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 Art

[0002] Patent Document 1 discloses a vibration control device for a vehicle. The vibration control device acquires, as preview information, a road surface displacement related value at a predicted passing position based on measurement data, and controls a control force generator based on a final target control force including a first target control force calculated using the preview information to perform preview vibration control. 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 at which the road surface displacement related value is acquired. When the vibration control device determines that the probability that the road surface state has changed from a past time point is high, it sets the magnitude of the first target control force to be small.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a vehicle 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 controlled by the vibration control of the active suspension and there is no need to control the vibration of the sprung structure by the damping of the absorber, the damping coefficient of the absorber may be set lower than normal. As a result, 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 medium and high frequency bands may deteriorate.

[0005] Here, an active suspension system is known that performs both preview vibration damping control and feedback control. In this configuration, if the input to the sprung mass structure is sufficiently reduced by preview vibration damping control, and the input in the mid-to-high frequency range, which may be worsened by feedback control, is relatively large, then reducing the feedback gain is effective because it suppresses the deterioration of vibrations in the mid-to-high frequency range due to feedback control without substantially adversely affecting vibrations in the low frequency range.

[0006] However, with preview vibration control, if a vehicle travels through an area where the road surface displacement-related values ​​in the measurement data map are incorrect due to changes in road surface conditions such as road construction, if the vehicle travels through an area where the presence or absence of road surface displacement-related values ​​in the map is mixed, or if the accuracy of the predicted passing position is poor due to poor vehicle position accuracy, then the road surface displacement-related values ​​of the predicted passing position acquired as preview information are likely to be inappropriate. In this case, the input cannot be sufficiently reduced by preview vibration control, so while reducing the feedback gain when the input in the mid-to-high frequency band is relatively large can suppress the deterioration of vibrations in the mid-to-high frequency band, there is a possibility that vibrations in the low frequency band will increase. In such situations, it is desirable to appropriately adjust the feedback gain.

[0007] The objective of the present invention is to provide a suspension control system that can appropriately adjust the feedback gain. [Means for solving the problem]

[0008] To solve the above problems, a suspension control system according to one aspect of the present invention comprises an actuator for adjusting the suspension stroke of a controllable wheel of a vehicle, and a control device for controlling the actuator. The control device includes a first acquisition unit for acquiring road surface displacement-related values ​​related to the vertical displacement of the road surface in front of the vehicle, a second acquisition unit for acquiring state quantities related to the vertical displacement of the sprung mass or unsprung mass of the vehicle, a derivation unit for deriving the 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 higher than the first frequency band in the time-series data of the acquired road surface displacement-related values ​​or state quantities, a control unit for controlling the actuator to perform feedforward control to reduce vibration of the sprung mass based on the acquired road surface displacement-related values, and to perform feedback control to reduce vibration of the sprung mass based on the acquired state quantities, and a setting unit for setting the feedback gain of the feedback control to be larger than when the feedforward control is properly performed if the derived ratio is greater than or equal to a threshold value and the feedforward control is not properly performed. The setting unit identifies that feedforward control is being performed appropriately 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 the reference value, and identifies that feedforward control is not being performed appropriately if the acquired road surface displacement-related value is inappropriate, or if the reliability is below the reference value. [Effects of the Invention]

[0009] According to the present invention, a suspension control system that can appropriately adjust the feedback gain can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram schematically shows the configuration of the vehicle according to the embodiment. [Figure 2] This diagram schematically shows the configuration of the suspension shown in Figure 1. [Figure 3] This is a block diagram showing an example configuration of the suspension control system according to the embodiment. [Figure 4] This is a block diagram showing an example configuration of the map management device according to the embodiment. [Figure 5]This is a flowchart showing the suspension control process of the embodiment. [Figure 6] Figure 5 is a flowchart showing the feedback gain setting process. [Modes for carrying out the invention]

[0011] The embodiments for implementing this disclosure will be described in detail below with reference to the drawings. In this description, the same elements will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate.

