David Andreu

A distributed architecture for activating the peripheral nervous system

We present a new system for functional electrical stimulation (FES) applications based on networked stimulation units. They embed an advanced analog circuit, which provides multipolar and multiphasic stimulation profiles, and digital circuits, which ensure safety, locally executed programmed profiles, and communication with the master controller. This architecture is thus based on distributed stimulation units (DSU) that need only a two-wire bus to communicate, regardless of the number of poles of each DSU-driven electrode. This structure minimizes the required bandwidth between master and distributed units, increases the safety and stimulation features and decreases the complexity of the surgical approach. We have successfully tested this network-based stimulation architecture on benchtop stimulators. This original approach allows broad exploration of all possible methods to stimulate peripheral nerves, particularly in the goal of restoring the motor function. It provides a powerful research device to determine the optimal, least aggressive and the most efficient way to activate the peripheral nervous system using an implanted FES system that is less invasive than other existing devices.

Petri Net Based Rapid Prototyping of Digital Complex System

This paper deals with the automatic translation of interpreted generalized Petri Nets with time into VHDL, for rapid prototyping on programmable logic device purposes. This approach is based on the component orientation of the VHDL language, and defines two elementary VHDL components: the place and the transition. This transition component is a pivot element of the approach, since it supports all the interconnections between places and transitions (i.e. it allows the structure of the PN to be built). Moreover, with the aim to reduce power consumption, we proposed to control the VHDL components activity according to an approach based on the activity propagation principle since PNs are oriented graphs.

Internet enhanced teleoperation toward a remote supervised delay regulator

Network based control of remote systems has been widely tackled and numerous methods have been proposed to deal with small and or constant delays. However, on long distance network, bandwidth and network delays may notably vary (beyond hundreds of milliseconds) according to events occurring along the transmission lines. This paper presents the long distance remote control of a small mobile robot. To face important network delay variations and possible connection rupture, a supervised delay regulator based architecture is proposed. Results of experiences that have been performed from Mexico to France are given and explained.

Remote secure decentralized control strategy for mobile robots

The main goal of this paper is to define, study and analyze a remote control architecture for a set of non-holonomic robotic vehicles. This project gathers three laboratories and the French Army Research Office. Each of these laboratories deals with a part of this multidisciplinary project which includes coordinated control, control architecture, control with time delay and monitoring of the wireless network. In this paper, we present the whole goal of this project including the basic experimental setup developed to validate our control algorithm. We also focus on a new decentralized control strategy that uses the Leader–Follower principle. The originality of this paper stems from the use of the signal level of wireless connection as a control vector. Indeed, each vehicle is fitted with two wireless devices. One of them is equipped with a sector antenna fitted on a DC motor to track the direction of best reception. Thus, it allows us to find the relative angular position of the Follower pointing out the Leader. Using wireless technology as a sensor, instead of vision for instance, allows a longer distance of the coordinated control loop between each vehicle (approximately 100 m) even if GPS information is not available.

Teleoperation over an IP network: from control to architectural considerations

For the teleoperation of a robot over an IP network, we must deal with the variable network delays as well as with events that can occur during the teleoperation. In this paper both control and architectural aspects are exposed. We first present a stable remote position/force control scheme for manipulator robot, based on a delay regulator and Smiths predictor principle. Some experiments show the improvement obtained by this method. However to face very important network delay variations and possible connection rupture, we designed a supervised delay regulator based architecture. This architecture, embedded on a mobile robot, is presented and results of experiments are also given and explained. All these experiments, performed on long distance (Mexico-France: /spl sim/8000 km), show the improvement obtained on both themes, that conjointly enhances and secures the teleoperation through the Internet.

Model-Based Design and Experimental Validation of Control Modules for Neuromodulation Devices

Goal: The goal of this paper is to propose a model-based control design framework, adapted to the development of control modules for medical devices. A particular example is presented in which instantaneous heart rate is regulated in real-time, by modulating, in an adaptive manner, the current delivered to the vagus nerve by a neuromodulator. Methods: The proposed framework couples a control module, based on a classical PI controller, a mathematical model of the medical device, and a physiological model representing the cardiovascular responses to vagus nerve stimulation (VNS). In order to analyze and evaluate the behavior of the device, different control parameters are tested on a “virtual population,” generated with the model, according to the Latin Hypercube sampling method. In particular, sensitivity analyses are applied for the identification of a domain of interest in the space of the control parameters. The obtained control parameter domain has been validated in an experimental evaluation on six sheep. Results: A range of control parameters leading to accurate results was successfully estimated by the proposed model-based design method. Experimental evaluation of the control parameters inside such a domain led to the best compromise between accuracy and time response of the VNS control. Conclusion: The feasibility and usefulness of the proposed model-based design method were shown, leading to a functional, real-time closed-loop control of the VNS for the regulation of heart rate.

Formal Validation of a Deterministic MAC Protocol

This article deals with the formal validation of STIMAP, a medium access protocol that has been designed to meet the specific requirements of an implantable network-based neuroprosthesis. This article presents the modeling and the validation of its medium access, using model checking on Time Petri Nets. Doing so, we show that existent formal methods and tools are not perfectly suitable for the validation of real systems, especially when some hardware parameters have to be considered. This article then presents how these difficulties have been managed during the modeling and verification phases, and gives the validation results for STIMAP, providing constraints to respect.

Events as a key of an autonomous robot controller

Abstract The paper focuses on the development of an event-driven autonomous robot controller. Such systems being intrinsically hybrid, the model that is exposed is a hybrid model based on the cooperation of a discrete-event part and a continuous part. Then, continuous and discrete models are concurrently dealt with; the articulation models different parts results from event interactions. According to this event-based conception, the controller architecture is hierarchically organized in three levels. The supervisory control is based on the management of contexts of execution.

Complex Digital System Design: A Methodology and Its Application to Medical Implants

In the context of specification of complex digital systems and their implementation on FPGA, a tool-based methodology is developed using a component-based approach. The components behavior is described by means of Interpreted Prioritized Time Petri nets which are formalized in this article. Formal analysis is used to validate the models properties and to optimize its implementation. Our approach is illustrated on the micro machine of a distributed stimulation unit.

Wireless Distributed Architecture for Therapeutic FES: Metrology for muscle control

This paper presents a Functional Electro-Stimulation distributed architecture based on a wireless network, for therapeutic training of disabled patients. On this distributed architecture, the movement (of disabled members) is artificially controlled by means of a global controller which pilots a set of stimulation units. The closed loop control system we developed for controlling muscle is based on a high order sliding mode method. In such wireless network-based control, the variable delay introduced by the network must be taken into account to ensure the stability of the closed loop. Thus, in order to characterize the medium on which the control is performed, we carried out accurate measurements of the architecture performances (stack-crossing, round-trip time, etc.). We then propose the use of a Kalman filter to predict the communication delay evolution, with the aim to exploit it within the closed loop control.