Vehicle suspension control device and vehicle suspension control method

Abstract

To enable vehicle posture to be controlled while balancing responsiveness with output.SOLUTION: A vehicle suspension control device comprises a first actuator, a second actuator and an electronic control unit. The first actuator controls a suspension stroke of a first control object wheel. The second actuator controls a suspension stroke of the first control object wheel or a second control object wheel which is different from the first control object wheel, and has higher responsiveness and lower output than the first actuator. The electronic control unit executes a calculation process to calculate a demand control amount for vehicle posture control. In a case where only a first maximum control amount, which is a maximum amount of the first control amount that the first actuator can output, is not enough to satisfy the demand control amount, the electronic control unit also instructs the first actuator to output the first maximum control amount and executes an instruction process to instruct the second actuator to output a second control amount to compensate for a shortage in the control amount.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a vehicle suspension control device and a vehicle suspension control method that include first and second actuators having different responsiveness and output for controlling a suspension stroke. [Background technology]

[0002] Patent Document 1 discloses an active suspension device that includes an electric actuator on each wheel of a vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-251636 A Summary of the Invention [Problem to be solved by the invention]

[0004] A large force is required to control the posture of a vehicle. The responsiveness and output of the actuator that controls the suspension stroke are generally in a trade-off relationship. Specifically, in order for an actuator to generate a large output, the actuator must be large, and a large actuator will have low responsiveness. For this reason, it is difficult to achieve both responsiveness and output.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a vehicle suspension control device and a vehicle suspension control method that are capable of performing vehicle posture control while achieving both responsiveness and output. [Means for solving the problem]

[0006] A vehicle suspension control device according to the present disclosure includes a first actuator, a second actuator, and an electronic control unit. The first actuator controls a suspension stroke of a first control target wheel. The second actuator controls a suspension stroke of the first control target wheel or a second control target wheel different from the first control target wheel, and has a higher responsiveness and a lower output than the first actuator. The electronic control unit executes a calculation process to calculate a required control amount for vehicle attitude control. In addition, when a first maximum control amount, which is a maximum value of the first control amount that the first actuator can output, is insufficient for the required control amount, the electronic control unit executes a command process to command the first actuator to the first maximum control amount and to command the second actuator to a second control amount to compensate for the shortage.

[0007] The vehicle attitude control may include at least one of a first attitude control for a vehicle operation input and a second attitude control for a road surface input, and the required control amount may include at least one of a first required control amount for the first attitude control and a second required control amount for the second attitude control.

[0008] The vehicle attitude control may include both a first attitude control and a second attitude control. In the calculation process, the electronic control unit may calculate the required control amount as a sum of the first required control amount and the second required control amount.

[0009] The first attitude control may include a roll control of the vehicle, and the first required control amount may include a roll required control amount for the roll control.

[0010] The first control target wheel to which the first actuator is applied may be one of the left / right front wheels and the left / right rear wheels of the vehicle. The second actuator is applied to a second control target wheel, and the second control target wheel may be the other of the left / right front wheels and the left / right rear wheels of the vehicle. In the calculation process, the electronic control unit may calculate the total roll required control amount of all wheels of the vehicle as the required control amount.

[0011] The first attitude control may include a pitch control of the vehicle, and the first required control amount may include a pitch required control amount for the pitch control.

[0012] The second attitude control may include vibration control for reducing vibration of a sprung structure of the vehicle in response to a road surface input, and the second required control amount may include a required control amount for vibration control.

[0013] In command processing, if the required control amount can be satisfied by only the first control amount of the first actuator, the electronic control unit may command the first actuator for the entire required control amount, and may not need to issue a command regarding the required control amount to the second actuator.

[0014] A vehicle suspension control method according to the present disclosure controls a vehicle suspension including a first actuator that controls a suspension stroke of a first control target wheel, and a second actuator that controls a suspension stroke of the first control target wheel or a second control target wheel different from the first control target wheel and has higher responsiveness and lower output than the first actuator. This control method includes a calculation process for calculating a required control amount for vehicle attitude control, and, when a first maximum control amount, which is a maximum value of the first control amount that the first actuator can output, is insufficient for the required control amount, a command process for issuing a first maximum control amount to the first actuator and a second control amount to the second actuator to compensate for the shortage. Effect of the Invention

[0015] According to the vehicle suspension control device and vehicle suspension control method disclosed herein, a first and a second actuator having different responsiveness and output are used in combination to realize a required control amount for vehicle posture control. Then, the first actuator with high output is used as the main actuator for vehicle posture control, and the control amount for realizing the required control amount can be supplemented by the second actuator with high responsiveness as necessary. This makes it possible to perform vehicle posture control while achieving both responsiveness and output. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram illustrating an example of a configuration of a vehicle according to an embodiment; [Diagram 2] 1 is a conceptual diagram showing a configuration example of a suspension according to an embodiment; [Diagram 3] FIG. 2 is a conceptual diagram for explaining preview control. [Figure 4] 4 is a flowchart showing a process related to vehicle attitude control according to the embodiment. [Diagram 5] 4 is a time chart showing a schematic relationship between a required control amount X, a first maximum control amount X1max, and a second control amount X2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the embodiments described below, when the number, quantity, amount, range, etc. of each element is mentioned, the technical idea of ​​the present disclosure is not limited to the mentioned number unless otherwise specified or clearly specified in principle.

