Driving assistance device

Abstract

The present invention relates to a driving assistance device. The present invention is directed to a situation in which a driver is more accurately informed of a tire force generation condition than ever before in a race or the like. A tire force generation estimation section calculates a maximum tire force generation and a tire force generation current value of each tire of a vehicle based on detection values detected by a plurality of sensors. A sound control section causes a speaker to output a sound. The sound is at least one set of sounds corresponding to a difference between the maximum tire force generation and the tire force generation current value. As the sound, the sound control section causes the speaker to output a pulse sound that is intermittently emitted. The closer the tire force generation current value is to the maximum tire force generation from 0, the shorter the sound control section sets an emission interval of the sound.

Description

Technical Field

[0001] This specification discloses a driving assistance device. Background Technology

[0002] For example, when a vehicle turns, both longitudinal and lateral grip forces act on the tires. These grip forces are also known as tire-generated forces. The maximum tire-generated force of each tire is determined based on the vertical load applied to each tire. If the current value of the tire-generated force is lower than the maximum tire-generated force, it can be said that the tire has a grip margin. That is, when the current value of the tire-generated force is lower than the maximum tire-generated force, it can be determined that there is room to shorten the turning time.

[0003] As a means of evaluating tire force, for example, a tire friction circle as disclosed in Patent Documents 1-3 is used. The tire friction circle is a circle with the maximum tire force as its diameter. Furthermore, the vector combining the tire force in the longitudinal direction and the tire force in the lateral direction is drawn inside or outside the circle (in which case, corresponding to slippage).

[0004] For example, in Patent Document 3, the tire force margin is calculated based on the difference between the maximum tire force (tire force limit value) and the current value of the tire force (tire force current value). The calculated tire force margin is communicated to the driver via image or sound.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-157538

[0006] Patent Document 2: Japanese Patent Application Publication No. 2022-157716

[0007] Patent Document 3: Japanese Patent Application Publication No. 2024-80840 Summary of the Invention

[0008] Furthermore, by informing the driver of the tire force conditions in real time, travel time can be reduced. Therefore, this specification discloses a driving assistance device that, particularly in vehicle racing and other applications, can inform the driver of the tire force conditions more accurately than ever before.

[0009] This specification discloses a driving assistance device. The driving assistance device includes a tire force estimation unit and a sound control unit. Multiple sensors detect the dynamics of the vehicle. The tire force estimation unit calculates the maximum tire force and the current tire force value of each tire based on the detection values ​​obtained from the multiple sensors. The sound control unit causes a speaker to output sound. This sound is at least one set of sounds corresponding to the difference between the maximum tire force and the current tire force value. As the sound, the sound control unit causes the speaker to output intermittently emitted pulse sounds. The closer the current tire force value is from 0 to the maximum tire force, the shorter the sound emission interval is set by the sound control unit.

[0010] During racing, it is difficult for the driver to visually discern images. By using sound pulse intervals that vary according to the difference between the current tire force and the maximum tire force, the driver can adjust their driving actions.

[0011] Furthermore, in the above structure, among the multiple tires of the vehicle, the sound control unit can determine the sound emission interval based on the difference between the current value of the tire generating force of the tire with the highest maximum tire generating force and the maximum tire generating force.

[0012] Based on the above structure, it is possible to control the tire's force output by focusing on the tire that is most important in controlling the force generated by the tire.

[0013] Furthermore, in the above structure, when the current value of the tire's generating force exceeds the maximum tire generating force, the sound control unit can output a continuous tone as sound. In this case, the sound control unit sets a tone different from the pulse tone as the tone of the continuous tone.

[0014] Based on the above structure, the driver can easily identify that the force generated by the tire has deviated from the tire friction circle.

[0015] Furthermore, in the above structure, the driver assistance device may include a display control unit. The display control unit displays the friction circle and the current value of the tire force on a screen. The friction circle represents the maximum tire force. The display control unit also plots coordinate points on the screen. These coordinate points correspond to a vector formed by the longitudinal and lateral components of the current combined tire force. The driver assistance device also includes a normalization processing unit. The normalization processing unit scales the maximum tire force and the current tire force value to make the radius of the friction circle a constant value.

[0016] Based on the above structure, by setting the maximum tire force to a constant value, it is easy to identify the trajectory of the tire force in places such as maintenance areas.

[0017] Furthermore, in the above structure, the display control unit can set the color of the coordinate point based on the maximum tire force before scaling.

[0018] Based on the above structure, it is possible to select the coordinate points that should be of interest within a limited time, such as during the repair period in the maintenance area.

[0019] Invention Effects

[0020] The driving assistance devices disclosed in this manual can inform the driver of the tire force conditions more accurately than ever before. Attached Figure Description

[0021] Figure 1 This is a diagram illustrating the hardware structure of a vehicle that includes the driving assistance device according to this embodiment.

[0022] Figure 2 This is a diagram illustrating the functional blocks of a driver assistance device.

[0023] Figure 3 This is a diagram illustrating the driver assistance process.

[0024] Figure 4 This is a diagram illustrating the relationship between roll angle and suspension displacement in a vehicle model.

[0025] Figure 5 This is a diagram illustrating a vehicle model used to correct the steering angle.