[0012] 1. Suspension and road surface displacement related values Figure 1 schematically shows the configuration of vehicle 1 according to the embodiment. Vehicle 1 comprises a left front wheel 2FL, a right front wheel 2FR, a left rear wheel 2RL, a right rear wheel 2RR, suspension 3FL, suspension 3FR, suspension 3RL, suspension 3RR, and a suspension control system 10. A corresponding suspension from among suspension 3FL, suspension 3FR, suspension 3RL, and suspension 3RR is provided for each of the left front wheel 2FL, right front wheel 2FR, left rear wheel 2RL, and right rear wheel 2RR. Hereafter, unless otherwise necessary, each wheel will be referred to as wheel 2 and each suspension as suspension 3.

[0013] Figure 2 schematically shows the configuration of the suspension 3 in Figure 1. The suspension 3 is provided to connect 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, damper 3D, and 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 constant of the spring 3S is K. The damping coefficient of the damper 3D is 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, actuator 3A is, for example, an electrically operated or hydraulically operated active actuator, and is an actuator that constitutes a so-called fully active suspension. Alternatively, actuator 3A may be, for example, an actuator that varies the damping force generated by damper 3D, or an actuator of an active stabilizer device. Furthermore, the “actuator” of this disclosure may be, for example, an actuator such as an electric motor that generates the longitudinal vehicle forces in a vehicle equipped with a suspension configured to convert the longitudinal vehicle forces acting on the wheels, namely driving force and braking force, 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 an electric motor capable of driving the wheel via the vehicle drive shaft.

[0015] Here, we define the terms. "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. Note that the sign of each parameter is positive when it is upward and negative when it is downward.

[0016] 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 road surface displacement-related values ​​include road surface displacement Zr, road surface displacement velocity Zr' (which is the time derivative of road surface displacement Zr), unsprung displacement Zu, unsprung velocity Zu', unsprung acceleration Zu'', sprung displacement Zs, sprung velocity Zs', or sprung acceleration Zs''. Road surface displacement-related values ​​can also be said to be "vertical motion parameters" that relate to the vertical motion of wheel 2.

[0017] As an example, the case where the road surface displacement related value is the displacement Zu under the spring will be described below. In the case of generalization, the "displacement under the spring" in the following description shall be read as the "road surface displacement related value".

[0018] Here, an example of the displacement calculation process under the spring will be described. First, the acceleration Zs'' above the spring is detected by the acceleration sensor 22 above the spring installed on the structure 5 above the spring. Next, the displacement Zs above the spring is calculated by double integrating the acceleration Zs'' above the spring.

[0019] Next, the stroke ST, which is the relative displacement between the structure 5 above the spring and the structure 4 below the spring, is obtained. "Stroke ST" = "displacement Zs above the spring" - "displacement Zu under the spring". For example, the stroke ST is detected by a stroke sensor installed on the suspension 3. As another example, the stroke ST may be estimated based on the acceleration Zs'' above the spring 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, filtering processing is performed on the time series data of the displacement Zs above the spring. Similarly, filtering processing 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 to include the resonance frequency above the spring of the vehicle 1. For example, the specific frequency band is 0.3 to 10 Hz.

[0021] Next, the difference between the displacement Zs above the spring and the stroke ST is calculated as the displacement Zu under the spring.

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

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

[0024] 2. Suspension control system Figure 3 is a block diagram showing an example configuration of the suspension control system 10 according to the embodiment. The suspension control system 10 is mounted on the 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 vehicle 1 and supplies the detection result to the ECU 70. The vehicle state sensor 20 includes a vehicle speed sensor 21 for detecting the vehicle speed V of vehicle 1, a sprung mass acceleration sensor 22 for detecting the sprung mass acceleration Zs'', and a stroke sensor 23 for detecting the stroke ST. The vehicle state sensor 20 may also include an unsprung mass acceleration sensor. The vehicle state sensor 20 may also 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 GNSS (Global Navigation Satellite System) receiver.

