Vehicle posture control device and method based on rear wheel steering system

Abstract

The present invention relates to a vehicle posture control apparatus based on a rear wheel steering system, characterized in that: a vehicle state reference generator generates a reference representing a vehicle state based on a front wheel steering angle, a driving mode, and a sensor signal transmitted from an in-vehicle network; a vehicle state estimator that estimates lateral velocity and disturbance on the basis of a front wheel steering angle, a rear wheel steering angle, and a sensor signal transmitted from an in-vehicle network; a rear wheel steering system target position calculator generating a rear wheel steering system target position value based on the reference generated by the vehicle state reference generator, the sensor signal transferred from the in-vehicle network, the front wheel steering angle, and the lateral velocity and disturbance estimated by the vehicle state estimator; and a rear wheel steering system position controller generating a target motor torque based on the rear wheel steering system target position value and the rear wheel steering system rack position value calculated by the rear wheel steering system target position calculator.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for controlling the posture of a vehicle based on a Rear Wheel Steering (RWS) system. Specifically, the present invention relates to a method and apparatus for controlling the posture of a vehicle based on a Rear Wheel Steering system, which can apply an independent posture control function using the RWS. Background Art

[0002] A Rear Wheel Steering (RWS) system is a driver assistance system that enables faster steering response by reducing the turning radius when the vehicle is traveling at low speed, and increases vehicle stability during turning when the vehicle is traveling at high speed. The RWS is particularly helpful in improving maneuverability in narrow spaces and driving stability at high speeds.

[0003] Existing RWS control methods operate using a feedforward control method. That is, the RWS control method is a method of deriving a target value for the rack position of the RWS system by setting a specific ratio for the steering angles of the front wheels and the rear wheels. When the vehicle is traveling at low speed, the steering angles of the front wheels and the rear wheels are adjusted in opposite directions (reverse directions) to enable more agile turning. When the vehicle is traveling at high speed, the two steering angles are adjusted in the same direction (same direction) to enable stable turning.

[0004] However, existing feedforward control methods require tuning to match each vehicle and driving conditions, and this process requires a considerable amount of time and experience. Sub-optimally tuned values may make it difficult to achieve stable posture control of the vehicle. Therefore, it can be said that ratio tuning is very important. However, this ratio tuning depends on experience and is not intuitive, and it consumes a very long time. In addition, even with sufficient tuning, exact operation may not be achieved due to disturbances such as road surface conditions or changes in vehicle characteristics, so the vehicle may be in an unstable state or a dangerous situation.

[0005] Although posture control functions such as ESC (Electronic Stability Control) are being developed and applied, there is an urgent need for an independent posture control function using the RWS for misoperation, defects, and component conditions of such functions. Accordingly, there is a need to implement vehicle posture control in a new way, rather than a feedforward control method that is difficult to respond nimbly to changes in the surrounding environment.

[0006] Patent Document 1: Korean Patent Registration No. 10-2263187 (June 3, 2021)

[0007] Patent Document 2: Korean Patent Grant Publication No. 10-2463701 (November 1, 2022) Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The present invention is for solving the problems described above, and its purpose is to provide a vehicle posture control method and device based on a rear-wheel steering system that can achieve intuitive and effective tuning and can replace the existing method.

[0010] In addition, the purpose of the present invention is that, from the perspective of vehicle dynamics, intuitive tuning can be performed, thereby reducing the time required for tuning and enabling a more effective vehicle performance optimization process.

[0011] In addition, the purpose of the present invention is to display other response characteristics according to the driving mode, thereby diversifying the experience of vehicle users and providing a matching driving environment that matches each driver's driving style and conditions.

[0012] However, the technical problems to be achieved by the present invention are not limited to the technical problems described above, and there may be other technical problems.

[0013] Means for Solving the Problems

[0014] To achieve the above object, a vehicle posture control device based on a rear-wheel steering system according to an embodiment of the present invention includes: a vehicle state reference generator that generates a vehicle state reference based on the front-wheel steering angle, the driving mode, and sensor signals transmitted from an in-vehicle network; a vehicle state estimator that estimates the lateral speed and disturbance based on the front-wheel steering angle, the rear-wheel steering angle, and sensor signals transmitted from the in-vehicle network; an RWS target position calculator that generates an RWS target position value based on the reference representing the vehicle state generated by the vehicle state reference generator, sensor signals transmitted from the in-vehicle network, and the lateral speed and disturbance estimated by the vehicle state estimator using the front-wheel steering angle; and an RWS position controller that generates a target motor torque based on the RWS target position value calculated by the RWS target position calculator and the RWS rack position value.

[0015] According to an embodiment, the vehicle state reference generator may include a vehicle parameter curve set unit, a target vehicle parameter selector, and a reference calculator. The vehicle parameter curve set unit determines one curve set among a plurality of curve sets each constituted by a pair of a wheelbase curve and a center of gravity (C.O.G.) curve that define vehicle response characteristics based on a driving mode. The target vehicle parameter selector selects a wheelbase and a C.O.G. position based on the current speed of the vehicle and the curve set determined by the vehicle parameter curve set unit. The reference calculator calculates a reference based on the front wheel steering angle and the wheelbase and C.O.G. position selected by the target vehicle parameter selector.

