JP5195524B2 - Vehicle travel control device - Google Patents

Description

  The present invention includes lateral acceleration estimating means for estimating the lateral acceleration of the vehicle based on the left and right wheel speeds of the vehicle wheels, and controls the running state of the vehicle based on the lateral acceleration estimated by the lateral acceleration estimating means. The present invention relates to a vehicle travel control device. In this specification, unless otherwise specified, “rotational speed” means “rotational speed per unit time”, that is, “rotational speed”.

  2. Description of the Related Art Conventionally, a vehicle travel control device described in Patent Document 1 is known as a vehicle travel control device for controlling the travel state of a vehicle, and this control device estimates a lateral acceleration of a vehicle for anti-lock control of a vehicle brake or the like. In this case, the right / left front / rear wheel speed ratio (rear wheel speed / front wheel speed) RAl, RAr is calculated as the ratio of the integrated wheel speed, and the right / left wheel speed ratio RAl, The correction ratio RA is calculated by dividing the larger one of Rar by the smaller one. Then, 1 is subtracted from the correction ratio, multiplied by the square of the vehicle body speed, and further divided by the rear wheel tread TR and the gravitational acceleration g, is calculated as a deviation amount TKYG from the true lateral acceleration.

This is expressed by the following formula.
RA = max [RAl, RAr] / min [Ral, Rar]
TKYG = V × V × (RA-1) / (TR × g)

JP 2007-030735 A

  However, since the conventional control device is configured to include the wheel speeds of all four wheels, it is driven in a two-wheel drive vehicle such as front engine / front wheel drive (FF) or front engine / rear wheel drive (FR). There is a problem that the error due to wheel slip is reflected in the correction value, and the estimation accuracy of the lateral acceleration of the vehicle is lowered.

  The vehicle travel control device according to the present invention calculates, as a correction coefficient, a value obtained by dividing one wheel speed of the left and right wheel speeds of the driven wheel among the wheels of the vehicle by the other wheel speed. A value obtained by multiplying the correction coefficient is output as one wheel speed correction value, and the lateral acceleration estimation means estimates the lateral acceleration based on the one wheel speed correction value and the other wheel speed. is there.

  According to the vehicle travel control apparatus of the present invention, since the lateral acceleration of the vehicle is estimated using the correction coefficient based on the left and right wheel speeds of only the driven wheels, the front engine / front wheel drive (FF) and the front engine / rear wheels are estimated. Even in a two-wheel drive vehicle such as a drive (FR), an error due to slip of the drive wheel is not reflected in the correction value, and therefore the accuracy of estimating the lateral acceleration of the vehicle can be improved.

It is explanatory drawing which shows the system configuration | structure of the motor vehicle carrying the transmission control unit which comprises one Embodiment of the vehicle travel control apparatus of this invention. It is a block diagram which shows functionally the structure of the traveling control apparatus for vehicles of the said embodiment. It is a block diagram which shows an example of the calculation process of the correction | amendment lateral acceleration which the vehicle travel control apparatus of the said embodiment performs. It is a block diagram which shows another example of the calculation process of the correction | amendment lateral acceleration which the vehicle travel control apparatus of the said embodiment performs. It is a graph which respectively shows the time change of each factor at the time of going from the curve driving | running | working of the motor vehicle using the driving control apparatus for vehicles of the said embodiment, and the motor vehicle using the control apparatus which concerns on a prior art from a curve driving | running | working. It is a graph which shows each time change of each factor at the time of returning from a straight run to a straight run through a curve run from a straight run of a car using a run control device for vehicles of the above-mentioned embodiment, and a control device concerning a prior art. . It is a graph which each shows the time change of each factor at the time of the repetition of the linear driving | running | working of a motor vehicle and the curve driving | running | working using the vehicle travel control apparatus of the said embodiment.

  Embodiments of a vehicle travel control device of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a system configuration of an automobile equipped with a transmission control unit that constitutes an embodiment of the vehicle travel control apparatus of the present invention, and FIG. 2 is a vehicle travel control apparatus of the above embodiment. FIG. 1 is a block diagram functionally showing the configuration of FIG.

