Driving force control system for vehicle and the method thereof

• US 5,826,209 A
• Filed: 03/27/1997
• Issued: 10/20/1998
• Est. Priority Date: 06/27/1994
• Status: Expired due to Fees

• Current Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Matsuno, Koji
• Primary Examiner(s): ZANELLI, MICHAEL J
• Application Number:
  US08/827,166
• Time in Patent Office: 572 Days
• Field of Search: 701/69, 701/82, 701/84, 701/87, 701/88, 701/89, 303/140, 303/143, 303/146, 303/190, 180/197, 180/248
• US Class Current: 701/69
• CPC Class Codes: B60K 23/0808 for varying torque distribution between driven axles, e.g. by transfer clutch
• CPC Class Codes: B60K 28/16 responsive to, or preventing, skidding of wheels brake control systems for vehicle drive stability B60T8/1755; arrangements responsive to a speed condition for adjusting wheel braking force B60T8/32; control of vehicle driving stability otherwise than by controlling the propulsion unit only B60W30/02; preventing wheel slippage by reducing power in rail vehicles B61C15/00
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 2710/0616 Position of fuel or air injector
• CPC Class Codes: B60W 30/18145 Cornering

Abstract

In a driving force control system for a vehicle, an angular velocity of the course direction of the vehicle body is calculated. On the other hand, a target angular velocity of the course direction is determined based on a steering angle and a vehicle speed. Then, based on the degree of the deviation of the calculated angular velocity from the target angular velocity, a correction coefficient for reducing an engine power is generated. When the vehicle traces off the course in the marginal condition on the low friction coefficient road, the correction coefficient reduces the engine power to prevent the vehicle from going out of the course.

Claims

1. A driving force control system of a vehicle having an engine, a fuel injector, a front wheel and a rear wheel for controlling a driving force so as to control a behavior of said vehicle during running, comprising:

directional angular velocity calculating means for estimating a directional angular velocity of said vehicle;

target directional angular velocity determining means for determining a target directional angular velocity of said vehicle;

correction coefficient generating means for generating a correction coefficient based on said directional angular velocity and said target directional angular velocity; and

torque distribution control means for distributing a torque between said front wheel and said rear wheel based on said correction coefficient.

2. A driving force control system of a four wheel drive vehicle having an engine, a fuel injector, a front wheel, a rear wheel for controlling a driving force so as to control a behavior of said vehicle during running by controlling a torque distribution ratio between said front wheel and said rear wheel, comprising:

a yaw rate sensor for detecting an actual yaw rate of said vehicle;

a lateral acceleration sensor for detecting an actual lateral acceleration of said vehicle;

a steering angle sensor for detecting a steering angle of said vehicle;

a vehicle speed sensor for detecting a vehicle speed;

directional angular velocity calculating means for calculating a target yaw rate, a target lateral acceleration and for estimating a directional angular velocity by using equations of motion;

deviation calculating means for calculating a deviation of said target yaw rate from said actual yaw rate based on said target yaw rate and said actual yaw rate and a deviation of said target lateral acceleration from said actual lateral acceleration based on said target lateral acceleration and said actual lateral acceleration;

tire characteristic control means for estimating a cornering power of said front wheel and a cornering power of said rear wheel based on said deviation of said target yaw rate from said actual yaw rate and said deviation of said target target acceleration from said actual lateral acceleration;

said directional angular velocity calculating means calculates said target yaw rate, said target lateral acceleration and estimates said directional angular velocity by using said equations of motion parameterizing said steering angle, said vehicle speed, said cornering power of said front wheel and said cornering power of said rear wheel;

target directional angular velocity determining means for determining a target directional angular velocity by using said equations of motion parameterizing said steering angle, said vehicle speed, a predetermined cornering power of said front wheel and a predetermined cornering power of said rear wheel;

correction coefficient generating means for generating a correction coefficient based on said directional angular velocity and said target directional angular velocity; and

torque distribution control means for determining a torque distribution ratio between said front wheel and said rear wheel based on said correction coefficient.

3. The driving force control system according to claim 2, wherein

said correction coefficient is a coefficient determined according to a deviation ratio obtained by dividing a deviation of said directional angular velocity from said target angular velocity and said coefficient corresponds to said torque distribution ratio between said front wheel and said rear wheel.

4. The driving force control system according to claim 2, wherein

said predetermined cornering powers of front and rear wheels are derived from the tire characteristics on a road with a high friction coefficient.

5. A method of controlling a driving force of a vehicle having an engine, a fuel injector, a front wheel and a rear wheel, comprising the steps of:

estimating a directional angular velocity of said vehicle;

determining a target directional angular velocity of said vehicle;

generating a correction coefficient based on said directional angular velocity and said target directional angular velocity; and

distributing a torque between said front wheel and said rear wheel based on said correction coefficient.

