JP6740741B2 - Road gradient estimating device and road gradient estimating method - Google Patents

Description

The present invention relates to a road surface gradient estimation device and a road surface slope estimation method, and more particularly to a road surface gradient estimation device and a road surface gradient estimation method for estimating a road surface gradient with high accuracy.

When estimating the vehicle inclination angle, if the fluctuation range of the road surface gradient during traveling of the vehicle is within a predetermined range, a device that estimates the vehicle inclination angle while the vehicle is stopped has been proposed (for example, Patent Document 1). reference). If there are steps, irregularities, obstacles, etc. on the road surface during driving and the road surface temporarily changes in the vertical direction, the fluctuation range of the road surface gradient is large and it is possible that the road surface gradient is estimated to be unrealistic. is there. Therefore, in such a case, this device prohibits the estimation of the vehicle inclination angle while the vehicle is stopped.

JP, 2005-141157, A

By the way, even when the driving state of the vehicle changes suddenly, there is a possibility that the unrealistic road surface gradient is estimated.

However, if there is a possibility of estimating an unrealistic road surface gradient as in the above-mentioned device, if the estimation is prohibited, the frequency of estimating the road surface gradient may decrease. Therefore, there is a possibility that the acceleration control, the shift control, the deceleration control, or the like based on the road surface slope may be hindered.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a road surface gradient estimation device and a road surface gradient estimation method that estimate a road surface gradient with high accuracy without reducing the estimation frequency of the road surface gradient. It is to be.

A road gradient estimating device of the present invention to achieve the above object, a vehicle speed acquisition means for acquiring the vehicle speed of the vehicle, an acceleration acquisition means for acquiring the longitudinal acceleration of the vehicle, the vehicle speed acquired by the vehicle speed acquisition means and The acceleration acquired by the acceleration acquisition unit is input, and the estimation unit estimates the estimated value of the road surface gradient on which the vehicle is traveling based on the input vehicle speed and acceleration, and the estimation estimated by the estimation unit. A value is input, based on the gradient change rate of the input estimated value with respect to the travel distance or travel time of the vehicle, the limiting means for limiting the estimated value, and the value output from the limiting means. Filter means for performing a filtering process with a low-pass filter having a variable time constant, and a numerical value relating to the factor of the posture change of the vehicle are input, and the time constant is determined according to the input numerical value relating to this factor. And changing means for changing .

A road surface gradient estimating method of the present invention for achieving the above object obtains a vehicle speed and a longitudinal acceleration of the vehicle, and a road surface on which the vehicle is traveling based on the obtained vehicle speed and acceleration. In the road surface gradient estimating method for estimating the gradient, the gradient change rate for the moving distance or the traveling time of the vehicle based on the estimated value estimated based on the vehicle speed and acceleration is calculated, and based on the calculated gradient change rate, The estimated value is limited, and the value obtained by limiting the estimated value is filtered by a low-pass filter having a time constant that is changed based on a numerical value related to a factor of the posture change of the vehicle. Is the method.

According to the present invention, since the estimated value is limited based on the gradient change rate of the estimated value, an unrealized estimated value is obtained due to a change in the posture of the vehicle caused by the driving state of the vehicle or the road surface condition. Even if estimated, the estimated value can be brought closer to the actual road gradient by the limitation. This is advantageous for suppressing the deviation of the estimated value from the actual road surface slope, and the road surface slope estimation error can be reduced. As a result, the road surface gradient can be estimated with high accuracy without reducing the frequency of estimating the road surface gradient.

It is explanatory drawing which illustrates 1st embodiment of the road surface gradient estimation apparatus of this invention. It is a block diagram which illustrates the control apparatus of FIG. FIG. 3 is a block diagram illustrating a road surface gradient calculation unit in FIG. 2. It is a correlation diagram which illustrates the relationship between a vehicle speed and a reference gradient rate. It is a flowchart which illustrates 1st embodiment of the road surface gradient estimation method of this invention. It is a block diagram which illustrates the road surface gradient calculation part of 2nd embodiment of the road surface gradient estimation apparatus of this invention. FIG. 4 is a relationship diagram illustrating a relationship between an engine speed and a fuel injection amount, and an output torque of the engine. It is a relationship diagram which illustrates the relationship between a vehicle speed and a high time constant. It is a relationship diagram which illustrates the relationship between a vehicle speed and a low time constant. It is a flowchart which illustrates 2nd embodiment of the road surface gradient estimation method of this invention.

