WO2009013114A1

WO2009013114A1 - Method for ascertaining the speed of a lift cabin and a control unit for implementing this method

Info

Publication number: WO2009013114A1
Application number: PCT/EP2008/058722
Authority: WO
Inventors: Steffen Grundmann
Original assignee: Inventio Ag
Priority date: 2007-07-20
Filing date: 2008-07-04
Publication date: 2009-01-29

Abstract

The invention relates to a method for ascertaining the speed of a lift cabin (14) which can move along a travel path (20) in a lift shaft (12), wherein for a first travel path section (22) of the travel path (20) between a first position (P1) and a second position (P2) a speed v0 of the lift cabin (14) is detected at the first position (P1), a plurality of accelerations am(n) of the lift cabin (14) are detected in a plurality of measurement intervals, a time ΔTZF is detected which the lift cabin (14) takes in order to travel from the first position (P1) to the second position (P2) and a speed vkorr for the second position (P2) is ascertained as follows: (I), wherein εoff,real is a correction value which is determined by comparing an actual path length (ΔXZF) between the first position (P1) and the second position (P2) with a theoretical calculated path length (ΔXth), Δt is the duration of the measurement interval, am(n) are the accelerations detected in the travel path section (22), v0 is the speed at the first position (P1) and n is the number of the measurement intervals for which accelerations have been detected. The invention furthermore relates to a lift system for implementing this method and to a control unit for implementing this method and for use in a corresponding lift system.

Description

METHOD FOR DETERMINING THE SPEED OF AN ELEVATOR'S CABIN AND A CONTROL UNIT FOR CARRYING OUT THIS METHOD

The present invention relates to a method for determining the speed of an elevator car which can be moved along a travel path, to an elevator installation in which the speed of an elevator car is determined by this method, and to a control unit for carrying out this method or for use in this elevator installation.

Known safety devices for monitoring an elevator car include a speed or acceleration sensor and a position sensor for determining the current position of the elevator car. Such a position sensor detects, for example, in the area of the floors in the elevator shaft mounted position marks. Such a system is known, for example, from EP 1 602 610 A1.

As is known, measuring systems with acceleration sensors are error-prone. In particular, deviations may result if, for example, an installation position changes or if a measuring system is inclined. Also, as a result of environmental influences such as, for example, temperature effects, an accelerometer can itself undergo deviations. If, as described in EP 1 602 610 A1, an acceleration sensor is used to determine the driving speed, such deviations can lead to a faulty result. Therefore, such a signal can not be said to be safe and other measurement systems are needed to determine a safe speed signal.

The invention is therefore based on the object to provide a method for determining a precise, error-free speed of the elevator car. The method should be easy to use in an elevator installation. Thus, a correspondingly designed elevator system should be specified. To achieve this object, in accordance with claim 1, a method for determining the speed of an elevator car movable along a track is provided, wherein for a first track section of the track between a first position and a second position - a speed v _{0 of} the elevator car at the first position is detected, several accelerations a _m ( _n ) of the elevator car in several measuring intervals .DELTA.t are detected, a time period .DELTA.T _{ZF is} detected, which requires the elevator car to get from the first position to the second position, a speed v _corr for the second Position is determined as follows:

^V cor = ^V 0 + ^{At •} Σ ^a m (n) ^~ «^ off, real

where ε _{o # reα / is} a correction value obtained by comparing a real one

Distance ΔX _ZF ) between the first position and the second position and a theoretically calculated distance ΔX _{th is} determined,

Δt is the duration of the measurement interval, a _m ( _n ) are the detected accelerations in the travel path section, V _{0 is} the speed at the first position, n is the number of measurement intervals for which the accelerations have been detected.

