Suspension control system

Abstract

To provide a suspension control system which can suppress occurrence of vibration and lateral force at a boundary between presence and absence of a road surface displacement-related value.SOLUTION: In a suspension control system 10, an actuator adjusts a suspension stroke of a control object wheel of a vehicle. An acquisition part 80 acquires a road surface displacement related value related to displacement in a vertical direction of a road surface at a prediction passage position of the control object wheel after a predetermined time from a current time, from a road surface data map in which the road surface displacement related value and a position are related with each other. A calculation part 86 calculates target control force on the basis of the acquired road surface displacement related value. A control part 88 controls the actuator, so that the control force generated by the actuator coincides with the target control force, when the control object wheel passes through the prediction passage position. When a winker of the vehicle starts an operation, the calculation part 86 calculates the target control force so that a change amount per unit time of the target control force is decreased compared with a case in which the winker is not operated.SELECTED DRAWING: Figure 4

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 generating device 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 and position information indicating a position when the road surface displacement related value is acquired are associated. When the vibration control device determines that there is a high probability that the road surface state has changed from a past time point, 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] When a vehicle is under preview vibration control, compared with when going straight, when changing lanes or turning right or left at an intersection, the probability of traveling in a place where there is no road surface displacement related value in the map of the measurement data increases. In this case, at the boundary of the presence or absence of the road surface displacement related value, the road surface displacement related value changes from a certain value to zero. Therefore, even when there is actually no step on the road surface at this boundary, vibration may occur. Also, due to the control when crossing the boundary, lateral forces due to roll steer, camber, lateral displacement of the contact point, etc. are generated on the tire contact surface, and lateral vibration may occur or a difference may occur with respect to the driving trajectory aimed by the driver. It is desirable to suppress the occurrence of such vibration and lateral force.

[0005] The object of the present invention is to provide a suspension control system that can suppress the generation of vibrations and lateral forces at the boundary between the presence and absence of road surface displacement-related values. [Means for solving the problem]

[0006] 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 wheel to be controlled by a vehicle, and a control device for controlling the actuator. The control device includes an acquisition unit that acquires road surface displacement-related values ​​at a predicted passing position of the wheel to be controlled after a predetermined time from the current time, from a road surface data map which associates road surface displacement-related values ​​related to vertical displacement of the road surface with position; a calculation unit that calculates a target control force based on the acquired road surface displacement-related values; and a control unit that controls the actuator so that the control force generated by the actuator when the wheel to be controlled passes the predicted passing position matches the target control force. When the turn signal of the vehicle starts to operate, the calculation unit calculates the target control force so that the amount of change of the target control force per unit time is smaller compared to when the turn signal is not operating. [Effects of the Invention]

[0007] According to the present invention, a suspension control system can be provided that can suppress the generation of vibrations and lateral forces at the boundary between the presence and absence of road surface displacement-related values. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of a map of road surface displacement-related values. [Figure 2] This diagram schematically shows the configuration of the vehicle according to the embodiment. [Figure 3] Figure 2 is a schematic diagram showing the configuration of the suspension. [Figure 4] This is a block diagram showing an example configuration of the suspension control system according to the embodiment. [Figure 5]This is a block diagram showing an example configuration of the map management device according to the embodiment. [Figure 6] This is a flowchart showing the suspension control process of the embodiment. [Modes for carrying out the invention]

[0009] Before describing the specific embodiments, let's explain the underlying knowledge. As previously mentioned, compared to driving straight, the probability of a vehicle traveling in areas where there are no road surface displacement-related values ​​on the map increases when changing lanes or turning right or left at intersections.

