Automatic lawn mower

• US 4,133,404 A
• Filed: 08/25/1976
• Issued: 01/09/1979
• Est. Priority Date: 04/25/1975
• Status: Expired due to Term

• Current Assignee: Agile Systems Inc. (Allient, Inc.)
• Original Assignee: Agile Systems Inc. (Allient, Inc.)
• Inventors: Griffin, Hugh A.
• Primary Examiner(s): Pekar, John A.
• Application Number:
  US05/717,870
• Time in Patent Office: 867 Days
• Field of Search: 56/10.2, 56/1, 56/4, 180/79.1, 180/98, 180/79, 180/131, 250/202
• US Class Current: 180/169
• CPC Class Codes: A01D 2101/00 Lawn-mowers
• CPC Class Codes: A01D 34/008 for automated or remotely controlled operation
• CPC Class Codes: B62D 1/28 non-mechanical , e.g. following a line or other known markers
• CPC Class Codes: G05D 1/0231 using optical position detecting means position-fixing by using electromagnetic waves other than radio waves, e.g. optical position detecting means G01S5/16
• CPC Class Codes: G05D 1/0242 using non-visible light signals, e.g. IR or UV signals

Abstract

An automatic lawn mower operable to cut about the periphery of a lawn, moving inwardly, and automatically shutting off at the conclusion of the cutting operation. A cut border is placed about the periphery of the lawn to be mowed and also about any obstacles within the area. The mower utilizes an array of light sensitive resistors and a columnized light source to detect the transition between cut and uncut grass in order to track in an irregularly shaped spiral to the center of the lawn. A portion of the sensor system provides for proper guidance of the mower around the cut perimeter of any obstacles in the cutting area. The mower may utilize an array of light sensitive resistors, a columnized light source and actuated light reflectors to detect the transition between cut and uncut grass in order to track in an irregularly shaped spiral to the center of the lawn.

Claims

1. Guidance apparatus for a self-propelled mower comprising:

first sensor means, including several photosensitive receptors and light source means for directing light towards said receptors, for producing output signals associated with each said receptor dependent upon the light received by each said receptor;

first comparator means for comparing predetermined combinations of said output signals and for producing comparator output signals dependent upon said comparisons; and

control means for producing guidance signals for a self-propelled mowing apparatus in response to the content of said comparator output signals, said photosensitive receptors being in an array whose principal dimension is essentially transverse to the normal direction of travel of the mower, the path of light from said light source means to said receptors being such that the presence of a substance to be mowed in the vicinity of one of said receptors affects the amount of light received by said receptor, said control means and said first comparator means including means responsive to said several receptors for detecting a boundary between mowed and unmowed vegetation.

2. The apparatus of claim 1 in which the light source of the sensor means comprises a plurality of columnized light compartments and each photosensitive receptor is in a corresponding compartment.

3. The apparatus of claim 2 in which the photosensitive receptors are photosensitive resistors.

4. The apparatus of claim 1 in which the sensor means includes a first sensor assembly and a second sensor assembly, each said assembly comprising a plurality of photosensitive receptors and light source means for directing light toward said receptors.

5. The apparatus of claim 4 in which the control means includes logic circuit means for producing guidance signals for the mowing apparatus in response to comparator output signals associated with the first sensor assembly of the sensor means and for establishing a priority over comparator output signals from outputs associated with the second sensor assembly.

6. The apparatus of claim 5 in which the control means further includes means for responding to signals associated with the first sensor assembly when said signals indicate a transition between mowed and unmowed substance between the receptors and light source means of the first sensor assembly, and for otherwise responding to the signals associated with the second sensor assembly.

7. The apparatus of claim 1 in which the comparator means includes means for sequentially comparing predetermined pairs of sensor means outputs.

8. The apparatus of claim 1 in which said control means includes means for producing signals representing the position beneath and array of the existence of and the location of the boundary between the mowed and unmowed areas.

9. The apparatus of claim 8 in which said transverse array includes more than ten photosensitive receptors.

10. The apparatus of claim 8 in which the sensor means includes a first sensor assembly and a second sensor assembly, each said assembly comprising a plurality of photosensitive receptors and light source means for directing light toward said receptors.

11. The apparatus of claim 1 in which said light source means and said receptors are contained in a dust protective enclosure having a non-glare window allowing light to traverse out of and reflect back through the window to said receptors.

12. The apparatus of claim 11 in which said light source means is operable to emit light through a first light polarizer, said light being directed at said non-glare window at the Brewster angle for the window material resulting in attenuation of the reflected portion of said light by orthogonally polarizing it from the direction of said first light polarizer, said window transmitting the remaining portion of said light.

13. The apparatus of claim 11 in which the extent of light reflected back through said window to said receptors is determined by several light reflective elements, said elements positioned to be deflected to an extent dependent upon the height of vegetation in the vicinity of said elements, deflection of said elements resulting in a change of light reflected back through the window.

14. The apparatus of claim 1 in which said photosensitive receptors are in a linear array, there being at least six photosensitive receptors in the array and in which said comparator means compares receptors spaced apart from one another by at least two spaces.

15. The apparatus of claim 1 which further comprises:

second sensor means, including several second photosensitive receptors and second light source means for directing light toward said second receptors, for producing second output signals associated with each of said second receptors; and

second comparator means including means for producing second comparisons of predetermined combinations of said second output signals and for producing second comparator output signals dependent upon said second comparisons, and in which said control means includes means for giving

(1) first priority to said first sensor means and first comparator means when a mowed-unmowed substance interface is detected by said first sensor means and first comparator means,

(2) second priority to the second sensor means and second somparator means when a mowed-unmowed substance interface is detected by said second sensor means and second comparator means, and

(3) third priority to a preprogrammed control routine.

