Robotic lawnmower

A lift detection arrangement (100, 200) in a robotic lawnmower for detecting a lift of a body (110, 210) relative a chassis (105, 205) of the robotic lawnmower is provided. The lift detection arrangement (100, 200) comprises a connection between the chassis (105, 205) and the body (110, 220). The connection comprises a joystick element (115, 215) 5 arranged to allow a displacement of the body (1110, 210) relative the chassis (105, 205) in a collision plane during a collision, and a lift element (120, 220) arranged to provide a flexibility between the chassis (105, 205) and the body (110, 210) in a lift direction during the lift. The lift detection arrangement (100, 200) further comprises a lift sensor configured to detect a displacement over a predetermined threshold of the lift element (120, 220) 10 during the lift by detecting a change in spacing between two sensor parts (125, 126, 225, 226). One of the two sensor parts (125, 126, 225, 226) is arranged on the lift element and the two sensor parts (125, 126, 225, 226) are arranged to be relatively displaceable only in the lift direction.

TECHNICAL FIELD

Embodiments herein relate to a lift detection arrangement in a robotic lawnmower. In particular, embodiments herein relate to a lift detection arrangement for detecting a lift of a body of the robotic lawnmower relative a chassis of the robotic lawnmower.

BACKGROUND

A robotic lawnmower is a device configured to autonomously move across a lawn to cut grass by means of a rotating cutting blade. The robotic lawnmower comprises a chassis to which ground engaging wheels and the cutting blade are attached. The robotic lawnmower further comprises a body arranged above the chassis. A function of the body is to prevent people from being injured by the cutting blade, as well as to protect the chassis and cutting blade from rain, dirt and clippings which may cause clogging and malfunction of the robotic lawnmower.

The body may be flexibly attached relative the body in the travelling plane or collision plane, such that a relative displacement of the body relative the chassis is possible if the body collides with an obstacle. This is to enable the robotic lawnmower to detect the obstacle and move away from it.

For this purpose, the connection between the body and the chassis may be arranged to allow relative movement between the body and the chassis in the collision plane, i.e. in a plane essentially parallel to the lawn that is being cut.

A further feature of the robotic lawnmower is an arrangement for lift detection.

This is important for protecting people from being injured by the cutting blade when the robotic lawnmower is lifted during operation, and lift detection arrangements are therefore usually arranged to automatically stop rotation of the cutting blade when a lift is detected.

By having a lift detection arrangement for detecting a lift of the body relative the chassis, it is possible to quickly stop rotation of the cutting blade. Such detection requires a connection of the body to the chassis which allows flexibility in a lift direction.

A problem is that it is difficult to distinguish a lift from a collision, since both lifts and collisions cause the body to flex relative the chassis.

This may cause false lift detections and unnecessary stops of the robotic lawnmower.

SUMMARY

In view of the discussion above, it is an object for embodiments herein to provide an improved lift detection arrangement in a robotic lawnmower.

According to a first aspect, the object is achieved by a lift detection arrangement in a robotic lawnmower for detecting a lift of a body of the robotic lawnmower relative a chassis of the robotic lawnmower. The lift detection arrangement comprises a connection between the chassis and the body. The connection comprises a joystick element and a lift element. The joystick element is arranged to allow a displacement of the body relative the chassis in a collision plane during a collision of the robotic lawnmower. The lift element is arranged to provide flexibility between the chassis and the body in a lift direction during the lift. The lift detection arrangement further comprises a lift sensor. The lift sensor is configured to detect a displacement over a predetermined threshold of the lift element during the lift by detecting a change in spacing between two sensor parts. One of the two sensor parts is arranged on the lift element and the two sensor parts are arranged to be relatively displaceable only in the lift direction.

Thanks to the two sensor parts being arranged to be relatively displaceable only in the lift direction, false lift detections during collisions can be avoided while the lift detection arrangement still allows for flexibility in the collision plane.

This provides an improved lift detection arrangement.

