Autonomous Robotic Lawnmower Comprising Suspension Means Progressively Limiting Pivotal Movement of a Cutting Unit

Abstract

An autonomous robotic lawnmower (1) is disclosed comprising a driving unit (3) comprising one or more drive wheels (5), and a cutting unit (7) configured to cut grass during operation of the lawnmower (1). The cutting unit (7) comprises one or more support wheels (9) configured to support the cutting unit (7) by abutting against a ground surface (11) during operation of the lawnmower (1). The cutting unit (7) is movably arranged relative to the driving unit (3). The lawnmower (1) comprises a suspension assembly (13, 13′) configured to progressively limit movement between the cutting unit (7) and the driving unit (3) during operation of the lawnmower (1).

Claims

1. An autonomous robotic lawnmower comprising: a driving unit comprising one or more drive wheels, and a cutting unit configured to cut grass during operation of the lawnmower, wherein the cutting unit comprises one or more support wheels configured to support the cutting unit by abutting against a ground surface during operation of the lawnmower, wherein the cutting unit is movably arranged relative to the driving unit, and wherein the lawnmower comprises a suspension assembly configured to progressively limit movement between the cutting unit and the driving unit during operation of the lawnmower.

2. The lawnmower according to claim 1, wherein the cutting unit is pivotally arranged around a pivot axis relative to the driving unit.

3. The lawnmower according to claim 2, wherein the pivot axis is substantially parallel to a forward direction of travel of the lawnmower.

4. The lawnmower according to claim 2, wherein the lawnmower comprises a shaft, and wherein the cutting unit is pivotally arranged relative to the driving unit via the shaft.

5. The lawnmower according to claim 2, wherein the suspension assembly comprises one or more suspension units arranged at a distance from the pivot axis.

6. The lawnmower according to claim 2, wherein the suspension assembly comprises a first suspension unit arranged on a first side of a vertical plane extending along the pivot axis and a second suspension unit arranged on a second side of the vertical plane extending along the pivot axis.

7. The lawnmower according to claim 2, wherein the suspension assembly is configured to limit pivoting movement between the cutting unit and the driving unit.

8. The lawnmower according to claim 7, wherein the suspension assembly is configured to limit pivoting movement between the cutting unit and the driving unit to a maximum pivoting movement within the range of 7 degrees to 15 degrees.

9. The lawnmower according to claim 1, wherein the suspension assembly comprises one or more suspension units each comprising a spring element.

10. The lawnmower according to claim 1, wherein the driving unit comprises two or more drive wheels and the cutting unit comprises two or more support wheels.

11. The lawnmower according to claim 1, wherein the suspension assembly is configured to bias the cutting unit towards a neutral position relative to the driving unit.

12. The lawnmower according to claim 11, wherein the neutral position constitutes a position of the cutting unit relative to the driving unit in which each ground engaging portion of said drive wheels and said support wheels extend along a flat plane.

13. The lawnmower according to claim 11, wherein the suspension assembly is configured to bias the cutting unit towards the neutral position with a magnitude that increases with increasing offset of the cutting unit from the neutral position.

14. The lawnmower according to claim 1, wherein the lawnmower comprises a driving unit chassis and a cutting unit chassis, and wherein the suspension assembly is configured to progressively limit movement between the cutting unit chassis and the driving unit chassis.

15. The lawnmower according to claim 1, wherein the driving unit comprises one or more electrical motors configured to rotate said one or more drive wheels to provide motive power to the lawnmower.

16. The lawnmower according to claim 1, wherein the lawnmower comprises a control unit configured to propel the lawnmower in an autonomous manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Various aspects of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:

[0036] FIG. 1 illustrates an autonomous robotic lawnmower, according to some embodiments,

[0037] FIG. 2 illustrates a lawnmower chassis of the autonomous robotic lawnmower illustrated in FIG. 1,

[0038] FIG. 3 illustrates a top view of the lawnmower chassis illustrated in FIG. 2, and

[0039] FIG. 4 illustrates a cross section of the lawnmower chassis illustrated in FIG. 3.

DETAILED DESCRIPTION

[0040] 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.

