JP2008062788A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle facilitating the driving of the vehicle by suitably controlling the turned state of a turned wheel relative to the operation of a steering wheel by a driver. <P>SOLUTION: An operation state determination part 42 determines the turning operation state of the steering wheel 11 by the driver. A reference point setting part 43 sets a steering-holding operation point, a cutting-in operation point and a returning operation point as reference points based on the determined operation state of the steering wheel 11. A turning angle variation characteristic determination part 44 determines a cutting-in operation variation characteristic of a non-linear shape that the variation characteristic of the turning angle δ varied to the reference point and the maximum operation point is downward projected or a returning operation variation characteristic of a non-linear shape that the variation characteristic of the turning angle δ varied to the reference point and a neutral operation point is upwardly projected using the determined operation state of the steering wheel 11 and the set reference point. Thereby, it can be controlled such that the turned state the left and right front wheels FW1, FW2 can be controlled so as to always become equal in turned states according to turning operation of the steering wheel 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steering wheel operated by a driver to steer a vehicle, a steering actuator for steering a steered wheel, and a steered wheel by driving and controlling the steered actuator according to the operation of the steering handle. The present invention relates to a steering device for a steering-by-wire vehicle including a control device that steers the vehicle.

  In recent years, the development of this type of steering-by-wire steering system has been actively carried out. For example, in Patent Document 1 below, when the vehicle is traveling at a low speed, the steering angle ratio is calculated based on the steering angle ratio characteristic based on the primary proportionality in the case of an increase operation, and the secondary curve is used in the return operation. A steering angle ratio control device for a vehicle that calculates a steering angle ratio based on a steering angle ratio characteristic is shown. In this vehicle steering angle ratio control device, it is possible to improve the stability of the return operation while ensuring a natural increase operation without a sense of incongruity in a low speed range.

Further, for example, in Patent Document 2 below, when a deviation occurs between the detected steering angle and a specified value of the steering gear ratio set at that time, the linearity of the steering gear ratio at the time of the return operation is disclosed. A vehicle steering device is shown in which the characteristics are changed to pass through a neutral position. And in this vehicle steering device, the neutral deviation of the turning angle when the steering angle is in the neutral position can be avoided, and the deterioration of the steering feeling can be prevented.
JP 2003-81109 A JP-A-2005-170135

  By the way, in the conventional steering angle ratio control device for a vehicle shown in Patent Document 1, the steering angle ratio characteristic of a quadratic curve that protrudes downward is adopted at the time of the return operation. Based on this, a steering angle ratio representing a ratio of an actual steering angle (steering angle) to a steering angle (steering angle) is calculated. In this case, for example, when the steering wheel (steering handle) is turned back from a state in which the steering angle is large, the steering angle ratio is calculated to be large immediately after the start of the operation, so that the actual steering angle is relatively large. Will change. Thus, when the change amount of the actual steering angle is large, the steering operation of the front wheels (steering wheels) suddenly occurs, so that the behavior of the vehicle changes sensitively to the steering wheel operation, that is, the operability deteriorates. To do. Therefore, in a state where the steering angle is large, the driver needs to carefully operate the steering wheel, and as a result, it may be difficult to drive the vehicle.

  In the conventional vehicle steering apparatus disclosed in Patent Document 2, the steering gear ratio representing the ratio of the steering angle to the steering angle changes linearly, and the steering gear ratio that changes linearly is used to change the steering angle. The turning angle is calculated. Even in this case, when the steering wheel (steering handle) is turned back from a state where the steering angle is large, the turning angle is calculated based on a relatively large steering gear ratio immediately after the start of the operation. The turning angle changes with a relatively large change amount. Therefore, also in this conventional vehicle steering device, the steering operation of the steered wheels (steered wheels) may occur abruptly and the operability may deteriorate, and as a result, the driving of the vehicle may become difficult. is there.

    SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to appropriately control the steered state of the steered wheels with respect to the steering wheel operation by the driver, thereby facilitating driving of the vehicle. To provide an apparatus.

  In order to achieve the above object, the present invention is characterized in that a steering handle operated by a driver to steer a vehicle, a steering actuator for turning a steered wheel, and an operation of the steering handle. A steering-by-wire vehicle steering apparatus comprising: a steering control device that drives the steering actuator to nonlinearly control the steered wheels; and operates the steering control device with respect to the steering handle. An operation input value detecting means for detecting an operation input value of the operator, an operation state determining means for determining an operation state by the driver of the steering handle using the detected operation input value, and the determined steering Based on the operation state of the steering wheel, the operation point determined by the absolute value of the operation input value when the operation state is switched and the absolute value of the turning angle of the steered wheel is Reference point setting means for setting as a quasi-point, and a change characteristic of the turning angle of the steered wheels in a cutting operation state in which the absolute value of the operation input value of the steering handle increases using the set reference point. Up to the maximum operating point determined by the absolute value of the maximum operation input value that defines the upper limit value of the operable range of the steering wheel and the absolute value of the maximum turning angle of the steered wheel corresponding to the maximum operation input value. A non-linearly changing cutting operation change characteristic and a change characteristic of the turning angle of the steered wheel in a turn-back operation state in which the absolute value of the operation input value of the steering wheel is reduced, and 0 representing the neutral position of the steering wheel A turning angle change characteristic determining means for determining a return operation changing characteristic that changes nonlinearly to a neutral operation point determined by a point and a zero point representing a neutral position of the steered wheel; Based on the change characteristic of the steered wheel turning angle, target turning angle calculating means for calculating a target turning angle of the steered wheel with respect to the detected operation input value, and according to the calculated target turning angle The present invention resides in that the turning actuator is configured by turning control means for turning the steered wheel to the calculated target turning angle by controlling the turning actuator. The vehicle steering device may be further provided with a reaction force device that applies a reaction force to the operation of the steering wheel.

  In this case, the operation speed of the steering handle represented by the time differential value of the operation input value detected from the cutting operation state or the switchback operation state by the operation state determination unit is determined by the reference point setting unit. Operation point when it is determined that the state smaller than the preset reference operation speed has been switched to the steering operation state that continues for a predetermined time or more, when it is determined that the state has been switched directly from the cutting operation state to the switching operation state And the operation point when it is determined that the switching operation state has been directly switched to the cutting operation state may be set as the reference point.

  The steering control device further includes vehicle speed detection means for detecting a vehicle speed of the vehicle, and the operation state determination means is configured such that the detected vehicle speed is equal to or higher than a predetermined vehicle speed and the time differentiation is performed. If the value is less than the predetermined value, it may be determined that the operation state of the steering wheel is the steering operation state. The operation state determination means may determine the operation state of the steering wheel when the transmission ratio in a normal operation state of the steering wheel is larger than a predetermined transmission ratio.

  Further, the turning angle change characteristic determining means is based on the determination by the operation state determining means, and when the steering handle is in a cutting operation state, the detection from the set reference point to the maximum operation point is detected. The turning angle of the steered wheel with respect to the detected operation input value from the set reference point to the maximum operating point is lower than the linear change of the steered wheel with respect to the manipulated input value. A cutting operation change characteristic that is a convex non-linear change is determined, and when the steering handle is in the switchback operation state, the rotation with respect to the detected operation input value from the set reference point to the neutral operation point is determined. Compared to the linear change in the steering angle of the steered wheel, at least the detected operation input value in the vicinity of the set reference point from the set reference point to the neutral operation point. The good steering angle of the steered wheels determines the failback operation change characteristic becomes nonlinear variation convex upward.

  In this case, based on the determination by the operation state determination unit, the turning angle change characteristic determination unit is configured to perform the operation from the set reference point to the neutral operation point when the steering handle is in the return operation state. Compared with a linear change of the turning angle of the steered wheel with respect to the detected operation input value, the turning angle of the steered wheel with respect to the detected operation input value in the vicinity of the set reference point is convex upward. It is preferable to determine a return change characteristic that changes nonlinearly so that the turning angle of the steered wheels is convex downward with respect to the detected operation input value in the vicinity of the neutral operation point. In this case, the turning angle change characteristic determining means is configured to cause the nonlinear change to be convex upward between the set reference point and the neutral operation point according to the magnitude of the detected operation input value. And the ratio of the non-linear change projecting downward may be changed.

  The steering control device includes vehicle speed detection means for detecting the vehicle speed of the vehicle, and vehicle speed determination means for determining the magnitude of the detected vehicle speed, and the target turning angle calculation means includes the When the detected vehicle speed is greater than a preset reference vehicle speed by the vehicle speed determining means, the target turning angle that is in a power or exponent relationship with the operation input value for the steering wheel is detected. It is good to calculate using the operation input value.

  According to these, the operation state of the steering wheel by the driver is determined by the operation state determination unit, and based on this determination, the reference point setting unit is configured to operate the operation point when the operation state of the steering wheel is switched, for example, Set the operation point when switching to the operating state, the operating point when switching from the cutting operation state to the switching back operation state, and the operating point when switching from the switching back operation state to the cutting operation state as reference points Can do. Then, the turning angle change characteristic determining means uses the set reference point to determine the cutting operation change characteristic that changes nonlinearly up to the maximum operating point and the switching operation change characteristic that changes nonlinearly up to the neutral operating point. can do. Moreover, the target turning angle calculation means can calculate the target turning angle of the steered wheels based on the cutting operation change characteristic or the switchback operation change characteristic determined as described above. Further, the target turning angle calculation means can calculate a target turning angle that has a power or exponent relation with the operation input value when the vehicle speed is higher than the reference vehicle speed by the vehicle speed determination means.

