JP2766588B2 - Vehicle yaw angular velocity detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a yaw angular velocity of a vehicle.
It relates to an angular velocity detection method, in particular, Ru to enhance the inexpensive and detection accuracy <br/> degree about the yaw angular velocity detecting how suitable vehicle <br/>.

[0002]

2. Description of the Related Art Generally, to detect the angular velocity of a moving body, there is a method using an optical fiber gyro / gas rate sensor or the like. These are called yaw rate sensors and are disclosed in JP-A-62-261575, JP-A-62-71866,
JP-A-63-219829, JP-A-3-153364
As described in Japanese Patent Application Laid-Open Publication No. H10-209, the mounting on a vehicle is being studied. However, the yaw rate sensor has not been applied to actual detection of the yaw angular velocity of an automobile because the sensor itself is expensive and lacks in output stability against a temperature change.

On the other hand, in the prior art described in Japanese Patent Application Laid-Open No. 63-218866, a wheel speed sensor for detecting the left and right ground speeds of a vehicle is provided, and the difference between the left and right ground speeds of the vehicle from both wheel speed sensors is calculated. Thus, the yaw angular velocity is obtained, and a technique that is less expensive than the yaw rate sensor is proposed.

In the prior arts described in JP-A-62-70666 and JP-A-64-12272, G (acceleration) sensors are fixed to two positions of a moving body so that detection axes are parallel to each other. The angular acceleration of the moving body is calculated from the output difference between the two G sensors. Then, the yaw angular velocity is obtained by integrating the angular acceleration. This also proposes a technique that is less expensive than a yaw rate sensor.

[0005]

However, in the above-mentioned method using the difference between the left and right wheel speeds, an accurate yaw angular speed is obtained when the wheel speed is different from the ground speed of the vehicle, that is, when the wheels are slipping. There is a problem that you can not. In the wheel slip state at the time of acceleration, only the drive wheel slips and the driven wheel does not slip. Therefore, this problem can be solved by using the wheel speed of the driven wheel. However, in the wheel slip state at the time of braking, all the wheels slip, so that even if the wheel speed of the driven wheel is used, the error between the calculated yaw angular speed and the actual yaw angular speed increases. In particular, during the ABS operation, the temporal change of the wheel speed is large, and the error of the calculated yaw angular speed is large.

In the method of calculating the yaw angular velocity based on the difference between the outputs of the two G sensors and integrating the yaw angular velocity to obtain the yaw angular velocity, the error is accumulated at the time of integration. It becomes big and there is anxiety about performing various controls using this.

An object of the present invention is that the detection accuracy is to provide a high addition yaw angular velocity detecting how inexpensive vehicle.

[0008]

The object of the present invention is to provide a yaw angular velocity based on a difference between the left and right wheel speeds and a true yaw angular velocity except when braking, including a right and left wheel speed sensor and two G sensors. At this time, the yaw angular velocity calculated based on the value of the G sensor is ignored, and conversely, during braking, the yaw angular velocity calculated based on the values of the two G sensors is regarded as a true yaw angular velocity. This is achieved by ignoring the value of the yaw angular velocity due to the wheel speed difference.

[0009]

During non-braking including acceleration, deceleration, and constant-speed running, the yaw angular velocity is detected based on the speed difference between the left and right driven wheels. Since the wheel speed at this time may be regarded as the speed of the vehicle body, the required yaw angular speed is accurate.

At the time of braking, the yaw angular velocity is calculated based on the values of the two G sensors. At this time, the acceleration is not affected whether the wheels are locked or the wheel speed is suddenly changed by the operation of the ABS, so that the yaw angular velocity can be accurately detected. Further, as for the integration error, the effect of the error is small because the braking time for one cycle is about 20 seconds at the longest.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to the detection of yaw angular acceleration of an automobile will be described below with reference to the drawings. FIG. 1 is a configuration diagram of the angular velocity detecting device. When the front-rear direction of the vehicle body 8 is the X axis, the horizontal direction is the Y axis, and the vertical direction is the Z axis, the first G sensor 4 and the second G sensor 5 are separated by a distance of 2r in the Y axis direction of the vehicle body. And fixed so that the respective acceleration detection directions are in the X-axis direction.

