Apparatus for steering by wire of vehicle and control method thereof

Abstract

The present invention relates to an electronic steering system for a vehicle and a control method thereof. The electronic steering system for a vehicle comprises: a vehicle speed sensor; a steering angle sensor for detecting a steering angle; an inertia sensor for measuring the inertia of a vehicle; a road wheel drive module; and a processor operatively coupled to the vehicle speed sensor, the steering angle sensor, the inertia sensor, and the road wheel drive module. The processor calculates the inclination angle of the vehicle based on the inertia of the vehicle, adjusts the variable TGR gear ratio based on the inclination angle, and calculates the front wheel steering angle based on the steering angle and vehicle speed by applying the variable TGR gear ratio to drive the road wheel drive module.

Description

Technology Field

[0001] The present invention relates to an electronic steering system for a vehicle and a control method thereof, and more specifically, to an electronic steering system for a vehicle and a control method thereof that variably adjusts the TGR gear ratio according to the bank angle of the vehicle. Background Technology

[0002] Generally, power steering systems have been developed and applied to vehicle steering devices to assist the driver's steering wheel operation force and provide convenience in driving. These power steering systems include hydraulic types utilizing hydraulic pressure, electro-hydraulic types utilizing both hydraulic pressure and motor power, and electric types utilizing only motor power.

[0003] Recently, electronic steering systems using the SBW (Steer By Wire) method have been developed and are being applied. These systems eliminate mechanical connecting devices between the steering wheel and the wheels, such as steering columns, universal joints, and pinion shafts, and control the driving of motors connected to rack bars using electrical signals to enable vehicle steering.

[0004] Such an electronic steering system may be configured to include a steering wheel for steering operation by a driver, a reaction motor installed on one side of the steering wheel to provide a reaction torque according to the rotation of the steering wheel, a steering motor connected to a rack bar to implement steering operation, a sensor for detecting steering angle, vehicle speed, and torque of the steering wheel, and an ECU that drives the steering motor and the reaction motor according to an electrical signal input from the sensor.

[0005] Since this type of SBW electronic steering system has no mechanical connections, it can reduce driver injuries caused by mechanical parts during a collision. Additionally, it offers the advantages of vehicle weight reduction by eliminating mechanical components and decreasing unnecessary energy consumption during steering, as well as the ability to achieve ideal steering performance through ECU programming, leading to a growing trend in its use.

[0006] The background technology of the present invention is disclosed in Korean Published Patent Application No. 10-2022-0064012 (published May 18, 2022, Steering control device and method of SBW system).

[0007] The information described above disclosed in the background technology of this invention is intended only to enhance understanding of the background of the present invention and may therefore include information that does not constitute prior art. The problem to be solved

[0008] As such, the SBW-type electronic steering system eliminates the mechanical connection structure of conventional steering systems, thereby increasing the layout freedom according to the steering system configuration, and since the steering column is eliminated, various driving control techniques such as variable gear ratios can be applied without physical constraints.

[0009] However, most conventional vehicle driving control systems are designed based on fixed gear ratios and steering angles, which limits their ability to deliver optimal turning performance under special road conditions such as inclines.

[0010] When driving on an incline, the turning characteristics according to the change in the vehicle's bank angle are not sufficiently reflected, so the driver is required to take unnecessary or excessive steering angles, which results in the steering response becoming overly sensitive at high speeds and the efficiency of torque transmission decreasing at low speeds.

[0011] In addition, there is a problem in that using a fixed gear ratio on inclines makes it difficult to optimize the vehicle's turning radius.

[0012] The present invention has been devised to improve the aforementioned problems, and the objective of the present invention according to one aspect is to provide an electronic steering device for a vehicle and a control method thereof that improves driving stability and fuel efficiency by maintaining the same turning radius through optimizing the ratio of the tire angle to the steering angle even when driving on an incline by variably adjusting the TGR gear ratio according to the vehicle's inclination angle.

