Inés Tejado

Improved fractional Kalman filter and its application to estimation over lossy networks

This paper presents improvements on the fractional Kalman filter (FKF) based on the infinite dimensional form of a linear discrete fractional order state-space system. Furthermore, taking into account the considerable interest in estimation over networks with packet losses, the application and extension of the improved FKF are included. Some simulation cases are given in order to demonstrate the effectiveness of the proposed algorithms, with significant improvements in terms of estimation and smoothing results.

Stability of fractional order switching systems

This paper studies the stability problem for fractional order switching systems. The conditions for the stability of such systems are presented in terms of common Lyapunov theory, generalized to fractional order systems, and in frequency domain, an approach equivalent to the previous one. The effectiveness of the developed theory is shown through some illustrative examples.

Experimental Application of Hybrid Fractional-Order Adaptive Cruise Control at Low Speed

This brief deals with the design and experimental application of a hybrid fractional adaptive cruise control (ACC) at low speeds. First, an improved fractional-order cruise control (CC) is presented for a commercial Citroën C3 prototype-which has automatic driving capabilities-at low speeds, which considers a hybrid model of the vehicle. The quadratic stability of the system is proved using a frequency domain method. Second, ACC maneuvers are implemented with two different distance policies using two cooperating vehicles-one manual, the leader, and the other, automatic-also at very low speeds. In these maneuvers, the objective is to maintain a desired interdistance between the leader and follower vehicles, i.e., to perform a distance control-with a proportional differential (PD) controller in this case-in which the previously designed fractional-order CC is used for the speed control. Simulation and experimental results, obtained in a real circuit, are given to demonstrate the effectiveness of the proposed control strategies.

Data-driven fractional PID control: application to DC motors in flexible joints

Abstract Recent advances in data-driven (or model-free) control have permitted to enhance the closed loop behavior of linear and especially nonlinear systems using very simple control structures. As a result, unknown or badly known dynamics are compensated and disturbances are rejected without any learning or on-line identification procedure. However, the ultra-local phenomenological models on which this control technique rely have not yet exploited the fractional nature of many processes and the nonlocal nature of the fractional integrodifferential operators. In this paper, fractional derivatives are used in the so called model free control structure in order to explore the advantages they provide in terms of robustness and dynamic response. Fractional and integer order data driven PIDs will be compared for a DC motor in a robot flexible joint control application in a simulation environment.

Low Speed Control of an Autonomous Vehicle by Using a Fractional PI Controller

Abstract Highly non-linear vehicle dynamics plays an important role in autonomous driving systems, especially in congested traffic situations at very low speeds. Due to this fact, accurate controllers are needed in order to ensure safety during navigation. This paper focuses on the design and experimental implementation of a fractional PIα controller for the low speed control problem in an autonomous prototype Citroen vehicle. Experimental tests at low speeds, obtained with a real vehicle on a real circuit at the Center for Automation and Robotics facilities, show the effectiveness of the proposed controller.

Remote stabilization for fractional-order systems via communication networks

In this study, the problem of remote stabilization for fractional-order (FO) systems with input time-varying delay via communication networks is investigated. The order of the FO system denoted by α considered in this paper is in the range of 0 to 2. Additionally, the network induced time-varying delay is considered as being generated by a known FO dynamic system. We show how the delay dynamics can be explicitly incorporated into the Networked Control System controller design. The basic idea is to use linear matrix inequality and receding horizon control framework. We use the receding horizon method to design a stabilizing control law that sets the poles of the closed-loop system. The proposed control law explicitly takes into account an estimation of the delay dynamics. Finally, numerical examples are offered to demonstrate the effectiveness of the proposed method.

Identifying a non-commensurable fractional transfer function from a frequency response

This paper extends Levy?s identification method to non-commensurable fractional models. This identification method allows finding a transfer function that models a frequency response. Explicit expressions for the calculations, using five different variations of the method, are given. A sensitivity analysis supports an empirical way of finding the orders involved. Two application examples, concerning the identification of a model for a viscoelastic material and a model the human arm, are given. HighlightsLevy?s identification method is expanded to non-commensurable fractional models.Numerical and empirical ways of finding the orders involved are justified.Models for the human arm are found as an application.

Adaptive gain-order fractional control for network-based applications

This paper deals with the application of adaptive fractional order control to networked control systems (NCSs) to compensate the effects of time-varying network-induced delays. In essence, it adapts both the gains and the orders of a local PIαDμ controller in accordance with the current network condition in order to avoid a decreased control performance. A frequency domain framework is provided to analyze the system stability on the basis of the switching systems theory. The velocity control of a servomotor through the Internet is given to show the effectiveness of the proposed adaptive controller, including a comparison with non- and gain scheduled controllers.

GPC strategies for the lateral control of a networked AGV

The performance of a Networked Control System (NCS) is affected directly and indirectly by transmission time delays and data losses in the communications network. Based on the communications network model, this paper presents the validity of two different predictive control strategies and the study of the network effects on the lateral (guidance) control of an Autonomous Guided Vehicle (AGV) in the presence of sensor noise. Simulation results are presented to validate the proposed strategies.

A method for the design of robust controllers ensuring the quadratic stability for switching systems

In recent years, it has been remarkable to see the increasing number of studies related to the theory and application of fractional-order controllers, especially PIλDμ controllers, in many areas of science and engineering. Research activities are focused on developing new analysis and design methods to ensure robustness in new or classical control problems. In this paper, we investigate switching systems. A frequency-domain design method is developed for switching systems for both integer- or fractional-order controllers, taking into account specifications regarding performance and robustness and ensuring the quadratic stability of the controlled system. Some examples are given to show the applicability and effectiveness of the proposed tuning method.