Vehicle steering control device and steer-by-wire type vehicle

Abstract

This vehicle steering control device is adapted to a steer-by-wire type vehicle in which a reaction force mechanism that provides a reaction force in response to steering wheel manipulation by a driver and a turning mechanism that steers a turning angle of tires on the basis of the steering wheel manipulation are mechanically separated, the vehicle steering control device comprising: a vehicle state cause determination unit (52) that, in a case where the vehicle is in a state of being unable to travel in the direction intended by the driver by means of the steering wheel manipulation, determines the cause of why the vehicle has fallen into the state on the basis of a steering wheel angle and the turning angle, and generates a state cause signal; and a vibration signal generation unit (53) that generates a vibration signal to be added to the reaction force mechanism on the basis of the state cause signal.

Description

Vehicle steering control device and steer-by-wire vehicle

[0001] The present disclosure relates to a vehicle steering control device and a steer-by-wire vehicle.

[0002] In recent years, many steer-by-wire (SBW) vehicles (hereinafter referred to as "SBW vehicles") have been developed, in which the steering side and the steering side of the vehicle are mechanically separated. SBW vehicles are equipped with a reaction mechanism that uses a reaction motor to apply a reaction force to the driver's steering of the steering wheel, and a steering mechanism that converts the movement of the steering wheel into an electrical signal and controls the steering angle of the tires based on that signal. In conventional vehicles, the driver can sense the load from the road surface through the steering wheel, but in SBW vehicles, the driver cannot directly sense the road load, so a method has been developed to simulate the road load using a reaction force.

[0003] In SBW vehicles, because the reaction force mechanism and the steering mechanism are separate, even if the driver steers the steering wheel, the vehicle may not turn as intended by the driver. For example, in a curb-strike state, in which the tire is in contact with a curb, the driver cannot steer the tire even if he turns the steering wheel, and a deviation occurs between the steering wheel angle and the steering angle, resulting in a state in which the vehicle does not turn as intended even if he steers the steering wheel. Furthermore, even in a rack-end state, in which the steering angle has reached its maximum angle and reached the rack end, the steering wheel can be turned further, so the driver may not notice the rack-end state and may steer the steering wheel excessively, causing a deviation between the steering wheel angle and the steering angle.

[0004] The following Patent Document 1 discloses a method for transmitting the deviation between the steering wheel angle and the turning angle by vibrating the steering wheel with a reaction motor when a difference occurs between the steering wheel angle and the turning angle. Furthermore, the following Patent Document 2 discloses a method for transmitting the rack end state to the driver by vibrating the steering wheel with a reaction motor when the turning angle reaches a maximum angle.

[0005] JP 2004-182008 JP 04-133864

[0006] However, if the vehicle continues to run into a curb, the tire or wheel of the vehicle may come into contact with and rub against the curb, causing damage that could impede running, requiring the driver to steer the vehicle to avoid the curb. Meanwhile, in a rack-end state, in a conventional vehicle, further steering input could damage components including mechanisms that limit steering, such as the knuckles or tie rods. However, in a SBW vehicle, damage to these components can be prevented by limiting the output of the steering motor when the steering angle reaches its maximum. Therefore, as long as the driver is aware of the discrepancy between the steering wheel angle and the steering angle, there is no problem with continuing to run in a rack-end state. Of course, the driver may also turn the steering wheel back slightly to avoid a rack-end state.

[0007] However, when frequently driving in the rack end state, such as when backing into a parking space, it is extremely time-consuming to turn the steering wheel slightly back every time the rack end is reached, and the vehicle's turning radius becomes larger, making it difficult to handle. Vehicle handling is also important when driving on curves with large curvatures or when making U-turns, and so driving in the rack end state is desirable even in the above cases.

[0008] The method disclosed in the above-mentioned Patent Document 1 causes a deviation between the steering wheel angle and the turning angle due to steering wheel steering in both the curb hitting state and the rack end state. As a result, vibration is generated in both states, so the driver cannot grasp whether the deviation between the steering wheel angle and the turning angle is caused by the curb hitting state or the rack end state. As a result, the driver cannot determine how to steer.

[0009] The method disclosed in the above-mentioned Patent Document 2 can determine the rack end state, but does not work in the curb hit state. Therefore, even if the vehicle hits the curb, the driver cannot recognize that the vehicle is in the curb hit state, and even if the driver steers the steering wheel, the vehicle does not turn in the intended direction, which may confuse the driver.

[0010] The present disclosure has been made in consideration of the above circumstances, and aims to provide a vehicle steering control device and a steer-by-wire vehicle that, when the vehicle does not turn in the intended direction even when the steering wheel is steered, can urge the driver to steer appropriately by vibrating the steering wheel in accordance with the cause of the state.

[0011] In order to solve the above problems, a vehicle steering control device according to one aspect of the present disclosure is a vehicle steering control device that has a reaction force mechanism that applies a reaction force to steering wheel steering by a driver, and a steering mechanism that steers the steering angle of tires based on the steering wheel steering, and is adapted to a steer-by-wire vehicle in which the reaction force mechanism and the steering mechanism are mechanically separated, and is equipped with: a vehicle state cause determination unit that, when the vehicle is in a state in which the steering wheel steering prevents it from traveling in the direction intended by the driver, determines a cause of the state from the steering wheel angle and the steering angle and generates a state cause signal; and a vibration signal generation unit that generates a vibration signal to be applied to the reaction force mechanism based on the state cause signal.

[0012] Moreover, a steer-by-wire vehicle according to one aspect of the present disclosure includes a reaction force mechanism that applies a reaction force to steering of the steering wheel by a driver, a steering mechanism that is mechanically separated from the reaction force mechanism and steers the steering angle of the tires based on the steering of the steering wheel, and the vehicle steering control device according to the above-described one aspect of the present disclosure.

[0013] According to the present disclosure, when the vehicle does not turn in the intended direction even when the steering wheel is turned, the steering wheel is vibrated in accordance with the cause of the condition, thereby encouraging the driver to steer appropriately.

[0014] 1 is a diagram showing the configuration of a main part of a steer-by-wire vehicle according to Embodiment 1. FIG. 2 is a block diagram showing an SBW system controller and its controlled object according to Embodiment 1. FIG. 3 is a block diagram showing the configuration of a reaction force control unit according to Embodiment 1. FIG. 4 is a block diagram showing the configuration of a vehicle state cause determination unit according to Embodiment 1. FIG. 5 is a block diagram showing another configuration of the vehicle state cause determination unit according to Embodiment 1. FIG. 6 is a flowchart showing processing performed by the cause determination unit according to Embodiment 1. FIG. 7 is a diagram showing the relationship between the value of a state cause signal and a determination result of a vehicle state according to Embodiment 1. FIG. 8 is a block diagram showing the configuration of a vibration signal generation unit according to Embodiment 1. FIG. 9 is a diagram showing an example of a vibration waveform designated by a vibration waveform determiner according to a state cause signal according to Embodiment 1. FIG. 10 is a diagram showing an example of a vibration period determined by a vibration period determiner according to a state cause signal according to Embodiment 1. FIG. 11 is a diagram showing an example of a sampling period determined by a sampling determiner according to a state cause signal according to Embodiment 1. FIG. 12 is a flowchart showing processing performed by a vibration signal generator according to Embodiment 1. FIG. 13 is a block diagram showing a first modified example of a vibration signal generation unit according to Embodiment 1. FIG. 14 is a diagram showing a vibration signal generated by a vibration signal generation unit according to Embodiment 1. FIG. 15 is a block diagram showing a first modified example of a vibration signal generation unit according to Embodiment 1. FIG. 10 is a diagram showing a vibration signal generated by a vibration signal generation unit according to a second modified example of embodiment 1. FIG. 11 is a block diagram showing a third modified example of the vibration signal generation unit according to embodiment 1. FIG. 12 is a diagram showing a vibration signal generated by a vibration signal generation unit according to a third modified example of embodiment 1. FIG. 13 is a flowchart showing processing performed by a cause determination unit according to embodiment 2. FIG. 14 is a flowchart showing processing performed by a cause determination unit according to embodiment 3. FIG. 15 is a flowchart showing processing performed by a cause determination unit according to embodiment 4. FIG. 16 is a block diagram showing the configuration of a reaction force control unit according to embodiment 5. FIG. 17 is a block diagram showing the configuration of a vehicle state cause determination unit according to embodiment 5. FIG. 18 is a diagram showing an example of a state quantity according to embodiment 5. FIG. 19 is a block diagram showing the configuration of a vibration signal generation unit according to embodiment 5.10 is a diagram showing an example of an excitation amplitude generated in the fifth embodiment. FIG. 11 is a diagram showing examples of an excitation amplitude and an excitation waveform generated in the fifth embodiment. FIG. 12 is a block diagram showing a configuration of a reaction force control unit in the sixth embodiment. FIG. 13 is a block diagram showing a configuration of a vehicle state cause determination unit in the sixth embodiment. FIG. 14 is a block diagram showing another configuration of the vehicle state cause determination unit in the sixth embodiment. FIG. 15 is a flowchart showing processing performed by the cause determination unit in the sixth embodiment. FIG. 16 is a diagram showing a relationship between the value of the state cause signal and the determination result of the vehicle state in the sixth embodiment. FIG. 17 is a block diagram showing a configuration of a vibration signal generation unit in the sixth embodiment. FIG. 18 is a diagram showing an example of an excitation waveform designated by the excitation waveform determiner in accordance with the state cause signal in the sixth embodiment. FIG. 19 is a diagram showing an example of a vibration period determined by the vibration period determiner in accordance with the state cause signal in the sixth embodiment. FIG. 19 is a diagram showing an example of a sampling period determined by the sampling determiner in accordance with the state cause signal in the sixth embodiment. FIG. 19 is a flowchart showing processing performed by the vibration signal generator in the sixth embodiment. FIG. 19 is a diagram showing another example of an excitation waveform designated by the excitation waveform determiner in accordance with the state cause signal in the sixth embodiment. FIG. 19 is a diagram showing another example of a vibration period determined by the vibration period determiner in accordance with the state cause signal in the sixth embodiment. 10 is a flowchart showing processing performed in a cause determination unit according to a first modified example of Embodiment 6. FIG. 11 is a flowchart showing processing performed in a cause determination unit according to a second modified example of Embodiment 6. FIG. 12 is a flowchart showing processing performed in a cause determination unit according to a third modified example of Embodiment 6. FIG. 13 is a block diagram showing the configuration of a reaction force control unit according to Embodiment 6. FIG. 14 is a block diagram showing the configuration of a vehicle state cause determination unit according to Embodiment 7. FIG. 15 is a diagram showing an example of a deviation state quantity according to Embodiment 7. FIG. 16 is a diagram showing an example of a slip state quantity according to Embodiment 7. FIG. 17 is a block diagram showing another configuration of the vehicle state cause determination unit according to Embodiment 7. FIG. 18 is a flowchart showing processing performed in a state quantity selection unit according to Embodiment 7. FIG. 19 is a diagram showing an example of an excitation amplitude generated in Embodiment 7. FIG. 19 is a diagram showing examples of an excitation amplitude and an excitation waveform generated in Embodiment 7.13A to 13C are diagrams illustrating other examples of excitation amplitudes and excitation waveforms generated in the seventh embodiment.

[0015] Hereinafter, a vehicle steering control device and a steer-by-wire vehicle according to embodiments of the present disclosure will be described in detail with reference to the drawings. In each embodiment, the same or corresponding parts are designated by the same reference numerals, and a description of overlapping parts will be omitted.

[0016] [Embodiment 1] Figure 1 is a diagram showing the configuration of the main parts of a steer-by-wire vehicle according to embodiment 1. As shown in Figure 1, the steer-by-wire vehicle includes a reaction force mechanism 100, a steering mechanism 101, and an SBW system controller 3. Reaction force mechanism 100 includes a steering wheel (steering wheel) 1 and a reaction force motor 2. Steering mechanism 101 includes a steering motor 4, a rack and pinion gear 5, a knuckle arm 6, a tie rod 7, tires 8, and wheels 9. In a steer-by-wire vehicle configured in this manner, SBW system controller 3 controls reaction force motor 2 and steering motor 4, thereby generating a reaction force to be applied to the driver and steering the tires.

[0017] Figure 2 is a block diagram showing the SBW system controller and its controlled objects according to embodiment 1. As shown in Figure 2, SBW system controller 3 includes reaction force control unit 31, reaction force motor current control unit 32, steering control unit 33, and steering motor current control unit 34. Reaction force control unit 31 generates a reaction force motor current command based on the steering wheel angle detected by steering wheel angle sensor 23, the steering angle detected by steering angle sensor 43, and vehicle behavior values ​​such as vehicle speed, yaw rate, and lateral acceleration. Details of reaction force control unit 31 will be described later.

