CN106597986B

CN106597986B - Control device and method for double-stage pushing centrifugal machine based on PID

Info

Publication number: CN106597986B
Application number: CN201710058918.5A
Authority: CN
Inventors: 杨有; 张二兵; 尚晋; 余平; 崔旭东
Original assignee: Chongqing Normal University
Current assignee: Chongqing Normal University
Priority date: 2017-01-23
Filing date: 2017-01-23
Publication date: 2023-05-16
Anticipated expiration: 2037-01-23
Also published as: CN106597986A

Abstract

The invention discloses a control device and a control method of a double-stage pushing centrifugal machine based on PID, which are designed by adopting the principles of simplicity, practicability, stability and low cost, have the centrifugal revolution lower than 3000r/min, are suitable for separating crystalline and fibrous material suspensions of particles, and are also suitable for materials with higher solid content in the suspension to be washed. The hardware of the invention consists of a PLC, a main motor, an oil pump motor, a power module, a sensor, an electric appliance protection switch and some peripheral circuits. The invention has the advantages of stable operation, easy maintenance, improved production efficiency and product quality, cost saving, easy operation and maintenance, manual control and automatic control, flexible control mode and great convenience for users to operate.

Description

Control device and method for double-stage pushing centrifugal machine based on PID

Technical Field

The invention relates to the field of automatic control, in particular to a control device and method of a two-stage pushing centrifugal machine based on PID.

Background

The centrifugal machine is widely applied to industries such as food, pharmacy, agriculture, chemical industry and the like, and the development trend of the centrifugal machine is towards intellectualization, energy conservation, specialization and large-scale development ^[1] . The centrifuge control system of the present invention is suitable for separating suspensions of crystalline or fibrous materials of medium particles, such as potassium nitrate, potassium chloride, ammonium bicarbonate, sodium sulfate, potassium sulfate, polyethylene, polypropylene, cellulose, etc.

The centrifugal principle is to separate solid particles from liquid in suspension or separate two liquids with different densities and mutual incompatibility in emulsion by using centrifugal force; it can also be used to remove liquids from wet solids.

The centrifugal machine is often used in a severe workplace, such as inflammable, explosive and dust-rich places, but the transmission system is complex in structure, large in mechanical abrasion and frequent in faults, and the traditional double-stage pushing centrifugal machine is controlled by a relay, so that the stability is poor, the working efficiency is low, and the centrifugal machine is easily disturbed by the outside. FIG. 1 shows a conventional relay control circuit of a two-stage pusher centrifuge, mainly comprising a relayThe electric appliance, the switch and the contactor are in linkage control, so that the wiring is complex and the volume is large. And the working environment is dusty and wet, so that the working environment is easy to break down, the fault is not easy to find, and the production efficiency is greatly reduced. As is known from analysis of the circuit diagram: SA1 is a main power switch, when being pressed, a power indicator lamp HL1 is on, SB1 is an oil pump motor stop button, SB2 is an oil pump motor start button, SB3 is a main motor stop button, and SB4 is a main motor start button. HL2 oil pump motor operation pilot lamp, HL3 is the main frame star start pilot lamp, HL4 is the main frame triangle operation pilot lamp. KT1, KT2, KT3 are timers, KAn is an intermediate relay coil, KMn is a contactor coil (n is 1,2,3, …) KA _i-j The j-th contact of the i-th intermediate relay, KM _i-j The j-th contact of the i-th contactor, (i, j is 1,2,3, …).

