Vehicle control device and vehicle control method

Abstract

A vehicle control device controls a vehicle behavior control device capable of controlling a movement of a vehicle body in a roll direction, including: a presumption unit that presumes a lateral acceleration generated by the vehicle; and a gain calculation unit that calculates information indicating a roll control gain for driving the vehicle behavior control device to move the vehicle body in the roll direction, based on the lateral acceleration presumed by the presumption unit. The presumption unit presumes the lateral acceleration based on information indicating a last roll control gain.

Description

Technical Field

[0001] This invention relates to a technology for performing roll control of a vehicle body. Background Technology

[0002] Japanese Patent Application Publication No. 2017-105395 discloses a vehicle control device. This device comprises multiple units. First, a "lateral acceleration estimation unit" estimates the lateral acceleration acting on the vehicle based on driving state information stored in a memory, including equivalent cornering force, front wheel steering angle, rear wheel steering angle, vehicle speed, and yaw rate. Next, if the deviation between the estimated lateral acceleration and the measured lateral acceleration exceeds a threshold, a "tire characteristic change judgment unit" determines that the equivalent cornering force has changed. Then, a "tire characteristic value inference unit" estimates the actual equivalent cornering force based on the measured lateral acceleration and driving state information. Finally, a "tire characteristic value correction unit" corrects the equivalent cornering force stored in the memory based on the estimated equivalent cornering force.

[0003] The control input of the active stabilizer is calculated based on the lateral acceleration derived from the modified equivalent cornering dynamics. Summary of the Invention

[0004] In the technology disclosed in Japanese Patent Application Publication No. 2017-105395, an active stabilizer device causes the vehicle body to tilt during steering. At this time, suspension characteristics such as toe angle, camber angle, and lateral movement of the contact point change.

[0005] As a result, the estimated equivalent cornering force deviates from the actual value. Consequently, there is a possibility that the deviation between the estimated lateral acceleration derived from the estimated equivalent cornering force and the actual lateral acceleration may increase.

[0006] The purpose of this invention is to provide a technique for estimating the lateral acceleration of a vehicle with high accuracy.

[0007] To address the aforementioned issues, one aspect of the present invention is a vehicle control device for controlling a vehicle behavior control device capable of controlling the movement of the vehicle body in the lateral tilt direction, comprising:

[0008] The presumption part estimates the lateral acceleration generated by the vehicle; and

[0009] The gain calculation unit calculates information representing the roll control gain based on the lateral acceleration estimated by the estimation unit. This roll control gain is used to drive the vehicle behavior control device to move the vehicle body in the roll direction.

[0010] The estimation unit estimates the lateral acceleration based on information representing the previous roll control gain.

[0011] Another aspect of the present invention is a vehicle control method. This method is executed by a vehicle control device, which controls a vehicle behavior control device capable of controlling the movement of the vehicle body in the lateral direction, wherein the method includes:

[0012] The steps for estimating the lateral acceleration generated by the vehicle; and

[0013] The step of calculating information representing the roll control gain based on the estimated lateral acceleration, wherein the roll control gain is used to drive the vehicle behavior control device to move the vehicle body in the roll direction.

[0014] In the estimation step, the lateral acceleration is estimated based on information representing the previous roll control gain.

[0015] According to the present invention, a technique is available that can provide a high-precision estimate of the lateral acceleration of a vehicle. Attached Figure Description

[0016] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which similar reference numerals denote similar parts, and wherein:

[0017] Figure 1 This is a diagram illustrating the functional configuration of the vehicle control system in an embodiment;

[0018] Figure 2 This is a graph showing the relationship between roll control gain and equivalent cornering dynamics;

[0019] Figure 3 This is a graph showing the relationship between roll control gain and the delay time constant of lateral force;

[0020] Figure 4 It is a diagram showing the turning state of a vehicle in a two-wheeled model; and

[0021] Figure 5 This is a flowchart of a vehicle control method according to an embodiment. Detailed Implementation

[0022] Figure 1 This is a diagram illustrating the functional configuration of the vehicle control system 1 in an embodiment. Figure 1 In this document, the various elements described as functional blocks performing various processes can be configured as follows: In hardware, they can be composed of circuit blocks, memory, and other LSIs. In software, they are implemented through programs loaded into memory, etc. Therefore, those skilled in the art should understand that these functional blocks can be implemented in various forms, either solely by hardware, solely by software, or through combinations thereof, and are not limited to any one of these methods.

