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 arm’s end effector (claw) in space. These coordinates are fed through an inverse kinematics algorithm which outputs the corresponding angles (θ 1, θ 2, θ 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. 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 UNIVERSITY of PENNSYLVANIA Robotic Arm for Children with Disabilities ESE Group 19 SYSTEM BLOCK DIAGRAM Z Axis XY Plane R1 R2 R3 Θ2Θ2 Θ2Θ2 Θ3Θ3 Θ1Θ1 TEAM MEMBERS: Nimish D. Verma & Devang V. Shah ADVISOR: Dr. Vijay Kumar DEMO TIME & PLACE: RCA Lab, 2pm-3:30pm ROBOTIC ARM INVERSE KINEMATICS MODEL