He Bo ^[2] The problem that the two-stage pusher centrifuge adopting the traditional relay control is easy to occur is analyzed and improved, but the problems are difficult to fundamentally solve and the automatic control is realized because the traditional relay control is still adopted. Yu Hao ^[3] The frequency converter is added on the basis of the traditional relay control, so that the motor speed can be effectively controlled, but the automatic control cannot be better performed. Li Shengli ^[4] The centrifugal machine controlled by the relay is changed into the PLC control by the Mitsubishi series, so that some problems caused by the relay control are solved, and the safety and stability are basically achieved, but the debugging and maintenance are difficult. Guo Hong ^[5] Yang Peiwen ^[6] The Siemens series PLC is combined with the frequency converter to perform speed regulation control, and although good effect can be achieved, the frequency converter is high in price, and if mass production is performed, huge cost is increased for companies. Zhou Gongyan ^[7] The speed regulation control of the main motor is performed by adopting the optical-ocean series PLC in combination with frequency conversion, and meanwhile, the judgment of a working mode, namely manual control and automatic control, is added, and the single-step operation can be performed in a manual mode during debugging, so that the later maintenance difficulty is simplified.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a control device and a control method of a double-stage pushing centrifugal machine based on PID, which are used for replacing the double-stage pushing centrifugal machine controlled by a traditional relay with PLC control, saving a frequency converter, saving cost, achieving small starting current by adopting star-delta starting, and preventing impact on a power grid caused by overlarge starting current. In addition, in order to prevent the machine vibration caused by uneven feeding from being excessively strong, besides the conventional vibration detection sensor, a closed-loop controller, namely a PID controller, is added, the flow value detected by the flow sensor is compared with the preset flow value, if the flow value is excessively large, the opening of the electromagnetic valve is reduced, otherwise, the opening of the valve is increased, and thus the machine vibration caused by uneven feeding can be effectively slowed down.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the control device of the double-stage pushing centrifugal machine based on the PID comprises a material pipe, an outer rotary drum, an inner rotary drum, a hydraulic pushing system, a pushing disc, a material distribution disc, a main motor, an oil pump motor and a feeding electromagnetic valve, wherein the outer rotary drum and the inner rotary drum are sequentially arranged from outside to inside and are mutually communicated, and the pushing disc is arranged in the inner rotary drum and is connected with the hydraulic pushing system; the material pipe is communicated with the material distribution disc, and the material distribution disc is connected with the material pushing disc; the outer rotary drum is linked with the inner rotary drum and the pushing disc and is connected with the main motor; the oil pump motor is connected with the hydraulic pushing system through an oil circuit system; the feeding electromagnetic valve is connected to the pipe orifice of the material pipe;

the control device of the two-stage pushing centrifugal machine based on the PID comprises a PLC microprocessor, wherein the PLC microprocessor is connected with a main motor, an oil pump motor and a feeding electromagnetic valve of the two-stage pushing centrifugal machine; in addition, the PLC microprocessor is also connected with a vibration sensor and a flow sensor, wherein the vibration sensor is arranged on a machine base, the flow sensor is arranged in a material pipe of the double-stage pushing centrifugal machine and is connected with a PID controller; the PID controller is also connected with the PLC microprocessor.

Further, the PLC microprocessor is also connected with an oil temperature sensor and a temperature alarm circuit.

Further, the PLC microprocessor is also connected to an alarm circuit.

Further, the PLC microprocessor is also connected with a device starting button, a manual mode selection button, an automatic mode selection button, a manual feeding button, a main motor starting button and an oil pump motor starting button.

The method for controlling the double-stage pusher centrifuge by the double-stage pusher centrifuge control device based on PID comprises the following steps:

s1, after a device starting button is pressed, a power indicator lamp is lightened, and meanwhile, a PLC microprocessor starts self-checking and starts to operate after finishing;

s2, pressing an oil pump motor starting button, and starting the oil pump motor to run; after three minutes, the PLC microprocessor sends a starting signal to the main motor, the main motor is automatically started in a star-shaped manner by depressurization, after 15 seconds, the main motor runs at full speed at power frequency, meanwhile, the PLC microprocessor sends the starting signal to the electromagnetic valve, the electromagnetic valve is opened, materials start to enter the material pipe, the flow sensor converts the read signal into a current value of 4-20ma and sends the current value to the PID controller through A/D conversion, the PID controller compares the current value with a preset value, and sends a signal to the PLC microprocessor according to a comparison result, the PLC microprocessor controls the opening of the electromagnetic valve to control the balance of the material flow, when the opening of the electromagnetic valve is higher than the preset value, the opening of the electromagnetic valve is controlled to be smaller, and when the opening of the electromagnetic valve is lower than the preset value, the opening of the electromagnetic valve is controlled to be larger; the vibration sensor transmits the detected vibration signal to the PLC controller, and if the amplitude of the vibration is overlarge, the PLC controller controls the main motor to stop rotating;