One idea of the invention is to determine a correction value ε _{off real} by comparing a calculated distance on the basis of the measured values of the accelerations a _m ( _n ) with a real distance ΔX _ZF between the first position and the second position. Then, starting from a velocity v ₀ measured or predetermined for the first position, the measured accelerations a _m ( _n ). and the number n of the measurement intervals for which the accelerations have been detected, the current corrected speed v _korr for the second position of the first travel path section or another travel path section or a travel path comprising a plurality of travel path sections are calculated. For example, the value 0 is obtained for the speed v ₀ when the elevator car is moved from standstill. The elevator car is usually installed in a lift shaft in a building. The building has several floors which are connected by the elevator shaft, and the elevator car serves for the substantially vertical transport of persons and / or goods between these floors. The travel path of the elevator car is determined by the elevator shaft. Under the track section is a section of the available track understood, in particular, this section is the distance between two floors and / or the position marks provided there. Furthermore, the distance between two floors can also be subdivided by additional additional positions or position marks (intermediate marks). Thus, during a service run, a travel path can be traveled that includes one or more sections of travel path. In the event that the operating travel comprises several sections of track, the method according to the invention is repeated for each track section, wherein the determined travel speed v _{korr of} the preceding track section is set for the speed v _{0 of} a subsequent track section.

With the method according to the invention, a safe, corrected speed _value v _{korr of} the elevator car can be determined. This speed value can advantageously be used in particular for a safety system in such a way that a brake signal is triggered in the event of exceeding a maximum speed value. Furthermore, this speed value for controlling the opening and closing of the shaft doors and / or car doors when approaching a floor towards the end of a service run can be advantageously used.

Further advantages of the method according to the invention are, in particular, that the accelerations a _m ( _n ) can be detected by means of a low-cost accelerometer, which is for example installed directly in a control unit (board). Furthermore, components already present in the elevator shaft, for example the position markers for approaching the floors, can be used for the method anyway. In this way, the installation of a separate measuring system can be dispensed with. Alternatively, however, an additional system for speed determination can be installed, so that the speed is detected by means of two measuring systems in order to create a further increased safety or to further reduce sources of error. Furthermore, by using an acceleration sensor and the signal determined therefrom, further information useful for monitoring the elevator installation can be obtained, such as, for example with regard to a wear indicator or bearing damage. In particular, the method and the associated elevator installation can trigger a signal for triggering emergency braking or a safety alarm if the speed and / or acceleration values are too high.

Further, the errors which occur as a result of subsidence and changes in length of the building by a change made to maintenance, for example, in the context of adjustment of the values for the distances .DELTA.X _ZF can be reduced. For this purpose, the distances of the individual sections of track can be redefined and stored in the control unit. It is particularly advantageous that the participating evaluation units such as accelerometer, position sensor, control unit, data storage and required processors are arranged together, advantageously directly integrated in the control unit, in the elevator car. As a result, the device can be built compact and secure and long transmission paths omitted. Such a compact device or control unit can be advantageously used for retrofitting in an existing elevator installation or it can be replaced in the event of a possible repair as a whole. Thus, the safety standard of an existing elevator system can be easily improved, in particular since many existing position marks in the shaft can be used.

In a particularly preferred embodiment of the method according to the invention or of the elevator installation, the elevator cabin is provided with an acceleration sensor which measures the instantaneous acceleration continuously in several time intervals Δt in accordance with a clock measurement frequency. Furthermore, the elevator shaft is provided with position markers in the area of the floors, wherein in the area of each floor a position mark is provided which forms the first position and / or the second position. Each adjacent positions or position marks are spaced by a distance corresponding to the distance .DELTA.X _ZF . During the process of the elevator car, the time duration which the elevator car requires in order to move from the first position mark to the second position mark of the first travel path section and optionally further travel path sections is then detected. The respectively associated distance ΔX _ZF is retrieved from a data memory of the control unit. Based on these data, the correction value ε _{o # reα /} the current corrected vehicle speed v is then computed _corr under investigation. This determined driving speed v _korr is transmitted to the control unit as effective driving speed. tion or control unit or a security monitoring system forwarded.

In the following, advantageous developments of the method according to the invention will now be described according to claims 2 to 15.

