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

Abstract

An automatic milking arrangement (110) visited by dairy animals on a voluntary basis is controlled by controller (100) such that an animal (120) is allowed to be milked only if a permission condition (MP) is fulfilled for that animal (120). Respective points in time (ti, t2, ts) for three consecutive milking sessions for the animal (120) are registered as well as second and third volumes of milk (V2, V3) extracted from the animal (120) at the second and third milking sessions. A primary milk production per unit time (Pvi) for the animal (120) in a time interval ( I12) between the first and second points in time (tT; t2) is determined. A secondary milk production per unit time (PV2> for the animal (120) in a time interval (I23) between the second and third points in time (t2; ts) is determined. It is checked if the primary and secondary milk productions per unit time (Pvi, PV2) fulfill a linearity requirement with respect to one another. Only if the linearity requirement is fulfilled, the permission condition (MP) for the animal (120) is set with respect to a fourth milking session subsequent to the third milking session such that a time interval (I34) between the third and fourth milking sessions must be longer than a time interval (I23) between the second and third milking sessions.

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 an automatic milking arrangement to which the animals seek their way on a voluntary basis and an overall high milk production per unit time of the automatic milking arrangement.

[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 installation for extracting high volumes of milk from the dairy animals.

[0012] 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, 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 for that animal. The controller is configured to register respective points in time for three consecutive milking sessions for the animal. The point in time when the milking session is performed may consistently be defined as either a point in time when the milking session is initiated, or a point in time when the milking session is completed. The controller is also configured to register respective second and third volumes of milk from the animal at the second and third milking sessions of said three consecutive milking sessions. Based on the registered points in time and extracted volumes of milk extracted, the controller is configured to determine a primary milk production per unit time for the animal in a time interval between the first and second points in time, and determine a secondary milk production per unit time for the animal in a time interval between the second and third points in time. The controller is further configured to check if the primary and secondary milk productions per unit time fulfill a linearity requirement with respect to one another. Only if the linearity requirement is fulfilled, the controller is configured to set the permission condition for the animal with respect to a fourth milking session subsequent to the third milking session such that a time interval between the third and fourth milking sessions must be longer than a time interval between the second and third milking sessions.

[0013] This controller is advantageous because it ensures that each of the animals is milked at occasions being sufficiently separated in time to allow maximal milk production per unit time in between the milking occasions, and thus avoid unnecessary milkings. As a result, a larger number of animals can be milked by a given automatic milking arrangement.

[0014] According to one embodiment of this aspect of the invention, if the linearity requirement is not fulfilled at the third milking session, the controller is configured to set the permission condition for the animal with respect to the fourth milking session equal to the permission condition applied between the second and third milking sessions for that animal. 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 mil- kings. 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 fourth milking session may instead be set so that a somewhat shorter time interval is accepted to future milking sessions than between the third and fourth milking sessions.

[0015] According to another embodiment of this aspect of the invention, if the linearity requirement was fulfilled at the third milking session, at the fourth milking session for the animal, the controller is configured to execute the steps: register a fourth point in time, register a fourth volume of milk extracted from the animal, determine a ternary milk production per unit time for the animal in a time interval between the third and fourth points in time, and check if the ternary milk production per unit time fulfils the linearity requirement with respect to the primary milk production per unit time. Only if the linearity requirement is fulfilled, the controller is configured to set the permission condition for the animal with respect to a later milking session subsequent to the fourth milking session such that a time interval between the fourth and the later milking session must be longer than a time interval between the third and fourth milking sessions for that animal. Thus, it is possible to extend the time intervals between the milking sessions even further seeking for a tipping point where the milk production per unit time ceases to be linear for the animal in question.

[0016] According to yet another embodiment of this aspect of the invention, if the linearity requirement is not fulfilled at the fourth milking session, the controller is configured to set the permission condition for the animal with respect to milking sessions subsequent to the milking session at which the linearity requirement was not ful- filled equal to a latest applied permission condition for the animal. Hence, analogous to the above, the permission condition is set such that a slight deviation from a linear milk production is accepted. This reduces the risk of any unnecessary milkings at the expense of a potential risk of milkings being performed somewhat too seldom.

