WO2020218960A1

WO2020218960A1 - Propulsion control arrangement, robotic tool, and method of propelling robotic tool

Info

Publication number: WO2020218960A1
Application number: PCT/SE2020/050358
Authority: WO
Inventors: Michel Chedid
Original assignee: Husqvarna Ab
Priority date: 2019-04-25
Filing date: 2020-04-07
Publication date: 2020-10-29
Also published as: SE543150C2; SE1950503A1

Abstract

A propulsion control arrangement (1) for a self-propelled robotic tool (3) is disclosed. The control arrangement (1) is configured to, in a starting procedure of the robotic tool (3), turn the robotic tool (3) to obtain a starting direction (d1) in which a start inclination angle (a1) of the robotic tool (3) is less than or equal to a threshold inclination angle (ax), and initiate propulsion of the robotic tool (3) in the starting direction (d1). The present disclosure further relates to a self-propelled robotic tool (3), a self-propelled robotic lawnmower (3), a method (100) of propelling a self-propelled robotic tool (3), a computer program, and a computer- readable medium (200).

Description

Propulsion Control Arrangement, Robotic Tool, and Method of Propelling

Robotic Tool

TECHNICAL FIELD

The present disclosure relates to a propulsion control arrangement for a self-propelled robotic tool. The present disclosure further relates to a self-propelled robotic tool comprising a propulsion control arrangement, a self-propelled robotic lawnmower comprising a propulsion control arrangement, a method of propelling a self-propelled robotic tool, a computer program, and a computer-readable medium.

BACKGROUND

Self-propelled robotic tools, such as self-propelled autonomous robotic lawnmowers, have become increasingly popular, partly because they usually are capable of performing work which previously was made manually. A Self-propelled robotic tool is capable of navigating in an area in an autonomous manner, i.e. without the intervention of a user. Some robotic tools require a user to set up a border wire around an area that defines the area to be operated by the robotic tool. Such robotic tools use a sensor to locate the wire and thereby the boundary of the area to be operated. As an alternative, or in addition, robotic tools 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 tool may move in a systematic and/or random pattern to ensure that the area is completely covered.

Many areas comprise more or less slopes which may pose problems for the traction and navigability of the robotic tool, especially in wet conditions. Such problems may adversely affect the coverage of an area operated by a robotic tool. Moreover, wheel slip of one or more wheels of the robotic tool may cause unwanted marks in the area operated by the robotic tool.

Moreover, generally, on today’s consumer market, it is an advantage if products, such as robotic tools and their associated devices, have conditions and/or characteristics suitable for being developed and manufactured in a cost-efficient manner.

SUMMARY

It 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 a first aspect of the invention, the object is achieved by a propulsion control arrangement for a self-propelled robotic tool. The control arrangement is configured to, in a starting procedure of the robotic tool, turn the robotic tool to obtain a starting direction in which a start inclination angle of the robotic tool is less than or equal to a threshold inclination angle, and initiate propulsion of the robotic tool in the starting direction.

In this manner, a propulsion control arrangement is provided capable of improving starting procedures of a robotic tool. This because the control arrangement is configured to turn the robotic tool to obtain a starting direction in which the start inclination angle of the robotic tool is less than or equal to the threshold inclination angle, and then initiate propulsion of the robotic tool in the starting direction. As a result thereof, upon propulsion of the robotic tool in the starting direction, the start inclination angle of the robotic tool will be less than or equal to the threshold inclination angle. Thereby, the risk of wheel slip can be reduced when initiating propulsion of the robotic tool in the starting direction. As a further result thereof, the risk of unwanted marks in the area operated by the robotic tool can also be reduced.

Moreover, as a result of these features, a propulsion control arrangement is provided capable of improving coverage of an area operated by a robotic tool. This because wheel slip of one or more wheels of the robotic tool may cause an unexpected change of direction of the robotic tool, which, due to the topography of the area, may result in that some parts of the area are operated more frequently, and some other parts of the area are operated less frequently.

Accordingly, since the propulsion control arrangement is capable of reducing the risk of wheel slip when initiating propulsion of the robotic tool in the starting direction, a propulsion control arrangement is provided capable of improving coverage of an area operated by a robotic tool.

Still further, since the propulsion control arrangement can improve coverage of an area operated by the robotic tool, the operational result of the robotic tool can be improved.

Moreover, the time required for operating an area can be reduced, as well as the travelling distance required for operating the area. Accordingly, a propulsion control arrangement is provided capable of reducing energy consumption, as well as wear and tear of robotic tools.

Accordingly, a propulsion control arrangement 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 threshold inclination angle is less than 8 degrees. Thereby, the risk of wheel slip is reduced when initiating propulsion of the robotic tool in the starting direction.

Optionally, the threshold inclination angle is approximately 0 degrees. Thereby, the risk of wheel slip is significantly reduced when initiating propulsion of the robotic tool in the starting direction.

Optionally, the control arrangement is configured to propel the robotic tool in the starting direction after initiating the propulsion in the starting direction. Thereby, a control arrangement is provided capable of propelling the robotic tool with a reduced risk of wheel slip.

