METHOD FOR DETERMINING AN ABSOLUTE POSITION OF A MOVING TRAVEL UNIT OF A STATIONARY TRANSPORT SYSTEM

Abstract

Methods for determining an absolute position of a moving travel unit of a stationary transport system, the travel unit movable along a travel path inside the system. The travel unit is driven by at least one linear motor along the path. The linear motor is a synchronous motor including a plurality of stator units installed along the travel path configured to provide a magnetic field traveling along the travel path. At least one rotor unit is attached to the travel unit and is configured to be driven along the travel path by the traveling magnetic field. Wherein respectively by analysis of regulating parameters of a vector regulation of the linear motor an active stator unit is determined from the plurality, which presently provides the magnetic field driving the rotor unit and a relative position of the rotor unit in relation to the active stator unit is computed.

Claims

1.-10. (canceled)

11. A method for determining an absolute position of a moving travel unit of a stationary transport system, the travel unit being movable along a travel path inside the transport system, wherein the travel unit is driven by at least one linear motor along the travel path, wherein the linear motor is embodied as a synchronous motor, the linear motor, comprising: a plurality of stator units installed along the travel path and configured to provide a magnetic field traveling along the travel path, at least one rotor unit attached to the travel unit and configured to be driven along the travel path by the traveling magnetic field, the method including: analyzing regulating parameters of a vector regulation of the linear motor to: determine which of the plurality of stator units is active and provides the magnetic field driving the rotor unit, and compute a relative position of the rotor unit in relation to the active stator unit.

12. The method of claim 11, including determining the absolute position of the travel unit by adding an absolute position of the active stator unit to the relative position of the rotor unit.

13. The method of claim 12, wherein for at least some of the plurality of stator units, each respective associated absolute positions are stored in a database, and in that they can be queried from the database for the determination of the absolute position of the travel unit.

14. The method of claim 11, wherein a further linear drive comprising stator units and a further rotor unit is provided, wherein the further rotor unit is attached to the travel unit, respectively by analysis of variables of a vector regulation of the linear motor on the one hand of the plurality of stator units, a further active stator unit, which presently provides the magnetic field driving the further rotor unit, is determined, and on the other hand, a relative position of the further rotor unit in relation to the further active stator unit is computed.

15. The method of claim 11, wherein the transport system comprises a plurality of travel units, which are movable independently of one another along a common travel path.

16. The method of claim 15, wherein a plurality of present absolute positions are determined, which are initially not associated with any of the travel units from the plurality of the travel units, on the basis of an identification assembly, a plurality of present identified rough positions are determined, at which travel units are located, and based on a comparison of the determined identified rough positions and the determined absolute position one of the determined absolute positions is associated with an individual travel unit.

17. The method of claim 11, wherein the vector regulation is a position-sensorless vector regulation.

18. A transport system, comprising: at least one moving travel unit, which is movable along a travel path of the stationary transport system and which is driven by means of a linear motor, and the linear motor comprising: a plurality of stator units installed along the travel path and configured to provide a magnetic field traveling along the travel path, at least one rotor unit attached to the travel unit and configured to be driven along the travel path by the traveling magnetic field, a control unit configured to determine the absolute position of the travel unit by analyzing regulating parameters of a vector regulation of the linear motor by: determining which of the plurality of stator units is active and provides the magnetic field driving the rotor unit, and computing a relative position of the rotor unit in relation to the active stator unit.

19. The transport system of claim 18, comprising a plurality of travel units, which are movable along a common travel path and are driven by means of the linear motor.

20. The transport system of claim 19, wherein the common travel path is a common elevator shaft.

21. The transport system of claim 18, wherein the transport system is an elevator system, and in that the travel unit or the plurality of travel units is a car or a plurality of cars, respectively, and in that the travel path is arranged at least in sections in an elevator shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention will be explained in greater detail hereafter on the basis of drawings. In the figures:

[0019] FIG. 1 shows an elevator system comprising a linear drive, in which the method according to the invention is used;

[0020] FIG. 2 shows a current control circuit of the elevator system according to FIG. 1 for vector regulation of the linear synchronous motor;

[0021] FIG. 3 shows a superordinate control circuit of the elevator system according to FIG. 1 for travel regulation of the elevator;

[0022] FIG. 4 shows an elevator system comprising multiple travel units in an elevator shaft, in which the method according to the invention is used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] An elevator system 1 according to the invention is shown in FIG. 1. A car 2 is movably accommodated as a travel unit in an immobile elevator shaft 7. A rail system (not shown) defines a travel path 6, linear in this case, along which the car 2 is movable. The car 2 is driven in the direction of the travel path 6 by a linear motor 3, which is designed as a synchronous motor. The linear motor 3 comprises a plurality of stator units 4, which are fixedly installed along the travel path 6. Furthermore, the linear motor 3 comprises a rotor 5, which is fastened on the car 2 and moves jointly with the car 2 along the travel path 6.

