SE2351130A1 - A method for operating an autonomous robot - Google Patents

Abstract

Abstract A method for operating at least one autonomous robot (2), in particular an autono- mous vegetation working robot, preferably an autonomous lawn robot, within an operating area, the robot (2) comprising (i) at least one energy storage (4) for storing electric en- ergy and for supplying the robot (2) with electric energy and (ii) at least one photo- electric device (3) for converting energy from illuminating light, in particular sun- light, into electric energy for storing in the energy storage and optionally for sup- plying the robot (2) directly and (iii) at least one magnetic field sensor (25), the method comprising the following features: a) b) c) d) f) 9) the robot (2) works, in an autonomous working mode, within at least one working area (15) within the operating area, a charging status of the energy storage (4) is determined, and if the charging status is below a minimum threshold, the robot (2) moves, in a recharging mode, to a charging position (CP1) for recharging the energy storage (4) using the photoelectric device (3), wherein at least one magnetic guiding path (6) is provided within the operat- ing area, preferably within the working area (15), comprising at least one magnetic strip (5, 5 and 52) elongated along a longitudinal trajectory and emitting a static magnetic field, wherein the at least one magnetic strip (5, 5 and 52) comprises, preferably at respective ends, two marker portions (50 or 52), where the magnetic field (H, H1, H2) changes along the longitudinal trajectory, wherein the at least one magnetic strip (5, 5 and 52) is formed as an open loop or open circuit with a gap (7) arranged between the two marker portions (50 or 52), wherein the robot (2), when moving to the charging position (CP1) for re- charging, detects, by means of the magnetic sensor (25), the magnetic field of the magnetic strip (5) and moves along the magnetic strip (5), wherein, when the robot (2) or its magnetic sensor (25) reaches the gap (7) between the two marker portions (50, 52) of the magnetic strip (5) and de- tects the change of the magnetic field, the robot (2) stops at a position in or at or close to that gap (7) of the magnetic strip (5) as the charging position (CP1) for recharging.

Description

The invention relates to a method for operating an autonomous robot, in particular an autonomous vegetation working robot such as an autonomous lawn robot, and to an autonomous robot system.

Background of the Invention Autonomous lawn robot systems are used for keeping a lawn (or: grass surface) permanently cut or mowed (with autonomous lawn mowers or lawn mowing robots) and, in some cases, for maintaining the lawn in other ways such as mulching, scari- fying, irrigating or fertilizing.

Such autonomous lawn robots are autonomous (or: independent) with regard to the navigation within a specified lawn or working area and with regard to energy sup- ply, so that no human supervision or interaction is necessary for navigating the ro- bot or providing the robot with energy, at least for a certain working time or pe- riod.

For an autonomous navigation of a robot a variety of features need to be imple- mented to make the navigation independent of humans and yet fully reliable, in- cluding in particular sensing and using real time signals from external systems such as bordering or boundary wires, guide wires, antennas or beacons, using known po- sitioning systems and also using mapping of the area. A special mapping naviga- tional system is disclosed in WO 2021/209277 A1.

In order to keep the robot within a specified working area the working area is de- fined either within a map or by a bordering or boundary system. The border or boundary may be defined by a bordering or boundary wire emitting an AC boundary magnetic signal which is dynamic, i.e. varies in strength and direction with time and is detected by means of a magnetic or inductive sensor of the robot. Systems with bordering or boundary wires are disclosed for instance in EP 1512053 Bl.

In EP 2 437 130 Bl a travel-scheduled area for a robot is stored in a map. In order to improve the control of the robot magnetic nails are positioned on the border of the travel-scheduled area at specific locations such as corners. The embedded posi- tions of the magnetic nails are also stored in the map. The magnetic field of the magnetic nails is measured by means of a geomagnetic sensor having x-axis, y-axis and z-axis outputs, mounted on the robot and used to control the robot in a specific way including detecting angular velocity by means of an angular velocity sensor and a wheel speed sensor. The magnetic nails are therefore only used to improve the boundary control of a working area of the robot.

WO 2020/156684 A1 suggests a static magnetic boundary system for a self-moving device in particular a lawn mower, where the boundary or border is made up by a chain of, preferably flexible, permanent magnetic strips whose magnetic field or N- S-orientation is transversal to the longitudinal direction of the magnetic strips. The static magnetic field, static meaning its strength and direction not varying over time, created by the connected magnetic strips is detected by a magnetic field sen- sor on the robot. The magnetic strips are connected with each other at their ends by special connectors in such a way that their polarities or magnetic field directions are not opposite to each other, which they would assume naturally and which would result in blind spots at the ends of two strips meeting each other, where the mag- netic field would cancel each other, in particular in such a way that the polarities are perpendicular to each other. In WO 2020/156684 A1 the static magnetic field is explicitly not used as a track or for guiding the robot, but as a border of a working area for the robot, from which the robot should turn away or retreat to stay within the working area. When the magnetic field strength detected by the sensor exceeds a threshold, the robot retreats.

WO 2021/190514 A1 discloses an automatic working system with a self-mobile de- vice, in particular a lawn mower, configured to move and work automatically within a working area set by the user by means of a boundary cable. A magnetic strip is provided and positioned for guiding the self-mobile device from the boundary cable to a charging station positioned in particular outside of the working area. The mag- netic strip reaches from the boundary cable into the charging station. The magnetic signal of the magnetic strip is detected by a magnetic sensing module of the self- mobile device.