[0013] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems can be clearly understood by those skilled in the art from the description of the invention below. means of solving the problem

[0014] An electronic steering system for a vehicle according to one aspect of the present invention comprises: a vehicle speed sensor; a steering angle sensor for detecting a steering angle; an inertia sensor for measuring the inertia of a vehicle; a road wheel drive module; and a processor operatively coupled to the vehicle speed sensor, the steering angle sensor, the inertia sensor, and the road wheel drive module; wherein the processor calculates the inclination angle of the vehicle based on the inertia of the vehicle, adjusts the variable TGR gear ratio based on the inclination angle, and calculates the front wheel steering angle based on the steering angle and vehicle speed by applying the variable TGR gear ratio to drive the road wheel drive module.

[0015] In the present invention, the processor is characterized by adjusting the variable TGR gear ratio to maintain the same turning radius as on flat ground.

[0016] In the present invention, the processor is characterized by switching from a fixed TGR gear ratio to a variable TGR gear ratio and applying it when the inclination angle exceeds a set inclination angle.

[0017] In the present invention, the processor is characterized by gradually transitioning through an exponential smoothing filter when switching from a fixed TGR gear ratio to a variable TGR gear ratio.

[0018] In the present invention, the processor calculates the inclination angle of the vehicle and, when the inclination angle is less than the set inclination angle, calculates the front wheel steering angle based on the fixed TGR gear ratio, steering angle, and vehicle speed to drive the road wheel drive module.

[0019] A control method for an electronic steering system of a vehicle according to another aspect of the present invention comprises the steps of: a processor receiving vehicle speed, steering angle, and vehicle inertia; a processor calculating a vehicle inclination angle based on the vehicle inertia; a processor adjusting a variable TGR gear ratio based on the vehicle inclination angle; and a processor applying the variable TGR gear ratio to calculate a front wheel steering angle based on the steering angle and vehicle speed and driving a road wheel drive module.

[0020] In the present invention, the step of adjusting the variable TGR gear ratio is characterized by the processor adjusting the variable TGR gear ratio so that it maintains the same turning radius as on flat ground.

[0021] In the present invention, when applying a variable TGR gear ratio, the processor is characterized by switching from a fixed TGR gear ratio to a variable TGR gear ratio and applying it when the inclination angle exceeds a set inclination angle.

[0022] In the present invention, when switching from a fixed TGR gear ratio to a variable TGR gear ratio, the processor is characterized by gradually switching by applying an exponential smoothing filter.

[0023] The present invention is characterized by further including the step of driving a road wheel drive module by calculating a front wheel steering angle based on a fixed TGR gear ratio, a steering angle, and a vehicle speed when the vehicle's inclination angle is less than a set inclination angle. Effects of the invention

[0024] An electronic steering device for a vehicle and a control method thereof according to one aspect of the present invention can optimize steering sensitivity on inclines and reduce unnecessary steering angles by optimizing the ratio of tire angle to steering angle even when driving on an incline by variably adjusting the TGR gear ratio according to the vehicle's incline angle, thereby maintaining the same turning radius, and can improve driving stability and fuel efficiency by providing stable turning performance.

[0025] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by those skilled in the art from the description of the invention below. Brief explanation of the drawing

[0026] FIG. 1 is a block diagram showing an electronic steering system of a vehicle according to one embodiment of the present invention. FIG. 2 is a flowchart illustrating a control method for an electronic steering system of a vehicle according to an embodiment of the present invention. Specific details for implementing the invention

[0027] Hereinafter, an example of an electronic steering device for a vehicle and a control method thereof according to one embodiment of the present invention will be described.

[0028] In this process, the thickness of lines or the size of components depicted in the drawings may be exaggerated for the sake of clarity and convenience of explanation. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intent or convention of the user or operator. Therefore, the definitions of these terms should be based on the content throughout this specification.

