T. K. Roy

Position control of a small helicopter using robust backstepping

In this paper, a robust control strategy applied on a small helicopter is proposed. An approximate small-scale helicopter model with decoupled dynamics is adopted for the controller design which uses the backstepping method based on the Lyapunov function. The Lyapunov function is used to show the robustness of the proposed control method under conditions of wind gusts. Finally simulation results, which show the effectiveness of the proposed controller and its ability to cope with external wind gusts on a plant model, are presented.

Adaptive backstepping controller for altitude control of a small scale helicopter by considering the ground effect compensation

In this paper, a nonlinear adaptive control technique is proposed to control the altitude of a small-scale helicopter for hovering as well as vertically take-off/landing near ground surface in the presence of strong horizontal wind gusts. In general, the control of small scale helicopter is a difficult task, because the helicopter system is highly nonlinear, coupled and sensitive. For simplicity, only vertical flight motion is focused on here. This type of system has only two degrees of freedom, including helicopter altitude and collective pitch angle of blade. A vertical dynamics motion model of small-scale helicopter is considered to derive the proposed controller for the purposes of capturing dynamic variations of thrust due to the horizontal wind gusts and ground effect. In order to stabilize the vertical dynamics of the small-scale helicopter, a recursive (backstepping) design procedure is used to design the adaptive controller based on Lyapunov approach. Simulation results demonstrate that the proposed adaptive backstepping controller is capable of controlling the altitude for hovering flight of a small-scale helicopter near ground surface in the presence of strong horizontal wind gusts.

Altitude control of an unmanned autonomous helicopter via robust backstepping controller under horizontal wind gusts

In this paper, a nonlinear robust control technique is proposed to control heave motion for hover as well as vertically take-off/landing of an unmanned autonomous helicopter in the presence of external wind gusts. A heave motion model of a small helicopter is considered to derive the proposed controller for the purposes of capturing dynamic variations of thrust due to the external disturbances. A recursive (backstepping) design procedure is used to design the robust controller for vertical dynamics based on Lyapunov approach. To show the effectiveness of the proposed control method and its ability to cope with the external uncertainties in the vertical dynamics, results are compared with a classical PD controller. Comparative studies demonstrate that the proposed robust backstepping control method greatly enhance the performance over the classical PD controller and it is applied to RUAV hovering condition as well as vertical take-off/landing.

Performance analysis of low pass FIR filters design using Kaiser, Gaussian and Tukey window function methods

Digital filter plays an important role in the advanced era of communication system. Digital filters basically provide high attenuation to the unwanted ones and offer very low or ideally zero attenuation to desired signal components when its impulse response is adjusted as per requirement. But the design of a digital filter satisfying all the required conditions is a challenging task. In this paper, design techniques of low pass FIR filters using Tukey window, Kaiser Window, and Gaussian window methods are presented. The magnitude and phase responses are demonstrated in the simulation section for the different design techniques of digital low pass FIR filters. From the simulation results, it is observed that for a longer length the FIR filter has a sharper cut-off FIR filter and a narrow transition band.

Adaptive controller design for grid current regulation of a CSI based PV system

A nonlinear adaptive controller for regulating the grid of a current source inverter (CSI) based three-phase grid-connected photovoltaic (PV) system is proposed in this paper. The proposed control structure is composed of an outer current loop which is responsible for controlling the DC-side inductor current and the inner current control loop is responsible for controlling injected current into the grid. The proposed controller is designed recursively by considering some parameters of the system parameters as unknown and these unknown parameters are estimated through the adaption laws. In order to prove the overall stability of the whole system control Lyapunov functions (CLFs) are formulated at different stages of the design process. Finally, the effectiveness of the proposed control scheme is tested on a CSI based three-phase grid-connected PV system under different atmospheric conditions. Simulation results show that the proposed control scheme can effectively meet the desired control objectives.

