Marine autopilot system

Claim 1

A marine autopilot system comprising, a first transducer for producing an electrical signal corresponding to the deviation of a ship''s heading from a set course; a first means for producing an electrical signal corresponding to a rudder order receiving the output of said first transducer; a servo loop including a servo amplifier and a relay-like operation device for producing a rudder command receiving the electrical signal from said first means; a means provided in said relay-like operation device for making its off-voltage substantially zero and its on-voltage substantially equal to its hysteresis voltage, and an adjusting means provided in said servo amplifier for adjusting its gain, whereby the voltage of said signal applied to said servo loop which makes said relay-like operation device turn on, can be changed in accordance with a gain determined by said adjusting means and the voltage of said signal applied to said servo loop, which makes said relay-like operation device turn off, is kept at substantially zero irrespective of said adjusted gain, said relay-like operation device including a first operational amplifier and a circuit connected between the negative input terminal and the output terminal of said first operational amplifier for achieving relay-like operation, said means provided in said relay-like operation devIce being provided in a positive feedback circuit of said first operational amplifier for making off-voltage substantially zero, said servo amplifier including a second operational amplifier and said adjusting means connected in a negative feedback circuit of said second operational amplifier, said negative feedback circuit including a variable resistor and a feedback resistor and said variable resistor serving as a weather adjustment device.