Control apparatus

Abstract

A controller (21) serving as a control apparatus controls a shock absorber (7, 10) that serves as a force generation mechanism. The controller (21) comprises a distance delay output processing unit (22E), a pitch rate calculation / determination unit (22J), and a correction value calculation unit (22K). The distance delay output processing unit (22E) determines an estimated unsprung acceleration value on a rear wheel (4) side of a vehicle (1) on the basis of an unsprung acceleration on a front wheel (3) side. The pitch rate calculation / determination unit (22J) detects a nose-down state of a vehicle body (2). The correction value calculation unit (22K) corrects the estimated unsprung acceleration value on the rear wheel (4) side on the basis of output from the pitch rate calculation / determination unit (22J).

Description

control device

[0001] The present disclosure relates to a control device that is mounted on a vehicle such as an automobile and controls a force generating mechanism such as a damping force adjustable shock absorber.

[0002] For example, Patent Document 1 describes a control device that estimates the unsprung acceleration of rear wheels from the unsprung acceleration of front wheels and uses the estimated value to perform feedforward control of a shock absorber (damping force adjustable shock absorber).

[0003] International Publication No. 2022 / 024758

[0004] The control device of Patent Document 1 calculates the delay (time delay, distance delay) of the rear wheels relative to the front wheels from the vehicle speed, which is the speed of the vehicle. The control device then estimates the unsprung acceleration of the rear wheels by outputting the acceleration (front wheel unsprung acceleration signal) captured by the unsprung acceleration sensor of the front wheels as an estimated unsprung acceleration value of the rear wheels (estimated rear wheel unsprung acceleration signal) at the timing when the delay has elapsed. With this configuration, for example, when the vehicle passes over a bumpy road, the estimation accuracy of the unsprung acceleration of the rear wheels can be ensured. However, for example, when the vehicle passes over a trapezoidal road or a concave road, the estimation accuracy of the unsprung acceleration of the rear wheels may decrease due to fluctuations in the dynamic load of the vehicle at that time.

[0005] An object of one embodiment of the present invention is to provide a control device that can improve the estimation accuracy of rear wheel unsprung acceleration (rear wheel unsprung acceleration estimated value).

[0006] One embodiment of the present invention is a control device that controls a force generating mechanism that is provided between the body and wheels of a vehicle and generates an adjustable force between the body and the wheels, and includes a rear wheel unsprung acceleration estimation unit that calculates an estimated value of the unsprung acceleration of the rear wheels based on the unsprung acceleration of the front wheels of the vehicle, a front sloping state detection unit that detects a front sloping state of the body, and a rear wheel unsprung acceleration correction unit that corrects the estimated value of the unsprung acceleration of the rear wheels based on the output of the front sloping state detection unit.

[0007] According to one embodiment of the present invention, it is possible to improve the estimation accuracy of the estimated unsprung acceleration value of the rear wheels (estimated rear wheel unsprung acceleration value).

[0008] 1 is an overall configuration diagram showing a four-wheeled vehicle equipped with a control device according to an embodiment. FIG. 2 is a block diagram showing the control device (ECU), force generating mechanism (variable damping force damper), etc. in FIG. 1. FIG. 3 is a characteristic diagram showing an example of time changes in sensor values ​​of front wheel unsprung acceleration and rear wheel unsprung acceleration, and time changes in sensor values ​​and estimated values ​​of rear wheel unsprung acceleration when passing over a protruding road. FIG. 4 is an explanatory diagram showing a vehicle traveling on a trapezoidal road. FIG. 5 is a characteristic diagram showing an example of time changes in sensor values ​​of front wheel unsprung acceleration and rear wheel unsprung acceleration, and time changes in sensor values ​​and estimated values ​​(reference example) of rear wheel unsprung acceleration when passing over a trapezoidal road. FIG. 6 is a characteristic diagram showing an example of time changes in sensor values ​​of front wheel unsprung acceleration and rear wheel unsprung acceleration, and time changes in sensor values ​​and estimated values ​​(embodiment) of rear wheel unsprung acceleration when passing over a trapezoidal road. FIG. 7 is a characteristic diagram showing an example of time changes in sensor values ​​of front wheel unsprung acceleration and rear wheel unsprung acceleration, and time changes in pitch rate when passing over a trapezoidal road. 1 is a characteristic diagram showing an example of time-varying sensor values ​​of front wheel unsprung acceleration and rear wheel unsprung acceleration, and time-varying pitch rate when traveling over a protruding road, a concave road, and a trapezoidal road; FIG. 2 is a characteristic diagram showing an example of time-varying sensor values ​​and estimated values ​​of pitch rate; FIG. 3 is a characteristic diagram showing an example of time-varying rear wheel unsprung acceleration and ground load;

[0009] Hereinafter, a control device according to an embodiment will be described with reference to the accompanying drawings, taking as an example a case where the control device is used in an automobile (more specifically, a four-wheeled automobile).

[0010] 1, a total of four wheels 3, 4, for example, left and right front wheels 3 and left and right rear wheels 4 (only one shown), are provided on the underside of a vehicle body 2 that constitutes the body of a vehicle 1, which is an automobile. Front-wheel suspensions 5, 5 (hereinafter referred to as front wheel suspensions 5) are provided between the left and right front wheels 3 and the vehicle body 2. The front wheel suspensions 5 include suspension springs 6 (hereinafter referred to as springs 6) and adjustable damping shock absorbers 7 (hereinafter referred to as shock absorbers 7) that are provided in parallel with the springs 6.

[0011] Rear-wheel suspensions 8, 8 (hereinafter referred to as rear wheel suspensions 8) are provided between the left and right rear wheels 4 and the vehicle body 2. The rear wheel suspensions 8 include suspension springs 9 (hereinafter referred to as springs 9) and adjustable damping shock absorbers 10 (hereinafter referred to as shock absorbers 10) provided in parallel with the springs 9. The shock absorbers 7, 10 are configured, for example, with semi-active dampers that are hydraulic cylinder devices (variable damping shock absorbers) that allow for adjustable damping force. In other words, the vehicle 1 is equipped with a semi-active suspension system that uses variable damping shock absorbers.

[0012] Here, the shock absorbers 7, 10 are force generating mechanisms provided between the body 2 and the wheels 3, 4 of the vehicle 1. More specifically, the shock absorbers 7, 10 are variable damping force generating devices (variable damping force shock absorbers). The characteristics of the generated damping force (damping force characteristics) of the shock absorbers 7, 10 are variably controlled by a controller 21, which will be described later. For this purpose, the shock absorbers 7, 10 are provided with actuators (not shown) including a damping force adjustment valve and a solenoid or the like, for continuously (or in multiple stages) adjusting the damping force characteristics from hard characteristics (hard characteristics) to soft characteristics (soft characteristics). The damping force characteristics of the shock absorbers 7, 10 are variably adjusted in accordance with a command current (control signal) supplied from the controller 21 to the actuator.

[0013] The damping force adjustment valve may have a conventionally known structure, such as a pressure control system that controls the pilot pressure of a damping force generating valve or a flow control system that controls the passage area. The shock absorbers 7 and 10 may be any force generating mechanism that can continuously (or multi-stagely) adjust the damping force, such as a pneumatic damper, an electromagnetic damper, an electrorheological fluid damper (ER damper), or a magnetic fluid damper. The shock absorbers 7 and 10 may also be force generating mechanisms, such as an air damper (air suspension) that uses an air spring, a hydraulic damper in which front, rear, left, and right hydraulic cylinders are connected by piping, or a stabilizer that applies force to the movement of the left and right wheels.

