US 12,119,175 B2
Electromagnetically controlled segmented mirror, electromagnetic actuator for use therein and method for manufacturing the same
Stefan Kuiper, Zwolle (NL); and Thomas Paulus Cornelis Van Adrichem, Eindhoven (NL)
Assigned to Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO, 's-Gravenhage (NL)
Appl. No. 17/927,116
Filed by Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO, 's-Gravenhage (NL)
PCT Filed May 27, 2021, PCT No. PCT/NL2021/050336
§ 371(c)(1), (2) Date Nov. 22, 2022,
PCT Pub. No. WO2021/242101, PCT Pub. Date Dec. 2, 2021.
Claims priority of application No. 20177104 (EP), filed on May 28, 2020.
Prior Publication US 2023/0207174 A1, Jun. 29, 2023
Int. Cl. H01F 7/16 (2006.01); H01F 7/08 (2006.01)
CPC H01F 7/081 (2013.01) [H01F 7/16 (2013.01)] 19 Claims
OG exemplary drawing
 
1. An electromagnetic actuator comprising a soft-ferromagnetic yoke, with an at least substantially cylindrical circumferential wall covered at a first end with a base and at a second end with a top,
wherein the circumferential wall defines an axis in an axial direction from the base end to the top,
wherein the soft-ferromagnetic yoke comprises, in the axial direction, a base yoke section, an intermediate yoke section and a top yoke section,
wherein the base yoke section forms the base and a first axial section of the circumferential wall, as well as a base protrusion surrounded with space by the first axial section of the circumferential wall,
wherein the intermediate yoke section forms a second axial section of the circumferential wall, and
wherein the top yoke section forms the top and a third axial section of the circumferential wall, as well as a top protrusion surrounded with space by the third axial section of the circumferential wall,
wherein the base yoke section and/or the top yoke section house an electromagnetic coil in the space between their protrusion and their axial section of the circumferential wall,
wherein the intermediate yoke section holds at least one permanent magnet fixed with a first magnetic pole facing an inner surface of the cylindrical wall, and with a second magnetic pole facing an inner space in the intermediate yoke section,
wherein the permanent magnet exerts an attractive force having negative stiffness on an axially movable core element housed in the inner space,
wherein at least one of the base and the top define an axially extending opening through which protrudes an actuation rod fixed to the axially movable core element,
wherein the actuator further comprises:
a first membrane and a second membrane of an at least substantially non-magnetic material,
wherein the first membrane is arranged between the base yoke section and the intermediate yoke section and
wherein the second membrane is arranged between the intermediate yoke section and the top yoke section,
wherein the axially movable core element is flexibly restrained between the first and the second membrane, and
wherein the first membrane and the second membrane, together, form a resilient element having a stiffness with a value that is equal to or greater than a magnitude of the negative stiffness.