A block diagram is a specialized flowchart used in engineering to visualize a system at a high level. SmartDraw helps you make block diagrams easily with built-in automation and block diagram templates. As you add shapes, they will connect and remain connected even if you need to move or delete items.
Control Systems - Block Diagram Reduction
Create your block diagram to identify the most important components of your system so you can focus on rapidly pointing out potential trouble spots.
A block diagram is especially useful for visualizing the inputs and outputs of your system, while what happens inbetween can remain in a black box. You can also share files with non SmartDraw users by simply emailing them a link. Whether you're in the office or on the go, you'll enjoy the full set of features, symbols, and high-quality output you get only with SmartDraw. When you diagram is complete, share it with your team or clients, by sending them a link, or exporting it as a PDF.
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Create Block Diagrams and More:. Electric plans Schematics Circuit panels And other engineering diagrams!A control-flow diagram CFD is a diagram to describe the control flow of a business processprocess or review. Control-flow diagrams were developed in the s, and are widely used in multiple engineering disciplines.
They are one of the classic business process modeling methodologies, along with flow chartsdrakon-chartsdata flow diagramsfunctional flow block diagramGantt chartsPERT diagrams, and IDEF. Suitably annotated geometrical figures are used to represent operations, data, or equipment, and arrows are used to indicate the sequential flow from one to another. In software and systems development, control-flow diagrams can be used in control-flow analysisdata-flow analysisalgorithm analysisand simulation.
Control and data are most applicable for real time and data-driven systems. These flow analyses transform logic and data requirements text into graphic flows which are easier to analyze than the text.
PERT, state transition, and transaction diagrams are examples of control-flow diagrams. A flow diagram can be developed for the process control system for each critical activity. Process control is normally a closed cycle in which a sensor. The application determines if the sensor information is within the predetermined or calculated data parameters and constraints. The results of this comparison, which controls the critical component.
This feedback may control the component electronically or may indicate the need for a manual action. This closed-cycle process has many checks and balances to ensure that it stays safe. It may be fully computer controlled and automated, or it may be a hybrid in which only the sensor is automated and the action requires manual intervention. Further, some process control systems may use prior generations of hardware and software, while others are state of the art.
The figure presents an example of a performance-seeking control- flow diagram of the algorithm. The control law consists of estimation, modeling, and optimization processes. In the Kalman filter estimator, the inputs, outputs, and residuals were recorded. At the compact propulsion-system-modeling stage, all the estimated inlet and engine parameters were recorded. In addition to temperatures, pressures, and control positions, such estimated parameters as stall margins, thrust, and drag components were recorded.
In the optimization phase, the operating-condition constraints, optimal solution, and linear-programming health-status condition codes were recorded. Finally, the actual commands that were sent to the engine through the DEEC were recorded. From Wikipedia, the free encyclopedia.
This article is about flow diagrams in business process modeling [ clarification needed ]. For directed graphs representing the control flow of imperative computer programs, see control flow graph. Gilyard and John S.We have discussed in our previous article that for the easiness of analysis of a control systemwe use block diagram representation of the control system.Roadmaster midi s te koop
Basically we know that a complex system is difficult to analyze as various factors are associated with it. Thus it is always better to draw the block diagram of the system in the easiest possible way thereby making the analysis simple.
But as we also know that the block diagram representation of a system involves summing points, functional blocks, and take-off points connected through branches and flow of signal shown by the arrowheads. In the previous section, we have seen a simple form of a closed-loop system that has single forward and feedback blocks with the inclusion of a summing and a take-off point.
However, when we deal with control systems, then we come across various complex block diagram representation of systems that holds various functional blocks with multiple summing points and take-off points.
So, such a complex diagram must be reduced to its simple or canonical form. However, while reducing the block diagram it is to be kept in mind that the output of the system must not be altered and the feedback should not be disturbed. So, to reduce the block diagram, proper logic must be used.
Hence for the reduction of a complicated block diagram into a simple one, a certain set of rules must be applied. Here in this section, we will discuss the rules needed to be followed. So, one by one we will discuss the various rules that can be applied for simplifying a complex block diagram. When blocks are connected in series then the overall transfer function of all the blocks is the multiplication of the transfer function of each separate block in the connection.
Thus we can replace two blocks with different transfer functions into a single one having the transfer function equal to multiplication of each transfer function without altering the output. In case the blocks are connected parallely then the transfer function of the whole system will be the addition of the transfer function of each block considering sign.