6. A method of controlling a driving force of a four wheel drive vehicle having an engine, a fuel injector, a front wheel and a rear wheel, comprising the steps of:

detecting an actual yaw rate of said vehicle;

detecting an actual lateral acceleration of said vehicle;

detecting a steering angle of said vehicle;

detecting a vehicle speed;

calculating a target yaw rate, a target lateral acceleration and estimating a directional angular velocity by using equations of motion;

calculating a deviation of said target yaw rate from said actual yaw rate based on said target yaw rate and said actual yaw rate and a deviation of said target lateral acceleration from said actual lateral acceleration based on said target lateral acceleration and said actual lateral acceleration;

estimating a cornering power of said front wheel and a cornering power of said rear wheel based on said deviation of said target yaw rate from said actual yaw rate and said deviation of said target lateral acceleration from said actual lateral acceleration;

determining a target directional angular velocity by using said equations of motion parameterizing said steering angle, said vehicle speed, a predetermined cornering power of said front wheel and a predetermined cornering power of said rear wheel;

generating a correction coefficient based on said directional angular velocity and said target directional angular velocity; and

determining a torque distribution ratio between said front wheel and said rear wheel based on said correction coefficient.

7. A driving force control system of a vehicle having an engine mounted on said vehicle, fuel injection control means operatively connected to said engine for controlling a fuel injection amount thereto via an injector, a differential connected to said engine via a clutch for changing torque distribution between a front wheel and a rear wheel of the vehicle, a yaw rate sensor mounted on said vehicle for detecting an actual yaw rate and for generating a yaw rate signal, a lateral acceleration sensor for sensing an actual lateral acceleration amount in a lateral direction of said vehicle and for producing an acceleration signal, a steering angle sensor mounted on said vehicle for detecting steering angle of said front wheel and for generating a steering angle signal, and a vehicle speed sensor mounted on said vehicle for sensing vehicle speed and for producing a vehicle speed signal, comprising:

target directional angular velocity determining means responsive to said steering angle signal and said vehicle speed signal for setting a target directional angular velocity based upon standard turning characteristics corresponding to a friction coefficient of a surface of a road and for producing a target directional angular velocity signal;

deviation value calculating means responsive to said yaw rate signal and said acceleration signal for calculating a deviation value by subtracting each of said actual yaw rate and said actual lateral acceleration amount from a predetermined value and for generating a deviation signal;

tire characteristic control means responsive to said deviation signal for setting a cornering power of said front and rear wheels in a threshold range and for outputting a cornering power signal;

directional angular velocity calculating means responsive to said steering angle signal and said vehicle speed signal and said cornering power signal for calculating a calculated directional angular velocity of said vehicle and for producing a calculated directional angular velocity signal;

correction coefficient generating means responsive to said calculated directional angular velocity signal and said target directional angular velocity signal for generating a correction coefficient indicating a deviation from a desired course of said vehicle and for outputting a correction coefficient signal; and

torque distribution control means responsive to said correction coefficient signal for controlling the torque distribution between said front wheel and said rear wheel by said differential and said clutch so as to provide optimum driving conditions of the vehicle by improving cornering and traction.

8. The driving force control system according to claim 7, wherein:

said directional angular velocity calculating means uses an equation of motion with parameters of said steering angle, said vehicle speed and said cornering power to derive said calculated directional angular velocity.

9. The driving force control system according to claim 7, wherein:

said cornering power is derived from tire frictional characteristics against the road with a high frictional coefficient.

10. The driving force control system according to claim 7, wherein:

said correction coefficient generating means determines said correction coefficient for changing said torque distribution, and said correction coefficient is determined by a deviation ratio in accordance with a distribution ratio between said front wheel and said rear wheel.

11. A method for driving force control of a vehicle having an engine mounted on said vehicle, fuel injection control means operatively connected to said engine for controlling a fuel injection amount thereto via an injector, a differential connected to said engine via a clutch for changing torque distribution between a front wheel and a rear wheel of the vehicle, the method comprising the steps of:

calculating a directional angular velocity of said vehicle;

setting a target directional angular velocity based upon standard turning characteristics corresponding to a friction coefficient of a road surface;

changing said torque distribution between said front wheel and said rear wheel so as to provide an optimum driving condition of said vehicle by improving corning and traction.

12. The method for driving force according to claim 11, further comprising the steps of

detecting an actual yaw rate,

sensing an actual acceleration amount in a lateral direction of said vehicle,

computing a deviation value by subtracting each of said actual yaw rate and said actual lateral acceleration amount from a predetermined value,

determining a cornering power of the front and rear wheels in a threshold range from said deviation value, and wherein

said calculating step calculates said directional angular velocity from said cornering power.

13. The method for driving force control according to claim 12, further comprising the steps of

detecting a steering angle of said front wheel,

sensing a vehicle speed, and wherein

said calculating step uses an equation of motion with parameters of said steering angle, said vehicle speed and said cornering power to derive said directional angular velocity.