Patent Description:
Active noise cancellation (ANC) systems generally provide an effective approach to cancel low frequency interior noise in a vehicle. Such a low frequency interior noise may comprise engine and road noise. The ANC system generally applies a multiple input multiple output (MIMO) system which includes a plurality of accelerometer sensors, a plurality of error microphones, and a plurality of loudspeakers to collect or deliver information indicative of at least the interior noise. Generally, in order to couple or connect the sensors, microphones, and loudspeakers; a large amount of electrical cable or wiring may be required. Various bus systems or data buses may be utilized to reduce the amount of electrical wiring in the vehicle. However, such data busses may have inherent limitations.

Publication <CIT> discloses a control system that provides centralized active noise control (ANC) and active vibration control (AVC) through a digital network. The control system includes a controller, an audio sub-system, and a vibration sub-system. The audio-sub system includes at least one sound monitoring component and at least one sound outputting component. The vibration sub-system includes at least one vibration monitoring component and at least one vibration actuating component. The controller and the sub-systems are interconnected through the digital network. The controller controls the sub-systems through the digital network to perform the ANC and AVC functions in a holistic approach.

In at least one embodiment, an active noise cancellation system is disclosed. The system includes a first controller, a data bus, and a second controller. The first controller is programmed to receive first information from a plurality of noise sensing devices and second information from an audio system positioned in a vehicle. The first controller is programmed to employ a time division multiplexing scheme on the first information and the second information received to generate a multiplexed stream of data including the first information and the second information. The data bus is configured to transmit the multiplexed stream of data on a single data channel. The second controller is programmed to receive the multiplexed stream of data on the single data channel and to separate the first information from the second information on the multiplexed stream of data to perform ANC functionality. The second information of the multiplexed stream of data is indicative of audio being played back in the vehicle.

In at least another embodiment, an active noise cancellation method is disclosed. The method includes receiving first information from a plurality of noise sensing devices and second information from an audio system positioned in a vehicle and employing a time division multiplexing scheme on the first information and the second information received to generate a multiplexed stream of data including the first information and the second information. The method further includes transmitting the multiplexed stream of data on a single data channel of a data bus and separating the first information from the second information on the multiplexed stream of data to perform ANC functionality. The second information of the multiplexed stream of data is indicative of audio being played back in the vehicle.

The embodiments of the present disclosure are pointed out with particularity in the appended claims. However, other features of the various embodiments will become more apparent and will be best understood by referring to the following detailed description in conjunction with the accompany drawings in which:.

It is recognized that the controllers as disclosed herein may include various microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, such controllers as disclosed utilizes one or more microprocessors to execute a computer-program that is embodied in a non-transitory computer readable medium that is programmed to perform any number of the functions as disclosed. Further, the controller(s) as provided herein includes a housing and the various number of microprocessors, integrated circuits, and memory devices ((e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM)) positioned within the housing. The controller(s) as disclosed also include hardware-based inputs and outputs for receiving and transmitting data, respectively from and to other hardware-based devices as discussed herein.

Active noise cancellation (ANC) systems generally detect disturbances and undesired noise and transmit signals indicative of the undesired noise to an ANC controller. In one example, accelerometers mounted exterior to the vehicle may provide information indicative of road noise and error microphones positioned in an interior of the vehicle may provide information indicative of road noise or engine noise present in the interior of the vehicle. In turn, the ANC controller may transmit sound that is out of phase via one or more loudspeakers in the vehicle. The out of phase audio transmitted by the loudspeakers may cancel the disturbing noise present in the interior of the vehicle.

In general, the disclosed system and method may increase the capability of the sensors and devices in an ANC system and reduce the number of data bus channels. While reducing the number of data bus channels, the disclosed system and method may maintain high levels of ANC system performance. For example, with TDM technology, the ANC system transmits multiple signals on one common channel. Similarly, with TMD, multiplexing and demultiplexing methods are employed to obtain a mixed signal and restore originally transmitted multiple signals.

