Device and method for controlling electronically controlled suspension

Abstract

To provide a device and method for controlling an electronically controlled suspension with which deterioration in damping performance can be suppressed even if the accuracy of estimating an unsprung state of rear wheels decreases.SOLUTION: A variable damper 7 is provided to a vehicle having front wheels and rear wheels. A controller 11 is provided with a trajectory correspondence detection unit 24 that detects the correspondence between the trajectories of the front wheels and the rear wheels when the vehicle is traveling, and a command value calculation unit 25 that calculates a control amount command value, which is a control amount of the variable damper 7 of the rear wheels, in accordance with the correspondence relationship of the trajectories.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a control device and a control method for an electronically controlled suspension that is preferably used in a vehicle such as a four-wheeled automobile. [Background technology]

[0002] Patent Document 1 discloses an estimation device that detects front wheel unsprung vibration information such as front wheel displacement, speed, acceleration, etc., and estimates rear wheel unsprung vibration information based on this front wheel unsprung vibration information and the wheelbase of the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-190621 Summary of the Invention [Problem to be solved by the invention]

[0004] The estimation device disclosed in Patent Document 1 estimates rear wheel unsprung vibration information from front wheel unsprung vibration information delayed by the wheelbase. However, this estimation method assumes that the front and rear wheels follow the same trajectory. Therefore, estimation accuracy deteriorates under conditions where the front and rear wheels follow different trajectories. Conditions where the trajectories of the front and rear wheels differ include (1) extremely low speeds where the difference between the front and rear wheel trajectories is large, (2) large steering angles or skidding where the difference between the front and rear wheel trajectories is large, (3) an incorrect vehicle speed signal that makes it impossible to calculate the delay, and (4) reverse driving where the rear wheels receive road surface input before the front wheels.

[0005] An object of one embodiment of the present invention is to provide a control device and control method for an electronically controlled suspension that can suppress deterioration of vibration damping performance even when the estimation accuracy of the rear wheel unsprung state decreases. [Means for solving the problem]

[0006] One embodiment of the present invention is a control device for an electronically controlled suspension provided on a vehicle having front and rear wheels, and includes a trajectory correspondence detection unit that detects the correspondence between the trajectories of the front wheels and the rear wheels while the vehicle is running, and a command value calculation unit that calculates a control variable command value, which is a control variable for the electronically controlled suspension of the rear wheels, in accordance with the trajectory correspondence.

[0007] Moreover, one embodiment of the present invention is a control method for an electronically controlled suspension provided on a vehicle having front wheels and rear wheels and capable of adjusting damping force, the control method comprising: a front wheel state quantity calculation step of calculating a front wheel state quantity which is a state quantity of the front wheels; a rear wheel state quantity calculation step of calculating a rear wheel state quantity which is a state quantity of the rear wheels using the front wheel state quantity; and a command value calculation step of calculating a control variable command value which is a control variable of the electronically controlled suspension of the rear wheels, wherein when one or more conditions of the running state of the vehicle are all true, the control variable command value is calculated using the rear wheel state quantity, and when one or more of the conditions are false, the command value calculation step calculates the control variable command value different from when all of the conditions are true. [Effects of the Invention]

[0008] According to one embodiment of the present invention, even if the accuracy of estimating the state of the unsprung parts of the rear wheels decreases, deterioration of vibration damping performance can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a front view showing a vehicle to which a controller according to a first and second embodiment is applied. [Figure 2] FIG. 2 is a diagram schematically illustrating a controller according to the first and second embodiments. [Figure 3] FIG. 2 is a control block diagram showing a controller according to the first embodiment. [Figure 4] FIG. 10 is an explanatory diagram showing conditions under which the trajectories of the front and rear wheels deviate from each other based on the relationship between the vehicle speed and lateral acceleration. [Figure 5]4 is a characteristic diagram showing time variations in the relative velocity between the sprung and unsprung parts, the command current value, and the sprung part acceleration. FIG. [Figure 6] FIG. 10 is a characteristic diagram showing the frequency characteristics of the acceleration PSD. [Figure 7] FIG. 6 is a control block diagram showing a controller according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description will be given of an example in which a control device for an electronically controlled suspension according to an embodiment of the present invention is applied to a four-wheeled automobile, with reference to the accompanying drawings.

[0011] 1 and 2 show a vehicle behavior control device 1 according to an embodiment. The vehicle behavior control device 1 is made up of a suspension device 5 constituting a damping force generating device, and a controller 11 constituting a control device. In FIG. 2, for example, left and right front wheels and left and right rear wheels (hereinafter collectively referred to as wheels 3) are provided on the underside of a vehicle body 2 constituting the body of the vehicle. The wheels 3 are made up of tires 4, which act as springs that absorb small irregularities in the road surface.

