Patent Application
20130030602
This application claims priority to and the benefit of Korean Patent Application No. 10-2011-0075163 filed in the Korean Intellectual Property Office on Jul. 28, 2011, the entire contents of which are incorporated herein by reference.
(a) Field of the Invention
The present invention relates to lane assistance system using an in-wheel system. More particularly, the present invention relates to a lane assistance system that calculates a demand yaw rate and distributes a driving torque of a torque vector to prevent a vehicle from straying out of its intended lane.
(b) Description of the Related Art
A lane assistance system (LAS) is a driver aide to alert a driver that the car is straying from its intended lane of travel and prevent accidents. In general, LAS systems detect when a vehicle has drifted into an adjacent lane of travel and a lane change signal has not been activated by the driver due to e.g., the driver dozing off or not paying attention, an emergency sound is generated and then a steering force is applied to a steering system to help the driver stay in the traffic lane and hopefully avoid an accident.
The LAS (1) detects numerous points of vehicle data, e.g., a steering angle, vehicle speed, and yaw rate through various sensors located throughout the vehicle, (2) uses the data collected as input signals, (3) predicts vehicle movement through a control logic unit that detects and monitors a lane, a curvature radius, a deviation angle, a lateral displacement, etc., and determines intervention timing at which time the steering system compensates for the lane departure by applying a steering torque calculated by the control logic unit. The compensation of the steering torque is typically performed by motor drive power steering (MDPS). In this case, a camera can be disposed on a vehicle to detect and recognize a traffic lane.
In the conventional art, when a steering torque is applied against the force of the driver, the driver can feel repulsion in steering wheel, and further, when an excessive assist steering torque is applied thereto by a calculation error, movement of the vehicle may become unsafe and over compensating, unfortunately causing accidents in extreme cases. Accordingly, additional measures are necessary to ensure the integrity of the system.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
The present invention has been made in an effort to provide a lane assistance system which is able to minimize repulsion felt by a driver from the system by controlling torque vectoring according to a yaw rate. A lane assistance system using an in-wheel system according to an exemplary embodiment of the present invention may include a control device, e.g., a controller that is configured to determine when a vehicle is in danger of deviating from a lane, calculate a necessary yaw rate for assisting in maintaining the vehicle in the lane, calculate a demand yaw rate through a difference between the calculated necessary yaw rate and an actual yaw rate, and calculate a distribution amount of a driving torque from torque vectoring to achieve a demand yaw rate.
The lane deviation may be detected by an increment of a lateral displacement or a relative yaw angle or alternatively by the relative yaw angle and speed of a vehicle in a case of the relative yaw angle.
The necessary yaw rate may be achieved by a calculation of a predicted deviation amount that is caused by the lateral displacement and the relative yaw angle. The demand yaw rate may be calculated by the equation below.
Here, δdesired is a demand yaw rate. Δ{dot over (ψ)} is a difference between a demand yaw rate and an actual yaw rate. V is a vehicle speed, and L is a track (distance between wheels) of a vehicle.
The distribution amount of the torque vectoring driving torque may be set by adding a distribution amount of a driving torque of a torque vectoring through a deviation amount and a driving torque of torque vectoring through a road curvature. The distribution amount of a driving torque of torque vectoring through the deviation amount may be calculated by the equation below.
Here, FTV1 is a driving torque distribution amount through a deviation amount. M is a demand moment. Kp is a proportional coefficient, and t is a tread (a distance between left/right tires).
The driving torque distribution amount of torque vectoring through the road curvature may be calculated through road curvature and vehicle speed. Control timing may be determined by the demand yaw rate when, for example, the vehicle speed is more than 40 km/h or/and when the demand yaw rate is larger than a predetermined value.
An exemplary embodiment of the present invention uses the change in torque applied to a rear wheel rather than applying a steering wheel torque to the steering wheel when a vehicle deviates from a lane so that repulsion is not transferred to a driver. That is, the present invention uses a change in torque applied to a rear wheel to minimize the repulsion felt by a driver in a steering wheel.
Additionally, a vision device may add to the in-wheel system which may be incorporated into an electronic driving system in the vehicle as well.
Hereinafter, with reference to the accompanying drawings, the present invention will be described in order for those skilled in the art to be able to implement the invention.
It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.
A lane assistance system according to an exemplary embodiment of the present invention uses an in-wheel system to keep a vehicle from unintentionally departing from its intended lane of travel. More specifically, the in-wheel includes a motor that is disposed in or around each wheel of a vehicle to direct operation of the wheel or independently control the drive torque applied to the wheel based upon a lane assistance system detecting that a vehicle is beginning to depart from its intended lane of travel. The in-wheel system independently operates each wheel and independently controls torque of a front/rear/left/right wheel to improve movement and performance of a vehicle, and particularly, to be able to independently control the steering of the wheels. This is achieved by a lateral force that is generated by controlling a torque difference between left and right wheels.
