Steering control device, steering control method, and steering device

Abstract

A steering control device, a steering control method, and a steering device according to one embodiment of the present invention: acquire a first physical quantity relating to a steering operation amount of a steering input member, and a second physical quantity generated when a vehicle turns; the ratio of the steering operation amount of the steered wheel to the steering angle is changed according to the traveling state of the vehicle, and when the ratio is small, the change of the steering angle with respect to the change of the steering operation amount is delayed. On the basis of the second physical quantity, a target steering angle at which the degree of delay of the change in the steering angle with respect to the change in the steering operation amount is increased is acquired, and the steering motor is controlled so that the steering angle becomes the target steering angle. As a result, it is possible to suppress a steering response in which the driver feels too sensitive while ensuring good maneuverability.

Description

Technical Field

[0001] This invention relates to a steering control device, a steering control method, and a steering mechanism. Background Technology

[0002] The steering system of Patent Document 1 is configured such that, in a first steering angle region, the ratio of the change in wheel steering angle to the change in steering angle is larger than that in a second steering angle region, and the second steering angle region is a region where the change in steering angle is smaller than that in the first steering angle region. Regardless of whether it is a yaw increase operation or a yaw return operation, in the first steering angle region, compared to the second steering angle region, the delay of the change in wheel steering angle relative to the change in steering angle is increased. When the steering angle is in the second steering angle region, compared to a low vehicle speed, the ratio of the change in wheel steering angle to the change in steering angle is decreased, and the delay of the change in wheel steering angle relative to the change in steering angle is reduced. When the steering angle is in the first steering angle region, compared to a low vehicle speed, the ratio of the change in wheel steering angle to the change in steering angle is increased, and the delay of the change in wheel steering angle relative to the change in steering angle is increased.

[0003] Prior technology documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 7091995 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In a steer-by-wire steering system, the lower the vehicle speed, the smaller the ratio of the steering input to the steering wheel angle, i.e., the steering ratio (set as the quickratio), thereby improving maneuverability.

[0008] However, for example, when making a U-turn, the driver may sometimes feel an overly sensitive steering response because a small amount of steering input produces a large vehicle movement (yaw rate, lateral acceleration, etc.).

[0009] The present invention was made in view of the existing situation, and its purpose is to provide a steering control device, steering control method and steering mechanism that can ensure good handling and suppress the driver’s overly sensitive steering response.

[0010] Methods for solving problems

[0011] In one embodiment of the steering control device, steering control method, and steering apparatus of the present invention, a first physical quantity related to the steering operation amount of a steering input component receiving a steering operation performed by a driver, and a second physical quantity generated when the vehicle turns, are obtained such that the ratio of the steering operation amount to the steering wheel's steering angle is variable according to the vehicle's driving state. When the ratio of the steering operation amount to the steering angle is small, the delay of the change in the steering angle relative to the change in the steering operation amount is considered. Based on the second physical quantity, a target steering angle is obtained that increases the degree of delay of the change in the steering angle relative to the change in the steering operation amount. The motor that applies steering force to the steering wheel is controlled in such a way that the steering angle becomes the obtained target steering angle.

[0012] Invention Effects

[0013] According to the present invention, good handling can be ensured and the overly sensitive steering response felt by the driver can be suppressed. Attached Figure Description

[0014] Figure 1 This is a schematic diagram showing a vehicle equipped with a steer-by-wire system.

[0015] Figure 2 This is a block diagram representing the steering control function of the steering control device.

[0016] Figure 3 It is a line graph showing the correlation between vehicle speed and steering ratio.

[0017] Figure 4 This is a diagram illustrating the variable characteristics of the cutoff frequency in a deflection increase operation.

[0018] Figure 5 This is a diagram illustrating the variable characteristics of the cutoff frequency during the aligning (returning) operation.

[0019] Figure 6 This is a graph illustrating the characteristic that as the relative yaw rate increases, the cutoff frequency gradually decreases.

[0020] Figure 7 It is a line graph showing the changes in steering input and vehicle behavior when there is no delay between the change in steering angle and the change in steering input.

[0021] Figure 8 It is a line graph that shows the changes in steering input, steering angle, and vehicle behavior when the degree of delay is variable according to the steering input.