[0029] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0030] Throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0031] The implementations described herein may be implemented, for example, as methods or processes, devices, software programs, data streams, or signals. Even if discussed only in the context of a single form of implementation (e.g., discussed only as a method), the implementation of the discussed features may also be implemented in other forms (e.g., devices or programs). Devices may be implemented in appropriate hardware, software, and firmware, etc. Methods may be implemented in devices such as processors, which generally refer to processing devices including, for example, computers, microprocessors, integrated circuits, or programmable logic devices.

[0032] FIG. 1 is a block diagram showing an electronic steering system of a vehicle according to one embodiment of the present invention.

[0033] As illustrated in FIG. 1, an electronic steering device for a vehicle according to one embodiment of the present invention may include a vehicle speed sensor (10), a steering angle sensor (20), an inertia sensor (30), a road wheel drive module (60), a memory (40), and a processor (50).

[0034] The vehicle speed sensor (10) can detect the vehicle speed.

[0035] The steering angle sensor (20) can detect the steering angle of the steering wheel that the driver is steering.

[0036] The inertial sensor (30) measures the lateral acceleration of the vehicle, the y-axis acceleration (ay), and the vertical acceleration, the z-axis acceleration (az), to calculate the angle of inclination (θ) of the vehicle.

[0037] Here, the vehicle's inclination angle (θ) can be calculated as arctan(ay / az).

[0038] The inertial sensor (30) may include any one of an accelerometer, a gyroscope, an IMU sensor, a yaw rate sensor, and a gravity sensor.

[0039] The road wheel drive module (50) can drive the front wheel according to the front wheel steering angle to steer.

[0040] The memory (20) can store data related to an execution program for the operation of the electronic steering system of the vehicle and a fixed TGR gear ratio for flat terrain set by the manufacturer of the vehicle, and the stored information can be independently selected by the processor (30) as needed.

[0041] That is, various types of data generated during the execution of an operating system or application (program or applet) for driving the electronic steering system of a vehicle are stored in the memory (20). At this time, the memory (20) is a general term for a non-volatile storage device that retains stored information even when power is not supplied, and a volatile storage device that requires power to retain stored information. In addition, the memory (20) can perform the function of temporarily or permanently storing data processed by the processor (30).

[0042] Here, the memory (20) may include a magnetic storage medium or a flash storage medium in addition to a volatile storage device that requires power to maintain stored information, but the scope of the present invention is not limited thereto.

[0043] The processor (50) is operatively coupled to the vehicle speed sensor (10), steering angle sensor (20), inertia sensor (30), road wheel drive module (50) and memory (40) to control the overall operation of the electronic steering system of the vehicle, and can perform various operations by copying various programs stored in memory (20) to RAM and executing them.

[0044] In various embodiments, the processor (30) may be implemented as a digital signal processor (DSP) that processes digital signals, a microprocessor, or a time controller (TCON). However, it is not limited thereto, and the processor (30) may include one or more of a central processing unit (CPU), a micro controller unit (MCU), a micro processing unit (MPU), a controller, an application processor (AP), a communication processor (CP), or an ARM processor, or may be defined by such terms. Additionally, the processor (30) may be implemented as a System on Chip (SoC) or a large-scale integration (LSI) with a built-in processing algorithm, or may be implemented in the form of a Field Programmable Gate Array (FPGA).

[0045] That is, the processor (50) can run an execution program for an electronic steering device stored in memory (40), receive vehicle speed, steering angle and vehicle inertia from the vehicle speed sensor (10), steering angle sensor (20) and inertia sensor (30), calculate the vehicle's inclination angle based on the vehicle's inertia, and then adjust the variable TGR gear ratio based on the inclination angle.

[0046] The reason for adjusting the variable TGR gear ratio based on the angle of inclination in this invention is to enable the vehicle to drive stably when entering a left or right slope. For a vehicle to drive stably on an inclined road, it can drive stably when gravity and centrifugal force are in balance.