Embodiments of a road surface gradient estimating device and a road surface gradient estimating method of the present invention will be described below. In the following, the estimated road surface slope is the longitudinal slope of the road, and the road surface slope of the uphill road is positive and the road surface slope of the downhill road is negative.

The road surface gradient estimation device 30 of the first embodiment illustrated in FIGS. 1 to 4 is a device that is mounted on a vehicle 10 and estimates the road surface gradient on which the vehicle 10 is traveling.

As illustrated in FIG. 1, in a vehicle 10 in which a road surface gradient estimation device 30 is mounted, a driver's cab (cab) 12 is arranged as a driver unit on the front side of a chassis 11, and a body 13 is arranged on the rear side of the chassis 11. Has been done.

An engine 14, a clutch 15, a transmission 16, a propeller shaft 17, and a differential gear 18 are installed in the chassis 11. The rotational power of the engine 14 is transmitted to the transmission 16 via the clutch 15. The rotational power changed by the transmission 16 is transmitted to the differential gear 18 through the propeller shaft 17 and distributed as a driving force to a pair of driving wheels 19 which are rear wheels.

The control device 20 is electrically connected to the engine 14, the clutch 15, the transmission 16, and various sensors via a signal line indicated by a chain line. As various sensors, the driver's cab 12 is provided with an accelerator opening sensor 22 for detecting an accelerator opening based on a depression amount of an accelerator pedal 21, and a position sensor 24 for detecting a position of a shift lever 23. The chassis 11 is provided with an engine rotation speed sensor 25, a vehicle speed sensor 26, and an acceleration sensor 27 that detect the rotation speed of a crankshaft (not shown) of the engine 14.

The control device 20 is hardware that includes a CPU that performs various types of information processing, an internal storage device that can read and write programs used to perform the various types of information processing, and information processing results, and various interfaces.

As illustrated in FIG. 2, the control device 20 includes the engine 14, the clutch 15, and the transmission 1.
6, a control unit 28 for controlling the vehicle 6, a vehicle weight calculation unit 29 for calculating the vehicle weight of the vehicle 10, and a road surface gradient calculation unit 31 for calculating the road surface gradient on which the vehicle 10 is traveling. There is. In this embodiment, each functional element is stored as a program in the internal storage device, but each functional element may be configured by individual hardware.

The road surface gradient estimation device 30 of the present invention includes a road surface gradient calculation unit 31, a vehicle speed sensor 26, and an acceleration sensor 27. The detection values of these sensors are input, and the calculation result based on each detection value is calculated. Output as the output value θx. The road surface gradient calculation unit 31 functions as a vehicle speed acquisition unit, an acceleration acquisition unit, an estimation unit, and a restriction unit by using those sensors.

The vehicle speed sensor 26 is a device that functions as a vehicle speed acquisition unit. In this embodiment, the vehicle speed sensor 26 is a sensor that reads a pulse signal proportional to the rotation speed of the propeller shaft 17 and acquires the vehicle speed vx by the vehicle speed calculation process of the control device 20. .. Since the vehicle speed sensor 26 acquires the vehicle speed vx based on the pulse signal proportional to the rotation speed, the acquired vehicle speed vx is not negative but a value of zero or more. As the vehicle speed sensor 26, a sensor that acquires the vehicle speed vx from the rotational speeds of an output shaft (not shown) of the transmission 16, the drive wheels 19, the driven wheels, and the like may be used. When using a sensor that acquires the vehicle speed vx from the rotational speeds of the driving wheels 19 and the driven wheels, the rotational speeds of the pair of left and right wheels may be acquired and the average value thereof may be used as the vehicle speed vx. The vehicle speed sensor 26, which obtains the vehicle speed vx from the wheel rotation speed, is not affected by the rotation speed fluctuation of the propeller shaft 17 at the time of starting or accelerating, and is therefore preferably used when the rotation speed fluctuation of the propeller shaft 17 is large.

The acceleration sensor 27 is a device that functions as an acceleration acquisition unit. In this embodiment, the acceleration sensor 27 operates by an acceleration component accompanying a speed change in the longitudinal direction of the vehicle 10 and a gravitational acceleration component accompanying a posture change of the vehicle 10, This is a sensor that acquires an acceleration component parallel to the road surface, which is a combination thereof, that is, an acceleration Gx in the front-rear direction of the vehicle 10. Examples of the acceleration sensor 27 include a mechanical displacement measuring method, an optical method, and a semiconductor method.