[0018] The vehicle behavior values ​​may be detected by a vehicle speed sensor, a yaw rate sensor, and a lateral acceleration sensor mounted on the vehicle. Although not shown, the detected values ​​of the sensors mounted on the vehicle are transmitted to the SBW system controller 3 via an in-vehicle communication network. The in-vehicle communication network is a communication network that is mounted on the vehicle, connects the in-vehicle electrical components, and transmits and receives data. Examples of in-vehicle communication networks include CAN (Controller Area Network) (registered trademark), FlexRay (registered trademark), and Ethernet (registered trademark). The in-vehicle communication network may be connected to the SBW system controller 3 according to the type of network mounted on the vehicle.

[0019] Reaction force motor current control unit 32 applies a voltage to the reaction force motor based on the reaction force motor current command generated by reaction force control unit 31, the reaction force motor angle detected by angle sensor 21, and the reaction force motor current detected by current sensor 22. Reaction force motor current control unit 32 may perform motor current control in general dq-axis coordinates based on the deviation between the reaction force motor current command and the reaction force motor current, or may use other known motor current control methods.

[0020] Steering control unit 33 generates a steering motor current command based on the steering wheel angle detected by steering wheel angle sensor 23, the steering angle detected by steering angle sensor 43, and vehicle behavior values ​​such as vehicle speed, yaw rate, and lateral acceleration. Steering control unit 33 generates a steering angle command based on the steering wheel angle detected by steering wheel angle sensor 23. Thereafter, control is performed to make the steering angle follow the generated steering angle command, and a known angle follow-up control method may be used. Furthermore, when a steering angle command or a steering motor current command is generated based on vehicle behavior values ​​such as vehicle speed, yaw rate, and lateral acceleration, it may be generated using a known method.

[0021] Steering motor current control section 34 applies a voltage to the reaction motor based on the steering motor current command generated by steering control section 33, the steering motor angle detected by angle sensor 41, and the steering motor current detected by current sensor 42. Steering motor current control section 34 may perform motor current control in general dq axis coordinates based on the deviation between the steering motor current command and the steering motor current, or may use another known motor current control method.

[0022] The steering wheel angle detected by the steering wheel angle sensor 23 may be replaced by the reaction motor angle detected by the angle sensor 21. Because the steering wheel and the reaction motor are mechanically connected, the steering wheel angle may be calculated from the reaction motor angle according to the gear ratio between the steering wheel and the reaction motor. When the steering wheel angle is calculated from the reaction motor angle, the steering wheel angle sensor 23 may be omitted.

[0023] Furthermore, the steering angle detected by steering angle sensor 43 may be substituted by the steering motor angle detected by angle sensor 41. Because the tires and the steering motor are mechanically connected, the steering angle may be calculated from the steering motor angle according to the gear ratio between the tires and the steering motor. When the steering angle is calculated from the steering motor angle, steering angle sensor 43 may be omitted. Note that instead of directly detecting the steering angle, a sensor that detects the stroke amount of the rack may be used, and the steering angle may be calculated from the stroke amount.

[0024] Fig. 3 is a block diagram showing the configuration of the reaction force control unit in Embodiment 1. As shown in Fig. 3, the reaction force control unit 31 includes a target steering torque calculation unit 51, a vehicle state cause determination unit 52, an excitation signal generation unit 53, a current command conversion unit 54, and an addition unit 55. The target steering torque calculation unit 51 generates a target steering torque a that gives the driver a reaction force feeling that is unrelated to the state cause signal generated by the vehicle state cause determination unit 52.

[0025] A known method can be used to generate the target steering torque a. For example, the target steering torque a may be generated so that the magnitude increases as the steering wheel angle increases. Alternatively, the target steering torque a may be generated in accordance with the steering wheel angular velocity obtained by differentiating the steering wheel angle. Furthermore, the target steering torque a may be generated in accordance with the vehicle behavior with reference to the vehicle speed, yaw rate, lateral acceleration, etc.

[0026] The vehicle state cause determination unit 52 determines the state of the vehicle, and when the vehicle cannot be driven as intended even when the driver steers the steering wheel, determines the cause of the state and generates a state cause signal indicating the determination result. The vehicle state cause determination unit 52 will be described in detail later. The vibration signal generation unit 53 generates a vibration signal in accordance with the state cause signal generated by the vehicle state cause determination unit 52. The vibration signal generation unit 53 will be described in detail later. The adder 55 adds the target steering torque a generated by the target steering torque calculation unit 51 and the vibration signal generated by the vibration signal generation unit 53 to generate a target steering torque b.

[0027] The current command conversion unit 54 generates a reaction motor current command based on the target steering torque b generated by the adder 55. The target steering torque b can be generated by a known method. For example, assuming that the gear ratio between the reaction motor and the steering wheel is Gn and the torque constant of the reaction motor is Kt, the reaction motor current command may be obtained by multiplying the value obtained by dividing the target steering torque b by Gn and the resulting value by Kt. Furthermore, taking friction of the reaction mechanism into consideration, the reaction motor current command may be obtained by subtracting the friction from the target steering torque b, dividing the result by Gn, and multiplying the result by Kt. Furthermore, if a steering torque sensor (not shown) is included in the configuration, the reaction motor current command may be generated based on the detection value of the steering torque sensor and the target steering torque b. Even in this case, the reaction motor current command may be generated by a known method. For example, PID control may be performed in response to the deviation between the detection value of the steering torque sensor and the target steering torque b.

[0028] Next, the vehicle state cause determination unit 52 will be described in detail. As described above, the vehicle state cause determination unit 52 determines the cause of a state in which the driver cannot drive the vehicle as intended even when steering the steering wheel. Specifically, possible causes of a state in which the driver cannot drive the vehicle as intended even when steering the steering wheel include a tire hitting a curb or the steering angle reaching the rack end. In either case, the steering wheel can be turned, but in the curb hit state, further steering in the direction of the curb is impossible, and in the rack end state, further steering in a direction beyond the maximum steering angle is impossible. Therefore, when the steering wheel is turned and a deviation occurs between the steering wheel angle and the steering angle, the driver cannot drive the vehicle as intended even when steering the steering wheel.

[0029] If the driver tries to turn the steering wheel toward the curb without noticing the curb when the vehicle is in a curb-hitting state, the steering control unit 33 will try to align the steering angle with the steering angle, which will result in a large force being applied to the point where the tire and the curb are in contact. The contact points are likely to be the tire and wheel, and there is a risk of damage due to the large force being applied to these. Damage to these parts could impede the vehicle's travel, so if the driver becomes aware of the curb-hitting state, they must immediately steer to avoid the curb.

[0030] On the other hand, when the vehicle is in the rack end state, the operation differs depending on whether the vehicle is a conventional vehicle (i.e., a vehicle other than an SBW vehicle) or an SBW vehicle. In the case of a conventional vehicle, the steering wheel and the tires are connected, so if the steering wheel is turned further in the turning direction in the rack end state, a large force is applied to the stopper portion of the knuckle or tie rod that limits the steering angle, which could result in damage. In contrast, in the case of an SBW vehicle, the steering wheel and the tires are not connected, so even if the steering wheel is turned beyond the maximum steering angle, the steering control unit 33 applies a limit, thereby preventing a large force from being applied to the above-mentioned components.

[0031] For example, by limiting the steering angle command generated by steering control unit 33 so that the maximum steering angle is the upper limit, it is possible to prevent the steering motor from attempting to rotate beyond the maximum steering angle, and as a result, a large force is not applied to the above-mentioned parts. In this case, a deviation between the steering wheel angle and the steering angle occurs due to excessive turning of the steering wheel, but as long as the driver is aware of the deviation and can drive in accordance with that condition, there is no problem at all even if steering is performed with the deviation occurring in the rack end state.

[0032] Of course, there is no problem if the driver immediately turns the steering wheel back to avoid the rack end state after recognizing the rack end state. However, depending on the vehicle's driving conditions, such steering may result in unnecessary trouble. For example, when backing into parking, frequent steering into the rack end state is expected. However, if an attempt is made to back into parking to avoid the rack end state, the vehicle will be driven with a steering angle smaller than the maximum steering angle, increasing the vehicle's minimum turning radius. This makes the vehicle less maneuverable, resulting in increased parking effort. In addition to backing into parking, vehicle maneuverability is also important when turning a curve with a large curvature or making a U-turn, and there are often situations in which it is desirable to drive in the rack end state. Therefore, when a deviation occurs between the steering wheel angle and the steering angle, the steering that the driver should perform in the curb hit state and the rack end state differs, so it is necessary to accurately communicate the vehicle's state to the driver.

[0033] 4 is a block diagram showing the configuration of the vehicle state cause determination unit in Embodiment 1. Vehicle state cause determination unit 52 includes deviation determination unit 521, rack end determination unit 522, and cause determination unit 523. Deviation determination unit 521 performs calculations using the steering wheel angle and the turning angle based on the gear ratio Gt between the steering wheel angle axis and the turning angle axis. Here, the gear ratio Gt between the steering wheel angle axis and the turning angle axis is the ratio of the steering wheel angle to the turning angle. The steering wheel angle value is divided by Gt to calculate the absolute value of the deviation between the value converted into the turning angle axis and the turning angle value.

[0034] In the following, the absolute value of the deviation calculated above will be expressed as the deviation between the steering wheel angle and the turning angle. Also, gear ratio Gt may be a gear ratio controlled by variable gear ratio control or the like. Deviation determination unit 521 outputs "1" as deviation determination signal Y1 when the magnitude of the deviation between the steering wheel angle and the turning angle obtained by the above calculation exceeds deviation threshold T1, which is a threshold value set by the designer, and outputs "0" as deviation determination signal Y1 when the magnitude is equal to or less than deviation threshold T1.

[0035] When the deviation threshold T1 is set to 0, the deviation determination unit 521 outputs a deviation determination signal Y1 of "1" when the deviation is not strictly 0. In practice, noise from the sensors used to detect the steering wheel angle or the turning angle may cause a momentary erroneous determination that a deviation has occurred, even when no deviation actually occurs. Therefore, the deviation threshold T1 may be set to a value greater than or equal to 0. For example, the deviation threshold T1 may be set by first determining the maximum errors that can occur in the sensors that detect the steering wheel angle and the turning angle, and then setting the sum of the maximum errors as the deviation threshold T1, thereby preventing erroneous determination due to noise. A state in which the deviation determination signal Y1 = 1 indicates a deviation occurring state in which a deviation has occurred between the steering wheel angle and the turning angle, and the deviation occurring state indicates either a curb hit state or a rack end state.

[0036] Rack end determination unit 522 determines whether the value obtained by subtracting the maximum steering angle value from the absolute value of the steering angle value is greater than angle threshold value T2, which is a threshold value set by the designer. Rack end determination unit 522 outputs "1" as rack end determination signal Y2 when the value obtained by subtracting the maximum steering angle value from the absolute value of the steering angle value is greater than angle threshold value T2, and outputs "0" as rack end determination signal Y2 when the value is equal to or less than angle threshold value T2.

[0037] When angle threshold T2 is set to 0, rack end determination unit 522 outputs "1" as rack end determination signal Y2 when the absolute value of the steering angle is strictly equal to the maximum steering angle value. In practice, due to the influence of the sensor used to detect the steering angle, the steering angle value may momentarily become smaller than the maximum steering angle due to noise, even if the steering has reached the maximum steering angle. Therefore, angle threshold T2 may be set to a negative number less than 0. As a setting method, for example, the maximum value of error that can occur in each sensor that detects the steering angle is found in advance, and the value obtained by adding a negative sign to the maximum error is set as angle threshold T2, thereby suppressing erroneous determination due to noise.

[0038] FIG. 5 is a block diagram showing another configuration of the vehicle state cause determination unit in the first embodiment. In vehicle state cause determination unit 52 shown in FIG. 5, rack end determination unit 522 makes a determination based on the steering wheel angle rather than the turning angle. Specifically, rack end determination unit 522 outputs "1" as the rack end determination signal Y2 when the value obtained by subtracting the maximum steering angle value from the value obtained by multiplying the absolute value of the steering wheel angle by the gear ratio Gt is greater than angle threshold T2, and outputs "0" as the rack end determination signal Y2 when the value is equal to or less than angle threshold T2. Even in the configuration shown in FIG. 5, the angle threshold T2 may be set by a method similar to the method described for setting using the steering angle, taking into account the influence of noise from the sensor used to detect the steering wheel angle.

[0039] The cause determination section 523 generates a state cause signal based on the deviation determination signal Y 1 output from the deviation determination section 521 and the rack end determination signal Y 2 output from the rack end determination section 522 .

