Robust Adaptive Controls for Shipboard Landing of Multi-Rotor Unmanned Aerial Vehicles

Alex Bryant and Lauren Ingmire in the lab.

A newly funded project in the School of Aerospace and Mechanical Engineering makes use of close collaboration between researchers in different fields to improve a critical technology for national defense. Dr. Keith Walters and Dr. Andrea L’Afflitto (now a faculty member at Virginia Tech) are combining their respective expertise in aerodynamics and controls to address a difficult challenge for unmanned aerial vehicles (UAVs).

It is well known that UAVs are increasingly being used for both commercial and military applications. The United States Department of Defense (DoD) currently employs multi-rotor helicopters (quadcopters) for remote sensing missions, such as surveillance and search and rescue. In the future, they will support troops by performing tactical tasks, such as picking up and dropping off payloads and surveying cluttered environments. Of particular interest are vehicles that operate autonomously, that is without any direct control by human pilots. These vehicles use onboard computers and mathematical control algorithms to perform necessary aerial maneuvers, travel to desired locations, avoid obstacles, and perform whatever tasks are required of their mission. The development of new and improved control algorithms is, therefore, an active area of research with the potential for substantial impact on next-generation UAVs.

This project focuses on the development of improved control algorithms specifically designed for the landing of UAVs on U.S. Navy ships. Shipboard landing is a complex task for UAVs because 1) the deck is highly unsteady in rough seas; 2) adverse sea conditions are often accompanied by adverse weather and high winds; 3) the superstructure of a moving ship induces a wake in the air, which further perturbs the UAVs landing on its deck; 4) near hard surfaces, the ‘ground effect’ alters the thrust produced by the propellers; and 5) UAVs returning from a mission may be damaged. To land on the deck of a ship, a UAV’s control system regulates the thrust forces of each propeller so that the aircraft approaches the ship with some desired relative velocity and orientation, leading to (hopefully) a gentle touch down in the appropriate location.

The primary objective of this research is to design a robust adaptive control system for multi-rotor UAVs that allows precise landing on the deck of moving ships. The work builds on prior research by former AME faculty member Andrea L’Afflitto and will make use of a model reference adaptive control (MRAC) architecture. Such an approach guarantees robustness of the closed-loop feedback system to both uncertainties in system parameters and unknown state-dependent disturbances that affect the control inputs, such as wind gusts or the swinging of an attached cargo payload.

The control algorithm will also be improved by adopting more realistic functional relationships between propeller rotational speed (RPM) and the generated thrust. Currently, it is assumed that thrust is simply proportional to RPM squared under all conditions. While this is often nearly true when a UAV is hovering in calm air, it does not hold during complex aerial maneuvers, under the action of strong wind disturbances, or when the vehicle is close to a solid surface such as the deck of a ship. Keith Walters and his students will perform computational fluid dynamics (CFD) simulations of quadrotor propellers to more accurately determine the relationship between thrust and RPM under these conditions. The simulations will be used to develop an analytical function that will be included in the control algorithm developed by Dr. L’Afflitto.

The scientific advances made by this project will be disseminated in the technical literature and will provide opportunities for graduate students to participate in national or international conferences. The improvement to UAV performance during shipboard landing will be critical to increasing the value of these vehicles to U.S. Navy missions, and the technology can be translated to other branches of the armed forces to improve design and operation of their next-generation UAV systems. Eventually, the research may be adopted by the commercial sector to improve, for example, the use of UAVs for package delivery or remote sensing in adverse weather conditions.

Development of Zero-Liquid Discharge Freeze System to Remove Dissolved Salt from Contaminated Water

Management of waste water is a challenging issue in many municipal and industrial sectors. The oil and gas industry produces a massive amount of waste water during production. The production of one barrel of oil results in approximately nine barrels of water that is contaminated with salt, heavy metals, and organic compounds. The development of methods for cost-efficient disposal and re-use of produced water without damage to the environment is a critical need for the oil and gas industry. Also, re-use of the water for agricultural purposes will be helpful because the agricultural sector is a primary consumer of increasingly scarce freshwater (accounting for 63% of U.S. surface water withdrawals, according to the U.S. Geological Survey).

