Damping force control device

Abstract

This damping force control device is provided with: a calculation unit that estimates a second physical quantity from a measured value of a first physical quantity by using a trained model into which the first physical quantity, which relates to the movement of a vehicle other than the acceleration of the vehicle in the vertical direction, is input and from which the second physical quantity, which relates to the movement of the vehicle in the vertical direction, is output, the calculation unit then calculating a target damping coefficient of a shock absorber on the basis of the estimated second physical quantity; and a damping force control unit that controls the damping force of the shock absorber on the basis of the calculated target damping coefficient.

Description

Damping force control device

[0001] An embodiment of the present invention relates to a damping force control device.

[0002] There is a damping force control device that is provided in a vehicle and controls the damping force of a shock absorber of a suspension to improve ride comfort and driving stability. For example, a damping force control device of this type is known that calculates the ratio between mid-frequency components and low-frequency components in the vertical vibration of the vehicle based on the output value of a vertical acceleration sensor mounted on the vehicle, and controls the damping force of the shock absorber based on this ratio (see, for example, Patent Document 1).

[0003] Patent No. 6478063

[0004] In the above-mentioned conventional technology, a vertical acceleration sensor dedicated to controlling the damping force of the shock absorber is provided in the vehicle, which causes a problem of making the structure of the vehicle complex.

[0005] One of the problems that the embodiments of the present invention aim to solve is to provide a damping force control device that can suppress the complexity of the vehicle structure when controlling the damping force of a shock absorber.

[0006] A damping force control device according to an embodiment of the present invention is a damping force control device that controls a shock absorber interposed between a wheel of a vehicle and a body of the vehicle, and includes: a calculation unit that uses a trained model that inputs a first physical quantity related to the movement of the vehicle other than the vertical acceleration of the vehicle and outputs a second physical quantity related to the vertical movement of the vehicle, estimates the second physical quantity from an actual measured value of the first physical quantity, and calculates a target damping coefficient of the shock absorber based on the estimated second physical quantity; and a damping force control unit that controls the damping force of the shock absorber based on the calculated target damping coefficient.

[0007] According to the damping force control device of the embodiment of the present invention, the calculation unit uses the trained model to calculate the target damping coefficient of the shock absorber from the actual measured value of the first physical quantity related to the vehicle motion other than the vehicle's vertical acceleration, eliminating the need to provide the vehicle with a vertical acceleration sensor dedicated to controlling the damping force of the shock absorber. This makes it possible to prevent the vehicle structure from becoming complicated when controlling the damping force of the shock absorber.

[0008] FIG. 1 is a schematic diagram showing a schematic configuration of an example of a vehicle according to the first embodiment. FIG. 2 is a schematic diagram showing a schematic configuration of an example of a suspension device in the vehicle according to the first embodiment. FIG. 3 is a functional block diagram of a control device of an example of a vehicle according to the first embodiment. FIG. 4A is an explanatory diagram for explaining deformation of a wheel of the vehicle according to the first embodiment. FIG. 4B is an explanatory diagram for explaining deformation of a wheel of the vehicle according to the first embodiment. FIG. 5 is a flowchart showing an example of a damping force control process executed by the control device according to the first embodiment. FIG. 6 is a flowchart showing an example of a calculation process of an index value (a swing vibration index value) indicating the degree of swing vibration in the damping force control process according to the first embodiment. FIG. 7 is a flowchart showing an example of a calculation process of an index value (a thudding vibration index value) indicating the degree of thudding vibration in the damping force control process according to the first embodiment. FIG. 8 is a diagram showing an example of a map showing the relationship between the ratio of the thudding vibration index value to the swing vibration index value and a correction coefficient according to the first embodiment. Fig. 9 is a diagram showing another example of a map showing the relationship between the ratio of the thump vibration index value to the tilt vibration index value and the correction coefficient according to the first embodiment. Fig. 10 is a diagram showing an example of a map showing the relationship between the relative speed of the vehicle body and the wheels in the vertical direction, the target damping force, and the control stage of the shock absorber according to the first embodiment. Fig. 11 is a flowchart showing an example of a damping force control process executed by the control device according to the second embodiment. Fig. 12 is a flowchart showing an example of a damping force control process executed by the control device according to the third embodiment.

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. The following embodiments include similar components. These similar components are assigned common reference numerals, and redundant explanations will be omitted.

[0010] First Embodiment FIG. 1 is a schematic diagram illustrating a general configuration of an example of a vehicle 1 according to a first embodiment. In this embodiment, the vehicle 1 may be, for example, an automobile (internal combustion engine automobile) using an internal combustion engine (engine, not shown) as a drive source, an automobile (electric automobile, fuel cell automobile, etc.) using an electric motor (motor, not shown) as a drive source, or an automobile using both of these as a drive source (hybrid automobile). The vehicle 1 may be equipped with various transmissions and various devices (systems, components, etc.) required to drive the internal combustion engine or the electric motor. The type, number, layout, etc. of devices related to the drive of the wheels 3 of the vehicle 1 may be variously configured. In this embodiment, as an example, the vehicle 1 is a four-wheeled vehicle (four-wheeled automobile) having two front wheels 3F (left and right) and two rear wheels 3R ​​(left and right). In FIG. 1 , the forward direction (direction Fr) in the fore-and-aft direction of the vehicle is the left side.