[0040] 6 is a flowchart showing the processing performed by the cause determination unit in Embodiment 1. First, in step S1, the cause determination unit 523 determines whether the deviation determination signal Y1 is "1." If it is determined in step S1 that the deviation determination signal Y1 is not "1," the cause determination unit 523 outputs "0" as the state cause signal X in step S3. On the other hand, if it is determined in step S1 that the deviation determination signal Y1 is "1," the cause determination unit 523 determines in step S2 whether the rack end determination signal Y2 is "1."

[0041] If the cause determination unit 523 determines that the rack end determination signal Y2 is not "1," it outputs "1" as the state cause signal X in step S4. On the other hand, if the cause determination unit 523 determines that the rack end determination signal Y2 is "1" in step S4, it outputs "2" as the state cause signal X in step S5.

[0042] 7 is a diagram showing the relationship between the value of the state cause signal and the determination result of the vehicle state in the first embodiment. As shown in FIG. 7, when the value of the state cause signal X is "0," it means "a state in which the vehicle moves as intended due to steering operation." In contrast, when the value of the state cause signal X is "1," it means "a curb hit state," and when the value of the state cause signal X is "2," it means "a rack end state." In this way, it is possible to determine "a state in which the vehicle moves as intended due to steering operation," "a curb hit state," or "a rack end state" depending on the value of the state cause signal X output from the cause determination unit 523 of the vehicle state cause determination unit 52.

[0043] Fig. 8 is a block diagram showing the configuration of the excitation signal generator in embodiment 1. As shown in Fig. 8, the excitation signal generator 53 includes an excitation waveform determiner 531, an oscillation period determiner 532, a sampling determiner 533, an excitation amplitude generator 534, and an excitation signal generator 535. The excitation waveform determiner 531 determines the waveform of the excitation signal (excitation waveform) according to the value of the state cause signal X. Examples of the excitation waveform include a sine wave waveform, a square wave waveform, a triangular wave waveform, a trapezoidal wave waveform, etc., and are not limited to a specific waveform.

[0044] 9 is a diagram showing an example of an excitation waveform designated by the excitation waveform determiner 531 in accordance with the state cause signal in embodiment 1. In the example shown in Fig. 9, the excitation waveform determiner 531 designates a sine wave waveform when the value of the state cause signal X is "1", and designates a square wave waveform when the value of the state cause signal X is "2". Note that when the value of the state cause signal X is "0", no excitation is performed, and therefore the excitation waveform determiner 531 does not make any designation.

[0045] The vibration period determiner 532 determines the vibration period of the vibration signal according to the value of the state cause signal X. The vibration period may be any period that allows the driver to recognize the vibration, and may be set to, for example, 1 s, 0.5 s, or the like.

[0046] Fig. 10 is a diagram showing an example of a vibration period determined by the vibration period determiner 532 in accordance with the state cause signal in embodiment 1. In the example shown in Fig. 10, the vibration period determiner 532 specifies "1 s" as the vibration period when the value of the state cause signal X is "1", and specifies "0.5 s" as the vibration period when the value of the state cause signal X is "2". Note that when the value of the state cause signal X is "0", no vibration is applied, and therefore the vibration period determiner 532 does not make any particular specification.

[0047] The sampling determiner 533 determines the sampling period of the vibration signal in accordance with the value of the state cause signal X. The sampling time may be shorter than the vibration period set by the vibration period determiner 532 and longer than the reaction force control period. For example, if the reaction force control period is 0.001 s, the sampling time may be 0.001 s, 0.1 s, etc.

[0048] Fig. 11 is a diagram showing an example of a sampling period determined by the sampling determiner 533 in accordance with the state cause signal in embodiment 1. In the example shown in Fig. 11, the sampling determiner 533 specifies "0.001 s" as the sampling period when the value of the state cause signal X is "1", and specifies "0.1 s" as the sampling period when the value of the state cause signal X is "2". Note that when the value of the state cause signal X is "0", no vibration is applied, and therefore the sampling determiner 533 does not make any particular specification.

[0049] The excitation amplitude generator 534 generates the amplitude of the excitation signal. The amplitude of the excitation signal may be any amplitude that can be output by the reaction motor and that allows the driver to sense the excitation by the excitation signal. For example, if the torque that can be output by the reaction motor is 10 Nm, the excitation amplitude may be set to 1 Nm or the like, so that a value of 10 Nm or less is sufficient for the driver to sense. The amplitude that can be sensed by the driver may be set by previously vibrating the reaction motor at multiple excitation amplitudes and having the designer actually steer the steering wheel.

[0050] The excitation signal generator 535 generates an excitation signal based on the specifications of the excitation waveform determiner 531 , the vibration period determiner 532 , and the sampling determiner 533 .

[0051] 12 is a flowchart showing processing performed by the excitation signal generator in embodiment 1. In step S21, the excitation signal generator 535 determines whether the value of the state cause signal X is "0." If it is determined that the value of the state cause signal X is not "0," the excitation signal generator 535 references the excitation waveform specified in step S22, the vibration period specified in step S23, and the sampling specified in step S24. Then, in step S25, the excitation signal generator 535 generates and outputs an excitation signal based on the values ​​referenced in steps S22, S23, and S24. On the other hand, if it is determined in step S21 that the value of the state cause signal X is "0," the excitation signal generator 535 outputs "0" as the excitation signal in step S26.

[0052] The multiplier 536 multiplies the excitation amplitude value generated by the excitation amplitude generator 534 by the signal generated by the excitation signal generator 535 to generate and output an excitation signal.

[0053] For example, the excitation waveform, vibration period, and sampling period designated by the excitation waveform determiner 531, vibration period determiner 532, and sampling determiner 533 according to the value of the state cause signal X are assumed to be as shown in Figures 9, 10, and 11, respectively. When the value of the state cause signal X is "1," the excitation waveform determiner 531 designates a sine wave waveform, the vibration period determiner 532 designates "1 s," and the sampling determiner 533 designates "0.001 s." Furthermore, if the excitation amplitude value generated by the excitation amplitude generator 534 is always 1 Nm, the excitation signal output from the excitation signal generator 53 will be as shown in Figure 13.

[0054] 13 is a diagram showing an example of an excitation signal generated by the excitation signal generator in embodiment 1. As shown in Fig. 13, the excitation signal output from the excitation signal generator 53 has a sinusoidal waveform with an amplitude (maximum amplitude) of 1 Nm and a vibration period of 1 s. Here, as shown enlarged, the excitation signal shown in Fig. 13 has an amplitude that changes stepwise with a sampling period of 0.001 s.

[0055] 9 to 12, the vibration signal generator 53 shown in FIG. 8 specifies three elements (vibration waveform, vibration period, and sampling period) according to the value of the state cause signal X, but it is not necessary to specify all three elements. If the driver can sense the difference in vibration, it is sufficient to specify any one or more of the above three elements. For example, it is also possible to specify only the vibration waveform according to the value of the state cause signal X, and to set the vibration period and sampling period as fixed values ​​in advance.

[0056] Fig. 14 is a block diagram showing a first modified example of the excitation signal generator in Embodiment 1. The excitation signal generator 53 shown in Fig. 14 differs from the excitation signal generator 53 shown in Fig. 8 in that the state cause signal X is input only to the excitation waveform determiner 531 and the excitation signal generator 535, and is not input to the vibration period determiner 532 and the sampling determiner 533. In the excitation signal generator 53 shown in Fig. 14, for example, the excitation waveform determiner 531 specifies the excitation waveform shown in Fig. 9 in accordance with the value of the state cause signal X.

[0057] Furthermore, the vibration period determiner 532 and the sampling determiner 533 specify fixed values, and the vibration amplitude value generated by the vibration amplitude generator 534 is a fixed value. For example, the vibration period specified by the vibration period determiner 532 is 1 s (fixed value), the sampling period specified by the sampling determiner 533 is 0.001 s (fixed value), and the vibration amplitude value generated by the vibration amplitude generator 534 is 1 Nm (fixed value). This simplifies the configuration.

[0058] Fig. 15 is a diagram showing vibration signals generated by a vibration signal generator according to a first modified example of Embodiment 1. When the value of the state cause signal X is "1", a sine wave vibration signal shown in the upper part of Fig. 15 is generated, and when the value of the state cause signal X is "2", a square wave vibration signal shown in the lower part of Fig. 15 is generated. In this way, even if only the vibration waveform is specified according to the value of the state cause signal X, the driver can sense the state from the difference in the vibration signal according to the value of the state cause signal X.

[0059] Fig. 16 is a block diagram showing a second modified example of the excitation signal generator in Embodiment 1. The excitation signal generator 53 shown in Fig. 16 differs from the excitation signal generator 53 shown in Fig. 8 in that the state cause signal X is input only to the vibration period determiner 532 and the excitation signal generator 535, and is not input to the vibration waveform determiner 531 and the sampling determiner 533. In the excitation signal generator 53 shown in Fig. 16, for example, the vibration period determiner 532 specifies the vibration period shown in Fig. 10 in accordance with the value of the state cause signal X.

[0060] Furthermore, the excitation waveform determiner 531 and the sampling determiner 533 specify fixed values, and the excitation amplitude value generated by the excitation amplitude generator 534 is also a fixed value. For example, the excitation waveform specified by the excitation waveform determiner 531 is a sine wave waveform (fixed value), the sampling period specified by the sampling determiner 533 is 0.001 s (fixed value), and the excitation amplitude value generated by the excitation amplitude generator 534 is 1 Nm (fixed value). This simplifies the configuration.

[0061] Fig. 17 is a diagram showing vibration signals generated by a vibration signal generator according to a second modification of Embodiment 1. When the value of the state cause signal X is "1", a sine wave vibration signal shown in the upper part of Fig. 17 is generated, and when the value of the state cause signal X is "2", a square wave vibration signal shown in the lower part of Fig. 17 is generated. In this way, even if only the vibration period is specified according to the value of the state cause signal X, the driver can sense the state from the difference in the vibration signal according to the value of the state cause signal X.

[0062] Fig. 18 is a block diagram showing a third modified example of the excitation signal generator in Embodiment 1. The excitation signal generator 53 shown in Fig. 18 differs from the excitation signal generator 53 shown in Fig. 8 in that the state cause signal X is input only to the sampling determiner 533 and the excitation signal generator 535, and is not input to the excitation waveform determiner 531 and the vibration period determiner 532. In the excitation signal generator 53 shown in Fig. 18, for example, the sampling determiner 533 specifies the sampling period shown in Fig. 11 in accordance with the value of the state cause signal X.

[0063] Furthermore, the excitation waveform determiner 531 and the vibration period determiner 532 specify fixed values, and the excitation amplitude value generated by the excitation amplitude generator 534 is also a fixed value. For example, the excitation waveform specified by the excitation waveform determiner 531 is a sine wave waveform (fixed value), the vibration period specified by the vibration period determiner 532 is 1 s (fixed value), and the excitation amplitude value generated by the excitation amplitude generator 534 is 1 Nm (fixed value). This simplifies the configuration.

[0064] Fig. 19 is a diagram showing vibration signals generated by a vibration signal generator according to a third modification of Embodiment 1. When the value of the state cause signal X is "1", a substantially sinusoidal vibration signal shown in the upper part of Fig. 19 is generated, and when the value of the state cause signal X is "2", a sinusoidal vibration signal shown in the lower part of Fig. 19 is generated. In this way, even if only the sampling period is specified according to the value of the state cause signal X, the driver can sense the state from the difference in the vibration signal according to the value of the state cause signal X.

[0065] 14, 16, and 18, the vibration signal generator 53 according to the first, second, and third modifications specifies one of the three elements (vibration waveform, vibration period, and sampling period) according to the value of the state cause signal X. However, the vibration signal generator 53 may be configured to specify any two of the three elements according to the value of the state cause signal X.

[0066] As described above, in this embodiment, when the vehicle cannot be driven in the direction intended by the driver by steering the steering wheel, the vehicle state cause determination unit 52 determines the cause of the state from the steering wheel angle and the turning angle, and generates a state cause signal. Then, the vibration signal generation unit 53 generates a vibration signal to be applied to the reaction force mechanism 100 based on the state cause signal. As a result, when the vehicle cannot be turned in the intended direction by steering the steering wheel, the steering wheel is vibrated in accordance with the cause of the state, and the driver can be prompted to steer appropriately.

[0067] Furthermore, in this embodiment, vehicle state cause determination unit 52 can determine, based on the steering wheel angle and the steering angle, whether a state in which the vehicle cannot travel in the direction intended by the driver due to steering of the steering wheel is a rack end state in which the steering angle has reached the rack end, or a curb hit state in which the tire is in contact with a curb.

