Capacitive Cable Speed Measurement via Phase Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring the speed of traction cables in cable cars, such as chairlifts and gondolas, are not precise due to cable slippage and sensor wear, and existing solutions are not suitable for cables with non-metallic coatings or are affected by thermal expansion and tensile forces.
Innovation Solution
A device using capacitive sensors to detect the presence of markers on the cable, determining speed by calculating the phase difference between signals from two sensors located at a reference distance, which is less than the distance between markers, allowing for accurate speed measurement regardless of cable elongation or coating type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rotational speed sensors (encoder or tachometer) are used to measure cable speed, then the measurement can be implemented, but the precision is insufficient due to cable slippage and sensor wear
Solution Approach 1:
The patent replaces mechanical rotational speed sensors with capacitive sensors that detect markers on the cable. This substitution eliminates the problem of cable slippage on the pulley and sensor wear, as the capacitive sensors measure cable speed by detecting the passage of markers directly on the cable surface, providing more precise and reliable measurements
Solution Approach 2:
The patent introduces markers as an intermediary element on the cable surface. These markers serve as a reference for the capacitive sensors to detect cable position and speed. The markers act as a mediator between the cable and the sensing system, enabling accurate speed measurement without direct mechanical contact that causes wear and slippage
2Adaptability or versatility
If electrostatic charge sensors are used to measure cable speed, then speed measurement is possible, but the device is not suitable for cables with non-metallic coatings
Solution Approach 1:
The patent changes the sensing parameter from electrostatic charge detection to capacitive distance measurement. Capacitive sensors measure the distance to markers on the cable surface by detecting changes in capacitance, which works effectively with non-metallic coatings. This parameter change allows the system to adapt to different cable types while maintaining measurement precision
Solution Approach 2:
The patent replaces electrostatic charge sensors with capacitive distance sensors. This substitution enables the system to detect markers on cables with non-metallic coatings by measuring the capacitive distance to the markers, rather than relying on electrostatic charges that do not work with insulating materials
3Measurement precision
If markers are affixed on the cable surface, then speed measurement can be performed, but additional calibration steps and adjustments are required
Solution Approach 1:
The patent makes the cable itself serve the dual function of being the object to be measured and providing the markers for measurement. The cable's own construction features (strands, grooves, or helical patterns) are used as markers, eliminating the need for separate calibration procedures. The system automatically uses the cable's inherent structure as the reference, reducing device complexity and calibration requirements
4Device complexity
If a reference distance greater than or equal to the marker spacing is used, then the measurement system is simpler, but cable elongation affects measurement accuracy
Solution Approach 1:
The patent applies local quality by using a reference distance that is specifically smaller than the marker spacing. This local optimization ensures that within the measurement interval between two capacitive sensors, the cable elongation is negligible, maintaining measurement precision. The reference distance is locally adapted to be smaller than the distance between markers, compensating for cable elasticity effects
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 solution provides precise and reliable speed measurement with minimal calibration requirements, unaffected by cable elongation or non-metallic coatings, ensuring safe and reliable transportation.
Implementation Method 1
the first and second sensors are capacitive distance sensors configured to each transmit a information signal of the distance between the marks of the cable and said sensor
Data Source
Figure 1
Figure 2
AI summary
The device (1) has two sensors (7, 8) e.g. inductive distance sensors, arranged to transmit two information signals (S1, S2) relative to presence of reference marks, respectively. One of the sensors is located at a reference distance (dx) from the other sensor. A determination unit (10) determines a phase shift between the information signals and another determination unit (11) for determining speed information (V) of a traction cable (2) from determined phase shift and the reference distance. An independent claim is also included for a method for measuring speed of a traction cable of an aerial tramway.