Optical Transducer Offset Compensation for Piano Hammer Position
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Solution Overview
Problem
Existing optical position transducers in automatic player pianos suffer from aged deterioration, leading to unstable incident light-to-hammer position characteristics, which affects the accurate determination of hammer motion and tone production.
Innovation Solution
A transducer system that converts analog position signals to digital signals using a gain controller and offset voltage compensation, where the potential range is adjusted to determine and correct for offset values, ensuring accurate digital signal representation of hammer motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical position transducer is used to monitor hammer motion, then the monitoring range and measurement capability are improved, but the system suffers from aged deterioration leading to unstable characteristics
Solution Approach 1:
The system uses feedback by continuously monitoring the actual hammer position and comparing it with the expected position based on music data. When deviations are detected due to aged deterioration of the optical transducer, the system automatically adjusts the monitoring parameters to compensate for the drift, thereby maintaining measurement precision over time.
Solution Approach 2:
The patent changes the operating parameters of the optical position transducer to compensate for aged deterioration. By adjusting the incident light intensity, detection sensitivity, or signal processing parameters, the system adapts to the degraded state of the transducer and maintains stable measurement characteristics throughout its service life.
2Adaptability or versatility
If the monitoring range is expanded to cover the entire hammer trajectory, then the measurement coverage is improved, but the device complexity increases
Solution Approach 1:
The monitoring range is divided into multiple segments or zones along the hammer trajectory. Instead of using a single complex transducer to cover the entire range, the system uses multiple simpler transducers or detection points that collectively monitor the complete motion path. Each segment can be independently calibrated and maintained.
Solution Approach 2:
The system transitions from monitoring only the physical position of the hammer to also monitoring the temporal and digital aspects of hammer motion. By capturing the hammer position at specific time points and representing it as digital data, the system expands its monitoring capability without adding physical complexity to the mechanical monitoring apparatus.
3Productivity
If analog position signals are converted to digital signals, then the signal processing capability is improved, but offset voltage affects the accuracy
Solution Approach 1:
The system performs preliminary calibration to determine the offset voltage before actual hammer motion monitoring begins. By pre-characterizing the offset characteristics of the analog-to-digital converter, the system can compensate for this error source during normal operation, thereby maintaining high measurement precision while benefiting from efficient digital signal processing.
Solution Approach 2:
The patent replaces purely hardware-based offset compensation methods with software-based digital signal processing techniques. Through digital filtering, calibration algorithms, and computational correction, the system eliminates offset voltage effects without requiring additional hardware components, thereby maintaining precision while improving processing efficiency.
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 eliminates the influence of aged deterioration, providing stable and accurate digital signals that accurately represent hammer motion and tone production, enhancing the fidelity of music reproduction.
Implementation Method 1
The optical position transducer includes a light emitting element and a light detecting element, and the amount of light incident on the light detecting element is varied depending upon the position of the hammer shank on the trajectory
Data Source
AI summary
An electronic system, which serves as a recorder and an automatic player, is installed in an automatic player piano, and hammer sensors, which are implemented by photo couplers, report current hammer positions through analog signals to a data processor so that the data processor analyzes pieces of hammer data for recording the performance in a set of music codes; the analog signals are amplified through an operational amplifier and, thereafter, converted to discrete values of digital hammer signals so that an offset voltage is unavoidably introduced into the analog signals; when the photo couplers vary the light-to-photocurrent converting characteristics due to the aged deterioration, the data processor takes the offset voltage into account, and calibrates the hammer sensors, thereby making the digital hammer signals correctly express the current hammer positions.