[0022] Figure 9It is a line graph illustrating the changes in steering input, steering angle, and vehicle behavior when the degree of delay varies according to the yaw rate and vehicle speed. Detailed Implementation

[0023] Hereinafter, based on the accompanying drawings, embodiments of the steering control device, steering control method, and steering device of the present invention will be described.

[0024] Figure 1 This is a schematic diagram showing one configuration of a vehicle 100 equipped with a steer-by-wire steering system 200.

[0025] Vehicle 100 is a four-wheeled automobile with a pair of front wheels 101 and 102 on the left and right and a pair of rear wheels 103 and 104 on the left and right.

[0026] The steering system 200 includes: a steering input device 300 that inputs the driver's steering operation of the vehicle 100 via a steering input component 310; a wheel steering device 400 that includes a wheel steering motor 410 (load wheel actuator) for imparting steering force to the steering wheels (front wheels 101, 102) of the vehicle 100; and a steering control device 500 that serves as an electronic control device for controlling the steering input device 300 and the wheel steering device 400.

[0027] Here, the steering input component 310 is mechanically separated from the front wheels 101 and 102, which are steering wheels, and the steering device 200 has a steer-by-wire steering system that changes the steering angle (in other words, tire angle) of the steering wheels by controlling the wheel steering motor 410 with a signal based on the driver's steering operation.

[0028] The steering input device 300 includes a steering input component 310, a steering reaction force application device 320, and a steering operation amount sensor 330.

[0029] The steering input unit 310 is an operating unit that accepts steering operations performed by the driver. In addition to the steering wheel, steering input units such as dial type and lever type are also used.

[0030] Furthermore, as detailed below, the present invention has the following effects: it ensures good handling and suppresses overly sensitive steering response felt by the driver.

[0031] Therefore, the present invention is more suitable for vehicles that employ a new type of steering input component 310, such as a dial type, which changes the steering angle with less steering operation by the driver.

[0032] The steering reaction force application device 320 is a unit that applies force to the steering input component 310 toward the neutral position (the straight position of the vehicle 100) and applies steering reaction force to the steering input component 310 by means of a motor or the like.

[0033] The steering operation amount sensor 330 is a sensor that detects the operation amount of the steering input component 310, i.e., the steering operation amount.

[0034] For example, when the steering input component 310 is a steering wheel or dial type steering input component, the steering operation amount sensor 330 detects the rotation angle of the steering shaft and dial, i.e., the steering operation angle θ, as the steering operation amount.

[0035] The wheel steering device 400 includes a wheel steering mechanism 420.

[0036] The wheel steering mechanism 420 is a mechanism that converts the rotational motion of the wheel steering motor 410 into the linear motion of the rack shaft 421 through a gear and rack pair, thereby changing the steering angle (tire angle) of the front wheels 101 and 102 connected to the rack shaft 421.

[0037] In addition, the wheel steering device 400 includes a rack stroke sensor 430 that detects the amount of travel of the rack shaft 421 related to the steering angle of the front wheels 101 and 102, i.e., rack travel RS [mm] (in other words, actual rack position), and a motor rotation angle sensor 440 that detects the rotation angle θ m [deg] of the wheel steering motor 410.

[0038] The steering control device 500 is an electronic control device that has a control unit, namely MCU (Micro Controller Unit) 510, which performs steering control methods.

[0039] Furthermore, the steering control device 500 controls the operation of the steering device 200 by controlling the steering reaction force application device 320 and the wheel steering motor 410 provided by the steering device 200.

[0040] In detail, the MCU510 processes various signals obtained from the outside to determine the control signals of the steering reaction force application device 320 and the wheel steering motor 410, and outputs the determined control signals.

[0041] In addition, MCU510 can also be called a microcomputer, processor, processing device, computing device, etc.

[0042] In addition, the vehicle 100 is equipped with wheel speed sensors 621-624 that detect the rotational speed of each wheel 101-104, i.e., wheel speed WS1-WS4; acceleration sensor 630 that detects the forward and backward acceleration and lateral acceleration of the vehicle 100; and yaw rate sensor 640 that detects the yaw rate generated by the vehicle 100.

