Rotating Optical Flow Sensing for Low-Speed Obstacle Distance Measurement
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Solution Overview
Problem
Existing obstacle detection systems using optical flows in aircraft, such as drones and helicopters, struggle to accurately measure distances to obstacles, especially when the aircraft is stationary or moving slowly, as they rely solely on the movement of the aircraft, making it difficult to detect nearby obstacles like rocks or walls.
Innovation Solution
A device with a rotary element and an optical flow sensor that measures optical flow radially or axially, allowing for distance calculation based on the amplitude of the optical flow, the radius of the circle, and the speed of rotation, even when the aircraft is stationary, by introducing a tangential velocity component through off-centering the sensor, which enables detection of obstacles in all directions, including frontal ones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the aircraft moves slowly or remains stationary, then energy consumption is reduced, but the ability to detect nearby obstacles using optical flow deteriorates
Solution Approach 1:
The patent applies the dynamics principle by making the optical flow sensor mobile through mounting it on a rotating element (such as a helicopter rotor blade). This transforms the sensor from a static position to a dynamic one, where the rotation of the element provides the necessary motion for optical flow measurement even when the aircraft itself is stationary or moving slowly. The sensor's movement relative to the scene enables obstacle detection without requiring the entire aircraft to be in motion.
2Device complexity
If the optical flow sensor is mounted on the axis of rotation, then the system is simple, but the sensor cannot detect obstacles on the axis of movement
Solution Approach 1:
The patent applies the asymmetry principle by positioning the optical flow sensor at an eccentric location relative to the rotation axis, specifically at a distance e from the center. This asymmetric positioning creates a non-zero radial velocity component during rotation, which generates measurable optical flow signals. The eccentric mounting breaks the symmetry that would otherwise result in zero net optical flow for an on-axis sensor, enabling the detection of obstacles including those on the axis of movement.
3Measurement precision
If the aircraft moves faster, then optical flow measurement is more accurate, but collision risk increases
Solution Approach 1:
The patent applies dynamics by using the rotation of a rotor blade or similar element to provide controlled motion for the optical flow sensor. This allows the sensor to achieve the necessary velocity for accurate optical flow measurement through its rotational movement, while the aircraft itself maintains a slower forward speed, reducing collision risk. The separation of sensor motion from aircraft translation resolves the contradiction between measurement accuracy and safety.
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 solution allows for precise detection and measurement of obstacles in various orientations, including small ones on the axis of movement, and maintains accuracy even at low speeds, enhancing safety by providing reliable distance and orientation data for navigation and collision avoidance.
Implementation Method 1
optical flow is frequently considered in drone collision avoidance systems... The optical flow in the image is thus used qualitatively or differentially
Data Source
Figure 1A~2
Figure 3~5
AI summary
The invention relates to a system for measuring the distance of an obstacle (14), in which an optical flow is radially measured in rotation around a circle (12) in a plane intersecting the obstacle; and the distance of the obstacle is determined according to the amplitude of the optical flow, the radius of the circle, and the speed of rotation.