HAPTIC ELECTROMAGNETIC ACTUATOR
A haptic electromagnetic actuator for track pad is provided. The actuator includes an array of electromagnets with alternating South and North poles on a first end, each magnet comprising a metal core and an electrical wire around the metal core. The array of magnets is coupled to a base plate on a second end opposite to the first end. The actuator also includes an attraction plate at a distance from the first end of the array of the magnets such that the attraction plate moves toward the magnets when an electrical current flows through the electrical wire around the metal core and moves away from the magnets when the current becomes zero. The array of magnets is configured to form a uniform gap from the attraction plate.
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority to U.S. Provisional Application No. 61/658,764, entitled “Haptic Electromagnetic Actuator,” filed Jun. 12, 2012, and U.S. Provisional Application No. 61/800,092, entitled “Haptic Electromagnetic Actuator,” filed Mar. 15, 2013, the disclosures of which are incorporated herein as if fully set forth.
The present invention generally relates to an electromagnetic actuator for providing haptic feedback in a computing device, and more particularly to an electromagnetic actuator generating linear motion parallel to an input surface.
Haptics is a tactile feedback technology which pertains to the sense of touch by applying forces, vibrations or motions to a user. This mechanical stimulation may be used to provide tactile feedback in response to an input command or system state. Haptic devices may incorporate actuators that apply forces or motion to the skin for providing touch feedback. One example of a haptic actuator provides mechanical motion in response to an electrical stimulus. Most haptic feedback mechanisms use mechanical technologies such as vibratory motors, like a vibrating alert in a cell phone, in which a central mass is moved to create vibrations at a resonant frequency. The kinetic energy of these vibrations may be sensed by a user. These motors provide strong feedback, but produce a limited range of sensations.
There remains a need for developing actuators with flat shape, but sufficient travel distance or working distance and sufficient force and fast response.
Embodiments described herein may provide a flat actuator which generates relatively large travel distance and high magnetic force. The disclosure provides methods for fabricating the actuator from a flat laminated metal sheet. Such fabrication methods may be cost effective and may provide the dimensional precision as needed.
In an embodiment, a haptic electromagnetic actuator for trackpad is provided. The actuator includes an array of electromagnets with alternating South and North poles on a first end, each magnet comprising a metal core and an electrical wire around the metal core. The array of magnets is coupled to a base plate on a second end opposite to the first end. The actuator also includes an attraction plate at a distance from the first end of the array of the magnets such that the attraction plate moves toward the magnets when an electrical current flows through the electrical wire around the metal core and moves away from the magnets when the current becomes zero. The array of magnets is configured to form a uniform gap from the attraction plate.
In another embodiment, a track pad is provided to include a haptic electromagnetic actuator. The track pad includes a housing, and a track plate coupled to the housing by bending beams. The track pad also includes an actuator having a baseplate coupled to the housing on a first end. The baseplate supports an array of electromagnets with alternating South and North poles on a second end opposite to the first end. The actuator has an attraction plate coupled to the track plate.
In a further embodiment, a method is provided for fabricating an actuator. The method includes providing a laminated sheet metal and stamping the sheet metal to an array of metal cores with a support base. The method also includes annealing the sheet metal. The method further includes placing electrical wires around the metal cores, and soldering two ends of each wire to the support base.
Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the invention. A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure may be understood by reference to the following detailed description, taken in conjunction with the drawings as briefly described below. It is noted that, for purposes of illustrative clarity, certain elements in the drawings may not be drawn to scale.
Generally, embodiments described herein may take the form of an actuator for providing a haptic output to a surface. The actuator may provide the haptic output in response to an input signal or an output signal, or as part of an output signal. The actuator may vary its output in order to shape and control the haptic response and thus the sensation experienced by a user. In some embodiments, the actuator may be electromagnetically controlled. Embodiments described herein may be incorporated into a variety of electronic or electrical devices, such as a track pad, mouse, or other input (or output) device. Embodiments may likewise be incorporated into a variety of different electronic devices, including smart phones, tablet computing devices, portable computing devices, feedback or outputs for appliances, automobiles, and the like, touchscreens, and so on.