[0047] In this case, since gravity acts vertically on the slope, it must be distributed according to the incline, and the component of the force pushing the vehicle horizontally on the slope acts horizontally on the incline, balancing the centrifugal force. In other words, the centrifugal force and the force acting horizontally on the slope must be equal.

[0048]

[0049] Here, m is the weight of the vehicle, V is the vehicle speed, R is the turning radius of the vehicle, θ is the angle of inclination, and g is the acceleration due to gravity.

[0050] At this point, if both sides of Equation 1 are simplified and the angle of inclination (θ) is expressed using the vehicle's lateral acceleration (ay) and vertical acceleration (az), it is as Equation 2.

[0051]

[0052] And, when rearranged into the turning radius (R) of the vehicle using Equation 2, it is as shown in Equation 3.

[0053]

[0054] Meanwhile, the turning radius (R) refers to the distance from the center of rotation of the vehicle to the center of gravity, and the rear wheel turning radius (Rr) is the distance from the rear wheel to the center of rotation and can be expressed as Equation 4.

[0055]

[0056] In this case, b is the front wheel turning radius, which is the distance from the front wheel to the center of rotation.

[0057] And, the rear wheel turning radius (Rr) is determined by the front wheel steering angle (δf) as in Equation 5.

[0058]

[0059] Here, L is the vehicle's wheelbase, which is the distance between the front and rear wheels.

[0060] Therefore, by substituting the turning radius (R) based on Equations 4 and 5, it can be rearranged as Equation 6.

[0061]

[0062] Then, by rearranging Equations 3 and 6 and simplifying both sides, the front wheel steering angle (δf) can be derived as shown in Equation 7.

[0063]

[0064] In other words, the front wheel steering angle required for a vehicle to turn stably on an incline can be dynamically derived as shown in Equation 7.

[0065] Therefore, by dynamically adjusting the front wheel steering angle by considering the vehicle's turning dynamics through mathematical equation 7, both lateral acceleration and vertical acceleration that may occur on an incline are taken into account, thereby preventing excessive slipping or unstable turning of the vehicle and enabling safe driving.

[0066] Meanwhile, the relationship between the TGR gear ratio and the front wheel steering angle can be calculated by multiplying the steering angle and the TGR gear ratio as shown in Equation 8.

[0067]

[0068] Therefore, the front wheel steering angle can be expressed using the steering angle and TGR gear ratio as shown in Equation 9.

[0069]

[0070] In this way, the front wheel steering angle is calculated by adjusting the steering angle and the variable TGR gear ratio, enabling stable turning to be maintained.

[0071] Accordingly, the processor (50) can calculate the front wheel steering angle based on the steering angle and vehicle speed by switching from a fixed TGR gear ratio to a variable TGR gear ratio when the vehicle enters an incline and the incline angle exceeds the set incline angle.

[0072] At this time, the processor (50) can adjust the variable TGR gear ratio to maintain the same turning radius as on flat ground.

[0073] After adjusting the variable TGR gear ratio in this way, the processor (50) can gradually switch through an exponential smoothing filter to prevent abrupt changes when switching from a fixed TGR gear ratio to a variable TGR gear ratio, or when switching from a variable TGR gear ratio to a fixed TGR gear ratio.

[0074] That is, as shown in mathematical formula 10, the gain (K) can be varied over time for the fixed TGR gear ratio (A) and the variable TGR gear ratio (B) to gradually switch.

[0075]

[0076] Here, the value of K can vary from 0 to 1 or from 1 to 0.

[0077] In this way, the processor (50) can calculate the front wheel steering angle by applying a variable TGR gear ratio and then drive the road wheel drive module (60).

[0078] Meanwhile, the processor (50) can calculate the inclination angle of the vehicle and, in the case of a flat surface, calculate the front wheel steering angle based on the fixed TGR gear ratio, steering angle, and vehicle speed initially set by the vehicle manufacturer and drive the road wheel drive module (60).