As illustrated in FIG. 3, in this embodiment, the road surface gradient calculation unit 31 includes an estimation unit 32 and a restriction unit 33 as each functional element. Each functional element of the road surface slope calculation unit 31 is stored in the internal storage device as a program, but each functional element may be configured by individual hardware.

The estimation unit 32 is a functional element that receives the vehicle speed vx acquired by the vehicle speed sensor 26 and the acceleration Gx acquired by the acceleration sensor 27 and outputs an estimated value θz of the road surface gradient on which the vehicle 10 is traveling. The estimation unit 32 has a differentiation block 32a, an addition block 32b, a division block 32c, and an arc sine function block 32d. When it is considered that the road gradient is small, sin θ≈θ, and therefore the inverse sine function block 32d may not be used.

The limiting unit 33 is a functional element that receives the vehicle speed vx acquired by the vehicle speed sensor 26 and the estimated value θz output from the estimating unit 32, and outputs the output value θx with the estimated value θz limited based on them. .. In this embodiment, the limiting unit 33 has a late limiter block 33a, a look-up table block 33b, and a multiplication block 33c, and limits the estimated value θz by their functions.

The late limiter block 33a is a functional element that limits the input estimated value θz. Specifically, the rate limiter block 33a determines whether or not the gradient change rate α(dθz/dt) of the estimated value θz exceeds the limiting change rate βlim(vx·β), and the gradient change rate α is the limiting change rate. When βlim is exceeded, the estimated value θz is limited, while when the gradient change rate α is equal to or smaller than the limited change rate βlim, the estimated value θz is not limited.

The gradient change rate α is a change rate of the estimated value θz with respect to the travel time Δt of the vehicle 10, and is a value obtained by differentiating the estimated value θz output from the estimation unit 32 with respect to time. As the gradient change rate α, for example, a value obtained by dividing the estimated value θz estimated by the estimation unit 32 by a constant period (sampling time) for estimating the estimated value θz may be used.

The limit change rate βlim is a limit value of the change rate with respect to time, and is a value with which the unrealistic gradient change rate α can be specified. In this embodiment, the limit change rate βlim is obtained by multiplying the reference slope rate β (more accurately, dθb/dx), which is the change rate of the gradient with respect to the moving distance, by the vehicle speed vx to obtain the limit value of the change rate with respect to the moving time. It has been converted.

The lookup table block 33b is a functional element to which the vehicle speed vx acquired by the vehicle speed sensor 26 is input and which outputs to the multiplication block 33c a value corresponding to the input vehicle speed vx of the plurality of reference gradient rates β. The lookup table block 33b has a plurality of reference gradient ratios β set therein, and selects a reference gradient ratio β corresponding to the vehicle speed vx from the plurality of reference gradient ratios β.

The multiplication block 33c is a functional element that receives the vehicle speed vx and the reference gradient rate β and outputs the limited change rate βlim calculated by multiplying them to the late limiter block 33a.

In this embodiment, the reference gradient rate β(dθb/dx) is the longitudinal gradient specified by the Road Structure Ordinance of Japan. The vertical gradient is defined according to the road classification and road design speed. Roads are classified according to the combination of the area where the road exists (local area, urban area) and the function of the road (highway national road, motorway, general road). Design speed is the speed of the vehicle on which the road design is based.

As illustrated in FIG. 4, the reference gradient ratio β in this embodiment has a negative relationship with the vehicle speed vx, and becomes smaller stepwise as the vehicle speed vx becomes faster. The map data illustrated in FIG. 4 is obtained in advance by experiments and tests and stored in the lookup table block 33b. Further, the reference gradient rate β may use a constant value or a value specified by the Road Structure Ordinance.

Next, the road surface gradient estimating method according to the first embodiment of the present invention will be described as each function of the road surface gradient calculating section 31 with reference to the flowchart of FIG. The following road surface gradient estimation method is started when the control device 20 of the vehicle 10 is energized, and is repeatedly performed at regular intervals (sampling time) to estimate the road surface gradient in real time. Then, when the control device 20 loses power, the process ends.

