JP3454032B2 - Control start judgment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control start determination method for determining a control start time when controlling a wheel motion to a predetermined motion state, and more specifically, to a braking for slip speed based on wheel speed time series data. The present invention relates to a control start determination method for estimating a torque gradient and determining a control start time point for anti-lock braking operation, traction control, etc. based on the braking torque gradient.

[0002]

2. Description of the Related Art Antilock brake control devices (AB
S) controls the braking force acting on the wheels so as to prevent the wheels from locking and obtain a braking torque close to the maximum value.

As a technique for determining a control start time of such ABS, conventionally, obtains the wheel deceleration dV _R / dt by differentiating the time wheel speed V _R, the value of the wheel deceleration is a predetermined value - There was a technique of reducing the brake pressure to prevent the tire from locking when it was lower than a ₀ (wheel deceleration set value) (Japan ABS Co., Ltd .: ABS research for automobiles, P47-51).

[0004]

However, in such a conventional ABS start determination method, when the brake is applied gently so that the wheel deceleration does not reach the constant value -a ₀ on a low μ road, the ABS There is a problem that the wheel is locked without determining the control start. It is to be noted that this problem is caused by the fact that when the traveling road surface has a low μ, the generated braking torque is small and the wheels are locked even with a loose brake.

Such a problem is caused by a technique for controlling the wheel motion to a predetermined motion state such as traction control (TRC) as well as ABS, for example, peak μ.
It is seen in the technology that keeps the motion state immediately before the lock by keeping track of, and maintains it in the range of the predetermined slip ratio, and that the dynamic characteristics of the wheel motion change depending on the μ value of the running road surface etc. Has a root cause.

The present invention has been made in order to solve the above-mentioned problems, and the control start time of the control for bringing the wheel motion into a predetermined motion state is accurately set without depending on the μ value of the traveling road surface or the gradual braking. Moreover, it is an object of the present invention to provide a control start determination method that enables stable determination.

[0007]

In order to achieve the above object, the invention of claim 1 detects the wheel speed at every predetermined sample time, and the wheel speed detection step detects the wheel speed. only the detection versus time-series data of the wheel speed
Used as elephants, and the torque gradient estimating step to estimate the gradient of the braking torque with respect to the slip speed, based on the gradient of the estimated braking torque by the torque gradient estimating step,
A determination step of determining a control start time point of control for bringing the wheel motion into a predetermined motion state.

According to a second aspect of the present invention, the torque gradient estimating step of the first aspect uses time series data of detected wheel speeds.
Based on only the first calculation step of calculating a physical quantity related to the change of the wheel speed and a physical quantity related to the change of the change of the wheel speed, and a physical quantity related to the change of the wheel speed and the wheel speed calculated by the first calculation step . A second calculation step of calculating a physical quantity history relating to a change in wheel speed and a physical quantity history indicating a history of a physical quantity relating to change in wheel speed, and estimating a gradient of the braking torque from the physical quantity, based on the physical quantity relating to a change in change. And consist of.

According to a third aspect of the present invention, in the first calculation step of the second aspect, the sample times k (k = 1, 2, ...) At the wheel of the wheel number i (i = 1, 2, 3, 4). When the time series data of the wheel speed detected in .....) is ω _i [k], the sample time is τ, and the wheel inertia is J, as a physical quantity related to the change of the wheel speed, Is calculated, and y _i [k] = − ω _i [k] + 2ω _i [k−1] −ω _i [k−2] is calculated as a physical quantity related to the change of the wheel speed, and the second In the calculation step of, a physical quantity θ _i representing a history of physical quantities related to changes in wheel speed and a history of physical quantities related to changes in changes in wheel speed, a forgetting factor λ, and transposition of a matrix as “ ^T ”, It is characterized in that it is obtained as a torque gradient.

(Principle of the Present Invention) The braking force acts on the road surface via the surface of the tread of the tire that is in contact with the road surface. In practice, however, this braking force is mediated by the frictional force between the road surface and the wheels. It acts on the vehicle body as a reaction force (braking torque) from the road surface. When the vehicle body is traveling at a certain speed, slipping occurs between the wheels and the road surface when the braking force is applied.The braking torque that acts as a reaction force from the road surface at this time is expressed by the following equation. The slip velocity ω _s (converted into angular velocity) changes as shown in FIG.

Ω _s = ω _v −ω _i where ω _v is the vehicle speed (equivalently expressed as an angular velocity), and ω _i is the i-th wheel (i is the wheel number, i = 1,2,3,4). ) Is the wheel speed converted into angular velocity.

As shown in FIG. 4, the braking torque initially increases with an increase in slip speed, reaches a maximum value f _i0 at a slip speed ω ₀ , and decreases with an increase in slip speed at a slip speed higher than ω _0. . The slip speed ω ₀ corresponds to the slip speed when the friction coefficient between the wheel and the road surface is the maximum value (peak μ).

[0013] Thus, as is apparent from FIG. 4, the gradient of the braking torque with respect to the slip speed (hereinafter referred to as "braking torque gradient") is, omega _s <positive at _{ω 0 (> 0), ω} s = ω 0
0, and negative (<0) when ω _s > ω ₀ . That is, when the braking torque gradient is positive, the wheels are gripping the road surface, when the braking torque gradient is 0, the peak μ state, and when the braking torque gradient is negative, the wheels shift to the lock state. Thus, the motion state of the wheel motion can be estimated from the braking torque gradient. The present invention focuses on this point, and determines the control start point of time such as ABS and TRC based on the braking torque gradient. In particular, the slip ratio and the magnitude of the braking torque that reach the peak μ vary greatly depending on the μ value of the running road surface, but it is always true that the braking torque gradient is always 0 at the point where the braking torque becomes maximum, regardless of the running road surface. This is a property that holds and enables stable and accurate determination.

(Principle of Estimating Braking Torque Gradient of the Present Invention) Wheel motion and vehicle motion of each wheel are described by the following equation of motion.

