SE2150336A1

SE2150336A1 - Robotic lawnmower

Info

Publication number: SE2150336A1
Application number: SE2150336A
Authority: SE
Inventors: Jonathan Björn; Kent Askenmalm
Original assignee: Husqvarna Ab
Priority date: 2021-03-24
Filing date: 2021-03-24
Publication date: 2022-09-25
Also published as: DE112022001682T5; WO2022203561A1

Abstract

A self-propelled robotic lawnmower (1) is disclosed comprising a lawnmower body (3) and a number of lawnmower support members (5, 5’, 6) configured to support the lawnmower body (3) by abutting against a ground surface (2) in a first plane (P1) during operation of the robotic lawnmower (1). The robotic lawnmower (1) further comprises a first cutting unit (11), a second cutting unit (12), and a control arrangement (21) configured to control operation of the first and second cutting units (11, 12) based on whether the robotic lawnmower (1) is propelled in a forward moving direction (fd) or in a reverse moving direction (rd) of the robotic lawnmower (1).

Description

A self-propelled robotic lawnmower is a lawnmower capable of cutting grass in areas in an autonomous manner, i.e. without the intervention or the direct control of a user. Some robotic lawnmowers require a user to set up a border wire around a lawn that defines the area to be mowed. Such robotic lawnmowers use a sensor to |ocate the wire and thereby the boundary of the area to be trimmed. As an alternative, or in addition, robotic lawnmowers may comprise other types of positioning units and sensors, for example sensors for detecting an event, such as a collision with an object within the area. The robotic lawnmower may move in a systematic and/or random pattern to ensure that the area is completely cut.

A robotic lawnmower usually comprises one or more batteries and one or more electrically driven cutting units being powered by the one or more batteries. ln some cases, the robotic lawnmower uses the wire to |ocate a recharging dock used to recharge the one or more batteries. Generally, robotic lawnmowers operate unattended within the area in which they operate. Examples of such areas are lawns, gardens, parks, sports fields, golf courts and the like.

Cutting grass requires a lot of energy, and as indicated above, most robotic lawnmowers comprise an electric motor configured to rotate the cutting unit and one or more electric propulsion units configured to provide motive power to the robotic lawnmower. Therefore, a problem associated with robotic lawnmowers is available operational time. That is, when batteries of the robotic lawnmower are emptied, they must be recharged. One solution to prolong the available operational time could be to increase the size and/or the number of batteries. However, such a solution adds weight and costs to the lawnmower and in many cases, these is a practical limit for the size of the batteries of a lawnmower.

Another problem associated with robotic lawnmowers is cutting result, Which can be subdivided into visual cutting result and uniformity of cutting. The visual cutting result can be defined as the visual cutting result determined by a person viewing a mowed lawn. The uniformity of the cutting can be defined as uniformity of a length of the grass of a mowed lawn, i.e. if straws of the grass in a lawn are cut to a uniform length. ln particular, a problem associated with robotic lawnmowers is that they normally have a limited ability to cut grass 2 close to objects and borders. That is, normally, the cutting unit is arranged at an underside of a lawnmower body of the robotic lawnmower and portions of the lawnmower body, and/or wheels attached thereto, may hinder the cutting unit from reaching grass close to objects and borders. lf so, the cutting result is impaired because there will be uncut grass close to object such as trees, stones, furniture, building walls, and the like.

Another problem associated with robotic lawnmowers is build-up of vegetation, such as grass, onto various components of the lawnmower. The area of the lawnmower surrounding the cutting unit is particularly problematic. Firstly, the build-up of vegetation, such as grass, is most common in this area, and secondly, the build-up of grass in this area may significantly increase the energy consumption of the lawnmower, may impair the cutting result, and may even cause an obstruction of the cutting unit stopping the cutting unit from operating.

Still another problem associated with robotic lawnmowers is collision between the cutting unit and objects other than grass and softer types of vegetation, such as stumps, stones, sticks, and the like. Collision betvveen the cutting unit and such objects constitutes a problem because the cutting unit, as well as other parts of the lawnmower, may become damaged and/or subjected to premature wear. Moreover, due to safety reasons, collision between the cutting unit and objects other than grass and softer types of vegetation should preferably be avoided.

Furthermore, generally, on today's consumer market, it is an advantage if products, such as robotic lawnmowers and associated components, systems, and arrangements, have conditions and/or characteristics suitable for being operated and manufactured in a cost- efficient manner.

SUMMARY lt is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks.

According to an aspect of the invention, the object is achieved by a self-propelled robotic lawnmower comprising a lawnmower body and a number of lawnmower support members configured to support the lawnmower body by abutting against a ground surface in a first plane during operation of the robotic lawnmower. The robotic lawnmower further comprises a first cutting unit and a second cutting unit. Moreover, the robotic lawnmower comprises a control arrangement configured to control operation of the first and second cutting units 3 based on whether the robotic lawnmower is propelled in a forward moving direction or in a reverse moving direction of the robotic lawnmower.

Since the robotic lawnmower comprises a control arrangement configured to control operation of the first and second cutting units based on whether the robotic lawnmower is propelled in the fonNard and reverse moving directions, a robotic lawnmower is provided having conditions for different cutting characteristics in the forward and reverse moving directions. ln this manner, an improved final cutting result can be obtained.

This is because in most cases, a cutting unit is optimized for cutting grass in the forward moving direction of the robotic lawnmower. Thus, by optimizing one of the first and second cutting units for cutting grass upon movement of the robotic lawnmower in the reverse moving direction, the final cutting result can be improved. ln addition, a different cutting characteristics of the first and second cutting units can be utilized to improve the final cutting result.

Moreover, a robotic lawnmower is provided having conditions for obtaining an improved final cutting result while having conditions for a reduced energy consumption. This is because the control arrangement may render one of the first and second cutting unit inoperable when the robotic lawnmower is moving in one of the forward and reverse moving directions. As a further result thereof, conditions are provided for obtaining an increased available operational time of the robotic lawnmower in a cost-efficient manner. ln addition, by not operating the first and second cutting units simultaneously, the noise generated by the robotic lawnmower can be lowered.

Accordingly, a robotic lawnmower is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Optionally, the control arrangement is configured to operate the first cutting unit when the robotic lawnmower is propelled in the fon/vard moving direction and is configured to operate the second cutting unit when the robotic lawnmower is propelled in the reverse moving direction. Thereby, a robotic lawnmower is provided having conditions for different cutting characteristics in the fon/vard and reverse moving directions so as to obtain an improved final cutting result. ln addition, a robotic lawnmower is provided having conditions for obtaining an improved final cutting result while having conditions for a reduced energy consumption and accordingly conditions for an increased available operational time of the robotic lawnmower.

Optionally, the control arrangement is configured to cancel operation of the second cutting unit when the robotic lawnmower is propelled in the forward moving direction. Thereby, a robotic lawnmower is provided having conditions for obtaining an improved final cutting result while having conditions for a reduced energy consumption and accordingly conditions for an increased available operational time of the robotic lawnmower. This is because the control arrangement is configured to cancel operation of the second cutting unit when the robotic lawnmower is propelled in the forward moving direction.

Optionally, the first cutting unit is larger in size than the second cutting unit. Thereby, a robotic lawnmower is provided having conditions for different cutting characteristics in the fon/vard and reverse moving directions so as to obtain an improved final cutting result of the robotic lawnmower.

Optionally, the first and second cutting units are arranged with different inclination angles relative to the first plane. Thereby, a robotic lawnmower is provided having conditions for different cutting characteristics in the fon/vard and reverse moving directions so as to obtain an improved final cutting result of the robotic lawnmower. Moreover, a robotic lawnmower is provided having conditions for obtaining a good cutting result in both of the forward and reverse moving directions.

Optionally, the first cutting unit is arranged with an inclination angle relative to the first plane such that a leading portion of the first cutting unit is closer to the first plane than a trailing portion of the first cutting unit when the robotic lawnmower is moving in the forward moving direction, and wherein the second cutting unit is arranged with an inclination angle relative to the first plane such that a leading portion of the second cutting unit is closer to the first plane than a trailing portion of the second cutting unit when the robotic lawnmower is moving in the reverse moving direction. Thereby, a robotic lawnmower is provided having conditions for obtaining a good cutting result in both of the forward and reverse moving directions. That is, due to the inclination angles of the first and second cutting units, the first cutting unit is obtaining an advantageous inclination angle when the robotic lawnmower is moving in the forward moving direction and the second cutting unit is obtaining an advantageous inclination angle when the robotic lawnmower is moving in the reverse moving direction.

Optionally, the first cutting unit is configured to rotate around a first rotation axis during operation and the second cutting unit is configured to rotate around a second rotation axis during operation, and wherein each of the first and second rotation axis is transversal to the first plane. Thereby, conditions are provided for obtaining a good cutting result using a low amount of energy in both of the forward and the reverse moving directions.

