Adaptive reduction of ultrasonic emissions in vehicle object detection systems

Abstract

A remote object detection in a motor vehicle includes an ultrasonic sensor for emitting ultrasonic bursts from an ultrasonic transducer at a standard rate. At least one object is tracked, the at least one object reflecting the ultrasonic bursts to the sensor. The transducer is adaptively set to emit ultrasonic bursts at a reduced rate less than the standard rate based on the results of object tracking. In one embodiment, the ultrasonic bursts are set at the reduced rate when the tracked object maintains a stable relative position. The stable relative position may include the tracked object having a relative velocity less than a threshold. In another embodiment, an extraneous ultrasonic burst originating from the tracked object and a subsequent echo between the motor vehicle and the tracked object can be used by the vehicle to monitor the tracked object while turning off the emission of bursts from the vehicle.

Description

Technical Field

[0001] The present invention relates generally to automotive remote sensing systems and, more particularly, to ultrasonic sonar systems with reduced ultrasonic emissions. Background Art

[0002] As driver assistance and autonomous features continue to evolve, modern vehicles are accumulating a large array of sensors to monitor and measure the driving environment. Ultrasonic sensors, which use radiated ultrasonic waves to measure short-range distances, are an inexpensive addition to the wide variety of sensors typically used in passenger vehicles. The ultrasonic sensors are used to enhance or add redundancy to features such as parking assist, collision avoidance, and adaptive cruise control.

[0003] Passengers cannot hear ultrasonic sound energy because it is beyond the range of human hearing. The biological effects of applying ultrasound directly to the human body (for example, as in ultrasound imaging) are being studied. In the context of factory / work environments, some jurisdictions have adopted exposure limits due to potential complaints of nausea, headaches, dizziness, confusion, and stomach pain from workers using drills, welding tools, or other industrial equipment that may generate high volume levels of ultrasound. Although there is no health risk from accidental exposure to ultrasound generated by automotive sensors, it may still be desirable to reduce exposure. For example, there may be potential effects on sensitive electronic devices used by passengers brought into or near the vehicle (for example, pedestrians) or used in other vehicles. It may also be desirable to consider potential effects on nearby animals such as bats or insects, some of which rely on the ultrasonic sound range for mating, hunting, communication, and navigation.

[0004] In high traffic conditions where the density of vehicles on the road is high, multiple ultrasonic equipped vehicles may be traveling next to each other. Even though interference between nearby systems may not cause problems for object detection and tracking, the presence of multiple systems can cause even higher ultrasonic sound levels in the surrounding environment due to the additive nature of noise. It is desirable to reduce ultrasonic emissions in such conditions. Summary of the invention

[0005] In one aspect of the invention, an object detection device for a motor vehicle includes an ultrasonic ranging sensor having at least one ultrasonic transducer for generating ultrasonic bursts at a controllable rate. A controller tracks at least one object that reflects the ultrasonic bursts to the sensor. The controller provides a command signal to the sensor to adaptively set the controllable rate based on the results of the object tracking. For example, the controller sets the controllable rate to a standard rate, with the exception that when the tracked object maintains a stable relative position, the controllable rate is set to a reduced rate that is less than the standard rate.

[0006] In another embodiment, the controller is configured to identify an incoming ultrasonic burst originating from a tracked object and an echo of the incoming ultrasonic burst due to multiple reflections of the burst between the motor vehicle and the tracked object. The controller uses the incoming ultrasonic burst and the echo to calculate an incoming distance to the tracked object. If the calculated distance and the incoming distance match (i.e., are substantially the same), the ultrasonic burst generated by the ultrasonic ranging sensor is temporarily turned off.

[0007] In another embodiment, the vehicle further comprises a camera-based tracking system in the motor vehicle, the camera-based tracking system being used to determine a visually determined distance to a tracked object using image analysis. The difference between the sonar distance and the visually determined distance is used to determine a calibration factor to adjust the visually determined distance. After determining the calibration factor, the ultrasonic bursts generated by the ultrasonic ranging sensor may be turned off while continuing to monitor the visually determined distance. When the camera-based tracking system is no longer tracking the tracked object, the ultrasonic bursts generated by the ultrasonic ranging sensor are turned back on. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagram showing a vehicle equipped with the ultrasonic remote sensing system of the present invention.

