POLITECHNIKA WARSZAWSKA

6. ANN sensorless Field Oriented Conrol of IM
6 ANN SENSORLESS FIELD ORIENTED CONTROL OF IM
6.1 Principles of field oriented control (FOC)
6.1.1 Introduction
In this chapter the short description of vector control will be presented. The field
orientation concept (vector control) [126, 122] is widely used for high-performance
control of ac motors. The main feature of field oriented approach is to enable
decoupling control of torque and flux similar to the control of a separately excited dc
motor.
In the further part the block diagrams of direct and indirect FOC will be described,
and the design of current and speed controllers will be shown.
6.1.2 FOC description
The principle of vector control method is based on a mathematical model of induction
motor in the rotating reference coordinate frame. It is very convenient to select the
angular speed of the coordinate system ω K = ω sψ . In this case the coordinate system is
oriented along the space vector of the rotor flux linkages ψ r (see fig. 6.1).
We can assume that:
and
= ψ
r r ψ rx
(6.1)
ψ =
ψ = 0
(6.2)
ry
Let us assume, moreover, that it is a cage motor, i.e.
u u = 0
(6.3)
rx = ry
120