[0018] 1. Example of vehicle configuration FIG. 1 is a diagram showing a schematic example of a configuration of a vehicle 1 according to an embodiment. The vehicle 1 is equipped with wheels 2 and suspensions 3. The wheels 2 include a left front wheel 2FL, a right front wheel 2FR, a left rear wheel 2RL, and a right rear wheel 2RR. Suspensions 3FL, 3FR, 3RL, and 3RR are provided for the left front wheel 2FL, the right front wheel 2FR, the left rear wheel 2RL, and the right rear wheel 2RR, respectively. In the following description, unless there is a particular need to distinguish between them, each wheel will be referred to as a wheel 2, and each suspension will be referred to as a suspension 3.

[0019] FIG. 2 is a conceptual diagram showing a configuration example of a suspension 3 according to an embodiment. The suspension 3 is provided to connect between an unsprung structure 4 and a sprung structure 5 of a vehicle 1. The unsprung structure 4 includes a wheel 2. The suspension 3 includes a first actuator 3A1 and a second actuator 3A2 as well as a spring 3S and a damper (shock absorber) 3D. The spring 3S, the damper 3D, and the first and second actuators 3A1 and 3A2 are provided in parallel between the unsprung structure 4 and the sprung structure 5. The spring 3S has a spring constant K. The damper 3D has a damping coefficient C. The first and second actuators 3A1 and 3A2 control the stroke of the suspension 3 by exerting vertical control forces Fc1 and Fc2 between the unsprung structure 4 and the sprung structure 5, respectively.

[0020] More specifically, the suspension 3 is configured as an active suspension by including the first and second actuators 3A1, 3A2. The first actuator 3A1 and the second actuator 3A2 are configured as follows. That is, the second actuator 3A2 has higher responsiveness and lower output than the first actuator. The first and second actuators 3A1, 3A2 having such different characteristics can be configured, for example, as follows.

[0021] That is, the first actuator 3A1, which has a relatively high output (control force Fc1) but low responsiveness, is, for example, a hydraulic active actuator (an actuator constituting a so-called full active suspension). On the other hand, the second actuator 3A2, which has a relatively high responsiveness but low output (control force Fc2), is, for example, an electric active actuator (an actuator constituting a so-called full active suspension). More specifically, the second actuator 3A2 corresponds to, for example, a linear motor included in a linear motor type active suspension device (see, for example, JP 2019-162909 A).

[0022] Furthermore, the vehicle 1 is equipped with an electronic control unit (ECU) 10. The ECU 10 is equipped with a processor, a storage device, and an input / output interface. The input / output interface takes in sensor signals from sensors 12 attached to the vehicle 1, and outputs operation signals to the first actuator 3A1 and the second actuator 3A2. The storage device stores various control programs for controlling the actuators 3A1 and 3A2. The processor reads out and executes the control programs from the storage device, thereby realizing control of an "active suspension" using the actuators 3A1 and 3A2 (including vehicle attitude control, which will be described later).

[0023] The sensors 12 include, for example, an acceleration sensor that detects the lateral acceleration LA and longitudinal acceleration FA acting on the vehicle 1, a sprung acceleration sensor that detects the vertical acceleration of the sprung structure 5, a suspension stroke sensor, and a wheel speed sensor provided on each wheel 2. The wheel speed sensor can detect the vehicle speed V. The sensors 12 also include, for example, an accelerator position sensor and a brake position sensor that detect the depression amounts of an accelerator pedal and a brake pedal, respectively, and a steering angle sensor for the wheels 2. The sensors 12 further include a position sensor that detects the position and orientation of the vehicle 1. The position sensor includes, for example, a GNSS (Global Navigation Satellite System) receiver.

[0024] The vehicle 1 also includes a communication device 14. The ECU 10 communicates with the outside of the vehicle 1 via the communication device 14.

[0025] 2. Vehicle attitude control The vehicle attitude control, which is the attitude control of the vehicle 1, includes at least one of a first attitude control for a vehicle operation input and a second attitude control for a road surface input. In this embodiment, the first attitude control and the second attitude control are combined and executed as the vehicle attitude control.

[0026] 2-1. First attitude control The first attitude control for the vehicle operation input includes at least one of roll control during turning accompanying steering of the vehicle 1 and pitch control accompanying acceleration / deceleration of the vehicle 1. In this embodiment, a combination of roll control and pitch control is executed as the first attitude control.

[0027] The roll control here refers to control for generating a reverse roll moment by controlling the control forces Fc1 and Fc2 of the actuators 3A1 and 3A2 so as to cancel the roll generated during turning due to steering of the vehicle 1. More specifically, "canceling the roll" refers to suppressing the roll generated compared to the case without roll control, or generating a roll in the opposite direction to the generated roll. Similarly, the pitch control here refers to control for generating a reverse pitch moment by controlling the control forces Fc1 and Fc2 of the actuators 3A1 and 3A2 so as to cancel the pitch generated during acceleration and deceleration of the vehicle 1. More specifically, "canceling the pitch" refers to suppressing the pitch generated compared to the case without pitch control, or generating a pitch in the opposite direction to the generated pitch.