[0010] Figure 1 shows an example of a map of road surface displacement-related values. In this map, the intensity of the color represents the magnitude of the road surface displacement-related values. Region 302, where the intensity of the color is uniform, represents the absence of a map and the road surface displacement-related value being zero. This map is generated along each lane of a straight road. Regions 300a, 300b, and 300c each correspond to different lanes. Within regions 300a, 300b, and 300c, there is a map, and road surface displacement-related values ​​are set at each location. Region 302 is the region other than regions 300a, 300b, and 300c. Within region 302, there is no map, and the road surface displacement-related values ​​are uniformly zero regardless of location. In this example, regions 302 between two adjacent lanes, i.e., region 302 between region 300a and region 300b, and region 302 between region 300a and region 300c, do not have maps because the vehicle used to collect measurement data has not traveled through these areas in the past.

[0011] When a vehicle changes lanes from a lane with high input along route 304 to an adjacent lane, it moves from a location in region 300a with high road surface displacement-related values, across region 302 where the road surface displacement-related values ​​are zero, to another lane corresponding to region 300b where road surface displacement-related values ​​exist. Therefore, when crossing a map boundary, even if there is no actual road surface input, the road surface displacement-related values ​​change significantly, causing large vibrations in the vehicle. As previously mentioned, lateral forces are also generated.

[0012] If vibrations or lateral forces occur at the boundary between the presence and absence of a map, the vehicle user may experience an unnatural ride quality due to the execution of preview control.

[0013] Therefore, in this embodiment, when the vehicle's turn signal starts operating, the amount of change in the target control force per unit time is reduced by lowering the gain of the preview control, etc. This makes it possible to suppress the generation of vibration and lateral force when the turn signal is operating, which is likely to cross a boundary, without affecting the control performance when the turn signal is not operating.

[0014] 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.

[0015] 1. Suspension and road surface displacement related values Figure 2 schematically shows the configuration of the vehicle 1 of the embodiment. The 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.

[0016] Figure 3 schematically shows the configuration of the suspension 3 in Figure 2. 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.

[0017] 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.

[0018] Here, the definitions of terms are given. "Road surface displacement Zr" is the vertical displacement of the road surface RS. "Displacement Zu under the spring" is the vertical displacement of the structure 4 under the spring. "Displacement Zs above the spring" is the vertical displacement of the structure 5 above the spring. "Velocity Zu' under the spring" is the vertical velocity of the structure 4 under the spring. "Velocity Zs' above the spring" is the vertical velocity of the structure 5 above the spring. "Acceleration Zu'' under the spring" is the vertical acceleration of the structure 4 under the spring. "Acceleration Zs'' above the spring" is the vertical acceleration of the structure 5 above the spring. Note that the sign of each parameter is positive when upward and negative when downward.

[0019] The wheel 2 moves on the road surface RS. Hereinafter, the values related to the road surface displacement Zr are 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 differential value of the road surface displacement Zr, the displacement Zu under the spring, the velocity Zu' under the spring, the acceleration Zu'' under the spring, the displacement Zs above the spring, the velocity Zs' above the spring, or the acceleration Zs'' above the spring, etc. It can also be said that the road surface displacement related values are "vertical motion parameters" which are parameters related to the vertical motion of the wheel 2.

[0020] As an example, hereinafter, the case where the road surface displacement related value is the displacement Zu under the spring will be described. When generalizing, the "displacement under the spring" in the following description shall be replaced with the "road surface displacement related value".

[0021] Here, an example of the displacement Zu under the spring calculation process is 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.

[0022] Next, the stroke ST, which is the relative displacement between the sprung mass structure 5 and the unsprung mass structure 4, is obtained. "Stroke ST" = "Sprung mass displacement Zs" - "Unsprung mass displacement Zu". 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 sprung mass acceleration Zs'' by an observer configured based on a single-wheel two-degree-of-freedom model.

[0023] Next, filtering is performed on the time-series data of the sprung displacement Zs to suppress the effects of sensor drift and other factors. Similarly, filtering is performed on the time-series data of the stroke ST. For example, the filter is a bandpass filter that allows signal components in a specific frequency band to pass through. The specific frequency band may be set to include the sprung resonance frequency of vehicle 1. For example, the specific frequency band is 0.3 to 10 Hz.

[0024] Next, the difference between the sprung displacement Zs and the stroke ST is calculated as the unsprung displacement Zu.