s3, distributing materials to a material distribution disc of the double-stage pushing centrifugal machine through a material pipe, pushing the material disc to rotate together with the material distribution disc under the driving of a main motor, throwing the materials to an inner rotary drum with small holes of the double-stage pushing centrifugal machine under the action of centrifugal force, enabling liquid in the materials to flow out from the small holes, enabling solid filter residues to be reserved on the wall of the inner rotary drum to form a ring shape, enabling an oil pump motor to drive a hydraulic pushing system to push the material pushing disc together with the material distribution disc and the inner rotary drum to do reciprocating motion in the horizontal direction while driving the inner rotary drum to rotate at a high speed, enabling the solid filter residues to push a distance forwards when the inner rotary drum returns, enabling the inner wall with the small holes to form a new filter residue layer when the inner rotary drum returns, enabling the solid filter residues to be pushed to an outer rotary drum through the repeated motion of the inner rotary drum, enabling the solid filter residues to be further dried under the driving of the outer rotary drum to be driven by the main motor, and finally pushing the solid filter residues to a material collecting groove of the double-stage pushing centrifugal machine.

The invention has the beneficial effects that:

1. the double-stage pushing centrifugal machine controlled by the traditional relay is replaced by PLC control, a frequency converter is omitted, cost is saved, star-delta starting is adopted, starting current is small, and impact on a power grid caused by overlarge starting current is prevented.

2. The machine vibration caused by uneven feeding can be effectively relieved.

Drawings

FIG. 1 is a schematic diagram of a conventional relay control scheme;

FIG. 2 is a schematic circuit diagram of the device of the present invention;

FIG. 3 is a schematic flow chart of the method of the present invention;

FIG. 4 is a schematic circuit diagram of a dual stage pusher centrifuge;

FIG. 5 is a schematic diagram of a dual stage pusher centrifuge;

FIG. 6 is a schematic diagram of the process automation procedure of the present invention;

FIG. 7 is a schematic diagram of a manual operation procedure of the method of the present invention;

fig. 8 is a schematic diagram of a manual/automatic selection procedure of the method of the present invention.

Detailed Description

The present invention will be further described with reference to the accompanying drawings, and it should be noted that, while the present embodiment provides a detailed implementation and a specific operation process on the premise of the present technical solution, the protection scope of the present invention is not limited to the present embodiment.

As shown in fig. 4 and 5, the two-stage pusher centrifuge mainly comprises a material pipe 1, an outer rotary drum 4, an inner rotary drum 3, a hydraulic pushing system 9, a pusher tray 10, a material distribution tray 2, a main motor (not shown in fig. 5), an oil pump motor (not shown in fig. 5) and a feeding electromagnetic valve (not shown in fig. 5), wherein the outer rotary drum 4 and the inner rotary drum 3 are sequentially arranged from outside to inside and are communicated with each other, and the pusher tray 10 is arranged in the inner rotary drum 3 and is connected with the hydraulic pushing system 9; the material pipe 1 is communicated with the material distribution disc 2, and the material distribution disc 2 is connected with the material pushing disc 10; the outer rotary drum 4 is linked with the inner rotary drum 3 and the pushing disc 10 and is connected with the main motor; the oil pump motor is connected with the hydraulic pushing system 9 through an oil circuit system; the feeding electromagnetic valve is connected to the orifice of the material pipe 1.

