GB2540424A

GB2540424A - Acoustic sensor for use in a vehicle

Info

Publication number: GB2540424A
Application number: GB1512588.3A
Authority: GB
Inventors: Bhimani Alan; Hoare Edward
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2015-07-17
Filing date: 2015-07-17
Publication date: 2017-01-18
Anticipated expiration: 2035-07-17
Also published as: GB2540424B; GB201512588D0

Abstract

An acoustic sensor 12 for mounting on a vehicle 10 has dual proximity detection and terrain identification modes of operation. A grazing angle 92 of a centre line 94 of the transmitted signal when the sensor 12 is in the proximity detection mode of operation is less than the grazing angle of the centre line of the transmitted signal when the sensor is in the terrain identification mode of operation. There may be separate subsystems for the proximity and terrain identification modes. The sensor 12 may be controlled by an input signal to operate in either mode. The proximity detection mode may include a parking assistance mode. The sensor 12 may change its physical orientation to switch between modes, such as by rotation. Switching modes may also be accomplished electronically by shifting the phase of the sensor.

Description

ACOUSTIC SENSOR FOR USE IN A VEHICLE

TECHNICAL FIELD

The invention relates to an acoustic sensor for mounting on a vehicle and particularly, but not exclusively, to a sensor whose mode of operation is adaptable depending on the operation of the vehicle. Aspects of the invention relate to a vehicle-mounted acoustic sensor and to a vehicle itself.

BACKGROUND

Modern vehicles commonly have a number of different sensors for providing sensor output data relating to characteristics of the vehicle and/or its surroundings to a host of vehicle systems. Whilst the use of multiple sensors in vehicles provides an increasing level of sophistication which is desirable, the increased weight, cost and complexity that accompanies the use of such sensors prohibits their widespread use across all vehicle ranges. However, many systems rely on these sensors, so that there exists currently an incompatibility between the desire for sophisticated vehicles and the requirement for more affordable and lightweight vehicle systems. This is a particular problem in vehicles fitted with a terrain identification system which relies on the use of radar and acoustic sensors, all of which add cost, weight and complexity to the vehicle which is not always acceptable.

It is an object of the present invention to address the aforementioned problem. SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a system, a method and a vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided a system for use in a vehicle, the vehicle including at least one vehicle-mounted acoustic sensor operable in a proximity detection mode to send acoustic sensor output data to a proximity detection subsystem of the vehicle and operable in a terrain identification mode to send acoustic sensor output data to a terrain identification subsystem of the vehicle. The system includes an input arranged to receive vehicle output data from at least one vehicle subsystem or sensor, a processor arranged to determine whether to operate the vehicle-mounted acoustic sensor in the proximity detection mode or in the terrain identification mode in dependence on the received vehicle output data, and an output arranged to send a control signal to the at least one acoustic sensor. The system is operable to send a control signal from the output to instruct the at least one acoustic sensor to operate in the determined one of said proximity detection mode and terrain identification mode.

As used herein it will be understood that the phrase “the processor is arranged” means that the processor is provided with a series of electronically executable instructions that are stored in an associated memory means which are executable on the processor so as to carry out the associated stated function.

The proximity detection subsystem is used to warn a vehicle user, either by visual or audible means, of the vehicle’s proximity to an obstacle. In the case of an audible warning, a warning tone may sound with increasing frequency as the obstacle becomes closer to the vehicle. The at least one acoustic sensor used to provide sensor output data to the proximity detection subsystem is able to detect obstacles at short-range (about 0.25 to about 8 metres) but typically only warns the driver of objects within a close range, for example closer than 1.5 to 2 m. The propagated signal generally has a wide angle from the direction in which the sensor is pointed. The acoustic sensor transmits acoustic pulses and then receives back any reflected signal from an obstacle, which is then processed by the proximity detection subsystem to calculate the distance between the vehicle and the obstacle.

The terrain identification system is used to inform the vehicle user of the type of terrain ahead of, or more generally in the vicinity of, the vehicle. This allows the user to alter their driving style or to alter the setup of the vehicle, as appropriate, in order to best negotiate the particular terrain type. Alternatively, the vehicle may be arranged to adjust the vehicle setup automatically. In particular, vehicle-mounted acoustic sensors transmit signals towards the terrain away from the vehicle, and the terrain identification system analyses the received reflected signals in order to determine an indication of the type of terrain in the vicinity of the vehicle.

The system is advantageous in that it can use measurements from various systems on the vehicle to ensure that the at least one acoustic sensor is being used in the most suitable manner. In particular, the system can determine automatically which of the proximity detection or terrain identification mode is more suitable for a particular set of driving conditions, in particular based on the received vehicle output data, and advantageously sends a control signal to adjust the setup of the acoustic sensor so that it may provide useful sensor output data to either the proximity detection or terrain identification subsystem, as appropriate.

The input may be an electrical input and the processor may be an electrical processor. The system may also comprise an electronic memory device electrically coupled to the electronic processor and having instructions stored therein. In such an embodiment the processor is configured to access the memory device and execute the instructions stored therein such that it is operable to determine whether to operate the vehicle-mounted acoustic sensor in the proximity detection mode or in the terrain identification mode and to send a control signal from the output to instruct the at least one acoustic sensor to operate in the determined one of said proximity detection mode and terrain identification mode.

