Control method for suspension device, control device for suspension device, and control system for suspension device

Abstract

The present invention relates to a series type suspension device and provides a control method for a suspension device capable of improving vibration suppression performance of a sprung structure and enhancing vehicle behavior stability. The present invention is such that an actuator mechanism, a suspension spring, and a damper mechanism are arranged in series between an unsprung structure and a sprung structure, and a plurality of bushes are arranged between the unsprung structure and the sprung structure, and is provided with: an unsprung acceleration acquisition step for acquiring acceleration in the vertical direction of the unsprung structure; a wheel movement amount estimation value computation step for estimating wheel movement amount in the vertical direction of the unsprung structure; a reference stroke command value computation step for calculating a reference extension / compression value for the actuator mechanism; and a bush influence correction value computation step for calculating a bush influence correction value of the actuator mechanism extension / compression amount by taking into consideration deformation of the bushes.

Description

Suspension device control method, suspension device control device, and suspension device control system

[0001] The present invention relates to a control method, a control device, and a control system for a suspension device that allows adjustment of the vehicle height of a vehicle.

[0002] Conventionally, there has been known an active suspension for improving the behavioral stability of a vehicle, in which a damper mechanism for absorbing impacts from the road surface and an actuator mechanism for adjusting the vehicle height and controlling the posture of the vehicle body are provided in parallel between the sprung structure and the unsprung structure of the vehicle. For example, as shown in Patent Document 1, there is known a suspension device for suspending each wheel from the vehicle body, in which a first actuator consisting of an air spring and a shock absorber and a second actuator consisting of an active actuator are arranged in parallel and interposed between the suspension arm and the vehicle body.

[0003] In this suspension system, the first actuator functions as a suspension spring that absorbs shocks from the road surface and can adjust the vehicle height by controlling the stroke, while the second actuator can be used for vibration control to improve ride comfort by suppressing vertical vibrations on the spring caused by input from the road surface.

[0004] Japanese Patent Application Laid-Open No. 2023-37113

[0005] Generally, in a conventional suspension system in which a damper mechanism D and an actuator mechanism A are arranged in parallel as shown in FIG. 14 (hereinafter referred to as a parallel-type suspension system), when adjusting the vehicle height using the actuator mechanism A, the damper mechanism D must also be extended and contracted at the same time, which has the problem of increasing power consumption.

[0006] Furthermore, in the conventional parallel suspension device, the shock from the road surface is received not only by the damper mechanism D but also by the actuator mechanism A, so the structure poses a risk of damage to the actuator mechanism A, which does not have the function of absorbing shock.

[0007] In order to solve the above problems, it is conceivable to construct a suspension device in which a damper mechanism D and an actuator mechanism A are arranged in series between the sprung structure and the unsprung structure of a vehicle (hereinafter referred to as a series-type suspension device). As an example, a series-type suspension device can have a structure in which a damper mechanism 10 and an actuator mechanism 40 are arranged in series, as in the suspension device 1 shown in Figure 1.

[0008] The suspension device 1 is attached between the vehicle body and a lower arm 5. A wheel 6 is attached via the upper arm 4 and the lower arm 5 so as to be movable up and down relative to the vehicle body.

[0009] The upper arm 4 and the lower arm 5 are rotatably attached to the vehicle body via a plurality of bushings 4a and 5a, respectively. The bushings 4a and 5a are made of elastic material and have properties of a spring or a damper.

[0010] In this specification, the vehicle body is considered to be included in the sprung structure, and the upper arm 4, the lower arm 5, and the wheel 6 are considered to be included in the unsprung structure.

[0011] When vehicle height is adjusted using suspension unit 1, which is an in-line suspension unit, actuator mechanism 40 is driven to change the distance between the unsprung structure and the sprung structure. In this case, due to the influence of bushings 4a, 5a, which have spring and damper properties, a discrepancy may occur between the stroke command value that drives actuator mechanism 40 and the actual change in vehicle height. For this reason, when suspension unit 1 is made to function as an active suspension, there is a problem in that the desired performance cannot be obtained when controlling the up and down vibration of the sprung structure.

[0012] In a conventional parallel suspension device, as shown in the conceptual diagram of Figure 15, the displacement of the actuator mechanism A directly becomes the displacement between the sprung structure and the unsprung structure, so the above-mentioned problem does not occur.

[0013] The present invention has been made to solve the above-mentioned problems, and aims to provide a control method for a serial suspension device that improves the vibration suppression performance of the sprung structure and increases the behavioral stability of the vehicle by controlling the stroke command value that drives the actuator mechanism to include a correction value corresponding to the movement of the unsprung structure.

