Ground load estimation device, vehicle control device, and ground load estimation method

Abstract

The present invention achieves a technology capable of estimating a ground contact load in a vehicle with sufficiently high accuracy. A ground contact load estimation device according to the present invention is configured to estimate a ground contact load of a vehicle by: acquiring a wheel angular velocity of the vehicle, a steady load, and an inertial load; calculating a first gain using the steady load and the inertial load; estimating a road surface load using the first gain, a prescribed vehicle specification, and a second gain representing a hysteresis characteristic of a tire mounted on the vehicle; and referring to the road surface load.

Description

TECHNICAL FIELD

[0001] The present application relates to a ground load estimation device, a vehicle control device, and a ground load estimation method. BACKGROUND

[0002] In the related art, there is a technology for estimating a ground load of a wheel of a vehicle and controlling a braking force, a driving force, or the like of the vehicle using the estimation result, thereby improving the running stability of the vehicle. From the viewpoint of improving the running stability of the vehicle, the estimation of the ground load needs to have sufficiently high accuracy. As a technology for estimating the ground load, there is a technology for estimating the ground load from a detected vehicle state quantity based on a vehicle motion model obtained by modeling behavior of the vehicle (for example, refer to Patent Literature 1).

[0003] REFERENCE LIST

[0004] PATENT LITERATURE

[0005] Patent Literature 1: JP 2006-131062 A SUMMARY

[0006] PROBLEM TO BE SOLVED BY THE INVENTION

[0007] However, the ground load also varies due to the influence of unevenness of a road surface. Therefore, in the related art as described above, since the model for estimating the ground load is a model that considers only a change in load due to a change in posture of the vehicle body, reflection of the influence of the road surface on the vehicle can be insufficient. Therefore, from the viewpoint of improving the accuracy of the ground load of the vehicle, there is still room for study.

[0008] An object of one aspect of the present application is to achieve a technology capable of estimating a ground load in a vehicle with sufficiently high accuracy.

[0009] SOLUTION TO PROBLEM

[0010] In order to solve the above problem, a ground load estimation device according to an aspect of the present application is a ground load estimation device for estimating a ground load of a vehicle with reference to a road load of the vehicle. The ground load estimation device includes a wheel speed sensor configured to acquire a wheel angular velocity of the vehicle, and a road load estimation unit configured to estimate a road load of the vehicle by multiplying a change in the wheel angular velocity acquired by the wheel speed sensor, a first gain, and a second gain, respectively, the first gain representing a characteristic related to a motion of the vehicle, the second gain representing a hysteresis characteristic of a tire of the vehicle.

[0011] To solve the above problems, a vehicle control device according to an aspect of the present application includes the above-described ground contact load estimation device, and is configured to control other devices in the vehicle by using the ground contact load estimated by the ground contact load estimation device.

[0012] Further, to solve the above problems, a ground contact load estimation method according to an aspect of the present application is a ground contact load estimation method for estimating a ground contact load of a vehicle with reference to a road load of the vehicle. The ground contact load estimation method includes a step of acquiring a wheel angular velocity of the vehicle by a wheel speed sensor, and a road load estimation step of estimating a road load of the vehicle by multiplying a change in the wheel angular velocity acquired by the wheel speed sensor, a first gain, and a second gain, respectively, wherein the first gain represents a characteristic related to a motion of the vehicle, and the second gain represents a hysteresis characteristic of a tire of the vehicle.

[0013] Advantages of the Invention

[0014] According to one aspect of the present application, it is possible to estimate a ground contact load in a vehicle with sufficiently high accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a block diagram showing an example of a functional configuration of a ground contact load estimation device according to an embodiment of the present application.

[0016] Figure 2 is a block diagram showing an example of a functional configuration of a road load estimation unit according to an embodiment of the present application.

[0017] Figure 3 is a graph showing a physical quantity related to a wheel of a vehicle.

[0018] Figure 4 is a graph showing an example of a generalized Maxwell model that exhibits a hysteresis characteristic between a change in a wheel speed derived from a viscoelastic characteristic of a tire and a change in a road load in an embodiment of the present application.

[0019] Figure 5 is a graph showing another example of a generalized Maxwell model that exhibits a hysteresis characteristic between a change in a wheel speed derived from a viscoelastic characteristic of a tire and a change in a road load in an embodiment of the present application.

