JP2007253756A - Steering control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce unnatural changes of steering reaction force which is felt by a driver, by controlling steering assist force to suppress changes of the steering reaction force due to roll steering when adhesion abnormality of a roll stiffness control device occurs, to improve steering feeling more than ever, and to reduce steering holding torque. <P>SOLUTION: In case where adhesion abnormality occurs on an active stabilizer device on a front wheel side or on a rear wheel side, unnecessary steering torque ΔTs due to roll steering is computed when a vehicle is in a specified traveling state. The correction amount Tsa of the steering torque for reducing influences of the unnecessary steering torque ΔTs is computed on the basis of unnecessary steering torque ΔTs and vehicle speed V, and the steering torque Ts is subtracted and corrected by the correction amount Tsa of the steering torque. Target assist torque Ta is computed on the basis of the steering torque Ts after subtraction and correction and the vehicle speed V, and electric power steering device 26 is controlled to make the steering assist torque become the target assist torque Ta. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle steering control device, and more particularly to a vehicle steering control device including a steering assist force control device that controls a steering assist force and a roll stiffness control device that variably controls the roll stiffness of the vehicle. .

  As one of control devices for vehicles such as automobiles, for example, as described in Patent Document 1 below, an actuator that variably controls roll rigidity by relatively rotating and driving a pair of torsion bars and a pair of torsion bars In a vehicle equipped with an active stabilizer device having a steering wheel, the grip state of the steered wheels is estimated, and the active stabilizer device is controlled according to the grip state of the steered wheels, thereby controlling the roll rigidity of the vehicle and controlling the roll of the vehicle body. Control devices for controlling movement are conventionally known.

According to such a control device, since the roll rigidity of the vehicle is controlled according to the grip state of the steering wheel, the roll motion of the vehicle body is compared with the case where the roll rigidity of the vehicle is not controlled according to the grip state of the steering wheel. Can be controlled appropriately.
JP 2005-96672 A

[Problems to be Solved by the Invention]
In general, an active stabilizer device changes the roll rigidity of a vehicle by rotating the left and right torsion bars relative to each other with the actuator. For example, the actuator is operated with the left and right torsion bars rotated relative to each other while the vehicle is turning. When an abnormality that cannot be driven occurs, the left and right torsion bars remain in a state where they are relatively rotated by a certain angle, that is, a fixed state. Therefore, when the vehicle goes straight, one of the left and right wheels is in a bound state and the other wheel on the left and right is in a rebound state. The degree of the bound and rebound state is proportional to the relative rotation angle of the left and right torsion bars that are fixed.

  Further, in general, in a vehicle such as an automobile, the wheel is supported by a suspension arm that is pivotally supported by the vehicle body at one end and pivotally attached to the wheel support member at the other end. In other words, a roll steer occurs. This roll steer occurs only momentarily during normal driving of the vehicle, but if the bounce and rebound state of the wheel continues, the vehicle tries to deflect in the direction of toe change of the wheel due to the roll steer, and the driver You must drive the vehicle against this. For this reason, an unnatural steering feeling in which the steering reaction force varies depending on the turning direction of the vehicle is unavoidable, and when the driver tries to drive the vehicle straight, the steering wheel is against the relatively high steering reaction force. Must be retained.

  However, in the conventional control device as described above for controlling the active stabilizer device, the problems associated with roll steer due to the fixation of the active stabilizer device and the countermeasures have not been sufficiently studied, and this point has been improved. Is needed.

  The problem of the sticking of the active stabilizer device is not limited to the electric active stabilizer device in which the actuator includes the electric motor and the reduction gear mechanism, and similarly occurs in the hydraulic active stabilizer device in which the actuator is operated by hydraulic pressure. In some cases, the same problem may occur when the means for changing the roll rigidity is an active suspension that changes the spring force of the suspension spring.

  The present invention has been made in view of the above-described points in a conventional control device for a vehicle equipped with a roll stiffness control device, and the main problem of the present invention is that a sticking abnormality of the roll stiffness control device occurs. The steering assist force is controlled so as to suppress the change in the steering reaction force caused by the roll steer, thereby reducing the unnatural change in the steering reaction force felt by the driver. It is to improve the steering feeling and reduce the steering torque.

[Means for Solving the Problems and Effects of the Invention]
According to the present invention, the main problem described above is the configuration of claim 1, that is, the steering assist force control means for controlling the steering assist force based on at least the detected value of the steering reaction force, and the roll rigidity of the vehicle is changed. In the vehicle steering control device having the roll stiffness variable means, the steering assist force control means is operated when a sticking abnormality occurs in the roll stiffness variable means in which the roll stiffness of the vehicle varies depending on the roll direction of the vehicle. An unnecessary steering reaction force due to the sticking abnormality is estimated based on the steering operation amount of the person or the actual turning state amount of the vehicle and the detected value of the steering reaction force, and counters the unnecessary steering reaction force This is achieved by a vehicle steering control device that controls a steering assist force so that a force is generated.

  As will be described in detail later, when a sticking abnormality occurs in the roll stiffness variable means, it is possible to estimate the steering reaction force that should originally occur based on the steering operation amount of the driver or the actual turning state amount of the vehicle. Therefore, when a sticking abnormality occurs in the roll stiffness varying means, the sticking abnormality of the roll stiffness varying means is determined based on the driver's steering operation amount or the actual turning state amount of the vehicle and the detected value of the steering reaction force. Unnecessary steering reaction force caused can be estimated.

  According to the first aspect of the present invention, when an abnormality in fixing occurs in the roll stiffness variable means, the fixing is performed based on the driver's steering operation amount or the actual turning state amount of the vehicle and the detected value of the steering reaction force. Since the unnecessary steering reaction force due to the abnormality is estimated and the steering assist force is controlled so as to generate a force to counter the unnecessary steering reaction force, the unnecessary steering reaction force due to the abnormal fixation of the roll stiffness variable means is unnecessary. Steering reaction force can be reliably estimated, and changes in steering reaction force due to roll steer can be reliably suppressed, thereby reducing unnatural changes in steering reaction force felt by the driver, Steering feeling can be improved and steering torque can be reduced as compared with the prior art.

  Further, according to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1, the steering assist force control means is set to a driver's steering operation amount or an actual turning state amount. The unnecessary steering reaction force is configured to be estimated based on a deviation between the reference steering reaction force based on the detected value and the detected value of the steering reaction force.

  According to the second aspect of the present invention, the unnecessary steering reaction force is estimated based on the deviation between the reference steering reaction force based on the driver's steering operation amount or the actual turning state amount and the detected value of the steering reaction force. Therefore, unnecessary steering reaction force can be reliably estimated by detecting the driver's steering operation amount, actual turning state amount, and actual steering reaction force.

  According to the present invention, in order to effectively achieve the above-described main problems, in the configuration of the above-described claim 1 or 2, the steering assist force control means is configured such that the magnitude of the steering operation amount of the driver is a vehicle. The unnecessary steering reaction force is estimated on the basis of the detected value of the steering reaction force that is equal to or less than the reference value for straight-running determination and the actual amount of turning state is equal to or greater than the reference value for vehicle turning determination. (Structure of claim 3).

  According to the third aspect of the present invention, the magnitude of the driver's steering operation amount is equal to or less than the reference value for determining whether the vehicle is going straight, and the actual amount of turning state is equal to or greater than the reference value for determining whether the vehicle is turning. Since an unnecessary steering reaction force is estimated based on the detected value of the steering reaction force at the time, as will be described in detail later, unnecessary steering caused by roll steer of the front wheels due to abnormal fixation of the roll stiffness variable means The reaction force can be reliably estimated.

  Further, according to the present invention, in order to effectively achieve the main problem described above, in the configuration according to any one of claims 1 to 3, the steering assist force control means is configured to increase the amount of steering operation by the driver. The unnecessary steering reaction force based on the detected value of the steering reaction force when the length is equal to or greater than the vehicle turn determination reference value and the actual turning state amount is equal to or less than the vehicle straight drive determination reference value. (Embodiment 4).

