This application claims priority to EP application Serial No. 15185236.5 filed Sep. 15, 2015, the disclosure of which is hereby incorporated in its entirety by reference herein.
The disclosure relates to noise and vibration sensing systems, particularly for use in active road noise control systems, active road noise control systems and noise and vibration sensing methods.
Land based vehicles, when driven on roads and other surfaces, generate low frequency noise known as road noise. Even in modern vehicles, cabin occupants may be exposed to road noise that is transmitted through the structure, e.g., tires-suspension-body-cabin path, and through airborne paths, e.g., tires-body-cabin path, to the cabin. It is desirable to reduce the road noise experienced by cabin occupants. Active Noise, vibration, and harshness (NVH) control technologies, also known as active road noise control (RNC) systems, can be used to reduce these noise components without modifying the vehicle's structure as in active vibration technologies. However, active sound technologies for road noise cancellation may require very specific noise and vibration (N&V) sensor arrangements throughout the vehicle structure in order to observe road noise related noise and vibration signals.
An exemplary noise and vibration sensing system includes an acceleration sensor arrangement including at least one acceleration sensor and is configured to generate at least two sense signals representative of the acceleration that acts on the acceleration sensor arrangement, wherein the sense signals have dynamic ranges which are the ratios between maximum amplitudes of the sense signals and noise created by the acceleration sensor arrangement. The noise and vibration sensing system further includes a summer module configured to sum up the at least two sense signals to provide a sum signal. The sum signal includes noise created by the acceleration sensor arrangement and the sum signal has a dynamic range which is the ratio between a maximum amplitude of the sum signal and the noise included in the sum signal. The dynamic range of the sum signal is greater than an arithmetic mean of the dynamic ranges of the sense signals.
An exemplary road noise control system includes a noise and vibration sensing system, a road noise control module and at least one loudspeaker.
An exemplary noise and vibration sensing method includes generating, with an acceleration sensor arrangement, at least two sense signals representative of at least one of accelerations, motions and vibrations that act on the acceleration sensor arrangement. The sense signals have dynamic ranges that are ratios between maximum amplitudes of the sense signals and noise created by the acceleration sensor arrangement. The method further includes summing up the at least two sense signals to provide a sum signal. The sum signal includes noise created by the acceleration sensor arrangement. The sum signal has a dynamic range which is the ratio between a maximum amplitude of the sum signal and the noise included in the sum signal. The dynamic range of the sum signal is greater than an arithmetic mean of the dynamic ranges of the sense signals.
The disclosure may be better understood from reading the following description of non-limiting embodiments to the attached drawings, in which like elements are referred to with like reference numbers, wherein below:
Noise and vibration sensors provide reference inputs to active RNC systems, for example, multichannel feedforward active road noise control systems, as a basis for generating the anti-noise that reduces or cancels road noise. Noise and vibration sensors may include acceleration sensors such as accelerometers, force gauges, load cells, etc. For example, an accelerometer is a device that measures proper acceleration. Proper acceleration is not the same as coordinate acceleration, which is the rate of change of velocity. Single- and multi-axis models of accelerometers are available for detecting magnitude and direction of the proper acceleration, and can be used to sense orientation, coordinate acceleration, motion, vibration, and shock.
Airborne and structure-borne noise sources are monitored by the noise and vibration sensors in order to provide the highest possible road noise reduction (cancellation) performance between 0 Hz and 1 kHz. For example, acceleration sensors used as input noise and vibration sensors may be disposed across the vehicle to monitor the structural behavior of the suspension and other axle components for global RNC. Above a frequency range that stretches from 0 Hz to approximately 500 Hz, acoustic sensors that measure the airborne road noise may be used as reference control inputs. Furthermore, two microphones may be placed in the headrest in close proximity of the passenger's ears to provide an error signal or error signals in case of binaural reduction or cancellation. The feedforward filters are tuned or adapted to achieve maximum noise reduction or noise cancellation at both ears.
