Apparatus and method for controlling vehicle stability based on rear-wheel steering

Abstract

A vehicle stability control device based on RWS includes a vehicle state reference generator that generates a reference representing a vehicle state based on a front wheel steering angle, a drive mode, and a sensor signal transmitted from an in-vehicle network; a vehicle state estimator that estimates a lateral velocity and disturbance based on the front and rear wheel steering angles and the sensor signal transmitted from the in-vehicle network; an RWS target position calculator that generates an RWS target position value based on the reference generated by the vehicle state reference generator, the sensor signal transmitted from the in-vehicle network, the front wheel steering angle, and the lateral velocity and disturbance estimated by the vehicle state estimator; and an RWS position controller that generates the target motor torque.based on the RWS target position value calculated by the RWS target position calculator and an RWS rack position value.

Description

This application claims priority to Korean Patent Application No. 10-2024-0002160 filed on Jan. 5, 2024.TECHNICAL FIELDThe present disclosure generally relates to an apparatus and method for controlling vehicle stability based on a rear wheel steering (RWS) system. In particular, some embodiments of the present disclosure may provide an apparatus and method for controlling vehicle stability based on RWS to apply an independent stability control function using the RWS.BACKGROUND OF THE INVENTIONAn RWS system is a driver assistance system configured to enable a quick steering response by reducing a turning angle when a vehicle is running at low speeds and to increase vehicle stability during turning when the vehicle is running at high speeds. The RWS system contributes particularly to improved narrow space operability and driving stability during high speed driving.A conventional RWS control method is performed using a feedforward control method. In other words, this is a method of deriving a rack position target value of the RWS system by setting a specific ratio for the steering angles of front and rear wheels. When the vehicle is running at low speeds, the steering angles of the front and rear wheels are adjusted in opposite directions (out of phase) to enable more rapid rotation. When the vehicle is running at high speeds, both steering angles are adjusted in the same direction (in phase) to enable stable turning.However, the present feedforward control method requires tuning according to each vehicle and driving situation. This process requires considerable time and experience. An unoptimized tuning value may make it difficult to reliably control the vehicle stability, so that the ratio tuning is of great importance. However, this ratio adjustment is experience dependent, non-intensive and time consuming. In addition, despite sufficient matching, disturbance such as changes in road surface conditions or vehicle characteristics may prevent proper operation, resulting in the vehicle becoming unstable or leading to a dangerous situation.Although a stability control function such as an electronic stability control (ESC) is developed and applied, there is a need for an independent stability control function using an RWS in preparation for a malfunction, a defect, or an absence. Accordingly, there is a need to implement the vehicle stability by a new method instead of the feedforward control method in which it is difficult to quickly respond to changes in the environment.(Prior Art Document)(Patent Document 1) Korean Patent No. 10-2263187 (2021. 06. 03.)(Patent Document 1) Korean Patent No. 10-2463701 (2022. 11.01.)SUMMARYThe present disclosure may provide a method and apparatus for controlling vehicle stability based on RWS, which enables intuitive and efficient tuning and may replace a conventional method.Further, the present disclosure may provide intuitive tuning in vehicle dynamics, thereby reducing the time required for tuning and enabling vehicle performance to be optimized more efficiently.Further, the present disclosure may improve user experience by offering various response characteristics depending on a driving mode, and may provide a personalized driving environment tailored to individual drivers' driving styles and conditions.However, the technical challenges addressed by the present disclosure are not limited to the technical challenges described above, and there may be additional technical challenges.According to embodiments of the present disclosure, an apparatus for controlling vehicle stability based on rear wheel steering (RWS) may include a vehicle state reference generator that generates a reference representing a vehicle state based on a front wheel steering angle, a drive mode, and a sensor signal transmitted from an in-vehicle network; a vehicle state estimator that estimates a lateral speed and disturbance based on the front wheel and rear wheel steering angles and the sensor signal transmitted from the in-vehicle network; an RWS target position calculator that generates an RWS target position value based on the reference generated by the vehicle state reference generator, the sensor signal transmitted from the in-vehicle network, the front wheel steering angle, and the lateral speed and disturbance estimated by the vehicle state estimator; and an RWS position controller that generates the target motor torque based on the RWS target position value calculated by the RWS target position calculator and an RWS rack position value.