Controller for an automatic milking arrangement, computer-implemented method, computer program and non-volatile data carrier

Abstract

A controller controls an automatic milking arrangement that dairy animals visit on a voluntary basis, such that an animal is allowed to be milked only if a permission condition (MP(3), MP(4)) is fulfilled for that animal. The permission condition (MP(3), MP(4)) specifies an earliest point in time at which a repeated milking is allowed to occur for the animal following a previous milking session. The controller sets the permission condition (MP) based on at least one volume of milk (V2, V3) extracted from the animal during at least one earlier milking session (t2, t3), and sets an acceptance period (AP) after said earliest point in time within which acceptance period (AP) the animal should arrive at the automatic milking arrangement for a repeated milking. If the animal has not arrived at the automatic milking arrangement for the repeated milking at expiry of the acceptance period (AP), the controller triggers a belated-milking alarm (A) for the animal. The controller extends the acceptance period (AP) for the animal, at the repeated milking (t4) after expiry of the acceptance period (AP), a volume of milk (V4) extracted from the animal (120) during the repeated milking fulfils a linearity requirement with respect to a latest earlier milking session for the animal (120).

Description

[0001] Controller for an Automatic Milking Arrangement, Computer- Implemented Method, Computer Program and Non-Volatile Data Carrier

[0002] TECHNICAL FIELD

[0003] The present invention relates generally to automatic milking arrangements visited by dairy animals on a voluntary basis, and where milking is performed if a permission condition is fulfilled for the animal in question. Especially, the invention relates to a controller according to the preamble of claim 1 and a corresponding computer-implemented method. The invention also relates to a computer program and a non-volatile data carrier storing such a computer program.

[0004] BACKGROUND

[0005] During the later decades, an increasing fraction of the milking systems operate according to a principle enabling the dairy animals to be milked on a voluntary basis, or at least at occasions, which are not fixed on beforehand. This is generally beneficial from an animal-friendliness point-of-view.

[0006] EP 91 892 shows a system for milking loose-housing cows, which find their way individually to one or more feeding stalls where they are automatically identified and fed with the aid of a computer connected to the identification and feeding means. A computer is used for recording of the points of time each cow is milked and to activate a device, in connection with the identification of a cow arriving at the feeding stall to eat. Provided that a predetermined time has passed after the preceding milking operation, the device is activated for automatic application of the milking means to the cow's udder and for starting a milking operation.

[0007] EP 1 332 668 describes a technical solution for performing an animal related action on an animal. A machine is arranged to per- mit milking of the animal according to a process being determined by a number of adjustable parameters defining the nature of the process. The value of a variable related to one or more animals is determined for said animal by determining means. The animal related action is performed on the animal during a current animal related action by means of the machine, wherein at least one of said parameters is adjusted in response to said determined value by control means.

[0008] WO 2006 / 068568 discloses a milking arrangement comprising at least two milking positions, wherein each milking position comprises teat cups for milking an animal. The milking arrangement is arranged to remove the teat cups from animals when milking is finished and to remove the teat cups from all animals that are still being milked when all conditions in a set of conditions are fulfilled. The set of conditions comprises the condition that the teat cups have been removed from a predetermined number of animals and that all animals that are still being milked, in an earlier milking preceding the present milking, must have been milked until the milking was determined to be substantially finished.

[0009] Thus various solutions exist that allow dairy animals to be milked at relatively flexible time instances. It is, however, challenging to combine such solutions with a high degree of efficiency in terms of utilization of the milking arrangement to which the animals seek their way on a voluntary basis and an overall high milk production per unit time. In particular, animals that arrive too seldom at the milking arrangement are problematic because these animals must typically be manually fetched and brought to the milking arrangement for milking.

