A Vision-Based Navigation System for Perching Aircraft

This is the final version of the article. Available from Springer via the DOI in this record.This paper presents the investigation of the use of position-sensing diode (PSD) - a light source direction sensor - for designing a vision-based navigation system for a perching aircraft. Aircraft perching maneuvers mimic bird’s landing by climbing for touching down with low velocity or negligible impact. They are optimized to reduce their spatial requirements, like altitude gain or trajectory length. Due to disturbances and uncertainties, real-time perching is realized by tracking the optimal trajectories. As the performance of the controllers depends on the accuracy of estimated aircraft state, the use of PSD measurements as observations in the state estimation model is proposed to achieve precise landing. The performance and the suitability of this navigation system are investigated through numerical simulations. An optimal perching trajectory is computed by minimizing the trajectory length. Accelerations, angular-rates and PSD readings are determined from this trajectory and then added with experimentally obtained noise to create simulated sensor measurements. The initial state of the optimal perching trajectory is perturbed, and by assuming zero biases, extended Kalman filter is implemented for aircraft state estimation. It is shown that the errors between estimated and actual aircraft states reduce along the trajectory, validating the proposed navigation system

A Vision-Based Navigation System for Perching Aircraft

peer reviewedThis paper presents the investigation of the use of position-sensing diode (PSD) - a light source direction sensor - for designing a vision-based navigation system for a perching aircraft. Aircraft perching maneuvers mimic bird’s landing by climbing for touching down with low velocity or negligible impact. They are optimized to reduce their spatial requirements, like altitude gain or trajectory length. Due to disturbances and uncertainties, real-time perching is realized by tracking the optimal trajectories. As the performance of the controllers depends on the accuracy of estimated aircraft state, the use of PSD measurements as observations in the state estimation model is proposed to achieve precise landing. The performance and the suitability of this navigation system are investigated through numerical simulations. An optimal perching trajectory is computed by minimizing the trajectory length. Accelerations, angular-rates and PSD readings are determined from this trajectory and then added with experimentally obtained noise to create simulated sensor measurements. The initial state of the optimal perching trajectory is perturbed, and by assuming zero biases, extended Kalman filter is implemented for aircraft state estimation. It is shown that the errors between estimated and actual aircraft states reduce along the trajectory, validating the proposed navigation system

New stable by construction autonomous aerial vehicle: configuration and dynamic model.

[ES] En los últimos años, diferentes estrategias y modelos matemáticos se han desarrollado para el análisis y control de vehículos aéreos no tripulados. El presente artículo amplía este panorama al enfocarse en un sistema aéreo no tripulado estable por construcción. Gracias a su diseño, el sistema reportado disipa la energía que recibe por la acción de perturbaciones externas. El sistema propuesto cuenta con un rotor único para el desarrollo de diferentes tipos de vuelo. Este artículo reporta el concepto de diseño del sistema aéreo no tripulado, la estructura de su modelo dinámico de nueve grados de libertad, un conjunto de simulaciones numéricas que permiten analizar el comportamiento del modelo desarrollado y los primeros resultados experimentales que validan la estabilidad por construcción del vehículo aéreo autónomo. Los dos aspectos más significativos e innovadores reportados en este artículo son el uso de un rotor único orientable para la ejecución de diferentes modos de vuelo y la propiedad inherente del sistema tal que sus estructuras, externa e interna, son estables por construcción.[EN] In recent years, different strategies and mathematical models have been developed in order to analyze and control unmanned aerial vehicles. This article expands this panorama by focusing on a, stable by construction, unmanned aerial system. Thanks to its design, the reported system dissipates the energy received by the action of external disturbances. The proposed vehicle has a unique rotor in order to perform different flight modes. This article reports the design concept of the aerial system, the mathematical structure of its nine degrees of freedom dynamic model, a set of numerical simulations allowing the analysis of the behavior of the developed model and the first experimental results that validate the stability, by construction, of the aerial vehicle. The two most significant and innovative aspects reported in this article are the use of a single orientable rotor to perform different flight modes and the inherent property of the system that makes it stable by construction.Este trabajo fue apoyado por la Universidad Autónoma del Estado de México bajo el proyecto de investigación: Desarrollo de un Vehículo Esférico Aéreo Autónomo con clave 3818/2014/CIB. Eduardo Sánchez Fontes agradece el financiamiento por la beca CONACYT CVU 553663.Sánchez-Fontes, E.; Avila Vilchis, JC.; Vilchis-González, AH.; Saldivar, B.; Jacinto-Villegas, JM.; Martínez-Mendez, R. (2020). 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Distributed Coverage Control of Constrained Constant-Speed Unicycle Multi-Agent Systems

