JP2017075841A - Object detection device and object detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object detection device and an object detection method that can raise the temperature of an ultrasonic sensor by using a simpler configuration.SOLUTION: An object detection device receives as a reception wave a reflection wave from an object that reflects an ultrasonic wave transmitted as a transmission wave by an ultrasonic sensor 10, and detects the object around a host vehicle 50 on the basis of the reception wave. The object detection device comprises: a low temperature state determination unit for determining whether the ultrasonic sensor 10 is in a prescribe low temperature state or not; and a heating control unit for raising the temperature of the ultrasonic sensor 10 by heat generated by driving the ultrasonic sensor 10 on the condition that it is determined that the ultrasonic sensor 10 is in the low temperature state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an object detection apparatus and an object detection method for detecting an object existing around a host vehicle by transmitting and receiving ultrasonic waves by an ultrasonic sensor.

  2. Description of the Related Art An object detection device that detects an object existing around a host vehicle by transmitting and receiving ultrasonic waves using an ultrasonic sensor mounted on the host vehicle is known.

  Since this type of ultrasonic sensor is installed outside the vehicle, when the vehicle travels on a snowy road, or when the outside air temperature is below zero, the ultrasonic sensor is The sensor may be frozen. If the ultrasonic sensor is frozen, ultrasonic waves cannot be transmitted and received correctly, and the object detection accuracy may be reduced.

  Therefore, it has been proposed that a heating element is provided in the ultrasonic sensor, and heat is supplied to the ultrasonic sensor by energizing the heating element to eliminate the frozen state of the ultrasonic sensor (see Patent Document 1).

Japanese Utility Model Publication No. 60-189872

  However, adding a new heating element configuration to the ultrasonic sensor leads to an increase in the number of parts and an increase in cost.

  The present invention has been made in view of the above, and has as its main object to provide an object detection device and an object detection method capable of increasing the temperature of an ultrasonic sensor with a simpler configuration.

  In the present invention, when a reflected wave from an ultrasonic object transmitted as a transmitted wave from the ultrasonic sensor (10) is received as a received wave, an object existing around the host vehicle (50) based on the received wave A low temperature state determination unit that determines whether or not the ultrasonic sensor is in a predetermined low temperature state, and a condition that the ultrasonic sensor is determined to be in the low temperature state And a heat generation control unit that raises the temperature of the ultrasonic sensor with heat generated by driving the ultrasonic sensor.

  According to the present invention, when the ultrasonic sensor is in a low temperature state, snow or ice adheres to the ultrasonic sensor, and ultrasonic wave transmission / reception cannot be performed correctly, which may reduce object detection accuracy. Therefore, on the condition that the ultrasonic sensor is in a predetermined low temperature state, the temperature of the ultrasonic sensor is promoted by heat generated by driving the ultrasonic sensor. As described above, the low temperature state of the ultrasonic sensor can be eliminated with a simple configuration.

The top view which shows the attachment position of an ultrasonic sensor. The schematic diagram of the vertical cross section in the attachment position of an ultrasonic sensor. The timing chart of the drive signal of an ultrasonic sensor. The flowchart of the heat generation process of an ultrasonic sensor. The figure which shows the relationship between a low temperature state and the frequency of an ultrasonic wave.

  Hereinafter, an embodiment in which an object detection device is embodied will be described with reference to the drawings. In the present embodiment, an example will be described in which an object detection device is applied to a vehicle system 100 that detects an object existing around the host vehicle 50 by transmitting and receiving ultrasonic waves by the ultrasonic sensor 10 mounted on the host vehicle 50.

  1 and 2, a vehicle system 100 mounted on a host vehicle 50 includes an ultrasonic sensor 10, an ECU 20, an outside air temperature sensor 31, and a vehicle speed sensor 32, which can communicate with each other via a communication line. It is connected.

  The ultrasonic sensor 10 is attached to the bumper 15 at the front part of the vehicle and the rear part of the vehicle. The ultrasonic sensor 10 transmits ultrasonic waves in a predetermined frequency band (for example, 20 to 100 kHz) as a transmission wave, and reflects a reflected wave reflected by an object. Received as a received wave. Note that the number and installation positions of the ultrasonic sensors 10 illustrated in FIG. 1 are examples, and the number and installation positions of the ultrasonic sensors 10 are not limited thereto.