  An automobile 1 shown in FIG. 1 is of a so-called front engine / front wheel drive (FF) type, and includes an engine / transaxle 2 as a drive source, and the engine / transaxle 2 uses an automatic transmission to rotate the output of the engine. Decelerate and output right and left via differential gear mechanism. The operation of the automatic transmission of the engine / transaxle 2 is controlled by a transmission control unit 3 having a normal microcomputer. The left and right front wheels 4 and 5 of the automobile 1 are driven by output rotation from the engine / transaxle 2, while the left and right rear wheels 6 and 7 of the automobile 1 are driven wheels.

  The left and right rear wheels 6, 7 are provided with normal rotation speed sensors 8, 9. These rotation speed sensors 8, 9 detect the rotation speeds of the left and right rear wheels 6, 7 and input them to the transmission control unit 3. The transmission control unit 3 estimates the lateral acceleration (lateral G) applied to the automobile 1 based on the rotational speeds of the left and right rear wheels 6 and 7 as will be described later, and on the basis of the estimation result, the vehicle is running on a curve. Is determined to be excessive with respect to the frictional force of the left and right front wheels 4 and 5, which are driving wheels, the gear ratio is increased while reducing the engine output by cooperative control with an engine control unit (not shown). By shifting to the (small gear ratio) side, the traction of the left and right front wheels 4 and 5 is reduced to such an extent that it does not slip due to insufficient frictional force, and it is possible to travel with a neutral steer tendency along a curve.

  The transmission control unit 3 estimates the lateral acceleration (lateral G) applied to the automobile 1, for example, the processing shown in FIG. 3 corresponding to the configuration of the corrected lateral G calculation unit shown in the block diagram of FIG. Execute. In FIG. 3 corresponding to the configuration of FIG. 2, the transmission control unit 3 determines the reference wheel diameter and the circularity ratio in step S <b> 1 according to the rotational speeds of the left and right rear wheels 6 and 7 output from the rotational speed sensors 8 and 9 in advance. Multiply π to obtain the right rear wheel speed Vrr and the left rear wheel speed Vrl. In step S2, the wheel speed ratio calculation unit 11 divides them to obtain the wheel speed ratio Vrl / Vrr. In step S3, As the filter processing unit 12, a post-filtering wheel speed ratio Filter (Vrl / Vrr) obtained by smoothing (filtering) the wheel speed ratio Vrl / Vrr using a first-order lag filter is obtained as a lateral G correction coefficient.

  On the other hand, in step S4, the transmission control unit 3 uses the lateral G differential value obtained by time-differentiating the lateral acceleration (lateral G) previously obtained as described later as the straight line determination unit 14, as described later. If the lateral G differential value fluctuates in a plus or minus direction, it is judged that the vehicle is running straight, and the absolute value of the value obtained by filtering the lateral G differential value is a predetermined value. If it is above, it is determined that the vehicle is running on a curve. In step S5, the vehicle speed Vsp obtained as an average value of the right rear wheel speed Vrr and the left rear wheel speed Vrl is time-differentiated, and the vehicle travels from the longitudinal acceleration (longitudinal G) applied to the vehicle 1 in a steady running. The determination unit 15 determines that the vehicle 1 is traveling in a steady state (constant speed) if the longitudinal G is within a predetermined range, and determines that the vehicle is accelerating or decelerating if the longitudinal G is out of the predetermined range. To do.

  Therefore, if the transmission control unit 3 determines that the map storage & calculation unit 13 determines that the vehicle 1 is running straight and running in steps S4 and S5, the transmission control unit 3 performs the above-described filtering process in step S6. The wheel speed ratio Filter (Vrl / Vrr) is stored in the map as a value corresponding to the vehicle speed as shown on the left side in FIG. If it is determined in step S4 that the vehicle 1 is not traveling in a straight line, or if it is determined in step S5 that the vehicle 1 is not traveling in a steady state (constant speed), step S6 is skipped.

