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Introduction demonstration DPUsing models for MT218 Mechatronics in MT

H.T. GrimmeliusAssistant professor (lecturer) Marine EngineeringDelft University of Technology

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Lecture content

• A little background• Description of hard- and software• Some theory• Goal this afternoon

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Mechatronics

• Mechatronica is de naadloze combinatie van verschillende complementaire technologieën, die op een integrale wijze met elkaar samenwerken

(Federatie Hydrauliek en Pneumatiek)

• Mechatronics is the combination of MECHAnical systems with elecTRONics and informatICS

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Mechatronics

• Main components:• The actual system or process• Actuators to move or exert a force• Sensors to measure actual state• Controls to maintain required state or change

state

• Additionally required: data acquisition system

Mechatronics

•Measurements•Network theory•Digital signal-processing

•Filtering

•Digital real-time control

•Mechanics•Dynamics•Hydro

•Sensors•Actuators

project

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Available hard- & software

• System: model ship• Actuators: propulsors and servo’s• Sensors: position (x-y), heading and shaft

speeds• Controls: Simulink based system for “weather

vaning”• Data acquisition through PC

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Available hard- & software

• “COTS” equipment:• Model: standard kit• Actuators: all motors, speed controls and

servo’s• Communication: PC with standard I/O board

• Not “COTS”:• Sensors: developed for this application• Controls: Simulink based programme with

GUI

Commercial Of The Shelf

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• Wished:• Several possibilities for Weather vaning DP• Affordable and maintainable

• Implementation:• Two azimuthing thrusters (4 degrees of freedom)• Bow thruster (1 degree of freedom)• COTS• Controlled with PW signal

Actuators

t [ms]

U [V

]

10 2012

max min

~0

~5

t [ms]

U [V

]

10 2012

max min

~0

~5

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Location sensor

• Wished:• Affordable location sensor• Clear & simple working principle• Suitable to be used in towing tank

• Implementation:• Telescopic rod with angular (SITW: Stiff Inverted Taut Wire)

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Speed sensor

• Wished:• Shaft speed feedback of both thrusters• Clear & simple working principle• Accurate also at low rpm

• Implementation• Optical pick-up• Disc with 15 holes• Signal conversion (pulse DC)

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Communications

• Wished:• Continuous• Possibility for high resolution• Everything from within Matlab/Simulink• Good support

• Implementation:• Real time I/O card MF614 by HumoSoft• Digital: 8 in/8 out; analogue 8 in/4 out + 4 PWM

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Control system

• DP control• Only X-Y position controlled, heading is free• Two decoupled PID controllers with anti-wind

up

• Other controllers• Shaft speed controllers• Very suitable for application of Ziegler &

Nichols

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• Simulink models generated automatically• Three working environments

• On-line for actual sailing (closed loop)• On-line for testing harware (open loop)• Off-line simulation environment

Control system

• Graphical user interface within Matlab

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Control system: on-line

Controller Power configuration

Positiontransformation

Position error

Required

forced

Actuator

settings

Position data

Real-timeoutput

PWMsignals

Real-timeinput

Measured

voltages

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Control system: on-line testing

• On-line testing gives the possibility to directly control the actuators and read the sensor signals

Actuator

settings

Position data

Real-timeoutput

PWMsignals

Real-timeinput

Measured

voltages

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Control system: off-line

• For off-line simulation all hardware should be available in software modulesController Power

configurationPosition

transformation

Position error

Required

forced

Actuator

settings

Position data

Simulatedactuators

Simulatedship

Simulatedsensors

ForcesPosition

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Possible configurations

One thruster, full control Combined

Two thrusters, fixed relative angle

Combined

First thruster forward, second thruster lateral

First Second

One thruster forward, bow thruster

thruster

Bow thruste

r

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Education

• Two deliverables• Test: does it work• Report: why did it work

• Student reaction‘Thought we could do full DP, but problems

were already big enough now ...’