For an autonomous energy or power supply the known systems mainly use electric energy and rechargeable batteries as energy storage carried by the robot which supply the electric consumers in the robot, in particular the cutting or mowing sys- tem, the drive system and the control unit and display with the electric energy needed. For recharging the rechargeable batteries of a lawn robot two main solu- tions are known, either using charging stations connected to mains, which the robot visits when the residual charge is low, e.g. as disclosed in EP 1 302 147 Bl or EP 2 547 191 B, or using photovoltaic (or: photoelectric) cells or modules carried by the robot for converting the surrounding or illuminating light, usually sunlight, into electric energy, e.g. as disclosed in US 5,444,965 A, EP 3 503 205 B1, US 2015/0359185 A1 or WO 2018/215092 A1, or using both.

Robotic lawn mowers often need to find fixed spots in the lawn, such as a charging station or a place to perform certain tasks, such as, in the case of a solar mower, a charging position for recharging within the lawn. Using a satellite-based navigation system is expensive.

General Disclosure of the Invention An underlying problem (or: object) of the invention is to propose a new method for operating at least one autonomous robot and a corresponding new autonomous ro- bot system, both in particular for working on (or: treating) vegetation, in particular lawns, within a working area, wherein the autonomous robot should in particular be able to find a location within the working area, in particular within the lawn, for re- charging or another activity. The method and system should be easy to implement, provide a high level of reliability and not necessarily require a positioning system, in particular a satellite positioning system, or a digital mapping system.

A solution of this problem according to the invention is proposed by an embodiment according to any of the independent claims.

In the embodiments according to the (optionally independent) claims 1 and 3 a method is suggested for operating at least one autonomous robot, in particular an autonomous vegetation working robot, preferably an autonomous lawn robot, within an operating area.

The robot works, in an autonomous working mode (or: working routine), within at least one working area within the operating area. In a position searching mode(or: position searching routine), the robot searches for a predetermined or pre-defined position or a target position, preferably within the operating area or the working area.

Now, for searching and finding the target position in the position searching mode, at least one magnetic guiding path is provided within the operating area, preferably within the working area, comprising at least one (permanent) magnetic strip (or: magnetic band, magnetic element) elongated along a longitudinal trajectory or lon- gitudinal direction and emitting or generating a static magnetic field, In a first embodiment according to claim 1 the at least one magnetic strip com- prises, preferably at respective ends, two marker portions, at which or where the magnetic field changes along the longitudinal trajectory, and is formed as an open loop or open circuit with a gap arranged between the two marker portions.

The robot comprises at least one magnetic field sensor, in particular for detecting the magnetic field of the magnetic guiding path or magnetic strip, and in the posi- tion searching mode or when searching the target position, detects, by means of or using the magnetic sensor, the magnetic field of the magnetic strip and moves along the magnetic strip. When the robot or its magnetic sensor reaches the gap between the two marker portions of the magnetic strip and detects the change of the magnetic field, the robot assumes or positions itself at a position in or at or close to the gap of the magnetic strip as the target position.

At the gap preferably the two marker portions of the magnetic strip are arranged at a predetermined distance from each other and/or face each other.

This embodiment with the open loop magnetic strip with the gap allows for the ad- vantageous embodiment that the robot can move in either orientation or direction (clockwise or anti-clockwise) along the open loop magnetic strip to find the gap and the target position so that the safety of operation is high and the target position re- liably found. Preferably the robot moves, in one position searching mode, in the open loop of the magnetic strip in anti-clockwise orientation and moves, in another position searching mode, in the open loop of the magnetic strip in clockwise orien- tation, in both cases reaching the gap.

The magnetic strip. in an advantageous embodiment, has a constant polarity of the magnetic field along the longitudinal trajectory and an end portion of the magnetic strip serves as the marker portion for the robot. When the robot or its magnetic sensor reaches this end portion of the magnetic strip and detects the quick drop of the magnetic field there, the robot assumes or positions itself at a position at the end portion or within a certain range from the end portion, which may be a spatial range such as within a certain distance and/or a signal or field range, e.g. a range of a certain signal or field characteristic such as a strength or intensity, as the tar- get position.

In a second embodiment according to claim 5, that can be combined with the first embodiment, in particular according to claim 1, the magnetic strip has a constant polarity of the magnetic field along the longitudinal trajectory and at at least one portion within the magnetic strip or at an end or end portion of the magnetic strip, an additional end marker is arranged along the longitudinal trajectory, wherein the end marker emits a magnetic field having a different, preferably opposite, polarity to the magnetic field of the magnetic strip and serving as the marker portion for the robot. The robot or its magnetic sensor detects the change in polarity from the magnetic strip in direction or compared to the end marker and the robot assumes or positions itself at a position at the end marker or within a certain range from the end marker, which may be a spatial range such as within a certain distance and/or a signal or field range, e.g. a range of a certain signal or field characteristic such as a strength or intensity, as the target position. So the end marker marks the end of the robot's path.

Preferably the robot stops at the target position. Furthermore, in an embodiment, several target positions can be provided and the magnetic guiding path can be used for or moved to different target positions or respective individual magnetic guiding paths for different target positions can be provided.

The robot preferably comprises too|(s) and motion drive(s) which are typically acti- vated (or: switched on) during or in the working mode.

In an advantageous embodiment, the robot comprises at least one energy storage for storing electric energy and for supplying the robot, in particular too|(s) and mo- tion drive of the robot, with electric energy.

The target position where the robot may perform a task at a specific spot, such as for watering a specific garden spot or for finding a good spot for data transmission, in particular for positioning data, or simply a spot to be in stand-by mode, e.g. for waiting or recharging or the like.

In a preferred embodiment the target position is a charging position for recharging the energy storage, for instance at a charging station or, in case of photoelectric recharging an illuminated position within the operating area.