[0017] According to still another embodiment of this aspect of the invention, if the animal has not arrived at the automatic milking arrangement within an acceptance period after the expiry of a threshold time interval since a latest milking session, the controller is configured to generate an alarm with respect to the animal. In response to said alarm, in turn, a farm-worker may manually fetch the animal and bring it in for milking, and / or check the health status of the animal.

[0018] According to a further embodiment of this aspect of the invention, the linearity requirement is considered to be fulfilled if a linear function represented by the determined secondary milk production per unit time lies within a predefined slope coefficient margin from a slope coefficient of a linear function represented by the determined primary milk production per unit time.

[0019] Alternatively, the linearity requirement may be considered to be fulfilled if a value of the determined secondary milk production per unit time differs from a value of the determined primary milk production per unit time by less than a threshold difference. Thus, it is straightforward to determine whether the linearity requirement is fulfilled. If the value of the determined second milk production per unit time is substantially equal to the value of the determined primary milk procution per unit time the elapsed time to the earliest point in time at which a repeated milking is allowed to occur for the animal following a previous milking without any milking performed in between can 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 for that animal. The method involves: registering respective points in time for three consecutive milking sessions for the animal, registering respective second and third volumes of milk extracted from the animal at the second and third milking sessions of said three consecutive milking sessions, determining a primary milk production per unit time for the animal in a time interval between the first and second points in time, determining a secondary milk production per unit time for the animal in a time interval between the second and third points in time, and checking if the primary and secondary milk productions per unit time fulfill a linearity requirement with respect to one another. Only if the linearity requirement is fulfilled at the third milking session, the method involves setting the permission condition for the animal with respect to a fourth milking session subsequent to the third milking session such that a time interval between the third and fourth milking sessions must be longer than a time interval between the second and third milking sessions. 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. Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 1 schematically illustrates an automatic milking arrangement that is controllable by a controller according to one embodiment of the invention;

[0026] Figures 2a-b show diagrams exemplifying how permission conditions may be set according to one embodiment of the invention;

[0027] Figure 3 shows a diagram illustrating a typical milk yield as a function of days-in-milk for a dairy animal; and

[0028] Figure 4 illustrates, by means of a flow diagram, the general method according to the invention.

[0029] DETAILED DESCRIPTION

[0030] Figure 1 shows a simplified automatic milking arrangement 110 in respect of which the invention may be implemented. The automatic milking arrangement 110 is controllable by a controller 100 according to one embodiment of the invention.

[0031] Figure 2a shows a diagram exemplifying how a dairy animal may produce an amount of milk V as a function of time t between different milking sessions. Figure 2b shows, in detail, a diagram comparing the volumes of milk V2 and Ve extracted after having waited differently long time between consecutive milking sessions.

[0032] It is presumed that dairy animals visit the automatic milking arrangement 110 on a voluntary basis, and the controller 100 is configured to allow an animal 120 to be milked only if a permission con- dition MP is fulfilled for that animal 120. The permission condition MP namely specifies an earliest point in time at which a repeated milking is allowed to occur for the animal following a previous milking session for that animal.

[0033] 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 species. 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.

[0034] According to the invention, aiming at establishing optimal intervals between the milking sessions for each animal, the controller 100 is configured to apply the below described strategy to set the permission conditions MP.

[0035] The controller 100 is configured to register respective points in time for three consecutive milking sessions for the animal 120. Figure 2a exemplifies three such consecutive milking sessions at ti , t2 and ts respectively.

[0036] 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.

[0037] The controller 100 is also configured to register second and third volumes of milk V2 and V3 extracted from the animal 120 at the second and third milking sessions of said three consecutive milking sessions respectively.

[0038] Further, based on the registered points in time ti , t2 and ts respectively and the second and third volumes of milk V2 and V3 respectively, the controller 100 is configured to determine a primary milk production per unit time Pvi for the animal 120 in a time interval I12 between the first and second points in time ti and t2 respectively, and determine a secondary milk production per unit time P 2 for the animal 120 in a time interval I23 between the second and third points in time t2 and ts respectively.