When started, the vehicle speed sensor 26 acquires the vehicle speed vx, and the acceleration sensor 27 acquires the acceleration Gx (S110). Next, the road surface gradient calculation unit 31 estimates the estimated value θz of the road surface gradient on which the vehicle 10 is traveling by the function of the estimation unit 32 (S120). Specifically, the estimation unit 32 outputs a differential value vx′ obtained by time-differentiating the vehicle speed vx input by the differential block 32a. Next, the addition block 32b outputs a value obtained by subtracting the differential value vx' from the acceleration Gx as a gravitational acceleration component (Gx-vx') applied in the front-rear direction of the vehicle 10. Next, the division block 32c outputs a value obtained by dividing the gravitational acceleration component (Gx-vx') applied in the front-rear direction of the vehicle 10 by the gravitational acceleration g. Next, the inverse sine function block 32d estimates the estimated value θz by using the inverse sine function (sin ⁻¹ ) on the input value. When it is considered that the road gradient is small, sin θ≈θ, and therefore the inverse sine function block 32d may not be used.

Next, the road surface gradient calculating unit 31 calculates the limit change rate βlim by the function of the limiting unit 33 (S130). Specifically, in the limiting unit 33, the lookup table block 33b selects the reference gradient rate β(dθb/dx) based on the input vehicle speed vx. Then, the reference gradient rate β selected by the multiplication block 33c is multiplied by the vehicle speed vx to calculate the limit change rate βlim(vx·β).

Next, the road surface gradient calculation unit 31 determines whether the gradient change rate α based on the estimated value θz exceeds the limited change rate βlim by the function of the limitation unit 33 (S140). Next, when the road surface gradient calculation unit 31 determines that the slope change rate α exceeds the limit change rate βlim by the function of the limit unit 33, the road surface slope calculation unit 31 sets the estimated value θz to a value at which the slope change rate α becomes the limit change rate βlim. (S150). On the other hand, when it is determined that the gradient change rate α is less than or equal to the limit change rate βlim, the estimated value θz is output without limitation.

Specifically, in the limiting unit 33, the rate limiter block 33a calculates a gradient change rate α obtained by time-differentiating the estimated value θz, and when the gradient change rate α exceeds the limited change rate βlim, the estimated value θz is calculated. While limiting, when not exceeding, the estimated value θz is output.

Next, the road surface slope computing unit 31 outputs the value output from the late limiter block 33a as the output value θx by the function of the limiting unit 33 (S160). And it returns to the start.

As described above, since the estimated value θz is limited based on the estimated gradient change rate α of the estimated value θz, it is unrealistic due to the posture change of the vehicle 10 caused by the driving state of the vehicle 10 or the road surface condition. Even if such an estimated value θz is estimated, the estimated value θz can be brought close to the actual road surface gradient by the limitation. This is advantageous for suppressing the deviation of the estimated value θz from the actual road surface gradient, and the road surface gradient estimation error can be reduced. As a result, the road surface gradient can be estimated with high accuracy without reducing the frequency of estimating the road surface gradient.

Further, by limiting the estimated value θz, noise such as an error due to the accuracy or sensitivity of the sensor itself can be removed, which is advantageous for improving the road surface gradient estimation accuracy. In addition, there is no output delay due to the filter processing, and the responsiveness of the road surface gradient estimation can be secured, as compared with the conventional technique that uses only a low-pass filter that removes noise when estimating the road surface gradient. This is advantageous for estimating the road surface gradient in real time, and the accuracy of estimating the road surface gradient when the driving state of the vehicle 10 or the road surface temporarily changes can be improved.

In this embodiment, when the gradient change rate α exceeds the limiting change rate βlim, the estimated value θz is limited to a value at which the gradient change rate α becomes the limiting change rate βlim. Therefore, when the estimated value θz becomes a value that cannot be realistic, the estimated value θz can be brought close to the actual road surface slope by the restriction. This suppresses the deviation between the estimated value θz and the actual road surface gradient, which is advantageous for reducing the road surface gradient estimation error.

In this embodiment, since the limiting unit 33 limits the estimated value θz by the late limiter block 33a, the number of blocks required for parameter setting and estimation can be reduced. This is advantageous for reducing the number of sensors and simplifying the road surface gradient estimation process.

