PATENT DOCUMENT

Publication Number: US-9639187-B2
Application Number: US-23532608-A
Country: US
Kind Code: B2

Title: Using vibration to determine the motion of an input device

Abstract:
A method and apparatus for determining the speed and/or position of an input device from vibrational signals is disclosed herein. In one embodiment, a response spectrum is generated as the input device moves across a surface. Amplitude and frequency data associated with the response spectrum is analyzed to determine the magnitude of the velocity.

Claims:
What is claimed is: 
     
       1. An input device, comprising:
 a first module for detecting vibrations as the input device is moved across a surface, wherein the first module outputs a first signal corresponding to the detected vibrations; 
 a second module for storing data corresponding to the first signal; and 
 a third module for estimating a speed of the input device based on a first filtered signal, a second filtered signal, and a third filtered signal generated in parallel, 
 wherein the first filtered signal is generated by applying a first bandpass filter to the first signal, the second filtered signal generated by applying a second bandpass filter to the first signal, and the third filtered signal is generated by averaging the first signal over a period of time, and 
 wherein the first bandpass filter filters the first signal according to a first frequency band, the second bandpass filter filters the first signal according to a second frequency band, and the second frequency band is at least partially different than the first frequency band. 
 
     
     
       2. The input device of  claim 1 , wherein the first module comprises a vibrometer. 
     
     
       3. The input device of  claim 1 , wherein the first module comprises an accelerometer. 
     
     
       4. The input device of  claim 1 , wherein the third module is adapted to estimate the speed of the input device by processing at least one filtered signal. 
     
     
       5. The input device of  claim 4 , wherein said processing the at least one filtered signal comprises measuring the amplitude of the at least one filtered signal. 
     
     
       6. The input device of  claim 5 , wherein said measuring the amplitude of the at least one filtered signal comprises taking a root mean square level of the at least one filtered signal. 
     
     
       7. The input device of  claim 5 , wherein said measuring the amplitude of the at least one filtered signal comprises taking an absolute value of the at least one filtered signal. 
     
     
       8. The input device of  claim 1 , wherein the third module is adapted to estimate the speed of the input device by processing a plurality of acceleration metrics; wherein at least one of the metrics is based at least in part upon a measured amplitude of a filtered signal. 
     
     
       9. The input device of  claim 8 , wherein the third module is further adapted to assign a weight to each acceleration metric of the plurality. 
     
     
       10. A method of tracking a motion of an input device comprising:
 estimating a velocity of the input device based upon a first set of data and a second set of data; and 
 positioning a display object based at least in part upon said velocity, 
 wherein the first set of data is based at least in part upon a sensory value, and the second set of data comprises a first signal corresponding to vibrations associated with the input device moving across a surface; 
 filtering the first signal with a first bandpass filter and a second bandpass filter in parallel, wherein the first bandpass filter filters the first signal according to a first frequency band, the second bandpass filter filters the first signal according to a second frequency band, and the second frequency band is at least partially different than the first frequency band; 
 determining an average of the first signal over a period of time, and 
 estimating the velocity of the input device based on the output of the first bandpass filter and the second bandpass filter and the average of the first signal over the period of time. 
 
     
     
       11. The method of  claim 10  further comprising detecting the vibrations using an accelerometer disposed within the input device. 
     
     
       12. The method of  claim 11 , wherein the accelerometer comprises a micro electro-mechanical system. 
     
     
       13. The method of  claim 10  further comprising detecting the vibrations using a vibrometer disposed within the input device. 
     
     
       14. The method of  claim 10  further comprising detecting the vibrations using a microphone disposed within the input device. 
     
     
       15. The method of  claim 10  further comprising detecting the sensory value using a two-dimensional force sensor. 
     
     
       16. The method of  claim 10 , wherein said positioning a display object comprises updating a set of coordinates associated with the display object. 
     
     
       17. A method of tracking a motion of an input device comprising:
 estimating a velocity of the input device based upon a first set of data and a second set of data; and 
 positioning a display object based at least in part upon said velocity, 
 wherein the first set of data is based at least in part upon a sensory value, and the second set of data comprises a first signal corresponding to vibrations associated with the input device moving across a surface; 
 filtering the first signal with a first bandpass filter and a second bandpass filter in parallel, wherein the first bandpass filter filters the first signal according to a first frequency band, the second bandpass filter filters the first signal according to a second frequency band, and the second frequency band is at least partially different than the first frequency band; and 
 estimating the velocity of the input device based on the output of the first bandpass filter and the second bandpass filter, 
 wherein said positioning a display object comprises updating a set of coordinates associated with the display object, and 
 wherein said updating a set of coordinates associated with a display object comprises storing a fractional residue in an accumulator. 
 