  Here, the cutting operation change characteristic can be a non-linear change characteristic that protrudes downward with respect to the linear change from the reference point to the maximum operation point. Further, the switch back operation change characteristic can be a non-linear characteristic that is convex upward with respect to the linear change from the reference point to the neutral operation point. In particular, with respect to the switching operation changing characteristic, it is possible to adopt a non-linear characteristic that changes nonlinearly so as to protrude upward near the reference point and changes nonlinearly so as to protrude downward near the neutral operating point. . In addition, the ratio of the non-linear change that protrudes upward and the ratio of the non-linear change that protrudes downward can be changed in accordance with the magnitude of the operation input value.

  In this way, the cutting operation change characteristic from the reference point to the maximum operating point or the switching operation change characteristic from the reference point to the neutral operation point is determined according to the operation state of the steering wheel, that is, the cutting operation state or the returning operation state. Thus, even when the reference point changes, the target turning angle of the steered wheels can be calculated with respect to the operation input value based on the same change characteristics. As a result, even if the reference point changes in the cutting operation state or the switching back operation state, the turning operation state of the steered wheels to be steered according to the steering wheel operation by the driver is always the same. That is, the same operability can always be obtained. Therefore, the driver can always turn the vehicle while perceiving the same behavior change in the cutting operation state or the switching back operation state. Therefore, the driver can drive the vehicle easily.

  In addition, by making the cutting operation change characteristic a non-linear change characteristic that protrudes downward, it is possible to moderate the vehicle behavior change immediately after the start of the cutting operation, and to steer as the operation input value increases. The angle can be steered greatly, and the amount of operation of the steering wheel by the driver can be reduced. On the other hand, the change in behavior of the vehicle immediately after the start of the switchback operation can be moderated by setting the switchback operation change characteristic to be a non-linear change characteristic that is convex upward. In addition, by adopting a non-linear change characteristic that protrudes downward in the vicinity of the neutral operation point, it becomes easier to hold the steering handle near the neutral position, and the switch back operation and the cutting operation are switched over the neutral position. The change of the change characteristic in the case can be made extremely small. Then, by changing the ratio of the non-linear change characteristic that protrudes downward and the non-linear change characteristic that protrudes upward according to the magnitude of the operation input value, the sense of incongruity associated with the change between these non-linear change characteristics is greatly increased. Can be reduced. Therefore, the driver can obtain a good operation feeling.

  Another feature of the present invention is that the reference point setting unit is expressed by a time differential value of the operation input value detected from the cutting operation state or the switchback operation state by the operation state determination unit. A semi-steering operation in which the operation speed of the steering wheel continues for a predetermined time or more between a first reference operation speed set in advance and a second reference operation speed set larger than the first reference operation speed. The operation point when it is determined that the state has been switched to is set as a virtual reference point, and the turning angle change characteristic determining means is determined using the reference point set immediately before the virtual reference point is set Based on the cutting operation change characteristic or the switching operation change characteristic, and the cutting operation change characteristic or the switching operation change characteristic determined using the set virtual reference point, the immediately preceding From the set reference point in determining the turning operation variation characteristic or the failback operation change characteristics due to the transition to the virtual reference point.

  In this case, the turning angle change characteristic determining means is configured to determine the cutting operation determined using a reference point set immediately before the virtual reference point is set according to the operation speed of the steering handle. The change characteristic or the ratio of the switchback operation change characteristic and the ratio of the cut operation change characteristic or the switchback operation change characteristic determined using the virtual reference point are changed and set immediately before Determine the cutting operation change characteristic or the switch back operation change characteristic accompanying the transition from the reference point to the virtual reference point

  Further, the reference point setting means is switched to a steering operation state in which a state where the operation speed of the steering handle is lower than a first reference operation speed set in advance is continued for a predetermined time or longer by the operation state determination means. When determined, the operation point at the time of the determination is changed from the virtual reference point as a reference point, and the turning angle change characteristic determining means is changed from the virtual reference point to the set reference point It is good to change and to determine the said cutting operation change characteristic or the said switch back operation change characteristic.

  According to these, when it is determined that the operation state determination unit has switched to the semi-steering operation state, the reference point setting unit is on the cutting operation change characteristic or the switching operation change characteristic immediately before switching to the semi-steering operation state. To set a virtual reference point. In addition, when it is determined by the operation state determination unit that the semi-steering operation state is switched to the steering operation state, the reference point setting unit is configured to change the cutting operation change characteristic or the switching operation change characteristic determined using the virtual reference point. It is possible to set the operation point at the time of switching to the steering operation state as the formal reference point and change the virtual reference point to the formal reference point. Then, the turning angle change characteristic determining means determines the cutting operation change characteristic or the switch back operation change characteristic using the original reference point, the virtual reference point and the formal reference point set before the virtual reference point is set. can do.

  Thereby, according to switching of the operation state of the steering wheel, the original reference point can be gradually changed (shifted) from the original reference point to the formal reference point via the virtual reference point. As a result, a change (transition) from a cutting operation change characteristic or a switchback operation change characteristic determined using the original reference point to a cutting operation change characteristic or a switchback operation change characteristic determined using a formal reference point Is also performed slowly in time. Therefore, it is possible to effectively reduce the uncomfortable feeling associated with the transition from the original reference point to the formal reference point.

  Further, the turning angle change characteristic determining means includes the ratio of the cutting operation change characteristic or the switchback operation change characteristic determined using the original reference point, and the cutting operation change characteristic or the switchback operation determined using the virtual reference point. The change characteristic ratio can be changed according to the operation speed of the steering wheel to determine the cutting operation change characteristic or the switch back operation change characteristic accompanying the transition from the original reference point to the virtual reference point. In this way, the ratio between the change characteristic using the original reference point and the change characteristic using the virtual reference point is changed, and the change characteristic associated with the transition to the virtual reference point is determined, thereby changing extremely smoothly. The characteristics can be changed. Therefore, even when the virtual reference point is finally changed (transferred) from the virtual reference point, the uncomfortable feeling associated with the change (transfer) can be effectively reduced.

a. First Embodiment Hereinafter, a vehicle steering apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a common vehicle steering apparatus according to the first to third embodiments.

  This steering device includes a steering handle 11 that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and the lower end of the steering input shaft 12 is connected to a reaction force actuator 13 including an electric motor and a speed reduction mechanism. The reaction force actuator 13 applies a reaction force to the turning operation of the steering handle 11 by the driver.

  In addition, the steering device includes a steering actuator 21 including an electric motor and a speed reduction mechanism. The turning force by the turning actuator 21 is transmitted to the left and right front wheels FW1 and FW2 via the turning output shaft 22, the pinion gear 23, and the rack bar 24. With this configuration, the rotational force from the steering actuator 21 is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the rotation of the pinion gear 23. Due to the displacement in the axial direction, the left and right front wheels FW1, FW2 are steered left and right.

  Next, an electric control device that controls the rotation of the reaction force actuator 13 and the turning actuator 21 will be described. The electric control device includes a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a lateral acceleration sensor 34.

  The steering angle sensor 31 is assembled to the steering input shaft 12, detects a rotation angle from a neutral position as a detection reference point of the steering handle 11, and outputs it as a steering angle θ. The turning angle sensor 32 is assembled to the turning output shaft 22, detects the rotation angle from the neutral position of the turning output shaft 22, and sets the actual turning angle δ (the turning angle of the left and right front wheels FW1, FW2). Output). Here, in this specification, the neutral position refers to the positions of the steering handle 11, the steering input shaft 12, the steering output shaft 22, and the left and right front wheels FW1 and FW2 for maintaining the vehicle in a straight traveling state. The steering angle θ and the actual turning angle δ are represented by setting the neutral position to “0”, the left rotation angle as a positive value, and the right rotation angle as a negative value. The vehicle speed sensor 33 detects and outputs the vehicle speed V. The lateral acceleration sensor 34 detects and outputs the actual lateral acceleration G of the vehicle. The actual lateral acceleration G also represents leftward acceleration as a positive value and rightward acceleration as a negative value.

  These sensors 31 to 34 are connected to the electronic control unit 35. The electronic control unit 35 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls the operations of the reaction force actuator 13 and the turning actuator 21 by executing a program. Drive circuits 36 and 37 for driving the reaction force actuator 13 and the steering actuator 21 are connected to the output side of the electronic control unit 35, respectively. In the drive circuits 36 and 37, current detectors 36a and 37a for detecting a drive current flowing through the electric motor in the reaction force actuator 13 and the steering actuator 21 are provided. The drive current detected by the current detectors 36a and 37a is fed back to the electronic control unit 35 in order to control the drive of both electric motors.

  Next, the operation of the first embodiment configured as described above will be described with reference to the functional block diagram of FIG. 2 showing functions realized by computer program processing in the electronic control unit 35. The electronic control unit 35 calculates the target turning angles δf, δr, δk of the left and right front wheels FW1, FW2 based on the turning operation of the steering handle 11, and based on the calculated target turning angles δf, δr, δk. The steering control unit 40 includes a steering control unit 40 that controls the steering of the left and right front wheels FW1 and FW2, and a reaction force control unit 50 that controls the application of reaction force to the steering handle 11.

  When the steering handle 11 is turned by the driver, the steering angle sensor 31 detects the steering angle θ, which is the rotation angle of the steering handle 11, and uses the detected steering angle θ to control the turning control unit 40 and the reaction force. Output to the unit 50. When the vehicle starts traveling, the vehicle speed sensor 33 detects the vehicle speed V and outputs the detected vehicle speed V to the steering control unit 40.