[0020] Figure 6 is a graph schematically showing an example of a configuration of a vehicle to which a ground contact load estimation device according to an embodiment of the present application is applied.

[0021] REFERENCE LIST

[0022] 100 ground contact load estimation device

[0023] 110 inertia load estimation unit

[0024] 111 reference inertia load calculation unit

[0025] 112 correction value calculation unit

[0026] 120 road surface load estimation unit

[0027] 121 tire effective radius change calculation unit

[0028] 122 first gain calculation unit

[0029] 131 lateral acceleration sensor

[0030] 132 steering angle / yaw rate sensor

[0031] 133 wheel speed sensor

[0032] 141 constant load providing unit

[0033] 142, 304 delay unit

[0034] 143, 144, 303 addition unit

[0035] 150 suspension device (suspension)

[0036] 200 vehicle body

[0037] 300 wheel

[0038] 340 longitudinal acceleration sensor

[0039] 370 CAN

[0040] 450 vehicle speed sensor

[0041] 500 engine

[0042] 600 ECU

[0043] 900 vehicle DETAILED DESCRIPTION

[0044] In the embodiment of the present application, a ground contact load on a wheel of a vehicle is estimated with sufficiently high accuracy with reference to a physical quantity that can be acquired using a sensor that is generally used for control to improve the running stability of the vehicle. In the present specification, the "reference" physical quantity is a general term for directly or indirectly using a physical quantity, and means one or both of direct and indirect use of a physical quantity.

[0045] In the present embodiment, the sensors can be sensors that are generally used for standard controls related to vehicle running (hereinafter also referred to as "general-purpose sensors"), and can not include a roll rate sensor and a pitch rate sensor. Examples of the general-purpose sensors include a longitudinal acceleration sensor that acquires a longitudinal acceleration of the vehicle, a lateral acceleration sensor that acquires a lateral acceleration of the vehicle, a wheel speed sensor that acquires a wheel speed of the vehicle, and a steering information sensor that acquires steering information of the vehicle. Examples of the steering information sensor include a yaw rate sensor and a steering angle sensor.

[0046] In the present embodiment, examples of the physical quantities detected by the sensors include a constant load of the vehicle, an inertial load of the vehicle, a value of the longitudinal acceleration sensor, a value of the lateral acceleration sensor, a value of the wheel speed sensor, a value of the steering information sensor, a mass of the vehicle, a height of a center of gravity of the vehicle, a roll inertia moment, a pitch inertia moment, a distance between the centers of gravity of the front axle of the vehicle, a distance between the centers of gravity of the rear axle of the vehicle, a front track of the vehicle, and a rear track of the vehicle.

[0047] In the present embodiment, the road load means a change in the ground contact load due to an influence of a road surface such as unevenness of the road surface. The inertial load means a change in the ground contact load due to an influence of a turn and an influence of acceleration and deceleration of the vehicle. In the present embodiment, the constant load is a ground contact load of the vehicle in a 1G state, and can be, for example, a value calculated based on a mass of the vehicle or a constant specific to the vehicle. Further, in the present embodiment, the ground contact load of the vehicle can be estimated with reference to the road load of the vehicle, and the ground contact load of the vehicle can be estimated by, for example, adding the road load of the vehicle to the constant load and the inertial load of the vehicle.

[0048] Hereinafter, an embodiment of the present application will be described in detail.

[0049] [First Embodiment]

[0050] [Functional Configuration of Ground Contact Load Estimation Device]

[0051] Figure 1 is a block diagram showing an example of a functional configuration of a ground contact load estimation device according to the first embodiment of the present application. As shown in Figure 1 the ground contact load estimation device 100 includes an inertial load estimation unit 110, a road load estimation unit 120, a longitudinal acceleration and lateral acceleration sensor (longitudinal and lateral acceleration sensor) 131, a steering angle sensor or a yaw rate sensor (steering angle / yaw rate sensor) 132, a wheel speed sensor 133, a constant load providing unit 141, a delay unit 142, and addition units 143 and 144.

