lecture 4 traffic control system 1213v

7/30/2019 Lecture 4 Traffic Control System 1213V

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LECTURE 4Group Control; Group Supervisory Control;Computer Group Control; Duplex / Triplex System;Fixed Sectoring Priority Timed System;

CODE : EEE3444 Module Title: Lift andEscalator Engineering

Revised by: J. Cheng

Dynamic Based System;Computer Control System & Comparison


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Group Control

The control of lift systems present two different challenges single:

1. Some of commanding a lift car to move in both up and downdirection and to stop at a specified landing must be provided.

- Concerned drive system and drive control

2. To serve passenger demands (car & hall calls) and a group oflifts to work together to make efficient use of the individual lifts

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.

- Concerned traffic control


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All lifts installed in the recent years are push button/touchbutton automatic control. The Automatic control areclassified as followings:

- Single Call Automatic Control

- Collective Control Down Collective & Full/Selective Collective

- Group Supervisory Control

Group Control (Cont.)

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- Attendant Control

- Simplex Control

- Duplex Control

- Triplex Control

- Dual Control


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Automatic operation by means of one button in the car for each landingserved and one landing button are each landing, so arranged that if anycar or landing button has been actuated, the actuation of any other car orlanding operating button will have no effect on the operation of the car

until the response to the first button has been completed.This is the simplest and cheapest form of control, but is only capable ofaccepting a single call at a time. When a car is standing unoccupied at afloor and a passenger enters, a short delay in the landing call buttoncircuit, after the doors have been closed, will allow time to ress the car

Single Call Automatic Push Button

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push-button corresponding to the floor the passenger requires, and thecar will instantly respond and stop automatically at that floor.

Once the car commences to travel, all push-buttons are renderedinoperative until a few seconds after it has stopped and this enables thepassenger to alight before the car be called to another floor. The car,when stationary and unoccupied, can also be called to any floor in

response to a landing push-button, but it will not answer to any landingpush-button when traveling.


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Single Call Automatic Control

Automatic operation by means of one button in the car for eachlanding served and one landing button at each landing wherein allstops registered by the momentary actuation of landing or carbuttons are made irrespective of the number of buttons areactuated. With this type of operation the car stops at all landingsfor which buttons have been actuated, making the stops in theorder in which the landings are reached after the buttons havebeen actuated, but irrespective of its direction of travel.

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This type is suitable for short travel up to four floor. So it providesa very low carrying capability. This kind of control is used mainlyon hotels small offices, car parks etc.


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Collective Control

The system is the basis upon which modern supervisory controls, operate,

whether for a single or a group of lifts and overcomes the disadvantages

of automatic push-button control. There are two types:

- Down collective and

- Directional collective

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Down Collective:Automatic operation by means of one button at each landing, wherein allstops registered by the momentary actuation of the car buttons are madeas defined under Single Call Automatic Collective, but wherein the stops

registered by the momentary actuation of the landing buttons are made inthe order in which the landings are reached in the DOWN direction only.The system assume that all landing calls are down calls and collects only

in that direction.

This kind of control is used mainly on domestic buildings.


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Collective Control (Cont.)

Full/Selective Collective:

Automatic operation by means of one button in the car for each landingserved and by up-and-down buttons at the intermediate landings,wherein all stops registered by the momentary actuation of the carbuttons are made as defined under Single Call AutomaticCollectiveautomatic operation, but wherein the stops registered by themomentary actuation of the landing buttons are made in the order in

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buttons have been actuated. With this type of operation, all Uplandingcalls are answered when the car is traveling in the up direction and alldownlanding calls are answered when the car is traveling in the downdirection, except in the case of the uppermost or lowermost calls whichare answered as soon as they are reached irrespective of the direction of

travel of the car.This kind of control is used mainly on the office buildings.