Optionally, the control arrangement is configured to turn the robotic tool to a set direction after propulsion of the robotic tool in the starting direction. Thereby, a control arrangement is provided capable of turning the robotic tool towards the set direction with a reduced risk of wheel slip. This because upon initiation of the turn, the robotic tool is travelling in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a control arrangement is provided capable of turning the robotic tool towards a set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the control arrangement is configured to determine the set direction prior to initiating propulsion of the robotic tool in the starting direction. Thereby, a control

arrangement is provided capable of navigating the robotic tool towards a determined set direction with a reduced risk of wheel slip. This because upon initiation of the turn towards the determined set direction, the robotic tool is travelling in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a control arrangement is provided capable of turning the robotic tool towards a determined set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the set direction involves an inclination angle exceeding the threshold inclination angle. Thereby, a control arrangement is provided capable of navigating the robotic tool towards a set direction involving an inclination angle exceeding the threshold inclination angle with a reduced risk of wheel slip. This because upon initiation of the turn towards the set direction, the robotic tool is travelling in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a control arrangement is provided capable of turning the robotic tool towards a determined set direction involving an inclination angle exceeding the threshold inclination angle in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the control arrangement is configured to initiate the turn of the robotic tool towards the set direction based on reaching a predetermined velocity. Thereby, a control arrangement is provided capable of turning the robotic tool to the set direction with a reduced risk of wheel slip. This because the initiation of the turn is based on reaching a

predetermined velocity upon travelling in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a control arrangement is provided capable of turning the robotic tool towards a set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the control arrangement is configured initiate the turn of the robotic tool towards the set direction a predetermined time after initiating the propulsion in the starting direction. Thereby, a control arrangement is provided capable of turning the robotic tool to the set direction with a reduced risk of wheel slip. This because upon initiation of the turn towards the set direction, the robotic tool will have reached a certain velocity in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a control arrangement is provided capable of turning the robotic tool towards a set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the control arrangement is configured to perform a gradual turn from the starting direction towards the set direction. Thereby, a control arrangement is provided capable of turning the robotic tool from the starting direction towards the set direction with a reduced risk of wheel slip. As a further result thereof, a control arrangement is provided capable of turning the robotic tool towards a set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the control arrangement is configured to maintain the set direction after turning the robotic tool to the set direction. Thereby, a control arrangement is provided capable of navigating the robotic tool towards the set direction with a reduced risk of wheel slip, i.e. in a more reliable and controlled manner.

Optionally, the set direction is a random direction. Thereby, a control arrangement is provided capable of navigating the robotic tool towards a random set direction with a reduced risk of wheel slip. i.e. in a more reliable and controlled manner. As a further result, a propulsion control arrangement is provided capable of improving coverage of an area operated by a robotic tool.

That is, some prior art propulsion control arrangements may be configured to, in a starting procedure of the robotic tool, reversing the robotic tool to obtain a random starting direction and then initiate propulsion in the random starting direction. However, wheel slip of one or more wheels of the robotic tool may cause a change of direction of the robotic tool from the random direction to another direction, which, due to the topography of the area, may result in that some parts of the area are operated more frequently, and some other parts of the area are operated less frequently.

Since the propulsion control arrangement according to the present disclosure is capable of reducing the risk of wheel slip when initiating propulsion of the robotic tool in the starting direction, a propulsion control arrangement is provided capable of navigating a robotic tool to a random direction in a more controlled manner which improves coverage of an area operated by the robotic tool.

Optionally, the robotic tool comprises a sensor arranged to sense a current inclination angle of the robotic tool, and wherein the control arrangement is configured to turn the robotic tool to obtain the starting direction based on the sensed current inclination angle of the robotic tool. Thereby, a low-cost, and a non-complex solution is provided for obtaining a starting direction in which a start inclination angle of the robotic tool is less than or equal to the threshold inclination angle. According to a second aspect of the invention, the object is achieved by a self-propelled robotic tool comprising a propulsion control arrangement according to some embodiments of the present disclosure.

Thereby, a self-propelled robotic tool is provided capable of initiating propulsion in a starting direction with reduced risk of wheel slip. As a further result thereof, a self-propelled robotic tool is provided capable of starting with reduced risk of unwanted marks in the area operated by the robotic tool.

Still further, a self-propelled robotic tool is provided capable of operating an area with improved coverage and thereby an improved operational result. Moreover, the time required for operating an area can be reduced, as well as the travelling distance required for operating the area. Accordingly, a self-propelled robotic tool is provided having conditions for a reduced energy consumption, as well as wear and tear of the self-propelled robotic tool.

Accordingly, a self-propelled robotic tool 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.

According to a third aspect of the invention, the object is achieved by a self-propelled robotic lawnmower comprising a propulsion control arrangement according to some embodiments of the present disclosure.

Thereby, a self-propelled robotic lawnmower is provided capable of initiating propulsion in a starting direction with reduced risk of wheel slip. As a further result thereof, a self-propelled robotic lawnmower is provided capable of starting with reduced risk of unwanted marks in the area operated by the robotic lawnmower.

Still further, a self-propelled robotic lawnmower is provided capable of cutting an area with improved coverage and thereby an improved cutting result. Moreover, the time required for cutting an area can be reduced, as well as the travelling distance required for cutting the area. Accordingly, a self-propelled robotic lawnmower is provided having conditions for a reduced energy consumption, as well as wear and tear of the self-propelled robotic lawnmower. Accordingly, a self-propelled 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.