In this embodiment, the limit change rate βlim is set to a value based on the vehicle speed vx and the reference gradient rate β, and the reference gradient rate β is defined by the Road Construction Ordinance according to the design speed of the road. The vertical gradient is set. As a result, the limit change rate βlim can be varied according to the road surface gradient of the road on which the vehicle 10 is actually traveling, which is advantageous for reducing the road surface gradient estimation error.

As the reference gradient rate β, for example, in addition to the vehicle speed vx, the road division in the road structure ordinance may be input to the lookup table block 33b and selected from these two elements. As a result, the reference gradient ratio β is subdivided, which is advantageous for reducing the road surface gradient estimation error.

As described above, in this embodiment, the change rate of the estimated value θz with respect to the travel time Δt of the vehicle 10 is used as the gradient change rate α, but the estimated value θz with respect to the travel distance Δx of the vehicle 10 is used as the gradient change rate α. You may use the change rate of. In this case, the gradient change rate α may be obtained by dividing the estimated value θz by time differentiation and dividing the value by the vehicle speed vx. Further, as the limit change rate βlim, the vertical gradient defined by the Road Structure Ordinance can be used as it is. As a result, the parameters required for calculating the limit change rate βlim can be reduced, which is advantageous for reducing the number of sensors and simplifying the road surface gradient estimation process.

As illustrated in FIGS. 6 to 9, the road surface gradient estimation device 30 of the second embodiment is different from the first embodiment in that a filter unit 34 is interposed after the restriction unit 33.

As illustrated in FIG. 6, in this embodiment, the road surface gradient calculation unit 31 has a filter unit 34 and a changing unit 35 in addition to the functional elements of the first embodiment. Each of these functional elements is stored as a program in the internal storage device, but may be configured by individual hardware.

In this embodiment, the filter unit 34 is a low-pass filter with a first-order lag and is lower than a cutoff frequency fc (=1/(2π×Tc)) defined by a variable time constant tc with respect to the estimated value θz. It is a variable low-pass filter that allows low-frequency components to pass through without being substantially attenuated, while performing filtering to reduce high-frequency components higher than the cut-off frequency fc and outputting them. The variable low-pass filter is represented by the transfer function represented by the following mathematical expression (1). Here, K is a gain in the pass band, and S is a variable of Laplace transform. A discrete time transfer function is used by discretizing the transfer function represented by the following mathematical expression (1). It should be noted that the low-pass filter is not limited to only the first order, and a high-order low-pass filter may be applied.

As the filter unit 34, for example, a unit configured by a constant multiplication block, an addition block, and an integration block and performing feedback addition of the result of one-time integration may be used.

The changing unit 35 is a functional element that receives the output torque Tx of the engine 14 as a numerical value related to the factor of the posture change of the vehicle 10 and outputs a time constant tc corresponding to the output torque Tx to the filter unit 34.

In this embodiment, the changing unit 35 has a switch block 35a and data blocks 35b, 35c, and 35d, and changes the time constant tc of the variable low-pass filter by these functions. Specifically, when the output torque Tx exceeds the preset threshold value Ta, the changing unit 35 sets the time constant tc to the high time constant th. On the other hand, when the output torque Tx becomes equal to or less than the threshold value Ta, the changing unit 35 sets the time constant tc to the low time constant tl.

The threshold value Ta is set to a value that can specify the occurrence of the posture change of the vehicle 10 due to the pitching motion from the magnitude of the numerical value relating to the factor of the posture change of the vehicle 10 or the amount of change in the numerical value. In particular, it is desirable that the threshold value Ta be set to a value that can specify the occurrence of the posture change due to the pitching motion in the extremely low speed region. The extremely low speed region is a region where the vehicle speed sensor 26 cannot detect the vehicle speed vx or detects zero. That is, the extremely low speed region includes a state in which the vehicle 10 is not moving, a state in which the vehicle 10 is moving, or a state in which the vehicle 10 has a short moving distance and the vehicle speed sensor 26 cannot detect a pulse.

As illustrated in FIG. 7, the output torque Tx has a positive relationship with each of the engine rotation speed Nx and the fuel injection amount Qx, and increases as the engine rotation speed Nx increases and the fuel injection amount Qx increases. .. This map data is obtained in advance by experiments and tests and stored in the data block 35b.

The data block 35c is a functional element that receives the vehicle speed vx and outputs a high time constant th corresponding to the vehicle speed vx. The data block 35d is a functional element that receives the vehicle speed vx and outputs a low time constant tl corresponding to the vehicle speed vx. The high time constant th is set to a value larger than the low time constant tl at the same vehicle speed vx.