[0026] Figure 6 This is a diagram illustrating a vehicle model used to calculate the load movement of a vehicle in the forward and backward directions.

[0027] Figure 7 This is a diagram illustrating a four-wheeled vehicle model.

[0028] Figure 8 This is a diagram illustrating a four-wheeled vehicle model in a vehicle coordinate system.

[0029] Figure 9 This is an illustration of a four-wheeled vehicle model focusing on the side-slip angle.

[0030] Figure 10 It is a left-right directional graph showing the relationship between the tire's slip angle and the lateral force (the force generated by the tire in the left-right direction).

[0031] Figure 11 It is a front-to-back graph showing the relationship between the tire's slip ratio and the force generated by the tire in the front-to-back direction.

[0032] Figure 12 These are examples of various graphs displayed on a monitor.

[0033] Figure 13 This is a diagram (1 / 4) illustrating the relationship between the coordinate points inside the friction circle and the notification sound.

[0034] Figure 14This is a diagram (2 / 4) illustrating the relationship between the coordinate points inside the friction circle and the notification sound.

[0035] Figure 15 This is a diagram (3 / 4) illustrating the relationship between the coordinate points inside the friction circle and the notification sound.

[0036] Figure 16 This is a diagram (4 / 4) illustrating the relationship between the coordinate points inside the friction circle and the notification sound. Detailed Implementation

[0037] The driving assistance device according to the embodiments will now be described using the accompanying drawings. The shapes, materials, quantities, and values ​​described below are illustrative examples. These shapes, etc., can be appropriately changed depending on the specifications of the driving assistance device. Furthermore, the same elements are labeled with the same symbols in all the following drawings.

[0038] 1. Vehicle Structure

[0039] exist Figure 1 The diagram illustrates the structure of a vehicle. This vehicle is equipped with the driving assistance device 10 according to this embodiment. (See reference...) Figure 1 The steering angle sensor detects the steering amount of the steering wheel 31. The accelerator pedal sensor 32 detects the travel of the accelerator pedal 33. In addition, the brake pedal sensor 34 detects the travel of the brake pedal 35.

[0040] These detected values ​​are sent to the powertrain / chassis ECU 36. Based on the received sensor values, the powertrain / chassis ECU 36 controls the steering mechanism, braking mechanism, and drive source. In other words, the powertrain / chassis ECU 36 controls the vehicle's dynamics.

[0041] The vehicle's dynamics are detected by multiple onboard sensors. These sensors include a vehicle speed sensor, a yaw rate sensor, a lateral G-sensor, and wheel speed sensors. Additionally, the lateral G-sensor measures the lateral acceleration applied by the vehicle during cornering.

[0042] The detection values ​​from these multiple sensors are sent to the driving assistance device 10. As described later, the tire force estimation unit 17 of the driving assistance device 10 (reference) Figure 2 The maximum tire force and current tire force of each wheel are calculated based on the detection values ​​detected by each sensor 38. A driver assistance screen based on the maximum tire force and current tire force is displayed on a display 42. The display 42 may be, for example, a head-up display or a touch panel on the center console. Furthermore, an audio signal (announcing tone) based on the maximum tire force and current tire force is output by a speaker 40.

[0043] The driving assistance device 10 is composed of a computing device. The driving assistance device 10 includes a CPU 10A, RAM 10B, storage device 10C, ROM 10D, and input / output controller 10E.

[0044] CPU 10A is the central processing unit, also known as a processor. RAM 10B is a storage device that temporarily stores data during operation. ROM 10D is a storage device capable of reading data. Storage device 10C is a storage device capable of writing and reading data. Storage device 10C may be, for example, a hard disk drive (HDD) or a solid state drive (SSD).

[0045] The CPU 10A executes a program stored in the storage device 10C or ROM 10D to construct, for example, in the driving assistance device 10. Figure 2 The functional blocks illustrated are as follows. Specifically, the driver assistance device 10 includes a comparison unit 11, a Kalman gain setting unit 12, a vehicle model calculation unit 13, a suspension calculation unit 14, a load movement calculation unit 15, a correction unit 16, and a tire force estimation unit 17. Furthermore, the driver assistance device 10 includes a tire force vector calculation unit 18, a normalization processing unit 19, a voice control unit 20, and a display control unit 21. These functional blocks perform... Figure 3 The driving assistance process is illustrated in the example.

[0046] 2. Driving Assistance Procedures

[0047] Figure 3 The driving assistance process illustrated in the example is executed repeatedly. Furthermore, as in step S14 described later, the values ​​from the previous process are sometimes used for calculation.

[0048] refer to Figure 2 , Figure 3 Various sensors 38 detect the vehicle's dynamics (S10). The detection values ​​detected by the various sensors 38 are input to the vehicle model calculation unit 13. Various vehicle models are stored in the vehicle model calculation unit 13. The vehicle model calculation unit 13 substitutes the detection values ​​into the vehicle model (S12).

[0049] 2-1. Calculation of the correction amount for the tire's toe angle

[0050] exist Figure 4 The following example illustrates a suspension displacement model. In this model, tires 50L and 50R are shown. Based on this model, the suspension displacement z is calculated. By calculating the suspension displacement z, the load movement or steering angle correction, as described later, can be determined.