According to some embodiments herein, the lift element is a sliding member which is slidingly arranged relative the joystick element in the lift direction to provide the flexibility during the lift. In such embodiments, one of the two sensor parts may then be arranged on the joystick element and the other one of the two sensor parts may be arranged on the sliding member.

By slidingly arranged relative the joystick element in the lift direction it is understood that the sliding member is interconnected with the joystick element in such a way that it may slide, or move transversally, along the joystick element in the lift direction. Thereby the sliding member provides flexibility in the connection between the chassis and the body in the lift direction.

Thanks to one of the two sensor parts being arranged on the lift element and the other sensor part being arranged on the joystick member, the sensor parts are only movable relative each other in the lift direction, thereby preventing false lift detections during collisions.

The sliding member may be telescopically extendable from the joystick element in the lift direction.

This may facilitate the arrangement of the sensor parts on the sliding member and on the joystick member.

The two sensor parts may be arranged on respective downwardly protruding end portions of the joystick element and the lift element, which are arranged at a distance from a pivot connection between the joystick element and the chassis.

The two sensor parts may also be arranged on respective upwardly protruding end portions of the joystick element and the lift element, which are arranged at a distance from a pivot connection between the joystick element and the chassis.

This may facilitate assembly of the sensor parts and prevent unnecessary ware due to pivotations during collisions.

According to some embodiments herein, the lift element is a link arm supporting the joystick element, which link arm is rotatably connected to the chassis to provide the flexibility during the lift by being rotatable in the lift direction. In such embodiments, one of the two sensor parts may be arranged on the chassis and the other sensor part may be arranged on arranged on the link arm.

The link arm may then further be arranged to rest on a support extending from the chassis when it is not lifted.

According to some embodiments herein one of the two sensor parts is a Hall Effect sensor and the other one of the two sensor parts is a magnet.

According to some embodiments herein the magnet is arranged on the lift element. This may be advantageous since wires associated with the Hall Effect sensor can be kept shorter if the Hall Effect sensor is not arranged on the lift element because the Hall Effect sensor does not then move in the lift direction during the lift.

According to some embodiments herein the joystick element is arranged to be held in a neutral position relative the chassis by means of a spring element.

According to some embodiments herein the connection is a front suspension of the robotic lawnmower.

DETAILED DESCRIPTION

FIG. 1Adepicts, schematically and by way of example, a side view of a lift detection arrangement100in a robotic lawnmower according to some embodiments herein. The lift detection arrangement100comprises a connection between a chassis105, of which only an attachment portion is shown in theFIG. 1A, and a body110of the robotic lawnmower. The connection comprises a joystick element115. The joystick element115is pivotably attached to the chassis105, by means of a pivot connection140, to be pivotable in a collision plane relative the chassis105. This is to allow flexibility to the body110relative the chassis105during a collision. The collision plane may be essentially parallel to the travelling plane of the robotic lawnmower. It is to be understood that the part of the chassis105that is illustrated in theFIG. 1may form an integrated part of the chassis105or be a separate part for fixing the joystick element to the chassis105.

The connection further comprises a lift element120, which in the illustrated embodiment inFIG. 1is a sliding member120which is arranged to be slideable, i.e. transversally displaced, relative the joystick element115in a lift direction during a lift of the body110. The sliding member120hence provides flexibility between the body110and the chassis105during a lift. The sliding member120is in the illustrated example telescopically extendable from the joystick member. The sliding member120is at a top portion thereof attached to the body110.

The lift detection arrangement100further comprises a lift sensor. The lift sensor comprises two sensor parts125,126. The lift sensor is configured to detect a displacement over a predetermined threshold of the lift element120during the lift by detecting a change in spacing between the two sensor parts125,126. One of the two sensor parts, the sensor part125in this example, is arranged on the sliding member120and the other sensor part, the sensor part126, is in this example arranged on the joystick member115. The two sensor parts125,126are hence arranged to be relatively displaceable only in the lift direction since the sliding member120is only displaceable relative the joystick member115in the lift direction. TheFIG. 1Aillustrates the lift detection arrangement100in a neutral position, when there is no lift and no collision. Then, the sensor parts125,126are arranged to be situates essentially opposite each other such that the spacing between them is as small as possible. The two sensor parts125,126may be for example a Hall Effect sensor and a magnet.

