Control System Design of Automatic Feeding Machine

Shaoke Chen 1, 2

1 Mechatronic Engineering Department, Shantou University, Guangdong, 515063 China

2 Shantou Institute for Light Industrial Equipment Research, Guangdong, 515063 China

E-mail: skchen@stu.edu.cn

Keywords: fixed-time, fixed-quantity, feeding machine

Abstract. The research of the control system of automatic feeding machine in the present paper can

be applied in different mechanical designs – from simple key-press input of cycling days, multiple

time intervals and the feeding amount to setting steps of numbers of stepping motor via the control

of SMC by time setting. This not only realizes the objective of “fixed-time” and “fixed-quantity”

feeding, but also solves the problems of serious leaking, high failure rate, and loud noises during the

process of using warehouse-type feeding machines, which brings favorable economic and social

benefits for enterprises.

Introduction

With the expansion of the scale of social production, people set higher requirement for

mechanical automatic production. Traditional machines will inevitably be eliminated. Unmanned

operation or automatic production with as little manual work as possible will take the place of

traditional machines. The improvement of traditional machines or the development of new

intelligent machines is the developing direction of current machinery industry. The automatic

feeding machine combines transportation, weight measurement and fixed-quantity control together,

which belongs to high-tech product with electromechanical integration. The machine can adapt to

all kinds of industrial production environments, including continuous feeding measurement of

power/ grain/ lump-shaped granular material, and it is widely used in different industrial production

sectors, such as building materials, metallurgy, electricity, chemical engineering, and light industry,

etc.[1]

Based on the application of non-large-scale production, the present design aims at designing for

the electrical control system of automatic feeding machine. Because high manufacturing cost is a

disadvantage in market competition, the design should take its cost into consideration. The design

should follow two principles: practical and simple. According to actual situation and user demands,

no matter mechanical structure or circuit hardware should be as simple as possible. The objectives

of keeping simple are two: one is improving machine reliability; second is reducing production cost.

The designing development of the electrical control system of automatic feeding machine is

favorable to the improvement of working efficiency of the feeding machine, decrease of manual

intervention, economization of manpower, and promotion of large-scale production. [2]

System Design

Based on the task analysis of the electrical control system of automatic feeding machine, the

system realizes the design of hardware and software. The former includes the configuration of

master device, functional module, and detailed design of schematic circuit diagram; the latter

Applied Mechanics and Materials Vols. 157-158 (2012) pp 466-471Online available since 2012/Feb/27 at www.scientific.net© (2012) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMM.157-158.466

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designs for the program structure of the overall controlling system based on modular programming

ideas. The software can write modular programs, such as initialization, manual drive, automatic

drive, numerical calculation, data communications and monitoring, etc. The human-computer

interface of the design system can realize the interaction between users and the system. [3]

The overall schematic diagram of the feeding machine is shown in Figure 1. The storage box

stores feeding materials. The impeller hopper consists of several blades and the space between

every two blades is fixed. The impeller hopper is driven by the stepping motor. Timing control of

the rolling angle of the stepping motor can control the number of space for blade hopper rotation

and therefore realize quantitative control of the feeding amount.

Fig. 1 Overall Schematic Diagram of the Feeding Machine

The feeding amount can reach a fixed quantity every time the feeding machine works. Users can

set the required amount according to the real situation and their own will. Within each cycle

working time for starting the machine, one unit of feeding amount is enough. In the control segment,

the feeding machine can calculate and thus obtain the rotating angle and make sure the export of

feeding machine according to fixed demand and set time. At the same time, users should check

whether the feeding box is lack of feeding materials. If yes, the machine will give an alarm and stop

feeding.

Design of Hardware System

The electrical control system design of the present feeding machine can meet the requirement of

timed and fixed-quantity feeding from the aspects of both software and hardware. According to

different mechanical structures and via the change of procedure parameter (such as the conversion

set of feeding amount and the display setting of menu), the design can adapt to the timed and

fixed-quantity feeding of different objects. Control of the stepping motor can be realized via parallel

mode and thus achieve the goal of controlling multiple stepping motors of the same type and

realizing large-scale production. [4]

The feeding machine has three main functions, namely “timing”, “fixed quantity” and

“automatic feeding”. The design of its electrical control system is based on these three main

functions. Furthermore, the development of the electrical control system of the feeding machine is

mainly based on the AT89S51 SCM chip, the program of which is written by C Language and

displayed on the LCD Screen. After confirming the input, time counting starts. This system is

divided into three main parts:

Applied Mechanics and Materials Vols. 157-158 467

(1) Input and Display Part: Via high-and-low PWL judging method, four keys can be set,

namely “plus”, “minus”, “enter” and “return”. They can be displayed on the LCD1602A Screen.

(2) Time Accumulation Part: The time starts from “0” using the time accumulation method with

the minimum digit of 0.1 second and displays on the LCD1602A Screen.

(3) Quantitative Feeding Part of the Stepping Motor: Once the accumulated time has reached the

set time, the accumulator will stop working. After the SCM (Single-Chip Microcomputer) reads the

feeding amount set by the program, it will start the stepping motor and make it rotate corresponding

angle or rounds, and thus achieve certain feeding amount.

The control system mainly involves SCM design, including displaying operation signal

interface, etc. The SCM is the control core of the overall system and completes all monitoring

functions. The reason of choosing AT89S52 SCM is because it has advantages like rich hardware

resources, strong processing ability, fast operation velocity, and low power consumption, etc.