Optionally, the second rotation axis is located at distance from the first rotation axis in a |atera| direction of the robotic lawnmower. Thereby, a robotic lawnmower is provided having conditions for a higher ability to cut grass close to objects and borders in an energy efficient manner. Moreover, a robotic lawnmower is provided having conditions for different cutting characteristics in the fonNard and reverse moving directions so as to obtain an improved final cutting result.

Optionally, the second rotation axis is arranged behind the first rotation axis seen relative to the forward moving direction of the robotic lawnmower. Thereby, a robotic lawnmower is provided having conditions for obtaining good cutting results in both moving directions. Moreover, a robotic lawnmower is provided having conditions for different cutting characteristics in the fon/vard and reverse moving directions so as to obtain an improved final cutting result.

Optionally, the first rotation axis is located at a longitudinal centre plane of the robotic lawnmower. Thereby, a robotic lawnmower is provided having conditions for a good cutting result using a low amount of energy.

Optionally, the second rotation axis is arranged at a distance from a longitudinal centre plane of the robotic lawnmower. Thereby, a robotic lawnmower is provided having conditions for a higher ability to cut grass close to objects and borders in an energy efficient manner. Moreover, a robotic lawnmower is provided having conditions for different cutting characteristics in the fon/vard and reverse moving directions so as to obtain an improved final cutting result.

Optionally, the robotic lawnmower comprises a guard covering at least a portion of the second cutting unit. Thereby, a robotic lawnmower is provided having conditions for a higher ability to cut grass close to objects and borders in a safe and reliable manner.

Optionally, the guard covers at least a portion of a front section of the second cutting unit, and wherein the front section of the second cutting unit faces in the forward moving direction of the robotic lawnmower. Thereby, the at least portion of a front section of the second cutting unit is protected from impact with objects. As a further result, a robotic lawnmower is provided having conditions for a higher ability to cut grass close to objects and borders in a 6 safe and reliable manner. ln addition, any build-up of vegetation on the guard covering the portion of the front section of the second cutting unit can be removed in an efficient manner upon propulsion of the robotic lawnmower in the fon/vard moving direction.

Optionally, the second cutting unit comprises a first side facing towards a longitudinal centre plane of the robotic lawnmower and a second side facing away from the longitudinal centre plane, and wherein the guard covers a portion of the front section of the second cutting unit located at the second side of the second cutting unit. Thereby, the portion of the front section of the second cutting unit located at the second side of the second cutting unit is protected from impact with objects. As a further result, a robotic lawnmower is provided in which the second cutting unit is protected from impact with objects in a direction towards the longitudinal centre plane of the robotic lawnmower. Thereby, the safety during operation and handling of the robotic lawnmower is further improved. ln addition, any build-up of vegetation on the guard covering the portion of the front section of the second cutting unit can be removed in an efficient manner upon propulsion of the robotic lawnmower in the fonNard moving direction.

Optionally, the second cutting unit comprises a first side facing towards a longitudinal centre plane of the robotic lawnmower and a second side facing away from the longitudinal centre plane, and wherein the guard covers substantially the entire second side of the second cutting unit. Thereby, substantially the entire second side of the second cutting unit is protected from impact with objects moving towards the second cutting unit in directions toward the longitudinal centre plane of the robotic lawnmower. Thereby, the safety during operation and handling of the robotic lawnmower is further increased.

Optionally, the number of lawnmower support members comprises at least two drive wheels and at least one support wheel. Thereby, a simple and efficient robotic lawnmower can be provided.

Optionally, the number of lawnmower support members comprises two drive wheels and one support wheel, wherein the support wheel is attached to the lawnmower body at a longitudinal centre plane of the robotic lawnmower. Thereby, conditions are provided for a good cutting result in both of the fonNard and reverse moving directions. That is, in embodiments in which the first rotation axis is arranged at or near a longitudinal centre plane of the robotic lawnmower and the second rotation axis is arranged at a distance from the longitudinal centre plane of the robotic lawnmower, it can be ensured that no wheel of the 7 robotic lawnmower is flattening grass prior to cutting in both of the forward and reverse moving directions.

Optionally, a drive wheel of the at least two drive wheels is configured to rotate in a rotational plane, and wherein the second rotation axis is arranged closer to the rotational plane of the drive wheel than to a longitudinal centre plane of the robotic lawnmower. Thereby, a robotic lawnmower is provided having conditions for a higher ability to cut grass close to objects and borders in an energy efficient manner. Moreover, a robotic lawnmower is provided having conditions for different cutting characteristics in the fonNard and reverse moving directions so as to obtain an improved final cutting result.

Optionally, one or more radially outer portions of the second cutting unit orbits in a circular path, and wherein a drive wheel of the at least two drive wheels is configured to rotate in a rotational plane extending through the circular path. Thereby, a robotic lawnmower is provided having conditions for an even higher ability to cut grass close to objects and borders in an energy efficient manner. Moreover, a robotic lawnmower is provided having conditions for different cutting characteristics in the fonNard and reverse moving directions so as to obtain an improved final cutting result.

Optionally, the at least two drive wheels constitute front wheels and the at least one support wheel constitutes a rear wheel of the robotic lawnmower. Thereby, conditions are provided for a good cutting result in both of the fon/vard and reverse moving directions. That is, in embodiments in which the first rotation axis is arranged at or near a longitudinal centre plane of the robotic lawnmower and the second rotation axis is arranged at a distance from the longitudinal centre plane of the robotic lawnmower, it can be ensured that no wheel of the robotic lawnmower is flattening grass prior to cutting in both of the fonNard and reverse moving directions.

Optionally, the robotic lawnmower comprises an attachment assembly attaching one lawnmower support member of the number of lawnmower support members to the lawnmower body, and wherein the attachment assembly is configured to support the lawnmower body at different distances from the first plane based on the moving direction of the robotic lawnmower. Thereby, a different cutting characteristics between the first and second cutting units can be utilized to a higher degree for improving the final cutting result. As an example, conditions are provided for moving the second cutting unit to a position higher from the ground upon movement of the robotic lawnmower in the fonNard moving direction and moving the second cutting unit closer to a ground surface upon movement of 8 the robotic lawnmower in the reverse moving direction. ln this manner, it can be ensured that the second cutting unit does not disturb cutting when using the first cutting unit upon movement of the robotic lawnmower in the fonNard moving direction. Moreover, the second cutting unit will be less likely to bump into objects on a lawn and objects protruding from a lawn when the robotic lawnmower is moving in the fonNard moving direction.

Furthermore, by moving the second cutting unit closer to a ground surface upon movement of the robotic lawnmower in the reverse moving direction, the second cutting can cut grass in an efficient manner upon movement of the robotic lawnmower in the reverse moving direction. Moreover, a safer robotic lawnmower can be provided because the moving of the second cutting unit closer to the ground surface can reduce the likelihood of objects reaching the second cutting unit from sides of the robotic lawnmower during operation of the second cutting unit.

Furthermore, since the attachment assembly is configured to support the lawnmower body at different distances from the first plane based on the moving direction of the robotic lawnmower, more advantageous inclination angles of the first and second cutting units can be obtained upon movement of the robotic lawnmower in the fon/vard and reverse moving directions.

Optionally, the attachment assembly is configured to support the lawnmower body at a smaller distance to the first plane when the robotic lawnmower is moving in the reverse moving direction than when the robotic lawnmower is moving in the fonNard moving direction. Thereby, an improved cutting result can be obtained upon movement of the robotic lawnmower in the reverse moving direction as Well as upon movement of the robotic lawnmower in the fonNard moving direction. As an example, it can be ensured that the second cutting unit does not disturb cutting using the first cutting unit, and/or is flattening grass upon movement of the robotic lawnmower in the fon/vard moving direction and is moved closer to the ground upon movement of the robotic lawnmower in the reverse moving direction so as to improve the cutting result.

Furthermore, more advantageous inclination angles of the first and second cutting units can be obtained upon movement of the robotic lawnmower in the fon/vard and reverse moving directions. ln addition, a safer robotic lawnmower can be provided because it can be ensured that the second cutting unit is moved closer to the ground when the robotic lawnmower is moving in 9 the reverse moving direction so as to prevent objects from reaching the second cutting unit from sides of the robotic lawnmower.

Optionally, the attachment assembly comprises a swivel joint pivotally attaching the lawnmower support member to the lawnmower body around a pivot axis, and wherein the pivot axis is angled relative to a vertical direction of the lawnmower body. Thereby, a simple, an efficient, a reliable, and a low cost solution is provided for supporting the lawnmower body at different distances from the first plane based on the moving direction of the robotic lawnmower.

