JP2019189175A - Acceleration calculation device - Google Patents

Abstract

To provide an acceleration calculation device capable of improving calculation accuracy of acceleration even when a vehicle is inclined to a road surface by baggage or the like, and an axis of an acceleration sensor is inclined to a road surface due to assembly error.SOLUTION: An acceleration calculation device 30 comprises: an output part 40 for outputting an acceleration sensor value according to acceleration of a vehicle in a cross direction detected by an acceleration sensor 24, and travel driving force based on drive force of a drive source of the vehicle and air resistance which acts to the vehicle; and a calculation part 42 for calculating a correction value for correcting the acceleration sensor value on the basis of the plurality of the acceleration sensor values and the plurality of travel drive forces, and on the basis of the correction value, correcting the acceleration sensor value and calculating acceleration.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an acceleration calculation device.

  2. Description of the Related Art There is known an apparatus that calculates acceleration in the front-rear direction of a vehicle based on information detected by an acceleration sensor provided in the vehicle.

JP 2013-199961 A JP 2010-084867 A

  However, when the vehicle is tilted by luggage or the like, the acceleration sensor mounted on the vehicle is tilted with respect to the road surface and changes its direction, so that the above-described device has a problem that the longitudinal acceleration cannot be accurately calculated.

  The present invention has been made in view of the above, and an object of the present invention is to provide an acceleration calculation device capable of improving the calculation accuracy of acceleration even when the vehicle is inclined with respect to the road surface due to luggage or the like.

  In order to solve the above-described problems and achieve the object, an acceleration calculation device according to the present invention includes an acceleration sensor value corresponding to a longitudinal acceleration of a vehicle detected by an acceleration sensor, a driving force of a driving source of the vehicle, and An output unit that outputs a driving force based on air resistance acting on the vehicle, and a correction value that corrects the acceleration sensor value based on the plurality of acceleration sensor values and the plurality of driving force. A calculation unit that corrects the acceleration sensor value based on the correction value and calculates an acceleration.

  The acceleration calculation apparatus according to the present invention is an acceleration in which the direction in which acceleration is detected by the inclination of the vehicle and the acceleration sensor is determined based on correction values calculated from a plurality of acceleration sensor values and a plurality of travel driving forces. The acceleration sensor value detected by the sensor is corrected to calculate the longitudinal acceleration of the vehicle. Thereby, the acceleration calculation device can improve the calculation accuracy of acceleration even when the vehicle is inclined with respect to the road surface due to luggage or the like.

FIG. 1 is a schematic diagram of a vehicle on which the acceleration calculation system of the embodiment is mounted. FIG. 2 is a block diagram illustrating an overall configuration of an acceleration calculation system including the acceleration calculation apparatus according to the embodiment. FIG. 3 is a functional block diagram illustrating functions of the acceleration calculation device. FIG. 4 is a diagram for explaining the relationship between the acceleration sensor value and the driving force when the weight of the vehicle is the same. FIG. 5 is a diagram illustrating acceleration sensor values in a reference state in which the vehicle is not inclined with respect to the road surface. FIG. 6 is a diagram showing acceleration sensor values in an inclined state in which the vehicle is inclined with respect to the reference state of FIG. FIG. 7 is a graph showing the relationship between x and y in the reference state and the inclined state. FIG. 8 is a flowchart of acceleration calculation processing executed by the processing unit.

  Common constituent elements such as the following exemplary embodiments are denoted by common reference numerals, and redundant descriptions are omitted as appropriate.

<Embodiment>
FIG. 1 is a schematic diagram of a vehicle 10 on which the acceleration calculation system 22 of the embodiment is mounted. As shown in FIG. 1, the vehicle 10 includes a drive source 12, an automatic transmission 14, a differential device 16, an axle 18, a plurality of wheels 20, and an acceleration calculation system 22.

  The drive source 12 is a device that generates a driving force for driving the vehicle 10 such as an internal combustion engine such as an engine and an electric motor such as an electric motor. The drive source 12 may include both an internal combustion engine and an electric motor. The drive source 12 outputs the generated driving force to the automatic transmission 14.