[0028] 2-2. Second attitude control The second attitude control for the road surface input (in other words, ride comfort control) includes vibration control for reducing vibration (more specifically, vertical vibration) of the sprung structure 5 for the road surface input. Such vibration control can also be said to be control for suppressing changes in the attitude (behavior) of the sprung structure 5 caused by the road surface input in order to improve the ride comfort of the vehicle 1.

[0029] The second attitude control (ride comfort control) is, for example, a preview control based on road surface information ahead of the vehicle. FIG. 3 is a conceptual diagram for explaining the preview control. The road surface information ahead of the vehicle can be acquired, for example, by the vehicle 1 from a management server on the cloud via the communication device 14 as a road surface data map. This road surface data map is a map in which a road surface displacement-related value related to the vertical displacement Zr of the road surface is associated with a data storage position (position on a map). A specific example of this is an unsprung displacement map that uses an unsprung displacement Zu as an example of a road surface displacement-related value. The road surface data map is generated and updated in advance based on information collected from a large number of vehicles including the vehicle 1. The road surface information ahead of the vehicle may be acquired, for example, by using an image captured by a camera mounted in front of the vehicle, instead of acquiring the road surface information using the road surface data map.

[0030] In the preview control, the ECU 10 acquires a current position P0 of each wheel 2. The relative positional relationship between a reference point of the vehicle position in the vehicle 1 and each wheel 2 is known information. The position of each wheel 2 can be calculated based on the relative positional relationship and the vehicle position indicated by the position information. The position information here is acquired, for example, by using a position sensor included in the sensors 12. The position information may also be acquired by dead reckoning.

[0031] The ECU 10 calculates a predicted passing position Pf of the wheel 2 after the preview time tp. The preview time tp is set to, for example, a time equal to or longer than the time required for calculation processing and communication processing required to operate the actuators 3A1 and 3A2 of the suspension 3. The preview time tp may be fixed or may be variable depending on the situation. The preview distance Lp is given by the product of the preview time tp and the vehicle speed V. The predicted passing position Pf is a position that is the preview distance Lp ahead of the current position P0. As a modified example, the ECU 10 may calculate a predicted traveling route based on the vehicle speed V and the steering angle of the wheel 2, and calculate the predicted passing position Pf based on the predicted traveling route.

[0032] The ECU 10 reads out the unsprung displacement Zu at the predicted passing position Pf from the unsprung displacement map. Then, the ECU 10 calculates the target control force Fc_t of the actuators 3A1 and 3A2 of the suspension 3 based on the unsprung displacement Zu at the predicted passing position Pf. The target control force Fc_t is calculated, for example, as follows. This target control force Fc_t corresponds to a required value (i.e., a required control amount Xpv described later) of the control force Fc (Fc1 and Fc2) required for the preview control.

[0033] The equation of motion for the sprung structure 5 (see FIG. 2) is expressed by the following equation (1). m·Zs''=C(Zu'-Zs')+K(Zu-Zs)-Fc ···(1)

[0034] In equation (1), m is the mass of the sprung structure 5, Zs is the sprung displacement, C is the damping coefficient of the damper 3D, K is the spring constant of the spring 3S, and Fc (=Fc1+Fc2) is the vertical control force generated by the actuators 3A1 and 3A2. If the vibration of the sprung structure 5 is completely canceled by the control force Fc (Zs''=0, Zs'=0, Zs=0), the control force Fc is expressed by the following equation (2). Fc = C Zu' + K Zu (2)

[0035] The control force Fc that provides at least the vibration damping effect is expressed by the following formula (3). Fc=α·C·Zu'+β·K·Zu ···(3)

[0036] In formula (3), the gain α is greater than 0 and less than or equal to 1, and the gain β is also greater than 0 and less than or equal to 1. When the differential term in formula (3) is omitted, a control force Fc that provides at least a vibration damping effect is expressed by the following formula (4). Fc = β K Zu (4)

[0037] The ECU 10 calculates the target control force Fc_t (i.e., the required control amount Xpv) according to the above formula (3) or formula (4). That is, the ECU 10 calculates the target control force Fc_t (required control amount Xpv) by substituting the unsprung displacement Zu at the predicted passing position Pf into formula (3) or formula (4).

[0038] The ECU 10 controls the actuators 3A1 and 3A2 to generate a target control force Fc_t (required control amount Xpv) at the timing when the wheel 2 passes the predicted passing position Pf. The timing when the wheel 2 passes the predicted passing position Pf can be known from the preview time tp. A specific method of issuing commands for the required control amount X, including the required control amount Xpv, to the two actuators 3A1 and 3A2 will be described later with reference to FIG.

[0039] According to the preview control described above, it is possible to effectively suppress vibration of the vehicle 1 (sprung structure 5).

[0040] The second attitude control may be, instead of or in addition to the preview control, feedback control based on the skyhook control law for reducing vibration of the sprung structure 5 using at least one of the sprung displacement, the sprung velocity, and the sprung acceleration (see, for example, JP 2019-135120 A).

[0041] 2-3. Processing by ECU In this embodiment, in order to perform vehicle attitude control while achieving both responsiveness and output, the ECU 10 executes the following "calculation process" and "command process." That is, the ECU 10 executes a calculation process to calculate a required control amount X for vehicle attitude control. Then, when the first maximum control amount X1max, which is the maximum value of the first control amount X1 that the first actuator 3A1 can output, is insufficient for the control amount for the required control amount X, the ECU 10 executes a command process to command the first maximum control amount X1max to the first actuator 3A1 and to command the second actuator 3A2 to a second control amount X2 to compensate for the shortage.

