Human-machine interfaces can convey information via visual, audio and/or haptic cues during a navigation task. The
visual and audio technologies are mature, whereas research has to be focused on haptic technologies for mobile devices.
In this work, a tactile refreshable screen is proposed which allows its user the exploration of maps and navigational tasks
in an egocentric perspective. The proposed device consists of an array of actuators which can display various patterns.
The actuation technology is based on a magneto-rheological fluid which is injected in a chamber with an elastomeric
membrane using a micro pump. The fluid pressure deforms the membrane in order to display a pattern. The fluid
properties are used to form a valve in each cell. A permanent magnet, a ferromagnetic core, and a coil form a closed
magnetic circuit with a gap where the magneto-rheological fluid can flow; the magnetic field interacts with the fluid and
prevents the filling or draining of the chamber. Applying a current to the coil counteracts the magnetic field generated by
the magnet and the fluid can circulate freely in order to inflate or deflate the membrane. The design, fabrication and
integration of the device in addition to the results of finite element simulations and experimental measurements are
reported.
The two approaches presented in this paper consist of splitting the tracking action into two sub-systems. The
decoupling of local scanning and global scanning functions is an alternative solution to the use of fast-steering,
power-consuming galvanometric scanner. Applications targeted are multi-object tracking and 3D perception in
safe condition. This paper presents more specifically an approach based on a Risley prism configuration steering a
laser pattern dynamically shaped by a DMD allowing a good compromise for the refresh rate and the precision.
Optical Tweezers have become a widespread tool in Cell Biology, microengineering and other fields requiring
delicate micromanipulation. But for those sensitive tasks, it remains difficult to handle objects without damaging
them. As the precision in position and force measurement increase, the richness of information cannot
be fully exploited with simple interfaces such as a mouse or a common joystick. For this reason, we propose
a haptic force-feedback optical tweezer command and a force-feedback system controlled by one hand. The
system combines accurate force measurement using a fast camera and the coupling of these measured forces
with a human operator. The overall transparency allows even the feeling of the Brownian motion.
In this work, a robust metallic amplification unit for piezoelectric microactuators is presented. The mechanism which is
implemented with a sliced membrane structure made from a superelastic nickel titanium alloy is based on a mechanical
lever in order to amplify the small piezoelectrically induced deformation. Therefore, increased stroke can be provided up
to high frequencies. The fabrication process using laser ablation, the assembly process, the static and dynamic
simulations and experimental measurements are reported. An amplification factor of 9 has been achieved for a specific
load transmission point position. The dynamic response shows a quality factor of 25 at 11.97 kHz for the first mode.
Compared to silicon, nickel titanium shows enhanced properties against failure and facilitates the integration process.
The aim of this paper is to present a new micro-actuator, which is currently being used to design and develop high resolution, lightweight and compact interfaces for tactile information representation. Based on shape memory alloy (SMA) technology, the actuator is capable of producing a mechanic deformation on the skin of the user's fingertip in order to re-create a realistic touch sensation. This actuator of 1.5 mm diameter, 5 cm length, 150 mg weight, 0.7 mm total excursion, 170 mN pull force and 4 Hz bandwidth represents a high spatial and temporal resolution actuation principle for tactile feel displays. The SMA actuator's design concept, modeling and implementation are presented and described in detail. In conclusion, the prototype and preliminary performance results are reported and discussed.
Virtual Reality (VR) is gaining more importance in our society. For many years, VR has been limited to the entertainment applications. Today, practical applications such as training and prototyping find a promising future in VR. Therefore there is an increasing demand for low-cost, lightweight haptic devices in virtual reality (VR) environment. Electroactive polymers seem to be a potential actuation technology that could satisfy these requirements. Dielectric polymers developed the past few years have shown large displacements (more than 300%). This feature makes them quite interesting for integration in haptic devices due to their muscle-like behaviour. Polymer actuators are flexible and lightweight as compared to traditional actuators. Using stacks with several layers of elatomeric film increase the force without limiting the output displacement. The paper discusses some design methods for a linear dielectric polymer actuator for VR devices. Experimental results of the actuator performance is presented.
This paper reports on the development of a lightweight hyper-redundant manipulator driven by embedded dielectric polymer actuators. This manipulator uses binary actuation and belongs to a class of digital mechanisms that are able to perform precise discrete motions without the need for sensing and feedback control. The system is built from an assembly of modular parallel stages and has potential to be miniaturized for applications ranging from biomedical devices to space system components. The polymer actuators can make such devices feasible. This paper presents the design of a modular polymer actuator that can work under both tension and compression. The actuators achieve improved performance by incorporating an elastic passive element to maintain uniform force-displacement characteristic and bi-stable action. A flexible frame also insures nearly optimal pre-strain required by dielectric film based actuators.