First, the principle of detecting the yaw angular acceleration by the G sensor will be described. When the angular acceleration ω ′ shown in FIG. 1 is generated in the vehicle body 8, the first G sensor 4 moves the second G
In the sensor 5, acceleration is generated in the positive direction. The absolute value of the generated acceleration can be expressed by the following equation 1.

[0013]

G (ω ′) = r * ω ′ G (ω ′)... Acceleration generated by ω ′ r... Distance between vehicle body center 6 and acceleration sensor ω ′.・ Yaw angular acceleration.

The acceleration detected by each acceleration sensor is:
Actually, when the longitudinal acceleration at the center of gravity (Gbx) is taken into consideration, the following equation 2 is obtained for the G sensor 4.

[0015]

GL = Gbx-r * [omega] 'GL... Acceleration measured by G sensor 4 Gbx... Longitudinal acceleration at vehicle center of gravity.

In the acceleration sensor 5, the second
It is expressed by the following equation 4 in which only the sign of the term is reversed.

[0017]

## EQU3 ## GR = Gbx + r * .omega.'GR... The acceleration measured by the acceleration sensor 5.

The yaw angular acceleration is obtained by the following equation 4 using the measured values GL and GR.

[0019]

Ω ′ = (GR−GL) / 2r
.

That is, in principle, if Equation 4 is calculated,
The yaw angular acceleration can be determined. Further, the yaw angular velocity can be obtained by integrating the above yaw angular acceleration with time.

Next, the detection of the yaw angular velocity based on the wheel speed difference between the left and right driven wheels will be described. The required configuration consists of wheels 1a-1d and metal gears 2a-2d that rotate with each wheel.
And a wheel speed sensor 3 for converting a change in magnetic flux into a sinusoidal voltage
a to 3d, and a control device 29 for performing signal processing and calculation.

It is assumed that the vehicle 8 in FIG. 1 is a rear-wheel drive vehicle.
Assuming that a circular turn having a radius R is performed at the angular velocity ω, the speed VWR of the right driven wheel 1a is expressed by the following equation 5.

[0023]

VWR = (R + r) * ω VWR ··· Wheel speed of right driven wheel R ······· Rotating radius of vehicle (distance between turning center 7 and vehicle center of gravity 6) ω ··· Yaw angular velocity.

In the case of FIG. 1, the speed VWL of the left driven wheel 1b is smaller than that of the right driven wheel 1b, as shown in the following equation (6).

[0025]

## EQU6 ## VWL = (R-r) *. Omega.VWL... The wheel speed of the left driven wheel.

From equations (5) and (6),

[0027]

Ω = (VWR−VWL) / 2r
.

According to Equation 7, it is understood that the yaw angular velocity ω is proportional to the speed difference between the left and right driven wheels. More than,
4 is a description from a physical viewpoint of a method of calculating a yaw angular velocity of a vehicle from two G sensors or two wheel speed sensors.

Next, the hardware configuration and the flow of signals will be described with reference to the block diagram of FIG. A microcomputer 28 (hereinafter referred to as a microcomputer) is the center of the arithmetic processing. The microcomputer 28 is, for example, an AB of a car.
S (anti-skid brake system) and 4WS
Using a computer for other purposes such as (a four-wheel steering control device)
The calculation processing of the angular velocity may be incorporated in the form of software. Further, the microcomputer 28 may be a DSP (Digital Signal Processor).

When the signal flow is followed, the detection signals of the G sensors 4 and 5 are converted into digital signals by the A / D converter 22 and input to the microcomputer 28. In the microcomputer 28, the difference between the two acceleration signals is obtained, the coefficient is multiplied by a coefficient (1 / 2r) by the coefficient means 24, and the yaw angular acceleration ω'G is calculated. Thus, the yaw angular velocity ωG is obtained.

