Ely Carneiro de Paiva

Robotic Airships for Exploration of Planetary Bodies with an Atmosphere: Autonomy Challenges

Robotic unmanned aerial vehicles have great potential as surveying and instrument deployment platforms in the exploration of planets and moons with an atmosphere. Among the various types of planetary aerovehicles proposed, lighter-than-atmosphere (LTA) systems are of particular interest because of their extended mission duration and long traverse capabilities. In this paper, we argue that the unique characteristics of robotic airships make them ideal candidates for exploration of planetary bodies with an atmosphere. Robotic airships extend the capabilities of balloons through their flight controllability, allowing (1) precise flight path execution for surveying purposes, (2) long-range as well as close-up ground observations, (3) station-keeping for long-term monitoring of high science value sites, (4) transportation and deployment of scientific instruments and in situ laboratory facilities across vast distances, and (5) opportunistic flight path replanning in response to the detection of relevant sensor signatures. Implementation of these capabilities requires achieving a high degree of vehicle autonomy across a broad spectrum of operational scenarios. The paper outlines some of the core autonomy technologies required to implement the capabilities listed above, drawing on work and results obtained in the context of AURORA (Autonomous Unmanned Remote Monitoring Robotic Airship), a research effort that focuses on the development of the technologies required for substantially autonomous robotic airships. We discuss airship modeling and control, autonomous navigation, and sensor-based flight control. We also outline an approach to airborne perception and monitoring which includes mission-specific target acquisition, discrimination and identification, and present experimental results obtained with AURORA.

Influence of Wind Speed on Airship Dynamics

A new formulation of the equations of motion of an airship is derived to allow the analysis of the wind ine uence on the airship dynamics. Initially, theequations of motion arewritten via the Lagragian approach, considering the three kinetic energy terms associated with 1 ) the energy of the vehicle motion itself, 2 ) the energy of the air around the airship due to the relative velocities, and 3 ) the energy added to the buoyancy air. After that, the equations of motion are translated into Newton’ s second law formulation, yielding a new term, wind-induced force and torque. When the airship geometry approximated by an ellipsoid of revolution is considered the wind-induced terms are then explicitly derived, and their contribution on the longitudinal and lateral dynamics of the airship motion is analyzed. The results are illustrated using the model of a real airship, considering a given range of wind speed and a constant low airspeed.

Airship Hover Stabilization Using a Backstepping Control Approach

The present paper introduces a novel approach for the airship hover stabilization problem. A synthetic modeling of the airship dynamics is introduced using a quaternion formulation of the kinematics equations. Based on this model, a backstepping design formulation is deduced for the aircraft hovering control. To deal with limitations caused by reduced actuation, saturations are introduced in the control design, and the global asymptotic stability of the system under saturation is demonstrated. The control objective is finally modified to cope with the strong lateral underactuation. Simulation results are presented for the hover stabilization of an unmanned robotic airship, with wind and turbulence conditions selected to demonstrate the behavior and robustness of the proposed solution.

Project AURORA: Infrastructure and flight control experiments for a robotic airship

Project AURORA aims at the development of unmanned robotic airships capable of autonomous flight over user-defined locations for aerial inspection and environmental monitoring missions. In this article, the authors report a successful control and navigation scheme for a robotic airship flight path following. First, the AURORA airship, software environment, onboard system, and ground station infrastructures are described. Then, two main approaches for the automatic control and navigation system of the airship are presented. The first one shows the design of dedicated controllers based on the linearized dynamics of the vehicle. Following this methodology, experimental results for the airship flight path following through a set of predefined points in latitude/longitude, along with automatic altitude control are presented. A second approach considers the design of a single global nonlinear control scheme, covering all of the aerodynamic operational range in a sole formulation. Nonlinear control solutions under investigation for the AURORA airship are briefly described, along with some preliminary simulation results.

Sliding Mode Control Approaches for an Autonomous Unmanned Airship

[Abstract] This paper presents the research developments for the global nonlinear control of an autonomous airship, covering the full flight envelope from hovering to aerodynamic flight. It focuses on the longitudinal control of the airship using two different Sliding Mode control techniques that are the classical sliding mode and the unit vector approach. The design methodologies for both techniques are presented along with some representative simulation results.

