SE543077C2

SE543077C2 - Steering control arrangement and method of steering a robotic tool

Info

Publication number: SE543077C2
Application number: SE1851440A
Authority: SE
Inventors: Erik Starhagen
Original assignee: Husqvarna Ab
Priority date: 2018-11-21
Filing date: 2018-11-21
Publication date: 2020-10-06
Also published as: SE1851440A1; WO2020104242A1; DE112019005816T5

Abstract

A steering control arrangement (1) for a self-propelled robotic tool (3) is disclosed. The steering control arrangement (1) is configured to obtain a current fall line direction (fl) at the position of the robotic tool (3) and steer the robotic tool (3) based on a target angle (b) between the heading direction (hd) of the robotic tool (3) and the current fall line direction (fl). The present disclosure further relates to a self-propelled robotic tool (3), a self-propelled robotic lawnmower (3), a method (100) of steering a self-propelled robotic tool (3), a computer program, and a computer-readable medium (200).

Description

Steering Control Arrangement and Method of Steering a Robotic Tool TECHNICAL FIELD The present disclosure relates to a steering control arrangement for a self-propelled robotictool. The present disclosure further relates to a self-propelled robotic tool comprising asteering control arrangement, a self-propelled robotic lawnmower comprising a steeringcontrol arrangement, a method of steering 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, havebecome increasingly popular, partly because they are usually capable of performing workwhich previously was made manually. A Self-propelled robotic tool is capable of navigating inan area in an autonomous manner. Some robotic tools require a user to set up a border wirearound an area that defines the area to be operated by the robotic tool. Such robotic toolsuse a sensor to locate the wire and thereby the boundary of the area to be operated. As analternative, or in addition, robotic tools may comprise other types of positioning units andsensors, for example sensors for detecting an event, such as a collision with an object withinthe 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 andnavigability of the robotic tool, especially in wet conditions. Such problems may adverselyaffect the coverage of an area operated by a robotic tool. These problems may be mitigatedby measuring the roll angle of the robotic tool and trying to add compensation to the drivingwheels. lf so, unique compensation factors must be developed and verified for each different model of the robotic tool, which add costs to the robotic tool and the results can vary.

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

SUMMARYlt is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks. 2 According to a first aspect of the invention, the object is achieved by a steering controlarrangement for a self-propelled robotic tool. The steering control arrangement is configuredto obtain a current fall line direction at the position of the robotic tool, and steer the robotictool based on a target angle between the heading direction of the robotic tool and the current fall line direction.

Since the steering control arrangement is configured to steer the robotic tool based on thetarget angle between the heading direction and the current fall line direction, a steeringcontrol arrangement is provided which improves coverage of an area operated by a robotic tool in a simple and efficient manner.

Moreover, a steering control arrangement is provided which improves coverage of an areaoperated by a robotic tool independently of the mechanical characteristics of the robotic tool.ln addition, a steering control arrangement is provided requiring a low number of input SGHSOFS.

Thus, as a further result of these features, a steering control arrangement is provided capable of lowering development costs, as well as manufacturing costs, of robotic tools.

Still further, since the steering control arrangement improves coverage of an area operatedby the robotic tool, the operational result of the robotic tool is improved. Moreover, the timerequired for operating an area is reduced, as well as the travelling distance required foroperating the area. Accordingly, a steering control arrangement is provided capable of reducing energy consumption, as well as wear and tear of robotic tools.

Thus, a steering control arrangement is provided overcoming, or at least alleviating, at leastsome of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Optionally, the steering control arrangement is configured to steer the robotic tool to obtain ormaintain the target angle. Thereby, a steering control arrangement is provided which further improves coverage of an area operated by the robotic tool.

Optionally, the robotic tool comprises a sensor arranged to sense the orientation of therobotic tool, and wherein the steering control arrangement is configured to obtain the current fall line direction by estimating the current fall line direction based on the current sensed 3 orientation of the robotic tool. Thereby, the current fall line direction is obtained in a simple and efficient manner requiring one sensor only.

Optionally, the target angle is a previous angle between the heading direction and the currentfall line direction. Thereby, a steering control arrangement is provided capable of further improving coverage of an area operated by the robotic tool.