[0043] Furthermore, the MCU510 of the steering control device 500 acquires the output signals from the steering operation amount sensor 330, the rack travel sensor 430, the motor rotation angle sensor 440, the wheel speed sensors 621-624, the acceleration sensor 630, and the yaw rate sensor 640.

[0044] Here, the control process of the wheel steering motor 410 by the MCU 510 of the steering control device 500 is described in detail.

[0045] The MCU510 obtains information on the steering operation amount (steering operation angle) of the steering input unit 310 from the steering operation amount sensor 330. In addition, it obtains information on the vehicle speed of the vehicle 100 from the output signals of the wheel speed sensors 621-624.

[0046] Then, the MCU510 variably sets the steering ratio based on the vehicle speed information, and calculates the target rack travel (in other words, the target rack position) equivalent to the target steering angle of the front wheels 101 and 102 based on the steering operation amount and the steering ratio.

[0047] When the MCU510 calculates the target rack travel, the MCU510 obtains the information of the actual rack travel (in other words, the actual rack position or the actual steering angle) detected by the rack travel sensor 430, and controls the steering motor 410 to make the actual rack travel close to the target rack travel.

[0048] The aforementioned steering ratio is the ratio of the steering input amount of the steering input component 310 to the steering angle of the steering wheel, and is defined as "steering ratio = steering input amount / steering angle".

[0049] Furthermore, although in this embodiment, the MCU510 uses the rack travel sensor 430 to detect the actual rack travel, the MCU510 can also calculate the actual rack travel based on the rotation angle θm of the wheel steering motor 410 detected by the motor rotation angle sensor 440.

[0050] In addition, the MCU 510 can obtain the actual rack travel by using a rotation angle sensor to detect the rotation angle of the pinion shaft of the rack and pinion.

[0051] In addition, the MCU510 can use the rotation angle signal of the motor constituting the steering reaction force application device 320 as information on the steering operation amount of the steering input unit 310.

[0052] Furthermore, when the steering input device 300 has a mechanism that converts the rotational motion of the steering input member 310 into linear motion, the MCU 510 can obtain the signal of the sensor that detects the stroke of the movable part that performs linear motion according to the rotation of the steering input member 310 as information on the steering operation amount of the steering input member 310.

[0053] As described above, the MCU510 has the function of variably setting the steering ratio based on information about the vehicle speed, which is the driving state of the vehicle 100.

[0054] Furthermore, as detailed below, the MCU510 has the following function: when the steering gear ratio is small (in other words, when the vehicle speed is low), based on the physical quantities generated when the vehicle turns 100 degrees, to obtain a target steering angle that increases the degree of delay of the change in steering angle relative to the change in the steering operation amount.

[0055] In addition, physical quantities generated when vehicle 100 turns include yaw rate, lateral acceleration, and other physical quantities related to the turning behavior of vehicle 100.

[0056] Figure 2 This is a block diagram representing the steering angle control function of the MCU510 in the steering control device 500.

[0057] The MCU 510 obtains information about the steering operation amount of the steering input component 310 from the steering operation amount sensor 330, in other words, the first physical quantity about the steering operation amount.

[0058] In addition, the MCU 510 obtains information about the yaw rate generated in the vehicle 100 from the yaw rate sensor 640, which is a second physical quantity generated when the vehicle 100 turns.

[0059] Furthermore, the MCU510 in this embodiment uses yaw rate information as a second physical quantity generated when the vehicle turns at 100 degrees, but it can also use lateral acceleration as a second physical quantity, or it can use both yaw rate and lateral acceleration as a second physical quantity.

[0060] In addition, the MCU 510 obtains information about the vehicle speed of the vehicle 100 from the output signals of the wheel speed sensors 621-624.

[0061] The MCU510 has a steering ratio control unit 511, a low-pass filter processing unit 512, a steering control unit 513, a first cutoff frequency setting unit 514, a second cutoff frequency setting unit 515, and a deflection increase / deflection return determination unit 516.

[0062] The steering ratio control unit 511 obtains information on the steering input amount and vehicle speed.