[0012] The suspension device 5 is an electronically controlled suspension and is provided on a vehicle having front and rear wheels. The suspension device 5 is provided between the vehicle body 2 and the vehicle wheels 3. Therefore, the suspension device 5 is provided between the vehicle body 2 and the front wheels, and also between the vehicle body 2 and the rear wheels. The suspension device 5 is made up of a suspension spring 6 (hereinafter referred to as the spring 6) and an adjustable damping force shock absorber (hereinafter referred to as the variable damper 7) provided in parallel with the spring 6 between the vehicle body 2 and the wheels 3.

[0013] 2 shows a case where one set of suspension devices 5 is provided between the vehicle body 2 and the wheels 3. However, a total of four sets of suspension devices 5 are provided individually and independently between, for example, four wheels 3 and the vehicle body 2, and only one of these sets is shown schematically in FIG.

[0014] The variable damper 7 of the suspension device 5 is configured using a damping force adjustable hydraulic shock absorber interposed between the vehicle body 2 and the wheel 3. The variable damper 7 is provided with a damping force variable actuator 8, which is composed of a damping force adjustment valve or the like, for continuously adjusting the characteristics of the generated damping force (i.e., the damping force characteristics) from hard characteristics to soft characteristics. The variable damper 7 constitutes a force generating mechanism that generates an adjustable force between the vehicle body 2 and the wheel 3. Note that the damping force variable actuator 8 does not necessarily have to be configured to continuously adjust the damping force characteristics, and may be capable of adjusting the damping force in multiple stages, for example, two or more stages. The variable damper 7 may also be a pressure control type or a flow rate control type. The variable damper 7 may also be a type that controls viscosity, such as a magnetorheological fluid or an electrorheological fluid.

[0015] The sprung acceleration sensor 9 is a sprung vertical acceleration detection unit attached to the vehicle. The sprung acceleration sensor 9 is provided as a sprung part on the vehicle body 2 side of the vehicle. The sprung acceleration sensor 9 detects vertical vibration acceleration on the sprung part side of the vehicle body 2, and outputs detection signals of the sprung acceleration of the front and rear wheels to the controller 11.

[0016] The unsprung acceleration sensor 10 is an unsprung vertical acceleration detector attached to the vehicle. The unsprung acceleration sensor 10 is provided on the vehicle wheel 3 side. The unsprung acceleration sensor 10 detects vertical vibration acceleration on the wheel 3 side of the front wheels, which is the unsprung side, and outputs a detection signal of the front wheel unsprung acceleration to the controller 11.

[0017] The controller 11 constitutes a control device for the variable damper 7 (suspension device 5). The controller 11 controls the damping characteristics of the variable damper 7. The controller 11 is constituted by, for example, a microcomputer. The controller 11 is connected to, for example, a CAN 12 (Controller Area Network), which is a line network required for data communication. The controller 11 acquires vehicle driving parameters via the CAN 12. At this time, the vehicle driving parameters include, for example, vehicle speed and steering angle. The controller 11 is also connected to a sprung acceleration sensor 9 and an unsprung acceleration sensor 10. Therefore, the sprung acceleration, front wheel unsprung acceleration, vehicle speed, and steering angle are input to the controller 11. The controller 11 executes a front wheel state quantity calculation step of calculating a front wheel state quantity (front wheel unsprung acceleration), which is a state quantity of the front wheels, based on the detection signal input from the unsprung acceleration sensor 10. The output side of the controller 11 is connected to a damping force variable actuator 8 of the variable damper 7.

[0018] The controller 11 also has a storage unit 11A including a ROM, a RAM, a non-volatile memory, etc. The storage unit 11A of the controller 11 stores various programs, information (vehicle information), data, etc. for controlling the variable damper 7.

[0019] As shown in FIG. 3, the controller 11 includes a rear wheel unsprung acceleration estimating unit 20, a subtractor 21, integrators 22 and 23, a trajectory correspondence detecting unit 24, and a command value calculating unit 25.

[0020] The rear wheel unsprung acceleration estimator 20 is a rear wheel unsprung acceleration state quantity calculator that calculates the rear wheel unsprung acceleration, which is the unsprung acceleration of the rear wheels, as a rear wheel state quantity. The rear wheel unsprung acceleration estimator 20 executes a rear wheel state quantity calculation step and estimates the rear wheel unsprung acceleration based on the front wheel unsprung acceleration and the vehicle speed. Specifically, as disclosed in Patent Document 1, the rear wheel unsprung acceleration estimator 20 estimates the rear wheel unsprung acceleration from the front wheel unsprung acceleration based on the wheelbase and vehicle speed of the vehicle. In this case, the rear wheel unsprung acceleration as the rear wheel state quantity is a state quantity obtained by matching the front wheel unsprung acceleration, which is a state quantity related to the acceleration of the front wheels, with the phase of the rear wheels using the vehicle speed and the wheelbase of the vehicle.