  According to the configuration of the fourth aspect, the magnitude of the driver's steering operation amount is equal to or greater than the reference value for vehicle turning determination, and the actual amount of turning state is equal to or less than the reference value for vehicle straight-running determination. Since an unnecessary steering reaction force is estimated based on the detected value of the steering reaction force at the time, as will be described in detail later, it is unnecessary due to the roll steer of the rear wheel accompanying the abnormal fixing of the roll stiffness varying means. The steering reaction force can be reliably estimated.

  According to the present invention, in order to effectively achieve the above main problem, in the configuration according to any one of the first to fourth aspects, the steering assist force control means is configured to reduce the unnecessary steering reaction force. The target steering assist force is calculated based on the corrected steering reaction force detection value, and the steering assist force is controlled based on the target steering assist force.

  According to the above configuration, the target steering assist force is calculated based on the detected value of the steering reaction force corrected by the unnecessary steering reaction force, and the steering assist force is controlled based on the target steering assist force. Therefore, the target steering assist force in which the influence of the unnecessary steering reaction force is reduced can be calculated, and thereby the influence of the unnecessary steering reaction force can be surely reduced.

  According to the present invention, in order to effectively achieve the above main problem, in the configuration according to any one of the first to fourth aspects, the steering assist force control means is configured to reduce the unnecessary steering reaction force. Based on the corrected steering assist force, the provisional target steering assist force is calculated based on at least the detected value of the steering reaction force, and the temporary target steering assist force is corrected by the corrected steering assist force. Based on this, the steering assist force is configured to be controlled (configuration of claim 6).

  According to the above configuration, the corrected steering assist force is calculated based on the unnecessary steering reaction force, the provisional target steering assist force is calculated based on at least the detected value of the steering reaction force, and the provisional target steering assist is calculated. Since the steering assist force is controlled based on the target steering assist force corrected by the corrected steering assist force, the steering assist force is controlled based on the target steering assist force in which the influence of unnecessary steering reaction force is reduced. Thus, the influence of unnecessary steering reaction force can be surely reduced.

[Preferred embodiment of problem solving means]
According to one preferred aspect of the present invention, in the structure according to any one of claims 1 to 6, the roll stiffness changing means changes the roll stiffness of the vehicle by changing the torsional stiffness of the stabilizer. (Preferred embodiment 1).

  According to another preferred aspect of the present invention, in the configuration according to any one of claims 1 to 6, the roll stiffness variable means changes the roll stiffness of the vehicle on the front wheel side. And a rear wheel-side roll stiffness varying means for changing the roll stiffness of the rear wheel-side vehicle (preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 1, when the abnormality in fixing occurs in the roll rigidity variable means on the front wheel side or the rear wheel side, the other roll rigidity variable means. Is configured to be stopped (preferred aspect 3).

  According to another preferred aspect of the present invention, in any one of the first to sixth aspects or the preferred aspects 1 to 3, the steering control device is provided when the vehicle is in a steady running state. An unnecessary steering reaction force due to the sticking abnormality is estimated based on the driver's steering operation amount or the actual turning state amount of the vehicle and the detected value of the steering reaction force (Preferable aspect 4).

  According to another preferred aspect of the present invention, in any one of the first to sixth aspects or the preferred aspects 1 to 4, the steering control device operates when the vehicle is in a predetermined traveling state. The initial value of the unnecessary steering reaction force is estimated by estimating the initial value of the unnecessary steering reaction force due to the sticking abnormality based on the amount of the steering operation of the person or the actual amount of turning state of the vehicle and the detected value of the steering reaction force. A subsequent unnecessary steering reaction force is estimated based on the value and the vehicle speed (preferred aspect 5).

  According to another preferred aspect of the present invention, in any one of the above-described claims 2 to 6 or the preferred aspects 1 to 5, the steering control device is configured to perform the reference steering reaction force based on the steering angle and the vehicle speed. (Preferred aspect 6).

  According to another preferred aspect of the present invention, in any one of the second to sixth aspects or the preferred aspects 1 to 5, the steering control device is configured to perform a reference steering reaction based on the yaw rate and the vehicle speed of the vehicle. It is comprised so that force may be calculated (preferred aspect 7).

  According to another preferred aspect of the present invention, in the configuration according to the third aspect, the fifth aspect, or the sixth aspect, or the preferred aspects 1 to 5, the roll stiffness varying means is configured to control the roll stiffness of the vehicle on the front wheel side. The steering control device includes a front wheel side roll stiffness variable means and a rear wheel side roll stiffness variable means for changing the rear wheel roll stiffness of the vehicle. When the driver's steering operation amount is less than or equal to the reference value for vehicle straight-running determination and the actual turning state amount is greater than or equal to the vehicle turning determination reference value. The unnecessary steering reaction force is configured to be estimated based on a detected force value (preferred aspect 8).

  According to another preferred aspect of the present invention, in any one of the fourth to sixth aspects or the preferred aspects 1 to 5, the roll stiffness varying means changes the roll stiffness of the vehicle on the front wheel side. The steering control device includes a front wheel side roll stiffness varying means and a rear wheel side roll stiffness varying means for changing the roll stiffness of the rear wheel side vehicle. Steering reaction force when the amount of steering operation by the driver is greater than or equal to the reference value for vehicle turning determination and the actual amount of turning state is less than or equal to the reference value for vehicle straight determination The unnecessary steering reaction force is estimated based on the detected value (preferred aspect 9).

  According to another preferred aspect of the present invention, in the configuration according to claim 5 or any of preferred aspects 1 to 9, the steering control device determines the vehicle speed when an unnecessary steering reaction force is estimated. The reference vehicle speed is 1 when the vehicle speed is the reference vehicle speed, and a positive correction coefficient is calculated based on the vehicle speed so that the vehicle speed increases as the vehicle speed is higher than the reference vehicle speed and decreases as the vehicle speed is lower than the reference vehicle speed. A correction amount based on an unnecessary steering reaction force is calculated as a product of a correct steering reaction force and a correction coefficient, and a target steering assist force is calculated based on a detected value of the steering reaction force corrected by the correction amount. Constructed (preferred embodiment 10)

  According to another preferred aspect of the present invention, in the configuration of any one of the sixth aspect and the preferred aspects 1 to 9, the steering control device determines a vehicle speed when an unnecessary steering reaction force is estimated. The reference vehicle speed is 1 when the vehicle speed is the reference vehicle speed, and a positive correction coefficient is calculated based on the vehicle speed so that the vehicle speed increases as the vehicle speed is higher than the reference vehicle speed and decreases as the vehicle speed is lower than the reference vehicle speed. A correction amount based on an unnecessary steering reaction force is calculated as a product of a correct steering reaction force and a correction coefficient, and a correction steering assist force is calculated based on the correction amount (preferred aspect 11).

  The present invention will now be described in detail with reference to a few preferred embodiments with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing a first embodiment of a vehicle steering control device according to the present invention applied to a vehicle having an active stabilizer device on the front wheel side and the rear wheel side and having an electric power steering device.

  In FIG. 1, 10FL and 10FR indicate the left and right front wheels of the vehicle 12, respectively, and 10RL and 10RR indicate the left and right rear wheels of the vehicle 12, respectively. An active stabilizer device 16 is provided between the left and right front wheels 10FL and 10FR, and an active stabilizer device 18 is provided between the left and right rear wheels 10RL and 10RR. The active stabilizer devices 16 and 18 function as roll stiffness changing means for applying an anti-roll moment to the vehicle (vehicle body) and increasing / decreasing the roll stiffness on the front wheel side and the rear wheel side as required.

  The active stabilizer device 16 is integrally connected to a pair of torsion bar portions 16TL and 16TR extending coaxially with each other along an axis extending in the lateral direction of the vehicle, and to the outer ends of the torsion bar portions 16TL and 16TR, respectively. And a pair of arm portions 16AL and 16AR. The torsion bar portions 16TL and 16TR are respectively supported by a vehicle body not shown in the drawing via brackets not shown in the drawing so as to be rotatable around its own axis. The arm portions 16AL and 16AR extend in the longitudinal direction of the vehicle so as to intersect the torsion bar portions 16TL and 16TR, respectively, and the outer ends of the arm portions 16AL and 16AR are respectively left and right through rubber bush devices not shown in the drawing. The front wheels 10FL and 10FR are connected to suspension members 14FL and 14FR such as suspension arms.

