2018 International Conference on Computer, Control, Electrical, and Electronics Engineering (ICCCEEE)
Dynamics and Control of a Two-link Manipulator
using PID and Sliding Mode Control
1
st
Amin A. Mohammed
Mechanical Engineering Department
King Fahd University of Petroleum & Minerals
Dhahran 31261, Saudi Arabia
g201302850@kfupm.edu.sa
2
nd
Ahmed Eltayeb
Department of Control and Mechatronics Engineering
Universiti Teknologi Malaysia
81310 Johor Bahru, Johor, Malaysia
Eatahmed2@live.utm.my
Abstract—A robotic arm having two links is considered in
this report for modeling and control. First the dynamic model
of the robot is obtained using the so-called Lagrange equation,
then a robust control strategy based on the conventional sliding
mode control is introduced to control the motion of the robot at
specific position for pick and place tasks along with PID control
scheme. The results of the two controllers are compared. From
the simulation results the SMC is found to be superior to the PID
controller in term of fast and robust response yet with higher
control input. High join speeds are observed in case of SMC
which are related to the high control signals.
Index Terms—dynamic model, robot manipulator, PID control,
SMC control
I. INTRODUCTION
A robotic arm with two-degree of freedom is a classical ex-
ample of a simple nonlinear multi-input multi-output (MIMO)
dynamic system in robotic literature. It represents a benchmark
for testing and performance evaluation of different control
concepts and has been utilized by several researchers to study
and compare various control schemes.
In [1], modeling of 2-DOF robot arm and control was
proposed. According to the obtained results, the robot arm
has been controlled to reach and remain within a desired
joint angle position via the simulation and implementation
of PID controllers using MATLAB/Simulink. Moreover, the
results have shown that changes in initial joint angles of the
manipulator had led in different desired joint positions which
necessitated that the gains of the PID controllers should be
adjusted and tuned continuously in order to prevent overshoots
and oscillations. A basic example of PID control applied to a
robotic arm having two DOF was explained in [2] along with
an illustration of the dynamic model. Also it was shown how
to introduce the PID controller parameters to the dynamical
equation of the manipulator. A similar approach was followed
in [3].
Design of sliding mode controller (SMC) for two-link
manipulator was proposed in [4]. Sliding surfaces design for
position tracking control problem for two-link robotic arm
based on the back-stepping control (BC), the Lyapunov stabil-
ity theorem and the SMC has been tackled. When the system
is in the sliding mode, the perturbations were suppressed
and the asymptotic stability was achieved by applying the
adaptive technique in the design of the sliding surface. The
simulated results have revealed the robust tracking perfor-
mance. A MATLAB/SIMULINK realization of the PUMA
560 manipulator position control strategy was demonstrated in
details in [5]. Where the robot manipulator has been analyzed
and implemented by designing a nonlinear SMC. SMC is an
important nonlinear controller under the condition of partly
uncertain system dynamics and used popularly in the control of
highly nonlinear systems such as robot manipulators. However,
it has a major pitfall, namely, chattering. The chattering
phenomenon can be reduced by utilizing a linear saturation
boundary layer function in SMC law. On other hand, A
review of SMC for robotic manipulators is given in [6].
In which, over 90 publications have been reviewed and the
main subject of classical SMC was introduced. Moreover,
fuzzy control, adaptive fuzzy SMC, and neural network &
its application to SMC have been investigated to improve
the performance of the SMC. Sliding mode PID-controller
design using fuzzy tuning scheme for robot manipulators
is investigated in [7]. Furthermore, a sliding mode position
tracking control strategy for a 2 DOF robotic arm is proposed
in [8]. A nonlinear disturbance observer had been proposed
to enhance the performance. The control system stability had
been analyzed according to Lyapunov theory. The obtained
results had verified that the nonlinear disturbance observer
can estimate the time-varying disturbances effectively, and
the robot control structure has strong robustness and adequate
tracking performance. In this paper PID and SMC are designed
along with required implementation in the dynamic model
of the system. Then, numerical simulation results of the two
controller are compared considering a 2 DOF manipulator for
pick and place activities.
978-1-5386-4123-1/18/$31.00 ©2018 IEEE
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