Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes control for power source of drive-means
Reexamination Certificate
1999-12-15
2001-09-04
Salata, Jonathan (Department: 2837)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes control for power source of drive-means
C187S293000
Reexamination Certificate
active
06283252
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique of estimating a load applied to an output axis of a motor of an elevator car, and compensating a torque command current of the motor, and in particular to a leveling control device for an elevator system used for a level correction operating by a level difference between a designated floor bottom and an elevator car bottom generated when passengers get in/off after the elevator car stops at the designated floor.
2. Description of the Background Art
In general, a torque compensation method of compensating a torque corresponding to a load detected during movement by employing a load detector detecting a load of an elevator car (hereinafter, referred to as ‘car’) has been used in order to improve a ride comfort in an elevator system. According to the torque compensation method, there is a sufficient time to detect the load before closing a car door and moving the car, and thus the load of the car can be exactly detected. As a result, it is possible to control the motor to generate a torque compensation command appropriate to an amount of the detected load, and thus the ride comfort is relatively good.
However, when the car stops at the designated floor, the door is open and the passengers get in or off the car, a bottom level of the car is not identical to a bottom level of the designated floor according to a load variation, that is a level difference is generated. Here, the level difference is detected by using a position detection unit disposed at an upper portion of the car, and then out a level correction operating is carried out. However, the passengers constantly get in or off while the level correction operating is performed, and thus the load amount detected by the load detector has an error. Therefore, a speed control property of the elevator system compensating the load of the car is worsened. The conventional leveling control device for the elevator system will now be described in detail with reference to FIG.
1
.
In order to move the car in an elevator system employing an alternating current motor, in case a torque of the alternating current motor is controlled by dividing a control current supplied to the alternating current motor into two vectors, namely a torque component current and a magnetic flux component current, an almost identical property to the control property of a direct current motor can be obtained. Accordingly, the vector control method has been used for the alternating current motor control for the elevator system. As illustrated in
FIG. 3
, the conventional elevator system using the vector control method includes an alternating current power source AC and a converter
101
converting an alternating current from the alternating current power source AC into a direct current. A condenser
102
for smoothing a ripple component included in an output from the converter
101
is connected to the output from the converter
101
. An inverter
103
for converting a direct current voltage outputted from the condenser
102
into an alternating current voltage is connected across the condenser
102
. An alternating current motor
106
is connected to an output from the inverter
103
to be driven in a clockwise or counterclockwise by an alternating current supplied from the inverter
103
. A sheave
108
is connected to an output axis of the alternating current motor
106
, and rotated in a clockwise or counterclockwise. A rope winds around the sheave
108
. A car
109
lifted/lowered in a hoist way for loading passengers or cargo is connected to one end of the rope, and a balance weight
110
balancing with the car
109
is connected to the other end of the rope. The following control units are additionally connected for the speed and leveling control of the conventional elevator system. Current detectors
104
are connected to a current supply path from the inverter
103
to the alternating current motor
106
in order to detect a current flowing through the motor
106
. A pulse generator
107
detecting a rotation speed of the motor
106
and outputting a resultant pulse signal is connected to the output axis of the motor
106
. A load detector
111
is disposed at a low portion of the load detector
111
, and detects and outputs the load of the car
109
.
As depicted in
FIG. 2
, a position detection unit
112
disposed at an upper portion of the car
109
includes a pair of position detectors PA, PB. Each position detector PA, PB is provided with a photo-coupler or a magnetic switch (not shown). On the other hand, a shielding plate SP is disposed at a predetermined height from each floor bottom surface of the walls of the hoist way, and detects a position of the car
109
by intercepting an optical transmission or magnetic flux of the position detectors PA, PB.
According to output signals from the position detectors PA, PB, a level difference detection unit
113
detects a state where the bottom level of the car
109
is identical to the bottom level of the designated floor (FIG.
2
(
a
)), a state where the bottom level of the car
109
is higher than the bottom level of the designated floor (FIG.
2
(
b
)) or a state where the bottom level of the car
109
is lower than the bottom level of the designated floor (FIG.
2
(
c
)), thereby outputting an output signal corresponding to the respective states.
A level compensation operation command generator
114
is connected to an output from the level difference detection unit
113
. When the level difference is generated as shown in FIG.
2
(
b
) or
2
(
c
), the level compensation operation command generator
114
outputs a corresponding lifting or lowering level compensation operation command signal LCD as shown in
FIG. 3
d
according to an output signal from the level difference detection unit
113
.
A speed command generator
115
is connected to an output from the level compensation operation command generator
114
. In case the level compensation operation command generator
114
generates the lifting or lowering level compensation operation command signal LCD, the speed command generator
115
outputs a level compensation speed pattern signal LCV as shown in
FIG. 3
e.
A speed controller
116
is connected to an output from the speed command generator
115
and an output from the pulse generator
107
, computes a speed difference of the motor
5
according to a speed command value of the level compensation speed pattern signal LCV from the speed command generator
115
and a pulse signal from the pulse generator
107
, and outputs a torque component current command signal I&tgr;* of the motor corresponding to the difference value.
A load current converter
117
is connected to an output from the load detector
111
, and outputs a load compensation torque signal it_ub1 representing a detection load (a load resulting from a weight difference between the car
109
and the balance weight
110
, which must be torque-compensated) from the load detector
111
as a current value.
A current controller
118
is connected to an output from the speed controller
116
, an output from the current detector
104
and an output from the load current converter
117
, and adds a current value corresponding to a detection load amount represented by the load compensation torque signal it_ub1 from the load current converter
117
into a difference value between a torque component current command value represented by the torque component current command signal i&tgr;* from the speed controller
116
and a current value flowing through the motor
106
from the current detector
104
, thereby outputting a current command signal it* corresponding to the torque amount to be finally compensated.
A pulse width modulator
119
is connected to an output from the current controller
118
, generates a pulse width modulation signal corresponding to the current command signal it* from the current controller
118
, provides the pulse width modulation signal to the inverter
103
, and switching-controlling the inverter
103
.
The levelin
LG Industrial Systems Co. Ltd.
Salata Jonathan
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