The present invention relates to an electromagnetic actuator which may be used for example in a haptic display. More specifically, the electromagnetic actuator according to the present invention is arranged to be magnetically latched in two stable states. The invention also relates to an array of electromagnetic actuators and to a haptic display comprising the array of electromagnetic actuators.
Tactile displays, also referred to as haptic displays, are a promising technology to provide visually-impaired people with efficient and autonomous access to graphical information, such as maps and plots, explored using the sense of fine touch of fingertips. The displays are typically the size of a tablet, and able to refresh the graphical information every few seconds. Electromagnetic (EM) actuation has particularly appealing performance in terms of force, deflection, bandwidth, scaling, integration, robustness and portability. Several EM-based tactile display prototypes have been reported using wire-wound coils to attract or repel small permanent magnets.
One of the most challenging obstacles in a densely-packed matrix of EM actuators with strong magnets is to control the magnetic instabilities on the array due to magnet-magnet interactions. If destabilizing forces are comparable to the actuation forces, taxel (movable pin) displacements can no longer be reliably controlled. Only very few strategies are known to address this issue. One approach is to reduce the magnetic volume. While effective, this restricts the applications to very low-force stimuli because the magnetic interaction scales with magnetic volume. Another approach to reduce magnet-magnet interactions is to use immobile soft-magnetic material housings to enclose and guide the magnetic flux. This option adds significant mass, and is not well suited to light and portable devices. It has also been proposed an alternating up/down magnet orientation on the array to partially cancel the static magnetic field. In a further more effective solution, each permanent magnet is placed in a thin ferromagnetic material thus forming a pot-magnet, where only one surface of the magnet (the surface facing a coil) is unshielded. This allows a dense and compact array of EM actuators with the minimum quantity of soft-magnetic material. However, the problem with this approach is that it is only possible to obtain one stable latching position for the permanent magnet.
Another challenge when designing EM actuators is to keep the magnets stable either in their up or down position. It would be desirable to have two stable magnetic positions, i.e. one stable up position and another stable down position. It is to be noted that the problems identified above are not only present in the field of haptic displays, but these problems are equally faced in any field where EM actuators are used.
It is an object of the present invention to overcome at least some of the problems identified above related to EM actuators.
According to a first aspect of the invention, there is provided an electromagnetic actuator as recited in claim 1.
The proposed new electromagnetic actuator has the advantage that it
According to a second aspect of the invention, there is provided an electromagnetic actuator system as recited in claim 10.
According to a third aspect of the invention, there is provided a haptic display as recited in claim 12.
According to a fourth aspect of the invention, there is provided a method of operating the electromagnetic actuator as recited in claim 13.
Other aspects of the invention are recited in the dependent claims attached hereto.
Other features and advantages of the invention will become apparent from the following description of a non-limiting example embodiment, with reference to the appended drawings, in which:
An embodiment of the present invention will now be described in detail with reference to the attached drawings. This non-limiting embodiment is described in the context of a haptic display for blind and visually impaired people. However, the teachings of the present invention are not limited to this environment. The EM actuators according to the present invention may also be applied to a haptic interface for novel human-machine interfaces (e.g. wearables) or to a haptic interface for augmented reality (AR) or virtual reality (VR) applications. Further applications include microfluidic systems where an EM actuator array allows eliminating all the pneumatic pumps, and antenna pointing and beam steering solutions, where the EM actuators can be used for reconfiguring a surface. In the following description identical or corresponding functional and structural elements which appear in the different drawings are assigned the same reference numerals.
As shown in
A first latching layer 13, also referred to as a bottom or lower latching layer, is located directly below the bottom circuit board 9 while a second latching layer 15, also referred to as a top or upper latching layer, is located directly above the top circuit board 11. Thus, the bottom latching layer 13 is facing the bottom circuit board 9, while the top latching layer 15 is facing the top circuit board 11. In the present description the action of facing is to be interpreted broadly. This means for instance that when a first element is facing a second element, there can be further elements between the first and second elements or that the first and second elements may be offset with respect to each other. In this example, the bottom and top latching layers 13, 15 are each soft magnetic continuous plates of ferromagnetic material. Soft magnetic materials are those materials that are easily magnetized and demagnetized. In the present description they have intrinsic coercivity less than 1000 Am−1. Furthermore, these materials do not have intrinsic polarity and thus no permanent north and south poles as opposed to permanent magnets. In the present example, the bottom and top latching layers 13, 15 are substantially identical and are each of low-carbon steel, i.e. they have 0.05 to 0.25% carbon content by weight. Other metals could be used instead for the bottom and top latching layers 13, 15. The bottom and top latching layers do not have to be identical or substantially identical. For example, different materials and/or thickness may be used to give different latching forces for the bottom and top latching layers 13, 15. The thickness of the latching layers may be between 0.1 mm and 5 mm, or more specifically between 0.3 mm and 3 mm or 0.5 and 1.5 mm. Instead of using latching plates, individual latching elements could be used, optionally having different shapes. According to another variant, the bottom and top latching layers 13, 15 could be permanent magnets. In the present description, the EM actuator is understood to comprise the first magnet 5, the shielding element 7, at least one actuator inductor and the two latching layers 13, 15.
