HK1151018B - A method of determination of the loading state of an elevator, a method of movement control, and a elevator system - Google Patents

Description

Elevator load state determining method, motion control method and elevator system

Technical Field

The object of the invention is the determination of the loading state of an elevator system, the motion control of an elevator system, and a method for determining the loading state of an elevator system.

Background

In elevator systems with counterweight, the equilibrium position of the load is determined from the weight of the elevator car and counterweight. In the equilibrium position, the counterweight and the loaded elevator car exert substantially the same force effect on each other via the elevator ropes. In the equilibrium position, half of the nominal load of the elevator is normally loaded into the elevator car. In which case the counterweight is dimensioned to correspond to the weight of the elevator car and to half the weight of the nominal load. In practice, however, the equilibrium position may vary due to individual weight differences of e.g. the elevator car and the counterweight, and especially the weight of the elevator ropes.

So-called elevator systems without counterweight lack a counterweight to balance the load, so that there is always a certain degree of load imbalance in the elevator system from the point of view of the motor drive of the elevator.

The loading state of an elevator system is conventionally determined from measurements of the load of the elevator car, e.g. by load-weighing sensors fixed to the bottom of the elevator car or to the elevator ropes. The measurement results of the sensors determining the weight of the load almost always contain a certain degree of measurement error, which is perceived in a manner that impairs the ride comfort of the elevator, in particular when starting and when the elevator car arrives at the stopping floor. In addition, measurement errors impair the accuracy of the stopping of the elevator car at the floor.

Publication US6283252B1 describes determining the unbalance of an elevator on the basis of measured motor speeds. The determination is made in the case when the position of the bottom level of the elevator car differs from the landing level defined by the limit switch. The problem in this case is that only binary information is received from the limit switches as to whether the elevator car is at the stopping level, which increases the inaccuracy of the stopping at the floor and lengthens the movement of the elevator car to the floor in connection with the stopping.

Disclosure of Invention

Objects of the invention

It is an object of the invention to disclose a more accurate and faster determination of the imbalance of the elevator load than in the prior art.

Features of the invention

The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of expressions or implicit sub-tasks or from the point of view of advantages or categories of advantages achieved. In this context, an elevator system generally refers to a lifting system intended to lift a person or goods, such as a drum-driven elevator or other crane system, on the other hand, an elevator system also refers to a passenger elevator or a goods elevator.

The elevator system according to the invention comprises an elevator car and a motor drive for moving the elevator car. In this case, the load state of the elevator system according to the invention is determined on the basis of the elevator motor position deviation occurring during the determination of the load state. In this case, the motor drive comprises an elevator motor, which may be, for example, a motor, such as a direct current motor or an alternating current motor, for example a synchronous motor. The elevator motor may be a rotary motor or a linear motor. The motor may also be a permanent magnet motor. The motor drive is connected to the elevator car directly or e.g. via an elevator rope supporting the elevator car. The position deviation of the elevator motor in this context refers to the deviation from the starting position of the motor at the beginning of the determination of the load. When determining the load state on the basis of the elevator motor position deviation occurring during the load state, the position deviation is determined directly from the position of the rotor of the elevator motor, or the position of the traction sheave or some other part of the elevator system moving the elevator car.

In one embodiment of the invention the motor drive comprises a motion reference comprising a speed reference of the motor and a positive feedback of the motor torque. The motor drive comprises a lift motor, and a power supply device connected to the motor of the lift motor, which power supply device of the motor is adapted to move the lift motor on the basis of a speed reference of the motor. In determining the load state, a speed reference of the motor is determined on the basis of a position deviation of the elevator motor in determining the load state, and in determining the load state, a torque reference of the motor is determined on the basis of a comparison between an actual value and a reference value of the motor speed and on the basis of a position deviation of the elevator motor. The load state of the elevator system is determined from the aforementioned torque reference during the determination of the load state.

In one embodiment of the invention, the duration (duration) of the load state determination is set in advance.

In one embodiment of the invention the load status is determined after the machinery brake of the elevator motor has been opened, and in this case the position deviation of the elevator motor is determined starting from the position at which the elevator motor was locked by the machinery brake before the determination was made.