  The active stabilizer device 16 has an actuator 20F between the torsion bar portions 16TL and 16TR. Actuator 20F has a built-in electric motor, and rotationally drives a pair of torsion bar portions 16TL and 16TR as necessary, so that torsional stress is generated when the left and right front wheels 10FL and 10FR bounce and rebound in opposite phases to each other. Thus, the force to suppress the bounce and rebound of the wheel is changed, thereby increasing or decreasing the anti-roll moment applied to the vehicle at the position of the left and right front wheels, and variably controlling the roll rigidity of the vehicle on the front wheel side.

  Similarly, the active stabilizer device 18 has a pair of torsion bar portions 18TL and 18TR extending coaxially with each other along an axis extending in the lateral direction of the vehicle, and the outer ends of the torsion bar portions 18TL and 18TR, respectively. It has a pair of arm portions 18AL and 18AR connected together. The torsion bar portions 18TL and 18TR are respectively supported by a vehicle body not shown in the drawing via brackets not shown in the drawing so as to be rotatable around its own axis. The arm portions 18AL and 18AR extend in the longitudinal direction of the vehicle so as to intersect the torsion bar portions 18TL and 18TR, respectively, and the outer ends of the arm portions 18AL and 18AR are respectively left and right through rubber bushing devices not shown in the drawing. The suspension members 14RL and 14RR such as the suspension arms of the rear wheels 10RL and 10RR are connected.

  The active stabilizer device 18 has an actuator 20R between the torsion bar portions 18TL and 18TR. The actuator 20R has a built-in electric motor, and if necessary, the pair of torsion bar portions 18TL and 18TR are driven to rotate relative to each other, so that the left and right rear wheels 10RL and 10RR bounce and rebound in opposite phases. The force that suppresses the bounce and rebound of the wheel is changed by the stress, whereby the anti-roll moment applied to the vehicle at the positions of the left and right rear wheels is increased and decreased, and the roll rigidity of the vehicle on the rear wheel side is variably controlled.

  Since the structures of the active stabilizer devices 16 and 18 do not form the gist of the present invention, any structure known in the art can be used as long as the roll rigidity of the vehicle can be variably controlled. However, for example, the active stabilizer device described in the specification and drawings of Japanese Patent Application No. 2003-324212 (reference number PA03-374) relating to the application of the present applicant, that is, a drive gear fixed to the inner end of one torsion bar portion An electric motor having an attached rotating shaft and a driven gear that is fixed to the inner end of the other torsion bar portion and meshes with the driving gear. The driving gear and the driven gear transmit the rotation of the driving gear to the driven gear. The active stabilizer device is preferably a gear that does not transmit the rotation of the driven gear to the drive gear.

  The actuators 20F and 20R of the active stabilizer devices 16 and 18 are controlled by the electronic control device 22 controlling the control current for the motor. Although not shown in detail in FIG. 1, the electronic control unit 22 includes a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other via a bidirectional common bus and a drive circuit. It may be better.

  In the illustrated embodiment, as shown in FIG. 1, the left and right front wheels 10FL and 10FR are rack-and-pinion type electric power driven in response to the operation of the steering wheel 24 by the driver. The steering device 26 is steered through the rack bar 28 and the tie rods 30L and 30R.

  In the illustrated embodiment, the electric power steering device 26 is a rack coaxial type electric power steering device, and converts the electric motor 32 and the rotational torque of the electric motor 32 into a force in the reciprocating direction of the rack bar 28. For example, it has a ball screw type conversion mechanism 34 and functions as a steering assist force generating device that reduces the steering burden on the driver by generating a steering assist force that drives the rack bar 28 relative to the housing 36. To do. The electric power steering device 26 is controlled by controlling the control current for the motor 32 by the electronic control device 38. Although not shown in detail in FIG. 1, the electronic control unit 38 also has a CPU, a ROM, a RAM, and an input / output port unit, and these are connected to each other by a bidirectional common bus and a driving circuit. It may be better. Further, the steering assist force generating device may have any configuration known in the art.

  As shown in FIG. 1, the electronic control unit 22 includes a signal indicating the vehicle lateral acceleration Gy detected by the lateral acceleration sensor 40, a signal indicating the vehicle speed V detected by the vehicle speed sensor 42, a rotation angle sensor 44F, Signals indicating the actual rotation angles φF and φR of the actuators 20F and 20R detected by 44R are input.

  On the other hand, the electronic control unit 38 includes a signal indicating the steering angle θ detected by the steering angle sensor 46, a signal indicating the steering torque Ts detected by the torque sensor 48, and a signal indicating the vehicle yaw rate γ detected by the yaw rate sensor 50. Is entered. The electronic control units 22 and 38 communicate with each other and exchange necessary signals. The lateral acceleration sensor 40, the steering angle sensor 46, and the yaw rate sensor 50 detect the lateral acceleration Gy, the steering angle θ, and the yaw rate γ with positive values generated when the vehicle turns left, and the torque sensor 48 moves the front wheel in the left turning direction. The steering torque Ts is detected with the value at the time of turning being positive.

  The electronic control unit 22 determines whether or not a sticking abnormality has occurred in the front wheel side active stabilizer device 16 or the rear wheel side active stabilizer device 18 according to the flowchart shown in FIG. When 18 is normal, the roll moment acting on the vehicle is estimated based on at least the lateral acceleration Gy of the vehicle, and when the magnitude of the roll moment is greater than or equal to the reference value, the anti-roll moment in the direction to cancel the roll moment increases. The target anti-roll moment Mat of the vehicle is calculated.

  The electronic control unit 22 calculates the target anti-roll moment Maft of the front wheel and the target anti-roll moment Mart of the rear wheel based on the target anti-roll moment Mat and the target roll stiffness distribution ratio Rmf of the front wheel, and the target anti-roll moment Maft and Mart. Based on the above, the target rotation angles φFt and φRt of the actuators 20F and 20R of the active stabilizer devices 16 and 18 are calculated, respectively, and control is performed so that the rotation angles φF and φR of the actuators 20F and 20R become the corresponding target rotation angles φFt and φRt, respectively. Thus, the roll of the vehicle at the time of turning or the like is reduced with a roll rigidity having a preferable front-rear distribution ratio.

  Thus, the active stabilizer devices 16 and 18, the electronic control device 22, the lateral acceleration sensor 48, etc. function as roll stiffness variable means for increasing or decreasing the roll stiffness of the vehicle by increasing or decreasing the anti-roll moment when an excessive roll moment acts on the vehicle. And preventing excessive rolling of the vehicle.

  Further, the electronic control unit 22 sets a flag Ff indicating that when the front wheel side active stabilizer device 16 is stuck abnormally, and the rear wheel side active stabilizer device 18 is stuck abnormally. If it is, the flag Fr indicating that is set to 1. Signals indicating the flags Ff and Fr are output to the electronic control unit 38.

  It should be noted that the determination of whether or not there is a sticking abnormality in the active stabilizer devices 16 and 18 does not form the gist of the present invention, and may be achieved in any manner known in the art, for example, This may be done by determining whether or not the actuators 20F and 20R operate in response to the control currents for them and have changed corresponding to the actual rotation angles φF and φR.

  Further, the electronic control unit 38 calculates a provisional target assist torque Tab for achieving a predetermined steering characteristic based on the steering torque Ts detected by the torque sensor 48 and the vehicle speed V according to the flowchart shown in FIG. The electronic control device 38 sets the target assist torque Ta to the provisional target assist torque Tab when the active stabilizer devices 16 and 18 are normal, and the electric power steering device 26 so that the steering assist torque becomes the target assist torque Ta. To control. Thus, the electric power steering device 26, the electronic control device 38, the torque sensor 48, etc. function as steering assist force control means for increasing / decreasing the steering torque as the steering assist force, thereby reducing the driver's steering burden.

  As shown in FIG. 11A, a sticking abnormality occurs in the active stabilizer device 16 on the front wheel side, and the left and right front wheels 10FL and 10FR are steered by Δδf in the left turning direction with respect to the normal direction by the roll steer. Assuming that the vehicle is in a state, even when the steering wheel 24 is in the neutral position, the left and right front wheels 10FL and 10FR are steered by Δδf in the left turn direction with respect to the straight traveling direction of the vehicle.

