Showing papers by "Rogelio Lozano published in 2019"

Autonomous Navigation for Unmanned Underwater Vehicles: Real-Time Experiments Using Computer Vision

Abstract: This letter studies the problem of autonomous navigation for unmanned underwater vehicles, using computer vision for localization. Parallel tracking and mapping is employed to localize the vehicle with respect to a visual map, using a single camera, whereas an extended Kalman filter (EKF) is used to fuse the visual information with data from an inertial measurement unit, in order to recover the scale of the map and improve the pose estimation. A proportional integral derivative controller controller with compensation of the restoring forces is proposed to accomplish trajectory tracking, where a pressure sensor and a magnetometer provide feedback for depth control and yaw, respectively, while the remaining states are provided by the EKF. Real-time experiments are presented to validate the navigation strategy, using a commercial remotely operated vehicle (ROV), the BlueROV2, which was adapted to perform as an autonomous underwater vehicle with the help of the robot operative system.

Backstepping and Robust Control for a Quadrotor in Outdoors Environments: An Experimental Approach

Abstract: This paper addresses the tracking control of quadrotors flying outdoors. Two control laws are combined and tested in real-time experiments. The aircraft attitude and the translational displacement are controlled using the backstepping approach, while the altitude is controlled using the sliding mode control strategy. In both cases, new modifications are introduced with respect to the existing classical algorithms. Concerning the backstepping algorithm, we introduce the dynamical model of the quadrotor in the controller design and this guarantees that the virtual input is bounded. On the other hand, the proposed sliding mode control assures that the vehicle's altitude converges in finite time to the desired reference, even when uncertainties are considered in the system. The proposed controller is tested in an outdoor environment and the experiments highlighted the controllers' reliability. Additionally, the performance of the closed-loop plant with the proposed controllers is compared with the performance given by a proportional-derivative controller.

Robust Trajectory Tracking for Unmanned Aircraft Systems using a Nonsingular Terminal Modified Super-Twisting Sliding Mode Controller

Abstract: Precision trajectory tracking problem for Unmanned Aerial Systems (UAS) is addressed in this work. A novel algorithm that combines a Nonsingular Modified Super-Twisting Controller with a High Order Sliding Mode Observer to enable an aerial vehicle tracking a desired trajectory under the assumption that i) its translational velocities are not available and ii) there are unmodeled dynamics and external disturbances. The proposed Sliding Mode Controller is based on a nonlinear sliding mode surface that ensures that the position and velocity tracking errors of all system’s state variables converge to zero in finite time. Moreover, the proposed controller generates a continuous control signal eliminating the chattering phenomenon. Finally, simulation results and an extensive set of experiments are presented in order to illustrate the robustness and effectiveness of the proposed control strategy.

Energy-Based Control and LMI-Based Control for a Quadrotor Transporting a Payload

Abstract: This paper presents the control of a quadrotor with a cable-suspended payload. The proposed control structure is a hierarchical scheme consisting of an energy-based control (EBC) to stabilize the vehicle translational dynamics and to attenuate the payload oscillation, together with a nonlinear state feedback controller based on an linear matrix inequality (LMI) to control the quadrotor rotational dynamics. The payload swing control is based on an energy approach and the passivity properties of the system’s translational dynamics. The main advantage of the proposed EBC strategy is that it does not require excessive computations and complex partial differential equations (PDEs) for implementing the control algorithm. We present a new methodology for using an LMI to synthesize the controller gains for Lipschitz nonlinear systems with larger Lipschitz constants than other classical techniques based on LMIs. This theoretical approach is applied to the quadrotor rotational dynamics. Stability proofs based on the Lyapunov theory for the controller design are presented. The designed control scheme allows for the stabilization of the system in all its states for the three-dimensional case. Numerical simulations demonstrating the effectiveness of the controller are provided.

Visual detection and tracking with UAVs, following a mobile object

Abstract: Conception and development of an Unmanned Aerial Vehicle (UAV) capable of detecting, tracking and following a moving object with unknown dynamics is presented in this work, considering a human face...

High gain observer for a class of nonlinear systems with coupled structure and sampled output measurements: application to a quadrotor

Abstract: This paper proposes a new high gain observer for a class of non-uniformly observable nonlinear systems with coupled structure driven by sampled outputs. The considered class of systems is p...