[0042] On the other hand, if the required control amount X can be satisfied by only the first control amount X1, the ECU 10 commands the first actuator 3A1 to use the entire required control amount X as the first control amount X1, and does not command the second actuator 3A2 regarding the required control amount X.

[0043] Fig. 4 is a flowchart showing a process related to vehicle attitude control according to the embodiment. The process of this flowchart is repeatedly executed every predetermined time step Δt (see Fig. 5) while the vehicle 1 is traveling. In Fig. 4, the process of step S100 corresponds to an example of the above-mentioned "calculation process", and the processes of steps S102 to S110 correspond to an example of the above-mentioned "command process".

[0044] <Step S100> In step S100, the ECU 10 calculates a required control amount X. The required control amount X is a (total) required control amount for the entire vehicle attitude control performed in the vehicle 1. Specifically, in step S100, the ECU 10 calculates a roll required control amount Xr and a pitch required control amount Xp for the roll control and pitch control included in the first attitude control. The ECU 10 also calculates a required control amount Xpv for preview control, which is an example of the second attitude control. The ECU 10 then calculates the sum of the calculated required control amounts Xr, Xp, and Xpv as the total required control amount X.

[0045] The control laws of the roll control, pitch control, and preview control constituting the vehicle attitude control are not particularly limited. The calculation method of each of the required control amounts Xr, Xp, and Xpv is also not particularly limited, and any control request to the suspension 3 constituting the active suspension may be used. In addition, an example of the calculation method of each of the required control amounts Xr, Xp, and Xpv is described below.

[0046] First, the roll required control amount Xr corresponds to the required value of the control force Fc required for roll control. The pitch required control amount Xp corresponds to the required value of the control force Fc required for pitch control. The control force Fc corresponds to the sum of the control force Fc1 of the first actuator 3A1 and the control force Fc2 of the second actuator 3A2. In addition, in each wheel 2, the control force Fc, which is a suspension generated force, is positive when it acts to lift the sprung structure 5 upward. Accordingly, the required control amount X (Xr, Xp, and Xpv) is also positive when it acts to lift the sprung structure 5 upward. Therefore, the roll required control amount Xr is positive for the wheel 2 on the outside of the turn and negative for the wheel 2 on the inside of the turn. Similarly, the pitch required control amount Xp is negative for the front wheels 2FL and 2FR and positive for the rear wheels 2RL and 2RR during acceleration, and conversely, is positive for the front wheels 2FL and 2FR and negative for the rear wheels 2RL and 2RR during deceleration.

[0047] As an example, the roll required control amount Xr and the pitch required control amount Xp are expressed by the following formulas ( 5 ) and ( 6 The sum of the roll required control amount Xr and the pitch required control amount Xp corresponds to an example of the "first required control amount" according to the present disclosure. Xr = LA × Gr (5) Xp = FA × Gp (6)

[0048] As shown in equation (5), the roll required control amount Xr is given by the product of the lateral acceleration LA and the control gain Gr. As shown in equation (6), the pitch required control amount Xp is given by the product of the longitudinal acceleration FA and the control gain Gp. Note that the control gain Gr for roll control and the control gain Gp for pitch control may be the same or different.

[0049] In step S100, the ECU 10 calculates the roll request control amount Xr at the next sample time (k+1). The roll request control amount Xr is calculated, for example, by multiplying the lateral acceleration LA acquired at the current sample time (k) by a control gain Gr (proportional coefficient). Therefore, as the absolute value of the lateral acceleration LA increases, the absolute value of the roll request control amount Xr also increases. The control gain Gr is, for example, a fixed value determined in advance. However, the control gain Gr may be variable according to a parameter related to the vehicle attitude control. The lateral acceleration LA can be acquired, for example, by using a lateral acceleration sensor. The lateral acceleration LA may also be estimated, for example, based on information such as the vehicle speed V and the steering angle.

[0050] Furthermore, the ECU 10 calculates the pitch required control amount Xp at the next sample time (k+1). Similarly, the pitch required control amount Xp is calculated, for example, by multiplying the longitudinal acceleration FA acquired at the current sample time (k) by a control gain Gp (proportional coefficient). Therefore, as the absolute value of the longitudinal acceleration FA increases, the absolute value of the pitch required control amount Xp also increases. The control gain Gp is, for example, a fixed value determined in advance. However, the control gain Gp may be variable according to a parameter related to vehicle attitude control. The longitudinal acceleration FA can be acquired, for example, by using a longitudinal acceleration sensor. Furthermore, the longitudinal acceleration FA may be estimated, for example, based on required information of the vehicle longitudinal force (for example, required engine torque or required braking force).

[0051] An example of a method for calculating the required control amount Xpv (target control force Fc_t) for preview control, which is an example of the second attitude control, is as described above with reference to Fig. 3. The required control amount Xpv corresponds to an example of the "second required control amount" according to the present disclosure. In an example in which a required control amount for feedback control based on the skyhook control law is calculated together with the required control amount Xpv, the sum of these required control amounts corresponds to another example of the "second required control amount."

[0052] In step S100, the ECU 10 calculates, for each wheel 2, the sum of the three required control amounts Xr, Xp, and Xpv calculated as described above (i.e., the sum of the first required control amount and the second required control amount) as the required control amount X.