[0015] Where F _i 'is the braking force generated on the i-th wheel, T _bi is the brake torque applied to the i-th wheel in response to the pedaling force, M is the vehicle mass, R _c is the effective radius of the wheel, and J is the wheel. Inertia, v is vehicle speed. In addition, · represents a derivative with respect to time.
In equations (1) and (2), F _i 'is the slip speed (v /
R _c −ω _i ).

Here, the vehicle body speed is represented by an equivalent angular velocity ω _v of the vehicle body, and the braking torque R _c F _i 'is described as a linear function of the slip velocity (slope k _i , y intercept T _i ).

[0017]       v = R_cω_v                                           (3)       R_cF_i’(Ω_v−ω_i) = K_i× (ω_v−ω_i) + T_i       (Four) Furthermore, by substituting Eqs. (3) and (4) into Eqs. (1) and (2), the wheel speed
Degree ω_iAnd vehicle speed ω _vDiscretized at every sample time τ
Time series data ω_i[k], ω_v[k] (k is sample
Sample time in units of τ, k = 1,2, .....)
Expressed as Here, the equations (5) and (6) are combined, and the equivalent angular velocity ω of the vehicle body is_v
Is erased, To get

By the way, assuming that the maximum braking torque of R _c Mg / 4 (g is gravitational acceleration) is generated under the condition that the slip speed is 3 rad / s, To get Here, τ = 0.005 (se
c), R _c = 0.3 (m), M = 1000 (kg)
(k _i ) = 245. Therefore, And Eq. (7) can be approximated as

[0019] However, Is.

By rearranging in this way, equation (8) can be described in a linear form with respect to unknown coefficients k _i and f _i , and an online parameter identification method should be applied to equation (8). Thus, the braking torque gradient k _i with respect to the slip speed can be estimated.

That is, by repeating the following steps 1 and 2, the time series data of the braking torque gradient can be estimated from the time series data ω _i [k] of the detected wheel speed. The control start time is determined from the estimated value of the braking torque gradient.

Step 1: y _i [k] = − ω _i [k] + 2ω _i [k−1] −ω _i [k−2] (10). The first element of the matrix φ _i [k] in equation (9) is 1
It is a physical quantity related to the change of the wheel speed at the sample time, and the equation (10) is a physical quantity related to the change of the wheel speed at the one sample time at the one sample time.

Step 2: Is a forgetting factor (for example, λ = 0.98) indicating “ ^T ”
Indicates the transpose of the matrix.

The left side of the equation (11) is a physical quantity representing a history of physical quantities relating to changes in wheel speed and a history of physical quantities relating to changes in change in wheel speed.

Step 3: The control start time is determined by comparing the value of the Luk gradient with the reference value.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a control start determination device according to an embodiment of the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 shows the configuration of a control start determination device according to the first embodiment.

As shown in FIG. 1, the control start determination device 5 according to the first embodiment has a wheel speed detecting means 10 for detecting a wheel speed at every predetermined sample time τ, and a detected wheel speed. The torque gradient estimating means 12 for estimating the braking torque gradient from the time-series data, and the control means 16 by comparing the estimated braking torque gradient with the reference value (for example, an antilock brake control device, a traction control device, etc. described later) Determination means 14 for determining the control start time point or the control end time point (including).

The torque gradient estimating means 10 uses the time-series data of the detected wheel speed to calculate the physical quantity relating to the change of the wheel speed in one sample time from the expression (9) and the expression (10) to
A physical quantity related to the change in the wheel speed during the sample time is calculated for one sample time (step 1), and using the calculated physical quantity, the history of the physical quantity related to the change in the wheel speed and the change in the wheel speed are calculated from equation (11). The physical quantity representing the history of the physical quantity is calculated (step 2), and the braking torque gradient is estimated from the physical quantity.

FIG. 2 shows a configuration example in which the control start determination device 5 configured as described above is mounted on a vehicle body and the determination of the control start time by the device is applied to antilock brake control and traction control. It is a thing.

The first to fourth wheels of the vehicle body shown in FIG.
Brake discs 52a, 52b, 52c, 52d,
Front wheel cylinders 50a, 50b or rear wheel cylinders 50c, 50d and wheel speed sensors 10a, 10b, 10c, 10d as wheel speed detecting means 10 are attached, respectively. The wheel speed sensor 1
0a, 10b, 10c, and 10d are time-series data ω _i [k] (k is a sample time; _i ) of the i-th wheel (i is a wheel number, i = 1,2,3,4) attached. k = 1, 2
, .....) are detected.

Front wheel cylinders 50a, 50b
Pipes for brake fluid for supplying brake pressure are connected to the rear wheel cylinders 50c and 50d, and these pipes are connected to a brake hydraulic circuit 99. That is, each wheel cylinder applies a brake pressure corresponding to the hydraulic pressure supplied from the brake hydraulic circuit 99 to the corresponding brake disc.

Wheel speed sensors 10a, 10b, 10c, 1
A torque gradient estimating means 12 is connected to 0d,
Further, the torque gradient estimating means 12 is connected to the judging means 14.

Then, the ABS / TRC controller 18 which outputs a control signal for performing anti-lock brake control and traction control to the judging means 14.
The brake hydraulic circuit 99 is connected to the ABS / TRC controller 18.

The brake hydraulic circuit 99 supplies the hydraulic pressure corresponding to the pedaling force of the brake pedal 118 to each wheel cylinder, and switches the hydraulic circuit during the traction control or the antilock brake control to change the ABS.T.
The hydraulic pressure supplied to the wheel cylinders is controlled according to the control signal from the RC controller 18.

The engine of the vehicle body shown in FIG. 2 is provided with a main throttle valve 32 for controlling the amount of air taken into the engine in conjunction with the accelerator pedal 36. A sub-throttle valve 28 is provided on the upstream side. The sub throttle valve 28 is opened and closed by driving a sub throttle actuator 26 connected to the ABS / TRC controller 18.

The sub-throttle valve 28 is set to the fully open position by a return spring (not shown) or the like during non-traction control, and during the traction control, the sub-throttle actuator 26 is responsive to a control signal from the ABS / TRC controller 18.
The opening / closing amount is controlled by.

