Steering control device, steering control method, and steering control system

Abstract

To provide a steering control device and steering operation control method in which a driver can calmly operate a steering wheel even if a vehicle moves in an unexpected direction when restarting from a steering state under stopping.SOLUTION: A steering control device is used for a steering device of steer-by-wire system and includes: steering control means for controlling a steering actuator operating a steering mechanism on the basis of the rotation of a steering wheel. The steering control means memorizes a first steering angle ratio in which a first steering ratio at least with a large unit steering angle against a unit steering angle, which defines a relationship of a steering angle of the steering wheel to a steering angle of a steering wheel and a second steering ratio in which the unit steering angle is set to be small against the unit steering angle, and drives a steering actuator by using the second steering ratio when a vehicle restarts from a state where the vehicle stops.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a steering control device that controls a steering mechanism that steers an automobile, and more particularly to a steering control device, a steering control method, and a steering control system that are used in a steering mechanism that is mechanically disconnected from a steering wheel. [Background technology]

[0002] In the following explanation, the rotation angle of the steering wheel is defined as the "steering angle," the steering angle of the steered wheels (also called steered wheels) is defined as the "steering angle," and the ratio between the steering angle and the steering angle is defined as the "steering angle ratio."

[0003] In recent automobiles, "steer-by-wire" steering devices have been developed that separate the mechanical connection from the steering wheel and control the steering mechanism with an electric motor for purposes such as controlling the steering angle ratio, which is the relationship between the steering angle of the steering wheel and the steering angle of the steered wheels, and controlling autonomous driving.

[0004] With this steer-by-wire system, an electric motor installed in the steering mechanism is rotated separately from the steering wheel, so the steering angle ratio can be adjusted according to the vehicle's speed, or the vehicle can be steered automatically using camera information, navigation information, etc.

[0005] Such a steering device is described, for example, in Japanese Patent Application Laid-Open No. 2008-137612 (Patent Document 1). Patent Document 1 discloses a configuration in which the steering angle of the steered wheels is adjusted in response to the movement of a steering actuator controlled according to the steering angle of the steering wheel, without mechanically connecting the steering wheel to the steered wheels.

[0006] In Patent Document 1, the steering angle of the steering wheel and the vehicle speed are detected, and a target steering angle is calculated based on the steering angle and the vehicle speed.By increasing or decreasing the unit steering angle of the steered wheels relative to the unit steering angle of the steering wheel as the vehicle speed increases or decreases, the steering feel is set to, for example, a "low steering angle ratio (quick)" at low vehicle speeds and a "high steering angle ratio (slow)" at high vehicle speeds.

[0007] Here, a low steering angle ratio (quick) means that the unit steering angle of the steered wheels is set large relative to the unit steering angle of the steering wheel, and a high steering angle ratio (slow) means that the unit steering angle of the steered wheels is set small relative to the unit steering angle of the steering wheel. Note that each unit steering angle is relative.

[0008] According to this configuration, when the vehicle is traveling at low speeds or when the vehicle is stopped, the steering angle ratio becomes low and the steering feel is "quick," which reduces the steering load on the driver when steering at a stationary position (the amount of steering wheel rotation can be reduced).On the other hand, when the vehicle is traveling at high speeds, the steering angle ratio becomes high and the steering feel is "slow," which improves the sense of stability when steering at high speeds. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-137612 Summary of the Invention [Problem to be solved by the invention]

[0010] Incidentally, in a steer-by-wire system that employs a specification for setting a small steering ratio (low steering ratio) at low vehicle speeds to reduce steering load, as in Patent Document 1, when parking is performed while the steering wheel is turned and steered (the steered wheels remain at a steering angle), the steering ratio remains set to the same low steering ratio (quick) as at low vehicle speeds. As a result, the steering angle is displaced more than the steering angle during normal driving.

[0011] Therefore, if the vehicle is restarted while maintaining the steering angle of the steering wheel in this low steering angle ratio (quick) state, the vehicle's speed will increase and the vehicle will start moving in an unintended direction at the same time. At this time, the driver will frantically try to return the steering angle of the steering wheel to the neutral position in an attempt to correct the vehicle's direction of travel.

[0012] However, because the steering angle of the steering wheels is large compared to the steering angle of the steering wheel due to the low steering angle ratio (quick), the direction of travel of the vehicle changes suddenly and moves in an unintended direction, causing the driver to feel psychologically unsettled or confused. In other words, the vehicle's behavior becomes hypersensitive, and the driver is unable to operate the steering wheel calmly.

[0013] An object of the present invention is to provide a new steering control device, a steering operation control method, and a steering control system that allow a driver to calmly operate the steering wheel even if the automobile moves in an unexpected direction when restarting from a steering state when parking the automobile. [Means for solving the problem]

[0014] The present invention is a steering control device used in a steer-by-wire steering device in which the steering wheel and the steering mechanism that drives the steering wheels are not mechanically connected but separated, and is equipped with a steering control means that controls a steering actuator that operates the steering mechanism based on the rotation of the steering wheel, wherein the steering control means stores at least a first steering angle ratio that determines the relationship between the steering angle of the steering wheel and the steering angle of the steering wheels, in which the unit steering angle of the steering wheels is set to be larger than the unit steering angle of the steering wheel, and a second steering angle ratio that sets the unit steering angle of the steering wheels to be smaller than the unit steering angle of the steering wheel, and the steering control means drives the steering actuator using the second steering angle ratio when the vehicle starts again from a parked state. [Effects of the Invention]