[0023] The vehicle control system 1 performs autonomous driving control. In autonomous driving control, the vehicle control system 1 performs follow control to follow the vehicle in front and cruise control to travel at a prescribed speed within the driving lane. The vehicle control system 1 includes a vehicle control unit 10, a driving state detection sensor 12, an object detection sensor 14, a vehicle behavior control unit 16, and a driving device 18.

[0024] The driving status detection sensor 12 detects the driving status of the vehicle. The driving status detection sensor 12 includes a vehicle speed sensor, a steering angle sensor, an acceleration sensor, a brake pressure sensor, etc., and sends the results of detecting the driving status of the vehicle to the vehicle control device 10.

[0025] The object detection sensor 14 includes an onboard camera, millimeter-wave radar, photoradar, and acoustic sensor, etc., to detect objects located around the vehicle. The object detection sensor 14 can send information indicating the positional relationship between the object and the vehicle as object-related information to the vehicle control device 10, or it can send simple sensor values ​​as object-related information to the vehicle control device 10.

[0026] The vehicle behavior control device 16 is, for example, an active stabilizer device. The active stabilizer device can be located on both the front and rear wheel sides, or only on the front wheel side. Both ends of the active stabilizer device are connected to the left and right wheels, for example, the lower arms. The active stabilizer device has a right stabilizer bar, a left stabilizer bar, and an electric actuator that rotatably connects the right and left stabilizer bars relative to each other. The roll control device 20 drives the electric actuator to rotate the right and left stabilizer bars relative to each other, thereby applying a roll force to the vehicle body.

[0027] Alternatively, the vehicle behavior control device 16 can also be an active suspension system installed on each wheel. The active suspension system can be an air suspension system, an electric or hydraulic fully active suspension system. The active suspension system, under the control of the roll control device 20, causes one or both of the left and right wheels to move vertically, thereby enabling the vehicle body to move in the roll direction. In all cases, the vehicle behavior controller 16 controls the movement of the vehicle body in the roll direction.

[0028] The driving device 18 includes: a drive unit that applies driving force to the wheels, causing the wheels to rotate and thus propelling the vehicle; a steering unit that steers the wheels; and a braking unit that applies braking force to the wheels. The drive unit may be an engine, an electric motor, or a combination thereof. The driving device 18 can be driven by the driver's operation and can also be driven by automatic driving control. Automatic driving control is executed based on the driver's instructions.

[0029] The vehicle control unit 10 includes a roll control unit 20 and a driving control unit 22. The roll controller 20 controls the vehicle behavior control unit 16 to perform roll control, causing the vehicle body to move in the roll direction. The driving control unit 22 drives the driving unit 18 to perform automatic driving control. The roll control unit 20 and the driving control unit 22 can communicate via in-vehicle communication. Furthermore, the roll control unit 20 and the driving control unit 22 are not limited to separate ECUs (electronic control units), but can also be an integrated ECU.

[0030] The roll control device 20 includes an acquisition unit 24, a gain calculation unit 26, an estimation unit 27, a drive control unit 28, and a communication unit 30. The acquisition unit 24 acquires the detection results from the driving state detection sensor 12.

[0031] The gain calculation section 26 acquires information representing the roll control gain used to drive the vehicle behavior control device 16 based on the vehicle's lateral acceleration. The information representing the roll control gain is an indicator of the magnitude of the vehicle body movement in the roll direction caused by the vehicle behavior control device 16, and also information representing the magnitude of the roll control performed by the vehicle behavior control device 16 to suppress the vehicle body's velocity in the roll direction. The information representing the roll control gain can be the absolute value of the force generated by the actuator of the vehicle behavior control device 16. Alternatively, the information representing the roll control gain can be the absolute value of the actuator's torque. Alternatively, the information representing the roll control gain can be the ratio of lateral acceleration to the absolute value of the actuator's force or torque. Alternatively, the information representing the roll control gain can be the vehicle body roll angle. Alternatively, the information representing the roll control gain can be a target roll angle relative to the lateral acceleration.

[0032] The drive controller 28 drives the vehicle behavior control device 16 according to the roll control gain. As a result, when the vehicle is turning, the tilt of the vehicle body in the roll direction is suppressed, and the planar motion characteristics are improved.

[0033] Based on the detection results of the driving state detection sensor 12, the estimation unit 27 estimates the lateral acceleration of the vehicle used by the gain calculation unit 26. The lateral acceleration of the vehicle body mounted on the spring is the acceleration in the left-right direction of the vehicle, which is orthogonal to the longitudinal direction of the vehicle.