The proximity detection subsystem may include or comprise a parking assist subsystem. In such an embodiment the proximity detection mode is a parking assist mode, and the system is operable to send a control signal from the output to instruct the at least one acoustic sensor to operate in the parking assist mode. The processor may be arranged to determine whether the vehicle is undergoing a parking event in order to determine whether to operate the acoustic sensor in the parking assist mode. The parking assist control signal may be received from one of the systems described above after a determination by the system that a parking event is occurring. Alternatively, the control signal may be received directly from another subsystem or sensor of the vehicle. For example, a parking assist subsystem of the vehicle may be arranged to send the control signal to the acoustic sensor upon activation, or a human-machine interface of the vehicle may be arranged to send the parking assist control signal to the acoustic sensor in response to the driver selecting such a parking assist subsystem. The automatic selection of the parking assist subsystem may be dependent on another, dedicated parking acoustic sensor detecting an object in the vicinity of the vehicle. Similarly, the processor may be arranged to determine whether the vehicle is undergoing a terrain identification event in order to determine whether to operate the acoustic sensor in the terrain identification mode.

In an embodiment, the memory device is arranged to store predetermined vehicle output data, and the processor is arranged to compare the received vehicle output data with the predetermined vehicle output data in order to determine whether to operate the vehicle-mounted acoustic sensor in the proximity detection mode or in the terrain identification mode. The pre-determined data may be a standardized data set loaded onto the memory device before the point of sale of the vehicle and/or system. Alternatively, the predetermined data may be specific to a particular geographical area or climate. The predetermined data may advantageously also be supplemented by the vehicle output data received during use as part of a selflearning process.

The memory device may be arranged to store the data indicative of a current mode of the at least one acoustic sensor. In such an embodiment the processor may be arranged to instruct the at least one sensor to operate in the proximity detection mode or terrain identification mode only if the current mode is different from the corresponding determined mode. This advantageously reduces the number of control signals that need to be sent from the processor via the output. The processor may be arranged to update the current mode stored in the memory device in accordance with the sent control signal.

In an embodiment, the vehicle output data includes vehicle speed data and the at least one vehicle subsystem and/or sensor includes a vehicle speed subsystem or sensor. The current speed of the vehicle is likely to be a useful indicator as to which mode it is most suitable that the sensor is in.

The vehicle output data may include vehicle location data and the at least one vehicle subsystem and/or sensor may include a vehicle location subsystem or sensor. Certain geographical locations may be more likely to be associated with either the proximity detection mode (e.g. a known car park or house driveway) or the terrain identification mode (e.g. a known off-road section that needs to be traversed).

The vehicle output data may include vehicle steering input data and the at least one vehicle subsystem and/or sensor may include a vehicle steering input subsystem or sensor. Alternatively, or in addition, the vehicle output data may include data indicating that the proximity detection subsystem is activated, and this may be sufficient to indicate that the processor should instruct the acoustic sensor to switch to the proximity detection mode. Similarly, the vehicle output data may include data indicating that the terrain identification subsystem is activated. Also, the vehicle output data may include data from the parking assist subsystem indicating that the vehicle is not undergoing a parking event, and this may be sufficient to indicate that the acoustic sensor should not be in the proximity detection mode.

The vehicle output data may include data from a dedicated vehicle-mounted parking acoustic sensor that is arranged to send sensor output data to the parking assist subsystem, indicating that the vehicle is undergoing a parking event. The data from the dedicated parking sensor may alternatively indicate that the vehicle is not undergoing a parking event.

According to another aspect of the present invention there is provided a method for use in a vehicle, the vehicle including at least one vehicle-mounted acoustic sensor operable in a proximity detection mode to send acoustic sensor output data to a proximity detection subsystem of the vehicle and operable in a terrain identification mode to send acoustic sensor output data to a terrain identification subsystem of the vehicle. The method includes receiving vehicle output data from at least one vehicle subsystem or sensor, and determining whether to operate the vehicle-mounted acoustic sensor in the proximity detection mode or in the terrain identification mode in dependence on the received vehicle output data. The method also includes sending a control signal to the at least one acoustic sensor to instruct the at least one acoustic sensor to operate in the determined one of said proximity detection mode and terrain identification mode.

According to a further aspect of the invention there is provided a non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more processors causes the one or more processors to carry out the method disclosed above.

According to another aspect of the present invention there is provided an acoustic sensor for mounting on a vehicle, the sensor having a proximity detection mode of operation and a terrain identification mode of operation. The sensor includes a transmitter arranged to transmit an acoustic signal in a direction away from the vehicle and a receiver arranged to receive a reflected acoustic signal from terrain in the vicinity of the vehicle or from one or more obstacles in the vicinity of the vehicle. A grazing angle of the centre line of the transmitted acoustic signal when the sensor is in the proximity detection mode of operation is less than the grazing angle of the centre line of the transmitted signal when the sensor is in the terrain identification mode of operation.

