Vehicle control device

Abstract

A control device (10) for a vehicle (1) having detection means (21 to 24) that respectively detect a vehicle speed (V), a yaw rate (r), a lateral acceleration (Ay), and a longitudinal acceleration (Ax) of the vehicle (1), the control device (10) comprising: a first estimation unit (11) which estimates a specific coefficient that includes a rear wheel cornering power (Kr) of the vehicle (1), among coefficients included in a transfer function of the product of the vehicle speed (V) and the yaw rate (r) where the lateral acceleration (Ay) is an input; a second estimation unit (12) which, on the basis of at least the specific coefficient and the longitudinal acceleration (Ax), estimates a rear wheel grip degree (krg) indicating the slipperiness of a rear wheel (2R); and a control unit (13) which controls an actuator (3 to 8) or a notification device (9) of the vehicle (1) in accordance with the rear wheel grip degree (krg).

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device that estimates the slipperiness of rear wheels of a vehicle and controls an actuator of the vehicle in accordance with the estimation result. [Background technology]

[0002] Conventionally, suppression of vehicle spin behavior has been implemented as one of the vehicle motion controls. Spin behavior is a behavior in which the vehicle body rotates significantly inward when the cornering force of the rear wheels is reduced for some reason during cornering. Techniques for estimating the occurrence of such spin behavior are known. For example, in Patent Document 1, a frequency transfer characteristic is calculated based on the lateral acceleration (lateral G) acting on the vehicle, the rotational angular velocity around the center of gravity of the vehicle (hereinafter referred to as "yaw rate"), and the vehicle body speed, and the rear wheel cornering power of the vehicle is calculated based on this to determine rear wheel sideslip. When rear wheel sideslip occurs, the value of the rear wheel cornering power decreases significantly, so the presence or absence of sideslip can be determined from the calculated value of rear wheel cornering power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-202046 Summary of the Invention [Problem to be solved by the invention]

[0004] As in Patent Document 1, it is possible to determine rear wheel sideslip by calculating rear wheel cornering power, but the process leading up to calculating rear wheel cornering power can involve uncertainty (estimation error and calculation error).When determining the presence or absence of sideslip or when performing control such as control to suppress vehicle spin behavior, it is important to minimize errors in the values ​​used for determination and control (values ​​equivalent to rear wheel cornering power in Patent Document 1) to increase estimation accuracy.

[0005] The present invention has been devised in view of the above-mentioned problems, and one of its objectives is to reduce the cornering force of the rear wheels, i.e., to accurately estimate a value that indicates the tendency of the rear wheels to slip, thereby improving vehicle controllability. However, in addition to this objective, another objective of the present invention is to achieve effects that cannot be obtained by conventional techniques, which are derived from the configurations shown in the below-described embodiments of the invention. [Means for solving the problem]

[0006] The disclosed vehicle control device can be realized as the following disclosed aspects or application examples, and solves at least some of the above-mentioned problems. The disclosed vehicle control device is applied to a vehicle provided with a vehicle speed detection means for detecting the vehicle speed, a yaw rate detection means for detecting the yaw rate of the vehicle, a lateral acceleration detection means for detecting the lateral acceleration of the vehicle, and a longitudinal acceleration detection means for detecting the longitudinal acceleration of the vehicle. The control device includes a first estimation unit for estimating a specific coefficient including rear wheel cornering power of the vehicle among coefficients included in a transfer function of the product of the vehicle speed and the yaw rate, with the lateral acceleration as an input, a second estimation unit for estimating a rear wheel grip degree indicating the slipperiness of the rear wheels based on at least the specific coefficient and the longitudinal acceleration, and a control unit for controlling the vehicle in accordance with the rear wheel grip degree. At least one of the drive source, brake device, power steering device, AFS, ARS, and active suspension of , so as to stabilize the spin behavior of the vehicle. and a control unit for controlling the [Effects of the Invention]