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 may determine a curve set among a plurality of curve sets composed of pairs of a wheel base curve defining vehicle response characteristics depending on the driving mode and a center of gravity (C.O.G.) curve, the target vehicle parameter selector may select a wheel base and a C.O.G. position based on a current vehicle speed and the curve set determined by the vehicle parameter curve set unit, and the reference calculator may calculate a reference based on the front wheel steering angle and the wheel base and the C.O.G. position selected by the target vehicle parameter.Calculating the reference based on the wheel base and the C.O.G. position selected by the target vehicle parameter selector may include calculating the reference by receiving the wheel base and the C.O.G. position as input values for a two-wheel steering-based dynamic model.The two-wheel steering-assisted dynamic model may be a static (steady-state) dynamic model, and the static (steady-state or steady-state) dynamic model may be defined by the following equations 1 to 3, where L represents the wheel base of the vehicle, V x represents the longitudinal speed, K us represents an understeer (understeer) gradient, δ f represents the steering angle of the front wheel, l f= is L×x cog x cog represents a C.O.G. positional relationship, l r= is L-l f, l f represents a length between a front axle and the center of gravity, l r represents a length between a rear axle and the center of gravity, M represents a mass of the vehicle, C f represents a ^ cornering rigidity (cornering rigidity) of a front wheel, and C r represents a cornering rigidity of a rear wheel.The two-wheel steering-assisted dynamic model may be a single track (single track) dynamic model, and the single track dynamic model may be defined by the following equation 4, where l is f= L×x cog l is r= L-l is f L represents the wheel base of the vehicle, l is f represents a length between the front axle and the center of gravity, l is r represents a length between the rear axle and the center of gravity, x is cog represents a C.O.G. position relationship, C is af represents the cornering stiffness (cornering rigidity) of the front wheel, C ar represents cornering rigidity (corner rigidity) of the rear wheel, V x represents longitudinal speed, δ f represents steering angle of the front wheel, m represents mass of the vehicle, and I Z represents z-axis moment of rigidity of the vehicle.According to another embodiment of the present disclosure, a method for controlling vehicle stability based on an RWS performed by an electronic control unit (ECU) of a vehicle may include generating, by a vehicle state reference generator, a reference representing a vehicle state based on a front wheel steering angle, a drive mode, and a sensor signal transmitted from an in-vehicle network; estimating, by a vehicle state estimator, a lateral speed and disturbance based on the front wheel and rear wheel steering angles and the sensor signal transmitted from the in-vehicle network; calculating a RWS target position value based on the vehicle state reference, the sensor signal transmitted from the in-vehicle network, the front wheel steering angle, and the estimated lateral speed and disturbance by a RWS target position calculator; and generating a target motor torque based on the calculated RWS target position value and a RWS rack position value by a RWS position controller.Generating the reference representing the vehicle state may include determining a set of curves among a plurality of sets of curves composed of pairs of a wheel base curve defining vehicle response characteristics depending on the driving mode and a center of gravity curve (C.O.G.); selecting a wheel base and a C.O.G. position based on a current vehicle speed and the set of curves determined by the vehicle parameter set of curves; and calculating a reference based on the front wheel steering angle, the wheel base, and the C.O.G. position selected by the target vehicle parameter selector.Calculating the reference based on the wheel base and the C.O.G. position selected by the target vehicle parameter selector may include calculating the reference by receiving the wheel base and the C.O.G. position as input values for a two-wheel steering-based dynamic model.The two-wheel steering-based dynamic model may be either a static (steady-state) dynamic model or a single-track dynamic model.According to another embodiment of the present disclosure, an apparatus for controlling vehicle stability based on a rear wheel steering (RWS) system may include one or more memory units storing instructions; and one or more processors executing the instructions, wherein execution of the instructions by the one or more processors causes the one or more processors to receive sensor data collected in an electronic device of the vehicle; estimate a vehicle state using a vehicle state estimator; generate a reference representing a vehicle state using a vehicle state reference generator; calculate a target position value of the RWS system using a target position calculator of the RWS system; calculating a motor torque required for estimating a position of the RWS system using an RWS position controller; and driving a motor for estimating the position of the RWS system using the calculated motor torque.Executing the instructions by the one or more processors may further cause the one or more processors to estimate lateral velocity and disturbance based on a sensor signal transmitted from an in-vehicle network and front and rear wheel steering angles, when estimating the vehicle state using the vehicle state estimator.The execution of the instructions by the one or more processors may