[0039] The controller 100 is also configured to check if the primary and secondary milk productions per unit time Pvi and Pv2 fulfill a linearity requirement with respect to one another. Only if the linearity requirement is fulfilled, the controller 100 is configured to set the permission condition MP for the animal 120 with respect to a fourth milking session subsequent to the third milking session such that a time interval I34 between the third and fourth milking sessions must be longer than a time interval I23 between the second and third milking sessions. This namely enables an extended use of the animal’s 120 potentially longer linear production rate per unit time than what is represented by the time interval I34.

[0040] According to one embodiment of the invention, the linearity requirement is considered to be fulfilled if a milk production per unit time, say Pv2, determined for the animal 120 in a time interval subsequent to the time interval I12 between the first and second points in time ti and t2 lies within a predefined slope coefficient margin m from a slope coefficient of a linear function represented by the primary milk production per unit time Pvi , e.g. Pvmin < m < P max, with Pvmin < Pvi , where P max designates a maximal acceptable slope and Pvmin designates a minimal acceptable slope of the linear function represented by the primary milk production per unit time Pvi. Alternatively, the slope coefficient margin m may simply be defined as m > Pvmin . According to one embodiment of the invention, the linearity requirement is considered to be fulfilled if the value of the milk production per unit time for the animal 120 in a time interval subsequent to the time interval I12 between the first and second points in time ti and t2 differs from the value of the milk production per unit time for the animal 120 in the time interval I12 ) between the first and second points in time ti and t2 by less than a threshold difference.

[0041] Only if the linearity requirement is fulfilled at the third milking session, the controller 100 is configured to set the permission condition MP for the animal 120 with respect to a fourth milking session subsequent to the third milking session, such that a time interval I34 between the third and fourth milking sessions must be longer than a time interval I23 between the second and third milking sessions.

[0042] It should be noted that 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 later point in time. However, should an animal not have arrived at the automatic milking arrangement 110 within an acceptance period after a latest milking session, the controller 100 is preferably configured to generate an alarm A with respect to the animal 120. Thereby, in response to the alarm A, a farm-worker may manually fetch the animal 120 and bring it in for milking, and / or check the animal 120 to ascertain that it is healthy. Preferably, the acceptance period is prolonged if the permission condition MP is set such that the time interval between a latest performed milking session and a subsequent milking session must be longer than the time interval between the previous milking session and the latest performed milking session.

[0043] According to one embodiment of the invention, if the linearity requirement is not fulfilled at the third milking session, the controller 100 is configured to set the permission condition MP for the animal 120 with respect to the fourth milking session equal to the permission condition MP applied between the second and third milking sessions for that animal 120. In effect, this means that the animal 120 is expected to continue to be milked somewhat “too late” in order to produce milk according to a linear temporal relationship. However, provided that in the previous step the permission condition MP was set so that the time interval was only moderately extended in relation to when the linear relationship was fulfilled such a deviation from linearity is normally preferable to a somewhat “too short” time interval corresponding to allow milkings being slightly premature with respect to a maximal linear time interval. Naturally, if so desired, it is also possible to set back the permission condition MP to a value known to fulfill the linearity requirement.

[0044] In the example illustrated in Figure 2a, the linearity requirement is found not to be fulfilled at point in time te, where a milk production per unit time Pvs for the animal 120 in a time interval Isebetween a previous milking session at a point in time ts and the point in time telies outside of the predefined slope coefficient margin m from the slope coefficient of the linear function represented by the primary milk production per unit time Pvi . Each of the milk production per unit of time Pvi , P 2, Pvs, P 4 and Pvs is illustrated as a linear function in Figure 2a. Figure 2a also illustrates a steady state SS volume of milk equal to Ve, which is then amount of milk expected to be extracted from the animal 120 in each milking session after the point in time te.

[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.

[0046] Nevertheless, according to one embodiment of the invention, if the linearity requirement was fulfilled at the third milking session, at the fourth milking session for the animal 120, the controller 100 is configured to register a fourth point in time t4. At the fourth milking session for the animal 120, the controller 100 is also configured to register a fourth volume of milk V4 extracted from the animal 120. Further, the controller 120 is configured to determine a ternary milk production per unit time Pvs for the animal 120 in a time interval I34 between the third and fourth points in time to and t4 respectively. Analogous to the above, the controller 100 is configured to check if the ternary milk production per unit time Pvs fulfils the linearity requirement with respect to the primary milk production per unit time Pvi. Only if the linearity requirement is fulfilled, the controller 100 set the permission condition MP for the animal 120 with respect to a later milking session subsequent to the fourth milking session such that a time interval I45 between the fourth and the later milking session must be longer than a time interval between the third and fourth milking sessions for that animal 120.

