Matteo Lodi

Design of Synthetic Central Pattern Generators Producing Desired Quadruped Gaits

This paper is concerned with a method for design and analysis of specific neuronal networks, called central pattern generators (CPGs), which produce primary rhythmic patterns in animals. In particular, the paper is focused on synthetic CPGs made up of few basic elements and governing quadrupeds’ gaits and gait transitions, under the control of an external drive. The method combines the principles of bifurcation theory, geometric properties of symmetry, and numerical analysis based on the recently proposed toolbox CEPAGE. The method is applied to two CPGs, one bio-inspired and one purely synthetic. In both the cases, the method provides a way to obtain a desired sequence of gaits by continuously changing a bifurcation parameter related to the external drive.

CEPAGE: A toolbox for Central Pattern Generator analysis

This paper is focused on a new object-oriented toolbox, called CEPAGE, devoted to simulation and analysis of Central Pattern Generators (CPGs). A CPG is a little group of neurons producing periodical patterns, which control rhythmic activities of animals. CEPAGE is conceived to carry out brute-force bifurcation analysis, but can also generate data for subsequent continuation analysis through other widely-used packages, such as AUTO or MATCONT. Two case studies are considered, with three and four neurons, with the twofold purpose of illustrating the main CEPAGE functionalities and provide new analysis results.

Ferrite inductor models for switch-mode power supplies analysis and design

This paper discusses some models useful to analyze ferrite inductors operating in partial saturation in Switch-Mode Power Supplies (SMPSs). Inductance vs current curves are needed to assess if the level of saturation is sustainable for the inductor, in order to achieve SMPS volume reduction. The models discussed in the paper are generated from experimental voltage and current waveforms of the inductor in SMPSs. Two dual approaches are presented, based on the local and global characterization of the inductor under small- and large-amplitude current ripple conditions. The resulting curves provide inductor current prediction in agreement with experimental data.

High-speed explicit nonlinear model predictive control

In this paper a circuit-oriented approximate solution to an explicit nonlinear Model Predictive Control (NMPC) problem is proposed, based on piecewise-affine functions defined over simplicial domain partitions. The resulting controller is suitable for circuit implementation in programmable devices, such as microcontrollers or FPGA, enabling the application of NMPC to systems with low sampling times. The proposed approach is validated through hardware-in-the-loop simulations.

Model reduction for optimized online compensation of hysteresis and creep in piezoelectric actuators

In this brief, a strategy is proposed for the identification, starting from experimental measurements on piezoelectric actuators, of all the parameters of the recently proposed power-law hysteresis and creep model. The algorithm allows trading off modeling accuracy and speed of the inverse model (compensator) implemented in a digital device. An analysis of the relationships among parameters and their effects on modeling and circuit performances is also carried out. The proposed strategy is tested on two piezoelectric actuators, showing that the obtained models are able to fulfill the circuit specifications.

A Low-Cost Free-Space Optical Communication Prototype

In this paper a prototype of a free-space optical communication system is proposed. The transmitter is equipped with a blue 1W LED and a low-cost microcontroller implementing a digital modulation scheme. The receiver converts the incoming light into a current through a photodiode and another identical microcontroller is employed to demodulate and decode the signal, after proper analog amplification and filtering. The system is thought to be used underwater for communication, e.g., between an autonomous underwater vehicle and a buoy. Preliminary results in air are shown to validate the functioning of the system with different values of solar illuminance.

Design and circuit implementation of approximate switched MPC

This paper proposes a novel method for design and circuit implementation of approximate controllers for constrained hybrid or piecewise affine (PWA) systems, through switched model predictive control technique. The PWA solution (discontinuous, in general) provided by this method is approximated by another PWA function composed of continuous patches defined over regular simplices. Two circuit architectures for the implementation of this approximate controller are proposed, which allow achieving reduced complexity and shorter latency, with respect to the circuits implementing the exact controller. This makes it possible the control of systems with smaller sampling times. The performances of the approximate controller are shown through hardware-in-the-loop testings of the closed-loop system.