vehicle

Abstract

To suppress deviation of a vehicle resulting from at least one of stroke of a suspension and roll of a vehicle body.SOLUTION: A vehicle comprises a suspension which suspends wheels from a vehicle body, an actuator, and an electronic control unit. The actuator causes change on at least one of lateral force acting on the wheels and yaw moment acting on the vehicle body. The electronic control unit executes acquisition processing which acquires at least one of stroke information concerning stroke of the suspension and roll information concerning roll of the vehicle body. And then, the electronic control unit executes control processing which commands a demand control amount requested to reduce at least one of the lateral force and the yaw moment caused to result from at least one of the stroke and the roll, to the actuator.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to vehicles. [Background technology]

[0002] Patent Document 1 discloses a control device for a vehicle equipped with an active suspension device and a rear wheel steering device. The rear wheel steering device steers the rear wheels based on a predetermined steering ratio characteristic. The control device corrects the steering ratio characteristic so as to suppress changes in the steering characteristics when the target roll angle is changed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 02-185815 Summary of the Invention [Problem to be solved by the invention]

[0004] When the suspension strokes or the vehicle body rolls, a lateral force caused by at least one of the stroke and roll acts on the vehicle body. When such a lateral force acts on the vehicle body, the vehicle body is moved in at least one of the lateral direction and the yaw direction, so that vibration in at least one of the lateral direction and the yaw direction may occur in the vehicle body.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to suppress deflection of a vehicle caused by at least one of a suspension stroke and a vehicle body roll. [Means for solving the problem]

[0006] A vehicle according to the present disclosure includes a suspension that suspends wheels from a vehicle body, an actuator, and an electronic control unit. The actuator changes at least one of a lateral force acting on the wheels and a yaw moment acting on the vehicle body. The electronic control unit executes an acquisition process to acquire at least one of stroke information related to a stroke of the suspension and roll information related to a roll of the vehicle body. The electronic control unit then executes a control process to command the actuator a required control amount required to reduce at least one of the lateral force and the yaw moment caused by at least one of the stroke and the roll.

[0007] In the acquisition process, the electronic control unit may read ahead and acquire stroke information based on road surface displacement-related information relating to displacement of the road surface ahead of the vehicle's direction of travel, and in the control process, calculate a feedforward control amount based on the read-ahead acquired stroke information as a required control amount.

[0008] The actuator may include a steering actuator that controls a steering angle of at least one of front and rear wheels included in the wheels. In the control process, the electronic control unit may calculate a steering angle required to reduce at least one of the lateral force and the yaw moment as a required control amount, and command the calculated required control amount to the steering actuator.

[0009] In the control process, the electronic control unit may calculate, as a required control amount, a control amount required to reduce at least one of the lateral force and the yaw moment caused by the lateral movement of the ground contact point of the wheel due to the suspension stroke.

[0010] In the control process, the electronic control unit may calculate, as a required control amount, a control amount required to reduce at least one of the lateral force and the yaw moment caused by the lateral movement of the ground contact point of the wheel as the vehicle body rolls.

[0011] In the control process, the electronic control unit may calculate, as a required control amount, a control amount required to reduce at least one of a lateral force and a yaw moment caused by roll steer.

[0012] In the control process, the electronic control unit may calculate, as a required control amount, a control amount required to reduce at least one of the lateral force and the yaw moment caused by the roll camber. Effect of the Invention

[0013] According to the vehicle of the present disclosure, at least one of the lateral force and the yaw moment caused by at least one of the suspension stroke and the roll of the vehicle body is reduced by controlling the actuator, thereby making it possible to suppress deflection of the vehicle caused by at least one of the stroke and the roll. [Brief description of the drawings]

[0014] [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 steering control according to the embodiment. [Diagram 5] 11 is a diagram for explaining a method of calculating a lateral force Fy1 associated with a suspension stroke ST. FIG. [Figure 6] FIG. 11 is a diagram for explaining a method of calculating a lateral force Fy2 caused by a roll. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, when the number, quantity, amount, range, etc. of each element is mentioned in the following embodiments, the technical idea of ​​the present disclosure is not limited to the mentioned number unless otherwise specified or clearly specified in principle.

[0016] 1. 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 includes wheels 2 and suspensions 3 that suspend the wheels 2 from a vehicle body 6. 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.

[0017] FIG. 2 is a conceptual diagram showing an example of the configuration 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 sprung structure 5 includes a vehicle body 6. The suspension 3 includes a spring 3S, a damper (shock absorber) 3D, and a suspension actuator (also simply referred to as an "actuator") 3A. The spring 3S, the damper 3D, and the actuator 3A are provided in parallel between the unsprung structure 4 and the sprung structure 5. The spring 3S has a spring constant K. The damper 3D has a damping coefficient C.