[0041] FIG. 1 illustrates an autonomous robotic lawnmower 1, according to some embodiments. As is further explained herein, the autonomous robotic lawnmower 1 is a self-propelled autonomous robotic lawnmower 1 capable of navigating and cutting grass in an area without the intervention of a user. For the reason of brevity and clarity, the autonomous 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 driving unit 3 comprising drive wheels 5. According to the illustrated embodiments, the robotic lawnmower 1 comprises two drive wheels 5. According to further embodiments, the robotic lawnmower 1 may comprise another number of drive wheels 5, such as one, three, or the like.

[0042] Moreover, the robotic lawnmower 1 comprises a cutting unit 7 configured to cut grass during operation of the robotic lawnmower 1. According to the illustrated embodiments, the cutting unit 7 comprises two support wheels 9 configured to support the cutting unit 7 by abutting against a ground surface 11 during operation of the robotic lawnmower 1. According to further embodiments, the robotic lawnmower 1 may comprise another number of support wheels 9, such as one, three, four, or the like.

[0043] The robotic lawnmower 1 comprises a control unit 23. The control unit 23 is configured to propel and navigate the robotic lawnmower 1 in an autonomous manner without the intervention of a user by controlling electrical motors configured to rotate the driving wheels, using input from a sensor 25. The control unit 23 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 sensor 25 may 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. In addition, the robotic lawnmower 1 may comprise a communication unit connected to the control unit 23. 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 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.

[0044] The control unit 23 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 unit 23.

[0045] According to the illustrated embodiments, the control unit 23 is configured to steer the robotic lawnmower 1 by controlling drive wheels 5 on opposite sides of the driving unit 3 to rotate at different speeds. In FIG. 1, a forward direction fd of travel of the robotic lawnmower 1 is indicated. According to the illustrated embodiments, the forward direction fd of travel is a direction obtained when the drive wheels 5 of the driving unit are rotating at the same rotational speed in a forward rotational direction and the robotic lawnmower 1 is propelled on a flat horizontal surface with no wheel slip. According to the illustrated embodiments, the cutting unit 7 is arranged in front of the driving unit 3 seen in the forward direction fd. Moreover, according to the illustrated embodiments, the driving unit 3 is arranged behind the cutting unit 7 seen in the forward direction fd and the drive wheels 5 can, according to the illustrated embodiments, be referred to as rear wheels.

[0046] 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. The sports fields may include soccer fields, golf courses, and the like. According to some embodiments of the present disclosure, the weight of the robotic lawnmower is less than 100 kg, or less than 75 kg. Moreover, according to some embodiments of the present disclosure, the length of the robotic lawnmower 1, measured in the forward direction fd, is less than 1.5 metres, and the width of the robotic lawnmower 1, measured in a direction perpendicular to the forward direction fd, is less than 1.5 metres.

[0047] FIG. 2 illustrates a lawnmower chassis 1′ of the robotic lawnmower 1 illustrated in FIG. 1. Below, simultaneous reference is made to FIG. 1 and FIG. 2. As is evident from FIG. 2, the robotic lawnmower chassis 1′ of the robotic lawnmower 1 illustrated in FIG. 1 comprises a driving unit chassis 3′ and a cutting unit chassis 7′. The driving unit chassis 3′ form part of the driving unit 3 and is arranged to support components of the driving unit 3. The cutting unit chassis 7′ form part of the cutting unit 7 and is arranged to support components of the cutting unit 7.

[0048] Moreover, in FIG. 2, the support wheels 9 of the cutting unit 7, as well as the drive wheels 5 of the driving unit 3, are fully visible. Moreover, as is evident from FIG. 2, according to the illustrated embodiments, the robotic lawnmower 1 comprises one electrical motor 21 per drive wheel 5, wherein each electrical motor 21 is configured to rotate one drive wheel 5 to steer and propel, i.e. provide motive power to, the robotic lawnmower 1. According to further embodiments, the robotic lawnmower 1 may comprise another number of electrical motors 21, such as one electrical motor arranged to rotate more than one drive wheel to provide motive power to the robotic lawnmower 1.

