Group Control System

The control system for groups of two to eight lifts makes them operate smoothly. The single control units are interconnected by serial interfaces resp. by the CAN-bus. The control units reconcile lift positions, direction of travel and travel commands at hand with each other, but take autonomous decisions according to the preset travel algorithm with respect to starting, braking or stopping the lift. Thus a host computer has become obsolete. Modern group control systems are equipped with high-grade 32-bit processors, that can process lots of data from the whole group within a very short time and, basing on them, take the relevant decisions with regard to the group operation. Fundament of these functions is the application profile CiA-417 basing on CANopen.

On the bus the data of the commands of all components are placed at general disposal in a standardized way. Each controller within the group is thus enabled to decide upon the ideal sequence of executing the commands and by which group member it is specifically to be done. There is no need of a superimposed host computer for group functions.

Landing calls are entered via bus nodes located either in the landing push-button units or in the control cabinet. The node evaluates the signal entered and – stating direction, priority destination etc. - places it at the disposal of all group members on the CAN-bus.

It is the algorithm of the call control function within the group controllers, which – on the basis of the parameters set (e.g. collective up and down selective) – decides upon the sequence of landings to be approached and which lifts shall do it. If a lift does not participate in the group functions, for example as it has been switched to inspection operation for maintenance purposes, the respective information is immediately available to the other group members and can be considered in their computations.

Busy spots

To enhance the efficient servicing of busy points and to increase the transport performance the bp306 controller system is equipped with additional master programmes which govern those for the average daily traffic. It is the task of these programmes to recognise the respective traffic situation and to distribute the lifts accordingly. 

a) The first possibility of recognising a busy spot is the full load message. If a car sends the full load message another car is immediately sent to the floor relieve the situation. We recommend the additional load measuring features for part- resp. full load. 

b) Busy spots are recognised by the system when frequent calls are made on a floor in certain building areas, i.e. lobby,  within a period of 60 minutes.  The system registers the day and the time. If this busy spot occurs five times in sequence the group system then reacts automatically and makes lifts available on that floor at the times recorded. If the system recognises that only little traffic occurs at that time then the busy spot is cancelled again. In this way the group system adapts to the changing requirements in the building.

The WinMOS^®300 monitoring system enables the visualization of busy spots. If lifts are linked to the WinMOS^®300 monitoring system, all call requests, travel times, waiting times, door reversing, stop-delay times, loads carried and the number of people entering and leaving the lifts at each floor can be recorded, given a time stamp and then stored in a databank.

With the help of this data, the WinMOS^®300 statistics module can carry out an analysis to identify the distribution of the busy spots during each day and for each day of the week. As a result of this analysis, the lifts in the group can be dynamically allocated to the busy spots for the period concerned.

Group interruption

A lift is removed from the group when it shows no sign of reacting to a call within i.e. 20 seconds.  A possibly allocated call is then taken over by other lifts. This redistribution of tasks to other lifts takes place in the case of any operations or special switching actions which disturb group operation or respectively, interrupt it. 

External calls, collective calls 'non-directional and full collectiv' '1KS/2KS'

In order to optimise transport capacity all stored calls are continuously monitored and related to those lifts which are involved in group operation. Servicing external calls is mainly done via waiting-time optimisation.

There is basically no fixed allocation of a call to a car, each external call is stored for each car. The decision as to which car starts or delays is made by the respective controller.

The controller is responsible for achieving shortest possible waiting times through even call distribution and the continuous monitoring of external calls , internal calls and drive times. Under certain conditions (e.g. full load) cars with several car calls are temporarily not allocated any further external calls. 

To calculate the prospective execution of a landing call, the following, amongst other things, is considered:

• existing car and landing calls,
• calls on the same floor,
• drive distances,
• drive direction,
• time-loss at stops,
• call waiting times.

Using this data during the drive, the decision is made as to which car stops for a landing call. The car with the shortest servicing time is selected. If there is already a car call on a floor which has a landing call, this car receives priority – limited to a few stops in advance – because this car stops via a car call anyway. 

The final allocation of a landing call only takes place shortly before the delay point of the respective resting stop. If a lift which was selected to service a call is held up and then overtaken by another lift, the overtaking lift adopts the commands. This variable call allocation enables the group to remain flexible. 

If several cars are in resting position any incoming call is serviced by the lift with the shortest drive time.

Back-up start

If several calls are received for the same direction during a run it is possible that another lift services the landing call. This can be set in the base menu at next lift starts. The system decides how many landing calls in the same
direction may be placed before a second lift is sent as support. 

Additional facilities 

We recommend the following additional facilities: 

• Load measurement device with CANopen interface for absolut and full load values,
• next direction indicators and approach gong at every stop in the same direction 

Additional information

• parameter of the group functions
• parking programmes
• energy efficiency in lifts