As illustrated in FIG. 8, the high time constant th has a negative relationship with the vehicle speed vx until it becomes a constant value, and becomes smaller as the vehicle speed vx becomes faster. As illustrated in FIG. 9, the low time constant tl has a negative relationship with the vehicle speed vx until reaching the lower limit value t0, and becomes smaller as the vehicle speed vx becomes faster. These map data are obtained in advance by experiments and tests and stored in the data blocks 35c and 35d, respectively. The high time constant th and the low time constant tl are calculated by assuming that the vehicle speed vx is zero when the vehicle speed sensor 26 cannot detect the vehicle speed vx. The lower limit value t0 is a time constant capable of removing only noise that does not accompany changes in the attitude of the vehicle 10, such as an error due to the accuracy or sensitivity of the sensor itself, and is set by a weighted average (additional average).

As illustrated in FIG. 10, the road surface gradient estimating method according to the second embodiment of the present invention differs from the first embodiment in the step of performing the filtering process.

Similar to the first embodiment, the estimated value θz is limited by the function of the limiting unit 33, and at the same time, the time constant tc is changed by the function of the changing unit 35 by parallel processing. The road surface gradient estimation device 30 calculates the output torque Tx of the engine 14 by the function of the changing unit 35 (S210).

Next, the road surface gradient estimation device 30 determines whether or not the output torque Tx exceeds the threshold value Ta by the function of the changing unit 35 (S220). Next, when the road surface gradient calculating unit 31 determines that the output torque Tx exceeds the threshold value Ta by the function of the changing unit 35, it changes the time constant tc to the high time constant th (S230). On the other hand, when the output torque Tx is determined to be equal to or less than the threshold value Ta, the time constant tc is changed to the low time constant tl (S240).

Specifically, in the changing unit 35, the switch block 35a compares the output torque Tx with the threshold value Ta. When the output torque Tx exceeds the threshold value Ta, the data block 35c outputs the high time constant th corresponding to the vehicle speed vx as the time constant tc. On the other hand, when the output torque Tx does not exceed the threshold value Ta, the data block 35d outputs the low time constant tl corresponding to the vehicle speed vx as the time constant tc.

Next, the road surface slope computing unit 31 almost attenuates the frequency component lower than the cutoff frequency fc determined by the input time constant tc with respect to the estimated value θz limited by the limiting unit 33 by the filter unit 34. Filtering processing is performed to allow high frequency components higher than the cutoff frequency fc to be gradually reduced while allowing light to pass through without being processed (S250).

Next, the road surface gradient calculation unit 31 outputs the filtered value as the output value θx by the function of the filter unit 34 (S160).

Thus, in this embodiment, when the gradient change rate α exceeds the limiting change rate βlim by the limiting unit 33, the estimated value θz is limited to a value at which the gradient change rate α becomes the limiting change rate βlim. To do. Further, the filter unit 34 performs a filtering process on the value subjected to the limit by the limit unit 33. Therefore, when the estimated value θz becomes a value that is practically impossible, the estimated value θz can be approximated to the actual road surface slope by the restriction, and the noise can be removed by the filter processing. This reliably suppresses the deviation between the estimated value θz and the actual road surface gradient by both the restriction and the filtering process, which is advantageous for reducing the road surface gradient estimation error and makes the road surface gradient more accurate. Can be estimated.

Further, in this embodiment, since the value restricted by the restricting unit 33 is input to the filter unit 34, it is possible to perform the filtering process on the value that is restricted and is actually brought close to the road surface gradient. As a result, the time constant tc can be made smaller than in the conventional technique in which only the filter processing is performed, which is advantageous for reducing the estimation error due to both the limitation and the filter processing and avoiding the output delay due to the filter processing. The road gradient can be estimated with high accuracy and in real time.

In this embodiment, in addition to the restriction, when the output torque Tx of the engine 14 exceeds the threshold value Ta, it is specified that the vehicle 10 has a pitching motion, and the time constant tc of the filtering process is increased to increase the cutoff frequency fc. Lower. Therefore, even if the longitudinal acceleration of the vehicle 10 is actually generated, it is advantageous to identify the posture change due to the pitching motion in the extremely low speed region where the vehicle speed vx cannot be detected, and the posture change is regarded as a temporary change. Can be removed as noise by filtering. Thereby, the estimation error of the road surface gradient can be reduced.