[0063] Then, the steering ratio control unit 511 sets the steering ratio variably based on the vehicle speed, and converts the steering operation amount into the target rack stroke (target steering angle) based on the steering ratio.

[0064] Here, the lower the vehicle speed, the smaller the steering ratio control unit 511 sets the steering ratio to; in other words, the steering ratio is controlled to have a larger steering angle relative to the same steering operation amount in the same direction.

[0065] Furthermore, in this application, the steering operation amount and the steering angle represent the absolute value of the displacement from the neutral position (the straight position of vehicle 100).

[0066] Figure 3 It is a graph showing the correlation between vehicle speed and steering ratio.

[0067] Figure 3 It is a graph with the horizontal axis set as the steering input, the vertical axis set as the steering angle (tire angle), and the origin set as the neutral position. It serves as a representative value for vehicle speed and illustrates the characteristics of the steering gear ratio for 20km / h, 60km / h, and 120km / h.

[0068] Here, the steering angle increases proportionally to the increase in steering input, but the greater the ratio of the increase in steering angle to the increase in steering input, i.e., the greater the slope, the smaller the steering ratio.

[0069] Moreover, in Figure 3 The slope is largest at 20 km / h (minimum speed), smallest at 120 km / h (maximum speed), and the slope is set as the median at 60 km / h (intermediate speed).

[0070] Right now, Figure 3 This shows that the lower the vehicle speed, the smaller the steering ratio becomes. Relative to the same steering input in the direction, the lower the vehicle speed, the larger the steering angle is (quick ratio).

[0071] The steering ratio control unit 511 outputs the target rack travel (target steering angle) signal, which is calculated based on the steering operation amount and the steering ratio, to the low-pass filter processing unit 512.

[0072] The low-pass filtering processing unit 512 performs low-pass filtering processing on the signal of the target rack travel (target steering angle) calculated based on the steering operation amount, so that the change of the target steering angle is phase-delayed relative to the change of the steering operation amount.

[0073] That is, the low-pass filter processing unit 512 gradually reduces the frequency components in the signal of the target rack travel that are higher than the cutoff frequency, thereby delaying the change in steering angle relative to the change in steering operation amount and the turning action of the vehicle 100.

[0074] As described above, the MCU 510 uses a low-pass filter to determine the degree of delay in the change of steering angle relative to the change in steering input.

[0075] Here, as described later, the MCU510 has the function of changing the cutoff frequency in the low-pass filter processing unit 512 based on the physical quantity generated when the vehicle 100 turns, namely the yaw rate, and the vehicle speed representing the driving state of the vehicle 100.

[0076] The steering control unit 513 acquires the signal of the target rack travel that has been low-pass filtered by the low-pass filter processing unit 512, and also acquires the signal of the actual rack travel detected by the rack travel sensor 430 and the like.

[0077] Then, the steering control unit 513 controls the current of the wheel steering motor 410 so that the actual rack travel is close to the target rack travel, that is, the actual steering angle is close to the target steering angle.

[0078] On the other hand, the first cutoff frequency setting unit 514, the second cutoff frequency setting unit 515, and the deflection increase / deflection return determination unit 516 are functional units for making the degree of delay of the cutoff frequency in the low-pass filter processing unit 512, or in other words, the change in steering angle relative to the change in direction steering operation amount, variable.

[0079] Here, the first cutoff frequency setting unit 514 makes the cutoff frequency in the low-pass filter processing unit 512 variable when the driver's directional steering operation is an operation that increases the steering angle.

[0080] On the other hand, the second cutoff frequency setting unit 515 makes the cutoff frequency in the low-pass filter processing unit 512 variable when the driver's steering operation is a steering angle deflection return operation.

[0081] In addition, the yaw increase / yaw return determination unit 516 determines whether the driver's steering operation is a steering angle yaw increase operation or a steering angle yaw return operation based on the output of the steering operation amount sensor 330 or the output of the yaw rate sensor 640.

[0082] Furthermore, the steering angle increase operation refers to the operation of increasing the absolute value of the steering angle when the steering angle at the neutral position (straight position) is set to zero, while the steering angle return operation refers to the operation of decreasing the absolute value of the steering angle.

