Honda Giken Kogyo Kabushiki Kaisha

Honda Motor Co., Ltd.

Osamu Yano

Shuji Shiraishi

Osamu Yamamoto

Takashi Nishihara

Keiyu Kin

Toru Ikeda

Hiroyuki Urabe

Toru Takenaka

Yoshihiro Mori

Fumiaki Honjyo

Tomoya Ushimura

A road surface frictional coefficient estimating apparatus has a device for determining a first estimated value of a yaw moment Mnsp_estm generated at an NSP of a vehicle due to the resultant force of road surface reaction forces acting on each wheel by using, for example, a frictional coefficient estimated value that has been determined, and a device for determining a second estimated value of a yaw moment Mnsp_sens generated at the NSP from the observed value of motional state amounts defining an inertial force moment at the NSP. The increasing/decreasing manipulated variable of the frictional coefficient estimated value is sequentially determined on an error (Mnsp_sens&#x2212;Mnsp_estm) such that the error is converged to zero, and the road surface frictional coefficient is updated on the basis of the increasing/decreasing manipulated variable.

Road surface frictional coefficient estimating apparatus

A rotational speed Vof a left front wheel T, a rotational speed Vof a right front wheel T, a rotational speed Vof a left rear wheel T, and a rotational speed Vof a right rear wheel Tare detected by rotational speed sensors S-S, respectively. A front-wheel yaw rate &#x3b3;F arising due to a rotational speed difference between the front wheels T, Tand a rear-wheel yaw rate &#x3b3;R arising due to a rotational speed difference between the rear wheels T, Tare monitored. When a significant disparity between the both rotational speed differences is observed, it is determined that tire inflation pressure of any of the wheels T-Thas decreased. Upon detection, correction is made to an apparent yaw rate that would be observed in the properly inflated wheel as a result of steering for correction by a driver, thereby improving detection accuracy of underinflation of the tires.

Underinflation detector

A four-wheel vehicle is equipped with rotational speed sensors S -S that detect a rotational speed V of a left front wheel T , a rotational speed V of a right front wheel T , a rotational speed V of a left rear wheel T and a rotational speed V of a right rear wheel T , respectively, and a yaw rate sensor S&ggr; that detects a yaw rate of the vehicle. An underinflation detector includes a controller that calculates a front-wheel yaw rate &ggr;F derived from a difference in rotational speed between the front wheels T , T , a rear-wheel yaw rate &ggr;R derived from a difference in rotational speed between the rear wheels T , T , and deviations of the yaw rates &ggr;F, &ggr;R from an actually measured value output from the yaw rate sensor S&ggr;. A rate of change of the deviation with respect to change of vehicle speed is determined to thereby detect insufficiency of inflation pressure of tires with high reliability. Utilizing this underinflation detector , the outputs of the yaw rate sensor S&ggr; can be corrected.

Underinflation detector and method of correcting output of sensor using the same

In a vehicle motion control system based on a target yaw rate scheme, a brake force computing unit brakes an outer front wheel in a controlled manner when a sign of the yaw rate has changed and the yaw rate increment has become equal to or greater than a threshold value after a counter steer action has been detected and the vehicle body slip angle has become equal to or greater than a threshold value. Thus, suppose that a vehicle travels a winding road and a counter steer action is taken. If the vehicle body slip angle and actual yaw rate increment exceed threshold values, the outer front wheel is braked. Therefore, even when the vehicle body slip angle reaches a maximum value and an attempt is made to reduce it again by a counter steer action in a similar manner as a swinging pendulum, because the increases in the yaw rate and actual yaw rate increment are predicted and monitored before the vehicle body slip angle reaches its maximum value, the vehicle is enabled to travel in a stable fashion.

Vehicle motion control system

In a system for computing a road surface frictional coefficient for controlling a motion of a vehicle, the road surface frictional coefficient is estimated according to the deviation of the estimated vehicle body fore-and-aft/lateral acceleration from the actually detected vehicle body fore-and-aft/lateral acceleration, instead of estimating it directly from the tire slip ratio so that the road surface frictional coefficient is prevented from being estimated substantially higher than it actually is. In particular, by judging a sudden change in the road surface frictional coefficient only when a change in the road surface frictional coefficient, in particular an increase in the frictional coefficient, has persisted for more than a prescribed time period, an error in the estimation of the road surface frictional coefficient can be minimized, and a favorable vehicle motion control based on the estimated road surface frictional coefficient can be ensured under all conditions.

