Multicopter Altitude Estimation Using Differential Pressure Ground Effect
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Solution Overview
Problem
Current altitude estimation techniques for multicopters, such as vision and wave-based methods, are inadequate for vertical takeoff and landing (VTOL) operations due to their inability to sense ground effect and are often heavy and expensive, making them unsuitable for lightweight and resource-constrained VTOL multicopters.
Innovation Solution
The use of differential pressure sensors and a generalized flow model, combined with a non-linear filter, to estimate altitude by distinguishing between rotor interference and ground effect, allowing for accurate altitude measurement even in complex airflow conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vision or wave-based altitude estimation techniques are used, then altitude measurement is provided, but the system becomes heavy and expensive, and cannot sense ground effect
Solution Approach 1:
The patent replaces vision-based and wave-based sensing systems with a mechanical/differential pressure sensing approach. The differential pressure sensor measures pressure differences caused by rotor airflow and ground effect, providing altitude estimation without requiring heavy optical or electromagnetic sensing equipment. This substitution achieves lightweight altitude measurement while maintaining measurement capability.
Solution Approach 2:
The system uses the multicopter's own rotor airflow as the sensing mechanism. The differential pressure sensor exploits the pressure field naturally generated by the rotors during flight, particularly the ground effect when operating near the ground. This self-service approach eliminates the need for external sensing systems, reducing weight and cost while enabling ground effect detection.
2Measurement precision
If vision or wave-based altitude estimation techniques are used, then altitude measurement is provided, but the system cannot detect ground effect and becomes unsuitable for VTOL operations
Solution Approach 1:
The patent employs pneumatic sensing through differential pressure sensors that measure pressure differences in the airflow field. The sensor detects changes in static pressure caused by ground effect when the multicopter operates near the ground during VTOL operations. This pneumatic approach directly senses the aerodynamic phenomenon, providing reliable ground effect detection that optical or wave-based systems cannot achieve.
3Weight of moving object
If differential pressure sensors are used to estimate altitude, then the system becomes lightweight and can sense ground effect, but the measurement is affected by complex airflow interactions
Solution Approach 1:
The patent segments the pressure measurement into two components: static pressure and dynamic pressure. The differential pressure sensor measures the total pressure, which is then separated into static pressure (related to altitude) and dynamic pressure (related to rotor airflow velocity). This segmentation allows the system to compensate for rotor interference effects and extract accurate altitude information even in complex airflow conditions.
Solution Approach 2:
The system uses feedback from the differential pressure measurements to continuously estimate and compensate for rotor interference effects. By monitoring the pressure differential and comparing it with expected values based on rotor speed and position, the system can adjust its altitude estimation to account for complex airflow interactions, maintaining measurement accuracy despite the challenging environment.
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 provides accurate and lightweight altitude estimation for VTOL multicopters, effectively handling ground effect and complex airflow interactions, enhancing safety and operational efficiency by enabling precise control during vertical landings and takeoffs.
Implementation Method 1
a sensor dataset from a differential pressure sensor that is associated with a pressure difference between a first point in the rotor airflow and a second point in the rotor airflow
Data Source
AI summary
A plurality of sensor datasets is received including: (1) an interference sensor dataset which is associated with interference between airflow from a first rotor in a multicopter and airflow from a second rotor in the multicopter, (2) a first and a second isolated sensor dataset which are associated with isolated airflows from the first rotor and the second rotor, respectively. A generalized flow model associated with a generalized rotor is received and an altitude for the multicopter is generated based at least in part on the plurality of sensor datasets and the generalized flow model, including by using a non-linear filter that builds a consolidated probability function associated with altitude that reconciles the plurality of sensor datasets with the generalized flow model.