So, if in such an embodiment the position searching mode is used for recharging, typically a charging status of the energy storage is determined or monitored, typi- cally during or in the working mode, and if the charging status is below a minimum threshold, the position searching mode is initiated or started with the charging po- sition as the target position and a magnetic guiding path associated with or placed near that charging position. Determining or monitoring the charging status of the energy storage typically comprises determining or monitoring a residual or remain- ing or stored electric energy stored in the energy storage of the robot or a directly associated electric quantity such as electric capacity or electric charge of the en- ergy storage. Preferably, determining the stored electric energy or associated elec- tric quantity includes measuring, detecting or evaluating an electric output voltage or power of the energy storage. The minimum threshold for the charging status or charging quantity is typically a predefined or stored threshold value, assuming an energy consumption when all electric consumers including the tool and the motion drive of the robot being activated as is the case when the robot is working. Prefera- bly, the stored minimum working threshold can be adapted to the working condi- tions in the working area, for instance more slopes or higher grass etc. that may in- crease the average power consumption and thus the minimum threshold value. Of course the minimum threshold is chosen at a safety margin to allow for the search- ing movement of the robot to the charging position.

In a preferred embodiment the robot may also comprise at least one photoelectric device for converting energy from illuminating light, in particular sunlight, into elec- tric energy for storing in the energy storage and optionally for supplying the robot directly.

In this case, the charging position (or: high illumination position or position with high expected illumination or unshaded position) is preferably a pre-determined (or: pre-defined) position chosen from one or more pre-defined or specific charging po- sitions, where, at least for a minimum recharging time period, including a sequence of periods, required for recharging, the illumination intensity of the illuminating light will be higher than a high illumination threshold and/or where the illuminating light will essentially not be shaded by objects in or around the operating area, in particular vegetation objects such as hedges, bushes or trees or built objects such as buildings. There may be just one charging position or a plurality of charging po- sitions the robot may search for when recharging is required.

In particular in such photoelectric embodiments, a navigational map or solar is not necessary for recharging. Rather, an easier way of defining charging positions for the robot is suggested by simply placing the magnetic guiding path with the at least one magnetic strip in the working area defining the charging position, which typi- cally had been identified beforehand by a user, and have the robot search for that magnetic guiding path which then leads the robot to the charging position. A user can now simply inspect the working area before starting the operation of the robot and look for unshaded and well illuminated spots for the charging position and place a magnetic strip at at least one of these suitable spots. The user may also use a sun altitude app on a smart phone which uses the camera and the compass of the smart phone and shows the sun altitude and thus also the possible shading at the each position for each time of each day of the year and evaluate various posi- tions within or close to the working area accordingly. Also the user can choose only such spots where the robot will be not in the way when recharging. By using per- manent magnets, it is possible to guide the robot to fixed locations in the lawn. A magnetic sensor that senses permanent magnets in the lawn is an easy and inex- pensive way to guide a robotic lawn mower.

By the term “vegetation” any configuration or arrangement or cover of plants that grow, mainly in the spring and summer season, when sufficient sunlight and water is present, is comprised, including, without loss of generality, lawns, gardens, park areas, golf courses, woods, copses, groves, agricultural fields, vineyards, green houses or modern city buildings with integrated horizontal and vertical agriculture etc. The vegetation may in particular, without loss of generality, be decorative or ornamental or be used as a ground surface or as a fence or be used for gaining food or medicine or building or industrial materials or fabrics. The plants, therefore, include all kind of cultivars or agricultural or horticultural plants or crop and also wild plants or species or varieties, in particular, without loss of generality, grass or weed or bushes or trees or agricultural plants, in grown or mature form or as seed- lings etc.

By a “lawn” any surface is meant with grass or weed or other plants that grow, mainly in the spring and summer season, when sufficient sunlight and water is pre- sent, and can be cut regularly, including sowed lawns as well as wild grown mead- ows or grassland and anything in between.

The robot working on the vegetation (in the working mode) includes, without loss of generality, working activities to influence vegetation, its healthy growth, shape and constitution, including gardening or agricultural activities like cutting, mulch- ing, scarifying, collecting items such as leaves, cut off grass or even golf balls, trimming, irrigating, fertilizing, sowing or harvesting, pesticide or herbicide spray- ing or video monitoring.

What partial spectra (wavelengths, frequencies) of the illuminating light, in particu- lar sunlight, will be converted by the photovoltaic unit and to what extent (conver- sion rate), depends on the material and type of the photovoltaic device chosen. The term “light” includes electromagnetic radiation in the visible spectrum, typically from about 400 nm to about 800 nm wavelength, and in the infrared (IR) spectrum, preferably in the near infrared spectrum from about 800 nm to about 1200 nm wavelength.

Regarding the modus operandiduring the working mode, the robot may, in most of the embodiments or applications, be moving on the ground by means of ground moving units such as wheels or rolls or legs or crawlers and corresponding driving and steering devices or units, usually electric motors with transmission units such as gears. However, in some embodiments, it is also possible that the robot may be flying or moving through the air during the operation, alternatively or in addition to a ground movement, and may then be equipped with flying drives like e.g. drones, including for example propellers and electric drive motors.

Usually, the robot further comprises at least one control device for controlling the tool and the motion drive and, in particular in a centralized system, for navigating the robot within the operating area and/or preferably for energy management of the electric energy stored in the energy storage and the electric energy supplied to the tool and the motion drive. The robot may (further or alternatively) comprise, in particular in a distributed system, a remote communication device for communi- cating with external control devices and/or signal or information sources for naviga- tion or optionally for energy management.

Advantageous embodiments and improvements according to the invention are dis- closed in the dependent claims.