[0009] Figure 2A and Figure 2B The waveform diagrams of the transmitted signal and the received signal appearing at two different burst pulse rates are shown in Figure 2.

[0010] Figure 3 is a flow chart illustrating a preferred method of the present invention.

[0011] Figure 4 It is shown Figure 3 Flowchart of a preferred method for detecting stable tracking in.

[0012] Figure 5 is a diagram illustrating extraneous ultrasonic bursts and multiple echoes used in another embodiment for reducing ultrasonic emissions.

[0013] Figure 6 is a waveform diagram showing an extraneous burst pulse and an echo.

[0014] Figure 7 is a flow chart illustrating the method of the present invention using alien bursts and echoes.

[0015] Figure 8 is a block diagram illustrating another embodiment of the present invention, wherein a vehicle includes sonar tracking and camera-based object tracking.

[0016] Fig. 9 It is shown that the use Figure 8 Flow chart of a preferred method of the present invention for a tracking system. DETAILED DESCRIPTION

[0017] refer to Figure 1 , a motor vehicle 10 has a remote object tracking system (such as a parking assist system, a collision avoidance system, a back-up warning system, or other advanced driver assistance system) having a controller 11 coupled to an ultrasonic ranging sensor 12. The sensor 12 has at least one ultrasonic transducer and acts as an ultrasonic transceiver that transmits and receives ultrasonic sounds to perform a sonar function of detecting nearby objects using reflected ultrasonic waves. Typical ultrasonic sensors that have been commercially used on vehicles transmit ultrasonic waves at about 40 kHz to about 45 kHz, but frequencies from 30 kHz up to over 100 kHz may be used. The controller 11 includes a signal generation block 13, which is coupled to the sensor 12 via an amplifier 14; and a signal recognition block 15, which is coupled to the sensor 12 via an amplifier 16.

[0018] The ultrasonic ranging sensor 12 transmits an ultrasonic beam 17, which may reflect off a remote object 19 (e.g., a nearby vehicle), thereby sending an echo 18 back to the sensor 12. The signal discrimination block 15 detects the echo 18 and determines a time delay, which determines the relative distance to the object 19. The object tracking block 20 monitors the changing position of the object 19. Based on the position or changing position of the object 19, the interface 21 may generate a warning to the driver or may control the steering or braking of the vehicle 10.

[0019] In a typical sonar-type object tracking function, ultrasonic waves are generated in the form of bursts emitted toward a desired detection zone. Each burst has a specific duration and may include amplitude and / or frequency modulation during the burst to facilitate identification of return echoes. The bursts are repeated at a burst repetition rate sufficient to ensure that the speed of a moving object can be accurately assessed. In the present invention, the burst rate is controllable. For example, there may be a higher standard burst rate under normal circumstances, and there may be a reduced rate used in other circumstances. In other embodiments, the burst rate may be temporarily turned off while continuing to detect ultrasonic signals from an external source. Therefore, the signal generation block 13 provides a command signal that adaptively sets a controllable burst rate based on various results of the object tracking function.

[0020] Figure 2A shows an ultrasonic transmission signal 25 transmitted by an ultrasonic transducer acting as an ultrasonic speaker, and Figure 2BAn ultrasonic receive signal 26 picked up by an ultrasonic transducer acting as an ultrasonic microphone is shown. After the emission of a first ultrasonic burst 27, a reflected echo 28 is received after a certain time delay, which identifies the distance to a remote object within the detection zone of the sensor. A second burst 29 is emitted after a time t1 corresponding to the standard burst rate, and the subsequent echo 30 again determines the measured sonar distance to the tracked object. Under certain conditions, it is possible to reduce the burst rate (i.e., increase the time delay between adjacent bursts). Therefore, the controllable burst rate can be extended by correspondingly emitting subsequent ultrasonic bursts 31 and 32 after waiting for a time t2 corresponding to the reduced burst rate after the previous burst. Echoes 33 and 34 provide object tracking distance at a slower update rate, which is acceptable under special conditions.