[0014] The control method for a suspension device according to the present invention, which solves the above-mentioned problems, is a control method for a suspension device in which vehicle height can be adjusted by driving an actuator mechanism to extend and retract, wherein the actuator mechanism, a suspension spring, and a damper mechanism that suppresses the amplitude of the suspension spring are arranged in series between an unsprung structure and a sprung structure, and a plurality of bushes are arranged between the unsprung structure and the sprung structure, and the control method comprises an unsprung acceleration acquisition process for acquiring the vertical acceleration of the unsprung structure, a wheel movement amount estimation value calculation process for estimating the vertical movement amount of the unsprung structure based on the information acquired by the unsprung acceleration acquisition process, a reference stroke command value calculation process for calculating a reference extension / retraction amount of the actuator mechanism based on the information acquired by the wheel movement amount estimation value calculation process, and a bush influence correction value calculation process for calculating a bush influence correction value for the extension / retraction amount of the actuator mechanism taking into account deformation of the bush.

[0015] The control device for a suspension device according to the present invention, which solves the above-mentioned problems, is a control device for a suspension device that can adjust vehicle height by driving an actuator mechanism to expand and contract, wherein the actuator mechanism, suspension spring, and damper mechanism that suppresses the amplitude of the suspension spring are arranged in series between an unsprung structure and a sprung structure, and a plurality of bushes are arranged between the unsprung structure and the sprung structure, and is characterized by comprising: an unsprung acceleration acquisition means for acquiring the vertical acceleration of the unsprung structure; a wheel movement amount estimation value calculation means for estimating the vertical movement amount of the unsprung structure based on information acquired by the unsprung acceleration acquisition means; a reference stroke command value calculation means for calculating a reference expansion amount of the actuator mechanism based on information acquired by the wheel movement amount estimation value calculation means; and a bush influence correction value calculation means for calculating a bush influence correction value for the expansion amount of the actuator mechanism taking into account deformation of the bush.

[0016] In addition, the control system for a suspension device according to the present invention, which solves the above-mentioned problems, is a control system for a suspension device that can adjust vehicle height by driving an actuator mechanism to expand and contract, wherein the actuator mechanism, suspension spring, and damper mechanism that suppresses the amplitude of the suspension spring are arranged in series between an unsprung structure and a sprung structure, and a plurality of bushes are arranged between the unsprung structure and the sprung structure, and is characterized by comprising: an unsprung acceleration acquisition unit that acquires the vertical acceleration of the unsprung structure; a wheel movement amount estimation value calculation unit that estimates the vertical movement amount of the unsprung structure based on the information acquired by the unsprung acceleration acquisition unit; a reference stroke command value calculation unit that calculates a reference expansion amount of the actuator mechanism based on the information acquired by the wheel movement amount estimation value calculation unit; and a bush influence correction value calculation unit that calculates a bush influence correction value for the expansion amount of the actuator mechanism taking into account deformation of the bush.

[0017] The suspension control method, control device, and control system according to the present invention can calculate a final stroke command value taking into account the amount of expansion and contraction of the actuator that would be absorbed by deformation of the bushing, thereby controlling the actuator mechanism to an appropriate amount of expansion and contraction so as to suppress vibration of the sprung structure even when the unsprung structure is subjected to vibration or impact from the road surface.

[0018] 1 is a perspective view showing an example of a mounting state of a suspension device according to an embodiment of the present invention; FIG. 2 is a perspective view showing an example of a suspension device according to an embodiment of the present invention; FIG. 3 is a block diagram showing a control method for a conventional suspension device; FIG. 4 is a conceptual diagram showing a state in which the suspension device is driven using a conventional control method, where (a) is a vehicle stopped state, (b) is a state when acceleration of the unsprung structure is acquired, and (c) is a state in which the actuator mechanism is driven; FIG. 5 is a graph showing a stroke command value relative to a wheel movement amount estimated value; FIG. 6 is a graph showing the relationship between the stroke command value and the actual movement amount of the sprung structure; FIG. 7 is a block diagram showing a control method for a suspension device according to a first embodiment; FIG. 8 is a conceptual diagram showing a state in which the suspension device is driven using a control method according to the first embodiment, where (a) is a vehicle stopped state, (b) is a state when acceleration of the unsprung structure is acquired, and (c) is a state in which the actuator mechanism is driven; FIG. 9 is a graph showing a bushing influence correction value relative to a wheel movement amount estimated value; 1 is a graph showing the relationship between the damping coefficient of the damper device and the bush 4 and the time constant of the suspension device in a transient state. FIG. 2 is a reference diagram showing a conventional parallel suspension device. FIG. 3 is a conceptual diagram showing a conventional parallel suspension device.