[0011] In this embodiment, as an example, the vehicle control system 100 of the vehicle 1 includes a control device 10, a steering device 11, a steering sensor 12, a detection sensor 13, etc. The vehicle control system 100 also includes a suspension device 4, a rotation sensor 5, a torque sensor 6, etc. corresponding to each of the two front wheels 3F, and a suspension device 4, a rotation sensor 5, a torque sensor 6, etc. corresponding to each of the two rear wheels 3R.

[0012] 2 is a schematic diagram showing an example of the general configuration of the suspension device 4 in the vehicle 1 according to the first embodiment. As shown in Fig. 2, the portion of the vehicle 1 on the vehicle body 2 side with respect to the suspension device 4 is the sprung portion 2a (Fig. 2), and the portion of the vehicle 1 on the wheel 3 side with respect to the suspension device 4 is the unsprung portion 2b (Fig. 2).

[0013] 1 and 2 , the vehicle 1 includes other basic components as well, but only the configuration related to the vehicle control system 100 and the control related to that configuration will be described here. The two front wheels 3F and the two rear wheels 3R ​​are collectively referred to as wheels 3. The vertical relative speed of the wheels 3 of the vehicle 1 relative to the body 2 of the vehicle 1 is also referred to as stroke speed. The stroke speed is also the relative speed between the sprung portion 2a and the unsprung portion 2b.

[0014] The control device 10 receives signals, data, etc. from each component of the vehicle control system 100 via a network such as a Controller Area Network (CAN), and controls each component of the vehicle control system 100 and performs various calculations. In this embodiment, the control device 10 is an example of a damping force control device. The control device 10 is configured as a computer and includes an arithmetic processing unit (a microcomputer, an Electronic Control Unit (ECU), etc., not shown), a storage unit 10d (e.g., a Read Only Memory (ROM), a Random Access Memory (RAM), a flash memory, etc., see FIG. 3 ), etc. The arithmetic processing unit reads a program stored (installed) in the non-volatile storage unit 10d (e.g., a ROM, a flash memory, etc.), performs calculations in accordance with the program, and functions (operates) as each component shown in FIG. 3 . The storage unit 10d may store data (tables (data groups), functions, etc.) used in various calculations related to control, calculation results (including values ​​during calculation), etc. The storage unit 10d also stores a trained model 121. Details of the trained model 121 will be described later.

[0015] The steering device 11 includes, for example, a steering wheel, and steers (turns) the two front wheels 3F. The steering sensor 12 detects the steering angle (steering angle, turning angle, steering angle) of the front wheels 3F and outputs steering angle data indicating the detected steering angle.

[0016] The detection sensor 13 includes a yaw rate sensor that detects the yaw rate of the vehicle 1 (vehicle body 2) and outputs the detected yaw rate, a longitudinal acceleration sensor that detects longitudinal acceleration, which is the acceleration of the vehicle 1 (vehicle body 2) in the longitudinal direction, and outputs the detected longitudinal acceleration, and a lateral acceleration sensor that detects lateral acceleration, which is the acceleration of the vehicle 1 (vehicle body 2) in the lateral direction (width direction), and outputs the detected lateral acceleration.

[0017] The rotation sensor 5 can output a signal corresponding to the speed (rotational speed, angular velocity, number of rotations, rotation state) related to the rotation of each of the four wheels 3. The control device 10 can calculate the speed of the vehicle 1 from the detection results of the rotation sensor 5. Note that, in addition to the rotation sensor 5 for the wheels 3, a rotation sensor (not shown) that detects the rotation of a crankshaft, an axle, or the like may be provided, and the control device 10 may obtain the speed of the vehicle 1 from the detection results of this rotation sensor.

[0018] The torque sensors 6 are provided corresponding to the four wheels 3 , respectively, and detect the rotational torque input to each wheel 3 .

[0019] The outputs of the above sensors are also used for operations other than the damping force control process, which will be described later, among the operations (processes) executed by the vehicle 1. In other words, the sensors are not dedicated to the damping force control process.

[0020] FIG. 2 is a schematic diagram illustrating a general configuration of an example of a suspension system 4 for a vehicle according to the first embodiment. As shown in FIG. 2, the suspension system 4 is interposed between the wheels 3 and the vehicle body 2 to suppress transmission of vibrations and shocks from the road surface to the vehicle body. The suspension system 4 includes a coil spring 4a and a shock absorber 4b. The shock absorber 4b has a damping force (damping characteristics) that can be electrically controlled (adjusted). Specifically, the shock absorber 4b includes an actuator 4bb that operates based on an input current. The actuator 4bb can change the opening of an orifice provided in the piston of the shock absorber 4b or the opening between the valve body and the valve seat. This controls the amount of lubricating oil flowing between two oil chambers separated by the piston within the shock absorber 4b, thereby adjusting the damping force of the shock absorber 4b. A suspension device 4 is provided for each of the four wheels 3 (two front wheels 3F and two rear wheels 3R), and the control device 10 can control the damping force of each of the four wheels 3. The control device 10 can control the four wheels 3 so that the damping forces are different from one another. Specifically, in order to control the damping force of each shock absorber 4b (= damping coefficient x stroke speed), the damping coefficient is controlled. More specifically, the damping coefficient is controlled by controlling the current flowing through the actuator 4bb of the shock absorber 4b.

[0021] Each shock absorber 4b has a plurality of control stages, ranging from the control stage (soft) with the smallest damping coefficient of the shock absorber 4b to the control stage (hard) with the largest damping coefficient Ci.

