Speed control device and elevator having the same

Abstract

To reduce pulsation generated in the rotational speed of an electric motor for which feedback control of the rotational speed is performed, regardless of the rotational speed of the electric motor.SOLUTION: A speed control device 1 for controlling a rotational speed of an electric motor 3 of the present invention, includes: a notch filter 80 configured to reduce a frequency component belonging to a predetermined frequency band included in a control signal S; a switch 70; and control means 90. The switch 70 is provided to switch between a first signal path SC1 through which the control signal S is supplied to a driving device 2 via the notch filter 80 and a second signal path SC2 through which the control signal S is supplied to the driving device 2 without passing through the notch filter 80. The control means 90 switches the switch 70 such that the first signal path SC1 is set when a detection value U is equal to or larger than a predetermined first value Vs and the second signal path SC2 is set when the detection value U is smaller than the first value Vs.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a speed control device for an elevator or the like. [Background technology]

[0002] In elevators, feedback control is performed to control the rotation speed of the motor based on the detected speed detected by a detector such as an encoder that detects the rotation speed of the motor that runs the car. If vibrations occur in the detected speed due to misalignment of the encoder, pulsation occurs in the rotation speed of the motor, and vibrations occur in the car along the running direction of the car, which may deteriorate the ride comfort of the elevator. Patent Document 1 discloses an elevator that uses a notch filter or the like to reduce the vibrations of the car along the running direction even when vibrations occur in the detected speed detected by a detector such as an encoder. In Patent Document 1, the time constant of the notch filter is changed according to the detected speed to reduce the vibrations of the car along the running direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-064833 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the elevator of Patent Document 1, although the vibration of the car can be reduced in constant-speed sections where the rotational speed of the motor is approximately constant, there is a problem in that the vibration of the car actually worsens in acceleration and deceleration sections.

[0005] An object of the present invention is to provide a technique for reducing pulsation occurring in the rotation speed of an electric motor in which feedback control of the rotation speed is performed, even in an acceleration or deceleration section. [Means for solving the problem]

[0006] The speed control device of the present invention comprises: 1. A speed control device that controls a rotation speed of an electric motor by providing a control signal to a drive device that drives the electric motor, the control signal being calculated based on a detected speed value detected by a speed detector that detects the rotation speed of the electric motor and a speed command value that specifies the rotation speed of the electric motor, a notch filter for reducing frequency components in an input signal that belong to a predetermined frequency band; a first signal path that provides the control signal to the driver through the notch filter; a second signal path that provides the control signal to the driver without passing through the notch filter; a switch for switching between the first signal path and the second signal path; a control means for controlling the switch such that the first signal path is set when the detected speed value is equal to or greater than a predetermined first value, and the second signal path is set when the detected speed value is less than the first value; Equipped with.

[0007] the first value is determined based on a rated speed of the motor, a center frequency of the frequency band, and a second value; The second value can be the upper limit frequency of a frequency band in which the second noise elimination performance is worse when the signal path for providing the control signal to the drive device is fixed to the first signal path regardless of the rotational speed of the motor than the first noise elimination performance when the signal path for providing the control signal to the drive device is fixed to the first signal path regardless of the rotational speed of the motor.

[0008] The first value may be obtained by multiplying the rated speed by the center frequency and dividing the result by the second value.

[0009] Moreover, the elevator of the present invention includes the above-described speed control device. Effect of the Invention

[0010] According to the speed control device of the present invention, it is possible to suppress not only vibrations in a constant speed section where the rotation speed of the motor is approximately constant, but also vibrations in an acceleration section or a deceleration section. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an elevator drive system including a speed control device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart showing a procedure for setting the first value Vs, which is executed by an elevator installer or the like. [Diagram 3] FIG. 3 is a Bode plot showing the noise suppression performance with and without a notch. [Figure 4] FIG. 4 is a graph showing the relationship between the deterioration band crossover frequency f0 and the notch center frequency fn. [Diagram 5] FIG. 5 is a diagram illustrating the effect of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment in which a speed control device 1 of the present invention is applied to an elevator will be described with reference to the drawings.

[0013] Fig. 1 is a diagram showing an example of the configuration of an elevator drive system including a speed control device 1 according to an embodiment of the present invention. In addition to the speed control device 1, Fig. 1 shows an electric motor 3 that drives an elevator car, a drive device 2 that controls the drive of the electric motor 3 under the control of the speed control device 1, and a speed detector (referred to as a detector in Fig. 1, and the same applies hereinafter in this specification) 4 that detects the rotation speed of the electric motor 3. The detector 4 is an encoder such as a pulse generator. In Fig. 1, the elevator car raised and lowered by the electric motor 3, the rope attached to the car, the weight attached to the rope, and the like are not shown.