[0021] The subtractor 21 subtracts the unsprung acceleration from the sprung acceleration to calculate the difference between the sprung acceleration and the unsprung acceleration. This difference value corresponds to the relative acceleration between the vehicle body 2 and the wheels 3. At this time, the subtractor 21 calculates the relative acceleration of the front wheels by subtracting the detected value of the unsprung acceleration of the front wheels from the detected value of the sprung acceleration of the front wheels. The subtractor 21 calculates the relative acceleration of the rear wheels by subtracting the estimated value of the unsprung acceleration of the rear wheels from the detected value of the sprung acceleration of the rear wheels.

[0022] The integrator 22 integrates the relative acceleration output from the subtractor 21 to calculate the relative speed in the vertical direction between the vehicle body 2 and the wheels 3. At this time, the integrator 22 calculates the relative speed of the front wheels and the relative speed of the rear wheels. The integrator 22 outputs the relative speeds of the front wheels and the rear wheels.

[0023] The integrator 23 integrates the sprung acceleration to calculate the sprung velocity, which is the velocity in the vertical direction of the vehicle body 2. At this time, the sprung accelerations of the front and rear wheels are input to the integrator 23. Therefore, the integrator 23 calculates the sprung velocity of the front wheels and the sprung velocity of the rear wheels. The integrator 23 outputs the sprung velocities of the front wheels and the rear wheels.

[0024] The trajectory correspondence detection unit 24 detects the correspondence between the trajectories of the front and rear wheels while the vehicle is running. The trajectory correspondence detection unit 24 includes a front / rear wheel trajectory difference calculation unit 24A and a reverse / abnormality determination unit 24B.

[0025] The front and rear wheel trajectory difference calculation unit 24A receives inputs of the vehicle speed and steering angle. When the vehicle is traveling at a low speed, an inner wheel difference occurs when the steering angle is large. Therefore, when the vehicle speed is low, the front and rear wheel trajectory difference becomes large when the steering angle is large. Furthermore, when the vehicle is traveling at a high speed, even when the steering angle is small, skid occurs in the rear wheels of the vehicle, and the front and rear wheel trajectory difference becomes large.

[0026] FIG. 4 shows the conditions under which the trajectories of the front and rear wheels deviate from each other based on the relationship between vehicle speed and lateral acceleration when the steering angle (the turning angle of the steering wheel) is set to 30°, 60°, 90°, and 120°. As shown in FIG. 4, when the vehicle speed is low, for example, less than about 50 km / h, the lateral acceleration increases when the steering angle is large, such as 90° or 120°. When the vehicle speed is below a low-speed threshold, for example, about 50 km / h, and the steering angle is above a large-angle threshold, for example, about 120°, the difference in the trajectories of the front and rear wheels falls outside the allowable range (for example, 0.1 m). On the other hand, as shown in FIG. 4, when the vehicle speed is high, for example, greater than about 60 km / h, the lateral acceleration increases even when the steering angle is small, such as 30° or 60°, causing the rear wheels of the vehicle to skid, and the difference in the trajectories of the front and rear wheels increases.

[0027] When the vehicle speed is, for example, 60 km / h or higher and the steering angle is, for example, 60° or higher, the difference between the front and rear wheel trajectories falls outside the allowable range (for example, 0.1 m). Furthermore, when the vehicle speed is, for example, 100 km / h or higher and the steering angle is, for example, 30° or higher, the difference between the front and rear wheel trajectories falls outside the allowable range (for example, 0.1 m). For this reason, the front and rear wheel trajectory difference calculation unit 24A calculates and outputs the difference between the front and rear wheel trajectories based on the vehicle speed and steering angle, taking into account the lateral acceleration acting on the vehicle.

[0028] The reverse / abnormality determination unit 24B receives an input of the vehicle speed. Based on the vehicle speed, the reverse / abnormality determination unit 24B determines whether the vehicle is reversing or not, and whether an abnormality has occurred in the vehicle speed signal. Specifically, the reverse / abnormality determination unit 24B determines whether the vehicle is moving forward or backward based on the vehicle speed signal. Furthermore, the reverse / abnormality determination unit 24B determines that an abnormality has occurred in the vehicle speed signal when, for example, the vehicle speed signal does not fluctuate at a constant value or the vehicle speed signal is outside an allowable range. The reverse / abnormality determination unit 24B outputs these determination results.

[0029] The command value calculation unit 25 calculates a control amount command value, which is the control amount of the variable damper 7 of the front wheel suspension unit 5. In addition, the command value calculation unit 25 executes a command value calculation step to calculate a control amount command value, which is the control amount of the variable damper 7 of the rear wheel suspension unit 5, in accordance with the correspondence relationship of the trajectories. The command value calculation unit 25 includes a relative speed correction unit 25A, a bilinear optimum control unit 25B (hereinafter referred to as BLQ25B), and a control command calculation unit 25C.

[0030] Relative speed correction unit 25A corrects the relative speed of the rear wheels based on the correspondence between the trajectories of the front and rear wheels when the vehicle is traveling, detected by trajectory correspondence detection unit 24. The relative speeds of the front and rear wheels, the sprung speed of the rear wheels, the difference between the trajectories of the front and rear wheels, and the determination results of reverse and abnormality are input to relative speed correction unit 25A. Relative speed correction unit 25A outputs the relative speed of the front wheels output from integrator 22 as is as the corrected relative speed of the front wheels.

