Supervisory Control of A Bytronics Conveyor System - Research Proposal Example

The blueprint and accomplishment of a flexible manufacturing structure (FMS) ran podium centered on a programmable logic controller (PLC)as well as a desk top based illustration man- mechanism interface (MMI) as well as statistical acquisition component. The fundamental facet of a flexible manufacturing structure (FMS) is about its plasticity to acclimatize to variations in a demanding procedure maneuver. The coded reason regulator offers practicable solutions for FMS functions, utilize PC-centered MMI/DAS thereby PLCs are optimized to implement quick chronological direct stratagem. Computers that function on the MMI/DAS front ends construct intuitive operation interfaces, full commanding graphics as well as coverage apparatus. In succession from the PC could be spread out through a company's local area network or web functioning client-server expertise. Presently, with the convergence of underlying microprocessor expertise as well as software programming techniques, myriad users find that PLCs offers an economic resolve to real time regulation in diminutive- to medium sized process plants principally when integrated with regulatory PCs employing hybrid structures. The main work of this article illustrates that programmable logic circuits are responsive to quick and repetitious organized errands, that runs on PCs that present the flow of information automation and accept operator instructions, hereby offering the client a contrivance to enhance and observe the progression as the necessities vary. Large, modern and busy industries with state-of-the-art processing facilities require increased mechanization and improved technical facilities to increase efficiency, quality and volume productivity. An important system in these industries is the supervisory control of a bytronics conveyor system which provides the necessary control, analysis and monitoring of the industrial processes to provide reliable communication for safe and efficient operation. This paper therefore seeks to design and produce a model Bytronics Conveyor System that can be used to detect objects like baskets and control the conveyor system and research and recommend on sensors for use in a real conveyor system. Introduction In a multiplicity of artifact producing industries, flexible production structures have always been the automated form of production; this was incorporated in the 70s. The numbers of stretch manufacturing structures have evolved tremendously owing to the fact that they offer a high prospective for productivity augmentation in batch development. The speeding up right through the world is due to enhanced universal struggle, minimized fabrication sequence chapters, and diminution in fabrication expenses. Collectively, stretch production structures encompass a cluster or various automated workstations, which form into modular subsystems, such as CNC machines, robots, vision systems, as well as procedures station. These are integrated by elements handling structures and normally propelled by a computer. Every modular structure requires an independent modular regulatory structure, which has divergent components that are synchronized by computers as accustomed. The dogmatic carry out their respective functions under regulation of a superior echelon regulator. The regulatory apparatus and the flow of information in the structure need to be computerized. The central facet of an FMS is the aptitude to acclimatize to alterations in the control errands. The elasticity consists of the quantities and several of part types that can produce the order by which operations could be worked out, and its capacity to redirect parts back into stream conduits. In conclusion, the regulatory platform ought to have the audacity to mechanize the flow of in sequence. In many industries today, there is increased material processing volumes and longer distances to be covered between points of dispatch and storage and this call for a better and more reliable communications with high operating safety. We therefore need conveyor systems which can operate at different speeds based on the size of objects being transported on the belt system and must have controls systems which pass reliability, safety, and flexibility tests at all the times. To achieve good utility status, such a system employs the fiber optic technology whose cables and connectors are unaffected by noise, lightning and RF, EMI, EMF interferences. HMI and SCADA systems control the belt drives by varying the tension and belt speed for loading of different materials. Operator can set the desired belt speed for different conditions by using fiber optics to ensure safe operation. MAIN OJECTIVE To Design and Build a Control System using a PLC and SCADA System to control a model Bytronics Conveyor System ABSTRACT INTRODUCTION 1. PLC (Programmable Logic Controller) A programmable logic controller (PLC) is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, control of amusement rides, or control of lighting fixtures. PLCs are used in many different industries and machines such as packaging and semiconductor machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result. Characteristics PLC unit consists of separate elements namely; power supply, controller and relay units for in- and output. PLCs are made to withstand severe conditions such as dust, moisture, heat, cold, etc and have the facility for