Projects & Publications
To support the safe and effective integration of autonomous systems such as drones into everyday human environments by using both analytical research and hands-on experiments to demonstrate their capabilities and reliability.
In-flight system failure is one of the major safety concerns in the operation of unmanned aerial vehicles (UAVs) in urban environments. To address this concern, a safety framework consisting of following three main tasks can be utilized: (1) Monitoring health of the UAV and detecting failures, (2) Finding potential safe landing spots in case a critical failure is detected in step 1, and (3) Steering the UAV to a safe landing spot found in step 2. In this paper, we specifically look at the second task, where we investigate the feasibility of utilizing object detection methods to spot safe landing spots in case the UAV suffers an in-flight failure.
We propose an unmanned aerial vehicle (UAV) failure detection system as the first step of a three-step autonomous emergency landing safety framework for UAVs. We showed the effectiveness and feasibility of using vibration data with the k-means clustering algorithm in detecting mid-flight UAV failures for that purpose. Specifically, we measured vibration signals for different faulty propeller cases during several test flights, utilizing a custom-made hardware system. After we made the vibration graphs and extracted the data, we investigated to determine the combination of acceleration and gyroscope parameters that results in the best accuracy of failure detection in quadcopter UAVs. Our investigations show that considering the gyroscope parameter in the vertical direction (gZ) along with the accelerometer parameter in the same direction (aZ) results in the highest accuracy of failure detection for the purpose of emergency landing of faulty UAVs, while ensuring a quick detection and timely engagement of the safety framework. Based on the parameter set (gZ-aZ), we then created scatter plots and confusion matrices, and applied the k-means clustering algorithm to the vibration dataset to classify the data into three health state clusters—normal, faulty, and failure. We confirm the effectiveness of the proposed system with flight experiments, in which we were able to detect faults and failures utilizing the aforementioned clusters in real time.
A framework for autonomous waypoint planning, trajectory generation through waypoints, and trajectory tracking for multi-rotor unmanned aerial vehicles (UAVs) is proposed in this work. Safe and effective operations of these UAVs is a problem that demands obstacle avoidance strategies and advanced trajectory planning and control schemes for stability and energy efficiency. To address this problem, a two-level optimization strategy is used for trajectory generation, then the trajectory is tracked in a stable manner. The framework given here consists of the following components: (a) a deep reinforcement learning (DRL)-based algorithm for optimal waypoint planning while minimizing control energy and avoiding obstacles in a given environment; (b) an optimal, smooth trajectory generation algorithm through waypoints, that minimizes a combination of velocity, acceleration, jerk and snap; and (c) a stable tracking …
Autonomous trajectory generation in a complex environment is a challenging task for multi-rotor unmanned aerial vehicles (UAVs), which have high maneuverability in three-dimensional motion. Safe and effective operations for these UAVs demand obstacle avoidance strategies and advanced trajectory planning and control schemes for stability and energy efficiency. To solve those problems in one framework analytically is extremely challenging when the UAV needs to fly large distance in a complex environment. To address this challenge, a two-level optimization strategy is adopted. At the higher-level, a sequence of waypoints is selected that lead the UAV from its current position to the destination. At the lower-level, an optimal trajectory is generated between each pair of adjacent waypoints analytically. While the goal of trajectory generation is to maintain the stability of the UAV, the goal of the waypoints planning …
