Systems and methods for controlling steering of a marine drive

Abstract

A steering system for a marine drive includes a marine drive, wherein the marine drive is steerable about a steering axis, a steering actuator configured to steer the marine drive to a range of steering positions within a permitted steering range, a first steering sensor configured to sense the steering position of the marine drive and output a first sensed value, a second steering sensor configured to sense the steering position of the marine drive and output a second sensed value and a controller. The controller is configured to calculate a measured steering position for the marine drive based on the first sensed value and the second sensed value, and control the steering actuator based on the measured steering position.

We claim: 
     
         1 . A steering system for a marine drive, the steering system comprising;
 a marine drive, wherein the marine drive is steerable about a steering axis;   a steering actuator configured to steer the marine drive to a range of steering positions within a permitted steering range;   a first steering sensor configured to sense the steering position of the marine drive and output a first sensed value;   a second steering sensor configured to sense the steering position of the marine drive and output a second sensed value;   a controller configured to:
 calculate a measured steering position for the marine drive based on the first sensed value and the second sensed value; and 
 control the steering actuator based on the measured steering position. 
   
     
     
         2 . The system of  claim 1 , wherein the measured steering position is calculated as an average of the first sensed value and the second sensed value. 
     
     
         3 . The system of  claim 1 , wherein the measured steering position is a value between the first sensed value and the second sensed value. 
     
     
         4 . The system of  claim 1 , wherein the controller is further configured to detect a fault condition if a difference between the first sensed value and the second sensed value exceeds a difference threshold, wherein the difference threshold is based on a predetermined maximum tolerated uncommanded steering change effectuated in response to the fault condition. 
     
     
         5 . The system of  claim 1 , wherein the controller is further configured to:
 in response to detecting a fault condition of the first steering sensor or the second steering sensor, redetermine the measured steering position based on only the first sensed value or the second sensed value; and   adjust the steering position of the marine drive based on the redetermined measured steering position.   
     
     
         6 . The system of  claim 5 , wherein the controller is configured such that a difference between the first sensed value and the second sensed value does not exceed a difference threshold, wherein the difference threshold is configured such that the steering position of the marine drive is not adjusted by more than a predetermined maximum tolerated uncommanded steering change in response to the fault condition. 
     
     
         7 . The system of  claim 6 , wherein the difference threshold is based on a predetermined maximum tolerated uncommanded steering change effectuated in response to a fault condition. 
     
     
         8 . The system of  claim 7 , wherein the difference threshold is two times the predetermined maximum tolerated uncommanded steering change. 
     
     
         9 . The system of  claim 7 , wherein the predetermined maximum tolerated uncommanded steering change is a  3 -degree change in steering angle. 
     
     
         10 . The system of  claim 1 , wherein the controller is further configured to:
 determine a difference between the first sensed value and the second sensed value;   compare the difference to a difference threshold; and   detect a fault condition if the difference exceeds the difference threshold.   
     
     
         11 . The system of  claim 10 , wherein the controller is further configured to disable the steering actuator in response to the detection of the fault condition. 
     
     
         12 . The system of  claim 10 , in response to the detection of the fault condition, redetermine the measured steering position based on only one of the first steering sensor or the second steering sensor, operate the steering actuator to automatically change the steering position of the marine drive based on the redetermined measured steering position, wherein the difference threshold is associated with a predetermined maximum tolerated uncommanded steering change in response to the detection of the fault condition. 
     
     
         13 . The system of  claim 1 , wherein each of the first steering sensor and the second steering sensor is a Hall Effect sensor. 
     
     
         14 . A method of controlling steering of a marine drive configured to propel a marine vessel, the method comprising:
 sensing the steering position of the marine drive with a first steering sensor to output a first sensed value;   sensing the steering position of the marine drive with a second steering sensor to output a second sensed value;   calculating a measured steering position for the marine drive based on the first sensed value and the second sensed value; and   steering the marine drive based on the measured steering position.   
     
     
         15 . The method of  claim 14 , wherein the measured steering position is calculated as an average of the first sensed value and the second sensed value. 
     
     
         16 . The method of  claim 14 , wherein the measured steering position is a value between the first sensed value and the second sensed value. 
     
     
         17 . The method of  claim 14 , further comprising detecting a fault condition if a difference between the first sensed value and the second sensed value exceeds a difference threshold, wherein the difference threshold is based on a predetermined maximum tolerated uncommanded steering change effectuated in response to the fault condition. 
     
     
         18 . The method of  claim 14 , further comprising:
 in response to detecting a fault condition of the first steering sensor or the second steering sensor, redetermining the measured steering position based on only the first sensed value or the second sensed value; and   adjusting the steering position of the marine drive based on the redetermined measured steering position.   
     
     
         19 . The method of  claim 14 , further comprising continuing to control steering of the marine drive based on the measured steering position provided that a difference between the first sensed value and the second sensed value does not exceed a difference threshold, wherein the difference threshold is based on a predetermined maximum tolerated uncommanded steering change effectuated in response to a fault condition. 
     
     
         20 . The method of  claim 19 , wherein the difference threshold is two times the predetermined maximum tolerated uncommanded steering change. 
     
     
         21 . The method of  claim 19 , wherein the predetermined maximum tolerated uncommanded steering change is a 3-degree change in steering angle.