further cause the one or more processors to generate the reference representing the vehicle state based on a drive mode, a sensor signal transmitted from an in-vehicle network, and a front wheel steering angle, when generating the reference representing the vehicle state using the vehicle state reference generator.Executing the instructions by the one or more processors may further cause the one or more processors to update map data required for generating the reference representing the vehicle state using the vehicle state reference generator upon generating the reference representing the vehicle state using the vehicle state reference generator.The execution of the instructions by the one or more processors may further cause the one or more processors to calculate the target position value of the RWS system based on the front wheel steering angle, the vehicle state representative reference generated by the vehicle state reference generator, the sensor signal transmitted from the in-vehicle network, and the lateral speed and the disturbance estimated by the vehicle state estimator, in calculating the target position value of the RWS system using the target position calculator of the RWS system.Executing the instructions by the one or more processors may further cause the one or more processors to calculate a target motor torque based on an RWS target position value generated by the RWS target position generator and an RWS rack position value, in calculating the motor torque required to estimate the position of the RWS system using the RWS position controller.According to the present disclosure, it is possible to provide an independent stability control function using rear wheel steering (RWS), thereby preparing for the absence or failure of existing ESC stability control functions.Further, the present disclosure may provide intuitive tuning in vehicle dynamics, thereby reducing the time required for tuning and allowing vehicle performance to be optimized more efficiently.Further, the present disclosure may improve user experience by offering various response characteristics depending on a driving mode, and may provide a personalized driving environment tailored to individual drivers' driving styles and conditions.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a block diagram schematically showing the main operation part of an RWS system according to an embodiment of the present disclosure. FIG. 2 is a block diagram showing an apparatus for controlling vehicle stability based on RWS according to an embodiment of the present disclosure. FIG. 3 is a block diagram showing the configuration of a vehicle state reference generator. FIGS. 4A and 4B are diagrams showing a wheel base and an O.G. positional relationship. FIG. 5 is a diagram showing a method of changing a parameter when a drive mode changes. FIG. 6 is a flowchart illustrating a method of controlling vehicle stability based on RWS according to an embodiment of the present disclosure.DETAILED DESCRIPTIONEmbodiments of the present disclosure will be described in detail below with reference to the accompanying drawings so that those skilled in the art can easily practice the present disclosure. When the present disclosure is described with reference to the accompanying drawings, components may be denoted by different reference numerals in the drawings even if the components are denoted by the same name. The reference numerals are merely denoted for convenience of description, and the concept, feature, function, or effect of each component is not limited by the reference numerals.Hereinafter, a method and an apparatus for controlling vehicle stability based on an RWS system according to the present disclosure will be described in detail with reference to the accompanying drawings.FIG. 1 is a block diagram schematically showing the main operation part of an RWS system according to an embodiment of the present disclosure.Referring to FIG. 1, the RWS system 100 may be included in a vehicle 110 and include a sensor unit 101, an ECU 102, and an RWS motor 103.The sensor unit 101 may include an inertial measurement unit (IMU), a steering angle sensor, a wheel speed sensor, and so forth. The IMU may be a sensor configured to provide information about the motion of the vehicle 110 and measure the acceleration and yaw rate of the vehicle 110 by combining an accelerometer and a gyroscope. The measured data transmits information about the current state of motion of the vehicle 110, such as pitch, yaw, or roll, to the ECU, thereby providing data essential for controlling the stability of the vehicle 110. The steering angle sensor may be a sensor configured to detect a steering input of a driver and transmit the input to the ECU. The steering angle sensor may play an important role in determining the direction of the vehicle 110 that the driver intends. The wheel speed sensor may measure the rotational speed of each wheel and provide the speed information of the vehicle 110 to the ECU in real time. This is in particular information necessary to set the steering reaction of the RWS system depending on the speed of the vehicle 110.The ECU 102 may operate as the "brain" of the vehicle 110 and process and analyze data collected from sensors. The ECU 102 may integrate various pieces of data collected from the sensors of the vehicle 110 to provide overall information on the current state of the vehicle 110, and may apply control logic based on the integrated data to determine a task to be performed by the RWS engine 103. This may include the process of calculating the steering angle of a rear wheel to control the stability of the vehicle 110. Next, a