Hereinafter, a lane assistance system will be described according to an exemplary embodiment of the present invention. Firstly,
The lane assistance system according to an exemplary embodiment of the present invention determines a danger condition of a lane deviation while driving, and if it is determined that a vehicle is in approaching dangerous conditions, e.g., departing into an unintended lane of traffic, the illustrative embodiment of the present invention calculates a necessary yaw rate for maintaining the vehicle in its intended lane, calculates a demand yaw rate between the calculated necessary yaw rate and the actual yaw rate, and calculates a distribution amount of a torque vectoring driving torque to achieve the demand yaw rate so that the vehicle safely maintains its intended lane of travel.
Also, in addition to the method that determines a danger of a lane deviation of a vehicle 20 through the lateral displacement (D), as shown in
Here, the relative yaw angle (α) denotes an angle that is formed by a center line 10 of a road and a straight direction line 16 of the vehicle 20 in
The straight direction line 16 of the vehicle 20 signifies a frontal direction of the vehicle 20 regardless of the turning direction of the vehicle 20. Here, it is necessary to compensate the danger of the lane deviation.
Hereinafter, a method for maintaining a lane according to an exemplary embodiment of the present invention will be described.
The method includes calculating a necessary yaw rate so as to assist a driver in maintaining the vehicle in its intended lane of travel, which can be determined by calculating a predicted deviation amount that is caused by a lateral displacement (D) and a relative yaw angle.
This is calculated by Equation 1 below.
In the above Equation 1, {dot over (ψ)}p is a necessary yaw rate, ψp is a predicted deviation amount, and Tp is a predicted time. That is, the necessary yaw rate signifies a ratio of a yaw rate that is predicted and that deviates for a predetermined time.
Then, a demand yaw rate is calculated by a difference between the necessary yaw rate that is calculated by the equation and the actual yaw rate, and the demand yaw rate is calculated by Equation 2 below.
In the above Equation 2, δdesired is a demand yaw rate, L is a right/left wheel distance of a vehicle 20, V is vehicle speed, and Δ{dot over (ψ)} is a difference between the necessary yaw rate and the actual yaw rate. That is, Δ{dot over (ψ)}={dot over (ψ)}p−{dot over (ψ)}a, wherein {dot over (ψ)}p is a necessary yaw rate and {dot over (ψ)}a is an actual yaw rate.
A control intervention timing can be determined by the demand yaw rate. For example, if the demand yaw rate is greater than a predetermined value, the system intervenes in the control to maintain the vehicle in its intended lane of travel.
Also, a demand yaw moment is calculated to achieve the demand yaw rate according to an exemplary embodiment of the present invention, and a distribution amount of a torque vectoring driving torque is calculated to achieve this. Here, the driving torque distribution amount of the torque vectoring is calculated by adding a distribution amount of a torque vectoring driving torque through a deviation amount and a distribution amount of a torque vectoring driving torque through a road curvature. The torque vectoring driving torque by the deviation amount is compensated for by a deviation through the road curvature.
The driving torque distribution amount of the torque vectoring through the deviation amount is calculated by Equation 3 below.
In the above Equation 3, FTV1 is a driving torque distribution amount of torque vectoring through a deviation amount, M is a demand moment, Kp is a proportional coefficient, and t is a tread.
Also, the driving torque distribution amount of the torque vectoring through the road curvature is calculated by the road curvature and the vehicle's speed, which is calculated by Equation 4 below.
F
TV2
=f(k,V) (4)
In the above Equation 4, FTV2 is a driving torque distribution amount of torque vectoring by a road curvature, k is a road curvature, and V is a speed of a vehicle 20. Here, the road curvature can be calculated by a camera sensor. The driving torque distribution amount of the torque vectoring that is calculated by the above method is used to maintain the lane.
Hereinafter, referring to
Firstly, in
In the “B” section from this point (X), the system controls the vehicle according to the torque vectoring distribution amounts FTV1 and FTV2 to assist the driver in maintaining vehicle in the lane. Once the vehicle moves into an inner side of the lane through the vehicle assistance, the control intervention is released. That is, intervention control is released at a point where a control release line 19 intersects the vehicle moving line 25, particularly if the steering angle is greater than a predetermined value (for example, 14°). After the control is released, a driver may again normally operate the vehicle in the “C” section, because there is no longer any danger of the vehicle deviating from the traffic lane.
The control controls the vehicle according to the torque vectoring distribution amount calculated in “c”, the vehicle 20 is guided toward the central area of the lane to so that the vehicle does not cross the central line 100 in “d”, and then if it is determined that further control is not necessary in “e”, the control is released. In this case, the driving torque of the torque vectoring controls the system such that the driving torque 31 of the outer rear wheel becomes greater than the driving torque 30 of the inner side rear wheel.
As described above, the driving torque of the rear (front) wheel is used to make the vehicle stay within the lane thereof while at the same time preventing the driver from being a repulsion or additionally applied force in the steering wheel thereof.
Furthermore, the present invention may be embodied as computer readable media on a computer readable medium containing executable program instructions executed by a control device such as a processor, controller or the like. Examples of the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable recording medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, such as a telematics server and controller area network.
While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2011-0075163 | Jul 2011 | KR | national |
