Nacim Ramdani

• PhD, Eng.
• Head of Department at University of Orléans

The present study proposes an adaptive video delivery methodology that enhances quality of experience (QoE) and aids towards the wider adoption of wireless medical video communication systems in standard clinical practice.

This study proposes a safe robot navigation in healthcare spaces methodology and aids towards the wider application of studies on Human-Robot Interaction in less structured environments. Using state-of-the-art computer vision methods, the robots should be able to detect the presence and identify the type of dynamic obstacles inside their visual fie...

This work introduces a new approach based on an event‐triggered mechanism (ETM) to design finite‐gain interval observers for linear continuous‐time systems in the presence of unknown‐but‐bounded uncertainties with a priori known bounds on state disturbances and measurement noises. In this setting, aperiodic measurements sampling is controlled in a...

This paper addresses the modeling and the design of an interval state observer for a linear time-invariant plant in presence of sporadically available measurements corrupted by unknown-but-bounded errors and noise. The interval observer is modelled as an impulsive system where an impulsive correction is made whenever a measurement is available. The...

As an integral part of patient care, nursing is required to constantly adapt to changes in the healthcare system, as well as the wider financial and societal environment. Among the key factors driving these changes is the aging of population. Combined with an existing shortage of nursing and caregiving professionals, accommodating for the patients...

Ambient Assisted Living (AAL) aims to ease the activities of daily lives for elderly or disabled people living in smart homes. In these systems, the assisting services are provided by use of the sensors that detect the location of inhabitants. Even though the cost and performance efficiencies of sensor networks depend directly on the number of the...

This article proposes a robust tracking controller for an underactuated quadrotor model based on the flatness theory and Active Disturbance Rejection Control (ADRC). Exploiting the differential flatness characteristic, it is demonstrated that a nonlinear quadrotor system can be changed into a linear canonical form, where it is easier to create a st...

This work suggests flatness-based Active Disturbance Rejection Control (ADRC) to deal with the problem of trajectory tracking for Wheeled Mobile Robot (WMR). Based on the differential flatness theory, the nonlinear WMR system is transformed into two integral-chains, which makes the creation of a state feedback controller easier. In order to improve...

This paper proposes a box expanding method to reduce the economic dispatch (ED) cost in the box-based robust unit commitment model (BUC). As a non-anticipative robust unit commitment model for a power system under demand uncertainty, BUC co-optimizes the commitment schedule and the feasible set of the ED problem to minimize the total operating cost...

To design robust interval observers for uncertain continuous‐time linear systems, a new set‐integration approach is proposed to compute trajectory tubes for the estimation error. Because this approach, the order‐preserving condition on the dynamics of the estimation error is no longer required. Therefore, synthesis methods can be used to compute ob...

The deployment of autonomous robots/vehicles is increasing in several domains. To perform tasks properly, a robot must have a good perception about its environment while detecting dynamic obstacles. Recently, evidential grids have attracted more interest for environment perception since they permit more effective uncertainty handling. The latest st...

Hospitals are considered a field of logistic robotics of high commercial potential and therefore a handful of mobile robot solutions exist. However, they have failed to trigger widespread acceptance by the market. The ENDORSE system will pursue 4 innovation pillars: an infrastructure-less multi-robot navigation, i.e. minimum installation of sensors...

This letter focuses on a day-ahead scheduling problem on thermal power plants and storage batteries based on the information of the interval prediction of photovoltaic (PV) power and demand. To realize an optimal operation, there are three kinds of decision variables to plan, which correspond to a generating power schedule, a charge/discharge (C/D)...

The paper introduces a method for synthesising set-valued state estimators for uncertain discrete-time linear systems. Based on the past values of the input and output of the system and on its observability matrix, a non-conservative numerical scheme is proposed to characterise at each time instant a tight enclosure of the actual state vector of th...

Pyro-electric Infra Red (PIR) sensors have been widely used in different indoor localization applications during the last decade. These sensors are cheap, non-intrusive and nonwearable, nevertheless, the binary PIR sensor detects only the presence of a human motion in its field of view without any other information about the actual location. Theref...

