Vehicle suspension control system

Abstract

This technology provides simultaneous roll control through turning and pitch control through acceleration and deceleration. [Solution] The suspension control system 20 comprises an actuator that controls the suspension stroke of the wheel to be controlled, and an electronic control unit. The electronic control unit has a requested control amount calculation unit 24 that calculates a requested control amount for pitch control. In the process of calculating the requested control amount, the pitch gain used to calculate the requested control amount during acceleration is set to be smaller than the pitch gain used to calculate the requested control amount during deceleration.

Description

[Technical Field]

[0001] The present invention relates to a vehicle suspension control system including an actuator that controls suspension stroke. [Background Art]

[0002] Patent Document 1 discloses a vehicle suspension control apparatus including an actuator that controls suspension stroke of a controlled wheel, and an electronic control unit. The electronic control unit performs a first calculation process of calculating a first required control amount for riding comfort control against road surface input, and a second calculation process of calculating a second required control amount for attitude control responsive to vehicle operation input. When the sum of the first required control amount and the second required control amount exceeds a control amount range that can be output by the actuator, the electronic control unit executes arbitration processing that limits the second required control amount to a smaller value based on road surface input information. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2023-49946 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] A vehicle having an actuator that controls suspension stroke is provided with a function of actively controlling roll and / or pitch of the vehicle using the actuator to execute attitude control responsive to vehicle operation input. In such attitude control, increasing the control gain used for calculating the required control amount for the attitude control can enhance the effect of the attitude control and improve vehicle comfort.

[0005] On the other hand, actuator output has an upper limit, and if the requested control amount is excessive, it may exceed the actuator's capacity, leading to a state where active control is impossible and comfort may decrease. In particular, when turning and acceleration / deceleration coincide due to vehicle operation input, the roll control due to turning and the pitch control due to acceleration / deceleration are executed simultaneously, increasing the likelihood of the requested control amount becoming excessive. Therefore, the present invention aims to provide a method for controlling the suspension stroke in a way that maintains comfort even when roll control due to turning and pitch control due to acceleration / deceleration are executed simultaneously. Furthermore, the present invention also aims to provide a method for suitably controlling the suspension stroke in a way that does not decrease comfort even when pitch control is executed while roll control is not executed. [Means for solving the problem]

[0006] One aspect of the present invention is a vehicle suspension control system comprising an actuator for controlling the suspension stroke of a controlled wheel and an electronic control unit, wherein the electronic control unit includes a request control amount calculation unit for calculating a pitch request control amount for pitch control. In the process of calculating the pitch request control amount, the pitch gain used to calculate the pitch request control amount during acceleration is set to be smaller than the pitch gain used to calculate the pitch request control amount during deceleration. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram schematically shows the configuration of a vehicle according to the embodiment. [Figure 2] This is a schematic diagram showing the configuration of the suspension. [Figure 3] This diagram shows the functional blocks of a vehicle suspension control system. [Figure 4] This figure shows an example of a flowchart for performing attitude control in response to vehicle operation inputs. [Figure 5] This figure shows another example of a flowchart for performing attitude control in response to vehicle operation inputs. [Figure 6] (a) and (b) are diagrams illustrating examples of the relationship between roll gain and pitch gain. [Modes for carrying out the invention]

[0008] Figure 1 schematically shows the configuration of vehicle 1 according to an embodiment. Vehicle 1 comprises a plurality of wheels and a plurality of suspensions that suspend the plurality of wheels from the vehicle body 6. The plurality of wheels include the left front wheel 2FL, the right front wheel 2FR, the left rear wheel 2RL, and the right rear wheel 2RR, and the plurality of suspensions include suspension 3FL that suspends the left front wheel 2FL, suspension 3FR that suspends the right front wheel 2FR, suspension 3RL that suspends the left rear wheel 2RL, and suspension 3RR that suspends the right rear wheel 2RR. Unless otherwise specified below, each wheel will be referred to as wheel 2 and each suspension as suspension 3.

