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(11) | EP 1 233 505 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Driving signal for electrodynamic vibration devices |
| (57) The present invention relates to a method for driving an electrodynamic vibration
device for outputting a vibration signal with a predetermined vibration strength for
a mobile telecommunication means, whereby the electrodynamic vibration device is driven
by an alternating current driving signal. The driving signal comprises time successive
sinewave signals of varying periods, whereby the variation of the periods is set so,
that the duration of each alternating current signal with constant period is shorter
than 25 ms. Further, the present invention relates to a driving means (2) for driving an electrodynamic vibration device for outputting a vibration signal with a predetermined vibration strength for a mobile telecommunication means for carrying out this method. |
[0001] The present invention relates to a method for driving an electrodynamic or electromagnetic vibration device for outputting a vibration signal and a driving means for driving an electrodynamic or electromagnetic vibration device for outputting a vibration signal.
[0002] Vibration signal or alert is a standard feature for mobile telecommunication means like mobile phones for GSM (Global System for Mobile Telecommunication) or UMTS (Universal Mobile Telecommunication System). Known devices for generating vibration signals are often DC-motors with an excenter weight inside the mobile phone. The disadvantage of this solution is, that these motors are fairly expensive, they need space and they are heavy in weight.
[0003] These are the reasons why these motors are more and more replaced by electrodynamic transducers (further called electrodynamic vibration devices), which are driven with a sinewave current signal (further called sinewave signal) at their resonant frequency. Sometimes the vibration function is combined in one signalling device with a speaker, ringer and/or receiver function.
[0004] The function of an electrodynamic vibration device for generating a vibration signal bases on an elastically suspended weight of a predetermined mass, which is brought to oscillation by an alternating magnetic field. Therefore, the electrodynamic vibration device comprises a coil for generating an alternating magnetic field caused by a sinewave signal, and the elastically suspended weight, which is normally a magnetic yoke with a predetermined weight and is brought to oscillation by the alternating magnetic field. The oscillation of the weight is transmitted through the elastic suspension (e.g. spiral springs) to the fixing of the weight and consequently to the case of the mobile telecommunication means. The output vibration strength is thereby maximal at the resonant frequency.
[0005] The resonant frequency of those electrodynamic vibration devices is mostly between 100 and 200 Hz and is among other things determined by the elastic suspension (spring) and the weight. The bandwidth of the resonance frequency is rather small, around 10 Hz, and the resonant frequency of the mobile phone depends further on the mechanic load conditions like mass and the support of the mobile phone like suspension (strongly or loosely), clamping more or less tightly. Further, the resonant frequency varies if the mobile telecommunication means is held in the hand, laid on a table, etc. Also, the resonant frequency depends on aging, temperature, tolerance of manufacturing, etc. The resonant frequency thus varies with different external conditions and so it is difficult to determine the exact resonant frequency of the mobile phone for these actual conditions for outputting a vibration signal with a predetermined strength at a predetermined frequency, whereby the predetermined output strength is optimally the maximum output strength at the resonant frequency.
[0006] Figure 6 shows an example of the output vibration strength in dependence on the frequency f of the sinewave signal (solid line). The output vibration strength is maximal at the resonant frequency fres with a bandwidth Δf1. It is seen, that the output vibration strength decreases rapidly, when the frequency of the sinewave signal differs from the resonant frequency Δfres.
[0007] To solve this problem, the bandwidth Δf of the resonant frequency fres can be broadened by lowering the quality of the resonant system; see also dotted line of figure 6 with the broadened bandwidth Δf2. This can be achieved by enlarging the damping of the weight through the springs. However, the disadvantage of this solution is, that it is expensive, costly and the driving signal of the electrodynamic vibration device has to be more powerful to output the same strength of the vibration signal over the bandwidth. This reduces consequently the standby-time of the battery or accumulator powered mobile telecommunication means.
