Olivier Smal

Production and characterization of a hydraulic microactuator

In order to improve the power density of microactuators, recent research focuses on the applicability of fluidic actuation at the microscale. The main encountered difficulties in the development of small fluidic actuators are related to production tolerances and assembly requirements. In addition, these actuators tend to comprise highly three-dimensional parts, which are incompatible with traditional microproduction technologies. This paper presents accurate production and novel assembly techniques for the development of a hydraulic microactuator. Some of the presented techniques are widespread in precision mechanics, but have not yet been introduced in micromechanics. A prototype hydraulic microactuator with a bore of 1 mm and a length of 13 mm has been fabricated and tested. Measurements showed that this actuator is able to generate a force density of more than 0.23 N mm(-2) and a work density of 0.18 mJ mm(-3) at a driving pressure of 550 kPa, which is remarkable considering the small dimensions of the actuator.

Design and Testing of an Ortho-Planar Micro-Valve

This paper presents the production and testing of an ortho-planar one-way micro-valve. The main advantages of such valves are that they are very compact and can be made from a single flat piece of material. A previous paper presents and discusses a micro-valve assembly based on a spider spring. The present paper focuses on the valve assembly process and the valve performance.. Several prototypes with a bore of 0.2 mm have been built using two manufacturing techniques (μEDM and stereo-lithography) and tested for pressures up to 7 bars.

Modelling and characterisation of an ortho-planar micro-valve

The main difficulties encountered in the development of microscale fluidic pumping systems stem from the fact that these systems tend to comprise highly three-dimensional parts, which are incompatible with traditional microproduction technologies. Regardless of the type of pumping principle, most of the hydraulic systems contain valves and in particular a one-way valve. This paper presents the design and modelling of an ortho-planar one-way microvalve. The main advantages of such a valve are that it is very compact and can be made from a single flat piece of material. An analytical model of the spring deflection has been developed and compared to FEM. A prototype with a bore of 1.5 mm has been build using a micro EDM (electro discharge machining) machine and also tested.

Design and first experimentation of an electromagnetically actuated ferrofluidic micropump

A volumetric micropump whose ferrofluid piston is actuated by a fixed arrangement of ferromagnetic materials and windings is presented. The main steps of the design that led to this solution are detailed. The first implements an optimization approach to determine the shape of the magnetic circuit maximizing the static backpressure withstand by the ferrofluid piston. The result is a structure consisting of ferromagnetic teeth whose width and spacing are directly related to the pipe diameter of the pump. The second step consists in analyzing and using this solution to ensure the piston actuation in a to and fro motion. The solution is formed by the repetition of three identical basic structures angularly and linearly shifted along the pipe and supplied successively, like in a stepper motor. First experimental tests performed on a prototype show the validity of the concept and the interest of fragmenting the piston into several bubbles to increase the maximal working pressure of the pump.

Comparison of two seal technologies for hydraulic microactuators

In order to improve the power density of microactuators, recent research focuses on the applicability of fluidic power at microscale. One of the reasons that hydraulic actuators are still uncommon in micro system technology is due to the difficulty of fabricating powerful microseals. This paper presents two seal technologies that are suitable for sealing small-scale hydraulic actuators. Measurements on prototype actuators show that force densities up to 0.45 N/mm/sup 2/ (0.025 N/mm/sup 3/) and work densities up to 0.2 mJ/mm/sup 3/ can easily be achieved with the developed seal technology. These characteristics can still be improved as the maximum driving pressures of the actuators have not yet been determined.

Design of a micro-rotative actuator test bed

Within the context of miniaturization of mechatronic systems, the development of a powerful micro-rotative actuator is an important topic of research. Such new actuation systems need to be validated on a specific test bed. Due to the dimensions and the very small torque to be measured, special low friction bearings are necessary and very precise alignment procedure needs to be developed.