This work proposes an optimal trajectory generation and a robust flatness–based tracking controller design to create a new performance guidance module for the quadrotor in dense indoor environments. The properties of the differential flatness, the B‐spline, and the direct collocation method are exploited to convert the constrained optimization prob...

This work proposes guaranteed trajectory tracking control for a quadrotor based on feedforward flatness control and an interval observer. Using the exact feedforward linearization based on the differential flatness property, it is proven that the nonlinear quadrotor model can be transformed into the linear canonical system for which it is easier to...

This paper focuses on the day-ahead scheduling problem of generating power for thermal power plants and charging/discharging battery energy storage systems based on interval predictions of photovoltaic power. Our previous approach to this problem used the Jacobian of a solution with respect to the variation in demand. However, this study was limite...

State estimation is a key engineering problem when addressing control or diagnosis issues for complex dynamical systems. The issue is still challenging when the latter systems must be modelled as hybrid discrete–continuous dynamics, which is true for many complex and safety-critical systems. In this paper, we investigate nonlinear hybrid state esti...

This study proposes an efficient and automatic tool to understand and analyze the human natural and fast gait tasks. First, the gait tasks are modeled as a nonlinear optimal control problem along with a nonlinear model predictive control, usually used in the humanoid robots control. Second, under the assumption that the walking motions are the resu...

This paper deals with the problem of state estimation for linear continuous-time systems based on the prediction-correction (PC) set-membership approach. Although the abundant literature on using the PC estimation approach, the case of event-based measurement sampling is still poorly investigated. In the developed approach, the measurement in the c...

This paper studies a day-ahead scheduling problem on power generation of thermal power plants and charge/discharge of battery energy storage systems, where the confidence intervals of the prediction of photovoltaic (PV) and demand power are available. This problem is reduced to an interval optimization problem, where parameters having any values in...

In this study, we aim to recover the interval hull of the set of feasible cost functions that can make uncertain observations optimal for a class of nonlinear constrained parametric optimization problems when all uncertainty and disturbances acting on observations or modeling are taken bounded but otherwise unknown. Fostering on inverse Karush-Kuhn...

In this paper, a passive method for robust fault detection and isolation is elaborated in the context of set-membership approach. The basic idea behind the proposed method is to compute a feasible set containing the states of a nonlinear system states using an interval constraints propagation method. A consistency test is performed using the q-rela...

Hybrid systems exhibit continuous and discrete dynamics and are encountered in many complex and safety-critical systems. Due to their complex nature, the fault diagnosis task becomes very challenging. In this paper, we present a method to perform fault detection with a nonlinear hybrid system using set-membership parameter estimation in a bounded-e...

In this paper, we propose an interval quadratic programming method for the day-ahead scheduling of power generation and battery charge cycles, where the prediction uncertainty of power consumption and photovoltaic power generation is described as a parameter vector lying in an interval box. The interval quadratic programming is formulated as the pr...

Reachability analysis of nonlinear uncertain hybrid systems, i.e., continuous-discrete dynamical systems whose continuous dynamics, guard sets and reset functions are defined by nonlinear functions, can be decomposed in three algorithmic steps: computing the reachable set when the system is in a given operation mode, computing the discrete transiti...

The use of smart homes has been increasing greatly in recent years thanks to considerable achievements in technology. Home automation aims to improve person's autonomy and safety. For that reason, many indoor localization systems were developed recently. Nevertheless, their efficiency were improved for a single inhabitant and can not be applied in...

Within the framework of demographic changes and the constraint of permanent growth of the elderly number in European population (i.e. France) which the health sector is confronted to, the detection of abnormal behaviors in the supervisory framework has known a particular interest during these last years. Thereby, the main objective of this paper is...

A set-membership (SM) approach is proposed to design reliable static stabilizing controllers for non-linear dynamical systems. First, the control design problem is reformulated as a parameter identification issue in an unknown-but-bounded error framework. Then, a new dual set integration method for reachability computation is introduced. Finally, t...

In this paper, we apply inverse optimal control approaches in order to recover the cost function that can explain given observations, for a class of constrained optimization problems. The inverse optimal control was recently solved in an approximately optimal framework, meaning that the interest is in finding the proper criteria suitable for the sy...