[0018] The actuator 3A controls the stroke ST of the suspension 3 by applying a vertical control force Fc between the unsprung structure 4 and the sprung structure 5. The actuator 3A is, for example, an electric or hydraulic active actuator (an actuator constituting a so-called fully active suspension). Alternatively, the actuator 3A may be, for example, an actuator that varies the damping force generated by the damper 3D, or an actuator of an active stabilizer device.

[0019] Also, as an example, vehicle 1 is a steer-by-wire vehicle. As shown in Fig. 1, the steering device of vehicle 1 includes a steering wheel 7 and steering actuators 8F and 8R. The steering actuator 8F steers front wheels 2F (left and right front wheels 2FL and 2FR). The steering actuator 8R steers rear wheels 2R (left and right rear wheels 2RL and 2RR).

[0020] More specifically, the steering actuator 8F is, for example, an electric type. The front wheels 2F and the steering actuator 8F are mechanically separated from the steering wheel 7. The operation of the steering actuator 8F is controlled by an ECU 10, which will be described later, thereby steering the front wheels 2F.

[0021] Similarly, the steering actuator 8R is, for example, an electric type. The rear wheels 2R and the steering actuator 8R are mechanically separated from the steering wheel 7. The operation of the steering actuator 8R is controlled by the ECU 10, whereby the rear wheels 2R are steered.

[0022] According to the steering device configured as described above, the front wheels 2F and the rear wheels 2R can be steered independently. Therefore, it is possible to steer only the front wheels 2F without steering the rear wheels 2R, and it is also possible to steer only the rear wheels 2R without steering the front wheels 2F. It is also possible to steer the front wheels 2F and the rear wheels 2R simultaneously.

[0023] The vehicle 1 also includes a drive device and a brake device, both of which are omitted from the drawings. The drive device is a power source that generates a drive force. Examples of the drive device include an engine and an electric motor. The brake device generates a braking force.

[0024] 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 actuator 3A and the steering actuators 8F and 8R. The storage device stores various control programs for controlling the actuator 3A and the steering actuators 8F and 8R. The processor reads out and executes the control programs from the storage device. This realizes suspension control using the suspension actuator 3A. Also, steering control using the steering actuators 8F and 8R is realized.

[0025] The sensors 12 include, for example, a lateral acceleration sensor, 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, a steering angle sensor, a turning angle sensor, a yaw rate sensor, a roll rate sensor, and the like. The steering angle sensor detects the steering angle θ of the steering wheel 7. The turning angle sensor detects the turning angle δf of the front wheels 2F and the turning angle δr of the rear wheels 2R. The sensors 12 also 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.

[0026] 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.

[0027] 2.Vehicle Control The control of the vehicle 1 by the ECU 10 includes the following suspension control and steering control.

[0028] 2-1.Suspension control In this embodiment, the suspension control includes, for example, ride comfort control against road surface input. The ride comfort control here is executed to reduce vibration (more specifically, vertical vibration) of the sprung structure 5 against the road surface input.

[0029] The ride comfort control is, for example, a preview control based on road surface displacement related information ahead of the vehicle. FIG. 3 is a conceptual diagram for explaining the preview control. The road surface displacement related information ahead of the vehicle can be acquired as a road surface data map from a management server on the cloud via the communication device 14 by the vehicle 1. This road surface data map is a map in which road surface displacement related values ​​related to the vertical displacement Zr (see FIG. 2) of the road surface are associated with positions. Examples of the road surface displacement related values ​​include the above-mentioned road surface displacement Zr, road surface displacement velocity Zr' which is a time differential value of the road surface displacement Zr, unsprung displacement Zu, unsprung velocity Zu', unsprung acceleration Zu'', sprung displacement Zs, sprung velocity Zs', sprung acceleration Zs'', and the like. A specific example of the road surface data map is an unsprung displacement map that uses the unsprung displacement Zu (see FIG. 2) as an example of the 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 information relating to the road surface change ahead of the vehicle may be obtained, for example, by using a preview sensor instead of using a road surface data map. The preview sensor is, for example, a camera that captures an image ahead of the vehicle.

[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. Based on the relative positional relationship and the vehicle position indicated by the position information, the position of each wheel 2 can be calculated. The position information here is acquired, for example, by using a position sensor included in the sensors 12.

[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 actuator 3A 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 actuator 3A 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.

[0033] The equation of motion for the sprung structure 5 (see FIG. 2) is expressed by the following equation (1).