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Group Supervisory Control

Definition of group Control:

Automatic operation of two or more non-attendant elevators equippedwith power-operated car and hoistway doors. The operation of the cars iscoordinated by a supervisory control system including automaticdispatching means whereby selected cars at designated dispatchingpoints automatically close their doors and proceed on their trips in aregulated manner. It includes one button in each car for each floor servedand up and down buttons at each landing (single buttons at terminal

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.

buttons are made automatically in succession as a car reach thecorresponding landing irrespective of its direction of travel or thesequence in which the buttons are actuated. Hall calls set up by themomentary actuation of the landing buttons may be served by anyelevator in the group, and are made automatically by the first availablecar that approaches the landing in the corresponding direction of the

registered call. This control system can be very sophisticated by usingcomputer to supervise the answering of the calls. (Which included theZone control, Light traffic, Down peak & Up peak.


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Group Supervisory Control (Cont.)

Up Peak Traffic:when the dominant or only traffic flow is in an upward directionwith all the majority of passengers entering the lift system at the

main terminal of the building.Down Peak Traffic:when the dominant or only traffic flow is in a downward directionwith all or the majority of passengers leaving the lift system at the

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.

Light Traffic:when at non-busy period, only two cars running in balancecondition, one car up and the other down traffic at the same time.


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Zone control:

In a modern high rise building each lift car is not usually requiredto service every level, as this would imply a large number of stops

during each car trip, and consequently long journey times for thepassengers in the car. More commonly, a lift car serves only anumber of floors clustered together to form a zone. (also have lowrise, medium rise and high rise zone control).

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to co-ordinate the operation of individual lifts, which are all oncollective control and are inter-connected. The system regulatesthe dispatching of individual cars and provides service to all floorsas different traffic conditions arise, minimizing uneven service,excessive waiting time and the presence of idle cars. It also

determines which calls have waited the longest and which shouldbe answered first.

Low Zone Middle zone

High zone


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When there are more than two lifts at the same location, it isarranged to accept a call upon a single push on the landingbutton and to memorise the call until such a time that this call isanswered. this control system can be very sophisticated byusing computer to supervise the answering of the calls. (Whichincluded the Zone control, Light traffic, Down demand & Updemand.

A group of intensive passenger lifts require a supervisory


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system to co-ordinate the operation of individual lifts, which areall on collective control and are inter-connected. The systemregulates the dispatching of individual cars and provides serviceto all floors as different traffic conditions arise, minimizinguneven service, excessive waiting time and the presence of idlecars. It also determines which calls have waited the longest and

which should be answered first.


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Attendant control

The movement of the car is by means of a handle-operated switchwhich has UP, DOWN and STOP positions. The car moves up by theattendant moving the handle in the UP position and down by movingthe handle in the DOWN position. The car is brought to rest bymoving the handle to the OFF position when approaching a landing,the car stopping automatically at the landing.

Lift cars have either drop flag or illuminated indicators, which areo erated b ush-button on the landin s. Illuminated t es have two

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push-buttons labeled UP and DOWN (except for top and bottomlandings) so that the attendant knows both the landing at which thecar is required and the direction the intending passenger wishes totravel.

The cancellation of the call, registered in the car, is done

automatically when the car answers the call. The attendant controlsystem is now less common and the group supervisory system for agroup of passenger controlled lifts gives a more efficient service.


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Simplex Control

One lift controlled by one set of landing buttons. Can be usedDown Collective or Full Collective.

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Simplex control


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Duplex Control

Two cars working together.One car will park at themain floor, and the other at

the last landing served(normally). The main floorcar will service mostly themain floor and help out the

Two cars control by one set of landing buttons

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ree car w en nee e . efree car will service callsabove or below its landingand help out the main floorcar when needed.

Duplex control


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Triplex Control

Similar to duplex withthree cars workingtogether. Two cars wouldbe main floor cars and the

There are two set of landingbuttons and two set of floor

relays for both three lifts.

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.there are three lifts in thesame lift well it is alwaysadvisable that a call canbe answered by either lift.

Triplex Control


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Dual Control

This is essentially a directional-collective control system so

arranged that the lift may be operated by either passengers or an

attendant. When attendant operated, a NON-STOP or PASSbutton in the car becomes operative by use of a key-operated

switch. Continuous pressure on this button permits the car to

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special service.


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Example of group supervisory control systems

A Duplex/ Triplex System (THV)

Suitable for groups of two or three lifts in low rise buildings

Control algorithm requires full collective for small office building

Basically operates on car calls according to the directional distributivecontrol principles.

