METHOD AND SYSTEM FOR CHARGING A ROBOTIC WORK TOOL

Abstract

A method for charging a self-propelled robotic work tool (1) in a charging station (4), comprises the steps of: the robot (1) navigating towards a charging position in the charging station (4), and sensing an attaining of a predetermined charging position of the robotic work tool (1) in the charging station (4). A charging position sensor (6a) and a sensed feature (6b) are arranged in the self-propelled robotic work tool (1) and the charging station (4). A charging procedure is initiated once said charging position is attained, and the sensor (6a) detects the sensed feature (6b) in a contactless manner.

A system includes a charging station (4) and a robotic work tool (1), which each comprises one of a sensor (6a) and a sensed feature (6b), respectively, as well as first and second charging means (5a, 5b). The sensor (6a) and sensed feature (6b) are arranged for contactless detection.

A robotic work tool (1) for use in the system comprises a charging position sensor (6a), a chargeable battery, and a charging means (5a).

Claims

1. A method for charging a self-propelled robotic work tool in a charging station, the method comprising: navigating the robot towards a charging position in the charging station, sensing an attaining of a predetermined charging position of the robotic work tool in the charging station, by means of a charging position sensor in one of the self-propelled robotic work tool and the charging station and a sensed feature associated with the other of the self-propelled robotic work tool and the charging station, and initiating a charging procedure once said charging position is attained, and said sensor detects said sensed feature in a contactless manner.

2. The method according to claim 1, wherein the sensor is arranged in the robotic work tool and initiates said charging procedure.

3. The method according to claim 1, wherein the initiation of the charging procedure comprises transferring information via a short range, wireless interface.

4. The method according to claim 1, wherein sensing is based on emanated magnetic fields.

5. The method according to claim 1, wherein the sensed feature is a magnet, and the sensor is a Hall sensor.

6. The method according to claim 1, wherein the sensor is a 3D magnetic sensor.

7. The method according to claim 6, wherein the sensing of the attaining of the charging position of the robotic work tool comprises sensing a magnetic field above a threshold value and thereafter initiating the charging procedure.

8. The method according to claim 6, wherein the sensing of the position of the robotic work tool comprises sensing a peak in the magnetic field as the robotic work tool moves, and thereafter initiating the charging procedure.

9. A system for autonomous operation of a self-propelled robotic work tool, the system including a charging station and a robotic work tool, and the charging station and the robotic work tool each comprising one of a sensor and a sensed feature, respectively, and first and second charging means, respectively, wherein the sensor and sensed feature are arranged for contactless detection, and the robotic work tool and the charging station are arranged for initiating a charging procedure when a charging position has been attained.

10. The system according to claim 9, wherein the sensor is arranged in the robotic work tool.

11. The system according to claim 9, wherein a short range, wireless interface transceiver is arranged in each of the robotic work tool and the charging station.

12. The system according to claim 9, wherein sensing is based on emanated magnetic fields.

13. The system according to claim 9, wherein the sensor is a Hall sensor, and the sensed feature is a magnet.

14. The system according to claim 9, wherein the sensor is a 3D magnetic sensor.

15. A robotic work tool comprising a charging position sensor for positioning the robotic work tool in a charging station, a chargeable battery, and a charging means, wherein the charging position sensor is arranged for contactless detection of a sensed feature, and the robotic work tool is arranged for initiating a charging procedure when a charging position has been attained.

16. The robotic work tool according to claim 15, wherein the robotic work tool further comprises a short range, wireless interface transceiver or communication with the charging station.

17. The robotic work tool according to claim 15 or claim 16, wherein the sensor is a Hall sensor.

18. The robotic work tool according to claim 15, wherein the sensor is a 3D magnetic sensor.

19. The robotic work tool according to claim 15, wherein the charging position sensor is arranged between a set of contacts in the charging means.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The above, as well as additional objects, features and advantages of the present disclosure, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present disclosure, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:

[0043] FIG. 1 is a diagrammatic view from above of a work area with a robotic work tool and a charging station;

[0044] FIG. 2a is a perspective view of a charging station and a robotic work tool;

[0045] FIG. 2b is a view according to FIG. 2a of the robotic work tool only;

[0046] FIG. 3 is a schematic view from the side of the robotic work tool and the charging station; and

[0047] FIG. 4 is a flowchart of a method for charging the robotic work tool according to the disclosure.