Then, the transmission control unit 3 stores the post-filter wheel speed ratio Filter (Vrl / Vrr) corresponding to the current vehicle speed as the lateral G correction coefficient in step S7 as the post-correction wheel speed calculation unit 16 in the map. The calculated right rear wheel speed FVrr is calculated and output by multiplying the right rear wheel speed Vrr by the filtered wheel speed ratio Filter (Vrl / Vrr) in step S8, after reading from the map of the calculation unit 13. In step S9, the lateral G calculation unit 17 calculates an estimated value of the lateral acceleration (lateral G) from the corrected right rear wheel speed FVrr and the left rear wheel speed Vrl by the following equation. However, TR is a tread between the left and right rear wheels 6 and 7.
Horizontal G = (Vrl−FVrr) × (Vrl + FVrr) / (2 × TR)

  The transmission control unit 3 uses the estimated value of the lateral acceleration corrected for the lateral G error caused by different diameter tires or the like to control the gear ratio as described above, thereby maintaining the steering characteristics of the automobile 1 in a neutral steering tendency. can do.

  The transmission control unit 3 may execute the flowchart shown in FIG. 4 instead of the flowchart shown in FIG. 3. In FIG. 4, the transmission control unit 3 pre- The right and left rear wheel speeds Vrr and Vrl are obtained by multiplying the rotation speeds of the left and right rear wheels 6 and 7 output by 9 by the reference wheel diameter and the circumference ratio π, respectively. In step S12, these are divided. The wheel speed ratio Vrr / Vrl is obtained, and in step S13, the filtered wheel speed ratio Filter (Vrr / Vrl) obtained by smoothing the wheel speed ratio Vrr / Vrl using a first-order lag filter is corrected to lateral G. Calculated as a coefficient.

  On the other hand, in step S14, the transmission control unit 3 is running straight if the lateral G differential value swings positively or negatively from the lateral G differential value obtained by time-differentiating the previously obtained lateral acceleration (lateral G). If the lateral G differential value is biased to positive or negative, it is determined that the vehicle is running on a curve. Further, in step S15, from the longitudinal acceleration (longitudinal G) applied to the vehicle 1 obtained by time differentiation of the vehicle speed obtained as an average value of the right rear wheel speed Vrr and the left rear wheel speed Vrl, the longitudinal G Is within the predetermined range, it is determined that the vehicle 1 is in steady running, and if the front-rear G is out of the predetermined range, it is determined that acceleration / deceleration is in progress.

  Thus, when the transmission control unit 3 determines in steps S14 and S15 that the vehicle 1 is running straight and is steady running, in step S16, the wheel speed ratio Filter (Vrr / Vrl) is stored in the map as a value corresponding to the vehicle speed, as shown on the left side of FIG. If it is determined in steps S14 and S15 that the vehicle 1 is not running straight or is not running steady, step S16 is skipped.

In step S17, the transmission control unit 3 reads the post-filter wheel speed ratio Filter (Vrr / Vrl) corresponding to the current vehicle speed as the lateral G correction coefficient from the map storage & calculation unit 13 map, In step S18, the corrected left rear wheel speed FVrl is obtained by multiplying the left rear wheel speed Vrl by the filtered wheel speed ratio Filter (Vrr / Vrl), and then in step S19, the corrected left From the rear wheel speed FVrl and the right rear wheel speed Vrr, an estimated value of the lateral acceleration (lateral G) is calculated by the following equation. However, TR is a tread between the left and right rear wheels 6 and 7.
Horizontal G = (Vrr−FVrl) × (Vrr + FVrl) / (2 × TR)

