WO2024110034A1

WO2024110034A1 - Vehicle control in relation to a reference path

Info

Publication number: WO2024110034A1
Application number: PCT/EP2022/083125
Authority: WO
Inventors: Yangyan Gao; Timothy Gordon; Shammi RAHMAN; Jakub PROKES
Original assignee: Volvo Truck Corporation
Priority date: 2022-11-24
Filing date: 2022-11-24
Publication date: 2024-05-30

Abstract

A computer-implemented method is disclosed for controlling a vehicle in relation to a reference path when a vehicle location has a lateral offset from the reference path. The method is for execution by a processor device of a computer system. The method comprises determining a preview distance by the processor device, wherein a goal point on the reference path – to be steered towards from the vehicle location – is distanced along the reference path by the preview distance measured from a reference location associated with the vehicle location. The preview distance is determined based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset. Corresponding computer program product, non-transitory computer-readable storage medium, apparatus, control system, computer system, and vehicle are also disclosed.

Description

VEHICLE CONTROL IN RELATION TO A REFERENCE PATH

TECHNICAL FIELD

[0001] The disclosure relates generally to vehicle control. In particular aspects, the disclosure relates to vehicle control in relation to a reference path. The disclosure can be applied in heavy-duty vehicles, such as trucks, buses, and construction equipment. Although the disclosure may be described with respect to a particular vehicle, the disclosure is not restricted to any particular vehicle.

BACKGROUND

[0002] Vehicle control generally includes any approach to operating a vehicle. Vehicle operation may comprise interaction - through user interface devices - between a human operator and control systems of the vehicle. Alternatively or additionally, vehicle operation may comprise autonomous, or semi-autonomous, operation.

[0003] Advanced driver assistance systems (ADAS) and methods for controlling autonomous drive (AD) by autonomous vehicles normally base vehicle control on some form of path following algorithm. The control system first obtains (e.g., determines) a desired path - a reference path - to be followed by the vehicle. For example, the reference path may be determined based on a current transport mission and map data indicating possible routes to take in order to navigate the vehicle from one location to another.

[0004] Path following is a process concerned with how to operate the vehicle (e.g., which acceleration forces and steering to apply) at each instant of time to cause the vehicle to follow to the reference path as closely as possible. There are many different types of path following approaches.

[0005] Pure pursuit is an example path following approach. This approach determines a set of vehicle control parameters, including a steering angle, for moving the vehicle from its current location towards a goal point at a predetermined preview distance from the vehicle location on the reference path. The pure pursuit approach causes the vehicle to chase a goal point moving along the reference path and separated from the vehicle by the preview distance. [0006] Vector field guidance is another example path following approach. This approach bases vehicle control on a vector field, which is determined based on a preview distance measured from a reference location associated with the vehicle location to a goal point on the reference path.

[0007] Thus, the parameter termed as preview distance has an impact on the performance of at least some path following approaches.

[0008] In various situations, path following approaches may yield undesired vehicle behavior; e.g., oscillation in relation to the reference path, slow convergence towards the reference path, inability to follow the reference path, etc.

[0009] Therefore, there is a need for alternative path following approaches. Particularly, there is a need for alternative ways of determining the preview distance to be applied for path following.

SUMMARY

[0010] It is various aspects may aim to solve or mitigate, alleviate, or eliminate at least some of the above or other disadvantages.

[0011] According to a first aspect of the disclosure, a computer-implemented method is provided for controlling a vehicle in relation to a reference path when a vehicle location has a lateral offset from the reference path. The method is for execution by a processor device of a computer system. The method comprises determining a preview distance by the processor device based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset. A goal point on the reference path - to be steered towards from the vehicle location - is distanced along the reference path by the preview distance measured from a reference location associated with the vehicle location.

[0012] The first aspect of the disclosure may seek to improve the performance of at one or more path following approaches in one or more scenarios. A technical benefit may include decreased oscillation in relation to the reference path.

[0013] In some examples, the method further comprises controlling, by the processor device, the vehicle towards the goal point. [0014] In some examples, the preview distance increases with increasing value of the lateral deviation representation, and decreases with decreasing value of the lateral deviation representation. Thereby, a relatively large value of the lateral deviation representation results in a relatively long preview distance; and vice versa. Thus, when the vehicle is relatively far off from the reference path (large lateral offset magnitude) and/or when the vehicle is moving relatively quickly away from, or towards, the reference path (large magnitude of first order derivative of the lateral offset), a relatively long preview distance may be applied. A technical benefit may include that the path following approach has a smooth behavior in these situations; e.g., avoiding sharp steering towards the reference path when unsuitable, which may in turn decrease oscillation in relation to the reference path.

[0015] In some examples, the method further comprises limiting, by the processor device, the preview distance to be larger than, or equal to, a minimum preview distance. Thereby, the goal point will always be somewhat distanced from the vehicle location (even when the lateral offset is very small, or when the vehicle location is on the reference path). A technical benefit may include that the path following approach has a smooth behavior in these situations; e.g., avoiding sharp steering towards the reference path when unsuitable, which may in turn decrease oscillation in relation to the reference path.

[0016] In some examples, the preview distance is determined, by the processor device, based on the lateral deviation representation responsive to the lateral offset and the first order derivative of the lateral offset having a same sign. Thereby, the suggested preview distance is applied when the lateral offset magnitude is growing; i.e., when the vehicle is moving away from the reference path. A technical benefit may include that the path following approach has a smooth behavior in these situations; e.g., avoiding sharp steering towards the reference path when unsuitable, which may in turn decrease oscillation in relation to the reference path.

[0017] In some examples, the preview distance is determined, by the processor device, based on the lateral deviation representation responsive to the absolute value of the lateral offset being smaller than a first threshold value. Thereby, the suggested preview distance is applied when the lateral offset magnitude is relatively small. A technical benefit may include that the path following approach has a smooth behavior in these situations; e.g., avoiding sharp steering towards the reference path when unsuitable, which may in turn decrease oscillation in relation to the reference path. [0018] In some examples, the first threshold value is based on a distance between wheel axles of the vehicle and/or a minimum preview distance. A technical benefit may include that application of the suggested preview distance may be differentiated based on a vehicle steering radius.

[0019] In some examples, the preview distance is determined, by the processor device, based on the lateral deviation representation responsive to the absolute value of the first order derivative of the lateral offset being larger than a second threshold value. Thereby, the suggested preview distance is applied when the vehicle is moving relatively quickly away from, or towards, the reference path. A technical benefit may include that the path following approach has a smooth behavior in these situations; e.g., avoiding sharp steering towards the reference path when unsuitable, which may in turn decrease oscillation in relation to the reference path.

[0020] In some examples, the second threshold value is based on an absolute value of the lateral offset. A technical benefit may include that application of the suggested preview distance may be differentiated based on a relation between the lateral offset magnitude and how quickly the lateral offset magnitude changes. For example, when the vehicle is relatively far from the reference path, the suggested preview distance may be applied only when there are relatively fast changes of the lateral offset, while when the vehicle is relatively close to the reference path, the suggested preview distance may be applied also for relatively slow changes of the lateral offset.