Further, in the present embodiment, the two-stage pusher centrifuge further includes a liquid discharge port 6 and a solid discharge port 7, and is provided with a collecting tank 5 and a washing pipe 8.

In this embodiment, the working principle of the two-stage pusher centrifuge is mainly:

the material pipe 1 continuously enters the material distribution plate, after the main motor is started, the main motor drives the main shaft to rotate, and the material (suspension liquid) is uniformly thrown onto the inner wall of the inner rotary drum along the circumference under the action of the centrifugal force field. The inner walls of the inner and outer drums are provided with filtering holes, the bottom of the outer drum is connected with the main shaft, and is also connected with the inner drum and the pushing disc to rotate together with the main shaft. The pushing disc is kept fixed with the outer rotary drum in the axial direction and the radial direction. The bottom of the inner drum is connected with a pushing piston of the hydraulic pushing system and is linked with the outer drum, so that the inner drum can rotate along with the outer drum and can reciprocate along with the pushing piston. When the pushing piston makes return motion, the pushing disc sends solid filter residues in the inner rotary drum into the outer rotary drum; when the pushing piston moves in a progressive way, the inner drum also serves as a pushing disc of the outer drum, and filter residues of the outer drum are discharged. And (5) repeatedly completing the continuous working procedures of material distribution, separation, drying, discharging and the like. The collecting trough is positioned at the tail end of the outer rotary drum of the centrifugal machine and is fixed on the shell, and the outlet of the trough is communicated with the discharging trough on the shell. The pushing disc pushes the finished product out of the rotary drum and enters the collecting groove, and the scraper fixed on the outer rotary drum forcibly discharges the finished product in the collecting groove out of the machine from the tangential direction. The main motor drags the main shaft of the revolving body to rotate through the belt, and the reciprocating motion of the inner revolving drum is driven by a hydraulic system. The oil pump motor is connected with the hydraulic pushing system through an oil way system.

As shown in fig. 2 and 3, the control device of the two-stage pushing centrifugal machine based on the PID comprises a PLC microprocessor, wherein the PLC microprocessor is connected with a main motor, an oil pump motor and a feeding electromagnetic valve of the two-stage pushing centrifugal machine; in addition, the PLC microprocessor is also connected with a vibration sensor and a flow sensor, wherein the vibration sensor is arranged on a machine base, the flow sensor is arranged in a material pipe of the double-stage pushing centrifugal machine and is connected with a PID controller; the PID controller is also connected with the PLC microprocessor.

Further, the PLC microprocessor is also connected to an alarm circuit.

Further, the PLC microprocessor is also connected with a device starting button, a manual mode selection button, an automatic mode selection button, a manual feeding button, a main motor starting button and an oil pump motor starting button. The device start button is used for starting the whole control device, the manual mode selection button and the automatic mode selection button are used for selecting manual or automatic control modes of the two-stage pushing centrifugal machine, and the manual feeding button, the main motor start button and the oil pump motor start button are used for pressing the manual feeding button, the main motor start button and the oil pump motor start button to send signals to the PLC microprocessor when the manual control modes are selected, and the PLC microprocessor receives the signals and sends signals to the electromagnetic valve, the main motor and the oil pump motor to control the starting and stopping of the electromagnetic valve, the main motor and the oil pump motor.

The method for controlling the double-stage pusher centrifuge by the double-stage pusher centrifuge control device based on the PID comprises the following steps:

The present embodiment will be described in further detail below.

As shown in FIG. 4, the main circuit of the two-stage pusher centrifuge mainly comprises a main motor, an oil pump motor, a voltmeter, an ammeter, a thermal relay and a contactor. The main motor M1 provides centrifugal power, the oil pump motor M2 provides lubrication for mechanical components and serves as pushing power, the pushing piston of the hydraulic pushing system is pushed to reciprocate, solid filter residues separated from the inner drum are pushed to the collecting tank, and the solid filter residues are discharged through the solid discharge port. FR1, FR2 are thermal relay, mainly prevent motor overload, and when motor overload, thermal relay automatic disconnection prevents to burn out the motor, plays the effect of protection motor, and QF is the circuit breaker, when the circuit current is too big or circuit short circuit, automatic disconnection protects electrical components. PA1 and PA2 are ampere meters for displaying the working current of the motor, PV is a voltmeter, and voltages of circuits are displayed, KM1, KM2, KM3 and KM4 are main contacts of the contactor.