In one movement control of the elevator system according to the invention, the movement of the elevator car is set by the motor drive according to the movement reference. The movement reference here comprises a speed reference of the elevator motor and a positive feedback of the torque of the elevator motor. The positive feedback of the torque of the elevator motor is determined at least on the basis of a position deviation of the elevator motor occurring in the course of determining the loading state of the elevator system. The speed reference refers to a speed reference value profile which changes as a function of time or, for example, the position or location of the elevator car or the motor, said reference value profile consisting of reference values which follow one another in succession. The positive feedback of the motor torque refers to a reference value curve of the positive feedback of the torque, which in a corresponding manner consists of reference values of the positive feedback of the torque. The speed reference and the positive feedback of torque may be continuous or discrete.

In one method according to the invention for determining the loading state of an elevator system, a motor drive is mounted to the elevator system for moving the elevator car. In the method, a position deviation of the elevator motor is determined, and a loading state of the elevator system is determined based on the position deviation of the elevator motor.

In one method according to the invention for controlling the movement of an elevator system, the movement of the elevator car is set by means of a motor drive; the position deviation of the elevator motor is determined in the course of determining the loading state of the elevator system; positive feedback of motor torque is determined based on at least the aforementioned position deviation of the elevator motor; and the elevator motor is controlled based on the motion reference.

According to a preferred embodiment of the present invention, there is provided a method of determining a load state of an elevator system including an elevator car and a motor drive for moving the elevator car, wherein a reference value of a current proportional to a torque of the elevator motor is formed in response to a magnitude of a positional deviation occurring between a rotor and a stator of the elevator motor during determination of the load state; the positional deviation is determined starting from a starting position between the rotor and the stator before the determination; the current of the elevator motor is adjusted by a current regulator to correspond to the reference value of the current; and the loading state of the elevator system is determined by the aforementioned current and/or by a reference value for the current of the elevator motor.

In a preferred embodiment of the invention, the reference value for the current proportional to the torque of the elevator motor is also formed by the output of the speed regulator during the determination of the load state; the output of the speed regulator is set based on a speed reference of the motor and a measured value of the motor speed; the speed reference of the motor is formed in response to the magnitude of the position deviation (4) between the rotor and the stator of the elevator motor that occurs during the determination of the load state, for stabilizing the movement of the elevator motor.

According to a preferred embodiment of the present invention, there is provided an elevator system comprising a determination of a load state, the elevator system comprising an elevator car and a motor drive for moving the elevator car, wherein a reference value of a current proportional to a torque of the elevator motor is formed in response to a magnitude of a positional deviation occurring between a rotor and a stator of the elevator motor during the determination of the load state; the positional deviation is determined starting from a starting position between the rotor and the stator before the determination; the current of the elevator motor is adjusted by a current regulator to correspond to the reference value of the current; and the loading state of the elevator system is determined by the aforementioned current and/or by a reference value for the current of the elevator motor.

THE ADVANTAGES OF THE PRESENT INVENTION

By means of the invention, at least one of the following advantages is achieved:

when the loading state of the elevator system is determined on the basis of the position deviation of the elevator motor that occurs during the determination of the loading state, the determination is more accurate than in the prior art, because in this case any error in the unbalance of the loading of the elevator system will be compensated more accurately than in those prior art solutions in which the unbalance is determined with a sensor for measuring the weight of the loading, for example of the elevator car. By the determination according to the invention, also imbalances caused by non-idealities of the mechanical parts of the elevator system, such as for example imbalances caused by individual weight differences of the elevator car and the counterweight or imbalances caused by the weight of the elevator ropes are compensated. In addition, by this determination, it is also possible to solve the problem caused by measurement inaccuracy of the sensor that measures the load weight, such as offset and amplification error of the sensor that measures the load weight. Furthermore, the elevator system is cheaper, simpler and at the same time more reliable than prior art elevator systems, because a separate load-weighing sensor of the elevator car is not necessary for this determination.

In one embodiment of the invention, the reference value of the current proportional to the torque of the elevator motor is formed in response to the magnitude of a position deviation between the rotor and the stator of the elevator motor occurring during the determination of the load state, said position deviation being determined starting from a starting position between the rotor and the stator before said determination; in this case the current and thus the torque of the elevator motor can be adjusted more accurately as a function of the position change between the rotor and the stator than in prior-art solutions, in which the adjustment of the current/torque is performed by a speed regulator on the basis of the difference between a reference value and an actual value of the rotor speed. Also, during the determination, the movement of the elevator motor is substantially reduced, which improves the driving comfort of the elevator and the safety of the operation of the elevator. In this case, torque regulation of the motor is achieved without a speed regulator, so that the current supplied to the motor is regulated by a current regulator to correspond to a reference value of the current, and the polarity of the current is selected so that the torque of the motor generated by the current is in the opposite direction to the change in position between the rotor and the electrons, thus endeavouring to prevent the aforementioned change in position. In this case the torque of the motor is adjusted to compensate for the imbalance of the elevator system in an effort to keep the elevator car in its position in the elevator hoistway, and the load state of the elevator system can be determined from the current and/or the reference value of the current of the elevator motor without movement of the elevator motor impairing the ride comfort of the elevator.