[0009] Figure 2 schematically shows the configuration of the suspension 3. The suspension 3 is installed to connect the unsprung structure 4, which includes the wheels 2, and the sprung structure 5, which includes the vehicle body 6. The suspension 3 includes a spring 3S, a damper (shock absorber) 3D, and an actuator 3A. The spring 3S, damper 3D, and actuator 3A are installed in parallel between the unsprung structure 4 and the sprung structure 5. The spring constant of the spring 3S is K, and the damping coefficient of the damper 3D is C. The suspension 3 also includes a bump rubber (bump stopper) 3B installed concentrically with the damper 3D.

[0010] 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. Actuator 3A may be an electrically operated or hydraulic active actuator (a so-called fully active suspension actuator), but it may also be an actuator that varies the damping force generated by the damper 3D, or an actuator for an active stabilizer device.

[0011] Vehicle 1 may be a steer-by-wire vehicle. The steering system of Vehicle 1 comprises a steering wheel 7 and steering actuators 8F and 8R (hereinafter referred to as "steering actuator 8" unless otherwise specified). The steering actuator 8F steers the front wheels (left and right front wheels 2FL and 2FR), and the steering actuator 8R steers the rear wheels (left and right rear wheels 2RL and 2RR). The steering actuators 8 are mechanically separated from the steering wheel 7 and are controlled by an ECU 10, which will be described later. The steering system of Vehicle 1 allows for independent steering of the front and rear wheels. The steering actuators 8 may be provided on only one of the wheels, either the front or the rear.

[0012] Vehicle 1 may be a vehicle that uses only an internal combustion engine as its driving force source, or it may be an electric vehicle that uses an electric motor as its driving force source. Examples of electric vehicles include battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or fuel cell electric vehicles (FCEVs). Vehicle 1 may be a vehicle driven by a driver, or it may be an autonomous vehicle.

[0013] Vehicle 1 is equipped with an electronic control unit (ECU) 10 having a processor, a memory device, and an input / output interface. The input / output interface receives sensor signals from sensors 12 provided on Vehicle 1 and outputs control signals to the actuator 3A of the suspension 3. The memory device stores various control programs for controlling the actuator 3A of the suspension 3. The processor reads and executes the control programs from the memory device, thereby realizing active suspension control using the actuator 3A. Vehicle 1 is equipped with a communication device 14, and the ECU 10 communicates with the outside of Vehicle 1 via the communication device 14.

[0014] The sensors 12 may include acceleration sensors for detecting lateral acceleration LA and longitudinal acceleration FA acting on the vehicle 1, respectively; a sprung mass acceleration sensor for detecting vertical acceleration of the sprung mass structure 5; a suspension stroke sensor; and wheel speed sensors provided on each wheel 2. The sensors 12 may also include a steering angle sensor, a turning angle sensor, a yaw rate sensor, a roll rate sensor, etc., and may include an accelerator position sensor and a brake position sensor for detecting the amount of depression of the accelerator pedal and brake pedal, respectively. Furthermore, the sensors 12 may include a position sensor for detecting the position and orientation of the vehicle 1, and this position sensor may include, for example, a GNSS (Global Navigation Satellite System) receiver.

[0015] The ECU 10 in this embodiment has a function to perform attitude control in response to vehicle operation input. Attitude control in this embodiment includes roll control during turning associated with steering of the vehicle 1 and pitch control associated with acceleration and deceleration of the vehicle 1. In this embodiment, the case in which roll control and pitch control are performed simultaneously will be described.

[0016] In this embodiment, roll control generates a reverse roll moment by applying a control force Fc to counteract the roll generated during turning associated with steering the vehicle 1, thereby controlling the suspension stroke ST. Here, "counteracting the roll" means suppressing the generated roll or generating a roll in the opposite direction to the generated roll, compared to the case where no roll control is performed.

[0017] In this embodiment, pitch control involves applying a control force Fc to counteract the pitch generated during acceleration and deceleration of the vehicle 1, thereby controlling the suspension stroke ST and generating a reverse pitch moment. Here, "counteracting the pitch" means suppressing the generated pitch or generating a pitch in the opposite direction to the generated pitch, compared to the case where pitch control is not performed.