Thus, a robotic lawnmower is provided capable of supporting the lawnmower body at different distances from the first plane based on the moving direction of the robotic lawnmower while having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS Various aspects of the invention, including its particularfeatures and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which: Fig. 1 illustrates a side view of a self-propelled robotic lawnmower according to some embodiments, Fig. 2 illustrates a second side view of the robotic lawnmower illustrated in Fig. 1 where a number of components of the robotic lawnmower have been removed for reasons of visibility, Fig. 3 illustrates an underside of the robotic lawnmower according to the embodiments illustrated in Fig. 1, and Fig. 4 illustrates the robotic lawnmower illustrated in Fig. 2 in which a support wheel of the robotic lawnmower is pivoted to a position corresponding to a position that the support wheel is pivoted to when the robotic lawnmower is moving in a reverse moving direction.

DETAILED DESCRIPTION Aspects of the present invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

Fig. 1 illustrates a side view of a self-propelled robotic lawnmower 1 according to some embodiments. The self-propelled robotic lawnmower 1 is a robotic lawnmower 1 capable of cutting grass in an area in an autonomous manner, i.e. without the intervention or the direct control of a user. According to the illustrated embodiments, the robotic lawnmower 1 is configured to be used to cut grass in areas used for aesthetic and recreational purposes, such as gardens, parks, city parks, sports fields, lawns around houses, apartments, commercial buildings, offices, and the like. For the reason of brevity and clarity, the self- propelled robotic lawnmower 1 is in some places herein referred to as "the robotic lawnmower 1", or simply "the lawnmower 1".

The robotic lawnmower 1 comprises a lawnmower chassis 3 and a number of lawnmower support members 5, 5', 6 each configured to abut against a ground surface 2 in a first plane P1 during operation of the robotic lawnmower 1. As understood from the above described, the first plane P1 extends through ground engaging portions of the lawnmower support members 5, 5', 6 of the robotic lawnmower 1. Accordingly, the first plane P1 will extend along a ground surface 2 when the robotic lawnmower 1 is positioned on a flat ground surface 2 in an intended use position on the ground surface 2 as is the case in Fig. 1.

According to the illustrated embodiments, the lawnmower support members 5, 5', 6 is wheels 5, 5', 6 of the robotic lawnmower 1. According to further embodiments, the robotic lawnmower 1 may comprise one or more other types of lawnmower support members 5, 5', 6, such as one or more continuous track arrangements, one or more ground engaging protrusions, or the like. According to the illustrated embodiments, the robotic lawnmower 1 comprises three wheels 5, 5', 6, namely two drive wheels 5, 5' and one support wheel 6. ln Fig. 1, one of the drive wheels 5' is hidden behind the other drive wheel 5. The drive wheels 5, 5' of the robotic lawnmower 1 may each be powered by an electrical motor of the robotic lawnmower 1 to provide motive power and/or steering of the robotic lawnmower 1. Steering of the robotic lawnmower 1 may be provided by rotating the drive wheels 5, 5' at different rotational speeds. ln Fig. 1, a longitudinal direction ld of the robotic lawnmower1 is indicated. The longitudinal direction ld of the robotic lawnmower 1 extends in a central longitudinal plane of the robotic lawnmower 1, as is further explained herein. The longitudinal direction ld of the robotic lawnmower1 is parallel to the first plane P1 and thus also to a ground surface 2 when the robotic lawnmower1 is positioned in the intended use position onto a flat ground surface 2.

Moreover, the longitudinal direction ld of the robotic lawnmower 1 is parallel to a forward 11 moving direction fd of the robotic lawnmower 1 as Well as a reverse moving direction rd of the robotic lawnmower 1. The reverse moving direction rd is opposite to the fonNard moving direction fd. The fonNard moving direction fd of the robotic lawnmower 1 may be referred to as a fonNard direction of travel of the robotic lawnmower 1 or simply a fonNard direction of the robotic lawnmower 1. Likewise, the reverse moving direction rd of the robotic lawnmower 1 may be referred to as a reverse direction of travel of the robotic lawnmower 1 or simply a reverse direction of the robotic lawnmower 1.

According to the illustrated embodiments, the drive wheels 5, 5' of the robotic lawnmower 1 are non-steered wheels having a fix rolling direction in relation to the lawnmower chassis 3. The respective rolling direction of the drive wheels 5, 5'of the robotic lawnmower 1 is substantially parallel to the longitudinal direction ld of the robotic lawnmower 1. According to the illustrated embodiments, the support wheel 6 is a non-driven wheel. Moreover, according to the illustrated embodiments, the support wheel 6 can pivot around a pivot axis such that the rolling direction of the support wheel 6 can follow a travel/moving direction of the robotic lawnmower 1, as is further explained herein.

As understood from the above, when the drive wheels 5, 5' of the robotic lawnmower 1 are rotated at the same rotational velocity in a fonNard rotational direction, and no wheel slip is occurring, the robotic lawnmower 1 will move in the forward moving direction fd indicated in Fig. 1. Likewise, when the drive wheels 5, 5' of the robotic lawnmower 1 are rotated at the same rotational velocity in a reverse rotational direction, and no wheel slip is occurring, the robotic lawnmower1 will move in the reverse moving direction rd indicated in Fig. 1.

According to the illustrated embodiments, the robotic lawnmower 1 may be referred to as a three-wheeled front wheel driven robotic lawnmower 1. According to further embodiments, the robotic lawnmower 1 may be provided with another number of wheels 5, 5', 6 such as four Wheels. Moreover, according to further embodiments, the robotic lawnmower 1 may be provided with another configuration of driven and non-driven Wheels, such as a rear wheel drive or an all-wheel drive.

According to the illustrated embodiments, the robotic lawnmower 1 comprises a control arrangement 21. The control arrangement 21 may be configured to control propulsion of the robotic lawnmower 1, and steer the robotic lawnmower 1, by controlling electrical motors of the robotic lawnmower 1 arranged to drive the drive Wheels 5, 5' of the robotic lawnmower 1. According to further embodiments, the control arrangement 21 may be configured to steer the robotic lawnmower 1 by controlling the angle of steered Wheels of the robotic lawnmower 12 1. According to still further embodiments, the robotic lawnmower 1 may be an articulated robotic lawnmower, wherein the control arrangement 21 may be configured to steer the robotic lawnmower by controlling the angle between frame portions of the articulated robotic lawnmower.

The control arrangement 21 may be configured to control propulsion of the robotic lawnmower 1, and steer the robotic lawnmower 1, so as to navigate the robotic lawnmower 1 in an area to be operated. The robotic lawnmower 1 may further comprise one or more sensors arranged to sense a magnetic field of a wire, and/or one or more positioning units, and/or one or more sensors arranged to detect an impending or ongoing collision event with an object. ln addition, the robotic lawnmower 1 may comprise a communication unit connected to the control arrangement 21. The communication unit may be configured to communicate with a remote communication unit to receive instructions therefrom and/or to send information thereto. The communication may be performed wirelessly over a wireless connection such as the internet, or a wireless local area netvvork (WLAN), a cellular network, or a wireless connection for exchanging data over short distances using short-wavelength, i.e. ultra-high frequency (UHF) radio waves in the industrial, scientific, and medical (ISM) band from 2.4 to 2.485 GHz.

The control arrangement 21 may be configured to control propulsion of the robotic lawnmower 1, and steer the robotic lawnmower 1, so as to navigate the robotic lawnmower 1 in a systematic and/or random pattern to ensure that an area is completely covered, using input from one or more of the above described sensors and/or units. Furthermore, the robotic lawnmower 1 may comprise one or more batteries arranged to supply electricity to components of the robotic lawnmower 1. As an example, the one or more batteries may be arranged to supply electricity to electrical motors of the robotic lawnmower 1 by an amount controlled by the control arrangement 21.

The robotic lawnmower 1 comprises a first cutting unit 11 and a second cutting unit 12, wherein the second cutting unit 12 is separate from the first cutting unit 11. Each of the first and second cutting units 11, 12 is configured to cut grass when operated. The cutting characteristics of the second cutting unit 12 is different from the cutting characteristic of the first cutting unit 11, as is further explained herein. According to the illustrated embodiments, the robotic lawnmower 1 comprises a guard 13 covering at least a portion of the second cutting unit 12. 13 Fig. 2 illustrates a second side view of the robotic lawnmower 1 illustrated in Fig. 1 where a number of components of the robotic lawnmower 1 have been removed for reasons of visibility. As examples, in comparison to the robotic lawnmower 1 illustrated in Fig. 1, portions of the lawnmower body 3 has been removed as well as well as the drive wheel 5 visible in Fig. 1, the guard 13 covering the second cutting unit 12, and drive shafts of the first and second cutting units 11, 12. The drive wheel 5 visible in Fig. 1 is in some places below referred to as a first drive wheel 5 and the drive wheel 5' visible in Fig. 2 is in some places below referred to as a second drive wheel 5". A portion 3' of the lawnmower body is visible in Fig. 2, which below is referred to as the lawnmower body 3". ln Fig. 2, the first and second cutting units 11, 12 are more clearly seen. The first cutting unit 11 is configured to rotate around a first rotation axis ax1 during operation and the second cutting unit 12 is configured to rotate around a second rotation axis ax2 during operation. According to the illustrated embodiments, each of the first and second rotation axis ax1, ax2 is transversal to the first plane P1. ln Fig. 2, a cutting plane P11 of the first cutting unit 11 is indicated. The cutting plane P11 of the first cutting unit 11 is perpendicular to the first rotation axis ax1. Likewise, in Fig. 2, a cutting plane P12 of the second cutting unit 12 is indicated. The cutting plane P12 of the second cutting unit 12 is perpendicular to the second rotation axis ax2.

