A method and system for detecting sudden speed change of a vehicle based on a three-axis acceleration sensor

Abstract

The application provides a kind of automobile sudden speed change detection method based on three-axis acceleration sensor, comprising the following steps: S1, calibrating three-axis acceleration sensor;S2, calculating rotation matrix;S3, calculating the combined acceleration value in horizontal direction;S4, sudden speed change peak judgment;S5, judge whether it is sudden speed change behavior.The application also provides a kind of automobile sudden speed change detection system based on three-axis acceleration sensor.The beneficial effects of the application are: only through three-axis acceleration sensor can realize automobile sudden speed change detection, error is small, and installation is convenient.

Description

Technical Field

[0001] This invention relates to automobile inspection methods, and more particularly to a method and system for detecting rapid speed changes in automobiles based on a triaxial accelerometer. Background Technology

[0002] Currently, the detection equipment installed in industries such as car insurance and leasing mainly employs two methods: 1) calculating vehicle speed using GPS positioning information, and 2) obtaining vehicle speed by connecting to the car's OBD (On-Board Diagnostics) module. Ultimately, both methods use speed changes to determine whether the vehicle has undergone a sudden acceleration or deceleration.

[0003] The method of obtaining speed through GPS information is affected by the positioning effect, has a large error, poor real-time performance, and is prone to false alarms; the method of obtaining speed through OBD module is limited by installation location and occupies interface, which is extremely inconvenient. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a method and system for detecting rapid speed changes in automobiles based on a triaxial accelerometer.

[0005] This invention provides a method for detecting rapid speed changes in automobiles based on a triaxial accelerometer.

[0006] Includes the following steps:

[0007] S1. Calibrate the triaxial accelerometer;

[0008] S2. Calculate the rotation matrix;

[0009] S3. Calculate the resultant acceleration value in the horizontal direction;

[0010] S4. Judgment of rapid change peak;

[0011] S5. Determine if it is a sudden change in speed.

[0012] As a further improvement of the present invention, in step S1, when the vehicle is stationary, at least two sets of acceleration values ​​are continuously collected, and the triaxial average value (x0, y0, z0) is calculated.

[0013] As a further improvement of the present invention, in step S2, it is assumed that the vehicle system n has the Y-axis forward, i.e. the direction of the car's movement, the Z-axis vertically downward, and the X-axis to the right, i.e. perpendicular to the car door, and the equipment system b is based on the three directions defined by the triaxial acceleration sensor.

[0014] The three rotation angles corresponding to the rotation from equipment system b to vehicle system n are (Φ, θ, Ψ), and the rotation matrix is:

[0015]

[0016] Normalizing the three-axis averages (x0, y0, z0) at rest yields (x m y m , z m ), calculate two of the rotation angles;

[0017]

[0018] During initialization, the third rotation angle is unknown, so it is fixed at a certain value for now;

[0019] Ψ=0

[0020] The rotation matrix is ​​calculated in this way:

[0021]

[0022] As a further improvement of the present invention, in step S3, the subsequent triaxial input values ​​(x) bi y bi , z bi The projection value of ) in the vehicle coordinate system is (x ni y ni , z ni ):

[0023]

[0024] Then, the resultant acceleration value a in the horizontal direction on the vehicle body xy :

[0025]

[0026] As a further improvement of the present invention, in step S4, the resultant acceleration-time curve of the rapid acceleration behavior has a peak, and the peak is defined by the following characteristic quantity:

[0027] Threshold V t Threshold values ​​for the combined acceleration values ​​when entering and exiting the peak;

[0028] Peak V p The maximum value within the peak;

[0029] Duration T: The number of data entries and exits;

[0030] Peak offset V o The ratio of the time from peak to exit peak to the duration of the peak;

[0031] Right slope k r The slope of the red line on the right is the ratio of the peak value minus the threshold value to the time from the peak value to the exit of the peak value.

[0032] Suitable peaks are selected by threshold / peak value and duration, when either of the following two conditions is met, where V od V oa k ra k rd For testing experience values:

[0033] V o <=V od &&k r >=k rd This was determined to be a sudden deceleration behavior.

[0034] V o >=V oa &&k r <=k ra This is determined to be a rapid acceleration behavior. At this point, the third rotation angle is further calculated, and the triaxial data corresponding to the peak position is (x...). p y p , z p ),but:

[0035]

[0036] Recalculate the rotation matrix from equipment system b to vehicle system n. The main distinction between subsequent rapid acceleration and rapid deceleration is:

[0037] y ni =dcm[3]·x bi +dcm[4]·y bi +dcm[5]·z bi .

[0038] As a further improvement of the present invention, in step S5...