[0007] According to the disclosed vehicle control device, the rear wheel grip degree, which indicates the tendency of the rear wheels to slip, is estimated based on a specific coefficient included in a transfer function and longitudinal acceleration, and therefore, compared to conventional methods that calculate rear wheel cornering power from a transfer function, the number of calculation steps is reduced, thereby reducing uncertainty and improving estimation accuracy. Furthermore, since the vehicle actuator or alarm device is controlled according to the estimated rear wheel grip degree, vehicle controllability can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a configuration of a vehicle to which a control device according to an embodiment is applied; [Figure 2] FIG. 2 is a diagram for explaining a linear two-wheel model of a vehicle. [Figure 3] 2 is a block diagram showing a process performed by the control device of FIG. 1. FIG. [Figure 4] 2 is an example of a flowchart executed by the control device of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] A vehicle control device according to an embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or applications of techniques not explicitly described in the following embodiments. The configurations of the respective embodiments can be modified in various ways without departing from the spirit thereof. Furthermore, they can be selected or combined as needed. In the following description, the forward direction of the vehicle is defined as the forward direction (front of the vehicle), and left and right are defined based on the forward direction.

[0010] [1. Equipment configuration] The control device 10 of this embodiment is applied to a vehicle 1 illustrated in Fig. 1, and has the function of determining an index indicating at least the slipperiness of a rear wheel 2R of the vehicle 1 (rear wheel grip degree, which will be described later). The control device 10 is one of the electronic control units (ECU, Electronic Control Unit) mounted on the vehicle 1, and is represented as "ECU" in Fig. 1. The control device 10 is equipped with, for example, a processor (microprocessor) such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a non-volatile memory, and the like.

[0011] The processor is an arithmetic processing device that incorporates a control unit (control circuit), an arithmetic unit (arithmetic circuit), a cache memory (group of registers), etc. ROM, RAM, and non-volatile memory are memory devices that store programs and data in progress. The contents of the decisions and controls performed by the control device 10 are recorded and saved in memory as firmware or application programs, and when a program is executed, the contents of the program are expanded in memory space and executed by the processor.

[0012] The vehicle 1 is an engine vehicle, an electric vehicle (EV; Electric Vehicle, HEV; Hybrid Electric Vehicle, PHEV; Plug-in Hybrid Electric Vehicle), or a fuel cell vehicle (FCV; Fuel Cell Vehicle) equipped with a drive source 3 such as an engine or an electric motor. Braking devices 4 are provided on left and right front wheels 2FL, 2FR and left and right rear wheels 2RL, 2RR of the vehicle 1, and brakes of each of the four wheels are independently controlled. The vehicle 1 is also provided with a power steering device 5 that assists the driver's steering operation, an AFS (Active Front Steering) 6 that can actively control the steering amount (front wheel steering angle) of the front wheels 2F (2FL, 2FR), and an ARS (Active Rear Steering) 7 that can actively control the steering amount (rear wheel steering angle) of the rear wheels 2R (2RL, 2RR). The vehicle 1 of this embodiment is also provided with an active suspension 8 and an alarm device 9 that provides visual and audio announcements to the driver.

[0013] These devices 3 to 9 are individually controlled by an on-board control device (not shown). For example, the vehicle 1 is equipped with a control device (engine ECU and motor ECU) that controls the drive source 3, a brake ECU that controls the brake device 4, an ECU that controls the power steering device 5, an ECU that controls the AFS 6 and ARS 7, an ECU that controls the active suspension 8, and an ECU that controls the alarm device 9. In this embodiment, when the control device 10 controls the devices 3 to 9, it sends commands to these various ECUs, and the various ECUs control the corresponding devices 3 to 9. Of the devices 3 to 9, the devices 3 to 8 that play a role in converting energy into mechanical displacement or stress may be called "actuators." Note that a common ECU may have the function of controlling multiple devices 3 to 9.

[0014] The vehicle 1 is provided with sensors for acquiring various information about the vehicle 1. In the example shown in Fig. 1, a vehicle speed sensor 21, a yaw rate sensor 22, a lateral acceleration sensor 23, and a longitudinal acceleration sensor 24 are provided, and the sensors 21 to 24 are connected to the control device 10. The vehicle speed sensor 21 (vehicle speed detection means) is a sensor that detects the vehicle speed V of the vehicle 1, and the yaw rate sensor 22 (yaw rate detection means) is a sensor that detects the rotational angular velocity about a vertical axis passing through the center of gravity G of the vehicle 1 as the yaw rate r. In this embodiment, as indicated by the thick arrow in Fig. 1, the vehicle speed V is positive in the direction forward from the center of gravity G, and the yaw rate r is positive in the counterclockwise direction of the center of gravity G when the vehicle 1 is viewed from above.

