JP7600944B2 - Vehicle suspension control device and vehicle suspension control method - Google Patents

Description

The present disclosure relates to a vehicle suspension control device and a vehicle suspension control method that include first and second actuators that have different responsiveness and output to control the suspension stroke.

Patent document 1 discloses an active suspension device equipped with an electric actuator for each wheel of a vehicle.

JP 2011-251636 A

A large force is required to control the vehicle's posture. 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.

This disclosure has been made in consideration of the above-mentioned problems, and aims to provide a vehicle suspension control device and vehicle suspension control method that are capable of controlling vehicle attitude while achieving both responsiveness and output.

The 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 the suspension stroke of a first control target wheel. The second actuator controls the suspension stroke of the first control target wheel or a second control target wheel different from the first control target wheel, and has high responsiveness and low output compared to the first actuator. The electronic control unit executes a calculation process to calculate a required control amount for vehicle attitude control. In addition, when there is a shortage of control amount for the required control amount with only a first maximum control amount, which is the maximum value of the first control amount that the first actuator can output, 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 the second control amount to compensate for the shortage.

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. 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.

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

The first attitude control may include roll control of the vehicle. And the first required control amount may include a roll required control amount for the roll control.

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.

The first attitude control may include pitch control of the vehicle. And the first required control amount may include a pitch required control amount for the pitch control.

The second attitude control may include vibration control that reduces vibration of the vehicle's sprung structure in response to road input. And the second required control amount may include a required control amount for vibration control.

In command processing, if the required control amount can be satisfied by the first control amount of the first actuator alone, the electronic control unit may command the first actuator for the entire required control amount, and may not need to command the second actuator for the required control amount.

The vehicle suspension control method according to the present disclosure controls a vehicle suspension having a first actuator that controls the suspension stroke of a first control target wheel, and a second actuator that controls the 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 response and a lower output than the first actuator. This control method includes a calculation process that calculates a required control amount for vehicle attitude control, and a command process that commands the first actuator to the first maximum control amount and commands the second actuator to the second control amount to compensate for the shortage when the control amount is insufficient with respect to the required control amount using only the first maximum control amount, which is the maximum value of the first control amount that the first actuator can output.

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

1 is a diagram illustrating an example of a configuration of a vehicle according to an embodiment; 1 is a conceptual diagram showing a configuration example of a suspension according to an embodiment; FIG. 2 is a conceptual diagram for explaining preview control. 4 is a flowchart showing a process related to vehicle attitude control according to the embodiment. 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.

Below, an embodiment of the present disclosure will be described with reference to the attached 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.

1. Example of Vehicle Configuration Fig. 1 is a diagram that shows an example of the configuration of a vehicle 1 according to an embodiment. The vehicle 1 includes 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.

Figure 2 is a conceptual diagram showing an example of the configuration of the suspension 3 according to the embodiment. The suspension 3 is provided to connect between the unsprung structure 4 and the sprung structure 5 of the vehicle 1. The unsprung structure 4 includes the 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.

More specifically, by including the first and second actuators 3A1 and 3A2, the suspension 3 constitutes an active suspension. 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 and 3A2, which have such different characteristics, can be configured, for example, as follows.

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 that constitutes 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 that constitutes 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).

The vehicle 1 further includes an electronic control unit (ECU) 10. The ECU 10 includes a processor, a storage device, and an input/output interface. The input/output interface receives 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 and executes the control programs from the storage device, thereby achieving control of an "active suspension" using the actuators 3A1 and 3A2 (including vehicle attitude control, which will be described later).

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 amount of depression of the accelerator pedal and the brake pedal, respectively, and a steering angle sensor for the wheel 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.

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.

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 the present embodiment, the first attitude control and the second attitude control are combined and executed as the vehicle attitude control.

2-1. First Attitude Control The first attitude control for a 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.

The roll control referred to here is a control that generates a reverse roll moment by controlling the control forces Fc1 and Fc2 of the actuators 3A1 and 3A2 so as to cancel out the roll that occurs when the vehicle 1 turns due to steering. More specifically, "canceling the roll" refers to suppressing the roll that occurs compared to the case without roll control, or generating a roll in the opposite direction to the roll that occurs. Similarly, the pitch control referred to here is a control that generates a reverse pitch moment by controlling the control forces Fc1 and Fc2 of the actuators 3A1 and 3A2 so as to cancel out the pitch that occurs when the vehicle 1 accelerates or decelerates. More specifically, "canceling the pitch" refers to suppressing the pitch that occurs compared to the case without pitch control, or generating a pitch in the opposite direction to the pitch that occurs.

