ABSTRACT: The present study faces the problem of safely controlling the position trajectory of a multirotor aerial vehicle subjected to a conic constraint on the total thrust vector and a linear convex constraint on the position vector. The problem is solved using a linear state-space model predictive control strategy, whose optimization is made handy by replacing the original conic constraint set on the thrust vector by an inscribed pyramidal space, which renders a linear set of inequalities. The proposed method is evaluated on the basis of Monte Carlo simulations taking into account a random disturbance force. The simulation results show the effectiveness of the method in tracking the commanded trajectory while respecting the constraints. They also predict the effect of both the speed command and the maximum allowed inclination angle on the system performance.

ABSTRACT The cooperative control of small unmanned aerial vehicles such as the multicopters has been extensively investigated worldwide for functionality augmentation and cost reduction with respect to a single larger vehicle. The present paper proposes a software-in-the-loop simulation scheme for performance evaluation and demonstration of formation flight control systems of multicopters. The simulation scheme consists of a computer network where each computer simulates one of the vehicles using the MATLAB/Simulink for implementing the local control system and the X-Plane for simulating the flight dynamics and environment. For cooperation, the local control systems exchange position data by means of the network. In order to illustrate the proposed scheme, a group of 3 octocopters is taken into consideration and a leader-follower strategy is chosen for triangular position formation, with the leader moving in a straight line with constant speed.

A concepção de um satélite universitário de baixo custo busca atender as restrições de seu lançamento como carga útil secundária. A configuração girostato foi investigada para avaliar o desempenho do Sistema de Controle de Atitude (SCA) autônomo durante a aquisição de atitude quando o satélite se separa do veículo lançador em uma condição inicial desfavorável. A configuração girostato é controlada em três eixos e busca manter voltada para o Sol a única face com o painel solar. Uma roda de momentum, cujo eixo de rotação é ortogonal àquela face, provê rigidez giroscópica para, em conjunto com três bobinas de torque com núcleo de ar, gerar torques para controle de atitude em três eixos. O SCA inicia sua ação a partir da separação, operando em malha fechada com a estimação da atitude e da velocidade angular do satélite. Essas estimativas são fornecidas por um filtro de Kalman estendido (FKE) que processa medidas vetoriais da direção do Sol e do campo geomagnético oriundas de sensores de Sol e magnetômetro triaxial. Partindo de condições desfavoráveis, os resultados mostraram que o apontamento do satélite demanda cerca de um dia e meio dia para prover erro de apontamento inferior a 10º e menos de dois dias para manter o erro abaixo de 0,1º. Em torno do eixo da roda, ocorre oscilação do satélite em torno da referência, mas dentro de uma margem aceitável. A duração das manobras em relação à capacidade de carga das baterias embarcadas confirmou a viabilidade da configuração girostato. O desempenho e a complexidade dessa configuração foram comparados com a estabilização de corpo rígido com rotação spin visando selecionar configuração apropriada para a missão do satélite.

The design of a low cost university satellite ITASAT seeks to meet launch constraints as a secondary, piggyback payload. The dual-spin configuration has been investigated to determine the performance of the autonomous Attitude Control System (SCA) when the satellite separates from the launch vehicle in an unfavorable initial condition prior to attitude acquisition. The dual-spinner is controlled in three axes to acquire and maintain a single face pointing to the Sun by means of a momentum wheel whose rotation axis is orthogonal to that face, and a triad of air-core coil magnetotorquers that provide gyroscopic stiffness and control torques to maneuver and point the solar panel to the Sun. The SCA starts actuation as from separation, and operates in closed loop with estimates of the satellite attitude and angular velocity. These estimates are computed by an extended Kalman filter (FKE) that processes vector measurements of the Sun direction and the geomagnetic field provided by Sun sensors and a triaxial magnetometer. Starting from unfavorable initial conditions, approximately 1.5 day has been required to yield a pointing error under 10º, and less than two days to maintain the error below 0.1º. Satellite oscillations about the wheel axis have been within an acceptable margin. The duration of the maneuvers in relation to the capacity of the batteries on board have confirmed the feasibility of the dual-spin configuration. The resulting performance and complexity have been compared with those of the rigid-body spin stabilization to select an appropriate configuration for the satellite mission.