Showing papers by "Rogelio Lozano published in 2016"

Output based backstepping control for trajectory tracking of an Autonomous Underwater Vehicle

Abstract: This study describes the design of an output based controller for a 4-DOF (three dimensional position x-y-z as well as yaw angle) Autonomous Underwater Vehicle (AUV) using a mixed structure of a backstepping like control form and a Robust Exact Differentiator (RED). The class of AUV system allowed to control the AUV's vertical coordinate independently. To adjust the x-y plane trajectories, the angular velocity with respect to the z coordinate was used as a virtual control action. The controller was designed to solve the tracking problem of the AUV to a desired reference trajectory. The controller was originally designed under the assumption of using the whole state to construct the closed-loop structure. As the differentiator converged in finite-time, then the controller was adjusted to use the velocity information obtained by the RED. The tracking performance obtained by the proposed controller was evaluated by tracking two reference trajectories. An acceptable performance was obtained by the application of the mixed controller in terms of the mean-square error of tracking problem. A set of simulations with different reference trajectories was used to evaluate the implementation aspects of the solution suggested in this study.

Passivity-Based Control for a Micro Air Vehicle Using Unit Quaternions

Abstract: In this paper the development and practical implementation of a Passivity-Based Control (PBC) algorithm to stabilize an Unmanned Aerial Vehicle (UAV) described with unit quaternions are presented. First, a mathematical model based on Euler-Lagrange formulation using a logarithmic mapping in the quaternion space is introduced. Then, a new methodology: a quaternion-passivity-based control is derived, which does not compute excessive and complex Partial Differential Equations (PDEs) for synthesizing the control law, making a significant advantage in comparison with other methodologies. Therefore, the control design to a system as the quad-rotor is easily solved by the proposed methodology. Another advantage is the possibility to stabilize quad-rotor full dynamics which may not be possible with classical PBC techniques. Experimental results and numerical simulations to validate our proposed scheme are presented.

Quadrotor aerial manipulator based on dual quaternions

Abstract: This work presents the modeling and control of an aerial manipulator based on a quadrotor with a robotic arm using the dual quaternion approach. First the kinematic model of the complete system is obtained using dual quaternions to represent multiple rotations and translations, then the dynamic model is developed via the Newton-Euler formalism. A position control law is used to stabilize the vehicle around a desired position and orientation using a smooth trajectory. The closed-loop system is then numerically simulated to corroborate stability. In addition, experimental flight tests were performed for validation.

Optimized Discrete Control Law for Quadrotor Stabilization: Experimental Results

Abstract: This paper deals with the real-time stabilization of a Quadrotor mini helicopter applying a discrete optimal control. A discrete control strategy is better adapted to be executed in a micro-controller, therefore better results are expected with respect to continuous case. Furthermore, the optimal control law allows to helicopter to save energy and then increase its time of flight. The discrete optimal control law is synthesized considering an infinite horizon together with an exact linearization of the nonlinear dynamics of flying vehicle. At the end of this procedure the optimal control law obtained through an exact linearization is simple and easier to tune compared to the optimal strategy where the exact linearization is not performed. Taking into account the obtained experimental results, the proposed control technique produces an appropriate stabilization of the mini UAV.

The MAV3DSim hardware in the loop simulation platform for research and validation of UAV controllers

Abstract: The design and testing of unmanned aerial vehicles is a difficult task due to the high risk of damage to property during testing, to prevent accidents from happening it is indeed necessary to perform extensive simulation of controllers to ensure good stability and performance. We have been working to solve this problem by developing a realistic simulator by using a complete mathematical model of the UAV including the external variables, so we present a Multi-Aerial Vehicle 3D Simulator (MAV3DSim) that will help to the validation and verification of new controllers in a safety way. It is multi-aerial because it has the possibility to simulate a variety of types of UAVs. The multiple display options of the MAV3DSim has been proven a significant help in the development of the controllers. A hardware in the loop (HIL) implementation is used in combination with the autopilot hardware used in the experimental platform.

Altitude control improvement for a Quadrotor UAV using integral action in a sliding-mode controller

Abstract: In this paper, a robust altitude control scheme is proposed for a mini-Quadrotor UAV system based on sliding mode controller with an integral action to eliminate the steady-state error induced by the boundary layer in order to achieve asymptotic convergence to the desired altitude with continuous control input. The proposed integral sliding mode controller is chosen to ensure the stability and robustness of overall dynamics during the altitude control at a desired height reference on the z-axis. Furthermore, we propose a Control Lyapunov Function (CLF) via Lyapunov theory in order to construct the robust stabilizing controller and demonstrate the stability of the z-dynamics of our system. A suitable sliding manifold is designed to achieve the control objective. At last, the theoretical results are supported by different simulation tests to verify the robustness and effectiveness of proposed robust control scheme in presence of bounded external disturbances.

Altitude control of a quad-rotor using adaptive sliding mode

Abstract: This paper addresses simulation results about the altitude control of a quad-rotor unmanned flying vehicle (UAV) in the presence of uncertainty like wind gust. A sliding mode control was proposed, the gain of control can be decreased and, as a result, the chattering amplitude is reduced. The objective is to introduce an adaptation in the control law in order to decrease the gain to the minimal value preserving the sliding mode control and keeping his property of a finite-time convergence.