[0019] Hereinafter, embodiments of a suspension device control method according to the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0020] First, a suspension device 1 according to the present invention will be described.

[0021] FIG. 1 is a perspective view showing an example of an attached state of a suspension device according to an embodiment of the present invention, and FIG. 2 is a perspective view showing an example of a suspension device according to an embodiment of the present invention.

[0022] The suspension device 1 is disposed in correspondence with the wheels 6 provided on the front, rear, left and right sides of the vehicle, as shown in an example in Figure 1. The suspension device 1 absorbs vibrations and shocks input from the road surface while the vehicle is traveling, thereby ensuring running stability.

[0023] The wheel 6 is attached to the vehicle body (not shown) via an upper arm 4 and a lower arm 5 so as to be movable up and down.

[0024] The upper arm 4 and the lower arm 5 are rotatably attached to a vehicle body (not shown) via bushings 4a and 5a, respectively.

[0025] The bushings 4a, 5a are generally cylindrical members made of an elastic material such as rubber. Alternatively, the bushings 4a, 5a may be configured such that the outer and inner surfaces are each made of a thin-walled metal tube, with an elastic material disposed between these two thin-walled tubes. The bushings 4a, 5a having such a structure support the upper arm 4 and the lower arm 5 rotatably relative to the vehicle body. The bushings 4a, 5a function to prevent minute vibrations received by the wheel 6 from the ground from being transmitted to the vehicle body.

[0026] The suspension device 1 is attached between a lower arm 5 and the vehicle body. The suspension device 1 changes the angle of the lower arm 5 relative to the vehicle body by driving an actuator mechanism 40, which will be described later. This changes the vertical position of the wheel 6 relative to the vehicle body, making it possible to adjust the vehicle height. The suspension device 1 includes a fork 2, a suspension spring 3, a damper mechanism 10, and the actuator mechanism 40.

[0027] The fork 2 is located at the bottom of the suspension device 1. The fork 2 is formed so as to split into two parts in the longitudinal direction of the vehicle, and is provided with a mounting shaft that extends across the lower tips of the two forks. The fork 2 is attached to the lower arm 5 so as to be rotatable about the mounting shaft.

[0028] The suspension spring 3 is a compression coil spring disposed between the fork 2 and the actuator mechanism 40. The suspension spring 3 supports the vehicle weight, and the stiffness of the spring determines the amount of tilt of the vehicle body in the front, rear, left and right directions that occurs while traveling. The suspension spring 3 expands and contracts in response to unevenness in the road surface, keeping the wheels 6 from leaving the road surface.

[0029] The damper mechanism 10 is attached to connect the fork 2 with a shaft member 70 (described later) and suppresses the movement of the oscillating suspension spring 3. As an example, the damper mechanism 10 is preferably a damper that uses a functional fluid such as a magnetorheological fluid and has a structure that allows the damping force to be controlled by an electromagnetic coil. However, the structure of the damper mechanism 10 is not limited to this, and it may also be a structure that generates the damping force using hydraulic oil filled inside the damper body and a piston that is capable of reciprocating motion within the hydraulic oil.

[0030] 2, the actuator mechanism 40 is composed of an actuator main body 41 attached to the vehicle body, and a shaft member 70 supported so as to be movable in the up and down direction relative to the actuator main body 41. The actuator mechanism 40 changes the angle of the lower arm 5 relative to the vehicle body by changing the amount of up and down stroke of the shaft member 70 relative to the actuator main body 41, thereby adjusting the height of the vehicle body from the ground.

[0031] The actuator body 41 includes a drive unit 50 that generates power, and a nut member 60 that is arranged to surround the side surface of the shaft member 70 .

[0032] The drive device 50 includes, for example, a motor 51 controlled by a signal from a control system or the like provided in the vehicle, a gear 52 that transmits the power of the motor 51 to the nut member 60, and a non-excitation brake 53.

[0033] The non-excitation brake 53 can have a conventionally known structure and suppresses rotation of the gear 52 when the voltage applied to the motor 51 is cut off. By suppressing rotation of the gear 52, the nut member 60 becomes unable to rotate, thereby stopping the vertical movement of the shaft member 70. In this way, the non-excitation brake 53 prevents changes in the vertical stroke amount of the shaft member 70 even when the power supply to the motor 51 is cut off, and can prevent a drop in vehicle height due to its own weight.

