Method for determining an effective wind speed

Abstract

The invention relates to a method for determining a wind speed (vx_Wind) acting on the vehicle (1) in the direction of travel during operation of the vehicle (1), wherein the vehicle (1) has at least one aerodynamic element (A1 to An) that can be positioned from a non-use position into at least one use position, wherein a reference surface (A_a, A_p) of the vehicle (1) and a drag coefficient (cw_a, cw_p) of the vehicle (1) in the non-use position and the at least one use position of the at least one aerodynamic element (A1 to An) are determined. According to the invention, it is provided that - a first torque (M_p) of a drive unit of the vehicle (1) provided for generating a movement of the vehicle (1) is detected, wherein the at least one aerodynamic element (A1 to An) has the non-use position, - a second torque (M_a) of the drive unit is adjusted when the aerodynamic element (A1 to An) is positioned in the at least one use position such that a driving speed (vx_vehicle) of the vehicle (1) is maintained after changing the reference area (A_a) and the flow resistance coefficient (cw_a) compared to a driving speed (vx_vehicle) when the first torque (M_p) is detected, and - the wind speed (vx_Wind) is determined based on the first torque (M_p), the second torque (M_a) and a change in the drag coefficient (cw_p, cw_a) multiplied by the reference area (A_p, A_a).

Description

[0001] The invention relates to a method for determining a wind speed acting on the vehicle in the direction of travel during driving operation of the vehicle, wherein the vehicle has at least one aerodynamic element that can be positioned from a non-use position into at least one use position, wherein a reference surface of the vehicle and a flow resistance coefficient of the vehicle in the non-use position and the at least one use position of the at least one aerodynamic element are determined.

[0002] DE 10 2017 206 320 A1 discloses a method for determining a value for a wind speed using a vehicle. The vehicle travels at a speed in one direction of travel while traveling, and a value for the actual power applied by a machine designed to drive the vehicle is measured, assuming that this measured actual power is dependent on a value for the speed of air relative to which the vehicle is moving. A value for a calculated target power that the machine is supposed to deliver at the constant speed of the vehicle is calculated or determined. A power of the wind acting on the vehicle is calculated or determined from the difference between the value of the calculated target power and the value of the measured actual power. The wind speed is calculated from this difference in wind power.

[0003] Furthermore, DE 10 2021 000 520 A1 describes a method for recording and displaying the power consumption of vehicle components. This method sensitizes the driver to the influences of driving style and the chosen route on the vehicle's energy efficiency. From various driving resistances, the respective partial power of various resistance components of the vehicle is determined, which is displayed in relation to the current total power available to the vehicle.

[0004] Furthermore, DE 692 10 376 T2 shows a windscreen wiper system with a device for determining the relative wind speed, in particular for a motor vehicle, DE 10 2018 221 265 A1 shows a method and system for detecting a wind acting on a vehicle, and DE 10 2022 117 053 A1 shows an adjustable spoiler system for a motor vehicle and a motor vehicle with such a spoiler system.

[0005] The invention is based on the object of specifying a method for determining a wind speed acting on the vehicle in the direction of travel during driving of the vehicle.

[0006] The object is achieved according to the invention by a method which has the features specified in claim 1.

[0007] Advantageous embodiments of the invention are the subject of the subclaims.

[0008] A method for determining a wind speed acting on a vehicle in the direction of travel during operation of the vehicle, wherein the vehicle has at least one aerodynamic element that can be positioned from a non-use position into at least one use position, provides that a reference surface of the vehicle and a drag coefficient of the vehicle in the non-use position and the at least one use position of the at least one aerodynamic element are determined. The aerodynamic element can generate a non-zero wind resistance even in the non-use position, for example by the aerodynamic element not being fully folded in. However, it is also possible for the aerodynamic element to be fully folded in the non-use position and therefore generate no wind resistance at all.According to the invention, a first torque of a drive unit of the vehicle provided for generating movement of the vehicle is detected, wherein the at least one aerodynamic element is in the non-use position. A second torque of the drive unit is adjusted when the aerodynamic element is positioned in the at least one use position such that a driving speed of the vehicle is maintained after a change in the reference area and the drag coefficient, in particular due to the positioned aerodynamic element, compared to a driving speed when the first torque is detected, and the wind speed is determined based on the first torque, the second torque, and a change in the drag coefficient multiplied by the reference area.

[0009] By applying this method, the wind speed acting on the vehicle during driving can be determined, eliminating the need for a comparatively costly physical sensor to determine the wind speed acting on the vehicle in the direction of travel. This makes it possible to reduce manufacturing and material costs related to the vehicle.