According to a fourth aspect of the invention, the object is achieved by a method of propelling a self-propelled robotic tool, wherein the method comprises the steps of, in a starting procedure of the robotic tool:

turning the robotic tool to obtain a starting direction in which a start inclination angle of the robotic tool is less than or equal to a threshold inclination angle, and

initiating propulsion of the robotic tool in the starting direction.

Thereby, a method is provided capable of improving starting procedures of the robotic tools. This because the method comprises the step of turning the robotic tool to obtain a starting direction in which the start inclination angle of the robotic tool is less than or equal to the threshold inclination angle, and the step of initiating propulsion of the robotic tool in the starting direction. As a result thereof, upon propulsion of the robotic tool in the starting direction, the start inclination angle of the robotic tool will be less than or equal to the threshold inclination angle. Thereby, the risk of wheel slip can be reduced when initiating propulsion of the robotic tool in the starting direction. As a further result thereof, the risk of unwanted marks in the area operated by the robotic tool can also be reduced.

Moreover, as a further result of these features, a method is provided capable of improving coverage of an area operated by a robotic tool. This because wheel slip of one or more wheels of the robotic tool may cause an unexpected change of direction of the robotic tool, which, due to the topography of the area, may result in that some parts of the area are operated more frequently, and some other parts of the area are operated less frequently.

Accordingly, since the propulsion control arrangement is capable of reducing the risk of wheel slip when initiating propulsion of the robotic tool in the starting direction, a method is provided capable of improving coverage of an area operated by a robotic tool.

Still further, since the method can improve coverage of an area operated by the robotic tool, the operational result of the robotic tool can be improved. Moreover, the time required for operating an area can be reduced, as well as the travelling distance required for operating the area. Accordingly, a method is provided capable of reducing energy consumption, as well as wear and tear of robotic tools. Accordingly, a method 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 method comprises the step of:

propelling the robotic tool in the starting direction after the step of initiating the propulsion in the starting direction.

Thereby, a method is provided capable of propelling the robotic tool with a reduced risk of wheel slip.

Optionally, the method further comprises the step of:

turning the robotic tool to a set direction after the step of propelling the robotic tool in the starting direction.

Thereby, a method is provided capable of turning the robotic tool to the set direction with a reduced risk of wheel slip. This because upon initiation of the turn, the robotic tool is travelling in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a method is provided capable of turning the robotic tool towards a set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the method further comprises the step of:

determining the set direction prior to the step of initiating propulsion of the robotic tool in the starting direction.

Thereby, a method is provided capable of navigating the robotic tool towards a determined set direction with a reduced risk of wheel slip. This because upon initiation of the turn towards the determined set direction, the robotic tool is travelling in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a method is provided capable of turning the robotic tool towards a determined set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the method comprises the step of: initiating the turning of the robotic tool towards the set direction based on reaching a predetermined velocity.

Thereby, a method is provided capable of turning the robotic tool to the set direction with a reduced risk of wheel slip. This because the initiation of the turn is based on reaching a predetermined velocity upon travelling in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a method is provided capable of turning the robotic tool towards a set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the method comprises the step of:

initiating the turning of the robotic tool towards the set direction a predetermined time after the step of initiating the propulsion in the starting direction.

Thereby, a method is provided capable of turning the robotic tool to the set direction with a reduced risk of wheel slip. This because upon initiation of the turn towards the set direction, the robotic tool will have reached a certain velocity in the starting direction in which the inclination angle of the robotic tool is less than or equal to the threshold inclination angle. As a further result thereof, a method is provided capable of turning the robotic tool towards a set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the method comprises the step of:

performing a gradual turn from the starting direction towards the set direction.

Thereby, a method is provided capable of turning the robotic tool from the starting direction towards the set direction with a reduced risk of wheel slip. As a further result thereof, a method is provided capable of turning the robotic tool towards a set direction in a more reliable and controlled manner, which provides conditions for a further improved coverage of an area operated by the robotic tool.

Optionally, the method further comprises the step of:

maintaining the set direction after the step of turning the robotic tool to the set direction. Thereby, a method is provided capable of navigating the robotic tool towards the set direction with a reduced risk of wheel slip, i.e. in a more reliable and controlled manner.

Optionally, the robotic tool comprises a sensor, and wherein the method comprises the steps of:

sensing a current inclination angle of the robotic tool, and

turning the robotic tool to obtain the starting direction based on the sensed current inclination angle of the robotic tool.

Thereby, a low-cost, and a non-complex solution is provided for obtaining a starting direction in which a start inclination angle of the robotic tool is less than or equal to the threshold inclination angle

According to a fifth aspect of the invention, the object is achieved by a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments of the present disclosure. Since the computer program comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments, a computer program is provided which provides conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks.

According to a sixth aspect of the invention, the object is achieved by a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to some embodiments of the present disclosure. Since the computer-readable medium comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments, a computer-readable medium is provided which provides conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks.

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 particular features 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 self-propelled robotic tool, according to some embodiments, in a perspective view at four different positions in an area comprising a hill,

Fig. 2 illustrates a method of propelling a self-propelled robotic tool, and

Fig. 3 illustrates computer-readable medium according to some embodiments.

