[show abstract][hide abstract] ABSTRACT: An important issue in the trends of miniaturization
of systems-on-chips (SoCs) is to obtain a high energy efﬁciency.
This can be reached by dynamic voltage scaling (DVS) architec-
tures as the novel discrete Vdd-Hopping circuit. Generally, this
kind of systems present parameter uncertainties and delays. Like-
wise, current peaks and energy dissipation must be reduced. In this
paper, an optimal and robust saturated control law is proposed for
this Vdd-Hopping circuit via Lyapunov-Krasovskii theory that en-
sures asymptotic stability as well as system robustness with respect
to delay presence and parameter uncertainties. The closed-loop
system presents a regional stabilization due to the actuator sat-
uration. An estimation of an attraction domain is provided. This
controller also limits the current peaks and it provides an energy-
aware performance. The advantages achieved with this controller
are shown in simulation.
IEEE Transactions on Control Systems Technology 03/2013; 21(2):530. · 2.00 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper proposes an event-based scheme to control a networked control system and to manage the radio-modes of its smart sensor node. The smart node is battery driven and is in charge of sensing the system and computing the control law which is sent to the receiver using a wireless channel. To save energy and to limit the amount of communication with the receiver, the smart node combines two techniques: event-based control and radio-mode management. The control law and radio-mode switching policy are derived jointly in a predictive finite receding horizon optimization problem. We derive a Model Predictive Controller using Dynamic Programming and we prove the stability of the obtained control law using the Input-to-State Stability framework. The main contribution of this paper is to take into account several low consuming radio-modes, e.g. Idle and Sleep and the energy-transition costs between modes. Most of the existing literature only considers one mode when the radio is not transmitting, i.e., the scheduling problem. As illustrated via simulations, our proposal has the potential of significant energy savings.
Decision and Control (CDC), 2012 IEEE 51st Annual Conference on; 01/2012
[show abstract][hide abstract] ABSTRACT: Energy efficiency is one of the main issues in wireless Networked Control Systems. The control community has already shown large interest in the topics of intermittent control and event-based control, allowing to turn off the radio of the nodes, which is the main energy consumer, on longer time intervals than in the periodic case. While the existing literature only addresses policies using two radio-modes (Tx-Transmitting, and Sleep), this paper considers intermediate radio-modes, which consume more energy than the Sleep mode but have cheaper transition costs to the Transmitting mode. We propose an event-based radio-mode switching policy to perform a trade-off between energy saving and performance of the control application. To this end, we derive a switched model taking into account control and communication. We compute the optimal switching policy using Dynamic Programming and we illustrate the results in simulations.
[show abstract][hide abstract] ABSTRACT: The paper presents several aspects of modeling, observation and control towards a new generation of Electrical Power Steering(EPS) systems. In particular we design an optimal control to reject oscillations of the steering column, then we device a new observer to estimate the internal state variables of the steering column, the driver applied torque (steering wheel torque), and the load torque (tire/ground contact friction). Finally, we also revisited the LuGre tire dynamic friction model by improving the transient behavior between the sticking phases and the dynamic ones. Simulation of the proposed control and observer are shown at the end of the paper using the improved LuGre-tire friction model.
Proceedings of the IEEE International Conference on Control Applications, CCA 2011, Denver, CO, USA, September 28-30, 2011; 09/2011
[show abstract][hide abstract] ABSTRACT: This paper deals with the control of a fleet of non-linear systems representing AUVs (autonomous underwater vehicles). The purpose is here to design a control law to stabilize the fleet to time-varying formations which are not only circular. A novel framework is proposed to express a general control law for a large class of formations. This is produced by applying a sequence of affine transformations such as translations, rotations and scalings. The paper also includes a cooperative control to distribute the agents along the formation which takes into account the communication constraints. The system was implemented in computer simulation, accessible through Web 1 .
Proceedings of the American Control Conference 01/2011;
[show abstract][hide abstract] ABSTRACT: A mathematical driver model is given in the spacial equation form, which takes into account the previewed information of the path. Optimal control method is considered for the ideal no time-delay case and Lyapunov-Krasovskii functional approach is applied to deal with drivers' reaction time-delay. For both cases, exponential stability is guaranteed for the closed loop system.