[0022] The configuration of the vehicle control system 100 described above is merely an example, and can be modified in various ways. Known devices can be used as the individual devices that make up the vehicle control system 100. Furthermore, each component of the vehicle control system 100 can be shared with other components.

[0023] Specifically, for example, the control device 10 can function (operate) as an acquisition unit 10a, a calculation unit 10b, a damping force control unit 10c, etc., as shown in Fig. 3 through cooperation between hardware and software (programs). That is, for example, the programs can include modules corresponding to each block except for the memory unit 10d shown in Fig. 3.

[0024] The acquisition unit 10a acquires a first physical quantity related to the motion of the vehicle 1 other than the acceleration in the vertical direction of the vehicle 1. For example, the first physical quantity includes at least one of the following: a speed related to the wheels 3 according to the rotation of the wheels 3, an acceleration in the longitudinal direction of the vehicle 1, an acceleration in the lateral direction of the vehicle 1, a yaw rate of the vehicle 1, a steering angle of the wheels 3, a steering angular velocity of the wheels 3, a rotational torque of the wheels 3, and a value of a current input to the shock absorber 4b according to a target damping coefficient. Furthermore, the speed related to the wheels 3 includes at least one of the rotational speed of each of the plurality of wheels 3, a difference between the rotational speeds of two wheels 3 arranged diagonally among the plurality of wheels 3, and a difference between the rotational speeds of two wheels 3 arranged in the longitudinal direction of the vehicle 1.

[0025] Specifically, the acquisition unit 10a receives (acquires) the rotational speed of each wheel 3 from the rotation sensor 5. Furthermore, the acquisition unit 10a calculates, or acquires, from the rotational speeds of the plurality of wheels 3, the difference between the rotational speeds of two wheels 3 arranged diagonally among the plurality of wheels 3 and the difference between the rotational speeds of two wheels 3 arranged in the longitudinal direction of the vehicle 1. The pairs of two wheels 3 arranged diagonally are, for example, a pair of a right front wheel 3F and a left rear wheel 3R, and a pair of a left front wheel 3F and a right rear wheel 3R. The pairs of two wheels 3 arranged in the longitudinal direction of the vehicle 1 are, for example, a pair of a right front wheel 3F and a right rear wheel 3R, and a pair of a left front wheel 3F and a left rear wheel 3R. Furthermore, the acquisition unit 10a receives (acquires) the longitudinal acceleration of the vehicle 1 from the detection sensor 13. Furthermore, the acquisition unit 10a acquires the lateral acceleration of the vehicle 1 from the detection sensor 13. The acquisition unit 10a also receives (acquires) the yaw rate of the vehicle 1 from the detection sensor 13. The acquisition unit 10a also receives (acquires) the steering angle of the wheels 3 and the steering angular velocity of the wheels 3 from the steering sensor 12. The acquisition unit 10a also acquires the rotational torque of the wheels 3 from the torque sensor 6. The acquisition unit 10a also receives (acquires) from a current detection sensor (not shown) the value of the current input to the shock absorber 4b in accordance with the target damping coefficient.

[0026] As an example, the calculation unit 10b receives predetermined data (hereinafter also referred to as input data) acquired by the acquisition unit 10a. The calculation unit 10b estimates (determines) a second physical quantity (output value) from the actual measured value (input data) of the first physical quantity using a trained model 121 that inputs a first physical quantity related to the motion of the vehicle 1 other than the vertical acceleration of the vehicle 1 and outputs a second physical quantity related to the vertical motion of the vehicle 1. The calculation unit 10b calculates a target damping coefficient (damping coefficient) of the shock absorber 4b based on the estimated second physical quantity. The second physical quantity is, for example, a vertical relative velocity (i.e., stroke velocity) that is the relative velocity between the vehicle body 2 and the vehicle 1 in the vertical direction.

[0027] The trained model 121 is configured, for example, by a neural network. The trained model 121 is configured to have been trained in advance so as to input a first physical quantity related to the motion of the vehicle 1 other than the acceleration in the vertical direction of the vehicle 1 and output (estimate) a second physical quantity related to the motion of the vehicle 1 in the vertical direction. For example, the neural network of the trained model 121 is configured by an LSTM (Long Short-Term Memory). When the trained model 121 is trained, the input data is the first physical quantity. The output data as training data is, for example, an actual measurement value (true value) of the relative speed in the vertical direction of the wheels 3 of the vehicle body 2 and the vehicle 1, i.e., the stroke speed, measured by a stroke speed sensor (not shown).

[0028] The damping force control unit 10c controls the damping force of the shock absorber 4b based on the calculated target damping coefficient. Specifically, the damping force control unit 10c determines the current value to be input to the shock absorber 4b based on the calculated target damping coefficient, and inputs the current value to the shock absorber 4b.

[0029] 4A and 4B are explanatory diagrams illustrating deformation of the wheel 3 of the vehicle 1 according to the first embodiment. FIG. 4A shows the vehicle 1 traveling on a road surface with elevation differences. FIG. 4B shows the wheel 3 of the vehicle 1 deforming in accordance with the shape of the road surface. As shown in FIGS. 4A and 4B, the wheel 3 deforms in accordance with the shape of the road surface, causing the radius r of the wheel 3 to deform. As an example, FIG. 4B shows the radius r of the wheel 3 deforming from radius ra to radius rb and then to radius rb. As the radius of the wheel 3 deforms in this way, the rotational speed of the wheel 3 changes. In this embodiment, the control device 10 controls the damping force of the shock absorber 4b using the rotational speed of the wheel 3, as an example.