[0052] The longitudinal and lateral acceleration sensor 131, the steering angle / yaw rate sensor 132, and the wheel speed sensor 133 are connected to the inertial load estimation unit 110. The longitudinal and lateral acceleration sensor 131 and the wheel speed sensor 133 are connected to the road load estimation unit 120. The longitudinal and lateral acceleration sensor 131, the steering angle / yaw rate sensor 132, and the wheel speed sensor 133 supply physical quantities related to the vehicle acquired by the inertial load estimation unit 110 and the road load estimation unit 120, respectively, and serve as respective acquisition units of the inertial load estimation unit 110 and the road load estimation unit 120.

[0053] The inertial load estimation unit 110 outputs a signal of the calculated inertial load. The inertial load estimation unit 110 is connected to an addition unit 143 via a delay unit 142. A constant load providing unit 141 outputs a signal of the constant load. The constant load providing unit 141 is also connected to the addition unit 143. The addition unit 143 is connected to each of an addition unit 144 and the road load estimation unit 120. The road load estimation unit 120 is connected to the addition unit 144.

[0054] Although not shown, the inertial load estimation unit 110 and the road load estimation unit 120 are connected to a network of a control system in the vehicle (for example, a CAN described later) and acquire physical quantities specific to the vehicle, such as the mass of the vehicle, the height of the center of gravity of the vehicle, the roll inertia moment based on a point on the road surface corresponding to the center of gravity of the vehicle, the pitch inertia moment based on the point on the road surface, the distance between the centers of gravity of the front axle, the distance between the centers of gravity of the rear axle, the front track, and the rear track, via the network. The network also corresponds to the acquisition unit in the present embodiment.

[0055] [Contents of the estimation of the ground load]

[0056] The ground load in the present embodiment is represented by the following equation (1). In equation (1), F z0nom represents the ground load in the 1G state, dF z0,inertia represents the inertial load, and dF z0,road represents the road load.

[0057] F z0 = F z0nom+ dF z0，inertia +dF z0，road …(1)

[0058] The longitudinal and lateral acceleration sensor 131 detects and outputs the longitudinal and lateral accelerations of the vehicle, the steering angle / yaw rate sensor 132 detects and outputs the steering angle or the yaw rate of the vehicle, and the wheel speed sensor 133 detects and outputs the wheel speed of the wheel of the vehicle. The above network outputs various physical quantities related to the vehicle.

[0059] The inertia load estimation unit 110 estimates the inertia load with reference to the physical quantity. The inertia load estimation unit 110 outputs the inertia load dF z0,inertia to the delay unit 142. If necessary, the delay unit 142 delays the output of the inertia load to an appropriate time according to a subsequent control. For example, the delay unit 142 outputs the inertia load so as to have the same phase according to the delay movavg(ω) in Equation (11) which will be described later. The addition unit 143 sums the constant load F z0nom output from the constant load providing unit 141 and the inertia load. The total value of the constant load and the inertia load is output to the road load estimation unit 120 and the addition unit 144.

[0060] On the other hand, the road load estimation unit 120 outputs an estimated value of the road load with reference to a second gain which will be described later. The estimation of the road load will be described later.

[0061] The estimated value of the road load output from the road load estimation unit 120 is added to the above total value in the addition unit 144. Further, the total value of the constant load, the inertia load, and the road load is obtained as an estimated value F z0 of the ground contact load of the vehicle.

[0062] In the present application, the method for estimating the inertia load is not limited. The inertia load dF z0,inerti a can be obtained, for example, by the method described in paragraph 0042 of Japanese Patent No. 6695481 or paragraph 0024 of Japanese Patent JP 2008-074184 A.

[0063] Next, the functional configuration and the logic for estimating the road load in the present embodiment will be described below.

[0064] [Functional Configuration of Road Load Estimation Unit]

[0065] Figure 2 is a block diagram showing an example of the functional configuration of the road load estimation unit according to the present embodiment. In the present embodiment, as shown in Figure 2 , the road load estimation unit 120 includes a tire effective radius variation calculation unit 121 and a first gain calculation unit 122.

[0066] [Logic of Road Load Estimation]

[0067] The nonlinear tire characteristics of the wheels of the vehicle are represented by the following Equations (2) and (3). In Equation (3), "F z0 " is the sum of the constant load and the inertia load as shown in Equation (4).

