Linear Actuator Piston Position Sensing Using TOF Phase Difference
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Solution Overview
Problem
Existing linear actuators face challenges in accurately determining the absolute position of a piston due to limitations in reliability and cost-effectiveness of current position sensing methods, such as limit switches, resistive sensors, inductive sensors, and magnetic sensors, which can be affected by PVT variations and have size and cost constraints.
Innovation Solution
A linear actuator system that utilizes a time-of-flight (TOF) method by generating an electromagnetic waveform with a frequency corresponding to the maximum displacement of the piston, allowing for position determination based on the phase difference between the transmitted and received waveforms, providing a flexible, stable, and accurate method for piston position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional position sensing methods (limit switches, resistive sensors, inductive sensors, magnetic sensors) are used, then position detection is achieved, but reliability is reduced due to PVT variations and size/cost constraints
Solution Approach 1:
The patent replaces traditional mechanical and electromagnetic position sensing methods with an optical time-of-flight measurement system. The system uses a light source to emit light signals that travel along the piston, with detectors measuring the time for light to traverse the piston length. This optical substitution eliminates susceptibility to PVT variations affecting electrical sensors while maintaining high measurement precision through optical path length measurements.
Solution Approach 2:
The patent changes the measurement parameter from electrical field interactions (in traditional sensors) to optical path time measurement. By measuring the time of flight of light signals through the piston material, the system achieves position detection that is independent of electrical PVT variations. The refractive index of the piston material serves as a stable optical parameter for precise measurement.
2Reliability
If traditional sensors are used, then position detection is possible, but device size and cost increase
Solution Approach 1:
The patent makes the piston serve multiple functions: it acts as both the mechanical component providing linear motion and as the optical medium through which position is measured. The piston's transparent or translucent property allows it to function as both a mechanical element and an optical waveguide, eliminating the need for separate sensor components and reducing overall device complexity.
Solution Approach 2:
The patent merges the position sensing function with the piston structure itself. By embedding the optical measurement capability within the piston material (using its refractive properties), the system combines mechanical motion provision and position measurement into a single integrated component, reducing device complexity and cost.
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 enables reliable and cost-effective absolute position determination of the piston, offering flexibility, stability, and high accuracy in position sensing, capable of rapid updates and continuous monitoring, suitable for applications like automobile suspension systems.
Implementation Method 1
The transmitter is configured to generate a transmit electromagnetic waveform and direct the transmit electromagnetic waveform along a length of the piston
Implementation Method 2
determine a position of the piston based on a phase difference between the transmit electromagnetic waveform and the return electromagnetic waveform
Data Source
AI summary
A linear actuator includes a piston, a transmitter, and a receiver. The piston is configured to linearly extend and retract (such as within a cover tube). The transmitter is configured to generate a transmit electromagnetic waveform and direct the transmit electromagnetic waveform along a length of the piston. The receiver is configured to receive a return electromagnetic waveform that includes the transmit electromagnetic waveform after travelling to an extended end of the piston and returning to the receiver and determine a position of the piston based on a phase difference between the transmit electromagnetic waveform and the return electromagnetic waveform.