[0015] According to the present invention, even if the automobile moves in an unexpected direction when restarting, the steering angle of the steering wheels is smaller than the steering angle of the steering wheel and does not change excessively, so that the driver can operate the steering wheel calmly. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram showing the configuration of a steer-by-wire steering device to which the present invention is applied. [Figure 2] FIG. 2 is a block diagram showing the configuration of the steering control device shown in FIG. [Figure 3] FIG. 4 is a characteristic diagram showing the relationship between steering angle ratio and vehicle speed. [Figure 4] 5 is a flowchart illustrating a processing flow showing a flow of steering angle control during parking and a flow of steering angle control during restarting according to an embodiment of the present invention. [Figure 5] 5 is a flowchart illustrating a processing flow of the parking determination processing shown in FIG. 4. [Figure 6] 5 is a flowchart illustrating the processing flow of the steering angle ratio selection processing and the steering angle correction processing shown in FIG. 4. [Figure 7] 5 is a flowchart illustrating a processing flow of the system shutdown processing shown in FIG. 4. [Figure 8] 5 is a flowchart illustrating a process flow of the restart determination process shown in FIG. 4. [Figure 9] 5 is a flowchart illustrating the processing flow of the steering angle ratio selection processing and the steering processing shown in FIG. 4. [Figure 10] FIG. 10 is a chart illustrating changes in vehicle speed, shift position, ignition switch, and steering angle ratio when parking and restarting. DETAILED DESCRIPTION OF THE INVENTION

[0017] The embodiments of the present invention will be described in detail using the drawings, but the present invention is not limited to the following embodiments and includes various modifications and application examples within the technical concept of the present invention.

[0018] Before describing specific embodiments, the configuration of a steer-by-wire steering control device to which the present invention is applied will be described below.

[0019] First, we will explain a steer-by-wire steering control device, which separates the steering shaft from the steering axle, detects the steering angle and disturbance torque of the steering shaft using a rotation angle sensor, current sensor, etc., and controls the operation amount of the steering actuator based on these detection signals to drive the steering axle. Note that the detailed configuration of the steering mechanism will be omitted.

[0020] In Fig. 1, steering wheels 10 are configured to be steered by tie rods 11, which are connected to a steering shaft 17. A steering wheel 12 is connected to a steering shaft 13, which may be provided with a steering angle sensor or the like.

[0021] The steering shaft 13 is not connected to a steering shaft (sometimes called a rack bar) 17 of the steering mechanism 16, and a reaction force electric motor 18 serving as a reaction force actuator is provided at the tip of the steering shaft 13. In other words, the steering shaft 13 is not mechanically connected to the steering mechanism 16, and as a result, the steering shaft 13 and the steering mechanism 16 are separated. The reaction force electric motor 18 is driven by a steering control device 19.

[0022] In this embodiment, the steering shaft 13 is not mechanically connected to the steering mechanism 16. However, the following content can also be applied to a steering control device that realizes a steer-by-wire system by disposing a clutch mechanism that can be connected and disconnected between the steering shaft 13 and the steering mechanism 16 and disconnecting them using the clutch mechanism.

[0023] The reaction force electric motor 18 is provided with a rotation angle sensor 14, which is made up of an encoder or the like, and detects the rotation angle of the reaction force electric motor 18. The rotation angle sensor 14 can also be used as a steering angle sensor, but in this embodiment, a steering angle sensor 14A is provided on the steering shaft 13, which makes it possible to detect the steering angle of the steering wheel 12.

[0024] Furthermore, the reaction force electric motor 18 is provided with a current sensor 15, which detects the current flowing through the coil that constitutes the reaction force electric motor 18. This current is used, for example, when estimating disturbance torque.

[0025] The steering mechanism 16 including the steering shaft 17 is provided with a steering electric motor mechanism 21, which controls the steering operation of the steering shaft 17. Although a steering electric motor is used as the steering actuator, it goes without saying that other types of electric actuators may also be used.

[0026] The steering angle of the steering wheel 12 is detected by a steering angle sensor 14A, the rotation angle of the reaction force electric motor 18 is detected by a rotation angle sensor 14, and further the current flowing through the coil of the reaction force electric motor 18 is detected by a current sensor 15, and these detection signals are input to a steering control device 19. In addition to these, various detection signals are also input to the steering control device 19 from external sensors 20.

[0027] The steering control device 19 calculates the control amount of the steering electric motor mechanism 21 based on the input steering angle signal, rotation angle signal, current signal, etc., and further drives the steering electric motor mechanism 21. Note that the control amount of the steering electric motor mechanism 21 can of course use parameters other than the steering angle signal, rotation angle signal, and current signal, and in practice many parameters are used.

[0028] The rotation of the steering electric motor mechanism 21 rotates the output pulley (not shown) of the steering mechanism 16 via a belt (not shown) from an input pulley (not shown), and furthermore, a steering nut (not shown) strokes the steering shaft 16 in the axial direction to steer the steered wheels 10.

[0029] Furthermore, the steering control device 19 calculates the control amount of the reaction force electric motor 18 based on the input steering angle signal, rotation angle signal, current signal, etc., and further drives the reaction force electric motor 18. Note that the control amount of the reaction force electric motor 18 can also use parameters other than the steering angle signal, rotation angle signal, current signal, etc.

[0030] The steering mechanism 16 is provided with a rack position sensor 22, which detects the actual steering angle of the steered wheels 10 and outputs a steering angle signal. The rack position sensor 22 detects the amount of axial movement of the steering shaft 17. Although the rack position sensor 22 that detects the stroke amount of the steering shaft 17 is shown as the steering angle sensor, it may also be a rotation angle sensor provided in an electric steering motor that applies a steering force to the steering shaft 17.

[0031] The steering angle signal and the steering angle signal can be used to determine the current steering angle ratio, which can be used for feedback control of the steering angle while driving, or for determining the steering angle ratio when restarting, as described below.