A first heat dissipation layer 17, also referred to as a bottom or lower heat dissipation layer, may be located directly below the bottom latching layer 13 while a second dissipation layer 19, also referred to as a top or upper heat dissipation layer, is located directly above the top latching layer 15. The purpose of these optional heat dissipation layers 17, 19 is to ensure proper cooling of the system 1. In this example, the bottom heat dissipation layer 17 is in fact part of a housing of the system 1. There may further be at least one spacer layer for keeping the circuit boards apart from each other. The spacer layer(s) may advantageously be of light plastic or metallic material. As further shown in
The proposed EM actuators 2 are designed to avoid lateral magnetic crosstalk between neighbor actuators in the actuator array or matrix. This fact allows the assembly of dense arrays of magnetic actuators.
In the configuration of
When the shielded first magnets 5 are close enough (closer than a given distance threshold which depends on the thickness and/or surface area and/or material of the latching layers) to any of the first and second latching layers 13, 15, they get attracted to the respective latching layer 13, 15 and keep stable in either a first position, also referred to as a down position, or in a second position, also referred to as an up position. Actuator holding forces can be easily tuned during fabrication by changing the thickness and/or material of the latching layer(s) 13, 15. To switch the state of the actuator (i.e. to move the shielded first magnet 5 from the down position to the up position or vice versa), a short pulse of electrical current is driven in the coils 12 of the bottom and top circuit boards 9, 11. Typical current pulses are of 3-30 ms and 2-5 A, or more specifically of 4-15 ms and 3-4 A. A single pulse may be used for single switching (i.e. for single taxel displacement) or vibrating a specific taxel 27. Latching allows keeping the actuator in one of the two stable positions without any power consumption. Electrical current is only used for switching the actuator state. It is to be noted that in many prior art actuators, to keep a magnet in a given state, current is driven for the duration of the latching through the actuator coils 12. There is a tradeoff between having a larger latching force but using higher currents for switching; and both a lower latching force but also less actuation current, hence lower power consumption.
All the parts of a single actuator 2 can be designed to be easily scalable. Instead of using wire-wound coils around the first magnet 5, either rigid or flexible PCB coils 12 are used in the present invention. The latching layers 13, 15 or plates may be thin low-carbon steel shims, which can be machined easily. This is advantageous in production because complexity does not scale up proportionally to the number of taxels. Thus, the surface area of the circuit boards 9, 11 and/or the latching plates 13, 15 may be substantially the same as the horizontal cross-sectional area of the whole system 1. The assembly of each shielded magnet is the only fabrication step that scales up with the number of taxels. However, it can easily be automated by using a pick-and-place machine for example. The above teachings can be used to fabricate either flexible or rigid arrays of actuators. The layer stack can be modified by including flexible circuit boards, spacers, such as silicon spacers, and/or holders to obtain rigid shielded magnets combined with flexible inter-actuation layers as shown in
According to a further variant of the present invention, the EM actuator system 1 as described above may be used to sense inputs received from a user. These inputs may be received by the user pushing down the taxels 27 while the system 1 detects the vertical taxel displacements. More specifically, if a metallic element, such as a magnet moves inside a coil, this generates a voltage which can be detected by a voltage sensor. For this purpose, the pegs 25 may be metallic pegs or have a metallic coating. According to another implementation, the movement of the taxels 27 may be detected by another sensor, which may be located in the pin array interface 3 or elsewhere. According to this variant of the present invention, the system 1 is not only used to generate haptic outputs but also to detect inputs.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative and not restrictive, the invention being not limited to the disclosed embodiment. Other embodiments and variants are understood, and can be achieved by those skilled in the art when carrying out the claimed invention, based on a study of the drawings, the disclosure and the appended claims. For example, instead of having two unshielded surfaces per actuator, pot-magnets could be used to shield the first magnet 5. In this manner, only one surface (facing one of the circuit boards 9, 11) of the first magnetic element would be unshielded. However, if pot-magnets are used, then the actuators would only have one stable position.
Furthermore, it is to be noted that the order of the layers described above may be different from the order illustrated for instance in
In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be advantageously used.