In one embodiment of the invention, the reference value for the current proportional to the torque of the elevator motor is formed additionally during the determination of the load state by the output of a speed regulator, wherein the output of the speed regulator is set on the basis of a speed reference of the motor and a measured value of the motor speed, wherein the speed reference of the motor is formed in response to the magnitude of the position deviation between the rotor and the electronics of the elevator motor that occurs during the determination of the load state. In this case, the movement between the rotor of the elevator motor and the electrons is further damped, in which case the movement of the elevator motor can be stabilized.

If the load state of the elevator system is determined by the determination according to the invention and by the load-weighing sensors of the elevator cars of the prior art, the determination is more accurate than those of the prior art in which the imbalance is determined only by the load-weighing sensors of the elevator cars. In this case, the accuracy of the determination of the load state of the elevator system can also be improved in those elevator systems which already comprise the aforementioned load-weighing sensor of the elevator car.

When the load status of the elevator system is determined on the basis of the position deviation of the elevator motor as provided in the invention, this determination is quick and can be made at the start of the run, for example after the machinery brake has been opened.

The duration of the determination may be minimized when the load state of the elevator system is inferred to be determined after the change in speed of the elevator or the change in torque reference of the elevator motor has decreased to within a range of allowable values set around a zero value.

When the positive feedback of the torque of the elevator motor is determined on the basis of the elevator motor position deviation occurring in the course of determining the loading state of the elevator system, the improvement in the accuracy of said determination also affects the ride quality of the elevator due to the improvement in the accuracy of the positive feedback of the torque, since the measurement errors of the load-weighing sensor of the car and the errors of the positive feedback of the torque caused thereby already routinely lead to additional vibrations in the elevator car when the elevator car reaches the parking level, in particular at the start of a run and at the end of a run. At the same time, the accuracy of the stopping of the elevator car at the floor is improved.

When the positive feedback of the motor torque is determined on the basis of the elevator motor position deviation occurring in the course of determining the loading state of the elevator system, the positive feedback of the motor torque no longer needs to be determined separately on the basis of determining the loading state, which reduces the calculation of the motion reference and at the same time speeds up the motion control.

In one example of the invention, the starting value of the speed reference in the drive mode of the elevator is determined on the basis of the speed reference in the determination of the load state. In this case, the speed reference is continuous, which improves the ride quality of the elevator.

In one embodiment of the invention the speed of the elevator motor and the position of the elevator motor are determined by a rotating shaft connected to the elevator motor or an encoder, e.g. a traction sheave. The magnitude of the rotation angle of the encoder can be determined directly on the basis of the measured encoder pulses, in which case the encoder is suitable for determining the position deviation between the rotor and the stator of the elevator motor.

Drawings

The invention will be described in more detail hereinafter with the aid of some examples of embodiments of the invention, with reference to the accompanying drawings, in which:

fig. 1 shows an elevator system according to the invention;

fig. 2 illustrates motion control of an elevator system according to the prior art;

fig. 3 illustrates determining a loading state of an elevator system according to the present invention.

Detailed Description

Fig. 1 shows an elevator system according to the invention. The elevator car 2 and the counterweight 17 are moved in the elevator hoistway by the elevator motor 7 supported by the ropes 18. The power supply for the elevator motor 7 comes from the electricity network 15 via the frequency converter 8. The frequency converter 8 sets the motor 7 and at the same time also the elevator car 2 via the elevator ropes 18 according to the movement reference. In this case, the inverter 8 sets the torque of the motor 7 based on the torque reference 9. The motion controller measures the speed 10 and the position 12 of the measuring motor 7 for the friction operation by means of an encoder 16 mounted to the traction sheave. The encoder 16 can also be mounted on the shaft of the motor 7, in which case, in particular, the accuracy of the position measurement 12 is increased.

The elevator car 2 moves from floor to floor in the elevator hoistway. The location of the stop is indicated by a sensor at the stop floor. When the elevator car has stopped at a floor, the movement of the elevator car is prevented by locking the traction sheave of the elevator motor 7 with a mechanical brake. When a new run starts the machinery brake is opened, in which case the elevator car is held in place by the torque of the elevator motor so that it strives to compensate the imbalance of the load of the elevator system with the torque generated by the motor.

