JP7680146B2 - Acceleration sensor correction device, road gradient detection device, and driving recorder - Google Patents

Description

The present invention relates to an acceleration sensor correction device that corrects an acceleration sensor used in a road gradient detection device that detects whether a vehicle is located on a gradient, a road gradient detection device, and a driving recorder.

Conventionally, a vehicle operation management system that reflects road surface conditions such as slopes has been proposed (see Patent Document 1). The conventional operation management system described in Patent Document 1 measures air pressure using a barometer, calculates an altitude value for each unit of travel distance from the air pressure, and compares the altitude difference for each unit of travel distance with a predetermined altitude difference to determine whether the road surface on which the vehicle is traveling has a slope.

The invention described in Patent Document 1 uses a barometer to determine the gradient, but this requires a dedicated and expensive air pressure sensor and control circuit, and the accuracy deteriorates dramatically in environments where the vehicle is subject to sudden changes in air pressure, such as when a window is opened or closed, when wind blows while driving, or when the environment changes suddenly.

There is also a known method of detecting gradient that uses an acceleration sensor. This method calculates the gradient of the road on which the vehicle is traveling by calculating the vehicle body inclination detected by the acceleration sensor and the G (acceleration) value experienced while traveling. However, to ensure detection accuracy, it is important to correct the offset deviation of the acceleration sensor (also called zero point correction).

Patent document 2 describes how the gradient detection unit applies zero point correction to the G-sensor acceleration based on the change in G-sensor acceleration during the vehicle attitude learning period from when the door is opened to when it is closed, in accordance with the vehicle attitude that changes based on people and objects getting on and off. Patent document 2 also describes that when constant speed driving on a flat road is detected, the gradient detection unit further applies zero point correction to the G-sensor acceleration based on the difference between the actual acceleration during constant speed driving on a flat road and the G-sensor acceleration.

JP 2004-46439 A JP 2010-107244 A

The invention described in Patent Document 2 describes applying zero point correction to the G-sensor acceleration in accordance with the vehicle attitude, which changes as people or objects get on and off. However, the places where people or objects get on and off are not necessarily flat. For example, the vehicle attitude while stopped may differ between an inclined road such as a slope and a flat road, which may reduce the accuracy of the zero point correction.

In view of the above problems, the present invention aims to provide an acceleration sensor correction device, a road gradient detection device, and a driving recorder that can more accurately correct gradient detection based on acceleration.

The invention made to solve the above problem is an acceleration sensor correction device that is equipped with an acceleration sensor mounted on a vehicle and detects acceleration acting on the vehicle, a first determination means for determining whether atmospheric pressure information detected inside the vehicle can be received, a receiving means for receiving the atmospheric pressure information when it is determined that the atmospheric pressure information can be received, a second determination means for determining whether the road on which the vehicle is located is flat based on the atmospheric pressure information, and a correction means for performing a zero point correction of the acceleration sensor when it is determined that the road is flat.

As described above, according to the present invention, when atmospheric pressure information is available, it is determined whether the road on which the vehicle is located is flat based on the atmospheric pressure information, and zero point correction is performed if the road is flat, so that zero point correction can be performed reliably on flat ground. Therefore, gradient detection based on acceleration can be made more accurately.

1 is a schematic diagram of a road gradient detection device including an acceleration sensor correction device according to an embodiment of the present invention; 2 is a flowchart of the operation of the acceleration sensor correction device shown in FIG. 1 . 1 is a schematic configuration diagram of a driving recorder according to an embodiment of the present invention;

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a basic configuration diagram of a road gradient detection device 20 equipped with an acceleration sensor correction device according to an embodiment of the present invention. As shown in the figure, the road gradient detection device 20 includes a CPU 1, an EEPROM 2, a wireless communication unit 3, an acceleration sensor 14, a power supply circuit 4, an IGN (ignition) 5, an input I/F circuit 6, output I/F circuits 8 and 9, dials 12 and 13, and a map information storage unit 15. The road gradient detection device 20 receives a vehicle speed pulse 7 and outputs an up signal monitor 10 and a down signal monitor 11.

An ON signal is input to the CPU 1 from the IGN (ignition) 5 via the power supply circuit 4. Then, when the vehicle is traveling, a vehicle speed pulse 7 is supplied to the CPU 1 via the input I/F circuit 6. When the CPU 1 determines that the road surface on which the vehicle is traveling is a slope, it outputs a slope signal via the output I/F circuits 8 and 9 as an up signal monitor 10 and a down signal monitor 11. The CPU 1 also performs zero point correction processing for the acceleration sensor 14, which will be described later.

EEPROM2 has a program storage area that stores the processing programs executed by CPU1, a work area used in various processing steps by CPU1, and a data storage area that stores various data, and is provided so that it can be read and written freely.

