Microcomponent Thickness Comprehensive Detecting Plain Test

1Microcomponent Thickness Comprehensive Detecting Plain Test Control System DesigningZhenwei Duan Yanhua Li Denren Kong Changan DiDepartment of precision instrument of School of Mechanical Engineering in NUST, Nanjing, 210094 Phone (086)E-Mail: Abstract: This article introduces the overall plan of the testing & controlling system of the platform for testing the thickness of the microcomponent, the working principle and the design method. It introduces the driving system, controlled by the PLC programmed controlling step-motor, to accomplish the testing of microcomponent in the form of production chain. It introduces the communication and control method between the thickness-testing sensor and PC. It discusses how can the PLC controlling microcomponent material distribution machine accomplishes distribution task, when getting sort signals form PC. It discusses the realization method, in which all kind of status in operating process can be tested and the fault can be tolerated. This system was debugged in industrial location and its feasibility was proved well.keywords: microcomponent， detecting， classification automatization， ManipulateMicrocomponent is a critical unit in air condition and air compressor, whose geometry dimension, surface roughness, margin tolerance etc deeply effects the refrigeration and calefaction of them. Actually as the demand of air condition and air compressor are more and more vast, the demand of microcomponent is more and more vast too and the degree of accuracy of microcomponent is more and more higher. Now after the microcomponent was machininged and producted, which was mainly detected manually, the verification became where the shoe pinches. The traditional verification method has the problem of slow velocity, low efficiency and man induced factor effect. So we developed this Microcomponent Thickness Comprehensive Detecting Plain. The Programmable Logic Controller of S7-200 catena, which is made by the Siemens and the industrial control computer are the nucleus of this topic. We combination the deeply activation capability, the high reliability, the superior proportionaliny among the performance and the cost, the expedient application of The Programmable Logic Controller with the deeply data-processing capability, the amicable relation among man and computer, the high administration horizontal of the industrial control computer, then we develop this Microcomponent Thickness Comprehensive Detecting Plain Test Control System. We achieve the automatization of the examination of the microcomponent thickness and the exclusive classification process, and enhance the level of automatization, get together on better economic effect.I The design of the microcomponent thickness comprehensive detecting plainThe Microcomponent Thickness Comprehensive Detecting Plain is made up of the driving and measurement mechanics, the classification mechanics and the control section .In a general way, the concentrated and decentralized system can be fallen into three tiers: the top is management who manages the whole system; the middle is concentrated supervisory who monitor, control and deploy the whole system; the bottom is decentralized- implementation, whose task is control the local system. In the system, the industrial control computer undertakes the task belonging to the top and middle as supervisory management; PLC undertakes the bottom task as control implementation tier2. The industrial control computer transfers the management decision, control task, control parameter and deploy dictation to the control tier PLC by communication cable, PLC transfers the parameter, process control and data to the management tier by communication cable. The function flowchart of whole system is as fig 1.2Fig 1 The overall structure of the systemA The automated detecting plainThe automated detecting plain is made up of measurement plain and the driving mechanism. Measurement plain is the basic reference of the microcomponent s geometrical parameter, whose degree of accuracy is higher than that of the microcomponent. During the measurement process, the microcomponent slides with surface of the operating board. In order to guarantee the stationarity during the driving process, and eschew to lead in the additive lapse to engender the deformation because of the shock of the driving mechanics, the driving mechanics exploits the designing of fission constitutional formula to disbranch the measurement plain and the driving mechanics, then descend the influence of the driving mechanics by a long way. We need to measure five dots on the diagonal of every surface(it can be taken into one dot in the crossover). In this way, the microcomponent not only rotates 90 degree, but also rolls over 180 degree on the pipleline.By protracting favourable bandy on the measurement plain, we can make the microcomponent rotate favourable angular degree according to the primary locus, and to realize the turning of the microcomponent by designing the spatial texture of the industry chain.B classification organThe microcomponent is transferred to the classification organ down the slipway. The classification organ classifies the microcomponent by virtue of controlling stepper motor to rotate homologous angular degree when the PLC accepting classification information. The PLC controls the stepp motor in the way of PTO. PTO mode can export much impulse train, and enable impulse train to queue to establish conduit line. It can be classified two enominations including single conduit line and multiple conduit line1. This system adopts the multiple conduit line, and establishs the list in variable memory block to control periodic time of output impulse and pulse number, then achieves to control the stepper motor rate and angular degree exactly.The PLC reckons heterogeneous conditions by inductive switch in the classification process. For instance, the arrival signal, the align signal, the classification completion signal. If The PLC discovers false condition, it will deliver homologous alarm signal to the industrial control computer, then the operating force can eliminate the bug.C The control sectionThe PLC is the nucleus of the control section, which carried out the command of the industry control computer by the communication of them. When the industrial control computer interfaces with PLC, because PLC exploits standard RS-485, which is not compatible with the industrial control computer RS-232, we must switch over by PC/PPI communication cable2. The industrial control computer is the administrator of all the system, .It controls the sensor to measures the geometrical parameter of the microcomponent on the industry chain, and calculates to get the classification information of the microcomponent. The PLC is the manipulative nucleus of all the system, it completes the facility which includes the activation governing, the condition sense, the implementation of the dictation and so on. The PLC controls the performance of the classification mechanics and the driving mechanics by accepting the information of the industrial control computer.II The design of the control systemA The control demand of the system In order to accomplish the detecting, transmission and classification of the microcomponent, the system was demanded to accomplish the functions as follow:1) Can accomplish the steady transmission of the microcomponent in industry chain and ensure the queue of the microcomponent , which was formed by entry order of the chain, was orderliness and integrality. 