Structure and theoretical analysis of a novel rotary-linear isotropic brushless machine

Since the combination of a rotary and linear motion along the same axis is conveniently used in several applications, rotary-linear motors, able to provide both torque and force, represent one of the most interesting types of multi-degree-of-freedom machines. This paper deals with a novel type of rotary-linear permanent magnets synchronous machine that was recently proposed aiming to achieve a good controllability and inexpensive manufacturing using common solutions. The machine structure is illustrated as well as its ideal theoretical model derived from the usual sinusoidal approximated approach, highlighting the ideal possibility to simply achieve a decoupled linear control of force and torque by adjusting the d-q Park current components. Finally, considerations about regulation criteria and capability of the machine are reported.