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

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

[0029] The processor 71 includes 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 a storage device 72, thereby realizing 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 on a computer-readable recording medium. The ECU 70 corresponds to an example of a "control device" in this disclosure.

[0030] The memory device 72 stores the unsprung displacement map 200. Details of the unsprung displacement map 200 will be described later.

[0031] The ECU70 controls the suspension 3 by controlling the actuator 3A. Specifically, the ECU70 performs vibration damping control to suppress vibrations of the vehicle 1 by controlling the suspension 3. The ECU70 controls the actuator 3A to generate a vertical control force Fc between the unsprung mass structure 4 and the sprung mass structure 5, as shown in Figure 2. The vibration damping control includes "preview control" and "feedback control," which will be described later. Preview control can also be called feedforward control. Details of the vibration damping control will be described later.

[0032] 3. Map Management Device 3-1. Example Configuration Figure 4 is a block diagram showing an example configuration of the map management device 100 according to the embodiment. The map management device 100 is a computer that manages various types of map information. The management of map information includes the generation, updating, provision, and distribution of map information. Typically, the map management device 100 is a management server on the cloud. The map management device 100 may also 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 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 performs 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 necessary for processing by the processor 120. Examples of storage devices 130 include volatile memory, non-volatile memory, HDD, SSD, etc.

[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 on a computer-readable recording medium. The execution of the map management program by the processor 120 enables the functionality of the map management device 100.

[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 map information in response to requests 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 the unsprung displacement map 200. The unsprung displacement map 200 is a map relating to the 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 the "road surface data map in which road surface displacement-related values ​​related to the vertical displacement of the road surface are associated with position" as described in this disclosure.

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

[0039] The road area may be divided into a mesh-like structure on a horizontal plane. In other words, the road area may be divided into multiple unit areas (hereinafter referred to as "road surface sections") on a horizontal plane. A 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 a road surface section and the unsprung displacement Zu. The position of a road surface section may be defined by a representative position of that section, for example, the center position, or by the latitude and longitude range of that section. The unsprung displacement Zu of a road surface section is, for example, the average value of the unsprung displacement Zu obtained within that road surface section. The smaller the road surface section, the higher the resolution of the unsprung displacement map 200.

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

[0041] The position in the unsprung displacement map 200 represents the position that wheel 2 has passed through. The position of each wheel 2 is calculated based on the position information detected by the position sensor 40. Specifically, the relative positional relationship between the reference point of the vehicle position on vehicle 1 and each wheel 2 is known information. Based on this relative positional relationship and the vehicle position indicated by the positional information, the position of each wheel 2 can be calculated.

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

[0043] For example, while vehicle 1 is in motion, the ECU 70 of the suspension control system 10 calculates the unsprung displacement Zu in real time based on sensor-based information. The ECU 70 also associates the wheel position with the unsprung displacement Zu at the same time. The ECU 70 then transmits a set of time-series data of wheel position and time-series data of 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 wheel position and unsprung displacement Zu.

[0044] As another example, the ECU 70 of the suspension control system 10 associates the wheel position with sensor-based information at the same time. The ECU 70 then transmits a set of time-series data of wheel position and time-series data of 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 wheel position and time-series data of 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 wheel positions, which are the positions of the vehicle 1. The map update information also includes time-series data of sensor-based information necessary for calculating 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 map update information.

[0047] Furthermore, the suspension control system 10 of vehicle 1 may maintain a database of unsprung displacement maps 200 and generate and update its own unsprung displacement maps 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 maps The ECU 70 of the suspension control system 10 communicates with the map management device 100 via the communication device 50. The ECU 70 obtains an unsprung weight map 200 of the area including the current position of the vehicle 1 from the map management device 100. The unsprung weight map 200 is stored in the memory device 72. Then, based on the unsprung weight map 200, the ECU 70 performs preview control, which is a type of vibration damping control. Preview control is performed to reduce vibration of the sprung weight structure 5. Along with preview control, the ECU 70 also performs feedback control based on the detected values ​​of the sprung weight acceleration sensor 22 and the stroke sensor 23. Feedback control is also performed to reduce vibration of the sprung weight 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 perform the following processes for each of the four controlled wheels at each time step.