The robotic lawnmower 1 may comprise a first motor, such as a first electric motor, configured to rotate the first cutting unit 11 around the first rotation axis ax1 to operate the first cutting unit 11. Likewise, the robotic lawnmower 1 may comprise a second motor, such as a second electric motor, configured to rotate the second cutting unit 12 around the second rotation axis ax2 to operate the second cutting unit 12.

Below, simultaneous reference is made to Fig. 1 and Fig. 2, if not indicated othenNise. The control arrangement 21 of the robotic lawnmower 1 is configured to control operation of the first and second cutting units 11, 12 based on whether the robotic lawnmower 1 is propelled in the fonNard moving direction fd or in the reverse moving direction rd of the robotic lawnmower 1. ln more detail, according to the illustrated embodiments, the control arrangement 21 is configured to operate the first cutting unit 11 when the robotic lawnmower 1 is propelled in the fon/vard moving direction fd and is configured to operate the second cutting unit 12 when the robotic lawnmower 1 is propelled in the reverse moving direction rd.

Thereby, a robotic lawnmower 1 is provided having conditions for obtaining good cutting results in both moving directions fd, rd. Moreover, a robotic lawnmower 1 is provided having 14 conditions for different cutting characteristics in the forward and reverse moving directions fd, rd so as to obtain an improved final cutting result, as is further explained herein.

The control arrangement 21 may control operation of the first and second cutting units 11, 12 by controlling operation of a first and a second electric motor according to the above described. Moreover, according to the illustrated embodiments, the control arrangement 21 is configured to cancel operation of the second cutting unit 12 when the robotic lawnmower 1 is propelled in the forward moving direction fd and is configured to cancel operation of the first cutting unit 11 when the robotic lawnmower 1 is propelled in the reverse moving direction rd. ln this manner, a more energy efficient robotic lawnmower 1 is provided having conditions for an improved final cutting result. ln addition, by not operating the first and second cutting units 11, 12 simultaneously, the noise generated by the robotic lawnmower 1 can be lowered.

Fig. 3 illustrates an underside of the robotic lawnmower 1 according to the embodiments illustrated in Fig. 1 and Fig. 2. Below, simultaneous reference is made to Fig. 1 - Fig. 3, if not indicated othenNise. ln Fig. 3, the longitudinal centre plane LCP of the robotic lawnmower 1 is indicated. The longitudinal centre plane LCP extends through a lateral centre of the robotic lawnmower 1 in a vertical direction of the robotic lawnmower 1 and comprises the longitudinal direction ld of the robotic lawnmower 1. ln other words, the longitudinal direction ld of the robotic lawnmower 1 extends in the longitudinal centre plane LCP of the robotic lawnmower 1. Moreover, as clearly seen in Fig. 3, the longitudinal centre plane LCP is parallel to the fonNard moving direction fd and is parallel to the reverse moving direction rd of the robotic lawnmower 1. ln Fig. 1 and Fig. 2, the robotic lawnmower 1 is illustrated in a respective viewing direction which is perpendicular to the longitudinal centre plane LCP indicated in Fig. 3. ln Fig. 2, the vertical direction vd of the robotic lawnmower 1 is indicated. The vertical direction vd is perpendicular to the first plane P1 and is parallel to the longitudinal centre plane LCP. ln other words, the longitudinal centre plane LCP is perpendicular to the first plane P1.

With reference to Fig. 3, the feature that the longitudinal centre plane LCP extends through a lateral centre of the robotic lawnmower 1 in the vertical direction vd of the robotic lawnmower 1 means that the longitudinal centre plane LCP is located at equal distances from lateral sides 41, 42 of the robotic lawnmower 1. Moreover, according to the illustrated embodiments, the longitudinal centre plane LCP is located at equal distances from the drive wheels 5, 5' of the robotic lawnmower 1. According to the illustrated embodiments, the first rotation axis ax1 is located at the longitudinal centre plane LCP of the robotic lawnmower 1. ln more detail, according to the illustrated embodiments, the first rotation axis ax1 extends in the longitudinal centre plane LCP.

According to the illustrated embodiments, each of the first and second cutting units 11, 12 comprises a cutting disc and a number of cutting members pivotally arranged on the cutting disc. According to further embodiments, one or both of the first and second cutting units 11, 12 may comprise another type of cutting unit, such as a cutting arm, or the like. As indicated in Fig. 3, radia||y outer portions 28 of the first cutting unit 11 orbits in a first circu|ar path C1 upon rotation of the first cutting unit 11. Likewise, radia||y outer portions 29 of the second cutting unit 12 orbits in a second circu|ar path C2 upon rotation of the second cutting unit 12.

The first circu|ar path C1, as referred to herein, is a geometric shape which can be obtained by tracing the circu|ar movement of radia||y outer portions 28 of the first cutting unit 11 upon rotation of the first cutting unit 11 around the first rotation axis ax1. Likewise, the second circu|ar path C2, as referred to herein, is a geometric shape which can be obtained by tracing the circu|ar movement of radia||y outer portions 29 of the second cutting unit 12 upon rotation of the second cutting unit 12 around the second rotation axis ax2. As understood from the above described, the first circu|ar path C1 is located in the cutting plane P11 of the first cutting unit 11 indicated in Fig. 2. Likewise, the second circu|ar path C2 is located in the cutting plane P12 of the second cutting unit 12 indicated in Fig. 2.

According to the embodiments illustrated in Fig. 3, the radia||y outer portions 28 of the first cutting unit 11 is a portion of one of the cutting members 38 Which protrudes a further distance out from the first rotation axis ax1 than the other cutting members 38' of the first cutting unit 11. Therefore, radia||y outer portions of the other cutting members 38' do not reach the circu|ar path C1 illustrated in Fig. 3. Thus, according to the illustrated embodiments, the first cutting unit 11 comprises a number of cutting members 38, 38' protruding different radia| distances from the first rotation axis ax1. Thereby, the cutting result of the first cutting unit 11 can be further improved because the cutting members 38, 38' will cut grass at different radia| distances from the first rotation axis ax1. According to further embodiments, the first cutting unit 11 may comprise cutting members 38, 38' protruding the same radia| distances from the first rotation axis ax1.

According to the illustrated embodiments, the first cutting unit 11 comprises three cutting members 38, 38' pivotally attached to a cutting disc of the first cutting unit 11. According to further embodiments, the first cutting unit 11 may comprise other numbers of cutting members 38, 38', such as one, two, four, five, or the like. Moreover, according to the 16 illustrated embodiments, the second cutting unit 12 comprises two cutting members pivotally attached to a cutting disc of the second cutting unit 12. The cutting members of the second cutting unit 12 have not been provided with reference signs for reasons of brevity and clarity. However, the radially outer portion 29 of the second cutting unit 12 referred to above is a portion of one of the cutting members of the second cutting unit 12 according to the illustrated embodiments. According to further embodiments, the second cutting unit 12 may comprise other numbers of cutting members than two, such as one, three, four, five, or the like.

As clearly seen in Fig. 2 and Fig. 3, according to the illustrated embodiments, the first cutting unit 11 is larger in size than the second cutting unit 12. The size of the respective first and second cutting units 11, 12 can be determined by measuring the diameter of the first and second circular paths C1, C2. According to the illustrated embodiments, the diameter of the second circular path C2 is approximately 68.7% of the diameter of the first circular path C1. According to further embodiments, the diameter of the second circular path C2 may be within the range of 25% - 90% of the diameter of the first circular path C1 or may be within the range of 50% - 79% of the diameter of the first circular path C1. The diameter of the first circular path C1 may also be referred to as an effective cutting width of the first cutting unit 11 and the diameter of the second circular path C2 may also be referred to as an effective cutting width of the second cutting unit 12.

As best seen in Fig. 3, the second rotation axis ax2 is located at distance d1 from the first rotation axis ax1 in a lateral direction Ld of the robotic lawnmower 1. The lateral direction Ld of the robotic lawnmower 1 is perpendicular to the longitudinal centre plane LCP of the robotic lawnmower 1 and is thus parallel to the first plane P1. The second rotation axis ax2 is also arranged at a distance d2 from the longitudinal centre plane LCP of the robotic lawnmower 1. According to the illustrated embodiments, the distances d1, d2 are the same because the first rotation axis ax1 is located at the longitudinal centre plane LCP of the robotic lawnmower 1 according to the illustrated embodiments. Moreover, according to the embodiments illustrated in Fig. 3, the second rotation axis ax2 is arranged behind the first rotation axis ax1 seen relative to the fonNard moving direction fd of the robotic lawnmower 1. ln other words, the second rotation axis ax2 is arranged in front of the first rotation axis ax1 seen relative to the reverse moving direction rd of the robotic lawnmower 1.

