-Motivation:

Tactile feedback devices are able to provide physical feeling mimicking touch in order to 1) compensate the lack of sight for blind or visually impaired people, or again for people whose yese are already busy with another task, 2) enhance a sensorial experience in many situation by adding touch feedback to visual or auditive feedbacks, 3) provide a tunable surface on the point of view of touch in order to train and / or assist people in the field of medecine or material production processes.  

-Specificity in this field:

Tactile feedback systems rely on mechatronic sciences and electric energy conversion. Piezo-electric material are very relevant to achive this energy conversion and to render physical effect under the finger of a user. Skills in control and supply of electric energye conversion systems, electromagnetic and piezo-electric, allow to make relevant proposals for tactile feedback devices. 

-Tactile displays based on friction control 

Tactile displays based on friction control are either high frequency vibrating surfaces which create active lubrification under the finger which explores the surface, either high voltage surfaces which create an electrostatic attraction force between the finger pulp and the surface.  

Ultrasonic tactile feedback displays: we have been working since many years on transverse mode standing vibrations (resonance above 20kHz) which induce an intermittent contact between the finger pulp and the surface, leading to a lubrication effect that means a decrease of the apparent friction coefficient of the surface. This idea has been patented in 2008 and is currently used by HAP2U society.

More recently, we investigated the effect created by longitudinal standing modes, which induce also active lubrication, with a lower amount of energy supply. 

Friction control thanks to electro-adhesion: when supplying at high voltage a flat surface covered with an isolation film, it is possible to create eletro-static force between the surface and the finger pulp. As a consequence, the apparent friction coefficient of the surface increases. 

For both these friction control approaches, when modulating the friction according to the finger position, it is possible to create textures. Indeed, a specific device has been designed to combine both effects, which gives rise to a higher friction contrast. The reaction time of the two effects are compatible with the human perception. 

-Tactile displays to provide stimuli under a static finger

Tactile displays relying on friction control are very efficient to create virtual textures. However, as they work with friction,  finger displacement on the virtuel surface is mandatory. In order to create a physical stimulus on the finger pulp while the finger is static, other approaches have to be defined. Multi-modal control in particular has been proposed, in order to recreate the time reversal approach, but without the initial learning phase. 

More recently, in collaboration with HAP2U society, we proposed a soultion for static excitation based on vubration mode combination: for given locations on a glass plate, an accurate vibration mode combination may be generated thanks to piezo-actuators. These combined modes allow locally an elliptical vibrtion to occur. By the inversion of the rotating sense of this elliptical movement according to the finger pressure on that location, a very sensitive "clic" feeling may be perceived. 

-Context

Close to tactile feedback devices design and control, electricl energy management at large is also a field of interest. Thanks to Energetic Macroscopic Representation (EMR), a graphical tool for energu management proposed by Pr. A. Bouscayrol in 2000, the study of complex systems is simplified and the control structure of these systems may be obtained systematically. 

-Applications

EMR is a relevant tool to deduce Maximal Control Structure (MSC) and also to formalize Hardware In the Loop (HIL) simulation. Following this approach, we have proposed a "Human In the Loop" simulation in order to study the influence of the finger pulp characteristic dispersion on the friction contrast feeling on tactile feedback devices. This is a promising approach towards tactile device calibration, depending on each user perceptive capabilities. 

EMR and SMC are also used in the project "Smart Integrated Drives" (CE2I, Convertisseur d'Energie Intégrés Intelligents) I supervised from 2015 to 2022. This project aims at designing and control new association between static inverters, electric machines and thermal cooling systems in order to reduce the mass and the volume of the drive, and to propose fault tolerant algorithms. 

Last, EMR and SMC will be used as a common formalism for the COMASYS project (Continuum de l'énergie, du matériau aux systèmes) I co-supervise at University of Lille. The objective is to help designing new materials, components and systems and optimize their operating on the point of view of energy harvesting, storage and or generation.