Patent Description:
Elevator service gets interrupted due to a failure in a power supply to an elevator system. In an unfavorable situation an elevator car with passengers gets stuck between two floors and the situation needs to be solved somehow especially if the failure in the power supply continues a long period of time.

In some implementations the elevator system may be equipped with energy storages, such as batteries, configured to store an amount of energy allowing a transport of the elevator car to a floor under so-called rescue drive operation. The size of the energy storage is optimized, and the goal is to apply as small energy storages as possible to minimize their size and cost as well as to minimize their effect in overall design of the elevator system.

In a document <CIT> it is disclosed a prior art solution for operating an elevator in an event of power failure.

In order to enable the optimization of the energy storages there is a need to introduce novel approaches targeting to select an optimal path for rescue drive in view of an energy consumption at least in part.

An object of the invention is to present a method, an apparatus, an elevator system, and a computer program for selecting a travel direction of an elevator car.

The objects of the invention are reached by a method, an apparatus, an elevator system, and a computer program for selecting a travel direction of an elevator car as defined by the respective independent claims.

According to a first aspect, a method for selecting a travel direction of an elevator car for a rescue drive is provided, the method comprises:.

The amount of energy required to cause a movement of the first reference distance or a movement of the second reference distance may be derived from data indicative of an input current of an electric motor configured to cause the respective movement.

Further, the estimated position of the elevator car may be determined based on at least one of the following: data indicative of a position of the elevator car obtained from at least one sensor; position data of the elevator car stored in data storage. For example, the estimated position of the elevator car may be determined from the position data stored in the data storage by selecting the piece of data as the data for the estimated position which is stored to the data storage most recently prior to an event that caused the rescue drive.

The estimating of the amount of energy required to move the elevator car from its estimated position to the next landing in the first direction or to the next landing in the opposite direction to the first direction may be performed by estimating an amount of energy needed to generate a torque to the traction sheave to move the elevator car to respective directions.

The step of estimating the amount of energy required to move the elevator car from its estimated position to the next landing in the first direction or in the opposite direction to the first direction may comprise a determination of information indicative a change in balance of the elevator system over a first path from the estimated position of the elevator car to the next landing in the first direction and over a second path from the estimated position of the elevator car to the next landing in the opposite direction to the first direction.

Still further, the method may further comprise:.

The selection of the travel direction may comprise a generation of a control signal to an elevator drive to cause a generation of a control signal to the electric motor.

According to a second aspect, an apparatus for selecting a travel direction of an elevator car for a rescue drive is provided, the apparatus is configured to execute the method according to the first aspect as defined above.

According to a third aspect, an elevator system is provided the elevator system comprising an apparatus according to the second aspect as defined above.

According to a fourth aspect, a computer program is provided, the computer program comprising instructions to cause the apparatus according to the second aspect as defined above to carry out the method according to the first aspect as defined above.

<FIG> illustrates schematically an elevator system <NUM> according to an example embodiment into which a functionality according to the present invention may implemented to. The elevator system <NUM> as disclosed in <FIG> may comprise an elevator car <NUM> arranged to be moved or movable in an elevator shaft <NUM> e.g. along guide rails mounted in the elevator shaft <NUM>. The moving of the elevator car <NUM> may be implemented by a hoisting rope or belt <NUM> in connection with a counterweight <NUM> over a traction sheave <NUM> or the like. The operation of the elevator system <NUM> may be achieved by controlling a rotation of the traction sheave <NUM> with an electric motor <NUM> and elevator brakes <NUM>. Moreover, the electric motor <NUM> may be controlled with a frequency converter <NUM> configured to provide an input current to the electric motor <NUM> to cause the electric motor <NUM> to operate in a controlled manner. An overall controlling of the elevator system may be performed by an apparatus <NUM> corresponding e.g. to an elevator controller which, among other functionalities, receives a feedback from other elevator entities, such as from call giving devices and so on, so as to generate the control signals to the frequency converter <NUM> in accordance with the feedback.

