WO2023182908A1

WO2023182908A1 - Method and system for operating a solar robot with a wake-up charging position

Info

Publication number: WO2023182908A1
Application number: PCT/SE2022/051200
Authority: WO
Inventors: Martin HAMMARSTRÖM; Pär-Ola SVENSSON
Original assignee: Husqvarna Ab
Priority date: 2022-03-21
Filing date: 2022-12-18
Publication date: 2023-09-28
Also published as: SE2250350A1

Abstract

A method for operating at least one autonomous robot (2), in particular an autono- mous vegetation working robot (2), preferably an autonomous lawn robot, within an operating area (15), the robot comprising (i) at least one electrically driven tool (8), (ii) at least one electric motion drive (20) for moving the robot, and (iii) at least one photoelectric device (3) for converting energy from illuminating light, in particular sunlight (L), into electric energy for the tool and the motion drive, the method comprising the steps of a) the robot working in an autonomous working mode with the tool and the mo- tion drive both being activated, b) receiving darkness information that the intensity of the illuminating light is or will be below a minimum charging intensity, which is necessary for charging the energy storage by the photoelectric device, for a certain period of dark- ness, usually night or another period without sunlight such as heavy clouding or rain, c) the robot, after step b) of receiving of darkness information or based on the received darkness information, moving or being moved to a wake-up position (WP), d) which wake-up position (WP) is a position, where illuminating light after the period of darkness, usually sunlight (L) in the morning or after sunrise, will es- sentially not be shaded by objects in or around the operating area, in particu- lar vegetation objects such as trees (12) or hedges (13) or bushes (14) or built objects such as buildings, for a predetermined wake-up period of the robot.

Description

Method and System for operating a solar robot with a wake-up charging position

Field of Technology

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, scarifying, irrigating or fertilizing.

Such autonomous lawn robots are autonomous (or: independent) with regard to the navigation within a specified lawn area and with regard to energy supply, so that no human supervision or interaction is necessary for navigating the robot or providing the robot with energy.

For an autonomous navigation of a robot a variety of features need to be implemented to make the navigation independent of humans and yet fully reliable, including in particular sensing and using real time signals from external systems such as bordering wires, guide wires, antennas or beacons, using known positioning systems and also using mapping of the area.

A special mapping navigational system is disclosed in WO 2021/209277 Al .

For an autonomous energy or power supply the known systems mainly use electric energy and rechargeable batteries carried by the robot which supply the electric consumers in the robot, in particular the cutting or mowing system, the drive system and the control unit and display with the electric energy needed. Selecting the size and type of the rechargeable batteries is usually accomplished empirically on a case by case basis. The choice of the batteries is a compromise between inter alia (i) the weight, (ii) the maximum power (peak power) needed especially for the cutting and driving and for the controlling and sensing and (iii) the charging capacity, i.e. the overall energy that is needed for a specified lawn area to be maintained.

Usually, autonomous lawn mowing robots are operated or set on pre-mowed or low height lawns and afterwards by their permanent (or: continuous or steady) autonomous operation keep the height of the lawn low also in the growth period. Therefore, the maximum electric power needed for mowing and also driving and thus the size and weight of the batteries can be kept low.

For recharging the rechargeable batteries of a lawn robot two main solutions are known, using charging stations connected to mains, e.g. as disclosed in EP 1 302 147 Bl or EP 2 547 191 Bl or photoelectric charging with solar cells on the robot or hybrid solutions using both.

In solutions using photovoltaic (or: photoelectric) cells or modules carried by the lawn robot the surrounding light, usually sunlight, is converted into electric energy which is fed to and stored in the rechargeable batteries. Such an autonomous lawn robot driven by solar energy (or: solar-driven robot) does not need to return to a charging station for recharging, but will also not be supplied with new energy when there is no or not enough sunlight, such as during the night or when the infrared spectrum used by silicon photovoltaics is absorbed by rain or mist. However, the season a lawn robot is most needed is the growth season when there is the most sunlight, so from the perspective of availability of solar energy a solar driven lawn robot is an ideal match.

A solar-driven autonomous lawn robot was proposed in US 5,444,965 A and put into practice in the SolarMower sold by Husqvarna already in the 1990ties.

One of the tasks when using solar energy for autonomous robots is to keep the robot in the sun or exposed to the sunlight for long enough a time, so that the solar energy can be used directly during operation and also for sufficiently recharging the batteries, in particular to supply the control unit in the darkness, e.g. in the night. In particular, it is a task to stay out of shadow or shade by objects in or around the lawn area to be maintained, or only stay in the shade for a minimum time to maintain the lawn if necessary but then to leave the shade and to revert to an area lit by sunlight again.

In the solar-driven autonomous lawn mower described in US 5,444,965 A, mentioned above, a shade detection system is provided to avoid that the robot remains a long time in a shaded zone. The energy received by the photovoltaic cells at intervals corresponding to the width of one cell is compared to the energy received during the preceding interval. If the fall of energy caused by the passing of one row of cells from sun to shade exceeds a predetermined value, considered as a signal of entry into shaded zone, the robot continues its movement over a certain distance and if the energy received remains at its reduced level, the robot turns back to return to the sunny zone. An energy management system manages the state of charge of the battery and detects nocturnal periods and places the system in a waiting state with minimum consumption. The battery allows the operation of the electronics also in the darkness or the operation of the mower in shaded zones or during cloudy intervals and evening out the photovoltaic energy. When the voltage at the battery decreases below a critical value, the robot is stopped and waits until the voltage increases to an acceptable value and then may be started again. Before entering the waiting state the robot verifies that it is not in a shaded zone and if a shaded zone has been detected, the robot finishes the shade leaving routine before stopping. When night falls, the current coming from all photovoltaic cells decreases and fades out.

WO 2015/094054 Al discloses a robotic work tool system with a robotic work tool, in particular an autonomous lawn robot, comprising a satellite position determining, wherein an obstacle map is generated to determine when an area will be shadowed with regards to satellite reception based on said obstacle map the operation of the robotic work tool is scheduled accordingly. The obstacle map is a shadow map giving information on areas that are at least partially shadowed at specific times. When the robotic work tool is solar charged a shadow map is generated as well. The robotic work tool determines that an area is shadowed from the sun by a (sudden) drop in voltage over a solar panel which indicates that the robotic work tool has entered a shadowed area. The sun's position and movement is, as for the satellites, known and can be determined for future operations based on said shadow map. The robotic work tool generates as a shadow map an obstacle map indicating when certain areas will be shadowed with regards to the sun, and schedule its operation accordingly so that the robotic work tool is exposed to as much sunlight as possible during an operation.

EP 3 503 205 Bl discloses an automatic working system with a self-moving device, configured to move and work in a working area and comprising a photoelectric conversion unit (solar panel and converter) and an energy storage unit (batteries), configured to store the electric energy obtained from the photoelectric conversion unit, and a control module that receives positioning information and illumination intensity information at one or more locations of the self-moving device in the working area, and generates an illumination map of the working area based on the received positioning information and illumination intensity information and on time. The illumination map may also contain attitude information of the device at the locations. The illumination intensity information can be obtained from an illumination sensor or by estimating an output voltage of the photoelectric conversion unit. In a charging mode the self-moving device is moved, based on the illumination map, to a location at which illumination intensity satisfies a preset level and that is closest to a current location and the device recharges its batteries. In the charging mode the self-moving device changes, by rotating the solar panel on the device or by rotating the whole device, an angle at which the photoelectric conversion unit receives optical energy, and determines an optimal solar radiation angle. A cleaning apparatus for automatically cleaning the solar panel may be provided at the working area. Weather information obtained through the Internet may be used as illumination condition information. Furthermore, a stored season model comprising illumination condition information of different regions and different time periods can also be obtained based on the actual geographic location and date information of the working area. The illumination map may also contain attitude information of the device at the locations.