[0010] SUMMARY

[0011] The object of the present invention is therefore to offer a solution that mitigates the above problems, and enables an improved efficiency with respect to the utilization of an automatic milking arrangement for extracting high volumes of milk from the dairy animals. According to one aspect of the invention, the object is achieved by a controller for an automatic milking arrangement that dairy animals visit on a voluntary basis, and by which automatic milking arrangement an animal is allowed to be milked only if a permission condition is fulfilled for that animal. The permission condition specifies an earliest point in time at which a repeated milking is allowed to occur for the animal following a previous milking session. The controller is configured to set the permission condition based on at least one volume of milk extracted from the animal during at least one earlier milking session. The controller is also configured to set an acceptance period after said earliest point in time within which acceptance period the animal should arrive at the automatic milking arrangement for a repeated milking. If the animal has not arrived at the automatic milking arrangement for the repeated milking at expiry of the acceptance period, the controller is configured to trigger a belated-milking alarm for the animal. Further, the controller is configured to extend the acceptance period for the animal, if, at the repeated milking after expiry of the acceptance period, a volume of milk extracted from the animal during the repeated milking fulfils a linearity requirement with respect to a latest earlier milking session for the animal.

[0012] This controller is advantageous because it is capable of dynamically adapting the acceptance period to each animal’s milk production. Thus, as a further result, the milking arrangement may be utilized more efficiently in terms of the total amount of milk extracted from a herd of dairy animals per unit time.

[0013] According to one embodiment of this aspect of the invention, the linearity requirement is considered to be fulfilled if, a value of a milk production per unit time determined for the animal at the repeated milking differs from a value of a milk production per unit time determined for the animal at the latest earlier milking session for the animal by less than a threshold difference. Thus, it is straightforward check the linearity requirement.

[0014] According to another embodiment of this aspect of the invention, the linearity requirement is considered to be fulfilled if a linear function represented by the milk production per unit time determined for the animal at the repeated milking lies within a predefined slope coefficient margin from a slope coefficient of a linear function represented by a milk production per unit time at the latest earlier milking session for the animal. Thus, the linearity requirement may likewise be checked in an uncomplicated manner.

[0015] According to another embodiment of this aspect of the invention, the controller is configured to set the permission condition such that for each milking session being completed under fulfillment of the linearity requirement, the earliest point in time when the repeated milking is allowed to occur is postponed in relation to any previously set permission conditions for that animal. Thereby, it is possible to use a substantial portion of each animal’s linear production capacity, which, in turn, increases the overall utilization rate for the milking arrangement.

[0016] According to yet another embodiment of this aspect of the invention, the controller is configured to extend the acceptance period if the permission condition is postponed in relation to any previously set permission conditions for that animal. Namely, such adaption of the acceptance period to the changes in permission condition further reduces the risk that animals need to be manually fetched and brought to the milking arrangement for milking.

[0017] For example, the controller may be configured to extend the acceptance period by a secondary amount of time equal to a factor, say 1 , times a primary amount of time by which the permission condition is postponed. In other words, if the permission condition is postponed by one hour, the acceptance period may also be extended one hour.

[0018] According to still another embodiment of this aspect of the invention, if the linearity requirement is not fulfilled, the controller is configured to set the permission condition for the animal with res- pect to milking sessions subsequent to the milking session at which the linearity requirement was not fulfilled equal to a permission condition applied at the milking session when the linearity requirement was not fulfilled. Thereby, the permission condition is set such that a slight deviation from a linear milk production is accepted. This, in turn, further reduces the risk of any unnecessary milkings. If, however, the farmer considers it more important to avoid a non-linear milk production, the permission condition for the animal with respect to the future milking sessions may instead be set so that a somewhat shorter interval is accepted for these milking sessions.

[0019] According to embodiments of this aspect of the invention, the point in time when the milking session is performed is either consistently defined as a point in time when the milking session is initiated, or a point in time when the milking session is completed. Both alternatives provide straightforward bases for determining whether the linearity requirement is fulfilled, or if the acceptance period should be extended.

[0020] According to another aspect of the invention, the object is achieved by a computer-implemented method, which is performed in a processing unit in a controller, which controller, in turn, is arranged to control automatic milking arrangement that dairy animals visit for milk extraction on a voluntary basis, and by which automatic milking arrangement an animal is allowed to be milked only if a permission condition is fulfilled for that animal, which permission condition specifies an earliest point in time at which a repeated milking is allowed to occur for the animal following a previous milking session. The method involves setting the permission condition based on at least one volume of milk extracted from the animal during at least one earlier milking session. The method also involves setting an acceptance period after said earliest point in time within which acceptance period the animal should arrive at the automatic milking arrangement for a repeated milking. If the animal has not arrived at the automatic milking arrangement for the repeated milking at expiry of the acceptance period, the me- thod further involves triggering a belated-milking alarm for the animal. Additionally, if, at the repeated milking after expiry of the acceptance period, a volume of milk extracted from the animal during the repeated milking fulfils a linearity requirement with respect to a latest earlier milking session for the animal. Namely, in such a case, it is verified that the animal’s milk production was actually linear throughout the entire acceptance period. Therefore, it is considered safe to extend the acceptance period, and thus avoid future unnecessary manual fetching of the animalin question to the automatic milking arrangement. The advantages of this method, as well as the preferred embodiments thereof, are apparent from the discussion above with reference to the proposed system.

