JP2009056818A - Vehicular system for traveling road surface state estimation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a state detection system for a traveling road surface that quickly and accurately detects the state of a traveling road surface during vehicle traveling. <P>SOLUTION: Sensor units 100A, 100B detect x acceleration in a rotational tangential direction and y acceleration in a rotary-shaft direction in an idle wheel and a drive wheel, respectively. At least one of an integrated value, an average value, a variance value, skewness, or a kurtosis within a fixed measurement time of the x, y acceleration, and further, that of r acceleration generated by subjecting the x, y acceleration to vector synthesis are calculated in a main unit 200. An operation value of the calculation result and an operation value as pattern data for each state of a traveling road surface previously stored in a storage part 204 are compared with each other so as to estimate the state of a traveling road surface. Then, the estimation result is outputted to a high-order device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle traveling road surface state estimation system that detects an acceleration generated on a driving wheel of a vehicle and an acceleration generated on an idle wheel during traveling of the vehicle and estimates a state of a traveling road surface.

  Conventionally, matters that must be taken into consideration for safe driving in vehicles include setting the vehicle's tire air pressure to an appropriate level, and paying attention to tire wear and checking the tires. It is done.

  However, when the tires are inspected and the tires are kept in good condition, the brakes are applied when the frictional force between the road surface and the tire decreases, such as when the road surface is wet during rainy weather. Slip into the car and the vehicle may move in an unexpected direction, causing an accident.

  In order to prevent accidents caused by such slips and sudden starts, an anti-lock brake system (hereinafter referred to as ABS), a traction control system, and in addition to these A stability control system equipped with a YAW sensor has been developed.

  For example, ABS is a system that detects the rotational state of each tire and controls the braking force so as to prevent each tire from entering a locked state based on the detection result.

  As the rotation state of the tire, it is possible to detect the number of rotations of each tire, the state of air pressure, distortion, and the like, and use this detection result for control.

  Examples of such a control system include, for example, an automobile brake device disclosed in Japanese Patent Laid-Open No. 05-338528 (hereinafter referred to as Patent Document 1), and brake control disclosed in Japanese Patent Laid-Open No. 2001-018775. Device (hereinafter referred to as Patent Document 2), vehicle control method and apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-182578 (hereinafter referred to as Patent Document 3), and vehicle disclosed in Japanese Patent Application Laid-Open No. 2002-137721 A motion control device (hereinafter referred to as Patent Document 4), a brake device disclosed in JP 2002-160616 A (hereinafter referred to as Patent Document 5), and the like are known.

  In Patent Document 1, negative pressure is supplied from a vacuum tank to a vacuum booster connected to a brake pedal, and negative pressure is supplied from a vacuum pump to the vacuum tank, and the vacuum pump is driven by a pump motor. When the acceleration sensor 14 detects that the deceleration acceleration of the vehicle has reached a predetermined value, the pump motor for operating the vacuum pump is controlled so that the operation fee at the time of a sudden brake operation and the brake operation immediately thereafter is controlled. A brake device for preventing ring changes is disclosed.

  In Patent Document 2, in a brake control device including a control unit that executes ABS control, a lateral acceleration estimation unit that estimates a lateral acceleration generated in a vehicle and an estimation by the lateral acceleration estimation unit are included in the control unit. The lateral acceleration, the estimated lateral acceleration by the vehicle behavior detecting means, and the detected lateral acceleration detected by the lateral acceleration sensor included in the vehicle behavior detecting means are compared, and if the difference between the two is less than a predetermined value, the steering angle is met. Comparing and determining means for determining that the vehicle is turning normally and determining that the vehicle is turning abnormally if the difference is greater than or equal to a predetermined value is provided. Discloses a brake control device that switches control.

  Patent Document 3 discloses a vehicle acceleration method or a vehicle deceleration generated by a traveling road surface inclination in a vehicle control method and apparatus in which a control signal for adjusting a vehicle deceleration and / or acceleration is formed by a corresponding set value. A vehicle control method and apparatus are disclosed that improve the vehicle deceleration and / or acceleration settings by forming a correction factor representative of

In Patent Document 4, the lateral slip angle change speed β ′ of the center of gravity is acquired as the actual yawing motion state quantity of the vehicle having a plurality of wheels, and the absolute value of the change speed β ′ is greater than or equal to the set value β ₀ ′. For example, by applying the brake fluid pressure ΔP to one of the left and right rear brakes, the larger the value of the change speed β ′, the larger the value and the smaller the value of the change speed β ′. During the yawing moment control, it is determined whether or not the slip control is necessary for the wheel to which the brake fluid pressure ΔP is applied. If the slip control is necessary, the brake fluid pressure A vehicle motion control device that performs slip control that keeps the slip ratio within an appropriate range by suppressing ΔP is disclosed.

