Henrique C. Ferreira

Disturbance rejection in a fixed wing UAV using nonlinear H ∞ state feedback

This paper presents a nonlinear H∞ controller for the rejection of input disturbances in a fixed wing UAV. The proposed controller acts in all states of a complete nonlinear dynamic model. Simulation results show that the aircraft is successfully maintained in the desired stable condition after two different disturbances: a finite pulse and noise.

Galerkin Method and Weighting Functions Applied to Nonlinear H Control with Output Feedback

This paper considers two aspects of the nonlinear H ∞ control problem: the use of weighting functions for performance and robustness improvement, as in the linear case, and the development of a successive Galerkin approximation method for the solution of the Hamilton—Jacobi—Isaacs equation that arises in the output-feedback case. Design of nonlinear H ∞ controllers obtained by the well-established Taylor approximation and by the proposed Galerkin approximation method applied to a magnetic levitation system are presented for comparison purposes.

A high precision attitude determination and control system for the UYS-1 nanosatellite

This paper presents the design of a high precision attitude determination and control system for the UYS-1 Ukrainian nanosatellite. Its main task is the 3-axis stabilization with less than 0.5° angle errors, so the satellite may take high precision photos of Earths surface. To accomplish this task, this system comprises a star tracker and three reaction wheels. To avoid external disturbances and actuators faults, a PD-type and a PID-type robust controllers are simulated and the results are compared to an empirically adjusted PD controller.

A Low-Cost Attitude Determination and Control System for the UYS-1 nanosatellite

This paper considers the development of a Low-Cost Attitude Determination and Control Subsystem (LCADCS) for the first Ukrainian University Nanosatellite, UYS-1. For the attitude determination part, an attitude determination framework is implemented to combine all available data at each time sample using a modified Unscented Kalman Filter, based on the Unscented Quaternion Estimator (USQUE). For the attitude control part, the subsystem should rely only on magnetic actuation with magnetorquers operating in a relay mode. A proposed control strategy is presented. The choice of hardware and algorithms is addressed observing the LCADCS requirements, theoretical and practical considerations, ease of implementation, and time and cost budgets inherent to small-satellite projects. The validity and performance of the general proposed systems are evaluated using computer simulations.

Robust global bimodal rest-to-rest attitude control of rigid body using unit quaternion

Abstract This work proposes a hysteresis-based controller with two binary logic variables for the rest-to-rest control of attitude represented by quaternions. The control system has a hybrid nature given by the presence of a switching logic variable that indicates which quaternion representation of the reference attitude should be followed and by a second logic variable which indicates the chattering prone region and has the overall effect of adapting the hysteresis width. It is presented a formal proof that the proposed bimodal control leads to global stability without unwinding and is robust against chattering for any measurement noise with magnitude less than or equal to a given maximum value. Simulation results indicate that the proposed adaptive hysteresis width controller can be advantageous when the initial and final angular velocities have small magnitudes as is the case of the rest-to-rest attitude control problem.

Non linear controller and path planner algorithm for an autonomous variable shape formation flight

A formation flight controller can be used in a UAS fleet to avoid collision, reduce fuel consumption, or to execute interactions between the UASs, such as autonomous aerial refueling. In this paper, an autonomous formation flight (AFF) controller based on non linear dynamic inversion (NLDI) and a non-colliding path planner are proposed. The proposed NLDI AFF extends a NLDI controller found in literature to account a maneuvering leader and time-varying shape formations. The proposed path planner generates a time-varying shape formation in which a set of followers flies from their initial relative position to their desired final one, via non-colliding paths. Simulation results show that the proposed controller tracks the trajectories generated by the path planner and achieves lower formation errors than the NLDI AFF controller found in literature.

Robust steering control of spacecraft carrier rockets

In the year of 2003 it was established a cooperation agreement between Ukraine and Brazil for utilization of Cyclone-4 launch vehicle at Alcantara Launch Center. The company responsible for the marketing and operation of launch services is the company bi-national Alcantara Cyclone Space (ACS). The Cyclone-4 launch vehicle is the newest version of the Ukrainian Cyclone family launchers developed by Yuzhnoye State Design Office. This family has been used for many successful spacecrafts launches since 1969. This paper is concerned with the yaw stabilization problem around a nominal trajectory for the third stage of a satellite carrier rocket similar to the Cyclone-4. Only the steering machine of the main engine is considered as actuator. The dynamic behavior of the third stage around the nominal trajectory is modeled as a fourthorder time-varying linear system whereas the steering machine is modeled as a linear dynamical system up to third order. The values of the parameters of the steering machine model are unknown, however belonging to known intervals. As the main result, the stabilization problem is solved with a proportional derivative (PD) controller. The proposed tuning approach takes into account the robustness of the controller with respect to the steering machine model uncertainties. The performance of the PD controller is demonstrated by simulation results.