For the purpose of describing at least some embodiments of the present invention the elevator system may also comprise a number of sensors <NUM> residing in the elevator shaft <NUM> and/or in elevator car <NUM>, for example. The sensors <NUM> may be of any type suitable for generating measurement data from which it is possible to derive an estimation of a position of the elevator car <NUM> in the elevator shaft <NUM>. The estimation of the position shall be understood in a broad manner, and it may mean either an exact position or some inaccurate estimation of the position for the purpose of the present invention as is discussed in the forthcoming description. Some non-limiting examples of the sensors <NUM> applicable for generating the measurement data indicative of the position of the elevator car <NUM> may be contact sensors mounted in the shaft configured to interact mechanically, electrically, magnetically, or optically with a counterpart residing in the elevator car <NUM> in response to that the elevator car <NUM> passes by the respective sensors <NUM>. Alternatively or in addition, the number of sensors <NUM> may be mounted to the hoisting machine system, such as to the electric motor <NUM>. For example, measurement data may be obtained from the motor encoder based on which the estimate on the position may be determined. A non-limiting example of a sensor <NUM> associated to the elevator car <NUM> may be a barometer providing measurement data indicative of a pressure experienced in varied locations in the elevator shaft <NUM> from which it is possible to generate the estimate. Any other sensor type may also be applied in the context of the present invention for obtaining measurement data indicative, either directly or indirectly, of the position of the elevator car <NUM>.

The elevator system <NUM> is supplied with power from mains current in normal operation situations. In order to secure power supply to the elevator system <NUM> the elevator system in accordance with the present invention may be equipped with an energy storage <NUM> which may be arranged to supply power to the elevator system <NUM>, or at least to at least some entities of it, in special situations, such as in an emergency situation. The energy storage <NUM> suitable to store electrical energy may e.g. be a battery implemented in any known manner. The supply of the energy source <NUM> may be arranged so that the supply of the electrical energy may be automatically initiated in response to a detection that the power supply from the mains fails or the supply may be arranged by implementing a predefined functionality to the energy storage, or to the elevator system, so as to enable the supply of energy at a predefined event. The supply of the electrical energy may be arranged to a power network of the elevator system, or only to critical entities of the elevator system in order to perform a method as is described in the forthcoming description. In <FIG> the power supply is arranged through the frequency converter <NUM> so that at least the frequency converter <NUM> and the electric motor <NUM> are energized.

As already mentioned, the elevator system <NUM> comprises an apparatus <NUM> configured to perform at least part of a control operations of the elevator system <NUM> wherein the apparatus <NUM> may refer to an elevator controller. The apparatus <NUM> is communicatively connected to at least some entities of the elevator system <NUM> so as to deliver control signals thereto and receive data from the elevator system <NUM>, such as the sensor data. The apparatus <NUM> is at least configured to control an operation of the elevator drive system comprising at least both the frequency converter <NUM> and the electric motor <NUM>. The apparatus <NUM> is also arranged to receive power from the energy storage <NUM> in case of a power failure from the mains. For sake of completeness it shall be understood that even if the apparatus <NUM> and the frequency converter <NUM> are described and illustrated in <FIG> as separate entities and devices, their functionalities may also be integrated into a single device if seen convenient from an implementation point of view.

As known, the elevator system is arranged to travel between a plurality of landings <NUM>, or floors, so as to transport passengers and any other load between the landings <NUM> served by the elevator system <NUM>. An energy consumption of the elevator system <NUM> during a ride is also dependent on so-called balancing of the elevator system <NUM> in question. The balancing refers to a selection of an elevator car <NUM> and the respective counterweight <NUM> as well as the effect of the weight of the rope <NUM> on both sides divided by the traction sheave <NUM>. The elevator system <NUM> may be in balance at some position of the elevator car <NUM> in the elevator shaft <NUM> i.e. when the weights on both sides with respect to the traction sheave <NUM> are equal i.e. the elevator car <NUM> does not move even if elevator brakes are inactivated. On the other hand, from the perspective of the elevator car <NUM>, the balancing situation may be overbalanced or underbalanced at some other position of the elevator car <NUM> in the elevator shaft <NUM> due to the different portion of the rope <NUM> on each side divided by the traction sheave <NUM>. The overbalanced situation refers to that the elevator car <NUM> travels downwards if it is allowed to move freely and in the underbalanced situation the elevator car <NUM> travels upwards. Moreover, the elevator system <NUM> may be designed so that the system is in balance only at one end of the travel path in the elevator shaft <NUM>, or even so that there is no position in which the elevator system <NUM> is in balance. The balancing situation may be manipulated with so-called compensation ropes mounted below the elevator car <NUM> and the counterweight, respectively. By applying the compensation ropes it is possible to manipulate an amount of power needed to cause the movement of the system in various positions in the elevator shaft in a known manner. Still further, in at least some elevator implementations an effect of a weight of an elevator travelling cable may be taken into account in the consideration of the balancing together with the above mentioned other items, i.e. the elevator car <NUM>, the counterweigh <NUM>, the elevator rope <NUM>, and the compensation ropes if any.