A main throttle valve position sensor 34 and a sub-throttle valve position sensor 30 for detecting the opening / closing positions of the valves are attached to the main throttle valve 32 and the sub-throttle valve 28, respectively. An engine / transmission controller 24 that controls the engine and the transmission is connected to the main throttle valve position sensor 34 and the sub-throttle valve position sensor 30. Further, the engine / transmission controller 24 and the ABS / TRC controller 18 are bidirectionally connected, and the engine transmission 24 controls the engine of the vehicle body via the ABS / TRC controller 18 according to the opening / closing amount of the valve.

Next, the configuration of the brake hydraulic circuit 99 is shown in FIG.
Will be described in detail. As shown in FIG. 3, the brake hydraulic circuit 99 includes a reservoir 100 that stores brake fluid for the master cylinder system and the power supply system.
Is provided. The reservoir 100 is provided with a level warning switch 102 for detecting a decrease in the liquid level of the brake fluid stored inside, and a relief valve 104 for relieving the brake fluid to the reservoir 100 when the power supply system has an abnormally high pressure. There is.

A pump 106 for pumping the brake fluid from the reservoir 100 and discharging high hydraulic fluid is provided in the pipe arranged from the relief valve 104 side of the reservoir 100. Hydraulic pressure generated by pump (power supply system)
An accumulator 108 for accumulating pressure and a pressure sensor 110 for detecting the oil pressure of the accumulator 108 are provided. The pressure sensor 110 outputs a control signal for the pump 106 based on the hydraulic pressure of the accumulator 108 , and outputs a warning signal (ABS, T when the pressure is low).
The RC control prohibition signal) is output.

Further, a control signal for the pump 106 is output to the high hydraulic pressure side pipe of the accumulator 108 when the hydraulic pressure of the accumulator 108 is low, and a warning signal (ABS, TRC control prohibition signal) is output when the hydraulic pressure is low. A pressure switch 112 is provided.

A master cylinder 114 for generating a hydraulic pressure according to the pedaling force applied to the brake pedal 118 is connected to the other pipe extending from the reservoir 100. A brake booster 116 is disposed between the master cylinder 114 and the brake pedal 118 to regulate / introduce the high hydraulic pressure of the accumulator 108 into a hydraulic pressure corresponding to the pedaling force to generate a brake assisting force.

The brake booster 116 is connected to a pipe on the high oil pressure side of the accumulator and a pipe extending directly from the reservoir 100. When the depression amount of the brake pedal 118 is less than a certain value, the reservoir 100 is connected. From the accumulator 108 is introduced when the depression amount exceeds a certain value.

Further, a front master pressure pipe 164 and a rear master pressure pipe 166 for supplying the hydraulic pressure (master pressure) of the master cylinder 114 to the front and rear wheels are provided from the master cylinder 114. Then, the front master pressure pipe 164 and the rear master pressure pipe 16
A P & B valve 120 for adjusting the brake hydraulic pressure of the rear system is interposed at 6 so as to properly distribute the braking force to the front and rear wheels. The P & B valve 120 stops the pressure regulation of the rear system when the front system is lost.

The front master pressure pipe 164 extending from the P & B valve 120 has a pressure increasing device 122 for increasing the front wheel cylinder hydraulic pressure to secure a high braking force when the hydraulic pressure of the power supply system decreases. Is provided. A booster pipe 168 connected to the booster chamber of the brake booster 116 is connected to the pressure booster 122.
8 and the pressure intensifier 122, a pressure limiter 124
And the differential pressure switch 126 is interposed.

The pressure limiter 124 closes the path to the booster chamber so that the pressure booster 122 and the differential pressure switch 126 are not activated when an input exceeding the assisting force limit of the brake booster 116 is applied when the system is operating normally. Further, the differential pressure switch 126 detects a hydraulic pressure difference between the master cylinder 114 and the booster chamber.

The booster pipe 168 has a control solenoid valve 132 for the right front wheel (hereinafter referred to as "valve SF").
The R ”) pressure increasing valve 132a is connected to the left front wheel control solenoid valve 134 (hereinafter,“ valve SFL ”) pressure increasing valve 134a. Further valve SF
A low-pressure pipe 162 extending directly from the reservoir 100 is connected to the R pressure reducing valve 132b and the valve SFL pressure reducing valve 134b.

A switching solenoid valve 136 (hereinafter, "valve SA1") and a switching solenoid valve 138 (hereinafter, "valve SA2") are connected to the pressure supply side pipes of the valve SFR and the valve SFL, respectively. The pressure-increasing side pipe of the pressure-increasing device 122 is further connected to the valves SA1 and SA2. And
The pipe on the pressure supply side of the valve SA1 is connected to the front wheel cylinder 50a, and the valve SA2 is
It is connected to the front wheel cylinder 50b.

In the normal brake mode, the pressure from the pressure intensifying device 122 causes the valves SA1 and SA2 to
The valves are switched so as to be applied to the front wheel cylinders 50a and 50b, respectively, and the valve S
The valves are switched so that the pressures from the FR and the valve SFL are applied to the front wheel cylinders 50a and 50b, respectively. That is, in the front wheel, the normal brake mode and AB
It is possible to switch to the S mode independently for each of the left and right wheels.

Further, switching solenoid valves 129 and 130 (hereinafter referred to as "ST
R ”,“ SA3 ”), and the pressure increasing side valve 1 of the control solenoid valve 140 (“ valve SRR ”) for the right rear wheel.
40a and a control solenoid valve 142 for the left rear wheel
A pressure increasing valve 142a (“valve SRL”) is connected. Further, the pressure reducing valve 140b of the valve SRR
A low pressure pipe 162 extending directly from the reservoir 100 is connected to the pressure reducing valve 142b of the valve SRL.

The pipe on the pressure supply side of the valve SRR is connected to the rear wheel cylinder 50d, and the valve S
The RL is connected to the rear wheel cylinder 50c.