So, two parallely connected blocks can be replaced by a single block with a summation of the transfer function of each block. So, even after shifting p must be X s and for this, we have to add a block with gain which is reciprocal of the gain of the originally present block.
But with backward movement p will become X s. So, we have to add another block with the same gain as the original gain. Suppose we have a combination where we have a summing point present after the block as shown below:.
We need to move this summing point behind the position of the block without changing the response. So, for this, a block with gain which is reciprocal of the actual gain is to be inserted in the configuration in series.
We can use associative property and can interchange these directly connected summing points without altering the output. A summing point having 3 inputs can be split into a configuration having 2 summing points with separated inputs without disturbing the output.
Or three summing points can be combined to form a single summing point with the consideration of each given input. We have already derived in our previous article that the gain of a closed-loop system with positive feedback is defined as:. Till now we have seen the important rules to be kept in mind while reducing the block diagram.
Let us now see an example to have a better understanding of the same. Consider a closed-loop system shown here and find the transfer function of the system:. Further, we can see 3 blocks are present that are connected parallely. Thus on reducing blocks in parallel, we will have:.
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The speed control of the induction motor can be done by the stator as well as rotor end. Ns can be varied by varying the factor on which it depends upon i.
Control Systems/Block Diagrams
Supply Voltage control method 3. Pole changing method. Earlier the speed control was tried to done with the frequency as suggested by the Ns formula but we started to face the problem of the core saturation during the low frequency. When core is saturated then the magnetic field will not increasing upon increasing current in the winding coil.
Supply which reach to our home is of fixed voltage and fixed frequency so for varying the frequency and voltage both we convert the three phase AC to DC by using rectifier circuit and then we use a controlled inverter which convert the DC voltage to the AC of desired voltage and frequency.
The voltage and frequency can be varied by inverter using the different firing angle scheme. There is only one difference between the variable frequency voltage source and the variable frequency current source is of the DC link Heavy Inductor connected between the Rectifier and Inverter.
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Subscribe to: Post Comments Atom.Vector controlalso called field-oriented control FOCis a variable-frequency drive VFD control method in which the stator currents of a three-phase AC electric motor are identified as two orthogonal components that can be visualized with a vector.
One component defines the magnetic flux of the motor, the other the torque. The control system of the drive calculates the corresponding current component references from the flux and torque references given by the drive's speed control. Typically proportional-integral PI controllers are used to keep the measured current components at their reference values.
The pulse-width modulation of the variable-frequency drive defines the transistor switching according to the stator voltage references that are the output of the PI current controllers. FOC is used to control AC synchronous and induction motors. However, it is becoming increasingly attractive for lower performance applications as well due to FOC's motor size, cost and power consumption reduction superiority.
Hasse and Siemens' F. Blaschke pioneered vector control of AC motors starting in and in the early s. Hasse in terms of proposing indirect vector control, Blaschke in terms of proposing direct vector control. Yet it was not until after the commercialization of microprocessorsthat is in the early s, that general purpose AC drives became available.
The Park transformation has long been widely used in the analysis and study of synchronous and induction machines. The transformation is by far the single most important concept needed for an understanding of how FOC works, the concept having been first conceptualized in a paper authored by Robert H. The novelty of Park's work involves his ability to transform any related machine's linear differential equation set from one with time varying coefficients to another with time invariant coefficients.
While the analysis of AC drive controls can be technically quite involved "See also" sectionsuch analysis invariably starts with modeling of the drive-motor circuit involved along the lines of accompanying signal flow graph and equations.
In vector control, an AC induction or synchronous motor is controlled under all operating conditions like a separately excited DC motor. Vector control accordingly generates a three-phase PWM motor voltage output derived from a complex voltage vector to control a complex current vector derived from motor's three-phase stator current input through projections or rotations back and forth between the three-phase speed and time dependent system and these vectors' rotating reference-frame two- coordinate time invariant system.
Such complex stator current space vector can be defined in a d,q coordinate system with orthogonal components along d direct and q quadrature axes such that field flux linkage component of current is aligned along the d axis and torque component of current is aligned along the q axis. Components of the d,q system current vector allow conventional control such as proportional and integral, or PI, controlas with a DC motor. Projections associated with the d,q coordinate system typically involve:   .
