JP2016190603A - Road gradient estimation device and method of estimating road gradient - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a road gradient estimation device and a method of estimating road gradient that can improve accuracy of an estimation value of a road gradient by not directly detecting a centrifugal acceleration applied to a vehicle, when a driver operates a steering device.SOLUTION: The road gradient estimation device includes: wheel speed sensors 33a, 33b; radius calculation means 37 for calculating a turning radius R; steering angle calculation means 38 for calculating a steering angle θm; and component calculation means 39 for calculating a centrifugal acceleration Ac0 applied to a vehicle 10 on the basis of the turning radius R, and calculating a centrifugal acceleration component Ac on the basis of the centrifugal acceleration Ac0 and the calculated steering angle θm. Gradient estimation means 35 is configured to estimate an estimation gradient θx on the basis of a correction component Gc obtained by correcting a front-rear direction component Gs applied to the vehicle 10 by the centrifugal acceleration component Ac.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a road gradient estimation device and a road gradient estimation method, and more specifically, the accuracy of an estimated value of a road gradient without directly detecting the centrifugal acceleration applied to the vehicle when the driver operates the steering device. The present invention relates to a road gradient estimation device and a road gradient estimation method.

  While the vehicle is running, the vehicle is running for optimization of acceleration / deceleration control, regenerative control, and brake control of the vehicle, and for optimization of the start stage of the shift stage when starting the vehicle. Alternatively, it is necessary to accurately estimate the road gradient at which the vehicle is stopped.

  As a method of estimating a road gradient, a method of estimating based on a longitudinal component applied to a vehicle is common. This estimation method is, for example, an actual acceleration component of a vehicle acquired by a wheel speed sensor from a component parallel to the road surface among components applied to the vehicle acquired by a gravity sensor (G sensor), that is, a longitudinal component applied to the vehicle. Is a method of estimating the road gradient based on the gravitational acceleration component applied in the longitudinal direction of the vehicle calculated by subtracting. Examples of the longitudinal component applied to the vehicle include a gravitational acceleration component due to a road gradient and an acceleration component due to vehicle acceleration.

  However, when the vehicle changes its traveling path such as when turning right or left or during a U-turn, the longitudinal component applied to the vehicle includes a centrifugal acceleration component applied to the vehicle due to centrifugal acceleration. Cannot be estimated accurately.

  In view of this, there has been proposed an apparatus that calculates a centrifugal acceleration applied to a vehicle using a yaw rate sensor, a gyro sensor, or a lateral G sensor, and corrects the centrifugal acceleration to estimate a road gradient (for example, Patent Document 1). 2, 3).

  However, these devices use sensors that directly acquire the centrifugal acceleration applied in the left-right direction of the vehicle, such as a yaw rate sensor, a gyro sensor, or a lateral G sensor, so that the number of sensors mounted on the vehicle increases.

  In recent years, electronic control has become mainstream in vehicle control, and various sensors are mounted on the vehicle. As a result, it is necessary to devise the arrangement of the sensor, arrange complicated wiring, increase the number of connectors of the control device that receives the detection value of the sensor, and it is installed in addition to the cost of the sensor itself The cost on the vehicle side is also rising. Therefore, it is desired to reduce even the number of sensors mounted on the vehicle.

Japanese Patent Laid-Open No. 11-230742 JP-A 63-275913 JP 2001-356014 A

  The present invention has been made in view of the above problems, and the problem is that the accuracy of the estimated value of the road gradient is not detected without directly detecting the centrifugal acceleration applied to the vehicle when the driver operates the steering device. Is to provide a road gradient estimation device and a road gradient estimation method.