The present invention provides a solution for selecting an optimal direction for a rescue drive in case the operation of the elevator system <NUM> is halted due to a power failure. A method according to an example embodiment is schematically illustrated in <FIG> wherein the method provides a solution for selecting a travel direction of an elevator car <NUM> for a rescue drive, or similar. In accordance with the example embodiment the method may be performed by a computing unit, such as a controller, as is described in the forthcoming description. For example, the entity configured to perform at least part of the method may be the apparatus <NUM> configured to perform at least part of the control operations of the elevator system <NUM>. The method may be initiated by generating a first estimate <NUM> indicative of a total energy consumption of causing the elevator car <NUM> to travel from its estimated position to a next landing in a first direction and by generating a second estimate <NUM> indicative of a total energy consumption of causing the elevator car <NUM> to travel from its estimated position to a next landing in an opposite direction to the first direction. In other words, the apparatus <NUM> may determine, based on any applicable data it has access to, an estimated position of the elevator car <NUM> in the elevator shaft <NUM> where the elevator car <NUM> has stopped due to a specific situation, such as due to a power failure. In response to knowing the estimated position of the elevator car <NUM>, the apparatus <NUM> may be configured to generate a first estimate <NUM> indicative of a total energy consumption of causing the elevator car <NUM> to travel from its estimated position to a next landing in a first direction. Further, the apparatus <NUM> is configured to generate the second estimate indicative of a total energy consumption of causing the elevator car <NUM> to travel from its estimated position to a next landing in the opposite direction to the first direction. In other words, the apparatus <NUM> is configured to generate the first and the second estimation by utilizing the information on the estimated position of the elevator car <NUM> at least in part. The term total energy consumption in the context of the estimations shall be understood to cover a selected number of sources included in the generation of the total energy consumption as is described in the forthcoming description. Further, the first direction and the second direction opposite to the first direction in the context of the elevator system <NUM> substantially refer to vertical directions the elevator car <NUM> is arranged to travel in the elevator shaft <NUM>. For example, the first direction may be vertically upwards whereas the second direction may then be vertically downwards, or vice versa. The generations of the first estimate and the second estimate <NUM>, <NUM> may be performed concurrently at least in part or subsequently to each other.

In response to that the first estimate and the second estimate are generated <NUM>, <NUM> the apparatus <NUM> is configured to compare <NUM> the first estimate and the second estimate together. The aim of the comparison <NUM> is to determine the travel direction to the elevator car <NUM> to the next landing wherein an energy consumption of the travel is minimized. For sake of clarity, the comparison step <NUM> may be implemented so that the first estimation and the second estimation is compared together and the information on the one being smaller is obtained.

In response to the comparison <NUM> the apparatus <NUM> is arranged to select <NUM> the travel direction for the rescue drive corresponding to an estimate being smaller among the first estimate and the second estimate. Hence, the apparatus <NUM> maintains the information linking the total energy consumption to each of the direction and the respective travel direction and generates as an output of the selection step <NUM> data indicative of the travel direction. For example, the apparatus <NUM> may be configured to generate a control signal to power generation means, such as to a frequency converter <NUM> so as to control an electric motor of the elevator system <NUM>, to cause a travel of the elevator car <NUM> to the selected travel direction in the elevator shaft <NUM>.

