JP2006131023A - Vehicle cruise controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the stability of a vehicle in yaw direction and roll direction by properly distributing the desired amount of control over turning to steering control and to controlling/driving force control depending on the steering condition of a driver and the driving condition of the vehicle. <P>SOLUTION: The desired yaw moment Mt of the vehicle for stabilizing the behavior of the vehicle is computed (S20, 30). A distribution ratio Rb is variably set according to the driver's steering operation, the weight W of the vehicle, and the friction coefficient μ of the road surface (S40-170). Based on the distribution ratio Rb, the desired yaw moment Mt is distributed to the desired yaw moment Mts achieved by steering angle control and to the desired yaw moment Mtb achieved by the control of braking forces (S180). The steering angles of the right and left front wheels and the desired braking forces of all the wheels are controlled so that the desired yaw moments are attained (S190-210). When the driver steers the vehicle suddenly with a large steering angle, the distribution ratio Rb is computed in such a manner that the longer the time Tf elapsed since the time of the steering gets, the smaller the value that the distribution ratio Rb assumes gets in comparison to its initial value Rbo (S70, 100). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle travel control device, and more particularly to a travel control device that controls the travel of a vehicle by controlling the steering angle of a steered wheel and the braking / driving force of the wheel.

  As one of travel control devices for vehicles such as automobiles, for example, as described in the following Patent Document 1 filed by the applicant of the present application, a wheel that can steer the steered wheels independently of the driver's steering operation can be used. Rudder means, braking / driving force control means for controlling the braking / driving force of each wheel, means for calculating a target turning control amount such as a target yaw moment of the vehicle, and a target turning control amount of the steered wheels at a predetermined ratio. The distribution means for allocating the target turning control amount by the turning angle control and the target turning control amount by the control of the braking / driving force, and the turning means are controlled based on the target turning control amount by the turning angle control of the steered wheels. 2. Description of the Related Art A vehicle travel control device having control means for controlling braking / driving force control means based on a target turning control amount based on driving force control is already known.

  In general, the steering of the steered wheels by the steering means can control the traveling motion of the vehicle without acceleration / deceleration of the vehicle. Responsiveness is low and it is difficult to cope with the understeer condition of the vehicle. On the other hand, according to the control of the braking / driving force of the wheels, the traveling motion of the vehicle can be controlled more responsively than in the case of the traveling motion control by turning the steered wheels. Accompanying deceleration is inevitable.

According to the above-described travel control device according to the above proposal, the target turning control amount is set to the target by the steering angle control of the steered wheels at a predetermined ratio based on the responsiveness and characteristics of the steering means and the braking / driving force control means. Since it is distributed to the turning control amount and the target turning control amount based on the braking / driving force control, compared to the case where the traveling motion of the vehicle is controlled only by the turning angle control of the steering wheel or the braking / driving force control, The running motion of the vehicle can be controlled preferably and effectively.
JP 2003-175749 A

  However, in the above-described travel control device, the predetermined ratio is determined by the response and characteristics of the turning means and the braking / driving force control means for achieving the target turning control amount in order to stabilize the movement of the vehicle in the yaw direction. Since the driver's steering operation and vehicle driving conditions that affect the movement of the vehicle in the roll direction are not taken into account, depending on the driver's steering operation and vehicle driving conditions, the vehicle roll vibration can be effectively In some cases, the stability of the vehicle in the roll direction cannot be prevented.

  For example, when steering with a large steering operation amount and a change rate thereof such as emergency avoidance steering is performed, the vehicle rolls greatly. For this reason, particularly in a vehicle having a high center of gravity such as SUV, bottoming of the suspension of the turning outer wheel occurs, and the reaction force causes roll vibration of the vehicle, which may make the vehicle unstable.

  Therefore, the target turning control amount is controlled by controlling the braking / driving force by distributing the target turning control amount to the target turning control amount by controlling the steering angle of the steered wheel and the target turning control amount by controlling the braking / driving force at a predetermined ratio. When the amount becomes a relatively high value, the braking force of the front wheels on the outside of the turn is particularly high, and not only a high antispin moment is applied to the vehicle but also a pitch moment and a roll moment are applied. In some cases, the roll of the vehicle is promoted by the control, and the roll behavior of the vehicle is deteriorated.

  The present invention relates to a conventional travel control device including a turning means capable of turning a steered wheel independently of a driver's steering operation and a braking / driving force control means for controlling the braking / driving force of each wheel. The present invention has been made in view of the above-described problems, and the main problem of the present invention is that the target turning control amount is divided into a target turning control amount based on steering wheel turning angle control and a target turning control amount based on braking / driving force control. Steering means according to the situation of the steering operation of the driver and the driving situation of the vehicle by taking into account the situation of the steering operation of the driver and the driving situation of the vehicle which influence the movement in the roll direction of the vehicle when allocating The target turning control amount is appropriately distributed to the braking / driving force control means, thereby improving the stability of the vehicle in the yaw direction and effectively preventing excessive rolling of the vehicle to stabilize the rolling direction of the vehicle. Is to improve the performance.

