Vector control method applied to a traveling wave in a finite beam

This paper presents the closed-loop control of exciters to produce a traveling wave in a finite beam. This control is based on a dynamical modeling of the system established in a rotating reference frame. This method allows dynamic and independent control of the phase and amplitude of two vibration modes. The condition to obtain the traveling wave is written in this rotating frame, and requires having two vibration modes with the same amplitude, and imposing a phase shift of 90° between them. The advantage of the method is that it allows easy implementation of a closed loop control that can handle parameter drift of the system, after a temperature rise, for example. The modeling is compared with measurement on an experimental test bench which also implements real-time control. We managed to experimentally obtain a settling time of 250 ms for the traveling wave, and a standing wave ratio (SWR) of 1.3

Analysis of the energy harvesting performance of a piezoelectric bender outside its resonance

When the frequency of the source of vibration of a piezolectric generator is significantly different from its eigenfrequency, the dielectric power losses become prominent and decrease the amount of power which is practically harvested. For off-resonance vibrating frequencies, the optimal operating conditions can be obtained with a Maximum Power Point Tracking method. This paper introduces complex phasors in the study of power conversion for piezoelectric generators. These complex phasors are used to describe three strategies which help simplify the tracking of the optimal generator output power for vibration frequencies which are away from resonance. Experimental results obtained on a prototype illustrate and confirm the approach with the phasor approaches illustrate and confirm the success of the proposed optimal power tracking strategies. Finally, we show that the efficiency results of each strategy depend on whether they are used inside or outside a frequency bandwidth around the eigenfrequency, and that the length of this bandwidth depends on the excitation amplitude.IRCICA Stimtac Project, INRIA Mint Project

Control of a multi-degree of freedom worktool for vibrations assisted forging

This paper addresses the control of a tool developed to superimpose vibrations along several directions on a piece during forging. Piezoelectric actuators are used to provide the required forces and speeds. Due to the minute displacements of the actuators, flexible hinges are used in a special arrangement in order realize the specified movements and to ensure controllability. The experimental results confirm the approach

Preliminary design of a multi-touch ultrasonic tactile stimulator

This paper presents a method to control ultrasonic waves on a beam, allowing to obtain a Multi-touch ultrasonic tactile stimulation in two points, to give the sensation to two fingers, from two piezoelectric transducers. The multi-modal approach and the vector control method are used to regulate the vibration amplitude, in order to modulate the friction coefficient with the fingers. An analytical modelling is presented, with experimental validation. Finally a psychophysical experiment shows that a multi-touch ultrasonic tactile stimulation is possible.This work has been carried out within the framework of the project StimTac of IRCICA (institut de recherche sur les composants logiciels et matériel pour la communication avancée), and the Project Mint of Inria

Modelling, identification and control of a Langevin transducer

The control of the vibration amplitude, and the resonance frequency tracking for ultrasonic transducer have been established. However, some applications require to control the vibration amplitude and its relative phase at a fixed frequency as the generation of travelling wave. In this paper, the transducer is modelled in rotating frame, and the decoupling according to two-axis allows to obtain a double independent closed loop control to address this issue. It is possible to control the transducer vibration amplitude and its relative phase, in steady state even in transient by acting on the amplitude of the supply voltage. Thanks to vector control method. This approach will be confirmed with experimental and simulation results.This work has been carried out within the framework of the project StimTac of IRCICA (institut de recherche sur les composants logiciels et matériel pour la communication avancée), and the Project Mint of Inria

Electrovibration Modeling Analysis

International audienceElectrostatic attraction may be used to modulate the apparent friction coefficient between two surfaces. Applied to the human finger and a polarized interface, the principle can modify the user perception of the interface surface. In this paper, the different steps towards the modeling of the electrovibration phenomenon are developed. An investigation on the current modeling will be carried out, with a focus on the temporal evolution and frequency dependence of the stimulus. Thus, an improvement of the modeling will be proposed to take into account this major effect, and then, it will be checked with an experimental setup and compared with literature results. The last few years have seen an increasing interest for haptic stimulation and simulation. Different technologies are available to provide a tactile feedback to a user by modifying his perception of a surface. In particular, it is possible to control the friction between a surface and a finger thanks to squeeze film effect or to electrovibra-tion. This study is focused on the electrovibration effect: the modulation of the perceived friction coefficient due to the induced electrostatic force between a finger and a high voltage supplied plate [1]. The effect is known since the mid fifties [2], but the interest has raised only recently. Firstly, spatial division of electrode was developed to provide precise and complex stimulus pattern of conductive pads, but this solution suffered from its complexity and turned out difficult to apply [5]. Recently, electrovi-bration took advantage of technological improvements of fingertip's position sensor based on optical or resistive solutions. The possibility to track precisely the position of the finger leads to fine gratings simulation thanks to spatial-stimulus relation. With spatio-temporal transformation, the stimulator itself becomes easier to manufacture and it becomes possible to produce tactile feedback on transparent surfaces [1] or merge it with another tactile stimulation technique [3]. If the efficiency of the process to provide successful tactile feedback is clear, the physical modeling of the phenomenon involving the finger is not yet satisfactory. Th

Vector Control of Piezoelectric Transducers and Ultrasonic Actuators

This paper presents the implementation of a novel vibration amplitude control and resonant frequency tracking for piezoelectric transducers (PTs) and ultrasonic motors (USMs). It is based on a generalization of the vector control method to the PT and the USM, which is explained in the first part. We show that two independent controllers with a similar structure are required: one tracks the resonant frequency and the second controls the amplitude. We then present the implementation into a low-cost digital signal processing controller with a sampling period of 200 µs. Experimental results on a Langevin transducer achieved a time response of 20 ms approximately, and the generality of the method is further demonstrated on a 2-D tactile stimulator at the end of this paper

Design of a Haptic Magnifier using an Ultrasonic Motor

International audienceThe paper presents a serial architecture of an actuated manipulator which uses an ultrasonic motor. The serial architecture allows to modify the kinetic relationship between user's input and a tool. The design of the device is presented. A load, which exhibits fine details, is used in order to show how a zooming effect of its haptic rendering can be achieved with the haptic magnifier. Finally, the design is validated through an experimental analysis

Dtact: a tactile device which changes how a surface is perceived

International audienceAmong human senses, touch is much less understood than hearing or sight. However, today, new emerging technologies are placing tactile interaction at the heart of the communication with smart devices (smartphones, tablets, …). Hence, studying the sense of touch is now very important, in order to better understand the mechanisms induced from the mechanical excitation of skin to the feeling experienced by a user. Also, being able to detect and measure tactile disabilities, and to propose rehabilitation is a challenge; otherwise, numerous people can drift away from these objects as they can't be used easily by them. In the paper, we present Dtact, a device which stimulates the finger pulp with a calibrated stimulation. It is designed to be used during experimental studies aiming at recording nerves and brain activity of a user touching its surface. It will be used to detect tactile disabilities, and perhaps some exercises could be programmed for the purpose of rehabilitation

Using an Ultrasonic Transducer to Produce Tactile Rendering on a Touchscreen

International audienceFriction reduction based tactile devices use an ultrasonic vibration to create an overpressure between a user's fingertip and the vibrating surface. This phenomenon is called "the squeeze film effect". This is an emerging technology to produce a haptic feedback on the touchscreen of handheld electronic devices. In this paper, we present the technology and the main technological issues to be improved