Motors with two mechanical degrees of freedom (rotation-translation)
Linear and compound electric motors

Electromagnetic forces can be used to create rotational, translational or both movements simultaneously, resulting in a linear rotating machine (also known as a two-degree-of-freedom actuator). The use of these machines means that mechanical transmissions are eliminated, high positioning accuracy is achieved, and the number of conventional machines in manipulators and robots is reduced. All these improvements lead to greater servomechanism reliability and shorter relaxation times (electromechanical time constant).

Linear rotating machines are most often derived from the topological modification of rotating machines; these machines, studied since 1973