In an embodiment, in particular according to claim 11, an autonomous robot system is suggested comprising at least one autonomous robot, in particular an autono- mous vegetation working robot, preferably an autonomous lawn robot, within an operating area, the robot comprising preferably one of more of the features men- tioned with regard to the method. The system with the robot is configured to carry out a method according to any of the embodiments according to the invention or any of the claims for operating the robot within the operating area and comprises, for that purpose, the at least one magnetic guiding path with the at least one mag- netic strip as defined or described herein with regard to the method.

The embodiments disclosed herein are only examples, and the scope of this disclo- sure is not limited to them. Particular embodiments may include all, some, or none of the components, elements, features, functions, operations, or steps of the em- bodiments disclosed herein. Embodiments according to the invention are in particu- lar disclosed in the attached claims directed to a method and a system, wherein any feature mentioned in one claim category, e.g. method or system, can be claimed in another claim category, e.g. storage medium, system, and computer program prod- uct as well. The dependencies or references back in the attached claims are chosen for formal reasons only. However any subject matter resulting from a deliberate ref- erence back to any previous claims (in particular multiple dependencies) can be claimed as well, so that any combination of claims and the features thereof are dis- closed and can be claimed regardless of the dependencies chosen in the attached claims. The subject-matter which can be claimed comprises not only the combina- tions of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be com- bined with any other feature or combination of other features in the claims. Fur- thermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and/or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims. 11 Exemplarv Embodiments The invention will, in the following, be described further with reference to exem- plary embodiments of methods and systems, also referring to the schematic draw- |ngs.

FIG 1 shows a vegetation working robot with a photovoltaic device in a working area with two examples of magnetic guiding paths to charging positions.

FIG 2 depicts a loop-shaped magnetic guiding path which may be used in FIG 1, FIG 3 illustrates a magnetic guiding strip that can be used for the magnetic guid- ing paths of FIG 1 or 2, FIG 4 depicts the magnetic guiding strip of FIG 3 with an additional end marker of opposite polarity at its end and FIG 5 shows a linear magnetic guiding path which may be used for instance in FIG 1. Corresponding entities, parts and quantities are designated by the same reference signs in the figures, if not indicated otherwise.

In FIG 1 an autonomous vegetation working robot, in particular lawn robot 2, is shown with ground wheels 21, at least some of them driven by an electric motion drive comprising at least one electric drive motor for moving the robot 2 on and over a surface of a lawn 10 within a pre-determined operating area, comprising at least one working area 15, and according to autonomous navigation algorithms or routines provided by a navigational system.

The working area 15 is confined by a boundary (or: border) 16 which may be de- fined by a bordering wire or border cable 56 which is supplied with a boundary or bordering signal by a control station 60 to be sensed by the robot 2. Alternatively, the boundary 16 may be defined by beacons or mapping or obstacles such as walls or hedges or other known systems. Besides the lawn 10 the working area 15 com- prises other vegetation such as for example trees or bushes or hedges. Examples of a tree 12, a hedge 13 and a bush 14 are depicted in FIG 1. Also an operating area for the robot with several working areas may be provided (not shown).

The robot 2 has at least one electrically driven working tool for working on the lawn including an electric tool drive comprising at least one electric tool drive motor. 12 The tool comprises in particular a cutting tool or b|ade(s), in particular rotating and/or pivoting blades or cutting tool, for mowing or cutting the lawn 10 and possi- bly, in addition or alternatively, a mulching tool and/or scarifying tool.

A navigational system for the robot 2 typically comprises navigational software, im- plemented in a control device of the robot 2 alone or, in a distributed system, in control hardware in the robot 2 and external hardware, the control device or hard- ware typically comprising at least one digital processor and digital storage for digi- tal data processing. Any of the navigational systems known per se from the state of the art may be used for guiding and navigating the robot 2 within its working area 15. The robot 2 further comprises sensor and/or communication equipment sensing and/or transmitting and receiving signals used for navigation.

As for the boundary 16 the robot 2 may for instance have sensing or detection equipment for sensing or detecting the boundary signal in the boundary cable 56 and the navigational system navigates the robot 2 to revert or turn back (“reflex- ion") depending on the detection of the boundary signal so as not to cross the boundary 16 and stay inside the working area 15, as is known per se in the art. As is shown in FIG 1, exemplary partial paths or trajectories of the robot 2 within the working area 15 during a free movement are illustrated by dotted lines and the re- turn or “reflexion” of the robot 2 at the boundary 16 are shown in the partial (free) paths FP1 and FP2.

At least one magnetic field sensor 25 is provided at or within the robot 2 for sens- ing (also) not time varying static magnetic fields or signals of magnetic guiding means for guiding the robot 2 which will be explained further hereinafter. Examples for such a magnetic field sensor are Hall sensors or magnetoresistive sensors.

Furthermore, the robot 2 comprises one or several rechargeable batteries as energy storage 4 for storing electric energy and at least one photoelectric device (or: pho- tovoltaic device or module) 3, usually comprising several photoelectric or photovol- taic cells for converting light energy, in particular sunlight L, into electric energy and for supplying the electric energy directly to the electric consumers in the robot 2 and/or to the batteries for recharging. In addition, the robot 2, preferably, com- prises a battery monitoring system which monitors the remaining capacity or charge 13 of the batteries of the energy storage 4 and determines the charging status of the energy storage 4.

If the charging status is critical, i.e. the remaining capacity or charge is too low or a recharging of the energy storage 4 is necessary, the robot 2 enters a recharging search mode and moves to a charging position for recharging.

At least one charging position, for instance the charging position CP1 shown in FIG 1, is chosen within the working area 15 or the operating area at a, at least during the charging time, mostly unshaded spot or location (an ideally shadow-free spot) for recharging using the photoelectric device 3.