steering signal may be sent to the RWS motor 103 to control the stability of the vehicle 110. Further, the ECU 102 may diagnose the problems of the system and manage communication with other vehicle systems.The RWS motor 103 may be a driving device configured to adjust the steering angle of the rear wheel in response to a control signal received from the ECU 102. The RWS motor 102 may have a precise controllability and a fast response speed, and may exert sufficient force to overcome friction between a steering mechanism of the vehicle 110 and a road surface.The operational relationship among the sensors of the sensor unit 101, the ECU 102, and the RWS motor 103 may include a sequential and repetitive process. The sensors may continually collect data and the data collected by the sensors may be transmitted to the ECU 102. The ECU 102 may process the transmitted data and give an instruction to the RWS motor 103 to set the RWS angle. The adjustment of the steering angle may change the trajectory of the vehicle 110 and the changed trajectory may be detected again by the sensors, thereby generating a continuous loop of feedback and adjustment. The closed loop system (closed loop system) may enable a highly sensitive and adaptable RWS system. When the driver can make the steering input, the steering angle sensor may inform the ECU 102 of an intended direction, the ECU 102 may calculate an optimum RWS angle based on the current dynamic data of the vehicle 110, and set the RWS motor 103. The RWS engine 103 may adjust the rear wheel to assist maneuverability while maintaining stability of the vehicle 110. The result of this adjustment can be continuously monitored by the sensors and adjusted in real time.FIG. 2 is a block diagram showing an apparatus for controlling vehicle stability based on RWS according to an embodiment of the present disclosure.The vehicle stability control device 200 based on the RWS shown in FIG. 2 may be performed by the ECU 102 shown in FIG. 1 and may be performed by at least one processor included in the ECU 102. Instructions for operating the processors may be stored in a memory included in the ECU 102, but the processor may be integrated with the memory instead of being separate from the memory. For example, the memory may be implemented as a nonvolatile memory such as ROM, PROM, EPROM, EEPROM, flash memory, PRAM, MRAM, RRAM, or FRAM, or may be implemented as a volatile memory such as DRAM, SRAM, SDRAM, PRAM, RRAM, or FeRAM.Referring to FIG. 2, the vehicle stability control apparatus 200 based on the RWS may include a vehicle state reference generator 210, a vehicle state estimator 220, an RWS target position calculator 230, and an RWS position controller 240.The vehicle state reference generator 210 may receive a front wheel steering angle, a drive mode, and a sensor signal transmitted from an in-vehicle network, and may generate a reference indicating a vehicle state. The front wheel steering angle may be transmitted to the vehicle state reference generator 210 in the form of data or information. The driving mode may be, for example, a normal mode, an eco mode, a sport mode, a winter mode, etc. The data or information indicating the driving mode may be transmitted to the vehicle state reference generator 210. Further, acceleration and angular velocity from the IMU, the rotational speed of each wheel from the wheel speed sensor, and data from other sensors indicating the vehicle stability may be transmitted to the vehicle state reference generator 210. That is, data on the front wheel steering angle, data on the drive mode, and data from the sensors through the in-vehicle network may be transmitted to the vehicle state reference generator 210. For example, the in-vehicle network may use a controller area network (CAN), a local interconnect network (LIN), FlexRay, Ethernet, etc.The vehicle state reference generator 210 may generate a "reference signal" or a "reference" indicating the vehicle state based on data on the front wheel steering angle, data on the drive mode, and data from the sensors through the in-vehicle network.The vehicle state estimator 220 may receive sensor signals and front / rear steering angles transmitted from the in-vehicle network, and may estimate lateral speed and disturbance. The lateral speed may refer to the speed at which the vehicle can move laterally even while traveling straight, and the lateral speed may directly influence the vehicle stability and steering response. The disturbance may include environmental factors such as road grade, irregularities, and wind, or internal factors such as a change in vehicle load.The RWS target position calculator 230 may receive the reference signal generated by the vehicle state reference generator 210 and the lateral speed and disturbance estimated by the vehicle state estimator 220 to calculate an RWS target position value. The RWS target position calculator 230 may analyze the reference signal transmitted from the vehicle state reference generator 210 and may process data on the lateral speed and disturbance provided from the vehicle state estimator 220. The RWS target position calculator 230 may calculate a target position value to be reached by the RWS based on the received data.The RWS position controller 240 may receive an RWS target position value generated by the RWS target position calculator 230 and an RWS rack position value, and may calculate a target motor torque value. The RWS position controller 240 may generate the target motor torque value based on the received RWS target position value and the current rack position value. The target torque value may define a torque to be generated by the engine of the RWS system and may provide force required to adjust the steering angle of the vehicle by the RWS system.FIG. 3 is a block diagram showing the configuration of a vehicle state reference generator 300.The vehicle state reference generator 300 of FIG. 3 may include and perform the function and operation of the vehicle state reference generator 210 according to the embodiment of FIG. 2. Referring to FIG. 