This acoustic sensor is advantageous in that it is capable of receiving reflected signals from a particular area relative to the vehicle depending on the current needs of the vehicle or driver. The sensor is arranged to switch between the modes of operation depending on the current driving situation.

In an embodiment the sensor includes an output arranged to send acoustic sensor output data indicative of the received reflected signal to a proximity detection subsystem of the vehicle when in the proximity detection mode of operation and to a terrain identification subsystem of the vehicle when in the terrain identification mode of operation.

This reduces the number of acoustic sensors needed on a vehicle while maintaining the same functionality, saving on cost and space on the vehicle (i.e. the present solution is compact).

The sensor may include an input arranged to receive a proximity detection control signal when the vehicle is undergoing a proximity detection event and arranged to receive a terrain identification control signal when the vehicle is undergoing a terrain identification event. In this case the sensor is arranged to operate in the proximity detection mode or the terrain identification mode in dependence on the received control signal. This ensures that the sensor operates in the mode that has been determined either automatically or by the driver to be the most appropriate or useful at a given point in time.

The proximity detection mode of operation may includes a parking assist mode of operation. The input may be arranged to receive a parking assist control signal when the vehicle is undergoing a parking event, and the sensor may be arranged to operate in the parking assist mode when the parking assist control signal is received.

The central grazing angle of the transmitted signal when the sensor is in the proximity detection mode of operation may be less than 5°. More specifically, the central grazing angle when the sensor is in the proximity detection mode of operation may be substantially equal to 0°. The central grazing angle of the transmitted signal when the sensor is in the terrain identification mode may be substantially equal to, or greater than, 10°.

In some embodiments, the sensor is arranged to change its physical orientation with respect to the vehicle in order to switch between the terrain identification mode and the proximity detection mode. The sensor may be arranged to rotate about an axis substantially parallel to the terrain in the vicinity of the vehicle in order to switch between the terrain identification mode and the proximity detection mode. Alternatively, or in addition, the sensor may rotate about the axis through a predetermined angle of rotation in order to switch between the terrain identification mode and the proximity detection mode. The sensor may include an actuator that is operable to change the physical orientation of the sensor with respect to the vehicle. In some embodiments the sensor is arranged to alter the transmitted signal electronically in order to switch the sensor between the terrain identification mode and the proximity detection mode. The transmitted signal may include an upper section and a lower section, and the sensor may be arranged to shift the phase of the lower section of the transmitted signal relative to the upper section in order to switch the sensor between the terrain identification mode and the proximity detection mode. The upper and lower sections may be hemispherical in shape.

The receiver may be arranged to receive a reflected Doppler-shifted signal derived from the acoustic signal transmitted by the transmitter. In such an embodiment the receiver is arranged to receive signals over a range of bandwidths. Therefore, the receiver can receive signals that have undergone zero or a small Doppler-shift when the vehicle is stationary or travelling at low speed, like the receiver of a typical parking sensor. The receiver of the present invention can, however, also receive signals that have undergone a more significant Doppler-shift when the vehicle is moving at greater speed. This is more likely to occur when the vehicle is undergoing a terrain identification event.

According to yet another aspect of the invention there is provided a vehicle including a system as disclosed above and/or an acoustic sensor as disclosed above.

For the purposes of this disclosure, it is to be understood that the control system described herein can comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. As used herein, the term “vehicle control system” will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the method(s) described below). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present invention is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows an overhead view of a vehicle including a vehicle control system (VCS) and acoustic sensors according to an embodiment of the present invention;

Figure 2 is shows the component parts of the VCS shown in Figure 1, together with the inputs to, and outputs from, the VCS;

Figure 3 shows the component parts of one of the acoustic sensors shown in Figure 1, together with the inputs to, and outputs from, the sensor;

Figure 4 is a flow diagram which illustrates a process undertaken by the VCS in Figure 2 according to an embodiment of the invention for determining whether the vehicle is undergoing either a parking event or a terrain identification event;

Figure 5a shows one of the acoustic sensors of Figure 1 in a terrain identification mode according to an embodiment of the invention and Figure 5b shows one of the acoustic sensors of Figure 1 in a parking assist mode according to an embodiment of the invention; and

Figure 6a is a schematic diagram showing the acoustic sensors of Figure 1 transmitting a signal in which the waves in the upper and lower part of the signal are in phase such that the signal is directed substantially parallel to the surface and Figure 6b is a schematic diagram showing the acoustic sensors of Figure 1 transmitting a signal in which the wave in the lower part of the signal is delayed with respect to the wave in the upper part of the signal such that the signal is angled towards the surface.

DETAILED DESCRIPTION

With reference to Figure 1, there is shown a vehicle 10 that includes front, rear and side mounted acoustic sensors 12 and a vehicle control system (VCS) 14. Figure 1 also shows a section of terrain 16 and an obstacle 18 ahead of the vehicle 10. In practice, the obstacle 18 is intended to represent any object that may need to be avoided by the vehicle 10 when it is parking (i.e. during a parking event). Such obstacles could include but are not limited to roadside kerbs, lampposts and other vehicles. The acoustic sensors 12 are sonar sensors, and have a terrain identification mode in which they are arranged to receive a reflected signal from the terrain 16 ahead of the vehicle 10 and a parking assist mode in which they are arranged to receive a reflected signal from the obstacle 18 ahead of the vehicle 10. This is described in greater detail below.