[0021] According to a further aspect of the invention, the object is achieved by a computer program loadable into a non-volatile data carrier communicatively connected to a processing unit. The computer program includes software for executing the above method when the program is run on the processing unit.

[0022] According to another aspect of the invention, the object is achieved by a non-volatile data carrier containing the above computer program.

[0023] Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.

[0026] Figure 1 schematically illustrates an automatic milking arrangement that is controllable by a controller according to one embodiment of the invention;

[0027] Figures 2a-b show diagrams exemplifying how acceptance pe- riods may be set according to one embodiment of the invention;

[0028] Figure 3 shows a diagram illustrating a typical milk yield as a function of days-in-milk for a dairy animal; and

[0029] Figure 4 illustrates, by means of a flow diagram, the general method according to the invention.

[0030] DETAILED DESCRIPTION

[0031] Figure 1 shows a simplified automatic milking arrangement 1 10 in respect of which the invention may be implemented. The automatic milking arrangement 1 10 is controllable by a controller 100 according to one embodiment of the invention.

[0032] Figure 2a shows a diagram over an extracted volume of milk V as a function of time t for a particular animal 120.

[0033] Figure 2b shows, in detail, a diagram comparing different volumes of milk V2, V3, V41 and V42 extracted after having waited differently long time between consecutive milking sessions for the animal 120.

[0034] In the present disclosure, it is presumed that dairy animals visit the automatic milking arrangement 1 10 on a voluntary basis, and the controller 100 is configured to allow an animal 120 to be milked only if a permission condition MP is fulfilled for that animal 120. The permission condition MP specifies an earliest point in time at which a repeated milking is allowed to occur for the animal 120 following a previous milking session. Figure 2a illustrates examples of such permission conditions MP(3) MP(4)and MP(5) after milking sessions performed at points in time t2, ts and t4 respectively.

[0035] In a milk-producing animal, such as cattle, buffaloes, goats, sheep, camels, yaks, horses, reindeers and donkeys, the milk is produced in alveoli in the animal’s udder. The capacity of the alveoli may vary considerably between individuals of the same spe- cies. Therefore, for different individuals, it may take different amounts of time to fill the alveoli after a previous milking. For efficiency reasons, it is desired that each animal is neither milked too often nor too seldom. Namely, in the former case, the milking equipment could have been better used to extract milk from another animal; and in the latter case, an overall smaller amount of milk will be extracted from the animal than had it been milked earlier. Namely, after a threshold degree of filling the alveoli may only produce a very small further amount of milk. In other words, the milk production per unit time becomes non-linear after reaching the threshold degree of filling.

[0036] To decide whether a particular animal shall be granted access to the milking arrangement 110, the animal 120 may for example have an ear tag 112 configured to allow contactless registering of identification information I DA of the animal 120, e.g. through radiofrequency identification (RFID) or near field communication (NFC) technology via a reader unit 111 of the milking arrangement 110. If the controller 100 determines that the animal 120 has permission to be milked, the controller 100 is configured to allow the animal 120 access to the automatic milking arrangement 110 via an entry gate 115. After that the milking session has been completed, the controller 100 is configured to enable the animal 120 to leave the automatic milking arrangement 110 via an exit gate 116.

[0037] According to the invention, the controller 100 is configured to set the permission condition MP based on at least one volume of milk extracted from the animal 120 during at least one earlier milking session. Figure 2a, exemplifies two such earlier milking sessions by points in time t2 and ts respectively and respective extracted volumes of milk V2 and V3.

