Method for controlling a self-propelled lawn mower

p0001The invention relates to a method for operating a self-propelled, battery-powered working equipment, in particular a self-propelled mower according to the preamble of claim 1.

p0002Self-propelled lawn mowers are known per se. Thus discloses<patcit id="pcit0001" dnum="EP1025472B1"><text>EP 025 472 B1 1</text></patcit> a system comprising a battery-powered lawn mower having an electric drive, which is driven to determine the driving direction and the driving speed by a control unit. The to be mowed by the mower area is defined by a deckle wire, on which wire loop two signals are abandoning at the same time. A first alternating voltage signal oscillating at a first frequency and a second AC signal resonates with a double frequency. In receiving coils in lawnmowers induce alternating electromagnetic fields of the permanent transmitted alternating voltage signals received signals, which are evaluated by an evaluation unit so that a statement can be made as to whether the implement is inside or outside the wire loop. Going through the first signal the zero line, a reference point is set. In this time, the system where the following maximum of the oscillating at twice the frequency second signal is checked. Is this on the plus side, the receiving coil Robot mower is inside the wire loop; is it on the minus side, the receiving coil Robot mower is outside the wire loop. Depending on this evaluation, the direction of travel of the mower is controlled.

p0003From the <patcit id="pcit0002" dnum="EP1512054A1"><text>EP 1512054 A1</text></patcit> is a controller for a self-propelled, battery-powered lawnmower known, the field strength of the received electromagnetic field is evaluated by transmitted on the wire loop signals. The direction of travel of the implement is determined by the reception strength of the received signal.

p0004A problem with known self-propelled lawn mowers is the occurrence of random external and internal electromagnetic field interference that may reach the magnitude of the received signals received and in practice greater. Such disturbances may be caused internally by the drive motors of the lawn mower or the engine power electronics or caused externally by external high voltage power lines, radio signals or other adjacent robotic mower. If errors occur, is difficult a precise determination of the location of the robot mower inside or outside the wire loop, or even impossible.

p0005The invention addresses the problem of specifying a method for operating a self-propelled, battery-powered working machine that works safely with little technical effort, even in areas of high electromagnetic field disturbances and trouble free.

p0006The object is achieved according to the features of claim 1.

p0007The discontinued to the wire loop of the edge delimitation wire electrical signal for determining the location of the implement is designed as a signal having a predetermined pattern. The pattern is selected so that it even with heavy distortion resulting from electromagnetic interference is still recognizable and evaluated with a reasonable outlay.

p0008The evaluation unit of the working machine processes the received signal of the receiving coil as a pattern, the received signal with a predetermined, stored reference pattern is compared. information on the location of the receiving coil inside or outside the border perimeter wire and thus on the whereabouts of the implement on the surface can be obtained from the comparison result. Depending on the comparison result, the control unit perform the driving direction of the implement so with the aim that the receiver coil comes to rest inside the deckle wire again and the implement edited the entire area defined by the edge of the perimeter wire.

p0009The inventive method is insensitive to interference from accidental external or internal electromagnetic fields. Such noise can be triggered within the working unit of the drive motors and the motor power electronics or caused by external high voltage power lines, radio signals or adjacent robot systems.

p0010Advantageously, the checked on the wire loop signal is a burst signal with a digital pattern, and in particular with a digital stochastic pattern which securely remains recognizable even under extreme field disturbances. The pattern of the burst signal is preferably made of solid high levels and low levels solid. The pattern is shaped by the fact that the time period the level is different. Other forms and shapes of a pattern of the burst signal may be advantageous.

p0011In a development, a break is provided between consecutive burst signals so that the receiver coil downstream evaluation unit can clearly detect the beginning and end of a burst signal. As a result, the technical outlay for evaluating the signals are held low. Furthermore, it is ensured that the sample is received in its entirety, that is in its full length in time for evaluation.

p0012The time sequence of the burst signals on the loop of wire may be random; appropriate pauses between consecutive burst signals are provided with a fixed period.

