KR101308994B1 - Apparatus for determining slipping of road surface using wheel rotation speed and vehicle speed, and method for the same - Google Patents

Abstract

~

) 및 가속도 임계값(

~

)과 각각 비교하여, 비교 결과에 따라 노면 미끄럼 상태를 분류하는 노면 미끄럼 판단모듈을 포함하되, 노면 미끄럼 판단모듈에서 산출된 슬립 값(s)은 차량과 노면의 미끄러운 정도를 정량화한 값으로, 주행중인 차륜 회전속도의 상대적인 차이와 차량의 절대속도에 의해 정해진다.The wheel speed measurement sensor attached to the wheel and the GPS module installed in the car calculate the wheel rotation speed and vehicle speed, respectively, and transmit the sliding information to the following vehicles to warn the dangers of the road in advance, thereby ensuring the safety of subsequent vehicles. Provided is a road slip determination apparatus and method using a wheel rotation speed and a vehicle speed that enable driving. The road slip determination apparatus using the wheel rotation speed and the vehicle speed may include: a GPS module configured to calculate a vehicle speed for a driving vehicle; A wheel rotation speed sensor attached to a wheel of a running vehicle to measure a rotation speed of the wheel; And calculate a slip value (s), acceleration, and deceleration based on the vehicle speed and the wheel rotation speed received from the GPS module and the wheel speed measurement sensor, and calculate the calculated slip value, acceleration, and deceleration by the predetermined slip threshold value. (

~

) And the acceleration threshold (

~

And a road slip determination module for classifying the road slip state according to the comparison result, wherein the slip value (s) calculated by the road slip determination module is a value quantifying the slipperiness of the vehicle and the road surface. This is determined by the relative difference in the wheel rotation speed and the absolute speed of the vehicle.

Description

Road slip determination device using wheel rotation speed and vehicle speed and method thereof {APPARATUS FOR DETERMINING SLIPPING OF ROAD SURFACE USING WHEEL ROTATION SPEED AND VEHICLE SPEED, AND METHOD FOR THE SAME}

The present invention relates to the measurement and determination of the road slip of the vehicle, and more particularly, the road slip determination device for determining the slip of the road surface by measuring the wheel rotation speed and the vehicle speed of the vehicle driving the road and to transmit the road slip information And to a method thereof.

According to a survey by the National Statistical Office, as of 2007, the number of deaths from domestic road traffic accidents was estimated at 6,166, and the cost of social loss is estimated to be about 2.3 trillion won per year. In addition, the average death toll per 100,000 vehicles is 3.1, about twice that of the OECD average of 1.6, which is the third highest among 30 OECD countries. In addition, as of 2007, the number of bad weather days was 8% of road traffic accidents, and as shown in FIG. 1, 1,433 road traffic deaths due to bad weather and bad weather damage, freezing, etc. accounted for about 23 of all deaths. %to be. Estimated social loss cost is estimated at about 540 billion won per year. 1 is a photograph showing a traffic accident due to deterioration (fog, freezing, etc.) of bad weather road conditions.

As the huge loss cost of road traffic accidents hinders the socio-economic development of the country, it provides information by detecting road hazards and establishes strategies to prevent road accidents in case of bad weather. There is an urgent need for countermeasures.

On the other hand, as the prior art, Korean Patent Publication No. 2001-0047235 discloses an invention named "road surface warning device and method," which will be described with reference to FIG.

2 is a block diagram of a road surface state warning device according to the prior art.

Referring to Figure 2, the road surface state warning device according to the prior art, the sensors 11, 14, 15 for measuring the speed of the engine 11, the transmission, the wheel, respectively, the sensor 13 for measuring the position of the throttle And an arithmetic unit 18 which calculates a coefficient of friction by arithmetic processing according to the detection signals of the sensors 12, 13, 14 and 15, and information on the road surface directly to the driver through the arithmetic unit 18. It consists of an audiovisual alarm device (16, 17) to provide.

At this time, the calculation device 18 estimates the coefficient of friction based on the measured signals measured from the sensors 12, 13, 14, and 15, and if the current vehicle speed is greater than or equal to the safe speed, the audiovisual alarm devices 16, 17 are operated. Will alert you. That is, the arithmetic unit 18 estimates the engine torque from the actual measured throttle position and the engine rpm with reference to the engine torque map, and, in the case of automatic shifting, calculates the transmission from the throttle position and the vehicle speed measured with reference to the torque converter map. Estimate the gear ratio and the torque ratio, and in the case of manual shift, estimate the gear ratio or the gear ratio from the ratio of the engine rpm and the transmission rpm, respectively, and estimate the drive shaft torque, and refer to the vehicle parameters and use the powertrain and wheel motion equations to determine the slip ratio, Estimate driving force and coefficient of friction.

The road surface state warning device according to the prior art estimates the state of the road surface, alerts the driver of the degree of slippery, and allows the driver to moderately decelerate, thereby preventing accidents due to sliding in advance.

Meanwhile, as another prior art, Korean Patent Application Publication No. 2009-0080033 discloses an invention entitled “Surface Friction Prediction Method and Apparatus and Program thereof”, which will be described with reference to FIG. 3.

3 is a block diagram of a sliding friction predicting apparatus of a road surface according to the prior art.

Referring to FIG. 3, a sliding friction predicting apparatus according to the related art includes an information processing unit 20 which performs information processing necessary for determining a sliding friction coefficient; A setting data storage section 50 for storing setting data relating to prediction points necessary for information processing; A transmission / reception unit 30 for transmitting and receiving data to and from the detection devices 31 to 34 disposed along the predicted road, and a storage unit 40 for storing programs and data necessary for information processing; A display unit 60 for displaying a prediction result or the like; And an input unit 70 for inputting setting data and the like.

In addition, the sliding friction predicting apparatus according to the prior art is connected to a communication network 80 such as the Internet, and data transmission and reception are possible with an external server.