  FIG. 5 shows the time change of each factor when the vehicle 1 using the vehicle travel control device of the above embodiment and the vehicle 1 using the control device according to the prior art travel from the curve travel to the straight travel. As shown in the figure, while the vehicle 1 is running on a curve, there is a difference between the inner and outer wheels corresponding to the turning radius of the curve between the wheel speeds Vrl and Vrr of the left and right rear wheels 6 and 7 as driven wheels, and the turning radius. The actual lateral G corresponding to the vehicle speed is generated. On the other hand, the lateral G correction coefficient (the wheel speed ratio after filtering in this embodiment) is obtained from the wheel speeds Vrl and Vrr, and the lateral G correction coefficient is further used. The lateral G calculated from the wheel speed is obtained. Thereafter, when the vehicle moves to straight running, the lateral G correction coefficient is constantly updated during straight line determination and steady running in this embodiment. Therefore, when straight line judgment is made at time t1, the lateral G correction coefficient is corrected immediately thereafter. The lateral G is immediately corrected in the correction direction. On the other hand, in the conventional control device, since the wheel speed is integrated for a certain period of time, the correction of the lateral G correction coefficient is not performed immediately but is delayed after time t2, and the correction of lateral G is also delayed after time t2. Further, the lateral G correction coefficient is affected by the running state during integration, and the convergence amount of the lateral G changes.

  FIG. 6 shows the change over time of each factor when the vehicle 1 using the vehicle travel control device of the above embodiment and the vehicle 1 using the control device according to the prior art return from the straight travel to the straight travel through the curve travel. As shown in the figure, during the straight traveling of the automobile 1, there is no difference between the inner and outer wheels between the wheel speeds Vrl and Vrr of the left and right rear wheels 6 and 7 as driven wheels, and the actual lateral G is also a wheel. No speed calculation lateral G occurs. When the vehicle moves to a curve, the inner and outer wheel difference corresponding to the turning radius of the curve is generated between the wheel speeds Vrl and Vrr of the left and right rear wheels 6 and 7, as in the curve driving of FIG. On the other hand, the lateral G correction coefficient (filtered wheel speed ratio in this embodiment) is obtained from the wheel speeds Vrl and Vrr, and the wheel speed is calculated using the lateral G correction coefficient. The lateral G calculated from the above is obtained. At this time, in this embodiment, the lateral G correction coefficient is updated only during straight running and steady running, so the correction coefficient does not change during curve running, but the conventional control device also corrects the wheel speed during curve running. Since it is included in the calculation, the correction coefficient is corrected at time t3 including the integration result of the wheel speed during curve traveling when returning to straight traveling. Accordingly, during the subsequent straight running, in this embodiment, the lateral G is calculated as zero as intended, but the conventional control device calculates the lateral G to a non-zero value due to disturbance during curve traveling.

  FIG. 7 shows the time change of each factor at the time of repeating the straight traveling and the curved traveling of the automobile 1 using the vehicle travel control device of the above embodiment, and the actual lateral G is as shown in the figure. It is zero during straight running and ascends and descends during curved running. And it becomes almost constant during the curve steady (constant speed) traveling between times t4 and t5. On the other hand, the differential value obtained by differentiating the wheel speed calculation lateral G with respect to time fluctuates finely between plus (+) and minus (−) during straight running, and plus (+) at the beginning and end during curve running. And biased to minus (-). Then, during the steady curve (constant speed) running between the time points t4 and t5, as in the straight running, the vibration swings positively (+) and minus (−), so it is confusing as it is during the straight running. Therefore, in the present embodiment, the start and end of the curve are determined from the deviation of the lateral G differential value for a predetermined time or more, and the lateral G differential value is used as the primary for the steady curve running between the start and end. A smoothing process (filter process) is performed using a delay filter, the absolute value of the lateral G differential value after the filter process is compared with a predetermined positive threshold value S, and a curve is obtained when the lateral G differential value is equal to or greater than the threshold value S. When the vehicle is in steady running and the lateral G differential value is less than the threshold value S, it is determined that the vehicle is running straight.