Large-scale penetration of photovoltaic (PV) power generators and storage batteries is expected into the power system in Japan. To maintain the supply-demand balance with energy storage, the optimal power generation and the charge/discharge power of storage batteries can be determined in a manner of the model predictive control of generators. In vi...

Home automation is now implemented in many retirement homes in order to improve elderly's autonomy and safety. Smart homes allow to monitor the activities of elderly persons using information coming from different sensors. The ADL (Activities of Daily Living) are used to evaluate the ability of a person to perform on their own a selection of the ac...

This paper deals with the general problem of the estimation of physical parameters in the presence of nuisance parameters for which an explicit characterisation of the uncertainty is available. Within a bayesian context, the maximum a posteriori estimation is used. The asymptotic confidence ellipsoid is then determined. The projection of the latter...

This paper investigated the possibility of estimating 3D lower limb joint kinematics during five popular rehabilitation exercises of the hip and knee joints based on the data collected from a single inertial measurement unit located on the shank. The leg was modeled as a four-degree-of-freedom serial chain, and the relevant joint angles were repres...

Computing the reachable set of hybrid dynamical systems in a reliable and verified way is an important step when addressing verification or synthesis tasks. This issue is still challenging for uncertain nonlinear hybrid dynamical systems. We show in this paper how to combine a method for computing continuous transitions via interval Taylor methods...

The concern with renewable energy has been growing. Large-scale installation of photovoltaic (PV) generation and electricity storage is expected to be installed into the power system in Japan. In this situation, we need to keep supply-demand balance by systematically using not only traditional power generation systems but also the PV generation and...

The concern with renewable energy has been growing. Large-scale installation of photovoltaic (PV) generation and electricity storage is expected to be installed into the power system in Japan. In this situation, we need to keep supply-demand balance by systematically using not only traditional power generation systems but also the PV generation and...

The computation of reachable sets for hybrid systems with nonlinear continuous dynamics is addressed. In this context, the computation of the intersection of the reachable set with the guard set is a challenging problem. In a previous work, we have proposed a guaranteed relaxation method expressed as a constraint satisfaction problem to solve the e...

In this paper, a method for computing reachable sets of uncertain nonlinear continuous-time systems is proposed. The approach, based on Linear Parameter-Varying (LPV) inclusions of nonlinear systems, relies on a time-varying change of coordinates which ensures some monotony properties in the new base. A sufficient condition ensuring the non diverge...

Reachability computation formulates the problem of simulating the behavior of a continuous or hybrid dynamical system in a set-theoretical framework. Compared to the stochastic approach, it provides guaranteed results and has been shown highly valuable for verification or synthesis tasks. This issue is still quite challenging for uncertain nonlinea...

In this study, we endeavor to better understand the human motor control system in order to help transposing some of its features onto humanoid robots. The postural coordination task investigated is related to an experimental paradigm that consists in visual target tracking task while balancing. We want to test whether the human biomechanical respon...

Set membership estimation (SME) of nonlinear hybrid systems is still a challenging issue. Although SME of nonlinear continuous systems has made significant progress recently, the direct extension of these methods to the hybrid case is not easy. Meanwhile, satisfiability (SAT) checkers for Boolean combinations of arithmetic constraints over real-and...

Résumé Les systèmes dynamiques hybrides sont des systèmes complexes où coexistent des dynamiques continues et événementielles. Ce sont souvent des systèmes embarqués ou cyber-physiques critiques. Lorsque les dynamiques mises en jeu sont non linéaires ou incertaines, la vérification et synthèse des lois de commande robustes pour ces systèmes, et l'e...

A hierarchical state bounding estimation method is presented for nonlinear dynamic systems where different sensors offer several measurements of the same state vector, each of which is subject to unknown but bounded disturbances and is equipped with a local processor. For each sampling time, the proposed algorithm proceeds in two stages. At the pre...

This paper introduces effective numerical methods for the planning and fast replanning of safe motions to ensure the safety, balance, and integrity of humanoid robots over the whole motion duration. Our safe methods do not depend on, nor are connected to, any type of modeling or constraints. To plan safe motions, certain constraints have to be sati...