In particular, in this embodiment, the output torque Tx of the engine 14 is compared with the threshold value Ta, so that even if the vehicle speed sensor 26 cannot detect the vehicle speed vx at the moment when the vehicle 10 starts, a pitching motion is specified for the vehicle 10. it can. This is advantageous for reducing the estimation error due to the pitching motion occurring in the vehicle 10.

Further, in this embodiment, since the time constant tc is made variable according to the vehicle speed vx, it is possible to optimize the noise removal effect and the responsiveness that are in a trade-off relationship according to the changing speed of the road surface gradient. As a result, when the vehicle speed vx is high and there is little noise, the time constant tc can be reduced to improve the responsiveness of road surface gradient estimation. On the other hand, when the vehicle speed vx is slow and the response may be slow, the time constant tc can be increased to enhance the noise removal effect.

In this embodiment, the example in which the output torque Tx of the engine 14 is used as the numerical value regarding the factor of the attitude change of the vehicle 10 has been described. The numerical value related to the factor is a numerical value that changes the posture of the vehicle 10 due to the change of the numerical value.

Numerical values related to this factor include the differential value vx′ of the vehicle speed vx, the variation amount of the differential value vx′, the acceleration Gx, the variation amount of the acceleration Gx, the estimated variation amount of the estimated value θz, the torque required for driving, and the variation amount of the torque. The operation command of the driver of the vehicle that adjusts the torque, or the change amount of the operation command can be exemplified. When the acceleration Gx is used, it is preferable to use a filter so as to exclude the gravitational acceleration component due to the posture change of the vehicle 10. As the amount of change in the estimated value θz, the difference between the estimated value θz and the output value θ(x−1) which is the previous value can be exemplified. Examples of the torque include the output torque Tx of the engine 14 and the drive torque Tw transmitted to the drive wheels 19 via the propeller shaft 17. Examples of the operation command include an accelerator opening Ax indicating the amount of depression of the accelerator pedal 21, and an amount of depression of a brake pedal (not shown).

In this embodiment, the configuration in which the changing unit 35 changes the time constant tc depending on the magnitude of the output torque Tx has been described as an example, but the changing unit 35 may change the time constant tc. For example, in addition to the magnitude of the output torque Tx, the time constant tc may be changed depending on the magnitude of the differential value vx′, the magnitude of the accelerator opening Ax, and the like. In this case, the maximum value of the values output from the plurality of changing units is output as the time constant tc, or the plurality of changing units are prioritized, and the value with the higher priority is set to the time constant tc. As the output torque Tx, the magnitude of the output torque Tx, the magnitude of the differential value vx′, and the magnitude of the accelerator opening Ax, and perform a logical operation on each threshold determination result, and change the time constant tc based on the result. To do

Further, the time constant tc may be changed by distinguishing the situation between the case where the driving force of the vehicle 10 is positive, the case where the braking force is positive, and the case other than that. Here, regardless of whether the vehicle 10 is moving forward or backward, the driving force when the driving force of the driving wheel 19 is generated is positive, and the braking force when the driving force of the driving wheel 19 is generated is positive.

For example, when the driving force is positive, the time constant tc is changed by a plurality of changing units such as the output torque Tx, the differential value vx′, and the accelerator opening Ax. , The time constant tc is changed only by the magnitude of the differential value vx′, and the lower limit t0 is set otherwise.

In this way, if the time constant tc is changed by a plurality of changing parts, the vehicle 10 becomes large even if the vehicle speed or acceleration cannot be detected in an extremely low vehicle speed region, or the weight of the vehicle 10 becomes light and the output torque Tx is equal to or less than the threshold value Ta. The error due to the pitching motion such as acceleration can be removed as noise. This is advantageous for reducing the estimation error of the road surface gradient, and the road surface gradient can be estimated with high accuracy. Further, when the time constant tc is changed based on not only the physical quantity such as the output torque Tx and the differential value vx′ but also the operation quantity such as the accelerator opening Ax, the estimation error of the road surface gradient is reduced even when the physical quantity cannot be acquired. Will be an advantage.

In addition, when the driving force is positive, the braking force is positive, and the other cases, the conditions are differentiated and the time constant tc is changed to a time constant tc corresponding to the traveling condition of the vehicle 10. Since it can be set, it is advantageous to reduce the estimation error of the road surface gradient which differs depending on the driving situation.