[0018] Furthermore, for each wheel 2, the control force Fc, which is the force generated by the suspension, is defined as positive when it acts to lift the sprung structure 5 upward. Accordingly, each required control amount for suspension control (the roll required control amount Xr and the pitch required control amount Xp) also becomes positive when it acts to lift the sprung structure 5 upward. Therefore, the roll required control amount Xr is positive for the wheels 2 on the outer side of a turn, and negative for the wheels 2 on the inner side of the turn. Similarly, during acceleration, the pitch required control amount Xp is negative for the left and right front wheels 2FL and 2FR, and positive for the left and right rear wheels 2RL and 2RR; conversely, during deceleration, the pitch required control amount Xp is positive for the front wheels 2FL and 2FR, and negative for the rear wheels 2RL and 2RR.

[0019] Figure 3 shows functional blocks of a vehicle suspension control system mounted on a vehicle. The suspension control system 20 includes an actuator 3A that controls the suspension stroke of a controlled wheel, and an ECU 10, and executes attitude control in response to vehicle operation inputs. The suspension control system 20 includes a state quantity acquisition unit 22, a required control amount calculation unit 24, a control amount adjustment unit 30, and a control unit 32. The required control amount calculation unit 24 includes a first calculation unit 26 that calculates a roll required control amount for roll control during turning accompanying steering of the vehicle 1, and a second calculation unit 28 that calculates a pitch required control amount for pitch control accompanying acceleration / deceleration of the vehicle 1. The functional blocks shown in Figure 3 are implemented by the ECU 10.

[0020] Figure 4 shows an example of a flowchart for executing attitude control in response to vehicle operation inputs. The state quantity acquisition unit 22 acquires the state quantity of the vehicle 1 based on sensor signals (measured values) provided from various sensors included in the sensors 12 (S10). In the embodiment, the state quantity acquisition unit 22 acquires the state quantity of the vehicle 1 necessary for performing attitude control in response to vehicle operation inputs. Specifically, the state quantity acquisition unit 22 may acquire lateral acceleration LA measured by a lateral acceleration sensor and longitudinal acceleration FA measured by a longitudinal acceleration sensor at a predetermined cycle.

[0021] The first calculation unit 26 calculates a required roll control amount Xr for roll control (S12). The required roll control amount Xr corresponds to a required value of the control force Fc required for roll control, and the required roll control amount Xr is calculated for each wheel 2 on which the actuator 3A is disposed. The first calculation unit 26 may calculate the required roll control amount Xr using, for example, the following formula (1). Xr=LA×Gr ···(1) As shown in formula (1), the required roll control amount Xr is calculated as the product of the lateral acceleration LA and the roll gain Gr, which is a control gain.

[0022] According to the required roll control amount Xr calculated by formula (1), as the absolute value of the lateral acceleration LA increases, the absolute value of the required roll control amount Xr also increases. The roll gain Gr may be a predetermined fixed value. As described above, the lateral acceleration LA may be acquired as a measurement value from a lateral acceleration sensor, or may be estimated and acquired based on information such as vehicle speed and steering angle, for example.

[0023] The second calculation unit 28 calculates a required pitch control amount Xp for pitch control (S14). The required pitch control amount Xp corresponds to a required value of the control force Fc required for pitch control, and the required pitch control amount Xp is calculated for each wheel 2 on which the actuator 3A is disposed. The second calculation unit 28 may calculate the required pitch control amount Xp using, for example, the following formula (2). Xp=FA×Gp ···(2) As shown in formula (2), the required pitch control amount Xp is calculated as the product of the longitudinal acceleration FA and the pitch gain Gp, which is a control gain.

[0024] According to the pitch request control amount Xp calculated by equation (2), the absolute value of the pitch request control amount Xp increases as the absolute value of the longitudinal acceleration FA increases. The pitch gain Gp may be a predetermined fixed value. The longitudinal acceleration FA may be obtained as a measured value from the longitudinal acceleration sensor as described above, but it may also be estimated and obtained based on, for example, vehicle longitudinal force request information (e.g., requested engine torque or requested braking force). It is preferable that the pitch gain Gpa used to calculate the pitch request control amount Xp during acceleration is set to be smaller than the pitch gain Gpd used to calculate the pitch request control amount Xp during deceleration.