  A road gradient estimation apparatus according to the present invention for solving the above-described problem is a road gradient estimation apparatus including gradient estimation means for estimating an estimated road gradient based on a longitudinal component applied to the vehicle. Wheel speed acquisition means for acquiring each of the right wheel speed and the left wheel speed of the left front wheel, turning radius calculation means for calculating the turning radius of the vehicle, and cutting angle for calculating the turning angle of the right front wheel and the left front wheel. A centrifugal acceleration applied to the vehicle is calculated based on the angle calculation means, the right wheel speed and the left wheel speed acquired by the wheel speed acquisition means, and the turning radius calculated by the turning radius calculation means; Component calculating means for calculating a centrifugal acceleration component applied to the vehicle by the centrifugal acceleration based on the acceleration and the cutting angle calculated by the cutting angle calculating means, The estimation means, is characterized in that the front-rear direction component acting on the vehicle was configured to estimate the road gradient based on the correction component obtained by the correction in the centrifugal acceleration component.

  The road gradient estimation method of the present invention for solving the above problem is a road gradient estimation method for estimating an estimated gradient of a road based on a longitudinal component applied to the vehicle, wherein the right wheel speed of the right front wheel of the vehicle is And the left wheel speed of the left front wheel of the vehicle, the turning radius of the vehicle is calculated, the turning angle of the right front wheel and the left front wheel is calculated, and the acquired right wheel speed and the left wheel speed A centrifugal acceleration applied to the vehicle is calculated based on the calculated turning radius, and a centrifugal acceleration component applied to the vehicle is calculated based on the calculated centrifugal acceleration and the calculated cut angle. The road gradient is estimated based on a correction component obtained by correcting the longitudinal component applied to the vehicle with the centrifugal acceleration component.

  According to the road gradient estimation device and the road gradient estimation method of the present invention, when the driver operates the steering device, the turning radius and the turning angle are not used without using sensors such as a yaw rate sensor, a gyro sensor, and a lateral G sensor. The centrifugal acceleration applied to the vehicle is calculated based on the left wheel speed, the right wheel speed and the turning radius, and the centrifugal acceleration component applied to the vehicle is calculated based on the centrifugal acceleration and the cut angle. Since the road gradient is estimated based on the correction component obtained by correcting the longitudinal component applied to the vehicle with the centrifugal acceleration component, the accuracy of the estimated value of the road gradient can be improved without increasing the number of sensors.

  In particular, when the estimated gradient estimated when the centrifugal acceleration component due to the centrifugal acceleration applied to the vehicle is large, the estimated gradient can be eliminated by correcting the shift with the centrifugal acceleration component, By outputting a highly accurate estimated value of the road gradient, it is possible to prevent a gear having a high gear ratio from being selected at the time of start.

It is explanatory drawing which illustrates embodiment of the road gradient estimation apparatus of this invention. It is a flowchart which illustrates 1st embodiment of the road gradient estimation method of this invention. FIG. 2 is a bottom view of the vehicle in FIG. 1, illustrating the turning radius when the vehicle turns right, that is, when the left wheel is outside the turn and the right wheel is inside the turn. It is a block diagram which illustrates the radius calculation means of FIG. It is a block diagram which illustrates the cut angle calculation means of FIG. It is explanatory drawing which illustrates the centrifugal acceleration component applied to the vehicle of FIG. 1, and the centrifugal acceleration component based on the centrifugal acceleration. It is a block diagram which illustrates the component calculation means of FIG. It is a block diagram which illustrates the gradient estimation means of FIG. It is a block diagram which illustrates the correction means of FIG. It is a flowchart which illustrates 2nd embodiment of the road gradient estimation method of this invention. It is a block diagram which illustrates the cut angle calculation means of FIG. It is a block diagram which illustrates the radius calculation means of FIG.

  Hereinafter, the road gradient estimation apparatus and the road gradient estimation method of the present invention will be described. FIG. 1 illustrates the configuration of a road gradient estimation apparatus 30 according to an embodiment of the present invention. The road gradient estimation device 30 is mounted on the vehicle 10 and obtains an estimated value θz of the road gradient on which the vehicle 10 is traveling.

