Due to the rapid advances in technology, all industrial processing systems, factories, machinery, test facilities, etc. turned from mechanization to automation. A mechanization system needs human intervention to operate the manual operated machinery. As new and efficient control technologies evolved, computerized automation control is being driven by the need for high accuracy, quality, precision and performance of industrial processes.
Automation is step beyond the mechanization which makes use of high control capability devices for an efficient manufacturing or production processes.
What is Industrial Automation?The word ‘Automation’ is derived from ancient Greek words of Auto (means self) Matos (means moving). Thus, a mechanism move by itself or self dictated is called automation. As compared with manual systems, automation systems provides superior performance in terms of precision, power and speed of operation. Industrial automation is the use of control devices such as PC/PLCs/PACs etc. to control industrial processes and machinery by replacing as much as possible labour intervention and dangerous assembly operations with automated ones.
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In industrial control a wide number of process variables such as temperature, flow, pressure, distance, and liquid levels can be sensed simultaneously. All these variables are acquired, processed and controlled by complex microprocessor systems or PC based data processing controllers. Control systems are the essential parts of an automation system. The various types of closed loop control techniques ensure the process variables to follow the set points. In addition to this basic function, automation system employs different other functions such as computing set points for control systems, plant start up or shutdown, monitoring system performance, equipment scheduling, etc. The control systems along with monitoring adapted to the operating environment in an industry for flexible, efficient and reliable production system.
The automated system needs special dedicated hardware and software products for implementing control and monitoring systems. In recent years, the number of such products have been developed from various vendors which providing their specializing software and hardware products. Some of these vendors are Siemens, ABB, AB, National Instruments, Omron and so on.
Reasons for AutomatingAs we are living in the highly competitive business environment, the industry or in other words manufacturers is challenged by the factors like withstand to harsh manufacturing environments, meeting latest energy efficient standards and to offer a robust level of security, etc. Some the following are the reasons used to justify the automation.
To Increase the Labor ProductivityAutomation increases the production rate by producing greater output for a given labor input. It is not possible for human workers to work for long hours without losing accuracy. In other hand, without compromising on accuracy, automated control systems able to work for long hours. Hence increased productivity and efficiency per hour of labor input.
To improve the Product QualityOne of the chief benefits of the automation is that the reduction of fraction defect rate. With the manual operation of manufacturing process, there may be a compromise on quality specifications of the product. But the automation system performs operations with greater conformity and uniformity to the quality specifications. By using the automation systems, industrial processes are controlled and monitored at all stages in order to produce a qualitative end product.
To Reduce the Labor or Production CostThe automated systems help the industries to save a great deal in the long term by substituting automated machinery in place of human labor so that unit production cost is reduced. Automation equipment running smoothly or uniformly 24 × 7 not only increases the productivity, but also consequently results excellent return on investment by saving salaries, workforce costs, pensions and costs with employees. The automated system also reduces the labor shortage by substituting automated operations in place of labor.
To Reduce Routine Manual TasksIn many industrial applications, process variables like temperature, liquid level, pressure, etc. are to be periodically monitored as a routine task to maintain their set levels. Thus an automation system creates the automatic working condition by employing closed loop control systems.
To Improve SafetyBy implementing automated system, work is made safer by transferring the worker from an active participation location in the process to the supervising role. The automated machines are able to work in the hazardous environments and other extreme environments. Also, these systems make use of industrial robots in place of human workers, especially in life-threatening conditions (chemical and high temperature conditions). Thus an industrial automation system prevents the accidents and injuries to the workers.
To Assist Remote MonitoringMost of the industrial operations have to be controlled remotely for convenient and long distance monitor and control of process variables. For such cases, automated systems provide a communication link between the process area and supervising (monitor and control) area, thereby allowing operators to control and monitor the industrial processes from a remote location. The best example of this remote control is the automated electric power grid control.
