Controlling an evacuation ride

Abstract

Disclosed is a method for controlling an elevator drive (1.3) in an evacuation ride, the elevator drive (1.3) being configured to move a car (1.1), the elevator drive (1.3) including an electric motor (2) with a rotor (2.1) and a stator with number of phases (2.2), the method including: a) determining, using a signal injection method, an initial rotor position of the rotor (2.1); b) energizing the phases (2.2) with a motor current vector, the motor current vector being aligned with an initial quadrature (q) axis as defined by the initial rotor position, the motor current vector having a setpoint motor current value; wherein the rotor (2.1) is at stillstand for steps (a) to (b); c) continuously c1) rotating the motor current vector, thereby generating a rotating magnetic stator field, wherein the motor current vector is rotated in a motor current vector rotation direction and with a motor current vector rotational speed, wherein the motor current vector rotation direction corresponds to a rotor rotation direction for moving the car (1.1) in an evacuation ride direction and the motor current vector rotational speed is determined in accordance with a desired speed of the car (1.1) for the evacuation ride, wherein a direction of the motor current vector is imprinted to the phases (2.2) without sensor feedback; c2) determining, based at least in part on at least one electric feedback signal of the phases, an adjustment current value and modifying the setpoint motor current value by the adjustment current value, thereby counteracting rotor oscillations.

Description

[0001] CONTROLLING AN EVACUATION RIDE

[0002] The present disclosure lies in the field of elevators and in particular the evacuation of passengers by way of an evacuation ride. Specifically, the disclosure concerns methods for controlling an elevator drive in an evacuation ride, evacuation methods as well as elevator drive controllers and elevators.

[0003] In the use of elevators, situations can occur where passengers are trapped in a car of an elevator and need to be rescued respectively evacuated. Typical scenarios that may require evacuation are a longer breakdown of a grid power supply of the elevator as well as various technical defects.

[0004] In dependence of the design of the elevator and the cause for the evacuation, a number of evacuation procedures may be used. According to one type of evacuation procedure, a machine brake of the elevator drive is manually mechanically opened without the elevator drive being active. Due to the generally present unbalance of the elevator, gravity will cause the car to move upwards or downward in dependence of the balancing situation. E. g. the load in the car might be so light that a torque acting on the traction sheave at the counterweight side exceeds an opposing torque acting on the traction sheave at the car side. The counterweight will accordingly move downwards, and the car will move upwards. At latest as the car reaches an evacuation landing, typically the next landing in the movement direction, the machine brake is again closed respectively the manual opening is cancelled, resulting in the machine brake stopping the car at the evacuation landing. Such procedure, however, requires in any case the physical presence of qualified and trained personnel.

[0005] In another approach, the machine brake that is in regular operation normally passively closed by way of spring force and is opened, e.g., electromagnetically or hydraulically for movement of the car in a controlled manner by way of a corresponding power supply, e.g. a battery in case of grid supply breakdowns, to allow movement of the car due to unbalance. Opening and closing of the machine brake may be controlled manually by a trained person or in some cases automatically. An evacuation ride according to this approach is typically carried out in a number of steps, each involving a temporary opening of the machine brake. In some cases, the physical presence of a qualified and trained person is again required and in any case the car movement is rather jerky and the ride at least uncomfortable due to the multiple stop-and go changes. Some further evacuation procedures rely on the elevator drive and its hoisting machine for the evacuation, as generally the case in regular operation. While being in principle favorable, such evacuation procedure requires the elevator drive to be fully operable and safe.

[0006] A particular scenario where evacuation is required are defects that concern the encoder, e.g. rotary encoder, that is present in the elevator drive and coupled to the drive shaft. During regular operation, the encoder signal is used for controlling the electric motor of the elevator drive, in particular by way of field-oriented vector control and may be used for further purposes such as speed control and monitoring purposes. Typical defects that are related to the encoder include a defect of the encoder itself, defects of the wiring, as well as mechanical defects of the mounting, de-adjustments and the like. Presently, the elevator drive cannot be used for the evacuation in such cases.

[0007] It is an overall objective of the present disclosure to improve the situation regarding the evacuation of an elevator. In particular, the situation for cases where no encoder signals are available for controlling the elevator drive shall be improved. Favorably, drawbacks that are present according to the state of the art are reduced or eliminated. It is noted that while reference is made in generally to the evacuation of passengers, the same approach may be used for other types of exceptional rides. Such exceptional ride may, e.g. be a service ride by a service person on the elevator top for maintaining, repairing or replacing the encoder.

[0008] In an aspect, the present disclosure concerns a method for controlling an elevator drive in an evacuation ride. The elevator drive being configured to move a car, the elevator drive including an electric motor with a rotor and a stator with number of phases. The method for controlling the elevator drive includes: a) determining, using a signal injection method, an initial rotor position of the rotor; b) energizing the phases with a motor current vector, the motor current vector being aligned with an initial quadrature (q) axis as defined by the initial rotor position, the motor current vector having a setpoint motor current value; wherein the rotor is at stillstand for steps (a) to (b); c) continuously cl) rotating the motor current vector, thereby generating a rotating magnetic stator field, wherein the motor current vector is rotated in a motor current vector rotation direction and with a motor current vector rotational speed, wherein the motor current vector rotation direction corresponds to a rotor rotation direction for moving the car in an evacuation ride direction and the motor current vector rotational speed is determined in accordance with a desired speed of the car for the evacuation ride, wherein a direction of the motor current vector is imprinted to the phases without sensor feedback; c2) determining, based at least in part on at least one electric feedback signal of the phases an adjustment current value an adjustment current value and modifying the setpoint motor current value by the adjustment current value, thereby counteracting rotor oscillations.

