VEHICLE TRAVEL CONTROL DEVICE

• US 20130096778A1
• Filed: 06/09/2011
• Published: 04/18/2013
• Est. Priority Date: 06/11/2010
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Goto, Takeshi, Yamamoto, Junro, Niki, Keitaro, Masuda, Tomihide, Ouchi, Mitsuyuki, Fujita, Shuji, Kunihiro, Yoji
• Granted Patent: US 9,050,998 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 5/008 Changing the transfer ratio between the steering wheel and the steering gear by variable supply of energy, e.g. by using a superposition gear
• CPC Class Codes: B62D 6/002 computing target steering angles for front or rear wheels B62D7/159 takes precedence

Abstract

A travel control device for a vehicle has a steered angle varying device 14 or a by-wire type steering device 96 which modifies a relationship of steered angle of steerable wheels to steering operation amount by a driver. When the control device decides that vehicle trajectory control is to be initiated or renewed, it calculates a target steered angle of the steerable wheels for driving the vehicle along a target trajectory which is required for the vehicle to arrive at a target arrival position in a target traveling direction on the basis of steering operation amount by a driver and vehicle speed at a time point of the decision. The control device controls the steered angle of the steerable wheels according to the target steered angle in feed-forward or feed-back manner.

Claims

1. A vehicle travel control device having a steered angle control means which changes a relationship of steered angle of steerable wheels to steering operation amount by a driver, wherein when said vehicle travel control device follows a predetermined procedure to decide that vehicle trajectory control is to be initiated or renewed, said device determines a target arrival position and derives a target trajectory which is required for the vehicle to arrive at said target arrival position in a target traveling direction and extends from a position of the vehicle at a time point of the decision to said target arrival position on the basis of steering operation amount by a driver and vehicle speed at the time point of the decision, calculates target steered angle of the steerable wheels for driving the vehicle along said target trajectory, and controls the steered angle of the steerable wheels by said steered angle control means according to said target steered angle.

2. A vehicle travel control device according to claim 1, wherein said target trajectory is a exponential curve having an exponent including a variable of elapsed time since said time point on a hypothetical orthogonal coordinates having a time-related coordinate which is a straight line indicating said target traveling direction and a distance-related coordinate which is a perpendicular line dropped from a vehicle position at said time point to said time-related coordinate.

3. A vehicle travel control device according to claim 1, wherein said target trajectory is an arc curve which has contact with a straight line indicating longitudinal direction of the vehicle at said time point at a position of the vehicle at said time point and has contact with a straight line indicating said target traveling direction at said target arrival position.

4. A vehicle travel control device according to claim 1, wherein said device modifies the steered angle of the steerable wheels so that a difference between the steered angle of the steerable wheels at said time point and said target steered angle decreases.

5. A vehicle travel control device according to claim 1, wherein said device modifies the steered angle of the steerable wheels so that a difference between actual steered angle of the steerable wheels and said target steered angle decreases.

6. A vehicle travel control device according to claim 1, wherein said target arrival position is determined on the basis of steering operation amount by a driver and vehicle speed at said time point and said target traveling direction is determined on the basis of steering operation amount by a driver at said time point.

7. A vehicle travel control device according to claim 6, wherein with an angle which is determined on the basis of steering operation amount by a driver at said time point being a reference angle, said target arrival position is on a straight line which is dropped from a position of the vehicle at said time point in a direction inclined at said reference angle relative to a longitudinal direction of the vehicle and the distance from a position of the vehicle at said time point to said target arrival position is a value which is dependent on vehicle speed.

8. A vehicle travel control device according to claim 7, wherein with a straight line connecting a position of the vehicle at said time point and said target arrival position being a direction reference line, said target traveling direction is determined to a direction which is inclined at said reference angle relative to a direction reference line at said target arrival position.

9. A vehicle travel control device according to claim 1, wherein said device decides that vehicle trajectory control is to be initiated when the magnitude of change rate of steering operation amount by a driver becomes lower than a second reference value for control initiation decision after the magnitude of change rate of steering operation amount by a driver exceeded a first reference value for control initiation decision under a situation where said trajectory control is not executed.

10. A vehicle travel control device according to claim 1, wherein said device decides that vehicle trajectory control is to be renewed when the magnitude of change rate of steering operation amount by a driver becomes lower than a second reference value for control initiation decision after the magnitude of change rate of steering operation amount by a driver exceeded a first reference value for control initiation decision under a situation where said trajectory control is executed.

11. A vehicle travel control device according to claim 2, wherein with a distance from a position of the vehicle at said time point to said time-related coordinate being a reference distance, a target distance is calculated to a product of said reference distance and a natural exponential including a variable of elapsed time since said time point and said target trajectory is determined as a line connecting points which are at target distances from said time-related coordinate.

12. A vehicle travel control device according to claim 11, wherein with a general time being represented by Δ

T which is necessary for a person to perceive a change of vehicle exterior visual information relevant to necessity of steering operation after the change occurred;

Weber ratio being represented by −

k; and

a elapsed time since said time point being represented by t, the exponent of said natural exponential is −

(k/Δ

T)t.

13. A vehicle travel control device according to claim 1, wherein said steered angle control means is of semi-by-wire type having a steering transfer ratio varying means which modifies the steered angle of the steerable wheels by virtue of actuating the steerable wheels relative to a steering input means operated by a driver and a control means which controls said steering transfer ratio varying means.

14. A vehicle travel control device according to claim 13, wherein the vehicle has a steering assist force generation means which generates steering assist force for assisting steering operation by a driver and a steering assist force control means which controls said steering assist force generation means according to a target steering assist force for alleviating steering load of a driver, and said steering assist force control means, under a situation where said trajectory control is executed, estimates an amount of steering force change due to the control of the steered angle of the steerable wheels by said steered angle control means;

corrects detected steering force with said amount of steering force change;

calculates a steering assist force necessary to alleviate steering load of a driver on the basis of the corrected steering force; and

sets said target steering assist force to a sum of said necessary steering assist force and said amount of steering force change.

15. A vehicle travel control device according to claim 1, wherein said steered angle control means is of by-wire type having a wheel-steer-drive means for varying steered angle of the steerable wheels, a detection means for detecting steering operation amount to a steering input means by a driver, and a control means for controlling said wheel-steer-drive means according to steering operation amount by a driver under a normal situation and controlling said wheel-steer-drive means as necessary independently of steering operation by a driver.

16. A vehicle travel control device according to claim 15, wherein the vehicle has a steering reaction force generation means which generates steering reaction force and a steering reaction force control means for controlling said steering reaction force generation means according to a target steering reaction force, and said steering reaction force control means calculates a basic steering reaction force which is not influenced by steered angle control of the steerable wheels by said steered angle control means on the basis of steering operation amount by a driver and calculates a target steering reaction force on the basis of a value which is derived by subtracting a basic steering force reducing amount for alleviating steering load of a driver from said basic steering reaction force.

17. A vehicle travel control device according to claim 1, wherein said vehicle travel control device restrains said trajectory control when at least one of said steered angle control means and a means for attaining steering operation amount by a driver is not normal.