Profiled Target Sensing for Lightweight Propeller Blade Pitch Measurement

The patent replaces complex mechanical position sensors (RVDT or LVDT) with a simplified optical sensing system. A target portion with a coded pattern (e.g., reflective or absorptive regions) is coupled to the pitch actuator, and an optical sensor detects the pattern to determine pitch position. This substitution eliminates heavy mechanical components while maintaining measurement accuracy through optical detection of the coded pattern's position or orientation.

The patent uses a coded pattern on the target portion that encodes pitch position information. Instead of directly measuring physical displacement with complex sensors, the system captures an optical image or signal representing the coded pattern and decodes it to determine pitch angle. This copying approach converts mechanical position information into an optical signal that can be processed electronically, reducing mechanical complexity.

The sensing system is designed to be self-calibrating or self-configuring. The coded pattern on the target portion provides reference features that enable the sensor to automatically determine its own position and orientation relative to the pitch mechanism. This eliminates the need for external calibration equipment and procedures at aircraft level, allowing the system to be calibrated during manufacturing or initial setup and then operate autonomously throughout its service life.

The calibration and configuration of the sensing system is performed in advance during manufacturing or system assembly, rather than requiring field calibration. The coded pattern is pre-configured with known geometric features, and the sensor is pre-aligned with reference markers. This preliminary setup ensures the system is ready for immediate safe operation upon installation, optimizing dispatchability.

The patent changes the measurement parameter from direct mechanical displacement to optical detection of a coded pattern. The target portion includes regions with different optical properties (reflective, absorptive, transparent) arranged in a coded pattern. The optical sensor detects these optical parameter variations to determine pitch position, enabling lightweight construction while maintaining reliability through robust optical signal detection and error-correcting code design.

The sensing system incorporates redundancy and error tolerance in its design. The coded pattern uses error-correcting codes or redundant encoding schemes that can tolerate some signal degradation or sensor errors. Multiple sensor elements or multiple readings can be averaged or cross-checked. This beforehand cushioning against potential failures ensures reliable operation even with lightweight, less robust components.