TriP: A Python package for the kinematic modeling of serial-parallel hybrid robots

Abstract

Robots can be classified according to their mechanical structure. Serial mechanisms like robotic arms are mechanisms where each moving part (called a link) is connected to only the one before and the one after it. They are often used when a large workspace is required, meaning the robot needs a long reach. In parallel mechanisms, the links of the robot form loops causing them to be structurally stronger and stiffer. If both a large workspace and structural strength are required, hybrids that contain both serial and parallel mechanisms are used. While hybrid mechanisms combine the mechanical advantages of both parallel and serial mechanisms, they also combine their modeling disadvantages: • Finding an explicit solution for either forward or inverse kinematics is often impossible. Using numerical approaches instead leads to complicated constrained optimization problems for both forward and inverse kinematics. • While serial mechanisms are very well supported by current robotic frameworks, parallel mechanisms and hybrid mechanisms especially are often not supported at all. A great overview of the supported robot types for different robotic frameworks was compiled by Kumar (2019).