JP2018016088A - Road surface gradient estimation device and road surface gradient estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a road surface gradient estimation device for accurately estimating a road surface gradient by reducing an estimation error caused by a pitching motion generated in a vehicle, and a road surface gradient estimation method.SOLUTION: A road surface gradient estimation device 30 comprises a vehicle speed sensor 26, an acceleration sensor 27 and a road surface gradient calculation part 31. The road surface gradient calculation part 31 comprises: an estimation part 32 for estimating a road surface gradient; a filter part 34 for applying filter processing to an inputted value by using a low-pass filter having a variable time constant tc, and outputting it; and a change part 35 to which a differential value vx' which is obtained by time-differentiating a vehicle speed vx obtained by the vehicle speed sensor 26 is input, and which changes the time constant tc according to the differential value vx'.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a road surface gradient estimation device and a road surface gradient 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.

  There has been proposed an apparatus for performing a filtering process on the acquired vehicle speed time-differentiated value or the acquired longitudinal acceleration of the vehicle and estimating a road surface gradient based on the filtered value (see, for example, Patent Document 1). ). In this apparatus, when performing the filtering process, if the change rate of the road surface gradient is high, the filter gain in the filtering process is increased, that is, the time constant is decreased to weaken the filter characteristics and improve the responsiveness. .

JP 2013-184673 A

  By the way, even when the vehicle speed is high, if the acceleration of the vehicle increases, the vehicle undergoes a posture change such as a pitching motion. Therefore, the above device sets the strength of the filter characteristics using only the road surface gradient change speed as a parameter, so it is strongly influenced by noise caused by posture changes that occur when the vehicle suddenly accelerates or suddenly brakes. Therefore, the estimation accuracy of the road surface gradient may be reduced.

  The present invention has been made in view of the above, and an object thereof is to reduce an estimation error caused by pitching motion generated in a vehicle, and to estimate a road surface gradient with high accuracy and a road surface gradient. It is to provide an estimation method.

  The road surface gradient estimation device of the present invention that achieves the above object includes vehicle speed acquisition means for acquiring the vehicle speed of the vehicle, acceleration acquisition means for acquiring the longitudinal acceleration of the vehicle, vehicle speed acquired by the vehicle speed acquisition means, and The acceleration acquired by the acceleration acquisition means is input, the estimation means for estimating and outputting the road surface gradient on which the vehicle is traveling based on the input vehicle speed and acceleration, and the output from the estimation means A filter means for inputting a value, filtering the output value with a low-pass filter having a variable time constant for the inputted value, and outputting the vehicle speed obtained by the vehicle speed obtaining means, and calculating by time differentiation. Either calculated value or the value obtained by removing the gravitational acceleration component accompanying the change in posture of the vehicle from the acceleration acquired by the acceleration acquisition means is input. Is in, depending on the calculated acceleration input, it is characterized in that and a changing means for changing the time constant.

  The road surface gradient estimation method of the present invention that achieves the above object obtains the vehicle speed of the vehicle and the acceleration in the longitudinal direction of the vehicle, and calculates the road surface gradient on which the vehicle is traveling based on the acquired vehicle speed and acceleration. In the road surface gradient estimation method to be estimated, when filtering is performed with a low-pass filter having a variable time constant with respect to the estimated estimated value, the acquired vehicle speed is time-differentiated or the acquired acceleration is changed to the attitude change of the vehicle. In this method, the time constant is changed in accordance with one of the calculated accelerations excluding the accompanying gravitational acceleration component.

  According to the present invention, since the time constant of the low-pass filter used for the filter processing is changed to a value corresponding to the calculated acceleration, the vehicle posture change due to the pitching motion caused by the magnitude of the calculated acceleration is filtered as a temporary change. Can be removed as noise. This is advantageous in reducing the estimation error of the road surface gradient when the acceleration is large, such as when the vehicle starts, sudden acceleration, or sudden braking, and the road surface gradient can be estimated with high accuracy.

