Method of providing a scenario-based overlay torque request signal in a road vehicle steer torque manager

Abstract

Disclosed is a method of providing a scenario-based overlay torque request signal in a steer torque manager (1) during driver-override of an auxiliary steering assistance system (2) function in a road vehicle (3) having an EPAS system (4). The steer torque manager (1) has a wheel angle controller (1b) for providing an assistance torque request related signal, and a driver-in-the-loop functionality (1a) for determining driver-override and providing a driver-override related signal. The method comprises receiving signals related to: assistance torque request; driver-override; road vehicle velocity; steering pinion angle; distance to an adjacent lane marker (5a, 5b); and distance to an adjacent potential threat object (6), and producing, from the received signals, during ongoing driver-override, a signal representative of a resistance torque request corresponding to one of a finite number of pre-defined scenarios for different signal combinations, and producing the scenario-based steering wheel overlay torque request signal through combining the assistance torque request and the resistance torque request signals.

Claims

1. A method of providing a scenario-based overlay torque request signal in a steer torque manager (1) during driver-override of an auxiliary steering assistance system (2) function in a road vehicle (3) having an electrical power assisted steering system (4), the steer torque manager (1) including a wheel angle controller (1b) that provides an assistance torque request related signal from an auxiliary steering assistance system (2) function overlay torque request and a torque request from the electrical power assisted steering (4); and a driver-in-the-loop functionality (1a) that determines driver-override of the auxiliary steering assistance system (2) function through considering both a current steering wheel torque and a weighted average of a measured steering wheel torque over the last couple of seconds and providing a driver-override related signal, the method comprising: receiving the assistance torque request related signal; receiving the driver-override related signal; receiving a road vehicle velocity related signal; receiving a steering pinion angle related signal; receiving a signal representative of a distance to an adjacent lane marker; receiving a signal representative of a distance to an adjacent potential threat object; producing from the received signals, when the driver-override related signal indicates ongoing driver-override, a signal representative of a resistance torque request corresponding to one of a finite number of pre-defined scenarios for which a resistance torque previously has been separately tuned for different signal combinations; and producing, by the steer torque manager (1), a scenario-based steering wheel overlay torque request signal through combining the assistance torque request signal and the resistance torque request signal.

2. A method according to claim 1, wherein it further comprises receiving as the signal representative of a distance to an adjacent potential threat object (6) a signal representative of an estimated Times to Collision (TTC) with an adjacent potential threat object (6).

3. A method according claim 2, wherein producing the signal representative of a resistance torque request further comprises scaling the signal with the functions: f(x).sub.i: x∈[−1,1], i∈Ω g(TTC).sub.i: TTC∈[0, TTC.sub.max], i∈Ω where the set Ω contains a finite number of pre-defined scenarios for which a resistance torque previously has been separately tuned, and x is a normalized distance from an adjacent lane marker (5a, 5b) to a center of a lane (5) currently travelled; a left-hand lane marker (5a) being located at x=−1 a right-hand lane marker (5b) being located at x=1.

4. A method according to claim 3, wherein it further comprises receiving a signal representative of classified potential threat objects (6) determined through fusion of sensor data from multiple vehicle (3) born sensors and systems and determining a current scenario from the set Ω of pre-defined scenarios based on the signal representative of classified potential threat objects (6).

5. A method according to claim 3, wherein it further comprises using, for a determined pre-defined scenario with no potential threat objects (6) to the right or to the left of the road vehicle (3), a function ƒ(x) being a convex bathtub shaped function with a flat minimum at x=0 and monotonically increasing with increasing |x| as the road vehicle (3) approaches a lane marker (5a,5b).

6. A method according to claim 3, wherein it further comprises using, for a determined scenario with threat objects (6) either to the left or to the right of a lane (5) currently travelled by the road vehicle (3), a function ƒ(x) being asymmetric around the center x=0 of the lane (5) currently travelled and increasing as the road vehicle (3) approaches threat objects (6).

7. A method according to claim 3, wherein it further comprises using, in case that a driver of the road vehicle (3) is pulling against the auxiliary steering assistance system (2) function towards a collision with a potential threat object (6), a function g(TTC).sub.i arranged to increase the resistance torque, the function g(TTC).sub.i being increasing with decreasing Time to Collision (TTC).