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Research projects

• thruster interaction: angles• thruster interaction: rpm• thruster – hull interaction

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Demonstration & publicity

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Manoeuvring & wind modelling

• Manoeuvring modelling• Wind modelling

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Equations of motion

pqIIrINrpIIqIMqrIIpIK

qupwwmZpwruvmY

rvqwumX

yyxxzz

xxzzyy

zzyyxx

)()()(

)()()(

Body with 6 degrees of freedom

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Reducing degrees of freedomAssumptions• no waves• no change in total mass during manoeuvre• no change in distribution of mass during manoeuvre• rotation around y-axis does not influence motion in

x-y plane

rIMruvmYrvumX

zz

)()( only forces and moments

in the x-y plane influence manoeuvring behaviour

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Hull forces

• Forces depend on:• Speed of the ship through the water• Rate at which this velocity changes• Shape of the hull• Characteristic of the water

• No confinements present (deep water, open sea)

• No waves( , , , , , )HULLF f u v r u v r

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Hull forces

• From Taylor expansion to the third power:

• Which leads for X to:

2 212!

3 2 2 313!

( , ) ( , ) [ ( , ) ( , )][( ) ( , ) 2 ( , ) ( ) ( , )][( ) ( , ) 3( ) ( , ) 3( ) ( , ) ( ) ( , )] ...

x y

xx xy yy

xxx xxy yyx yyy

f x x y y f x y x f x y y f x y

x f x y x y f x y y f x y

x f x y x y f x y y x f x y y f x y

02 2 21

2!3 3 3 2 21

3!2

[ ][ ... 2 2 ... 2 ][ ... 3 3 ..3 6 6 ... 6

hull u v r u v r

uu vv rr uv ur vr

uuu vvv rrr uuv uur

rrv uvr uvu uvr

X X X u X v X r X u X v X rX u X v X r X uv X ur X vrX u X v X r X u v X u rX r v X uvr X uvu X

]uvr

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Hull forces

• Simplification by Inoue( ) ( )hull x y vrX m u m X vr X u

22 ( ' ' ' ' ' ' ' ' ' ' ' ' ')hull y x v r v v v r r rY m v m ur LTU Y v Y r Y v v Y v r Y r r

2 22 ( ' ' ' ' ' ' ' ' ' ' ' ' ' ' ')hull zz v r vvr vrr r rN J r LTU N v N r N v v r N v r r N r r

212

212

2 212

2 2

'

'

'

XXLTUYYLTUNNLTU

U u v

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Hull forces

• Coefficients estimated based on L, B, T and cB

2

3 2

' 4' 1.42' 0.435 1.7 (1 )

' 0.472 (1 )'' 0.54

' 25.34 4.66 0.44 0.098

' 0.44 0.065

' 34197

r

bb

br b

rr b

r

b b brr

brr

br

Y k

C BY kL

TY CB

TY CB

N kN k k

B C B C B CNL L L

C TNBB CN

L

4 3 2

18941 3909 353.8 11.9b b bB C B C B CL L L

gyrrk

L

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Hull forces

• Other parameters to be estimated• Hydrodynamic mass in x and y direction• Hydrodynamic mass moment of inertia I• Straight line resistance

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Hull forces

• For low Fr and large β:• No longer valid

because of Munk’smoment

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Wind forces

• Calculated with wind speed only (ship speed very low)

2

2

2

( ) 2( ) 2( ) 2

wind X wind lat wind

wind Y wind front wind

wind N wind lat wind

X C A U

Y C A U

N C A L U

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Source of constants

• Brix:• Semi emperical

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AD converter

time

ampl

itude

time

ampl

itude

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AD converter: resolution

• Number of values = 2bits

• 8 bits: 256 levels• 10 bits: 1024 levels• 12 bits: 4096 levels

• Error1 Full Scale2b

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Aliasing

time

amplitude

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Anti-aliasing

• Sample at at least twice the highest frequency• Filter out high frequency components before

sampling

• Highest frequency: closed loop gain > 3 dB• Use bode plot!

• Rule of thumb: 2 to 4 samples during rise time of step response

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High frequency aliasing

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DA converter

-

+

U 1

Uo = ?

R2

R1

R1U 2

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DA converter

01 01 01 01 01 01 01 01

B7 B6 B5 B4 B3 B2 B1 B0

Ub

-+

Rt

Uu1K 2K 4K 8K 16K 32K 64K 128K

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Goal of today

• Checkout system• Set controller variables• Check results