[0083] In other words, the yaw increase / yaw return determination unit 516 determines whether the driver's steering operation is an operation of the steering input unit 310 in the direction of yaw increase from the neutral position, or an operation of the steering return from the neutral position.

[0084] Therefore, the yaw increase / yaw return determination unit 516 can determine whether the driver's yaw operation is a yaw increase operation or a yaw return operation based on whether the yaw operation amount changes in a direction away from the neutral position or in a direction closer to the neutral position.

[0085] Furthermore, as the steering angle deflects, the yaw rate increases; conversely, as the steering angle returns to center, the yaw rate decreases.

[0086] Therefore, the yaw increase / yaw return determination unit 516 can also determine whether the driver's steering operation is a steering angle yaw increase operation or a steering angle yaw return operation based on the increase or decrease of the yaw rate.

[0087] Then, based on the determination signal output by the deflection increase / deflection return determination unit 516, in the case of deflection increase operation, the first cutoff frequency setting unit 514 performs cutoff frequency variable processing, and in the case of deflection return operation, the second cutoff frequency setting unit 515 performs cutoff frequency variable processing.

[0088] In other words, the MCU510 has the function of changing the cutoff frequency in the low-pass filter processing of the target rack travel (target steering angle) based on whether the driver's directional steering operation is a steering angle deflection increase operation or a steering angle deflection return operation.

[0089] Figure 4 It is a cutoff frequency map that represents the variable characteristics of the cutoff frequency in the first cutoff frequency setting unit 514.

[0090] in addition, Figure 5 It is a cutoff frequency mapping diagram that represents the variable characteristics of the cutoff frequency in the second cutoff frequency setting unit 515.

[0091] In the cutoff frequency mapping diagrams in the first cutoff frequency setting unit 514 and the second cutoff frequency setting unit 515, the horizontal axis represents vehicle speed and the vertical axis represents yaw rate, and the cutoff frequency data is determined at each intersection point.

[0092] In addition, Figure 4 as well as Figure 5 In the cutoff frequency mapping diagram shown, the cutoff frequency is set to any one of the four: very low, low, medium, and high. However, it can also be a mapping diagram with more finely switched cutoff frequencies.

[0093] The first cutoff frequency setting unit 514 and the second cutoff frequency setting unit 515 acquire vehicle speed signals and yaw rate signals, and extract cutoff frequency data corresponding to the combination of the acquired vehicle speed signals and yaw rate signals from the cutoff frequency mapping.

[0094] Then, the first cutoff frequency setting unit 514 and the second cutoff frequency setting unit 515 set the cutoff frequency extracted from the cutoff frequency mapping to the cutoff frequency in the low-pass filter processing unit 512.

[0095] Here, the cutoff frequency diagrams in the first cutoff frequency setting unit 514 and the second cutoff frequency setting unit 515 are set such that when the vehicle speed is low (low vehicle speed domain), the cutoff frequency is lower than when the vehicle speed is high (medium-high vehicle speed domain), and the attenuation domain expands to the low frequency side.

[0096] In other words, the cutoff frequency mapping is set such that at low vehicle speeds, the change in steering angle is delayed more significantly relative to the change in steering input compared to at high vehicle speeds.

[0097] In addition, the cutoff frequency diagrams in the first cutoff frequency setting unit 514 and the second cutoff frequency setting unit 515 are set such that in the low vehicle speed region, the higher the yaw rate (the second physical quantity), the lower the cutoff frequency, and the greater the delay of the change in steering angle relative to the change in the amount of steering operation.

[0098] That is, the first cutoff frequency setting unit 514 and the second cutoff frequency setting unit 515 make the cutoff frequency variable in such a way that the lower the vehicle speed, the greater the delay of the change in steering angle relative to the change in steering input, and the greater the yaw rate, the greater the delay of the change in steering angle relative to the change in steering input.

[0099] By setting the degree of delay between changes in steering angle and changes in steering input as described above, the MCU 510 can suppress large vehicle movements (yaw rate, lateral acceleration, etc.) with a small steering input, for example, when the yaw rate is large at low speeds, such as when the vehicle 100 is making a U-turn.