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[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 is the vertical control force generated by the actuator 3A. If the vibration of the sprung structure 5 is completely cancelled out by the control force Fc (Zs''=0, Zs'=0, Zs=0), the control force Fc is expressed by the following equation (2).

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[0035] The control force Fc that provides at least the vibration damping effect is expressed by the following formula (3).

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[0036] In formula (3), control gain α1 is greater than 0 and less than or equal to 1, and control gain α2 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).

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[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 by substituting the unsprung displacement Zu at the predicted passing position Pf into formula (3) or formula (4).

[0038] The ECU 10 controls the actuator 3A so as to generate a target control force Fc_t at the timing when the wheel 2 passes through the predicted passing position Pf. The timing when the wheel 2 passes through the predicted passing position Pf can be known from the preview time tp.

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

[0040] 2-2.Steering control 2-2-1. Basic configuration example of steering control In the steering control, the ECU 10 calculates a basic steering angle δb. The basic steering angle δb corresponds to a basic value of the target steering angle δ_t. More specifically, the ECU 10 calculates a basic steering angle δbf which is a basic value of the target steering angle δf_t of the front wheels 2F, and a basic steering angle δb which is a basic value of the target steering angle δb_t of the rear wheels 2R. The specific calculation method of the basic steering angles δbf and δbr differs depending on the driving entity of the vehicle 1.

[0041] When the driving subject is a driver (human) who operates the steering wheel 7, each of the basic steering angles δbf and δbr is basically calculated based on the steering angle θ of the steering wheel 7. More specifically, each of the basic steering angles δbf and δbr is calculated so as to increase as the steering angle θ increases. Also, each of the basic steering angles δbf and δbr may be calculated based on the vehicle speed V, for example, and more specifically, may be calculated so as to decrease as the vehicle speed V increases.

[0042] The vehicle 1 may be configured to be capable of automatic driving. When the vehicle 1 is an automatic driving vehicle, the driving subject of the vehicle 1 is an automatic driving system (including the ECU 10) that controls the automatic driving of the vehicle 1. In this example, each of the basic steering angles δbf and δbr is calculated based on a target trajectory of the vehicle 1 generated by the automatic driving system.

[0043] The ECU 10 controls the steering actuator 8F based on the target steering angle δf_t to steer the front wheels 2F. Similarly, the ECU 10 controls the steering actuator 8R based on the target steering angle δr_t to steer the rear wheels 2R.

[0044] 2-2-2.Control of steering angle based on lateral force The final target steering angle δf_t is calculated by adding a correction steering angle δcf, which is calculated in consideration of the following problem, to the basic steering angle δbf. Similarly, the final target steering angle δr_t is calculated by adding a correction steering angle δcr, which is calculated in consideration of the following problem, to the basic steering angle δbr.

[0045] When the suspension strokes or the vehicle body rolls, the ground contact points of the wheels (tires) move laterally (displace in the lateral direction of the vehicle) due to the geometric characteristics of the suspension. At this time, if the vehicle moves forward or backward, a slip angle is generated in the wheels due to the forward or backward traveling speed of the vehicle (vehicle speed V) and the lateral movement speed Vy of the ground contact points of the wheels, and lateral forces (lateral forces Fy1 and Fy2 described below) are generated. The lateral forces Fy1 and Fy2 generated in the wheels act on the vehicle body. In addition, when the vehicle body rolls, lateral forces Fy3 and Fy4 caused by roll steer and roll camber, respectively, are also directly generated and act on the vehicle body. When these lateral forces Fy act on the vehicle body, the vehicle body is moved in at least one of the lateral and yaw directions, so that vibrations in at least one of the lateral and yaw directions may occur in the vehicle body. As a result, the comfort of the vehicle may decrease.

[0046] In particular, when highly controllable ride comfort control such as the above-mentioned preview control is implemented, vibrations other than those in the lateral and yaw directions are significantly reduced, so that the lateral and yaw vibrations become relatively noticeable. In addition, when the suspension stroke is actively increased by such suspension control such as ride comfort control, the suspension stroke may become larger than in the case without suspension control. As a result, the generated lateral force Fy may become larger, and the lateral and yaw vibrations may become larger.

[0047] Therefore, the process executed by the ECU 10 for the steering control in this embodiment includes the following “acquisition process” and “control process.” An example of these processes will be described with reference to the flowchart shown in FIG.

[0048] The acquisition process is, broadly speaking, a process for acquiring at least one of stroke information related to the stroke ST of the suspension 3 and roll information related to the roll of the vehicle body 6. In the example shown in Fig. 4, stroke information is acquired.