[0032] Next, Fig. 2 shows the general configuration of the steering control device 19 that controls the reaction force electric motor 18 and the steering electric motor 28. Note that this steering control device 19 is equipped with a controller 29 that functions as both a reaction force actuator controller unit and a steering actuator controller.

[0033] The controller 29 is equipped with a reaction force actuator controller unit and a steering actuator controller unit, as will be explained below. The basic configurations and operations of these controller units are well known, so detailed explanations will be omitted here. It is also possible to combine the reaction force actuator controller unit and the steering actuator controller unit. In this case, each function will be executed by a single microcomputer.

[0034] A rotation angle sensor 14 and a current sensor 15 are provided on the reaction force electric motor 18 connected to the steering shaft 13, and the reaction force electric motor 18 is mechanically connected to the steering wheel 12 via the steering shaft 13. The rotation angle sensor 14 is a sensor that detects the rotation angle of the reaction force electric motor 18, and the current sensor 15 is a sensor that detects the current flowing through the coil of the reaction force electric motor 18. In addition, the steering angle sensor 14A is a sensor that detects the steering angle, which is the rotation angle of the steering wheel 12.

[0035] The reaction force electric motor 18 is an electric motor that applies a steering reaction force to the steering shaft 13 via a motor driver 23 controlled by the steering control device 19. The reaction force electric motor 18 monitors inputs such as a steering angle signal, a rotation angle signal, and a current signal, and applies a predetermined steering reaction force to the steering shaft 13.

[0036] In addition, the steering control device 19 provides a driving signal to a steering electric motor 28 mechanically connected to the steering shaft 17 via a motor driver 24 in response to detection signals such as a steering angle signal, a rotation angle signal, and a current signal.

[0037] The steering control device 19 is provided with a steering angle signal from the steering angle sensor 14A, a rotation angle signal from the rotation angle sensor 14, a current signal from the current sensor 15, and further provided with vehicle running state detection signals that affect steering from running state sensors such as a vehicle speed sensor 25 and a yaw rate sensor 26. In addition, the steering control device 19 is provided with a detection signal (steering angle signal) of the movement position of the steering shaft 17 from a rack position sensor 22 (see FIG. 1) attached to the middle part of the housing that covers the steering shaft 17.

[0038] Here, the rack position sensor 22 detects the position of the steering shaft 17, and because the steering shaft 17 is directly connected to the tie rod 11, it is possible to detect the steering angle of the steered wheels 10 from the detection value of the rack position sensor 22. In this way, the rack position sensor 22 functions as a steering angle detector for the steered wheels 10.

[0039] In addition, the steering control device 19 receives an external steering command value from an automatic steering system (ADAS system) 27. The external steering command value is a command value calculated by the automatic steering system 27, and is used to steer the steering wheels 10 by the steering mechanism 16 when the vehicle deviates from a white line on the road or when an obstacle is to be avoided due to lane keeping control.

[0040] The steering control device 19 takes in, at a predetermined sampling period, detection signals of the steering angle, rotation angle, current, steering angle, driving state quantity, and external steering command value, etc., given by the steering angle sensor 14A, rotation angle sensor 14, current sensor 15, rack position sensor 22, driving state sensors 25, 26, and automatic steering system 27.

[0041] In addition, the steering control device 19 appropriately combines the input detection signals and external steering command values ​​to determine the control amount to be applied to the steering shaft 17, calculates the coil current to be passed through the steering electric motor 35 to obtain this control amount, and provides a control signal corresponding to this calculation result to the motor driver 24.

[0042] Similarly, the steering control device 19 determines the steering reaction force to be applied to the steering wheel 12 by appropriately combining the rotation angle, current, steering angle, detection signals of driving state quantities, and external steering command values, etc., calculates the coil current to be passed through the reaction force electric motor 18 in order to obtain this steering reaction force, and provides a control signal corresponding to this calculation result to the motor driver 23.

[0043] The steering control device 19 is also provided with a memory unit 30 that stores the steering angle ratio. Note that the memory unit 30 stores not only the steering angle ratio but also other calculation formulas required for steering control and coefficients used in the calculations. However, since the following explanation is about the steering angle ratio, it is indicated that the steering angle ratio is stored in the memory unit 30.

[0044] The memory unit 30 stores at least a first steering angle ratio (low steering angle ratio) in which the unit steering angle of the steering wheels 10 is set large relative to the unit steering angle of the steering wheel 12, and a second steering angle ratio (high steering angle ratio) in which the unit steering angle of the steering wheels 10 is set small relative to the unit steering angle of the steering wheel 12, which determine the relationship between the steering angle of the steering wheel 12 and the steering angle of the steered wheels 10.

[0045] The first steering ratio and the second steering ratio are connected by a straight line or a predetermined curve. This steering ratio is selected depending on the vehicle speed. In the following explanation, the first steering ratio is considered to be a low steering ratio (quick) and the second steering ratio is considered to be a high steering ratio (slow).

[0046] The steering control device 19 has a function of detecting the steering angle of the steering wheel 12 and the vehicle speed, and calculating a target steering angle based on the steering angle and the vehicle speed. For example, the target steering angle can be regarded as equivalent to the rotation angle of the steering electric motor 28, so the rotation angle (θ M )teeth, (θ M ) = Steering angle ratio (τ) × Steering angle (θ S )…(1) It can be found by:

[0047] By increasing or decreasing the steering angle of the steered wheels 10 relative to the steering angle of the steering wheel 12 as the vehicle speed increases or decreases, the steering feel can be made to be a low steering angle ratio (quick) at low vehicle speeds and a high steering angle ratio (slow) at high vehicle speeds. The vehicle speed (VP) and the steering angle ratio (τ) can be stored in a two-dimensional map, and the steering angle ratio (τ) can be read out corresponding to the vehicle speed (VP) to perform the calculation shown in the above equation (1).