[0048] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0049] FIG. 1 illustrates a robotic work tool 1 according to the disclosure, working in a work area 2. The work area 2 is delimited by a boundary cable 3 in the embodiment disclosed in FIG. 1, but other means of defining the work area 2, e. g. physical boundaries, such as walls, or satellite navigation, such as GPS, may be used in some embodiments.

[0050] The robotic work tool 1 is propelled by an electric motor powered by a battery, which may be charged in a charging station 4 somewhere in or near the work area 2. When the battery in the robotic work tool 1 is running low, the robotic work tool 1 may navigate back to the charging station 4 according to any procedure known in the art, i. e. with the aid of the boundary cable 3, a guide wire, satellite navigation, etc.

[0051] When the robotic work tool 1 has reached the charging station 4, it may dock therewith, as shown in FIG. 2a. The charging contacts 5a, see e. g. FIG. 2b, of the robotic work tool 1 need to come into contact with the corresponding charging contacts of the charging station 4, for a charging to take place.

[0052] The navigation procedures that may direct the robotic work tool 1 to the charging station 4 are usually not accurate enough to direct the robotic work tool 1 into a position where the charging contacts are in perfect contact with one another, which has hitherto involved the problems mentioned above in relation to the prior art.

[0053] In a disclosed embodiment, shown schematically in FIG. 3, the robotic work tool 1 is provided with a sensor 6a for sensing a sensed feature 6b, which is provided in the charging station 4. Various types of sensors 6a may be used, as long as they are adapted to sensing the sensed feature 6b in the charging station 4. Some embodiments utilize an optical sensing, such as the scanning of a barcode etc., sensing a LED light, or the like. Under certain circumstances, acoustic sensing, Doppler technology, etc. may be utilized. In further embodiments the sensed feature 6b may be a magnet, preferably a permanent magnet. A permanent magnet 6b need not be supplied with electricity in order to emanate a magnetic field and may hence work independently of an electric supply. However, other embodiments where a sensing of electromagnetic fields is utilized, e. g. by induction, a resonant circuit etc. are also possible variations.

[0054] In some advantageous embodiments, where the sensed feature 6b is a magnet, the sensor 6a is a Hall sensor.

[0055] Regardless of the type of sensor 6a and sensed feature 6b used in many embodiments of the disclosure, they may be arranged in a similar way in most cases. The sensor 6a may sense the sensed feature 6b at some distance away. Preferably the sensor 6a is adapted to the size and position of the sensed feature 6b, as well as to its field strength and the configuration of the field. The sensor 6a may be adapted to sense a threshold value of the sensed feature 6b, as a basis for the determination that the robotic work tool 1 has reached a correct charging position, where the charging contacts 5a, 5b are in close contact with one another. In other embodiments of the system, the sensor 6a is adapted to sense a peak in the sensed value. In this case the sensor 6a may sense an increase in the sensed value as the as the robotic work tool 1 moves closer 1 to the ideal charging position, and a decrease as the robotic work tool 1 moves away therefrom after passing it. The ideal mutual position of the charging contacts 5a, 5b should be arranged to coincide with a position of the robotic work tool 1 where the peak in the sensed value occurs.

[0056] The sensor 6a and the sensed feature 6b need not necessarily be arranged close to the charging contacts 5a, 5b in all embodiments. As long as the respective distances between the sensor 6a and the sensed feature 6b to their respective charging contacts 5a, 5b are known and rigid, a reasonable positioning is achievable. However, the accuracy in the positioning of the robotic work tool 1 in the charging station 4 may be maximised if the distance between the sensor 6a and the charging contacts 5a and the sensed feature 6b and the charging contacts 5b in the charging station, respectively, is kept low. Typically, any angular deviations in the mutual positioning of the sensor 6a and the sensed feature 6b may be more noticeable at an increased distance therefrom. Such deviations may cause a less than optimal contact between one or both pairs of charging contacts 5a, 5b. In a favorable embodiment of the disclosure, the sensor 6a and the sensed feature 6b are arranged between the charging contacts 5a, 5b on the robotic work tool 1 and the charging station 4, respectively. Of course a test signal can be applied to verify the positioning once the contactless sensing procedure has been concluded.

