Elevator scheduling algorithm Summary

ArticleDirectory

• 1.5 SAFT Algorithm
• FD-SCAN algorithm 2.4

1. Traditional elevator SchedulingAlgorithm 1.1 Service algorithms first(FCFS)

Service first(FCFS-first come first serve)The algorithm is a kind of instant service algorithm. It is not only not optimized for finding floors, but also has no real-time features. It is the simplest elevator scheduling algorithm. It is scheduled according to the order in which passengers request to take the elevator. The advantage of this algorithm is that it is fair and simple, and each passenger's request can be processed in sequence, so that the request of a passenger will not be satisfied for a long time.[12]. The performance of this method is acceptable in environments with relatively simple loads. However, when the load is large, the performance of this algorithm will seriously decrease or even deteriorate. There are two reasons for people to study this algorithm that is almost unavailable when the load is large:

(1)The length of any scheduling algorithm in the Request queue is1When the request rate is extremely low or the interval between adjacent requests is infinite, the first-come-first-served algorithm will not affect the scheduling efficiency, and implementation of this algorithm is extremely simple.

(2)First, the Service algorithm can be used as a standard to measure other algorithms.

1.2 shortest floor time Priority Algorithm(Sstf)

Minimum floor search time preferred(Sstf-Shortest seek time first) [14]Algorithm, which focuses on optimization of elevator floor searching. The principle of selecting the next service object based on the shortest floor time priority algorithm is the shortest floor time. In this way, the request signal from the floor that can be reached first in the Request queue is the next service object. In the case of heavy loads, the average response time of the shortest time priority algorithm is short, but the response time variance is large, because some requests in the queue may not be responded for a long time, there is a so-called "starved to death" phenomenon.

1.3 scan algorithm(SCAN)

Scan Algorithm(SCAN)It is a kind of service request in order by floor, which enables the elevator to run round-trip continuously between the bottom and top layers, during the operation, the response lies in the requests on the same floor as the elevator operation direction. It is efficient in searching for floors, but it is a non-real-time algorithm. The scanning algorithm effectively solves the problem of elevator movement. In this algorithm, the order in which each elevator responds to a passenger request to enable a passenger to receive services is determined by the distance between the position of the passenger who sends the request and the current location of the elevator, all requests of passengers with the same operation direction as the elevator are completed during an electric upward or downward operation, eliminating the need to move the elevator back and forth frequently.[2].

The average response time of the scanning algorithm is longer than that of the shortest floor time priority algorithm, but the response time variance is smaller than the shortest floor time priority algorithm. From a statistical perspective, the scanning algorithm is more stable than the shortest floor time priority algorithm.

1.4 look Algorithm

LookAlgorithm[18]Is an improvement in scanning algorithms. PairLookIn terms of algorithms, the elevator also runs between the bottommost layer and the bottommost layer. However, whenLookThe algorithm immediately changes the operation direction when the request is no longer sent to the elevator, and the scanning algorithm changes the operation direction only when it moves to the bottom or top layer.

1.5 SAFT Algorithm

Satf (Shortest access time first) [15, 19]Algorithm andSstfThe idea of an algorithm is similar. The only difference is thatSatfAlgorithm setSstfIn the algorithm, the time used to find a floor is changed to the access time. This is because the elevator technology has developed to this day, and the time for finding a floor has been greatly improved. However, during the operation of the elevator, waiting for a passenger to climb the ladder is not controlled by humans.SatfThe algorithm takes into account the influence of the time when a passenger climbs the ladder during the elevator operation.

2 Real-time elevator Scheduling Algorithm 2.1 Earliest Deadline Priority Scheduling Algorithm

Earliest Deadline priority(EDF-Earliest Deadline First) [16]The scheduling algorithm is the simplest real-time elevator scheduling algorithm. Its disadvantage is that the elevator can be searched for any floor, resulting in extremely low elevator throughput. It correspondsFCFSThe scheduling algorithm is similar,EDFThe algorithm is the simplest Scheduling Algorithm in the real-time elevator scheduling algorithm. It responds to the earliest request in the Request queue and is a benchmark and special case for measuring the performance of other real-time elevator scheduling algorithms.