[0031] On the other hand, the relative speed correction unit 25A corrects the relative speed of the rear wheels based on the front and rear wheel trajectory difference output from the front and rear wheel trajectory difference calculation unit 24A and the reverse / abnormality determination result output from the reverse / abnormality determination unit 24B.

[0032] The relative speed correction unit 25A determines whether the following three conditions (A) to (C) are satisfied. (A) The absolute value of the difference between the front and rear wheel trajectories is less than a predetermined threshold value. (B) The vehicle is moving forward (C) Vehicle speed signal is normal

[0033] At this time, the threshold value of the front and rear wheel trajectory difference is set in consideration of the case where the tire trajectories are clearly different in consideration of, for example, the tire width of the front and rear wheels (the width dimension of the tire 4). That is, the threshold value of the front and rear wheel trajectory difference is set based on, for example, the tire width of the wheel 3 as a value at which an unacceptable difference occurs in the unsprung acceleration between the front and rear wheels. As an example, the threshold value of the front and rear wheel trajectory difference is set to a value half the tire width. The threshold value of the front and rear wheel trajectory difference is set appropriately with reference to the actual unsprung acceleration of the front and rear wheels, etc.

[0034] If any of these three conditions (A) to (C) is false, relative speed correction unit 25A outputs a value obtained by multiplying a predetermined value (e.g., 0.1 m / s) by the sign of the sprung speed corresponding to the rise or fall of the rear wheels as the corrected relative speed of the rear wheels, as shown in equation 1. In other words, if at least one of conditions (A) to (C) is not satisfied, relative speed correction unit 25A outputs a value calculated based on equation 1 as the corrected relative speed of the rear wheels.

[0035]

number

[0036] The predetermined value is determined according to the relative speed on an undulating road where control is frequently performed, and is set appropriately within the range of 0.08 to 0.3 m / s, for example. The predetermined value may be changed appropriately according to the damping force characteristics of the variable damper 7.

[0037] For example, when it is determined that the front and rear wheel trajectory difference output from the front and rear wheel trajectory difference calculation unit 24A is greater than half the width dimension of the wheel 3, the relative speed correction unit 25A calculates and outputs the corrected relative speed of the rear wheel based on equation 1.

[0038] When it is determined that the vehicle is reversing based on the reverse / abnormality determination result output from the reverse / abnormality determination unit 24B, the relative speed correction unit 25A calculates and outputs the corrected relative speed of the rear wheels based on the formula 1.

[0039] When it is determined that an abnormality has occurred in the vehicle speed signal based on the reverse / abnormality determination result output from the reverse / abnormality determination unit 24B, the relative speed correction unit 25A calculates and outputs the corrected relative speed of the rear wheels based on the formula 1.

[0040] On the other hand, when all of the conditions (A) to (C) are true, the relative speed correction unit 25A outputs, as the corrected relative speed, the relative speed of the rear wheels output from the integrator 22. In other words, when all of the conditions (A) to (C) are satisfied, the relative speed correction unit 25A outputs, as the corrected relative speed, the relative speed of the rear wheels output from the integrator 22.

[0041] The BLQ25B receives the sprung mass velocity and the corrected relative velocity as input. Based on bilinear optimal control theory, the BLQ25B calculates the damping force and damping coefficient of the variable damper 7 to reduce the vertical vibration of the sprung mass from the sprung mass velocity and the corrected relative velocity. The BLQ25B outputs the calculated damping force and the like as target commands.

[0042] Control command calculation unit 25C calculates a command value (control amount command value) of a current to be supplied to damping force variable actuator 8, which is a control amount of variable damper 7, based on the target command output from BLQ 25B. At this time, the control amount command value corresponds to a damping force command value that is a command value for the damping force of the front wheels and rear wheels. Controller 11 outputs a command signal (command current) corresponding to this control amount command value (command current value) to damping force variable actuator 8. In this way, controller 11 controls the damping force generated by variable damper 7 according to the control amount command value.

[0043] The vehicle behavior control device 1 according to the embodiment has the configuration as described above. Next, a process for variably controlling the damping force characteristics of the variable damper 7 using the controller 11 will be described.

[0044] In the variable damper 7, which is provided between the vehicle body 2 and the wheel 3, a command value (control command) from the controller 11 is input as a command current to the damping force variable actuator 8. This drives the damping force variable actuator 8 to variably control the flow path area of ​​the oil flowing through the variable damper 7. As a result, the damping force characteristics of the variable damper 7 are variably controlled between hard characteristics (hard characteristics) and soft characteristics (soft characteristics) in accordance with the command value.