Optionally, the steering control arrangement is configured to obtain a current slope inclinationat the position of the robotic tool, and wherein the steering control arrangement is configuredto set the target angle to the angle between the heading direction and the current fall linedirection obtained when the current slope inclination reaches above a first slope inclinationlimit value. Thereby, the steering control arrangement steers the robotic tool in a morevarying manner because new target angles can be obtained each time the robotic toolreaches an area where the current slope inclination reaches above the first slope inclination limit value, which further improves coverage of an area operated by the robotic tool.

Optionally, the steering control arrangement is configured to obtain a current slope inclinationat the position of the robotic tool, and wherein the steering control arrangement is configuredto initiate the steering of the robotic tool based on the target angle when the current slopeinclination reaches above a second slope inclination limit value. Thereby, a steering controlarrangement is provided which can initiate the steering control when needed, i.e. when the current slope inclination reaches above a second slope inclination limit value.

Optionally, the steering control arrangement is configured to cancel the steering of therobotic tool based on the target angle when the current slope inclination drops below a thirdslope inclination limit value. Thereby, a steering control arrangement is provided capable ofcancelling the steering control when not needed, i.e. when the current slope inclination drops below the third slope inclination limit value.

Optionally, the self-propelled robotic tool comprises a sensor arranged to sense theorientation of the robotic tool, and wherein the steering control arrangement is configured toestimate the current slope inclination based on the current sensed orientation of the robotictool. Thereby, the current slope inclination is obtained in a simple and efficient mannerrequiring one sensor only. Accordingly, a steering control arrangement is provided capable of lowering manufacturing costs of robotic tools. 4 According to a second aspect of the invention, the object is achieved by a self-propelledrobotic tool comprising a steering control arrangement according to some embodiments of the present disclosure.

Since the self-propelled robotic tool comprises a steering control arrangement according tosome embodiments, a self-propelled robotic tool is provided capable of operating an areawith improved coverage in a simple and efficient manner. ln addition, a self-propelled robotic tool is provided requiring a low number of input sensors for the steering control thereof.

Thus, as a further result, a self-propelled robotic tool is provided having conditions andcharacteristics suitable for being developed, manufactured, and assembled in a cost-efficient mannef.

Still further, since the self-propelled robotic tool improves coverage of an area operated bythe robotic tool, the operational result of the robotic tool is improved. Moreover, the timerequired for operating an area is reduced, as well as the travelling distance required foroperating the area. Accordingly, as a further result thereof, a self-propelled robotic tool isprovided capable of reducing energy consumption during operation, as well as wear and tear of the robotic tool.

Accordingly, a self-propelled robotic tool is provided overcoming, or at least alleviating, atleast 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 roboticlawnmower comprising a steering control arrangement according to some embodiments of the present disclosure.

Since the self-propelled robotic lawnmower comprises a steering control arrangementaccording to some embodiments, a self-propelled robotic lawnmower is provided capable ofcutting an area with improved coverage in a simple and efficient manner. ln addition, a self-propelled robotic lawnmower is provided requiring a low number of input sensors for the steering control thereof.

Thus, as a further result, a self-propelled robotic lawnmower is provided having conditionsand characteristics suitable for being developed, manufactured, and assembled in a cost- efficient manner.

Still further, since the self-propelled robotic lawnmower improves coverage of an areaoperated by the robotic lawnmower, the operational result of the robotic lawnmower, i.e. thecutting result, is improved. Moreover, the time required for cutting an area is reduced, as wellas the travelling distance required for cutting the area. Accordingly, as a further resultthereof, a self-propelled robotic lawnmower is provided capable of reducing energy consumption during operation, as well as wear and tear of the robotic lawnmower.

Accordingly, a self-propelled robotic lawnmower is provided overcoming, or at leastalleviating, 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 steering aself-propelled robotic tool, wherein the method comprises: - obtaining a current fall line direction at the position of the robotic tool, and - steering the robotic tool based on a target angle between the heading direction of the robotic tool and the current fall line direction.

Since the method comprises the step of steering the robotic tool based on the target anglebetween the heading direction and the current fall line direction, a method is provided which improves coverage of an area operated by a robotic tool in a simple and efficient manner.