8. A road vehicle (3) steer torque manager (1) comprising: a wheel angle controller (1b) that provides an assistance torque request related signal from an auxiliary steering assistance system (2) function overlay torque request and a torque request from the electrical power assisted steering (4); a driver-in-the-loop functionality (1a) that determines driver-override of the auxiliary steering assistance system (4) function through considering both a current steering wheel torque and a weighted average of a measured steering wheel torque over the last couple of seconds and providing a driver-override related signal; a memory for storing a program and a finite number of pre-defined scenarios; a processor for executing the program stored in the memory; a first signal interface for receiving signals from sensors on-board the road vehicle and converting these signals into forms suitable for processing by the processor; and a second signal interface for outputting the scenario-based steering wheel overlay torque request signal produced adopted to execute the method of claim 1.

9. A computer program embodied on a non-transitory computer-readable storage medium, the computer program comprising instructions when executed by a processing circuit are configured to cause a road vehicle (3) steer torque manager (1) to execute the method of claim 1, said road vehicle steer torque manager including: a wheel angle controller (1b) that provides an assistance torque request related signal from an auxiliary steering assistance system (2) function overlay torque request and a torque request from the electrical power assisted steering (4); and a driver-in-the-loop functionality (1a) that determines driver-override of the auxiliary steering assistance system (4) function through considering both a current steering wheel torque and a weighted average of a measured steering wheel torque over the last couple of seconds and providing a driver-override related signal.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) In the following, embodiments herein will be described in greater detail by way of example only with reference to attached drawings, in which:

(2) FIG. 1 illustrates schematically an example resistance torque tuning with respect to left- and right-hand lane markers without additional threat objects;

(3) FIG. 2 illustrates schematically an example resistance torque tuning with respect to threat objects to the left of the ego road vehicle;

(4) FIG. 3 illustrates schematically an example resistance torque tuning with respect to a threat object to the right of the ego road vehicle;

(5) FIG. 4 illustrates schematically an example resistance torque tuning with respect to a curve entry;

(6) FIG. 5 illustrates schematically a road vehicle that comprises a steer torque manager having means adopted to execute the method according to the embodiments described herein.

DESCRIPTION OF EMBODIMENTS

(7) In the following will be described, with reference to the attached drawings, some example embodiments of an improved method of providing a scenario-based overlay torque request signal in a steer torque manager 1 during driver-override of an auxiliary steering assistance system 2 function in a road vehicle 3, as illustrated in FIG. 5, and thus providing for a threat-based steering feel, during driver-override of an auxiliary steering assistance system 2 function, e.g. override of a lane centering ADAS or autonomous driving (AD) function, in a road vehicle 3.

(8) A lane traveled by the road vehicle 3 will in the following be denominated by the reference numeral 5 and that lane 5 will usually be delimited by left- and right-hand lane markers 5a, 5b.

(9) The road vehicle 3 is assumed to have an electrical power assisted steering system 4, and an auxiliary steering assistance system 2 function arranged to selectively apply a steering wheel overlay torque to a normal steering assistance torque in the electrical power assisted steering system 4 of the road vehicle 3.

(10) The steer torque manager 1 of the road vehicle 3 is further assumed to have a driver-in-the-loop functionality 1a, for determining when and how to hand over control from the auxiliary steering assistance system 2 function to a driver of the road vehicle 3 and when a driver of the road vehicle 3 wishes to override the auxiliary steering assistance system 2 function without handing over control. This is done by the driver-in-the-loop functionality 1a through considering both a current steering wheel torque and a weighted average of a measured steering wheel torque over the last couple of seconds. As a result thereof the driver-in-the-loop functionality 1a will provide a driver-override related signal.

(11) The steer torque manager 1 of the road vehicle 3 is also assumed to have a wheel angle controller 1b for providing, from an auxiliary steering assistance system 2 function wheel angle request, an overlay torque request to be added to a torque request from the electrical power assisted steering 4. Thus, the wheel angle controller 1b is arranged to provide an assistance torque request related signal from an auxiliary steering assistance system 2 function overlay torque request and a torque request from the electrical power assisted steering 4.

(12) The method comprises receiving, from the wheel angle controller 1b the assistance torque request related signal and receiving, from the driver-in-the-loop functionality 1a, the driver-override related signal.