[0015] The lateral acceleration sensor 23 (lateral acceleration detection means) and the longitudinal acceleration sensor 24 (longitudinal acceleration detection means) detect the lateral acceleration A y and longitudinal acceleration A x In this embodiment, as shown by the thick arrow in FIG. y The left direction from the center of gravity G is considered to be the positive direction, and the longitudinal acceleration A x The direction from the center of gravity G toward the front is considered to be the positive direction. Information detected by each of the sensors 21 to 24 is sent to the control device 10.

[0016] The means for detecting the vehicle speed V is not limited to the vehicle speed sensor 21. For example, a wheel speed sensor for detecting the angular velocity of each wheel 2 may be provided, and the vehicle speed V may be calculated from the detected value of the wheel speed sensor. Similarly, a means for detecting the yaw rate r, a means for detecting the lateral acceleration A y Means for detecting longitudinal acceleration A x The means for detecting the lateral acceleration A is not limited to the yaw rate sensor 22, the lateral acceleration sensor 23, and the longitudinal acceleration sensor 24. For example, the lateral acceleration A may be detected based on the steering angle or the vehicle speed V. y The lateral acceleration A is calculated by estimating the lateral acceleration A and correcting the estimated value and the value detected by the lateral acceleration sensor 23 based on another sensor value. y Similarly, the values ​​detected by the yaw rate sensor 22 and the values ​​detected by the longitudinal acceleration sensor 24 may be corrected based on values ​​from other sensors to obtain the yaw rate r and the longitudinal acceleration A. x In such a case, the estimation unit and the correction unit (functional elements of the control device) can serve as the respective detection means.

[0017] [2. Control configuration] The control device 10 of this embodiment uses information detected by the various sensors 21 to 24 to calculate the "rear wheel grip degree k" which is an index indicating the slipperiness of the rear wheels 2R of the vehicle 1. rg The control device 10 estimates the rear wheel grip degree k rg The vehicle 1 may also have a function to determine the road surface conditions while the vehicle 1 is traveling based on the above information. The road surface conditions that can be determined here include, for example, dry paved roads, wet roads, snow-covered roads, frozen roads, gravel (unpaved roads), muddy roads, etc.

[0018] Rear wheel grip level k rg is a value that indicates the degree of slipperiness (friction force, rear wheel cornering power) of the rear wheels 2R of the vehicle 1, and the more slippery it is, the smaller the value becomes, and the less slippery it is, the larger the value becomes. rg The control device 10 of this embodiment has a function of determining road surface conditions, and therefore the control device 10 includes a function of determining the rear wheel grip degree krg The correspondence between the vehicle speed and road surface conditions is stored in advance.

[0019] The control device 10 calculates the rear wheel grip degree k rg The control device 10 of this embodiment includes a first estimation unit 11, a second estimation unit 12, and a control unit 13 as functional elements for estimating the degree of rear wheel grip k and controlling the actuator or the notification device 9 of the vehicle 1. rg The control device 10 includes a determination unit 14 as a functional element for determining road surface conditions from the vehicle speed. These elements are shown by conveniently classifying the functions of the control device 10. Each of these elements can be written as an independent program, or multiple elements can be written as a composite program. The programs corresponding to each element are stored in the memory or storage device of the control device 10 and executed by the processor.

[0020] The first estimation unit 11 estimates the lateral acceleration A y Among the coefficients included in the transfer function G(s) of the product of the vehicle speed V and yaw rate r, which are input, the rear wheel cornering power K r The transfer function G(s) is expressed by the following equation 1. Note that a1, b1, and b2 in equation 1 are coefficients. In this way, the transfer function G(s) is an equation with a linear numerator and a quadratic denominator, with the steady-state gain set to 1.

