The invention relates to a method and an arrangement for determining elevator data based on the position of an elevator cabin according to the independent claims.

The position of an elevator cabin in an elevator system is best determined directly using a sensor or encoder which is directly linked to the elevator cabin. This is however expensive since it is necessary to provide a supplementary arrangement for measuring the position of the elevator cabin.

Another approach is, as described exemplarily in the WO 2012/032020, to use an incremental rotary encoder connected with a pulley of the elevator system to determine the position of the cabin.

This method is not particularly satisfying, since the traction and suspension means of the elevator may stretch over time and due to the loading of the cabin, leading to a drift of the cabin position and consequently to stopping inaccuracy of the cabin. Slipping of the traction means may also cause inaccuracy in the determination of the position of the cabin.

In addition, when a cabin is reaching stopping at a floor, the cabin may be too fast or too slow. This may impede the rotary encoder of the drive or the control unit of the elevator system to properly control the elevator system and stop the elevator cabin such as the flag reading sensor lies in the middle of the flag marking, as suggested by WO 2012/032020. This also leads to a stopping inaccuracy of the cabin such that a step is present between the cabin floor and the building floor, said step being e.g. potentially dangerous for passengers of the elevator cabin.

It is therefore aim of the present invention to provide a method and an arrangement for the determination of elevator data based on the position of an elevator cabin by which stopping inaccuracy, drifting and/or slippage of the elevator cabin may be determined in a reliable way without the need of additional cost and maintenance intensive components.

The problem is solved with a method and an arrangement according to the independent claims. Dependent claims describe preferred embodiments of the invention.

The method according to the present invention is performed in an elevator system comprising an elevator cabin with a flag reading sensor. The elevator cabin is niovably arranged in a hoistway and can be moved by a drive over a traction sheave and at least one suspension means along the hoistway can be stopped at a plurality of stopping positions of the hoistway. Alternatively, the elevator system can be operated by means of an hydraulic traction means. Each stopping position has a flag marker with a known flag height

F. The movement of the elevator cabin is determined by a control unit connected to an encoder.

Means for measuring movements of the elevator cabin can be preferably an encoder. The encoder is preferably a rotary encoder, in particular an incremental rotary encoder, and is preferably coupled to the traction sheave.

In order to indirectly determine the stopping inaccuracy at the stopping position, the travelled distance D of the elevator cabin between the stopping position and the flag edge passed by the flag reading sensor when the elevator cabin is leaving the stopping position for a subsequent ride is measured by the control unit, This is done using the signals of the encoder and the flag reading sensor. Alternatively other door zone sensors may be used instead of said flag reading sensor. instead of flag markers other door zone markers are also conceivable. Door zone markers may be, for example, stripes of reflective tape or magnet bands each having a given height which can be sensed or read by a magnetic sensor.

As a next step, the stopping inaccuracy I can be determined by taking into consideration the value F/2-D. With this value or just with the value for D it can be determined whether the stop is over or below the middle of the flag.

Preferably, the stopping inaccuracy I is determined according to I=ABS(F/2-D), wherein ABS is the absolute value of the difference between the half of the flag height F and the measured travelled distance D, It is assumed that, as cited above, the control unit controls the elevator cabin such that it stops with the flag reading sensor in the middle of the flag. If this is not the case, this should be taken into consideration when determining the stopping inaccuracy I. It is further assumed that the spatial relationships between position of the flag markers and the building floor as well as the relationship between flag reading sensor as the preferred door zone sensor, and cabin floor are not variable.

Preferably, the measured stopping inaccuracy I is taken into account when stopping the elevator cabin during a further ride.

This is done preferably by storing the determined stopping inaccuracy I, preferably with other data related to the elevator such as a load of the elevator cabin, the ride path (from the stopping position n to the stopping position m) as well as a time stamp of the ride, in a storage means connected to the control unit. By doing this, the control unit can also continuously monitor the evolution of the stopping inaccuracy (and/or based on the measured travelled distances D) and based on the determined stopping inaccuracies I (and/or based on the measured travelled distances D) determine a drift or slippage of the elevator cabin by taking into account the time interval between car rides. Whether drift issues occur or not can be determined when subsequent trips of the elevator car are done right after the former one. Whether slippage issues occur or not can be determined when subsequent trips of the elevator car are done after a long standstill period (e.g. night sleep of the car). So the respective data can be used as an example for determining if the suspension means have reached a maximal allowed stretching over time or after a long standstill period, and/or for determine if slipping of the suspension means occurs. If the slipping exceeds a predefined threshold value, then may be an auto-call of service is triggered.

