I. Summary:

Keywords: elevator, PLC, speed regulation

In high-rise buildings, elevators are indispensable and important equipment. Early elevators used relay contact system. However, due to the complexity of elevator control system, the wiring of relay contact control system is complicated and the reliability is low. In order to improve its reliability, we adopt PLC programming control system and simple, economical and practical single/double speed AC motor drive system. As shown in figure 1.

Second, the analysis of the drag system

There are many kinds of elevator drive systems, such as DC generator-motor SCR excitation drive system, variable frequency voltage regulation and speed regulation system, etc., which are expensive. Simple AC voltage regulation and speed regulation system and single/double speed AC motor drive system are simple in structure, economical and practical.

The two main movements of the elevator-ascending and descending-can be realized by the forward and reverse rotation of the motor. Just change two live wires connected to the motor. This function can be realized by 1KM and 2KM (motor forward and reverse contactor).

A two-speed motor has two sets of windings. During normal operation, the high-speed winding is 3KM, and the low-speed winding is 4KM.

When the elevator starts running, the high-speed winding is connected, but when it starts directly, it will impact the power grid. In order to reduce the starting current, reduce the impact of parts and improve the comfort of passengers, a current limiting resistor or reactance is generally connected in series in the starting circuit, as shown in figure 1. The working process is as follows: when starting, close 3KM, and then connect 5KM. The current-limiting inductor L 1 is connected in series in the starting circuit. After the start is completed (for example, after 5 seconds), the motor is turned on for 5 kilometers, and the motor turns into normal high-speed operation. When the elevator stops, it changes from high-speed operation to low-speed operation. That is, 3KM is disconnected and 4KM is connected at the same time. Because of the large speed difference, feedback braking will occur at this time. In order to reduce the braking current and prevent the impact on the device, the current limiting resistor and reactance are also added, and two current limiting resistors (reactances) are adopted here. The working process is: 3KM is disconnected and 4KM is connected, but at this time, 6KM and 7KM are not connected, L2 and R are introduced into the brake circuit, and after a period of time (for example, 1s), 6KM is connected to remove the current limiting resistor. After 7KM, the current-limiting reactance is cut off and the motor runs normally at low speed. Finally, the control circuit is cut off 1KM or 2KM, and the motor stops.

By adjusting the magnitude and series of series resistance or reactance, and gradually adjusting the time to remove resistance or reactance, the acceleration and deceleration of start and stop can be changed to meet the requirements of comfort, start and stop current limiting and acceleration and deceleration.

Third, determine the number of I/O points and the choice of PLC.

Because the number of floors is different, the size of elevators is different, and the number of I/O is also very different. Take the five-story elevator as an example.

1. Determination of input devices

First, investigate the operation in the elevator car. There should be a floor selection button on each floor of the operation room.

There are five on the fifth floor. When there are drivers and passengers, there must be the driver's door switch button and the up and down button, which need to be input at 4 o'clock. Considering the safety of passengers, it is forbidden to start the elevator without closing the door. Limit switches shall be set for the switch limit in the car and hall door, which requires 3 inputs. In order to prevent the passenger from being pinched when the door is closed, an infrared sensing input should be set. * * * Requires 13 switch input points.

Considering the relationship between the hoistway and the car, each floor in the hoistway should be equipped with sensors to sense the current floor where the car is located. Because the ascending and descending order of the car entering this floor is different, each floor is equipped with two ascending and descending floor sensors. In order to ensure the accuracy of car parking, the car is equipped with an upper level sensor, a lower level sensor and a door pivot sensor to sense whether parking is on the upper side or the lower side. When the parking floor is accurate, all three large sensors are turned on.

When calling passengers in each hall, there is only one call button on the ground floor and the top floor, two call buttons on other floors, and eight input buttons on the fifth floor.

Other inputs are overloaded, with switches or contacts such as drive/no drive mode selection. From the above analysis, we can see that * * * needs a 36-point switch input port.

