Patent Application
20070178942
The present invention generally relates to portable communication devices and more particularly to a method for abruptly stopping a vibration motor providing tactile feedback to the user of a portable communication device.
Given the rapid introduction of new types of portable electronic devices (e.g., Personal Digital Assistants, Text messaging pagers, MP3 players, cell phones), and the rapid development of novel functionality, an important objective in designing electronic devices is to provide intuitive user interfaces. Computer mouse-like keys and qwerty keyboards are some examples providing intuitive interfaces. However, these interfaces are directed more at providing input to the electronic device rather than providing content related feedback to a user. Touch screens along with graphical user interfaces (GUI) provide information to the user, but only if the user is looking at the screen.
Devices more recently are actively responding to user input by providing tactile cues or responses to the user. The vibrator in a cell phone or pager is a good example. Other examples include an input key that provides a clicking sound when moved; a key or touch screen that moves suddenly or vibrates in an opposed direction to the input; and a key that moves suddenly or vibrates perpendicular to the direction of input in response to a transducer attached to the device housing.
One area in which efforts have been made to improve the user's experience, is audio quality and tactile stimulation. Tactile stimulation is related to audio in the sense that low frequency audio can drive a resonant mass structure to produce a tactile stimulation.
Both audio and tactile stimulation can be provided by a single device known as a multi-function transducer (MFT). Certain types of MFT comprise a resiliently mounted speaker cone connected to a voice coil, and a resiliently mounted magnetic assembly that provides a magnetic field in which the voice coil operates. The resiliently mounted magnetic assembly and the speaker cone can be driven to oscillate by applying signals to the voice coil. The magnetic assembly owing to its mass and the compliance of its mounting will oscillate at a relatively low frequency within the range of frequencies that are easily perceptible by tactile sensation. Alternatively, a separate vibrating device for providing tactile stimulation, and a separate speaker for generating audio are used.
Multifunction transducers (MFTs) and AC linear vibration motors are becoming an often used alternative to DC motors in cellular phones. Such devices are resonant electromagnetic transducers which are typically driven by standard audio signals that contain frequency content at the transducer resonant frequency. One advantage to these types of motors is that they can provide a richer haptic experience, e.g., ramps and envelopes, when compared to their DC counterparts. Also, since they are included in the audio chain, these devices can provide haptic content which is easily incorporated within audio files and thus perfectly synchronized with audio. Finally, in the case of MFTs, a single transducer acts as both speaker and vibration motor, thereby reducing components and overall size of the cellular phone.
A key driver for utilizing MFTs and linear motors is a desire to enhance and improve the user experience. For this reason, much care must be taken in the design of “haptic waveforms”. It may be desired to provide multiple vibrations in succession, and the user must be able to differentiate between the multiple vibrations. However, this is a critical issue as known MFT devices and linear vibration motors require up to 200 milliseconds to decay from their peak acceleration value to 10% of the peak.
Accordingly, it is desirable to provide a method for abruptly stopping a vibration motor providing tactile feedback to the user of a portable communication device. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
A method is provided for abruptly stopping a vibration motor providing tactile feedback to the user of a portable communication device. The method comprises providing a drive waveform including an attack signal, and a stop signal out of phase with the attack signal, to one of the vibration motor or the multi-function transducer to quickly stop the vibration. The drive waveform may include an optional sustain signal subsequent to the attack signal and prior to the stop signal. A file stored in memory is accessed to provide the drive waveform.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.
A method is described for abruptly stopping a multi-function transducer (MFT) or other AC linear resonant vibration motor allowing for a user to more readily discern different haptic vibratory signals. One or more cycles of a sinusoid or multisine signal at the MFT resonant frequency (a “stop” signal) is applied 180 degrees out of phase with an attack signal used to initiate the MFT's vibration. The entire driving waveform may comprise three distinct sections: an “attack” signal, an optional “sustain” signal, and the “stop” signal. The transition from the sustain signal to the stop signal preferably occurs as the sustain signal passes zero volts. A discontinuity in the waveform derivative may occur (sensed as high frequency noise); however, this discontinuity may be substantially removed by the application of a low pass filter which acts to smooth the transition from the sustain signal to the stop signal.