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 device of FIG. It is a block diagram which illustrates the road surface gradient calculating part of FIG. It is a relationship diagram which illustrates the relationship between a differential value and a regulation value. It is a flowchart which illustrates 1st embodiment of the road surface gradient estimation method of this invention. FIG. 6 is a flowchart illustrating a process of changing the time constant of FIG. 5. It is a block diagram which illustrates the road surface gradient calculating part of 2nd embodiment of the road surface gradient estimation apparatus of this invention. It is a flowchart which illustrates the process of changing the time constant of the road surface gradient calculating part of FIG. It is a block diagram which illustrates the road surface gradient calculating part of 3rd embodiment of the road surface gradient estimation apparatus of this invention. It is a block diagram which illustrates the road surface gradient calculating part of 4th embodiment of the road surface gradient estimation apparatus of this invention. It is a relationship diagram which illustrates the relationship between an engine speed and fuel injection quantity, and the output torque of an 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 block diagram which illustrates the road surface gradient calculating part of 5th embodiment of the road surface gradient estimation apparatus of this invention. It is a block diagram which illustrates the road surface gradient calculating part of 6th embodiment of the road surface gradient estimation apparatus of this invention.

  Embodiments of a road surface gradient estimation apparatus and a road surface gradient estimation method of the present invention will be described below. In the following, the road surface gradient to be estimated is a vertical road gradient, and the road gradient on the uphill road is positive, and the road gradient on the downhill road is negative.

  The road surface gradient estimation device 30 of the first embodiment illustrated in FIGS. 1 to 3 is a device that is mounted on the vehicle 10 and estimates the road surface gradient on which the vehicle 10 is traveling.

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

  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 is distributed as a driving force to the pair of driving wheels 19 as rear wheels.

The control device 20 is electrically connected to the engine 14, the clutch 15, the transmission 16, and various sensors via signal lines indicated by alternate long and short dash lines. As various sensors, the cab 12 includes
An accelerator opening sensor 22 that detects the accelerator opening degree from the depression amount of the accelerator pedal 21 and a brake opening sensor 24 that detects the brake opening degree from the depression amount of the brake pedal 23 are provided. The chassis 11 is provided with an engine speed sensor 25, a vehicle speed sensor 26, and an acceleration sensor 27 that detect the speed of a crankshaft (not shown) of the engine 14.

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

  As illustrated in FIG. 2, the control device 20 includes a control unit 28 that controls the engine 14, the clutch 15, and the transmission 16, a vehicle weight calculation unit 29 that calculates the vehicle weight of the vehicle 10, and the vehicle 10 traveling. A road surface gradient calculating unit 31 for calculating the road surface gradient is provided as each functional element. 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, an accelerator opening sensor 22, a brake opening sensor 24, a vehicle speed sensor 26, and an acceleration sensor 27, and the detection values of these sensors are input. The result calculated based on each detected value is output as the output value θx. The road surface gradient calculation unit 31 functions as vehicle speed acquisition means, acceleration acquisition means, drive factor acquisition means, braking factor acquisition means, estimation means, filter means, and change means using these sensors.

  The accelerator opening sensor 22 is a device that functions as a drive factor acquisition unit that acquires an operation command for adjusting the torque required to drive the vehicle 10 as one of numerical values related to the drive factor that defines the driving force of the vehicle 10. In this embodiment, the accelerator opening sensor 22 is a sensor that digitizes and outputs the depression amount of the accelerator pedal 21 as an operation command for adjusting the output torque Tx output from the engine 14 to the accelerator opening Ax.

  The brake opening sensor 24 is a device that functions as a braking factor acquisition unit that acquires an operation command for adjusting the braking force of the vehicle 10 as one of numerical values related to the braking factor that defines the braking force of the vehicle 10. In this embodiment, the brake opening sensor 24 depresses the brake pedal 23 as an operation command for adjusting the braking force applied to the driving wheel 19 and the driven wheel from a brake device (not shown) (mechanical brake, motor generator, etc.). Is a sensor that outputs a numerical value as a brake opening Bx. Instead of the brake opening sensor 24, a brake pressure sensor for acquiring a brake pressure such as a mechanical brake may be used.

  The vehicle speed sensor 26 is a device that functions as vehicle speed acquisition means. In this embodiment, the vehicle speed sensor 26 reads a pulse signal proportional to the rotational speed of the propeller shaft 17 and acquires it as 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 has a value of zero or more. As the vehicle speed sensor 26, a sensor that acquires the vehicle speed vx from the rotational speed of an output shaft (not shown) of the transmission 16, the drive wheel 19, the driven wheel, or the like may be used. In addition, when using the sensor which acquires vehicle speed vx from rotational speeds, such as a driving wheel 19 and a driven wheel, it is good to acquire each rotational speed of a pair of left and right wheels, and let the average value be the vehicle speed vx. The vehicle speed sensor 26 that obtains the vehicle speed vx from the rotational speed of the wheel is not affected by the rotational speed fluctuation of the propeller shaft 17 at the time of starting or accelerating, and is therefore preferably used when the rotational speed fluctuation of the propeller shaft 17 is large.