[0021] Generally, the preview distance may be determined based on the lateral deviation representation responsive to one or more conditions being met (e.g., the lateral offset and the first order derivative of the lateral offset having a same sign, the absolute value of the lateral offset being relatively small, the absolute value of the first order derivative of the lateral offset being relatively large). In other situations, another preview distance determination may be applied (e.g., according to any suitable approach of the prior art). Thereby, benefits of other approaches for determining preview distance (e.g., fast convergence towards the reference path, robustness regarding ability to follow the reference path, etc.) may be experienced while oscillation caused by the other approaches for determining preview distance can be avoided. [0022] In some examples, the method further comprises smoothing, by the processor device, the preview distance before application for vehicle control. A technical benefit may include that the path following approach has a smooth behavior; e.g., avoiding sudden changes in steering due to sudden changes in preview distance. Sudden changes of the preview distance may, for example, occur responsive to a change of approach for determining preview distance (e.g., due to changes regarding the lateral offset and/or the first order derivative of the lateral offset).

[0023] According to a second aspect of the disclosure, a computer program product is provided. The computer program product comprises program code for performing, when executed by the processor device, the method of the first aspect.

[0024] The second aspect of the disclosure may seek to convey program code for determination of the preview distance. A technical benefit may include that new vehicles and/or legacy vehicles may be conveniently configured, by software installation/update, to determine the preview distance.

[0025] According to a third aspect of the disclosure, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium comprises instructions, which when executed by a processor device, cause the processor device to perform the method of the first aspect.

[0026] The third aspect of the disclosure may seek to convey program code for determination of the preview distance. A technical benefit may include that new vehicles and/or legacy vehicles may be conveniently configured, by software installation/update, to determine the preview distance.

[0027] According to a fourth aspect of the disclosure, an apparatus is provided for controlling a vehicle in relation to a reference path when a vehicle location has a lateral offset from the reference path. The apparatus comprises controlling circuitry configured to cause determination of a preview distance, wherein a goal point on the reference path - to be steered towards from the vehicle location - is distanced along the reference path by the preview distance measured from a reference location associated with the vehicle location, and wherein the preview distance is determined based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset. [0028] The fourth aspect of the disclosure may seek to provide a device for determination of the preview distance. A technical benefit may include that new vehicles and/or legacy vehicles may be conveniently configured, by installation of the apparatus in the vehicle, to determine the preview distance.

[0029] In some examples, the controlling circuitry may comprise a determiner configured to determine the preview distance.

[0030] According to a fifth aspect of the disclosure, a control system is provided, which comprises the apparatus of the fourth aspect. The control system is configured to control a vehicle for following a reference path. To this end, the control system is configured to obtain the reference path, determine the preview distance, determine the goal point on the reference path, and control the vehicle towards the goal point.

The fifth aspect of the disclosure may seek to provide a system for improved vehicle control. [0031] According to a sixth aspect of the disclosure, a control system is provided, which comprises one or more control units configured to perform the method of the first aspect. [0032] The sixth aspect of the disclosure may seek to provide a system for determination of the preview distance. A technical benefit may include that a path following approach using the preview distance has a smooth behavior; e.g., avoiding sharp steering towards the reference path when unsuitable, which may in turn decrease oscillation in relation to the reference path.

[0033] The control systems of the fifth and sixth aspects may be a same control system, or may be different control systems.

[0034] According to a seventh aspect of the disclosure, a computer system is provided, which comprises a processor device configured to determine a preview distance for controlling a vehicle in relation to a reference path when a vehicle location has a lateral offset from the reference path, wherein a goal point on the reference path - to be steered towards from the vehicle location - is distanced along the reference path by the preview distance measured from a reference location associated with the vehicle location, and wherein the preview distance is determined based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset. [0035] The seventh aspect of the disclosure may seek to provide a system for determination of the preview distance. A technical benefit may include that a path following approach using the preview distance has a smooth behavior; e.g., avoiding sharp steering towards the reference path when unsuitable, which may in turn decrease oscillation in relation to the reference path.

[0036] According to an eighth aspect of the disclosure, a vehicle is provided, which comprises one or more of: the apparatus of the fourth aspect, the control system of any of the fifth and sixth aspects, the computer system of the seventh aspect, and a processor device configured to perform the method of the first aspect.

[0037] The eighth aspect of the disclosure may seek to provide a vehicle configured for improved motion control.

[0038] In some examples, any of the above aspects may additionally have features identical with or corresponding to any of the various features as explained above for any of the other aspects.

[0039] The above aspects, accompanying claims, and/or examples disclosed herein above and later below may be suitably combined with each other as would be apparent to anyone of ordinary skill in the art.

[0040] Additional features and advantages are disclosed in the following description, claims, and drawings, and in part will be readily apparent therefrom to those skilled in the art or recognized by practicing the disclosure as described herein. There are also disclosed herein control units, computer readable media, and computer program products associated with the above discussed technical benefits.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] With reference to the appended drawings, below follows a more detailed description of aspects of the disclosure cited as examples.

[0042] Further objects, features and advantages will appear from the detailed description, with reference being made to the accompanying drawings.

[0043] The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the examples. [0044] FIG. 1 is a flow chart of a method to determine a preview distance and control a vehicle according to one example.

[0045] FIG. 2 is a schematic drawing of a vehicle according to one example.

[0046] FIG. 3A is a schematic drawing of a path following approach based on pure pursuit according to one example.

[0047] FIG. 3B is a schematic drawing of a path following approach based on vector field guidance according to one example.

[0048] FIG. 3C is a schematic drawing of a vector field for path following based on vector field guidance according to one example.

[0049] FIG. 3D is a schematic block diagram of a vehicle control system according to one example.

[0050] FIG. 4 is a collection of schematic plots illustrating preview distance and corresponding path following performance according to various examples.

[0051] FIG. 5 is a schematic block diagram of an apparatus according to one example.

[0052] FIG. 6 is a schematic block diagram of a vehicle motion control system according to one example.

[0053] FIG. 7 is a schematic diagram of a computer system according to one example.

[0054] FIG. 8 is a schematic drawing of a computer readable medium according to one example.

[0055] FIG. 9 is a schematic block diagram of a control unit according to one example.

DETAILED DESCRIPTION

[0056] Aspects set forth below represent the necessary information to enable those skilled in the art to practice the disclosure.

[0057] Examples of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the examples set forth herein.

[0058] Generally, a vehicle may refer to any suitable vehicle. For example, a vehicle may be a heavy-duty vehicle and/or an articulated vehicle; e.g., a multi-unit commination vehicle comprising a tractor unit and one or more trailer units. [0059] In various situations, path following approaches may yield undesired vehicle behavior; e.g., oscillation in relation to the reference path, slow convergence towards the reference path, inability to follow the reference path, etc.

[0060] This disclosure focuses on alternative preview distance determination to mitigate such undesired vehicle behavior, and/or other disadvantages related to vehicle control by path following.

[0061] According to some examples, a preview distance determination is provided which automatically increases the preview distance when the speed of lateral movement increases for the vehicle.

[0062] Path following approaches, such as pure pursuit and vector field guidance, typically rely on a preview distance (sometimes referred to as a look-a-head distance). Generally, the preview distance relates to how distant a goal point is from the vehicle location along the reference path. Intuitively, a shorter preview distance results in an increased control effort (i.e., more powerful steering control action) to more quickly reduce the lateral offset of the vehicle in relation to the reference path, and a longer preview distance results in a decreased control action for smoother reduction of the lateral offset. A long preview distance typically reduces the ability of the vehicle to successfully negotiate corners and other sharp turns.

[0063] Generally, the term control effort may be interpreted as the effort spent in bringing the vehicle closer to the reference path. For example, control effort may be measured in terms of one or more of: lateral acceleration, yaw rate, side-slip, steering angle, energy consumed by vehicle actuators, etc.