Aiming at automatic verification and analysis techniques for hybrid discrete-continuous systems, we present a novel combination of enclosure methods for ordinary differential equations (ODEs) with the iSAT solver for large Boolean combinations of arithmetic constraints. Improving on our previous work, the contribution of this paper lies in combinin...

A hierarchical state bounding estimation method is presented for a nonlinear dynamic system where different sensors offer several potentially faulty measurements of the same state vector, each of which is subject to unknown but bounded disturbances and is equipped with a local processor. The proposed algorithm works at two levels : at each sampling...

Optimal motions are usually used as joint refer- ence trajectories for repetitive o rc omplex motions. In th ec ase of soccer robots, the kicking motion is usuall ya benchmark motion, computed off-line, withou tt aking int oa ccoun tt he current position o ft h er obot or the direction o ft he goal. Moreover, robots must react quickly t oa ny situa...

This paper proposes a closed-loop optimal control model predicting changes between in-phase and anti-phase postural coordination during standing and related supra-postural activities. The model allows the evaluation of the influence of body dynamics and balance constraints onto the adoption of postural coordination. This model minimizes the instant...

We investigate solution techniques for numerical constraint-satisfaction problems and validated numerical set integration methods for computing reachable sets of nonlinear hybrid dynamical systems in the presence of uncertainty. To use interval simulation tools with higher-dimensional hybrid systems, while assuming large domains for either initial...

In this paper we design an interval observer for nonlinear uncertain continuous-time dynamical systems, in the unknown-but-bounded error framework. We show how to generate two coupled hybrid observers, which yield the best conservative upper and lower component-wise bounds for the state, provided bounds are available for initial conditions and unce...

The estimation of the centre of mass position in humans is usually based on biomechanical models developed from anthropometric tables. This method can potentially introduce errors in studies involving elderly people, since the ageing process is typically associated with a modification of the distribution of the body mass. In this paper, an alternat...

This paper investigates guaranteed methods for estimating feasible parameter sets when the system under study is modelled with ordinary differential equations (ODE). The issue is to find the set of parameters such that the solution of the ODE remains within specified intervals at known time-data points. These intervals correspond usually to measure...

We address nonlinear reachability computation for uncertain monotone systems, those for which flows preserve a suitable partial orderings on initial conditions. In a previous work Ramdani (2008) [22], we introduced a nonlinear hybridization approach to nonlinear continuous reachability computation. By analysing the signs of off-diagonal elements of...

This paper deals with set-membership state estimation for continuous-time systems from discrete-time measurements, in the unknown but bounded error framework. The classical predictor–corrector approach to state estimation uses interval Taylor methods for solving the prediction phase, which are known to have poor performance in presence of large mod...

A closed-loop model with actuator dynamics and sensory feedback has been developed to capture the complex postural behaviors observed in a human head tracking task. In motor-control literature, spindle feedback gains are scaled by the central nervous system to adapt muscle stiffness depending on the postural task. We propose to identify spindle ref...

In this paper, we show how to compute an over-approximation for the reachable set of uncertain nonlinear continuous dynamical systems by using guaranteed set integration. We introduce two ways to do so. The first one is a full interval method which handles whole domains for set computation and relies on state-of-the-art validated numerical integrat...

This paper models recent data in the field of postural coordination showing the existence of self-organized postural states, and transition between them, underlying suprapostural tracking movements. The proposed closed-loop controller captures the complex postural behaviors observed in humans and can be used to implement efficient and simple balanc...

This paper is devoted to set membership parameter estimation for non-linear complex-valued models. In such a context, the error between the measured data and the output model is supposed to be bounded with known prior bounds. The proposed approach is based on set inversion via complex interval analysis. A first contribution of this paper is the ext...

RÉSUMÉ. L'approximation garantie de l'espace d'état atteignable par un système dynamique continu incertain, permet de contribuer à la résolution de problèmes en automatique. Dans cette optique, nous présentons dans cet article une approche de caractérisation garantie et efficace de cet espace d'état atteignable. Cette méthode s'appuie sur les modèl...