     
     
       18. A computer readable storage device storing computer executable instructions which, when executed by a computer, performs a process comprising:
 receiving a signal generated by a vibration sensor indicative of contact with a surface; and 
 determining a speed of the input device based at least in part upon the signal, including:
 filtering the signal through a first bandpass filter and a second bandpass filter in parallel, wherein the first bandpass filter filters the signal according to a first frequency band, the second bandpass filter filters the signal according to a second frequency band, and the second frequency band is at least partially different than the first frequency band and 
 determining an average of the first signal over a period of time. 
 
 
     
     
       19. The computer readable storage device of  claim 18 , wherein the process further comprises:
 receiving an input from a force sensor; and 
 updating a set of coordinates based at least in part upon the input and based at least in part upon the signal. 
 
     
     
       20. The computer readable storage device of  claim 19 , wherein the input comprises an indication of direction. 
     
     
       21. The computer readable storage device of  claim 19 , wherein the input comprises an estimate of speed. 
     
     
       22. The computer readable storage device of  claim 19 , wherein said updating a set of coordinates is adapted to orient a graphical object upon a display screen. 
     
     
       23. The computer readable storage device of  claim 18 , wherein the vibration sensor comprises a vibrometer. 
     
     
       24. The computer readable storage device of  claim 18 , wherein the vibration sensor comprises an accelerometer. 
     
     
       25. A system comprising:
 an input device adapted to interact with a surface; 
 a computing device adapted to receive a signal from the input device; and 
 a graphical object adapted to respond to a command issued by the computing device, 
 wherein the signal comprises a value representing a speed of the input device, in which the value is determined at least in part based upon a vibration induced by the input device moving upon a surface and wherein the value is determined by:
 filtering a measurement signal corresponding to the vibration with a first bandpass filter and with a second bandpass filter in parallel, wherein the first bandpass filter filters the measurement signal according to a first frequency band, the second bandpass filter filters the measurement signal according to a second frequency band, and the second frequency band is at least partially different than the first frequency band; and 
 determining an average of the measurement signal over a period of time. 
 
 
     