[0050] First, let's explain the preview control. 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 this relative positional relationship and the vehicle position indicated by the positional information, the position of each wheel 2 can be calculated.

[0051] The first acquisition unit 80 calculates the predicted passing position Pf of 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, the time required from when the first acquisition unit 80 identifies 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 the position in the direction of vehicle travel that is forward from the current position by a preview distance Lp along the predicted path of movement in which wheel 2 is expected to move. The predicted path of movement can be determined, for example, based on the direction of travel of vehicle 1 and the current position P0 of wheel 2. The direction of travel can be determined, 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 identifies the direction from the current position of the previous time step to the current position P0 of the current time step as the direction of travel. As a modified example, the first acquisition unit 80 may calculate a predicted driving route based on the vehicle speed V and the steering angle of the wheels 2, and calculate a predicted passing position Pf based on the predicted driving route.

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

[0053] The calculation unit 88 calculates a target control force for 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 preview control is calculated, for example, using the following equation (3) or equation (4).

[0054] The equation of motion for the spring structure 5 in Figure 2 is given 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 mass 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 mass 5 is completely canceled 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 a vibration damping effect is expressed by the following equation (3).

[0059] Fc=α·C·Zu'+β·K·Zu ···(3)

[0060] In equation (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. If the derivative term in equation (3) is omitted, the control force Fc that provides at least a vibration damping effect is expressed by the following equation (4).

[0061] Fc = β·K·Zu ···(4)

[0062] Next, we will describe the feedback control that is performed simultaneously with the preview control. The second acquisition unit 82 acquires state quantities related to the vertical displacement of the sprung mass structure 5 or unsprung mass structure 4 of the vehicle 1 from the vehicle state sensor 20 installed on the vehicle 1. Any of the following may be used as the state quantity: sprung mass displacement Zs, sprung mass velocity Zs', sprung mass acceleration Zs'', unsprung mass displacement Zu, unsprung mass velocity Zu', and unsprung mass acceleration Zu''. Below, we will describe the case where the state quantity is unsprung mass velocity Zu' as an example. When generalizing, "unsprung mass velocity" in the following description should be read as "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 derivative of the stroke ST detected by the stroke sensor 23, from the sprung velocity Zs', which is the first integral of the sprung acceleration Zs'' detected by the sprung velocity Zs' detected by the sprung velocity 22.

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

[0065] Fc=β·K·Zu+γ·Zu' ···(5)

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

[0067] The calculation unit 88 calculates the target control force Fc_t for preview control with feedback control according to equation (5) above. 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 calculating the target control force Fc_t into equation (5). This target control force Fc_t corresponds to the required value of the control force Fc required for preview control and feedback control.

[0068] One of the features of this embodiment is that the feedback gain γ in equation (5) above 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. For the derivation of the reliability, known techniques such as the following derivation method can be used.

[0070] For example, as a first derivation method, the derivation unit 84 may derive a higher reliability of the unsprung displacement Zu of the predicted passing position Pf the smaller the difference between the unsprung displacement Zu of the current passing position of the vehicle 1's wheel 2 obtained from the unsprung displacement map 200 and the unsprung displacement Zu of the current passing position of the wheel 2 derived based on the detected values ​​of the sprung acceleration sensor 22 and the stroke sensor 23. 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 has been created, the reliability of the unsprung displacement Zu of the predicted passing position Pf will decrease. The first derivation method is disclosed in Japanese Patent Application Publication No. 2022-064361 and Japanese Patent Application Publication No. 2023-047040, so further detailed explanation is omitted.

[0071] Furthermore, as a second derivation method, the derivation unit 84 may convert 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 that 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. 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 Japanese Patent Application Publication No. 2022-024499, so further detailed explanation is omitted.

[0072] Furthermore, 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 the higher the reliability of the position information, the higher the reliability of the unsprung displacement Zu of the predicted passing position Pf. 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 the accuracy and certainty, the larger the value. The third derivation method is disclosed in Japanese Patent Application Publication No. 2023-054955, so further detailed explanation is omitted.