[0025] Instead of filtering the time-series data of the sprung displacement Zs and stroke ST, filtering may be performed on the time-series data of the calculated unsprung displacement Zu.

[0026] As 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''.

[0027] 2. Suspension control system Figure 4 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 turn signal detection unit 30, a position sensor 40, a communication device 50, an actuator 3A, and an ECU 70. The ECU 70 is an electronic control unit.

[0028] 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.

[0029] The turn signal detection unit 30 detects the operating status of the turn signals of the vehicle 1 and supplies the detection result to the ECU 70. The turn signal detection unit 30 detects whether or not the turn signals are operating. Known techniques can be used to detect the operating status of the turn signals. The turn signal detection unit 30 may also detect whether or not the turn signal switch inside the vehicle 1's cabin has been operated.

[0030] 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.

[0031] The communication device 50 communicates with the outside of the vehicle 1.

[0032] 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.

[0033] The processor 71 includes an acquisition unit 80, a prediction unit 82, a calculation unit 86, and a control unit 88. The functions of the acquisition unit 80, prediction unit 82, calculation unit 86, and control unit 88 are realized when the processor 71 executes a suspension control program stored in the storage device 72. 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.

[0034] The memory device 72 stores the unsprung displacement map 200. Details of the unsprung displacement map 200 will be described later.

[0035] The ECU 70 controls the suspension 3 by controlling the actuator 3A. Specifically, the ECU 70 performs vibration damping control to suppress vibrations 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 mass structure 4 and the sprung mass structure 5, as shown in Figure 3. The vibration damping control includes "preview control," which will be described later. Details of the vibration damping control will be described later.

[0036] 3. Map Management Device 3-1. Example Configuration Figure 5 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The processor 120 of the map management device 100 generates and updates the unsprung displacement map 200 based on map update information.

[0051] 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.

[0052] 4. Preview 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 obtains an unsprung displacement map 200 of the area including the current position of the vehicle 1 from the map management device 100. The unsprung displacement map 200 is stored in the memory device 72. Then, based on the unsprung displacement map 200, the ECU 70 performs preview control, which is a type of vibration damping control. Preview control is performed to reduce vibrations of the sprung mass structure 5.

[0053] The acquisition unit 80, prediction unit 82, calculation unit 86, and control unit 88 repeatedly perform the following processing for each of the four controlled wheels at each time step.

[0054] The 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.

[0055] The 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, which is set in advance to be, for example, the time required from when the 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 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 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.

[0056] The acquisition unit 80 reads and acquires the unsprung displacement Zu at the calculated predicted passing position Pf from the unsprung displacement map 200.

[0057] If the turn signal is not operating, the calculation unit 86 performs normal preview control. That is, if the turn signal is not operating, the calculation unit 86 calculates the target control force Fc_t of the actuator 3A of the suspension 3 based on the unsprung displacement Zu at the predicted passing position Pf acquired by the acquisition unit 80. The target control force Fc_t is calculated, for example, as follows. This target control force Fc_t corresponds to the required value of the control force Fc needed for preview control.

[0058] The equation of motion for the spring structure 5 in Figure 3 is given by the following equation (1).

[0059] m·Zs''=C(Zu'-Zs')+K(Zu-Zs)-Fc ···(1) 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).

[0060] Fc = C·Zu' + K·Zu ···(2) The control force Fc that provides at least a vibration damping effect is expressed by the following equation (3).

[0061] Fc=α·C·Zu'+β·K·Zu ···(3) 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).

[0062] Fc = β·K·Zu ···(4) The calculation unit 86 calculates the target control force Fc_t according to equation (3) or equation (4) above. That is, the calculation unit 86 calculates the target control force Fc_t by substituting the unsprung displacement Zu at the predicted passing position Pf into equation (3) or equation (4). If the turn signals are not operating, the calculation unit 86 sets the control gain α and the control gain β to predetermined reference values. The reference values ​​for control gain α and the reference values ​​for control gain β may be different or the same. The reference values ​​can be appropriately determined by experiment or simulation. When using equation (4), it is sufficient that the control gain β is set to the reference value.