[0068] dF z0,road= -a1dR e …(2)

[0069] a1= a 11 F z0 + a 12 …(3)

[0070] F z0 = F z0nom + dF z0,inertia …(4)

[0071] In the above equation, dR e represents a change in the effective radius of the tire, a1represents a first gain, a 11 represents a first parameter, and a 12 represents a second parameter.

[0072] The first gain a1represents the rigidity of the wheel of the vehicle. The first gain a1is represented by the spring constant in the relationship of the spring constant and the ground contact load of the tire. The relationship is represented by a nonlinear curve, but can be approximated as a linear expression as shown in equation (3).

[0073] The first parameter a 11 and the second parameter a 12 are adjustment parameters for applying the first gain a1to a wide range of conditions. The first parameter is represented by the slope in the linear expression obtained by the above approximation, and the second parameter is represented by the intercept of the linear expression.

[0074] Figure 3 is a graph showing a physical quantity related to the wheel of the vehicle. In Figure 3 , R e represents the effective radius of the tire, ω represents the angular velocity of the tire, and u0represents the circumferential velocity of the tire. Considering the slip ratio of the tire, the effective radius R e of the tire is represented by the following equation (5). The following equation (6) is derived from the total differential of equation (5).

[0075]

[0076]

[0077] If it is assumed that the slip ratio does not change, equation (7) is derived from equation (6), and equation (8) is further derived. In the following equation, a2represents a second gain. The second gain will be described in detail later.

[0078]

[0079]

[0080] The value in the bracket in Equation (8) can be approximated as shown in Equation (9). In Equation (9), "movavg(ω)" represents a moving average value of the angular velocity. Therefore, Equation (10) is derived from Equation (8).

[0081]

[0082]

[0083] When Equation (9) is substituted into Equation (2), Equation (11) is derived. The road load is calculated in accordance with Equation (11). Equation (11) includes movavg(ω). The calculation of the road load is delayed (for example, 0.05 seconds) in accordance with the time required to acquire movavg(ω).

[0084]

[0085] <Second Gain>

[0086] The second gain a2 represents a transfer function model that exhibits a hysteresis characteristic between a change in the wheel angular velocity and a change in the road load.

[0087] When the wheel speed change and the road load change are measured in accordance with an actual vehicle that travels on a road surface having a wavy undulation, the correlation between them has the following characteristics.

[0088] • Although there is a positive correlation, the positive correlation exists in a region having a slight width with respect to the inclination direction thereof.

[0089] • As the travel speed increases, the slope increases.

[0090] • As the travel speed increases, the width in the inclination direction increases.

[0091] • As the travel speed increases, the length in the inclination direction increases.

[0092] As described above, a hysteresis characteristic is considered to exist between the wheel speed change and the road load change. In the present embodiment, the hysteresis characteristic between the wheel speed change and the road load change is referred to as a second gain in the road load estimation.

[0093] In the present embodiment, it is assumed that the hysteresis characteristic between the wheel speed change and the road load change is derived from the viscoelastic characteristic of the tire, and the hysteresis characteristic is expressed as a transfer function model using a generalized Maxwell model.

[0094] Figure 4is a graph showing an example of a generalized Maxwell model that expresses a hysteresis characteristic between a change in wheel speed derived from the viscoelastic characteristics of a tire and a change in road load. In the graph, f represents a road load on the generalized Maxwell model, K0 and K1 represent tire elastic constants, and x 11 represents an elastic displacement. C1 represents a damping coefficient of a tire in a suspension device, and x 12 represents a displacement of a tire damping system portion. Furthermore, x represents the total value of x 11 and x 12 .

[0095] In the generalized Maxwell model, when the force on the elastic member and the damper on this side is f1 and the force in only the column of the elastic member is f0, the resultant force of the parallel elements is represented by the following formula (12). When a Laplace transform is performed on both sides of formula (12), formula (13) is obtained. When each term of formula (13) is represented by a capital letter F, the formula is represented as formula (14). When both sides of formula (14) are divided by X, formula (15) is obtained. In formula (15), X represents Figure 4 the Laplace transform (L(x)) of x in formula (12).