[0025] Comparing vehicle behavior during deceleration and acceleration, greater jerks and G-forces occur during deceleration. Therefore, the pitch gain Gpa used to calculate the pitch request control amount Xp during acceleration may be set smaller than the pitch gain Gpd used to calculate the pitch request control amount Xp during deceleration. For example, if the pitch gain Gpd during deceleration is set to 1, the pitch gain Gpa during acceleration may be set to 0.5.

[0026] In this embodiment, the suspension control system 20 performs roll control and pitch control simultaneously. Therefore, by setting a small pitch gain Gpa during acceleration, even when the roll control amount Xr is large during acceleration, the possibility of generating the control force Fc necessary for attitude control within the capabilities of the actuator 3A is increased. Furthermore, even if roll control is not performed and only pitch control is executed, since larger jerks and Gs are generated during deceleration, it becomes possible to set the pitch gain Gpa during acceleration to be smaller than the pitch gain Gpd during deceleration.

[0027] The control unit 32 executes a process for each wheel 2 instructing the actuator 3A to generate a requested control amount X which is the sum of the requested control amount Xr and the requested control amount Xp, and drives each actuator 3A (S16). Therefore, each actuator 3A is controlled to generate a control force Fc corresponding to the commanded requested control amount X.

[0028] This section examines the relationship between the roll gain Gr used to calculate the roll control amount Xr and the pitch gain Gp used to calculate the pitch control amount Xp. Since the tread is typically smaller than the wheelbase, when the same control force Fc (suspension stroke) is generated, roll control can create a larger vehicle attitude angle than pitch control, resulting in a greater reduction in perceived G relative to the actual G. In other words, increasing the roll control amount Xr in the overall control amount X reduces the total perceived G. Therefore, it is preferable for the first calculation unit 26 to calculate the roll control amount Xr using a roll gain Gr that is larger than the pitch gain Gp used by the second calculation unit 28 to calculate the pitch control amount Xp. For example, if the pitch gain Gp is ​​1, the roll gain Gr may be set to 1.5. In this way, by setting the roll gain Gr to be larger than the pitch gain Gp, it becomes possible to effectively reduce the total perceived G.

[0029] Figure 5 shows another example of a flowchart for performing attitude control in response to vehicle operation input. The state quantity acquisition unit 22 acquires state quantities of the vehicle 1 based on sensor signals (measured values) provided by various sensors included in the sensors 12 (S20). In this embodiment, the state quantity acquisition unit 22 may acquire lateral acceleration LA and longitudinal acceleration FA at predetermined intervals as state quantities of the vehicle 1 necessary for performing attitude control in response to vehicle operation input.

[0030] The first calculation unit 26 calculates the roll request control amount Xr for roll control using equation (1) (S22), and the second calculation unit 28 calculates the pitch request control amount Xp for pitch control using equation (2) (S24). The control amount adjustment unit 30 determines whether or not adjustment is necessary for the total request control amount X, which is the sum of the roll request control amount Xr and the pitch request control amount Xp (S26).

[0031] Specifically, the control amount adjustment unit 30 determines whether the total requested control amount X for the actuator 3A is close to a predetermined upper limit or exceeds a predetermined upper limit. Being close to a predetermined upper limit means that the requested control amount X is Y% or more of the predetermined upper limit, where Y may be between 90 and 100.

[0032] Furthermore, the predetermined upper limit may be a capability limit value determined by the capability (specifications) of the actuator 3A, or an upper limit value set in attitude control. If, in addition to attitude control in response to vehicle operation input in the embodiment, attitude control (ride comfort control) in response to road surface input is also performed, for example, the total required control amount X for the actuator 3A may be calculated as the sum of the required control amounts for all attitude control.