THV algorithm is the allocation of each landing call to the lift car which isconsidered to be the best laced to answer this articular call.

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The allocation procedure assigns each landing call to the car presentingthe highest figure of suitability for the particular call.

If the figures on suitability are the same for two or more cars, the call isassigned to the nearest of these cars or, in case of equality of distance,to the first lift reached that figure of suitability some time earlier. Cars

loaded up to capacity are not considered in the allocation procedure.However, if all cars are fully loaded, the landing calls are temporarilyallocated to the best placed car. A car in these circumstances will notstop at such landing calls unless the car becomes less than fully loadedas the result of a passenger alighting before reaching such a landing call.


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Example of group supervisory control systems (Cont.)

When a car is not assigned to any landing call and nocar calls are registered, it is made to stop at its currentfloor, with its doors closed. Thus. No parking algorithm

is provided to improve the distributive of cars in thebuilding. Stationary cars are ready to move as soon asthey become assigned to a landing call.

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= moving car up = moving car down

= free car

= landing call up

= landing call down

= car call

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4

3

2

1

MT

1 2 3


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Operation of a triplex control system

A Fixed Sectoring Priority Timed System (FS4)

Group supervisory control system and implementation of a directional fixedsectoring scheme

The landings in the zone served by the group of cars are grouped into up anddown sectors

Each sector is timed as soon as a landing call is registered within its limits.

The timing is measured in predefined periods of times, designated prioritylevels, one to six.

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Six priority levels may not comprise equal time steps. Up-peak traffic: after a car leaves the mains terminal with a load in excess of

50-60%, and while a timer does not expire, if the NEXT car is only car at themain terminal, then a dummy call is set up at the lobby to bring another car.

A light traffic algorithm and shut down procedure is also provided. After about10 min without demand, the NEXT car is shut down and another available caris returned to the main terminal and assigned as NEXT. If the state ofinactively continues, the process is repeated until all cars are shut down.Theshut down cars have their doors closed, except the last one.


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Operation of a triplex control system (Cont.)

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A Fixed Sectoring Common-Sector System (FS0) FS0 devised for dealing with off-peak traffic is available in the

CAD suite. It can be complemented with special features tocater for heavy unbalanced traffic.

System divides the building into a number of static demandsectors equal to the number of cars. A sector includesboth the up and down landing calls all the floors withinits limits.

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the sector is not committed to another car. Fully loaded cars are not considered for allocation. An assigned car operates on the directional collective

principle within the limits of its range of activity.


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A Fixed Sectoring Common-Sector System (FS0) An assigned car operates on the directional collective

principle within the limits of its range of activity. The car responds to the landing calls registered inside its

sector and to landing calls in adjacent vacant sectors above, italso responds to landing calls below the car sector.

Up-peak algorithm, a car leaving the main terminal floor in theup direction, loaded above a certain level or with a

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,

demand condition and selects the up-peak algorithm. While the up-peak condition applies, the cars answer car callsonly, bypassing the landing calls. Thus, as soon as a cardischarges its last passenger on its way upwards, it reversesdirection and travels non-stop to the main terminal.


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A Dynamic Sectoring System (DS)

Included in the computer-aided design suite LSD suite (Lift Simulationand Design suite) of programs provides a basic algorithm and issuitable to deal with light to heavy balanced interfloor traffic.

Complemented by a number of other control algorithms to cater forunbalanced traffic conditions.

Basic algorithm groups landing calls into dynamic sectors. Each lift

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the landing calls in the sector according to the directional collectiveprocedure.

Usually a car defines a single sector; however if a car is located atthe same floor as a higher reference car, or if the car is fully loaded,then the car does not define a sector.Free car control algorithm isintended to insert free cars ahead of cars allocated to a high demandsector, in order to provide service where the traffic is heavier.


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Dynamic Sectors

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Example of a dynamic sectoring scheme with free cardynamic sectors

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Reading Materials

Reference

Ch. 1 to Ch. 2 (P.1 to P. 29)

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lecture 4 traffic control system 1213v

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