[0068] More specifically, from the gear ratio between the axis of the steering wheel angle and the axis of the turning angle, one of the steering wheel angle and the turning angle is converted to the other axis, and the absolute value of the deviation between the steering wheel angle and the turning angle is calculated.In a deviation occurrence state in which the absolute value of the calculated deviation between the steering wheel angle and the turning angle is greater than a predetermined deviation threshold, if the absolute value of the steering wheel angle or the turning angle exceeds the predetermined angle threshold, it is determined to be a rack end state, and if it does not exceed the predetermined angle threshold, it is determined to be a curb hit state, thereby making it possible to determine whether the vehicle is in a rack end state or a curb hit state.

[0069] In this embodiment, the vibration signal generator 53 determines at least one of the vibration waveform, the vibration period, and the sampling period based on the state cause signal, and then generates the vibration signal. This allows vibration to be applied depending on whether the vehicle is in the rack-end state or the curb-hitting state, making it possible to notify the driver of the current state.

[0070] [Embodiment 2] A vehicle steering control device and a steer-by-wire vehicle according to embodiment 2 have the same configuration as the vehicle steering control device and the steer-by-wire vehicle according to embodiment 1. However, in this embodiment, the operation of the cause determination unit 523 is different from that in embodiment 1. The following mainly describes the parts that are different from embodiment 1.

[0071] This embodiment is intended to solve the problem that occurs in the first embodiment when a curb hit state occurs near the rack end state. In the first embodiment, when a curb hit state occurs near the rack end state, it is first determined that a deviation has occurred. If the steering wheel is then turned further, the vehicle hits the curb and is determined to be in the rack end state. In the rack end state, there is no problem in continuing to drive, but in the curb hit state, steering is required to avoid the curb.

[0072] Here, there is no problem if steering can be performed to avoid the curb when the vehicle is in a curb hit state, but if the rack end state is reached immediately after the curb hit state is determined, the driver may perceive the vehicle as being in a rack end state without realizing that the vehicle is in a curb hit state.For this reason, it may be better to notify the driver that the vehicle is in a curb hit state even if the rack end state occurs when the vehicle is in a curb hit state.

[0073] In this embodiment, if the vehicle is in a curb hit state, the cause determination unit 523 continues to determine that the vehicle is in a curb hit state even when the vehicle reaches the rack end. Specifically, the cause determination unit 523 refers to the previous value of the state cause signal X and avoids overwriting the determination of the curb hit state with the determination of the rack end state, thereby continuing to determine that the vehicle is in a curb hit state.

[0074] Fig. 20 is a flowchart showing the processing performed by the cause determination unit in embodiment 2. In Fig. 20, steps that are the same as those in the flowchart shown in Fig. 6 are given the same reference numerals. The flowchart shown in Fig. 20 differs from the flowchart shown in Fig. 6 in that step S6 is provided between step S1 and step S2.

[0075] First, in step S1, the cause determination unit 523 determines whether the deviation determination signal Y1 is "1." If it is determined in step S1 that the deviation determination signal Y1 is not "1," the cause determination unit 523 outputs "0" as the state cause signal X in step S3. On the other hand, if it is determined in step S1 that the deviation determination signal Y1 is "1," the cause determination unit 523 determines in step S6 whether the previous value of the state cause signal X output from the cause determination unit 523 is not "1."

[0076] If the cause determination unit 523 determines that the previous value of the state cause signal X is "1," then in step S4 it outputs "1" as the state cause signal X. On the other hand, if it determines in step S6 that the previous value of the state cause signal X is not "1," then in step S2 the cause determination unit 523 determines whether the rack end determination signal Y2 is "1."

[0077] If the cause determination unit 523 determines that the rack end determination signal Y2 is not "1," then in step S4 it outputs "1" as the state cause signal X. On the other hand, if the cause determination unit 523 determines in step S4 that the rack end determination signal Y2 is "1," then in step S5 it outputs "2" as the state cause signal X.

[0078] As described above, in this embodiment, if it is determined in step S1 that the deviation determination signal Y1 is "1" and the determination of the curb hit state could be overwritten with the determination of the rack end state, the previous value of the state cause signal X is referenced in step S6. If the previous value of the state cause signal X is "1," the state cause signal X is maintained at "1" in step S4. This makes it possible to prevent the determination of the curb hit state from being overwritten with the determination of the rack end state.

[0079] In this embodiment, once a curb hit state is determined, the curb hit state remains determined even if the rack end is reached. If the tire or wheel hits a curb, there is a possibility that the tire or wheel will be damaged even if the rack end has been reached, and the driver must immediately avoid the curb, so the curb hit state is transmitted with priority. Note that if the driver steers the steering wheel in the direction away from the curb while in the curb hit state, and then reaches the rack end in a place without a curb, the rack end state is determined to be the rack end state.

[0080] As described above, in this embodiment, the state is determined by referring to the previous value of the state cause signal X. This prevents the determination of the curb hit state from being overwritten by the determination of the rack end state, and the state can be clearly communicated to the driver even if the curb is hit near the rack end.

[0081] [Embodiment 3] A vehicle steering control device and a steer-by-wire vehicle according to embodiment 3 have the same configuration as the vehicle steering control device and the steer-by-wire vehicle according to embodiment 1. However, in this embodiment, the operation of the cause determination unit 523 is different from that in embodiment 1. The following mainly describes the parts that are different from embodiment 1.

[0082] This embodiment is intended to solve the problem in the first embodiment when the responsiveness of the tracking control of steering control unit 33 is low. When steering an SBW vehicle, as long as the vehicle is not in a curb hit state or rack end state, there is basically no deviation between the steering wheel angle and the steering angle. However, if the responsiveness of the tracking control unit 33 is low, for example, when the steering wheel is quickly steered, such as in emergency steering, a momentary deviation may occur between the steering wheel angle and the steering angle even when the vehicle is not in a curb hit state or rack end state.

[0083] In the first embodiment, if a deviation between the steering wheel angle and the turning angle occurs momentarily, there is a possibility that cause determination unit 523 will erroneously determine that the vehicle has hit a curb or that the vehicle is in a rack-end state. A momentary deviation will resolve over time, but vibrations caused by a momentary deviation may confuse the driver. This embodiment prevents erroneous determination when a deviation between the steering wheel angle and the turning angle occurs momentarily due to sudden steering, even when the responsiveness of the tracking control of turning control unit 33 is low.

[0084] Fig. 21 is a flowchart showing the processing performed by the cause determination unit in embodiment 3. In Fig. 21, steps that are the same as those in the flowchart shown in Fig. 6 are given the same reference numerals. The flowchart shown in Fig. 21 differs from the flowchart shown in Fig. 6 in that step S7 is provided before step S1, step S8 is provided between step S1 and step S2, and step S9 is provided between step S1 and step S3.

[0085] First, in step S7, the cause determination unit 523 counts time. Specifically, the initial time when the SBW system controller 3 is started is set to "0," and the elapsed time thereafter is counted as a time count value. In step S1, the cause determination unit 523 determines whether the deviation determination signal Y1 is "1." If it is determined in step S1 that the deviation determination signal Y1 is not "1," the cause determination unit 523 resets the counted elapsed time (time count value) in step S9, and outputs "0" as the state cause signal X in step S3.

[0086] 21 starts again after the time count value is reset, the time elapsed since the time count value was reset is counted as the time count value in step S7. After that, if the deviation determination signal Y1 is determined to be "1" in step S1, the cause determination unit 523 determines in step S8 whether the time count value is greater than a time threshold T3 that is set by the designer.

[0087] If it is determined in step S8 that the time count value is equal to or less than the time threshold value T3, the cause determination unit 523 outputs "0" as the state cause signal X in step S3. On the other hand, if it is determined that the time count value is greater than the time threshold value T3, the cause determination unit 523 determines in step S2 whether the rack end determination signal Y2 is "1".

[0088] If the cause determination unit 523 determines that the rack end determination signal Y2 is not "1," then in step S4 it outputs "1" as the state cause signal X. On the other hand, if the cause determination unit 523 determines in step S4 that the rack end determination signal Y2 is "1," then in step S5 it outputs "2" as the state cause signal X.

[0089] As described above, in this embodiment, the time count value is reset each time the deviation determination signal Y1 is determined to be "0" in step S1. Even if the deviation determination signal Y1 is determined to be "1" in step S1, the system does not immediately determine that the vehicle is in a curb hit state or rack end state. Instead, the system determines whether the vehicle is in a curb hit state or rack end state when it is determined in step S8 that the elapsed time since the deviation occurred is greater than the time threshold T3. This prevents erroneous determination when a momentary deviation occurs between the steering wheel angle and the turning angle due to sudden steering.

[0090] The time threshold value T3 may be determined according to the responsiveness of the tracking control of the steering control unit 33. For example, a SBW vehicle may be used to perform test steering on a road surface without curbs, at a speed that can be expected in actual steering, so as not to reach the rack end. Then, the maximum continuous time during which a deviation occurs may be calculated from the steering wheel angle and the steering angle during the test steering, and this time may be set as the time threshold value T3.

[0091] As described above, in this embodiment, the time that the deviation state continues is referenced, and if this time exceeds the time threshold T3, it is determined whether the vehicle is in the curb hit state or the rack end state. This makes it possible to prevent erroneous determination even when a momentary deviation occurs between the steering wheel angle and the turning angle due to sudden steering.

[0092] [Embodiment 4] A vehicle steering control device and a steer-by-wire vehicle according to embodiment 4 have the same configuration as the vehicle steering control device and the steer-by-wire vehicle according to embodiment 1. However, in this embodiment, the operation of the cause determination unit 523 is different from that in embodiment 1. The following mainly describes the parts that are different from embodiment 1.

[0093] This embodiment is a combination of Embodiments 2 and 3. That is, this embodiment solves the problem that occurs when a curb hit state occurs near the rack end state, and prevents erroneous determination when a deviation between the steering wheel angle and the turning angle occurs instantaneously due to sudden steering.

[0094] Fig. 22 is a flowchart showing the processing performed by the cause determination unit in embodiment 4. In Fig. 22, the same steps as those in the flowcharts shown in Fig. 6, Fig. 20, and Fig. 21 are denoted by the same reference numerals. The flowchart shown in Fig. 22 differs from the flowchart shown in Fig. 6 in that step S7 is provided before step S1, steps S8 and S6 are provided between steps S1 and S2, and step S9 is provided between steps S1 and S3.

[0095] First, in step S7, the cause determination unit 523 counts time. Specifically, the initial time when the SBW system controller 3 is started is set to "0," and the elapsed time thereafter is counted as a time count value. In step S1, the cause determination unit 523 determines whether the deviation determination signal Y1 is "1." If it is determined in step S1 that the deviation determination signal Y1 is not "1," the cause determination unit 523 resets the counted elapsed time (time count value) in step S9, and outputs "0" as the state cause signal X in step S3.

[0096] 21 starts again after the time count value is reset, the time elapsed since the time count value was reset is counted as the time count value in step S7. After that, if the deviation determination signal Y1 is determined to be "1" in step S1, the cause determination unit 523 determines in step S8 whether the time count value is greater than a time threshold T3 that is set by the designer.

[0097] If it is determined in step S8 that the time count value is equal to or less than the time threshold value T3, the cause determination unit 523 outputs "0" as the state cause signal X in step S3. On the other hand, if it is determined that the time count value is greater than the time threshold value T3, the cause determination unit 523 determines in step S6 whether the previous value of the state cause signal X output from the cause determination unit 523 is "1."

[0098] If the cause determination unit 523 determines that the previous value of the state cause signal X is "1," then in step S4 it outputs "1" as the state cause signal X. On the other hand, if it determines in step S6 that the previous value of the state cause signal X is not "1," then in step S2 the cause determination unit 523 determines whether the rack end determination signal Y2 is "1."

[0099] If the cause determination unit 523 determines that the rack end determination signal Y2 is not "1", it outputs "1" as the state cause signal X in step S4. On the other hand, if the cause determination unit 523 determines that the rack end determination signal Y2 is "1" in step S4, it outputs "2" as the state cause signal X in step S5. The time threshold T3 may be set by the method described in the third embodiment.

[0100] As described above, in this embodiment, the state is determined by referring to the previous value of the state cause signal X. Also, in this embodiment, the time that the deviation state continues is referenced, and if this time is greater than the time threshold T3, a determination is made as to whether the state is a curb strike state or a rack end state. This prevents the determination of the curb strike state from being overwritten by the determination of the rack end state, and makes it possible to clearly communicate the state to the driver even if the curb is struck near the rack end. Also, erroneous determinations can be prevented even when a momentary deviation occurs between the steering wheel angle and the turning angle due to sudden steering.