<FIG> depicts one example of a system <NUM> having a signal flow between various devices of an ANC system <NUM>. It is recognized that the ANC system <NUM> generally includes a plurality of accelerometers <NUM>, a plurality of error microphones <NUM>, a plurality of loudspeakers <NUM>, and an audio system <NUM>. It is also recognized that the audio system <NUM> may include an audio controller and amplifier (not shown) that is programmed to transmit one or more audio signals to the loudspeakers <NUM> for playback in a vehicle <NUM>. In general, the ANC system <NUM> is utilized for a vehicle <NUM>. In this regard, the accelerometers <NUM> may be mounted on an external portion of the vehicle <NUM> and the error microphones <NUM> and the loudspeakers <NUM> may be positioned internally, within the vehicle <NUM>. An ANC controller <NUM> is coupled to the accelerometers <NUM>, the error microphones <NUM>, and the loudspeakers <NUM>. The digital bus <NUM> may enable bi-directional transfer of information between the ANC controller <NUM> and the accelerometers <NUM>, the error microphones <NUM>, and the loudspeakers <NUM>. In one example, the digital bus <NUM> may be implemented as a single Automotive Audio Bus (A2B) to enable bi-directional data transmission between the ANC controller <NUM> and the accelerometers <NUM>, the loudspeakers <NUM>, and the loudspeakers <NUM>. A front-end controller <NUM> may be operably coupled to the accelerometers <NUM>, the error microphones <NUM>, and the loudspeakers <NUM>. The front-end controller <NUM> may convert the data received from the accelerometers <NUM>, the error microphones <NUM>, and the loudspeakers <NUM> into a digital format for transmission on the A2B <NUM>.

The A2B <NUM> may be implemented as a single wire communication bus to reduce the number of wires that would otherwise be coupled between the ANC controller <NUM> and the accelerometers <NUM>, the error microphones <NUM>, and the loudspeakers <NUM>. The front-end controller <NUM> may convert (e.g., analog to digital conversion) the data received from the accelerometers <NUM> the error microphones <NUM>, and the loudspeakers <NUM> into a digital format for transmission on the A2B <NUM> to the ANC controller <NUM>. The front-end controller <NUM> may convert (e.g., digital to analog conversion) for data that is received from the ANC controller <NUM> and intended for transmission to the loudspeakers <NUM>.

It is recognized that the ANC system <NUM> generally provides narrow band noise cancellation (e.g., engine noise cancellation) and/or broad band noise cancellation (e.g., road noise cancellation) to reduce noise in an interior cabin of the vehicle <NUM>. In general, the ANC system <NUM>, may need a large number of different types of input sensors to satisfy ANC system performance requirements. In this case, it may be desirable to provide twenty-eight channels. In general, the A2B <NUM> may have a constant bandwidth and a fixed number of channels <NUM>. For example, the A2B <NUM> may support the twenty-eight channels with each channel <NUM> supporting <NUM> bits. In the event additional channels are needed that exceed the twenty-eight channels, an additional cable and more hardware for the A2B <NUM> may be required which increases the overall cost and complexity of the ANC system <NUM>. Thus, embodiments disclosed herein provide, inter alia, for an advanced ANC system which obviates the need to add additional channels while maintaining ANC system performance. In addition, the embodiments disclosed herein also enable the transfer of higher bandwidth signals in one wire, such as for example, <NUM> bits/s or higher.