The acceleration sensor 27 is a device that functions as acceleration acquisition means. In this embodiment,
An acceleration component parallel to the road surface, which is operated 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, that is, an acceleration Gx in the longitudinal direction of the vehicle 10. It is a sensor which acquires. Examples of the acceleration sensor 27 include a mechanical displacement measurement 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, a filter unit 34, and a change unit 35 as functional elements. Each functional element of the road surface gradient calculation unit 31 is stored as a program in the internal storage device, 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 includes a differentiation block 32a, an addition block 32b, a division block 32c, and an inverse sine function block 32d. When it is considered that the road gradient is small, since sin θ≈θ, the inverse sine function block 32d may not be used.

  The filter unit 34 has a variable time constant tc, and is a functional element that receives the estimated value θz output from the estimating unit 32 and outputs an output value θx obtained by filtering the estimated value θz. is there. The time constant tc is output from the changing unit 35 described later.

In this embodiment, the filter unit 34 is a first-order low-pass filter, and almost eliminates low frequency components lower than the cutoff frequency fc (= 1 / (2π × tc)) defined by the time constant tc with respect to the estimated value θz. This is a variable low-pass filter that performs transmission with a high frequency component that is higher than the cut-off frequency fc while performing transmission without being attenuated. The variable low-pass filter is represented by a transfer function expressed by the following formula (1). Here, K is a passband gain and S is a Laplace transform variable. The transfer function shown in the following formula (1) is discretized and a discrete-time transfer function is used. Note that the low-pass filter is not limited to the first order but may be a high-order low-pass filter.

  The change unit 35 is a functional element that receives a differential value vx ′ obtained by time-differentiating the vehicle speed vx as a calculated acceleration and outputs a time constant tc corresponding to the differential value vx ′ to the filter unit 34.

  In this embodiment, the changing unit 35 includes a selection block 35a, a switch block 35b, a data block 35c, and an absolute value block 35d. The changing unit 35 changes the time constant tc of the variable low-pass filter with these functions. Specifically, when the driving force is positive, and when the driving force is equal to or less than zero and the braking force is equal to or less than zero, the changing unit 35 determines when the absolute value of the differential value vx ′ exceeds the threshold value α. While the constant tc is set to a specified value ts that is larger than the lower limit value t0, the time constant tc is set to the lower limit value t0 when the absolute value of the differential value vx ′ is less than or equal to the threshold value α. In addition, when the driving force is zero or less and the braking force is positive, the changing unit 35 sets the time constant tc to the specified value ts when the absolute value of the differential value vx ′ exceeds the threshold value β. When the absolute value of the differential value vx ′ falls below the threshold value β, the time constant tc is set to the lower limit value t0. That is, when the driving force is zero or less and the braking force is positive, the changing unit 35 sets the time constant tc to the specified value ts when the differential value vx ′ falls below the negative threshold (−β). On the other hand, when the differential value vx ′ exceeds the negative threshold value (−β), the time constant tc is set to the lower limit value t0.

  The threshold values α and β are set to values that can specify the occurrence of the posture change of the vehicle 10 due to the pitching motion from the differential value vx ′. In this embodiment, the threshold value α is a threshold value when the driving force is positive (during acceleration), and the threshold value β is a threshold value when the driving force is zero or less and the braking force is positive (during deceleration). The threshold values α and β may be set to different numerical values, or may be set to the same numerical value. When the threshold values α and β are set to the same numerical value, the selection block 35a can be omitted.

  The lower limit value t0 is a time constant that can remove only noise that does not accompany changes in the attitude of the vehicle 10, such as errors due to the accuracy and sensitivity of the sensor itself.

  The specified value ts is a time constant set to a value larger than the lower limit value t0. In this embodiment, the specified value ts is set according to the differential value vx ′, and even if the change in the estimated value θz becomes large due to the influence of the posture change of the vehicle 10 due to the pitching motion, the change is removed as noise. Possible time constant. The specified value ts may be set to a different value when the driving force is positive, and when the driving force is zero or less and the braking force is positive, or may be set to the same value.

  As illustrated in FIG. 4, the specified value ts has a positive relationship with the differential value vx ′ when the absolute value of the differential value vx ′ exceeds the threshold value α (β), and the differential value vx ′ is The bigger it gets, the bigger it gets. The map data illustrated in FIG. 4 is obtained in advance by experiments and tests and stored in the data block 35c. The specified value ts can be a constant value instead of the map data. As the prescribed value ts, for example, a time constant that makes the absolute value of the differential value vx ′ less than or equal to the threshold value α (β) may be used.