The signals from the wheel speed sensors 3a and 3b are converted from sine waves into rectangular waves by the waveform shaper 23,
Is input to In the microcomputer 28, the difference between the two wheel speed signals is calculated, and the coefficient (1 / 2r) is calculated by the coefficient means 25.
And the yaw angular velocity ωv is obtained.

One of the yaw angular velocity ωG calculated from the detected values of the two G sensors 4 and 5 and the yaw angular velocity ωv calculated from the detected values of the two wheel speed sensors 3a and 3b are actually either one depending on the driving state of the vehicle. Yaw angular velocity. Therefore, in this embodiment, the yaw angular velocity ωG or ωv that accurately represents the actual yaw angular velocity is selected according to the driving state of the vehicle, and control is performed using the selected yaw angular velocity.

In this embodiment, the yaw angular velocity ωG obtained from the G sensor is selected during braking of the vehicle, and
The yaw angular velocity ωv obtained from the wheel speed sensor is selected. The switch 27 determines the condition of braking or non-braking, and selects the yaw angular velocities ωG and ωv. For the condition determination at this time, for example, a signal of the brake lamp switch 21 can be used.

Next, a method of calculating the yaw angular velocity used for control in the internal processing of the microcomputer 28 will be described with reference to the flowchart of FIG. This flowchart is
The processing from START to END is performed by interruption every predetermined time.

In step 31, it is determined whether the brake lamp is on or off. This is to determine whether the vehicle is in a braking state or a non-braking state. If the vehicle is in the non-braking state, in order to select the wheel speed sensor side, in step 35, the above equation 7 is calculated and the yaw angular velocity ωv
Ask for. In the next step 36, the value of ωv is stored as an integral initial value ω0 used when integrating the yaw angular acceleration by the G sensor. Finally, in step 37, the value of ωv is substituted as the true yaw angular velocity ω.

When the vehicle is in the braking state, the yaw angular acceleration ωG ′ is obtained by calculating the equation (4) in step 32 in order to select the G sensor. In the next step 33, the yaw angular acceleration ωG ′ is integrated. At this time, the value of ωv immediately before the brake lamp is turned on is used as the integral initial value ω0. Finally, in step 34, the value of ωG is substituted as the true yaw angular velocity ω.

As described above, by selecting the G sensor side during braking and the wheel speed sensor side during non-braking, both drawbacks can be complemented, and an accurate yaw angular velocity can always be obtained.

Next, an embodiment in which the above-described yaw angular velocity detecting device is applied to an anti-skid control device will be described with reference to FIG.
This will be described with reference to FIG. The front right wheel 1a, the front left wheel 1b, the rear right wheel 1c, and the rear left wheel 1d are respectively provided with wheel cylinders 43a to 43d for transmitting brake fluid pressure to the wheels, and wheel speed sensors 3a to 3d. The brake fluid pressure supplied to the wheel cylinders 43a to 43d is generated in the master cylinder 44 by being operated from the brake pedal 47, and is transmitted to the hydraulic unit 45. The oil pressure is transmitted to the cylinders 43a to 43d.

The hydraulic unit 45 has solenoid valves 45a-4 for increasing, maintaining, and reducing the brake fluid pressure transmitted to the wheels 1a-1d.
5d is arranged, and operates in response to a control command from the control device 46. In addition, other sensors that provide input signals to the control device 46 include wheel speed sensors 3a to 3d, a steering angle sensor 48 that detects the rotational position of the steering wheel 49, and an acceleration sensor 4 that detects the longitudinal G of the vehicle. , 5 are provided. Further, as an output, a plurality of transistors (not shown) for driving the hydraulic solenoid valves 45a to 45d are provided.

The basic operation of the anti-skid control device will be described. Conventionally, various systems have been reported for the anti-skid control device, but the basic operation is the same. Here, suppose Vfr: the wheel speed value of the front right wheel Vfl: the wheel speed value of the front left wheel Vrr: the wheel speed value of the rear right wheel Vrl: the wheel speed value of the rear left wheel V: the speed of the vehicle body, and the slip ratio of each wheel is expressed by the following formulas 8 to 11.

