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Industrial Automation and Control Interview Questions

What is derating factor?

The factor by which the ratings of component parts are reduced to provide additional safety margins in critical applications or when the parts are subjected to extreme environmental conditions for which their normal ratings do not apply.

What do mean by interconnection system?

The electrical and mechanical interconnection of any one or all of the six levels of interconnections generally common to electronic equipment. The six levels of interconnections are: intramodule, module to motherboard, intramotherboard, motherboard to back panel, backpanel wiring and input/output.

What is manual control in industrial automation?

Control in which a direct or indirect human manipulation of the final controlling element is carried out. In the process industry, this is generally done via a standardized signal. Can also be defined as direction of a computer by means of manually operated switches.

What is automatic control system?

A control system which operates without human intervention. It is subdivided into a controlling system and controlled system.

What do you mean by automatic zero-and full-scale calibration?

Zero and sensitivity stabilization by servos for comparison of demodulated zero-and full-scale signals with zero and full-scale references.

What are pneumatic system?

A system which makes use of air for operating control valves and actuators (cylinders,motors).

What is a natural function generator?

An analog device or a specific program based on some physical law, such as one used with a digital computer to solve a particular differential equation.

What is negative acknowledgement, NAK?

In binary synchronous communications, a line control character sent by a receiving terminal to indicate that an error was encountered in the previous block and that the receiving terminal is ready to accept another transmission of the erroneous block.

What do you mean by the term ripple?

Periodic deviations around an average measured or supplied value, occuring at frequencies which may be related to that of the mains supply or of some other definite source, such as chopper. Ripple is determined under specified conditions.

What is rise time?

For a step response, the time interval between the instant when the output signal, starting from zero, reaches a small specified percentage (for instance 10%) of the final steady-state value, and the instant when it reaches for the first time a specified large percentage (for instance 90%) of the same steady-state value.

What is a thyristor converter ?

An operative unit comprising one or more thyristor sections together with converter transformers, essential switching devices, and other auxiliaries, if any of these items exist. System control equipments are optionally included.

What is time constant ?

The time constant T is the time required to complete 63.2% of the total rise or decay of the output of a first-order linear system, initiated by a step or an impulse to the input.

What does the term asynchronous means?

A mode of operation in which an operation is started by a signal before the operation on which this operation depends is completed. When referring to hardware devices, it is the method in which each character is sent with its own synchronizing information. The hardware operations are scheduled by “ready” and “done” signals rather than by time intervals. This implies that a second operation can begin before the first operation is completed.

What is time division multiple access?

TDMA An advanced networking method used to communicate over satellites. It is a digital transmission technique. All signals are converted to digital bit streams. These bits are combined into a single stream for transmission, then separated at the receive station into separate bit streams and decoded to obtain the original message signals.

What is ATE (automatic test equipment)?

control software Software used during execution of a test program which controls the no testing operations of the ATE. This software is used to execute a test procedure but does not contain any of the stimuli or measurement parameters used in the testing of the Unit Under Test (UUT). Where test software and control software are combined in one inseparable program, that program will be treated as test software not control software.

DCS is a distributed control system?

The term Distributed Control System generally referred to as DCS. It is a process control and process monitoring via a link of communication network consisting of multi-level computer systems (servers and clients), communication technologies like Field Bus, 4C technology (CRT)  for trend monitoring and the most important process control (via PID and different controllers), the The basic idea is to decentralized the control and centralized operation and management at different levels, flexible and convenient configurations are integral parts of DCS.

What is the the concept of statistical process control?

Statistical process control (SPC) is the application of statistical techniques to evaluate and monitor the various stages of the process and to establish and maintain the process at acceptable and stable level to ensure that products and services meet the requirements of a Quality Control . It is part of the process control from the content is mainly two aspects: First, the use of the stability of the control chart analysis and process calculations capability index to analyze the stability of the process to check the ability of system to meet the technical requirements and quality of the process is evaluated.

What are control Charts?

They are used to monitor the state of the process, measurements, diagnosis and for improvement of the current and future state of the process.

Statistical Process Control commonly use these nine control chart types:

The histogram : That is based on the interval column chart based on performance characteristics of the frequency distribution charts, visually shows the distribution of the data.

Pareto chart : That is also known as the Pareto diagram, it is a tool to display the impact of the various projects to be marked from most crucial to nominal orders. Distinguish between primary, secondary impact on product quality, the general problem, and to identify the main factors affecting the quality of products, identify opportunities for improvement of the quality.