[0008] A further solution is to sweep the frequency of the driving signal in the tolerance range of the resonant frequency, whereby a driving signal is generated, which contains signals with different ascending or descending frequencies at different times. Alternatively the signal could be a sequence of sinewave signals with fixed frequencies in the tolerance range of the resonant frequency. Both solutions have the disadvantage, that the strength of the vibration signal appears to change over time depending on the vibration transmission properties for the momentary frequency.
[0009] It is also possible to drive the electrodynamic vibration device with a noise signal with a bandwidth covering the expected range of the resonant frequency. However, it is difficult to generate a noise signal with constant noise power in the range of that predetermined bandwidth. Alternatively a driving signal with different frequencies at the same time (a so called multitone signal) could be provided to the electrodynamic vibration device. Both signals have the disadvantage of a high crest factor and a pronounced time structure, which could be perceived as changing vibration strength over time.
[0010] Another possibility is to establish a feedback loop for the driving signal, using a sensor for the movement of the vibrating mass and thereby tuning the frequency of the driving signal automatically to the actual mechanic resonant frequency. However, this is a costly solution requiring also additional space.
[0011] It is therefore the object of the present invention, to provide a method for driving an electrodynamic vibration device for outputting a vibration signal for a mobile telecommunication means and a driving means for driving an electrodynamic vibration device, which output a vibration signal, which is time-invariant and independent of the mechanic load conditions. Further, this signal should generate minimum audible noise, i.e. it should have as low as possible components at frequencies higher than the vibration frequency.
[0012] The above object is achieved by a method for driving an electrodynamic or electromagnetic vibration device for outputting a vibration signal with a predetermined vibration strength for a mobile telecommunication means according to claim 1. The above object is also achieved by a driving means for driving an electrodynamic or electromagnetic vibration device for outputting a vibration signal with a predetermined vibration strength for a mobile telecommunication means according to claim 8.
[0013] According to the present invention, the electrodynamic vibration device is driven by a driving signal, which comprises time successive alternating current signals of varying periods, whereby the variation of the periods is set so, that the perceived vibration strength is essentially constant for a user over time. Experiments show that the vibration strength is perceived constant for periodical changes of amplitude if the amplitude modulation frequency is higher than 20 Hz. That means that the maximum duration for a signal with constant period is 25 ms in the case that only two signals with different periods are output alternately. If more alternating current signals with different periods are output alternately, the mentioned duration of a signal with constant period will have to be accordingly shorter.
[0014] The advantage of the present invention is, that the strength of the vibration signal is time-invariant and independent of the mechanic load conditions, so that the output vibration strength is varying barely noticeable for a user of the mobile telecommunication means. Further, the present invention is easily to implement in existing systems, since the driving signal according to the present invention can be generated digitally from a processor to get a digital signal with the predetermined periods. Then, the digital signal is converted to analog to get a sinewave signal for driving the electrodynamic vibration device. In another embodiment, the vibration device may also be driven digitally.
[0015] In one embodiment of the present invention the alternating current signals are sinewave signals of the same amplitudes.
[0016] In a further embodiment of the present invention, each signal contains n half periods, whereby n is equal to or larger than one. Preferred, each signal contains one whole-numbered period. If the period of the sinewave signals is varied after one or a few whole-numbered periods, for example between one to three periods, the variation of periods is so fast, that a variation of the output vibration strength is essentially constant and consequently barely noticeable for the user of the mobile telecommunication means.
[0017] Further, the periods are dependent on the resonant frequency of the vibration device and varying in a narrow bandwidth in the range of the expected resonant frequency in order to output a maximum of vibration strength, whereby the resulting vibration strength is little below the maximum output vibration strength by driving the vibration device at exact the resonant frequency.
[0018] Advantageously, the successive sinewave signals of the driving signal are concatenated at equal values in order to obtain a continuous function. Further advantageously the successive sinewave signals are concatenated at points of equal slope in order to obtain a differentiable function as a result. This avoids bounces and edges at the concatenations in order to avoid generating frequencies higher than the vibration frequency, i. e. audible frequencies. When two sinewave signals of equal amplitude are concatenated, this is advantageously done at their common maximum value or minimum value respectively. As both concatenated sinewave functions have the same value and a slope of zero, both above mentioned conditions are fulfilled this way.