Besides, it makes development, debugging and application more flexible and convenient. The

design diagram of the hardware system is shown in Figure 2. [5]

Fig. 2 Design Diagram of the Hardware System

The stepping motor is controlled by the SCM. However, the controlling system cannot drive the

charged component directly. It needs the power circuit to expand and export the electric current so

as to meet the demand of electric current and voltage of the charged component. The series product

of ULN2XXXX High-voltage & Strong-current Darlington Transistor Array belongs to this kind of

controllable high-power device. Because of its great function and wide field of application, the

ULN2003A chip is chosen as the driver.

Design of Software System

The system has the functions of setting and changing parameter. Control modes, feeding amount,

upper and lower limits can be set online; feeding amount, limit value of alarm, and mechanical

parameter of the system can also be changed online. The program design can be divided into three

parts: first part is the input and display of menu design, time interval, input and display of the

feeding amount; second part is time accumulation and its display; third part is the driving motion of

the stepping motor and the control of its rotating rounds, angles, and velocity, etc. The flow chart of

menu input is shown in Figure 3. [6]

468 Mechatronics and Applied Mechanics

Fig. 3 Menu Input Flow Chart

The section of data input contains 4 parts, namely the input of the number of days (D), input of

initial time interval t0, input of No.1-4 time intervals t1~t4, input of feeding amount (G).

Input of the number of days (D): First line on the LCD1602 shows the sample “Days input:

(D)”; the first and second spaces in the second line can be filled in with a two-digit number of days,

the data range of which is from “00~31” days. The data can be entered via a “while” cycle criterion.

K1 means data plus 1; K2 means data minus 1; K3 is confirmation and switch to the next menu (t0

means entering the menu). The input of time t0~t4: it is the same as the input method of the number

of days (D), except changing the menu requires one more key, K4. The function of K4 is return to

the previous menu, which can be used when you mistakenly enter the next menu because of

modification, incorrect input or sensitivity of the press button.

Input of feeding amount: It slightly differs from the time input because the feeding amount

displayed is a 4-digit letter. The display of the input shows the last four digits, with a unit “g”. The

maximum number of input is 5000g. The key functions are consistent. However, the “+” button

written on the program means adding 50g of feeding materials each time, that is, the division value

is 50g.

In order to get a visualized view of each input amount on the screen and make full use of the

LCD1602 resources, the second line of each input amount is kept on the screen. When you enter the

next menu, the input amount does not clear the screen. Therefore, the writing of each data is

allocated to different addresses, from 0xc0 to 0xcf respectively. This is why every cycle of menu

program has to write the program for LCD individually, instead of using a common function.

The section of time accumulation is the core of the overall program because it involves time

setting and how to control the stepping motor. Its flow chart of time control is shown in Figure 4.

Applied Mechanics and Materials Vols. 157-158 469

Fig. 4 Time Control Flow Chart

After entering the “while” cycle, the time is accumulated by a unit of 0.1s. When it first reaches

t0, time accumulation stops. Then the procedure turns to the subprogram of the start-up of the

stepping motor and control quantitative feeding. Once the feeding completes, the time accumulator

will be reset and use “if” sentence to judge whether t1 is 0. If not, the number of days will be

subtracted by 1 after the time accumulates to 24 hours. Then the program goes to the subprogram of

controlling feeding materials and enters the cycle.

If t1 is not 0, use “go to” sentence and turn to “run1”. The function of “run1” is to start from 0

and re-accumulate time. Control the feeding amount when the time accumulated reaches T=t1.

Similarly, once feeding completes, use “if” conditional statement to judge t2. T2 means 0 to run5.

Otherwise, 0 turns to run2. The function of run2 is slightly different from run1. The reason is that

the time accumulator keeps accumulating on the basis of the original time, without resetting. When

the time accumulated reaches T=t1+t2, the subprogram is applied to quantitative feeding. The

functions of run3 and run4 are basically consistent with run2, except the value of accumulator T is

the total accumulation time without t0.

No matter the section of t0 timing or the section of t1~t4 timing is applied, the same “while”

statement is used to cycle the subprogram of 0.1s delay. The variable of the time accumulator t0_1

should be compared to tn (n=0;1;2;3;4) to realize the function of time setting. Therefore, when the

time accumulates to t0_1=10, the result of time accumulation is no longer 10s, but 1s. Before tn

enters the program and compares with t0_1, it should be changed into the same unit as t0_1.

Users can observe the procedure parameter and status required from the on-the-spot controlling

board. The setting of feeding amount and limit values, direct modification and setting of controlling

parameter, start and cessation of the system equipment, the switchover of different working modes,

etc. can be completed.

470 Mechatronics and Applied Mechanics

Summary

Through the installation and site debugging of the automatic feeding machine and electricity, it

shows that the present system works steadily and realizes all expected functions. The on-the-spot

application demonstrates it has a positive meaning towards improving production efficiency and

guaranteeing product quality, which achieves a better result. The machine has a better calculating

ability, controlling performance and high practical engineering value. Meanwhile, it reduces the

construction costs, which enhances the performance price ratio of the system.

Acknowledgement

The authors wish to thank the Natural Technology Innovation Fund of Technology-based SMEs

(Small and Medium-sized Enterprises), P. R. China for providing a grant (No:11C26214403131)

and the Co-operation of Industry-University-Research Institute, Guangdong Province & Ministry of

Education, P. R. China for providing a grant (No:2009B090300175) for this project.

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