[0014] Furthermore, the shock absorbers 7, 10 may be force generating mechanisms capable of generating thrust, i.e., full active dampers configured with hydraulic actuators, electric actuators, or pneumatic actuators. In other words, the vehicle 1 may be equipped with a full active suspension system using full active dampers. That is, the shock absorbers 7, 10 are force generating mechanisms capable of adjusting the force generated between the body 2 side and the wheels 3, 4 side of the vehicle 1, and various force generating mechanisms may be used, such as variable damping force hydraulic dampers, electrorheological fluid dampers, pneumatic dampers, electromagnetic dampers, hydraulic actuators, electric actuators, pneumatic actuators, etc.

[0015] Next, the various sensors 11, 12A, 12B, 12C, 13A, and 13B that detect the state of the vehicle 1 will be described.

[0016] 1, a vehicle 1 is provided with a vehicle speed sensor 11, sprung acceleration sensors 12A, 12B, and 12C, and unsprung acceleration sensors 13A and 13B. In this embodiment, three sprung acceleration sensors 12A, 12B, and 12C are provided on the vehicle body 2 side, and two unsprung acceleration sensors 13A and 13B are provided on the front wheel 3 side.

[0017] The vehicle speed sensor 11 is provided, for example, on an output shaft (not shown) of a transmission mounted on the vehicle 1. The vehicle speed sensor 11 detects the vehicle speed (body speed) of the vehicle 1 (body 2). The detected information (signal corresponding to the vehicle speed) of the vehicle speed sensor 11 is output to a controller 21 (described later) via a communication line (CAN) such as an in-vehicle LAN. The vehicle speed can also be calculated from the detected information (signal corresponding to the wheel speed) of a wheel speed sensor (not shown) that detects the rotational speed of the wheels 3, 4.

[0018] The sprung acceleration sensors 12A, 12B, and 12C are provided, for example, on the vehicle body 2, which is the sprung side of the vehicle 1. In this embodiment, the sprung acceleration sensors 12A, 12B, and 12C are provided at a position corresponding to the left front wheel 3, a position corresponding to the right front wheel 3, and a position corresponding to one of the left and right rear wheels 4 (for example, the right rear wheel 4). The sprung acceleration sensors 12A, 12B, and 12C detect the vertical acceleration of the vehicle 1 (vehicle body 2) at their respective positions. That is, the left front sprung acceleration sensor 12A provided on the left front wheel 3 side detects the vertical acceleration on the left front side of the vehicle body 2 (left front sprung acceleration).

[0019] The right front sprung acceleration sensor 12B provided near the right front wheel 3 detects the vertical acceleration (right front sprung acceleration) on the right front side of the vehicle body 2. The right rear sprung acceleration sensor 12C provided near the right rear wheel 4 detects the vertical acceleration (right rear sprung acceleration) on the right rear side of the vehicle body 2. The detected information (signals corresponding to the vertical acceleration) of the sprung acceleration sensors 12A, 12B, 12C is output to a controller 21 (described later) via a communication line (CAN) such as an in-vehicle LAN communication line. The vertical acceleration on the left rear side of the vehicle body 2 is estimated by the controller 21 using the vertical accelerations of the three sprung acceleration sensors 12A, 12B, 12C.

[0020] The unsprung acceleration sensors 13A, 13B are provided, for example, on the wheel 3 side, which is the unsprung side of the vehicle 1. In this embodiment, the unsprung acceleration sensors 13A, 13B are provided respectively on the left front wheel 3 side and the right front wheel 3 side. The unsprung acceleration sensors 13A, 13B detect the vertical acceleration of the unsprung front wheels 3, 3 at their respective positions. That is, the left front unsprung acceleration sensor 13A provided on the left front wheel 3 side detects the vertical acceleration of the unsprung part on the left front wheel 3 side (left front unsprung acceleration).

[0021] The right front unsprung acceleration sensor 13B provided on the right front wheel 3 side detects the vertical acceleration (right front unsprung acceleration) of the unsprung parts on the right front wheel 3 side. The detection information (signals corresponding to the vertical acceleration) of the unsprung parts on the right front wheel 3 side is output to a controller 21 (described later) via a communication line (CAN) such as an in-vehicle LAN communication line. As will be described later, the vertical acceleration of the unsprung parts on the left rear wheel side and the vertical acceleration of the unsprung parts on the right rear wheel 4 side are estimated by the controller 21 using the vertical accelerations of the unsprung parts acceleration sensors 13A, 13B on the two front wheel 3, 3 sides and the travel distance (delay distance) of the vehicle 1.

[0022] The sprung acceleration sensors 12A, 12B, 12C and the unsprung acceleration sensors 13A, 13B constitute a part of a vehicle behavior detection means for detecting the behavior of the vehicle. The vehicle behavior detection means is not limited to an acceleration sensor, and may be constituted by, for example, a vehicle height sensor, a stroke sensor, a displacement sensor, a preview sensor, etc. The vehicle height sensor is, for example, a sensor that detects the displacement amount of a suspension arm corresponding to the vehicle height. The stroke sensor and the displacement sensor are, for example, sensors that detect the stroke amount (extension amount, contraction amount) of the shock absorbers 7, 10. The preview sensor is, for example, an external environment recognition sensor that recognizes the state around the vehicle 1 (e.g., the state of the road surface).

[0023] The external environment recognition sensor measures the positions of objects around the vehicle 1 (for example, vertical displacement of the road surface). The external environment recognition sensor may be, for example, a camera such as a stereo camera or a single camera (for example, a digital camera), and / or a radar such as a laser radar, an infrared radar, or a millimeter-wave radar (for example, a light-emitting element such as a semiconductor laser and a light-receiving element that receives the light), a LiDAR, or a sonar. Note that the external environment recognition sensor is not limited to a camera, radar, LiDAR, or sonar, and various sensors (detection devices, measurement devices, radio wave detectors) that can recognize (detect) the state of the external environment around the vehicle 1 may be used. The external environment recognition sensor may be provided, for example, at a position corresponding to the upper side of the windshield of the vehicle 1, on the front bumper of the vehicle, or the like.

[0024] Next, the controller 21 that controls the shock absorbers 7 and 10 will be described.

[0025] The controller 21 is a control device including a microcomputer, a power supply circuit, and a drive circuit, and is also called an ECU (Electronic Control Unit). The controller 21 is a control device for the suspension system, i.e., a suspension ECU (shock absorber ECU). The controller 21 controls the shock absorbers 7 and 10 (adjusts the damping force) based on sensor information detected by the sensors 11, 12A, 12B, 12C, 13A, 13B, etc.

[0026] For this purpose, the input side of the controller 21 is connected to the sensors 11, 12A, 12B, 12C, 13A, and 13B. A signal corresponding to the vehicle speed detected by the vehicle speed sensor 11, a signal corresponding to the vertical acceleration of the sprung part detected by the sprung part acceleration sensors 12A, 12B, and 12C, and a signal corresponding to the vertical acceleration of the unsprung part detected by the unsprung part acceleration sensors 13A and 13B are input to the controller 21. On the other hand, the output side of the controller 21 is connected to the shock absorbers 7 and 10, which serve as control dampers. The controller 21 outputs a control signal (command current) to actuators of the shock absorbers 7 and 10 (for example, solenoids that adjust the valve opening pressure of damping force control valves).