extensive input/output arrangements. The Input/output facilities connect the PLC to sensors and actuators. PLCs read variables such as temperature and pressure, limit switches and complex positioning systems. When it comes to an actuator, PLCs operate electric motors, hydraulic cylinders, magnetic relays, solenoids, or analog outputs. PLC System scale A model PLC such as the one we shall use for this particular design has a fixed number of built in inputs and outputs connections. Expansions can be done if the base model does not have enough I/O. Modular PLCs have a chassis also known as a rack where modules with different functions are placed. We shall customize the processor and selection of I/O modules depending on our need. Once installed, a single processor can run several racks with many inputs and outputs. process How to Use a PLC in Designing a Bytronics Conveyor System In a model Bytronics Conveyor System, PLCs are used to configure, alarm reporting and routine controls. We shall use a Human-Machine Interface (HMI) also known as MMIs (Man Machine Interface) or GUI (Graphical User Interface) for this purpose. A simple system like the one we intend to design will use buttons and lights to interact with the user. Otherwise, we also have the option of using a programming and monitoring software installed on the system, with the PLC connected through a communication interface. How PLCs Communicate We are going to use PLCs with built in communications ports preferably a 9-Pin RS232 and we shall include a DF1 or Modbus as our communication protocol. If not very efficient, then we shall resort to use a fieldbus such as Profibus. With the use of these facilities, our PLCs will be able to communicate with another system of SCADA (Supervisory Control and Data Acquisition). We may also choose a more enhanced peer-to-peer (P2P) communication between processors as this has the ability to allow separate parts of any process individual control while subsystems coordinates the communication link. Such system will achieve good network speed but may be technically advance for our model Bytronics Conveyor System. ASSEMBLY OF A BYTRONICS CONVEYOR MACHINE This is a system which sorts out two components that is a metal body with a peg and a plastic ring. This ring is assembled on to the peg and the finished design is inspected and parts which are not assembled are rejected. In our case, we want to produce a PLC programme that will sort out our two components. Procedure The conveyor machine will be fitted with a start and stop switch as well as an emergency stop that will not be connected to the PLC and is not included in the programme. The machine is going to have two conveyor belts namely Chain Conveyor on which the two components are going to be placed in any order and the belt conveyor that will transport the baskets to the inspection point. Here are the five procedures that will be carried out to ensure the system works. The requirement here is that each programme should be devised and tested separately before combining them into one single programme. Requirements 1. A flow chart style programme for each section 2. A truth table for each section 3. A logic functional block diagram for each section 4. A complete Ladder programme 5. A name facility on the PLC to allocate tags labels to the input/output. 6. A hard copy of a complete programme which will include the ladder and a statement version plus the labels and comments. Programme 1: SART AND STOP Devising a simple routine to start the two conveyors when the start switch is pressed and stop when the stop switch is pressed. The start switch which is green in colour is an open push button and is marked X406. The stop switch which is red in colour is closed push button switch marked X407. The chain conveyor shall be driven by a motor connected to the output marked Y434. PROGRAMME 2: SORTING STATION Here is where a routine to detect whether or not the component is a metal peg or a plastic ring. This will operate as follows;-If it is a plastic peg, it has to be knocked down the chute into the magazine plastic peg, it has to be knocked down the chute into the magazine Y the operation of a linear solenoid and on the other hand, if it is a metal peg, it is allowed to pass on and fall down the end chute onto the belt conveyor. X400 is an inductive proximity switch that comes on when a metal peg is close to it. X401 is a focused infra-red detector that comes on when a surface at the focal point reflects light. This comes on when either a plastic ring or metal peg is passing. Y431 is for ejection mechanism. PROGRAMME 3: ASSEMBLY STATION The plastic rings were timed up in the magazine and were prevented from falling into the assembly station by a rotary solenoid. Here is how it works: When the assembly point is empty, the solenoid operates to allow one ring to enter and close before the next falls on top of it. The rings are automatically dropped onto the metal peg as it passes and carry along with it on the belt conveyor. X402 is a focused infra-red sensor that is used to detect if the ring is in the assembly point. Y 432 is the rotary solenoid that must operate in order to allow one into the assembly point. Y432 PROGRAMME 4: INSPECTION STATION This programme will ensure that when components leave the assembly station, they pass an inspection station where it is determined whether the components are assembled or just single components. X403 will be used as a capacity