As shown in FIG 1, each of the higher or taller parts of vegetation in or close to the working area 15 cast shadows (or: shades) facing away from the sun, the tree 12 a shadow 12A, the hedge 13 a shadow 13A and the bush 14 a shadow 14A. At least one charging position CP1 is chosen or selected to lie at least mostly outside of any of these shadows 12A, 13A and 14A of tree 12, hedge 13 or bush 14 (or any other obstacles that cast shadows) during at least a certain (current or expected) time period, which is preferably larger than the charging time needed for recharging the batteries to reach a capacity or charge for restarting. Other shadow-free spots within the working area 15 may be chosen as additional charging positions which may be used for or at different times of the day or the year. Preferably, to find an optimal spot for the charging position such as the charging position CP1 the ap- pearance and altitude of the sun (or: solar altitude) at the geographic location of the working area 15 at and the shadows which obstacles situated on or near the working area 15 cast onto the working area 15 are observed or calculated for each day during a certain working period or season and the charging position is chosen (empirically) in an area where there is direct sunlight without shadows of obstacles. The observations are made empirically by measurement or video or human visual observation, for instance by means of a sun altitude app. Such empirical decisions allow for an easy and flexible definition or distribution of charging positions such as CP1 by the user or in situ. The calculations are typically based on models or simula- tions as are known per se. 14 In order to allow the robot 2 to find the charging position CP1 or another charging position or, in general, target position(s) within the working area 15 or within the operating area in a reliable and quick manner, at least one magnetic guiding path 6 or (charging) position finding path is provided and can preferably be chosen freely by a user. When the robot 2 is in the recharging search mode it looks for the mag- netic guiding path 6 and follows it towards the charging or target position.

Each magnetic guiding path 6 is preferably defined or formed by at least one, pref- erably flexible, magnetic strip 5 comprising permanent magnetic material and thus generating a static, i.e. time-independent, magnetic field which is sensed by the magnetic sensor 25 of the robot 2 in a passive manner i.e. without the need of sup- plying electric energy or current as in the case of inductively generated magnetic fields around an electrical wire.

The magnetic strip 5 is elongated along a longitudinal direction and may be formed by continuous permanent magnetic material or, in other words, as a continuous strip or, alternatively, by a sequence of individual permanent magnets arranged at a distance to each other and connected with, for instance glued to, or embedded in a matrix or carrier material which is preferably flexible such as a tape. Exemplary embodiments of such magnetic strips 5 are shown in FIG 3 and 4 besides FIG 1, 2 and 5.

According to FIG 3 the magnetic strip 5 has a constant or continuous polarity, i.e. the direction of the magnetic field H does not change along the longitudinal direc- tion of the magnetic strip 5 up to the very end portion 50 or front face of the mag- netic strip 5. For instance the magnetic North pole N of the permanent magnetic material of the magnetic strip 5 may for example be on the top and the magnetic South pole S on the bottom as shown, so that the magnetic field H inside the mag- net is directed from Sto N and outside the magnet from N to S and directly above the magnetic strip 5 is directed substantially vertical and upwards as indicated and follows the closing curved field lines of the magnetic field (not illustrated).

In this embodiment, when the robot 2 reaches the end portion 50 of the magnetic strip 5 the magnetic field H sensed by the magnetic sensor 25 will quickly drop and disappear also when moving sideways and thus the robot 2 will detect when an end of the magnetic guiding path 6 is reached, at which end the charging position CP1 or position P is located, and may stop there for recharging.

According to FIG 4 the magnetic strip 5 has, similar to FIG 3, a constant or continu- ous polarity or direction of the magnetic field H1 along the longitudinal direction of the magnetic strip 5 (in this case directed downwards with the North pole N on the bottom and the South pole S on the top) up to an intermediate end portion 50. At the end portion 50 an additional end marker 52 is added in the longitudinal direc- tion, the end marker 52 having opposite polarity to the magnetic strip 5, thus with the North pole N on the top and the South pole S on the bottom or with the mag- netic field H2 above the end marker 52 being opposite to the magnetic field H1 above the magnetic strip 5. The magnetic strip 5 and the end marker 52 form a composed magnetic strip or magnetic guiding path 6. The end marker may, in an embodiment not shown, also be arranged not at an end but at a position within the magnetic strip.

In this embodiment, when the robot 2 reaches the end marker 52 of the magnetic strip 5 the magnetic field H sensed by the magnetic sensor 25 will be reverted or change polarity from H1 to H2. The robot 2 will detect this change of polarity as an indication that an end of the magnetic guiding path 6 is reached, at which end the charging position CP1 or position P is located, and may stop there for recharging. This change of polarity is an unambiguous indication for having reached the final position and increases the safety of the system.

The end portion 50 in FIG 3 as well as the end marker 52 in FIG 4 both form re- spective marker portions of the magnetic strip 5 or 5 and 52, at which marker por- tions the magnetic field changes abruptly or rapidly (e.g. H down to 0 or low or H1 to H2) which change is recognized or detected by the robot 2 as an indication that the final position CP1 or P is reached and the robot 2 stops at that position, in par- ticular in a recharging mode or waiting mode.

In the embodiments of FIG 3 and 4 the magnetic poles N and S and thus the mag- netic field F may be arranged differently, for instance just be reverted or arranged in a tilted or inclined manner. 16 The magnetic guiding path 6 is, in an advantageous embodiment, e.g. shown in FIG 1, 2 or 6, formed as an open loop or open circuit with a gap 7 defining or placed at the desired charging position CP1 as is shown in FIG 1 and in greater detail for a general position P (such as the charging position CP1) in FIG 2 and .

At the gap 7 of the magnetic guiding path 6 two end portions 50 or end markers 52 of the magnetic strip 5 are arranged at a predetermined distance from each other, in particular face each other or are in close vicinity to each other.

In the embodiment of FIG 5 an at least approximately linear or straight magnetic strip 5 is provided as a magnetic guiding path 8.

