JP4797869B2 - Vehicle suspension system - Google Patents

Description

  The present invention relates to a vehicle suspension system that includes a fluid spring as a suspension spring and includes an actuator that exerts a force to bring a vehicle body and a wheel closer to and away from each other in the vertical direction.

A vehicle suspension system including a fluid spring such as an air spring has a function of changing the vehicle height by allowing fluid to flow into and out of the fluid spring, as described in Patent Document 1 below, for example. Is present. On the other hand, as described in Patent Document 2, for a vehicle suspension system, a system including an actuator that exerts a force for moving a vehicle body and a wheel in the vertical direction is also being studied. In the described system, the vehicle height can be quickly changed by the inflow / outflow of the fluid to / from the fluid spring and the force of the actuator.
Japanese Patent Application No. 10-338015 JP 2006-117210 A

  When the vehicle height is changed using a fluid spring, the vehicle body may be twisted due to various influences such as the road surface where the vehicle is stopped, the order when changing the vehicle height for each wheel, etc. Force, that is, warp force may remain. Such a warp force is a cause of lowering the ride comfort, running stability, etc. of the vehicle, so it is desirable to remove it. In the system described in Patent Document 1, the warp phenomenon is suppressed by optimizing the process of inflow / outflow of fluid with respect to the fluid spring. However, the optimization method described in that document is complicated and simple. If it becomes possible to remove the warp force by the vehicle, it is possible to improve the practicality of a system having a fluid spring capable of changing the vehicle height. This invention is made | formed in view of such a situation, and makes it a subject to improve the practicality of the system provided with the fluid spring and actuator mentioned above.

In order to solve the above problems, a vehicle suspension system according to the present invention is a suspension system including a fluid spring capable of changing a vehicle height, and an actuator that exerts a force for moving a vehicle body and a wheel closer to and away from each other. When the warp force due to the vehicle height change is resolved using the force of the actuator , the vehicle height change is executed, the warp force generated by the vehicle height change is grasped, and the recognized warp The present invention is characterized in that after the vehicle height is changed again in a state where the actuator force for releasing the force is exerted and the actuator force is exerted, the actuator force is released .

According to the vehicle suspension system of the present invention, by using the actuator force, the warp force can be easily eliminated, and the actuator force for eliminating the warp force in the vehicle travel after changing the vehicle height is not required. Thus, an excellent system can be realized from the viewpoint of energy saving. Therefore, the vehicle suspension system of the present invention is a highly practical system.

Aspects of the Invention

  In the following, some aspects of the invention that can be claimed in the present application (hereinafter sometimes referred to as “claimable invention”) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is merely for the purpose of facilitating the understanding of the claimable inventions, and is not intended to limit the combinations of the constituent elements constituting those inventions to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which some constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention.

In each of the following items, in (1), “the vehicle height change is executed, the warp force generated by the vehicle height change is grasped, and the actuator force for canceling the grasped warp force is demonstrated. In addition, the technical feature that “actuator force is released after the vehicle height change is performed again in a state where the actuator force is exerted” corresponds to claim 1, and (4) in claim 1 The technical features of (5) and (5) are added to claim 2, the technical features of (6) are added to claim 2, and claims 3 to 3 are added. What added the technical feature of (8) to any one of them is Claim 4, and what added the technical feature of (9) to any one of Claims 1 to 4 is Claim 5, Each corresponds.

(1) It is provided corresponding to four wheels on the front, rear, left and right, each elastically connecting the wheel corresponding to itself and the vehicle body, and the wheel corresponding to itself by inflow and outflow of fluid to itself Four fluid springs that change the distance between the vehicle body wheels, which is the distance in the vertical direction from the vehicle body,
A fluid inflow / outflow device for flowing in / out of fluid to each of the four fluid springs;
Four actuators provided corresponding to the four wheels, each exhibiting an actuator force that is a force for approaching and separating the corresponding wheel and the vehicle body in the vertical direction;
A device that controls the operation of the fluid inflow / outflow device and the four actuators, and (a) controls the operation of the fluid inflow / outflow device and changes the distance between the vehicle wheels for each of the four wheels. A vehicle height change control unit that changes the vehicle height, and (b) an actuator force for controlling the operation of the four actuators to counteract the warp force acting on the vehicle body due to the vehicle height change, A vehicle suspension system comprising: a control device having a warp elimination control unit that is exerted on the four actuators.

  According to the aspect of this item, since the force exerted by the actuator is used, it is possible to easily eliminate the warp force resulting from the change in the vehicle height by the fluid spring.

  The specific structure of the “fluid spring” in the aspect of this section is not particularly limited. For example, a diaphragm type air spring in which compressed air as a fluid is sealed in a pressure chamber, hydraulic oil as a fluid It is possible to adopt various structures such as a hydraulic spring that includes a cylinder that is filled with and an accumulator that communicates with the cylinder. The specific structure of the “fluid inflow / outflow device” is not particularly limited, and includes a fluid supply device, a discharge device, and the like suitable for the fluid to be employed, such as a compressor and a pump. Anything is acceptable.

  As the “actuator” in this aspect, various types such as a hydraulic type and an electromagnetic type can be adopted. For example, if an electromagnetic actuator is adopted, it is possible to execute vibration damping control and body posture control by the actuator, taking advantage of its good controllability, etc., and an active suspension can be easily constructed. it can. Further, in view of providing various functions to the “control device”, for example, it is possible to adopt a device mainly composed of a computer.

  (2) The vehicle suspension according to (1), wherein the control device is capable of controlling the operation of the four actuators by the warp elimination control unit after the vehicle height is changed by the vehicle height control unit. system.

  In short, the aspect of this section is an aspect in which the warp force generated by the execution of the vehicle height can be canceled after the vehicle height has been changed once. According to the aspect of this section, the generated warp force can be quickly eliminated.

  (3) In the item (1) or (2), the control device can change the vehicle height by the vehicle height change control unit while the operation of the four actuators is being controlled by the warp elimination control unit. The suspension system for a vehicle according to item).

  In short, the aspect of this section is an aspect in which the vehicle height can be changed in anticipation of the warp force that will occur after the vehicle height is changed. If the vehicle height is changed in a state where the actuator force for eliminating the warp force generated after the vehicle height is changed in advance, the actuator force is released after the vehicle height is changed, so that the warp force remains after the vehicle height is changed. Can be prevented. According to the aspect of this section, since the actuator force for eliminating the warp force is not required in the vehicle travel after the vehicle height is changed, an excellent system can be realized from the viewpoint of energy saving. In the aspect of this section, for example, the control device once executes the vehicle height change by the vehicle height change control unit, grasps the warp force generated by the vehicle height change, and the grasped warp force. It is also possible to execute a warp elimination control that exerts an actuator force for solving the problem, and execute a vehicle height change by the vehicle height change control unit again under the execution of the control.

