Torque Limiter Overload Detection for Servo Motor Fin Protection
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Solution Overview
Problem
Underwater vehicle navigational components, particularly fins and servo motors, are prone to damage when fins inadvertently impact obstacles, leading to instability and increased maintenance costs due to the need for frequent repairs of internal equipment.
Innovation Solution
A system incorporating a high-resolution servo motor, a torque limiter based on the ball-recess principle, and an inductive proximity sensor to detect and respond to over-torque conditions, physically disengaging the fin from the motor and alerting the CPU to control the servo motor's operation, thereby preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If stiff plastic fins are used to maintain vehicle stability and control, then vehicle stability is improved, but the likelihood of motor damage when fins impact obstacles increases
Solution Approach 1:
A torque limiter is introduced as an intermediary component between the servo motor and the fin. This torque limiter includes a driving part connected to the motor shaft, a driven part connected to the fin, and torque-limiting elements (balls and recesses) that allow the driving part to slip relative to the driven part when excessive torque is applied, thereby protecting the motor from damage while maintaining fin effectiveness
Solution Approach 2:
The torque limiter changes the torque transmission parameter dynamically. Under normal conditions, it transmits full torque for effective fin control. When impact torque exceeds the torque-limiting threshold, the balls are pushed out of their recesses, causing slippage and limiting the transmitted torque to protect the motor
2Reliability
If soft rubber fins are used to absorb impact and reduce stress on the motor, then motor damage risk is reduced, but vehicle dynamics are significantly affected making control more difficult
Solution Approach 1:
The torque limiter serves as a mechanical intermediary that provides motor protection through controlled slippage, allowing the use of stiff fins for optimal control stability. The ball-recess mechanism acts as a safety device that engages only during overload conditions, separating the protection function from the fin material selection
Solution Approach 2:
The patent replaces the soft rubber fin material approach (mechanical compliance) with a mechanical torque-limiting device. Instead of relying on fin material softness to protect the motor, a dedicated torque limiter with ball-recess elements provides precise torque control and motor protection while allowing stiff fins to maintain vehicle control stability
3Reliability
If a cage is added to protect the rudder from impacting objects, then protection is improved, but unwanted weight and drag are added requiring more power
Solution Approach 1:
The patent extracts the protection function from the fin structure itself and places it in a dedicated torque limiter component. The torque limiter is positioned inside the pressure vessel where it can protect the motor without adding external structures like cages that would increase drag and weight
Solution Approach 2:
The torque limiter acts as an internal intermediary protection mechanism that eliminates the need for external protective cages. By placing the torque limiter between the motor and fin inside the pressure vessel, protection is achieved without adding external weight or drag
4Stability of the object's composition
If fins and motors are located on opposite sides of a sealed pressure vessel with motors inside, then vehicle stability is maintained, but repairing damaged equipment becomes very time consuming and expensive
Solution Approach 1:
The torque limiter serves as a sacrificial intermediary component that protects the motor from damage. Since the torque limiter is positioned between the motor and fin, it absorbs impact forces and prevents motor damage in the first place, eliminating the need for complex repairs inside the pressure vessel
Solution Approach 2:
The torque limiter acts as a protective sacrificial component that can be replaced more easily than the motor. By positioning it at the interface between the motor and fin, it absorbs damage forces and can be serviced independently, reducing the complexity and cost of repairs compared to motor replacement
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
The system effectively protects the servo motor and fin by disconnecting them during torque overload, allowing for immediate intervention to prevent damage and maintaining vehicle stability and control.
Implementation Method 1
An inductive proximity sensor is arranged near a metal moving part of the torque limiter. The inductive proximity sensor generates an electromagnetic field that creates eddy currents in the metal moving part when it is in a first position, producing an output signal.
Implementation Method 2
The inductive proximity sensor generates an electromagnetic field that creates eddy currents in the metal moving part when it is in a first position
Data Source
AI summary
A system that includes a driving component, such as a motor, and a driven component. The system also includes a torque limiter positioned between the driving component and the driven component. The driving component is coupled to a driving end of the torque limiter and the driven component is coupled to a driven end of the torque limiter. The torque limiter is configured to assume a normal operating state with no slippage between the driving and driven ends of the torque limiter and an over-torque operating state with slippage occurring between the driving and driven ends of the torque limiter. The torque limiter includes a metal moving part that assumes a first position when the torque limiter is in the normal operating state and a second position different than the first position when the torque limiter assumes the over-torque operating state. An inductive proximity sensor monitors the position of the metal moving part.