**1. Introduction**

246 Induction Motors – Modelling and Control

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A demand for sophisticated motion control is steadily increasing in several advanced application fields, such as robotics, tooling machines, pick-and-place systems, etc. These kinds of applications require implementation of at least two or more conventional motors/actuators, often operating with different type of mechanical gear. Electric motors/actuators that are able directly perform complex motion (with multiple degrees of mechanical freedom – multi-DoMF) may provide appreciable benefits in terms of performances, volume, weight and cost.

This chapter is organized as follows. Section 2 provides a brief overview of the main typologies of induction motors with two degrees of mechanical freedom (IM-2DoMF) structure. Section 3 introduces the mathematical model for helical-motion induction motors. Section 4 discusses the phenomenon known end effect caused by finite length of the armature and its negative influences on the motor performance. Section 5 presents a construction of a twin-armature rotary-linear induction motor with solid double layer rotor, its design data and the performance prediction of the motor. The results obtained from FEM modeling are then verified by the test carried out on experimental model of the motor what validates the theoretical modeling of the motor.