proximity detector at the height of the assembled ring and it shall only be activated if the ring is present. X410 shall be an inductive proximity detector and will be operated only when a metal peg is present. However, this programme does not switch anything on physically but it sets kind of an internal flag to tell the eject station to eject when the component passes it. There shall be another sensor X404 that detects any thing passing out of the assembly point. PROGRAMME 5: REJECTION STATION In this programme the component travels on along the conveyor to the rejection point and here, sensor X405 which is an infra-red detector detects the component when it is at the rejection point. In case the component is to be rejected that is if it is a ring or a peg on its own, then linear solenoid Y433 is operated and it knocks it off. If the component is assembled correctly then it passes to the end and falls into a bin. USING SCADA FOR CONTROLING BYTRNICS CONVEYOR SYSTEM SCADA stands for Supervisory Control And Data Acquisition and the SCADA System refers to a control system that monitors and controls a process such as detection of baskets in an industrial process. Such control actions are done automatically by remote terminal units (RTUs) or by Programmable Logic Controllers (PLCs). In our case we shall use PLCs as a means of controlling our system. Whereas host control procedures are chiefly restricted to basic supervisory level intervention, SCADA System can allow change of process and record desired results. Therefore it refers to a system that coordinates, but does not control processes. In a SCADA System, there exist subsystems as bellow: HMI (Human-Machine Interface) which relays processed data to the operator monitoring and controlling the process. A data gathering system which sends commands for execution. Remote Terminal Units which converts sensor signals to digital data and sends it to the supervisory system. Field devises in this case we shall use the PLCs(Programmable Logic Controller) A communication system which is going to connect the supervisory system and the RTU. GETTING DATA FOR A SCADA SYSTEM Getting data for a SCADA system begins at the PLC level which include meter readings and status report for the particular equipment. Data obtained shall then be compiled and formatted for ease of use by the operator who can change controls depending on available information. The SCADA System shall implement a tag database where a point represents a single input or output value controlled by the system. Such points are either soft or hard and where soft means outcome of logic and math operation while hard stands for the actual input or output in the system. It is with the tags that we shall store the additional metadata such as the path to the PLC used, provide time comments and provide alarm information. We shall link an HMI to the SCADA system's database and software programmes to give management information when maintenance is to be done, programmed schematics for a given sensor and troubleshooting guides. Supervisory Station for SCADA System This will include the software for communicating with the PLCs. How SCADA Operates Hardware for a SCADA system is ruggedized to withstand temperature, vibration, and voltage extremes, but in most critical installations reliability is enhanced by having redundant hardware and communications channels, up to the point of having multiple fully equipped control centres. A failing part can be quickly identified and its functionality automatically taken over by backup hardware. A failed part can often be replaced without interrupting the process. The reliability of such systems can be calculated statistically and is stated as the mean time to failure, which is a variant of mean time between failures. Conveyor System with a PLC and SCADA SENSORS FOR A REAL CONVEYOR SYSTEM RESEARCH AND RECOMMENDATIONS SELECTION OF SENSORS REASONING Range Sensing Technology is used to monitor, regulate and control automated processing in industries. They help to verify if a process is completed as intended. A sensor can be defined as a device for detecting and signaling a change of condition i.e. the presence or absence of a material or object or quantities such as distance, color or size. We have discrete and analogue sensing respectively where in discrete sensing, the sensor sends on and off signal depending on the presence or absence of the target while an analogue sensor detects position and quantity or proportion. Sensor Technologies We have two sensor technologies namely contact and noncontact sensors where the earlier detects change through direct physical contact with the target object while the later detects change by creating energy field and react to a disturbance in the field. Contact sensors are usually easier to understand and diagnose. Non-contact sensors do not require physical contact and hence experience less ware, are faster and flexible in its applications. Examples of contact sensors are encoders, limit switches and safety switches while noncontact sensors are capacitive, ultrasonic, photoelectric and inductive. In the model conveyor belt we use contact sensor to cunt each basket as it enters the reception zone to determine their sizes and the number going through the belt. When the buckets leave the contact zone, a noncontact sensor will determine the number that has been rejected. Such a change to noncontact is done to ensure no disturbance is made to the