  Patent Document 5 includes at least two of an acceleration sensor that detects acceleration in the vehicle longitudinal direction, a wheel speed sensor that detects wheel speed of each wheel, and a brake pressure sensor that detects brake pressure. The target brake pressure is calculated by feedback from at least two sensors, and based on the calculation result, the command current is calculated by the command current calculation unit, and the command current is supplied to the brake drive actuator to obtain the magnitude of the command current. A brake device is disclosed that can suppress an output abnormality even if a disturbance occurs or one sensor breaks down by generating a corresponding braking force.

  Further, as disclosed in Japanese Patent No. 3787608 (Patent Document 6), the friction between the traveling road surface and the wheel when the wheel is locked is estimated using the ABS, and the ABS is based on the estimated friction. A technique for changing the control parameter is disclosed.

  In Patent Document 6, road surface friction force information corresponding to a road surface friction force F acting between a vehicle wheel and a traveling road surface, and a brake torque force T acting between the vehicle wheel and a brake device are used. An ABS device having an arbitrary number of first sensors capable of obtaining brake torque information, and calculating a difference parameter M corresponding to a difference between road surface friction force information from the first sensor and brake torque information. A difference parameter calculation means, a wheel speed parameter calculation means for calculating the wheel speed parameter Mω to be zero when the wheel is locked by correcting and integrating the difference parameter M calculated by the difference parameter calculation means; Brake hydraulic pressure control means for controlling the hydraulic pressure of the brake device using the wheel speed parameter Mω calculated by the speed parameter calculating means. The ABS apparatus characterized by these is disclosed.

  Further, as disclosed in Japanese Patent No. 3448995 (Patent Document 7), there is a technique for estimating the friction when the wheel slips on the road surface during acceleration and controlling the throttle opening based on the estimated friction. Are known.

  In Patent Document 7, a second throttle valve that is arranged in series with a throttle valve in an intake passage of an engine and is controlled to be switched in two stages of a fully open position and a fully closed position of a predetermined opening degree, and a drive wheel of a vehicle. Slip state detecting means for detecting a slip state; first driving force reduction control means for reducing the driving force of the vehicle by controlling the second throttle valve to a fully closed position in accordance with the detected slip state; Road surface state detecting means for detecting the state of the friction coefficient of the road surface, second driving force reduction control means for controlling the driving force of the vehicle to decrease more responsively than the first driving force reduction control means, and first driving force Driving force reduction control limiting means for limiting the operation of the reduction control means, and when the road surface condition has a high friction coefficient, the driving force reduction control limiting means limits the operation of the first driving force reduction control means, and the necessary drive Force reduction control for the second drive Driving force control apparatus for a vehicle, characterized in that the cover in force reduction control means is disclosed.

In recent years, more and more passenger cars are equipped with safety equipment using the latest high-tech technology. For example, a millimeter wave radar or infrared camera is used to detect the vehicle ahead and automatically decelerate and stop to prevent rear-end collisions, or to detect pedestrians on dark night roads or to Accident avoidance technology, such as the ability to stop, has started to be put into practical use. By using such technology, efforts are being made to avoid the occurrence of serious accidents such as rear-end collisions of vehicles and hitting people walking on the shoulders.
Japanese Patent Laid-Open No. 05-338528 JP 2001-018775 A Japanese Patent Laid-Open No. 2001-182578 JP 2002-137721 A Japanese Patent Laid-Open No. 2002-160616 Japanese Patent No. 3787608 Japanese Patent No. 3442995

  One of the reasons for requiring the anti-lock brake system as described above is a change in the state of the road surface on which the vehicle travels. When the road surface condition changes depending on the weather and the environment, the vibration of the vehicle body and the stability decrease, and further, the change of the braking effect and the slip of the wheel at the time of the brake operation occur. For this reason, technology development for quickly and accurately detecting the road surface state is being performed.

  However, for example, ABS has parameters determined by the standard new car tires selected by automakers at the development stage, but in practice it varies depending on conditions such as tire wear, replacement, number of passengers, weather, road surface, etc. Therefore, it is extremely difficult to achieve optimum control with a single parameter.

  In addition, tire wear, change of clothes, number of passengers, weather, and road surface are dry when braking control of vehicles based on detection results using millimeter wave radars and infrared cameras to prevent rear-end collisions, etc. Depending on the condition of the road surface, such as wet or frozen, the distance traveled from the start of braking to the stop of the vehicle varies, making it difficult to perform appropriate braking control.

  In the technologies disclosed in Patent Documents 6 and 7, the control parameter can be changed at the start of traveling or at low speed traveling, and it is extremely difficult to change the parameter during vehicle traveling, particularly at high speed traveling. That is.

  In view of the above problems, an object of the present invention is to provide a traveling road surface state detection system that can quickly and accurately detect a traveling road surface state during vehicle travel.

