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Question 5 Four double acting pneumatic cylinders, namely A, B, C and D, are used to assemble a component in a production process. An electro-pneumatic circuit which are controlled by double solenoid valves is required for the application. The cylinder motion sequence is as below: Step 1 mi to nooo Description Initially cylinders A, D are in their extension states while cylinders B, C are in their retraction states. When a pushbutton Normally Open type) is pressed momentarily, cylinder A retracts to its fully retracted position while B extends to its fully extended position simultaneously. Next, cylinder B retracts to its fully retracted position. Next, cylinder extends to its fully extended position. Next, cylinder D retracts to its fully retracted position. Next, cylinder retracts to its fully retracted position. Next, cylinder D extends to its fully extended position. Lastly, cylinder A extends to its fully extended position. System halts and await for another input signal to run the above cycle again Other requirements: (i) Each step of motion can only be started right after the previous step motion ended. (ii) Retraction stroke of cylinder B and C is speed adjustable. (111) Extension stroke of cylinder A and D is speed adjustable. Reed switches or micro-switches or IR sensors, with NO and NC contacts, may be used for position sensors. (a) Group the motion sequence by the Cascade method. (6 marks) (b) Draw the electro-pneumatic sub-circuit of the system. (12 marks) (c) By using the Cascade method, design an electrical ladder diagram for driving the above sequence of the four pneumatic cylinders, (22 marks)