  As shown in FIG. 2, the ultrasonic sensor 10 includes an ultrasonic transducer (hereinafter referred to as a transducer 11), a drive circuit 12, and a temperature sensor 13, which are accommodated in a housing H. The vibrator 11 has a vibration surface 11a that forms the bottom of a bottomed vibration case, and a piezoelectric element 11b that is bonded to the inner surface of the vibration surface 11a, and is vibrated at the resonance frequency of the vibration surface 11a. Sends and receives ultrasonic waves.

  The drive circuit 12 is connected to the vibrator 11 via the wirings L1 and L2, and applies a voltage to the piezoelectric element 11b of the vibrator 11 or a voltage output from the vibrator 11 (piezoelectric element 11b). Or receive. The drive circuit 12 has a control function, and transmits and receives signals to and from the ECU 20.

  The ECU 20 is a computer that includes a CPU, a ROM, a RAM, an I / O, and the like, and implements various functions when the CPU executes a program stored in the ROM.

  For example, the ECU 20 performs an object detection process for detecting an object based on the result of transmission / reception of ultrasonic waves by the ultrasonic sensor 10. The object detection process will be described in detail with reference to FIG. 3. First, at time t0 to t1, based on a command signal from the ECU 20, an electric signal (from the drive circuit 12 to the piezoelectric element 11b as shown in FIG. 3A) ( When the voltage is applied, the piezoelectric element 11b converts the voltage into vibration energy. As a result, as shown in FIG. 3B, the vibration surface 11a is vibrated at the resonance frequency, and an ultrasonic wave (transmission wave) is output. Is done.

  Thereafter, as shown in FIG. 3B, when the ultrasonic wave (received wave) reflected by the object is received by the vibrator 11 at time t2 after a predetermined time has elapsed, the vibration of the vibrating surface 11a is piezoelectric. It is converted into an electric signal (voltage) by the element 11b. The drive circuit 12 performs amplification and filtering processing on the electrical signal input from the piezoelectric element 11b, and outputs the processed signal to the ECU 20. The ECU 20 performs a predetermined calculation process based on the signal received from the drive circuit 12. For example, the distance from the transmission to reception of the ultrasonic wave is obtained to measure the distance to the object.

  The ECU 20 performs an object detection process using the ultrasonic sensor 10 on the condition that the vehicle speed of the host vehicle 50 detected by the vehicle speed sensor 32 is less than a predetermined value. This is because the accuracy of object detection using the ultrasonic sensor 10 is reduced in a high vehicle speed state in which the detection distance of the ultrasonic sensor 10 is relatively short and the vehicle speed of the host vehicle 50 is equal to or higher than a predetermined value. .

  In addition, when the ultrasonic sensor 10 is in a predetermined low temperature state, the ECU 20 of the present embodiment performs a heat generation process for urging the temperature increase by forcibly driving the ultrasonic sensor 10.

  That is, as shown in FIG. 2, when the vibration surface 11a of the ultrasonic sensor 10 is provided outside the vehicle, the vehicle 50 travels on a snowy road, or the outside air temperature is below zero. As a result, snow and ice may adhere to the ultrasonic sensor 10 (vibrating surface 11a). At this time, if the ultrasonic sensor 10 is in a low temperature state, the ultrasonic sensor 10 (vibrating surface 11a) is frozen, and ultrasonic wave transmission / reception cannot be performed correctly, which may reduce object detection accuracy.

  Therefore, the ECU 20 forcibly drives the ultrasonic sensor 10 when the ultrasonic sensor 10 is in a predetermined low temperature state. For example, the ECU 20 determines that the ultrasonic sensor 10 is in a low temperature condition on the condition that the outside air temperature detected by the outside air temperature sensor 31 is a predetermined value (for example, zero degree) or less. In addition to this, the ECU 20 determines the low temperature state of the ultrasonic sensor 10 on the condition that the sensor temperature detected by the temperature sensor 13 built in the ultrasonic sensor 10 is not more than a predetermined value. Also good. Alternatively, the low temperature state of the ultrasonic sensor 10 may be determined based on both the outside air temperature and the sensor temperature.

  Then, the ECU 20 vibrates the vibrator 11 so that no ultrasonic wave is output from the vibrator 11 of the ultrasonic sensor 10 on the condition that the ultrasonic sensor 10 is determined to be in a low temperature state. That is, the vibration surface 11a of the vibrator 11 is vibrated at a frequency other than the resonance frequency. When the vibrator 11 is vibrated at a frequency other than the resonance frequency, no ultrasonic wave is output from the vibrator 11, and the vibration is consumed as heat.