  According to the present invention, the main problem described above is the configuration of claim 1, that is, the steering means that can steer the steered wheels independently of the driver's steering operation, and the braking / driving force of each wheel is controlled. A braking / driving force control means, a means for calculating a target turning control amount of the vehicle, and a target turning control amount by controlling the turning angle of the steered wheel and a target by controlling the braking / driving force at a predetermined ratio of the target turning control amount. The steering means is controlled based on the target turning control amount based on the braking / driving force control, and the braking / driving is controlled based on the target turning control amount based on the braking / driving force control. In the vehicle travel control device having a control means for controlling the force control means, the distribution means is a steering operation detection means for detecting the steering operation of the driver, and the magnitude or change of the steering operation amount of the driver. When the rate is large, the amount of steering operation by the driver is large. Alternatively, the predetermined ratio can be varied in accordance with the magnitude of the driver's steering operation amount or the rate of change so that the distribution to the target turning control amount by controlling the braking / driving force is smaller than when the rate of change is small. It is achieved by a vehicle travel control device characterized by having a ratio variable means for setting.

  According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 1, the ratio variable means has a magnitude of the steering operation amount or a rate of change of the steering operation amount equal to or higher than a reference value. The predetermined ratio is set so that the distribution with respect to the target turning control amount by the control of the braking / driving force is reduced with a time delay from the time when the steering operation of a certain driver is detected. Constitution).

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1 or 2, the steering operation detecting means detects a driver's rapid turn-back steering operation, The ratio variable means is configured to variably set the predetermined ratio so that a distribution with respect to a target turning control amount by control of braking / driving force becomes small when a driver's sudden turn-back steering operation is detected. Configuration of Item 3).

  According to the present invention, in order to effectively achieve the above-mentioned main problems, in the configuration of the above-described claims 1 to 3, the steering operation detecting means is used when a steady running state of the vehicle is detected. Further, the predetermined ratio is configured to return to a standard value (configuration of claim 4).

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claims 1 to 4, the travel control device further includes means for detecting the weight of the vehicle, The variable ratio means variably sets the predetermined ratio according to the weight of the vehicle so that the distribution to the target turning control amount by controlling the braking / driving force is smaller when the weight of the vehicle is large than when the weight of the vehicle is small. (Structure of claim 5).

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claims 1 to 5, the travel control device further includes means for detecting a friction coefficient of the road surface, When the road surface friction coefficient is high, the ratio variable means reduces the distribution to the target turning control amount by controlling the braking / driving force compared to when the road surface friction coefficient is low, according to the road surface friction coefficient. The ratio is variably set (structure of claim 6).

  According to the first aspect of the present invention, when the magnitude of the steering operation amount of the driver or the rate of change thereof is large, the braking / driving force is smaller than when the magnitude of the steering operation amount of the driver or the rate of change thereof is small. The predetermined ratio is variably set according to the magnitude of the steering operation amount of the driver or the rate of change thereof so that the distribution to the target turning control amount by the control becomes small. In situations where the rate of change is large and the roll of the vehicle is large, the pitch moment and roll moment applied to the vehicle can be reduced by relatively reducing the distribution to the target turning control amount by controlling the braking / driving force. As a result, the roll control of the vehicle is promoted by the control of the traveling control device, and the risk of deterioration of the roll behavior of the vehicle is surely reduced, and the stability of the roll direction of the vehicle is improved. The anti-spin moment applied to the vehicle can be prevented from decreasing by relatively increasing the target turning control amount by the steering angle control of the steered wheel, thereby preventing the vehicle from rotating in the yaw direction. Stability can be improved effectively.

  Further, according to the configuration of the second aspect, the control is performed by controlling the braking / driving force with a time delay from the time when the steering operation of the driver whose magnitude of the steering operation amount or the rate of change of the steering operation is equal to or greater than the reference value is detected. Since the predetermined ratio is set so that the distribution with respect to the target turning control amount becomes small, the braking / driving force is not detected from the time when the steering operation of the driver whose magnitude of the steering operation amount or the rate of change thereof is equal to or higher than the reference value is detected. Respecting the driver's steering intention when a steering operation is performed in which the magnitude of the steering operation amount or the rate of change thereof is equal to or greater than the reference value, compared to the case where the distribution to the target turning control amount by the control is reduced The turning motion of the vehicle can be ensured, and the possibility that the roll behavior of the vehicle is promoted and the roll behavior of the vehicle is deteriorated can be reliably reduced, and the stability in the roll direction of the vehicle can be improved.

  According to the third aspect of the present invention, the predetermined ratio is variably set so that the distribution with respect to the target turning control amount by the control of the braking / driving force becomes small when the driver's rapid turn-back steering operation is detected. Therefore, as compared with the case of the configuration of claim 1, the distribution with respect to the target turning control amount by the control of the braking / driving force is reduced in a situation other than the sudden turn-back steering operation such as the sudden steering for avoiding the danger. This makes it possible to cause the vehicle to perform a sharp running motion as in the sports running mode.

  According to the fourth aspect of the present invention, when the steady running state of the vehicle is detected, the predetermined ratio is returned to the standard value, so that the behavior of the vehicle in the yaw direction and the roll direction may be deteriorated. Therefore, it is possible to reliably prevent the distribution to the target turning control amount by the control of the braking / driving force from being unnecessarily reduced in a situation where the braking / driving force is low.

  According to the fifth aspect of the present invention, when the weight of the vehicle is large, the distribution with respect to the target turning control amount by controlling the braking / driving force is smaller than when the weight of the vehicle is small, according to the weight of the vehicle. Since the predetermined ratio is variably set, the distribution ratio can be appropriately variably set according to the weight of the vehicle. When the weight of the vehicle is large and there is a high possibility that the behavior of the vehicle in the roll direction will be deteriorated, it is surely controlled. The distribution with respect to the target turning control amount by controlling the driving force can be reduced.