  In addition, the smoothing process (filter process) in the filter processing unit 12 and steps S3 and S13 can be performed using target value tracking control such as PID (proportional integral derivative) control instead of using a first-order lag filter, If it does in this way, optimal control can be selected according to the specification etc. of car 1. Further, the lateral G correction coefficient may be obtained by filtering a wheel speed difference such as (1- (Vrr-Vrl) / Vsp) with a first-order lag filter or the like instead of filtering the wheel speed ratio. In this way, an optimal calculation method can be selected according to the specifications of the automobile 1 and the like.

  Accordingly, the lateral G calculation unit 17 corresponds to a lateral acceleration estimation unit, the wheel speed ratio calculation unit 11 corresponds to a correction coefficient calculation unit, and the corrected wheel speed calculation unit 16 corresponds to a wheel speed correction unit. According to the vehicle travel control apparatus of the present embodiment described above, the correction coefficient Filter (Vrl / Vrr) or Filter (Vrr / Vrl) based on the left and right wheel speeds Vrl and Vrr of only the driven wheels 6 and 7 is used. Thus, the lateral acceleration of the vehicle 1 is estimated, so even the front engine / front-wheel drive (FF) vehicle 1 does not reflect the error caused by the slip of the drive wheels 4 and 5 in the correction value. The estimation accuracy can be increased.

  Moreover, according to the vehicle travel control apparatus of the present embodiment, the Map storage & calculation unit 13 corresponding to the correction coefficient storage means stores the correction coefficient corresponding to the vehicle speed, and the corrected wheel corresponding to the wheel speed correction means. The speed calculation unit 16 calculates the wheel speed correction value based on the correction coefficient corresponding to the vehicle speed stored in the Map storage & calculation unit 13, so that the left and right rear wheels 6, 7 caused by tire rigidity and tire pressure are calculated. Corresponding to the change in the moving radius, the lateral acceleration can be corrected stably from a low vehicle speed to a high vehicle speed.

  Furthermore, according to the vehicle travel control apparatus of the present embodiment, the Map storage & calculation unit 13 corresponding to the correction coefficient storage means stores the correction coefficient when the automobile 1 is traveling straight as shown in FIG. The correction coefficient is not stored when running on a curve (turning), so incorrect correction of lateral acceleration due to changes in the radius of the left and right rear wheels 6 and 7 due to lateral acceleration while driving on a curve, disturbances, etc. It can be avoided. In addition, the Map storage & calculation unit 13 stores the correction coefficient when the automobile 1 is running steadily, and does not store the correction coefficient during acceleration / deceleration. Therefore, the left and right rear wheels due to the longitudinal acceleration during acceleration / deceleration are stored. It is possible to avoid erroneous correction of lateral acceleration due to a change in the moving radius of 6, 7 or disturbance.

  Furthermore, according to the vehicle travel control apparatus of the present embodiment, the straight travel determination unit 14 corresponding to the straight travel determination means performs a primary operation with respect to the estimated differential value of the lateral acceleration and the differential value as shown in FIG. Since it is determined whether or not the vehicle travels straight based on the absolute value of the value subjected to the delay process, the lateral acceleration can be immediately corrected in the convergence direction when the diameter difference between the left and right rear wheels 6 and 7 occurs.

  Furthermore, according to the vehicle travel control apparatus of the present embodiment, instead of the transmission speed control unit 3 filtering the wheel speed ratio as the correction coefficient calculation means, for example, (1- (Vrr-Vrl) / Vsp), etc. By filtering the wheel speed difference and obtaining the lateral G correction coefficient, an optimal calculation method can be selected according to the specifications of the automobile 1 and the like.

  According to the vehicle travel control apparatus of the present embodiment, the filter processing unit 12 corresponding to the correction coefficient calculation means obtains a value obtained by dividing one wheel speed by the other wheel speed, or one wheel speed as described above. The difference between the wheel speed and the other wheel speed is smoothed by a first-order lag filter, target value tracking control, etc., and the value after the smoothing process is calculated as a correction coefficient. Fluttering under the influence of disturbance and the like can be suppressed.