[0048] The relationship between the vehicle speed (VP) and the steering angle ratio (τ) is set to the characteristics shown in Figure 3, for example. That is, at low vehicle speeds, the steering angle ratio (τ) is set to a low ratio (quick), and as the vehicle speed (VP) increases, the steering angle ratio (τ) becomes larger, and at high vehicle speeds, the steering angle ratio (τ) is set to a high ratio (slow). Note that these values ​​of the steering angle ratio (τ) are arbitrary and are set appropriately according to the specifications of the vehicle.

[0049] In such a steer-by-wire steering device, when parking while turning the steering wheel, the steering angle ratio (τ) remains set to the same low steering angle ratio (quick) as when the vehicle is traveling at low speeds.

[0050] Therefore, if the car is parked with a low steering angle ratio (quick) and then restarted while maintaining the steering angle of the steering wheel, the car will start moving in an unintended direction as the car speeds up, keeping the current steering angle. At this time, the driver will frantically try to return the steering angle of the steering wheel to the neutral position in order to correct the car's direction of travel. The neutral position here is the steering angle in the direction in which the car will go straight.

[0051] However, because the steering angle of the steering wheels is large compared to the steering angle of the steering wheel due to the low steering angle ratio (quick), the direction of travel of the vehicle changes suddenly and moves in an unintended direction, causing the driver to feel psychologically unsettled. In other words, the vehicle's behavior becomes hypersensitive, and the driver is unable to operate the steering wheel calmly.

[0052] In this embodiment, in order to avoid such an event, the following steering control device is proposed.

[0053] In this embodiment, the relationship between the steering angle of the steering wheel and the steering angle of the steering wheels is determined by storing at least a low steering angle ratio (quick) in which the unit steering angle of the steering wheels is set large relative to the unit steering angle of the steering wheel, and a high steering angle ratio (slow) in which the steering angle of the steering wheels is set small relative to the steering angle of the steering wheel, and when the vehicle starts moving again from a stopped state, the steering actuator is driven using the high steering angle ratio (slow).

[0054] According to this embodiment, even if the vehicle moves in an unexpected direction when restarting, the steering angle of the steering wheels is smaller than the steering angle of the steering wheel and does not change excessively, which has the effect of allowing the driver to operate the steering wheel calmly.

[0055] A specific processing flow of an embodiment of the present invention will be described below. First, the general flow of steering angle control during parking and steering angle control during restart will be described based on the processing flow shown in Fig. 4. In the following description, it is assumed that the steering wheels are steered away from the neutral position during parking, and the vehicle is parked in a state where it cannot travel straight.

[0056] <Step S10> In step S10, a parking determination process is executed to determine whether the vehicle has been parked by the driver. At this time, the vehicle is traveling at a low speed, so the steering angle ratio (τ) is set to a low steering angle ratio (quick). Therefore, the vehicle is in a state where the steered wheels are turned to a large extent relative to the rotation of the steering wheel. If a parking state is determined in step S10, the process of step S20 is executed.

[0057] <Step S20> In step S20, the steering angle ratio (τ) is changed from a low steering angle ratio (quick) to a high steering angle ratio (slow), and a process for selecting the steering angle ratio (τ) is executed. This process is for changing the steering angle to a high steering angle ratio (slow), since the steering angle is determined at a low steering angle ratio (quick) for the current steering angle. When the steering angle ratio (τ) is changed to a high steering angle ratio (slow) in step S20, the process of step S30 is executed.

[0058] <Step S30> In step S10, the steering angle of the steered wheels is set large in correspondence with the low steering angle ratio (quick). Then, in step S20, the steering angle is changed to the high steering angle ratio (slow), so the current steering angle (corresponding to the low steering angle ratio (quick)) does not correspond to the steering angle of the high steering angle ratio (slow). Therefore, in step S30, processing is executed to correct the steering angle of the steered wheels so that it corresponds to the high steering angle ratio (slow).

[0059] For example, for the same steering angle, the steering angle of the steered wheels at a low steering ratio (quick) is determined to be a predetermined steering angle relative to the neutral position, but the steering angle of the steered wheels at a high steering ratio (slow) is corrected toward the neutral position from the predetermined steering angle relative to the neutral position. This makes it possible to achieve consistency between the steering angle ratio (τ) when restarting and the steering angle when parking. Once the correction of the steering angle of the steered wheels is complete, the process of step S40 is executed.

[0060] <Step S40> In step S40, in order to park the vehicle, a system shutdown process is executed to completely cut off power to at least the steering system of the vehicle. This shuts down the steering system. Therefore, steering control during parking is terminated and the vehicle is prepared for the next restart.

[0061] Next, the processing flow when the automobile is restarted will be described.

[0062] <Step S50> In step S50, a restart determination process is executed to determine whether the driver has restarted the vehicle. The steering angle ratio (τ) at this time is set to a high steering angle ratio (slow) when the vehicle is parked. Therefore, the steering angle of the steered wheels is small relative to the steering angle of the steering wheel. If it is determined in step S50 that the vehicle is in a restart state, the process of step S60 is executed.

[0063] <Step S60> In step S60, a process is executed to select a steering angle ratio (τ) that corresponds to the vehicle speed. However, since a high steering angle ratio (slow) is set when restarting, the steering angle ratio is gradually shifted to a low steering angle ratio (quick) until a predetermined vehicle speed threshold is reached. This prevents the steering angle of the steered wheels from reacting too sensitively to the rotation of the steering wheel, allowing the driver to perform steering operations calmly.