As shown in fig. 2, the input end of the PLC microprocessor has a manual/automatic mode selection key, a start key, an oil pump operation, an oil pump stop and oil pump failure (oil pump output end), a host operation and host failure (host output end), and a vibration alarm (connected with a vibration sensor). The vibration sensor is used for detecting the vibration intensity of the machine during operation, when the vibration intensity exceeds a preset safety range, the PLC sends out an alarm signal, the machine operation is stopped, and the machine parts are damaged by the excessively strong vibration, so that safety accidents are even caused. The working principle is that the sensor converts the detected vibration signal into a current signal of 4-20Ma through the transformer, the analog signal is converted into a corresponding digital signal through A/D, the digital signal is sent to the PLC, and the internal logic operation of the PLC is used for outputting and controlling the vibration alarm circuit and the motor to stop rotating. Temperature alarm (connected with an oil temperature sensor) and alarm reset. The output signals include oil pump operation, host start, host operation, various indicator lights, alarm and the like. The switch power supply module provides power for the PLC microprocessor and each sensor.

The oil temperature sensor is mainly used for detecting the temperature of hydraulic oil, the detected value is transmitted to the PLC input port through the transformer and is compared with a preset value, when the oil temperature sensor detects that the hydraulic oil temperature exceeds a safety range, the PLC microprocessor sends out an alarm signal to drive an alarm circuit, meanwhile, the PLC microprocessor controls all parts of the device to stop, and the device is automatically stopped. The pushing piston of the hydraulic pushing system moves horizontally back and forth under the action of hydraulic oil, so that the temperature of the hydraulic oil is increased, the oil is easy to age before aging at high temperature to lose effect, and furthermore, when the temperature reaches the ignition point of the oil, fire disaster is caused, when the oil temperature is too low, the pushing frequency is reduced, and the overload and the excessive current of a main motor are caused.

The alarm reset function is that after the PLC outputs an alarm signal through the alarm circuit, the oil pump motor and the main motor stop running, and meanwhile, the alarm signal lamp is on, as shown in fig. 6, after the alarm signal is output, the middle coils M1.0 and M1.1 are connected, and the Q1.1 outputs a high level to drive the alarm. At this time, the normally closed contact M1.1 connected with the oil pump motor is electrically disconnected (as shown in fig. 8), the output contact Q0.1 of the oil pump motor is disconnected, and the main motor is automatically stopped after the oil pump motor is stopped. At this time, the normally closed contacts M1.1 and M1.0 are opened. Whether the oil start button is pressed or the main engine start button is turned off, the operation is stopped by the disconnection of M1.1. I1.0 is a manual reset alarm signal, only when I1.0 is pressed down, the middle coil M0.2 is switched on, the normally closed contact M0.2 is switched off, the coils M1.0 and M1.1 are powered off, the Q1.1 is powered off, the normally closed contacts M1.1 and M1.0 are restored to be on, and the alarm is released.

As shown in fig. 2, the circuit hardware of the device of the present invention includes a PLC controller, a switching power supply, a flow sensor, an oil temperature sensor, a vibration sensor, a contactor, and indicator lamps.

