Suspension control system

Abstract

To provide a suspension control system which can adjust feedback gain adequately.SOLUTION: A first acquisition part 80 acquires a road surface displacement related value related to displacement in a vertical direction of a road surface in front of a vehicle. A second acquisition part 82 acquires a state quantity related to displacement in a vertical direction of a spring upper structure body or a spring lower structure body of the vehicle. A lead-out part 84 leads out a rate of a magnitude of a component of a first frequency band and a magnitude of a component of a second frequency band in time series data of the acquired road surface displacement related value or the acquired state quantity. The control part 90 executes feed-forward control for reducing vibration of the spring upper structure body on the basis of the acquired road surface displacement related value and also executes feedback control for reducing vibration of the spring upper structure body on the basis of the acquired state quantity. A setting part 86 sets a feedback gain largely if feed-forward control is not executed adequately when the led-out rate is threshold value or more.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a suspension control system. [Background technology]

[0002] Patent Document 1 discloses a vibration-damping control device for a vehicle. The vibration-damping control device acquires a road surface displacement-related value at a predicted passing position as preview information based on measurement data, and executes preview vibration-damping control that controls a control force generating device based on a final target control force including a first target control force calculated using the preview information. The measurement data includes data in which a road surface displacement-related value acquired when a measurement vehicle actually travels on a road surface is associated with position information indicating a position when the road surface displacement-related value was acquired. When the vibration-damping control device determines that there is a high probability that the road surface condition has changed since a past point in time, it sets the magnitude of the first target control force to a small value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-064361 Summary of the Invention [Problem to be solved by the invention]

[0004] In vehicles equipped with an active suspension that performs feedback control, for example, in a torsion bar type active suspension, the wheel rate may be set higher than normal. Also, since the vibration of the sprung structure can be damped by the vibration damping control of the active suspension and there is no need to damp the vibration of the sprung structure by the damping of the absorber, the damping coefficient of the absorber may be set lower than normal. For these reasons, if the feedback gain of the feedback control is too small, the vibration may become too large. On the other hand, if the feedback gain is too large, the vibration in the low frequency band can be suppressed, but the vibration in the mid-to-high frequency band may worsen.

[0005] Here, an active suspension that performs feedback control in addition to preview vibration suppression control is known. In this configuration, if the input to the sprung structure can be sufficiently reduced by the preview vibration suppression control, and if the input in the mid- to high-frequency range that may cause vibration to worsen due to feedback control is relatively large, the feedback gain can be reduced to suppress the worsening of vibration in the mid- to high-frequency range caused by the feedback control without substantially affecting vibration in the low-frequency range, which is effective.

[0006] However, in the preview vibration suppression control, when the vehicle travels in a place where the road surface displacement-related value of the map of the measurement data is incorrect due to a change in the road surface condition caused by road construction or the like, when the vehicle travels in an area where the road surface displacement-related value of the map is mixed, or when the accuracy of the predicted passing position is poor due to poor position accuracy of the vehicle, the road surface displacement-related value of the predicted passing position acquired as the preview information is likely to be inappropriate. In this case, since the input cannot be sufficiently reduced by the preview vibration suppression control, by reducing the feedback gain when the input of the mid-high frequency band is relatively large, the deterioration of the vibration of the mid-high frequency band can be suppressed, but the vibration of the low frequency band may become large. In such a situation, it is desirable to appropriately adjust the feedback gain.

[0007] An object of the present invention is to provide a suspension control system capable of appropriately adjusting a feedback gain. [Means for solving the problem]

[0008] In order to solve the above problems, a suspension control system according to an embodiment of the present invention includes an actuator that adjusts a suspension stroke of a controlled wheel of a vehicle, and a control device that controls the actuator. The control device includes a first acquisition unit that acquires a road surface displacement-related value related to a vertical displacement of a road surface in front of the vehicle, a second acquisition unit that acquires a state quantity related to a vertical displacement of a sprung structure or an unsprung structure of the vehicle, a derivation unit that derives a ratio between a magnitude of a component of a predetermined first frequency band in time-series data of the acquired road surface displacement-related value or the state quantity and a magnitude of a component of a predetermined second frequency band higher than the first frequency band, a control unit that controls the actuator to execute feedforward control to reduce vibration of the sprung structure based on the acquired road surface displacement-related value and execute feedback control to reduce vibration of the sprung structure based on the acquired state quantity, and a setting unit that sets a feedback gain of the feedback control to be larger when the feedforward control is not being executed appropriately when the derived ratio is equal to or greater than a threshold value, compared to when the feedforward control is executed appropriately. Effect of the Invention

[0009] According to the present invention, it is possible to provide a suspension control system capable of appropriately adjusting a feedback gain. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a schematic configuration of the suspension of FIG. [Diagram 3] 1 is a block diagram showing a configuration example of a suspension control system according to an embodiment; [Figure 4] 1 is a block diagram showing an example of a configuration of a map management device according to an embodiment; [Diagram 5] 4 is a flowchart showing a suspension control process according to the embodiment. [Figure 6] 6 is a flowchart showing a feedback gain setting process in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and duplicated description will be omitted as appropriate.

[0012] 1. Suspension and road surface displacement related values 1 shows a schematic configuration of a vehicle 1 according to an embodiment. The vehicle 1 includes a left front wheel 2FL, a right front wheel 2FR, a left rear wheel 2RL, a right rear wheel 2RR, a suspension 3FL, a suspension 3FR, a suspension 3RL, a suspension 3RR, and a suspension control system 10. The left front wheel 2FL, the right front wheel 2FR, the left rear wheel 2RL, and the right rear wheel 2RR are provided with corresponding suspensions 3FL, 3FR, 3RL, and 3RR, respectively. Hereinafter, unless otherwise required, each wheel will be referred to as a wheel 2, and each suspension will be referred to as a suspension 3.

[0013] FIG. 2 shows a schematic configuration of the suspension 3 in FIG. 1. The suspension 3 is provided to connect between the unsprung structure 4 and the sprung structure 5 of the vehicle 1. The unsprung structure 4 includes the wheels 2. The suspension 3 includes a spring 3S, a damper 3D, and an actuator 3A. The damper 3D is also called a shock absorber. The spring 3S, the damper 3D, and the actuator 3A are provided in parallel between the unsprung structure 4 and the sprung structure 5. The actuator 3A controls the stroke of the suspension 3. The spring 3S has a spring constant K. The damper 3D has a damping coefficient C. The actuator 3A applies a vertical control force Fc between the unsprung structure 4 and the sprung structure 5, thereby adjusting the stroke of the suspension 3.