  The automatic transmission 14 is also referred to as an automatic transmission, and switches the gear ratio or the gear position according to the throttle opening or the rotational speed of the output shaft 14a. The automatic transmission 14 outputs the converted rotational driving force to the differential device 16 via the output shaft 14a.

  The differential device 16 is provided, for example, on the rear axle 18. The differential device 16 transmits the rotational driving force output from the automatic transmission 14 to the rear wheel 20 via the axle 18 while absorbing the difference in rotational speed between the left and right wheels 20.

  Each of the pair of axles 18 connects the left and right wheels 20 on the front side or the rear side. The rear axle 18 transmits the rotational driving force transmitted from the differential device 16 to the wheels 20.

  A total of four wheels 20 are provided on the front, rear, left and right of the vehicle 10. The rear wheel 20 receives the rotational driving force output from the drive source 12 via the axle 18 and transmits the rotational driving force to the road surface to cause the vehicle 10 to travel.

  The acceleration calculation system 22 calculates the acceleration of the vehicle 10. The acceleration calculation system 22 may control the automatic transmission 14 based on the calculated acceleration. The acceleration calculation system 22 includes an acceleration sensor 24, a vehicle speed sensor 26, an opening degree sensor 28, a braking sensor 29, and an acceleration calculation device 30.

  The acceleration sensor 24 detects the acceleration in the longitudinal direction of the vehicle 10 and outputs an acceleration sensor value corresponding to the detected acceleration to the acceleration calculation device 30. The acceleration sensor 24 may be, for example, an element that converts an acceleration acting on the vehicle 10 into an electrical signal by a piezoelectric element or a MEMS (Micro Electro Mechanical System) and outputs the electric signal.

  The vehicle speed sensor 26 detects vehicle speed information for calculating the speed of the vehicle 10 in the front-rear direction and outputs the vehicle speed information to the acceleration calculation device 30. The vehicle speed sensor 26 includes, for example, a hall element provided in the vicinity of the output shaft 14a of the automatic transmission 14. In this case, the vehicle speed sensor 26 may output the rotational speed of the output shaft 14a of the automatic transmission 14 as vehicle speed information, for example. Note that the vehicle speed information may be, for example, either the rotation speed of the wheel 20 or the rotation speed of the output shaft of the drive source 12.

  The opening degree sensor 28 detects opening degree information that is an opening degree of a throttle valve for adjusting the supply amount of air-fuel mixture or air to the drive source 12 and outputs the detected opening degree information to the acceleration calculating device 30. The opening sensor 28 may be, for example, a position sensor provided in the vicinity of the throttle valve. The opening degree information may be an accelerator opening degree.

  The braking sensor 29 is provided in the vehicle 10, detects braking information for calculating the braking force by the brake, and outputs it to the acceleration calculating device 30. The brake sensor 29 may output, for example, brake hydraulic pressure generated by a brake operation by the driver, position information of a brake pedal operated by the driver, and the like as braking information.

  The acceleration calculation device 30 calculates a correction value for correcting the acceleration sensor value, corrects the acceleration sensor value based on the correction value, and calculates the acceleration in the front-rear direction of the vehicle 10.

  FIG. 2 is a block diagram illustrating an overall configuration of the acceleration calculation system 22 including the acceleration calculation device 30 according to the embodiment. As shown in FIG. 2, the acceleration calculation system 22 includes an acceleration sensor 24, a vehicle speed sensor 26, an opening degree sensor 28, an acceleration calculation device 30, and an in-vehicle network 32.

  The acceleration calculation device 30 is a computer such as an ECU (Electronic Control Unit). The acceleration calculating device 30 includes a CPU (Central Processing Unit) 30a, a ROM (Read Only Memory) 30b, a RAM (Random Access Memory) 30c, and an SSD (Solid State Drive) 30d. The CPU 30a, ROM 30b, and RAM 30c may be integrated in the same package.

  The CPU 30a is an example of a hardware processor, reads a program stored in a nonvolatile storage device such as the ROM 30b or the SSD 30d, and executes various arithmetic processes and controls according to the program. CPU30a performs the acceleration calculation process which calculates the acceleration of the vehicle 10, for example.