[0009] In an aspect, the present disclosure concerns an evacuation method for an elevator, wherein the elevator includes an elevator drive, the elevator drive being configured to move a car, wherein the elevator drive includes an encoder, in particular a rotary encoder. The encoder is coupled to a drive shaft of the electric motor and is configured to provide, when operating correctly, an encoder signal indicative of a movement of the drive shaft. The evacuation method includes determining that the encoder signal is missing and / or corrupted and executing a method for controlling an elevator drive according to any embodiment as discussed above and / or further below.

[0010] In an aspect, the present disclosure concerns an elevator drive controller, the elevator drive controller being configured to operatively couple to an elevator drive of an elevator and to control the elevator drive to execute the evacuation method and / or a method for controlling an elevator drive according to any embodiment as discussed above and / or further below.

[0011] In an aspect, the present disclosure concerns an elevator. The elevator includes a car, a suspen- sion / traction member, an elevator drive with an electric motor, and an elevator drive controller according to any embodiment as discussed above and / or further below.

[0012] As discussed further below in more detail, the present disclosure enables the execution of an evacuation ride using the elevator drive in a safe and rather comfortable manner, thereby reducing and ideally avoiding the mental and physical stress and discomfort for the passengers which generally is present in an evacuation ride. The expression “evacuation ride” relates in this document to a ride of a car with passengers that moves the car to an evacuation landing where the passengers can safely exit the car. In particular embodiments, the evacuation ride may be executed in an automatized manner, without requiring the direct presence of a mechanic, technician, or the like at the site of the elevator. Executing an evacuation ride in accordance with the present disclosure can in particular be used in situations where no signal from an encoder is available for controlling the elevator drive, in particular its electric motor. This situation is given if the typically present encoder is, e.g., defective, its wiring has a loose connection, or the like. During regular operation respectively if an encoder coupled to the electric motor operates correctly, commutation is generally controlled based on signals provided by the encoder. Typically, the elevator drive controller is configured for vector-orient current control and includes a corresponding current control loop.

[0013] Determining the initial rotor position may generally be carried out using any signal injection method that can be executed without the rotor moving respectively can be executed at standstill. Such injection signal methods are known in the art and described, e.g., in EP3706306A1, W02009 / 130363A1, or the paper “High-Frequency Voltage-Injection Methods and Observer Design for Initial Position Detection of Permanent Magnet Synchronous Machines”, Xinhai JIN et al, IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 33, NO. 9, SEPTEMBER 2018. Other methods known in the art may be used as well. Signal injection methods generally include providing one or more excitation signals to the motor phases and evaluating corresponding electric response signals.

[0014] The expression “rotor position” refers to the unique angular position of the rotor in a stator- fixed, i.e., non-rotating reference coordinate system and may have any value in a range of 0° to 360°. In some suited signal injection methods, for example the methods as mentioned above, the initial rotor position is determined in two sub-steps. In a first sub-step, an angle of the rotor axis is determined with respect to the stator-fixed reference coordinate system with a first signal injection. The angle of the rotor axis generally determines the direction of the direct (d) axis that corresponds to the magnetic rotor axis, and a thereto perpendicular quadrature (q) axis. In combination, the direct (d) axis and the quadrature (q) axis define a rotating respectively rotor-fixed cartesian coordinate system. A magnetic stator field that is aligned with the direct (d) axis does not exert any torque on the rotor, while a magnetic field that is aligned with the quadrature (q) axis does exert a torque on the rotor. The angle of the rotor axis as determined in the first substep, however, is not unique but has an ambiguity, also referred to as 180-degrees-ambiguity. That is, a first rotor position and a second rotor position that is rotated by 180° with respect to the first rotor position generally result in the same angle of the rotor angle. Once the rotor axis is known, however, the ambiguity can be resolved in a second sub-step by way of a second signal injection, thereby determining the rotor position in a unique manner. It is noted that applying a magnetic stator fded in opposite directions along the quadrature (q) axis results in oppositely directed torques being exerted on the rotor.

[0015] Once the rotor position is known, the phases are energized in step (b) with a motor current vector in a well-defined direction that is specifically defined by the quadrature (q) axis and accordingly results in a torque being exerted on the rotor. Further aspects regarding the setpoint motor current value and its direction are discussed further below. For a vector variable, such as the motor current vector, the expression “value” refers to the absolute value of the vector variable.

[0016] It is noted that the expression “axis” does as such not imply a particular direction along the axis. Accordingly, a vector that is aligned with either of the axes can have to opposite directions respectively have two directions that differ by 180°. The expression “aligned” is to be understood as parallel or anti -parallel.