The robot 2, in a typical movement, follows a free path FP1 which is determined by its navigational routine or algorithm and then hits the magnetic guiding path 6 sensing the magnetic field (H or H1) of the magnetic strip 5.

Now, if the robot 2 needs recharging i.e. is in the recharging search mode, the ro- bot 2 follows the magnetic guiding path 6 along a guided path GP1 parallel or along the magnetic strip 5. The guided path GP1 can set off in either direction or orienta- tion, to the left or to the right, but typically one orientation is chosen as a default.

If the robot 2 does not need recharging it may ignore the magnetic strip 5 or the magnetic field sensed and may continue along the free path FP1 rather than the guided path GP1.

In order to find and follow the magnetic strip 5 of the magnetic guiding path 6 the robot 2 by means of the magnetic field sensor 25 senses whether the sensed value is within a range of the magnetic field generated by the magnetic strip 5 in a cer- tain close distance to the magnetic strip 5 corresponding to a respective threshold of the magnetic field, e.g. 80 % of the maximum magnetic field, and keeping the sensor value sensed by the magnetic sensor 25 above this threshold by steering the robot 2 accordingly. Thus, the robot 2, i.e. its magnetic sensor 25, keeps within a small distance from the magnetic strip 5 and the robot 2 follows the magnetic strip 5 along its guided path GP1. 17 Finally the robot 2 reaches an end of the magnetic strip 5, in particular at the gap 7 in the magnetic loop like guiding path 6 as shown in FIG 1 and 2 or at the end of the more linear magnetic guiding path 8 of FIG 5. When the robot 2 reaches the end of the magnetic strip 5 the magnetic field quickly drops below the threshold (e.g. FIG 3) and no immediate steering action increases the senor value any more indicating the final position CP1 or P is reached or the magnetic field even inverted (e.g. FIG 4).

For instance, when following the magnetic strip 5, the steering is continuously reg- ulated towards the magnetic strip 5 by using a control mechanism such as a PID- regulator. If the field values detected at the end of the strip indicates a drop in magnetic field, the regulator tries to compensate for it. If it cannot succeed by driv- ing slightly to the left or the right, it is assumed that the end has been reached.

As described in these embodiments, in particular according to FIG 1 to 5, a method and a system are implemented or provided for operating at least one autonomous robot, in particular an autonomous vegetation working robot, preferably an autono- mous lawn robot, within an operating area. The robot comprises (i) at least one en- ergy storage for storing electric energy and for supplying the robot with electric en- ergy and (ii) at least one photoelectric device for converting energy from illuminat- ing light, in particular sunlight, into electric energy for storing in the energy stor- age and optionally for supplying the robot directly and (iii) further comprises at least one magnetic field sensor. The robot works or operates, in an autonomous working mode, within at least one working area within the operating area. A charg- ing status of the energy storage is determined, and if the charging status is below a minimum threshold, the robot moves, in a recharging mode, to a charging position for recharging the energy storage using the photoelectric device. At least one (per- manent) magnetic strip which is elongated along a longitudinal trajectory or direc- tion and emits a static magnetic field is provided within the operating area, prefera- bly within the working area, and used as a magnetic guiding path for the robot. The at least one magnetic strip comprises or is equipped with at least one marker por- tion, where the magnetic field changes along the longitudinal trajectory or direc- tion. The robot, in the recharging mode or when moving to the charging position for recharging, detects, by means of the magnetic sensor, the magnetic field of the magnetic strip and moves along the magnetic strip. When or as soon as the robot 18 or its magnetic sensor reaches the marker portion of the magnetic strip, i.e. detects the change of the magnetic field, the robot stops at a position at or close to that marker portion of the magnetic strip, which position is then used as the charging position for recharging In a first preferred embodiment the magnetic strip has a constant polarity of the magnetic field along the longitudinal trajectory and, at a portion, in particular an end portion, of the magnetic strip, an additional end marker is arranged along the longitudinal trajectory. This end marker emits a magnetic field that has a different, preferably opposite, polarity to the magnetic field of the magnetic strip and serves or is used as the marker portion for the robot. The robot detects the change in po- larity of the magnetic field, in particular when moving from the magnetic strip to the end marker, as an indication the final position has been reached as a charging position _ In a second preferred embodiment that can be combined with the first preferred embodiment the at least one magnetic strip comprises two marker portions, where in each case the magnetic field changes along the longitudinal trajectory, and is formed as an open loop or open circuit with a gap arranged between the two marker portions, wherein, preferably, at the gap the two marker portions of the magnetic strip are arranged at a predetermined distance from each other and/or face each other or are in close vicinity to each other. Now, when the robot (2) or its magnetic sensor reaches the gap between the two marker portions of the mag- netic strip and detects the change of the magnetic field, the robot stops at a posi- tion in or at or close to that gap of the magnetic strip, which position is used as the charging position for recharging.

A hybrid solution of robot 2 is also possible with external recharging in a charging station, in particular equipped with stationary solar cells itself, and/or a plug in ca- ble or manual recharging in case of emergency. For instance as shown in FIG 1 the control station 60 may also be a charging station defining a second charging posi- tion CP2 which can be reached and found by means of a magnetic guiding path 8 e.g. according to FIG 4, the end marker 52 of which may be arranged at or close to the charging position CP2. The robot 2 in this case follows a free path FP2 then hits the magnetic guiding path 8 and follows it along the guided path GP2 up to the 19 charging position CP2 in or at the control/charging station 60. In this case the mag- netic guiding path 8 replaces the usual guide wires used to find the charging sta- tion.

