VEHICLE DYNAMIC CONTROL USING PULSED ACTIVE STEERING STRATEGY

• US 20080033615A1
• Filed: 08/03/2007
• Published: 02/07/2008
• Est. Priority Date: 08/03/2006
• Status: Active Grant

• Current Assignee: Amir Khajepour, Che-Jen Kuo, John Mcphee
• Original Assignee: Amir Khajepour, Che-Jen Kuo, John Mcphee
• Inventors: McPhee, John, Kuo, Che-Jen, Khajepour, Amir
• Granted Patent: US 8,762,004 B2
• Time in Patent Office: Days
• US Class Current: 701/42
• CPC Class Codes: B60W 10/20 including control of steering systems
• CPC Class Codes: B60W 2050/0009 Proportional differential [PD] controller
• CPC Class Codes: B60W 2050/0028 Mathematical models, e.g. for simulation
• CPC Class Codes: B62D 6/001 the torque NOT being among the input parameters

Abstract

A pulse active steering control system and method for use in a motor vehicle for improving vehicle stability by reducing a likelihood for rollover and/or skidding sends pulses to the steerable wheels whenever a rollover coefficient and/or the difference between the estimated and actual yaw rate is outside a predetermined range. The pulses are asymmetrical in the form of a smooth curve with a gradually increasing rapid rising edge and a slower falling edge and provide steering input that, along with the driver steering input, returns the rollover coefficient and/or yaw rate to the predetermined range to reduce the likelihood of rollover and/or skidding.

Claims

1. A pulse active steering control system for use in a motor vehicle to improve vehicle stability by reducing a likelihood of rollover and/or skidding, said motor vehicle having at least four wheels, at least two of which are steerable wheels and a driver, said system comprising a rollover estimator that calculates a rollover coefficient of said vehicle, a controller being programmed to determine whether said rollover coefficient is beyond a predetermined range for said rollover threshold for said vehicle, if said rollover coefficient is within said range for said rollover threshold said controller being programmed not to interfere with operation of said vehicle, if said rollover coefficient is beyond said range of said rollover threshold said controller immediately activating steering pulses, modifying an amplitude of said pulses with respect to a current steering input from said driver and an error signal of said rollover coefficient, said controller sending pulses to provide extra steering to steering provided by said driver input in order to reduce a likelihood of rollover by varying said rollover coefficient to a value closer to or within said range of said rollover threshold and ultimately to be within said range of said rollover threshold.

2. A pulse active steering control system as claimed in claim 1 wherein said pulses have a shape selected from the group of rectangular, sinusoidal and asymmetrical in the form of a smooth curve with a gradually increasing rapid rising edge and a slower falling edge.

14. A control system as claimed in any one of claims 1, 3, or 4 wherein said pulses are sent as a negative pulse that is subtracted from a steering input from said driver.

15. A control system as claimed in any one of claims 1, 3 or 4 wherein a driver'"'"'s steering input feeds into a tire model which calculates tire forces and then feeds the resulting tire forces to the yaw/roll model, said yaw/roll model then calculating the longitudinal and lateral velocity as well as the yaw rate, roll angle and roll rate of said vehicle and feeds said data to said rollover estimator to calculate said rollover coefficient.

3. A pulse active steering control system for use in a motor vehicle to improve vehicle stability by reducing a likelihood for rollover and/or skidding, said motor vehicle having at least four wheels, at least two of which are steerable wheels and a driver, said system comprising a rollover estimator and a controller in said vehicle, said rollover estimator calculating a rollover coefficient, said controller comparing said rollover coefficient to a predetermined range for a rollover threshold, if said rollover coefficient is beyond said range for said rollover threshold said controller providing pulses to said steerable wheels to vary said rollover coefficient to a value closer to or within said range for said rollover threshold.

4. A pulse active steering control system as claimed in claim 3 wherein said pulses have a shape selected from the group of rectangular, sinusoidal and asymmetrical in the form of a smooth curve with a gradually increasing rapid rising edge and a slower falling edge.

5. A steering control system as claimed in claim 3 wherein each of said pulses is a smooth curve with a gradually increasing rapid rising edge and a slower falling edge.