The working process is to press a circuit main switch QF (shown in figure 1), the PLC is powered by an L wire and an N wire, meanwhile, a switching power supply is connected, the output 24V direct current voltage is used for supplying power to a PLC input point and a relay coil, after a start SA1 is pressed, the PLC starts self-checking, meanwhile, a power indicator is lightened, a manual/automatic SA2 button is selected, automatic operation is defaulted, and manual operation is performed if SA2 is pressed. When the oil pump is operated automatically, after the oil pump starting button SB2 is pressed down, the KM1 coil is electrified, the normally open contact of the contactor KM1 is connected (as shown in fig. 4), the oil pump motor is operated, meanwhile, the oil pump indicator lamp is on, after three minutes waiting, the KM2 coil is electrified, the main motor is started in a star shape, meanwhile, the main motor starting indicator lamp is on, after 15 seconds, the KM4 coil is electrified, the main motor enters into a triangle operation, meanwhile, the main machine operation indicator lamp is on, the main machine starting indicator lamp is off, meanwhile, the KM5 coil is electrified, the feeding valve is opened, and feeding is started. The feeding, washing, spin-drying and discharging are operated at the full speed of the main machine at the same time without interruption. After the host stop button SB3 is pressed, the KM4 coil is powered off, the host stops running, the same host running indicator light is turned off, after three minutes, the KM1 coil is powered off, the oil pump motor stops running, and meanwhile the oil pump indicator light is turned off. When the operation is performed manually, the host operation button SB4 is manually pressed, the host starts to operate instead of waiting for the oil pump motor to operate for three minutes and then automatically start, and when the operation is finished, the host stop button SB3 and the oil pump stop button SB1 are also manually pressed. FR1, FR2 are thermal relay, and when oil pump motor or main motor current are too big, automatic disconnection plays the guard action, and the alarm makes sound simultaneously. After the alarm reset button SB5 is manually pressed, the alarm is released. And similarly, when the vibration sensor and the oil temperature sensor continuously send detected values to the PLC to be compared with preset values, if the detected values exceed the preset values, the PLC outputs an alarm signal, and meanwhile, the output signal stops the operation of the motor, and when the fault is solved, the alarm reset SB5 is pressed down, and the alarm is released.

As shown in fig. 3, the control flow is that after the start button is pressed, the oil pump motor starts to operate, after waiting for three minutes, the main motor automatically starts to step down in a star shape, after 15 seconds, the main motor operates at full frequency, meanwhile, the feeding electromagnetic valve is opened to start feeding, the flow sensor converts the read signal into a current value of 4-20ma, the current value is converted into a PID value through A/D (analog-to-digital) conversion and is compared with a preset value, and then the opening of the valve is controlled by the PLC to control the balance of the flow of the suspension liquid. The suspension is distributed on a distribution plate through a feed pipe, the suspension is thrown on an inner rotary drum with small holes due to the action of centrifugal force, the liquid flows out from the small holes, solid filter residues are left on the wall of the inner rotary drum to form a ring shape, the inner rotary drum rotates at high speed and simultaneously moves back and forth in the horizontal direction under a pull rod pushing mechanism, when the inner rotary drum returns, a filter residue layer is pushed forward for a certain distance, when the inner rotary drum returns, a new filter residue layer is formed on the vacated net surface, and the filter residues are pushed to an outer rotary drum to be further spin-dried through the repeated movement of the inner rotary drum and finally pushed to a collecting tank.

After the automatic mode selection button is pressed, that is, the automatic selection mode is selected, all subsequent processes are automatically performed after the device start button is pressed.

After the manual mode selection button is pressed, the manual mode is selected, and the starting of the device, the starting and stopping of the main motor, the starting and stopping of the oil pump motor and the opening and closing of the feeding electromagnetic valve are controlled by manually pressing a main engine starting button, an oil pump motor starting button and a manual feeding button.

The device of the invention has the advantages of controlling the two-stage pushing centrifugal machine to continuously feed at full speed and simultaneously carrying out the processes of washing, dewatering, spin-drying, discharging and the like. Some necessary security measures are adopted in programming: the main motor overload overheat protection is mainly provided, when the main motor overload overheat protection is started, the oil pump motor must be started first to run for 3 minutes, if the oil pump motor is not started or the starting running time is not reached, the main motor cannot be started to run, when the main motor is shut down, the oil pump motor can be stopped only after the main motor stops running for 3 minutes, and when the main motor is in a running state, the oil pump motor still runs when an oil pump motor closing button is pressed. When the oil pump motor stops due to unexpected failure, the main motor also stops running immediately. Therefore, in order to protect the main motor, the service life of the main motor is prolonged. Because the main motor is operated without lubricating oil, wear of the main motor is accelerated.

