Sensorless Mooring Winch Torque Control
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Solution Overview
Problem
Existing mooring winch systems face challenges in maintaining optimal mooring rope tension due to variations in water levels, cargo loading, and wave-induced forces, which can lead to hazardous situations as they are susceptible to hard weather conditions and lack efficient tension control mechanisms.
Innovation Solution
A mooring winch system incorporating an alternating current motor, a frequency conversion unit, and a control unit that computes a torque estimate based on stator flux and currents to indicate rope tension, allowing for sensorless vector control and maintaining tension within safe limits without the need for force sensors or speed indicators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force sensor and/or speed indicator is provided to measure mooring rope tension, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical measurement devices (force sensors and speed indicators) with an electrical parameter-based measurement system. The control unit calculates torque estimate based on electrical parameters (stator flux space vector and stator currents space vector) from the alternating current motor, thereby inferring mooring rope tension without direct mechanical sensing. This substitution eliminates the need for additional mechanical sensors and indicators while maintaining measurement capability.
2Reliability
If hard weather conditions are endured with conventional speed indicators, then reliability deteriorates, but device complexity must be increased to protect against environmental factors
Solution Approach 1:
The patent replaces the mechanical speed indicator with an electrical parameter-based control system. The control unit uses electrical parameters (stator flux and stator currents) that are inherently insensitive to hard weather conditions such as salt spray, moisture, and temperature extremes. This eliminates the reliability issues associated with mechanical indicators in harsh marine environments without requiring additional protection mechanisms.
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 effectively maintains mooring rope tension within safe limits, preventing rope failure and ensuring safety by continuously monitoring and adjusting the torque to counteract fluctuating forces, thus enhancing operational safety and reducing the risk of damage.
Implementation Method 1
an alternating current motor arranged to drive the winding drum
Implementation Method 2
a frequency conversion unit arranged to supply electrical power to the alternating current motor
Data Source
AI summary
An electrically driven mooring includes a winding drum (101), an alternating current motor (103) arranged to drive the winding drum, a frequency conversion unit (104) connected to the alternating current motor, and a control unit (105) arranged to control the frequency conversion unit on the basis of an indicator for tension of the mooring rope. The control unit is arranged to compute a flux space vector for modelling a stator flux of the alternating current motor, to compute a torque estimate on the basis of the flux space vector and a space vector of stator currents, and to use the torque estimate as the indicator for the tension of the mooring rope. Hence, a need for a force sensor on the mooring rope and a need for a speed/position sensor on the motor shaft can be avoided.