[0024] To drive the rotor 5 and thus the car 2 by way of the linear motor 3, the stator units 4 of the linear motor 3 are to be regulated in a complex manner. Each stator unit 4 thus comprises a plurality of poles, in the present case three poles each, u, v, w. In the state of the elevator system shown in FIG. 1, the stator unit 4 is the stator unit which impinges the rotor 5 vertically upward by generating a magnetic field at the pole w and thus drives the car 2. The presently driving stator unit is referred to in the scope of the present application as the active stator unit 4. If the rotor 5 subsequently enters the influence region of the pole u of the stator unit 4 located above this (this is the third stator unit 4 seen from the top in FIG. 1) during the further upward movement, this stator unit thus becomes the active stator unit, while the stator unit 4 active up to that point loses its status as the active stator unit as soon as the rotor 5 leaves the influence region of all poles u, v, w of this stator unit.

[0025] The regulation of the current supply to the windings of the poles of the stator units 4 is carried out via a vector regulation. The accurate knowledge of the relative position of the rotor 5 in relation to the stator units 4 is significant in this case. In this case, this relative position can be determined by separate position sensor means, which in particular comprise route markings attached along the travel path. According to the invention, sensorless regulating algorithms are preferably used, in which the relative positions may be derived from regulating parameters within the control circuit of the vector regulation. In this sensorless regulation, the circumstance is utilized that the rotor induces a current flow in the respective winding as a function of its relative position and relative speed in relation to the respective windings of the stator unit. This induced current flow may be determined by analyzing the stator currents. Reference is made to AN93637 PSoC 4 Sensorless Field-Oriented Control (FOC), Bob Hu, Cypress Semiconductor Corp., 26.08.2015, for the details of a sensorless vector regulation, retrievable under http://www.cypress.com/documentation/application-notes/an93637-psoc-4-sensorless-field-oriented-control-foc; explained therein on the basis of a rotating synchronous motor, which is similarly applicable to a linear motor.

[0026] FIG. 2 shows the control circuit 8 of such a vector regulation in simplified form. The stator currents I.sub.u, I.sub.v, I.sub.w of the windings u, v, w are determined via current sensors 11 and supplied to a Clark-Park transformer 12. This Clark-Park transformer 12 firstly converts the stator currents into a two-axis rotating system having the transformed actual current values I.sub.d and I.sub.q. The relative alignment H.sub.95 in relation to the windings u, v, w of the active stator unit 4 and thus in relation to a reference point 9 (FIG. 1) of the active stator unit 4 may be computed from values of this transformation via mathematical models, which can also be determined experimentally, in a slide mode observer 13. Moreover, it is known by observation of the control circuit which of the stator units is the active stator unit 4.

[0027] If the active stator unit 4 is known, a reference position H.sub.9 for its reference point 9 can thus be retrieved from a database 15, in which the reference positions for a plurality of stator units 4 are stored. The determined reference position H.sub.9 represents the absolute position of this reference point 9 along the travel path 6. Since the car 2 is movable only in one direction dimension along the travel path 6, a one-dimensional variable is fundamentally sufficient as a unique position specification. The travel path can in principle also have a nonlinear course.

[0028] In the further course of the regulation, the transformed actual current values I.sub.d and I.sub.q are compared to corresponding setpoint values I.sub.dS and I.sub.qS. The regulating difference generated therefrom is supplied to a regulator 14 having inverse Clark transformer and motor driver, which generates the stator currents I.sub.u, I.sub.v, I.sub.w there from and supplies them to the windings u, v, w of the active stator unit 4.