  The ROM 30b stores each program executed by the CPU 30a and data such as parameters necessary for executing the program. The RAM 30c functions as a program work area executed by the CPU 30a, and temporarily stores various data used in program operations. The SSD 30d is a rewritable nonvolatile storage device, and maintains data even when the power of the acceleration calculation device 30 is turned off. The SSD 30d stores each program executed by the CPU 30a and data such as parameters necessary for executing the program.

  The in-vehicle network 32 includes, for example, a CAN (Controller Area Network) and a LIN (Local Interconnect Network). The in-vehicle network 32 connects the acceleration sensor 24, the vehicle speed sensor 26, the opening degree sensor 28, the braking sensor 29, the acceleration calculating device 30, and the automatic transmission 14 so as to be able to transmit and receive information to and from each other.

  FIG. 3 is a functional block diagram illustrating functions of the acceleration calculation device 30. As illustrated in FIG. 3, the acceleration calculation device 30 includes a processing unit 34 and a storage unit 36.

  The processing unit 34 is realized as a function of the CPU 30a, for example. The processing unit 34 functions as the output unit 40 and the calculation unit 42. For example, the processing unit 34 may function as the output unit 40 and the calculation unit 42 by reading the acceleration calculation program 44 stored in the storage unit 36. A part or all of the output unit 40 and the calculation unit 42 may be configured by a circuit such as an application specific integrated circuit (ASIC) and a field-programmable gate array (FPGA).

  The output unit 40 corrects the acceleration sensor value detected by the acceleration sensor 24 to acquire or calculate information for calculating acceleration and outputs the information to the calculation unit 42. For example, the output unit 40 obtains an acceleration sensor value from the acceleration sensor 24 and outputs the acceleration sensor value to the calculation unit 42. The output unit 40 repeatedly calculates the driving force based on the driving force of the driving source 12 and the air resistance acting on the vehicle 10 and outputs the traveling driving force to the calculating unit 42.

  The calculation unit calculates a correction value for correcting the acceleration sensor value based on the plurality of acceleration sensor values and the plurality of travel driving forces acquired from the output unit 40, and corrects the acceleration sensor value based on the correction value. Then, the longitudinal acceleration of the vehicle 10 is calculated. For example, the calculation unit 42 calculates a linear expression indicating the relationship between the acceleration sensor value and the travel driving force when the vehicle 10 is inclined with respect to the road surface (hereinafter referred to as an inclined state) due to loading of luggage or the like. To do. The calculation unit 42 calculates a difference between a reference value in a reference state (hereinafter referred to as a reference state) in which the luggage 10 is hardly loaded and the vehicle 10 is not inclined with respect to the road surface, and the y-intercept of the primary expression of the inclined state. Based on the above, a correction value is calculated. The reference value will be described later. The calculation unit 42 corrects the acceleration sensor value based on the correction value, and calculates acceleration in the front-rear direction of the vehicle 10 (hereinafter, corrected acceleration). For example, the calculation unit 42 may output the corrected acceleration to a control unit that controls the automatic transmission 14.

  The storage unit 36 is realized as a function of the ROM 30b, the RAM 30c, and the SSD 30d, for example. The storage unit 36 may be an external storage device connected via a network or the like. The storage unit 36 stores a program executed by the processing unit 34, data necessary for executing the program, data generated by executing the program, and the like. For example, the storage unit 36 stores an acceleration calculation program 44 executed by the processing unit 34. The acceleration calculation program 44 may be provided by being stored in a computer-readable storage medium such as a CD-ROM (Compact Disc Read Only Memory) or a DVD-ROM (Digital Versatile Disc Read Only Memory). It may be provided via a network. The storage unit 36 stores numerical data 46 necessary for the processing unit 34 to execute the acceleration calculation program 44.

  FIG. 4 is a diagram illustrating the relationship between the acceleration sensor value and the driving force when the weight of the vehicle 10 is the same.