If the two sensor elements are placed tight together, a Hall Effect sensor and a magnet can be used, while keeping the total travel of the lift member small. It also makes it possible to remove the magnet and replace the Hall Effect sensor with a micro switch, where the micro switch is actuated by the lift member.

FIG. 1Billustrates, in a side view, how the lift detection arrangement100as described in relation toFIG. 1Aoperates during a lift. During the lift, the body110is lifted relative the chassis110thanks to the lift element120, i.e. the sliding member120in this example being attached to the body110and slidable attached to the joystick member115which in turn is attached to the chassis105. As the sliding member120is displaced in the lift direction during the lift, sliding along the joystick member115, there is a change in the spacing between the two sensor parts125,126. As the sensor part125in this example, slides upward with the sliding member120, it is displaced relative the other sensor part126. When the displacement is over a certain predetermined threshold, as small as possible, for example 5-10 mm, the lift sensor detects the displacement and determines that there is a lift. In response to the lift detection, the lift sensor may trigger a stop of the robotic lawnmower. This may be done by the lift sensor sending a trigger signal to a not shown control device handling the operation of the robotic lawnmower. It is to be understood, that “sliding” is not limiting, and that the “sliding” movement between the joystick member115and the sliding member120may be any translational movement in the lift direction, provided for by various ways.

FIG. 1Cillustrates, in a side view, how the lift detection arrangement100as described in relation toFIGS. 1A and 1Boperates during a collision of the robotic lawnmower. During the collision, the body110is displaced relative the chassis105thanks to the pivotal connection140between the joystick element115and the chassis105, which allows pivotation of the joystick element115relative the chassis105in the collision plane.

Further, the sliding member120, on which one sensor part125is arranged, pivotates along with the joystick member115on which the other sensor part126is arranged. Hence, thanks to the two sensor parts125,126being arranged such that they are only displaceable in the lift direction, the collision do not cause a change in the spacing between the two sensor parts125,126, and false lift detection by the lift sensor can be avoided.

According to some embodiments herein, as previously mentioned, one of the two sensor parts125,126is a Hall Effect sensor and the other one of the two sensor parts125,126is a magnet. As also previously mentioned, the magnet may then be arranged on the lift element, i.e. the sliding member120in this example.

This may be advantageous since wires associated with the Hall effect sensor can be kept shorter if the Hall effect sensor is not arranged on the lift element120because the Hall effect sensor does not then move in the lift direction during the lift.

According to some embodiments herein the joystick element115is arranged to be held in a neutral position relative the chassis105by means of not shown a spring element.

According to some embodiments herein the connection is a front suspension of the robotic lawnmower. This may be advantageous for example if one or more rear suspensions are used which have the same, or a similar, joystick elements as the joystick element115, such that all suspensions provide a stable and desired neutral position during operation of the robotic lawnmower.

FIG. 2Adepicts, schematically and by way of example, a side view of a lift detection arrangement200in a robotic lawnmower according to some embodiments herein. The lift detection arrangement200comprises a connection between a chassis205, of which only an attachment portion is shown in the figure, and a body210of the robotic lawnmower. The connection comprises a joystick element215. The joystick element215is pivotably attached to the chassis205, by means of a pivot connection240to the supporting link arm220, to be pivotable in a collision plane relative chassis205. This allows flexibility to the body210relative the chassis205during a collision.

The connection further comprises a lift element220which in the illustrated embodiment inFIG. 2Ais a link arm220. The link arm220carries the joystick element115in a first end portion250thereof, and is rotatably arranged on the chassis205at a second end portion245thereof to be rotatable relative the chassis205in a lift direction. Thanks to the link arm220being rotatable relative the chassis205in the lift direction flexibility between the chassis205and the body210in the lift direction during a lift is provided.

The first end portion250may be arranged to rest on a not shown support extending from the chassis205, when there is no lift.