  Therefore, the left and right front wheels 10FL and 10FR are acted on by a moment Mf that turns the wheels in the right turn direction and returns them to the straight position of the vehicle as a reaction force of the turning lateral force. Thus, unnecessary steering torque ΔTs in the same direction as when the vehicle is turned to the left is applied to the steering system.

  Therefore, although the active stabilizer devices 16 and 18 are normal, the actuators 20F and 20R do not operate, and the steering angle θ and the steering torque Ts in the case where the active stabilizer devices 16 and 18 function as a conventional general stabilizer are obtained. Assuming that the relationship shown in FIG. 11B is obtained at a certain vehicle speed V, the steering angle θ and the steering torque Ts are the same in the situation where the fixing abnormality occurs in the active stabilizer device 16 on the front wheel side. In the vehicle speed, the relationship shown by the solid line in FIG. That is, the curve indicating the relationship between the steering angle θ and the steering torque Ts is shifted in the opposite direction to Δθ along the axis of the steering angle θ by the steering angle Δθ corresponding to the turning angle Δδf of the front wheels by roll steer.

  It should be noted that a sticking abnormality occurs in the active stabilizer device 16 on the front wheel side, and the steering angle θ and steering torque in a situation where the left and right front wheels 10FL and 10FR are steered Δδf in the right turn direction with respect to the normal direction by roll steer. Ts has the relationship indicated by the phantom line in FIG. 11C at the same vehicle speed. Further, since there is a certain relationship between the steering angle θ and the vehicle yaw rate γ, the same relationship is established even if the horizontal axis in FIGS.

  Therefore, when there is a sticking abnormality in the front wheel side active stabilizer device 16, the steering torque Ts when the steering angle θ is substantially 0 and the vehicle is in a turning state is the front wheel side active stabilizer device. An unnecessary steering torque ΔTs caused by roll steer of the front wheels accompanying the 16 sticking abnormality is shown.

  Therefore, the electronic control unit 38 has the steering angle θ substantially equal to 0 and the magnitude of the yaw rate γ as the amount of turning state of the vehicle when a sticking abnormality has occurred in the active stabilizer device 16 on the front wheel side. The steering torque Ts when it is equal to or greater than the vehicle turning determination reference value is calculated as an unnecessary steering torque ΔTs.

  Further, as shown in FIG. 12A, a sticking abnormality occurs in the active stabilizer device 18 on the rear wheel side, and the left and right rear wheels 10RL and 10RR are turned leftward (right side) with respect to the normal direction by roll steer. Assuming that the vehicle is steered to Δδr, even if the steering wheel 24 is in the neutral position and the left and right front wheels 10FL and 10FR are in the straight traveling direction of the vehicle, the vehicle tends to deflect leftward.

  Therefore, a lateral turning force acts on the left and right front wheels 10FL and 10FR, and as a reaction force, the wheels are steered in the right turning direction so as to have the same turning angle as that of the rear wheels, and the vehicle is caused to travel straight ahead. And the unnecessary steering torque ΔTs in the same direction as when turning the vehicle to the left acts on the steering system due to the moment Mf.

  Therefore, although the active stabilizer devices 16 and 18 are normal, the steering angle θ and the steering torque Ts in the case where the active stabilizer devices 16 and 18 function as a conventional general stabilizer without the actuators 20F and 20R operating. Assuming that the relationship shown in FIG. 12B is obtained at a certain vehicle speed V, the steering angle θ and the steering torque Ts are the same in a situation in which a sticking abnormality has occurred in the active stabilizer device 18 on the rear wheel side. The relationship shown by the solid line in FIG. That is, the curve indicating the relationship between the steering angle θ and the steering torque Ts shifts in the opposite direction from Δθ along the axis of the steering angle θ by the steering angle Δθ corresponding to the turning angle Δδr of the rear wheel by roll steer.

  In addition, a sticking abnormality occurs in the active stabilizer device 18 on the rear wheel side, and the right and left rear wheels 10RL and 10RR are steered by Δδr to the right turning direction (left side) with respect to the normal direction by the roll steer. The steering angle θ and the steering torque Ts in the situation have the relationship indicated by the phantom line in FIG. 12C at the same vehicle speed. Also in this case, since there is a certain relationship between the steering angle θ and the vehicle yaw rate γ, the same relationship is established even if the horizontal axis in FIGS. 12B and 12C is set to the vehicle yaw rate γ. To do.

  Further, when the driver steers the left and right front wheels 10FL and 10FR in the right turning direction of the vehicle as shown by the phantom line in FIG. Without making a left turn, in other words, with the yaw rate γ substantially zero, the vehicle travels straight while moving slightly to the right.

  Therefore, when a sticking abnormality has occurred in the active stabilizer device 18 on the rear wheel side, the steering torque Ts when the steering angle θ is an angle corresponding to the turning of the vehicle and the vehicle is in a substantially straight traveling state. Represents an unnecessary steering torque ΔTs caused by roll steer of the rear wheel due to the abnormal fixation of the active stabilizer device 18 on the rear wheel side.

  Therefore, the electronic control unit 38 determines that the magnitude of the steering angle θ is equal to or larger than the vehicle turning determination reference value and the yaw rate γ of the vehicle when the rear wheel side active stabilizer device 18 is stuck abnormally. The steering torque Ts when the magnitude is equal to or less than the reference value for determining whether the vehicle is going straight is calculated as an unnecessary steering torque ΔTs.

  The electronic control unit 38 once calculates the unnecessary steering torque ΔTs, then calculates the steering torque correction amount Tsa based on the unnecessary steering torque ΔTs, and the steering torque Ts for calculating the target assist torque Ta. Is subtracted and corrected by the steering torque correction amount Tsa, the target assist torque Ta is calculated based on the steering torque after the subtraction correction, and the electric power steering device 26 is controlled so that the steering assist torque becomes the target assist torque Ta. .

  In this case, even if the turning angle of the front wheels or the rear wheels due to roll steer is constant, the magnitude of unnecessary steering torque that is actually generated is smaller as the vehicle speed V is lower, and is larger as the vehicle speed V is higher. Using the vehicle speed V when the unnecessary steering torque ΔTs is calculated as the reference vehicle speed Vc, the steering torque correction amount Tsa increases as the vehicle speed V is higher than the reference vehicle speed Vc and the deviation from the reference vehicle speed Vc increases. The vehicle speed V is variably set according to the vehicle speed V so that the vehicle speed V is lower than the reference vehicle speed Vc and decreases as the deviation from the reference vehicle speed Vc increases.

  Next, the vehicle travel control in the illustrated embodiment 1 will be described with reference to the flowcharts shown in FIGS. 2 and 3 are flow charts showing a control routine for roll rigidity and a control routine for steering assist torque, respectively. Each control is started by closing an ignition switch not shown in the figure, and is performed at predetermined time intervals. Repeatedly executed. The same applies to other embodiments described later.

  In step 210 of the roll stiffness control routine shown in FIG. 2, a signal indicating the vehicle lateral acceleration Gy is read, and in step 215, an abnormal sticking to the front wheel side active stabilizer device 16 is detected. 2 is determined. When an affirmative determination is made, the flag Ff is set to 1 in step 220, and then the control by the routine shown in FIG. If yes, go to step 225.

  In step 225, it is determined whether or not a sticking abnormality has occurred in the active stabilizer 18 on the rear wheel side. If an affirmative determination is made, the flag Fr is set to 1 in step 230. Thereafter, when the control by the routine shown in FIG. 2 is completed and a negative determination is made, the flag Ff and Fr are reset to 0 in step 235, and then the process proceeds to step 240.

In step 240, the target roll stiffness distribution ratio Rmf of the front wheels is calculated as a value larger than 0 and smaller than 1 so that it increases as the vehicle speed V increases. In step 245, for example, the magnitude of the lateral acceleration Gy of the vehicle is increased. The target anti-roll moment Mat is calculated on the basis of the lateral acceleration Gy of the vehicle so that the target anti-roll moment Mat increases as the value increases. In step 250, the target anti-roll moment of the front wheels according to the following equations 1 and 2, respectively. Maft and rear wheel target anti-roll moment Mart are calculated.
Maft = RmfMat (1)
Mart = (1-Rmf) Mat (2)

  In step 255, the target rotational angles φft and φrt of the actuators 20F and 20R of the active stabilizer devices 16 and 18 are calculated based on the front wheel target anti-roll moment Maft and the rear wheel target anti-roll moment Mart, respectively. In this case, the rotation angles φf and φr of the actuators 20F and 20R are controlled to be the target rotation angles φft and φrt, respectively.