[0017] In step (c), the motor current vector is continuously rotated. Due to the resulting rotating magnetic field, a rotating torque is exerted on the rotor. At each point in time, the rotating motor current vector drags the rotor into the direction as defined by the direction of the motor current vector. The direction of the motor current vector being imprinted to the phases without sensor feedback means that the energization of the phases respectively the commutation is pre-determined by the elevator drive controller, such as an inverter. Neither an encoder signal nor other feedback signals are used for the commutation. In contrast to the direction of the motor current vector, its value is in step (c2) continuously monitored and adjusted in a closed control loop respectively based on an electric feedback signal. In this way, superimposed oscillations of the rotor are counteracted and accordingly dampened and ideally fully or largely eliminated. Such oscillations would occur due to a tendency of the rotor to oscillate around the imprinted motor current vector. without feedback and directly influence the movement of the car and accordingly the ride quality of the evacuation ride. Due to controlling the motor current value in accordance with the present disclosure, the comfort respectively ride quality for the evacuation ride is increased and the evacuation ride can be carried out with passengers in a safe manner.

[0018] In an embodiment, a direction of the motor current vector is such that a drive torque that is ex- erted by elevator drive counteracts respectively brakes the rotation of the rotor in the rotor rotation direction. The electric motor is accordingly controlled such that the elevator drive serves as electrodynamic brake. This type of embodiment is particularly favorable if the evacuation ride direction corresponds to a natural car movement direction as discussed further blow in more detail. However, the evacuation ride direction may also be opposite to the natural car movement direction. In this latter case, the direction of the motor current vector is such that the drive torque that is exerted by elevator drive drives the rotation of the rotor in the rotor rotation direction. The motor current vector is in both cases aligned with the quadrature (q) axis, but with in each case opposite directions.

[0019] In an embodiment, the motor current value exceeds a holding current value, the holding current value being a motor current value for maintaining the car at standstill. Energizing the phases with a motor current value corresponding to the holding current would result in the elevator drive generating a torque that maintains the car at standstill without applying an additional braking torque, e.g. by an elevator brake such as a machine brake of the elevator drive. The corresponding torque is commonly referred to as holding torque. Appling a motor current vector with a value that exceeds the value for generating the holding torque avoids the occurrence of undesired pole jumps that would otherwise occur for feedback-less commutation.

[0020] In an embodiment, the setpoint motor current value is varied during the evacuation ride, in particular in step (c). The setpoint motor current value may be varied in a predetermined, e.g. preprogrammed manner. In particular, the setpoint motor current value may be selected to be larger for an acceleration phase than for a subsequent steady phase. The setpoint motor current value is in any case selected such that a permissible maximal current value is not exceeded. The permissible maximal current value may, e.g. be a maximal current of the elevator drive controller, such as an inverter, or of the electric motor. In another embodiment, the setpoint motor current value is fixed respectively constant for the evacuation ride.

[0021] In an embodiment, the motor current vector is not established abruptly in step (b), but a value of the motor current vector is increased over time stepwise or continuously over a time in a range of, e.g., 0.5s to the aet motor current value.

[0022] In an embodiment, the method includes determining a natural car movement direction, the natural car moving direction corresponding to a direction in which the car would move as a result of unbalance without drive torque. The evacuation ride direction corresponds to the natural car movement direction. This type of embodiment is favorable in that the drawn power is low, which is crucial in particular if a backup energy storage such as a battery is used for powering the elevator for the evacuation ride. However, in alternative embodiments the evacuation ride direction is opposite to the natural car moving direction. In another embodiment, the evacuation ride direction may correspond to or be opposite to the natural car movement direction. By way of example, an evacuation method may include determining which landing, being it upwards or downwards with respect to a current car position, can be reached within the shortest time period and / or is closest to the current car position, and define this landing as evacuation landing. In another embodiment, the evacuation landing may be a pre-defined landing of the building, such as a ground floor landing.

[0023] Typically, an elevator includes a car and a counterweight that are coupled via a suspension / trac- tion member such as one or more ropes, belts or chains. The car and the counterweight are further coupled to the elevator drive via the suspension / traction member with the counterweight moving downwards in the hoistway if the car moves upwards, and vice versa. The side of the traction sheave where it couples to the car is referred to as car side and the side where it couples to the counterweight is referred to as counterweight side. As generally known, the weights of the car and the counterweight are generally not identical, but the weight of the counterweight is chosen larger, e.g. corresponding to the weight of the empty car plus 50% of the rated load. Without any torque being applied by a brake or the elevator drive, an empty or lightly loaded car would accordingly tend to move upwards as natural car moving direction due to the larger weight of the counterweight. For the total weight of the car and the load exceeding the weight of the counterweight, in contrast, the car would tend to move downwards as natural car moving direction. In addition to different weights of the loaded car and the counterweight, the weight of the portion of the suspension / traction members at the side of the car adds to the weight of the car and the weight of the suspension / traction member at the side of the counterweight adds to the weight of the counterweight. Unless the car and the counterweight being at the same height, the weights of the suspension / traction member portions are different. The weighs including the suspension / traction member portions can be referred to as effective weight of the car respectively effective weight of the counterweight. The difference of the effective weights is also referred to as unbalance. The unbalance takes into account the weights of the car (including load) and the counterweight as well as the weights of the corresponding portions of the suspension / traction member at the car side and the counterweight side. If, however, compensation means such as compensation ropes are present, the suspension / traction member does not influence the balance situation. It is noted that the unbalance can be positive or negative, i.e., result in an upwards-directed or downwards directed force on the car.