[0014] More specifically, the actuator 3A is, for example, an electric or hydraulic active actuator, and is an actuator constituting a so-called full active suspension. Alternatively, the actuator 3A may be, for example, an actuator that varies the damping force generated by the damper 3D, or an actuator of an active stabilizer device. Furthermore, the "actuator" of the present disclosure may be, for example, an actuator such as an electric motor that generates a vehicle longitudinal force in a vehicle equipped with a suspension configured to be able to convert the driving force and braking force acting on the wheels, which are the vehicle longitudinal forces, into a control force Fc by utilizing the suspension geometry. The electric motor may be, for example, an in-wheel motor (IWM) provided on the wheel, or may be an electric motor capable of driving the wheel via a vehicle drive shaft.

[0015] Here, the terms are defined. "Road surface displacement Zr" is the vertical displacement of the road surface RS. "Unsprung displacement Zu" is the vertical displacement of the unsprung structure 4. "Sprung displacement Zs" is the vertical displacement of the sprung structure 5. "Unsprung velocity Zu'" is the vertical velocity of the unsprung structure 4. "Sprung velocity Zs'" is the vertical velocity of the sprung structure 5. "Unsprung acceleration Zu''" is the vertical acceleration of the unsprung structure 4. "Sprung acceleration Zs''" is the vertical acceleration of the sprung structure 5. The sign of each parameter is positive when pointing upward and negative when pointing downward.

[0016] The wheel 2 moves on the road surface RS. Hereinafter, values ​​related to the road surface displacement Zr will be referred to as "road surface displacement-related values". Examples of the road surface displacement-related values ​​include the road surface displacement Zr, the road surface displacement velocity Zr' which is the time derivative value of the road surface displacement Zr, the unsprung displacement Zu, the unsprung velocity Zu', the unsprung acceleration Zu'', the sprung displacement Zs, the sprung velocity Zs', and the sprung acceleration Zs'', etc. The road surface displacement-related values ​​can also be said to be "vertical movement parameters" which are parameters related to the vertical movement of the wheel 2.

[0017] As an example, the case where the road surface displacement-related value is the unsprung displacement Zu will be described below. When generalizing, the "unsprung displacement" in the following description should be read as the "road surface displacement-related value".

[0018] Here, an example of the unsprung displacement calculation process will be described. First, the sprung acceleration Zs'' is detected by the sprung acceleration sensor 22 installed in the sprung structure 5. Next, the sprung displacement Zs is calculated by integrating the sprung acceleration Zs'' twice.

[0019] Next, a stroke ST, which is a relative displacement between the sprung structure 5 and the unsprung structure 4, is obtained. "Stroke ST" = "Sprung displacement Zs" - "Unsprung displacement Zu". For example, the stroke ST is detected by a stroke sensor installed in the suspension 3. As another example, the stroke ST may be estimated based on the sprung acceleration Zs'' by an observer configured based on a single wheel two-degree-of-freedom model.

[0020] Next, in order to suppress the influence of sensor drift and the like, a filtering process is performed on the time series data of the sprung displacement Zs. Similarly, a filtering process is performed on the time series data of the stroke ST. For example, the filter is a band-pass filter that passes signal components in a specific frequency band. The specific frequency band may be set so as to include the sprung resonance frequency of the vehicle 1. For example, the specific frequency band is 0.3 to 10 Hz.

[0021] Next, the difference between the sprung displacement Zs and the stroke ST is calculated as the unsprung displacement Zu.

[0022] Instead of performing filtering processing on the time series data of the sprung displacement Zs and the stroke ST, filtering processing may be performed on the time series data of the calculated unsprung displacement Zu.

[0023] As yet another example, the unsprung acceleration Zu'' may be detected by an unsprung acceleration sensor, and the unsprung displacement Zu may be calculated from the unsprung acceleration Zu''.

[0024] 2.Suspension control system 3 is a block diagram showing an example of the configuration of a suspension control system 10 according to an embodiment. The suspension control system 10 is mounted on a vehicle 1. The suspension control system 10 includes a vehicle state sensor 20, a position sensor 40, a communication device 50, an actuator 3A, and an ECU 70. The ECU 70 is an electronic control unit.

[0025] The vehicle state sensor 20 detects the state of the vehicle 1 and supplies the detection result to the ECU 70. The vehicle state sensor 20 includes a vehicle speed sensor 21 that detects the vehicle speed V of the vehicle 1, a sprung acceleration sensor 22 that detects the sprung acceleration Zs'', and a stroke sensor 23 that detects the stroke ST. The vehicle state sensor 20 may include an unsprung acceleration sensor. The vehicle state sensor 20 may include a lateral acceleration sensor, a yaw rate sensor, a steering angle sensor, etc.

[0026] The position sensor 40 detects the position and orientation of the vehicle 1, and supplies the detected position information to the ECU 70. For example, the position sensor 40 includes a Global Navigation Satellite System (GNSS) receiver.

[0027] The communication device 50 communicates with the outside of the vehicle 1 .

[0028] The ECU 70 is a computer that controls the vehicle 1. The ECU 70 includes a processor 71 and a storage device 72. The processor 71 executes various processes. For example, the processor 71 includes a CPU (Central Processing Unit). The storage device 72 stores various information required for processing by the processor 71. Examples of the storage device 72 include a volatile memory, a non-volatile memory, a HDD (Hard Disk Drive), and an SSD (Solid State Drive).

[0029] The processor 71 has a first acquisition unit 80, a second acquisition unit 82, a derivation unit 84, a setting unit 86, a calculation unit 88, and a control unit 90. The processor 71 executes a suspension control program stored in the storage device 72 to realize the functions of the first acquisition unit 80, the second acquisition unit 82, the derivation unit 84, the setting unit 86, the calculation unit 88, and the control unit 90. The suspension control program may be recorded in a computer-readable recording medium. The ECU 70 corresponds to an example of a "control device" in the present disclosure.