[0045] Furthermore, the controller 11 according to this embodiment estimates the unsprung acceleration of the rear wheels based on detection signals from the unsprung acceleration sensors 10 provided on the front wheels. At this time, the accuracy of estimating the unsprung acceleration of the rear wheels may decrease depending on the vehicle's running state, etc. In consideration of this, the trajectory correspondence detection unit 24 of the controller 11 detects the correspondence between the trajectories of the front and rear wheels while the vehicle is running. The command value calculation unit 25 calculates a control amount command value, which is a control amount for the suspension device 5 of the front wheels. In addition, the command value calculation unit 25 calculates a control amount command value, which is a control amount for the suspension device 5 of the rear wheels, in accordance with the trajectory correspondence. The controller 11 controls the variable dampers 7 of the front and rear wheels based on these control amount command values. This makes it possible to suppress deterioration of vibration damping performance even in a situation where the accuracy of estimating the unsprung acceleration of the rear wheels decreases.

[0046] To confirm the effect of this embodiment in suppressing deterioration of vibration damping performance, simulation tests were conducted on this embodiment, in which the variable dampers 7 for the rear wheels are controlled in accordance with the correspondence between the trajectories of the front and rear wheels, and on a comparative example, in which the variable dampers 7 for the rear wheels are always controlled using the estimated results for the rear wheels. The results are shown in FIGS. 5 and 6. As shown in FIG. 5, in the comparative example, when the vehicle speed becomes abnormal, the estimation accuracy of the rear wheel unsprung acceleration and the like deteriorates, causing the control timing to deviate from normal, resulting in high acceleration, i.e., a deterioration in ride comfort. In contrast, this embodiment achieves acceleration close to normal, i.e., ride comfort.

[0047] 6, the results of the acceleration power spectral density (PSD) for the rear wheel sprung acceleration also show that the ride comfort is best in the following order: (1) normal, (2) abnormal vehicle speed in this embodiment, and (3) abnormal vehicle speed in the comparative example. Therefore, it can be seen that in this embodiment, even when abnormal vehicle speed occurs, deterioration of vibration damping performance can be suppressed, and ride comfort can be improved compared to the comparative example.

[0048] Thus, this embodiment is a controller 11 for a variable damper 7 of a suspension device 5 provided on a vehicle having front and rear wheels, and includes a trajectory correspondence detection unit 24 that detects the correspondence between the trajectories of the front and rear wheels while the vehicle is running, and a command value calculation unit 25 that calculates a control quantity command value, which is the control quantity for the variable damper 7 of the rear wheels, in accordance with the correspondence between the trajectories.

[0049] At this time, when the correspondence relationship of the trajectories is true for one or all of two or more conditions, the command value calculation unit 25 calculates a control amount command value using a rear wheel state quantity (rear wheel unsprung acceleration) which is a state quantity of the rear wheels calculated with reference to a front wheel state quantity (front wheel unsprung acceleration) which is a state quantity of the front wheels, and when false is included in the condition, it calculates a control amount command value different from when all of the conditions are true.

[0050] Specifically, when all of conditions (A) to (C) based on the front and rear wheel trajectory difference output from front and rear wheel trajectory difference calculation unit 24A and the reverse / abnormality determination result output from reverse / abnormality determination unit 24B are true, command value calculation unit 25 estimates the unsprung acceleration of the rear wheels from the unsprung acceleration of the front wheels and controls variable dampers 7 of the rear wheels based on this estimated value. On the other hand, when any of conditions (A) to (C) is false, command value calculation unit 25 controls variable dampers 7 of the rear wheels using a value different from the estimated value of unsprung acceleration of the rear wheels. Therefore, in this embodiment, when the front and rear wheel trajectory difference is greater than a predetermined threshold, when the vehicle is reverse, or when an abnormality occurs in the vehicle speed signal, it is possible to operate variable dampers 7 of the rear wheels in the same manner as a passive damper, for example, and to suppress deterioration of vibration control performance.

[0051] In addition, the front wheel state quantity is a state quantity related to the acceleration of the front wheels (for example, the unsprung acceleration of the front wheels) obtained by differentiating or integrating the unsprung acceleration of the front wheels, and the rear wheel state quantity is a state quantity (for example, the unsprung acceleration of the rear wheels) obtained by matching the state quantity related to the acceleration of the front wheels with the phase of the rear wheels using the vehicle speed and the wheelbase of the vehicle.

[0052] At this time, if all of the conditions (A) to (C) are true, the command value calculation unit 25 calculates the control variable command value using a rear wheel state quantity (for example, rear wheel unsprung acceleration) calculated with reference to a front wheel state quantity (for example, front wheel unsprung acceleration). If all of the conditions (A) to (C) are true, the accuracy of the rear wheel state quantity calculated with reference to the front wheel state quantity is high. Therefore, the command value calculation unit 25 can obtain the desired vibration damping performance by calculating the control variable command value using the rear wheel state quantity calculated with reference to the front wheel state quantity.