[0064] Although path following approaches are exemplified herein by pure pursuit and vector field guidance, it should be noted that the approaches for determining preview distance can be equally applicable for other path following approaches where a goal point on the reference path - to be steered towards from the vehicle location - is distanced along the reference path by the preview distance measured from a reference location associated with the vehicle location.

[0065] FIG. 1 illustrates an example method 100 for determination of a preview distance and corresponding vehicle control according to one example. The vehicle control comprises control of the vehicle in relation to a reference path, when a vehicle location has a lateral offset from the reference path; e.g., according to a path following approach.

[0066] The method 100 may be a computer-implemented method, for execution by a processor device of a computer system. Typically, the processor device is mounted/mountable in the vehicle; e.g., in a tractor unit. However, it should be understood that the processor device may be external to the vehicle in some scenarios. For example, the processor device may be comprised in a server node; e.g., as part of a wireless communication network, a cloud computing network, an autonomous drive control network, or similar. For example, step 110 may be performed by a processor device external to the vehicle, and the resulting preview distance may be provided to an on-board processor device for use in vehicle control.

[0067] The method 100 comprises determining a preview distance by the processor device, as illustrated by step 110. The preview distance is determined based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset. Thus, the preview distance is determined based on a magnitude of a (possibly weighted) combination of the lateral offset and the change rate of the lateral offset.

[0068] The linear combination of the lateral offset and a first order derivative of the lateral offset may generally be expressed as S_y + where S_y denotes the lateral offset, t

denotes time, and T is a linear combination coefficient. Thus, the lateral deviation representation y may be represented as y = + T ^|.

[0069] The coefficient T may be seen as a design parameter, or a tuning parameter. For example, T may represent a characteristic time for closed-loop dynamics relating to offset control for path following.

[0070] The value of the parameter T may be chosen according to any suitable approach. For example, the value of T may be based on an expected speed of response for the path following; e.g., the value of T may be a decreasing function of the expected speed of response (i.e., small value of T for fast expected response, and vice versa). Alternatively or additionally, the value of T may be based on a (maximum) steering radius of the vehicle; e.g., the value of T may be an increasing function of the steering radius (i.e., small value of T for small steering angle, and vice versa).

[0071] Choosing an excessively low value of T may lead to overshoot for the path following, and choosing an excessively high value of T may lead to slow reaction for the path following.

[0072] Using the lateral deviation representation (e.g., as opposed to using only the lateral offset) for determination of the preview distance may improve the performance of path following approaches in one or more scenarios. For example, oscillation in relation to the reference path may be decreased compared to other approaches.

[0073] The preview distance may be determined based on the lateral deviation representation in any suitable way. Generally, the preview distance L may be expressed as L = f(y), where (■) represents a suitable function.

[0074] In some examples, the preview distance increases with increasing value of the lateral deviation representation, and decreases with decreasing value of the lateral deviation representation. Thus, the function (■) may comprise a strictly increasing function. More generally, the function (■) may comprise an increasing function.

Uv

[0075] In one particular example, L = (y) = -^==, where U may represent longitudinal velocity, a may be a first tuning parameter (e.g., an acceleration parameter), and b may be a second tuning parameter.

[0076] Alternatively, another function /(y) may be applied; e.g., depending on one or

more of U, a, and b. The function L = f(y) can be derived based on an

assumption of constant lateral acceleration and/or relatively small curvature of the reference path. Other assumptions regarding lateral acceleration and/or curvature may be applied; typically leading to other expressions for L = f(y).

[0077] More generally, the function (■) may increase with increasing longitudinal velocity U. This means that a smoother vehicle control is configured when the vehicle drives at high velocity, compared to when the vehicle is moving more slowly, which is beneficial because abrupt turning maneuvers are typically not desired at high velocity. Alternatively or additionally, the function (■) may decrease with increasing value of the first tuning parameter a. Yet alternatively or additionally, the function (■) may decrease with increasing value of the second tuning parameter b.

[0078] According to some examples, the first tuning parameter a may be based on how fast the vehicle is converging towards the reference path. Thus, the first tuning parameter may be seen as a convergence parameter.

[0079] For example, the first tuning parameter may be decreased from a nominal value for a vehicle location on the inside of a curve of the reference path (e.g., to avoid excessive acceleration for the convergence towards the reference path), and/or the first tuning parameter may be increased from a nominal value for a vehicle location on the outside of a curve of the reference path.

[0080] Alternatively or additionally, a may be based on a vehicle status (e.g., weight, tire wear, etc.) and/or a vehicle configuration. For example, the first tuning parameter may have a relatively high value for a passenger vehicle and a relatively low value for a high cargo vehicle.

[0081] A relatively high value of the first tuning parameter typically entails relatively fast convergence towards the reference path (which may be unsuitable for high vehicles due to increased risk of rolling or other types of instability) and a relatively low value of the first tuning parameter may entail relatively slow convergence.

[0082] In some examples, the first tuning parameter may be set to a value in the interval ]0 ... 1] m/s² (e.g., approximately 0.2 m/s²),

[0083] The first tuning parameter may be configured from a remote entity (e.g., by a processor device external to the vehicle), by a technician during vehicle service, by the driver, or by other persons (e.g., in connection with vehicle loading/off-loading).

[0084] Benefits can be obtained by adapting the preview distance according to the curvature or mean curvature of the reference path; e.g., to improve precision when maneuvering in restricted spaces. Such adaptation may occur indirectly via speed reduction, but further advantages can be achieved by adapting the first tuning parameter a according to an equation of the form a = $(/<), where K is any suitable curvature metric for the reference path, and $(/<) may be an increasing function. Thereby, increased path following control effort may be enabled to when greater precision is beneficial. [0085] According to some examples, the second tuning parameter satisfies b > 0. The second tuning parameter may be seen as an adjustment parameter, which can, for example, be used to control path following behavior for small lateral offsets; e.g., by reducing nonlinearities.

[0086] In some examples, the second tuning parameter b relates to an angle of attack y for the vehicle location, in relation to the reference path. The angle of attack may be an angle at which the vehicle approaches the reference path. For example, the second tuning parameter may be an increasing function of the angle of attack. Alternatively or additionally, the second tuning parameter may be set based on U and y; e.g., according to b = (17 tan y)² or b = (f/y) ². Yet alternatively or additionally, the angle of attack may be set to a value in the interval ]0 ... 3] degrees (e.g., approximately 1 degree), and/or the second tuning parameter may be set to a value in the interval ]0 ... 0.1] (m/s)².

[0087] Typically, the second tuning parameter and/or the angle of attack may be set to a relatively small value (e.g., below a threshold value). Choosing an excessively high value of b and/or y may lead to overshoot for the path following.

[0088] In some examples, the preview distance is limited to be larger than, or equal to, a minimum preview distance L_o), ^as illustrated by optional sub-step 112. Hence, the preview distance may be determined according to L = max( (y), L₀); e.g., L

[0089] The value of the minimum preview distance may be fixed or dynamically adjustable; e.g., based on current conditions of the vehicle (such as tire characteristics, brake characteristics, etc.), and/or based on the vehicle environment (such as weather conditions, road friction, etc.). Alternatively or additionally, the value of the minimum preview distance may be set based on one or more of: calculations, (field) testing, and simulations. Yet alternatively or additionally, the value of the minimum preview distance may be a value in the interval ]2 ... 5] m; e.g., approximately 3 m.