A high pressure pipe 167 extending from the accumulator 108 is connected to the valve STR, and the valve STR is switched so that the high hydraulic pressure of the booster pipe 168 is applied to the valve SA3 in the ABS mode. , In the TRC mode, the valves are switched so that a high hydraulic pressure irrelevant to the pedal effort of the high pressure pipe 167 is applied to the valve SA3. Thus, in the TRC mode, high hydraulic pressure can be applied to each rear wheel cylinder even when the driver does not step on the brake pedal 118.

The valve SA3 is switched so that the master pressure from the rear master pressure pipe 166 is applied to the valves SRL and SRR in the normal brake mode, and the valve ST3 is operated in the ABS (TRC) mode.
Hydraulic pressure supplied via R (hydraulic pressure of booster pipe 168 in ABS mode, high pressure pipe 167 in TRC mode)
Switch the valve so that That is, for the rear wheels, the normal brake mode and ABS (TRC)
Switching to the mode is done on the left and right.

The above switching solenoid valve S
A1, SA2, SA3, STR and control solenoid valves SRL, SRR, SFL, SFR are ABS / TRC.
It is connected to the controller 18, and the opening / closing and the valve position are switched according to a control signal from this controller.

Next, a first control example when ABS is carried out by the vehicle body of FIG. 2 will be described with reference to the flowchart of FIG.
In the region where the ABS is operated, the wheel acceleration (ω _i
[k] −ω _i [k−1] / τ) is negative and this logic is executed when the wheel acceleration is negative.

As shown in FIG. 5, the determination means 14 of FIG.
However, it is determined whether the braking torque gradient k estimated by the torque gradient estimating means 12 is smaller than the reference value E (> 0) (step 200). The reference value E corresponds to the value of the braking torque gradient with respect to the lower limit value of the slip speed in the ABS control region that follows the peak μ in FIG.

When it is determined that the braking torque gradient is equal to or larger than the reference value E (NO at step 200), that is,
In the case of a slip speed region smaller than the lower limit value of the peak μ tracking region in FIG. 4, the switching valve (SA1, SA2, S in FIG.
A3) is set to non-ABS mode (step 20)
2). In this case, a braking force corresponding to the master pressure is applied to the wheel cylinder.

On the other hand, the braking torque gradient k is equal to the reference value E.
When it is determined that it is smaller (Yes in step 200), that is, when it is in the slip velocity region of the peak μ tracking region of FIG. 4, the switching valve is set to the ABS mode (step 204), and then the braking force is set. Decrease (step 206). When reducing the braking force,
The pressure increasing valves 132a, 134a, 140a, 142a of the valves SFL, SFR, SRL, SRR of FIG. 3 are closed, and the pressure reducing valves 132b, 134b, 140b, 14 are closed.
Open 2b. As a result, the hydraulic pressure of the low-pressure pipe 162 is applied to each wheel cylinder, and the braking force is reduced.

As described above, in the ABS of FIG. 5, when the braking torque gradient k is equal to or larger than the reference value E, the ABS is not operated because the ABS is not operated, and when the braking torque gradient is smaller than the reference value E, the peak μ is reduced. Considering that the braking force is applied in the vicinity or beyond the peak μ, the ABS mode is switched to and the braking force is reduced. This gives the peak μ
The brake operation that follows can be realized and the lock of the tire can be prevented.

Next, a second control example in the case where ABS is performed on the vehicle body of FIG. 2 will be described with reference to the flowchart of FIG.

As shown in FIG. 6, the determination means 14 of FIG.
However, it is determined whether the braking torque gradient k estimated by the torque gradient estimating means 12 is smaller than the reference value E (> 0) (step 210).

When it is determined that the braking torque gradient k is equal to or greater than the reference value E (NO at step 210), the switching valves (SA1, SA2, SA3 in FIG. 3) are set to the non-ABS mode (step 212). In this case, a braking force corresponding to the master pressure is applied to the wheel cylinder.

On the other hand, the braking torque gradient k is equal to the reference value E.
When it is determined that it is smaller (step 210, affirmative determination), that is, when the braking torque gradient falls within the range for starting the ABS control, the switching valve is set to the ABS mode (step 214). Then, it is further determined whether or not the braking torque gradient k is smaller than the reference value −e (<0, e <E) (step 216).

When it is determined that the braking torque gradient is smaller than the reference value -e (Yes in step 216), that is, when it is determined that the braking force exceeds the peak μ, the braking force is reduced ( Step 21
8) Then, the process returns to step 210 again and the same processing is executed.

When it is determined that the braking torque gradient is equal to or greater than the reference value -e (NO in step 216), it is determined whether the braking torque gradient exceeds the reference value e (> 0) (step 220).

When it is determined that the braking torque gradient exceeds the reference value e (Yes in step 220), that is, when it is considered that the braking torque gradient is slightly away from the peak μ, the braking force is increased (step 222). Returning to step 210 again, the same processing is executed. When the braking force is increased, the valves SFL, SFR, SR shown in FIG.
L, SRR pressure reducing valves 132b, 134b, 140
b, 142b are closed, and the pressure increasing side valves 132a, 134a
a, 140a, 142a are opened. As a result, a high hydraulic pressure of the booster pipe 168 is applied to each wheel cylinder, and the braking force is increased.

When it is determined that the braking torque gradient is equal to or less than the reference value e (No in step 220), that is, when the braking torque gradient is in the peak μ region (-e to e) including 0, the braking force is increased. Hold it (step 224),
Returning to step 210 again, the same processing is executed. When the braking force is maintained, the valves SFL, S shown in FIG.
FR, SRL, SRR pressure reducing valves 132b, 134
b, 140b, 142b and pressure increasing side valves 132a, 1
34a, 140a and 142a are closed together. As a result, the hydraulic pressure applied to each wheel cylinder is retained.

As described above, in the ABS shown in FIG. 6, when the braking torque gradient becomes smaller than the reference value E, the ABS control is started and the braking torque gradient is maintained in the peak μ range including 0. The control start judgment for decreasing, holding, and increasing the braking force is performed. As a result, it is possible to realize a braking operation that follows the finer peak μ than that of the ABS shown in FIG. 5 and to perform a stable braking operation with a minimum braking distance.