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 self-propelled robotic tool 3, according to some embodiments, in a perspective view at four different positions P0 - P3 in an area comprising a hill 6. The self- propelled robotic tool 3 is capable of navigating in the area in an autonomous manner without the intervention of a user. According to the illustrated embodiments, the self-propelled robotic tool 3 is a self-propelled autonomous robotic lawnmower 3 capable of navigating and cutting grass in the area in an autonomous manner without the intervention of a user. For the reason of brevity and clarity, the self-propelled robotic tool 3 is in some places herein referred to as “the robotic tool 3”.

According to the illustrated embodiments, the robotic tool 3 comprises two front wheels 4 and one rear wheel 4’. The front wheels 4 are driven wheels and the rear wheel 4’ is a supporting wheel, i.e. a non-driven wheel. Thus, according to the illustrated embodiments, the robotic tool 3 may be referred to as a three-wheeled front wheel driven robotic tool 3. According to further embodiments, the robotic tool 3 may be provided with another number of wheels 4, 4’, such as four wheels. Moreover, according to further embodiments, the robotic tool 3 may be provided with another configuration of driven and non-driven wheels, such as a rear wheel drive, a front wheel drive, or an all-wheel drive.

As mentioned, In Fig. 1 , the robotic tool 3 is illustrated in a perspective view at four different positions P0 - P3. The robotic tool 3 is illustrated in dotted lines in an initial position P0. The robotic tool 3 comprises a propulsion control arrangement 1. For the reason of brevity and clarity, the propulsion control arrangement 1 is only illustrated and indicated on the robotic tool 3 when positioned at the position P2. Moreover, for the reason of brevity and clarity, the propulsion control arrangement 1 is in some places herein referred to as“the control arrangement 1”. According to the illustrated embodiments, the propulsion control

arrangement 1 is configured to control propulsion of the robotic tool 3, and steer the robotic tool 3, by controlling electrical motors of the robotic tool 3 arranged to drive the driven wheels 4 of the robotic tool 3. According to further embodiments, the propulsion control arrangement 1 may be configured to steer the robotic tool 3 by controlling the angle of steered wheels of the robotic tool 3. According to still further embodiments, the robotic tool is an articulated robotic tool, wherein the propulsion control arrangement 1 is configured to steer the robotic tool by controlling the angle between frame portions of the articulated robotic tool.

The propulsion control arrangement 1 may be configured to control propulsion of the robotic tool 3, and steer the robotic tool 3, so as to navigate the robotic tool 3 in an area to be operated. The robotic tool 3 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. In addition, the robotic tool 3 may comprise a communication unit connected to the propulsion control arrangement 1. 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.

The propulsion control arrangement 1 may be configured to control propulsion of the robotic tool 3, and steer the robotic tool 3, so as to navigate the robotic tool 3 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 tool 3 may comprise one or more batteries arranged to supply electricity to components of the robotic tool 3. As an example, the one or more batteries may be arranged to supply electricity to electrical motors of the robotic tool 3 by an amount controlled by the propulsion control arrangement 1.

The robotic tool 3 is at stand still at the initial position P0. The robotic tool 3 may for example be at stand still as a result of an event, such as a collision with an object within the area, a detection of a nearby boundary wire, or the like. As another example, the robotic tool 3 may be at stand still as a result of a recent activation of the robotic tool 3. At the initial position P0, the robotic tool 3 is in a position in which the heading direction d of the robotic tool 3 points up against the hill 6. The heading direction d of the robotic tool 3 is herein defined as a direction coinciding with the travelling direction of the robotic tool 3 when the robotic tool 3 is travelling in a forward direction along a straight line. Moreover, the heading direction d of the robotic tool 3, as defined herein, is parallel to a flat ground surface when the robotic tool 3 is placed on the flat ground surface. Furthermore, as defined herein, the heading direction d of the robotic tool 3 may coincide with a longitudinal axis of the robotic tool 3.

At the initial position P0, a horizontal plane hp is indicated, as well as an inclination angle aO of the robotic tool 3 in the heading direction d thereof. Since the heading direction d of the robotic tool 3, as defined herein, is parallel to a flat ground surface when the robotic tool 3 is placed on the flat ground surface, the inclination angle aO of the robotic tool 3, in the heading direction d thereof, may be defined as the angle a between the heading direction d and the horizontal plane hp, and/or the angle a between the longitudinal axis of the robotic tool 3 and the horizontal plane hp.

As mentioned, at the initial position P0, the robotic tool 3 is in a position in which the heading direction d of the robotic tool 3 points up against the hill 6. As a result thereof, the inclination angle aO of the robotic tool 3 is a positive angle. If the robotic tool 3 is positioned in a position in which the heading direction d of the robotic tool 3 points down a slope, the inclination angle of the robotic tool 3, in the heading direction d thereof, will be a negative inclination angle, as defined herein. In Fig. 1 , the inclination angle aO of the robotic tool 3, in the heading direction d thereof, is approximately 20 degrees.

According to embodiments of the present disclosure, the control arrangement 1 is configured to, in a starting procedure of the robotic tool 3, turn the robotic tool 3 to obtain a starting direction d1 in which a start inclination angle a1 of the robotic tool 3 is less than or equal to a threshold inclination angle ax. The robotic tool 3 illustrated in solid lines at the position P1 is illustrated in such a position. That is, in relation to the robotic tool 3 illustrated in dotted lines at the initial position P0, the control arrangement 1 has turned the robotic tool 3 to obtain a starting direction d1 in which a start inclination angle a1 of the robotic tool 3 is less than or equal to a threshold inclination angle ax at the position P1.