System for computing a road surface frictional coefficient

A traction control system for a vehicle, which, during normal driving of the vehicle, if a driven wheel speed becomes less than a deceleration-control starting reference value which is set lower than a vehicle speed, a feed-back control of an opening degree of a throttle valve is started so as to converge the driven wheel speed into a target driven wheel speed. If a downshifting is conducted, the feed-back control of the throttle valve opening degree is feed-back controlled by using, in place of the driven wheel speed, a pseudo driven wheel speed calculated based on the number of revolutions of an engine and a gear position. With this arrangement, it is possible to open the throttle valve at an earlier stage to increase a driven wheel torque, and to avoid a deceleration slip at the time of downshifting at a high speed.

Driven wheel slip controlling system for vehicle

A reduction in tire pressure in follower wheels and driven wheels is precisely determined irrespective of slipping states of the driven wheels through the use of apparatus wherein in a driven wheel slip amount calculating means M4 calculates a driven wheel slip amount KIDD as a left and right follower wheel speed difference FID and a left and right driven wheel speed difference RID; in a driven wheel torque calculating means M5, a driven wheel torque TQDW is calculated; in a driven wheel slip amount estimating means M6, a characteristic of variation in driven wheel slip amount KIDD relative to the variation in driven wheel torque TQDW is estimated using a least squares method; in a deviation calculating means M7, a deviation CKID between the follower wheel speed difference FID and the driven wheel speed difference RID in a state in which the driven wheels are not slipping, is calculated as an intercept of the driven wheel slip amount KIDD at a driven wheel torque equal to 0 (zero) in a graph of the variation characteristic; and in a wheel pressure-reduction determining means M8, a reduction in tire pressure is determined from a difference in diameter between the follower wheels and the driven wheels by comparing the deviation CKID with a reference value.

Wheel pressure-reduction determining system for vehicle

A slip rate of the driven wheel is calculated (at step S1). When the slip rate is smaller and when the slip rate is larger (at steps S2 and S3), estimated road surface friction coefficients MUTG and MUFG are determined by searching a table, based on a total grip force TGS or a longitudinal grip force FG determined from a vehicle acceleration (at steps S4, S7, S5 and S9). The larger one of the estimated road surface friction coefficients MUTG and MUFG is selected as MUCON (at steps S10, S11 and S12). A minimum total grip force TGMIN determined by searching a table and based on MUCON is compared with the total grip force TGS determined from the vehicle acceleration (at step S13), and the larger one of the minimum total grip force TGMIN and total grip force TGS is delivered as a total grip force TG for traction control (at steps S14 and S15). Thus, it is possible to estimate a correct total grip force, taking the road surface friction coefficient into consideration.

Total grip force estimating system for vehicle, and slip control system

A wheel diameter judging system and wheel speed correcting system which calculates a driven wheel slip rate, and a driven wheel torque. A variation characteristic of the driven wheel slip rate relative to the variation in driven wheel torque is presumed using the method of least squares. A correction value corresponding to a ratio of the number of revolutions of a follower wheel to the number of revolutions of a driven wheel in a condition in which the driven wheel is not in a slipping state is calculated as an intercept of the driven wheel slip rate at the driving torque equal to zero in a graph of the variation characteristic. The driven wheel speed is corrected by the correction value. The driven wheel speed is corrected by the correction value. Thus, even if the driven wheel is in the slipping state, a difference in diameter between the follower and driven wheels can be accurately judged, and the follower wheel speed or the driven wheel speed can be accurately corrected.

Wheel diameter difference judging system and wheel speed correcting

A reference value for a traction control is calculated based on a vehicle speed. When a vehicle is in a predetermined turning state, so that a driven wheel speed is equal to or lower than a predetermined value and a lateral acceleration is equal to or larger than a predetermined value, a correction value is searched from a table based on the vehicle speed and a steering angle to correct an error of the reference value generated due to a difference between the locus of the driven wheels and the locus of the follower wheels during turning of the vehicle. The reference value is corrected by subtracting the correction value from the reference value (when the vehicle is a rear wheel drive vehicle) or by adding the correction value to the reference value (when the vehicle is a front wheel drive vehicle. Thus, the reference value for the fraction control such as a reference value for a target slip rate can be accurately in accordance with the turning state of the vehicle.