  (4) The vehicle suspension system includes a warp force estimation device that estimates a warp force, and the control device executes the warp elimination control based on an estimation result of the warp force estimation device. The vehicle suspension system according to any one of items (1) to (3).

  The “warp force estimation device” in the aspect of this section is not particularly limited by the warp force estimation process. For example, it may be an apparatus that estimates based on a change in the distance between vehicle body wheels described later. Further, for example, a device that estimates the warp force based on the fluid pressure in the fluid spring may be used.

(5) The control device
A warp force estimating unit for causing each of the four actuators to exert an actuator force having a set magnitude and estimating a warp force based on a variation in a distance between vehicle body wheels for each of the four wheels. Have
The vehicle suspension system according to item (4), wherein the warp force estimation device includes the warp force estimation unit.

  The aspect of this section is an aspect which makes it possible to estimate the warp force using the actuator force. Specifically, based on the variation in the distance between the vehicle body wheels, for example, the characteristic difference between the fluid springs at that time (for example, the characteristic difference due to the influence of the fluid amount inside the left and right fluid springs, etc.) This is a mode in which the warp force at that time can be estimated. When the warp force is estimated based on the fluid pressure in the fluid spring, a pressure sensor for detecting the fluid pressure is required, so that the structure of the system is complicated accordingly. Since the embodiment of this section does not require such a pressure sensor, the structure of the system can be simplified. Note that the “actuator force of a set magnitude” in the aspect of this section may be a force set to the same magnitude for all actuators, or a force set to a different magnitude for each actuator. It may be.

  (6) The warp force estimation unit estimates a spring constant of each of the four fluid springs based on a change in the distance between vehicle body wheels for each of the four wheels, and warp force based on the estimated spring constant The vehicle suspension system according to item (5), wherein the vehicle suspension system is estimated.

  The spring constant of the fluid spring is a typical parameter indicating the characteristics of the fluid spring. If the spring constant of each fluid spring is grasped, the warp force that easily acts on the vehicle body based on the distance between the vehicle bodies of each wheel. Can be estimated.

  (7) The vehicle suspension system includes four vehicle body wheel distance sensors that are provided corresponding to the four wheels and detect the vehicle wheel distances for the wheels corresponding to the vehicle wheels. The vehicle suspension system according to any one of items 1 to (6).

  The structure of the “vehicle body wheel distance sensor” in the aspect of this section is not particularly limited, and a structure that has already been adopted or studied in various suspension systems can be widely used. It is. The detection value by the sensor can be used for the control by the vehicle height change control unit and the estimation by the warp force estimation unit.

  (8) The control device includes a vibration damping control unit that controls the operation of each of the four actuators and causes each actuator force to be exerted as a damping force for at least one of sprung vibration and unsprung vibration. The vehicle suspension system according to any one of items (1) to (7).

  The mode of this section is a mode that enables the actuator to function as a so-called shock absorber. According to the aspect of this section, active damping force control such as vibration damping control based on the Skyhook damper theory can be executed.

  (9) The control device includes an attitude control unit that controls the operation of each of the four actuators and exerts each actuator force as a force for suppressing at least one of a roll and a pitch of the vehicle body. The vehicle suspension system according to any one of items (1) to (8).

  The aspect of this term is an aspect which makes it possible to suppress the inclination of the vehicle body which occurs when the vehicle turns, for example, when the vehicle accelerates or decelerates, by the actuator. According to the aspect of this section, active posture control of the vehicle body can be executed in accordance with, for example, the vehicle speed, the steering angle, the lateral acceleration generated in the vehicle body, the longitudinal acceleration, and the like.

  (10) The vehicle suspension according to any one of (1) to (9), wherein the actuator has an electric motor and exhibits an actuator force depending on a force generated by the electric motor. system.

  The mode of this section is a mode in which an electromagnetic actuator is employed as the actuator. The electromagnetic actuator has good controllability, and according to the actuator, active vibration damping control and vehicle body posture control can be easily executed. The electric motor may be a rotary motor or a linear motor.

  (11) The actuator includes: (a) a male thread portion that is not movable relative to one of the sprung member and the unsprung member; and (b) the other of the sprung member and the unsprung member. And a male screw portion that is screwed into the male screw portion and that rotates relative to the male screw portion as the vehicle body and wheels approach and separate in the vertical direction, and the male screw is driven by the electric motor. The vehicle suspension system according to the item (10), wherein the actuator is configured to exert an actuator force by applying a relative rotational force to the portion and the female screw portion.

  The mode described in this section is a mode related to an electromagnetic actuator using a so-called screw mechanism. If a screw mechanism is employed, an electromagnetic actuator can be simply configured.

  Hereinafter, embodiments of the claimable invention will be described in detail with reference to the drawings. In addition to the following examples, the claimable invention is implemented in various modes including various modifications and improvements based on the knowledge of those skilled in the art, including the mode described in the above [Mode of Invention]. can do.

≪Configuration and function of suspension system≫
FIG. 1 schematically shows a vehicle suspension system 10 according to an embodiment. The suspension system 10 includes four independent suspension type suspension devices corresponding to the front, rear, left and right wheels 12, each of which is a spring absorber in which a suspension spring and a shock absorber are integrated. Assy20. The wheel 12 and the spring absorber assembly 20 are generic names, and when it is necessary to clarify which of the four wheels corresponds, as shown in FIG. In some cases, FL, FR, RL, and RR are attached to the front wheel, the right front wheel, the left rear wheel, and the right rear wheel.

  As shown in FIG. 2, the spring absorber assembly 20 connects a suspension lower arm 22 as an unsprung member for holding the wheel 12 and a mount portion 24 as a sprung member provided on the vehicle body. And an actuator 26 as an electromagnetic absorber, and an air spring 28 as a fluid spring provided in parallel therewith.

