Introduction to Industrial Automation

Figure 4.31  A chemical reactor for mixing two liquids and compounding a new product.

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144

 

◾

  Introduction to Industrial Automation

For the code assignment shown i
 

Turn ON A L BC,

Turn OFF A L BC

Turn ON B L AC,

Tu

=

=

=

3

1

2

rrn OFF B TAC

Turn ON C HS V AB,

Turn OFF C STR A

=

=

⋅

=

⋅

1

BB

Applying logical Equation (1) to three auxiliary variables, we obtain:

 

A L BC L BC A

L B C L BC A

B TAC L AC B

T

=

+

=

+ +

+

=

+ =

1

3

1

3

2

(

) (

)(

)

(

) (

++ +

+

=

⋅

⋅

+

=

+ +

⋅

A C L AC B

C STR AB HS V AB C

STR A B HS

)(

)

(

) (

)(

2

1

V

V AB C

1

+

)

For the operation of the two machines (STR and RFG), valves, and the timer, we obtain:

 

RFG ABC

RFG A B C

=

⇒

= + +

 

STR ABC ABC ABC ABC AB AC

=

+

+

+

=

+

 

V

ABC, V

ABC V

ABC T ABC

1

2

3

=

=

=

=

,

,

By converting the above equations to an automation circuit, we obtain the automation circuit pre-

sented i
S

5

S

0

L

1

S

1

HS•V

1

T

RFG=ON

V

2

=ON

S

4

ABC

000

001

S

3

S

2

STR

011

010

110

100

HS=hand-operated switch

L

2

RFG=ON

STR=ON

V

2

=OFF

RFG=ON

STR=ON

V

3

=ON

L

3

RFG=ON

STR=ON

T=ON

V

3

=OFF

RFG=ON

STR=ON

V

1

=ON

Figure 4.32  State diagram for Example 4.11.

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Logical Design of Automation Circuits 

◾

 

145

I
investigate how the corresponding logical design method allows for the simplification in the design 

of solutions for complex problems using a systematic and straightforward approach, especially in 

cases where the empirical approach will not work. In the following examples, the description of 

N

A

R

RFG

Α

Α

C

Β

A

B

Α

A

C

C

B

C

A

B

STR

C

Β

C

B

A

C

Β

Α

Β

L

1

L

3

L

2

T

STR

V

1

HS

C

V

1

Α

Β

V

2

Α

Β

V

3

Α

Β

T

Α

Β

C

C

C

C

Figure 4.33  Automation circuit for Example 4.11 based on the state diagram o

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◾

  Introduction to Industrial Automation

the desired industrial application will be provided at the beginning, followed by the presentation 

of the logic state diagram construction and the logical expressions derived from equation (1), and 

finally, the corresponding automation circuit.

The lead screw moving worktable is presented i

two-direction motor and two rotational speeds. The limit switches that are indicated in the same 

figure have been placed in those points where we would like to change the speed direction, or the 

moving speed. Thus, the desired automation should be able to achieve the following:

  1. With the press of a button b

1

, the lead screw worktable (T) should move to the right with a 

low speed (R

LS

).

  2. When the limit switch x is energized, the table should continue to move towards the right, 

but with the high speed (R

HS

), until it reaches the limit switch y, where it returns to the low 

speed of motion (R

LS

).

  3. As soon as the limit switch z is energized, the direction of the movement should be 

inverted, which means that the table should move to the left (L

LS

) without a change in the 

speed.

  4. The movement to the left should continue in a similar way until the press of the limit switch 

y, where it continues at low speed (L

LS

). From the limit switch y until the limit switch x, the 

movement is happening at high speed (L

HS

) and from the x until the w at low speed (L

LS

), 

where again the motion is reversed.

  5. This palindromic movement of the table continues until a button b

0

 is pressed, only while 

the lead screw table moves toward the right at low speed.

For the described problem, the state diagram is displayed i

gram has five states and thus three auxiliary variables are needed, which are coded in the same 

figure.

Limit

switch

w

x

y

z

Worktable

Lead screw 

Low

speed

Low

speed

Motion

reverse

Motion

reverse

Motor

(n1, n2, 

)

High

speed