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> Control / MCU > Design of elevator call control system based on PIC18F258 microcontrol

Design of elevator call control system based on PIC18F258 microcontroller and CAN module

게시 된 시간: 2020-03-30 12:02:56

1 Introduction

The current situation of elevator production and use has become one of the signs of a country's modernization. Elevators are complex transportation equipment for mechatronic high-rise buildings. It involves many scientific fields such as mechanical engineering, electronic technology, power electronics technology, motor and drag theory, and automatic control theory. The elevator call controller is an important part of the elevator. It is located on the left or right side of the elevator door of each floor. It is the calling device of each floor. It is used to give the call request information of each floor and display the current status of the elevator. Operation. Passengers can learn a lot of information about the operation of the elevator through the display and buttons. This article adopts CAN bus technology to design the call controller. Each controller only needs a pair of twisted pairs to connect with a certain network topology. It is extremely convenient to install and has high reliability. For control systems with different floors, only a corresponding number of call controllers need to be added to the CAN bus. The main controller hardware and software do not need to be changed, making the installation of the elevator control system more flexible and convenient.


2.Introduction to elevator call controller

The elevator call controller is the calling part of the elevator system. According to the function, the call controller includes three parts: the elevator display unit, the call receiving unit and the communication unit.

(1) Display unit:

The call display unit is the part of the human-machine communication between the passenger and the elevator. Its role is to wait for the elevator passengers in the elevator door area to know the current operating floor of the elevator, the current operating direction of the elevator, and the current call status of the floor. This system uses two 8-segment light-emitting LEDs as the floor display, and two LEDs with up and down arrows as the direction display of the elevator running up and down. The call controller communicates with the main control to obtain the current elevator situation and display it.

(2) Call receiving unit:

When the passenger needs to take the elevator, the passenger needs to make a call through the two call buttons on the call panel in each floor, and send the call to the elevator control system (the call that needs to reach the place above the current floor) and the next call (required Call to a place below the current floor) request. After receiving the call request, the call controller sends the call request to the main controller through the communication unit.

(3) Communication unit:

In the traditional elevator control system, the communication between the caller and the main control is a point-to-point communication method, that is, the direct I / O control method. The main controller uses 16 floor display lines, 2 direction display lines, and 2 calls. Multiple signal lines such as registration are directly connected to the call board of each floor. When the elevator floor is increased, the system connection is extremely complicated. Therefore, this system uses CAN bus to complete the communication between the caller and the master, which greatly simplifies the system structure.

3. System hardware design

The elevator call controller uses the PIC18F258 single-chip microcomputer as the core, which has a CAN transceiver interface. The peripheral circuit is composed of CAN driver module, input module, display module and DIP switch, up button, down button and debugging interface. The elevator call controller is a node of the CAN bus network. The CAN drive module is the interface between the call controller and the physical bus, and provides differential sending and receiving functions to the CAN bus. The input module receives the call from the main control. The call-down and door-opening signals, etc., are processed in accordance with the requirements of the communication protocol, loaded into the mailbox, and sent to the CAN bus. The display unit includes three parts: key lamp display, dot matrix display, and maintenance lamp display. The array display can also achieve the scrolling effect of the number of floors and direction arrows.

3.1 CAN driver module

CAN (Control Area Network, Control Area Network) was first introduced by Germany's BOSCH company for data communication between automotive internal measurement and execution components. Its bus specification has been formulated as an international standard by the ISO International Standards Organization and is widely used in discrete control systems. The CAN protocol is also based on the open system interconnection model of the International Standards Organization, but its model structure has only three layers, that is, only the physical layer, the data link layer, and the uppermost application layer of OSI. Its signal transmission medium is twisted pair. The communication rate can reach 1Mbps / 40m, and the direct transmission distance can reach up to 10km / kbps. Up to 110 devices can be mounted. CAN belongs to a serial communication network that effectively supports distributed control and real-time control. It uses many new technologies and unique designs. Compared with the general communication bus, CAN bus data communication has outstanding reliability, real-time performance and flexibility.

The CAN transceiver uses PCA82C250 from PHILIPS. It is an interface chip between the widely used CAN controller and the physical bus, which can differentially send and receive information on the bus. In order to improve the anti-interference ability of the system, a high-speed optical barrier 6N137 was added between PCA 82C250 and PIC18F258. In order to ensure the stability of the CAN bus, the power of the CAN driver module is powered by DC2405 alone.

3.2 Display unit

The call controller display unit includes the display of key lights, floors, direction arrows, and maintenance lights. Traditional elevators use seven-segment codes to display the direction arrows and the number of floors. This system uses a 5 × 7 LED dot matrix display to display, and the arrows and the number of floors can be scrolled while the elevator is running. The PIC sends four 8-bit serial signals through the TX port. The sending order is in the direction of the arrow, ten floors, single floors, and row selection. Connect the parallel output terminal Q7 of the previous serial-to-parallel device 74HC164 to the serial input terminal A of the next 74HC164 to form a cascade of four 74HC164. The arrow direction signal sent first is transmitted to the last 74HC164. The output terminals Q0 to Q6 of the last three 74HC164 are connected to the column addresses A1 to A7 of the three dot matrixes respectively. The Q0 to Q4 of the first 74HC164 are connected to the row addresses B1 to B5 of the three dot matrixes through the unidirectional driving device MC1413. The dot matrix adopts the scanning method. One line is output every 1ms in the software, so it only takes 5ms for 5 lines, and the human eye will not feel flickering; the column signals are shifted by one every 50ms, so the scroll effect of arrows and the number of floors can be generated. . When the elevator fails, the one-chip computer outputs a high level through the I / O port to light the inspection lamp. The dot matrix display schematic is shown in Figure 1.

3.3 call unit

The call controller also includes a dial switch, an up button, a down button, and a debugging interface. The dial switch is used to set the floor number of the floor where the call controller is located. When the elevator goes up or down, the main controller compares the floor number of the current elevator with the floor number expected by the passenger. If not, continue to go up or down, while the arrows scroll up or down. The up and down buttons are the part of the passenger making a call. After the caller receives the call request, it is processed and sent to the main controller through the communication part. The debug interface is used to download programs or simulate debugging. The simulator uses ICD2 from Beneng.

4. System software design

4.1 CAN communication software design

The CAN module in this system works in configuration mode and normal working mode. First, in the configuration mode, the control and status registers, the baud rate control register, the I / 0 control register, the interrupt flag and control register, the reception mask register and the reception filter register are set according to the system requirements to ensure that the CAN bus is smooth. This register can only be set in configuration mode, and enters normal working mode after setting. Both the upper computer and the lower computer turn on their respective CAN receiving interrupts, waiting for data transmitted from the CAN bus.

When sending call information, the 16 bits of CAN set the format, data frame and bit data sent by CAN; 17 bits store the floor number as the ID number; 18 bits set to 0; 19 and 20 bits store the uplink information. Send 2 bytes FFFFH, if not, send 0000H; 21 and 22 bits store the downstream information.

4.2 Main program design

The software needs to realize the initial setting of the DIP switch, the initial setting of CAN, read the response of the master control and receive the information from the CAN bus, process the subroutine of key call, CAN transmission and dot matrix display.

5.Concluding remarks

This article takes PIC18F258 as the core and designs an elevator call controller with CAN communication interface. After nearly one year of field use, it shows that the controller has good functional characteristics and high reliability, and has strong anti-interference ability on the site. The performance price is relatively high. The simple system structure and convenient installation are the development trend of the elevator control system in the future. At present, it has been successfully put into mass production.

레이블: PIC18F258



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