  The actuator 26 includes an outer tube 30 and an inner tube 32 that is fitted into the outer tube 30 and whose upper portion protrudes upward from the upper end portion of the outer tube 30. The outer tube 30 is connected to the lower arm 22 via a mounting member 34 provided at the lower end portion thereof, while the inner tube 32 is connected to the mount portion 24 at a flange portion 36 formed at the upper end portion thereof. ing. The outer tube 30 is provided with a pair of guide grooves 38 on the inner wall surface thereof so as to extend in the direction in which the axis of the actuator 26 extends (hereinafter sometimes referred to as “axial direction”). Each of a pair of keys 40 attached to the lower end portion of the inner tube 32 is fitted into each of the outer tube 30 and the inner tube 32 by the guide groove 38 and the key 40. Relative rotation is impossible and relative movement is possible in the axial direction. Incidentally, a seal 42 is attached to the upper end portion of the outer tube 30 to prevent air leakage from the pressure chamber 44 described later.

  The actuator 26 includes a screw rod 50 as a male screw portion in which a thread groove is formed, and a nut 52 as a female screw portion that holds the bearing ball and is screwed with the screw rod 50. And a mechanism and an electric motor 54 (a three-phase DC brushless motor, which may be simply referred to as “motor 54” hereinafter). The motor 54 is fixedly accommodated in the motor case 56, and the flange portion of the motor case 56 is fixed to the upper surface side of the mount portion 24, and the flange portion 36 of the inner tube 32 is attached to the flange portion of the motor case 56. By being fixed, the inner tube 32 is connected to the mount portion 24 via the motor case 56. A motor shaft 58 that is a rotation shaft of the motor 54 is integrally connected to the upper end portion of the screw rod 50. That is, the screw rod 50 is disposed in the inner tube 32 with the motor shaft 58 extended, and is rotated by the motor 54. On the other hand, the nut 52 is fixedly supported on the upper end portion of the nut support cylinder 60 attached to the inner bottom portion of the outer tube 30 in a state of being screwed with the screw rod 50.

  The air spring 28 includes a housing 70 fixed to the mount portion 24, an air piston 72 fixed to the outer tube 30 of the actuator 26, and a diaphragm 74 connecting them. The housing 70 has a generally cylindrical shape with a lid, and is fixed to the lower surface side of the mount portion 24 on the upper surface side of the lid portion 76 in a state where the inner tube 32 of the actuator 26 is passed through a hole formed in the lid portion 76. Yes. The air piston 72 has a generally cylindrical shape, and is fixed to the upper portion of the outer tube 30 with the outer tube 30 fitted therein. The housing 70 and the air piston 72 are connected by a diaphragm 74 while maintaining airtightness, and the pressure chamber 44 is formed by the housing 70, the air piston 72, and the diaphragm 74. The pressure chamber 44 is filled with compressed air as a fluid. With such a structure, the air spring 28 elastically supports the lower arm 22 and the mount portion 24, that is, the wheel 12 and the vehicle body, by the pressure of the compressed air.

  When the vehicle body and the wheel 12 approach / separate, the outer tube 30 and the inner tube 32 move relative to each other in the axial direction. Along with the relative movement, the screw rod 50 and the nut 52 relatively move in the axial direction, and the screw rod 50 rotates with respect to the nut 52. The motor 54 can apply a rotational torque to the screw rod 50, and the rotational torque can generate a resistance force in a direction that prevents the approach and separation between the vehicle body and the wheel 12. It is possible. This resistance force becomes a damping force against the approach / separation between the vehicle body and the wheel 12, whereby the actuator 26 functions as a so-called absorber (also referred to as “damper”). In other words, the actuator 26 has a function of applying a damping force to the relative movement between the vehicle body and the wheel 12 by an actuator force that is an axial force exerted by the actuator 26 itself. The actuator 26 also has a function of moving the vehicle body and the wheel 12 closer to or away from each other by the actuator force. That is, the actuator force can be applied as a driving force, that is, a driving force with respect to the relative movement between the vehicle body and the wheel 12. This function enables the execution of skyhook control based on the sprung absolute speed, effectively suppresses the roll of the vehicle body during turning, the vehicle body pitch during acceleration / deceleration, the vehicle height, that is, the vehicle It is possible to change the height.

  An annular buffer rubber 77 is attached to the inner wall surface of the upper end of the outer tube 30, and a buffer rubber 78 is also attached to the inner bottom wall surface of the outer tube 30. When the vehicle body and the wheel 12 approach / separate, when the key 40 moves relative to some extent in a direction in which the vehicle body and the wheel 12 are separated (hereinafter, may be referred to as “rebound direction”), the key 40 is interposed via the buffer rubber 77. In contrast, when the vehicle body and the wheel 12 are relatively moved in a direction in which the vehicle body and the wheel 12 approach each other (hereinafter, may be referred to as a “bound direction”), the lower end of the screw rod 50 is the buffer rubber 78. It contacts with the inner bottom wall surface of the outer tube 30 via. That is, the spring absorber assembly 20 has stoppers (so-called bound stoppers and rebound stoppers) against the approach and separation between the vehicle body and the wheels 12.

  The suspension system 10 is a fluid / inflow / outflow device for inflowing / outflowing air (air) as a fluid to / from an air spring 28 of each spring / absorber assembly 20, more specifically, a pressure chamber 44 of the air spring 28. An air supply / discharge device 80 is connected to supply air to the pressure chamber 44 and discharge air from the pressure chamber 44. FIG. 3 shows a schematic diagram of the air supply / discharge device 80. The air supply / discharge device 80 includes a compressor 82 that supplies compressed air to the pressure chamber 44. The compressor 82 includes a pump 84 and a pump motor 86 that drives the pump 84. The pump 84 sucks air from the atmosphere through the filter 88 and the check valve 90, pressurizes the air, and performs a check. It discharges through the valve 92. The compressor 82 is connected to the pressure chambers 44 of the four air springs 28 via the individual control valve device 100. The individual control valve device 100 includes four individual control valves 102 which are provided corresponding to the pressure chambers 44 of the air springs 28 and are normally closed valves, and open and close the flow paths for the pressure chambers 44. It is. The compressor 82 and the individual control valve device 100 are common to each other via a dryer 104 that removes moisture from the compressed air, and a flow restriction device 110 in which a throttle 106 and a check valve 108 are provided in parallel with each other. They are connected by a passage 112. The common passage 112 branches from between the compressor 82 and the dryer 104, and an exhaust control valve 114 for exhausting air from the pressure chamber 44 is provided at the branching portion.

