JP6107082B2 - Vehicle stability factor calculation device - Google Patents

Description

  The present invention relates to a vehicle stability factor calculation device.

  As behavior control for a turning vehicle, a deviation obtained by subtracting a sensor value (hereinafter, also referred to as a “yaw rate sensor value”) detected by a yaw rate sensor from a reference yaw rate calculated using a vehicle stability factor or the like is “ One that controls vehicle behavior so as to approach "0 (zero)" is known.

  The stability factor is a value that serves as an index indicating the magnitude of a change due to the speed of a vehicle that performs a steady circular turn, and may change with changes in the vehicle weight or the weight distribution in the vehicle. Therefore, in order to optimize the start timing of the behavior control as described above and the control amount during the control, it is preferable to update the stability factor while the vehicle is running.

  Patent Document 1 discloses a method for estimating and calculating a stability factor during traveling of a vehicle. In this method, it is determined whether or not the current running state of the turning vehicle is a stable turning state. When it is determined that the current traveling state is a stable turning state, it can be estimated that the vehicle is unlikely to skid, and the vehicle speed, steering angle, and yaw rate sensor value at that time are considered to be The feasibility factor is calculated.

JP 2005-104346 A

  Here, when the vehicle is not skidding, the deviation changes in proportion to the change in the lateral acceleration of the vehicle, so that the stability factor can be calculated with high accuracy. On the other hand, when the vehicle is skidding, even if the stability factor estimation calculation is performed, the calculation accuracy is low. Therefore, in order to increase the calculation accuracy of the stability factor, it is necessary to accurately determine whether or not the vehicle is skidding. However, when it is unknown whether the stability factor at that time is an appropriate value, it is difficult to accurately determine whether the vehicle is skidding.

  Incidentally, in the method described in Patent Document 1, the vehicle is skidding when the yaw rate sensor value, the longitudinal acceleration, the lateral acceleration, the steering angle and the steering angular velocity of the steering are within preset ranges. It is estimated that the possibility is low, and the stability factor is calculated. However, in this method, even if it is estimated that the possibility that the vehicle is skidding is low, the vehicle may actually be skidding. In this case, the stability factor may be calculated based on various parameters detected during the skid of the vehicle, and there is a concern that the calculation accuracy may be reduced.

  It is an object of the present invention to provide a vehicle stability factor calculation device capable of improving the calculation accuracy of a vehicle stability factor.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
The vehicle stability factor calculation device that solves the above-described problem is a variation in the stability factor calculation values (Kh_cal, ΔDYr) that can be obtained in a situation where the lateral acceleration (Gy) of the vehicle changes (S102, S202: YES). And a vehicle stability factor (Kh) according to at least one value of a plurality of stability factor calculation values (Kh_cal, ΔDYr) evaluated as having small variations. And a determination unit (30, S111, S211) for determination.

  When the vehicle is skidding, assuming that the stability factor calculation values (Kh_cal, ΔDYr) are calculated under a situation where the lateral acceleration (Gy) of the vehicle changes, a plurality of calculated stability factor calculation values are calculated. (Kh_cal, ΔDYr) varies greatly. On the other hand, when the vehicle is not skidding, assuming that the stability factor calculation values (Kh_cal, ΔDYr) are calculated under a situation where the lateral acceleration (Gy) of the vehicle changes, a plurality of calculated stadiums are calculated. Variations in the performance factor calculation values (Kh_cal, ΔDYr) are reduced. Therefore, in the above configuration, the vehicle stability factor (Kh) is determined according to at least one value of the plurality of stability factor calculation values (Kh_cal) evaluated as having small variations. Thereby, the possibility that the stability factor (Kh) of the vehicle is determined by using various parameters acquired during the skidding of the vehicle is reduced. Therefore, the calculation accuracy of the vehicle stability factor (Kh) can be improved.

  Further, the stability factor calculation device described above is a stability calculation unit (30, 30) that calculates a stability factor calculation value (Kh_cal) every time a change in the lateral acceleration (Gy) of the vehicle is detected (S102: YES). S103) and a creation unit (30, S104) for creating a frequency distribution indicating the relationship between the calculated stability factor calculation value (Kh_cal) and the frequency (F) may be further provided. In this case, the evaluation unit (30, S109), when the number of calculations (Cnt) by the stability calculation unit (30, S103) exceeds the prescribed number (CntTh) (S106: YES), the creation unit (30 , It is preferable to evaluate the variation of each stability factor calculation value (Kh_cal) by a division value (P_hist) obtained by dividing the maximum frequency (Fmax) in the frequency distribution created by S104) by the specified number of times (CntTh).

  When a plurality of stability factor calculation values (Kh_cal) are calculated during a skid of the vehicle, the above-described division value (P_hist) becomes a small value because the stability factor calculation values (Kh_cal) vary greatly. On the other hand, when a plurality of stability factor calculation values (Kh_cal) are calculated when the vehicle is not skidding, the above-described division value (P_hist) is large because variations in the respective stability factor calculation values (Kh_cal) are small. Value. Therefore, in the above configuration, when the number of times (Cnt) of the stability factor calculation value (Kh_cal) exceeds the specified number (CntTh), each stability factor calculation value (P_hist) depends on the magnitude of the division value (P_hist). The variation of (Kh_cal) was evaluated. Thereby, the variation of each stability factor calculation value (Kh_cal) is appropriately evaluated, and the vehicle stability factor (Kh) may be set according to a plurality of stability factor calculation values (Kh_cal) having large variations. Becomes lower. That is, the possibility that the vehicle stability factor (Kh) is determined according to the stability factor calculation value (Kh_cal) calculated during the side skid of the vehicle is low, and the calculation accuracy of the vehicle stability factor (Kh) is reduced. Can be improved.