In addition, the information processing unit 20 may include a condition data setting unit 21, a snow state predicting unit 22, and a sliding friction determining unit 23. At this time, the condition data setting unit 21 connects to the server 81 of the meteorological association, for example, obtains prediction data about the weather condition of the prediction point from the prediction data DB 82 relating to the weather condition, and sets the setting data. It stores in the memory | storage part 50. Similarly, it connects to the server 83 of the road traffic information center, acquires the prediction data regarding the traffic conditions of the prediction point from the prediction data DB 84 regarding the traffic conditions, and stores it in the setting data storage unit 50. Furthermore, detection data are acquired from the detection device of the predicted point via the transmission / reception unit 30, and the predictive data is generated based on the detection data accumulated in the past and stored in the setting data storage unit 50. Further, the physical property value (road surface thickness, etc.) and the set value of the road surface layer with respect to the prediction point input from the input unit 70 are stored in the setting data storage unit 50, and the value of the sliding friction coefficient requested from the experimental results or the like. Is stored in the setting table 42.

The snow state predicting unit 22 reads the data of the predicted points stored in the setting data storage unit 50 and predicts the predicted points by simultaneous ductility analysis based on the heat balance model of the road surface ice layer and the ice, water and air balance models. Calculates the snow state prediction data of.

The sliding friction prediction apparatus according to the related art uses prediction data on weather conditions and traffic conditions to calculate the snow state prediction data in the road surface ice layer based on the heat balance model of the road surface ice layer and the ice, water, and air balance models. The sliding friction coefficient of the road surface may be determined based on the calculated snow ice state prediction data.

However, in the case of the road surface state warning device according to the related art described above, the vehicle itself while driving is for estimating the state of the road surface, and the engine torque is estimated from the throttle position and the engine rpm which are actually measured with reference to the engine torque map. Since the speed of the vehicle is measured, the speed of the vehicle is very complicated and the road slip information cannot be transmitted to subsequent vehicles. In addition, in the above-described conventional sliding friction prediction apparatus, there is a problem in that the sliding friction coefficient of the road surface is measured in a complicated manner, and road surface sliding information cannot be immediately transmitted to a subsequent vehicle.

Republic of Korea Patent Publication No. 2001-0047235 (published: June 15, 2001), the title of the invention: "Surface condition alarm device and method" Republic of Korea Patent No. 10-0330134 (filed December 29, 1999), the title of the invention: "Speed limit warning and traffic information guidance system and method" Republic of Korea Patent No. 10-0298602 (filed February 25, 1999), the title of the invention: "Slip resistance measurement system of highways and national roads" Republic of Korea Patent Publication No. 2009-0080033 (published: July 23, 2009), the title of the invention: "Slip friction prediction method and apparatus of the road surface and its program" Republic of Korea Patent Publication No. 2009-0034226 (published: April 07, 2009), the title of the invention: "DSRC system, vehicle terminal and communication method using the same"

Technical problem to be solved by the present invention for solving the above problems, the wheel speed measurement sensor attached to the wheel and the GPS module mounted in the vehicle, respectively, through the wheel speed and the vehicle speed calculated by using the road surface The present invention provides a road surface slip determination apparatus and method using a wheel rotation speed and a vehicle speed capable of classifying a slip state of a road to determine a hazard.

Another technical problem to be achieved by the present invention is to provide a road surface slip determination device using the wheel rotation speed and the vehicle speed to enable the safe driving of the subsequent vehicle by transmitting the sliding information to the following vehicles in advance to warn the danger of the road and its It is to provide a method.

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: 0<

<

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<1) 및 가속도 임계값(

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:

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)과 각각 비교하여, 상기 비교 결과에 따라 노면 미끄럼 상태를 정상, 미끄럼 주의, 미끄럼 경고 또는 판정 유보로 분류하는 노면 미끄럼 판단모듈을 포함하되, 상기 노면 미끄럼 판단모듈은, 상기 GPS 모듈로부터 차량 속도 데이터를 수신하고, 상기 차륜 회전수 측정센서로부터 차량 회전속도 데이터를 수신하는 데이터 수집부; 상기 데이터 수집부에서 수신된 차량 속도 및 차륜 회전속도에 근거하여 슬립 값(s), 가속도 및 감속도를 산출하는 데이터 전처리부; 상기 산출된 슬립 값(s), 가속도 및 감속도와 각각 비교하기 위한 제1 내지 제3 미끄럼 임계값(

~

) 및 제1 내지 제3 가속도 임계값(

~

)을 설정하는 임계값 설정부; 상기 산출된 슬립 값(s), 가속도 및 감속도와 상기 제1 내지 제3 미끄럼 임계값(

~

) 및 제1 내지 제3 가속도 임계값(

~

)과 각각 비교하여, 상기 비교 결과에 따라 노면 미끄럼 상태를 정상, 미끄럼 주의, 미끄럼 경고 또는 판정 유보로 분류하는 미끄럼 판단부; 및 상기 분류된 미끄럼 정보를 전송하는 미끄럼 정보 전송부를 포함하고, 상기 노면 미끄럼 판단모듈에서 산출된 슬립 값(s)은 차량과 노면의 미끄러운 정도를 정량화한 값으로, 주행중인 차륜 회전속도의 상대적인 차이와 차량의 절대속도에 의해 정해지며, 상기 미끄럼 판단부는, 가속도 또는 감속도가 제1 가속도 임계값보다 작지만 제3 미끄럼 임계값보다 큰 슬립 값(s)이 측정된 경우, 노면이 매우 미끄러운 미끄럼 경보 상태로 분류하는 것을 특징으로 한다.As a means for achieving the above-described technical problem, the road surface slip determination device using the wheel rotation speed and the vehicle speed according to the present invention, the GPS (Global Positioning System) module for calculating the vehicle speed for the running vehicle; A wheel rotation speed sensor attached to a wheel of a running vehicle to measure a rotation speed of the wheel; And calculating a slip value (s), an acceleration, and a deceleration based on the vehicle speed and the wheel rotation speed received from the GPS module and the wheel speed measurement sensor, and presetting the calculated slip value, acceleration, and deceleration. Slip threshold (

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: 0 <

<

<

<1) and the acceleration threshold (

~

:

