Download Viscous Damping - System Dynamics - Exam and more Exams Process Engineering in PDF only on Docsity!
CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2010/
Module Title: System Dynamics and Control Engineering
Module Code: MECH
School: Mechanical and Process Engineering
Programme Title: Bachelor of Engineering (Hons) in Mechanical Engineering – Year 3
Programme Code: EMECH_8_Y
External Examiner(s): Prof. Robin Clarke, Mr. John Hayes Internal Examiner(s): Dr. Michael J. O’Mahony
Instructions: Attempt 3 questions All questions carry equal marks
Duration: 2 hours
Sitting: Autumn 2011
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
- Determine the transfer function relating the output displacement X 1 (s) to the input force F(s) for the mechanical system shown in Fig. Q.1 where: M 1 , M 2 = Masses [kg] K 1 , K 2 = Spring stiffness [N/m] C 1 , C 2 , C 12 = Coefficients of viscous damping [N per m/s]
(25 marks) What is the order of the system and which elements of the system determine it?
(8 marks)
- (i) Discuss the relative advantages and disadvantages of open loop and closed loop control systems. (15 marks) (ii) A step input of 5 V was applied to the open loop speed control system shown in Fig.Q2. The following output response was recorded. Time t (^) Output speed s Rev/min 0 0 0.1 197 0.2 316 0.4 432 0.6 475 0.8 491 1.0 497 1.5 500 2.0 500 Plot the response and hence obtain the gain Km and time constant m for the system. (10 marks) (iii) State the equation that describes the response of the system in part (ii). (8 marks)
system performance. What practical difficulties may be experienced with derivative action and what alternative could be considered in such cases? (15 marks)
(b) The block diagram of the position control system for one of the axes of motion of a satellite is shown in Fig. Q.5. It is desired that the system should have a natural frequency of 5 rad/s and a damping ratio ξ = 0.72. Show how these specification can be met using:
(i) Proportional plus derivative control (ii) Proportional controller with velocity feedback. (2 x 6 marks)
Discuss the relative advantages and disadvantages of the above control strategies. (6 marks)
Fig. Q.
Fig.Q.
K
s
m
m 1
VC(s) (^) Ω(s)
Motor/Load
Open Loop
Closed Loop
K
s
m
m 1
KTacho
VC(s)^ Ω(s)