[0034] As an example, the shaft member 70 is formed in a large-diameter cylindrical shape. The shaft member 70 also has a spiral rolling element rolling groove 71 on its outer surface and a plurality of spline grooves 72 extending along the axial direction. The shaft member 70 is supported by anti-rotation portions 43 that engage with the spline grooves 72 so as to be non-rotatable about its axis but movable in the axial direction relative to the actuator body 41.

[0035] Furthermore, the damper mechanism 10 is disposed inside the cylindrical shaft member 70. With this structure, the suspension device 1 constitutes an in-line suspension device in which the actuator mechanism 40, the suspension spring 3, and the damper mechanism 10 are disposed in series and are disposed between the unsprung structure and the sprung structure.

[0036] As an example, the nut member 60 is formed in a low, generally cylindrical shape. The nut member 60 also includes a gear portion 62 and a bearing portion (not shown) on its outer surface. The nut member 60 is rotatably supported by the bearing portion relative to the actuator body 41. The gear portion 62 engages with the gear 52 of the drive device 50, and rotates the nut member 60 about its axis in response to rotation of the motor 51.

[0037] A loaded rolling element rolling groove is formed on the inner surface of the nut member 60, corresponding to the spiral rolling element rolling groove 71 formed on the outer surface of the shaft member 70. The loaded rolling element rolling groove is formed so as to circulate around the inner surface of the nut member 60. A plurality of rolling elements (not shown) are arranged between the loaded rolling element rolling groove and the rolling element rolling groove 71. Steel balls, for example, are preferably used as the rolling elements.

[0038] The nut member 60 is threadedly engaged with the shaft member 70 via rolling elements that roll between the loaded rolling element rolling grooves and the rolling element rolling grooves 71. The nut member 60 supports the shaft member 70 so that it can freely reciprocate in the axial direction in response to rotation of the nut member 60 about its axis.

[0039] With such an actuator mechanism 40, the vehicle height can be adjusted by the operation described below.

[0040] When a motor 51 of a drive unit 50 is rotated by a signal from a control system or the like provided in a vehicle, a gear 52 connected to the output shaft of the motor 51 rotates. The gear 52 is engaged with a gear portion 62 of a nut member 60, causing the nut member 60 to rotate.

[0041] The shaft member 70 that threads onto the nut member 60 is supported non-rotatably but axially movable by the engagement between the spline grooves 72 and the anti-rotation portion 43. Therefore, the shaft member 70 moves axially relative to the actuator body 41 in response to rotation of the nut member 60. At this time, the damper mechanism 10, suspension spring 3, and fork 2 move axially together with the shaft member 70.

[0042] The actuator body 41 is attached to the vehicle body, and the fork 2 moves axially together with the shaft member 70. Therefore, the distance between the vehicle body and the lower end of the fork 2 changes with the axial movement of the shaft member 70, and the lower arm 5 connected to the lower end of the fork 2 changes its angle relative to the vehicle body. This changes the vertical position of the wheel 6 relative to the vehicle body, making it possible to adjust the vehicle height.

[0043] In this embodiment, any part of the unsprung structure is provided with an acceleration sensor (not shown) that detects the acceleration of the unsprung structure in the vertical direction. The acceleration sensor is preferably attached to a part disposed near the wheel 6.

[0044] Next, a method for controlling the raising and lowering of the vehicle height using the suspension device 1 will be described using the following embodiment as an example.

[0045] [Embodiment Using Conventional Control Method] First, a case where the suspension device 1 is controlled using a conventional suspension device control method will be described. The following description will also be given of a case where the suspension device 1 is made to function as an active suspension, and is controlled so as not to change the vertical position of the sprung structure while the vehicle is traveling.

[0046] Figure 3 is a block diagram showing a conventional suspension system control method, and Figure 4 is a conceptual diagram showing the state of the suspension system driven by the conventional control method, with (a) showing the vehicle stopped, (b) showing the state when the acceleration of the unsprung structure is acquired, and (c) showing the state when the actuator mechanism is driven. In Figure 4(a), the mass of the unsprung structure is indicated as m1 and the mass of the sprung structure is indicated as m2. Also, the spring element of the suspension spring 3 is indicated as ks, the spring element of the bushings 4a and 5a is indicated as kb, and the damper element of the damper mechanism 10 is indicated as d1.

[0047] In step S1, position information of the unsprung structure and the sprung structure when the vehicle is stopped is acquired. In step S1, for example, when the system is started by pressing the vehicle's engine start button or when the parking brake is turned on, the position information of the sprung structure relative to the unsprung structure is initialized to acquire initial state position information. By appropriately initializing the position information of the sprung structure relative to the unsprung structure, it is possible to appropriately control the suspension device 1 even if the number of occupants or the vehicle weight changes. The position information of the sprung structure relative to the unsprung structure in the initial state acquired in step S1 corresponds to the distance z0 between mass m1 and mass m2 in Figure 4(a). In this embodiment, the process in step S1 is defined as an initial position acquisition process.