[0090] Application of the minimum preview distance may, for example, have the benefit of reducing sensitivity to time delays in a steering actuator and/or adapting to physical maneuvering limitations of large vehicles. Alternatively or additionally, application of the minimum preview distance (and thereby avoiding relatively small preview distances) may be beneficial to mitigate instability of the path following. [0091] A relatively small preview distance is more likely (even at relatively low speeds) to cause oscillations and/or instability, while a relatively large preview distance typically causes improved stability at the cost of worse path tracking performance.

[0092] The lateral deviation representation may be used to determine the preview distance for all situations. Alternatively, use of the lateral deviation representation to determine the preview distance may be conditional, as illustrated by optional sub-step 114. Then, another preview distance determination approach may be applied when the lateral deviation representation is not used.

[0093] For example, the other preview distance determination approach may comprise using only the lateral offset to determine the preview distance; e.g., using the preview distance formulas above with y_aU =

instead of y.

[0094] According to one example condition the preview distance is determined based on the lateral deviation representation responsive to the lateral offset and the first order derivative of the lateral offset having a same sign; i.e., when sign

= sign Thus,

the lateral deviation representation is used to determine the preview distance when the magnitude of the lateral offset is growing; i.e., the vehicle is moving away from the reference path.

[0095] According to one example condition the preview distance is determined based on the lateral deviation representation responsive to the absolute value of the lateral offset being smaller than a first threshold value; i.e., when |S_y | < thr^ Thus, the lateral deviation representation is used to determine the preview distance when the magnitude of the lateral offset is relatively small; i.e., the vehicle is relatively close to the reference path. For example, the first threshold value may be based on a distance between wheel axles of the vehicle (wheelbase) and/or on the minimum preview distance L_o; e.g., according to one or more of thr₁ « wheelbase, thr₁ < L_o, and thr being an increasing function of wheelbase and/or L_o. Alternatively or additionally, the first threshold value may be a value in the interval ]0 ... 10] cm.

[0096] According to one example condition the preview distance is determined based on the lateral deviation representation responsive to the absolute value of the first order derivative of the lateral offset being larger than a second threshold value; i.e., when > thr₂. Thus, the lateral deviation representation is used to determine the preview distance when the lateral offset changing relatively quickly; i.e., the vehicle is moving relatively quickly towards, or away from, the reference path. For example, the second threshold value may be based on the absolute value of the lateral offset; e.g., according to one or more of: thr₁ = |S_y |/T₀, where T_o is a time constant, and thr₂ being an increasing function of

. Alternatively or additionally, the second threshold value may be a value in the interval ]0 ... 10] m/s; e.g., approximately 1 m/s.

[0097] The above (and/or other) conditions may be combined in any suitable way. For example, the preview distance may be determined based on the lateral deviation representation (only) when sign(S_y) = sign (■“) and |S_y | < thr₁ and |^-| > thr₂ (which may be a preferable combination); or (only) when sign(S_y) = sign or |S_y | < thr₁ or

|^| > thr₂, or (only) when

< thr₁ and |^| > thr₂, or (only) when sign

= sign or using any other combination of two or more of these three

example conditions.

[0098] Generally, the preview distance may be determined based on the lateral deviation representation responsive to one or more conditions being met (e.g., one or more of the conditions mentioned above and/or other suitable condition(s)).

[0099] By combining use of the lateral deviation representation for preview distance determination with another preview distance determination approach, benefits of the other approach (e.g., fast convergence towards the reference path, robustness regarding ability to follow the reference path, lower computational complexity, etc.) may be enjoyed while oscillation caused by the other approach can be avoided.

[00100] In some situations, sudden changes of the preview distance may occur; e.g., when changing approach for determining preview distance, when switching between (y) and L_o in L = max( (y), L₀), when (y) has a discontinuous derivative, etc. To avoid (or mitigate) any performance problems of the vehicle control in such situations, the preview distance may be smoothed (e.g., by application of a suitable filter, such as a moving average filter) before it is applied for vehicle control (e.g., path following), as illustrated by optional sub-step 116. It should be noted that smoothing of the preview distance is not limited to these situations, but may be beneficial/applicable also in other situations. [00101] In any case, the preview distance determined in step 110 may be used to define a goal point on a reference path. The goal point is distanced along the reference path by the preview distance, as measured from a reference location associated with the vehicle location. [00102] The goal point may be defined as a point to be steered towards from the vehicle location; e.g., according to a path following approach. Thus, the goal point defined by the preview distance determined in step 110 may be used in vehicle control. This is illustrated by optional step 120, which exemplifies that the method 100 may further comprise controlling the vehicle towards the goal point.

[00103] Generally, the vehicle control may comprise any suitable approach for vehicle control based on a preview distance (e.g., a path following approach, such as pure pursuit or vector field guidance).

[00104] In a particular example, a vehicle control approach wherein an aim is that the vehicle should follow a reference path may comprise obtaining the reference path (e.g., previous to step 110), determining the preview distance (step 110), determining the goal point on the reference path based on the preview distance (e.g., as part of step 110 or step 120), and controlling the vehicle towards the goal point (step 120).

[00105] The reference path may be obtained according to any suitable approach. For example, the reference path may be determined based on map data and a transport mission to be accomplished, and/or according to a Lane Keep Assistance (LKA) function, where road markings observed using cameras are used to define the reference path. Furthermore, the vehicle location in relation to the reference path may be determined according to any suitable approach. For example, the vehicle location in relation to the reference path may be determined based on the reference path and vehicle location information from one or more on-board sensor (e.g., GPS receiver, radar transceiver, vision-based sensor, etc.).

[00106] It should be noted that controlling the vehicle towards the goal point (step 120) may be applied for individually steering one or more vehicle units of a multi-unit combination vehicle. For example, the vehicle control may be applied to a tractor unit as well as to one or more steerable trailer unit (e.g., a self-powered dolly vehicle unit or a powered trailer). When more than one vehicle unit of a vehicle are controlled according to the approaches exemplified herein, individual preview distances may be applied for the different vehicle units. [00107] In some examples, the method 100 is performed repeatedly; e.g., at predetermined or dynamically changing time intervals, and/or responsive to a triggering event. Thus, the preview distance may be repeatedly determined in step 110 and used in (e.g., continuous) vehicle control in step 120.

[00108] In conclusion, the method 100 provides approaches for determining preview distance, wherein the determination is based on the lateral deviation representation as defined above.

[00109] Typically, path following approaches apply inferior and/or ad-hoc algorithms for setting the preview distance. For example, the preview distance may be set proportional to longitudinal speed, or as a function of some road curvature criteria. This may reduce the preview distance when the curvature is high and/or when the longitudinal speed is low, and increase the preview distance when the curvature is low and/or when the longitudinal speed is high.

[00110] However, path following approaches may yield undesired vehicle behavior in some situations; e.g., oscillation in relation to the reference path, which may be particularly problematic for heavy-duty vehicles.

[00111] In some scenarios, the techniques disclosed herein improve the guidance of automated or semi-automated vehicles by adjusting the preview distance determination to depend on the lateral deviation representation as elaborated on above.

[00112] FIG. 2 is a schematic drawing of an example vehicle 200 (e.g., for cargo transport), wherein the herein disclosed techniques can be applied. In the illustrated example, the vehicle 200 is a multi-unit combination vehicle that comprises a tractor unit 210 (e.g., truck or towing vehicle) configured to tow one or more trailer unit(s) 211, 212.

[00113] The tractor unit 210 comprises a vehicle control unit (VCU) 290 - or other computer system comprising a processor device - configured to perform various vehicle control functions, such as path following and vehicle motion management.