The track pad 114 includes a trackpad plate 104, at least one position sensor 106, at least one touch sensor 116, and at least one force sensor 110, as well as an actuator 108. Each of the touch sensor(s) 116, the position sensor(s) 106, the force sensor(s) 110 and the actuator 108 are coupled to the trackpad 104 and the micro controller 102 and/or processing unit 118. The computer system 100 typically further includes a display and one or more additional user interfaces (not shown). In some embodiments, the position sensor(s) 106 may be an accelerometer, motion sensor or the like.
One example of providing haptic feedback is now discussed, but it should be understood that this is a single example and not meant to be limiting. When using the trackpad 114 to provide input to the computer system 100, a user may move his or her finger on the trackpad plate 104 to, and/or touch the trackpad plate at, a desired location. The touch sensor(s) 116 and the force sensor(s) 110 detect the location and force of the touch on the trackpad plate 104 respectively and send corresponding signals to the micro controller 102. The micro controller 102 communicates with processing unit 118 inside the computer system 100; the processing unit 118 may generally instruct the micro controller with respect to certain operations.
The processing unit 118 may employ these signals to determine if the location of the touch correlates with a specific application or a user interface (UI) element. If the location is within the range for the specific application or UI element, the processing unit further determines if the force signal is above a threshold. If so, the processor may validate the force signal as a selection of the application of UI element. In other words, the force signal is not a false signal. The micro controller 102 then activates the actuator 108, which moves the surface of the trackpad beneath the user's finger (as described in more detail below). The user may sense this motion, thereby experiencing haptic feedback in response to the application or UI element selection. The position sensor 106 detects how much the trackpad plate 104 moves relative to the actuator after an actuation event, or vice versa.
In another example, the track pad 114 may detect a user input, such as a user touch or a user force. In this example, substantially any type of user input detected may be used to provide feedback to the user. Based on the user input the track pad 114 may be activated by the processing unit 118 to move or vibrate to provide haptic feedback to a user. In some instances, the user input may be correlated to a specific application or UI element, in which case the location of the user input may be analyzed to determine if feedback is desired. In other instances, the mere reception of a user input may be sufficient to initiate haptic feedback.
It should be noted that haptic feedback may be provided in response not only to a user input, an example of which is provided above, but also in response to system operation, software status, a lack of user input, passage of user input over UI elements(s) (e.g., dragging a cursor over a window, icon, or the like), and/or any other operating condition of the computer system 100.
The gap 214 between the attraction plate and the actuator may be tightly controlled, since the force exerted by the actuator on the attraction plate drops with an increase in the gap distance. In some embodiments, the gap 214 may be controlled to equal 300 μm+/−50 μm, although this distance may vary between embodiments. It may be useful to place the attraction plate and the actuator in the same X-Y plane to prevent or reduce inducing torque or pitch-type motion in the trackpad plate. Similarly, aligning the actuator and attraction plate along the x axis may help reduce or prevent torquing of the trackpad plate in-plane, as well as yaw motion. In some embodiments, the actuator may be attached to one or one or more bending beams in addition to, or instead of, the housing.
The actuator 108 includes a number of metal cores or tines or arms 210, each metal core or tine being wound with a wire 218. The metal cores may be magnetized when an electric current goes through the wire and electrical contacts 212A-B. Essentially, the combination of cores and wires forms a series of electromagnets. The processing unit and/or the microcontroller 102 may activate the actuator 108 by flowing the electric current through the wire 218, and deactivate the actuator 108 by reducing the electric current to zero. When the actuator 108 is activated by the controller 102, the attraction plate 208 is attracted to poles 210 of the actuator 108 and moves toward the poles 210 such that the trackpad plate 104 moves toward the actuator 108 from its original position.