[0101] [Embodiment 5] A vehicle steering control device and a steer-by-wire vehicle according to embodiment 5 have substantially the same configuration as the vehicle steering control device and the steer-by-wire vehicle according to embodiment 1. However, in this embodiment, the configuration of the reaction force control unit 31 is different from that of embodiment 1. The following mainly describes the parts that are different from embodiment 1.

[0102] This embodiment allows the driver to not only know whether the vehicle is in a curb hit state or a rack end state, but also to know the degree of deviation between the steering wheel steering and the vehicle's traveling direction.

[0103] Fig. 23 is a block diagram showing the configuration of a reaction force control unit in embodiment 5. In Fig. 23, components corresponding to those shown in Fig. 3 are assigned the same reference numerals. The reaction force control unit 31 shown in Fig. 23 differs from the reaction force control unit 31 shown in Fig. 3 in that a vehicle state cause determination unit 52 outputs a state quantity indicating a measure of deviation between the steering wheel steering and the vehicle traveling direction to a vibration signal generation unit 53 in addition to a state cause signal. The target steering torque calculation unit 51, current command conversion unit 54, and addition unit 55 are the same as those shown in Fig. 3.

[0104] Fig. 24 is a block diagram showing the configuration of the vehicle state cause determination unit in embodiment 5. In Fig. 24, components corresponding to those shown in Fig. 4 and Fig. 5 are given the same reference numerals. The vehicle state cause determination unit 52 shown in Fig. 24 includes a deviation determination unit 521, a rack end determination unit 522, and a cause determination unit 523, similar to the vehicle state cause determination unit 52 shown in Fig. 4 and Fig. 5.

[0105] 4 and 5, deviation determination unit 521 outputs "1" as deviation determination signal Y1 when the magnitude of the deviation between the steering wheel angle and the turning angle exceeds deviation threshold T1, which is a threshold value set by a designer, and outputs "0" as deviation determination signal Y1 when the magnitude of the deviation is equal to or less than deviation threshold T1. Note that deviation threshold T1 may be set in the same manner as in the first embodiment.

[0106] 4 and 5 in that deviation determination unit 521 outputs, in addition to deviation determination signal Y1, a state quantity indicating a measure of deviation between the steering wheel steering and the vehicle's traveling direction. Since the state quantity output by deviation determination unit 521 indicates a measure of deviation between the steering wheel steering and the vehicle's traveling direction, it is sufficient that the state quantity has the characteristic of monotonically increasing with an increase in the deviation between the steering wheel angle and the turning angle. In other words, it is sufficient that the state quantity can represent the magnitude of the deviation between the steering wheel angle and the turning angle.

[0107] Fig. 25 is a diagram showing an example of a state quantity in the fifth embodiment. The state quantity shown in Fig. 25 increases linearly according to the deviation between the steering wheel angle and the steering angle. A limit value may be set for the state quantity so that it does not exceed a predetermined maximum value. The rack end determination unit 522 and the cause determination unit 523 are the same as those shown in Figs. 4 and 5.

[0108] Fig. 26 is a block diagram showing the configuration of the excitation signal generator in embodiment 5. In Fig. 26, components corresponding to those shown in Fig. 8 are denoted by the same reference numerals. The excitation signal generator 53 shown in Fig. 26 includes an excitation waveform determiner 531, an oscillation period determiner 532, a sampling determiner 533, an excitation amplitude generator 534, and an excitation signal generator 535, similar to the excitation signal generator 53 shown in Fig. 8.

[0109] The excitation waveform determiner 531, the vibration period determiner 532, the sampling determiner 533, and the excitation signal generator 535 are the same as those shown in Fig. 8. However, the excitation amplitude generator 534 differs from those shown in Fig. 8 in that it generates the amplitude of the excitation signal (excitation amplitude) according to the state quantity. Specifically, the excitation amplitude generator 534 generates an excitation amplitude that has the characteristic of monotonically increasing with respect to the state quantity.

[0110] Fig. 27 is a diagram showing an example of an excitation amplitude generated in the fifth embodiment. The excitation amplitude shown in Fig. 27 has a characteristic of increasing linearly according to the state quantity. A limit value may be set for the excitation amplitude so that it does not exceed a predetermined maximum value. Similar to that shown in Fig. 8 , the multiplication unit 536 generates an excitation signal by multiplying the excitation amplitude generated by the excitation amplitude generator 534 by the signal generated by the excitation signal generator 535.

[0111] Fig. 28 is a diagram showing an example of an excitation amplitude and an excitation waveform generated in the fifth embodiment. The upper part of Fig. 28 shows the excitation amplitude, and the lower part of Fig. 28 shows the excitation waveform. The excitation amplitude and the excitation waveform shown in Fig. 28 are generated when the value of the state cause signal X is "1". In other words, they are generated when the excitation waveform determiner 531 specifies a sine wave waveform, the vibration period determiner 532 specifies "1 s", and the sampling determiner 533 specifies "0.001 s" (see Figs. 9, 10, and 11).

[0112] The value of the state cause signal X becomes "1" when the vehicle is in a curb hit state. When the steering wheel is further turned toward the curb while the vehicle is in a curb hit state, the deviation between the steering wheel angle and the turning angle increases. This increases the state quantity, and as shown in the upper part of FIG. 28, the excitation amplitude increases with the turning. As a result, the generated excitation waveform becomes a sine wave whose amplitude (maximum amplitude) gradually increases, as shown in the lower part of FIG. 28.

[0113] As described above, in this embodiment, a state quantity corresponding to the deviation between the steering wheel angle and the turning angle is calculated, and an excitation amplitude corresponding to the state quantity is generated. This allows the driver to not only know whether the vehicle is in a curb hit state or a rack end state, but also to know the degree of deviation between the steering wheel steering and the vehicle's traveling direction.

[0114] In this embodiment, similarly to the first embodiment, the vibration signal generator 53 may be configured to specify one of three elements (vibration waveform, vibration period, and sampling period) according to the value of the state cause signal X. Alternatively, the vibration signal generator 53 may specify any two of the three elements according to the value of the state cause signal X.

[0115] Furthermore, the cause determination unit 523 described in the second embodiment may be applied to this embodiment. This prevents the determination of the curb hit state from being overwritten by the determination of the rack end state even when the vehicle hits a curb near the rack end state, and also enables the driver to grasp the degree of deviation between the steering wheel steering and the vehicle traveling direction.

[0116] Similarly, cause determination unit 523 described in embodiment 3 may be applied to this embodiment. This prevents erroneous determination when a momentary deviation occurs between the steering wheel angle and the turning angle due to sudden steering, and makes it possible to grasp the degree of deviation between the steering of the steering wheel and the traveling direction of the vehicle.

[0117] Similarly, the cause determination unit 523 described in the fourth embodiment may be applied to this embodiment. This makes it possible to prevent the determination of the curb hit state from being overwritten by the determination of the rack end state even when the vehicle hits a curb near the rack end state, to prevent erroneous determination when a momentary deviation occurs between the steering wheel angle and the turning angle due to sudden steering, and to grasp the degree of deviation between the steering wheel steering and the vehicle traveling direction.

[0118] [Embodiment 6] A vehicle steering control device and a steer-by-wire vehicle according to embodiment 5 have substantially the same configuration as the vehicle steering control device and the steer-by-wire vehicle according to embodiment 1. However, in this embodiment, the configuration of the reaction force control unit 31 is different from that of embodiment 1. The following mainly describes the parts that are different from embodiment 1.

[0119] This embodiment is intended to notify the driver of a slip state in addition to a curb hit state and a rack end state. When the vehicle is slipping due to oversteer, understeer, or the like, the vehicle will not turn in the intended direction even if the driver steers the steering wheel, even if there is no deviation between the steering wheel angle and the turning angle. Hereinafter, this state will be referred to as a "slip state."

[0120] A slip state is a phenomenon that occurs when the friction force between the tire and the road surface becomes saturated. To avoid a slip, the driver needs to steer the steering wheel gently or accelerate or decelerate gently. Therefore, a slip state requires a completely different response than a curb-hitting state or a rack-end state. Therefore, when the vehicle is in a slip state, it is necessary to determine that the vehicle is in a slip state and then notify the driver of the slip state. This embodiment makes it possible to notify the driver of a curb-hitting state or a rack-end state as well as a slip state.

[0121] Fig. 29 is a block diagram showing the configuration of a reaction force control unit in embodiment 6. In Fig. 29, components corresponding to those shown in Fig. 3 are assigned the same reference numerals. As shown in Fig. 29, in the reaction force control unit 31 of this embodiment, the vehicle behavior values, that is, the vehicle speed, yaw rate, and lateral acceleration, are also input to the vehicle state cause determination unit 52, and the configurations of the vehicle state cause determination unit 52 and the vibration signal generation unit 53 are different from those shown in Fig. 3. In addition, the target steering torque calculation unit 51, the current command conversion unit 54, and the addition unit 55 are the same as those shown in Fig. 3.

[0122] Fig. 30 is a block diagram showing the configuration of a vehicle state cause determination unit in Embodiment 6. In Fig. 30, components corresponding to those shown in Fig. 4 are assigned the same reference numerals. The vehicle state cause determination unit 52 shown in Fig. 30 includes a deviation determination unit 521, a rack end determination unit 522, and a cause determination unit 523, similar to the vehicle state cause determination unit 52 shown in Fig. 4. However, a slip determination unit 524 is added to the vehicle state cause determination unit 52 shown in Fig. 30, and accordingly the cause determination unit 523 is slightly different. The deviation determination unit 521 and the rack end determination unit 522 are the same as those shown in Fig. 4.

[0123] Slip determination unit 524 determines the vehicle's slip state from the steering angle, vehicle speed, yaw rate, and lateral acceleration, and outputs slip determination signal Y3. Specifically, slip determination unit 524 calculates a steering angle estimate from the vehicle speed, yaw rate, and lateral acceleration. Slip determination unit 524 outputs "1" as slip determination signal Y3 when the absolute value of the deviation between the steering angle estimate and the steering angle is greater than slip threshold T4, which is a threshold value set by the designer, and outputs "0" as slip determination signal Y3 when the absolute value is equal to or less than slip threshold T4. The steering angle estimate may be calculated using a two-wheel model used in general vehicle motion calculations, or may be calculated by another well-known method.

[0124] When the vehicle is not slipping, the vehicle's yaw rate and lateral acceleration are determined by the vehicle speed and steering angle, so the steering angle can be estimated by performing calculations based on the vehicle motion from the vehicle speed, yaw rate, and lateral acceleration. In contrast, when the vehicle is slipping, such as oversteering or understeering, the vehicle's yaw rate and lateral acceleration take values ​​that are independent of the steering angle, so the estimated steering angle in a slipping state will be significantly different from the actual steering angle. Therefore, it is possible to determine whether the vehicle is slipping from the deviation between the estimated steering angle and the steering angle, and the larger the absolute value of the deviation between the estimated steering angle and the steering angle, the greater the vehicle's slippage. Furthermore, as a method for setting the slip threshold T4, for example, test steering of the vehicle on a road surface where slippage is expected may be performed, and the slip threshold T4 may be determined from the deviation between the estimated steering angle and the steering angle when slippage occurs.

[0125] The cause determination unit 523 determines the cause of the vehicle state from the deviation determination signal Y1, the rack end determination signal Y2, and the slip determination signal Y3.

[0126] Fig. 31 is a block diagram showing another configuration of the vehicle state cause determination unit in Embodiment 6. The rack end determination unit 522 of the vehicle state cause determination unit 52 shown in Fig. 31 makes a determination based on the steering wheel angle rather than the turning angle, similar to the rack end determination unit 522 of the vehicle state cause determination unit 52 shown in Fig. 5. The deviation determination unit 521, cause determination unit 523, and slip determination unit 524 shown in Fig. 31 are the same as those shown in Fig. 30.

[0127] Fig. 32 is a flowchart showing the processing performed by the cause determination unit in embodiment 6. In Fig. 32, steps that are the same as those in the flowchart shown in Fig. 6 are given the same reference numerals. The flowchart shown in Fig. 32 differs from the flowchart shown in Fig. 6 in that steps S10 and S11 are provided between step S1 and the END terminal.

[0128] First, in step S1, the cause determination unit 523 determines whether the deviation determination signal Y1 is "1." If it is determined in step S1 that the deviation determination signal Y1 is not "1," the cause determination unit 523 determines in step S10 whether the slip determination signal Y3 is "1." If it is determined that the slip determination signal Y3 is not "1," the cause determination unit 523 outputs "0" as the state cause signal X in step S3. On the other hand, if it is determined in step S10 that the slip determination signal Y3 is "1," the cause determination unit 523 outputs "3" as the state cause signal X in step S11.