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 RAM or ROM, and may change a curve set based on the driving mode.To be more specific, the vehicle state reference generator 300 may use a dynamic model based on two-wheel steering. The dynamic model based on two-wheel steering may use, for example, static (steady-state) dynamics or single-track (single-track) dynamics. The two-wheel steering-based dynamic model applied to the present disclosure will be described in detail later.The vehicle parameter curve set unit 310 may change or adjust the curve set representing the dynamic response of the vehicle according to the driving mode of the vehicle. Using data stored in the memory such as RAM or ROM, the response characteristics of the vehicle can be set differently for each drive mode. For example, in sport mode, a curve may be adjusted for a faster steering response. In ecomode, a curve for optimizing fuel efficiency may be adjusted. A method of changing or adjusting the parameter graph according to the driving mode will be described in detail in FIG. 5, which will be described later.The target vehicle parameter selector 320 may determine a wheel base and a center-of-gravity (C.O.G.) position of the vehicle based on the vehicle speed and the curve set changed in the vehicle parameter curve set unit 310.FIGS. 4A and 4B are diagrams showing a wheel base and a C.O.G. positional relationship.When the wheel base and the C.O.G. positional relationship may be described with reference to FIGS. 4A and 4B, the wheel base (also referred to as wheel base or wheel distance) may refer to a length between front and rear wheel axles of the vehicle. By adjusting the wheel base according to the vehicle speed, a desired vehicle response can be generated. For example, when traveling at high speeds, the wheel base may be extended to increase stability. When driving at low speeds, the wheel base may be shortened to improve maneuverability. This adjustment can be made by electronic or mechanical means.The C.O.G. positional relationship may refer to a relationship of a length from the front wheel to the C.O.G. point of the vehicle to an entire wheel base. By adjusting the C.O.G. position ratio, the center of gravity of the vehicle may be moved forward or backward to produce the desired vehicle response. As the center of gravity moves forward, more weight may be applied to the front wheel of the vehicle, thereby increasing responsiveness to the steering. When the center of gravity can move backward, the stability of the rear wheel may increase. That is, the wheel base and C.O.G. positional relationship may be adjusted such that the vehicle may be optimized by the design and adjustment of the vehicle for given driving conditions.Referring back to FIG. 3, the vehicle state reference generator 300 may change the response characteristics of the vehicle by adjusting the wheel base and the C.O.G. position ratio of the vehicle in real time according to the vehicle speed.The reference calculator 330 may calculate the yaw rate and lateral speed of the vehicle in consideration of the wheel base and the C.O.G. position together with the front wheel steering angle. That is, the vehicle parameter curve set unit 310 may determine a curve set among a plurality of curve sets composed of pairs of a wheel base curve defining vehicle response characteristics depending on the driving mode and a C.O.G. curve, the target vehicle parameter selector 320 may determine the wheel base and the C.O.G. position based on the current vehicle speed and the curve set, and the reference calculator 330 may combine the information with the front wheel steering angle to calculate the yaw rate and lateral speed of the vehicle. The dynamic state reference of the vehicle generated by this process may be used by a vehicle control system and may serve as a standard for ensuring vehicle stability and the response to the driver's steering intention.FIG. 5 is a diagram showing a method of changing a parameter when a drive mode changes. Referring to FIG. 5, parameters that determine the response characteristics of the vehicle may be changed depending on the driving mode of the vehicle. That is, the parameter curve set may be changed depending on the driving mode, and references having different response characteristics may be generated depending on the combination of the wheel base of the vehicle and the C.O.G. position curve set. Here, the x-axis of a wheel base diagram may represent the vehicle speed and the y-axis may represent the vehicle wheel base value, which may be set to a value greater than 0. Further, the x-axis of the C.O.G. plot may represent vehicle speed and the y-axis represents the center of gravity of the vehicle and may be a value between 0 and 1. When the center of gravity is located at the front of the vehicle, the value is set to 0. When the center of gravity is located at the rear of the vehicle, the value is set to 1.Depending on the driving mode, another set of curves composed of the wheel base curve and the C.O.G. curve may be selected. A selected set of curves, for example one of a set of curves for mode 1, a set of curves for mode 2, and a set of curves for mode N, may be selected. The wheel base and C.O.G. position