The wireless communication unit 3 wirelessly communicates with an information communication terminal 30 that is arranged outside the road gradient detection device 20. The wireless communication unit 3 acquires atmospheric pressure information from the information communication terminal 30. Note that, although in this embodiment, the wireless communication unit 3 is connected to the information communication terminal 30 wirelessly, it may also be connected by wire, for example, via USB (Universal Serial Bus). In other words, the wireless communication unit 3 functions as a receiving means for receiving atmospheric pressure information.

The acceleration sensor 14 measures (detects) the acceleration acting on the vehicle, for example in the direction of travel, and the inclination of the vehicle itself.

Dials 12 and 13 set a threshold value for determining whether the road surface on which the vehicle is traveling is a slope (gradient). In this embodiment, the threshold value is set to, for example, 2.5%.

The map information storage unit 15 stores map information such as road map data for the whole of Japan, facility data for various associated facilities, and data for map matching. The road map data is provided as link data consisting of a road network in which roads on a map are represented by lines, with intersections, branching points, etc., divided into multiple parts as nodes, and the parts between each node defined as links. This link data includes data such as a link-specific link ID, link length, position data (longitude, latitude) of the start and end points (nodes) of the link, angle (direction) data, road width, road type, and road attributes.

In addition, information (zero gradient information) indicating roads and points with zero gradient (flat roads) is added to the road map data. This zero gradient information corresponds to flat land information. Furthermore, the points indicated by the zero gradient information are not limited to roads, but may also include points where vehicles can pass, such as parking lots. This zero gradient information may be included not only in the road map data, but also in facility data such as parking lots. Furthermore, it is preferable to investigate and set accurate zero gradient points using a spirit level or the like. Note that the zero gradient (flat) in this embodiment does not only refer to completely flat zero degrees or zero%, but also includes a gradient that can be calculated as flat when correcting the acceleration sensor 14 described later, such as within 0±0.5%, for example.

In this embodiment, map information is stored in advance in the map information storage unit 15, but it may be configured to download map information from an external server, for example, or the map information of the car navigation device may include flat ground information and the map information may be acquired from the car navigation device. Alternatively, the map information storage unit 15 may not be provided, and information consisting only of latitude and longitude information of zero-gradient points may be generated (acquired) as zero-gradient information (flat ground information). Such zero-gradient information can be obtained by conducting a preliminary survey of roads that are normally used in operation, such as roads at company entrances and exits, or bridges.

The information communication terminal 30 is, for example, a smartphone or a tablet terminal. The information communication terminal 30 has built-in devices and circuits that can measure air pressure, such as an air pressure sensor. The information communication terminal 30 transmits the air pressure information that it measures to the wireless communication unit 3. The information communication terminal 30 is disposed in a vehicle in which the road gradient detection device 20 is installed. This disposition is not limited to being fixed in the vehicle, but also includes, for example, being placed on a seat. Even if it is fixed, it may be detachable so that it can be taken out of the vehicle.

The information communication terminal 30 does not have to be a terminal specialized for measuring atmospheric pressure, such as a smartphone, as described above, but if a barometer is installed in the vehicle, atmospheric pressure information may be obtained from the barometer.

In the above-mentioned configuration, the CPU 1, the wireless communication unit 3, the acceleration sensor 14, and the map information storage unit 15 constitute an acceleration sensor correction device 100 according to one embodiment of the present invention.

Next, the operation of the acceleration sensor correction device 100 configured as described above will be described with reference to the flowchart in FIG. 2. The flowchart shown in FIG. 2 is executed by CPU 1.

First, the CPU 1 performs zero offset processing (zero point correction processing) of the acceleration sensor 14 (step S11). The zero point correction processing in this step may be a well-known method of storing the output of the acceleration sensor 14 at the point where the gradient is zero as the output of the acceleration sensor at the gradient zero point. It is preferable to execute step S11 by investigating the exact gradient zero point using a spirit level or the like. The correction results (such as the voltage value corresponding to the zero point) are stored in, for example, EEPROM 2 or the like.

Next, the CPU 1 determines whether atmospheric pressure information inside the vehicle can be obtained (step S12). That is, the CPU 1 functions as a first determination means for determining whether atmospheric pressure information measured (detected) inside the vehicle can be received. In step S12, it is determined whether an information communication terminal 30 is placed inside the vehicle (presence or absence). The presence or absence of the information communication terminal 30 can be determined, for example, by pairing the road gradient detection device 20 and the information communication terminal 30 in advance using Bluetooth (registered trademark) or the like, and if the paired information communication terminal 30 is detected, it can be determined that the information communication terminal 30 is present, that is, that atmospheric pressure information can be obtained inside the vehicle. In the case of a wired connection, the presence or absence of a wired connection can be detected.

