**2.2 Switched reluctance actuator**

*Computational Optimization Techniques and Applications*

**2. Classification of linear actuator**

with internal or external moving part.

suited to the case where the fixed stator.

complex geometry for its manufacture.

position of maximum flux.

**Figure 1** [6].

direction.

**2.1 Permanent magnet actuator**

reluctance linear.

In the first part of this chapter the theory of switched reluctance machines well be explained. Then, the principle of operation as well as the analytical modeling of a linear actuator will be also studied. The last part of this chapter is devoted to the presentation of the control techniques dedicated for switched

There are mainly three types of incremental linear actuator which differentiate

These three types of actuators can have structures with a planar or tubular geometry [5, 6]. Contrarily to rotating machines where the rotor and stator are generally coaxial. Linear machines can be presented in flat form or cylindrical form. They consist of a moving part and a fixed stator whose positions can be reversed. For flat structures, it is possible to realize actuators with single stator or with double stator. For cylindrical structures, it is possible to consider tubular actuators

The single stator actuator is a simple variance which is easily integrated in current applications but which presents a significant force of attraction between the stator and the moving part [7]. The double stator structure makes it possible to obtain, on the one hand, higher thrust forces than for the single stator structure and on the other hand to lighten the mobile part, because if the latter is well centered the resultant of the forces attraction is then zero. This structure is particularly well

The linear actuator can also have two symmetrical inductors in order to create a greater force compared to its single inductor counterpart. Nevertheless, it has a

They are composed of a fixed part (the stator) and a mobile part (the translator) whose displacement is governed by the tendency of the magnetic circuits to be in a

The permanent magnet linear actuator consists of an armature comprising one or more permanent magnets and a stator comprising a number of coils. There are two configurations of this type of actuator. The first is with fixed coils and moving magnets. The second is with moving coils and fixed magnets,

The operation of this type of actuator is provided by the action of an electromagnetic field on the armature made up of permanent magnets. The magnetic field in the air gap created by the supply of the phase coils orients the magnets in one

by the physical phenomenon which is at the origin of their movement.

**60**

**Figure 1.**

*Permanent magnet linear actuator.*

The switched reluctance actuator is among the simplest actuators. Regarding its construction, its basic structure consists of a coiled mobile part and an iron stator part which does not contain neither magnets or coils. The stator consists of an iron part rolled to form salient poles, **Figure 2**.

The principle of operation of a switched reluctance actuator is based on the tendency of an electromagnetic system to achieve a stable equilibrium position, which minimizes reluctance of the magnetic circuit. The aligned position of a phase is defined as the situation where the teeth of the stator and the modulus teeth of the mobile of the phase are perfectly aligned with each other reaching a position where reluctance is minimal [8].

**Figure 3** shows an incremental reluctant linear actuator with transverse flux configuration comprising three modules separated by a non-magnetic material, each phase of the actuator is composed of two windings in series. The feeding of a phase creates a force allowing the movement of the mobile towards a stable equilibrium position, which it keeps as long as the power is maintained.

For this type of actuator, if the poles of one module are aligned with the poles of the stator then the poles of the other module must be offset in order to create a propelling force. Indeed, magnetic separations between the modules are necessary to impose a regular offset between the mobile modules.
