Int. J. Com. Dig. Sys. 2, No. 3, 109-121 (2013) 109
A Practical Neuro-fuzzy Mapping and Control for a 2 DOF
Robotic Arm System
Ebrahim Mattar
Dept. of Electrical and Electronics Engineering,
College of Engineering, University of Bahrain, P.O. Box 32038, Kingdom of Bahrain.
E-mail addresses: ebmattar@theiet.org, ebmattar@ieee.org
Received 23 Sep. 2012, Revised 9 Feb. 2013, Accepted 15 Mar. 2013, Published 1 Sep. 2013
Abstract: Relating an arm Cartesian space to joint space and arm dynamics, is an essential issue in arm control that
has been given a substantial attention by number of researches. Arm inverse kinematic, is a nonlinear relation, and a
closed form solution is not a straight forward, or does not even always exist. This research is presenting a practical use
of Neuro-Fuzzy system to solve inverse kinematics problem that used for a two links robotic arm. The concept here is
to learn kinematics relations for a robotic arm system. This is to learn and map its environment and remembers what it
learnt. For learning the inverse kinematics, Neuro-fuzzy needs information about coordinates, joint angles and actuator
position. Information flow needed for the training for a Neuro-fuzzy network is slow and difficult to get by measuring
the real structure. Desired Cartesian coordinates are given as input to a Neuro-fuzzy that returns actuator positions.
Hence to express them as linguistics fuzzy rules. Neuro-fuzzy system is to generalize and produce an appropriate
output. The assembled system has been equipped with C
++
interface routines, as being executed from a MATLAB
environment, in addition to high-speed low-level communication with the robotic arm sensing devices.
Keywords: UOB Robotic Arm; Inverse Dynamics; Computed Torque Law; Neuro-fuzzy mapping.
I. INTRODUCTION
Robotics arms are widely used and employed for
industrial and non-industrial applications. However, for
more precise and accurate motion control, dynamic
model do play important role for such applications. It is
always not an easy task to get the forward and the inverse
models for robotics structure, specifically, once
redundancy exists. Kinematics models are always
nonlinear relations, and closed form solutions are not
easy tasks to be achieved. There are a number of
approaches that have been reported in literature regarding
building kinematics models. In its boarder sense,
manipulator kinematics is the study of motion without
regard to the forces which cause it. Within kinematics, it
is possible to study position, velocity and acceleration,
and all higher order derivatives of an arm position
variables. The kinematics of manipulators involves the
study of the geometric and time based properties of the
motion, and in particular how the various links move
with respect to one another and with time. Typical robots
are serial-link manipulators comprising a set of bodies,
(links), in a chain, connected by joints. Each joint has a
single Degree of Freedom (DOF), either translational or
rotational. For a manipulator with (n joints numbered
from 1 to n, there are (n+1) links, numbered from 0 to
(n). Link 0 is the base of the manipulator, generally
fixed, and link n carries the end-effector. Joint ( i)
connects links (i) and i first and last links are
meaningless, but are arbitrarily chosen to be 0. Joints
may be described by two parameters. The link ( o) set is
the distance from one link to the next along the axis of
the joint. The joint angle is the rotation of one link with
respect to the next about the joint axis. To facilitate
describing the location of each link we affix a coordinate
frame to it, frame (i) is attached to link (i).
Denavit and Hartenberg [1] proposed a matrix method
of systematically assigning coordinate systems to each
link of an articulated chain. Axis of revolute joint (i) is
aligned with (Z
i
). Parallel link and serial/parallel hybrid
structures are possible, though much less common in
industrial manipulators.
International Journal of Computing and Digital Systems
http://dx.doi.org/10.12785/ijcds/020302
© 2013 UOB SPC,
University of Bahrain