When the actuator 108 is deactivated by reducing the electric current to zero, the attraction plate 208, along with the trackpad plate 104, is biased away from the actuator 108 such that it returns to its original position. In the present embodiment, the gel(s) may act as a spring, returning the trackpad plate 104 to its original position when the attractive force of the haptic actuator 108 terminates. It should be appreciated that other biasing elements may be used instead of the pictured gels. For example, a spring may be used instead, as may other elastic materials.
In a particular embodiment, the wires for each metal core or tine 210 may be positioned on either side of the metal core. The contacts 212A-B are all connected to a printed circuit board (PCB) (not shown) that may have connections to a specialized circuit board, such as an input device board. Electric current is provided to the wires through the two connections on the PCB. The PCB may attach to a support base.
Typically, movement of the track pad plate 104 is in the plane of the track pad, that is, lateral or in-plane movement. The movement of the trackpad gives the user's finger a sensation or a feedback. The sensation generated by such a back and forth movement is different from a sensation from a typical vibration as used in a cell phone. The sensation generated by the actuator 108 may be more forceful and abrupt than the sensation resulting from vibration induced by an off-center motor or other mechanical actuators.
The metal core 210 and the attraction plate 208 may be made of a relatively soft magnetic material, such as iron or steel. The soft magnetic material has a small hysteresis loop and a small coercive force as well as a small remanence such that no magnetism remains when the magnetic field is removed. In the actuator, the external magnetic filed is generated by the electric current. In a sample embodiment, the metal core 210 may be made of silicon steel. The attraction plate may be formed from iron or another suitable material. Generally, silicon steel has a higher magnetic saturation limit and a better magnetic permeability than iron or many other ferrous materials, may help improve efficiency of the system. That is, more flux may be produced with the same electric current. The material for the attraction plate may vary with the dimension of the attraction plate. For example, for a relatively thin attraction plate, silicon steel may be used. For a relatively thick plate, electrical iron 430 or even electrical iron 1010 may be used without saturation under normal operating conditions.
The metal core 210 may have a rectangular shape as shown in
The attraction plate 608 has a series of recesses contoured by edge 602. Each recess may be matched to the shape of the triangular portion 604A of the actuator 600 such that equal spacing is formed between the attraction plate 608 and the actuator 600.
Although the examples in
For both actuators 300 and 400, assuming that the gap 302 remains the same and the total distance between the two ends 324A and 324B of the actuator are the same except the pole width variation, the integrated magnetic force is about the same. However, the magnetic field distribution across the X-axis is more uniform for actuator 400 with different pole widths than that for actuator 300 with constant pole width.
It will be appreciated by those skilled in the art that the number of turns of the wires may vary, and the number of layers of the wires, the wire diameter, and the height of the metal core may vary.
As illustrated in some embodiments, the actuator is flat and small in height, which is suitable for use in small and thin portable computer devices, such as notebook computers, tablet devices, music and media devices and smart phones. The actuator also has a relatively high magnetic force to attract a attraction plate to move forward and back quickly. The actuator may also have a uniform magnetic field from one end to the other end across the attraction plate.
The actuator can be constructed as a single unit from a laminated sheet metal. The metal cores are formed by stamping to remove some material to form spaces between each core from the laminated sheet metal. The laminated sheet metal is stamped to form an integral support 306 for a series of metal cores. The series of metal cores is not attached to the support 306. Such a layered unit construction method for the actuator may increase dimensional precision of each pole and reduces the need for integration of different components which are fabricated separately. The number of poles may be optimized for efficiency versus working distance. In a particular embodiment, the number of poles is four. Such a fabrication process is relatively low cost, as the actuator is made from a flat laminated metal. Commercially, high performance steel sheets are available. The metal sheets may be cut into the desired pattern.
Method 900 may also include winding electrical wires around a bobbin and sliding the wound wires on the metal cores at operation 914. Method 900 further includes soldering two ends of each wire to a printed circuit board (PCB) on a support base at operation 918.
This layered unit construction also may reduce eddy currents that may otherwise be generated in the actuator. Potential benefits of reducing the eddy current include reducing heat generation and increasing power efficiency for the actuator.