Moreover, a method is provided which improves coverage of an area operated by a robotictool independently of the mechanical characteristics of the robotic tool. ln addition, a method is provided requiring a low number of input sensors.

Thus, as a further result of these features, a method is provided capable of lowering development costs, as well as manufacturing costs, of robotic tools.

Still further, since the method improves coverage of an area operated by the robotic tool, theoperational result of the robotic tool is improved. Moreover, the time required for operating anarea is reduced, as well as the travelling distance required for operating the area.Accordingly, as a further result thereof, a method is provided capable of reducing wear and tear of robotic tools.

Thus, 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 step of steering the robotic tool comprises the step of: - steering the robotic tool to obtain or maintain the target angle.

Thereby, a method is provided which further improves coverage of an area operated by the robotic tool.

Optionally, the self-propelled robotic tool comprises a sensor arranged to sense theorientation of the robotic tool, and wherein the step of obtaining the current fall line directioncomprises the steps of: - sensing the orientation of the robotic tool, and - estimating the current fall line direction based on the sensed orientation of the robotic tool.

Thereby, the current fall line direction is obtained in a simple and efficient manner requiringone sensor only. Accordingly, a method is provided capable of lowering manufacturing costs of robotic tools.

Optionally, the method further comprises: - obtaining a current slope inclination at the position of the robotic tool, and - setting the target angle to the angle between the heading direction and thecurrent fall line direction obtained when the current slope inclination reaches above a first slope inclination limit value.

Thereby, the method steers the robotic tool in a more varying manner because new targetangles can be obtained each time the robotic tool reaches an area where the current slopeinclination reaches above the first slope inclination limit value, which further improves coverage of an area operated by the robotic tool.

Optionally, the method further comprises:- obtaining a current slope inclination at the position of the robotic tool, and- initiating the steering of the robotic tool based on the target angle when the current slope inclination reaches above a second slope inclination limit value.

Thereby, a method is provided which initiates the steering control when needed, i.e. when the current slope inclination reaches above a second slope inclination limit value.

Optionally, the method further comprises:- cancelling the steering of the robotic tool based on the target angle when the current slope inclination drops below a third slope inclination limit value.

Thereby, a method is provided Which cancels the steering control When not needed, i.e. when the current slope inclination drops below the third slope inclination limit value.

Optionally, the self-propelled robotic tool comprises a sensor arranged to sense theorientation of the robotic tool, and wherein the step of obtaining the current slope inclinationcomprises the steps of: - sensing the orientation of the robotic tool, and - estimating the current slope inclination based on the current sensed orientation of the robotic tool.

Thereby, the current slope inclination is obtained in a simple and efficient manner requiringone sensor only. Accordingly, a method is provided capable of lowering manufacturing costs of robotic tools.

According to a fifth aspect of the invention, the object is achieved by a computer programcomprising 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 bya computer, cause the computer to carry out the method according to some embodiments, acomputer program is provided which provides conditions for overcoming, or at leastalleviating, at least some of the above-mentioned drawbacks. As a result, the above- mentioned object is achieved.

According to a sixth aspect of the invention, the object is achieved by a computer-readablemedium 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 executed by acomputer, cause the computer to carry out the method according to some embodiments, acomputer-readable medium is provided which provides conditions for overcoming, or at leastalleviating, at least some of the above-mentioned drawbacks. As a result, the above- mentioned object is achieved.

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 DRAWINGSVarious aspects of the invention, including its particularfeatures and advantages, will bereadily 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,Fig. 2 illustrates a method of steering a self-propelled robotic tool, and Fig. 3 illustrates computer-readable medium.