In a preferred _{embodiment of} the method, the correction _value z _{off> rml is} determined by:

_ 2 - [AX _th - AX _ZP ]

^ off, real

AT ^ where

AX _11, AT = _ZF ^■ V ₀ + f K "_" ^■ At ²⁾ + £ ^'■' ^■ ^{'' At}

1 1 ^ where ε _{o # rml is} the correction _value ,

Δt is the duration of the measuring interval, a _{m (n) are} the detected accelerations in the track section, ΔX _{th is} the theoretically calculated distance between the first position and the second position,

ΔX _{ZF is} the actual distance between the first position and the second position,

ΔT _{ZF is} the time required for the elevator car to move from the first position to the second position,

V _{0 is} the speed at the first position, n is the number of measurement intervals for which the accelerations have been detected.

In a further advantageous refinement of the method, it is provided that the speed v _korr for the second position of the second track section is determined between a first position and a second position of a second track section of the track, wherein the speed v determined for the second position of the first track section _{corr is set} as the speed v ₀ for the first position of the second track section, with the above parameters relating to the second track section, in particular a _{m being} the detected accelerations in the second track section. In this way, a continuous investigation can be Perform the current corrected driving speed for successive sections of track.

Advantageously, the first position is assigned to a first floor and the second position is assigned to a second floor. Advantageously, for this purpose, the mounted to start the floors in the elevator shaft position marks, for example in the form of sheet steel strips used.

It is also advantageous if the distance .DELTA.X _ZF between the first position and the second position of the respective track section in a control unit, in particular a storage unit, is stored and retrieved. In a preferred embodiment, the distance ΔX _ZF can be adapted for at least one section of track. This can advantageously also be done later. As a result, any errors that occur, for example, as a result of setting the building, can be counteracted.

In a preferred refinement, each path section is assigned a plurality of measurement intervals, wherein the measurement interval is determined by a predetermined clock measurement frequency and the clock measurement frequency determines the duration of the measurement interval Δt. Typical measurement intervals are approximately 5 to 50 milliseconds. For safety-relevant applications, preferably shorter measurement intervals are selected. This prevents a dangerous condition between two measuring intervals. Of course, depending on elevator data such as driving speed, other measuring intervals can be defined.

In a preferred embodiment, a position mark is provided for each position, which is detectable by a position sensor. Advantageously, the position sensor, for example a light barrier, is attached to the elevator car and is preferably configured in such a way that the absolute position of the position marker in the driving bay can be detected.

In a further preferred development, an instantaneous travel speed v _{act of} the elevator car is determined by nv _akt = v ₀ + Δ? ^• 2 ^ a _{m (n)} - n - ε _{off> real}

1 in which

V _{0 is} the speed at the first position of the respective track section, ε _{off rea} i dsr correction value of the last track section a _m ( _n ) are the currently detected accelerations in the respective track section, n is the number of measurement intervals for which the accelerations in the respective track section have been detected.

In a preferred embodiment, the speed v _akt for controlling the start of a floor and / or for monitoring the speed of the elevator car is transmitted to the control unit. Thus, the value determined for the speed of the elevator car can be used in many ways.

In a further preferred embodiment, in the case of a deviation of the correction _value z _{off> rml} and / or the speed v _korr and / or the speed v _act from a limit value by a predetermined value, a signal is issued for emergency braking or maintenance.

In order not to produce erroneous values when at low speed values, it is preferably provided that the speed v _act is not detected or maintaining, when the amount of sensed acceleration a _{m (n)} falls below a predetermined limit ^■ &_&. This limit ^■ &_& is preferably between about 0.03 and about 0.05 m / s ^2.