If atmospheric pressure information can be acquired inside the vehicle (step S12; Y), the CPU 1 determines whether there is no change in atmospheric pressure during driving or whether it is within a specified range based on the acquired atmospheric pressure information (step S13). In step S13, a flat road is determined based on the atmospheric pressure information. The specified range indicates the range of change in atmospheric pressure that can be determined to be flat, and may be set appropriately. In other words, the CPU 1 determines whether the road on which the vehicle is located is flat or not based on the atmospheric pressure information.

If it is not possible to obtain air pressure information inside the vehicle (step S12; N), or if the air pressure has changed during driving or is outside the specified range (step S13; N), the CPU 1 determines whether the vehicle is passing through a road or point with a zero gradient based on the map information stored in the map information storage unit 15 (step S14). If the determination in step S13 is N, this means that there is no air pressure sensor, or that the air pressure sensor is not good at detecting elevation differences due to gradients or air pressure fluctuations, and is therefore not suitable for detecting flat roads, so flat roads are detected by another means.

In step S14, the zero gradient information included in the map information is referenced to determine whether the current position acquired from a current position acquisition means (not shown) such as a GPS (Global Positioning System) is traveling on a zero gradient road or point. That is, when it is determined that atmospheric pressure information cannot be received, the CPU 1 determines whether the road on which the vehicle is located is flat or not based on the flat ground information included in the map information. This method can also be used to make a similar determination using a GPS or the like when using separate flat ground information not included in the map information described above.

If there is no change in air pressure during driving or it is within a specified range (step S13; Y), or if the vehicle is passing through a road or point with a zero gradient (step S14; Y), the CPU 1 determines that the vehicle is driving on a flat road and performs additional correction processing of the acceleration sensor 14 (step S15). In other words, the CPU 1 functions as a correction means that performs zero point correction of the acceleration sensor when it determines that the road is flat.

The additional correction process in step S15 may be a well-known method of, for example, comparing the acceleration detected by the acceleration sensor 14 with the acceleration (actual acceleration) calculated from the time change in the detected vehicle speed based on the vehicle speed pulse 7, and correcting the zero point of the acceleration sensor 14 according to the difference (deviation) between the detected value of the acceleration sensor 14 and the actual acceleration. The corrected result (such as a voltage value corresponding to the zero point) is stored in, for example, the EEPROM 2.

After the additional correction process in step S15 is completed, or if the vehicle is not passing through a zero-gradient road or point (step S14; N), the CPU 1 returns to the normal slope detection process using the acceleration sensor 14 (step S16).

A slope detection process using a normal acceleration sensor 14 may use a well-known method, such as that described in Patent Document 2, in which a value corresponding to the actual acceleration obtained from the detected vehicle speed detected based on the vehicle speed pulse 7 while the vehicle 1 is traveling is subtracted from the output value of the acceleration sensor 14, and the road gradient is detected from the output of the acceleration sensor 14 after subtraction. In addition, when detecting this road gradient, a threshold value set by the dials 12 and 13 may be used to determine whether or not there is a gradient.

If the result of the determination in step S14 is that the vehicle is not passing through a zero-gradient road or point (step S14; N), the CPU 1 may warn that a correction process for the acceleration sensor 14 should be performed taking into account the ambient temperature and changes over time before returning to the slope detection process in step S16. If the determination in step S14 is N, no additional correction process is performed, but since the correction result performed in step S11 is used, at least a decrease in detection accuracy is suppressed. However, it is known that the output of the acceleration sensor 14 varies depending on the ambient temperature and the results over time, and the detection accuracy of the acceleration sensor 14 can be improved by taking these factors into account.

The warning may be, for example, a warning sound or a warning message output from a speaker (not shown) or displayed by an indicator (not shown). The speaker or indicator serves as a warning means. It is preferable for the driver or the like who receives the warning to promptly perform the zero point correction process of step S11 (or the additional correction process of step S15).

Specifically, the ambient temperature of the acceleration sensor 14 can be detected by adding a temperature detection means such as a temperature sensor, and if the CPU 1 determines that the temperature is outside a predetermined temperature range (outside the predetermined range), a warning can be issued. In other words, a warning is issued if the ambient temperature is too high or too low. Changes over time can be measured by adding a time detection means such as a timer or clock function built into the CPU 1, and a warning can be issued when a certain amount of time has passed since the previous zero point correction process. For example, at the same time as the warning, flat roads (roads/points with zero gradient) close to the current location can be displayed on a display device or the like based on map information.

According to this embodiment, the acceleration sensor correction device 100 is equipped with an acceleration sensor 14 mounted on a vehicle to detect the acceleration acting on the vehicle, and a wireless communication unit 3 to receive atmospheric pressure information detected inside the vehicle. The acceleration sensor correction device 100 further includes a CPU 1 that determines whether atmospheric pressure information can be received by the wireless communication unit 3, and if so, determines whether the road on which the vehicle is located is flat based on the atmospheric pressure information received by the wireless communication unit 3, and performs zero point correction of the acceleration sensor 14 if it is determined that the road is flat.

