Synchronizing multiple steering inputs to marine rudder/steering actuators

Abstract

A steering system (,) includes an incremental helm (,), a control panel (,), and an autopilot (,) that are electrically connected to a command processor (,). The steering system further includes an autopilot attitude controller (,) and an incremental servo (,) for actuating the rudder. The incremental helm acts as a course selector for the autopilot. Upon autopilot engagement, the set heading is the current heading plus any heading change received from the helm after engagement. A course selection controller (,) employs a helm increment summer (,) and a washout filter (,) that are initialized to zero upon engagement. The washout filter follows short-term course changes but forgets them over a longer time. A disengage threshold block (,) receives the washout filter output and disengages the autopilot if the threshold is exceeded. The course selection controller allows a helmsman to make occasional course changes without automatically disengaging the autopilot unless the helmsman rotates the helm at a rate that exceeds the threshold. Upon disengagement, the autopilot is inhibited from re-engaging for a short time, after which the autopilot can re-engage when the turning rate approaches zero. The steering system further includes a helm rotation stop that provides the helmsman with rudder stop position feedback, responds to the rudder stops regardless of the current steering ratio, incorporates a powerful braking action with a low-power mechanism, and provides unidirectional braking at either rudder stop in response to a single steering limit signal.