[0024] In an embodiment, the motor current vector rotational speed is continuously increased in an initial phase of the evacuation ride and constant in a subsequent steady phase of the evacuation ride. In the initial phase of the evacuation ride, the car accelerates to an evacuation ride steady speed which is subsequently kept generally constant. Rotation of the motor current vector starts at a motor current vector rotational speed of zero. Increasing the motor current vector rotational speed may follow a pre-determined course that limits the jerk and acceleration of the car.

[0025] In a particular embodiment, the motor current vector rotational speed is based on linear growing or decreasing of the motor current vector rotational acceleration, which correlates to either a positive, zero or negative constant value of the motor current vector rotational jerk, in accordance with a desired travel profile of the car. As mentioned before, the setpoint motor current value may be larger for the acceleration phase than for the steady phase, respectively be reduced at the transition from the acceleration phase to the steady phase.

[0026] In an embodiment, the method includes determining an unbalance of the elevator, wherein determining the unbalance in particular includes determining a load of the car and / or a position of the car. The load may in particular be determined by a load sensor of the elevator. For the load sensor, various designs and arrangements which may be used are known in the art. In a further embodiment, determining the natural car movement direction includes evaluating a position of the car and / or the counterweight. Such positions are generally known from a car position measurement system and / or counterweight position measurement system of the elevator. Form the position of the car and / or counterweight, the weights of the portions of the suspension / traction member at the side of the car and the counterweight and accordingly the effective weight of the car and the effective weight of the counterweight and accordingly the unbalance as discussed above can be determined. It is noted that determining the unbalance includes determining the sign respectively the direction of the unbalance. The amount of unbalance may or may not be determined. Further, an elevator drive controller may directly receive and process dedicated signals indicating the load and position of the car or counterweight, or may receive from an overall elevator controller a signal that includes the corresponding information. By way of example, an overall elevator controller may receive a load signal and a position signal and compute from the load signal and the position signal a holding torque that needs to be exerted by the elevator drive to maintain the car in position respectively at stillstand. Such holding torque includes information on the amount and direction of the unbalance.

[0027] In an embodiment, an elevator brake of the elevator is in a closed state for step (a) and step (b), wherein the method for controlling an elevator drive further includes opening the elevator brake between step (b) and step (c). The elevator brake may, e.g., be a machine brake as generally known that acts on a traction sheave and / or drive shaft of the elevator drive. Alternatively, or additionally, the elevator brake may be or include a car brake that is directly arranged at the car and interacts with a guide rail or guide rails that are arranged in the hoistway. The elevator brake is a controllable brake that is controllable by a controller, in particular the elevator drive controller. It may in particular be controllable to be alternatively in a closed or open state. The elevator brake is controlled by corresponding circuitry of the elevator controller, in particular the elevator drive controller. In the closed state, the elevator brake can break the car to standstill and maintain it at standstill. In accordance with the here-described type of embodiment, the elevator brake is accordingly closed, and no movement of the car occurs when determining the initial rotor position and initially energizing the phases. Only subsequently, the elevator brake is opened. It is noted that for the setpoint motor current value corresponding to the holding current value as mentioned before, the car would start moving in a smooth manner. Since the setpoint motor current value, however, generally exceeds the holding current value as discussed before, there will be a jolt as the elevator brake is opened.

[0028] In an embodiment, the feedback signal includes at least a voltage signal and / or a current signal. Voltage and current measurement for the motor phases are well known in the art. Corresponding circuitry and / or procedures may be implemented in the elevator drive controller, for example inverter.

[0029] In an embodiment, step (c) includes determining from the electric feedback signal a state variable, the state variable including at least one of an actual rotor angle and / or actual rotor speed and / or actual rotor acceleration, or a variable correlated with at least one of the actual rotor angle and / or actual rotor speed and / or actual rotor acceleration, and determining the adjustment current value based on the state variable. The state variable is indicative of the movement of the rotor and also reflects oscillations of the rotor. Specifically, the rotor speed as a function of time is in principle proportional to the car speed and rotor oscillations may be associated with changes of sign of the rotor speed, resulting in an upwards and downwards movement of the car. However, undesired oscillations may also be reflected by changes of sign of the rotor acceleration, while the rotor velocity does not change sing. In such case, the car movement is always in the same direction, specifically the evacuation ride direction, but in an unsteady manner. It is noted that a change of sign of the rotor velocity is necessarily also associated with a change of sign of the rotor acceleration. In an embodiment, step (c) includes evaluating the electric feedback signal by way of an observer, in particular a Luenberger observer and / or filtering the electric feedback signal. Also, filtering may be applied to one or more output signals of the observer.