However, it is not uncommon for sources to use three-to-two, a,b,c -to- d,q and inverse projections. While d,q coordinate system rotation can arbitrarily be set to any speed, there are three preferred speeds or reference frames: . Decoupled torque and field currents can thus be derived from raw stator current inputs for control algorithm development. Whereas magnetic field and torque components in DC motors can be operated relatively simply by separately controlling the respective field and armature currents, economical control of AC motors in variable speed application has required development of microprocessor-based controls  with all AC drives now using powerful DSP digital signal processing technology.
There are two vector control methods, direct or feedback vector control DFOC and indirect or feedforward vector control IFOCIFOC being more commonly used because in closed-loop mode such drives more easily operate throughout the speed range from zero speed to high-speed field-weakening. In IFOC, flux space angle feedforward and flux magnitude signals first measure stator currents and rotor speed for then deriving flux space angle proper by summing the rotor angle corresponding to the rotor speed and the calculated reference value of slip angle corresponding to the slip frequency.
Sensorless control requires derivation of rotor speed information from measured stator voltage and currents in combination with open-loop estimators or closed-loop observers. Stator phase currents are measured, converted to complex space vector in a,b,c coordinate system. Transformed to a coordinate system rotating in rotor reference frame, rotor position is derived by integrating the speed by means of speed measurement sensor.
While PI controllers can be used to control these currents, bang-bang type current control provides better dynamic performance.When designing or analyzing a system, often it is useful to model the system graphically. Block Diagrams are a useful and simple method for analyzing a system graphically. A "block" looks on paper exactly what it means:. When two or more systems are in series, they can be combined into a single representative system, with a transfer function that is the product of the individual systems.
If we have two systems, f t and g twe can put them in series with one another so that the output of system f t is the input to system g t. Now, we can analyze them depending on whether we are using our classical or modern methods. If two or more systems are in series with one another, the total transfer function of the series is the product of all the individual system transfer functions.
But, in the frequency domain we know that convolution becomes multiplication, so we can re-write this as:. If we have two systems in series say system F and system Gwhere the output of F is the input to system G, we can write out the state-space equations for each individual system. And we can write substitute these equations together form the complete response of system H, that has input u, and output y G :. Blocks may not be placed in parallel without the use of an adder.
Blocks connected by an adder as shown above have a total transfer function of:. Since the Laplace transform is linear, we can easily transfer this to the time domain by converting the multiplication to convolution:. The state-space equations, with non-zero A, B, C, and D matrices conceptually model the following system:. In this image, the strange-looking block in the center is either an integrator or an ideal delay, and can be represented in the transfer domain as:.
Depending on the time characteristics of the system.Sendgrid logs
If we only consider continuous-time systems, we can replace the funny block in the center with an integrator:. The state space model of the above system, if ABCand D are transfer functions A sB sC s and D s of the individual subsystems, and if U s and Y s represent a single input and output, can be written as follows:.
We will explain how we got this result, and how we deal with feedforward and feedback loop structures in the next chapter.Variable Frequency Drive(VFD) Basics -- VFD V/f Control -- VFD PLC Interfacing
Some systems may have dedicated summation or multiplication devices, that automatically add or multiply the transfer functions of multiple systems together.Block diagrams consist of a single block or a combination of blocks. These are used to represent the control systems in pictorial form.
The basic elements of a block diagram are a block, the summing point and the take-off point. Let us consider the block diagram of a closed loop control system as shown in the following figure to identify these elements. The above block diagram consists of two blocks having transfer functions G s and H s. It is also having one summing point and one take-off point. Arrows indicate the direction of the flow of signals.
Let us now discuss these elements one by one. The transfer function of a component is represented by a block. Block has single input and single output. The following figure shows a block having input X soutput Y s and the transfer function G s. The summing point is represented with a circle having cross X inside it.
It has two or more inputs and single output.
Control Systems - Block Diagrams
It produces the algebraic sum of the inputs. It also performs the summation or subtraction or combination of summation and subtraction of the inputs based on the polarity of the inputs. Let us see these three operations one by one. The following figure shows the summing point with two inputs A, B and one output Y.Cladding systems pdf
Here, the inputs A and B have a positive sign. So, the summing point produces the output, Y as sum of A and B. Here, the inputs A and B are having opposite signs, i. So, the summing point produces the output Y as the difference of A and B.
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