Anti-skid control based on duty cycle adjustment

• US 4,800,498 A
• Filed: 06/24/1986
• Issued: 01/24/1989
• Est. Priority Date: 06/26/1985
• Status: Expired due to Fees

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Kuno, Akira, Imani, Yuuichi, Hattori, Yoshiyuki, Nomura, Yoshihisa, Matsui, Kazuma
• Primary Examiner(s): Chin, Gary
• Application Number:
  US06/877,729
• Time in Patent Office: 945 Days
• Field of Search: 364/426, 180/197, 303/95, 303/97, 303/99, 303/100, 303/102, 303/105, 303/DIG. 4, 303/103
• US Class Current: 701/79
• CPC Class Codes: B60T 8/17616 Microprocessor-based systems
• CPC Class Codes: B60T 8/58 responsive to speed and another condition or to plural speed conditions
• CPC Class Codes: B60T 8/885 using electrical circuitry
• CPC Class Codes: Y10S 303/04 Pressure signal used in electrical speed controlled braking circuit

Abstract

Disclosed is an anti-skid control system incorporated in the hydraulic pressure braking apparatus of a motor vehicle including a wheel braking cylinder responsive to a hydraulic pressure developed by a master cylinder for braking a wheel of the vehicle. The anti-skid control system comprises a hydraulic pressure supplying device and a directional control valve provided between the wheel braking cylinder and the hydraulic pressure supplying device. The directional control valve is actuated to shut off the communication therebetween and the actuation thereof is controlled in accordance with a duty cycle, which is in turn updated in accordance with the difference between a wheel speed and a target wheel speed so that the slip ratio of the wheel becomes equal to a target slip ratio.

Claims

1. An anti-skid control system incorporated in a hydraulic pressure braking apparatus of a vehicle at least including a wheel braking cylinder for braking a wheel of said vehicle, comprising:

means for detecting a speed of said wheel and generating a signal indicative of the detected wheel speed;

hydraulic pressure supplying means coupled to said wheel braking cylinder for supplying a hydraulic pressure thereto;

directional control valve means provided between said hydraulic pressure supplying means and said wheel braking cylinder for shutting off a communication therebetween in response to an actuation;

means for determining a vehicle speed and a wheel acceleration on the basis of the detected wheel speed;

means for determining a target wheel speed on the basis of the obtained vehicle speed and a predetermined target slip ratio of said wheel;

means for obtaining a wheel parameter on the basis of the obtained wheel acceleration and a difference between the determined target wheel speed and the detected wheel speed;

means for determining a duty cycle representing an operating time of said directional control valve means on the basis of the obtained wheel parameter;

means, for driving said directional control valve means so as to effect the determined duty cycle; and

means responsive to said wheel parameter obtaining means, for updating the duty cycle to converge to a predetermined value when the obtained wheel parameter is out of a predetermined range with upper and lower limits.

2. An anti-skid control system as claimed in claim 1, wherein said wheel parameter Wpa is derived in accordance with the following equation:

space="preserve" listing-type="equation">Wpa=(Vsh-Vw)+Ao.Dwa

where Vsh represents said target wheel speed, Vw designates the detected wheel speed, Dwa is the wheel acceleration and Ao is a constant.

3. An anti-skid control system as claimed in claim 1, wherein the duty cycle is updated to be decreased by a first predetermined value when the obtained wheel parameter is greater than said upper limit and to be increased by a second predetermined value when the obtained wheel parameter is smaller than said lower limit.

4. An anti-skid control system incorporated in a hydraulic pressure braking apparatus of a vehicle at least including a master cylinder for developing a hydraulic pressure in response to the operation of a brake pedal and a wheel braking cylinder responsive to the hydraulic pressure developed by said master cylinder for braking a wheel of said vehicle, comprising:

means for detecting a speed of said wheel and generating a signal indicative of the detected wheel speed;

a first directional control valve switched to shut off the communication between said master cylinder and said wheel braking cylinder;

hydraulic pressure supplying means coupled to said wheel braking cylinder for supplying a hydraulic pressure thereto;

a second directional control valve provided between said hydraulic pressure supplying means and said wheel braking cylinder for shutting off a communication therebetween in response to an actuation; and

control means responsive to the signal from said wheel speed detecting means, for;

(1) deriving a vehicle speed and a wheel acceleration from the detected wheel speed, (2) determining a target wheel speed on the basis of the derived vehicle speed and a predetermined target slip ratio of said wheel,

(3) deriving a parameter as a function of the wheel acceleration and a difference between the determined target wheel speed and the detected wheel speed,

(4) comparing the derived parameter with a predetermined value,

(5) setting said first directional control valve to the shut-off condition when the derived parameter exceeds the predetermined value,

(6) determining a duty cycle in terms of a time of the actuation of said second directional control valve in accordance with the determined duty cycle.

5. An anti-skid control system as claimed in claim 4, wherein said parameter Wpa is derived in accordance with the following equation:

space="preserve" listing-type="equation">Wpa=(Vsh-Vw)+Ao.Dwa

where Vsh represents said target wheel speed, Vw designates the detected wheel speed, Dwa is the wheel acceleration and Ao is a constant.

