Rule 4 − If there is difficulty with take-off point while simplifying, shift it towards right. Each input has its own appropriate plus or minus sign. A block diagram can be used simply to represent the composition and interconnection of a system. The modified block diagram is shown in the following figure. Because of their simplicity and versatility, block diagrams are often used by control engineers to describe all types of systems. Functional block – each element of the practical system represented by block with its T.F. block diagram representation of the control system, Difference Between Half Wave and Full Wave Rectifier, Difference between Half Adder and Full Adder, Difference between Centre Tapped and Bridge Rectifier, Intelligent Electronic Devices (IED) in SCADA. Obtain the Transfer function of the given block diagram, 2. BLOCK DIAGRAM SIMPLIFICATIONS Figure 5: Cascade (Series) Connections Figure 6: Parallel Connections . Step 1 − Find the transfer function of block diagram by considering one input at a time and make the remaining inputs as zero. Step 3 − Get the overall transfer function by adding all those transfer functions. Copyright © 2018-2021 BrainKart.com; All Rights Reserved. Rule 5 − If there is difficulty with summing point while simplifying, shift it towards left. No information about the physical construction, Tutorial Problems: Control Systems - Systems and their Representation, Important Short Questions, Answers: Control Systems - Systems and their Representation. Block diagram reduction technique Because of their simplicity and versatility, block diagrams are often used by control engineers to describe all types of systems. The transfer function is given inside the block. A takeoff point is used to allow a signal to be used by more than one block or summing point. Obtain the transfer function for the system shown in the fig, 3. Consider the block diagram shown in the following figure. Your email address will not be published. Block Diagram Reduction Figure 1: Single block diagram representation ... Block diagram of a closed-loop system with a feedback element . Rule 2 − Check for the blocks connected in parallel and simplify. Step 2 − Repeat step 1 for remaining inputs. This is the simplified block diagram. Now determine the transfer function of the overall closed-loop simplified system. Disadvantages of Block Diagram Representation, o   No information about the physical construction, Simple or Canonical form of closed loop system. A pictorial representation of the functions performed by each component and of the flow of signals. Procedure to solve Block Diagram Reduction Problems, Step 1: Reduce the blocks connected in series Step, 2: Reduce the blocks connected in parallel Step 3: Reduce the minor feedback loops, Step 4: Try to shift take off points towards right and Summing point towards left, Step 5: Repeat steps 1 to 4 till simple form is obtained, Step 6: Obtain the Transfer Function of Overall System, 1. Block Diagram Reduction Rules – Control System. The modified block diagram is shown in the following figure. Rule 1 − Check for the blocks connected in series and simplify. Note − The transfer function present in this single block is the transfer function of the overall block diagram. A summing point has only one output and is equal to the algebraic sum of the inputs. Although blocks are used to identify many types of mathematical operations, operations of addition and subtraction are represented by a circle, called a summing point. Because, we have to draw the (partially simplified) block diagram after each step. Step 1 − Use Rule 1 for blocks $G_1$ and $G_2$. Repeat the above-discussed steps to have a simplified system. So, to overcome this drawback, use signal flow graphs (representation). Electrical Analogies of Mechanical Systems. A block diagram of a system is a pictorial representation of the functions performed by each component and of the flow of signals. The block diagram is to represent a control system in diagram form. The block diagram reduction process takes more time for complicated systems. Step 5 − Use Rule 1 for blocks connected in series. Rule 3 − Check for the blocks connected in feedback loop and simplify. Follow these rules for simplifying (reducing) the block diagram, which is having many blocks, summing points and take-off points. Note − Follow these steps in order to calculate the transfer function of the block diagram having multiple inputs. Step 2 − Use Rule 3 for blocks $G_1G_2$ and $H_1$. The reasons might be need to draw the (partially simplified) block diagram after each step. To overcome this you need use signal flow graphs (representation). Obtain the transfer function C/R for the block diagram shown in the fig, The take-off point is shifted after the block G2. Now reduce the internally connected minor feedback loops. Branches – lines showing the connection between the blocks, Arrow – associated with each branch to indicate the direction of flow of signal, Summing point – comparing the different signals, Take off point – point from which signal is taken for feed back, Advantages of Block Diagram Representation, o   Very simple to construct block diagram for a complicated system, o   Function of individual element can be visualized, o   Individual & Overall performance can be studied.