Automatic steering apparatus and method for small watercraft

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. The heading error and yaw rate feedback signal are processed to generate a steering rate command to which the steering control loop responds by pumping hydraulic fluid at a rate proportional to the steering rate command into the hydraulic cylinder to deflect a steering actuator (38) of an outboard motor (18).

Dependencies are inferred from the claim text.