[0030] In an embodiment, the method for controlling an elevator drive includes terminating the evacuation ride as the car reaches an evacuation landing. Terminating the evacuation ride may include interrupting a safety chain of the elevator, causing the power supply to the elevator drive being interrupted and the elevator brake changing into a closed state. This corresponds to the typical procedure for an emergency stop as generally known in the art.

[0031] In an embodiment, the elevator drive includes an encoder, in particular a rotary encoder, the encoder being coupled to a drive shaft of the electric motor and being configured to provide an encoder signal when operating correctly, wherein the method for controlling an elevator drive does not include evaluating the encoder signal.

[0032] During regular operation, the encoder may be configured to provide speed measurement values as input signal respectively feedback signal for a current control loop of a drive controller, respectively for controlling the commutation. In an embodiment, the elevator drive controller is configured for controlling the electric motor respectively the energization of its phases by way of field-oriented control or vector control, respectively. Further, the encoder may be configured and in regular operation used to provide speed measurement values as input signal respectively feedback signal for a speed control unit. In an embodiment of an elevator drive controller, the elevator drive controller is a cascade controller with an inner current control loop and an outer speed control loop.

[0033] In the following, exemplary embodiments in accordance with the present disclosure are discussed in more detail with additional reference to the figures. The figures are showing: Fig. 1 an exemplary elevator in accordance with the present disclosure in a highly schematic side view;

[0034] Fig. 2 an exemplary electric motor of an elevator drive in a highly schematic view;

[0035] Fig. 3 a schematic control scheme for an evacuation ride drive control in accordance with the present disclosure;

[0036] Fig. 4 a schematic operational flow for an evacuation ride in accordance with the present disclosure;

[0037] Fig.5 a highly schematic car speed in an initial phase of an evacuation ride as a function of time;

[0038] In the following, reference is first made to Fig. 1, showing an elevator 1 in accordance with the present disclosure in a highly schematic view. The elevator 1 includes a car 1.1 and a counterweight 1.2 that are arranged vertically movable in a hoistway 1.5. The car 1.1 and the counterweight 1.2 are coupled via a flexible suspension / traction member 1.4, the suspension / traction member 1.4 including, e.g., one or more ropes or belts as generally known in the art. The suspension / traction member 1.4 can also serve as suspension member for suspending the car 1.1 and the counterweight 1.2 against gravity. The elevator 1 further includes an elevator drive 1.3 with an electric motor 2 as hoisting machine.

[0039] The elevator drive 1.3 includes a traction sheave 1.3.2 which is mounted to or formed integrally with a rotor shaft (not referenced dashed line) of the electric motor 2. The suspension / traction member 1.4 is wound around a section of the traction sheave 1.3.2 and couples to the traction sheave 1.3.2 such that rotation of the traction sheave 1.3.2 via the elevator drive 1.3 and / or gravity causes the car 1.1 and the counterweight 1.2 to move vertically in the hoistway 1.5 in opposite directions. The elevator drive 1.3 further includes one or more machine brakes 1.3.3 as elevator brake. The machine brake(s) 1.3.3 are arranged to selectively break the rotor shaft respectively the traction sheave 1.3.2.

[0040] Further, an encoder 3, such as an incremental rotary encoder is coupled to the drive shaft and is configured to provide an encoder signal indicative of a movement of the drive shaft and coupled to the elevator drive controller 1.6 via a communication link. The signal provided by the encoder 3 is used by elevator drive controller 1.6 in regular operation of the elevator 1 as feedback signal in a current control loop for real-time control of the current that is provided to the phases of the electric motor 2. Further, it may be used, e.g., by elevator drive controller 1.6 as feedback signal for a speed control loop. The elevator drive controller 1.6 may in an embodiment implement a state machine with a current control loop, a speed control loop and optionally further control loops.

[0041] In the shown design, the elevator 3 further includes a load sensor 4 and a car position measurement system 5. The load sensor 4 is configured to determine a load in the car 1.1. The load sensor 4 may, e.g., include at least one load cell and be configured to measure a gravitational force that is exerted by a load, e.g. passengers, on a floating floor (not separately shown) of the car 1. 1 and / or include strain gauges that measure a deformation of a part of the car 1. 1 due to the load. The car position measurement system 5 may include an e.g. optical or magnetic scale 5.2 that extends along a travel path of the car 1.1. in the hoistway 1.5 and a corresponding position sensor 5.1 at the car 1. 1. Other arrangements may be used as well.

[0042] The load sensor 4 and the position sensor 5.1 are coupled to the elevator drive controller 1.6 via communication links. From the weights of the car 1.1. and the counterweight 12, the weight of the portion 1 ,4a of the suspension / traction member 1.4 at the car 1.1 side and the weight of the portion 1 ,4b of the suspension / traction member 1.4 at the counterweight 1.2 side, the elevator drive controller 1.6 can, together with the load in the car 1.1, determine the effective weight of the counterweight 1.2 and the effective weight of the car 1.1 and accordingly the unbalance.