[0019] Further advantageously the resulting driving signal is differentiable in each part of it, likewise in order to avoid bounces at the transfer between signals of different periods and consequently to avoid generating frequencies above the vibration frequency.
[0020] This has the advantage, that the driving signal according to the present invention generates minimum audible noise, i.e. it has low as possible components at frequencies higher than the vibration frequency, so that the present invention is advantageously used for combined signal outputting means, for example a vibration means combined with a loudspeaker for outputting a vibration signal as well as an alert tone.
[0021] In a further embodiment of the present invention, the resulting driving signal is amplitude modulated before it is output to the electrodynamic vibration device. This modulation can simply happen by switching on and off the driving signal, e.g. according to the timing of a call sign of an incoming call or according to the setting of the mobile telecommunication means by a user. Advantageously, the driving signal is switched on and/or off at a phase, where the unmodulated value of the driving signal is zero, i.e. at a phase which is zero, π or 2*π, again to avoid generating frequencies above the vibration frequency.
[0022] In the following description, preferred embodiments of the present invention are explained in more detail in relation to the enclosed figures in which
figure 1 shows a schematic diagram of the electrodynamic vibration device combined in one device with a speaker,
figure 2 shows a diagram of the resulting driving signal,
figure 3 to 5 show different examples of the construction of an electrodynamic vibration device, and
figure 6 shows a diagram of the output vibration strength dependent on the frequency of the driving signal.
[0023] Figure 1 shows an example of a signalling device 1 for outputting acoustic and vibration signals in a mobile telecommunication means, whereby the signalling device 1 is a combination of an electrodynamic vibration device and a speaker. Thus, the signalling device 1 is designed to output an acoustic signal like an alert tone as well as a vibration signal. This signalling device 1 is usually mounted inside on the backside of the case of the mobile telecommunication means.
[0024] The signalling 1 device comprises a membrane 11 for outputting the acoustic signal, a weight 12, which represents the driven mass for the vibration device (and the mobile telecommunication means respectively) and is permanent magnetic, and a coil 13 for driving the membrane 11 and the weight 12. The weight 12 is connected by one or more elastic suspensions 14 (e.g. spiral springs) to a casing 15. The weight 12 with a predetermined mass and the elastic suspensions 14 in combination with the casing 15 builds the resonant system, which generates the vibration.
[0025] The signalling device 1 is driven by a driving signal generated by the signal generating means 3 of the driving means 2, whereby the coil 13 is driven by an alternating current signal either in the range of the mechanical resonant frequency in order to output a vibration signal or in the range of an audible signal for outputting an alert tone.
[0026] For outputting an acoustic alert signal the driving means 2 generates a driving signal in kHz-range. This frequency, which is significantly higher than the described resonant frequency for outputting a vibration signal, causes the membrane 11 to oscillate and therefore to output an acoustic signal.
[0027] For outputting an vibration signal, the driving means 2 generates a driving signal according to the present invention. This signal contains frequencies, which are in the range of the (mechanical) resonant frequency of the mobile telecommunication means and causes the weight 12 to oscillate; this frequencies are mostly between 100 and 200 Hz with a predetermined bandwidth, for example with a bandwidth of around 10 Hz.
[0028] Figure 2 shows a schematic diagram of the example of a resulting driving signal according to the present invention, by which the electrodynamic vibration device is driven.
[0029] In this example the periods are varying every whole-numbered period and are concatenated at the maximum amplitude; the time of the periods is given with t1, t2 and t3. The periods can thereby vary time sequentially ascending or descending in period or vary arbitrary. According to the present invention it is more important, that the variation of periods happens fast, that means after one or a few periods, so that the output variation strength is essentially constant.
[0030] Essentially constant means, that the output vibration signal is so low in variation over time, so that the user of the mobile phone barely notes a variation of the vibration strength over time caused by varying the periods during driving the electrodynamic vibration device.