[0096] f = f0 + f1… (12)

[0097]

[0098] F = F0 + F1… (14)

[0099]

[0100] With respect to f0, f0 is represented in accordance with formula (16) of a balance of forces with respect to f0. When a Laplace transform is performed on both sides of formula (16), both sides are represented by formula (17), and when each term in formula (17) is represented by a capital letter, the formula is represented by formula (18), and formula (19) is derived from formula (18).

[0101] f0 = K0x… (16)

[0102]

[0103] F0 = K0X… (18)

[0104]

[0105] With respect to f1, f1 is represented by formulas (20) and (21) in accordance with a balance of forces with respect to f1. In formula (21), x 12 dot represents x 12The differential values of f and x are substituted into formula (15), and the result is formula (28). When the Laplace transform is performed on both sides of formula (28), formulas (29) and (30) are derived, and formulas (31) and (32) are derived by expressing each term of the formula with a capital letter.

[0106] f1= K1x 11 …(20)

[0107]

[0108]

[0109]

[0110] F1= K1X 11 …(24)

[0111] F1= sC1X 12 …(25)

[0112]

[0113]

[0114] When formulas (19) and (27) are substituted into formula (15), formula (28) is obtained, and the following formula (29) is obtained when the formula is arranged. In formula (29), d1, d0, n1, and n0 are used, respectively, d1 is represented by formula (30), d0 is represented by formula (31), n1 is represented by formula (32), and n0 is represented by formula (33).

[0115]

[0116]

[0117] d1= C1K0+ C1K1…(30)

[0118] d0= K0K1…(31)

[0119] n1= C1…(32)

[0120] n0= K1…(33)

[0121] Here, in the generalized Maxwell model, f is set to correspond to the road load, and x is set to correspond to the following formula (35), whereby the "hysteresis characteristic between the wheel speed change and the road load change" is represented by the following formula (34). Thus, the road load dFz0 road is represented by formula (36). The second gain a2 is represented by formula (37).

[0122]

[0123]

[0124]

[0125]

[0126] Coefficients in the denominator and the numerator of Equation (34) can be appropriately determined by using measured data of an actual vehicle and using an optimization method or the like.

[0127] In the above description, a model expressing hysteresis characteristics is derived based on the assumption of a first-order model, but a model expressing hysteresis characteristics can be derived based on the assumption of a higher-order model. Figure 5 is a graph showing another example of a generalized Maxwell model expressing hysteresis characteristics between a change in wheel speed derived from viscoelastic characteristics of a tire and a change in road load. As shown in Figure 5 , a model expressing hysteresis characteristics can be derived based on the assumption of a higher-order (third-order) model. In this case, similarly to the first-order model, a model expressing hysteresis characteristics can be derived by combining models obtained by the resultant forces of parallel elements. It is advantageous to use such a higher-order model from the viewpoint of obtaining a more accurate estimation result of a change in road load.

[0128] [Estimation of Road Load]

[0129] In the road load estimation unit 120, the first gain calculation unit 122 calculates the first gain al using at least the steady load and the inertial load (see Equation (3)). Figure 2 The road load estimation unit 120 acquires an estimated value of the inertial load obtained by the inertial load estimation unit 110 and a total value of the steady load output from the steady load provision unit 141. The first gain al is represented by the stiffness (elastic constant) of the wheel (tire) of the vehicle as described above, and can be represented by a linear expression approximating a nonlinear curve of the elastic constant with respect to the ground load. Here, the ground load is the total value of the steady load and the inertial load. The first gain calculation unit 122 calculates the first gain by substituting the total value into Equation (3).

[0130] The tire effective radius change calculation unit 121 multiplies the change in wheel angular velocity by the second gain. The change in wheel angular velocity is a value including a change value dω of the wheel angular velocity ω, and is, for example, dω / ω in Equation (8). Specifically, the tire effective radius change calculation unit 121 calculates the tire effective radius change based on Equation (10).

[0131] The road surface load estimation unit 120 refers to the calculation results of the first gain calculation unit 122 and the tire effective radius variation calculation unit 121 and the above-mentioned second gain, and calculates the road surface load based on, for example, the above-mentioned equation (11). As described above, the road surface load estimation unit 120 estimates the road surface load of the vehicle by multiplying the variation of the wheel angular velocity acquired by the wheel speed sensor, the first gain indicating the characteristics related to the motion of the vehicle, and the second gain indicating the hysteresis characteristics of the tires of the vehicle, respectively.