<A ₂ <

And a road slip determination module for classifying the road slip state into normal, slip notice, slip warning, or reservation reserved according to the comparison result, wherein the road slip determination module includes vehicle speed data from the GPS module. A data collector configured to receive a vehicle speed data from the wheel speed sensor; A data preprocessor for calculating a slip value (s), an acceleration and a deceleration based on the vehicle speed and the wheel rotation speed received by the data collector; First to third slip threshold values (1) for comparison with the calculated slip values (s), accelerations and decelerations, respectively;

~

) And the first to third acceleration thresholds (

~

Threshold setting unit for setting; The calculated slip value s, acceleration and deceleration and the first to third slip thresholds (

~

) And the first to third acceleration thresholds (

~

A slip determination unit for classifying a road surface slip state into a normal, sliding caution, sliding warning, or determination reservation according to the comparison result; And a slip information transmission unit for transmitting the classified slip information, wherein the slip value s calculated by the road slip determination module is a value quantifying the slipperiness of the vehicle and the road surface, and is a relative difference between wheel rotation speeds while driving. Is determined by the absolute speed of the vehicle, and the slip determination unit is a sliding warning that the road surface is very slippery when a slip value s of which the acceleration or deceleration is smaller than the first acceleration threshold but larger than the third sliding threshold is measured. Characterized in the state.

이 휠의 각도에 따른 차륜 각속도이고,

가 유효 휠 반경이며,

가 차량 절대속도이고,

가 차륜 회전속도일 때,

로 주어질 수 있다.Here, the slip value s is

Wheel angular velocity according to the angle of this wheel,

Is the effective wheel radius,

Is the absolute speed of the vehicle,

Is the wheel speed,

Lt; / RTI &gt;

delete

) 미만인 경우, 노면의 미끄럼이 위험하지 않은 정상 상태로 분류할 수 있다.Here, the slip determination unit, the slip value (s) is the first slip threshold (

If less than), it can be classified as a normal state where the slip of the road surface is not dangerous.

delete

delete

Here, the slip determination unit, if the number of acceleration or deceleration (acceleration and deceleration) data is smaller than the set value (N) to perform a regression analysis, but the slip value is larger than the first sliding threshold value and smaller than the third sliding threshold value. According to the maximum slip value, the road surface state can be classified as a slip warning state or a slip warning state without estimating acceleration or deceleration (acceleration / deceleration).

Here, when the number of acceleration or deceleration (acceleration / deceleration) data is greater than the set value N, the slip determination unit approximates the maximum acceleration / deceleration by the regression curve when the regression curve fitting can be performed. According to the approximated maximum acceleration / deceleration and the maximum slip value, the road surface state may be classified as a slip warning, a slip warning, or a normal state.

The road surface slip determination device using the wheel rotation speed and the vehicle speed according to the present invention further includes a roadside base station apparatus (RSE) which receives the slide information from the road surface slip determination module and transmits the slip information to a subsequent vehicle that is driving. can do.

~

: 0<

<

<

<1) 및 가속도 임계값(

~

:

<A₂<

)과 각각 비교하는 단계; 및 d) 상기 비교 결과에 따라 노면 미끄럼 상태를 정상, 미끄럼 주의, 미끄럼 경고 또는 판정 유보로 분류하는 단계를 포함하되, 상기 슬립 값(s)은 차량과 노면의 미끄러운 정도를 정량화한 값으로, 주행중인 차륜 회전속도의 상대적인 차이와 차량의 절대속도에 의해 정해지며, 상기 c) 단계에서 가속도 또는 감속도가 제1 가속도 임계값보다 작지만 제3 미끄럼 임계값보다 큰 슬립 값(s)이 측정된 경우, 상기 d) 단계에서 노면이 매우 미끄러운 미끄럼 경보 상태로 분류하는 것을 특징으로 한다.On the other hand, as another means for achieving the above-described technical problem, the road slip determination method using the wheel rotation speed and the vehicle speed according to the present invention, a) measuring the wheel rotation speed and the vehicle speed of the vehicle being driven; b) calculating a slip value (s), an acceleration (Acc.) and a deceleration (Dec.) according to the wheel rotation speed and the vehicle speed; c) The calculated slip value (s), acceleration and deceleration are set to a predetermined slip threshold value (

~

: 0 <

<

<

<1) and the acceleration threshold (

~

:

<A ₂ <

), Respectively; And d) classifying the road slip state into a normal, slip notice, slip warning, or reservation hold according to the comparison result, wherein the slip value s is a value quantifying the slipperiness of the vehicle and the road surface. Is determined by the relative difference between the wheel rotation speed and the absolute speed of the vehicle, and in step c), when the acceleration value or the deceleration rate is smaller than the first acceleration threshold but larger than the third sliding threshold, the slip value s is measured. In step d), the road surface may be classified as a very slippery warning state.

The road slip determination method using the wheel rotation speed and the vehicle speed according to the present invention comprises the steps of: e) transmitting the classified slip information to a roadside base station apparatus (RSE); And f) transmitting the sliding information to a subsequent vehicle on which the roadside base station apparatus (RSE) is driving.

Here, the wheel rotation speed of the vehicle of step a) may be measured by a wheel rotation speed sensor, and the vehicle speed may be measured by a GPS (Global Positioning System) module.

According to the present invention, the wheel rotation speed and the vehicle speed are respectively calculated through the wheel speed measurement sensor attached to the wheel and the GPS module mounted in the vehicle, and the risk factors are determined by classifying the slip state on the road surface using the wheel rotation speed and the vehicle speed. can do.

According to the present invention, when a risk factor is detected through a slip determination device, a roadside base station apparatus (Road) located on a roadside by the on-board equipment (OBE) mounted on a vehicle may transmit risk information such as a caution and a slip warning. Side Equipment (RSE), and the roadside base station device transmits sliding information to the following vehicles to warn of dangers on the road in advance, thereby enabling safe driving of subsequent vehicles.

