Abstract:
The present invention relates to a technique for an elevator car to perform an emergency operation during a power failure, and in particular to a method for controlling a rescue operation of an elevator car which can rescue passengers by performing an emergency operation with an electromotive force of a permanent magnet-type synchronous motor during the power failure, in an elevator system employing the synchronous motor as a lifting motor. The method for controlling the rescue operation of the elevator car includes: a step for obtaining the electromotive force by rotating the synchronous motor due to the weight difference between the balance weight and the car during the power failure; a step for charging the electromotive force in the condenser; and a step for gradually increasing a rotation speed of the synchronous motor from a starting time thereof to a predetermined time for speed controlling matched with a charging voltage of the condenser at an initial stage of the power failure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a technique for an elevator car to perform an emergency operation at a state of emergency such as power failure, and in particular to a method for controlling a rescue operation of an elevator car which can rescue passengers by performing an emergency operation with an electric power generating of a permanent magnet-type synchronous motor when an emergency such as power failure takes place in an elevator system employing the synchronous motor as a lifting motor. 
     2. Description of the Background Art 
     When a permanent magnet-type synchronous motor is employed as a lifting motor in an elevator system, a permanent magnet is used as a magnetic field source, and thus a magnetic component current is not necessary. In addition, in general, the permanent magnet-type synchronous motor is more efficient than an induction motor, and accordingly improves efficiency of the whole elevator system and reduces energy consumption. Therefore, the permanent magnet-type synchronous motor has been used in the elevator system. In the elevator system using the permanent magnet-type synchronous motor as the lifting motor, a conventional apparatus for controlling an operation of an elevator car at a state of emergency, such as power failure, and a method therefor will now be described with reference to FIG.  1 . 
     As illustrated in FIG. 1, the conventional apparatus for controlling the operation of the elevator car (hereinafter referred to as ‘car’) includes: a converter  102  converting an alternating current from a three-phase alternating current power source  101  to a direct current; a condenser  103  charging and smoothing a direct current outputted from the converter  102 ; an inverter  104  for inverting a direct current outputted from the condenser  103  to an alternating current by switching of a switching device; a synchronous motor  105  driven by an output from the inverter  104 ; a contactor  105 A closed during the power failure for grounding a three-phase output terminal of the synchronous motor  105  through a ground resistance  105 B; a current detector  106  detecting a current supplied from the inverter  104  to the synchronous motor  105 ; a speed and position detector (such as a rotary encoder outputting a pulse signal corresponding to a rotation speed of the synchronous motor) connected to the synchronous motor  105 , and detecting a rotation speed of the synchronous motor  105  and a moving position of the car  110 ; a traction machine  108  receiving a rotation force from the synchronous motor  105 , and driving the car  110  and a balance weight  111  in opposite directions; a brake  109  of the traction machine  108 ; a power failure detector  112  detecting a state where the three-phase alternating current power source  101  is abnormally inputted or interrupted; a controller  113  outputting a speed command driving the synchronous motor  105  during a normal operation, and outputting a corresponding speed command when the power failure or abnormality detection signal is outputted from the power failure detector  112 ; an inverter controller  114  receiving an output signal from the current detector  106  and the speed and position detector  107 , and outputting a pulse width modulation signal according to a control command of the controller  113 ; and a gate driving unit  115  receiving the pulse width modulation signal, amplifying it to a predetermined level, and outputting it to the inverter  104 . The operation of the conventional apparatus for controlling the operation of the elevator car will now be explained. 
     In the normal operation, the three-phase alternating current power source  101  is converted into the direct current through the converter  102 , and smoothed by the condenser  103 . The smoothed direct current is inputted into the inverter  104 . 
     In this state, when the controller  113  transmits the speed command to the inverter controller  114 , the inverter controller  114  outputs the pulse width modulation signal having a predetermined pattern which is a gate driving signal to the inverter  104  through the gate driving unit  115 . Accordingly, the switching devices in the inverter  104  are switched, and thus a three-phase driving voltage is supplied to the synchronous motor  105 . 
     The synchronous motor  105  rotates at a speed corresponding to the inputted three-phase driving voltage, the rotation force thereof is transmitted to the traction machine  108 , and thus the car  110  starts to move to a designated floor. 