[0053] <Step S102> Next, in step S102, the ECU 10 calculates a first maximum control amount X1max that can be output by the first actuator 3A1. More specifically, the first maximum control amount X1max corresponds to the maximum first control amount X1 that can be output by the first actuator 3A1, including the time when the first control amount X1 changes over time. In step S102, the ECU 10 calculates the first maximum control amount X1max that can be output at the next sample time (k+1).

[0054] Here, the maximum change speed V1max and maximum value F1max (see FIG. 5) of the control force Fc1 that can be output by the first actuator 3A1 are basically determined by the specifications of the first actuator 3A1. Therefore, the maximum change speed V1max and maximum value F1max can be known in advance. The storage device of the ECU 10 stores information on the basic operating characteristics of the first actuator 3A1, such as the maximum change speed V1max and maximum value F1max. More specifically, the maximum change speed V1max corresponds to the maximum change amount ΔF1max (see FIG. 5) per unit time (time step Δt).

[0055] FIG. 5 is a time chart that shows a schematic relationship between the required control amount X, the first maximum control amount X1max, and the second control amount X2. FIG. 5 shows an example of turning caused by steering the vehicle 1, but for the sake of simplicity, it is assumed that the pitch required control amount Xp and the required control amount Xpv other than the roll required control amount Xr are zero. Therefore, in this example, the required control amount Xr is equal to the required control amount X. The relationship shown in FIG. 5 is for the wheel 2 that is on the outside of the turn during turning. In the relationship for the wheel 2 that is on the inside of the turn during turning, the signs of the required control amount X and the first maximum control amount X1max are opposite to those in the relationship shown in FIG. 5.

[0056] In the example shown in Fig. 5, with the start of steering at the sample time (k = 0), the lateral acceleration LA increases over time, and the required control amount X increases accordingly. In this example, the vehicle then enters a steady circular turning state where the vehicle speed V and lateral acceleration LA are constant, and the required control amount X remains constant over time. More specifically, Fig. 5 shows the required control amount X (solid line and dashed line) during two types of turning that differ in the lateral acceleration LA that occurs during turning.

[0057] The first maximum control amount X1max of the first actuator 3A1 at each sample time k can be calculated based on, for example, the maximum change rate V1max and the maximum value F1max described above. Specifically, as shown in FIG. 5, first, the first maximum control amount X1max at the sample time (k=0) is zero. The first maximum control amount X1max at the next sample time (k=1) is calculated as the maximum change amount ΔF1max, which is the product of the maximum change rate V1max stored in the storage device and the time step Δt. The first maximum control amount X1max at each sample time k during the period from the next sample time (k=2) onwards until the first maximum control amount X1max reaches the maximum value F1max is calculated by adding the maximum change amount ΔF1max to the previous value. The first maximum control amount X1max after the first maximum control amount X1max reaches the maximum value F1max is calculated as the maximum value F1max. In addition, when the first maximum control amount X1max calculated in this manner is compared with the required control amount X indicated by the solid line, the time waveform of the first maximum control amount X1max corresponds to the time waveform obtained by rate-limiting the waveform of the required control amount X by the maximum change speed V1max and by upper-limit-limiting it by the maximum value F1max.

[0058] In the example shown in FIG. 5, the requested control amount X remains constant over time and then decreases toward zero. To realize the requested control amount X that changes in this way, the first control amount X1 must also decrease over time. The maximum rate of change when the first control amount X1 decreases (i.e., the slope of the time waveform of the first maximum control amount X1max) is V1max (a negative value). Therefore, for example, when the first control amount X1 is decreased from the sample time (k=m), the first maximum control amount X1max at each sample time k can be calculated by subtracting the negative maximum change amount ΔF1max from the previous value, as when the requested control amount X is increasing.

[0059] In addition, the information on the basic operating characteristics of the first actuator 3A1 stored in the storage device for calculating the first maximum controlled variable X1max may include information on dynamic characteristics such as dead time characteristics and first-order lag characteristics. The first maximum controlled variable X1max may be calculated taking into consideration, for example, one or both of the dead time characteristics and the first-order lag characteristics.

[0060] <Step S104> Next, in step S104, the ECU 10 determines whether or not the first maximum control amount X1max that the first actuator 3A1 can output is insufficient for the required control amount X. This determination can be made, for example, based on whether or not the difference ΔX1 is zero. The difference ΔX1 is a value (=X-X1max) obtained by subtracting the first maximum control amount X1max calculated in step S102 from the required control amount X calculated in step S100.

[0061] Specifically, when the required control amount X increases over time as shown in Fig. 5, the required control amount X is greater than the first maximum control amount X1max, and so the above difference ΔX1 is positive. Also, as shown in the figure, when the required control amount X, which remains constant, is greater than the first maximum control amount X1max (maximum value F1max), the difference ΔX1 is positive. In this way, a positive difference ΔX1 means that the first maximum control amount X1max alone is insufficient to provide a control amount.

[0062] Furthermore, the "insufficient control amount" determined in step S104 also occurs when the difference ΔX1 is negative, as in the hatched area shown in Fig. 5. This hatched area occurs because, for example, the slope (solid line) of the required control amount X when it decreases due to a sudden return movement of the steering wheel by the driver of the vehicle 1 becomes larger than the slope of the first maximum control amount X1max. In this hatched area, the first maximum control amount X1max at each sample time k becomes larger than the required control amount X. That is, the difference ΔX1 becomes negative.