Nonlinear Control Approaches for an Autonomous Unmanned Robotic Airship

[Abstract] This paper presents the research developments for the global nonlinear control of an autonomous airship, covering the full flight envelope from hovering to aerodynamic flight. The preliminary reports for the three nonlinear control solutions under investigation were presented, that are Dynamic Inversion, Backstepping, and the Sliding Mode Control, along with some representative simulation results. A complete airship mission, with vertical take-off, path tracking, hovering, and vertical landing was successfully simulated using the Backstepping Aproach.

Erratum on "Influence of Wind Speed on Airship Dynamics"

I N THIS Erratum the authors revise the paper “Influence of Wind Speed on Airship Dynamics” [1]. After a careful mathematical deduction, it was verified that this influence under a constant translation wind indeed does not exist, and the results presented by Thomasson [2,3] are confirmed. In other words, the airship dynamics equation is the same when expressed in terms of the inertial velocity with no wind or in terms of the relative air velocity under a constant translation wind. To confirm the results, the airship dynamics is expressed using the Lagrangian approach, instead of the originalNewtonianmethod used in Azinheira et al. [1]. In addition, the new kinematics representation with quaternions used in Azinheira et al. [4], describing the velocity changes from local to Earth frames, is used in the derivation of a compact form of the force equation. Assuming a constant translation wind, the new force equation written in terms of inertial and wind velocities is then transformed to be a function of the relative velocities. The force equation expressed in this way shows the same structure and the same terms as the one expressed with the inertial andwind velocities, confirming the invariance of the dynamics under a constant translation wind. In a last step, some terms in the kinematics force equation are discarded, as they are already accounted for in the aerodynamic forces. These terms are proportional to the squared relative velocity, and their influence is already considered through the aerodynamic coefficients measured in wind-tunnel experiments. This final step is particularly important for simulation purposes, otherwise some terms would be considered twice in the dynamicmodel. Simulation results, obtained using the AURORA simulator platform support the theoretical conclusions.

SLIDING MODE CONTROL FOR THE PATH FOLLOWING OF AN UNMANNED AIRSHIP

Abstract Project AURORA aims at the development of unmanned robotic airships capable of autonomous flight for aerial inspection and environmental monitoring missions. In this article the authors present the design of two MIMO Sliding Mode Controllers for the guidance and navigation system of the AURORA airship (for the longitudinal and lateral modes). The path tracking strategy minimizes the angular and distance tracking errors with respect to a given reference trajectory. The bounded stability of the system is proved, and the results are illustrated through a simulation example where the airship is submitted to a large airspeed variation.

Modelling, Control and Perception for an Autonomous Robotic Airship

Robotic unmanned aerial vehicles have an enormous potential as observation and data-gathering platforms for a wide variety of applications. These applications include environmental and biodiversity research and monitoring, urban planning and traffic control, inspection of man-made structures, mineral and archaeological prospecting, surveillance and law enforcement, communications, and many others. Robotic airships, in particular, are of great interest as observation platforms, due to their potential for extended mission times, low platform vibration characteristics, and hovering capability. In this paper we provide an overview of Project AURORA (Autonomous Unmanned Remote Monitoring Robotic Airship), a research effort that focusses on the development of the technologies required for substantially autonomous robotic airships. We discuss airship modelling and control, autonomous navigation, and sensor-based flight control. We also present the hardware and software architectures developed for the airship. Additionally, we discuss our current research in airborne perception and monitoring, including mission-specific target acquisition, discrimination and identification tasks. The paper also presents experimental results from our work.

Lateral/directional control for an autonomous, unmanned airship

Project AURORA aims at the development of an unmanned airship capable of autonomous flight over user‐defined locations for aerial inspection and imagery acquisition. Presents a guidance control strategy for the trajectory path following of the AURORA airship, where the objective is to make the vehicle follow a set of pre‐defined points. The guidance strategy is based on a path tracking error generation methodology that takes into account both the distance and the angular errors of the airship with respect to the desired trajectory. The guidance system is composed of a path tracking guidance controller (as outer loop) and a heading controller (as inner loop), using the rudder deflection. Also proposes an additional roll controller, using the aileron input, in order to reduce rolling oscillations during yaw maneuvering and due to atmospheric turbulence.