Classifications, applications, and design challenges of drones: A review

Path planning techniques for unmanned aerial vehicles: A review, solutions, and challenges

Unmanned vehicles (UVs) play a key role in autonomous surveillance scenarios. A major task needed by these UVs in undertaking autonomous patrol missions is to detect the targets and find their locations in real-time. In this paper, a new vision-based target detection and localization system is presented to make use of different capabilities of UVs as a cooperative team. The scenario considered in this paper is a team of an unmanned aerial vehicle (UAV) and multiple unmanned ground vehicles (UGVs) tracking and controlling crowds on a border area. A customized motion detection algorithm is applied to follow the crowd from the moving camera mounted on the UAV. Due to UAVs lower resolution and broader detection range, UGVs with higher resolution and fidelity are used as the individual human detectors, as well as moving landmarks to localize the detected crowds with unknown independently moving patterns at each time point. The UAVs localization algorithm, proposed in this paper, then converts the crowds’ image locations into their real-world positions, using perspective transformation. A rule-of-thumb localization method by a UGV is also presented, which estimates the geographic locations of the detected individuals. Moreover, an agent-based simulation model is developed for system verification, with different parameters, such as flight altitude, number of landmarks, and landmark assignment method. The performance measure considered in this paper is the average Euclidean distance between the estimated locations and simulated geographic waypoints of the crowd. Experimental results demonstrate the effectiveness of the proposed framework for autonomous surveillance by UVs.

Vision-Based Target Detection and Localization via a Team of Cooperative UAV and UGVs

Due to the flying nature of unmanned aerial vehicles (UAVs), it is very attractive to deploy UAVs as aerial base stations and construct airborne networks to provide service for on-ground users at temporary events (such as disaster relief, military operation, and so on). In the constructing of UAV airborne networks, a challenging problem is how to deploy multiple UAVs for on-demand coverage while at the same time maintaining the connectivity among UAVs. To solve this problem, we propose two algorithms: a centralized deployment algorithm and a distributed motion control algorithm. The first algorithm requires the positions of user equipments (UEs) on the ground and provides the optimal deployment result (i.e., the minimal number of UAVs and their respective positions) after a global computation. This algorithm is applicable to the scenario that requires a minimum number of UAVs to provide desirable service for already known on-ground UEs. Differently, the second algorithm requires no global information or computation, instead, it enables each UAV to autonomously control its motion, find the UEs and converge to on-demand coverage. This distributed algorithm is applicable to the scenario where using a given number of UAVs to cover UEs without UEs’ specific position information. In both algorithms, the connectivity of the UAV network is maintained. Extensive simulations validate our proposed algorithms.

Deployment Algorithms for UAV Airborne Networks Toward On-Demand Coverage

http://apmonitor.com/wiki/uploads/Main/apmonitor_2014.pdf

Nonlinear modeling, estimation and predictive control in APMonitor

Applying the selective harmonic elimination (SHE) technique to grid-connected-cascaded modular multilevel inverters has been widely discussed in the literature. However, due to the difficulties of solving high-order nonlinear transcendental equations, the SHE technique cannot be implemented in real time so its applications are limited. This paper presents a technique to convert the nonlinear equations to a specific control system and use a look-up table, integral controllers and a decoupling controller to help the system converge to a zero-error steady state. An inner instantaneous observer is introduced to directly extract the harmonic spectrum of the output voltages without applying FFT algorithm to output step voltage waveforms. It can not only simplify software design but also eliminate the phase delay generated by conventional spectrum extracting algorithm. The proposed technique can achieve an accurate switching angle control and a fast response. Simulation and experimental results verified that the system can achieve zero-error steady state within one line period.

A Real-Time Selective Harmonic Elimination Based on a Transient-Free Inner Closed-Loop Control for Cascaded Multilevel Inverters

In this paper, we present a decentralized multitarget tracking system for cooperative unmanned aerial vehicles (UAVs) with limited sensing capabilities. The proposed system distributively incorporates a clustering algorithm, an optimal sensor manager, and an optimal path planner to track multiple mobile targets. A set of extended Kalman filters is used by each UAV to estimate the locations of mobile targets. The UAVs are equipped with gimbaled cameras with a limited field of view and sensing range. To make the system scalable, the density-based spatial clustering of applications with noise algorithm is used to group targets, sensor managers determine optimal gimbal poses and path planners collectively coordinate UAVs’ movements. The effective performance of the proposed system is shown through simulation results.

A Scalable Multitarget Tracking System for Cooperative Unmanned Aerial Vehicles

In this brief, we present a novel decentralized controller for multiple unmanned aerial vehicles (UAVs) to fly in a symmetric formation surrounding a hostile mobile target while maintaining and controlling the network connectivity. The multi-UAV information exchange topology is considered as a time-varying function of interagent distances. We investigate the impact of controller parameters on UAV group behavior to maintain connectivity. We also explore the use of the proposed controller to track a desired connectivity profile along with steering UAVs in a target-centric formation. Simulation results validate the effectiveness of the proposed controller.

A Decentralized Formation and Network Connectivity Tracking Controller for Multiple Unmanned Systems

A method for aerial rendezvous of small unmanned aircraft systems is proposed. The system includes placing a passively towed drogue into an orbit that is suitable for a small unmanned aircraft systems to follow, and a seeker guidance method for use with a monocular camera mounted on the centerline of the unmanned aircraft systems. The principle contributions of the work include a method for controlling the drogue path in moderate winds by manipulating the mothership orbit and airspeed, and a vision-based nonlinear pursuit tracking method that uses pitch rate and roll commands to guide the unmanned aircraft systems to an aerial rendezvous with the drogue. Simulation and flight-test results are presented to demonstrate the suitability of these methods.

/pdf/aerial-rendezvous-of-small-unmanned-aircraft-using-a-passive-4xqccw3x06.pdf

Aerial rendezvous of small unmanned aircraft using a passive towed cable system

This paper studies trajectory generation for a mothership that tows a drogue using a flexible cable. The contributions of this paper include model validation for the towed cable system described by a lumped mass extensible cable using flight data, and optimal trajectory generation for the towed cable system with tension constraints using model predictive control. The optimization problem is formulated using a combination of the squared error and L1-norm objective functions. Different desired circular trajectories of the towed body are used to calculate optimal trajectories for the towing vehicle subject to performance limits and wind disturbances. Trajectory generation for transitions from straight and level flight into an orbit is also presented. The computational efficiency is demonstrated, which is essential for potential real-time applications. This paper gives a framework for specifying an arbitrary flight path for the towed body by optimizing the action of the towing vehicle subject to constraints.

/pdf/optimal-trajectory-generation-using-model-predictive-control-1sye5tdtbq.pdf

Liang Sun

Papers

A Real-Time Selective Harmonic Elimination Based on a Transient-Free Inner Closed-Loop Control for Cascaded Multilevel Inverters

A Scalable Multitarget Tracking System for Cooperative Unmanned Aerial Vehicles

A Decentralized Formation and Network Connectivity Tracking Controller for Multiple Unmanned Systems

Aerial rendezvous of small unmanned aircraft using a passive towed cable system

Optimal Trajectory Generation Using Model Predictive Control for Aerially Towed Cable Systems