  Due to the above-described structure, the suspension system 10 can adjust the amount of air in the pressure chamber 44 of each air spring 28 by the air supply / discharge device 80, and the vertical direction can be adjusted by adjusting the amount of air. It is possible to change the distance between the vehicle body and the wheel 12 (hereinafter sometimes referred to as “vehicle-wheel-wheel distance”). Specifically, it is possible to increase the distance between the vehicle body wheels by increasing the amount of air in the pressure chamber 44, and to decrease the distance between the vehicle body wheels by decreasing the amount of air.

  In the present suspension system 10, the suspension electronic control unit (ECU) 140 operates the spring absorber assembly 20, that is, controls the actuator 26 and the air spring 28. Specifically, the operation of the motor 54 of the actuator 26 and the operation of the air supply / discharge device 80 is controlled. The ECU 140 includes a controller 142 mainly composed of a computer having a CPU, ROM, RAM, etc., a driver 144 as a drive circuit for the air supply / discharge device 80, and a drive circuit corresponding to the motor 54 included in each actuator 26. As an inverter 146. The driver 144 and the inverter 146 are connected to a battery 150 as a power supply source through a converter 148, and each control valve 102, pump motor 86, etc., and each actuator 26 of the air supply / discharge device 80 are provided. Electric power is supplied to the motor 54 from the battery 150. Since the motor 54 is driven at a constant voltage, the amount of power supplied to the motor 54 is changed by changing the amount of supplied current, and the force of the motor 54 becomes a force corresponding to the amount of supplied current. Incidentally, the amount of supplied current is determined by each inverter 146 changing the ratio (duty ratio) between the pulse on time and the pulse off time by PWM (Pulse Width Modulation).

The vehicle includes an ignition switch [I / G] 160, a vehicle speed sensor [v] 162 for detecting a vehicle traveling speed (hereinafter sometimes abbreviated as “vehicle speed”), and a vehicle body wheel distance for each wheel 12. Four stroke sensors [St] 164 to be detected, a vehicle height change switch [HSw] 166 operated by the driver for a vehicle height change instruction, a vehicle height change mode changeover switch [MSw] for switching modes related to vehicle height change 168, an operation angle sensor [δ] 170 for detecting an operation angle of the steering wheel, a longitudinal acceleration sensor [Gx] 172 for detecting an actual longitudinal acceleration which is a longitudinal acceleration actually generated in the vehicle body, and actually generated in the vehicle body The lateral acceleration sensor [Gy] 174 that detects the actual lateral acceleration that is the lateral acceleration of the vehicle body, and each mount portion 24 of the vehicle body corresponding to each wheel 12 Longitudinal acceleration four longitudinal acceleration sensor for detecting (vertical acceleration) [Gz _U] 176, 4 one longitudinal acceleration sensor for detecting a longitudinal acceleration of each wheel 12 [Gz _L] 178, a throttle sensor for detecting an accelerator opening of the throttle [Sr] 180, a brake pressure sensor [Br] 182 for detecting the master cylinder pressure of the brake, a rotation angle sensor [ω] 184 for detecting the rotation angle of the motor 54, and the like are provided and connected to the controller 142. The ECU 140 controls the operation of the spring absorber assembly 20 based on signals from these switches and sensors. Incidentally, the character [] is a symbol used when the above-mentioned switch, sensor, etc. are shown in the drawing.

  The ROM included in the computer of the controller 142 stores a program related to vehicle height adjustment, a program related to control of actuator force, various data, and the like, which will be described later. In this suspension system 10, the set standard vehicle height (N vehicle height), the set high vehicle height (Hi vehicle height) higher than the set standard vehicle height, and the set standard vehicle height can be selected by the driver. Three low set low vehicle heights (Low vehicle height) are set, and the vehicle height is selectively changed to a desired set vehicle height by the driver's operation of the vehicle height change switch 166. The vehicle height change switch 166 issues a command for shifting the set vehicle height to a higher set vehicle height or a lower set vehicle height, that is, a vehicle height increase command or a vehicle height decrease command. It is structured.

≪Basic control of suspension system≫
In the present suspension system 10, the four spring absorber assemblies 20 can be controlled independently. In each of the spring absorber assemblies 20, the actuator force of the actuator 26 is independently controlled to control the vibration of the vehicle body and the wheel 12, that is, the control for damping the sprung vibration and the unsprung vibration (hereinafter referred to as “vibration damping”). Control ”(sometimes referred to as“ control ”), control for suppressing the roll of the vehicle body (hereinafter also referred to as“ roll suppression control ”) and control for suppressing the pitch of the vehicle body (hereinafter referred to as“ pitch suppression control ”). That is, the attitude control of the vehicle body is executed as a control combining them. The vibration damping control, roll suppression control, and pitch suppression control are executed by causing the actuator force to act as a damping force, a roll suppression force, and a pitch suppression force, respectively. Specifically, the target actuator force is determined by adding the damping force component, roll suppression force component, and pitch suppression force component, which are the components of the actuator force for each control of vibration damping control, roll suppression control, and pitch suppression control, The actuator 26 is centrally executed by being controlled so as to exert its target actuator force. Further, in the present suspension system 10, control for changing the vehicle height of the vehicle by changing the distance between the vehicle body wheels for each wheel 12 by the air spring 28 (hereinafter, sometimes referred to as “vehicle height change control”). Is executed. In the following description, the actuator force and the component thereof are positive values in the direction in which the vehicle body and the wheel 12 are separated (rebound direction), and those in the direction in which the vehicle body and the wheel 12 are brought closer (bound direction). Is treated as a negative value.

i) Vibration Attenuation Control In the vibration attenuation control, the damping force component F _V is determined so as to exert an actuator force having a magnitude corresponding to the speed of the vibration in order to attenuate the vibration of the vehicle body and the wheel 12. Specifically, the operating speed in the vertical direction of the mount 24 of the vehicle body calculated by the longitudinal acceleration sensor 176 provided on the mount 24 of the vehicle body, the so-called sprung speed V _U, and the lower arm 22 are provided. The damping force component F _V is calculated according to the following equation based on the vertical movement speed of the wheel detected by the vertical acceleration sensor 178, that is, the so-called unsprung speed V _L.
F _V = C _U・ V _U −C _L・ V _L
Here, C _U is a gain for exerting a damping force corresponding to the vertical operating speed of the mount 24 of the vehicle body, and C _L is a damping force corresponding to the vertical operating speed of the wheel 12. It is a gain to show it. That is, C _U and C _L are damping coefficients for so-called sprung and unsprung absolute vibrations. Note that the damping force component F _V can be determined by other methods. For example, in order to execute control that exerts a damping force based on the unsprung unsprung relative speed, an index value of the relative speed between the vehicle body and the wheel 12 is obtained from the detection value of the rotation angle sensor 184 provided in the motor 54. Based on the rotation speed V of the obtained motor 54, it can be determined according to the following equation.
F _V = C · V (C: damping coefficient)