In this case, after the brake has been opened, the loading state of the elevator system is determined on the basis of the position deviation 4 of the elevator motor that occurs during the determination 1 of the loading state. The position deviation is determined starting from position 11 when the elevator motor was locked by the machinery brake before said determination. The load state of the elevator system is deduced to be determined when the change in the elevator speed 10 or the change in the torque reference 9 of the elevator motor has been within a set time set for the permissible value range around zero. In other words, when the absolute value of the speed change or the absolute value of the torque reference change has remained sufficiently small for a desired time, it is concluded that the load state is determined and the elevator starts to drive to the specified floor. In this case, the positive feedback of the torque of the elevator motor used in the motion control is also determined in the course of determining the load state. In an embodiment of the invention the load status of the elevator and the positive feedback of the torque of the elevator motor are also determined by a separate load weight measuring sensor 14 fixed to the bottom of the elevator car 2, but it is also possible to dispense with a separate load weight measuring sensor.

Fig. 2 illustrates motion control of a prior art elevator system. The movement of the elevator motor 7 is set by the speed regulator on the basis of comparing the speed reference 5 of the motor and the measured speed value 10 of the motor. A signal proportional to a torque reference of the elevator motor is received as an output of the speed regulator. In addition to this signal, the torque reference 9 is formed by a so-called positive feedback 6 of the torque. Positive feedback of the torque refers to an evaluation which is independent of the speed regulator and is based on the load of the elevator system, on the control situation or e.g. on the position of the elevator car, or is time-dependent, which is required for the torque of the elevator motor.

Here, the positive feedback of the torque is determined from the measurement signal 14 representing the load of the elevator car with a sensor of the weight of the load of the elevator car. In addition, certain parameters 22 of the elevator system, such as the inertial mass of the elevator moving in the elevator hoistway, affect the determination of the positive feedback of the torque. The motion control also comprises a torque regulator 24 which strives to set the torque of the elevator motor in accordance with the torque reference 9. The torque of the elevator motor is here proportional to the current of the elevator motor, so that the measured value of the current of the elevator motor functions as a measurement feedback 25 of the torque and the current regulator functions as a torque regulator 24.

Fig. 3 shows a determination 1 of the loading state of an elevator system according to the invention. In this case the determination 1 of the load state is adapted to the motion control of the elevator system associated as shown in fig. 2. The determination 1 of the load state starts to determine the position deviation 4 of the elevator motor when the machinery brake of the elevator motor is open. This deviation is determined by comparing the position 12 of the rotor of the elevator motor with the starting position of the rotor at the beginning of the determination. On the basis of this comparison, a speed reference 13 of the elevator motor is formed in the course of determining the load state, which speed reference is fed to the speed regulator 20. In addition, the aforementioned speed reference 13 of the elevator motor is sent to the determination 26 of the positive feedback 6 of the torque of the elevator motor after confirmation 21. The load signal 14 of the elevator car measured with the sensor measuring the weight of the load is here also used for determining the positive feedback 6, but the determination of the load state according to the invention does not necessarily comprise the sensor measuring the weight of the load/load signal 14, in which case the positive feedback 6 can be determined completely without a separate sensor measuring the weight of the load.

In fig. 3, the torque reference 9 of the elevator motor is formed by the output signal of the speed regulator 20 and the output signal of the positive feedback 6 of the torque. A measured speed signal 10 of the elevator is derived and the absolute value of the derivation is calculated. The absolute value is compared with a range of allowed values set around zero, and when the absolute value has been in the allowed region for a set time, the loading state of the elevator system is inferred to have been determined. In this case, the load state may be caused by the torque reference 9. By means of the determined load state, a possible overload of the elevator car can also be monitored. When the determination of the loading state is completed, the motor drive 3 is ready to drive the elevator car 2 to the designated floor according to the drive mode of the motion control. In this case, a positive feedback 6 based on the position deviation 4 of the elevator motor and the torque developed in connection with the determination of the loading state is registered and the registered positive feedback is used to develop the movement reference during the drive mode. In the drive mode, the movement of the elevator motor 7 and thus of the elevator car 2 is set according to the speed reference 5. In other words, the sign switch as shown in fig. 3 changes its state when the drive mode starts, and the speed reference 5 of the drive mode is sent to the speed regulator 20. In this case, however, the starting value of the speed reference 5 of the drive mode is determined on the basis of the speed reference 13 during the determination of the load state, in which case the starting value of the speed reference 5 of the drive mode is the same as the speed reference value at the end of the speed reference 13 during the determination of the load state, which speed reference value is continuous.