A simple single-channel feedforward active RNC system may be constructed as shown in
A transfer characteristic W(z) of a controllable filter 108 is controlled by an adaptive filter controller 109 which may operate according to a known least mean square (LMS) algorithm based on the error signal e(n) and on the road noise signal x(n) filtered with a transfer characteristic F′(z) by a filter 110, wherein W(z)=−P(z)/F(z). F′(z)=F(z) and F(z) represents the transfer function between a loudspeaker and the microphone 105. A signal y(n) having a waveform inverse in phase to that of the road noise audible within the cabin is generated by an adaptive filter formed by controllable filter 108 and filter controller 109, based on the thus identified transfer characteristic W(z) and the noise and vibration signal x(n). From signal y(n) a waveform inverse in phase to that of the road noise audible within the cabin is then generated by the loudspeaker 111, which may be arranged in the cabin, to thereby reduce the road noise within the cabin. The exemplary system described above employs a straightforward single-channel feedforward filtered-x LMS control structure 107 for the sake of simplicity, but other control structures, for example, multi-channel structures with a multiplicity of additional channels, a multiplicity of additional noise sensors 112, a multiplicity of additional microphones 113, and a multiplicity of additional loudspeakers 114, may be applied as well.
In conventional active RNC systems, the frequency range of noise to be reduced is limited to a low frequency range. That is, the conventional systems are not intended to reduce noise over its entire frequency range. Further, adaptive digital filters used in these systems have such characteristics as to be able to reduce only low frequency noise components, although processing noise over a wide frequency range is desired. In the active RNC systems disclosed herein, careful arrangement of the sensors allows for more sensitivity and a broader operating frequency range.
RNC systems as described above may exhibit a limited noise reduction capability when the acceleration sensors' dynamic ranges, i.e., the ratios between maximum amplitudes of signals output by the sensors and noise that originates from the sensors and that is contained in the signals output by the sensors (i.e., signal-to-noise ratio), are not sufficient, as is the case with conventional acceleration sensors used for suspension set-up and vibration control. However, it is rather costly to provide sensors with better dynamic ranges. In the following, simple ways are described that allow for using acceleration sensors with minor dynamic ranges in active road noise systems.
Referring to
Furthermore, an array with a multiplicity of (e.g., four) acceleration sensors 501-504, which are arranged in a specific pattern, for example, evenly distributed over a virtual or real sphere's surface and pointing radial (r) outward from the sphere, may be employed as shown in
The summing modules 305, 405 and 505 may include, in case of digital signal processing, simple digital hardware adders or signal processors that perform respective adding operations, or may include, in case of analog signal processing, analog summing circuits such as the example circuit shown in
Referring to
In RNC applications acceleration sensors are used as noise and vibration sensors, delivering the desired reference signals. If those signals exhibit a considerable noise floor, which is noise generated by the sensors themselves in contrast to noise and vibrations to be measured, and thus exhibit a small dynamic range, the whole RNC system is doomed to fail. However, acceleration sensors and acceleration sensor arrangements often output a multiplicity of sense signals. If sensor signals stem from multi-axis sensors or sensor arrangements mounted at almost the same local area and/or having the same orientation (x, y or z axis), these signals may be combined as described above to increase the system's dynamic. Thus, an underperforming RNC system may be enhanced by combining appropriate sense signals of a multiplicity of under-performing sensors. Furthermore, multiple cheap low-performing acceleration sensors may be used instead of a single expensive high-performing acceleration sensor to reduce overall costs, balancing out sensor costs and differences in their performance.
The description of embodiments has been presented for purposes of illustration and description. Suitable modifications and variations to the embodiments may be performed in light of the above description or may be acquired from practicing the methods. For example, unless otherwise noted, one or more of the described methods may be performed by a suitable device and/or combination of devices. The described methods and associated actions may also be performed in various orders in addition to the order described in this application, in parallel, and/or simultaneously. The described systems are exemplary in nature and may include additional elements and/or omit elements.
As used in this application, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is stated. Furthermore, references to “one embodiment” or “one example” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. The terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.
Number | Date | Country | Kind |
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15185236 | Sep 2015 | EP | regional |
Number | Name | Date | Kind |
---|---|---|---|
5386372 | Kobayashi | Jan 1995 | A |
6324290 | Murakami | Nov 2001 | B1 |
9404899 | Konopka | Aug 2016 | B1 |
20070265736 | Mensler | Nov 2007 | A1 |
20110142248 | Sakamoto | Jun 2011 | A1 |
20120189132 | Sakamoto | Jul 2012 | A1 |
Number | Date | Country |
---|---|---|
3644858 | Dec 2013 | DE |
0721178 | Jul 1996 | EP |
0762146 | Mar 1997 | EP |
2293116 | Mar 2011 | EP |
2455410 | Jun 2009 | GB |
Entry |
---|
European Search Report for corresponding Application No. 15185236.5, dated Mar. 16, 2016, 7 pages. |
Number | Date | Country | |
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20170076712 A1 | Mar 2017 | US |