1 is a photograph showing a traffic accident due to deterioration (fog, freezing, etc.) of bad weather road conditions.
2 is a block diagram of a road surface state warning device according to the prior art.
3 is a block diagram of a sliding friction predicting apparatus of a road surface according to the prior art.
4 is a diagram illustrating that the road slip determination device using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention is applied to the DSRC system.
FIG. 5 is a diagram schematically illustrating a case where a road surface slip determination device using a wheel rotation speed and a vehicle speed according to an embodiment of the present invention is implemented in a vehicle.
6 is a block diagram of a road slip determination apparatus using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention.
7 is a flowchart illustrating a road slip determination method using a wheel rotation speed and a vehicle speed according to an exemplary embodiment of the present invention.
8A and 8B are detailed flowcharts illustrating a road slip determination method using a wheel rotation speed and a vehicle speed according to an exemplary embodiment of the present invention.
9 is a diagram illustrating a regression curve used in the road slip determination method using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. Also, the term "part" or the like, as described in the specification, means a unit for processing at least one function or operation, and may be implemented by hardware, software, or a combination of hardware and software.

4 is a diagram illustrating a road slip determination apparatus using a wheel rotation speed and a vehicle speed according to an embodiment of the present invention applied to a DSRC system, and FIG. 5 illustrates a wheel rotation speed and a vehicle speed according to an embodiment of the present invention. FIG. 1 is a diagram schematically illustrating a case where a road surface slip determination apparatus using the same is implemented in a vehicle.

The road slip determination apparatus using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention may be applied to a DSRC system, as shown in FIG. 4.

Intelligent Transport System (ITS) is being introduced that can expect improved transportation effect by using information and communication technology that is being developed recently. This ITS is a next-generation traffic system that enables the driver to drive safely, comfortably and quickly by intelligentizing the car and road environment, and combines the existing traffic system with advanced technologies such as information communication, electronics, control, and computers. It is a transportation system to improve the mobility, safety, efficiency and transportation environment.

In order to construct such ITS, it is necessary to introduce a system that can collect and distribute high-quality traffic information efficiently. For this, a dedicated short range communication (DSRC) technology has been proposed.

The DSRC uses roadside station equipment (RSE) 200a, 200b having a communication radius of several m to several hundred m using the information communication technology that has been developed so far, and a vehicle-mounted device that passes through the communication area of the RSE. It is a bidirectional high-speed wireless communication technology between board equipment (OBE) (or terminal). Here, the RSE (200a, 200b) is installed on the side of the road, transmits the unique ID of the OBEs received from the various OBEs to the local server, and requests the desired information from the local server, and sends this information to the OBE (100a, 100b) It serves to transmit.

In addition, the roadside base station apparatus (200a, 200b) serves to collect the traffic situation and transmit it to the traffic information center (300). In addition, when the traffic conditions thus collected are analyzed and processed by the traffic information center 300 and transmitted to the roadside base station devices 200a and 200b, the traffic information is transmitted to the drivers again.

In addition, the OBE (or terminal) (100a, 100b) is mounted on the vehicle, and transmits raw data such as OBE unique ID and inter-road driving time, accident information for the traffic information to the RSE, RSE (200a, 200b) requests desired information, and receives traffic information such as unique ID of RSE, driving speed between road sections, traffic accident information and general broadcasting information, and provides the user with LCD or voice.

The road slip determination device using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention may be implemented in the OBE (or terminal) 100a, 100b, the GPS (Global Positioning System) module 110, wheel rotation The water measurement sensor 120 and the road surface slip determination module 130 may be included.

The road slip determination device using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention measures the vehicle speed from the GPS module 110, and measures the wheel rotation speed from the wheel rotation speed measurement sensor 120, such a vehicle The slip value, the acceleration and the deceleration are calculated based on the speed and the wheel rotation speed, and the calculated slip value, the acceleration and the deceleration are compared with the predetermined slip threshold value and the acceleration threshold value, respectively, and the road surface according to the comparison result. Slip states are classified as normal, slip notice, slip warning, or reservation hold. Thereafter, the road slip information may be transmitted to the RSEs 200a and 200b.

Referring to FIG. 5, in a road slip determination apparatus using a wheel rotation speed and a vehicle speed according to an embodiment of the present invention, the road slip determination module 130 may include a CPU 130a, a USB / Serial port converter 130b, and a USB. It may be implemented in hardware, such as hub (130c), in this case, the USB hub (130c) can communicate with the GPS module 110, it can also be connected to other in-vehicle device 140, for example, a laptop. have.

6 is a block diagram of a road slip determination apparatus using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention.

Referring to FIG. 6, the road slip determination apparatus using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention may include a GPS module 110, a wheel rotation speed measurement sensor 120, and a road slip determination module 130. In this case, the road surface slip determination module 130 includes a data collector 131, a data preprocessor 132, a threshold setting unit 133, a slip determination unit 134, and a slip information transmission unit 135. It may include, but is not limited to.

The GPS module 110 calculates a vehicle speed for a driving vehicle. For example, in response to the recent explosion of DSRC-based high-pass vehicles, most vehicles are car-navigation-equipped vehicles equipped with the GPS module 110, so that accurate speeds of vehicles can be collected. have.

The wheel rotation speed measurement sensor 120 is attached to the wheel of the driving vehicle to measure the rotation speed of the wheel.

~

) 및 제1 내지 제3 가속도 임계값(

~

)과 각각 비교하여, 상기 비교 결과에 따라 노면 미끄럼 상태를 정상, 미끄럼 주의, 미끄럼 경고 또는 판정 유보로 분류한다.The road surface slip determination module 130 calculates a slip value s and an acceleration / deceleration based on the vehicle speed and the wheel rotation speed received from the GPS module 110 and the wheel rotation speed measurement sensor 120. The calculated slip value, acceleration / deceleration, and the predetermined first to third slip threshold values (

~

) And the first to third acceleration thresholds (

~

), The road surface slip state is classified into normal, slippery, slip warning, or decision hold according to the comparison result.

Specifically, the data collection unit 131 of the road surface slip determination module 130 receives the vehicle speed data from the GPS module 110 and receives the vehicle rotation speed data from the wheel speed measurement sensor 120. .