In order to be able to calibrate the speed if necessary, the determined speed v ₀ can be set to a predetermined value or, at a predetermined time, to a reference value, in particular to zero. Particularly suitable as a predetermined event is the stop of the elevator car in a floor that lasts for a certain period of time, in particular when the doors are open and the brake is closed. Further, this calibration can be done over a long period of time with no acceleration or a time period that is longer than the maximum expected driving time. In a preferred development, it can be provided that a plurality of speed values are determined, wherein the speed v _korr according to one of the preceding claims is determined as a first speed _value , and wherein at least one second speed value is determined by means of own sensors and if at least one of the determined speed values is exceeded an error is detected and a brake signal is output. This creates a particularly secure surveillance system.

Moreover, in order to achieve the abovementioned object, an elevator installation with an elevator car which can be moved in a lift shaft along a travel path is proposed, wherein the travel path comprises at least one track section with a first position and a second position, and wherein at the elevator car an acceleration sensor for detecting the acceleration a _m ( _n ) of the elevator car and a position sensor for detecting the position of the elevator car are provided. The elevator installation furthermore comprises a control unit, in which the distance ΔX _ZF between the first position and the second position for the at least one track section is deposited, and a time detection unit for detecting a time duration ΔT _ZF , which the elevator car requires to move from the first position to get to the second position. The acceleration sensor, the position sensor, the control unit and the time recording unit are set up to carry out the method according to one of claims 1 to 15.

An elevator system formed in this way makes use in particular of the advantages of the method according to the invention. Advantageous embodiments of the elevator installation according to the invention are described in claims 17 to 20.

In an advantageous development, it is provided that a position mark detectable by the position sensor is provided in the region of the position. This position mark is advantageously a sheet metal strip, preferably a coded sheet metal strip. As a position sensor, preferably a light barrier can be provided. In a further advantageous embodiment, the first position forms a first end of the track section and the second position forms a second end of the track section. Thus, a track section may correspond to a distance between two floors. The coding allows a determination of the floor, with which also different floor distances can be safely detected and assigned. Advantageously, the acceleration sensor, the position sensor, the control unit and the time recording unit are assembled directly in the control unit and / or installed in a common housing or device. Such a compact device or control unit can advantageously be used for retrofitting in an existing elevator installation as described in claims 21 and 22, or it can be replaced as a whole in the case of a possible repair. Thus, the safety standard of an existing elevator system can be easily improved, in particular, since many already existing position marks can be used in the shaft.

The invention will be further explained with reference to the drawings. This show schematically

1 shows a section of a building with an elevator installation according to the invention with an elevator car, and

2 shows a speed-time diagram and an acceleration time

Diagram for the method according to the invention for determining the speed of the elevator car according to FIG. 1.

1 schematically shows a detail of a building with an elevator installation 10 with an elevator car 14 that can be moved in a lift shaft 12 along a travel path 20. The building has a multiplicity of floors, wherein in FIG. 1 a first floor 15, a second floor 16 , a third floor 17 and a fourth floor 18 are shown.

In the area of each of these floors 15 to 18, in each case a position mark 50 in the form of a sheet-steel strip is attached to the inside of the hoistway 12. Each cursor 50 includes a zero position 56 and an upper first end 52 and a lower second end 54. The cursor has a height of about 24 cm and the two ends 52, 54 have a height of 12 cm each.

These position markers 50 and in particular their respective zero position 56 mark a first position P1 and / or a second position P2 in the respectively associated floor (see FIG. 1). Thus, the zero position 56 in the fourth floor 18 in the in FIG.

1, the first position P1 of the first section of track 22. ge 56 of the position mark 50 at the level of the third floor 17 determines the second position P2 of the first track portion 22 and the first position P1 of the second Fahrwegabschnitts 24. Further, the zero position 56 of the position mark 50 of the second floor 16 forms the second position P2 of the second Fahrwegabschnitts 24 and also the first position P1 of the third travel section 26. The position marks are provided with a coded hole pattern (not shown). This makes it possible to associate the position mark and thus the individual track section 22, 24, 26 with an associated floor.