As indicated above, the drive wheels 5, 5' of the robotic lawnmower 1 constitute front wheels of the robotic lawnmower 1 and the support wheel 6 of the robotic lawnmower 1 constitutes a rear wheel of the robotic lawnmower 1. The drive wheels 5, 5' are thus in front of the support 17 wheel 6 when the robotic lawnmower 1 is moving in the forward moving direction fd and the support wheel 6 is in front of the drive wheels 5, 5' when the robotic lawnmower 1 is moving in the reverse moving direction rd. As is best seen in Fig. 3, according to the illustrated embodiments, the support wheel 6 is attached to the lawnmower body 3 at the longitudinal centre plane LCP of the robotic lawnmower 1. Moreover, the drive wheels 5, 5' are arranged at a respective |atera| side 41, 42 of the robotic lawnmower 1. Moreover, the first circular path C1 of the first cutting unit 11 is fully contained within the rotational planes of the drive wheels 5, 5' of the robotic lawnmower 1.

Due to these features, cutting can be performed in an efficient manner in the fon/vard moving direction fd using the first cutting unit 11 because the drive wheels 5, 5' will not flatten grass prior to reaching the first cutting unit 11. Likewise, cutting can be performed in an efficient manner in the reverse moving direction rd using the second cutting unit 12 because the support wheel 6 will not flatten grass prior to reaching the second cutting unit 12. ln addition, because the second rotation axis ax2 of the second cutting unit 12 is arranged at a distance d3 from the longitudinal centre plane LCP of the robotic lawnmower 1, a robotic lawnmower 1 is provided having a higher ability to cut grass close to objects and borders so as to improve the final cutting result. ln the following, the drive wheel 5 provided with the reference sign "5" is referred to as a first drive wheel 5 and the drive wheel 5' provided with the reference sign is referred to as a second drive wheel 5. ln Fig. 3, a rotational plane rP of the first drive wheel 5 is indicated. As clearly seen in Fig. 3, according to the illustrated embodiments, the second rotation axis ax2 is arranged closer to the rotational plane rP of the first drive wheel 5 than to the longitudinal centre plane LCP of the robotic lawnmower 1. ln more detail, according to the illustrated embodiments, the distance d3 betvveen the second rotation axis ax2 and the rotational plane rP of the first drive wheel 5 is approximately 21 .2% of the distance d2 between the second rotation axis ax2 and the longitudinal centre plane LCP of the robotic lawnmower 1. According to further embodiments, the distance d3 between the second rotation axis ax2 and the rotational plane rP of the first drive wheel 5 may be within the range of 5% - 80% of the distance d2 between the second rotation axis ax2 and the longitudinal centre plane LCP of the robotic lawnmower1 or may be within the range of 11% - 31% of the distance d2 between the second rotation axis ax2 and the longitudinal centre plane LCP of the robotic lawnmower 1.

As can be seen in Fig. 3, the robotic lawnmower 1 according to the illustrated embodiments is arranged such that the rotational plane rP of the first drive wheel 5 extends through the 18 second circular path C2. ln other words, the radius of the second circular path C2 is greater than the distance d3 between the second rotation axis ax2 and the rotational plane rP of the first drive wheel 5. Since the second cutting unit 12 is arranged this close to the |atera| side 41 of the robotic lawnmower 1, a robotic lawnmower 1 is provided having a higher ability to cut grass close to objects and borders so as to improve the final cutting result of a lawn. Moreover, as understood from the above described, the first drive wheel 5 will not disturb cutting using the second cutting unit 12 when the robotic lawnmower 1 is moving in the reverse moving direction rd.

According to the illustrated embodiments, the first and second cutting units 11, 12 are arranged such that an overlap of the circular paths C1, C2 thereof are formed as seen in the forward and reverse moving directions fd, rd of the robotic lawnmower 1. That is, in other words, if the robotic lawnmower1 is moving in the forward moving direction fd or in the reverse moving direction rd over a lawn, at least a section of the cutting unit 11 and at least a section of the second cutting unit 12 will be moved over the same area of the lawn. This is achieved by the fact that, according to the illustrated embodiments, the distance d1 from the first rotation axis ax1 to the second rotation axis ax2, measured in the |atera| direction Ld of the robotic lawnmower 1, is smaller than the combined effective radiuses of the first and second cutting units 11, 12. That is, according to the illustrated embodiments, the distance d1 from the first rotation axis ax1 to the second rotation axis ax2, measured in the |atera| direction Ld of the robotic lawnmower 1, is smaller than the combined radiuses of the first and second circular paths C1, C2. ln this manner, an effective and efficient cutting can be performed in the forward and reverse moving directions fd, rd of the robotic lawnmower 1. ln addition, the robotic lawnmower 1 will have a high ability to cut grass close to objects and borders so as to improve the final cutting result of a lawn.

Moreover, as seen in Fig. 3, the second cutting unit 12 is arranged relatively close to a |atera| side 41 of the robotic lawnmower 1. ln Fig. 3, a |atera| outer portion 41' of the lawnmower body 3 is indicated, i.e. a portion 41' of the lawnmower body 3 located furthest from the longitudinal centre plane LCP of the robotic lawnmower 1. According to the illustrated embodiments, the greatest distance from the longitudinal centre plane LCP to the second circular path C2 is approximately 83% of the distance d6 between the longitudinal centre plane LCP and the |atera| outer portion 41' of the lawnmower body 3. The greatest distance from the longitudinal centre plane LCP to the second circular path C2 corresponds to the sum of the distance d2 between the longitudinal centre plane LCP and the second rotation axis ax2 and the radius of the second circular path C2. According to further embodiments, the greatest distance from the longitudinal centre plane LCP to the second circular path C2 19 may be within the range of 20% - 100%, or 75 % - 95%, of the distance d6 between the longitudinal centre plane LCP and the |atera| outer portion 41' of the lawnmower body 3. Since the second cutting unit 12 is arranged relatively close to a |atera| side 41 of the robotic lawnmower 1, the robotic lawnmower 1 will have a high ability to cut grass close to objects and borders so as to improve the final cutting result of a lawn.

According to the embodiments illustrated in Fig. 3, the lawnmower body 3 is arranged such that the |atera| outer portion 41' of the lawnmower body 3 protrudes a short distance further out from the longitudinal centre plane LCP of the robotic lawnmower 1 than the drive wheel 5 of the robotic lawnmower 1. According to further embodiments, the lawnmower body 3 may be arranged such that no portions of the lawnmower body 3 protrudes further out from the longitudinal centre plane LCP than one or more the drive wheels 5, 5' of the robotic lawnmower 1. ln other words, according to such embodiments, one or more the drive wheels , 5' of the robotic lawnmower 1 may form a |atera| outer portion of the robotic lawnmower 1.

As indicated above, according to the illustrated embodiments, the robotic lawnmower 1 comprises a guard 13 covering at least a portion of the second cutting unit 12. As indicated in Fig. 3, the guard 13 covers at least a portion of a front section 23 of the second cutting unit 12. The front section 23 of the second cutting unit 12 faces in the forward moving direction fd of the robotic lawnmower 1. Moreover, the second cutting unit 12 comprises a first side 25 facing towards the longitudinal centre plane LCP of the robotic lawnmower 1 and a second side 27 facing away from the longitudinal centre plane LCP.

According to the embodiments illustrated in Fig. 3, the guard 13 covers a portion of the front section 23 of the second cutting unit 12 located at the second side 27 of the second cutting unit 12. ln more detail, according to the illustrated embodiments, the guard 13 covers substantially the entire second side 27 of the second cutting unit 12. The guard 13 may also be referred to as a cover. Due to the features of the guard 13, the guard 13 can prevent impact between the second cutting unit 12 and objects moving towards the second cutting unit 12 from the |atera| side 41 of the robotic lawnmower 1 in a direction towards the longitudinal centre plane LCP. Moreover, accumulation of clippings can be avoided and can be removed in an efficient manner from the guard 13 when the robotic lawnmower 1 is moving in the forward moving direction fd.