  In step 310 of the steering assist torque control routine shown in FIG. 3, a signal indicating the steering torque Ts is read, and in step 315, it is determined whether or not the flag Fa is 1. That is, it is determined whether or not the calculation of the unnecessary steering torque ΔTs caused by the abnormal fixing of the front wheel side active stabilizer device 16 or the rear wheel side active stabilizer device 18 is completed, and an affirmative determination is made. If YES, the process proceeds to step 355. If a negative determination is made, the process proceeds to step 320.

  In step 320, it is determined whether or not the flag Ff is 1, that is, whether or not a sticking abnormality has occurred in the active stabilizer device 16 on the front wheel side. Proceed to 330, and if an affirmative determination is made, proceed to step 325.

  In step 325, the absolute value of the steering angle θ is equal to or less than the reference value θ1 (positive constant close to 0) for determining the neutral position of the steering angle, and the absolute value of the steering torque Ts is the reference value Ts1 (positive constant). Whether or not the absolute value of the yaw rate γ of the vehicle is greater than or equal to the reference value γ1 (positive constant), that is, the steering torque Ts is determined even though the steering wheel 24 is substantially in the neutral position. Whether or not the vehicle is in a turning state is determined. If a negative determination is made, the process proceeds to step 345. If an affirmative determination is made, the process proceeds to step 350.

  In step 330, it is determined whether or not the flag Fr is 1, that is, whether or not a sticking abnormality has occurred in the active stabilizer device 18 on the rear wheel side, and when a negative determination is made. In step 335, after the steering torque correction amount Tsa used for calculating the target assist torque Ta is set to 0, the process proceeds to step 365. If an affirmative determination is made, the process proceeds to step 340.

  In step 340, the absolute value of the steering angle θ is not less than the reference value θ2 (positive constant) for determining the turning position of the steering angle, and the absolute value of the steering torque Ts is not less than the reference value Ts2 (positive constant). In addition, it is determined whether or not the absolute value of the yaw rate γ of the vehicle is equal to or less than a reference value γ2 (a positive constant close to 0) for determining whether the vehicle is going straight, that is, the steering wheel 24 is at the turning position of the vehicle and the steering torque Ts is In spite of the occurrence, it is determined whether or not the vehicle is substantially in a straight traveling state. If a negative determination is made, the correction amount Tsa of the steering torque is set to 0 in step 345. At the same time, after the flag Fa is reset to 0, the routine proceeds to step 365. If an affirmative determination is made, the unnecessary steering torque ΔTs is set to the steering torque Ts at step 350, and the reference vehicle speed Vc is set to the current vehicle speed. Set to V Are, the process proceeds to step 355 after the flag Fa is set to 1.

  In step 355, the correction coefficient Ka decreases as the vehicle speed V decreases, the correction coefficient Ka increases as the vehicle speed V increases, and the correction coefficient Ka becomes 1 when the vehicle speed V is Vc. The correction coefficient Ka is calculated from the map corresponding to the graph shown in FIG. 6, and in step 360, the correction amount Tsa of the steering torque is calculated as the product of the correction coefficient Ka and the unnecessary steering torque ΔTs.

  In step 365, the steering torque Ts is subtracted and corrected by the steering torque correction amount Tsa. In step 370, the steering assist torque Tab is increased so that the basic assist torque Tab increases as the steering torque Ts increases. The basic assist torque Tab is calculated from the map corresponding to the graph shown in FIG. 4 based on the torque Ts, and corresponds to the graph shown in FIG. 5 based on the vehicle speed V so that the vehicle speed coefficient Kv decreases as the vehicle speed V increases. The vehicle speed coefficient Kv is calculated from the map, and the target assist torque Ta is calculated as the product of the vehicle speed coefficient Kv and the basic assist torque Tab.

  In step 395, the electric motor 32 of the electric power steering device 26 is controlled so that the steering assist torque becomes the target assist torque Ta.

  Thus, according to the illustrated embodiment 1, when the active stabilizer devices 16 and 18 are normal, a negative determination is made in steps 215 and 225, and in step 240, the target roll stiffness distribution ratio Rmf of the front wheels is calculated. In step 245, the target anti-roll moment Mat is calculated based on the lateral acceleration Gy of the vehicle. In step 250, the front anti-roll target Mat for achieving the target anti-roll moment Mat with the target roll stiffness distribution ratio Rmf is calculated. The roll moment Maft and the rear wheel target anti-roll moment Mart are calculated, and in steps 255 and 260, the active stabilizer devices 16 and 18 are controlled so that the target anti-roll moments Maft and Mart are achieved. Rolls are prevented.

  On the other hand, when an abnormality occurs in the front wheel side active stabilizer device 16, an affirmative determination is made in step 215, and a flag Ff is set to 1 in step 220. Accordingly, a negative determination is first made at step 315, and an affirmative determination is made at step 320, whereby a determination at step 325 is made.

  When the steering torque Ts is generated and the vehicle is turning even though the steering wheel 24 is substantially in the neutral position, an affirmative determination is made at step 325 and unnecessary steering is performed at step 350. The torque ΔTs is set to the steering torque Ts, the reference vehicle speed Vc is set to the current vehicle speed V, and the flag Fa is set to 1.

  Therefore, when a sticking abnormality occurs in the active stabilizer device 16 on the front wheel side and the calculation of the unnecessary steering torque ΔTs is completed, an affirmative determination is made in step 315, and unnecessary steering torque in steps 355 and 360. A steering torque correction amount Tsa for reducing the influence of ΔTs is calculated based on the unnecessary steering torque ΔTs and the vehicle speed V, and in step 365, the steering torque Ts is subtracted and corrected by the steering torque correction amount Tsa. In step 370, the target assist torque Ta is calculated based on the steering torque Ts and the vehicle speed V after the subtraction correction.

  Further, although the front wheel side active stabilizer device 16 is normal, if a sticking abnormality occurs in the rear wheel side active stabilizer device 18, a negative determination is made in step 215, and an affirmative determination is made in step 225. In step 230, the flag Fr is set to 1. Accordingly, a negative determination is first made in steps 315 and 320, and an affirmative determination is made in step 330, whereby the determination in step 340 is performed.

  If the steering wheel 24 is in the turning position of the vehicle and the steering torque Ts is generated, but the vehicle is in a substantially straight traveling state, an affirmative determination is made in step 340 and step 350 is executed. The unnecessary steering torque ΔTs is set to the steering torque Ts, the reference vehicle speed Vc is set to the current vehicle speed V, and the flag Fa is set to 1.

  Accordingly, when a sticking abnormality occurs in the active stabilizer device 18 on the rear wheel side and the calculation of the unnecessary steering torque ΔTs is completed, an affirmative determination is made in step 315, and unnecessary steering is performed in steps 355 and 360. The steering torque correction amount Tsa for reducing the influence of the torque ΔTs is calculated based on the unnecessary steering torque ΔTs and the vehicle speed V, and in step 365, the steering torque Ts is subtracted and corrected by the steering torque correction amount Tsa. In step 370, the target assist torque Ta is calculated based on the steering torque Ts and the vehicle speed V after the subtraction correction.

  As can be seen from the above description, according to the illustrated first embodiment, when the front wheel side active stabilizer device 16 is abnormally fixed and roll steer is generated on the left and right front wheels 10FL and 10FR, and the rear wheel side In any case where a sticking abnormality occurs in the active stabilizer device 18 and roll steer occurs in the left and right rear wheels 10RL and 10RR, the unnecessary steering torque ΔTs caused by the roll steer is reliably and It can be estimated accurately.

  Further, according to the first embodiment shown in the figure, the target assist torque Ta can be calculated based on the steering torque excluding the influence of the unnecessary steering torque ΔTs, so that the change in the steering reaction force caused by the roll steer can be reliably ensured. Thus, an unnatural change in the steering reaction force felt by the driver can be reduced, and the steering feeling can be improved and the steering torque can be reduced as compared with the conventional case.