An acceleration sensor 30 and a position sensor 40 are arranged on the elevator car. The position sensor 40 interacts with the position marks 50 of the floors 15 to 18 and detects the respective floor position of the elevator car 14. In the present embodiment, the position sensor 40 comprises a light barrier. The elevator car 14 is further provided with a control unit 60, which evaluates the data determined by the accelerometer 30 and the position sensor 40. Finally, the elevator installation 10 comprises the control unit, a memory unit and a time recording unit (not shown). In the illustrated example, the position sensor 40, the control unit 60 and the acceleration sensor 30 are arranged in decentralized modules. Alternatively, these parts can be combined into a single module. This is inexpensive, since such an assembly may contain required operating units such as voltage and emergency power, data storage and interfaces. The elevator installation is set up in order to be able to carry out the method explained below.

In this method, the elevator car 14 is in the initial situation shown in Fig. 1 at the level of the fourth floor 18. The elevator car 14 is in the position shown at a standstill with a speed v ₀ with the value zero. After entering the elevator car, the user sets the desired destination call. In the present example, the user wants to be moved to the first floor 15. After discontinuation of the corresponding destination call, an elevator control sends a corresponding signal to a drive unit of the elevator installation 10, so that the elevator car 14 is accelerated out of the rest position. In order to achieve the desired destination of the user on the first floor 15 in the present case, the elevator car 14 must therefore cover a travel path 20 which comprises the first to third travel sections 22 to 26. During this operating run, the method steps explained below with reference to FIGS. 1 and 2 proceed. First, the speed v ₀ is detected at the first position P1 of the first track section 22 having the value zero. This can be done for example by a speed measuring device in the drive unit. Subsequently, with continuous movement of the elevator car 14 by means of the acceleration pickup 30, the acceleration a _{m (n)} is continuously measured and stored in successively connected measuring intervals of predetermined duration .DELTA.t, ie corresponding to a predetermined clock measuring frequency (see also FIG. 2). Upon reaching the second position P2 of the first track section 22 on the third floor 17, the position sensor 40 detects the position mark 50 and informs the control unit. Further, the number n of the measurement intervals for which the accelerations a _m ( _n ) for the first travel route section 22 have been detected and the time duration ΔT _ZF required for the elevator car 14 to move from the first position P <b> 1 to the second position P <b> 2 to get to the control unit.

Furthermore, the distance between the first position P1 and the second position P2 of the first track section 22 and the further track sections 24 and 26 are retrievably stored in the control unit. Likewise, the clock measuring frequency of the measuring interval .DELTA.t is stored in the memory unit. All values either stored in the control unit or currently determined are then processed to determine the correction value ^ε _{off rea} i ^{un, followed} by the determination of the current corrected speed v _cor according to the formulas given in claims 1 and 2. The value for the speed v _cor determined accordingly for the second position P2 is then set as the new value for the speed v ₀ for the first position P1 of the second travel section 24 (see also FIG. 2).

FIG. 2 shows a speed-time diagram (vt diagram) and an acceleration-time diagram (at diagram), FIG. 2 showing below the two diagrams the route sections 22, 24, 26 already indicated in FIG can be seen. The curve indicated in the speed-time diagram shows the exemplary course of the speed v over the time t, starting with the speed v _0, for example, on the fourth floor 18. By means of the velocity-time diagram of the integration of the speed profile indicated by the in the individual measurement intervals with time duration .DELTA.t determined mean acceleration values a _m (i), a _{m (2} ) to a _{m (n} ) (see at-diagram) the distance .DELTA.X _th calculated using determined in Fig. 2 formulas determined. In addition, in Fig. 2, the individual summands of the formula given in claim 2 for the theoretically calculated distance .DELTA.X _{th are} explained.

In accordance with the above procedure, the accelerations a _m ( _n ) are now detected at several measuring intervals along the second travel path section 24 by means of the acceleration pickup 30. As soon as the elevator car 14 has reached the second position P2 of the second travel path section 24, that is to say the second floor 16, the values for the number n of the measurement intervals and the time duration ΔT _ZF which the elevator car 14 has needed can be changed from the first position P1 to reach the second position P2 of the second travel section 24, are determined. On the basis of these values measured and calculated for the second track section 24, the new current corrected speed v _korr for the second position P2 of the second track section 24 can then be determined on the basis of the above formulas.