[0053] On the other hand, when any of the conditions (A) to (C) is false, the command value calculation unit 25 calculates a control amount command value that is different from the case where all of the conditions (A) to (C) are true, by referring to the sprung speed of the vehicle. Specifically, when any of the conditions (A) to (C) is false, the command value calculation unit 25 calculates the control amount command value using the corrected relative speed that takes into account the sign of the sprung speed of the vehicle. As a result, when any of the conditions (A) to (C) is false, it is possible to operate, for example, the variable damper 7 of the rear wheel in the same way as a passive damper, and to suppress deterioration of vibration damping performance.

[0054] The conditions (A) to (C) are either that the absolute value of the difference in the trajectories between the front and rear wheels (the difference in the trajectories between the front and rear wheels) based on the vehicle speed and steering angle is equal to or less than a threshold value, that the vehicle is moving forward, and that the detection or estimation state of the vehicle speed is normal. Therefore, the controller 11 can grasp whether the estimation accuracy of the rear wheel state quantity is reduced by determining whether the conditions (A) to (C) are true or false.

[0055] Furthermore, the controller 11 includes a rear wheel unsprung acceleration estimating unit 20 (rear wheel unsprung state quantity calculating unit) that calculates the rear wheel unsprung acceleration, which is the unsprung acceleration of the rear wheels, as the rear wheel state quantity. Therefore, the rear wheel unsprung acceleration estimating unit 20 can calculate the rear wheel unsprung acceleration based on the front wheel unsprung acceleration.

[0056] The rear wheel unsprung state quantity calculation unit is not limited to the rear wheel unsprung acceleration estimation unit 20 that calculates the rear wheel unsprung acceleration, but may be a rear wheel unsprung velocity estimation unit that calculates the rear wheel unsprung velocity. In this case, the rear wheel unsprung velocity estimation unit estimates the rear wheel unsprung velocity based on the front wheel unsprung velocity and the vehicle speed.

[0057] Furthermore, this embodiment is a control method for variable dampers 7 of suspension devices 5 provided on a vehicle having front and rear wheels and capable of adjusting damping force, the method comprising: a front-wheel state quantity calculation step for calculating front-wheel state quantities, which are state quantities of the front wheels; a rear-wheel state quantity calculation step for calculating rear-wheel state quantities, which are state quantities of the rear wheels, using the front-wheel state quantities; and a command value calculation step for calculating control variable command values, which are control variables of the electronically controlled suspensions of the rear wheels, in which, when one or more conditions of the vehicle's running state are all true, the control variable command value is calculated using the rear-wheel state quantities, and when any of the conditions is false, the command value calculation step calculates the control variable command value different from when all of the conditions are true. As a result, when any of conditions (A) to (C) is false, for example, variable dampers 7 of the rear wheels can be operated in the same manner as passive dampers, thereby suppressing deterioration of vibration control performance.

[0058] Next, Fig. 7 shows a second embodiment. The second embodiment is characterized in that the command value calculation unit calculates an unsprung vibration damping control command as a control amount command value. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0059] The controller 31 constitutes a control device according to the second embodiment. The controller 31 is configured similarly to the controller 11 according to the first embodiment, and controls the damping characteristics of the variable damper 7. The controller 31 is constituted, for example, by a microcomputer. The controller 31 is connected to the sprung acceleration sensor 9, the unsprung acceleration sensor 10, the CAN 12, etc. The sprung acceleration, the front wheel unsprung acceleration, the vehicle speed, and the steering angle are input to the controller 31. The output side of the controller 31 is connected to the damping force variable actuator 8 of the variable damper 7. The controller 31 has a memory unit 31A made up of a ROM, a RAM, a non-volatile memory, etc. Various programs, information (vehicle information), data, etc. for controlling the variable damper 7 are stored in the memory unit 31A of the controller 31.

[0060] As shown in FIG. 7, the controller 31 includes a rear wheel unsprung acceleration estimating unit 20, a subtractor 21, an integrator 22, a trajectory correspondence detecting unit 24, and a command value calculating unit 32.

[0061] The command value calculation unit 32 calculates a control amount command value, which is the control amount of the variable damper 7 of the front wheel suspension unit 5. In addition, the command value calculation unit 32 calculates a control amount command value, which is the control amount of the variable damper 7 of the rear wheel suspension unit 5, in accordance with the correspondence relationship of the trajectories. The command value calculation unit 32 includes an unsprung vibration damping control unit 32A and an unsprung vibration damping control command correction unit 32B.

[0062] The unsprung vibration damping control unit 32A calculates an unsprung vibration damping control command for suppressing unsprung vibration based on the relative speed. At this time, the unsprung vibration damping control command is a control amount for the variable damper 7, and is a command value (control amount command value) for a current to be supplied to the damping force variable actuator 8. Note that the unsprung vibration damping control unit 32A may calculate the unsprung vibration damping control command for suppressing unsprung vibration based on the unsprung accelerations of the front wheels and rear wheels.

