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RUDDER ROLL STABI LI ZATI ON AND SHI P DESI GN: A CONTROL POI NT OF VI EW

P.G.M. van der Kl ugt *, HR van Nauta Lemke **

- I nt roducti on

Duri ng the l ast t wo decades much r esearch has been car r i ed out at t he Cont rolLaboratory of t he Facul t y of El ectr i cal Engi neeri ng o f Del f t Uni versi t y ofTechnol ogy i n the f i el d o f shi p cont rol systems. A recent r esul t i s an aut opi l otwhi ch uses the r udder not onl y to cont rol t he headi ng of t he shi p but t o r educe t herol l moti ons as wel l (Van Amerongen, Van der Kl ugt & Van Nauta Lemke, 1987). Thi sRudder Rol l St abi l i zat i on (RRS) autopi l ot was devel oped at Del f t Uni versi t y ofTechnol ogy i n cl ose cooperat i on w t h the Royal Netherl ands Navy and w t h thecompany Van Ri et schoten & Houwens, Rot terdam I t w l l be i nst al l ed on board t he newM cl ass f r i gat es o f t he Royal Netherl ands Navy.

One of t he obj ect i ves of t he research on thi s RRS aut opi l ot was to i nvest i gatewhi ch modi f i cati ons i n a shi p desi gn are requi red t o enabl e a successf ulappl i cat i on of an RRS syst em Van Amerongen & Van Naut a Lemke (1982) descr i bed t hei nf l uence of a l i mted rudder angl e and a l i mt ed rudder speed on t he per f ormanceo f a rol l cont rol l er. Van Amerongen & Van der Kl ugt (1982) demonst rated that t herudder i nduced rol l moment i s equal l y i mportant . Van der Kl ugt (1987) proposed anadapt i ve cont r ol l er whi ch takes i nto account t hese and other restr i ct i ons posed bythe shi p and i ts st eer i ng machi ne. However , even the best cont rol l er cannot gi ve asati sf actory perf ormance i f t he shi p desi gn or t he st eeri ng machi ne are not sui t edf or RRS. Thi s short paper summari zes t he requi rement s t o be posed t o t he shi pdesi gn and the steer i ng machi ne f r oma cont rol poi nt of vi ew

- The st eer i nq machi ne

The requi rement s t o be posed to the st eeri ng machi ne are f ormul ated by usi ng t he

bl ockdi agram of Fi g.1.

i n combi nat i on w th some r ul es of t humb i n cont rolengi neeri ng (Van der Kl ugt , 1987).

Fig. 1 The steering machi ne

*

**Van Ri etschot en & Houwens, p. o. box 5054, 3008 AB Rot t erdam the Nether l ands.Del f t Uni versi t y of Technol ogy, Facul t y of El ectr i cal Engi neer i ng, Cont rol

Laboratory, Del f t , t he Netherl ands.

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Two different modes of operation are distinguished:

a During "large" changes in the set-point rudder the perfo rmance of a steering

machine is dominated by the limitations of the rudder angle and the ru dder speed.

In that case, t he followi ng should hold:

0.2 O.lTnT*<---

% H

where U = the natural frequency of t he ship (rad/sec)

=6 = the largest time delay between th e required and the actual

rudder.

For a change of the set-point rudder with a step function changing f rom 0 to the

maximum allowed r udd er angle 6eff t10% should meet th e fol lowing requirement:

b During "small" change s i n the set-point rudder the limitations of t he steering

machine have hardly any influence. In that case, requirements should be posed tothe settling time Ts, the bandwith B and the phase lag at -3dB 'p:

T, i 0 . 4 1 ~ ~ ( 3 )

'p i - 6 5 degrees

- The ship desiqn

7 :I:--------7---------

I t........................ L......................... L......

F i g . 2 Th e control model

Van Amerongen and Van der Klugt (1987) described the resul ts of a s eries ofexperim ents at the Maritim e Research Institute Netherl ands ( M A R I N ) in Wageningen.

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Duri ng t hese experi ment s a l aboratory real i zat i on of an RRS aut opi l ot wasconnect ed to the MARIN manoeuvr i ng si mul ator . Two di f f erent shi ps were consi dered.The cont rol al gor i t hms were based on t he sympl i f i ed shi p model shown i n Fig. 2 . I nadvance, the parameters of t hi s model were i dent i f i ed f romzi g- zag t r i al s w th

each shi p. From a compari son of t he resul t s of t he experi ment s w th both shi ps t hef ol l ow ng requi rement s t o be posed on a shi p desi gn can be deri ved:

1 The rudder i nduced rol l moment K A ~houl d be l arge2 The rudder i nduced sway vel oci t y v ' shoul d i nduce a l arge rol l moment as wel l3 The shi p shoul d r eact t o the rudder i nduced rol l moment wel l before i t r eact s t o

t he rudder i nduced yaw moment .

I n addi t i on, i t i s advant ageous i f t he r udder - t o- rol l - t r ansf er has a non- mni mumphase charact er.

- Concl usi ons

Thi s shor t paper poses several demands on t he shi p desi gn to enabl e a subst ant i al

rol l r educt i on. The most i mpor t ant desi gn parameters are the maxi mumrudder speedand the i nf l uence of t he rudder on t he rol l mot i ons. I f t he rudder has a l argei nf l uence on t he rol l moti ons, i t has a l arge rol l - reduct i on potent i al as wel l . Therudder speed shoul d be suf f i ci ent l y hi gh t o enabl e a l arge rol l moment around thenatural rol l f r equency of t he shi p.A detai 1 l ed deri vati on of t hese requi rement s can be f ound i n Van der Kl ugt (1987).

References

Amerongen, J. van, and HA. an Nauta Lemke, Rudder Roil Stubiiizanon, Proceeding of the 4th ISSOA

International Symposium on Ship Operation Automation, Genua, Italy, pp. 43-50, September U)-Q 1982.

Xmerongen, J. van and P.GM. van der Kl- Rudder RO N Stabilization - Mennuemencs at h e N SM B, Internal

report no. R82.051, Control Laboratory, Fac of EL Eng., Delft University of Technology, 1982.

Amerongen, J. van and P.GM. van der Klugt, Rudder Roli Stabiiizniion-

Meprwements at the MARIN, Internalreport no. R87.004, Control Laboratory, Fac of El.Eng., Delft University of Technology, 1987a

Amerongen, J. van, P.G.M. van der Klugt an d JBM. Pieffers, Rudder Roil Stabiiizniion - Conmiler design and

erperimenrd resulfs, Proceedings of the 8th Ship Control Systems Symposium, the Hague, the Netherlands,

1987.

Klugt, P . G M v an d e r, "RudderRoll Stabilization",PLD. thesis, Delft University of Technology, October 1987.

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