  The changing unit 35 is also a functional element that receives the accelerator opening Ax as a numerical value related to a driving factor and the brake opening Bx as a numerical value related to a braking factor, and selects threshold values α and β according to conditions.

  Specifically, the changing unit 35 assumes that the driving force is positive when the accelerator opening Ax is positive, and inputs the threshold value α to the switch block 35b by the function of the selection block 35a. On the other hand, when the accelerator opening Ax is equal to or smaller than zero and the brake opening Bx is positive, the braking force is regarded as positive and the threshold value β is input to the switch block 35b. When the accelerator opening Ax is less than or equal to zero and the brake opening Bx is less than or equal to zero, a threshold value α is input to the switch block 35b.

  The case where the driving force is positive is a case where a force for driving the driving wheels 19 is generated regardless of whether the vehicle 10 moves forward or backward. The case where the driving force is zero or less and the braking force is positive is a case where a force for braking the driving wheel 19 is generated, and a case where the brake device is operating. As a case where the driving force is zero or less and the braking force is zero or less, a case where the vehicle 10 is coasting can be exemplified.

  In this embodiment, the accelerator opening Ax is used as a numerical value related to the driving factor that defines the driving force of the vehicle 10. The numerical value related to the driving factor is a numerical value that can be acquired before the driving force of the vehicle 10 actually changes due to the change in the numerical value. Examples of numerical values relating to the driving factor include the output torque Tx of the engine 14 and the driving torque Tw transmitted to the driving wheels 19 via the propeller shaft 17, and the accelerator opening Ax as an operation command for adjusting those torques. Can be illustrated.

  Further, the brake opening degree Bx is used as a numerical value relating to a braking factor that defines the braking force of the vehicle 10. The numerical value related to the braking factor is a numerical value that can be acquired before the braking force of the vehicle 10 actually changes due to the change in the numerical value. Examples of the numerical value relating to the braking factor include the brake pressure of the brake device and the brake opening Bx as an operation command for adjusting the brake pressure.

  Next, the road surface gradient estimation method of the present invention will be described as each function of the road surface gradient calculation unit 31 with reference to the flowcharts of FIGS. 5 and 6. 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, the control device 20 ends when a power failure occurs.

  When this flow starts, the road surface gradient estimation device 30 uses the accelerator opening sensor 22 to set the accelerator opening Ax, the brake opening sensor 24 to use the brake opening Bx, the vehicle speed sensor 26 to use the vehicle speed vx, and the acceleration sensor 27 to use the acceleration sensor 27 to accelerate. Gx is acquired (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 differentiation block 32a. Next, a value obtained by subtracting the differential value vx ′ from the acceleration Gx by the addition block 32 b is output as a gravitational acceleration component (Gx−vx ′) in the longitudinal direction of the vehicle 10. Next, a value obtained by dividing the gravitational acceleration component (Gx−vx ′) by the gravitational acceleration g is output by the division block 32c. Next, the inverse sine function block 32d estimates the estimated value θz using the inverse sine function (sin ⁻¹ ) as the input value. When it is considered that the road gradient is small, since sin θ≈θ, the inverse sine function block 32d may not be used.

  Next, the road surface gradient estimation device 30 changes the time constant tc by the function of the changing unit 35 (S130). Specifically, the time constant tc is changed as illustrated in FIG.

  First, the road surface gradient estimation device 30 determines whether or not the driving force is positive by the function of the changing unit 35 (S200). Next, it is determined whether or not the braking force is positive (S210). Based on these two determinations, the threshold value α is selected when the driving force is positive, the threshold value β is selected when the driving force is zero or less and the braking force is positive, and the driving force is zero or less and the braking force is zero. The threshold value α is selected in the following cases. Specifically, the changing unit 35 sets the threshold value β when the accelerator opening Ax is zero and the brake opening Bx is positive based on the accelerator opening Ax and the brake opening Bx input by the selection block 35a. Otherwise, the threshold α is selected.

  When the threshold value α is selected, the road surface gradient estimation device 30 determines whether or not the absolute value of the differential value vx ′ exceeds the threshold value α by the function of the changing unit 35 (S220). If it is determined that the absolute value of the differential value vx ′ exceeds the threshold value α, the road surface gradient calculating unit 31 changes the time constant tc to the specified value ts by the function of the changing unit 35 (S230). On the other hand, when it is determined that the absolute value of the differential value vx ′ is equal to or less than the threshold value α, the time constant tc is changed to the lower limit value t0 (S240).