[0063] The control unit 88 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. 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 88 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.

[0064] Thus, with preview control using the unsprung displacement map 200, when the turn signal is not operating, 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. This effectively suppresses vibrations of the sprung structure 5.

[0065] On the other hand, when the turn signals are activated, there is a possibility of lane changes or right / left turns at intersections, increasing the probability of driving in areas where there is no unsprung displacement Zu in the unsprung displacement map 200. Therefore, assuming that the control described above based on the acquired unsprung displacement Zu is continued, there is a high concern that lateral forces that would not normally occur may be generated, or that the control may increase vibrations beyond the original input. For this reason, a process to reduce vibrations is executed.

[0066] When the turn signal starts operating, the calculation unit 86 calculates the target control force Fc_t such that the rate of change of the target control force Fc_t per unit time is smaller compared to when the turn signal is not operating. The rate of change of the target control force Fc_t per unit time is the difference between the target control force Fc_t calculated in the previous time step and the target control force Fc_t calculated in the current time step. The rate of change of the target control force Fc_t per unit time is assumed to be expressed as an absolute value.

[0067] For example, when the turn signal starts operating, the calculation unit 86 gradually decreases the control gain α and control gain β from a reference value to a predetermined reduction value, and when the turn signal stops operating, it gradually increases the control gain α and control gain β from the reduction value back to the reference value. This process is called vibration reduction processing. The reduction values ​​for control gain α and control gain β may be different or the same. The reduction values ​​can be appropriately determined by experiment or simulation so as to reduce vibration. The reduction value may also be zero. In this case, preview control is stopped while control gain α and control gain β are zero. When using equation (4), it is sufficient to change the control gain β.

[0068] With this control, compared to the case where the turn signal is not operating, the change in the target control force Fc_t per unit time is smaller even when vehicle 1 passes the boundary between the presence and absence of unsprung displacement Zu in the unsprung displacement map 200. Therefore, the generation of vibration and lateral force in the sprung structure 5 can be suppressed. For example, if vehicle 1 travels along the path 304 in Figure 1 and the turn signal starts operating while traveling in region 300a, the generation of vibration and lateral force in the sprung structure 5 can be suppressed when crossing region 302, compared to the comparative example where vibration reduction processing is not performed. Since the control gain decreases from the reference value only during the operation of the turn signal and for a certain period of time afterward, it does not affect vibration damping control at other times.

[0069] In this case, if the rate of change per unit time of control gain α and control gain β is too large, vibrations and lateral forces may be generated due to the abrupt changes in control gain α and control gain β. Therefore, they are changed gradually to an extent that does not generate vibrations or lateral forces. This suppresses abrupt changes in the target control force Fc_t, thereby more effectively suppressing the generation of vibrations and lateral forces.

[0070] When the turn signal starts operating, the prediction unit 82 predicts whether vehicle 1 will change lanes or turn left or right. For example, the prediction unit 82 may make a prediction based on guidance information from a car navigation system (not shown). Alternatively, the prediction unit 82 may predict that the vehicle will change lanes if the current location is not an intersection, and that it will turn left or right if the current location is an intersection, based on map information. If vehicle 1 is in autonomous driving mode, the prediction unit 82 may also make a prediction based on future route information. The prediction unit 82 may predict that the vehicle will change lanes if the steering speed or steering amount is below a predetermined threshold, and that it will turn left or right if the steering speed or steering amount is greater than the threshold.

[0071] The calculation unit 86 may calculate the target control force Fc_t such that, when the prediction unit 82 predicts that vehicle 1 will change lanes, the reduction in the amount of change of the target control force Fc_t per unit time is greater compared to when vehicle 1 is predicted to turn right or left. In other words, when turning right or left, there is a higher probability that the unsprung displacement Zu in the unsprung displacement map 200 will continue to exist compared to when changing lanes, so the reduction in the amount of change of the target control force Fc_t per unit time may be smaller. In the case of turning right or left, if vehicle 1, or another vehicle, has traveled the route on which it will turn right or left in the past, then the unsprung displacement Zu in the unsprung displacement map 200 will exist. On the other hand, in the case of changing lanes, there is a low probability of changing lanes in the same place, and there is a very low probability that the unsprung displacement Zu in the unsprung displacement map 200 will exist on the route on which the vehicle will travel when changing lanes.