[0063] <Step S106> If the determination result in step S104 is No (i.e., there is no shortage of control amount), the process proceeds to step S106. For example, if the required control amount X is represented by a dashed line in FIG. 5, the determination result is No. In step S106, the ECU 10 commands the first actuator 3A1 to generate a first control amount X1 that is equal to the required control amount X calculated in step S100. As a result, the first actuator 3A1 is controlled to generate a control force Fc1 according to the commanded required control amount X.

[0064] <Step S108> On the other hand, if the result of the determination in step S104 is Yes (i.e., if there is a shortage of the control amount), the process proceeds to step S108. For example, if the required control amount X is represented by a solid line in FIG. 5, the result of this determination is Yes.

[0065] In step S108, the ECU 10 calculates a second control amount X2 which is a control amount of the second actuator 3A2. More specifically, the ECU 10 calculates the second control amount X2 at the next sample time (k+1). The second control amount X2 is calculated as a value required to compensate for the "deficiency of the control amount".

[0066] Specifically, the second control amount X2 is a value obtained by subtracting the first maximum control amount X1max calculated in step S102 from the required control amount X calculated in step S100, that is, the difference ΔX1. The reason is that, as illustrated in FIG. 5, when the difference ΔX1 is positive, it is necessary to increase the control force Fc2 of the second actuator 3A2 by the amount (difference ΔX1) that is insufficient with only the first maximum control amount X1max of the required control amount X. On the other hand, when the difference ΔX1 is negative, the control amount is insufficient by the negative difference ΔX1 with only the first maximum control amount X1max. For this reason, it is necessary to control the control force Fc2 of the second actuator 3A2 so as to decrease it by the negative difference ΔX1.

[0067] <Step S110> In step S110 following step S108, the ECU 10 commands the first actuator 3A1 to use the first maximum control amount X1max calculated in step S102 as the first control amount X1, and commands the second actuator 3A2 to use the second control amount X2 calculated in step S108. As a result, the first actuator 3A1 is controlled to generate a control force Fc1 according to the commanded first maximum control amount X1max. Also, the second actuator 3A2 is controlled to generate a control force Fc2 according to the commanded second control amount X2.

[0068] In addition, in the example shown in FIG. 5, if the slope of the required control amount X that starts to decrease from the sample time (k=m) is the same as or smaller than the slope of the first maximum control amount X1max (dashed line), then during the period in which the required control amount X is larger than the first maximum control amount X1max, the second control amount X2 can be reduced to zero over time from the sample time (k=m), and thereafter the required control amount X can be satisfied with only the first control amount X1.

[0069] 3.Effects A large force is required to control the attitude of a vehicle. However, in general, the responsiveness and output of an actuator of an active suspension are in a contradictory relationship, and it is difficult to achieve both. More specifically, in general, when emphasis is placed on responsiveness, the output of the actuator is small. As a result, it becomes difficult to satisfactorily perform the first attitude control for the vehicle operation input (i.e., roll control for steering and pitch control for acceleration / deceleration). This is also true for the second attitude control (ride comfort control) for the road surface input, and it becomes difficult to satisfactorily perform the ride comfort control for a large road surface amplitude. On the other hand, when emphasis is placed on output, it becomes difficult to ensure a satisfactory response of these controls when the required control amounts Xr and Xp change transiently in the first attitude control (roll and pitch control). Similarly, it becomes difficult to ensure a satisfactory response of the ride comfort control for a sudden change in the road surface.

[0070] In contrast, according to the present embodiment, a required control amount X, which is a combination of a plurality of required control amounts Xr, Xp, and Xpv for the first attitude control and the second attitude control, is distributed to two actuators 3A1 and 3A2 of the suspension 3, which is an active suspension. In this manner, the first and second actuators 3A1 and 3A2, which have different responsiveness and output, are used in combination to realize the required control amount X. More specifically, in the command process, when the first maximum control amount X1max that the first actuator 3A1 can output is insufficient for the control amount for the required control amount X, the first maximum control amount X1max is commanded to the first actuator 3A1, and the second control amount X2 to compensate for the shortage is commanded to the second actuator 3A2.

[0071] This makes it possible to use the first actuator 3A1 with high output as the main actuator for vehicle attitude control (i.e., first attitude control and second attitude control), while using the second actuator 3A2 with high responsiveness as necessary to supplement the control amount for achieving the required control amount X. This makes it possible to perform vehicle attitude control while achieving both responsiveness and output.

[0072] In addition, by using the second actuator 3A2, which has a high response, as a sub actuator, it is possible to compensate for the response delay of the first actuator 3A1 when the required control amount X changes transiently (increases or decreases). As a result, the total control amount of the two actuators 3A1 and 3A2 can be suitably brought close to the required control amount X during the transient period. Furthermore, by using two types of actuators 3A1 and 3A2, the maximum control amount that each of the actuators 3A1 and 3A2 can output can be used as necessary. As a result, the required control amount X, which cannot be satisfied by using only one of the actuators 3A1 and 3A2, can be realized in the vehicle attitude control while maintaining both responsiveness and output. Therefore, the comfort of the vehicle 1 is improved. Specifically, the performance of the first attitude control for at least one of steering and acceleration / deceleration, which has a large rate of change and / or absolute amount, is improved. Furthermore, the performance of the second attitude control (ride comfort control) for a large and fast road surface input is improved. As a result, when applied to feedforward control (e.g., preview control), it is possible to efficiently suppress vibration of the sprung structure 5. In addition, when applied to feedback control (e.g., feedback control based on the skyhook control law), the feedback control amount is reduced, so that it is possible to reduce energy consumption by the actuator and heat generation by the actuator.

