TECHNICAL FI ELD

The present invention relates generally to rotary milking parlors. More particularly the invention relates to a control system for a rotary milking parlor, a rotary milking parlor and method of con trolling a rotary milking parlor. The invention also relates to a computer program and a non-volatile data carrier.

BACKGROUND

A rotary milking parlor, also referred to as a rotolocator, enables efficient milking of larger livestocks. The first rotary milking parlor was put into operation in 1930. Since then , the basic technical concept has been gradually refined. Inter alia, for sa fety reasons and to ensure consistent operation, it is important to keep track of the position of the equipment’s movable plat form.

US 2010/0147221 describes an apparatus and methods for ope rating a carousel milking facility with a plurality of milking sta tions, which are arranged on a movable platform. Movement of the platform is determined in relation to a reference point and the position of at least one milking station can be calculated with a position detection device. It is here proposed that a periodic pattern, visual and/or magnetic, is arranged on the outer peri phery of a carousel, where the local height of the line and angle on the carousel can be assigned unequivocally by determining the height of the line with the aid of an optical and/or magnetic sensor.

However, due to its sensitivity to soling, the design risks provi ding unreliable results in a farm environment, particularly if the positioning is based exclusively on optical registration. SUMMARY

The object of the present invention is therefore to mitigate the above problem and offer a more reliable system for controlling a rotary milking parlor. According to one aspect of the invention, the object is achieved by a control system for a rotary milking parlor. The control sys tem contains a sensor arrangement, a control unit, a first trans mitter unit, at least three receiver stations and a processing unit. The sensor arrangement is configured to measure a parameter representing a position of a movable platform of the rotary parlor relative to a stationary reference point. The control unit is confi gured to receive the parameter, and based thereon generate a control signal influencing a movement of the movable platform. The first transmitter unit has a first transmitter antenna, and is configured to be placed on the movable platform so as to move along with any movements of the movable platform. The first transmitter unit is further configured to emit a first radio signal, preferably in the ultra-wideband spectrum from the transmitter antenna, which first radio signal contains a timing reference and uniquely identifies the first transmitter unit. Each of the at least three receiver stations is configured to be placed stationary with a receiver antenna thereof located such that, during operation of the rotary milking parlor, the first radio signal may propagate along a line-of-sight from the first transmitter antenna to the res- pective receiver antenna. Each of the at least three receiver stations is further configured to receive the first radio signal, and based thereon produce a respective sensor signal. The proces sing unit is configured to receive the sensor signals from the at least three receiver stations, and based on respective propa- gation times derived from the timing reference contained in the first radio signal generate the parameter.

This control system is advantageous because it is insensitive to soling. The proposed radio positioning is further beneficial be cause it may be conveniently expanded to include additional transmitter units for enhanced precision. Moreover, it is straight forward to gradually improve the quality of the positioning by collecting multiple measurement values over time. This improve ment becomes especially remarkable if two or more transmitter units are employed.

According to one embodiment of this aspect of the invention, the stationary reference point is a fixed point in space whose posi tion is: known through coordinates stored in a memory of the processing unit; measured repeatedly via the at least three re- ceiver stations and by means of a second transmitter unit having a second transmitter antenna located at the stationary reference point, where the second transmitter antenna emits a second ra dio signal containing the timing reference and uniquely identi fying the second transmitter unit; and/or measured repeatedly by means of at least one sensor being uncorrelated with the sensor arrangement. Thus, there are many alternative ways to determi ne the actual physical position of the movable platform.

According to another aspect of the invention, the object is achie ved by a rotary parlor containing the above-described control system, a movable platform and a drive unit configured to control the movement of the movable platform in response to the control signal. The advantages of this rotary parlor are apparent from the discussion above with reference to the proposed control system. According to one embodiment of this aspect of the invention, a first detector member is arranged at the stationary reference point, a second detector member is arranged at well-defined lo cation on the movable platform, and the control unit is configured to receive a detector signal from at least one of the first and se- cond detector members. Based thereon, the control unit is confi gured to determine when the well-defined location on the movab le platform passes the stationary reference point. This means that it is uncomplicated to register for example the exact point in time when a first milking station is located in front of an entry gate.