In the forthcoming description it is provided further details on the generation of the estimate <NUM>, <NUM> indicative of the total energy consumption for causing the elevator car <NUM> to travel from its estimated position to the next landing. The details provided herein, and as illustrated in <FIG>, are applicable to both the generation of the first estimate <NUM> and the generation of the second estimate <NUM>. In accordance with the invention the total energy consumption may consists of at least two aspects. For the first aspect an amount of energy required to cause the elevator car <NUM> to move to a selected direction is determined <NUM> and the determination is performed by controlling the elevator car <NUM> to move a reference distance to the selected direction. In addition, a second aspect related to the total energy consumption in accordance with the example embodiment is that an amount of energy required to move the elevator car <NUM> from its estimated position to the next landing in the selected direction is estimated <NUM>. Regarding the first aspect and its implementation the apparatus <NUM> may be configured to generate a control signal to the power generation means to instruct the power generation means to generate a force to move the elevator car <NUM> the reference distance to the selected direction wherein the selected direction may first be the first direction or the second direction. In response to the movement of the elevator car <NUM> the reference distance to the first direction the apparatus <NUM> may be configured to generate another control signal to the power generation means to instruct the power generation means to generate a force to move the elevator car <NUM> another reference distance to the second direction opposite to the first direction. The movement of a reference distance to the second direction may be initiated from the position the elevator car <NUM> resides after the movement of a reference distance to the first direction, or the elevator car <NUM> may be returned to the starting position, or a reference position, i.e. to the position from where the movement to the first direction was initiated, before the movement to the second direction is instructed. Advantageously, the selection of the starting point for the second direction is taken into account in the estimation of the energy consumption in the manner as described in the forthcoming description. In other words, the elevator car <NUM> is caused to travel to both directions opposite to each other reference distances defined for the travel directions. The reference distance in the first direction and in the second direction may be the same or differ from each other. At least one aim of the movement of the elevator car <NUM> to the first direction and to the second direction is to determine how much energy is required to initiate the travel to the respective directions. As a non-limiting example of the reference distance may be some centimeters which allows a determination of the required energy e.g. by deriving it from data indicative of an input current of an electric motor configured to cause the force for the respective movement. For example, the derivation of the input current of the electric motor may be based on measurements of one or more signal values indicative of current and/or voltage applied in the elevator drive system. In other words, commonly known equations may be applied to the determination of the required energy. Further, advantageously the reference distances are small in order to avoid an unnecessary consumption of the energy in the context of determining
As regards to the second aspect an estimation is made <NUM> on an amount of energy required to move the elevator car <NUM> from its estimated position to the next landing. Such an estimation is performed both to the first direction and to the second direction, separately. The estimations may be performed mathematically e.g. based on the estimated position of the elevator car <NUM> and its travel distance to the next landing in the first direction and in the second direction. Naturally, at least some parameters of the power generation means, such as input current and the duration of provision the input current to reach the respective landings may be applied to. Alternatively or in addition, the estimations may be based on information obtained from a travel history of the elevator car <NUM> e.g. so that a corresponding section from the travel path of the elevator car <NUM> is determined and the energy consumption used for the respective section, or sections, are determined and obtained so as to receive the estimations of the amount of energy required to cause the elevator car <NUM> to move to the respective landings.

In response to the generation of the results from the steps <NUM> and <NUM> to the first direction and to the second direction as described the apparatus <NUM> may be arranged to sum up <NUM> the amount of energy required to cause the elevator car to move to the selected direction and the amount of energy required to move the elevator car <NUM> from its estimated position to the next landing in the same selected direction for generating the respective estimate. For sake of clarity, the sum up <NUM> is performed separately to the determined terms in the steps <NUM> and <NUM> with respect to the first direction and to the second direction. Hence, the apparatus <NUM> may be configured to associate the terms with respect to the travel directions so that the amount of energy required to cause the elevator car <NUM> to travel in a direction is summed up <NUM> with the estimation of an amount of energy required to travel to the next landing in the same direction so as to generate the first estimate and the second estimate for the comparison <NUM>.

In some example embodiments of the invention the determination of the estimated amount of energy required to move the elevator car <NUM> to the landing in question is performed by taking into account information indicative of a balance of the elevator system <NUM> at the position the elevator car <NUM> resides. Further, preferable the information of the balance of the elevator system <NUM> is taken into account over the travel to the respective distances. This may be advantageous since the balance changes during the travel since the mutual positions of the elevator car <NUM> and the counterweight <NUM> change during the run. This is due to that the weight of the hoisting rope <NUM> on both sides of the traction sheave <NUM> changes as the length of the rope <NUM> varies in the respective sides. In other words, the balance may vary during the travel which, in turn, may have effect on the required energy to move the elevator car <NUM> to the respective landings.