[0132] [Estimation of Ground Load]

[0133] The inertial load estimation unit 110 outputs the inertial load dF z0,inertia to the delay unit 142 (see Figure 1 ). If necessary, the delay unit 142 delays the output of the inertial load to an appropriate time according to the subsequent control. For example, the delay unit 142 outputs the inertial load so as to have the same phase according to the delay movavg(ω) in the above-mentioned equation (11). The addition unit 143 adds the constant load F z0nom output from the constant load providing unit 141 to the inertial load. The total value of the constant load and the inertial load is output to the road surface load estimation unit 120 and the addition unit 144.

[0134] On the other hand, the road surface load estimation unit 120 outputs the estimated value of the road surface load. The estimated value of the road surface load is obtained with reference to the constant load and the inertial load.

[0135] In the addition unit 144, the estimated value of the road surface load output from the road surface load estimation unit 120 is added to the above-mentioned total value. In this way, the total value of the constant load, the inertial load, and the road surface load is obtained as the estimated value F z0 of the ground load of the vehicle.

[0136] According to the present embodiment, when the vehicle is driven under predetermined conditions, the estimated value substantially matching the actual measured value of the ground load is obtained. As described above, in the present embodiment, the ground load can be estimated with higher accuracy compared to the case where the second gain is a constant gain.

[0137] In the present embodiment, since the road surface load is estimated using the second gain indicating the above-mentioned hysteresis characteristics, the road surface load can be estimated while sufficiently reflecting the influence of the unevenness of the road surface. Further, since the ground load is estimated with reference to such road surface load, the ground load in the vehicle can be estimated with sufficiently high accuracy. In the present embodiment, such highly accurate ground load can also be estimated by simpler control.

[0138] In the present embodiment, in the estimation of the road surface load, the reference steady load and the estimated inertial load are referred to. Therefore, it is possible to estimate the road surface load with higher accuracy compared to the case where the reference steady load and the estimated inertial load are not involved.

[0139] Further, in the present embodiment, the reference inertial load is calculated using a physical quantity that can be acquired by a general-purpose sensor, and the inertial load correction value is calculated. Therefore, it is possible to reduce the cost of the sensor.

[0140] Second Embodiment: Embodiment of Control Device for Suspension Device

[0141] An example in which the above-described ground contact load estimation device is applied to a control device that controls a suspension device in a vehicle will be described below. For ease of description, members having the same functions as those described in the above-described embodiments are denoted by the same reference numerals, and the description thereof will not be repeated.

[0142] The control device according to the present embodiment estimates a ground contact load acting on a vehicle including a suspension device, and controls a damping force of the suspension device in accordance with the ground contact load. The control device can be configured in the same manner as a known control device in a suspension device, except that the control device includes the above-described ground contact load estimation device and controls the damping force of the suspension device in accordance with the ground contact load estimated by the ground contact load estimation device.

[0143] Figure 6 is a diagram schematically showing an example of a configuration of a vehicle including the above-described ground contact load estimation device. As Figure 6 shown, the vehicle 900 includes a suspension device (suspension) 150, a vehicle body 200, a wheel 300, a vehicle speed sensor 450 that detects a vehicle speed (V), an engine 500, and an electronic control unit (ECU) 600. The ECU 600 corresponds to the above-described processor, and includes the above-described ground contact load estimation device.

[0144] The letters A to D in the reference numerals respectively indicate positions in the vehicle 900. A indicates a front left position of the vehicle 900, B indicates a front right position of the vehicle 900, C indicates a rear left position of the vehicle 900, and D indicates a rear right position of the vehicle 900.

[0145] The vehicle 900 includes various sensors such as a longitudinal acceleration sensor 340 that detects an acceleration of the vehicle 900 in a longitudinal direction. The sensors correspond to the above-described general-purpose sensors. The vehicle 900 includes a storage medium. The storage medium stores various information required for estimation of physical quantities. Examples of the information include various physical quantities related to the vehicle such as a wheel radius and a vehicle mass (vehicle weight).