Researchers Discuss Equipment with Assistants Castillo Alejandro and Aly Elhefny

In this project sponsored by the US Department of Energy, Drs. Shabgard, Cai and Parthasarathy are working on the development of a novel, zero-liquid discharge freeze system to remove dissolved salt from contaminated water. Freeze-desalination processes are well suited for these situations because pure ice crystals can be produced even in highly concentrated brine. However, current freeze-desalination technologies have some deficiencies that hinder their widespread use. A new method of eutectic freeze desalination will be used with a cooling approach that maximizes efficiency. Thus, the need for energy-intensive evaporation methods is avoided. The density differences between water, ice, and salty brine are used to separate the components. The system will operate under atmospheric pressure and be capable of treating highly concentrated/contaminated water. If successful, the treated water will be suitable for agricultural use, providing an abundant new water source. The goal is to develop a zero-liquid discharge (ZLD) freeze-desalination system capable of treating water with total dissolved solids (TDS) values up to 250,000 mg/l (milligrams per liter). For comparison, the TDS content of seawater is approximately 35,000 mg/l.

The proposed system offers a sustainable solution for the increasing water demand in industrial and oil and gas sectors by recycling the otherwise wasted water, without putting pressure on increasingly scarce freshwaterresources also in demand by local communities for agricultural and municipal purposes. Also, the environmental concerns related to disposing highly contaminated water are avoided by the use of the proposed ZLD desalination system.

Student Research Spotlight: BBDL Member Devin Laurence

The AME Student Research Spotlight this month is Devin Laurence, a member of the Biomechanics and Biomaterials Design Lab (BBDL). Laurence is a graduate student in the BBDL at the University of Oklahoma studying mechanical engineering. His specific research project involves computational modeling of the tricuspid heart valve to move towards patient-specific therapeutics. He plans to pursue his Ph.D. with an emphasis on cardiovascular biomechanics and to continue into academia afterwards. In his free time, Devin enjoys playing chess, disc golf, and hiking/camping.

Click here for more information about the BBDL.

Student Research Spotlight: BBDL Member Sam Jett

The AME Student Research Spotlight this month is Sam Jett, a member of the Biomechanics and Biomaterials Design Lab (BBDL). Jett is a graduate student at the University of Oklahoma, working on his master’s degrees in mechanical engineering. Sam started out in the BBDL working on the biaxial testing project for heart valve leaflet tissue and is currently working to design a collagen imaging system that will integrate with the biaxial tester to study how dynamic loading affects collagen fiber orientation and alignment in biological tissues. In the lab, he enjoys exploring the biological imaging field, writing code to gain valuable insights from data, collaborating with other lab members, and exercising the freedom to work with teams to develop innovative solutions to research goals. Outside of school, Sam spends time walking his dog, reading, exercising, hanging out with his friends, and enjoying the occasional night out on the town. He hopes to work on biomedical device and software design and after completing his M.S. studies at OU.

Click here for more information about the BBDL.

Student Research Spotlight: BBDL Member Colton Ross

The AME Student Research Spotlight this month is Colton Ross, a member of the Biomechanics and Biomaterials Design Lab (BBDL). Ross is a senior student studying mechanical engineering in the Accelerated BS/MS program. In the BBDL, Colton’s research involves mechanical characterizations of heart valve structures. Specifically, his research project involves analysis of the chordae tendineae of the atrioventricular heart valves. Upon completing his thesis and receiving his MS, Colton plans to pursue a Ph.D. to continue performing research in the field of biomedical engineering. In his future Ph.D. research and career (in either academia or industry), Colton wants to focus on the development and improvement of medical devices or limb prosthesis. Outside of his coursework and the BBDL, Colton enjoys playing guitar, going to concerts, and playing video games with his friends.

Click here for more information about the BBDL.

