Kinematics of a 6-R serial manipulator
Date
2003
Authors
Numanoglu, Levent
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Abstract
This project will attempt to solve the displacement, velocity, and the inverse force problems of an existing 6R(R..lR/ /R..lR..lR..lR) 6 degree of freedom (DOF) serial joystick that does not have a spherical wrist. Chapters two and three of the thesis include the solution of the forward displacement and the inverse displacement problems of the manipulator. The fourth chapter contains the solution of the velocity problem and the inverse force problem of the manipulator.
The implementation of the manipulator was made by Levent Numanoglu and Cassidy Taylor. This implementation required replacing the wiring system of the manipulator and some potentiometers that weren't working properly. Each joint of the manipulator has a potentiometer. These potentiometers are used to measure the displacement of each joint as a voltage thorough a data acquisition card (DAQ). The voltage changes depending on the change of the joint angle. The program that allowed the PC to have the output voltage through the DAQ was written by Paul Sobejko.
In order to obtain the forward displacement solution (FDS) of the manipulator, all of the link lengths and the offset distances between the lengths are measured and entered in the program, created in Matlab. The distance from the end-effector to the origin was manually measured and compared to the one obtained by the program for different positions to verify the FDS.
The inverse displacement soution (IDS) of the manipulator is achieved with two different techniques. The first method is the method created by M. Raghavan and B. Roth. The second method involves an exhaustive search over an assumed 01 , which is the angle of the first joint, followed by finding the possible solutions for the rest of the joint angles.
The velocity problem is solved using two different Jacobian matrices. The first Jacobian matrix calculates the velocity of the end effector with a tool tip translational velocity reference point and a zero frame reference orientation. The second Jacobian matrix uses computationally more appropriate references with the translational velocity reference being a point considered to be attached to the end effector and coincident with the origin of the third frame. The reference orientation of this appropriate Jacobian matrix is with respect to the orientation of the third frame.