  Further, according to the configuration of the sixth aspect, when the road surface friction coefficient is high, the road surface friction coefficient is reduced so that the distribution to the target turning control amount by controlling the braking / driving force is smaller than when the road surface friction coefficient is low. Since the predetermined ratio is variably set in accordance with the road surface, the distribution ratio can be appropriately variably set in accordance with the road surface friction coefficient, and the road surface friction coefficient is high, which may deteriorate the behavior of the vehicle in the roll direction. When it is high, the distribution to the target turning control amount by controlling the braking / driving force can be surely reduced.

[Preferred embodiment of problem solving means]
According to one preferable aspect of the present invention, in the configuration of the first to sixth aspects, the steering means steers the steering wheel relative to the steering operator operated by the driver. The steering wheel is configured to be steered and driven independently of the driver's steering operation (preferred aspect 1).

  According to another preferred embodiment of the present invention, in the configuration of the above-mentioned claims 1 to 6 or the preferred embodiment 1, the braking / driving force control means includes means for independently controlling the braking force of each wheel. In addition, the braking / driving force of each wheel is controlled by controlling the braking force of each wheel (preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration of the first to sixth aspects or the preferred aspect 1 or 2, the means for calculating the target turning control amount of the vehicle causes the vehicle to travel stably. The target turning control amount is calculated as a control amount for this purpose (preferred aspect 3).

  According to another preferred embodiment of the present invention, in the configuration of the above-described claims 1 to 6 or the preferred embodiments 1 to 3, the ratio variable means is configured so that the magnitude of the steering operation amount of the driver and the rate of change thereof are the same. When the driver's steering operation amount is large, the driver's steering operation amount and its size are reduced so that the distribution to the target turning control amount by controlling the braking / driving force is smaller than when the driver's steering operation amount and the rate of change are small. The predetermined ratio is variably set according to the change rate (preferred aspect 4).

  According to another preferred aspect of the present invention, in the configuration of claim 2, the distribution means distributes the target turning control amount by controlling the braking / driving force when the first time has elapsed from the time point. The predetermined ratio is set so as to gradually decrease, and when the second time has elapsed from the time point, the predetermined ratio is set to a constant value (preferred aspect 5).

  According to another preferred embodiment of the present invention, in the preferred embodiments 3 to 5, the vehicle target turning control amount is configured to be a vehicle target yaw moment (preferred embodiment 6).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 6 described above, when the distribution means is the target yaw moment for reducing the drift-out state of the vehicle, The target yaw moment is allotted to the target yaw moment by controlling the braking / driving force (preferred aspect 7).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 6 or 7 described above, when the distribution means is the target yaw moment for reducing the spin state of the vehicle, the distribution means is the target yaw moment. When the magnitude or rate of change of the steering operation of the driver is large, the allocation to the target turning control amount by controlling the braking / driving force is larger than when the magnitude of the steering operation of the driver or the rate of change is small. The predetermined ratio is variably set in accordance with the magnitude of the steering operation amount of the driver or the rate of change thereof (preferable aspect 8) so as to decrease.

  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 configuration diagram showing one embodiment of a vehicle behavior control device according to the present invention applied to a vehicle equipped with a turning angle varying device that functions as an automatic turning device.

  In FIG. 1, 10FL and 10FR respectively indicate left and right front wheels as steering wheels of the vehicle 12, and 10RL and 10RR respectively indicate left and right rear wheels. The left and right front wheels 10FL and 10FR, which are steering wheels, are rotated via a rack bar 18 and tie rods 20L and 20R by a rack-and-pinion type power steering device 16 driven in response to an operation of the steering wheel 14 by a driver. Steered.

  The steering wheel 14 is connected to a pinion shaft 30 of the power steering device 16 via an upper steering shaft 22 as a first steering shaft, a turning angle varying device 24, a lower steering shaft 26 as a second steering shaft, and a universal joint 28. Drive connected. In the illustrated embodiment, the turning angle varying device 24 is connected to the lower end of the upper steering shaft 22 on the housing 24A side, and is connected to the upper end of the lower steering shaft 26 on the rotor 24B side. An electric motor 32 for turning driving is included.

  Thus, the steering angle varying device 24 drives the lower steering shaft 26 to rotate relative to the upper steering shaft 22, so that the ratio of the steering angles of the left and right front wheels 10 FL and 10 FR, which are the steering wheels, with respect to the rotation angle of the steering wheel 14. In other words, it functions as a steering gear ratio variable device that changes the steering gear ratio, and also functions as an automatic steering device that drives the left and right front wheels 10FL and 10FR relative to the steering wheel 14 for the purpose of behavior control. Then, it is controlled by the steering control unit of the electronic control unit 34.

  In particular, the turning angle variable device 24 rotates the lower steering shaft 26 relative to the upper steering shaft 22 by the electric motor 32 so that the steering gear ratio becomes a gear ratio that achieves a predetermined steering characteristic in a normal state. At the time of auxiliary steering driving, the lower steering shaft 26 is actively rotated relative to the upper steering shaft 22 by the electric motor 32, whereby the left and right front wheels 10FL and 10FR are automatically steered as necessary.