[0014] The electric motor 3 receives power from the driving device 2 and rotates the rotor at a rotation speed according to the power. In this embodiment, the electric motor 3 is a DC motor, but the electric motor 3 may be an AC motor. The driving device 2 converts the power supplied from a power source (not shown) into a current having a current value according to a control signal S given from the speed control device 1 and supplies the current to the electric motor 3. In this embodiment, the driving device 2 is a current converter of the thyristor Leonard type, but if the electric motor 3 is an AC motor, an inverter can also be used as the driving device 2.

[0015] 1, the speed control device 1 includes subtractors 10 and 60, an integrator 20, multipliers 30 and 50, an adder 40, a switch 70, a notch filter 80, and a control means 90. The subtractor 10, integrator 20, multiplier 30, adder 40, multiplier 50, subtractor 60, switch 70, notch filter 80, and control means 90 shown in Fig. 1 can be configured as software modules realized by operating a computer such as a CPU (Central Processing Unit) included in the speed control device 1 according to software.

[0016] 1, a rotation speed detection value U (detected speed value in the present invention) output from detector 4 is provided to subtractor 10, multiplier 50, and control means 90. The configuration of speed control device 1 is not particularly different from that of a conventional speed control device, except that it has a switch 70, a notch filter 80, and control means 90. The roles of the subtractor 10, integrator 20, multiplier 30, adder 40, multiplier 50, and subtractor 60 in speed control device 1 are roughly as follows:

[0017] The subtractor 10 generates a speed command specifying the rotation speed of the electric motor 3 according to the difference between a target value U* of the rotation speed (a speed command value in the present invention) and a detected value U of the rotation speed. The integrator 20 integrates the output of the subtractor 10 (i.e., the difference between the target value U* and the detected value U) and outputs the integrated value to the multiplier 30. The multiplier 30 multiplies the output of the integrator 20 by a gain K1 and outputs the result to the adder 40. The adder 40 performs a calculation to add the output of the multiplier 30 to the output of the subtractor 10, and outputs the result of this calculation to the subtractor 60. The multiplier 50 multiplies the detected value U by a gain K2 and outputs the multiplication result to the subtractor 60. The subtractor 60 generates a control signal S specifying the output torque of the electric motor 3 by subtracting the output of the multiplier 50 from the output of the adder 40.

[0018] The notch filter 80 is a filter for reducing frequency components in an input signal that belong to a predetermined frequency band. For example, a band-stop filter with a narrow stop band and a high Q value can be used as the notch filter 80. The frequency at which the Q value of the notch filter 80 is the highest (the frequency of the frequency component with the greatest attenuation) is called the notch center frequency. The notch center frequency fn in this embodiment is 3.5 Hz. The switch 70 is provided to switch between a first signal path SC1 that supplies the control signal S to the drive device 2 via the notch filter 80 and a second signal path SC2 that supplies the control signal S to the drive device 2 without passing through the notch filter 80. The control means 90 switches the switch 70 so that the first signal path SC1 is set when the detection value U is equal to or greater than a predetermined first value Vs, and the second signal path SC2 is set when the detection value U is less than the first value Vs.

[0019] The first value Vs can be determined based on the rated speed V of the motor 3, the notch center frequency fn, and the deterioration band crossover frequency f0. The deterioration band crossover frequency f0 is determined based on the noise elimination performance (hereinafter, first noise elimination performance) of the elevator drive system when the signal path of the control signal S is fixed to the second signal path SC2 regardless of the rotation speed of the motor 3, and the noise elimination performance (hereinafter, second noise elimination performance) of the elevator drive system when the signal path of the control signal is fixed to the first signal path SC1 regardless of the rotation speed of the motor 3. The noise elimination performance of the elevator drive system refers to the transfer characteristic of the rotation speed of the motor 3 (or the running speed of the car) with respect to disturbance caused by the core misalignment of the encoder. The deterioration band crossover frequency f0 in this embodiment is the upper limit frequency of the frequency band where the second noise elimination performance is worse than the first noise elimination performance. The deterioration band crossover frequency f0 is an example of the second value in the present invention. The first value Vs is determined in the following manner as one embodiment.

[0020] 2 is a flowchart showing a procedure for setting the first value Vs, which is executed by, for example, an elevator installer, a maintenance worker, etc. In step SA1, the installer determines the noise elimination performance (the above-mentioned first noise elimination performance) of the elevator drive system when the signal path of the control signal S is fixed to the second signal path SC2 regardless of the rotation speed of the electric motor 3.

[0021] In step SA2 following step SA1, the installer determines the noise removal performance (the above-mentioned second noise removal performance) for the elevator drive system when the signal path of the control signal is fixed to the first signal path SC1 regardless of the rotation speed of the electric motor 3. In step SA3 following step SA2, the installer identifies a frequency band in which the noise removal performance determined in step SA2 is worse than the noise removal performance determined in step SA1, and sets the upper limit frequency of the frequency band as the deterioration band crossover frequency f0.