[0030] Next, an example of a damping force control process executed by the control device 10 will be described. Fig. 6 is a flowchart showing an example of a process for calculating an index value (tilt vibration index value) indicating the degree of tilt vibration in the damping force control process according to the first embodiment. Fig. 7 is a flowchart showing an example of a process for calculating an index value (rough vibration index value) indicating the degree of thump vibration in the damping force control process according to the first embodiment. Fig. 8 is a diagram showing an example of a map representing the relationship between the ratio of the thump vibration index value to the tilt vibration index value and the correction coefficient according to the first embodiment. Fig. 9 is a diagram showing another example of a map representing the relationship between the ratio of the thump vibration index value to the tilt vibration index value and the correction coefficient according to the first embodiment. Fig. 10 is a diagram showing an example of a map representing the relationship between the relative speed of the vehicle body and the wheels in the vertical direction, the target damping force, and the control stage of the shock absorber according to the first embodiment.

[0031] Fig. 5 is a flowchart showing an example of a damping force control process executed by the control device 10 according to the first embodiment. The damping force control process shown in Fig. 5 is repeatedly executed, for example, for a plurality of wheels 3 in a predetermined order at predetermined time intervals when an ignition switch (not shown) is on. In the following description, the control of the damping force may be simply referred to as "control."

[0032] First, the acquisition unit 10a acquires input data to be input to the trained model 121 (S101).

[0033] Next, the calculation unit 10b inputs the input data to the trained model 121 and calculates the vertical relative velocity Vrei, which is the relative velocity in the vertical direction between the vehicle body 2 and the vehicle 1, for each wheel 3 (S102). Specifically, the calculation unit 10b inputs the rotational speed of each wheel 3, the longitudinal acceleration of the vehicle 1, the lateral acceleration of the vehicle 1, the yaw rate of the vehicle 1, the steering angle of the wheel 3, the steering angular velocity of the wheel 3, the rotational torque of the wheel 3, and the value of the current input to the shock absorber 4b according to the target damping coefficient, into the trained model 121 and calculates the vertical relative velocity Vrei for each wheel 3.

[0034] Next, the calculation unit 10b calculates the target damping force Fti of each shock absorber 4b based on the calculated vertical relative velocity Vrei. The target damping force Fti is calculated based on the following formula (1). Csf in formula (1) is, for example, a damping coefficient of skyhook control. Note that Csf may be a damping coefficient of any damping force control (for example, H∞ control) that damps vibrations of the car body 2 to improve the ride comfort of the vehicle 1. Fti = Csf × Vrei (1)

[0035] Next, the calculation unit 10b calculates a tilt vibration index value (I1i) which is an index value indicating the degree of tilt vibration (first vibration) (S104). The tilt vibration is, for example, a vibration in a frequency range in which an occupant of the vehicle 1 can feel a bouncy vibration of the vehicle body 18. As an example, the tilt vibration is in the resonant frequency range of the vehicle body 2 in the sprung portion 2a. The resonant vibration frequency range of the vehicle body 2 is, for example, 1 to 2 Hz.

[0036] The process of S104 will be described in detail with reference to the flowchart shown in FIG. 6 . As shown in FIG. 6 , the calculation unit 10b extracts a tilt component from the rotational speed of the wheel 3 acquired by the acquisition unit 10a (S201). Specifically, the rotational speed of the wheel 3 includes at least one of (for example, all of) the rotational speed of each wheel 3, the difference between the rotational speeds of two wheels 3 arranged diagonally from the plurality of wheels 3, and the difference between the rotational speeds of two wheels 3 arranged in the longitudinal direction of the vehicle 1. More specifically, the rotational speed of the wheel 3 includes at least one of (for example, all of) the rotational speed of the wheel 3 corresponding to the shock absorber 4b to be controlled (hereinafter also referred to as the first wheel 3), the difference between the rotational speeds of the wheel 3 arranged diagonally from the first wheel 3 and the first wheel 3, and the difference between the rotational speeds of the wheel 3 arranged in the longitudinal direction of the vehicle 1 and the first wheel 3. Note that the rotational speed of the wheel 3 is not limited to all of the above and may be a part of them. The calculation unit 10b extracts a tilt component for each of the rotational speeds (rotational speed, difference). Specifically, the calculation unit 10b processes the signal indicating the wheel rotational speed using a high-pass filter having a predetermined cutoff frequency (e.g., 1 Hz), and then processes it using a low-pass filter having a predetermined cutoff frequency (e.g., 2 Hz). As a result, a tilt component Gz1i in a frequency range of, for example, 0.5 to 2 Hz is extracted as a first vibration component from the signal indicating the wheel rotational speed. Note that the first vibration component is not limited to 0.5 to 2 Hz and may be in another frequency range. Furthermore, the rotational speed of the wheel 3 is not limited to the above and may be, for example, the difference between the rotational speeds of two wheels 3 arranged laterally.

[0037] Next, the calculation unit 10b converts the tilt component signal into an absolute value by full-wave rectifying the signal (S202). This converts negative values ​​of the tilt component signal into positive values ​​with the same absolute value. Next, the calculation unit 10b removes predetermined noise from the tilt component signal using a filter (S203). Next, the calculation unit 10b calculates the maximum value of the tilt component converted into an absolute value within a preset time Tc (positive constant) up to the present as the tilt vibration index value (I1i) (S204). In this way, the calculation unit 10b calculates the tilt vibration index value (I1i) for each rotation speed (rotation speed, difference).