Scatter plot : These are the variables which reflect the distribution of points that are used to discover and display the type and extent of the relationship between the two sets of data, or to confirm the expected relationship via diagram tool.

Process Capability Index : That graph shows the analysis of process capability to meet quality standards, the degree of process specifications.

Frequency analysis : That forms a concept table showing the distribution variables measured at different levels.

Descriptive statistics analysis : That states to the average, maximum, minimum, range, variance, to understand some general characteristics of the process.

Close correlation analysis :That is the relationship between the study variables, and the assumed variables randomly changed and in misplaced priorities.

Regression analysis : That is the most important one it shows the relationship between different analysis variables.

What do you mean by term Expert Systems?

Expert system is an intelligent computer software system whose interior contains a large number of a certain level of experts in the field of knowledge and experience and ability to utilize human expert knowledge and problem-solving methods to deal with the problems of practical field. That is we can say the expert system is a system program which has a lot of expertise and experience that’s why it is called expert system and it is the special application of artificial intelligence technology and computer technology, according to one or more experts in a certain knowledge of field and experience, reasoning and judgment and ability to simulate a human expert software program for decision making process, in order to resolve problems of field it may also require human experts to deal with the complex issues. In short expert system is a simulation of human experts to solve field problems.

What are the different types of Expert Systems?

According to the knowledge based partitioning this technology can be divided into these types:

  1. Logic-based expert systems
  2. Rule-based expert system
  3. Expert system based on semantic networks
  4. Frame-based expert system.

While partitioning according to tasks performed are:

Interpreted Expert Systems: That performs analysis of symbolic data also it can be used to elaborate the practical significance of these data.

The predicted type Expert Systems: That performs analysis on object’s past and present behavior to infer the objects of the future from evolution of the analysis results.

Diagnostic Expert System: It performs analysis according to the input information to find the faults and defects of the under observation object.

Debug type Expert System: It given the failure to process itself for exclusion of program.

Maintenance-type Expert System: That analysis specify and implement the plan to correct certain types of fault.

Planning type Expert System: That tool plan the action drawn up according to a given target.

Design Expert System: In accordance with the given requirements that type form the desired scheme and pattern.

The Guardianship type Expert System: That is a complete real-time monitoring of all tasks.

Control type Expert System: That is responsible for completing the implementation of the control tasks.

Education type Expert System: That is a combination of diagnostic and debugging type Expert System which is used for teaching and training.

What are Three types of expert system development tools?Skeleton Type Expert System:

It is the basis for the successful expert system application, removing the specific content of knowledge retention and the shell reasoning of knowledge representation and a special tool to enhance knowledge acquisition subsystem functionality.

Universal Type Expert System: That is a knowledge representation via language, such tools provide a more generic configuration and this type of language corresponds to the reasoning facts. The user can enter production in the form of knowledge and facts, such as OPS-5 production system-oriented language which is equipped with a forward reasoning for process which rely on internal reasoning mechanism for the solution to the problem.

Toolbox type Expert System: That type is in middle of general and special development tools. It provides the framework for the several expert systems components (such as reasoning frame, blackboard framework, etc.), and each frame is composed of several modules. Description added according to the needs of designers and system automatically generate the expert system for process with certain areas targeted. Example of such development tools are AGE, ZDEST-1

What is Artificial Intelligence?

Artificial Intelligence (AI) language is adapted for the field of artificial intelligence and knowledge engineering, symbolic processing and logical reasoning ability combined in  computer program. That computer program can be used to solve numerical/non-numerical calculation, intelligent knowledge processing, reasoning, planning, decision-making, such as a variety of complex issues. The typical AI language are LISP, Prolog, Smalltalk, C + +, etc.

What are the basic components of Artificial Intelligence?

The basic components are:

Knowledge representation technology

Knowledge, reasoning techniques

Fuzzy logic

Neural network technology

Genetic algorithms

Expert systems

Machine learning

Swarm intelligence

What is model reference control?

The basic idea of adaptive control lies in control system design, a constantly measurements of the states of the controlled object, performance and parameters, thus finds out the master of the current health of the system which can have positive effects on system state. Analyze the current state of system performance indicators and expectation indicators so as to make decisions based on the comparison results and to change the structure and parameters of the controller and to change state variables according to the laws of the adaptive control action to ensure that the system is running in optimal state.

Generally speaking, the adaptive control system is coupled with feedback control systems with basic control loop and adaptive mechanism is also constituted. It has three functions:

(1) Real time identification.
(2) The decision-making control.
(3) Real Time correction

What is a PLC?