  In order to achieve the above object, the present invention provides a vehicle traveling road surface state estimation system that estimates the state of a traveling road surface during vehicle traveling by detecting acceleration in a predetermined detection direction provided on the driving wheels of the vehicle. A driving wheel acceleration sensor that outputs an electrical signal corresponding to the acceleration value, and an idler wheel that is provided on an idler wheel of a vehicle and detects an acceleration in the detection direction of the idler wheel and outputs an electrical signal corresponding to the acceleration value A first calculation for inputting an acceleration sensor and an electric signal output from the driving wheel acceleration sensor and obtaining a frequency distribution within a certain measurement time of the acceleration detected by the driving wheel acceleration sensor based on the electric signal. An electric signal output from the processing means and the idle wheel acceleration sensor is input, and an additive detected by the idle wheel acceleration sensor based on the electric signal is input. Second calculation processing means for obtaining a frequency distribution within the measurement time, frequency distribution obtained by the first calculation processing means, and information on the frequency distribution obtained by the second calculation processing means for each state of the road surface The stored storage means, the frequency distribution obtained by the first arithmetic processing means, the frequency distribution obtained by the second arithmetic processing means, and the storage information of the storage means are compared to estimate the state of the traveling road surface. A vehicle travel road surface state estimation system including road surface state estimation means for outputting information of the estimation result is proposed.

  In order to achieve the above object, the present invention provides a vehicle road surface state estimation system for estimating the road surface state during vehicle travel, and detects acceleration in a predetermined detection direction provided on the drive wheel of the vehicle. And a driving wheel acceleration sensor that outputs an electrical signal corresponding to the acceleration value, and an acceleration signal that is provided on the idler wheel of the vehicle and detects the acceleration in the detection direction of the idler wheel, and outputs an electrical signal corresponding to the acceleration value. An idle wheel acceleration sensor and an electric signal output from the driving wheel acceleration sensor are input, and based on the electric signal, an integrated value or an average value within a fixed measurement time of the acceleration detected by the driving wheel acceleration sensor Or a first arithmetic processing means for calculating an arithmetic value by calculating at least one of a variance value, a skewness or a kurtosis, and the idle wheel acceleration sensor. A second arithmetic processing means for inputting an electrical signal output from the sensor, performing the arithmetic processing on the acceleration detected by the idle wheel acceleration sensor based on the electric signal, and calculating an arithmetic value; and the first arithmetic operation Storage means for storing information on the calculation value by the processing means and the calculation value by the second calculation processing means for each state of the road surface, the calculation value by the first calculation processing means and the calculation by the second calculation processing means A vehicle traveling road surface state estimating system is provided that includes a road surface state estimating unit that compares the value and the stored information of the storage unit to estimate the state of the traveling road surface and outputs information of the estimation result.

  According to the vehicle traveling road surface state estimation system of the present invention, the acceleration generated in the driving wheel and the acceleration generated in the idle wheel during the traveling of the vehicle are detected, and the integrated value, average value, variance value, or By obtaining the skewness or kurtosis, the traveling road surface state during vehicle traveling can be estimated quickly and accurately.

  Hereinafter, an embodiment of the present invention will be described.

  FIG. 1 is a block diagram showing an electric system circuit of a sensor unit 100 (100A, 100B) and a main unit 200 in a vehicle travel road surface state estimation system according to an embodiment of the present invention.

  The sensor unit 100 (100A, 100B) includes an acceleration sensor 101, an analog / digital (A / D) conversion circuit 102, an arithmetic processing unit 103, a transmitter 104, a transmission antenna 105, a receiver 106, and a reception antenna 107. Has been. One sensor unit 100A is provided on the drive wheel of the vehicle, and the other sensor unit 100B is provided on the idler wheel of the vehicle. As shown in FIG. 2, the rotation tangent direction x and the rotation axis direction y of the wheel (tire) are respectively shown. The generated acceleration is fixed to the rim so that the acceleration sensor 101 can detect it. In FIG. 2, the sensor unit 100 is fixed to the rim 306, and the tire 300 is, for example, a well-known tubeless radial tire, and in this embodiment includes a wheel and a rim. The tire 300 includes a tire body 305, a rim 306, and a wheel (not shown). The tire body 305 includes a known cap tread 301, under tread 302, belts 303A and 303B, carcass 304, and the like.

  The acceleration sensor 101 detects an acceleration generated in the rotational tangent direction x of the tire 300 and an acceleration generated in the rotational axis direction y, and outputs an analog electric signal representing the value of these accelerations.

  The A / D conversion circuit 102 digitally outputs the analog electrical signal corresponding to the acceleration generated in the rotational tangent direction x and the analog electrical signal corresponding to the acceleration generated in the rotational axis direction y output from the acceleration sensor 101. Convert to value and output.