As understood from the above described, according to the embodiments illustrated in Fig. 3, the guard 13 is open in the reverse moving direction rd. That is, the second cutting unit 12 comprises a rear section 32 facing in the reverse moving direction rd of the robotic lawnmower 1. The feature that the guard 13 is open in the reverse moving direction rd means that the guard 13 does not cover the rear section 32 of the second cutting unit 12. ln this manner, the guard 13 does not disturb cutting or bend any grass when the robotic lawnmower 1 is moving in the reverse moving direction rd. ln addition, as indicated in Fig. 3, the guard 13 comprises t\No adjacent elongated openings 13' extending in a direction parallel to the reverse moving direction rd of the robotic lawnmower 1. Moreover, the two adjacent elongated openings 13' are open in the reverse moving direction rd of the robotic lawnmower 1 and are closed in the fon/vard moving direction fd of the robotic lawnmower 1. The two adjacent elongated openings 13' are configured to allow passage of grass upon movement of the robotic lawnmower 1 in the reverse moving direction rd. According to further embodiments, the guard 13 may comprise another number of adjacent elongated openings 13' than two, such as one, three, four, five, six, or the like. Due to the features of the guard 13, and the design of the adjacent elongated openings 13', accumulation of clippings can be avoided and can be removed in an efficient manner from the guard 13 and the adjacent elongated openings 13' when the robotic lawnmower1 is moving in the fonNard moving direction fd.

However, according to further embodiments, the guard 13 may be arranged to cover a portion of the rear section 32 of the second cutting unit 12. According to some embodiments, the guard 13 covers a portion of the rear section 32 of the second cutting unit 12 located at the second side 27 of the second cutting unit 12. ln this manner, the guard 13 can prevent impact between the second cutting unit 12 and objects moving towards the second cutting unit 12 from the lateral side 41 in directions having a moving vector component in the forward moving direction fd of the robotic lawnmower 1.

Portions of the guard 13 covering the rear section 32 of the second cutting unit 12 may comprise one or more open sections allowing passage of grass. According to such embodiments, the portion of the guard 13 covering the rear section 32 of the second cutting unit 12 may be formed as a grid, a lattice, a grating, or the like. Moreover, according to some embodiments, the guard 13 may be open in the fonNard moving direction fd and may not cover a portion of the front section 23 of the second cutting unit 12. Moreover, according to some embodiments, the robotic lawnmower 1 may comprise a guard covering at least a portion of the first cutting unit 11.

As is best seen in Fig. 2, according to the illustrated embodiments, the first and second cutting units 11, 12 are arranged with different inclination angles a1, a2 relative to the first 21 plane P1. ln general, a positive angle of a cutting unit relative to a ground surface can be defined as an angle in which the leading edge of the cutting unit is closer to the ground surface than the trailing edge of the cutting unit.

Normally, the best cutting result is obtained if the angle between the cutting plane and a ground plane is close to zero but still on the positive side. A positive angle helps keeping the operation speed of the cutting unit up and it will improve the energy efficiency of the lawnmower. This is because the cutting members or cutting edges at the trailing edge of the cutting unit, and the radial centre portion of the cutting unit, will be located at a greater distance from the ground surface than the leading edge of the cutting unit and will thereby not be subjected to grass during movement of the lawnmower. However, if the angle is too big on the positive side, the cutting result may be affected to the negative. This because a large positive angle of the cutting unit relative to the ground surface may create a more curved cutting track. Curved cutting tracks may form visible cutting tracks in the lawn which impairs the cutting result.

According to the illustrated embodiments, the first cutting unit 11 is arranged with an inclination angle a1 relative to the first plane P1 such that a leading portion 11' of the first cutting unit 11 is closer to the first plane P1 than a trailing portion 11" of the first cutting unit 11 when the robotic lawnmower 1 is moving in the forward moving direction fd. Moreover, according to the illustrated embodiments, the second cutting unit 12 is arranged with an inclination angle a2 relative to the first plane P1 such that a leading portion 12" of the second cutting unit 12 is closer to the first plane P1 than a trailing portion 12' of the second cutting unit 12 when the robotic lawnmower 1 is moving in the reverse moving direction rd. As understood from the above, when the robotic lawnmower 1 is moving in the forward moving direction fd, the section 12" indicated with reference sign "12"" in Fig. 2 will be a trailing section 12" of the second cutting unit 12 and the section 12' indicated with reference sign "12"' in Fig. 2 will be a leading section 12' of the second cutting unit 12. Thus, according to the illustrated embodiments, the second cutting unit 12 is arranged with an inclination angle a2 relative to the first plane P1 such that a trailing portion 12" of the second cutting unit 12 is closer to the first plane P1 than a leading portion 12' of the second cutting unit 12 when the robotic lawnmower 1 is moving in the forward moving direction fd. Thereby, the first cutting unit 11 can be utilized to cut grass in an efficient manner with a good cutting result when the robotic lawnmower 1 is moving in the forward moving direction fd and the second cutting unit 12 can be utilized to cut grass in an efficient manner with a good cutting result when the robotic lawnmower 1 is moving in the reverse moving direction rd. This because the second 22 cutting unit 12 has a positive inclination angle a2 relative to the first plane P1 when the robotic lawnmower 1 is moving in the reverse moving direction rd. ln Fig. 2, two planes P1' are indicated which each is parallel to the first plane P1. The two planes P1' are illustrated for the purpose of facilitating indication of the inclination angles a1, a2 of the first and second cutting units 11, 12. As can be seen in Fig. 2, the inclination angle a1 of the first cutting unit 11 may be defined as the angle a1 bet\Neen the cutting plane P11 of the first cutting unit 11 and the first plane P1. Likewise, the inclination angle a2 of the second cutting unit 12 may be defined as the angle a2 between the cutting plane P12 of the second cutting unit 12 and the first plane P1. ln Fig. 2, the first inclination angle a1 is approximately 3 degrees and the second inclination angle a2 is approximately 5 degrees. As understood from the above, according to the illustrated embodiments, the inclination angle a1 of the first cutting unit 11 relative to the first plane P1 can be said to be a positive inclination angle a1 when the robotic lawnmower1 is moving in the fonNard moving direction fd and can be said to be a negative inclination angle a1 when the robotic lawnmower1 is moving in the reverse moving direction rd. Likewise, according to the illustrated embodiments, the inclination angle a2 of the second cutting unit 12 relative to the first plane P1 can be said to be a negative inclination angle a2 when the robotic lawnmower1 is moving in the fon/vard moving direction fd and can be said to be a positive inclination angle a2 when the robotic lawnmower 1 is moving in the reverse moving direction rd.

As indicated above, the support wheel 6 can pivot around a pivot axis such that the rolling direction of the support wheel 6 can follow a travel direction of the robotic lawnmower 1. The robotic lawnmower 1 comprises an attachment assembly 31 attaching and supporting the support wheel 6 relative to the lawnmower body 3, 3". The attachment assembly 31 may also be referred to as a supporting assembly or a wheel supporting assembly. As can be seen in Fig. 2, the attachment assembly 31 comprises a swivel joint 33 pivotally attaching the support wheel 6 to the lawnmower body 3, 3' around a pivot axis pA. According to the illustrated embodiments, the support wheel 6 may also be referred to as a swivel caster wheel. ln Fig. 1 - Fig. 3, the support wheel is illustrated in a position corresponding to a position that the support wheel 6 is pivoted to when the robotic lawnmower 1 is moving in the forward moving direction fd.

Fig. 4 illustrates the robotic lawnmower 1 illustrated in Fig. 2 in which the support wheel 6 is pivoted to a position corresponding to a position that the support wheel 6 is pivoted to when the robotic lawnmower 1 is moving in the reverse moving direction rd. Below, simultaneous reference is made to Fig. 2 and Fig. 4, if not indicated otherwise. As can be seen in these 23 figures, the pivot axis pA is angled relative to the vertical direction vd of the lawnmower body 3'. Thereby, the attachment assembly 31 will support the lawnmower body 3' at different distances d4, d5 from the first plane P1 based on the moving direction of the robotic lawnmower 1. This is because the attachment assembly 31 will hold the support wheel 6 at different distances from the lawnmower body 3' based on the pivoting angle of the support wheel 6 around the pivot axis pA.

According to the i||ustrated embodiments, the pivot angle pA is angled such that the attachment assembly 31 supports the lawnmower body 3' at a smaller distance d5 to the first plane P1 when the robotic lawnmower 1 is moving in the reverse moving direction rd than when the robotic lawnmower 1 is moving in the fonNard moving direction fd. This is obtained by the pivot axis pA being tilted backwards as seen relative to the fon/vard moving direction fd of the robotic lawnmower 1. That is, in other words, the pivot axis pA is tilted towards the reverse moving direction rd of the robotic lawnmower 1 as seen along a direction opposite to the vertical direction vd indicated in Fig. 1 and in Fig. 2.

Thereby, a simple, an efficient, a reliable, and a low cost solution is provided for supporting the lawnmower body 3' at different distances d4, d5 from the first plane P1 based on the moving direction fd, rd of the robotic lawnmower 1. According to the i||ustrated embodiments, the angle a3 between the pivot axis pA and the vertical direction vd of the robotic lawnmower 1 is approximately 11 degrees. According to further embodiments, the angle a3 between the pivot axis pA and the vertical direction vd of the robotic lawnmower 1 may be within the range of 1 - 30 degrees or may be within the range of 5 - 17 degrees. As indicated above, the vertical direction vd of the robotic lawnmower 1 is perpendicular to the first plane P1.