  In the vehicle 10, a cab 12 is disposed on the front side of the chassis 11, and a body 13 is disposed on the rear side of the chassis 11.

  In the vehicle 10, when a driver who has boarded the cab 12 operates the accelerator pedal 14 and the shift lever 15, a control device (not shown) controls the engine 16, the power transmission device (clutch) 17, and the transmission 18. With this control, the power output from the engine 16 is transmitted to the transmission 18 via the power transmission device 17, and further transmitted from the transmission 18 to the differential device 20 via the propulsion shaft 19. The vehicle travels by being transmitted from the moving device 20 to the rear wheels (drive wheels) 22 via the drive shaft 21. Further, when the driver operates the steering (steering device) 23 and the right front wheel 24a (the left front wheel 24b (not shown)) is steered via a steering system (not shown) during traveling, the traveling direction of the vehicle 10 is changed. change.

  In order to optimize the acceleration / deceleration control, regenerative control, and brake control of the vehicle 10 as described above, or to optimize the start stage of the transmission 18 when the vehicle starts, the vehicle 10 travels. It is required to accurately estimate the road gradient. Therefore, the vehicle 10 includes the road gradient estimation device 30 to estimate the road gradient during traveling.

  The road gradient estimation device 30 includes an electronic computer 31, a G sensor 32, a wheel speed sensor 33a (33b not shown), and a steering angle sensor 34.

  The electronic computer 31 has a gradient estimation unit 35 and a correction unit 36, and sequentially executes the gradient estimation unit 35 and the correction unit 36 while the vehicle 10 is running to estimate the road gradient and estimate the value. θz is obtained. As the gradient estimation means 35 and the correction means 36, a program stored and executed in the electronic computer 31 can be exemplified.

  The G sensor 32 acquires a component parallel to the road surface among the force components applied to the vehicle 10, that is, a longitudinal component Gs applied to the vehicle 10, and the wheel speed sensor 33a is a right wheel speed Va of the right front wheel 24a, a wheel speed sensor. 33b acquires the left wheel speed Vb of the left front wheel 24b. Further, the steering angle sensor 34 acquires the steering angle θn of the right front wheel 24a and the left front wheel 24b by the driver's operation of the steering wheel 23.

  The gradient estimation means 35 acquires the front-rear direction component Gs of the force applied to the vehicle 10 as a detection value of the G sensor 32, and the right wheel speed Va and the left wheel speed Vb as detection values of the wheel speed sensors 33a and 33b. Thus, the road gradient is estimated based on the longitudinal component Gs applied to the vehicle 10 and the actual acceleration component Av of the vehicle 10 to obtain the estimated gradient θx.

  The correcting unit 36 acquires the estimated gradient θx estimated by the gradient estimating unit 35, and the amount of change in the estimated gradient θx (the difference between the estimated gradient θx and the previous estimated value θ (z−1)) is included in the estimated gradient θx. In the case where the value is equal to or greater than a predetermined limit value θa, the correction gradient θy is obtained by correcting the amount of change to be equal to or less than the limit value θa.

  In other words, the correction means 36 is a means for eliminating the influence of the disturbance when the estimated gradient θx estimated by the estimation means 35 changes greatly due to the influence of the disturbance. Examples of the disturbance corrected by the correction unit 36 include unpredictable disturbances such as a change in road surface condition and a change in centrifugal acceleration due to the operation of the steering wheel 23 by the driver.

  The limit value θa is set to a value that eliminates the influence of the disturbance when the estimated gradient θx fluctuates greatly due to the influence of the disturbance or the like, that is, when the change amount becomes large. In this embodiment, a limit value is provided for the amount of change in the estimated gradient θx in a predetermined travel distance of the vehicle 10.

  For example, the upper limit of the change amount of the road gradient is 1% with respect to a distance of 1 m. Therefore, when the limit value θa is set to 1%, the change amount of the estimated gradient θx when the travel distance of the vehicle 10 is 1 m is set to 1% at the maximum, so that the change amount does not exceed 1% due to the influence of the disturbance. Thus, the estimation accuracy of the estimated value θz of the road gradient can be improved. The limit value θa is not limited to the above value, and may be any value that eliminates the influence of disturbance.