<FIG> depicts a system <NUM> for providing time division multiplexing (TDM) for the ANC system <NUM> in accordance with one embodiment. The front-end controller <NUM> may transmit data from each of the plurality of accelerometers <NUM>, the plurality of error microphones <NUM>, and the plurality of loudspeakers <NUM> (e.g., through one common channel) via a time-division multiplexing (TDM) scheme to the ANC controller <NUM>. The front-end controller <NUM> includes a multiplexer circuit <NUM> for transmitting data via the TDM scheme. The front-end controller <NUM> transmits multiple signals into one common signal (or one mixed signal) to the ANC controller <NUM>. In particular, with TDM, it is possible to multiplex four or eight channel signals into one channel in a time iteration (e.g., see channel <NUM> where data is transmitted every fourth time iteration). The ANC controller <NUM> includes a demultiplexer circuit <NUM> that can demultiplex the mixed signal and restore the four channel signals.

<FIG> depicts one example of a data transmission scheme employed by the system <NUM> and another example of the TDM scheme employed by the system <NUM> of <FIG> both in accordance with one embodiment. As noted above, the system <NUM> generally employs a plurality of channels <NUM> while utilizing the A2B <NUM>. This is generally shown at <NUM> in <FIG>. Conversely, the system <NUM> generally employs a TDM scheme that utilizes a single channel <NUM> based on the utilization of the multiplexer circuit <NUM> and the demultiplexer circuit <NUM>. The multiplexing aspect is generally shown at <NUM> and the demultiplexing aspect is generally shown at <NUM>.

As shown at <NUM>, the system <NUM> transmits data over, for example, <NUM> data channels 120a - 120d. In one example, the data transmitted over the channel 120a may correspond to data transmitted from a first accelerometer <NUM> via the front-end controller <NUM>, the data transmitted over the channel 120b may correspond to data transmitted from a second accelerometer <NUM> via the front-end controller <NUM>, the data transmitted over the channel 120c may correspond to data transmitted from a first error microphone <NUM>, and the data transmitted over the channel 120d may correspond to data transmitted from the audio system <NUM>. Due to noise and vibration that originates from a wheel moving on the road surface and/or from an engine compartment, one or more of the accelerometers <NUM> collect the noise and/or vibration information, which has a high correlation to the interior noise. Each of the accelerometers <NUM> may output a related noise and vibration signal (which is indicative of the collected noise and vibration information) that is transferred to the front-end controller <NUM> as ANC system inputs. The front-end controller <NUM> transmits a digital version of the noise and vibration signals for each noise and vibration signal received to the ANC controller <NUM> over a corresponding data channel 120a - 120n. The ANC controller <NUM> then updates an ANC algorithm, accordingly, based on each received noise and vibration signal. To receive the interior noise information, one or more of the error microphones <NUM> may, for example, be positioned in a headliner and/or headrest of seats. Each error microphone <NUM> may output an error signal that is transmitted to the front-end controller <NUM>. Each error signal generally represents noise present in the cabin of the vehicle <NUM> as detected by the error microphones <NUM>. The front-end controller <NUM> transmits a digital version of the error signals for each noise and vibration signal received to the ANC controller <NUM> over the corresponding data channels 120a - 120n. The ANC controller <NUM> then updates an ANC algorithm, accordingly, based on each received error signal and vibration signal.

In general, when the audio system <NUM> plays back audio in the vehicle <NUM>, such audio may affect ANC system performance. Thus, the ANC system (i.e., the ANC controller <NUM>) requires information pertaining to the audio that is being played back in the vehicle <NUM>. The ANC controller <NUM> receives the audio signal that is being played by the audio system <NUM> and prevents the ANC system from canceling the audio (e.g., FM signal, etc.) while the audio system <NUM> plays back the audio in the vehicle <NUM>.

As shown at <NUM>, the system <NUM> (or the front-end controller <NUM> via the multiplexer circuit <NUM>) transmits data for the first accelerometer <NUM>, the second accelerometer <NUM>, the first error microphone <NUM>, and the audio system <NUM> on a single channel <NUM> to the ANC controller <NUM>. The data from as transmitted from each of the first accelerometer <NUM>, the second accelerometer <NUM>, the first error microphone <NUM>, and the audio system <NUM> is divided into corresponding data packets in time slots. Thus, the data is divided over the time slots for transmission one a single channel to the ANC controller <NUM>.