  If an abnormality in which the lower steering shaft 26 cannot be driven to rotate relative to the upper steering shaft 22 occurs in the turning angle varying device 24, a lock device not shown in FIG. The relative rotation of the housing 24A and the rotor 24B is mechanically prevented so that the relative rotation angle of the lower steering shaft 26 with respect to 22 does not change.

  The power steering device 16 may be either a hydraulic power steering device or an electric power steering device. However, the power steering device 16 is generated by the auxiliary steering driving of the front wheels by the steering angle varying device 24 and transmitted to the steering wheel 14. A rack coaxial type electric motor having, for example, an electric motor and a conversion mechanism such as a ball screw type that converts the rotational torque of the electric motor into a reciprocating force of the rack bar 18 so that an auxiliary steering torque for reducing the force torque is generated. A power steering apparatus is preferable.

  The braking force of each wheel is controlled by controlling the pressure Pi (i = fl, fr, rl, rr) in the wheel cylinders 40FL, 40FR, 40RL, 40RR, that is, the braking pressure, by the hydraulic circuit 38 of the braking device 36. It has become so. Although not shown in the drawing, the hydraulic circuit 38 includes an oil reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven in response to the depression operation of the brake pedal 42 by the driver. It is controlled by the master cylinder 44 and individually controlled by the electronic control unit 34 as will be described in detail later if necessary.

  In the illustrated embodiment, the upper steering shaft 22 is provided with a steering angle sensor 50 for detecting the rotation angle of the upper steering shaft as a steering angle θ. The steering angle variable device 24 includes a housing 24A and A rotation angle sensor 52 that detects the relative rotation angle of the rotor 24B as the relative rotation angle θre of the lower steering shaft 26 with respect to the upper steering shaft 22 is provided, and the output of these sensors is supplied to the electronic control unit 34. The steering angle sensor 52 may be replaced with a sensor that detects the rotation angle θs of the lower steering shaft 28B, and the relative rotation angle θre may be obtained as a steering angle difference θs−θ.

  The electronic control unit 34 also indicates a signal indicating the vehicle lateral acceleration Gy detected by the lateral acceleration sensor 54, a signal indicating the vehicle yaw rate γ detected by the yaw rate sensor 56, and the vehicle speed V detected by the vehicle speed sensor 58. A signal indicating a vehicle roll rate Rr detected by the roll rate sensor 60 is inputted, and a signal indicating the master cylinder pressure Pm detected by the pressure sensor 62 and braking of each wheel detected by the pressure sensors 64FL to 64RR. A signal indicating the pressure Pi is input.

  Although not shown in detail in FIG. 1, the electronic control unit 34 is a steering control unit that controls the steering angle varying device 24, a braking force control unit that controls the braking force of each wheel, and the behavior of the vehicle. Each control unit includes a CPU, a ROM, a RAM, and an input / output port device, which include a microcomputer connected to each other via a bidirectional common bus. Good. Further, the steering angle sensor 50, the rotation angle sensor 52, the lateral acceleration sensor 54, and the yaw rate sensor 56 are respectively set to the steering angle θ, the relative rotation angle θre, and the lateral acceleration when the vehicle is steered, steered, or turned in the left turn direction. Gy and yaw rate γ are detected.

  The electronic control unit 34 indicates a spin state amount SS indicating the degree of vehicle spin (oversteer state) based on a driving operation amount such as a steering angle θ and a vehicle state amount such as a lateral acceleration Gy of the vehicle that change as the vehicle travels. And a vehicle target yaw moment Mt for calculating a drift-out state quantity DS indicating the degree of drift-out (understeer state) of the vehicle and stabilizing the behavior of the vehicle based on the spin-state quantity SS and the drift-out state quantity DS. Calculate the target deceleration Gxbt of the vehicle.

  The electronic control unit 34 uses the distribution ratio of the target yaw moment Mt to the target yaw moment Mtb by controlling the braking force of each wheel as Rb (a positive value between 0 and 1), and sets the target yaw moment Mt to (1-Rb). ): The target yaw moment Mts by the steering angle control of the left and right front wheels and the target yaw moment Mtb by the control of the braking force of each wheel are distributed at the ratio of Rb, and the target turning angle Δδt of the left and right front wheels is based on the target yaw moment Mts. And the turning angle varying device 24 is controlled so that the left and right front wheels 10FL and 10FR are turned by the target turning angle Δδt.

  In particular, as is well known in the art, when the vehicle is in a spin state, the electronic control unit 34 decelerates the vehicle and applies a yaw moment in a turning suppression direction to the vehicle and a vehicle target yaw moment Mt and vehicle. Therefore, the turning direction of the target turning angle Δδt in this case is the direction opposite to the turning direction, that is, the switchback direction, and in the process where the behavior of the vehicle is stabilized by the behavior control. In this case, the left and right front wheels are steered relatively in the turning direction, that is, in the direction of additional turning.

  In addition, as is well known in the art, the electronic control unit 34 decelerates the vehicle and applies the yaw moment in the turning assist direction to the vehicle and applies the vehicle target yaw moment Mt and The target deceleration Gxbt of the vehicle is calculated. In this case, the lateral force of the front wheels is saturated and the lateral force cannot be increased by turning the front wheel and turning it. The target yaw moment Mtb is controlled by controlling the braking force of each wheel, and the target turning angle Δδt is calculated as zero.