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

Fig. 1 illustrates a self-propelled autonomous robotic tool 3, according to someembodiments. According to the illustrated embodiments, the self-propelled robotic tool 3 is aself-propelled autonomous robotic lawnmower 3. For the reason of brevity and clarity, theself-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 andone rear wheel 4”. The front wheels 4 are driven wheels and the rear wheel 4' is a supportingwheel, i.e. a non-driven wheel. Thus, according to the illustrated embodiments, the robotictool 3 may be referred to as a three-wheeled front wheel driven robotic tool 3. According tofurther 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 beprovided with another configuration of driven and non-driven wheels, such as a rear wheel drive or an all-wheel drive. ln Fig. 1, the robotic tool 3 is illustrated in a perspective view when travelling across a slopeof a hill 6 at a position P1. The robotic tool 3 illustrated in dotted lines at the positions P0' andP0 illustrates the robotic tool 3 in two previous positions P0', P0. The robotic tool 3 illustrated in dotted lines at the position P2 illustrates the robotic tool 3 in a subsequent position P2. 9 When a robotic tool 1 is travelling across the direction of a slope, its supporting wheels, i.e.its non-driving wheels 4', tend to fall down in the direction of the slope. As a reason thereof, itis difficult to travel straight in such circumstances. A front wheel driven robotic tool 1 tend toclimb and a rear wheel driven robotic tool tend to fall in the direction of the slope. Theproblem typically results in upper parts of a sloped area being cut less frequently or morefrequently, depending on the characteristics of the robotic tool, such as the mechanicalcharacteristics of the robotic tool. This because the robotic tool, when climbing or descending, will follow a curved path pulling it either downwards or upwards.

According to embodiments herein, the robotic tool 1 comprises a steering controlarrangement 1. The steering control arrangement 1 is configured to obtain a current fall linedirection fl at the position of the robotic tool 3. The steering control arrangement 1 isconfigured to steer the robotic tool 3 based on a target angle b between the heading directionhd of the robotic tool 3 and the current fall line direction fl. According to the illustratedembodiments, the steering control arrangement 1 is configured to steer the robotic tool 3 toobtain or maintain the target angle b in a continuous manner. The steering controlarrangement 1 may be configured to estimate a current angle between the heading directionhd and the current fall line direction fl, and to compare the current angle and the target angleb, and may steer the robotic tool 3 based on the comparison to obtain or maintain the targetangle b in a continuous or repeated manner. That is, if the comparison indicates a deviationbetween the current angle and the target angle b, the steering control arrangement 1 mayadjust the heading direction hd of the robotic tool 3, by steering the robotic tool 3, in order toobtain the target angle b between the heading direction hd and the current fall line directionfl.

According to the illustrated embodiments, the robotic tool 3 comprises a sensor 5 arranged tosense the orientation of the robotic tool 3, wherein the steering control arrangement 1 isconfigured to obtain the current fall line direction fl by estimating the current fall line directionfl based on the current sensed orientation of the robotic tool 3. According to further embodiments, the sensor 5 may be comprised in the steering control arrangement 1.

The sensor 5 may be configured to sense the orientation of the robotic tool 3 relative thegravitational field at the location of the robotic tool 3. According to such embodiments, thesensor 5 may comprise an accelerometer. As an alternative, or in addition, the sensor 5 maybe configured to sense angular displacements of the robotic tool 3. According to suchembodiments, the sensor 5 may comprise a gyroscope. Moreover, the steering control arrangement 1 may be arranged to obtain reference values at one or more predetermined locations, such as at a charging dock. According to still further embodiments, the steeringcontrol arrangement 1 may be configured to obtain the current fall line direction fl at theposition of the robotic tool 3 by receiving the current fall line direction fl from an externalsource and/or by comparing the current position of the robotic tool 3 and a map comprising data indicative of fall line directions at the area.

Moreover, the steering control arrangement 1 is configured to obtain a current slopeinclination si at the position of the robotic tool 3. According to the illustrated embodiments,the steering control arrangement 1 is configured to estimate the current slope inclination sibased on the orientation of the robotic tool 3, relative the gravitational field at the location ofthe robotic tool 3, sensed by the sensor 5. The estimation of the current slope inclination si,based on the orientation of the robotic tool 3, may encompass an estimation of the inclinationof the robotic tool 3 relative a horizontal plane HP. According to further embodiments, thesteering control arrangement 1 may be configured to obtain a current slope inclination si atthe position of the robotic tool 3 by receiving the current slope inclination si from an externalsource and/or by comparing the current position of the robotic tool 3 and a map comprising data indicative of slope inclinations at the area.

According to the illustrated embodiments, the target angle b is a previous angle b' betvveenthe heading direction hd and the current fall line direction fl obtained when the robotic tool 3was located at a previous position P0. That is, according to the illustrated embodiments, thesteering control arrangement 1 is configured to set the target angle b to the angle b' betweenthe heading direction hd and the current fall line direction fl obtained when the current slopeinclination si reaches above a first slope inclination limit value. ln Fig. 1, this occurs when the robotic tool is at the position P0.