이 휠의 각도에 따른 차륜 각속도이고,

가 유효 휠 반경이며,

가 차량 절대속도이고,

가 차륜 회전속도일 때,

로 주어질 수 있다.The data preprocessor 132 of the road slip determination module 130 calculates a slip value s, an acceleration, and a deceleration based on the vehicle speed and the wheel rotation speed received from the data collector 131. In this case, the calculated slip value s is a value quantifying the slipperiness of the vehicle and the road surface, and may be determined by a relative difference of the wheel rotation speed while driving and an absolute speed of the vehicle, wherein the slip value s is ,

Wheel angular velocity according to the angle of this wheel,

Is the effective wheel radius,

Is the absolute speed of the vehicle,

Is the wheel speed,

Lt; / RTI &gt;

~

) 및 제1 내지 제3 가속도 임계값(

~

)을 설정 및 저장한다.The threshold setting unit 133 of the road surface slip determination module 130 may include first to third slip thresholds for comparing with the calculated slip value s, acceleration, and deceleration, respectively.

~

) And the first to third acceleration thresholds (

~

Set up and save.

~

) 및 제1 내지 제3 가속도 임계값(

~

)과 각각 비교하여, 상기 비교 결과에 따라 노면 미끄럼 상태를 정상, 미끄럼 주의, 미끄럼 경고 또는 판정 유보로 분류한다.The slip determination unit 134 of the road surface slip determination module 130 may include the calculated slip value s, acceleration and deceleration, and the first to third slip threshold values (

~

) And the first to third acceleration thresholds (

~

), The road surface slip state is classified into normal, slippery, slip warning, or decision hold according to the comparison result.

The sliding information transmitter 135 of the road surface slip determination module 130 transmits the classified sliding information to a roadside base station apparatus (RSE). Subsequently, the roadside base station apparatus RSE may receive the sliding information from the road surface slip determination module 130 and transmit the sliding information to a subsequent vehicle that is driving.

The road slip determination device using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention, the wheel rotation speed sensor and the wheel rotation speed sensor 120 attached to the wheel and the GPS module 110 mounted in the vehicle, respectively, The vehicle speed is calculated and the hazard is classified by classifying the slippery state on the road surface. When the risk factor is detected through the road slip determination device, the road slip determination module 130 implemented in the on-board equipment (OBE) is configured to display the hazard information such as a caution or a slip warning on the roadside. It transmits to a roadside base station apparatus (RSE).

Thereafter, the roadside base station apparatus (RSE) warns in advance of a hazard of the road by transmitting sliding information to subsequent driving vehicles, thereby enabling safe driving of the vehicle.

Hereinafter, the slip determination principle of the road surface slip determination device using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention will be described in detail.

First, the road surface slip determination apparatus using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention, the collected data of the GPS module 110 and the wheel speed measurement sensor 120 mounted on the wheel for classification of the road slip state Is used. The wheel rotation speed of the vehicle being driven may be calculated through the collection data of the wheel rotation speed measurement sensor 120, and the vehicle speed of the vehicle may be calculated through the GPS module 110 collected data.

~

) 및 제1 내지 제3 가속도 임계값(

~

)과 비교함으로써 노면의 미끄럼 상태를 분류할 수 있다.The wheel rotation speed and the vehicle speed calculated as described above may be calculated as a slip value s, which is a parameter value for sliding state classification, and an acceleration / deceleration of a vehicle Dec. The slip value s and the acceleration / deceleration are respectively set as the first to third slip threshold values (

~

) And the first to third acceleration thresholds (

~

), The sliding state of the road surface can be classified.

Specifically, in order to determine the sliding state according to the embodiment of the present invention, the slip value s quantifying the slipperiness of the vehicle and the road surface being driven and the acceleration / deceleration of the vehicle are required.

In the case of the slip value (s), it is defined by the relative difference of the wheel rotation speed while driving and the absolute speed of the vehicle. For example, when the driving shaft of the vehicle is accelerated so that the wheel rotation speed is higher than the vehicle absolute speed, there is a slip in the vehicle, and the value increases when the wheel rotation speed is relatively higher than the vehicle absolute speed. The calculation method of the slip value s may be given by Equation 1 below.

는 휠의 각도에 따른 차륜 각속도이고,

는 유효 휠 반경이며

는 차량 절대속도이고,

는 차륜 회전속도이다. 이때, 슬립 값(s)은 0 ≤ s ≤ 1의 값을 갖고, 슬립 값(s)이 클수록 미끄러운 상태를 나타낸다. 예를 들면, 슬립 값(s)이

보다 작으면 미끄럼이 거의 없는 상태를 나타내고, 0 <

<

<

< 1로 주어질 수 있다.here,

Is the wheel angular velocity according to the wheel angle,

Is the effective wheel radius

Is the absolute speed of the vehicle,

Is the wheel speed. At this time, the slip value s has a value of 0 ≦ s ≦ 1, and the slip value s represents a slippery state as the slip value s is larger. For example, the slip value s

A smaller value indicates a state of little slippage, where 0 <

<

<

Can be given as <1.

In addition, in the case of acceleration and deceleration, the speed change amount is defined as a ratio of an increase in absolute speed of the vehicle collected by the GPS module 110 and an increase in time, which is given by Equation 2 below.

는 차량 절대속도의 증가분을 나타내고,

는 시간의 증가분을 나타낸다. 따라서 가속도 a는 속도의 변화량을 나타낸다.here,

Represents the increase in absolute vehicle speed,

Represents an increase in time. Therefore, acceleration a represents the amount of change of speed.

)는 다음의 수학식 3과 같이, 종방향 타이어-도로의 마찰력(

) 및 수직항력(normal force:

)으로 정의된다.According to this definition, the slip value s has a value between 0 and 1. Friction coefficient (Because only friction and slip in the direction of travel of the vehicle are handled)

) Is the frictional force of the longitudinal tire-road (

) And normal force

).

For the approximation of the tire-road friction coefficient, it is assumed that only the driving wheel slip of the vehicle and the acceleration of the vehicle are included, and the side tire-road frictional force is negligible. In addition, parameters such as wheel rolling resistance, aerodynamics, and road type are assumed to be negligible.

Therefore, the relationship between the acceleration / deceleration of the vehicle, the static frictional force and the deceleration force can be obtained by using Equation 4 below using Newton's second law.