[0039] The calculation of the third rotation angle needs to be completed before proceeding to the result judgment;

[0040] First, satisfy the peak conditions for rapid acceleration or deceleration, then determine the y-axis of the vehicle coordinate system. ni To distinguish the type of rapid speed change, use the third rotation angle Ψ corresponding to the peak value. p Eliminate false alarms;

[0041] The third rotation angle Ψ for peak value calculation m The difference between this and the previously recorded third rotation angle Ψ is:

[0042] ΔΨ=|Ψ p -Ψ|

[0043] The judgment logic is as follows: there are two cases;

[0044] y ni <=-V t&&(ΔΨ>=170&&ΔΨ<=190), rapid deceleration behavior was detected.

[0045] y ni >=V t &&(ΔΨ<=10||ΔΨ>=350), rapid acceleration behavior was detected.

[0046] As a further improvement of the present invention, in step S1, the vehicle is kept on a horizontal plane.

[0047] The present invention also provides a vehicle rapid speed change detection system based on a triaxial accelerometer, for implementing the method described in any one of the above.

[0048] The beneficial effects of this invention are: through the above solution, rapid speed change detection of automobiles can be achieved using only a three-axis accelerometer, with small error and convenient installation. Attached Figure Description

[0049] Figure 1 This is a resultant acceleration-time curve of a vehicle rapid speed change detection method based on a triaxial accelerometer according to the present invention. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0051] like Figure 1 As shown, a method for detecting rapid speed changes in automobiles based on a triaxial accelerometer specifically includes the following steps:

[0052] (1) Equipment installation:

[0053] The testing equipment can be fixedly installed at any angle; the data acquisition frequency of the triaxial accelerometer is fixed at 5Hz.

[0054] (2) Equipment calibration:

[0055] After powering on the equipment, perform installation and calibration, and try to ensure that the car is on a level road surface;

[0056] When the vehicle is stationary, 100 sets of acceleration values ​​are continuously collected, and the average values ​​of the three axes (x0, y0, z0) are calculated.

[0057] (3) Calculate the rotation matrix:

[0058] Assume vehicle system n, with the Y-axis pointing forward (in the direction of vehicle movement), the Z-axis pointing vertically downward, and the X-axis pointing to the right (perpendicular to the door). Equipment system b is based on the three directions defined by the triaxial sensor;

[0059] The three rotation angles corresponding to the rotation from equipment system b to vehicle system n are (φ, θ, Ψ), and the rotation matrix is:

[0060]

[0061] Normalizing the average values ​​(x0, y0, z0) at rest yields (x m y m , z m This allows us to calculate two of the rotation angles;

[0062]

[0063] During initialization, the third rotation angle is unknown, so it is fixed at a certain value for now;

[0064] Ψ=0

[0065] This allows us to calculate the rotation matrix:

[0066]

[0067] (4) Calculate the resultant acceleration in the horizontal direction:

[0068] Subsequent triaxial input values ​​(x) bi y bi , z bi The projection value of ) in the vehicle coordinate system is (x ni y ni , z ni ):

[0069]

[0070] Then, the resultant acceleration value a in the horizontal direction on the vehicle body xy :

[0071]

[0072] (5) Judgment of rapid change peak

[0073] The resultant acceleration-time curve of rapidly changing behavior will have a peak. We define the peak as a characteristic quantity as follows:

[0074] Threshold V t Threshold values ​​for the combined acceleration values ​​upon entering and exiting the peak.

[0075] Peak V p The maximum value within the peak

[0076] Duration T: Number of data entries and exits

[0077] Peak offset V o The ratio of the time from peak to exit peak to the duration of the peak.

[0078] Right slope kr The slope of the red line on the right is the ratio of the peak value minus the threshold value to the time from the peak value to the exit of the peak value.

[0079] Filter suitable peaks by threshold / peak value and duration. The following two conditions must be met:

[0080] Where V od V oa k ra k rd For testing experience values:

[0081] V o <=V od &&k r >=k rd This was determined to be a sudden deceleration behavior.

[0082] V o >=V oa &&k r <=k ra This was determined to be a rapid acceleration behavior.

[0083] At this point, the third rotation angle can be calculated, and the triaxial data corresponding to the peak position is (x... p y p , z p ),but:

[0084]

[0085] Recalculate the rotation matrix from equipment system b to vehicle system n. The main distinction between subsequent rapid acceleration and rapid deceleration is:

[0086] y ni =dcm[3]·x bi +dcm[4]·y bi +dcm[5]·z bi

[0087] (6) Judgment result:

[0088] The calculation of the third rotation angle needs to be completed before proceeding to the result judgment;

[0089] First, satisfy the peak conditions for rapid acceleration or deceleration, then determine the y-axis of the vehicle coordinate system. ni To distinguish the type of rapid speed change, use the third rotation angle Ψ corresponding to the peak value. p False alarms such as those caused by uphill or downhill slopes have been eliminated.

