JP2006349446A - Moving distance calculator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moving distance calculator capable of calculating precisely a moving distance of a vehicle. <P>SOLUTION: A moving speed based on an acceleration data detected by an acceleration sensor 12 is brought into zero, based on stop determination by an imaging part 13. An off-set value is calculated based on the acceleration data stored sequentially in a storage part 14 during a stop determination period, to calibrate the acceleration sensor 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a movement distance calculation device that accurately calculates the movement distance of a vehicle.

  When the vehicle is parked, the camera image of the in-vehicle camera mounted on the vehicle is displayed on the display in the passenger compartment, and an auxiliary image indicating the guidance route to the target parking section is superimposed and displayed, and the driver displays the image. There is a parking assistance device that allows easy parking while watching.

  In such a parking assistance device, it is expected to accurately calculate the moving distance of the camera, that is, the vehicle in the display image, and sequentially update the guidance route (auxiliary image) superimposed according to the moving distance. .

  As one method for calculating the moving distance of the camera, there is a method of calculating the moving distance by integrating the vehicle speed obtained by the wheel speed sensor conventionally installed in the vehicle by the first floor.

  However, the wheel speed sensor is connected to a unit that requires precise processing such as an ABS (Antilock Braking System) unit or an ASC (Active Stability Controller) unit. Therefore, it is necessary to distinguish it from a camera application such as a parking assistance device, which is inappropriate.

  As another method for calculating the moving distance of the camera, there is a method of calculating the moving distance by first-order integrating the vehicle speed obtained by a speedometer conventionally installed in the vehicle.

  However, the accuracy of the speed detected by the speedometer is 1 km or more per hour, and when accuracy of several centimeters per second is required such as traveling at a very low speed as in parking operation, the accuracy is not enough.

  Therefore, a method of newly installing an acceleration sensor applicable to a camera application such as a parking assistance device and calculating the moving distance of the camera can be considered.

  However, if the movement distance of the camera is calculated only by the acceleration sensor, the acceleration detected at a very low speed, such as at the time of parking operation, is detected by the detection error, for example, as shown in FIG. The voltage value 41 fluctuates up and down in the vicinity of the ideal output voltage value 42 corresponding to the actual acceleration. Therefore, the speed v calculated by integrating the first order is increased by errors 51 to 54 as shown in FIG. 5, and the moving distance x calculated by further integrating the first order is shown in FIG. Thus, the errors 61 to 64 are further increased. Therefore, for example, although the vehicle is stopped and the moving distance is zero, the moving distance calculated by the error detected by the acceleration sensor has a non-zero value.

  In addition, although a highly accurate acceleration sensor can reduce the accumulated error, there is a problem that the cost is increased.

  Therefore, an object of the present invention is to provide a movement distance calculation device that can accurately calculate the movement distance of a vehicle (that is, the movement distance of an imaging unit) from an acceleration sensor with an inexpensive configuration.

  In order to solve the above-mentioned problem, a moving distance calculation device according to claim 1 is based on an acceleration sensor that detects acceleration of a vehicle and outputs acceleration data, a storage unit that sequentially stores the acceleration data, and the acceleration data. A speed calculation unit that calculates the movement speed of the vehicle, a movement distance calculation unit that calculates a movement distance of the vehicle based on the movement speed calculated by the speed calculation unit, An image capturing unit that captures an image of the periphery of the vehicle and outputs a captured image; an image processing unit that determines stop of the vehicle based on the captured image; and the image processing unit determines that the vehicle is stopped If it is, the acceleration sensor calibrates the moving speed calculated by the speed calculation unit to zero and calculates an offset value based on the acceleration data during the stop determination period. In which and a calibration unit for calibrating.

  According to the first aspect of the invention, the error of the acceleration sensor mounted on the vehicle is corrected to the zero point based on the image captured by the imaging unit, and the moving distance of the vehicle is calculated based on the acceleration data detected after the correction. Therefore, it is possible to accurately calculate the moving distance of the vehicle (that is, the moving distance of the imaging unit) using an inexpensive acceleration sensor.

<Configuration>
FIG. 1 is a diagram showing a vehicle equipped with a travel distance calculation device according to an embodiment of the present invention, and FIG. 2 shows a travel distance calculation device according to an embodiment of the present invention and a parking assistance device using the travel distance calculation device. It is a block diagram. The moving distance calculation device 10 is composed of, for example, an acceleration sensor 12 mounted on a vehicle 11, an imaging unit 13 that images the periphery of the vehicle 11, and a microcomputer MC to which the acceleration sensor 12 and the imaging unit 13 are connected. Yes.

