International Journal of Computer Applications (0975 – 8887) Volume 37– No.5, January 2012 1 Adaptive Control for Torque Ripple Minimization in PM Synchronous Motors Mahmoud M. Saafan, Amira Y. Haikal, Sabry F. Saraya, Fayez F.G. Areed Computer and Systems Engineering Department, Faculty of Engineering Mansoura University, Egypt. ABSTRACT This paper presents two methods for designing special purpose controllers for permanent magnet synchronous motor. The main target of the designed controllers is to reduce torque ripples of this type of motors. The first proposed adaptive method is based on two loop controllers (current controller and speed controller) in addition to using space vector pulse width modulation to maximize fundamental component of torque. The second proposed method is based on PI current controllers enabling tracking of quadrature current command values. Simulation results of the suggested adaptive controller are compared with that of the PI controller. Comparative analysis proves the effectiveness of the suggested adaptive controller than the classical PI one according to ripple reduction as well as dynamic response. Moreover, the suggested adaptive controller when compared with other controllers shows great success in torque ripples reduction, enabling speed tracking while minimizing the torque ripple. Keywords Model reference adaptive system, PM synchronous motor, torque control. 1. INTRODUCTION We ask that authors follow some simple guidelines. In essence, we ask you to make your paper look exactly like this document. The easiest way to do this is simply to download the template, and replace the content with your own material. Permanent magnet synchronous motor (PMSM) is wildly used from home appliance to electric vehicles since PMSM has high power density and efficiency than reluctance and induction motor. The magnetic and thermal capabilities of the PM were increased by employing the high-coercive PM material, and thus, the PMSM is often employed as an effective actuator in special purpose applications. The PMSM is essentially a wound rotor AC synchronous machine with no damper windings. The idea resides in the fact that the rotor excitation is fixed and provided by permanent magnets instead of being supplied by an external circuit through slip rings and brushes. Actually PMSMs are distinguishable due to several advantages compared to their counterparts [1]:  It operates at a higher power factor compared to induction motor (IM) due to the absence of magnetizing current.  It doesn’t require regular brush maintenance like conventional wound rotor synchronous machines due to absence of external rotor excitation.  Rotor doesn’t require any supply nor does it incur any loss due to absence of rotor windings.  Low noise and vibration than switched reluctance motors (SRM) and IMs.  Lower rotor inertia leading to rapid response.  Larger energy density and compact structure. However, PMSMs suffer from torque ripples. Since PMSMs aim for high performance applications such as machine tools or direct drive robotics, torque oscillations are not acceptable. Torque ripples lead to speed oscillations, which cause deterioration in system performance. In machine tool applications, these oscillations leave visible patterns in high- precision machined surfaces. In fact, the electromagnetic torque generated by a PMSM are divided into Fundamental, slot and reluctance torque components, in which each can contribute to higher ripples in total torque. Fundamental torque is the desired torque, which is generated by the stator current and rotor flux linkage. While, Slot torque is due to the slotting in the stator. Reluctance torque is due to the rotor’s variable reluctance. Reluctance torque can be negligible if the d-axis current is controlled to be nearly zero (i d ≈0) or the rotor saliency is not significant. Researchers presented various techniques for torque ripple minimization [2]. These techniques either depends on changing motor design with the aim of reaching ideal characteristics [1], [3]-[4].or on designing special purpose controller to manage the problem of ripples which is the aim of the proposed work. The approach proposed in this work is based on harmonic cancellation using the pre-programmed current waveforms [5], [6]. This approach relies on knowing torque ripple characteristics of the specific motor, and using the torque production model to get the optimal currents that need to be injected to cancel the undesired value of the torque. This approach is sensitive to parameter variations so, its performance degrades when changing the operating conditions. However, on-line estimation of parameter variations during the motor operation can deal with that [6]– [10]. Common control strategy for PMSM is vector control oriented in rotor dq reference frame. Control approaches have two alternatives, either dealing with speed loop or current loop. When choosing torque controller current loop can be replaced with the torque loop due to mathematical relation joining both then use motor torque observers to get the necessary feedback. Different methods have been investigated for torque observation, such as recursive least squares [8] and model