocity of a water current comprising:

speed means for measuring a position of at least two points on Earth and a time required to travel between the two points and for obtaining the speed of the ship with respect to the ground based on the measured positions and time;

transmitting means for transmitting ultrasonic signals into the water;

receiving means for receiving echo signals generated at a plurality of depths;

Fourier means for implementing Fourier transformations on signals resulting from the received echo signals and for computing the speed of a ship with respect to the water at the plurality of the depths based on the Fourier spectra data obtained from the Fourier transformations; and

velocity means for computing the velocity of water currents at the plurality of the depths based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water at the plurality of depths.

34. An apparatus for measuring a speed of a ship with respect to ground and a speed of the ship with respect to water and determining a velocity of a water current comprising:

speed means for measuring a position of at least two points on Earth and a time required to travel between the two points and for obtaining the speed of the ship with respect to the ground based on the measured positions and time;

transmitting means for transmitting ultrasonic signals into the water;

receiving means for receiving echo signals generated at a plurality of depths;

multiplying means for multiplying signals resulting from the echo signals by a Hanning window to produce product signals;

Fourier means for implementing Fourier transformations on said product signals to obtain Fourier spectra;

first means for applying a frequency interpolation on the Fourier spectra to obtain Doppler frequencies;

speed means for computing the speeds of the ship with respect to the water at the plurality of the depths based on the Doppler frequencies; and

velocity means for computing the velocity of the water current at the plurality of depths based on the speed of the ship with respect to the ground of the and the speed of the ship with respect to the water at the plurality of depths.

35. An apparatus for measuring a speed of a ship with respect to ground and a speed of the ship with respect to water and determining a velocity of a water current comprising:

navigational means for measuring the speed of the ship with respect to ground using navigational data;

transmitting means for transmitting ultrasonic signals into the water;

receiving means for receiving echo signals generated at a depth;

Fourier means for implementing a Fourier transformation on signals resulting from the received echo signals and for computing the speed of a ship with respect to the water at the depth based on the Fourier spectrum data obtained from the Fourier transformation; and

velocity means for computing the velocity of the water current at the depth based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water.

36. An apparatus for measuring a speed of a ship with respect to ground and a speed of the ship with respect to water and determining a velocity of a water current comprising:

navigational means for measuring the speed of the ship with respect to the ground using navigational data;

transmitting means for transmitting ultrasonic signals into water;

receiving means for receiving echo signals generated at a plurality of depths;

Fourier means for implementing Fourier transformations on signals resulting from the received echo signals and for computing the speed of the ship with respect to the water at the plurality of the depths based on the Fourier spectra data obtained from the Fourier transformations; and

velocity means for computing the velocity of water currents at the plurality of the depths based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water at the plurality of depths.

37. An apparatus for measuring a speed of a ship with respect to ground and a speed of the ship with respect to water and determining a velocity of a water current comprising:

navigational means for measuring the speed of the ship with respect to the ground using navigational data;

transmitting means for transmitting ultrasonic signals into the water;

receiving means for receiving echo signals generated at a plurality of depths;

multiplying means for multiplying signals resulting from the echo signals by a Hanning window to produce product signals;

Fourier means for implementing Fourier transformations on and product signals to obtain Fourier spectra;

first means for applying a frequency interpolation on the Fourier spectra to obtain Doppler frequencies;

means for computing the speeds of the ship with respect to the water at the plurality of the depths based on the Doppler frequencies; and

velocity means for computing the velocity of the water current at the plurality of depths based on the speed of the ship with respect to the ground and the speed of the ship with respect to the water at the plurality of depths.