ii) Roll suppression control In roll suppression control, when the vehicle turns, the actuator force in the bounce direction is applied to the actuator 26 on the inner ring side and the actuator 26 on the outer ring side in the rebound direction according to the roll moment resulting from the turn. The actuator force is exhibited as a roll restraining force. Specifically, first, as the lateral acceleration indicating the roll moment received by the vehicle body, the estimated lateral acceleration Gyc estimated based on the steering angle δ of the steering wheel and the vehicle speed v, and the actual acceleration measured by the lateral acceleration sensor 174 are used. Based on the lateral acceleration Gyr, a control lateral acceleration Gy ^* , which is a lateral acceleration used for control, is determined according to the following equation.
Gy ^* = K ₁ · Gyc + K ₂ · Gyr (K ₁ , K ₂ : gain)
Such based on the determined control-use lateral acceleration Gy ^*, the roll restraining force component F _R is determined according to the following equation.
F _R = K ₃ · Gy ^* (K ₃ : Gain)

iii) Pitch suppression control In the pitch suppression control, for the nose dive of the vehicle body that occurs during braking of the vehicle body, the actuator 26FL, FR on the front wheel side in the rebound direction depends on the pitch moment that causes the nose dive. Actuator force is exerted on the actuators 26RL, RR on the rear wheel side in the bound direction as the pitch restraining force. For the squat of the vehicle body generated during acceleration of the vehicle body, the actuator force in the rebound direction is applied to the actuators 26RL, RR on the rear wheel side according to the pitch moment that generates the squat, and the actuator 26FL on the front wheel side. , FR causes the actuator force in the bounce direction to be exhibited as a pitch suppression force. Specifically, as longitudinal acceleration indicative of the pitch moment acting on the vehicle body, is employed the actual longitudinal acceleration Gx that is actually measured by the longitudinal acceleration sensor 172, and based on the actual longitudinal acceleration Gx, the pitch restraining force component F _P is the following Determined according to the formula.
F _P = K ₄ · Gx (K ₄ : Gain)
Note that the pitch suppression force is generated when the throttle opening detected by the throttle sensor 180 or the master cylinder pressure detected by the brake pressure sensor 182 exceeds a set threshold. Yes.

iv) Vehicle height change control In the vehicle height change control, the vehicle height is changed when the target vehicle height that is the vehicle height to be realized is changed by the operation of the vehicle height change switch 166 based on the driver's intention. Is done. A target vehicle body wheel distance for each wheel 12 is set according to each of the three set vehicle heights, and a vehicle body wheel distance for each wheel 12 based on a detection value of the stroke sensor 164. Thus, the operation of the air supply / discharge device 80 is controlled such that the distance between the vehicle bodies of each wheel 12 is changed to a distance corresponding to the target vehicle height.

  Specifically, in the operation of the air supply / discharge device 80 for raising the vehicle height (hereinafter sometimes referred to as “vehicle height increase operation”), the pump motor 94 is first activated and the four wheels 12 are operated. By opening the individual control valves 102 for all, compressed air is supplied to the pressure chambers 44 of the air springs 28. After the state is continued, the four individual control valves 102 are sequentially closed from the one corresponding to the wheel 12 at which the distance between the vehicle body wheels becomes the target distance, and the distance between the vehicle body wheels for all the wheels 12 is set as the target. After reaching the distance, the operation of the pump motor 94 is stopped. In the operation of the air supply / discharge device 80 for lowering the vehicle height (hereinafter, sometimes referred to as “vehicle height reduction operation”), the exhaust control valve 114 is first opened and all the individual control valves 102 are By opening the valve, the air is discharged from the pressure chamber 44 of each air spring 28 to the atmosphere. After that, the four individual control valves 102 are sequentially closed from the one corresponding to the wheel 12 whose distance between the vehicle wheels becomes the target distance, and after the distance between the vehicle wheels for all the wheels 12 becomes the target distance, The exhaust control valve 114 is closed.

  However, in the present suspension system 10, the vehicle height change control is performed only when the vehicle is stopped on a relatively flat road surface. Specifically, the vehicle speed detected by the vehicle speed sensor 162 is substantially zero, and the difference between the maximum and minimum vehicle body wheel distances for each wheel 12 detected by the stroke sensor 164. It is determined that the vehicle height change control is an allowable condition for the vehicle height change control, and the vehicle height change control is executed only when the condition is satisfied.

  In the vehicle height change control of the suspension system 10, the change in the distance between the vehicle body wheels for the four wheels 12 is executed simultaneously, but each wheel 12 corresponds to one or more than one wheel 12. A plurality of groups may be set, and the vehicle body wheel distance may be changed step by step for each group. In the present suspension system 10, the vehicle height change control is executed by the driver's operation of the vehicle height change switch 166, but the vehicle height is automatically controlled without being based on such driver's operation. Change control may be executed. Specifically, for example, a control that automatically adjusts the distance between the vehicle body wheels for each wheel 12 due to changes in passengers, cargo, etc., and the vehicle height is automatically lowered when the vehicle speed increases. Such control, or control that automatically raises or lowers the vehicle height when a passenger gets on or off may be executed.

≪Warp force caused by vehicle height change and control to eliminate it≫
i) Vehicle height change and warp force The forces acting on the vehicle body can be divided into heave force, roll force, pitch force, and warp force, each of which is a component of that force. These forces are received by the spring absorber assembly 20 provided for each wheel 12. When the warp force of the vehicle body is acting, as conceptually shown in FIG. 4, the spring absorber assembly 20 of each diagonal wheel receives the same rebound force in the opposite direction, while the other The spring absorber assembly 20 of each of the diagonal wheels receives a force in the bounce direction that is the same magnitude as the force in the rebound direction (black arrow). The warp force determined by the force received by each spring / absorber Assy 20 acts as a force for twisting the vehicle body, but the rigidity of the vehicle body is relatively high, so the variation in the distance between the vehicle body wheels for each of the four wheels 12 is changed. It can occur with little.