  The gradient estimating unit 35 and the correcting unit 36 calculate the estimated gradient θx and the corrected gradient θy while the vehicle 10 travels a unit distance (1 m). However, it is not limited to the unit distance, and may be calculated as needed when the unit time or the acceleration and speed of the vehicle 10 change.

  As described above, the road gradient estimation device 30 sets the estimated value θz to the estimated gradient θx when the change amount of the estimated gradient θx is less than the limit value θa, and estimates when the change amount of the estimated gradient θx is equal to or greater than the limit value θa. The estimated value of the road gradient can be accurately estimated by setting the value θz as the correction gradient θy and eliminating the influence of an unexpected disturbance.

  On the other hand, when the centrifugal acceleration component Ac based on the centrifugal acceleration applied to the vehicle 10 increases when the steering wheel 23 is steered by the driver, the value of the longitudinal component Gs applied to the vehicle 10 changes greatly. . Therefore, when the centrifugal acceleration component Ac increases, it is necessary to estimate the estimated gradient θx using the correction component Gc obtained by correcting the longitudinal component Gs with the centrifugal acceleration component Ac.

  Therefore, the road gradient estimation device 30 of the present invention includes a wheel speed sensor 33a provided as a wheel speed acquisition unit that acquires the right wheel speed Va of the right front wheel 24a and the left wheel speed Vb of the left front wheel 24b of the vehicle 10, 33b, radius calculating means 37 for calculating the turning radius R of the vehicle 10, turning angle calculating means 38 for calculating the turning angle θm of the right front wheel 24a and the left front wheel 24b, and detected values and calculation of the wheel speed sensors 33a and 33b. Component calculating means 39 for calculating the centrifugal acceleration Ac0 applied to the vehicle 10 based on the turning radius R and calculating the centrifugal acceleration component Ac based on the centrifugal acceleration Ac0 and the calculated turning angle θm. The The gradient estimation means 35 is configured to estimate the estimated gradient θx based on the correction component Gc obtained by correcting the longitudinal component Gs applied to the vehicle 10 with the centrifugal acceleration component Ac.

  As the radius calculation unit 37, the cut angle calculation unit 38, and the component calculation unit 39, a program stored and executed in the electronic computer 31 can be exemplified.

  A road estimation method performed by the road gradient estimation device 30 including the radius calculation unit 37, the turning angle calculation unit 38, the component calculation unit 39, and the gradient estimation unit 35 that estimates the estimated gradient θx based on the correction component will be described with reference to FIG. Will be described with reference to the flowcharts shown in FIG. 4 and the block diagrams shown in FIGS.

In this road estimation method, as shown in FIG. 2, first, in step S10, steps S100 to S170 are performed, and the right wheel speed Va and the left wheel speed Vb detected by the wheel speed sensors 33a and 33b are A turning radius R is calculated based on the wheel range (tread) T of the wheel shaft 25.

  Next, in step S20, steps S200 to S210 are performed, and the turning angle θm is calculated based on the turning radius R calculated in step S10 and the shaft distance (wheelbase) W of the drive shaft 21 and the front wheel shaft 25.

  Next, in step S30, steps S300 to S330 are performed to calculate the centrifugal acceleration Ac0 based on the right wheel speed Va, the left wheel speed Vb, and the turning radius R, and based on the centrifugal acceleration Ac0 and the turning angle θm. Thus, the centrifugal acceleration component Ac is calculated.

  Next, in step S40, steps S400 to S440 are performed to calculate the estimated gradient θx. Next, in step S50, steps S500 to S550 are performed to calculate the correction gradient θy. When the change amount of the estimated gradient θx is less than the limit value θa, the estimated value θz is set to the estimated gradient θx, and the estimated gradient θx When the amount of change in is more than the limit value θa, the estimated value θz is set to the correction gradient θy and the process returns to the start.

