Kinematic Chain Modelling of Rotary System as Applied to a Selectric Typewriter

Abstract

Kinematic chains were created for the rotation and tilting mechanisms of an IBM Selectric II Typewriter. The chain for the rotation mechanism was used to create a homogeneous transform matrix system that allowed the position of the printing character in a local coordinate system to be represented in the global coordinate system through a series of shape and joint matrix transforms. This allowed the position and rotation of the character of interest to be calculated based on a commanded motion at a certain joint. A drive error in that joint, representing a spring losing stiffness, was also included in the transform system and influenced the final values of position and rotation. A particular error value of .01745 radians was used along with a commanded motion of .07667 radians. This resulted in a final rotation of the printhead of .3079 radians, which is an increase of .0233 over the value obtained with no drive error. This same technique could be applied to determine the feasibility of future rotary manufacturing systems.