[0038] The controller 100 is also configured to set an acceptance period AP after the earliest point in time MP(4) within which acceptance period AP the animal 120 should arrive at the automatic milking arrangement 110 for a repeated milking. Namely, the permission condition MP defines an earliest point in time when the animal 120 is allowed to be milked again. Since the animals visit the automatic milking arrangement 110 on a voluntary basis they may very well decide to arrive there at any point in time later than the earliest point in time MP(4). Should, however, the animal 120 not have arrived at the automatic milking arrangement 110 within the acceptance period AP after the earliest point in time MP(4), the controller 100 is configured to generate an alarm A with respect to the animal 120. Thereby, in response to the alarm A, a farmworker may manually fetch the animal 120 and bring it in for milking, and possibly also check the animal 120 to ascertain that it is healthy.

[0039] Moreover, once the animal 120 is milked after that the controller 100 has generated the alarm A with respect to the animal 120, the controller 100 is configured to check if a volume of milk extracted from the animal 120 during the repeated milking fulfils a linearity requirement with respect to a latest earlier milking session for the animal 120. Here, the latest earlier milking session for the animal 120 was carried out at the point in time ts, and at this occasion, a volume of milk V3 was extracted. If, at this repeated milking, the linearity requirement is fulfilled, the controller 100 is configured to extend the acceptance period AP for the animal 120.

[0040] In the example illustrated in Figure 2a, we assume that two earlier milking sessions have been completed in respect of the animal 120 at points in time t2 and ts respectively under fulfillment of the linearity criterion. At the second point time t2, a volume of milk V2 was extracted from the animal 120. This means that during a first interval I12 between the first and second points in time ti and t2 respectively the animal 120 had a first milk production rate Pvi . During a second interval I23 between the second and third points in time t2 and ts respectively the animal 120 had a second milk production rate P 2. Moreover, since the linearity criterion is fulfilled, the first and second milk production rates Pvi and P 2 are essentially equal to one another. As a result of the linearity criterion being fulfilled at the milking session that was completed at the third point in time ts, the permission condition by MP is set such that the earliest point in time MP(4) after the third point in time ts, when a subsequent milking session in respect of the animal 120 is allowed to occur is somewhat extended in relation to the earliest point in time MP(3) set by a previous permission condition MP.

[0041] Additionally, the acceptance period AP after the earliest point in time MP(4) is set. If, after expiry of the acceptance period AP after the earliest point in time MP(4) after the third point in time ts, the animal 120 is milked at a fourth point in time t4 and such an amount of milk V41 is extracted that a milk production rate P 4i in an interval I34 between the third and fourth points in time ts and t4 fulfils the linearity requirement with respect to the latest earlier milking session for the animal 120, i.e. at the third point in time ts, the controller 100 is configured to extend the acceptance period AP further. Namely, even though the animal 120 was milked “too late”, it turned out that the animal’s 120 milk production continued to be linear throughout the thus extended interval.

[0042] According to one embodiment of the invention, the controller 100 is configured to set the permission condition MP such that for each milking session being completed under fulfillment of the linearity requirement, the earliest point in time MP(4) when the repeated milking is allowed to occur is postponed in relation to any previously set permission conditions MP for that animal 120. For example, the acceptance period AP may be extended by an amount corresponding to an interval between the earliest point in time MP(4) and the point in time when the latest milking session was performed.

[0043] Figure 2a, exemplifies a scenario where the milk production rate P 4i in the interval I34 fulfils the linearity requirement with respect to the latest earlier milking session for the animal 120. In other words, the milk production rate P 4i is essentially the same as the milk production rates Pvi and P 2 during the two nearest previous milking sessions for the animal 120. In Figure 2a the milk production rate Pvi and P 2 and P 4i are each illustrated as a linear function.

[0044] Figure 2b exemplifies an alternative scenario, where instead the fourth milking session is performed at such a late point in time that the animal’s 120 milk production rate Pv42 has entered a non-linear stage. This is expressed by the fact that a liner function represented by the milk production per unit time Pv42 lies outside of a predefined slope coefficient margin m from a slope coefficient of a linear function represented by a milk production per unit time at the latest earlier milking session for the animal 120, i.e. here P 2 that is shown in Figure 2a. The predefined slope coefficient margin m may be defined as. Pvmin < m < Pvmax, with Pvmin < P 2 , where Pvmax designates a maximal acceptable slope and Pvmin designates a minimal acceptable slope of a linear function represented by the milk production rate P 42. Alternatively, the slope coefficient margin m may simply be defined as m > Pvmin .

