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1 «Υποβοήθηση πρόωσης πλοίου σε πραγματικές καταστάσεις θάλασσας με βιομιμιτικά συστήματα» BIO-PROPSHIP, κωδ.444 Παραδοτέο τεχνικό υλικό προετοιμασίας για υποβολή ευρεσιτεχνίας Κύριος Ερευνητής: Κων/νος Α. Μπελιμπασάκης ΕΘΝΙΚΟ ΜΕΤΣΟΒΙΟ ΠΟΛΥΤΕΧΝΕΙΟ ΣΧΟΛΗ ΝΑΥΠΗΓΩΝ ΜΗΧΑΝΟΛΟΓΩΝ ΜΗΧΑΝΙΚΩΝ ΤΟΜΕΑΣ ΝΑΥΤΙΚΗΣ & ΘΑΛΑΣΣΙΑΣ ΥΔΡΟΔΥΝΑΜΙΚΗΣ Τηλ , Fax: kbel@fluid.mech.ntua.gr Αθήνα, Οκτώβριος

2 Η παρούσα τεχνική έκθεση περιλαμβάνει πληροφορίες και τεχνικά στοιχεία που θα υποστηρίξουν την μελλοντική υποβολή ευρεσιτεχνίας σε ότι αφορά τη κατοχύρωση δικαιωμάτων του εξεταζόμενου συστήματος παλλομένων πτερυγίων, το οποίο μελετήθηκε και αναπτύχθηκε στα πλαίσια του παρόντος έργου για την υποβοήθηση της πρόωσης του πλοίου σε κυματισμούς σε πραγματικές καταστάσεις θάλασσας. Τα αναφερόμενα τεχνικά στοιχεία και πληροφορίες περιλαμβάνουν τον πειραματικό μηχανισμό, το μοντέλο του συστήματος παλλομένων πτερυγίων τα ηλεκτρονικά και τον αλγόριθμο ενεργητικού ελέγχου, ο οποίος αναπτύχθηκε με τη συστηματική χρήση του αριθμητικού προσομοιωτή της λειτουργίας του εξεταζόμενου συστήματος. 1

Flapping wave propulsor Α novel wave thruster for ships, extracting energy from waves with direct conversion

School of Naval Architecture and Marine Engineering of National Technical University of Athens.

BIOPROPSHIP project; more information and technical data are available from the webpage http://arion.naval.

In the context of the above project the innovative biomimetic-wing system is investigated and experimentally

appropriate control methods for optimizing real-time performance.

3 Flapping wave propulsor Α novel wave thruster for ships, extracting energy from waves with direct conversion to thrust, is developed and studied in the last period in the Ship & Marine Hydrodynamics Laboratory of the School of Naval Architecture and Marine Engineering of National Technical University of Athens. The flapping system is developed, based on biomimetic system theory and applications, in the framework of BIOPROPSHIP project; more information and technical data are available from the webpage In the context of the above project the innovative biomimetic-wing system is investigated and experimentally demonstrated for augmenting ship propulsion in waves, in operating conditions corresponding to realistic sea states. New and existing computational models have been produced and integrated, supporting the development of appropriate control methods for optimizing real-time performance. For testing and evaluation of the validity of the present methods, and demonstration of the whole idea, a prototype model is constructed and tested in the towing tank of LMHS NTUA, The system will be tested both standalone and attached to the ship hull; see Fig.1. Fig.1 Model (left) and system drive electronics (right). 2

4 In the experimental phase which will follow the present project the following set-up has been designed and developed: - NACA 0012 foil oscillating below the water level, under the vessel, - driven by a DC motor and time belt, and - controlled by the developed algorithm using standard electronics including accelerometers and sonic position meters Details of the design are included in the figures and pictures in the present report. The foil follows prescribed self-pitching motion in order to develop the desired angle of attack in waves so to always produce a positive thrust, with minimum power required for the controlled motion. The electronic drive and control of the motor was custom-implemented by the research team. The whole system is prepared for systematic measurements of the resistance of the hull model with and without the flapping wave thruster, for various combinations of foil arrangements, ship speeds and wave conditions. First experimental results that will be reported below are very promising. The next phase (after the end of the present project) will include systematic experimental investigation and validation the whole system and further optimization by means of the numerical hydrodynamic simulations with exploitation of measured data. 3

5 Fig.2 Drawing of the system of oscillating foil thruster below the ship model 4

6 Fig.3 Arrangement of the system on the ship model 5

7 Fig.4 3D drawing for arrangement and positioning of the system at the bow of the ship model. The longitudinal position and the clearance below the ship hull are tunable parameters. 6

8 Fig.5 3D drawing of flapping thruster and its support 7

9 Fig.6 Detail of the fixing and positioning of the flapping thruster on the ship hull model 8

10 Fig.7 Model of the flapping thruster on the ship hull model 9

11 Fig.8 Model of the flapping thruster on the ship hull model 10

12 Fig.9 Model of the flapping thruster on the ship hull model 11

13 Fig.10 Model of the flapping thruster on the ship hull model. The angle of the foil is dynamically controllable 12

For testing the method an experimental setup has been developed and tested in the ship

thrust from sea waves through a foil mechanism, in a small marine craft (see Figs.

