Ratiometric Acoustic Position Sensing Without Sound Speed Sensors
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Solution Overview
Problem
Existing ultrasonic position sensors in fluid control systems require knowledge of the speed of sound in the medium, which varies with temperature and fuel type, adding complexity, size, and cost, especially in applications like fuel valves and pressure regulators.
Innovation Solution
A position sensor system that emits acoustic waveforms towards both ends of a moveable body within a fluid effector, determining position without needing to know the speed of sound by calculating the time of flight and phase differences of the waveforms, allowing for ratiometric position measurement independent of sound speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing time of flight ultrasonic position sensors are used to measure position, then position detection is achieved, but the system complexity, size, cost, and weight increase due to the need for additional sensors to determine sound speed
Solution Approach 1:
The patent extracts and eliminates the need for separate sound speed sensing components from the ultrasonic position measurement system. By using a differential measurement approach that compares waveforms traveling through the same medium over different distances, the system removes the requirement for additional temperature or sound speed sensors, thereby reducing system complexity while maintaining position detection accuracy
Solution Approach 2:
The patent introduces an intermediary reference measurement path. A second ultrasonic waveform is transmitted through the same medium (fluid or gas) as the primary measurement path, serving as a reference that allows the system to calculate the speed of sound in the medium without requiring separate sensors. This intermediary measurement enables accurate position detection while avoiding additional hardware
2Measurement precision
If existing time of flight ultrasonic position sensors are used to measure position, then position detection is achieved, but the system size and weight increase due to additional sensors
Solution Approach 1:
The patent removes the need for separate sound speed or temperature sensors from the system. By implementing a differential ultrasonic measurement technique where a reference waveform travels through the same medium as the measurement waveform, the system achieves accurate position detection without additional sensing components, thereby reducing overall system weight
3Measurement precision
If LVDTs are installed through the piston rod for position tracking, then position measurement is achieved, but actuator sizing is constrained
Solution Approach 1:
The patent replaces the mechanical LVDT system with an ultrasonic acoustic field-based measurement system. Instead of installing a mechanical transformer through the piston rod that constrains actuator design, the system uses ultrasonic wave transmission through the fluid or gas medium to measure position, freeing the mechanical design from LVDT installation requirements while maintaining measurement accuracy
Solution Approach 2:
The ultrasonic transceiver serves multiple functions: it acts as both the actuator driver and the position sensor. The same device that controls the fluid effector also measures its position through ultrasonic time-of-flight measurements, eliminating the need for separate measurement components and providing design flexibility
4Measurement precision
If additional sensors are added to determine sound speed in the medium, then measurement accuracy is maintained, but system cost increases
Solution Approach 1:
The patent extracts and eliminates the need for separate sound speed or temperature sensing components. By using a differential measurement approach where a reference ultrasonic waveform travels through the same medium as the primary measurement, the system calculates sound speed from the reference measurement itself, removing the need for additional sensors and reducing system cost
Solution Approach 2:
The system uses its own reference ultrasonic measurement path to determine the sound speed in the medium. The reference waveform measurement serves the dual purpose of being a timing reference and providing the data needed to calculate sound speed, allowing the system to be self-sufficient without external or additional sensors
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 approach simplifies system design, reduces size and weight, and improves measurement accuracy by eliminating the need for additional sensors to determine sound speed, while maintaining precise position and speed measurement of moveable components.
Implementation Method 1
an acoustic receiver system configured to detect a first reflected acoustic waveform based on a first reflection of the first emitted acoustic waveform based on the first face, and detect a second reflected acoustic waveform based on a second reflection of the second emitted acoustic waveform based on the second face
Implementation Method 2
determine a first time of flight of the first emitted acoustic waveform and the first reflected acoustic waveform, and determine a second time of flight of the second emitted acoustic waveform and the second reflected acoustic waveform
Data Source
AI summary
The subject matter of this specification can be embodied in, among other things, a position sensor system that includes a sensor housing defining a first cavity having a first face, a fluid effector including an actuator housing having an inner surface defining a second cavity, and a moveable body having a second face and configured for reciprocal movement within the second cavity, an acoustic transmitter system configured to emit a first emitted acoustic waveform toward the first face, and emit a second emitted acoustic waveform toward the second face, and an acoustic receiver system configured to detect a first reflected acoustic waveform based on a first reflection of the first emitted acoustic waveform based on the first face, and detect a second reflected acoustic waveform based on a second reflection of the second emitted acoustic waveform based on the second face.