[0027] The controller 21 includes a control unit 21A (see FIG. 1) that performs arithmetic processing such as a CPU (Central Processing Unit), and a storage unit 21B (see FIG. 1) that includes memories such as a ROM, a RAM, a non-volatile memory, etc. The storage unit 21B stores a processing program that calculates (estimates) the vehicle state (vehicle motion, vehicle behavior) from information (input signals) from the sensors 11, 12A, 12B, 12C, 13A, and 13B.

[0028] More specifically, the memory unit 21B stores a processing program for calculating (estimating) the sprung velocity and relative velocity (stroke velocity) at the positions of the shock absorbers 7 and 10 from the information (input signals) of the sensors 11, 12A, 12B, 12C, 13A, and 13B. The memory unit 21B also stores a processing program for calculating the damping force to be generated in the shock absorbers 7 and 10 from the sprung velocity and relative velocity (stroke velocity) at the positions of the shock absorbers 7 and 10, a processing program for outputting a control signal corresponding to the damping force to be generated, and the like.

[0029] As a control law (control law for ride comfort and control law for handling stability) for calculating the damping force of the shock absorbers 7, 10, for example, a skyhook control law, a BLQ control law (bilinear optimal control law), an H∞ control law, or the like can be used. For example, when the motion (behavior) of the sprung vehicle body 2 is to be decelerated by the damping force of the shock absorbers 7, 10, the controller 21 increases the damping force of the shock absorbers 7, 10, and when the motion (behavior) of the sprung vehicle body 2 is to be accelerated by the damping force of the shock absorbers 7, 10, the controller 21 reduces the damping force of the shock absorbers 7, 10. The shock absorbers 7, 10, which are variable damping force dampers, have the function of suppressing vibration of the vehicle body 2 by varying the damping force to appropriately damp the up and down movement of each wheel 3, 4.

[0030] The aforementioned Patent Document 1 describes a control device that estimates the unsprung acceleration of the rear wheels from the unsprung acceleration of the front wheels and uses the estimated value to perform feedforward control of a shock absorber (damping force adjustable shock absorber). The control device of Patent Document 1 calculates the delay (time delay, distance delay) of the rear wheels relative to the front wheels from the vehicle speed. The control device then estimates the unsprung acceleration of the rear wheels by outputting the acceleration (front wheel unsprung acceleration signal) captured by the unsprung acceleration sensor of the front wheels as an estimated value of the unsprung acceleration of the rear wheels (estimated rear wheel unsprung acceleration signal) when the delay has elapsed.

[0031] With this configuration, for example, when the vehicle passes over a bumpy road, the estimation accuracy of the rear wheel unsprung acceleration can be ensured. However, for example, when the vehicle passes over a trapezoidal road or a concave road, the estimation accuracy of the rear wheel unsprung acceleration may be reduced due to fluctuations in the dynamic load of the vehicle. Furthermore, the estimation accuracy of the rear wheel unsprung acceleration may be reduced due to vehicle behavior, such as when the vehicle dives or squats. This reduction in the estimation accuracy of the rear wheel unsprung acceleration may result in a deterioration in ride comfort.

[0032] Figure 3 shows time variations in the sensor values ​​of the front wheel unsprung acceleration and the rear wheel unsprung acceleration, as well as time variations in the sensor value and estimated value of the rear wheel unsprung acceleration when the vehicle 1 passes over a bumpy road. The dashed characteristic line 51 in Figure 3 corresponds to the sensor value of the front wheel unsprung acceleration (front sensor value), and the solid characteristic line 52 in Figure 3 corresponds to the sensor value of the rear wheel unsprung acceleration (rear sensor value). The two-dot chain characteristic line 53 in Figure 3 corresponds to the estimated value of the rear wheel unsprung acceleration (rear estimated value) that is output by shifting the sensor value of the front wheel unsprung acceleration by the amount of delay between the front and rear wheels.

[0033] 3, the difference (deviation) between the estimated value of the rear wheel unsprung acceleration and the sensor value of the rear wheel unsprung acceleration is small. Therefore, when the vehicle travels over a bumpy road, the estimation accuracy of the estimated value of the rear wheel unsprung acceleration can be ensured. On the other hand, FIG. 4 shows a vehicle 101 traveling on a trapezoidal road 102 (trapezoidal ridge 102A).

[0034] Fig. 5 shows time variations in the sensor values ​​of the front wheel unsprung acceleration and the rear wheel unsprung acceleration, and time variations in the sensor value and estimated value of the rear wheel unsprung acceleration when the vehicle 101 passes over the trapezoidal road 102 shown in Fig. 4. A dashed characteristic line 61 in Fig. 5 corresponds to the sensor value of the front wheel unsprung acceleration (front sensor value), and a solid characteristic line 62 in Fig. 5 corresponds to the sensor value of the rear wheel unsprung acceleration (rear sensor value). Furthermore, a two-dot chain characteristic line 63 in Fig. 5 corresponds to the estimated value of the rear wheel unsprung acceleration (rear estimated value) that is output by shifting the sensor value of the front wheel unsprung acceleration by the amount of delay between the front and rear wheels.

[0035] Comparing characteristic line 62 and characteristic line 63 in Figure 5 shows that there is a large difference (deviation) between the estimated value of rear wheel unsprung acceleration and the sensor value of rear wheel unsprung acceleration. Specifically, when descending trapezoidal protrusion 102A, the estimated value of rear wheel unsprung acceleration is larger than the actual value (sensor value). Therefore, simply delaying the sensor value of front wheel unsprung acceleration and outputting it as the estimated value of rear wheel unsprung acceleration may reduce the estimation accuracy of the estimated value when passing over trapezoidal road 102. In other words, the difference between the rear unsprung acceleration and the front unsprung acceleration due to road surface input may reduce the estimation accuracy of the estimated value of rear unsprung acceleration.

[0036] Therefore, in the embodiment, the estimation accuracy of the unsprung acceleration (rear wheel unsprung acceleration estimated value) is improved by correcting the unsprung acceleration on the rear wheel 4 side in consideration of fluctuations in the dynamic load and behavior of the vehicle 1. Specifically, when estimating the unsprung signal on the rear wheel 4 side (rear wheel unsprung acceleration) from the unsprung signal on the front wheel 3 side (front wheel unsprung acceleration), the unsprung signal on the rear wheel 4 side (rear wheel unsprung acceleration) is corrected based on the pitch state (front downward state) of the vehicle 1. In other words, the pitch rate of the vehicle 1 is used to correct the estimated value of the unsprung signal on the rear wheel 4 side (rear wheel unsprung acceleration). As a result, as shown in FIG. 6 described later, the estimation accuracy of the unsprung signal on the rear wheel 4 side (rear wheel unsprung acceleration) is improved, and ride comfort is improved.

[0037] The controller 21 of the embodiment will be described in detail below with reference to FIG.

[0038] 2 , a controller 21 serving as a control device (suspension control device) is connected to each of the sensors 11, 12A, 12B, 12C, 13A, and 13B directly or via a communication line (CAN). The controller 21 controls the shock absorbers 7 and 10, which are variable damping force dampers, based on detection signals from the sensors 11, 12A, 12B, 12C, 13A, and 13B. In this embodiment, the controller 21 controls the shock absorbers 10 of the control target wheels (rear wheels 4) located behind the detection target portions (front wheels 3) of the unsprung acceleration sensors 13A and 13B based on detection values ​​from the unsprung acceleration sensors 13A and 13B of the front wheels 3 and 3 provided on the vehicle 1.

