Operation for a robotic work tool

1 . A robotic work tool system comprising a robotic work tool arranged to operate in an operational area wherein the robotic work tool comprises an obstacle sensor and a controller configured to:

receive sensor input from the obstacle sensor,

detect an obstacle and determine a dimension of the obstacle,

determine whether the dimension exceeds a threshold size large enough to obstruct a view of a human on an opposite side of the obstacle relative to the robotic work tool, and if so

circumvent the obstacle while maintaining a safety distance to the obstacle such that the robotic work tool does not approach the obstacle at a distance shorter than the safety distance prior to a view of the opposite side of the obstacle being obtained by the robotic work tool,

determine whether the human is behind the obstacle, and

take evasive action in response to determining the human is behind the obstacle and operate in an area in which the view is obtained in response to determining the human is not behind the obstacle.

2 . The robotic work tool system according to claim 1 , wherein the controller is further configured to determine that there is no human behind the obstacle and if so continue operating.

3 . The robotic work tool system according to claim 1 , wherein the controller is further configured to determine whether there is an animal behind the obstacle.

4 . The robotic work tool system according to claim 1 , wherein the robotic work tool is configured to maintain the safety distance to the obstacle by maintaining the safety distance to an edge of the obstacle.

5 . The robotic work tool system according to claim 1 , wherein the robotic work tool is configured to determine that the dimension of the obstacle exceeds a second threshold and in response thereto approach the obstacle at distances shorter than the safety distance but maintain the safety distance to an edge of the obstacle.

6 . The robotic work tool system according to claim 1 , wherein the robotic work tool is configured to circumvent the obstacle as part of planned operation, by a movement to a side of the robotic work tool, following a contour of the obstacle, or by circling the obstacle.

7 . The robotic work tool system according to claim 1 , wherein the evasive action includes moving back to a side from which the obstacle was approached and continue operating on the side from which the obstacle was approached.

8 . The robotic work tool system according to claim 1 , wherein evasive action includes stopping and deactivating a work tool, stopping until it is detected that the human is no longer detectable, or operating in another part of the operational area and return at a later time.

9 . The robotic work tool system according to claim 8 , wherein the robotic work tool is configured to stop for a predetermined time.

10 . The robotic work tool system according to claim 1 , wherein the obstacle sensor includes an image sensor and wherein the controller is configured to detect the obstacle by the controller performing image analysis on a captured image.

11 . The robotic work tool system according to claim 1 , wherein the obstacle sensor includes a radar sensor or a laser sensor and wherein the controller is configured to detect the obstacle by the controller performing analysis on received radar data or laser data.

12 . The robotic work tool system according to claim 1 , wherein the obstacle sensor is comprised in a satellite navigation sensor and/or a deduced reckoning sensor, wherein the controller is configured to detect the obstacle by the controller comparing a determined position for the robotic work tool to a map application in which the location and dimensions of obstacles are stored.

13 . The robotic work tool system according to claim 1 , wherein the safety distance depends on the width of the obstacle.

14 . The robotic work tool system according to claim 1 , wherein the safety distance depends on the size of the robotic work tool or on a size of a work tool of the robotic work tool.

15 . The robotic work tool system according to claim 1 , wherein the safety distance depends on the speed of the robotic work tool.

16 . The robotic work tool system according to claim 1 , wherein the safety distance depends on the rotational speed of a work tool of the robotic work tool.

17 . The robotic work tool system according to claim 1 , wherein the safety distance is in a range between 10-20 meters.

18 . The robotic work tool system according to claim 1 , wherein the robotic work tool is a robotic lawnmower.

19 . A method for use in a robotic work tool system comprising a robotic work tool arranged to operate in an operational area, wherein the method comprises:

receiving sensor input from the obstacle sensor,

detecting an obstacle and determine a dimension of the obstacle,

determining whether the dimension exceeds a threshold size large enough to obstruct a view of a human on an opposite side of the obstacle relative to the robotic work tool, and if so

circumventing the obstacle while maintaining a safety distance to the obstacle such that the robotic work tool does not approach the obstacle at a distance shorter than the safety distance prior to a view of the opposite side of the obstacle is being obtained by the robotic work tool,

determining whether the human is behind the obstacle, and

taking evasive action in response to determining the human is behind the obstacle and operate in an area in which the view is obtained in response to determining the human is not behind the obstacle.

20 . A non-transitory computer-readable medium carrying computer instructions that when loaded into and executed by a controller of a robotic work tool enables the robotic work tool to implement the method according to claim 19 .