Week7_Chap7_multi actutaor control cylinder control

pneumatic cascade sequential system

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

2. 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-

3. A+ action generates sensor signal a 1 , which is used for B+ action. B+ action generates sensor signal b 1 , which is used for B- action. B+ action generates sensor signal b , which is used for A- action. A- action generates sensor signal a , which is used for A+ action. Week # 7 Multiple Actuator Control A start signal is also required along with a signal for obtaining A+ action. (Signal generated due to the last control action in the sequence)

4. Week # 7 Multiple Actuator Control

5. Week # 7 Multiple Actuator Control When the start push button is pressed, signal appears at port 14 of valve through sensor a Signal is also present at port 12 of valve, resulting in a signal conflict. When cylinder B extends fully, sensor b 1 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

6. Week # 7 Multiple Actuator Control Idle-return Rollers Reversing valves (memory valves) Modules as combination of valves Elimination of signal conflicts Idle-return Rollers

7. Week # 7 Multiple Actuator Control This method is not reliable The end position cannot be sensed accurately. Fast control system cannot be setup. Elimination of signal conflicts

8. Week # 7 Multiple Actuator Control Two of the possible designs used to remove signal conflicts through reversing valves are Cascade Method Shift-Register Method Elimination of signal conflicts 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-

9. Week # 7 Multiple Actuator Control Two of the possible designs used to remove signal conflicts through reversing valves are Cascade Method Shift-Register Method Elimination of signal conflicts 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

10. Week # 7 Multiple Actuator Control 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

11. Week # 7 Multiple Actuator Control Cascade Method Initially the supply is in the last group

12. Week # 7 Multiple Actuator Control

13. Week # 7 Multiple Actuator Control

14. END