[0021]

number

[0022] Here, as shown in Figure 2, the vehicle 1 is considered as a linear two-wheel model. The linear two-wheel model is a mathematical model of the vehicle 1 in which the vehicle 1 is regarded as a single rigid body and linearized by reducing the degrees of freedom of movement. Here, the vehicle 1 is regarded as a rigid body with one front wheel 2F and one rear wheel 2R, and only planar movement in the lateral and yaw directions when the vehicle speed is constant is considered. It is also assumed that the cornering force generated by the wheel 2 is proportional to the sideslip angle.

[0023] The equation of motion for this two-wheel model is expressed by the following equation 2. Note that m is the vehicle mass, β is the slip angle of the center of gravity, I is the yaw moment of inertia, and K f is the front wheel cornering power, β f is the front wheel slip angle (side slip angle of the front 2F wheels), β r is the rear wheel slip angle (side slip angle of rear wheel 2R), L f is the longitudinal distance between the front axle and the center of gravity G, L r is the longitudinal distance between the rear axle and the center of gravity G.

[0024]

number

[0025] Here, the slip angle β of the front wheel 2F and the rear wheel 2R is f ,β r is expressed by the following equation 3. Note that δ is the steering angle of the vehicle 1.

number

[0026] In the above equation 3, if we assume that the vehicle speed V is constant, then the above equation 2 becomes linear with respect to the center of gravity slip angle β and yaw rate r. Under this assumption, if equation 2 is subjected to a Laplace transform and rearranged, we obtain the following equation 4, where L is the wheelbase (the distance between the front and rear axles).

[0027]

number

[0028] As is clear from the above equation 4, among the coefficients a1, b1, and b2, the coefficients a1 and b2 contain the rear wheel cornering power K r Also, m and L included in these coefficients a1 and b2 f , I, L are predetermined vehicle specification values, so the change in coefficients a1 and b2 is rTherefore, the first estimating unit 11 estimates the value of the specific coefficient by using a predetermined estimation method, with at least one of the coefficients a1 and b2 as the specific coefficient. r The change in can be estimated.

[0029] The first estimator 11 of this embodiment estimates the quadratic coefficient b2 of the denominator as a specific coefficient. Examples of the predetermined estimation method include an estimation method using a Kalman filter and a recursive least squares method. In these estimation methods, the current state quantity estimate (specific coefficient b2) is estimated by adding a value obtained by multiplying a deviation between a value (output measurement value) detected by the detection means (sensors 21 to 24) and an output estimate estimated by applying the state quantity estimate one time step ago to a mathematical model stored in the electronic control device, to the state quantity estimate estimated by applying the state quantity estimate one time step ago to a mathematical model stored in the electronic control device.

[0030] The inventors have found that estimating the quadratic denominator coefficient b2 as a specific coefficient provides higher accuracy than estimating the linear numerator coefficient a1 as a specific coefficient. Therefore, the first estimator 11 of this embodiment estimates coefficient b2 as a specific coefficient, but may also estimate coefficient a1 as a specific coefficient, or may estimate these two coefficients a1 and b2 as specific coefficients and take a weighted average of these two estimated values ​​a1 and b2.

[0031] The second estimation unit 12 estimates at least the specific coefficient estimated by the first estimation unit 11 and the longitudinal acceleration A detected by the longitudinal acceleration sensor 24. x Based on the above rear wheel grip degree k rg The second estimation unit 12 of this embodiment estimates the rear wheel grip degree k rg As shown in FIG. 3 and the following equations 5 and 6, the specific coefficient b2 estimated by the first estimation unit 11 and the longitudinal acceleration A x The rear axle load W is calculated from r It is calculated as the reciprocal of the product of

[0032]

number

[0033] As shown in Equation 6, the rear axle load W r is the rear axle load W of vehicle 1 when it is stationary r0 (Fixed value) Load shift amount ΔW on the front and rear axles x The load shift amount ΔW on the front and rear axles x In calculating the longitudinal acceleration A x is used. cg is the center of gravity height (fixed value).

[0034] That is, the second estimation unit 12 of the present embodiment estimates the detected longitudinal acceleration A x and the rear axle load W r The specific coefficient b2 estimated by the first estimation unit 11 and the rear axle load W r and rear wheel grip degree k rg The second estimation unit 12 estimates (calculates) the estimated rear wheel grip degree k rg is sent to the control unit 13.