  The heat generated by the vibration of the vibrator 11 is accumulated in the ultrasonic sensor 10, so that the temperature increase of the ultrasonic sensor 10 can be promoted. As described above, the ultrasonic sensor 10 can be prevented from being in a low temperature state.

  In the present embodiment, in the heat generation process of the ultrasonic sensor 10, the vibrator 11 is vibrated at a frequency higher than the resonance frequency. In this case, since the calorific value per unit time increases, the time required for the temperature increase of the ultrasonic sensor 10 can be shortened.

  Then, the ECU 20 monitors the sensor temperature of the ultrasonic sensor 10 detected by the temperature sensor 13, and ends the heat generation process on condition that the sensor temperature has reached a predetermined value. For example, when the sensor temperature reaches 5 to 20 ° C., the heat generation process is terminated.

  Further, the heat generation process performed by the ECU 20 is preferably performed at a timing that does not interfere with object detection by the ultrasonic sensor 10. Therefore, in the present embodiment, heat generation processing is performed when the vehicle speed of the host vehicle 50 is a high vehicle speed that is equal to or higher than a predetermined value.

  Next, a procedure of heat generation processing by the ECU 20 will be described with reference to the flowchart of FIG. The following processing is repeatedly performed by the ECU 20 at a predetermined cycle.

  First, it is determined whether or not the ultrasonic sensor 10 is in a low temperature state (S11). This process is affirmed when the outside air temperature detected by the outside air temperature sensor 31 is less than a predetermined value. If S11 is affirmed, it is determined whether or not heat generation processing is permitted (S12). This process is affirmed when the vehicle speed is greater than or equal to a predetermined value. When S12 is affirmed, it is determined whether the sensor temperature is equal to or lower than a predetermined value (S13). If it is determined in S13 that the sensor temperature is equal to or lower than the predetermined temperature, heat generation processing is performed (S14). That is, the temperature of the ultrasonic sensor 10 is raised by heat generated by driving the vibrator 11 at a frequency other than the resonance frequency. On the other hand, if it is determined in S13 that the sensor temperature is not lower than the predetermined temperature, the heat generation process is stopped (S15). If S11 and S12 are denied, the process is terminated.

  According to the above, the following excellent effects can be achieved.

  -When the ultrasonic sensor 10 is in a low temperature state, snow or ice adheres to the ultrasonic sensor 10, and ultrasonic wave transmission / reception cannot be performed correctly, which may reduce object detection accuracy. Therefore, on the condition that the ultrasonic sensor 10 is in a predetermined low temperature state, the temperature of the ultrasonic sensor 10 is promoted by heat generated by driving the ultrasonic sensor 10. As described above, the low temperature state of the ultrasonic sensor 10 can be eliminated with a simple configuration.

  When the vibrator 11 is vibrated at a frequency different from the resonance frequency of the vibrator 11, the ultrasonic sensor 10 does not output an ultrasonic wave, and the vibration of the vibrator 11 is converted into heat. By utilizing this fact, the temperature increase of the ultrasonic sensor 10 can be promoted with a simple configuration.

  By vibrating the vibrator 11 at a frequency higher than the resonance frequency of the vibrator 11, the number of vibrations per unit time of the vibrator 11 increases, and the amount of heat generated is increased accordingly. Thereby, the time required for the temperature rise of the ultrasonic sensor 10 can be shortened.

  -When the low temperature state of the ultrasonic sensor 10 is eliminated, it is possible to suppress the generation of unnecessary heat loss by stopping the heat generation by driving the ultrasonic sensor 10.

  -In the state of the high vehicle speed in which the vehicle speed of the own vehicle 50 becomes more than predetermined, the accuracy of the object detection using the ultrasonic sensor 10 is lowered. Further, it is conceivable that the ultrasonic sensor 10 detects an object at a relatively close distance. Considering this point, the temperature of the ultrasonic sensor 10 is increased by heat generated by driving the ultrasonic sensor 10 on the condition that the vehicle speed of the host vehicle 50 is higher than a predetermined value. In this case, the temperature increase of the ultrasonic sensor 10 can be promoted without hindering the object detection by the ultrasonic sensor 10.