The invention has been described above with the aid of some examples of embodiments of the invention. It is obvious to the person skilled in the art that the invention is not limited to the embodiments described above, but that other applications are possible within the scope of the inventive concept.

Claims (9)

1. A method of determination of a load state of an elevator system, which elevator system comprises an elevator car (2) and a motor drive (3) for moving the elevator car, characterized in that a reference value for the current, which is proportional to the torque of the elevator motor of the motor drive (3), is formed in response to the magnitude of the position deviation (4) occurring between the rotor and the stator of the elevator motor during the determination of the load state;

the positional deviation is determined starting from a starting position between the rotor and the stator before the determination;

-the current (25) of the elevator motor is regulated by a current regulator to correspond to the aforementioned reference value of the current; and

the load state of the elevator system is determined by the aforementioned current and/or by a reference value for the current of the elevator motor.

2. A method for determining a load condition according to claim 1, characterized in that a reference value for the current proportional to the torque of the elevator motor is also formed by the output of the speed regulator (20) during the determination of the load condition;

the output of the speed regulator (20) is set based on a speed reference (5, 13) of the elevator motor and a measured value (10) of the speed of the elevator motor;

the speed reference (5, 13) of the elevator motor is formed in response to the magnitude of the position deviation (4) between the rotor and the stator of the elevator motor that occurs during the determination of the load state for stabilizing the movement of the elevator motor.

3. A method for determining a load condition according to any one of the preceding claims 1-2, characterised in that the motor drive (3) comprises a movement reference comprising a speed reference (5, 13) of the elevator motor and a positive feedback (6) of the torque of the elevator motor, and in that the motor drive comprises a motor supply (8) connected to the elevator motor, which motor supply is mounted to move the elevator motor on the basis of the speed reference (5, 13) of the elevator motor, and in that during the determination (1) of the load condition the speed reference (13) of the elevator motor is determined on the basis of a position deviation (4) of the elevator motor during the determination of the load condition and in that during the determination of the load condition, the torque reference of the elevator motor is determined on the basis of a comparison between a measured value (10) of the speed of the elevator motor and the speed reference (13) and on the basis of a position deviation (4) of the elevator motor, and in that the loading state of the elevator system is determined from the aforementioned torque reference during the determination (1) of the loading state.

4. A method for determining a load state according to any one of the preceding claims 1-2, characterized in that the duration of the determination of the load state is set in advance.

5. Method for determining the load state according to any one of the preceding claims 1-2, characterized in that the load state of the elevator system is deduced to be determined when the change value of the speed (10) of the elevator motor or the change value of the torque reference of the elevator motor has been within a range of allowed values set around zero and has been within this range for a set time.

6. A method for determining a load condition according to any one of claims 1-2, characterised in that the load condition is determined after the machinery brake of the elevator motor (7) has been released, and in that the position deviation (4) of the elevator motor in this case is determined starting from the position (11) at which the elevator motor was locked by the machinery brake before the determination.

7. Method for determining a load state according to any of the preceding claims 1-2, characterized in that the determination (1) of the load state is carried out without separate measurement feedback from a load weight measuring sensor (14) of the elevator car.

8. A method of movement control of an elevator system, wherein the movement of the elevator car is set by means of a motor drive (3) on the basis of movement references, which comprise a speed reference (5, 13) of the elevator motor and a positive feedback (6) of the torque of the elevator motor, characterized in that the positive feedback (6) of the torque of the elevator motor is determined on the basis of a position deviation (4) between the rotor and the stator of the elevator motor, which occurs during the determination of the loading state of the elevator system.

9. Elevator system comprising a determination (1) of a load state, which elevator system comprises an elevator car (2) and a motor drive (3) for moving the elevator car, characterized in that a reference value for the current proportional to the torque of the elevator motor of the motor drive is formed in response to the magnitude of the position deviation (4) occurring between the rotor and the stator of the elevator motor during the determination of the load state;

the positional deviation is determined starting from a starting position between the rotor and the stator before the determination;

-the current (25) of the elevator motor is regulated by a current regulator to correspond to the aforementioned reference value of the current; and

the load state of the elevator system is determined by the aforementioned current and/or by a reference value for the current of the elevator motor.