[0016] According to an embodiment, calculating the reference based on the wheelbase and C.O.G. position selected by the target vehicle parameter selector may be calculating the reference by receiving the wheelbase and the C.O.G. position as input values based on a two-wheel steering dynamics model.

[0017] According to an embodiment, the dynamics model is a normal state dynamics model, and the normal state dynamics model may be defined by the following formulas 1 to 3.

[0018] [Formula 1]

[0019]

[0020] [Formula 2]

[0021]

[0022] [Formula 3]

[0023]

[0024] Wherein, L is the wheelbase of the vehicle, V x is the longitudinal velocity, K us is the understeer gradient, δ f is the steer angle of the front wheel, L f = L × x cog , x cog is the C.O.G. position ratio. l f is the distance between the front axle and the center of gravity (length b / w front axle and center of gravity), lr is the distance between the rear axle and the center of gravity (length b / w rear axle and center of gravity), M is the mass of the vehicle (Mass of vehicle), C f is the cornering stiffness of the front tire, C r is the cornering stiffness of the rear tire.

[0025] According to one embodiment, the dynamic model is a single-track dynamic model, and the single-track dynamic model can be defined by the following formula 4,

[0026] [Formula 4]

[0027]

[0028] where, l f = L × x cog and l r = L - l f , L is the wheelbase of the vehicle, l f is the distance between the front axle and the center of gravity (length b / w front axle and center of gravity), l r is the distance between the rear axle and the center of gravity (length b / w rear axle and center of gravity), x cog is the C.O.G. position ratio, C αf is the cornering stiffness of the front tire (cornering stiffness of front tire), C αr is the cornering stiffness of the rear tire (cornering stiffness of front tire), V x is the longitudinal velocity, δ f is the steer angle of the front wheel, m is the mass of the vehicle (Mass of vehicle), I z is the z-axis moment of inertia of the vehicle (z-axis moment of inertia of vehicle).

[0029] A method for controlling the posture of a vehicle based on a rear-wheel steering (RWS) system according to another embodiment of the present invention, which is implemented by an electronic control unit (ECU) of the vehicle, may include: a reference step of generating a reference for representing the vehicle state by a vehicle state reference generator based on the front-wheel steering angle, the driving mode, and sensor signals transmitted from an in-vehicle network; a step of estimating the lateral speed and disturbance by a vehicle state estimator based on the front-wheel steering angle, the rear-wheel steering angle, and sensor signals transmitted from the in-vehicle network; a step of calculating an RWS target position value by an RWS target position calculator based on the vehicle state reference, sensor signals transmitted from the in-vehicle network, the front-wheel steering angle, and the estimated lateral speed and disturbance; a step of generating a target motor torque by an RWS position controller based on the calculated RWS target position value and the RWS rack position value.

[0030] According to an embodiment, the step of generating the vehicle state reference may include: a step of determining one curve set among a plurality of curve sets formed by a wheelbase curve and a center-of-gravity curve that define the vehicle response characteristics based on the driving mode; a step of selecting the wheelbase and the center-of-gravity position (C.O.G position) based on the current speed of the vehicle and the curve set determined by the vehicle parameter curve set unit; a step of calculating a reference based on the front-wheel steering angle and the wheelbase and the center-of-gravity position (C.O.G position) selected by the target vehicle parameter selector.

[0031] According to an embodiment, the step of calculating a reference based on the wheelbase and the center-of-gravity position (C.O.G position) selected by the target vehicle parameter selector may include: a step of calculating a reference by receiving the wheelbase and the center-of-gravity position as input values based on the dynamic model of two-wheel steering.

[0032] According to an embodiment, the dynamic model of two-wheel steering may be a normal state dynamic model or a single-track dynamic model.

[0033] An apparatus for controlling the posture of a vehicle based on a Rear Wheel Steering (RWS) system according to another embodiment of the present invention, the apparatus may include: one or more memory units for storing a plurality of commands; and one or more processors for executing the commands, the one or more processors performing the following processes by executing the plurality of commands: receiving sensor data collected by an electronic device of the vehicle, a vehicle state estimator estimating the vehicle state, a vehicle state reference generator generating a vehicle state reference, a Rear Wheel Steering (RWS) system target position calculator calculating a target position value of the RWS, an RWS position controller calculating a motor torque required to estimate the position of the RWS, and driving a motor for estimating the position of the RWS using the calculated motor torque.

[0034] According to an embodiment, the one or more processors may further perform the following processes by executing the plurality of commands: in the step of the vehicle state estimator estimating the vehicle state, estimating a lateral velocity and a disturbance based on sensor signals transmitted from an in-vehicle network, a front wheel steering angle, and a rear wheel steering angle.