[0035] The control unit 13 calculates the rear wheel grip degree k estimated by the second estimation unit 12. rg The control unit 13 controls the actuator or the notification device 9 of the vehicle 1 in accordance with the degree of rear wheel grip k. The actuator controlled here is at least one of the drive source 3, the brake device 4, the power steering device 5, the AFS 6, the ARS 7, and the active suspension 8, and may be all of them. rg The smaller the rear wheel grip degree k is (i.e., the more likely the rear wheel 2R is to slip), the more likely the vehicle 1 is to spin (or the situation is such that spin is more likely to occur). Therefore, the control unit 13 controls the actuators to stabilize the behavior of the vehicle 1. rg is compared with a preset first threshold value, and the rear wheel grip degree k rg If the first threshold value is less than the first threshold value, the actuator may be controlled to stabilize the behavior of the vehicle 1.

[0036] On the other hand, the control unit 13 controls the rear wheel grip degree k rg When the rear wheel 2R is large (when the vehicle is in a normal running state with no skidding of the rear wheels 2R), the actuator is controlled in accordance with the torque required for the vehicle 1, the pedal operation by the driver, the vehicle speed V, etc. This control is called normal control. The normal control may be performed by the control device 10 or by another on-vehicle control device. The determination of whether to perform normal control is made, for example, by the control unit 13 based on the rear wheel grip degree k rg This can be determined by checking whether the second threshold value exceeds a predetermined second threshold value. Here, it is assumed that the other on-board control device performs normal control. The second threshold value is a value greater than the first threshold value.

[0037] The control unit 13 of this embodiment is configured to calculate the rear wheel grip degree k rg The vehicle 1 includes a first control unit 13A that adjusts the control amount of at least one of the driving force and braking force of the vehicle 1 in accordance with the vehicle speed. When adjusting the control amount of the driving force, the first control unit 13A sends a command to a control device of the driving source 3 to control the output (driving force) of the driving source 3. If the vehicle 1 is equipped with a power transmission device, the driving force may be adjusted by controlling the power transmission device. When adjusting the control amount of the braking force, the first control unit 13A sends a command to a control device of the brake device 4 to control the output (braking force) of the brake device 4. The brake device 4 can control each wheel 2 individually, allowing for more precise adjustment. It is also possible to adjust the control amount of the braking force by controlling the driving source 3.

[0038] When normal control is performed, the first control unit 13A of this embodiment adjusts the control amount so as not to impede the performance of normal control. On the other hand, when the normal control is not performed, the first control unit 13A controls the rear wheel grip degree k rgThe control amount is adjusted so that the more likely the rear wheel 2R is to slip, the more the torque transfer in the front-rear and left-right directions is limited. That is, in this case, the first control unit 13A adjusts the control amount of at least one of the driving force and braking force so as to limit the torque transfer with respect to the driving force and braking force under normal control. In this adjustment, the first control unit 13A may switch the control map, or may increase or suppress the control output calculated under normal control.

[0039] The control unit 13 of this embodiment is configured to calculate the rear wheel grip degree k rg and a second control unit 13B that adjusts the steering assist torque of the vehicle 1, the steering amount of each wheel 2, and at least one control amount of the active suspension 8 in accordance with the steering assist torque. When controlling the steering assist torque, the second control unit 13B sends a command to the control device of the power steering device 5 to control the output (steering assist torque) of the power steering device 5. When controlling the steering amount, the second control unit 13B sends a command to the control devices of the AFS 6 and ARS 7 to control the outputs (front wheel steering angle, rear wheel steering angle) of the AFS 6 and ARS 7. When controlling the active suspension 8, the second control unit 13B sends a command to the control device of the active suspension 8 to control energy sources such as hydraulic pressure, air pressure, and an electric motor.

[0040] The steering assist torque of the vehicle 1, the steering amount of each wheel 2, and the active suspension 8 are all controlled in accordance with the steering operation by the driver, the vehicle speed V, etc., during normal driving when no skidding of the rear wheels 2R is occurring (i.e., during normal control). When normal control is being performed, the second control unit 13B of this embodiment does not impede its implementation.