2-2. Second attitude control The second attitude control for the road surface input (in other words, ride comfort control) includes vibration control that reduces vibration (more specifically, vertical vibration) of the sprung structure 5 in response to the road surface input. Such vibration control can also be said to be control that suppresses changes in the attitude (behavior) of the sprung structure 5 associated with the road surface input in order to improve the ride comfort of the vehicle 1.

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 road surface displacement-related values related to the vertical displacement Zr of the road surface are associated with data storage positions (positions on the map). A specific example of this is an unsprung displacement map that uses 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, 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.

In the preview control, the ECU 10 acquires the current position P0 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. 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, using a position sensor included in the sensors 12. The position information may also be acquired by dead reckoning.

The ECU 10 calculates the predicted passing position Pf of the wheel 2 after the preview time tp. The preview time tp is set, for example, to be equal to or longer than the time required for the calculation and communication processes 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 variant, the ECU 10 may calculate a predicted driving 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 driving route.

The ECU 10 reads the unsprung displacement Zu at the predicted passing position Pf from the unsprung displacement map. The ECU 10 then 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 the required value of the control force Fc (Fc1 and Fc2) required for preview control (i.e., the required control amount Xpv described below).

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)

In formula (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 cancelled out by the control force Fc (Zs''=0, Zs'=0, Zs=0), the control force Fc is expressed by the following formula (2).
Fc=C・Zu'+K・Zu...(2)

A control force Fc that provides at least a vibration damping effect is expressed by the following equation (3).
Fc=α・C・Zu'+β・K・Zu...(3)

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)

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 substitutes the unsprung displacement Zu at the predicted passing position Pf into formula (3) or formula (4) to calculate the target control force Fc_t (required control amount Xpv).

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 is known from the preview time tp. A specific method for issuing commands to the two actuators 3A1 and 3A2 for the required control amount X, including the required control amount Xpv, will be described later with reference to FIG. 4.

The preview control described above makes it possible to effectively suppress vibrations of the vehicle 1 (sprung structure 5).

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, sprung velocity, and sprung acceleration (see, for example, JP 2019-135120 A).

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 the second control amount X2 to compensate for the shortage.

On the other hand, if the required control amount X can be satisfied by the first control amount X1 alone, 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.

Figure 4 is a flowchart showing the process related to vehicle attitude control according to the embodiment. The process of this flowchart is repeatedly executed every predetermined time step Δt (see Figure 5) while the vehicle 1 is traveling. Note that in Figure 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".

<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.

The control laws of the roll control, pitch control, and preview control that constitute the vehicle attitude control are not particularly limited. The method of calculating the required control amounts Xr, Xp, and Xpv is also not particularly limited, and any control request to the suspension 3 that constitutes the active suspension may be used. An example of the method of calculating the required control amounts Xr, Xp, and Xpv is described below.

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. Furthermore, in each wheel 2, the control force Fc, which is the 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 request 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.

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 ), respectively. Note that 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)

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.

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 depending on parameters related to vehicle attitude control. The lateral acceleration LA can be acquired, for example, using a lateral acceleration sensor. The lateral acceleration LA may also be estimated based on information such as the vehicle speed V and the steering angle.

The ECU 10 also 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 depending on a parameter related to vehicle attitude control. The longitudinal acceleration FA can be acquired, for example, using a longitudinal acceleration sensor. The longitudinal acceleration FA may also be estimated, for example, based on required information of the vehicle longitudinal force (for example, required engine torque or required braking force).

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."

In step S100, the ECU 10 calculates 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) for each wheel 2 as the required control amount X.

<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).

The maximum change rate 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 rate 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 rate V1max and maximum value F1max. More specifically, the maximum change rate V1max corresponds to the maximum change amount ΔF1max (see FIG. 5) per unit time (time step Δt).