SCAN-EDF algorithm 2.2

SCAN-EDF [16]The algorithm isScanAlgorithm andEDFThe combination of algorithms.SCAN-EDFThe algorithm first followsEDFThe algorithm selects the next service object in the Request queue. For requests with the same time limitScanEach request of the algorithm service. Its efficiency depends on the sameDeadlineTherefore, the efficiency is limited.

2.3 PI algorithm Pi (priority inversion) [16] The algorithm divides requests in the Request queue into two priorities. It first ensures that requests in the high-priority queue are responded in a timely manner, and then requests in the corresponding priority queue when the priority queue is empty. FD-SCAN algorithm 2.4 FD-SCAN (feasible deadline scan) [17] The algorithm first finds the request with the earliest time limit and moves from the current position in the Request queue and can buy the request with the time limit required. Scan . When the request signal is sent from the floor where the elevator is located, the request signal is in the same direction as that of the elevator and the elevator can pass through. This algorithm is ignored Scan The algorithm does not guarantee that the service object time limit is met. 3 high level of elevator Scheduling

The above two summaries describe several simple elevator scheduling algorithms that can be studied on my own capabilities. But it does not mean that elevator scheduling only develops to this level. Currently, elevator control technology has entered the age of elevator group control.

With the application of Microcomputer in the elevator system and the development of artificial intelligence technology, the intelligent group control technology has developed rapidly. As a result, a number of new methods have been developed for elevator group control, including: elevator Group Control Method Based on expert system, elevator group control method based on fuzzy logic, Elevator Group Control Method Based on legacy algorithm, Elevator Group Control Method Based on Shengjing network and Elevator Group Control Method Based on Fuzzy Neural Network.

4. Analysis of elevator Problems

4.1 Initial elevator status

The initial status of the elevator I set is the elevator setting for the residential building.

(1)Total buildings21It contains an underground layer (the ground layer is a parking lot and a place for cargo transportation ).

(2)There are two elevators in the building.ALadder,BLadder.

(3)The elevator has23Button, including the button for opening, closing, and floor-1,1,2,3,4 ...... 20.

(4)There are two buttons outside the elevator, that is, the push button and the push button. Except for the top floor and the ground floor of a building, only the downward OPERATION button is set on the top floor of the building, and only the upward OPERATION button is set on the ground floor.

(5)Set the elevator door switch completion time1Seconds. The time when the elevator reaches the next floor is set8Seconds. The time for the elevator to run from static to next layer is set2Seconds, and the time passed by a layer during running is1Seconds.

(6)In the early morning2:00--4:30If there is no request signal,AThe ladder stops automatically.14Layer,BThe ladder stops automatically.6Layer.

(7)When the elevator goes down-1The elevator automatically returns1Layer

4.2 elevator button function

The floor button inside the elevator: the button corresponding to each floor inside the elevator becomes the floor button, that is, the number mentioned in the first end of this chapter is-1,1,2,3,4 ...... 20. When a passenger enters the elevator and presses the floor button, the button is displayed in gray, indicating that it cannot be used. This means that the passenger will go to this layer, and the elevator will go to the corresponding layer. When the elevator reaches this layer, the button is ready for use.

Button for opening the door inside the elevator: when the elevator reaches a certain floor that the passenger wants to go to, the passenger needs to leave the elevator. When the elevator stops, the passenger can press the button to open the door and the elevator will open, let the user leave. If the elevator reaches the floor that the passenger once pressed, but no passenger presses the button to open the door, the elevator will automatically stop after1Automatically opens the door in seconds.

Close button inside the elevator: When all the passengers who want to take the elevator enter the elevator, they need to press the close button to close the elevator door, let the elevator enter the running status. Set the automatic closing time of the elevator8Seconds.

Push Button outside the elevator: This button indicates the request to go upstairs. When you press this button, if the elevator reaches the floor where the button is pressed and the elevator is running in the upward direction, the elevator will stop when it rings, and automatically opens the door after the elevator is stopped. After the request is responded, the request signal is canceled.

Downward button outside the elevator: This button indicates a request to go downstairs. When you press this button, if the elevator reaches the floor where the button is pressed and the elevator is running downward, the elevator will stop when it rings, and automatically opens the door after the elevator is stopped. After the request is responded, the request signal is canceled.

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