     On the other hand, when the emergency such as the power failure is detected by the power failure detector  112 , and when the detection signal is inputted to the controller  113 , the driving of the inverter  104  is interrupted. At the same time, the brake  109  of the traction motor  108  is operated, and thus the car  110  stops at a current position. An auxiliary power source which is prepared for the emergency state such as the power failure, namely a battery (not shown) is supplied to the controller  113 , the contactor  105 A is closed according to the control of the controller  113 , and thus an output terminal of the synchronous motor  105  is connected to the ground through the contactor  105 A and the ground resistance  105 B. 
     In this state, when the brake  109  is released, the car  110  starts to move towards a heavier side between the car  110  and the balance weight  111 , and thus the synchronous motor  105  is rotated. Accordingly, a electric power is generated by the synchronous motor  105 , that is the synchronous motor  105  operates as a power generator. A generated current flows through the contactor  105 A and the ground resistance  105 B, and a braking torque is generated in the synchronous motor  105 . 
     Accordingly, in a state where the driving of the inverter stops, the car  110  moves at such a speed that the braking torque of the synchronous motor  105  and the torque by the weight difference between the car  110  and the balance weight  111  could be balanced. When the car  110  reaches to a door zone of the nearest floor, the brake  109  of the traction motor  108  is driven, and thus the movement of the car  110  stops. At this time, the door is opened, and the passengers are rescued. 
     However, the conventional apparatus for controlling the operation of the elevator car includes the contactor and the resistor in the circuit of synchronous motor and the inverter, and further includes a control circuit in order to short the output terminal of the synchronous motor to the ground by controlling the contactor during the emergency operation, thereby incurring additional expenses. Moreover, the operational speed of the car is determined merely by the weight difference between the car and the balance weight, and the ground resistance value. Accordingly, there is a disadvantage in that the operational speed is varied according to a load status of the car, namely the number of the passengers and cargo. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide a method for controlling a rescue operation of an elevator car during a power failure by controlling a speed and a torque of a permanent magnet-type synchronous motor with an electricity generating power thereof, not by operating the car with a battery power and a balance of a braking torque and a torque by a weight difference between the car and a balance weight 
     It is another object of the present invention to provide a method for controlling a rescue operation of an elevator car during a power failure, without using a contactor and a ground resistance. 
     In order to achieve the above-described objects of the present invention, there is provided a method for controlling a rescue operation of an elevator car during a power failure by using an elevator system including: a rope; an elevator car connected to one end portion of the rope for transferring passengers or cargo; a balance car connected to the other end portion of the rope for keeping the balance with the elevator car; a traction motor moving the car in a vertical direction by winding or releasing the rope; a three-phase alternating current synchronous motor for providing a driving force rotating the traction motor in a clockwise or counterclockwise, and having a permanent magnet generating electric power by rotating of a rotor due to a weight difference between the balance weight and the car during the power failure; a three-phase alternating current power source supplying an alternating current power; a converter converting an alternating current from the three-phase alternating current power source into a direct current; an inverter having switching devices for each phase provided with a gate for switching control, respectively, converting a direct current from the converter into a three-phase alternating current, and outputting it to the motor; a condenser for charging, smoothing and outputting a direct current from the converter during the normal operation, and receiving a generated current from the motor through the inverter, and charging, smoothing and outputting it during the power failure; a power failure detector connected to the three-phase alternating current power source for detecting the power failure; a controller receiving a power failure detection signal output from the power failure detector, and outputting a speed command signal and a magnetic excitation component current command signal to the motor; a speed and position detector having an encoder for outputting a pulse signal corresponding to a rotation angle of the motor; a current detector for detecting and outputting each phase current of the three-phase alternating current outputted from the inverter to the motor; an inverter controller outputting voltage command signals of pulse width-modulated three phases on the basis of the speed command signal and the excitation component current command signal from the controller, each phase current from the current detector, and the pulse signal from the encoder; a gate driving unit driving a gate of the inverter; and a direct current voltage detector for detecting a direct current voltage at both ends of the condenser, and for supplying the direct current voltage to the inverter controller, the inverter controller being provided with a speed detector for computing a current speed of the car depending on the pulse signal from the encoder, and outputting a computed speed signal; a speed controller for outputting a torque component current command signal to compensate a difference between a command speed according to the speed command signal from the controller and a detection speed according to the detection speed signal from the speed detector; a first coordinate converter for converting and outputting the current signal from the current detector into an excitation component current detection signal and a torque component current detection signal depending on the pulse signal from the encoder; an excitation component current controller outputting an excitation component voltage control signal for compensating