     
       26. The system of  claim 25 , wherein the input device comprises a computer mouse. 
     
     
       27. The system of  claim 25 , wherein the computing device comprises a console. 
     
     
       28. The system of  claim 25 , wherein the graphical object comprises a cursor.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of data input. More particularly, the present invention is directed in one exemplary aspect to determining the speed and/or position of an input device based on one or more response signals. 
     DESCRIPTION OF RELATED TECHNOLOGY 
     In principle, an inertial device can be used as an input source for a computing device. For example, an inertial input device comprising an accelerometer can measure the acceleration of the input device and thereafter calculate an estimated velocity and/or position of the input device based upon the measured acceleration. Such estimated velocity and/or position data can then be provided to one or more requesting applications. 
     However, a number of adverse effects have prevented the production of a workable accelerometer-based input device. Some problems associated with an accelerometer-based input device are cursor drift and kickback errors in tracking the motion of the input device. For example, after a consecutive number of calculations, errors in accelerometer readings, offsets, or noise, for example, can cause the resulting calculated velocity of the input device to be incorrect. This can cause a cursor to continue moving even though the input device is stationary. 
     Certain changes in the orientation of the input device also tend to yield undesirable effects. This is because accelerometers cannot distinguish between acceleration due to gravity and acceleration due to dynamic motion. While an acceleration offset typically compensates for the effects of gravity, a problem arises when the accelerometer changes its orientation with respect to the direction of the offset (e.g., if the input device is placed upon a non-horizontal or non-flat surface). Since the change in offset due to gravity cannot be separated from dynamic motion, the offset becomes unknown, and incorrect and unstable velocities often result. 
     Additionally, while an accelerometer driven input device performs well at high speeds, its performance declines substantially at lower speeds where the acceleration values are close to the measurable limits of the device. 
     What is needed is a means or mechanism for addressing each of the aforementioned concerns. More specifically, methods and apparatus are needed for implementing an accelerometer-based input device without significant tracking errors. Ideally, the method and apparatus would account for changes in the orientation of the input device while retaining desirable performance characteristics at lower speeds. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the foregoing needs by disclosing various apparatus and methods for using vibration to determine the speed of a motion-based input device. 
     In a first aspect of the invention, an input device is disclosed. In one embodiment, the input device comprises: a first module for detecting vibrations as the input device is moved across a surface; and a second module for estimating a speed of the input device based on the detected vibrations. 
     In a second aspect of the invention, a method of tracking a motion of an input device is disclosed. In one embodiment, the method comprises: estimating a velocity of the input device based upon a first set of data and a second set of data; and positioning a display object based at least in part upon said velocity, wherein the first set of data is based at least in part upon a sensory value, and wherein the second set of data is based at least in part upon vibrations associated with the input device moving across a surface. 
     In a third aspect of the invention, a computer readable medium storing computer executable instructions is disclosed. In one embodiment, the instructions are adapted to perform a process comprising: receiving a signal generated by a vibration sensor indicative of contact with a surface; and determining a speed of the input device based in part upon the signal. 
     In a fourth aspect of the invention, a system is disclosed. In one embodiment, the system comprises: an input device adapted to interact with a surface; a computing device adapted to receive a signal from the input device; and a graphical object adapted to respond to a command issued by the computing device, wherein the signal comprises a value that is based in part upon a vibration induced by the input device moving upon a surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a typical environment in which an input device may be used according to one embodiment of the present invention. 
         FIG. 2  is a flow diagram illustrating a high level method of updating cursor position according to one embodiment of the present invention. 
         FIG. 3  is a system diagram of a modular arrangement of an input device according to one embodiment of the present invention. 
         FIG. 4  is a block diagram of an initial model for sliding friction according to one embodiment of the present invention. 
         FIG. 5  is a flow diagram illustrating a method of calculating the direction of a dynamic force according to one embodiment of the present invention. 
         FIG. 6  is set of graphs illustrating an exemplary functional transformation of a set of inputs according to one embodiment of the present invention. 
         FIG. 7  is flow diagram illustrating a method of combining acceleration metrics according to one embodiment of the present invention. 
         FIG. 8  is a flow diagram illustrating a method of updating cursor position according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following description of exemplary embodiments, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     As used herein, the term “application” includes without limitation any unit of executable software which implements a specific functionality or theme. The unit of executable software may run in a predetermined environment; for example, a downloadable Java Xlet™ that runs within the JavaTV™ environment. 