  In the turning control unit 40, it is determined whether or not the vehicle is currently traveling at a vehicle speed V higher than a predetermined reference vehicle speed Vo based on the detected vehicle speed V input from the vehicle speed sensor 33 by the vehicle speed determination unit 41. . More specifically, if the detected vehicle speed V is greater than a predetermined reference vehicle speed Vo, the vehicle speed determination unit 41 determines that the vehicle is currently traveling at a high speed. Then, the vehicle speed determination unit 41 outputs travel information indicating that the vehicle is traveling at a vehicle speed V higher than a predetermined reference vehicle speed Vo to a turning angle calculation unit 45 described later. On the other hand, if the detected vehicle speed V is equal to or lower than the predetermined reference vehicle speed Vo, the vehicle speed determination unit 41 determines that the vehicle is currently traveling at a low speed. Then, the vehicle speed determination unit 41 outputs travel information indicating that the vehicle is traveling at a vehicle speed V equal to or lower than a predetermined reference vehicle speed Vo to the operation state determination unit 42.

  The operation state determination unit 42 determines the rotation operation state of the steering handle 11 by the driver based on the detected steering angle θ input from the steering angle sensor 31. That is, the driver turns the steering handle 11 or holds it at an arbitrary turning position in order to turn the vehicle in an intended manner. Thus, since the driver rotates the steering handle 11 according to various operation states, the operation state determination unit 42 appropriately determines the operation state of the steering handle 11 by the driver.

  More specifically, the operation state determination unit 42 has the absolute value of the detected steering angle θ increased, and the time differential value dθ / dt of the detected steering angle θ (hereinafter, this differential value is referred to as the steering angular velocity dθ / When the absolute value of the steering wheel 11 continues to be larger than the predetermined absolute value dθ0 / dt set in advance, the absolute value of the detected steering angle θ increases. It is determined as “continuation state”. In addition, the operation state determination unit 42 continues when the absolute value of the detected steering angle θ is decreasing and the absolute value of the steering angular velocity dθ / dt is larger than the predetermined absolute value dθ0 / dt. Then, the operation state of the steering wheel 11 is determined as the “continuation state of the return operation” in which the absolute value of the detected steering angle θ decreases. Further, the operation state determination unit 42 is in a state where the absolute value of the steering angular velocity dθ / dt is equal to or less than the predetermined absolute value dθ0 / dt for a predetermined time th in a situation where the absolute value of the detected steering angle θ is slightly increased or decreased. When the steering wheel 11 continues, the operation state of the steering wheel 11 is determined as the “steering operation state” in which the absolute value of the detected steering angle θ is maintained at a constant value.

  The operation state determination unit 42 also determines an operation state in which a cutting operation, a switching back operation, and a steering operation are combined. More specifically, the operation state determination unit 42 satisfies the above-described determination condition of the “steering operation state” and then satisfies the above-described determination condition of the “continuation state of the cutting operation”, that is, “ When the "steering operation state" is temporarily changed from the "continuation state of the cutting operation" or "continuation state of the turning back operation", and then the steering handle 11 is turned, it is determined as "the cutting operation state from the steering operation" To do. On the other hand, the operation state determination unit 42, when the above-described determination condition of the “steering operation state” is satisfied and then the above-described determination condition of the “continuation state of the switchback operation” is satisfied, that is, “the operation of the cutting operation”. When the "steering operation state" is once changed from the "continuation state" or "continuation state of the switchback operation" and then the steering handle 11 is switched back, it is determined as the "switchback operation state from the steering operation". .

  Furthermore, the operation state determination unit 42 also determines an operation state to be switched back from the cutting operation to the switching back operation or from the switching back operation to the cutting operation. Specifically, the operation state determination unit 42 suddenly decreases the absolute value of the detected steering angle θ and the steering angular velocity from the situation where the determination condition of the “continuation state of the cutting operation” described above is satisfied. When the absolute value of dθ / dt is larger than the predetermined absolute value dθ0 / dt, the operation state of the steering handle 11 is determined as “a return operation state from the cutting operation”. On the other hand, the operation state determination unit 42 suddenly increases the absolute value of the detected steering angle θ and the steering angular velocity dθ / dt from the situation where the determination condition “continuation state of the switch back operation” described above is satisfied. When the absolute value of the steering wheel 11 becomes larger than the predetermined absolute value dθ0 / dt, the operation state of the steering handle 11 is determined as the “cutting operation state from the return operation”. In the following description, the “switching operation state from the cutting operation” and the “cutting operation state from the switching operation” are also collectively referred to as the “switching operation state”.

  Based on the determination of the operation state of the steering handle 11 by the operation state determination unit 42, the reference point setting unit 43 has a change characteristic of the turning angle δ with respect to the detected steering angle θ. Set a reference point to determine Specifically, when the operation state determination unit 42 determines that the steering handle 11 is currently switched to the “steering operation state”, the reference point setting unit 43 detects the detected steering angle of the steering handle 11 being held. A point determined by θ and an actual turning angle δ detected by the turning angle sensor 32 that is the turning angle of the left and right front wheels FW1 and FW2 that are steered corresponding to the steering angle θ (hereinafter referred to as the turning angle sensor 32). This point is referred to as the steering operation point) as a reference point.

  The reference point setting unit 43 also sets a reference point when the operation state determination unit 42 determines that the steering handle 11 is in the “turning operation state”. More specifically, when the operation state determination unit 42 determines that the steering handle 11 is in the “return operation state from the cutting operation”, the reference point setting unit 43 directly changes from the cutting operation to the return operation. A point determined by the detected steering angle θ when the vehicle is switched to and the actual turning angle δ of the left and right front wheels FW1, FW2 corresponding to the detected steering angle θ (hereinafter, this point is referred to as a switchback operation point) is a reference point Set as. In addition, when the operation state determination unit 42 determines that the steering handle 11 is in the “cutting operation state from the switchback operation”, the reference point setting unit 43 switches directly from the switchback operation to the cutting operation. A point determined by the detected steering angle θ and the actual turning angle δ of the left and right front wheels FW1, FW2 corresponding to the detected steering angle θ (hereinafter, this point is referred to as a cutting operation point) is set as a reference point.

  When the reference point is set in this way, the reference point setting unit 43 supplies the set reference point, that is, the steering operation point, the return operation point, or the cutting operation point to the turning angle change characteristic determination unit 44. The turning angle change characteristic determination unit 44 acquires the reference point supplied from the reference point setting unit 43, acquires operation state information indicating the operation state of the steering handle 11 from the operation state determination unit 42, and steers the steering handle. The change characteristic of the turning angle δ of the left and right front wheels FW1, FW2 according to the 11 operation states is determined. This will be specifically described below.

  The turning angle change characteristic determination unit 44 roughly determines different change characteristics of the turning angle δ depending on whether the steering handle 11 is being turned or not. That is, when the steering handle 11 is turned, the turning angle change characteristic determination unit 44 rotates the reference point set by the reference point setting unit 43 and the steering handle 11 as shown in FIG. A straight line connecting a point determined by the maximum steering angle θe as the upper limit value of the possible range and the maximum turning angle δe of the left and right front wheels FW1, FW2 corresponding to the maximum value (hereinafter, this point is referred to as the maximum operating point) On the other hand, a non-linear change characteristic that protrudes downward (hereinafter, this change characteristic is referred to as a cutting operation change characteristic) is determined.

  On the other hand, when the steering handle 11 is being turned back, the turning angle change characteristic determining unit 44, as shown in FIG. 4, and the neutral position of the steering handle 11 set by the reference point setting unit 43 A point determined by the zero point (steering angle θ is “0”) and the zero point (the actual turning angle δ is “0”) indicating the neutral position of the left and right front wheels FW1, FW2 (hereinafter, this point is neutral) A nonlinear change characteristic that protrudes upward with respect to a straight line connecting the operation points) (hereinafter, this change characteristic is referred to as a switch-back operation change characteristic) is determined. In the following, the determination of the cutting operation change characteristic and the switching operation change characteristic will be described with specific examples, but for the sake of easy understanding, each point is represented in the coordinate format of the steering angle θ and the turning angle δ. The neutral operation point is (0, 0), the maximum operation point is (θe, δe), and the reference point is (θp, δp).

First, the case where the steering handle 11 is in the “steering operation state” at the neutral position will be described. In this case, the absolute value of the detected steering angle θ always increases with a somewhat large steering angular velocity dθ / dt, even when the steering handle 11 is rotated in either the left or right direction. Therefore, the turning angle change characteristic determination unit 44 determines the cutting operation change characteristic. That is, as shown in FIG. 3, the turning angle change characteristic determining unit 44, according to the following formula 1, tilts a straight line connecting the reference point (θp, δp) and the maximum operating point (θe, δe) (hereinafter, this The slope is referred to as a reference slope Tb1).
Tb1 = (δe−δp) / (θe−θp) Equation 1
However, in the “steering operation state” at the neutral position, the reference point (θp, δp) as the steering operation point coincides with the neutral operation point (0, 0). Tb1 is specifically represented by the following equation 2.
Tb1 = δe / θe Equation 2

Then, the turning angle change characteristic determination unit 44 determines the turning operation change characteristic of the turning angle δ of the left and right front wheels FW1 and FW2 with respect to the detected steering angle θ according to the following formula 3.
δ = δp + Ka · Tb1 · θ Equation 3
However, δp in the equation 3 represents the turning angle δp of the left and right front wheels FW1 and FW2 at the reference point, and Tb1 represents the reference inclination Tb1 calculated by the equation 1. In the case of the “steering operation state” at the neutral position, since the reference point (θp, δp) coincides with the neutral operation point (0, 0), the reference inclination Tb1 is calculated according to the above equation 2. . Further, θ in Equation 3 represents the steering angle θ of the steering handle 11 detected by the steering angle sensor 31.