[0031] According to the present invention, the electrodynamic vibration device is driven by a signal which consists of single or few sinewave periods with slightly changing frequency in the range of the bandwidth around the resonant frequency. By doing this, a narrow band signal is generated which causes no noticeable change in vibration strength over time, in contrary to a sweep or longer periods with changing frequency. In order to limit the spectrum of the generated signal to the desired narrow frequency band, the segments are concatenated such that the resulting signal is continuous. Higher frequency products can be even further reduced if the resulting signal is also differentiable. This can be achieved best when the periods are concatenated either at maximum or minimum value.
[0032] In Figure 6 is shown, that the resulting vibration strength, caused by the inertia of the weight, is little below the maximum output vibration strength by the driving the vibration device at exact the resonant frequency fres.
[0033] The present invention is for example implemented as software, whereby the driving signal for driving the signalling means 1 is generated digitally from a processor to get a digital signal with the predetermined periods. Then, the digital signal is converted to analog to get a sinewave signal for driving either the electrodynamic vibration device or the loudspeaker. In another embodiment, the vibration device or loudspeaker may also be driven digitally.
[0034] Figure 3 to 5 shows different examples of the construction of an electrodynamic vibration device, which can be driven by a driving signal according to the present invention, whereby the driving means for generating this driving signal is not shown.
[0035] Figure 3 to 5 shows examples of electrodynamic vibration devices with different constructions of the driven weight 12. Additional, this constructions contain at a time an iron core 16 of different constructions instead of a membrane, so that these devices are only designed for outputting a vibration signal. The iron core 16, however, amplifies the magnetic field generated by the coil 13, so that the output vibration strength is stronger than the output vibration strength by a combined signalling device according to fig. 1 at the same amplitude of the driving signal.
[0036] The different constructions of the weights shown in fig. 2 and 3 causes likewise different vibration strengths of the electrodynamic vibration device at the same amplitude of the driving signal, whereby the construction shown in fig. 3 outputs a stronger vibration signal. However, the simple construction of the weight 12 is less costly than the construction of the weight 12 as shown in fig. 3.
[0037] In Figure 5 the elastic suspension 14 is designed as a leaf spring, at which the weight 12 is suspended. Further, the elastic suspension 14 comprises a permanent magnet 17.
1. Method for driving an electrodynamic or electromagnetic vibration device for outputting
a vibration signal with a predetermined vibration strength for a mobile telecommunication
means, whereby the electrodynamic or electromagnetic vibration device is driven by
an alternating current driving signal, the driving signal comprising time successive
alternating current signals of varying periods (t1...t3), whereby the variation of the periods is set so, that the duration of each alternating
current signal with constant period t1 is shorter than 25 ms.
2. Method according to claim 1,
characterized in
that the alternating current signals are sinewave signals.
characterized in
that the alternating current signals are sinewave signals.
3. Method according to claim 1 or 2,
characterized in
that the alternating current signals feature equal amplitudes.
characterized in
that the alternating current signals feature equal amplitudes.
4. Method according to claim 1, 2 or 3,
characterized in
that the periods (t1...t3) are varying in a narrow bandwidth in the range of the resonant frequency.
characterized in
that the periods (t1...t3) are varying in a narrow bandwidth in the range of the resonant frequency.
5. Method according to one of the claims 1 to 4,
characterized in
that the successive sinewave signals of the driving signal are concatenated at equal value.
characterized in
that the successive sinewave signals of the driving signal are concatenated at equal value.
6. Method according to one of the claims 1 to 5,
characterized in
that the successive sinewave signals of the driving signal are concatenated at equal slope.
characterized in
that the successive sinewave signals of the driving signal are concatenated at equal slope.
7. Method according to one of the claims 1 to 6,
characterized in
that the successive sinewave signals of the driving signal are concatenated at minimum or maximum value.
characterized in
that the successive sinewave signals of the driving signal are concatenated at minimum or maximum value.