2, the determination of the output device

Two-point output is needed to control the elevator's rising and falling (that is, the motor rotates forward and backward), two-point output is needed to control the elevator's fast and slow operation, and three-point output is needed to cut off the fast-start current-limiting resistor and the slow-running current-limiting resistor (reactance).

Switch door contactor two-point output

Floor indicator output at 5 o'clock position

The upper and lower indicator lights output.

Overload indication, alarm output.

After analysis, * * * needs 17 switch output port.

Schematic diagram of partial input and output of lobby and car 2

3, the choice of PLC

Elevator control only has on-off input and output, and its response to time is not high, but there are many input and output points. Based on this, NEZA PLC of Modicon is selected. When the input and output points are tight, I/O expansion unit can be equipped, and I/O points can be saved by combining encoder and decoder, so that PLC with fewer points can be selected and the cost can be saved.

Fourthly, I/O address allocation table is established.

See table 1 for the elevator control I/O address allocation table.

I/O address allocation table for elevator control

I0.0 1-5 floor rising floor induction reed switch contact M 1-M5 floor indicating intermediate relay Q0.0 floor indicator light.

I0. 1 Q0. 1

I0.2 Q0.2

I0.3 Q0.3

I0.4 Q0.4

I0.5 1-5 downward floor induction reed switch contact M6-M 10 floor induction intermediate relay Q0.5 upward indicator light.

I0.6 Q0.6 downlink indicator light

I0.7 M 12 uplink intermediate relay

I0.8 M 13 downlink intermediate relay

I0.9 M 14 running intermediate relay.

I0. 10 Uplink Flat Sensor M 15 Uplink Flat Intermediate Relay

I0. 1 1 Lower cover sensor M 16 Lower cover intermediate relay

I 1.0 1-5 elevator button instruction M20-M24 elevator button instruction intermediate relay Q0.7 upward contactor.

I 1. 1 Q 1.0 downward contactor

I 1.2 M44 Cancel the variable-speed intermediate relay Q 1. 1 Quick-running contactor.

I 1.3 M45 Q 1.2 slow running contactor

I 1. 10 Q 1.3 door opening relay

I 1. 1 1 with/without driver selection switch Q 1.4 door closing relay

I2. 10 Driver uplink selector switch M26 Driver uplink intermediate relay Q 1.5 Slow running 1 contactor

I2. 1 1 Driver Down Select Switch M27 Driver Down Intermediate Relay Q 1.6 Slow Operation 2 Contactor

I 1. 10 Open button

I 1. 1 1 Close button

I 1. 10 infrared sensor M42 of infrared intermediate relay for people entering and leaving.

I 1..5 door pivot sensor M43 door pivot sensing intermediate relay

I2.0 1-4 floor uplink call button M30-M33 1-4 floor uplink call intermediate relay Q 1.7 Run the contactor at full speed.

I2. 1

I2.2

I2.3

I2.4 Door lock contact

I2.5 Open the door of the lifting input contact M35, and allow the intermediate relay Q2.0 to give a lifting indication alarm.

I2.6 Call down the buttons M36-M4 1 2-5 to call down the intermediate relay.

I2.7

I2. 10

I2. 1 1

I2. 10 door opening travel switch

I2. 1 1 door closing travel switch

Table 1

Five, draw the flow chart

Generally speaking, elevator operation can be divided into normal operation state, fire-fighting operation state and slow maintenance state, which are realized by a switch. The three running states are parallel and the relationship is simple, so this flow chart can be omitted. Among the three states, normal operation is the most critical and complicated, and elevator operation has no obvious state steps, that is, non-sequential operation. Therefore, the design is based on experience, and the control circuit is divided into several parts, which is not unified.

VI. Programming of User Programs

Considering the complexity and disorder of elevator operation, elevator control circuit can be divided into floor induction, door call, car control, elevator direction selection, elevator speed change, elevator leveling and elevator start.