p0013It may be appropriate to send in a pause between consecutive burst signals any other signals, eg. As more burst signals with different patterns.

p0014In another advantageous embodiment of the invention, the signal transmitted on the edge perimeter wire is a deterministic analog AC signal with a period of predetermined time length.

p0015It may be appropriate to specify a defined time of reception window within which the hub receives the transmitted signal on the wire loop in a receiving coil. The opening and the closing of the receiving window is advantageously matched to the sequence of the signals transmitted on the wire loop and whose period duration.

p0016The received reception signal in the receiver coil is a time derivative of U ~ dI / dt of the signal transmitted on the wire the deckle, whereby to obtain a meaningful comparison result the pattern of the received signal is analyzed as a whole.

p0017Advantageously, the comparison of the pattern of a received signal by correlation with a reference pattern takes place. The result of the correlation, that is the comparison result, the value of an output signal W which is in the range "1" ≤ W ≤ "-1" and representing a statement about the similarity of the pattern of a reception signal with the reference pattern. If the value W of the output signal at "-1", an inverted match the pattern occurs with the reference pattern in the received signal RM E1. The value of W = "0" indicates that no match of the pattern is present; the value W is "1", a full match of the pattern is given in the received signal with the reference pattern RM. Depending on the value W of the similarity of the compared pattern a statement is possible if there is the receiving coil of the implement within the wire loop (similarity "1") or outside the wire loop (similarity "-1"). The result of the correlation is a value w in the range of 1 ≤ w ≤ -1; as part of the comparison, a respective calculated result of z. B. 0.92 is assigned the value "1", while a calculated result of z. B. -0.86 the value "-1" is assigned.

p0018The signal processing of the invention is the possibility that a first surrounded by a first edge perimeter wire surface and a second area surrounded by a second edge boundary wire surface can overlap without the reception signals of working on the land tools interfere with each other. The wires can also lie on one another, so that the wire loop in the form of a can form eight, z. B. consisting of two circles or rectangles. In the middle of a common wire or two wires can directly be successive. Even this form of a wire loop is within the meaning of the claim understood as overlapping.

p0019Further features of the invention result from the additional claims, the description and the drawing, in which an in detail hereinafter described embodiment of the invention is shown. Show it:<dl id="dl0001"><dt>Fig. 1</dt><dd>in a schematic plan view of a self-propelled, battery-operated implement the example of a self-propelled lawn mower within a boundary perimeter wire,</dd><dt>FIG. 2</dt><dd>a schematic view of a sequence of transmitted on the deckle wire electrical signals as stochastic digital AC signals,</dd><dt>Fig. 3</dt><dd>in an enlarged view a single signal of a result of <figref idrefs="f0001">FIG. 2</figref>.</dd><dt>Fig. 4</dt><dd>a schematic representation of the voltage induced in a receiver coil of the implement receiving signals,</dd><dt>Fig. 5</dt><dd>an embodiment of a sequence of different transmitted on the deckle wire electrical signals, </dd><dt>Fig. 6</dt><dd>is a schematic flow diagram for evaluation of the received in a receiving coil in the working device receiving signals,</dd><dt>Fig. 7</dt><dd>a schematic representation of the arrangement of several overlapping wire loops of neighboring systems,</dd><dt>Fig. 8</dt><dd>a schematic view of transmitted on the wire the deckle alternative electrical signals as a deterministic analog AC signals.</dd></dl>

p0020In <figref idrefs="f0001">Fig. 1</figref> is generally a working machine 1, which is designed in the embodiment as a self-propelled lawn mower. 2 The working device 1 mainly consists of a chassis with rear drive wheels 3 and 4, each of which an electric drive motor is preferably 5 and 6 assigned. In a front portion 8 of the housing 9 of the working machine 1 is a self-steering third wheel 7 is arranged. The third wheel 7 preferably lies on a longitudinal central axis 10 of the housing 9, so that the working device 1 is constructed in the manner of a three-wheel. A chassis with four wheels may be expedient, where two or more wheels may be steerable.

