Autopilot system

In apparatus for steering a vessel wherein steering control means is provided for maintaining said vessel on a preset heading, the improvement comprising:

• incremental encoder means operative to generate a magnitude pulse for each increment of movement and a directional signal representing the direction of movement of said vessel in a port or starboard direction away from said preset heading;
• counting means including adjustable reference position setting means for setting said counting means at a zero count corresponding to its preset heading, said counting means responsive to magnitude pulses generated to count up in succession from said zero count in response to one or more magnitude pulse in succession received either in a port or starboard direction;
• directional sensing means operative in response to each said directional signal received by said counting means to cause said counting means to add to or subtract from each preceding count;
• reference position sensing means operative in response to each magnitude pulse received, after a magitude pulse resetting said counting means to zero, to reverse the count sequence of said counting means;
• and
• means producing a correction signal in response to the magnitude and direction of each increment of movement received by said counting means to cause said steering control means to return said vessel to said preset heading.

In a closed loop autopilot system for steering a vessel and including steering control means for maintaining said vessel on a predetermined heading in which a digital compass is provided with a sensing disk operative in response to angular displacement of said vessel away from a predetermined heading to generate a signal representing a predetermined increment of movement of said vessel in a port or starboard direction away from its predetermined heading and direction logic means is operative in response to the signals received from said disk to generate a magnitude pulse for each said increment of movement together with a directional signal representing the direction of movement of said disk, the combination therewith comprising:

• an up/down counter unit including adjustable reference position setting means for setting said counter unit to zero when said vessel is maintained on said predetermined heading, said counter unit including means responsive to each magnitude pulse received from said direction logic to count up one count from zero and to generate a correctional pulse for each count, and including means for generating a zero output signal when said counter unit is returned to zero;
• a control circuit including direction sensing means producing a positive or negative signal representing the direction of movement in a port or starboard direction of each magnitude pulse received by said counter unit, said direction sensing means applying a signal to said counter unit in response to a change in the directional signal received from said direction logic means to reverse the count sequence of said counter unit;
• reference position sensing means operative in response to each said zero output signal received from said counter unit to cause a change in the directional signal applied to said direction sensing means whereby to reverse the count sequence of said counter unit independently of a change in the directional signal received by said direction sensing means from said direction logic;
• and
• means producing a correction signal in response to the magnitude and direction of each correctional pulse generated by said counting circuit whereby to cause said steering control means to return said vessel to said preset heading.