As a non-limiting example the information on the balance may, in accordance with an embodiment, be taken into account in the evaluation of the required energy to cause the elevator car <NUM> to move from its estimated position to the next landing in the first direction or in the second direction by estimating mathematically an energy needed to generate a cumulative torque of a traction sheave <NUM> of the elevator over the distance from the position of the elevator car <NUM> to the landings in both directions. The cumulative torque may be mathematically estimated by obtaining a load information of the elevator car <NUM> (e.g. from weight sensors positioned in the floor of the elevator car <NUM>), a position of the elevator car <NUM> as well as weights of any other relevant entities, such as a changing weight of the elevator rope with respect to the position of the elevator car <NUM> on both sides of the traction sheave <NUM> as well as changing weights of compensation ropes on both sides in accordance with the position of the elevator car <NUM> and take such pieces of information into account over the travel path to the evaluated directions to evaluate the cumulative torque, and, thus, the energy consumption to both directions. For example, the energy needed to generate the cumulative torque may e.g. be derived from an input current needed to be supplied to the electric motor <NUM> to generate the cumulative torque to the traction sheave <NUM> as estimated. Naturally, the same may be evaluated based on control signals generatable by the drive system, such as the frequency converter <NUM>.

As disclosed in the foregoing description the estimation of the amount of energy required to move the elevator car to the respective landing is based on an estimated position of the elevator car <NUM> in the elevator shaft <NUM>. The estimation of the position, i.e. the estimated position, may refer to an exact position of the elevator car <NUM> or to an estimation of the position with an acceptable accuracy, such as at least a knowledge of the landings between which the elevator car <NUM> resides. For example, the estimated position of the elevator car <NUM> may be obtained from a sensor configured to generate data indicative of the position of the elevator car <NUM> or from data storage configured to store position data of the elevator car <NUM>. In the former case, the sensor may be provided with power from energy storage even during the power failure from the mains in order to receive data indicative of the position of the elevator car <NUM>. In the latter case a processing entity of the apparatus <NUM> may be configured to determine the estimated position of the elevator car <NUM> from position data stored in the data storage. The determination may be performed by selecting the piece of data as the data for the estimated position which is stored to the data storage most recently prior to an event that caused the rescue drive. Such an approach is based on an arrangement that in response to the power failure an input of data to the data storage is canceled and only the data stored prior to the power failure, or a similar event, may be found from the data storage and the last stored piece of data may be identified. For example, the stored data may origin from one or more sensors suitable of generating data indicative of the position of the elevator car <NUM>, or may store data obtained from the electric motor, such as from an encoder therefrom, based on which data the position of the elevator car <NUM> may be determined. The data may e.g. be indicative of the position, a speed, or an acceleration of the elevator car prior to the unexpected stop. Furthermore, a determination of the position of the elevator car <NUM> may take into account other data stored in data storage, and accessible therefrom, such as information on a deceleration of the elevator car <NUM> when the elevator car <NUM> is instructed to stop due to the specific situation e.g. by applying an emergency stop mechanism. Hence, the travel distance over the deceleration may be determined and added to the latest known position to generate the estimation of the position. Further aspects, such as the load of the elevator car <NUM>, may also be taken into account for determining the travel distance during the deceleration before the stop. Alternatively or in addition, the estimation of the position of the elevator car <NUM> may also comprise a step in which an accuracy of the estimation in an implementation in which there is only information available on a landing the elevator car <NUM> passed by at the last time before the stop is improved by evaluating a time after the detection of the bypass of the landing and based on that an estimation is made how long the elevator car <NUM> may have traveled during the determined time to the travel direction before the stop. Adding that distance to the position of the landing, an estimation of the position of the elevator car <NUM> may be generated. All in all, the estimation of the position with a predefined accuracy may provide needed information to determine a travel distance to a next landing in a first direction and another travel distance to a next landing to a second direction being opposite to the first direction. Hence, in addition to the estimation of the position of the elevator car <NUM> the apparatus <NUM> have access to data defining positions of the landings in a manner that travel distances may be determined in any of the manners as described.

As an outcome of the method as described so far is the direction towards which the elevator car <NUM> shall be moved in order to consume as little energy as possible, or at least less than to move the elevator car <NUM> to the opposite direction. The information on the direction is based on the generated estimate, or estimation, indicative of the total energy consumption of causing the elevator car to travel from its estimated position to a respective landing. In view of this, an embodiment of the invention may comprise a further step of determining an amount of energy available from an energy source <NUM> for the rescue drive, and then determining if the amount of energy available from the energy source <NUM> exceeds the estimate indicative of the total energy consumption corresponding to the selected travel direction. In response to a detection that the amount of energy available from the energy source <NUM> for the rescue drive exceeds the estimate indicative of the total energy consumption corresponding to the selected travel direction an indication of an allowance to initiate the rescue drive to the selected travel direction is generated. This kind of approach is arranged to confirm that the elevator car <NUM> really reaches the landing in the selected direction.