은 모든 휠을 포함한 차량 질량이고,

는 종방향 가속도,

는 차량의 구동바퀴에 인가되는 총 정지마찰력을 뜻한다. 앞 타이어와 뒷 타이어에 작용하는 일반 힘이 동일하다고 가정하면 그것들의 총 합은 차량 중량과 거의 일치한다.here,

Is the mass of the vehicle, including all wheels,

Is the longitudinal acceleration,

Is the total static frictional force applied to the drive wheel of the vehicle. Assuming that the general forces acting on the front and rear tires are the same, their sum is almost equal to the vehicle weight.

In addition, the friction coefficient is obtained by using the vertical force and the friction coefficient when the vehicle accelerates, the friction coefficient can be approximated by the following equation (5) by the longitudinal acceleration of the vehicle.

On the other hand, when the vehicle is accelerated, the friction force is operated not only on the driving wheel but also on the other two wheels (based on the two-axis vehicle) at the same time, so that similar approximations can be obtained for the friction coefficients of all wheels as shown in Equation 6 below.

)의 임계값은 차량의 가속도/감속도(감가속도)로 대신할 수 있다. 이때, 근사값은 다음과 같은 수학식 7과 같이 해석할 수 있다.In order to determine the road slip state by applying the above methodology, it is estimated by using the acceleration and deceleration of the vehicle.

) Can be replaced by the acceleration / deceleration (deceleration) of the vehicle. In this case, the approximation value may be interpreted as Equation 7 below.

는 ij번째의 바퀴에 인가되는 힘을 의미하며

은 차량의 질량,

는 중력상수,

는 모든 타이어에 같다고 가정한다. 그러므로 측정된 최대 가속은 최대 마찰계수

이하가 된다. 반면에 최대 마찰계수는 최대 가속을 가능하게 한다. 그러므로 도로의 한 부분에서 측정된 최대 가능 감속이 0.5

일 때 최대 마찰계수는 0.5보다 크게 된다.here,

Is the force applied to the ijth wheel,

Is the mass of the vehicle,

Is the gravity constant,

Is assumed to be the same for all tires. Therefore, the maximum acceleration measured is the maximum coefficient of friction

Or less. On the other hand, the maximum coefficient of friction allows for maximum acceleration. Therefore, the maximum possible deceleration measured on one part of the road is 0.5

, The maximum coefficient of friction is greater than 0.5.

As a result, according to the road slip determination device using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention, the wheel rotation speed collected from the wheel rotation speed sensor 120 and the GPS module 110 mounted on the vehicle, respectively; If the slip state is judged based on the slip value (s) and acceleration / deceleration (deceleration) calculated through the data preprocessing for the vehicle speed, it is determined that the road surface is normal, slip warning, slip notice or judgment hold state. You can get the result.

Meanwhile, FIG. 7 is a flowchart illustrating a road slip determination method using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention, and FIGS. 8A and 8B illustrate the wheel rotation speed and the vehicle speed according to the embodiment of the present invention. Detailed operation flow chart of the road slip determination method.

7, 8A and 8B, the road slip determination method using the wheel rotation speed and the vehicle speed according to an embodiment of the present invention, first measuring the wheel rotation speed and the vehicle speed of the vehicle being driven ( S110 ). . In this case, the wheel rotation speed of the vehicle is measured by a wheel rotation speed sensor, and the vehicle speed is measured by a GPS (Global Positioning System) module.

Next, the slip value s, the acceleration Acc. And the deceleration Dec. according to the wheel rotation speed and the vehicle speed are calculated ( S120 ). In this case, the slip value s is a value quantifying the slipperiness of the vehicle and the road surface, and may be determined by the relative difference between the wheel rotation speeds while driving and the absolute speed of the vehicle.

~

) 및 제1 내지 제3 가속도 임계값(

~

)과 각각 비교한다(S130). 이때, 미끄러운 정도를 정량화한

~

(0<

<

<

<1)의 세 가지 미끄럼 임계값과

~

(

<A₂<

)의 세 가지 가속도 임계값, 측정데이터 수에 대한 임계값(N)이 있다.Next, the calculated slip values S, accelerations or decelerations may be set in the first to third sliding threshold values (

~

) And the first to third acceleration thresholds (

~

) And each ( S130 ). At this time, the slippery degree was quantified

~

(0 <

<

<

With three slip thresholds of <1)

~

(

<A ₂ <

Are three acceleration thresholds, and a threshold value N for the number of measured data.

)보다 작은지 확인한다(S131). 산출된 슬립 값(S)이 제1 미끄럼 임계값(

)보다 작은 경우는, 아스팔트와 같이 높은 마찰계수를 갖는 표면에서의 일반적인 운전 조건으로서, 이때 슬립 값은 대개

미만이다. 즉, 상기 아스팔트와 같이 마찰계수가 높은 운전조건 하에서 상기 슬립 값(s)은 제1 미끄럼 임계값(

) 미만인 경우, 노면의 미끄럼이 위험하지 않은 정상 상태로 분류하게 된다.Specifically, referring to FIG. 8A, the calculated slip value S is the first slip threshold value (

Check whether it is smaller than ( S131 ). The calculated slip value S is the first slip threshold value (

Less than), this is a general operating condition on surfaces with high coefficients of friction, such as asphalt, where slip values are usually

. That is, the slip value s is a first slip threshold value (s) under an operating condition having a high friction coefficient such as asphalt.

If it is less than), the road surface is classified as a non-hazardous steady state.

)보다 크고, 가속도가 제1 가속도 임계값(

)보다 작거나 또는 감속도가 2

보다 작은지 확인한다(S132). 이러한 조건은 얼음이나 기름진 표면과 같이 예외적으로 미끄러운 표면을 구분하기 위한 것으로, 상기 가감속이 제1 가속도 임계값(

)보다 작지만 제3 미끄럼 임계값(

)보다 큰 슬립 값(s)이 측정된 경우, 노면이 매우 미끄러운 미끄럼 경보 상태로 분류하게 된다.Thereafter, the calculated slip value S is a third slip threshold value (

Greater than), and the acceleration is greater than the first acceleration threshold (

Is less than or equal to 2

Check if it is smaller than ( S132 ). This condition is used to distinguish exceptionally slippery surfaces, such as ice or oily surfaces.

) But less than the third sliding threshold (

If a slip value (s) greater than) is measured, the road surface is classified as a slippery slip alarm condition.