In the same way as already described for the second path section 24, the detection and measurement is made of the further values for the third path section 26. Thus, among other things, determined for the second path section 24 current velocity is v _corr as the new value for the velocity v ₀ set in the first position P1 of the third Fahrwegabschnitts 26.

Based on this method, a safe speed value can be determined v _corr so all of the following track sections and thus over the entire travel path 20, to obtain a more accurate compared with the prior art velocity value and sources of error are reduced further. Furthermore, the values stored in the memory unit for the distances .DELTA.X _{ZF can be} easily changed, whereby a simple adaptation of the resulting after the erection of the building subsidence and thus changes in these distances is possible.

Claims

claims

A method for determining the speed of a lift cage (14) movable along a track (20), wherein for a first track section (22) of the track between a first position (P1) and a second position

(P2) a speed v _{0 of} the elevator car (14) is detected at the first position (P1), a plurality of accelerations a _m ( _n ) of the elevator car (14) are detected in a plurality of measuring intervals .DELTA.t, a time period .DELTA.T _ZF detected If the elevator car (14) requires, in order to move from the first position (P1) to the second position (P2), a speed v _korr for the second position (P2) is determined as follows:

^V cor = ^V 0 + ^{At •} £ ^a m (n) ^~ ^{'' £} off, rec

where ε _{o # reα / is} a correction value obtained by comparing a real one

Distance (.DELTA.X _ZF ) between the first position (P1) and the second position (P2) and a theoretically calculated distance (.DELTA.X _th ) is determined, .DELTA.t is the duration of the measuring interval, a _m ( _n ) the detected accelerations in the Fahrwegabschnitt ( 22),

V _{0 is} the speed at the first position (P1), n is the number of measurement intervals for which the accelerations have been detected.

2. The method according to claim 1, characterized in that the correction value z _o ff _{, times} determined by: _ 2 - [AX _th - AX _ZP ]

^ off, real

AT ^ where

AX _th = AT _ZF - V _{0 +} ] JT

where z _{off real is} the correction value,

Δt is the duration of the measuring interval, a _m ( _n ) are the detected accelerations in the track section (22), ΔX _{th is} the theoretically calculated distance between the first position (P1) and the second position (P2), ΔX _{ZF is} the actual distance between the first position (P1) and the second position (P2),

ΔT _{ZF is} the time required for the elevator car (14) to move from the first position (P1) to the second position (P2),

3. The method according to claim 1 or 2, characterized in that between a first position (P1) and a second position (P2) of a second Fahrwegabschnittes (24) of the guideway (20) the speed v _corc for the second position (P2) of second Fahrwegabschnittes (24) is determined, wherein for the second position (P2) of the first Fahrwegabschnittes (22) determined speed v _{corr is set} as the speed v ₀ for the first position (P1) of the second Fahrwegabschnittes (24) and wherein .DELTA.t the Duration of the measuring interval is, a _m ( _n ) are the detected accelerations in the second travel section (24),

ΔX _{ZF is} a distance between the first position (P1) and the second position (P2) of the second travel section (24), ΔT _{ZF is} the time required for the elevator car (14) to move from the first position (P1) to the second position second position (P2) of the second travel path section (24), n is the number of measurement intervals for which the accelerations of the second travel path section (24) have been detected.

4. The method according to any one of claims 1 to 3, characterized in that the first position (P1) a first floor (15, 16, 17, 18) and the second position (P2) a second floor (15, 16, 17, 18) is assigned.

5. The method according to any one of claims 1 to 4, characterized in that the distance .DELTA.X _ZF between the first position (P1) and the second position (P2) of the respective track section (22, 24, 26) is stored in a control unit and retrieved becomes.