     As used herein, the terms “computer program” and “software” include without limitation any sequence of human or machine cognizable steps that are adapted to be processed by a computer. Such may be rendered in any programming language or environment including, for example, C/C++, Fortran, COBOL, PASCAL, Perl, Prolog, Python, Matlab, assembly language, scripting languages, markup languages (e.g., HTML, SGML, XML, VoXML), functional languages (e.g., APL, Erlang, Haskell, Lisp, ML, F# and Scheme), as well as object-oriented environments such as the Common Object Request Broker Architecture (CORBA), Java™ (including J2ME, Java Beans, etc.). 
     As used herein, the term “display” includes any type of device adapted to display information, including without limitation cathode ray tube displays (CRTs), liquid crystal displays (LCDs), thin film transistor displays (TFTs), digital light processor displays (DLPs), plasma displays, light emitting diodes (LEDs) or diode arrays, incandescent devices, and fluorescent devices. Display devices also include less dynamic devices such as printers, e-ink devices, and other similar structures. 
     As used herein, the term “interface” refers to any signal or data interface with a component or network including, without limitation, those compliant with USB (e.g., USB2), FireWire (e.g., IEEE 1394b), Ethernet (e.g., 10/100, 10/100/1000 Gigabit Ethernet, 10-Gig-E, etc.), MoCA, Serial ATA (e.g., SATA, e-SATA, SATAII), Ultra-ATA/DMA, Coaxsys (e.g., TVnet™), radio frequency tuner (e.g., in-band or OOB, cable modem, etc.), modem, WiFi (802.11a,b,g,n), WiMAX (802.16), PAN (802.15), or IrDA families. 
     As used herein, the term “memory” includes any type of integrated circuit or other storage device adapted for storing digital data including, without limitation, ROM, PROM, EEPROM, DRAM, SDRAM, DDR/2 SDRAM, EDO/FPMS, RLDRAM, SRAM, “flash” memory (e.g., NAND/NOR), and PSRAM. 
     As user herein, the term “module” refers to any unit or combination of units incorporating software, firmware, hardware, or any combination thereof that is designed and configured to perform a desired function. 
     As used herein, the terms “processor,” “microprocessor,” and “digital processor” include all types of digital processing devices including, without limitation, digital signal processors (DSPs), reduced instruction set computers (RISC), general-purpose (CISC) processors, microprocessors, gate arrays (e.g., FPGAs), programmable logic devices (PLDs), reconfigurable compute fabrics (RCFs), array processors, and application-specific integrated circuits (ASICs). Such processors may be contained on a single unitary IC die or distributed across multiple components. 
     As used herein, the terms “receiving device” and “receiver” include without limitation video game consoles, set-top boxes, televisions, personal computers (whether desktop, laptop, or otherwise), digital video recorders, communications equipment, terminals, and display devices. 
     As used herein, the term “wireless” refers to any wireless signal, data, communication, or other interface including, without limitation, Wi-Fi, Bluetooth, 3G, HSDPA/HSUPA, TDMA, CDMA (e.g., IS-95A, WCDMA, etc.), FHSS, DSSS, GSM, PAN/802.15, WiMAX (802.16), 802.20, narrowband/FDMA, OFDM, PCS/DCS, analog cellular, CDPD, satellite systems, millimeter wave or microwave systems, acoustic, and infrared (i.e., IrDA). 
       FIG. 1  is a block diagram illustrating a typical environment in which an input device  102  may be used according to one embodiment of the present invention. The input device  102  is initially positioned upon a surface  104  such as a desk or a tabletop. In order to generate input data, a user manipulates the input device relative to the surface  104 . 
     Note that in  FIG. 1 , the surface  104  is depicted as being flat or substantially flat; however, a flat surface  104  is not strictly necessary according to embodiments of the present invention. Also note that in some embodiments, the surface  104  need not necessarily be situated beneath the input device  102 . For example, the surface  104  may be tilted, above the input device  102 , or vertically oriented. Also note that in certain embodiments, multiple surfaces  104  may be utilized. 
     A receiving device (such as the depicted computer  106 ) is adapted to receive input data generated from the input device  102 . In some embodiments, the receiving device comprises at least one network interface adapted to receive the generated data. The input device  102  may connect to the receiving device over a wireless or wired communication link (such as a serial bus cable or other physical connector). 
     The receiving device is adapted to display a navigational object (for example, a pointer, cursor, selector box, or other such indicator) upon its display screen  108 . During operation, when the user manipulates the input device  102  relative to the surface  104 , the input signals are received at the computer  106  and the navigational object responds according to the user&#39;s input. It is understood that the receiving device can be any type of computing device having a display such as an iMac™ computer or a personal computer having a separate display monitor, for example. Other types of computing devices having displays for displaying navigational objects would be readily apparent to those of ordinary skill in the art. 
     In other embodiments, the input data is used for purposes other than for orienting a navigational object on a display screen. For instance, in some embodiments (as may be implemented in certain video games and/or graphical applications), the speed of the input device  102  is calculated, but not its direction. In one application, the color of a display screen  108  is predicated upon how fast the input device  102  is moving. For example, moving the input device  102  at a first speed may generate a red color, while moving the input device  102  at a second speed may generate a blue color. 