By using permanent magnets, it is in particular possible to guide the mower to fixed locations in the lawn without the need of an expensive satellite-based navigation system. A magnetic sensor that senses permanent magnets in the lawn is an easy and inexpensive way to guide a robotic lawn mower. The magnetic strip can be placed as an “open circuit", making the mower travel until the gap is found. The magnetic strip can be placed with a different magnetic polarity at the destination spot. The mower may follow the magnetic field, until the reversed polarity is found. The magnetic strip can be placed to have different polarities upwards. The mower can make different decisions depending on the polarity. One possible use case is to guide the mower to a charging station.

The robot or photoelectric device 3 may also be equipped with orienting (or: align- ing) drives for orienting the illumination surface(s) of the photovoltaic device 3 to- wards the light source, typically the sun, or means for increasing or decreasing its illumination area for instance folding or pivoting means for several photoelectric de- vice parts joint together by joints (not shown). A further adjustment to the sun po- sition can be achieved in particular by a movement of the robot and/or by a move- ment of the photoelectric device relative to a robot body or chassis. In a preferred embodiment the following adjustment routines use only movements of the robot 2 or only the motion drive 20 of the robot 2. For instance, when the robot arrives at the respective charging position CP1 it stops and performs an azimuthal adjustment of its photoelectric device by rotating or turning or circling about a vertical axis by an (azimuth) angle of 360°, i.e. at least one full turn or revolution. During this full turn or revolution the effect or output of the photoelectric device 3 is monitored and a maximum output (or: highest output) during the rotation or turn and the cor- responding rotational position or azimuth angle are identified. The robot is then ro- tated to the rotational position or azimuth angle, where the maximum output of the photoelectric device was observed or detected. The charging position CP1 may also be chosen at a specified slope or sloped surface within the operating area or work- ing area 15 to optimize the position with regard to the sun.

Although in the exemplary embodiments a charging position for recharging is searched, the method and system are not limited to such embodiments. In fact any desired or predetermined position (target position) other than charging position can be searched and found by the robot 2 in all embodiments described, for instance a position where positioning in particular GPS signal reception is better and not shaded or a waiting or sleeping position or a position at a charging station for re- charging or shelter for the robot or for other purposes or actions to be performed by the robot at the target position. . The recharging mode is then replaced in gen- eral by a position search mode and the charging status does not need to be deter- mined and even a photoelectric device is not compulsory. This is also described in the general description of the invention and also in the claims.

Many searching routines are suitable and can be implemented for searching the magnetic guiding path and be integrated into or follow the normal navigational rou- tines and movement patterns applied during normal operation of the robot, such as random search routines or following certain search pattern such as parallel lines in a meandered fashion or spirals or zick-zack movements etc. Preferably, the naviga- tional routines or algorithms used during the working mode are also used during the recharging search routine for searching the charging position.

It is understood that, as is usual in autonomous systems, any of the conditions and steps taken on the fulfillment or non-fulfillment of a condition according to the in- vention may be of lower priority than higher priority conditions such as for instance failure or hazard detection, critical charge conditions, or severe weather conditions or a time schedule defining non-working periods. The method according to the in- vention is however carried out in particular in the absence of such higher priority conditions, which usually rarely occur.

The invention is by no means delimited by or to the exemplary embodiments. Vari- ous other embodiments are also possible and fall within the scope of the invention. For instance, although the exemplary embodiments describe an autonomous vegeta- tion working robot, in particular lawn robot 2, the invention can be applied also to other types of autonomous robots operating in an operating area, e.g. cleaning ro- bots, service robots, surveillance or guarding robots, or any robots as described in 21 the prior art mentioned in the beginning. Furthermore, other locomotion or propel- ling drive systems can be provided as well for moving the robot on ground as a ground robot, for instance rolls or balls or legs or chain drives instead or in addition to wheels, or air propelling drives, in the air, as a flying robot like a drone or as a carrier drone for flying the ground robot from one place to the other (not shown). Instead of the sun 6 also artificial light sources may be used, for instance lights or lamps or floodlights, e.g. in an application for final cutting of lawn in sports like football, tennis or golf. The robot could also just comprise solar cells without re- chargeable batteries or at most at least one capacitor or small buffer battery for smoothing the electric voltage or power. Finding a wake up position according to embodiments of the invention will be even more useful for such a pure solar robot as it has no safety margin by the batteries. The robot could also, instead of or in addition to rechargeable batteries, include power to fuel or power to hydrogen technology converting the electric energy to fuel such as methanol or methane or hydrogen for storage in form of chemical energy and using a fuel cell for converting the energy in the fuel or hydrogen back into electric energy esp. once such systems become small and light and efficient enough for such an autonomous robot.

Claims (8)