The front 102 and rear 104 housing parts enclose a circuit board 122. In
A multi-function transducer (MFT) 130 is mounted in a semi-cylindrical sleeve 132 that is integrally formed in the back housing part 104. A first pair of spring contacts 134 are coupled (e.g., by soldering) to a first pair of terminals 136 of the MFT 130. When the cellular telephone 100 is assembled the pair of spring contacts 134, make contact with a second pair of contact terminals 138 on the circuit board 122. The MFT 130 is capable of emitting sound and is also capable of vibrating at frequencies within the range of tactile perception, and at sufficient amplitude to be perceptible by tactile perception. The MFT 130 can be used to output multimedia content including audio and vibration signals that are derived from a variety of sources including MIDI files, and compressed audio format files, e.g., .WAV, .MP3 files.
The transceiver module 202 is coupled to the antenna 106. Carrier signals that are modulated by data, e.g., digitally encoded signals for driving the MFT or digitally encoded voice audio, pass between the antenna 106, and the transceiver 202.
A microphone 222 is coupled to the A/D 206. Audio, including spoken words, is input through the microphone 222 and converted to a stream of digital samples by the A/D 206.
The input device 110 is coupled to the input decoder 208. The input decoder 208 serves to identify depressed keys, for example, and provide information identifying each depressed key to the processor 204. The display driver 214 is coupled to a display 226.
The D/A 218 is coupled through an audio amplifier 232 to a speaker 234 and vibratory motor 235. The D/A 218 converts decoded digital audio to analog signals and drives the speaker 234 and vibratory motor 235. The audio amplifier 232 may comprise a plurality of amplifiers with each driving a separate speaker/vibratory motor combination. Alternatively, instead of driving the speaker 234 and vibratory motor 235, the audio amplifier 232 may be coupled to a multi-function transducer 130 as shown by the dotted line 228.
One or more programs for processing data structures that include digitally encoded signals for driving the MFT 130 are stored in the memory 212, and executed by the processor 204. Standard audio format files that include digitally encoded drive signals for the MFT 130 are optionally preprogrammed into the memory 212, or received through the transceiver 202.
The memory 212 is also used to store programs that control other aspects of the operation of the cellular telephone 100. The memory 212 is a form of computer readable medium.
The transceiver 202, the processor 204, the A/D 206, the input decoder 208, the memory 212, the display driver 214, the D/A 218, the audio amplifier 232, and the digital signal bus 220, are embodied in the electrical circuit components 124 and in interconnections of the circuit board 122 shown in
A first spiral arm leaf spring 320 includes an outer ring 322 that is secured between the first 302, and second 304 rings of the housing 312, an inner ring 324 that is fixed (e.g., by spot welding) to a back surface 326 of the cup shaped back plate 314, and two spiral spring arms 328 that extend between the outer ring 322 and the inner ring 324. Similarly, a second spiral arm leaf spring 330 includes an outer ring 332 that is secured between the second 304, and third 306 rings of the housing 312, an inner ring 334 that is fixed (e.g., by spot welding) to a front surface 336 of the cup shaped back plate 314, and two spiral spring arms 338 that extend between the outer ring 332 and the inner ring 334. The magnet 316, pole piece 358, and back plate 314 make up a magnetic assembly 360. The magnetic assembly 360 is biased to a resting position by the first 320, and second 330 spiral arm leaf springs, which serve as a resilient support.