[0021] For example, a vehicle using ultrasonic sensors in stop-and-go traffic can reduce the burst rate of its ultrasonic speakers when there is a low rate of change in the measured distance, or in other words when there is little activity or movement. When the relative distance to the tracked object begins to change (for example, when the vehicle ahead starts moving again after stopping), the ultrasonic system can resume its normal burst rate to update the distance at the frequency required for a quick reaction. This modification has the potential to greatly minimize the impact of ultrasonic emissions by significantly reducing the total amount of ultrasonic waves distributed throughout the surrounding environment.

[0022] Figure 3 A preferred method is shown in which ultrasonic remote sensing is employed using a normal (i.e., standard) burst rate in step 35. The normal rate is configured so that the updated distance measurement is fast enough to characterize the speed or speed change of the tracked object to provide sufficient reaction time to provide a collision warning and / or take automatic evasive action. However, when the tracking result obtained is stable (or remains stable for a predetermined time), the need for rapid updates is reduced. Therefore, the method checks in step 36 whether the tracking result (e.g., the relative distance of the object) is stable. If not, ultrasonic transmission is continued at the normal rate, and the method continuously rechecks stability in step 36. If the result is stable, a command signal is sent to the sensor in step 37, which causes a switch to a reduced burst rate. While continuing to track the object using the reduced rate, the method checks in step 38 whether the tracking result is still stable. If stable, step 37 continuously rechecks stability. If not, a command signal is sent to the sensor in step 39, which causes a switch back to the normal burst rate, and the method returns to step 36.

[0023] Figure 4An example method for checking stability is shown in FIG. 40 . Step 40 checks whether any object is currently being tracked. If not, a stable condition cannot be assumed to exist and it is concluded that the condition is unstable. If an object is being tracked, a check is performed in step 41 to determine whether the relative speed of the tracked object is less than a threshold. If not, the condition is unstable. If the speed is below the threshold, the condition is judged to be stable.

[0024] A second embodiment of the present invention utilizes ultrasonic bursts transmitted by other vehicles in a manner that allows the host vehicle to pause its own transmissions. Figure 5 As shown, host vehicle 45 carries ultrasonic ranging sensor 46. Nearby vehicle 47 carries its own ultrasonic sensor 48. Vehicles 45 and 47 are arranged so that sonar operation on vehicle 47 causes its sensor 48 to emit ultrasonic waves toward ultrasonic sensor 46 on vehicle 45. In conventional systems, these extraneous ultrasonic bursts would be ignored by the sonar system in vehicle 45 because they do not match any intrinsic ultrasonic bursts emitted by sensor 46. However, as Figure 5 As shown, the original incoming ultrasonic burst may often have enough power to be reflected multiple times between vehicles 45 and 47. The reflection of the incoming ultrasonic wave by the host vehicle 45 produces echo #1, which propagates back toward vehicle 47, where it is reflected again to produce echo #2 directed back toward sensor 46 on vehicle 45. Figure 6 Incoming bursts 50 and 52 are shown as received by sensor 46 on host vehicle 45, and subsequent second echo bursts 51 and 53 are also received by sensor 46. If there is sufficient signal strength to discern the signal nature of the burst, then the time delay t d The sonar distance between vehicles 45 and 47 is identified in the same manner as the intrinsic burst pulses emitted from sensor 46 .

[0025] Figure 7A preferred method for this second embodiment is shown in . In step 60, the host vehicle performs object detection and tracking in step 60 with its ultrasonic sensor activated in normal mode. A check is performed in step 61 to determine whether an incoming ultrasonic emission is received from a nearby vehicle. When an incoming emission is detected, one or more characteristics (e.g., burst frequency, duration, and / or modulation) of the received emission are stored in step 62. After storing at least one characteristic, step 63 checks for received echoes with matching characteristics. In order to distinguish an echo from another direct emission of the original burst from a nearby vehicle, the check may include a check of the signal amplitude. A burst identified as a potential echo should have an amplitude that is reduced by a predetermined amount based on reflection and propagation losses. If no matching echo is detected, return to step 61.