[0039] That is, the controller 21 delays an input signal corresponding to the detection value of the unsprung acceleration sensors 13A, 13B on the front wheels 3, 3 side, and controls a location (on the rear wheels 4 side) different from the location where the detection value was detected. Specifically, the controller 21 calculates a movement distance (delay distance) from the detection target portion (front wheels 3, 3) from the vehicle speed for each control cycle, and controls the shock absorbers 10, 10 of the control target wheels (rear wheels 4) located behind the detection target portions (front wheels 3, 3) using the detection values ​​of the unsprung acceleration sensors 13A, 13B on the front wheels 3, 3 that are delayed by this movement distance (delay distance). In other words, the controller 21 calculates a movement distance from the detection target portion (front wheels 3, 3) from the vehicle speed for each control cycle, and controls the shock absorbers 10, 10 of the control target wheels located behind the control target wheels (rear wheels 4) based on this movement distance and the detection values ​​of the unsprung acceleration sensors 13A, 13B on the front wheels 3, 3 side. In this case, the controller 21 estimates the suspension behavior on the rear wheel 4 side using the "sprung acceleration" obtained directly from the sprung acceleration sensors 12A, 12B, 12C and the "unsprung acceleration" on the front wheel 3, 3 side taking into account distance delay.

[0040] For this purpose, the controller 21 includes a vehicle state quantity calculation unit 22 and a suspension control unit 23. The vehicle state quantity calculation unit 22 receives as input the "vehicle speed" from the vehicle speed sensor 11, the "left front sprung acceleration," the "right front sprung acceleration," and the "right rear sprung acceleration" from the sprung acceleration sensors 12A, 12B, and 12C, and the "left front unsprung acceleration" and the "right front unsprung acceleration" from the unsprung acceleration sensors 13A and 13B.

[0041] The vehicle state quantity calculation unit 22 calculates the "left front sprung velocity," "right front sprung velocity," "left rear sprung velocity," "right rear sprung velocity," "left front relative velocity," "right front relative velocity," "left rear relative velocity," and "right rear relative velocity" based on the three sprung accelerations (sprung vertical accelerations) and the two unsprung accelerations (unsprung vertical accelerations). The vehicle state quantity calculation unit 22 outputs the calculated "left front sprung velocity," "right front sprung velocity," "left rear sprung velocity," "right rear sprung velocity," "left front relative velocity," "right front relative velocity," "left rear relative velocity," and "right rear relative velocity" to the suspension control unit 23.

[0042] Here, the sprung velocity is the vertical velocity of the sprung part, i.e., the vertical velocity at the corresponding position on the vehicle body 2. The "left front sprung velocity" is the vertical velocity of the vehicle body 2 at a position corresponding to the left front wheel 3, and can be calculated from the "left front sprung acceleration". The "right front sprung velocity" is the vertical velocity of the vehicle body 2 at a position corresponding to the right front wheel 3, and can be calculated from the "right front sprung acceleration".

[0043] The "right rear sprung velocity" is the vertical velocity of the vehicle body 2 at a position corresponding to the right rear wheel 4, and can be calculated from the "right rear sprung acceleration." The "left rear sprung velocity" is the vertical velocity of the vehicle body 2 at a position corresponding to the left rear wheel, and can be estimated (calculated) from the "left front sprung acceleration," "right front sprung acceleration," and "right rear sprung acceleration," or from the "left front sprung velocity," "right front sprung velocity," and "right rear sprung velocity."

[0044] Furthermore, the relative speed is the vertical relative speed between the sprung side and the unsprung side, i.e., the relative speed between the wheel 3 (4) at the corresponding position and the vehicle body 2. The "left front relative speed" is the vertical relative speed between the left front side of the vehicle body 2 and the left front wheel 3, and can be calculated from the "left front sprung acceleration" and the "left front unsprung acceleration". The "right front relative speed" is the vertical relative speed between the right front side of the vehicle body 2 and the right front wheel 3, and can be calculated from the "right front sprung acceleration" and the "right front unsprung acceleration".

[0045] The "right rear relative speed" is the vertical relative speed between the right rear side of the vehicle body 2 and the right rear wheel 4, and can be calculated from the "right rear sprung acceleration" and the "right rear unsprung acceleration." In this case, the "right rear unsprung acceleration" is the value of the "right front unsprung acceleration" detected by the right front unsprung acceleration sensor 13B going back from the current time, specifically, the value detected at a time before the right front unsprung acceleration sensor 13B moved a distance equivalent to the wheelbase.

[0046] The "left rear relative velocity" is the vertical relative velocity between the left rear side of the vehicle body 2 and the left rear wheel, and can be calculated from the "left rear sprung acceleration" and the "left rear unsprung acceleration". In this case, the "left rear sprung acceleration" can be estimated (calculated) from the "left front sprung acceleration", the "right front sprung acceleration", and the "right rear sprung acceleration". The "left rear unsprung acceleration" is the "left front unsprung acceleration" detected by the left front unsprung acceleration sensor 13A going back from the current point in time, specifically, the value detected at a point in time before the left front unsprung acceleration sensor 13A moved a distance equivalent to the wheelbase.

[0047] 2 illustrates control of the right side of the vehicle 1, i.e., control of the shock absorber 7 on the right front side (Fr) and the shock absorber 10 on the right rear side (Rr). That is, FIG. 2 illustrates a case in which the "right front sprung velocity," "right rear sprung velocity," "right front relative velocity," and "right rear relative velocity" are calculated based on the "right front sprung acceleration" detected by the right front sprung acceleration sensor 12B, the "right rear sprung acceleration" detected by the right rear sprung acceleration sensor 12C, and the "right front unsprung acceleration" detected by the right front unsprung acceleration sensor 13B. Control of the left side of the vehicle 1, i.e., control of the shock absorber 7 on the left front side and the shock absorber 10 on the left rear side, is similar to control of the right side, except that the left rear sprung acceleration is an estimated value rather than a detected value. Therefore, hereinafter, control of the shock absorbers 7, 10 on the right side of the vehicle 1 will be mainly described.

[0048] 2, the vehicle state quantity calculation unit 22 includes a first integrator 22A, a first subtractor 22B, a second integrator 22C, a distance calculation unit 22D, a distance delay output processor 22E, a second subtractor 22F, and a third integrator 22G. The vehicle state quantity calculation unit 22 also includes a sampling unit 22H, a pitch rate calculation / determination unit 22J, and a correction value calculation unit 22K.

[0049] The "right front sprung acceleration" detected by right front sprung acceleration sensor 12B and the "right rear sprung acceleration" detected by right rear sprung acceleration sensor 12C are input to a first integration unit 22A via a sampling unit 22H. In addition, the "right front sprung acceleration" detected by right front sprung acceleration sensor 12B and the "right rear sprung acceleration" detected by right rear sprung acceleration sensor 12C are input to a pitch rate calculation / determination unit 22J.

[0050] Furthermore, the "right front sprung acceleration" detected by right front sprung acceleration sensor 12B is input to first subtraction unit 22B via sampling unit 22H, and the "right rear sprung acceleration" detected by right rear sprung acceleration sensor 12C is input to second subtraction unit 22F via sampling unit 22H. Furthermore, the "right front unsprung acceleration" detected by right front unsprung acceleration sensor 13B is input to first subtraction unit 22B and distance delay output processing unit 22E via sampling unit 22H. Furthermore, the "vehicle speed" detected by vehicle speed sensor 11 is input to distance calculation unit 22D.