[0035] According to an embodiment, the one or more processors may further perform the following processes by executing the plurality of commands: in the step of the vehicle state reference generator generating a vehicle state reference, generating a vehicle state reference according to a driving mode, sensor signals transmitted from an in-vehicle network, and a front wheel steering angle.

[0036] According to an embodiment, the one or more processors may further perform the following processes by executing the plurality of commands: in the step of the vehicle state reference generator generating a reference of the vehicle state, updating map data required for the vehicle state reference generator to generate a vehicle state reference.

[0037] According to an embodiment, the one or more processors may further perform the following processes by executing the plurality of commands: in the step of the Rear Wheel Steering (RWS) system target position calculator calculating the target position value of the RWS, calculating the target position value of the RWS based on a front wheel steering angle, a vehicle state reference generated by the vehicle state reference generator, sensor signals transmitted from an in-vehicle network, and a lateral velocity and a disturbance estimated by the vehicle state estimator.

[0038] According to an embodiment, the one or more processors may further perform the following processes by executing the plurality of commands: in the step of the RWS position controller calculating a motor torque required for estimating the position of the RWS, calculating a target motor torque based on an RWS target position value generated by the RWS target position generator and an RWS rack position value.

[0039] Advantages of the Invention

[0040] According to the present invention, since an independent attitude control function can be applied by using a rear-wheel steering system (RWS), there is an effect that it is possible to compare with components or failures of an existing ESC attitude control function.

[0041] In addition, according to the present invention, there is an effect as follows: from the viewpoint of vehicle dynamics, intuitive tuning can be performed, thereby reducing the time required for tuning and enabling more effective optimization of vehicle performance.

[0042] In addition, according to the present invention, since different response characteristics are displayed according to the driving mode, it is possible to diversify the experience of a vehicle user and provide a matching driving environment that matches each driver's driving style and conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 FIG. is a block diagram schematically showing main operation parts of a rear-wheel steering system according to an embodiment of the present invention.

[0044] Figure 2 FIG. is a block diagram of a vehicle attitude control device based on a rear-wheel steering system according to an embodiment of the present invention.

[0045] Figure 3 FIG. is a block diagram showing a configuration of a vehicle state reference generator.

[0046] Figure 4A and Figure 4B FIG. is a diagram showing an axle length and a center of gravity position ratio.

[0047] Figure 5 FIG. is a diagram showing a parameter change method based on a change in driving mode.

[0048] Figure 6 FIG. is a flowchart of a method for controlling an attitude of a vehicle based on a rear-wheel steering system according to an embodiment of the present invention.

[0049] DESCRIPTION OF REFERENCE NUMERALS

[0050] 100: Rear-wheel steering system (RWS) 101: Sensor unit

[0051] 102: Electronic control unit (ECU) 103: RWS motor

[0052] 200: Vehicle attitude control device based on rear-wheel steering system

[0053] 210: Vehicle state reference generator

[0054] 220: Vehicle state estimator 230: RWS target position calculator

[0055] 240: RWS position controller 300: Vehicle state reference generator

[0056] 310: Vehicle parameter curve set unit 320: Target vehicle parameter selector

[0057] 330: Reference calculator Detailed implementation mode

[0058] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those with ordinary knowledge in the technical field to which the present invention pertains can easily implement it. In the process of describing with reference to the drawings, even for components denoted by the same name, the reference numerals may be different according to the drawings. The reference numerals are only recorded for convenience of description, and the corresponding reference numerals should not be used to limit the interpretation of the concept, feature, function, or effect of each component.

[0059] Hereinafter, with reference to the accompanying drawings, a method and an apparatus for controlling the posture of a vehicle based on a rear-wheel steering system (RWS) according to the present invention will be described in detail.

[0060] Figure 1 is a block diagram schematically showing the main operation parts of a rear-wheel steering system according to an embodiment of the present invention.

[0061] Refer to Figure 1 As shown in, the rear-wheel steering system 100 can be provided on the vehicle 110 and can include a sensor unit 101, an electronic control unit (ECU) 102, and a rear-wheel steering system motor 103.

[0062] The sensor unit 101 can include an inertial measurement unit (IMU), a steering angle sensor, a wheel speed sensor, etc. The IMU is a sensor for providing information on the movement of the vehicle 110, and measures the acceleration and rotation rate of the vehicle 110 by combining an accelerometer and a gyroscope. For the measured data, information on the current motion state of the vehicle 110, such as pitch, yaw, and roll, is transmitted to the electronic control unit 102, thereby providing necessary data in the posture control of the vehicle 110. The steering angle sensor is a sensor that senses the driver's steering input and transmits it to the electronic control unit 102. The steering angle sensor plays an important role in determining the direction of the vehicle 110 that the driver has in mind. The wheel speed sensor measures the rotational speed of each wheel and provides the speed information of the vehicle 110 to the electronic control unit 102 in real time. In particular, it is information required in the process of adjusting the steering reaction of the RWS system according to the speed of the vehicle 110.