Next, a control example in the case of performing the TRC on the vehicle body of FIG. 2 will be described with reference to the flowchart of FIG. In addition,
In the region where the TRC is activated, the wheel acceleration is positive, and this logic is executed when the wheel acceleration is positive.

As shown in FIG. 7, the determination means 14 of FIG.
However, it is determined whether the braking torque gradient k estimated by the torque gradient estimating means 12 is smaller than the reference value F (> 0) (step 230). The reference value F is set as an upper limit value of the braking torque gradient when the TRC is performed while keeping the braking torque gradient within a predetermined range (see the traction control area in FIG. 4). When it is determined that the braking torque gradient k is equal to or greater than the reference value F (No determination in step 230), the switching valve (SA1, SA2, SA3 in FIG. 3) is set to the non-TRC mode (step 232). Then, the sub throttle valve 28 of FIG. 2 is fully opened (step 234). As a result, in the non-TRC mode, the braking force corresponding to the master pressure is applied to the wheel cylinders, and the main throttle valve 3 shown in FIG.
A normal traveling operation is performed in which the air amount that depends only on the opening / closing amount of 2 is supplied to the engine.

On the other hand, the braking torque gradient k is the reference value F
When it is determined that it is smaller (step 230, affirmative determination), that is, when the braking torque gradient is within the range of TRC control start, the switching valve is set to the TRC mode (step 236).

Then, the ABS / TRC controller 18 of FIG. 2 controls the opening degree of the sub-throttle valve 28 so that the estimated braking torque gradient matches the reference value (step 238), and the estimated braking torque is calculated. The control solenoid valve is controlled to adjust the braking force so that the gradient matches the reference value (step 240). In this case, the braking force is applied as needed even when the driver does not step on the brake pedal 118.

Even in the control of steps 238 and 240, the determination means 14 compares the braking torque gradient with the reference value, and ABS / TR is determined based on the result of the comparison.
The timing (control start time) for increasing / decreasing the braking force and adjusting the opening of the sub-throttle valve 28 by the C controller 18 is determined.

As described above, in the TRC shown in FIG. 7, the TRC is performed based on the braking torque gradient so as to prevent the motion state from exceeding the peak μ, so that the vehicle attitude can be kept stable.

As described above, in the first embodiment, the braking torque gradient is estimated only from the time series data of the wheel speed,
Based on the value of the braking torque gradient, the control start time of the ABS or TRC and the control start time of the increase / decrease of the braking force and the adjustment of the opening of the sub-throttle valve are determined. As a result, even if the slip speed that reaches the peak μ changes depending on the road surface condition on which the vehicle is traveling, the fact that the braking torque gradient becomes 0 at the peak μ does not change, so stable ABS and T
RC control can be performed.

Further, in the present embodiment, since it is not necessary to estimate the vehicle body speed, the speed v _w obtained from the wheel speed for estimating the vehicle body speed and the actual vehicle body speed v _{v *} are different from the conventional case. If the braking force is repeatedly increased and decreased at a relatively low frequency until the values match or become close to each other, or if the vehicle speed compared with the reference speed is significantly different from the actual vehicle speed, the wheels may be locked for a long time. It is possible to avoid problems such as the braking force being extremely reduced due to the return, and to realize a comfortable ABS.

(Second Embodiment) In the second embodiment, the ABS device for controlling the braking force to the peak μ based on the vibration characteristic of the wheel speed when the braking force is excited is applied to the ABS device . The control start determination device according to the embodiment is applied.

FIG. 8 shows the configuration of the second embodiment. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 8, in the vehicle body according to the second embodiment, together with the control start determination device 5, the wheel speed when the tire is actively gripping the braking force commanded by the driver. and the resonant frequency f ₁ and small braking force excitation command calculating unit 152 for calculating a micro-amplitude command P _v at the time of adding the fine vibrations of the same frequency, the resonant frequency f ₁ component of the detected wheel speed amplitude value omega _d Amplitude value detection unit 1 for detection
54, the detected value ω _d, and the minute braking force excitation amplitude command P _v
And a braking force reduction command calculation unit 150 that calculates a braking force reduction command P _r based on the above.

The braking force reduction command calculation unit 150 and the minute braking force excitation command calculation unit 152 include a braking force reduction command P _r from the braking force reduction command calculation unit 150, a braking force P _{d from} the driver operation unit 156, and a minute amount. The vehicle motion system 158 to be controlled is based on the minute braking force excitation amplitude command P _v from the braking force excitation command calculation unit 152.
It is connected to a brake valve driver 160 that generates a braking force command that is an input to the vehicle, and applies the braking force command to the vehicle motion system 158.

Further, the minute braking force excitation command calculation unit 15
Reference numeral 2 is connected to the determination means 14 of the control start determination device 5, and instructs the brake valve driver 160 to start or stop the excitation of the braking force according to the determination of the control start time point of the determination means 14.

In the second embodiment, the minute braking force excitation command calculation unit 152 has the same frequency as the resonance frequency f ₁ of the wheel speed when the tire grips the braking force commanded by the driver. The small amplitude command P _v when applying the small vibration is calculated, and the small vibration having the same frequency as the resonance frequency f ₁ of the wheel speed when the tire is actively gripping the braking force commanded by the driver is generated. By adding, the change of the resonance frequency f ₁ is detected from the amplification characteristic.

As shown in FIG. 11, in the frequency characteristic of the wheel resonance system, the peak of the wheel speed gain at the resonance frequency becomes lower as the friction coefficient μ approaches the peak value.
When the friction coefficient μ exceeds the peak value, the resonance frequency shifts to a frequency side higher than the resonance frequency f ₁ when the tire grips. As for the component of the resonance frequency f _{1 when} the tire is gripped, the amplitude of the resonance frequency f ₁ component decreases as the peak μ state is approached. Therefore, the resonance frequency f that appears in the wheel speed
It is possible to detect the approach to the peak μ state from the gain of the minute vibration component of ₁ .

