Vector control of AC motors, supplied by a PWM voltage inverter helps to carry out electric actuating systems; these systems have the performances required by various scopes, such as haptics, robotics, precision machining or the spatial field [GUS 03, KHA 06].

In order to achieve this, the torque control of synchronous motors aims to control the electromagnetic torque of the machine through the regulation of its Park currents of the d and q axes [LOU 99]. This control, whose principle has been described in the previous chapters, needs, among other things:

– the inverse transformation of the line currents;

– the estimate (ê_d ,ê_q) of the coupling terms (e_d ,e_q) due to the transformations;

– and the estimate ê₀ of the EMF, induced in the machine, noted e₀ .

In this chapter, we take particular interest in the digital implementation of the vector control of synchronous motors. This is why these different stages are not described in the following. The estimate of the coupling terms and of the

electromotive force (emf) is assumed to be perfect and thus these terms are perfectly compensated. The motor model is thus simplified and its electric part consists only of the equations of the d and q axes voltages, leading to the following first order transfer functions:

[5.1] images