[0051] The sampling unit 22H receives as input the “right front sprung acceleration” detected by the right front sprung acceleration sensor 12B, the “right rear sprung acceleration” detected by the right rear sprung acceleration sensor 12C, and the “right front unsprung acceleration” detected by the right front unsprung acceleration sensor 13B. The sampling unit 22H also receives as input the travel distance from a distance calculation unit 22D, which will be described later.

[0052] At the timing when a certain moving distance (for example, 5 cm) has been reached, the sampling unit 22H outputs the "right front sprung acceleration" detected by the right front sprung acceleration sensor 12B, the "right rear sprung acceleration" detected by the right rear sprung acceleration sensor 12C, and the "right front unsprung acceleration" detected by the right front unsprung acceleration sensor 13B. That is, the sampling unit 22H outputs the "right front sprung acceleration", "right rear sprung acceleration", and "right front unsprung acceleration" every certain moving distance (for example, 5 cm).

[0053] The first integrator 22A receives the "right front sprung acceleration" detected by the right front sprung acceleration sensor 12B and the "right rear sprung acceleration" detected by the right rear sprung acceleration sensor 12C via the sampling unit 22H. The first integrator 22A calculates the "right front sprung velocity" by integrating the "right front sprung acceleration" detected by the right front sprung acceleration sensor 12B. The first integrator 22A also calculates the "right rear sprung velocity" by integrating the "right rear sprung acceleration" detected by the right rear sprung acceleration sensor 12C. The first integrator 22A outputs the calculated "right front sprung velocity" and "right rear sprung velocity" to the suspension control unit 23.

[0054] The first subtraction unit 22B receives the "right front sprung acceleration" detected by the right front sprung acceleration sensor 12B and the "right front unsprung acceleration" detected by the right front unsprung acceleration sensor 13B via the sampling unit 22H. The first subtraction unit 22B calculates a "right front relative acceleration" by subtracting the "right front unsprung acceleration" detected by the right front unsprung acceleration sensor 13B from the "right front sprung acceleration" detected by the right front sprung acceleration sensor 12B. The first subtraction unit 22B outputs the calculated "right front relative acceleration" to the second integration unit 22C.

[0055] The second integrator 22C receives the "right front relative acceleration" calculated by the first subtractor 22B. The second integrator 22C calculates the "right front relative velocity" by integrating the "right front relative acceleration" calculated by the first subtractor 22B. The second integrator 22C outputs the calculated "right front relative velocity" to the suspension control unit 23.

[0056] The distance calculation unit 22D receives an input of the "vehicle speed" detected by the vehicle speed sensor 11. The distance calculation unit 22D calculates the travel distance of the vehicle 1 by multiplying the vehicle speed by time (the control period of the controller 21). The distance calculation unit 22D outputs the calculated travel distance to the distance delay output processing unit 22E. The distance calculation unit 22D also outputs the calculated travel distance to the sampling unit 22H.

[0057] The distance traveled calculated by the distance calculation unit 22D is input to the distance delay output processing unit 22E. That is, the distance traveled by the vehicle 1 is input to the distance delay output processing unit 22E for each control cycle. In addition, the "right front unsprung acceleration" detected by the right front unsprung acceleration sensor 13B is input to the distance delay output processing unit 22E via the sampling unit 22H. That is, the "right front unsprung acceleration" sampled by the sampling unit 22H for every fixed distance traveled (for example, 5 cm) is input to the distance delay output processing unit 22E.

[0058] The distance delay output processing unit 22E memorizes (stores) the "right front unsprung acceleration" for each fixed moving distance (for example, 5 cm). The distance delay output processing unit 22E outputs the "right front unsprung acceleration" as the "right rear unsprung acceleration" at a timing that takes into account a delay according to the moving distance (more specifically, at the timing when the vehicle 1 has moved by the wheelbase). In this way, the distance delay output processing unit 22E performs control to output the "right front unsprung acceleration" as the "right rear unsprung acceleration" at a timing that takes into account a distance delay, i.e., output timing control (delay distance control).

[0059] Here, the distance delay output processing unit 22E is provided with the table shown in Table 1 below. This table is stored in the storage unit 21B (memory) of the controller 21. The table stores (memorizes) the "right front unsprung acceleration" for each index corresponding to the moving distance (delay distance). In Table 1, the wheelbase of the vehicle 1 is set to 2.6 m, and the interval is set to the moving distance of the sampling unit 22H (for example, 5 cm).

[0060]

[0061] The distance delay output processing unit 22E acquires the right front unsprung acceleration sampled by the sampling unit 22H from the right front unsprung acceleration sensor 13B every fixed movement distance (for example, 5 cm) and stores it in an internal memory (storage unit 21B of the controller 21). In other words, the distance delay output processing unit 22E acquires new right front unsprung acceleration every fixed movement distance (for example, 5 cm) and shifts the previously acquired table of right front unsprung acceleration by the amount of movement distance. Then, the distance delay output processing unit 22E outputs the value of right front unsprung acceleration at which the total movement distance becomes the wheelbase after the shift as the right rear unsprung acceleration. In other words, the distance delay output processing unit 22E outputs the right front unsprung acceleration, the output timing of which has been adjusted (controlled) based on the movement distance, to the correction value calculation unit 22K as the right rear unsprung acceleration (estimated unsprung acceleration).

[0062] In this way, the distance delay output processing unit 22E associates the table index with the delay distance, and when a certain distance is traveled, the table index is incremented by one. In the table of Table 1 above, the wheelbase of the vehicle 1 is set to 2.6 m, the increment width is set to 5 cm, and the index shifts by one for each 5 cm travel. This configuration makes it possible to reduce the amount of data stored internally (total memory capacity). Furthermore, shortening the increment width can improve control performance. The increment width can be set according to the required performance and memory size (storage capacity).

[0063] The pitch rate calculation / determination unit 22J receives as input the "right front sprung acceleration" detected by the right front sprung acceleration sensor 12B and the "right rear sprung acceleration" detected by the right rear sprung acceleration sensor 12C. The pitch rate calculation / determination unit 22J corresponds to a front sloping state detection unit that detects a front sloping state of the vehicle body 2. The pitch rate calculation / determination unit 22J calculates (estimates) the pitch rate of the vehicle 1 based on the right front sprung acceleration (front wheel sprung acceleration) and the right rear sprung acceleration (rear wheel sprung acceleration). The pitch rate (estimated pitch rate value) is calculated, for example, using the following equation 1.

[0064]

[0065] Fig. 9 shows changes over time in the sensor value and estimated value of the pitch rate. In Fig. 9, a solid line 81 corresponds to the sensor value of the pitch rate, and a dashed line 82 corresponds to the estimated value of the pitch rate. As shown in Fig. 9, a highly accurate pitch rate (estimated pitch rate value) can be obtained using Equation 1. Note that the sensor value of a pitch rate sensor provided in the vehicle 1 (vehicle body 2) may also be used as the pitch rate.

[0066] The pitch rate calculation / determination unit 22J calculates the correction amount for the unsprung acceleration on the rear wheel 4 side (rear) output from the distance-delay output processing unit 22E, i.e., the correction amount for the right rear unsprung acceleration, based on the calculated pitch rate (pitch rate estimate value). The pitch rate calculation / determination unit 22J outputs the correction amount for the right rear unsprung acceleration corresponding to the pitch rate at that time to the correction value calculation unit 22K.