[0129] On the other hand, if it is determined in step S1 that the deviation determination signal Y1 is "1," the cause determination unit 523 determines in step S2 whether the rack end determination signal Y2 is "1." If the cause determination unit 523 determines that the rack end determination signal Y2 is not "1," it outputs "1" as the state cause signal X in step S4. On the other hand, if it is determined in step S4 that the rack end determination signal Y2 is "1," the cause determination unit 523 outputs "2" as the state cause signal X in step S5.

[0130] 33 is a diagram showing the relationship between the value of the state cause signal and the determination result of the vehicle state in the sixth embodiment. As shown in FIG. 33, when the value of the state cause signal X is "0," it means "a state in which the vehicle moves as intended due to steering operation." In contrast, when the value of the state cause signal X is "1," it means "a curb-hitting state," and when the value of the state cause signal X is "2," it means "a rack-end state." Furthermore, when the value of the state cause signal X is "3," it means "a slip state."

[0131] In this manner, in this embodiment, it is possible to determine whether the vehicle is in a "state in which the vehicle moves as intended due to steering operation," "curb hitting state," "rack end state," or "slip state" based on the value of the state cause signal X output from the cause determination unit 523 of the vehicle state cause determination unit 52.

[0132] 34 is a block diagram showing the configuration of the excitation signal generator in embodiment 6. As shown in Fig. 34, the excitation signal generator 53 includes an excitation waveform determiner 531, an oscillation period determiner 532, a sampling determiner 533, an excitation amplitude generator 534, and an excitation signal generator 535. The excitation waveform determiner 531 determines the waveform of the excitation signal (excitation waveform) according to the value of the state cause signal X. Examples of the excitation waveform include a sine wave waveform, a square wave waveform, a triangular wave waveform, a trapezoidal wave waveform, etc., and are not limited to a specific waveform.

[0133] Fig. 35 is a diagram showing an example of an excitation waveform designated by the excitation waveform determiner 531 in accordance with the state cause signal in embodiment 6. In the example shown in Fig. 35, the excitation waveform determiner 531 designates a sine wave waveform when the value of the state cause signal X is "1", a square wave waveform when the value of the state cause signal X is "2", and a triangular wave waveform when the value of the state cause signal X is "3". Note that when the value of the state cause signal X is "0", no excitation is performed, and therefore the excitation waveform determiner 531 does not make any particular designation.

[0134] The vibration period determiner 532 determines the vibration period of the vibration signal according to the value of the state cause signal X. The vibration period may be any period that allows the driver to recognize the vibration, and may be set to, for example, 1 s, 0.5 s, 0.25 s, or the like.

[0135] Fig. 36 is a diagram showing an example of a vibration period determined by the vibration period determiner 532 in accordance with the state cause signal in embodiment 6. In the example shown in Fig. 36, the vibration period determiner 532 specifies "1 s" as the vibration period when the value of the state cause signal X is "1", specifies "0.5 s" as the vibration period when the value of the state cause signal X is "2", and specifies "0.25 s" as the vibration period when the value of the state cause signal X is "3". Note that when the value of the state cause signal X is "0", no vibration is applied, and therefore the vibration period determiner 532 does not make any particular specification.

[0136] The sampling determiner 533 determines the sampling period of the vibration signal in accordance with the value of the state cause signal X. The sampling time may be shorter than the vibration period set by the vibration period determiner 532 and longer than the reaction force control period. For example, if the reaction force control period is 0.001 s, the sampling time may be 0.001 s, 0.01 s, 0.1 s, etc.

[0137] Fig. 37 is a diagram showing an example of a sampling period determined by the sampling determiner 533 in accordance with the state cause signal in embodiment 6. In the example shown in Fig. 37, the sampling determiner 533 specifies "0.001 s" as the sampling period when the value of the state cause signal X is "1", "0.1 s" as the sampling period when the value of the state cause signal X is "2", and "0.01 s" as the sampling period when the value of the state cause signal X is "3". Note that when the value of the state cause signal X is "0", no vibration is applied, and therefore the sampling determiner 533 does not make any particular specification.

[0138] The excitation amplitude generator 534 generates the amplitude of the excitation signal. The amplitude of the excitation signal may be determined in advance by the designer as long as it is large enough to be output by the reaction motor and allows the driver to sense the excitation by the vibration signal. For example, if the torque that can be output by the reaction motor is 10 Nm, the excitation amplitude may be set to 1 Nm or less, which is large enough to be sensed by the driver.

[0139] The excitation signal generator 535 generates an excitation signal based on the specifications of the excitation waveform determiner 531 , the vibration period determiner 532 , and the sampling determiner 533 .

[0140] Fig. 38 is a flowchart showing the processing performed by the excitation signal generator in embodiment 6. In Fig. 38, the same steps as those in the flowchart shown in Fig. 12 are denoted by the same reference numerals. The flowchart shown in Fig. 38 includes steps S21 to S26, similar to the flowchart shown in Fig. 12.

[0141] In step S21, the vibration signal generator 535 determines whether the value of the state cause signal X is "0." If it is determined that the value of the state cause signal X is not "0," the vibration signal generator 535 references the vibration waveform specified in step S22, the vibration period specified in step S23, and the sampling specified in step S24. Then, in step S25, the vibration signal generator 535 generates and outputs a vibration signal based on the values ​​referenced in steps S22, S23, and S24. On the other hand, if it is determined in step S21 that the value of the state cause signal X is "0," the vibration signal generator 535 outputs "0" as the vibration signal in step S26.

[0142] The multiplier 536 multiplies the excitation amplitude value generated by the excitation amplitude generator 534 by the signal generated by the excitation signal generator 535 to generate and output an excitation signal.

[0143] 35 to 37, the vibration signal generator 53 shown in Fig. 34 specifies three elements (vibration waveform, vibration period, and sampling period) according to the value of the state cause signal X, but it is not necessary to specify all three elements. If the driver can sense the difference in vibration, it is sufficient to specify any one or more of the above three elements.

[0144] For example, only the excitation waveform may be specified according to the value of the state cause signal X, with the vibration period and sampling period being set as fixed values ​​in advance. Alternatively, only the vibration period may be specified according to the value of the state cause signal X, with the excitation waveform and sampling period being set as fixed values ​​in advance. Alternatively, only the sampling period may be specified according to the value of the state cause signal X, with the excitation waveform and vibration period being set as fixed values ​​in advance. Of course, the excitation signal generator 53 may specify any two of the three elements according to the value of the state cause signal X.

[0145] It is sufficient if the curb hitting state, rack end state, and slip state can be distinguished by a combination of the excitation waveform, vibration period determination, and sampling. For this reason, for example, as shown in Fig. 39, the excitation waveform designated by the excitation waveform determiner 531 may be common to the curb hitting state and rack end state, and as shown in Fig. 40, the vibration period designated by the vibration period determiner 532 may be common to the rack end state and slip state.

[0146] Fig. 39 is a diagram showing another example of an excitation waveform designated by the excitation waveform determiner 531 in accordance with the state cause signal in embodiment 6. In the example shown in Fig. 39, the excitation waveform determiner 531 designates a sine wave waveform when the value of the state cause signal X is "1" or "2", and designates a square wave waveform when the value of the state cause signal X is "3". Note that when the value of the state cause signal X is "0", no excitation is performed, and therefore the excitation waveform determiner 531 does not make any particular designation.

[0147] Fig. 40 is a diagram showing another example of the vibration period determined by the vibration period determiner 532 in accordance with the state cause signal in embodiment 6. In the example shown in Fig. 40, the vibration period determiner 532 specifies "1 s" as the vibration period when the value of the state cause signal X is "1", and specifies "0.5 s" as the vibration period when the value of the state cause signal X is "2" or "3". Note that when the value of the state cause signal X is "0", no vibration is applied, and therefore the vibration period determiner 532 does not make any particular specification.

[0148] 41 is a diagram showing another example of an excitation signal generated by the excitation signal generator in embodiment 6. Here, the sampling period designated by the sampling determiner 533 is 0.001 s (fixed value), and the excitation amplitude value generated by the excitation amplitude generator 534 is 1 Nm (fixed value).

[0149] When the value of the state cause signal X is "1", the excitation signal shown in the upper part of Fig. 41 is generated. When the value of the state cause signal X is "1", the excitation waveform determiner 531 specifies a sine wave waveform, and the vibration period determiner 532 specifies a vibration period of "1 s". Therefore, when the value of the state cause signal X is "1", the excitation signal generated by the excitation signal generator 53 is a sine wave waveform with an amplitude (maximum amplitude) of 1 Nm and a vibration period of 1 s, as shown in the upper part of Fig. 41.

[0150] When the value of the state cause signal X is "2", the excitation signal shown in the middle part of Fig. 41 is generated. When the value of the state cause signal X is "2", the excitation waveform determiner 531 specifies a sine wave waveform, and the vibration period determiner 532 specifies "0.5 s" as the vibration period. Therefore, when the value of the state cause signal X is "2", the excitation signal generated by the excitation signal generator 53 is a sine wave waveform with an amplitude (maximum amplitude) of 1 Nm and a vibration period of 0.5 s, as shown in the middle part of Fig. 41.

[0151] When the value of the state cause signal X is "3", the vibration signal shown in the lower part of Fig. 41 is generated. When the value of the state cause signal X is "3", the vibration waveform determiner 531 specifies a square wave waveform, and the vibration period determiner 532 specifies a vibration period of "0.5 s". Therefore, when the value of the state cause signal X is "3", the vibration signal generated by the vibration signal generator 53 is a square wave waveform with an amplitude (maximum amplitude) of 1 Nm and a vibration period of 0.5 s, as shown in the middle part of Fig. 41.

[0152] 41, the excitation signals generated by the excitation signal generator 53 differ depending on the value of the state cause signal X. Therefore, the driver can distinguish between the curb hit state, the rack end state, and the slip state.

[0153] As described above, in this embodiment, when the vehicle is unable to travel in the direction intended by the driver due to steering, the vehicle state cause determination unit 52 determines whether the state is a rack end state, a curb hit state, or a slip state based on the steering wheel angle, the turning angle, and the vehicle behavior value, and generates a state cause signal. Then, the vibration signal generation unit 53 generates a vibration signal to be applied to the reaction force mechanism 100 based on the state cause signal. In this way, when the vehicle is unable to travel in the direction intended by the driver due to steering, it is possible to notify the driver that the state is a rack end state, a curb hit state, or a slip state.

[0154] The second embodiment described above may be applied to this embodiment, so that the cause determination unit 523 is prevented from overwriting the determination of the curb strike state with the determination of the rack-end state when a curb is struck near the rack end (first modification). The third embodiment described above may be applied to this embodiment, so that the cause determination unit 523 is prevented from making an erroneous determination when a sudden deviation between the steering wheel angle and the turning angle occurs instantaneously due to sudden steering (second modification). The fourth embodiment described above may be applied to this embodiment, so that the cause determination unit 523 is prevented from overwriting the determination of the curb strike state with the determination of the rack-end state when a curb is struck near the rack end, and is also prevented from making an erroneous determination when a sudden deviation between the steering wheel angle and the turning angle occurs instantaneously due to sudden steering (third modification). The first, second, and third modifications will be described below in order.

[0155] Fig. 42 is a flowchart showing the processing performed by the cause determination unit according to the first modification of embodiment 6. In Fig. 42, steps that are the same as those in the flowcharts shown in Fig. 20 and Fig. 32 are given the same reference numerals. The flowchart shown in Fig. 42 differs from the flowchart shown in Fig. 32 in that step S6 of Fig. 20 is provided between step S1 and step S2.

[0156] First, in step S1, the cause determination unit 523 determines whether the deviation determination signal Y1 is "1." If it is determined in step S1 that the deviation determination signal Y1 is not "1," the cause determination unit 523 determines in step S10 whether the slip determination signal Y3 is "1." If it is determined that the slip determination signal Y3 is not "1," the cause determination unit 523 outputs "0" as the state cause signal X in step S3. On the other hand, if it is determined in step S10 that the slip determination signal Y3 is "1," the cause determination unit 523 outputs "3" as the state cause signal X in step S11.

[0157] On the other hand, if it is determined in step S1 that the deviation determination signal Y1 is "1," the cause determination unit 523 determines in step S6 whether the previous value of the state cause signal X output from the cause determination unit 523 is not "1." If the cause determination unit 523 determines that the previous value of the state cause signal X is "1," the cause determination unit 523 outputs "1" as the state cause signal X in step S4. On the other hand, if it is determined in step S6 that the previous value of the state cause signal X is not "1," the cause determination unit 523 determines in step S2 whether the rack end determination signal Y2 is "1."