Motion databasing is an important topic in robotics research. Humanoid robots have a large number of degrees of freedom and their motions have to satisfy a set of constraints (balance, maximal joint torque velocity and angle values). Thus motion planning cannot efficiently be done on-line. The computation of optimal motions is performed off-line to...

This paper presents a contribution for restoring standing in paraplegia while using functional electrical stimulation (FES). Movement generation induced by FES remains mostly open looped and stimulus intensities are tuned empirically. To design an efficient closed-loop control, a preliminary study has been carried out to investigate the relationshi...

This paper presents our work related to restoring standing in paraplegia induced by functional electrical stimulation (FES) and investigates the relationship between body posture and voluntary upper-body movements. A method is presented for upper-body posture estimation in the sagittal plane from force and torque measurements exerted on supporting...

This paper models recent data in the field of postural coordination showing the existence of self-organized postural states, and transition between them, underlying supra-postural tracking movements. The proposed closed-loop controller captures the complex postural behaviors observed in humans and can be used to implement efficient and simple balan...

This paper introduces a new method for planning safe motions for complex systems such as humanoid robots. Motion planning consists on finding the best joint trajectories. By using trajectory parameterization, the motion planning problem can be seen as a semi-infinite programming problem (SIP) since it involves a finite number of parameters over an...

This work is about state estimation in the bounded error context for non linear continuous time systems. The main idea is to seek to estimate not an optimal value for the unknown state vector but the set of feasible values, thus to characterize simultaneously the value of the vector and its uncertainty. Our contribution resides in the use of compar...

J.D. Pryce and N.S. Nedialkov have developed a Taylor series method and a C++ package, DaeTs, for solving numerically an initial-value problem differential-algebraic equation (DAE) that can be of high index, high order, nonlinear, and fully implicit. Numerical results have shown this method to be efficient and very accurate, and particularly suitab...

This paper reports the first results of an ongoing work which aims at providing numerical tools useful to the design of a family of high speed parallel robots. The objective is to find sets of feasible values for the design parameters unlike more usual design procedures relying on optimization techniques. These tools are mainly based on interval an...

This paper introduces a lower mobility parallel kinematic crane able to generate Scara motions (three translations and one rotation about a vertical axis). A crane is an underconstrained cable robot: it requires gravity acting on the traveling plate in order to tense the cables. The proposed crane can resist, to a certain extent, against outside fo...

In this paper we show how to compute the reachable space for uncertain nonlinear continuous dynamical systems by using guaranteed set integration. We introduce two ways to do so. The first one is a full interval method which handles whole domains for set computation and relies on Taylor series and interval analysis. The second one relies on the the...

Dans cet article, nous présentons une méthode générale de planification de trajectoires sécurisées, appliquée à l'optimisation d'un pas dans le plan sagittal pour le robot humanoïde HOAP-3. La planification de trajectoires sécurisées utilise les mêmes algorithmes d'optimisation que les méthodes de planifications classiques, mais remplace la discrét...

In this paper, we investigate nonlinear reachability computation in presence of model uncertainty, via guaranteed set integration. We show how this can be done by using the classical Müller’s existence theorem. The core idea developed is to no longer deal with whole sets but to derive instead two nonlinear dynamical systems which involve no model u...

The problem addressed in this paper deals with the parameter estimation of in vitro uptake kinetics of drugs into living cells in presence of timing noise. Effects of the timing noise on the bias and variance of the output error are explicitly determined. A bounded-error parameter estimation approach is proposed as a suited solution to handle this...

This work is about state estimation in the bounded error context for non linear continuous time systems. The main idea is to seek to estimate not an optimal value for the unknown state vector but the set of feasible values, thus to characterize simultaneously the value of the vector and its uncertainty. Our contribution resides in the use of compar...

Path planning issues are often solved via constrained optimization methods but with constraints which must be satisfied over a whole interval of time or space. The use of fast numerical toolboxes implementing state-of-the-art constrained needs to discretize the continous constraints over a time grid. Thus, the obtained solution, in this way, will s...