  When a frequency distribution is created based on a plurality of calculated stability factor calculation values (Kh_cal), it can be estimated that the value at which the frequency is maximum is closest to the actual stability factor of the vehicle at that time. Therefore, the determination unit (30, S111), when the evaluation unit (30, S109) evaluates that the variation of each stability factor calculation value (Kh_cal) is small (S109: YES), the creation unit (30, S111) A stability factor calculation value (Kh_cal1) corresponding to the maximum frequency (Fmax) is extracted from the frequency distribution created in S104) (S110), and the vehicle stability factor (Kh_cal1) is determined according to the stability factor calculation value (Kh_cal1). It is preferred to determine Kh). Thereby, the calculation accuracy of the stability factor (Kh) can be improved.

  When the stability factor calculation values (Kh_cal) vary greatly, such as when there are many stability factor calculation values (Kh_cal) calculated based on various parameters acquired during the skid of the vehicle, each of these stability factors The vehicle stability factor (Kh) is not updated according to the factor calculation value (Kh_cal). Thereby, the fall of the calculation precision of the stability factor (Kh) of a vehicle can be suppressed now.

  Further, when the vehicle is not skidding, there is a first-order proportional relationship between the change amount of the lateral acceleration (Gy) of the vehicle and the change amount of the deviation (DYr). On the other hand, when the vehicle is skidding, there is no primary proportional relationship between the amount of change in the lateral acceleration (Gy) of the vehicle and the amount of change in the deviation (DYr). Therefore, when the variation of the change gradient of the deviation with respect to the change in the lateral acceleration (Gy) is small, it can be estimated that the vehicle is not skidding.

  Therefore, the above-described stability factor calculation device calculates the reference yaw rate calculated using the stability factor (Kh) at each time when a change in the lateral acceleration (Gy) of the vehicle is detected (S202: YES). A deviation calculating unit (30, S204) for calculating a deviation (DYr) obtained by subtracting the yaw rate sensor value (Yr_R) detected by the yaw rate sensor (SE4) from (Yr_Trg) may be further provided. In this case, when the number of calculations (Cnt) by the deviation calculation unit (30, S204) exceeds the specified number (CntTh) (S207: YES), the evaluation unit (30, S209) determines the lateral acceleration (Gy ), It is preferable to evaluate the variation of the stability factor calculation value (Kh_cal) according to the change mode of the deviation change amount (ΔDYr) with respect to the change. As a result, the vehicle stability factor (Kh) is determined according to at least one of the plurality of stability factor calculation values (ΔDYr) evaluated as having small variations. As a result, the calculation accuracy of the vehicle stability factor (Kh) can be improved.

  For example, the evaluation unit (30, S209), when the number of calculations (Cnt) by the deviation calculation unit (30, S204) exceeds a specified number (CntTh) (S207: YES), the deviation calculation unit (30, S204). The deviations (DYr) calculated by the first lateral acceleration area (A1) with a small deviation change amount (ΔDYr) and the second lateral acceleration area (A2) with a large deviation change amount (ΔDYr). ) And may be classified. In this case, the determination unit (30, S111) preferably determines the vehicle stability factor (Kh) according to the deviation (DYr) classified in the first lateral acceleration region (A1). Thereby, when determining the stability factor (Kh) of a vehicle, possibility that the various parameters acquired during the skid of a vehicle will be used becomes low. Therefore, the calculation accuracy of the vehicle stability factor (Kh) can be improved.

The block diagram which shows schematic structure of the braking system of the vehicle in 1st Embodiment. The flowchart explaining the processing routine which a control apparatus performs in order to determine the stability factor of a vehicle in 1st Embodiment. The frequency distribution table which shows the relationship between a stability factor calculation value and frequency in 1st Embodiment. The frequency distribution table which shows the relationship between a stability factor calculation value and frequency in 1st Embodiment. In 2nd Embodiment, the graph which shows the relationship between the horizontal direction acceleration and deviation of a vehicle. The flowchart explaining the processing routine which a control apparatus performs in order to determine the stability factor of a vehicle in 2nd Embodiment. (A) is the graph which shows a mode that the calculated deviation was plotted for every lateral acceleration, (b) is the enlarged view to which a part of FIG. 7 (a) was expanded. The graph which shows an example of the relationship between deviation variation | change_quantity and the horizontal direction acceleration of a vehicle.

(First embodiment)
Hereinafter, a first embodiment of a vehicle braking system will be described with reference to FIGS.
As shown in FIG. 1, the vehicle braking system includes a braking device 20 that applies a braking force to a plurality of (for example, four) wheels 10 and a control device 30 as an example of a stability factor calculation device. It has been. The braking device 20 includes a hydraulic pressure generating device 21 having a booster, a master cylinder and a reservoir, and a brake actuator 22. When the driver operates the brake pedal 23, the hydraulic pressure in the master cylinder of the hydraulic pressure generating device 21 rises, and the amount of brake fluid corresponding to the hydraulic pressure passes through a hydraulic circuit (not shown) of the brake actuator 22. Then, the air flows into the wheel cylinder of the braking mechanism 24 provided for each wheel 10. As a result, the braking mechanism 24 applies a braking force corresponding to the hydraulic pressure in the wheel cylinder to the wheel 10.

  The brake actuator 22 of the present embodiment is configured so that the braking force for each wheel 10 can be individually adjusted even when the driver does not operate the brake pedal 23. For example, the brake actuator 22 includes a differential pressure adjusting valve that generates a differential pressure between the hydraulic pressure in the master cylinder and the hydraulic pressure in the wheel cylinder, and an electric pump for supplying brake fluid into the wheel cylinder. It has. The brake actuator 22 is provided with various valves for individually adjusting the hydraulic pressure in each wheel cylinder.

