Abdenbi Mohand-Ousaid

Haptic interface transparency achieved through viscous coupling

Electromagnetic drives are subjected to an inherent inertia–torque tradeoff that fundamentally limits transparency: the higher the torque, the higher the inertia. We describe a dual-stage design that is not subjected to this tradeoff and that is able to approach perfect transparency for human users. It comprises a large, proximal motor and a small, distal motor to reproduce the transients. The two stages are coupled by a viscous clutch based on eddy currents that, without contact, accurately transforms slip velocity into torque. Such a system can, in general, be controlled to achieve a variety of objectives. Here, we show that an advanced, discrete-time, RST polynomial pole-placement controller can achieve near-perfect transparency. Experimental validation evaluated the human ability to detect small haptic details when using this drive and compared it with when using a conventional, single-motor interface.

Stability and transparency analysis of a teleoperation chain for microscale interaction

Microscale teleoperation with haptic feedback requires scaling gains in the order of 104 -107. These high gains impose a trade-off between stability and transparency. Due to the conservative approach used in most designs, transparency is reduced since damping is added to the system to guarantee stability. Starting from the fact that series, negative feedback and parallel connection of passive systems is a passive system, a new approach is addressed in this work. We propose here a complete teleoperation chain designed from the ground up for full transparency and stability, including a novel self-sensing probe and a high fidelity force-feedback haptic interface. By guaranteeing the passivity of each device and assuming that the human operator and the environment are passive systems, a homothetic direct coupling can be used without jeopardizing the stability and provides best transparency. The system is experimentally demonstrated in the complex case of a probe interacting with a water droplet under human control, while accurately transcribing the interaction back to operator.

3D-Printing: A promising technology to design three-dimensional microsystems

System miniaturization remains an important challenge in the field of microrobotics. Several works have been raised in this context. Maybe the most known and widespread are MEMS devices based on clean room technologies. Although they give option to design small systems with mico/nano features, such technologies are limited to planar structures with two or three degrees of freedom (DOF). To tackle this limitation, a new approach is proposed in this paper. Instead of planar construction, we proposed here to design three-dimensional micro-systems by taking advantages of additive manufacturing technology, namely 3D printing. The final objective consists to design a monolithic structure in one operation without assembly. Then functionalization could be achieved by equipping the structure with actuators and sensors. Starting from the fact that any complex structure could be decomposed into basic elements such as articulations or flexures, this paper will focus on how articulations could be fabricated without assembly using 3D printing facilities. Combining those articulations which are considered as fundamental bricks will make possible to design complex monolithic structures. As an illustration, a pivot articulation is experimentally demonstrated using 3D printing.

Dynamic characterization of an electrothermal actuator devoted to discrete MEMS positioning

This paper focuses on the dynamic characterization of an electrothermal actuator devoted to discrete MEMS positioning. Based on U-shape structure, such actuator has been employed in several MEMS applications where fine and repeatable positioning is required. The studied electrothermal actuator here is microfabricated on a doped SOI substrate and its dynamic response, during heating and cooling cycles, is recorded using precise and high-speed camera. To explain its dynamic behavior, FEM simulations, using Comsol multiphysics software facility, are carried out. The result of this numerical analysis shows a strong relationship between the temperature distribution and the displacement provided by the actuator. Finally, the influence of the dynamic behavior on the control of the actuator is discussed using experimental characterizations of its displacements under several voltage pulses with different frequencies.

Design, static modeling and simulation of a 5-DOF precise piezoelectric positioner

This paper presents the design, the static modeling and the performances simulation of a five degrees of freedom precise positioner. Based on piezoelectric stack actuators, the positioner is able to perform high resolution x-y-z linear motions and angular motions about x and about y axes. After presenting the design, the static modeling is carried out in order to understand the functioning of the positioner. The simulation of the model is afterwards carried out to estimate the ranges of motions that it can perform. The positioner is very promising in various applications that require dexterity and high resolution displacement such as in images scanning with atomic force microscopes, in micromanipulation or microassembly, etc.

Modeling and Experimental Characterization of an Active MEMS Based Force Sensor

Active force sensors are based on the principle of force balancing using a feedback control. They allow, unlike passive sensors, the measurement of forces in a wide range with nanoNewton resolutions. This capability is fundamental when dealing with the mechanical characterization of samples with a wide range of stiffness. This paper deals with the modeling and the experimental characterization of a new active MEMS based force sensor. This sensor includes folded-flexure type suspensions and a differential comb drive actuation allowing a linear force/voltage relationship. A control oriented electromechanical model is proposed and validated experimentally in static and dynamic operating modes using a stroboscopic measurement system. The sensor has a resonant frequency of 2.2 kHz, and a static passive measurement range of

Additive manufacturing: Design of a basic pivot articulation actuated with SMA wire

\pm 2.45\mu \mathbf{N}

Design, modeling and simulation of a three-layer piezoelectric cantilevered actuator with collocated sensor

. This work is the first step toward new dynamic measuring capabilities and sensing at the micro/nano-scales when high dynamic, large measurement range and nanoNewton resolution are required.

Optimizing transparency of haptic device through velocity estimation

Today, the rapid advance of additive manufacturing, namely 3D printing, gives options and capabilities to simplify the fabrication of three-dimensional complex structures. In fact, such technology brings a real rupture comparing to conventional technologies in terms of design and manufacturing. Taking those advantages, this paper presents the design and the fabrication of a monolithic pivot articulation. First, the skeleton of the articulation is designed as a monolithic bloc. Then, the articulation is fabricated in one operation without assembly. To functionalize the articulation a Shape Alloy Memory (SMA) wire is utilized. Its advantage is the ease of integration thanks to the low diameter of the wire and the expected grooves within the printed structure, making possible the realization of miniaturized complex structures and the introduction of the actuation even inside this latter. The whole actuated structure has a centimeter size and serves as a proof of concept. Experiments are carried out to demonstrate the interest of the realized prototype and thus to highlight that 3D printing could be potential in the development of complex actuated structures.

Displacement Amplifier Mechanism for Piezoelectric Actuators Design Using SIMP Topology Optimization Approach

A new piezoelectric actuator with collocated sensor is designed, modeled and simulated. The structure has three piezoelectric layers where the two external layers serve for the actuation by a convenient application of electrical potentials, and the middle layer serves as the sensor. After presenting the principle of the structure, a model is developed for the actuator and as well as for the sensor. Then simulation is carried out to evaluate their performances. The novel structure is very promising for applications that require control and automation, especially in situations where the use of sensors is unfeasible or difficult.