A Robotic Work Tool and a Method for Use in a Robotic Work Tool Comprising a Lift and Collision Detection

Abstract

A robotic work tool (100) comprising a chassis (110), a body (120) and a controller (400) for controlling operation of the robotic work tool (100) and at least one three-dimensional sensor arrangement (200) for detecting relative movement of the body (100) and the chassis (110), wherein the sensor arrangement (200) comprises a sensor element (210) arranged in one of the body (120) and the chassis (110) and a detection element (220) arranged in the other of the body (120) and the chassis (110), wherein the controller (400) is configured to: receive sensor input indicating relative movement of the sensor element (210) and the detection element (220) and; determine, from the sensor input, whether a collision or a lift has been detected.

1 . A robotic work tool comprising a chassis, a body and a controller for controlling operation of the robotic work tool and at least one three-dimensional sensor arrangement for detecting relative movement of the body and the chassis, wherein the sensor arrangement comprises a sensor element arranged in one of the body and the chassis and a detection element arranged in the other of the body and the chassis, wherein the controller is configured to:
 receive sensor input indicating relative movement of the sensor element and the detection element; and 
 determine, from the sensor input, whether a collision or a lift has been detected. 
 
     
     
         2 . The robotic work tool according to  claim 1 , wherein said sensor element is configured to sense the position of the detection element in three dimensions. 
     
     
         3 . The robotic work tool according to  claim 1 , wherein the detection element is a magnet and the sensor element is a three-dimensional sensor configured to detect magnetic field in a plane and in a direction, which is normal to the plane. 
     
     
         4 . The robotic work tool according to  claim 1 , wherein the detection element is a magnet and the sensor element is configured to detect the magnitude and direction in three-dimensional space of the magnetic field of the magnet, and wherein the sensor element comprises a Hall sensor. 
     
     
         5 . (canceled) 
     
     
         6 . The robotic work tool according to  claim 2 , wherein the sensor element is configured as an integrated unit encapsulated in a single integrated circuit package. 
     
     
         7 . The robotic work tool according to  claim 1 , wherein the three-dimensional sensor arrangement is positioned, as seen from above, at a distance from a geometrical center of the robotic work tool. 
     
     
         8 . The robotic work tool according to  claim 1 , wherein the controller is configured to receive sensor input indicating lateral movement of the sensor element and the detection element relative each other, and in response thereto, determine that the collision has been detected. 
     
     
         9 . The robotic work tool according to  claim 1 , wherein said at least one three-dimensional sensor arrangement comprises a first and a second three-dimensional sensor arrangement, each of said first and second three-dimensional sensor arrangements comprising a respective sensor element arranged in one of the body and the chassis and a respective detection element arranged in the other of the body and the chassis. 
     
     
         10 . The robotic work tool according to  claim 1 , wherein the controller is configured to determine, from the sensor input, the direction of the collision. 
     
     
         11 . The robotic work tool according to  claim 1 , wherein the controller is configured to receive sensor input indicating vertical movement of a sensor element and the detection element relative each other, and in response thereto, determine that the lift has been detected. 
     
     
         12 . The robotic work tool according to  claim 1 , wherein the controller is configured to receive sensor input indicating lateral and vertical movement of the sensor element and the detection element relative each other and, in response thereto, determine whether collision or lift has been detected by comparing the sensor input with a threshold value. 
     
     
         13 . The robotic work tool according to  claim 1 , comprising at least one suspension device for movably supporting the body on the chassis, the suspension device comprising an elongate, rigid support member having a first end that is supported on the chassis and a second end that supports the body, wherein the elongate support member is extendable and pivotal such that the body is movable laterally and vertically relative to the chassis. 
     
     
         14 . The robotic work tool according to  claim 13 , wherein the first end of the elongate support member is configured to be pivotally supported on the chassis and the second end of the elongate support member is joined to the body. 
     
     
         15 . The robotic work tool according to  claim 13 , wherein the elongate support member comprises a base member and a lift member, respectively configured such that at least a portion of one of the base member and the lift member is slidably receivable in the other of the base member and the lift member, so that the elongate support member is telescopically extendable. 
     
     
         16 . The robotic work tool according to  claim 15 , wherein the elongate support member comprises a first biasing element arranged to bias the lift member towards the base member. 
     
     
         17 . The robotic work tool according to  claim 16 , wherein the base member comprises an elongate guide opening and wherein the first biasing element is arranged in the base member and comprises a guide element that extends through the elongate guide opening and is attached to the lift member. 
     
     
         18 . The robotic work tool according to  claim 13 , wherein the suspension device comprises a second biasing element arranged to bias the elongate support member from a pivoted position to an upright position, or wherein the three-dimensional sensor arrangement and the at least one suspension device are arranged laterally separated from each other. 
     
     
         19 . (canceled) 
     
     
         20 . The robotic work tool according to  claim 13 , comprising at least a first and a second suspension device, wherein a number of the suspension devices is greater than a number of the three-dimensional sensor arrangements. 
     
     
         21 . (canceled) 
     
     
         22 . The robotic work tool according to  claim 13 , comprising at least a first and a second suspension device and wherein a three dimensional sensor arrangement is arranged between the first and the second suspension devices, and wherein the robotic work tool comprises a robotic lawnmower. 
     
     
         23 . (canceled) 
     
     
         24 . A method for use in a robotic work tool comprising a chassis; a body; a controller for controlling operation of the robotic work tool and at least one three-dimensional sensor arrangement for detecting relative movement of the body and the chassis, wherein the sensor arrangement comprises a sensor element arranged in one of the body and the chassis and a detection element arranged in the other of the body and the chassis, the method comprising:
 receiving sensor input indicating relative movement of the sensor element and the detection element; and   determining, from the sensor input, that a collision or a lift has been detected.