The vehicle 10 includes a parking assist subsystem 20. Although Figure 1 shows the acoustic sensors 12 in communication with the parking assist subsystem 20 only via the VCS 14, in practice the subsystem 20 will be in direct communication with the sensors 12. The parking assist subsystem 20 is arranged to warn the driver of the vehicle 10, either by visual or audible means, of the vehicle’s proximity to the obstacle 18. In the case of an audible warning, a warning tone may sound with increasing frequency as the obstacle becomes closer to the vehicle. When in the parking assist mode, the acoustic sensors 12 transmit acoustic signals 22 and then receive back any reflected signal 24 from the obstacle 18. The sensors 12 then send sensor output data indicative of the reflected signal 24 to the parking assist subsystem 20, the sensor output data then being processed to calculate the distance between the vehicle 10 and the obstacle 18.

The vehicle 10 includes a terrain identification subsystem 26. Again, although Figure 1 shows the acoustic sensors 12 in communication with the terrain identification subsystem 26 only via the VCS 14, in practice the subsystem 26 will be in direct communication with the sensors 12. The terrain identification subsystem 26 is arranged to determine the particular type of terrain 16 ahead of, or perhaps more generally in the vicinity of, the vehicle 10. When in the terrain identification mode, the acoustic sensors 12 transmit the acoustic signals 22 and then receive back any reflected signal 24 from the terrain 16. The sensors 12 then send sensor output data indicative of the reflected signal 24 to the terrain identification subsystem 26, the sensor output data being compared against pre-determined data in order to determine the terrain type. Possible types of terrain include grass, gravel, sand, asphalt and snow. The driver is alerted to the determined terrain type so that he/she may adjust his/her driving style and/or the vehicle setup so as to best negotiate the terrain 16. Alternatively the terrain identification subsystem may automatically adjust the vehicle setup to achieve the same.

In more detail, the acoustic sensor 12 generates an acoustic signal (for example, a conical beam) which a transmitter of the sensor 12 then transmits towards the surface 16 ahead of the vehicle 10. The transmitted acoustic signal scatters upon incidence with, and deflection off, the terrain 16. The physical shape / texture / roughness of the terrain 16 changes certain characteristics of the transmitted acoustic signal. Some of the deflected acoustic signal is reflected back towards the acoustic sensor 12. The received signal is then amplified by an amplifier. A plurality of parameters is then calculated based on the received signal, for example the signal duration above a threshold value and the signal power above the threshold value. The values of these parameters differ for different types of terrain. The particular type of terrain is then determined based on the calculated acoustic parameters, and this may be done using a neural network (NN) algorithm. For example, the NN algorithm may be a Multi-Layer Perceptron (MLP) NN model. Alternatively, any other suitable artificial NN model may be used. The MLP model comprises multiple layers of nodes (or perceptrons) in a multidimensional matrix, with each layer connected to nodes in the next layer. A pre-determined weighting factor (or simply a ‘weight’) is applied to each node in order to maximise the probability of correct terrain classification by the NN algorithm.

The inputs to the NN algorithm are the acoustic parameter values mentioned above. The outputs from the NN algorithm are the possible terrain types in the vicinity of the vehicle 10. When executed, the NN algorithm determines a value relating to the probability of correct classification for each of the outputs (i.e. terrain types) in dependence on a given set of input parameter values. In other words, the NN algorithm maps sets of input acoustic parameters (that are based on collected sensor output data) onto a set of appropriate outputs, where each output represents a different terrain type. The output with the highest value relating to the probability of correct classification represents the determined indication of terrain type ahead of the vehicle 10.

The vehicle 10 also includes other vehicle subsystems, sensors or devices 32 in communication with the VCS 14. These other subsystems 32 provide data to the VCS 14 in order that the VCS 14 may determine whether the vehicle 10 is undergoing a parking event or a terrain identification event. A parking event is taken to be any situation in which the vehicle 10 is parking (i.e. coming to a permanent stop) or moving off from a parked position, and usually occurs at relatively low speed. Typically, a parking event involves: reversing rearwards and sideways into a space between two vehicles before coming to a halt; driving forwards or in reverse into a space flanked by two vehicles before coming to a halt; and/or turning the wheel to steer the car slowly towards the kerbside before coming to a halt. A terrain identification event is taken to be any situation in which the terrain in the vicinity of the vehicle 10 is being determined. In some cases, an indication that the vehicle 10 is not undergoing a parking event is an indication that it is undergoing a terrain identification event.

The other subsystems 32 includes a human machine interface (HMI) 34 which incorporates a display. Via the HMI display, the user receives alerts or advice, relating to a host of vehicle systems, for example, satellite navigation or in-vehicle entertainment systems. The HMI 34 includes a touch-screen keyboard, dial, or voice activation to enable user selection of a particular input for the various vehicle systems which can be controlled. In particular, the user may control manually the setup of various subsystems of the vehicle 10 in dependence on an alert from the VCS 14. The HMI 34 is arranged to enable driver-input (i.e. manual input) to the VCS 14 in relation to the vehicle 10 undergoing either a parking assist event or a terrain identification event following determination of such by the driver.