[0100] Therefore, in situations with low speeds and high yaw rates, such as when the vehicle is making a U-turn at 100 degrees, it is possible to suppress the driver's overly sensitive steering response.

[0101] Here, when the cutoff frequency derived from the cutoff frequency mapping is directly applied to the low-pass filter processing unit 512, and the cutoff frequency in the low-pass filter processing unit 512 is gradually changed, the steering angle response changes drastically, and the driver's steering performance and ride comfort may deteriorate.

[0102] Therefore, when the cutoff frequency extracted from the cutoff frequency diagram is applied to the low-pass filter processing unit 512, the first cutoff frequency setting unit 514 and the second cutoff frequency setting unit 515 gradually decrease the cutoff frequency set in the low-pass filter processing unit 512 relative to the gradual increase of the yaw rate.

[0103] Figure 6 This is a graph illustrating the gradual decrease in cutoff frequency relative to a gradual increase in yaw rate.

[0104] Should Figure 6 This represents the case where the cutoff frequency gradually decreases linearly as the relative yaw rate gradually increases, and the case where the cutoff frequency gradually decreases with a quadratic curve as the relative yaw rate gradually increases.

[0105] When the cutoff frequency derived from the mapping graph gradually increases with the yaw rate, for example, switching from medium to low to extremely low, such as... Figure 6 As shown by the solid line, the MCU 510 can linearly and gradually decrease the cutoff frequency set in the low-pass filter processing unit 512 as the yaw rate gradually increases.

[0106] Furthermore, when the cutoff frequency derived from the graph gradually increases with the yaw rate, for example, switching from medium to low to extremely low, such as... Figure 6 As shown by the dashed line, the MCU 510 can gradually decrease the cutoff frequency set in the low-pass filter processing unit 512 as the yaw rate gradually increases, so that the slope increases in a quadratic curve manner.

[0107] If the relative yaw rate gradually increases, and the cutoff frequency gradually decreases in a quadratic manner as the tilt increases, the driver will hardly notice the change in responsiveness compared to a linearly decreasing change.

[0108] In this way, if the cutoff frequency set in the low-pass filter processing unit 512 gradually decreases relative to the gradual increase in yaw rate, the driver will hardly notice the change in steering response, and the driver's discomfort related to the handling of the vehicle 100 can be suppressed.

[0109] Next, the difference between the cutoff frequency during the deflection increase operation and the cutoff frequency during the deflection return operation will be explained.

[0110] The cutoff frequency set by the second cutoff frequency setting unit 515 during deflection return operation is set to a frequency lower than the cutoff frequency set by the first cutoff frequency setting unit 514 during deflection increase operation.

[0111] That is, during the yaw return operation, in order to increase the delay of the change in steering angle relative to the change in steering input, the cutoff frequency set in the yaw return operation state is set lower than the cutoff frequency set in the yaw increase operation state.

[0112] Drivers often experience an overly sensitive steering response during yaw correction maneuvers.

[0113] Therefore, compared to the increase in deflection, the MCU 510 increases the degree of delay between changes in steering angle and changes in steering input, in order to suppress the driver from feeling an overly sensitive steering response while ensuring good maneuverability.

[0114] Additionally, when switching between deflection increase and deflection return operations, if the cutoff frequency changes drastically, the direction turning operation will become stiff.

[0115] Therefore, regardless of the vehicle speed, the MCU 510 sets the cutoff frequency (delay level) when the yaw rate is zero to be the same during both the yaw return operation and the yaw increase operation.

[0116] exist Figure 4 , Figure 5 In one embodiment, during the deflection increase operation, the cutoff frequency set by the first cutoff frequency setting unit 514 is "low" at a vehicle speed of 0 km / h, "medium" at a vehicle speed of 20 km / h, and "high" at a vehicle speed of 40 km / h or higher. Similarly, during the deflection return operation, the cutoff frequency set by the second cutoff frequency setting unit 515 is "low" at a vehicle speed of 0 km / h, "medium" at a vehicle speed of 20 km / h, and "high" at a vehicle speed of 40 km / h or higher.

[0117] That is, when switching between the deflection increase operation and the deflection return operation, the yaw rate is temporarily zero.