  Further, the electronic control unit 34 calculates the target braking pressure Pti of each wheel based on the target deceleration Gxbt and the target yaw moment Mtb, and sets the hydraulic circuit 38 so that the braking pressure Pi of each wheel becomes the corresponding target braking pressure Pti. And the braking force of each wheel is controlled so that the target deceleration Gxbt and the target yaw moment Mtb are achieved.

Although not shown in the flowchart, the electronic control unit 34 resonates the vehicle in a manner known in the art every predetermined time based on the vehicle roll rate Rr detected by the roll rate sensor 60. The frequency fv is calculated, and the weight W of the vehicle is calculated according to the following equation 1 using Ka as a positive coefficient.
W = Ka ・ fv …… (1)

The electronic control unit 34 is not shown in the flowchart, but the vehicle lateral direction detected by the lateral acceleration sensor 54 when the absolute value of the target yaw moment Mt becomes equal to or greater than the reference value Mto (positive constant). Based on the acceleration Gy, the friction coefficient μ of the road surface is calculated according to the following equation 2 with Kb being a positive coefficient.
μ = Kb · | Gy | (2)

  Further, as will be described in detail with reference to the flowchart shown in FIG. 2, the electronic control unit 34 is operated when the driver suddenly steers a large steering angle in a situation where the vehicle is not in an understeer state. The distribution ratio Rb is calculated to be gradually smaller than the standard value Rbn as the elapsed time Tf from the time when it is determined that the large steering angle is suddenly steered, and thereby the target by the steering angle control of the left and right front wheels is calculated. The distribution of the target yaw moment Mt with respect to the yaw moment Mts is gradually increased, and the distribution of the target yaw moment Mt with respect to the target yaw moment Mtb by controlling the braking force of each wheel is gradually decreased. In this case, the distribution ratio Rb is variably set according to the weight W of the vehicle and the friction coefficient μ of the road surface so as to decrease as the vehicle weight W increases and the road friction coefficient μ increases.

  Next, with reference to the flowchart shown in FIG. 2, the vehicle travel control by the control of the steering angle of the left and right front wheels and the control of the braking force in the illustrated embodiment will be described. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch not shown in the figure, and is repeatedly executed at predetermined time intervals.

  First, in step 10, a signal indicating the steering angle θ is read, and in step 20, the degree of vehicle spin is used as an index value for determining vehicle behavior in a manner known in the art. And a drift-out state quantity DS indicating the degree of vehicle drift-out are calculated. In step 30, the vehicle behavior is stabilized based on the spin-state quantity SS and the drift-out state quantity DS. The target yaw moment Mt of the vehicle and the target deceleration Gxbt of the vehicle are calculated in a manner known in the art.

  In step 40, for example, based on the deviation Δγ between the target yaw rate γt of the vehicle calculated based on the steering angle θ and the vehicle speed V and the actual yaw rate γ of the vehicle detected by the yaw rate sensor 56, the vehicle enters a drift-out state. If a negative determination is made, the process proceeds to step 60. If an affirmative determination is made, the distribution ratio Rb is set to 1 in step 50, and then the process proceeds to step 180.

  In step 60, it is determined whether or not the flag Fs is 1, that is, whether or not the control of the distribution ratio Rb corresponding to the sudden steering of the large steering angle being performed by the driver is being executed. If a determination is made and an affirmative determination is made, the process proceeds to step 110. If a negative determination is made, the process proceeds to step 70.

  In step 70, for example, the absolute value of the steering angle θ is greater than or equal to the reference value θc (positive constant), and the absolute value of the change rate dθ / dt of the steering angle θ is the reference value (dθ / dt) c (positive Constant) or not, it is determined whether or not the driver has suddenly steered a large steering angle. If a negative determination is made, the distribution ratio Rb is initially set in step 80. After setting the value Rbo (a positive constant larger than 0 and smaller than 1 and may be a standard value of the distribution ratio Rb), the routine proceeds to step 180. When an affirmative determination is made, the routine proceeds to step 90.

  In step 90, the flag Fs is set to 1, and in step 100, the map shown in FIG. 3 is selected according to the road friction coefficient μ and the vehicle weight W, and the flag Fs is set to 0. The distribution ratio Rb is calculated from the selected map on the basis of the elapsed time Tf from the time when the value is changed to 1, and then the process proceeds to step 180.

  In step 110, for example, by determining whether or not the absolute value of the target yaw moment Mt of the vehicle has become equal to or less than a reference value Mte (positive constant) for the end of control, the left and right front wheels are steered based on the target yaw moment Mt of the vehicle. It is determined whether or not the corner control and braking force control end conditions are satisfied. If an affirmative determination is made, the distribution ratio Rb is set to the initial value Rbo in step 120, and then step 170 is performed. When a negative determination is made, the process proceeds to step 130.

  In step 130, it is determined whether or not the elapsed time Tf from the time when the flag Fs changes from 0 to 1 is longer than the reference value Tfe (positive constant), that is, when the flag Fs changes from 0 to 1. It is determined whether or not a time equal to or more than Tfe has elapsed. If an affirmative determination is made, the process proceeds to step 150. If a negative determination is made, the process proceeds to step 140.