[00114] The VCU 290 may be configured to perform one or more method steps of the method 100 of FIG. 1. Thus, the preview distance may be determined and used for controlling the vehicle 200 as already exemplified herein.

[00115] Although not shown, it should be understood that a VCU may be comprised - additionally or alternatively - in one or more of the trailer unit(s) 211, 212. Also alternatively or additionally, a control unit (e.g., a parametrized VCU) may be comprised in a remote server node to which the vehicle 200 may be connected via wireless link. Generally, approaches described herein (e.g., the method 100 of FIG. 1) may be performed by any VCU or other control unit; alone or in combination. For example, step 120 of FIG. 1 may be performed by the VCU 290 and step 110 of FIG. 1 may be performed remotely (e.g., by cloud computing), or vice versa.

[00116] FIG. 3A schematically illustrates principles of a path following approach based on pure pursuit. In the illustration, the vehicle location 312 has a lateral offset 314 relative the reference path 310.

[00117] The applied path following approach includes steering - from the vehicle location 312 - towards a goal point 311 on the reference path 310. For example, steering from the vehicle location 312 towards a goal point 311 may comprise striving for following the adjustment path 315. An example angle of attack is illustrated by 319.

[00118] The goal point 311 is distanced along the reference path 310 by a preview distance 320 measured from a reference location associated with the vehicle location 312. In the illustrated example, the vehicle location 312 is used as reference location, and the preview distance 320 is measured in a straight line from the reference location (i.e., the vehicle location 312) to the goal point 311. The vehicle location 312 is in a vicinity of the reference path 310, and the straight line from the vehicle location 312 to the goal point 311 may be seen as occurring along the reference path 310 such that the goal point 311 is distanced from the reference location 312 along the reference path 310 by the preview distance 320.

[00119] A preview distance determined as described herein (compare with step 110 of FIG. 1) may be used as the preview distance 320.

[00120] FIG. 3B schematically illustrates principles of a path following approach based on vector field guidance. In the illustration, the vehicle location 332 has a lateral offset 334 relative the reference path 330.

[00121] The applied path following approach includes steering - from the vehicle location 332 - towards a goal point 331 on the reference path 330. For example, steering from the vehicle location 332 towards a goal point 331 may comprise striving for following a locationspecific guiding vector w (e.g., with a speed that corresponds to the magnitude of the guiding vector w). An example angle of attack is illustrated by 339. [00122] Generally, some path following approaches based on vector field guidance determines the location-specific guiding vector w based on one or more of the vector 351 (which is specific to the vehicle location 332, and points towards the goal point 331), the vector 352 (which is specific to the reference location 333, and points along the tangent of the reference path 330), and the vector 353 (which is specific to the goal point 331, and points along the tangent of the reference path 330).

[00123] The goal point 331 is distanced along the reference path 330 by a preview distance 340 measured from a reference location associated with the vehicle location 332. In the illustrated example, the reference location 333 is a point on the reference path 330, which corresponds to an orthogonal projection of the vehicle location 332 on the reference path 330. Thus, the reference location 333 may be a point on the reference path 330 intersected by a straight line, wherein the straight line passes through the vehicle location 332 and is orthogonal to the reference path 330 at the reference location 333. Furthermore, the preview distance 340 is measured in a line that follows the reference path 330 from the reference location 333 to the goal point 331, in the illustrated example. The line that follows the reference path 330 from the reference location 333 to the goal point 331 may be seen as occurring along the reference path 330 such that the goal point 331 is distanced from the reference location 333 along the reference path 330 by the preview distance 340.

[00124] A preview distance determined as described herein (compare with step 110 of FIG. 1) may be used as the preview distance 340.

[00125] It should be noted that other ways (than those illustrated in FIG. 3A and FIG. 3B) to define the goal point based on the preview distance may be equally applicable in various situations. For example, the preview distance may be measured in a line that follows the adjustment path 315 from the reference location 312 to the goal point 311 in FIG. 3A, and/or the preview distance may be in measured in a straight line from the reference location 333 to the goal point 331 in FIG. 3B.

[00126] Alternatively or additionally, other ways (than those illustrated in FIG. 3A and FIG. 3B) to define reference location based on the vehicle location and the reference path may be equally applicable in various situations. For example, the reference location may be another point on the reference path than that illustrated in FIG. 3B. [00127] Yet alternatively or additionally, it should be noted that the lateral offset from a reference path may be determined in various different ways. In FIG. 3A and FIG. 3B, the lateral offset 314, 334 is the distance from the vehicle location 312, 332 to the reference path 310, 330 measured along a straight line that passes through the vehicle location 332, 334 and is orthogonal to the reference path 310, 330 at the intersection between the straight line and the reference path 310, 330. Alternatively or additionally, the lateral offset may be defined as the shortest distance from the vehicle location to the reference path. The approaches disclosed herein are generally applicable also to other definitions of lateral deviation.

[00128] Thus, FIG. 3A and FIG. 3B illustrate two example path following approaches where techniques disclosed herein may be used.

[00129] FIG. 3A shows an example of how pure pursuit may be used control a vehicle to follow a reference path 310. Pure pursuit typically does not rely on an underlying vehicle model, but is based on a geometric algorithm. A general idea in relation to the pure pursuit approach may be seen as comprising calculation of a curvature (compare with the adjustment path 315) that will take the vehicle from its current position 312 to the goal point 311 on the reference path 310. For example, a circle having some radius and passing through both the goal point 311 and the vehicle location 312, may be used to define the adjustment path 315, wherein the circle radius is typically related to steering limitation of the vehicle (e.g., wheelbase, maximum steering angle, etc.). The calculated curvature may then be translated to a steering angle request; e.g., based on steering geometry of the vehicle. The reference point may be chosen as a suitable point on the vehicle (e.g., the center of the rear axle).

[00130] Pure pursuit approaches are typically, insensitive to small deviations from the reference path. Furthermore, tracking performance may suffer for transitions in the reference path (e.g., changing character from a straight path to a curved path); the vehicle typically ‘cuts the corner’ for such transitions. A proportional-integral-derivative (PID) controller may be used for feedback errors of the lateral position, which can address the low sensitivity to small deviations from the reference path. However, use of the PID controller may result in abrupt motion adaptation when the lateral offset is large, and careful parameter tuning is needed to mitigate oscillation. Gain scheduling may be used to address such issues, but the corresponding controller performance is unreliable due to the ad-hoc nature of gain scheduling. [00131] Using the preview distance determination as suggested herein, the preview distance may be adapted according to the effects of speed and lateral offset, which may enable control actions to remain within bounds and/or make additional lateral offset control

(e.g., PID controller) unnecessary.

[00132] FIG. 3B illustrates an example of how vector field guidance may be used control a vehicle to follow a reference path 330. A general idea in relation to the vector field guidance approach may be seen as generating a vector field with location-specific guiding vectors, and controlling the vehicle according to the guiding vector at the current position 332 of the vehicle. One example of vector field guidance is artificial flow guidance (AFG).

[00133] For AFG, the preview distance is preferably adapted according to the effects of speed and lateral offset to guarantee that control actions remain within bounds; e.g.,

Uy according to L ]2ay+b'

[00134] FIG. 3C schematically illustrates an example vector field 360 for path following based on vector field guidance.

[00135] A location-specific guiding vector w of the vector field 360 may, for example, be determined such that it points from the location at hand towards the goal point on the reference path; e.g., w = t₃ where t₃ is a unit-length vector pointing directly towards the goal point for the location at hand (compare with 351 of FIG. 3B).