Number | Date | Country | Kind |
---|---|---|---|
17163181 | Mar 2017 | EP | regional |
Number | Name | Date | Kind |
---|---|---|---|
3781736 | Parker | Dec 1973 | A |
4775862 | Kent | Oct 1988 | A |
6137129 | Bertin | Oct 2000 | A |
6184755 | Barber | Feb 2001 | B1 |
6617185 | Geisberger | Sep 2003 | B1 |
6786070 | Dimig | Sep 2004 | B1 |
6824739 | Arney | Nov 2004 | B1 |
RE42064 | Fish | Jan 2011 | E |
7924145 | Yuk et al. | Apr 2011 | B2 |
20010002329 | Ling | May 2001 | A1 |
20010024401 | Short | Sep 2001 | A1 |
20020050923 | Petersen | May 2002 | A1 |
20020140050 | Bohlin | Oct 2002 | A1 |
20040004252 | Madurawe | Jan 2004 | A1 |
20040004298 | Madurawe | Jan 2004 | A1 |
20040047546 | Gasparyan | Mar 2004 | A1 |
20040069028 | Dimig | Apr 2004 | A1 |
20040125536 | Arney | Jul 2004 | A1 |
20040214389 | Madurawe | Oct 2004 | A1 |
20060012576 | Hafez et al. | Jan 2006 | A1 |
20060143342 | Kim et al. | Jun 2006 | A1 |
20060243318 | Feldmeier | Nov 2006 | A1 |
20070299388 | Chan | Dec 2007 | A1 |
20080182228 | Hafez et al. | Jul 2008 | A1 |
20080227060 | Esashi et al. | Sep 2008 | A1 |
20080246737 | Benali-Khoudja et al. | Oct 2008 | A1 |
20080307786 | Hafez et al. | Dec 2008 | A1 |
20120056733 | Ramsay et al. | Mar 2012 | A1 |
20120279845 | Bachman | Nov 2012 | A1 |
20130082301 | Onozawa | Apr 2013 | A1 |
20130236337 | Gummin et al. | Sep 2013 | A1 |
20140009411 | Cho et al. | Jan 2014 | A1 |
20140104047 | Bolzmacher et al. | Apr 2014 | A1 |
20140184947 | Bolzmacher et al. | Jul 2014 | A1 |
20140325910 | Faris | Nov 2014 | A1 |
20150317915 | Nelson et al. | Nov 2015 | A1 |
20160224116 | Hagedorn | Aug 2016 | A1 |
20180277292 | Zarate | Sep 2018 | A1 |
Number | Date | Country |
---|---|---|
30 42 390 | Jun 1982 | DE |
42 33 524 | Apr 1994 | DE |
103 49 100 | May 2005 | DE |
2 894 061 | Jun 2007 | FR |
1485 698 | Sep 1977 | GB |
1557 001 | Dec 1979 | GB |
2466102 | Jun 2010 | GB |
2002-351306 | Dec 2002 | JP |
2005-055767 | Mar 2005 | JP |
2009-123688 | Jun 2009 | JP |
10-2013-0091140 | Aug 2013 | KR |
10-1626949 | Jun 2016 | KR |
10-2016-0122491 | Oct 2016 | KR |
02080134 | Oct 2002 | WO |
2015039047 | Mar 2015 | WO |
2015077846 | Jun 2015 | WO |
2015175193 | Nov 2015 | WO |
2016198602 | Dec 2016 | WO |
Entry |
---|
Benali-Khoudja, M., et al., “VITAL: An electromagnetic integrated tactile display,” ScienceDirect, Displays, vol. 28, pp. 133-144 (2007). |
Gallo, S., et al., “A flexible multimodal tactile display for delivering shape and material information,” Sensors and Actuators A: Physical, vol. 236, pp. 180-189 (Dec. 1, 2015). |
Strasnick, E., and Follmer, S., “Applications of Switchable Permanent Magnetic Actuators in Shape Change and Tactile Display,” Proceeding UIST '16 Adjunct Proceedings of the 29th Annual Symposium on User Interface Software and Technology, pp. 123-125 (Jul. 6, 2016). |
Streque, J., et al., “Pulse-driven magnetostatic micro-actuator array based on ultrasoft elastomeric membranes for active surface applications,” IOP Publishing Ltd, J. Micromech. Microeng, vol. 22, No. 9, pp. 1-10 (2012). |
Szabo, Z., and Enikov, E.T., “Electromagnetic Microactuator-Array Based Virtual Tactile Display,” Department of Aerospace and Mechanical Engineering, ICCHP 2016, Part II, LNCS, vol. 9759, pp. 53-60 (Oct. 16, 2016). |
Extended European search Report dated Oct. 9, 2017 as received in Application No. 17163181.5. |
CH Search Report dated Feb. 9, 2017 as received in Application No. 17-30028. |
Number | Date | Country | |
---|---|---|---|
20180277292 A1 | Sep 2018 | US |