[0064] Then, when a predetermined vehicle speed threshold is reached, a steering angle ratio (τ) corresponding to the vehicle speed is selected, and finally a steering angle ratio (τ) corresponding to the vehicle speed and following the characteristics shown in Fig. 3 is selected. Once the steering angle ratio (τ) is selected corresponding to the vehicle speed, the process of step S70 is executed.

[0065] <Step S70> In step S70, the steering angle is calculated by the equation (1) in accordance with the steering angle ratio (τ) selected in step S60 and the steering angle of the steering wheel, and the steering process is performed. Therefore, after restarting, normal steering control is performed.

[0066] Next, each of the above-mentioned processes will be explained. First, the processing flow of the parking determination process (S10) will be explained with reference to FIG.

[0067] <Step S11> In step S11, it is determined whether the current vehicle speed of the vehicle is greater than "0 km / h". In other words, it is determined whether the vehicle is stopped, and if the vehicle is moving (determined as No), the process ends. On the other hand, if it is determined that the vehicle is stopped (determined as Yes), the process proceeds to step S12.

[0068] <Step S12> In step S12, it is determined whether the gear position of the transmission is in parking (P) or neutral (N). In other words, it is determined whether the vehicle is stopped with the brakes applied. If the gear position of the transmission is not in parking (P) or neutral (N) (No), it is determined that the brakes are applied in drive (D) and the process ends. On the other hand, if the gear position is in parking (P) or neutral (N) (Yes), the process proceeds to step S13.

[0069] <Step S13> In step S13, it is determined whether the ignition switch is "OFF." In other words, if the ignition switch is not "OFF" (No determination), it is determined that the car is not yet finally parked, and the process ends. On the other hand, if it is determined that the ignition switch is "OFF," it is determined that the car is finally parked, and the process proceeds to step S14.

[0070] Here, even if the ignition switch is turned "OFF," the power relay of the steering control device 19 is not cut off, and power is supplied to the steering control device 19.

[0071] <Step S14> In step S14, the vehicle is deemed to have finally entered a parked state due to the "Yes" determination processes in steps S11 to S13, and the parking determination process S10 is terminated. When this process is completed, the process proceeds to the steering angle ratio selection process S20 and the steering angle correction process S30.

[0072] Next, the processing flows of the steering angle ratio selection processing S20 and the steering angle correction processing S30 will be described with reference to FIG.

[0073] <Step S21> In step S21, it is determined whether the current steering angle ratio (τ) of the vehicle is a low steering angle (quick). Since the vehicle speed is "0 km / h" before actual parking, the steering angle ratio (τ) is a low steering angle ratio (quick). Therefore, if it is a low steering angle ratio (quick) (Yes determination), the process proceeds to step S22. On the other hand, if it is not a low steering angle ratio (quick) (No determination), the process proceeds to step S31, determining that it is a high steering angle ratio (slow).

[0074] <Step S22> In step S22, the steering angle ratio (τ) is set to a high steering angle ratio (slow). Normally, as shown in FIG. 3, the steering angle ratio is set to a low steering angle ratio (quick) when the vehicle is parked, but in this embodiment, the steering angle ratio (τ) when parking is changed to a high steering angle ratio (slow) in advance. This is to reduce the sense of discomfort felt by the driver compared to when the steering angle ratio is changed to a high steering angle ratio (slow) when the vehicle is restarted. The reason for this will be explained in step S32.

[0075] <Step S23> Here, it is possible to add a determination step as shown by the broken line before step S21. Step S23 determines whether the current steering angle of the steered wheels is steered by a predetermined angle or more.

[0076] If the steering angle is smaller than the predetermined angle (closer to the neutral position), the vehicle will move in a state close to going straight when restarting, and the vehicle will not move in an unexpected direction, so the driver will not have to operate the steering wheel in a panic. Therefore, if it is determined that the steering angle of the steering wheel is not equal to or greater than the predetermined angle (No determination), the process may be terminated, and if it is determined that the steering angle of the steering wheel is equal to or greater than the predetermined angle (Yes determination), the process may proceed to step S21.

[0077] The process including the above-mentioned steps S21, S22, or S23 corresponds to the steering angle ratio selection process S20. Next, the steering angle correction process S30 will be described.

[0078] <Step S31> In step S31, it is determined whether the relationship between the current steering angle of the steered wheels and the steering angle of the steering wheel is consistent with the current steering angle ratio (τ).

[0079] In step S21, the steering angle ratio was set to a low steering angle ratio (quick), so the steered wheels are steered accordingly, and the steering angle becomes large. Meanwhile, in step S22, the steering angle ratio (τ) is changed to a high steering angle ratio (slow). Therefore, the relationship between the current steering angle of the steered wheels and the steering angle of the steering wheel may not match the steering angle ratio (τ). The current actual steering angle ratio (τ) can be obtained by detecting the steering angle of the steered wheels and the steering angle of the steering wheel.

[0080] Therefore, if the current relationship between the steering angle of the steering wheel and the steering angle of the steered wheels is consistent with a high steering angle ratio (slow) (Yes determination), the process ends. On the other hand, if the current relationship between the steering angle of the steering wheel and the steering angle of the steered wheels is not consistent with a high steering angle ratio (slow) (No determination), the process proceeds to step S32.

[0081] <Step S32> In step S32, the relationship between the steering angle and the steering angle is optimized to match the high steering angle ratio (slow). In this case, the steering angle is corrected.

[0082] As described above, in the state of step S31, the steering angle is set large in correspondence with the low steering angle ratio (quick). Then, since the steering angle ratio is changed to the high steering angle ratio (slow) in the above-mentioned step S22, the current steering angle (corresponding to the low steering angle ratio (quick)) does not correspond to the steering angle of the high steering angle ratio (slow). Therefore, in step S32, the steering angle of the steered wheels is corrected so as to correspond to the high steering angle ratio (slow).