)보다 크거나 또는 감속도가 2

보다 큰지 확인한다(S133). 이러한 조건은 미끄럼 판단 결과로부터 눈에 두드러진 슬립 값이 없는 약한 자극(가감속)의 경우를 판별하는 조건이다. 약한 자극 때문에, 즉, 낮은 마찰력 때문에 슬립 값을 이용하여 도로 미끄럼 상태 판단이 용이하지 않다. 따라서 판단 유보 상태가 되며, 이것은 후속적인 노면 미끄럼 상태 판단을 위한 결정적인 데이터가 아니란 것을 의미한다. 구체적으로, 낮은 마찰력에 대응하여 상기 제1 미끄럼 임계값(

)보다 크고 제3 미끄럼 임계값(

)보다 작은 슬립 값(s)이 측정되지만, 가속도가 제1 가속도 임계값보다 작거나 감속도가 2

보다 작은 경우, 도로 미끄럼 상태 판별이 어려운 미끄럼 판단 유보 상태(S144)로 분류하게 된다.Then, the calculated acceleration is the first acceleration threshold (

Greater than or less than 2

Check if greater than ( S133 ). This condition is a condition for discriminating the case of a weak stimulus (acceleration / deceleration) having no noticeable slip value from the slip determination result. Because of the weak stimulus, i.e., the low frictional force, slippage is not easy to determine by using slip values. Thus, the judgment is in a reserved state, which means that it is not critical data for subsequent road slip determination. Specifically, the first sliding threshold value corresponding to the low friction force (

Greater than) and the third sliding threshold (

A slip value s less than) is measured, but the acceleration is less than the first acceleration threshold or the deceleration is 2

If smaller, it is classified as a slip determination reserved state ( S144 ) that is difficult to determine the road slip state.

Thereafter, it is checked whether the number of acceleration or deceleration (acceleration / deceleration) data N obtained at predetermined time intervals for a predetermined time period is sufficient for regression analysis ( S134 ). In this case, the time interval means a period between two acceleration / deceleration points. For example, FIG. 9 is a diagram illustrating a regression curve used in a road slip determination method using a wheel rotation speed and a vehicle speed according to an embodiment of the present invention, and illustrates a regression analysis using acceleration / deceleration data. Here, the X axis represents the slip rate as an independent variable, the Y axis represents the acceleration or deceleration data as a dependent variable, and accordingly, the correlation between the acceleration or deceleration of the dependent variable is established according to the slip rate as the independent variable. Will be. 9 is only to illustrate that regression analysis may be performed using acceleration / deceleration data, and it is apparent to those skilled in the art that a correlation between dependent variables according to independent variables may be estimated using a regression curve. Therefore, detailed description is omitted. As a result, when the acceleration or deceleration data number N is large, the slipperiness of the road surface can be accurately determined by estimating the acceleration or deceleration corresponding to the regression curve, and when the acceleration or deceleration data number N is small. The slipperiness of the road surface is determined using the maximum slip value.

Subsequently, referring to FIG. 8B, when the acceleration or deceleration data number N is small, the data number is insufficient to perform a regression analysis, but the slip threshold value is high. At this time, acceleration or deceleration estimation is impossible, but if the slip value is larger than the second sliding threshold value, the road surface state is divided into a slip warning state and a slip attention state. For example, when the maximum slip value is greater than the second slip threshold and less than the third slip threshold ( S135 ), it is determined as a slip attention state, and when the maximum slip value is greater than the third slip threshold ( S136 ), it is slipped. The warning state is determined.

Also, if the acceleration or deceleration is greater than the first acceleration threshold and the number of acceleration or deceleration data (N) is sufficient to fit the regression curve (regression curve), then the maximum acceleration / deceleration is added to the nonlinear regression curve. It can be approximated by ( S137 ). Based on this approximated maximum acceleration / deceleration and the measured maximum slip value, the road conditions are divided into three types: slip warning, slip warning or normal. For example, when the maximum acceleration is greater than the second acceleration threshold A ₂ and less than the third acceleration threshold A ₃ (or the maximum deceleration is greater than 2A _{2 and} greater than the third acceleration threshold A ₃ ). Small) and when the maximum slip value is smaller than the third sliding threshold ( S138 ), it is determined as a slip attention state, and the maximum acceleration is smaller than the second acceleration threshold A ₂ (or the maximum deceleration is If less than 2A ₂ ) and the maximum slip value is greater than the third slip threshold value ( S139 ), it is determined as a slip warning state.

According to the above-described comparison result, the road surface slip state is classified into normal ( S141 ), sliding attention ( S142 ), sliding warning ( S143 ), or determination reservation ( S144 ) ( S140 ).

Next, referring back to FIG. 7, the classified slide information is transmitted to the roadside base station apparatus RSE ( S150 ), and the roadside base station apparatus RSE transmits the sliding information to a subsequent vehicle that is driving ( S160). ).

That is, the data collected from the sensor mounted on the vehicle is monitored in real time through the analysis software, and if it is determined that the sliding state by the road surface slip determination module according to an embodiment of the present invention, transmits the information to the RSE, and transmits As the information is transmitted to the rear vehicle, the rear vehicle is aware of the front road slip state (freezing, sand, oil, rainfall, etc.) in advance. As a result, it is possible to prevent traffic accidents caused by sudden slippage of the road ahead, and to prevent unnecessary traffic jams caused by traffic accidents.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

100: road surface skid determination device
100a, 100b: On-Board Equipment (OBE)
200, 200a, 200b: Road Side Equipment (RSE)
300: Traffic Information Center
110: GPS module
120: wheel speed sensor
130: road surface slip determination module
140: other in-vehicle devices
131: data collector
132: data preprocessor
133: threshold setting unit
134: slip determination unit
135: sliding information transmission unit

Claims (18)

A Global Positioning System (GPS) module for calculating a vehicle speed with respect to a driving vehicle;
A wheel rotation speed sensor attached to a wheel of a running vehicle to measure a rotation speed of the wheel; And
A slip value (s), an acceleration, and a deceleration are calculated based on the vehicle speed and the wheel rotation speed received from the GPS module and the wheel speed measurement sensor, and the calculated slip value, acceleration, and deceleration are pre-set sliding. Threshold (