  In step 140, for example, the absolute value of the rate of change θd of the steering angle θ is equal to or less than the reference value θds (positive constant), and the absolute value of the rate of change dGy / dt of the lateral acceleration Gy of the vehicle is the reference value (dGy / It is determined whether or not a steady state equal to or less than dt) s (positive constant) continues for Ts time or longer. If a negative determination is made, the process proceeds to step 100. If an affirmative determination is made, step 150 is performed. Proceed to

  From the map corresponding to the graph shown in FIG. 4 based on the elapsed time Te from the time when the positive determination is first made in step 130 or 140 after the flag Fs is set to 1 in step 150. The increase amount ΔRb of the distribution ratio Rb is calculated, and the current distribution ratio Rbn is set to Rb (n−1) + ΔRb, with the previous distribution ratio being Rb (n−1).

  In step 160, it is determined whether or not the distribution ratio Rb is the initial value Rbo. If a negative determination is made, the process proceeds to step 180. If an affirmative determination is made, the flag Fs is determined in step 170. After is reset to 0, the routine proceeds to step 180.

In step 180, based on the target yaw moment Mt and the distribution ratio Rb, the target yaw moment Mts by controlling the steering angle of the left and right front wheels and the target yaw moment Mtb by controlling the braking force of each wheel are calculated according to the following equations 3 and 4. The
Mts = (1-Rb) Mt (3)
Mtb = Rb ・ Mt (4)

  In step 190, a target turning angle Δδts for steering angle control of the left and right front wheels to achieve the target yaw moment Mts is calculated in a manner known in the art, and in step 200, the left and right front wheels are calculated. The steered angle varying device 24 is controlled so that the steered angle becomes the target steered angle Δδts.

  In step 210, the target braking force of each wheel for achieving the target yaw moment Mtb and the vehicle target deceleration Gxbt is calculated in a manner known in the art, and each wheel is calculated based on the target braking force. Target braking pressure Pti (i = fl, fr, rl, rr) is calculated, and the braking device 36 is controlled so that the braking pressure Pi of each wheel becomes the corresponding target braking pressure Pti.

  Thus, according to the illustrated embodiment 1, the spin state quantity SS indicating the degree of vehicle spin and the drift-out state quantity DS indicating the degree of vehicle drift-out are calculated in step 20, and the spin state quantity DS is calculated in step 30. Based on the state quantity SS and the drift-out state quantity DS, a vehicle target yaw moment Mt and a vehicle target deceleration Gxbt for stabilizing the vehicle behavior are calculated.

  In steps 40 to 170, the distribution ratio Rb is variably set to a value between 0 and 1 in accordance with the driver's steering operation, the vehicle weight W, and the road friction coefficient μ. In step 180, the distribution ratio Rb is set. The target yaw moment Mt is distributed to the target yaw moment Mts by the steering angle control of the left and right front wheels and the target yaw moment Mtb by the control of the braking force of each wheel. The steering angle of the left and right front wheels and the target braking force of each wheel are controlled so that the target yaw moment Mtb by controlling the braking force of the wheels is achieved, thereby ensuring the stability of the vehicle in the yaw direction.

  In particular, in a situation where the vehicle is not in an understeer state, when the driver steers a large steering angle, an affirmative determination is made in step 70 and a flag Fs is set to 0 to 1 in step 100. As the elapsed time Tf from the point of time of change to becomes longer, the distribution ratio Rb is calculated to a value that is gradually smaller than the initial value Rbo, thereby distributing the target yaw moment Mt to the target yaw moment Mts by the steering angle control of the left and right front wheels. While gradually increasing, the distribution of the target yaw moment Mt to the target yaw moment Mtb by controlling the braking force of each wheel is gradually reduced.

  Therefore, in a situation where the driver is steered at a large steering angle and the roll of the vehicle becomes large, the distribution of the target yaw moment Mt is reduced, and the braking force applied to the wheels is reduced, thereby reducing the vehicle. Since the pitch moment and roll moment applied to the vehicle can be reduced, it is possible to effectively reduce the possibility that the roll of the vehicle is promoted and the roll behavior of the vehicle is deteriorated by the control for achieving the target yaw moment Mt. In addition, since the distribution of the target yaw moment Mts by controlling the steering angle of the left and right front wheels can be increased, the required anti-spin moment can be applied to the vehicle, so that the effect of improving the stability in the yaw direction of the vehicle is reduced. This can be surely prevented.

  FIG. 5 shows the steering angle control of the left and right front wheels and the control of the braking force in the second embodiment of the vehicle travel control device according to the present invention applied to a vehicle equipped with a turning angle varying device functioning as an automatic steering device. It is a flowchart which shows the traveling control routine of a vehicle. In FIG. 5, the same steps as those shown in FIG. 2 are assigned the same step numbers as those shown in FIG.

  In the second embodiment, the steps other than steps 70 and 140 are executed in the same manner as in the first embodiment. In step 70, for example, (1) a predetermined time T1 up to the present time ( (2) The absolute value of the change amount Δθ of the steering angle at a predetermined time T2 (positive constant) up to the present time is not less than the reference value Δθc and (3) Risk avoidance by the driver by determining whether or not the absolute value of the change rate dθ / dt of the steering angle at a predetermined time T3 (positive constant) up to the present is equal to or greater than a reference value (dθ / dt) c It is determined whether or not sudden steering is performed. When a negative determination is made, the process proceeds to step 80, and when an affirmative determination is performed, the process proceeds to step 90.