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

[0074] The first frequency band is the frequency band in which feedback control has a vibration suppression effect on the sprung structure 5, for example, the low frequency band of 1-2 Hz. The second frequency band is the frequency band in which the vibration of the sprung structure 5 worsens due to feedback control, for example, the mid-to-high frequency band of 3-8 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 component to the first frequency band, which is used to determine whether or not to lower the feedback gain γ, is derived from the information in the unsprung displacement map 200.

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

[0077] To derive the ratio of the component in the second frequency band to the component in the first frequency band, any type of the previously described road surface displacement-related value can be used. For example, any type of state variable for which the input is known can be used, 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''. For example, by using the unsprung velocity Zu', the input to suspension 3 can be directly determined, and in the case of a typical road surface characteristic where the road surface amplitude has a 1 / f characteristic with respect to frequency, that is, when the frequency is increased 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, making it easy to compare the relative magnitudes of the input in the first frequency band and the input in the second frequency band.

[0078] The control methods considered are feedback control based on sprung or unsprung state variables, and any control method is acceptable as long as the first and second frequency bands can be identified. For example, in the most common sprung skyhook damper control, which provides a control force proportional to the sprung velocity, vibration damping effects and vibration deterioration can be observed in the two frequency bands within the aforementioned frequency range.

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

[0080] Since the reliability of the unsprung displacement Zu at the predicted passing position Pf is low, using the information from the unsprung displacement map 200 may lead to misjudgment. Therefore, a ratio for judgment is derived using the unsprung velocity Zu' based on the detected values ​​from the sprung acceleration sensor 22 and the stroke sensor 23. The method for deriving the ratio is the same as the method described above.

[0081] To derive the ratio of the component in the second frequency band to the component in the first frequency band, any of the aforementioned state variables can be used instead of the unsprung velocity Zu', such as 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 on the sprung is known.

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

[0083] In this way, the derivation unit 84 derives the ratio of the magnitude of the component in the first frequency band to the magnitude of the component in the second frequency band 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 identifies that preview control is being performed appropriately if the unsprung displacement Zu acquired by the first acquisition unit 80 is appropriate, or if the reliability of the unsprung displacement Zu is higher than the reference value. Appropriate execution of preview control indicates that the vibration damping effect of preview control is relatively high. The setting unit 86 may also identify that preview control is being performed appropriately if the acquired unsprung displacement Zu is appropriate and the reliability of the unsprung displacement Zu is higher than the reference value.

[0085] The setting unit 86 identifies that preview control is not being performed properly if the unsprung displacement Zu acquired by the first acquisition unit 80 is inappropriate, or if the reliability of the unsprung displacement Zu is below a reference value. Not being performed properly by preview control indicates that the vibration damping effect of preview control is relatively low.

[0086] In other words, if the reliability of the unsprung displacement Zu is below the reference value, the setting unit 86 determines that the preview control is not being performed properly because there is a high possibility that the vibration damping effect of the preview control is low. Also, if the reliability of the unsprung displacement Zu is below the reference value, the calculation unit 88 may lower the control gain α and control gain β of the preview control. In this case as well, the setting unit 86 determines that the preview control is not being performed properly because the vibration damping effect of the preview control is low.

[0087] If the unsprung displacement Zu is set to zero for a position where no unsprung displacement map 200 exists, then an appropriate unsprung displacement Zu indicates that the unsprung displacement Zu has not remained at zero for a predetermined time. An inappropriate unsprung displacement Zu indicates that the unsprung displacement Zu has remained at zero for a predetermined time. The predetermined time can be appropriately determined through experimentation or simulation.

[0088] Furthermore, if a flag is set for a position where the unsprung displacement map 200 does not exist, a valid unsprung displacement Zu indicates that the flag has not been acquired, while an invalid unsprung displacement Zu indicates that the flag has been acquired.