  The control device 30 includes a brake switch SW1 that detects whether the brake pedal 23 is operated, a wheel speed sensor SE1 that detects the wheel speed VW of the wheel 10, and a steering that detects the steering angle θ of the steering wheel 25. The angle sensor SE2 is electrically connected. Further, the control device 30 is electrically connected to a lateral acceleration sensor SE3 that detects a lateral acceleration Gy of the vehicle and a yaw rate sensor SE4 that detects a yaw rate of the vehicle. Then, the control device 30 operates the brake actuator 22 based on the on / off state of the brake switch SW1 and various parameters detected by the various sensors SE1 to SE4 to stabilize the behavior of the vehicle.

  Such a control device 30 includes a microcomputer constructed with a CPU, a ROM, a RAM, and the like. Various programs and maps executed by the CPU are stored in advance in the ROM, and information (for example, vehicle body speed) that is updated as appropriate is stored in the RAM.

  By the way, in a vehicle having the above braking system, when a side slip such as oversteer or understeer occurs during turning, the brake actuator 22 is controlled to eliminate the side slip. Specifically, the control device 30 calculates a deviation DYr obtained by subtracting the yaw rate sensor value Yr_R detected by the yaw rate sensor SE4 from the standard yaw rate Yr_Trg determined by the driver operating the steering wheel 25 or the like. Then, it is determined whether or not a side slip has occurred in the vehicle based on the magnitude of the deviation DYr. When it is determined that a side slip has occurred, the brake actuator is set so that the deviation DYr approaches “0 (zero)”. 22 is controlled.

  Here, as a calculation method of the above-mentioned standard yaw rate Yr_Trg, there is a method using the following relational expression (formula 1). That is, the standard yaw rate Yr_Trg can be calculated by the vehicle body speed VS, the steering angle θ of the steering wheel 25, the gear ratio N of the vehicle steering device, the wheel base length WB of the vehicle body, and the vehicle stability factor Kh. In order to increase the calculation accuracy of the reference yaw rate Yr_Trg using the relational expression (Expression 1), it is preferable to set the vehicle stability factor Kh to a value according to the vehicle state at that time.

  Next, a processing routine executed by the control device 30 to update the vehicle stability factor Kh while the vehicle is running will be described with reference to the flowchart shown in FIG. 2 and the frequency distribution tables shown in FIGS. 3 and 4. To do.

  The processing routine shown in FIG. 2 is a processing routine that is executed every preset predetermined cycle. In this processing routine, the control device 30 acquires the current lateral acceleration Gy detected based on the signal output from the lateral acceleration sensor SE3, and the previous lateral acceleration Gy_h set in step S113 described later. Is acquired (step S101). Subsequently, the control device 30 determines whether or not the difference (= | Gy−Gy_h |) between the current lateral acceleration Gy and the previous lateral acceleration Gy_h is greater than a preset reference determination value GyTh. (Step S102). This reference determination value GyTh is a value set as a determination reference for determining whether or not the absolute value of the lateral acceleration is large. That is, in step S102, it is determined whether or not the vehicle is in a state where the lateral acceleration changes.

  When the difference (= | Gy−Gy_h |) is equal to or smaller than the reference determination value GyTh (step S102: NO), it is determined that the lateral acceleration of the vehicle has hardly changed, and the control device 30 The processing routine is temporarily terminated. On the other hand, when the above difference is larger than the reference determination value GyTh (step S102: YES), it is determined that the lateral acceleration of the vehicle is changing, and the control device 30 obtains the following relational expression (formula 2). The stability factor calculation value Kh_cal is calculated using this (step S103). In this regard, in this embodiment, the control device 30 also functions as a “stability calculation unit” that calculates the stability factor calculation value Kh_cal each time a change in the lateral acceleration of the vehicle is detected. Note that “Kh_base” in the relational expression (Expression 2) is an initial value of a stability factor preset in the vehicle. In addition, the reference yaw rate calculated using the relational expression (formula 1) is substituted into “Yr_Trg” in the relational expression (formula 2).

  Then, the control device 30 creates a frequency distribution table (frequency distribution) in which the vertical axis is the frequency F and the horizontal axis is the stability factor calculation value Kh_cal (step S104). Therefore, in the present embodiment, the control device 30 also functions as a “creating unit” that creates a frequency distribution indicating the relationship between the calculated stability factor calculated value Kh_cal and the frequency F.

  3 and 4 show an example of a frequency distribution indicating the relationship between the frequency F and the stability factor calculation value Kh_cal. In the frequency distribution table shown in FIG. 3, the variation of the plurality of stability factor calculation values Kh_cal is relatively small, and in the frequency distribution table shown in FIG. 4, the variation of the plurality of stability factor calculation values Kh_cal is relatively large.

  Returning to FIG. 2, after executing step S104, the control device 30 increments the calculation count Cnt as the number of calculations by “1” (step S105). Then, the control device 30 determines whether or not the updated calculation number count Cnt exceeds a preset specified number CntTh (for example, 150) (step S106). The specified number of times CntTh is set in advance as a criterion for determining whether the number of samples of the stability factor calculation value Kh_cal is large or small when creating the frequency distribution table.

  When the calculation count Cnt is equal to or less than the specified count CntTh (step S106: NO), it is determined that the calculation number of the stability factor calculation value Kh_cal is still small, and the control device 30 proceeds to step S113 described later. Transition. On the other hand, when the calculation number count Cnt exceeds the specified number CntTh (step S106: YES), the control device 30 determines the maximum frequency Fmax (FIG. 3 and FIG. 3) among the frequencies F for each stability factor calculation value Kh_cal. 4) is acquired (step S107).