[0063] Unsprung vibration suppression control command corrector 32B corrects the unsprung vibration suppression control command for the rear wheels based on the correspondence between the trajectories of the front and rear wheels while the vehicle is running, detected by trajectory correspondence detector 24. Unsprung vibration suppression control command corrector 32B receives the unsprung vibration suppression control commands for the front and rear wheels, the front and rear wheel trajectory difference, and the determination results of reverse motion and abnormality. Unsprung vibration suppression control command corrector 32B outputs the unsprung vibration suppression control command for the front wheels output from unsprung vibration suppression controller 32A as is, as the corrected unsprung vibration suppression control command for the front wheels.

[0064] On the other hand, unsprung vibration damping control command corrector 32B corrects the unsprung vibration damping control command for the rear wheels based on the front and rear wheel trajectory difference output from front and rear wheel trajectory difference calculator 24A and the reverse / abnormality determination result output from reverse / abnormality determiner 24B. Similar to relative speed corrector 25A according to the first embodiment, unsprung vibration damping control command corrector 32B determines whether or not the above-mentioned three conditions (A) to (C) are satisfied.

[0065] If any of these three conditions (A) to (C) is false, unsprung vibration damping control command corrector 32B outputs a predetermined corrective current command as the corrected unsprung vibration damping control command for the rear wheels. That is, if at least one of conditions (A) to (C) is not satisfied, unsprung vibration damping control command corrector 32B outputs the predetermined corrective current command as the corrected relative speed of the rear wheels.

[0066] In this case, the predetermined correction current command is a constant current command that can suppress unsprung vibration. Specifically, the predetermined current command is, for example, the minimum current value that can suppress unsprung flutter, and is appropriately set based on test results of an actual vehicle or simulation. Therefore, by supplying a current based on this command to the variable damper 7, for example, the variable damper 7 of the rear wheel can be made to operate in the same manner as a passive damper. Note that the predetermined current command may be changed as appropriate depending on the damping force characteristics of the variable damper 7.

[0067] For example, when it is determined that the front and rear wheel trajectory difference output from front and rear wheel trajectory difference calculation unit 24A is larger than half the width dimension of wheel 3 (tire 4), unsprung vibration damping control command corrector 32B outputs a predetermined correction current command. When it is determined that the vehicle is reversing according to the reverse / abnormality determination result output from reverse / abnormality determination unit 24B, unsprung vibration damping control command corrector 32B outputs a predetermined correction current command. When it is determined that an abnormality has occurred in the vehicle speed signal according to the reverse / abnormality determination result output from reverse / abnormality determination unit 24B, unsprung vibration damping control command corrector 32B outputs a predetermined correction current command.

[0068] In contrast, when all of the conditions (A) to (C) are true, the unsprung vibration damping control command correction unit 32B outputs the unsprung vibration damping control command for the rear wheels output from the unsprung vibration damping control unit 32A as is as the corrected unsprung vibration damping control command for the rear wheels.

[0069] The controller 31 outputs a command signal (command current) according to the command value of the corrected unsprung vibration damping control command output from the unsprung vibration damping control command corrector 32B to the damping force variable actuator 8. In this way, the controller 31 controls the damping force generated by the variable damper 7 according to the command value.

[0070] Thus, the second embodiment can also achieve substantially the same effects as the first embodiment.

[0071] In the first embodiment, the command value calculation unit 25 calculates the control amount command value, which is the control amount of the suspension device 5, using the BLQ control law (bilinear optimal control law), but the present invention is not limited to this. The command value calculation unit 25 may calculate the control amount command value using the skyhook control law, the H∞ control law, etc.

[0072] The command value calculation unit 25 according to the first embodiment outputs a control command for sprung vibration damping, and the command value calculation unit 25 according to the second embodiment outputs a control command for unsprung vibration damping. The present invention is not limited to this, and the command value calculation unit may calculate the control command value taking into account both the control command for sprung vibration damping and the control command for unsprung vibration damping. Furthermore, the command value calculation unit may calculate the control command value taking into account various control commands, such as control commands for handling stability control.

[0073] The command value calculation units 25 and 32 according to the above embodiments determine whether or not the three conditions (A) to (C) include "false." However, the present invention is not limited to this, and the command value calculation units may determine whether or not one of the three conditions (A) to (C) includes "false," or may determine whether or not two of the conditions include "false," or may determine whether or not four or more of the conditions include "false."

[0074] In the above-described embodiments, the front wheel state quantity is the front wheel unsprung acceleration and the rear wheel state quantity is the rear wheel unsprung acceleration, but the present invention is not limited to this. The front wheel state quantity may be, for example, the front wheel unsprung jerk obtained by differentiating the front wheel unsprung acceleration, or the front wheel unsprung velocity obtained by integrating the front wheel unsprung acceleration. Similarly, the rear wheel state quantity may be, for example, the rear wheel unsprung jerk or the rear wheel unsprung velocity.