US 2015/0359185 Al discloses an irrigation mobile robot having a battery and a sloped photovoltaic panel and a positioning system using radio signals from moisture beacons and historical movement vectors and a camera vision system. When an irrigation cycle is completed, the mobile robot recharges its battery using solar energy. Use of solar energy is optimized by moving the robot to a location in the working area that provides the brightest sun based on historical information, the time of day, and the calendar date. The mobile robot rotates on its axis so that the photovoltaic panel faces the sun as the sun's position in the sky changes. As charging continues, the mobile robot determines based on historical information for that time of day whether there is a location offering brighter. Sun brightness may be determined by historical photovoltaic panel output power or by an ambient light sensor. When charging is complete the cycle ends and the mobile robot enters a low power hibernate state until the next irrigation cycle. During the hibernate state the radio receiver in the control module is still active allowing reception of periodic moisture messages from the moisture beacons.

WO 2018/215092 Al discloses a method of configuring a charging system as part of an energetically autonomous sustainable intelligent robot using a computer vision based system and an artificial intelligence system to track and learn the best charging spots, for example, the best locations in the garden to charge the robot by means of a solar panel mounted on the robot. Based on location, time and weather, the robot inspects and measures how much sun falls on a given location of the map. Obstacles causing shadows are taken into account when measuring. Based on the available spots, and the real time weather, the robot calculates and estimates the best charging times and locations. It is not disclosed in more detail how this is accomplished in practice.

CN 104393359 A discloses an intelligent smart home cleaning robot for automatically cleaning the floor in a room. When this known smart robot is active in the set virtual wall (i.e. within the working area), it determines and records, when the light intensity value measured by its photosensitive sensor exceeds a light intensity threshold, a corresponding position coordinate (high intensity position) of the robot. The robot further determines whether the battery power of the intelligent robot is lower than a power threshold, and, if yes, moves to any of the high intensity position coordinates and the solar battery is charged by light energy. The high intensity position coordinates of the robot may be mapped with corresponding time points and the robot may move to a high intensity position coordinate mapped by a recorded time point closest to the current time point. The robot may, for recharging, also move to the position coordinate with the highest light intensity value mapped previously or, alternatively, to the nearest high intensity position coordinate. The robot may also only run during the day for instance between 8:00-17:00 and stand by during the night or a period of time without sunlight when the battery is too low, and will then automatically search for areas with light to charge when it is sunny in the morning. A search for the position with the highest light intensity value near the memorized coordinates avoids errors caused by the offset of the illumination position over time.

Pionski et al., "Environment and solar map construction for solar-powered mobile systems", IEEE Transactions on Robotics, Vol. 32, No. 1, February 2016, discloses the theoretical construction of an environment and solar map for solar-driven mobile robots to compute energy efficient paths within a working area of the mobile robot. The purpose of these energy efficient trajectories is to harvest more solar energy for mobile robots operating in environments for a long time, where the environments have objects like trees of bushes cast varying shadows. The solar map is determined by using simplified assumption such as only sunny with direct sunlight or completely shadowed and clear sky. However, it is disclosed to establish a solar map of a working area of a mobile robot that includes the expected (or: predicted or estimated) solar power (or: insolation or probability of sun) at a plurality of locations within the working area at various times during a day or longer period of time. The map is constructed using previous insolation measurements along with models about the environment and computing the estimated insolation for any position at any time. The robot may follow an algorithm with, in principle, arbitrary trajectories and plan its future energy efficient trajectories based on the estimate of the solar map.

It is also possible to provide a solar charger a charging station powered by solar cells in or close to the working area, such as the Husqvarna Solar charger https://www.husqvarna.com/us/maintenance-tools/automower-solar-charqer/

A future concept by Husqvarna is shown in the Youtube-video https://youtu.be/rp0npJDS0s8 under the title „Husqvarna Solea - An autonomous lawn mower system concept". A large carrier drone carries a small observation drone on top and several Automower robots, for instance nine in stacks of three. Mowing areas within a city are defined from the air by assessing need of grass maintenance and prioritizing working route. Fixed sensors collect real-time health of park areas. The Automowers are charged by the carrier drone. The observation drone scans and defines the areas and observes the working Automowers. There is cloud data upload and remaining time estimation. The Automowers are put down on the ground by the carrier drone and mow in groups by systematic cutting, contour following optimized cut, close to edge cutting (e.g. around trees), obstacle detection (e.g. fallen branches) and cloud data upload (e.g. to alert maintenance per- sonal). Furthermore, air pollution sensors, soil scanners, humidity sensors and object recognition systems are included. Unidirectional carbon fiber structure, dirt repellent nano-coated inside, sound absorbing membrane, solar cell membrane at the surface of the housing, batteries circularly arranged, electro magnets moving diamond coated cutting knives and fan blades (electric motor without central axis) may be incorporated as well.

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 new autonomous robot system, both in particular for working on (or: treating) vegetation, in particular lawns, and using, at least partially, electric energy converted from surrounding illuminating radiation, in particular sunlight.

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

In the embodiment according to claim 1 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 (or: working area). The robot typically comprises (i) at least one electrically driven tool, (ii) at least one electric motion drive for moving the robot, (iii) at least one photoelectric device (or: photovoltaic unit) for converting energy from illuminating light, in particular sunlight, into electric energy (used or to be used) for the tool and the motion drive and preferably also (iv) at least one energy storage, in particular one or several rechargeable batteries, for storing electric energy charged or supplied by the photoelectric device and.

The method comprises at least the following steps:

In a first step a) of the method, the normal operation is performed by the robot. The robot works in an autonomous working mode in which both the tool and the motion drive are activated (or: switched on) and thus use electric energy supplied by the photoelectric device and, preferably, the energy storage.

In a second step b) of the method, darkness information is received (in particular by the robot or another component of the system), the darkness information indicating or including that the intensity of the illuminating light is already below a minimum charging intensity, which is necessary for charging the energy storage by the photoelectric device, or will be below such a minimum charging intensity for a certain period of darkness, usually the night or another period without sunlight such as heavy clouding or rain.

In a third step c) of the method, after the step b) of receiving of darkness information or based on the received darkness information, the robot moves (or: travels) to a wake-up position and, preferably goes into or enters or adopts a stand-by mode at the wake-up position during the period of darkness.

The wake-up position (or: stand-by position, sleeping position) is a, usually pre-determined (or: pre-defined), position, where or at which illuminating light appearing or shining after the period of darkness, usually sunlight in the morning or after sunrise, will not be shaded by objects in or around the operating area, in particular vegetation objects such as bushes or trees or built objects such as buildings, for a predetermined wake-up period of the robot.

The invention is based on or at least starts from the idea that at least one specific wake-up (or: starting) position is selected for the robot which is not shaded by objects in or at the working area at the wake up time when the robot wakes up after a sleeping or stand-by mode during a period of darkness, in particular after a night, so that the photoelectric device can provide sufficient electric energy at the wake up time and the robot can resume operating in the working mode quickly, preferably after recharging first.

In the prior art mentioned above it is known that robots may look for sunny spots with high sunlight intensity while operating during the day to improve energy efficiency. When night comes and no more solar energy is available the known robots go to stand-by and wait for the sunlight to re-appear the next morning. On that new day the robots may also resume looking for sunny spots for recharging their batteries (see e.g. CN 104393359 A).

