ADAPTIVE WAVELETS SLIDING MODE CONTROL FOR A CLASS OF SECOND ORDER UNDERACTUATED MECHANICAL SYSTEMS

The control of underactuated mechanical systems (UMS) remains an attracting field where researchers can develop their control algorithms. To this date, various linear and nonlinear control techniques using classical and intelligent methods have been published in literature. In this work, an adaptive controller using sliding mode control (SMC) and wavelets network (WN) is proposed for a class of second-order UMS with two degrees of freedom (DOF).This adaptive control strategy takes advantage of both sliding mode control and wavelet properties. In the main result, we consider the case of un-modeled dynamics of the above-mentioned UMS, and we introduce a wavelets network to design an adaptive controller based on the SMC. The update algorithms are directly extracted by using the gradient descent method and conditions are then settled to achieve the required convergence performance.The efficacy of the proposed adaptive approach is demonstrated through an application to the pendubot

Induction motor mechanical defect diagnosis using DWT under different loading levels

The information extraction capability of the widely used signal processing tool, FFT for diagnosing induction machines, is commonly used at a constant load or at different levels. The loading level is a major influencing factor in the diagnostic process when the coupled load and the machine come with natural mechanical imperfections, and at a low load, the mechanical faults harmonics are strongly influenced. In this context, the main objective of this work is the detection of the mechanical faults and the study of the effect of the loading level on the induction motor diagnostic process. We have employed a diagnosis method based on discrete wavelet transform (DWT) for the multi-level decomposition of stator current and extracting the fault’s energy stored over a wide frequency range. The proposed approach has been experimentally tested on a faulty machine with dynamic eccentricity and a shaft misalignment for three loading levels. The proposed method is experimentally tested and the results are provided to verify the effectiveness of the fault detection and to point out the importance of the coupled load

Analysis of output voltage ripple for dual randomized PWM buck converter operating in continuous and discontinuous conduction modes

Dual Randomized Pulse Width Modulation (DRPWM) is renowned for its better effectiveness than Simple Randomized Pulse Width Modulation (SRPWM) in reducing conducted Electro-Magnetic Interferences (EMI) in power converters. However, the introduction of low-frequency ripples into the output voltage by dual randomization has not yet been addressed; this effect is investigated in this paper for a buck converter operating in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). First, the modulating principle is presented. Then, a general analytical expression for power spectral density (PSD) of the input current is derived and validated for the proposed DRPWM scheme for both the CCM and DCM. A comparison of the PSDs of the input current for all RPWM schemes in both the CCM and DCM shows the PSD spreading effectiveness of the dual scheme as compared to simple schemes. Finally, the low-frequency output ripple is analysed using the PSD of output voltage. The results reveal that the output voltage ripple is affected by all the randomized schemes in both the CCM and the DCM. Also, the dual scheme (RCFM-RPPM) introduces the highest low-frequency voltage ripple, especially in the CCM and for low duty cycles. In DCM, the RPPM scheme gives the lowest voltage ripple, while the RCFM scheme gives the lowest voltage ripple in the CCM. The results are confirmed by both theory and simulations

Combined random space vector modulation for a variable speed drive using induction motor

and analyzed in steady-state characteristics of the motor B Aimad Boudouda [email protected] Nasserdine Boudjerda [email protected] Khalil El Khamlichi Drissi [email protected] Kamal Kerroum [email protected] 1 Department of Electrical Engineering, University Mohamed Seddik Ben Yahia, Jijel, Algeria 2 Pascal Institute, Blaise Pascal University, Clermont Ferrand, France in closed loop, which is advantageous in reducing acoustic nois

Spread spectrum in three-phase inverter by an optimised dual randomised PWM technique

Randomised pulse width modulation (RPWM) technique has become a viable alternative to deterministic pulse width modulation (DPWM). By spreading the power spectrum in a continuous noise, this new technique better complies with electromagnetic compatibility (EMC) requirements for conducted electromagnetic interferences (EMI) and allows reducing the emitted acoustic noise in variable speed drives (VSDs). The most popular RPWM schemes are randomised pulse position modulation (RPPM) and randomised carrier frequency modulation (RCFM). The combination (RCFM-RPPM) or dual RPWM (DRPWM) has also been proposed. In this article, we propose an optimised DRPWM (ODRPWM) for the three-phase inverter. First, the modulating principle is proposed, and then, a mathematical model of power spectral density (PSD) of the output voltage is developed and validated for the three schemes, namely RPPM, RCFM and RCFM-RPPM. PSD analysis shows that the proposed scheme is more effective on spreading PSD. Moreover, this analysis reveals optimal parameters of randomisation for a maximum spread of the PSD. The optimisation problem is then modelled and solved using two powerful non-linear method