The expanding use of civilian unmanned aerial vehicles (UAVs) has brought forth a crucial need to address the safety risks they pose in the event of failure, especially when flying in populated areas. This paper reviews recent advancements in recovery systems designed for the emergency landing of civilian UAVs. It covers a wide range of recovery methods, categorizing them based on different recovery approaches and UAV types, including multirotor and fixed-wing. The study highlights the diversity of recovery strategies, ranging from parachute and airbag systems to software-based methods and hybrid solutions. It emphasizes the importance of considering UAV-specific characteristics and operational environments when selecting appropriate safety systems. Furthermore, by comparing various emergency landing systems, this study reveals that integrating multiple approaches based on the UAV type and mission requirements can achieve broader cover of emergency situations compared to using a single system for a specific scenario. Examples of UAVs that utilize emergency landing systems are also provided. For each recovery system, three key parameters of operating altitude, flight speed and added weight are presented. Researchers and UAV developers can utilize this information to identify a suitable emergency landing method tailored to their mission requirements and available UAVs. Based on the key trends and challenges found in the literature, this review concludes by proposing specific, actionable recommendations. These recommendations are directed towards researchers, UAV developers, and regulatory bodies, and focus on …
This article proposes a novel integral geometric control attitude tracking scheme, utilizing a coordinate-free representation of attitude on the Lie group of rigid body rotations, SO(3). This scheme exhibits almost global asymptotic stability in tracking a reference attitude profile. The stability and robustness properties of this integral tracking control scheme are shown using Lyapunov stability analysis. A numerical simulation study, utilizing a Lie Group Variational Integrator (LGVI), verifies the stability of this tracking control scheme, as well as its robustness to a disturbance torque. In addition, a numerical comparison study shows the effectiveness of the proposed geometric integral term, when compared to other state-of-the-art attitude controllers. In addition, software-in-the-loop (SITL) simulations show the advantages of utilizing the proposed attitude controller in PX4 autopilot compared to using PX4’s original attitude controller.
A discrete time, optimal trajectory planning scheme for position trajectory generation of a vehicle is given here, considering the mission duration as a free variable. The vehicle is actuated in three rotational degrees of freedom and one translational degree of freedom. This model is applicable to vehicles that have a body-fixed thrust vector direction for translational motion control, including fixed-wing and rotorcraft unmanned aerial vehicles (UAVs), unmanned underwater vehicles (UUVs) and spacecraft. The lightweight scheme proposed here generates the trajectory in inertial coordinates, and is intended for real time, on-the-go applications. The unspecified terminal time can be considered as an additional design parameter. This is done by deriving the optimality conditions in a discrete time setting, which results in the discrete transversality condition. The trajectory starts from an initial position and reaches a desired …
Growing concern over the effects of carbon emissions and resulting climate change have highlighted the need to move away from fossil fuels and towards renewable sources of energy. Wind energy is a popular and proven renewables technology that it is mostly implemented in rural environments. For urban settings, building mounted wind turbines could be a solution as a local source of renewable energy generation. In this study, the open-source Computational Fluid Dynamics software OpenFOAM is used to determine the wind speed on a high-rise rooftop. The simulation results are then used in tandem with real wind data from the 2020 calendar year to determine the performance of a turbine on the roof of the building. The reference turbine is the QuietRevolution QR6 vertical axis wind turbine, a real commercial turbine with an energy rating of 7 kW. The total annual energy yield was calculated to be 42,557 kWh …
Our collaborative XRchaeology works began in 2019 with the intent to overcome obstacles that arise from the inability to access museum and remote archaeological collections from various parts of the world, and the more specific aim to emphasize the contextual associations of systematically excavated objects residing in those collections using web-based VR technology. In 2021, we expanded our work to incorporate a new AI assistant using natural language processing techniques known to the computer sciences and engineering to advance our understanding of in situ phenomena to promote creative inquiry on artifact collections under study. These combined techniques have become part of our standard information dissemination repertoire. This year, we began development of a neural network to help overcome site recording and accessibility issues we will will face during future site survey and recording operations. With this range of experience an our most recent advances, our successes and failures, it is our primary aim to contribute to the dialogue at this transformational moment in archaeology.