[0047] For example, the permission condition MP may be set such that each extension of the time interval between consecutive milkings may be in the order of half an hour to two hours.

[0048] In further analogy to the above, according to one embodiment of the invention, if the linearity requirement is not fulfilled at the fourth milking session, 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 latest applied permission condition MP for the animal 120. Preferably, the permission condition MP is set such that all later milking sessions must be separated by an equal time interval D after that the linearity condition was found not to be fulfilled as illustrated in Figure 2b.

[0049] 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.

[0050] 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.

[0051] It is generally advantageous if the controller 100 is configured to effect the above-described procedure in 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 .

[0052] 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.

[0053] In a first step 410, respective points in time are registered for three consecutive milking sessions for a dairy animal. In step 410, respective second and third volumes of milk extracted from the animal at the second and third milking sessions are also registered. In a subsequent step 420, a primary milk production per unit time is determined for the animal in a time interval between the first and second points in time. In step 420, a secondary milk production per unit time is also determined for the animal in a time interval (I23) between the second and third points in time.

[0054] In a step 430 thereafter, it is checked if the primary and secondary milk productions per unit time fulfill a linearity requirement with respect to one another. If so, a step 440 follows; and otherwise, a step 450 follows.

[0055] In step 440, a permission condition is set for the animal with respect to a fourth milking session subsequent to the third milking session, such that a time interval between the third and fourth milking sessions must be longer than a time interval between the second and third milking sessions. Thereafter, the procedure loops back to step 410 for potential additional adjustment of the permission condition, so that the time interval between future milking sessions is further extended.

[0056] In step 450, the permission condition is set such that time interval used between second and third milking sessions is maintained. Thereafter the procedure ends. It should be noted that this does not mean that the milking ceases. Here, the end of the procedure merely means that the permission condition for future milking sessions is fixed to the value set in step 450.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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 controller (100) is configured to: register respective points in time (ti , t2, ts) for three consecutive milking sessions for the animal (120), register respective second and third volumes of milk (V2, V3) extracted from the animal (120) at the second and third milking sessions of said three consecutive milking sessions, determine a primary milk production per unit time (Pvi) for the animal (120) in a time interval (I12) between the first and second points in time (ti ; t2), determine a secondary milk production per unit time ( 2) for the animal (120) in a time interval (I23) between the second and third points in time (t2j ts), check if the primary and secondary milk productions per unit time (Pvi, P 2) fulfill a linearity requirement with respect to one another, and only if the linearity requirement is fulfilled set the permission condition (MP) for the animal (120) with respect to a fourth milking session subsequent to the third milking session such that a time interval (I34) between the third and fourth milking sessions must be longer than a time interval ( I23) between the second and third milking sessions.

2. The controller (100) according to claim 1 , wherein if the linearity requirement is not fulfilled at the third milking session, the controller (100) is configured to: set the permission condition (MP) for the animal (120) with respect to the fourth milking session equal to the permission condition (MP) applied between the second and third milking sessions for that animal (120).

3. The controller (100) according to claim 1 , wherein, if the linearity requirement was fulfilled at the third milking session, at thefourth milking session for the animal (120), the controller (100) is configured to: register a fourth point in time (t4), register a fourth volume of milk (V4) extracted from the animal (120), determine a ternary milk production per unit time (Pvs) for the animal (120) in a time interval (I34) between the third and fourth points in time (ts; t4) check if the ternary milk production per unit time (Pvs) fulfils the linearity requirement with respect to the primary milk production per unit time (Pvi), and only if the linearity requirement is fulfilled set the permission condition (MP) for the animal (120) with respect to a later milking session subsequent to the fourth milking session such that a time interval (I45) between the fourth and the later milking session must be longer than a time interval between the third and fourth milking sessions for that animal (120).

