Betty Semail

STIMTAC: a tactile input device with programmable friction

We present the STIMTAC, a touchpad device that supports friction reduction. Contrary to traditional vibrotactile approaches, the STIMTAC provides information passively, acting as a texture display. It does not transfer energy to the user but modifies how energy is dissipated within the contact area by a user-initiated friction process. We report on the iterative process that led to the current hardware design and briefly describe the software framework that we are developing to illustrate its potential.

A torque estimator for a traveling wave ultrasonic motor - application to an active claw

Depending on its electrical-to-mechanical energy conversion process, the torque on a traveling wave ultrasonic motor (TWUM) s shaft is not directly proportional to a measurable electrical variable, such as current or voltage. But it is derived from a complicated process at the stator/rotor interface. The load torque is thus quite unknown, and this can be a disadvantage in applications in which a torque limitation is required or a torque measurement is needed. The aim of this article is to come up with a straightforward torque estimator on a TWUM. For that purpose, the motor is modeled; this modeling leads to different estimator strategies. More specifically, we chose a strategy for which a speed sensor is useless, relying only on the stators resonant behavior. The parameters of the motor needed for the estimator are measured afterward, and some nonlinearities are identified and taken into account. Several experimental trials then are carried out to check the performance of the estimator. A claw actuated by a TWUM is presented because this is a typical application in which the knowledge of the torque helps guarantee the safety of the device

Analysis and control of a piezo-electric travelling wave ultrasonic motor for haptic stick application

An original modelling of a travelling wave ultrasonic motor is established in order to provide a new torque control law for this kind of actuator. Especially, self-control is implemented, avoiding the classical drawbacks of frequency control, that is pull-out phenomenon. With such a robust control, force feedback application is available. Experimental results are obtained on an active haptic stick.

A simplified power supply for piezoelectric actuators used in forging processes

In this paper, we propose a power supply for piezoelectric actuators that can generate arbitrary waveforms at frequencies ranging from low to medium frequency. The actuators are used in a forging process and require high voltage. The converter is based on an original combination of a boost DC-DC converter and a rectifier circuit, thus reducing the number of components needed. Moreover, no transformer is required. Experimental results on a single and three phase version are presented and validate the proposed converter.

Modelling and Control of an Ultrasonic Motor: Application to a Mechanical Claw Drive

Properties of the travelling wave ultrasonic motor (TWUM) - among which we find a high-torque to mass ratio, locking without supply, ultrasonic operation - are very attractive A. modeling overview for embedded application, such as human prothesis for example. But unfortunately, its control for high precision or high dynamic motion is not easy to achieve because of many non linearities induced by its particular energy conversion process. This is why this paper deals with the modelling of a TWUM, based on a physical causal approach. According to the inversion principle, control strategies are deduced as well as a novel torque estimation structure. A mechanical claw control using this torque estimator no sliding is considered between the ideal rotor and the stator, is then achieved and experimental results check the accuracy of the proposed control scheme