6. An anti-skid control system as claimed in claim 4, wherein the duty cycle is updated to be decreased by a first predetermined value when the obtained parameter is greater than an upper limit and to be increased by a second predetermined value when the obtained parameter is smaller than a lower limit.

7. An anti-skid control system as claimed in claim 4, wherein said duty cycle is successively updated in response to variations of the parameter so that the target slip ratio is obtained.

8. An anti-skid control system incorporated in a hydraulic pressure braking apparatus of a vehicle at least including a master cylinder for developing a hydraulic pressure in response to the operation of a brake pedal and a wheel braking cylinder responsive to the hydraulic pressure developed by said master cylinder for braking a wheel of said vehicle, comprising:

means for detecting a speed of said wheel and generating a signal indicative of the detected wheel speed;

a first directional control valve selectively switched to a shut off condition to shut off the communication between said master cylinder and said wheel braking cylinder;

hydraulic pressure supplying means coupled to said wheel braking cylinder for supplying a hydraulic pressure thereto;

a second directional control valve provided between said hydraulic pressure supplying means and said wheel braking cylinder and actuated to shut off the communication therebetween; and

control means responsive to the signal from said wheel speed detecting means, for;

(1) deriving a vehicle speed and a wheel acceleration from the detected wheel speed,

(2) determining a target wheel speed on the basis of the derived vehicle speed and a predetermined target slip ratio of said wheel,

(3) deriving a parameter as a function of the derived wheel acceleration and the difference between the determined target wheel speed and the detected wheel speed,

(4) comparing the derived parameter with a first predetermined value,

(5) switching said first directional control valve to the shut-off condition when the derived parameter exceeds the first predetermined value, and

(6) determining a duty cycle in terms of a time of the actuation of said second directional control valve,

(7) comparing the derived parameter with a second predetermined value,

(8) decreasing the duty cycle by a predetermined correction value when the derived parameter exceeds the second predetermined value, and

(9) controlling the switching of said second directional control valve in accordance with the decreased duty cycle.

9. An anti-skid control system incorporated in a hydraulic pressure braking apparatus of a vehicle at least including a master cylinder for developing a hydraulic pressure in response to the operation of a brake pedal and a wheel braking cylinder responsive to the hydraulic pressure developed by said master cylinder for braking a wheel of said vehicle, comprising:

means for detecting the speed of said wheel and generating a signal indicative of the detected wheel speed;

a first directional control valve switched to shut off the communication between said master cylinder and said wheel braking cylinder;

hydraulic pressure supplying means coupled to said wheel braking cylinder for supplying a hydraulic pressure thereto;

a second directional control valve provided between said hydraulic pressure supplying means and said wheel braking cylinder and actuated to shut off the communication therebetween; and

control means responsive to the signal from said wheel speed detecting means for;

(1) deriving a vehicle speed and a wheel acceleration from the detected wheel speed,

(2) determining a target wheel speed on the basis of the derived vehicle speed and a predetermined slip ratio of said wheel,

(3) deriving a parameter as a function of the derived wheel acceleration and the difference between the determined target wheel speed and the detected wheel speed,

(4) comparing the derived parameter with a first predetermined value,

(5) switching said first directional control valve to the shut-off condition when the derived parameter exceeds the first predetermined value,

(6) determining a duty cycle in terms of the time of the actuation of said second directional control valve,

(7) comparing the derived parameter with a second predetermined value and reducing the duty cycle by a first correction value when the derived parameter is greater than said second predetermined value,

(8) comparing the derived parameter with a third predetermined value and enlarging the duty cycle by a second correction value when the derived parameter is smaller than said third predetermined value, and

(9) controlling the switching of said second directional control valve in accordance with the reduced or enlarged duty cycle.

10. An anti-skid control system as claimed in claim 9, wherein the hydraulic pressure applied to said wheel braking wheel is returned to a reservoir coupled to said master cylinder when said second directional control valve is set to the shut-off condition.

11. A method for performing anti-skid control for a vehicle at least including a master cylinder for developing a hydraulic pressure in response to the operation of a brake pedal and a wheel braking cylinder responsive to the hydraulic pressure developed by said master cylinder for braking a wheel of said vehicle, comprising the steps of:

detecting a speed of said wheel of said vehicle;

deriving a vehicle speed from the detected wheel speed;

determining a target wheel speed on the basis of the derived vehicle speed and a predetermined target slip ratio of said wheel;

calculating a wheel acceleration on the basis of the detected wheel speed;

deriving a parameter as a function of a difference between the determined target wheel speed and the detected wheel speed and the calculated wheel acceleration;

comparing the derived parameter with a first predetermined value;

setting a first directional control valve provided between said master cylinder and said wheel braking cylinder to the shut-off condition when the derived parameter is greater than the first predetermined value;

determining a duty cycle in terms of the time of the actuation of a second directional control valve provided between said wheel braking cylinder and said master cylinder, said second directional control valve being actuated to shut off the communication between said wheel braking cylinder and said master cylinder;

comparing the derived parameter with second and third predetermined values;

updating the duty cycle when the derived parameter is out of a range between said second and third predetermined values; and

controlling said second directional control valve in accordance with the updated duty cycle.