A Hybrid Adaptive Control Strategy for Industrial Robotic Joints

Abstract: This paper presents a hybrid adaptive approximation-based control (HAAC) strategy for a class of uncertain robotic joints' system The proposed control structure consists of a robust sliding mode controller and an adaptive approximation-based controller The robust sliding mode controller is designed by using the super-twisting algorithm, which is a particularly effective method to decrease the chattering caused by the traditional sliding mode control (SMC) and compensate the disturbances Another improvement of the robust sliding mode controller is that the robust control parameters only subject to the upper bound of the derivative of the external disturbances, rather than choosing a relatively large value Moreover, the designed adaptive approximation-based controller has the following two distinctive features: 1) the control parameters are designed to be adjusted in real time and 2) the prior knowledge of actual robotic model is not required to be known These features contribute to compensating the uncertainties The stability of the closed-loop system is proved by using the Lyapunov theory, and the simulation results demonstrate the effectiveness of the proposed control method Finally, the proposed HAAC could apply in the experiments of industrial robotic joints' system

A Special Kind of Sliding Mode Control for Nonlinear System With State Constraints

Abstract: This paper presents a control strategy named auxiliary surfaces sliding mode control (AS-SMC) by using Positive Invariant Set (PIS) to control a class of continuous nonlinear systems with state constraints. The PIS can be regarded as a special kind of sliding surface, and its invariance ensures that the system state can satisfy the constraints in the convergence process. The stability analysis and a PIS theory proof are given. The control strategy is successfully tested in numerical simulations and even effectively applied to the coaxial unmanned helicopter flight control system on hardware in the loop (HIL) platform. The results verify the effectiveness of the proposed control strategy for the experimental set-up.

Design and Construction of a UAV VTOL in Ducted-Fan and Tilt-Rotor Configuration

Abstract: This paper presents the development of an hybrid Unmanned Aerial Vehicle that combines the capabilities of Vertical Takeoff and Landing (VTOL) as well as the hover flight of an helicopter, with the autonomy, load capacity and speed offered by an airplane. We start from an aircraft concept that uses the Tilt-Rotor configuration to perform the transition phase from one flight mode to another and simultaneously we used Ducted-Fans for increasing the flight performance during the vertical flight phase. The aerodynamic design is developed using computational tools, such as XFLR5 for preliminary design and ANSYS FLuent®for the verification of the preliminary fixed wing design. While for the vertical flight, experimental tests were conducted in order to determine the lift system requirements by using Ducted-Fans. Afterwards, the manufacturing process derived from the aerodynamic design is presented. The avionics developed is described for handling the control surfaces during the airplane mode and the main lift system during the vertical flight as well as the integration of mechanism and sensors used. Finally, the obtained results from the conducted vertical flight tests at outdoors environments are presented in order to show the effectiveness of the aircraft concept.

Sun Tracking Technique Applied to a Solar Unmanned Aerial Vehicle

Abstract: In recent years, solar energy has been used as an energy source for many different applications. Currently in the area of Unmanned Aerial Vehicles (UAVs), there are research studies that incorporate this renewable energy technology to increase the vehicle’s autonomy. This technique also needs particular construction techniques and electronic boards, designed to reduce weight and increase the efficiency of all solar systems on board the UAV. As is well known, the amount of generated solar energy could be increased throughout a day a sun tracking technique is added. The present paper proves that the roll angle of a fixed wing UAV can be used to track the sun to increase the energy generated by the solar panels placed on the wing. In that case, the plane’s attitude must be compensated with the yaw angle control to be able to perform a photogrammetric mission. This will be achieved using a control strategy based on the super-twisting technique that ensures convergence in finite time even in the presence of bounded perturbations. The design of the control laws as well as the numerical simulation and real flight results are shown to validate the use of the sun tracking system.

