Abstract
Torque ripples caused by cogging torque, flux harmonics, and current measurement error seriously restrict the application of a permanent magnet synchronous motor (PMSM), which has been paid more and more attention for the use in inertial stabilized platforms. Sliding mode control (SMC), in parallel with the classical proportional integral (PI) controller, has a high advantage to suppress the torque ripples as its invariance to disturbances. However, since the high switching gain tends to cause chattering and it requires derivative of signals which is not readily obtainable without an acceleration signal sensor. Therefore, this paper proposes a robust SMC scheme based on a rapid nonlinear tracking differentiator (NTD) and a disturbance observer (DOB) to further improve the performance of the SMC. The NTD is employed to providing the derivative of the signal, and the DOB is utilized to estimate the system lumped disturbances, including parameter variations and external disturbances. On the one hand, DOB can compensate the robust SMC speed controller, it can reduce the chattering of SMC on the other hand. Experiments were carried out on an ARM and DSP-based platform. The obtained experimental results demonstrate that the robust SMC scheme has an improved performance with inertia stability and it exhibits a satisfactory anti-disturbance performance compared to the traditional methods.
Highlights
As its attractive characteristics such as efficiency, power density, torque-to-inertia ratio, reliability, etc., the application of permanent magnet synchronous motors (PMSM) on inertial stabilized platforms have been paid more and more attention
The obtained experimental results demonstrate that the robust Sliding mode control (SMC) scheme has an improved performance with inertia stability and it exhibits a satisfactory anti-disturbance performance compared to the traditional methods
To verify the effectiveness of the proposed robust SMC scheme in this paper, experiments are carried out under different strength sinusoidal disturbance conditions added by the swing platform, including d = 3 sin(2π × 0.1t), d = 6 sin(2π × 0.1t), d = sin(2πt), and d = sin(2π × 2t)
Summary
As its attractive characteristics such as efficiency, power density, torque-to-inertia ratio, reliability, etc., the application of permanent magnet synchronous motors (PMSM) on inertial stabilized platforms have been paid more and more attention. An airborne inertial stabilization photoelectric platform is equipped with visible or infrared cameras, and if we want to obtain stable and clear images, the stability of the platform must be high enough. Due to the influence of inherent factors, such as the cogging torque of the permanent magnet synchronous motor, the torque ripples caused by the motor during operation seriously affects the performance of the motor. The torque ripples will produce noise when the servo system is running at high speed and even cause the system to vibrate mechanically at low speed [1,2,3]. There are several ways to weaken the torque ripple from the optimization design of the motor, and it is the most effective means, such as skew of the stator lamination stack or rotor magnetization, skewing and fractional slot pitch windings, increasing the number of phases, dummy slots, and dummy teeth, optimization of the air gap flux distribution, and the magnet pole arc width and position, etc. [4].
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