[0049] The control process is, broadly speaking, a process for commanding the actuators with a required control amount required to reduce at least one of the lateral force and the yaw moment caused by at least one of the stroke ST and the roll. In the example shown in Fig. 4, the steering actuators 8F and 8R are controlled to realize a required control amount required to reduce the lateral force Fy1 caused by the stroke of the suspension 3.

[0050] In addition, in the acquisition process in this embodiment in which preview control is executed as suspension control, ECU 10 reads ahead and acquires stroke information based on road surface displacement related information relating to the displacement of the road surface ahead in the traveling direction of vehicle 1. Then, in the control process, ECU 10 calculates a feedforward control amount based on the read-ahead acquired (in other words, predicted) stroke information as a required control amount, and commands the calculated feedforward control amount to steering actuators 8F and 8R.

[0051] Fig. 4 is a flowchart showing a process related to steering control according to the embodiment. The process of this flowchart is repeatedly executed at predetermined time steps while the vehicle 1 is traveling. In Fig. 4, the process of step S100 corresponds to an example of the above-mentioned "acquisition process", and the processes of steps S102 to S106 correspond to an example of the above-mentioned "control process".

[0052] <Step S100> In step S100, the ECU 10 acquires stroke information of the suspension 3. Specifically, as an example, the ECU 10 pre-reads and acquires the stroke information based on "road surface displacement related information" acquired in advance for the preview control.

[0053] Acquisition of stroke information based on road surface displacement related information can be performed, for example, as follows. That is, the preview control is executed so as to stroke the suspension 3 by an amount corresponding to a road surface displacement related value (e.g., unsprung displacement Zu or road surface displacement Zr) at the predicted passing position Pf. Therefore, it may be assumed that the stroke ST at the predicted passing position Pf is equivalent to the unsprung displacement Zu or road surface displacement Zr at the predicted passing position Pf. Then, the unsprung displacement Zu or road surface displacement Zr at the predicted passing position Pf may be acquired as information on the stroke ST at the predicted passing position Pf. Alternatively, the stroke ST may be estimated according to a predetermined relational expression from a road surface displacement related value such as the unsprung displacement Zu acquired in advance.

[0054] <Step S102> In step S102, the ECU 10 calculates, for each wheel 2, a lateral force Fy1 that is generated due to the lateral movement of the ground contact point of the wheel 2 accompanying the stroke of the suspension 3, based on the stroke information acquired in step S100.

[0055] FIG. 5 is a diagram for explaining a method of calculating the lateral force Fy1 associated with the stroke ST of the suspension 3. Here, the explanation is given assuming that the vehicle 1 is traveling straight at a vehicle speed V. The upward direction on the paper of FIG. 5 corresponds to the straight traveling direction of the vehicle 1. Due to the geometric characteristics of the suspension 3, when the suspension 3 of the left wheel 2 strokes in the contracting direction and the suspension 3 of the right wheel 2 strokes in the extending direction, a lateral force Fy1 is generated in the left and right wheels 2 in the vehicle leftward direction. As a result, the vehicle body 6 moves leftward.

[0056] FIG. 5 illustrates the right front wheel 2FR. When the suspension 3 of the right front wheel 2FR has an extension stroke as described above, the ground contact point of the right front wheel 2FR moves at a lateral ground contact point velocity Vy1 (=2H f / T f ×(Zu fr '-Zs frThe above-mentioned lateral movement occurs so that the vehicle moves to the right (to the right on the paper surface of FIG. 5) at the speed of 1'). Due to the occurrence of this lateral movement, a slip angle is generated in the right front wheel 2FR, the slip angle being in accordance with the value obtained by dividing the contact point lateral movement speed Vy1 by the vehicle speed V, as shown in FIG. 5. As a result, a lateral force Fy1 is generated in the vehicle leftward direction. fr In this case, the lateral force Fy1 is generated on the right front wheel 2FR. fr is expressed by the following equation (5).

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[0057] In formula (5), C pf is the conical ring power, which is a constant specific to the wheel (tire) and is calculated in advance. f is the roll center height of the front wheel 2F, which can be calculated by a known method. f is the tread of the front wheel 2F, a value calculated in advance. fr '-Zu fr The lateral force Fy1 of the left front wheel 2FL is calculated based on the stroke information acquired in step S100. fl The lateral force Fy1 of the left and right rear wheels 2RL and 2RR can be calculated in the same manner. rl and FY1 rr Regarding cornering power, roll center height and tread, the value C of rear wheel 2R pr , H r , and T r can be calculated in the same manner by replacing

[0058] In addition, the lateral force Fy1 calculated in this manner is generated purely due to the occurrence of the stroke ST, regardless of whether the vehicle body 6 is moving (for example, whether the vehicle body 6 is rolling or pitching).