[0118] Therefore, if the cutoff frequency when the yaw rate is zero is the same during the yaw return operation and the yaw increase operation, then the cutoff frequency (delay level) remains unchanged when switching between the yaw increase operation and the yaw return operation, and the suppression direction turning operation becomes stiff.

[0119] Next, refer to Figures 7 to 9 The effect of the MCU510 control cutoff frequency (delay level) is explained.

[0120] Figure 7This example illustrates the change in vehicle behavior relative to the steering angle (=steering angle) assuming there is no delay in the change of steering angle relative to the change of steering operation angle (operation amount).

[0121] In addition, vehicle motion refers to the changes in a second physical quantity, such as yaw rate and lateral acceleration, that occur when a vehicle makes a 100° turn.

[0122] Here, even in the absence of a delay between the change in steering angle and the change in steering operation angle, vehicle movement is generated with a delay relative to the movement of the steering wheels.

[0123] in addition, Figure 8 Examples illustrate the changes in steering angle, steering angle, and vehicle behavior when the lag between changes in steering angle and changes in steering angle is increased in regions with large steering angles compared to regions with small steering angles.

[0124] exist Figure 8 Even when the yaw rate is still high when the yaw returns to center, the steering angle becomes smaller, thus reducing the delay between the change in steering angle and the change in steering angle. Therefore, the driver does not feel an overly sensitive steering response.

[0125] In other words, when the degree of delay is variable based on the steering angle regardless of vehicle movement (yaw rate, lateral acceleration, etc.), the degree of delay is changed to be smaller even when the steering angle is small but the yaw rate is still large, so the driver will feel overly sensitive.

[0126] on the other hand, Figure 9 Examples illustrate the changes in steering angle, steering angle, and vehicle motion when the MCU510 adjusts the cutoff frequency (delay level) based on yaw rate and vehicle speed.

[0127] Because the MCU 510 lowers the cutoff frequency (increases the delay) when the yaw rate is large compared to when the yaw rate is small, the MCU 510 can keep the cutoff frequency low even when the steering angle is small, thus suppressing the occurrence of oversensitive vehicle movements.

[0128] In addition, because the MCU510 has a higher cutoff frequency in the medium-high speed range than in the low speed range (reducing the degree of delay), the response of steering operations is improved in the medium-high speed range compared to the low speed range, for example, ensuring the emergency avoidance capability of vehicle 100.

[0129] The technical ideas described in the above embodiments can be appropriately combined and used as long as they do not contradict each other.

[0130] Furthermore, the present invention has been specifically described with reference to preferred embodiments, but it is self-evident that those skilled in the art can adopt various modifications based on the basic technical ideas and teachings of the present invention.

[0131] For example, instead of performing low-pass filtering on the target rack travel (target steering angle), the MCU510 performs low-pass filtering on the steering operation amount signal detected by the steering operation amount sensor 330, and sets the target rack travel (target steering angle) based on the low-pass filtered steering operation amount signal, thereby controlling the degree of delay of the change in steering angle relative to the change in steering operation amount.

[0132] In addition, instead of the cutoff frequency retrieved from the low-pass filter in the diagram, the MCU 510 can set the cutoff frequency based on a function that uses vehicle speed and yaw rate as variables.

[0133] In addition, the steering control device 500 can independently possess a first microcomputer for calculating the target rack travel (target steering angle) and a second microcomputer for controlling the wheel steering motor 410 based on the target rack travel (target steering angle).

[0134] In addition, the steering control device 500 can make the cutoff frequency in the low-pass filter processing variable based on the yaw rate and lateral acceleration.

[0135] Explanation of reference numerals in the attached figures

[0136] 100…Vehicle, 101, 102…Front wheel (steering wheel), 200…Steering device, 300…Steering input device, 310…Steering input component, 330…Steering operation amount sensor, 400…Wheel steering device, 410…Wheel steering motor, 500…Steering control device, 510…MCU, 511…Steering ratio control unit, 512…Low-pass filter processing unit, 513…Steering control unit, 514…First cutoff frequency setting unit, 515…Second cutoff frequency setting unit, 516…Yaw increase / yaw return determination unit, 621-624…Wheel speed sensor, 630…Acceleration sensor, 640…Yaw rate sensor.

