Marja-Liisa Siikonen - People Flow in Buildings

Figure 2.4 Access control system built in turnstiles (KONE Corporation).

In buses, the weigh in motion ( WIM ) systems enable the estimation of the number of passengers through the ground loading of the vehicle detected before and after the stops. The counting is performed by load sensors either on the ground or on the suspensions. The dead weight of the vehicle load on the ground is measured. The difference between the dead weight and the vehicle with passenger load is measured, and the number of people is calculated by dividing the difference by the average weight of a person (Pinna et al. 2010 ).

In elevators, a car load weighing device ( LWD ) is always required for safety reasons. At least 80% load for comfort reasons, 100% for full load and 120% for overload limit load values should be detected. Several methods exist to measure car load. One of them is to use elastomer pads below the cabin platforms. The deflections of the pads are measured with various loads which are actuated by micro switches as shown in Figure 2.5a (Strakosch 1983 ). A strain gauge LWD can be mounted on the crosshead beam on the top of the car, or other place in the support structure (Wittur 2002 ). The device measures the strain on an object, which consists of an insulating flexible backing that supports a metallic foil pattern. As the foil is deformed, its electrical resistance changes, which is then measured, see Figure 2.5b. One type of LWD load uses inductive proximity sensors to detect linear movements of the car platform when it is loaded or unloaded. An object plate and a sensor are placed under the car platform where the distance between the sensor and the object plate is transformed to analog signal (KONE 2006 ).

Figure 2.5 Load‐weighing by platform deflection

( Source: Strakosch (1983 ). © 1983, John Wiley & Sons) (a), and strain gauge techniques (b)

( Source: Wittur (2002 ). © 2002, WITTUR Austria GmbH).

Measurement of the car load gives only a hint of how many passengers are inside the car. The usual method is to measure load difference during a stop, and convert it to passenger counts by dividing it by the average passenger mass, e.g. 75 kg. The simplest approach to estimate passenger transfers is to measure the difference between the arrival and the departure load during a stop. This assumption produces error in the passenger counting since the passenger weights can vary from a few kilograms to more than 100 kg. People may also carry heavy objects, such as suitcases or shopping bags, causing even more error in the counting. A second method uses accurate LWD information to distinguish the difference of car loads between the car arrival to the floor, minimum load during the stop, and the departure load when it leaves the floor. This method assumes that the people first exit the car, and then new people enter in the car. The load difference between the arrival and minimum load correlate with the passenger mass of those who have exited the car. The difference between minimum load and the departure load correlates with the passenger mass entered in the car. A third method uses accurate load information during a stop to distinguish incremental and diminishing steps in the car load (Siikonen 1997 ). An incremental step in car load indicates that a passenger has entered the car, and a diminishing step that someone has exited the car, respectively. The method does not pay attention to the passenger mass, it only counts the stepwise changes in the load during the stop. Passenger transfers in and out from the car can occur in mixed order.

Figure 2.6 Step‐counting method to count the number of entering and exiting passengers during an elevator stop

( Source: Based on Siikonen (1997 ). © John Wiley & Sons).

Most of the elevator manufacturers provide elevator monitoring system ( EMS ) that is attached to the elevator control system. Control systems have the real‐time information elevator status data. The control system can utilize the APC devices mentioned earlier, or other sensors of the elevator cabin. Inbuilt EMS systems have the advantage that they enable to measure vertical traffic continuously from all floors instead of taking samples of traffic patterns on some days from some floors. EMS can make statistics of the service quality level and elevator performance. Traffic display shows real time information of the elevator floor position, direction, door position and call status and vertical passenger‐counting ( Figure 2.7).

Figure 2.7 Traffic view of E‐Link monitoring system (KONE Corporation).

Information of elevator and escalator systems from several buildings can be gathered by Remote elevator monitoring systems (REMS). A standard protocol associated with REMS was suggested by Beebe to enable the development of sophisticated applications for the IoT platform (Beebe 2016 ). In tall buildings, often a computer‐based Building Management System (BMS) is installed to control and monitor the building's mechanical and electrical equipment including elevators (Chapman 1994 ). A widely used data protocol is the Building Automation and Control Networks (BACnet) which has become a standard (ANSI/ASHRAE 135 1995; ISO 16484‐5 2003 ). The open source protocol provides a common interface for a number of building services such as elevator group, escalators, heating, and ventilation.

Vertical passenger movements inside buildings can be followed by modern mobile phones, or counted automatically with APC devices. If the APC sensors are placed on every floor, the number of sensors can become vast. The number of devices can be decreased if the APC s are placed inside the cars. In addition to recognizing the entering and exiting passengers, additional sensors should be placed in the car to detect elevator motion synchronously with the APC data. Even the vertical floor position can be determined with sophisticated methods. External devices with cameras can be used inside elevator cabins to count the number of people entering and exiting the elevators (De Coi et al. 2005 ). Figure 2.8shows the elevator performance analyzer ( EPA ) which is used in people counting (Batey and Kontturi 2016 ).

Figure 2.8 Elevator performance analyzer setup in an elevator

( Source: Batey and Kontturi (2016 ). © 2016, The International Association of Elevator Engineers).

Elevator site survey requires a more demanding installation in the machine room of an existing system. Elevator site surveys were used already with relay systems where signals were detected through an interface attached to the elevator control board (Lustig 1986 ). Elevator door‐to‐door time is an important measure for modernization studies. It can be measures simply by stop watch (Kaakinen and Roschier 1991 ). Modern digital logging devices for elevator trips can use accelerometers inside a cabin which analyze elevator kinematics from elevator movements, and estimate people flow from the number of elevator starts (Peters and Peters 2019 ). Depending on the measured signals, site survey can reveal e.g. number of passengers from photocell cuts and call status, or elevator system parameters such as masses, frictions and hoist way efficiencies (Tyni et al. 2017 ).