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Algorithm for AC brushless motor and AC brushed motor

• Scalar control

Scalar control (or V/Hz control) is a simple method of controlling the speed of an instruction motor
The steady-state model of the command motor is mainly used to acquire technology, so transient performance is not possible.The system has no current loop.To control the motor, the three-phase power supply varies only in amplitude and frequency.

• Vector control or field oriented control

The torque in the motor varies with the function of the stator and rotor magnetic fields and reaches its peak when the two magnetic fields are orthogonal to each other.In scalar – based control, the Angle between the two magnetic fields changes significantly.
Vector control tries to recreate orthogonality in AC motors.In order to control the torque, the current generated from the magnetic flux is generated respectively to achieve the responsiveness of the DC machine.
The vector control of an AC command motor is similar to that of a single excited DC motor.In A DC motor, the magnetic field energy Φ F generated by the excitation current IF is orthogonal to the armature magnetic flux tangent A generated by the armature current IA.These magnetic fields are decoupled and stable to each other.Thus, when the armature current is controlled to control the torque, the magnetic field energy remains unaffected and faster transient response is achieved.
The field-oriented control (FOC) of a three-phase AC motor includes operation imitating that of a DC motor.All controlled variables are mathematically converted to DC instead of AC.Its target is independently controlled by torque and flux.

• There are two methods of field-oriented control (FOC) :

Direct FOC: the Rotor flux Angle is calculated directly by the flux observer
Indirect FOC: The Rotor flux Angle is obtained indirectly by estimating or measuring the Rotor speed and slip.
Vector control requires an understanding of the position of the rotor flux and can be calculated using advanced algorithms based on knowledge of the terminal current and voltage (using dynamic models of AC induction motors).However, from an implementation point of view, the need for computing resources is critical.

The vector control algorithm can be implemented in different ways.Feedforward techniques, model estimation, and adaptive control techniques can all be used to enhance response and stability.

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