  Further, Ka in Equation 3 is a coefficient for changing the turning angle δ nonlinearly (convexly downward) with respect to the change in the steering angle θ, and can be expressed as shown in FIG. That is, the coefficient Ka changes according to a change in the steering angle θ, more specifically, according to a change in (θ−θp) / (θe−θp), and linearly increases as the steering angle θ increases. This is a variable that is set to “1” when the steering angle θ increases and coincides with the steering angle θe at the maximum operating point.

  Thus, by determining the cutting operation change characteristic, when the steering handle 11 is cut from the “steering operation state” at the neutral operation point (0, 0), the neutral operation point (0, 0) is determined. 0) to the maximum operating point (θe, δe), the steered angle δ can be changed so as to have a downwardly convex non-linear characteristic. As a result, the driver can perceive good change characteristics of the left and right front wheels FW1, FW2 with respect to the turning operation of the steering handle 11.

  Next, the case of “the cutting operation state from the steering operation” will be described. Even in this case, since the steering handle 11 is turned, the turning angle change characteristic determination unit 44 determines the turning operation change characteristic. In this “cutting operation state from the steering operation”, as shown in FIG. 7, the reference point setting unit 43 sets the steering operation point as the reference point (θp, δp). For this reason, the turning angle change characteristic determination unit 44 calculates the reference gradient Tb1 from the reference point (θp, δp) to the maximum operation point (θe, δe) according to the equation 1. Then, according to Equation 3, the cutting operation change characteristic of the turning angle δ of the left and right front wheels FW1, FW2 with respect to the detected steering angle θ is determined.

  As a result, even when the steering operation point, that is, the reference point (θp, δp) is different, a nonlinear characteristic that is convex downward uniformly from the reference point (θp, δp) to the maximum operation point (θe, δe) is obtained. As can be seen, the turning angle δ can be varied. Thereby, for example, when the steering handle 11 is turned to a large steering angle θ and the left and right front wheels FW1 and FW2 are steered to a large turning angle δ, the steering handle 11 is further turned and operated. , The sharp turning operation of the left and right front wheels FW1, FW2 can be reduced, and the driver can drive the vehicle more easily.

  Next, the case of “the cutting operation state from the switching back operation” will be described. Even in this case, since the steering handle 11 is turned, the turning angle change characteristic determination unit 44 determines the turning operation change characteristic. In this “cutting operation state from cutback operation”, as shown in FIG. 7, the cutting point is set as a reference point (θp, δp) by the reference point setting unit 43. Therefore, also in this case, the turning angle change characteristic determination unit 44 calculates the reference gradient Tb1 from the reference point (θp, δp) to the maximum operation point (θe, δe) according to the above-described equation 1. Then, according to Equation 3, the cutting operation change characteristic of the turning angle δ of the left and right front wheels FW1, FW2 with respect to the detected steering angle θ is determined.

  As a result, even when the cutting operation point, that is, the reference point (θp, δp) at the time of the switchback operation is different, the reference point (θp, δp) is always uniformly reduced from the maximum operation point (θe, δe). The steered angle δ changes so as to have a convex non-linear characteristic. Thus, for example, even in a situation where the steering handle 11 is suddenly turned from the return operation, the steep turning operation of the left and right front wheels FW1, FW2 can be reduced, and the driver can easily operate the vehicle. You can drive.

Next, the case of the “switchback operation state from the steering operation” will be described. In this case, since the steering handle 11 is turned back, the turning angle change characteristic determination unit 44 determines the return operation change characteristic. In this “switchback operation state from the steering operation”, the steering point is set as the reference point (θp, δp) by the reference point setting unit 43. Then, as shown in FIG. 4, the turning angle change characteristic determination unit 44 follows the following equation 4 to incline the straight line connecting the reference point (θp, δp) and the neutral operation point (0, 0) (hereinafter, this The slope is referred to as a reference slope Tb2.
Tb2 = δp / θp Equation 4

Then, the turning angle change characteristic determination unit 44 determines the return operation change characteristic of the turning angle δ of the left and right front wheels FW1 and FW2 with respect to the detected steering angle θ according to the following formula 5.
δ = Kb · Tb2 · θ Equation 5
However, Tb2 in the equation 5 represents the reference inclination Tb2 calculated by the equation 4, and θ represents the steering angle θ of the steering wheel 11 detected by the steering angle sensor 31. Further, Kb in Equation 5 is a coefficient for changing the turning angle δ non-linearly (convexly upward) with respect to the change in the steering angle θ, and can be expressed as shown in FIG. That is, the coefficient Kb changes according to a change in the steering angle θ, more specifically, according to a change in θ / θp. When the steering angle θ is “0” or coincides with the steering angle θp at the reference point, The variable is set to “1” and changes nonlinearly to “1” or more as the steering angle θ increases or decreases. Θp represents the steering angle θp at the reference point.

  In this way, by determining the switchback operation change characteristic, when the steering handle 11 is switched back from the “steering operation state” at the reference point (θp, δp), the reference point (θp, The steered angle δ can be changed so as to have a non-linear characteristic that is convex upward uniformly from δp) to the neutral operating point (0, 0). Thus, for example, when the steering handle 11 is turned to a large steering angle θ and the left and right front wheels FW1, FW2 are steered to a large turning angle δ, the steering handle 11 is turned back. , The sharp turning operation of the left and right front wheels FW1, FW2 can be reduced, and the driver can drive the vehicle more easily.

  Next, the case of the “switching back operation state from the cutting operation” will be described. Even in this case, the steering wheel 11 is turned back, so that the turning angle change characteristic determination unit 44 determines the return operation change characteristic. In this “returning operation state from the cutting operation”, as shown in FIG. 7, the reference point setting unit 43 sets the switching back operation point as the reference point (θp, δp). For this reason, also in this case, the turning angle change characteristic determination unit 44 calculates the reference inclination Tb2 from the reference point (θp, δp) to the neutral operating point (0, 0) according to the equation 4. And according to the said Formula 5, the switchback operation change characteristic of the turning angle (delta) of the left-right front wheels FW1 and FW2 with respect to the detected steering angle (theta) is determined.

  As a result, even when the return operation point at the time of the cutting operation, that is, the reference point (θp, δp) is different, the reference point (θp, δp) is always uniformly increased from the neutral operation point (0, 0). The turning angle δ can be changed so as to have a convex non-linear characteristic. Thereby, for example, even in a situation where the steering handle 11 is suddenly turned back from the turning operation, the steep turning operation of the left and right front wheels FW1, FW2 can be reduced, and the driver can easily drive the vehicle. You can drive.

  Here, in a situation where the “continuation state of the cutting operation” or the “continuation state of the switching operation” is determined by the operation state determination unit 42, the turning angle change characteristic determination unit 44 switches to these states. It goes without saying that the cutting operation change characteristic or the cutting operation change characteristic set at the time is maintained. As a result, in the “continuation state of the cutting operation” or the “continuation state of the switching operation”, the change characteristic of the turning angle δ with respect to the steering angle θ can be made constant, so that the driver may feel uncomfortable. Absent.

  As described above, when the turning operation change characteristic or the return operation change characteristic is determined, the turning angle change characteristic determination unit 44 outputs change characteristic determination information representing the determined change characteristic to the turning angle calculation unit 45. The turning angle calculation unit 45 acquires the output change characteristic determination information, and calculates target turning angles δf and δr with respect to the detected steering angle θ based on the change characteristic represented by the change characteristic determination information. Further, the turning angle calculation unit 45 is set in advance with respect to the detected steering angle θ when the vehicle is traveling at a vehicle speed V higher than a predetermined reference vehicle speed Vo based on the acquired traveling information. A target turning angle δk that is in a power relation is calculated. Hereinafter, calculation of the target turning angles δf, δr, and δk by the turning angle calculation unit 45 will be described.

The turning angle calculation unit 45 inputs the detected steering angle θ from the steering angle sensor 31 and the detected vehicle speed V from the vehicle speed sensor 33, and changes from the travel information and the turning angle change characteristic determination unit 44 from the vehicle speed determination unit 41. Get characterization information. Then, when the vehicle is traveling at a predetermined reference vehicle speed Vo or less, the turning angle calculation unit 45 calculates target turning angles δf and δr according to the change characteristics represented by the acquired change characteristic determination information. That is, if the cutting operation change characteristic is acquired from the turning angle change characteristic determination unit 44, the target turning angle δf at the time of the cutting operation is calculated according to the following expression 6 configured similarly to the expression 3.
δf = δp + Ka · Tb1 · θ Equation 6
Moreover, if the turning angle calculation part 45 has acquired the switching back operation change characteristic from the turning angle change characteristic determination part 44, according to the following formula | equation 7 comprised similarly to the said Formula 5, at the time of switching back operation A target turning angle δr is calculated.
δr = Kb · Tb2 · θ Equation 7

On the other hand, when the vehicle is traveling at a high speed at a vehicle speed V greater than a predetermined reference vehicle speed Vo, the turning angle calculation unit 45 performs a target turning that changes in a power function with respect to the input steering angle θ. The steering angle δk is calculated according to the following formula 8.
δk = a · θ ^{I (} Formula 8)

  However, the coefficient a in the equation 8 is a vehicle speed coefficient that varies depending on the detected vehicle speed V. As shown in FIG. 8, the detected vehicle speed V is within a relatively small range (that is, in the middle speed range). It has a characteristic that it is larger than 1 and is smaller than “1” within a range where the detected vehicle speed V is large (that is, in a high speed range) and decreases nonlinearly with “1” sandwiched as the detected vehicle speed V increases. Yes. Further, θ in Equation 8 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is a positive value, the coefficient a is a positive value and the detected steering angle θ is a negative value. If so, the value of the coefficient a is set to a negative value having the same absolute value as the positive value. Further, I in Equation 8 is a constant representing a power exponent and is set to a value larger than “1”.