p0021In the embodiment, the driving wheels 3 and 4 rotate about a common drive axis 11 which is perpendicular to the substantially longitudinal center axis 10 of the housing. 9 The driving wheels 3, 4 can be driven synchronously via their electric drive motors 5 and 6 when traveling straight or drive separated when cornering, whereby the working device 1 can be steered in any direction you wish to 30th

p0022Between the driving wheels 3 and 4, a working tool 12 is disposed on the surface to be machined 20 facing side of the chassis, in the shown embodiment a about a vertical axis of rotation 28 rotating cutting knife of a lawn mower second

p0023The control of the electric drive motors 5 and 6 via a control unit 13, which is connected via schematically indicated electric wires 14 with the appropriate separate drive motors 5 and 6. FIG.

p0024The electrical supply of the control unit 13 and the drive motors 5 and 6 is ensured by a battery pack 15 that is inserted into the housing 9 of the working unit 1.

p0025By suitable control of the drive motors 5 and 6 moves the controller 13 the implement 1 on the surface to be machined 20, which is surrounded by a deckle wire 21st The deckle wire 21 is provided as a closed wire loop 22, whose ends 23 and 24 are connected to a transmitting unit 25th

p0026The transmitting unit connected to the deckle wire 21 25 may be part of a docking station 26, in which the battery pack 15 of the implement 1 is charged. To this end, driving the working device 1 in the docking station 26, where electrical contacts for charging the battery pack 15 to connect with a charger dock 26th

p0027The transmitting unit 25 fed into the wire loop a 22 electrical signals 16, against which the working device 1 is controlled. The message sent on the deckle wire 21 of the wire loop 22 sequence of signals 16 is exemplified in<figref idrefs="f0001">FIG. 2</figref> shown.

p0028One embodiment of an on the edge boundary wire 21 of the wire loop 22 transmitted electric signal 16 is in an enlarged representation in <figref idrefs="f0002">Fig. 3</figref> shown. The electrical signal 16 is preferably formed as a burst signal B1 having a predetermined pattern M. The pattern M of the burst signal B1 is a digital, in particular a stochastic digital signal which consists of fixed high levels H and solid low levels L, wherein the period .DELTA.t_i the H level, L is different. Between each transmitted on the deckle wire 21 of the wire loop 22 burst signals B1 a pause P is provided with a dead time .DELTA.T in the exemplary embodiment.

p0029As <figref idrefs="f0001">FIG. 2</figref> shows the pause time .DELTA.T between consecutive burst signals B1 may each have a fixed period of time. It may be advisable to choose the timing of burst signals on the wire loop 22 randomly; the pauses P then have random pauses .DELTA.T.

p0030The pattern M of the digital burst signal B1 is determined in that the time duration .DELTA.t₁, .DELTA.t₂, .DELTA.t₃... .DELTA.t_i the respective levels H and L - is designed differently - as shown in the exemplary embodiment. By the time duration of the levels H and L, the pattern M of the burst signal is determined. Such a burst signal B1 is different as a result of current pulses with high-levels H and low levels L duration .DELTA.t_i abandoned on the edge of the perimeter wire.

p0031Each of the edge boundary wire 21 sent electrical burst signal B1 generates an alternating electromagnetic field around the edge perimeter wire 21, which is received by receiver coils 17 and 18 in the housing 9 of the work unit 1. In the illustrated embodiment is located in the housing 9 on each longitudinal side of the longitudinal central axis 10 of the implement leash receiving coil 17 and 18; in the working device 1 advantageously further receiving coils may be provided, or the intended receiving coils 17, 18 may be located elsewhere, such as on the longitudinal center axis 10 of the operating device 1 each have a receiving coil 17 and 18 front and rear.