According to the illustrated embodiments, the threshold inclination angle ax is approximately 0 degrees, and as can be seen in Fig. 1 at the position P1 , the start inclination angle a1 of the robotic tool 3 is approximately 0 degrees. After turning the robotic tool 3 to obtain the starting direction d1 in which the start inclination angle a1 of the robotic tool 3 is less than or equal to the threshold inclination angle ax, the control arrangement 1 is configured to initiate propulsion of the robotic tool 3 in the starting direction d1. The starting direction d1 of the robotic tool 3 coincides with the heading direction of the robotic tool 3. Since the start inclination angle a1 of the robotic tool 3 is approximately 0 degrees at the position P1 , the angle a1 between the starting direction d1 , i.e. the heading direction, and the horizontal plane hp is approximately 0 degrees. In this manner, the risk of wheel slip is significantly reduced when initiating propulsion of the robotic tool 3 in the starting direction d1.

According to further embodiments, the threshold inclination angle ax may be less than 8 degrees, or less than 4 degrees. Thereby, the risk of wheel slip can be reduced when initiating propulsion of the robotic tool 3 in the starting direction d1. The threshold inclination angle ax may be a predetermined threshold inclination angle ax, or a threshold inclination angle ax set dynamically, for example based on current traction conditions, current weather conditions, or the like.

According to the illustrated embodiments, the control arrangement 1 is configured to turn the robotic tool 3 from the initial position P0 to obtain the starting direction d1 at the position P1 by controlling only one driven wheel 4 to rotate in a first rotational direction. According to further embodiments, the control arrangement 1 may be configured to turn the robotic tool 3 from the initial position P0 to obtain the starting direction d1 at the position P1 by controlling one driven wheel 4 to rotate in a first rotational direction and another driven wheel, arranged on the opposite side of the robotic tool 3, to rotate in a second rotational direction being opposite to the first rotational direction. Furthermore, when the control arrangement 1 is arranged on a robotic tool of another configuration, the control arrangement 1 may be configured to turn the robotic tool from the initial position P0 to obtain the starting direction d1 at the position P1 in another manner. As an example, in cases where the robotic tool comprises four wheels, the control arrangement 1 may be configured to turn the robotic tool from the initial position P0 to obtain the starting direction d1 by controlling one or more wheels on a first side of the robotic tool 3 to rotate in a first rotational direction, and as an alternative or in addition, may be configured to control one or more wheels on an opposite second side of the robotic tool 3 to rotate in a second rotational direction being opposite to the first rotational direction.

According to the illustrated embodiments, the robotic tool 3 comprises a sensor 5 arranged to sense a current inclination angle aO of the robotic tool 3. The propulsion control arrangement 1 is configured to turn the robotic tool 3 to obtain the starting direction d1 based on the sensed current inclination angle aO of the robotic tool 3. According to further embodiments, the sensor 5 may be comprised in the propulsion control arrangement 1. The sensor 5 may be configured to sense the orientation of the robotic tool 3 relative the gravitational field at the location of the robotic tool 3. According to such embodiments, the sensor 5 may comprise an accelerometer. As an alternative, or in addition, the sensor 5 may be configured to sense angular displacements of the robotic tool 3. According to such embodiments, the sensor 5 may comprise a gyroscope. Moreover, the propulsion control arrangement 1 may be arranged to obtain reference values at one or more predetermined locations, such as at a charging dock. According to such embodiments, the sensor 5 may obtain the current inclination angle aO by monitoring changes in inclination angle, for example by sensing changes in inclination angle of the robotic tool 3 and comparing such changes with one or more reference values.

According to still further embodiments, the propulsion control arrangement 1 may be configured to obtain the current inclination angle aO of the robotic tool 3 at the position of the robotic tool 3 by receiving the current inclination angle aO of the robotic tool 3 from an external source, and/or by comparing the current position of the robotic tool 3 and a map comprising data indicative of slope inclination angles at the area. As understood from the herein described, the start inclination angle a1 of the robotic tool 3 is the inclination angle a1 of the robotic tool 3 in the starting direction d1 thereof relative to a horizontal plane hp at the location of the robotic tool 3. Therefore, throughout this disclosure, the wording“start inclination angle a1 of the robotic tool 3” may be replaced with the wording“inclination angle a1 of the robotic tool 3 in the starting direction d1 of the robotic tool 3”. Accordingly, in embodiments in which the robotic tool 3 comprises a sensor 5 arranged to sense the current inclination angle aO of the robotic tool 3, the control arrangement 1 may be configured to utilize the sensed current inclination angle aO of the robotic tool 3 to turn the robotic tool 3 to obtain a starting direction d1 in which a start inclination angle a1 of the robotic tool 3, i.e. in which the sensed current inclination angle aO of the robotic tool 3 in the starting direction d1 , is less than or equal to the threshold inclination angle ax. The control arrangement 1 may then initiate propulsion of the robotic tool 3 in the starting direction d1.