[0072] For example, if the calculation unit 86 predicts a lane change when the turn signal starts operating, it may gradually decrease the control gain α and control gain β from a reference value to a predetermined first reduction value, and then gradually increase the control gain α and control gain β from the first reduction value to the reference value when the turn signal stops operating. This process can also be called a strong vibration reduction process. On the other hand, if the calculation unit 86 predicts a right or left turn when the turn signal starts operating, it may gradually decrease the control gain α and control gain β from a reference value to a predetermined second reduction value, and then gradually increase the control gain α and control gain β from the second reduction value to the reference value when the turn signal stops operating. This process can also be called a weak vibration reduction process.

[0073] The first reduction value of control gain α is less than the second reduction value of control gain α. The first reduction value of control gain β is less than the second reduction value of control gain β. The first reduction value may be zero. The first reduction value of control gain α and the first reduction value of control gain β may be different or the same. The second reduction value of control gain α and the second reduction value of control gain β may be different or the same. The first and second reduction values ​​can be appropriately determined by experiment or simulation so as to reduce vibration.

[0074] This allows for more effective vibration suppression during lane changes, where the probability of passing through the boundary between the presence and absence of unsprung displacement Zu in the unsprung displacement map 200 is higher compared to right and left turns.

[0075] Alternatively, the control gains α and β may be fixed. In this case, when the turn signal starts operating, the calculation unit 86 may calculate the target control force Fc_t by applying a rate limiter to the time-series data of unsprung displacement Zu acquired in the current time step and past time steps, so that the amount of change of the target control force Fc_t per unit time is small. The rate limiter limits the amount of change of unsprung displacement Zu per unit time to a predetermined limit value or less. It can also be said that the rate limiter suppresses the amount of change of unsprung displacement Zu from the previous time step to the current time step.

[0076] In other words, the calculation unit 86 corrects the value of the unsprung displacement Zu acquired in the current time step using a rate limiter, thereby reducing the rate of change of the unsprung displacement Zu per unit time compared to before the correction. Then, the calculation unit 86 substitutes the corrected unsprung displacement Zu into equation (3) or equation (4) to calculate the target control force Fc_t.

[0077] The calculation unit 86 calculates the target control force Fc_t in such a way that it limits the rate of change of the target control force Fc_t per unit time by applying a rate limiter while the turn signal is operating, or for a predetermined control time after the turn signal has finished operating. In other words, when the turn signal finishes operating, or when the control time has elapsed after the turn signal has finished operating, the limit on the rate of change of the target control force Fc_t per unit time ends. The limit value and control time can be appropriately determined by experiment or simulation so as to reduce the vibration of the sprung mass structure 5. This process can also be used to obtain the same effect as when the control gain is changed.

[0078] Furthermore, when the turn signal starts operating, the calculation unit 86 may apply a low-pass filter instead of a rate limiter to the time-series data of unsprung displacement Zu acquired in the current time step and past time steps, either during the operation of the turn signal or during the control time after the turn signal has finished operating. The calculation unit 86 can also limit the amount of change of the target control force Fc_t per unit time by this process. That is, the calculation unit 86 corrects the value of unsprung displacement Zu acquired in the current time step using a low-pass filter, thereby reducing the amount of change of unsprung displacement Zu per unit time compared to before correction, and suppressing sharp changes in unsprung displacement Zu. The cutoff frequency of the low-pass filter can be appropriately determined by experiment or simulation so as to reduce vibration of the sprung structure 5.