[0059] <Step S104> In step S104, ECU 10 calculates the corrective steering angles δcf and δcr of the front and rear wheels 2F and 2R required to reduce the lateral force Fy1. These corrective steering angles δcf and δcr are expressed by the following equations (6) and (7), respectively. Note that the lateral force Fy1 takes a positive value when it acts in the left direction of the vehicle as shown in Fig. 5, and the corrective steering angles δcf and δcr take positive values ​​when the wheel 2 is steered to the right.

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[0060] In formula (6), Fy1 f is the total lateral force Fy1 acting on the two front wheels 2F, i.e., lateral force Fy1 fr and lateral force Fy1 fl It is the sum of l f is the distance between the front wheel axle and the center of gravity, which is a value calculated in advance. r is the yaw rate, which can be obtained, for example, by using a yaw rate sensor. In addition, the slip angle β can be calculated, for example, by using the vehicle speed V measured by a wheel speed sensor and the integrated value of a lateral acceleration sensor.

[0061] In addition, in formula (7), Fy1 r is the total lateral force Fy1 acting on the two rear wheels 2R, i.e., lateral force Fy1 rr and lateral force Fy1 rl It is the sum of C pr is the cornering power of the rear wheel 2R, and l r is the distance between the rear wheel axle and the center of gravity. pf and l r is a previously calculated value.

[0062] Then, in step S104, the ECU 10 calculates the final target steering angle δf_t by adding the corrected steering angle δcf to the basic steering angle δbf. Next, the ECU 10 calculates the required control amount (feedforward control amount) Xf_ff for the front wheels 2F by multiplying the calculated target steering angle δf_t by a predetermined control gain. In one example of the processing in step S104, the lateral force Fy1 is calculated by calculating the required control amount Xf_ff. f A required amount of control required to reduce is obtained.

[0063] Similarly, the ECU 10 calculates the final target steering angle δr_t by adding the corrected steering angle δcr to the basic steering angle δbr. Next, the ECU 10 calculates the required control amount (feedforward control amount) Xr_ff for the rear wheels 2R by multiplying the calculated target steering angle δr_t by a predetermined control gain. In one example of the process of step S104, the lateral force Fy1 is calculated by calculating the required control amount Xr_ff. r The required amount of control required to reduce is obtained.

[0064] <Step S106> In step S106, ECU 10 commands the feedforward control amount Xf_ff calculated in step S104 to the steering actuator 8F of the front wheels 2F. As a result, the front wheels 2F are steered so as to realize the target steering angle δf_t including the corrected steering angle δcf.

[0065] More specifically, road surface displacement related information for preview control (unsprung displacement Zu or road surface displacement Zr at predicted passing position Pf) is used as stroke information. Therefore, stroke information of suspension 3 at predicted passing position Pf can be predicted, so that feedforward control amount Xf_ff required to reduce lateral force Fy1 occurring at predicted passing position Pf can be calculated in advance. Therefore, ECU 10 controls steering actuator 8F so that feedforward control amount Xf_ff based on the stroke information obtained by reading ahead in this manner is realized at the timing when wheel 2 passes predicted passing position Pf.

[0066] In step S106, ECU 10 similarly commands the feedforward control amount Xr_ff calculated in step S104 to steering actuator 8R of rear wheel 2R. As a result, rear wheel 2R is steered so as to realize target steering angle δr_t including corrected steering angle δcr. More specifically, ECU 10 controls steering actuator 8F so as to realize feedforward control amount Xr_ff based on stroke information obtained by looking ahead at the timing when wheel 2 passes predicted passing position Pf.

[0067] In addition, in step S106, ECU 10 may command the following feedback control amount Xf_fb to steering actuator 8F together with the feedforward control amount Xf_ff. Specifically, in step S104, ECU 10 may also calculate a feedback control amount Xf_fb based on the difference between target steering angle δf_t and actual steering angle δaf of the front wheels 2F. The actual steering angle δaf is obtained from a steering angle sensor. Then, ECU 10 may calculate the sum of the two control amounts Xf_ff and Xf_fb as a required control amount, and command the required control amount to steering actuator 8F. Similarly, in step S104, ECU 10 may calculate a feedback control amount Xr_fb based on the difference between target steering angle δr_t and actual steering angle δar of the rear wheels 2R. The actual steering angle δar is obtained from a steering angle sensor. Then, in step S106, ECU 10 may issue a command of the sum of the two control amounts Xr_ff and Xr_fb (required control amount) to steering actuator 8R.