8. Method according to one of the claims 1 to 7,
characterized in
that the resulting driving signal is amplitude modulated before it is output to the electrodynamic or electromagnetic vibration device.
characterized in
that the resulting driving signal is amplitude modulated before it is output to the electrodynamic or electromagnetic vibration device.
9. Method according to claim 8,
characterized in that the resulting driving signal is modulated by switching on and off.
characterized in that the resulting driving signal is modulated by switching on and off.
10. Method according to claim 9,
characterized in
that the driving signal is switched on and/or off at a phase, where the unmodulated value of the driving signal is zero.
characterized in
that the driving signal is switched on and/or off at a phase, where the unmodulated value of the driving signal is zero.
11. Driving means (2) for driving an electrodynamic or electromagnetic vibration device
for outputting a vibration signal with a predetermined vibration strength for a mobile
telecommunication means, whereby the electrodynamic or electromagnetic vibration device
is driven by an alternating current driving signal, comprising
a signal generating means (3) for generating a driving signal comprising time successive alternating current signals of varying periods (t1...t3), whereby the variation of the periods (t1...t3) is set so, that the duration of each alternating current signal with constant period (t1) is shorter than 25 ms.
a signal generating means (3) for generating a driving signal comprising time successive alternating current signals of varying periods (t1...t3), whereby the variation of the periods (t1...t3) is set so, that the duration of each alternating current signal with constant period (t1) is shorter than 25 ms.
12. Driving means (2) according to claim 11,
characterized in
that the alternating current signals output by the signal generating means (3) are sinewave signals .
characterized in
that the alternating current signals output by the signal generating means (3) are sinewave signals .
13. Driving means (2) according to claim 11 or 12,
characterized in
that the alternating current signals output by the signal generating means (3) feature equal amplitudes.
characterized in
that the alternating current signals output by the signal generating means (3) feature equal amplitudes.
14. Driving means (2) according to claim 11, 12 or 13,
characterized in
that the signal generating means (3) generates sinewave signals, the periods (t1...t3) of which are varying in a narrow bandwidth in the range of the resonant frequency.
characterized in
that the signal generating means (3) generates sinewave signals, the periods (t1...t3) of which are varying in a narrow bandwidth in the range of the resonant frequency.
15. Driving means (2) according to one of the claims 11 to 14,
characterized in
that the signal generating means (3) concatenates the successive sinewave signals of the driving signal at equal value.
characterized in
that the signal generating means (3) concatenates the successive sinewave signals of the driving signal at equal value.
16. Driving means (2) according to one of the claims 11 to 15,
characterized in
that the signal generating means (3) concatenates the successive sinewave signals of the driving signal at equal slope.
characterized in
that the signal generating means (3) concatenates the successive sinewave signals of the driving signal at equal slope.
17. Driving means (2) according to one of the claims 11 to 16,
characterized in
that the signal generating means (3) concatenates the successive sinewave signals of the driving signal either at maximum or at minimum value.
characterized in
that the signal generating means (3) concatenates the successive sinewave signals of the driving signal either at maximum or at minimum value.
18. Driving means (2) according to one of the claims 11 to 17,
characterized in
that the signal generating means (3) modulates the resulting driving signal in amplitude before the driving signal is output to the electrodynamic or electromagnetic vibration device.
characterized in
that the signal generating means (3) modulates the resulting driving signal in amplitude before the driving signal is output to the electrodynamic or electromagnetic vibration device.
19. Driving means (2) according to claim 18,
characterized in
that the signal generating means (3) modulates the resulting driving signal by switching on and off.
characterized in
that the signal generating means (3) modulates the resulting driving signal by switching on and off.
20. Driving means (2) according to claim 19,
characterized in
that the signal generating means (3) switches the driving signal on and/or off at a phase, where the unmodulated value of the driving signal is zero.
characterized in
that the signal generating means (3) switches the driving signal on and/or off at a phase, where the unmodulated value of the driving signal is zero.