6. The method according to any one of claims 1 to 5, characterized in that the distance .DELTA.X _ZF for at least one track section (22, 24, 26) can be adjusted.

7. The method according to any one of claims 1 to 6, characterized in that each track section (22, 24, 26) are assigned a plurality of measuring intervals, wherein the measuring interval is determined by a predetermined clock measuring frequency and the clock measuring frequency, the duration of the measuring interval (.DELTA.t) certainly.

8. The method according to any one of claims 1 to 7, characterized in that for each position (P1, P2), a position mark (50) is provided which is detectable by a position sensor (40).

9. The method according to any one of claims 1 to 8, characterized in that a current driving speed (v _act ) of the elevator car is determined,

- n - ε _ofUeal

V ₀ the speed at the first position (P1) of the respective

Fahrwegabschnittes (22, 24, 26), £ _{Off, rea} i is the correction value of the last track section (22, 24, 26) is a _{m (n)} the currently detected accelerations in the respective track section (22, 24, 26), n is the number of measurement intervals for which the accelerations in the respective track section (22, 24, 26) have been detected.

10. The method according to claim 9, characterized in that the speed v _akt for controlling the startup of a floor (15, 16, 17, 18) or for monitoring the speed of the elevator car (14) is transmitted to the control unit.

1 1. A method according to any one of claims 1 to 10, characterized in that in the deviation of the correction _value z _{off> rml} or the speed v _corr or the speed v _act from a threshold by a predetermined value, a signal for emergency braking or maintenance delivered becomes.

12. The method according to any one of claims 1 to 1 1, characterized in that the speed v _{akt is} not determined or maintained when the amount of detected acceleration a _{m (n)} falls below a predetermined limit value a _G.

13. The method according to claim 12, characterized in that the limit value a _{G is} about 0.03 to about 0.05 m / s ² .

14. The method according to any one of claims 1 to 13, characterized in that the determined speed v _{0 is set} to a predetermined event or at a predetermined time to a reference value, in particular to zero.

15. Method according to claim 1, characterized in that a plurality of speed values are determined, wherein the speed _{v.sub.actu is} determined as a first speed _value according to one of the preceding claims, and wherein at least one second speed value is determined by means of own sensors and at Exceeding at least one of the determined speed values, an error is detected and a brake signal is output.

16. elevator installation (10) with an along a track (20) movable elevator car (14), wherein the track (20) at least one track section (22, 24, 26) with a first position (P1) and a second position ( P2), and wherein an acceleration sensor (30) for detecting the acceleration a _{m (n} ) of the elevator car (14) and a position sensor (40) for detecting the position of the elevator car (14) are provided on the elevator car (14), with a control unit in which the distance .DELTA.X _ZF between the first position (P1) and the second position (P2) for the at least one track section (22, 24, 26) is deposited, and with a time detection unit for detecting a time duration .DELTA.T _ZF , the elevator car (14) required to get from the first position (P1) to the second position (P2), wherein the accelerometer (30), the position sensor (40), the

Control unit and the time detection unit for implementing the method according to one of claims 1 to 15 are arranged.

17. elevator installation (10) according to claim 16, characterized in that in the area of the position (P1, P2) from the position sensor (40) detectable position mark (50) is provided.

18. Elevator installation (10) according to one of claims 16 or 17, characterized in that the first position (P1) has a first end of the track section (22, 24, 26) and the second position (P2) has a second end of the track section (22 , 24, 26).

19. elevator installation (10) according to one of claims 17 to 18, characterized in that the position mark (50) is a sheet-metal strip, preferably a coded sheet metal strip.

20. elevator installation (10) according to any one of claims 16 to 19, characterized in that a photoelectric barrier is provided as a position sensor (40).

21. Control unit with accelerometer for carrying out the method according to one of claims 1 to 15 or for use in an elevator installation according to one of claims 16 to 20.

22. Control unit with accelerometer according to claim 21 for retrofitting in an existing elevator installation.