a difference between an excitation component current command value according to the excitation component command signal from the controller and an excitation component current detection value according to the excitation component current detection signal from the first coordinate converter; a torque component current controller for outputting a torque voltage control signal to compensate a difference between a torque component current detection value according to the torque component current detection signal from the first coordinate converter and a torque component current command value according to the torque component current command signal from the speed controller; a second coordinate converter for converting and outputting the excitation component voltage control signal from the excitation component current controller and the torque voltage control signal from the torque component current controller into voltage control signals of three phases according to the pulse signal from the encoder; and a pulse width modulator respectively pulse width modulating and outputting the voltage control signals of three phases outputted from the second coordinate converter, the method comprising; a step for obtaining the electricity generation by rotating the synchronous motor due to the weight difference between the balance weight and the car during the power failure; a step for charging the generated electricity into the condenser; and a step for gradually increasing a rotation speed of the synchronous motor from a starting time thereof to a predetermined time for speed controlling matched with a charging voltage of the condenser at an initial stage of the power failure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein: 
     FIG. 1 is a block diagram illustrating a conventional apparatus for controlling an operation of an elevator car; 
     FIG. 2 is a block diagram illustrating an apparatus for controlling an operation of an elevator car in accordance with a first embodiment of the present invention; 
     FIG. 3 is a detailed block diagram illustrating an example of an inverter controller in FIG. 2; 
     FIG. 4 is a block diagram illustrating an apparatus for controlling an operation of an elevator car in accordance with a second embodiment of the present invention; and 
     FIG. 5 is a block diagram illustrating an apparatus for controlling an operation of an elevator car in accordance with a third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The operation of a apparatus and method for controlling an operation of an elevator car in accordance with the present invention will now be described in detail with reference to the accompanying drawings. 
     FIG. 2 is a block diagram illustrating the apparatus for controlling the operation of the elevator car in accordance with a first embodiment of the present invention. As shown therein, an elevator car  210  is connected to one end portion of the rope, and transfers passengers or cargo. A balance weight  211  is connected to the other end portion of the rope, and keeps a balance with the elevator car  210 . 
     A traction machine  208  moves the car  210  in a vertical direction by winding or releasing the rope. A brake  209  brakes or releases the traction machine  208 . The three-phase alternating current synchronous motor  205  provides a driving force rotating the traction machine  208  in a clockwise or counterclockwise, and has a permanent magnet generating an electricity by rotating of a rotor due to a weight difference between the balance weight  211  and the car  210  during the power failure. 
     The three-phase alternating current power source  201  serve to supply an alternating current of three phases, and the alternating current from the three-phase alternating current power source  201  is converted into a direct current by a converter  202 . 
     An inverter  204  includes switching devices for each phase provided with a gate for switching control, respectively, converts a direct current from the converter  202  into a three-phase alternating current, and outputs it to a motor  205 . 
     A condenser  203  charges, smoothes and outputs a direct current from the converter  202  during the normal operation, and receives generated electricity from the motor  205  through the inverter  204 , and charges, smoothes and outputs it during the power failure. 
     A power failure detector  212  connected to the three-phase alternating current power source  201 , and detects the power failure. An output thereof is connected to a controller  213 . The controller  213  receives a power failure detection output from the power failure detector  212 , and generates a speed command signal and an excitation component current command signal id* of the motor  205 . 
     An encoder of a speed and position detector  207  is connected to an output from the motor  205 , and outputs a pulse signal corresponding to a rotation angle of the motor  205 . 
     A current detector  206  is connected to a supply path of the three-phase alternating current outputted from the inverter  204  to the motor  205 , detects the currents for each phase, and outputs them to an inverter controller  214 . The inverter controller  214  receives the speed command signal ωm* and the excitation component current command signal id* from the controller  213 , the current values for each phase from the current detector  206 , and the pulse signal from the encoder  207 , and outputs voltage command signals of pulse width-modulated three phases. 
     A gate driving unit  215  drives a gate of the inverter according to the voltage command signal from the inverter controller  214 . 
     FIG. 3 is a detailed block diagram illustrating an example of the inverter controller  214  in FIG.  2 . The operation of the inverter controller will now be described. 
     A speed detector  307  computes a current speed of the car  210  based on the pulse signal from the encoder  207 , and outputs a detection speed signal ωm. 
     A speed controller  302  outputs a torque component current command signal iq* for compensating a difference between a command speed according to the speed command signal ωm* from the controller  213  and a detection speed according to the detection speed signal ωm from the speed detector  302 . 
     A first coordinate converter  301  converts and outputs current signals for each phase ia, ib, ic from the current detector  206  into an excitation component current detection signal id and a torque component current detection signal iq. 