  Subsequently, the control device 30 divides the acquired maximum frequency Fmax by the calculation count Cnt updated in step S105 to obtain a variation index P_hist (= Fmax / Cnt) as an example of a division value (step S108). The variation index P_hist is an index indicating the degree of variation of each stability factor calculation value Kh_cal calculated for creating the frequency distribution table. Therefore, the variation index P_hist becomes a large value when the variation of each stability factor calculation value Kh_cal is small (see FIG. 3), and is small when the variation of each stability factor calculation value Kh_cal is large (see FIG. 4). Value.

  Then, the control device 30 determines whether or not the calculated variation index P_hist is larger than a variation determination value HTh as an example of a preset specified division value (step S109). The variation determination value HTh is a value set in advance as an evaluation criterion as to whether or not the variation of each stability factor calculated value Kh_cal calculated for creating the frequency distribution table is large. Therefore, in the present embodiment, the control device 30 also functions as an “evaluation unit” that evaluates variations in the plurality of stability factor calculation values Kh_cal acquired under the situation where the lateral acceleration of the vehicle changes.

  When the variation index P_hist is less than or equal to the variation determination value HTh (step S109: NO), it is determined that the variation of each stability factor calculation value Kh_cal is large, and the control device 30 does not update the stability factor Kh. The process proceeds to step S112 described later. On the other hand, when the variation index P_hist is larger than the variation determination value HTh (step S109: YES), it is determined that the variation of each stability factor calculation value Kh_cal is small. Then, control device 30 extracts a stability factor calculation value Kh_cal1 corresponding to maximum frequency Fmax from the frequency distribution table (step S110).

  Subsequently, the control device 30 sets the stability factor calculation value Kh_cal1 extracted in step S110 as the stability factor Kh at this time (step S111). Therefore, in the present embodiment, when the variation of the plurality of stability factor calculation values Kh_cal that are the evaluation targets is small, the control device 30 determines the vehicle according to at least one of the respective stability factor calculation values Kh_cal. It also functions as a “determination unit” that determines the stability factor Kh. And the control apparatus 30 transfers the process to following step S112.

  In step S112, the control device 30 performs a reset process for clearing the frequency distribution table while setting the calculation count Cnt to “0 (zero)”. Thereafter, the control device 30 moves the process to the next step S113.

  In step S113, the control device 30 sets the current lateral acceleration Gy acquired in step S101 to the previous lateral acceleration Gy_h. Thereafter, the control device 30 once ends this processing routine.

Next, the operation of the present embodiment will be described with reference to FIG.
Under circumstances where the lateral acceleration Gy changes, such as when the vehicle is turning, a stability factor calculation value Kh_cal is calculated every predetermined cycle. When the calculation count Cnt, which is the number of times the stability factor calculation value Kh_cal is calculated, is larger than the specified number CntTh, the degree of variation of the plurality of stability factor calculation values Kh_cal to be evaluated is evaluated.

  When the variation index P_hist obtained by dividing the maximum frequency Fmax by the calculation count Cnt is larger than the variation determination value HTh, it is determined that the variation is small. Examples of such a case where the variation is determined to be small include a case where the stability factor calculation value Kh_cal has no or few opportunities to be calculated in a situation where skidding has occurred. Then, in this case, the stability factor calculation value Kh_cal1 corresponding to the maximum frequency Fmax is set as the vehicle stability factor Kh.

  FIG. 5 shows the relationship between the lateral acceleration Gy of the vehicle and the deviation DYr obtained by subtracting the yaw rate sensor value Yr_R from the standard yaw rate Yr_Trg. As shown in the first lateral acceleration area A1 in FIG. 5, when the skid does not occur in the vehicle, a linear proportional relationship exists between the lateral acceleration Gy and the deviation DYr. . The change gradient of the deviation DYr with respect to the change in the lateral acceleration Gy substantially matches the vehicle stability factor Kh at that time.

  On the other hand, as shown by the second lateral acceleration region A2 in FIG. 5, when the vehicle is slipping, the deviation DYr changes rapidly with respect to the change in the lateral acceleration Gy. It becomes. Therefore, the change gradient of the deviation DYr with respect to the change in the lateral acceleration Gy varies depending on the magnitude of the lateral acceleration Gy at that time. That is, it is difficult to obtain the vehicle stability factor Kh at that time.

  As is clear from the graph shown in FIG. 5, when there is no or few opportunities to calculate the stability factor calculation value Kh_cal under the situation where skidding has occurred, a plurality of calculated stability factor calculations are performed. The value Kh_cal substantially matches the slope of the line in the first lateral acceleration area A1. That is, when the frequency distribution table is created, the frequency distribution has a steep tapered shape as shown in FIG. 3, for example. In this case, the degree of variation is small.

  On the other hand, when the variation index P_hist is less than or equal to the variation determination value HTh, it is determined that the variation is large. A case where it is determined that the variation is large in this way includes a case where there are a large number of stability factor calculation values Kh_cal calculated when skidding has occurred. In this case, the stability factor Kh of the vehicle is not changed.

  That is, while the vehicle is skidding, the stability factor calculation value Kh_cal is calculated in the second lateral acceleration region A2 in FIG. When the frequency distribution table is created while there are many opportunities for calculating the stability factor calculation value Kh_cal during skidding, the frequency distribution has a gentle hill shape as shown in FIG. 4, for example. In this case, the degree of variation is assumed to be large.

Next, a comparison between this embodiment and a comparative example that does not evaluate the degree of variation of the plurality of stability factor calculation values Kh_cal will be described.
In the comparative example, steps S108 and S109 are omitted from the processing routine shown in FIG. In this case, the stability factor calculation value Kh_cal1 corresponding to the maximum frequency Fmax is determined as the vehicle stability factor Kh without evaluating the magnitude of variation of the calculated plurality of stability factor calculation values Kh_cal.