may then be adjusted based on the set of curves selected depending on the vehicle speed.Referring again to FIG. 3, the reference calculator 330 may generate a reference by substituting the wheel base and the C.O.G. position value into the dynamic model based on two-wheel steering.In an embodiment of the present disclosure, the two-wheel steering-based dynamic model may be either the static (steady-state or steady-state) dynamic model or the single-track (single-track) dynamic model. But without being limited thereto, the two-wheel steering-assisted dynamic model can be selected in various ways depending on the requirements of the person skilled in the art.When the static (steady-state or steady-state) dynamic model according to an embodiment of the present disclosure is used, a yaw rate y, a lateral velocity V y, and an understeer gradient (understeer gradient) K us may be calculated according to Equations 1 to 3 below.Here, L represents the wheel base of the vehicle, V x represents the longitudinal speed, K us represents the understeer gradient, and δ f represents the steering angle of the front wheel.Here, l is f= L × x cog and l is r= L - l is f, L represents the wheel base of the vehicle, l is f represents a length between the front axle and the center of gravity, l is r represents a length between the rear axle and the center of gravity, x is cog represents a C.O.G. positional relationship, V is x represents a longitudinal speed, K is us represents the understeer gradient, δ is f represents the steering angle of the front wheel, and M represents the mass of the vehicle.Here, l is f= L × x cog and l is r= L - l is f, L represents the wheel base of the vehicle, l is f represents the length between the front axle and the center of gravity, l is r represents the length between the rear axle and the center of gravity, x is cog represents a C.O.G. positional relationship, M represents the mass of the vehicle, C is f represents the cornering rigidity of a front wheel, and C is r represents the cornering rigidity of a rear wheel.When the single track (single track) dynamic model according to another embodiment of the present disclosure is used, the yaw rate y and the lateral speed V y may be calculated according to Equation 4 below. where l is f= L×x cog l is r= L- l is f L represents the wheel base of the vehicle, l is f represents a length between the front axle and the center of gravity, l is r represents a length between the rear axle and the center of gravity, x is cog represents a C.O.G. positional relationship, C af represents the cornering rigidity (cornering rigidity) of the front wheel, C ar represents the cornering rigidity (cornering rigidity) of the rear wheel, V x represents the longitudinal speed, δ f represents the steering angle of the front wheel, m represents the mass of the vehicle, and I Z represents a z-axis moment of rigidity of the vehicle.FIG. 6 is a flowchart illustrating a method of controlling vehicle stability based on an RWS system according to an embodiment of the present disclosure.The method shown in FIG. 6 may be performed by an electronic control unit (ECU) of the vehicle and may be performed by at least one processor included in the electronic control unit. Each function performed by at least one processor included in the electronic control unit may be divided into hardware according to the internal function of the processor to perform individual functions. Moreover, the electronic control unit may include a memory, and the memory may store instructions to perform the following steps.Referring to FIG. 6, when the vehicle ignition is in an ON state in step S 601, sensor data may be received from the sensors of the vehicle in step S 602. The sensors of the vehicle may include an inertial measurement unit (IMU), a steering angle sensor, and a wheel speed sensor, etc.In step S 603, the vehicle state estimator may estimate a vehicle state. More preferably, the sensor signal and the front and rear wheel steering angles transmitted from the in-vehicle network may be received to estimate lateral speed and disturbance.In step S 604, the driving mode of the vehicle may be received and updated from the vehicle state reference generator. In step S 605, map data required for generating the vehicle state reference may be received and updated.In step S 606, the vehicle state reference generator may generate a vehicle state reference. More preferably, the vehicle state reference generator may generate a reference representing the vehicle state using the two-wheel steering-based dynamic model. The two-wheel steering-based dynamic model may use the static (steady-state) dynamic model described above or a single-track dynamic model.In step S 607, the target position calculator of the RWS system may calculate the target position value of the RWS. More preferably, the front wheel steering angle, the reference representing the vehicle state generated by the vehicle state reference generator, the sensor signal transmitted from the in-vehicle network, and the lateral speed and disturbance estimated by the vehicle state estimator may be received, and the target position value of the RWS system may be calculated.In step S 608, the RWS position controller may calculate an engine torque required to estimate the position of the RWS system. More preferably, the RWS target position value generated by the RWS target position generator and the RWS rack position value may be received, and then the required target motor torque may be calculated.In step S 609, the motor for estimating the position of the RWS system may be driven by the calculated motor torque.In step S 610, it is