As shown in FIG. 10, the amplitude value detector 154 includes a band pass filter 162 and a band pass filter whose pass band is set in a predetermined range including the resonance frequency f ₁ of the wheel speed when the tire is gripped. It is configured by a full-wave rectifier 164 that rectifies the output of the filter 162, and a low-pass filter 166 that smoothes the output of the full-wave rectifier 164 into a direct current. Amplitude value detection section 154, a tire is only detected component of the resonance frequency f ₁ of the wheel speed when on grip, since the component of the resonance frequency f ₁ of the wheel speed and outputs the direct current, the detection value omega _d Is the amplitude value of the resonance frequency f ₁ component of the wheel speed.

Further, the braking force reduction command calculation unit 150
As shown in FIG. 12, a calculation unit 168 that calculates a minute excitation gain g _d that is a gain of the detected value ω _d with respect to the minute braking force excitation amplitude command P _v , a minute excitation gain g _d, and a reference value g _s . Difference g _d −g _s , the proportional gain G _Pr1 and the integral gain G _Ir1 are used to calculate the reduced braking force by the PI controller 170, and the braking force P _d by the driver's operation is not exceeded. As described above, the positive value is removed, only the negative value is adopted, and the positive value removing unit 172 that outputs the reduced braking force command P _r is formed.

Next, the control flow of the second embodiment will be described with reference to the flowchart of FIG.

As shown in FIG. 9, the judging means 14 of FIG. 8 judges whether the braking torque gradient estimated by the torque gradient estimating means 12 is equal to or less than the reference value G (step 2).
50). The reference value G is determined from the value of the braking torque gradient with respect to the slip speed that is judged to be appropriate when starting the excitation of the braking force.

When the braking torque gradient is equal to or less than the reference value G (Yes at Step 250), the minute braking force excitation command calculation unit 152 issues an excitation command, and the brake valve driver 160 which receives this instruction outputs the resonance frequency of the wheel speed. the braking force is small excited at f ₁ (step 252).

Next, if the minute excitation gain g _d is larger than the reference value g _s (Yes at Step 254), that is, the detected value ω _d when excited by the minute braking force excitation amplitude command P _v is the reference value g _s P 11 is larger than _v (where ω _d is the rotational speed in [rad / s] and P _v is pressure or torque in [Pa] or [Nm]).
As described above, the average braking force P _m is maintained assuming that the tire is gripping (step 25).
8). If the contrary the fine excitation gain g _d is equal to or less than the reference value g _s step 254 a negative decision), i.e. becomes smaller than the detection value omega _d is the reference value g _s P _v when excited with very small braking force excitation amplitude command P _v For example, since the friction coefficient is approaching the peak μ, the average braking force P _m is reduced (step 256).

Then, returning to step 250, when the braking torque gradient is maintained at the reference value G or less, the minute braking force excitation is maintained and the peak μ follow-up control is performed in the same manner. When it exceeds (Step 25
0 negative determination), the minute braking force excitation is stopped assuming that the grip state is away from the peak μ (step 26).
0).

The average braking force P _m applied by the braking force control of FIG. 9 is P _m = P _d + P _r , P _r ≦ 0 as shown in FIG. _{and r} is always negative, does not mean braking force P _m exceeds the braking force P _d by the driver operation is commanded. According to this ABS, when a frictional force reaches a peak μ state when a braking force as a sum of a braking force by a driver's operation and a minute vibration braking force is applied to a wheel, the average braking force is further reduced. The increase in braking force is suppressed, which prevents the tire from locking.

Further, in the above braking force control, FIG.
As shown in FIG. 9A, the braking force P _{b is changed} to the minute excitation P from the minute excitation start time when the positive determination is made in step 250 of FIG.
_It can be seen that _v is superimposed.

On the other hand, A using the conventional microexcitation is used.
As shown in FIG. 13 (b), the change in the braking force of the BS with time is such that the minute excitation P is added to the braking force P _b from the time when the driver depresses the brake pedal to apply the braking force to the wheels.
_v is superimposed. As described above, when the brake pedal is depressed to immediately perform the micro-excitation, the micro-excitation must be performed for a longer time than in the second embodiment. Further, there is a case where it is not necessary to perform ABS even when the brake pedal is depressed, and it is useless to minutely excite the braking force.

In the second embodiment, since the braking force is minutely excited from the control start time when the judging means 14 judges based on the braking torque gradient, the minute braking force can be obtained without lowering the detection accuracy of the peak μ. The excitation time can be shortened and the minute excitation of the braking force can be efficiently performed.

The embodiments of the present invention have been described above, but the present invention is not limited to the above examples. For example, an example in which the above-described embodiment is applied to ABS and TRC is shown, but if it is a technique for controlling the wheel motion to a predetermined motion state, ABS
It is applicable not only to TRC and TRC.

Further, an example in which the control start determination device of the present invention is applied to the technique of performing TRC by using both the opening of the sub-throttle valve and the braking force is shown. The above-described embodiment can be applied to the technique of performing TRC with any one of the above.

Further, the above embodiment can be applied to not only automobiles but also trains and the like.

[0098]

[Embodiment] With the wheel speed of 50 rad / s as the initial speed, the ABS control start determination is performed by the control start determination device 5 of the above-described embodiment in each case of the slow braking, the rapid braking and the follow-up braking by the braking force. Experimental results are shown in FIGS.
7 shows. In this experiment, the reference value of the braking torque gradient k was set to 50. That is, the time when k <50 is determined as the control start time when the braking force is reduced and the ABS is started. However, in this experiment, only the control start point was judged and the actual control was not performed.

FIGS. 14A, 14B, and 14C show temporal changes in wheel speed, vehicle body speed, slip ratio, and braking torque gradient in the case of gentle braking in which the wheels are not locked. . In the case of such slow braking, even if the braking is applied after 2 seconds and the slip ratio tends to increase,
The minimum braking torque gradient is 1 near the time when braking is applied.
It becomes 50 and does not fall below the reference value 50. Therefore, in this case, the ABS control start determination is not performed.

