The numerical integration of switching circuits is known to be a tough issue when the number of switches is large, or when sliding modes exist. Then, classical analog simulators may behave poorly, or even fail. In this paper, it is shown on two examples that the nonsmooth dynamical systems (NSDS) approach, which is made of: 1) a specific modeling of the piecewise-linear electronic devices (ideal diodes, Zener diodes, transistors); 2) the Moreau's time-stepping scheme; and 3) specific iterative one-step solvers, supersedes simulators of the simulation program with integrated circuit emphasis (SPICE) family and hybrid simulators. An academic example constructed in [Maffezzoni,, IEEE Trans. CADICS, vol 25, no. 11, Nov. 2006], so that the Newton–Raphson scheme does not converge, and the buck converter are used to make extensive comparisons between the NSDS method and other methods of the SPICE family and a hybrid-like method. The NSDS method, implemented in thesiconosplatform developed at INRIA, proves to be on these two examples much faster and more robust with respect to the model parameter variations.

The new generation of implanted neuroprostheses allows muscles to be controlled with fine accuracy, high selectivity and the repeatability of the muscle's response can be achieved. Thus, the closed loop control of such systems becomes possible. The SUAW project succeeded in the implantation of an advanced neuroprosthetic device on two patients, but the movement generation remains open loop and is tuned empirically. Nevertheless, the good results obtained give us the opportunity to envisage the system evolves towards closed loop control and automatic synthesis of the stimulation patterns generating the desired movement. To achieve this goal, some preliminary researches have to be carried out, beginning with a specific modelling that can be used in the context of functional electrical stimulation (FES). The main issues concern muscle modelling including the interaction with the skeleton, fatigue, FES parameters as inputs, and the identification of dynamic parameters, and afterwards, the motion synthesis and the closed loop control based on this model. Besides, the scientific approach is the same as in robotics so that the theoretical tools used in the control theory are the same and directly applicable. This paper describes the results obtained in the previous project SUAW and how we attempt, through the new project DEMAR, to enhance the global performances of the system.

Presents an experimental comparison between four nonlinear controllers for flexible joint manipulators. These control inputs theoretically guarantee global tracking of any admissible reference trajectory. The experimental set-up is a 2-degree-of-freedom (DOF) manipulator, with an elasticity at the second joint. This work follows and confirms a previous comparative study based on theoretical and numerical investigations. The main conclusion of the work is that some controllers may behave quite differently when applied to a particular device, despite of their apparent theoretical resemblance.

The aim of this note is threefold: i) to introduce a rigorous mathematical model of impulsive collisions dynamics through the use of Schwartz's distributions; ii) to study the relationships between impulsive and continuous dynamics models of impacts (i.e. models composed of mass, spring, damper); and iii) to analyze the difficulties associated with the transition phase control. The authors start a tentative comparison on two models of impacts through a simple example of a mass colliding with a wall. Numerical simulations illustrating the examples are presented.>

The authors address the problem of controlling rigid robot manipulators subject to bounded torque input disturbances and to joint velocity measurements bounded noise. The advantages of the control scheme presented are mainly that global convergence is guaranteed without prior knowledge of the bounds on the plant parameters and disturbances. If these bounds are known a priori, they can be used to improve the control scheme performance. Disturbances on the plant input as well as on the plant output are considered. The cases discussed are for when the disturbances are bounded and the upperbounds may be known or unknown. and for when the disturbances are linear with respect to some unknown parameters.>

The problem of modeling and compensation of friction velocities close to zero is analyzed. A model, linear in parameters, which captures the downward bends at low velocity is used to adaptively compensate for friction. The need for this type of model is mainly motivated by instability phenomena that can be caused by overcompensation when simple models (such as Coulomb friction models) are used as a basis for the friction compensation. This model, in combination with an adaptive computed torque method, is tested experimentally in the last link of a robot manipulator. The prediction error e/sub k/, which directly gives the accuracy of the predicted friction, remains within the preestablished threshold of +or-0.8 Nm. The experiments were realized using an IBM PC-compatible computer, leading to a sampling time of 13 ms.>