  On the other hand, when the threshold value β is selected, the road surface gradient estimation device 30 determines whether or not the absolute value of the differential value vx ′ exceeds the threshold value β by the function of the changing unit 35 (S250). If it is determined that the absolute value of the differential value vx ′ exceeds the threshold value β, the road surface gradient calculating unit 31 changes the time constant tc to the specified value ts by the function of the changing unit 35 (S260). On the other hand, when it is determined that the absolute value of the differential value vx ′ is equal to or less than the threshold value β, the time constant tc is changed to the lower limit value t0 (S240).

Specifically, in the changing unit 35, the switch block 35b compares the absolute value of the differential value vx ′ with the threshold values α and β selected by the selection block 35a. When the differential value vx ′ absolute value exceeds the threshold values α and β, the specified value ts corresponding to the absolute value of the differential value vx ′ input by the data block 35c is output as the time constant tc. On the other hand, when the absolute value of the differential value vx ′ does not exceed the threshold values α and β, the lower limit value t0 is output as the time constant tc.

  Next, as illustrated in FIG. 5, the road surface gradient calculation unit 31 causes the filter unit 34 to substantially attenuate the frequency component lower than the cutoff frequency fc determined by the input time constant tc with respect to the estimated value θz. The filter processing is performed such that the high frequency components higher than the cut-off frequency fc are gradually reduced (S140). At this time, the filter unit 34 sets the specified value ts as the time constant tc when the differential value vx ′ exceeds the threshold values α and β, that is, when the posture change of the vehicle 10 due to the pitching motion occurs. The cut-off frequency fc is lowered. On the other hand, when the differential value vx ′ is less than or equal to the threshold values α and β, that is, when no pitching motion has occurred, the lower limit value t0 is set as the time constant tc, and the cutoff frequency fc increases.

  Next, the road surface gradient calculation unit 31 outputs the value subjected to the filter process as the output value θx by the function of the filter unit 34 (S150). Then, return to the start.

  As described above, since the time constant tc of the low-pass filter used for the filter processing is changed to a value corresponding to the differential value vx ′, the posture change of the vehicle 10 due to the pitching motion caused by the magnitude of the differential value vx ′ is temporarily changed. As a major change, it can be removed as noise by filtering. This is advantageous in reducing the estimation error of the road surface gradient when the acceleration changes greatly, such as when the vehicle 10 starts, sudden acceleration, or sudden braking, and the road surface gradient can be estimated with high accuracy.

  In this embodiment, when the absolute value of the differential value vx ′ exceeds the threshold values α and β, it is specified that the pitching motion has occurred in the vehicle 10, and the time constant tc of the filter processing is increased to increase the cutoff frequency fc. Lower. That is, the transmission range by the filter process is narrowed. Therefore, the posture change of the vehicle 10 due to the pitching motion can be regarded as a temporary change and removed as noise by the filter processing. Thereby, particularly when the weight of the vehicle 10 is relatively light, for example, when the load is small in a large vehicle such as a truck, it is advantageous in reducing the estimation error of the road surface gradient when sudden acceleration or sudden deceleration is likely to occur. become.

  There is a trade-off between the noise removal effect by filter processing and responsiveness. That is, if an attempt is always made to remove a temporary posture change due to pitching motion as noise by filter processing, there is a risk that the responsiveness of the estimation of the road surface gradient will deteriorate.

  On the other hand, in this embodiment, except when the absolute value of the differential value vx ′ exceeds the threshold value α, the time constant tc is decreased and the cutoff frequency fc is increased, so that output delay due to filter processing can be suppressed. As a result, when the posture change occurs in the vehicle 10 due to the pitching motion, the change is removed as noise, and when the posture change does not occur, the time constant tc is decreased, and the response of the estimation of the road surface gradient is reduced. Can be secured.

  In this embodiment, when the differential value vx ′ absolute value is less than or equal to the threshold values α and β, the time constant tc is set to the lower limit value t0 that can remove only noise that does not accompany the change in the attitude of the vehicle 10, so Output delay can be minimized. This is advantageous for ensuring the responsiveness of estimating the road surface gradient. Note that the lower limit t0 may be determined so that the necessary responsiveness can be sufficiently secured.

In this embodiment, the filter unit 34 is arranged so as to perform the filter process immediately before the output value θx is output. Therefore, the filter process may be performed on the value after the restriction or correction based on another parameter is applied. It becomes possible. This is advantageous in reducing the output delay due to the filter process, compared to the case where the filter process is applied to the vehicle speed and acceleration.