  In the present suspension system 10, the vehicle height change control is executed when the vehicle is stopped on a relatively flat road surface, and each of the vehicle body wheel distances for the four wheels 12 is set. Therefore, it can be considered that not only the heave force but also the roll force and the pitch force do not occur. However, even if all the distances between the vehicle body wheels for the four wheels 12 are matched to the set distance, there are subtle undulations on the road surface, the order of the order in which the supply and discharge of air from the four air springs 28 are stopped, and the like Due to this, there is a possibility that the warp force remains. More specifically, for example, the spring constants of the left and right air springs 28 are different depending on the amount of air in the pressure chambers 44, and as a result, the warp force remains. It is.

  If the vehicle travels with the warp force acting on the vehicle body as described above, for example, a difference in turning characteristics between the left and right occurs, and as a result, the ride comfort, traveling stability, etc. of the vehicle are reduced. It will be. Therefore, it is desirable to eliminate the warp force acting on the vehicle body.

ii) Estimating the warp force As shown in FIG. 5 (a), the weight of the vehicle body received by the spring absorber assembly 20 is W, and the length of the spring absorber assembly 20 ("distance between wheels", "spring length" L), the length of the spring absorber assembly 20 when the shared load is assumed to be 0, L ₀ , the force exerted by the air spring 28, Fs, and the spring constant of the air spring 28 Assuming K, the following equation is generally satisfied.
W = Fs = K · (L ₀ −L)
If a certain amount of actuator force Fa is exerted in the state shown in FIG. 5A, the length of the spring absorber assembly 20 changes by ΔL as shown in FIG. 5B. The force exerted by the spring 28 is Fs ′, and the following expression is generally established.
W = Fa + Fs ′ = Fa + K (L ₀ −L−ΔL)
Therefore, if the set actuator force Fa is exerted and the variation ΔL of the distance between the wheel bodies in the state is detected, the spring constant K of the air spring 28 can be estimated from the above two equations, and the set wheel body is set. It is possible to estimate the shared load of the vehicle body that the spring / absorber assembly 20 receives when the distance is between them.

If the load sharing of the spring absorber assembly 20 for the left front wheel, right front wheel, left rear wheel, and left rear wheel is W _FL , W _FR , W _RL , W _RR , respectively, the warp force Ww acting on the vehicle body is formula,
Ww = (W _FL −W _FR ) − (W _RL −W _RR )
Can be obtained. Normally, the load sharing on the left and right sides of the vehicle can be considered to be equal, and when air is supplied and discharged in an appropriate balance with respect to the pressure chamber 44 of the air spring 28 of each wheel 12, the left and right air Since it can be considered that the spring constants K of the springs are equal, no warp force due to the vehicle height change occurs, but as described above, when an appropriate vehicle height change is not performed due to some influence, Warp force will be generated.

  In the present suspension system 10, after the vehicle height change control described above is executed, each actuator 26 of the spring absorber assembly 20 of the four wheels 12 is controlled, and in detail, to the electric motor 54 of each actuator 26. By controlling the power to be supplied, control is performed so that each actuator 26 simultaneously exerts the actuator force in the same direction and the same magnitude. Then, in a state where the actuator force is exerted, the stroke sensor 164 detects a change in the distance between the vehicle body wheels for each of the four wheels 12, and based on the detection result, the warp force acting on the vehicle body according to the above method is detected. It is supposed to be estimated. The system 10 can easily estimate the warp force remaining due to the change in the vehicle height by executing such a warp force estimation process.

If the suspension system is provided with an air pressure sensor 190 capable of detecting the air pressure in the pressure chamber 44 of each air spring 28 (see FIG. 3), the left front wheel, right front wheel, Based on the air pressures P _FL , P _FR , P _RL , P _RR in the pressure chamber 44 of the air spring 28 for each of the left rear wheel and the right rear wheel, the warp force Ww can be estimated according to the following equation.
_{Ww = (P FL · S FL} -P FR · S FR) - (P RL · S RL -P RR · S RR)
Note that S _FL , S _FR , S _RL , S _RR in the above formulas are virtual pressure receiving areas of the air springs 28 determined according to the structure.

iii) Eliminating warp force In order to eliminate the warp force caused by the vehicle height change, the suspension system 10 executes control for causing each actuator 26 to exert a force to cancel the warp force, that is, warp force elimination control. Has been. This warp force elimination control can be executed in two modes. More specifically, a mode relating to a vehicle height change depending on the state of the vehicle height change mode changeover switch 168 described above (hereinafter referred to as “vehicle height change mode”). Depending on the situation), the execution mode is selected.

One of the two vehicle height change modes set is a mode in which the warp force generated due to the vehicle height change is canceled by continuously exerting the actuator force during the subsequent vehicle travel. (Hereinafter, it may be referred to as “warp elimination force imparting travel allowable mode”), that is, a mode in which the warp force is eliminated afterward by the actuator force. In this mode, when the warp force Ww estimated by the warp force estimation process is greater than or equal to a set threshold, each of the left front wheel, the right front wheel, the left rear wheel, and the left rear wheel is based on the warp force Ww. As the actuator force component of the actuator 26, the warp elimination force components F _W · _FL , F _W · _FR , F _W · _RL , F _W · _RR are determined as follows:
F _W · _FL = -Ww / 4
F _W · _FR = Ww / 4
F _W · _RL = Ww / 4
_FW・_RR = -Ww / 4
These warp resolving force components F _W · _FL , F _W · _FR , F _W · _RL , F _W · _RR (hereinafter may be collectively referred to as “warp resolving force component F _W ”) are exhibited as actuator force. Thus, each actuator 26 is controlled. In other words, the actuator 26 continues to apply a force opposite to the warp force caused by the vehicle height change to the vehicle body by the actuator 26. As a result, the warp caused by the vehicle height change is generated. The force is eliminated (see the white arrow in FIG. 4). Therefore, the warp force elimination control is a control that is always executed in the warp elimination force imparting travel permission mode.