p0032In the <figref idrefs="f0001">Fig. 1</figref> Receiving coils 17, 18 shown are electrically connected to the control unit thirteenth Each transmitted on the edge perimeter wire 21 electric signal 16 and burst signal B1 will induce an AC voltage across its generated electromagnetic alternating field into a receiving coil 17, 18th The induced received signal E1 is sent to the time derivative of the wire loop 22 burst signal B1; the pattern of the reception signal E1 is thus approximately the time derivative M'~ dI / dt of the pattern M of the burst signal B1. This pattern M 'of the received signal E1 (<figref idrefs="f0002">Fig. 4</figref>) Is fed to an evaluation 19th In the evaluation unit 19, the pattern M 'of the induced E1 reception signals are evaluated and in dependence of a comparison made generates an output signal which is passed on by the evaluating unit 19 to the control unit thirteenth The control unit 13 controls in accordance with the output signal, the drive motors 5 and 6 of the drive mechanism and thus determines the direction of travel 30 (<figref idrefs="f0001">Fig. 1</figref>) Of the working unit 1.

p0033The field generated by the pattern M of the burst signal B1 electromagnetic field is always received by at least one of the receiver coils 17 and 18 of the implement 1, wherein in the arrangement of two receiver coils 17, 18 the same burst signal B1 is received at the same time twice, the received signal E1 thus doubly present. Are both receiving coils 17 and 18 inside or outside the wire loop 22, the pattern M 'of the received signals E1 are approximately the same; by linking the same time received reception signals E1 disorders can also be filtered out as reception gaps. If the received pattern M 'different, a receiving coil is 17 inside and a receiving coil 18 outside the wire loop 22; the implement is thus located on the edge of the perimeter wire 21st

p0034The evaluation unit 19 of the working machine 1 processes the pattern M 'of the induced receiver signal E1 each of the receiver coils 17 and 18. This pattern M' corresponding approximately to the time derivative of M '~ dI / dt of the pattern M of the transmitted on the wire loop 22 signal 16. In <figref idrefs="f0003">Fig. 6</figref> is shown schematically the processing of the received pattern M 'in accordance with the method. The electromagnetic field of the sent on the loop of wire 22 electric signals 16 induced in the receiving coils 17, 18, a reception signal E1 which is fed to the evaluation unit 19th The evaluation unit 19 compares the pattern M 'of the reception signal E1 to a reference pattern RM, which is made available to the evaluation unit 19, for. Example, via a memory 27 are available.

p0035The pattern M 'of the received signal E1 is evaluated by means of correlation; The detection of the reference pattern RM is realized in the pseudo-stochastic reception signal E1 as an algorithm in the frequency domain. After an appropriate correlation process, the output from the receiving coil 17, 18 pattern M 'of the reception signal E1 is constantly compared with the reference pattern RM and detected as an output signal a sliding degree of the similarity evaluation unit in the nineteenth The output of the correlation is between the value W = -1 (inverted match the pattern M 'in the received signal E1 to the reference pattern RM), the value W = 0 (no match the pattern matched) and the value = 1 (full correlation of pattern M 'in the received signal E1 to the reference pattern RM). The value W of the output signal of the evaluation unit 19 is communicated to the control unit 13, which determines a function of the value W of the output signal whether the receiver coil of the implement 1 inside the wire loop 22 (similarity "1") or outside the wire loop 22 (similarity "- 1 "); is no similarity value calculated by the correlation method, an output signal "0". If a "0" for a predetermined period, the working device 1 is shut down for safety reasons.

p0036The result of the correlation is not a fixed value "1" or "-1"; as a result of any values ​​W W ≤ 1 occur in a range between -1 ≤ in practice, the values ​​of W are 19 then assigned to the similarity of the evaluation to the state "1" or "-1". . If there is a similarity value of W, for example 0.83, this value is associated with the state "1"; . Is the similarity value W at for example 0.3, a reliable statement about the similarity of the pattern is not possible - it is a "0" output.