  In addition, in this embodiment, the threshold values α and β are selected by distinguishing between the case where the driving force is equal to or less than zero and the braking force is positive, and the case where the braking force is positive. It can be set to a corresponding time constant tc. This is advantageous in reducing the estimation error of the road surface gradient that varies depending on the traveling situation.

  The road surface gradient estimation apparatus 30 of the second embodiment illustrated in FIG. 7 is different from the first embodiment in the selection block 35a of the changing unit 35. In this embodiment, the selection block 35a selects the threshold values α and β based on whether the differential value vx ′ is positive or negative. Specifically, the selection block 35a selects the threshold value α because the vehicle 10 is accelerating when the differential value vx ′ is positive. On the other hand, when the differential value vx ′ is negative, the vehicle 10 is decelerating, so the threshold value β is selected. When the differential value vx ′ is zero, either the threshold value α or β may be selected, but in this embodiment, the threshold value α is selected.

  As illustrated in FIG. 8, in this embodiment, instead of selecting the threshold values α and β by using two determinations, that is, whether the driving force is positive and whether the braking force is positive. The threshold values α and β are selected based on the sign of the differential value vx ′.

  Thus, even if the threshold values α and β are selected based on the sign of the differential value vx ′, the time constant tc according to the traveling state of the vehicle 10 can be set. This is advantageous for reducing errors.

  In the first embodiment and the second embodiment, when the threshold values α and β are set to the same numerical value, the determination for the threshold value may be omitted. When the absolute value of the differential value vx ′ is larger than the threshold value α, the specified value ts is set as the time constant tc, whereas when it is smaller than the threshold value α, the lower limit value t0 is set as the time constant tc.

  The road surface gradient estimation apparatus 30 of the third embodiment illustrated in FIG. 9 is different from the first embodiment in a changing unit 35. In this embodiment, the changing unit 35, when the differential value vx ′ is out of the range (−β <vx ′ <α) between the negative threshold (−β) and the positive threshold α set in advance, When the time constant tc falls within the specified value ts and falls within the range, the time constant tc is set to the lower limit value t0.

  When the differential value vx ′ is negative, the driving force is zero or less and the braking force is positive. On the other hand, the case where the differential value vx ′ is positive is the other case.

  In this way, the time constant tc is changed by comparing whether the differential value vx ′ as the calculated acceleration is within the range between the negative threshold value (−β) and the positive threshold value α or out of the range. May be.

  That is, whether or not the absolute value of the differential value vx ′ of the first embodiment exceeds the threshold values α and β, and the differential value vx ′ of the second embodiment is between the negative threshold value (−β) and the positive threshold value α. It is synonymous with whether it is outside the range. In either embodiment, when the numerical value of the differential value vx ′ is small (| vx ′ | ≦ α, β; −β <vx ′ <α), the time constant tc is set to the lower limit value t0, and the differential value vx ′ When the numerical value is large, the time constant tc is set to a specified value ts larger than the lower limit value t0.

The road surface gradient estimation apparatus 30 of the fourth embodiment illustrated in FIGS. 10 to 13 is different from the first embodiment in a changing unit 35. In this embodiment, the changing unit 35 changes the strength of the time constant tc according to the differential value vx ′ and the vehicle speed vx. The changing unit 35 uses the output torque Tx of the engine 14 as a numerical value related to the driving factor.

  As illustrated in FIG. 10, in this embodiment, the changing unit 35 includes a selection block 35 a, a switch block 35 b, data blocks 35 e, 35 f, which use the output torque Tx of the engine 14 based on them as numerical values relating to driving factors. 35g.

  The selection block 35a receives the output torque Tx and the brake opening Bx output from the data block 35e, and selects one of the threshold values α and β based on them.

  The data block 35e receives the engine rotational speed Nx and the fuel injection amount Qx, and outputs the output torque Tx of the engine 14 based on them as numerical values related to the driving factor.

  As illustrated in FIG. 11, the output torque Tx has a positive relationship with respect to each of the engine rotational speed Nx and the fuel injection amount Qx, and increases as the engine rotational 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 35e.

  When the driving force is positive, the switch block 35b sets the time constant tc to the high time constant th when the absolute value of the differential value vx ′ exceeds the threshold value α, while the absolute value of the differential value vx ′ is The time constant tc is set to the low time constant tl when the threshold value α is below the threshold value α. Further, when the driving force is zero or less and the braking force is positive, the changing unit 35 sets the time constant tc to the high time constant th when the absolute value of the differential value vx ′ exceeds the threshold value β. Thus, when the absolute value of the differential value vx ′ becomes equal to or less than the threshold value β, the time constant tc is set to the low time constant tl.