Another vehicle height change mode is a mode in which the vehicle height change control is executed again in a state where the actuator force is exerted on each wheel 12 when a warp force exceeding a certain threshold value is generated due to the vehicle height change (hereinafter referred to as “vehicle height change control”). This is sometimes referred to as “re-car height change execution mode”, which realizes vehicle height change without generating warp force and does not require actuator force to eliminate the warp force in subsequent driving. . In this mode, after the vehicle height change control, the warp force Ww is estimated by the warp force estimation process, and when the warp force Ww is equal to or greater than the set threshold, the air supply / discharge device 80 is controlled and temporarily , Return to the state before the vehicle height change, and then _apply the actuator force consisting of the warp-resolving force components F _W · _FL , F _W · _FR , F _W · _RL , F _W · _RR according to the above four formulas to the four actuators In this state, the air supply / discharge device 80 is controlled, and the vehicle height change control is executed again. In other words, in anticipation of the warp force that would be caused by the vehicle height change, the vehicle height change control is completed with the warp force being applied to the vehicle body by the actuator 26 with the opposite force. By removing the actuator force later, a state in which no warp force acts on the vehicle body is realized. In this vehicle height change execution mode, the time required for the vehicle height change may be longer than in the warp elimination force imparting travel permission mode, but the actuator force is not required for vehicle travel after the vehicle height change. Therefore, the energy consumption of the suspension system 10 can be reduced.

≪Control program≫
The control of the actuator force in the suspension system 10 and the control of the air spring 28 when the vehicle height is changed, that is, the control of the air supply / discharge device 80 are shown in FIG. This is done by executing a vehicle height changing program. These programs are executed by the controller 142 at a short time interval (for example, several milliseconds to several tens of milliseconds) from when the ignition switch 160 is turned on to when it is turned off.

i) Actuator control program The actuator control program is executed for each of the actuators 26 of the spring absorber assembly 20 provided on each of the four wheels 12. In the following description, processing by this program for one actuator 26 will be described in consideration of simplification of description.

In the process in accordance with the actuator control program, first, in step 1 (hereinafter abbreviated as “S1”, other steps are also the same), as described above, the sprung detected by the longitudinal acceleration sensors 176 and 178 is detected. Based on the speed V _U and the unsprung speed V _L , the damping force component F _V is determined. Next, in S2 and S3, as described above, the roll restraining force component F _R and the pitch restraining force component _FP are determined. In subsequent S4, the actuator force Fa is determined by summing those components. In the S4, after the warp resolved force component F _W determined in the vehicle height changing program described also added, further, it is also added warp estimation component F _T of the actuator forces is exerted in the warped power estimation process. That is, the warp elimination force component F _W and the warp estimation component F _T are unified, and the actuator force Fa is determined. After the actuator force Fa is determined, the direction of the force generated by the motor 54 of the actuator 26 and the power supplied to the motor 54, that is, the duty ratio are determined based on the actuator force Fa. A signal is sent to the inverter 146.

  As will be described in detail later, since the actuator force of each actuator 26 is controlled as described above, when the vehicle height change mode is the warp elimination force imparting travel allowance mode described above, each actuator No. 26 will continue to exhibit appropriate warp resolution, and when the vehicle height change execution mode is set, appropriate warp resolution will be demonstrated when the vehicle height is changed again. Will be.

ii) Vehicle height change program In the process according to the vehicle height change program, first, in S11, it is determined whether or not a vehicle height change command by operation of the vehicle height change switch 166, that is, a target set vehicle height has been changed, If it is determined that there is no vehicle height change command, one execution of the program is completed. If it is determined that there is a vehicle height change command, the vehicle height change allowance condition described above is satisfied in S12. It is judged whether or not. When the vehicle is running, if the difference between the maximum and minimum of the actual distance between wheels of each vehicle body wheel 12 exceeds the threshold, the vehicle height should not be changed. The program ends.

If it is determined in S12 that the change in vehicle height is permitted, the warp resolution component is considered in S13 in consideration of the case where some warp resolution component _FW has already been exhibited. _FW is reset to zero. In subsequent S14, it is determined whether the vehicle height is to be raised or lowered by comparing the previous target set vehicle height with the new target set vehicle height. When the vehicle height is to be raised, the vehicle is to be lowered in S15. In S16, the air supply / discharge device 80 is controlled, and the vehicle height increasing operation and the vehicle height decreasing operation described above are executed. The processes of S15 and S16 are continued until the distance between the vehicle bodies of each wheel 12 reaches the target distance corresponding to the new target set vehicle height.

After the process of S15 or S16 is completed, a warp force estimation process subroutine shown in the flowchart of FIG. 8 is executed in S17. In the process according to this subroutine, first, in S171, in order to exhibit the actuator force for previously-described warp force estimating component for warp estimator F _T is set to a value F _T0 set in advance. Since the vehicle is stopped on a flat road surface and the warp elimination force component _FW has already been set to 0, the actuator force exerted by each actuator 26 when this processing is executed is warp estimated. only to become use component F _T. In a state where the predetermined actuator force is exerted, the warp force Ww acting on the vehicle body after the vehicle height is changed according to the above-described method is calculated by the process of S173, and after the calculation, the warp force Ww is exerted in S174. In order to release the existing actuator force, the warp estimation component _FT is set to zero.

After the processing by the warping force estimation processing subroutine in S18, whether the estimated warp force Ww is the threshold value Ww ₀ or more it is determined. If it is less than the threshold value Ww ₀ , the execution of this program ends, assuming that an appropriate vehicle height change has been performed. If the warp force Ww is greater than or equal to the threshold value Ww ₀ , the vehicle height change mode is determined to be the warp elimination force imparting travel allowance mode and the re-vehicle height change execution mode based on the operation state of the vehicle height change mode changeover switch 168 in S19. It is judged whether or not. In the warp elimination force imparting travel permission mode, the warp elimination force component _FW for each actuator 26 is determined to be Ww / 4 or -Ww / 4 according to the method described above in S20, and this program is followed. The process ends. After the process of S20 is executed, each actuator 26 continues to exhibit the determined warp elimination force component _FW until the next vehicle height change is performed.

On the other hand, in the re-vehicle height change execution mode, the return operation is executed in S21. In the return operation, the air supply / discharge device 80 is controlled to return to the state before the vehicle height change is executed, and the distance between the vehicle bodies of each wheel 12 is based on the detection value of the stroke sensor 164. Returned to the distance. After the return operation, in S22, the warp elimination force component _FW is determined to be Ww / 4 or -Ww / 4 as in the process of S20. Since the actuator force is zero at the time before this processing is executed, each actuator 26 is in a state of exerting the actuator force composed of the determined warp elimination force component _FW by executing S22. .

In a state where the actuator force is exerted, in the subsequent S23, it is determined whether the vehicle height is to be raised or lowered, similarly to the determination in S14. In S24 or S25, the vehicle height increasing operation similar to S15, S16 or The vehicle height reduction operation is executed, and the vehicle height change is performed again. After the vehicle height change is completed again, the warp resolution component _FW is set to 0 in S26 in order to cancel the warp resolution component _FW that is being exhibited, and the processing by this program ends. In the re-vehicle height change execution mode, the vehicle height is changed again using the actuator force through such a series of processes, and the warp force Ww does not remain.

