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Showing papers by "Rogelio Lozano published in 2020"


Journal ArticleDOI
TL;DR: This research work focuses on the design of a robust-adaptive control algorithm for a 4DOF Unmanned Underwater Vehicle (UUV) based in a Non-Singular Terminal Sliding Mode Control with adaptive gains, where the proposed adaptation mechanism ensures that the gains remain bounded.
Abstract: This research work focuses on the design of a robust-adaptive control algorithm for a 4DOF Unmanned Underwater Vehicle (UUV). The proposed strategy is based in a Non-Singular Terminal Sliding Mode Control (NTSMC) with adaptive gains, where the proposed adaptation mechanism ensures that the gains remain bounded. In this control strategy a non-singular terminal sliding surface is proposed to obtain a faster convergence of the tracking errors. The NTSMC ensures Practical Finite-Time Stability for the closed-loop system as well as exhibits a chattering reduction. In order to demonstrate the satisfactory performance of the proposed controller, a set of experiments was performed with a Non-Singular Terminal Sliding Mode Controller and an Adaptive Non-Singular Terminal Sliding Mode Control (ANTSMC) in real time for trajectory tracking in the X-Y plane, the graphs showed that the ANTSMC converges faster to a smaller region and reduces oscillations.

34 citations


Journal ArticleDOI
TL;DR: A Nonsingular Fast Terminal Sliding Mode Control (RNFTSMC) is proposed to regulate the position of a mobile lower limb exoskeleton powered by linear actuators with four degrees of freedom, and reducing the chattering effect produced by the nature of the controller actuators.

23 citations


Journal ArticleDOI
TL;DR: A real-time robust altitude control strategy for a quadrotor aircraft is proposed, also a convolutional neuronal network for crack recognition is developed and a database of cracks was built from images taken from the Internet.
Abstract: Building inspection is a vital task because infrastructure damage puts people at risk or causes economic losses. Thanks to the technological breakthroughs in regard to Unmanned Aerial Vehicles (UAVs) and intelligent systems, there is a real possibility to implement an inspection by means of these technologies. UAVs allow reaching difficult places and, depending on the hardware carried onboard, take data or compute algorithms to understand the environment. This paper proposes a real-time robust altitude control strategy for a quadrotor aircraft, also a convolutional neuronal network for crack recognition is developed. The main idea of this proposal is to lay the background for an autonomous system for the inspection of structures using a UAV. For the robust control, a combination of two control actions, one linear (PD) and another nonlinear (Sliding Mode) is used. The combination of these control actions allows increasing the system’s performance. To verify the satisfactory performance of proposed control law, simulations and experimental results with a quadrotor, in the presence of disturbances, are presented. For crack recognition in images, several experiments were carried out validating the proposed model. For CNN training, a database of cracks was built from images taken from the Internet.

18 citations


Journal ArticleDOI
25 Nov 2020
TL;DR: The UAV complete dynamic model is obtained using the Newton–Euler formulation, which includes aerodynamic effects, as the drag and lift forces of the wings, which are a function of airstream generated by the rotors, the cruise speed, tilt-wing angle and angle of attack.
Abstract: Hybrid Unmanned Aerial Vehicles (H-UAVs) are currently a very interesting field of research in the modern scientific community due to their ability to perform Vertical Take-Off and Landing (VTOL) and Conventional Take-Off and Landing (CTOL). This paper focuses on the Dual Tilt-wing UAV, a vehicle capable of performing both flight modes (VTOL and CTOL). The UAV complete dynamic model is obtained using the Newton–Euler formulation, which includes aerodynamic effects, as the drag and lift forces of the wings, which are a function of airstream generated by the rotors, the cruise speed, tilt-wing angle and angle of attack. The airstream velocity generated by the rotors is studied in a test bench. The projected area on the UAV wing that is affected by the airstream generated by the rotors is specified and 3D aerodynamic analysis is performed for this region. In addition, aerodynamic coefficients of the UAV in VTOL mode are calculated by using Computational Fluid Dynamics method (CFD) and are embedded into the nonlinear dynamic model. To validate the complete dynamic model, PD controllers are adopted for altitude and attitude control of the vehicle in VTOL mode, the controllers are simulated and implemented in the vehicle for indoor and outdoor flight experiments.

10 citations


Journal ArticleDOI
TL;DR: Results look very promising compared to non-adaptive controls and may help to construct more polyvalent and efficient gimbals which would further facilitate their expansion.
Abstract: Inertial stabilised platforms are increasingly popular with a large range of products available mainstream. Most items are controlled using popular algorithms that sometimes do not offer best achie...

5 citations


Proceedings ArticleDOI
01 Sep 2020
TL;DR: A non-linear mathematical model is developed that includes the UAV complete dynamics, which presents significant changes in aerodynamic characteristics, especially during the transition flight of a hybrid UAV of Dual Tilt-Wing type.
Abstract: A hybrid unmanned autonomous vehicle (UAV) combines the high-speed cruise capability of a fixed-wing airplane, with the hovering flight, vertical take-off and landing capabilities of a helicopter. The change between both flight modes refers to as a transition flight process. This paper presents the flight dynamics during the transition stage of a hybrid UAV of Dual Tilt-Wing type. A non-linear mathematical model is developed that includes the UAV complete dynamics, which presents significant changes in aerodynamic characteristics, especially during the transition flight. These changes are analyzed and characterized by flight tests and CFD simulations. The adaptation to the variation of aerodynamic characteristics caused by tilt angle changes of transition system is verified, so a PD controller for altitude is implemented.