  The data block 35f is a functional element that receives a vehicle speed vx and outputs a high time constant th corresponding to the vehicle speed vx. The data block 35g is a functional element that receives a 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. 12, the high time constant th has a negative relationship with the vehicle speed vx until it reaches a constant value, and decreases as the vehicle speed vx increases. As illustrated in FIG. 13, the low time constant tl has a negative relationship with the vehicle speed vx until the lower limit t0 is reached, and decreases as the vehicle speed vx increases. These map data are obtained in advance by experiments and tests and stored in each of the data blocks 35f and 35g. The high time constant th and the low time constant tl are calculated when the vehicle speed sensor 26 cannot detect the vehicle speed vx, assuming that the vehicle speed vx is zero.

  Thus, 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 in a trade-off relationship according to the change speed of the road surface gradient. As a result, when the vehicle speed vx is high and the noise is low, the time constant tc can be reduced to increase the responsiveness of estimating the road surface gradient. On the other hand, when the vehicle speed vx is slow and the responsiveness may be slow, the time constant tc can be increased to enhance the noise removal effect.

  The road surface gradient estimation device 30 of the fifth embodiment illustrated in FIG. 14 is different from the above-described embodiment in a changing unit 35.

  The specified value ts of this embodiment is set smaller than the first embodiment by the average value of the difference between the high time constant th and the low time constant tl. That is, in this embodiment, the specified value ts functions as a correction value for the high time constant th.

  Thus, in this embodiment, when the absolute value of the differential value vx ′ exceeds the threshold values α and β, the time constant tc is determined according to the specified value ts corresponding to the differential value vx ′ and the vehicle speed vx at that time. Since the high time constant th is set to the added value, in addition to the change in the differential value vx ′, the change in the posture of the vehicle 10 due to the pitching motion according to the vehicle speed vx can be removed as noise by the filter processing. This is advantageous for reducing the estimation error of the road surface gradient.

  The road surface gradient estimation device 30 of the sixth embodiment illustrated in FIG. 15 is different from the above-described embodiment in a changing unit 35, and the attitude of the vehicle 10 from the acceleration Gx acquired by the acceleration sensor 27 as the calculated acceleration. The value excluding the gravity acceleration component accompanying the change is used.

  In this embodiment, the changing unit 35 has an absolute value block 35i and a filter block 35j.

  The filter block 35j has a low-pass filter with a fixed time constant td, unlike the filter unit 34 with a variable time constant tc. The time constant td is set to a value obtained by removing the gravitational acceleration component accompanying the posture change of the vehicle 10 from the acceleration Gx acquired by the acceleration sensor 27.

  In this embodiment, when the acceleration Gx acquired by the acceleration sensor 27 is used as the calculated acceleration, the acceleration Gx is filtered to remove the gravitational acceleration component accompanying the posture change of the vehicle 10 from the acceleration Gx. Calculated acceleration approximated to 'can be used. This is advantageous for reducing the estimation error of the road surface gradient in the extremely low vehicle speed region where the vehicle speed sensor 26 cannot detect the vehicle speed vx. 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 where the vehicle 10 is not moving, a state where the vehicle 10 is moving, or a state where the moving speed of the vehicle 10 is short and pulses cannot be detected by the vehicle speed sensor 26.

  Note that the filter unit 34 may be interposed between the vehicle speed sensor 26 and the estimation unit 32, and between the acceleration sensor 27 and the estimation unit 32, respectively. In this case, the filter unit 34 receives the vehicle speed vx and the acceleration Gx, filters the vehicle speed vx and the acceleration Gx, and outputs them to the estimation unit 32.

  As described above, each of the vehicle speed vx and acceleration Gx acquired instead of the estimated value θz may be subjected to the filtering process. A filter unit 34 for filtering the vehicle speed vx is interposed between the differentiation block 32a and the addition block 32b of the estimation unit 32, and instead of the vehicle speed vx, noise of the differential value vx ′ obtained by time differentiation of the vehicle speed vx is detected. It may be removed. In addition, the time constant tc may be different between the filter unit 34 that removes noise of the vehicle speed vx and the filter unit that removes noise of the acceleration Gx.

  As in the embodiment described above, the calculated acceleration is either a differential value vx ′ obtained by time-differentiating the vehicle speed vx acquired by the vehicle speed sensor 26 or a value obtained by filtering the acceleration Gx acquired by the acceleration sensor 27. May be used. For example, in a very low speed region where the vehicle speed vx is zero, a value obtained by filtering the acceleration Gx may be used, and otherwise, a differential value vx ′ may be used.