According to the illustrated embodiments, the steering control arrangement 1 is configured toinitiate the steering of the robotic tool 3 based on the target angle b when the current slopeinclination si reaches above a second slope inclination limit value. The second slopeinclination limit value may be different from the first slope inclination limit value. However,according to the illustrated embodiments, the second slope inclination limit value has thesame value as the first slope inclination limit value. Accordingly, in Fig. 1, the steering controlarrangement 1 initiates the steering of the robotic tool 3 based on the target angle b when the robotic tool 3 is at the position P0.

Moreover, according to the illustrated embodiments, the steering control arrangement 1 is configured to cancel the steering of the robotic tool 3 based on the target angle b when the 11 current slope inclination si drops below a third slope inclination limit value. The third slopeinclination limit value may be different from the first and second slope inclination limit values.Thereby, a frequent initiation and cancellation of steering based on the target angle b isavoided in cases where the robotic tool 3 is traveling in an area in which the current slopeinclination si is close to the second slope inclination limit value. However, according to theillustrated embodiments, the third slope inclination limit value has the same value as the firstand second slope inclination limit values. Purely as examples, the first, the second, and thethird slope inclination limit values may each be within the range of 3 - 40 degrees, or within the range of 3 - 12 degrees.

To summarize with reference to Fig 1, when the robotic tool 3 is traveling in an area in whichthe current slope inclination si is below the second and third slope inclination limit values,such as when the robotic tool 3 is at position P0' in Fig. 1, the steering control arrangement 1may steer the robotic tool 3 in a manner independent of the target angle b and the current fallline direction fl, such as a control configured to obtain a straight direction of travel of the robotic tool 3.

When the robotic tool 3 reaches a position P0, in which the current slope inclination sireaches above the first slope inclination limit value, the steering control arrangement 1 setsthe target angle b to the angle b' between the heading direction hd and the current fall linedirection fl. Moreover, when the robotic tool 3 reaches a position P0 in which the currentslope inclination si reaches above the second slope inclination limit value, the steeringcontrol arrangement 1 initiates the steering of the robotic tool 3 based on the target angle b.Then the steering control arrangement 1 steers the robotic tool 3 based on the target angle bbetween the heading direction hd of the robotic tool 3 and the current fall line direction fl in amanner independent of changes in the current slope inclination si, given that the currentslope inclination si is above the third slope inclination limit value. During the steering of therobotic tool 3 based on the target angle b, the robotic tool 3 follows the terrain in a visuallyadvanced and intelligent manner even though a simple control algorithm can be used, andeven though a low number of input sensors are required for achieving the steering control. ln fact, only one sensor is needed for achieving the steering control, as described herein.

The steering control arrangement 1 steers the robotic tool 3 based on the target angle b untilthe robotic tool 3 reaches a position P2 in which the current slope inclination si drops below the third slope inclination limit value, or until a direction changing event is occurring, such asa detection of a collision between the robotic tool 3 and an object, a detection of a boundary wire, or the like. When cancelling the steering based on the target angle b, the steering 12 control arrangement 1 may initiate a steering control of the robotic tool 3 being independentof the current fall line direction fl and the target angle b, such as a control configured to obtain a straight direction of travel of the robotic tool 3.

According to the illustrated embodiments, the steering control arrangement 1 is configured tosteer the robotic tool 3 by controlling electrical motors of the robotic tool 3 arranged to drivethe driven wheels 4 of the robotic tool 3. According to further embodiments, the steeringcontrol arrangement 1 may be configured to steer the robotic tool 3 by controlling the angleof steered wheels of the robotic tool 3. According to still further embodiments, the robotic toolis an articulated robotic tool, wherein the steering control arrangement 1 is configured tosteer the robotic tool by controlling the angle between frame portions of the articulated robotic tool.

The term fall line direction fl, as used herein, refers to the direction of a line, at the position ofthe robotic tool 3, which is most directly downhill. That is, the fall line direction fl, as usedherein, is the direction in which a ball would accelerate if it were free to move on the slopeunder gravity. Similarly, term fall line direction fl, as used herein, refers to the direction of aline along the ground surface, at the position of the robotic tool 3, forming the largest angle relative the horizontal plane HP.

