Path Optimization for an Earth-Based Demonstration Balloon Flight

2020

This paper presents an optimal guidance approachfor a UAV point-to-point navigation in 2D, under wind perturbation, with a general desired airspeed profile. A cost function weighting the travel time and the control effort is minimized through the Pontryagin’s Minimum Principle, involving the derivatives of the airspeed velocities. Two iterative procedures for a guidance algorithm under general wind fields were developed, including an analytical solution for the optimal heading in minimum-time paths. Different cases from the literature are compared and a hard wind scenario test is presented.

Robotics, 2017

This paper presents a comparative study of the effects of grid resolution, vehicle velocity and wind vector fields on the trajectory planning of unmanned airships. A wavefront expansion trajectory planner that minimizes a multi-objective cost function consisting of flight time, energy consumption and collision avoidance while respecting the differential constraints of the vehicle is presented. Trajectories are generated using a variety of test environments and flight conditions to demonstrate that the inclusion of a high terrain map resolution, a temporal vehicle velocity and a spatial wind vector field yields significant improvements in trajectory feasibility and energy economy when compared to trajectories generated using only two of these three elements.

IEEE Transactions on Control Systems Technology, 2017

High-altitude balloons are a promising technology for providing high-speed wireless Internet to the entire Earth. These balloons float passively on wind currents in the stratosphere and connect to nearby Internet users on Earth. To connect to everyone on Earth, a fleet of several thousands balloons must be arranged in an evenly spread-out formation, so that every user is close to at least one balloon. Since the balloons naturally move with the wind, an important problem is to control the formation of the fleet of balloons. In this paper, we show that distributed extremum-seeking control (ESC) can be used to control the balloon formation. This approach is based on the minimization of a cost function and does not require a model of wind currents or Internet users. We provide several cost functions, which can be used by the ESC and are based on the distance between balloons, Voronoi partitions, a variant of Lloyd's algorithm, Internet bandwidth, and the number of Internet users. As the control architecture is fully distributed, the computational burden is shared between all the balloons, and the algorithm can be scaled to an arbitrarily large network of balloons. Several simulations involving 1200 balloons are used to verify the effectiveness of this approach. The simulations use realistic nonlinear wind models, which are obtained by interpolating gridded weather data obtained from the National Oceanic and Atmospheric Administration.

Airborne Wind Energy

To achieve a high conversion efficiency and at the same time robust control of a pumping kite power system it is crucial to optimize the three-dimensional flight path of the tethered wing. This chapter extends a dynamic system model to account for a realistic, turbulent wind environment and adds a flight path planner using a sequence of attractor points and turn actions. Path coordinates are calculated with explicit geometric formulas. To optimize the power output the path is adapted to the average wind speed and the vertical wind profile, using a small set of parameters. The planner employs a finite state machine with switch conditions that are highly robust towards sensor errors. The results indicate, that the decline of the average power output of pumping kite power systems at high wind speeds can be mitigated. In addition it is shown, that reeling out towards the zenith after flying figure eight flight maneuvers significantly reduces the traction forces during reel-in and thus increases the total efficiency.

2010 IEEE International Conference on Robotics and Automation, 2010

Aerial vehicles are appealing systems for possible future exploration of planets and moons such as Venus and Titan, because they combine extensive coverage with highresolution data collection and in-situ science capabilities. Recent studies have proposed the use of a montgolfiere balloon, which controls its altitude by changing the heating rate or venting gas from the balloon, but has no actuation capability in the horizontal plane. A montgolfiere can use the variation in wind with altitude to guide itself to a desired location. This paper considers the problems of determining the altitude profile that the montgolfiere should follow in order to reach its target most quickly. We provide a new method that solves this path planning problem for all possible target locations, thereby providing a reachability analysis for the entire globe. The key idea is to perform a principled simplification and decoupling of the dynamics of the montgolfiere. We then discretize the search space, converting the planning problem into a graph search problem, and use Dijkstra's algorithm to calculate the minimum-time path from the start location to every possible location in the graph. We demonstrate the approach on a possible Titan mission scenario.

2012

Dynamic soaring can save fuel by the extraction of low-altitude wind shear energy. The problem of generating energy-saving trajectories in real time for an unmanned powered sailplane is considered. A method called 'inverse dynamics in the virtual domain' is investigated. The method results in rapid solution generation and is suitable for real-time applications. Threedimensional unmanned aerial vehicle equations of motion and a non-linear wind gradientmodel are used. Trajectories are generated to minimize the total power used per horizontal distance travelled for cross-wind travelling and in the total power used per total time in air for loitering mode. Trajectory following issues are addressed and an architecture for the control system is briefly described. A method for the estimation of wind shear gradient parameters is proposed. Validation is performed using a full six-degree-of-freedom model of a powered sailplane to verify the trajectory generation method.

In order to comply with the objectives of a balloon mission, it is usually necessary to forecast ground wind and weather conditions for launch operations and to predict, monitor and track the flight trajectory. In the framework of the PRORA-USV program, CIRA has developed several methodologies and tools useful to evaluate balloon mission feasibility, predict and optimize flight trajectory and assess on trajectory prediction errors. These methodologies are based on the characterization of the micrometeorological features of launch site, on weather and wind forecasts during the flight campaign, on meteorological data provision for trajectory computation and on the use of ACHAB a proprietary software for the prediction of flight trajectory and thermal behavior of high altitude zero-pressure balloons.

2020

Quadrotor unmanned aerial vehicles have a limited quantity of embedded energy. To preserve and guaranty the success of the UAV mission, we should manage energy consumption during the mission. In this study, we introduce an optimization algorithm to minimize the consumed energy in the flying vehicle mission under windy conditions. In order to calculate the energy consumed by the quadrotor, we present a power loss model, where the energy is formulated as a function of rotor speed and acceleration. Then, we formulate the energy minimization problem as an optimal control problem and solve this problem in order to calculate minimum energy for a point-to-point quadrotor mission under windy conditions. In order to highlight the proposed optimization approach, we compare energy consumption obtained by optimization algorithm with an adaptive control approach in simulation experiment.

2017

The objective of this paper is to demonstrate the application of optimal control for generating dynamically constrained minimal time trajectories in micro unmanned airships. By design, airships are generally underactuated and underpowered limiting their maneuvering capabilities. Using a simplified dynamic model derived with experimentally derived coefficients, two trajectory planning simulations are solved using optimal control. The generated trajectories are then evaluated experimentally on a micro airship to demonstrate that optimal control can be used in open loop over short distances.

Lecture Notes in Control and Information Sciences, 2009

In this paper, we show that a minimum time solution for the trajectory planning problem in the presence of wind for a micro air vehicle with a minimum turn radius constraint exists. For a non-zero, time-varying wind vector field, we provide easily checked sufficient conditions under which a minimum-time solution exists. We also prove uniqueness for almost every combination of initial and final conditions in the case of a wind vector field that varies with time but is constant in the spatial variable for each time instant. We note here that the well known Pontryagin's Maximum Principle only yields necessary conditions for the optimal solution but does not yield its existence. We use Filippov's Theorem [13] to conclude existence of the minimum time solution, after demonstrating the existence of one solution, provided certain conditions are satisfied by the wind vector field. * R. V. Iyer and R. L. McNeely are with the Department of Mathematics and Statistics, Texas Tech University, Lubbock, TX 79409-1042. † P. Chandler is with the U.S. Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433-7531.