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Cork Institute of Technology
Batchelor of Engineering in Mechanical Engineering
Award
(EMECH_7_Y3)
Summer 2008
Engineering Systems and Design - ENGINEERING S YSTEMS
(Time: 3 Hours)
Answer Four Questions Examiner: Dr. M. J. O’Mahony Mr. A. Bateman Dr. P. Delassus
- The following sequence is to be implemented using a PLC and bistable directional control valves.
A+ B+A-B-A+A-
Treat the sequence as a cascade circuit
(i) How many groups are required are required if a cascade system is used? 5 Marks (ii) Draw a ladder diagram for the above sequence. Assume that all internal PLC relays have to be latched. 20 Marks
Use the attached pneumatic circuit (Fig. Q1) as a aid to numbering the solenoids and limit switches.
- The following sequence is to be implemented using a PLC and monostable directional control valves.
A+ B+C+B-C-A-
Due to space restrictions in the system it is impossible to fit a limit switch to indicate the extend condition of cylinder B.
(i) Suggest a method to initiate C+ 4 Marks (ii) How many groups are required are required if a cascade system is used? 3 Marks
(iii) Draw a PLC ladder diagram for the above sequence. Assume that all internal PLC relays have to be latched. 18 Marks
Use the attached pneumatic circuit (Fig Q2) as a aid to numbering the solenoids and limit switches.
The following nomenclature is to be used:
A, B, C: Double acting pneumatic cylinders A+, etc:The extend stroke of cylinder A A+p: The pilot signal to cause the A+ stroke of cylinder A A-p: The pilot signal which initiates the return stroke of cylinder A A (^) d : The logic complement of A-p, used to reset single solenoid valves by disabling the latch function.
V,W: Internal PLC relays which can be set on or off V (^) p : Signal which sets relay V _ V (^) p : Signal which resets relay V V (^) d : The logical complement of Vp which disables relay V by disabling the latch.
Inputs I0.0, I0.1, I0.2 etc Outputs Q0.0, Q0.1, Q0.3 etc Internal relays M10.0, M10.1, M10.2 etc Timers T63, T64 etc
Note : The nomenclature suggested is as a guide. It does not imply that all the inputs, outputs, internal relays, etc are required to solve this question.
- (a) Distinguish between Simplex, Half Duplex and Duplex communication modes. 10 Marks (b) Distinguish between Balanced and Unbalanced transmission lines in a data communications system. 15 Marks
The following nomenclature is to be used:
A, B, :Double acting pneumatic cylinders A+, etc:The extend stroke of cylinder A A+p: The pilot signal to cause the A+ stroke of cylinder A A-p: The pilot signal which initiates the return stroke of cylinder A
V,W: Internal PLC relays which can be set on or off V (^) p : Signal which sets relay V _ V (^) p : Signal which resets relay V V (^) d : The logical complement of Vp which disables relay V by disabling the latch.
Inputs I0.0, I0.1, I0.2 etc Outputs Q0.0, Q0.1, Q0.2 etc Internal relays M10.0, M10.1, M10.2 etc Counters C60, C61, C62 etc
Note : The nomenclature suggested is as a guide. It does not imply that all the inputs, outputs, internal relays, etc are required to solve this question.
Fig Q
Input Data Parameter Value Units Load: 700 Kg Incline angle: 0.0 degrees Static Friction coefficient: 0. Dynamic Friction coefficient: 0.
Transfer time (t) 15 seconds Accel model: (^) Linear ---
Accel time: 0.1t seconds Decel time: 0.1t seconds Dwell time: 0.000 seconds Total forward Move time: 15 seconds
Move distance: 2 m
Cylinder Mech. efficiency: 90% Percentage Gravitational constant (g) (^10) ms -
Hydraulic rod structural requirements
Rod Ø (^25) mm
Cylinder bore 50 mm Table Q.
Equations of motion
2 2 2
2 1 2
v u at v u as s ut at
= + = + = +