According to another embodiment of this aspect of the invention, at least one receiver station of the at least three receiver sta tions is placed with the receiver antenna thereof located in a central area of the rotary milking parlor around which central area the movable platform rotates during operation of the rotary milking parlor. Such an arrangement is advantageous because it is space efficient, and reduces that other equipment in the barn influences the propagation of the radio signals. According to yet another embodiment of this aspect of the inven tion, at least one receiver station of the at least three receiver stations is placed with the receiver antenna thereof located in a peripheral area outside of an outer periphery of the movable platform. This arrangement may be beneficial if the inner area of the platform is used for other purposes, and/or if the barn offers alternative locations for the receiver stations.

According to still another embodiment of this aspect of the in vention, the first transmitter unit is arranged on a particular piece of equipment on the movable platform. The first transmitter unit is further configured to emit the first radio signal to enable posi tioning of said piece of equipment on the movable platform du ring operation of the rotary milking parlor. Hence, the piece of equipment and the movable platform as such can be positioned jointly. According to another embodiment of this aspect of the invention, the first transmitter unit also has a movement sensor, which is configured to detect micro movements of the first transmitter unit with respect to an orientation of the first transmitter unit relative to a fix reference frame. Moreover, the first transmitter unit is configured to check if an amount of micro movements exceeds a threshold value; and if so, the first transmitter unit generates an alert signal. Thereby, for example undesirable and/or harmful vibrations in the movable platform can be noticed at an early stage, and appropriate corrective measures can be taken before the movable platform is damaged.

Preferably, if the amount of micro movements exceeds the thres hold value, the first transmitter unit is configured to emit the first radio signal repeatedly at a first repetition frequency, say 5 to 10 Hz. If, instead, the amount of micro movements is below or equal to the threshold value, the first transmitter unit is configured to emit the first radio signal repeatedly at a second repetition fre quency below the first repetition frequency, say 1 Hz. In fact, to conserve energy, the second repetition frequency may even be zero. In other words, the first radio signal is not emitted at all. This may be especially advantageous if it is reasonable to ex pect that the low amount of micro movements is a result of the movable platform is standing still. According to embodiments of this aspect of the invention, the movement sensor is configured to register displacements in three dimensions and/or accelerations in three dimensions. Hen ce, highly accurate movement patterns can be recorded and an alyzed. According to another aspect of the invention, the object is achie ved by a method of controlling a rotary milking parlor. The me thod involves the following: measuring, via a sensor arrange ment, a parameter, which represents a position of a movable platform of the rotary parlor relative to a stationary reference point. More precisely, a first transmitter unit is placed on the mo vable platform, so that the first transmitter unit moves along with any movements of the movable platform. The first transmitter has a transmitter antenna from which a first radio signal is emit ted. The first radio signal contains a timing reference and uni- quely identifying the first transmitter unit. The first radio signal is received in at least three receiver stations, each of which is placed stationary with a receiver antenna thereof located such that during operation of the rotary milking parlor the first radio signal may propagate along a line-of-sight from the first trans- mitter antenna to the receiver antenna. A respective sensor sig nal is produced in each of the at least three receiver stations; and on the further basis of the sensor signals, a parameter is ge nerated reflecting respective propagation times derived from the timing reference contained in the first radio signal. Finally, a control signal is generated based on the parameter, which con trol signal is configured to influence a movement of the movable platform. The advantages of this method, as well as the prefer red embodiments thereof, are apparent from the discussion above with reference to the proposed control system and rotary milking parlor.

According to a further aspect of the invention the object is achieved by a computer program loadable into a non-volatile da ta 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.

According to another aspect of the invention the object is achie ved 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.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

Figures 1 -2 show examples of rotary milking parlors and con trol systems therefor according to embodiments of the invention;

Figure 3 shows a diagram exemplifying how a repetition frequency of an emitted radio signal may vary over time in response to a registered amount of micro movements on the movable platform; and

Figure 4 illustrates, by means of a flow diagram, the gene ral method according to the invention of controlling a rotary milking parlor. DETAILED DESCRIPTION

Figure 1 shows a first example of rotary milking parlor 100 and a control system therefor according to one embodiment of the invention. The proposed control system contains a sensor arran gement and a control unit 150. The sensor arrangement is configured to measure a parameter P representing a position of a movable platform 1 10 of the rotary parlor 100 relative to a stationary reference point P _ref. The con trol unit 150 is configured to receive the parameter P, and based thereon generate a control signal Ctrl that influences a move- ment of the movable platform 1 10, for example its rotation velo city.