[0041]

Sfr = (V−Vfr) / V: Slip ratio of front right wheel

[0042]

Sfl = (V−Vfl) / V: Slip rate of front left wheel

[0043]

Srr = (V−Vrr) / V: rear right wheel slip ratio

[0044]

Srl = (V−Vrl) / V: Slip ratio of the rear left wheel.

In the μ-S characteristic shown in FIG. 7, the slip ratio of each wheel is set to around 0.2 so that the friction coefficient is maximized. When the slip ratio is large, the solenoid valves 45a to 45d are operated, and the wheel cylinders are operated. The hydraulic pressure of 43a to 43d is reduced. As a result, the wheel speed is gradually increased to the speed of the vehicle body, so that the slip ratio is reduced.

When the slip ratio is extremely small, the hydraulic pressure of the wheel cylinders 43a to 43d is increased to apply braking torque to the wheels to increase the slip ratio.

As described above, by repeatedly changing the hydraulic pressures of the wheel cylinders 43a to 43d, the slip ratio is brought close to a predetermined value, the braking force is maximized, and the lateral drag which contributes to the stability during running is also reduced. It is possible to brake stably without lowering.

However, the above operation assumes that the four wheels are on the same road surface. As shown in FIG. 6, the braking force obtained from each wheel is represented by Ffr: braking force of the front right wheel Ffl: braking force of the front left wheel Frr: braking force of the rear right wheel Frl: braking force of the rear left wheel. Assuming that there is no difference between the left and right vertical loads Wf and Wr applied to the wheels and that the friction coefficient μ of the road surface is the same

[0049]

[Equation 12] Ffl = Ffr = μ · Wf

[0050]

## EQU13 ## Frl = Frr = .mu.Wr
.

Thus, there is no difference. Therefore, no force acting in the lateral direction is generated on the vehicle, and the steering stability of the vehicle can be obtained.

However, when the friction coefficient μ of the road surface is different between the left and right wheels, for example, when the right road surface μ is high,
When the road surface μ shown in FIG. 6 is μr> μl

[0053]

[Formula 14] Ffr = μr · Wf> Ffl = μl · Wf

[0054]

[Equation 15] Frr = μr · Wr> Frl = μl · Wr
.

And the position around the center of gravity of the vehicle

[0056]

Mb = Lr (Ffr + Frr) -Ll (Ffl + Frl) -La (Cfr + Cfl) -Lb (Crr + Crl)
.

The following moment is generated. Where Cf
r, Cfl, Crr, and Crl are cornering forces generated by the front right, front left, rear right, and rear left wheels, and the maximum value thereof is equal to or less than the value of the lateral drag in FIG.

Here,

[0059]

Lr (Ffr + Frr) -Ll (Ffl + Frr) <La (Cfr + Cfl) + Lb (Crr + Crl)
.

At this time, the generation of the moment due to the difference between the braking forces of the left and right wheels is canceled out by the lateral drag of the tire, and the vehicle does not actually generate the yaw moment, that is, the yaw.

However, as the difference between μ on the left and right increases,

[0062]

Lr (Ffr + Frr) -Ll (Ffl + Frr)> La (Cfr + Cfl) + Lb (Crr + Crl)
.

And yaw occurs. This yaw is not caused by the driver's steering operation, but is caused by the condition of the road surface, which is against the driver's will. In addition, there is a case that an accident is caused by sudden yaw generation, which is unexpected for a driver.

As a countermeasure against this, an anti-skid control system in which the following yaw angular velocity is fed back is effective. This will be described with reference to the control block diagram of FIG.

The yaw angular acceleration ω calculated in the flowchart of FIG. 3 is compared with a target (reference) yaw angular velocity created based on the steering angle of the steering wheel. In general, it is known that the steering angle is proportional to the yaw angular velocity, and a proportional component is generated in step 51 to generate a reference yaw angular velocity ωR from the steering angle θ. The reference yaw angular acceleration ωR is shown in FIG.
Is compared with the yaw angular velocity ω calculated in the flowchart of
The deviation β is obtained.