[0049] Moreover, as can be seen in FIG. 2, the cutting unit 7 comprises a number of cutting members 12 arranged to cut grass during operation of the robotic lawnmower 1. According to the illustrated embodiments, the cutting unit 7 comprises three cutting members 12 in the form of cutting discs. According to further embodiments, the cutting unit 7 may comprise another number of cutting members 12, and another type of cutting members 12, such as one or more cutting arms.

[0050] According to the embodiments explained herein, the cutting unit 7 is movably arranged relative to the driving unit 3. According to the illustrated embodiments, the cutting unit 7 is pivotally arranged to the driving unit 3 to pivot around a pivot axis ax. As can be seen in FIG. 1, the robotic lawnmower 1 comprises a shaft 15, and wherein the cutting unit 7 is pivotally arranged relative to the driving unit 3 via the shaft 15. The direction of elongation of the shaft 15 extends in a direction substantially coinciding with the forward direction fd of travel of the robotic lawnmower 1. Thus, due to these features, the cutting unit 7 is pivotally arranged to the driving unit 3 around a pivot axis ax being substantially parallel to a forward direction fd of travel of the robotic lawnmower 1, as well as being substantially parallel to a horizontal flat plane p2 onto which the robotic lawnmower 1 is positioned.

[0051] Moreover, according to the embodiments explained herein, the robotic lawnmower 1 comprises a suspension assembly 13, 13′. The suspension assembly 13, 13′ is configured to progressively limit movement between the cutting unit 7 and the driving unit 3 during operation of the robotic lawnmower 1. As is evident from FIG. 2, according to the illustrated embodiments, this is achieved by the suspension assembly 13, 13′ being configured to progressively limit movement between the cutting unit chassis 7′ and the driving unit chassis 3′. Due to these features, when the robotic lawnmower 1 is travelling/moving over a ground surface 11 having irregularities, the suspension assembly 13, 13′ will to progressively limit movement between the cutting unit 7 and the driving unit 3. As a result, the cutting unit 7 may move relative to the driving unit 3 in a more controlled manner so as to follow the terrain of the ground surface 11 in a smoother and more controlled manner, which provides conditions for a further improved cutting result. As understood from the herein described, the feature that the suspension assembly 13, 13′ is configured to progressively limit movement between the cutting unit 7 and the driving unit 3 during operation of the robotic lawnmower 1 means that the suspension assembly 13, 13′ is configured to progressively limit movement between the cutting unit 7 and the driving unit 3 during travel/movement of the robotic lawnmower 1 over a ground surface 11. The cutting unit 7 may be active or inactive during such travel/movement of the robotic lawnmower 1.

[0052] FIG. 3 illustrates a top view of the lawnmower chassis 1′ illustrated in FIG. 2. As best seen in FIG. 3, the suspension assembly 13, 13′ comprises a first suspension unit 13 arranged on a first side s1 of a vertical plane p1 extending along the pivot axis ax and a second suspension unit 13′ arranged on a second side s2 of the vertical plane p1 extending along the pivot axis ax. The vertical plane p1 is a plane perpendicular to a horizontal plane onto which the robotic lawnmower 1 is positioned. Such a horizontal plane p2 is indicated in FIG. 2. Moreover, in FIG. 3, the electrical motors 21 of the respective drive wheel 5 are fully visible.

[0053] FIG. 4 illustrates a cross section of the lawnmower chassis 1′ illustrated in FIG. 3. Below, simultaneous reference is made to FIG. 1-FIG. 4. The cross section of FIG. 4 is made in a vertical plane perpendicular to the pivot axis ax at a portion of the lawnmower chassis 1′ comprising the suspension assembly 13, 13′. As can be seen in FIG. 4, each suspension unit 13, 13′ is arranged at a distance d from the pivot axis ax. Moreover, each suspension unit 13, 13′ comprises a spring element 15, 15′.

[0054] According to the illustrated embodiments, the suspension assembly 13, 13′ is configured to bias the cutting unit 7 towards a neutral position relative to the driving unit 3. In FIG. 1-FIG. 4, the cutting unit 7 is illustrated in the neutral position. As indicated in FIG. 2, the neutral position constitutes a position of the cutting unit 7 relative to the driving unit 3 in which each ground engaging portion 19 of said drive wheels 5 and said support wheels 9 extend along a flat plane p2.