[0038] Returning to FIG. 5 , the calculation unit 10b calculates a rugged vibration index value (I2i), which is an index value indicating the degree of rugged vibration (second vibration). The rugged vibration is vibration in a frequency range in which occupants of the vehicle 1 experience a rough ride. The rugged vibration is, for example, vibration in a frequency range (e.g., 6 to 10 Hz) between the resonant frequency range of the vehicle body 2 of the sprung portion 2a and the resonant frequency range of the wheels 3 and wheel carriers (not shown) of the unsprung portion 2b. Note that the frequency range is not limited to the above. For example, the lower limit of the frequency range may be lower than 6 Hz as long as it is higher than the resonant frequency range of the unsprung portion 2b.

[0039] The process of S105 will be described in detail with reference to the flowchart shown in FIG. 7 . As shown in FIG. 7 , the calculation unit 10b extracts a bumpy component from the rotational speed of the wheel 3 acquired by the acquisition unit 10a (S301). Specifically, as in the case of extracting the tailpipe component, the rotational speed of the wheel 3 includes at least one of (for example, all of) the rotational speed of each wheel 3, the difference between the rotational speeds of two wheels 3 arranged diagonally from the plurality of wheels 3, and the difference between the rotational speeds of two wheels 3 arranged in the longitudinal direction of the vehicle 1. More specifically, the rotational speed of the wheel 3 includes at least one of (for example, all of) the rotational speed of the wheel 3 corresponding to the shock absorber 4b to be controlled (hereinafter also referred to as the first wheel 3), the difference between the rotational speeds of the wheel 3 diagonally arranged from the first wheel 3 and the first wheel 3, and the difference between the rotational speeds of the wheel 3 arranged in the longitudinal direction of the vehicle 1 from the first wheel 3 and the first wheel 3. The speeds related to the rotation of the wheel 3 are not limited to all of the above and may be only some of them. The calculation unit 10b extracts a rugged component from each of the above rotational speeds (rotational speed, difference). Specifically, the calculation unit 10b processes the signal indicating the rotational speed of the wheel 3 using a high-pass filter having a predetermined cutoff frequency (e.g., 6 Hz), and then processes it using a low-pass filter having a predetermined cutoff frequency (e.g., 10 Hz). As a result, a rugged component (Gz2i) in a frequency range of, for example, 4 to 10 Hz is extracted as a second vibration component from the signal indicating the rotational speed of the wheel. The second frequency range is not limited to the above and may be another frequency range. The speed related to the rotation of the wheel 3 is not limited to the above and may be, for example, the difference between the rotational speeds of two wheels 3 arranged laterally.

[0040] Next, the calculation unit 10b full-wave rectifies the signal of the rugged component to convert it into an absolute value (S302), thereby converting the negative value of the signal of the rugged component into a positive value with the same absolute value.

[0041] Next, the calculation unit 10b processes the absolute valued signal of the rugged component using a low-pass filter having a cutoff frequency (e.g., 2 Hz) for removing high-frequency noise, thereby removing noise with frequencies higher than the frequency of the rugged component (S303).

[0042] Next, the calculation unit 10b calculates the maximum value of the ruggedness component, which has been converted into an absolute value and noise-removed within a preset time Tc up to the present, as the ruggedness vibration index value (I2i) (S304). In this way, the calculation unit 10b calculates the ruggedness vibration index value (I2i) for each rotation-related speed (rotation speed, difference). Note that Japanese Patent Application Laid-Open No. 8-216646 can be referenced for the calculation of the maximum values ​​of the tilt component and ruggedness component.

[0043] Next, the calculation unit 10b calculates a correction coefficient (Kri) (S106). Specifically, the calculation unit 10b calculates the ratio (I2i / I1i) of the thump vibration index value (I2i) to the tilt vibration index value (I1i) for each rotation speed (rotation speed, difference). The calculation unit 10b then determines the largest ratio (I2i / I1i) among the calculated ratios (I2i / I1i) as the final ratio (I2i / I1i) of the thump vibration index value (I2i) to the tilt vibration index value (I1i). Next, the calculation unit 10b calculates the correction coefficient (Kri) from the determined ratio I2i / I1i and the map shown in FIG. 8 or 9. FIG. 9 shows an example in which the correction coefficient includes multiple stages. When the tilt vibration index value I1i is 0, the calculation unit 10b sets the tilt vibration index value (I1i) to a preset constant greater than 0, and calculates the ratio (I2i / I1i). The preset constant is, for example, a positive value close to 0.

[0044] Next, the calculation unit 10b modifies the correction coefficient Kri (S107). Specifically, the calculation unit 10b applies low-pass filtering to the correction coefficient (Kri) to modify the correction coefficient (Kri) so as to limit the rate of change of the correction coefficient (Kri). Note that the limit on the rate of change of the correction coefficient (Kri) is not limited to the above and may be achieved by other means. Examples of other means include guarding the magnitude of the amount of change in the correction coefficient per unit time, performing moving average processing on the correction coefficient, or holding the correction coefficient at a constant value for a preset holding time. Note that the means for limiting the rate of change of the correction coefficient Kri are similar to those for the correction coefficients in other embodiments described below.