  The arithmetic processing unit 103 is composed mainly of a well-known CPU, for example, and it receives a transmission start command designating identification information unique to itself from the antenna 108 and the receiver 107 until a transmission stop command is received. As a measurement time, only during this measurement time, a digital value of acceleration is input from the A / D conversion circuit 102, acceleration information of a predetermined format including this digital value is generated, and this acceleration information is transmitted via the transmitter 105. Transmission is performed from the antenna 106 by radio waves of a predetermined frequency. Note that the self identification information is stored in the storage unit 104 in advance.

  In order to eliminate the influence of noise or the like, the output signal of the acceleration sensor may be input to the A / D conversion circuit 102 after passing through a high-pass filter or a band-pass filter.

  The main unit 200 is provided in a vehicle body between a driving wheel and an idler wheel of the vehicle, and operates with electric power supplied from a battery via an ignition switch, and includes a receiving antenna 201, a receiver 202, and an arithmetic processing unit. 203, a storage unit 204, a transmitter 205, and a transmission antenna 206.

  The receiver 202 receives acceleration information transmitted from the sensor unit 100 (100A, 100B) via the antenna 201, and outputs it to the arithmetic processing unit 203 as digital data.

  The arithmetic processing unit 203 is configured mainly with a well-known CPU, for example, and inputs acceleration information from the receiver 202 within the measurement time, as described later, and sets the acceleration value during the measurement pause time after the measurement time ends. Based on the calculated value and the calculated value as the pattern data stored in the storage unit 204, the state of the traveling road surface is estimated based on the calculated value based on the calculated value. Output to the host device.

  The storage unit 204 has a predetermined storage medium such as a rewritable nonvolatile memory or a magnetic disk device. The storage medium includes identification information of each of the sensor units 100 (100A, 100B), an experiment or the like in advance. A plurality of calculated values corresponding to the state of the traveling road surface obtained by the above are stored as pattern data.

  As described above, the storage unit 204 of the main unit 200 stores, in advance, the acceleration in the rotational tangential direction x of the tire 300 detected by the acceleration sensor 101 for each state of the traveling road surface (hereinafter, x An average value, a variance value, a skewness, and a vector synthesized acceleration r (hereinafter, referred to as r acceleration) within a measurement time, respectively. Accumulated values of kurtosis and r acceleration are obtained by experiments as data patterns for each of the idler wheels and the drive wheels and stored in advance.

  For example, when the traveling road surface is in a dry state (DRY), a wet state (WET), and a frozen state (ICE), the average value, the variance value, the skewness, the peak value of the x acceleration in each of the idler wheel and the drive wheel The calculation values shown in FIGS. 3 to 6 are stored in the storage unit 204 as pattern data.

  Here, when there are n x accelerations (n is a natural number) detected within the measurement time and each value is x1, x2,... Xn, each of the average value, the variance value, the skewness, and the kurtosis. Is obtained using the following equations (1) to (4).

尚、本実施形態では、これらの演算値を算出する際に、次の４つの積算値すなわち検出加速度の４乗値の積算値と、検出加速度の３乗値の積算値と、検出加速度の２乗値の積算値と、検出加速度の積算値とを求めることにより、上記の（１）〜（４）式を用いて、平均値、分散値、歪度、尖度を瞬時に算出する。

In the present embodiment, when calculating these calculated values, the following four integrated values, that is, the integrated value of the detected acceleration fourth power, the integrated value of the detected acceleration third power, and the detected acceleration of 2 are calculated. By calculating the integrated value of the multiplier value and the integrated value of the detected acceleration, the average value, variance value, skewness, and kurtosis are instantaneously calculated using the above equations (1) to (4).

また、上記のパターンデータの他に、図７乃至図１０に示す走行路面が乾燥した状態（ＤＲＹ）、濡れた状態（ＷＥＴ）、及び凍った状態（ＩＣＥ）のときの、遊動輪と駆動輪それぞれにおけるｙ加速度の平均値、分散値、歪度、尖度の演算値、及び、図１１乃至図１４に示す走行路面が乾燥した状態（ＤＲＹ）、濡れた状態（ＷＥＴ）、及び凍った状態（ＩＣＥ）のときの、遊動輪と駆動輪それぞれにおけるｒ加速度の平均値、分散値、歪度、尖度の演算値がパターンデータとして記憶部204に記憶されている。

In addition to the above-described pattern data, idle wheels and drive wheels when the road surface shown in FIGS. 7 to 10 is dry (DRY), wet (WET), and frozen (ICE). Calculated values of average value, variance value, skewness, kurtosis of y acceleration and dry road surface (DRY), wet state (WET), and frozen state shown in FIGS. In the case of (ICE), the average value, variance value, skewness, and kurtosis calculated values of r acceleration in each of the idler wheel and the drive wheel are stored in the storage unit 204 as pattern data.

  As described above, the average of the x acceleration, y acceleration, and r acceleration in each of the idler wheel and the drive wheel when the traveling road surface is dry (DRY), wet (WET), and frozen (ICE). Since the calculated values of variance, variance, skewness, and kurtosis have a specific pattern according to the condition of the road surface, the condition of the road surface is calculated by the calculated value calculated from the detected value measured during vehicle travel. Can be estimated.