Figure 2 shows the VCS 14 in more detail. The VCS 14 includes a data processor 40 for determining whether the vehicle 10 is undergoing either a parking event or a terrain identification event. The VCS 14 also includes a data memory or memory device 42 having instructions stored therein, the data processor 40 being arranged to execute said instructions in order to make the above determination. The data memory 42 may be an electronic, non-transitory, computer-readable storage medium. The data memory 42 also includes predetermined vehicle output data with certain data values for the subsystems 32 being associated with a vehicle parking event and/or a terrain identification event. This predetermined data is used by the processor 40 in order that the above determination may be made.

The data processor 40 has an input 44 that is arranged to receive data from the other subsystems 32. It is based on this received data that the processor 40 makes the determination mentioned above. The input 44 from the subsystems 32 includes manual input from the driver via the HMI 34. The other subsystems and sensors 32 can include, for example, a vehicle speed subsystem or sensor, a sensor determining when a reverse gear is selected, a vehicle steering input subsystem or sensor, a brake pedal position sensor, a suspension articulation sensor, an acceleration sensor, a wheel slip sensor, a pitch rate sensor, a yaw rate sensor, an automatic park subsystem, a vehicle location subsystem or sensor such as a Global Positioning

System (GPS), one or more further acoustic sensors, an optical sensor and/or a vehicle-mounted radar sensor.

The data processor 40 has an output 46 that is arranged to send a control signal to the acoustic sensor 12. In particular, the control signal controls the acoustic sensor 12 to switch from the terrain identification mode to the parking assist mode, or from the parking assist mode to the terrain identification mode, as is discussed below.

With reference to Figure 3, the acoustic sensor 12 includes an acoustic transmitter 50 and an acoustic receiver 52. The acoustic sensor 12 includes an input 54 arranged to receive a control signal when the vehicle 10 is determined to be undergoing a parking assist event or a terrain identification event. This control signal is received from the VCS 14. The transmitter 50 is arranged to generate a pulsed or modulated acoustic signal 56 which is to be transmitted by a transmitting antenna in a direction away from the vehicle 10. The direction of the transmitted signal 56 with respect to the vehicle 10 is dependent on whether the acoustic sensor 12 is in the parking assist mode or the terrain identification mode. The direction of the transmitted signal 56 is controlled by changing the physical orientation of the acoustic sensor unit 12 with respect to the vehicle 10. In particular, the acoustic sensor 12 may be mounted on the vehicle 10 such that it is free to rotate about an axis substantially horizontal to the terrain 16, as is discussed later.

Upon incidence with the terrain 16 and/or obstacle 18, some of the transmitted signal 56 will be reflected back towards the acoustic sensor 12, and this reflected signal 58 is received by a receiving antenna of the receiver 52. The power of the received acoustic signal is to be amplified by an amplifier. The acoustic sensor 12 further includes an output 60 arranged to send sensor output data indicative of the received reflected signal 58 to either the parking assist subsystem 20 or the terrain identification subsystem 26, depending on whether the acoustic sensor 12 is in the parking assist mode or the terrain identification mode.

Typically, an acoustic sensor that is dedicated for use by a parking assist subsystem (i.e. sensor output data is sent to the parking assist subsystem only, such as the dedicated parking sensor 13) will be arranged to receive signals covering a relatively narrow range of frequencies (i.e. low bandwidth). This may also be described as having a high ‘quality factor’ or ‘Q factor’. This is in part caused by the piezoelectric material (e.g. quartz) that is used by such sensors, in particular the size and shape of the piezoelectric crystals. For example, the parking sensor 13 transmits signals at a frequency of 50 kHz and typically receives no signals (that is, the reflected part of the transmitted signal, or otherwise) outside the frequency range between about 49 kHz and about 51 kHz. This is sufficient for the dedicated acoustic parking sensor 13 providing sensor output data to a parking assist subsystem only, because parking events typically occur at relatively low vehicle speed and so there is a relatively insignificant Doppler shift between the transmitted and received signals. Such sensors are also relatively inexpensive and they detect a relatively small amount of noise from signals other than the reflections of the transmitted signal.

Since the vehicle 10 may be travelling at a greater speed when the terrain identification subsystem 26 is activated, the Doppler shift between the transmitted signal and the reflected received signal will be greater. In this case the reflected signal may not be received by the acoustic sensor. For example, for a vehicle travelling at 15 m/s, a transmitted signal of frequency 50 kHz may return a reflected signal of frequency 53 kHz, meaning that the parking sensor mentioned above would not detect this reflected signal.