Although omitted in the flowchart, when the vehicle is driven during the execution of the vehicle height changing program, the processing being executed at that time is stopped, and the vehicle body wheel of each wheel 12 at that time is stopped. The distance is maintained, and the warp elimination force component F _W and the warp estimation component _FT are set to 0, and the execution of the program is terminated in a corrective manner. The fact that the program has been forcibly terminated is displayed on an indicator provided on the instrument panel.

≪Functional structure of controller≫
It can be considered that the controller 142 that executes the above-described actuator control program and vehicle height change program has various functional units that execute various processes according to these programs. Specifically, as shown in FIG. 9, the controller 142 executes the process of S <b> 1 as a functional unit that determines the damping force component F _V , performs the process of S <b> 2, and roll suppression force as the functional unit that determines the damping force component F _V. as a functional unit for determining the component F _R, the roll control section 202, as a functional portion to determine the pitch restrain force component F _P and executes the process of S3, the pitch reduction control unit 204 has each A posture control unit 206 that is a functional unit that controls the posture of the vehicle body is configured including the roll suppression control unit 202 and the pitch suppression control unit 204. As for the vehicle height change, the functions of S14 to S16 are executed according to the determination of S11 and S12, and the function of executing the processes of S21 and S23 to S24 depending on the vehicle height change mode is as follows. A change control unit 208 is included. The vehicle height change mode is determined by the vehicle height change mode determination unit 210, which is a functional unit that executes the process of S19.

Further, the controller 142 has a warp force estimation unit 212 as a function unit for executing the process of estimating the warp force due to the vehicle height change, that is, the process of S17. Based on the estimated warp force, the warp resolution control unit 214 is provided as a function unit that executes the process of determining the warp resolution force component _FW of the actuator force, that is, the process of S20 or S22.

It is a figure which shows the whole structure of the suspension system of an Example. FIG. 2 is a cross-sectional view of a spring absorber assembly that includes an actuator and an air spring that constitutes the suspension system shown in FIG. 1. FIG. 2 is a circuit diagram of an air supply / discharge device included in the suspension system shown in FIG. 1. It is a conceptual diagram which shows the warp force which acts on a vehicle body, and the warp cancellation force which is the force for canceling it. It is a conceptual diagram for demonstrating the fluctuation | variation of the distance between vehicle body wheels at the time of applying an actuator force. 2 is a flowchart of an actuator control program executed by a controller included in the suspension system shown in FIG. 1. It is a flowchart of the vehicle height change program performed by the controller which the suspension system shown in FIG. 1 has. It is a flowchart of the warp force estimation process subroutine which comprises the vehicle height change program shown in FIG. It is a block diagram regarding the function of the controller which the suspension system shown in FIG. 1 has.

Explanation of symbols

10: Vehicle suspension system 12: Wheel 20: Spring absorber assembly 22: Lower arm (unsprung member) 24: Mount part (sprung member) 26: Actuator 28: Air spring (fluid spring) 44: Pressure chamber 50: Screw Rod (male thread part) 52: Nut (female thread part) 54: Electric motor 80: Air supply / discharge device (fluid inflow / outflow device) 140: Suspension electronic control unit (ECU) 142: Controller (control device) 144: Driver 146 : Inverter 162: Vehicle speed sensor 164: Stroke sensor 166: Vehicle height change switch 168: Vehicle height change mode changeover switch 170: Operating angle sensor 172: Longitudinal acceleration sensor 174: Lateral acceleration sensor 176: Vertical acceleration sensor (on spring) 178: Longitudinal acceleration sensor (Unsprung) 200: Vibration damping control unit 202: Roll suppression control unit 204: Pitch suppression control unit 206: Attitude control unit 208: Vehicle height change control unit 210: Vehicle height change mode determination unit 212: Warp force estimation unit 214: Warp resolution controller

Claims (5)

It is provided corresponding to the four wheels on the front, rear, left and right, each elastically connecting the wheel corresponding to itself and the vehicle body, and by the inflow and outflow of fluid to itself, the wheel and vehicle body corresponding to itself are connected. Four fluid springs that can change the distance between the vehicle wheels, which is the distance in the vertical direction,
A fluid inflow / outflow device for flowing in / out of fluid to each of the four fluid springs;
Four actuators provided corresponding to the four wheels, each exhibiting an actuator force that is a force for approaching and separating the corresponding wheel and the vehicle body in the vertical direction;
A device that controls the operation of the fluid inflow / outflow device and the four actuators, and (a) controls the operation of the fluid inflow / outflow device and changes the distance between the vehicle wheels for each of the four wheels. A vehicle height change control unit that changes the vehicle height, and (b) an actuator force for controlling the operation of the four actuators to counteract the warp force acting on the vehicle body due to the vehicle height change, A vehicle suspension system comprising: a control device having a warp elimination control unit to be exhibited by the four actuators ,
The control device is
After changing the vehicle height by the vehicle height change control unit, grasping the warp force generated by the vehicle height change, after returning the vehicle height to the vehicle height before the change by the vehicle height change control unit, After controlling the operation of the four actuators by the warp cancellation control unit so as to cancel the grasped warp force, and after changing the vehicle height by the vehicle height change control unit again under the execution of the control A suspension system for a vehicle configured to stop control of operations of the four actuators by the warp elimination control unit. The control device is
A warp force estimating unit for causing each of the four actuators to exert an actuator force having a set magnitude and estimating a warp force based on a variation in a distance between vehicle body wheels for each of the four wheels. Prepared,
Based on the estimation result of the warp force estimating unit, the vehicle suspension system of claim 1, which is intended to perform a warping elimination control. The warp force estimation unit estimates a spring constant of each of the four fluid springs based on a change in a distance between vehicle body wheels for each of the four wheels, and estimates a warp force based on the estimated spring constant. The vehicle suspension system according to claim 2 , which is a vehicle. The control device includes a vibration damping control unit that controls the operation of each of the four actuators so that each actuator force is exerted as a damping force for at least one of sprung vibration and unsprung vibration. The vehicle suspension system according to any one of claims 3 to 4. The control device includes an attitude control unit that controls the operation of each of the four actuators and exerts each actuator force as a force for suppressing at least one of a roll and a pitch of the vehicle body. The vehicle suspension system according to any one of claims 4 to 4.

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