p0037Depending on the associated similarity values ​​"-1" and "+1", the control unit 13 control the direction of travel of the implement 1 in such a way that each one direction is 30 chosen with a stay of the receiver coils 17, 18 is ensured within the wire loop 22 and so that the working implement is held within one of the surface to be machined 20th

p0038The comparison of the pattern M 'of the received signal E1 with the reference signal RM allows a simple way to determine whether the location of the implement 1 inside or outside the border perimeter wire 21 is so inside or outside the wire loop 22. Depending on this information is from the control unit 13 the direction of travel 30 of the implement changes in order to move the working device 1 again within the wire loop 22nd

p0039Advantageously receives a receive coil 17, 18 a complete burst signal B1 in a time window F of the predetermined reception period of time T, as shown in <figref idrefs="f0002">Fig. 4</figref> is shown. is suitably opening and closing a receiving window F is matched to the sequence of burst signals B1 on the wire loop 22, so that a burst signal B1 always completely received, so it is a complete pattern M 'in the reception signal E1 shown.

p0040Because in addition to the burst signals B1 to the wire loop in the workspace of such a working machine 1 intersperse electromagnetic interference and the like. Regularly, the received signal E1 is superposed by appropriate interference. However, over the correlation secure recognition of the pattern M and the pattern M 'possible and a definitive statement about achievable if the similarity is the patterns to be compared with "-1" or "+1", the implement 1 so within or moved outside the wire loop 22nd

p0041The for determining the similarity calculated correlation value can be averaged, thus providing information about the quality of the received signal E1.

p0042The inventive method also buy several burst signals B1, B2, ..., Bn can be sent on a wire loop 22, as in <figref idrefs="f0002">Fig. 5</figref> is shown. So it may be expedient to B to send 1, any other signals, eg. As second burst signals B2 in a pause between successive first burst signals. The patterns of the burst signals B1 and B2 are different as shown schematically in<figref idrefs="f0002">Fig. 5</figref> reproduced; therefore a first working unit 1 can operate without interference with the burst signal B1, while at the same time next working implement with the burst signal B2 is working correctly. Mutual influencing of adjacent systems can thus by selecting different patterns of M burst signals B1, B2 be avoided; thereby opens up the possibility to use a single deckle wire 21 as a separation between two different devices work surfaces to be machined.

p0043As in <figref idrefs="f0003">Fig. 7</figref> illustrated, the wire loops 22, 22 can ', 22 "adjacent systems also overlap so that two or more also lying interengaging surfaces 20, 20', 20" result, the two or more working devices 1, 1 ', 1 " are to be processed. Since the signals transmitted on the wire loops have different patterns, the tools 1, 1 ', 1 can "to their assigned reference patterns each in the memory 27 (<figref idrefs="f0003">Fig. 6</figref>) Of the respective working device 1, 1 ', 1 "are stored orient. Each working device 1, 1', 1" edited exclusively assigned to it by the stored reference pattern surface 20, 20 ', 20 ", without the on the wire loops 22, 22 ', 22 "transmitted signals or in the working devices 1, 1', 1" evaluated reception signals interfere with each other. it is possible to transmit the signals on the wire loops temporally independent of each other, so that the different patterns of the various systems overlap each other or even overlap. Due to the evaluation by correlation yet accurate, reliable detection of an implement associated pattern is possible.

p0044Also, with only one operation unit 1, the surfaces are machined successively by being compared to be used reference pattern of the work tool on the corresponding signal of the wire loop 22, 22 ', 22 "is changed. Depending on the selected reference pattern the same working device inside the wire loop 22 or 22 'or 22' work. Thus, with only one implement a variety of surfaces are processed automatically, eg by a time-dependent switch to be used reference pattern is made, suitably via an appropriate programming. Thus a plurality of reference patterns can be stored and depending on the application a predetermined reference pattern for evaluating the pattern of the received signals are activated in a single device. The same work unit is suitable for various systems with signals of different patterns.

p0045The embodiment was explained using a quasi stochastic digital signal 16 with embossed pattern M. Alternatively, signal 16 can be used as a deterministic analog signal 116, which a corresponding pattern M is impressed. Such a deterministic analog AC signal may be a signal 116, as shown in<figref idrefs="f0003">figure 8</figref> is shown. The pattern M of the signal 116 has appropriate τ a period.