Obstacle following sensor scheme for a mobile robot
A robot obstacle detection system including a robot housing which navigates with respect to a surface and a sensor subsystem aimed at the surface for detecting the surface. The sensor subsystem includes an emitter which emits a signal having a field of emission and a photon detector having a field of view which intersects the field of emission at a region. The subsystem detects the presence of an object proximate the mobile robot and determines a value of a signal corresponding to the object. It compares the value to a predetermined value, moves the mobile robot in response to the comparison, and updates the predetermined value upon the occurrence of an event.
1. A method for operating a mobile robot, the method comprising:
detecting the presence of an object proximate the mobile robot by emitting an infrared signal and detecting a reflected infrared signal;
sensing a value of the reflected infrared signal corresponding to the object;
comparing the sensed value to a threshold value corresponding to a detected surface having a threshold level of reflectivity;
moving the mobile robot with respect to the detected object in response to the comparison of the sensed value and the threshold value; and
updating the threshold value upon the occurrence of an event, the event comprising at least one of a physical contact between the mobile robot and the object and when the updated threshold value is less than the non-updated threshold value.
2. The method of claim 1 , wherein updating the threshold value comprises multiplying the threshold value by a constant.
3. The method of claim 2 , wherein the event comprises when the updated threshold value is less than the non-updated threshold value.
4. The method of claim 1 , wherein moving with respect to the detected object comprises moving toward the detected object, when the sensed value is less than the threshold value.
5. The method of claim 1 , wherein moving with respect to the detected object comprises moving away from the detected object, when the sensed value is greater than the threshold value.
6. The method of claim 1 , further comprising conditioning the sensed value of the reflected signal.
7. The method of claim 1 , further comprising executing a first detection at a first distance to the object and executing a second detection at a second distance to the object.
8. The method of claim 1 , further comprises detecting a plurality of reflected signals, averaging the detected signals, and sensing a value of the averaged reflected signal.
9. The method of claim 1 , wherein detecting the presence of an object proximate the mobile robot comprises detecting a reflected signal by a plurality of sensors disposed on the mobile robot in a pattern to accommodate a variation in object reflectivity.
10. The method of claim 1 , further comprising varying power of the emitted signal.
11. The method of claim 1 , further comprising varying sensitivity of at least one sensor emitting the signal.
12. The method of claim 1 , wherein the emitted signal comprises light having at least one of a visible wavelength and an infrared wavelength.
13. The method of claim 1 , wherein the emitted signal comprises an acoustic wave having at least one of an audible frequency and an ultrasonic frequency.
14. The method of claim 1 , wherein detecting the presence of an object proximate the mobile robot comprises:
emitting a directed signal emission; and
detecting the reflected signal emission within a detection field of view;
wherein the directed signal emission and the detection field of view at an angle with respect to each other and have an intersection region occurring at a distance away from the robot.
15. The method of claim 1 , wherein the sensed value corresponds to at least one of a distance to the object and an albedo of the object.
16. A method for operating a mobile robot, the method comprising the mobile robot:
detecting a transition between a reflection state and a non-reflection state of an emitted infrared signal for determining the presence and absence of an object proximate the mobile robot, respectively;
sensing a value of the reflected infrared signal corresponding to the object;
comparing the sensed value to a threshold value corresponding to a detected surface having a threshold level of reflectivity;
in response to the comparison of the sensed value and the threshold value, causing the robot to move a travel distance in a first direction with respect to the detected object and to rotate in a second direction about a fixed point; and
updating the threshold value upon the occurrence of an event, the event comprising at least one of a physical contact between the mobile robot and the object and when the updated threshold value is less than the non-updated threshold value.
17. The method of claim 16 , wherein the travel distance moved by the mobile robot relates at least in part to an offset distance from a sensor located on the robot to a robot wheel axis.
18. The method of claim 16 , wherein the first direction is defined at least in part by a direction of motion of the robot prior to detecting the absence of the object.
19. The method of claim 16 , wherein the fixed point comprises a point between a first wheel of the robot and the object.
20. The method of claim 16 , further comprising ceasing rotation upon detecting a presence of an object.
21. The method of claim 16 , further comprising ceasing rotation upon contacting an object.
22. The method of claim 16 , further comprising moving in a third direction.