[0068] 2-3.Effects According to the process shown in Fig. 4 described above, the steering actuators 8F and 8R are controlled to reduce the lateral force Fy1 generated in each of the front wheels 2F and the rear wheels 2R due to the stroke of the suspension 3. For example, in an example in which the lateral force Fy1 is generated to the left of the vehicle as shown in Fig. 5, the wheels 2 are steered to the right in order to reduce the lateral force Fy1. This makes it possible to suppress lateral vibration of the vehicle body 6 caused by the stroke of the suspension 3, and to suppress deflection of the vehicle 1. In addition, in an example in which the steering control is executed while autonomous driving is being performed, the tracking ability of the autonomous driving can be improved by reducing the lateral vibration of the vehicle body 6.

[0069] Further, in a method of controlling the steering actuators 8F and 8R to reduce the lateral force Fy1 caused by the suspension 3 stroke after detecting the actual stroke of the suspension 3, a delay occurs in the steering control. In contrast, according to the process shown in FIG. 4, the feedforward control amounts Xf_ff and Xr_ff based on the stroke information obtained by looking ahead are calculated as the required control amounts, and the steering actuators 8F and 8R are controlled to realize the calculated feedforward control amounts Xf_ff and Xr_ff. This makes it possible to control the steering actuator 8F in advance so as to reduce the lateral force Fy1 generated at the road surface position (predicted passing position Pf) where the vehicle 1 will pass in the near future. This eliminates the delay in the steering control, and makes it possible to more suitably suppress the deflection of the vehicle 1.

[0070] 3. Modifications of steering control 3-1. Other examples of acquisition and control processes The stroke information acquired in the "acquisition process" according to the present disclosure is not necessarily limited to that acquired by reading ahead, and may be acquired using any method. That is, for example, the stroke ST of the suspension 3 may be directly measured using a stroke sensor, or may be estimated from the sprung acceleration using an observer. In addition, in an example of steering control that is not performed together with the preview control, the required control amount commanded to the steering actuators 8F and 8R may be only the feedback control amounts Xf_fb and Xr_fb based on the stroke information acquired without reading ahead in this way. In addition, the above-mentioned steering control may be applied to a vehicle in which suspension control that actively controls the stroke ST is not performed.

[0071] 3-2. Examples of calculations for other lateral forces to be reduced As already explained, in addition to the stroke of the suspension 3, the lateral force Fy is generated due to the pure roll of the vehicle body 6, and is also generated due to roll steer or roll camber.

[0072] 3-2-1. Lateral force Fy2 caused by roll 6A and 6B are diagrams for explaining a method of calculating the lateral force Fy2 caused by roll. More specifically, Fig. 6A is a rear view of the vehicle 1, and Fig. 6B is a plan view of the vehicle 1.

[0073] Regardless of whether the suspension 3 is in stroke or not, the vehicle body 6 rolls around the center of gravity as shown in FIG. 6(A), causing a lateral movement velocity Vy2 (=H g φ') occurs. H g is the height of the center of gravity of the vehicle, and φ' is the roll rate. With the occurrence of such lateral movement, as shown in FIG. 6(B), a slip angle is generated in each wheel 2, the slip angle being in accordance with the value obtained by dividing the contact point lateral movement speed Vy2 by the vehicle speed V. As a result, a lateral force Fy2 is generated. For example, when a roll occurs such that the right side of the vehicle sinks as shown in FIG. 6(A), a lateral movement occurs in the left direction of the vehicle, and accordingly, a lateral force Fy2 is generated in the right direction of the vehicle.

[0074] Lateral force Fy2 generated on the left and right front wheels 2FL and 2FR due to roll fl and FY2 fr is expressed by the following equation (8). Therefore, these lateral forces Fy2 fl and FY2 fr The total lateral force Fy2 on the front wheels is the sum of f In addition, the lateral force Fy2 generated on the left and right rear wheels 2RL and 2RR can be calculated. rl and FY2 rr is expressed by the following equation (9). Therefore, these lateral forces Fy2 rl and FY2 rr The total lateral force Fy2 on the rear wheels is the sum of r can also be calculated.

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[0075] Side force Fy2 on front wheel 2F and rear wheel 2R f and FY2 r The roll information used in the calculation of is, for example, the roll rate φ' and the vehicle center of gravity height H g The roll rate φ′ may be measured directly by a roll rate sensor, or may be calculated from the roll angle φ calculated as a value corresponding to the lateral acceleration obtained by a lateral acceleration sensor. g can be calculated using a known method.