A speaker cone 340 is located concentrically in the housing 312. A speaker cone suspension 342 that is peripherally coupled to the speaker cone 340 is fixed between the third housing ring 306 and the fourth housing ring 308. The speaker cone suspension 342 is flexible to allow for axial movement of the speaker cone 340 in the housing 312. A cylindrical sleeve 344 is attached to a back surface 346 of the speaker cone 340. The cylindrical sleeve 344 is located in the annular gap 318. A voice coil solenoid 348 is wound on the cylindrical sleeve 344. Leads 350 of the voice coil solenoid 348 extend radially along the back surface 346 of the speaker cone 340, between the third 306 and fourth 308 housing rings and out to the terminals 136 of the first MFT 130 that are located on a radial extension 352 of the fourth housing ring 308. A perforated cover 354 is located in front of the speaker cone 340, and is secured (e.g., by press fitting) to the fifth housing ring 310. The speaker cone 340 comprises a front surface 356, which together with the back surface 346 serve to excite sound waves in a surrounding acoustic medium (e.g., air), when the speaker cone 340 is caused to oscillate.
In operation, broadband oscillating signals including audio signals, and vibration signals, that are applied to the leads 350 of the voice coil solenoid 348 produce commensurate currents in the voice coil solenoid 348. Owing to the fact that the voice coil solenoid 348 is immersed in the magnetic field crossing the annular gap 318, the currents flowing in the voice coil result in commensurate Lorentz forces between the voice coil solenoid 348, and the magnetic assembly 360. At any given instant the Lorentz force urges the speaker cone 340, and the magnetic assembly 360 in opposite directions. In so far as oscillating signals are applied to the voice coil solenoid, the Lorentz forces are oscillatory and therefore induce the voice coil solenoid 348, and the magnetic assembly 360 to oscillate. The voice coil solenoid 348 serves as a transducer motor, that is to say an element that converts electrical signals to mechanical forces and motion, in the MFT 130.
The magnetic assembly 360, supported by the spiral arm leaf springs 320, 330, constitutes a first mechanical resonator that exhibits a first resonance characterized by a center frequency and a Quality (Q) factor. The center frequency of the first mechanical resonator can be adjusted by altering the total mass of the magnetic assembly 360 and by altering the resiliency of the spiral arm leaf springs 320, 330 using the formula for the resonant frequency of a simple harmonic oscillator (SHO) given in equation 1, as a guide.
where, k is the spring constant of the SHO; and
m is the mass of the SHO.
The center frequency of the first resonance can advantageously be between 120 and 180 Hz. Frequencies in the aforementioned range have been found to be useful in exciting vibrations that can be felt by users holding, or otherwise mechanically coupled to the cellular telephone 100. More particularly, the center frequency of the first resonance can advantageously be between about 140 and 160 Hz. Frequencies in the latter range have been found to be particularly efficacious.
The speaker cone 340 supported by the speaker cone suspension 342 forms a second resonator. The second resonator exhibits a second resonance that is characterized by a center frequency that is higher than the center frequency of the first resonance. However, the resonance of the second resonator is highly damped by excitation of the sound waves by the speaker cone 340, and thus the speaker cone 340, voice coil solenoid 348 system is able to operate effectively over a broad range of frequencies, to generate sound waves.
The attack signal 402 is typically a sinusoidal drive signal at the resonant frequency of the vibration device. An alternative would be to use a multi-sine signal when the resonant frequency is not known, or when using multiple devices having different resonant frequencies.
Referring to
A series of three cycles of “attack” and “sustain” modes are illustrated in
Referring to
A series of three cycles of “attack”, “sustain”, and stop modes in accordance with the exemplary embodiment are illustrated in
Application of the stop signal 411 that is out of phase with the attack signal 402 immediately following the sustain signal 407 to initiate the stop mode 412, may result in discontinuities in the waveform derivative 414 (i.e. a rapid change in signal direction) as seen in
It has been demonstrated that the method disclosed herein abruptly stops MFTs and AC linear vibration motors to produce crisp, sharp haptic effects which may be placed very close together in time without interfering with adjacent haptic signals.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