[0063] The electronic control unit 102 acts as the "brain" of the vehicle 110, processes and analyzes the data collected from the sensors. The electronic control unit 102 integrates various data collected from multiple sensors of the vehicle 110, provides comprehensive information on the current state of the vehicle 110, and determines the operations to be performed by the RWS motor 103 based on the integrated data and applying control logic. This includes the process of calculating the steering angle of the rear wheels for adjusting the posture of the vehicle 110. Then, a steering signal is transmitted to the RWS motor 103, thereby adjusting the posture of the vehicle 110. In addition, the electronic control unit 102 diagnoses problems in the system and manages the communication with other vehicle systems.

[0064] The RWS motor 103 is a driving device that adjusts the steering angle of the rear wheels according to the control signal received from the electronic control unit 102. The RWS motor 102 needs to have precise adjustment capabilities and a fast response speed, and needs to exert the steering mechanism of the vehicle 110 and sufficient force to overcome the friction with the road surface.

[0065] The operating relationship among the multiple sensors of the sensor unit 101, the electronic control unit 102, and the RWS motor 103 has a sequential and repetitive process. The multiple sensors continuously collect data, and the data collected from the multiple sensors is transmitted to the electronic control unit 102. The electronic control unit 102 processes the multiple data received and issues a command to the RWS motor 103 to adjust the steering angle of the rear wheels. By adjusting the steering angle, the trajectory of the vehicle 110 is changed, and the changed trajectory is sensed again by the multiple sensors, thus forming a loop that continuously performs feedback and adjustment. Such a closed-loop system can achieve a very sensitive and highly adaptable RWS system. When the driver inputs a steering operation, the steering angle sensor informs the electronic control unit 102 of the direction the driver intends, and the electronic control unit 102 calculates the optimal rear-wheel steering angle based on the current dynamic data of the vehicle 110, thereby controlling the RWS motor 103. The RWS motor 103 adjusts the rear wheels to help with the operation while maintaining the stability of the vehicle 110, and the results of the adjustment are continuously monitored by the multiple sensors and applied in real time.

[0066] Figure 2 It is a block diagram of a vehicle posture control device based on a rear-wheel steering system according to an embodiment of the present invention.

[0067] Figure 2 The vehicle posture control device 200 based on the rear-wheel steering system described in Figure 1The electronic control unit 102 shown is executed, and can be executed by at least one processor included in the electronic control unit 102. A plurality of commands for operating a plurality of processors can be stored in a memory provided in the electronic control unit 102, but the processors can be configured separately from the memory or integrally with the memory. The memory can be implemented by a non-volatile memory such as ROM (Read Only Memory), PROM (Programmable Read Only Memory), EPROM (Electrically Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), flash memory, PRAM (Phase Change Memory), MRAM (Magnetoresistive Random Access Memory), RRAM (Resistive Random Access Memory), FRAM (Ferroelectric Random Access Memory), etc., or can be implemented by a volatile memory such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), SDRAM (Synchronous Dynamic Random Access Memory), PRAM (Phase Change Random Access Memory), RRAM (Resistive Random Access Memory), FeRAM (Ferroelectric Memory), etc.

[0068] Referring to Figure 2 , the vehicle posture control device 200 for a rear-wheel steering system can include a vehicle state reference generator 210, a vehicle state estimator 220, a rear-wheel steering system target position calculator 230, and a rear-wheel steering system position controller 240.

[0069] The vehicle state reference generator 210 receives the front-wheel steering angle, the driving mode, and sensor signals transmitted from the in-vehicle network, and generates a reference for representing the vehicle state. The front-wheel steering angle is transmitted to the vehicle state reference generator 210 in the form of data or information. For example, the driving mode can be a normal mode, an energy-saving mode, a sport mode, a winter mode, etc. Data or information for representing the driving mode is transmitted to the vehicle state reference generator 210. In addition, the acceleration and angular velocity from an IMU (Inertial Measurement Unit), the rotational speed of each wheel from a wheel speed sensor, and data for representing the vehicle posture from a plurality of other sensors are transmitted to the vehicle state reference generator 210. That is, data for the front-wheel steering angle, data for the driving mode, and data from a plurality of sensors based on the in-vehicle network can be transmitted to the vehicle state reference generator 210. For example, the in-vehicle network can use CAN (Controller Area Network), LIN (Local Interconnect Network), FlexRay (etc. network), the Internet, etc.

[0070] The vehicle state reference generator 210 generates a "reference signal" or "reference" representing the vehicle state based on data for the front wheel steering angle, data for the driving mode, and data from multiple sensors based on the in-vehicle network.

[0071] The vehicle state estimator 220 receives multiple sensor signals transmitted from the in-vehicle network and the steering angles of the front / rear wheels, and estimates the lateral velocity and disturbance. The lateral velocity refers to the speed at which the vehicle can move laterally even during straight driving, and this lateral velocity has a direct impact on the stability and steering response of the vehicle. The disturbance can include environmental main factors such as the inclination and irregularity of the road, wind, or internal main factors such as changes in the vehicle's load.