The prior art does, however, not teach to move the robot when darkness has or is about to come, for instance at sunset or nightfall, to a predetermined wake-up position, where there may be or is no sufficient sun light intensity for operating or charging any more on that ending day, but where the light source, in particular the sun, is predicted or expected to provide sufficiently high light intensity without shades for resuming work, in particular recharging, at the wake-up time or in the next morning, and only then, when the wake-up position is reached, to enter the stand-by mode, as is suggested by embodiments of the invention. The wake-up position or stand-by position of the robot according to embodiments of the invention is optimized as a predicted unshaded spot at wake-up time after darkness, typically in the next morning. Therefore, the robot can resume work or recharge the next morning without having to move to an unshaded spot first and, preferably also at a comparatively low remaining charge of the batteries when going into stand-by mode. This improves the availability of the robot for operation in many instances.

In the prior art, if the night falls, while the known robot is in an area shaded during the day, for instance below a tree, the known robots will not move out of this area according to their algorithm to find a sunnier spot as, after nightfall, there is no spot with higher light intensity anywhere else. So the known robots will stay in that area and go to stand-by mode for the night. Now, if that area is still shaded in the morning, for instance an area under a bigger tree, the known robots according to the prior art will need a long time to recharge the batteries.

According to embodiments of the invention, on the other hand, the robot will not stay under the tree for stand-by in the evening. Rather, the robot will first move, still in that very evening, to the wake-up position. The wake-up position is a position, which will not be shaded by this tree or other objects in the next morning . The robot will then, in the next morning, wake-up at the wake-up position, take advantage of the unshaded light and will, in particular after some recharge time, be ready for operation quickly.

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, vinyards, 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 seedlings 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 present, and can be cut regularly, including sowed lawns as well as wild grown meadows 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, mulching, scarifying, collecting items such as leaves, cut off grass or even golf balls, trimming, irrigating, fertilizing, sowing or harvesting, pesticide or herbicide spraying or video monitoring.

What partial spectra (wavelengths, frequencies) of the illuminating light, in particular sunlight, will be converted by the photovoltaic unit and to what extent (conversion 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.

The working area for the robot is the area where the robot works autonomously in the working mode using the tool(s) or with the tool(s) being activated. The working area may be composed of several connected or non-connected sub areas such as for instance several sections of a garden or lawn. An operating area of the robot, however, may be larger than the working area and may include further areas or paths for movement of the robot in between time periods in the working mode or working cycles and/or areas in which the robot operates also with the tool(s) being deactivated. Regarding the modus operand/ during 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. Here the operating area may comprise distanced working areas and further areas for charging or accommodating of the robot which areas can be reached by the flying movement.

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 communicating with external control devices and/or signal or information sources for navigation or optionally for energy management.

Advantageous embodiments and improvements according to the invention are disclosed in the dependent claims.

In preferred embodiments the darkness information is chosen to be at least one of

(i) an information indicating a low or zero illuminating light intensity, preferably derived from the electric output of the photoelectric device of the robot or derived from measurements using a light sensor, which is preferably carried by the robot;

(ii) a time and date indicating the beginning of darkness such as sunset or vanishing sunlight and the duration of darkness such as the time until the next sunrise or appearance of sunlight,

(iii) a weather reporting information indicating the beginning of darkness by weather conditions such as heavy clouds or rain, (iv) an end of work time (or stop work time) of a time schedule, in particular a time schedule set daily or for a specific date or week day, the end of work time indicating the time when the robot is to stop working.

(v) information about a working or mowing period concluded or done.

(vi) sensor and sensor algorithm information no more need for cutting for the time being, for example cutting resistance sensors.

(vii) Command from user or back-end service to cease operation

In a preferred embodiment, the method comprises a fourth step d), that can be performed before or after or at the same time as step b) of receiving the darkness information, and a fifth step e), wherein, in the fourth step d), the electric energy stored in the energy storage of the robot or an electric quantity directly associated with the stored energy such as electric capacity or electric charge of the energy storage, is determined or monitored, and, in the fifth step e), compared with a minimum operating (or: working) threshold (or: level) needed for (fully) operating the robot in the working mode, in particular with all electric consumers including the tool and the motion drive of the robot. Preferably, determining the electric energy or associated electric quantity includes measuring or evaluating an electric output voltage or power of the energy storage.

Now according to that embodiment of the method, the step c) of the robot moving or being moved to a wake-up position is only performed or carried out, if, as a further condition, the stored energy or the directly associated electric quantity of the energy storage is below the minimum operating threshold, i.e. if steps d) and e) yield or provide the result that the stored energy or associated quantity of the energy storage is below the minimum operating level.

The steps a) to c) or a) to e) of the method are preferably performed repeatedly or in iterations or cycles within predetermined monitoring or control time intervals in between the iterations or cycles.

In an embodiment, if the stored energy or the directly associated electric associated quantity of the energy storage is still above the minimum operating threshold, the robot may or will continue to operate in the working mode until the stored energy or the directly associated electric associated quantity of the energy storage reaches or is below the minimum operating threshold.

Preferably, during step c), when the robot moves or is moved to the wake-up position, the tool of the robot is deactivated and the motion drive is activated. But the tool may also stay activated to use the travelling time to the wake up position also for working.

Further preferably, after step c), when the robot has reached the wake up position, the robot goes into a stand-by mode (or: sleep mode) at the wake-up position during the period of darkness or until a wake-up time has been reached or a wake-up signal or command been received, wherein in the stand-by mode the tool and the motion drive of the robot are both deactivated.

In an advantageous embodiment more than one wake-up positions are defined within or close to the operating area, in particular to decrease the distance and time for the robot to find one of the wake-up positions and/or to provide different wake-up positions for different dates during the year or at different seasons of the year.

In a preferred embodiment the or at least one wake-up position is defined by a corresponding wake-up position token or marker, placed or arranged in or close to the operating area, preferably on or in the lawn or also at or close to a building and/or integrated into a control station, and the robot comprises a sensor or detector for sensing or detecting the wake-up position token, wherein the robot when moving to the wake-up position will preferably search for the token or a token signal using the sensor and will stop close to the token when the token is found or when the sensor is within a certain distance from the token.

The at least one wake-up position token or marker, in a preferred embodiment, contains permanent magnetic material and/or is made as a magnetic strip or body and the sensor of the robot is a magnetic field sensor for sensing the magnetic field of the magnetic marker. The at least one wake-up position token may also be a token based on RFID technology or NFC or Bluetooth or radar technology or ultrasound technology.

In a further embodiment the or at least one wake-up position is defined as stored positional data for the wake-up position, which is used by a navigational system for the robot, which navigates the robot to the stored wake-up position using the (implemented) positioning system of the navigational system, such as RTK, GPS, D- GPS, UWB or other positioning systems like for instance the system known from WO 2021/209277 Al or as a position in an illumination map of the operating area.

In an embodiment the robot itself determines one or more wake-up positions automatically or autonomously, for instance by storing or mapping the illumination intensity in the operating area at darkness ending times or wake-up times, preferably on a plurality of days over the year and in the morning or after sunrise.

In a preferred embodiment, in a wake-up routine after the period of darkness, when the intensity of the illuminating light is above the minimum charging intensity, the robot stays at the wake-up position until the photovoltaic device has recharged the energy storage sufficiently, so that the stored energy or the directly associated electric quantity of the energy storage is at a wake-up value above the minimum operating threshold and, preferably, when the wake-up value is reached, the robot resumes operating in the working mode.

