Introduction demonstration DP

1. Introduction demonstration DP Using models for MT218 Mechatronics in MT • H.T. Grimmelius • Assistant professor (lecturer) • Marine Engineering • Delft University of Technology

2. Lecture content • A little background • Description of hard- and software • Some theory • Goal this afternoon

3. 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

4. Mechanica Electronica Informatica MECHATRONICA

5. 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

6. Mechanica Elektronica Informatica Mechatronics • Sensors • Actuators • Measurements • Network theory • Digital signal-processing • Filtering • Mechanics • Dynamics • Hydro project • Digital real-time control

7. 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

8. Commercial Of The Shelf 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

9. Actuators • 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

10. 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)

11. 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)

12. 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

13. 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

14. Control system • 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 • Graphical user interface within Matlab

15. Position data Position error Required forced Actuator settings Real-time input Real-time output Measured voltages PWM signals Control system: on-line Position transformation Controller Power configuration

16. Position data Actuator settings Real-time input Real-time output Measured voltages PWM signals Control system: on-line testing • On-line testing gives the possibility to directly control the actuators and read the sensor signals

17. Position data Position error Required forced Actuator settings Position transformation Controller Power configuration Simulated sensors Simulated ship Simulated actuators Position Forces Control system: off-line • For off-line simulation all hardware should be available in software modules

18. Possible configurations

19. 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 ...’

20. Research projects • thruster interaction: angles • thruster interaction: rpm • thruster – hull interaction

21. Demonstration & publicity

22. Manoeuvring & wind modelling • Manoeuvring modelling • Wind modelling

23. Equations of motion Body with 6 degrees of freedom

24. only forces and moments in the x-y plane influence manoeuvring behaviour Reducing degrees of freedom Assumptions • 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

25. 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

26. Hull forces • From Taylor expansion to the third power: • Which leads for X to:

27. Hull forces • Simplification by Inoue

28. Hull forces • Coefficients estimated based on L, B, T and cB

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

30. Hull forces • For low Fr and large β: • No longer valid because of Munk’s moment

31. Wind forces • Calculated with wind speed only (ship speed very low)

32. Source of constants • Brix: • Semi emperical

33. AD converter

34. AD converter: resolution • Number of values = 2bits • 8 bits: 256 levels • 10 bits: 1024 levels • 12 bits: 4096 levels • Error

35. Aliasing

36. 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

37. High frequency aliasing

38. R2 R1 U 1 - R1 + U 2 Uo = ? DA converter

39. DA converter Ub B7 B6 B5 B4 B3 B2 B1 B0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 Rt 1K 2K 4K 8K 16K 32K 64K 128K Uu - +

40. Goal of today • Checkout system • Set controller variables • Check results