Moreover, as best seen at the position P2, the current slope inclination si refers to the anglesi between a line L along the ground surface the horizontal plane HP, at the position of therobotic tool 3. Similarly, the current slope inclination si can be defined as the angle sibetween the ground plane and the horizontal plane HP, at the position of the robotic tool 3.For the reason of brevity and clarity, the current slope inclination si is only schematicallyindicated at the positions P0', P0 and P1.

Fig. 2 illustrates a method 100 of steering a self-propelled robotic tool 3. The robotic tool 3may 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: - obtaining 110 a current fall line direction fl at the position of the robotic tool 3, and- steering 120 the robotic tool 3 based on a target angle b between the heading direction hd of the robotic tool 3 and the current fall line direction fl.

According to some embodiments, the step 120 of steering the robotic tool 120 comprises the step of: 13 steering 121 the robotic tool 3 to obtain or maintain the target angle b.

According to some embodiments, the step 121 of steering the robotic tool 3 to obtain or maintain the target angle b, may comprise the steps of: estimating 122 a current angle between the heading direction hd and thecurrent fall line direction fl, comparing 123 the current angle and the target angle b, and steering 124 the robotic tool 3, based on the comparison, in a manner such that the current angle is equal to the target angle b.

According to some embodiments, the self-propelled robotic tool 3 comprises a sensor 5 arranged to sense the orientation of the robotic tool 3, and wherein the step of obtaining 110 the current fall line direction fl comprises the steps of: sensing 111 the orientation of the robotic tool 3, andestimating 112 the current fall line direction fl based on the sensed orientation of the robotic tool 3.

According to some embodiments, the method 100 further comprises: obtaining 101 a current slope inclination si at the position of the robotic tool 3,and setting 113 the target angle b to the angle b' between the heading direction hdand the current fall line direction fl obtained when the current slope inclination si reaches above a first slope inclination limit value.

According to some embodiments, the method 100 further comprises: obtaining 101 a current slope inclination si at the position of the robotic tool 3,and initiating 114 the steering of the robotic tool 3 based on the target angle b whenthe current slope inclination si reaches above a second slope inclination limit value.

According to some embodiments, the method 100 further comprises: cancelling 126 the steering of the robotic tool 3 based on the target angle bwhen the current slope inclination si drops below a third slope inclination limit value. 14 According to some embodiments, the self-propelled robotic tool 3 comprises a sensor 5arranged to sense the orientation of the robotic tool 3, and wherein the step of obtaining 101the current slope inclination si comprises the steps of: - sensing 102 the orientation of the robotic tool 3, and - estimating 103 the current slope inclination si based on the current sensed orientation of the robotic tool 3. lt will be appreciated that the various embodiments described for the method 100 are allcombinable with the steering control arrangement 1 as described herein. That is, the steeringcontrol arrangement 1 may be configured to perform any one of the method steps 101, 102,103,110,111,112,113,114,120,121,122,123,124 and 126 ofthe method 100.

Fig. 3 illustrates computer-readable medium 200 comprising instructions which, whenexecuted 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 computerprogram 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 steering a self-propelled robotictool 3 may be implemented by programmed instructions. These programmed instructions aretypically constituted by a computer program, which, when it is executed in the steeringcontrol arrangement 1, ensures that the steering control arrangement 1 carries out thedesired control, such as the method steps 101, 102, 103, 110, 111, 112, 113, 114, 120, 121,122, 123, 124 and 126 described herein. The computer program is usually part of a computerprogram product 200 which comprises a suitable digital storage medium on which the computer program is stored.

The steering control arrangement 1 may comprise a calculation unit which may take the formof substantially any suitable type of processor circuit or microcomputer, e.g. a circuit fordigital signal processing (digital signal processor, DSP), a Central Processing Unit (CPU), aprocessing unit, a processing circuit, a processor, an Application Specific Integrated Circuit(ASIC), a microprocessor, or other processing logic that may interpret and executeinstructions. The herein utilised expression “calculation unit” may represent a processingcircuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.