[0041] On the other hand, when the normal control is not performed, the second control unit 13B controls the rear wheel grip degree k rgIn accordance with this, the more likely the rear wheel 2R is to slip, the more the second control unit 13B adjusts the control amount of at least one of the steering assist torque, the steering amount, and the active suspension 8 so as to ensure maneuverability while suppressing lateral slip of the rear wheel 2R. In this adjustment, the second control unit 13B may switch the control map, or may increase or suppress the control output calculated in normal control.

[0042] The control by the first control unit 13A and the control by the second control unit 13B may be combined in any way. For example, the first control unit 13A may control both the driving force and the braking force, and the second control unit 13B may control all of the steering assist torque, the steering amount, and the active suspension 8. Alternatively, the first control unit 13A may control only the braking force, and the second control unit 13B may control only the steering assist torque. Alternatively, the first control unit 13A may control both the driving force and the braking force, and the second control unit 13B may not perform any control. In this way, by using two or more controls in combination, the degree of freedom of control is increased, enabling more precise vehicle motion control.

[0043] The control unit 13 calculates the rear wheel grip degree k estimated by the second estimation unit 12. rg is smaller than a predetermined third threshold, the alarm device 9 may be controlled to notify the driver that the vehicle 1 is in a skidding state. The third threshold is a value smaller than the second threshold, and may be the same as or different from the first threshold.

[0044] The determination unit 14 determines the rear wheel grip degree k estimated by the second estimation unit 12. rg In this determination, the road surface condition on which the vehicle 1 is traveling is determined based on, for example, the rear wheel grip degree k rg As an example, the determination unit 14 may use the correspondence relationship between the rear wheel grip degree k rg is equal to or greater than a first predetermined value, the road is determined to be dry, and the rear wheel grip degree k rgis less than the first predetermined value and is equal to or greater than a second predetermined value that is smaller than the first predetermined value, the determination unit 14 determines that the road is a wet road. rg is less than the second predetermined value and is equal to or greater than a third predetermined value which is smaller than the second predetermined value, the determination unit 14 determines that the road is snowy. rg If the difference is less than the third predetermined value, the road surface is determined to be frozen. The same determination may be made for other road surface conditions (unpaved road, muddy road, etc.).

[0045] Further, instead of or in addition to the control of the actuator, the control unit 13 may estimate the rear wheel grip degree k estimated by the second estimation unit 12. rg For example, the control unit 13 may announce the result of the road surface condition determination by the determination unit 14 to the driver by voice or display.

[0046] [3. Flowchart] FIG. 4 shows an example of a flowchart executed by the control device 10 described above. This flowchart is executed at a predetermined calculation cycle, for example, when the main power supply of the vehicle 1 is on. First, in step S1, information from the various sensors 21 to 24 is acquired. In step S2, the first estimation unit 11 estimates the specific coefficient b2 included in the transfer function G(s) of the above equation 1. Next, the second estimation unit 12 estimates the rear axle load W r is calculated (step S3), and the rear wheel grip degree k rg In step S5, the control unit 13 (first control unit 13A, second control unit 13B) estimates (calculates) the rear wheel grip degree k rg The actuator or the notification device 9 is controlled in response to the command, and the flow chart returns.

[0047] [4. Actions and Effects] Rear wheel cornering power K r The rear wheel grip degree k based on specific coefficients a1 and b2 including rgis a parameter that indicates the slipperiness of the rear wheels 2R and can express the friction state between the rear wheels 2R and the road surface. In the control device 10 described above, the rear wheel cornering power K r Focusing on the fact that it is possible to know the change of the lateral acceleration A y , yaw rate r, vehicle speed V). Furthermore, the specific coefficients a1, b2 and longitudinal acceleration A x and rear wheel grip degree k rg In this way, the present control device 10 estimates the rear wheel cornering power K from the transfer function G(s). r Compared to the conventional method of calculating the longitudinal acceleration A, the calculation process is fewer, which reduces uncertainty and improves estimation accuracy. x Since the information is taken into account, the degree of rear wheel grip k according to the driving condition is rg This also improves the estimation accuracy.

[0048] In addition, in the above-described control device 10, the specific coefficients a1, b2 and the longitudinal acceleration A x Rear wheel grip degree k based on rg The actuator or the notification device 9 of the vehicle 1 is controlled in accordance with the vehicle speed, thereby improving the controllability of the vehicle 1. This can contribute to improving the control of suppressing spin behavior, which is one of the vehicle motion controls, for example.