Since the attachment assembly 31 is configured to support the lawnmower body 3' at different distances d4, d5 from the first plane P1 based on the moving direction fd, rd of the robotic lawnmower 1, several advantages can be obtained as is explained in the following. One advantage is that the second cutting unit 12 is lifted to a position higher from a ground surface 2 when the robotic lawnmower 1 is moving in the fonNard moving direction fd. Thereby, it can be ensured that the second cutting unit 12 does not disturb cutting when using the first cutting unit 11 upon movement of the robotic lawnmower 1 in the forward moving direction fd. Moreover, the second cutting unit 12 is less likely to bump into objects on a lawn and objects protruding from a lawn when the robotic lawnmower 1 is moving in the forward moving direction fd. 24 Another advantage is that the second cutting unit 12 is moved closer to a ground surface 2 when the robotic lawnmower 1 is moving in the reverse moving direction rd. Thereby, the second cutting 12 can cut grass in an efficient manner upon movement of the robotic lawnmower 1 in the reverse moving direction rd. Moreover, a safer robotic lawnmower 1 can be provided because the moving of the second cutting unit 12 closer to the ground surface 2 can reduce the likelihood of objects reaching the second cutting unit 12 from sides of the robotic lawnmower 1 during operation of the second cutting unit 12.

A further advantage is that more advantageous inc|ination angles a1, a2 of the first and second cutting units 11, 12 can be obtained upon movement of the robotic lawnmower1 in the fonNard and reverse moving directions fd, rd. That is, as can be seen when comparing Fig. 2 and Fig. 4, the inc|ination angles a1, a2 of the first and second cutting units 11, 12 changes as a result of the attachment assembly 31 changing the distances d4, d5 from the lawnmower body 3' to the first plane P1. This is because the robotic lawnmower 1 according to the illustrated embodiments comprises two lawnmower support members 5, 5' arranged at a fix distance relative to the lawnmower body 3', namely the drive wheels 5, 5' of the robotic lawnmower 1. The first and second cutting units 11, 12 may be attached to the lawnmower body 3' in a respective rotation axis ax1, ax2 whose inc|ination angle relative to the lawnmower body 3' is chosen considering the effect of the support characteristics of the attachment assembly 31.

As indicated above, according to the illustrated embodiments, the robotic lawnmower 1 comprises three wheels 5, 5', 6, namely two drive wheels 5, 5' and one support wheel 6. According to further embodiments, the robotic lawnmower 1 may comprise two or more support wheels 6. According to such embodiments, such two or more support wheels 6 may comprise the same features, functions, and advantages, as the support wheel 6 explained herein. Moreover, according to such embodiments, the two or more support wheels 6 may be attached to the lawnmower body 3 relatively close to each other to not disturb cutting or flatten grass prior to reaching the second cutting unit 12 when the robotic lawnmower 1 is moving in the reverse moving direction rd.

As explained above, according to the illustrated embodiments, the attachment assembly 31 is capable of changing the distances d4, d5 between the lawnmower body 3' and the first plane P1 by comprising a swivel joint 33 pivotally attaching the support wheel 6 to the lawnmower body 3, 3' around a pivot axis pA being angled relative to the vertical direction vd of the robotic lawnmower 1. However, according to further embodiments, the robotic lawnmower 1 may comprise another type of structure, device, or arrangement capable of supporting the lawnmower body 3, 3' at different distances d4, d5 from the first plane P1 based on the moving direction fd, rd of the robotic lawnmower 1. Such a structure, device, or arrangement may for example comprise one or more of an actuator, a solenoid, a cam surface, or the like. Thus, such a structure, device, or arrangement may for example be used to support the lawnmower body 3 at different distances d4, d5 from the first plane P1 by changing the relative distance between one or more support wheels 6 and the lawnmower body 3.

As an alternative to, or in addition to, a structure, device, or arrangement for support the lawnmower body 3 at different distances d4, d5 from the first plane P1, the robotic lawnmower 1 may comprise an arrangement capable of changing the position of one or both of the first and second cutting units 11, 12 relative to the lawnmower body 3 so as to change the distance from the cutting unit 11, 12 to the first plane P1. According to some embodiments, the robotic lawnmower1 may comprise a manual adjustment arrangement allowing a user to manually adjust the cutting hight of one or both of the first and second cutting units 11, 12 by manually adjusting the position of one or both of the first and second cutting units 11, 12 relative to the lawnmower body 3.

According to further embodiments, the robotic lawnmower 1 may comprise an automatic adjustment arrangement configured to automatically adjust the cutting hight of one or both of the first and second cutting units 11, 12 by automatically adjusting the position of one or both of the first and second cutting units 11, 12 relative to the lawnmower body 3. Such an automatic adjustment arrangement may comprise one or more electric actuators or motors for changing the position of one or both of the first and second cutting units 11, 12 relative to the lawnmower body 3. According to these embodiments, the control arrangement 21 of the robotic lawnmower 1 may be operably connected to the automatic adjustment arrangement and may be configured to control the automatic adjustment arrangement based on whether the robotic lawnmower 1 is moving in the forward or reverse moving directions fd, rd.

As an example, according to these embodiments, the control arrangement 21 may cause the automatic adjustment arrangement to lower the first cutting unit 11 to a position closer to the first plane P1, and/or to raise the second cutting unit 12 to a higher position from the first plane P1, when the robotic lawnmower1 is moving in the forward moving direction fd. Likewise, according to these embodiments, the control arrangement 21 may cause the automatic adjustment arrangement to lower the second cutting unit 12 to a position closer to the first plane P1, and/or to raise the first cutting unit 11 to a higher position from the first plane P1, when the robotic lawnmower1 is moving in the reverse moving direction rd. 26 One skilled in the art will appreciate the control performed by the control arrangement 21 described herein may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, Which, when it is executed in the control arrangement 21, ensures that the control arrangement 21 carries out the desired control. The computer program is usually part of a computer program product which comprises a suitable digital storage medium on which the computer program is stored.

The control arrangement 21 may comprise a calculation unit which may take the form of substantially any suitable type of processor circuit or microcomputer, e.g. a circuit for digital signal processing (digital signal processor, DSP), a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The herein utilised expression "calculation unit" may represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.

The control arrangement 21 may further comprise a memory unit, wherein the calculation unit may be connected to the memory unit, which may provide the calculation unit with, for example, stored program code and/or stored data which the calculation unit may need to enable it to do calculations. The calculation unit may also be adapted to store partial or final results of calculations in the memory unit. The memory unit may comprise a physical device utilised to store data or programs, i.e., sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory unit may comprise integrated circuits comprising silicon-based transistors. The memory unit may comprise e.g. a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile or non-volatile storage unit for storing data such as e.g. ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc. in different embodiments.

The control arrangement 21 is connected to components of the robotic lawnmower 1 for receiving and/or sending input and output signals. These input and output signals may comprise waveforms, pulses, or other attributes which the input signal receiving devices can detect as information and which can be converted to signals processable by the control arrangement 21. These signals may then be supplied to the calculation unit. One or more output signal sending devices may be arranged to convert calculation results from the calculation unit to output signals for conveying to other parts of the control system and/or the 27 component or components for which the signals are intended. Each of the connections to the respective components of the robotic lawnmower 1 for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, or some other bus configuration, or a wireless connection. ln the embodiments illustrated, the robotic lawnmower 1 comprises a control arrangement 21 but might alternatively be implemented wholly or partly in two or more control arrangements or t\No or more control units.

The computer program product may be provided for instance in the form of a data carrier carrying computer program code for performing the desired control when being loaded into one or more calculation units of the control arrangement 21. The data carrier may be, e.g. a CD ROM disc, or a ROM (read-only memory), a PROM (programable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non- transitory manner. The computer program product may furthermore be provided as computer program code on a server and may be downloaded to the control arrangement 21 remotely, e.g., over an lnternet or an intranet connection, or via other Wired or wireless communication systems.

The control arrangement 21 may be configured to control propulsion of the robotic lawnmower 1, and steer the robotic lawnmower 1, so as to navigate the robotic lawnmower 1 in an area to be operated. The robotic lawnmower 1 may further comprise one or more sensors arranged to sense a magnetic field of a wire, and/or one or more positioning units, and/or one or more sensors arranged to detect an impending or ongoing collision event with an object. The one or more positioning units may comprise a space based satellite navigation system such as a Global Positioning System (GPS), The Russian GLObal NAvigation Satellite System (GLONASS), European Union Galileo positioning system, Chinese Compass navigation system, or Indian Regional Navigational Satellite System. As an alternative, or in addition, the control arrangement 21 may be configured to obtain data from, or may comprise, one or more positioning units utilizing a local reference source, such as a local sender and/or a wire, to estimate or verify a current position of the robotic lawnmower 1. ln addition, the robotic lawnmower 1 may comprise a communication unit connected to the control arrangement 21. The communication unit may be configured to communicate with a 28 remote communication unit to receive instructions therefrom and/or to send information thereto. The communication may be performed wirelessly over a wireless connection such as the internet, or a wireless local area network (WLAN), or a wireless connection for exchanging data over short distances using short-wavelength, i.e. ultra-high frequency (UHF) radio waves in the industrial, scientific, and medical (ISM) band from 2.4 to 2.485 GHz.

