David Lara

Real-time embedded control system for VTOL aircrafts: Application to stabilize a quad-rotor helicopter

In this paper, we present the design of an autopilot embedded control system for VTOL aircrafts using low cost sensors. The embedded control system uses parallel processing architecture. In addition, multitasking software is used to implement the data acquisition, control law computation, and correction output to get the desired set point. The control law can be easily tuning to improve the performance of the vehicle. We evaluate the performance of this platform in a quad-rotor helicopter. The main goal is to achieve the stationary flight using two control strategies, a linear PD control and nonlinear nested saturations control. Real time experiments show that the autopilot is a platform relievable with low cost components.

Minimum-energy path generation for a quadrotor UAV

A major limitation of existing battery-powered quadrotor UAVs is their reduced flight endurance. To address this issue, by leveraging the electrical model of a brushless DC motor, we explicitly determine minimum-energy paths between a predefined initial and final configuration of a quadrotor by solving an optimal control problem with respect to the angular accelerations of the four propellers. As a variation on this problem, if the total energy consumption between two boundary states is fixed, minimum-time and/or minimum-control-effort trajectories are computed for the aerial vehicle. The theory is illustrated for the DJI Phantom 2 quadrotor in three realistic scenarios.

Fuzzy State Feedback for Attitude Stabilization of Quadrotor

In this paper, we propose an application of an algorithm, based on the T-S (Takagi-Sugeno) technique, to stabilize a quadrotor helicopter. After giving the nonlinear model of the vehicle, its representation by a T-S fuzzy model is discussed. Following this, a fuzzy controller is synthesized, which will guarantee the stability of the quadrotor. The proposed T-S controller is designed with measurable premise variables and the conditions of stability are given in terms of linear matrix inequality (LMI). Simulations and real-time experiments using a test-bed platform prove the performance of a PDC control algorithm to stabilize the vehicle robustly at a desired set point.

Parametric Robust Stability Analysis for Attitude Control of a Four-rotor mini-rotorcraft

This paper presents new results to compute the robustness margin of an attitude control system of a four-rotor mini-rotorcraft. The maximum parametric uncertainty is computed when a multivariable PD control is used to stabilize the attitude of the aerial vehicle. This work is based on the value set characterization of the mathematical model for the control system. This mathematical model is represented by an interval plant with time delay. The zero exclusion principle is used to compute the robustness margin of the closed loop control system. This approach transforms the original robust stability problem into simple graphic inspection problem where we only need to verify if a graph on the complex plane contains the origin or not. Furthermore, real-time experiments are presented which show the satisfactory performance of the proposed control strategy

Robust Control Design Techniques Using Differential Evolution Algorithms Applied to the PVTOL

In this paper, we present a strategy to stabilize the attitude of a planar vertical take off and landing (PVTOL) vehicle with variable pitch propeller (VPP) rotors. In the VPP configuration, the thrust is obtained with the propeller pitch angle, instead of changing the rotor speed, and this concept adds maneuverability to the vehicle. The PVTOL used in this paper is highly unstable in its natural hovering flight state, therefore the main goal is to achieve a stable attitude. First of all, a simplified dynamic model that includes the VPP dynamics is obtained. Then, a methodology to select the parameters of a nonlinear controller using Differential Evolution algorithms (DEA) will be presented. The controllers parameters are selected with two purposes: to guarantee the asymptotic stability of the closed-loop system while taking into account the uncertainty, and to improve its robustness margin. And finally, The results are validated with real-time experiments.

A Hamiltonian approach to fault isolation in a planar vertical take-off and landing aircraft model

Abstract The problem of fault detection and isolation in a class of nonlinear systems having a Hamiltonian representation is considered. In particular, a model of a planar vertical take-off and landing aircraft with sensor and actuator faults is studied. A Hamiltonian representation is derived from an Euler-Lagrange representation of the system model considered. In this form, nonlinear decoupling is applied in order to obtain subsystems with (as much as possible) specific fault sensitivity properties. The resulting decoupled subsystem is represented as a Hamiltonian system and observer-based residual generators are designed. The results are presented through simulations to show the effectiveness of the proposed approach.

New results on robust stability for differential-difference systems with affine linear parametric uncertainty

This article presents sufficient conditions to verify the robust stability property of convex combinations for quasipolynomials that represent the characteristic equation of differential-difference dynamics systems. It considers affine linear parametric uncertainty structure in the coefficients of quasipolynomials and also, interval uncertainty in the time delay. First of all, a transformation of the delays operator is performed in order to get a two variable polynomial; after this, to obtain the robust stability property, a result based on the Hurwitz matrix is applied.

Methods engineering for designing a didactic low cost small wind turbine generator

This paper presents a methodology used for design a small wind turbine of low cost for domestic use. Method engineering is used to planning the construction and assembly of the prototype in a easy way and safely. The methodology of this paper establishes the steps for the construction. First, the wind turbine mechanical system design can be done using the computer aided design (CAD), which allows developing drawings of the full system and spared parts in 3D. Then, in this manner, the entire system can be visualized before its construction to see if all part fits in a suitable way. The results of this methodology are validated building a wind turbine prototype.

New Method for Tuning Robust Controllers Applied to Robot Manipulators

This paper presents a methodology to select the parameters of a nonlinear controller using Linear Matrix Inequalities (LMI). The controller is applied to a robotic manipulator to improve its robustness. This type of dynamic system enables the robust control law to be applied because it largely depends on the mathematical model of the system; however, in most cases it is impossible to be completely precise. The discrepancy between the dynamic behaviour of the robot and its mathematical model is taken into account by including a nonlinear term that represents the models uncertainty. The controllers parameters are selected with two purposes: to guarantee the asymptotic stability of the closed-loop system while taking into account the uncertainty, and to increase its robustness margin. The results are validated with numerical simulations for a particular case study; these are then compared with previously published results to prove a better controller performance.

Robust Control Techniques Applied to the Hot-Dip Galvanizing Process

This paper presents new results to compute the time-delay margin of the hot-dip galvanizing control system. Compared to previous works on this issue, this paper considers a mathematical model of the plant with two inputs and one output. The inputs are used to regulate the output, which represents the Zinc mass coating of steel strip. To achieve this objective, a multivariable PI controller is used, this controller is tuned applying the well known Ziegler and Nichols method, and then the maximum time-delay is computed in order to guarantee the stability property of the close loop control system. The work bases its results on a transformation of the time-delay operator and it is performed in order to get a two variable polynomial; after this, to obtain the robust stability property, a result based on the Hurwitz matrix is applied.