[0051] In the suspension displacement model, the vehicle's roll angle φ and suspension displacement z are represented by the following formula (1).

[0052] [Formula 1]

[0053]

[0054] Wheelbase d f It is given as a constant inherent to the vehicle. Here, in φ << 1 [rad], the following equation (2) holds.

[0055] [Formula 2]

[0056]

[0057] Furthermore, the roll angle φ is difficult to measure using a sensor. Therefore, the lateral G-φ characteristic graph (e.g., a characteristic line graph) showing the relationship between the acceleration in the vehicle width direction detected by the lateral G sensor and the roll angle φ is stored in the vehicle model calculation unit 13. The vehicle model calculation unit 13 calculates the roll angle φ based on the lateral G value obtained from the lateral G sensor and the lateral G-φ characteristic graph. Moreover, by substituting the roll angle φ into equation (1), the vehicle model calculation unit 13 calculates the suspension displacement z.

[0058] The steering angle correction is calculated based on the suspension displacement and suspension characteristics. The actual steering angle (toe-in) of each tire differs from the steering angle based on the steering wheel 31. For example, the orientation of each wheel changes depending on variations in the loads involved in the suspension. Furthermore, the orientation of each wheel changes depending on the lateral forces applied to the wheels (described later). Reference Figure 3 As explained below, the suspension calculation unit 14 calculates the steering angle correction (corrected steering) (S14).

[0059] This suspension characteristic is based on the suspension's dynamic and compliant characteristics. As explained below, dynamic characteristics refer to the suspension's dynamic performance. Suspension compliance refers to the softness of the suspension mechanism in the forward, backward, left, and right directions.

[0060] The variations in steering angle (toe-in) of each tire derived from suspension dynamics include yaw steering based on changes in ground contact load. Furthermore, the angular difference between the actual left and right steering angles based on the Ackermann mechanism is also included in the aforementioned variations.

[0061] When the vehicle turns, the vehicle body tilts, causing a change in the load input to each tire. It is known that the tires change in the toe-in direction due to the compression and tension of the suspension. The vehicle model calculation unit 13 stores a compression-toe-in change chart (e.g., a characteristic line chart), which stores the relationship between the amount of suspension compression and the amount of change along the toe-in direction of the tires. In addition, the compression-toe-in change chart may be different for the front tires and the rear tires. The vehicle model calculation unit 13 calculates the change in the toe-in angle of each tire by inputting the amount of suspension displacement obtained from the above equation (1) into the compression-toe-in change chart.

[0062] Furthermore, the steering knuckle arm (not shown) that rotates the steering wheels is set with toe-in open based on Ackermann geometry. By setting this angle, the deflection angle of the inner wheel can be made greater than the steering angle of the outer wheel. As a result, the rotation center of the outer wheel can be aligned with the rotation center of the inner wheel.

[0063] The actual steering angle (i.e., the tire toe angle) based on Ackerman geometry varies according to the amount of steering wheel 31 operation. For example, the vehicle model calculation unit 13 stores a steering-Ackerman graph (e.g., a characteristic line graph) that stores the relationship between the angle at the steering gearbox exit (exit angle) and the actual steering angle based on Ackerman geometry. The vehicle model calculation unit 13 obtains the steering gearbox exit angle from the steering angle sensor. Then, the vehicle model calculation unit 13 calculates the actual steering angle (tire toe angle) based on Ackerman geometry based on the obtained exit angle and the steering-Ackerman graph.

[0064] The ways in which the steering angle of each wheel changes based on suspension compliance include changes in toe angle based on lateral force, changes in toe angle based on self-aligning torque, and changes in toe angle based on torque around the kingpin.

[0065] In addition, when calculating these three items, the lateral force input to each tire is used. When the vehicle turns, the lateral force generated by the tires is input to the tires. This lateral force is in balance with the centrifugal force. That is, the lateral force can be translated into grip force in the vehicle width direction. Furthermore, lateral force will also be referred to below as lateral force and the force generated by the left and right tires.

[0066] Here, as mentioned above, in Figure 3 In the process, the steps from start to return are executed repeatedly. Moreover, sometimes the result of the k-th calculation is used as the result of the (k+1)-th calculation.

[0067] For example, in the changes in toe angle based on lateral force, toe angle based on self-aligning torque, and toe angle based on torque around the kingpin, the lateral force, i.e., the lateral force generated by the tire, is used. This lateral force uses the value obtained in the previous process. Specifically, in step S28 of the previous process, equation (13) is calculated. The lateral force Y in equation (13) fl Y fr Y rl Y rr In the current process, it is used in step S14.

[0068] Additionally, Y will be used as the symbol for lateral force below. fl Y fr Y rl Y rr and F y Both represent the same force. The lateral force Y acting on each tire... fl Y fr Y rl Y rr The general term, using lateral force F y .

[0069] Regarding the change in toe-in caused by lateral forces, elastic bodies (buffers) such as rubber bushings are installed in the linkage mounting section of the suspension mechanism. When a lateral force is applied to the tire, the elastic body is compressed, for example, in the vehicle width direction. As a result, the tire's toe-in angle changes. For example, the relationship between the lateral force input to the tire and the amount of change in the tire's toe-in direction is stored in the vehicle model calculation unit 13. For example, it is assumed that the change in toe-in varies as a linear function with respect to the lateral force. In this case, for example, a scaling factor is determined for the front tire and the rear tire separately.

