Cajetan M. Akujuobi

Load Disturbance Resistance Speed Controller Design for PMSM

This paper presents an linear-quadratic-regulator-based proportional-integral-differential equivalent controller design method for a permanent-magnet synchronous motor. The disturbance rejection is achieved based on a multi-objective observer in which observation error is purposely retained and utilized in load disturbance compensation. This makes disturbance rejection tuning independent of the adjustment for speed command tracking; and the disturbance compensation is an integrated part of the controller output, which reduces the chance of input or state saturation. A robust stability analysis is also included for the modeling error. The proposed methodology is implemented through the dSPACE digital signal processor system, and the experimental result confirms its effectiveness

Software-defined radio: a brief overview

This paper overviews the software-defined radio (SDR), also called software radio (SR), refers to wireless communication in which the transmitter modulation is generated or defined by a computer. The receiver then also uses a computer to recover the signal intelligence. SDR is an enabling technology that is useful in a wide range of areas within wireless systems. The primary goal of SDR is to replace as many analog components and hardwired digital VLSI devices of the transceiver as possible with programmable devices. This technology is receiving enormous recognition and generating widespread interest in the telecommunication industry. The SDR Forum is an international, nonprofit organization that includes members from academia, the military, vendors, wireless service providers, and regulatory bodies. SDR has been described as the cornerstone in the evolution of GSM.

Real-time random delay compensation with prediction-based digital redesign.

Todays technological demands require challenging control solutions such as real-time applications of Networked Control System (NCS). However, due to communication protocol and shared data bus, NCS experiences uncertain and unpredictable time delays in both input and output channels. These delays cause asynchronization between the controller and the plant thereby degrading the performance of closed-loop control systems. To address this problem, this paper proposes to utilize digital redesign technique to provide real-time random delay compensation.

Electrostatic discharge (ESD)

Electrostatic discharge (ESD) refers to the sudden transfer (discharge) of static charge between objects at different electrostatic potentials. ESD belongs to a family of electrical problems known as electrical overstress (EOS). ESD poses a serious threat to electronic devices, such as microcircuits, transistors, and diodes, and affects the operation of the systems that contain those devices. Most electronic companies regard all semiconductor devices as ESD sensitive because of the damage ESD can cause. For this reason, ESD is a major concern in the microelectronic and electronic industry in manufacture and testing. ESD concerns also exist in nonelectronic components such as disk drives, magnetic recording heads, and sensors. The article describes the causes of ESD, its damaging effects and how the effects can be prevented or minimized.

Application of Wavelets and Self-similarity to Enterprise Network Intrusion Detection and Prevention Systems

Securing enterprise networks has so far been considered under two broad topics (i. e. intrusion detection systems - IDS and intrusion prevention systems - IPS). So far, there is no algorithm, which guarantees absolute protection for a given network from intruders. Most existing IDS and IPS techniques introduce high false positive and false negative rates, which need to be eliminated or reduced considerably. This paper will concentrate on network packets behavior leading to network-based intrusion detection. It will employ anomaly detection as its analysis strategy. In the field of signal analysis, the methods of wavelet transform have gotten wide application because of its unique merit. That idea will be tapped in this paper. The self-similarity property of real network traffic will be used together with the signal detection abilities of wavelets in detecting attacks. The technique used here will also try to reduce the effectiveness of distributed attacks, which deny authorized users access to system resources. Securing of all network security data, which is an important limitation to existing IDS and IPS is ensured by this technique.

Wavelets and fractals: a comparative study

Wavelets and fractals can be used as analyzing tools in many areas of sciences and engineering. However, they seem to have many areas of similarities. This paper explores these potential areas, what they are and how they can be used, at least, in a theoretical sense. Some promising results have been found and are documented.<<ETX>>

Sparseness Measures of Signals for Compressive Sampling

Recent theoretical developments in compressive sampling (or compressed sensing) show that if a signal has a sparse representation in some basis, then it is possible to capture the signal information via a small number of projections. Furthermore, the signal can be accurately reconstructed using low complexity algorithms. Although the information encoding process may be agnostic to signal type - random projections can capture the information with high probability - accurate reconstruction of the signal often depends on proper selection of a reconstruction basis. In this paper, we evaluate techniques for measuring sparseness, including some not traditionally used in signal processing, and apply them to compressive sampling with the goal of selecting the best basis for signal reconstruction.

Application of Analytic Wavelet Transform for Signal Detection in Nyquist Folding Analog-to-Information Receiver

One of the challenges in Cognitive Radio (CR) is efficiently monitoring a wideband radio frequency (RF) spectrum in order to identify unoccupied bands. Compressive Sensing (CS) has recently been proposed to address this problem. Typical CS techniques, however, involve random projections followed by a computationally intensive signal reconstruction process. Since spectral monitoring does require full signal reconstruction - only identification of occupied regions to avoid - we propose a novel spectrum monitoring approach based on the Nyquist Folding Receiver (NYFR) in conjunction with the Analytic Wavelet Transform. The NYFR performs analog compression via a non-uniform sampling process that induces a chirp-like modulation on each received signal. This induced modulation can be measured using time-frequency analysis techniques to determine the original RF band of origin without full signal reconstruction. This paper investigates the feasibility of using the Analytic Wavelet Transform to perform NYFR information recovery in support of CR wideband spectrum sensing.

Wavelet-based differential nonlinearity testing of mixed signal system ADCs

This paper discusses the work done in the testing and measurement of differential nonlinearity (DNL) of analog- to-digital converters (ADCs) by applying a novel testing technique of wavelet transform. The results of the new method are compared with conventional testing methods. The wavelet transform technique shows significant advantage over the conventional techniques.

A new parallel greedy bit-loading algorithm with fairness for multiple users in a DMT system

This letter first reviews the multiuser bit-loading algorithms for discrete multitone systems. Then an improved algorithm is proposed, which allows several users to get additional bits in parallel. It reduces the number of iterations dramatically. A new fairness coefficient is also introduced to reduce the variance of the data rate among users