Research Article
Real-Time Inverse Optimal Neural Control for Image Based
Visual Servoing with Nonholonomic Mobile Robots
Carlos López-Franco, Michel López-Franco, Alma Y. Alanis,
Javier Gómez-Avila, and Nancy Arana-Daniel
Computer Science Department, CUCEI, University of Guadalajara, 44430 Guadalajara, JAL, Mexico
Correspondence should be addressed to Carlos L´ opez-Franco; clzfranco@gmail.com
Received 1 November 2014; Revised 21 January 2015; Accepted 21 January 2015
Academic Editor: Luis Rodolfo Garcia Carrillo
Copyright © 2015 Carlos L´ opez-Franco et al. Tis is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
We present an inverse optimal neural controller for a nonholonomic mobile robot with parameter uncertainties and unknown
external disturbances. Te neural controller is based on a discrete-time recurrent high order neural network (RHONN) trained
with an extended Kalman flter. Te reference velocities for the neural controller are obtained with a visual sensor. Te efectiveness
of the proposed approach is tested by simulations and real-time experiments.
1. Introduction
Traditionally, robot motion control approaches have feedback
provided by a taco-meter or encoder, whose advantages are
its easy implementation and its low cost. However, in mobile
robotics such information is not accurate due to the appear-
ance of slip phenomenon. One sensor that can be used to over-
come these problems is the visual sensor. In this work, we use
computer vision techniques to overcome such disadvantages.
Although a visual sensor is more accurate, it can suf-
fer from unknown external disturbances due to the robot
motion. In addition, the robot model is inaccurate and it suf-
fers from parameter uncertainties. To overcome such prob-
lems, we propose the use of a discrete-time recurrent high
order neural network (RHONN) trained with an extended
Kalman flter with visual feedback.
Te main goal of optimal control theory is to determine
the control signals that will force a process to satisfy physical
constraints and minimize a performance criterion simul-
taneously [1]. In optimal control theory, a cost functional
is defned as function of the state and the control vari-
ables. Unfortunately it requires solving the Hamilton-Jacobi-
Bellman (HTB) equation, which is not an easy task. To avoid
the solution of a HTB equation an inverse optimal control can
be used [2]. In inverse optimal control, we start with the def-
nition of a stabilizing feedback control, and then we have to
show that it optimizes a cost functional.
In this work, the input of the inverse optimal control is
determined by visual feedback. Te visual sensor is responsi-
ble of tracking the target and the estimation of the robot velo-
cities to achieve the desired task. In our case the task consists
in moving the robot from an initial pose to a desired pose
with respect to a target object.
1.1. State of the Art. An extensive class of controllers have
been proposed for mobile robots [3–9]. Most of these refer-
ences present only simulation results and the controllers are
implemented in continuous time. A common problem when
applying standard control theory is that the required parame-
ters are ofen either unknown at time or are subject to change
during operation. For example, the inertia of a robot as
seen at the drive motor has many components, which might
include the rotational inertia of the motor rotor, the inertia
of gears and shafs, rotational inertia of its tires, the robot’s
empty weight, and its payload. Worse yet, there are elements
between these components such as bearings, shafs, and belts
which may have spring constants and friction loads [10].
1.2. Main Contribution. Te paper main contributions are as
follows: (1) presenting a controller for mobile robots which
includes the robot dynamics and does not need the previous
knowledge of robot parameters or model; (2) computing the
trajectory references for the controller on real-time using
Hindawi Publishing Corporation
Mathematical Problems in Engineering
Volume 2015, Article ID 347410, 12 pages
http://dx.doi.org/10.1155/2015/347410