[00136] According to some examples, the directions of the location-specific guiding vector w of the vector field 360 are adjusted in dependence of the curvature of the reference path; e.g., to avoid ‘cutting corners/curves’. For example, the location-specific guiding vector w may be defined as w = t₃ +

*² where t₃ is a unit-length vector pointing directly towards

the goal point for the location at hand (compare with 351 of FIG. 3B), and t₂ are unitlength tangent vectors at the reference point and the goal point, respectively (compare with 352, 353 of FIG. 3B), and the angle 0 corresponds to half the angle between

and t₂. The term may be seen as a directional adjustment relating to reference path curvature; i.e., relating to the case G A t₂.

[00137] FIG. 3D schematically illustrates an example vehicle control system 370, that may be used for path following approaches such as pure pursuit or vector field guidance. The vehicle control system 370 is illustrated in relation to a vehicle representation 374, and comprises a goal point adjustment module 373, a path following module 371, and map module 372. The map module 372 may be configured to provide geometric data based on map information in relation to a vehicle location 384.

[00138] For example, the vehicle control system 370 may apply techniques described herein to operate as a goal point supervisor acting in real time according to, for example, speed (or velocity), reference path curvature, and lateral offset. To this end, the goal point adjustment module 373 may apply preview distance determination as elaborated on herein.

[00139] The goal point adjustment module 373, may determine the preview distance based on geometric data 381 from the map module 372 and optional feedback 385 from the vehicle 374. For example, the optional feedback 385 may comprise only variables that change relatively slowly (e.g., speed and lateral offset). In vector field guidance, the optional feedback 385 may comprise only variables that relate to the vector field.

[00140] The determined preview distance 386 is provided to the path following module

371, which may implement any suitable path following approach (e.g., pure pursuit or vector field guidance). The vehicle 374 is controlled by the path following module 371 via control signaling 383. The control signaling 383 may comprise any suitable control information; e.g., one or more of: a steering angle request, a curvature request, a direction request, or similar. For example, the path following module 371 may use the preview distance 386 together with geometric data 382 from the map module 372 to generate the control signaling 383.

[00141] FIG. 4 is a collection of plots (a)-(f) illustrating preview distance and corresponding pure pursuit path following performance over time according to some examples. The examples relate to a reference path requiring lateral maneuvering (e.g., a lane change) at a speed of 88 km/h. The reference path is representing by a dashed line changing from a first lateral placement 401 to a second lateral placement 402.

[00142] Plots (a) and (b) illustrates the preview distance 411 and the corresponding path following performance, respectively, when the preview distance is determined according to

L , = |. The resulting lateral placement of the vehicle is

represented by 412. The vehicle follows the reference path reasonably well, but some oscillation lingers after the lane change, as seen in 412. Particularly, the preview distance 411 may be seen as being reduced to L_o too quickly, which leads to the oscillation in 412 after the lane change. It may be noted that the amplitude of the oscillation is increasing with time, which indicates impending instability.

[00143] Plots (c) and (d) illustrates the preview distance 421 and the corresponding path following performance, respectively, when the preview distance is determined according to

L + T^ , with T = 3. The resulting lateral placement of

dt the vehicle is represented by 422. The vehicle follows the reference path reasonably well, but some oscillation occurs after the lane change, as seen in 422. The amplitude of the first oscillation peak in 422 is larger than that of 412. However, the oscillation in 422 is considerably slower than that of 412, and reduces faster than that of 412. Thus, comparing 422 with 412, it may be concluded that stability is improved, but the preview distance 421 still seems more volatile than preferable; jumping between a high value and L_o.

[00144] Plots (e) and (f) illustrates the preview distance 431 and the corresponding path following performance, respectively, when the preview distance is determined according to the preview distance

undergoes moving average filtering (using a 500-point - 5s - moving average filter) before being used for path following. The resulting lateral placement of the vehicle is represented by 432. The vehicle follows the reference path reasonably well, as seen in 432. The deviation from the reference path barely has oscillation character; i.e., the vehicle converges towards the reference path very quickly. The amplitude of the first peak in 432 is smaller than that of both 422 and 412. Thus, comparing 432 with 422, it may be concluded that the path tracking is improved, and the preview distance 431 does not jump around between a high value and L_o, as did the preview distance 421 (which results in less abrupt control efforts).

[00145] Thus, the example of FIG. 4 illustrates benefits of determining the preview distance as disclosed herein.

[00146] As already mentioned, the approaches suggested herein may be applicable to any vehicle control method that use a preview distance. Examples of such vehicle control methods include vector field guidance (e.g., AFG), preview driver models (e.g., pure pursuit), and Lane Keep Assistance (LKA) curvature controller. [00147] Generally, the vehicle control may use the goal point as defined via the preview distance to generate a motion target (e.g., a course angle, a path curvature, or similar). Then, lower-level control systems of the vehicle may preform tracking based on the motion targets. [00148] FIG. 5 schematically illustrates an example apparatus 500. The apparatus 500 is for controlling a vehicle in relation to a reference path when a vehicle location has a lateral offset from the reference path.

[00149] For example, the apparatus 500 may be comprised in a control system 510; e.g., a VCU. Alternatively or additionally, the apparatus 500 may be configured to perform (or cause performance of) one or more method steps of the method 100 of FIG. 1.

[00150] The apparatus 500 comprises a controller (e.g., controlling circuitry, control module, or control unit) 520. For example, the controller 520 may be, may comprise, or may be comprised in, a processor device.

[00151] The controller 520 may be configured to cause determination of a preview distance based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset (compare with 110 of FIG. 1)

[00152] To this end, the controller 520 may comprise a determiner (e.g., determining circuitry, determination module, or determination unit) 521. The determiner 521 may be configured to determine the preview distance based on the lateral deviation representation. [00153] The controller 520 may also be configured to cause vehicle control (e.g., path following) based on the determined preview distance (compare with 120 of FIG. 1).

[00154] To this end, the controller 520 may comprise a vehicle controller (e.g., vehicle controlling circuitry, vehicle control module, or vehicle control unit) 522. The vehicle controller 522 may be configured to control the vehicle based on the determined preview distance.

[00155] FIG. 6 schematically illustrates the function of an example vehicle motion control system 600. The vehicle motion control system 600 may, for example, utilize the preview distance determination as elaborated on previously herein.

[00156] The vehicle motion control system 600 controls a wheel 610 of a vehicle, via one or more motion support devices (MSDs) 620; exemplified in FIG. 6 by a power steering arrangement 621 and a propulsion device 622 such as an electric machine (EM). The power steering arrangement 621 and the propulsion device 622 are examples of actuators. Generally, the MSDs 620, such as the actuators 621, 622, may be controlled by one or more MSD control unit 640.

[00157] According to the example vehicle motion control system 600, a traffic situation management (TSM) function 670 plans driving operations with some time horizon; e.g., 1-10 seconds. The time horizon may, for example, correspond to the time it takes for the vehicle to negotiate a curve, make an evasive maneuver, or halt the vehicle. Vehicle maneuvers, as planned and executed by the TSM, can be associated with acceleration profiles and curvature profiles which describe a desired vehicle velocity and turning for a given maneuver.

[00158] The TSM function 670 may send requests (e.g., continuously or with some periodicity) corresponding to desired acceleration profiles and curvature profiles to a vehicle motion management (VMM) function 650, which performs force allocation to meet the requests from the TSM function 670 in a safe and robust manner.