According to the illustrated embodiments, the control arrangement 1 is configured to propel the robotic tool 3 in the starting direction d1 after initiating the propulsion in the starting direction d1. The robotic tool 3 is illustrated at the position P2 in Fig. 1 after a certain time of propulsion of the robotic tool 3 in the starting direction d1 from the position P1. Moreover, according to the illustrated embodiments, the control arrangement 1 is configured to turn the robotic tool 3 to a set direction d2 after propulsion of the robotic tool 3 in the starting direction d1. The control arrangement 1 may be configured to determine the set direction d2 prior to initiating propulsion of the robotic tool 3 in the starting direction d1. According to some embodiments, the set direction d2 is a random direction. According to such embodiments, the set direction d2 may be randomly set within an interval. According to the illustrated embodiments, the control arrangement 1 is configured to initiate the turn of the robotic tool 3 towards the set direction d2 based on reaching a predetermined velocity. According to embodiments illustrated in Fig. 1 , the robotic tool 3 reaches the predetermined velocity at the position P2. The predetermined velocity may for example be a percentage of an operational velocity of the robotic tool 3 wanted during normal operation of the robotic tool 3, such as 50 - 70 % of such an operational velocity of the robotic tool 3. According to further embodiments, the control arrangement 1 may be configured initiate the turn of the robotic tool 3 towards the set direction d2 a predetermined time after initiating the propulsion in the starting direction d1. The predetermined time may for example be within the range of 0.5 - 3 seconds. Due to these features, the control arrangement 1 can initiate a turn towards the set direction d2 with reduced risk of wheel slip of one or more wheels 4, 4’ of the robotic tool 3.

Moreover, according to the illustrated embodiments, the control arrangement 1 is configured to perform a gradual turn from the starting direction d1 towards the set direction d2. The control arrangement 1 may be configured to perform the gradual turn in a manner such that an angular velocity of the heading direction of the robotic tool 3 is kept below a threshold value, and/or such that the radius of curvature of the turn is kept above a threshold radius of curvature. In this manner, the risk of wheel slip is further reduced when turning the robotic tool 3 from the starting direction d1 towards the set direction d2. As can be seen in Fig. 1 , according to the illustrated embodiments, the control arrangement 1 is configured to maintain the set direction d2 after turning the robotic tool 3 to the set direction d2.

According to some embodiments of the present disclosure, the starting procedure of the robotic tool 3 encompasses a stopping procedure of the robotic tool 3. That is, according to such embodiments, the control arrangement 1 may be configured to, in a stopping procedure of the robotic tool 3, sense a current inclination angle of the robotic tool 3 in the heading direction of the robotic tool 3, and if the current inclination angle is greater than the threshold inclination angle ax, turn the robotic tool 3 from the current direction to a stop direction in which a stop inclination angle a1 of the robotic tool 3 is less than or equal to the threshold inclination angle ax. If the sensed current inclination angle is smaller than or equal to the threshold inclination angle ax, the control arrangement 1 may stop the robotic tool 3 in the current direction without performing any further turning of the robotic tool 3. In this manner, the robotic tool 3 can subsequently be started in a starting direction d1 , corresponding to the stopping direction, in which a start inclination angle a1 of the robotic tool 3 is less than or equal to a threshold inclination angle ax. According to the illustrated embodiments, at the position P0 and P1 , the set direction d2 involves an inclination angle a3 exceeding the threshold inclination angle ax. According to some embodiments of the present disclosure, the control arrangement 1 may be configured to, in the starting procedure of the robotic tool 3, turn the robotic tool 3 from the initial heading direction d, indicated at the position P0, to the set direction d2 at the position P0 and sense a current inclination angle a3 of the robotic tool 3 when turned to the set direction d2, and if the current inclination angle a3 is greater than the threshold inclination angle ax, turn the robotic tool 3 from the set direction d2 to a starting direction d1 in which a start inclination angle a1 of the robotic tool 3 is less than or equal to the threshold inclination angle ax. If the sensed current inclination angle a3 is smaller than or equal to the threshold inclination angle ax when turned to the set direction d2, the control arrangement 1 may initiate propulsion of the robotic tool 3 in the set direction d2 without performing any further turning of the robotic tool 3. In this manner, the robotic tool 3 can be navigated in an area with reduced risk of wheel slip in a simple and efficient manner using a simple sensor 5 capable of sensing the current inclination angle aO of the robotic tool 3 only in the heading direction of the robotic tool 3.

However, according to further embodiments of the present disclosure, the robotic tool 3 may comprise a sensor 5 capable of sensing the current inclination angle a3 of the robotic tool 3 also in lateral directions of the robotic tool 3, and/or in one or more other directions differing from the heading direction d of the robotic tool 3. According to such embodiments, the control arrangement 1 may be configured to determine whether the set direction d2 involves an inclination angle a3 exceeding the threshold inclination angle ax at the initial position P0 of the robotic tool 3. According to such embodiments, if it is determined that set direction d2 involves an inclination angle a3 exceeding the threshold inclination angle ax at the initial position P0, the control arrangement 1 may turn the robotic tool 3 to obtain a starting direction d1 in which a start inclination angle a1 of the robotic tool 3 is less than or equal to a threshold inclination angle ax. If it is determined that set direction d2 does not involve an inclination angle a3 exceeding the threshold inclination angle ax at the position P0 of the robotic tool 3, the control arrangement may turn the robotic tool 3 directly to the set direction d2 and initiate propulsion in the set direction d2.