To wind the wire on the metal core, the wire may be first wound on a bobbin. Then, the wound wire slides on the metal core. The wire is heated as the wire is wound on the bobbin, so that various turns are glued to each other to provide better packing.
Having described several embodiments, it will be recognized by those skilled in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention.
Those skilled in the art will appreciate that the presently disclosed embodiments teach by way of example and not by limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween.
1. A haptic electromagnetic actuator for trackpad, the actuator comprising:
- an array of electromagnets with alternating poles at a first end, each magnet comprising a metal core and an electrical wire around the metal core; and
- an attraction plate at a distance from the first end of the array of the magnets such that the attraction plate moves toward the magnets when an electrical current flows through the electrical wire around the metal core and moves away from the magnets when the current becomes zero, the array of magnets being configured to form a uniform gap from the attraction plate.
2. The actuator of claim 1, wherein the array of the electromagnets comprises four magnets.
3. The actuator of claim 1, wherein each of the electromagnets is coupled to a base plate at a first end.
4. The actuator of claim 3, wherein each of the electromagnets defines a pointed end opposite the first end.
5. The actuator of claim 4, wherein the attraction plate defines a sawtooth shape, the sawtooth shape comprising a plurality of projections.
6. The actuator of claim 5, wherein each of the plurality of projections is received between at least two electromagnets.
7. The actuator of claim 1, wherein each adjacent electromagnetic actuator cooperates to form an electromagnetic field.
8. The actuator of claim 7, wherein the array of electromagnets define a non-uniform field.
9. The actuator of claim 1, wherein the array of electromagnets are non-uniform in at least one dimension.
10. A method for forming an electromagnetic actuator, comprising:
- stamping a metal sheet to form an array of metal cores;
- annealing the array of metal cores;
- winding one of a plurality of wires about each of the array of metal cores; and
- affixing each end of the plurality to a power source.
11. The method of claim 10, wherein each of the plurality of wires is wound about a bobbin prior to being wound about each of the array of metal cores.
12. An input device, comprising:
- a plate;
- an actuator operatively connected to the plate;
- a force sensor operatively connected to the plate;
- a touch sensor operatively connected to the plate; and
- a controller operatively connected to at least one of the touch sensor, actuator, and force sensor; wherein
- the controller actuates the actuator, causing the plate to move to provide a haptic feedback in response to the an input to the force sensor.
13. The input device of claim 12, further comprising:
- a position sensor operatively connected to the plate; wherein
- the position sensor is operative to detect a motion of the plate.
14. The input device of claim 13, wherein the controller operative to actuate the plate to provide the haptic feedback in response to a signal from the controller.
15. The input device of claim 14, wherein the position sensor is operative to detect a motion of the plate relative to the actuator.
16. The input device of claim 12, wherein the plate is a track pad plate.
17. The input device of claim 13, wherein the position sensor comprises an accelerometer.
18. The input device of claim 12, further comprising a force sensor operative to determine an approximate force exerted on the plate.
19. The input device of claim 18, further comprising a touch sensor operative to determine a location at which a touch is present on the plate.
20. The input device of claim 19, wherein the controller is operative to correlate the approximate force with the location.
21. The input device of claim 12, wherein the plate moves in-plane when moved by the actuator.
22. The input device of claim 21, wherein the plate moves laterally with respect to the actuator.
Filed: Jun 10, 2013
Publication Date: Apr 23, 2015
Inventors: Patrick Kessler (Cupertino, CA), Dhaval Chandrakant Patel (Cupertino, CA), Jonah A. Harley (Cupertino, CA), Brett W. Degner (Cupertino, CA), Nicholas Alan Rundle (Cupertino, CA), Peteris K. Augenbergs (Cupertino, CA), Nicholaus Lubinski (San Francisco, CA), Kenneth L. Staton (San Carlos, CA), Omar Sze Leung (Palo Alto, CA)
Application Number: 14/404,156
International Classification: G06F 3/01 (20060101); H01F 41/02 (20060101); G06F 3/041 (20060101); H01F 41/06 (20060101);