It is therefore furthermore possible to correct the stopping method of the elevator cabin in order to avoid a step between the elevator floor and the building floor. Preferred storage means are non-volatile computer storage means such as hard disk drives, solid state drives, memory cards, etc. The storage means are not necessarily physically present in the elevator system but may be remote arranged and connected to the control unit via a data connection, such as the internet.

A possible way to determine whether a drift occurred is to evaluate if the subsequent trip is done right after the former one or the two trips are separated by a long standstill time. By making separate statistics for subsequent trips and trips separated by long time intervals and by analyzing these statistics will allow to decide if the elevator had drifting issues, slippage issues or both.

Preferably, the travelled distance D and/or the stopping inaccuracy I of the elevator cabin is determined and stored for every of the plurality of the stopping positions. This takes into account that a stopping inaccuracy, which may be caused by stretching of the suspension means may be proportional to the length of the suspension means suspending the cabin. In other words, stretching of the suspension means is more pronounced when the suspension means are long, meaning that the elevator cabin is at a low stopping position. The stopping inaccuracy I can therefore be determined for each of the stopping positions such that a correction of the stopping method can be performed for every stopping position separately.

Preferably, the travelled distance D and/or the stopping inaccuracy I of the elevator cabin is determined and stored for every direction of travel of the elevator cabin. This takes into account that the travelled distance and/or the stopping inaccuracy at a given stopping position may be different depending of the travelling direction (e.g. upward or downward) of the elevator cabin. Preferably, this is done, as cited above, for each stopping position separately.

Preferably, the travelled distance D and/or the stopping inaccuracy I of the elevator cabin is only determined if a load L of the elevator cabin determined by a load sensor is within a given range. Since stopping accuracy may be related to the load L of the elevator cabin, it is useful to compare the stopping inaccuracy only if the load L of the elevator cabin is within a certain range of comparable loads. As an alternative, the stopping inaccuracy I can be determined and stored together with the measured load L in order to allow a correlation between stopping inaccuracy I and load L as well as other factors such speed of the cabin etc. as described above.

Preferably, the given load range is calculated according to L ± x, wherein x is a factor dependent on the elevator system, the elevator car and/or the suspension means type. Preferably, the travelled distance D and/or the stopping inaccuracy I of the elevator cabin is only determined if an elevator cabin ride takes place within a given time interval t. Therefore, the method can be used to determine stopping inaccuracy I only if rides of the elevator cabin take place within a short period of time, while if the elevator cabin stands still for long periods, the stopping inaccuracy I is not determined or is not taken into consideration when correcting a stopping method. However, the value for D or for ABS(F/2- D) may be used cabin with an elevator cabin stands still for long periods in order to be able whether drifting occurred or not. By making separate statistics for subsequent trips and trips separated by long time and by analyzing these statistics will allow to decide if the elevator has drifting issues, slippage issues or both.

The invention further solves the problem with an arrangement according to claim 10.

The arrangement comprises, for example, a flag reading sensor for an elevator cabin, flag markers with a flag height F for every of a plurality of stoppmg positions of a hoistway and means, typically an encoder, for measuring movement of the elevator cabin. The elevator cabin is movabiy arranged in the hoistway by means of at least one suspension means and a traction sheave coupled with a drive. The drive for moving the elevator cabin preferably is coupled to a traction sheave and at least one suspension means The arrangement further comprises a control unit for controlling the elevator system connected to an encoder or other means for measuring movements of the elevator cabin. The control unit is able of measuring a travel distance D of the elevator cabin between the stopping position and a flag edge when the elevator cabin is leaving a stopping position by means of the encoder and the flag reading sensor and then can determine a stopping inaccuracy I or an other parameter which refers to the position of an elevator cabin.

Preferably, the stopping inaccuracy is determined according to I=ABS(F/2-D), wherein ABS is the absolute value of the difference between the half of the flag height F and the measured travelled distance D.

A method as cited above is preferably used with the arrangement according to the present invention. Preferably, the encoder is a rotary encoder, in particular an incremental rotary encoder, preferably coupled to the traction sheave. It is therefore possible to provide an accurate determination of stopping inaccuracy without the need of means for determining the position of the elevator cabin directly (e.g. without the need of a position encoder on the elevator cabin).

Preferably, the control unit is further connected to storage means for storing the determined stopping inaccuracy I.

Preferably, the control unit is further connected to a load sensor for measuring a load L of the elevator cabin.

As cited above regarding the method, the stopping inaccuracy may be stored in storage means in order to determine changes over time. This can be done taking into consideration other factors such as a direction of travel, a stopping position, a time between rides, a load L of the cabin etc.