  As another example having such a specific data pattern depending on the state of the traveling road surface, FIGS. 15 to 26 show the frequency of appearance of acceleration within the measurement time in a spectrum.

  FIG. 15 is a spectrum in which the r acceleration obtained by vector synthesis of the x acceleration and the y acceleration when the road surface is wet is drawn on the xy plane. FIGS. 16 to 18 show the x acceleration, the y acceleration, and the r acceleration at this time. Each frequency of appearance is represented by the absolute value of acceleration on the horizontal axis and the frequency on the vertical axis. FIG. 19 shows a spectrum in which the r acceleration obtained by vector synthesis of the x acceleration and the y acceleration when the road surface is snowy is drawn on the xy plane, and FIGS. 20 to 22 show the x acceleration, y acceleration and r acceleration at this time. Each frequency of appearance is represented by the absolute value of acceleration on the horizontal axis and the frequency on the vertical axis. Thus, it can be seen that the appearance frequency spectrum is completely different between the wet road surface and the snowy state.

  Also, FIG. 23 shows the appearance of r acceleration obtained by vector synthesis of the x acceleration and y acceleration of the idler wheel in the measurement time when the vehicle travels at a speed of 40 km / h when the road surface is dry on the xy plane. FIG. 24 shows the frequency spectrum, and FIG. 24 shows the r acceleration obtained by vector synthesis of the x acceleration and the y acceleration of the drive wheel within the measurement time when the vehicle travels at a speed of 40 km when the road surface is dry. 25 is a spectrum of the appearance frequency depicted in FIG. 25, and FIG. 25 shows r acceleration obtained by vector synthesis of the x acceleration and y acceleration of the idler wheel within the measurement time when the vehicle travels at a speed of 40 km when the traveling road surface is wet. Is a spectrum of the appearance frequency drawn on the xy plane, and FIG. 26 is a measurement time when the vehicle travels at a speed of 40 km / h when the traveling road surface is wet. The x acceleration and y acceleration of the driving wheels in the inner is a spectrum of frequency of occurrence of r acceleration vector-synthesized depicted in the xy plane. Thus, it can be seen that the appearance frequency spectrum is completely different between when the road surface is dry and when it is wet.

  FIG. 27 is a graph showing a value obtained by integrating the absolute values of the r acceleration detected within the measurement time, and is an integrated value when traveling at a speed of 20 km, 40 km, 60 km, and 80 km per hour. In the figure, A represents a value obtained by accumulating absolute values of r acceleration on idle wheels when the road surface is dry, and B represents an absolute value of r acceleration on idle wheels when the road surface is wet. C represents an integrated value, C represents an integrated value of the absolute value of r acceleration on the driving wheel when the road surface is dry, and D represents an absolute value of the r acceleration on the driving wheel when the road surface is wet. Represents the value obtained by integrating. Thus, it can be seen that the absolute value of the r acceleration is greater in the wet state than in the dry state, and the difference is more significant as the traveling speed is increased. It is possible to determine whether the road surface is wet by reading the current traveling speed and determining the integrated value of the absolute value of r acceleration at that time as a threshold value. In the case of this embodiment, the difference is more noticeable with the idle wheel, and the determination can be made with only the idle wheel. In addition, since the difference is more conspicuous as the traveling speed increases, more reliable estimation is possible for high-speed traveling with higher risk. On the other hand, the difference is small and difficult to judge at low speeds, but low-speed traveling is inherently less dangerous, so there is no problem even if it is difficult to estimate the road surface. In other words, at low speeds, it is preferable to reduce power consumption of the system by canceling road surface estimation and reducing the number of times of wireless transmission.

  In the present embodiment, as shown in FIG. 28, the measurement time t1 and the measurement pause time are alternately set, and the measurement time t1 is set to a time within the range of 0.1 seconds to 10 seconds. Is set to a time within a range of 5 seconds to 5 minutes.

  Next, the processing operation of the sensor unit in this embodiment will be described with reference to the flowchart shown in FIG.

  When the operation starts, the sensor unit 100 (100A, 100B) monitors whether or not a transmission start command specifying its own identification information is received from the main unit 200 (SA1), and when this transmission start command is received. Assuming that the measurement time has started, x acceleration and y acceleration are detected at a predetermined sampling time (SA2), and this detected data is transmitted to the main unit 200 together with its own identification information (SA3). Thereafter, it is monitored whether or not a transmission end command designating its own identification information is received from the main unit 200 (SA4). If not received, the processes of SA2 and SA3 are repeated. Transition to processing.

  By the above processing, the sensor unit 100 (100A, 100B) detects acceleration only during the measurement time and transmits the detection data to the main unit 200, so that consumption of the battery or the like can be minimized.

  Next, an example of the road surface state determination processing operation of the main unit in the present embodiment will be described with reference to the flowchart shown in FIG.