[0022] For example, if the noise removal performance obtained in step SA1 is represented by graph GA1 in the Bode plot shown in FIG. 3, and the noise removal performance obtained in step SA2 is represented by graph GA2 in the Bode plot shown in FIG. 3, the installer determines the frequency F0 in FIG. 3 as the deterioration band crossover frequency f0.

[0023] In step SA4 following step SA3, the installer sets the first value Vs based on the deterioration band crossover frequency f0 obtained in the above manner. In this embodiment, the first value Vs is set by multiplying the rated speed V by the notch center frequency fn and dividing the result by the deterioration band crossover frequency f0, that is, by the value calculated by the following formula (1). Vs = V × fn / f0 (1)

[0024] In this embodiment, the deterioration band crossover frequency f0 is obtained by comparing the noise removal performance when the signal path of the control signal S is fixed to the first signal path SC1 and when it is fixed to the second signal path SC2. However, the relationship between the deterioration band crossover frequency f0 and the notch center frequency fn may be expressed as a function or a database, and the deterioration band crossover frequency f0 may be determined based on the notch center frequency fn by referring to the function or database.

[0025] For example, in the case where the stopband width ζ of the notch filter 80 is 0.1, 0.2, 0.3, and 0.4, and the notch depth is -40 dB, the relationship between the deterioration band crossover frequency f0 and the notch center frequency fn is obtained as shown in Fig. 4 by a simulation or the like regarding the noise removal performance, and the following formulas (2) to (5) are obtained as approximation expressions showing the relationship between the deterioration band crossover frequency f0 and the notch center frequency fn. In this case, each of the formulas (2) to (5) may be made into a function or a database. Note that the solid line graph in Fig. 4 is a graph obtained by linearly interpolating values ​​calculated for each frequency by the simulation, and the dotted line graph is a graph showing the above approximation expressions.

[0026] ζ=0.1:f0=0.797×fn+0.3595 (2) ζ=0.2:f0=0.673×fn+0.5255 (3) ζ=0.3:f0=0.585×fn+0.6325 (4) ζ=0.4:f0=0.519×fn+0.6965 (5)

[0027] FIG. 5 is a diagram for explaining the effect of this embodiment. Each of the graphs GB1, GB2, and GB3 in FIG. 5 is a graph showing the time change of the acceleration of the car along the traveling direction, with the horizontal axis showing the time and the vertical axis showing the acceleration. The graph GB1 corresponds to the case where the signal path of the control signal S is fixed to the second signal path SC2 regardless of the rotation speed of the motor 3, the graph GB2 corresponds to the case where the signal path of the control signal S is fixed to the first signal path SC1 regardless of the rotation speed of the motor 3, and the graph GB3 corresponds to the case where the signal path is switched by the control of this embodiment. In the example shown in FIG. 5, the misalignment of the detector 4 with respect to the rotating shaft of the motor 3 is 0.005 mm to 0.1 mm, and the vibration caused by this misalignment appears as a pulsation of the acceleration.

[0028] As is clear from the comparison between the graphs GB1 and GB2, when the signal path of the control signal S is fixed to the first signal path SC1 regardless of the rotation speed of the motor 3, minute fluctuations in the acceleration of the car in the constant speed section (i.e., vibration of the car along the running direction) can be reduced, while there is a speed section (the speed section marked with a circle in the graph GB2) in which the vibration of the car worsens in the deceleration section. On the other hand, as is clear from the comparison between the graphs GB3 and GB2, according to this embodiment, in the acceleration section and the constant speed section, in addition to reducing the vibration of the car in the same manner as when the signal path of the control signal is fixed to the first signal path SC1 regardless of the rotation speed of the motor 3, the deterioration of the vibration of the car is also reduced in the speed section (the speed section marked with a circle in the graph GB2) in which the vibration of the car worsens in the deceleration section. In this way, according to this embodiment, it is possible to reduce the pulsation occurring in the rotation speed of the motor 3, in which the feedback control of the rotation speed is performed, even in the deceleration section.

[0029] As is clear from the above formulas (2) to (5), there is a certain relationship between the notch center frequency fn and the deterioration band crossover frequency f0, and it would appear that the same effect as in this embodiment can be obtained by varying the notch center frequency fn in accordance with the rotation speed of the electric motor 3. However, the inventors of the present application did not adopt a configuration in which the notch center frequency fn is varied in accordance with the rotation speed of the electric motor 3. The first reason is that the corresponding frequency range is narrow, and it is possible to deal with the problem without making the notch center frequency fn variable. The second reason is that if the notch center frequency fn is made variable, the effect of the notch filter is not exerted if there is an error in reading the rotation speed.

