Optimal commutation laws in the frequency domain for PM synchronous direct-drive motors

Abstract

Abstract-This paper presents a new model for torque generation of permanent-magnet synchronous motors and their control based on Fourier coefficients. A new commutation strategy delivers ripple-free torque and simultaneously minimizes copper losses for the case when the motor's servo amplifier dynamics are negligible. However, multipole motors give rise to high frequency control signals, and often the dynamics of the current amplifier are no longer negligible. For this case, we present a new commutation strategy which minimizes the torque ripple and the velocity induced change in the torque transfer function. The performance of both commutation laws is validated via simulations based on experimental data from a synchronous motor. Minimal computational requirements make these algorithms ideal for real time implementation.

Energy-Efficient and Fault-Tolerant Control of Multiphase Nonsinusoidal PM Synchronous Machines

“…Various optimal or nonoptimal indirect torque control of unideal PMSMs by taking into account the presence of harmonics in the back-EMF [42]. Various techniques are presented in [7] and [43]- [49] for torque-ripple minimization of nonsinusoidal PMSMs by making use of individual harmonics of the back-EMF to obtain stator currents. Optimalcurrent determination for multiphase nonsinusoidal PMSMs in real time is reported in [7], [9], and [50].…”

“…Various techniques are presented in [7] and [43]- [49] for torque-ripple minimization of nonsinusoidal PMSMs by making use of individual harmonics of the back-EMF to obtain stator currents. Optimalcurrent determination for multiphase nonsinusoidal PMSMs in real time is reported in [7], [9], and [50]. Optimal and ripplefree torque control of servo motors in the presence of back-EMF harmonics is derived in [38] based on Lagrangian optimization to minimize power dissipation and deferring voltage saturation.…”

Fourier Series Methods for Optimal Periodic Position Control

“…Fourier series methods have been previously employed to determine optimal motor excitation currents; see, for example, [1], [4] and [5]. In these works, the mechanical dynamics is ignored since motor torque is viewed as the output signal.…”

A Modular and High-Precision Motion Control System With an Integrated Motor

“…Such a controller is briefly described in this section. Control approaches for accurate torque production in direct-drive systems and their underlying models have been studied by several researchers [6], [12], [25]- [28]. The control problem is radically simplified when the motor's phase currents are considered as the inputs.…”

“…Multipole motors require complex designs with many slots and windings, which increases the cost. In addition, they require high-frequency control signals that can be challenging for electronic commutators [6], [12]. Therefore, the number of poles and slots should be determined by a tradeoff between manufacturing capability and controllability.…”