[0072] The RWS target position calculator 230 receives the reference signal generated by the vehicle state reference generator 210 and the lateral velocity and disturbance estimated by the vehicle state estimator 220 to calculate the RWS target position value. The RWS target position calculator 230 analyzes the reference signal transmitted from the vehicle state reference generator 210 and processes the data of the lateral velocity and disturbance provided by the vehicle state estimator 220. The RWS target position calculator 230 calculates the target position value to be achieved by the rear wheel steering based on the received data.

[0073] The RWS position controller 240 receives the RWS target position value generated by the RWS target position calculator 230 and the RWS rack position value to calculate the target motor torque value. The RWS position controller 240 generates the target motor torque value based on the received RWS target position value and the current rack position value. The target torque value can define the torque that needs to be generated by the motor of the RWS system, and this target torque value provides the required power during the process of adjusting the steering angle of the vehicle through the rear wheel steering system.

[0074] Figure 3 is a block diagram showing the configuration of the vehicle state reference generator 300.

[0075] Figure 3 The vehicle state reference generator 300 of Figure 2 can perform the functions and operations of the vehicle state reference generator 210 in the embodiment of Figure 3, the vehicle state reference generator 300 may include a vehicle parameter curve set unit 310, a target vehicle parameter selector 320, and a reference calculator 330. The vehicle parameter curve set unit 310 may store data in a memory such as a random access memory (RAM) or a read only memory (ROM), and change the curve set based on the driving mode.

[0076] Specifically, the vehicle state reference generator 300 uses a two-wheel steering-based dynamic model. For example, the two-wheel steering-based dynamic model may use a normal state dynamics or a single track dynamics model. The two-wheel steering-based dynamic model applicable to the present invention will be described in detail later.

[0077] The vehicle parameter curve set unit 310 changes or adjusts the curve set for representing the dynamic response of the vehicle according to the driving mode of the vehicle. The response characteristics of the vehicle are set differently for each driving mode using the data stored in a memory such as a random access memory (RAM) or a read only memory (ROM). For example, in the sport mode, curves for making a more agile steering response may be set, while in the energy saving mode, curves for optimizing the energy efficiency may be set. The method for changing or adjusting the parameter curve set based on the driving mode will be described in detail in the Figure 5 described later.

[0078] The target vehicle parameter selector 320 determines the wheelbase and the center of gravity position (C.O.G position) of the vehicle based on the vehicle speed and the curve set changed by the vehicle parameter curve set unit 310.

[0079] Figure 4A and Figure 4B are diagrams showing the wheelbase and the center of gravity position ratio.

[0080] Refer to Figure 4A and Figure 4B to describe the wheelbase and the center of gravity position ratio. The wheelbase refers to the distance between the front axle and the rear axle of an automobile. The wheelbase is adjusted according to the vehicle speed so as to achieve the desired vehicle response. For example, at high speed, the stability can be improved by adjusting the wheelbase to a longer wheelbase, while at low speed, the maneuverability can be improved by adjusting the wheelbase to a shorter wheelbase. This adjustment can be achieved by an electronic or a mechanical device.

[0081] The center of gravity position ratio (C.O.G Position Ratio) refers to the ratio of the distance from the front wheel to the center of gravity (C.O.G) position of the vehicle to the entire wheelbase. By adjusting the center of gravity position ratio, the center of gravity of the vehicle can be moved forward or backward to achieve the desired vehicle response. If the center of gravity moves forward, more weight is applied to the front wheels of the vehicle, increasing the responsiveness to steering. If the center of gravity moves backward, the stability of the rear wheels increases. That is, the wheelbase and the center of gravity position ratio are optimized through the design and adjustment of the vehicle to best suit the driving conditions given by the vehicle.

[0082] Refer back to Figure 3 The vehicle state reference generator 300 adjusts the wheelbase and the center of gravity position (C.O.G position) of the vehicle in real time according to the vehicle speed, so that the response characteristics of the vehicle can be changed.

[0083] The reference calculator 330 calculates the yaw rate and the lateral speed of the vehicle while considering the front wheel steering angle, the wheelbase, and the center of gravity position. That is, the vehicle parameter curve set unit 310 determines one curve set among multiple curve sets composed of a wheelbase curve and a C.O.G. curve that define the vehicle response characteristics according to the driving mode. The target vehicle parameter selector 320 determines the wheelbase and the center of gravity position based on the current speed of the vehicle and the curve set. The reference calculator 330 calculates the yaw rate and the lateral speed of the vehicle by combining this information with the front wheel steering angle. The dynamic state reference of the vehicle generated through this process can be used by the vehicle control system and can be formed as a benchmark for ensuring compliance with the stability of the vehicle and the steering intention of the driver.

[0084] Figure 5 It is a diagram showing a parameter change method based on a change in the driving mode. Refer to Figure 5 According to the driving mode of the vehicle, multiple parameters that determine the response characteristics of the vehicle can be changed. That is, the curve set of parameters can be changed according to the driving mode, and references with various response characteristics can be generated according to the combination of the wheelbase (Wheel Base) and the center of gravity position (C.O.G Position) curve sets of the vehicle. Here, in the wheelbase graph, the x-axis represents the vehicle speed, the y-axis represents the vehicle wheelbase value, and it is set to a value greater than 0. In addition, in the C.O.G. graph, the x-axis represents the vehicle speed, the y-axis represents the center of gravity of the vehicle, as a value between 0 and 1, the case where it is located at the very front of the vehicle is set to 0, and the case where it is located at the very rear of the vehicle is set to 1.