  When the operation starts, the main unit 200 starts measuring the measurement time (SB1) and simultaneously transmits a transmission start command designating identification information to each of the sensor units 100 (100A, 100B) (SB2).

  Thereafter, the detection data transmitted from each sensor unit 100 (100A, 100B) is received, and the detection data is divided into idle wheels and drive wheels and stored in the storage unit 204 (SB3), and the measurement time is finished. Is determined (SB4). As a result of the determination, if the measurement time has not ended, the process of SB3 is repeated, and when it ends, a transmission end command designating identification information is transmitted to each of the sensor units 100 (100A, 100B) ( SB5).

  Next, the main unit 200 starts measuring the measurement pause time (SB6), and calculates the above-described calculation value based on the detection data stored in the storage unit 204 (SB7). Further, the pattern data stored in advance in the storage unit 204 is read out and compared with the calculated value calculated by the process of SB7 (SB8), and the state of the traveling road surface is estimated from the comparison result (SB9). The estimation result is output to the host device (SB10). Thereafter, it is determined whether or not the measurement pause time has ended (SB11). When the measurement pause time has ended, the process proceeds to SB1.

  Next, another example of the road surface state determination processing operation of the main unit in the present embodiment will be described with reference to the flowchart shown in FIG. Here, a part of the threshold determination process performed by changing a part of the above process will be described in detail, and the description of the same process as above will be omitted.

  When the main unit 200 starts operation, the main unit 200 receives detection data from each of the sensor units 100A and 100B of the idler wheel and the drive wheel (SC1), performs a filtering process on the received data to remove noise components, and stores them. The data is stored in the unit 204 (SC2). Thereafter, the above-described calculation value is calculated based on the detection data (SC3). In this calculation process, an average value or an integrated value of r accelerations of the idle wheel and the drive wheel is calculated.

  Next, the main unit 200 acquires vehicle travel speed information (SC4), and determines whether the vehicle travel speed is lower than 25 km / h (SC5). As a result of the determination, when the vehicle traveling speed is lower than 25 km / h, the process proceeds to SC1. Here, when the vehicle traveling speed is lower than 25 km / h, the acceleration change due to the difference in the road surface is small, and the risk is low even if the road surface condition is not judged. By canceling the determination of the road surface state, the number of times of wireless transmission is reduced to reduce power consumption.

  If the vehicle running speed is 25 km / h or higher as a result of the determination in SC5, the threshold value of the r acceleration calculation value for each of the idler wheel and the drive wheel stored in advance in the storage unit 204 is read (SC6 ), It is determined whether or not the calculated value of the drive wheel is larger than a threshold value (SC7). As a result of the determination, when the r acceleration calculated value of the driving wheel is equal to or smaller than the threshold value, the process proceeds to SC11 described later, and when the r acceleration calculated value of the driving wheel is larger than the threshold value, the r acceleration calculated value of the idle wheel is After determining whether or not it is larger than the threshold value (SC8), and when the r acceleration calculation value of the idler wheel is larger than the threshold value, it is estimated that the traveling road surface is wet (WET), and this estimation result is output. The process proceeds to SC1 (SC9). If the result of SC8 determination is that the r acceleration calculation value of the idle wheel is equal to or less than the threshold value, it is estimated that the traveling road surface is frozen (ICE), and after the output of this estimation result, the process proceeds to SC1. (SC10).

  If the result of the SC7 determination is that the r acceleration calculated value of the driving wheel is equal to or less than the threshold value, it is determined whether or not the r acceleration calculated value of the idle wheel is smaller than the r acceleration calculated value of the driving wheel (SC11). . As a result of this determination, when the r acceleration calculation value of the idle wheel is smaller than the r acceleration calculation value of the driving wheel, it is estimated that the traveling road surface is frozen (ICE) and the estimation result is output, and then the above SC1. The process proceeds to (SC12). If the result of the SC11 determination is that the r acceleration calculation value of the idle wheel is equal to or greater than the r acceleration calculation value of the drive wheel, it is estimated that the traveling road surface is dry (DRY) and this estimation result is output. Later, the process proceeds to SC1 (SC13).

  In this example, the road surface state is estimated using the average value or the integrated value of the r acceleration as the calculated value. However, the present invention is not limited to this, and the road surface is similarly applied even if the kurtosis or the skewness is used as the calculated value. It goes without saying that the state can be estimated.

  As described above, according to the present embodiment, the acceleration generated in the driving wheel and the acceleration generated in the idle wheel during vehicle travel are detected, and the integrated value, average value, variance value, or By obtaining the skewness or kurtosis, the traveling road surface state during vehicle traveling can be estimated quickly and accurately. Therefore, safer traveling can be realized by using the estimation result of the traveling road surface state estimation system of the present embodiment for a vehicle traveling control device such as an anti-lock brake system.