4. The controller (100) according to claim 3, wherein if the linearity requirement is not fulfilled at the fourth milking session, 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 (D) a latest applied permission condition (MP) for the animal (120).

5. The controller (100) according to any one of the preceding claims, wherein if the animal (120) has not arrived at the automatic milking arrangement (110) within an acceptance period after the expiry of a threshold time interval since a latest milking session, the controller (100) is configured to generate an alarm (A) with respect to the animal (120).

6. The controller (100) according to any one of the preceding claims, 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.

7. The controller (100) according to any one of the preceding claims, wherein the linearity requirement is considered to be fulfilled if a linear function represented by the determined secondary milk production per unit time (P 2) lies within a predefined slope coefficient margin (m) from a slope coefficient of a linear function represented by the determined primary milk production per unit time (Pvi).

8. The controller (100) according to any one of claims 1 to 6, wherein the linearity requirement is considered to be fulfilled if a value of the determined secondary milk production per unit time (P 2) differs from a value of the determined primary milk production per unit time (Pvi) by less than a threshold difference.

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 method is performed in processing unit (101 ) in a controller (100), the method comprising: registering respective points in time (ti , t2, ts) for three consecutive milking sessions for the animal (120), registering respective second and third volumes of milk (V2, V3) extracted from the animal (120) at the second and third milking sessions of said three consecutive milking sessions, determining a primary milk production per unit time (Pvi) for the animal (120) in a time interval (I12) between the first and second points in time (ti ; t2), determining a secondary milk production per unit time (P 2) for the animal (120) in a time interval (I23) between the second and third points in time (t2j ts) checking if the primary and secondary milk productions perunit time (Pvi), P 2) fulfill a linearity requirement with respect to one another, and only if the linearity requirement is fulfilled setting the permission condition (MP) for the animal (120) with respect to a fourth milking session subsequent to the third milking session such that a time interval (I34) between the third and fourth milking sessions must be longer than a time interval (I23) between the second and third milking sessions.

10. The method according to claim 9, wherein if the linearity requirement is not fulfilled at the third milking session, the method comprises: setting the permission condition (MP) for the animal (120) with respect to the fourth milking session equal to the permission condition (MP) applied between the second and third milking sessions for that animal (120).

11. The method according to claim 9, wherein, if the linearity requirement was fulfilled at the third milking session, at the fourth milking session for the animal (120), the method comprises: registering a fourth point in time (t4), registering a fourth volume of milk (V4) extracted from the animal (120), determining a ternary milk production per unit time (Pvs) for the animal (120) in a time interval (I34) between the third and fourth points in time (ts; t4) checking if the ternary milk production per unit time (Pvs) fulfils the linearity requirement with respect to the primary milk production per unit time (Pvi), and only if the linearity requirement is fulfilled setting the permission condition (MP) for the animal (120) with respect to a later milking session subsequent to the fourth milking session such that a time interval (I45) between the fourth and the later milking session must be longer than a time interval between the third and fourth milking sessions for that animal (120).

12. The method according to claim 11 , wherein if the linearity requirement is not fulfilled at the fourth milking session, the method comprises: setting 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 (D) a latest applied permission condition (MP) for the animal (120).

13. The method (100) according to any one of the claims 9 to 12, wherein if the animal (120) has not arrived at the automatic milking arrangement (110) within an acceptance period after the expiry of a threshold time interval since a latest milking session, the method comprises: generating an alarm (A) with respect to the animal (120).

14. The method according to any one of the claims 9 to 13, 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.

15. The method (100) according to any one of the claims 9 to 14, wherein the linearity requirement is considered to be fulfilled if a linear function represented by the determined secondary milk production per unit time ( P 2) lies within a predefined slope coefficient margin (m) from a slope coefficient of a linear function represented by the determined primary milk production per unit time (Pvi).

16. The method (100) according to any one of claims 9 to 14, wherein the linearity requirement is considered to be fulfilled if a value of the determined secondary milk production per unit time (P 2) differs from a value of the determined primary milk production per unit time (Pvi) by less than a threshold difference.

17. A computer program (103) loadable into a non-volatile datacarrier (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 17.

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