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

[0090] The setting unit 86 sets the feedback gain γ to be smaller than the reference gain γ0 if the ratio of the second frequency band component to the derived first frequency band component is greater than or equal to a threshold. This suppresses the deterioration of vibrations in the mid-to-high frequency band when the ratio of the second frequency band component to the first frequency band component is greater than or equal to a threshold.

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

[0092] Specifically, the setting unit 86 sets the feedback gain γ to a predetermined first gain γ1 when the derived ratio is greater than or equal to a threshold and the preview control is being performed appropriately. The first gain γ1 is smaller than the reference gain γ0. Since the spring structure 5 can be properly damped even with only the preview control, the feedback gain γ is made smaller than the reference gain γ0.

[0093] On the other hand, if the derived ratio is greater than or equal to a threshold and preview control is not being performed properly, 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 by experiment or simulation. In situations where the vibration of the sprung structure 5 would increase if feedback control were not performed, the feedback gain γ is made larger than the first gain γ1.

[0094] When traveling through a location where the unsprung displacement Zu in the unsprung displacement map 200 is incorrect, there is a high probability that the unsprung displacement Zu of the acquired predicted passing position Pf is also incorrect. Therefore, preview control may not be performed properly. In this case, the preview control may not be able to sufficiently reduce the input to the sprung structure 5, but by increasing the feedback gain γ compared to when the preview control is performed properly, the deterioration of vibrations in the low frequency band can be suppressed more effectively than when the first gain γ1 is used. Also, since the second gain γ2 is smaller than the reference gain γ0, the deterioration of vibrations in the mid-to-high frequency band can be suppressed more effectively than when the reference gain γ0 is used. Thus, the feedback gain γ can be adjusted appropriately.

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

[0096] The control unit 90 transmits a control command to the actuator 3A, including the target control force Fc_t, so that the actuator 3A generates a control force Fc corresponding to the target control force Fc_t calculated according to equation (5). The actuator 3A generates a control force Fc corresponding to the target control force Fc_t at a timing that is a preview time tp after the current time, i.e., 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 matches the target control force Fc_t.

[0097] Thus, by using preview control based on the unsprung displacement map 200, a control force Fc can be generated at an appropriate timing to suppress vibrations of the sprung structure 5 caused by the unsprung displacement Zu at the predicted passing position Pf of the wheel 2. Furthermore, vibrations of the sprung structure 5 can also be suppressed by feedback control. As a result, vibrations of the sprung structure 5 can be effectively suppressed.

[0098] Figure 5 is a flowchart showing the suspension control process of the embodiment. The process in this flowchart is repeatedly executed at predetermined time steps for each of the controlled wheels while the vehicle 1 is in motion.

[0099] The first acquisition unit 80 acquires the current position of the wheel 2 (S10), acquires the 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 performs the feedback gain setting process shown in Figure 6, which will be described later (S16). The calculation unit 88 calculates the target control force Fc_t according to equation (5) (S18), the control unit 90 controls the actuator 3A (S24), and the process ends.

[0101] Figure 6 is a flowchart showing the feedback gain setting process in S16 of Figure 5. If the reliability of the unsprung displacement Zu at the predicted passing position Pf is high (Y in S30), the derivation unit 84 derives the ratio of low-frequency components to mid-to-high-frequency components based on the unsprung displacement Zu of the unsprung displacement map 200 (S32), and the process moves 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 components to mid-to-high-frequency components based on the unsprung velocity Zu' detected by the sprung acceleration sensor 22 and the stroke sensor 23 (S34), and the process moves to S36.

[0103] Next, if the derived ratio is greater than the threshold (Y in S36), and if the preview control is performed correctly (Y in S38), the setting unit 86 sets the feedback gain γ to the first gain γ1 (S40) and returns to the process shown in Figure 5. If the preview control is not performed correctly in S38 (N in S38), the setting unit 86 sets the feedback gain γ to the second gain γ2 (S42) and returns to the process shown in Figure 5.

