![]() On the contrary, in AC motors, the armature current of the stator affects both the magnetic field and the produced torque. Therefore, the two currents are electrically and magnetically decoupled. In the dc motor the magnetic flux is separately controlled by the excitation current, while the torque is controlled by the armature current. įOC was proposed during the 1970s from Hasse and Blaschke and is based on the analogy of the ac motor with the dc motor, where the current commutation is achieved mechanically. DFOC acquires the value of rotor flux by mounting two different Hall-effect sensors to the air gap of the controlled ACIM, where the block diagram of such a control system is illustrated in Fig. The FOC can be defined as direct FOC (DFOC) or indirect FOC (IFOC), according to the method used to determine the flux position. The performed transformation allows decoupling of the flux and torque values of the controlled ACIM to a two-axis frame. If the rotor flux is assigned to the direct axis ( d-axis) of the reference frame, the d parameter denoting flux of the stator current and the q parameter denoting torque component of the stator current are used. The parameters of the rotating flux frame at the synchronous speed are transformed to a DC component. The FOC scheme, based on obtaining the rotor flux data, acquires all parameters of the rotating frame and transforms them to rotor flux. Comparisons of reaction times for a modified four-wheel electric vehicle equipped with a permanent magnet synchronous motor under neutral-sliding-status, FOC based braking, and short-circuit braking were conducted.The implementation of the FOC algorithm ensures motor parameters in steady state and transient operations with high reliability are obtained. Compared to the regenerative brake and rheostatic brake, the proposed braking system has a powerful braking torque and shorter reaction time. This provides a smoother and more accurate motor control than sinusoidal commands with Hall feedback. When the motor receives a brake command, the controller changes the inverter-switching sequence to generate reverse torque and a magnetic field to complete the driving or braking function using field-oriented control (FOC). It calculates the rotor position angle of the motor by detecting variation in the stator current and completes a closed-loop control. This research proposes a sensor-free, integrated driving and braking control system that uses a space-vector-pulse-width module to synthesize stator current by purpose. ![]() Most electric vehicles use regenerative brakes, since this kind of braking system design recycles electromotive force to increase electric power endurance during braking. ![]()
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