FIGS. 15 (a), 15 (b) and 15 (c) show temporal changes in the wheel speed, the vehicle body speed, the slip ratio, and the braking torque gradient in the case of sudden braking in which the wheels are not locked. . In the case of such a sudden braking, even if the slip ratio tends to increase more rapidly than in FIG. 14 after 2 seconds, the braking torque gradient has a minimum value 110 near the time when the braking is applied. However, the standard value is not less than 50. Therefore, also in this case, the ABS control start determination is not performed.

FIGS. 16 (a), 16 (b) and 16 (c) show changes with time in wheel speed and vehicle body speed, slip rate and braking torque gradient in the case of sudden braking in which the wheels are locked. . In the case of such sudden braking, the difference between the wheel speed and the vehicle body speed becomes large from 2.2 seconds after the braking is applied, and the slip ratio sharply increases. The braking torque gradient sharply decreases from the time when the slip ratio sharply increases, and becomes the reference value 50 or less from the time t ₁ onward. It can be easily understood from FIG. 16 that the locking can be prevented in the slip ratio region where the wheels are locked by actually reducing the braking force from the time t ₁ .

17 (a), 17 (b) and 17 (c) show wheel speeds and vehicle body speeds in the case of follow-up braking in which the wheels are locked.
It is a graph showing changes over time of the slip ratio degree and the braking torque gradient. In the case of such follow-up braking, the slip rate gradually increases from 2.5 seconds after the braking is applied, and the slip rate sharply increases in 3.2 seconds. The braking torque gradient sharply drops from the time when the slip ratio sharply rises, and becomes a reference value of 50 or less after time t ₂ . It can be easily understood from FIG. 17 that the locking can be prevented in the slip ratio region in which the wheels are locked by actually reducing the braking force from the time t ₂ .

From the experimental results shown in FIGS. 14 to 17, by properly setting the reference value of the braking torque gradient, the control start determination device 5 of the present embodiment can accurately determine whether the control start determination device 5 is locked or not. AB just before making a decision and locking
It was shown that the S control start time was accurately determined.

Next, the result of a comparison experiment of the control start determination method by the control start determination device 5 of the present embodiment and the control start determination method using the wheel deceleration of the above-mentioned prior art on a low μ road and a medium μ road. Are shown in FIGS. 18 to 20, respectively.

FIG. 18 shows the behavior of the front wheels when the brake torque T _b = 400 Nm is applied stepwise on a low μ road. (A) is the wheel speed and vehicle speed, (b)
Shows the temporal changes in the braking torque gradient and the wheel deceleration.

As shown in FIG. 18 (a), the difference (slip speed) between the wheel speed and the vehicle body speed suddenly increases from time 1 sec. After that, the wheel shifts to the slip speed region where the wheel may be locked. . Then, as the slip speed increases, the braking torque gradient and the wheel deceleration shown in FIG. 18B decrease. From FIG. 18 (b), the time when the braking torque gradient is below the reference value (50), that is, the ABS control start time is T _{1 and the} time when the wheel deceleration is below the reference value, that is, the conventional control. The start time is S ₁ , which is earlier than T ₁ .

As is apparent from FIG. 18, in both the present embodiment and the prior art, the ABS control start is judged before the lock is reached. However, in the prior art, the braking force is reduced from an unnecessarily early time. It can be seen that the judgment is made.

FIG. 19 shows the behavior of the rear wheels when the brake torque T _b = 200 Nm is applied stepwise on a low μ road. (A) is the wheel speed and vehicle speed, (b)
Shows the temporal changes in the braking torque gradient and the wheel deceleration.

From FIG. 19 (a), the difference between the wheel speed and the vehicle body speed starts to gradually increase from time 1 sec.
This difference (slip speed) suddenly increases from around sec. That is, after this time of 2.2 seconds, the vehicle shifts to a slip speed region where the wheels may be locked.

However, the braking torque gradient falls below the reference value (50) at time T ₂ when the wheel shifts to the slip speed region where the wheels may be locked, but the wheel deceleration does not fall below the reference value. That is, under the conditions shown in FIG. 19, it can be seen that the ABS control start is accurately determined before the lock is reached in the present embodiment, whereas the control start time cannot be determined in the prior art.

FIG. 20 shows the behavior of the front wheels when the braking torque T _b = 700 Nm is applied stepwise on the medium μ road. (A) is the wheel speed and vehicle speed, (b) is
Shows the temporal changes in the braking torque gradient and the wheel deceleration.

As shown in FIG. 20 (a), a difference between the wheel speed and the vehicle body speed occurs immediately after 1 second, but thereafter, this difference (slip speed) decreases. That is, under this condition, there is no risk of the wheels being locked.

However, as shown in FIG. 20B, the braking torque gradient does not fall below the reference value (50) even when the wheel speed and the vehicle body speed differ from each other, whereas the wheel deceleration immediately after the time 1 sec. When the difference between the wheel speed and the vehicle body speed occurs, it falls below the reference value. That is, under the condition of FIG. 20, although the lock is not reached in the present embodiment, it is accurately determined in the present embodiment that the lock is not reached, whereas in the conventional technique, the control start time is determined. You can see that

From the above experimental results, the determination of the control start time according to the present embodiment is more accurate and stable than the conventional determination using the wheel deceleration, regardless of the condition of the road surface μ and the speed of braking. It has been shown that the starting time can be determined. The determination in this embodiment is based on the normal ABS.
Not only ABS but also TRC and braking force are slightly excited.
It goes without saying that excellent effects can be obtained in the case of.

[0115]

As described above, claims 1 to 3 are as described above.
According to the invention, the control start point is determined based on the braking torque gradient that accurately and stably reflects the wheel motion state. The control start time can be determined stably,
The effect is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a control start determination device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram when the control start determination device according to the first embodiment is mounted on a vehicle body and the determination of the control start time by the device is applied to antilock brake control and traction control.