       FIG. 2  is a high-level flow diagram illustrating a method of updating cursor position according to one embodiment of the present invention. Cursor position is updated based upon motion of the input device  102 , where the motion comprises both a direction and a speed. At step  202 , the direction of motion is received. At step  204 , a speed of motion is received. Once both speed and direction have been received, the velocity and/or position of the input device are calculated at step  206 . Based upon the velocity and/or positional data, cursor position may then be updated at step  208 . 
       FIG. 3  is a system diagram of a modular arrangement of the input device  102  according to one embodiment of the present invention. The input device  102  houses a printed circuit board  304  enabling communication and data transfer between the connected modules. 
     A power supply  306  provides a source of power to modules electrically connected to the printed circuit board  304 . In some embodiments, power is supplied externally by one or more conductive wires, for example, from a power cable or a serial bus cable. In other embodiments, a battery may be used as a source of power. 
     A memory  312  comprises any type of module adapted to enable digital information to be stored, retained, and retrieved. Additionally, the memory  312  may comprise any combination of volatile and non-volatile storage devices, including without limitation RAM, DRAM, SRAM, ROM, and/or flash memory. Note also that the memory  312  may be organized in any number of architectural configurations utilizing, for example, registers, memory caches, data buffers, main memory, mass storage, and/or removable media. 
     One or more processors  308  are adapted to execute sequences of instructions by loading and storing data to the memory  312 . Possible instructions include, without limitation, instructions for data conversions, formatting operations, communication instructions, and/or storage and retrieval operations. Additionally, the processors  308  may comprise any type of digital processing devices including, for example, reduced instruction set computer processors, general-purpose processors, microprocessors, digital signal processors, gate arrays, programmable logic devices, reconfigurable compute fabrics, array processors, and/or application-specific integrated circuits. Note also that the processors  308  may be contained on a single unitary IC die or distributed across multiple components. 
     An interface module  310  enables data to be transmitted and/or received between two or more devices. In one embodiment, data transmitted to a receiving device is first packetized and processed according to one or more standardized network protocols. The interface module  310  may accommodate any wired or wireless protocol including, without limitation, USB, FireWire, Ethernet, Gigabit Ethernet, MoCA, radio frequency tuners, modems, WiFi, Bluetooth, WiMax, and/or Infrared Data Association. 
     A direction detection module  320  comprises logic adapted to determine the direction of the velocity of the input device  102  during a given instant, or alternatively, over a given period of time. In some embodiments, the direction detection module  320  comprises a force sensor  322  adapted to sense external forces acting upon the input device  102 . In one embodiment, the force sensor  322  may be adapted to measure a vertical force exerted upon the input device  102 , as described in more detail in Applicant&#39;s U.S. patent application Ser. No. 12/233,478 filed on Sep. 19, 2008, and titled “Using Measuring Lateral Force for Tracking an Input Device”,the content of which is incorporated by reference herein in its entirety for all purposes. In another embodiment, the force sensor may be adapted to finely track control of a mouse cursor, as described in more detail in Applicant&#39;s U.S. patent application Ser. No. 12/233,502,filed on Sep. 18, 2008, and titled “Force Sensing for Fine Tracking Control of Mouse Cursor”, the content of which is also incorporated by reference herein in its entirety for all purposes. 
     After a force value has been detected, a translation logic module  324  (which may be implemented as any combination of software, firmware, and/or hardware according the scope of the present invention) can determine the direction of the velocity of the input device  102  from the input force value. Note that in some embodiments, a force value indicated by the force sensor  322  is written to a local memory source  326  (such as a register or local cache) before being provided as input to the translation logic module  324 . In other embodiments, this data is directly written and retrieved from the memory  312 . In still other embodiments, this data is stored in external memory (e.g. a hard drive of the computer  106 ) and the input device transmits raw data to the computer  106  for processing. 
     Note also that even though  FIG. 3  depicts the translation logic module  324  as being disposed within the direction detection module  320 , this is not strictly necessary according to some embodiments of the present invention. Additionally, according to some embodiments, one or more separate modules comprise at least a portion of the logic necessary to derive the direction of the velocity of the input device  102  from a detected force value. For example, in one embodiment, the force sensor  322  provides raw data (e.g., a detected force value) to a data integration module  314 , and the data integration module  314  comprises logic necessary for determining the direction of the velocity of the input device  102  from the detected force value. 
     The input device  102  also comprises a speed detection module  330  adapted to detect vibrational “sliding noise” resulting from the input device  102  moving across a surface  104 . In some embodiments, when the input device  102  slides across a surface  104 , the speed detection module  330  records signaling data from one or more vibration response spectrums. The speed of the input device  102  can be estimated based upon the specific vibration response detected since the speed of the input device  102  monotonically increases with the amplitude of the vibration response. In other words, there is a one-to-one relationship between vibrational energy and speed. 