     An excitation component current controller  303  (so called d-axis current controller) outputs an excitation component voltage control signal Vd* for compensating a difference between an excitation component current command value according to the excitation component current command signal id* from the controller  213  and an excitation component current detection value according to the excitation component current detection signal id from the first coordinate converter  301 . 
     A torque component current controller  304  (so called q-axis current controller) outputs a torque voltage control signal Vq* for compensating a difference between a torque component current detection value according to the torque component current detection signal iq from the first coordinate converter  310  and a torque component current command value according to the torque component current command signal iq* from the speed controller  302 . 
     A second coordinate converter  305  converts and outputs the excitation component voltage control signal Vd* from the excitation component current controller  303  and the torque voltage control signal Vq* from the torque component current controller  304  in to voltage control signals of three phases Va*, Vb*, Vc*. 
     A pulse width modulator  306  respectively pulse width modulates the voltage control signals of three phases from the second coordinate converter  305 , and outputs them to the gate driving unit  215 . The operation of the present invention will now be described in detail with reference to FIGS. 4 and 5. 
     The operation control process during the normal state operation is similar to the conventional art. 
     The three-phase alternating current power source  201  is converted into the direct current via the converter  202 , smoothed through the condenser  203 , and supplied as an input power source of the inverter  204 . 
     At this state, when the speed command is inputted from the controller  213  to the inverter controller  214 , the inverter controller  214  outputs the gate driving signal to the gate driving unit  215 . Accordingly, the switching devices in the inverter  204  are switched, and thus the driving voltage is provided to the synchronous motor  205 . The rotation force of the synchronous motor  205  rotating at a speed corresponding to the inputted driving power source is transmitted to the traction machine  208 , and the car  210  starts to move to a destination floor. 
     The gate driving signal outputted from the inverter controller  214  is a pulse width modulation signal having a predetermined pattern generated by receiving the output signal from the current detector  206  and the speed and position detector  207 . The pulse width modulation signal is amplified to a predetermined level through the gate driving unit  215 , and supplied to the inverter  204 . 
     On the other hand, when the power failure is detected by the power failure detector  212 , and when the detection signal is supplied to the controller  213 , the driving of the inverter  204  stops. At the same time, the brake  209  of the traction motor is operated, and thus the car  210  stops at a current position. 
     Here, the auxiliary power source prepared for the emergency such as the power failure is supplied to the controller  213 . The controller  213  examines a safety state of a hoist way and a normal/abnormal state of each control circuit, and performs the emergency operation as follows, when there is no abnormality. 
     Firstly, the brake  209  is released, and thus the car  210  starts to move towards a heavier side between the car  210  and the balance weight  211 . That is, when the car  210  is heavier than the balance weight  211 , the car  210  moves to a lower direction. In the opposite case, the car  210  moves to an upper direction 
     As described above, when the car  210  starts to move towards one side due to a weight difference between the car  210  and the balance weight  211 , the rotation force is transmitted to the synchronous motor  205  through a power transmission system between the car  210  and the synchronous motor  205 . thereby rotating the synchronous motor  205 . 
     A stator of the synchronous motor  205  includes the permanent magnet, and thus a rotor cuts a magnetic flux from the permanent magnet. Accordingly, the motor  205  is operated as a generator, thus generating an electricity. The electricity is charged in the condenser  203  through the inverter  204 . 
     In case a charging voltage level of the condenser  203  is increased to a predetermined level, namely to a driving level of the inverter  204 , the inverter  204  is controlled by the inverter controller  214  and the gate driving unit  215 , thereby controlling the rotation speed and torque of the synchronous motor  205 . 
     That is, when the charging voltage is increased to a predetermined level, the inverter  204  is controlled as in the normal operation mode, and thus the synchronous motor  205  can be driven. Therefore, differently from the conventional art, the contractor and the resistance are not necessary. 
     On the other hand, the inverter control operation of the inverter controller  214  will now be explained in detail with reference to FIG.  3 . 
     The control operation of the synchronous motor  205  is performed based on the rotation angle of the rotor and the synchronous coordinate system. Here, an in-phase component in regard to the magnet flux of the permanent magnet, namely an excitation component is set to be axis d, and an orthogonal component, namely a torque component is set to be axis q. 
     The first coordinate converter  301  converts the currents of each phase ia, ib, ic detected from the current detector  206  into the magnetic excitation current id and the torque component current iq on the synchronous coordinate system, centering around the rotation angle θm of the synchronous motor  205  detected by the speed and position detector  207 . 