[0076] 3-2-2. Lateral force Fy3 due to roll steer When the suspension 3 strokes as the vehicle body 6 rolls, roll steer occurs (i.e., the toe angle of the wheels 2 changes). As a result, a slip angle occurs in each wheel 2, and a lateral force Fy3 occurs in each wheel 2. The lateral force Fy3 generated in each wheel 2 due to such roll steer is fl , FY3 fr , FY3 rl , and FY3 rrare expressed, for example, by the following equations (10) to (13), respectively. Note that in equations (10) to (13), roll steer is expressed taking into consideration up to the second-order component.

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[0077] In formulas (10) to (13), R 1f and R 2f R corresponds to the roll steer coefficient of the front wheel 2F. 1r and R 2r and Fy3 correspond to the roll steer coefficient of the rear wheel 2R. As shown in the formulas (10) to (13), each lateral force Fy3 can be calculated based on the information of the stroke ST (=Zs-Zu). More specifically, the lateral force Fy3 fl and FY3 fr The sum of the two front wheels is the total lateral force Fy3 f The lateral force Fy3 can be calculated as rl and FY3 rr The sum of the two rear wheels is the total lateral force Fy3. r It can be calculated as:

[0078] 3-2-3. Lateral force Fy4 caused by roll camber When the suspension 3 strokes as the vehicle body 6 rolls, roll camber occurs (the camber angle γ of the wheels 2 changes). As a result, a lateral force Fy4 is generated in each wheel 2. The lateral force Fy4 generated in each of the left and right front wheels 2FL and 2FR due to such roll camber is fl and FY4 fr For example, the lateral force Fy4 is expressed by the following formula (14). fl and FY4 fr The total lateral force Fy4 on the front wheels is the sum of fSimilarly, the lateral force Fy4 generated on the left and right rear wheels 2RL and 2RR can be calculated. rl and FY4 rr is expressed by the following equation (15). Therefore, these lateral forces Fy4 rl and FY4 rr The total lateral force Fy4 on the rear wheels is the sum of r can also be calculated.

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[0079] In formulas (14) and (15), C sf and C sr are the canvas stiffnesses of the front wheel 2F and the rear wheel 2R, respectively, and are determined in advance. R cf and R cr are the roll camber cancellation rates of the front wheel 2F and the rear wheel 2R, respectively, and are calculated in advance. f and γ r can be calculated based on stroke information of the suspension 3, for example.

[0080] The steering control according to the above-described embodiment may be executed to reduce any one of the lateral forces Fy2, Fy3, and Fy4 described herein, instead of the lateral force Fy1 caused by the stroke of the suspension 3. Furthermore, the lateral force Fy to be reduced by the steering control may be the sum of any two or more of the lateral forces Fy1, Fy2, Fy3, and Fy4.

[0081] 3-3. Reduction of yaw moment Mz As described above, when the direction of the lateral force Fy generated is the same on the front wheel 2F side and the rear wheel 2R side, and the magnitude of the lateral force Fy generated differs between the front wheel 2F side and the rear wheel 2R side, a yaw moment Mz about the center of gravity of the vehicle may be generated in the vehicle body 6. In addition, depending on the road surface conditions, the direction of the lateral force Fy may differ between the front wheel 2F side and the rear wheel 2R side, and in this case, a yaw moment Mz is also generated. f The total lateral force of the rear wheels is called Fy r Then, the yaw moment Mz is expressed by the following equation (16).

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[0082] In the case of a vehicle 1 having steering actuators 8F and 8R on the front wheels 2F and the rear wheels 2R, respectively, the lateral force Fy f The steering actuator 8F is controlled so as to reduce the lateral force Fy r By controlling steering actuator 8R so as to reduce yaw moment Mz, it is possible to reduce yaw moment Mz. However, even in a vehicle 1 equipped with steering actuators 8F and 8R, correction steering angles δcf and δcr may be calculated according to a predetermined relational expression so as to obtain a required control amount necessary to reduce yaw moment Mz.

[0083] Furthermore, the "vehicle" according to the present disclosure may be equipped with, for example, only one of the steering actuators 8F and 8R. In such a vehicle, the steering actuator may be controlled so as to reduce only the lateral force Fy acting on the steered wheel, which is the wheel (front wheel 2F or rear wheel 2R) on which the steering actuator is equipped. Alternatively, the steering actuator may be controlled so as to reduce only the total lateral force Fy of the front wheel 2F and the rear wheel 2R, or only the yaw moment Mz.