This paper proposes a novel distributed coverage controller for a multi-agent system with constant-speed unicycle robots (CSUR). The work is motivated by the limitation of the conventional method that does not ensure the satisfaction of hard state- and input-dependent constraints and leads to feasibility issues for multi-CSUR systems. In this paper, we solve these problems by designing a novel coverage cost function and a saturated gradient-search-based control law. Invariant set theory and Lyapunov-based techniques are used to prove the state-dependent confinement and the convergence of the system state to the optimal coverage configuration, respectively. The controller is implemented in a distributed manner based on a novel communication standard among the agents. A series of simulation case studies are conducted to validate the effectiveness of the proposed coverage controller in different initial conditions and with control parameters. A comparison study in simulation reveals the advantage of the proposed method in terms of avoiding infeasibility. The experiment study verifies the applicability of the method to real robots with uncertainties. The development procedure of the method from theoretical analysis to experimental validation provides a novel framework for multi-agent system coordinate control with complex agent dynamics

Adaptive and Optimal Motion Control of Multi-UAV Systems

This thesis studies trajectory tracking and coordination control problems for single and multi unmanned aerial vehicle (UAV) systems. These control problems are addressed for both quadrotor and fixed-wing UAV cases. Despite the fact that the literature has some approaches for both problems, most of the previous studies have implementation challenges on real-time systems. In this thesis, we use a hierarchical modular approach where the high-level coordination and formation control tasks are separated from low-level individual UAV motion control tasks. This separation helps efficient and systematic optimal control synthesis robust to effects of nonlinearities, uncertainties and external disturbances at both levels, independently. The modular two-level control structure is convenient in extending single-UAV motion control design to coordination control of multi-UAV systems. Therefore, we examine single quadrotor UAV trajectory tracking problems to develop advanced controllers compensating effects of nonlinearities and uncertainties, and improving robustness and optimality for tracking performance. At fi rst, a novel adaptive linear quadratic tracking (ALQT) scheme is developed for stabilization and optimal attitude control of the quadrotor UAV system. In the implementation, the proposed scheme is integrated with Kalman based reliable attitude estimators, which compensate measurement noises. Next, in order to guarantee prescribed transient and steady-state tracking performances, we have designed a novel backstepping based adaptive controller that is robust to effects of underactuated dynamics, nonlinearities and model uncertainties, e.g., inertial and rotational drag uncertainties. The tracking performance is guaranteed to utilize a prescribed performance bound (PPB) based error transformation. In the coordination control of multi-UAV systems, following the two-level control structure, at high-level, we design a distributed hierarchical (leader-follower) 3D formation control scheme. Then, the low-level control design is based on the optimal and adaptive control designs performed for each quadrotor UAV separately. As particular approaches, we design an adaptive mixing controller (AMC) to improve robustness to varying parametric uncertainties and an adaptive linear quadratic controller (ALQC). Lastly, for planar motion, especially for constant altitude flight of fixed-wing UAVs, in 2D, a distributed hierarchical (leader-follower) formation control scheme at the high-level and a linear quadratic tracking (LQT) scheme at the low-level are developed for tracking and formation control problems of the fixed-wing UAV systems to examine the non-holonomic motion case. The proposed control methods are tested via simulations and experiments on a multi-quadrotor UAV system testbed

Alocação de controle desacoplada rápida em sistemas de controle superatuados

Over-actuated systems usually require nonlinear control allocation methods to map Virtual Control Actions (VCAs) into Real Control Actions (RCAs). This process requires computational efforts sometimes not available on embedded robotic platforms. It is in this context that this work presents the design of an Quadrotor Tilt-Rotor (QTR) through a new concept of control allocation with uncoupled RCAs, where the initial nonlinear system is divided into partially dependent linear subsystems with fast and robust convergence. For this purpose, the RCAs are divided into smaller sets, used sequentially to linearize and solve the system. The reduction of the initial nonlinear control effectiveness matrix is improved by selecting each subset in a different arrangement of VCAs. However, the choice of this arrangement may lead to absence, partial or full superposition of VCAs in the subsystems. The technique was validated through mathematical tutorial cases, QTR simulation tests and open field flight and gyroscopic test bench experimental tests. Finally, the control allocation technique proved to be reliable, robust, efficient and applicable in the QTR when there is full superposition of VCAs between the subsystems.Sistemas superatuados geralmente requerem métodos de alocação de controle não lineares para mapear as Ações de Controle Virtuais (ACVs) em Ações de ControleReais (ACRs). Esse processo exige esforços computacionais que, as vezes, são limitados em plataformas robóticas embarcadas. E neste contexto que este trabalho apresenta o projeto de um Veículo Aéreo Não-Tripulado (VANT) do tipo Quadrotor Tilt-Rotor (QTR) superatuado, utilizando de um novo conceito de alocação de controle com ACRs desacopladas, onde o sistema não-linear inicial é dividido em subsistemas lineares parcialmente dependentes. Para esse propósito, as ACRs são divididas em conjuntos menores, usados sequencialmente para linearizar e resolver o sistema. Para melhorar a redução da matriz de eficácia de controle não-linear inicial, é possível selecionar para cada subconjunto um arranjo diferente de ACVs. Contudo, a escolha deste arranjo pode gerar ausência, parcial ou completa superposição das ACVs nos subsistemas. A validação da técnica foi realizada através de exemplos matemáticos tutoriais, testes de simulação e experimentais do QTR em uma bancada giroscópica e em campo aberto. Por fim, a técnica de alocação de controle se mostrou confiável, robusta, eficiente e aplicável no QTR quando se tem superposição completa das ACVs entre os subsistemas