[0146] Supply of output values of various sensors to the ECU 600 and transmission of control signals from the ECU 600 to the corresponding units are performed via a controller area network (CAN) 370. The respective sensors can be newly provided for estimating the physical quantity to be described later, but it is preferable from the viewpoint of cost that the existing sensors in the vehicle 900 are used.

[0147] According to the present embodiment, the damping force of the suspension device is controlled on the basis of an estimated value having the same accuracy as an actual measured value of the ground contact load of the vehicle. Therefore, it is possible to sufficiently improve the running stability of the vehicle without using a special sensor other than a general sensor.

[0148] In the present embodiment, the damping force of the suspension device of the vehicle is controlled by directly using the ground contact load estimated by the control device. In the present application, similarly to the suspension device, the estimated ground contact load can be used to control various devices in the vehicle. Examples of such devices include, in addition to the conventional suspension device, an electronically controlled suspension, a steering device, and an electronically controlled drive force transmission device. The estimated ground contact load can be used to control one or more of these devices in the vehicle.

[0149] In the control of these devices, the estimated result of the ground contact load can be directly or indirectly used to control the devices in the present embodiment. Indirect use of the estimated result of the ground contact load means, for example, conversion into another state quantity and control of other devices using the estimated value of the converted state quantity. By using the estimated value of the ground contact load in the control of the above-mentioned other devices, as in the present embodiment, it is possible to sufficiently or further improve the running stability of the vehicle without using a special sensor other than a general sensor.

[0150] [Embodiment using software]

[0151] The control blocks of the ground contact load estimation device 100 (specifically, the inertial load estimation unit 110 and the road surface load estimation unit 120) can be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or can be realized by software.

[0152] In the latter case, the ground contact load estimation device 100 includes a computer that executes instructions of a program as software that realizes each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. Further, in the computer, the processor reads the program from the recording medium and executes the program, thereby realizing the object of the present application. As the processor, for example, a central processing unit (CPU) can be used.

[0153] Examples of the recording medium include "non-transitory tangible media" such as a read only memory (ROM), a magnetic tape, a magnetic disk, a card, a semiconductor memory, and a programmable logic circuit. A random access memory (RAM) or the like in which a program is deployed can be further provided.

[0154] The program can be provided to a computer via any transmission medium (such as a communication network or broadcast wave) capable of transmitting the program. One aspect of the present application can also be implemented in the form of a data signal in which the program is implemented by electronic transmission and loaded in a carrier wave.

[0155] [Modification]

[0156] The present application is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the different embodiments are also included in the technical scope of the present application. The functional configuration for estimating the ground load in the above-described embodiments can be appropriately simplified according to the desired accuracy.

[0157] For example, in the present application, the inertial load of the vehicle can be acquired by another known technique instead of the above-described inertial load estimating unit. In the present application, instead of the above-described first gain calculating unit, another physical quantity substantially including the first gain or the first gain of the vehicle can be acquired by another known technique.

[0158] In the present application, in the range in which the hysteresis characteristic of the tire of the vehicle represented by the second gain can be obtained, a hysteresis characteristic other than the hysteresis characteristic between the change in the wheel angular velocity due to the viscoelastic characteristic of the tire and the change in the road surface load can be employed. In this case, a part of the above-described functional configuration of the road surface load estimating unit can be appropriately changed so as to accommodate the employed characteristic.

[0159] Further, in the present application, the hysteresis characteristic can be represented by an appropriate expression other than the transfer function model. In this case, a part of the above-described functional configuration of the road surface load estimating unit can be appropriately changed so as to accommodate the employed expression.

[0160] [Summary]

[0161] As is clear from the above description, the ground load estimation device (100) according to the embodiment of the present application is a ground load estimation device configured to estimate a ground load of a vehicle with reference to a road load of the vehicle, and includes a wheel speed sensor (133) configured to acquire a wheel angular velocity of the vehicle, and a road load estimation unit (120) configured to estimate a road load of the vehicle by multiplying a change in the wheel angular velocity acquired by the wheel speed sensor, a first gain, and a second gain, respectively, the first gain representing a characteristic related to a motion of the vehicle, the second gain representing a hysteresis characteristic of a tire of the vehicle. According to this configuration, it is possible to estimate a ground load in a vehicle with sufficiently high accuracy that is closer to an actual measurement.