In any of the configurations, the value limited by the limiting unit 33 is input to the filter unit 34, so that the value that is actually limited to the road surface gradient can be filtered. This is advantageous in reducing the time constant tc of the filter processing as compared with the case of removing the noise only by the filter processing, and the estimation delay can be avoided.

In the above-described embodiment, the vehicle 10 is described as an example of a large vehicle such as a truck, but the road surface gradient estimation device 30 of the present invention can be applied to a bus, an ordinary vehicle, and a towing vehicle (tractor). The type is not limited.

Further, in the above-described embodiment, the road surface gradient estimation device 30 is described as an example including the road surface slope calculation unit 31, the vehicle speed sensor 26, and the acceleration sensor 27, but the present invention is not limited to this. For example, the road surface gradient estimation device 30 may be composed of one sensor that functions as a vehicle speed acquisition unit, an acceleration acquisition unit, an estimation unit, and an output unit, and hardware that functions as a restriction unit.

In the above-described embodiment, the configuration in which the limiting unit 33 has the late limiter block 33a has been described as an example, but the present invention is not limited to this. For example, the block for calculating the gradient change rate α by differentiating the estimated value θz with time, the block for determining whether or not the calculated gradient change rate α exceeds the input limit change rate βlim, and the gradient change rate α are A block that limits the estimated value θz when the limit change rate βlim is exceeded, and a block that does not limit the estimated value θz when the gradient change rate α is equal to or less than the limit change rate βlim may be used.

Further, in the above-described embodiment, the limiting unit 33 limits the estimated value θz to a value at which the gradient change rate α becomes the limited change rate βlim when the gradient change rate α exceeds the limited change rate βlim. Although the configuration has been described as an example, the present invention is not limited to this. For example, a value obtained by adding an integrated value obtained by time-integrating the limiting change rate βlim to the previous value θ(x−1) output before estimating the estimated value θz may be output.

10 vehicle 26 vehicle speed sensor 27 acceleration sensor 30 road surface gradient estimation device 31 road surface gradient calculation unit 32 estimation unit 33 restriction unit θz estimated value vx vehicle speed Gx acceleration α slope change rate βlim limit change rate

Claims (5)

Vehicle speed acquisition means for acquiring the vehicle speed of the vehicle,
Acceleration acquisition means for acquiring the longitudinal acceleration of the vehicle,
The vehicle speed acquired by the vehicle speed acquisition means and the acceleration acquired by the acceleration acquisition means are input, and an estimation means for estimating an estimated value of a road gradient on which the vehicle is traveling based on the input vehicle speed and acceleration. When,
An estimated value estimated by the estimating means is input, and based on a gradient change rate with respect to the moving distance or traveling time of the vehicle of the input estimated value, limiting means for limiting the estimated value,
Filter means for performing filter processing with a low-pass filter having a variable time constant for the value output from the limiting means, and outputting
A road surface gradient estimating device comprising: a change means for inputting a numerical value relating to a factor of the vehicle attitude change and changing the time constant in accordance with the inputted numerical value relating to this factor . When the gradient change rate exceeds a preset limit change rate, the limiting unit limits the estimated value to a value at which the gradient change rate becomes the limit change rate. Road gradient estimating device. The road gradient estimating device according to claim 2, wherein the limit change rate is a value based on the vehicle speed and a reference gradient rate set according to the vehicle speed. A configuration in which the vehicle speed acquired by the vehicle speed acquisition means is input to the restriction means, and based on the vehicle speed, the restriction means selects a reference gradient rate corresponding to the vehicle speed from among the plurality of reference gradient rates. The road surface gradient estimating device according to claim 3. In a road surface gradient estimating method for acquiring a vehicle speed and a longitudinal acceleration of the vehicle, and estimating a road surface gradient on which the vehicle is traveling based on the acquired vehicle speed and acceleration,
Calculate a gradient change rate for the travel distance or travel time of the vehicle based on the estimated value estimated based on the vehicle speed and acceleration,
Based on the calculated rate of change of the gradient, limit the estimated value ,
A method of estimating a road surface gradient , wherein a value obtained by limiting the estimated value is filtered by a low-pass filter having a time constant changed based on a numerical value relating to a factor of a change in the attitude of the vehicle .

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