[0048] In step S2, the vertical acceleration acting on the unsprung structure caused by vibrations and shocks received by the wheels 6 of the vehicle from the road surface while the vehicle is in motion is acquired. The vertical acceleration acting on the unsprung structure is acquired by an acceleration sensor or the like installed on any member of the unsprung structure. The acceleration acquired in step S2 corresponds to the vertical acceleration of mass m1 in FIG. 4(b). In this embodiment, the process in step S2 is defined as an unsprung acceleration acquisition process. The acceleration sensor or the like functions as unsprung acceleration acquisition means in the control device of the suspension device and as an unsprung acceleration acquisition unit in the control system of the suspension device.

[0049] In step S3, the vertical movement distance of the unsprung structure (hereinafter referred to as the wheel movement amount estimate) is estimated based on the vertical acceleration of the unsprung structure acquired in step S2. The wheel movement amount estimate estimated in step S3 corresponds to the distance za from the position of the unsprung structure m1 in the initial state to the position of the unsprung structure m1 at the time the acceleration is acquired in Figure 4(b). In this embodiment, the process in step 3 is defined as a wheel movement amount estimate value calculation process. Note that the wheel movement amount is estimated by control means having a conventionally well-known microprocessor or the like, and this control means functions as wheel movement amount estimation calculation means in a control device for the suspension device and a wheel movement amount estimation calculation unit in a control system for the suspension device.

[0050] In step S4, the expansion / contraction amount of the actuator mechanism 40 (hereinafter referred to as the stroke command value) is calculated based on the initial position (distance z0) of the sprung structure acquired in step S1 and the wheel movement amount estimated value (distance za) acquired in step S3. The stroke command value is calculated so as to be a predetermined value relative to the wheel movement amount estimated value (distance za). Figure 5 is a graph showing the stroke command value relative to the wheel movement amount estimated value.

[0051] The stroke command value is calculated so as to suppress vibration of the sprung structure when the unsprung structure receives vibrations or impacts from unevenness in the road surface. The stroke command value is calculated taking into consideration the case where vibrations, etc. received by the unsprung structure from the road surface are absorbed by the suspension springs 3 and the damper mechanism 10. The stroke command value corresponds to the distance zb from the position of the sprung structure m2 in the initial state shown in Figure 4(a) to the position of the sprung structure m2 at the time of acquiring the acceleration of the unsprung structure shown in Figure 4(b). In this embodiment, the process in step S4 is defined as a stroke command value calculation process.

[0052] In step S5, the actuator mechanism 40 is driven based on the stroke command value (distance zb) calculated in step S4. The stroke command value (distance zb) calculated in step S4 is input to the drive device 50 of the actuator mechanism 40, which drives the motor 51 to move the shaft member 70 in the axial direction by the distance zb. The amount of movement of the shaft member 70 of the actuator mechanism 40 driven in step S5 corresponds to the actuator movement distance zb in FIG. 4(c). In this embodiment, the process in step S5 is defined as an actuator control execution process.

[0053] In addition, in FIG. 4C, the distance that the sprung structure m2 actually moves as a result of driving the actuator mechanism 40 in step S5 is shown as distance zb'.

[0054] According to the conventional suspension device control method, as shown in Figure 4(c), a discrepancy occurs between the stroke command value (distance zb) for driving the actuator mechanism 40 and the distance (distance zb') that the sprung structure m2 actually moves. This is because the bushings 4a, 5a provided on the upper arm 4 and lower arm 5 have the characteristics of the spring element kb, and so when the actuator mechanism 40 expands or contracts, the bushings 4a, 5a deform and absorb the expansion or contraction of the actuator mechanism 40. For this reason, not all of the expansion or contraction of the actuator mechanism 40 translates into the movement of the sprung structure m2.

[0055] FIG. 6 shows the relationship between the stroke command value (distance zb) for driving the actuator mechanism 40 and the actual movement amount (distance zb') of the sprung structure m2. The solid line in FIG. 6 represents a case where control is performed using a conventional suspension system control method. The dashed line in FIG. 6 represents a case where the stroke command value (distance zb) and the movement amount (distance zb') of the sprung structure m2 are equal. In other words, the difference between the solid line and the dashed line in the vertical direction represents the deviation amount of the movement amount of the sprung structure m2 from the stroke command value (distance zb).