As shown at <NUM>, the system <NUM> (or the ANC controller <NUM> via the demultiplexer circuit <NUM>) aggregates or collects the data and partitions the data to coincide with dedicated channels for the data provided by the first accelerometer <NUM>, the second accelerometer <NUM>, the first error microphone <NUM>, and the audio system <NUM>.

<FIG> depicts one example of a first frame of data <NUM> for one channel on a data bus (e.g., the A2B <NUM>) that employs TDM and a second frame of data <NUM> for one channel on the data bus (e.g., the A2B <NUM>) that employs TDM in accordance with one embodiment. In general, the first frame of data <NUM> may include a total of <NUM> bits of data. Similarly, the second frame of data <NUM> also includes <NUM> bits of data. The second frame of data <NUM> generally illustrates digital data that is generated by the front-end controller <NUM> for information transmitted from the accelerometer <NUM>, the error microphone <NUM>, and the audio system <NUM>.

The second frame of data <NUM> includes a SYNC field <NUM>, a first MAGIC field <NUM>, a first data field <NUM>, a second MAGIC filed <NUM>, a second data field <NUM>, a third MAGIC field <NUM>, and a third data field <NUM>. The second frame of data <NUM> generally corresponds to an example of data transfer for a road noise cancellation (RNC) system that may include, for example, twelve accelerometers <NUM>, eight error microphones <NUM>, and eight loudspeakers <NUM>. The SYNC field <NUM> is fixed as <NUM> x <NUM> and is used to synchronize the data in one physical A2B data channel. Each of the first MAGIC field <NUM>, the second MAGIC field <NUM>, and the third MAGIC field <NUM> includes four bytes that include the following:.

The first MAGIC field <NUM> serves as an identifier that the following data corresponds to data from the accelerometers <NUM> (e.g., see data in the first data field <NUM>), the second MAGIC field <NUM> servers as an identifier that the following data corresponds to data (e.g., see data in the second data field <NUM>) from the error microphones <NUM>, and the third MAGIC field <NUM> serves as an identifier that the following data corresponds to data from the loudspeakers <NUM> (e.g., see data in the second data field <NUM>). The frequency for the transmission of the single channel <NUM> may be, for example, fs / <NUM> = <NUM>/<NUM> = <NUM>.

<FIG> depicts a method <NUM> for providing TDM for the ANC system <NUM> in accordance with one embodiment. In operation <NUM>, the front-end controller <NUM> receives analog information from the accelerometers <NUM>, the error microphones <NUM>, and the loudspeakers <NUM>. In operation <NUM>, the front-end controller <NUM> converts the analog information received from the accelerometers <NUM>, the error microphones <NUM>, and the loudspeakers <NUM> into a digital format. In operation <NUM>, the front-end controller <NUM> employs TDM on the digital data to provide the digital data on a single channel <NUM> to the ANC controller <NUM>. In operation <NUM>, the ANC controller <NUM> demultiplexes the digital data and aggregates (or collects) the information for the accelerometers <NUM>, the error microphones <NUM>, and the loudspeakers <NUM> and processes such information to perform the ANC functionality.

Claim 1:
An active noise cancellation system (<NUM>), the system comprising:
a first controller (<NUM>) programmed to receive first information from a plurality of noise sensing devices and second information from an audio system (<NUM>) positioned in a vehicle, the first controller being programmed to employ a time division multiplexing scheme on the first information and the second information received to generate a multiplexed stream of data including the first information and the second information;
a data bus (<NUM>) configured to transmit the multiplexed stream of data on a single data channel (<NUM>); and
a second controller (<NUM>) programmed to receive the multiplexed stream of data on the single data channel (<NUM>) and to separate the first information from the second information on the multiplexed stream of data to perform ANC functionality,
characterised in that
the second information of the multiplexed stream of data is indicative of audio being played back in the vehicle.