Autonomous mower navigation system and method

• US 10,698,417 B2
• Filed: 05/05/2017
• Issued: 06/30/2020
• Est. Priority Date: 05/06/2016
• Status: Active Grant

• Current Assignee: Mtd Products Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Mtd Products Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Churavy, Christopher J., Blanchard, Edward J.
• Primary Examiner(s): Wallace, Donald J
• Application Number:
  US15/588,025
• Publication Number:
  US 20170322562A1
• Time in Patent Office: 1,152 Days
• CPC Class Codes: A01D 2101/00 Lawn-mowers
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: G01S 2205/01 specially adapted for specific applications
• CPC Class Codes: G01S 5/0205 Details
• CPC Class Codes: G05D 1/0265 using buried wires
• CPC Class Codes: G05D 1/0276 using signals provided by a source external to the vehicle involving a plurality of vehicles G05D1/0287; automatically controlling vehicle speed responsive to externally generated signals B60K31/0058
• CPC Class Codes: H03M 13/156 Encoding or decoding using time-frequency transformations, e.g. fast Fourier transformation

Abstract

A method for autonomous mower navigation includes receiving a return-to-zero encoded signal including a pseudo-random sequence, transforming the received signal to a non-return-to-zero representation, digitally sampling the non-return-to-zero signal representation in a time domain, filtering the sampled signal utilizing a reference data array based on the return-to-zero encoded signal to produce a filter output, and determining a location of the autonomous mower relative to a defined work area based on an evaluation of the filter output.

Claims

1. A computer implemented method for autonomous mower navigation, comprising:

receiving a return-to-zero encoded signal including a neutral condition between bits and comprising at least one pseudo-random sequence, wherein the neutral condition comprises a value halfway between a condition representing a 1 bit and a condition representing a 0 bit;

transforming the received signal to a non-return-to-zero phase-shift keyed representation, wherein the non-return-to-zero phase-shift keyed representation comprises a binary code in which binary 0'"'"'s are represented by a negative voltage and binary 1'"'"'s are represented by a positive voltage, and wherein the non-return-to-zero phase-shift keyed representation does not include a neutral condition;

digitally sampling the non-return-to-zero signal representation in a time domain;

filtering the sampled signal utilizing a reference data array based on the return-to-zero encoded signal to produce a filter output; and

determining a location of the autonomous mower relative to a defined work area based on an evaluation of the filter output.

2. The method for autonomous mower navigation of claim 1, comprising receiving a plurality of return-to-zero encoded signals each signal comprising at least one pseudo-random sequence, wherein the pseudo-random sequences comprise a set of sequences having good auto-correlation properties and a low cross-correlation with other sequences in the set.

3. The method for autonomous mower navigation of claim 2, wherein at least one return-to-zero encoded signal is associated with the defined work area, and at least one return-to-zero encoded signal is associated with a guide wire.

4. The method for autonomous mower navigation of claim 1, wherein the pseudo-random sequence comprises at least one of Barker Codes, Gold Codes, Kasami Codes, Walsh Hadamard Codes, and/or similarly derived codes.

5. The method for autonomous mower navigation of claim 1, wherein filtering the sampled signal comprises utilizing a time domain matched filter based on the non-return-to-zero representation to produce at least one correlation maxima and/or at least one correlation minima.

6. The method for autonomous mower navigation of claim 5, wherein the at least one correlation maxima and/or at least one correlation minima comprises a single correlation maxima and/or a single correlation minima.

7. The method for autonomous mower navigation of claim 1, comprising

converting the digitally sampled signal from a time domain to a representation in a frequency domain;

and

wherein filtering the sampled signal comprises computing a cross-correlation by multiplying the frequency domain representation by the reference data array to obtain a product, and performing an inverse fast Fourier transform on the product to produce at least one correlation maxima and/or at least one correlation minima.

8. The method for autonomous mower navigation of claim 7, wherein the at least one correlation maxima and/or at least one correlation minima comprises a single correlation maxima and/or a single correlation minima.

9. The method for autonomous mower navigation of claim 1, wherein the evaluation comprises one or more of a count of correlation minima and/or maxima, a ratio of correlation minima and/or maxima, and a frequency of correlation minima and/or maxima, occurring within an acquisition period.