The control arrangement 21 may be configured to control propulsion of the robotic lawnmower 1, and steer the robotic lawnmower 1, so as to navigate the robotic lawnmower 1 in a systematic and/or random pattern to ensure that an area is completely covered, using input from one or more of the above described sensors and/or units. Furthermore, the robotic lawnmower 1 may comprise one or more batteries arranged to supply electricity to components of the robotic lawnmower 1. As an example, the one or more batteries may be arranged to supply electricity to propulsion motors of the robotic lawnmower 1 configured to rotate the drive wheels 5, 5' by an amount controlled by the control arrangement 21. Moreover, the one or more batteries may be arranged to supply electricity to a motor configured to power the first cutting unit 11 and to supply electricity to a motor configured to power the second cutting unit 12 by an amount controlled by the control arrangement 21.

The control arrangement 21 may be configured to receive data indicative of whether the robotic lawnmower 1 is propelled in the fonNard moving direction fd or in the reverse moving direction rd of the robotic lawnmower 1 and may be configured to control operation of the first and second cutting units 11, 12 in response thereto. As an alternative, or in addition, the control arrangement 21 may control propulsion of the robotic lawnmower 1 in the fonNard and reverse moving directions fd, rd and may be configured to control operation of the first and second cutting units 11, 12 in response to whether the control arrangement is propelling the robotic lawnmower 1 in the fonNard moving direction fd or is propelling the robotic lawnmower 1 in the reverse moving direction rd. ln line with the embodiments described herein, the control arrangement 2 may operate the first cutting unit 11 upon propulsion in the fonNard moving direction fd and may operate the second cutting unit 12 upon propulsion in the reverse moving direction fd. The control arrangement 21 may trigger a reversal of the moving direction from the fonNard moving direction fd to the reverse moving direction rd and may trigger a cancellation of operation of the first cutting unit 11, and trigger operation of the second cutting unit 12 to cut vegetation close to borders and objects such as trees, stones, furniture, building walls, and the like, using the second cutting unit 12. 29 The wording "substantially parallel to", as used herein, may encompass that the angle between the objects referred to is less than 10 degrees, or less than 7 degrees. lt is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended independent claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the present invention, as defined by the appended independent claims.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components, or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions, or groups thereof.

Claims

1. A self-propelled robotic lawnmower (1) comprising: - a lawnmower body (3), - a number of lawnmower support members (5, 5', 6) configured to support the lawnmower body (3) by abutting against a ground surface (

2. ) in a first p|ane (P1) during operation of the robotic lawnmower (1 ), - a first cutting unit (11), and - a second cutting unit (12), wherein the robotic lawnmower (1) comprises a control arrangement (21) configured to control operation of the first and second cutting units (11, 12) based on whether the robotic lawnmower (1) is prope||ed in a forward moving direction (fd) or in a reverse moving direction (rd) of the robotic lawnmower (1). The robotic lawnmower (1) according to c|aim 1, wherein the control arrangement (21) is configured to operate the first cutting unit (11)when the robotic lawnmower (1) is prope||ed in the forward moving direction (fd) and is configured to operate the second cutting unit (12) when the robotic lawnmower (1) is prope||ed in the reverse moving direction (rd). The robotic lawnmower (1) according to c|aim 1 or 2, wherein the control arrangement (21) is configured to cancel operation of the second cutting unit (12) when the robotic lawnmower (1) is prope||ed in the forward moving direction (fd). _ The robotic lawnmower (1) according to any one of the preceding claims, wherein the first cutting unit (11) is larger in size than the second cutting unit (12). The robotic lawnmower (1) according to any one of the preceding claims, wherein the first and second cutting units (11, 12) are arranged with different inclination angles (a1, a2) relative to the first p|ane (P1). The robotic lawnmower (1) according to any one of the preceding claims, wherein the first cutting unit (11) is arranged with an inclination angle (a1) relative to the first p|ane (P1) such that a leading portion (11') of the first cutting unit (11) is closer to the first p|ane (P1) than a trailing portion (11”) of the first cutting unit (11)when the robotic lawnmower (1) is moving in the forward moving direction (fd), and wherein the second cutting unit (12) is arranged with an inclination angle (a2) relative to the first p|ane (P1) such that a leading portion (12”) of the second cutting unit (12) is closer to the first p|ane(P1) than a trailing portion (12') of the second cutting unit (12) when the robotic lawnmower (1) is moving in the reverse moving direction (rd). _ The robotic lawnmower (1) according to any one of the preceding claims, wherein the first cutting unit (11) is configured to rotate around a first rotation axis (ax1) during operation and the second cutting unit (12) is configured to rotate around a second rotation axis (ax2) during operation, and wherein each of the first and second rotation axis (ax1, ax2) is transversal to the first p|ane (P1). The robotic lawnmower (1) according to claim 7, wherein the second rotation axis (ax2) is located at distance (d1) from the first rotation axis (ax1) in a |atera| direction (Ld) of the robotic lawnmower (1 ). The robotic lawnmower (1) according to claim 7 or 8, wherein the second rotation axis (ax2) is arranged behind the first rotation axis (ax1) seen relative to the fonNard moving direction (fd) of the robotic lawnmower (1 ). The robotic lawnmower (1) according to any one of the claims 7 - 9, wherein the first rotation axis (ax1) is located at a |ongitudina| centre p|ane (LCP) of the robotic lawnmower (1 ). The robotic lawnmower (1) according to any one of the claims 7 - 10, wherein the second rotation axis (ax2) is arranged at a distance (d2) from a |ongitudina| centre p|ane (LCP) of the robotic lawnmower (1 ). The robotic lawnmower (1) according to any one of the preceding claims, wherein the robotic lawnmower (1) comprises a guard (13) covering at least a portion of the second cutting unit (12). The robotic lawnmower (1) according to any one of the preceding claims, wherein the number of lawnmower support members (5, 5', 6) comprises at least two drive wheels (5, 5') and at least one support wheel (6). The robotic lawnmower (1) according to any one of the preceding claims, wherein the number of lawnmower support members (5, 5', 6) comprises two drive wheels (5, 5') and one support wheel (6), wherein the support wheel (6) is attached to the lawnmower body

3. (3) at a |ongitudina| centre p|ane (LCP) of the robotic lawnmower (1).15. The robotic lawnmower (1) according to any one of the claims 7 - 11 and claim 13 or 14, wherein a drive wheel (5) of the at least tvvo drive wheels (5, 5') is configured to rotate in a rotationa| plane (rP), and wherein the second rotation axis (ax2) is arranged closer to the rotationa| plane (rP) of the drive wheel (5) than to a longitudinal centre plane (LCP) of the robotic lawnmower (1 ).

4. The robotic lawnmower (1) according to any one of the claims 13 - 15, wherein one or more radially outer portions (29) of the second cutting unit (12) orbits in a circular path (C2), and wherein a drive wheel (

5. ) of the at least two drive wheels (5, 5') is configured to rotate in a rotationa| plane (rP) extending through the circular path (C2). The robotic lawnmower (1) according to any one of the claims 13 - 16, wherein the at least two drive wheels (5, 5') constitute front wheels and the at least one support wheel (6) constitutes a rear wheel of the robotic lawnmower (1 ). The robotic lawnmower (1) according to any one of the preceding claims, wherein the robotic lawnmower (1) comprises an attachment assembly (31) attaching one lawnmower support member (6) of the number of lawnmower support members (5, 5',

6. ) to the lawnmower body (3), and wherein the attachment assembly (31) is configured to support the lawnmower body (3) at different distances (d4, d5) from the first plane (P1) based on the moving direction of the robotic lawnmower (1 ). The robotic lawnmower (1) according to claim 18, wherein the attachment assembly (31) is configured to support the lawnmower body (3) at a smaller distance (d5) to the first plane (P1) when the robotic lawnmower (1) is moving in the reverse moving direction (rd) than when the robotic lawnmower (1) is moving in the fonNard moving direction (fd). The robotic lawnmower (1) according to claim 18 or 19, wherein the attachment assembly (31) comprises a swivel joint (33) pivotally attaching the lawnmower support member (6) to the lawnmower body (3) around a pivot axis (pA), and wherein the pivot axis (pA) is angled relative to a vertical direction (vd) of the lawnmower body (3).