[0085] Select a set of curves composed of the wheelbase curve and the C.O.G. curve differently according to the driving mode. As the selected set of curves, for example, any one of the set of curves for mode 1, the set of curves for mode 2, and the set of curves for mode N can be selected. Then, the wheelbase and the C.O.G. position can be adjusted based on the set of curves selected according to the vehicle speed.

[0086] Return again to Figure 3 And explain. Substitute the wheelbase and C.O.G. position values into the dynamic model based on two-wheel steering with reference to calculator 330 and generate a reference.

[0087] In an embodiment of the present invention, the dynamic model based on two-wheel steering can use the normal state dynamics or the single-track dynamic model. However, it is not limited thereto, and the dynamic model based on two-wheel steering can be variously selected according to the needs of those of ordinary skill in the art.

[0088] In an embodiment of the present invention, in the case of using the normal state dynamic model, the yaw angular velocity γ, the lateral velocity V y , and the understeer gradient K us .

[0089] [Equation 1]

[0090]

[0091] Where L is the wheelbase of the vehicle, V x is the longitudinal velocity, K us is the understeer gradient, and δ f is the steer angle of the front wheel.

[0092] [Equation 2]

[0093]

[0094] Where l f = L×x cog , l r = L - l f , L is the wheelbase of the vehicle, l f is the distance between the front axle and the center of gravity, and l ris the distance between the rear axle and the center of gravity (length b / w rear axle and center of gravity), x cog is the C.O.G. position ratio, V x is the longitudinal velocity, K us is the understeer gradient, δ f is the steer angle of the front wheel, and M is the mass of the vehicle (Mass of vehicle).

[0095] [Equation 3]

[0096]

[0097] where, l f = L × x cog , l r = L - l f , L is the wheelbase of the vehicle, l f is the distance between the front axle and the center of gravity (length b / w front axle and center of gravity), l r is the distance between the rear axle and the center of gravity (length b / w rear axle and center of gravity), x cog is the C.O.G. position ratio, M is the mass of the vehicle (Mass of vehicle), C f is the cornering stiffness of the front tire, C r is the cornering stiffness of the rear tire.

[0098] In another embodiment according to the present invention, in the case of using a single track dynamic model, the yaw angular velocity γ and the lateral velocity V are obtained by the following Equation 4 y .

[0099] [Equation 4]

[0100]

[0101] where, l f = L × x cog , l r = L - l f , L is the wheelbase of the vehicle, l fis the distance between the front axle and the center of gravity (length b / w front axle and center of gravity), l r is the distance between the rear axle and the center of gravity (length b / w rear axle and center of gravity), x cog is the C.O.G. position ratio, C αf is the cornering stiffness of the front tire, C αr is the cornering stiffness of the rear tire (should be 'cornering stiffness of rear tire' in the original), V x is the longitudinal velocity, δ f is the steer angle of the front wheel, m is the mass of the vehicle, I z is the z-axis moment of inertia of the vehicle.

[0102] Figure 6 is a flowchart showing a method for controlling the posture of a vehicle based on a rear-wheel steering system (RWS) according to an embodiment of the present invention.

[0103] Figure 6 The method in can be implemented by the electronic control unit (ECU) of the vehicle and can be executed by at least one processor in the electronic control unit. Each function executed by at least one processor in the electronic control unit can be divided into a hardware form according to the internal function of the processor and execute separate functions. Moreover, the electronic control unit may include a memory, and the memory may store multiple commands for executing the following method.

[0104] Refer to Figure 6 , in step S601, if the vehicle startup is in the ON state, then in step S602, sensor data is received from multiple sensors of the vehicle. The multiple sensors of the vehicle may include an inertial measurement unit (IMU), a steering angle sensor, a wheel speed sensor, etc.

[0105] In step S603, the vehicle state is estimated by the vehicle state estimator. More preferably, sensor signals transmitted from the in-vehicle network and the steering angles of the front / rear wheels are received, and the lateral velocity and disturbances are estimated.

[0106] It should be noted that in the original text, there is a mistake in where it says 'cornering stiffness of front tire' which should be 'cornering stiffness of rear tire' for clarity, and this has been corrected in the translation.In step S604, the vehicle state reference generator receives and updates the driving mode of the vehicle. In step S605, it receives and updates the map data required in the process of generating the vehicle state reference.

[0107] In step S606, the vehicle state reference generator generates a vehicle state reference. More preferably, the vehicle state reference generator uses a two-wheel steering-based dynamics model to generate a reference for representing the vehicle state. The two-wheel steering-based dynamics model can use the normal state dynamics model or the single track dynamics model as described above.