  Particularly, according to the illustrated embodiment 1, the steering torque Ts is subtracted and corrected by the steering torque correction amount Tsa, and the target assist torque Ta is calculated based on the steering torque Ts and the vehicle speed V after the subtraction correction. As in Examples 2 and 4 described later, the target assist torque is obtained by subtracting the correction amount of the assist torque corresponding to the unnecessary steering torque ΔTs from the provisional target assist torque including the influence of the unnecessary steering torque ΔTs. The target assist torque Ta can be calculated more efficiently than when Ta is calculated.

  FIG. 7 is a flowchart showing a steering assist torque control routine in the second embodiment of the vehicle steering control device according to the present invention configured as a modification of the first embodiment. In FIG. 7, steps corresponding to the steps shown in FIG. 3 are given the same step numbers as the step numbers given in FIG. 3.

  The electronic control unit 38 according to the second embodiment once calculates the unnecessary steering torque ΔTs, and then increases or decreases the steering reaction force felt by the driver due to the unnecessary steering torque based on the unnecessary steering torque ΔTs. A steering torque correction amount Tsa for suppressing the steering torque is calculated, and an assist torque correction amount ΔTab is calculated based on the steering torque correction amount Tsa. Further, the electronic control unit 38 calculates the provisional assist torque Tpa based on the steering torque Ts, calculates the target assist torque Ta by subtracting and correcting the provisional assist torque Tpa by the assist torque correction amount ΔTab, and the steering assist torque. The electric power steering device 26 is controlled so that becomes the target assist torque Ta.

  As shown in FIG. 7, in the steering assist torque control routine of the second embodiment, the assist torque correction amount ΔTab is set to 0 in step 335, and the assist torque is adjusted in step 345. The correction amount ΔTab is set to 0, and the flag Fa is reset to 0.

  In step 375 executed after step 360, the assist torque correction amount ΔTab is calculated from the map corresponding to the graph shown in FIG. 4 based on the steering torque correction amount Tsa. In the next step 380, the temporary target assist torque Tpa is calculated from the map corresponding to the graph shown in FIG. 4 based on the steering torque Ts.

  In step 385, the basic assist torque Tab is calculated as a value obtained by subtracting the assist torque correction amount ΔTab from the provisional target assist torque Tpa. In step 390, the vehicle speed coefficient Kv decreases as the vehicle speed V increases. Based on the vehicle speed V, the vehicle speed coefficient Kv is calculated from a map corresponding to the graph shown in FIG. 5, and the target assist torque Ta is calculated as the product of the vehicle speed coefficient Kv and the basic assist torque Tab.

  Thus, according to the illustrated second embodiment, unnecessary steering torque caused by roll steer is produced regardless of whether the front wheel side active stabilizer device 16 or the rear wheel side active stabilizer device 18 is stuck abnormally. ΔTs can be reliably and accurately estimated, and the assist torque correction amount ΔTab corresponding to the unnecessary steering torque ΔTs is subtracted from the provisional target assist torque Tpa including the influence of the unnecessary steering torque ΔTs. Since the target assist torque Ta that eliminates the influence of the unnecessary steering torque ΔTs can be calculated, the change in the steering reaction force caused by the roll steer can be reliably suppressed, thereby preventing the driver from feeling uncomfortable. Natural change in steering reaction force can be reduced, steering feeling can be improved and steering torque can be reduced. .

  In particular, according to the first and second embodiments shown in the drawing, it is discriminated whether a sticking abnormality has occurred in the active stabilizer device 16 on the front wheel side or a sticking abnormality has occurred in the active stabilizer device 18 on the rear wheel side, Since an unnecessary steering torque ΔTs is calculated when the vehicle is in an optimum traveling state depending on which of the active stabilizer devices on the front wheel side or the rear wheel side the sticking abnormality occurs, the sticking abnormality is detected on the front wheels. The unnecessary steering torque ΔTs can be calculated more accurately than when the unnecessary steering torque ΔTs is calculated in the same manner regardless of the active stabilizer device on the side or rear wheel side. can do.

  Further, according to the first and second embodiments shown in the figure, when a sticking abnormality has occurred in the active stabilizer device 16 on the front wheel side, the steering wheel 24 is substantially in the neutral position in step 325, When it is determined that the steering torque Ts is generated and the vehicle is in a turning state, an unnecessary steering torque ΔTs is calculated, and when there is a sticking abnormality in the active stabilizer device 18 on the rear wheel side, step 340 is executed. In this case, an unnecessary steering torque ΔTs is calculated when it is determined that the vehicle is substantially in a straight traveling state even though the steering wheel 24 is at the turning position of the vehicle and the steering torque Ts is generated. Therefore, the unnecessary steering torque ΔTs is corrected as compared with the case where the unnecessary steering torque ΔTs is calculated when the vehicle is in another traveling state. It can be calculated to.

  Further, according to the first and second embodiments shown in the drawings, either a case where a sticking abnormality occurs in the front wheel side active stabilizer device 16 or a case where a sticking abnormality occurs in the rear wheel side active stabilizer device 18 occurs. In addition, once the unnecessary steering torque ΔTs is calculated in step 350, the flag Fa is set to 1, and an affirmative determination is made in step 315, whereby steps 325 or 340 and step 350 are performed. Since step 355 and subsequent steps are not executed, the steering assist torque can be easily controlled as compared with the case where the unnecessary steering torque ΔTs is calculated each time.

  Further, according to the illustrated embodiments 1 and 2, if an affirmative determination is made in step 325 or 340, the unnecessary steering torque ΔTs may be set to the detected steering torque Ts. Since it is not necessary to calculate the standard steering torque based on the vehicle speed V or the difference between the standard steering torque and the detected steering torque Ts, compared to the cases of Examples 3 and 4 described later. An unnecessary steering torque ΔTs can be easily calculated.

  FIG. 8 shows steering assist torque control in a third embodiment of the vehicle steering control device according to the present invention applied to a vehicle having an active stabilizer device on the front wheel side and the rear wheel side and having an electric power steering device. It is a flowchart which shows a routine.

  As described above, the curve indicating the relationship between the steering angle θ and the steering torque Ts in the situation where the sticking abnormality occurs in the front wheel side active stabilizer device 16, and the situation where the sticking abnormality occurs in the rear wheel side active stabilizer device 18. The curves indicating the relationship between the steering angle θ and the steering torque Ts in FIG. 2 indicate the steering corresponding to the steering angle Δδf of the front wheels by roll steering with respect to the position where the active stabilizer devices 16 and 18 function as normal stabilizers. A shift is made in the opposite direction to Δθ along the axis of the steering angle θ by the steering angle Δθ corresponding to the angle Δθ and the steering angle Δδf of the front wheel accompanying the turning of the rear wheel by roll steer.

  Further, in the situation where the active stabilizer devices 16 and 18 function as a normal stabilizer, the magnitude of unnecessary steering torque Ts generated by turning the front wheels without turning the rear wheels, and the rear As shown in FIG. 9A, the magnitude of the unnecessary steering torque Ts generated when the front wheels are steered to cancel the turning motion of the vehicle due to the wheels being steered is as follows. The larger the rudder angle is, the larger it is, and the smaller the vehicle speed V is, the smaller the steering angle is.

  Therefore, as shown in FIG. 9B, a curve indicating the relationship between the steering angle θ and the steering torque Ts is specified based on the vehicle speed V, and the vehicle speed V and the steering angle are determined based on the specified curve and the steering angle θ. The steering torque Ts corresponding to θ can be calculated as the standard steering torque Tsb, and the deviation between the standard steering torque Tsb and the steering torque Ts detected by the torque sensor 48 is unnecessary steering caused by the wheel roll steer. Represents the torque ΔTs.

  Therefore, the vehicle speed V, steering angle θ, steering torque can be obtained even when the vehicle is in a steady running state except when the vehicle is in a specific running state as in the first and second embodiments. Based on Ts, an unnecessary steering torque ΔTs can be obtained as a deviation between the standard steering torque Tsb and the steering torque Ts.