Therefore, the dual-function acoustic sensor 12 of the present embodiment has a lower quality factor such that it is arranged to receiving the Doppler-shifted reflected signal 58 derived from the transmitted signal 56 when the vehicle 10 is travelling at relatively high speed. In other words, the receiver 52 is arranged to receive signals over a range of bandwidths, the range being sufficient to account for a Doppler shift between the acoustic signal transmitted by the transmitter 50 and the reflected signal 58 arriving at the receiver 52. However, adapting the piezoelectric sensor 12 in this way (i.e. so that it receives signals over a greater range of frequencies) can result in interference having a negative effect on the received reflected signals. For example, the sensor 12 may detect signals caused by tyre noise and/or lorry air brakes. The reflected signal from the terrain 16 or obstacle 18 may be selected for processing from all of the received signals by filtering the received signal. The parking assist subsystem 20 or the terrain identification subsystem 26 may perform such noise filtering on the signals received by the receiver 52. Knowledge of the properties of the transmitted signal 56 can assist with this process because it can be used to predict the frequency of the signal that is expected to be received back. In particular, vehicle speed data may be used in order to predict the Doppler shift between the transmitted signal 56 and the reflected signal 58. In the described embodiment the transmitter 50 and receiver 52 are different units: the transmitter 50 is arranged to transmit a signal with a relatively narrow bandwidth, and the receiver 52 is arranged to receive a relatively wide range of bandwidths (before the processor 40 filters out the noise). In different embodiments the transmitter 50 and receiver 52 may be a single unit; however, more energy may need to be put into the transmitted signal in such a case to get back a received signal of comparative power.

Figure 4 shows the steps of a method 70 undertaken by the VCS 14 in order to determine which of the two modes (parking assist or terrain identification) the acoustic sensor 12 should be operating in. At step 72 the VCS 14 receives vehicle output data from at least one of the subsystems or sensors 18. The vehicle output data includes vehicle speed data: if the speed of the vehicle 10 falls below a predetermined constant or adaptive threshold value then this may be indicative that the vehicle 10 is undergoing or about to undergo a parking event. The vehicle output data also includes gear selection data: if a reverse gear is selected then this may be indicative that the vehicle 10 is undergoing a parking event. The vehicle output data also includes vehicle location data such as Global Positioning System (GPS) data. When the vehicle 10 approaches a known parking location (such as a driveway or place of work car park) then this may be indicative that the vehicle 10 is about to undergo a parking event. The vehicle output data also includes vehicle steering input data: if a steering input from the driver is detected then this may be indicative of a parking event. The vehicle output data also includes data received from the dedicated parking acoustic sensor 13. If the dedicated parking sensor 13 detects an object in the vicinity of the vehicle 10 then this may be indicative of a parking event. The vehicle output data includes vehicle slip data: a high degree of vehicle slip may be indicative that the vehicle 10 is traversing challenging terrain and it should be considered as a terrain identification event so that the vehicle setup can be adjusted as appropriate. This list of examples is, of course, not exhaustive.

At step 76 the processor 40 retrieves from the data memory 42 the predetermined vehicle output data corresponding to the subsystems 32 from which the vehicle output data has been received. This includes GPS data of known parking locations as well as thresholds or sliding scale indicators of vehicle speed, steering input, vehicle slip etc. together with an associated likelihood that parking event or terrain identification event is occurring. The vehicle output data also includes the mode in which the acoustic sensor 12 is currently in (i.e. either the parking assist mode or the terrain identification mode).

At step 78 the processor 40 uses the predetermined data to determine whether the vehicle 10 is undergoing a parking event or a terrain identification event. In the presently-described embodiment, the processor 40 determines how many of the subsystems and sensors 32 are sending vehicle output data indicative of a parking event, and if this number is over a predetermined number then it is determined that the vehicle 10 is undergoing a parking event. Alternatively, a value indicative of the probability that the vehicle 10 is undergoing a parking event may be calculated based on the vehicle output data. In this case, if the calculated probability value was greater than a predetermined probability value then the processor 40 would command the acoustic sensor 12 to switch to the parking assist mode.

At step 80 the processor 40 then compares the determined current vehicle event with the mode which the acoustic sensor 12 is currently in. If the determined current vehicle event and the current sensor mode are the same, the processor 40 does not send a control signal to the acoustic sensor 12. If the determined current vehicle event is different from the current sensor mode then at step 80 the processor 40 sends a control signal to the acoustic sensor 12 to switch from the current mode to the mode corresponding to the current vehicle event. For definiteness, this means that if the processor 40 determines that the vehicle 10 is undergoing, or is about to undergo, a parking event when the acoustic sensor 12 is in the terrain identification mode, then the processor 40 is arranged to send a control signal from the output 46 to the acoustic sensor 12 to switch to the parking assist mode.

In the presently-described embodiment, the default mode of the acoustic sensor 12 is the terrain identification mode. Expressed differently, when it is determined that the vehicle 10 is not undergoing a parking event and that the acoustic sensor 12 is currently in the parking assist mode, the processor 40 sends a control signal to the acoustic sensor 12 via the output 46 to switch from the parking assist mode to the terrain identification mode.

Figure 5a shows the acoustic sensor 12 in the terrain identification mode 90. As can be seen in the figure, the acoustic sensor 12 is physically oriented with respect to the vehicle 10 such that the transmitted acoustic signal or beam 56 is directed towards the terrain or surface 16. The transmitted beam 56 insonifies a section of the terrain (or surface) 16, the signal 56 having a central grazing angle 92, that is, the angle the centre 94 of the transmitted signal 56 makes with the terrain 16. In this embodiment the grazing angle 92 is 10°; however, more generally the angle 92 may be between about 8° to about 12°, but generally at least above about 5°. The larger the grazing angle 92, the earlier the beam 56 hits the surface 16, which means the terrain closer to the vehicle 10 is measured.