Student Research Spotlight: BBDL Member Cortland Johns

The AME Student Research Spotlight this month is Cortland Johns, a member of the Biomechanics and Biomaterials Design Lab (BBDL). Johns is a junior pre-medicine student majoring in mechanical engineering at the University of Oklahoma. She is a national merit scholar from Bettendorf, Iowa. Cortland is currently working on the heart valve biaxial testing project, specifically assisting the data driven testing project. In the past, Cortland worked on the regional testing, layer testing, and Langendorff teams. Cortland is also a Fall 2018 MRF recipient. She is a member of the Tau Beta Pi and Pi Tau Sigma honor societies, and she is a certified pharmacy technician. Cortland plans to attend medical school and pursue a career in surgery.

Click here for more information about the BBDL.

Graduate Student Receives 2019 NSF GRF

Graduate student Devin Laurence was selected on April 8, 2019 to receive a 2019 National Science Foundation (NSF) Graduate Research Fellowship (GRF). Devin Laurence is a graduate student in the BBDL at the University of Oklahoma studying mechanical engineering.

Congratulations on this outstanding achievement, Devin!

 

Student Research Spotlight: BBDL Member Robert Kunkel

The AME Student Research Spotlight this month is Robert Kunkel, a member of the Biomechanics and Biomaterials Design Lab (BBDL). Kunkel is pursuing his master’s degree in mechanical engineering. He conducts research as a part of the BBDL under Dr. Chung-Hao Lee. His primary focus is on the development of novel treatment devices for aneurysms in the brain. Outside of the lab, he plays ultimate frisbee with the OU Apes of Wrath team and participates on the manipulation sub-team of the Sooner Rover Team. Robert plans to graduate in May of 2019 and enter into an industry position where he can continue to apply mechanical engineering principles to the field of human medicine.

Click here to learn more about the BBDL.

Video Series Features Dr. Lee and his Students in the BBDL

Dr. Lee and his students are working on research projects in the BBDL to further their knowledge about the biomechanics and biomedical industry. We will be featuring a video each month about BBDL members and their specific projects in the lab.

Click here for more information about the BBDL.

Dr. Song Receives Multiple Awards for Current Research

Dr. Li Song, an associate professor at AME, received three awards for her current research projects. Two awards are from the Department of Energy, and the third award is from Battelle – Pacific Northwest National Laboratory.

Song is the lead PI for the development and validation of a home comfort system for total performance deficiency/fault detection and optimal control project, which received a DOE fund of $993,149. The research team will develop and validate a smart thermostat-integrated low-cost home energy management system, including a data connection framework; a computationally efficient, self-learning home thermal model; automatic fault detection and analysis algorithms; and home energy management information and controls based on in-situ measured efficiencies of heating and cooling equipment, the air distribution system, and the building envelope.

The second DOE fund is $551,566 for the performance demonstration of an occupancy sensor-enabled integrated solution for commercial buildings project. The research team will validate the performance and savings of three HVAC control (fan, cooling coil valve, outside air) algorithms integrated with occupancy sensing data to optimize ventilation delivery.

A $50,000 award was given to Song from Battelle – Pacific Northwest National Laboratory for her Transactive-Control Based Connected Home Solution for Existing Residential Units and Communities project.

This is a summary of Song’s research proposal sent to Battelle: To obtain the overall project aims, the development of machine learning techniques to calibrate the initial physical model that estimates and predicts energy use of a house and its response to control signals is extremely important. An effective home thermal model, that can predict the indoor air temperature dynamics under different weather, HVAC output and internal gains from appliances and occupants, is essential for the development.

BEEL initiated the development of a self-learning home thermal model two years ago. The BEEL home model, currently limited for a house with an A/C and gas-furnace heater, can automatically identify the model parameters with minimum data needed and precisely predict the space temperature and home HVAC energy uses for a house. To enhance the connectivity and compatibility of the platform proposed by PNNL, BEEL is committed to expand the home thermal model for a heat pump system and test enhanced home model using two houses located in Oklahoma through the partnership with OG&E. The challenge of modeling the heat pump is that the heating output from a heat pump is no longer constant as is for a gas furnace heater. A correlation of the heating output of a heat pump and outdoor air temperature needs to be formulated and similarly, a correlation between cooling output of a heat pump and weather might be needed for cooling season as well.

Congratulations Dr. Song!