As understood from the above, since the control arrangement 1 is capable of reducing the risk of wheel slip when initiating propulsion of the robotic tool 3 in the starting direction d1 , a propulsion control arrangement 1 is provided capable of navigating the robotic tool 3 in an improved manner with improved coverage of an area operated by the robotic tool 3. This because wheel slip of one or more wheels of a robotic tool 3 may cause an unexpected change of direction of the robotic tool 3, which, due to the topography of the area, may result in that some parts of the area are operated more frequently, and some other parts of the area are operated less frequently.

Thus, due to the features of the propulsion control arrangement 1 , the robotic tool 3 can be navigated to a set direction d2, involving an inclination angle a2, a3 exceeding the threshold inclination angle ax, in a more control manner, which improves coverage of the area operated by the robotic tool 3. As further results thereof, the operational result of the robotic tool 3 can be improved, the time required for operating an area can be reduced, the travelling distance required for operating the area can be reduced, as well as the risk of unwanted marks in the area operated by the robotic tool 3. Accordingly, as further results thereof, the propulsion control arrangement 1 , as described herein, is capable of reducing energy consumption, as well as wear and tear of robotic tools 3.

Fig. 2 illustrates a method 100 of propelling a self-propelled robotic tool 3. The robotic tool 3 may be a robotic tool 3 according to the embodiments illustrated in Fig. 1. Therefore, below, simultaneous reference is made to Fig 1 and Fig. 2. The method 100 comprises the steps of, in a starting procedure of the robotic tool 3:

turning 110 the robotic tool 3 to obtain a starting direction d1 in which a start inclination angle a1 of the robotic tool 3 is less than or equal to a threshold inclination angle ax, and

initiating 120 propulsion of the robotic tool 3 in the starting direction d1.

According to some embodiments, the method 100 comprises the step of:

propelling 122 the robotic tool 3 in the starting direction d1 after the step of initiating 120 the propulsion in the starting direction d1.

According to some embodiments, the method 100 further comprises the step of:

turning 130 the robotic tool 3 to a set direction d2 after the step of propelling 122 the robotic tool 3 in the starting direction d1.

According to some embodiments, the method 100 further comprises the step of

determining 101 the set direction d2 prior to the step of initiating 120 propulsion of the robotic tool 3 in the starting direction d1.

According to some embodiments, the method 100 comprises the step of: initiating 126 the turning of the robotic tool 3 towards the set direction d2 based on reaching a predetermined velocity.

According to some embodiments, the method 100 comprises the step of:

initiating 128 the turning of the robotic tool 3 towards the set direction d2 a predetermined time after the step of initiating 120 the propulsion in the starting direction d1.

According to some embodiments, the method 100 comprises the step of:

performing 132 a gradual turn from the starting direction d1 towards the set direction d2.

According to some embodiments, the method 100 further comprises the step of:

maintaining 140 the set direction d2 after the step of turning 130 the robotic tool 3 to the set direction d2.

According to some embodiments, the robotic tool 3 comprises a sensor 5, and wherein the method 100 comprises the steps of:

sensing 102 a current inclination angle aO of the robotic tool 3, and turning 112 the robotic tool 3 to obtain the starting direction d1 based on the sensed current inclination angle aO of the robotic tool 3.

It will be appreciated that the various embodiments described for the method 100 are all combinable with the propulsion control arrangement 1 as described herein. That is, the propulsion control arrangement 1 may be configured to perform any one of the method steps 101 , 102, 110, 112, 120, 122, 126, 128, 130, 132, and 140 of the method 100.

Fig. 3 illustrates computer-readable medium 200 comprising instructions which, when executed by a computer, cause the computer to carry out the method 100 according to some embodiments of the present disclosure.

According to some embodiments, the computer-readable medium 200 comprises a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method 100 according to some embodiments.

One skilled in the art will appreciate that the method 100 of propelling a self-propelled robotic tool 3 may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, which, when it is executed in the propulsion control arrangement 1 , ensures that the propulsion control arrangement 1 carries out the desired control, such as the method steps 101 , 102, 110, 112, 120, 122, 126, 128, 130, 132, and 140 described herein. The computer program is usually part of a computer program product 200 which comprises a suitable digital storage medium on which the computer program is stored.

The propulsion control arrangement 1 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 propulsion control arrangement 1 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 propulsion control arrangement 1 is connected to components of the robotic tool 3 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 propulsion control arrangement 1. 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 robotic tool's control system and/or the component or components for which the signals are intended. Each of the connections to the respective components of the robotic tool 3 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.

The propulsion control arrangement 1 may be configured to turn the robotic tool 3 to obtain a starting direction d1 in which a start inclination angle a1 of the robotic tool 3 is less than or equal to a threshold inclination angle ax using control loops, setpoint values, intervals, and the like. In the embodiments illustrated, the robotic tool 3 comprises a propulsion control arrangement 1 but might alternatively be implemented wholly or partly in two or more control arrangements or two or more control units.

The computer program product 200 may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the method steps 101 , 102, 110, 112, 120, 122, 126, 128, 130, 132, and 140 according to some embodiments when being loaded into one or more calculation units of the propulsion control arrangement 1. The data carrier may be, e.g. a CD ROM disc, as is illustrated in Fig. 3, 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 propulsion control arrangement 1 remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems.

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.