In a further embodiment, when the robot reaches the wake-up position or when the robot wakes up the orientation of the robot and/or the photoelectric device may be adjusted towards the source of the illuminating light, in particular the sun, in order to increase or optimize the intensity area density of the incident illuminating light on the surface of the photoelectric device.

In an embodiment, in particular according to claims 14 and 15, an autonomous robot system is suggested comprising a) at least one autonomous robot, in particular an autonomous vegetation working robot, preferably an autonomous lawn robot, within an operating area, the robot comprising al) at least one electric tool, a2) at least one electric motion drive for moving the robot, a3) at least one photoelectric device for converting energy from illuminating light, in particular sunlight, into electric energy and a4) preferably at least one energy storage for storing electric energy charged by the photoelectric device and for supplying the tool and the motion drive with electric energy.

In the embodiment of claim 14 the system with the robot is configured to carry out a method according to an embodiment of the invention.

In the embodiment of claim 15 the autonomous robot system further comprises a system component, in particular the robot, configured to receive darkness information that the intensity of the illuminating light is or will be below a minimum charging intensity, which is necessary for charging the energy storage by the photoelectric device, for a certain period of darkness, usually night or another period without sunlight such as heavy clouding, a system component configured for determining an 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 energy storage and comparing the stored energy or the directly associated electric quantity with a minimum operating threshold needed for operating the robot in the working mode, the robot being configured to, if darkness information is received and if the stored energy or the directly associated electric quantity of the energy storage is below the minimum operating threshold, move to a wake-up position and to go into a stand-by mode at the wake-up position during the period of darkness, wherein the wake-up position is a position, where illuminating light after the period of darkness, usually sunlight in the morning or after sunrise, will essentially not be shaded by objects in or around the operating area, in particular vegetation objects such as bushes or trees or built objects such as buildings, for a predetermined wake-up period of the robot.

The embodiments disclosed herein are only examples, and the scope of this disclosure is not limited to them. Particular embodiments may include all, some, or none of the components, elements, features, functions, operations, or steps of the embodiments disclosed herein. Embodiments according to the invention are in particular 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 product 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 reference 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 disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject-matter which can be claimed comprises not only the combinations 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 combined with any other feature or combination of other features in the claims. Furthermore, 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.

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 invention may be of lower priority than higher priority conditions such as for instance failure or hazard detection. The method according to the invention is however carried out in the absence of such higher priority conditions.

Exemplary Embodiments

The invention will, in the following, be described further with reference to exemplary embodiments, also referring to the schematic drawings.

FIG 1 shows a vegetation working robot with a photovoltaic device in a selected wake-up (or: starting) position defined by a wake-up (or: starting) position token for defining a wake-up (or: starting) position for starting the robot after a darkness time interval such as the night or heavy clouds, FIG 2 shows a vegetation working robot with a photovoltaic device in a selected wake-up (or: starting) position defined by a wake-up (or: starting) position token, as shown in FIG 1, within a vegetation working area in the morning when the sun is still in the East,

FIG 3 shows a go-to-sleep routine for a vegetation working robot in a flow diagram and

FIG 4 shows a wake-up routine for a vegetation working robot after a go-to- sleep routine according to FIG 3 in a flow diagram.

Corresponding entities, parts and quantities are designated by the same reference signs in the figures if not indicated otherwise.

In FIG 1 and 2 an autonomous vegetation working robot, in particular lawn robot 2, is shown with ground wheels or rolls or balls 21 driven by an electric drive system comprising at least one electric drive motor (not shown) for moving the robot 2 on and over a surface of a lawn 10 within a pre-determined operating area, esp. working area 15, and according to autonomous navigation algorithms or routines provided by a navigational system.

The working area 15 is confined by a border 16 which may be defined by a bordering wire or beacons or mapping or obstacles such as walls or hedges or other known systems. Besides the lawn 10 the working area 15 comprises 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 2. An operating area of the robot 2 may comprise more than one working area.

The robot 2 has at least one electrically driven working tool 8 for working on the lawn 10 including an electric tool drive comprising at least one electric tool drive motor. The tool 8 comprises in particular a cutting tool or blade(s), in particular rotating and/or pivoting blades or cutting tool, for mowing or cutting the lawn 10 and possibly, in addition or alternatively, a mulching tool and/or scarifying tool.

The navigational system for the robot 2 typically comprises navigational software, implemented in a control device 7 of the robot 2 alone or, in a distributed system, in control hardware in the robot 2 and external hardware, the control device or hardware typically comprising at least one digital processor and digital storage for digital data processing. The robot 2 further comprises sensor and/or communication equipment sensing and/or transmitting and receiving signals used for navigation. The signals used for navigation may, without loss of generality, be position or positioning signals from positioning systems or signals from bordering wires or beacons.

Suitable positioning systems are, without loss of generality, Real-Time Kinematic (RTK) positioning, Global Positioning System (GPS) positioning, Differential Global Positioning System (D-GPS) positioning or Ultra-Wideband (UWB) positioning systems and/or other positioning systems like for instance the system known from WO 2021/209277 Al (LONA) and/or local electromagnetic, in particular radiofrequency (RF), emitter or beacon systems, such as Bluetooth, Near-Field Communication (NFC) or radio-frequency identification (RFID) technology based systems, with corresponding emitters or beacons at the working area or also signals from wires defining borders (bordering wire) of the working area or paths (guide wire) within the working area. 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.

The robot 2 comprises one or several rechargeable batteries as energy storage 4 for storing electric energy and at least one photoelectric device (or: photovoltaic device or module) 3 usually comprising several photoelectric or photovoltaic cells for converting light energy, in particular sunlight L of the sun 6, into electric energy by means of the photoelectric effect and for supplying the electric energy directly to the electric consumers in the robot 2 and/or to the batteries for recharging .

The photoelectric device 3 or its cells are preferably based on p-n-junctions or diodes of semiconductor materials such as, mostly monocrystalline or polycrystalline Silicon (Si) or, esp. in thin film technology, GaAs, ZnSe or CdS, which generate an output photoelectric voltage and change their electric impedance depending on the intensity of the incident light. A great variety of photoelectric devices or cells are suitable and can be used for the robot 2 together with suitable electronic converters or power controllers. The photoelectric device 3 may, topologically, be composed of a contiguous illumination area (or: surface) or several disjunct or disjoint illumination areas (or: surfaces) and each area may be composed of one or more parts or cells. The robot or photoelectric device 3 may also be equipped with orienting (or: aligning) drives for orienting the illumination surface(s) of the photovoltaic device 3 towards the light source, typically the sun, in particular at the wake up position WP. The photoelectric device 3 may also include means for increasing or decreasing its illumination area for instance folding or pivoting means for several photoelectric device parts joint together by joints (not shown), in particular at the wake up position WP.

As, even with all these measures to increase the area, the maximum illumination area of the photoelectric device 3 is limited as the size of the robot must be kept small enough to reach also narrow areas of the lawn 10, a photoelectric device 3 or cells with high efficiency or photoelectric conversion rate is or are chosen.

The photoelectric device 3 may be made rigid or of rigid cells and mounted onto the robot 2, as is known in many varieties and may reach single layer efficiencies of typically 22 % and even up to 30 % for monocrystalline silicon and up to 20 % for polycrystalline silicon and well above 30 % for stapled layers (e.g. tandem cells). But also photoelectric material flexible in shape can be used for the photoelectric device 3 such as photoelectric foils or solar membranes or photoelectric coatings or thin-film photovoltaics applied onto the housing of the robot 2 which mostly have an efficiency of up to 10 % but are recently reported to reach efficiencies of about 20 %. Some of these or all of these efficiency values may well change to the better in future products. Further, albeit small, losses occur in the converter electronics associated with the photoelectric device 3.