  In such a comparative example, when a frequency distribution table is created based on a plurality of calculated stability factor calculated values Kh_cal, the value corresponding to the maximum frequency Fmax is estimated to be closest to the actual stability factor of the vehicle at that time. Is done. Therefore, the stability factor calculation value Kh_cal1 corresponding to the maximum frequency Fmax is determined as the vehicle stability factor Kh. In this case, since the variation of the plurality of stability factor calculation values Kh_cal used to create the frequency distribution table is not evaluated, the stability factor calculation value Kh_cal1 corresponding to the maximum frequency Fmax adopted as the stability factor Kh is The suspicion of values based on various parameters acquired in the second lateral acceleration area A2 is not wiped out. Therefore, in the comparative example, there is a possibility that the calculation accuracy of the stability factor calculation value Kh_cal in the case of the present embodiment is lower.

  In this regard, in the present embodiment, the variation of the plurality of stability factor calculation values Kh_cal used for creating the frequency distribution table is evaluated, and the update of the stability factor Kh is permitted only when the variation is low. Therefore, the reliability of the stability factor calculation value Kh_cal is higher than in the comparative example.

As described above, in the present embodiment, the following effects can be obtained.
(1) When the vehicle is skidding, if the stability factor calculation value Kh_cal is calculated under a situation where the lateral acceleration Gy of the vehicle changes, the variation of each stability factor calculation value Kh_cal increases. On the other hand, when the vehicle is not skidding, if the stability factor calculation value Kh_cal is calculated under the situation where the lateral acceleration Gy of the vehicle changes, the variation of each stability factor calculation value Kh_cal becomes small.

  Therefore, in the present embodiment, the vehicle stability factor Kh is determined according to one value among the plurality of stability factor calculation values Kh_cal evaluated to have small variations. Thereby, the possibility that the stability factor Kh of the vehicle is determined according to the stability factor calculation value Kh_cal calculated using various parameters acquired during the skid of the vehicle is reduced. Therefore, the calculation accuracy of the vehicle stability factor Kh can be improved.

  (2) In this embodiment, when the calculation count Cnt updated every time the stability factor calculation value Kh_cal is calculated becomes larger than the specified count CntTh, the variation index P_hist obtained by dividing the maximum frequency Fmax by the calculation count Cnt. Thus, the variation of the plurality of stability factor calculation values Kh_cal is evaluated. Only when it is evaluated that the variation is small, the vehicle stability factor Kh is determined according to one of the plurality of stability factor calculation values Kh_cal. On the other hand, if it is evaluated that the variation is large, each stability factor calculation value Kh_cal is likely to contain many values calculated during the side skid of the vehicle. Not updated. Therefore, the calculation accuracy of the vehicle stability factor Kh can be improved.

  (3) The stability factor calculation value Kh_cal1 corresponding to the maximum frequency Fmax is a value calculated most frequently in a predetermined period from the calculation number count Cnt exceeding “0 (zero)” to the specified number CntTh. Such a stability factor calculation value Kh_cal1 can be said to be the most reliable value among the plurality of stability factor calculation values Kh_cal that have been evaluated, that is, a value close to the actual stability factor of the current vehicle. Therefore, in this embodiment, when the calculation count Cnt exceeds the specified count CntTh and it is evaluated that the variation of each stability factor calculation value Kh_cal is small, the stability factor calculation value Kh_cal1 corresponding to the maximum frequency Fmax is It is assumed that the ability factor is Kh. Therefore, the vehicle stability factor Kh can be determined to an appropriate value corresponding to the vehicle state at that time.

  (4) When the stability factor Kh is calculated with high accuracy in this way, it is possible to optimize the start timing of behavior control using the stability factor Kh as one of the parameters and the control amount during the control. it can. As a result, it becomes possible to contribute to further stabilization of the behavior of the vehicle.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. The second embodiment is different from the first embodiment in the contents of a processing routine executed by the control device 30. Therefore, in the following description, parts different from those of the first embodiment will be mainly described, and the same components as those of the first embodiment will be denoted by the same reference numerals and redundant description will be omitted. .

  FIG. 5 shows the relationship between the lateral acceleration Gy of the vehicle and the deviation DYr obtained by subtracting the yaw rate sensor value Yr_R from the standard yaw rate Yr_Trg. As shown in the first lateral acceleration area A1 in FIG. 5, when the skid does not occur in the vehicle, a linear proportional relationship exists between the lateral acceleration Gy and the deviation DYr. . The change gradient of the deviation DYr with respect to the change in the lateral acceleration Gy substantially matches the vehicle stability factor Kh at that time.

  On the other hand, as shown by the second lateral acceleration region A2 in FIG. 5, when the vehicle is slipping, the deviation DYr changes rapidly with respect to the change in the lateral acceleration Gy. It becomes. Therefore, the change gradient of the deviation DYr with respect to the change in the lateral acceleration Gy varies depending on the magnitude of the lateral acceleration Gy at that time. That is, it is difficult to obtain the vehicle stability factor Kh at that time.

  Therefore, in the present embodiment, the deviation DYr is calculated for each predetermined cycle under the situation where the lateral acceleration Gy changes. The plurality of deviations DYr calculated in this way are classified into a first lateral acceleration area A1 having a small variation in the obtainable stability factor calculation value Kh_cal and a second lateral acceleration area A2 having a large variation. . Then, the stability factor Kh of the vehicle at that time is determined based on the plurality of deviations DYr classified in the first lateral acceleration region A1.

Next, a processing routine executed by the control device 30 of the present embodiment will be described with reference to the flowchart shown in FIG. 6 and the graphs shown in FIGS.
The processing routine shown in FIG. 6 is a processing routine that is executed every preset predetermined cycle. In this processing routine, the control device 30 acquires the current lateral acceleration Gy and the previous lateral acceleration Gy_h (step S201). Then, when the difference (= | Gy−Gy_h |) between the current lateral acceleration Gy and the previous lateral acceleration Gy_h is equal to or less than the reference determination value GyTh (step S202: NO), the control device 30 performs this process. The routine is temporarily terminated, and when the difference is larger than the reference determination value GyTh (step S202: YES), the process proceeds to the next step S203.