In the described embodiment, the transmitted signal 56 is transmitted from a height of 0.65 m above the surface 16 i.e. the sensor 12 is mounted to the vehicle 10 at a height of 0.65 m above the surface 16. Of course, the sensor 12 may be mounted to the vehicle 10 at any other suitable height above the surface 16. Therefore in the present embodiment the distance between the points marked A and B is 3.69 m (to two decimal places). The antenna half-width angle 96 of the acoustic beam 56 transmitted by the sensor 12 is 25°; however, any other suitable beamwidth may be used. The transmitted beam 56 is not incident with the surface 16 between the points A and C.

When, at step 82, the processor 40 sends the control signal to switch from the terrain identification mode 90, the acoustic sensor 12 rotates about an axis 98 that is substantially horizontal to the terrain 16 such that it is in the parking assist mode 100, as shown in Figure 5b. As is seen in the figure, transmitted signal 56 of the parking assist mode is angled (with respect to the surface 16) differently compared with the terrain identification mode 90. Specifically, the central grazing angle 92 in this embodiment is 0°. More generally, in the parking assist mode 100 the angle 92 may be at least less than 5°. In this case the transmitted signal 56 reflects mainly from the obstacle 18 back towards the acoustic sensor 12 and not the surface 16, as in Figure 5a.

The sensor 12 rotates about the axis 98 by a predetermined amount, i.e. by a set angle of rotation, in order to switch between different modes of operation. The sensor 12 is caused to rotate by an actuator 99 (such as a linear displacement actuator). The actuator may be electromagnetic (e.g. a solenoid) or may use solid state electronics. Such an actuator could be a piezo actuator or a rotary actuator such as a stepper motor.

If at step 80 the determined current vehicle event is different from the current sensor mode then at step 84 the processor 40 also communicates with the data memory 42 to update the current mode of the acoustic sensor 12, ready to be retrieved and used for the comparison step 80 in the next cycle of the method 70.

In the above-described embodiment, the input 54 receives a control signal from the VCS 14; however, the input 54 may receive a control signal directly from one or more of the other subsystems 18 to switch between parking assist and terrain identification modes (with no determination needed by a separate processor). This may be the case if a determination based on data from more than one subsystem or sensor is not needed, i.e. the switch in mode is dependent only on data from a single subsystem or sensor. For example, if a vehicle speed sensor determines that the speed has dropped below a predetermined threshold value then it may be operable to directly control the acoustic sensor 12 to switch from the parking assist mode to the terrain identification mode, or simply to remain in the parking assist mode. The control signal received by the input 54 may be sent directly from the parking assist subsystem 20 or the terrain identification subsystem 26 automatically in response to one of these subsystems 20, 26 being activated.

In the above-described embodiment, the direction of the transmitted signal 56 is altered by changing the physical orientation of the actual sensor unit. Alternatively, this could be achieved by changing the transmitted signal itself, that is, by altering the beam by electronic means (rather than by mechanical means). The transmitter 50 may comprise an upper and a lower transmitter section, which may be hemispherical. By delaying the wave of the signal in one section of the transmitter 50 relative to the other a phase difference between the signals transmitted between the respective upper and lower signals is created. The amount that the part of the wave transmitted from one section is delayed with respect to the other will determine the particular direction of the transmitted beam.

Figure 6a shows a schematic diagram of the waveforms 110, 112 of the upper hemisphere and lower hemisphere, respectively, of the transmitted signal 56 from the sensor 12 in the case when the (sinusoidal) waves are in phase. As Figure 6a shows, in this case the wave front 114 (that is, the straight line between equivalent points on the waveforms 110, 112) is vertical. The transmitted signal 56 propagates perpendicularly to the wave front 114. Therefore, with the sensor 12 oriented as shown in Figure 6a, the transmitted signal 56 propagates in a direction substantially parallel to the surface 16 when the waves 110, 112 are in phase. Such an arrangement may be used when the sensor 12 is in the proximity detection mode or parking assist mode.

In contrast, Figure 6b shows the case in which the wave 112 transmitted from the lower section of the transmitter is delayed with respect to the wave 110 transmitted in the upper section, i.e. the waves 110, 112 are out of phase. As Figure 6b shows, the wave front 114 is not perpendicular to the surface 16 in this case, and so the transmitted signal 56, which propagates perpendicularly to the wave front, will propagate towards the surface (i.e. the transmitted signal 56 is angled towards the surface 16).

When the processor 40 of the system 14 determines that the sensor 12 should be switched from the proximity detection mode to the terrain identification mode, it sends a control signal from the output 46 to instruct the sensor 12 to delay the wave 112 transmitted from the lower section with respect to the wave 110 transmitted from the upper section, by an appropriate amount, so as to angle the transmitted signal 56 towards the surface 16.

More generally, the transmitter and/or the transmitted signal 56 need not be round or spherical, with upper and lower hemispherical sections as described above, but the sensor 12 may instead be arranged to transmit signals of any suitable shape having upper and lower sections.