objects. Sensing Characteristics a) Sensing Distance; when choosing a sensor, nominal and effective sensing distances must be evaluated to determine its suitability. b) Switching Frequency; number of switching operations per second which can be achieved under set standard conditions i.e. the relative speed of the sensor. c) Hysteresis; Is the difference between switch on and switch off points when a target is moved away from the sensor face, and is usually expressed as a percentage of the sensing distance. d) Response Time; is the total amount of time which elapses between the detection of a target and change of state of the output device i.e. switching ON to OFF or OFF to ON, on when the target is no longer detectable by the sensor. It is a function of target size and speed of passing the sensor. e) Repeatability; is the ability of a sensor to detect the same object at the same distance all the times and is a factor of constant voltage and temperature supply. STANDARDS Factors vital for safe installations are; Environmental Conditions; Restrictions may deter detection function in a particular area but may be reliably performed while the work piece is in transit. System Design Installation Equipment Selection and application Operating practices Maintenance The underlying factor here is that sensors and switches must be installed as per specific national and international codes. It is not just done from without. Installation in the European countries follow CENELEC specifications, those done in America follow the NEMA standards while international standards follow IEC Scale. Sensor Selection A sensor being a devise used to detect the changing conditions of an action or event, can only be of good use and value if it detects operations or processes and more specifically smaller events. We have t be sure where sensors are required by identifying key operations within the system an define focus areas where conditions are to be verified. The functions of a Bytronics Conveyor System a) Sort Products(Baskets by size) b) Perform quality check where if the shorter basket is on the conveyor, it is rejected by pulsing the eject solenoid. c) Count products in our case Baskets to determine if their number is two. Areas of Focus in a Bytronics Conveyor System These are areas where action is taking place and in this research, with focus to sensors used to verify sizes and machine current, we have to verify components which must be present and the mechanisms for the components to work amicably. Location of sensor depends on the sensing functions that should be achieved and how best to achieve it and it is done in accordance to specific physical limitations. Definitions of the Application The sensors are to be used to verify sizes and measure machine current. Available Source of Power For a model Bytronics Conveyor system, we shall use a DC source while for a real conveyor System of approximately 1000 mm width; an AC source will be used. Therefore for a DC Source, DC Sensors shall be applicable while for an AC Source AC Sensors and switches shall be used. A model conveyor System uses a Voltage of 30 V or less and DC is considered safer than AC for such use. OUTPUT TIMING AND LOGIC Photoelectric Sensors as a special sensor with enhanced capabilities is able to offer integral timing or logic functions and are available either as built-in or as plug-in cards. ON and OFF Delay Timing Modules An ON Delay Timer will delay the operation of an output after a target is detected while an OFF delay Times will delay the operation of an output after the target is no longer detected. The delay time of sensor is adjustable. The OFF Timer (Pulse Stretcher) is necessary to slow down response time to allow a relatively slower PLC to respond to the movement of the baskets or any objects. One Short Logic Provides a single pulse out regardless of speed of target, on passing the sensor and the length of pulse is adjustable. In a relatively high speed operation like a conveyor system of delay time of 300 seconds, it provides a pulse that is enough to allow other logic like PLC to respond each time an object passes a sensor. Delayed One Short Logic Adds an adjustable time delay before the one-short output pulse occurs. Motion Detector Logic This provides the capability to detect the continuous movement of targets. The sensor sends an output if it does not detect the motion of successive targets within the adjustable delay time. This sensor will help in the system when a basket of any size is not detected for more than 30 seconds of the delay time; it will provide an out put signal that the conveyor should stop automatically. Use of sensors to Measure Machine current Discrete signals behave as binary switches producing an ON of OFF signal denoted by 1 or 0 respectively. As a device providing discrete signal, photoelectric sensors use either voltage or current where a specific range is designated as ON and another as OFF. An example of how the current -voltage ON and OFF sensors are designed in a PLC is when a 30 V DC I/O, with values above 28 V DC representing ON while values below 4 V DC representing OFF and intermediate values undefined. Because originally, PLCs had only discrete I/O, and again because current inputs are less sensitive to electrical noise than voltage inputs, these sensors measure machine current more accurately. References: Huntington S.S (2006) Supervisory control Conveyor system; Harvard University Press, Read More