Cogging Torque Reduction in Brushless Motors by a Nonlinear Control Technique

Abstract

This work addresses the problem of mitigating the effects of the cogging torque in permanent magnet synchronous motors, particularly brushless motors, which is a main issue in precision electric drive applications. In this work, a method for mitigating the effects of the cogging torque is proposed, based on the use of a nonlinear automatic control technique known as feedback linearization that is ideal for underactuated dynamic systems. The aim of this work is to present an alternative to classic solutions based on the physical modification of the electrical machine to try to suppress the natural interaction between the permanent magnets and the teeth of the stator slots. Such modifications of electric machines are often expensive because they require customized procedures, while the proposed method does not require any modification of the electric drive. With respect to other algorithmic-based solutions for cogging torque reduction, the proposed control technique is scalable to different motor parameters, deterministic, and robust, and hence easy to use and verify for safety-critical applications. As an application case example, the work reports the reduction of the oscillations for the angular position control of a permanent magnet synchronous motor vs. classic PI (proportional-integrative) cascaded control. Moreover, the proposed algorithm is suitable to be implemented in low-cost embedded control units.

Design of an Observer-Based Architecture and Non-Linear Control Algorithm for Cogging Torque Reduction in Synchronous Motors

“…In [24] is presented a non-linear control architecture based on feedback linearization technique which exploits knowledge on the cogging torque through the definition of a closed form modelling of it. The authors present the experimental results in terms of a desired position trajectory tracking followed by a parametric robustness analysis and a computational analysis for low-cost embedded platform implementation.…”

“…In this section we report in detail the control algorithm, used in one of our previous works [24] concerning the reduction of the cogging torque through a control technique, and the configuration chosen for the EKF, which is different from most of the works reported in the literature.…”

Reduction of Ripple Toothed Torque in the Internal Permanent Magnet Electric Motor by Creating Optimal Combination of Holes in the Rotor Surface Considering Harmonic Effects

“…The spatial harmonics in the magnetic field have three sources [1][2][3]. In terms of toothed ripple or cogging torque, several known methods were presented to reduce it in many kinds of motors that have a uniform (multilayer) axial structure [4,5]. However, owing to differences in motor structure, these techniques cannot be used in all electric motors.…”

Cogging torque analysis in permanent magnet synchronous generators using finite elements analysis

“…As this study will focus on machine-based optimizations, information about studies conducted with control-based methods can be accessed in the literature. [16][17][18][19][20] In the machine-based studies, on the other hand, optimizations on stator, rotor, magnet geometry or material type are performed. In Popescu et al, 21 the change in the cogging torque in relation to magnet radius change, combinations of pole/rotor slot numbers and skew amount of the rotor was examined.…”