Next, based on the yaw angular velocity deviation β, the target slip rates Sfrt, Sflt, Srrt, Srlt of each wheel are calculated.
Is obtained by each of the blocks 52a to 52d. Each of these blocks has a table for calculating a target slip ratio from the yaw angular velocity deviation β, and has a form as shown in FIG.

The essential meaning of this table is to lower the target slip ratio of the right wheel when a yaw angular velocity clockwise exceeds the target yaw acceleration ωR in the vehicle. As a result, in the description of FIG. 7, the target slip ratio of the right wheel was around 0.2, but it was reduced to 0.1 or less, the friction coefficient μ of the right wheel became small, and a counterclockwise yaw moment was generated in the vehicle. I do.

Next, in each of the subsequent blocks 53a to 53d, the estimated vehicle speed V and the target slip rates Sfrt, Sflt, Srr
From t, Srlt and each wheel speed, a target wheel speed value is calculated by the following equation (19).

[0069]

Vfrt = V * (1−Sfrt) The same formula is used for the subscripts flt, rrt, and rlt.

Based on the difference between the target wheel speed value and the actual wheel speed value, pressure increase, hold, and pressure reduction of each of the solenoid valves 45a to 45d are determined.

Next, the calculation for controlling each wheel to the above-mentioned target slip ratio will be described with reference to FIGS.

FIG. 8 is an explanatory diagram of the operation for controlling the target wheel speed Vfrt obtained by substituting the target slip ratio into the above equation (19). A to D in FIG. 8 indicate conditions of the operation of the hydraulic valve.

A condition ... Wheel acceleration Gfr <hold at GL B condition ... Wheel speed Vfr <target wheel speed Vfrt decompression C condition ... Wheel acceleration Gfr> GH hold D condition ... Pressure increase under conditions other than A, B and C.

FIG. 9 is a flowchart showing the above conditions. This routine is executed, for example, by ΔT (= 10 m
It is calculated every s). First, in step 901, a target wheel speed is calculated. In the next step 902, the wheel acceleration is calculated, which is obtained from the difference from the previously calculated Vfr. In step 903, the B condition in FIG. 8 is determined. Step 90
In 4, the C condition in FIG. 8 is determined. In step 905,
The A condition determination in FIG. 8 is performed. Here, when the conditions A to C are not satisfied, the condition D is satisfied, and the solenoid valve is in a pressure increasing state.

As described above, the block shown in FIG.
Although 53a has been described, similar processing is performed for the other blocks 53b to 53d so that the wheel speed follows the target wheel speed.

The processing shown in the flowchart of FIG. 9 is actually performed by the microcomputer 28.

[0077]

According to the present invention, when braking is not performed, the yaw angular velocity due to the difference between the left and right wheel speeds is regarded as the true yaw angular velocity, and the yaw angular velocity calculated based on the value of the G sensor is ignored at this time. Even if the yaw angular velocity is detected for a long time, the error does not increase.

Conversely, during braking, the yaw angular velocity calculated based on the values of the two G sensors is regarded as the true yaw angular velocity, and the value of the yaw angular velocity due to the difference between the left and right wheel speeds is ignored. Accordingly, the acceleration is not affected whether the wheels are locked or the wheel speed is suddenly changed by the operation of the ABS, so that the yaw angular velocity can be accurately detected. Regarding the integration error, the magnitude of the error can be ignored because the braking time for one cycle is about 20 seconds at the longest.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an angular velocity detection device.

FIG. 2 is a block diagram of the angular velocity detecting device.

FIG. 3 is a flowchart of a control procedure.

FIG. 4 is a configuration diagram of an anti-skid control system.

FIG. 5 is a control block diagram of the anti-skid control system shown in FIG.

FIG. 6 is a diagram showing generation of a yaw moment.

FIG. 7 is a μ-s characteristic diagram.