[0045] Figure 2b illustrates a tipping point Vi_max after which the amount of milk V produced by the animal 120 ceases to have a linear relationship to time t. Thus, it is possible to extend the time intervals between consecutive milking sessions seeking for the tipping point for the animal in question, which, for example, may vary from 8 to 12 hours.

[0046] According to one embodiment of the invention, the controller 100 is also configured to extend the acceptance period AP if the permission condition MP is postponed in relation to any previously set permission conditions MP for that animal 120. Namely, the controller 100 is only configured to set the permission condition MP such that an earliest possible subsequent milking is postponed if the animal’s 120 milk production has proven to be linear throughout a longer period that what was estimated initially.

[0047] The controller 100 may for example be configured to extend the acceptance period AP by a secondary amount of time equal to a factor, say 1 , 1 .5 or 2, times a primary amount of time, say 30, 60 or 90 minutes, by which the permission condition MP is postponed in response to the animal’s 120 milk production having been found to be linear throughout a longer period that what was estimated initially.

[0048] According to one embodiment of the invention, if the linearity requirement is not fulfilled, the controller 100 is configured to set the permission condition MP for the animal 120 with respect to milking sessions subsequent to the milking session at which the linearity requirement was not fulfilled equal to a permission condition applied at the milking session when the linearity requirement was not fulfilled. This means that the permission condition MP is set such that a slight deviation from a linear milk production is accepted. As a result, the risk of any unnecessary milkings is further reduced. If, however, the farmer considers it more important to avoid a non-linear milk production than to maximize the utilization degree of the milking arrangement 110, the permission condition MP for the animal 120 with respect to the future milking sessions may instead be set so that a somewhat shorter interval is accepted for these milking sessions.

[0049] In this disclosure, the point in time when the milking session is performed is consistently defined as a point in time when the milking session is initiated. Alternatively, the point in time when the milking session is performed may be consistently defined as a point in time when the milking session is completed.

[0050] Normally, immediately after calving, the milk yield Y from a dairy animal increases gradually during an initial period P01. Figure 3 shows a diagram illustrating a schematic milk yield Y as a function of days-in-milk DIM for a dairy animal after calving at a point in time to. Here, the initial period P01 extends from the point in time to at 0 DIM to a point in time ti , say at 30 - 90 DIM, after which the milk yield Y is relatively constant at a level YP until a point in time tm, say around 210 DIM, when the milk yield Y begins to fall off slightly.

[0051] Since the invention aims at attaining a linear milk production per unit time between consecutive milking sessions for each dairy animal in order to utilize the automatic milking arrangement 110 as efficiently as possible, it is advantageous to mainly employ the invention for dairy animals being in a part of their lactation cycle that spans from the point in time ti to the point in time tm. During at least a first part of the initial period P01 it is generally preferable if the dairy animal is milked comparatively often to stimulate the milk production, say around once every fifth hour. After the point in time tm, the dairy animal may be set to dry off, i.e. prepare for the so-called dry period prior to a next calving.

[0052] It is generally advantageous if the controller 100 is configured to effect the above-described procedure in an automatic manner by executing a computer program. Therefore, the controller 100 may include a memory unit 105, i.e. non-volatile data carrier, storing a computer program 103, which, in turn, contains software for making processing circuitry in the form of at least one processor 101 in the controller 100 execute the actions mentioned in this disclosure when the computer program 103 is run on the at least one processor 101 .

[0053] In order to sum up, and with reference to the flow diagram in Figure 4, we will now describe the computer-implemented method according to the invention, which method is performed in the at least one processor 101 of the controller 100.

[0054] In a first step 405, the permission condition for an animal is set based on at least one volume of milk extracted from the animal during at least one earlier milking session.

[0055] Subsequently, in a step 410, an acceptance period is set after said earliest point in time, within which acceptance period the animal should arrive at the automatic milking arrangement for a repeated milking.