Figure 5 is a time chart that shows the relationship between the required control amount X, the first maximum control amount X1max, and the second control amount X2. Figure 5 shows an example of turning accompanied by steering of the vehicle 1, but for the sake of simplicity, the pitch required control amount Xp and the required control amount Xpv other than the roll required control amount Xr are assumed to be zero. Therefore, in this example, the required control amount Xr is equal to the required control amount X. Furthermore, the relationship shown in Figure 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 Figure 5.

In the example shown in FIG. 5, as steering begins at sample time (k=0), 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 turns that differ in the lateral acceleration LA that occurs during the turn.

The first maximum control amount X1max of the first actuator 3A1 at each sample time k can be calculated, for example, based on 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 way is compared with the required control amount X shown 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 rate V1max and upper-limiting it by the maximum value F1max.

In the example shown in FIG. 5, the required control amount X remains constant over time and then decreases toward zero. To achieve the required 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 decreasing the first control amount X1 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 required control amount X is increasing.

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

<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 equal to 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.

Specifically, as illustrated in FIG. 5, when the required control amount X increases over time, the required control amount X is greater than the first maximum control amount X1max, and the above difference ΔX1 is positive. Also, as illustrated in the same 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 in control amount.

Furthermore, the "insufficient control amount" determined in step S104 also occurs when the difference ΔX1 is negative, as in the hatched area in FIG. 5. This hatched area occurs because, for example, the slope of the required control amount X (solid line) as it decreases in response to a sudden steering wheel return action by the driver of vehicle 1 becomes greater 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 greater than the required control amount X. In other words, the difference ΔX1 becomes negative.

<Step S106>
If the determination result in step S104 is No (i.e., if 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 will be 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 corresponding to the requested control amount X.

<Step S108>
On the other hand, if the determination result 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 determination result is Yes.

In step S108, the ECU 10 calculates the second control amount X2, which is the 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."

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 for this 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 that it decreases by the negative difference ΔX1.

<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 corresponding to the commanded first maximum control amount X1max. Also, the second actuator 3A2 is controlled to generate a control force Fc2 corresponding to the commanded second control amount X2.

In addition, in the example shown in FIG. 5, if the slope of the requested 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 (dash line), then during the period in which the requested control amount X is greater than the first maximum control amount X1max, the second control amount X2 is reduced to zero over time from the sample time (k=m), and it is then possible to satisfy the requested control amount X with only the first control amount X1.

3. Effects In order to control the attitude of a vehicle, a large force is required. 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 for the road surface input (ride comfort control), 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 the responsiveness 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 the responsiveness of the ride comfort control for a sudden road surface change.

In contrast, according to the present embodiment, the required control amount X, which is a combination of multiple required control amounts Xr, Xp, and Xpv for the first attitude control and the second attitude control, is distributed to the two actuators 3A1 and 3A2 of the suspension 3, which is an active suspension. In this way, 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, if the first maximum control amount X1max that the first actuator 3A1 can output is insufficient for the control amount of 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.

This allows the first actuator 3A1, which has high output, to be used as the main actuator for vehicle attitude control (i.e., first attitude control and second attitude control), while the control amount for achieving the required control amount X can be supplemented, as necessary, by the second actuator 3A2, which has high responsiveness. This makes it possible to perform vehicle attitude control while achieving both responsiveness and output.

In addition, by using the second actuator 3A2, which has high responsiveness, 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. In addition, 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 needed. 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 achieving 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 with a large rate of change and/or absolute amount is improved. In addition, the performance of the second attitude control (ride comfort control) for 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), it is possible to reduce energy consumption by the actuator and heat generation by the actuator because the feedback control amount is reduced.

4. Supplementary explanation of vehicle attitude control The following supplementary explanation is given regarding the implementation of the "vehicle attitude control" according to the present disclosure.

4-1. Specific Example of Vehicle Attitude Control Instead of the example described with reference to Fig. 4, only one of the first attitude control for vehicle operation input and the second attitude control for 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 road surface input such as preview control may be executed.

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'".

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 opposite-phase control forces Fc1 (moments) for the left and right front wheels 2FL and 2FR, or for the left and right rear wheels 2RL and 2RR.

The first actuator 3A1' can be used in combination with the second actuator 3A2 (e.g., a linear motor) for roll control as follows:

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. As an example, this roll required control amount Xrt is the required value of the roll moment at the center of gravity of the vehicle, and is expressed as the product of the lateral acceleration LA and a predetermined control gain.