1, floor induction circuit

The floor induction signal is an important signal in the circuit, because it involves many links in its control area circuit, such as car instruction, hall call, floor pointing, direction selection and so on. It is generally believed that when the elevator rises, the bottom of the car is the starting signal of the floor, and the bottom of the car leaves the floor is the end of the signal. When the elevator descends, the signal from the top of the car shall prevail, which is why each floor is equipped with an upward sensor and a downward sensor. The induced signal should be continuous. If the pulse induction signal is used, a holding link is needed. As shown in fig. 3, I0.0~I0.4 are uplink floor induction pulse signals, I0.5~I0.9 are downlink induction signals, and M50~M54 are floor induction intermediate relays. Working principle: When the car is on the second floor, M2 is opened and held; When the car rises to the third floor, M52 passes M6544. M 15 immediately opens and keeps M23, while M 15 closes M2. If it is descending, when the car reaches 1 floor, M50 opens M23 through M 13, I0.5, then opens M50 and keeps it, and closes M2 at the same time.

2. Hall call circuit

Hall door call is a holding link (the call button is usually a pulse signal). There is only one down call on the top floor and one up call on the bottom floor, and all other floors have up and down call buttons. What needs to be considered is how to eliminate the responding call. The ladder diagram is shown in Figure 5, in which I2.0~I2.3 are the call buttons on the 1~4 floor, and M30~M33 are the corresponding intermediate relays. I2.6~I2. 1 1 are the call buttons on the second to fifth floors, and M36~M4 1 are the corresponding intermediate relays; M 1~M5 is the floor signal of 1~5.

Working principle: For example, when the elevator is on the 1 floor, there is an uplink call on the 4th floor and an uplink call on the 3rd floor at the same time, then M33, M32 and M37 are connected at the same time, and the elevator goes up. When the elevator arrives at the 3rd floor, M32 keeps the link disconnected, that is, it has responded to the uplink call of the 3rd floor, but M37 will not be disconnected, that is, the downlink call is kept.

3. Instructions in the car

The circuit for selecting floors in the car is relatively simple, with only two functions: signal holding and signal cancellation. As shown in figure 4, I1.0 ~ I1.10 is the floor selection button, M 1~M5 is the floor sensing signal, and I2. 10 is the door opening travel switch.

How it works: For example, if you press the 3rd floor button, M8 will open and hold, but it will not cancel the numbering when the elevator reaches the 3rd floor, and it will not close and cancel the numbering until the elevator door is opened in place.

4. Elevator direction selection circuit

Alternating current traction elevator can realize steering by changing the phase sequence motor of three-phase power supply. In the figure 1, when 1KM is connected, the motor rotates forward, and when 2KM is connected, the motor rotates backward, corresponding to the output ports Q0.7 and Q 1.0 of PLC. Because this signal is still used in other circuit control, M 12 is used for convenience.

Generally speaking, the direction selection circuit is controlled by two signals. First of all, it is controlled by the floor selection signal in the car. The principle of control is to respond to signals in one direction. When all signals in this direction respond, the signals in the other direction, such as the elevator, are on the second floor. If you press the button on the third floor, the uplink relay will work. At this point, if you press the buttons of 1 floor and the fourth floor, the elevator will reach the third floor. We should also respond to the button on the 4th floor instead of the signal of 1 building, and respond to the downward signal only after all the upward signals are responded. If the select button on the 5th floor is pressed during the uplink operation, we should also respond to the 5th floor before responding to the downlink signal. If the elevator is in the downward direction, the downward signal will be given priority. Secondly, it is controlled by calling the hall door to door. The control principle is that the elevator only responds to the descending call from the current floor of the elevator in the descending process and only responds to the ascending call from the current floor of the elevator in the ascending process. Because the top floor and the bottom floor are special, they need to be handled separately. The downlink call on the top floor is actually an uplink signal, which can only be responded when the elevator goes up, while the uplink call on the bottom floor is actually a downlink signal, which needs to be responded when the elevator goes down.

Direction control ladder diagram, as shown in Figure 7, M6~M 10 is the intermediate relay in the car, M30~M33 is the call intermediate relay of hall floor 1~4, and M36~M4 1 is the call intermediate relay of floors 2~5. Working principle: For example, when the elevator is on the second floor, press the button on the third floor, and the uplink intermediate relay and uplink output port will be activated. The response loop of M 13 is cut off due to interlocking, so pressing the button on floor 1 at this time can't get a response, while pressing the button on floor 4 will lead to a line M9, M5, M23 connecting M 12 and Q0.5. Only when three or four signals respond, the elevator will be on floor 4, M8, M9.

