Intelligent Control: Mobile Robot

This practical project explores the design and implementation of fuzzy logic controllers for mobile robots. It covers the kinematic model of the robot, fuzzy control simulation, and fuzzy ANFIS control. The project also discusses the use of hybrid systems and odometry for robot navigation. The simulation is performed using MATLAB Fuzzy logic toolbox and other Simulink models.

UNIVERSITY OF WOLLONGONG
DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
INTELLIGENT CONTROL- ECTE441/841/941
TITLE: PRACTICAL PROJECT II
STUDENT NAME
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INTELLIGENT CONTROL: MOBILE ROBOT
INTRODUCTION
The mobile robot is designed so as to use artificial intelligence to enable its propagation
in different situations. Artificial intelligence seeks to find a pattern in the activities of a human
being or a device as the human beings make very concrete decisions even when the input is not
precise or numerically accurate. For instance, it is very easy for a human being to change
direction while walking without even had prior information unlike the mobile robot which moves
in a given direction until instructed to propagate elsewhere. These mobile robots have sensors
installed so as to detect obstacles and targets as well as define the trajectories. Researchers have
constantly sought methods and models to solve the motion control problems in a mobile robot.
Some of the models used are fuzzy logic controllers, neural networks, genetic algorithms, and a
combination of the highlighted methods. The outstanding model used in the mobile robot
currently is the fuzzy logic controller (Aguirre & Gonzales, 2000). The fuzzy controller is based
on rules which provide reasoning and decision making when uncertain and imprecise
information is used as the input. The control model is quite tolerant to disturbance and errors
found in the information that is obtained from the sensory system. The system has found
application in the multivariable input-output systems, MIMO systems. One of the main caveats
the mobile robot faces is in the measurement of distances to the obstacles and the optical
encoders to provide the actual position and speeds (Alyahmedi, et al., 2009). The goal reaching
behavior tends to drive the robot from a given initial position to a stationary or moving target
position. This behavior drives the robot to the left to the right or forward depending on θ-error,
the difference between the desired heading and the actual current heading.
The kinematic model of the mobile robot
The configuration of the robot is set up using the x, y scale coordinates. In this case, the position
of the robot is set at, (3.4, 5.8). there are a number of parameters that need to be taken into
consideration: linear velocity of left and right wheels, angular velocity of the mobile robot,
abscissa of the robot, intercept of the robot, actual position coordinates of the robot, orientation
of the robot, and the distance between the driving wheels. The kinematic model equations are
based on these parameters such that,

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dx
dt =V L+V R
2 cos θ
dy
dt =V L+V R
2 sin θ
dθ
dt = V L−V R
2
Figure 1 Kinematic model of the mobile robot [source: Hindawi.com]
These equations are used in the MATLAB simulation of the mobile robot. The kinematic
equation can also be expressed in discrete form,
X k+1= Xk+ T ( V rk +V lk )
2 cos θk
Y k +1=Y k +T ( V rk +V lk )
2 sin θk
θk+1=θk+T ( V rk+V lk )
2

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PROJECT OBJECTIVES
(i) To design one fuzzy controller for the trajectory and obstacle avoidance for the
mobile robot using sensors.
METHODOLOGY
The simulation is performed using the MATLAB Fuzzy logic toolbox alongside other Simulink
models. Some of the robot models used in the implementation are the kinematic model and the
trajectory tracking model using the MIMO fuzzy controller.
Figure 2 Implementing a fuzzy logic controller to control the trajectory of the mobile robot [source: Hindawi.com]
RESULTS AND OBSERVATIONS
TASK 1: FUZZY CONTROL SIMULATION
The fuzzy controller has 3 sections namely fuzzification, inference, and defuzzification. It
collects the real value inputs, uses rules to analyze them using the membership type MAMDANI
and the system is later defuzzied. The syntax of the rules is
¿ IF { antecedents } THEN { conclusions } rules
The outputs of the fuzzy logic control system are the speeds of the left and right wheels of the
mobile robot. The controller uses the following equations to determine the navigation of the
mobile robot towards the target,
d= √ ( XT −X )
2 + ( Y T −Y )
2 ¿ ¿
φ=θT −θ

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θ=tan−1
( Y T−Y
XT− X )

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To avoid obstacles as one gets to the target, the following considerations are focused on,
(i) Right fast
(ii) Right slow

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(iii) Straight
(iv) Left slow
(v) Left fast
The inputs are obtained as,
Ob_loc1 Ob_loc2 Ob_loc3 Ob_loc4 Ob_loc5 Ob_loc6
-9 -5 -2.5 0 2.5 5
Negative Left-slow Right-slow Right-fast Left-slow Left-fast Left-slow
Zero Straight Right-slow Right-fast Left-fast Left-fast Left-slow
Positive Right-slow Right-slow Right-fast Right-slow Left-fast Left-slow
The rules are formulated as shown in the rule viewer below,
There are 18 rules

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The surface viewer based on the rules is given as,

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Implementing the control in the simulation

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TASK II: FUZZY ANFIS CONTROL
The task seeks to develop a neural controller or an optimized adaptive neural fuzzy inference
system controller for the mobile robot. Training data is obtained from task one parameters.
The first step taken is to load data onto the ANFIS as training data.

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Odometry seeks to use the data obtained from the moving sensors, in this case, the
ultrasonic sensors, to estimate the change in position over time. The method seeks to estimate the
robot’s position with reference to the starting location. The use of odometry checks the errors
that are as a result of the integration of velocity measurement over a given time to give position
estimates. Odometry requires very accurate and swift data collection and equipment calibration
techniques (Fatmi, et al., 2006).

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Hybrid Systems are combinations of two separate systems or techniques to produce a more
efficient and optimal solution. The product of the combination usually takes advantage of each
technique’s merit and decreases the limitation of their demerits. An example of such hybrid
system is a Neuro-Fuzzy system which combines neural network and fuzzy logic into one model
(Saffiotti, 2007). Neural networks are well suited for learning and adaptive tasks. The training
and testing is performed as illustrated below,

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The simulation results are improved,

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Neural networks are well suited for learning and adaptive tasks (Jacobsen, 2008, p.45) but
difficult to understand the modalities of its operation. On the other hand, fuzzy logic controllers
are well suited for incorporation and interpretation of knowledge but limited in learning and
adaptation. Odometry seeks to use the data obtained from the moving sensors, in this case, the
ultrasonic sensors, to estimate the change in position over time. The method seeks to estimate the
robot’s position with reference to the starting location.
In a nutshell, the two tasks achieved to control the robot to get to its target while the second task
enabled the optimization and improvement of the trajectory.
REFERENCES

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Aguirre, E. & Gonzales, A., 2000. Fuzzy behaviours for mobile robot navigation: Design,
coordination and fusion. International ournal of approximate reasoning, Volume 25, pp. 255-289.
Alyahmedi, A. S., El-Tahir, E. & Perez, T., 2009. Behaviour based control of a robotic based
navigation aid for the blind. Control and applications conference, p. 15.
Fatmi, A., Alyahmedi, A. S., Khirji, L. & Masmoudi, N., 2006. A Fuzzy logic based navigation
of a mobile robot. World Academy of science, engineering, and technology, pp. 169-174.
Saffiotti, A., 2007. The uses of fuzzy logic for autonomous robot navigation: A catalogue
raisonn'e. Software Computing research journal, 1(4), pp. 180-197.