determined whether the ignition is OFF. When the ignition is OFF, the operation may be stopped. In contrast, when the ignition is not OFF, steps S 602 to S 609 may be repeated again.The apparatus and method described above may be implemented with hardware components, software components, and / or a combination of hardware components and software components. For example, devices and components described in embodiments may be implemented using one or more general purpose or special purpose computers, such as a processor, controller, arithmetic logic unit (ALU), digital signal processor, microcomputer, field programmable gate array (FPGA), programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. A processing device may execute an operating system (OS) and one or more software applications running on the OS. Further, in response to execution of software, the processing device may access, store, manipulate, process, and generate data. For example, the processing device may include a plurality of processors, or a processor and a controller. Further, other processing configurations, such as a parallel processor, are possible.Although embodiments of the invention have been described with reference to the accompanying drawings, it will be apparent to those skilled in the art that various changes and modifications can be made from the above description. For example, even if the described techniques are performed in an order different from the described method, and / or components of the described system, structure, device, circuit, etc. are coupled or combined in a form different from the described method, or are replaced or replaced with other components or equivalents, proper results may be achieved.Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the claims described below.[List of Reference Numerals]100: RWS system 101: sensor unit 102: ECU 103: RWS engine 200: apparatus for controlling vehicle stability based on RWS 210: vehicle state reference generator 220: vehicle state estimator 230: RWS target position calculator 240: RWS position controller 300: vehicle state reference generator 310: vehicle parameter curve set unit 320: target vehicle parameter selector 330: reference calculatorReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedKR 10-2024-0002160

[0001] KR 10-2263187

[0006] KR 10-2463701

[0006]

Claims

An apparatus for controlling vehicle stability based on rear wheel steering (RWS), the apparatus comprising: a vehicle state reference generator that generates a reference representing a vehicle state based on a front wheel steering angle, a drive mode, and a sensor signal transmitted from an in-vehicle network; a vehicle state estimator that estimates a lateral speed and disturbance based on the front wheel and rear wheel steering angles and the sensor signal transmitted from the in-vehicle network; an RWS target position calculator that generates an RWS target position value based on the reference generated by the vehicle state reference generator, the sensor signal transmitted from the in-vehicle network, the front wheel steering angle, and the lateral speed and the disturbance estimated by the vehicle state estimator; 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 an RWS rack position value.The apparatus according to claim 1, wherein the vehicle state reference generator comprises a vehicle parameter curve set unit, a target vehicle parameter selector, and a reference calculator, the vehicle parameter curve set unit determines a curve set among a plurality of curve sets composed of pairs of a wheel base curve defining vehicle response characteristics depending on the driving mode and a center of gravity curve (C.O.G.), the target vehicle parameter selector selects a wheel base and a C.O.G. position based on a current vehicle speed and the curve set determined by the vehicle parameter curve set unit, and the reference calculator calculates a reference based on the front wheel steering angle, the wheel base, and the C.O.G. position selected by the target vehicle parameter selector.The apparatus of claim 2, wherein calculating the reference based on the wheel base and the C.O.G. position selected by the target vehicle parameter selector comprises calculating the reference by receiving the wheel base and the C.O.G. position as input values for a two-wheel steering-based dynamic model.The apparatus of claim 3, wherein the two-wheel steering-based dynamic model is a static (steady-state) dynamic model, and the static (steady-state) dynamic model is defined by the following equations 1 to 3, γ = V x L + K u s V x 2 δ f V y = V x ( l r - ( M l f V x 2 C r L ) ) ) L + K u s V x 2 δ f K u s = M L ( l r C f - l f C r ) where L represents the wheel base of the vehicle, V x represents the longitudinal speed, K us represents an understeer (understeer) gradient, δ f represents the steering angle of the front wheel, l f= is L × x cog x cog represents a C.O.G. positional relationship, l f= is L - l f l f represents a length between a front axle and the center of gravity, l r represents a length between a rear axle and the center of gravity, M represents a mass of the vehicle, C f represents a cornering rigidity (cornering rigidity) of a front wheel, and C r represents cornering rigidity of a rear wheel.The apparatus of claim 3, wherein the two-wheel steering-based dynamic model is a single-track dynamic model, and the single-track dynamic model is defined by the following equation 4, [V%0020̇ yγ%0020̇] = [- 2 (C α f + C α r) m V x - V x - 2 (C α f l f - C α r l r) m V x - 2 (C α f l f + C α r l r) I z V x - 2 (C α f l f 2 + C α r l r 2) I z V x] [V y γ] + [2 C α f m 2 C α f l