Field-oriented control and direct torque control are becoming the industrial standards for induction motors torque control. This paper is aimed to give a contribution for a detailed comparison between the two control techniques, emphasizing advantages and disadvantages. The performance of the two control schemes is evaluated in terms of torque and current ripple, and transient response to step variations of the torque command. The analysis has been carried out on the basis of the results obtained by numerical simulations, where secondary effects introduced by hardware implementation are not present. Index Terms-Digital signal processor, direct field oriented control, direct signal processor, direct torque control, discrete space vector modulation, field oriented control, pulse-width modulation. I. INTRODUCTION A LMOST 30 years ago, in 1971 F. Blaschke [1] presented the first paper on field-oriented control (FOC) for induction motors. Since that time, the technique was completely developed and today is mature from the industrial point of view. Today field oriented controlled drives are an industrial reality and are available on the market by several producers and with different solutions and performance [2]-[19]. Thirteen years later, a new technique for the torque control of induction motors was developed and presented by I. Takahashi as direct torque control (DTC) [20]-[22], and by M. Depenbrock as direct self control (DSC) [23]-[25]. Since the beginning, the new technique was characterized by simplicity, good performance and robustness [20]-[31]. Using DTC or DSC it is possible to obtain a good dynamic control of the torque without any mechanical transducers on the machine shaft. Thus, DTC and DSC can be considered as "sensorless type" control techniques. The basic scheme of DSC is preferable in the high power range applications, where a lower inverter switching frequency can justify higher current distortion. In this paper, the attention will be mainly focused on the basic DTC scheme, which is more suitable in the small and medium power range applications. Several papers have been published on FOC and DTC in the last 30 years, but only few of them was aimed to emphasize differences, advantages and disadvantages.

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