[0030] The storage device 72 stores an unsprung displacement map 200. The unsprung displacement map 200 will be described in detail later.

[0031] The ECU 70 controls the suspension 3 by controlling the actuator 3A. Specifically, the ECU 70 performs vibration suppression control to suppress vibration of the vehicle 1 by controlling the suspension 3. The ECU 70 controls the actuator 3A to generate a vertical control force Fc between the unsprung structure 4 and the sprung structure 5, as shown in FIG. 2. The vibration suppression control includes a "preview control" and a "feedback control" which will be described later. The preview control can also be called a feedforward control. The vibration suppression control will be described in detail later.

[0032] 3.Map management device 3-1. Configuration example 4 is a block diagram showing an example of a configuration of a map management device 100 according to an embodiment. The map management device 100 is a computer that manages various types of map information. The management of map information includes the generation, update, provision, and distribution of the map information. Typically, the map management device 100 is a management server on a cloud. The map management device 100 may be a distributed system in which multiple servers perform distributed processing.

[0033] The map management device 100 includes a communication device 110. The communication device 110 is connected to a communication network N1. For example, the communication device 110 communicates with a large number of vehicles 1 via the communication network N1.

[0034] The map management device 100 further includes a processor 120 and a storage device 130. The processor 120 executes various information processing. For example, the processor 120 includes a CPU. The storage device 130 stores various map information. The storage device 130 also stores various information required for processing by the processor 120. Examples of the storage device 130 include a volatile memory, a non-volatile memory, a HDD, and an SSD.

[0035] The map management program is a computer program for map management, and is executed by the processor 120. The map management program is stored in the storage device 130. Alternatively, the map management program may be recorded in a computer-readable recording medium. The functions of the map management device 100 are realized by the processor 120 executing the map management program.

[0036] The processor 120 communicates with the suspension control system 10 of the vehicle 1 via the communication device 110. The processor 120 collects various information from the suspension control system 10, and generates and updates map information based on the collected information. The processor 120 distributes the map information to the suspension control system 10. The processor 120 provides the map information in response to a request from the suspension control system 10.

[0037] 3-2.Unsprung displacement map One of the map information managed by the map management device 100 is an unsprung displacement map 200. The unsprung displacement map 200 is a map relating to unsprung displacement Zu, which is a road surface displacement-related value. The unsprung displacement map 200 is stored in the storage device 130. The unsprung displacement map 200 corresponds to an example of a "road surface data map in which a road surface displacement-related value related to the vertical displacement of the road surface is associated with a position" in the present disclosure.

[0038] The unsprung displacement map 200 represents the correspondence relationship between the position (X, Y) and the unsprung displacement Zu on the XY plane. In other words, the unsprung displacement map represents the unsprung displacement Zu as a function of the position (X, Y). The XY plane represents a horizontal plane. For example, the absolute coordinate system on the horizontal plane is defined by the latitude and longitude directions, and the position is defined by the latitude and longitude.

[0039] The road area may be divided into a mesh shape on a horizontal plane. That is, the road area may be divided into a plurality of unit areas (hereinafter referred to as "road surface sections") on a horizontal plane. The road surface section is, for example, a square. The length of one side of the square is, for example, 10 cm. The unsprung displacement map 200 represents the correspondence between the position of the road surface section and the unsprung displacement Zu. The position of the road surface section may be defined by a representative position of the road surface section, for example, a central position, or may be defined by a latitude range and a longitude range of the road surface section. The unsprung displacement Zu of the road surface section is, for example, an average value of the unsprung displacement Zu acquired within the road surface section. The smaller the road surface section is, the higher the resolution of the unsprung displacement map 200 is.

[0040] 3-3. Map generation and update processing The processor 120 collects information from multiple vehicles 1 via the communication device 110. Then, the processor 120 generates and updates the unsprung displacement map 200 based on the information collected from the multiple vehicles 1.

[0041] The positions in the unsprung displacement map 200 are positions through which the wheels 2 have passed. The position of each wheel 2 is calculated based on position information detected by the position sensor 40. Specifically, the relative positional relationship between a reference point of the vehicle position on the vehicle 1 and each wheel 2 is known information. The position of each wheel 2 can be calculated based on the relative positional relationship and the vehicle position indicated by the position information.

[0042] The unsprung displacement Zu is calculated by the method described above. That is, the sprung displacement Zs and the stroke ST are obtained by using the vehicle state sensor 20 mounted on the vehicle 1. For convenience, the sprung displacement Zs and the stroke ST are called "sensor-based information." The unsprung displacement Zu is calculated based on this sensor-based information.

[0043] For example, while the vehicle 1 is traveling, the ECU 70 of the suspension control system 10 calculates the unsprung displacement Zu in real time based on the sensor-based information. The ECU 70 also associates the wheel position and the unsprung displacement Zu at the same timing. The ECU 70 then transmits a set of time series data of the wheel position and time series data of the unsprung displacement Zu to the map management device 100. The processor 120 of the map management device 100 generates and updates an unsprung displacement map based on the time series data of the wheel position and the time series data of the unsprung displacement Zu.

[0044] As another example, the ECU 70 of the suspension control system 10 associates the wheel positions with the sensor-based information at the same timing. Then, the ECU 70 transmits a set of time-series data of the wheel positions and time-series data of the sensor-based information to the map management device 100. The processor 120 of the map management device 100 calculates the unsprung displacement Zu based on the received sensor-based information. Furthermore, the processor 120 generates and updates an unsprung displacement map based on the time-series data of the wheel positions and the time-series data of the unsprung displacement Zu.

[0045] The processor 120 of the map management device 100 acquires map update information from the suspension control system 10 of the vehicle 1 via the communication device 110. The map update information includes time series data of the wheel positions, which are the positions of the vehicle 1. The map update information also includes time series data of sensor-based information required to calculate the unsprung displacement Zu. Alternatively, the map update information may include time series data of the unsprung displacement Zu calculated by the ECU 70 of the suspension control system 10.

[0046] The processor 120 of the map management device 100 generates and updates the unsprung displacement map 200 based on the map update information.

[0047] The suspension control system 10 of the vehicle 1 may hold a database of the unsprung displacement map 200 and generate and update its own unsprung displacement map 200. In other words, the map management device 100 may be included in the suspension control system 10.