  Therefore, as the detected vehicle speed V increases, the target turning angle δk calculated according to Equation 8 decreases with respect to the detected steering angle θ. As a result, the behavior stability of the vehicle in the medium / high speed range is ensured well, so that the driver can obtain a good steering feeling.

  Here, the calculation of the target turning angle δk is not limited to the calculation by the power function described above. That is, in a situation where the vehicle is traveling in the middle / high speed range, the target turning angle calculated when the steering angle θ changes within a certain small range, in other words, when the steering handle 11 is rotated near the neutral position. When the change amount of δk is reduced and the steering angle θ changes within a certain range, in other words, when the steering handle 11 is rotated outside the vicinity of the neutral position, the calculated change amount of the target turning angle δk is large. A function such as an exponential function can be employed. Note that the target turning angle δk may be calculated using a conversion table having characteristics as shown in FIG. 9 in which the target turning angle δk with respect to the steering angle θ is stored instead of the calculation of the equation 8.

The target turning angle δf, δr or the target turning angle δk calculated in this way is supplied to the turning angle correction unit 46. The turning angle correction unit 46 inputs the vehicle speed V detected by the vehicle speed sensor 33 and the actual lateral acceleration G detected by the lateral acceleration sensor 34, and uses the detected vehicle speed V and the actual lateral acceleration G as follows: The corrected target turning angles δfa and δra or the corrected target turning angle δka are calculated by correcting the target turning angles δf and δr or the target turning angle δk according to the formulas 9 to 11.
δfa = δf + J · (Gd−G) Equation 9
δra = δr + J · (Gd−G) Equation 10
δka = δk + J · (Gd−G) Equation 11

  However, the coefficient J in the equations 9 to 11 is a predetermined constant. Gd represents a target lateral acceleration generated by the vehicle at the time of turning of the vehicle, and when the vehicle travels while changing the vehicle speed V and the turning angle δ of the left and right front wheels FW1, FW2 is changed. This is an actual measurement of the generated lateral acceleration. Further, the coefficient J and the target lateral acceleration Gd are respectively positive values if the calculated target turning angle δd is positive, and are respectively positive coefficients if the calculated target turning angle δd is negative. It is a negative value having the same absolute value as J and the target lateral acceleration Gd.

  The corrected target turning angle δfa, δra or the corrected target turning angle δka calculated in this way is supplied to the drive control unit 47. The drive control unit 47 inputs the actual turning angle δ detected by the turning angle sensor 32, and the left and right front wheels FW1, FW2 are turned to the corrected target turning angles δfa, δra or the corrected target turning angle δka. The rotation of the electric motor in the steering actuator 21 is feedback-controlled so that it is steered. The drive control unit 52 also inputs a drive current that flows from the drive circuit 37 to the electric motor, and feedback-controls the drive circuit 37 so that a drive current having a magnitude corresponding to the steering torque appropriately flows to the electric motor. To do. By the drive control of the electric motor in the steering actuator 21, the rotation of the electric motor is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the pinion gear 23. Due to the displacement of the rack bar 24 in the axial direction, the left and right front wheels FW1, FW2 are steered to the calculated corrected target turning angles δfa, δra or the corrected target turning angle δka.

Next, the reaction force control unit 50 that applies reaction force to the turning operation of the steering handle 11 by the driver will be described. In the reaction force control unit 50, the reaction force torque calculation unit 51 calculates the reaction force torque Tz according to the following equation 12 using the detected steering angle θ.
Tz = b · θ ^{K (} 12)

  However, the coefficient b in the equation 12 is a predetermined constant. In the equation 12, θ represents the absolute value of the detected steering angle θ. If the detected steering angle θ is a positive value, the coefficient b is a negative value and the detected steering angle θ is a negative value. If so, the value of the coefficient b is set to a positive value having the same absolute value as the negative value. Furthermore, K in the equation 12 is a constant representing a power exponent, and is set to a value smaller than “1”.

  The reaction torque Tz calculated in this way is supplied to the drive control unit 52. The drive control unit 52 inputs a drive current that flows from the drive circuit 36 to the electric motor in the reaction force actuator 13, and feedback-controls the drive circuit 36 so that a drive current corresponding to the reaction force torque Tz flows through the electric motor. . By the drive control of the electric motor in the reaction force actuator 13, the electric motor applies a reaction force torque Tz to the steering handle 11 via the steering input shaft 12. Thus, the driver can perceive an appropriate reaction force according to the turning operation state of the steering handle 11.

  As can be understood from the above description, according to the first embodiment, the operation state determination unit 42 determines the operation state of the steering wheel 11 by the driver. Based on this determination, the reference point setting unit 43 operates the operation point when the operation state of the steering wheel 11 is switched, that is, the steering operation point in the “steering operation state”, the “return operation from the cutting operation”. The cut back operation point in the “state” and the cut operation point in the “cut operation state from the cut back operation” can be set as the reference points (θp, δp).

  As a result, the turning angle change characteristic determination unit 44 uses the set reference points (θp, δp) to change the cutting operation change characteristics that change nonlinearly up to the maximum operation point (θe, δe), and the neutral operation point. It is possible to determine a switching operation change characteristic that changes nonlinearly up to (0, 0). Here, the cutting operation change characteristic can be a non-linear change characteristic that protrudes downward with respect to the linear change from the reference point (θp, δp) to the maximum operation point (θe, δe). Further, the switching operation change characteristic can be a non-linear characteristic that is convex upward with respect to a linear change from the reference point (θp, δp) to the neutral operation point (0, 0).

  Further, the turning angle calculation unit 45 can calculate the target turning angles δf and δr of the left and right front wheels FW1 and FW2 based on the cutting operation change characteristic or the switchback operation change characteristic thus determined. Further, when the vehicle speed V is higher than the reference vehicle speed Vo by the vehicle speed determination unit 41, the turning angle calculation unit 45 can calculate the target turning angle δk that is in a power relationship (or exponential relationship) with the steering angle θ. it can.

  As described above, in accordance with the operation of the steering handle 11, that is, the cutting operation or the returning operation, the cutting operation change characteristic from the reference point (θp, δp) to the maximum operating point (θe, δe) or the reference point (θp, δp). By determining the switchback operation change characteristic from to the neutral operation point (0, 0), the position of the reference point (θp, δp) is always based on the same change characteristic. The target turning angles δf and δr of the left and right front wheels FW1 and FW2 can be calculated with respect to the steering angle θ. Therefore, even when the reference point (θp, δp) changes in the cutting operation state or the switching back operation state, the left and right front wheels FW1, FW2 to be steered according to the operation of the steering handle 11 by the driver. The steering operation state is always the same, that is, the same steering feeling can always be obtained. Thereby, the driver can always turn the vehicle while perceiving the same behavior change in the cutting operation state or the switching back operation state. Therefore, the driver can drive the vehicle easily.

  In addition, by making the cutting operation change characteristic a non-linear change characteristic that protrudes downward, the vehicle behavior change immediately after the start of the cutting operation can be moderated, and as the steering angle θ increases, the left and right front wheels FW1 and FW2 can be steered greatly, and the amount of operation of the steering handle 11 by the driver can be reduced. On the other hand, the change in behavior of the vehicle immediately after the start of the switchback operation can be moderated by setting the switchback operation change characteristic to be a non-linear change characteristic that is convex upward. Therefore, the driver can obtain a good operation feeling.

b. Second Embodiment In the first embodiment, the turning angle δ with respect to the steering angle θ is determined from the reference point (θp, δp) as the neutral operation point as the switchback operation change characteristic determined by the turning angle change characteristic determination unit 44. Up to (0,0) was carried out so as to change with a convex non-linear characteristic. Thereby, for example, when the driver performs a turning operation so as to perform a turning-back operation from a turning operation, the steering operation of the left and right front wheels FW1, FW2 can be made gentle, and as a result, the vehicle can be operated easily. can do.

  However, in this case, the reference point (θp, δp) is sequentially set according to the switching of the operation state of the steering wheel 11 by the driver, and particularly in the vicinity of the neutral operation point (0, 0). The change characteristics of the turning angle δ with respect to the steering angle θ are different. More specifically, the amount of change in the turning angle δ in the vicinity of the neutral operating point (0, 0) is different, and it may be difficult to hold the steering handle 11 at the neutral operating point (0, 0). Further, when the driver turns the steering handle 11 to pass the neutral operation point (0, 0), the switchover operation state is switched to the cutting operation state. In this way, in the situation where the switchback operation state is switched from the switchback operation state across the neutral operation point (0, 0), the switchback operation change characteristic is instantaneously switched to the cutting operation change characteristic. Change characteristics change greatly. As a result, the driver may feel uncomfortable.

  Therefore, in this second embodiment, the switching operation change characteristic is determined so that the change characteristic of the turning angle δ in the vicinity of the neutral operation point (0, 0) becomes a non-linear characteristic convex downward. Hereinafter, although this 2nd Embodiment is described in detail, about the same part as the said 1st Embodiment, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.

  In the second embodiment, as shown in the functional block diagram of FIG. 9 representing functions realized by computer program processing in the electronic control unit 35, the turning angle change characteristic determining unit 44 of the first embodiment is described. Instead, a turning angle change characteristic determination unit 61 that determines the above-described switching operation change characteristic is provided.