Nonlinear backstepping controller design for a three-phase grid-connected photovoltaic system using DPC approach

A new direct power control (DPC) approach for a voltage source inverter (VSI) based three-phase grid-connected solar photovoltaic (PV) system is proposed in this paper. The proposed DPC is designed using the nonlinear backstepping control scheme based on the power dynamics rather than the conventional dp current dynamics. As a result, the inner current control loop is eradicated in this paper which simplifies the system modeling and controller design and enhances the transient performance. Conversely, the outer voltage loop is used to generate the active power reference from the closed loop control of the dc-link voltage dynamics. The proposed controller is designed recursively based on the Lyapunov function theory and overall stability of the whole system is confirmed with the formulation of control Lyapunov functions (CLFs) at every design stage of the controller. Finally, the performance of the designed controller is tested on a three-VSI based three-phase grid-connected PV system under different operating conditions. The performance is also compared with an existing controller and it is clear that designed controller can better performance than the existing controller in terms of the total harmonic distortion (THD) of the injected current and quality of power.

Active noise control using filtered-xLMS and feedback ANC filter algorithms

Active noise control (ANC) is one of the most popular applications for adaptive filters. In the emerging application area of adaptive signal processing is active noise control. The basic idea behind the active control of acoustic noise is to inject a secondary sound (anti-noise) into an environment so as to cancel the primary sound using destructive interference. So, ANC is a method of reducing the unwanted noise by actively generating an anti-sound, cancelling out the noise. To achieve this, in this paper, we describe a well-known filtered-X Least Mean Square (filtered-x LMS) and feedback active noise control algorithms which provide a new structure for improving noise reduction. Finally, simulation results have shown the effectiveness of the proposed algorithm.

Performance comparison of three optimized alternative pulse shaping filters with the raised cosine filter for wireless applications

This paper is concerned with the performance and cost analysis of different pulse shaping filters such as raised cosine, finite impulse response (FIR) Nyquist, FIR half-band and infinite impulse response (IIR) linear phase half-band for wireless applications. Note that the pulse shaping is the process of changing the waveform of transmitting pulses to reduce the interferences keeping a signal in an allotted bandwidth. This paper proposes an optimal design for the pulse shaping filters to reduce their effective costs in the area of wireless communication applications. Here, we analyze the performance of pulse shaping filters based on the minimum stop band attenuation required to suppress the inter-symbol interference (ISI) and inter-channel interference (ICI). Finally, we compare the performance of raised cosine, FIR Nyquist, FIR half-band and IIR linear phase half-band filters in terms of bit-error rate (BER) and hardware requirements. Our results demonstrate that the hardware implementation costs for the FIR Nyquist, FIR half-band and IIR half-band filters are about 60% to 90% less than the raised cosine filter.

Nonlinear adaptive backstepping controller design for grid currents regulation of a CSI based PV system with external disturbances

In this paper, a nonlinear adaptive controller for regulating the grid of a current source inverter (CSI) based three-phase grid-connected photovoltaic (PV) system is proposed. The proposed control structure is composed with an outer control loop-responsible for controlling the DC-side inductor current and the inner current control loop-responsible for controlling injected current into the utility grid. The proposed adaptive controller is designed recursively by considering external disturbances within the system and these unknown external disturbances are estimated through the adaption laws. The overall stability of the whole CSI based three-phase grid-connected PV system is verified by formulating the control Lyapunov functions (CLFs) at different stages throughout the design process of the proposed controller. Finally, the performance of the designed controller is tested on a similar CSI based three-phase grid-connected PV system under different atmospheric conditions. Simulation results demonstrate that the proposed control scheme can effectively meet the desired control objectives as compared to the existing controller in terms of settling time and power quality.

Robust adaptive backstepping controller design for PWM based DC-DC buck converter based on projection method

DC-DC power converter is a most important power source for driving a DC system in contemporary power electronic systems. However, owing to the time-varying and nonlinear characteristics of load resistance, it is often very challenging issue to ensure the stability of such converters. This paper is concerned about the regulation of the output voltage of a DC-DC buck converter using a nonlinear robust adaptive technique. The proposed controller is designed recursively based on the Lyapunov theory where the load resistance is considered as an unknown parameter. This unknown load resistance is estimated through the parameter adaptation law based on the projection method. Note that the projection method is a robustness augmentation technique that bounds the unknown parameter variations in a convex set which confirm through the formulation of control Lyapunov functions (CLFs) at different stages. The advantages of the proposed controller are that it can provide robust performance against external turbulence and also conquer the over-parameterization difficulty. At last the usefulness of the designed controller is verified through simulation results and compared with an existing controller. From the simulation results, it is obvious that the designed controller provides a significant performance improvement than the existing controller in terms of settling time and fast tracking desired output voltage.