[0045] Next, the calculation unit 10b calculates the final target damping force (Ffti) of each shock absorber 4b (S108). Specifically, the calculation unit 10b performs the calculation based on the corrected correction coefficient (Kri) and the following equation (2). Kri in equation (2) is the corrected correction coefficient (Kri). Ffti = Kri × Fti (2)

[0046] Next, the calculation unit 10b calculates the target damping coefficient (Cti) of each shock absorber 4b (S109). Specifically, the calculation unit 10b determines the target control stage of each shock absorber 4b based on the calculated vertical relative velocity (Vrei), the calculated target damping force (Fti), and the map shown in Figure 10. In other words, the target damping coefficient (Cti) of each shock absorber 4b is calculated.

[0047] Next, the damping force control unit 10c controls the damping force by controlling the control stage of each shock absorber 4b so that the control stage becomes the target control stage calculated in step 210. In other words, the damping force control unit 10c controls the damping coefficient (Ci) of each shock absorber 4b to the target damping coefficient (Cti), thereby controlling the damping force Fi to become the final target damping force Ffti.

[0048] As can be seen from the above description, in S102, the trained model 121 is used to calculate the vertical relative velocity Vrei between each wheel 3 and the vehicle body 2 for each wheel 3. In S103, the target damping force Fti of each shock absorber 4b is calculated based on the vertical relative velocity Vrei. In S104 and S105, the tilt vibration index value I1i and the thumping vibration index value I2i are calculated based on the rotational speed of the wheel 3. Note that the calculation of the tilt vibration index value I1i and the thumping vibration index value I2i is not limited to the above. For example, the trained model 121 may be configured to output the vertical acceleration of the sprung portion 2a (vehicle body 2) in addition to the above output data based on input data, and the tilt vibration index value I1i and the thumping vibration index value I2i may be extracted in a known direction from the vertical acceleration.

[0049] In S106, a correction coefficient (Kri) is calculated based on the ratio (I2i / I1i) of the bumpy vibration index value (I2i) to the tilt vibration index value (I1i). The correction coefficient (Kri) is calculated so that it decreases as the ratio (I2i / I1i) increases and increases as the vehicle speed increases. In S107, the correction coefficient (Kri) is modified so that the rate of change is limited.

[0050] In step S108, the final target damping force (Ffti) is calculated as the product of the corrected correction coefficient (Kri) and the vertical relative velocity (Vrei). In steps S109 and S110, the damping force (Fi) of each shock absorber 4b is controlled to become the final target damping force (Ffti).

[0051] That is, the processing performed by the control device 10 includes the following: (a) The control device 10 estimates (calculates) the vertical relative velocity Vrei using the trained model 121. (b) The control device 10 calculates the target damping force (Fti) from the vertical relative velocity (Vrei) and the damping coefficient (Csf). (c) The control device 10 calculates the thudding vibration index value (I2i) and the sideways vibration index value (I1i) using the rotational speed of each wheel 3, the difference between the rotational speeds of two diagonal wheels 3, and the difference between the rotational speeds of two front-rear wheels 3. (d) The control device 10 calculates the ratio (I2i / I1i) between the calculated thudding vibration index value (I2i) and the sideways vibration index value (I1i). (e) The control device 10 selects the maximum value of the ratio between the calculated thudding vibration index value (I2i) and the sideways vibration index value (I1i). (f) The control device 10 performs a hold process for a predetermined period of time on the maximum value of the obtained ratio. (g) The control device 10 calculates a correction coefficient (Kri) from the relationship between the value obtained by the hold process and the vehicle speed. (h) If the change in the obtained correction coefficient (Kri) is equal to or greater than a threshold, the control device 10 performs a change guard process (correction coefficient correction) to obtain the maximum change. (i) The control device 10 calculates a final target damping force (Ftfi) from the obtained target damping force (Fti) and the maximum change. (j) The control device 10 calculates a target damping coefficient (Cti) from the obtained final target damping force (Ftfi) and executes damping force control. According to the above process, the control device 10 determines whether the road surface has a large thump vibration index value (I2i) compared to the sideways vibration index value (I1i), and if it is determined that the road surface has a large thump vibration index value (I2i) compared to the sideways vibration index value (I1i), it can perform control to reduce the damping force.

[0052] As described above, in this embodiment, the control device 10 (damping force control device) controls the shock absorber 4b interposed between the wheel 3 of the vehicle 1 and the body 2 of the vehicle 1. The control device 10 includes a calculation unit 10b and a damping force control unit 10c. The calculation unit 10b uses the trained model 121, which inputs a first physical quantity related to the motion of the vehicle 1 other than the vertical acceleration of the vehicle 1 and outputs a second physical quantity related to the vertical motion of the vehicle 1, to estimate the second physical quantity from the actual measured value of the first physical quantity, and calculates the target damping coefficient of the shock absorber 4b based on the estimated second physical quantity. The damping force control unit 10c controls the damping force of the shock absorber 4b based on the calculated target damping coefficient.

[0053] According to the above configuration, the calculation unit 10b uses the trained model 121 to calculate the target damping coefficient of the shock absorber 4b from the actual measurement value of the first physical quantity related to the motion of the vehicle 1 other than the vertical acceleration of the vehicle 1, so there is no need to provide the vehicle 1 with a vertical acceleration sensor dedicated to controlling the damping force of the shock absorber 4b. This makes it possible to prevent the structure of the vehicle 1 from becoming complicated when controlling the damping force of the shock absorber 4b.