The peak power of the photoelectric device at maximum light intensity available at the working area may vary a lot depending on the type and size of the robot, but may typically be in the range of 5 W to 300 W. The peak power consumed by all electric consumers of the robot 2 simultaneously may for instance be in the range of ii to 500 W.

Therefore, usually, with the power needed at some instances of time for the mechanical tools and drives of the robot 2 and also its electronics, operating the robot 2 with photovoltaics alone without any batteries is not feasible over the working period and for a reasonably large working area and the rechargeable batteries are needed for buffering and smoothing the power supply. The photoelectric device 3 does not necessarily have to supply the maximum electric power or power peaks of the robot 2 on its own as the (charged) batteries provide additional electric power. Nevertheless, the photoelectric device 3 should, in a fully energy autonomous embodiment, provide at least the overall or accumulated energy for a given working period and given working area and desired working result (e.g. keeping the lawn maintained), so that no external charging means become necessary.

Of course a hybrid solution with external recharging in a charging station, if the photoelectric or solar recharging is not sufficient, is also possible, and/or a plug in cable or manual recharging in case of emergency.

The rechargeable batteries of the energy storage 4 of the robot 2 are preferably Lithium-ion (Li-ion) batteries, in particular because of their high energy-to-weight ratio (that may be well above 200 Wh/kg), low memory effect and slow self-dis- charge. Typically battery packs of several Li-ion battery cells are used each of whic may have a cell voltage of typically 3.6 V. Preferably, in order to achieve the desired total battery voltage of the battery pack, for instance 18 V to 36 V, groups of battery cells are switched in series, e.g. 5 for 18 V and 10 for 36 V, and in order to achieve the desired electric capacity or electric discharge current groups of cells are switched in parallel in the battery pack. The geometric configuration of the battery pack can be adapted to the shape and space within the robot 2. Voltage, capacity, life duration, thermal stability and safety of a lithium-ion battery cell depend on the material for the anode, cathode, and electrolyte. A typical material used for the anode is graphite. For the cathode typically a layered oxide such as lithium cobalt oxide or a polyanion such as lithium iron phosphate or a spinel such as lithium manganese oxide may be used.

The capacity and size of the batteries selected depends on the maximum discharge current needed for supplying the electric power for the working tool(s) and/or the drive system and the control unit(s). The electric power is approximately the product of the battery discharge voltage and the discharge current at the various instants of time. The capacity of the battery determines the overall electric energy, i.e. the time integral over the electric power, the robot 2 may consume during one working cycle until recharging is needed. A higher electric capacity of the batteries is typically needed for covering a larger working area. Typically, the maximum electric capacity of the batteries of the robot 2 is selected in a range from 1 Wh to 300 Wh.

The robot 2 further comprises an energy or battery monitoring system which monitors the remaining capacity or charge of the batteries. This is an embodiment of determining an 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 energy storage (step c) mentioned above).

When the capacity or charge C(t) at an instant of time t drops below a minimum working capacity or charge threshold Cmin , i.e. C(t) < Cmin, the working tool operation of the robot 2 is stopped and the robot 2 needs recharging of its batteries. This is an embodiment of determining an 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 energy storage (the step d) mentioned above).

When the capacity or charge C(t) however drops down below a critical minimum capacity or charge threshold C_cr, in particular before the waiting position is reached, the robot 2 is stopped immediately to save the batteries from deep discharge which would not allow recharging again and to keep a high life duration. The critical minimum capacity or charge threshold C_cr is smaller than the minimum working capacity or charge threshold Cmin. The minimum working capacity or charge Cmin of the batteries of the robot 2 is chosen large enough to still allow for some movement of the robot 2 towards the wake up position. Typical values for the critical minimum capacity or charge threshold C_cr are 2 to 10 % of the maximum capacity or charge of the batteries and for the minimum working capacity or charge threshold Cmin 10 to 25 % of the maximum capacity or charge of the batteries. The minimum working capacity as well as a maximum charging capacity may be chosen to achieve a long lifetime of the batteries, so that the charge of the batteries may be kept for instance between approximately 15 % to 90 %, preferably 20 % to 80 %, of the maximum capacity. There are several methods known per se for determining or estimating the actual remaining capacity or charge and thus the remaining electric energy of a battery. The remaining charge or capacity (measured in Ah or C) is a direct measure for the remaining electric energy (measured in J or Wh) that can be supplied by the battery, at constant output voltage U the remaining electric energy E is E = C U. The State of Charge (SOC) is the ratio of the remaining charge or capacity and the maximum or rated charge or capacity of a battery. In order to determine the remaining charge or capacity or the SOC known battery or energy management systems may use various SOC estimation methods for instance using MPPT (Maximum Power Point Tracking) or current integration (Coulomb counting) or Kalman filters or Neural Networks or impedance measurement or output voltage measurement (terminal voltage) or combinations thereof, in particular using the converters or electronics and corresponding algorithms of the energy management system. For evaluating the SOC or the remaining electric energy electric parameters like the voltage, current, capacity, impedance, charging/discharging rate may be used and the temperature band chemical type of the battery be taken into account as well. Also State of Health (SOH) calculations or estimations can be taken into account.

The robot 2 also comprises a photoelectric monitoring system which monitors the photoelectric output voltage V_out of the photoelectric device 3 and compares this photoelectric output voltage V_out with a minimum voltage threshold Vmin which corresponds to a low light intensity of the illuminating light or sunlight L or too dim light for recharging the batteries.

If the photoelectric monitoring system detects that the photoelectric output voltage Vout drops and stays below the minimum voltage threshold Vmin and/or decreases further down to 0 V within a specified (minimum) monitoring interval At of e.g. 1 to 15 minutes after a starting time to , i.e. V_{o u}t(t) < Vmin for to < t < to + At, this event or condition is interpreted by the navigational system as entering a dark period or a period of darkness with a longer lack of light, esp. lack of sunlight L such as nightfall or in general as a period without (sufficient) sunlight, e.g. due to heavy clouds or rain. Alternatively or in addition entering of a period of darkness may be detected also by an illumination sensor comprised by the robot 2 which yields a corresponding low intensity signal when the light has faded and the darkness begun.

So, a general condition for entering a period of darkness is I(t) < Imin for to < t < to + At with the light intensity I(t) at a time t, the minimum intensity threshold Imin, the starting time to and the detecting or monitoring time interval At. The monitoring time interval At is chosen long enough so that a nightfall or sunset can be distinguished from shades for instance when driving under a dense bush and shades do not lead to switching off the tool of the robot 2 all the time. The length of the monitoring time interval At should however not be too long so that the batteries are not discharged too much during the monitoring interval. In general, the monitoring time interval At may be chosen, for example, between 5 minutes and 60 minutes.

Another possibility of detecting the entering of a period of darkness is monitoring the time derivative of the light intensity dl/dt, i.e. how fast it decreases over time t, which allows for distinction between a rather sudden decrease when entering shades and a slower decrease at sunset or nightfall. Also, as another possibility, comparing the output signals of different cells of the photovoltaic device cells may be used and if the output voltages of all cells simultaneously drop below the minimum voltage threshold this is an indication of sunset or nightfall and if, on the other hand, the output voltages of only some of the cells drop below the minimum voltage threshold and of the other cells do not this is an indication of entering just a shade during the day.