f I z] δ f where l is f= L × x cog l is r= L - l f L represents the wheel base of the vehicle, l f represents a length between the front axle and the center of gravity, l r represents a length between the rear axle and the center of gravity, x cog represents a C.O.G. positional relationship, C af represents the cornering rigidity (cornering rigidity) of the front wheel, C ar represents the cornering rigidity (cornering rigidity) of the rear wheel, V x represents the longitudinal speed, δ f represents the steering angle of the front wheel, m represents the mass of the vehicle, and I Z represents a z-axis moment of rigidity of the vehicle.A method for controlling vehicle stability based on an RWS performed by an electronic control unit (ECU) of a vehicle, the method comprising: generating, by a vehicle state reference generator, a reference representing a vehicle state based on a front wheel steering angle, a drive mode, and a sensor signal transmitted from an in-vehicle network; estimating, by a vehicle state estimator, lateral speed and disturbance based on front wheel and rear wheel steering angles and the sensor signal transmitted from the in-vehicle network; calculating, by an RWS target position calculator, an RWS target position value based on the vehicle state reference, the sensor signal transmitted from the in-vehicle network, the front wheel steering angle, and the estimated lateral speed and disturbance; and generating, by an RWS position controller, a target motor torque based on the calculated RWS target position value and an RWS rack position value.The method of claim 6, wherein generating the reference representing the vehicle state comprises: determining a set of curves among a plurality of sets of curves composed of pairs of a wheel base curve defining vehicle response characteristics depending on the driving mode and a center of gravity curve (C.O.G.); selecting a wheel base and a C.O.G. position based on a current vehicle speed and the set of curves determined by the vehicle parameter set unit; and calculating a reference based on the front wheel steering angle, the wheel base, and the C.O.G. position selected by the target vehicle parameter selector.The method of claim 7, wherein calculating the reference based on the wheel base and the C.O.G. position selected by the target vehicle parameter selector comprises calculating the reference by receiving the wheel base and the C.O.G. position as input values for a two-wheel steering-based dynamic model.The method of claim 8, wherein the two-wheel steering-based dynamic model is one of a static (steady-state) dynamic model and a single-track dynamic model.An apparatus for controlling vehicle stability based on a rear wheel steering (RWS) system, the apparatus comprising: one or more memory units storing instructions; and one or more processors executing the instructions, wherein execution of the instructions by the one or more processors causes the one or more processors to: receive sensor data collected in an electronic device of the vehicle; estimate a vehicle state using a vehicle state estimator; generate a reference representing a vehicle state using a vehicle state reference generator; calculate a target position value of the RWS system using a target position calculator of the RWS system; calculating a motor torque required for estimating a position of the RWS system using an RWS position controller; and driving a motor for estimating the position of the RWS system using the calculated motor torque.The apparatus of claim 10, wherein executing the instructions by the one or more processors causes the one or more processors to estimate lateral velocity and disturbance based on a sensor signal transmitted from an in-vehicle network and front and rear wheel steering angles, when estimating the vehicle state using the vehicle state estimator.The apparatus of claim 10 or 11, wherein executing the instructions by the one or more processors causes the one or more processors to generate the reference representing the vehicle state based on a drive mode, a sensor signal transmitted from an in-vehicle network, and a front wheel steering angle, when generating the reference representing the vehicle state using the vehicle state reference generator.The apparatus of one or more of claims 10 to 12, wherein executing the instructions by the one or more processors causes the one or more processors to update map data required for generating the reference representing the vehicle state using the vehicle state reference generator upon generating the reference representing the vehicle state using the vehicle state reference generator.The apparatus of one or more of claims 10 to 13, wherein executing the instructions by the one or more processors causes the one or more processors to calculate the target position value of the RWS system based on the front wheel steering angle, the vehicle state representative reference generated by the vehicle state reference generator, the sensor signal transmitted from the in-vehicle network, and the lateral velocity and the disturbance estimated by the vehicle state estimator, in calculating the target position value of the RWS system using the target position calculator of the RWS system.The apparatus of one or more of claims 10 to 14, wherein executing the instructions by the one or more processors causes the one or more processors to calculate a target motor torque based on a target RWS position value generated by the target RWS position generator and a rack RWS position value, in calculating the motor torque required to estimate the position of the RWS system using the RWS position controller.

Images