  The turning angle change characteristic determination unit 61 acquires the reference point (θp, δp) supplied by the reference point setting unit 43 that functions in the same manner as in the first embodiment, and functions in the same manner as in the first embodiment. The operation state information supplied by the operation state determination unit 42 is acquired. Then, the turning angle change characteristic determination unit 61 determines the turning angle δ of the left and right front wheels FW1 and FW2 according to the operation state of the steering handle 11, similarly to the turning angle change characteristic determination unit 44 of the first embodiment. Determine cutting operation change characteristics.

  On the other hand, as shown in FIG. 10, the turning angle change characteristic determination unit 61 connects the reference point (θp, δp) and the neutral operation point (0, 0) when the steering handle 11 is turned back. A non-linear change characteristic that has a non-linear change characteristic that protrudes upward in the vicinity of the reference point (θp, δp) with respect to a straight line and that protrudes downward in the vicinity of the neutral operation point (0, 0). Determining the cutting operation change characteristic to have. Hereinafter, this cutting operation change characteristic will be described in detail with specific examples.

First, the case of the “switchback operation state from the steering operation” will be described. In this “switchback operation state from the steering operation”, the steering point is set as the reference point (θp, δp) by the reference point setting unit 43. For this reason, the turning angle change characteristic determination unit 61 calculates the reference gradient Tb2 according to the equation 4 as in the first embodiment. Then, the turning angle change characteristic determining unit 61 uses the reference point (θp, δp) and the neutral operation point (0) as the change characteristic of the turning angle δ of the left and right front wheels FW1, FW2 with respect to the detected steering angle θ according to the following equation 13. , 0) to calculate the linear change characteristic.
δs = Tb2 · θ Equation 13
However, δs in the equation 13 represents a turning angle δs having a linear change characteristic with respect to the detected steering angle θ in the return operation. In the equation 13, Tb2 represents the reference inclination Tb2 calculated according to the equation 4, and θ represents the steering angle θ of the steering wheel 11 detected by the steering angle sensor 31.

Further, the turning angle change characteristic determination unit 61 sets the change characteristic of the turning angle δ of the left and right front wheels FW1 and FW2 with respect to the detected steering angle θ in the vicinity of the neutral operating point (0, 0) according to the following formula 14. Calculate the non-linear change characteristic that becomes convex.
δg = Kc · Tb2 · θ Equation 14
However, Tb2 in the equation 14 represents the reference inclination Tb2 calculated by the equation 4, and θ represents the steering angle θ of the steering wheel 11 detected by the steering angle sensor 31. Further, Kc in the equation 14 is a coefficient for changing the turning angle δ nonlinearly (convexly downward) with respect to the change of the steering angle θ, and can be expressed as shown in FIG. That is, the coefficient Kc changes according to a change in the steering angle θ, more specifically, changes in θ / θp, and is set to “1” when the detected steering angle θ matches the reference point θp. , Θ / θp is a variable that linearly decreases as the steering wheel 11 is turned to the neutral position. Θp represents the steering angle θp at the reference point.

Then, the turning angle change characteristic determination unit 61 follows the following equation 15 using the turning angle δs that changes based on the linear change characteristic and the turning angle δg that changes based on the non-linear change characteristic that protrudes downward. Then, the switching operation change characteristic of the turning angle δ of the left and right front wheels FW1, FW2 with respect to the detected steering angle θ is determined.
δ = (1−Kw) · δg + Kw · δs Equation 15
Here, Kw in Equation 15 is a coefficient that determines the ratio (ratio) at which the turning angle δ changes linearly with respect to the change in the steering angle θ, and can be expressed as shown in FIG. That is, the coefficient Kw changes according to a change in the steering angle θ, more specifically, according to a change in θ / θp. When the detected steering angle θ matches the reference point θp, the coefficient Kw is a value larger than “1”. And changes to “0” as θ / θp decreases, that is, as the steering wheel 11 is turned to the neutral position.

  As described above, since the switching operation change characteristic is determined, the value of the coefficient Kw is set to “1” or more in the vicinity of the reference point (θp, δp). The steering angle δ is larger than the steering angle δs having the linear change characteristic calculated according to the equation 13. As a result, in the vicinity of the reference point (θp, δp), the turning angle δ with respect to the detected steering angle θ changes based on the upward convex non-linear change characteristic, as in the first embodiment. Therefore, as shown in FIG. 14, the steering handle 11 is turned off from the situation where the steering handle 11 is turned to a large steering angle θ and the left and right front wheels FW1, FW2 are steered to a large turning angle δ. In the returning operation, it is possible to reduce the sharp turning operation of the left and right front wheels FW1, FW2.

  Also, in the vicinity of the neutral operating point (0, 0), the value of the coefficient Kw is set to “0”, so the turning angle δ calculated according to the equation 15 is a non-linear change calculated according to the equation 14. It coincides with the turning angle δg having characteristics. As a result, in the vicinity of the neutral operating point (0, 0), the turning angle δ with respect to the detected steering angle θ changes based on the downwardly convex non-linear change characteristic, similarly to the cutting operation change characteristic. Thereby, for example, when the steering handle 11 is rotated across the neutral operation point (0, 0), even when the switching operation is instantaneously switched from the switching operation to the cutting operation, the switching operation change characteristic is obtained. And the cutting operation change characteristic can be made into a convex non-linear change characteristic.

  Even in the case of the “returning operation state from the cutting operation”, the turning angle change characteristic determining unit 61 calculates the return operation changing characteristic by calculating the above formulas 13 to 15. That is, the turning angle change characteristic determination unit 61 determines the turning angle δs based on the linear change characteristic from the reference point (θp, δp) as the switchback operation point to the neutral operation point (0, 0) according to the equation (13). calculate. Further, the turning angle change characteristic determination unit 61 calculates the turning angle δg based on the non-linear change characteristic that protrudes downward in accordance with the equation 14. Then, the turning angle change characteristic determination unit 61 determines the return operation change characteristic of the turning angle δ of the left and right front wheels FW1 and FW2 with respect to the detected steering angle θ according to the equation 15.

  As a result, even when a switching operation is performed from a cutting operation, as shown in FIG. 14, it has an upward convex non-linear variation characteristic in the vicinity of the reference point (θp, δp), and a neutral operating point (0 , 0) vicinity, it is possible to determine a switching operation change characteristic having a non-linear change characteristic convex downward. Thereby, it is possible to reduce the sharp turning operation of the left and right front wheels FW1, FW2 in the vicinity of the reference point (θp, δp). Further, when the steering handle 11 is turned over the neutral operation point (0, 0), the return operation change characteristic and the cut operation change characteristic are similarly set to a convex non-linear change characteristic. it can.

  The other program processing executed by the electronic control unit 35 is the same as that in the first embodiment. In the functional block diagram of FIG. 10, the same reference numerals as those in FIG. 2 of the first embodiment are given, and the description thereof is omitted.

  As can be understood from the above description, in this second embodiment, the turning angle change characteristic determination unit 61 changes nonlinearly so as to protrude upward in the vicinity of the reference point, and decreases downward in the vicinity of the neutral operation point. It is possible to determine a switching operation change characteristic that changes nonlinearly so as to be convex. Further, the turning angle change characteristic determining unit 61 can change the ratio of the non-linear change protruding upward and the ratio of the non-linear change protruding downward in the non-linear characteristic according to the magnitude of the operation input value. .

  As described above, the non-linear change characteristic that protrudes downward in the vicinity of the neutral operation point makes it easier to hold the steering handle 11 in the vicinity of the neutral position, and also performs the return operation and the cutting operation across the neutral position. The change of the change characteristic when switching between and can be made extremely small. Then, by changing the ratio of the non-linear change characteristic that protrudes downward and the non-linear change characteristic that protrudes upward in accordance with the magnitude of the steering angle θ, the sense of incongruity associated with the change between these non-linear change characteristics is greatly increased. Can be reduced. Therefore, the driver can obtain a good operation feeling. As for other effects, the same effects as in the first embodiment can be expected.

c. Third Embodiment In the first embodiment and the second embodiment, when the operation state determination unit 42 determines the “steering operation state”, the reference point setting unit 43 sets the steering operation point as a reference point (θp). , Δp). Then, the turning angle change characteristic determination units 44 and 48 use the set reference points (θp, δp) to determine the cutting operation change characteristic or the return operation change characteristic according to the operation state of the steering handle 11. Was carried out as follows. Thus, after the reference point (θp, δp) is set by the reference point setting unit 43, the appropriate steering operation change characteristic or the return operation change characteristic is determined, so that the steering handle by the driver is determined. The steering operation of the left and right front wheels FW1, FW2 with respect to the turning operation of 11 becomes gentle, and the driving of the vehicle is simplified.

  By the way, in the said 1st Embodiment and 2nd Embodiment, if the operation state determination part 42 determines with a "steering operation state", the reference point setting part 43 will immediately use the steering operation point as a reference point (θp, δp), and accordingly, the turning angle change characteristic determination units 44 and 61 determine the turning operation change characteristic or the return operation change characteristic. For this reason, depending on the change (transition) timing of the reference point (θp, δp) by the reference point setting unit 43, switching of the change characteristic of the turning angle δ by the turning angle change characteristic determining units 44, 48 becomes unnatural, The driver may feel uncomfortable.

  Therefore, in the third embodiment, the reference point (θp, δp) is set so that the change (transition) timing of the reference point (θp, δp) becomes gradual in time. Hereinafter, although this 3rd Embodiment is described in detail, about the same part as the said 1st Embodiment and 2nd Embodiment, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.