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, according to a predetermined calculation formula.

Then, 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. The ECU 10 then determines whether the calculated first maximum control amount X1max alone is sufficient to provide a control amount that is insufficient relative to the roll required control amount Xrtf. If the control amount is not insufficient, the ECU 10 commands the first actuator 3A1' to provide the first control amount X1 that is equal to the roll required control amount Xrtf. On the other hand, if the control amount is insufficient, the ECU 10 commands the first actuator 3A1' to provide the first maximum control amount X1, and commands the insufficient amount (=Xrtf-X1max) to the second actuator 3A2 of the left and right front wheels 2FL and 2FR. The ECU 10 also performs similar processing for the left and right rear wheels 2RL and 2RR.

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 a second attitude control (e.g., preview control).

4-3. Specific examples of controlled wheels (wheels that are subject to suspension stroke control) As shown in the examples in Figures 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.

The wheels controlled by the "first actuator" may be different from the wheels controlled by the "second actuator". For example, the wheels controlled by the "first actuator" (first controlled wheels) may be the left and right rear wheels, and the wheels controlled by the "second actuator" (second controlled wheels) may be the left and right front wheels. Conversely, the wheels controlled by the "first actuator" (first controlled wheels) may be the left and right front wheels, and the wheels controlled by the "second actuator" (second controlled wheels) may be the left and right rear wheels.

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 and right front wheels and the left and right rear wheels, and a "second actuator" is applied to the other, the responsiveness of the actuators differs between the front and rear of the vehicle.

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

Next, the ECU 10 calculates the first maximum control amount X1max of the first actuator. In this case, examples of the first actuator include the 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 to both the left and right front wheels (or the left and right rear wheels).

Next, the ECU 10 determines whether the calculated first maximum control amount X1max alone is insufficient for the total roll required control amount Xrt. If the result shows that there is no shortage of control amount, the ECU 10 commands the first actuator to provide the first control amount X1, which is equal to the roll required control amount Xrt. On the other hand, if there is a shortage of control amount, the ECU 10 commands the first actuator to provide the first maximum control amount X1, and commands the shortage (=Xrt-X1max) to the second actuator (e.g., the second actuator 3A2).

In addition, if 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.

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 being executed, the ECU 10 follows the principles already explained and uses the first actuator with high output as the main actuator, and if there is a shortage in the control amount, it can make up for the shortage by using the second actuator with high response.

In addition, in an example of preview control, which is an example of 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 as possible, which is necessary for the first actuator with higher output to satisfy the required control amount Xpv, 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 shortage of the second control amount X2, 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.

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 is equivalent to feedforward control. Therefore, ECU 10 may instruct the second actuator to realize the required control amount of the feedback control with the second actuator, which has high responsiveness, and may instruct the first and second actuators to realize the required control amount Xpv of the preview control using a method that follows the above-mentioned principle.

1 Vehicle 2 Wheel 3 Suspension 3A1 First actuator (high output and low response)
3A2 Second actuator (high response and low output)
5 sprung structure 10 electronic control unit (ECU)
12 Sensors 14 Communication devices

Claims (7)

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: the vehicle attitude control includes both the first attitude control and the second attitude control,
2. The vehicle suspension control device according to claim 1 , wherein in the calculation process, the electronic control unit calculates the required control amount as a sum of the first required control amount and the second required control amount. the first attitude control includes roll control of the vehicle;
3. The vehicle suspension control device according to claim 1 , wherein the first required control amount includes a roll required control amount for the roll control. 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,
4. The vehicle suspension control device according to claim 3 , wherein in the calculation process, the electronic control unit calculates a total required roll control amount for all wheels of the vehicle as the required control amount. the first attitude control includes pitch control of the vehicle;
5. The vehicle suspension control device according to claim 1 , wherein the first required control amount includes a pitch required control amount for the pitch control. the second attitude control includes vibration control that reduces vibration of a sprung structure of the vehicle due to the road surface input,
6. The vehicle suspension control device according to claim 1 , wherein the second required control amount includes a required control amount for vibration control. A vehicle suspension control device as described in any one of claims 1 to 6, characterized in that in the command processing, if 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 all of the required control amount, and does not issue a command regarding the required control amount to the second actuator .

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