[0079] Alternatively, when the turn signal starts operating, the calculation unit 86 may apply a rate limiter or low-pass filter to the time-series data of the target control force Fc_t calculated in the current time step and past time steps, instead of the unsprung displacement Zu. In this case as well, the calculation unit 86 may apply the rate limiter or low-pass filter while the turn signal is operating, or during the control time after the turn signal has finished operating. Through this process, the calculation unit 86 can calculate the target control force Fc_t in such a way that the amount of change of the target control force Fc_t per unit time is small.

[0080] In other words, the calculation unit 86 calculates the target control force Fc_t by substituting the unsprung displacement Zu acquired by the acquisition unit 80 into equation (3) or equation (4) without correction. The calculation unit 86 applies a rate limiter or low-pass filter to correct the value of the target control force Fc_t calculated in the current time step, thereby reducing the rate of change of the target control force Fc_t per unit time compared to before correction. The calculation unit 86 then supplies the corrected target control force Fc_t to the control unit 88.

[0081] Furthermore, the calculation unit 86 may increase the strength of the rate limiter by reducing the limit value of the rate limiter when the prediction unit 82 predicts that vehicle 1 will change lanes, compared to when vehicle 1 is predicted to turn right or left. Also, the calculation unit 86 may increase the strength of the low-pass filter by reducing the cutoff frequency of the low-pass filter or increasing the order or number of stages of the low-pass filter when a lane change is predicted, compared to when a right or left turn is predicted. In other words, even when using a rate limiter or a low-pass filter, the calculation unit 86 may increase the reduction in the amount of change of the target control force Fc_t per unit time when a lane change is predicted, compared to when a right or left turn is predicted.

[0082] Figure 6 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.

[0083] The 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).

[0084] The ECU 70 acquires the operating status of the turn signal from the turn signal detection unit 30 (S16). If the turn signal is operating (Y in S18), or if a lane change is predicted (Y in S20), the calculation unit 86 performs a strong vibration reduction process to calculate the target control force Fc_t (S22), the control unit 88 controls the actuator 3A (S24), and the process ends.

[0085] If no lane change is predicted in S20 (N in S20), the calculation unit 86 performs a weak vibration reduction process to calculate the target control force Fc_t (S26), and the process moves to S24.

[0086] If the turn signal is not operating in S18 (N in S18), the calculation unit 86 calculates the target control force Fc_t without performing vibration reduction processing (S28), and the process moves to S24.

[0087] According to this embodiment, when the turn signal starts operating, the target control force Fc_t is calculated so that the amount of change of the target control force Fc_t per unit time is small. This suppresses the generation of vibrations and lateral forces at the boundary when the turn signal is operating, which is likely to cross the boundary between the presence and absence of road surface displacement-related values. It also does not affect the control outside the boundary between the presence and absence of road surface displacement-related values. Therefore, it is possible to suppress the feeling of discomfort in ride comfort caused by the execution of preview control.

[0088] 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.

[0089] (First variation) The control unit 88 may perform the following feedback control as vibration damping control in addition to the preview control described above by controlling the actuator 3A. That is, the feedback control is performed to reduce the vibration of the sprung mass structure 5. In an example in which preview control is performed with the feedback control, the control force Fc is expressed by, for example, the following equation (5). In this example, the calculation unit 86 calculates the target control force Fc_t according to equation (5).

[0090] Fc = β·K·Zu + γ·Zs ···(5) 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 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 the sprung displacement Zs when the target control force Fc_t is calculated. Note that instead of the sprung displacement Zs in the feedback term, any of the sprung velocity Zs', sprung acceleration Zs'', unsprung displacement Zu, unsprung velocity Zu', and unsprung acceleration Zu'' when the target control force Fc_t is calculated may be used.

[0091] The calculation unit 86 sets the basic gain γ0 as the feedback gain γ for feedback control when the turn signal is not operating.

[0092] When the turn signal starts operating, the calculation unit 86 increases the feedback gain γ during the vibration reduction process compared to when the turn signal is not operating. In other words, in this case, the calculation unit 86 sets the feedback gain γ1 to be greater than the basic gain γ0. In this case, the target control force Fc_t calculated according to equation (5) above is greater than when the feedback gain γ is the basic gain γ0. That is, when the turn signal starts operating, feedback control is actively utilized compared to when the turn signal is not operating.