Further advantages of the invention will be better understood with the aid of the following description together with the Figures. It is shown in

Fig. 1 a schematical view of an elevator system;

Fig. 1A a detailed view of the detail A of Figure 1 ;

Fig. 2 a schematical view of the detail A of Figure 1.

In Fig. 1 an elevator system 1 with a hoistway 2 is shown. An elevator cabin 3 and a counterweight 4 are movab!y arranged in the hoistway 2 and connected to each other by means of a suspension means, in this case a steel rope 5. The steel rope 5 is conducted over a pulley 6 and a traction sheave 9 connected to an electric motor 8. The traction sheave 9 has an incremental rotary encoder 12 connected to it in order to detect movement and of the traction sheave 9 and therefore movement and direction of travel of the elevator cabin 3.

A control unit 10 is also present and is connected amongst others with the electric motor 8 and the incremental rotary encoder 12. A data connection 1 7 allows remote connection and/or diagnosis of the elevator system 1 .

Each floor 7, T and 7" of the hoistway 2 has a building floor 18, which corresponds to a stopping position of the elevator cabin 3. Accordingly, a cabin floor 3.1 of the elevator cabin 3 is aligned with the respective building floor 18 when the elevator cabin 3 is standing still at a floor 7, T or 7", In Fig, 1, the elevator cabin 3 has stopped at floor 7'.

In order to correctly stop the cabin at the desired floor 7', every floor building 18 is marked with a flag marker 13 with a flag height F. However, it would also be conceivable to use other door zone markers or other markers in the hoistway. The elevator cabin 3 has a flag reading sensor 15 as a preferred example of a door zone sensor. Flag marker 13 and flag reading sensor 15 are arranged with respect to each other such that when the building floor 18 and the cabin floor 3.1 are perfectly aligned, this means that building floor 18 and cabin floor 3.1 are at the same height, the flag reading sensor is positioned exactly in the middle of the flag marker 13. In other words, the distance between the flag reading sensor 15 and a flag edge 14, in this case the lower flag edge, is exactly half of the height F of the flag marker 13.

When an elevator cabin 3 is moving to the desired floor 7', e.g. moving upwards, the control unit 10 can estimate the position of the elevator cabin by means of the incremental rotary encoder 12.

In addition, the flag reading sensor 15 may be used when passing a flag marker 13 to correct or increase the precision of the data from the rotary encoder 19.

When arriving at the desired floor 7', the flag reading sensor 13 detects the flag edge 14 and sends a signal to the control unit 10. The control unit 10 uses the rotary encoder 12 and the drive 8 to move the elevator cabin 3 for a further travel of half the height F of the flag marker 13 (F/2), such that the flag reading sensor 15 is exactly positioned in the middle of the flag marker 13 and the building floor 1 8 and the cabin floor 3.1 are aligned with each other.

It is however possible that due to slipping or stretching of the steel rope 5 or due to wrong speed of the elevator cabin 3, that stopping does not occur at the desired stopping posi- tion. Such a case is schematically shown in Fig. 2.

The control unit 10 can determine this stopping inaccuracy in an indirect way when moving the cabin for a further ride.

If the elevator cabin 3 is moved upward within a given time gap t from the last ride, and the load L of the elevator cabin 3, measured by means of a load sensor 1 1 , is within a given range L ± x, the travelled distance D from start until the detected end of the flag marker 13 (in this case the upper flag edge) is measured by means of the rotary encoder 12. A stopping inaccuracy I is then determined according to I=(F/2-D). Taking into account the direction of travel of the elevator cabin 3, the control unit 10 can therefore determine if the cabin was positioned correctly during the last stop or if a step (upward or downward) was present between the building floor 18 and the cabin floor 3.1. In the configuration shown in Fig. 2, the cabin floor 3.1 would be higher than the building floor 7.

The determined stopping inaccuracy I is then used to correct a distance/speed profile used to control the elevator cabin in order to increase the stopping precision of the elevator cabin 3.

The determined stopping inaccuracy is preferably stored in a storage 16 of the control unit 10 and also used to determine if stopping inaccuracy of the elevator system 1 is increasing over time and thus detect a drift of the elevator cabin 3. The detected drifting may be then compared with a maxima! drifting threshold, whereby if the detected drift is above the threshold, an alarm for a technician requesting inspection or the like may be generated, and sent to a maintenance center over the data connection 17. For determining a slippage only values for the travelled distance D and/or the stopping inaccuracy I of the elevator cabin 3 if an elevator cabin ride takes place exceeds a given time interval t two trips are separated by a long standstill time are used or taken into consideration for the determination of the slippage. This long time interval t can be 2 hours, preferably 4 hours or most preferably 6 hours (e.g. night sleep of the car).