[0073] 4. Supplementary explanation of vehicle attitude control Regarding the implementation of the "vehicle attitude control" according to the present disclosure, the following supplementary explanation will be given.

[0074] 4-1. Specific examples of vehicle attitude control Instead of the example described with reference to Fig. 4, only one of the first attitude control for the vehicle operation input and the second attitude control for the road surface input may be executed as the vehicle attitude control. As a specific example, for example, only at least one of the roll control and the pitch control included in the first attitude control may be executed. Also, only the second attitude control for the road surface input such as the preview control may be executed.

[0075] 4-2. Use of active stabilizer device (first actuator) 1 and 2, the first actuator 3A1 is disposed for each of the four wheels 2. Instead of the first actuator 3A1, the "first actuator" according to the present disclosure may be, for example, an actuator (e.g., an electric motor) of an active stabilizer device (see, for example, Japanese Patent Application Laid-Open No. 2013-001225). Hereinafter, for convenience, this actuator will be referred to as the "first actuator 3A1'".

[0076] In such an active stabilizer device, one first actuator 3A1' is shared by the suspensions 3FL and 3FR corresponding to the left and right front wheels 2FL and 2FR. Similarly, one first actuator 3A1' is shared by the suspensions 3RL and 3RR corresponding to the left and right rear wheels 2RL and 2RR. These first actuators 3A1' generate control forces Fc1 (moments) of opposite phases for the left and right front wheels 2FL and 2FR, or for the left and right rear wheels 2RL and 2RR.

[0077] The first actuator 3A1' can be used for roll control in combination with a second actuator 3A2 (eg, a linear motor) as follows.

[0078] Specifically, the roll control referred to here may be executed as follows, for example, for each of the left and right front wheels 2FL and 2FR and the left and right rear wheels 2RL and 2RR. That is, the ECU 10 first calculates the total roll required control amount Xrt for the four wheels (all wheels) 2. This roll required control amount Xrt is, for example, a required value of the roll moment at the center of gravity of the vehicle, and is expressed by the product of the lateral acceleration LA and a predetermined control gain.

[0079] Next, the ECU 10 converts the total roll request control amount Xrt into a roll request control amount Xrtf for the left and right front wheels 2FL and 2FR and a roll request control amount Xrtr for the left and right rear wheels 2RL and 2RR in accordance with a predetermined arithmetic expression.

[0080] Next, the ECU 10 calculates the first maximum control amount X1max of the first actuator 3A1' of the left and right front wheels 2FL and 2FR. Then, the ECU 10 judges whether or not the calculated first maximum control amount X1max alone is insufficient in the control amount for the roll required control amount Xrtf. As a result, if there is no shortage of the control amount, the ECU 10 commands the first actuator 3A1' to the first control amount X1 equal to the roll required control amount Xrtf. On the other hand, if there is a shortage of the control amount, the ECU 10 commands the first actuator 3A1' to the first maximum control amount X1, and commands the shortage (=Xrtf-X1max) to the second actuator 3A2 of the left and right front wheels 2FL and 2FR. The ECU 10 also executes the same process for the left and right rear wheels 2RL and 2RR.

[0081] It should be noted that the combination of the first actuator 3A1' and the second actuator 3A2 may be used not only for roll control, but also for a combination of roll control and second attitude control (for example, preview control), for example.

[0082] 4-3.Specific examples of controlled wheels (wheels that are subject to suspension stroke control) 1 and 2, the controlled wheels of the "first actuator" according to the present disclosure may be the same as the controlled wheels of the "second actuator" (i.e., both of these controlled wheels may correspond to the "first controlled wheels" according to the present disclosure). However, when the controlled wheels of the "first actuator" and the "second actuator" are the same, the controlled wheels are not limited to all wheels of the vehicle, and may be, for example, only the left and right front wheels, or only the left and right rear wheels.

[0083] Furthermore, the controlled wheels of the "first actuator" may be different from the controlled wheels of the "second actuator." For example, the controlled wheels (first controlled wheels) of the "first actuator" may be the left and right rear wheels, and the controlled wheels (second controlled wheels) of the "second actuator" may be the left and right front wheels. Conversely, the controlled wheels (first controlled wheels) of the "first actuator" may be the left and right front wheels, and the controlled wheels (second controlled wheels) of the "second actuator" may be the left and right rear wheels.

[0084] 4-4. When responsiveness differs between the front and rear of the vehicle For example, in the example described above where a "first actuator" is applied to one of the left / right front wheels and the left / right rear wheels, and a "second actuator" is applied to the other, the responsiveness of the actuators will be different between the front and rear of the vehicle.

[0085] When the responsiveness of the actuators at the front and rear of the vehicle differs in this way, the roll control may be executed, for example, as follows: That is, as described in the above item 4-2, the ECU 10 first calculates the total roll required control amount Xrt of the four wheels (all wheels) 2 as the required control amount X.