     The speed controller  302  receives the speed ωm of the synchronous motor  205  detected by the speed and position detector  207  and the speed command ωm* which is an output from the controller  213 , and outputs the torque component current command iq*. 
     On the other hand, the magnetic flux is determined by the permanent magnet, and thus the d-axis current command id* is generally set to be ‘0’. However, in order to control the magnetic flux of the permanent magnet, it may be set to be a different value. 
     The d-axis current controller  303  receives the current command id* and the current id converted in the first coordinate converter  301 , and outputs the d-axis voltage command Vd*. The q-axis current controller  304  receives the current command iq* outputted from the speed controller  302  and the current iq converted in the first coordinate converter  301 , and outputs the q-axis voltage command Vq*. The second coordinate converter  305  coordinate-converts the d-axis and q-axis voltage commands Vd*, Vq*, according to the rotation angle θm, and outputs the command values Va*, Vb*, Vc* of a phase voltage. 
     The pulse width modulator  306  computes a pulse width of the pulse width modulation signal to be supplied to the gate of the switching device of the inverter  204  according to the command values Va*, Vb*, Vc* of the phase voltage outputted from the second coordinate converter  305 , and outputs a corresponding pulse width modulation signal. The switching devices of the inverter  204  are switched according to the pulse width modulation signal, the driving force is supplied to the synchronous motor  205 , and thus the torque is generated thereto, thereby controlling the speed of the synchronous motor  205 . 
     When the car  210  reaches to a door zone of the nearest floor by operating the synchronous motor  205  at a low speed through the inverter controller  214 , the door is opened in order for the passengers to get off. 
     However, the electricity generated from the synchronous motor  205  is slight at an initial stage of the emergency operation, and thus a level of the direct current voltage outputted from the condenser may be lower than a rated value. Accordingly, the speed control may not be smoothly performed by using the speed controller  302 . Thus, in order to smoothly control the synchronous motor  205  during the emergency operation, it is necessary to limit the torque component current command iq* below the rated value until the voltage is sufficiently charged in the condenser  203  after starting the emergency operation of the car  210 . That is, it is necessary to gradually increase a limit value of the torque component current command iq* which is the output from the speed controller  302  according to the rotation speed of the synchronous motor  205  or the time elapsed. 
     Also, the level of the charging direct current voltage of the condenser  203  may be lower than the rated value before the synchronous motor  205  is rotated and accelerated at a predetermined speed. Accordingly, it is necessary to limit the output values of the dais and q-axis voltage commands Vd*, Vq* of the d-axis current controller  303  and the q-axis current controller  304  according to the rotation speed of the synchronous motor  205  or the time elapsed after the starting of the motor  205 . 
     That is to say, the limit values of the d-axis and q-axis voltage commands Vd*, Vq* of the d-axis current controller  303  and the q-axis current controller  304  are gradually increased according to the rotation speed of the synchronous motor  205  or the time elapsed. As another example, to limit the command values Va*, Vb*, Vc* of the phase voltage outputted from the second coordinate converter  305  obtains the same effect. 
     As discussed earlier, the direct current voltage is charged in the condenser  203  by the back electromotive force generated according to the rotation of the synchronous motor  205 , and thus the direct current voltage supplied to the inverter  204  can not maintain a constant potential. In order to exactly synthesize the command values Va*, Vb*, Vc* of the phase voltage in the pulse width modulator  306 , it is required to exactly know the level of the varied direct current voltage. As illustrated in FIG. 4, it is possible to exactly measure the level of the direct current voltage to be varied, by adding a direct current voltage detector  401  measuring a direct current voltage charged in the condenser  203 , and outputting it to the inverter controller. The pulse width modulator  306  outputting the pulse width modulation signal to the gate driving unit  215  controls a pulse width modulation signal generating time according to the output from the direct current voltage detector  401 . That is, in accordance with the output from the direct current voltage detector  401 , when the direct current voltage charged in the condenser  203  is lower than the rated value, a pulse width of the pulse width modulation signal is controlled to be short, and when the direct current voltage is higher than the rated value, the pulse width thereof is controlled to be long, or to be gradually increased. 
     As described above, in accordance with the present invention, when the emergency such as the power failure takes place, the car is not operated by the weight difference between the car and the balance weight, and the ground resistance value. That is to say, the low-speed emergency operation is operated by controlling the speed and torque of the synchronous motor through the inverter with the back electromotive force of the motor. Accordingly, a special device is not required, which results in the reduced fabrication cost. In addition, the emergency operation may be stably performed. 
     As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.