[0043] In the following, reference is additionally made to Fig. 2, showing an electric motor 2 of an elevator drive in accordance with the present disclosure in a highly schematic view along the rotor axis A that also defines the axis of the drive shaft. The electric motor 2 may be a permanentmagnet (PM) synchronous motor that is for illustrative purposes shown with a rotor 2.1 having a single pole pair with a north (N) pole and a south (S) pole. Further, the electric motor 2 has a stator with exemplarily three phases 2.2 that are arranged around the stator 2.1 in a rotational symmetric manner. The phase 2.2 are energized via the elevator drive controller and may be, e.g., in a star or delta configuration. It is noted that the electric motor 2 could also be of a different type, such as a hybrid synchronous reluctance motor.

[0044] The stator defines a non-rotating respectively stator-fixed reference coordinate system (x, y) with an origin being given by the rotor axis A. Further, the rotor 2. 1 defines a rotating respectively rotor-fixed coordinate system (x’, y’) with an origin given by the rotor axis. The direct (d) axis is defined by the poles of the rotor 2.1, the quadrature (q) axis is thereto orthogonal. Both the direct (d) and quadrature (q) axis cross the rotor axis A. The x’-direction is aligned with the direct (d) axis and the y’-direction is aligned with the quadrature (q) axis. The rotor angle a uniquely defines the rotor position and is measured from the non-rotating reference coordinate system, exemplarily the x-axis, to a reference at the rotor 2.1, exemplarily the x’-direction respectively the direct (d) axis. Other conventions could, of course also be used.

[0045] In the following, reference is additionally made to Fig. 3, schematically showing the control scheme for an evacuation ride in accordance with the present disclosure. The control scheme is implemented by the elevator drive controller 1.6. The single functions and units of the elevator drive controller 1.6 as discussed in the following may be implemented by way of hardware and / or software respectively firmware as applicable and best suited.

[0046] The elevator drive controller 1.6 implements a field-oriented respectively vector controller.

[0047] Generally, the elevator drive controller 1.6 is configured to separately control the components of the motor current vector in direction of the quadrature (q) and the direct (d) axis, respectively. However, in the context of an evacuation ride in accordance with the present disclosure only a component of the current vector in the direction of the quadrature (q) axis is used. Therefore, the control scheme of Fig. 3 only shows the branch related to the quadrature (q) axis. Further, as discussed above and further below, the direction of the current vector is imprinted for the evacuation ride without any sensor feedback indicative of the rotor position. Therefore, the direction of the quadrature (q) axis is an assumed or estimated direction that may deviate from the actual direction of the quadrature (q) axis.

[0048] The control scheme of Fig. 3 further assumes that the initial direct (d) and quadrature (q) axis before the beginning of the evacuation ride are known respectively have been determined using a signal injection method.

[0049] The elevator drive controller 1.6 implements a closed-loop control with a current controller 1.6.1 for the motor current as follows: As electric feedback signal, the actual motor current Iq ain the assumed direction of the quadrature (q) axis is used. As setpoint current Iq_set, a fixed current value. The error signal Iq ethat is fed back into the current controller 1.6.1 is formed by the difference of the setpoint current Iq_set and a feedback current Iqfeedback as feedback signal The feedback current Iqfeedback is partly formed by the actual motor current Iq a. To this extent, the control scheme corresponds to a motor current control controller as known in the art. In accordance with the present disclosure, however, the feedback current I q_feedback has a further component in form of an adjustment current value Iqadjust as discussed further below.

[0050] For controlling the energization of the phases of the electric motor 2, a current controller 1.6.1 is foreseen. The electric motor 2 is a permanent magnet (PM) synchronous machine with, e.g. three phases. During the evacuation ride, the rotor current vector is continuously rotated in a predefined respectively imprinted manner, without relying on feedback from encoder 3 nor other sensorless rotor position determination procedures as known in the art, such as back-EMF evaluation.

[0051] As a consequence of the imprinted rotation of the motor current vector, the rotor of the electric motor 2 generally tends to rotate with superimposed oscillations, resulting in an unsteady up- and-down movement of the car 1.1 when only relying on the actual motor current Iq aas feedback signal in the current control loop as mentioned before. In accordance with the present disclosure, such undesirable rotor oscillations are dampened and ideally suppressed by an additional oscillation damping unit 1.6.2 which is implemented as part of the elevator drive controller 1.6.

[0052] In the shown design, the oscillation damping unit 1.6.2 includes an observer 1.6.2.1 that is configured to receive and process an electric feedback signal. In the shown example, the electric feedback signal is the actual motor current Iq act in the direction of the assumed quadrature (q) axis. From the actual motor current Iq act, the observer 1.6.2. 1 determines a state variable that corresponds to the rotor speed or is correlated therewith. In any case, the state variable reflects the rotor oscillations. The output of the observer 1.6.2. 1 is fed into a filter 1.6.2.2 and the output of the filter 1.6.2.2 is exemplarily amplified by an amplifier 1.6.2.3. The filter 1.6.2.2. may, e.g., be a bandpass filter or lowpass filter that is designed to extract respectively isolate a signal corresponding to the rotor oscillations. It is noted that the amplification factor of amplifier 1.6.2.3 may be larger or smaller than one as needed. The output signal of the amplifier 1.6.2.3 is an adjustment current value Iq adj that is added to the actual motor current Iq ato form the feedback current Ifeed k. In other designs, other electric feedback signals, such as the value of a voltage vector in the assumed direction of the quadrature (q) axis could be used as input for the observer 1.6.2.1. Further in the shown design, an output signal of the current controller 1.6.1, in particular a voltage signal, is used as further input signal to the observer 1.6.2.1. In the following, reference is additionally made to Fig. 4, schematically showing an operational flow for an evacuation ride and in particular a method for controlling an elevator drive in accordance with the present disclosure.