[0162] In the present embodiment, the ground load estimation device can further include an inertial load estimation unit (110) configured to estimate an inertial load, the inertial load being a change in a ground load due to an inertial motion of the vehicle, and the road load estimation unit can further include a first gain calculation unit (122) configured to calculate the first gain using the inertial load estimated by the inertial load estimation unit. This configuration is more effective in terms of improving estimation accuracy of a ground load.

[0163] In the embodiment of the present application, the hysteresis characteristic of a tire in a vehicle represented by the second gain can be a hysteresis characteristic between a change in a wheel angular velocity and a change in a road load due to a viscoelastic characteristic of a tire of the vehicle. This configuration is more effective in terms of improving estimation accuracy of a ground load.

[0164] In the embodiment of the present application, the second gain can be represented by a transfer function model representing a hysteresis characteristic. This configuration is more effective in terms of improving estimation accuracy of a ground load and reducing a load of estimation control.

[0165] The vehicle control device according to the embodiment of the present application includes the above-described ground load estimation device, and controls other devices in the vehicle by using a ground load estimated by the ground load estimation device. According to this configuration, it is possible to estimate a ground load in a vehicle with sufficiently high accuracy that is closer to an actual measurement, and it is possible to accurately control a vehicle in a desired state.

[0166] The ground load estimation method according to the embodiment of the present application is a ground load estimation method for estimating a ground load of a vehicle with reference to a road load of the vehicle, and includes a step of acquiring a wheel angular velocity of the vehicle by a wheel speed sensor, and a road load estimation step of estimating a road load of the vehicle by multiplying a change in the wheel angular velocity acquired by the wheel speed sensor, a first gain, and a second gain, respectively, wherein the first gain represents a characteristic related to a motion of the vehicle, and the second gain represents a hysteresis characteristic of a tire of the vehicle. According to these configurations, it is possible to estimate a ground load in a vehicle with a sufficiently high accuracy that is closer to an actual measurement.

Claims

1. A road load estimation device for estimating road load, the road load being a change in the ground contact load of a vehicle caused by the influence of the road surface, the road load estimation device comprising: A wheel speed sensor configured to acquire the wheel angular velocity of the vehicle; as well as A road load estimation unit is configured to estimate the road load of the vehicle by multiplying the change in wheel angular velocity acquired by the wheel speed sensor, a first gain, and a second gain, respectively, where the first gain represents the stiffness of the vehicle's wheels and the second gain represents the hysteresis characteristic between the change in wheel angular velocity and the road load.

2. The road load estimation device according to claim 1, wherein, The stiffness is represented by the elastic constant of the tire of the wheel in relation to the ground load.

3. The road load estimation device according to claim 1 or 2, wherein, The hysteresis characteristic of the vehicle, represented by the second gain, is the hysteresis characteristic between the change in wheel angular velocity caused by the viscoelastic properties of the vehicle's tires and the road load.

4. The road load estimation device according to claim 3, wherein, The second gain is represented by a transfer function model that represents the hysteresis characteristic.

5. The road load estimation device according to claim 1, further comprising: An inertial load estimation unit is configured to estimate an inertial load, which is the change in the ground load caused by the inertial motion of the vehicle, wherein... The road load estimation unit further includes a first gain calculation unit, which is configured to calculate the first gain by using a linear expression of the inertial load estimated by the inertial load estimation unit.

6. A vehicle control device, comprising: The road load estimation device according to any one of claims 1 to 4, wherein, The vehicle control device is configured to control one or more devices in the vehicle selected from the group consisting of suspension devices, electronically controlled suspension, steering devices, and electronically controlled drive force transmission devices by using the road load estimated by the road load estimation device.

7. A road surface load estimation method for estimating road surface load, wherein the road surface load is a change in the ground contact load of a vehicle caused by the influence of the road surface, the road surface load estimation method comprising: The step of obtaining the wheel angular velocity of the vehicle using wheel speed sensors; as well as The step of estimating the road load of the vehicle by multiplying the change in wheel angular velocity obtained by the wheel speed sensor, a first gain, and a second gain, respectively, wherein the first gain represents the stiffness of the vehicle's wheels, and the second gain represents the hysteresis characteristic between the change in wheel angular velocity and the road load.

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