As shown in FIG. 4, the values of the three axes are the driving force, the acceleration sensor value, and the actual acceleration that is the actual acceleration of the vehicle 10. The actual acceleration of the vehicle 10 is the longitudinal acceleration of the vehicle 10 obtained by differentiating the vehicle speed information from the vehicle speed sensor 26 that is the output rotation of the output shaft 14 a of the automatic transmission 14. In this case, when the weight of the vehicle 10 is the same, the relationship between the travel driving force and the acceleration sensor value is a plane (hereinafter referred to as an equal vehicle weight surface WP) indicated by a one-dot chain line. Here, since the equal vehicle weight surface WP is parallel to the coordinate axis of the actual acceleration of the vehicle 10, the equal vehicle weight surface WP can be expressed in two dimensions including the travel driving force and the acceleration sensor value. Incidentally, etc. vehicle weight surface WP is at the origin is offset in the negative direction of the acceleration sensor values g * mu _r only. In addition, g is a gravitational acceleration and μr is a rolling coefficient.

  Next, the correction and calculation of the acceleration of the vehicle 10 by the output unit 40 and the calculation unit 42 will be described. FIG. 5 is a diagram illustrating the acceleration sensor value GS in a reference state in which the vehicle 10 is not inclined with respect to the road surface. FIG. 6 is a diagram illustrating the acceleration sensor value GS in a tilted state in which the vehicle 10 is tilted with respect to the reference state in FIG. It is assumed that the weight of the vehicle 10 does not change during traveling in a short time for calculating the correction value. That is, in each state in FIGS. 5 and 6, the weight of the vehicle 10 does not change, and the driving force RF and the acceleration sensor value GS satisfy the relationship of the equal vehicle weight surface WP shown in FIG. 4.

It is assumed that the vehicle 10 is traveling on a road surface that is inclined by a road surface gradient angle θ in the vertical direction with respect to the horizontal direction. In this case, as shown in FIG. 5, the acceleration sensor value GS of the vehicle 10 in the reference state running on the road surface with the road surface gradient angle θ is calculated from the components g * sin θ along the road surface of the actual acceleration VA and the gravitational acceleration g to VA + g. * Sin θ. The equation of motion of the vehicle 10 can be expressed by the following equation (1). In addition, the left side (DF-BF-AR) of Formula (1) is the driving force RF. The output unit 40 may obtain the driving force DF from the driving force characteristics associated in advance with the opening degree of the throttle valve (or the opening degree of the accelerator), the rotational speed of the output shaft 14a, and the like. The driving force characteristic may be stored in advance in the storage unit 36 as a part of the numerical data 46.
(DF-BF-AR) −RW * g * sin θ−RW * g * μ _r = RW * VA
→ DF-BF-AR = RW * (VA + g * sin θ + g * μ _r ) (1)
DF: Driving force of the driving source of the vehicle 10 BF: Braking force by the brake of the vehicle 10 AR: Air resistance (= λ * S * VV ² )
λ: Air resistance coefficient S: Area of the vehicle 10 (for example, vertical cross-sectional area)
VV: Speed of the vehicle 10 RW: Weight of the vehicle 10 Note that the braking force BF may be “0” except when the brake is being operated. Alternatively, the output unit 40 may calculate the braking force BF from the position information detected by the braking sensor 29.

When formula (1) is transformed, the following formula (2) is obtained.
VA + g * sin θ = (DF−BF−AR) / RW−g * μ _r (2)
Here, when the traveling driving force RF (= DF−BF−AR) is x ₁ and the acceleration sensor value GS (= VA + g * sin θ) is y ₁ , the equation (2) becomes the following equation (3). .
y ₁ = RW ⁻¹ * x ₁ −g * μ _r (3)

Further, when the equation (2) is transformed, the actual acceleration VA becomes the following equation (4).
VA = (DF−BF−AR) / RW− (g * μ _r + g * sin θ) (4)