  It can be determined whether or not the ultrasonic sensor 10 is in a low temperature state based on at least one of the temperature of the ultrasonic sensor 10 and the outside air temperature.

  For example, the above embodiment may be modified as follows. In the following description, the same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the flowchart of FIG. 4 described above, in the heat generation process of S14, the ultrasonic sensor 10 may be vibrated at a frequency different from the resonance frequency. For example, the temperature of the ultrasonic sensor 10 may be promoted by heat generated when the ultrasonic sensor 10 is vibrated at a frequency lower than the resonance frequency. When the vibrator 11 is vibrated at a frequency lower than the resonance frequency of the vibrator 11, the number of vibrations per unit time of the vibrator 11 is reduced. Therefore, the temperature of the ultrasonic sensor 10 is considered while considering energy efficiency. It can encourage a rise.

  -It is assumed that the lower the outside air temperature is, the more difficult the low temperature state of the ultrasonic sensor 10 is resolved (or the low temperature state is likely to be). Therefore, as shown in the map of FIG. 5, the degree of heat generation by the ultrasonic sensor 10 may be set according to the outside air temperature. In the example of FIG. 5, the frequency of the vibrator 11 is determined such that the difference from the resonance frequency increases as the outside air temperature decreases. Note that the degree of heat generation by the ultrasonic sensor 10 may be set according to the sensor temperature instead of the outside air temperature.

  As described above, in consideration of the fact that the ultrasonic sensor 10 is likely to be in a low temperature state as the sensor temperature and the outside air temperature of the ultrasonic sensor 10 are lower, the vibrator 11 is based on at least one of the sensor temperature and the outside air temperature. By setting the frequency at which the ultrasonic sensor 10 is vibrated, the temperature increase of the ultrasonic sensor 10 can be promoted according to the ease of eliminating the low temperature state of the ultrasonic sensor 10.

  In the above, in the case where the ultrasonic wave transmission / reception by the ultrasonic sensor 10 is performed only by transmission / reception by the single ultrasonic sensor 10, that is, when the ultrasonic wave transmission / reception by the ultrasonic sensor 10 is performed only by the direct wave. The temperature of the ultrasonic sensor 10 can be increased by heat generated by increasing the period for outputting the ultrasonic wave while vibrating the vibrator 11 at the resonance frequency. In this case, the temperature increase of the ultrasonic sensor 10 can be promoted while the object detection by the ultrasonic sensor 10 is continued.

  In the above, as shown in FIG. 1, when a plurality of ultrasonic sensors 10 (10 a, 10 b) are provided in the host vehicle 50, the ECU 20 performs object detection by the ultrasonic sensors 10 a, 10 b. The timing of outputting ultrasonic waves from the ultrasonic sensors 10a and 10b is sequentially switched so as to be performed in order. At this time, for example, when the object detection by the ultrasonic sensor 10a is performed, it becomes a rest period in which the object detection by the ultrasonic sensor 10b is not performed. Thus, the heat generation processing of each ultrasonic sensor 10a, 10b during the pause period may be performed using the pause period of object detection in each ultrasonic sensor 10a, 10b. That is, the vibrator 11 of each of the ultrasonic sensors 10a and 10b that is in a rest period is vibrated at a frequency other than the resonance frequency.

  As described above, the temperature of the ultrasonic sensor 10 is promoted by the heat generated by vibrating the vibrator 11 included in the ultrasonic sensor 10 during the object detection pause period at a frequency other than the resonance frequency. it can. At this time, even if object detection is performed by another ultrasonic sensor 10, the ultrasonic sensor 10 during the rest period is vibrated at a frequency other than the resonance frequency, and therefore no ultrasonic wave is output. Therefore, the temperature of the ultrasonic sensor 10 during the rest period can be increased without hindering object detection by the other ultrasonic sensors 10.

  In the above, the temperature of the ultrasonic sensor 10 can be raised by driving the drive circuit 12 in a state where the connection between the vibrator 11 and the drive circuit 12 is cut off to generate a voltage. For example, in FIG. 2, a switch (not shown) is provided in at least one of the wirings L1 and L2 that connect the piezoelectric element 11b and the drive circuit 12. When it is determined that the ultrasonic sensor 10 is in a predetermined low temperature state, the switches provided in the wirings L1 and L2 are turned off (open state). In this state, the drive circuit 12 is driven to generate a voltage. At this time, the voltage generated in the drive circuit 12 is not converted into vibration energy for vibrating the vibrator 11 but is consumed as heat energy. By utilizing this fact, the temperature increase of the ultrasonic sensor 10 can be promoted.