[0026] If the echo is verified as being the result of a direct burst previously received from a nearby vehicle, then the sonar range is calculated based on the time difference between the foreign direct burst and the echo in step 64. In step 65, a check is performed to determine if the calculated foreign distance matches the calculated distance as determined using the active burst from the ultrasonic sensor on the host vehicle. The criteria for a match may include the foreign distance being within a predetermined percentage of the onboard calculated distance. If not, the method returns to step 61.

[0027] When a match is detected in step 65, the transmission of the ultrasonic transducer on the host vehicle can be turned off and the sonar distance is then calculated using the paired external direct burst and the corresponding echo burst. To ensure the ongoing proper determination of the sonar distance, an occasional ultrasonic burst is emitted from the on-board intrinsic ultrasonic sensor and the corresponding calculated distance is compared to the external distance. A check is performed in step 68 to determine whether the two distances are still consistent (i.e., within a predetermined percentage of each other). If consistent, the method returns to step 67 to recheck using the intrinsic burst and distance calculation occasionally. If the distances are no longer consistent, the intrinsic ultrasonic sensor is turned back on in step 69 and the method returns to step 61.

[0028] In such Figure 8 In another embodiment shown, bumper-to-bumper traffic can provide a unique opportunity for sensor fusion. When following the same vehicle for a sufficient amount of time, the forward ultrasonic sensor can be used to calibrate or verify the camera image of the vehicle with reference to ground truth. The distance measurement can be matched to the camera reading frame by frame to produce a visual understanding of depth and distance (by relating the ultrasonic distance measurement to the size of the vehicle ahead). This allows the ultrasonic sensor to be turned off until the vehicle ahead changes lanes, or traffic otherwise changes.

[0029] The vehicle 70 combines the operation of a sonar object detection system 71 with a camera-based tracking system 75 to track nearby vehicles 74. The sonar system 71 has an ultrasonic sensor 72 that transmits ultrasonic bursts 73 toward the vehicle 74. The camera system 75 includes a camera 76 or other optical sensor to obtain an image that includes the nearby vehicle 74. The apparent size 77 within the image is monitored by the tracking system 75 to obtain a visually determined distance (e.g., the actual size of the vehicle 74 estimated based on the specific vehicle model or type identified in the image is combined with the field of view occupied by the target vehicle in the image to derive the visually determined distance). The visually determined distance and the sonar distance are provided to a controller 78, which uses the inherently higher accuracy of the sonar distance to improve the performance of the camera-based system, enabling the sonar system to be temporarily turned off.

[0030] Fig. 9 A preferred method for this embodiment is shown in FIG. A check is performed in step 80 to determine whether the sonar system and the camera tracking system are tracking the same object. If the system is tracking, a calibration (i.e., correction) factor is determined in step 81. The calibration factor can be calculated in response to the difference between the distances obtained simultaneously by the sonar system and the camera system (e.g., as a percentage by which the visually determined distance can be multiplied in order to match the sonar-determined distance). Once the calibration factor is available, the ultrasonic sensor is turned off in step 82. In step 83, the ultrasonic wave is used to track nearby vehicles and their distances are continuously monitored. A check is performed in step 84 to determine whether an object (e.g., a nearby vehicle) is still being tracked. In other words, it is determined whether the vehicle still occupies the detection zone of the sonar-based system. If so, camera monitoring is continued by returning to step 83. If not (e.g., if the vehicle changes lanes or enters a different road), the ultrasonic wave is turned back on and the process returns to step 80.

[0031] The different embodiments described herein may be implemented separately, or may be combined within a single tracking system.Thus, the amount of ultrasound transmission may be adaptively adjusted such that unnecessary transmissions can be avoided.

Claims

1. An object detection device in a motor vehicle, the object detection device comprising: An ultrasonic distance measuring sensor having at least one ultrasonic transducer for generating ultrasonic burst pulses at a controllable rate; as well as a controller for tracking at least one object that reflects the ultrasonic burst to the sensor, wherein the controller provides a command signal to the sensor to adaptively set the controllable rate based on a result of object tracking; wherein the controller sets the controllable rate to a standard rate, except that when the tracked object maintains a stable relative position, the controllable rate is set to a reduced rate less than the standard rate; The stable relative position includes that the tracked object has a relative speed less than a threshold.