  In the third embodiment, as shown in the functional block diagram of FIG. 15 representing functions realized by computer program processing in the electronic control unit 35, the operation state determination in the first embodiment and the second embodiment is performed. Instead of the unit 42, an operation state determination unit 71 is provided. Further, instead of the reference point setting unit 43 of the first embodiment and the second embodiment, a reference point setting that is set by changing (shifting) the reference point (θp, δp) gradually as described above. A portion 72 is provided. Moreover, it replaces with the turning angle change characteristic determination part 44 of the said 1st Embodiment, and the turning angle change characteristic determination part 61 of the said 2nd Embodiment, and it cuts according to the reference point set by the reference point setting part 72 A turning angle change characteristic determining unit 73 that determines an operation change characteristic or a switchback operation change characteristic is provided.

  In the third embodiment, the operation state determination unit 71 determines the “semi-steering operation state” in addition to the determination of the operation state of the steering handle 11 in the first embodiment and the second embodiment. Hereinafter, determination of the “semi-steering operation state” by the operation state determination unit 71 will be described.

  In a situation where the absolute value of the detected steering angle θ slightly increases or decreases, the operation state determination unit 71 determines that the absolute value of the steering angular velocity dθ / dt is a predetermined absolute value dθ0 / dt as the first reference operation speed. When the state between the predetermined absolute value dθ1 / dt as the second reference operation speed set larger than the predetermined absolute value dθ0 / dt continues for a predetermined time th, the steering handle 11 Is determined as a “semi-steering operation state” in which the absolute value of the detected steering angle θ is maintained at a substantially constant value.

  The reference point setting unit 72 sets virtual reference points (θpv, δpv) based on the determination of the “semi-steering operation state” by the operation state determination unit 71. That is, when the operation state determination unit 71 determines that the steering handle 11 is currently switched to the “semi-steering operation state”, the reference point setting unit 72 detects the detected steering angle θ and the detected actual turning angle δ at the same determination point. Are set as virtual reference points (θpv, δpv). As described above, when the virtual reference point (θpv, δpv) is set, the reference point setting unit 72 supplies the set virtual reference point (θpv, δpv) to the turning angle change characteristic determination unit 73.

  In the turning angle change characteristic determination unit 73, the supplied virtual reference point (θpv, δpv) is acquired, and an operation indicating “semi-steering operation state” as the operation state of the steering wheel 11 from the operation state determination unit 71 is obtained. Get status information. Then, the turning angle change characteristic determination unit 73 determines a change characteristic of the turning angle δ of the left and right front wheels FW1 and FW2 according to the “semi-steering operation state” and the “steering operation state” of the steering handle 11.

That is, as shown by the broken line in FIG. 16, the turning angle change characteristic determination unit 73 illustrates the original change characteristic in which the virtual reference point (θpv, δpv) exists (in FIG. 15, the switch back operation change characteristic is illustrated. ) And a change characteristic determined by setting the virtual reference point (θpv, δpv) as shown by a one-dot chain line in FIG. The change characteristic of the turning angle δ represented by these two change characteristics is determined according to the following equation 16.
δ = (1−Kv) · δt + Kv · δvt Equation 16
Here, δt in the equation 16 represents a turning angle that changes based on the original change characteristic in which the virtual reference point (θpv, δpv) exists, and δvt sets the virtual reference point (θpv, δpv). The turning angle which changes based on the change characteristic determined by is represented.

  Further, Kv in the equation 16 is a coefficient that determines the ratio (ratio) between the turning angle δt and the turning angle δvt, and as shown in FIG. 17, the change in the steering angular velocity dθ / dt of the steering handle 11 It will change according to. That is, the coefficient Kv is set to “0” if the absolute value of the steering angular velocity dθ / dt is equal to or larger than the predetermined absolute value dθ1 / dt, and is less than the predetermined absolute value dθ1 / dt and the predetermined absolute value dθ0 / dt. Is set to a value between “0” and “1”, and is set to “1” if it is equal to or less than a predetermined absolute value dθ0 / dt.

  Thus, by determining the change characteristic of the turning angle δ according to the above equation 16, when the steering angular velocity dθ / dt is larger than the predetermined absolute value dθ1 / dt, the value of the coefficient Kv is set to “0”. Therefore, the turning angle δ calculated according to the equation 16 is consistent with the turning angle δt, that is, changes according to the original change characteristic in which the virtual reference point (θpv, δpv) exists. When the steering angular velocity dθ / dt is less than the predetermined absolute value dθ1 / dt and larger than the predetermined absolute value dθ0 / dt, the value of the coefficient Kv changes between “0” and “1”. For this reason, the change characteristic of the turning angle δ determined according to the equation 16 is, as shown by a thick line in FIG. 16, the change characteristic of the turning angle δt and the change characteristic of the turning angle δvt are the steering angular velocity dθ / According to dt, it is changed continuously, that is, gradually in time. Thereby, the transition from the reference point (original reference point) used to determine the original change characteristic to the virtual reference point (θpv, δpv), in other words, from the original change characteristic to the virtual reference point (θpv, δpv). ) Can be used to make the transition to the change characteristic extremely smoothly.

  Further, when the steering angular velocity dθ / dt is equal to or less than a predetermined absolute value dθ0 / dt, the value of the coefficient Kv is set to “1”. This is consistent with the change characteristics using the reference points (θpv, δpv). By the way, when the steering angular velocity dθ / dt is equal to or less than the predetermined absolute value dθ0 / dt, the operation state determination unit 71 is the steering wheel as in the operation state determination unit 42 of the first and second embodiments. 11 is determined to be in the “steering operation state”. Therefore, the reference point setting unit 72 sets the steering operation point as the formal reference point (θp, δp) instead of the virtual reference point (θpv, δpv) based on the determination of the operation state determination unit 71.

  Here, the formal reference points (θp, δp) set by the reference point setting unit 72 are on the change characteristics determined by setting the virtual reference points (θpv, δpv) as shown in FIG. Exists. In addition, the transition from the virtual reference point (θpv, δpv) to the formal reference point (θp, δp) gradually becomes smaller than the predetermined absolute value dθ0 / dt as the steering angular velocity dθ / dt gradually decreases. When complete. Therefore, based on the determination of the “steering operation state” by the operation state determination unit 71, the reference point for the reference point setting unit 72 to determine the change characteristic of the turning angle δ is a virtual reference point (θpv, δpv). Is changed (transferred) to the formal reference point (θp, δp), the change (transfer) becomes gradual in time.

  Here, when the reference state setting unit 72 sets the formal reference point (θp, δp), if the operation state determination unit 71 determines the “semi-steering operation state”, the reference point setting unit again. 72 sets virtual reference points (θpv, δpv). Then, the reference point setting unit 72 determines the reference point for determining the change characteristic of the turning angle δ from the virtual reference point (θpv, δpv) based on the determination of “steering operation state”. Change to (θp, δp).

  Then, the turning angle change characteristic determination unit 73 uses the official reference point (θp, δp) to obtain the change characteristic of the turning angle δ with respect to the steering angle θ, that is, the turning operation change characteristic or the return operation change characteristic. decide. Therefore, the change of the change characteristic accompanying the transition from the virtual reference point (θpv, δpv) to the formal reference point (θp, δp) becomes gradual in time, and the driver does not feel uncomfortable.

  As can be understood from the above description, in the third embodiment, when the operation state determination unit 71 determines that the operation mode has been switched to the “semi-maintained operation state”, the reference point setting unit 72 performs the virtual reference operation. A point (θpv, δpv) can be set. In addition, when the operation state determination unit 71 determines that the “semi-steering operation state” has been switched to the “steering operation state”, the reference point setting unit 72 is switched to the “steering operation state”. The steering control point can be changed from the virtual reference point (θpv, δpv) as the formal reference point (θp, δp). Then, the turning angle change characteristic determination unit 73 uses the original reference point, the virtual reference point (θpv, δpv), and the formal reference point (θp, δp) set before the virtual reference point is set, to perform cutting. An operation change characteristic or a switchback operation change characteristic can be determined.

  As a result, in accordance with the switching of the operation state of the steering wheel 11, the original reference point is gradually changed (shifted) from the original reference point to the formal reference point (θp, δp) via the virtual reference point (θpv, δpv). )can do. As a result, the original reference point (or virtual reference point (θpv, δpv)) is determined using the formal reference point (θp, δp) from the cutting operation change characteristic or the cutback operation change characteristic determined using the virtual reference point (θpv, δpv). The change (transition) of the cutting operation change characteristic or the switch back operation change characteristic is also performed gradually in time. Therefore, it is possible to effectively reduce the sense of discomfort associated with the transition from the original reference point (or virtual reference point (θpv, δpv)) to the formal reference point (θp, δp).

  Further, the turning angle change characteristic determination unit 73 determines the ratio of the cutting operation change characteristic or the return operation change characteristic (that is, the turning angle δt) determined using the original reference point, and the virtual reference point (θpv, δpv). The ratio of the cutting operation change characteristic or the return operation changing characteristic (that is, the turning angle δvt) determined by using is changed according to the steering angular velocity dθ / dt of the steering handle 11, and the virtual reference point is changed from the original reference point. The cutting operation change characteristic or the switchback operation change characteristic (that is, the turning angle δ) associated with the shift to (θpv, δpv) can be determined. In this way, by changing the ratio between the change characteristic using the original reference point and the change characteristic using the virtual reference point (θpv, δpv), the change characteristic accompanying the transition to the virtual reference point (θpv, δpv) By determining, the change characteristic can be changed very smoothly. Therefore, even when the virtual reference point (θpv, δpv) is finally changed (transferred) to the formal reference point (θp, δp), the uncomfortable feeling associated with the change (transfer) can be effectively reduced. Can do. Therefore, it is possible to effectively reduce the sense of discomfort associated with the transition from the virtual reference point (θpv, δpv) to the formal reference point (θp, δp).