[0070] Next, the tire's toe angle changes due to the self-centering torque. It is known that during cornering, the tire's point of contact with the ground is located further rearward than the tire's contact patch center. A lateral force is input towards this point of contact. Therefore, a torque is generated in the tire about the contact patch center. This torque is called the self-centering torque.

[0071] The vehicle model calculation unit 13 stores the relationship between the lateral force input to the tire and the change in the tire's toe angle based on the self-alignment torque. For example, it is assumed that the change in the toe angle varies linearly with respect to the lateral force. In this case, a scaling factor is determined for the front tire and the rear tire, respectively.

[0072] Furthermore, a kingpin is set as the steering axis of the tire. For example, in the case of a strut-type suspension, the straight line connecting the upper end of the strut and the lower ball joint becomes the kingpin.

[0073] exist Figure 5The middle section shows the side view, plan view and front view of tire 50 in sequence from top to bottom. A torque (returning torque) based on lateral force is generated on the kingpin L1. This torque is calculated by the following equation (3).

[0074] [Formula 3]

[0075]

[0076] Here, the lean-back trail ξ c This refers to the distance between the contact patch center of tire 50 and the kingpin axle L1 on the road surface 100. (Flat tire trail ξ) n This refers to the distance between the contact patch center of tire 50 and the point where the lateral force is applied.

[0077] Additionally, regarding the lean-back distance ξ c The following equation (4) holds true. Furthermore, regarding the tire trail ξ... n , the following equation (5) holds.

[0078] [Formula 4]

[0079]

[0080] [Formula 5]

[0081]

[0082] In equation (4), the backslope offset d c This refers to the distance in the longitudinal direction between the kingpin L1 and the center point of the tire. Figure 5 d is shown in the middle c =0. Backslope angle θ c This refers to the angle formed by the vertical axis passing through the tire's center point and the kingpin axis L1. Kingpin angle θ k It refers to the angle formed by the kingpin L1 and the vertical axis when the tire is viewed from the front.

[0083] As described above, the correction value for the tire's toe angle is determined. (This will be discussed later.) Figure 10 In the lateral force chart, the above correction value is used as the correction input value, namely the side slip angle value.

[0084] 2-2. Calculation of Grounding Load

[0085] refer to Figure 2 , Figure 3 The load movement associated with the vehicle's roll is calculated. During vehicle rotation, the load moves in the vehicle width direction (left-right direction) due to the lateral G and the vehicle's roll. As described later, the ground load Fz is included in the parameters used to calculate the tire force. Therefore, the load movement calculation unit 15 is divided into the front and rear sides of the vehicle, and calculates the load movement (S16).

[0086] The balance between the tilting moment on the spring and the moment caused by gravity after the center of gravity shifts due to the tilting is shown in the following equation (6).

[0087] [Formula 6]

[0088]

[0089] Here, the weight on the spring refers to the weight supported by the suspension spring.

[0090] Furthermore, the torque balance of the roll axis is shown in the following equation (7).

[0091] [Formula 7]

[0092]

[0093] Here, the center of gravity height - the distance between the roll axes h in equations (6) and (7) s Forward roll height h f and rear roll height h r It varies depending on the displacement of the suspension. Therefore, the relationship between the amount of change in the suspension and its respective height is stored in the load movement calculation unit 15 as a suspension roll height chart (e.g., characteristic line diagram).

[0094] Regarding the forward load shift ΔW f and the amount of load movement ΔW r By summing up expressions (6) and (7), we can obtain the following expression (8).

[0095] [Formula 8]

[0096]

[0097] Equation (8) describes the load movement in the vehicle width direction (left-right direction). In situations such as when a vehicle is going uphill, the load movement in the front-rear direction is referenced... Figure 6 , is represented by the following formula (9).

[0098] [Formula 9]

[0099]

[0100] Based on equation (9), the load W in front of the vehicle is calculated. f and the load W behind r Furthermore, based on equation (8), the load movement ΔW in the left and right directions in front of the vehicle is calculated. f and the load movement ΔW in the left and right directions behind the vehicle. r That is, calculate the ground load of all four wheels of vehicle 60. (This will be discussed later.) Figure 10 , Figure 11In this calculation, the contact load of each tire is used as a parameter to determine the tire forces in the lateral and longitudinal directions. The contact load W of each tire is calculated here. fl W fr W rl W rr Send to the tire force estimation unit 17.

[0101] 2-3. Updates to Four-Wheel Vehicle Models

[0102] The tire force estimation unit 17 stores a four-wheel vehicle model represented by the following formulas (10) to (14). The tire force estimation unit 17 compares the physical quantities estimated by the four-wheel vehicle model with the physical quantities detected by various sensors 38. Then, the tire force estimation unit 17 corrects the parameters in the four-wheel vehicle model based on the comparison results. As will be described later, in particular, the friction coefficient μ of the road surface is corrected by this correction. The friction coefficient μ becomes the... Figure 10 , Figure 11 The parameters of the tire force in the left-right and front-back directions are obtained.