[0034] Here, if the vehicle behavior control device 16 performs roll control during steering, suspension characteristics such as toe angle, camber angle, and lateral movement of the contact point change, thereby altering the cornering characteristics. Furthermore, the amount of change in cornering characteristics is not constant but varies depending on the roll control gain. Based on the change in cornering characteristics, the deviation between the estimated lateral acceleration and the actual lateral acceleration increases, posing a risk of performing roll control with a lateral acceleration that deviates significantly from the actual lateral acceleration. Therefore, the estimation unit 27 estimates the lateral acceleration based on the previous roll control gain, and the gain calculation unit 26 calculates the current roll control gain based on the estimated lateral acceleration. The previous roll control gain refers to the roll control gain calculated by the gain calculation unit 26 in the previous control cycle.

[0035] Figure 2 This is a graph showing the relationship between roll control gain and equivalent cornering dynamics. Figure 2 The horizontal axis represents the roll angle RA, which serves as the roll control gain, and the vertical axis represents the equivalent cornering power ratio CPr.

[0036] The roll angle RA is the roll angle (unit: [deg / G]) corresponding to the detected lateral acceleration and can be the target control value of the vehicle behavior control device 16. The roll angle RA is zero and horizontal, and increases as the vehicle body tilts outward during cornering. Sometimes, the tilt outward during cornering is referred to as the positive roll angle.

[0037] The typical equivalent cornering power ratio 44 is the ratio of the equivalent cornering power without roll control to the equivalent cornering power without roll control, which is 1. The equivalent cornering power ratio 46 is the ratio of the equivalent cornering power with roll control to the equivalent cornering power without roll control.

[0038] The equivalent cornering power ratio 46 indicates that the equivalent cornering power decreases as the roll angle RA increases. That is, it means that when roll control towards the outside of the turn is applied, the equivalent cornering power decreases, and wheel grip decreases. At the intersection of equivalent cornering power ratios 44 and 46, the roll angle RA shows no deviation in equivalent cornering power caused by roll control.

[0039] Information relating the roll control gain (i.e., roll angle RA) to the equivalent cornering dynamics can be pre-stored in the roll control device 20. That is, the estimation unit 27 can estimate the equivalent cornering dynamics of the vehicle behavior control device 16 corresponding to the roll control gain based on the pre-stored two-dimensional mapping. This relationship is generated through experiments on each vehicle model, etc. Alternatively, the estimation unit 27 can also estimate the equivalent cornering dynamics corresponding to the roll control gain using mathematical formulas.

[0040] The relationship between roll control gain and equivalent cornering forces is as follows: as the roll control gain causes the vehicle body to lean outwards during cornering, the equivalent cornering forces decrease. Therefore, the equivalent cornering forces that change accordingly with the roll control gain can be appropriately estimated. Furthermore, this applies to situations where the suspension geometry and tire characteristics differ significantly from those of typical vehicles, and are not limited to... Figure 2 The relationship shown.

[0041] Figure 3 This is a graph showing the relationship between the roll control gain and the delay time constant of the lateral force. Figure 3 The horizontal axis and Figure 2 The same, where RA is the roll angle and Tr is the ratio of the lateral force delay time constant. The lateral force delay time constant represents the responsiveness of the lateral force generated in the wheel relative to the slip angle or steering angle.

[0042] The typical lateral force delay time constant ratio of 48 is the ratio of the lateral force delay time constant without roll control to the lateral force delay time constant without roll control, which is 1. The lateral force delay time constant ratio of 50 is the ratio of the lateral force delay time constant with roll control to the lateral force delay time constant without roll control.

[0043] The ratio of the lateral force delay time constant to 50 indicates that the lateral force delay time constant increases as the roll angle RA increases. That is, when roll control towards the outside of the turn is applied, the lateral force delay time constant becomes larger than usual.

[0044] The estimation unit 27 estimates the delay time constant of the lateral force of the vehicle behavior control device 16 corresponding to the roll control gain based on pre-stored information representing the relationship between the roll control gain and the delay time constant of the lateral force. The information representing the relationship between the roll control gain and the delay time constant of the lateral force can be stored in the roll control device 20 in the form of a mathematical formula or a mapping.

[0045] The information representing the relationship between roll control gain and the lateral force delay time constant is that the lateral force delay time constant increases as the roll control gain causes the vehicle body to tilt outwards during cornering. Therefore, the lateral force delay time constant, which varies accordingly with the roll control gain, can be appropriately estimated.