[0158] If the cause determination unit 523 determines that the rack end determination signal Y2 is not "1," it outputs "1" as the state cause signal X in step S4. On the other hand, if the cause determination unit 523 determines that the rack end determination signal Y2 is "1" in step S4, it outputs "2" as the state cause signal X in step S5.

[0159] By performing the above processing in the cause determination unit 523 according to the first modification, it is possible to prevent the determination of the curb hit state from being overwritten with the determination of the rack end state when the vehicle hits a curb near the rack end. Note that the cause determination unit 523 according to the first modification can also determine the curb hit state, rack end state, and slip state.

[0160] Figure 43 is a flowchart showing the processing performed by the cause determination unit according to the second modification of embodiment 6. In Figure 43, steps that are the same as those in the flowcharts shown in Figures 21 and 32 are given the same reference numerals. The flowchart shown in Figure 43 differs from the flowchart shown in Figure 32 in that step S7 of Figure 21 is provided before step S1, step S8 of Figure 21 is provided between steps S1 and S2, and step S9 of Figure 21 is provided between steps S1 and S10.

[0161] First, in step S7, the cause determination unit 523 counts time. Specifically, the initial time when the SBW system controller 3 is started is set to "0," and the elapsed time thereafter is counted as a time count value. In step S1, the cause determination unit 523 determines whether the deviation determination signal Y1 is "1." If it is determined in step S1 that the deviation determination signal Y1 is not "1," the cause determination unit 523 resets the counted elapsed time (time count value) in step S9. Then, in step S10, the cause determination unit 523 determines whether the slip determination signal Y3 is "1."

[0162] If the cause determination unit 523 determines that the slip determination signal Y3 is not "1," it outputs "0" as the state cause signal X in step S3. On the other hand, if the cause determination unit 523 determines that the slip determination signal Y3 is "1" in step S10, it outputs "3" as the state cause signal X in step S11.

[0163] 43 starts again after the time count value is reset, the time elapsed since the time count value was reset is counted as the time count value in step S7. After that, if the deviation determination signal Y1 is determined to be "1" in step S1, the cause determination unit 523 determines in step S8 whether the time count value is greater than a time threshold T3 that is set by the designer.

[0164] If it is determined in step S8 that the time count value is equal to or less than the time threshold value T3, the cause determination unit 523 outputs "0" as the state cause signal X in step S3. On the other hand, if it is determined that the time count value is greater than the time threshold value T3, the cause determination unit 523 determines in step S2 whether the rack end determination signal Y2 is "1".

[0165] If the cause determination unit 523 determines that the rack end determination signal Y2 is not "1," then in step S4 it outputs "1" as the state cause signal X. On the other hand, if the cause determination unit 523 determines in step S4 that the rack end determination signal Y2 is "1," then in step S5 it outputs "2" as the state cause signal X.

[0166] The above processing is performed by the cause determination unit 523 according to the second modification, thereby preventing erroneous determination when a sudden steering error occurs and the steering angle deviates instantaneously. The cause determination unit 523 according to the second modification can also determine whether the vehicle is in a curb hit state, a rack end state, or a slip state.

[0167] Figure 44 is a flowchart showing the processing performed by the cause determination unit according to the third modification of embodiment 6. In Figure 44, steps that are the same as those in the flowcharts shown in Figures 22 and 32 are given the same reference numerals. The flowchart shown in Figure 44 differs from the flowchart shown in Figure 32 in that step S7 of Figure 22 is provided before step S1, steps S8 and S6 of Figure 22 are provided between steps S1 and S2, and step S9 of Figure 22 is provided between steps S1 and S10.

[0168] First, in step S7, the cause determination unit 523 counts time. Specifically, the initial time when the SBW system controller 3 is started is set to "0," and the elapsed time thereafter is counted as a time count value. In step S1, the cause determination unit 523 determines whether the deviation determination signal Y1 is "1." If it is determined in step S1 that the deviation determination signal Y1 is not "1," the cause determination unit 523 resets the counted elapsed time (time count value) in step S9. Then, in step S10, the cause determination unit 523 determines whether the slip determination signal Y3 is "1."

[0169] If the cause determination unit 523 determines that the slip determination signal Y3 is not "1," it outputs "0" as the state cause signal X in step S3. On the other hand, if the cause determination unit 523 determines that the slip determination signal Y3 is "1" in step S10, it outputs "3" as the state cause signal X in step S11.

[0170] 43 starts again after the time count value is reset, the time elapsed since the time count value was reset is counted as the time count value in step S7. After that, if the deviation determination signal Y1 is determined to be "1" in step S1, the cause determination unit 523 determines in step S8 whether the time count value is greater than a time threshold T3 that is set by the designer.

[0171] If it is determined in step S8 that the time count value is equal to or less than the time threshold value T3, the cause determination unit 523 outputs "0" as the state cause signal X in step S3. On the other hand, if it is determined that the time count value is greater than the time threshold value T3, the cause determination unit 523 determines in step S6 whether the previous value of the state cause signal X output from the cause determination unit 523 is not "1". If the cause determination unit 523 determines that the previous value of the state cause signal X is "1", it outputs "1" as the state cause signal X in step S4. On the other hand, if it is determined in step S6 that the previous value of the state cause signal X is not "1", the cause determination unit 523 determines in step S2 whether the rack end determination signal Y2 is "1".

[0172] If the cause determination unit 523 determines that the rack end determination signal Y2 is not "1," it outputs "1" as the state cause signal X in step S4. On the other hand, if the cause determination unit 523 determines that the rack end determination signal Y2 is "1" in step S4, it outputs "2" as the state cause signal X in step S5.

[0173] By performing the above processing in the cause determination unit 523 according to the third modification, it is possible to avoid the determination of the curb hit state being overwritten by the determination of the rack end state when the vehicle hits a curb near the rack end, and to prevent erroneous determination when a deviation between the steering wheel angle and the turning angle occurs instantaneously due to sudden steering.The cause determination unit 523 according to the third modification can also determine the curb hit state, rack end state, and slip state.

[0174] [Embodiment 7] A vehicle steering control device and a steer-by-wire vehicle according to embodiment 7 have substantially the same configuration as the vehicle steering control device and the steer-by-wire vehicle according to embodiment 6. However, in this embodiment, the configuration of the reaction force control unit 31 is different from that of embodiment 6. The following mainly describes the parts that are different from embodiment 6.

[0175] In this embodiment, when a deviation occurs between the steering wheel steering and the vehicle traveling direction, the measure of the deviation can be communicated to the driver.

[0176] Fig. 45 is a block diagram showing the configuration of a reaction force control unit in embodiment 6. In Fig. 45, components corresponding to those shown in Fig. 29 are assigned the same reference numerals. The reaction force control unit 31 shown in Fig. 45 differs from the reaction force control unit 31 shown in Fig. 29 in that a vehicle state cause determination unit 52 outputs a state quantity indicating a measure of deviation between the steering wheel steering and the vehicle traveling direction to a vibration signal generation unit 53 in addition to a state cause signal. The target steering torque calculation unit 51, current command conversion unit 54, and addition unit 55 are the same as those shown in Fig. 29.

[0177] Figure 46 is a block diagram showing the configuration of a vehicle state cause determination unit in Embodiment 7. In Figure 46, components corresponding to those shown in Figure 30 are assigned the same reference numerals. The vehicle state cause determination unit 52 shown in Figure 46 includes a deviation determination unit 521, a rack end determination unit 522, a cause determination unit 523, and a slip determination unit 524, similar to the vehicle state cause determination unit 52 shown in Figure 30. However, a state quantity selection unit 525 is added to the vehicle state cause determination unit 52 shown in Figure 46.

[0178] 30 , deviation determination unit 521 outputs "1" as deviation determination signal Y1 when the magnitude of the deviation between the steering wheel angle and the turning angle exceeds deviation threshold T1, which is a threshold value set by a designer, and outputs "0" as deviation determination signal Y1 when the magnitude of the deviation is equal to or less than deviation threshold T1. Note that deviation threshold T1 may be set in the same manner as in embodiment 6.

[0179] 30 in that deviation determination unit 521 outputs, in addition to deviation determination signal Y1, a deviation state quantity indicating a measure of deviation between the steering wheel steering and the vehicle's traveling direction. Since the deviation state quantity output by deviation determination unit 521 indicates a measure of deviation between the steering wheel steering and the vehicle's traveling direction, it is sufficient that the deviation state quantity has the characteristic of monotonically increasing as the deviation between the steering wheel angle and the turning angle increases. In other words, it is sufficient that the deviation state quantity can represent the magnitude of the deviation between the steering wheel angle and the turning angle.

[0180] Fig. 47 is a diagram showing an example of the deviation state quantity in embodiment 7. The deviation state quantity shown in Fig. 47 increases linearly according to the deviation between the steering wheel angle and the steering angle. A limit value may be set for the deviation state quantity so that it does not exceed a predetermined maximum value.

[0181] Slip determination unit 524 determines the vehicle's slip state based on the steering angle, vehicle speed, yaw rate, and lateral acceleration, and outputs slip determination signal Y3. Specifically, slip determination unit 524 calculates a steering angle estimate based on the vehicle speed, yaw rate, and lateral acceleration. Slip determination unit 524 outputs "1" as slip determination signal Y3 when the absolute value of the deviation between the steering angle estimate and the steering angle is greater than slip threshold T4, which is a threshold value set by a designer, and outputs "0" as slip determination signal Y3 when the absolute value is equal to or less than slip threshold T4. The steering angle estimate may be calculated using a two-wheel model used in general vehicle motion calculations, or may be calculated using other known methods. The slip threshold T4 may be set using the same method as in embodiment 6.

[0182] Slip determination unit 524 differs from slip determination unit 524 shown in Fig. 30 in that, in addition to slip determination signal Y3, it outputs a slip state quantity that indicates a measure of deviation between the steering wheel steering and the vehicle's traveling direction. Since the slip state quantity output by slip determination unit 524 indicates a measure of deviation between the steering wheel steering and the vehicle's traveling direction, it is sufficient that the slip state quantity has the characteristic of monotonically increasing with an increase in the absolute value of the deviation between the steering angle estimated value and the steering angle. In other words, it is sufficient that the slip state quantity can represent the magnitude of the deviation between the steering angle estimated value and the steering angle.

[0183] Fig. 48 is a diagram showing an example of a slip state quantity in the seventh embodiment. The slip state quantity shown in Fig. 48 increases linearly according to the deviation between the steering angle estimated value and the steering angle. A limit value may be set for the slip state quantity so that it does not exceed a predetermined maximum value.

[0184] The rack end determination unit 522 and the cause determination unit 523 are the same as those shown in FIG.

[0185] Fig. 49 is a block diagram showing another configuration of the vehicle state cause determination unit in Embodiment 7. The rack end determination unit 522 of the vehicle state cause determination unit 52 shown in Fig. 49 makes a determination based on the steering wheel angle rather than the turning angle, similar to the rack end determination unit 522 of the vehicle state cause determination unit 52 shown in Fig. 49. The deviation determination unit 521, cause determination unit 523, and slip determination unit 524 shown in Fig. 49 are the same as those shown in Fig. 46.

[0186] The state quantity selection unit 525 selects the deviation state quantity output from the deviation determination unit 521 or the slip state quantity output from the slip determination unit 524 according to the value of the state cause signal X output from the cause determination unit 523, and outputs it as a state quantity.

[0187] 50 is a flowchart showing the processing performed by the state quantity selection unit in the seventh embodiment. First, in step S31, the state quantity selection unit 525 determines whether the value of the state cause signal X is "0", "1" or "2", or "3". If it is determined in step S31 that the value of the state cause signal X is "0", the state quantity selection unit 525 sets the state quantity to "0" in step S32. This is because when the value of the state cause signal X is "0", the driver can steer the steering wheel and drive the vehicle as intended.

[0188] If it is determined in step S31 that the value of the state cause signal X is "1" or "2," the state quantity selection unit 525 selects the deviation state quantity output from the deviation determination unit 521 as the state quantity in step S33. If the value of the state cause signal X is "1" or "2," this is because the vehicle is in a curb hit state or a rack end state. If it is determined in step S31 that the value of the state cause signal X is "3," the state quantity selection unit 525 selects the slip state quantity output from the slip determination unit 524 as the state quantity in step S34. If the value of the state cause signal X is "3," this is because the vehicle is in a slip state. Then, in step S35, the state quantity selection unit 525 outputs the state quantity for which the value has been set or the selected state quantity.