  In step 140, for example, (1) the absolute value of the steering angle θ is equal to or less than a reference value θo (a positive constant close to 0), and (2) the vehicle speed V is a reference value Vo (a positive constant close to 0). It is determined whether or not the sudden steering for avoiding danger has been completed by determining whether or not the following is true. If a negative determination is made, the process proceeds to step 100. If an affirmative determination is made, the process proceeds to step 100. Proceed to 150.

  Thus, according to the second embodiment shown in the figure, the distribution ratio Rb becomes the initial value Rbo as the elapsed time Tf from the time when the flag Fs changes from 0 to 1 when the driver performs sudden steering for avoiding danger is increased. Is gradually reduced to a value smaller than the target yaw moment Mt with respect to the target yaw moment Mts for the steering angle control of the left and right front wheels, and the target yaw for controlling the braking force of each wheel is gradually increased. The distribution of the target yaw moment Mt with respect to the moment Mtb is gradually reduced.

  Accordingly, since the distribution of the target yaw moment Mt to the target yaw moment Mtb is reduced only when the driver performs sudden steering for avoiding danger, the vehicle in the case where sudden steering for avoiding danger is performed by the driver. It is possible to effectively reduce the possibility of deterioration of the roll behavior of the vehicle, reliably prevent the improvement of the stability improvement effect of the yaw direction of the vehicle, and to target in situations other than sudden steering for avoiding danger Since the distribution of the target yaw moment Mt with respect to the yaw moment Mtb is not reduced, the possibility that the distribution of the target yaw moment Mt with respect to the target yaw moment Mtb will be unnecessarily reduced as compared with the case of the first embodiment is surely reduced. As a result, the vehicle can be vividly moved as in the sport driving mode.

  According to the first and second embodiments shown in the drawings, the distribution ratio Rb increases as the elapsed time Tf from the point of time becomes longer than the point at which the large steering angle sudden steering and the dangerous avoidance sudden steering are detected. The value is calculated to be gradually smaller than the initial value Rbo, whereby the distribution of the target yaw moment Mt to the target yaw moment Mts by the steering angle control of the left and right front wheels is gradually increased, and the target yaw moment by the control of the braking force of each wheel is gradually increased. The distribution of the target yaw moment Mt with respect to Mtb is gradually reduced.

  Therefore, compared with the case where the distribution ratio Rb is calculated to be smaller than the initial value Rbo from the point at which the large steering angle sudden steering and the dangerous avoidance sudden steering are detected, the large steering angle rapid steering and the risk avoidance are avoided. It is possible to ensure a turning motion of the vehicle that respects the driver's intention to steer when sudden steering is performed, and then gradually increase the distribution of the target yaw moment Mts by the steering angle control of the left and right front wheels, and By gradually reducing the distribution of the target yaw moment Mtb by controlling the braking force of the vehicle, the roll of the vehicle is promoted and the possibility that the roll behavior of the vehicle is deteriorated is surely reduced and the stability of the roll direction of the vehicle is improved. be able to.

  Further, according to the first and second embodiments shown in the drawings, the distribution ratio Rb is variably set according to the vehicle weight W and the road surface friction coefficient μ so that the vehicle weight W increases and the road surface friction coefficient μ increases. Therefore, the distribution ratio Rb can be reduced as the vehicle weight W is large, the road friction coefficient μ is high, and the roll of the vehicle is likely to be large. Therefore, the distribution ratio Rb is reduced to the vehicle weight W and the road friction coefficient μ. Accordingly, it is possible to reliably reduce the possibility that the roll of the vehicle is promoted and the roll behavior of the vehicle is deteriorated as compared with the case where the setting is not variably set.

  Further, according to the first and second embodiments shown in the figure, when the vehicle is in an understeer state, an affirmative determination is made in step 40, and in step 50, the distribution ratio Rb is set to 1, and all the target yaw moments Mt are set. Is distributed to the target yaw moment Mtb by controlling the braking force of each wheel, so that the vehicle can be driven stably while effectively suppressing the understeer state of the vehicle by controlling the braking / driving force of each wheel. .

  In this case, the target turning angle Δδt for the left and right front wheels is set to 0, and the steering angle control for the left and right front wheels is not executed. Therefore, it is possible to reliably prevent the left and right front wheels from being unnecessarily increased and steered in a situation where the lateral force of the left and right front wheels cannot be increased even if the left and right front wheels are turned and turned.

  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 turning angle varying device 24 as the turning means rotates the lower steering shaft 26 relative to the upper steering shaft 22 so that the left and right front wheels 10FL and 10FR is automatically steered, but as long as the steerable means can steer the steered wheels as needed, for example, a type of steered angle variable device or a steer-by-wire system that expands and contracts the tie rods 20L and 20R. Any configuration known in the art may be used, such as a steering device.

  In each of the above-described embodiments, the map shown in FIG. 3 is selected according to the road surface friction coefficient μ and the vehicle weight W, and the distribution ratio Rb is set based on the elapsed time Tf. Although calculated, one map showing the relationship between the elapsed time Tf and the distribution ratio Rb that gradually decreases as the elapsed time Tf increases is set, and is based on the road friction coefficient μ and the vehicle weight W. Correction coefficients Kaa and Kab (values greater than 0 and less than 1) that are smaller as they are higher are calculated, and the distribution ratio Rb calculated from the map is multiplied by the correction coefficients Kaa and Kab to obtain the distribution ratio Rb. It may be modified so as to be variably set according to the friction coefficient μ of the road surface and the weight W of the vehicle.