[0086] Next, the ECU 10 calculates a first maximum control amount X1max of the first actuator. In this case, an example of the first actuator is a first actuator 3A1 applied to each of the left and right front wheels (or the left and right rear wheels), or a single first actuator 3A1' applied commonly to the left and right front wheels (or the left and right rear wheels).

[0087] Next, the ECU 10 judges whether the calculated first maximum control amount X1max alone is insufficient for the total roll request control amount Xrt. If the result shows that there is no shortage of control amount, the ECU 10 commands the first actuator to obtain the first control amount X1 equal to the roll request control amount Xrt. On the other hand, if there is a shortage of control amount, the ECU 10 commands the first actuator to obtain the first maximum control amount X1, and commands the shortage (=Xrt-X1max) to the second actuator (for example, the second actuator 3A2).

[0088] In addition, when the responsiveness of the actuators at the front and rear of the vehicle differs, a phase difference may occur between the output of the first actuator and the output of the second actuator. In relation to such a phase difference, the following measures may be taken.

[0089] First, when comparing the first actuator and the second actuator, if the difference in frequency response characteristics is small and it can be said that there is simply a difference in stroke speed, the phase difference can be ignored. In such a case, regardless of the type of vehicle attitude control to be executed, the ECU 10 can use the first actuator with high output as the main actuator according to the principle already described, and if there is a shortage of the control amount, make up for the shortage by using the second actuator with high response.

[0090] In addition, in an example of preview control, which is an example of the second attitude control, the following measures may be taken in consideration of at least one of the frequency responses of the first and second actuators and the system dead time. That is, the ECU 10 determines the above-mentioned preview time (look-ahead time) tp in the preview control in accordance with the response characteristics of the first actuator with lower responsiveness. Then, in this example as well, the ECU 10 generates as much of the first control amount X1 required for the first actuator with higher output to satisfy the required control amount Xpv as possible according to the principle already described. In addition, when there is a shortage of the control amount and the second actuator with higher responsiveness generates the second control amount X2 to make up for the shortage, the ECU 10 delays the timing of the command for the second control amount X2 to the second actuator by the response time difference between the second actuator and the first actuator.

[0091] Furthermore, in an example in which feedback control based on the above-mentioned skyhook control law is performed together with preview control as the second attitude control, the following measures may be taken. That is, it is important for feedback control to ensure high responsiveness compared to preview control, which corresponds to feedforward control. Therefore, ECU 10 may instruct the second actuator to realize the required control amount of the feedback control by the second actuator with high responsiveness, and may instruct the first and second actuators to realize the required control amount Xpv of the preview control by a method following the above-mentioned principle. [Explanation of symbols]

[0092] 1 vehicle 2 wheels 3. Suspension 3A1 First actuator (high output and low response) 3A2 Second actuator (high response and low output) 5. Spring structure 10 Electronic Control Unit (ECU) 12 Sensors 14 Communication equipment

Claims

1. a first actuator that controls a suspension stroke of a first control target wheel; a second actuator that controls a suspension stroke of the first control target wheel or a second control target wheel different from the first control target wheel, and has a higher responsiveness and a lower output than the first actuator; An electronic control unit; A vehicle suspension control device comprising: The electronic control unit includes: A calculation process for calculating a required control amount for vehicle attitude control; a command process for commanding the first actuator to a first maximum control amount, which is a maximum value of a first control amount that the first actuator can output, when the control amount is insufficient for the required control amount, and commanding the first actuator to a second control amount for compensating for the insufficiency; Run The vehicle attitude control includes at least one of a first attitude control in response to a vehicle operation input and a second attitude control in response to a road surface input, The required control amount includes at least one of a first required control amount for the first attitude control and a second required control amount for the second attitude control. A vehicle suspension control device comprising:

2. the vehicle attitude control includes both the first attitude control and the second attitude control, In the calculation process, the electronic control unit calculates the sum of the first required control amount and the second required control amount as the required control amount.

2. The vehicle suspension control device according to claim 1.

3. the first attitude control includes roll control of the vehicle; The first required control amount includes a roll required control amount for the roll control.

3. The vehicle suspension control device according to claim 1 or 2.

4. The first control target wheel to which the first actuator is applied is one of the left and right front wheels and the left and right rear wheels of the vehicle, The second actuator is applied to the second controlled wheel, and the second controlled wheel is the other of the left and right front wheels and the left and right rear wheels of the vehicle, In the calculation process, the electronic control unit calculates a total roll required control amount of all wheels of the vehicle as the required control amount.

4. The vehicle suspension control device according to claim 3.

5. the first attitude control includes pitch control of the vehicle; The first required control amount includes a pitch required control amount for the pitch control.

5. A vehicle suspension control device according to claim 1, wherein the suspension control device is a suspension control device for a vehicle.

6. the second attitude control includes vibration control that reduces vibration of a sprung structure of the vehicle due to the road surface input, The second required control amount includes a required control amount for the vibration control.

6. A vehicle suspension control device according to claim 1, wherein the suspension control device is a suspension control device for a vehicle.

7. In the command process, when the required control amount can be satisfied by only the first control amount of the first actuator, the electronic control unit commands the first actuator for the entire required control amount, and does not command the second actuator regarding the required control amount.

7. A vehicle suspension control device according to claim 1, wherein the suspension control device is a suspension control device for a vehicle.

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