Bow Thruster and Stern Propulsion Control for Hull Position and Azimuth
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Solution Overview
Problem
Existing watercraft propulsion systems struggle to precisely maintain the position and azimuth of the hull, particularly failing to effectively address lateral positional offsets and azimuthal offsets, as they often rely solely on bow thrusters or propulsive forces without optimal mode switching conditions.
Innovation Solution
A watercraft propulsion system that utilizes a combination of bow thrusters and propulsion devices on the stern, with mode switching based on predetermined conditions, allowing for precise position and azimuth maintenance by allocating functions between the bow thruster and stern propulsion devices, including translation and bow turning modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the bow thruster alone is used to eliminate azimuthal offset, then the system is simple, but the precision of azimuth control is insufficient
Solution Approach 1:
The patent combines the bow thruster and stern propulsion device into a coordinated control system. The bow thruster handles azimuthal offset elimination while the stern propulsion device handles positional offset elimination, merging their functions to achieve both simplicity and precision.
Solution Approach 2:
The control function is segmented between two propulsion devices: the bow thruster is dedicated to azimuth control while the stern propulsion device handles position control. This segmentation allows each device to specialize in one function, improving overall precision without excessive complexity.
2Adaptability or versatility
If the propulsive force of stern propulsion device is shared to adjust hull azimuth, then azimuth control is possible, but the precision of position adjustment deteriorates
Solution Approach 1:
The patent segments the control functions by dedicating the bow thruster to azimuth control and the stern propulsion device to position control. This prevents the stern propulsion device from being used for azimuth adjustment, thereby maintaining high position adjustment precision while still providing azimuth control capability through the bow thruster.
3Speed
If bow turning mode is used to adjust azimuth when significantly offset, then azimuth adjustment speed increases, but position stability deteriorates
Solution Approach 1:
The patent implements feedback control by continuously monitoring both azimuthal and positional offsets. When azimuth offset exceeds a threshold, the system switches to bow turning mode for rapid azimuth correction. The stern propulsion device simultaneously compensates for position drift caused by this mode switch, maintaining position stability through coordinated feedback from both sensors.
Data Source
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AI summary
A watercraft propulsion system (100) includes a bow thruster (BT) to generate a lateral propulsive force, a propulsion device (OM) on a stern (3) of a hull (2) and having a variable steering angle, and a controller (50) configured or programmed to control the bow thruster (BT) and the propulsion device (OM) to perform a fixed point holding control to maintain a position and an azimuth of the hull (2). The fixed point holding control includes a translation mode in which the hull position is maintained by controlling the propulsive force of the propulsion device (OM) with the steering angle set to a translation mode steering angle and the hull azimuth is adjusted by controlling the propulsive force of the bow thruster (BT), and a bow turning mode in which the hull azimuth is adjusted by controlling the propulsive forces of the bow thruster (BT) and the propulsion device (OM) with the steering angle set to a bow turning mode steering angle.