[0090] The third rotation angle Ψ for peak value calculation m The difference between this and the previously recorded third rotation angle Ψ is:

[0091] ΔΨ=|Ψ p -Ψ|

[0092] The judgment logic is as follows: there are two cases;

[0093] y ni <=-V t &&(ΔΨ>=170&&ΔΨ<=190), rapid deceleration behavior was detected.

[0094] y ni >=V t &&(ΔΨ<=10||ΔΨ>=350), rapid acceleration behavior was detected.

[0095] The present invention provides a method and system for detecting rapid acceleration and deceleration in automobiles based on a triaxial accelerometer, which has the following advantages:

[0096] 1. Low cost, detection can be completed with just a common triaxial sensor.

[0097] 2. Easy to install, and more suitable for most application scenarios.

[0098] 3. High accuracy, with an active learning mechanism, it can make very accurate judgments after obtaining the installation angle and eliminate false alarms.

[0099] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for detecting rapid speed changes in automobiles based on a triaxial accelerometer, characterized in that, Includes the following steps: S1. Calibrate the triaxial accelerometer; S2. Calculate the rotation matrix; S3. Calculate the resultant acceleration value in the horizontal direction; S4. Judgment of rapid change peak; S5. Determine if it is a sudden speed change; In step S4, the resultant acceleration-time curve of the rapid acceleration behavior has a peak, and the peak is defined by the following characteristic quantity: Threshold V t Threshold values ​​for the combined acceleration values ​​when entering and exiting the peak; Peak V p The maximum value within the peak; Duration T: The number of data entries and exits; Peak offset V o The ratio of the time from peak to exit peak to the duration of the peak; Right slope k r The slope of the red line on the right is the ratio of the peak value minus the threshold value to the time from the peak value to the exit of the peak value. Suitable peaks are selected by threshold / peak value and duration, when either of the following two conditions is met, where V od V oa ,k ra ,k rd For testing experience values: V o <=V od &&k r >=k rd This was determined to be a sudden deceleration behavior; V o >=V oa &&k r <=k ra This was determined to be a rapid acceleration behavior; At this point, the third rotation angle is further calculated, and the triaxial data corresponding to the peak position is (x p ,y p ,z p ),but: Recalculate the rotation matrix from device system b to vehicle system n. The main difference between subsequent rapid acceleration and rapid deceleration is: y ni =dcm[3]·x bi +dcm[4]·y bi +dcm[5]·z bi ; In step S5, The calculation of the third rotation angle needs to be completed before proceeding to the result judgment; First, satisfy the peak conditions for rapid acceleration or deceleration, then determine the y-axis of the vehicle coordinate system. ni To distinguish the type of rapid speed change, use the third rotation angle Ψ corresponding to the peak value. p Eliminate false alarms; The third rotation angle Ψ for peak value calculation m The difference between this and the previously recorded third rotation angle Ψ is: ΔΨ=|Ψ p -Ψ| The judgment logic is as follows: there are two cases; y ni <=-V t &&(ΔΨ>=170&&ΔΨ<=190), rapid deceleration was detected; y ni >=V t &&(ΔΨ<=10||ΔΨ>=350), rapid acceleration behavior was detected.

2. The method for detecting rapid acceleration and deceleration of a vehicle based on a triaxial accelerometer according to claim 1, characterized in that: In step S1, when the vehicle is stationary, at least two sets of acceleration values ​​are continuously collected, and the three-axis average value (x0, y0, z0) is calculated.

3. The method for detecting rapid acceleration and deceleration of a vehicle based on a triaxial accelerometer according to claim 2, characterized in that: In step S2, assume the vehicle system n has the Y-axis pointing forward (the direction of the car's movement), the Z-axis pointing vertically downward, and the X-axis pointing to the right (perpendicular to the car door). The equipment system b is based on the three directions defined by the triaxial accelerometer. The three rotation angles corresponding to the rotation from equipment system b to vehicle system n are (Φ, θ, Ψ), and the rotation matrix is: Normalizing the three-axis averages (x0, y0, z0) at rest yields (x m ,y m ,z m ), calculate two of the rotation angles; During initialization, the third rotation angle is unknown, so it is initially fixed at Ψ = 0. The rotation matrix is ​​calculated in this way: 。 4. The method for detecting rapid acceleration and deceleration of a vehicle based on a triaxial accelerometer according to claim 3, characterized in that: In step S3, the subsequent triaxial input values ​​(x) bi ,y bi ,z bi The projection value of ) in the vehicle coordinate system is (x ni ,y ni ,z ni ): Then, the resultant acceleration value a in the horizontal direction on the vehicle body xy : 。 5. The method for detecting rapid acceleration and deceleration of a vehicle based on a triaxial accelerometer according to claim 1, characterized in that: In step S1, the vehicle is kept on a level surface.

6. A vehicle rapid speed change detection system based on a triaxial accelerometer, characterized in that: Used to implement the method as described in any one of claims 1 to 5.

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