Marine Steering Actuator Torque Couple Reduction
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Solution Overview
Problem
Existing marine steering systems face inefficiencies and reduced load-carrying capacity due to torque couples that cause overturning moments and side loads, which affect the performance and durability of electric actuators in propulsion units.
Innovation Solution
The electric actuator incorporates a roller screw assembly with a central screw and rotatable rollers, a DC brushless motor, and guide bushings to ensure axial translation of the output shaft within the housing, while a tiller extension and resilient inserts minimize side loads and provide shock absorption, ensuring the line of action remains in the same plane as the tiller axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a traditional electric actuator design is used in marine steering systems, then the structure is simpler, but torque couples cause overturning moments and side loads that reduce load-carrying capacity and performance
Solution Approach 1:
The actuator is divided into functionally independent segments: the roller screw assembly for linear motion generation, guide bushings for constraint, and a tiller extension for steering connection. This segmentation allows each component to optimize its specific function while reducing unwanted torque couples and side loads between components.
Solution Approach 2:
Guide bushings are introduced as intermediary elements between the roller screw assembly and the housing, and between the output shaft and the tiller extension. These intermediaries constrain motion paths and eliminate side loads by providing dedicated guidance, preventing unwanted lateral forces from affecting the roller screw and motor assembly.
2Reliability
If the output shaft is not fully received within the housing, then assembly is easier, but torque couples cause overturning moments that affect performance and durability
Solution Approach 1:
Instead of allowing the output shaft to extend beyond the housing for easier assembly, the design inverts the approach by fully receiving the output shaft within the housing. The tiller extension is then separately coupled to the housing, reversing the traditional arrangement and eliminating the harmful torque couples while maintaining assembly feasibility through the separate coupling interface.
Solution Approach 2:
The housing serves as an intermediary structure that fully contains the output shaft, isolating it from external moments. The tiller extension couples to the housing rather than directly to the output shaft, creating a decoupled arrangement where the housing absorbs and redirects forces, protecting the internal components from overturning moments.
3Productivity
If side loads are not minimized, then the structure is simpler, but load-carrying capacity and efficiency are reduced
Solution Approach 1:
Guide bushings act as intermediary elements that specifically address side load minimization. These bushings are positioned to provide guidance in directions perpendicular to the primary motion, intercepting and redirecting side loads before they can affect the roller screw assembly or motor, thereby protecting these critical components from damaging lateral forces.
Solution Approach 2:
The guide bushings provide localized guidance and support at specific critical points within the actuator structure. Rather than requiring the entire structure to be overly robust to handle side loads, the guide bushings concentrate the load-management function at precise locations where side loads occur, allowing the rest of the structure to remain efficient and lightweight.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the efficiency and load-carrying capacity of the electric actuator by reducing torque couples and side loads, improving the overall performance and durability of the marine steering system.
Implementation Method 1
The roller screw assembly includes a plurality of rollers and a central screw received by the rollers. The rollers are rotatable about the central screw and the central screw is coupled to the output shaft.
Implementation Method 2
There may be a guide bushing disposed within the housing near the motor. The guide bushing may reciprocatingly receiving the output shaft.
Data Source
AI summary
The propulsion unit comprises an electric actuator and a tiller coupled the electric actuator. The electric actuator includes a housing having a first end and second end. There is an output shaft fully received within the housing. The output shaft includes a coupling portion and a tiller is coupled the coupling portion of the output shaft such that such that a line of action of the actuator is in the same plane as the tiller.