16. The apparatus of claim 1 in which said comparator means includes means for producing output signals which are indicative of the presence of a mowed-unmowed substance interface between two of said receptors spaced apart from one another and in which said control means also includes means for producing guidance signals based upon a plurality of said interface comparator output signal indications from a preselected number of said comparator output signals.

17. The apparatus of claim 1 which includes means for making the comparator means unresponsive to a false indication from an error output condition of one of said receptors.

18. Guidance apparatus for a self-propelled mower comprising:

first sensor means for detecting a differential of vegetation height of a first boundary of a mowing area;

second sensor means for detecting a differential of vegetation height at a second boundary of a mowing area; and

control means for producing guidance signals for a self-propelled mower suitable for use in tracking either said first or second boundary in response to detection of a differential of vegetation height by said second sensor means when said first sensor means does not detect a boundary but said second sensor means does detect a boundary and by said first sensor means when said first sensor means does detect a boundary.

19. The apparatus of claim 18 wherein said first sensor means and said second sensor means include several photosensitive receptors and light source means for directing light toward said receptors for producing output signals associated with each said receptor dependent upon light received by each said receptor.

20. Guidance apparatus for a self-propelled mower comprising:

first sensor means positioned to the side of the mower in its normal direction of travel nearest the outer boundary of a mowing area;

second sensor means positioned to the side of the mower in its normal direction of travel farthest from the outer boundary of a mowing area;

multiple detector means within each of said first and second sensor means, said detector means including detectors positioned to monitor an assigned area of vegetation within its path, said detectors positioned in an array whose principal sensing dimension is essentially transverse to the normal direction of travel of the mower, each of said detectors including means for producing a detector output signal dependant upon the vegetation height within its path;

comparator means for producing comparisons of predetermined combinations of said detector output signals and for producing comparator output signals dependent upon said comparisons, said comparator means coupled to said first and second sensor means;

processing means for converting comparator output signals to control signals, said processing means coupled to said first and second sensor means, said processing means including means for providing a status indication signal of the presence of a vegetation height differential within the monitored areas of the detectors within an array, said processing means also including means for providing a location indication signal dependent upon the location of transition of vegetation heights within the monitored areas of said detectors; and

control means for producing guidance signals for a self-propelled mower from the status indication signal and the location indication signal of said processing means.

22. Guidance apparatus for a self-propelled vehicle comprising:

sensor means including a plurality of switches in an array whose principal dimension is essentially transverse to the normal direction of travel of the vehicle, said sensor means operable to produce output signals associated with each switch dependent upon the closed or open status of said switch;

a plurality of actuator means each for controlling the closed or open status of one of said plurality of switches dependent upon the height of vegetation within its path;

comparator means operable to produce comparisons of predetermined combinations of said output signals and for producing comparator output signals dependant upon said comparisons; and

control means operable to produce guidance signals for a self-propelled vehicle in response to the content of said comparator output signals.

21. The apparatus of claim 22 wherein:

said processing means includes means for producing a status indication signal and a location indication signal for each of said first sensor means and said second sensor means; and

said control means includes means for giving priority of control to the status indication signal and the location indication signal of the first sensor means over the like signals of the second sensor means.

23. The apparatus of claim 22 in which said comparator means includes a scanner for sequentially sampling output signals of said comparator means.

24. The apparatus of claim 22 wherein said comparator means includes means for making the comparator means unresponsive to a false indication from an error output condition of one of said detectors.

25. The apparatus of claim 22 wherein said plurality of switches are of a light sensing type and said plurality of actuator means are movable and have a reflective surface positionable to control light reaching said switches.

26. The apparatus of claim 22 in which the sensor means includes a first sensor assembly and a second sensor assembly, each assembly comprising a plurality of switches in an array whose principal dimension is essentially transverse to the normal direction of travel of the vehicle, said comparator means includes a first comparator means for processing output signals from said first sensor assembly and a second comparator means for processing output signals from said second sensor assembly, each of said first and second comparator means producing output signals.

27. The apparatus of claim 26 in which said control means includes means for establishing priority for said first comparator means over said second comparator means.

28. Guidance apparatus for a self-propelled mower comprising:

sensor means, including several detectors positioned in an array whose principal sensing dimension is essentially transverse to the normal direction of travel of the mower, each of said detectors positioned to monitor an assigned area of vegetation within its path, each of said detectors producing a detector output signal dependent upon the vegetation height within its path;

comparator means operable to produce comparisons of predetermined combinations of said detector output signals and for producing comparator output signals dependent upon said comparisons;

processing means for converting comparator output signals to control signals, said processing means providing a status indication signal of the presence of a vegetation height differential within the monitored areas of the detectors within the array, said processing means also providing a location indication signal dependent upon the location of transition of vegetation heights within the monitored areas of the detectors;

control means for producing guidance signals for a self-propelled mower from the status indication signal and the location indication signal of the processing means.

29. The apparatus of claim 28 in which said comparator means includes a scanner for sequentially sampling output signals of said comparator means.

30. The apparatus of claim 28 wherein said comparator means includes means for making the comparator means unresponsive to a false indication from an error output condition of one of said detectors.