[0055] As understood from the herein described, according to the illustrated embodiments, the suspension assembly 13, 13′ is configured to limit pivoting movement between the cutting unit 7 and the driving unit 3. If the cutting unit 7 is pivoted counterclockwise around the pivot axis ax in FIG. 4, from the neutral position to an offset position, a first spring element 15 of the first suspension unit 13 will be compressed and a second spring element 15′ of the second suspension unit 13′ will be expanded. Similarly, if the cutting unit 7 is pivoted clockwise around the pivot axis ax in FIG. 4, from the neutral position to an offset position, a first spring element 15 of the first suspension unit 13 will be expanded and a second spring element 15′ of the second suspension unit 13′ will be compressed. The distanced between each suspension unit 13, 13′ and the pivot axis ax and the biasing force of each suspension unit 13, 13′ may be adapted to provide a certain returning torque of the cutting unit 7 towards the neutral position.

[0056] Moreover, as understood from the above described, according to the illustrated embodiments, the suspension assembly 13, 13′ is configured to bias the cutting unit 7 towards the neutral position with a magnitude that increases with increasing offset of the cutting unit 7 from the neutral position. The first and second spring elements 15, 15′ may each provide a small biasing force, i.e. a small pre-tension, when the cutting unit 7 is in the neutral position.

[0057] According to further embodiments, the suspension assembly, as referred to herein, may comprise a torsion spring configured to limit pivoting movement between the cutting unit 7 and the driving unit 3.

[0058] According to some embodiments of the present disclosure, the suspension assembly 13, 13′ may be configured to progressively limit movement between the cutting unit 7 and the driving unit 3 with a limiting force that increases with increased rate of movement between the cutting unit 7 and the driving unit 3. According to such embodiments, the robotic lawnmower 1 may comprise one or more dampers, such as one or more mechanical or hydraulic shock absorbers, each being configured to limit movement between the cutting unit 7 and the driving unit 3 with a limiting force that increases with increased rate of movement between the cutting unit 7 and the driving unit 3. Such a damper or dampers are not illustrated in the figures for the reason of brevity and clarity. Alternatively, the suspension assembly 13, 13′ and the robotic lawnmower 1 may be free from such a damper or such dampers.

[0059] According to the illustrated embodiments, the suspension assembly 13, 13′ is configured to limit pivoting movement between the cutting unit 7 and the driving unit 3 to a maximum pivoting movement of approximately 10 degrees. According to further embodiments, the suspension assembly 13, 13′ may be configured to limit pivoting movement between the cutting unit 7 and the driving unit 3 to a maximum pivoting movement within the range of 7 degrees to 15 degrees, or within the range of 8 degrees to 12 degrees.

[0060] According to the illustrated embodiments, the first suspension unit 13 comprises a pair of stop surfaces 18 arranged to abut against each other when the first spring element 15 has been compressed a compression distance d2, to hinder further compression of the first spring element 15. According to the illustrated embodiments, compression distance d2 and distance d between the first suspension unit 13 and the pivot axis ax are arranged such that the pair of stop surfaces 18 abut against each other when the cutting unit 7 is pivoted approximately 5 degrees counterclockwise around the pivot axis ax from the neutral position illustrated in FIG. 4 to a first stop position. Likewise, the second suspension unit 13′ comprises a pair of stop surfaces 18′ arranged to abut against each other when the second spring element 15′ has been compressed a compression distance d2, to hinder further compression of the second spring element 15′. According to the illustrated embodiments, compression distance d2 and distance d between the second suspension unit 13′ and the pivot axis ax are arranged such that the pair of stop surfaces 18′ abut against each other when the cutting unit 7 is pivoted approximately 5 degrees clockwise around the pivot axis ax from the neutral position illustrated in FIG. 4 to a second stop position. In this manner, the stop surfaces 18, 18′ of the suspension assembly 13, 13′ will limit pivoting movement between the cutting unit 7 and the driving unit 3 to a maximum pivoting movement of approximately 10 degrees. As understood from the above, the wording maximum pivoting movement, as used herein, refers to a pivoting movement of the cutting unit 7 from the first stop position, past the neutral position, to the second stop position.

[0061] It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended 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 claims.

[0062] 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.