PLC (Programmable Logic Controller ) is a control device which uses memory that can be programmed for its permanently stored program, that is used for the implementation of logical, sequential control, timing, counting and arithmetic operations such as user-oriented instruction and digital or analog input / output control of various types of machinery or production processes.

What is the working principle of PLC?

When programmable logic controller is put into operation, the course of their work are generally divided into three :

1.Input sample stage
2.User program execution stage
3.Output refresh stage

What is the input stage execution of PLC?

In the input sampling stage, the programmable logic controller sequentially scan/reads the status of all inputs and data and they are stored in the corresponding cell in the I/O memory area.

What is user program execution stage?

Programmable logic controllers are always followed by a top-down order to scan the user program (ladder/FBD). Scanning each ladder by the contact form on the left of the control line and process the first left and right line and execution continued the first after the other and according to the result of logic operation it refresh the status of the corresponding logic bit of the coil in the system RAM storage area.

What is the output refresh stage of PLC?

After the end of the scan and execution of user program, programmable logic controllers starts the output refresh stage. During this period, the CPU status and data in accordance with the I/O from memory area refresh all of the output latch circuit.

At present, what are the three levels of industrial automation ?

1.Classical control theory

2.Modern control theory

3.Intelligent control theory

Give some example of intelligent control?

Typical examples of intelligent control the fuzzy logic that is considered as the automatic control systems it uses artificial intelligent and neural networks comparatively for automatic control.

Give some examples of automatic control systems?

Basically automatic control system can be divided into two types

1.open-loop control system
2.closed-loop control system

What are the integral components of control systems?

A control system includes a controller (PID, PI, P), sensors, transmitters, actuators, input and output interfaces. The output of the controller output sends signals to actuator which controls the required dynamics of system according to set points.

Do we use the same sensors on every control system theory?

No, different control systems requires different sensors, transmitters, actuators. For example, in a pressure control system we use pressure sensor for calculation of pressure. Electric heating control system uses temperature sensor.

What is the smart regulator function (intelligent regulator) of PID controller?

Major companies that are developing PID controllers have the feature of self-tuning of parameters this technology is called the smart regulator function or intelligent regulator. This type of PID controller adjust parameters automatically through intelligent adjustment or self-tuning adaptive algorithm to achieve optimized system dynamics.

How PID(Proportional Integral Differential controller) is linked with PLC(Programmable Logic Controller) and DCS(Distributed Control System)?

PID controller generates gain for actuator for the optimized values of pressure, temperature, flow, levels etc by its comprehensive Proportional gain, integral time and deferential time which are converted to electric signal and sent to PLC for communication of PLC, PID, Actuator, DCS(Distributed Control System) operator who just set the set points of system dynamics.

What is an open-loop control system?

Open-loop control system can be referred as the output of system has no effect on the output of the controller. In this type of control system controller gain is usually very high.

What is the closed-loop control system?

Closed-loop control systems a type of system in which output of system is sent (feed) back to controller to affect the output of the controller.

What do you mean by positive and negative feedback system?

If output of system is added to controller then we can say it is a positive feedback, if output of system is subtracted from controller then it is called negative feedback system.

Give some example of negative feedback system?

We can say a person is a closed-loop control system with negative feedback, the eye is the sensor which sends signals to the brain and brain acts as controller, what we see is sent to brain as negative feedback, the human brain system performs constant correction to finally make the correct action. If no eyes (Sensor) there will be no feedback loop, system at this stage could be assumed as an open-loop control system. Another interesting example is the automatic washing machine which continuously check the clothes are washed or not (via a sensor output) when it sees clothes are washed properly it cut off power automatically that example is also a closed-loop control system.

What is the step response of a system?

Step response is the output of system when step input (step function) is applied to the system, .

What do you mean by steady-state error (Offset error)?

The steady-state error refers as in steady state response of the system, the difference between the desired output (Set point) and the actual output (Process Value).

Define Stability of system?

A bounded input to the system generates the bounded output is referred to as stable system, that deals with the system poles, if all poles of the system lies at negative half plane then it is BIBO(Bounded Input Bounded Output System), however if some (Not all) poles of system lies at axis of plane system can be considered as marginally stable.

What is cascade amplifier?

A multiple-stage amplifier in which the output of each stage is connected to the input of the next stage.

What do you mean by cascade control?

Control in which the output variable of a controller is the reference variable of another controller(s).

What is command in Control Systems?

Command is an operative order which initiates a movement or a function. The order may be:1. direct input to the machine in coded form;

  1. results from a logical interaction of instructions from an outside source with conditions sensed
    by the machine;
  2. outputs derived from the computing or comparing function.

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