Patent Application
20200065553
The present invention relates generally to remote sensing, more particularly, to a remote sensing architecture that utilizes a fleet of drones, or UAVs, each of which carries one or more sensors, to create sparse sampling measurement matrices for a compressed sensing system.
Remote sensing is most effective for detecting substances in a large area and is used in numerous fields such as defense, natural resource exploration, agriculture and environmental protection.
In remote sensing systems, various types of sensors are used for a variety of applications in the area of detecting, ranging, mapping, topography and geological survey. Chemical sensors used to detect chemical substances, gases such as carbon dioxide and methane. Physical sensors detect physical parameters such as distance, speed, acceleration, pressure, density and temperature. Optical sensors detect optical properties, such as reflection, interference, imaging, and spectral characteristics.
In the area of remote sensing, the development of hyperspectral imaging has emerged as a very promising technology. Hyperspectral cameras deployed in airborne or satellite systems can cover the visible and near-infrared wavelengths to provide a wide array of spectral information for numerous applications. Different acquisition techniques for hyperspectral imaging allow data to be visualized as sections of the hyperspectral data cube with its two spatial dimensions (x, y) and one sensor dimension (lambda). There are four basic techniques for acquiring this multi-dimensional (x, y, and lambda) dataset of the data cube: spatial scanning, spectral scanning, non-scanning and spatial-spectral scanning. Various remote sensing methods and apparatuses are used to detect physical, chemical, thermal, spectral, and biological properties of the objects as stated above. There are two basic scanner designs for remote sensing. A “whisk-broom” scanner uses an oscillating mirror to scan terrain reflectance along scan lines perpendicular to the sensor's flight line. The second design is a “push-broom” scanner that uses a linear array of sensor elements to simultaneously record reflectance at uniform intervals along the scan line. No matter what acquisition technique is employed and what property of the target is to be explored, due to extremely large volume of data received during processing, compression in data acquisition has become a critical factor in obtaining satisfactory measurements.
Compressed sensing is a signal processing technique for efficiently acquiring and reconstructing a signal. For convenience of illustration, the abbreviation “CS” will be used to identify “Compressed sensing” in the description hereafter. This is based on the principle that, through optimization, the sparsity of a signal can be exploited to recover it from far fewer samples than required by the Shannon-Nyquist sampling theorem. Theoretically, there are two conditions under which recovery is possible. The first one is sparsity which requires the signal to be sparse in some domain. The second is incoherence which is applied through the isometric property which is sufficient for sparse signals. CS has attracted considerable attention and now has been successfully used in various applications. In the area of remote sensing, CS is one of the most common data compression approaches to exploiting signal's sparsity to substantially reduce the data file size and to obtain faster overall results.
One of the most notable and widely recognized achievements of CS is a single-pixel camera designed by Rice University, which is a new type of camera architecture based on a digital micro mirror device (DMD) and a single detector element. The DMD includes a two-dimensional array of programmable micro mirrors, each of which is configured to independently and controllably switch between two orientation states. With help of DMD, the camera can scan an image with much fewer measurements than a pixel-by-pixel scanning system to drastically reduce data size, saving processing time and yielding system performance.
In recent years, autonomous drones, a type of Unmanned Aerial Vehicle (UAV), have been developed with explosive growth and have captured the global market attention. The amazing versatility of drones, achieved by its multiple flight modes and patterns, and affordability, achieved by its dramatic price drop trend in recent and upcoming years, has attracted many developers to explore potential drone applications. The number of emerging applications of drones has increased in a handful of industries including aerial surveillance, agriculture, land management, energy, utilities, mining and others. People have reason to believe that, in the future, commercial drones will open up even more possibilities in applications.
The primary objective of this invention is to provide a unique remote sensing architecture utilizing multiple UAVs, such as a fleet of drones, equipped with a single or plural of sensors to construct a CS measurement matrix in 3-D space.
In compressed sensing system, measurement matrix plays a very significant role in signal sampling and signal reconstruction. Recently, much research has been conducted on design of new measurement matrix, because the implementation of CS largely depends on utilizing a suitable random or structured measurement matrix. Measurement matrix design is not the focus in this discussion, and current invention is not limited to work only for one type of CS algorithm.
The present invention presents a novel remote sensing architecture utilizing UAVs such as a fleet of drones. The fleet of drones or UAVs is patterned in the space to form a sparse measurement matrix based on the modulation sequence of a compressed sensing algorithm, to provide sampling data for CS processing and reconstruction. Each drone in the CS measurement matrix is equipped with one or a plurality of airborne sensors and functions as a floating pixel in the sparse matrix, to output sampling data for CS processing and reconstruction. The said sensors can be programed on or off independently according to CS algorithms.
Some preferred embodiments of the present invention are illustrated by accompanying figures, but the current invention is not limited to the embodiments set forth herein. For purposes of exemplification, drone and fleet of drones are used in present embodiments but are not limited to. Any UAV or other type of aerial vehicle can be used as sensor carrier shown further in the embodiments of FIGS.
The terminology used herein is for the purpose of describing particular embodiments only but is not intended to be limiting of the invention.
The present disclosure proposed a novel remote sensing and imaging architecture to exploit a fleet of drones as a sensor array to work as a sparse sampling measurement matrix in compressed sensing algorithm.
The location of each drone, accurately controlled by GPS or other means to its coordinate in 3-D space, functions as a particular floating pixel in the CS matrix and the sensors mounted on it can be independently switched on or off, similar to the micro mirrors of DMD working in CS camera system. For each measurement in the sampling circle, the position of each drone in the fleet, and on or off status of the sensors in each drone are regulated by CS algorithm. Therefore, a flight pattern of a drone fleet is arranged to form a floating sparse matrix in the space, as required by the CS algorithm. The number of total measurements is determined by CS algorithm. Furthermore, through a higher level of computation, CS performs the signal recovery and reconstruction from the measurements coming from the output of the drone matrix, where the number of measurements is much fewer than the number of reconstructed pixels. Since the drone can fly in 3-D space, which add one dimension to the DMD camera system, the images can be reconstructed and presented in a multi-dimensional image with the CS data sets.
One or multiple sensors are mounted on each drone to provide sensor signals to the CS system. Any types of sensors, such as physical, or chemical, or optical, or any combination of type of the sensors mentioned above, can be employed to provide corresponding specific information to CS. For example, multiple hyperspectral sensors mounted on each drone will provide spectral image information across a multitude of spectral bands to enable CS algorithms to reconstruct hyperspectral images in different spectral bands.
The advantage of the invented architecture is that it is utilizing drones to work as floating sampling points of a sparse matrix in space to provide a means of mobilized, rapid, and economic multi-dimensional sensing and imaging methodology.
It is yet another advantage of the present invention, via multiple remote sensors mounted on the drone, to enable the drone to measure corresponding specific properties for a variety of substances and purposes simultaneously.
Finally, it is a further advantage of the present invention, due to variability and versatility of drone positioning adjustment, and the fact that CS sparse matrix contains fewer pixels resulting in much less drones needed in the fleet than actually measured pixels, to make invented architecture an ideal candidate for large-scale remote sensing, geodetic survey, rapidly deploying an area in urgent need, such as forestry fire, earthquake, explosion site, etc.
This application is in-part a continuation of the U.S. provisional Patent Application Ser. No. 62/551,208, filed Aug. 28, 2017, and entitled “Remote sensing architecture utilizing UAVs as sparse sampling matrix for compressed sensing system”.