[0033] If no adjustment of the requested control amount X is required, that is, if the requested control amount X is less than Y% of a predetermined upper limit (N in S26), the control unit 32 executes a process for each wheel 2 to command the actuator 3A to a requested control amount X that is the sum of the roll requested control amount Xr and the pitch requested control amount Xp, and drives each actuator 3A (S30). Therefore, each actuator 3A is controlled to generate a control force Fc corresponding to the commanded requested control amount X.

[0034] On the other hand, if adjustment of the requested control amount X is necessary, that is, if the requested control amount X is greater than or equal to Y% of a predetermined upper limit (Y in S26), the control amount adjustment unit 30 adjusts the requested control amount X to reduce it (S28). As described above, the larger the roll requested control amount Xr is in the overall requested control amount X, the greater the reduction in the total perceived G. Therefore, the control amount adjustment unit 30 adjusts the requested control amount X by limiting the pitch requested control amount Xp to a small value without changing the roll requested control amount Xr. Specifically, the control amount adjustment unit 30 may limit the pitch requested control amount Xp to a small value by setting the pitch gain Gp used to calculate the pitch requested control amount Xp to a small value.

[0035] If adjustment of the requested control amount X is necessary, the control amount adjustment unit 30 may set the pitch gain Gp smaller as the roll requested control amount Xr increases. Figure 6(a) shows an example of the relationship between roll gain Gr and pitch gain Gp. The horizontal axis represents lateral acceleration. In the example shown in Figure 6(a), regardless of the magnitude of the lateral acceleration, Gr>GPa>Gpd The magnitudes of each control gain are set such that the acceleration pitch gain GPa and deceleration pitch gain Gpd decrease as the roll request control amount Xr, which is proportional to the lateral acceleration, increases.

[0036] Figure 6(b) shows another example of the relationship between roll gain Gr and pitch gain Gp. The horizontal axis represents lateral acceleration. In the example shown in Figure 6(b), when the roll demand control amount Xr, which is proportional to the lateral acceleration, is small, the magnitudes of each control gain are set to be the same. As the roll demand control amount Xr increases, both the acceleration pitch gain GPa and the deceleration pitch gain Gpd are set to decrease, but the acceleration pitch gain GPa may be reduced by a greater degree than the deceleration pitch gain Gpd.

[0037] The present invention has been described above based on embodiments. The embodiments are merely illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of each component and each processing process, and that such modifications also fall within the scope of the present invention. [Explanation of Symbols]

[0038] 1...Vehicle, 2...Wheels, 3...Suspension, 3A...Actuator, 3S...Spring, 3D...Damper, 3B...Bump rubber, 4...Unsprung structure, 5...Sprung structure, 6...Vehicle body, 7...Steering wheel, 8...Steering actuator, 10...ECU, 12...Sensors, 14...Communication device, 20...Suspension control system, 22...State quantity acquisition unit, 24...Requested control quantity calculation unit, 26...First calculation unit, 28...Second calculation unit, 30...Control quantity adjustment unit, 32...Control unit.

Claims

1. An actuator that controls the suspension stroke of the wheel to be controlled, A vehicle suspension control system comprising an electronic control unit, The aforementioned electronic control unit is It includes a request control amount calculation unit that calculates the pitch request control amount for pitch control, The pitch gain used to calculate the pitch request control amount during acceleration is set to be smaller than the pitch gain used to calculate the pitch request control amount during deceleration. A vehicle suspension control system characterized by the following features.

2. The requested control amount calculation unit is: A first calculation unit that calculates the roll request control amount for roll control, It has a second calculation unit that calculates a pitch request control amount for pitch control, The first calculation unit calculates the roll request control amount using a roll gain that is larger than the pitch gain used by the second calculation unit to calculate the pitch request control amount. The vehicle suspension control system according to feature 1.

3. The system further includes a control amount adjustment unit that limits the pitch request control amount to a smaller value if the total requested control amount for the actuator is close to or exceeds a predetermined upper limit. The vehicle suspension control system according to feature 2.

4. The control amount adjustment unit limits the pitch request control amount to a small value by setting a small pitch gain used in calculating the pitch request control amount. The vehicle suspension control system according to feature 3.

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