  The microcomputer MC includes a storage unit 14 such as a CPU, a ROM, and a RAM, and an auxiliary image storage unit 19A. By executing an embedded control program, the microcomputer MC calculates a moving distance and controls parking assistance using the same. Execute.

  Note that the speed calculation unit 15, the movement distance calculation unit 16, the image processing unit 17, and the calibration unit 18 in FIG. 2 illustrate a functional configuration related to the calculation of the movement distance of the vehicle 11 realized by executing the control program. .

  Moreover, the display control part 19 has shown the functional structure regarding the parking assistance implement | achieved by execution of a program, and performs display control of the display part 110 connected to microcomputer MC.

  Below, each component is demonstrated in detail.

  The acceleration sensor 12 detects acceleration in the front-rear direction of the vehicle 11 and has, for example, a piezoelectric element. The piezoelectric element is distorted by an impact (acceleration) applied to the vehicle 11, and the magnitude of the distortion is increased. By detecting the voltage generated accordingly, the acceleration of the vehicle 11 is detected and stored in the storage unit 14.

  The storage unit 14 is, for example, a rewritable non-volatile storage device such as a flash ROM or HDD, and sequentially stores acceleration data detected by the acceleration sensor 12 by changing the address of the storage area. In addition, software programs executed by the speed calculation unit 15 and the movement distance calculation unit 16 are stored.

  The speed calculation unit 15 is configured by a CPU or the like, and is a functional element that operates according to a software program stored in advance in the storage unit 14. The speed calculation unit 15 calculates the moving speed of the vehicle based on the acceleration data stored in the storage unit 14. It has become.

  The movement distance calculation unit 16 is a functional element that is configured by a CPU or the like and operates according to a software program stored in advance in the storage unit 14. The movement distance calculation unit 16 moves the vehicle 11 based on the movement speed calculated by the speed calculation unit 15. The distance is calculated.

  The imaging unit 13 includes an imaging element such as a CCD (Charge Coupled Device), and is installed at the center of the rear end of the vehicle 11 as shown in FIG. A wide viewing angle image including the direction can be obtained.

  In the present embodiment, the imaging unit 13 is installed at the center of the rear end of the vehicle 11. However, if necessary, one or more imaging units 13 may be installed at the center of the front end and both the left and right sides. good.

  As a result, during normal driving of the vehicle 11, it is possible to provide driving assistance or the like by imaging a blind spot area from the driver and displaying it on the display unit 110 as necessary.

  The image processing unit 17 is connected to the imaging unit 13 by a wire harness as a video transmission path. Based on each captured image captured in time series by the imaging unit 13, for example, each corresponding pixel of each video Whether or not the vehicle 11 is stopped based on whether or not there is a change in each image (that is, whether or not the imaging unit 13 is stopped). It is possible to determine whether to stop.

  The calibration unit 18 recognizes the result of the stop determination performed by the image processing unit 17 at a predetermined frequency (for example, about once / second). At this time, when the image processing unit 17 determines that the vehicle 11 is stopped, calibration is performed so that the moving speed calculated by the speed calculating unit 15 becomes zero. When it is confirmed that a predetermined time (for example, about 1 second) has elapsed since the stop determination was made during the stop determination period, the acceleration sequentially stored in the storage unit 14 within the predetermined time. The latest offset value is calculated and updated based on the data.

  The display unit 110 is connected to the imaging unit 13 by a wire harness serving as a video transmission path. For example, an LCD (Liquid Crystal Display) is applied, and the display unit 110 is installed in the vehicle 11 and captured by the imaging unit 13. The video is displayed.

  The auxiliary image storage unit 19A includes auxiliary images for performing parking assistance, for example, a pair of straight lines obtained by extending the vehicle width of the vehicle 11 and a plurality of straight lines corresponding to the distance from the rear end of the vehicle 11. An auxiliary image such as a guidance route is stored, and the display control unit 19 corrects the auxiliary image as appropriate during parking assistance, and then superimposes the captured image on the captured image and displays it on the display unit 110.

<Operation>
The operation of the movement distance calculation apparatus 10 having the above configuration will be described with reference to the flowchart of FIG. First, during normal travel of the vehicle 11, the imaging unit 13 captures the periphery of the vehicle 11 (step S1), and the image processing unit 17 stops the vehicle 11 (that is, the imaging unit 13) based on the captured image. Stop determination (step S2) is performed. The acceleration sensor 12 detects the acceleration applied to the vehicle 11 (step S6), and sequentially updates and stores acceleration data for a predetermined time in the storage unit 14, and the speed calculation unit 15 and the movement distance calculation unit 16 perform these accelerations. Based on the data, the calculation of the moving speed (step S7) and the calculation of the moving distance (step S8) are sequentially executed.