  More specifically, first, the electronic calculator 31 performs steps S100 to S170 by the radius calculating means 37 to calculate the turning radius R.

  FIG. 3 is a bottom view of the vehicle 10, and shows the turning radius R when the vehicle 10 turns right, that is, when the right front wheel 24a is inside the turn and the left front wheel 24b is outside the turn. Further, the wheel distance (tread) of the front wheel shaft 25 is T, the shaft distance (wheel base) which is the distance between the drive shaft 21 and the front wheel shaft 25 is W, the inner turning radius of the right front wheel 24a is Ra, and the outer side of the left front wheel 24b. Let the turning radius be Rb. Accordingly, the angular speed of the inner turning radius Ra is the right wheel speed Va, the angular speed of the outer turning radius Rb is the left wheel speed Vb, and the angular speed of the turning radius R is the speed V. In the present specification, it is assumed that the turning radius R passes through the middle of the wheel distance T of the front wheel shaft 25.

  Since the three angular velocities on the turning radius R, the inner turning radius Ra, and the outer turning radius Rb are all equal, the ratio of the turning radius R and the inner turning radius Ra is equal to the ratio of the speed V and the right wheel speed Va. The ratio of the turning radius R and the outer turning radius Rb is equal to the ratio of the speed V and the left wheel speed Vb. When the turning angle θm between the right front wheel 24a and the left front wheel 24b is small, the difference between the inner turning radius Ra and the outer turning radius Rb is substantially equal to the wheel distance T. Therefore, the difference between the turning radius R and the inner turning radius Ra is The distance between the outer turning radius Rb and the turning radius R is equal to the half of the distance T.

From the above, the first turning radius R1 based on the right wheel speed Va is calculated using the following formula (1), and the second turning radius R2 based on the left wheel speed Vb is used using the following formula (2). The average value of the calculated first turning radius R1 and second turning radius R2 is defined as the turning radius R.

  As shown in FIG. 4, first, in step S100, the right wheel speed Va and the left wheel speed Vb are added. Next, in step S110, an average value (speed of the vehicle 10) V of the right wheel speed Va and the left wheel speed Vb is calculated.

  Next, in step S120, the right wheel speed Va is subtracted from the speed V. Next, in step S130, the speed V is divided by the result of step S120. Next, in step S140, the first turning radius R1 is calculated by multiplying the result of step S130 by a half of the wheel distance T.

  Next, in step S150, the speed V is subtracted from the left wheel speed Vb. Next, in step S160, the speed V is divided by the result of step S150. Next, in step S170, the second turning radius R2 is calculated by multiplying the result of step S160 by a half value of the wheel distance T.

  Next, in step S180, the first turning radius R1 and the second turning radius R2 are added. Next, in step S190, an average value of the first turning radius R1 and the second turning radius R2 is calculated, and the turning radius R is calculated.

  In step S10, it is preferable to determine whether or not the speed V is equal to or higher than a predetermined extremely low speed Vd. The extremely low speed Vd is set based on the performance of the wheel speed sensors 33a and 33b. For example, if the performance limit of the wheel speed sensors 33a and 33b, that is, the speed limit value at which the wheel speed sensors 33a and 33b can accurately detect the wheel speeds Va and Vb is set to 5 km / h, the speed is set to 5 km / h. Is done. By making such a determination, it is possible to prevent erroneous estimation by using a turning radius R having a low accuracy at an extremely low speed Vd or less where the accuracy of the wheel speed sensors 33a and 33b is reduced. Further, in the situation where the speed V is less than the extremely low speed Vd, it is possible to eliminate the influence of disturbance such as when either the right front wheel 24a or the left front wheel 24b slips.

  Further, the accuracy can be further improved by detecting the slip of the right front wheel 24a and the left front wheel 24b and correcting the turning radius R based on the slip amount.