[0056] When the actuator mechanism is driven using this conventional suspension system control method, a discrepancy occurs between the stroke command value and the actual change in vehicle height, resulting in the problem that the suppression of vertical vibrations of the sprung structure cannot be properly controlled.

[0057] [First Embodiment] Next, a description will be given of a suspension system control method according to a first embodiment of the present invention, which solves the problems associated with conventional suspension system control methods. Note that steps that are the same as or similar to those in the above-described conventional embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0058] FIG. 7 is a block diagram showing a control method for a suspension device according to the first embodiment, and FIG. 8 is a conceptual diagram showing the state in which the suspension device is driven by the control method according to the first embodiment, where (a) shows the vehicle stopped, (b) shows the state when the acceleration of the unsprung structure is acquired, and (c) shows the state in which the actuator mechanism is driven.

[0059] The process from step S1 to step S3 is the same as that of the embodiment according to the conventional control method.

[0060] In step S4a, a reference extension / contraction amount of the actuator mechanism 40 (hereinafter referred to as a reference stroke command value) is calculated based on the initial position (distance z0) of the sprung structure acquired in step S1 and the estimated wheel movement amount (distance za) acquired in step S3. The reference stroke command value is calculated so as to be a predetermined value relative to the estimated wheel movement amount (distance za), as shown in FIG.

[0061] The reference stroke command value is calculated to suppress vibration of the sprung structure when the unsprung structure receives vibrations or impacts from road irregularities, similar to the stroke command value obtained in step S4 of the embodiment using the conventional control method. The reference stroke command value is calculated taking into account the case where the suspension springs 3 and the damper mechanism 10 absorb vibrations and other shocks received by the unsprung structure from the road surface. The reference stroke command value corresponds to the distance zb from the position of the sprung structure m2 in the initial state shown in FIG. 8(a) to the position of the sprung structure m2 at the time of acquiring the acceleration of the unsprung structure shown in FIG. 8(b). In this embodiment, the process in step S4a is defined as a reference stroke command value calculation process. The calculation of the reference stroke command value is performed by the control means described above, and the control means functions as a reference stroke command value calculation means in the control device for the suspension device and a reference stroke command value calculation unit in the control system for the suspension device.

[0062] In step S4b, a correction value for the expansion / contraction amount of the actuator mechanism 40 (hereinafter referred to as a bushing influence correction value (distance zc)) is calculated based on the wheel movement amount estimated value (distance za) acquired in step S3. The bushing influence correction value (distance zc) is calculated so as to be a predetermined value with respect to the wheel movement amount estimated value (distance za). Figure 9 is a graph showing the bushing influence correction value with respect to the wheel movement amount estimated value.

[0063] As an example, the bushing influence correction value (distance zc) can be obtained by measuring the relationship between the estimated wheel movement amount (distance za) and the vertical movement amount of the sprung structure before shipping a produced vehicle. In addition to this method, the bushing influence correction value (distance zc) may also be obtained by using a laser sensor or the like attached to the sprung structure to measure the height of the sprung structure from the ground while the vehicle is stopped and the height of the sprung structure from the ground while subjected to vibration, and then calculating the relationship between the estimated wheel movement amount (distance za). In this embodiment, the process in step S4b is defined as a bushing influence correction value calculation process. The calculation of the bushing influence correction amount is performed by the control means described above, and the control means functions as bushing influence correction value calculation means in the control device for the suspension device and as a bushing influence correction value calculation unit in the control system for the suspension device.

[0064] In step S4-2, the reference stroke command value (distance zb) calculated in step S4a and the bushing influence correction value (distance zc) calculated in step S4b are added together to calculate the expansion / contraction amount (hereinafter referred to as the final stroke command value (distance zb+zc)) that will actually drive the actuator mechanism 40. In this embodiment, the process in step S4-2 is defined as a final stroke command value calculation process.

[0065] In step S5, as in the conventional control method, the actuator mechanism 40 is driven based on the final stroke command value (distance zb+zc) calculated in step S4-2. The final stroke command value (distance zb+zc) calculated in step S4-2 is input to the drive device 50 of the actuator mechanism 40, which drives the motor 51 to move the shaft member 70 axially by the distance zb+zc.

[0066] According to the suspension control method of the first embodiment, the final stroke command value can be calculated taking into account the amount of expansion and contraction of the actuator that is absorbed by the deformation of the bushings 4 a, 5 a. Therefore, as shown in Figure 8(c), even if the unsprung structure m1 is subjected to vibrations or impacts from unevenness in the road surface, the actuator mechanism 40 can be controlled to an appropriate amount of expansion and contraction so as to suppress vibrations of the sprung structure m2.