[0084] 4. Actuators other than steering actuators The "actuator" according to the present disclosure is not limited to the above-mentioned steering actuators 8F and 8R, but may be, for example, an actuator A provided on at least one of the front wheels 2F and the rear wheels 2R and capable of applying a driving force difference to the left and right wheels. Specifically, the actuator A may be, for example, an electric motor (e.g., an in-wheel motor (IWM)) capable of driving the left and right wheels individually, or may be an active differential gear device. In order to control such actuator A, a required control amount may be calculated so as to generate a difference in driving force (vehicle longitudinal force) required to reduce the above-mentioned yaw moment Mz.

[0085] Furthermore, the "actuator" according to the present disclosure may be, for example, an actuator B that actively controls the suspension geometry. Specifically, the actuator B may be, for example, an actuator configured to extend and retract a suspension arm. In order to reduce at least one of the lateral force Fy and the yaw moment Mz, the actuator B may be used to, for example, directly move the wheel 2 in the lateral direction of the vehicle, change the toe angle, or change the camber angle γ.

[0086] Furthermore, the "actuator" according to the present disclosure may be, for example, an actuator C that drives an aerodynamic part mounted on a vehicle. The aerodynamic part referred to here is one that is operated by the actuator C, and thereby, for example, utilizes an air flow to apply a yaw moment to the vehicle body 6. Specifically, the aerodynamic part may be, for example, a variable flap or spoiler provided independently on the left and right sides of the rear of the vehicle. In order to reduce the yaw moment Mz, for example, the actuator C may be used to operate one of the left and right flaps (or spoilers) to change the air resistance on the left and right sides of the vehicle. [Explanation of symbols]

[0087] 1 vehicle 2 wheels 2F Front wheel 2R rear wheel 3. Suspension 4. Unsprung structure 5. Spring structure 6. Body 7. Steering Wheel 8F, 8R steering actuator 10 Electronic Control Unit (ECU) 12 Sensors

Claims

1. A suspension that suspends the wheels from the vehicle body; an actuator that changes at least one of a lateral force acting on the wheel and a yaw moment acting on the vehicle body; An electronic control unit; A vehicle comprising: The electronic control unit includes: an acquisition process for acquiring at least one of stroke information related to a stroke of the suspension and roll information related to a roll of the vehicle body; a control process for commanding the actuator a required control amount required to reduce at least one of a lateral force and a yaw moment caused by at least one of the stroke and the roll; Run The electronic control unit includes: In the acquisition process, the stroke information is acquired by reading ahead based on road surface change-related information related to changes in the road surface ahead in the traveling direction of the vehicle. In the control process, a feedforward control amount based on the stroke information obtained by reading ahead is calculated as the required control amount. A vehicle characterized by:

2. the actuator includes a steering actuator for controlling a steering angle of a steered wheel which is at least one of a front wheel and a rear wheel included in the wheels, In the control process, the electronic control unit calculates a steering angle required to reduce at least one of the lateral force and the yaw moment as the required control amount, and commands the calculated required control amount to the steering actuator.

2. The vehicle according to claim 1 .

3. In the control process, the electronic control unit calculates, as the required control amount, a control amount required to reduce at least one of a lateral force and a yaw moment caused by a lateral movement of a ground contact point of the wheel accompanying a stroke of the suspension.

3. A vehicle as claimed in claim 1 or 2.

4. In the control process, the electronic control unit calculates, as the required control amount, a control amount required to reduce at least one of a lateral force and a yaw moment caused by a lateral movement of a ground contact point of the wheel accompanying a roll of the vehicle body. A vehicle according to any one of claims 1 to 3.

5. In the control process, the electronic control unit calculates a control amount required to reduce at least one of a lateral force and a yaw moment caused by roll steer as the required control amount. A vehicle according to any one of claims 1 to 4.

6. In the control process, the electronic control unit calculates a control amount required to reduce at least one of a lateral force and a yaw moment caused by a roll camber as the required control amount. A vehicle according to any one of claims 1 to 5.

7. A suspension that suspends the wheels from the vehicle body; an actuator that changes at least one of a lateral force acting on the wheel and a yaw moment acting on the vehicle body; An electronic control unit; A vehicle comprising: The electronic control unit includes: an acquisition process for acquiring at least one of stroke information related to a stroke of the suspension and roll information related to a roll of the vehicle body; a control process for commanding the actuator a required control amount required to reduce at least one of a lateral force and a yaw moment caused by at least one of the stroke and the roll; Run In the control process, the electronic control unit calculates a control amount required to reduce at least one of a lateral force and a yaw moment caused by roll steer as the required control amount. A vehicle characterized by:

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