[0108] In step S607, the Rear Wheel Steering (RWS) target position calculator calculates the target position value of the RWS. More preferably, it receives the front wheel steering angle, the reference for representing the vehicle state generated by the vehicle state reference generator, the sensor signals transmitted from the in-vehicle network, the lateral speed estimated by the vehicle state estimator, and the disturbance to calculate the target position value of the RWS.

[0109] In step S608, the RWS position controller calculates the motor torque required to estimate the position of the RWS. More preferably, it receives the RWS target position value generated by the RWS target position generator and the RWS rack position value to calculate the required target motor torque.

[0110] In step S609, the motor for estimating the position of the RWS is driven by the calculated motor torque.

[0111] In step S610, it is judged whether the vehicle start is in the OFF state. If the start is in the OFF state, the operation is stopped. If the start is not in the OFF state, steps S602 to S609 are repeated again.

[0112] The devices and methods described above can be implemented by hardware components, software components, and / or a combination of hardware components and software components. For example, the devices and components described in multiple embodiments can utilize one or more general-purpose computers or special-purpose computers such as a processor, a controller, an ALU (arithmetic logic unit), a digital signal processor, a microcomputer, an FPGA (field programmable gate array), a PLU (programmable logic unit), a microprocessor, or any other device capable of executing instructions and responding. The processing device can execute an operating system (OS) and one or more software applications that can run on the operating system. Additionally, the processing device accesses, stores, operates, processes, and generates data in response to the running of the software. For example, the processing device can include multiple processors or one processor and one controller. Additionally, it can also be other processing configurations such as a parallel processor.

[0113] As described above, although multiple embodiments have been described with reference to limited embodiments and drawings, various modifications and variations can be made by those of ordinary skill in the art. For example, even if the techniques described can be executed in an order different from the described methods, and / or the components of the systems, structures, devices, circuits, etc. described can be combined or assembled in a form different from the described methods, or can be replaced or substituted by other components or equivalents, the exact effects can still be achieved.

[0114] Therefore, all content equivalent to other implementations, other embodiments, and the claims falls within the scope of the appended claims.

Claims

1. A vehicle posture control device based on a rear-wheel steering system, characterized in that, Comprising: A vehicle state reference generator that generates a reference for representing the vehicle state based on the front wheel steering angle, driving mode, and sensor signals transmitted from the in-vehicle network; A vehicle state estimator that estimates the lateral speed and disturbance based on the front wheel steering angle, rear wheel steering angle, and sensor signals transmitted from the in-vehicle network; A rear wheel steering system target position calculator that generates a rear wheel steering system target position value based on the reference generated by the vehicle state reference generator, sensor signals transmitted from the in-vehicle network, the front wheel steering angle, and the lateral speed and disturbance estimated by the vehicle state estimator; and A rear wheel steering system position controller that generates a target motor torque based on the rear wheel steering system target position value calculated by the rear wheel steering system target position calculator and the rear wheel steering system rack position value.

2. The vehicle posture control device based on a rear wheel steering system according to claim 1, characterized in that: The vehicle state reference generator includes a vehicle parameter curve set unit, a target vehicle parameter selector, and a reference calculator; The vehicle parameter curve set unit determines one curve set from a plurality of curve sets formed by pairs of a wheelbase curve and a center of gravity curve that define the vehicle response characteristics based on the driving mode; The target vehicle parameter selector selects the wheelbase and the center of gravity position based on the current speed of the vehicle and the curve set determined by the vehicle parameter curve set unit; The reference calculator calculates a reference based on the front wheel steering angle and the wheelbase and center of gravity position selected by the target vehicle parameter selector.

3. The vehicle posture control device based on a rear wheel steering system according to claim 2, characterized in that: Calculating the reference based on the front wheel steering angle and the wheelbase and center of gravity position selected by the target vehicle parameter selector is to calculate the reference by receiving the wheelbase and the center of gravity position as input values based on the dynamic model of two-wheel steering.

4. The vehicle posture control device based on a rear wheel steering system according to claim 3, characterized in that: The dynamic model of two-wheel steering is a normal state dynamic model; The normal state dynamic model is defined by the following formulas 1 to 3; [Formula 1] [Formula 2] [Formula 3] where L is the wheelbase of the vehicle, V x is the longitudinal speed, K us is the understeer gradient, δ f is the front wheel steering angle, l f = L × x cog , x cog is the center of gravity position ratio, l r = L - l f , l f is the distance between the front axle and the center of gravity, l r is the distance between the rear axle and the center of gravity, M is the mass of the vehicle, C f is the cornering stiffness of the front tire, C r is the cornering stiffness of the rear tire.

5. The vehicle posture control device based on a rear wheel steering system according to claim 3, characterized in that: The dynamic model of two-wheel steering is a single-track dynamic model; The single-track dynamic model is defined by the following formula 4; [Formula 4] where l f = L × x cog , l r = L - l f , L is the wheelbase of the vehicle, l f is the distance between the front axle and the center of gravity, l r is the distance between the rear axle and the center of gravity, x cog is the center of gravity position ratio, C αf is the cornering stiffness of the front tire, C αr is the cornering stiffness of the rear tire, V x is the longitudinal speed, δ f is the front wheel steering angle, m is the mass of the vehicle, I z is the z-axis rotational inertia moment of the vehicle.

