Simrad ROBERTSON AP45 manual RF45X principle

Robertson AP45 Autopilot	Page 3-3
Design and theory of operation

Rudder Feedback Units

RF45X Rudder Feedback Unit

RF14XU Rudder Feedback Unit (optional)

The rudder feedback unit transmits rudder angle information to the control unit and rudder angle indicators. It is mounted close to the rudder stock and mechanically connected to the rudder tiller arm by a transmission link.

The RF45X contains a circular PCB carrying all the electronics and a long life potentiometer connected to the PCB by three wires. The unit is repairable in that the electronics and the potentiometer can be replaced.

The electronics have two output circuits. One circuit outputs frequency of 3400Hz as midposition reference. It varies at a rate of 20Hz/degree, increasing when the rudder moves to port and vice versa.

The other circuit outputs a current (0.1-1.1mA), to the rudder angel indicator(s) (RI35 and RI9).

The RF45X is supplied with a fixed 4-wire, screened cable of 2 m (6 ft.). This cable is meant to be spliced in the enclosed splash-proof junction box.

The shaft of the feedback unit is free to travel 360 degrees, but only ± 70 degrees from midposition are used for signal control.

The transmission link mechanically connects the feedback unit to the rudder tiller arm. It is made of stainless steel and has standard length of 450 mm.

Fig. 3-4

RF45X principle

The RF14XU Rudder Feedback Unit consists of a glass-reinforced fire inhibiting polyester housing with a mounting plate of seawater resistant aluminium. Potentiometer, limit switches and an electronic drive module are also contained in the unit. The electronic drive module comprises a voltage section and a frequency section.

The voltage section outputs a voltage to the rudder angle indicator(s) which is proportional to the rudder angle. The voltage varies ±9V with half of the supply voltage as reference. The voltage should read zero volts with the rudder in midposition.

The frequency section outputs a signal to the control unit with 3400 Hz as midposition reference. It varies at a rate of 20 Hz/degree, increasing when the rudder moves to port and vice versa.

The shaft of the Feedback Unit is free to travel 360 degrees, but only ±90 degrees from midposition are used for signal control.

Simrad Robertson AS

Egersund - Norway