[0057] Neither the position nor the mutual close contact of the charging contacts 5a, 5b need be confirmed by a test current or a signal through the contacts 5a, 5b. The risks of excessive heating or sparks forming in case of an insufficient contact are hence eliminated, both by the enhanced positioning and by the fact that there is no voltage over the charging contacts 5a, 5b before the optimal charging position has been ascertained.

[0058] In a preferred embodiment, the robotic work tool 1 and the charging station 4 are provided with transceivers 7a, 7b, e. g. with a wireless interface such as Bluetooth or similar. Bluetooth may be useful for other purposes in the robotic work tool. Other suitable communication schemes include ANT and ZigBee, for instance. With the use of such transceivers 7a, 7b, information of a docking, i. e. of a successful positioning of the robotic work tool 1 in the charging station 4, may be transferred from the robotic work tool 1 to the charging station 4, or vice versa.

[0059] The unit carrying the sensor 6a, in a preferred embodiment the robotic work tool 1, is arranged to transfer the information of the attained charging position via the transceiver 7a to the transceiver 7b in the charging station 4. Such a transfer of information is arranged to take place as soon as the sensed feature 6b has been sufficiently confirmed, i. e. in dependence of the detection of a peak value or a threshold value. Also, the robotic work tool 1 may stop moving when the charging position has been attained, in order not to lose the mutual contact between the charging contacts 5a, 5b. Thereby the charging procedure is initiated. The charging station 4 is arranged to energize the charging contacts 5b, when it has received the information that the robotic work tool 1 is in its charging position, which implies that the charging contacts 5a, 5b are in sufficient mutual contact.

[0060] The method for charging the robotic work tool 1 is laid out schematically in FIG. 4. In step 8 the robotic work tool 1 is navigating towards the charging station 4 by any means known in the art, such as GPS, a guide wire etc.

[0061] In step 9, after the robotic work tool 1 has reached the charging station 4, the sensor 6a in the robotic work tool 1 starts detecting the sensed feature 6b. The robotic work tool 1 may move slowly and may adjust its position one or more times in order to find the optimal charging position, based on information from the sensor 6a.

[0062] In step 10, the charging position has been attained, and the sensor 6a detects the sensed feature to the highest degree, i. e. where a peak value of the sensed feature 6b is obtained. In some embodiments, this step 10 of the method involves sensing a threshold value of the sensed feature 6b, in order to attain the optimal charging position.

[0063] Step 11 is the initiation of the charging procedure. In this step 11, the transceiver 7a of the robotic work tool 1 wirelessly sends a confirmation signal to the transceiver 7b in the charging station 4. When the confirmation signal has been received, the charging station 4 is instructed to energize the charging contacts 5b. The charging contacts may not be energized before the confirmation of the attained charging position has been received, in order to ensure that the charging contacts 5b of the charging station 4 are in secure contact with the charging contacts 5a of the robotic work tool 1.

[0064] After the completion of step 11, the charging will take place according to any charging procedure known to the skilled person.

[0065] The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

[0066] For example, the sensed feature 6b in the charging station 4 has been described as a passive feature, e. g. a magnet, which always emanates a magnetic field constantly over time, and independently of electricity. It is of course possible to use a sensed feature 6b which depends on electricity, such as an electromagnet, an LED, etc.

[0067] Another variation is that the sensor 6a is arranged in the charging station 4 and the sensed feature 6b is arranged in the robotic work tool 1. In some such embodiments, sending a wireless message between the charging station 4 and the robotic work tool 1 may be considered superfluous, since the sensor 6a in the charging station 4, may communicate directly with the control system energizing the charging contacts 5b in the charging station 4, without involving the robotic work tool 1. On the other hand, there may be embodiments with such an arrangement of the sensor 6a and the sensed feature 6b, where a wireless message to the robotic work tool 1 may be useful to transfer the information that the charging position has been attained. For example, the information may be used by the robotic work tool 1 in order to interrupt the search for a charging position, as soon as such a position has been attained.

[0068] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.