Luis Henrique Carvalho Ferreira

This article presents a set of sufficient conditions that allows synchronization protocols for discrete-time homogeneous linear multi-agent systems based on state feedback to be not only implemented but also designed in a fully distributed manner, that is, without the need to use global information about the entire communication topology. The results are obtained from a guaranteed synchronization region determined from an auxiliary problem that considers only the dynamics of a single agent. Numerical examples are presented to illustrate the application of the proposed conditions.

This article presents an analysis of mean-square stability and robustness margins for networked systems. We consider an architecture in which the controller-to-actuator channel is subject to packet losses, and a zero-input strategy is used to deal with the losses. For this situation, we obtain guaranteed mean-square gain and phase margins based on the $\mathcal {H}_{\infty }$ norm of sensitivity and complementary sensitivity functions. We also analyze guaranteed mean-square $S$-based and $T$-based disk margins, which in the case of single-input, single-output systems and losses modelled by Bernoulli processes can be translated into a tool based on Nyquist plots. A numerical example is presented to illustrate the use of the proposed results.

This paper presents a real-time, low-power R-peak detector implemented in an FPGA. It is different from other implementations as it runs at the same signal sampling rate, rather than utilizing a high clock frequency as utilized in batch processing with high throughput systems. Such implementation relies on a Savitzky-Golay filter for power line noise filtering, and on an adapted version of the Difference Operation Method (DOM) algorithm. The modification in DOM is needed in order to be able to process the data either without increasing the clock to process data in a batch fashion or unsustainably increasing latency. It uses the Savitzky-Golay Digital Differentiator, eliminating further filtering stages. The prototype was characterized using both the MIT-BIH database and Fluke Prosim 8 Vital Signal Simulator. The proposed system features a high degree of matched R-peaks even being extremely efficient regarding power dissipation. Moreover, it shows similar performance when compared to the original Difference Operation Method implementation.The whole system consumes 260- uW operating at 192-Hz in an FPGA model 10M50DAF484C7G, which belongs to the MAX10 family of Altera devices.

This article concerns the problem of synchronization of homogeneous linear multi-agent systems considering a robust control and small gain theorem perspective. The analyses are performed based on an auxiliary state feedback problem in which only the dynamics of a single agent is considered. This point of view allows an unified approach to continuous- and discrete-time cases and provides insights that, in addition to enabling the analysis of feasibility of the synchronization problem in terms of a guaranteed synchronization region, assists in choosing the distributed protocol design parameters. Numerical examples are presented to illustrate the analyses performed.

This manuscript presents a fully differential difference transconductance amplifier (FDDTA) architecture based on CMOS inverters. Designed in a 130-nm CMOS process it operates in weak inversion when supplied with 0.25 V. In addition, the FDDTA requires no supplementary external calibration circuit, like tail current or bias voltage sources, since it relies on the distributed layout technique that intrinsically matches the CMOS inverters. For analytical purposes, we carried out a detailed investigation that describes all the concepts and the whole operation of the FDDTA architecture. Furthermore, a comparison between the modeling equations and measured data assures high performance.

In this article, we presented guaranteed independent and uniform multivariable stability margins for the $\mathcal {H}_{\infty }$ /LTR control, both in continuous and discrete time. In previous works, it was shown that the $\mathcal {H}_{\infty }$ /LTR control generalizes the linear quadratic Gaussian (LQG)/LTR setup, allowing the designer to better impose bounds on the complementary sensitivity frequency peak in the loop-shaping procedure. In this article, we extend this result by showing that $\mathcal {H}_{\infty }$ /LTR control is able to recover better robustness properties than those recovered in the LQG/LTR case. Numerical examples are presented for multivariable and monovariable cases.

A new solution for a fully differential bulk-driven Operational Transconductance Amplifier (OTA) for ultra-low-voltage applications is proposed herein. The amplifier eliminates the tail current source, performs a common-mode control and a transconductance adjust in parallel. All transistors in the project are biased in the weak inversion region. The minimum supply voltage is 150 mV using a transistor stack up of two. Simulations indicate that the Common Mode Rejection Ratio (CMRR), transconductance and Total Harmonic Distortion (THD) are compatible with biomedical applications.