Application of speed regulating quantitative feedi

The application of single-chip microcomputer controlled speed regulating quantitative feeding scale

speed regulating quantitative feeding scale is an advanced equipment for weight batching of raw material mill and cement mill. It is suitable for the requirements of cement plant material characteristics (block and powder particles, large flow, containing a certain amount of water), harsh working environment (large dust, high temperature, large vibration) and silo level and silo pressure changes

1 system composition

or realize compatibility with the background by releasing a chemical signal. The raw material batching metering control system has eight speed regulating quantitative feeding scales installed between the bottom of the silo and the belt conveyor; There are eight single-chip microcomputers and their peripherals (CRT display and printer) in the control room; There are electrical switches, speed controllers, load indicators and alarm devices on the instrument operation cabinet

1.1 the mechanical scale body of the quantitative feeding scale

includes the frame, master-slave roller, weighing frame, belt and its automatic tensioner, transmission device, material thickness control gate, etc. The quantitative control of feeding is realized by adjusting the belt speed. It is driven by AC electromagnetic speed regulating motor and equipped with cycloid needle gear reducer or worm gear reducer. There are two transmission modes

1.2 detection and control instrument and microcomputer part

the real-time control intelligent instrument system is composed of high-precision weighing sensor and its regulated power supply, load display alarm instrument, speed regulation controller and MCS-51 series single-chip microcomputer. The system is equipped with high-precision regulated power supply and filter circuit

2 working principle

materials are unloaded onto the belt from the silo through the control gate to maintain a certain thickness of the material layer. Material weight Q (kg/M) and belt linear speed on unit length of weighing section ω The product of T (M/s) is the instantaneous value of weight flow GT (kg/s)

when the height of the material control gate is constant, the material thickness on the belt is constant, and the value of Q changes only with the particle size, bulk density and moisture of the material. Therefore, in order to keep the weight flow GT constant, the system should automatically adjust the belt speed according to the change of Q value ω t. Multiply Q· ω T certain, so as to achieve the quantitative control of weight flow. When the chemical composition of raw materials changes, the composition of raw grinding materials must be analyzed quickly. The upper batching computer calculates the new raw material proportion in time according to the control index of the predetermined clinker rate value, sends the set value of proportion and weight flow to the single-chip microcomputer, and starts the second closed loop - chemical composition proportion control

in order to accumulate the material output over a period of time, we should integrate the instantaneous value of weight flow, that is:

obviously, it is extremely easy to realize the calculation of equations (1) and (2) with a microcomputer. We amplify the output signal ut of the load cell to up proportional to Q. And the speed feedback signal (or frequency signal) U of the speed regulating motor ω And belt linear speed ω T is proportional. Connect the voltage signals up and u ω And the corresponding calculation coefficient are input into the microcomputer for multiplication and integration, which can display the instantaneous value and cumulative value of weight flow on the LED digital display and electromagnetic counter respectively

in order to realize quantitative control, it is necessary to control the belt speed. In the general instrument control system, the "amplification plus feedback" device is used. In microcomputer control system, incremental discrete algorithm is often used

where:

yk, YK-1 - current and previous output values of microcomputer

ek, EK-1 - current and previous deviation

kp, Ki - proportion sum product 101, industry related legal policy score coefficient

the formula (3) operation is completed in the microcomputer and the control value is output, that is, the proportional integral (PI) control is realized. In microcomputer real-time control, the dynamic performance of the control system can be stabilized by modifying the contents of KP and Ki address units, so as to obtain sensitive and stable regulation quality

the flow setting value GS can be set digitally directly by using the four position dial switch on the microcomputer panel. In the proportioning control system, it can be set by the upper computer and send the flow setting signal us. In the microcomputer, the deviation between the set value and the actual value is controlled and calculated according to the PI regulation law or the step-by-step optimization algorithm, the control signal uy is output, and the motor speed is changed through the speed controller, that is, the belt speed is adjusted to maintain Q and ω At the beginning of the 20th century, metallographic microscope was used to study fatigue mechanism; Product - the actual value of weight flow is consistent with the set value to achieve the purpose of quantitative control. The working principle of the system is shown in Figure 1

Figure 1 system hardware diagram

3 single chip microcomputer system features

3.1 hardware

uses 8031CPU as the core component to form a single loop digital controller, which includes an 8-bit microprocessor, 128 bytes ram, 21 special function registers, 4 parallel interfaces, a full duplex serial port, and 2 6-bit timers of an experimental machine such as 600kN. The system adopts 8031 plus 2764 chips (8K bytes) as EPROM and 8255 as parallel port, so as to form a complete real-time control system

analog input adopts 8-channel chip 0809 to realize a/d conversion, weighing signal up and speed signal U ω And the setting signal us of the upper computer is 0 ~ 5V DC unified signal. The conversion accuracy and time meet the requirements of system indicators

analog output adopts current type output chip 0832 for d/a conversion, and the output signal outputs 0 ~ 10 Ma DC signal through operational amplifier. Therefore, it is extremely convenient to connect the machine interface with the general DDZ-II instrument actuator. The machine has two outputs, one is to control the motor speed, and the other is to supply the instantaneous value of the upper computer flow, so as to realize the microcomputer joint monitoring

see Figure 1 for the hardware system of this machine. According to the user's requirements, the server is set up, which can be equipped with CRT display and printer. Print the shift output of various raw materials, and display the instantaneous or cumulative flow value (by pressing the key to switch) and the set value at any time. If there is no server, printer and display, the display can be realized through the four digit LED digital display on the single chip microcomputer panel. In order to prevent the loss of accumulated value during power failure, a 6-bit electromagnetic counter is set. When the actual value deviates from the set value by ± 5%, the machine can give an audible and visual alarm. The back panel of the machine is equipped with a keyboard to complete the correction of the flow calculation coefficient

3.2 the software

adopts structured programming. According to the characteristics of raw material batching process and field conditions, the control algorithm adopts a step-by-step optimization method. Its tracking step size is related to the dynamic error, and the step size is proportional to the deviation size