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 propulsion control arrangement (1) for a self-propelled robotic tool (3), wherein the control arrangement (1) is configured to, in a starting procedure of the robotic tool (3): turn the robotic tool (3) to obtain a starting direction (d1) in which a start inclination angle (a1) of the robotic tool (3) is less than or equal to a threshold inclination angle (ax), and

initiate propulsion of the robotic tool (3) in the starting direction (d1).

2. The control arrangement (1) according to claim 1 , wherein the threshold inclination angle (ax) is less than 8 degrees.

3. The control arrangement (1) according to claim 1 or 2, wherein the threshold inclination angle (ax) is approximately 0 degrees.

4. The control arrangement (1) according to any one of the preceding claims, wherein the control arrangement (1) is configured to propel the robotic tool (3) in the starting direction (d1) after initiating the propulsion in the starting direction (d1).

5. The control arrangement (1) according to any one of the preceding claims, wherein the control arrangement (1) is configured to turn the robotic tool (3) to a set direction (d2) after propulsion of the robotic tool (3) in the starting direction (d1).

6. The control arrangement (1) according to claim 5, wherein the control arrangement (1) is configured to determine the set direction (d2) prior to initiating propulsion of the robotic tool (3) in the starting direction (d1).

7. The control arrangement (1) according to claim 5 or 6, wherein the set direction (d2) involves an inclination angle (a2) exceeding the threshold inclination angle (ax).

8. The control arrangement (1) according to any one of the claims 5 - 7, wherein the control arrangement (1) is configured to initiate the turn of the robotic tool (3) towards the set direction (d2) based on reaching a predetermined velocity.

9. The control arrangement (1) according to any one of the claims 5 - 7, wherein the control arrangement (1) is configured initiate the turn of the robotic tool (3) towards the set direction (d2) a predetermined time after initiating the propulsion in the starting direction (d1).

10. The control arrangement (1) according to any one of the claims 5 - 9, wherein the control arrangement (1) is configured to perform a gradual turn from the starting direction (d1) towards the set direction (d2).

11. The control arrangement (1) according to any one of the claims 5 - 10, wherein the

control arrangement (1) is configured to maintain the set direction (d2) after turning the robotic tool (3) to the set direction (d2).

12. The control arrangement (1) according to any one of the claims 5 - 11 , wherein the set direction (d2) is a random direction.

13. The control arrangement (1) according to any one of the preceding claims, wherein the robotic tool (3) comprises a sensor (5) arranged to sense a current inclination angle (aO) of the robotic tool (3), and wherein the control arrangement (1) is configured to turn the robotic tool (3) to obtain the starting direction (d1) based on the sensed current inclination angle (aO) of the robotic tool (3).

14. A self-propelled robotic tool (3) comprising a propulsion control arrangement (1)

according to any one of the preceding claims.

15. A self-propelled robotic lawnmower (3) comprising a propulsion control arrangement (1) according to any one of the claims 1 - 13.

16. A method (100) of propelling a self-propelled robotic tool (3), wherein the method (100) comprises the steps of, in a starting procedure of the robotic tool (3):

turning (110) the robotic tool (3) to obtain a starting direction (d1) in which a start inclination angle (a1) of the robotic tool (3) is less than or equal to a threshold inclination angle (ax), and

initiating (120) propulsion of the robotic tool (3) in the starting direction (d1).

17. The method (100) according to claim 16, wherein the method (100) comprises the step of:

propelling (122) the robotic tool (3) in the starting direction (d1) after the step of initiating (120) the propulsion in the starting direction (d1).

18. The method (100) according to claim 17, wherein the method (100) further comprises the step of:

turning (130) the robotic tool (3) to a set direction (d2) after the step of propelling (122) the robotic tool (3) in the starting direction (d1).

19. The method (100) according to claim 18, wherein the method (100) further comprises the step of:

determining (101) the set direction (d2) prior to the step of initiating (120) propulsion of the robotic tool (3) in the starting direction (d1).

20. The method (100) according to claim 18 or 19, wherein the method (100) comprises the step of:

initiating (126) the turning of the robotic tool (3) towards the set direction (d2) based on reaching a predetermined velocity.

21. The method (100) according to claim 18 or 19, wherein the method (100) comprises the step of:

initiating (128) the turning of the robotic tool (3) towards the set direction (d2) a predetermined time after the step of initiating (120) the propulsion in the starting direction (d1).

22. The method (100) according to any one of the claims 18 - 21 , wherein the method (100) comprises the step of:

performing (132) a gradual turn from the starting direction (d1) towards the set direction (d2).

23. The method (100) according to any one of the claims 18 - 22, wherein the method (100) further comprises the step of:

maintaining (140) the set direction (d2) after the step of turning (130) the robotic tool (3) to the set direction (d2).

24. The method (100) according to any one of the claims 16 - 23, wherein the robotic tool (3) comprises a sensor (5), and wherein the method (100) comprises the steps of:

sensing (102) a current inclination angle (aO) of the robotic tool (3), and

turning (112) the robotic tool (3) to obtain the starting direction (d1) based on the sensed current inclination angle (aO) of the robotic tool (3).

25. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method (100) according to any one of the claims 16 - 24.

26. A computer-readable medium (200) comprising instructions which, when executed by a computer, cause the computer to carry out the method (100) according to any one of the claims 16 - 24.