The sensor arrangement, in turn, contains a first transmitter unit 210, at least three receiver stations 221 , 222 and 223 respec tively and a processing unit 230. The first transmitter unit 210 has a first transmitter antenna, and is configured to be placed on the movable platform 1 10 so as to move along with any movements of the movable platform 1 10. The first transmitter unit 210 is further configured to emit a first radio signal SID from the transmitter antenna. The first radio sig- nal SID contains a timing reference and uniquely identifies the first transmitter unit 210, e.g. via a signature code.

Each of the at least three receiver stations 221 , 222 and 223 is configured to be placed stationary with a receiver antenna the reof located such that, during operation of the rotary milking par lor 100, the first radio signal SID may propagate along a line-of- sight from the first transmitter antenna to the receiver antenna. Thus, the first radio signal S I D preferably has relatively high fre quency, e.g. in the ultra-wideband spectrum, whose propagation properties are similar to those of visible light.

Each of the at least three receiver stations 221 , 222 and 223 is further configured to receive the first radio signal S I D , and based thereon produce a respective sensor signal R1 , R2 and R3 res pectively. The sensor signals R1 , R2 and R3 reflect a respective propagation delay that the first radio signal S I D has experienced while travelling from the transmitter antenna to the receiver an- tenna of the receiver station in question, i.e. 221 , 222 and 223 respectively. Since the first radio signal S I D contains a timing re ference, the propagation delays may be determined by com paring the timing reference of the first radio signal S I D with a local timing reference in the receiver station, which is synchro- nized with the timing reference of the first radio signal S I D .

The processing unit 230 is configured to receive the sensor signals R1 , R2 and R3 from the at least three receiver stations. Based on the respective propagation times derived from the ti ming reference of the first radio signal S I D , the processing unit 230 is further configured to generate the parameter P, i.e. the position of the movable platform 1 10 of the rotary parlor 100 re lative to the stationary reference point P _ref .

Thus, the parameter P may express a rotation angle in relation to a central axis through the movable platform 1 10. Provided that the configuration of the movable platform 1 10 is known and ade quately described, the different individual positions of all ele ments on the movable platform 1 10 can be established based on the parameter P. Preferably, the physical configuration of the movable platform 1 10 is described in a computer model acces- sible by the processing unit 230. For example, in order to gain information about all stalls’ respective positions, the first trans mitter unit 210 may be associated with a particular location in a given stall. Provided that the movable platform 1 10 has a num ber, say 60, of identical and evenly distributed stalls, the para- meter P also reveals the respective positions of all the other stalls and their respective equipments. After having recorded the parameter P over a period, and assuming a linear movement all these positions can be determined very accurately. This is espe- cially so, if more than one transmitter unit is arranged on the mo vable platform 1 10.

The spatial position of the stationary reference point P _ref may be known through the following: coordinates stored in a memory of the processing unit 230; measurements that are repeated by use of the at least three receiver stations 221 , 222 and 223; and by means of a second transmitter unit, which has a second trans mitter antenna located at the stationary reference point P _ref. He re, the second transmitter antenna emits a second radio signal that contains the timing reference and uniquely identifies the se- cond transmitter unit. Thus, the receiver stations 221 , 222 and 223 can determine the stationary reference point P _ref analogous ly to how the parameter P is determined. Moreover, if the measu rements are repeated, the position of the stationary reference point P _ref may be determined very accurately, for example via an averaging process.

Naturally, the position for the stationary reference point P _ref may also be measured repeatedly by means of at least one sensor that is uncorrelated with the sensor arrangement, such as an op tical and/or magnetic sensor arrangement. According to one embodiment of the invention, the above-descri bed control system is arranged to control the movable platform 1 10 of the rotary milking parlor 100. To this aim, the parameter P is fed to a control unit 150, which is configured to generate a control signal Ctrl based on the parameter P. A drive unit 140 is configured to receive the control signal Ctrl, and in response the reto control the movement of the movable platform 1 10.

For reference and orientation purposes, the position of the sta tionary reference point P _ref must be known to the control system. Therefore, a first detector member may be arranged at the sta tionary reference point P _ref , and a second detector member may be arranged at well-defined location on the movable platform 1 10. It is normally practical to co-locate the stationary reference point Pr _ef with an important position of the rotary milking parlor 100, for example an entry area 120 where animals step onto the movable platform 1 10, an exit area 130 where animals step off the mov able platform 1 10, or where a robot for washing the animals’ teats is located.

