Abstract--This research article deals with the two closed loop speed control techniques namely Vector Control and Direct Torque Control for Permanent Magnet Synchronous Motor Drive. These two control techniques are critically evaluated for the performance comparison in terms of starting response, steady state response and transient condition. The simulation models of the two controllers are developed in Matlab/Simulink and experimental verification is obtained on Digital Signal Processor based hardware setup. The implementation algorithms are developed in assembly codes and power circuit is realized with standard Voltage Source Inverter. The simulation and experimental results shows close agreements and provide good inside for the evaluation of these two control techniques. Index Terms-- Digital Signal Processor, Direct Torque Control, Evaluation, Implementation, Permanent Magnet Synchronous Motor, Vector Control, Voltage Source Inverter. I. INTRODUCTION HE Permanent Magnet Synchronous Motor (PMSM) now a days becoming more and more popular due to its higher energy efficiency, higher torque to weight ratio, higher life and recent development in permanent magnet technology. The high efficiency and high torque density make PMSM as a good competitor of Induction Motor Drive. Unlike the induction motors, which can run with fixed frequency AC mains, special techniques are needed for PMSM synchronization between the frequency of AC excitation source and the position of the rotor magnets. Therefore, PMSMs are particularly advantageous for variable speed drive (VSD) application where cost of power electronics can be justified by the inherent advantages like attractive efficiency and fast dynamic response of the PMSM drives [1-5]. Moreover, the availability of low-cost power electronic devices and the improvement of PM characteristics enable the use of PM motors even in some more demanding applications. In the closed loop speed control mode PMSM utilizes two high-performance control techniques which are Vector Control (VC) [6-10] and direct torque control (DTC) [11-16]. These control techniques are invented respectively in the 70’s and in the 80’s for Induction Motor Drive which are well situated for PMSM control also. The vector control technique invented by Blaschke [4] in Sanjeet Dwivedi is with Control Engineering Design Center Denmark, Danfoss Power Electronics A/s, DK 6300, Denmark (e-mail: sanjeet@danfoss.com). Bhim Singh is with the Department of Electrical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016 India (e-mail: bsingh@ee.iitd.ac.in). 978-1-4244-7781-4/10/$26.00 ©2010 IEEE 1970’s which is also known as Field Oriented Control (FOC). It is used to control the space vector of magnetic flux, current and voltage. In this technique the stator current is decomposed into flux and torque producing components for obtaining the decoupled control of PMSM drive in a way similar to the separately excited DC motor. Takahashi et. al. [11] and Depenbrock [12] have invented the DTC scheme for the control of induction motors in the mid of 1980’s, since then it is becoming popular due to its simple control and easy implementation. For high performance control of PMSM, many researchers have explored the DTC scheme. The DTC has advantages over the vector control as it is simple owing to the absence of PWM current controller, good robustness to parameter variation, less sensitive to external disturbances, needs no reference frame transformation, only sector wise rotor position information is needed, and most importantly, it has also good dynamic response [11-13]. These two control techniques are extensively used in the industrial application and therefore it is necessary to evaluate the performance of these two methods. In this work a critical comparison is made considering the starting response, transient response, load perturbation responses and transient response of PMSM drive. This paper presents modeling, simulation and implementation of these two control techniques for Interior PMSM (IPMSM). These two control methods are evaluated based on simulation and experimental responses. The salient features of these two control techniques are also presented for comparison In this work, these two control schemes vector and direct torque control are developed for PMSM drive, which uses minimum number of components employing a dedicated motion control DSP (ADMC401) developed by Analog Devices (AD) for power electronics and motion control applications [18]. The control performances of these two methods are analyzed with simulated and experimental test results obtained from developed hardware for PMSM drive. II. DESCRIPTION OF PMSM DRIVE SYSTEM The Fig.1 shows the basic building blocks of the vector controlled PMSM drive. The DTC building blocks are shown in Fig.2. The drive consists of speed controller, resolver Sin and Cos position signals demodulation circuit, current sensors, current controlled pulse width modulator (CC-PWM), the PMSM and IGBT based VSI. The rotor speed (ω r ) is compared with the reference speed (ω r *). The error in speed (ω e ) is processed in the PI speed controller, which generates the reference torque (T k *). In vector control drive this reference torque is limited using a limiter and the limited reference torque (T ref *) is used to generate q-axis reference T Vector Control Vs Direct Torque Control Comparative Evaluation for PMSM Drive Sanjeet Dwivedi, Senior Member, IEEE, and Bhim Singh, Fellow, IEEE