TMQ AP4 Autopilot (AP4S10) 53 of 62 Version 4.96 9/10/2017
Adjusting the PID Control
Keeping the Heading
PID stands for Proportion, Integral and Derivative, which are the three
calculated values that the sums results in the control law value. This value is the
position to where the Rudder must be driven. Following it is described how
each of these values contributes to the control of the vessel.
Proportional value:
The bigger the error from the desired direction from the current
direction of the vessel, the bigger is this value. It provides more
responsiveness when the boat is too far from its desired direction.
However, this proportional value may be not enough when the vessel's
direction is being disturbed by some force that takes it from its route
(unbalanced load, wind, tide currents, etc.).
In the autopilot, the gain (contribution) of this value is adjusted with the
rudder ratio.
Integral value:
This portion of the control value integrates the error, adding an offset
on the rudder position, for compensating the forces and disturbances
that the proportional control value can't cope. It is intended to keep the
direction inside the dead band.
The adjustment of the gain for this parameter was explained in the
section “AP4 Special Modes” (display selection 918);
Derivative value:
After setting the proportional value for getting the desired
responsiveness, it may be experienced some overshoot (“hunting”).
Than, the value of the derivative has to be increased until there is no
more overshoot.
This value controls the speed of the movement, especially near to the
desired direction. It will have no effect when the vessel is not turning,
and will oppose the to the turn movement when it happens.
The adjustment of the gain for this parameter is explained in the section
“AP4 Special Modes” (display selection 919).
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