These embodiments are examples for receiving darkness information that the intensity of the illuminating light is or will (soon) be below a minimum charging intensity, which is necessary for charging the energy storage by the photoelectric device, for a certain period of darkness, usually the night or another period without sunlight such as heavy clouding (step b) mentioned above).

The darkness information may also be obtained directly from schedule time information and/or weather forecast information. An example of a schedule time information is a scheduling time table week schedule or day schedule which defines operating hours or time (which may for example depend also on rest hours during noon for neighbours or working hours of staff etc.) and which can be set by a user, for instance by means of the user interface on the robot or an App for a mobile device and/or can be set or rescheduled by the system for instance based on a weather forecast, defining non-working periods during a thunderstorm or heavy rain clouds. The darkness information will then be derived from the end of work time set for the present day. The robot will usually start moving to the wake up position a sufficient time earlier to reach the or the next wake up position before the end of work time as to fulfill the schedule and stop or having stopped working when the end of work time is reached.

According to an embodiment of the invention special routines for recharging the batteries of the robot 2 are provided. This is shown also in the flow diagrams of FIG 3 and 4.

A Go-to-sleep-routine is shown in FIG 3. The robot 2 is operated in normal working mode, with the working tool(s) and the drive(s) and the navigation and control systems being powered with electric energy and working, as long as there is enough charge and illumination (STEP 100).

The battery monitoring system permanently checks the charging status of the batteries of the robot 2 (STEP 101). If the battery charging status is ok and the battery is not low, i.e. in particular not below a minimum working capacity or charge Cmin, the robot 2 continues to operate in the working mode (STEP 100).

If, however, the battery charge is low, i.e. below a minimum working capacity or charge Cmin, and thus the batteries cannot provide enough electric energy required for working properly in the working mode for much longer, it is checked in a next step whether darkness is or has been detected (STEP 102). The entering of a period of darkness is monitored by a darkness detection system such as the photoelectric monitoring system or an illumination sensor as already described.

If darkness is not detected (STEP 102 NO), i.e. there is still daylight available for recharging, the robot 2 either stays at the position for recharging or, preferably, is navigated to a recharging position with high light intensity, preferably with the tool being switched off or deactivated (STEP 105) and the batteries of the robot 2 are recharged at the recharging high intensity position by the photoelectric device (STEP 106) according to one of the routines known per se from the prior art.

If, however, darkness is detected at a point in time or darkness time ti (STEP 102 YES) and if, at the same time (in STEP 101) the battery monitoring system has detected a too low actual capacity or charge C(ti) of the battery at this darkness time ti, i.e. lower than the minimum working capacity or charge threshold Cmin , i.e. C(ti) < Cmin, the robot 2 discontinues working or operating in the working mode and switches off (or: deactivates or disengages) the electric tool drive in order to save energy and is now, as the last activity in the twilight or darkness, navigated by the navigational system to a predetermined or pre-defined wake-up (or: waiting, sleeping) position (STEP 103). In another embodiment, the robot may, during that navigation to the wake-up position continue working in the working mode keeping the tool 8 switched on to use the movement for working operation.

The robot 2 sleeps at the wake-up position, sleeping meaning going into a stand-by mode and switching off or deactivating all electric consumers apart from those control and monitoring systems needed for waking up or starting the robot 2 again when the darkness ends.

This is an exemplary embodiment of the robot, after receiving of darkness information and if the stored energy or the directly associated electric quantity of the energy storage is below the minimum operating threshold, moving to a wake-up position and going into a stand-by mode at the wake-up position during the period of darkness (step e) mentioned above).

A wake-up routine will be explained next referring to FIG 4.

The robot 2 still sleeps (or: is in stand-by mode) at STEP 200. However, the photoelectric monitoring system or illumination sensor is active and monitors the intensity of light falling on the photoelectric device 3 (STEP 201).

If light of sufficient intensity for recharging is not detected (STEP 201 NO), the robot stays in stand-by mode or continues to sleep (STEP 200). If light of sufficient intensity for recharging is detected (STEP 201 YES) at or after a darkness ending time t2, meaning the photoelectric output voltage V_out(t) exceeds the minimum voltage threshold Vmin for a time t with t2 < t, then the batteries are recharged (STEP 202), while the robot 2 stays or rests at the wake-up position.

The battery monitoring system permanently checks the charging status of the batteries (STEP 203). If the battery charging status is not ok yet and the battery is still too low (STEP 203 NO), i.e. in particular below the minimum working capacity or charge Cmin, the robot 2 remains in the charging mode and the batteries are charged further (STEP 202).

If the battery charging status is ok or the battery sufficiently charged for restarting or waking up the robot 2, (STEP 203 YES), i.e. the capacity or charge of the battery is above a pre-defined wake-up capacity or charge Cwak, which is typically higher than the minimum working capacity or charge Cmin, the robot 2 resumes operating in the working mode, i.e. the working tool(s) and drive(s) and navigational system are powered or switched on again (STEP 204). The wake-up capacity or charge Cwak can be chosen within a wide range with the minimum working capacity or charge Cmin, typically being the lower boundary and a value close or equal to the maximum capacity or charge being the upper boundary. The range for wake-up capacity or charge Cwak typically comprises 15 % to 90%, preferably 40 % to 80 %, of the maximum capacity or charge of the batteries.

The wake-up position is a position, where illuminating light after the period of darkness, usually sunlight in the morning or after sunrise, will essentially not be shaded by objects in or around the working area, in particular vegetation objects such as bushes or trees or built objects such as buildings, for a predetermined wake-up period of the robot (see feature or "step" f) mentioned above). The wake-up position is, in other words, a position where illuminating light or sunlight is expected or predicted at a sufficiently high intensity after the period of darkness, for example where the sun or future sunshine most probably will appear next.

Preferably, the wake-up position is a position or spot, where, after darkness has ended at a darkness ending time (or wake up time) t2, the photoelectric device 3 will, due to the lack of shade, be exposed to illuminating light of sufficiently high intensity for recharging the batteries, the intensity I(t2) at the darkness ending time t2 and at the wake-up position being larger than the minimum intensity threshold Imin for recharging and typically, at the darkness ending time t2, not lying in a shadow of an obstacle between the light source, typically the sun, and the wake-up position.

There are several ways of determining a suitable wake-up position or spot.

Preferably, to find an optimal spot for the wake-up position WP the appearance and altitude of the sun (or: solar altitude) at the geographic location of the working area 15 at and after sunrise and the shadows obstacles situated on or near the working area 1 cast onto the working area 15 are observed or calculated for each day during a certain working period and the wake-up 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. The calculations are typically based on models or simulations as are known per se for instance from the prior art mentioned above, e.g. Pionski et al.

Also solar maps with time stamps contain such illumination data may be used to pre-define suitable wake-up position, for instance solar maps known from the prior art mentioned above, e.g. WO 2015/094054 Al or CN 104393359 A or EP 3 503 205 Bl or Pionski et al.

Typically, in all embodiments, a period of darkness will be a night between sunset or one day and sunrise of the next day or a time of low light intensity such as heavy clouds or rain.

But it is also possible to wait for a couple of days for instance over the weekend, if such a period of several days is defined as a pre-set non-working time period by a time schedule or by weather conditions, for instance when it is too dry or too wet or too windy for working or mowing. Then although there may be sunlit intervals and several periods of darkness in the whole period, the robot will wait in stand-by mode at the wake up position until that pre-set non-working period is terminated. In other words a condition of higher priority such as a pre-set time schedule might shift the wake-up time to a time after more than one periods of darkness with daylight periods in between, but it will also after such a period of several days be at the wake-up position with sufficient light at the wake-up time.