  The electronic control device 38 according to the third embodiment pays attention to the above points, and when the fixing abnormality occurs in the active stabilizer device 16 on the front wheel side or the active stabilizer device 18 on the rear wheel side, the vehicle is stationary. A curve indicating the relationship between the steering angle θ and the steering torque Ts is specified based on the vehicle speed V when the vehicle is in a smooth running state, the reference steering torque Tsb is calculated based on the specified curve and the steering angle θ, and the reference steering torque An unnecessary steering torque ΔTs is calculated as a deviation between Tsb and the steering torque Ts detected by the torque sensor 48.

  Further, as in the case of the above-described first embodiment, the electronic control device 38 of the third embodiment once calculates the unnecessary steering torque ΔTs, and then causes the unnecessary steering torque based on the unnecessary steering torque ΔTs. Then, the steering torque correction amount Tsa for suppressing the increase and decrease of the steering reaction force felt by the driver is calculated, and the steering torque Ts for calculating the target assist torque Ta is subtracted and corrected by the steering torque correction amount Tsa. Then, the target assist torque Ta is calculated based on the steering torque after the subtraction correction, and the electric power steering device 26 is controlled so that the steering assist torque becomes the target assist torque Ta.

  As shown in FIG. 8, in the steering assist torque control routine of the third embodiment, steps 810 to 830, 840, 850 to 865, and 890 are steps 310 to 810 in the above-described first embodiment, respectively. 320, 330, 335, 355-370, and 390 are executed.

  If an affirmative determination is made in step 820 or 825, that is, if a sticking abnormality has occurred in the active stabilizer device 16 on the front wheel side or the active stabilizer device 18 on the rear wheel side, the vehicle speed V is determined in step 835. Is equal to or greater than the vehicle travel determination reference value Vo (positive constant), and the absolute value of the longitudinal acceleration Vd of the vehicle calculated as, for example, a time differential value of the vehicle speed V is a positive reference value Vdo (a positive value close to 0). Or the absolute value of the steering angular velocity θd calculated as a time differential value of the steering angle θ is equal to or less than a reference value θdo (a positive constant close to 0) for steady turning determination, that is, It is determined whether or not the vehicle is in a steady running state. If a negative determination is made, the process proceeds to step 840, and if an affirmative determination is made, the process proceeds to step 845.

  In step 845, a map corresponding to the graph shown in FIG. 9A is specified based on the vehicle speed V, and shown in FIG. 9B from the specified map based on the steering angle θ. As shown, the steering torque Ts corresponding to the vehicle speed V and the steering angle θ is calculated as the standard steering torque Tsb, and the unnecessary steering torque ΔTs is calculated as the difference between the standard steering torque Tsb and the steering torque Ts detected by the torque sensor 48. After the reference vehicle speed Vc is set to the current vehicle speed V and the flag Fa is set to 1, the routine proceeds to step 850.

  Thus, according to the third embodiment shown in the drawing, when there is a sticking abnormality in the active stabilizer device 16 on the front wheel side or the active stabilizer device 18 on the rear wheel side, the vehicle speed when the vehicle is in a steady running state. The reference steering torque Tsb is calculated based on V and the steering angle θ, and an unnecessary steering torque ΔTs is calculated as a deviation between the reference steering torque Tsb and the steering torque Ts, so that unnecessary steering torque due to roll steer is calculated. ΔTs can be reliably and accurately estimated, and the roll is obtained by calculating the target assist torque Ta based on the steering torque excluding the influence of the unnecessary steering torque ΔTs as in the case of the first embodiment. Steering-induced changes in steering reaction force can be reliably suppressed, which reduces unnatural changes in steering reaction force felt by the driver. Steering feeling Te can be reduced fixed steering torque improves the.

  In particular, according to the third embodiment shown in the figure, the steering torque Ts is subtracted and corrected by the steering torque correction amount Tsa, and the target based on the steering torque Ts and the vehicle speed V after the subtraction correction, as in the first embodiment. Since the assist torque Ta is calculated, for example, as in the case of the above-described second embodiment and the fourth embodiment described later, it corresponds to the unnecessary steering torque ΔTs than the provisional target assist torque including the influence of the unnecessary steering torque ΔTs. The target assist torque Ta can be calculated more efficiently than when the target assist torque Ta is calculated by subtracting the correction amount of the assist torque to be performed.

  FIG. 10 is a flowchart showing a steering assist torque control routine in the fourth embodiment of the vehicle steering control apparatus according to the present invention, which is configured as a modification of the second embodiment. In FIG. 10, steps corresponding to the steps shown in FIG. 8 are assigned the same step numbers as those shown in FIG.

  As in the case of the above-described third embodiment, the electronic control device 38 according to the fourth embodiment is used when the front wheel side active stabilizer device 16 or the rear wheel side active stabilizer device 18 is stuck abnormally. Identifying a curve indicating the relationship between the steering angle θ and the steering torque Ts based on the vehicle speed V when the vehicle is in a steady running state, calculating a reference steering torque Tsb based on the identified curve and the steering angle θ, An unnecessary steering torque ΔTs is calculated as a deviation between the reference steering torque Tsb and the steering torque Ts detected by the torque sensor 48.

  Similarly to the case of the second embodiment, the electronic control unit 38 of the fourth embodiment once calculates the unnecessary steering torque ΔTs, and then causes the unnecessary steering torque based on the unnecessary steering torque ΔTs. Then, the assist torque correction amount ΔTab for suppressing the increase or decrease in the steering reaction force felt by the driver is calculated, and the target assist torque Ta is calculated by subtracting and correcting the provisional target assist torque Ta by the correction amount ΔTab. The electric power steering device 26 is controlled so that the steering assist torque becomes the target assist torque Ta.

  As shown in FIG. 10, in the steering assist torque control routine of the fourth embodiment, steps 810 to 855 and 890 are the same as steps 810 to 855 and 890 of the third embodiment, respectively. Executed. Steps 870 and 875 to 885 executed after step 855 are executed in the same manner as steps 375 and 880 to 390 in the second embodiment.

  Thus, according to the fourth embodiment shown in the figure, as in the case of the above-described third embodiment, when there is a sticking abnormality in the active stabilizer device 16 on the front wheel side or the active stabilizer device 18 on the rear wheel side, the vehicle is Since the standard steering torque Tsb is calculated based on the vehicle speed V and the steering angle θ when the vehicle is in a steady running state, and an unnecessary steering torque ΔTs is calculated as a deviation between the standard steering torque Tsb and the steering torque Ts, Unnecessary steering torque ΔTs caused by roll steer can be reliably and accurately estimated.

  Further, according to the illustrated embodiment 4, as in the case of the above-described embodiment 2, the correction amount of the assist torque corresponding to the unnecessary steering torque ΔTs than the provisional target assist torque Tpa including the influence of the unnecessary steering torque ΔTs. By subtracting ΔTab, it is possible to calculate the target assist torque Ta that eliminates the influence of unnecessary steering torque ΔTs, so that it is possible to reliably suppress changes in the steering reaction force caused by roll steer. Thus, an unnatural change in the steering reaction force felt by the driver can be reduced, the steering feeling can be improved and the steering torque can be reduced as compared with the conventional case.

  In particular, according to the above-described third and fourth embodiments, even when the vehicle is in a specific traveling state as in the first and second embodiments described above, the traveling state of the vehicle may be a steady traveling state. For example, since the unnecessary steering torque ΔTs can be calculated as a deviation between the standard steering torque Tsb and the steering torque Ts based on the vehicle speed V, the steering angle θ, and the steering torque Ts, the front wheel side active stabilizer device 16 or the rear When a sticking abnormality occurs in the active stabilizer device 18 on the wheel side, an unnecessary steering torque ΔTs can be calculated earlier than in the case of the first and second embodiments described above, thereby steering due to roll steer. Suppression of reaction force changes and reduction in unnatural steering reaction force changes felt by the driver can be achieved at an early stage.