Proceedings of the IFAC Word Congress 2011. 01/2011;
[show abstract][hide abstract] ABSTRACT: In this paper we introduce an integration framework for Control/Communication/Computation (3C) co-design based on the motivating example of fleet control of Autonomous Underwater Vehicles (AUVs) supervised by an Autonomous Surface Vehicle (ASV). Specifically, we address the problem of almost sure stability of an unstable system with multiple observations over the packet erasure channel with emphasize on coding computational complexity. We look at the tradeoff between duty cycle for feedback channel use, coding computational complexity, and performance. We compare coding computational complexity and performance for two cases: a) No feedback channel at all, and b) Feedback channel all the time. It is shown that the strategy of using feedback channel results in a better performance.
[show abstract][hide abstract] ABSTRACT: Dynamic voltage scaling (DVS) is an important method in managing dynamically the system supply voltage for efficient power reduction. This approach is applied in very large scale integration (VLSI). A dc-dc converter is an electronic device which allows to vary the voltage and, thus, to implement DVS tech- nique. In this paper, a high-performancecontroller is presented for a novel discrete DVS converter. This controller is developed with the aim to deal with the unknown resistive component of the load as well as to minimize the dissipated energy and current peaks, what is very important in the field of microelectronics. Current peaks and power consumption are minimized by computing an optimal evolution for the voltage reference. Likewise, an adaptive controller is proposed to deal with the unknown load resistive parameter. Consequently, the obtained advanced controller can acquires a high consideration on electronic devices. IndexTerms—Adaptivecontrol, dynamic voltagescaling, energy aware, Lyapunov's methods, optimal control.
Circuits and Systems I: Regular Papers, IEEE Transactions on 01/2011; 58-I:2919-2930. · 2.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: The travel time spent in traffic networks is one of the main concerns of the societies in developed countries. A major requirement for providing traffic control and services is the continuous prediction, for several minutes into the future. This paper focuses on an important ingredient necessary for the traffic forecasting which is the real-time traffic state estimation using only a limited amount of data. Simulation results illustrate the performances of the proposed state-estimation technique.
Proceedings of the American Control Conference 01/2011;
[show abstract][hide abstract] ABSTRACT: In this paper, a novel control strategy for a nonlinear boost inverter is proposed. The idea is based on generating an autonomous oscillator that does not need an external reference signal. This aim is achieved by using energy shaping methodology with a suitable Hamiltonian function which defines the desired system behavior. A phase controller is added to the control law in order to achieve 180◦-synchronization between both parts of the circuit as well as synchronize the voltage output with a pre-specified signal, e.g. synchronization with the electrical grid. An adaptive control is designed for dealing with the common problem of unknown load. In order to analyze the stability of the full system, singular perturbation approach is used. The resulting control is tested by means of simulations.
[show abstract][hide abstract] ABSTRACT: This work proposes a novel control algorithm dedicated to multi-agent systems with nonlinear dynamics. The aim of this paper is for the agents to form a circular formation whose center is fixed and whose radius is given by a time-varying reference. The problem of uniform distribution of all the agents along the circle is also addressed under the assumption of limited communication range. This communication constraint is tackled by using a cooperative control scheme which includes the Laplacian matrix of the communication graph (distance-dependent). The multi-agent system is simulated with Matlab. Videos showing the simulations are accessible though Web.
[show abstract][hide abstract] ABSTRACT: This work proposes a control algorithm to stabilize a circular formation of AUVs tracking a time-varying center. We also consider the problem of uniform distribution of all the agents along the circle from two approaches: all-to-all and limited communication. We tackle with this communication constraint using a cooperative control strategy which includes the Laplacian matrix of the communication graph (fixed or distance-dependent). The system was implemented in computer simulation, accessible though Web.
Decision and Control, 2009 held jointly with the 2009 28th Chinese Control Conference. CDC/CCC 2009. Proceedings of the 48th IEEE Conference on; 01/2010
[show abstract][hide abstract] ABSTRACT: In low-power electronics, achieving a high energy efficiency has great relevance. Nowadays, global asynchronous local synchronous systems enables to use a local dynamic voltage scaling architecture. This technique allows to reach a high energy efficiency. Moreover, local dynamic voltage scaling can be implemented using different approaches. One of them is the Vdd-hopping technique. In this paper, we propose an innovative control approach which aims for minimizing the energy dissipated during the Vdd-hopping transients. In addition, our control also includes the ability to limit the current peaks during such transients. Stability of the closed-loop system is analyzed. A discrete version of this controller is obtained, which coincides with energy-aware control (ENARC) that is patent pending. And a comparison of this last one with another published is done.