  In step S203, the control device 30 acquires the yaw rate sensor value Yr_R detected based on the signal output from the yaw rate sensor SE4 and the reference yaw rate Yr_Trg calculated using the above relational expression (formula 1) (step S203). S203). Subsequently, the control device 30 obtains a deviation DYr obtained by subtracting the yaw rate sensor value Yr_R from the reference yaw rate Yr_Trg (step S204). Therefore, in the present embodiment, the control device 30 also functions as a “deviation calculator” that calculates the deviation DYr each time a change in the lateral acceleration of the vehicle is detected.

  Then, the control device 30 creates a graph shown in FIG. 7A based on the deviation DYr obtained in step S204 and the current lateral acceleration Gy obtained in step S201 (step S205). Subsequently, the control device 30 increments the calculation count Cnt by “1” (step S206), and determines whether or not the calculation count Cnt is larger than the specified count CntTh (step S207). When the calculation count Cnt is equal to or less than the specified count CntTh (step S207: NO), the control device 30 proceeds to step S213 described later. On the other hand, when the calculation count Cnt is larger than the specified count CntTh (step S207: YES), the deviation change amount ΔDYr corresponding to the change slope of the deviation DYr is shown for each point P (Gy, DYr) shown in FIG. Is calculated (step S208). The deviation change amount ΔDYr calculated in this way may be called a stability factor calculation value.

  For example, as shown in FIGS. 7A and 7B, the deviation change amount ΔDYr at the first point P1 is calculated using the following relational expression (formula 3). Here, the second point P2 is a point having a lateral acceleration Gy2 smaller than the lateral acceleration Gy1 of the first point P1. Further, the deviation DYr1 is a deviation at the first point P1, and the deviation DYr2 is a deviation at the second point P2.

  Returning to FIG. 6, after executing step S208, the control device 30 sets the first lateral acceleration region A1 and the second lateral acceleration region A2 based on the deviation change amount ΔDYr for each point P (step S209). ). That is, the calculated deviations DYr are classified into the first lateral acceleration region A1 and the second lateral acceleration region A2. Therefore, in the present embodiment, when the calculation count Cnt exceeds the specified count CntTh, the control device 30 evaluates the variation of the obtainable stability factor calculation value Kh_cal according to the change mode of the deviation change amount ΔDYr. It also functions as an “evaluation unit”.

  For example, as shown in FIG. 8, a section in which the deviation change amount ΔDYr is equal to or less than the change determination value ΔDYrTh is defined as the first lateral acceleration region A1, and a section in which the deviation change amount ΔDYr is greater than the change determination value ΔDYrTh. 2 lateral acceleration areas A2. The change determination value ΔDYrTh is determined in advance to a value slightly larger than the initial value Kh_base of the stability factor.

  Returning to FIG. 6, after execution of step S209, the control device 30 obtains the slope Slp of the first-order approximate expression based on each point P (Gy, DYr) classified in the set first lateral acceleration region A1. (Step S210). In the present embodiment, the inclination “Slp” is an average value of the deviation change amount ΔDYr at each point P classified in the first lateral acceleration region A1. Then, the control device 30 sets the obtained slope Slp as the vehicle stability factor Kh (step S211). In other words, in the present embodiment, the vehicle stability factor Kh is determined based on a plurality of deviation variation amounts ΔDYr (stability factor calculation values) that are classified into the first lateral acceleration region A1 and have small variations. . Therefore, in the present embodiment, the control device 30 also functions as a “determination unit” that determines the vehicle stability factor Kh based on the plurality of deviations DYr classified in the first lateral acceleration region A1.

  Then, the control device 30 resets the calculation count Cnt to “0 (zero)” and performs a reset process for clearing the graph shown in FIG. 7A (step S212), and the process is performed in the next step S213. Migrate to

  In step S213, the control device 30 sets the current lateral acceleration Gy acquired in step S201 to the previous lateral acceleration Gy_h. Thereafter, the control device 30 once ends this processing routine.

As described above, in the present embodiment, the following effects can be obtained.
(5) When the vehicle is skidding, even if the stability factor calculation value is calculated under a situation where the lateral acceleration Gy of the vehicle changes, the calculated plurality of stability factor calculation values greatly vary. On the other hand, when the vehicle is not skidding, assuming that the stability factor calculation value is calculated under a situation where the lateral acceleration Gy of the vehicle changes, there is a variation in the calculated plurality of stability factor calculation values. Get smaller.

  Therefore, in the present embodiment, the vehicle stability factor Kh is determined based on the plurality of deviations DYr classified in the first lateral acceleration region A1. Thereby, the possibility that the stability factor Kh of the vehicle is determined based on the deviation DYr calculated using various parameters acquired during the skid of the vehicle is reduced. Therefore, the calculation accuracy of the vehicle stability factor Kh can be improved.

  (6) When the vehicle is not skidding, the change amount of the deviation DYr with respect to the change of the lateral acceleration Gy, that is, the deviation change amount ΔDYr is substantially constant regardless of the magnitude of the lateral acceleration Gy. On the other hand, when the vehicle is skidding, the deviation change amount ΔDYr increases as the absolute value of the lateral acceleration Gy increases. Therefore, in the present embodiment, a lateral acceleration section in which the deviation change amount ΔDYr is equal to or smaller than the change determination value ΔDYrTh is defined as the first lateral acceleration region A1, and the lateral acceleration in which the deviation change amount ΔDYr exceeds the change determination value ΔDYrTh. Is a second lateral acceleration region A2. Then, the vehicle stability factor Kh is determined according to the deviation change amount ΔDYr (that is, the stability factor calculation value) at each point P classified in the first lateral acceleration region A1. As a result, when the stability factor Kh is updated, the possibility that the value acquired during the skidding of the vehicle is used is reduced. Therefore, the calculation accuracy of the vehicle stability factor Kh can be improved.

