Mario E. Magaña

Fuzzy-logic control of an inverted pendulum with vision feedback

In this paper, the authors present an experimental setup of a fuzzy-logic controller of an inverted pendulum that uses vision feedback. The experimental testbed is used at Oregon State University, USA, in senior and first-year graduate courses on automatic control systems to illustrate the usefulness and limitations of this approach. The results that are obtained support the claim, within certain limits, that it is possible to control an inverted pendulum using fuzzy-logic control and vision feedback.

Nonlinear Model Predictive Control of a Point Absorber Wave Energy Converter

This paper presents the application of nonlinear model predictive control (NMPC) to a point absorber wave energy converter (WEC). Model predictive control (MPC) is generally a promising approach for WECs, since system constraints and actuator limits can be taken into account. Moreover, it provides a framework for defining optimal energy capture and it can benefit from predictions. Due to possible nonlinear effects, such as the mooring forces, an NMPC is proposed in this paper, whose performance is compared to that of a linear MPC. Both controllers are supposed to control a nonlinear point absorber model. Computer simulations show that the proposed NMPC is able to optimize the energy capture while satisfying system limits.

Antenna Characterization for Bluetooth-Based Travel Time Data Collection

Several approaches for travel time data collection based on the reading of time-stamped media access control addresses from Bluetooth-enabled devices have been reported in the literature recently. This new approach offers a number of advantages over more conventional methods, including lower costs of hardware and software, the volume of data that can be collected over time, and ease of implementation. A fundamental component that may affect the quantity and the quality of the travel time samples collected with a Bluetooth-based system is the antenna type utilized. Antenna characteristics such as polarization and gain must be matched to specific application environments to optimize the performance of a Bluetooth reader unit. However, experimental data that focuses on antenna characterization as it relates to the use of Bluetooth technology to assess the performance of transportation facilities is lacking. In this study, five different types of antennas were characterized to assess their suitability to support a Bluetooth-based travel time data collection system. The results indicate that vertically polarized antennas with gains between 9dBi and 12dBi are good candidates for travel time data collection. Also, different antenna types are better suited to different uses of the Bluetooth-based system. If the main focus is the collection of travel time data, then an antenna with a lower sampling rate may provide more accurate travel time samples.

Variable Sampling Approach to Mitigate Instability in Networked Control Systems With Delays

This paper analyzes a new alternative approach to compensate for the effects of time delays on a dynamic networked control system (NCS). The approach is based on the use of time-delay-predicted values as the sampling times of the NCS. We use a one-step-ahead prediction algorithm based on an adaptive time delay neural network. The application of pole placement and linear quadratic regulator methods to compute the feedback gains taking into account the estimated time delays is investigated.

Model Predictive Control of a Nonlinear 2-Body Point Absorber Wave Energy Converter With Estimated State Feedback

Ocean wave energy has the potential to significantly contribute to sustainable power generation in coastal regions. Much of the research effort has gone into developing time domain state space models of point absorber wave energy converters (WECs) and subsequently into model-based optimal control to efficiently harvest the maximum possible amount of energy. The resulting controllers require knowledge of the states of the WEC in order to achieve the design goals. The purpose of this paper is to design and apply an extended Kalman filter-based estimation algorithm to a nonlinear two-body WEC model and to evaluate its performance in conjunction with a model predictive controller (MPC), which maximizes energy yield while satisfying operational constraints.

Performance of an optimally spaced PPM ultra-wideband system with direct sequence spreading for multiple access

We analyze the error performance of an ultra-wideband (UWB) system with pulse position modulation (PPM) for data modulation and direct sequence (DS) spreading for multiple access in indoor lognormal fading channels. A RAKE receiver is used to combine a subset of the resolvable multipath components using the maximal ratio combining technique. Inter-path and multiple-access interferences are modeled and incorporated into the BER expressions. As two special cases, the performances of the optimally-spaced and orthogonal signaling schemes are compared. The presented results allow comprehensive evaluation of system performances with any combination of parameters.

Active Control of Cable-Stayed Bridges

In this work we propose the design of an automatic control system for a cablestayed bridge to actively counteract external environmental forces generated by earthquakes. The introduction of this intelligent feature in the structure turns an otherwise passive bridge into a smart bridge, capable of reducing the amplitude of the deflections of its deck down to a desired level automatically. The control strategy proposed here uses a subset of the stay cables as active tendons to provide control forces through appropriate actuators. Each individual actuator is controlled by a decentralized controller that uses local linear velocity and local linear relative displacement information only. The effectiveness of the control algorithm herein proposed is tested on a three-dimensional model of the Quincy Bayview bridge [1,2]. This bridge has been chosen because it is fairly representative of the new generation of cable-stayed bridges. The mathematical model is derived using a finite element approach. Although some work has been done in this field by other researchers [3–6], to our knowledge, no results that use three-dimensional full-scale models have been published in the literature.

Non-Data-Aided Parametric- and Nonparametric-Based Carrier Frequency Estimators for Burst GMSK Communication Systems

In this paper, we propose non-data-aided (NDA) parametric- and nonparametric-based methods for carrier frequency estimation of burst Gaussian minimum-shift keying (GMSK), which have improved performance over ad hoc methods such as delay and multiply and have higher resolution capability. Specifically, three methods are developed for burst GMSK data to improve carrier estimation performance, and their results are compared with the standard delay-and-multiply method. Two of them are parametric-based estimators, and one is a fast nonparametric-based estimator. Parametric-based estimators were studied in detail in this paper due to their high-resolution capabilities and proven performance. However, their computational complexities were found to be relatively high in comparison to nonparametric-based estimators such as the autocorrelation method. The tradeoffs involved with respect to computational load and performance are presented.

Linear radio frequency power amplifier design using nonlinear feedback linearization techniques

This paper presents the results of the research conducted on the feedback linearization of radio frequency (RF) power amplifiers (PA) used in digital communication applications. The proposed design takes into account not only the nonlinear behavior of the power amplifier but also its dynamic behavior. First, a faithful mathematical model of the voltage I/O characteristic of the PA is developed, i.e., a sigmoidal function model which closely describes its nonlinear gain behavior is derived and a multiplicative nonlinear feedback controller is applied to it to render the overall amplifiers response linear. Simulation results obtained using Matlab/Simulink are presented, and power amplifier linearity properties are quantified in terms of the output power spectrum when the input is a BPSK waveform, the classic two-tone test, the white noise test, and the AM/AM and AM/PM conversion curves.

Performance of frequency hopped noncoherent GFSK in correlated Rayleigh fading channels

An analytical treatment of the performance of frequency hopped Gaussian frequency shift keying (GFSK) with differential detection in time-varying Rayleigh fading channels corrupted by additive white Gaussian noise (AWGN) is presented. Closed-form expressions for the bit error rate (BER) as a function of E/sub b//N/sub 0/, modulation index, channel Doppler shift, and the time-bandwidth product of the pre-modulation filter are derived. A pilot symbol-assisted scheme to lower the error floor caused by frequency hopping is analyzed.