[0049] In the above-described control device 10, the rear wheel grip degree k rg In response to this, the control amount of at least one of the driving force and braking force of the vehicle 1 is adjusted. Therefore, the control amount of at least one of the driving force and braking force can be increased, decreased, or adjusted in accordance with the slipperiness (magnitude of frictional force) of the rear wheels 2R (for example, torque transfer in the front, rear, left, and right directions can be suppressed when the wheels are slippery), which contributes to improving the control of suppressing spin behavior and makes it possible to achieve, for example, a desired behavior.

[0050] In addition, in the above-described control device 10, the rear wheel grip degree k rgAt least one of the control amounts of the steering assist torque of the vehicle 1, the steering amount of each wheel 2, and the active suspension 8 is adjusted according to the degree of slippage (magnitude of frictional force) of the rear wheels 2R. This makes it possible to ensure maneuverability by increasing or decreasing the control amounts of the steering assist torque and the steering amount according to the degree of slippage (magnitude of frictional force) of the rear wheels 2R. In addition, the ground contact state of the wheels 2 can also be controlled by adjusting the control amounts (hydraulic pressure and air pressure) of the active suspension 8. These contribute to improved control of suppression of spin behavior, making it possible to achieve, for example, a desired behavior.

[0051] In the above-described control device 10, the rear wheel grip degree k is calculated using the above-described equations 5 and 6. rg Therefore, the rear wheel grip degree k according to the driving condition can be calculated by simple calculation. rg can be estimated. Furthermore, the control device 10 uses the quadratic coefficient b2 of the denominators of the above-mentioned formulas 1 and 4 as the specific coefficient. This is because the inventors have found that coefficient b2 produces a value closer to the true state in estimation using, for example, a Kalman filter. Therefore, by using this coefficient b2 as the specific coefficient, the degree of rear wheel grip k rg This can further improve the estimation accuracy.

[0052] [5. Other] The configuration of the control device 10 described above is an example and is not limited to the above. For example, in the control device 10 described above, the control unit 13 is provided with two functions, a first control unit 13A and a second control unit 13B, but these functions do not have to be separated. Furthermore, the six control objects described above (driving force, braking force, steering assist torque, steering amount, active suspension 8, and alarm device 9) may be controlled independently or in combination.

[0053] In the control device 10, the determination unit 14 determines the road surface conditions, but this determination may be omitted. r The method for obtaining is not limited to the above method. In the above embodiment, the coefficient b2 of the quadratic denominator is estimated as the specific coefficient, but the coefficient a1 of the linear denominator may be estimated as the specific coefficient. rg The estimation method is not limited to the above, but at least a specific coefficient and longitudinal acceleration A x It is sufficient if it is based on the above.

[0054] Furthermore, the configuration of the vehicle 1 to which the control device 10 is applied is also an example and is not limited to the above. For example, if the vehicle 1 is equipped with an active stability control (ASC), the rear wheel grip degree k estimated by the control device 10 may be calculated. rg In addition, the AFS 6 and the ARS 7 may be omitted from the vehicle 1, and each wheel 2 may be provided with a drive source 3 (for example, an in-wheel motor). [Explanation of symbols]

[0055] 1 vehicle 2 wheels 2FL Left front wheel (front wheel, wheel) 2FR Right front wheel (front wheel, wheel) 2RL Left rear wheel (rear wheel, wheel) 2RR Right rear wheel (rear wheel, wheel) 3. Drive source (actuator) 4 Brake device (actuator) 5 Power steering device (actuator) 6 AFS (actuator) 7 ARS (actuator) 8 Active suspension (actuator) 9. Alarm device 10 Control device 11 First Estimation Department 12 Second estimation part 13 Control Unit 13A First control section 13B Second control section 14 Judgment section 21 Vehicle speed sensor (vehicle speed detection means) 22 Yaw rate sensor (yaw rate detection means) 23 Lateral acceleration sensor (lateral acceleration detection means) 24. Longitudinal acceleration sensor (longitudinal acceleration detection means) A x Longitudinal acceleration A y lateral acceleration a1 coefficient (specific coefficient) b1 coefficient b2 coefficient (specific coefficient) G center of gravity G(s) transfer function I Yaw moment of inertia k rg Rear wheel grip K r Rear wheel cornering power L Wheelbase (distance between front and rear axles) L f The distance between the front axle and the center of gravity G in the longitudinal direction L r The distance between the rear axle and the center of gravity G in the longitudinal direction m Vehicle mass r Yaw rate V Vehicle speed W r rear axle load W r0 Stationary rear axle load β Center of gravity slip angle β f Front wheel slip angle β r Rear wheel slip angle δ steering angle

