Abstract: A steering system (100) includes an incremental helm (102), a control panel (104), and an autopilot (106) that are electrically connected to a command processor (108). The steering system further includes an autopilot attitude controller (110) and an incremental servo (112) 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 (120) employs a helm increment summer (122) and a washout filter (124) 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 (126) receives the washout filter output and disengages the autopilot if the threshold is exceeded.

Abstract: An automatic steering system (10) has a control subsystem (14) that employs a yaw rate control loop (90) and a steering control loop (92) to drive a hydraulic subsystem (12) in which the deflection rate of a steering actuator (16) is controlled without need for either a steering actuator angle sensor or an electronic steering bias integrator. Rather, the control subsystem employs a proportional rate servosystem to control the steering actuator deflection rate and a double-acting hydraulic cylinder (34) to provide the steering bias integral action. The control subsystem employs an electric compass (96) to generate heading data that are stored in a heading command register (102). An heading error is formed by calculating a difference between a desired heading and the current heading. A rate taker (94) generates a yaw rate feedback signal by differentiating changes in the current heading, or alternatively, a rate sensor (302) generates the yaw rate feedback signal directly.