This is the combined action of proportional, derivative and integral controls. The deviation signal has to be generated under the following conditions: –
- when the ship deviates from the set course and
- when the set course is changed.
In both these cases the ship’s heading on compass and set course signals are fed to the control unit. This unit calculates the rudder angle on the basis of PID control and the set values of rudder control, yaw control etc.
In the control unit, the Proportional control determines the rudder angle to be used, the Derivative control takes care of the counter helm to be used and the Integral control considers the effect of ship’s parameters. Additionally, there is a Filter System for action of wind and waves.
The output of Control unit is given to the Error Amplifier, which also gets feedback from rudder. On the basis of these inputs the Error Amplifier works out the order to be given to rudder via Telemotor system.