[0079] As described above, according to the electronic steering system of a vehicle according to an embodiment of the present invention, the TGR gear ratio is variably adjusted according to the vehicle's inclination angle to optimize the ratio of the tire angle to the steering angle even when driving on an incline, thereby maintaining the same turning radius. This optimizes steering sensitivity on an incline, reduces unnecessary steering angles, and provides stable turning performance, thereby increasing driving stability and fuel efficiency.

[0080] FIG. 2 is a flowchart illustrating a control method for an electronic steering system of a vehicle according to an embodiment of the present invention.

[0081] As illustrated in FIG. 2, in a control method for an electronic steering device of a vehicle according to an embodiment of the present invention, first, a processor (50) runs an execution program stored in a memory (40) and then receives vehicle speed, steering angle, and vehicle inertia from a vehicle speed sensor (10), a steering angle sensor (20), and an inertia sensor (30) (S10).

[0082] After receiving the vehicle speed, steering angle, and vehicle inertia in step S10, the processor (50) calculates the vehicle's inclination angle based on the vehicle's inertia (S20).

[0083] The vehicle's lateral acceleration, y-axis acceleration (ay), and vertical acceleration, z-axis acceleration (az), measured through the inertial sensor (30) can be input to calculate the vehicle's inclination angle (θ).

[0084] Here, the vehicle's inclination angle (θ) can be calculated as arctan(ay / az).

[0085] After calculating the vehicle's inclination angle in step S20, the processor (50) compares the inclination angle with the set inclination angle to determine whether the vehicle is driving on an inclination greater than the set inclination angle (S30).

[0086] In step S30, when comparing the angle of inclination with the set angle of inclination and the angle of inclination is less than the set angle of inclination, the processor (50) determines that the vehicle is driving on flat ground and calculates the front wheel steering angle based on the steering angle and vehicle speed by applying a fixed TGR gear ratio (S40).

[0087] After calculating the front wheel steering angle in step S40, the processor (50) drives the road wheel drive module (60) with the calculated front wheel steering angle (S70).

[0088] Meanwhile, in step S30, when comparing the angle of inclination with the set angle of inclination and the angle of inclination exceeds the set angle of inclination, the processor (50) determines that the vehicle is driving on an incline and adjusts the variable TGR gear ratio based on the angle of inclination of the vehicle (S50).

[0089] At this time, the processor can adjust the variable TGR gear ratio to maintain the same turning radius as on flat ground.

[0090] When the vehicle enters a left or right slope, the variable TGR gear ratio is adjusted based on the vehicle's angle of inclination to enable stable driving while maintaining the same turning radius through the balance of gravity and centrifugal force.

[0091] In other words, the front wheel steering angle required for a vehicle to turn stably on an incline can be dynamically derived as shown in Equation 7.

[0092] Therefore, by dynamically adjusting the front wheel steering angle by considering the vehicle's turning dynamics through mathematical equation 7, both lateral acceleration and vertical acceleration that may occur on an incline are taken into account, thereby preventing excessive slipping or unstable turning of the vehicle and enabling safe driving.

[0093] Therefore, the front wheel steering angle can be expressed using the steering angle and TGR gear ratio as shown in Equation 9.

[0094] In this way, the front wheel steering angle is calculated by adjusting the steering angle and the variable TGR gear ratio, enabling stable turning to be maintained.

[0095] After adjusting the variable TGR gear ratio in step S50, the processor (50) calculates the front wheel steering angle based on the steering angle and vehicle speed by applying the variable TGR gear ratio (S60).

[0096] At this time, the processor (50) can gradually switch through an exponential smoothing filter to prevent abrupt changes when switching from a fixed TGR gear ratio to a variable TGR gear ratio, or when switching from a variable TGR gear ratio to a fixed TGR gear ratio.

[0097] That is, as shown in mathematical formula 10, the gain (K) can be varied over time for the fixed TGR gear ratio (A) and the variable TGR gear ratio (B) to gradually switch.