  In this state, for example, when the driver switches the shift position from drive to reverse to park the vehicle 11 backward in a certain parking section and stops the vehicle 11 once, the image processing unit 17 captures an image captured by the imaging unit 13. Is determined to stop the vehicle 11 (step S2). The determination result is given to the calibration unit 18, and the calibration unit 18 calibrates the moving speed calculated by the speed calculation unit 15 to be zero (step S3). When it is confirmed that a predetermined time (for example, about 1 second) has elapsed since the stop determination has been made (step S4), it is based on the acceleration data sequentially stored in the storage unit 14 within the predetermined time. The latest offset value is calculated and updated (step S5).

  Thereafter, when the vehicle 11 starts to move backward, the acceleration sensor 12 detects acceleration using the latest offset value and stores it in the storage unit 14 (step S6). The speed calculation unit 15 calculates a movement speed based on the acceleration data detected using the latest offset value and stored in the storage unit 14 (step S7), and the movement distance calculation unit 16 is based on the calculated movement speed. The movement distance is calculated (step S8).

  At the same time, the display control unit 19 expands or contracts the guide route stored in the auxiliary image storage unit 19A based on the movement distance calculated by the movement distance calculation unit 16, or indicates the distance from the rear end of the vehicle 11. It moves up and down on a straight display screen and is superimposed on the captured image and displayed on the display unit 110.

  As described above, the zero point correction is performed on the error of the acceleration sensor 12 based on the image captured by the imaging unit 13, so that the moving distance of the vehicle 11 can be accurately calculated with an inexpensive configuration. Moreover, since the movement distance calculation part 16 correct | amends the guidance route of the vehicle 11 based on the calculated movement distance, and displays it on the speed calculation part 15, it becomes possible to perform parking operation easily.

{Modification}
In addition to the travel distance calculation device according to the above embodiment and the parking assist device using the same, for example, a normal speedometer (not shown) is connected to the image processing unit 17, and the image processing unit 17 The stop determination of the imaging unit 13 may be performed only when the traveling speed is equal to or less than a predetermined threshold value (for example, 5 km per hour). As a result, it is not necessary to always perform the stop determination process by the image processing unit 17, and the arithmetic processing of the image processing unit 17 can be reduced.

  Further, for example, a shift sensor (not shown) for detecting the operation position of the shift lever is further provided so that the stop of the imaging unit 13 is determined only when the shift lever is at a predetermined position (for example, reverse). May be. Accordingly, it is not necessary to always perform the stop determination process by the image processing unit 17, and the arithmetic processing of the image processing unit 17 can be reduced.

It is a figure which shows the movement distance calculation apparatus which concerns on embodiment of this invention, and a parking assistance apparatus using the same. It is a block diagram which shows the movement distance calculation apparatus which concerns on embodiment of this invention, and a parking assistance apparatus using the same. It is a flowchart which shows operation | movement of the movement distance calculation apparatus which concerns on embodiment of this invention. It is a figure which shows the output waveform of the conventional acceleration sensor. It is a figure which shows the speed calculated by the output data of the conventional acceleration sensor. It is a figure which shows the movement distance calculated by the output data of the conventional acceleration sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Movement distance calculation apparatus 11 Vehicle 12 Acceleration sensor 13 Imaging part 14 Storage part 15 Speed calculation part 16 Movement distance calculation part 17 Image processing part 18 Calibration part 19 Display control part 19A Auxiliary image storage part 110 Display part MC Microcomputer

Claims (1)

An acceleration sensor that detects vehicle acceleration and outputs acceleration data;
A storage unit for sequentially storing the acceleration data;
A speed calculating unit that calculates a moving speed of the vehicle based on the acceleration data;
A moving distance calculating unit that calculates a moving distance of the vehicle based on the moving speed calculated by the speed calculating unit;
An imaging unit mounted on the vehicle for imaging the periphery of the vehicle and outputting a captured image;
An image processing unit that determines stop of the vehicle based on the captured image;
When the image processing unit determines that the vehicle is stopped, the moving speed calculated by the speed calculation unit is calibrated to zero, and the acceleration during the stop determination period A moving distance calculation apparatus comprising: a calibration unit that calculates an offset value based on data and calibrates the acceleration sensor.

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