  Further, according to the above-described embodiments, in step 355 or 850, the correction coefficient Ka decreases as the vehicle speed V decreases, the correction coefficient Ka increases as the vehicle speed V increases, and the correction coefficient Ka when the vehicle speed V is Vc. A positive correction coefficient Ka is calculated based on the vehicle speed V so that Ka becomes 1, and in step 360 or 855, the correction amount Tsa of the steering torque is calculated as the product of the correction coefficient Ka and the unnecessary steering torque ΔTs. Therefore, the steering torque correction amount Tsa can be calculated to an optimum value regardless of the change in the vehicle speed V, for example, compared to the case where the unnecessary steering torque ΔTs is set as the steering torque correction amount Tsa. This suppresses the change in the steering reaction force according to the unnecessary steering torque actually generated due to the roll steer regardless of the change in the vehicle speed V, and reduces the unnatural change in the steering reaction force felt by the driver. The right It can be carried out.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in each of the above-described embodiments, the vehicle turning state amount is the vehicle yaw rate γ. The vehicle turning state amount is, for example, a value obtained by dividing the vehicle lateral acceleration Gy or the vehicle lateral acceleration by the vehicle speed V. Etc.

  In each of the above-described embodiments, once the unnecessary steering torque ΔTs is calculated, the unnecessary steering torque ΔTs is not updated, but the flag Fa is omitted and the unnecessary steering torque is omitted. It may be modified so that ΔTs is calculated every time, and when a predetermined time elapses from the time when unnecessary steering torque ΔTs is calculated or updated, the process proceeds to step 320, whereby unnecessary steering torque ΔTs is updated. It may be modified so that.

  In the above-described first and second embodiments, when there is a sticking abnormality in the active stabilizer device 16 on the front wheel side, the determination in step 325 is performed, and a sticking abnormality occurs in the active stabilizer device 18 on the rear wheel side. In step 340, the determination in step 340 is performed. However, when a sticking abnormality has occurred in the active stabilizer device on the front wheel side or the rear wheel side, determination in step 325 is first performed, and step 325 is performed. In this case, it may be modified so as to proceed to step 340 when a negative determination is made.

  In the first and second embodiments described above, it is not determined whether or not the vehicle is in a steady state, but the vehicle is in a steady state. It may be modified so that the determination in step 325 or 340 is performed only when the vehicle is in a steady traveling state.

  In the above-described third and fourth embodiments, the vehicle is in a steady running state when there is a sticking abnormality in the active stabilizer device 16 on the front wheel side or the active stabilizer device 18 on the rear wheel side. A curve indicating the relationship between the steering angle θ and the steering torque Ts is specified based on the vehicle speed V, and the reference steering torque Tsb is calculated based on the specified curve and the steering angle θ. Thus, since the relationship between the steering angle θ and the steering torque Ts can be replaced with the relationship between the vehicle yaw rate γ and the steering torque Ts, a curve indicating the relationship between the vehicle yaw rate γ and the steering torque Ts is specified based on the vehicle speed V, Modifications may be made to calculate the reference steering torque Tsb based on the identified curve and the vehicle yaw rate γ.

  In Examples 3 and 4 described above, the friction coefficient of the road surface is not taken into consideration, but it actually occurs even if the turning angle of the front wheels or the rear wheels due to roll steer is constant. Since the unnecessary steering torque is smaller as the road friction coefficient is lower, and the road friction coefficient is higher, the map is specified in step 845 based on the vehicle speed V and the road friction coefficient. The steering torque Ts corresponding to the vehicle speed V and the steering angle θ may be corrected so as to be calculated as the standard steering torque Tsb from the map specified based on the angle θ.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram illustrating a first embodiment of a vehicle steering control device according to the present invention applied to a vehicle having an active stabilizer device on a front wheel side and a rear wheel side and including an electric power steering device. 3 is a flowchart showing a roll rigidity control routine in the first embodiment. 3 is a flowchart showing a steering assist torque control routine in the first embodiment. 5 is a graph showing a relationship between steering torque Ts (steering torque correction amount Tsa) and basic assist torque Tab (temporary assist torque Tpa, assist torque correction amount ΔTab). It is a graph which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kv. It is a graph which shows the relationship between the vehicle speed V and the correction coefficient Ka. 7 shows a steering assist torque control routine in a second embodiment of a vehicle steering control device according to the present invention applied to a vehicle having an active stabilizer device on the front wheel side and the rear wheel side and an electric power steering device. It is a flowchart. 7 shows a steering assist torque control routine in a third embodiment of the vehicle steering control device according to the present invention applied to a vehicle having an active stabilizer device on the front wheel side and the rear wheel side and an electric power steering device. It is a flowchart. FIG. 5 is a graph (A) showing a relationship between the steering angle θ and the vehicle speed V and the steering torque Ts, and an explanatory diagram (B) showing a procedure for calculating the reference steering torque Tsb based on the steering angle θ and the vehicle speed V. 7 shows a steering assist torque control routine in a fourth embodiment of a vehicle steering control device according to the present invention applied to a vehicle having an active stabilizer device on the front wheel side and the rear wheel side and an electric power steering device. It is a flowchart. Explanatory drawing (A) which shows the situation where sticking abnormality has occurred in the active stabilizer device on the front wheel side and roll steer has occurred on the front wheel, the steering angle when the active stabilizer devices on the front wheel side and the rear wheel side are normal A graph (B) showing the relationship between θ and the steering torque Ts, the steering angle θ and the steering torque Ts in the case where a sticking abnormality has occurred in the active stabilizer device on the front wheel side and roll steer has occurred in the front wheel. It is a graph (C) which shows the relationship between. Explanatory drawing (A) which shows the situation where the sticking abnormality has occurred in the active stabilizer device on the rear wheel side and the roll steer is generated in the rear wheel, in the case where the active stabilizer devices on the front wheel side and the rear wheel side are normal A graph (B) showing a relationship between the steering angle θ and the steering torque Ts, and the steering angle θ in the case where a sticking abnormality has occurred in the active stabilizer device on the rear wheel side and roll steer has occurred in the rear wheel. It is a graph (C) which shows the relationship between steering torque Ts.

Explanation of symbols

16, 18 Active stabilizer device 20F, 20R Actuator 22 Electronic control device 26 Electric power steering device 38 Electronic control device 40 Lateral acceleration sensor 42 Vehicle speed sensor 44F, 44R Rotation angle sensor 46 Steering angle sensor 48 Torque sensor 50 Yaw rate sensor

Claims (6)

  In a vehicle steering control device, comprising: steering assist force control means for controlling steering assist force based on at least a detected value of steering reaction force; and roll stiffness variable means for changing roll stiffness of the vehicle. The control means detects the steering operation amount of the driver or the detected value of the actual turning state of the vehicle and the steering reaction force when a sticking abnormality in which the roll rigidity of the vehicle varies depending on the roll direction of the vehicle occurs in the roll stiffness variable means. The vehicle steering control is characterized in that an unnecessary steering reaction force caused by the sticking abnormality is estimated on the basis of the above, and a steering assist force is controlled so as to generate a force that opposes the unnecessary steering reaction force. apparatus.   The steering assist force control means estimates the unnecessary steering reaction force based on a deviation between a reference steering reaction force based on a driver's steering operation amount or an actual turning state amount and a detected value of the steering reaction force. The vehicle steering control device according to claim 1, characterized in that:   The steering assist force control means performs steering when the magnitude of the driver's steering operation amount is equal to or less than a reference value for determining whether the vehicle is going straight and the actual amount of turning state is equal to or greater than the reference value for determining whether the vehicle is turning. The vehicle steering control device according to claim 1, wherein the unnecessary steering reaction force is estimated based on a detection value of the reaction force.   The steering assist force control means performs steering when the magnitude of the driver's steering operation amount is equal to or greater than a reference value for vehicle turning determination and the actual amount of turning state is equal to or less than the reference value for vehicle straight determination. The vehicle steering control device according to claim 1, wherein the unnecessary steering reaction force is estimated based on a detection value of the reaction force.   The steering assist force control means calculates a target steering assist force based on a detected value of the steering reaction force corrected by the unnecessary steering reaction force, and controls the steering assist force based on the target steering assist force. The vehicle steering control device according to claim 1, wherein the vehicle steering control device is a vehicle steering control device. The steering assist force control means calculates a corrected steering assist force based on the unnecessary steering reaction force, calculates a provisional target steering assist force based on at least a detected value of the steering reaction force, and the provisional target steering assist force. The vehicle steering control device according to any one of claims 1 to 4, wherein the steering assist force is controlled based on a target steering assist force that is corrected by the corrected steering assist force.

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