[00159] The VMM function 650 communicates the force allocation to the relevant MSDs via the MSD control unit 640. The VMM function 650 typically manages both force allocation and MSD coordination; i.e., it may determine what forces are required where to fulfil the requests from the TSM function 670. The forces may comprise any suitable forces, e.g., yaw moments, longitudinal forces, lateral forces, torques, etc.

[00160] The MSD control unit 640, the VMM function 650, and the TSM function 670 have access to sensor data from vehicle sensors 660 (e.g., on-board sensors), which sensor data may be used for the vehicle control. The sensors may comprise any suitable sensors; e.g., one or more of: global positioning system (GPS) receivers, vision-based sensors (such as cameras), wheel speed sensors, radar sensors, lidar sensors, etc.

[00161] The sensor data may be used for determination of a vehicle location in relation to a reference path. The function 670 and/or VMM function 650 may be configured to apply a preview distance determination as described herein for a path following approached used by the vehicle motion control system 600.

[00162] FIG. 7 is a schematic diagram of a computer system 700 for implementing examples disclosed herein. The computer system 700 may be comprised - or comprisable - in a vehicle according to some examples. [00163] For example, the computer system 700 may be configured to execute, or cause execution of, one or more of the method steps as described in connection with FIG. 1. [00164] Alternatively or additionally, the computer system 700 may be configured to determine (e.g., by the processor device 702) a preview distance based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset.

[00165] The computer system 700 is adapted to execute instructions from a computer- readable medium to perform these and/or any of the functions or processing described herein. The computer system 700 may be connected (e.g., networked) to other machines in a LAN, an intranet, an extranet, or the Internet. While only a single device is illustrated, the computer system 700 may include any collection of devices that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. Accordingly, any reference in the disclosure and/or claims to a computer system, computing system, computer device, computing device, control system, control unit, electronic control unit (ECU), processor device, etc., includes reference to one or more such devices to individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. For example, control system may include a single control unit or a plurality of control units connected or otherwise communicatively coupled to each other, such that any performed function may be distributed between the control units as desired. Further, such devices may communicate with each other or other devices by various system architectures, such as directly or via a Controller Area Network (CAN) bus, etc.

[00166] The computer system 700 may comprise at least one computing device or electronic device capable of including firmware, hardware, and/or executing software instructions to implement the functionality described herein. The computer system 700 may include a processor device 702 (may also be referred to as a control unit), a memory 704, and a system bus 706. The computer system 700 may include at least one computing device having the processor device 702. The system bus 706 provides an interface for system components including, but not limited to, the memory 704 and the processor device 702. The processor device 702 may include any number of hardware components for conducting data or signal processing or for executing computer code stored in memory 704. The processor device 702 (e.g., control unit) may, for example, include a general-purpose processor, an application specific processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a circuit containing processing components, a group of distributed processing components, a group of distributed computers configured for processing, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The processor device may further include computer executable code that controls operation of the programmable device.

[00167] The system bus 706 may be any of several types of bus structures that may further interconnect to a memory bus (with or without a memory controller), a peripheral bus, and/or a local bus using any of a variety of bus architectures. The memory 704 may be one or more devices for storing data and/or computer code for completing or facilitating methods described herein. The memory 704 may include database components, object code components, script components, or other types of information structure for supporting the various activities herein. Any distributed or local memory device may be utilized with the systems and methods of this description. The memory 704 may be communicably connected to the processor device 702 (e.g., via a circuit or any other wired, wireless, or network connection) and may include computer code for executing one or more processes described herein. The memory 704 may include non-volatile memory 708 (e.g., read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.), and volatile memory 710 (e.g., randomaccess memory (RAM)), or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a computer or other machine with a processor device 702. A basic input/output system (BIOS) 712 may be stored in the non-volatile memory 708 and can include the basic routines that help to transfer information between elements within the computer system 700.

[00168] The computer system 700 may further include or be coupled to a non-transitory computer-readable storage medium such as the storage device 714, which may comprise, for example, an internal or external hard disk drive (HDD) (e.g., enhanced integrated drive electronics (EIDE) or serial advanced technology attachment (SATA)), HDD (e.g., EIDE or SATA) for storage, flash memory, or the like. The storage device 714 and other drives associated with computer-readable media and computer-usable media may provide nonvolatile storage of data, data structures, computer-executable instructions, and the like. [00169] A number of modules can be implemented as software and/or hard-coded in circuitry to implement the functionality described herein in whole or in part. The modules may be stored in the storage device 714 and/or in the volatile memory 710, which may include an operating system 716 and/or one or more program modules 718. All or a portion of the examples disclosed herein may be implemented as a computer program product 720 stored on a transitory or non-transitory computer-usable or computer-readable storage medium (e.g., single medium or multiple media), such as the storage device 714, which includes complex programming instructions (e.g., complex computer-readable program code) to cause the processor device 702 to carry out the steps described herein. Thus, the computer-readable program code can comprise software instructions for implementing the functionality of the examples described herein when executed by the processor device 702. The processor device 702 may serve as a controller or control system for the computer system 700 that is to implement the functionality described herein.

[00170] The computer system 700 also may include an input device interface 722 (e.g., input device interface and/or output device interface). The input device interface 722 may be configured to receive input and selections to be communicated to the computer system 700 when executing instructions, such as from a keyboard, mouse, touch-sensitive surface, etc. Such input devices may be connected to the processor device 702 through the input device interface 722 coupled to the system bus 706 but can be connected through other interfaces such as a parallel port, an Institute of Electrical and Electronic Engineers (IEEE) 1394 serial port, a Universal Serial Bus (USB) port, an IR interface, and the like. The computer system 700 may include an output device interface 724 configured to forward output, such as to a display, a video display unit (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)). The computer system 700 may also include a communications interface 726 suitable for communicating with a network as appropriate or desired.

[00171] The operational steps described in any of the exemplary aspects herein are described to provide examples and discussion. The steps may be performed by hardware components, may be implemented in machine-executable instructions to cause a processor to perform the steps, or may be performed by a combination of hardware and software.

Although a specific order of method steps may be shown or described, the order of the steps may differ. In addition, two or more steps may be performed concurrently or with partial concurrence.

[00172] The described examples and their equivalents may be realized in software or hardware or a combination thereof. The examples may be performed by general purpose circuitry. Examples of general purpose circuitry include digital signal processors (DSP), central processing units (CPU), co-processor units, field programmable gate arrays (FPGA) and other programmable hardware. Alternatively or additionally, the examples may be performed by specialized circuitry, such as application specific integrated circuits (ASIC). The general purpose circuitry and/or the specialized circuitry may, for example, be associated with or comprised in an electronic apparatus such as a vehicle control unit.

[00173] The electronic apparatus may comprise arrangements, circuitry, and/or logic according to any of the examples described herein. Alternatively or additionally, the electronic apparatus may be configured to perform method steps according to any of the examples described herein.

[00174] According to some examples, a computer program product comprises a non- transitory computer readable medium such as, for example, a universal serial bus (USB) memory, a plug-in card, an embedded drive, or a read only memory (ROM). FIG. 8 illustrates an example computer readable medium in the form of a compact disc (CD) ROM 800. The computer readable medium has stored thereon a computer program 840 comprising program instructions. The computer program is loadable into a data processor (e.g., a data processing unit) 820, which may, for example, be comprised in a vehicle control unit 810. When loaded into the data processor, the computer program may be stored in a memory 830 associated with, or comprised in, the data processor. According to some examples, the computer program may, when loaded into, and run by, the data processor, cause execution of method steps according to, for example, any of the methods described herein.