[0093] This allows for more aggressive vibration damping using feedback control during the execution of vibration reduction processing, when the damping effect of preview control is temporarily weakened, thereby suppressing the deterioration of vibration of the sprung mass structure 5.

[0094] Furthermore, when using the prediction results from the prediction unit 82, the calculation unit 86 may increase the feedback gain γ when it is predicted that vehicle 1 will change lanes compared to when it is predicted that it will turn left or right. In other words, the calculation unit 86 may set gain γ1 as the feedback gain γ when it is predicted that vehicle 1 will change lanes, and set gain γ2 as the feedback gain γ when it is predicted that vehicle 1 will change lanes. Gain γ2 is greater than the basic gain γ0 and less than gain γ1.

[0095] The fundamental gains γ0, γ1, and γ2 can be determined as appropriate through experimentation or simulation. For example, the fundamental gains γ0, γ1, and γ2 are fixed values.

[0096] As a result, when changing lanes, where the vibration damping effect of preview control is weaker compared to when turning left or right, vibration damping using feedback control can be performed more actively, thereby more effectively suppressing the deterioration of vibration of the sprung mass structure 5.

[0097] (Second variation) When the turn signal starts operating, the control unit 88 may, while the vibration reduction process is running, perform preview control for the rear wheels using the unsprung displacement Zu1 calculated for the position of the front wheels, in addition to the preview control using the unsprung displacement map 200 described above. Since the rear wheels are expected to follow the path of the front wheels, such control may be performed. In this case, the control force Fc is expressed by, for example, the following equation (6). In this example, the calculation unit 86 calculates the target control force Fc_t according to equation (6) while the vibration reduction process is running.

[0098] Fc=β·K·Zu+γa·Zu1 ···(6) The first term on the right-hand side of equation (6) is the same as in equation (4) above, and is a feedforward term relating to preview control using the unsprung displacement map 200. The second term on the right-hand side is a feedforward term relating to preview control using the unsprung displacement Zu1 calculated for the position of the front wheel. The second term on the right-hand side is the product of the gain γa and the unsprung displacement Zu1 at the position of the front wheel when the target control force Fc_t is calculated. The unsprung displacement Zu1 can be calculated using the detected value of the sprung acceleration sensor 22, as described above. The gain γa can be appropriately determined by experiment or simulation.

[0099] As a result, during the vibration reduction process, in which the damping effect by preview control using the unsprung displacement map 200 is temporarily weakened, the deterioration of vibration of the sprung structure 5 can be suppressed by damping the rear wheels using preview control based on the unsprung displacement Zu1 calculated for the position where the front wheels passed.

[0100] Furthermore, when using the prediction results from the prediction unit 82, the calculation unit 86 may set the gain γa to be larger when it is predicted that vehicle 1 will change lanes compared to when it is predicted that it will turn right or left. In other words, the calculation unit 86 may set the gain γa1 as the gain γa when it is predicted that vehicle 1 will change lanes, and set the gain γa2, which is smaller than the gain γa1, as the gain γa when it is predicted that vehicle 1 will turn right or left. Gains γa1 and γa2 can be appropriately determined by experiment or simulation.

[0101] As a result, when changing lanes, where the damping effect of preview control using the unsprung displacement map 200 is weaker compared to when turning left or right, damping can be more actively performed using preview control with the unsprung displacement Zu1 calculated for the position of the front wheels, thereby more effectively suppressing the deterioration of vibration of the sprung structure 5.

[0102] (Third variation) When the turn signal starts operating, the control unit 88 may, in addition to the preview control using the unsprung displacement map 200 described above, perform preview control using a known preview sensor while the vibration reduction process is being executed. 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 of the road surface in front of the vehicle 1. In this case, the control force Fc is expressed by, for example, the following equation (7). In this example, the calculation unit 86 calculates the target control force Fc_t according to equation (7) while the vibration reduction process is being executed.

