טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentBloch Victor
SubjectSingle Motor Closed Robot Chain Robotrex - Static Analysis
and Motion Algorithms Development
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Elon Rimon
Full Thesis textFull thesis text - English Version


Abstract

Mechanism locomotion on rough terrains can be applied in various areas: agriculture, rescue, defense, etc. Track locomotion on is a widespread solution, which greatly increases robot traversability on non-solid and non-smooth terrain. This thesis presents an analysis of a non-conventional close chain named RoboTrek, allowing passage over obstacles with heights comparable with the chain length. Unlike conventional tracks tensed with the help of wheels on a solid frame, this chain is not tensed and uses its natural degrees of freedom at the connection of each link. The chain is driven by a single wheel-frame mechanism, giving high power and reliability to the chain. The connection of each link can exist in three modes: free to rotate, locked by a locking mechanism in a specific angle, and locked in its natural limit position. Each locking mechanism is controlled mechanically in basic motion and with the help of a Central Control Unit in advanced motion modes.

Since this configuration of the mechanism has never been considered before, the work consists of the following preliminary design parts: mechanism synthesis, analysis, and basic locomotion algorithms. At the initial stage of development the assumption of quasi-static motion is made.

Mass-kinematic models of the chain are built for the obstacle passing problem. Right angled stairs are considered to be the obstacles. The synthesis problem is defined as finding the minimal length of the chain, which is able to climb on given obstacles. Rules for the minimal chain length calculation with given obstacles and basic chain parameters are developed.

Because of a large number of degrees of freedom, even basic chain motion demands a motion algorithm, which is a set of commands for the locking mechanism keeping the chain shape, and for the motor providing advancement. A number of basic algorithms for obstacle passing are developed.

The developed motion algorithms are applied and visualized by a CAD chain model built using the “Open Dynamics Engine” library.

Results obtained in the thesis represent a guideline for mechanical and motion design of a closed chain mechanism driven by a single motor.