A complete set-up for local annealing of Shape Memory Alloys (SMA) is proposed. Such alloys, when plastically deformed at a given low temperature, have the ability to recover a previously memorized shape simply by heating up to a higher temperature. They find more and more applications in the fields of robotics and micro engineering. There is a tremendous advantage in using local annealing because this process can produce monolithic parts, which have different mechanical behavior at different location of the same body. Using this approach, it is possible to integrate all the functionality of a device within one piece of material. The set-up is based on a 2W-laser diode emitting at 805nm and a scanner head. The laser beam is coupled into an optical fiber of 60(mu) in diameter. The fiber output is focused on the SMA work-piece using a relay lens system with a 1:1 magnification, resulting in a spot diameter of 60(mu) . An imaging system is used to control the position of the laser spot on the sample. In order to displace the spot on the surface a tip/tilt laser scanner is used. The scanner is positioned in a pre-objective configuration and allows a scan field size of more than 10 x 10 mm2. A graphical user interface of the scan field allows the user to quickly set up marks and alter their placement and power density. This is achieved by computer controlling X and Y positions of the scanner as well as the laser diode power. A SMA micro-gripper with a surface area less than 1 mm2 and an opening of the jaws of 200(mu) has been realized using this set-up. It is electrically actuated and a controlled force of 16mN can be applied to hold and release small objects such as graded index micro-lenses at a cycle time of typically 1s.
In order to improve the reliability of micro-spot welding of metal parts in production such as e.g. in electron guns for TV picture tubes, real-time information about the evolution of the welding process should be available to allow on-line modification of the laser parameters. Such information can be derived from a set of sensors that are mounted on a laser-scanning head. Different sensors are used to monitor the optical fiber output power to determine the evolution of temperature during the spot welding process, to measure plasma emission and back-reflected laser light. A vision channel and a CCD camera are used to control the position of the laser spot on the parts to be processed. The compact scanning head is composed of a tip/tilt laser scanner, a collimating lens and a focusing lens. The scanner is fast steering, with a bandwidth of 700Hz, and can tilt by +/- 3.5 degree(s) with a repeatability better than 50(mu) rad. The settling time for maximum deflection is less that 10ms. The scanning lens is a newly developed focusing lens designed to replace commercial cumbersome scanning lenses such as F-(theta) lenses, which have large volume, weight and price. This lens is based on the well-known Cooke triplet design and guarantees a constant shape of the spot all over the scan surface and is specially well suited for high power beam delivery. The scan field achieved by the system is limited to 25mm x 25mm. The laser used for this application is a pulsed Nd:YAG laser delivered by an optical fiber to the optical head. However, the system can be adapted to different types of lasers. Laser micro-spot welding on copper substrate has been performed in the frame of the Brite-Euram project MAIL. Smaller tolerances (a factor of 2 less) on the spot diameters were obtained in the case of a sensor controlled operation compared to the case where sensor control is not used.
Compact fast-steering two axis-tilt mirrors are key components in astronomy, laser communications, material processing applications, imaging systems, biomedical and ophthalmologic applications. The laser scanner presented in this paper can perform a variety of functions such as tracking, beam stabilization and alignment, pointing and scanning. The small overall volume of 30 X 40 X 50 mm3 can lead to a very stable and compact system design. The fact that the steered mirror has a single point of rotation for the two tilt axes is a clear advantage for systems with scanning lenses designed for this purpose. The scanner is composed of one single mirror driven by two pairs of push-pull linear electromagnetic actuators. The suspension of the mirror is based on a cone-ball bearing with optimized friction and wear behavior. A Position Sensitive Detector integrated in the module is used for the closed loop feedback positioning. The mirror can be tilted by more than +/- 52 mrad (+/- 3 degree(s)) with an accuracy better than 50 (mu) rad. A differential resolution of the order of 5 (mu) rad and a settling time for maximum deflection of 9 ms is achieved. Due to the large active area of the mirror (30 mm X 40 mm), very small spot diameters can be reached (less than 1 micrometers ) using high quality laser beams. Therefore, the scanner can be used e.g. in high precision micro-material processing of semiconductor and sensor industry.
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