  When the ECU 20 can determine abnormality due to snow or ice adhering to the ultrasonic sensor 10, heat generation by driving the ultrasonic sensor 10 may be performed based on a command signal from the ECU 20.

  DESCRIPTION OF SYMBOLS 10 ... Ultrasonic sensor, 12 ... Drive circuit, 20 ... ECU, 50 ... Own vehicle.

Claims (11)

An object that detects an object existing around the vehicle (50) based on the received wave when a reflected wave from the ultrasonic object transmitted as a transmitted wave from the ultrasonic sensor (10) is received as the received wave A detection device,
A low temperature state determination unit for determining whether or not the ultrasonic sensor is in a predetermined low temperature state;
A heat generation control unit that raises the temperature of the ultrasonic sensor with heat generated by driving the ultrasonic sensor on the condition that the ultrasonic sensor is determined to be in the low temperature state;
An object detection apparatus comprising: The ultrasonic sensor includes a vibrator that transmits and receives ultrasonic waves,
The object detection apparatus according to claim 1, wherein the heat generation control unit raises the temperature of the ultrasonic sensor by heat generated by vibrating the vibrator at a frequency different from a resonance frequency of the vibrator.   The object detection device according to claim 2, wherein the heat generation control unit raises the temperature of the ultrasonic sensor with heat generated by vibrating the vibrator at a frequency higher than the resonance frequency of the vibrator.   The object detection apparatus according to claim 2, wherein the heat generation control unit raises the temperature of the ultrasonic sensor with heat generated by vibrating the vibrator at a frequency lower than the resonance frequency of the vibrator.   The object detection according to any one of claims 2 to 4, wherein the heat generation control unit sets a frequency for vibrating the vibrator based on at least one of a sensor temperature and an outside air temperature of the ultrasonic sensor. apparatus. The ultrasonic sensor is applied to a vehicle provided with a first sensor (10a) and a second sensor (10b),
When the ultrasonic wave is transmitted and received by the first sensor, the ultrasonic wave is not transmitted and received by the second sensor, and when the ultrasonic wave is transmitted and received by the second sensor, the ultrasonic wave is transmitted and received by the first sensor. Is set to not occur,
The heat generation control unit is configured to set the vibrator included in the sensor to a frequency other than the resonance frequency of the vibrator during a rest period of the first sensor and the second sensor that do not transmit / receive ultrasonic waves. The object detection apparatus according to any one of claims 2 to 5, wherein the object detection apparatus is driven by a motor. The ultrasonic sensor includes a vibrator that transmits and receives ultrasonic waves, and a voltage application unit (12) that is connected to the vibrator and applies a voltage so that the vibrator vibrates at a predetermined frequency. ,
The heat generation control unit applies a voltage from the voltage application unit in a state where the connection between the vibrator and the voltage application unit is cut off on condition that the ultrasonic sensor is determined to be in the low temperature state. The object detection apparatus according to claim 1, wherein the temperature of the ultrasonic sensor is increased by heat generated by the operation.   The object detection device according to claim 1, wherein the heat generation control unit stops heat generation by driving the ultrasonic sensor on condition that the low temperature state of the ultrasonic sensor is eliminated. A vehicle speed detector (32) for detecting the vehicle speed of the vehicle on which the ultrasonic sensor is mounted;
The heat generation control unit determines that the ultrasonic sensor is in the low temperature state, and the heat generated by the driving of the ultrasonic sensor on the condition that the vehicle speed is higher than a predetermined value. The object detection device according to claim 1, wherein the temperature is increased.   The low temperature state determination unit determines that the ultrasonic sensor is in a low temperature state when it is determined that at least one of the temperature of the ultrasonic sensor and the outside air temperature is lower than a predetermined value. The object detection apparatus according to claim 1. An object that detects an object existing around the vehicle (50) based on the received wave when a reflected wave from the ultrasonic object transmitted as a transmitted wave from the ultrasonic sensor (10) is received as the received wave An object detection method applied to a detection device,
Determining whether the ultrasonic sensor is in a predetermined low temperature state;
Increasing the temperature of the ultrasonic sensor with heat generated by driving the ultrasonic sensor on the condition that the ultrasonic sensor is determined to be in the low temperature state;
An object detection apparatus comprising:

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