[0103] exist Figure 7 The illustration shows a four-wheeled vehicle model in a front-to-rear direction. In this model, the front left tire 50FL and the front right tire 50FR are connected by the front axle 54A. Furthermore, the rear left tire 50RL and the rear right tire 50RR are connected by the rear axle 54B. The front axle 54A and the rear axle 54B are connected via a front differential 52A, a driveshaft 55, and a rear differential 52B. (Reference) Figure 7 Regarding the front and rear directions of the vehicle, the following equation (10) holds true.

[0104] [Formula 10]

[0105]

[0106] Here, the front and rear tires generate force F. fl F fr F rl F rr This can be described as grip in the front-to-back direction. Furthermore, below, F will be used as the symbol for the force generated by the front and rear tires. fl F fr F rl F rr and F x F fl F fr F rl F rr and F x This represents the same force. That is, the front and rear tires, acting as the individual tires, generate a force F. fl F fr F rlF rr The general term for the force F generated by the front and rear tires. x .

[0107] Furthermore, the braking force Brk fl Brk fr Brk rl Brk rr This refers to the force applied to the brake pads. In other words, the braking force (Brk). fl Brk fr Brk rl Brk rr It can be described as the braking torque acting on the tires.

[0108] exist Figure 8 The figure shows a four-wheeled vehicle model in the left-right direction (vehicle width direction). Referring to the figure, the following equation (11) holds true regarding the left-right direction of the vehicle 60.

[0109] [Formula 11]

[0110]

[0111] Furthermore, in Figure 9 The example illustrates a four-wheeled vehicle model focusing on the slip angles of each tire: 50FL, 50FR, 50RL, and 50RR. Based on this vehicle model, the following equation (12) holds.

[0112] [Formula 12]

[0113]

[0114] If we summarize the equations of motion of equations (10) and (11), we can obtain the following equation (13).

[0115] [Formula 13]

[0116]

[0117] The first term on the right side of equation (13) contains the vehicle speed at the current time (step k): V k Angular velocity of each tire: ω flk ω frk ω rlk、 ω rrk Yaw rate: r k Friction coefficient μ k and horizontal G:d 2 Y k / dx 2 By adding the parameters of the first term on the right to the parameters of the second term on the right, the vehicle speed in the next step k+1 is estimated: V k+1Angular velocity of each tire: ω flk+1、 ω frk+1 ω rlk+1 ω rrk+1 Yaw rate: r k+1 Friction coefficient μ k+1 and horizontal G:d 2 Y k+1 / dx 2 .

[0118] refer to Figure 2 The vehicle model calculation unit 13 estimates the aforementioned physical quantities in the current process based on the process results from one week ago. Figure 3 (Step S18). For example, as parameters of the second term on the right side of equation (13), the vehicle model calculation unit 13 uses the physical quantity estimated in the k-th process to estimate the physical quantity X in the (k+1)-th process. k+1 Next, the vehicle model calculation unit 13 compares the estimated physical quantity X. k+1 The physical quantities detected by various sensors 38 (S20).

[0119] Furthermore, among the physical quantities listed in the first term on the right side of equation (13), the friction coefficient μ was not detected by the sensor. Therefore, for parameters other than the friction coefficient μ, the estimated values ​​are compared with the measured values.

[0120] The vehicle model calculation unit 13 sends the physical quantities estimated by the vehicle model to the comparison unit 11. Furthermore, it sends the measured values ​​of the physical quantities from various sensors to the comparison unit 11. In the comparison unit 11, the differences in physical quantities other than the friction coefficient μ are calculated. Based on the calculated differences in each physical quantity, a correction amount relative to equation (13) is calculated. Figure 3 S22).

[0121] The Kalman gain is used as the correction factor. The corrected state variables (including the friction coefficient μ) are obtained by adding the product of the Kalman gain and the difference mentioned above to the uncorrected state variables. The method for setting the Kalman gain is known and therefore omitted here.

[0122] The Kalman gain setting unit 12 sets the values ​​of the Kalman gain based on the difference between the physical quantities estimated by the vehicle model and the measured values ​​of the physical quantities detected by various sensors. Various parameters of equation (13) are corrected using the Kalman gain. Figure 3 (S24). The corrected parameters include the friction coefficient μ.

[0123] Based on the revised vehicle model, the vehicle model calculation unit 13 recalculates the physical quantities (S26). Based on the recalculated physical quantities of each tire, the tire slip angle β is calculated. fl β frβ rl β rr and slip ratio κ fl κ fr κ rl κ rr Side slip angle β fl β fr β rl β rr The slip ratio κ is obtained from equation (12). fl κ fr κ rl κ rr This is the value obtained by dividing the difference between the vehicle's speed and the wheel's rotational speed by the vehicle's speed. Slip ratio κ fl κ fr κ rl κ rr Based on the angular velocity recalculated in step S26 using equation (13): ω flk+1 ω frk+1 ω rlk+1 ω rrk+1 and vehicle speed V k+1 Let's find out.

[0124] Side slip angle β of each tire fl β fr β rl β rr and slip ratio κ fl κ fr κ rl κ rr The friction coefficient μ, recalculated in step S26, is also sent to the tire force estimation unit 17.