Pitching moment analysis and adjustment for tilt-wing UAV in VTOL mode

Abstract: This paper presents the pitching moment stability analysis and adjustment for tilt-wing unmanned aerial vehicle (UAV) in hovering flight and vertical take-off and landing (VTOL). The tilt-wing UAVs combine the features of fixed-wing UAVs with VTOL capabilities by tilting the wing and rotor system for the transition between flight modes. Due to its hybrid configuration, the altitude control study, position and attitude, poses a major problem during the entire flight for a given mission. Namely, in the first flight phase the pitching moment could present instabilities with different disturbances, such as wind, that are difficult to compensate. In this paper this problem is analyzed and possible solutions for the stabilization are presented and evaluated in a test bench. These solutions were implemented in new test prototypes demonstrating satisfactory results in outdoor flight tests.

Hybrid autogyro: Airborne wind gust energy conversion using autorrotation

Abstract: An hybrid autogyro aircraft with wind energy conversion using autorotation is proposed. The fixed wing addition to classic autogyro assists the aircraft lifting reducing speed minimum wind for the flight. A PID control strategy is used to attitude aircraft stabilization. In order to verify the generation of energy, the relationship between energy and wind speed are recorded during experimental flights.

Attitude and altitude control for a fixed wing UAV applied to photogrammetry

Abstract: The use of autonomous vehicles in daily life is more commonly every day, we can find it in security missions, agriculture, windmills inspection and one of its main uses the processes of photogrammetry, because the new systems and technologies to perform the last one could give errors of centimeters in a topographic map. The studies of large areas are carried out with fixed-wing UAV, so it is necessary to ensure that the vehicle could follow a desired path even in presence of external disturbances, in order to avoid uncovered or wrong defined areas during the post-processing. In this article we analyzed and compared by simulation the use of a non-linear control technique with a PID control to stabilize the airplane’s attitude and height, to prove that in some cases only a linear control technique is enough to stabilize the UAV and also probe that the amount of energy to control the UAV is similar in both techniques. So the majority of computational resources can be assigned to object detection and collision avoidance tasks, for vehicles under 5 kilograms.

Design and Implementation of an Artificial Neural Network Wavelet for Load Transportation with two Unmanned Aircraft Systems

Abstract: This paper deals with the problem of enabling a team of two Unmanned Aircraft Systems to perform an autonomous load transportation task. We propose a strategy whose main objective is to ensure a stable flight of the team of agents when cooperatively transporting the load. The strategy is based on the implementation of a neural network controller and a neural network estimator, using wavelet activation functions in combination with a cooperative multi-agent control approach. To show the effectiveness and applicability of the proposed framework, a real time experimental implementation is presented. Additionally, a comparison with respect to a classic control law is also provided, demonstrating the superior performance attained when adopting the proposed controller.

Non-Linear Control for PVTOL Without Algebraic Restrictions

Abstract: This paper presents a Proportional-Derivative Control strategy for the non-linear PVTOL system without algebraic restrictions. The total thrust is computed using a non-linear feedback compensation so that the altitude reaches the desired reference. The horizontal position $x$ is then controlled by choosing the orientation angle $\theta$ as a smooth saturation function of $x$ and $\dot{x}$ . A proof of convergence is presented using a Lyapunov approach. The proposed control strategy is successfully tested in numerical simulations.

Teleoperation of a drone based on a virtual environment

Abstract: In this paper, a teleoperation system for a quadrotor using a virtual environment is presented. A virtual aerial vehicle was introduced by applying the dynamic model of a quadrotor. An attitude controller was implemented for an operator to pilot the drone. The behavior of the virtual drone is communicated to a real vehicle through a mapping between the real and virtual spaces. This mapping is introduced in a robust quaternion-based controller ensures a safe flight in the real world. Simulations and experimental results are carried out to validate the proposal. With this idea of controlling a drone virtually, the performance of beginner and expert drone pilots is improved.

Collaborative training of far infrared and visible models for human detection

Abstract: This paper is about the collaborative training of a far infrared and a visible spectrum human detector; the idea is to use the strengths of one detector to fill the weaknesses of the other detector and vice versa. At first infrared and visible human detectors are pre-trained using initial training datasets. Then, the detectors are used to collect as many detections as possible. The validity of each detection is tested using a low-level criteria based on an objectness measure. New training data are generated in a coupled way based on these detections and thus reinforce both the infrared and the visible human detectors in the same time. In this paper, we showed that this semi-supervised approach can significantly improve the performance of the detectors. This approach is a good solution to generate infrared training data, this kind of data being rarely available in the community.