Concepción A. Monje

Fractional PID Controllers for Industry Application. A Brief Introduction

In recent years the increasing amount of work related to the application of Fractional Calculus (FC) is remarkable in many areas of science and engineering. In relation to automatic control, the use of Fractional Order Control (FOC) needs, for real applications, to develop methods for controller design and parameter tuning, and efficient strategies for controller implementation. On the other hand, the Proportional Integral Derivative (PID) controller is currently by far the most widely used form of feedback controller in industrial applications. This paper, after an introduction to FC and FOC, briefly presents methods for fractional PID controller tuning, including auto-tuning, and some software and hardware strategies for efficient implementations of controllers in industrial applications.

The fractional order lead compensator

In this paper the fractional order lead compensator (FOLC) is discussed, which, with respect to the traditional lead compensator, introduces a new parameter, alpha, the fractional order of the structure. Two methods are proposed for the design, one of them analytical and the other graphical. The analytical one forces the condition that the compensator gives its maximum phase, phim at the gain crossover frequency, omega m The graphical one allows the use of a graphical criterion for the obtaining of the parameters of the FOLC. This criterion is based on the lead regions defined for the compensator in the complex plane, depending on the value of alpha. This second method allows a flexible and direct selection of the parameters of the fractional structure, taking into account considerations of robustness and overphase. An illustrative example of application is presented and simulation results show the effectiveness of the proposed methods of design

Incorporation of fractional-order dynamics into an existing PI/PID DC motor control loop.

The problem of changing the dynamics of an existing DC motor control system without the need of making internal changes is considered in the paper. In particular, this paper presents a method for incorporating fractional-order dynamics in an existing DC motor control system with internal PI or PID controller, through the addition of an external controller into the system and by tapping its original input and output signals. Experimental results based on the control of a real test plant from MATLAB/Simulink environment are presented, indicating the validity of the proposed approach.

Conceptual design of a selectable fractional-order differentiator for industrial applications

In the past decade, researchers working on fractional-order systems modeling and control have been considering working on the design and development of analog and digital fractional-order differentiators, i.e. circuits that can perform non-integer-order differentiation. It has been one of the major research areas under such field due to proven advantages over its integer-order counterparts. In particular, traditional integer-order proportional-integral-derivative (PID) controllers seem to be outperformed by fractional-order PID (FOPID or PIλDμ) controllers. Many researches have emerged presenting the possibility of designing analog and digital fractional-order differentiators, but only restricted to a fixed order. In this paper, we present the conceptual design of a variable fractional-order differentiator in which the order can be selected from 0 to 1 with an increment of 0.05. The analog conceptual design utilizes operational amplifiers and resistor-capacitor ladders as main components, while a generic microcontroller is introduced for switching purposes. Simulation results through Matlab and LTSpiceIV show that the designed resistor-capacitor ladders can perform as analog fractional-order differentiation.

AUTO-TUNING OF FRACTIONAL LEAD-LAG COMPENSATORS

Abstract In this paper, a method for auto-tuning of a fractional order lead-lag compensator using relay feedback tests is proposed. A design method for this kind of compensators is discussed, based on the magnitude and phase measurement of the plant to be controlled from relay feedback tests at a frequency of interest. Simple relationships among the parameters of this fractional controller are established and specifications such as the static error constant (kss), phase margin (φm) and gain crossover frequency (ωc) can be fulfilled, with a robustness argument by inspecting the flatness of phase Bode plot of the compensator. The auto-tuning method proposed can be taken as a first step for a latter generalization of these lead-lag compensators to the fractional PIΛDμ controllers.

Using Fractional Calculus for Lateral and Longitudinal Control of Autonomous Vehicles

Here it is presented the use of Fractional Order Controllers (FOC) applied to the path-tracking problem in an autonomous electric vehicle. A lateral dynamic model of a industrial vehicle has been taken into account to implement conventional and Fractional Order Controllers. Several control schemes with these controllers have been simulated and compared . First, different controllers with similar parameters have been implemented and then they have been improved by using optimization methods. The preliminary results are presented here.

DE-based tuning of PI(λ)D(μ) controllers.

A new method that relies on evolutionary computation concepts is proposed in this paper to tune the parameters of fractional order PI(λ)D(μ) controllers, in which the orders of the integral and derivative parts, λ and μ, respectively, are fractional. The main advantage of the fractional order controllers is that the increase in the number of parameters in the controller allows an increase in the number of control specifications that can be met. A Differential Evolution (DE) algorithm is proposed to make the controlled system fulfill different design specifications in time and frequency domains. This method is based on the minimization of a fitness function. Experiments have been carried out in simulation and in a real DC motor platform. The results illustrate the effectiveness of this method.

TEO: FULL-SIZE HUMANOID ROBOT DESIGN POWERED BY A FUEL CELL SYSTEM

This article deals with the design of the full-size humanoid robot TEO, an improved version of its predecessor Rh-1. The whole platform is conceived under the premise of high efficiency in terms of energy consumption and optimization. We will focus mainly on the electromechanical structure of the lower part of the prototype, which is the main component demanding energy during motion. The dimensions and weight of the robotic platform, together with its link configuration and rigidity, will be optimized. Experimental results are presented to show the validity of the design.

Usability assessment of ASIBOT: a portable robot to aid patients with spinal cord injury

The usability concept refers to aspects related to the use of products that are closely linked to the users degree of satisfaction. Our goal is to present a functional evaluation methodology for assessing the usability of sophisticated technical aids, such as a portable robot for helping disabled patients with severe spinal cord injuries. The specific manipulator used for this task is ASIBOT, a personal assistance robot totally developed by RoboticsLab at the University Carlos III of Madrid. Our purpose is also to improve some aspects of the manipulator according to the users perception. For our case study, a population of six patients with spinal cord injury is considered. These patients have been suffering spinal cord injuries for a period of time longer than 1 year before the tests are carried out. The methodology followed for the information gathering is based on the Quebec User Evaluation of Satisfaction with assistive Technology (QUEST). Different daily functions, such as drinking, brushing ones teeth and washing ones face, are considered to assess the users perception when using ASIBOT as a technical aid. The human factor in this procedure is the main base to establish the specific needs and tools to make the end product more suitable and usable.

Modelling and control of the humanoid robot RH-1 for collaborative tasks

This work deals with the modelling and control of the humanoid robot RH-1, a full scale humanoid prototype totally developed in the University Carlos III of Madrid and the only one existing in our country. The main objective is to develop an advanced control system that allows cooperation tasks to be carried out semi-autonomously between humanoid robots and humans in real working environments. The kinematic model and a simplification of the dynamic model of the robot are presented in this paper, together with a control strategy for the stabilization of the system during the walking and collaborative actions. Several simulation and experimental results are also given along the paper to illustrate the work.