[0054] In addition, the first physical quantity includes at least one of the speed of the wheel 3 according to the rotation of the wheel 3, the longitudinal acceleration of the vehicle 1, the lateral acceleration of the vehicle 1, the yaw rate of the vehicle 1, the steering angle of the wheel 3, the steering angular velocity of the wheel 3, the rotational torque of the wheel 3, and the value of the current input to the shock absorber 4b according to the target damping coefficient.

[0055] With this configuration, the target damping coefficient can be calculated from at least one of the speed of the wheel 3, the longitudinal acceleration of the vehicle 1, the lateral acceleration of the vehicle 1, the yaw rate of the vehicle 1, the steering angle of the wheel 3, the steering angular velocity of the wheel 3, the rotational torque of the wheel 3, and the value of the current input to the shock absorber 4b according to the target damping coefficient.

[0056] Furthermore, the calculation unit 10b calculates the target damping coefficient of the shock absorber 4b based on the estimated second physical quantity and the speed of the wheels 3. The speed of the wheels 3 includes at least one of the rotational speed of each of the plurality of wheels 3, the difference between the rotational speeds of two wheels 3 arranged diagonally among the plurality of wheels 3, and the difference between the rotational speeds of two wheels arranged in the longitudinal direction of the vehicle 1.

[0057] Here, for example, even when the vehicle 1 is traveling on a so-called choppy road, which is a road where concrete slabs are laid continuously and the joints between the concrete slabs are formed at intervals, the unevenness of the choppy road is likely to be reflected in the difference in rotational speed between two wheels 3 arranged diagonally and two wheels 3 arranged laterally of the vehicle 1. Therefore, with the above configuration, a more appropriate target damping coefficient can be calculated when the speed related to the wheels 3 includes at least one of the difference in rotational speed between two wheels 3 arranged diagonally and the difference in rotational speed between two wheels 3 arranged in the longitudinal direction of the vehicle 1.

[0058] Second Embodiment FIG. 11 is a flowchart showing an example of a damping force control process executed by a control device according to a second embodiment.

[0059] This embodiment differs from the first embodiment in that the second physical quantity related to the vertical movement of the vehicle 1 output by the trained model 121 is the sprung velocity, which is the velocity of the sprung portion 2a (vehicle body 2), and in the damping force control processing performed by the control device 10.

[0060] In the damping force control process of this embodiment, as shown in FIG. 11, S402 and S403 are performed instead of S102 and S103 in FIG. 5, and the other S401, and S404 to S410 are performed in the same manner as S101, and S104 to S110 in FIG.

[0061] In S402, the calculation unit 10b inputs the input data to the trained model 121 and calculates the sprung velocity Vz, which is the velocity of the sprung portion 2a (vehicle body 2), for each wheel 3. Specifically, the calculation unit 10b inputs the rotational speed of each wheel 3, the longitudinal acceleration of the vehicle 1, the lateral acceleration of the vehicle 1, the yaw rate of the vehicle 1, the steering angle of the wheel 3, the steering angular velocity of the wheel 3, the rotational torque of the wheel 3, and the value of the current input to the shock absorber 4b according to the target damping coefficient, into the trained model 121 to calculate the sprung velocity Vz.

[0062] In S403, the calculation unit 10b calculates the target damping force Fti of each shock absorber 4b based on the calculated sprung velocity Vz. The target damping force Fti is calculated based on the following equation (3): Fti=Csf×Vz (3)

[0063] Third Embodiment FIG. 12 is a flowchart showing an example of a damping force control process executed by a control device according to a third embodiment.

[0064] This embodiment differs from the first embodiment in the damping force control process executed by the control device 10.

[0065] The damping force control process of this embodiment is performed alternately for, for example, the two front wheels 3 and the two rear wheels 3, in accordance with the flowchart shown in Fig. 12. S501 to S505, S509, and S510 are the same as S101 to S105, S109, and S110 in the first embodiment. Then, instead of S106 to S108 in the first embodiment, S506 to S508 are executed, respectively.

[0066] In this embodiment, the larger of the swing vibration index values ​​I1FL, I1FR corresponding to the two front wheels 3 is set to the swing vibration index value I1fr of the vehicle body 2 at a position corresponding to the two front wheels 3. Furthermore, the larger of the swing vibration index values ​​I1RL and I1RR corresponding to the two rear wheels 3 is set to the swing vibration index value I1re of the vehicle body 2 at a position corresponding to the two rear wheels 3. Similarly, the larger of the thud vibration index values ​​I2FL and I2FR corresponding to the two front wheels 3 is set to the thud vibration index value I2fr of the vehicle body 18 at a position corresponding to the two front wheels 3. The larger of the thud vibration index values ​​I2RL and I2RR corresponding to the two rear wheels 3 is set to the thud vibration index value I2re of the vehicle body 18 at a position corresponding to the two rear wheels 3.

[0067] In S506, the ratios I2fr / I1fr and I2re / I1re of the thump vibration index values ​​I2fr and I2re to the tilt vibration index values ​​I1fr and I1re, respectively, are calculated. Furthermore, based on the ratios I2fr / I1fr and I2re / I1re, the maps shown in Figure 8 or 9 are referenced to calculate correction coefficients Krfr and Krre for the two front wheels 3 and the two rear wheels 3, respectively.

[0068] In S507, the correction coefficients Krfr and Krre are subjected to low-pass filtering, thereby modifying the correction coefficients Krfr and Krre so that the rate of change is limited.