  In addition, in this embodiment, the speeds of the right front wheel 24a and the left front wheel 24b are detected by the wheel speed sensors 33a and 33b. Instead, a wheel speed sensor is disposed on the driving wheel 22 to detect the speed of the rear wheel. The turning radius R may be calculated, and in this case, errors due to the tread can be eliminated. Thus, for the turning radius R, an optimal calculation method can be selected depending on the position of the G sensor 32 and the like.

  Next, the electronic calculator 31 performs step S200 and step S210 by the cutting angle calculation means 38 to calculate the cutting angle θm.

As shown in FIG. 5, first, in step S200, the axial distance W is divided by the turning radius R. Next, in step S210, the cutting angle θm is calculated using the inverse sine function (sin ⁻¹ ) as the result of step S200. The axial distance W is determined by the type of the vehicle 10. For example, in a large vehicle such as a truck, the axial distance W is longer than that of a normal passenger car.

  Next, the electronic calculator 31 performs steps S300 to S330 by the component calculation means 39 to calculate the centrifugal acceleration Ac0 applied to the vehicle 10 based on the turning radius R, and based on the centrifugal acceleration Ac0 and the turning angle θm. Thus, the centrifugal acceleration component Ac is calculated.

  FIG. 6 shows a centrifugal acceleration Ac0 applied to the vehicle 10 and a centrifugal acceleration component Ac based on the centrifugal acceleration Ac0.

  As shown in FIG. 7, first, in step S300, the speed V calculated in steps S100 and S110 is squared. Next, in step S310, the result calculated in step S300 is divided by the turning radius R to calculate the centrifugal acceleration Ac0.

  Next, in step S320, a sine function (sin) is used for the cutting angle θm.

  Next, in step S330, the centrifugal acceleration Ac0 calculated in step S310 is multiplied by the sine function (sin θm) calculated in step S320, and a centrifugal acceleration component Ac is output.

  Since this centrifugal acceleration component Ac is proportional to the square of the speed V of the vehicle 10, the value becomes large when the speed V is high. In addition, the influence of the length of the axle distance W is also great. When the axle distance W is long, for example, in the case of a large vehicle such as a truck, the value is small, and when the axle distance W is short, for example, In some cases, the value will increase.

  Next, the electronic calculator 31 performs steps S400 to S440 by the gradient estimation means 35 to estimate the estimated gradient θx.

  As shown in FIG. 8, first, in step S400, the actual acceleration component Av of the vehicle 10 is calculated by differentiating the speed V calculated in step S100 and step S110 with respect to time, that is, calculating a time change of the speed V.

  Next, in step S410, the correction component Gc is calculated by correcting the centrifugal acceleration component Ac from the longitudinal component Gs. Next, in step S420, the acceleration component Av is subtracted from the correction component Gc to calculate the gravitational acceleration component Gr.

In step S430, the gravitational acceleration component Gr is divided by the gravitational acceleration component Gr. Next, in step S440, the estimated gradient θx is calculated using the inverse sine function (sin ⁻¹ ) as the result of step S430.

  Next, the electronic calculator 31 performs steps S500 to S550 by the correction unit 36 to estimate the correction gradient θy.

  As shown in FIG. 9, first, in step S500, an estimated value θ (z−1) of the previous road gradient is acquired. Next, in step S510, the previous estimated value θ (z−1) is subtracted from the estimated gradient θx. Next, in step S520, the absolute value of the result of step S510 is calculated. Next, in step S530, it is determined whether or not the result of step S520 is less than the absolute value of the limit value θa, and the determination result is sent to step S540.