~

: 0 <

<

<

<1) and the acceleration threshold (

~

:

<A ₂ <

), And the road slip determination module classifies the road slip state into normal, slip warning, slip warning, or pending reservation according to the comparison result.
Including, but the road surface slip determination module,
A data collector configured to receive vehicle speed data from the GPS module and to receive vehicle rotation speed data from the wheel speed measurement sensor;
A data preprocessor for calculating a slip value (s), an acceleration and a deceleration based on the vehicle speed and the wheel rotation speed received by the data collector;
First to third slip threshold values (1) for comparison with the calculated slip values (s), accelerations and decelerations, respectively;

~

) And the first to third acceleration thresholds (

~

Threshold setting unit for setting;
The calculated slip value s, acceleration and deceleration and the first to third slip thresholds (

~

) And the first to third acceleration thresholds (

~

A slip determination unit for classifying a road surface slip state into a normal, sliding caution, sliding warning, or determination reservation according to the comparison result; And
Sliding information transmission unit for transmitting the classified sliding information
Lt; / RTI &gt;
The slip value s calculated by the road slip determination module quantifies the slippery degree between the vehicle and the road surface, and is determined by a relative difference between the wheel rotation speeds being driven and the absolute speed of the vehicle. Or when the slip value s of which the deceleration is smaller than the first acceleration threshold but larger than the third slip threshold is measured, the road surface is classified into a slippery slip warning state. Road surface slipper device. The method of claim 1,
The slip value s is

Wheel angular velocity according to the angle of this wheel,

Is the effective wheel radius,

Is the absolute speed of the vehicle,

Is the wheel speed,

Road slip determination device using the wheel rotation speed and the vehicle speed, characterized in that given by. delete The method of claim 1,
The slip determination unit may include the slip value s being equal to the first slip threshold value under an operating condition with a high friction coefficient.

Less than), the road surface slip determination device using the wheel rotation speed and the vehicle speed, characterized in that the slip of the road surface is classified as a non-hazardous steady state. delete delete The method of claim 1,
If the slip determination unit cannot perform the regression analysis because the number of acceleration or deceleration (acceleration / deceleration) data is smaller than the set value (N), but the slip value is larger than the first sliding threshold value and smaller than the third sliding threshold value, the acceleration Or the road surface slip determination device using the wheel rotation speed and the vehicle speed, characterized in that the road condition is classified as a slip warning state or a slip warning state according to the maximum slip value without deceleration (deceleration). The method of claim 1,
When the number of acceleration or deceleration (acceleration / deceleration) data is greater than the set value N, the slip determination unit approximates the maximum acceleration / deceleration by the regression curve when the regression curve fitting can be performed. A road slip determination apparatus using a wheel rotation speed and a vehicle speed, characterized in that the road condition is classified into a slip warning, slip caution, or a normal state according to an approximate maximum acceleration / deceleration and a maximum slip value. The method of claim 1,
A roadside base station apparatus (RSE) which receives the sliding information from the road surface slip determination module and transmits the sliding information to a subsequent vehicle that is driving.
Road slip determination device using the wheel rotation speed and the vehicle speed further comprising a. a) measuring the wheel rotation speed and the vehicle speed of the running vehicle;
b) calculating a slip value (s), an acceleration (Acc.) and a deceleration (Dec.) according to the wheel rotation speed and the vehicle speed;
c) The calculated slip value (s), acceleration and deceleration are set to a predetermined slip threshold value (

~

: 0 <

<

<

<1) and the acceleration threshold (

~

:

<A ₂ <

), Respectively; And
d) classifying the road slip state as normal, slip warning, slip warning, or pending reservation according to the comparison result;
Including but not limited to:
The slip value s is a value quantifying the slipperiness of the vehicle and the road surface, and is determined by the relative difference between the wheel rotation speed and the absolute speed of the vehicle.
In step c), when the slip value s of which the acceleration or the deceleration is smaller than the first acceleration threshold but greater than the third sliding threshold is measured, classifying the road surface as a very slippery slip state in step d). A road slip determination method using the wheel rotation speed and the vehicle speed characterized in that. The method of claim 10,
e) transmitting the classified sliding information to a roadside base station apparatus (RSE); And
f) transmitting the sliding information to a subsequent vehicle on which the roadside base station apparatus (RSE) is driving;
Road slip determination method using the wheel rotation speed and the vehicle speed further comprising a. The method of claim 10,
The wheel rotation speed of the vehicle of step a) is measured by the wheel speed sensor, and the vehicle speed is measured by the GPS (Global Positioning System) module, characterized in that the road surface slip determination using the vehicle speed and the vehicle speed Way. The method of claim 10,
The slip value s is

Wheel angular velocity according to the angle of this wheel,

Is the effective wheel radius,

Is the absolute speed of the vehicle,

Is the wheel speed,

Road slip determination method using the wheel rotation speed and the vehicle speed, characterized in that given by. The method of claim 10,
In the step c), the slip value s becomes a first sliding threshold value under a high friction coefficient.

Less than), the road slip determination method using the wheel rotation speed and the vehicle speed, characterized in that in step d) is classified as a normal state that the slip of the road surface is not dangerous. delete delete The method of claim 10,
In step c), if the number of acceleration or deceleration (acceleration / deceleration) data is smaller than the set value (N), regression analysis cannot be performed, but if the slip value is larger than the first sliding threshold and smaller than the third sliding threshold, the acceleration Or the road surface slip determination method using the wheel rotation speed and the vehicle speed, characterized in that the road surface state is classified as a slip warning state or a slip warning state according to the maximum slip value without deceleration (acceleration and deceleration) estimation. The method of claim 10,
In step c), when the number of acceleration or deceleration (acceleration / deceleration) data is larger than the set value (N) to perform a regression curve fitting (regression curve) fitting, the regression curve approximates the maximum acceleration / deceleration accordingly. A road slip determination method using a wheel rotation speed and a vehicle speed, characterized in that the road condition is classified as a slip warning, a slip warning or a normal state according to the approximate maximum acceleration / deceleration and the maximum slip value.

Images