Moreover, a further aspect to determine, prior to an initiation of the rescue drive, may be that the energy storage is capable of providing a peak power occurring at start when the movement is initiated and/or at the end of the drive when braking the elevator car <NUM> to stop at the landing. This may e.g. be determined so that it is confirmed that the energy storage is capable of providing necessary current level to initiate the travel as well as to allow the braking to establish the required peak power. More specifically, this approach may be implemented so that the apparatus <NUM> configured to perform the method is configured to determine a first peak power required by elevator car <NUM> to travel from its estimated position to the next landing in the first direction and to determine a second peak power required by elevator car <NUM> to travel from its estimated position to the next landing in the opposite direction to the first direction. The determinations of the peak powers, respectively, may be performed so that required peak powers for initiating the travel to the respective directions are determined with the movements of the elevator car controlled for determining the first and the second estimates of the total energy consumption as already described. The remaining part of the required power may be estimated mathematically by taking into account the travel distance to the respective floors (e.g. evaluating that the required power is liner over the travel distance) and estimating the required power to perform the braking e.g. based on history data or similar. By summing up these items the required peak powers to both directions may be estimated and determined. In response to the determinations of the peak powers each of them may be compared to a reference value. The reference value may be dependent on one or more characteristics of the energy source, i.e. its capability to provide the power, and the information on the reference value may be stored in a memory accessible to the apparatus in order to obtain the reference value for the comparison. Upon the comparison and its outcome the travel direction selected based on the comparison of the first estimate and the second estimate of the total energy consumption for the rescue drive may be confirmed upon a detection that a determined peak power to a same travel direction as the selected travel direction is below the reference value. In other words, if the required peak power may be provided the selection of the travel direction based on the estimates of the total energy consumption of the elevator car may be confirmed. On the other hand, if it turns out in the comparison of the peak powers that a determined peak power to a same travel direction as the selected travel direction based on the comparison of the first estimate and the second estimate for the rescue drive exceeds the reference value, the travel direction in question may be prevented. In other words, the travel direction is prevented since the energy source cannot provide the necessary power throughout the travel even if it stores enough energy to the respective travel. Naturally, in the latter case it is to be confirmed that the other direction is possible in terms of power and energy consumption in order to allow the travel to that direction. For sake of clarity it is worthwhile to mention that the estimation of the peak powers and the conclusions based on the estimation as described herein may be performed at least partly concurrently to the evaluation of the total energy consumption. Hence, at least one of the travel directions may be prevented based on the peak power estimation prior to that the selection of the travel direction based on the total energy consumption is concluded.

Still further, the selection of the travel direction may, in some embodiments, also comprise a generation of a control signal to an elevator drive to cause a generation of a control signal to the electric motor to initiate the rescue drive.

For sake of clarity it is worthwhile to mention that the landings called as the next landings in the first and the second direction do not necessarily refer to the next physical landings, but the ones defined to be used for rescue operations. Hence, the determinations of the total energy consumption are performed with respect to those next landings.

An example of an apparatus <NUM> configurable to perform the method as described is schematically illustrated in <FIG>. For sake of clarity, it is worthwhile to mention that the block diagram of <FIG> depicts some components of an entity that may be employed to implement a functionality of the apparatus <NUM>. The apparatus <NUM> comprises a processor <NUM> and a memory <NUM>. The memory <NUM> may store data, such pieces of data as described but also computer program code <NUM> causing the safety operation in the described manner. The apparatus <NUM> may further comprise a communication interface <NUM>, such as a wireless communication interface or a communication interface for wired communication, or both. The communication interface <NUM> may thus comprise one or more modems, antennas, and any other hardware and software for enabling an execution of the communication e.g. under control of the processor <NUM>. Furthermore, I/O (input/output) components may be arranged, together with the processor <NUM> and a portion of the computer program code <NUM>, to provide a user interface for receiving input from a user, such as from a technician, and/or providing output to the user of the apparatus when necessary. In particular, the user I/O components may include user input means, such as one or more keys or buttons, a keyboard, a touchscreen, or a touchpad, etc. The user I/O components may include output means, such as a loudspeaker, a display, or a touchscreen. The components of the apparatus may be communicatively connected to each other via data bus that enables transfer of data and control information between the components.