In fig. 7, I1.1indicates whether there is a driver's contact person, and i2. 10 and i2. 1 1 indicate the driver's up and down selection buttons. Before the elevator starts, the driver can forcibly change the running direction of the elevator.

5. Elevator start and speed change circuit

The startup and speed change circuits of the elevator are shown in Figure 6 and Figure 9, where M 14 is the elevator running intermediate relay; Q 1. 1, Q 1.2 are the output of variable speed and slow operation, and the contactors 3KM and 4KMQ5.3 in figure 1 are the output of full speed operation, corresponding to 5KM in figure 1, and the user cuts off the current-limiting reactance (resistance) in the fast winding; Q 1.5 and Q 1.6 correspond to 6 km and 7 km, and are used to switch the first and second current limiting resistors (reactance) in the slow winding.

Working principle: when the elevator door is closed, Q 1 is opened, and the elevator winding is opened at high speed, which can be started quickly. After the startup is completed (for example, 5s), Q5.3 is turned on, the current limiting reactance is cut off, and the elevator runs at full speed. When the elevator approaches the stopping floor, the low-speed winding is turned on for braking, the high-speed winding Q 1 is turned off, and the low-speed winding Q65438 is turned on.

6, elevator floor control

The elevator leveling control circuit is shown in Figure 8. I0. 10 and I0. 1 1 are the input terminals of the rising leveling sensor and the falling leveling sensor respectively, and I1.1is the input terminal of the door-to-door rotation sensor. When the elevator goes up, it crosses the flat floor, so I0.66 and I0. 1 1 are still connected, which will disconnect the upward contactor (controlled by Q0.7) and connect the downward contactor (controlled by Q 1.0), and the elevator will be flat. After leveling, i0. 10, i0. 1 1, i65438+.

7, switch door control circuit

The control circuit of the switch door is shown in figure 10.

Working principle: Only when the elevator is not running after leveling, the door is allowed to open, and M35 is the intermediate relay that allows the door to open. There are two kinds of door opening: manual and automatic: automatic. After allowing the door to open for a period of time (for example, 2S), the door opening relay Q 1.3 opens due to the action of the time relay TM3. If it is manual, press the door opening button I 1. 10 to act immediately. Closing doors can also be divided into automatic and manual. Press the door closing button i 1. 1 manually to close the door immediately. In the automatic mode, when the door is in place, touch the limit switch I2. 10 and turn on the door closing timer TM4 for a period of time (for example, 3S). The door is closed by TM4. In order to prevent passengers from being caught in the process of closing the door, an infrared detector I 1. 10 is set. When it detects an obstacle between doors, it will stop closing the door and reconnect the door opening relay.

In addition, in order to prevent overload, an overload sensor I2.5 is set. When the elevator is overloaded, it will call the police and refuse to close the door.

Note: In addition to the above control requirements, the elevator does not respond to any call during fire fighting operation and goes straight to the ground floor. The slow maintenance operation has nothing to do with door protection. Attention should be paid to the safety protection of each hall during operation.

Seven. procedure

Floor Induction Ladder Figure 3

end of program

Eight. refer to

1 edited by Wang. Practical technology of small programmable controller.

Beijing: Machinery Industry Press, 1996.

2 Peng, Xu Yaosheng and Wang Xinbian. Principle and application of programmable controller. Xi an:

Xidian university Publishing House, 1999.

Yang Changxing, Zhang Xingyi. The foundation and application of programmable controller (PC);

Chongqing: Chongqing University Press

4 Zhu Shanjun et al. Application and Maintenance of the Principle of Programmable Control System.

Beijing: Tsinghua University Publishing House, 1992.

Wang Weixing, Fu Lisi and Sun Yaojie. Principle and application of programmable controller.