(13) The method further comprises receiving, from road vehicle 3 on-board sensors, signals relating to road vehicle 3 velocity and steering pinion angle, a signal representative of a distance to an adjacent lane marker 5a, 5b and a signal representative of a distance to an adjacent potential threat object 6.

(14) The road vehicle 3 is assumed to have a number of on-board sensors for providing some of the signals used in the described method, however such sensors does not form part of the present invention, only the ability to receive and utilize the signals emanating therefrom.

(15) In accordance with the method, the steer torque manager 1 is, when the driver-override related signal indicates ongoing driver-override, configured to produce, from the received signals, a signal representative of a resistance torque request corresponding to one of a finite number of pre-defined scenarios for different signal combinations.

(16) Finally, the method comprises producing, by the steer torque manager 1, the scenario-based steering wheel overlay torque request signal through combining the assistance torque request signal and the resistance torque request signal.

(17) Thus, the scenario-based steering wheel overlay torque request signal is a combination of the assistance torque request signal, i.e. a signal for pulling in the same direction as a driver of the road vehicle 3, and the resistance torque request signal, i.e. a signal for pulling against the driver of the road vehicle 3.

(18) The resistance torque requested will thus be a function of road vehicle 3 velocity, driver-in-the-loop impulse, steering pinion angle, distance to lane markers 5a, 5b, and distance to threat objects 6.

(19) The term steering pinion angle is used as a rotation angle (steering angle) of a rotary shaft, which rotation angle can be converted into a steered angle of steered wheels of the road vehicle 3.

(20) The driver-in-the-loop (DIL) impulse is, as described earlier, a measure of driver activity over a time window, i.e. a weighted steering wheel torque average over a time window, usually a time window of the most recent couple of seconds.

(21) In a further embodiment the method comprises receiving as the signal representative of a distance to an adjacent potential threat object 6 a signal representative of an estimated Times to Collision (TTC) with that adjacent potential threat object 6, that is, an estimated period of time until the own vehicle 3 collides with that threat object 6, based on, for example, a distance between the own vehicle 3 and that threat object 6 and a relative velocity between the own vehicle 3 and that threat object 6.

(22) In a yet further embodiment producing the signal representative of a resistance torque request in accordance with the method further comprises scaling the signal with the functions: ƒ(x).sub.i: x∈[−1,1], i∈Ω g(TTC).sub.i: TTC∈[0, TTC.sub.max], i∈Ω where the set Ω contains a finite number of pre-defined scenarios for which a resistance torque previously has been separately tuned, and x is a normalized distance from an adjacent lane marker 5a, 5b to a center of a lane 5 currently traveled; a left-hand lane marker 5a being located at x=−1 and a right-hand lane marker 5b being located at x=1.

(23) Some examples of resistance torque tuning for such pre-defined scenarios will be described later.

(24) In a still further embodiment the method further comprises receiving a signal representative of classified potential threat objects 6 determined through fusion of sensor data from multiple vehicle 3 born sensors and systems, such as camera sensors, radar sensors, lidar sensors, satellite navigation systems and digital maps. For consistent and predictable behavior, the scenarios that form up the set Ω of scenarios should be easily identified by both a driver and the auxiliary steering assistance system 2, e.g. ADAS or AD system.

(25) The method further comprises determining a current scenario from the set Ω of pre-defined scenarios based on the signal representative of classified potential threat objects 6.

(26) Classified threat objects 6 are suitably provided by a classifier relying on fused sensor data, including fusion of road geometry data. The signal representative of classified potential threat objects 6 is used to determine a current scenario from the set Ω of scenarios based thereupon, and thus the shape of the functions ƒ(x).sub.i and g(TTC).sub.i.

(27) An example of a classified threat object 6 may e.g. be a lorry or truck at the right-hand side of an ego road vehicle 3 in a road coordinate system. The classifier is suitably arranged to only present such a classified threat object 6 if it has been determined to exist with a predetermined high probability.

(28) Thus, the scenarios that should be in the set Ω of scenarios needs to be defined and the desired resistance torque for each scenario specified, i.e. the shape of the functions ƒ(x).sub.i and g(TTC).sub.i.

(29) In the following will be given some, non-exhaustive, examples how to tune the functions ƒ(x).sub.i and g(TTC).sub.i for different scenarios.