Next, as shown in FIG. 6, when the vehicle 10 is tilted at a tilt angle θ _err further from the road surface gradient angle θ by loading luggage, the actual acceleration VA acting on the acceleration sensor 24 in the detection direction is VA *. cos θ _err , and the gravitational acceleration g acting on the acceleration sensor 24 in the detection direction is g * sin (θ + θ _err ). Therefore, the acceleration sensor value GS of the acceleration sensor 24 is VA * cos θ _err + g * sin (θ + θ _err ). When the actual acceleration VA of Expression (4) is substituted into the acceleration sensor value GS, the following Expression (5) is obtained.
VA * cos θ _err + g * sin (θ + θ _err )
= [(DF-BF-AR) / RW- (g * [mu] _r + g * sin [theta])] * cos [theta] _err + g * sin ([theta] + [theta] _err ).
= [(DF−BF−AR) / RW] * cos θ _err − [(g * μ _r + g * sin θ)] * cos θ _err + g * sin (θ + θ _err )
... (5)
Here, when the traveling driving force RF (= DF−BF−AR) is x ₂ and the acceleration sensor value GS (= VA * cos θ _err + g * sin (θ + θ _err )) is y ₂ , the equation (5) is The following equation (6) is obtained.
y ₂ = cos θ _err * RW ⁻¹ * x ₂ −g * μ _r * cos θ _err −g * sin θ * cos θ _err + sin (θ + θ _err ) (6)

Here, since the road surface gradient angle θ and the inclination angle θ _err are both small values, they are approximated by the following equations (7a) and (7b).
cos θ _{err ≈1} (7a)
sin (θ + θ _err ) ≈sin θ + sin θ _err (7b)
Substituting Equation (7a) and Equation (7b) into Equation (6) yields the following Equation (8).
y ₂ = RW ⁻¹ * x ₂ −g * μ _r + g * sin θ _err (8)

  FIG. 7 is a graph showing the relationship between x and y in the reference state and the inclined state. y is the acceleration sensor value GS, and x is the driving force RF.

As a straight line shown in FIG. 7, a linear expression indicating the relationship between x ₁ and y ₁ in the reference state and a linear expression indicating the relationship between x ₂ and y ₂ in the inclined state can be expressed. Here, since the left sides y ₁ and y ₂ of the expressions (3) and (8) are both acceleration sensor values GS in each state, the expressions (3) and (3) are determined depending on the presence / absence of the inclination angle θ _err of the attitude of the acceleration sensor 24. A difference occurs in the y intercept of y ₁ and y _{2 in} (8). That is, the difference between the y-intercept of equation (3) and the y-intercept of equation (8) is an error caused by the inclination angle θ _err . Therefore, the calculation unit 42 may calculate the difference between the y-intercept of Equation (3) and the y-intercept of Equation (8) as a correction value CV that corrects the error of the acceleration sensor value GS due to the inclination angle θ _err .

Specifically, the output unit 40, in a state where the vehicle 10 is inclined at an inclination angle θ _err with respect to the road surface, the driving force RF that is the value of y ₂ and the acceleration sensor value GS that is the value of x _2. Are sampled at predetermined sampling periods and output to the calculation unit 42. In order to improve the calculation accuracy of the acceleration, the output unit 40 preferably performs sampling not only during acceleration when the accelerator pedal is operated but also when the accelerator brake is not operated. The calculation unit 42 substitutes the plurality of sampled x ₂ values and y ₂ values into Equation (8) to calculate the slope and the y intercept. For example, the calculating unit 42 may calculate the slope and the y-intercept by a least square method using a plurality of sampled x ₂ values and y ₂ values.

The calculation unit 42 may calculate the difference between the y-intercept of equation (3) and the y-intercept of equation (8) as the correction value CV. Here, g * mu _r is the value of the y-intercept of the equation (3), since the constant that does not depend on the inclination angle theta _err or the like may be stored in advance in the storage unit 36 as a part of the numerical data 46. Incidentally, g * μ _r is the reference value described above. The calculation unit 42 may calculate the correction value CV by the following equation (9).
CV = − (y ₀₂ −g * μ _r ) (9)
y ₀₂ : y intercept of y ₂