Functional Elements of Industrial AutomationAn industrial automation (IA) is an integrated, flexible and low-cost system platform that consists of various elements which performs a wide variety of functions like sensing, control, supervision and monitoring related to industrial processes. The figure below shows the structure of industrial automation which describes the various functional elements of IA.
Sensing and Actuating ElementsThe sensors or sensing elements convert the physical process variables such as flow, pressure, temperature, etc. into electrical or pneumatic form. Various sensors include thermocouples, RTDs, strain gauges, etc. The signals from these sensors are used for processing, analysing, and decisions in order to produce the control output. The various control techniques are implemented to produce the required output by comparing current sensed process variable with set values. Finally the controllers produce the computed outputs and are applied as electrical or pneumatic signal inputs to the actuating elements. Actuators convert the electrical or pneumatic signals to the physical process variables. Some of the actuators include control valves, relays, motors, etc. A special category of the instruments is smart instruments which are integrated systems of sensing or actuating elements with the capability of communicating with field buses. These smart devices consist of signal conditioning circuit internally and facilitates to connecting directly to the communication link in the industrial bus system.
Control System ElementsThese are the microprocessor based electronic controllers or simply industrial computers that accept the signals from various sensors as well as command signals from supervisory systems or from human operators. These controllers can be continuous control systems or sequential/logic control depends on the structure of control nature. The controller processes the sensing values and supervisory values and depends on the control structure, it produce the control output to various actuating devices. A modern type of control device used in automation systems is the Programmable Logic Controller (PLC). PLCs are come with dedicated software so that these are capable of being programmed to perform corresponding control operations. PLCs have rugged CPU, digital I/O, analog I/O and communication modules such that they can operate at industry environment conditions to control the various process parameters. Human Machine Interface or operator interface is a graphical interface for the operators which displays the process information such as process variable status, logging results to the database, generating alarm signals, etc. SCADA is one of the graphical user interface which remotely controls the industrial operations. Also, Distributed control systems (DCS) provide their own HMI for the graphical display of various industrial parameters.
Supervisory Control ElementsSupervisory control performs higher level control over the automatic controllers which further controls the smaller subsystems. The major elements of this level are process station PCs and Human Machine Interfaces. These process station PCs are responsible for functions like set point computations, performance monitoring, diagnostics, startup, shutdown and other emergency operations. Human Machine Interface or operator interface is a graphical interface for the operators which displays the process information such as process variable status, logging results to the database, generating alarm signals, etc. SCADA is one of the graphical user interface which remotely controls the industrial operations. Also, Distributed control systems (DCS) provide their own HMI for the graphical display of various industrial parameters.
Types of Industrial Automation SystemsIndustrial automation is the use of computer and machinery aided systems to operate the various industrial operations in well controlled manner. Depends on the operations involved, the industrial automation systems are majorly classified into two types, namely process plant automation and manufacturing automation.
Process Plant AutomationIn process industries, the product results from many chemical processes based on some raw materials. Some of the industries are pharamaceutical, petrochemical, cement industry, paper industry, etc. Thus the overall process plant is automated to produce the high quality, more productive, high reliable control of the physical process variables. The above figure shows the process automation system hierarchy. It consists of various layers representing widespread of components in a process plant. Level 0 or Plant: This level consists of machines which are closest to processes. In this, sensors and actuators are used to translate the signals from the machines and physical variables for the purpose of analysis and to produce the control signals. Direct Process Control: In this level, automatic controllers and monitoring systems acquire the process information from sensors and correspondingly drives the actuator systems. Some of the tasks of this level are-
- Data acquisation
- Plant monitoring
- Dara checking
- Open and closed loop control
- Plant monitoring performance
- Optimal process control
- Plant coordination
- Failure detection, etc.
- Production dispatch
- Inventory control
- Production supervision, production reporting, etc.
- Market and Customer analysis
- Orders and sale statistics
- Production planning
- Capacity and order balance, etc.