The lift detection arrangement200further comprises a lift sensor. The lift sensor comprises two sensor parts225,226, which are not shown in theFIG. 2A, but which are illustrated in theFIG. 2Bthat will be discussed further down in this document.

The lift sensor is configured to detect a displacement over a predetermined threshold of the lift element220during the lift by detecting a change in spacing between the two sensor parts225,226. One of the two sensor parts, the sensor part225in this example, is arranged on the link arm220and the other sensor part, the sensor part226, is in this example arranged on the joystick element215, at a distance from the rotational connection to the chassis205, for example at the first end portion250. The two sensor parts225,226are hence arranged to be relatively displaceable only in the lift direction since the link arm220is only is only rotatable relative the chassis205in the lift direction.

FIG. 2Bschematically depicts a top view of the lift detection arrangement200depicted inFIG. 2A. In the view inFIG. 2B, it is illustrated how the two sensor parts225,226may be arranged on the lift detection arrangement200. In the illustrated example, the sensor part225arranged on the link arm220is a magnet, and the sensor part225arranged on the chassis is a Hall Effect sensor. In other embodiments the sensor parts225,226may be arranged in the opposite way. In some embodiments, the sensor parts225,226may be of other types. TheFIG. 2Billustrates the lift detection arrangement in a normal state, where there is no lift and no collision. The two sensor parts225,226are then positioned opposite each other and there is a small spacing between them.

FIG. 2Cillustrates, in a side view, how the lift detection arrangement200as described in relation toFIGS. 2A and 2Boperates during a lift. During the lift, the body210is lifted relative the chassis210thanks to the lift element220i.e. the link arm220in this example being rotatable relative the chassis205in the lift direction. As the link arm220is rotated, or displaced, in the lift direction during the lift, there is a change in the spacing between the two sensor parts225,226, since as the sensor part225attached to the link arm220in this example, moves upward with the link arm220, it is displaced relative the other sensor part226. When this displacement is over a certain predetermined threshold, as small as possible, for example 5-15 mm, the lift sensor detects the displacement and determines that there is a lift. In response to the lift detection, the lift sensor may trigger a stop of the robotic lawnmower. This may be done by the lift sensor sending a trigger signal to a not shown control device handling the operation of the robotic lawnmower.

FIG. 2Dillustrates, in a side view, how the lift detection arrangement200as described in relation toFIGS. 2A,2B and2C operates during a collision of the robotic lawnmower. During the collision, the body210is displaced relative the chassis205thanks to the pivot connection240thanks to which the joystick element115is pivotable relative the chassis105in the collision plane.

The link arm220, on which one sensor part225is arranged, remains still and does not move relative the chassis205on which the other sensor part126is arranged. Hence, thanks to the two sensor parts225,226being arranged such that they are only displaceable relative each other in the lift direction, the collision does not cause a change in the spacing between the two sensor parts225,226, and false lift detection by the lift sensor is avoided.

According to some embodiments herein, one of the two sensor parts225,226is a Hall effect sensor and the other one of the two sensors225,226parts is a magnet If the two sensor elements are placed tight together, a Hall effect sensor and a magnet can be used, while keeping the total travel of the lift member small. It also makes it possible to remove the magnet and replace the Hall Effect sensor with a micro switch, where the micro switch is actuated by the lift member.

According to some embodiments herein the magnet is arranged on the lift element, i.e. on the link arm220in this example. This may be advantageous since wires associated with the Hall effect sensor can be kept shorter if the Hall effect sensor is not arranged on the lift element220because the Hall effect sensor does not then move in the lift direction during the lift.

According to some embodiments herein, the joystick element215is arranged to be held in a neutral position relative the chassis205by means of a not shown spring element.

According to some embodiments herein the connection is a front suspension of the robotic lawnmower. This may be advantageous for example if one or more rear suspensions are used which have the same, or a similar, joystick elements as the joystick element115, such that all suspensions provide a stable and desired neutral position when there during operation of the robotic lawnmower.

The term “arranged to” used herein may also be referred to as “configured to”.