Carrier Synchronous Signal Averaging for Trending Casing Crack Propagation in Planetary Gearbox

Area of Science:

• Mechanical Engineering
• Vibration Analysis
• Structural Health Monitoring

Background:

• Cracks in planetary gearbox casings produce distinct vibration responses.
• These vibrations offer potential for monitoring structural degradation.
• Existing methods may lack sensitivity or reliability in detecting casing cracks.

Purpose of the Study:

• To develop and validate a signal processing framework for tracking crack-related features in planetary gearbox casings.
• To utilize the carrier synchronous signal average (C-SSA) for enhanced crack detection.
• To establish a reliable health condition indicator for monitoring crack propagation.

Main Methods:

• Processing the hunting-tooth synchronous signal average (H-SSA) to extract the C-SSA.
• Calculating the root mean square (RMS) of the C-SSA as a health condition indicator.
• Applying the Hilbert transform (HT) to derive a squared envelope signal for enhanced trending.
• Employing singular spectrum analysis technique (SSAT) to remove temperature influences and isolate damage progression.

Main Results:

• The C-SSA signal effectively captures the cyclic interaction between gear loading and casing response.
• The RMS of C-SSA and its squared envelope signal demonstrate good capability in tracking crack progression.
• Consistent performance was observed across different load levels (100%, 125%, 150%), with improved results at higher loads.
• Experiments with three casing-mounted sensors validated the method's effectiveness.

Conclusions:

• The proposed C-SSA framework significantly enhances the sensitivity and reliability of vibration-based casing crack detection.
• The method provides a practical tool for long-term structural health monitoring of planetary gearboxes.
• The squared envelope of C-SSA further improves trending capabilities for damage assessment.