  Furthermore, in carrying out the present invention, the present invention is not limited to the first to third embodiments, and various modifications can be made without departing from the object of the present invention.

  For example, in the first to third embodiments, the steering handle 11 that is turned to steer the vehicle is used. However, instead of this, for example, a joystick-type steering handle that is linearly displaced may be used, or any other one that can be operated by the driver and instructed to steer the vehicle is used. May be.

  In the first to third embodiments, the left and right front wheels FW1 and FW2 are steered by rotating the steered output shaft 22 using the steered actuator 21. However, instead of this, the left and right front wheels FW1, FW2 may be steered by linearly displacing the rack bar 24 using the steering actuator 13.

It is the schematic of the steering apparatus of the vehicle common to 1st thru | or 3rd embodiment of this invention. FIG. 2 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to the first embodiment of the present invention. It is a graph which shows the relationship between the steering angle and steering angle for demonstrating the change characteristic of the turning angle at the time of cutting operation. It is a graph which shows the relationship between the steering angle and the turning angle for demonstrating the change characteristic of the turning angle at the time of switchback operation. It is a graph which shows the change with respect to the steering angle of the coefficient Ka. It is a graph which shows the change with respect to the steering angle of coefficient Kb. It is a figure for demonstrating concretely the cutting operation change characteristic and switchback operation change characteristic which are determined according to the operation state of a steering wheel. It is a graph which shows the relationship between a vehicle speed and a vehicle speed coefficient. It is a graph which shows the relationship between a steering angle and a target turning angle. FIG. 9 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to the second embodiment of the present invention. It is a graph which shows the relationship between the steering angle and the turning angle for demonstrating the change characteristic of the turning angle at the time of switchback operation. It is a graph which shows the change with respect to the steering angle of the coefficient Kc. It is a graph which shows the change with respect to the steering angle of the coefficient Kw. It is a figure for demonstrating concretely the switchback operation change characteristic determined according to the operation state of a steering wheel. FIG. 10 is a functional block diagram functionally representing computer program processing executed by the electronic control unit of FIG. 1 according to the third embodiment of the present invention. It is a figure for demonstrating concretely the change (migration | transfer) of the reference point via a virtual reference point. It is a graph which shows the change with respect to steering angular velocity of coefficient Kv.

Explanation of symbols

FW1, FW2 ... front wheels, 11 ... steering handle, 12 ... steering input shaft, 13 ... reaction actuator, 21 ... steering actuator, 22 ... steering output shaft, 31 ... steering angle sensor, 32 ... steering angle sensor, 33 ... Vehicle speed sensor, 34 ... Lateral acceleration sensor, 35 ... Electronic control unit, 40 ... Steering control unit, 41 ... Vehicle speed determination unit, 42, 71 ... Operation state determination unit, 43, 72 ... Reference point setting unit, 44, 61 , 72 ... Steering angle change characteristic determination unit, 45 ... Steering angle calculation unit, 50 ... Reaction force control unit, 61 ... Reaction force torque calculation unit

Claims (10)

A steering handle operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered wheel by driving the steered actuator according to the operation of the steering handle In a steering-by-wire vehicle steering apparatus provided with a steering control apparatus that performs steering control automatically, the steering control apparatus includes:
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
An operation state determination means for determining an operation state by a driver of the steering wheel using the detected operation input value;
Based on the determined operation state of the steering wheel, an operation point determined by the absolute value of the operation input value when the operation state is switched and the absolute value of the turning angle of the steered wheels is set as a reference point. A reference point setting means,
A change characteristic of a turning angle of the steered wheel in a cutting operation state in which an absolute value of an operation input value of the steering wheel increases using the set reference point, and an upper limit of an operable range of the steering wheel A cutting operation change characteristic that changes nonlinearly to a maximum operation point determined by an absolute value of a maximum operation input value that defines a value and an absolute value of a maximum turning angle of the steered wheel corresponding to the maximum operation input value, and the steering A change characteristic of a turning angle of the steered wheel in a return operation state in which an absolute value of an operation input value of the steering wheel decreases. A turning angle change characteristic determining means for determining a switching operation changing characteristic that changes nonlinearly to a neutral operating point determined by a point;
A target turning angle calculation means for calculating a target turning angle of the steered wheel with respect to the detected operation input value based on the determined change characteristic of the steered wheel of the steered wheel;
Steering-by-wire comprising steering control means for controlling the steering actuator in accordance with the calculated target turning angle and turning the steered wheels to the calculated target turning angle. Type vehicle steering device. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The reference point setting means includes
The operation speed of the steering wheel represented by the time differential value of the operation input value detected from the cutting operation state or the switchback operation state by the operation state determination means is smaller than a preset reference operation speed. Operation point when it is determined that the state has been switched to the steering operation state that continues for a predetermined time or more, operation point when it is determined that the state has been switched directly from the cutting operation state to the switching operation state, and the switching operation state A steering-by-wire vehicle steering apparatus, wherein an operation point when it is determined that the state has been directly switched to a cutting operation state is set as the reference point. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The turning angle change characteristic determining means includes
When the steering handle is in the cutting operation state based on the determination by the operation state determination means, the turning angle of the steered wheels with respect to the detected operation input value from the set reference point to the maximum operation point In comparison with the linear change, a turning operation change characteristic is determined in which the turning angle of the steered wheel with respect to the detected operation input value from the set reference point to the maximum operation point becomes a non-linear change convex downward. And
When the steering handle is in the return operation state, as compared with a linear change in the turning angle of the steered wheel with respect to the detected operation input value from the set reference point to the neutral operation point, Switchback in which the turning angle of the steered wheels is a convexly non-linear change with respect to the detected operation input value at least in the vicinity of the set reference point from the set reference point to the neutral operation point A steering-by-wire vehicle steering apparatus characterized by determining an operation change characteristic. In the steering device for a steering-by-wire vehicle according to claim 3,
The turning angle change characteristic determining means includes
When the steering handle is in the switchback operation state based on the determination by the operation state determination means, the steered wheels are steered with respect to the detected operation input value from the set reference point to the neutral operation point. Compared to a linear change in angle, the neutral operation point changes nonlinearly so that the turning angle of the steered wheel with respect to the detected operation input value in the vicinity of the set reference point becomes convex upward, and the neutral operation point A steering-by-wire vehicle steering apparatus characterized by determining a non-linear change-back change characteristic so that a turning angle of the steered wheel is convex downward with respect to the detected operation input value in the vicinity. In the steering device for a steering-by-wire vehicle according to claim 4,
The turning angle change characteristic determining means includes
Depending on the magnitude of the detected operation input value, the ratio of the non-linear change that protrudes upward and the ratio of the non-linear change that protrudes downward between the set reference point and the neutral operation point. And a steering-by-wire steering apparatus for vehicles. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The steering control device further includes:
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
Vehicle speed determining means for determining the magnitude of the detected vehicle speed,
The target turning angle calculation means includes
When the detected vehicle speed is greater than a preset reference vehicle speed by the vehicle speed determining means, the detected steering angle that is in a power relationship or exponential relationship with the operation input value for the steering wheel is detected. Steering-by-wire vehicle steering apparatus characterized in that calculation is performed using the operated input value. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The reference point setting means includes
A first reference operation speed in which an operation speed of the steering wheel represented by a time differential value of the operation input value detected from the cutting operation state or the return operation state is preset by the operation state determination unit. And the second reference operation speed set larger than the first reference operation speed is set as a virtual reference point when the operation point is determined to be switched to the semi-steering operation state that continues for a predetermined time or more. And
The turning angle change characteristic determining means includes
The cutting operation change characteristic or the switching operation change characteristic determined using the reference point set immediately before the virtual reference point is set, and the cutting operation change determined using the set virtual reference point The cutting operation changing characteristic or the switching operation changing characteristic accompanying the transition from the reference point set immediately before to the virtual reference point is determined based on the characteristic or the switching operation changing characteristic. Steering-by-wire vehicle steering device. The steering apparatus for a steering-by-wire vehicle according to claim 7,
The turning angle change characteristic determining means includes
The ratio of the cutting operation change characteristic or the return operation change characteristic determined using the reference point set immediately before the virtual reference point is set according to the magnitude of the operation speed of the steering wheel, Change the ratio of the cutting operation change characteristic or the switch back operation change characteristic determined using the virtual reference point, and the transition from the reference point set immediately before to the virtual reference point A steering-by-wire type steering apparatus for a vehicle that determines a cutting operation change characteristic or the cut-back operation change characteristic. The steering apparatus for a steering-by-wire vehicle according to claim 7,
The reference point setting means includes
When it is determined by the operation state determination means that the state in which the operation speed of the steering wheel is lower than the first reference operation speed set in advance is switched to a steering operation state that continues for a predetermined time or more, the determination is made. Change the virtual reference point from the virtual reference point as the reference point
The turning angle change characteristic determining means includes
A steering-by-wire type steering apparatus for a vehicle that changes from the virtual reference point to the set reference point to determine the cutting operation change characteristic or the switching operation change characteristic. The steering device for a steering-by-wire vehicle according to claim 1, further comprising a reaction force device that applies a reaction force to the operation of the steering handle.

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