[0030] The reason for the narrow compatible frequency range is as follows. When the detector 4 is misaligned, as shown in graph GB1 in FIG. 5, the car vibrates in the constant speed section, acceleration section, and deceleration section, but the vibrations tend to be smaller in the low speed ranges of the acceleration section and deceleration section. By using a notch filter, the influence of disturbance signals caused by the misalignment of the detector 4 can be reduced, but there is a disadvantage in that the target value tracking performance deteriorates (overshoot of the car's running speed or delay in reaching the designated speed, etc.). This disadvantage tends to be more pronounced when the notch filter is made compatible with the low speed range. Due to such disadvantages, it is desirable to narrow the range of rotational speeds (rotational frequencies) that the notch filter can accommodate. Also, if there are no disturbance signals, it is better not to use a notch filter.

[0031] Furthermore, even if vibration occurs in the detection value by the detector 4 in the low-speed range, the notch filter cannot handle it. When a notch filter is included in the feedback control in an elevator control system, there is a disadvantage that the system becomes more likely to become unstable. If the system becomes unstable, the control signal may diverge, and there is a risk that the car may run out of control. Furthermore, the lower the notch center frequency, the more likely the system becomes unstable. For this reason, when a notch filter is included in the feedback control in an elevator control system, it is common to set the applicable lower limit value of the notch center frequency with a certain amount of margin. Since the rotation frequency of the rated speed of the motor 3 (and the detector 4) is low, if the notch center frequency fn is made variable to accommodate the acceleration and deceleration sections, the applicable lower limit value will be reached immediately.

[0032] Next, the second reason will be described in detail. When the notch center frequency is made variable, if the value of the notch center frequency is suddenly switched, vibrations may occur due to incorrect switching. For this reason, control is required to gradually switch the value of the notch center frequency. On the other hand, in the acceleration section or deceleration section, the running speed of the car changes at a predetermined acceleration. If a deviation occurs between the notch center frequency and the rotation frequency of the detector 4 due to the time required for the speed calculation process and the switching control of the notch center frequency, the effect of the notch filter will not be exerted. Also, adjustment to correct an error in the rotation speed read by the detector 4 becomes difficult.

[0033] For the reasons explained above, the inventors of the present application did not adopt a configuration in which the notch center frequency fn is changed in accordance with the rotation speed of the electric motor 3.

[0034] As described above, according to this embodiment, it is possible to reduce the pulsation occurring in the rotation speed of the motor in which the feedback control of the rotation speed is performed, even in the deceleration section. In the above embodiment, an example of application of the present invention to the control of the rotation speed of the motor that runs the elevator car has been described, but the application of the present invention is not limited to the motor that runs the elevator car. As with the motor that runs the elevator car, if the motor is one that performs an acceleration operation in which the rotation speed is gradually increased to a predetermined rotation speed, a constant speed operation that maintains the predetermined rotation speed, and a deceleration operation in which the rotation speed is gradually decreased from the predetermined rotation speed and stopped based on the detection value of the rotation speed, the application of the present invention can suppress the pulsation of the rotation speed caused by the misalignment of the detector that detects the rotation speed.

[0035] The above description of the embodiment is for the purpose of explaining the present invention, and should not be interpreted as limiting the invention described in the claims or narrowing its scope. Furthermore, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications are possible within the technical scope described in the claims. [Explanation of symbols]

[0036] 1 Elevator drive system 2 AC power supply 3 Electric motor 10 Speed ​​control device 70 Switch 80 Notch Filter 90 Control Means

Claims

1. 1. A speed control device that controls the rotation speed of an electric motor by providing a control signal to a drive device that drives the electric motor, the control signal being calculated based on a detected speed value detected by a speed detector that detects the rotation speed of the electric motor and a speed command value that specifies the rotation speed of the electric motor, a notch filter for reducing frequency components in an input signal that belong to a predetermined frequency band; a first signal path that provides the control signal to the driver through the notch filter; a second signal path that provides the control signal to the driver without passing through the notch filter; a switch for switching between the first signal path and the second signal path; a control means for controlling the switch such that the first signal path is set when the detected speed value is equal to or greater than a predetermined first value, and the second signal path is set when the detected speed value is less than the first value; A speed control device comprising:

2. the first value is determined based on a rated speed of the motor, a center frequency of the frequency band, and a second value; the second value is an upper limit frequency of a frequency band in which the second noise elimination performance is worse when the signal path for providing the control signal to the drive device is fixed to the first signal path regardless of the rotation speed of the motor than the first noise elimination performance when the signal path for providing the control signal to the drive device is fixed to the second signal path regardless of the rotation speed of the motor; The speed control device of claim 1 .

3. The first value is obtained by multiplying the rated speed by the center frequency and dividing the resultant value by the second value. The speed control device according to claim 2 .

4. An elevator comprising a speed control device according to any one of claims 1 to 3.

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