Mongi Besbes

An LMI-based robust dynamic controller design for the improvement of robot behavior walk, ZMP based

This work aims to design an optimal dynamic controller to stabilize the walk of a biped robot even in the presence of input and output constraints. In a first time, the robots trajectory is generated via the Zero Moment Point criterion based on the resolution of a convex optimization problem with Linear Matrix Inequalities. In a second time, the tracking of a reference trajectory is insured by the design of an optimal dynamic controller based on the predictive control theory. The synthesized dynamic controller allows for the Lyapunov stability of the robots walk. Moreover, it ensures the reducing of the overshoot and undershoot of the output signal that are difficult to be adjusted by classical methods based on solving the algebraic Riccati equation. This study is validated by a simulation via Matlab of some illustrative examples. Results are presented to prove the effectiveness of the proposed work.

New topology of cascaded multilevel inverter with reduced number of switches control considering lower order harmonics elimination

In this paper a new topology of cascaded H-bridge (CHB) multilevel inverter employing less number of switches, is presented.

A robust dynamic controller with observer for the tracking of a ZMP reference trajectory: A biped robot's walking under constraints

In this work, we propose a novel robust dynamic controller in order to stabilize a walking biped robot with input and output constraints. Firstly, the trajectory of the robot is generated via the Zero Moment Point method based on the resolution of a convex optimization problem with Linear Matrix Inequalities. Then, the tracking of a referential trajectory is insured by the design of an optimal dynamic controller with predictive control theory. The synthesized dynamic controller allows the Lyapunov stability of the robots walk. Moreover, it ensures the reducing of the overshoot and undershoot of the output signal, difficult to be adjusted by classical methods. This work is validated by a simulation via Matlab of some illustrative examples and results highlight the efficiency of the proposed study.

Development of monitoring algorithm for controlling a biped robot: norm bounded uncertainties system-based

It is well known that the biped walking gait is represented as a steady periodic gait. Investigation of such passive natural motion leads to different strategies of control; these strategies require a sharp mathematical model of the walking dynamics. One of the most used models is the Kajitas one. In this paper, we present an algorithm of controllers design used for the stabilisation of biped robots gait. Using the Kajitas model as a reference, we include a Norm bounded uncertainties to ensure a more realistic numerical model. The modified model allows us to include constraints on both inputs, outputs and states. The synthesis of the dynamic controller relies on the use of predictive control theory (MPC) and the resolution of a convex optimisation problem with linear matrix inequalities (LMIs) at every sampling period. The generated control law allows a real-time walking robot even in rough ground or unknown environment.

Flying Capacitor Multilevel Inverter Control Considering Lower Order Harmonics Elimination Based on Newton-Raphson Algorithm

Abstract Newton-Raphson-based flying capacitor multilevel inverter modeling is investigated for capacitor voltage balancing. Without using voltage feedback, Newton-Raphson method determines the best switching pattern for maintaining nil mean current in all capacitors, hence minimizing the capacitor voltage fluctuation and eliminating certain harmonic orders. Flying capacitor multilevel inverter (FCMI) modeling is developed to work with the selective harmonic elimination (SHE) technique to obtain a programmable pulse generator for multilevel inverter commutation cell control. Theoretical results are verified by experiments and simulations for a flying capacitor four-level inverter. Results show that the proposed method does effectively eliminate a number of specific low order harmonics, and the output voltage is resulted in low total harmonic distortion and with balanced flying capacitors.

Robust walking control algorithm of biped robot in rough ground

This paper presents an algorithm of a robust controller used for the stabilization of biped robot walking gait. The robot is described by a kajitas model with norm bounded uncertainties to ensure a more realistic numerical model. The proposed robust dynamic controller relies on the use of predictive control theory (MPC) and the resolution of a convex optimization problem with Linear Matrix Inequalities (LMI) at every sampling period. The generated control law allows a realtime working robot even in rough ground or unknown environment.

Cascaded multilevel inverter control considering low harmonic content based on comparison study between firefly and Newton Raphson Algorithm

This paper deals with the control design of an asymmetrical cascaded multilevel inverter. This structure therefore provides the capability to produce higher voltages at higher speeds with low switching frequency which has inherent low switching losses and high converter efficiency. Selective harmonic elimination(SHE) for asymmetrical multilevel CHB inverter control is proposed. The technique utilized in the estimation of switching angles involves Firefly Algorithm (FFA). Compared to Newton Raphson algorithm (NR), FFA is more robust and entails less computation time. Simulation results prove the effectiveness of FFA technique compared to NR algorithm. The proposed method does effectively eliminate a number of specific low order harmonics, and the output voltage is resulted in low total harmonic distortion. FFA and NR algorithm for asymmetrical cascaded H-bridge nine level inverter control are experimentally tested on a prototype using FPGA.

Time-varying actuator fault reconstruction based on adaptive observer for LPV systems

In this paper, the problem of fault isolation and detection is treated for a particular class of linear polytopic parameter-varying system (LPV). In this context, an adaptive observer design is formulated for a given polyquadratic Lyapunov function. As a result, new sufficient conditions are given in terms of Linear Matrix Inequalities (LMIs), which guarantee asymptotic convergence to zero of the estimation error, and to detect and isolate actuator faults. A tentative application was made to show the effectiveness of the proposed algorithm.

Switched Control of a Time Delayed Compass Gait Robot

the analysis and control of delayed systems are becoming more and more research topics in progress. This is mainly due to the fact that the delay is frequently encountered in technological systems. Most control command laws are based on current digital computers and delays are intrinsic to the process or in the control loop caused by the transmission time control sequences, or computing time. In other hand, the controls of humanoid walking robot present a common problem in robotics because it involves physical interaction between an articulated system and its environment. This close relationship is actually a common set of fundamental problems such as the implementation of robust stable dynamic control. This paper presents acomplete approach, based on switched system theory, for the stabilization of a compass gait robot subject to time delays transmission. The multiple feedback gains designed are based on multiple linear systems governed by a switching control law. The establishment of control law in real time is affected by the unknown pounded random delay. The results obtained from this method show that the control law stabilize the compass robot walk despite a varying delay reaching six times sampling period.

Adaptive observer design for fault detection: Application to drying blower system

In this paper, a comparison between two observers has been made; an adaptive observer and multiobserver for linear time-varying system. This observer has been designed to estimate simultaneously the state space and faults detection (sensors and actors). The convergence of the adaptive observer is implemented under certain condition. An example of a drying blower system is used to show the effectiveness of the proposed observers.