The process flow of the batching system is designed with an automated feeding system. The hardware design and software design of the PLC dosing production system are described in detail with the example of a brewery's homebrew mixing. The system consists of a programmable controller and a touch screen to form a two-stage computer system. The field control part adopts PLC to control the production process, and PLC makes real-time response according to the data collected by the sensors. The system adopts modular design, featuring flexible system configuration, simple operation, convenient maintenance and reliable operation. This system has a strong generality, only need to modify the program can realize the production requirements of similar enterprises, there is a very large practical value.

1 Ingredients platform design

The main raw material for brewing consists of malt 1#, malt 2#, malt 3#, malt 4# and malt 5#. Before starting the dosage, the technician selects the raw material formula on the touch screen, inputs the total amount of dosage and the weight of single bag product, the system adopts the "upper and lower" measurement mode, that is, the weighing barrel measurement module is responsible for the weight collection of the upper material part, and the discharging barrel sensor is responsible for the discharging part of the weight collection. After the operator inputs the data and clicks on the feeding button, the controller drives the motor of the feeding machine through the frequency converter according to the settings of the formula. The motor drives the screw feeder of the loading machine to transfer the malt to the weighing bucket, after reaching the set weight, the malt in the weighing bucket is put into the discharging bucket, then the controller switches the motor to finish all the raw materials in the formula in turn, then the mixing motor in the discharging bucket is utilized to mix the raw materials evenly, and then after the mixing is finished, the operator will then quantitatively output the products according to the needs. Set the number of bags, the weight of a single bag, click on the discharge button, in order to complete the process of discharging.

2 dosage control system structure design

The core controller of the feeding system for the PLC, mainly by the production line, the operator console (touch screen), speed sub-systems, weight measurement system, actuators, material level detection and power supply and other ancillary equipment, to build the entire system of equipment needed to connect with the PLC relationship. The system is equipped with an emergency stop button when the system is abnormal during the loading process, emergency stop can be carried out. Installation of the buzzer is used when the system is abnormal, with the upper computer interface, to make the appropriate prompts to facilitate the staff to deal with. The system uses five proximity switches installed at the bottom of the silo to detect whether the material level is sufficient. Frequency converter through five contactor switch time-sharing control of five motors, for malt raw materials sequential feeding. Data acquisition part of the analog signal acquisition through the sensor, sent to the transmitter for A/D sampling after sending to the PLC for processing, using 8-way load cell. The reason is to consider the actual production process, due to the weighing bin and mixing bin is relatively large, need to rack the entire weighing barrel, mixing barrel. Designed four load cells in series, in the form of a rectangle mounted on the bottom of the weighing bin, and ultimately add up the signals from each channel to get the weight information. The top and bottom of each four-way very good to ensure that the load cell force vertical down, can be very good to ensure the measurement accuracy of the weighing barrel and mixing barrel.

Weighing instruments and inverters are connected to the PLC through the RS485 serial port, because the PLC only has a 485 serial port, so the transmitter is connected in series with the inverter, and the PLC accesses the slave device using the addressing method.

3 electronic control system hardware selection and electrical design

The controller selects S7-200smart, which can meet the control needs of most small automation equipment. Adopt Siemens series 1000IE touch screen to realize the upper computer interface design of the dosage system, the main advantages: simple operation, graphical programming, short development cycle and S7-200smart perfect compatibility. According to the three-phase asynchronous frequency converter motor matching the technical parameters, choose Siemens V20 frequency converter, rated power 1.5kW. considering the economic and functional requirements to achieve the selection of load cell group to weight measurement, select the Z6FC3, Z6FC6 group for the weight collection.

Feeding system: single sensor error 5g, four-way cumulative error 20g, four-way measuring range 0~200kg.

Discharging system: single sensor error 10g, four-way accumulated error 40g, four-way measurement range 0~400kg.

Considering the production conditions, malt raw materials exist a certain amount of dust, the use of photoelectric switch is likely to cause error in judgment of the material level, so the system does not choose photoelectric switch, the use of proximity switches to complete the material level detection function.

4 control system software design

4.1 System function requirements

The functions of the brewing automatic dosage system include automatic loading and discharging, recipe storage, material level detection, fault diagnosis and status message prompts, etc. The dosage master control program is controlled by PLC. The main control program of batching is completed by PLC, and the formula storage and data input are completed by touch screen. Recipe modification, data display, record the actual value of the dosage and other functions are completed by the two together. The system adopts ladder language programming, the whole system consists of system initialization module, speed control module, formula selection module, data acquisition module, feeding module, discharging module, etc., which cooperate with each other to complete the whole dosage work. The whole system can be divided into the following three parts: preparation stage, feeding stage and discharging stage.

4.2 Preparation stage

Preparation stage mainly completes the initialization of the system to clear all the state bits, data reset. Before feeding the touch screen will prompt the equipment check to ensure that the equipment is empty before dosing. Then material level detection to ensure that can meet the requirements of a feeding, do not have to stop in the process of feeding. After completing the preparation of the equipment in the touch screen to select, enter the production data, through the touch screen will be transferred to the PLC data storage area.

4.3 Feeding stage

Feeding to complete the whole system of dosing work, due to 5 kinds of malt sequential feeding, to a malt for example, before starting to feed open the weighing module for data acquisition, PLC will be speed data through the 485 serial port written in the inverter, high-speed start the motor, fast feeding. When the real-time weight of raw materials reaches the set value 1 (according to the system pre-experiment data), frequency conversion speed regulation for low-speed loading, when the real-time weight reaches the predetermined value 2 (according to the system pre-experiment), turn off the motor and delay for error collection, if the error range is greater than the dosage required error, according to the error size dynamically adjust the motor low-speed turn step length, until the required error of 50g or less, the system through a reasonable setup parameters into the jittering stage, the system will be able to achieve the required error. The system can reach the required error within 50g by setting the parameters reasonably and entering the jittering stage, basically, the error requirement can be reached in 3 times, and the rapidity can be guaranteed. When a certain kind of malt feeding is completed, open the weighing valve to release the malt, and at the same time close the current motor and switch to the next malt corresponding to the motor, start the next malt feeding, until the completion of all the malt feeding work.

4.4 Discharging stage

Discharging to complete the whole system of discharging work, start discharging barrel mixing motor before the start of discharging the malt will be mixed evenly, and then in the touch screen to enter the necessary data bags, bags of weight, input is complete, click the discharging button to start discharging. When the real-time weight of the material to reach the set value of 3 (according to the system pre-test data, different equipment set value is different), PLC control linear motor off small discharging valve, when the remaining amount of discharging into the requirements of the error range, close the discharging valve, the buzzer sounded to indicate that discharging is complete, ready for the next bag of discharging.

5 Conclusion

PLC-based weighing and dosage system has been put into use in a winery, the results show that the system is stable and reliable. Through the optimization of the software algorithm, the dosage time is about 5min when dosing 150kg, the discharging time is about 5min, and the total weight deviation of single feeding can be controlled within 50g, which realizes fast and high-precision dosage. In addition, the system has the function of fault alarm, which can be prompted through the alarm screen to the point of failure when PLC fails, which is convenient for the maintenance of the equipment.