In the above-described embodiment, if the current vehicle event and the current sensor mode are determined to be the same then no control signal is sent. However, it is possible that a control signal to maintain the current sensor mode is sent to the acoustic sensor 12 from the processor 40. Alternatively to the above-described embodiment, the default mode of the acoustic sensor 12 may be the parking assist mode, or it may be that there is no default mode such that a positive determination of a current vehicle mode is needed before the processor 40 sends a control signal to the acoustic sensor 12 to switch its mode of operation.

The processor 40 in the above-described embodiment sends a control signal only to a single vehicle-mounted sensor; however, it is of course possible that control signals are sent to any number of vehicle-mounted acoustic sensors to switch their mode of operation.

The parking assist subsystem 20 in the above-described embodiment may more generally be a proximity detection subsystem, and the processor 40 determines whether to operate the acoustic sensor 12 in a proximity detection mode or a terrain identification mode. A proximity detection subsystem may be used to detect obstacles around the vehicle 10 even when the vehicle 10 is not undergoing a parking event, but is, for example, travelling off-road or along a narrow path. Such a situation may be referred to a proximity detection event, which may be taken to include, but be more general than, a parking event.

It will be appreciated by a person skilled in the art that the invention could be modified to take many alternative forms to that described herein, without departing from the scope of the appended claims.

Claims

1. An acoustic sensor for mounting on a vehicle, the sensor having a proximity detection mode of operation and a terrain identification mode of operation, and the sensor comprising: a transmitter arranged to transmit an acoustic signal in a direction away from the vehicle; and a receiver arranged to receive a reflected acoustic signal from terrain in the vicinity of the vehicle or from one or more obstacles in the vicinity of the vehicle; wherein a grazing angle if a centre line of the transmitted acoustic signal when the sensor is in the proximity detection mode of operation is less than the grazing angle of the centre line of the transmitted signal when the sensor is in the terrain identification mode of operation.

2. A sensor according to Claim 1, the sensor comprising an output arranged to send acoustic sensor output data indicative of the received reflected signal to a proximity detection subsystem of the vehicle when in the proximity detection mode of operation and to a terrain identification subsystem of the vehicle when in the terrain identification mode of operation.

3. A sensor according to Claim 1 or Claim 2, the sensor comprising an input arranged to receive a proximity detection control signal when the vehicle is undergoing a proximity detection event and arranged to receive a terrain identification control signal when the vehicle is undergoing a terrain identification event, wherein the sensor is arranged to operate in the proximity detection mode or the terrain identification mode in dependence on the received control signal.

4. A sensor according to any previous claim, wherein the proximity detection mode of operation includes a parking assist mode of operation.

5. A sensor according to Claim 4 when dependent on Claim 3, wherein the input is arranged to receive a parking assist control signal when the vehicle is undergoing a parking event, and wherein the sensor is arranged to operate in the parking assist mode when the parking assist control signal is received.

6. A sensor according to any previous claim, wherein the central grazing angle of the transmitted acoustic signal when the sensor is in the proximity detection mode of operation is less than 5°.

7. A sensor according to Claim 6, wherein the central grazing angle of the transmitted acoustic signal when the sensor is in the proximity detection mode of operation is substantially equal to 0°.

8. A sensor according to any previous claim, wherein the central grazing angle of the transmitted acoustic signal when the sensor is in the terrain identification mode is substantially equal to 10°.

9. A sensor according to any previous claim, wherein the sensor is arranged to change its physical orientation with respect to the vehicle in order to switch between the terrain identification mode and the proximity detection mode.

10. A sensor according to Claim 9, wherein the sensor is arranged to rotate about an axis substantially parallel to the terrain in the vicinity of the vehicle in order to switch between the terrain identification mode and the proximity detection mode.

11. A sensor according to Claim 9 or Claim 10, wherein the sensor rotates about the axis through a predetermined angle of rotation in order to switch between the terrain identification mode and the proximity detection mode.

12. A sensor according to any of Claims 9 to 11, wherein the sensor includes an actuator that is operable to change the physical orientation of the sensor with respect to the vehicle.

13. A sensor according to any of Claims 1 to 8, wherein the sensor is arranged to alter the transmitted acoustic signal electronically in order to switch the sensor between the terrain identification mode and the proximity detection mode.

14. A sensor according to Claim 13, wherein the transmitted acoustic signal includes an upper section and a lower section, and wherein the sensor is arranged to shift the phase of the lower section of the transmitted acoustic signal relative to upper section in order to switch the sensor between the terrain identification mode and the proximity detection mode.

15. A sensor according to Claim 14, wherein the upper and lower sections are substantially hemispherical in shape.

16. A sensor according to Claim 14 or Claim 15, wherein the phase difference between the signals transmitted between the respective upper and lower sections is created by delaying the wave of the signal in one section of the transmitter relative to the other.

17. A sensor according to any previous claim, wherein the receiver is arranged to receive a reflected Doppler-shifted signal derived from the acoustic signal transmitted by the transmitter.

18. A vehicle comprising an acoustic sensor according to any of Claims 1 to 17.

19. An acoustic sensor or a vehicle substantially as described herein with reference to the accompanying drawings.