Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
2000-04-28
2002-02-26
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S799000, C318S599000, C318S611000, C198S322000, C187S292000
Reexamination Certificate
active
06351096
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an operation control technique for improving the ride comfort of an escalator, and in particular, to an operation control apparatus for an escalator which is capable of suppressing running vibration due to a footplate by using a vibration-damping control compensator.
In the escalator, an automatic operation means an operation mode for stopping an operation when no passenger intending to use the escalator, in order to save energy and broaden the product's life time. For this, there is provided a detection device for detecting the entrance and passage of a passenger. When the entrance of a passenger is detected, the escalator is operated at a constant acceleration, and then when a passenger reaches the point of entrance to a step, the escalator is operated at a nominal speed thereafter. With the lapse of certain amount of time since the last passenger's passing by the escalator, the operation of the escalator is stopped.
In order to perform the above automatic operation, an inverter having a power rectifier is usually employed. In addition, a power transmission device for the movement of the footplate of the escalator is constructed in such a way that a machine shaft having an induction motor and a gear is connected with a shaft of a sprocket having a terminal gear by a chain, to thereby rotate the sprocket. That is, a groove of semi-circumferential shape is formed at the circumferential portion of the sprocket, which is rotated, being engaged with a roller connected to a lower portion of the footplate. When they are engaged with each other, imbalance of torque occurs to thereby generate vibration, which vibration is transmitted to the footplate, thus decreasing the ride comfort.
The present invention is intended to remove electric components sensed on the footplate by detecting a position at which the roller and the sprocket are engaged using a position sensor attached on the shaft of the sprocket, inputting a detection signal thereof to the control apparatus, extracting a pulse component of the torque by a speed detector installed at the shaft of the induction motor, and then applying a torque whose magnitude and phase are opposite to the above torque to the induction motor.
2. Description of the Background Art
FIG. 1
is a block diagram of an operation control apparatus for an escalator in accordance with the conventional art. As illustrated therein, an operation control apparatus for the escalator includes: a power rectifier
2
for converting a three-phase AC utility power into an AC power of variable voltage and variable frequency in order to control the operation speed of the escalator; an induction motor
3
which is driven by output power of the power rectifier; a gear
4
and a sprocket for running a footplate using rotatory force generated from the induction motor
3
; a current detector
6
for detecting a current flowing in the induction motor
3
; an electromagnetic contactor
7
for transmitting the utility power to the power rectifier
2
in an operation mode and interrupting the same in a non-operation mode; a display device
8
for displaying a running condition and failure of the escalator; a passenger detecting device
9
for detecting an access of a passenger intending to use the escalator; and a control device
10
for appropriately controlling the driving of the induction motor
3
by the power rectifier
2
, for thereby operating the escalator at a target speed.
The control device
10
includes: a CPU
11
for performing an operation for driving the induction motor
3
at a variable voltage and variable frequency according to a program stored in a ROM
12
; a RAM
13
in which data needed in the CPU
11
is stored; an input device
14
for a signal inputted from the current detector
6
, the passenger detecting device
9
and a rotational speed detector
20
into an appropriate form; an output device
15
for driving the display device
8
and the electromagnetic contactor
7
under the control of the CPU
11
; a failure detection device
16
for detecting a failure on the basis of an output signal of the input device
14
and an operation pattern setting device
17
for setting a subsequent operation pattern; a pulse width modulation signal generator
18
for generating a pulse width modulation signal according to a signal of the CPU
11
in order to generate an AC power of target form from the power rectifier
2
. The operation of the control device
10
will be explained in detail with reference to
FIGS. 2 and 5
.
When a passenger intending to use the escalator approaches to the entry of the escalator in a state in which the operation of the escalator is stopped, the approach is detected by the passenger detection device
9
and a signal thereof is inputted into the input device
14
of the control device
10
. At this time, the CPU
11
performs the operation for driving the induction motor
3
at a variable voltage and variable frequency and operates the electromagnetic contactor
7
according to the program stored in the ROM
12
. According to this, an a contact switch
7
A of the electromagnetic contactor
7
is short-circuited and thus the three-phase AC utility power
1
is inputted into the power rectifier
2
. In addition, the pulse width modulation signal generator
18
generates a pulse width modulation signal corresponding to the operation result of the CPU
11
, and accordingly the power rectifier
2
converts the three-phase AC utility power
1
supplied by the a contact switch
7
A into a DC voltage and then generates an AC of variable voltage and variable frequency in order to control the torque corresponding to the target speed and load of the induction motor
3
, whereby the induction motor
3
is rotated at the corresponding speed. The rotatory force of the induction motor
3
is transmitted to the sprocket
5
through the gear
4
and the chain, and thus the groove positioned on the circumference of the sprocket
5
and the step roller of the footplate are engaged to thereby be rotated. By this, the passenger can move up to a target story using the escalator.
Thereafter, when the absence of a passenger is detected by the passenger detecting device
9
, the CPU
11
slows down the escalator according to the automatic operation program stored in the ROM
12
to thus stop it. According to circumstances, a low speed idle operation is performed without stopping the escalator in order to prevent a failure confusion phenomenon. In this state, when the presence of a passenger is detected by the passenger detecting device
9
, the escalator is operated at a normal speed by the above process.
Meanwhile,
FIG. 3
is a functional block diagram illustrating the inverter control process of the power rectifier
2
in order for the CPU
11
of the control device
10
to control the rotational speed of the induction motor according to the program stored in the ROM
12
. The difference between a speed command value Wr* of a speed command unit
11
A and an actually detected speed value Wr is obtained by a substractor
11
B and then is inputted to a speed controller
11
C, and the difference between an output current I* of the speed controller
11
C and an actual current value I of the induction motor
3
detected by the current detector
6
is obtained by a substractor
11
D and then is inputted to a current controller
11
E. Herein, the inverter of the power rectifier
2
is driven by the output value amplified by a predetermined operational process, and thus an induction motor
11
F is rotated at a predetermined speed Nr.
FIG. 4
is a signal flow chart illustrating the inverter control process of the power rectifier in accordance with the conventional art, which will be described in detail as follows.
First, it is determined whether or not there is an inverter operation command in S
1
. If there is an operation command, it is determined whether or not t is a speed control period in S
2
. If so, a motor speed value Wr is inputted in S
3
, a speed control
Birch & Stewart Kolasch & Birch, LLP
Martin Edgardo San
Nappi Robert E.
Otis Elevator Company
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