[00175] FIG. 9 schematically illustrates, in terms of a number of functional units, the components of a control unit 900 according to some examples. The control unit may be comprised in a vehicle, e.g., in the form of a vehicle motion management (VMM) unit. A processor device in the form of processing circuitry 910 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), or similar; capable of executing software instructions stored in a computer program product, e.g. in the form of a storage medium 930. The processing circuitry 910 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

[00176] Particularly, the processing circuitry 910 is configured to cause the control unit 900 to perform a set of operations, or steps; for example, any one or more of the methods discussed in connection to FIG. 1.

[00177] For example, the storage medium 930 may store a set of operations, and the processing circuitry 910 may be configured to retrieve the set of operations from the storage medium 930 to cause the control unit 900 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 910 is thereby arranged to execute methods as herein disclosed.

[00178] The storage medium 930 may comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[00179] The control unit 900 may further comprise an interface 920 for communication with at least one external device. As such, the interface 920 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication.

[00180] The processing circuitry 910 controls the general operation of the control unit 900, e.g., by sending data and control signals to the interface 920 and the storage medium 930, by receiving data and reports from the interface 920, and by retrieving data and instructions from the storage medium 930. Other components, as well as the related functionality, of the control node are omitted in order not to obscure the concepts presented herein.

[00181] In some examples, the control unit 900 may be seen as a control system, or may be comprised in a control system. Such a control system may, for example, comprise the apparatus 500 as described in connection with FIG. 5 (e.g., the processing circuitry 910 may comprise the controller 520 of FIG. 5).

[00182] The control system may be configured for vehicle motion management (VMM). In some examples, the control system is configured to determine a preview distance based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset. Furthermore, the control system may be configured to control a vehicle for following a reference path, by obtaining the reference path, determining the preview distance, determining the goal point on the reference path, and controlling the vehicle towards the goal point.

[00183] For example, the VCU 290 of FIG. 2 may comprise one or more of the apparatus 500 of FIG. 5, the control system 510 of FIG. 5, the computer system 700 of FIG. 7, the vehicle control unit 810 of FIG. 8, and the control unit 900 of FIG. 9.

[00184] It should be noted that a feature or advantage mentioned herein in relation to one of the figures may be equally applicable, as suitable, to any other one of the figures; even if not mentioned explicitly in relation thereto.

[00185] The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including" when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[00186] It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure.

[00187] Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe a relationship of one element to another element as illustrated in the figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the figures. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

[00188] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[00189] Reference has been made herein to various examples. However, a person skilled in the art would recognize numerous variations to the described examples that would still fall within the scope of the claims.

[00190] For example, the methods described herein discloses example methods through steps being performed in a certain order. However, it is recognized that these sequences of events may take place in another order without departing from the scope of the claims. Furthermore, some method steps may be performed in parallel even though they have been described as being performed in sequence. Thus, the steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step.

[00191] In the same manner, it should be noted that the partition of functional blocks into particular units is by no means intended as limiting. Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. Furthermore, functional blocks described herein as being implemented as two or more units may be merged into fewer (e.g. a single) unit.

[00192] Any feature of any of the examples disclosed herein may be applied to any other example, wherever suitable. Likewise, any advantage of any of the examples may apply to any other examples.

[00193] It is to be understood that the present disclosure is not limited to the aspects described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the present disclosure and appended claims. In the drawings and specification, there have been disclosed aspects for purposes of illustration only and not for purposes of limitation, the scope of the inventive concepts being set forth in the following claims.

Claims

Claims What is claimed is:

1. A computer-implemented method (100) for controlling a vehicle (200) in relation to a reference path (310, 330) when a vehicle location (312, 332) has a lateral offset (314, 334) from the reference path, for execution by a processor device (290) of a computer system, the method comprising: determining (110) a preview distance (320, 340) by the processor device, wherein a goal point (311, 331) on the reference path - to be steered towards from the vehicle location - is distanced along the reference path by the preview distance measured from a reference location (312, 333) associated with the vehicle location, and wherein the preview distance is determined based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset.

2. The method of claim 1, further comprising controlling (120), by the processor device, the vehicle towards the goal point.

3. The method of any of claims 1 through 2, wherein the preview distance increases with increasing value of the lateral deviation representation, and decreases with decreasing value of the lateral deviation representation.

4. The method of any of claims 1 through 3, further comprising limiting (112), by the processor device, the preview distance to be larger than, or equal to, minimum preview distance.

5. The method of any of claims 1 through 4, wherein the preview distance is determined (110, 114), by the processor device, based on the lateral deviation representation responsive to the lateral offset and the first order derivative of the lateral offset having a same sign.

6. The method of any of claims 1 through 5, wherein the preview distance is determined (110, 114), by the processor device, based on the lateral deviation representation responsive to absolute value of the lateral offset being smaller than a first threshold value.

7. The method of claim 6, wherein the first threshold value is based on distance between wheel axles of the vehicle and/or minimum preview distance.

8. The method of any of claims 1 through 7, wherein the preview distance is determined (110, 114), by the processor device, based on the lateral deviation representation responsive to absolute value of the first order derivative of the lateral offset being larger than a second threshold value.

9. The method of claim 8, wherein the second threshold value is based on absolute value of the lateral offset.

10. The method of any of claims 1 through 9, further comprising smoothing (116), by the processor device, the preview distance before application for vehicle control.

11. A computer program product comprising program code (840) for performing, when executed by the processor device, the method of any of claims 1 through 10.

12. A non-transitory computer-readable storage medium (800) comprising instructions, which when executed by the processor device (820), cause the processor device to perform the method of any of claims 1 through 10.

13. An apparatus (500) for controlling a vehicle (200) in relation to a reference path (310, 330) when a vehicle location (312, 332) has a lateral offset from the reference path, the apparatus comprising controlling circuitry (520) configured to cause: determination of a preview distance (320, 340), wherein a goal point (311, 331) on the reference path - to be steered towards from the vehicle location - is distanced along the reference path by the preview distance measured from a reference location (312, 333) associated with the vehicle location, and wherein the preview distance is determined based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset.

14. The apparatus of claim 13, wherein the controlling circuitry comprises: a determiner (521) configured to determine the preview distance.

15. A control system (510) comprising the apparatus of any of claims 13 through 14, wherein the control system is configured to control a vehicle (200) for following a reference path (310, 330), and wherein the control system is configured to: obtain the reference path; determine the preview distance; determine the goal point on the reference path; and control the vehicle towards the goal point.

16. A control system (510, 810) comprising one or more control units (520, 820) configured to perform the method of any of claims 1 through 10.

17. A computer system (700) comprising a processor device configured to determine a preview distance (320, 340) for controlling a vehicle (200) in relation to a reference path (310, 330) when a vehicle location (312, 332) has a lateral offset (314, 334) from the reference path, wherein a goal point (311, 331) on the reference path - to be steered towards from the vehicle location - is distanced along the reference path by the preview distance measured from a reference location (312, 333) associated with the vehicle location, and wherein the preview distance is determined based on a lateral deviation representation, which is an absolute value of a linear combination of the lateral offset and a first order derivative of the lateral offset.

18. A vehicle (200) comprising one or more of: the apparatus of any of claims 13 through 14, the control system of any of claims 15 through 16, the computer system of claim 17, and a processor device configured to perform the method of any of claims 1 through 10.