[0046] The estimation unit 27 estimates the lateral acceleration related to the vehicle based on the estimated cornering characteristics of the vehicle. The estimation unit 27 estimates the lateral acceleration based on the estimated equivalent cornering power ratio CPr and the ratio of the delay time constant of the lateral force Tr. As a result, it is possible to estimate the lateral acceleration affected by the roll control with high accuracy.

[0047] Figure 4 This diagram illustrates the turning state of a vehicle in a simplified two-wheeled model. In this simplified two-wheeled model, the lateral force F on the front wheel is... f And the lateral force F of the rear wheel r The calculation is performed using the following formulas (1) and (2). In the simplified two-wheel model, the center of gravity is located between one front wheel and one rear wheel.

[0048] F f = C pf C cf (δ-β-rl) f / V) / (1+T) f T cf S)・・・Form (1)

[0049] C pf It is the normal equivalent cornering power of the front wheels, which is not C. cf The corrected value. C cf This is the equivalent cornering power ratio of the front wheels corresponding to the roll control gain. δ is the steering angle. β is the slip angle. r is the yaw angle at the center of gravity. f It is the distance from the center of gravity to the front wheels. V is the vehicle speed. T f It is the time constant of the typical lateral force delay of the front wheel, which is not affected by T. cf The corrected value. T cf It is the ratio of the delay time constant of the lateral force of the front wheel corresponding to the roll control gain. S is a pre-defined Laplace operator.

[0050] F r = C pr C cr (δ-β-rl) r / V) / (1+T) r T cr S)・・・Form (2)

[0051] C pr It is the normal equivalent cornering power of the rear wheels, which is not C cr The corrected value. C cr It is the equivalent cornering power ratio of the rear wheels corresponding to the roll control gain. T r It is the time constant of the typical lateral force delay of the rear wheel, which is not affected by T. cr The corrected value. T cr It is the ratio of the delay time constant of the lateral force of the rear wheel corresponding to the roll control gain.

[0052] The lateral force of the wheel, corrected for by the ratio of the equivalent cornering power ratio and the ratio of the delay time constant of the lateral force, is calculated using formulas (1) and (2). Alternatively, in formulas (1) and (2), correction can be performed using only either the equivalent cornering power ratio or the ratio of the delay time constant of the lateral force. f and T r The values ​​may differ from the actual values. To make the phase lead greater than the actual value, it can be adjusted to be shorter than the actual vehicle length. If roll control is not implemented, the equivalent cornering power ratio C... cf C cr The value is 1. If roll control is not implemented, the time constant of the lateral force delay is greater than T. cf T cr The value is 1.

[0053] By substituting the modified lateral force of the wheel into the motion equations of equations (3), (4), and (5) below, the lateral acceleration y" at the vehicle's center of gravity, the angular velocity r' of the yaw angle, and the angular velocity β' of the slip angle can be calculated. Therefore, the vehicle motion under the influence of the roll control gain can be estimated.

[0054] y" = (2F) f +2F r ) / M・・・Form (3)

[0055] r' = (2l) f F f -2l r F r ) / I z ...Form (4)

[0056] β' = y" / Vr

[0057] y is the lateral movement of the center of gravity, and its second derivative y'' is the lateral acceleration. M is the vehicle weight. I z is the moment of inertia of the center of gravity. r is the deflection angle.

[0058] According to equation (3), the lateral acceleration is calculated by the ratio of the equivalent cornering dynamic ratio and the delay time constant of the lateral force corresponding to the roll control gain. In addition, although the estimation unit 27 estimates the lateral acceleration using a simple two-wheel model to reduce the computational load, it is not limited to this method and can also estimate the lateral acceleration using a four-wheel model.

[0059] The estimation unit 27 estimates the lateral acceleration corresponding to the change in cornering characteristics caused by the previous roll control gain. The gain calculation unit 26 calculates the current roll control gain based on the lateral acceleration estimated by the estimation unit 27. The drive control unit 28 controls the vehicle behavior control device 16 based on the current roll control gain.

[0060] The driving control unit 22 includes a communication unit 32, a drive control unit 36, an acquisition unit 38, a parsing unit 40, and a calculation unit 42. The acquisition unit 38 acquires the detection results from the driving status detection sensor 12 and the object detection sensor 14. The acquisition unit 38 acquires destination and map information from the navigation device, and acquires the vehicle's position information calculated using the Global Positioning System.

[0061] The analysis unit 40 identifies information related to the object, such as the object's location, based on the detection results from the object detection sensor 14. The analysis unit 40 can use neural network methods, such as deep learning, to identify the object from the camera image. The object is an obstacle or a road feature. The analysis unit 40 identifies the position of the preceding vehicle and the driving lane used for tracking, generating information related to the driving target. The analysis unit 40 can set the target position and target yaw angle in autonomous driving control.