Claims

1. A control device for a vehicle, comprising: a vehicle speed detection means for detecting a vehicle speed of the vehicle; a yaw rate detection means for detecting a yaw rate of the vehicle; a lateral acceleration detection means for detecting a lateral acceleration of the vehicle; and a longitudinal acceleration detection means for detecting a longitudinal acceleration of the vehicle, a first estimation unit that estimates a specific coefficient that includes a rear wheel cornering power of the vehicle, among coefficients included in a transfer function of a product of the vehicle body speed and the yaw rate, with the lateral acceleration as an input; a second estimation unit that estimates a rear wheel grip degree indicating the ease of slippage of the rear wheels based on at least the specific coefficient and the longitudinal acceleration; a control unit that controls at least one of a drive source, a brake device, a power steering device, an AFS, an ARS, and an active suspension of the vehicle according to the degree of rear wheel grip so as to stabilize the spin behavior of the vehicle. A vehicle control device comprising:

2. The control unit includes a first control unit that adjusts a control amount of at least one of the driving force and the braking force of the vehicle in accordance with the degree of rear wheel grip so that the smaller the degree of rear wheel grip, the more the torque transfer in the front, rear, left and right directions is limited.

2. The vehicle control device according to claim 1.

3. The control unit includes a second control unit that adjusts at least one control amount of the steering assist torque of the vehicle, the steering amount of each wheel, and the active suspension according to the degree of rear wheel grip so that the smaller the degree of rear wheel grip, the more suppressed is the lateral slip of the rear wheels while ensuring steerability.

3. The vehicle control device according to claim 1 or 2.

4. The second estimation unit calculates a rear axle load of the vehicle based on a stationary rear axle load when the vehicle is stationary and the longitudinal acceleration, and calculates the reciprocal of the product of the specific coefficient and the rear axle load as the degree of rear wheel grip.

3. The vehicle control device according to claim 1 or 2.

5. The second estimation unit calculates a rear axle load of the vehicle based on a stationary rear axle load when the vehicle is stationary and the longitudinal acceleration, and calculates the reciprocal of the product of the specific coefficient and the rear axle load as the degree of rear wheel grip.

4. The vehicle control device according to claim 3.

6. The first estimation unit is configured to estimate a quadratic coefficient b of the denominator of the transfer function expressed by the following equation 1: 2 is estimated as the specific coefficient, The second estimation unit estimates the rear wheel grip degree using the following equation 2:

3. The vehicle control device according to claim 1 or 2. [Equation 1]

7. The first estimation unit is configured to estimate a quadratic coefficient b of the denominator of the transfer function expressed by the following equation 1: 2 is estimated as the specific coefficient, The second estimation unit estimates the rear wheel grip degree using the following equation 2:

4. The vehicle control device according to claim 3. [Equation 2]

8. The first estimation unit is configured to estimate a quadratic coefficient b of the denominator of the transfer function expressed by the following equation 1: 2 is estimated as the specific coefficient, The second estimation unit estimates the rear wheel grip degree using the following equation 2:

5. The vehicle control device according to claim 4. [Equation 3]

9. The first estimation unit is configured to estimate a quadratic coefficient b of the denominator of the transfer function expressed by the following equation 1: 2 is estimated as the specific coefficient, The second estimation unit estimates the rear wheel grip degree using the following equation 2:

6. The vehicle control device according to claim 5. [Equation 4]

10. The control unit controls an alarm device of the vehicle according to the degree of rear wheel grip, and announces to the driver the result of a road surface condition judgment based on the skidding state of the vehicle or the degree of rear wheel grip.

2. The vehicle control device according to claim 1.

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