1. Claims 1. A method for operating at least one autonomous robot (2), in particular an autonomous vegetation working robot, preferably an autonomous lawn robot, within an operating area, the method comprising the following features: a) the robot (2) works, in an autonomous working mode, within at least one working area (15) within the operating area, and searches, in a position searching mode, a target position (CP1), b) at least one magnetic guiding path (6) is provided within the operating area, preferably within the working area (15), comprising at least one magnetic strip (5, 5 and 52) elongated along a longitudinal trajectory and emitting a static magnetic field, c) the at least one magnetic strip (5, 5 and 52) comprises, preferably at respec- tive ends, two marker portions (50 or 52), where the magnetic field (H, H1, H2) changes along the longitudinal trajectory, d) the at least one magnetic strip (5, 5 and 52) is formed as an open loop or open circuit with a gap (7) arranged between the two marker portions (50 or 52), e) the robot (2) comprises at least one magnetic field sensor (25), f) the robot (2), in the position searching mode, detects, by means of the mag- netic sensor (25), the magnetic field of the magnetic strip (5) and moves along the magnetic strip (5) towards the gap (7), and, g) when the robot (2) or its magnetic sensor (25) reaches the gap (7) between the two marker portions (50, 52) of the magnetic strip (5) and detects the change of the magnetic field, the robot (2) assumes or positions itself at a po- sition in or at or close to the gap (7) of the magnetic strip (5) as the target position (CP1).
2. 2. A method according to claim 1, wherein the magnetic strip (5) has a constant polarity of the magnetic field (H) along the longitudinal trajectory and wherein an end portion (50) of the magnetic strip (5) serves as the marker portion (52) for the robot (2), wherein, when the robot (2) or its magnetic sensor (25) reaches the end portion (50) of the magnetic strip (5) and detects the quick drop of the magnetic field (H), the robot (2) assumes the target position (CP1) at the end portion (50) orwithin a certain range from the end portion (50), which range may be a spatial range such as within a certain distance and/or a signal or field range, e.g. a range of a certain signal or field characteristic such as a strength or intensity.
3. 3. Method according to claim 1 or claim 2, wherein at the gap (7) the two marker portions (50 or 52) of the magnetic strip (5) are arranged at a predeter- mined distance from each other and/or face each other.
4. 4. Method according to any of claims 1 to 3, wherein the robot (2) moves, in one position searching mode, in the open loop of the magnetic strip (5) in anti- clockwise orientation and moves, in another position searching mode, in the open loop of the magnetic strip (5) in clockwise orientation, in both cases reaching the gap (7)-
5. 5. A method for operating at least one autonomous robot (2), in particular an autonomous vegetation working robot, preferably an autonomous lawn robot, within an operating area, in particular a method according to any of the preceding claims, the method comprising the following features: a) the robot (2) works, in an autonomous working mode, within at least one working area (15) within the operating area, and searches, in a position searching mode, a target position (CP2), b) at least one magnetic guiding path (6) is provided within the operating area, preferably within the working area (15), comprising at least one magnetic strip (5, 5 and 52) elongated along a longitudinal trajectory and emitting a static magnetic field, c) the magnetic strip (5) has a constant polarity of the magnetic field (H1) along the longitudinal trajectory and wherein, at at least one portion, preferably one end portion (50), of the magnetic strip (5), an additional end marker (52) is arranged along the longitudinal trajectory, the end marker (52) emitting a magnetic field (H2) having a different, preferably opposite, polarity to the magnetic field (H1) of the magnetic strip (5) and serving as the marker portion (52) for the robot (2), which detects the change in polarity, d) the robot (2), in the position searching mode or when searching the target po- sition (CP2), detects, by means of the magnetic sensor (25), the magnetic field of the magnetic strip (5) and moves along the magnetic strip (5), and, e) when the robot (2) or its magnetic sensor (25) reaches the marker portion (50, 52) of the magnetic strip (5) and detects the change of the magnetic field, the robot (2) assumes or positions itself at a position at the marker por- tion (50) or within a certain range from the marker portion (50, 52), which may be a spatial range such as within a certain distance and/or a signal or field range, e.g. a range of a certain signal or field characteristic such as a strength or intensity, as the target position (CP2).
6. 6. A method according to any of the preceding claims , wherein the robot (2) comprises at least one energy storage (4) for storing electric energy and for supplying the robot (2), in particular tool(s) and/or motion drive(s) of the robot (2) with electric energy and wherein the target position is a charging position (CP1) for recharging of the at least one energy storage, wherein preferably a charging status of the energy storage (4) is determined, and if the charging status is below a minimum threshold, the position searching mode is initiated wherein preferably determining the charging status comprises determining a residual or remaining or stored electric energy stored in the energy storage or a directly associated electric quantity such as electric capacity or electric charge of the energy storage,
7. 7. A method according to claim 6, wherein the robot (2) comprises at least one photoelectric device (3) for converting energy from illuminating light, in particular sunlight, into electric energy for storing in the energy storage and optionally for supplying the robot (2) directly, and/or wherein the charging position (CP1, CP2) is a position, where, at least for a mini- mum recharging time period, the illumination intensity of the illuminating light will be or is expected to be higher than a high illumination threshold and/or where the illuminating light will essentially not be or be expected to be shaded by objects in or around the operating area, in particular vegetation objects such as hedges, bushes or trees or built objects such as buildings,
8. 8. A method according to any of the preceding claims comprising at least one of the following further features: (i) the robot (2) moves along the magnetic strip (5) by keeping the sensed value of the magnetic field above a certain threshold, (Ü) (in) UV) 11. a) D) c)the at least one or each magnetic strip (5) is placed within the operating area or within the at least one working area (15), in particular on or in the lawn, in particular by a user, the at least one or each magnetic strip (5) is portable, in particular as to be placed at various different charging positions in case of changes in the envi- ronment within or close to the operating area or weather conditions, and/or is removeably fixed, in particular by means of an anchor or peg or the like or by burying it at the ground surface or by gluing or releasably fixing it to an object in or next to the operating area, at least two or more target positions, in particular charging positions (CP1, CP2) are provided for the position searching mode) at least one magnetic strip (5) is used at or moved between different targeting positions. A method according to any of the preceding claims wherein the longitudinal trajectory of or for the magnetic strip (5) forms at least partially a curved, preferably convex, line and/or forms at least partially a straight line. A method according to any of the preceding claims, wherein the magnetic field is oriented essentially vertically above the magnetic strip (5). An autonomous robot system comprising at least one autonomous robot (2), in particular an autonomous vegetation working robot, preferably an autonomous lawn robot, within an operating area (15), the system with the robot (2) being configured to carry out a method for oper- ating the robot within the operating area according to any of the preceding claims and comprising the at least one magnetic guiding path (5) with the at least one magnetic strip (5).