Magnetic linear actuators
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Limited Angle Torque for fine angular positioning
19 June 2023
A Limited Angle Torque (LAT) actuator has been designed by Cedrat upon request of the European Space Agency (ESA) for fine pointing applications based on gimbals assembly. The required angular stroke for this application is 13°. Other required features are controllability, high resolution, no micro vibration. Therefore the selected concept is a coil-redounded electromagnetic actuator using Lorentz force. The functional test shows that the generated torque is linear until 200mN.m, but torques up to 300mN.m are achievable.
Control of magnetic actuators in electric contactors by current shapping
19 June 2023
Most of present electric contactors use magnetic actuators of reluctant type (so called electromagnets) that are supplied with a simple voltage source. The use of a reluctant actuator in this condition leads to a considerable force increase when the magnetic circuit is closing, which creates damaging rebounds of the electrical contacts. To have a better control of the closing dynamics, we develop an electric drive method to reduce impact speed and to improve the closing dynamics. In this method, the reluctant actuator structure is unchanged. The appropriate current shape to be injected into the actuator is determined using a calculation method.
Design of a 2 stages compressor for mobility applications, using compact and efficient Moving Iron Controllable Actuators
19 June 2023
An actuator is rescaled for integration into a compressor used for the liquefaction of hydrogen vapor boil off, into a propellant storage system. The goal is to evaluate the feasibility of liquid hydrogen zero boil off, for long duration storage at 20 Kelvin cryogenic liquid condition. This article presents the actuator trade off, selection and special features imposed by the application. The actuator design is presented, its characteristics are measured, and resulting performances are presented and discussed.
Development of the plain bearing and flexure bearing MICA300CM actuator
7 May 2018
The MICATM linear actuator family (Moving Iron Controllable Actuator) is being continuously improved at CEDRAT TECHNOLOGIES (CTEC) for applications needing high controllable stroke, force, and power. The MICA300CM is a new actuator model, having improved configuration based on cylindrical shape. A first version based on plain bearing offers up to 12mm stroke and 300N continuous force with a weigh of only 3kg. A second version is based on new frictionless flexure bearings. The former one is especially designed to achieve zero maintenance over several years of operation, with high efficiency, infinite resolution, and high controllability performance. This version of the MICA300CM has been derived to offer a proof mass configuration, for vibrationcancellation applications on machining processes. A latest version is also currently under design, and prototyping, specifically for reciprocating power piston applications, such as compressors, pressure wave generators, and pumps. Its high efficiency, ultra-long lifetime capability, and compactness, makes it perfectly suitable for embedded thermal machines based on Stirling, Joules Thomson, and Rankin Thermodynamic cycles. This paper presents this 4 design concepts, their test results and perspective for applications.
Characterisation of magneto-rheological fluids for actuators applications
19 June 2023
Magnetorheological fluids (MRF) are magnetically controlled fluids and they find more and more industrial applications in actuation functions. These include shock absorbers, semi-active dampers, clutches, brakes, haptic actuators & devices. Several of these applications have been studied by Cedrat Technologies for its industrial customers, and a device-oriented test bench has been developed in order to characterise the magneto-mechanical properties of MRF such as the magnetisation curve, the yield stress ….
Giant dynamic strains in magnetostrictive actuators and transducers
19 June 2023
Magnetostriction occurs in the most ferromagnetic materials and leads to many effects [1,2]. The most useful one to refer to is the Joule effect. It is responsible for the expansion (positive magnetostriction) or the contraction (negative) of a rod subjected to a longitudinal static magnetic field. In a given material, this magnetostrain is quadratic and occurs always in the same direction whatever is the field direction. Giant Magnetostrictive Materials (GMM), especially Rare earth-iron discovered by A.E.Clark [3], feature magnetostrains which are two orders of magnitude larger than Nickel. Among them, bulk Tb0.3Dy0.7Fe1.9, called Terfenol-D, presents the best compromise between a large magnetostrain and a low magnetic field, at room temperature.