Autonomous mower navigation system and method

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 l'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; and

determining a location of the autonomous mower relative to a defined work area based on an evaluation of the digitally sampled non-return-to-zero signal representation.

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 , comprising

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

wherein the evaluation of the digitally sampled non-return-to-zero signal representation includes an evaluation of the filter output.

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

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

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

filtering the sampled signal comprising computing a cross-correlation by multiplying the frequency domain representation by a reference data array based on the return-to-zero encoded signal 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.

6. The method for autonomous mower navigation of claim 5 , wherein the reference data array comprises a discrete time domain representation of a model non-return-to-zero received signal.

7. The method for autonomous mower navigation of claim 5 , wherein the reference data array comprises a discrete frequency domain transformation of a discrete time domain representation of a model received signal.

8. The method for autonomous mower navigation of claim 1 , comprising filtering the digitally sampled signal 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.

9. The method for autonomous mower navigation of claim 1 , wherein the evaluation of the digitally sampled non-return-to-zero signal representation 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 of the digitally sampled non-return-to-zero signal representation 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. 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 l'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;

wherein the processing component is configured to receive the digitally sampled non-return-to-zero signal representation and to determine a location of the autonomous mower relative to the defined work area based on an evaluation of digitally sampled non-return-to-zero signal representation.

12. The system for autonomous mower navigation of claim 11 , 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.

13. The system for autonomous mower navigation of claim 11 , 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.

14. The system for autonomous mower navigation of claim 11 , comprising a filter in communication with the processing component configured to filter 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 is configured to receive the filter output.

15. 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.

16. 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.

17. 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.

18. 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.

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 18 , wherein the evaluation comprises one or more of a count of correlation minima and/or maxima, a ratio of correlation minima and/or maxima, a distribution of correlation minima and/or maxima, a threshold value of correlation minima and/or maxima, and a frequency of correlation minima and/or maxima occurring within an acquisition period.