The steering control arrangement 1 may further comprise a memory unit, wherein thecalculation unit may be connected to the memory unit, which may provide the calculation unitwith, for example, stored program code and/or stored data which the calculation unit mayneed to enable it to do calculations. The calculation unit may also be adapted to store partialor final results of calculations in the memory unit. The memory unit may comprise a physicaldevice utilised to store data or programs, i.e., sequences of instructions, on a temporary orpermanent basis. According to some embodiments, the memory unit may compriseintegrated 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 ornon-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 steering control arrangement 1 is connected to components of the robotic tool 3 forreceiving and/or sending input and output signals. These input and output signals maycomprise waveforms, pulses, or other attributes which the input signal receiving devices candetect as information and which can be converted to signals processable by the steeringcontrol arrangement 1. These signals may then be supplied to the calculation unit. One ormore output signal sending devices may be arranged to convert calculation results from thecalculation unit to output signals for conveying to other parts of the robotic tool's controlsystem and/or the component or components for which the signals are intended. Each of theconnections to the respective components of the robotic tool 3 for receiving and sendinginput 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 steering control arrangement 1 may be configured to steer the robotic tool 3 to obtain ormaintain the target angle b between the heading direction hd of the robotic tool 3 and thecurrent fall line direction fl using control loops, setpoint values, intervals and the like. Thesteering control arrangement 1 may be configured to estimate a current angle between theheading direction hd and the current fall line direction fl and may be configured to steer therobotic tool 3 in a manner such that the current angle is equal to the target angle b, in a continuous or repeated manner.

As is evident from the present disclosure, the steering of the robotic tool 3 involves an adjustment of the heading direction hd of the robotic tool 3. Thus, throughout this disclosure, 16 the wording “steering the robotic tool 3” may be replaced by the wording “adjusting theheading direction hd of the robotic tool 3”. Likewise, throughout this disclosure, the wording“steer the robotic tool 3” may be replaced by the wording “adjust the heading direction hd of the robotic tool 3” ln the embodiments illustrated, the robotic tool 3 comprises a steering control arrangement 1but might alternatively be implemented wholly or partly in two or more control arrangements or t\No or more control units.

The computer program product 200 may be provided for instance in the form of a data carriercarrying computer program code for performing at least some of the method steps 101, 102,103,110,111,112,113,114,120,121,122,123,124 and 126 according to someembodiments when being loaded into one or more calculation units of the steering controlarrangement 1. The data carrier may be, e.g. a CD ROM disc, as is illustrated in Fig. 3, or aROM (read-only memory), a PROM (programable read-only memory), an EPROM (erasablePROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a memorystick, an optical storage device, a magnetic storage device or any other appropriate mediumsuch as a disk or tape that may hold machine readable data in a non-transitory manner. Thecomputer program product may furthermore be provided as computer program code on aserver and may be downloaded to the steering control arrangement 1 remotely, e.g., over an lnternet or an intranet connection, or via other Wired or Wireless communication systems. lt is to be understood that the foregoing is illustrative of various example embodiments andthat the invention is defined only by the appended claims. A person skilled in the art willrealize that the example embodiments may be modified, and that different features of theexample embodiments may be combined to create embodiments other than those describedherein, 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 ormore stated features, elements, steps, components, or functions but does not preclude thepresence or addition of one or more other features, elements, steps, components, functions, or groups thereof.

Claims

17 CLA||\/IS

1.A steering control arrangement (1) for a self-propelled robotic tool (3), wherein thesteering control arrangement (1) is configured to:- obtain a current fall line direction (fl) at the position of the robotic tool (3), and- steer the robotic tool (3) based on a target angle (b) between the headingdirection (hd) of the robotic tool (3) and the current fall line direction (fl).

2. The steering control arrangement (1) according to claim 1, wherein the steering controlarrangement (1) is configured to steer the robotic tool (3) to obtain or maintain the targetangle (b).

3. The steering control arrangement (1) according to claim 1 or 2, wherein the robotic tool(3) comprises a sensor (5) arranged to sense the orientation of the robotic tool (3), andwherein the steering control arrangement (1) is configured to obtain the current fall linedirection (fl) by estimating the current fall line direction (fl) based on the current sensedorientation of the robotic tool (3).