4 citations


Journal ArticleDOI
TL;DR: In this article, a brief overview evaluation of popular control algorithms for multi-rotor aerial systems, especially for VTOL -Vertical Take-Off and Landing aircraft, is presented.
Abstract: Control theory applied to multirotor aerial systems (MAS) has gained attention with the recent increase on the power computation for embedded systems. These systems are now able to perform the calculations needed for a variety of control techniques, with lower cost of sensors and actuators. These types of control algorithms are applied to the position and the attitude of MAS. In this paper, a brief overview evaluation of popular control algorithms for multirotor aerial systems, especially for VTOL - Vertical Take-Off and Landing aircraft, is presented. The main objective is to provide a unified and accessible analysis, placing the classical model of the VTOL vehicle and the studied control methods into a proper context. In addition, to provide the basis for beginner users working in aerial vehicles. In addition, this work contributes in presenting a comprehensive analysis of the implementation for the Nonlinear and Linear Backstepping, Nested Saturation and the Hyperbolic Bounded Controllers. These techniques are selected and compared to evaluate the performance of the aircraft, by simulations and experimental studies.

3 citations



Journal ArticleDOI
TL;DR: A detailed robustness analysis considering parametric uncertainty and time delay in the multi-agent system is performed to guarantee the consensus on the speed of DC motors in actual practice.
Abstract: DC motor speed synchronization is a critical problem in industrial and robotic applications. To tackle this problem, we propose to use a multi-agent consensus-based control scheme that guarantees the convergence of the DC motor speeds to either fixed or time-varying reference. A detailed robustness analysis considering parametric uncertainty and time delay in the multi-agent system is performed to guarantee the consensus on the speed of DC motors in actual practice. The results obtained concerning the robustness analysis allowed us to implement experimental tests on a three-motor system using a wireless communication system to achieve satisfactory performance.

2 citations


Proceedings ArticleDOI
20 Sep 2020
TL;DR: A robust linear control scheme for nonlinear aerial system is proposed based on the structural properties of the system such as parametric uncertainties and external disturbances, which presents high efficiency in disturbance rejection, smoother convergence to the desired reference and a low computational demand.
Abstract: Disturbance rejection is a major concern nowadays for the development of autonomous aerial vehicles technology In this way, in the control community, the researchers propose complex and robust nonlinear controllers that are in several cases so difficult to be applied in real time In this paper, a robust linear control scheme for nonlinear aerial system is proposed The scheme is based on the structural properties of the system such as parametric uncertainties and external disturbances The control scheme is validated experimentally in real time to corroborate their properties on disturbance rejection Experimental results illustrate the easy implementation and feasibility of the proposed scheme when the vehicle faces three different scenarios; wind-gust disturbance, variable mass and motor failure In addition, the scheme presents high efficiency in disturbance rejection, smoother convergence to the desired reference and a low computational demand

2 citations


Proceedings ArticleDOI
11 Nov 2020
TL;DR: In this article, the authors presented the mechanical design and simulation of a two-degree-of-freedom exoskeleton robot to assist the sit-to-stand (StoS) transfer of a person with reduced mobility due to spinal cord injury.
Abstract: This article presents the mechanical design and simulation of a two-degree-of-freedom exoskeleton robot to assist the Sit-to-Stand (StoS) transfer of a person with reduced mobility due to spinal cord injury (SCI).Also featured is the simulation of a Robust, Non-singular, Fast Terminal Sliding Mode Control (RNFTSMC) to control the StoS transfer.The exoskeleton will be mounted on a base with four wheels and two brushless DC motors, it has a rechargeable battery allowing the translation of the prototype for up to 8 hr of continuous use, moreover this base has a center with the ability to compensate for changes in the inclination of the surface, thus reducing the sensation of falling when making use of service ramps in the translation of the user.

Journal ArticleDOI
TL;DR: The implementation of a suboptimal nonlinear discrete control to optimize the energy consumption in a hybrid exoskeleton for the elbow joint is presented.
Abstract: In this brief, the implementation of a suboptimal nonlinear discrete control to optimize the energy consumption in a hybrid exoskeleton for the elbow joint is presented. The exoskeleton is used to amplify the strength of the user and is hybrid in the sense that it combines two types of actuators: pneumatic muscles and Harmonic Drive motors, which give power and precision to the system, respectively. The exoskeleton is autonomous in the energetic sense, and it is driven by compressed air and batteries. The suboptimal control is used to increase the operation time of the exoskeleton. This control law penalizes the energy consumption, and it has a direct effect on the operation time of the prototype.

Journal ArticleDOI
TL;DR: Simulation results based on the consensus task of a group of inverted pendulums demonstrate the effectiveness of the proposed ELIC for stabilization of nonlinear MAS.