[0125] Furthermore, refer to Figure 2 In the correction unit 16, the toe angle correction value calculated by the suspension calculation unit 14 in step S14 is reflected in the steering angle detected by the steering sensor 30. That is, in the vehicle model calculation unit 13, the slip angle β of each tire is calculated based on the corrected steering angle of each tire. fl β fr β rl β rr Furthermore, the ground load of each tire calculated by the load movement calculation unit 15 is sent to the tire force estimation unit 17.

[0126] 2-4. Estimation of Tire Force

[0127] The tire force estimation unit 17 calculates the current value of the tire force of each tire based on various parameters sent from the vehicle model calculation unit 13, the suspension calculation unit 14 and the load movement calculation unit 15 (S28).

[0128] Specifically, based on the friction coefficient μ and the slip angle β fl β fr β rl β rr and the ground load W of each tire fl W fr W rl W rr The tire force estimation unit 17 calculates the lateral force Y of each tire. fl Y fr Y rl Y rr .

[0129] exist Figure 10 The image shows a lateral force graph. The lateral force graph is stored in the tire force estimation unit 17. For example, the lateral force graph is a curve with the slip angle as the horizontal axis and the lateral force as the vertical axis. In the lateral force graph, characteristic curves are set according to the ground load. Furthermore, in... Figure 10 Only one lateral force graph is shown, but the lateral force graph varies depending on the friction coefficient μ. For example, the tire force estimation unit 17 stores lateral force graphs with different friction coefficients μ.

[0130] This transverse force diagram is based on the Magic Formula shown in equation (14). The contents of the Magic Formula are known, so the explanation is omitted below.

[0131] [Formula 14]

[0132]

[0133] Based on the received friction coefficient μ, the tire force estimation unit 17 selects a lateral force graph for estimating the lateral force. Furthermore, based on the received ground load W... fl W fr W rl W rr The tire force estimation unit 17 selects characteristic curves for lateral force estimation. Furthermore, it calculates the characteristic curve relative to the received slip angle β. fl β fr β rl β rr The corresponding left and right tire forces, i.e., the lateral force Y, are currently present. fl Y fr Y rl Y rr .

[0134] Next, based on the friction coefficient μ and slip ratio κ fl κ fr κrl κ rr and the ground load W of each tire fl W fr W rl W rr The tire force estimation unit 17 calculates the current value F of the tire force generated in the front and rear directions for each tire. fl F fr F rl F rr .

[0135] exist Figure 11 The image shows a front-to-rear tire force graph. The front-to-rear tire force graph is stored in the tire force estimation unit 17. For example, the front-to-rear tire force graph is a curve with the slip ratio on the horizontal axis and the front-to-rear tire force on the vertical axis. In the front-to-rear tire force graph, characteristic curves are provided according to the ground load. Furthermore, the front-to-rear tire force graph is created according to the friction coefficient μ. In addition, the front-to-rear tire force graph is created based on the MagicFormula exemplified in the above formula (14).

[0136] Based on the received friction coefficient μ, the tire force estimation unit 17 selects a front-rear tire force graph for estimating the front-rear tire force. Furthermore, based on the received ground load W... fl W fr W rl W rr The tire force estimation unit 17 selects characteristic curves for estimating the tire force in the front and rear directions. Furthermore, it calculates the characteristic curves relative to the received slip ratio κ. fl κ fr κ rl κ rr The corresponding current value F of the force generated by the tires in the front and rear directions. fl F fr F rl F rr .

[0137] In addition, the tire force estimation unit 17 calculates the maximum tire force F. mfl F mfr F mrl F mrr (S30). In Figure 11 In the characteristic curve illustrated, as shown by width W1, an upward-convex maximum value is provided. This maximum value corresponds to the maximum tire force F. m Extract and calculate the current value Y of the lateral force. fl Y fr Y rl Y rrThe maximum value of the selected characteristic curve is used as the estimated tire force. The tire force estimation unit 17 sets the extracted value as the maximum tire force F. mfl F mfr F mrl F mrr The current value.

[0138] The current value of the force F generated by the four tires (50FL, 50FR, 50RL, 50RR) in the front and rear directions. fl F fr F rl F rr and the current value of the lateral force Y fl Y fr Y rl Y rr The force is sent to the vehicle model calculation unit 13 and the tire force vector calculation unit 18. In the vehicle model calculation unit 13, the front-rear tire force F in the second term on the right side of equation (13) is... fl F fr F rl F rr Replaced with the current value F of the force generated by the tires in the front and rear directions. fl F fr F rl F rr Furthermore, the lateral force Y fl Y fr Y rl Y rr Current value of the lateral force Y fl Y fr Y rl Y rr Replacement. Furthermore, these values ​​are used in step S14 and so on in the next process.

[0139] Furthermore, based on the current value F of the force generated by the tires in the front and rear directions. fl F fr F rl F rr and the current value of the lateral force Y fl Y fr Y rl Y rr The tire force vector calculation unit 18 calculates the tire force vector (S32). The tire force vector is a vector formed by combining the longitudinal and lateral components of the current value of the tire force. That is, it is calculated by combining the current value F of the tire force in the longitudinal direction. fl F fr F rl F rr and the current value of the lateral force Y fl Y fr Yrl Y rr This allows you to obtain the current value of the force vector generated by the tire.

