Anti-skid control system for motor vehicle

• US 4,825,371 A
• Filed: 03/20/1987
• Issued: 04/25/1989
• Est. Priority Date: 03/20/1986
• Status: Expired due to Fees

• Current Assignee: Akebono Brake Industry Company Limited (Akebono Brake Corporation), Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Miyake, Katsuya, Yamaki, Isao, Akima, Hideo, Hoashi, Akira
• Primary Examiner(s): Chin, Gary
• Application Number:
  US07/028,544
• Time in Patent Office: 767 Days
• Field of Search: 364/426, 364/565, 180/197, 303/94-96, 303/102, 303/103, 303/105, 303/109, 303/110, 303/113
• US Class Current: 701/79
• CPC Class Codes: B60T 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• CPC Class Codes: B60T 8/17636 Microprocessor-based systems
• CPC Class Codes: B60T 8/5006 Pressure reapplication by pulsing of valves B60T8/5012, B60T8/5018, B60T8/505, B60T8/5056 take precedence
• CPC Class Codes: B60T 8/58 responsive to speed and another condition or to plural speed conditions
• CPC Class Codes: Y10S 303/05 Acceleration peak detection

Abstract

An anti-skid control system for a motor vehicle, includes a brake fluid pressure buildup-control mode and a brake fluid pressure reduction mode, each of which occur cyclically. In each buildup-control mode, a control valve is repetitively opened and closed so that brake fluid pressure buildup and holding operations are performed alternately. The time period of each buildup-control mode is from a high peak of a wheel speed signal until a point of intersection between a reference velocity V_W0 and the wheel speed V_W. The reference velocity V_W0 has an initial point Q positioned under the high peak V_HP of the wheel speed V_W by a velocity value ΔV and extending straight at a gradient θ. The speed value ΔV, the gradient θ, and an initial pressure buildup time T_P, in each building-control mode, are determined in accordance with the wheel acceleration in the preceding wheel acceleration, i.e., coefficient of friction of the road surface.

Claims

1. An anti-skid control system for a motor vehicle, including a brake fluid pressure buildup-control mode and a brake fluid pressure reduction mode, which occur in anti-skid cycles, said anti-skid control system comprising:

first valve means for alternately building up and holding brake fluid pressure during said brake fluid pressure buildup-control mode;

wheel speed measuring means for measuring a speed of each wheel of the motor vehicle and for providing a wheel velocity signal V_W responsive to said speed;

peak detecting means for receiving said velocity signal V_W and for detecting a high peak value V_HP and a low peak value V_LP of said velocity signal V_W when said anti-skid control system is operated;

controller means for repetitively opening and closing said first valve means during said brake fluid pressure buildup-control mode, from a first time when said velocity signal V_W has said high peak value V_HP to a second time when said velocity signal V_W has a value R, said value R corresponding to said velocity signal V_W being equal to a reference velocity V_WO at the second time, said reference velocity V_WO having an initial value at the first time being less than said high peak value V_HP by a predetermined velocity value Δ

V, having values which vary between the first time and the second time dependent upon a gradient θ

, and having a final value equal to said velocity signal V_W at the second time corresponding to said value R;

acceleration measuring means for measuring wheel acceleration during a time after detection of said low peak value V_LP by said peak detecting means on the basis of said velocity signal V_W between a first value Va and a second value Vb of said velocity signal V_W, said first value Va being dependent upon a predetermined rate of wheel velocity and said low peak value V_LP, said second value Vb being dependent upon another predetermined rate of wheel velocity and said first value Va; and

determining means for determining at least one of said predetermined velocity value Δ

V, said gradient θ and

an initial pressure buildup time T_P, for said brake fluid pressure buildup-control mode and in accordance with said measured wheel acceleration.

2. An anti-skid control system according to claim 1, wherein said predetermined velocity value Δ

V, said gradient θ

, and said initial pressure buildup time T_P are determined in accordance with said measured wheel acceleration in a preceding anti-skid cycle.

3. An anti-skid control system according to claim 1, wherein said acceleration determining means includes means for calculating a value R_O corresponding to said value R of a preceding anti-skid cycle, so that said first value Va and said second value Vb of said velocity signal V_W are defined as follows:

space="preserve" listing-type="equation">Va=K.sub.1 ([V.sub.WO ]R.sub.O -V.sub.LP)+V.sub.LP

space="preserve" listing-type="equation">Vb=K.sub.2 ([V.sub.WO ]R.sub.O -V.sub.LP)+V.sub.LP

where O<

K₁ <

K₂.

4. An anti-skid control system according to claim 3, wherein K₁ =0.15 and K₂ =0.8.

5. An anti-skid control system according to claim 1, further comprising selection means for selecting said predetermined velocity value Δ

V, said gradient θ

, and said initial pressure buildup time T_P for an anti-skid cycle in accordance with a value of said measured wheel acceleration.

6. An anti-skid control system according to claim 1, wherein said acceleration determining means further includes:

means for determining said first value V_a of said velocity signal V_W in accordance with a first predetermined value of velocity of said low peak value V_LP ; and

means for determining said second value V_b of said velocity signal V_W in accordance with a second predetermined value of velocity and said low peak value V_LP.

7. An anti-skid control system for a motor vehicle, including a brake fluid pressure buildup-control mode and a brake fluid pressure reduction mode, each of which occurs in anti-skid cycles, said anti-skid brake control system comprising:

first valve means for alternately building-up and holding brake fluid pressure during said brake fluid pressure buildup-control mode;

second valve means for reducing brake fluid pressure during said brake fluid pressure reduction mode;

wheel speed measuring means for measuring a speed of each wheel of the motor vehicle and for providing a wheel velocity signal V_W responsive to said speed;

peak detecting means for receiving said velocity signal V_W and for determining a high peak value V_HP and a low peak value V_LP of said velocity signal V_W when a wheel is braked;

controller means for repetitively opening and closing said first valve means during said brake fluid pressure buildup-control mode, from a first time when said velocity signal V_W has said high peak value V_HP to a second time when said velocity signal V_W has a value R, said value R corresponding to said velocity signal V_W being equal to a reference velocity V_WO at the second time, said reference velocity V_WO having an initial value at the first time being less than said high peak value V_HP by a predetermined velocity value Δ

V, having values which vary between the first time and the second time dependent upon a gradient, and having a final value equal to said velocity signal V_W at the second time corresponding to said value R;

acceleration measuring means for measuring wheel acceleration during a time after detection of said low peak value V_LP by said peak detecting means on the basis of said velocity signal V_W between a first value Va and a second value Vb of said velocity signal V_W, said first value Va being dependent upon a predetermined rate of wheel velocity and said low peak value V_LP, said second value Vb being dependent upon another predetermined rate of wheel velocity and said first value Va;

determining means for determining at least one of said predetermined velocity value Δ

V, said gradient θ and

an initial pressure buildup time T_P, for said brake fluid pressure buildup-control mode in accordance with said measured wheel acceleration; and

reduction control means for controlling opening of said second valve means during said brake fluid pressure reduction mode, from a time corresponding to an occurrence of said value R until a time corresponding to an occurrence of said low peak value V_LP of said velocity signal V_W.

8. An anti-skid control system according to claim 7, wherein said acceleration determining means further includes:

means for determining said first value V_a of said velocity signal V_W in accordance with a first predetermined value of velocity; and

means for determining said second value V_b of said velocity signal V_W in accordance with a second predetermined value of velocity.