Claims

1. A steering control device disposed in a vehicle, the vehicle having a steering input component that receives a steering operation performed by a driver, and a motor that imparts steering force to steering wheels of the vehicle mechanically separated from the steering input component, the steering control device controlling the motor based on the driver's steering operation, thereby controlling the steering angle of the steering wheels. Obtain a first physical quantity related to the steering input amount of the steering input component and a second physical quantity generated when the vehicle turns. The ratio of the steering input to the steering angle is variable depending on the vehicle's driving state. When the ratio of the steering input to the steering angle is small, the target steering angle that increases the degree of delay in the change of the steering angle relative to the change of the steering input is obtained based on the second physical quantity, with respect to the delay in the change of the steering angle relative to the change of the steering input. The motor is controlled so that the steering angle becomes the target steering angle.

2. The steering control device according to claim 1, wherein, The second physical quantity is a physical quantity related to the yaw rate generated by the vehicle.

3. The steering control device according to claim 2, wherein, The steering control device performs: The physical quantity related to the vehicle speed is obtained as the driving state. The ratio of the steering input to the steering angle is made variable so that it decreases at lower vehicle speeds. Compared to when the vehicle speed is high, when the vehicle speed is low, the degree of delay in the change of the steering angle relative to the change of the directional steering operation amount is increased.

4. The steering control device according to claim 2, wherein, The steering control device performs: It determines whether the driver's steering operation is an operation of increasing directional deflection from the neutral position by the steering input component, or an operation of turning back to the center direction from the neutral position. When performing the operation to return the deflection to the center direction, compared to performing the operation to increase the deflection direction, the degree of delay in the change of the steering angle relative to the change in the amount of steering operation in the direction is increased.

5. The steering control device according to claim 4, wherein, The steering control device performs: Obtain the physical quantities related to the vehicle speed. When the second physical quantity is 0, regardless of the driving state, during the deflection increase operation and the deflection return operation, the magnitude of the delay in the change of the steering angle relative to the change in the directional steering operation amount is the same.

6. The control device according to claim 1, wherein, The magnitude of the delay between the change in the steering angle and the change in the steering input is determined using a low-pass filter.

7. The steering control device according to claim 6, wherein, The cutoff frequency of the low-pass filter gradually decreases as the second physical quantity increases.

8. The steering control device according to claim 7, wherein, The cutoff frequency of the low-pass filter gradually decreases as the second physical quantity increases, with the slope increasing in a quadratic manner.

9. A steering control method, performed by a steering control device disposed in a vehicle having a steering system, the steering system having a steering input component that receives a steering operation performed by a driver, and a motor that applies steering force to the steering wheels of the vehicle mechanically separated from the steering input component, the steering system controlling the motor based on the driver's steering operation to thereby change the steering angle of the steering wheels. Obtain a first physical quantity related to the steering input amount of the steering input component and a second physical quantity generated when the vehicle turns. The ratio of the steering input to the steering angle is variable depending on the vehicle's driving state. When the ratio of the steering input to the steering angle is small, the target steering angle that increases the degree of delay in the change of the steering angle relative to the change of the steering input is obtained based on the second physical quantity, with respect to the delay in the change of the steering angle relative to the change of the steering input. The motor is controlled so that the steering angle becomes the target steering angle.

10. A steering device, comprising: The steering input unit accepts steering inputs from the driver. A motor that imparts steering force to the steering wheels of a vehicle, which are mechanically separated from the steering input component. as well as The steering control device controls the motor based on the driver's directional steering operations, thereby controlling the steering angle of the steering wheels. The steering control device performs: Obtain a first physical quantity related to the steering input amount of the steering input component and a second physical quantity generated when the vehicle turns. The ratio of the steering input to the steering angle is variable depending on the vehicle's driving state. When the ratio of the steering input to the steering angle is small, the target steering angle that increases the degree of delay in the change of the steering angle relative to the change of the steering input is obtained based on the second physical quantity, with respect to the delay in the change of the steering angle relative to the change of the steering input. The motor is controlled so that the steering angle becomes the target steering angle.

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