[0056] Thereafter, a step 415 checks if the animal in question has arrived at the milking arrangement. If so, a step 420 follows, and otherwise, the procedure continues to a step 430. Step 420 checks if, according to the permission condition, the animal is allowed to be milked. If so, a step 425 follows; and otherwise, the procedure loops back to step 415.

[0057] In step 425, the animal is milked; and thereafter, the procedure loops back to step 405.

[0058] Step 430 checks if the acceptance period is still running. If so, step 415 follows; and otherwise, the procedure continues to a step 435.

[0059] In step 435, a belated-milking alarm is triggered for the animal, in response to which alarm a farm-worker is prompted to manually fetchthe animal to the automatic milking arrangement for milking.

[0060] In a subsequent step 440, it is presumed that the animal has arrived at the milking arrangement, and the animal is milked.

[0061] In a step 445 thereafter, it is checked if a linearity requirement is fulfilled with respect to the milk extracted in step 440 in relation to at least two earlier milking sessions for the animal. If so, a step 450 follows; and otherwise, the procedure loops back to step 405.

[0062] In step 450, in the light of the linearity requirement being fulfilled, the acceptance period for the animal is extended. Thereafter, the procedure loops back to step 405.

[0063] The process steps described with reference to Figure 4 may be controlled by means of a programmed processor. Moreover, although the embodiments of the invention described above with reference to the drawings comprise processor and processes performed in at least one processor, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The program may either be a part of an operating system, or be a separate application. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for example a DVD (Digital Video / Versatile Disk), a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Programmable Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal, which may be conveyed, directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes.

[0064] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0065] The term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components. The term does not preclude the presence or addition of one or more additional elements, features, integers, steps or components or groups thereof. The indefinite article "a" or "an" does not exclude a plurality. In the claims, the word “or” is not to be interpreted as an exclusive or (sometimes referred to as “XOR”). On the contrary, expressions such as “A or B” covers all the cases “A and not B”, “B and not A” and “A and B”, unless otherwise indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope. It is also to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

[0066] The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.

Claims

Claims1. A controller (100) for an automatic milking arrangement (110) that dairy animals visit on a voluntary basis, and by which automatic milking arrangement (110) an animal (120) is allowed to be milked only if a permission condition (MP) is fulfilled for that animal (120), which permission condition (MP) specifies an earliest point in time (MP(4)) at which a repeated milking is allowed to occur for the animal (120) following a previous milking session, the controller (100) being configured to: set the permission condition (MP) based on at least one volume of milk (V2, V3) extracted from the animal (120) during at least one earlier milking session (t2, ts), and set an acceptance period (AP) after said earliest point in time (MP(4)) within which acceptance period (AP) the animal (120) should arrive at the automatic milking arrangement (110) for a repeated milking, and trigger a belated-milking alarm (A) for the animal (120) if the animal (120) has not arrived at the automatic milking arrangement (110) for the repeated milking at expiry of the acceptance period (AP), characterized in that the controller (100) is configured to extend the acceptance period (AP) for the animal (120), if, at the repeated milking (t4) after expiry of the acceptance period (AP), a volume of milk (V41) extracted from the animal (120) during the repeated milking fulfils a linearity requirement with respect to a latest earlier milking session for the animal (120).

2. The controller (100) according to claim 1 , wherein the linearity requirement is considered to be fulfilled if a value of a milk production per unit time (Pv4i) determined for the animal (120) at the repeated milking differs from a value of a milk production per unit time (P 2) determined for the animal (120) at the latest earlier milking session for the animal (120) by less than a threshold difference.

3. The controller (100) according to claim 1 , wherein the linea-rity requirement is considered to be fulfilled if a linear function represented by a milk production per unit time (Pv4i) determined for the animal (120) at the repeated milking lies within a predefined slope coefficient margin (m) from a slope coefficient of a linear function represented by a milk production per unit time (P 2) at the latest earlier milking session for the animal (120).

4. The controller (100) according to any of the preceding claims, wherein the controller (100) is configured to set the permission condition (MP) such that for each milking session being completed under fulfillment of the linearity requirement, the earliest point in time (MP(4)) when the repeated milking is allowed to occur is postponed in relation to any previously set permission conditions (MP(3)) for that animal (120).

5. The controller (100) according to claim 4, wherein the controller (100) is configured to extend the acceptance period (AP) if the permission condition (MP(4)) is postponed in relation to any previously set permission conditions (MP(3)) for that animal (120).