  In each of the above-described embodiments, the weight W of the vehicle and the friction coefficient μ of the road surface are calculated according to the above formulas 1 and 2 based on the resonance frequency fv of the vehicle and the lateral acceleration Gy of the vehicle, respectively. However, the weight W of the vehicle and the friction coefficient μ of the road surface may be calculated in any manner known in the art.

  Further, in the above-described second embodiment, in step 70, it is determined whether or not the driver has performed sudden steering for avoiding danger in place of the determination in step 70 of the first embodiment. However, for example, after the completion of step 100, it is determined whether or not the sudden steering at the large steering angle is a sudden steering for avoiding danger, and when an affirmative determination is made, the distribution ratio Rb is corrected to be further reduced. May be.

  In each of the above-described embodiments, the left and right front wheels are steered in order to achieve the target yaw moment Mts for turning angle control, but a predetermined steering characteristic is achieved based on the vehicle speed V. The steering gear ratio Rg is calculated, the temporary target steering angle δst is calculated based on the steering angle θ indicating the amount of steering operation of the driver and the steering gear ratio Rg, and the steering angle of the left and right front wheels is normally set to the temporary target steering angle. In the case of a vehicle controlled to be δst, the rudder angle of the left and right front wheels is controlled to be the sum of the provisional target rudder angle δst and the turning amount to achieve the target yaw moment Mts for turning angle control. May be.

  Further, in each of the above-described embodiments, the braking / driving force of each wheel is controlled by controlling the braking force of each wheel, but each wheel can be controlled like a wheel-in-motor type vehicle. In the case of a vehicle in which the braking / driving force can be controlled independently of each other, the braking / driving force of each wheel may be performed by controlling the braking force and driving force of each wheel.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows one Example 1 of the traveling control apparatus of the vehicle by this invention applied to the vehicle provided with the turning angle variable apparatus which functions as an automatic turning apparatus. 3 is a flowchart illustrating a vehicle travel control routine based on steering angle control and braking force control of left and right front wheels in the first embodiment. 6 is a graph showing a relationship between a road surface friction coefficient μ, a vehicle weight W, an elapsed time Tf from the time when a flag Fs changes from 0 to 1, and a distribution ratio Rb. It is a graph which shows the relationship between elapsed time Te and increase amount (DELTA) Rb of distribution ratio Rb about the various values of the current distribution ratio Rb. 7 is a flowchart showing a vehicle travel control routine based on steering angle control and braking force control of left and right front wheels in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 16 Power steering apparatus 14 Steering wheel 24 Steering angle variable apparatus 34 Electronic controller 36 Braking apparatus 44 Master cylinder 50 Steering angle sensor 52 Rotation angle sensor 54 Lateral acceleration sensor 56 Yaw rate sensor 58 Vehicle speed sensor 60 Roll rate sensor 62, 64FL-64RR Pressure sensor

Claims (6)

  Steering means capable of turning the steered wheels independently of the driver's steering operation; braking / driving force control means for controlling the braking / driving force of each wheel; means for calculating a target turning control amount of the vehicle; Distribution means for allocating the target turning control amount to the target turning control amount by controlling the turning angle of the steered wheel and the target turning control amount by controlling the braking / driving force at a predetermined ratio, and by the turning angle control of the steered wheel In a vehicle travel control device comprising: control means for controlling the turning means based on a target turning control amount; and controlling means for controlling the braking / driving force control means based on a target turning control amount based on control of the braking / driving force. The distribution means is a steering operation detecting means for detecting the steering operation of the driver, and when the magnitude of the steering operation amount of the driver or the change rate thereof is large, the magnitude of the steering operation amount of the driver or the change rate thereof is small. Compared to the control of braking / driving force And a ratio variable means for variably setting the predetermined ratio in accordance with the magnitude of the steering operation amount of the driver or the rate of change thereof so that the distribution with respect to the target turning control amount is reduced. Control device.   The ratio variable means distributes to the target turning control amount by controlling the braking / driving force with a time delay from the time when the steering operation of the driver whose magnitude of the steering operation amount or the rate of change thereof is equal to or greater than a reference value is detected. The vehicle travel control apparatus according to claim 1, wherein the predetermined ratio is set so as to be small.   The steering operation detection means detects a driver's rapid turnback steering operation, and the ratio variable means distributes the target turning control amount by controlling the braking / driving force when the driver's rapid turnback steering operation is detected. The vehicle travel control apparatus according to claim 1, wherein the predetermined ratio is variably set so that the value becomes smaller.   4. The vehicle travel control device according to claim 1, wherein the steering operation detecting means returns the predetermined ratio to a standard value when a steady travel state of the vehicle is detected.   The travel control device further includes means for detecting the weight of the vehicle, and the ratio variable means distributes the target turning control amount by controlling the braking / driving force when the weight of the vehicle is large compared to when the weight of the vehicle is small. The vehicle travel control device according to any one of claims 1 to 4, wherein the predetermined ratio is variably set in accordance with a weight of the vehicle so as to be reduced. The travel control device further includes means for detecting a friction coefficient of the road surface, and the ratio variable means controls the target turning by controlling the braking / driving force when the friction coefficient of the road surface is high compared with when the friction coefficient of the road surface is low. 6. The vehicle travel control device according to claim 1, wherein the predetermined ratio is variably set according to a friction coefficient of a road surface so that a distribution with respect to the amount becomes small.

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