Marine Engineering Simulation and Modeling
21526/NM951
2018 -2019
Marine Engineering Simulation and Modeling
Coursework
•You should provide a comprehensive report following the numbering system on the questions.
•You should also include an electronic copy of your programs.
For each of the questions you should include:
1.A full description of any mathematical models which you (may) have developed including FBD’s.
2.A brief description of your Simulink model and how it works.
3.A full discussion of the results obtained.
4.Make sure that you run your model over an appropriate amount of time; the system wil default to only 10
seconds you wil often have to change this.
Read the questions very carefuly.
LO1 –Exam
•2 Courseworks 50% each.
•1
st
Coursework: Simulink Coursework –Report , Deadline wek 7.
Marine Engineering Simulation and Modeling
Coursework: Hydraulic actuator
a)Build a mathematical model, for the single action hydraulic ram shown below. The surface area of the piston head is 0.1
m
2
. Mases !and "are 10 Kg and 5 Kg respectively. Spring #has a stifness of 2 N/m while damper $has a friction
of 1 N/m/s. (Include for the presence of leakage betwen the piston and the cylinder wal using leakage coeficient , %=
0.00001. The total leakage rate is m
3
. The bulk modulus of the fluid may be asumed infinite.)
b)Plot the position, velocity, and aceleration of mas, ", for a step input flow rate of 0.1 m
3
/sec.
c)Determine the time taken for piston to stop moving -increase the simulation time.
d)By refering to the FBD of the system explain why the piston stops moving.
e)What is the value of the leakage when the piston has stoped moving?
The input flow rate is changed to a sinusoid of amplitude 0.1m
3
/sec and frequency π/40 rad/s.
()
*()"
0
,()
vent
!
#
$
f)Calculate and plot the cylinder presure.
g)Calculate and plot the leakage flow rate and hence determine the volume of fluid which has leaked over 50 seconds
of continuous operation.
h)Discus your results.
Marine Engineering Simulation and Modeling
Coursework: Electronic Servo Valve
A typical control system for an electronic servo valve is shown below.
The system comprises a DC motor coupled to a mechanical valve. The input signal represents the instantaneous desired
valve position. An input level of zero (0) comands the valve to close and an input value of one (1 ) comands the valve
fuly open.
The output represents the actual position of the valve. The relationship betwen the input and output depends on the
physical parameters of the valve, the motor and the control system layout.
The transfer function represents the dynamics of the motor and valve asembly:
!
"#$#%'()'*
= 0.01 Kgm
2
+
"#$#%'()'*,*(),
= 0.1 Nm/rad/sec
-
"
(motor torque constant) = 0.1 Nm/Amp.
a)Build a time domain model of the system and use only the simulation to investigate the efects of gains Ka, Kv, and Kpon
the dynamic response of the servo valve. i.e. damping and natural frequency.
b)Asuming the input is a step of magnitude 1,find apropriate values of Ka, Kvand Kp, so that the desired final position is
obtained in les than 0.3 seconds with a maximum overshoot of les than 5%.
Marine Engineering Simulation and Modeling
Coursework: Tank Level Open Loop System
Water flows into a cylindrical tank of cros sectional area 1.34 m
2
at a rate !
"
#and out to the atmosphere through a
capilary type restrictor at rate !
$
#.
a)Build a model relating the depth of liquid in the tank, ℎ#to the input flow rate. Where !
$
#=0.8 ℎ#. The volume
of the tank is 10 m
3
. There wil be two outputs, one indicating volume the other height of water. Before ading any
sources or sinks to your model, select al the blocks, (CRTL-A), then using the edit menu on the tolbar create a
subsystem. Label this system ‘Tank Dynamics’. Double clicking on the subsystem wil alow you to enter it. Do this and
label the inputs and outputs accordingly. Return back to the uper level from the task bar. Now enter the sliders
section in the dials and blocksetlibrary. Ad a tank to your volume output and set its maximum volume to 10 Ad a
suitable block to represent the input flow rate (The slider shown below is no longer available). Numerical LED displays
may then also be aded to display the input flow rate and head of water. Your model should now lok similar to the
one show below. In the simulation parameters menu set the stop time to 100s and the maximum step size to
0.01seconds. The tank must not be filed more than 95% .
b)Run the simulation and adjust the flow control manualy until equilibrium is achieved at maximum capacity.
c)What is the flow rate and head in the tank?
Marine Engineering Simulation and Modeling
Coursework: Tank Level Closed Loop Control System
In this question combine the systems in Question No.2 and No. 3:
a)Copy and paste the servo valve model into a new project.
b)Select the dynamics and make it into a subsystem.
c)Copy the tank level subsystem into the same project.
d)Combine the two subsystems with other functions, so that with a mean input flow rate of 60 m
3
/s with standard
deviation of 5 m
3
/s the tank is never filed more than 95%. Your system should resemble a typical fedback control
scheme.
e)Explain the nature of the input flow rate.
f)Reduce the system a further layer (put it in a subsystem), and ad suitable gauges to display the valve position, input
flow rate, and tank volume.
g)Tune the system (se Question No.2) if necesary to give an ‘aceptable’ servo valve response.
h)Explain the nature of the input flow rate and coment on the results.
The uper layer of system should be similar to that shown below.