FIG. 3 is a diagram showing details of the configuration of a brake hydraulic circuit according to the first embodiment.

FIG. 4 is a graph showing changes in braking torque and braking torque gradient with respect to slip speed.

FIG. 5 shows the ABS in the control start determination device according to the first embodiment.
5 is a flowchart showing the first control of the ABS when the control start determination is performed.

FIG. 6 is a block diagram showing an ABS in the control start determination device according to the first embodiment.
5 is a flow chart showing a second control of the ABS when the control start determination is performed.

FIG. 7 shows a TRC in the control start determination device according to the first embodiment.
5 is a flowchart showing TRC control when the control start determination is performed.

FIG. 8 is a configuration diagram in the case where the determination of the control start time point by the control start determination device of the second embodiment is applied to ABS by minute braking force excitation.

FIG. 9 is a flowchart showing ABS control when the control start determination device of the second embodiment makes a control start determination of minute braking force excitation.

FIG. 10 is a diagram showing a configuration of an amplitude value detection unit of a vehicle body according to a second embodiment.

FIG. 11 is a graph showing a relationship between an excitation frequency and a wheel speed gain when a braking force is slightly excited in the vehicle body according to the second embodiment.

FIG. 12 is a diagram showing a configuration of a braking force reduction command calculation unit for a vehicle body according to a second embodiment.

FIG. 13 is a diagram showing a temporal change in braking force,
(A) is a figure which shows the time change of the braking force micro-excited by ABS which concerns on 2nd Embodiment, and (b) is a figure which shows the time change of the braking force micro-excited by the conventional ABS.

FIG. 14 is a diagram showing a temporal change of a physical quantity relating to a wheel in the case of slow braking in which the wheel is not locked, (a) shows a temporal change of a wheel speed and a vehicle body speed, and (b) shows a temporal change of a slip ratio. Changes and (c) are diagrams showing temporal changes in the braking torque gradient.

FIG. 15 is a diagram showing a temporal change of a physical quantity relating to a wheel in the case of sudden braking in which the wheel is not locked; Changes and (c) are diagrams showing temporal changes in the braking torque gradient.

FIG. 16 is a diagram showing a temporal change of a physical quantity relating to a wheel in the case of sudden braking in which the wheel locks, wherein (a) shows a temporal change of a wheel speed and a vehicle body speed, and (b) shows a temporal change of a slip ratio. Changes and (c) are diagrams showing temporal changes in the braking torque gradient.

FIG. 17 is a diagram showing a temporal change of a physical quantity relating to a wheel in the case of the follow-up braking in which the wheel is locked,
FIG. 4 is a diagram showing a temporal change of a wheel speed and a vehicle body speed, (b) a temporal change of a slip ratio, and (c) a temporal change of a braking torque gradient.

FIG. 18: Brake torque T _b = 400 on a low μ road
It is a figure which shows the behavior of a front wheel when Nm is added stepwise, (a) is a time change of a wheel speed and a vehicle body speed,
(B) is a diagram showing temporal changes in the braking torque gradient and the wheel deceleration.

FIG. 19 shows a braking torque T _b = 200 on a low μ road.
It is a figure which shows the behavior of the rear wheel when Nm is added stepwise, (a) is a time change of a wheel speed and a vehicle body speed,
(B) is a diagram showing temporal changes in the braking torque gradient and the wheel deceleration.

FIG. 20: Brake torque T _b = 700 on medium μ road
It is a figure which shows the behavior of a front wheel when Nm is added stepwise, (a) is a time change of a wheel speed and a vehicle body speed,
(B) is a diagram showing temporal changes in the braking torque gradient and the wheel deceleration.

[Explanation of symbols]

10 Wheel speed detection means 12 Torque gradient estimating means 14 Judgment means

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Umeno Nagakute-cho, Aichi-gun, Aichi-gun, Oocho-Chaji 1 41 Yokomichi Toyota Central Research Institute Co., Ltd. 1 at Yokomichi 41 Toyota Central Research Institute Co., Ltd. (56) Reference JP-A-8-318842 (JP, A) JP-A-8-201235 (JP, A) JP-A-7-186928 (JP, A) Kaihei 8-324414 (JP, A) JP 4-224447 (JP, A) JP 8-183439 (JP, A) JP 3-143760 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) B60T 8 / 00,8 / 32-8/96

Claims (3)

(57) [Claims] 1. A wheel speed detection step of detecting a wheel speed at every predetermined sample time, and a braking torque with respect to a slip speed using only time-series data of the wheel speed detected by the wheel speed detection step as a detection target. a torque gradient estimating step to estimate a gradient of, based on the gradient of the estimated braking torque by the torque gradient estimating step, a determination step of controlling start of the control of the wheel motion and a predetermined state of motion, A control start determination method, comprising: 2. The torque gradient estimating step includes a first calculating step for calculating a physical quantity relating to a change in wheel speed and a physical quantity relating to a change in wheel speed, based only on time series data of detected wheel speeds. A physical quantity history relating to a change in wheel speed and a physical quantity history relating to a change in wheel speed based on the physical quantity relating to a change in wheel speed and the physical quantity relating to a change in wheel speed calculated in the first computing step. The control start determination method according to claim 1, further comprising: a second calculation step of calculating a physical quantity represented and estimating a gradient of the braking torque from the physical quantity. 3. In the first calculation step, the wheel of wheel number i (i = 1, 2, 3, 4) is detected at sample time k (k = 1, 2, ...). Assuming that the time series data of the wheel speed is ω _i [k], the sample time is τ, and the wheel inertia is J, the physical quantity relating to the change of the wheel speed is Is calculated, and y _i [k] = − ω _i [k] + 2ω _i [k−1] −ω _i [k−
2] is calculated, and in the second calculation step, a physical quantity θ _i representing a history of physical quantities related to changes in wheel speed and a history of physical quantities related to changes in changes in wheel speed, a forgetting factor λ, and a matrix transpose As " ^T ", [Formula 2] 3. The control start determination method according to claim 2, wherein the gradient is obtained as a braking torque gradient.