[0069] In S508, the final target damping force Ffti of each shock absorber 4b is calculated using the corrected correction coefficients Krfr and Krre according to the following equations (4) to (7): FftFL = Krfr × FtFL (4) FftFR = Krfr × FtFR (5) FftRL = Krre × FtRL (6) FftRR = Krre × FtRR (7)

[0070] The program for realizing each function of the above-described embodiments on a computer (e.g., the control device 10, etc.) may be configured to be provided by being recorded in an installable or executable format on a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk).

[0071] The program may also be configured to be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network, or may be configured to be provided or distributed via a network such as the Internet.

[0072] The second physical quantity output by the trained model 121 is not limited to those described in the above embodiment. For example, the second physical quantity may be the roll angular velocity of the vehicle 1 (vehicle body 2), the pitch angular velocity of the vehicle 1 (vehicle body 2), the heave velocity of the vehicle 1 (vehicle body 2), or the like.

[0073] Summary of the Present Embodiment The damping force control device (10) of the present embodiment includes at least the following configuration: That is, the damping force control device (10) controls a shock absorber (4 b) interposed between a wheel (3) of a vehicle (1) and a body (2) of the vehicle (1), and includes: a calculation unit (10 b) that estimates a second physical quantity from an actual measurement value of the first physical quantity using a trained model (121) that inputs a first physical quantity related to the motion of the vehicle (1) other than the acceleration in the vertical direction of the vehicle (1) and outputs a second physical quantity related to the motion of the vehicle (1) in the vertical direction, and calculates a target damping coefficient of the shock absorber (4 b) based on the estimated second physical quantity; and a damping force control unit (10 c) that controls the damping force of the shock absorber (4 b) based on the calculated target damping coefficient.

[0074] According to this configuration, the calculation unit (10b) uses the trained model (121) to calculate the target damping coefficient of the shock absorber (4b) from the actual measurement value of the first physical quantity related to the motion of the vehicle (1) other than the vertical acceleration of the vehicle (1), so there is no need to provide the vehicle (1) with a vertical acceleration sensor dedicated to controlling the damping force of the shock absorber (4b). Therefore, it is possible to prevent the structure of the vehicle (1) from becoming complicated when controlling the damping force of the shock absorber (4b).

[0075] Furthermore, it is preferable that the first physical quantity includes at least one of a speed of the wheel (3) according to the rotation of the wheel (3), a longitudinal acceleration of the vehicle (1), a lateral acceleration of the vehicle (1), a yaw rate of the vehicle (1), a steering angle of the wheel (3), a steering angular velocity of the wheel (3), a rotational torque of the wheel (3), and a value of a current input to the shock absorber (4 b) according to a target damping coefficient.

[0076] With this configuration, the target damping coefficient can be calculated from at least one of the speed of the wheel (3), the longitudinal acceleration of the vehicle (1), the lateral acceleration of the vehicle (1), the yaw rate of the vehicle (1), the steering angle of the wheel (3), the steering angular velocity of the wheel (3), the rotational torque of the wheel (3), and the value of the current input to the shock absorber (4b) according to the target damping coefficient.

[0077] Furthermore, the calculation unit (10b) calculates a target damping coefficient of the shock absorber (4b) based on the estimated second physical quantity and the speed of the wheel (3), and it is preferable that the speed of the wheel (3) includes at least one of the rotational speed of each of the plurality of wheels (3), the difference between the rotational speeds of two wheels (3) arranged diagonally among the plurality of wheels (3), and the difference between the rotational speeds of two wheels (3) arranged in the longitudinal direction of the vehicle (1).

[0078] According to this configuration, when the speed of the wheel (3) includes at least one of the difference between the rotational speeds of two wheels (3) arranged diagonally around the wheel (3) and the difference between the rotational speeds of two wheels (3) arranged in the fore-and-aft direction of the vehicle (1), a more appropriate target damping coefficient can be calculated.

[0079] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0080] DESCRIPTION OF SYMBOLS 1 Vehicle 2 Vehicle body 3 Wheel 4b Shock absorber 10 Control device (damping force control device) 10a Acquisition unit 10b Calculation unit 10c Damping force control unit 121 Trained model

Claims

1. A damping force control device that controls a shock absorber interposed between a wheel of a vehicle and a body of the vehicle, comprising: a calculation unit that utilizes a trained model that inputs a first physical quantity related to the movement of the vehicle other than the vertical acceleration of the vehicle and outputs a second physical quantity related to the vertical movement of the vehicle, estimates the second physical quantity from an actual measured value of the first physical quantity, and calculates a target damping coefficient of the shock absorber based on the estimated second physical quantity; and a damping force control unit that controls the damping force of the shock absorber based on the calculated target damping coefficient.

2. A damping force control device as described in claim 1, wherein the first physical quantity includes at least one of the following: a speed of the wheel in response to the rotation of the wheel, a longitudinal acceleration of the vehicle, a lateral acceleration of the vehicle, a yaw rate of the vehicle, a steering angle of the wheel, a steering angular velocity of the wheel, a rotational torque of the wheel, and a value of a current input to the shock absorber in response to the target damping coefficient.

3. A damping force control device as described in claim 1, wherein the calculation unit calculates a target damping coefficient of the shock absorber based on the estimated second physical quantity and a speed related to the wheel, and the speed related to the wheel includes at least one of the rotational speeds of each of the plurality of wheels, the difference between the rotational speeds of two of the wheels diagonally arranged among the plurality of wheels, and the difference between the rotational speeds of two of the wheels arranged in the fore-and-aft direction of the vehicle.

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