Further, it may be advantageous to arrange the first transmitter unit 210 on a particular piece of equipment that is fixedly posi tioned on the movable platform 1 10. Namely, as a result, during operation of the rotary milking parlor 100, the position of this piece of equipment is immediately known.

In any case, the control unit 150 is configured to receive a detec tor signal from at least one of the first and second detector mem bers, and based thereon, determine when the well-defined loca tion on the movable platform 1 10 passes the stationary reference point Pr _ef . Consequently, it can be established exactly when the movable platform 1 10 has a predefined orientation. Analogous to the above, the quality of this information likewise improves over time, i.e. after having recorded multiple registrations.

As can be seen, in the embodiment shown in Figure 1 , the recei- ver stations 221 , 222 and 223 are all placed with their receiver antennas located in a central area AC of the rotary milking parlor 100 around which central area AC the movable platform 1 10 ro tates RF during operation of the rotary milking parlor 100. Prefe rably, to economize space, at least one of the at least three re- ceiver stations is placed with the receiver antenna thereof loca ted in the central area AC.

Figure 2 shows another example of rotary milking parlor and a control system therefor according to an embodiment of the in- vention. Here, all three receiver stations 224, 225 and 226 are instead placed with their receiver antennas located in a peri pheral area outside of an outer periphery of the movable plat form 1 10. For improved precision and reliability, it is advanta- geous to separate the receiver antennas from one another by so me distance. Therefore, according to one embodiment of the in vention, at least one of the at least three receiver stations is pla ced with the receiver antenna thereof located in a peripheral area outside of the outer periphery of the movable platform 1 10. Moreover, in general, the position precision can be improved by repeated registrations both by increasing the number of transmit ters and by recording multiple registrations over time based on one and the same transmitter(s) and receivers. For example, if the position registration is updated at a frequency of 5 Hz, with one transmitter the overall positioning is effected five times per second; with two transmitters the overall positioning is effected ten times per second; with ten transmitters the overall positio ning is effected 50 times per second, and so on. Thus, the mea surement error decreases with an increased number of transmit- ters.

Additionally, provided that the movable platform 1 10 is rotatable, i.e. performs a rotating movement around an axis, each transmit ter unit on the movable platform 1 10 moves along a circular path. Therefore, over time, not only the angular position of the transmitter unit will be determined with improved precision, how ever also the magnitude of the radius of this circular path will be determined more accurately. Naturally, if a series of measure ment values is recorded, the movable platform’s 1 10 velocity can also be determined relatively accurately. Assuming that the velo- city is comparatively constant, the positioning can be further en hanced.

Even if the precision in each registration is relatively low, say ±10 cm, the use of multiple transmitter units may reduce a resul ting uncertainty Dc as follows: where D, is the uncertainty in each measurement and N is the number of measurements. For instance, N = 5 and D, = 10 cm gi ves Dc = 4,5 cm; and N = 10 and D, = 10 cm gives Dc = 1 ,4 cm. If an adaptive filter is applied, e.g. of Kalman type, the uncer tainty can be reduced even further.

According to one embodiment of the invention, the first trans mitter unit 210 also contains a movement sensor configured to detect micro movements of the first transmitter unit 210 with respect to an orientation of the first transmitter unit 210 relative to a fix reference frame, e.g. the earth as such.

Thus, the movement sensor in the first transmitter unit 210 (or any other transmitter unit included in the system) is configured to register displacements in three dimensions and/or accelera- tions in three dimensions. Thereby, the start and/or stop pat terns of the movable platform 1 10 can be very accurately recor ded. This, in turn, provides valuable basis for diagnosing the ro tary milking parlor 100 and the operation of its movable platform 1 10. In particular, according to one embodiment of the invention, the first transmitter unit 210 is further configured to check if an amount of micro movements exceeds a threshold value. If the first transmitter unit 210 finds that the threshold value is ex ceeded, the first transmitter unit 210 is configured to generate an alert signal. Thereby, undesirable and/or harmful vibrations in the movable platform 1 10 can be noticed at an early stage, and appropriate corrective measures can be taken before the rotary milking parlor 100 is damaged.

According to one embodiment of the invention, a repetition fre- quency at which the first transmitter unit 210 emits depends on the amount of micro movements. More precisely, if the amount of micro movements exceeds the threshold value, the first trans mitter unit 210 is configured to emit the first radio signal S I D re peatedly at a first repetition frequency.

