ABSTRACT:

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UNIVERSITY of PENNSYLVANIA
ESE 441 - Group 19
Robotic Arm for Children with Disabilities
ABSTRACT Children with disabilities are often
confined to life in a wheelchair, facing simple
motor functions such as opening a door and
picking up a book with difficulty. One approach
to this problem is designing a robotic wheelchair
arm that can be controlled by a simple game pad
or joystick, simplifying unnecessary difficulties
from an already challenging life. Previous
attempts by the Moore School of Engineering to
design a system for those restricted to a
wheelchair have struggled with overall
ineffectiveness. These efforts were unsuccessful
in designing a free range arm system that could
mimic the movements of a human arm through the
manipulation of a joystick. Earlier setbacks were
due mostly to a failure to incorporate the
kinematics of the robotic arm into the system.
This resulted in erratic movement before the arm
reached its desired position. Further, the arm
could only move in the x, y or z axis at one
time. Learning from the problems of earlier
approaches, understanding and focus on kinematics
is essential. This project required comprehension
of how to interpret a desired x, y, and z
position into the proper arm motion in order to
set it apart from the previous disappointments.
In the chosen approach to redesigning the control
system, the user sends the intended arm position
to a microcontroller through joystick
manipulation. This data is then converted to the
specific motor positions of the arm through the
implementation of an inverse kinematics
algorithm.
PROJECT OVERVIEW In order to control the
robotic arm with three degrees of freedom, the
user manipulates the joystick. Individual signals
are sent from the joystick to the HC11
Microprocessor, corresponding to the x, y, and z
axis and the buttons. The A/D converter of the
HC11 converts each signal into integer values,
which are used to calculate the desired (x, y, z)
coordinates of the arms end effector (claw) in
space. These coordinates are fed through an
inverse kinematics algorithm which outputs the
corresponding angles (?1, ?2, ?3) for each motor
of the arm. Each motor has an optical encoder
which updates the motors current position into
the HCTL 2016 Encoder Counter chip. This chip
has a 16 bit counter that is used to count the
encoder pulses. By monitoring the amount of
overflows this counter goes through we are able
to map specific angles to a specific position.
The HC11 then gives the motion signal to each
motors corresponding H-Bridge, which allows
direction control. To switch control to the
claw, the trigger of the joystick must be pressed.
ROBOTIC ARM
TEAM MEMBERS Nimish D. Verma Devang V.
Shah ADVISOR Dr. Vijay Kumar DEMO
TIME PLACE RCA Lab, 2pm-330pm
We would like to especially thank Siddharth M.
Deliwala, Terry L. Kientz, Ethan A. Stump
Gaurang V. Shah whose guidance and efforts were
invaluable to this project
INVERSE KINEMATICS MODEL
SYSTEM BLOCK DIAGRAM