By configuring the acceleration sensor correction device 100 as described above, it is possible to determine whether the road on which the vehicle is located is flat based on the air pressure information, and perform zero point correction if the road is flat, so that zero point correction can be performed reliably on flat ground. This makes it possible to more accurately detect gradients based on acceleration. In addition, since the air pressure information is only used to detect flat roads, an air pressure sensor included in an external device such as the information communication terminal 30 can be used instead of a dedicated air pressure sensor.

The wireless communication unit 3 also receives atmospheric pressure information via wireless communication from an information communication terminal 30 that has an atmospheric pressure sensor installed inside the vehicle. This allows the use of equipment equipped with an atmospheric pressure sensor, and reduces costs because there is no need to install a dedicated, expensive atmospheric pressure sensor.

The vehicle also includes a map information storage unit 15 that stores map information including zero gradient information. When the wireless communication unit 3 cannot receive atmospheric pressure information, the CPU 1 determines whether the road on which the vehicle is located is flat or not based on the zero gradient information included in the map information. In this way, even when atmospheric pressure information cannot be received, flat roads, etc. can be identified based on the map information, and zero point correction can be performed on the identified flat road.

In addition, since the road gradient detection device 20 is equipped with the acceleration sensor correction device 100 configured as described above, it is possible to suppress a decrease in the detection accuracy of the acceleration sensor, which is one of the factors that reduces the detection accuracy of the road gradient. Furthermore, since zero point correction is performed when a flat road or the like is detected, it is possible to perform accurate gradient detection even when using an inexpensive acceleration sensor that is not highly accurate.

The road gradient detection device 20 described in the above embodiment may be provided in a vehicle operation recording device. An example of providing a road gradient detection device 20 in an operation recording device is shown in FIG. 3. FIG. 3 is a schematic diagram of an operation recording device 200 provided with a road gradient detection device 20. The operation recording device 200 is also called a digital tachograph, and sequentially records driving information such as vehicle speed and engine RPM, and information related to operation conditions such as entering and leaving the vehicle along with the time of occurrence.

The operation recording device 200 includes a road gradient detection device 20 and an operation recording unit 201. The operation recording unit 201 collects various operation information such as the vehicle speed, engine RPM, entry and exit, and records it on an SD card 202. Note that the various information is not limited to being recorded on the SD card, and may be transmitted to an external server, etc.

The operation recording device 200 shown in FIG. 3 is equipped with a road gradient detection device 20, so gradient information detected with high accuracy can be acquired. Therefore, it is possible to associate whether or not the vehicle is traveling on a slope with the driving information, and appropriate operation management that reflects the driving state can be performed.

Furthermore, the present invention is not limited to the above-mentioned embodiment. In other words, a person skilled in the art can implement various modifications according to conventional knowledge without departing from the gist of the present invention. As long as such modifications still include the configuration of the acceleration sensor correction device, road gradient detection device, and driving recorder of the present invention, they are of course included in the scope of the present invention.

1 CPU (first determination means, second determination means, correction means, road gradient detection unit)
3 Wireless communication unit (receiving means)
7 Vehicle speed pulse 14 Acceleration sensor 15 Map information storage unit (acquisition means)
20 Road gradient detection device 30 Information communication terminal 100 Acceleration sensor correction device 200 Operation record device

Claims (4)

An acceleration sensor mounted on a vehicle to detect acceleration acting on the vehicle;
a first determination means for determining whether atmospheric pressure information measured inside the vehicle can be received;
a receiving means for receiving the atmospheric pressure information when it is determined that the atmospheric pressure information can be received;
a second determination means for determining whether or not a road on which the vehicle is located is flat based on the atmospheric pressure information;
a correction means for performing a zero point correction of the acceleration sensor when the road is determined to be flat;
Equipped with
The acceleration sensor correction device according to claim 1, wherein the receiving means receives the atmospheric pressure information by communication from an information communication terminal having an atmospheric pressure sensor arranged inside the vehicle . An acquisition means for acquiring flat ground information,
the second determination means, when it is determined that the atmospheric pressure information cannot be received, determines whether or not a road on which the vehicle is located is flat based on the flat ground information.
2. The acceleration sensor correction device according to claim 1 , An acceleration sensor correction device according to claim 1 or 2 ,
a road gradient detection unit that detects a gradient of a road on which the vehicle is located based on the acceleration detected by the acceleration sensor;
A road gradient detection device comprising: 4. A driving recorder comprising the road gradient detection device according to claim 3 and which collects driving information of the vehicle.

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