(30) For the examples illustrated in FIGS. 1 through 4 the top views illustrates the different traffic scenarios and the graphs there below the suggested example tunings of the resistance torque in dependence of a normalized distance from the left- and right-hand side lane markers 5a, 5b to a center of a lane 5 currently traveled.

(31) The resistance torque may be distributed in dependence of a position of the road vehicle 3 in a lane 5, e.g. bathtub shaped, or linearly increasing towards the lane markers 5a, 5b at the sides of the lane 5, as illustrated in FIG. 1, i.e. low resistance torque in the middle of the lane 5 and increasingly more resistance towards the outer boundaries of the lane 5, e.g. as indicated by the left- and right-hand lane markers 5a, 5b.

(32) Higher resistance torque may e.g. be provided if the road vehicle 3 moves towards a solid lane marker 5a, 5b line than a dashed lane marker 5a, 5b line. Higher resistance torque may e.g. be provided if the road vehicle 3 moves towards concrete barriers and the resistance torque may be increased earlier as compared to when no concrete barriers are present.

(33) Additionally, the shape of the functions ƒ(x).sub.i and g(TTC).sub.i may also be dependent on lane 5 width as well as on curve radius.

(34) The functions ƒ(x).sub.i and g(TTC).sub.i may be tuned to provide less resistance torque at road works, making it easier to overrule the auxiliary steering assistance system 2 function for safely traversing a road work area.

(35) The functions ƒ(x).sub.i and g(TTC).sub.i may be tuned to provide less resistance torque when e.g. an emergency vehicle is determined to be approaching, making it easier to overrule the auxiliary steering assistance system 2 function and provide for an unobstructed passing by the emergency vehicle.

(36) The functions ƒ(x).sub.i and g(TTC).sub.i may be tuned to be velocity dependent, such that they are less aggressive in low-velocity situations, e.g. traffic jam situations, making it easier to negotiate a traffic jam.

(37) The functions ƒ(x).sub.i and g(TTC).sub.i may also be tuned to provide more resistance torque should the ego road vehicle 3 be steered towards a vehicle 6 driving in an adjacent lane 7, e.g. as illustrated in FIG. 2.

(38) The functions ƒ(x).sub.i and g(TTC).sub.i may further be tuned to provide resistance torque in dependence of what is present next to or adjacent a lane marker 5a, 5b line, e.g. a barrier beneath the lane marker, the width of a hard shoulder outside the lane marker 5a, 5b, etc.

(39) The functions ƒ(x).sub.i and g(TTC).sub.i may additionally be tuned to be situation based, e.g. to handle a “multiple threat” situation, such as an offset situation where less resistance torque may be preferred towards a (solid) barrier while overtaking a truck, because the truck might move towards the ego road vehicle 3 while the barrier will not move.

(40) The functions ƒ(x).sub.i and g(TTC).sub.i may also be tuned to take “freespace” into account, e.g. such that less resistance torque is provided for moving the ego road vehicle 3 in a direction of a determined “freespace”.

(41) The functions ƒ(x).sub.i and g(TTC).sub.i may in some cases be tuned to provide for different behavior based on map data, e.g. to provide for different resistance torque if the ego road vehicle 3 is close to a city center, is entering an urban area, or is traveling on a highway.

(42) The functions ƒ(x).sub.i and g(TTC).sub.i may also be tuned to take small road situations into account, e.g. by making it easier to cross a lane marker 5a, 5b with oncoming traffic or to overtake cyclists or pedestrians on the same site when traveling on smaller two-way traffic roads.

(43) The functions ƒ(x).sub.i and g(TTC).sub.i may furthermore be tuned to allow a driver to anticipate on a corner, e.g. to provide for a reduced resistance torque allowing for corner/curve cutting.

(44) The functions ƒ(x).sub.i and g(TTC).sub.i may still further be tuned to take into account fast vehicles approaching from behind, e.g. such as on the German Autobahn, and to provide for an increased distance to and a higher resistance torque towards an adjacent lane 7 wherein such a fast vehicle is approaching.

(45) The functions ƒ(x).sub.i and g(TTC).sub.i may additionally be tuned to consider the risk of kids or animals crossing the road, e.g. daytime dependent to provide for an increased distance to and a higher resistance torque for moving the ego vehicle 3 towards the side of the road when passing a school or playground.