     According to some embodiments, the speed detection module  330  comprises a vibration sensor  332  adapted to detect vibrational signals resulting from surface contact. In one embodiment, the vibration sensor  332  comprises an accelerometer. Note, however, that other means of vibration detection may also be utilized according to the scope of the present invention. This includes, for example, force sensors and/or microphones. In some embodiments, mechanical structures (e.g., resonant structures) are utilized in order to enhance the sensitivity to sliding vibration. 
     As the input device  102  slides across a surface  104 , the speed detection module  330  records attendant vibrational signals. Note that a given signal may be the result of several components: gravity, dynamic motion (about the XY plane), pressure (about the Z plane), frictional characteristics, vibration, external noise, and technological artifacts (for example, non-ideal accelerometer artifacts). Various embodiments of the present invention therefore utilize a number of methods for extracting dynamic motion from a given signal. 
     According to some embodiments, a response spectrum analysis module  334  initially executes one or more normalization sequences based upon a set of externally provided data (e.g., sensed data). The normalization sequences control for variable conditions exhibited within the surrounding environment or from the input device  102  itself. 
     In some embodiments, normalization accounts for varying effects of friction (both static and kinetic). As the input device  102  slides across a surface  104 , the friction acting upon it will largely depend upon the type of surface it is contacting (e.g., wood, glass, marble, plastic, metal, padding, etc.). Frictional coefficients associated with contacting region(s) of the input device  102  may also vary across models and/or housing materials. 
     An initial model for sliding friction is shown in  FIG. 4 . According to some embodiments, friction comprises the product of a frictional coefficient, μ 402  and a normal force N  404  exerting between contacting surfaces. This relationship is expressed in equation  400 . The direction of a frictional force opposes the direction of an applied force. Thus, as Mass m  406  moves in the direction designated by x 2   408  with a velocity v 2   410  and acceleration a 2   412 , a frictional force will oppose this motion in the direction indicated by the vector  414 . 
     An input device  102  sliding across a surface  104  will experience similar frictional forces. Thus, according to some embodiments of the present invention, frictional forces are initially discovered and subsequently normalized by one or more calibration sequences. In one embodiment, the input device  102  “learns” about the surface  104  during the first few seconds of operation. In some embodiments, the calibration process includes a predetermined sequence of user interactions with the input device  102  upon the surface  104 . 
     Various other effects may also be normalized according to embodiments of the present invention. These include, for example, the magnitude of the z-force presently acting upon the input device  102 . Experimental evidence has demonstrated that vibration intensity increases with increasing z-directional pressure applied to an input device  102 . However, since frictional force is proportional to normal force (as described in equation  400 ), this relationship can therefore be utilized in order to control for the z-directional pressure. Normalizing the vibration intensity removes the dependence of vibration amplitude, and thereby decreases the variability of the calculated velocity. Note that according to some embodiments, the applicable z-force is measured directly with a load cell or other sensor. 
     Referring again to  FIG. 3 , after preliminary adjustments have been calculated (e.g., normalizing for friction and/or z-directional pressure), the response spectrum analysis module  334  estimates the speed and/or position of the input device  102  from one or more provided signals. These estimates are possible since the relative amplitude and frequency of a given vibrational signal is proportional to the speed of the input device  102 . 
     In certain embodiments (particularly those embodiments where cursor tracking is not required), determining direction is not required. In these embodiments, the high frequency component of a response spectrum is initially extracted, and motion is then distinguished from static position by applying one or more thresholds to the extracted data. 
     In embodiments where the actual magnitude and direction of the velocity is required, a number of additional techniques may be utilized. Note that the following techniques are exemplary in nature and do not represent an exhaustive list of all techniques which can be employed in accordance with the scope of the present invention. Additionally, any of the following techniques can be used in conjunction with other techniques. 
     According to some embodiments, one or more force sensors  322  are utilized in order to calculate the direction of the velocity. In some embodiments, a two-dimensional force sensor  322  measures the sliding (i.e. frictional) force of the input device upon a surface  104 . The unit vectors calculated from the X and Y forces then yield the vector direction of movement. In other embodiments, one or more sensors determine direction without measuring force. 
       FIG. 5  is a flow diagram illustrating a method of calculating the direction of a dynamic force according to one embodiment of the present invention. At step  502 , the frictional force (both magnitude and direction) is determined for both the x and the y axes. At decision block  504 , if the magnitude of the force in either direction is equal to zero, the corresponding change in position will be set to zero at step  506 . Otherwise, the magnitude of the combined force is calculated at step  508 . In some embodiments, this value is given as:
 