6. The controller (100) according to claim 5, wherein the controller (100) is configured to extend the acceptance period (AP) by a secondary amount of time equal to a factor times a primary amount of time by which the permission condition (MP) is postponed.

7. The controller (100) according to any of the preceding claims, wherein if the linearity requirement is not fulfilled, the controller (100) is configured to: set the permission condition (MP(4)) for the animal (120) with respect to milking sessions subsequent to the milking session at which the linearity requirement was not fulfilled equal to a permission condition (MP(4)) applied at the milking session when the linearity requirement was not fulfilled.

8. The controller (100) according to any one of the precedingclaims, wherein the point in time when the milking session is performed is consistently defined as either: a point in time when the milking session is initiated, or a point in time when the milking session is completed.

9. A computer-implemented method for an automatic milking arrangement (110) that dairy animals visit for milk extraction on a voluntary basis, and by which automatic milking arrangement (110) an animal (120) is allowed to be milked only if a permission condition (MP) is fulfilled for that animal (120), which permission condition (MP) specifies an earliest point in time (MP(4)) at which a repeated milking is allowed to occur for the animal (120) following a previous milking session, and which method is performed in processing unit (101 ) in a controller (100), the method comprising: setting the permission condition (MP) based on at least one volume of milk (V2, V3) extracted from the animal (120) during at least one earlier milking session (t2, ts), and setting an acceptance period (AP) after said earliest point in time (MP(4)) within which acceptance period (AP) the animal (120) should arrive at the automatic milking arrangement (110) for a repeated milking, and triggering a belated-milking alarm (A) for the animal (120) if the animal (120) has not arrived at the automatic milking arrangement (110) for the repeated milking at expiry of the acceptance period (AP), characterized by extending the acceptance period (AP) for the animal (120), if, at the repeated milking (t4) after expiry of the acceptance period (AP), a volume of milk (V41) extracted from the animal (120) during the repeated milking fulfils a linearity requirement with respect to a latest earlier milking session for the animal (120).

10. The method according to claim 9, wherein the linearity requirement is considered to be fulfilled if a value of a milk production per unit time (Pv4i) determined for the animal (120) at the repeated milking differs from a value of a milk production per unit time (P 2) determined for the animal (120) at the latest earlier milking ses-sion for the animal (120) by less than a threshold difference.11 . The method according to claim 9, wherein the linearity requirement is considered to be fulfilled if a linear function of a milk production per unit time (Pv4i) determined for the animal (120) at the repeated milking lies within a predefined slope coefficient margin (m) from a slope coefficient of a linear function represented by a milk production per unit time (P 2) at the latest earlier milking session for the animal (120).

12. The method according to any of claims 9 to 11 , comprising: setting the permission condition (MP) such that for each milking session being completed under fulfillment of the linearity requirement, the earliest point in time (MP(4)) when the repeated milking is allowed to occur is postponed in relation to any previously set permission conditions (MP(3)) for that animal (120).

13. The method according to claim 12, comprising: extending the acceptance period (AP) if the permission condition (MP(4)) is postponed in relation to any previously set permission conditions (MP(3)) for that animal (120).

14. The according to any of claims 12 and 13, comprising: extending the acceptance period (AP) by a secondary amount of time equal to a factor times a primary amount of time by which the permission condition (MP) is postponed.

15. The method according to any of claims 9 to 14, wherein if the linearity requirement is not fulfilled, the method comprises: setting the permission condition (MP(4)) for the animal (120) with respect to milking sessions subsequent to the milking session at which the linearity requirement was not fulfilled equal to a permission condition (MP(4)) applied at the milking session when the linearity requirement was not fulfilled.

16. The method according to any of claims 9 to 15, wherein thepoint in time when the milking session is performed is consistently defined as either: a point in time when the milking session is initiated, or a point in time when the milking session is completed.

17. A computer program (103) loadable into a non-volatile data carrier (105) communicatively connected to a processing unit (101 ), the computer program (103) comprising software for executing the method according any of the claims 9 to 15 when the computer program (103) is run on the processing unit (101 ).

18. A non-volatile data carrier (105) containing the computer program (103) of the claim 16.

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