Week7_Chap7_multi actutaor control cylinder control

Hydraulics & Pneumatics
MCT-313
Fall 2023 – Session 2021
by
Dr. Muhammad Awais Hafeez
Chapter # 7
Week # 7

A stamping operation involves two cylinders A and B working in
sequence.
 Cylinder A extends and brings a job under a stamping cylinder B.
 Cylinder B then extends and stamps the job
 Cylinder A can return back only after cylinder B has retracted fully .
 A pneumatic circuit has to be developed for realizing this control task.
Multiple Actuator Control
Week # 7
Displacement–Event
Diagram
A+ B+ B- A-

 A+ action generates sensor signal a1, which is used for B+ action.
 B+ action generates sensor signal b1, which is used for B- action.
 B+ action generates sensor signal b0, which is used for A- action.
 A- action generates sensor signal a0, which is used for A+ action.
Week # 7 Multiple Actuator Control
A start signal is also required along with a0 signal
for obtaining A+ action. (Signal generated due to
the last control action in the sequence)

 When the start push button is pressed, signal
appears at port 14 of valve through sensor a0
 Signal is also present at port 12 of valve,
resulting in a signal conflict.
 When cylinder B extends fully, sensor b1
generates an output signal at port 12 of valve
 Signal is also present at port 12 of valve,
resulting in a signal conflict.
Look for signal conflicts

 Idle-return Rollers
 Reversing valves (memory valves)
 Modules as combination of valves
Elimination of signal conflicts
Idle-return Rollers

 This method is not reliable
 The end position cannot be sensed accurately.
 Fast control system cannot be setup.

Two of the possible designs used to remove signal conflicts through reversing valves are
 Cascade Method
 Shift-Register Method
Cascade Method
Sequence of operation of cylinders can be divided into appropriate number of groups
 There is a possibility of signals conflicts If any cylinder happen to appear twice in a group
 Hence, sequence is divided in such a way that A+ and A- fall into different groups
A+ B+ B- A-

Two of the possible designs used to remove signal conflicts through reversing valves are
 Cascade Method
 Shift-Register Method
Cascade Method
Sequence of operation of cylinders can be divided into appropriate number of groups
 There is a possibility of signals conflicts If any cylinder happen to appear twice in a group
 Hence, sequence is divided in such a way that A+ and A- fall into different groups
A+ B+ B- A-
Group 1 Group 2

Cascade Method
Number of groups increases, the number of
valves required also increases
Next is to divide the power supply for the control circuit into the same number of groups as for the
sequence of the operation
• Only one group will have supply with all other groups connected to the exhaust

Cascade Method
Initially the supply is in the last group

Week7_Chap7_multi actutaor control cylinder control

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