Lawn care robot
View Patent ↗A robot lawnmower includes a body and a drive system carried by the body and configured to maneuver the robot across a lawn. The robot also includes a grass cutter and a swath edge detector, both carried by the body. The swath edge detector is configured to detect a swath edge between cut and uncut grass while the drive system maneuvers the robot across the lawn while following a detected swath edge. The swath edge detector includes a calibrator that monitors uncut grass for calibration of the swath edge detector. In some examples, the calibrator comprises a second swath edge detector.
1. A robot lawnmower swath edge detector system comprising:
a controller carried by a body of a robot; and
a grass length sensor carried by the body of the robot and in communication with the controller, the grass length sensor comprising:
a sensor housing defining a cavity and a cavity opening directly downward configured to allow grass entry into the cavity while inhibiting direct sunlight into the cavity;
an emitter carried by the housing in the cavity and configured to emit an emission across the cavity opening; and
a receiver carried by the housing and configured to receive a grass-reflected emission, the receiver positioned in the cavity in a position where the housing blocks direct sunlight and the receiver positioned in the cavity on substantially the same side of the housing as the emitter in a location relative to the emitter such that the receiver receives emissions reflected from grass penetrating into the cavity;
wherein the controller compares outputs from multiple ones of the grass length sensors to determine a swath edge location.
2. The robot lawnmower swath edge detector system of claim 1 wherein the grass length sensor comprises a plurality of grass length sensors spans a distance comprising at least a steering error distance and a grass length sensor width.
3. The robot lawnmower swath edge detector system of claim 2 wherein the grass length sensors are substantially equally spaced apart.
4. The robot lawnmower swath edge detector system of claim 2 wherein the grass length sensors are separated by dividers.
5. The robot lawnmower swath edge detector system of claim 2 wherein the controller compares outputs from multiple ones of the grass length sensors to provide a calibration.
6. The robot lawnmower swath edge detector system of claim 2 wherein the grass length sensors acquire a grass height estimate.
7. The robot lawnmower swath edge detector system of claim 1 wherein the grass length sensor comprises a plurality of grass length sensors spans a distance of between about 4 and about 10 inches.
8. The robot lawnmower swath edge detector system of claim 1 wherein the grass length sensor comprises a plurality of grass length sensors spanning a distance of a width of the body of the robot.
9. The robot lawnmower swath edge detector system of claim 1 wherein the grass length sensor comprises plurality of grass length sensors spanning a distance of a portion of the width of the robot body.
10. The robot lawnmower swath edge detector system of claim 1 wherein the cavity is colored a light-absorbing color.
11. The robot lawnmower swath edge detector system of claim 10 wherein the cavity is colored black.
12. The robot lawnmower swath edge detector system of claim 1 wherein the sensor housing is configured to deflect uncut grass.
13. The robot lawnmower swath edge detector system of claim 12 wherein the sensor housing is configured to allow deflected uncut grass to self-straighten upward through the cavity opening and into the cavity.
14. The robot lawnmower swath edge detector system of claim 1 wherein the sensor housing is mounted to the body of the robot at a height relative to a ground surface that minimizes entrance of cut grass into the cavity.
15. The robot lawnmower swath edge detector system of claim 1 wherein the emitter includes a visible light emitter.
16. The robot lawnmower swath edge detector system of claim 1 wherein the receiver includes a visible light receiver.
17. The robot lawnmower swath edge detector system of claim 1 wherein the receiver is positioned below the emitter.
18. The robot lawnmower swath edge detector system of claim 1 wherein the receiver is positioned within the cavity so as to not receive any direct sunlight.
19. The robot lawnmower swath edge detector system of claim 1 wherein the receiver has a defined field of view that intersects a field of emission of the emitter.
20. The robot lawnmower swath edge detector system of claim 1 wherein the emitter and receiver are positioned within the cavity at a height such that grass below a specific height does not reflect grass-reflected emissions back to the receiver.