  (7) Unlike the first embodiment, this embodiment differs from the first embodiment in the first lateral acceleration among a plurality of deviations DYr calculated until the calculation count Cnt becomes larger than the specified count CntTh. The stability factor Kh is determined in accordance with each deviation DYr classified in the area A1. Therefore, on the assumption that the specified number of times CntTh is the same value, the vehicle stability factor Kh can be updated more frequently than in the first embodiment.

  (8) When the stability factor Kh is calculated with high accuracy in this way, the start timing of behavior control using the stability factor Kh as one of the parameters and the control amount during the control are optimized. be able to. As a result, it becomes possible to contribute to further stabilization of the behavior of the vehicle.

In addition, you may change each said embodiment into another embodiment as follows.
In the first embodiment, if the vehicle stability factor Kh is determined according to the stability factor calculation value Kh_cal1 corresponding to the maximum frequency Fmax, the stability factor Kh is not set to the stability factor calculation value Kh_cal1. Also good. For example, the stability factor Kh may be determined based on the stability factor calculation value Kh_cal1 and the stability factor calculation value Kh_cal corresponding to the second largest frequency following the maximum frequency Fmax.

  In the first embodiment, the latest stability factor Kh (n) is a value between the previous stability factor Kh (n−1) and the stability factor calculation value Kh_cal1 corresponding to the maximum frequency Fmax. (For example, an average value of these two values) may be used.

  In the first embodiment, when it is evaluated that the variation of the plurality of stability factor calculation values Kh_cal is small, the average value of all the stability factor calculation values Kh_cal may be set as the vehicle stability factor Kh. In this case, the stability factor Kh of the vehicle may be obtained by weighted average processing in which the weighting for the stability factor calculation value Kh_cal having a large frequency F is increased and the weighting for the stability factor calculation value Kh_cal having a small frequency F is increased. .

  In the first embodiment, when the calculation frequency count Cnt when the maximum frequency Fmax reaches a predetermined value is less than the predetermined number, it is evaluated that the variation of each stability factor calculation value Kh_cal calculated so far is small. Then, the stability factor Kh of the vehicle may be updated. On the other hand, when the calculation frequency count Cnt when the maximum frequency Fmax reaches a predetermined value is greater than or equal to the predetermined number of times, or when the maximum frequency Fmax is less than the predetermined value even if the calculation frequency count Cnt reaches the predetermined number, The stability factor calculation value Kh_cal calculated up to this point may be evaluated as having a large variation, and the vehicle stability factor Kh may not be updated.

  In the first embodiment, the stability factor calculation value Kh_cal may be calculated using the following relational expression (Formula 4).

  In the second embodiment, as a method of obtaining the slope Slp of the first-order approximation formula, a method using a known approximation method such as a least square method instead of the average value of the plurality of deviation change amounts ΔDYr may be adopted. Good.

  In addition, a frequency distribution table of the deviation change amount ΔDYr at each point P classified in the first lateral acceleration area A1 is created, and the value that maximizes the frequency is set as the vehicle stability factor Kh. Good.

  In the second embodiment, when the number of points P classified in the first lateral acceleration area A1 is smaller than the number of points P classified in the second lateral acceleration area A2, the vehicle slips. It can be determined that the number of operations of the deviation DYr is small in a situation in which it is not. Therefore, in such a case, the reset process in step S212 may be performed without updating the vehicle stability factor Kh. As a result, it is possible to further suppress a decrease in calculation accuracy of the vehicle stability factor Kh.

  In each embodiment, the lateral acceleration Gy is not a sensor value based on a signal output from the lateral acceleration sensor SE3, but a calculated value using a yaw rate sensor value Yr_R detected by the yaw rate sensor SE4. Good. In this case, a value obtained by multiplying the yaw rate sensor value Yr_R by the vehicle body speed VS is the lateral acceleration Gy.

Next, technical ideas that can be grasped from the above embodiments and other embodiments will be added below.
(A) a stability calculation unit (30, S103) that calculates a stability factor calculation value (Kh_cal) each time a change in the lateral acceleration (Gy) of the vehicle is detected (S102: YES);
A creation unit (30, S104) for creating a frequency distribution indicating the relationship between the calculated stability factor calculated value (Kh_cal) and the frequency (F);
When the number of calculations (Cnt) by the stability calculation unit (30, S103) exceeds a specified number (CntTh) (S106: YES), the maximum frequency is calculated from the frequency distribution created by the creation unit (30, S104). A determination unit (30, S111) for extracting a stability factor calculation value (Kh_cal1) corresponding to (Fmax) and determining a vehicle stability factor (Kh) according to the stability factor calculation value (Kh_cal1); A vehicle stability factor calculation device.

  When a frequency distribution is created based on a plurality of calculated stability factor calculation values (Kh_cal), it can be estimated that the value at which the frequency is maximum is closest to the actual stability factor of the vehicle at that time. Therefore, in the above configuration, the vehicle stability factor (Kh) is determined according to the stability factor calculation value (Kh_cal1) corresponding to the maximum frequency (Fmax). Thereby, the calculation accuracy of the stability factor (Kh) can be improved.

  (B) When the division value (P_hist) is larger than the specified division value (HTh) (S109: YES), the evaluation unit (30, S109) varies the stability factor calculation values (Kh_cal). It is preferable to evaluate that it is small.