FIG. 8 is an explanatory diagram of the operation of wheel speed control.

FIG. 9 is a flowchart of wheel speed control.

[Explanation of symbols]

1a-1d… wheels, 3a-3b… wheel speed sensors, 4,5… G sensors, 28… microcomputers, 45… hydraulic units, 46… control devices,
52a to 52d: Target slip rate table.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hayato Sugawara 2477 Kashimayatsu, Kata-shi, Ibaraki Pref., Hitachi Automotive Engineering Co., Ltd. Examiner Masayuki Akita (56) References JP 4-133825 (JP, A) JP-A-4-136708 (JP, A) JP-A-63-169064 (JP, A) JP-A-5-85321 (JP, A) JP-A-4-204059 (JP, A) A) JP-A-62-70766 (JP, A) JP-A-64-33071 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01P 7/00 G01P 15/00

Claims (4)

(57) [Claims] 1. Two acceleration sensors arranged at a distance in a direction perpendicular to the traveling direction of a vehicle and mounted so that each detection direction is parallel to the traveling direction of the vehicle, and two acceleration sensors of left and right wheels of the vehicle. In a vehicle equipped with a wheel speed sensor for detecting a speed, it is determined whether the driving state of the vehicle is braking or non-braking, and when it is determined that the driving state is braking, the two The yaw angular acceleration is obtained from the difference between the outputs of the acceleration sensors, and this is integrated to obtain the yaw angular velocity. When it is determined that the driving state is during non-braking, the yaw angular velocity is obtained from the difference between the left and right wheel speeds detected by the wheel speed sensor. A method for detecting a yaw angular velocity of a vehicle, wherein an angular velocity is obtained. 2. Two acceleration sensors, which are arranged at a distance in a direction perpendicular to the traveling direction of the vehicle and are attached so that their detection directions are parallel to the traveling direction of the vehicle, In a vehicle equipped with a wheel speed sensor for detecting a speed, it is determined whether the driving state of the vehicle is braking or non-braking, and when it is determined that the driving state is braking, the two The yaw angular acceleration is obtained from the difference between the outputs of the acceleration sensors, and the yaw angular speed is obtained by integrating the yaw angular acceleration. Calculating the angular velocity, and using the value of the yaw angular velocity obtained during the immediately preceding non-braking as the initial value of the integration when the vehicle shifts from the non-braking state to the braking state, detecting the yaw angular velocity of the vehicle. Method 3. Two acceleration sensors which are arranged at a distance in a direction perpendicular to the traveling direction of the vehicle and are attached so that their detection directions are parallel to the traveling direction of the vehicle, In a vehicle equipped with a wheel speed sensor for detecting a speed, a yaw angular acceleration ω is calculated from a difference between outputs of the two acceleration sensors when the vehicle makes a yaw motion.
G ′ is calculated to obtain the yaw angular velocity ωG by integrating the yaw angular velocity ωG, obtain the yaw angular velocity ωv from the difference between the left and right wheel speeds, select the ωG as the yaw angular velocity when the vehicle is braking, and select the ωv when the vehicle is not braking. A method for detecting a yaw angular velocity of a vehicle . 4. Two acceleration sensors arranged at a distance in a direction perpendicular to the traveling direction of the vehicle and mounted so that each detection direction is parallel to the traveling direction of the vehicle; In a vehicle equipped with a wheel speed sensor for detecting a speed, a yaw angular acceleration ω is calculated from a difference between outputs of the two acceleration sensors when the vehicle makes a yaw motion.
The yaw angular velocity ωG is obtained by integrating G ′ and the yaw angular velocity ωG is obtained, the yaw angular velocity ωv is obtained from the difference between the left and right wheel speeds, the ωG is selected as the yaw angular velocity when the vehicle is braking, and the ωv is selected when the vehicle is not braked. When the vehicle shifts from the non-braking state to the braking state, a value of the yaw angular velocity ωv obtained at the time of the immediately preceding non-braking is used as an initial value of the integration
Yaw angular velocity detection method.