[0067] The correction value calculation unit 22K receives the right rear unsprung acceleration (estimated unsprung acceleration) from the distance delay output processing unit 22E. The correction value calculation unit 22K also receives the correction amount for the right rear unsprung acceleration corresponding to the pitch rate at that time from the pitch rate calculation / determination unit 22J. The correction value calculation unit 22K corrects the right rear unsprung acceleration based on the right rear unsprung acceleration and the correction amount corresponding to the pitch rate. For example, the larger the pitch rate (front downward state), the smaller the right rear unsprung acceleration is corrected to. The correction amount varies depending on the vehicle, but for example, it is corrected to about 1 / 3 on a trapezoidal road. The correction value calculation unit 22K outputs the corrected right rear unsprung acceleration, which becomes the corrected unsprung acceleration (corrected unsprung acceleration), to the second subtraction unit 22F.

[0068] The second subtraction unit 22F receives the "right rear sprung acceleration" detected by the right rear sprung acceleration sensor 12C and the "corrected right rear unsprung acceleration" output from the correction value calculation unit 22K as input. The second subtraction unit 22F calculates the "right rear relative acceleration" by subtracting the "corrected right rear unsprung acceleration" corrected by the correction value calculation unit 22K from the "right rear sprung acceleration" detected by the right rear sprung acceleration sensor 12C. The second subtraction unit 22F outputs the calculated "right rear relative acceleration" to the third integration unit 22G.

[0069] The third integrator 22G receives the "right-rear relative acceleration" calculated by the second subtractor 22F. The third integrator 22G calculates the "right-rear relative speed" by integrating the "right-rear relative acceleration" calculated by the second subtractor 22F. The third integrator 22G outputs the calculated "right-rear relative speed" to the suspension control unit 23.

[0070] The suspension control unit 23 receives the "left front sprung speed," "right front sprung speed," "left rear sprung speed," "right rear sprung speed," "left front relative speed," "right front relative speed," "left rear relative speed," and "right rear relative speed" from the vehicle state quantity calculation unit 22. Note that FIG. 2 shows control of the right side of the vehicle 1. Therefore, in FIG. 2, the suspension control unit 23 receives the "right front sprung speed," "right rear sprung speed," "right front relative speed," and "right rear relative speed" from the vehicle state quantity calculation unit 22.

[0071] The suspension control unit 23 calculates the damping force to be generated in the shock absorbers 7, 10 in accordance with these inputs. For example, the suspension control unit 23 calculates the damping force to be generated in the shock absorbers 7, 10 based on a control law such as the skyhook control law. Then, the suspension control unit 23 outputs a control signal (command current) corresponding to the damping force to be generated in the shock absorbers 7, 10 to the shock absorbers 7, 10, which are control dampers. That is, the suspension control unit 23 outputs a command current (control signal) corresponding to the damper command value to an actuator of the shock absorber 7, 10 (for example, a solenoid that adjusts the valve opening pressure of a damping force control valve).

[0072] To summarize what has been discussed so far, the vehicle 1 is equipped with a controller 21 as a control device and shock absorbers 7, 10 as force generating mechanisms. The controller 21 controls the shock absorbers 7, 10. The shock absorbers 7, 10 are provided between the body 2 and the wheels 3, 4 of the vehicle 1. The shock absorbers 7, 10 generate a force that can be adjusted between the body 2 and the wheels 3, 4. The controller 21 has a distance delay output processing unit 22E as a rear wheel unsprung acceleration estimator, a pitch rate calculation / determination unit 22J as a front downward state detection unit, and a correction value calculation unit 22K as a rear wheel unsprung acceleration corrector.

[0073] The distance delay output processing unit 22E determines an estimated unsprung acceleration value of the rear wheels 4 based on the unsprung acceleration of the front wheels 3 of the vehicle 1. The unsprung acceleration of the front wheels 3 is detected by the unsprung acceleration sensors 13A, 13B. The pitch rate calculation / determination unit 22J detects a sloping front state of the vehicle body 2. The pitch rate calculation / determination unit 22J detects the sloping front state using the pitch rate. The correction value calculation unit 22K corrects the estimated unsprung acceleration value of the rear wheels 4 (estimated rear wheel unsprung acceleration value) based on the output of the pitch rate calculation / determination unit 22J. The correction value calculation unit 22K changes the unsprung acceleration of the rear wheels 4 (estimated rear wheel unsprung acceleration value) depending on the sloping front state.

[0074] The front sagging of the vehicle body 2 occurs, for example, when traveling on a trapezoidal road 102 or a recessed road. The front sagging of the vehicle body 2 also occurs, for example, when braking. That is, the front sagging of the vehicle body 2 includes the trapezoidal road 102, a recessed road, and braking.

[0075] As described above, the distance delay output processing unit 22E outputs the sensor value of the front unsprung acceleration (right front unsprung acceleration) stored in the table (memory) as the rear unsprung acceleration (right rear unsprung acceleration) at the timing when the delay of the rear wheels 4 relative to the front wheels 3 has elapsed. In this way, the distance delay output processing unit 22E estimates the rear unsprung acceleration (right rear unsprung acceleration) from the sensor value of the front unsprung acceleration (right front unsprung acceleration).

[0076] When estimating the rear unsprung acceleration in this manner, the estimation accuracy of the rear unsprung acceleration can be ensured if, for example, the front unsprung acceleration when the front wheels 3 pass point A is the same (or approximately the same) as the rear unsprung acceleration when the rear wheels 4 subsequently pass point A. However, on some road surfaces, for example, pitching of the vehicle 1 may cause the front and rear unsprung accelerations to change, resulting in a decrease in the estimation accuracy of the rear unsprung acceleration.

[0077] That is, based on fluctuations in the dynamic load of the vehicle, vehicle behavior, etc., there may be a difference between the front unsprung acceleration when passing point A and the rear unsprung acceleration when passing point A thereafter. For this reason, simply estimating the rear unsprung acceleration from the front unsprung acceleration by considering only the delay may result in a decrease in the estimation accuracy of the rear unsprung acceleration.

[0078] For example, consider a case where the vehicle 1 travels over a trapezoidal road 102 as shown in Fig. 4. In this case, the change in the unsprung acceleration of the front and the unsprung acceleration of the rear differs at the descending position of the trapezoidal bulge 102A. Specifically, as shown in Fig. 5 and Fig. 7 (described later), when the vehicle 1 descends the bulge 102A of the trapezoidal road 102, the change in the rear sensor value may be smaller than the change in the front sensor value due to a change in the dynamic load of the vehicle 1 (occurrence of pitching). Therefore, simply outputting the front sensor value as the rear estimated value at the timing when the delay of the rear wheels 4 relative to the front wheels 3 has elapsed will result in the rear estimated value being larger than the actual value.

[0079] As a result, the value (estimated relative velocity) calculated from this estimated rear value (unsprung acceleration) is also estimated to be larger than the actual value. In this case, if left as is, the suspension control unit 23 will calculate the control force of the shock absorbers 7, 10 by reading a map of a region where the piston speed is high, which will result in a damping force larger than the actual damping force. As a result, the actual damping force generated by the shock absorbers 7, 10 will be smaller than the damping force that is intended to be generated by control. As a result, there is a possibility that sprung vibration damping will be insufficient, resulting in increased rear vibration (unsprung vibration damping will be excessively controlled).

[0080] Therefore, in this embodiment, as described above, the estimated unsprung acceleration of the rear (rear wheel 4 side), i.e., the estimated value of the unsprung acceleration output from the distance delay output processing unit 22E, is corrected according to the pitch rate of the vehicle 1 at that time. That is, when traveling on a trapezoidal road, the rear unsprung acceleration becomes small when the vehicle leans forward (lowers forward). Therefore, it is determined from the pitch rate whether the vehicle body is leaning forward, and the estimated value of the unsprung acceleration on the rear side is corrected according to the determination result.