2. The apparatus of claim 1 , wherein the result of the object tracking includes a calculated distance to the tracked object, wherein the controller is configured to identify an incoming ultrasonic burst originating from the tracked object and an echo of the incoming ultrasonic burst due to multiple reflections of the incoming ultrasonic burst between the motor vehicle and the tracked object, wherein the controller is configured to calculate an incoming distance to the tracked object using the incoming ultrasonic burst and the echo, and wherein if the calculated distance and the incoming distance match, the ultrasonic burst generated by the ultrasonic ranging sensor is temporarily turned off.

3. The apparatus of claim 2, wherein the ultrasonic burst pulses generated by the ultrasonic ranging sensor are periodically turned back on to re-determine the calculated distance, wherein if the calculated distance and the external distance match, the ultrasonic burst pulses generated by the ultrasonic ranging sensor are temporarily turned off again, and wherein if the calculated distance and the external distance do not match, the controller turns the ultrasonic ranging sensor back on, wherein the controllable rate is set to a standard rate.

4. The apparatus of claim 2, wherein the motor vehicle and the tracked object each include a corresponding wireless transceiver for negotiating to select the motor vehicle or the tracked object to turn off the corresponding ultrasonic ranging sensor.

5. The apparatus of claim 1, further comprising a camera-based tracking system in the motor vehicle, the camera-based tracking system for determining a visually determined distance to a tracked object using image analysis; wherein the result of the object tracking includes a sonar distance to the tracked object; wherein a difference between the sonar distance and the visually determined distance is used to determine a calibration factor to adjust the visually determined distance; wherein after determining the calibration factor, turning off the ultrasonic burst pulses generated by the ultrasonic ranging sensor while continuing to monitor the visually determined distance; and When the camera-based tracking system is no longer tracking the tracked object, the ultrasonic burst pulses generated by the ultrasonic ranging sensor are turned back on.

6. A method for detecting an object in a motor vehicle, the method comprising the following steps: transmitting ultrasonic burst pulses from an ultrasonic transducer at a standard rate; tracking at least one object that reflects the ultrasonic burst to the transducer; as well as adaptively setting the transducer to transmit the ultrasonic bursts at a reduced rate less than the standard rate based on the object tracking result; wherein the ultrasonic burst pulses are set at the reduced rate when the tracked object maintains a stable relative position; The stable relative position includes that the tracked object has a relative speed less than a threshold.

7. The method of claim 6, wherein the result of the object tracking comprises a calculated distance to the tracked object, and wherein the method further comprises the steps of: identifying an incoming ultrasonic burst pulse originating from the tracked object and an echo of the incoming ultrasonic burst pulse due to multiple reflections between the motor vehicle and the tracked object; calculating an incoming distance to the tracked object using the incoming ultrasonic burst and the echo; as well as If the calculated distance and the external distance match, the ultrasonic burst emitted by the transducer is temporarily turned off.

8. The method according to claim 7, further comprising the steps of: periodically re-enabling the ultrasonic burst to re-determine the calculated distance; If the calculated distance and the external distance match, temporarily shutting off the ultrasonic burst emitted by the ultrasonic transducer again; and If the calculated distance and the foreign distance do not match, the burst is transmitted at the standard rate.

9. The method according to claim 7, further comprising the steps of: Negotiation is performed between the motor vehicle and the tracked object via a wireless link to select between the vehicle and the tracked object to shut off transmission of ultrasonic bursts.

10. The method of claim 6, wherein the motor vehicle further comprises a camera-based tracking system for determining a visually determined distance to the tracked object using image analysis, and wherein the method further comprises the steps of: determining a sonar range to the tracked object using the ultrasonic burst; determining a difference between the sonar range and the visually determined range; determining a calibration factor in response to the difference to adjust the visually determined distance; after determining the calibration factor, shutting off the ultrasonic bursts emitted by the ultrasonic transducer while continuing to monitor the visually determined distance using the calibration factor; as well as When the camera-based tracking system is no longer tracking the tracked object, the ultrasonic bursts emitted by the ultrasonic transducer are turned back on.

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