In this embodiment, the PLC microprocessor uses siemens S7-200CPU224XP, which has 14 input interfaces, 10 output interfaces, two analog inputs and one analog output, and the address allocation is shown in table 1, where the total number of input points is 10, the total number of output points is 11, and the redundant I/O ports can be used to expand other functions later.

TABLE 1

Input point

Output point

Name of the name

(Code)

Input point number

Name of the name

(Code)

Output point number

The circuit is electrified

SA1

I0.0

Power indicator lamp

HL1

Q0.0

Oil pump start

SB2

I0.1

Oil pump operation

KM1

Q0.1

Host start-up

SB4

I0.2

Oil pump operation indicator lamp

HL2

Q0.2

Host stop

SB3

I0.3

Host power-on

KM3

Q0.3

Stop of oil pump

SB1

I0.4

Y-shaped starting of host

KM2

Q0.4

Oil pump thermal relay

FR1

I0.5

Y-shaped running indicating lamp of host

KM4

Q0.5

Main machine thermal relay

FR2

I0.6

Triangle operation of host

HL3

Q0.6

Manual/automatic

SA2

I0.7

Triangle operation indicating lamp of host

HL4

Q0.7

Alarm reset

SB5

I1.0

Manual operation indicator lamp

HL5

Q1.0

Manual feed

SB6

I1.1

Alarm output

HA

Q1.1

Feeding material

KM5

Q1.2

PLC ladder diagram program design

The ladder diagram is composed of contacts, coils and functional blocks represented by boxes, wherein the contacts represent logic input conditions (normally open contacts are represented by two vertical lines in the diagram, normally closed contacts are represented by two vertical lines in the diagram, a diagonal line is added between the two vertical lines to represent normally closed contacts), the coils represent logic output results (represented by brackets in the diagram), and the functional blocks are used for representing additional instructions such as timers, counters and the like. The program is executed in a circular scanning mode, and the user program is executed in a mode from left to right and from top to bottom.

Program description: fig. 6 shows an automatic operation program, I0.0 to I1.1 represent input contacts, wherein I0.5 and I0.6 are thermal relay contacts, and when the current of the main motor and the oil pump motor is excessive or overloaded, the I0.5 and I0.6 contacts are automatically opened to protect the motor from being burnt. Q0.0 to Q1.2 represent the output results. M0.1 represents the intermediate process result. T37 to T39 are timers of 100ms, are used for controlling the delayed starting and the delayed stopping of the motor, and the normally closed contact of Q1.1 is mainly used for protecting the main motor, when the alarm is not released, the main motor is not started, the normally open contact of Q0.1 is used for protecting the main motor, and when the oil pump motor fails and stops running, the main motor also stops running.

Program operation process description: as known from the I/O allocation table, I0.0 represents the total switch of the control circuit, I0.0 is turned on (other addresses can be inquired according to the allocation table), Q0.0 outputs a high level, and a power indicator lamp (Q0.0) is on, so that the control circuit is powered normally. After the oil pump starting button I0.1 is pressed, Q0.1 and Q0.2 output high level, the oil pump motor is started, meanwhile, the oil pump motor working indicator lamp is on, and the timer T37 starts to count time. After 3 minutes, the normally open contact of the T37 timer is switched on, Q0.4 and Q0.5 output high level, the host computer is started in a star shape, the timer T38 starts to count, after 15S, the T38 timing time is up, the normally closed contact of the T38 is switched off, Q0.4 and Q0.5 output low level, the star start is completed, the indicator lamp is turned off, the normally closed contact of the Q0.4 is reset and closed, Q0.6 and Q0.7 obtain electricity to output high level, the main motor enters a triangle operation mode, the triangle operation indicator lamp is lightened, the KM5 coil is electrified, the feeding electromagnetic valve is opened, and feeding is started. When the work is completed, the stop button I0.3 is pressed, the coil of the M0.1 outputs a high level, the normally closed contact of the M0.1 is disconnected, the power-off outputs a low level of Q0.3, Q0.6 and Q0.7, and the main motor stops running. The indicator light is turned off. The MO0.1 normally open contact is closed, the timer T39 starts to time, after 3 minutes, the T39 is timed to be up, the T39 normally closed contact is opened, the Q0.1 and Q0.2 are powered off to output low level, and the oil pump motor stops running. When the oil pump is started by pressing the I0.1 next time, the automatic operation is started.

