Types Of Reference Signals Research Articles

Particle swarm optimization based novel adaptive step-size FxLMS algorithm with reference signal smoothing processor for feedforward active noise control systems

The unimproved filtered-x least mean square (FxLMS) algorithm is not enough to guarantee the convergence rate and stability when outliers appear in the reference signal Xn. To make up for this deficiency, a novel adaptive step-size FxLMS with reference signal smoothing processor (NASFSxLMS) algorithm is proposed to accelerate the convergence rate and weaken the impact of outliers. The reference signal smoothing processor integrates the Moving-Median filter and the Hampel filter to preprocess different types of reference signals. The novel adaptive step-size is developed by normalizing the step-size adjustment factor which takes the Euclidean Norm of Xn and error signal en into consideration. What’s more, different coefficients of the step-size adjustment factor h(n) in the normalization function result in different noise reduction effects. To further ameliorate the noise reduction performance of the proposed algorithm, we combine the NASFSxLMS algorithm with the particle swarm optimization (NASFSxLMS-PSO) algorithm to get the optimal coefficients of h(n). Simulation results demonstrate the faster convergence rate, enhanced stability and higher noise reduction of the proposed algorithms under different types of reference signals.

A Simplified Model Predictive Control of Four-Leg Two-Level Inverter

This article proposes current control strategy for four-leg two-level voltage source inverters (VSI). This strategy is based on model predictive control (MPC) approach and presents its comparison with finite control set (FCS) model technique. Besides providing a fast dynamic response, proposed technique replaces complex modulation stage and PI controller being used in earlier classical control techniques. Moreover, the proposed methodology selects the switching sequence which reduces tracking error between output and applied reference currents using cost function optimization. This shows the improvement of system response like FCS model technique. However, FCS model technique results in calculation stress and computation burden; resulting computational delay and extra power consumption by the processor. This problem is solved with the help of proposed single predictive technique which makes the inverter more suitable for large time horizon operations and small sampling time instants. The computational delay is reduced up to 6% compared to the case of FCS-MPC controlled inverter. Performance of proposed simplified technique is analyzed and compared with FCS-MPC controlled system with the help of different types of reference signals. This work will boost the industrial application of four-leg two-level VSI by increasing dynamic response and removing complex modulation stage.

Low-Complexity Multiuser Receiver for Massive Hybrid Array mmWave Communications

In this paper, we study the low complexity reception of multiuser signals in uplink millimeter wave (mmWave) communications using a partially connected hybrid antenna array. Exploiting the mmWave channel property, we propose a low-complexity user-directed multiuser receiver with three novel schemes for allocating subarrays to users. This receiver only requires the knowledge of angles-of-arrival (AoAs) for dominating paths and a small amount of equivalent channel information instead of perfect channel state information. For comparison, we also derive a successive interference cancellation-based solution as a performance benchmark. We design two types of reference signals with the channel estimation method to enable efficient and simple estimation for AoA and equivalent baseband channel. Also, we provide analytical results for the performance of the AoA estimation, using the lower bounds of mean square errors in line-of-sight dominated mmWave channels. The simulation results validate that the proposed channel estimation method is effective when employed in combination with a zero-forcing equalizer.

Robust backstepping decentralized tracking control for a 3-DOF helicopter

A three-degree-of-freedom helicopter attitude tracking control system can be described as a multi-input multi-output strict-feedback form system with unknown parameters, bounded disturbances, and nonlinear uncertain cross-couplings. Both norm-bounded and nonlinear uncertainties are discussed. The whole nonlinear system is divided into a nominal disturbance-free system and an equivalent disturbance part. A robust control method based on signal compensation technique and backstepping decentralized control is proposed. Robust practical tracking property of closed-loop system is proven, and the tracking error can be made as small as desired with expected convergence rate. Experimental results demonstrate the improved tracking performance of the attitude tracking control system with different types of reference signals, such as step signals, ramp signals, and nonstationary sinusoidal signals.

Robust Attitude Control and Virtual Reality Model for Quadrotor

This paper introduces an adaptive attitude control based on a backstepping control scheme for a quadrotor helicopter test bed. First, aerodynamics and motion equations are provided to model the dynamics of the quadrotor and a Virtual Reality (VR) model is developed incorporating the dynamic model to the virtual results of simulation. Then, an adaptive backstepping algorithm is applied to the attitude control and this algorithm is adaptive according to Lyapunov-based stability analysis. Finally, the simulation results with many types of reference signals are provided to demonstrate the good tracking performance of the proposed control algorithm.

Design of High Accuracy Tracking Systems with H∞ Preview Control

Positioning and tracking control systems are an important component of autonomous robot applications. This paper presents the design method of tracking control systems based on H1 preview control where the present and future desired positions of the robot are used to determine the control actions to be applied so that the robot describes the desired trajectory as close as possible. The performance improvements achieved with H1 preview control have been examined in the frequency and time domains for different types of reference signals when applied to a one-dimensional positioning system. It was found that preview control improves the tracking performance by improving the phase response of the tracking system.

Control of strain in a flexible beam using Ni-Ti-Cu shape memory alloy wire actuators

In this paper the development of an experimental test bench to analyze and control the strain of a flexible aluminum beam subjected to external disturbances is described. In the proposed platform, strain-gauges are used to measure the strain of the beam in a single cantilever mode while Ni-Ti-Cu Shape Memory Alloy (SMA) wires are used as force actuators. Data acquisition and control system are implemented with an ADuC microcontroller. The response of the structure in open-loop was used to identify the mathematical model of the system. To find the appropriate controller and to reach the best performance of the system, it was used techniques of direct tuning (pole-zero cancellation) in the identified model. The PI controller has been used to control the strain of the beam for different types of reference signals, as square, sinusoidal and triangular. The frequencies of the reference signals have been varied to observe to which bandwidth the system can respond. Experimental results are used to demonstrate the usefulness of the PI controller in the proposed smart structure.

Design and Implementation of Feedback Control for Counterflow Thrust Vectoring

Aircraft thrust vector control is currently implemented using movable control surfaces such as vanes and flaps. Counterflow thrust vectoring (CFTV) is a fluidic approach to thrust vectoring that has the potential to improve on the conventional approaches by reducing weight and increasing the reaction speed. Open-loop implementation of CFTV has been demonstrated in laboratory settings. However, ultimately this technology must be implemented using feedback control. The primary control objective is to achieve fast slew rates by compensating for the transportation delay and parameter uncertainties. The paper describes an experimental test bed for investigating feedback control of CFTV. System estimation results based on open-loop test data are presented. This paper then develops a PID control law, which is sometimes implemented with a Smith predictor to compensate for the transportation delay and/or an antiwindup scheme to compensate for actuator saturation. The control laws are experimentally demonstrated, and their performance is compared using different types of reference signals.