[0062] The calculation unit 42 calculates the target control values ​​to be executed in the automatic driving control in order to achieve the target position and target yaw angle based on the acquisition results of the acquisition unit 38 and the analysis results generated by the analysis unit 40. The target control values ​​include the target vehicle speed, the target steering angle, and the target deceleration.

[0063] When the vehicle behavior control device 16 performs roll control during steering, occupant comfort is improved. On the other hand, suspension characteristics such as toe angle, camber angle, and lateral movement of the contact point change, thereby altering the cornering characteristics. Furthermore, the amount of change in cornering characteristics is not constant but varies according to the roll control gain. The vehicle control device 10 in this embodiment adjusts the target steering angle in autonomous driving control based on information representing the roll control gain.

[0064] The communication unit 32 obtains information representing the roll control gain from the roll control device 20. The calculation unit 42 estimates the vehicle's cornering characteristics corresponding to the roll control gain. The cornering characteristics estimated by the calculation unit 42 are based on the suspension characteristics and may be at least one of the time constants of the equivalent cornering force and lateral force delay of the wheel during roll control.

[0065] The calculation unit 42 estimates the lateral acceleration based on the estimated cornering characteristics, and calculates the target steering angle for automatic driving control based on the estimated lateral acceleration. This improves driver comfort through roll control and enhances the ability to follow the target trajectory under automatic driving control. The drive control unit 36 ​​controls the driving device 18 according to the target control value calculated by the calculation unit 42.

[0066] Figure 5This is a flowchart of the vehicle control method of an embodiment. The acquisition unit 24 of the roll control device 20 acquires driving state information from the driving state detection sensor 12 (S10). In order to suppress the movement of the vehicle body in the roll direction, the gain calculation unit 26 calculates the roll control gain based on the lateral acceleration estimated by the estimation unit 27 (S12).

[0067] The estimation unit 27 estimates the vehicle's cornering characteristics corresponding to the roll control gain used in the previous control, specifically estimating the equivalent cornering power ratio and the ratio of the delay time constant of the lateral force (S16). Based on the estimated cornering characteristics, the estimation unit 27 estimates the lateral acceleration applied to the vehicle (S18). The gain calculation unit 26 calculates the roll control gain used in the current control based on the estimated lateral acceleration (S20). The drive control unit 28 controls the vehicle behavior control device 16 according to the current roll control gain.

[0068] The present disclosure has been described above based on embodiments. The present disclosure is not limited to the embodiments described above, and various design changes and modifications can be made based on the knowledge of those skilled in the art.

Claims

1. A vehicle control device for controlling a vehicle behavior control device capable of controlling the movement of the vehicle body in the lateral direction, wherein, include: Prediction section, presuming the lateral acceleration generated by the vehicle; as well as The gain calculation unit calculates information representing the roll control gain based on the lateral acceleration estimated by the estimation unit. This roll control gain is used to drive the vehicle behavior control device to move the vehicle body in the roll direction. The estimation unit estimates the lateral acceleration based on information representing the previous roll control gain.

2. The vehicle control device according to claim 1, wherein, The estimation unit estimates the vehicle's cornering characteristics corresponding to the previous roll control gain, and estimates the lateral acceleration based on the estimated cornering characteristics.

3. The vehicle control device according to claim 2, wherein, The estimation unit estimates at least one of the time constants of the equivalent cornering force and lateral force of the vehicle behavior control device relative to the previous roll control gain, as cornering characteristics.

4. The vehicle control device according to claim 3, wherein, The estimation unit estimates the equivalent cornering forces of the vehicle behavior control device corresponding to the previous roll control gain based on pre-stored information representing the relationship between roll control gain and equivalent cornering forces. The relationship between roll control gain and equivalent cornering power is as follows: as the roll control gain causes the vehicle to tilt outwards during cornering, the equivalent cornering power decreases.

5. A vehicle control method, executed by a vehicle control device, said vehicle control device controlling a vehicle behavior control device capable of controlling the movement of the vehicle body in the lateral direction, wherein, include: The steps for estimating the lateral acceleration generated by the vehicle; as well as The calculation steps involve determining information representing the roll control gain based on the estimated lateral acceleration. This roll control gain is used to drive the vehicle behavior control device to move the vehicle body in the roll direction. In the estimation step, the lateral acceleration is estimated based on information representing the previous roll control gain.

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