Fig. 7 is a manual operation program, which is basically the same as the automatic operation process except that each input button needs to be manually pressed. When the oil pump starting button I0.1 is pressed, after the timing time is up, the host starting button I0.2 is pressed, the host can be started, and after the work is finished, the oil pump motor is stopped, and I0.4 is manually pressed.

Fig. 8 shows an alarm program and a manual/automatic selection program, I0.7 shows the contact point of the manual/automatic selection switch, and when not turned on, the operation is automatic, and when turned on, the operation is manual. JMP is the program jump instruction, LBL is the jump label, and JMP corresponds in pairs. When JMP is valid, the program in between JMP and LBL is skipped, and the program after LBL is executed. And when the control of the centrifugal machine fails, manual debugging operation is performed after I0.7 is pressed. When the motor currents of the main engine and the oil pump are too high and the temperature is too high, the I0.6 and the I0.5 are connected, the middle coils M1.0 and M1.1 are connected, so that the Q1.1 outputs a high level, and the alarm is driven. I1.0 is a manual reset alarm signal, when I1.0 is pressed down, M0.2 is switched on, the normally closed contact is switched off, the coils M1.0 and M1.1 are powered off, Q1.1 is powered off, and the alarm is released. When an alarm occurs, the main motor can be started only after the alarm is released.

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it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The method for controlling the double-stage pusher centrifuge by utilizing the control device of the double-stage pusher centrifuge based on the PID is characterized in that the control device of the double-stage pusher centrifuge based on the PID comprises a material pipe, an outer rotary drum, an inner rotary drum, a hydraulic pushing system, a pusher tray, a distributing tray, a main motor, an oil pump motor and a feeding electromagnetic valve, wherein the outer rotary drum and the inner rotary drum are sequentially arranged from outside to inside and are mutually communicated, and the pusher tray is arranged in the inner rotary drum and is connected with the hydraulic pushing system; the material pipe is communicated with the material distribution disc, and the material distribution disc is connected with the material pushing disc; the outer rotary drum is linked with the inner rotary drum and the pushing disc and is connected with the main motor; the oil pump motor is connected with the hydraulic pushing system through an oil circuit system; the feeding electromagnetic valve is connected to the pipe orifice of the material pipe; the control device is characterized by comprising a PLC microprocessor, wherein the PLC microprocessor is connected with a main motor, an oil pump motor and a feeding electromagnetic valve of the double-stage pushing centrifugal machine; in addition, the PLC microprocessor is also connected with a vibration sensor and a flow sensor, the vibration sensor is arranged on the machine base, and the flow sensor is arranged in a material pipe of the two-stage pushing centrifugal machine and is connected with a PID controller; the PID controller is also connected with the PLC microprocessor;

the method comprises the following steps:

2. The method of claim 1, wherein the PLC microprocessor is further connected to an oil temperature sensor and a temperature alarm circuit.

3. The method of claim 1, wherein the PLC microprocessor is further coupled to an alarm circuit.

4. The method of claim 1, wherein the PLC microprocessor is further coupled with a device start button, a manual mode selection button, an automatic mode selection button, a manual feed button, a main motor start button, and an oil pump motor start button.