[0140] Specifically, the force vector generated by the tire is obtained by the following formula (15).

[0141] [Formula 15]

[0142]

[0143] Regarding the expression (15), the symbol F x This indicates the force generated by the tires in the forward and backward directions. Symbol: F y This indicates the force generated by the tires in the left and right directions (lateral force).

[0144] refer to Figure 2 The tire force vector and the maximum tire force are sent to the normalization processing unit 19. The normalization processing unit 19 normalizes the maximum tire force and the tire force vector (S34). That is, the normalization processing unit 19 scales the current values ​​of the tire force vector and the maximum tire force to make them... Figure 12 The radii of the friction circles FR, FL, RR, and RL illustrated in the example are constant values.

[0145] exist Figure 12 The diagram shows the friction circle and other parameters. That is, in... Figure 12 The friction circle FR of the front right tire, the friction circle FL of the front left tire, the friction circle RR of the rear right tire, and the friction circle RL of the rear left tire are shown in the figure.

[0146] Within these friction circles, the maximum tire-generated force F m The diameter of the circle is set to 1. In any friction circle, the diameter is set to 1. The normalization processing unit 19 performs a normalization process (S34) that scales the received maximum tire force value to 1. Furthermore, the normalization processing unit 19 normalizes the tire force vector with the same scaling ratio as the maximum tire force.

[0147] Furthermore, in the example above, the maximum tire force F was calculated regarding the forces generated by the tires in the front-to-rear directions. m However, besides this, the maximum tire force F can also be calculated regarding the force generated by the tires in the left and right directions. m In this case, for example Figure 10 The maximum values ​​of each characteristic curve in the lateral force graph and the maximum tire force F m Correspondingly. Furthermore, by calculating the different maximum tire forces F in the left-right and front-back directions... m The friction circle becomes an ellipse. The normalization processing unit 19 performs normalization processing to make the major axis or minor axis of the ellipse shape 1.

[0148] 3. Driving assistance based on tire-generated force

[0149] The normalized tire force vector data is sent to the sound control unit 20 and the display control unit 21. The sound control unit 20 causes the speaker 40 to output a sound corresponding to the difference between the maximum tire force (current value) and the tire force vector (current value) (S36). In other words, the sound control unit 20 causes the speaker 40 to output an informing tone based on the distance between the friction circle and the tire force vector (current value).

[0150] exist Figures 13-16 The diagram illustrates the relationship between the tire's force vector and the warning sound. In all diagrams, the friction circle is shown on the left. The tire's force vector is represented by the coordinates of the black circle. Furthermore, in each diagram, a graph of the warning sound is also shown on the right. The horizontal axis of the graph represents time. The vertical axis of the graph represents output (intensity).

[0151] like Figure 14 , Figure 15 As illustrated, the notification sound is an intermittent pulse sound. The closer the current value of the tire force vector is from 0 to the maximum tire force, the shorter the interval between the notification sounds is set by the sound control unit 20. Figure 13 The image shows a state where the tire's force vector is 0. At this time, the sound control unit 20 does not drive the speaker 40. That is, no notification sound will be played from the speaker 40. Figure 14 The diagram shows an example where the force vector generated by the tire is plotted at the center of the friction circle and the middle of the friction circle. At this time, the sound control unit 20 causes the speaker 40 to output a notification tone at a predetermined interval ΔT.

[0152] For example, when the magnitude F of the tire-generating force vector shown in equation (15) becomes the maximum tire-generating force F m When the force reaches 50% or more, the sound control unit 20 causes the speaker 40 to play a notification sound. At this time, the coordinate point of the tire force vector moves from 0 closer to the maximum tire force F. m The shorter the interval ΔT between the sound of the notification tone, the closer the coordinate point of the tire force vector is to the maximum tire force F. m The shorter the interval between impulse sounds, the better. Figure 15 The diagram shows the state where the tire force vector equals the maximum tire force. At this point, the interval ΔT between the announcement sounds is the shortest.

[0153] exist Figure 16 The diagram illustrates an example where the coordinate point of the tire's force vector exceeds the friction circle. In this case, to restore tire grip, the sound control unit 20 causes the speaker 40 to play a warning sound. This warning sound can be, for example, a continuous tone. Furthermore, the warning sound can be... Figure 14 , Figure 15The examples illustrate different tones for the notification sounds. For instance, a sound one octave higher than the notification sound is played as a warning tone from speaker 40.

[0154] For example, it is difficult to observe the display 42 to confirm the condition of the friction circle while driving. Therefore, in the driving assistance device according to this embodiment, the sound control unit 20 outputs an informing tone or a warning tone based on an output interval (sound interval) ΔT, which is determined based on the difference between the maximum tire force and the tire force vector. The driver can identify the condition of the friction circle by hearing.

[0155] For example, the sound control unit 20 causes the speaker 40 to play a notification or warning sound to each of the four wheels. Alternatively, the sound control unit 20 causes the notification or warning sound to be played from the speaker 40 based on at least one set of differences between the maximum tire force and the current value of the tire force.