10. The method for autonomous mower navigation of claim 1, wherein the evaluation comprises one or more of a distribution of correlation minima and/or maxima, and a threshold value of correlation minima and/or maxima, occurring within an acquisition period.

11. The method for autonomous mower navigation of claim 1, wherein the reference data array comprises a discrete time domain representation of a model non-return-to-zero received signal.

12. The method for autonomous mower navigation of claim 1, wherein the reference data array comprises a discrete frequency domain transformation of a discrete time domain representation of a model received signal.

13. The method for autonomous mower navigation of claim 1, wherein the reference data array comprises a discrete filtered frequency domain transformation of a discrete time domain representation of a model received signal.

14. A system for autonomous mower navigation, comprising:

at least one inductive sensor for receiving a return-to-zero encoded signal comprising at least one pseudo-random sequence transmitted over a wire defining a work area, wherein the return-to-zero encoded signal includes a neutral condition between bits, the neutral condition comprising a value halfway between a condition representing a 1 bit and a condition representing a 0 bit;

a processing component in communication with the at least one sensor and for receiving the signal data, wherein the processing component is configured to

i. transform the signal data to a non-return-to-zero phase-shift keyed representation of the signal data, wherein the non-return-to-zero phase-shift keyed representation comprises a binary code in which binary 0'"'"'s are represented by a negative voltage and binary 1'"'"'s are represented by a positive voltage, and wherein the non-return-to-zero phase-shift keyed representation does not include a neutral condition;

ii. digitally sample the non-return-to-zero signal representation in a time domain; and

a filter in communication with the processing component for filtering the sampled signal utilizing a reference data array based on the return-to-zero encoded signal to produce a filter output, wherein the processing component receives the filter output and is configured to determine a location of the autonomous mower relative to the defined work area based on an evaluation of the filter output.

15. The system for autonomous mower navigation of claim 14, comprising a plurality of return-to-zero encoded signals each signal comprising at least one pseudo-random sequence, wherein the pseudo-random sequences comprise a set of sequences having good auto-correlation properties and a low cross-correlation with other sequences in the set.

16. The system for autonomous mower navigation of claim 15, wherein at least one return-to-zero encoded signal is associated with the defined work area, and at least one return-to-zero encoded signal is associated with a guide wire.

17. The system for autonomous mower navigation of claim 14, wherein the pseudo-random sequence comprises at least one of Barker Codes, Gold Codes, Kasami Codes, Walsh Hadamard Codes, and/or similarly derived codes.

18. The system for autonomous mower navigation of claim 14, wherein the filter comprises a time domain matched filter based on the non-return-to-zero representation, and the filter output comprises at least one correlation maxima and/or at least one correlation minima.

19. The system for autonomous mower navigation of claim 18, wherein the at least one correlation maxima and/or at least one correlation minima comprises a single correlation maxima and/or a single correlation minima.

20. The system for autonomous mower navigation of claim 14, wherein the digitally sampled signal is converted from a time domain to a representation in a frequency domain;

and

wherein the filter is configured to calculate a cross-correlation by multiplying the frequency domain representation by the reference data array to obtain a product, and performing an inverse fast Fourier transform on the product to produce at least one correlation maxima and/or at least one correlation minima.

21. The system for autonomous mower navigation of claim 20, wherein the at least one correlation maxima and/or at least one correlation minima comprises a single correlation maxima and/or a single correlation minima.

22. The system for autonomous mower navigation of claim 14, wherein the evaluation comprises one or more of a count of correlation minima and/or maxima, a ratio of correlation minima and/or maxima, and a frequency of correlation minima and/or maxima, occurring within an acquisition period.

23. The system for autonomous mower navigation of claim 14, wherein the evaluation comprises one or more of a distribution of correlation minima and/or maxima, and a threshold value of correlation minima and/or maxima, occurring within an acquisition period.

24. The system for autonomous mower navigation of claim 14, wherein the reference data array comprises a discrete time domain representation of a model non-return-to-zero received signal.

25. The system for autonomous mower navigation of claim 14, wherein the reference data array comprises a discrete frequency domain transformation of a discrete time domain representation of a model received signal.

26. The system for autonomous mower navigation of claim 14, wherein the reference data array comprises a discrete filtered frequency domain transformation of a discrete time domain representation of a model received signal.