Robot kinematics: applications in virtual reality based pedagogy and sensor calibration

Abstract

Conventions exist to describe the kinematics of a robot concisely, providing information about both its form and pose (position and orientation). Although mathematically convenient, the physical correlation between the parameters of these conventions and the robot that they represent is not necessarily intuitively obvious. Those who are new to the field of robotics may find it especially difficult to visualize these relationships. After presenting relevant background information on kinematics, robotics, virtual reality, and inertial sensors, this thesis investigates the effectiveness of using desktop virtual reality tools to help university-level students with the visualization of fundamental concepts in robot kinematics. Specifically, it examines how the new “Rotation Tool” assists students in the visualization of fixed and mobile frame compound rotations while verifying their non-commutative nature. It also explains how the new “Build-A-Robot” aids students in identifying the role that each of the Denavit-Hartenberg parameters plays in the description of the position and orientation of a serial manipulator’s component links. To enable flexible, real-time user interaction, Build-A-Robot employed a novel approach wherein MATLAB was used to directly manipulate the fundamental geometry of Virtual Reality Modeling Language (VRML) objects. Survey feedback and examination results are presented which indicate the students’ increased understanding that resulted after using both of these tools. This improvement was especially apparent among students who struggled to understand the concepts when traditional teaching methods alone were used. Tolerances in the manufacturing and assembly of robot arms introduce errors to the nominal kinematic models specified by manufacturers. This thesis also considers the impact of non-ideal kinematic parameters on the motion of the end-effector of a SCARA robot, which was used to calibrate an attached dual-axis accelerometer. Two novel, in-place calibration routines that employ dynamic accelerations are presented and validated using experimental data