  In the above-described embodiment, data transmission from the sensor unit 100 (100A, 100B) is performed only during the measurement time according to a command from the main unit 200. Data transmission from the sensor unit 100 (100A, 100B) may be performed only when the vehicle is running and during the measurement time.

  Further, after the four integrated values described above are calculated in the sensor unit 100 (100A, 100B), the four integrated values and the number of data n may be transmitted to the main unit 200 together with the identification information. By doing so, it is possible to reduce the transmission power compared to transmitting the sampled detection data individually, the power consumption of the sensor units 100A and 100B can be reduced, and the battery life can be extended.

The block diagram which shows the electric system circuit of a sensor unit and a main unit in the vehicle travel road surface state estimation system of one Embodiment of this invention. The figure which shows the example of mounting | wearing of the sensor unit in one Embodiment of this invention. The figure which shows an example of the relationship between the road surface state and x acceleration average value in one Embodiment of this invention The figure which shows an example of the relationship between the road surface state and x acceleration dispersion value in one Embodiment of this invention. The figure which shows an example of the relationship between the road surface state and x acceleration distortion degree in one Embodiment of this invention The figure which shows an example of the relationship between the road surface state and x acceleration kurtosis in one Embodiment of this invention The figure which shows an example of the relationship between the road surface state and y acceleration average value in one Embodiment of this invention The figure which shows an example of the relationship between the road surface state and y acceleration dispersion value in one Embodiment of this invention. The figure which shows an example of the relationship between the road surface state and y acceleration distortion degree in one Embodiment of this invention The figure which shows an example of the relationship between the road surface state and y acceleration kurtosis in one Embodiment of this invention The figure which shows an example of the relationship between the road surface state and z acceleration average value in one Embodiment of this invention. The figure which shows an example of the relationship between the road surface state and z acceleration dispersion value in one Embodiment of this invention. The figure which shows an example of the relationship between the road surface state and z acceleration distortion degree in one Embodiment of this invention. The figure which shows an example of the relationship between the road surface state and z acceleration kurtosis in one Embodiment of this invention The figure which shows an example of the acceleration appearance frequency spectrum in the state where the driving | running | working road surface became wet in one Embodiment of this invention. The figure which shows an example of the x acceleration appearance frequency spectrum in the state where the driving | running | working road surface became wet in one Embodiment of this invention. The figure which shows an example of the y acceleration appearance frequency spectrum in the state in which the driving | running | working road surface was wet in one Embodiment of this invention. The figure which shows an example of the r acceleration appearance frequency spectrum in the state in which the driving | running | working road surface became wet in one Embodiment of this invention. The figure which shows an example of the acceleration appearance frequency spectrum in the snow-covered road surface in one Embodiment of this invention The figure which shows an example of the x acceleration appearance frequency spectrum in case the driving | running road surface in one embodiment of this invention is a snowy state. The figure which shows an example of the y acceleration appearance frequency spectrum when the driving | running road surface in one Embodiment of this invention is a snowy state. The figure which shows an example of r acceleration appearance frequency spectrum in case the driving | running road surface in one Embodiment of this invention is a snowy state. The figure which shows an example of the acceleration appearance frequency spectrum of the idler wheel in the dry state in the driving | running | working road surface in one Embodiment of this invention. The figure which shows an example of the acceleration appearance frequency spectrum of a driving wheel in the driving | running | working road surface in a dry state in one Embodiment of this invention. The figure which shows an example of the acceleration appearance frequency spectrum of the idler wheel in the state where the driving | running | working road surface became wet in one Embodiment of this invention. The figure which shows an example of the acceleration appearance frequency spectrum of a driving wheel in the state where the driving | running | working road surface became wet in one Embodiment of this invention. The figure which shows an example of the relationship between the driving | running | working road surface state in one Embodiment of this invention, and the r acceleration integrated value of a driving wheel and a driving wheel. The figure which shows the relationship between the measurement time in one Embodiment of this invention, and measurement rest time The flowchart explaining the processing operation of the sensor unit in one Embodiment of this invention. The flowchart explaining an example of the road surface state determination processing operation | movement of the main unit in one Embodiment of this invention. The flowchart explaining the other example of the road surface state determination processing operation of the main unit in one Embodiment of this invention.

Explanation of symbols

  100, 100A, 100B ... sensor unit, 101 ... acceleration sensor, 102 ... analog / digital (A / D) conversion circuit, 103 ... arithmetic processing unit, 104 ... transmitter, 105 ... transmitting antenna, 106 ... receiver, 107 ... Reception antenna, 200 ... main unit, 201 ... reception antenna, 202 ... receiver, 203 ... arithmetic processing unit, 204 ... storage unit, 205 ... transmitter, 206 ... transmission antenna.