6. A control system as claimed in claim 5 wherein said controller is configured to control a frequency of said pulses as well as an amplitude of said pulses compared to steering input from said driver.

7. A control system as claimed in claim 5 wherein said system has a steering pulse generator, a pulse control algorithm and said controller is selected from the group of a PD controller and a proportional gain K controller.

8. A control system as claimed in claim 5 wherein said rollover estimator continuously monitors said rollover coefficient to maintain said rollover coefficient between −

1 and +1.

9. A control system as claimed in claim 8 wherein said predetermined range of said rollover threshold is extends from substantially +0.7 and −

0.7 so that said controller activates said pulse generator whenever said rollover coefficient is outside of said range for said rollover threshold.

10. A control system as claimed in claim 3 wherein a frequency of said pulse is substantially 1 Hz to 3 Hz.

11. A control system as claimed in claim 3 wherein an amplitude of said pulses varies with driver input into steering said steerable wheels.

12. A control system as claimed in claim 3 wherein a time period for each duty cycle of one of said pulses is between 0.3 seconds and 0.5 seconds.

13. A control system as claimed in claim 11 wherein said pulses have an amplitude of substantially 2°

when said vehicle is under a constant 4°

steering input from said driver.

16. A pulse active steering control system for use in combination with a motor vehicle to improve vehicle stability by reducing a likelihood of rollover and/or skidding, said motor vehicle having at least four wheels, at least two of which are steerable wheels and a driver, said system comprising a rollover estimator and a controller in said vehicle, said rollover estimator calculating a rollover coefficient, said controller comparing the rollover coefficient to a pre-determined range for a rollover threshold, if the rollover coefficient is beyond said range of the rollover threshold, the controller providing pulses to said steerable wheels to vary the rollover coefficient to a value closer to or within said range for the rollover threshold.

17. A pulse active steering control system as claimed in claim 16 wherein said pulses have a shape selected from the group of rectangular, sinusoidal and asymmetrical in the form of a smooth curve with a gradually increasing rapid rising edge and a slower falling edge.

18. A pulse active steering control system for use in a motor vehicle for improving vehicle stability by reducing a likelihood for rollover and/or skidding, said motor vehicle having at least four wheels, at least two of which are steerable wheels and a driver, said system comprising an estimator to estimate the expected yaw rate for said vehicle on a continuous basis based upon sensors that provide information to said estimator of an angle of the steering wheel and a speed of said vehicle, a controller measuring the actual yaw rate of said vehicle using a yaw sensor on a continuous basis and calculating the difference between said expected yaw rate and said actual yaw rate, said difference being a yaw rate error, when said yaw rate error exceeds a predetermined threshold, said controller providing pulses to said steerable wheels to reduce or to eliminate said error.

19. A method of improving vehicle stability by reducing the likelihood of rollover and/or skidding of a motor vehicle using a pulse active steering control system, said motor vehicle having at least four wheels, at least two of which are steerable wheels, said motor vehicle having a rollover estimator and a controller, said method comprising activating said rollover estimator to calculate a rollover coefficient, having said controller compare said rollover coefficient to a predetermined range for a rollover threshold and if said rollover coefficient is beyond said range of said rollover threshold, having said controller provide pulses to said steerable wheels, and providing said pulses to vary said rollover coefficient to a value closer to or within said predetermined range rollover threshold.

20. A method as claimed in claim 19 including a step of choosing said pulses to have a shape selected from the group of rectangular, sinusoidal and asymmetrical in the form of a smooth curve with a gradually increasing rapid rising edge and a slower falling edge.

21. A method of improving vehicle stability for a motor vehicle by reducing a likelihood of skidding, said motor vehicle having at least four wheels, at least two of which are steerable wheels and a driver, using a system with an estimator to estimate the expected yaw rate for said vehicle on a continuous basis and a controller, said method comprising activating said estimator to estimate the expected yaw rate for said vehicle based on information received from sensors as to an angle of each of said wheels and a speed of said vehicle, having said controller compare said expected yaw rate with an actual yaw rate of said vehicle using a yaw sensor, said controller determining a difference between said expected yaw rate and said actual yaw rate, said difference being an error, and having said controller send pulses to said steerable wheels to reduce said error whenever said error exceeds a predetermined threshold.