[0067] Second Embodiment As described above, the suspension control method according to the first embodiment is a method for controlling the suspension device 1 by correcting the stroke command value for driving the actuator mechanism 40, taking into account the amount of expansion and contraction of the actuator that is absorbed by the bushings 4 a, 5 a.

[0068] The suspension device 1 according to this embodiment includes a suspension spring 3 and a damper mechanism 10. The bushings 4a, 5a are made of elastic materials, and therefore have not only spring characteristics but also damper characteristics. Therefore, when the actuator mechanism 40 is quickly driven to control the extension and contraction of the suspension device 1, resistance from the damper elements, which acts in the opposite direction to the resistance of the suspension spring 3 and bushings 4a, 5a as spring elements, is generated between the unsprung structure and the sprung structure.

[0069] In such cases, the correction value that takes into account only the steady-state spring elements of the bushings 4a and 5a may not be sufficient to provide sufficient correction, and there is room for improvement in order to improve the vertical vibration suppression of the sprung structure.

[0070] The suspension system control method according to the second embodiment of the present invention, which will be described next, differs from the suspension system control method of the first embodiment in that it takes into account the transient state of the suspension system 1, which expands and contracts in response to vibrations and shocks that a traveling vehicle receives from the road surface. Note that steps that are the same as or similar to those in the conventional embodiment and the first embodiment described above are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0071] FIG. 10 is a block diagram showing a control method for the suspension device according to the second embodiment.

[0072] The processes of steps S1 and S2 are the same as those in the embodiment according to the conventional control method.

[0073] In step S3a, the vertical movement distance of the unsprung structure (estimated wheel movement amount (distance za)) and the vertical speed of the unsprung structure (estimated wheel vertical speed) are estimated based on the vertical acceleration of the unsprung structure acquired in step S2. In this embodiment, the process in step S3a is defined as a wheel movement amount and speed estimate calculation process.

[0074] The processes of steps S4a and S4b are the same as those in the first embodiment.

[0075] In step S4c, a correction value for the expansion / contraction amount of the actuator mechanism 40 in a transient state (hereinafter referred to as a transient state correction value (distance zd)) is calculated based on the wheel movement amount estimated value (distance za) and the wheel up / down speed estimated value acquired in step S3a. In this embodiment, the process in step S4c is defined as a transient state correction value calculation process.

[0076] Next, the transient state correction value calculation step will be described with reference to Fig. 11, which is a block diagram showing the calculation method in the transient state correction value calculation step.

[0077] In step S11, the estimated wheel movement amount (distance za) obtained in step S3a is read.

[0078] In step S12, the estimated wheel vertical speed value obtained in step S3a is read.

[0079] In step S13, a correction coefficient K is obtained based on the estimated wheel movement amount (distance za) obtained in step S11 and the estimated wheel up-down speed obtained in step S12. The correction coefficient K can be obtained from a graph (hereinafter referred to as a correction coefficient detection map), an example of which is shown in FIG. In this embodiment, the process in step S13 is defined as a correction coefficient detection process.

[0080] A preset correction coefficient detection map can be used. In addition, in the case of the damper mechanism 10 provided in the suspension apparatus 1 according to this embodiment, where the damping force can be controlled using a functional fluid such as a magnetorheological fluid and an electromagnetic coil, the correction coefficient detection map may be switched appropriately in accordance with the damping force of the damper mechanism 10.

[0081] In step S14, the time constant Tm of the suspension unit 1 in a transient state is obtained. The time constant Tm can be obtained from a graph (hereinafter referred to as a time constant detection map), an example of which is shown in FIG. 13, based on a damping coefficient corresponding to the damping force of the damper mechanism 10 and the bushings 4a, 5a. A pre-set time constant detection map can be used. In this embodiment, the process in step S14 is defined as a time constant number detection process.

[0082] In step S15, a transient state correction value (distance zd) for the amount of expansion / contraction of the actuator mechanism 40 is calculated for the suspension unit 1 in a transient state. The transient state correction value (distance zd) is calculated using a predetermined formula based on the estimated wheel movement amount (distance za) read in step S11, the correction coefficient K obtained in step S13, and the time constant Tm obtained in step S14. As an example, the transient state correction value (distance zd) can be calculated using formula (1). Here, zd is a transient state correction value, K is a correction coefficient, Tm is a time constant, s is a variable of the Laplace transform, and za is an estimated wheel movement amount.

[0083] Through the processes from step S11 to step S15, the transient state correction value (distance zd) is calculated in step S4c.

