AC Servo Motor Load Balancing in Marine Turning Control
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Solution Overview
Problem
Existing marine propulsion systems with hydraulic turning apparatuses are complex, prone to oil leakage, and maintenance issues, while electric systems with AC servo motors face load imbalance and potential loss of control if any motor fails.
Innovation Solution
An electric turning control unit with multiple AC servo motors that share loads equally by calculating and correcting motor speed commands based on load amounts, ensuring stable operation even if one motor fails, using digital communications and load calculating means within each AC servo amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic turning apparatus is used, then turning function is achieved, but structure becomes complicated and maintenance becomes difficult
Solution Approach 1:
The patent replaces the hydraulic turning apparatus with an electric turning apparatus. Specifically, hydraulic motors and complex hydraulic piping are substituted with AC servo motors and a simplified mechanical transmission system consisting of pinions and a traversing gear, thereby eliminating hydraulic fluid requirements and reducing structural complexity while maintaining reliable turning control functionality
Solution Approach 2:
The patent extracts and removes the hydraulic system components (hydraulic pump, servo valve, suction filter, oil tank, and piping) from the turning apparatus, replacing them with an electric motor system. This extraction eliminates the sources of hydraulic fouling and leakage while simplifying the overall system structure and maintenance requirements
2Reliability
If multiple AC servo motors are used for turning, then control redundancy is improved, but load imbalance occurs causing loss of control
Solution Approach 1:
The patent implements a feedback mechanism where the turning control board calculates motor speed commands based on the deviation between handle signal and feedback signal from sensors. The system continuously monitors motor positions and adjusts speed commands to ensure balanced load distribution among multiple AC servo motors, preventing any single motor from being overloaded while maintaining control redundancy
Solution Approach 2:
The patent employs dynamic load sharing through independent speed control of each AC servo motor. The turning control board dynamically adjusts the speed commands for each motor based on real-time feedback, allowing the system to adapt to varying load conditions and external water forces, ensuring that load is evenly distributed across all motors during operation
Data Source
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AI summary
To allow plural AC servo motors of an electric turning control unit to share load equally. A turning control unit 2 for controlling a freely turnable marine propulsion machine includes: a turning control board 7 which calculates a digital motor-speed reading from a deviation between a signal from a sensor 6 for detecting a turning position of the marine propulsion machine and a handle signal; and a plurality of AC servo amplifiers A1, A2 which drive AC servo motors M1, M2 by receiving the motor-speed reading from the turning control board and outputting a motor speed command value. Each amplifier is adapted to reduce the motor speed command value according to a load amount when the motor performs power running, to increase the motor speed command value according to the load amount when the motor performs regenerative running, and to make no correction when the load amount of the motor is equal to or less than a fixed value. The respective loads on the plural AC servo motors can be dispersed to a uniform value.