The calculating unit 42 calculates the acceleration of the vehicle 10 by correcting the acceleration sensor value GS with the correction value CV. Specifically, when the corrected acceleration is the corrected acceleration CA, the calculation unit 42 may calculate the corrected acceleration CA based on the following equation (10).
CA = GS-CV (10)

Next, the difference between the case where the approximation according to the equations (7a) and (7b) is performed and the case where the approximation is not performed will be described. The road surface gradient corresponding to the road surface gradient angle θ is 2%, and the sum of the road surface gradient angle θ and the inclination angle θ _err is 0.02991 rad. Note that 0.02991 rad is equivalent to 3% in road gradient. In this case, the correction value CV when approximation is performed and when approximation is not performed is as follows. Thereby, it can be seen that the influence on the correction value CV by the above-described approximation is small.
Correction value CV when approximation is not performed: 0.293809
Correction value CV when approximation is performed: 0.293867

  FIG. 8 is a flowchart of acceleration calculation processing executed by the processing unit 34. The processing unit 34 reads the acceleration calculation program 44 and executes acceleration calculation processing.

  As shown in FIG. 8, in the acceleration calculation process, the output unit 40 acquires and outputs the acceleration sensor value GS (S102). The output unit 40 calculates the travel driving force RF (S104). The output unit 40 may calculate the travel driving force RF based on, for example, Expression (1) including the difference between the driving force DF of the driving source 12 and the air resistance AR. The output unit 40 outputs the acceleration sensor value GS and the travel driving force RF to the calculation unit 42 (S105). The output unit 40 executes S102 and S104 a predetermined number of times (S100a and S100b), and outputs a plurality of acceleration sensor values GS and a plurality of travel driving forces RF to the calculation unit 42. The set number of times may be set in advance and stored in the storage unit 36 as a part of the numerical data 46.

  The calculating unit 42 calculates the slope and y-intercept of Expression (8) based on the plurality of travel driving forces RF and the plurality of acceleration sensor values GS (S106). The calculation unit 42 may execute step S106 and subsequent steps every time S102 and S104 are executed after executing S102 and S104 a predetermined number of times.

Calculating section 42, based on the calculated y-intercept and expressions with a y-intercept g * mu _r of formula (3) in equation (8) (9), calculates the correction value CV of the acceleration sensor value GS (S108). The calculation unit 42 calculates the corrected acceleration CA based on the equation (10) using the calculated correction value CV and acceleration sensor value GS (S110). Thereafter, the processing unit 34 repeats step S102 and subsequent steps.

  As described above, the acceleration calculation device 30 corrects the acceleration sensor value GS that changes according to the inclination of the vehicle 10 based on the correction value CV calculated from the plurality of acceleration sensor values GS and the plurality of travel driving forces RF, and The corrected acceleration CA is calculated. Thereby, the acceleration calculation apparatus 30 can improve the calculation accuracy of the acceleration in the front-rear direction of the vehicle 10 calculated from the acceleration sensor value GS even when the vehicle 10 is inclined due to luggage or the like.

  The function, connection relationship, number, arrangement, and the like of the configuration of each embodiment described above may be changed or deleted as appropriate within the scope of the invention and the scope equivalent to the scope of the invention. You may combine each embodiment suitably. You may change the order of each step of each embodiment suitably.

  10: vehicle, 12: drive source, 22: acceleration calculation system, 24: acceleration sensor, 30: acceleration calculation device, 40: output unit, 42: calculation unit, 44: acceleration calculation program, AR: air resistance, CA: correction Acceleration, CV: correction value, DF: driving force, GS: acceleration sensor value, RF: traveling driving force.

Claims (1)

An output unit that outputs an acceleration sensor value corresponding to the longitudinal acceleration of the vehicle detected by the acceleration sensor, and a driving force based on the driving force of the driving source of the vehicle and the air resistance acting on the vehicle;
A calculation unit that calculates a correction value for correcting the acceleration sensor value based on the plurality of acceleration sensor values and the plurality of travel driving forces, and calculates the acceleration by correcting the acceleration sensor value based on the correction value. When,
An acceleration calculation device comprising:

Images