4. The steering control arrangement (1) according to any one of the preceding claims,wherein the target angle (b) is a previous angle (b') between the heading direction (hd)and the current fall line direction (fl).

5. The steering control arrangement (1) according to claim 4, wherein the steering controlarrangement (1) is configured to obtain a current slope inclination (si) at the position ofthe robotic tool (3), and wherein the steering control arrangement (1) is configured to setthe target angle (b) to the angle (b') between the heading direction (hd) and the currentfall line direction (fl) obtained when the current slope inclination (si) reaches above a first

6. slope inclination limit value.

7. The steering control arrangement (1) according to any one of the preceding claims,wherein the steering control arrangement (1) is configured to obtain a current slopeinclination (si) at the position of the robotic tool (3), and wherein the steering controlarrangement (1) is configured to initiate the steering of the robotic tool (3) based on thetarget angle (b) when the current slope inclination (si) reaches above a second slope

8. inclination limit value.

9. The steering control arrangement (1) according to claim 6, wherein the steering controlarrangement (1) is configured to cancel the steering of the robotic tool (3) based on the

10.

11.

12.

13.

14. 18 target angle (b) when the current slope inclination (si) drops below a third slopeinclination limit value. The steering control arrangement (1) according to any one of the claims 5 - 7, whereinthe self-propelled robotic tool (3) comprises a sensor (5) arranged to sense theorientation of the robotic tool (3), and wherein the steering control arrangement (1) isconfigured to estimate the current slope inclination (si) based on the current sensedorientation of the robotic tool (3). A self-propelled robotic tool (3) comprising a steering control arrangement (1) accordingto any one of the preceding claims. A self-propelled robotic lawnmower (3) comprising a steering control arrangement (1)according to any one of the claims 1 - 8. A method (100) of steering a self-propelled robotic tool (3), wherein the method (100) comprises: - obtaining (110) a current fall line direction (fl) at the position of the robotic tool (3),and - steering (120) the robotic tool (3) based on a target angle (b) between the headingdirection (hd) of the robotic tool (3) and the current fall line direction (fl). The method (100) according to claim 11, wherein the step (120) of steering the robotictool (120) comprises the step of:- steering (121) the robotic tool (3) to obtain or maintain the target angle (b). The method (100) according to claim 11 or 12, wherein the self-propelled robotic tool (3)comprises a sensor (5) arranged to sense the orientation of the robotic tool (3), andwherein the step of obtaining (110) the current fall line direction (fl) comprises the stepsOf: - sensing (111) the orientation of the robotic tool (3), and - estimating (112) the current fall line direction (fl) based on the sensed orientation of the robotic tool (3). The method (100) according to any one of the claims 11 - 13, wherein the method (100)further comprises:

15.

16.

17

18.

19. 19 - obtaining (101) a current slope inclination (si) at the position of the robotic tool (3),and - setting (113) the target angle (b) to the angle (b') between the heading direction (hd)and the current fall line direction (fl) obtained when the current slope inclination (si)reaches above a first slope inclination limit value. The method (100) according to any one of the claims 11 - 14, wherein the method (100) further comprises: - obtaining (101) a current slope inclination (si) at the position of the robotic tool (3),and - initiating (114) the steering of the robotic tool (3) based on the target angle (b) whenthe current slope inclination (si) reaches above a second slope inclination limit value. The method (100) according to claim 15, wherein the method (100) further comprises:- cancelling (126) the steering of the robotic tool (3) based on the target angle (b) when the current slope inclination (si) drops below a third slope inclination limit value. _ The method (100) according to any one of the claims 14 - 16, wherein the self-propelled robotic tool (3) comprises a sensor (5) arranged to sense the orientation of the robotictool (3), and wherein the step of obtaining (101) the current slope inclination (si)comprises the steps of: - sensing (102) the orientation of the robotic tool (3), and - estimating (103) the current slope inclination (si) based on the current sensed orientation of the robotic tool (3). A computer program comprising instructions which, when the program is executed by acomputer, cause the computer to carry out the method (100) according to any one of theclaims 11 - 17. A computer-readable medium (200) comprising instructions which, when executed by acomputer, cause the computer to carry out the method (100) according to any one of theclaims 11 - 17.