[0048] 4. Preview control and feedback control using unsprung displacement map The ECU 70 of the suspension control system 10 communicates with the map management device 100 via the communication device 50. The ECU 70 acquires an unsprung displacement map 200 of an area including the current position of the vehicle 1 from the map management device 100. The unsprung displacement map 200 is stored in the storage device 72. The ECU 70 then executes preview control, which is a type of vibration suppression control, based on the unsprung displacement map 200. The preview control is executed to reduce vibration of the sprung structure 5. In addition to the preview control, the ECU 70 also executes feedback control based on the detection values ​​of the sprung acceleration sensor 22 and the stroke sensor 23. The feedback control is also executed to reduce vibration of the sprung structure 5.

[0049] The first acquisition unit 80, the second acquisition unit 82, the derivation unit 84, the setting unit 86, the calculation unit 88, and the control unit 90 repeatedly execute the following process for each time step for each of the four control target wheels.

[0050] First, the preview control will be described. The first acquisition unit 80 acquires the current position of each wheel 2. The relative positional relationship between the reference point of the vehicle position on the vehicle 1 and each wheel 2 is known information. Based on the relative positional relationship and the vehicle position indicated by the position information, the position of each wheel 2 can be calculated.

[0051] The first acquisition unit 80 calculates a predicted passing position Pf of the wheel 2 after a preview time tp from the current time. The preview time tp is a predetermined time, and is set in advance to be, for example, a time required from when the first acquisition unit 80 specifies the predicted passing position Pf until the actuator 3A of the suspension 3 outputs a control force Fc corresponding to the target control force Fc_t. The preview distance Lp is given by the product of the preview time tp and the vehicle speed V. The predicted passing position Pf is a position forward in the vehicle traveling direction from the current position by the preview distance Lp along the predicted moving path along which the wheel 2 is predicted to move. The predicted moving path can be specified, for example, based on the traveling direction of the vehicle 1 and the current position P0 of the wheel 2. The traveling direction can be specified, for example, by the following method. That is, the first acquisition unit 80 maps the current position P0 of the previous time step and the current position P0 of the current time step to map information, and then specifies the direction from the current position of the previous time step to the current position P0 of the current time step as the traveling direction. As a modified example, the first acquisition unit 80 may calculate a predicted travel route based on the vehicle speed V and the steering angle of the wheels 2, and calculate the predicted passing position Pf based on the predicted travel route.

[0052] The first acquisition unit 80 reads out from the unsprung displacement map 200 and acquires the unsprung displacement Zu at the calculated predicted passing position Pf.

[0053] The calculation unit 88 calculates a target control force for the preview control of the actuator 3A of the suspension 3, based on the unsprung displacement Zu at the predicted passing position Pf acquired by the first acquisition unit 80. The target control force for the preview control is calculated using, for example, the following formula (3) or formula (4).

[0054] The equation of motion for the sprung structure 5 in FIG. 2 is expressed by the following equation (1).

[0055] m·Zs''=C(Zu'-Zs')+K(Zu-Zs)-Fc ···(1)

[0056] In equation (1), m is the mass of the sprung structure 5, C is the damping coefficient of the damper 3D, K is the spring constant of the spring 3S, and Fc is the vertical control force generated by the actuator 3A. If the vibration of the sprung structure 5 is completely cancelled out by the control force Fc, then Zs''=0, Zs'=0, Zs=0, and the control force Fc is expressed by the following equation (2).

[0057] Fc = C Zu' + K Zu (2)

[0058] The control force Fc that provides at least the vibration damping effect is expressed by the following formula (3).

[0059] Fc=α·C·Zu'+β·K·Zu ···(3)

[0060] In formula (3), the control gain α is greater than 0 and less than or equal to 1, and the control gain β is also greater than 0 and less than or equal to 1. When the differential term in formula (3) is omitted, a control force Fc that provides at least a vibration damping effect is expressed by the following formula (4).

[0061] Fc = β K Zu (4)

[0062] Next, the feedback control executed simultaneously with the preview control will be described. The second acquisition unit 82 acquires a state quantity related to the vertical displacement of the sprung structure 5 or the unsprung structure 4 of the vehicle 1 from the vehicle state sensor 20 installed in the vehicle 1. As the state quantity, any of the sprung displacement Zs, the sprung velocity Zs', the sprung acceleration Zs'', the unsprung displacement Zu, the unsprung velocity Zu', and the unsprung acceleration Zu'' may be used. Below, as an example, a case where the state quantity is the unsprung velocity Zu' will be described. When generalizing, the "unsprung velocity" in the following description should be read as the "state quantity".

[0063] When using the unsprung velocity Zu', the second acquisition unit 82 can calculate the unsprung velocity Zu' by subtracting ``sprung velocity Zs' - unsprung velocity Zu''', which is the first-order differential value of the stroke ST detected by the stroke sensor 23, from the sprung velocity Zs', which is the first-order integral value of the sprung acceleration Zs'' detected by the sprung acceleration sensor 22.

[0064] The control unit 90 controls the actuator 3A to execute the following feedback control as vibration damping control based on the unsprung velocity Zu' acquired by the second acquisition unit 82, in addition to the preview control described above. The control force Fc when the preview control is performed together with the feedback control is expressed by, for example, the following equation (5). In this example, the calculation unit 88 calculates the target control force Fc_t for the preview control together with the feedback control according to equation (5).

[0065] Fc=β·K·Zu+γ·Zu' ···(5)

[0066] The first term on the right side of equation (5) is the same as equation (4) above, and is a feedforward term related to the preview control. The first term on the right side may be the same as equation (3) above. The second term on the right side is a feedback term related to the feedback control. This feedback term is the product of the feedback gain γ and, for example, the unsprung velocity Zu' at the time of calculating the target control force Fc_t.

[0067] The calculation unit 88 calculates the target control force Fc_t for the preview control accompanied by the feedback control according to the above formula (5). That is, the calculation unit 88 calculates the target control force Fc_t by substituting the unsprung displacement Zu at the predicted passing position Pf and the unsprung velocity Zu' at the time of calculation of the target control force Fc_t into formula (5). This target control force Fc_t corresponds to the required value of the control force Fc required for the preview control and the feedback control.