FIG 2 depicts a working area 15 in the morning or at a wake-up time shortly after sunrise of the sun 6 close to the geographic East E.

Each of the higher or taller parts of vegetation cast, due to the low altitude of the sun comparatively long, shadows (or: shades) facing away from the sun 6, the tree 12 a shadow 12A, the hedge 13 a shadow 13A and the bush 14 a shadow 14A. The shadows 12A, 13A and 14A change and move over the working area 15 as the sun 6 rises to higher altitude towards the South S.

The wake-up position WP is chosen to lie 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 (predicted or expected) wake-up time period starting from the wake-up time darkness ending time t2, which is larger than the charging time needed for recharging the batteries to reach the desired wake-up capacity or charge Cwak. The wake up time period (sunny charging period) starting from the darkness ending time or wake up time t2 typically may comprise several minutes up to, preferably two, hours, for instance in the morning, and may be predicted depending on the desired recharging and the expected sun conditions.

A preferred position for the wake-up position WP will be, without loss of generality and depending on the obstacles present, towards the East E or East-South-East of the working area 15 and thus in the geographic direction of the sun 6 as shown in FIG 2.

Preferred embodiments include defining the wake-up position WP by a token or marker or wake-up position token 5 on or in the lawn 10 and are explained in the following and shown in FIG 1 and 2.

The wake-up position token 5 is laid and fixed onto or buried within the lawn 10 at the previously determined wake-up position WP. The robot 2 comprises a sensor 25 for sensing or detecting the token 5. Preferably, the wake-up position token 5 may be made of permanent magnetic material and/or as a magnetic strip and be detected by a magnetic sensor 25, for instance a MMES magnetic field sensor.

Therefore, when darkness is detected at the darkness time ti (FIG 3, STEP 102 YES) the navigational system will search for the characteristic signal or magnetic field of the token 5 using the magnetic sensor 25 and stop the robot 2 when the token 5 is found and reached, i.e. the sensor 25 is within a certain distance from the token 5 as can be seen best in FIG 1.

In a preferred embodiment the magnetic token 5 or other magnetic tokens 5 can also be used by turning them around into the opposite magnetic polarity (N to S or vice versa) to define a local boundary to prevent the robot 2 from proceeding into an area to be protected such as a flower bed.

Other types of tokens (or: tokens) and sensors other than magnetic tokens and sensors may be used for instance based on RFID technology or ultrasound technology, the latter of which could also be used to scare off moles or root voles, or radar technology, the token being used as a radar reflector, or a token being recognised by an image recognition system. In general the token or marker may be based on a passive configuration, i.e. the token changes or sends back a signal emitted by the robot, or an active configuration, i.e. the token sends out a signal (such as an electromagnetic or ultrasound signal mentioned above) or field (such as the magnetic field mentioned above) sensed by the robot.

Several pre-defined wake-up positions WP may be chosen or defined simultaneously, in particular several tokens 5 may be placed at associated wake-up positions WP, in order to decrease the distance and time for the robot 2 to find one of the wake-up positions WP in the Go-to sleep mode or routine.

Instead or in addition to tokens or tokens the wake-up position(s) can also be implemented and stored as positional data for the wake-up position in the navigational system. The navigational system then navigates, in particular in the Go-to- sleep routine (FIG 3), the robot 2 to the stored wake-up position using the (implemented) positioning system of the navigational system, such as RTK, GPS, D-GPS, UWB or other positioning systems like for instance the system known from WO 2021/209277 Al (LONA).

Also using a radio beacon, such as Bluetooth, NFC, RFID or SLAM for defining and finding the wake-up position is possible or even the following of bordering or guide wires to a wake-up position near the border 16 of the working area 15.

It is also possible that the system itself determines one or more wake-up positions automatically or autonomously, for instance by storing or mapping the illumination intensity over the working area and over time for the whole working season as disclosed in WO 2015/094054 Al and/or by the robot in previous working cycles and choosing stored spots or positions with high intensities at darkness ending times and wake-up times, usually in the morning or after sunrise, as the wake-up position^). For instance a SLAM system (Simultaneous Location And Mapping) where the robot creates its own map of the working area may be used or the Automower Intelligent Mapping system by Husqvarna (https://www.youtube.com/watch7v-KLdSLJu8acq), where the robot collects positional data and creates a virtual map of the working area and then users can define zones with cutting characteristics or other zone related data within the working area.

The pre-determined wake-up position WP may be determined by choosing or selecting an unshaded spot directed into the geographic direction or compass point of the sun extrapolating sufficiently high illuminating light intensity for recharging at a certain wake-up time, usually in the morning or after sunrise, and without significant shade, i.e. without objects between the wake-up spot and the sun.

A further embodiment according to the invention is described in the following: When the battery is low and the solar effect is poor, the robot goes to sleep to save batteries and stops at a position where the sun most probably will appear next. Choosing the optimal spot for future sunshine can be done automatically or by manually setting the position. When operating a solar powered mower, it is provided to preferably always charge at a sunny spot to get as many hours per day of sunshine. If the sunshine is poor, it is provided to stop at a position where the sun most probable will appear next. This is typically advantageous at sunset or during the day with large clouds. When the robot goes to sleep due to low battery and poor sunshine, it stops at a place where the sun most probably will appear next. In the morning, the sun often appears at the same spot or close by. During the day, that position may vary more depending on the time of day. Selecting that position can be done either manually, i.e. by a user, or automatically.

Manual setting of the position by the user can be done by many methods, such as:

- Selecting a position from RTK, GPS, D-GPS, UWB or other positioning systems.

Using so called LONA as disclosed in WO 2021/209277 Al gives better position

- Detecting a radio beacon, such as Bluetooth, NFC, RFID

- Detecting a token in the ground, such as a magnet strip with a certain polarity

- Following boundary or guide-wire to a position.

- Or a combination of above methods.

Automatic selection of the position can be:

- From previous detected positions by the robot moving around, recording solar effect.

- By compass or satellite position, to travel in certain direction.

The solar powered robot will wake up at a position where the sun is predicted to be. This maximizes the energy harvested from a solar panel.

Some advantages of a wake-up position according to embodiments of the invention are: There is less risk of running out of battery, e.g. in a scenario with cold nights or that an operating schedule is set to not operate over the weekend because it is supposed to be very dry, or rainy, or the user just does not want any operation. Also it may look nice and tidy and the robot can be avoided to be an obstacle somewhere in the garden.

A sensor of the robot may also sense the border or edge of lawn or wall or steps, in particular by vision or image detection.

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 invention 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 invention 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. Various other embodiments are possible also and fall within the scope of the invention.

For instance, although the exemplary embodiments describe an autonomous vegetation 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 robots, service robots, guarding robots, or any robots as described in the prior art mentioned in the beginning.

Furthermore, other locomotion or propelling drive systems can be provided as well for moving the robot on ground as a ground robot or 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). Also the robot 2 can, in embodiments not shown, be used for other purposes other than working on vegetation, for instance floor or ground cleaning or surveillance etc.

