Control Engineering

2. BLOCK DIAGRAM
PRESENTED BY:
17ME02 17ME03 17ME04
SUBMITTED TO: DR. DUR MUHAMMAD PATHAN

3. BLOCK DIAGRAM
▪A block diagram is a diagram of a system in which the principal parts or
functions are represented by blocks connected by lines that show the
relationships of the blocks.
▪The rectangle usually contains a description or the name of element or symbol
for mathematical operation to be performed on the input to yield the output.
The arrows represent the direction of signal flow.
INPUT OUTPUT
BLOCK

4. ▪ Many systems are composed of multiple sub systems hence a few more
schematic elements must be added to the Block Diagram. These new elements
are summing junctions and pick off points.
▪ The operation of addition or subtraction in a block diagram represented by a
circle called the summing point, with appropriate plus or minus sign associated
with arrow entering the circle. The output is the algebraic sum of input.
X
X-Y
Y
Y
X+Y
X
X
Y
Z
X+Y+Z
+
-
+
-
+
+

5. ▪ In order to employ the same signal or variable as an input more than one block
a take off point is used. This permits the signal to proceed unaffected several
different paths to several destinations.
Take Off Point
X
X
X
X X X
X

6. ❑ IMPORTANCE OF BLOCK DIAGRAM
▪A block diagram is a specialized, high-level flowchart used in engineering. It
is used to design new systems or to describe and improve existing ones. Its
structure provides a high-level overview of major system components, key
process participants, and important working relationships.
▪A block diagram provides a quick, high-level view of a system to rapidly
identify points of interest or trouble spots.

7. COMBINATION OF BLOCKS/REDUCTION TECHNIQUES
1)BLOCKS IN SERIES/CASCADE BLOCKS
▪The blocks connected in series in such a way that the output of one block is
input of preceding block.
▪Mathematically any finite number of such blocks can algebraically combined
by multiplication of transfer functions of each block.
G= 𝐺1* 𝐺2* 𝐺3* ……. * 𝐺𝑛
▪The Block diagram of such system is shown in figure
𝑞𝑖 𝑞𝑜
▪The transfer function of this system yields as:
𝑞𝑜/𝑞𝑖 = 𝐺1 * 𝐺2
𝐺1 𝐺2

8. 02) COMBINING BLOCKS IN PARALLEL
▪ The blocks which are connected in parallel will have the same input.
▪ That means we can represent the parallel connection of two blocks with a
single block. The transfer function of this single block is the sum of the
transfer functions of those two blocks.
𝑮𝟏
𝑮𝟐
q
𝑞𝑖 𝑞𝑜
+
+
▪ The transfer function of such system yields as:
𝑞𝑜/𝑞𝑖 = 𝐺1 + 𝐺2

9. 03) BLOCKS IN FEEDBACK LOOP
▪A system in which the output of system is fed back towards the desired
input of the system and an element is provided in feedback path
resulting block diagram.
▪The transfer function of such system yields as:
𝑞𝑜/𝑞𝑖 = G/(1+ GH)
G
H
𝑞𝑖 𝑞𝑜
e
f
-