[0068] One of the features of the embodiment is that the feedback gain γ in the above equation (5) is set as follows.

[0069] The derivation unit 84 derives the reliability of the unsprung displacement Zu of the predicted passing position Pf acquired by the first acquisition unit 80. To derive the reliability, for example, a known technique such as the following derivation method can be used.

[0070] For example, as a first derivation method, the derivation unit 84 may derive the reliability of the unsprung displacement Zu of the predicted passing position Pf higher as the difference between the unsprung displacement Zu of the current passing position of the wheel 2 of the vehicle 1 acquired from the unsprung displacement map 200 and the unsprung displacement Zu of the current passing position of the wheel 2 derived based on the detection values ​​of the sprung acceleration sensor 22 and the stroke sensor 23 is smaller. It can also be said that the higher the reliability of the unsprung displacement Zu of the predicted passing position Pf, the higher the reliability of the unsprung displacement map 200. For example, if the road surface condition changes due to road construction or the like after the unsprung displacement map 200 is created, the reliability of the unsprung displacement Zu of the predicted passing position Pf becomes lower. The first derivation method is disclosed in JP 2022-064361 A and JP 2023-047040 A, and therefore further detailed description will be omitted.

[0071] As a second derivation method, the derivation unit 84 converts the unsprung displacement Zu of the predicted passing position Pf acquired by the first acquisition unit 80 into a road surface displacement, and the smaller the difference between the road surface displacement and the road surface displacement of the predicted passing position Pf acquired by a known preview sensor (not shown), the higher the reliability of the unsprung displacement Zu of the predicted passing position Pf may be derived. It can also be said that the higher the reliability of the unsprung displacement Zu of the predicted passing position Pf, the higher the reliability of the unsprung displacement map 200. The second derivation method is disclosed in JP 2022-024499 A, and therefore further detailed description will be omitted.

[0072] As a third derivation method, the derivation unit 84 may derive the reliability of the position information of the vehicle 1 detected by the position sensor 40, and derive a higher reliability of the unsprung displacement Zu of the predicted passing position Pf as the reliability of the position information is higher. The reliability of the position information may be set as the reliability of the unsprung displacement Zu of the predicted passing position Pf. The reliability of the position information is an index value indicating the accuracy and certainty of the position, and the higher at least one of the accuracy and the certainty is, the larger the value becomes. The third derivation method is disclosed in JP 2023-054955 A, and therefore further detailed description will be omitted.

[0073] When the reliability of the derived unsprung displacement Zu of the predicted passing position Pf is higher than a reference value, the derivation unit 84 derives a ratio between the magnitude of a component in a predetermined first frequency band and the magnitude of a component in a predetermined second frequency band in the time series data of the unsprung displacement Zu. This ratio can also be called the ratio of the magnitude of the component in the second frequency band to the magnitude of the component in the first frequency band. This ratio can also be called an input ratio. The reference value can be appropriately determined by an experiment or a simulation.

[0074] The first frequency band is a frequency band in which feedback control has an effect of suppressing vibration of the sprung structure 5, and is, for example, a low frequency band of 1 to 2 Hz. The second frequency band is a frequency band in which feedback control worsens the vibration of the sprung structure 5, and is, for example, a medium to high frequency band of 3 to 8 Hz. The second frequency band is higher than the first frequency band.

[0075] Since the reliability of the unsprung displacement Zu at the predicted passing position Pf is high, the ratio of the second frequency band components to the first frequency band for determining whether or not to lower the feedback gain γ is derived from the information of the unsprung displacement map 200.

[0076] For example, the derivation unit 84 compares the FFT (Fast Fourier Transformation) values ​​of the first and second frequency bands in the time series data of the unsprung displacement Zu, and derives the input ratio of the first frequency band component to the second frequency band component. Alternatively, the derivation unit 84 may apply a band-pass filter of each of the first and second frequency bands to the time series data of the unsprung displacement Zu, and obtain a peak value within a specific time from the output signal of the band-pass filter, obtain a moving average value, or obtain a value to which a low-pass filter equivalent to the moving average is applied, and derive the input ratio of the first frequency band component to the second frequency band component from the obtained value. The ratio of the second frequency band component to the first frequency band component may be derived using other known techniques.

[0077] To derive the ratio of the second frequency band component to the first frequency band component, any type of road surface displacement related value described above can be used. For example, any type of state quantity whose input is known, such as road surface displacement Zr, road surface displacement velocity Zr', road surface displacement acceleration Zr'', unsprung displacement Zu, unsprung velocity Zu', unsprung acceleration Zu'', sprung displacement Zs, sprung velocity Zs', or sprung acceleration Zs'', can be used. For example, by using the unsprung velocity Zu', the input to the suspension 3 can be directly known, and in addition, in the case of a general road surface characteristic in which the road surface amplitude has a 1 / f characteristic with respect to frequency, that is, when the frequency is 10 times, the road surface amplitude becomes 1 / 10, the FFT characteristic has a flat characteristic with respect to frequency and is at the same level in all frequency bands, so that it is easy to compare the relative magnitude of the input of the first frequency band and the input of the second frequency band.

[0078] The target control is feedback control based on the sprung or unsprung state quantities, and any control can be used as long as the first and second frequency bands can be grasped. For example, in the most common sprung skyhook damper control that outputs a control force proportional to the sprung speed, the vibration damping effect and the deterioration of vibration are observed in the two frequency bands in the above-mentioned frequency range.

[0079] When the reliability of the unsprung displacement Zu at the predicted passing position Pf is below a reference value, the derivation unit 84 derives the ratio between the magnitude of the first frequency band component and the magnitude of the second frequency band component in the time series data of the unsprung velocity Zu' acquired by the second acquisition unit 82.

[0080] Since the reliability of the unsprung displacement Zu at the predicted passing position Pf is low, there is a risk of erroneous judgment if information from the unsprung displacement map 200 is used, and therefore the ratio for judgment is derived using the unsprung velocity Zu' based on the detection values ​​detected by the sprung acceleration sensor 22 and the stroke sensor 23. The method of deriving the ratio is the same as the method described above.

[0081] To derive the ratio of the second frequency band components to the first frequency band components, any type of state quantity can be used instead of the unsprung velocity Zu', such as the unsprung displacement Zu, unsprung acceleration Zu'', sprung displacement Zs, sprung velocity Zs', or sprung acceleration Zs'', as long as the input is known or the response of the sprung mass is known.