11 Experimental set up at SMHL-NTUA 1) The electromechanical module: The thrust is created

The whole arrangement is possible to move and installed at various longitudinal positions

14 For testing the method an experimental setup has been developed and tested in the ship towing tank of Ship and Marine Hydrodynamics Laboratory of National Technical Unicersity of Athens. The scaled model in conjunction with the control system is implemented in order to produce thrust from sea waves through a foil mechanism, in a small marine craft (see Figs. 7-10), consists of two separate modules: Fig.11 Experimental set up at SMHL-NTUA 1) The electromechanical module: The thrust is created by the rotational self pitching oscillation of foils about its pivot axis (Fig.11). The whole arrangement is possible to move and installed at various longitudinal positions of the ship, which is used to investigate the effect of horizontal location. Also, the arrangement of the flapping foils is possible for various depths below the keel of the ship, which is used to investigate clearance effects. 13

15 Fig.12 Controlled oscillatory motion of the foil The experimental prototype is built using NACA 0012 foils, which are made out of wood and are externally painted. A DC Maxon motor (90W), in combination with a gearbox with 1:14 ratio, are responsible for the rotation of the aforementioned foil. The gearbox is capable to withstand moments up to 6Nm. The selection of the motor was based on hydrodynamic and inertial forces which were calculated with the help of a CFD code, custom developed in our lab. The moment output of the gearbox (which is on the marine vessel) is transferred, with an elastic coupler and two time belt sprockets (with ratio 1:1), to the axe of the foil, which stands below sea level, without phenomena like slipping. The time belt and the foil is assembled on two small, vertical, low-drag supports. Closed type bearings were selected, in order to deal with any water-proof problems. All the drawings were created in Solidworks and Autocad. 2) The electronic module (Fig.13): The rotation of the foil, in order to reduce the hydrodynamic drag, follows in real time the angle of attack. Α 40 Mhz microcontroller of Microchip company, was utilised to drive the motor. This specific microcontroller was selected because it is very simple, passes all the specification requirements, as the mathematical model that is used is not very complex, and lastly it needs no further electronics for voltage converting, by the connection of this type microcontroller with the 14

16 sensors. The bare metal, custom programming of the microcontroller was compiled with an embedded C toolchain. The microcontroller has the following inputs: a) First there are specific pins in the microcontroller responsible for calculating (Incremental Quadrate Encoder Interface Module) the angle of the motor, from the incremental encoder sensor mounted on the motor. Because of the 1:1 ratio between the sprockets, the angle of the motor equals the angle of the foil. The resolution of the angle is below one degree and has high repeatability. The backlash problem because of the gearbox was eliminated with a digital controller using describing functions, compensating nonlinearities. Fig.13 Electronic Module b) The second input is the Analog to Digital Converter (ADC) of an Infra red (IR) sensor which measures the heave motion of the marine vessel, so as to be able to estimate in real time the wave motions. In order to smooth the measurements numerical differentiations with multiple points, and analog low pass filter was utilized. 15

17 The microcontroller through the inputs, is able to calculate the vertical and longitudinal velocity of the marine vessel. So an easy-implemented law of estimating in real time is implemented for the angle of the NACA foil. The motor, as well as the foil, rotates as a consequence of pulsed width modulation (PWM) at 20Khz of an H-Bridge drive (5A, 24V). The loop control has a frequency up to 100 Hz. The closed loop frequency suffices due to the slow dynamics of the vessel, the time constant of the dc motor, and the low cost infrared sensor. In order to record the measurements and further process them, a wireless communication, based on low-energy Zigbee protocol, between a laptop and the Microchip microcontroller was implemented. At laptop, a graphical user Interface (GUI) was created, using Matlab 2013a environment. The full experimental setup costed less than 1500 (procurements, labor, toll included), which shows the concept of simple analysis, design and implementation of these type of set-ups. Sample measured data from testing of the model prototype in the ship basin of SHML-NTUA are shown in Fig. 14. Fig.14. First results from testing in the ship model tank of NTUA, and measured data concerning responses of the ship and thrust development by the flapping foil in waves. 16

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