[0084] 10, the reference stroke command value (distance zb) calculated in step S4a, the bushing influence correction value (distance zc) calculated in step S4b, and the transient state correction value (distance zd) calculated in step S4c are added together to calculate the expansion / contraction amount (hereinafter referred to as the final stroke command value (distance zb+zc+zd)) that will actually drive the actuator mechanism 40. In this embodiment, the process in step S4-3 is defined as a final stroke command value calculation process.

[0085] The process of step S5 is the same as that of the embodiment according to the conventional control method.

[0086] According to the suspension control method of the second embodiment, the final stroke command value (distance zb+zc+zd) can be calculated taking into account the damping forces of the damper mechanism 10 and the bushings 4a, 5a. Therefore, even when the actuator mechanism 40 is quickly driven to expand or contract the suspension device 1, the actuator mechanism 40 can be controlled to expand or contract by an appropriate amount so as to suppress vibration of the sprung structure m2.

[0087] Although the suspension control method according to the present invention has been described in terms of controlling a suspension device mounted on a vehicle such as a passenger car or truck in which a driver rides, the present invention is not limited to this, and may also be applied to controlling a suspension device mounted on a vehicle such as a delivery robot that is operated from the outside without a driver on board. It is clear from the claims that such modified or improved embodiments are also included within the technical scope of the present invention.

[0088] 1 Suspension device, 3 Suspension spring, 4a, 5a Bushing, 10 Damper mechanism, 40 Actuator mechanism

Claims

1. A control method for a suspension device that can adjust vehicle height by driving an actuator mechanism to expand and contract, wherein the actuator mechanism, a suspension spring, and a damper mechanism that suppresses the amplitude of the suspension spring are arranged in series between an unsprung structure and a sprung structure, and a plurality of bushes are arranged between the unsprung structure and the sprung structure, the control method for a suspension device comprising: an unsprung acceleration acquisition step for acquiring the vertical acceleration of the unsprung structure; a wheel movement amount estimation value calculation step for estimating the vertical movement amount of the unsprung structure based on the information acquired by the unsprung acceleration acquisition step; a reference stroke command value calculation step for calculating a reference expansion amount of the actuator mechanism based on the information acquired by the wheel movement amount estimation value calculation step; and a bush influence correction value calculation step for calculating a bush influence correction value for the expansion amount of the actuator mechanism that takes into account deformation of the bush.

2. A method for controlling a suspension device as described in claim 1, characterized in that the bushing influence correction value is set based on an estimated value of the vertical movement amount of the unsprung structure and an actual measured value of the vertical movement amount of the sprung structure.

3. A method for controlling a suspension device as claimed in claim 1, characterized by comprising a transient state correction value calculation step of calculating a transient state correction value for the amount of expansion and contraction of the actuator mechanism taking into account the transient state of the suspension device.

4. A suspension control method according to claim 3, wherein the transient state correction value is calculated using a correction coefficient corresponding to the damping force of the damper mechanism and the bush.

5. A control device for a suspension device that can adjust vehicle height by driving an actuator mechanism to expand and contract, wherein the actuator mechanism, suspension spring, and damper mechanism that suppresses the amplitude of the suspension spring are arranged in series between an unsprung structure and a sprung structure, and a plurality of bushes are arranged between the unsprung structure and the sprung structure, the control device for a suspension device comprising: unsprung acceleration acquisition means for acquiring the vertical acceleration of the unsprung structure; wheel movement amount estimated value calculation means for estimating the vertical movement amount of the unsprung structure based on information acquired by the unsprung acceleration acquisition means; reference stroke command value calculation means for calculating a reference expansion amount of the actuator mechanism based on information acquired by the wheel movement amount estimated value calculation means; and bush influence correction value calculation means for calculating a bush influence correction value for the expansion amount of the actuator mechanism taking into account deformation of the bush.

6. A control system for a suspension device that can adjust vehicle height by driving an actuator mechanism to expand and contract, wherein the actuator mechanism, a suspension spring, and a damper mechanism that suppresses the amplitude of the suspension spring are arranged in series between an unsprung structure and a sprung structure, and a plurality of bushes are arranged between the unsprung structure and the sprung structure, the control system for a suspension device comprising: an unsprung acceleration acquisition unit that acquires the vertical acceleration of the unsprung structure; a wheel movement amount estimation value calculation unit that estimates the vertical movement amount of the unsprung structure based on information acquired by the unsprung acceleration acquisition unit; a reference stroke command value calculation unit that calculates a reference expansion amount of the actuator mechanism based on information acquired by the wheel movement amount estimation value calculation unit; and a bush influence correction value calculation unit that calculates a bush influence correction value for the expansion amount of the actuator mechanism taking into account deformation of the bush.

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