[0082] As described above, for example, by using the unsprung velocity Zu', the input to the suspension 3 can be directly determined, and the relative magnitude of the input in the first frequency band and the input in the second frequency band can be easily compared.

[0083] In this way, the derivation unit 84 derives the ratio between the magnitude of the first frequency band component and the magnitude of the second frequency band component in the time series data of the unsprung displacement Zu acquired by the first acquisition unit 80 or the unsprung velocity Zu' acquired by the second acquisition unit 82.

[0084] The setting unit 86 determines that the preview control is being executed appropriately when the unsprung displacement Zu acquired by the first acquisition unit 80 is appropriate, or when the reliability of the unsprung displacement Zu is higher than a reference value. The fact that the preview control is being executed appropriately indicates that the vibration damping effect of the preview control is relatively high. The setting unit 86 may determine that the preview control is being executed appropriately when the acquired unsprung displacement Zu is appropriate and the reliability of the unsprung displacement Zu is higher than a reference value.

[0085] When the unsprung displacement Zu acquired by the first acquisition unit 80 is inappropriate, or when the reliability of the unsprung displacement Zu is equal to or lower than a reference value, the setting unit 86 determines that the preview control is not being executed appropriately. When the preview control is not being executed appropriately, it indicates that the vibration damping effect of the preview control is relatively low.

[0086] In other words, when the reliability of the unsprung displacement Zu is equal to or less than a reference value, the vibration damping effect of the preview control is likely to be low, and therefore the setting unit 86 determines that the preview control is not being performed appropriately. Also, when the reliability of the unsprung displacement Zu is equal to or less than a reference value, the calculation unit 88 may lower the control gains α and β of the preview control. In this case as well, the vibration damping effect of the preview control is low, and therefore the setting unit 86 determines that the preview control is not being performed appropriately.

[0087] When the unsprung displacement Zu is set to zero for a position where the unsprung displacement map 200 does not exist, the unsprung displacement Zu being appropriate means that the unsprung displacement Zu has not remained at zero for a predetermined time or more. The unsprung displacement Zu being inappropriate means that the unsprung displacement Zu has remained at zero for a predetermined time or more. The predetermined time can be appropriately determined by experiment or simulation.

[0088] In addition, when a flag is set for a location where the unsprung displacement map 200 does not exist, the unsprung displacement Zu being appropriate indicates that the flag has not been obtained, and the unsprung displacement Zu being inappropriate indicates that the flag has been obtained.

[0089] When the ratio of the second frequency band components to the first frequency band components derived by the derivation unit 84 is smaller than a predetermined threshold, the setting unit 86 sets the feedback gain γ in the above equation (5) to a predetermined reference gain γ0. The threshold can be appropriately determined by experiment or simulation.

[0090] When the ratio of the second frequency band components to the derived first frequency band components is equal to or greater than a threshold value, the setting unit 86 sets the feedback gain γ to be smaller than the reference gain γ0. This makes it possible to suppress deterioration of vibrations in the mid-to-high frequency bands when the ratio of the second frequency band components to the first frequency band components is equal to or greater than a threshold value.

[0091] When the ratio of the second frequency band components to the derived first frequency band components is equal to or greater than a threshold value and the preview control is not being performed properly, the setting unit 86 sets the feedback gain γ to be larger than when the preview control is being performed properly.

[0092] Specifically, when the derived ratio is equal to or greater than a threshold value and the preview control is being executed appropriately, the setting unit 86 sets the feedback gain γ to a predetermined first gain γ1. The first gain γ1 is smaller than the reference gain γ0. Since the preview control alone is sufficient to adequately damp the vibration of the sprung structure 5, the setting unit 86 sets the feedback gain γ to a value smaller than the reference gain γ0.

[0093] On the other hand, when the derived ratio is equal to or greater than the threshold value and the preview control is not being performed appropriately, the setting unit 86 sets the feedback gain γ to a predetermined second gain γ2. The second gain γ2 is smaller than the reference gain γ0 and larger than the first gain γ1. The reference gain γ0, the first gain γ1, and the second gain γ2 can be appropriately determined through experiments or simulations. Since this is a situation in which the vibration of the sprung structure 5 would become large if feedback control were not performed, the feedback gain γ is set to be larger than the first gain γ1.

[0094] When the vehicle travels through a location where the unsprung displacement Zu in the unsprung displacement map 200 is incorrect, the unsprung displacement Zu at the acquired predicted passing position Pf is likely to be incorrect. Therefore, the preview control is not properly executed. In this case, the input to the sprung structure 5 is likely to be insufficiently reduced by the preview control, but by making the feedback gain γ larger than when the preview control is properly executed, the deterioration of vibration in the low frequency band can be suppressed more than when the first gain γ1 is adopted. In addition, since the second gain γ2 is smaller than the reference gain γ0, the deterioration of vibration in the medium and high frequency bands can be suppressed more than when the reference gain γ0 is adopted. Therefore, the feedback gain γ can be appropriately adjusted.

[0095] In addition, when the derived ratio is equal to or greater than a threshold value, if the reliability of the unsprung displacement Zu is equal to or less than a reference value, the setting unit 86 may set the feedback gain γ to be larger as the reliability decreases. The feedback gain γ is set in a range smaller than the reference gain γ0 and larger than the first gain γ1. This allows the effect of suppressing vibration in the low frequency band by the feedback control to be increased as the vibration suppression effect by the preview control decreases. Therefore, the feedback gain γ can be appropriately adjusted.

[0096] The control unit 90 transmits a control command including the target control force Fc_t to the actuator 3A so that the actuator 3A generates a control force Fc corresponding to the target control force Fc_t calculated according to the formula (5). The actuator 3A generates a control force Fc corresponding to the target control force Fc_t at a timing after the preview time tp from the current time, that is, at the timing when the wheel 2 passes the predicted passing position Pf. In other words, the control unit 90 controls the actuator 3A so that the control force Fc generated by the actuator 3A when the controlled wheel passes the predicted passing position Pf coincides with the target control force Fc_t.