If, on the other hand, the amount of micro movements is below or equal to the threshold value, the first transmitter unit 210 is configured to emit the first radio signal S I D repeatedly at a se cond repetition frequency below the first repetition frequency.

Figure 3 shows a diagram exemplifying how a repetition fre quency f of an emitted radio signal S I D may vary over time t in response to a registered amount of micro movements on the movable platform 1 10.

Here, we assume that the movable platform 1 10 is stationary until a first point in time ti at which the movable platform 1 10 starts to rotate, and as a result the amount of micro movements increases above the threshold value. Thus, up until the first point in time ti the first transmitter unit 210 emits the first radio signal S I D at a relatively low first repetition frequency f 1 , say 0-3 Hz. Then, as of the first point in time ti , the first transmitter unit 210 emits the first radio signal S I D at a second repetition frequency f 2 , which is higher than first repetition frequency f 1 , say equals

10-15 Hz.

Then, provided that, during a predetermined interval T thereafter the amount of micro movements of the first transmitter unit 210 remains above the threshold value, the first transmitter unit 210 continues to emit the first radio signal S I D repeatedly at the se cond repetition frequency until expiry of the predetermined in terval T. In the example illustrated in Figure 3, the predetermi ned interval T expires at a second point in time , and here, the first transmitter unit 210 starts to emit the first radio signal S I D repeatedly at a third repetition frequency f3, whose magnitude is between that of the first and second repetition frequencies fi and respectively, say f3 equals 5-8 Hz. Thereafter, i.e. as of the third point in time t3, the first transmitter unit 210 continues to emit the first radio signal S I D at the third repetition frequency f3, as long as the amount of micro movements exceeds the thres hold value. This procedure is advantageous because it provides relatively accurate position data in connection with starting the movable platform 1 10. At the same time, energy is economized during continuous operation.

It is generally advantageous if the above-described processing unit 230 is configured to effect the above-mentioned procedure in an automatic manner, for instance by executing a computer program 237. Therefore, the processing unit 230 may be com municatively connected to a memory unit, i.e. non-volatile data carrier 235, storing the computer program 237, which, in turn, contains software for making at least one processor in the pro cessing unit 230 execute the above-described actions when the computer program 237 is run in the processing unit 230.

In order to sum up, and with reference to the flow diagram in Figure 4, we will now describe the general method according to the invention of controlling a rotary milking parlor.

In a first step 410, a first transmitter unit is placed on a movable platform, so that the first transmitter unit and its transmitting antenna moves along with any movements of the movable plat form. Then, in a step 420, a first radio signal is emitted from the transmitter antenna. The first radio signal contains a timing refe rence. The first radio signal also uniquely identifies the first transmitter unit.

In a step 430, parallel to step 420, the first radio signal is re ceived in at least three receiver stations. Each of these stations is placed stationary with a receiver antenna thereof located such that, during operation of the rotary milking parlor, the first radio signal may propagate along a line-of-sight from the first transmit ter antenna to the receiver antenna. Thereby, the first transmitter antenna can be triangulated. Specifically, in a step 440 after step 430, a respective sensor signal is produced in each of the at least three receiver stations.

Subsequently, in a step 450 after steps 420 and 440, a parame ter is generated based on respective propagation times, which, in turn, have been derived from the timing reference contained in the first radio signal. Since the propagation velocity is the same to each receiver station (namely the speed of light), said pro pagation times correspond to respective distances between the transmitter antenna and the receiver antennas. Further, the pa rameter is used to influence the movement of the a movable plat- form, for example its rotation speed and/or start and stop se quence.

After step 450, the procedure loops back to steps 420 and 430.

Preferably, although illustrated as discrete steps in Figure 4, all the steps 420 to 450 are effected sequentially and yet simulta- neously, so that for example while the radio signal is emitted at a particular point in time in step 420, the parameter is generated in step 450 based on a radio signal emitted at a somewhat ear lier point in time.

All of the process steps, as well as any sub-sequence of steps, described with reference to Figure 4 may be controlled by means of a programmed processor. Moreover, although the em bodiments 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, ad apted 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 pro- cess 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 prog ram. For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for ex ample a DVD (Digital Video/Versatile Disk), a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Program mable 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 car rier may be a transmissible carrier such as an electrical or opti cal 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 de vice 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.

The term“comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components. However, the term does not preclude the presence or addition of one or more additional features, inte- gers, steps or components or groups thereof.

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