| F |=√{square root over (( Fx   2   +Fy   2 ))}
 
     After this value has been calculated, the corresponding unit vectors are derived at step  510 . According to some embodiments, the respective unit vectors are defined as:
 
 X  direction= Fx/|F|, Y  direction= Fy/|F| 
 
     The magnitude of the velocity can then be measured by analyzing a high frequency component of a vibrational response spectrum since vibrational energy is proportional to speed. 
       FIG. 6  is a set of graphs illustrating raw acceleration, filtered acceleration, and acceleration noise generated from a motion sequence of an input device  102 . The data points illustrated in the raw acceleration graph  602  were collected from a micro-electromechanical accelerometer disposed within the input device  102 . The filtered acceleration graph  604  illustrates the results of applying a low pass filter to the raw acceleration signal depicted in the raw acceleration graph  602 . The acceleration noise graph  606  illustrates the high frequency component of the same signal. In conventional input devices, this high frequency component is typically discarded. 
     However, as evidenced by the figure, the intensity of the high frequency component correlates with sliding motion. As depicted in graph  606 , the amplitude of the high frequency component is large when movement occurs, and is almost zero when no motion occurs. As such, this high frequency component may be analyzed in order to determine the speed of the input device  102 . 
     Any number of techniques may then be utilized to determine the speed of the input device  102  according to embodiments of the present invention. For example, in some embodiments, the magnitude of the velocity is determined by counting the number of vibrational spikes detected during a given interval. In this respect, one or more thresholds may be used for the purpose of defining a spike. In other embodiments, the magnitude of the velocity depends upon a total number of exhibited zero-crossings. In still other embodiments, the magnitude of the velocity is estimated by applying a Fourier transformation to a function modeled from a portion of the response spectrum. Note that in embodiments where multiple methods are utilized, outputs from each method may be weighted and averaged in order to estimate speed. 
     Referring again to  FIG. 3 , data comprising vibrational signals may be written to a local memory source  326  before being provided as input to the response spectrum analysis module  334 . In one embodiment, the response spectrum analysis module  334  is adapted to analyze the data in order to estimate the speed of the input device. In other embodiments, the data comprising vibrational signals is directly written to the memory  312 . In still other embodiments, the data comprising vibrational signals is stored in external memory (e.g. a hard disk of the computer  106 ) and the input device transmits raw data to the computer  106  for processing. 
     Also note that even though  FIG. 3  depicts the response spectrum analysis module  334  as being disposed within the speed detection module  330 , this is not strictly necessary according to some embodiments of the present invention. Additionally, one or more separate modules may comprise at least a portion of the logic necessary for analyzing the provided data. For example, in some embodiments, the force sensor  322  provides raw data to the data integration module  314 . The data integration module  314  comprises any logic necessary for response spectrum analysis. 
     According to some embodiments, data generated from the direction detection module  320  and from the speed detection module  330  is then provided to the data integration module  314 . The data integration module  314  synthesizes the data in order to determine the velocity and/or position of the input device  102 . In alternative embodiments, the data integration module  314  may be located in either the input device  102  or the receiving device  106 . 
     In some embodiments, the data provided to the data integration module  314  comprises calculated speeds of the input device  102 . In other embodiments, the data comprises one or more signals extracted from a response spectrum. According to embodiments where the direction detection module  320  is adapted to provide the data integration module  314  with an estimate of speed independent from the estimate of speed provided by the speed detection module  320 , these estimates may be weighted and/or averaged according to a predetermined set of criteria. 
     According to some embodiments, the estimate of speed generated by the speed detection module  330  is obtained by combining vibration and acceleration information across different frequency domains. Note that the frequency dependence of the input device  102  may depend upon its housing (input device body), the sensor response, the type of motion exhibited, the surface  104 , and the sliding speed. 
     In certain input devices  102  comprising ADXL203 accelerometers, for example, experimental vibration response measurements have indicated vibration peaks at approximately 1000 Hz and 5000 Hz. Data generated from these experiments indicate that the 5000 Hz peak is sensitive to high sliding speeds and has a better signal-to-noise ratio, while the 1000 Hz peak has a much higher sensitivity at lower speeds, but saturates (i.e. becomes non-linear) at higher speeds. Thus, according to some embodiments of the present invention, a combination of peaks or signals is utilized in order to optimize sliding speed prediction. In many cases, synthesizing data in this manner also yields a larger domain of detectable dynamic motion. 
     It has also been observed that the input device  102  can become dominated by certain “stick-slip” phenomena while operating at lower speeds. Stick-slip refers to surfaces alternating between sticking to each other and sliding over each other, and is often the result of friction varying with applied force. Typically, the static friction coefficient between two surfaces is larger than the corresponding kinetic coefficient. If an applied force is large enough to overcome static friction, then the input device  102  will suddenly move forward, or “slip.” During the course of this motion, the frictional coefficient will decrease from its static value to its kinetic value, while the amount of applied force will also decrease. Once the applied force is no longer able to overcome kinetic friction, the input device  102  will stop moving, or “stick,” while the applied force then increases. The resulting pattern of movement often resembles a series of small steps of “jerks” across a surface  104 . 
     In the present context, small steps or “jerks” are observed as sharp, quick spikes in the acceleration data. According to some embodiments, these “jerks” are detected by applying a root mean square level to the acceleration data recorded over 72-millisecond intervals. At very low speeds, this provides the best estimate of the overall displacement of the input device  102 . 
       FIG. 7  is flow diagram illustrating one method of combining acceleration metrics according to one embodiment of the present invention. At step  702 , acceleration is measured about a given axis. In one embodiment, a 12.50 kHz sample rate of a hundred points is taken over eight millisecond intervals. 