  Although the present invention has been described based on the illustrated examples, the present invention is not limited to the above-described examples, and can be appropriately changed within the scope of the claims. For example, in the above embodiment, the automobile 1 is a straight line. Even if the vehicle is running, it is not stored unless it is a correction coefficient during steady running. However, the present invention can also store the correction coefficient during acceleration / deceleration running if running straight. The above embodiment is applied to a front engine / front wheel drive (FF) type vehicle, but the present invention can also be applied to a front engine / rear wheel drive (FR) type vehicle, and the above embodiment is a transmission control. Although applied to a unit, the present invention can also be applied to other types of vehicle travel control devices such as an antilock brake system and a driving force distribution control system.

  Thus, according to the vehicle travel control device of the present invention, since the lateral acceleration of the vehicle is estimated using the correction coefficient based on the left and right wheel speeds of only the driven wheels, the front engine / front wheel drive (FF) and the front engine / rear Even in a two-wheel drive vehicle such as a wheel drive (FR), an error due to slip of the drive wheel is not reflected in the correction value, and therefore the accuracy of estimating the lateral acceleration of the vehicle can be improved.

DESCRIPTION OF SYMBOLS 1 Automobile 2 Engine transaxle 3 Transmission control unit (lateral acceleration estimation means, correction coefficient calculation means, wheel speed correction means, correction coefficient storage means, straight travel determination means)
4 Left front wheel 5 Right front wheel 6 Left rear wheel (driven wheel)
7 Right rear wheel (driven wheel)
8 Rotational speed sensor 9 Rotational speed sensor 11 Wheel speed ratio calculation unit (correction coefficient calculation means)
12 Filter processing unit (correction coefficient calculation means)
13 Map storage & calculation unit (correction coefficient storage means)
14 Straight line determination unit (straight line traveling determination means)
15 Steady Travel Determination Unit 16 Corrected Wheel Speed Calculation Unit (Wheel Speed Correction Unit)
17 Lateral G calculation part (lateral acceleration estimation means)

Claims (6)

Vehicle travel control comprising lateral acceleration estimation means for estimating the lateral acceleration of the vehicle based on the left and right wheel speeds of the vehicle wheel, and controlling the running state of the vehicle based on the lateral acceleration estimated by the lateral acceleration estimation means In the device
Correction coefficient calculation means for calculating a value obtained by dividing one wheel speed of the left and right wheel speeds of the driven wheel among the wheels as a correction coefficient;
Wheel speed correction means for outputting a value obtained by multiplying the one wheel speed by the correction coefficient as one wheel speed correction value;
With
The lateral acceleration estimating means estimates the lateral acceleration based on the one wheel speed correction value and the other wheel speed correction device, and is a vehicle travel control device. Correction coefficient storage means for storing the correction coefficient corresponding to the vehicle speed;
2. The vehicle travel control apparatus according to claim 1, wherein the wheel speed correction means calculates the one wheel speed correction value based on a correction coefficient stored in the correction coefficient storage means.   The correction coefficient storage means stores the correction coefficient when the vehicle is traveling straight, and does not store the correction coefficient when the vehicle is turning. Item 3. The vehicle travel control device according to Item 2.   The vehicle further comprises a straight travel determination unit that determines whether or not the vehicle travels straight based on the estimated differential value of the lateral acceleration and an absolute value of a value obtained by performing a delay process on the differential value of the lateral acceleration. The vehicle travel control device according to claim 3.   The correction coefficient calculating means calculates the value of the difference between the one wheel speed and the other wheel speed as the correction coefficient instead of the value obtained by dividing the other wheel speed by the one wheel speed. The vehicle travel control device according to any one of claims 1 to 4, wherein the vehicle travel control device is characterized by the following.   The correction coefficient calculation means performs a smoothing process on a value obtained by dividing the other wheel speed by the one wheel speed, or a value of a difference between the one wheel speed and the other wheel speed. 6. The vehicular travel control apparatus according to claim 1, wherein a value obtained by performing a conversion process is calculated as the correction coefficient.

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