  In the above-described embodiment, the vehicle 10 has been described as an example of a large vehicle such as a truck. However, the road surface gradient estimation device 30 of the present invention can also be applied to buses, ordinary vehicles, and traction vehicles (tractors). The type is not limited.

Moreover, although embodiment mentioned above demonstrated the example in which the road surface gradient estimation apparatus 30 was comprised from the road surface gradient calculating part 31, the vehicle speed sensor 26, and the acceleration sensor 27, this invention is not limited to this. For example, the road surface gradient estimation device 30 may be composed of one sensor that functions as vehicle speed acquisition means, acceleration acquisition means, and estimation means, and hardware that functions as filter means and change means.

  In the above-described embodiment, the primary transfer function block is used as the filter unit 34, but the present invention is not limited to this. As the filter unit 34, for example, a configuration that includes a constant multiple block, an addition block, and an integration block and that feedback-adds the result of integration once may be used, or the order of the low-pass filter may be higher. .

DESCRIPTION OF SYMBOLS 10 Vehicle 26 Vehicle speed sensor 27 Acceleration sensor 30 Road surface gradient estimation apparatus 31 Road surface gradient calculating part 32 Estimation part 34 Filter part 35 Change part (theta) z Estimated value vx Vehicle speed Gx Acceleration vx 'Differential value tc Time constant

Claims (7)

Vehicle speed acquisition means for acquiring the vehicle speed of the vehicle;
Acceleration acquisition means for acquiring acceleration in the longitudinal direction of the vehicle;
An estimation means for inputting the vehicle speed acquired by the vehicle speed acquisition means and the acceleration acquired by the acceleration acquisition means, and estimating and outputting the road gradient on which the vehicle is traveling based on the input vehicle speed and acceleration. When,
Filter means for inputting the value output from the estimating means, filtering the output value with a low-pass filter having a variable time constant, and outputting the filtered value.
Either the calculated acceleration obtained by time-differentiating the vehicle speed acquired by the vehicle speed acquiring unit or the value obtained by removing the gravitational acceleration component accompanying the change in the posture of the vehicle from the acceleration acquired by the acceleration acquiring unit is input. And a changing means for changing the time constant according to the inputted calculated acceleration. The time constant is set to a preset lower limit value,
2. The configuration according to claim 1, wherein when the calculated acceleration is out of a range between a preset negative threshold value and a positive threshold value, the time constant is set to be larger than the lower limit value by the changing unit. Road surface slope estimation device.   The road surface gradient estimation device according to claim 2, wherein when the calculated acceleration falls within the range, the changing means sets the time constant to the lower limit value or to approach the lower limit value. Driving factor acquisition means for acquiring a numerical value relating to a driving factor defining the driving force of the vehicle;
If the driving force of the vehicle based on the numerical value related to the driving factor acquired by the driving factor acquiring unit is positive and the calculated acceleration exceeds the positive threshold by the changing unit, the time constant is set to the time constant. The road surface gradient estimation apparatus according to claim 2 or 3, wherein the road surface gradient estimation apparatus is configured to be larger than the lower limit value. Braking factor acquisition means for acquiring a numerical value relating to a braking factor that defines the braking force of the vehicle;
If the braking force of the vehicle based on the numerical value related to the braking factor acquired by the braking factor acquiring unit is positive and the calculated acceleration falls below the negative threshold by the changing unit, the time constant is set to the time constant. The road surface gradient estimation apparatus according to any one of claims 2 to 4, wherein the road surface gradient estimation apparatus is configured to be larger than the lower limit value. The vehicle speed acquired by the vehicle speed acquisition means is input to the change means,
The road surface gradient estimation apparatus according to any one of claims 1 to 5, wherein the time constant is reduced as the vehicle speed increases by the changing means in accordance with the value of the vehicle speed. In the road gradient estimation method for acquiring the vehicle speed and the longitudinal acceleration of the vehicle, and estimating the road gradient on which the vehicle is traveling based on the acquired vehicle speed and acceleration,
When performing a filtering process with a low-pass filter having a variable time constant for the estimated value estimated,
Differentiating the acquired vehicle speed with respect to time, or calculating the calculated acceleration by removing the gravitational acceleration component accompanying the posture change of the vehicle from the acquired acceleration,
A road surface gradient estimating method, wherein the time constant is changed according to the calculated acceleration.

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