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 rechargeable batteries or at most at least one capacitor or small buffer battery for smoothening 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. Designating numerals

2 robot

3 photoelectric device

4 energy storage

5 wake-up position token

6 sun

7 control device

8 tool

10 lawn

11 slope

12 tree

12A shade

13 hedge

13A shade

14 bush

14A shade

15 working area

16 border

20 motion drive

21 wheels

25 sensor

E East

L light

N North

S South

W West

WP wake-up position

Claims

1. A method for operating at least one autonomous robot (2), in particular an autonomous vegetation working robot (2), preferably an autonomous lawn robot, within an operating area (15), the robot comprising (i) at least one electrically driven tool (8), (ii) at least one electric motion drive (20) for moving the robot, and (iii) at least one photoelectric device (3) for converting energy from illuminating light, in particular sunlight (L), into electric energy for the tool and the motion drive, the method comprising the steps of a) the robot working in an autonomous working mode with the tool and the motion drive both being activated, b) receiving darkness information that the intensity of the illuminating light is or will be below a minimum charging intensity, which is necessary for charging the energy storage by the photoelectric device, for a certain period of darkness, usually night or another period without sunlight such as heavy clouding or rain, c) the robot, after step b) of receiving of darkness information or based on the received darkness information, moving or being moved to a wake-up position (WP), d) which wake-up position (WP) is a position, where illuminating light after the period of darkness, usually sunlight (L) in the morning or after sunrise, will essentially not be shaded by objects in or around the operating area, in particular vegetation objects such as trees (12) or hedges (13) or bushes (14) or built objects such as buildings, for a predetermined wake-up period of the robot.

2. Method according to claim 1, wherein the darkness information is at least one of

(i) an information indicating a low or zero illuminating light intensity, preferably derived from the electric output of the photoelectric device of the robot or derived from measurements using a light sensor, which is preferably carried by the robot; (ii) a time and date indicating the beginning of darkness such as sunset or vanishing sunlight and the duration of darkness such as the time until the next sunrise or appearance of sunlight,

(iii) a weather reporting information indicating the beginning of darkness by weather conditions such as heavy clouds or rain,

(iv) an end of work time of a time schedule, in particular a time schedule set daily or for a specific date or week day, the end of work time indicating the time when the robot is to stop working,

(v) information about a working or mowing period concluded or done,

(vi) sensor and sensor algorithm information no more need for cutting for the time being, for example cutting resistance sensors,

(vii) Command from user or back-end service to cease operation.

3. Method according to claim 1 or claim 2, wherein the robot comprises at least one energy storage for storing electric energy charged by the photoelectric device and for supplying the tool and the motion drive with electric energy the method further comprising the steps of e) determining an 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 energy storage, f) comparing the stored energy or the directly associated electric quantity with a minimum operating threshold needed for operating the robot in the working mode, g) and only if, as a further condition, the stored energy or the directly associated electric quantity of the energy storage is below the minimum operating threshold, performing the step c) of the robot moving or being moved to a wake-up position and going into a stand-by mode at the wake-up position during the period of darkness,

4. Method according to claim 3, wherein h) if the stored energy or the directly associated electric associated quantity of the energy storage is still above the minimum operating threshold, the robot continues to operate in the working mode until the stored energy or the directly associated electric associated quantity of the energy storage reaches or is below the minimum operating threshold.

5. Method according to any of the preceding claims, wherein during step c), when the robot moves or is moved to the wake-up position, the tool of the robot is deactivated or activated and the motion drive is activated and/or wherein after step c), when the robot has reached the wake up position, the robot goes into a stand-by mode at the wake-up position during the period of darkness or until a wake up time or until a wake-up command or signal, wherein in the stand-by mode the tool and the motion drive of the robot are both deactivated.

6. Method according to any of the preceding claims, wherein several wake-up positions are defined within or close to the operating area, in particular to decrease the distance and time for the robot (2) to find one of the wake-up positions (WP) and/or to provide different wake-up positions for different dates during the year or at different seasons of the year.

7. Method according to any of the preceding claims, wherein the or at least one wake-up position is defined by a corresponding wake-up position token (5) placed in or close to the operating area (15), preferably on or in the lawn (10), and the robot (2) comprises a sensor (25) for sensing or detecting the wake-up position token (5), wherein the robot when moving to the wake-up position will preferably search for the token or a token signal using the sensor (25) and will stop close to the token when the token is found or the sensor (25) is within a certain distance from the token.

8. Method according to claim 7, wherein the wake-up position token contains permanent magnetic material and/or is made as a magnetic strip or body and the sensor (25) of the robot (2) is a magnetic field sensor.

9. Method according to claim 7 or claim 8, wherein at least one wake-up position token is a token based on RFID technology or NFC or Bluetooth or ultrasound technology or radar technology.

10. Method according to any of the preceding claims, wherein the or at least one wake-up position is defined as stored positional data for the wake-up position, which is used by a navigational system for the robot, which navigates the robot to the stored wake-up position using the (implemented) positioning system of the navigational system, such as RTK, GPS, D-GPS, UWB or other positioning systems or as a position in a illumination map of the operating area.

11. Method according to any of the preceding claims, wherein the robot itself determines one or more wake-up positions automatically or autonomously, for instance by storing or mapping the illumination intensity in the operating area at darkness ending times or wake-up times, preferably on a plurality of days over the year and in the morning or after sunrise.

12. Method according to claim 3 or any of the preceding claims referring directly or indirectly back to claim 3, wherein in a wake-up routine after the period of darkness, when the intensity of the illuminating light is above the minimum charging intensity, the robot stays at the wake-up position until the photovoltaic device has recharged the energy storage sufficiently, so that the stored energy or the directly associated electric quantity of the energy storage is at a wake-up value above the minimum operating threshold, wherein preferably, when the wake-up value is reached, the robot resumes operating in the working mode.

13. Method according to claim 12, wherein, when the robot reaches the wake-up position or when the robot wakes up, the orientation of the robot and/or the photoelectric device is adjusted towards the source of the illuminating light, in particular the sun, in order to increase or optimize the intensity area density of the incident illuminating light on the surface of the photoelectric device.

14. An autonomous robot system comprising a) at least one autonomous robot (2), in particular an autonomous vegetation working robot, preferably an autonomous lawn robot, within an operating area (15), the robot comprising al) at least one electric tool, a2) at least one electric motion drive for moving the robot, a3) at least one photoelectric device for converting energy from illuminating light, in particular sunlight, into electric energy and a4) preferably at least one energy storage for storing electric energy charged by the photoelectric device and for supplying the tool and the motion drive with electric energy; b) the system with the robot being configured to carry out a method according to any of the preceding claims.

15. An autonomous robot system, in particular according to claim 14, comprising a) at least one autonomous robot (2), in particular an autonomous vegetation working robot, preferably an autonomous lawn robot, within an operating area (15), the robot comprising al) at least one electric tool, a2) at least one electric motion drive for moving the robot, a3) at least one photoelectric device for converting energy from illuminating light, in particular sunlight, into electric energy and a4) at least one energy storage for storing electric energy charged by the photoelectric device and for supplying the tool and the motion drive with electric energy; a5) the robot having an autonomous working mode in which the tool and the motion drive both are activated for working within an operating area, c) a system component, in particular the robot, configured to receive darkness information that the intensity of the illuminating light is or will be below a minimum charging intensity, which is necessary for charging the energy storage by the photoelectric device, for a certain period of darkness, usually night or another period without sunlight such as heavy clouding, d) a system component configured for determining an 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 energy storage and comparing the stored energy or the directly associated electric quantity with a minimum operating threshold needed for operating the robot in the working mode, e) the robot being configured to, if darkness information is received and if the stored energy or the directly associated electric quantity of the energy storage is below the minimum operating threshold, move to a wake-up position and to go into a stand-by mode at the wake-up position during the period of darkness, f) wherein the wake-up position is a position, where illuminating light after the period of darkness, usually sunlight in the morning or after sunrise, will essentially not be shaded by objects in or around the operating area, in particular vegetation objects such as bushes or trees or built objects such as buildings, for a predetermined wake-up period of the robot.