Control Applications, (CCA) & Intelligent Control, (ISIC), 2009 IEEE; 08/2009
[show abstract][hide abstract] ABSTRACT: This paper investigates the closed-loop properties of the differential coding scheme known as Delta-modulation (Δ-M) when used in feedback loops within the context of feedback controlled systems. We propose a new modified scheme of the original form of the Δ-M algorithm which is better suited for applications where the sensed information is used in feedback. A state feedback controller is implemented with the state estimated by a predictor-based differential decoder. Stability of the resulting closed-loop system (controller–coder–decoder) is studied. These properties (stability and performance) depend on the quantization parameter Δ, which is assumed constant in the first part of this paper. In a further step, parameter Δ is made adaptive, by defining an adaptation law exclusively in terms of information available at both the transmitter and receiver side.With this approach both stability and performance is improved.
IEEE Transactions on Industrial Electronics 01/2009; · 5.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper addresses issues on coding design in the context of control of systems equipped with low-energy sensors networks. We particularly focus on issues concerning minimum bit and energy-aware coding. To this aim, we devise a coding strategy with the ability to quantify and to differentiate stand-still signal events from changes in the source (level crossing detector). Coding is effectuated by defining at least 3-valued alphabet for the minimum bit case, and ($2L+1$)-valued alphabet for a general case with a precision depending on $L$. Energy saves are studied in two different scenarios; (1) in the word-by-word transmission case, the stand-still signal event is modulated with a low power transmission mechanisms, whereas the changes of levels will be modulated with high-power, (2) in the package-based transmission case, an entropy variable length coding is added to the previous encoding process. Entropy coding assigns some probability distribution to the events, so that the mean transmission energy can be substantially improved for systems where the stand-still events have higher probability to arise (i.e. stable systems). The paper studies the stability properties needed for this type of coding to operate properly, and quantify the energy saves for each of the considered scenarios.
[show abstract][hide abstract] ABSTRACT: In low-power electronics, achieving a high energy efficiency has great relevance. Nowadays, global asynchronous local synchronous systems enables to use a local dynamic voltage scaling architecture, this technique allows achieve a high energy efficiency. Moreover, local dynamic voltage scaling can be implemented using different approaches. One of them is Vdd-Hopping technique. In this paper, different controllers are designed for a Vdd-Hopping system implemented in a novel discrete converter in order to search for control strategies that present better performance in terms of dissipated energy reduction. It is shown here that some of the provided control strategies not only reduce the dissipated energy, but also improves the current transients are improved.
[show abstract][hide abstract] ABSTRACT: Conventionally the control of dry clutch’s engagement during a standing start in AMT vehicles is assured by look-up tables whose values are carefully chosen to produce a smooth synchronisation at the expense of a long slipping time. This article proposes, instead, a new approach based on: an open-loop look-up table aiming to reduce the slipping time, combined with an observer-based optimal control assuring the engagement comfort. Particular attention has been given to the details of the on-line implementation on a Clio AMT prototype. Experimental results show both a close match between the predicted and the actual trajectories and a high level of comfort.
[show abstract][hide abstract] ABSTRACT: In this paper we investigate the problem of remote stabilization via communication networks involving some timevarying delays of known average dynamics. This problem arises when the control law is remotely implemented and leads to the problem of stabilizing an open-loop unstable system with time-varying delay. We use a time-varying horizon predictor to design a stabilizing control law that sets the poles of the closed-loop system. The computation of the horizon of the predictor is investigated and the proposed control law explicitly takes into account an estimation of the average delay dynamics. The resulting closed loop system robustness with respect to some uncertainties on the delay estimation is also considered. Simulation results are finally presented.
IEEE Transactions on Automatic Control 09/2007; · 2.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of this paper is to explore yet another variant of the Delta-Modulation Coding structure to improve data transmission efficiency in the context of Networked Controlled Systems. High compression rates can only be reached by the use of entropy coding. Entropy coding assigns some probability distribution to the events. In that way, the mean code length can be improved. The paper studies several issues resulting from this type of coding design and assets the stability properties needed for this type of coding to operate properly.
[show abstract][hide abstract] ABSTRACT: Without pretending to be exhaustive, the aim of this chapter is to give an overview on the use of the state predictor in the context of time-delay systems, and more particularly for the stabilisation of networked control systems. We show that the stabilisation of a system through a deterministic network can be considered as the stabilisation of a time-delayed system with a delay of known dynamics. The predictor approach is proposed, along with some historical background on its application to time-delayed systems, to solve this problem. Some simulation results are also presented.