Commande directe du couple | EPFL Graph Search

vignette|upright=2.0|Schéma bloc d'une commande directe du couple. Les transformées de Clarke ne sont pas représentées. Le capteur de vitesse est facultatif. La commande directe du couple (Direct torque control / DTC ou direct self-control / DSC en anglais) est une méthode de commande des variateurs de vitesse électrique. Comme son nom l'indique, elle se concentre sur la commande du couple, la vitesse du moteur électrique en découlant indirectement. La méthode estime le flux magnétique et le couple du moteur à partir de la mesure des tensions et des courants alimentant celui-ci. Si le couple ou le flux sortent d'une plage de tolérance prédéfinies, les transistors du variateur de vitesse sont commutés vers l'état suivant de telle manière à revenir dans la plage aussi vite que possible. Elle a été inventée en 1984. Au départ réservée aux machines asynchrones, des variantes permettent de l'utiliser pour les machines synchrones. Elle offre de très bonnes performances dynamiques et a un

Torque control of the three-phase direct reluctance motor

Michel Girardin

This paper describes an open-loop torque control for a three-phase direct reluctance motor which can generate high torque at low speed. The command strategy presente in this paper consists of feeding the motor with three-phase sinewave currents. The torque ripple at low speed is considerably reduced . Moreover, the reference currents of the motor are optimised by the use of a correction factor in such a manner that the ripple torque is minimised in steady-state conditions. the correction factor is stored once off-line and can be used in-line for any application. the acoustic noise level is also reduce by the proposed driving method.

1997

Review of control strategies for lower-limb exoskeletons to assist gait

Romain Pierre François Baud, Mohamed Bouri, Auke Ijspeert, Ali Reza Manzoori

Background Many lower-limb exoskeletons have been developed to assist gait, exhibiting a large range of control methods. The goal of this paper is to review and classify these control strategies, that determine how these devices interact with the user. Methods In addition to covering the recent publications on the control of lower-limb exoskeletons for gait assistance, an effort has been made to review the controllers independently of the hardware and implementation aspects. The common 3-level structure (high, middle, and low levels) is first used to separate the continuous behavior (mid-level) from the implementation of position/torque control (low-level) and the detection of the terrain or user's intention (high-level). Within these levels, different approaches (functional units) have been identified and combined to describe each considered controller. Results 291 references have been considered and sorted by the proposed classification. The methods identified in the high-level are manual user input, brain interfaces, or automatic mode detection based on the terrain or user's movements. In the mid-level, the synchronization is most often based on manual triggers by the user, discrete events (followed by state machines or time-based progression), or continuous estimations using state variables. The desired action is determined based on position/torque profiles, model-based calculations, or other custom functions of the sensory signals. In the low-level, position or torque controllers are used to carry out the desired actions. In addition to a more detailed description of these methods, the variants of implementation within each one are also compared and discussed in the paper. Conclusions By listing and comparing the features of the reviewed controllers, this work can help in understanding the numerous techniques found in the literature. The main identified trends are the use of pre-defined trajectories for full-mobilization and event-triggered (or adaptive-frequency-oscillator-synchronized) torque profiles for partial assistance. More recently, advanced methods to adapt the position/torque profiles online and automatically detect terrains or locomotion modes have become more common, but these are largely still limited to laboratory settings. An analysis of the possible underlying reasons of the identified trends is also carried out and opportunities for further studies are discussed.

BMC2021

Whole Body Model Predictive Control with a Memory of Motion:Experiments on a Torque-Controlled Talos

Rohan Budhiraja, Sylvain Calinon, Teguh Santoso Lembono

This paper presents the first successful experiment implementing whole-body model predictive control with state feedback on a torque-control humanoid robot. We demonstrate that our control scheme is able to do whole-body target tracking, control the balance in front of strong external perturbations and avoid collision with an external object. The key elements for this success are threefold. First, optimal control over a receding horizon is implemented with Crocoddyl, an optimal control library based on differential dynamics programming, providing state-feedback control in less than 10 msecs. Second, a warm start strategy based on memory of motion has been implemented to overcome the sensitivity of the optimal control solver to initial conditions. Finally, the optimal trajectories are executed by a low-level torque controller, feedbacking on direct torque measurement at high frequency. This paper provides the details of the method, along with analytical benchmarks with the real humanoid robot Talos.

IEEE2021

Review of control strategies for lower-limb exoskeletons to assist gait

Romain Pierre François Baud, Mohamed Bouri, Auke Ijspeert, Ali Reza Manzoori

BMC2021