[0081] The reason why the rear unsprung acceleration is small is thought to be due to fluctuations in the dynamic load of the vehicle 1 (vehicle body 2). Therefore, in a situation involving pitch, the estimation accuracy of the unsprung acceleration can be improved by correcting the estimated rear unsprung acceleration according to the pitch rate. Note that in a situation involving pitch, in addition to being caused by road surface input, for example, the vehicle 1 (vehicle body 2) may dive or squat. Therefore, in such a case as well, the estimation accuracy of the unsprung acceleration can be improved by correcting the estimated rear unsprung acceleration according to the pitch rate.

[0082] 7 shows the time changes in the sensor values ​​of the front wheel unsprung acceleration and the rear wheel unsprung acceleration, and the time changes in the pitch rate when passing over the trapezoidal road 102. As shown in FIG. 7, the unsprung acceleration on the front wheel side (front) and the unsprung acceleration on the rear wheel side (rear) differ in their tendency to change when going up and down the trapezoidal bulge 102A. That is, when going up the trapezoidal bulge 102A, the unsprung acceleration on the front wheel side (front) and the unsprung acceleration on the rear wheel side (rear) are almost the same in their tendency to change. In contrast, when going down the trapezoidal bulge 102A, the unsprung acceleration on the rear wheel side (rear) is smaller in tendency to change than the unsprung acceleration on the front wheel side (front).

[0083] Therefore, when estimating the rear unsprung acceleration, if the estimated value of the rear unsprung acceleration is output at a fixed ratio to the sensor value of the front unsprung acceleration, the rear unsprung acceleration (estimated value) may deviate from the actual rear unsprung acceleration. That is, if the sensor value of the front unsprung acceleration is used as the estimated value of the rear unsprung acceleration at the uphill position of the trapezoidal protrusion 102A, the estimated value at the downhill portion will not match the actual rear unsprung acceleration. Also, looking at the pitch rate at this time, it can be seen that when the front of the vehicle 1 (vehicle body 2) descends, the rear unsprung acceleration is smaller than the front unsprung acceleration.

[0084] This tendency is similar for other inputs. Figure 8 shows the time changes in the sensor values ​​of the front wheel unsprung acceleration and the rear wheel unsprung acceleration, as well as the time changes in the pitch rate, when traveling over a protruding road, a concave road, and a trapezoidal road. An example of a protrusion on a protruding road is a protrusion with a length of approximately 0.01 to 0.02 m in the direction of travel of the vehicle 1 and a height of approximately 0.02 m. An example of a recess on a concave road is a protrusion with a length of approximately 0.1 to 0.25 m in the direction of travel of the vehicle 1 and a depth of approximately 0.01 to 0.03 m. An example of a protrusion on a trapezoidal road is a protrusion with a length of approximately 14 m in the direction of travel of the vehicle 1, a length of approximately 12 m in the upper side, and a height of approximately 0.07 m. As shown in Figure 8 , when the front of the vehicle body drops on a concave road or a trapezoidal road, the rear unsprung acceleration is smaller than the front unsprung acceleration.

[0085] Therefore, in the embodiment, the pitch rate calculation / determination unit 22J calculates (estimates) the pitch rate using the above-mentioned equation 1. Then, the pitch rate calculation / determination unit 22J determines whether the front of the vehicle 1 (vehicle body 2) is tilted downward from the calculated pitch rate (pitch rate estimate value). Then, if the pitch rate calculation / determination unit 22J determines that the front of the vehicle 1 (vehicle body 2) is tilted downward, it calculates a correction amount for the right rear unsprung acceleration output from the distance delay output processing unit 22E, i.e., a correction amount for the right rear unsprung acceleration according to the pitch rate, and outputs the correction amount to the correction value calculation unit 22K. The correction value calculation unit 22K corrects the right rear unsprung acceleration based on the right rear unsprung acceleration output from the distance delay output processing unit 22E and the correction amount output from the pitch rate calculation / determination unit 22J, and outputs the corrected right rear unsprung acceleration (corrected right rear unsprung acceleration).

[0086] 10 shows the time-dependent changes in rear wheel unsprung acceleration and ground load. As shown in FIG. 10, the unsprung acceleration also decreases as the ground load decreases. That is, a correlation is observed between the decrease in ground load and the decrease in unsprung acceleration. Therefore, it is possible to detect the front sagging state of the vehicle 1 (vehicle body 2) based on the ground load, and correct the right rear unsprung acceleration (rear wheel unsprung acceleration) output from the distance delay output processing unit 22E.

[0087] According to this embodiment, it is possible to prevent a decrease in the estimation accuracy of the rear unsprung acceleration due to road surface input and driver input. As a result, it is possible to prevent changes in ride comfort and handling stability. That is, it is possible to improve the estimation accuracy of the rear unsprung acceleration and improve ride comfort when the dynamic load changes significantly due to the vehicle sprung mass input, such as on a road surface where the dynamic load changes significantly, such as a trapezoidal road, or when diving or squatting.

[0088] The control device according to the embodiment has the above-described configuration, and its operation will now be described.

[0089] When the behavior (state) of the vehicle 1 changes as the vehicle 1 travels, the change in behavior is detected by a vehicle speed sensor 11, three sprung acceleration sensors 12A, 12B, and 12C, and two unsprung acceleration sensors 13A and 13B mounted on the vehicle 1, and input to a controller 21 that controls the shock absorbers 7 and 10. The controller 21 outputs control signals (command currents) to the shock absorbers 7 and 10 to control the damping forces of the shock absorbers 7 and 10 based on the detection values ​​(detection signals) of the sensors 11, 12A, 12B, 12C, 13A, and 13B.

[0090] In this embodiment, the controller 21 controls the shock absorbers 10 on the rear wheel 4 side based on the "unsprung acceleration on the rear wheel 4 side" estimated from the "travel distance from the front wheels 3" and the "detection values ​​of the unsprung acceleration sensors 13A and 13B on the front wheel 3 side." That is, the controller 21 controls the shock absorbers 10 on the rear wheel 4 side using the "right front unsprung acceleration" detected by the unsprung acceleration sensors 13A and 13B on the front wheel 3 side, which is a value detected at a time before the unsprung acceleration sensors 13A and 13B on the front wheel 3 side moved a distance equivalent to the wheelbase. Therefore, the memory capacity can be kept constant depending on the travel distance (e.g., wheelbase and step size) regardless of vehicle speed. This avoids large memory consumption at extremely low speeds and makes it easier to estimate memory consumption at the design stage.

[0091] Moreover, the controller 21 has a correction value calculation unit 22K that corrects the unsprung acceleration estimate value of the rear wheels 4 (rear wheel unsprung acceleration estimate value) based on the forward sloping state of the vehicle body 2. That is, the rear wheel unsprung acceleration estimate value output from the distance delay output processing unit 22E is corrected by the correction value calculation unit 22K. Therefore, this correction value calculation unit 22K can suppress a decrease in accuracy of the rear wheel unsprung acceleration estimate value due to the forward sloping state of the vehicle body 2. This can improve the estimation accuracy of the rear wheel unsprung acceleration estimate value, and ultimately of estimates such as relative velocity calculated from this rear wheel unsprung acceleration estimate value.