In step S540, when the result of step S530 is less than the absolute value of the limit value θa, the estimated gradient θx is output as the estimated value θz of the road gradient. On the other hand, if the result of step S530 is equal to or greater than the absolute value of the limit value θa, the correction gradient θy is calculated by adding or subtracting the limit value θa to the previous estimated value θ (z−1) in step S550. In this step S550, if the value obtained by subtracting the previous estimated value θ (z−1) from the estimated gradient θx is positive, the limit value θa is subtracted, and if the value is negative, the limit value θa is added. In step S540, the correction gradient θy that is the result of step S550 is output as the estimated value θz.

  According to the road gradient estimation device 30 and the road gradient estimation method described above, when the driver operates the steering wheel 23, the turning radius R and the cut off are not used without using sensors such as a yaw rate sensor, a gyro sensor, and a lateral G sensor. The angle θm is calculated, the centrifugal acceleration Ac0 applied to the vehicle 10 is calculated based on the right wheel speed Va, the left wheel speed Vb, and the turning radius R, and the centrifugal acceleration Ac0 is calculated based on the centrifugal acceleration Ac0 and the turning angle θm. Is used to calculate the centrifugal acceleration component Ac applied to the vehicle 10, and the road gradient is estimated based on the correction component Gc obtained by correcting the longitudinal component Gs applied to the vehicle 10 with the centrifugal acceleration component Ac. The accuracy of the estimated value θz of the road gradient can be improved without increasing it.

  In particular, when the estimated gradient θx or the corrected gradient θy estimated when the centrifugal acceleration component Ac due to the centrifugal acceleration Ac0 applied to the vehicle 10 is large is significantly deviated from the actual road gradient, the deviation is expressed as a centrifugal acceleration component. It can be solved by correcting with Ac, and by outputting a highly accurate estimated value θz of the road gradient, it is possible to prevent a gear having a high gear ratio from being selected at the time of start.

  Further, according to the road gradient estimation device 30 and the road gradient estimation method, the turning radius R and the turning angle are used without using sensors other than the G sensor 32 and the wheel speed sensors 33a and 33b used in the gradient estimation means 35. The correction component Gc can be obtained by calculating θm and correcting the longitudinal component Gs applied to the vehicle 10 when the driver operates the steering wheel 23. That is, since the number of sensors is not increased, it is advantageous for cost reduction.

  FIG. 10 is a flowchart illustrating another example of the road gradient estimation method. In this road gradient estimation method, step S60 and step 70 are performed instead of step S10 and step S20, and in step S60, step S600 is performed based on the steering angle θn which is the detected value of the steering angle sensor 34. The cutting angle θm is calculated. Next, in step S70, steps S700 and S710 are performed, and the turning radius R is calculated based on the turning angle θm and the axial distance W.

  This road estimation method will be described with reference to the block diagrams shown in FIGS.

  First, the electronic calculator 31 performs step S600 by the cutting angle calculation means 38 to calculate the cutting angle θm.

  As shown in FIG. 11, in step S600, the steering angle θn which is the detected value of the steering angle sensor 34 is referred to the turning angle map M1 in which the turning angles θm of the front wheels 23a and 23b are set in advance based on the steering angle θn. Then, the cutting angle θm is calculated. This cut angle map M1 is set in advance with values obtained through experiments and tests.

  Next, the electronic calculator 31 performs steps S700 and S710 by the radius calculation means 37 to calculate the turning radius R.

As shown in FIG. 12, in step S700, a sine function (sin) is used for the cutting angle θm. Next, in step S710, the turning radius R is calculated by dividing the axial distance W by the result of step S700.

  According to this road estimation method, only by adding a steering angle sensor that is used in advance for controlling the steering system, without using sensors such as a yaw rate sensor, a gyro sensor, and a lateral G sensor, the turning radius R and the turning angle θm Since the centrifugal acceleration component Ac applied to the vehicle 10 is calculated, and the road gradient is estimated based on the correction component Gc obtained by correcting the longitudinal component Gs applied to the vehicle 10 with the centrifugal acceleration component Ac. The accuracy of the estimated value θz of the road gradient can be improved without increasing the number of sensors.