Claims (5)

In a vehicle travel road surface state estimation system that estimates the state of the travel road surface during vehicle travel,
A driving wheel acceleration sensor that is provided on a driving wheel of a vehicle and detects an acceleration in a predetermined detection direction in the driving wheel and outputs an electric signal corresponding to the acceleration value;
An idle wheel acceleration sensor that is provided on an idler wheel of a vehicle and detects an acceleration in the detection direction of the idler wheel and outputs an electrical signal corresponding to the acceleration value;
A first arithmetic processing means for inputting an electrical signal output from the driving wheel acceleration sensor and obtaining a frequency distribution within a predetermined measurement time of the acceleration detected by the driving wheel acceleration sensor based on the electrical signal;
Second arithmetic processing means for inputting an electrical signal output from the idle wheel acceleration sensor and obtaining a frequency distribution of the acceleration detected by the idle wheel acceleration sensor within the measurement time based on the electrical signal;
Storage means for storing the frequency distribution obtained by the first arithmetic processing means and the frequency distribution information obtained by the second arithmetic processing means for each state of the traveling road surface;
The frequency distribution obtained by the first arithmetic processing means, the frequency distribution obtained by the second arithmetic processing means and the storage information of the storage means are compared to estimate the state of the traveling road surface, and information on the estimation result is output. A vehicle road surface state estimation system, comprising: In a vehicle travel road surface state estimation system that estimates the state of the travel road surface during vehicle travel,
A driving wheel acceleration sensor that is provided on a driving wheel of a vehicle and detects an acceleration in a predetermined detection direction in the driving wheel and outputs an electric signal corresponding to the acceleration value;
An idle wheel acceleration sensor that is provided on an idler wheel of a vehicle and detects an acceleration in the detection direction of the idler wheel and outputs an electrical signal corresponding to the acceleration value;
An electric signal output from the driving wheel acceleration sensor is input, and based on the electric signal, an integrated value, an average value, a variance value, or a skewness within a certain measurement time of the acceleration detected by the driving wheel acceleration sensor. Or first arithmetic processing means for calculating an arithmetic value by performing arithmetic processing for calculating at least one of kurtosis;
Second arithmetic processing means for inputting an electric signal output from the idle wheel acceleration sensor, and calculating the calculation value by performing the calculation process on the acceleration detected by the idle wheel acceleration sensor based on the electric signal;
Storage means for storing information on the calculation value by the first calculation processing means and the calculation value by the second calculation processing means for each state of the traveling road surface;
Road surface state estimation that estimates the state of the traveling road surface by comparing the calculated value by the first arithmetic processing means, the calculated value by the second arithmetic processing means, and the storage information of the storage means, and outputs information of the estimation result A vehicle travel road surface state estimation system. The drive wheel acceleration sensor detects a first acceleration in a rotational tangent direction of the drive wheel and a second acceleration in a direction parallel to the rotation axis of the drive wheel, and outputs an electrical signal corresponding to each acceleration value. Having means,
The idle wheel acceleration sensor detects a third acceleration in a rotational tangential direction of the idle wheel and a fourth acceleration in a direction parallel to the rotation axis of the idle wheel, and outputs an electrical signal corresponding to each acceleration value. Having means,
The first arithmetic processing means is at least one of an integrated value, an average value, a variance value, a skewness, or a kurtosis within a certain measurement time of the first and second accelerations detected by the driving wheel acceleration sensor. A means for performing calculation processing to calculate one and calculating a calculation value;
The said 2nd arithmetic processing means has a means to perform the said arithmetic processing to the 3rd and 4th acceleration detected by the said idle wheel acceleration sensor, and to calculate a calculated value. Vehicle road surface state estimation system. The drive wheel acceleration sensor detects a first acceleration in a rotational tangent direction of the drive wheel and a second acceleration in a direction parallel to the rotation axis of the drive wheel, and outputs an electrical signal corresponding to each acceleration value. Having means,
The idle wheel acceleration sensor detects a third acceleration in a rotational tangential direction of the idle wheel and a fourth acceleration in a direction parallel to the rotation axis of the idle wheel, and outputs an electrical signal corresponding to each acceleration value. Having means,
The first arithmetic processing means calculates an absolute value of a vector obtained by combining the vector of the first acceleration and the vector of the second acceleration detected by the driving wheel acceleration sensor, and within a certain measurement time of the absolute value. Means for calculating an operation value by performing an operation process for calculating at least one of an integrated value, an average value, a variance value, a skewness, or a kurtosis.
The second arithmetic processing means calculates an absolute value of a vector obtained by combining the third acceleration vector and the fourth acceleration vector detected by the idle wheel acceleration sensor, and performs the arithmetic processing on the absolute value. The vehicle running road surface state estimation system according to claim 2, further comprising means for calculating a calculated value. The measurement time is set to a time within a range of 0.1 seconds to 10 seconds, and a measurement pause time between the measurement time and the next measurement time is set to a time within a range of 5 seconds to 5 minutes. The vehicle travel road surface state estimation system according to claim 2, wherein

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