[0097] In this way, the preview control using the unsprung displacement map 200 makes it possible to generate, at an appropriate timing, a control force Fc that suppresses vibration of the sprung structure 5 caused by the unsprung displacement Zu of the predicted passing position Pf of the wheel 2. In addition, the vibration of the sprung structure 5 can also be suppressed by feedback control. This makes it possible to effectively suppress the vibration of the sprung structure 5.

[0098] 5 is a flowchart showing the suspension control process according to the embodiment. The process of this flowchart is repeatedly executed for each of the control target wheels at predetermined time steps while the vehicle 1 is traveling.

[0099] The first acquisition unit 80 acquires the current position of the wheel 2 (S10), acquires a predicted passing position Pf of the wheel 2 (S12), and acquires the unsprung displacement Zu of the predicted passing position Pf of the wheel 2 from the unsprung displacement map 200 (S14).

[0100] The ECU 70 executes a feedback gain setting process shown in Fig. 6, which will be described later (S16). The calculation unit 88 calculates the target control force Fc_t according to equation (5) (S18), and the control unit 90 controls the actuator 3A (S24), and the process ends.

[0101] Fig. 6 is a flowchart showing the feedback gain setting process of S16 in Fig. 5. When the reliability of the unsprung displacement Zu of the predicted passing position Pf is high (Y of S30), the derivation unit 84 derives the ratio of the low frequency band components and the mid-high frequency band components based on the unsprung displacement Zu in the unsprung displacement map 200 (S32), and the process proceeds to S36.

[0102] If the reliability of the unsprung displacement Zu at the predicted passing position Pf is low (N in S30), the derivation unit 84 derives the ratio of low frequency band components and mid-to-high frequency band components based on the unsprung velocity Zu' detected by the sprung acceleration sensor 22 and the stroke sensor 23 (S34), and the processing proceeds to S36.

[0103] Next, if the derived ratio is greater than the threshold value (Y in S36), and if the preview control is being executed appropriately (Y in S38), the setting unit 86 sets the feedback gain γ to the first gain γ1 (S40) and returns to the processing of Fig. 5. If the preview control is not being executed appropriately in S38 (N in S38), the setting unit 86 sets the feedback gain γ to the second gain γ2 (S42) and returns to the processing of Fig. 5.

[0104] In S36, if the derived ratio is equal to or less than the threshold value (N in S36), the setting unit 86 sets the feedback gain γ to the normal gain γ0 (S44), and the process returns to the process of FIG.

[0105] According to the embodiment, when the reliability of the unsprung displacement Zu of the predicted passing position Pf acquired from the unsprung displacement map 200 is higher than a reference value, the ratio of the second frequency band component to the first frequency band component in the time series data of the unsprung displacement Zu of the predicted passing position Pf is derived, so that the feedback gain γ can be adjusted in advance. Therefore, it is possible to more appropriately suppress the deterioration of vibration in the mid-high frequency band due to feedback control.

[0106] In addition, when the reliability of the unsprung displacement Zu acquired from the unsprung displacement map 200 is equal to or lower than a reference value, the ratio of the second frequency band component to the first frequency band component in the time series data of the unsprung velocity Zu' based on the detection values ​​of the sprung acceleration sensor 22 and the stroke sensor 23 is derived, so that a more accurate ratio can be obtained. That is, when the vehicle 1 travels in a place where the unsprung displacement Zu in the unsprung displacement map 200 is incorrect due to a change in the road surface condition due to road construction or the like, when the vehicle 1 travels in an area where the unsprung displacement Zu in the unsprung displacement map 200 is mixed with the presence or absence of the unsprung displacement Zu, when the position accuracy of the vehicle 1 is poor and therefore the accuracy of the predicted passing position Pf is also poor, etc., it is possible to suppress the derivation of an incorrect input ratio based on the unsprung displacement map 200. Therefore, it is possible to suppress the feedback gain γ from being set erroneously.

[0107] In contrast, in the comparative example in which the ratio of the second frequency band components to the first frequency band components is always derived based on the unsprung displacement Zu obtained from the unsprung displacement map 200, there is a possibility that the feedback gain γ will be erroneously adjusted when, for example, the vehicle 1 is traveling through a location where the unsprung displacement Zu in the unsprung displacement map 200 is incorrect.

[0108] In addition, in the embodiment, when the ratio of the second frequency band components to the first frequency band components is equal to or greater than a threshold value, the feedback gain γ can be appropriately adjusted depending on whether the preview control is being performed appropriately, and therefore, the deterioration of vibration in the mid-high frequency bands due to the feedback control can be appropriately suppressed.

[0109] The present invention has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present invention.

[0110] (First Modification) It is not necessary to perform a process of changing the data to be used to derive the frequency characteristics depending on the reliability of the unsprung displacement Zu at the predicted passing position Pf. That is, in the flowchart of Fig. 6, the processes of S30 and S32 may be omitted, and the process of S34 may be performed first. According to this modification, the process can be simplified and the feedback gain γ can be appropriately adjusted.

[0111] (Second Modification) The control unit 90 may execute preview control using a known preview sensor instead of the above-described preview control using the unsprung displacement map 200. The following mainly describes the differences from the embodiment.

[0112] The preview sensor (not shown) includes, for example, at least one of a camera sensor, a LiDAR, and a radar sensor. The preview sensor acquires a road surface displacement Zr of the road surface ahead of the vehicle 1. In the second modified example, the road surface displacement-related value is the road surface displacement Zr. For generalization, the "road surface displacement" in the following description is to be read as the "road surface displacement-related value". The control force Fc in this case is expressed, for example, by the following formula (6). In this example, the calculation unit 88 calculates the target control force Fc_t according to formula (6).

[0113] Fc = γb Zr + γ Zs (6)

[0114] The first term on the right side of equation (6) is a feedforward term related to preview control using a preview sensor. The first term on the right side is the product of gain γb and the road surface displacement Zr ahead of the vehicle 1 acquired by the preview sensor when calculating the target control force Fc_t. Gain γb can be appropriately determined by experiment or simulation. Preview control using a preview sensor is well known, so further detailed description will be omitted.

[0115] The second term on the right-hand side is similar to the second term on the right-hand side of equation (5), and is a feedback term related to feedback control.