[0104] In S36, if the derived ratio is less than or equal to the threshold (N in S36), the setting unit 86 sets the feedback gain γ to the normal gain γ0 (S44), and returns to the process shown in Figure 5.

[0105] According to this embodiment, if the reliability of the unsprung displacement Zu at the predicted passing position Pf obtained from the unsprung displacement map 200 is higher than the reference value, the ratio of the component in the second frequency band to the component in the first frequency band in the time-series data of the unsprung displacement Zu at the predicted passing position Pf is derived, allowing the feedback gain γ to be adjusted in advance. Therefore, vibration degradation in the mid-to-high frequency band due to feedback control can be suppressed more appropriately.

[0106] Furthermore, if the reliability of the unsprung displacement Zu obtained from the unsprung displacement map 200 is below a reference value, the ratio of the component in the second frequency band to the component in the first frequency band in the time-series data of the unsprung velocity Zu' based on the detected values ​​of the sprung acceleration sensor 22 and the stroke sensor 23 is derived, thus obtaining a more accurate ratio. In other words, when vehicle 1 travels through a location where the unsprung displacement Zu in the unsprung displacement map 200 is incorrect due to changes in road surface conditions such as road construction, when vehicle 1 travels through a region where the presence or absence of unsprung displacement Zu in the unsprung displacement map 200 is mixed, or when the accuracy of the predicted passing position Pf is also poor due to poor position accuracy of vehicle 1, it is possible to suppress the deriving of an incorrect input ratio based on the unsprung displacement map 200. Therefore, it is possible to suppress the incorrect setting of the feedback gain γ.

[0107] In contrast, in the comparative example where the ratio of the component in the second frequency band to the component in the first frequency band 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 may be incorrectly adjusted when the vehicle 1 travels through a location where the unsprung displacement Zu in the unsprung displacement map 200 is incorrect.

[0108] Furthermore, in this embodiment, when the ratio of the component in the second frequency band to the component in the first frequency band is greater than or equal to a threshold, the feedback gain γ can be appropriately adjusted depending on whether or not the preview control is being properly executed. Therefore, the deterioration of vibrations in the mid-to-high frequency band due to feedback control can be appropriately suppressed.

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

[0110] (First variation) The process of differentiating the data used to derive the frequency characteristics according to the reliability of the unsprung displacement Zu at the predicted passing position Pf does not need to be performed. In other words, in the flowchart of Figure 6, processes S30 and S32 may be omitted, and process S34 may be performed first. This modified version allows for simplification of the process while appropriately adjusting the feedback gain γ.

[0111] (Second variation) The control unit 90 may perform preview control using a known preview sensor instead of the preview control using the unsprung displacement map 200 described above. The differences from the embodiment will be explained below.

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

[0113] Fc = γb·Zr + γ·Zs ···(6)

[0114] The first term on the right-hand side of equation (6) is a feedforward term relating to preview control using a preview sensor. The first term on the right-hand side is the product of the gain γb and the road surface displacement Zr in front of vehicle 1, which is obtained by the preview sensor when calculating the target control force Fc_t. The gain γb can be appropriately determined by experiment or simulation. Since preview control using a preview sensor is well known, further detailed explanation is omitted.

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

[0116] The first acquisition unit 80 acquires the road surface displacement Zr in front 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, the derivation unit 84 derives a high confidence level when there is an input that is sufficiently large relative to the resolution of the preview sensor, that is, when the detected value of the preview sensor is not zero. The derivation unit 84 derives a low confidence level when there is no input that is sufficiently large relative to the resolution of the preview sensor, that is, when the detected value of the preview sensor remains zero for a predetermined period of time or longer.

[0118] Alternatively, the derivation unit 84 may derive a higher reliability the closer the surrounding environment of the vehicle 1 is to 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, a moderate reliability if it is cloudy, and a low reliability if the weather is rough, such as rain or snow. The derivation unit 84 may derive a higher reliability the higher the illumination near the road surface. 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] If the reliability of the road surface displacement Zr is higher than the reference value, the derivation unit 84 derives the ratio of the component in the first frequency band to the component in the second frequency band in the time-series data of the road surface displacement Zr acquired from the preview sensor by the first acquisition unit 80.