(46) The functions ƒ(x).sub.i and g(TTC).sub.i may also be tuned to provide different resistance behavior depending on lighting or weather conditions, e.g. different behavior at night time, such as to provide for an increased distance to and a higher resistance torque for moving the ego vehicle 3 towards the side of the road.

(47) The functions ƒ(x).sub.i and g(TTC).sub.i may yet further be tuned to be driver state based, e.g. based on if a driver is in or out of the loop, such as by using a human machine interface (HMI), using a phone, or similarly distracted or preoccupied. This may e.g. be done through providing for a higher resistance torque for moving the ego vehicle 3 towards the side of the road when a driver is determined to be distracted or preoccupied.

(48) The functions ƒ(x).sub.i and g(TTC).sub.i may also be tuned to provide different resistance torque behavior during a driver overtake request from the auxiliary steering assistance system 2 function, e.g. to raise resistance torque or provide a higher maximum torque when a driver is not answering to the takeover request.

(49) Thus, for a determined current scenario with no threat objects 6 to the right or to the left of the ego road vehicle 3, a function ƒ(x) may be used that is a convex bathtub shaped function with a flat minimum at x=0 and monotonically increasing with increasing |x| as the road vehicle 3 approaches a lane marker 5a, 5b, i.e. as the distance between the ego road vehicle 3 and either side lane marker 5a, 5b decreases.

(50) For a determined current scenario with threat objects 6 either to the left or to the right of the lane 5 currently traveled a function ƒ(x) may be used that is asymmetric around the center x=0 of the lane 5 currently traveled, e.g. as illustrated in FIG. 2, where there are vehicles 6 in the adjacent lane 7 to the left of the ego road vehicle 3, or as illustrated in FIG. 3, where there is a pedestrian 6 at the right-hand side of the lane 5 traveled by the ego road vehicle 3.

(51) The functions ƒ(x).sub.i and g(TTC).sub.i may be tuned to provide different resistance torque behavior in a curve 8 entry or exit situation, e.g. as illustrated in FIG. 4, where the ego road vehicle 3 is entering a curve 8 to the right and more resistance torque is provided against any attempts to move the ego vehicle 3 towards the outside of the curve 8.

(52) The function g(TTC).sub.i may further be arranged to increase the resistance torque in case that a driver of the road vehicle 3 is pulling against the auxiliary steering assistance system 2 function, such as a lane centering function, towards a collision with a threat object 6, such that g(TTC).sub.i increases with decreasing Time to Collision TTC with that threat object 6, and if TTC>TTC.sub.max then g(TTC).sub.i=1.

(53) Furthermore, here envisaged is a road vehicle steer torque manager 1 having means adopted to execute the above method.

(54) Such a road vehicle 3 steer torque manager 1 has a wheel angle controller 1b for providing an assistance torque request related signal from an auxiliary steering assistance system 2 function overlay torque request and a torque request from the electrical power assisted steering 4. It further has a driver-in-the-loop functionality 1a, for determining driver-override of the auxiliary steering assistance system 2 function. Override is determined through considering both a current steering wheel torque and a weighted average of a measured steering wheel torque, DIL-impulse, over the last couple of seconds. From that determination it is arranged to provide a driver-override related signal. The road vehicle 3 steer torque manager 1 furthermore has means adopted to execute the above method.

(55) The means adapted to execute the above method may e.g. comprise: a memory for storing a program and a finite number of pre-defined scenarios; a processor or central processing unit (CPU) for executing the program written in the memory; a first signal interface for receiving from the road vehicle 3 on-board sensors the signals used in the herein described method and converting these signals into forms suitable for processing by the processor; and a second signal interface for outputting the scenario-based steering wheel overlay torque request signal produced.

(56) Still further here envisaged is a computer program comprising instructions to cause the above road vehicle 3 steer torque manager 1 to execute the above method as described above.

(57) The above described embodiments of the method, road vehicle steer torque manager 1, and computer program have the beneficial effects of facilitating the provision of a scenario-based resistance torque, and thus a threat-based steering feel, during driver-override of an auxiliary steering assistance system 2 function, such as an ADAS function, in a road vehicle 3.

(58) Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. In cases where advantages, benefits or solutions to problems are described herein, it should be appreciated that such advantages, benefits and/or solutions may be applicable to some example embodiments, but not necessarily all example embodiments. Thus, any advantages, benefits or solutions described herein should not be thought of as being critical, required or essential to all embodiments or to that which is claimed herein. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.