Marine Steering Actuator Control for Backlash and Torque Holding
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Solution Overview
Problem
Existing marine steering systems face challenges in accurately controlling steering movements, particularly in compensating for backlash and managing back driving torque, while also ensuring efficient power usage and preventing engine collisions.
Innovation Solution
The proposed solution involves an electric actuator with a motor and sensors that calibrate and compensate for backlash, utilize PWM to manage back driving torque, and implement a three-zone current limiting scheme to optimize power usage, along with a steering control unit that coordinates the actuation of multiple propulsion units to prevent collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If an electric actuator is used for marine steering, then steering automation is improved, but backlash compensation difficulty increases
Solution Approach 1:
The patent implements feedback mechanisms using absolute position sensors and relative position sensors to continuously monitor steering position and motor position. The control unit processes sensor signals to detect backlash conditions and automatically compensates by adjusting motor commands, creating a closed-loop system that eliminates manual intervention for backlash compensation.
Solution Approach 2:
The patent replaces mechanical backlash compensation mechanisms with electronic control systems. Instead of using mechanical pre-loading or anti-backlash gears, the system uses software algorithms that calculate and compensate for backlash based on sensor data, direction of movement, and predefined backlash parameters stored in memory.
2Measurement precision
If holding torque is increased to counter back driving torque, then position holding accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent implements dynamic holding torque adjustment where the motor controller continuously adapts the holding torque based on real-time conditions. The system monitors back driving torque magnitude and adjusts the holding torque accordingly, rather than maintaining a constant high torque level. This dynamic adjustment maintains position accuracy while minimizing energy consumption during different operating conditions.
Solution Approach 2:
The system changes operational parameters by adjusting PWM duty cycles and motor current levels to optimize holding torque. The controller modifies electrical parameters (voltage, current, frequency) based on feedback from position sensors and torque measurements, allowing the motor to maintain precise position holding with variable energy input rather than constant maximum power.
3Reliability
If multiple sensors are used for position sensing, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes the control unit multi-functional by integrating absolute position sensing, relative position sensing, backlash compensation, torque control, and fault detection all within a single control unit. This universal approach allows multiple sensors to be coordinated through one centralized controller, improving reliability through redundancy while managing complexity through integrated processing rather than separate control circuits for each function.
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 solution enhances the accuracy and reliability of steering control, optimizes power consumption, and prevents engine collisions by effectively compensating for backlash and managing torque, ensuring safe and efficient operation of marine vessels.
Implementation Method 1
The motor has a rotor and a stator. The rotor has a magnetic field and the stator has a magnetic field. Rotation of the rotor causes the output shaft to translate axially relative to the rotor and causes the output shaft to reciprocate relative to the housing.
Implementation Method 2
There is a sensor for sensing a position of the rotor.
Implementation Method 3
The steering control unit energizes the stator to align the magnetic field of the stator with the magnetic field of the rotor based on a position of the rotor sensed by the sensor for sensing the position of the rotor.
Data Source
AI summary
An actuator for imparting steering movement to a tiller of a propulsion unit of a marine vessel comprises an absolute position sensor which senses a steering position and a relative position sensor which senses a position of the motor. A steering control unit calibrates the relative position sensor based on a signal of the absolute position sensor. Calibration of the relative position sensor based on a signal of the absolute position sensor initializes an accumulative position which accumulates a relative position as the actuator moves over time.