     After sampling, three acceleration metrics are then calculated and analyzed. First, at step  710 , a root mean square level is calculated after applying a 5 kHz bandpass filter to the received signal. Second, at step  720 , a root mean square level is calculated after applying a 1 KHz bandpass filter to the signal. Third, at steps  730 - 734 , the average acceleration over an eight millisecond period is determined and analyzed, and a root mean square level is calculated over a 72 millisecond interval. 
     In each of the three cases, thresholds and exponential weighting are applied to each of the respective results. This is shown at steps  712 ,  722 , and  736 , respectively. Note that any thresholds and method of weighting known in the art may be used in accordance with various applications and embodiments of the present invention. The three determined metrics are then combined at step  750  and reported every eight milliseconds, in accordance with one embodiment of the invention. 
     The synthesis procedures described above advantageously mitigate the effects of errors in velocity detection. For example, if the direction detection module  320  erroneously indicates a non-zero velocity during a time when the input device was stationary, this error may be corrected upon synthesizing data from the direction detection module  320  with data from the speed detection module  330 . In this manner, unwanted cursor drift can be minimized and/or eliminated. Note also that data synthesis may be conducted by one module or distributed across multiple modules according to various embodiments of the present invention. 
     Once the direction and magnitude of the velocity have been ascertained, cursor position may then be updated in any number of ways. The logic for updating cursor position may be comprised entirely within the input device  102 , within one or more remote devices (such as the computer  106 ), or distributed across multiple devices according to various embodiments of the present invention. 
       FIG. 8  is a flow diagram illustrating a method of updating cursor position according to one embodiment of the present invention. Direction and magnitude of velocity (i.e. speed) are initially determined at steps  802  and  804 , respectively. Additionally, a display gain is determined at step  806 . The display gain comprises a multiplier that is used for correlating the speed of the input device  102  to a desired cursor speed. In this respect, a low gain corresponds to a large movement of the input device  102  that triggers a small amount of cursor displacement, while a high gain corresponds to a small movement of the input device  102  that triggers a large amount of cursor displacement. 
     Note that in certain embodiments, other types of non-linear gains are utilized in addition to, or in lieu of, the aforementioned display gain (for example, “acceleration curves” traditionally applied by a computer  106  and its operating system). However, for purposes of the embodiment depicted by  FIG. 8 , these gains are treated as being external to the updating algorithm. 
     In some display devices, cursor updating comprises calculating a separate change in pixels per each dimension of the display navigable by the user. For example, in an application for use on a standard two-dimensional computer monitor where the cursor can move both horizontally (i.e. parallel to the x-axis) and vertically (i.e. parallel to the y-axis), two separate change values are calculated for each update of the cursor. Note that even though the following discussion assumes cursor updating on a two-dimensional display, the invention is not strictly limited to two-dimensional displays. In fact, the same principles are readily extendible to three-dimensional displays and even n-dimensional displays according to the scope of the present invention. 
     After direction, speed, and display gain have been ascertained, the positional change in x and the positional change in y can then be determined at step  808 . In one embodiment, the positional change in x is given as the product of the magnitude of the velocity, the determined X direction unit vector, and the calculated display gain. Likewise, the positional change in y is given as the product of the magnitude of the velocity, the determined Y direction unit vector, and the calculated display gain. 
     According to one embodiment, cursor position is updated by integer amounts (i.e. a non-fractional number of pixels on the screen). However, additional techniques may be employed in order to register input device movement in an amount of less than one pixel. For example, in some embodiments, the positional change value of x and the positional change value in y are stored in separate modules adapted to store fractional movement (e.g., accumulators). This is shown in block  810 . Advantageously, these modules retain their fractional component for use during subsequent cursor update periods. 
     For example, suppose a user moves the input device a distance equivalent to 1.5 pixels during the period of a first cursor update. In the embodiments described above, where the cursor may be updated by integer values, the position of the cursor on the display will move to the right by 1 pixel. However, the fractional residue (0.5) is retained in the x accumulator for use during the subsequent update period. Thus, in the next update period, if the user moved the input device a distance equivalent to another 1.75 pixels, the cursor this time will move to the right by two pixels (1.75+0.5=2.25) with 0.25 stored in the accumulator for the next cursor update period. 
     Blocks  812 - 816  best illustrate this process. At decision block  812 , the system determines whether the value in an accumulator is greater than or equal to one. Note that in some embodiments where a signed value is used to indicate direction, logic adapted to calculate an absolute value is also utilized. In other embodiments, the values stored in one or more accumulators are compared against a negative value (i.e., negative one). If the condition in block  812  is not satisfied, no update to the cursor is necessary for that update period. This is shown at block  814 . Otherwise, if the condition in block  812  is satisfied, the cursor position is updated at block  816 . 
     Although the present invention has been fully described in connection with embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the present invention as defined by the appended claims. 
     Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as mean “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, a group of items linked with the conjunction “and” should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as “and/or” unless expressly stated otherwise. Similarly, a group of items linked with the conjunction “or” should not be read as requiring mutual exclusivity among that group, but rather should also be read as “and/or” unless expressly stated otherwise. Furthermore, although items, elements or components of the disclosure may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated. The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent.

Metadata:
Filing Date: 20080922
Publication Date: 20170502
Grant Date: 20170502
Priority Date: 20080922
Inventors: AMM DAVID T.
LEUNG OMAR S.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/03543", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0383", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/03543", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03543", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0383", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0383", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 42037128