[0075] In each of the above embodiments, the rear wheel unsprung state quantity calculation unit is the rear wheel unsprung acceleration estimation unit 20 that calculates the rear wheel unsprung acceleration, but the present invention is not limited to this. The rear wheel unsprung state quantity calculation unit may calculate, for example, rear wheel unsprung jerk or rear wheel unsprung velocity as the rear wheel state quantity.

[0076] In the above-described embodiments, the controllers 11 and 31 acquire vehicle travel parameters, including wheel speed and steering angle, via the CAN 12. However, the present invention is not limited to this. The controllers 11 and 31 may acquire detected values ​​of wheel speed and steering angle directly from, for example, a wheel speed sensor and a steering angle sensor. The steering angle is not limited to the turning angle of the steering wheel, but may be the turning angle of the steered wheels (front wheels).

[0077] In the above-described embodiments, the electronically controlled suspension (force generating mechanism) is described as a variable damper 7 made of a semi-active damper. The present invention is not limited to this, and an active damper (either an electric actuator or a hydraulic actuator) may be used as the electronically controlled suspension. In the above-described embodiments, the electronically controlled suspension that generates an adjustable force between the vehicle body 2 side and the wheel 3 side is described as a variable damper 7 made of a damping force adjustable hydraulic shock absorber. The present invention is not limited to this, and the electronically controlled suspension may be configured as an air suspension, a stabilizer (kinesus), an electromagnetic suspension, or the like, in addition to a hydraulic shock absorber.

[0078] In the above embodiments, the vehicle behavior control device used in a four-wheeled vehicle has been described as an example. However, the present invention is not limited to this and can also be applied to, for example, two-wheeled and three-wheeled vehicles, or work vehicles and transport vehicles such as trucks and buses.

[0079] The specific numerical values ​​described in the above embodiments are merely examples, and the present invention is not limited to the exemplified values. [Explanation of symbols]

[0080] 2: vehicle body, 3: wheels (front wheels, rear wheels), 5: suspension device (electronically controlled suspension), 7: adjustable damping force shock absorber (variable damper), 8: variable damping force actuator, 9: sprung acceleration sensor, 10: unsprung acceleration sensor, 11, 31: controller (control device), 20: rear wheel unsprung acceleration estimation unit, 24: trajectory correspondence detection unit, 25, 32: command value calculation unit

Claims

1. A control device for an electronically controlled suspension provided in a vehicle having front and rear wheels, a trajectory correspondence detection unit that detects a correspondence relationship between trajectories of the front wheels and the rear wheels while the vehicle is running; a command value calculation unit that calculates a control amount command value, which is a control amount of an electronically controlled suspension of the rear wheels, in accordance with the correspondence relationship of the loci; A control device for an electronically controlled suspension.

2. The command value calculation unit When the correspondence relationship of the loci is true for all of one or more conditions, the control variable command value is calculated using a rear wheel state quantity that is a state quantity of the rear wheels, which is calculated with reference to a front wheel state quantity that is a state quantity of the front wheels; If the condition is false, the control amount command value calculated is different from the case where all the conditions are true. The control device for an electronically controlled suspension according to claim 1.

3. the front wheel state quantity is an unsprung acceleration of the front wheel or a state quantity related to the acceleration of the front wheel obtained by differentiating or integrating the unsprung acceleration of the front wheel, The rear wheel state quantity is a state quantity obtained by matching the acceleration-related state quantity of the front wheels with the phase of the rear wheels using the vehicle speed and the wheelbase of the vehicle. The control device for an electronically controlled suspension according to claim 2.

4. The command value calculation unit When the condition is false, the control amount command value different from the case where all the conditions are true is calculated by referring to the sprung speed of the vehicle.

4. The control device for an electronically controlled suspension according to claim 2 or 3.

5. The condition is one of: an absolute value of a difference in trajectory between the front wheels and the rear wheels based on the vehicle speed and steering angle of the vehicle is equal to or less than a threshold value; the vehicle is moving forward; and the detection or estimation of the vehicle speed is normal.

4. The control device for an electronically controlled suspension according to claim 2 or 3.

6. a rear wheel unsprung state quantity calculation unit that calculates a rear wheel unsprung velocity that is an unsprung velocity of the rear wheel or a rear wheel unsprung acceleration that is an unsprung acceleration of the rear wheel as the rear wheel state quantity; 4. The control device for an electronically controlled suspension according to claim 2 or 3.

7. A control method for an electronically controlled suspension that is provided on a vehicle having front and rear wheels and has adjustable damping force, comprising: a front wheel state quantity calculation step of calculating a front wheel state quantity that is a state quantity of the front wheel; a rear wheel state quantity calculation step of calculating a rear wheel state quantity, which is a state quantity of the rear wheels, using the front wheel state quantity; a command value calculation step of calculating a control variable command value, which is a control variable of the electronically controlled suspension of the rear wheels, in which, when one or more conditions of the running state of the vehicle are all true, the control variable command value is calculated using the rear wheel state quantity, and when one or more of the conditions are false, the control variable command value different from when all of the conditions are true is calculated; A control method for an electronically controlled suspension comprising:

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