Dynamic collaboration of far-infrared and visible spectrum for human detection

Abstract: This paper is about the collaborative use of a far-infrared spectrum human detector and a visible spectrum human detector; the idea is to make collaborate these two detectors of different nature to automatically adapt the human detection whatever the luminosity changes and whatever the infrared emission changes of the scene. Our collaborative approach of detection handles: 1) gradual luminosity changes due, for instance, to the passage from night to day (and vice-versa), 2) sudden luminosity changes due, for instance, to navigation in a forest (when going through a glade in a forest), 3) infrared emission saturation when the global temperature of the scene is very high and does not permit to distinguish human people in infrared. Our approach of detection permits to detect people 24 hours a day and regardless the weather conditions. Furthermore, the proposed approach is relatively fast: it is practically as fast as using one detector alone whereas two are used in the same time.

Robust trajectory-tracking control design for a small Quad-rotor aircraft via sliding modes

Abstract: This article addresses the problem of a real-time implementation trajectory control for a miniature Quad-rotor aircraft along a time-depedent trajectory outdoor. A robust algorithm control based on sliding mode approach is proposed for the trajectory-tracking task, that ensures the convergence to a desired path r(t) in a finite time. A polynomial smooth curve trajectory is selected as reference signal in where the corresponding derivatives of the function are bounded. The proposed solution consists of implementing a real-time control law based on sliding mode using GPS measurements in order to obtain the position in the plane XY to accomplish the desired trajectory. A Lyapunov candidate function is used in order to obtain the control law as well as corresponding stability analysis of the system. Simulation and experimental results of trajectory-tracking control are presented to assess the performance and robustness of the proposed controller in the presence of small perturbations outdoor.

Estimation of velocity and position for a quadrotor aircraft in GPS denied environment

Abstract: This paper addresses the problem of autonomous navigation of a quadrotor helicopter using state estimators when the GPS signal is not available. The main objective is to estimate the translational position and velocity of the flying machine. The observer proposed uses a double integral approximation of the acceleration defined in the mathematical model in order to estimate the states previously mentioned. To apply this approach, a recursive least squares algorithm is programmed to get better estimations. Real-time experiments have been conducted in order to verify the validity and effectiveness of the proposed estimation approach, and the obtained results are presented and discussed.

Mathematical model and simulation of finger movement with electromyographic signals

Abstract: A mathematical model that describes the movement of the fingers of the hand is reported in this paper. Electromyographic signals (EMG) are recorded from the forearm and are analyzed to detect which of them are responsible of the movement of each finger. The way the EMG signals are analyzed to determine which of them produce the movement of the fingers is also described. These will be used in an ongoing project that consists of a glove used to enhance the force of the hand of a user.

Online UAS local path-planning algorithm for outdoors obstacle avoidance based on attractive and repulsive potential fields

Abstract: This paper addresses the problem of enabling Unmanned Aircraft Systems (UAS) to avoid mid-air collisions during path planning applications. We propose an improved strategy that allows the UAS to negotiate obstacles encountered during flight, while keeping the objective of finding a feasible path towards its destination. Our method computes multiple steps along the UAS's path based on GPS coordinates, a strategy which we refer to as dynamic waypoints generation. When a risk of collision is encountered, new dynamic waypoints are generated by taking into account the obstacle's planar coordinates, as well as an approximate circular envelope around it, which allows addressing a most type of obstacle's shapes. Real-time experiments performed outdoors with a holonomic UAS are provided, demonstrating the effectiveness and reliability of the proposed strategy.

Attitude and altitude control on board of an ornithopter

Abstract: This paper presents the modeling, the design of control laws, for Euler angles and altitude, and their implementation. The proposed controller is based on the backstepping procedure and uses a state feedback linearizing technique to guarantee tracking of the desired Euler angles and altitude on the ornithopter. The provided controller provides exponential convergence to the desired values. Numerical and experimental applications of the proposed algorithm illustrates the performance of the control technique.

Hybrid, discrete, non-linear, suboptimal force augmenting exoskeleton for the elbow joint

Abstract: The design and implementation of a force augmenting exoskeleton for the elbow joint is presented in this paper. The force augmentation comes from electric motors as well as from pneumatic muscles that are the actuators of the device. This is the reason to say that the device is hybrid. Electric motors are more easily and precisely controlled than pneumatic muscles, however the last ones can move heavier weights. The autonomy of a device of this kind is reduced due to the energy expenditure of the two types of actuators employed. For this reason a suboptimal discrete nonlinear control was implemented which improves performance and lengthens considerably the operation time. A dynamical model of the device is also presented and a comparison between a PD+G and a suboptimal control is made. Simulation results are presented.

Energy based control for a quadrotor using unit quaternions

Abstract: This paper presents the design and simulation of an energy-based control strategy to stabilize a quadrotor described with unit quaternions and their axis-angle representation. The mathematical model is based on Euler-Lagrange formulation using a logarithmic mapping in the quaternion space. The proposed solution introduces a new approach: a quaternion-energy-based control, which introduces an energy expression defined as a Lyapunov function. The designed control law allows the stabilization of the vehicle in all its states. Simulation results and an experimental validation are presented to corroborate the effectiveness of the proposed strategy.