[0029] The absolute position H.sub.5 of the rotor 5 thus determined is now used for the travel regulation of an elevator, which will be explained on the basis of FIG. 3. Moreover, the present speed or the speed curve may be derived from the absolute position H.sub.5. An elevator controller 10 specifies a setpoint position H.sub.5S or a setpoint speed V.sub.5S; a regulating difference is determined in comparison to the present position H.sub.5 or speed V.sub.5, respectively. The car is to be decelerated or accelerated depending on the regulating difference, which is effectuated by a corresponding specification of the current setpoint values in the control circuit 8. A conversion unit required for this purpose for converting the regulating difference into the current setpoint values is not shown in FIG. 3 for reasons of comprehensibility.

[0030] The method according to the invention for position determination of the car therefore manages without the use of additional position sensors. This method can thus be used alone; however, it can also be used as a cost-effective redundancy method for other, in particular sensor-based position determination methods.

[0031] The use of the method according to the invention in a so-called multi-elevator system will be explained on the basis of FIG. 4. In such systems, a plurality of cars 2 is located in a common elevator shaft 7. A first and a second car 2, 2 are shown in FIG. 4. In addition to the knowledge that an (any) undefined car 2 is located at a specific position H.sub.5 in the elevator shaft 7, it is otherwise unimportant in this case which car this is. This is because the different cars finally have different travel tasks to fulfill, which are also accompanied by different speed profiles, and are therefore to be accelerated and decelerated differently. To determine which of the cars is located in the region of the active stator unit, an identification assembly 16 is provided, on the basis of which an identified rough position H.sub.ID of the cars 2 is determined. The identified rough position H.sub.ID is understood essentially as the knowledge about the approximate position of a uniquely identifiable, thus individual car in the elevator shaft 7.

[0032] The identification assembly 16 comprises a plurality of in particular passive RFID tags 17, at least one of which is attached to a car 2. Furthermore, the identification assembly 16 comprises a plurality of RFID sensors 18, which are arranged along the elevator shaft 7, and with each of which a rough position is associated. If the car 2 comprising its RFID tag 17 then enters the range region 18 of the RFID sensor 18, a rough position H.sub.ID is thus assigned to the car 2.

[0033] The other car 2 is located with its RFID tag 17 arranged in the range region 19 and 19 of the other RFID sensors 18 and 18. One of the rough positions H.sub.ID or H.sub.ID, alternatively both rough positions H.sub.ID and H.sub.ID, can thus be assigned to the car 2. In this case, it is apparent from the signals of the RFID sensors 18 and 18 that the car 2 is located with its RFID tag 17 in the region between the two RFID sensors. The rough position can therefore also be refined further, for example, by averaging of the two assigned rough positions (H.sub.ID,refined=0.5H.sub.ID+0.5H.sub.ID).

[0034] It can already be established by the method which was explained on the basis of FIGS. 1 to 3 that any one of the cars is located in the exact absolute position H.sub.5, while any one of the other cars is located in the exact absolute position H.sub.5.

[0035] By similarity comparison of the determined identified rough positions H.sub.ID to the two absolute positions H.sub.5, precisely one of the determined, initially still masterless absolute positions H.sub.5 is associated with the individual car 2; the other absolute position H.sub.5 is associated with the individual car 2.

[0036] Only a small number of RFID sensors, which are arranged over quite a long interval along the travel path, are required for the determination of the exact position of a car and association of this position with an individual car. The regulating parameters can be used for the computation of the exact position; no noteworthy additional sensors are required which are not already present in any case for the motor regulation.

LIST OF REFERENCE SIGNS

[0037] 1 elevator system [0038] 2 car [0039] 3 linear motor [0040] 4 stator unit [0041] 5 rotor unit [0042] 6 travel path [0043] 7 elevator shaft [0044] 8 control circuit [0045] 9 reference point of the stator unit [0046] 10 elevator controller [0047] 11 current sensors [0048] 12 Clark-Park transformer [0049] 13 slide mode observer [0050] 14 regulator comprising inverse Clark transformer and motor driver [0051] 15 database [0052] 16 identification assembly [0053] 17 RFID tag [0054] 18 RFID sensor [0055] 19 range region of an RFID sensor [0056] H.sub.9 absolute position of the reference point (reference position) [0057] H.sub.95 relative position between the reference position and the rotor unit [0058] H.sub.5 absolute position of the rotor unit [0059] H.sub.ID identified rough position [0060] V.sub.5 speed of the rotor unit [0061] Index S setpoint value