Reference value correcting device in driven wheel slip control system

A reduction in pressure in tires fitted to follower wheels and driven wheels is precisely determined irrespective of slipping states of the driven wheels. A driven wheel slip rate calculating means M1 calculates driven wheel slip rates .lambda.L and .lambda.R. A driven wheel torque calculating means M2 calculates a driven wheel torque TQDW. A driven wheel slip rate estimating means M4 estimates a characteristic of variation in driven wheel slip rates .lambda.L and .lambda.R relative to the variation in driven wheel torque TQDW using a least squares method. A rotation-number ratio calculating means M5 calculates ratios CVWL and CVWR of the numbers of rotations of the follower wheels to the numbers of rotations of the driven wheels in a state in which the driven wheel torque in a graph of the variation characteristic is equal to zero. A tire pressure-reduction determining means M6 then determines a reduction in pressure from a difference in diameter between the follower wheels and the driven wheels by comparing the rotation-number ratios CVWL and CVWR with a reference value.

Tire pressure-reduction determining system for wheels of a vehicle

In a traction control system, an initial engine torque for a traction control is selected from the following engine torques: an engine torque calculated from a throttle opening degree and an engine revolution-number; a required engine torque calculated from a total acceleration and a vehicle speed; and an engine torque corresponding to a road surface of an extremely low friction coefficient, depending upon a slipping state determined by comparing a driven wheel speed with slip reference values. When the driven wheel speed repeatedly exceeds the slip reference value, it is determined that a hunting has been generated, and the engine torque corresponding to the road surface of the extremely low friction coefficient is selected, and the engine torque is largely reduced. Thus, when the friction coefficient of the road surface is low, the driven wheel speed is prevented from hunting.

Traction control system for vehicle

A first longitudinal grip force FGG is calculated by differentiating a vehicle body speed by time. A driven wheel torque is calculated from an engine torque and a second longitudinal grip force FGT is calculated from the driven wheel torque. The first longitudinal grip force FGG and the second longitudinal grip force FGT are compared with each other, and the higher one of such grip force is selected as a longitudinal grip force TG. When the vehicle travels on a normal flat road, the first longitudinal grip force FGG obtained from the vehicle body speed is selected. But when the vehicle travels on an ascent road, on which the first longitudinal grip does not indicate an accurate value, the second longitudinal grip force FGT obtained from the engine torque is selected. With this arrangement, the longitudinal grip force is accurately estimated even if the vehicle travels on such an ascent road.

Longitudinal grip force estimating device and slip control device for

The rotational speed difference between rotational speeds of front and rear road wheels of a motor vehicle is weighted by a first ratio, and the difference between the rotational speed difference between rotational speeds of front left and right road wheels and an average signal of reference steering angle or between the rotational speed difference between rotational speeds of rear left and right road wheels and the average signal of reference steering angle is weighted by a second ratio. A sum signal representative of the sum of the rotational speed difference weighted by the first ratio and the difference weighted by the second ratio is used to determine a pneumatic tire pressure reduction highly accurately even when running conditions of the motor vehicle change such as when the motor vehicle makes a turn.

System for determining pneumatic tire pressure for motor vehicle

A method for determining the fully-closed state of a subsidiary throttle valve. If a stable state judging circuit judges that there is no outside influence exerted on the operational state of the engine (a state in which the vehicle is stopped and the engine is in an idling state) even if the subsidiary throttle valve is fully closed, a valve closing circuit closes the subsidiary throttle valve and a fully-closed state determination is carried out. If the opening degree of the subsidiary throttle valve or the engine revolution number is largely varied during the determination process of the fully-closed state determination circuit, a valve-closing inhibiting circuit inhibits the closing of the subsidiary throttle valve to discontinue the determination. Even if all of the conditions for determination are satisfied again, the closing of the subsidiary throttle valve and the restarting of determination by the fully-closed state determination circuit are inhibited until the comparator circuit judges that the vehicle starts traveling and vehicle speed exceeds a reference value.

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Tochigi, Japan

Osamu Yano