[0092] FIG. 6 shows the time changes in the sensor values ​​of the front wheel unsprung acceleration and the rear wheel unsprung acceleration, and the time changes in the sensor value and estimated value of the rear wheel unsprung acceleration when the vehicle 1 passes through the trapezoidal road 102 shown in FIG. 4 according to an embodiment. The dashed characteristic line 71 in FIG. 6 corresponds to the sensor value (front sensor value) of the front wheel unsprung acceleration, and the solid characteristic line 72 in FIG. 6 corresponds to the sensor value (rear sensor value) of the rear wheel unsprung acceleration. The dashed-dotted characteristic line 73 in FIG. 6 corresponds to the corrected estimated value (rear estimated value) obtained by correcting the estimated value of the rear wheel unsprung acceleration output by shifting the sensor value of the front wheel unsprung acceleration by the amount of delay between the front and rear wheels, according to the pitch rate of the vehicle 1 (vehicle body 2). As is clear from a comparison of FIG. 5 and FIG. 6, according to the embodiment, the difference (deviation) between the estimated value of the rear wheel unsprung acceleration and the sensor value of the rear wheel unsprung acceleration can be reduced, thereby improving the estimation accuracy of the estimated value of the rear wheel unsprung acceleration. In the reference example of FIG. 5, the estimated unsprung acceleration value is not corrected by the pitch rate calculation / determination unit 22J and the correction value calculation unit 22K as in the embodiment.

[0093] In the embodiment, the correction value calculation unit 22K changes the rear wheel unsprung acceleration depending on the front-sloped state, so that the correction value calculation unit 22K can correct the rear wheel unsprung acceleration depending on the front-sloped state.

[0094] In this embodiment, the pitch rate calculation / determination unit 22J detects the front-sloping state using the pitch rate, and the correction value calculation unit 22K can correct the estimated rear wheel unsprung acceleration value based on the front-sloping state determined using the pitch rate of the pitch rate calculation / determination unit 22J.

[0095] In the above-described embodiment, the vehicle behavior detection means is the unsprung acceleration sensors 13A and 13B. However, this is not limiting, and the vehicle behavior detection means may be, for example, a vehicle height sensor, a stroke sensor, a displacement sensor, or a preview sensor. The preview sensor is, for example, an external environment recognition sensor that detects the state of the road surface of the vehicle 1 (displacement of the road surface). The external environment recognition sensor (preview sensor) may be, for example, a camera such as a stereo camera or a single camera (e.g., a digital camera), and / or a radar such as a laser radar, an infrared radar, or a millimeter-wave radar (e.g., a light-emitting element such as a semiconductor laser and a light-receiving element that receives the light), a LiDAR, or a sonar. The external environment recognition sensor (preview sensor) is not limited to a camera, radar, LiDAR, or sonar. Various sensors (detection devices, measurement devices, radio wave detectors) that can recognize (detect) the state of the external environment around the vehicle 1 may be used. The external environment recognition sensor (preview sensor) may be, for example, provided at a position corresponding to the upper side of the vehicle's windshield or on the front bumper of the vehicle.

[0096] When the vehicle behavior detection means is configured with a preview sensor, the control device (controller) can be configured to estimate the unsprung acceleration of the front wheels from the detection value of the preview sensor, i.e., the road surface condition ahead, and use this estimated unsprung acceleration of the front wheels as the unsprung acceleration of the rear wheels.Then, these estimated unsprung accelerations of the front wheels and the rear wheels are used to control the shock absorber, which serves as a force generating mechanism.In this case, too, the estimated unsprung acceleration of the rear wheels can be corrected depending on the forward sagging state of the vehicle (vehicle body).

[0097] In the embodiment, the sprung acceleration sensors 12A, 12B, 12C are provided at three locations, namely, the left front side, the right front side, and the right rear side, of the vehicle body 2. However, the present invention is not limited to this, and the sprung acceleration sensors may be provided at three locations, namely, the left front side, the right front side, and the left rear side, or at three locations, namely, the left front side, the left rear side, and the right rear side, of the vehicle body. In other words, if the vehicle body is considered to be a rigid body, the sprung acceleration sensors can be provided at three locations on the vehicle body to estimate the vertical movement of one remaining point from the vertical movements of three points on its surface.

[0098] In the embodiment, the shock absorber 10 on the left rear wheel (not shown) side and the shock absorber 10 on the right rear wheel 4 side are controlled based on the detection value of the left front unsprung acceleration sensor 13A on the left front wheel 3 side and the detection value of the right front unsprung acceleration sensor 13B on the right front wheel 3 side. However, the present invention is not limited to this. For example, by providing an unsprung acceleration sensor on the rear wheel side of one of the left and right rear wheels, the shock absorber on one rear side may be controlled based on the detection value of the unsprung acceleration sensor on the rear wheel side, and the shock absorber on the other rear side may be controlled based on the detection value (and movement distance) of the unsprung acceleration sensor on the front wheel side. In other words, the force generating mechanism of the control target wheel located behind the detection target portion of at least one vehicle behavior detection means provided on the vehicle may be controlled based on the detection value of the vehicle behavior detection means.

[0099] According to the embodiment described above, the control device includes a rear wheel unsprung acceleration correction unit that corrects the estimated rear wheel unsprung acceleration value (rear wheel unsprung acceleration estimate value) based on the front-sloped state of the vehicle body. Therefore, the rear wheel unsprung acceleration correction unit can prevent the accuracy of the estimated rear wheel unsprung acceleration value from decreasing due to the front-sloped state of the vehicle body. This improves the accuracy of the estimated rear wheel unsprung acceleration value, and ultimately the accuracy of the estimated values ​​of the relative velocity and the like calculated from the estimated rear wheel unsprung acceleration value.

[0100] According to the embodiment, the rear wheel unsprung acceleration correcting unit changes the rear wheel unsprung acceleration in accordance with the front-sloped state. Therefore, the rear wheel unsprung acceleration correcting unit can correct the rear wheel unsprung acceleration in accordance with the front-sloped state.

[0101] According to the embodiment, the front-sloping state detection unit detects the front-sloping state using the pitch rate, and therefore the rear-wheel unsprung acceleration correction unit can correct the rear-wheel unsprung acceleration estimate value based on the front-sloping state detected using the pitch rate.

[0102] REFERENCE SIGNS LIST 1 vehicle 2 vehicle body 3 front wheels (wheels) 4 rear wheels (wheels) 7, 10 shock absorber (force generating mechanism) 21 controller (control device) 22E distance delay output processing unit (rear wheel unsprung acceleration estimation unit) 22J pitch rate calculation / determination unit (front downward tilt state detection unit) 22K correction value calculation unit (rear wheel unsprung acceleration correction unit)

Claims

1. A control device that controls a force generating mechanism that is provided between a vehicle body and a wheel and generates an adjustable force between the body and the wheel, the control device having: a rear wheel unsprung acceleration estimating unit that calculates an estimated value of rear wheel unsprung acceleration based on the unsprung acceleration of the front wheels of the vehicle; a front sagging state detecting unit that detects a front sagging state of the vehicle body; and a rear wheel unsprung acceleration correcting unit that corrects the estimated value of rear wheel unsprung acceleration based on the output of the front sagging state detecting unit.

2. The control device according to claim 1, wherein the rear wheel unsprung acceleration correction unit changes the unsprung acceleration of the rear wheels in accordance with the front downward tilt state.

3. The control device according to claim 1, wherein the forward tilt state detection unit detects the forward tilt state using a pitch rate.

Images