[0189] The excitation signal generator 53 includes an excitation waveform determiner 531, an oscillation period determiner 532, a sampling determiner 533, an excitation amplitude generator 534, and an excitation signal generator 535, similar to the configuration shown in Fig. 34. The excitation waveform determiner 531, the oscillation period determiner 532, the sampling determiner 533, and the excitation signal generator 535 are similar to those shown in Fig. 34. However, the excitation amplitude generator 534 generates an excitation amplitude that has the characteristic of monotonically increasing with respect to the state quantity.

[0190] Fig. 51 is a diagram showing an example of an excitation amplitude generated in the seventh embodiment. The excitation amplitude shown in Fig. 51 has a characteristic of increasing linearly according to the state quantity. A limit value may be set for the excitation amplitude so that it does not exceed a predetermined maximum value. The excitation amplitude generated by the excitation signal generation unit 53 is multiplied by the excitation amplitude generated by the excitation amplitude generator 534 in the multiplication unit 536 shown in Fig. 34, thereby generating an excitation signal.

[0191] Fig. 52 is a diagram showing an example of the excitation amplitude and excitation waveform generated in the seventh embodiment. The excitation amplitude and excitation waveform shown in Fig. 52 are generated in the curb-hitting state (state cause signal X is "1"). That is, they are generated when the excitation waveform determiner 531 specifies a sine wave waveform, the vibration period determiner 532 specifies "1 s", and the sampling determiner 533 specifies "0.001 s" (see Figs. 35, 36, and 37). The upper part of Fig. 52 shows the excitation amplitude, and the lower part of Fig. 52 shows the excitation waveform.

[0192] When the steering wheel is turned further toward the curb while the vehicle is in the curb-hitting state, the deviation between the steering wheel angle and the turning angle increases. This increases the state quantity, and the excitation amplitude increases with the turning, as shown in the upper part of Figure 52. As a result, the generated excitation waveform becomes a sine wave whose amplitude (maximum amplitude) gradually increases, as shown in the lower part of Figure 58.

[0193] Fig. 53 is a diagram showing another example of the excitation amplitude and excitation waveform generated in the seventh embodiment. The excitation amplitude and excitation waveform shown in Fig. 53 are generated in the slip state (state cause signal X is "3"). That is, they are generated when the excitation waveform determiner 531 specifies a triangular waveform, the vibration period determiner 532 specifies "0.25 s", and the sampling determiner 533 specifies "0.01 s" (see Figs. 35, 36, and 37). The upper part of Fig. 53 shows the excitation amplitude, and the lower part of Fig. 53 shows the excitation waveform.

[0194] For example, when the vehicle is oversteering and turning more than the steering wheel is turning, the estimated steering angle value will be large. Even if the steering wheel is suddenly turned back, the slip does not disappear, so the estimated steering angle value remains unchanged and only the steering angle decreases, and the deviation between the estimated steering angle value and the steering angle increases. This increases the state quantity, and as shown in the upper part of Figure 53, the excitation amplitude increases with the steering angle. As a result, the generated excitation waveform becomes a triangular waveform with a gradually increasing amplitude (maximum amplitude), as shown in the lower part of Figure 58.

[0195] As described above, in this embodiment, a state quantity corresponding to the deviation between the steering wheel angle and the turning angle is calculated, and an excitation amplitude corresponding to the state quantity is generated. As a result, when a deviation occurs between the steering wheel steering and the vehicle traveling direction, a measure of the deviation can be communicated to the driver. Note that this embodiment can also determine the curb hit state, rack end state, and slip state.

[0196] In this embodiment, as in the sixth embodiment, it is not always necessary to specify all three elements (vibration waveform, vibration period, and sampling period) according to the value of the state cause signal X. If the driver can sense the difference in vibration, it is sufficient to specify any one or more of the above three elements.

[0197] Furthermore, the cause determination unit 523 according to the first, second, and third modifications of the sixth embodiment can be applied to this embodiment.

[0198] By applying the cause determination unit 523 according to the first modification (the cause determination unit 523 described with reference to FIG. 42 ) to the present embodiment, when a deviation occurs between the steering wheel steering and the vehicle traveling direction, it is possible to determine whether the vehicle is in a curb hit state, a rack end state, or a slip state. Furthermore, when the vehicle hits a curb near the rack end, it is possible to prevent the determination of the curb hit state from being overwritten by the determination of the rack end state. Furthermore, it is possible to communicate the measure of the deviation to the driver.

[0199] By applying the cause determination unit 523 according to the second modification (the cause determination unit 523 described with reference to FIG. 43 ) to the present embodiment, when a deviation occurs between the steering wheel steering and the vehicle traveling direction, it is possible to determine whether the vehicle is in a curb hit state, rack end state, or slip state. It is also possible to prevent erroneous determination when a deviation between the steering wheel angle and the turning angle occurs instantaneously due to sudden steering. Furthermore, it is possible to communicate a measure of the deviation to the driver.

[0200] By applying the cause determination unit 523 according to the third modification (the cause determination unit 523 described with reference to FIG. 44 ) to the present embodiment, when a deviation occurs between the steering wheel steering and the vehicle traveling direction, it is possible to determine whether the vehicle is in a curb strike state, a rack end state, or a slip state. Furthermore, when the vehicle strikes a curb near the rack end, it is possible to prevent the determination of the curb strike state from being overwritten by the determination of the rack end state, and it is also possible to prevent erroneous determinations when a deviation between the steering wheel angle and the turning angle occurs instantaneously due to sudden steering. Furthermore, it is possible to communicate a measure of the deviation to the driver.

[0201] The SBW system controller 3 in the first to seventh embodiments may be realized by a combination of software and hardware resources. That is, the SBW system controller 3 may be realized by recording a program for realizing each function of the SBW system controller 3 on a computer-readable recording medium and reading and executing the program recorded on the recording medium into a computer system. Of course, the SBW system controller 3 may also be realized by hardware such as an ASIC (Application Specific Integrated Circuit).

[0202] 1...Steering wheel, 2...Reaction force motor, 3...SBW system controller, 4...Steering motor, 5...Rack and pinion gear, 6...Knuckle arm, 7...Tie rod, 8...Tire, 9...Wheel, 21...Angle sensor, 22...Current sensor, 23...Steering wheel angle sensor, 31...Reaction force control unit, 32...Reaction force motor current control unit, 33...Steering control unit, 34...Steering motor current control unit, 41...Angle sensor, 42...Current sensor, 43...Steering angle sensor, 51...Target operation Steering torque calculation unit, 52...vehicle state cause determination unit, 53...excitation signal generation unit, 54...current command conversion unit, 55...addition unit, 100...reaction force mechanism, 101...steering mechanism, 521...deviation determination unit, 522...rack end determination unit, 523...cause determination unit, 524...slip determination unit, 525...state quantity selection unit, 531...excitation waveform determiner, 532...vibration period determiner, 533...sampling determiner, 534...excitation amplitude generator, 535...excitation signal generator, 536...multiplication unit

Claims

1. A vehicle steering control device for a steer-by-wire vehicle having a reaction force mechanism that provides a reaction force to the driver's steering wheel input, and a steering mechanism that steers the steering angle of the tires based on the steering wheel input, wherein the reaction force mechanism and the steering mechanism are mechanically separated, When the vehicle is unable to move in the direction intended by the driver due to steering, a vehicle state cause determination unit determines the cause of the state from the steering angle and steering angle and generates a state cause signal, An excitation signal generation unit generates an excitation signal to be added to the reaction force mechanism based on the state cause signal, Equipped with, The aforementioned vehicle condition cause determination unit is: Based on the gear ratio between the axis of the steering angle and the axis of the steering angle, the deviation between the steering angle and the steering angle is calculated by converting one of the steering angle and the steering angle to the other axis, and in a deviation occurrence state in which the absolute value of the calculated deviation between the steering angle and the steering angle is greater than a predetermined deviation threshold, If the absolute value of the steering angle or the turning angle exceeds a predetermined angle threshold, it is determined that the turning angle has reached the rack end, and if the absolute value of the steering angle or the turning angle is less than or equal to the angle threshold, it is determined that the tire is in contact with the curb, and the curb is in contact with the curb. Vehicle steering control device.

2. The vehicle steering control device according to claim 1, wherein the vehicle state cause determination unit determines whether the vehicle is in the rack end state or the curb contact state based on the steering angle and the steering angle, and generates the state cause signal.

3. The aforementioned vehicle condition cause determination unit is: Based on the gear ratio between the axis of the steering angle and the axis of the steering angle, the deviation between the steering angle and the steering angle is calculated by converting one of the steering angle and the steering angle to the other axis, and in a deviation occurrence state in which the absolute value of the calculated deviation between the steering angle and the steering angle is greater than a predetermined deviation threshold, The vehicle condition cause determination unit determines the rack end state if the previous determination was not the curb contact state and the absolute value of the steering angle or the steering angle exceeds a predetermined angle threshold, and determines the curb contact state if the previous determination was the curb contact state, or if the absolute value of the steering angle or the steering angle is less than or equal to the angle threshold. The vehicle steering control device according to claim 2.

4. The aforementioned vehicle condition cause determination unit is: Based on the gear ratio between the axis of the steering angle and the axis of the steering angle, the deviation between the steering angle and the steering angle is calculated by converting one of the steering angle and the steering angle to the other axis, and when the absolute value of the calculated deviation between the steering angle and the steering angle is greater than a predetermined deviation threshold, and the time during which the deviation occurs exceeds a predetermined time threshold, The rack end state is determined when the absolute value of the steering angle or the turning angle exceeds a predetermined angle threshold, and the curb contact state is determined when the absolute value of the steering angle or the turning angle is less than or equal to the angle threshold. The vehicle steering control device according to claim 2.

5. The aforementioned vehicle condition cause determination unit is: Based on the gear ratio between the axis of the steering angle and the axis of the steering angle, the deviation between the steering angle and the steering angle is calculated by converting one of the steering angle and the steering angle to the other axis, and when the absolute value of the calculated deviation between the steering angle and the steering angle is greater than a predetermined deviation threshold, and the time during which the deviation occurs exceeds a predetermined time threshold, The vehicle condition cause determination unit determines the rack end state if the previous determination was not the curb contact state and the absolute value of the steering angle or the steering angle exceeds a predetermined angle threshold, and determines the curb contact state if the previous determination was the curb contact state, or if the absolute value of the steering angle or the steering angle is less than or equal to the angle threshold. The vehicle steering control device according to claim 2.

6. The vibration signal generation unit associates one or more of the vibration waveform, vibration period, and sampling period with the rack end state and the curb contact state, respectively, and generates the vibration signal based on the state cause signal, as described in any one of claims 1 to 5.

7. The vehicle state cause determination unit generates a state quantity that indicates the degree of deviation between the steering wheel operation in the given state and the direction of travel of the vehicle, based on the steering wheel angle and the turning angle. The excitation signal generation unit associates one or more of the excitation waveform, vibration period, and sampling period with the rack end state and the curb contact state, determines the excitation amplitude based on the state quantities, and generates the excitation signal based on the association and the excitation amplitude. A vehicle steering control device according to any one of claims 1 to 5.

8. The vehicle steering control device according to any one of claims 1 to 5, wherein the vehicle state cause determination unit determines from the vehicle behavior value whether the state of the vehicle is in a slipping state when the deviation is not occurring, and generates the state cause signal.

9. The vehicle steering control device according to claim 8, wherein the vehicle behavior value includes vehicle speed, yaw rate, and lateral acceleration.

10. The vehicle steering control device according to claim 9, wherein the vehicle state cause determination unit determines that a slip state exists when the vehicle state is not in a state of deviation, and the deviation between the estimated steering angle calculated from the vehicle speed, the yaw rate, and the lateral acceleration and the steering angle is greater than a predetermined slip threshold.

11. The vehicle steering control device according to claim 10, wherein the excitation signal generation unit associates one or more of the excitation waveform, vibration period, and sampling period with the rack end state and the curb contact state, respectively, and generates the excitation signal based on the state cause signal.

12. The vehicle state cause determination unit generates a state quantity that indicates the scale of the deviation between the steering wheel operation in the state and the direction of travel of the vehicle, based on any of the steering wheel angle, the turning angle, and the vehicle behavior value. The excitation signal generation unit associates one or more of the excitation waveform, vibration period, and sampling period with each of the rack end state, curb contact state, and slip state, determines the excitation amplitude based on the state quantities, and generates the excitation signal based on the association and the excitation amplitude. The vehicle steering control device according to claim 10.

13. A reaction force mechanism that provides a reaction force to the driver's steering input, A steering mechanism is mechanically separated from the aforementioned reaction force mechanism and steers the steering angle of the tires based on the steering wheel operation, The vehicle steering control device according to claim 1, A steer-by-wire vehicle equipped with [a specific feature / system].