Prediction of Steering and Manoeuvring of Ships 



Input 1 

 Input 2 



Polaritj f OSCIL. 

 ohangea \ COIST. 



Integration period 

 Hold Condition 

 Condensers resetting 

 Pens swltohed OPP 



Sxample of a 

 constant signal 

 Integrated using 

 the COHST. 

 progransne • 



J I I 1 



Fig. 15 - Sequence of events controlled by 

 the programming circuits 



In the first integration period shown in Fig. 16, it is seen that because the 

 polarity is reversed at cot + (<P/2) - w, the cosine and any constant component 

 are eliminated and the sine component is measured. The integrated value is 

 designated OUT @ . The designation OUT is used to indicate that the measured 

 force is out of phase with angular displacement. The symbol ® indicates that 

 the force corresponds to positive yaw velocity, as the effective yaw velocity has 

 been positive throughout the whole of the integration period. 



The next quarter revolution of the mechanism is used for the hold condition, 

 activating the recording and output mechanism, and to discharge the condenser. 

 As a result, the second integration period starts at cot + (0/2) - n/i, and not at 

 cot + (4>/2) = as did the first. The polarity is reversed halfway through the inte- 

 grating period, now corresponding to cot + (0/2) = 377/2, and in this case the sine 

 and any constant components are eliminated, and the cosine component is meas- 

 ured. The final integrated value is designated IN © , as the measured force is 

 in phase with the angular displacement and corresponds to negative acceleration. 



In a similar way the third and fourth integration periods measure forces 

 corresponding to negative velocity and positive acceleration, and are designated 

 OUT (9 and IN ® respectively. The fifth integration period is the same as the 

 first, after which the cycle is repeated. 



Characteristic features of forces recorded during "pure yaw" tests are 

 illustrated in the typical records at the bottom right of Fig. 16. A margin pen, 

 activated by the mechanical microswitch once per revolution of the main shaft, 

 is used to identify the different force components and is shown symbolically on 



339 



