Propulsion with and without Wheels

Introduction of wheels in transportation from cart wheels, waterwheels, wheels on rail, wheeled automobiles and turbine wheels for air transportation and in harnessing energy spans thousands of years. It has revolutionized every aspect of human life. While most of the useful motion is linear, systems were forced to be built around rotating system due to the wheels. Replacement of wheels with linear motion systems is a gigantic step in breaking away from the long and familiar past and practice. This paper describes briefly the development of a class of linear devices to replace wheel based motive devices for transportation and in some other futuristic applications such as ropeless (cable free) elevators. Many of the concepts in the linear electric motor drives involve high cost systems using superconducting magnets, permanent magnets, or windings spread over the track in its entire length with the attendant increase in cost that is insurmountable in many applications including transportation. Low cost solutions for a majority of applications are sought after and such a quest in recent times is casting the development of linear electric motor drives in new directions. One such direction is in using linear switched reluctance motor drives. The work on such a linear electric motor drive, its rationale and its importance are described in this paper. Emphasis is placed on various forms of transportation concepts using such linear electric motor drives and also in applications ranging from elevator, door openers and others. Some of the applications are illustrated with working prototypes.