Method and system for determining velocity by using variable or distinct sampling rates

• US 7,652,618 B2
• Filed: 07/01/2008
• Issued: 01/26/2010
• Est. Priority Date: 02/15/2008
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Wanner, Jason J., Kearney, John R.
• Primary Examiner(s): Sotomayor; John B
• Application Number:
  US12/165,772
• Publication Number:
  US 20090207069A1
• Time in Patent Office: 574 Days
• Field of Search: 342/104, 342/106, 342/115, 342/116, 342/192, 342/196
• US Class Current: 342/104
• CPC Class Codes: G01S 13/60 wherein the transmitter and receiver are mounted on the moving object, e.g. for determining ground speed, drift angle, ground track G01S13/64 takes precedence

Abstract

A data processor applies transform processing to a first group of samples at a primary sampling rate, where the first group of samples is within a data window associated with at least one of the data blocks. A detector detects an estimated frequency shift between the transmitted signal and the reflected signal based on a primary peak frequency determined by the transform processing at the primary sampling rate. The data processor applies transform processing to a second group of samples at a secondary sampling rate, where the data window contains previously read samples and at least one new sample, if the estimated frequency shift falls within a target response frequency band. The detector detects an observed frequency shift between the transmitted signal and the reflected signal based on a secondary peak frequency determined by the transform processing at the secondary sampling rate. A velocity estimator for estimating a velocity of at least one of the object and the transmitter based on the estimated frequency shift, the observed frequency shift, or both.

Claims

1. A method for determining the velocity of a transmitter or an object, the method comprising:

transmitting a signal from a transmitter toward an object;

receiving a reflected signal of the transmitted signal from the object;

organizing the reflected signal into data blocks containing samples;

applying transform processing to a first group of the samples at a primary sampling rate, the first group of samples being within a data window associated with at least one of the data blocks;

detecting an estimated frequency shift between the transmitted signal and the reflected signal based on a primary peak frequency determined by the transform processing at the primary sampling rate;

applying transform processing to a second group of samples at a secondary sampling rate where the data window contains previously read samples and at least one new sample if the estimated frequency shift falls within a target response frequency band, the second group of samples being within the data window and comprising a lesser number of samples than the first group;

detecting an observed frequency shift between the transmitted signal and the reflected signal based on a secondary peak frequency determined by the transform processing at the secondary sampling rate; and

estimating a velocity of at least one of the object and the transmitter based on the estimated frequency shift, the observed frequency shift, or both.

2. The method according to claim 1 wherein the previously read samples and the at least one new sample are distributed within at least two of the data blocks.

3. The method according to claim 1 wherein the transmitter is carried by a vehicle and wherein target response frequency band is associated with an estimated frequency shift indicates that a vehicle speed is less than a threshold vehicle speed.

4. The method according to claim 1 wherein the primary sampling rate is at least approximately two times the maximum Doppler frequency that is associated with a maximum expected speed of an object or a vehicle.

5. The method according to claim 1 wherein the secondary sampling rate is greater than once per data block duration for storage, writing or collection of the data block into a data storage device.

6. The method according to claim 1 wherein:

placing the data block samples into a circular ring buffer, each of the data blocks having at least one data block pointer; and

creating a ring pointer to at least one of the data block samples, the ring pointer independent of the data block pointer.

7. The method according to claim 1 wherein the transform is selected from the group consisting of a Fourier transform, a Fast Fourier transform, a Discrete-time Fourier transform, a Continuous Fourier transform, a Laplace transform, a Mellin transform, and a Z-transform.

8. The method according to claim 1 further comprising:

filtering the peak frequency determined by the transform with a low pass filter to remove spurious data.

9. The method according to claim 1 wherein the estimating of the velocity comprises applying a hysteresis filtering to prevent oscillation between the estimated frequency shift or selection of the observed frequency shift as the basis for estimated velocity, the hysteresis filtering introducing a lag prior to a transition between the estimated frequency shift and the observed frequency shift that is proportional to a maximum acceleration or deceleration of a vehicle carrying the transmitter.

10. The method according to claim 1 wherein the receiving further comprises:

down-converting the received signal to an intermediate frequency signal; and

converting the intermediate frequency signal to a digital signal representation for the data block samples.

11. A system for determining the velocity of a transmitter or an object, the system comprising:

a transmitter for transmitting a signal from a transmitter toward an object;

a receiver for receiving a reflected signal of the transmitted signal from the object;

an organizer for organizing the reflected signal into data blocks containing samples;

a data processor for applying transform processing to a first group of the samples at a primary sampling rate, the first group of samples being within a data window associated with at least one of the data blocks;

the data processor arranged to perform transform processing to a second group of samples at a secondary sampling rate where the data window contains previously read samples and at least one new sample if the estimated frequency shift falls within a target response frequency band, the second group of samples being within the data window and comprising a lesser number of samples than the first group;

a detector for detecting an estimated frequency shift between the transmitted signal and the reflected signal based on a primary peak frequency determined by the transform processing at the primary sampling rate;

the detector arranged for detecting an observed frequency shift between the transmitted signal and the reflected signal based on a secondary peak frequency determined by the transform processing at the secondary sampling rate; and

a velocity estimator for estimating a velocity of at least one of the object and the transmitter based on the estimated frequency shift, the observed frequency shift, or both.

12. The system according to claim 11 wherein the previously read samples and the at least one new sample are distributed within at least two of the data blocks.

13. The system according to claim 11 wherein the transmitter is carried by a vehicle, the target response frequency band being associated with an estimated frequency shift indicating that a vehicle speed is less than a threshold vehicle speed.

14. The system according to claim 11 wherein the primary sampling rate is at least approximately two times the maximum Doppler frequency that is associated with a maximum expected speed of an object or a vehicle.

15. The system according to claim 11 wherein the secondary sampling rate is greater than once per data block duration for storage, writing or collection of the data block into a data storage device.

16. The system according to claim 11 wherein:

a circular ring buffer for storing the data block samples, each of the data blocks having at least one data block pointer; and

a ring pointer pointing to at least one of the data block samples, the ring pointer independent of the data block pointer.

17. The system according to claim 11 wherein the transform is selected from the group consisting of a Fourier transform, a Fast Fourier transform, a Discrete-time Fourier transform, a Continuous Fourier transform, a Laplace transform, a Mellin transform, and a Z-transform.

18. The system according to claim 11 further comprising:

a filter for filtering the peak frequency determined by the mathematical transform with a low pass filter to remove spurious data.

19. The system according to claim 11 wherein the receiver further comprises:

a down-converter for converting the received signal to an intermediate frequency signal; and

an analog-to-digital converter for converting the intermediate frequency signal to a digital signal representation for the data block samples.

20. The system according to claim 11 wherein the velocity estimator further comprises a hysteresis filter for filtering to prevent oscillation between the estimated frequency shift or selection of the observed frequency shift as the basis for estimated velocity, the hysteresis filter introducing a lag prior to a transition between the estimated frequency shift and the observed frequency shift that is proportional to a maximum acceleration or deceleration of a vehicle carrying the transmitter.