The memory <NUM> and a portion of the computer program code <NUM> stored therein may further be arranged, with the processor <NUM>, to cause the apparatus <NUM> to perform at least a portion of a method for selecting the travel direction as is described herein. The processor <NUM> may be configured to read from and write to the memory <NUM>. Although the processor <NUM> is depicted as a respective single component, it may be implemented as respective one or more separate processing components. Similarly, although the memory <NUM> is depicted as a respective single component, it may be implemented as respective one or more separate components, some, or all of which may be integrated/removable and/or may provide permanent / semi-permanent / dynamic / cached storage.

The computer program code <NUM> may comprise computer-executable instructions that implement functions that correspond to steps of the method when the computer program code <NUM> is loaded into the processor <NUM> of the controller <NUM> and executed therein. As an example, the computer program code <NUM> may include a computer program consisting of one or more sequences of one or more instructions. The processor <NUM> is able to load and execute the computer program by reading the one or more sequences of one or more instructions included therein from the memory <NUM>. The one or more sequences of one or more instructions may be configured to, when executed by the processor <NUM>, cause the apparatus <NUM> to perform a method as explicitly described in the description herein. Hence, the apparatus may comprise at least one processor <NUM> and at least one memory <NUM> including the computer program code <NUM> for one or more programs, the at least one memory <NUM> and the computer program code <NUM> configured to, with the at least one processor <NUM>, cause the apparatus to perform the method.

The computer program code <NUM> may be provided e.g. a computer program product comprising at least one computer-readable non-transitory medium having the computer program code <NUM> stored thereon, which computer program code <NUM>, when executed by the processor <NUM> causes the apparatus to perform the method. The computer-readable non-transitory medium may comprise a memory device or a record medium such as a CD-ROM, a DVD, a Blu-ray disc, or another article of manufacture that tangibly embodies the computer program. As another example, the computer program may be provided as a signal configured to reliably transfer the computer program.

Still further, the computer program code <NUM> may comprise a proprietary application, such as computer program code for causing an execution of the method in the manner as described in the description herein.

Any of the programmed functions mentioned may also be performed in firmware or hardware adapted to or programmed to perform the necessary tasks.

The entity performing the method may also be implemented with a plurality of apparatuses, such as the one schematically illustrated in <FIG>, as a distributed computing environment. For example, one of the apparatuses may be communicatively connected with other apparatuses, and e.g. share the data of the method, to cause another apparatus to perform at least one portion of the method. As a result, the method performed in the distributed computing environment allows the rescue operation in the elevator system <NUM> in the manner as described.

Claim 1:
A method for selecting a travel direction of an elevator car (<NUM>) for a rescue drive, characterized in that the method comprises:
generating (<NUM>) a first estimate indicative of a total energy consumption of the elevator car (<NUM>) to travel from its estimated position to a next landing (<NUM>) in a first direction by:
determining an amount of energy required to cause the elevator car (<NUM>) to move to the first direction by controlling the elevator car (<NUM>) to move a first reference distance to the first direction,
estimating an amount of energy required to move the elevator car (<NUM>) from its estimated position to the next landing in the first direction,
summing up the amount of energy required to cause the elevator car (<NUM>) to move to the first direction and the amount of energy required to move the elevator car (<NUM>) from its estimated position to the next landing (<NUM>) in the first direction for generating the first estimate,
generating (<NUM>) a second estimate indicative of a total energy consumption of the elevator car (<NUM>) to travel from its estimated position to a next landing (<NUM>) in an opposite direction to the first direction by:
determining an amount of energy required to cause the elevator car (<NUM>) to move to the opposite direction to the first direction by controlling the elevator car (<NUM>) to move a second reference distance to the opposite direction to the first direction,
estimating an amount of energy required to move the elevator car (<NUM>) from its estimated position to the next landing (<NUM>) in the opposite direction to the first direction,
summing up the amount of energy required to cause the elevator car (<NUM>) to move to the opposite direction to the first direction and the amount of energy required to move the elevator car (<NUM>) from its estimated position to the next landing (<NUM>) in the opposite direction to the first direction for generating the second estimate,
comparing (<NUM>) the first estimate and the second estimate, and
selecting (<NUM>) the travel direction for the rescue drive corresponding to an estimate being smaller among the first estimate and the second estimate.