[0098] After calculating the front wheel steering angle in step S60, the processor (50) drives the road wheel drive module (60) with the calculated front wheel steering angle (S70).

[0099] As described above, according to the control method of an electronic steering device of a vehicle according to an embodiment of the present invention, by variably adjusting the TGR gear ratio according to the vehicle's inclination angle to optimize the ratio of the tire angle to the steering angle even when driving on an incline and maintaining the same turning radius, the steering sensitivity on an incline can be optimized to reduce unnecessary steering angles and provide stable turning performance, thereby increasing driving stability and fuel efficiency.

[0100] Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom.

[0101] Therefore, the technical scope of protection of the present invention should be determined by the claims below. Explanation of the symbols

[0102] 10: Vehicle speed sensor 20: Steering angle sensor 30: Inertial sensor 40 : Memory 50 : Processor 60 : Road wheel drive module

Claims

Claim 1 An electronic steering device for a vehicle comprising: a vehicle speed sensor; a steering angle sensor for detecting a steering angle; an inertia sensor for measuring the inertia of a vehicle; a road wheel drive module; and a processor operatively coupled to the vehicle speed sensor, the steering angle sensor, the inertia sensor, and the road wheel drive module; wherein the processor calculates the inclination angle of the vehicle based on the inertia of the vehicle, adjusts the variable TGR gear ratio based on the inclination angle, and calculates the front wheel steering angle based on the steering angle and the vehicle speed by applying the variable TGR gear ratio to drive the road wheel drive module. Claim 2 An electronic steering device for a vehicle according to claim 1, wherein the processor adjusts the variable TGR gear ratio to maintain the same turning radius as on flat ground. Claim 3 An electronic steering device for a vehicle according to claim 1, characterized in that the processor switches from a fixed TGR gear ratio to a variable TGR gear ratio and applies it when the inclination angle exceeds a set inclination angle. Claim 4 An electronic steering system for a vehicle according to claim 1, characterized in that the processor transitions gradually through an exponential smoothing filter when transitioning from the fixed TGR gear ratio to the variable TGR gear ratio. Claim 5 An electronic steering device for a vehicle according to claim 1, characterized in that the processor calculates the inclination angle of the vehicle and, when the inclination angle is less than a set inclination angle, calculates the front wheel steering angle based on the fixed TGR gear ratio, the steering angle, and the vehicle speed to drive the road wheel drive module. Claim 6 A method for controlling an electronic steering device of a vehicle, characterized by comprising: a step in which a processor receives vehicle speed, steering angle, and vehicle inertia; a step in which the processor calculates the inclination angle of the vehicle based on the inertia of the vehicle; a step in which the processor adjusts a variable TGR gear ratio based on the inclination angle of the vehicle; and a step in which the processor calculates a front wheel steering angle based on the steering angle and vehicle speed by applying the variable TGR gear ratio and drives a road wheel drive module. Claim 7 A method for controlling an electronic steering system of a vehicle, wherein, in claim 6, the step of adjusting the variable TGR gear ratio is characterized by adjusting the variable TGR gear ratio so that the processor maintains the same turning radius as on flat ground. Claim 8 A control method for an electronic steering system of a vehicle according to claim 6, characterized in that when applying the variable TGR gear ratio, the processor switches from the fixed TGR gear ratio to the variable TGR gear ratio and applies it when the inclination angle exceeds the set inclination angle. Claim 9 A control method for an electronic steering system of a vehicle according to claim 8, wherein when switching from the fixed TGR gear ratio to the variable TGR gear ratio, the processor applies an exponential smoothing filter to gradually switch. Claim 10 A control method for an electronic steering device of a vehicle according to claim 6, further comprising the step of the processor calculating the front wheel steering angle based on the fixed TGR gear ratio, the steering angle, and the vehicle speed and driving the road wheel drive module when the inclination angle of the vehicle is less than the set inclination angle.

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