[0053] The evacuation ride generally starts with step SO 1. It is assumed that the car 1.1 is at stillstand, the elevator drive 1.3 respectively its electric motor 2 is deenergized, i.e., does not generate torque, and the machine brake 1.3.3 is closed. In step S02, the balance situation is determined as resulting from the effective weights of the car 1.1 and the counterweight 1.2. For determining the balance situation, signals provided by the car position measurement system 5 and the load sensor 4 are evaluated. As explained before, the natural movement direction of the car depends on the unbalance. The natural car movement direction is also used as evacuation ride direction for the evacuation ride.

[0054] With the machine brake 1.3.3 still being closed and the rotor of the electric motor 2 being at standstill, the initial rotor position and accordingly the direction of the quadrature (q) axis of the electric motor 2 are determined in subsequent step S03, using a signal injection method. It is noted the order of steps S02 and step S03 could be reversed.

[0055] With the machine brake 1.3.3 still being closed and the rotor of the electric motor 2 being at standstill, the phases of the electric motor 2 are energized with a motor current vector in subsequent step S04. The motor current vector is aligned with the quadrature (q) axis as determined in step S03 and directed such that the resulting torque that is generated by the electric motor 2 counteracts the rotation direction of the traction sheave 1.3.2 resulting from the unbalance, respective counteracts a rotation of the traction sheave 1.3.2 for the car 1. 1 moving in the natural movement direction. The motor current vector has a setpoint motor current value. The motor current vector is, however, not established with the setpoint motor current value in a single step, but the value of the motor current vector is increased in a number of incremental steps respectively continuously over a time of about, e.g. 0.5s until the setpoint motor current value is reached. The direction of the motor current vector as discussed before is kept constant. The setpoint motor current value is pre-determined.

[0056] In subsequent step S05, the machine brake 1.3.3 is opened, thereby allowing the car 1.1 and the counterweight 1.2 to start moving. In subsequent step S06, the motor current vector is controlled to rotate in a direction corresponding to the natural car movement direction respectively evacuation ride direction in an accelerated manner respectively with continuously increased rotational speed. Due to the direction of motor current vector and the resulting torque exerted by the electric motor 2 on the traction sheave 1.3.2, the elevator drive exerts a braking torque. The acceleration respectively the course of the rotational speed of the motor current vector is favorably determined such that the car 1.1 follows a travel curve with the speed, acceleration and speed of the car 1. 1 being limited. In a typical implementation, the jerk may be limited to 0.2m / s3and the acceleration to 0.2m / s2. The maximum travel speed for the evacuation ride may, e.g. 0.1 to 0.12m / s. It is noted that the values generally depend on factors such as the type of the electric motor 2 and the overall design of the elevator drive 1.1 and the elevator 1 in general.

[0057] As a final rotational speed of the motor current vector is reached, corresponding to the travel speed of the car 1. 1 for the evacuation ride, the operational flow proceeds to step S07. In step S06, the motor current vector is further rotated with constant rotational speed, corresponding the evacuation ride steady speed.

[0058] As the car 1. 1 reaches an evacuation landing, operational flow proceeds the step S08 and the evacuation ride terminates. In step S08, the power to the electric motor 2 is shut off respectively the electric motor 2 is deenergized and the machine brake 1.3.3 is closed. The evacuation landing may in particular be the next landing with respect to an initial position of the car 1. 1 in the natural movement direction.

[0059] In particular during steps S05 to S07, the motor current value is continuously modified and adjusted by an adjustment current value to counteract rotor oscillations as discussed before with reference to Fig. 3.

[0060] In the following, reference is additionally made to Fig. 5, illustrating in a highly schematical manner the speed v in m / s of car 1.1 for an exemplary evacuation ride in accordance with the present disclosure as a function of time t. Regarding the car movement, three phases a distinguished, namely a brake opening phase Pl, an acceleration phase P2 and a steady phase P3. Prior to the brake opening phase, the steps SOI to S04 according to Fig. 4 are carried out. The brake opening phase Pl corresponds to step S05, the acceleration phase to step S06 and the steady phase to step S07. Curve 100 corresponds to an ideal case respectively the desired reference of the speed v. In the steady phase, the speed of the car may be, e.g., in a range of O. lm / sec. Superimposed distortions, in particular oscillations, are indicated by curve 101. The oscillations 101 as indicated generally reflect a situation as it would occur without continuous adjusting the motor current value in accordance with the present disclosure. Ideally, no movement of the car 1.1 would occur in the brake opening phase, respectively step

[0061] S05 and the speed would be zero, due to the elevator drive 1. 1 providing a torque that would compensate for the opening of the machine brake 1.3.3 and hold the car 1.1 in position. However, since the setpoint motor current value exceeds the holding current value that would be needed for holding the car 1. 1. in position, some movement will generally occur as the machine brake 1.3.3 is opened. In the acceleration phase respectively during step S06, the car speed increases in a generally smooth manner. However, in the steady phase respectively in step S07, significant oscillations would generally occur. Due to the continuous adjustment of the motor current value, the oscillations are largely suppressed.