[0083] That is, for the same steering angle, the steering angle of the steered wheels at a low steering ratio (quick) is determined to a predetermined steering angle with respect to the neutral position, but the steering angle of the steered wheels at a high steering ratio (slow) is corrected to a position closer to the neutral position than the predetermined steering angle with respect to the neutral position. This makes it possible to achieve consistency between the steering angle ratio (τ) when restarting and the steering angle when parking.

[0084] In this way, by aligning the steering angle of the steering wheel and the steering angle of the steering wheels to a high steering angle ratio (slow) when parking, it is possible to reduce the sense of discomfort felt by the driver. When changing to a high steering angle ratio (slow) when restarting the vehicle, the steering angle of the steering wheels is corrected while the driver is in the vehicle, which can cause the driver to feel uneasy about the behavior of the steering wheels. For this reason, correcting the steering angle of the steering wheels while the vehicle is parked can reduce the sense of discomfort. Once the correction of the steering angle of the steering wheels is complete, the system shutdown process of step S40 is executed.

[0085] Next, the processing flow of the system shutdown processing (S40) will be described with reference to FIG.

[0086] <Step S41> In step S41, it is determined whether the current state is a parked state. If it is determined in step S41 that the vehicle is not parked (No determination), the process ends, and if it is determined that the vehicle is parked (Yes determination), the process proceeds to step S42. As shown in step S13 of FIG. 5, even if the ignition switch is "OFF," power is supplied to the steering control device 19. Therefore, in order to shut down the steering system, it is necessary to cut off the power supply relay. If it is determined that the vehicle is parked, the process proceeds to step S42.

[0087] <Step S42> In step S42, it is determined whether or not the steering angle correction process shown in Fig. 6 has been completed. If the steering angle correction process has not been completed, the process of step S42 is executed again, and if it is determined in that process that the steering angle correction process has been completed, the process proceeds to step S43.

[0088] <Step S43> In step S43, the power supply relay is turned "OFF" to cut off the power supply in order to finally shut down the steering control device 19. This shuts down the steering system. After that, the vehicle is prepared for restarting.

[0089] Next, steering control when restarting the automobile will be explained using Figures 8 and 9. First, the processing flow of the restart determination process S50 will be explained using Figure 8. In this case, the steering control device 19 is connected to the power supply by a power supply relay.

[0090] <Step S51> In step S51, it is determined whether the ignition switch is "ON". This determines whether the driver has gotten into the car and started the engine. Note that this can also be determined for electric cars and hybrid cars by a similar operation. If it is determined that the ignition switch is not "ON", the process ends. On the other hand, if it is determined that the ignition switch is "ON", the process proceeds to step S52.

[0091] <Step S52> In step S52, it is determined whether the current gear position is reverse (R) or drive (D). If it is not reverse (R) or drive (D) (parking, neutral), the vehicle will not start and the process ends. On the other hand, if it is reverse (R) or drive (D), the vehicle will start and the process proceeds to step S53.

[0092] <Step S53> In step S53, it is determined whether the vehicle speed is greater than "0 km / h" to determine whether the vehicle is actually traveling. Even if it is determined in step S52 that the vehicle is in reverse (R) or drive (D), if the brake is depressed, no vehicle speed is generated, so in this case the process ends. On the other hand, if it is determined that vehicle speed is generated, the process proceeds to step S54.

[0093] <Step S54> In step S54, since the vehicle is deemed to be moving due to the "Yes determination" in steps S51 to S53, it is finally determined that the vehicle is "restarting," and the restart determination process S50 is terminated. When this process is completed, the process proceeds to the steering angle ratio selection process S60 and the steering process S70.

[0094] Next, the processing flow of the steering angle ratio selection processing S60 and the steering processing S70 will be explained with reference to FIG.

[0095] <Step S61> The following steps S61 and S62 may be executed as needed, and are therefore indicated by dashed lines in the drawing.

[0096] In step S61, it is determined whether the steering angle ratio (τ) during the current parking is a high steering angle ratio (slow). In this case, the steering angle ratio (τ) selected during parking is stored and can be read out to make the determination.

[0097] In addition, the steering angle ratio (τ) can be determined from the relationship between the steering angle of the steering wheel and the steering angle of the steered wheels. If the steering angle ratio (τ) is determined from the steering angle and the steering angle, it can be corrected even if the steering wheel or the angle of the steered wheels changes for some reason during parking.

[0098] If it is determined that the current steering angle ratio (τ) is not a high steering angle ratio (slow), the process proceeds to step S62, and if it is determined that the current steering angle ratio (τ) is a high steering angle ratio (slow), the process proceeds to step S63.

[0099] <Step S62> In step S62, the steering electric motor 28 is driven to correct the steering angle of the steered wheels so that the current relationship between the steering angle of the steering wheel and the steering angle of the steered wheels is consistent with a high steering angle ratio (slow). When the correction is complete, the process proceeds to step S63.

[0100] <Step S63> In step S63, the current vehicle speed is detected. The reason for detecting the vehicle speed is to change the steering ratio (τ) that has been set to a high steering ratio (slow) to a low steering ratio (quick) in accordance with the vehicle speed. However, if the steering ratio is changed from a high steering ratio (slow) to a low steering ratio (quick) too quickly, the driver may feel confused or uncomfortable, as described in the problem section, so the following step S64 is executed.

[0101] <Step S64> In step S64, until the vehicle speed after restarting reaches a predetermined vehicle speed threshold, the steering angle ratio (τ) is gradually reduced, for example, as a function of time, from the current high steering angle ratio (slow) to a low steering angle ratio (quick). For example, if this processing flow is started by an interrupt at predetermined time intervals, it can be executed by reducing the steering angle ratio (τ) by a predetermined value in accordance with this start timing.