2) The speed of former driving organ must be not Sort control signalSensor signalPTO outputDrive controlControl signalMeasurement plainPLC RS-485Industry control computerRS-232Sort control systemPC/PPIMotor 1Mtor2Status signalStatus signal3faster than the later classification organ, and at the least ensure when the classification organ didnt accomplished the classification, there is no microcomponent entry the classification organ.3)Ensure the classification organ can auto reset when the step motor was out of step. 4) When not only one microcomponent entry the classification organ, the worker will be told the system was in trouble. In the mean time the motor can be estimated whether it works well and the angular displacement output is correct.5) The system must have certain fault-tolerant capacity, when it occurs common errors, the system can rehabilitate by itself. But when the fatal error was occurred, the system can clew the possible sort or approximately orientation.B The work principle of control system The control system is mainly made up of motor driving section, communication section, status detecting section and alarm section. Every section defined in the output and input of PLC as fig 2:Fig 2 The control system1) Step motor and driving section The step motor is execute component which converts the electric pulse output of PLC to angular displacement or rectilineal displacement which is in direct proportion to the electric pulse. The former driving section step motor mainly accomplishes the speed control of the industry chain, and the later classification section must accurately control the output angular displacement and direction of the step motor. When the step motor out of step in the process, the photoelectric encipheror must be used to control the phase output of the step motor and ensure the output accord with the practicality. The later classification section adopts the mode of auto reset to eliminate the accumulated error of the motor and ensure that the motor output certain angular degree from zero position every time.2) Status detecting and alarm designThe process status of the system could be estimated by inductive switch which were fixed in the certain position of the system. When the status didnt accord with the given status, the system should alarm. The mode of the alarm is designed in acousto-optic mode, according as the ponderance of the errors.3) The communication of the PLC and the computer.The program of the communication port, including the parity bit, the length of the data frames, realized the communication of the PLC and the computer.III The software design of the systemThe software of the industry control computer, which was adopted object-oriented windows application and programmed in Bland C+ compiler, had luxurious human-computer interaction, multilevel menu design and was operated easily. Using STEP7-Micro/WIN32 programmed the control software of PLC, which based on Windows application and designed specially for S7-200 series PLC of Siemens. It has the powerful function, was mainly used to develop program, at the same time also used to supervise the status of program implementation real time2.A The software design of PLCThe software of PLC can be separated into main program Main(), normal sort program Micro_Sort(),auto reset program Auto_Reset(), interrupt service routine(ISR) Interrupt(), initialization routine Ini_Install() and error handling program etc in structural. All the subroutines ware decided which could be called by main program according to industry control computer or external command .The main control flowchart graph manifest as fig 3.When the system was powerup, the initialization routine was called to accomplish the initialization of whole system and the scanning of all the inductive switch, which was according as whether the system was in gear .if not , the PLC will send initialization fail signal to industry control computer and wait for the worker to treat with. If the initialization was Direction controlI0.2I1.7 I0.0 I0.1InputPLC 226Communication portOutputQ0.5 Q0.2 Q0.1 Q0.0Alarm displayManual control inputStatus detecting sensorMotor 2Motor driverMotor 1Motor driverPC/PPI4accomplished well, the PLC will send ready signal to the industry control computer. Diagram 2 when the industry control computer received the signal, the system will be started to work. Fig 3 The control flow chart of the PLCIn the working process, the PLC was scaning all the inductive switch to supervise the work state of whole system. When the sort organ received the arrive signal of microcomponent, the PLC will control the sort organ to sort the microcomponent according to the sort signal, which received from industry control computer. Due to it has not only one sort; it may result in sort mistake because of breaking step of the motor. So after ejecting the microcomponent, the PLC judged whether the sort signal was accord with the complete signal .if not, the alarm will be started and the system will be hanged, the sort error will be send to industry control computer as well.B. Software fault-tolerant designIn the face of complicated industry circumstance, software fault-tolerant was the indispensability part of the system robustness. The errors were sorted into fatal error and common error after comprehensively considering all the possibility. In the software, an error-handling program was especially designed. When an error appeared, PLC program judged the sort of the error, by reading the code of the error and the state information of the system, and treated with it according to the ponderance of the error. The system alarm was designed in sound-light mode and differenced according to the ponderance of the error.In order to avoid the program was out of control, the software trop was setting in the blank memory of the PLC .The transfer instruction was also used to make the program, which was out of control, jumping to the error-handling program, and the system would set right.In the detecting process o