[0156] For example, the sound control unit 20 can select only the tire with the largest force F among the four wheels. m The highest-performing tire. That is, the sound control unit 20 obtains the maximum tire force before normalization from the tire force estimation unit 17 for the four tires. Then, the sound control unit 20 selects the tire with the highest maximum tire force. Then, based on the friction circle of that tire, that is, based on the difference between the maximum tire force (current value) and the tire force vector (current value), the sound control unit 20 sets the output interval, that is, the sound interval ΔT of the notification tone.

[0157] For example, when turning right, the front left tire generates more force than the other three tires. By focusing on the tires that affect the turning level and outputting notification or warning sounds, the driver's driving skills can be improved.

[0158] refer to Figure 2 The display control unit 21 will Figure 12 The various graphs illustrated are displayed on monitor 42. Figure 12 The diagram illustrates the friction circles FR, FL, RR, and RL for the front right wheel, front left wheel, rear right wheel, and rear left wheel. Additionally, graphs illustrating torque TQ, steering Steer, forward speed Vx, GPS position during the race, and ground load Fz are shown below. Figure 12 These graphs are displayed on the in-vehicle display 42. For example, in car racing such as rallies, the navigator (co-pilot) improves their driving skills by checking the display 42.

[0159] The display control unit 21 plots coordinates representing the current value of the tire's force vector on the friction circles FR, FL, RR, and RL over time. Figure 3(S38). For example, the leading edge of the current value of the tire force vector is represented by a coordinate point. The trajectory of the coordinate point represents the temporal variation of the tire force. As mentioned above, since the maximum tire force is normalized, the trajectory of the tire force can be easily identified.

[0160] Furthermore, by only confirming the tire power when the maximum tire power is relatively high, a short driving evaluation can be performed in places such as the maintenance area. Therefore, the display control unit 21 can set the color of the coordinate points based on the maximum tire power before scaling and normalization.

[0161] For example, regarding the maximum tire power calculated within a specified period, the display control unit 21 extracts the upper 15% of the maximum tire power. Furthermore, the display control unit 21 sets the color of the coordinate points representing the tire power vector corresponding to the extracted maximum tire power to red. The remaining coordinate points are set to green.

[0162] and, Figure 12 The various graphs shown can be linked together. For example, on the monitor (reference) Figure 2 In the case of a touch panel, the specified coordinate points of the curve FR are designated by the driver or other personnel. At this time, the display control unit 21 highlights the coordinate points in the curves FL, RL, and RR corresponding to the coordinate points at the same time as the designated coordinate points. Furthermore, in the respective curves of vehicle position GPS, torque TQ, steering Steer, forward speed Vx, and ground load Fz, the display control unit 21 displays the parameters at the same time as the coordinate points specified by the driver on the display screen 42.

[0163] Furthermore, in the above embodiment, a driving assistance device primarily used for assisting drivers in car racing has been described. However, the driving assistance device according to this embodiment can be used for other purposes. For example, it can be used to assist driving so-called driving robots or advanced driver assistance systems (AD-ADAS) for autonomous driving.

[0164] Symbol Explanation

[0165] 10-Driver assistance device, 13-Vehicle model calculation unit, 14-Suspension calculation unit, 15-Load movement calculation unit, 17-Tire force estimation unit, 18-Tire force vector calculation unit, 19-Normalization processing unit, 20-Sound control unit, 21-Display control unit, 38-Various sensors, 40-Speaker, 42-Display, 50FL-Front left tire, 50FR-Front right tire, 50RL-Rear left tire, 50RR-Rear right tire.

Claims

1. A driving assistance device, characterized in that, have: The tire force estimation unit calculates the maximum tire force and the current value of the tire force of each tire of the vehicle based on the detection values ​​detected by multiple sensors that detect the dynamics of the vehicle. and The sound control unit causes the speaker to output at least one set of sounds corresponding to the difference between the maximum tire power and the current value of the tire power. As the sound, the sound control unit causes the speaker to output intermittently emitted pulse sounds. The closer the current value of the tire's generating force is from 0 to the maximum tire generating force, the shorter the sound emission interval is set by the sound control unit.

2. The driving assistance device according to claim 1, characterized in that, Among the multiple tires of the vehicle, the sound control unit determines the sound emission interval based on the difference between the current value of the tire generating force of the tire with the highest maximum tire generating force and the maximum tire generating force.

3. The driving assistance device according to claim 2, characterized in that, When the current value of the tire's generating force exceeds the maximum tire's generating force, the sound control unit outputs a continuous tone as the sound. Furthermore, the sound control unit sets a pitch different from the pulse tone as the pitch of the continuous tone.

4. The driving assistance device according to claim 1, characterized in that, have: The display control unit displays the friction circle representing the maximum tire force and the current value of the tire force on the screen. The display control unit plots coordinate points on the display screen, and these coordinate points correspond to a vector formed by combining the longitudinal and lateral components of the current value of the tire's generated force. The driving assistance device includes a normalization processing unit that scales the maximum tire force and the current value of the tire force to make the radius of the friction circle a constant value.

5. The driving assistance device according to claim 4, characterized in that, The display control unit sets the color of the coordinate point based on the maximum tire force before scaling.

Images