(C) The determination unit (30, S111)
When the evaluation unit (30, S109) evaluates that the variation of the plurality of stability factor calculation values (Kh_cal) is large (S109: NO), the updating of the vehicle stability factor (Kh) is prohibited,
When it is evaluated that the variation is small (S109: YES), it is preferable to determine the vehicle stability factor (Kh) according to at least one of the respective stability factor calculation values (Kh_cal).

  When the stability factor calculation values (Kh_cal) vary greatly, such as when there are many stability factor calculation values (Kh_cal) calculated based on various parameters acquired during the skid of the vehicle, each of these stability factors The vehicle stability factor (Kh) is not updated according to the factor calculation value (Kh_cal). Thereby, the fall of the calculation precision of the stability factor (Kh) of a vehicle can be suppressed now.

(D) Every time a change in the lateral acceleration (Gy) of the vehicle is detected (S202: YES), the yaw rate sensor (SE4) is calculated from the reference yaw rate (Yr_Trg) calculated using the stability factor (Kh) at that time. ) A deviation calculation unit (30, S204) that calculates a deviation (DYr) obtained by subtracting the yaw rate sensor value (Yr_R) detected by
When the number of calculations (Cnt) by the deviation calculation unit (30, S204) exceeds a specified number (CntTh) (S207: YES), each deviation (DYr) calculated by the deviation calculation unit (30, S204) The first lateral acceleration region (A1) having a small deviation change amount (ΔDYr) with respect to the lateral acceleration (Gy) change and the second lateral acceleration region (A2) having a large deviation change amount (ΔDYr). ) And a classification unit (30, S209),
A vehicle stability factor calculation comprising: a determination unit (30, S211) that determines a vehicle stability factor (Kh) according to a deviation (DYr) classified in the first lateral acceleration region (A1). apparatus.

  30 ... Control device (evaluation unit, determination unit, stability calculation unit, creation unit, deviation calculation unit) as a stability factor calculation device, A1 ... first lateral acceleration region, A2 ... second lateral acceleration region , Cnt: Count of calculation counts, CntTh: Specified count, DYr: Deviation, F: Frequency, Fmax: Maximum frequency, Gy: Lateral acceleration, HTh: Variation determination value, Kh: Stability factor, Kh_cal, Kh_cal1 ... Stability factor calculation value, P_hist ... Variation index as a division value, SE4 ... Yaw rate sensor, Yr_R ... Yaw rate sensor value, Yr_Trg ... Reference yaw rate, ΔDYr ... Deviation change amount.

Claims (4)

A situation where the lateral acceleration of the vehicle (Gy) is changed (S10 2: YES) evaluation unit for evaluating the variation of possible stability factor calculation value acquisition (Kh_ca l) in the (30, S10 9),
Variation is small, the estimated plurality of the stability factor calculated value and at least according to one value determination unit that determines a vehicle stability factor (Kh) of (Kh_ca l) (30, S11 1),
A stability calculation unit (30, S103) that calculates a stability factor calculation value (Kh_cal) each time a change in the lateral acceleration (Gy) of the vehicle is detected (S102: YES);
A creation unit (30, S104) for creating a frequency distribution indicating the relationship between the calculated stability factor calculated value (Kh_cal) and the frequency (F),
When the number of calculations (Cnt) by the stability calculation unit (30, S103) exceeds a specified number (CntTh) (S106: YES), the evaluation unit (30, S109) determines the creation unit (30, S104). The stability factor calculation of the vehicle that evaluates the variation of each stability factor calculation value (Kh_cal) by the division value (P_hist) obtained by dividing the maximum frequency (Fmax) in the frequency distribution created by apparatus. When the evaluation unit (30, S109) evaluates that the variation of each stability factor calculation value (Kh_cal) is small (S109: YES), the determination unit (30, S111) 30, the stability factor calculation value (Kh_cal1) corresponding to the maximum frequency (Fmax) is extracted from the frequency distribution created in S104) (S110), and the vehicle stability is determined according to the stability factor calculation value (Kh_cal1). The vehicle stability factor calculation device according to claim 1 , wherein the factor (Kh) is determined. A situation where the lateral acceleration of the vehicle (Gy) is changed (S 202: YES) can be obtained in a stability factor calculation value (Kh_cal, ΔDYr) evaluation unit for evaluating the variation of the (30, S 209),
A determination unit (30 , S211) for determining a vehicle stability factor (Kh) according to at least one value of a plurality of stability factor calculation values (Kh_cal, ΔDYr) evaluated as having a small variation;
Every time a change in the lateral acceleration (Gy) of the vehicle is detected (S202: YES), the yaw rate sensor (SE4) detects the reference yaw rate (Yr_Trg) calculated using the stability factor (Kh) at that time. A deviation calculating unit (30, S204) for calculating a deviation (DYr) obtained by subtracting the yaw rate sensor value (Yr_R) to be obtained,
The evaluation unit (30, 209) changes the lateral acceleration (Gy) when the number of calculations (Cnt) by the deviation calculation unit (30, S204) exceeds a specified number (CntTh) (S207: YES). A stability factor calculation device for a vehicle that evaluates the variation of the stability factor calculation value (Kh_cal) according to the change mode of the deviation change amount (ΔDYr) relative to the vehicle. When the number of calculations (Cnt) by the deviation calculation unit (30, S204) exceeds a specified number (CntTh) (S207: YES), the evaluation unit (30, S209) determines the deviation calculation unit (30, S204). ) Are calculated by dividing the deviation (DYr) by the first lateral acceleration area (A1) having a small deviation variation (ΔDYr) and the second lateral acceleration area (ΔDYr) by a large deviation variation (ΔDYr). A2)
The vehicle according to claim 3 , wherein the determination unit (30, S211) determines a stability factor (Kh) of the vehicle according to a deviation (DYr) classified into the first lateral acceleration region (A1). Stability factor calculation device.