  Further, even when the accuracy of the detection values of the wheel speed sensors 33a and 33b is low due to the influence of disturbance, the turning radius R and the turning angle θm can be calculated. If the method of calculating the turning radius R in step S10, the accuracy may drop, but after calculating the turning angle θm from the steering angle θn, the turning radius R is calculated with high accuracy based on the turning angle θm. can do.

DESCRIPTION OF SYMBOLS 10 Vehicle 15 Shift lever 16 Engine 17 Power connection / disconnection apparatus 18 Transmission 30 Road gradient estimation apparatus 31 Computer 32 G sensor 33a, 33b Wheel speed sensor 34 Steering angle sensor 35 Gradient estimation means 36 Correction means 37 Radius calculation means 38 Cutting angle Calculation means 39 Component calculation means Gs Longitudinal direction component Av Acceleration component Gr Gravitational acceleration component Ac Centrifugal acceleration component Ac0 Centrifugal acceleration θx Estimated gradient θy Corrected gradient θz Estimated value θa Limit value Va Right wheel speed Vb Left wheel speed W Axle distance T Wheel distance R Turning radius θm Cutting angle θn Steering angle

Claims (6)

In a road gradient estimation device comprising gradient estimation means for estimating an estimated gradient of a road based on a longitudinal component applied to a vehicle,
Wheel speed acquisition means for acquiring the right wheel speed of the right front wheel and the left wheel speed of the left front wheel of the vehicle,
A turning radius calculating means for calculating a turning radius of the vehicle;
A cutting angle calculating means for calculating a cutting angle of the right front wheel and the left front wheel;
The centrifugal acceleration applied to the vehicle is calculated based on the right wheel speed and the left wheel speed acquired by the wheel speed acquisition means, and the turning radius calculated by the turning radius calculating means, and the centrifugal acceleration and the cutting angle are calculated. Component calculating means for calculating a centrifugal acceleration component applied to the vehicle by the centrifugal acceleration based on the turning angle calculated by the calculating means,
A road gradient estimation apparatus characterized in that the gradient estimation means is configured to estimate a road gradient based on a correction component obtained by correcting a longitudinal component applied to the vehicle with the centrifugal acceleration component.   The turning radius calculation means is configured to calculate the turning radius based on the right wheel speed and the left wheel speed acquired by the wheel speed acquisition means and a wheel distance of a front wheel axis of the right front wheel and the left front wheel. The road gradient estimation apparatus according to claim 1.   The road gradient estimation apparatus according to claim 1, wherein the turning radius calculation unit is configured to calculate the turning radius based on the turning angle acquired by the turning angle calculation unit and an axle distance of the vehicle. A steering angle obtaining means for obtaining a steering angle of the steering device of the vehicle;
4. The cut angle calculation unit according to claim 1, wherein the cut angle calculation unit is configured to calculate the cut angle with reference to a cut angle map in which the cut angle based on the steering angle is set in advance. 5. Road gradient estimation device.   3. The road gradient estimation device according to claim 1, wherein the turning angle calculation unit is configured to calculate the turning angle based on the turning radius acquired by the turning radius calculation unit and an axle distance of the vehicle. . In the road gradient estimation method for estimating the estimated gradient of the road based on the longitudinal component applied to the vehicle,
Obtaining the right wheel speed of the right front wheel of the vehicle and the left wheel speed of the left front wheel of the vehicle;
Calculating the turning radius of the vehicle,
Calculate the cutting angle of the right front wheel and the left front wheel,
Calculate the centrifugal acceleration applied to the vehicle based on the acquired right wheel speed and the left wheel speed and the calculated turning radius,
Calculating a centrifugal acceleration component applied to the vehicle by the centrifugal acceleration based on the calculated centrifugal acceleration and the calculated cut angle;
A road gradient estimation method for estimating a road gradient based on a correction component obtained by correcting a longitudinal component applied to the vehicle with the centrifugal acceleration component.