Recent advances in UAV-remote sensing technologies allowed us to begin collecting a range of data survey teams might encounter on the ground, in order to train an algorithm to detect objects and features in remote sensing data obtained by our UAV. While we expected the quality of data to improve dramatically using these superior techniques, we were also concerned about the feasibility of our proposed long-term research that relies on its success. With primary aims to collect high-quality data and reduce the time normally spent doing …
This paper presents a guidance and attitude tracking control scheme in continuous time for a rigid body in SO (3), using time-varying artificial potentials. This novel idea leads to generation of an attitude trajectory that passes through desired attitude waypoints and feedback tracking of this trajectory. These waypoints can also be used for avoiding attitude or pointing direction constraints so that safe attitude navigation is ensured. Artificial time-varying potential fields at these waypoints that are attractive, are introduced. Bump functions of time, which are smooth but not real analytic, are used to generate these potentials at the desired attitude waypoints. For the terminal attitude, a different type of smooth function is used. The rigid body attitude in these time-varying potential fields gets attracted towards the desired attitude waypoints during certain time periods. This generates an attitude trajectory passing through these desired waypoints sequentially in time. A Lyapunov analysis is carried out to show stable attitude tracking through the desired waypoints and ending at the terminal attitude, using these time-varying artificial potentials. Numerical simulations are carried out to test the performance of this attitude guidance and tracking scheme.
This paper presents a guidance and attitudCurrent Federal Aviation Administration (FAA) regulations limit operations of Unmanned Aerial Vehicles (UAVs) to flights within visual line-of-sight of a human observer to ensure safety. However, with the advances in onboard detection, communication and control capabilities, such a limiting regulation may not be necessary for safe operations, because a high level of safety and stability can be achieved and guaranteed even during beyond visual line-of-sight flights of autonomous vehicles.e tracking control scheme in continuous time for a rigid body in SO (3), using time-varying artificial potentials. This novel idea leads to generation of an attitude trajectory that passes through desired attitude waypoints and feedback tracking of this trajectory. These waypoints can also be used for avoiding attitude or pointing direction constraints so that safe attitude navigation is ensured. Artificial time-varying potential fields at these waypoints that are attractive, are introduced. Bump functions of time, which are smooth but not real analytic, are used to generate these potentials at the desired attitude waypoints. For the terminal attitude, a different type of smooth function is used. The rigid body attitude in these time-varying potential fields gets attracted towards the desired attitude waypoints during certain time periods. This generates an attitude trajectory passing through these desired waypoints sequentially in time. A Lyapunov analysis is carried out to show stable attitude tracking through the desired waypoints and ending at the terminal attitude, using these time-varying artificial potentials. Numerical simulations are carried out to test the performance of this attitude guidance and tracking scheme.
In recent years, flying vehicles have become an innovative way to transfer parcels efficiently over a short distance. Existing airspace regulations are slow to adapt to the anticipated rise in aircraft traffic resulting from this development. This is because the increase in unmanned aerial vehicles (UAVs) comes with an increased risk of personal injuries from faulty drones carrying a payload. Many national regulatory agencies, such as the FAA, rely on the Abbreviated Injury Scale (AIS) to determine the weight threshold of a UAV by evaluating the impact energy and correlating it to the severity of a potential injury. This research paper presents a test apparatus to investigate the effect of different safety systems on AIS.As an example, a passive safety system in the form of a geodesic shell is used to investigate the change in impact acceleration and therefore, the head injury sustained.
This article develops and proposes a geometric nonlinear proportional-integral-derivative (PID) type tracking control scheme on the Lie group of rigid body rotations, SO(3). Like PD-type attitude tracking control schemes that have been proposed in the past, this PID-type control scheme exhibits almost global asymptotic stability in tracking a desired attitude profile. The stability of this PID-type tracking control scheme is shown using a Lyapunov analysis. A numerical simulation study demonstrates the stability of this tracking control scheme, as well as its robustness to a disturbance torque. In addition, a numerical comparison study shows the effectiveness of the proposed integrator term.
This work proposes a distributed and decentralized observer for position estimation (localization) of a moving target being tracked by multiple mobile sensors. The possibly time-varying set of sensors that have the target in their field of view, is used to create an energy-like quantity that depends on errors in the estimated relative positions and relative velocities of the target as measured by the mobile sensors. The relative velocities need not be measured directly, and can be obtained by filtering the observed relative positions. Each sensor then implements a local version of this distributed observer, and shares relative position information with the other sensors that are tracking the target. The observer is in the form of a variational estimator that is obtained by taking an action functional constructed from the energy-like quantity and dissipating this energy. As a result, the observer is shown to be asymptotically stable …