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

[0121] The setting unit 86 identifies that preview control is being performed appropriately if the road surface displacement Zr acquired by the first acquisition unit 80 is appropriate, or if the reliability of the road surface displacement Zr is higher than the reference value. The setting unit 86 may also identify that preview control is being performed appropriately if the acquired road surface displacement Zr is appropriate and the reliability of the road surface displacement Zr is higher than the reference value.

[0122] The setting unit 86 identifies that preview control is not being performed properly 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 standard value.

[0123] An appropriate road surface displacement Zr indicates that the road surface displacement Zr has not remained at zero for a predetermined period of time. An inappropriate road surface displacement Zr indicates that the road surface displacement Zr has remained at zero for a predetermined period of time.

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

[0125] According to the second modified example, if the reliability of the road surface displacement Zr obtained from the preview sensor is below a reference value, the ratio of the first frequency band component to the second frequency band component in the time-series data of the unsprung velocity Zu' based on the detected values ​​of the sprung acceleration sensor 22 and the stroke sensor 23 is derived, thereby obtaining a more accurate ratio. In other words, when the surrounding environment of the vehicle 1 does not meet the conditions for the preview sensor to function correctly, and there is a high possibility that the detected value of the preview sensor is incorrect, it is possible to suppress the deriving of an incorrect input ratio based on the detected value of the preview sensor. Thus, it is possible to suppress the incorrect setting of the feedback gain γ. Other effects similar to those of the embodiment can also be obtained.

[0126] Furthermore, the first and second variations may be combined.

[0127] Furthermore, in this embodiment, the preview control is performed on all four wheels 2 of the vehicle 1. However, the wheels targeted for preview control are not limited to all wheels; for example, only the left and right front wheels, or only the left and right rear wheels, may be included. [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 Unit), 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 that adjusts the suspension stroke of the controlled wheel of the vehicle, A control device for controlling the actuator, Equipped with, The control device is A first acquisition unit acquires road surface displacement-related values ​​related to the vertical displacement of the road surface in front of the vehicle, A second acquisition unit that acquires state quantities related to the vertical displacement of the sprung mass or unsprung mass of the vehicle, A derivation unit that derives the 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 that is higher than the first frequency band in the time-series data of the acquired road surface displacement-related values ​​or state quantities, A control unit that controls the actuator and performs feedforward control to reduce vibration of the suprasterid structure based on the acquired road surface displacement-related values, and performs feedback control to reduce vibration of the suprasterid structure based on the acquired state quantities, When the derived ratio is greater than or equal to a threshold, and feedforward control is not being performed properly, a setting unit sets the feedback gain of the feedback control to be larger compared to when feedforward control is being performed properly. It has, The setting unit is, If the acquired road surface displacement-related values ​​are appropriate, or if the confidence level of the acquired road surface displacement-related values ​​is higher than the reference value, it is determined that the feedforward control is being performed appropriately. If the acquired road surface displacement-related values ​​are inappropriate, or if the reliability is below the reference value, it is determined that the feedforward control is not being performed properly. A suspension control system characterized by the following features.

2. The setting unit is, If the derived ratio is smaller than the threshold, the feedback gain is set to the reference gain. If the derived ratio is greater than or equal to the threshold, the feedback gain is set to be smaller than the reference gain. The suspension control system according to feature 1.

3. The aforementioned derivation section is, If the reliability of the acquired road surface displacement-related value is higher than the reference value, the ratio of the road surface displacement-related value in the time series data is derived. If the confidence level is below the threshold value, the proportion in the time-series data of the acquired state quantity is derived. The suspension control system according to claim 1 or 2, characterized in that it is the same as described in claim 1 or 2.

4. The setting unit, if the derived ratio is greater than or equal to the threshold, and the reliability is less than or equal to the reference value, sets the feedback gain to be larger the lower the reliability is. The suspension control system according to feature 1.

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