[0116] The first acquisition unit 80 acquires the road surface displacement Zr ahead of the vehicle 1 from the preview sensor. The derivation unit 84 derives the reliability of the road surface displacement Zr acquired by the first acquisition unit 80. The reliability of the road surface displacement Zr can also be called the reliability of the preview sensor.

[0117] For example, when there is an input that is sufficiently large relative to the resolution of the preview sensor, i.e., when the detection value of the preview sensor is not zero, the derivation unit 84 derives a high reliability. When there is no input that is sufficiently large relative to the resolution of the preview sensor, i.e., when the detection value of the preview sensor remains zero for a predetermined period of time or more, the derivation unit 84 derives a low reliability.

[0118] Alternatively, the derivation unit 84 may derive a higher reliability as the surrounding environment of the vehicle 1 approaches the conditions under which the preview sensor functions correctly. For example, the derivation unit 84 may derive a high reliability if the weather is sunny, derive a medium reliability if the weather is cloudy, and derive a low reliability if the weather is inclement, such as rain or snow. The derivation unit 84 may derive a higher reliability as the illuminance near the road surface is higher. The derivation unit 84 may derive a high reliability if the road surface is a detectable road surface, and a low reliability if the road surface is an undetectable road surface.

[0119] When the reliability of the road surface displacement Zr is higher than a reference value, the derivation unit 84 derives the ratio of the first frequency band components to the second frequency band components in the time series data of the road surface displacement Zr acquired from the preview sensor by the first acquisition unit 80.

[0120] When the reliability of the road surface displacement Zr is below a reference value, the derivation unit 84 derives the ratio of the first frequency band components to the second frequency band components in the time series data of the unsprung velocity Zu', which is a state quantity acquired by the second acquisition unit 82, as in the embodiment.

[0121] The setting unit 86 determines that the preview control is being executed appropriately when the road surface displacement Zr acquired by the first acquisition unit 80 is appropriate or when the reliability of the road surface displacement Zr is higher than a reference value. The setting unit 86 may determine that the preview control is being executed appropriately when the acquired road surface displacement Zr is appropriate and the reliability of the road surface displacement Zr is higher than a reference value.

[0122] If the road surface displacement Zr acquired by the first acquisition unit 80 is inappropriate, or if the reliability of the road surface displacement Zr is below a reference value, the setting unit 86 determines that the preview control is not being performed appropriately.

[0123] The road surface displacement Zr being appropriate means that the road surface displacement Zr has not remained at zero for a predetermined period of time or more, whereas the road surface displacement Zr being inappropriate means that the road surface displacement Zr has remained at zero for a predetermined period of time or more.

[0124] The setting of the feedback gain γ in the above equation (6) by the setting unit 86 is the same as in the embodiment.

[0125] According to the second modified example, when the reliability of the road surface displacement Zr acquired from the preview sensor is equal to or lower than a reference value, the ratio of the first frequency band components and the second frequency band components in the time series data of the unsprung velocity Zu' based on the detection values ​​of the sprung acceleration sensor 22 and the stroke sensor 23 is derived, so that a more accurate ratio can be obtained. In other words, when the detection value of the preview sensor is likely to be erroneous, such as when the surrounding environment of the vehicle 1 does not meet the conditions for the preview sensor to function correctly, it is possible to suppress the derivation of an erroneous input ratio based on the detection value of the preview sensor. Therefore, it is possible to suppress the feedback gain γ from being erroneously set. Other effects similar to those of the embodiment can also be obtained.

[0126] The first and second modified examples may be combined.

[0127] In the embodiment, the preview control is performed on all four wheels 2 of the vehicle 1. However, the wheels that are the subject of the preview control are not limited to all wheels, and may be, for example, only the left and right front wheels or only the left and right rear wheels. [Explanation of symbols]

[0128] 1...vehicle, 2...wheel, 3...suspension, 3A...actuator, 4...unsprung structure, 5...sprung structure, 10...suspension control system, 22...sprung acceleration sensor, 23...stroke sensor, 40...position sensor, 70...ECU (control device), 80...first acquisition unit, 82...second acquisition unit, 84...derivation unit, 86...setting unit, 88...calculation unit, 90...control unit, 200...unsprung displacement map.

Claims

1. An actuator for adjusting a suspension stroke of a controlled wheel of the vehicle; A control device for controlling the actuator; Equipped with The control device includes: A first acquisition unit that acquires a road surface displacement-related value that is related to a vertical displacement of a road surface in front of the vehicle; A second acquisition unit that acquires a state quantity related to a vertical displacement of a sprung structure or an unsprung structure of the vehicle; a derivation unit that derives a ratio between a magnitude of a component in a predetermined first frequency band in the acquired time-series data of the road surface displacement-related value or the state quantity and a magnitude of a component in a predetermined second frequency band higher than the first frequency band; a control unit that controls the actuator to execute feedforward control for reducing vibration of the sprung structure based on the acquired road surface displacement-related value, and executes feedback control for reducing vibration of the sprung structure based on the acquired state quantity; and a setting unit that sets a feedback gain of the feedback control to be larger when the derived ratio is equal to or larger than a threshold value and the feedforward control is not being properly performed, compared to when the feedforward control is being properly performed; A suspension control system comprising:

2. The setting unit is If the derived ratio is less than the threshold, setting the feedback gain to a reference gain; If the derived ratio is equal to or greater than the threshold value, the feedback gain is set to be smaller than the reference gain.

2. The suspension control system of claim 1.

3. The setting unit is If the acquired road surface displacement-related value is appropriate, or if the reliability of the acquired road surface displacement-related value is higher than a reference value, it is determined that the feedforward control is being performed appropriately; If the acquired road surface displacement-related value is inappropriate or if the reliability is equal to or less than the reference value, it is determined that the feedforward control is not being performed appropriately.

3. The suspension control system according to claim 1 or 2.

4. The lead-out portion is When the reliability of the acquired road surface displacement-related value is higher than a reference value, the ratio of the road surface displacement-related value in the time-series data is derived; deriving the ratio in the acquired time-series data of the state quantity when the reliability is equal to or less than the reference value; 3. The suspension control system according to claim 1 or 2.

5. When the derived ratio is equal to or greater than the threshold value, if the reliability is equal to or less than the reference value, the setting unit sets the feedback gain to be larger as the reliability is lower.

4. The suspension control system of claim 3.

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