[0103] Fc=β·K·Zu+γb·Z0 ···(7) The first term on the right-hand side of equation (7) is the same as in equation (4) above, and is a feedforward term relating to preview control using the unsprung displacement map 200. The second term on the right-hand side is a feedforward term relating to preview control using the preview sensor. The second term on the right-hand side is the product of the gain γb and the road surface displacement Z0 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. Preview control using the preview sensor is well known, so no further detailed explanation is provided.

[0104] As a result, while the vibration reduction process is being executed, during which the vibration damping effect by preview control using the unsprung displacement map 200 is temporarily weakened, vibration damping by preview control using the preview sensor can suppress the deterioration of vibration of the sprung structure 5.

[0105] Furthermore, when using the prediction results from the prediction unit 82, the calculation unit 86 may increase the gain γb when it is predicted that vehicle 1 will change lanes compared to when it is predicted that it will turn right or left. In other words, the calculation unit 86 may set gain γb1 as the gain γb when it is predicted that vehicle 1 will change lanes, and set gain γb2, which is smaller than gain γb1, as the gain γb when it is predicted that vehicle 1 will turn right or left. Gains γb1 and γb2 can be appropriately determined by experiment or simulation.

[0106] As a result, when changing lanes, where the damping effect of preview control using the unsprung displacement map 200 is weaker compared to when turning left or right, the deterioration of vibration of the sprung mass structure 5 can be effectively suppressed by more actively performing damping using preview control with the preview sensor.

[0107] Furthermore, at least two of the first, second, and third variations may be combined.

[0108] 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]

[0109] 1...Vehicle, 2...Wheel, 3...Suspension, 3A...Actuator, 5...Suspension structure, 10...Suspension control system, 30...Turn signal detection unit, 70...ECU (Control Unit), 80...Acquisition unit, 82...Prediction unit, 86...Calculation unit, 88...Control unit, 200...Unsprung displacement map (road surface data 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 An acquisition unit acquires road surface displacement-related values ​​at the predicted passing position of the controlled wheel after a predetermined time from the current time, from a road surface data map which associates road surface displacement-related values ​​and position related to the vertical displacement of the road surface, A calculation unit that calculates the target control force based on the acquired road surface displacement-related values, A control unit controls the actuator so that the control force generated by the actuator matches the target control force when the controlled wheel passes the predicted passing position, It has, When the vehicle's turn signal starts operating, the calculation unit calculates the target control force such that the amount of change in the target control force per unit time is smaller compared to when the turn signal is not operating. A suspension control system characterized by the following features.

2. The aforementioned arithmetic unit, Based on the acquired road surface displacement-related values ​​and gain, the target control force is calculated. If the aforementioned turn signal is not operating, the gain is set to the reference value. When the turn signal starts operating, the gain is gradually reduced from the reference value. When the turn signal stops operating, the gain is gradually increased to the reference value. The suspension control system according to feature 1.

3. The calculation unit calculates the target control force so as to limit the amount of change of the target control force per unit time during the operation of the turn signal, or during the operation of the turn signal and for a predetermined control time after the turn signal has finished operating. The suspension control system according to feature 1.

4. The control device further includes a prediction unit that, when the turn signal starts operating, predicts whether the vehicle will change lanes or turn left or right. The calculation unit calculates the target control force such that, when it is predicted that the vehicle will change lanes, the reduction in the amount of change of the target control force per unit time is greater compared to when it is predicted that the vehicle will turn right or left. The suspension control system according to any one of claims 1 to 3.

5. The control unit further performs feedback control to reduce vibration of the suprasprung structure by controlling the actuator. The aforementioned arithmetic unit, When the aforementioned turn signal starts operating, the feedback gain of the feedback control is increased compared to when the turn signal is not operating. When it is predicted that the vehicle will change lanes, the feedback gain is increased compared to when it is predicted that it will turn left or right. The suspension control system according to feature 4.

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