[0102] The gradient of the steering angle ratio (τ) in this gradual decrease control is arbitrary, but is set to a level that the driver does not feel uncomfortable. Also, as will be explained in Figure 10, the steering angle ratio is maintained at a high (slow) level for a predetermined time (Td / see Figure 10), and then the steering angle ratio (τ) is gradually decreased. In this state, the process proceeds to step S71.

[0103] <Step S71> In step S71, it is determined whether the vehicle speed detected in step S63 has reached a predetermined vehicle speed threshold (Sp). If it is determined that the predetermined vehicle speed threshold (Sp) has not yet been reached, the process returns to step S64, where the process of step S64 is executed again to gradually reduce the steering angle ratio (τ). On the other hand, if it is determined that the vehicle speed has reached the predetermined vehicle speed threshold (Sp), the process proceeds to step S72.

[0104] <Step S72> In step S72, since the vehicle speed has reached a predetermined vehicle speed threshold (Sp), from this point onwards, the steering angle ratio (τ) corresponding to the increase in vehicle speed is calculated from, for example, the characteristics shown in Figure 3, and control is executed to gradually increase the steering angle ratio (τ) towards a high steering angle ratio (slow). From this point onwards, normal control is carried out, and the steering angle control for restarting is terminated.

[0105] In this way, when the car starts again from a parked state, by driving the steering actuator from a high steering angle ratio (slow) state, even if the car moves in an unexpected direction when starting again, the steering angle of the steering wheels is smaller than the steering angle of the steering wheel and does not change excessively, allowing the driver to operate the steering wheel calmly.

[0106] Next, changes in vehicle speed, shift position, ignition switch, and steering angle ratio when the above-described processing flow is performed will be explained with reference to Fig. 10. In Fig. 10, the horizontal axis represents elapsed time, and the vertical axis represents, from top to bottom, vehicle speed, shift position, ignition switch, and steering angle ratio.

[0107] In FIG. 10, before the ignition switch is turned "OFF" at time (Tig), the vehicle speed decreases and finally reaches "0 km / h" in preparation for parking. Then, the driver changes the shift position from drive (D) to parking (P). Here, the steering ratio (τ) is set to a low steering ratio (quick) because the vehicle speed is "0 km / h."

[0108] Next, when the driver turns the ignition switch "OFF" at time (Tig), the steering angle ratio (τ) is changed to the high steering angle ratio (slow). Then, in this state, the steering angle of the steered wheels is corrected so that the steering angle and the steering angle match the high steering angle ratio (slow). Once the steering angle of the steered wheels has been corrected, the system shuts down at time (Tsd). This puts the car into a parking state.

[0109] Next, the driver turns the ignition switch "ON" at time (Tst) to restart the vehicle. Then, the driver changes the shift position from Parking (P) to Drive (D). When the driver releases the brake, the vehicle speed gradually increases.

[0110] In this state, the steering ratio (τ) is maintained at a high steering ratio (slow) for a predetermined time (Td), and after the predetermined time (Td) has elapsed, as the vehicle speed increases, it gradually decreases to a low steering ratio (quick). In this way, when restarting, the steering ratio (τ) is gradually reduced from a high steering ratio (slow), so even if the vehicle moves in an unexpected direction when restarting, the steering angle of the steering wheels is smaller than the steering angle of the steering wheel and does not change excessively, allowing the driver to operate the steering wheel calmly.

[0111] Next, when the vehicle speed reaches a predetermined vehicle speed threshold (Sp) at time (Tsp), the steering angle ratio (τ) is set to a larger value toward a high steering angle ratio (slow) in response to the increase in vehicle speed.

[0112] As described above, the present invention provides a steering control device used in a steer-by-wire steering device in which the steering wheel and the steering mechanism that drives the steered wheels are not mechanically connected but separated, and which includes a steering control means that controls a steering actuator that operates the steering mechanism based on the rotation of the steering wheel, and the steering control means stores at least a first steering angle ratio that determines the relationship between the steering angle of the steering wheel and the steering angle of the steered wheels, in which the unit steering angle of the steered wheels is set larger than the unit steering angle of the steering wheel, and a second steering angle ratio that sets the unit steering angle of the steered wheels smaller than the unit steering angle of the steering wheel, and the steering control means is configured to drive the steering actuator using the second steering angle ratio when the vehicle starts moving again from a stopped state.

[0113] According to this, even if the car moves in an unexpected direction when restarting, the steering angle of the steering wheels is smaller than the steering angle of the steering wheel and does not change too sensitively, so the driver can operate the steering wheel calmly.

[0114] The present invention is not limited to the above-described embodiments, but includes various modifications. The above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations with respect to the configuration of each embodiment. [Explanation of symbols]

[0115] 10...Steering wheel, 12...Steering wheel, 13...Steering shaft, 14...Rotation angle sensor, 14A...Steering operation angle sensor, 16...Steering mechanism, 17...Steering shaft, 18...Reaction force electric motor, 19...Steering control device, 28...Steering electric motor

Claims

1. A steering control device is used in a steer-by-wire steering device in which a steering wheel and a steering mechanism that drives steered wheels are not mechanically connected but separated, and includes a steering control means that controls a steering actuator that operates the steering mechanism based on the rotation of the steering wheel, The steering control means As a steering angle ratio which is a relationship between the steering angle of the steering wheel and the steering angle of the steered wheels, at least a first steering angle ratio in which the unit steering angle of the steered wheels is set to be larger than the unit steering angle of the steering wheel, and a second steering angle ratio in which the unit steering angle of the steered wheels is set to be smaller than the unit steering angle of the steering wheel are stored, The steering control means When the vehicle starts again from a parked state, the steering actuator is driven using the second steering angle ratio, and The steering control means When the vehicle is parked, if the steering angle of the steering wheels is equal to or greater than a predetermined angle, the currently set first steering angle ratio is changed to the second steering angle ratio and set. A steering control device characterized by:

2. A steering control device used in a steer-by-wire steering device in which a steering wheel and a steering mechanism that drives steered wheels are not mechanically connected but separated, and which includes steering control means that controls a steering actuator that operates the steering mechanism based on the rotation of the steering wheel, The steering control means As a steering angle ratio which is a relationship between the steering angle of the steering wheel and the steering angle of the steered wheels, at least a first steering angle ratio in which the unit steering angle of the steered wheels is set to be larger than the unit steering angle of the steering wheel, and a second steering angle ratio in which the unit steering angle of the steered wheels is set to be smaller than the unit steering angle of the steering wheel are stored, The steering control means When the vehicle starts again from a parked state, the steering actuator is driven using the second steering angle ratio, and The steering control means When the vehicle restarts, the second steering angle ratio is maintained for a predetermined time until the vehicle reaches a predetermined vehicle speed, and thereafter, the steering angle ratio is gradually changed from the second steering angle ratio to the first steering angle ratio. A steering control device characterized by:

3. A steering control device according to claim 2, The steering control means When the predetermined vehicle speed is reached, the steering angle ratio is changed to the steering angle ratio corresponding to the vehicle speed. A steering control device characterized by:

4. A steering control method for a steering control device used in a steer-by-wire steering device in which a steering wheel and a steering mechanism that drives the steering wheels are not mechanically connected but separated, the steering control method comprising a steering control means that controls a steering actuator that operates the steering mechanism based on the rotation of the steering wheel, the steering control means defining the relationship between the steering angle of the steering wheel and the steering angle of the steering wheels, the steering control means comprising a memory means that stores at least a first steering angle ratio in which the unit steering angle of the steering wheels is set large relative to the unit steering angle of the steering wheel, and a second steering angle ratio in which the unit steering angle of the steering wheels is set small relative to the unit steering angle of the steering wheel, The steering control means a step of reading out the second steering angle ratio from the storage means when the vehicle restarts from a parked state; a step of driving the steering actuator using the read second steering angle ratio; When the vehicle is parked, if the steering angle of the steering wheels is equal to or greater than a predetermined angle, the currently set first steering angle ratio is changed to the second steering angle ratio and set. A steering control method for a steering control device.

5. A steering control method for a steering control device used in a steer-by-wire steering device in which a steering wheel and a steering mechanism that drives the steering wheels are not mechanically connected but separated, the steering control method comprising a steering control means that controls a steering actuator that operates the steering mechanism based on the rotation of the steering wheel, the steering control means defining the relationship between the steering angle of the steering wheel and the steering angle of the steering wheels, the steering control means comprising a memory means that stores at least a first steering angle ratio in which the unit steering angle of the steering wheels is set large relative to the unit steering angle of the steering wheel, and a second steering angle ratio in which the unit steering angle of the steering wheels is set small relative to the unit steering angle of the steering wheel, The steering control means a step of reading out the second steering angle ratio from the storage means when the vehicle restarts from a parked state; a step of driving the steering actuator using the read second steering angle ratio; When the vehicle starts moving again, the second steering angle ratio is maintained for a predetermined time until the vehicle reaches a predetermined vehicle speed, and then the steering angle ratio is gradually changed from the second steering angle ratio to the first steering angle ratio. A steering control method for a steering control device.

6. A steering control method for a steering control device according to claim 5, The steering control means When the predetermined vehicle speed is reached, a step of changing the steering angle ratio to the steering angle ratio corresponding to the vehicle speed is executed. A steering control method for a steering control device.

7. A steering control system comprising a steering wheel, a steering mechanism for driving steered wheels that are not mechanically connected to but separated from the steering wheel, a steering actuator for driving the steering mechanism, and steering control means for controlling the steering actuator, The steering control means As a steering angle ratio which is a relationship between the steering angle of the steering wheel and the steering angle of the steered wheels, at least a first steering angle ratio in which the unit steering angle of the steered wheels is set to be larger than the unit steering angle of the steering wheel, and a second steering angle ratio in which the unit steering angle of the steered wheels is set to be smaller than the unit steering angle of the steering wheel are stored, The steering control means When the vehicle starts again from a parked state, the steering actuator is driven using the second steering angle ratio, and The steering control means When the vehicle is parked, if the steering angle of the steering wheels is equal to or greater than a predetermined angle, the currently set first steering angle ratio is changed to the second steering angle ratio and set. A steering control system characterized by:

8. A steering control system including a steering wheel, a steering mechanism that drives steered wheels that are not mechanically connected to the steering wheel but are separated from the steering wheel, a steering actuator that drives the steering mechanism, and a steering control means that controls the steering actuator, The steering control means As a steering angle ratio which is a relationship between the steering angle of the steering wheel and the steering angle of the steered wheels, at least a first steering angle ratio in which the unit steering angle of the steered wheels is set to be larger than the unit steering angle of the steering wheel, and a second steering angle ratio in which the unit steering angle of the steered wheels is set to be smaller than the unit steering angle of the steering wheel are stored, The steering control means When the vehicle starts again from a parked state, the steering actuator is driven using the second steering angle ratio, and The steering control means When the vehicle restarts, the second steering angle ratio is maintained for a predetermined time until the vehicle reaches a predetermined vehicle speed, and thereafter, the steering angle ratio is gradually changed from the second steering angle ratio to the first steering angle ratio. A steering control system characterized by:

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