6. A vehicle posture control method based on a rear-wheel steering system, which is executed by an electronic control unit of the vehicle, characterized in that, The vehicle posture control method includes: A step of generating a reference for representing the vehicle state by a vehicle state reference generator based on the front wheel steering angle, driving mode, and sensor signals transmitted from the in-vehicle network; A step of estimating the lateral speed and disturbance by a vehicle state estimator based on the front wheel steering angle, rear wheel steering angle, and sensor signals transmitted from the in-vehicle network; A step of calculating a target position value of the rear-wheel steering system by a rear-wheel steering system target position calculator based on a reference generated by the vehicle state reference generator, sensor signals transmitted from the in-vehicle network, the front-wheel steering angle, the estimated lateral speed, and the disturbance, and A step of generating a target motor torque by a rear-wheel steering system position controller based on the calculated target position value of the rear-wheel steering system and the rear-wheel steering system rack position value.

7. The vehicle posture control method based on a rear-wheel steering system according to claim 6, characterized in that The step of generating a reference for representing the vehicle state includes: A step of determining one set of curves among a plurality of sets of curves formed by a wheelbase curve and a center-of-gravity curve that define vehicle response characteristics based on a driving mode, A step of selecting a wheelbase and a center-of-gravity position based on the current speed of the vehicle and the set of curves determined by the vehicle parameter curve set unit, and A step of calculating a reference based on the front-wheel steering angle and the wheelbase and center-of-gravity positions selected by the target vehicle parameter selector.

8. The vehicle posture control method based on a rear-wheel steering system according to claim 7, characterized in that The step of calculating a reference based on the front-wheel steering angle and the wheelbase and center-of-gravity positions selected by the target vehicle parameter selector includes: A step of calculating a reference by receiving the wheelbase and the center-of-gravity position as output values based on a dynamic model of two-wheel steering.

9. The vehicle posture control method based on a rear-wheel steering system according to claim 8, characterized in that The dynamic model of two-wheel steering is a normal state dynamic model or a single-track dynamic model.

10. An apparatus for controlling the posture of a vehicle based on a rear-wheel steering system, characterized in that The apparatus includes: One or more memory units storing a plurality of commands, and One or more processors executing the plurality of commands; The one or more processors perform the following processes by executing the plurality of commands: Receiving sensor data collected by an electronic device of the vehicle; A vehicle state estimator estimating the vehicle state; A vehicle state reference generator generating a reference for representing the vehicle state; A rear-wheel steering system target position calculator calculating a target position value of the rear-wheel steering system; A rear-wheel steering system position controller calculating a motor torque required for estimating the position of the rear-wheel steering system; Driving a motor for estimating the position of the rear-wheel steering system using the calculated motor torque.

11. The apparatus for controlling the posture of a vehicle based on a rear-wheel steering system according to claim 10, characterized in that The one or more processors further perform the following processes by executing the plurality of commands: In the step of the vehicle state estimator estimating the vehicle state, estimating the lateral speed and the disturbance based on sensor signals transmitted from the in-vehicle network, the front-wheel steering angle, and the rear-wheel steering angle.

12. The apparatus for controlling the posture of a vehicle based on a rear-wheel steering system according to claim 10, characterized in that The one or more processors further perform the following processes by executing the plurality of commands: In the step of the vehicle state reference generator generating a reference for representing the vehicle state, a reference for representing the vehicle state is generated based on a driving mode, sensor signals transmitted from an in-vehicle network, and a front wheel steering angle.

13. The apparatus for controlling the posture of a vehicle based on a rear wheel steering system according to claim 10, wherein the one or more processors further perform the following processing by executing the plurality of commands: In the step of the vehicle state reference generator generating a reference for representing the vehicle state, map data required for the vehicle state reference generator to generate a reference for representing the vehicle state is updated.

14. The apparatus for controlling the posture of a vehicle based on a rear wheel steering system according to claim 10, wherein the one or more processors further perform the following processing by executing the plurality of commands: In the step of the rear wheel steering system target position calculator calculating a target position value of the rear wheel steering system, the target position value of the rear wheel steering system is calculated based on a front wheel steering angle, a reference for representing the vehicle state generated by the vehicle state reference generator, sensor signals transmitted from an in-vehicle network, a lateral speed estimated by the vehicle state estimator, and disturbances.

15. The apparatus for controlling the posture of a vehicle based on a rear wheel steering system according to claim 10, wherein the one or more processors further perform the following processing by executing the plurality of commands: In the step of the rear wheel steering system position controller calculating a motor torque required for estimating the position of the rear wheel steering system, a target motor torque is calculated based on the target position value of the rear wheel steering system generated by the rear wheel steering system target position generator and the rack position value of the rear wheel steering system.

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