Claims

CLAIMS1. Method for controlling an elevator drive (1.3) in an evacuation ride, the elevator drive (1.3) being configured to move a car (1.1), the elevator drive (1.3) including an electric motor (2) with a rotor (2.1) and a stator with number of phases (2.2), the method including: a) determining, using a signal injection method, an initial rotor position of the rotor (2. 1); b) energizing the phases (2.2) with a motor current vector, the motor current vector being aligned with an initial quadrature (q) axis as defined by the initial rotor position, the motor current vector having a setpoint motor current value; wherein the rotor (2.1) is at stillstand for steps (a) to (b); c) continuously cl) rotating the motor current vector, thereby generating a rotating magnetic stator field, wherein the motor current vector is rotated in a motor current vector rotation direction and with a motor current vector rotational speed, wherein the motor current vector rotation direction corresponds to a rotor rotation direction for moving the car (1.1) in an evacuation ride direction and the motor current vector rotational speed is determined in accordance with a desired speed of the car (1.1) for the evacuation ride, wherein a direction of the motor current vector is imprinted to the phases (2.2) without sensor feedback; c2) determining, based at least in part on at least one electric feedback signal of the phases, an adjustment current value and modifying the setpoint motor current value by the adjustment current value, thereby counteracting rotor oscillations.

2. Method according to claim 1, wherein a direction of the motor current vector is such that a drive torque that is exerted by elevator drive (1.3) counteracts the rotation of the rotor (2. 1) in the rotor rotation direction.

3. Method according to anyone of the preceding claims, wherein the motor current value exceeds a holding current value, the holding current value being a motor current value for maintaining the car at standstill.

4. Method according to anyone of the preceding claims, the method further including determining a natural car movement direction, the natural car moving direction corresponding to a direction in which the car (1.1) would move as a result of unbalance without drive torque,wherein the evacuation ride direction corresponds to the natural car movement direction.

5. Method according to claim 4, wherein the method includes determining an unbalance of the elevator (1), wherein determining the unbalance in particular includes determining a load of the car and / or a position of the car (1.1).

6. Method according to anyone of the preceding claims, wherein the setpoint motor current value is varied during the evacuation ride, in particular in step (c).

7. Method according to anyone of the preceding claims, wherein an elevator brake (1.3.3) of the elevator (1) is in a closed state for step (a) and step (b), wherein the evacuation ride drive control method further includes opening the elevator brake (1.3.3) between step (b) and step (c).

8. Method according to anyone of the preceding claims, wherein the feedback signal includes at least a voltage signal and / or a current signal.

9. Method to anyone of the preceding claims, wherein step (c) includes determining from the electric feedback signal a state variable, the state variable including at least one of an actual rotor angle (a) and / or actual rotor speed and / or actual rotor acceleration, or a variable correlated with at least one of the actual rotor angle (a) and / or actual rotor speed and / or the actual rotor acceleration, and determining the adjustment current value based on the state variable.

10. Method according to anyone of the preceding claims, wherein step (c) includes evaluating the electric feedback signal by way of an observer, in particular a Luenberger observer and / or by fdtering the electric feedback signal.

11. Method according to anyone of the preceding claims, wherein the evacuation ride drive control method includes terminating the evacuation ride as the car (1.1) reaches an evacuation landing.

12. Method according to anyone of the preceding claims, wherein the motor current vector rotational speed is continuously increased in an initial phase of the evacuation ride and constantin a subsequent steady phase of the evacuation ride.

13. Evacuation method for an elevator (1), wherein the elevator (1) includes an elevator drive(1.3), the elevator drive (1.3) being configured to move a car (1.1), wherein the elevator drive (1.3) includes an encoder (3), in particular a rotary encoder, the encoder (3) being coupled to a drive shaft of the electric motor (2) and being configured to provide, when operating correctly, an encoder signal indicative of a movement of the drive shaft, the evacuation method including: determining that the encoder signal is missing and / or corrupted and executing an evacuation ride drive control method according to anyone of the preceding claims in this case.

14. Elevator drive controller (1.6), the elevator drive controller (1.6) being configured to operatively couple to an elevator drive (1.3) of an elevator (1) and to control the elevator drive(1.3) to execute the evacuation method according to claim 13 and / or a method for controlling an elevator drive (1.3) according to anyone of claims 1 to 12.

15. Elevator (1), the elevator (X’) including: a car (1.1), a suspension / traction member (1.4), an elevator drive (1.3) with an electric motor (2), an elevator drive controller (1.6) according to claim 14.

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