[0010] If wind information determined by means of the method according to the invention is used, strategies for the driving operation of the vehicle, in particular for optimizing a range, can be derived, such as a reduction of the current driving speed, a lane recommendation, etc.

[0011] By means of the method according to the invention, a contribution can be made to increasing the efficiency of vehicles in a vehicle fleet, in particular vehicles of a vehicle manufacturer, wherein a consumption estimate can also be optimized.

[0012] The at least one aerodynamic element can be a front diffuser, a rear diffuser, closable louvres on a radiator grille, a spoiler, one or more vehicle windows, a convertible roof, or even an exterior mirror of the vehicle. For example, each aerodynamic element is coupled to an electric drive unit for positioning the aerodynamic element. The drive unit can therefore change the position of an associated aerodynamic element. The position can be determined, for example, based on signals detected by a sensor.

[0013] In one embodiment, the first torque of the drive unit is detected in a constant state of vehicle operation, so that it is possible to use this first torque to determine the wind speed acting on the vehicle.

[0014] In a further development of the method, the constant state of driving operation exists when the vehicle travels at a constant speed for at least a specified time window, the road gradient is constant, and the same transmission gear is engaged. Thus, the first torque can serve as the basis for determining the wind speed.

[0015] In a further embodiment, based on detected signals from an environmental sensor system and / or on map data available on the vehicle and / or on existing historical experience values, it is predicted or predicted for which section of the route and / or for which period of time the constant state of the vehicle's driving operation can be maintained, in particular for determining the second torque when the aerodynamic element is in the position of use.

[0016] In one possible embodiment, parameters representing the constant state are stored in a vector on the vehicle side, so that the constant state is documented via its parameters on the vehicle side in order to be able to set this constant state again if necessary.

[0017] In another possible implementation, an average speed is determined based on several wind speeds measured spatially and / or temporally in immediate succession. For this purpose, individual steps of the method are repeated. Thus, an average wind speed is determined as a typical value of a distribution of the measured wind speeds. Furthermore, by calculating the average speed, measurement inaccuracies and short-term wind changes can be largely compensated for.

[0018] In one embodiment, the currently determined wind speed and / or the determined average speed are displayed in the vehicle. This allows, for example, transparency regarding wind speed and vehicle fuel consumption to be presented in the vehicle.

[0019] In a further embodiment, the determined wind speeds and / or the determined average speeds are transmitted to a central computer unit connected to the vehicle via data technology. For example, the wind information can be aggregated with respect to the vehicles in the fleet. Wind information, i.e., wind speeds and / or average speeds, can also be historically aggregated in order to, for example, optimally identify routes with high wind susceptibility, such as coastal routes. Using historically aggregated wind information, route planning, particularly for an electric vehicle, can be improved, particularly with regard to range optimization.

[0020] One embodiment of the method provides for a wind map to be created on the vehicle and / or by the central computer unit based on the determined wind speeds and / or the determined average speeds. This wind map can then be made available to third parties, for example for a fee, for route planning purposes, in particular to optimize the range of a vehicle, especially an electric vehicle. For example, the wind map can be made available to wind power producers, farmers, etc. Such provision can be achieved, for example, via so-called "data room mobility."

[0021] Embodiments of the invention are explained in more detail below with reference to drawings.

[0022] Showing: Fig. 1 schematically shows a process sequence for checking the presence of a constant state of parameters relating to the driving operation of a vehicle, Fig. 2 schematically shows a further method sequence for determining a wind speed acting on the vehicle in the direction of travel during operation of the vehicle and Fig. 3 schematically shows a side view of a vehicle with a plurality of positionable aerodynamic elements.

[0023] Corresponding parts are provided with the same reference numerals in all figures.

[0024] Fig. 1 shows a process sequence V1 for checking the presence of a constant state of a driving operation of a Fig. 3 parameters relating to vehicle 1 shown as an example.

[0025] In Fig. 2 is a further process sequence V2 for determining a wind speed acting on the vehicle 1 in the direction of travel during the driving operation of the vehicle 1, and Fig. 3 shows a side view of a vehicle 1 with a plurality of positionable aerodynamic elements A1 to An, in particular to influence the flow around the vehicle 1.

[0026] It is generally known that wind speed and wind direction have a significant influence on fuel consumption and thus on the range of an electric vehicle 1. Using wind information, particularly with regard to the wind speed acting on the vehicle 1 in the direction of travel, strategies such as reducing the current driving speed of the vehicle 1, recommending a lane, recommending a route, etc., can be derived to increase the range of the vehicle 1.

[0027] Since wind sensors are comparatively difficult to install in the vehicle 1 and are relatively costly and maintenance-sensitive and, depending on their design, can increase the flow resistance of the vehicle 1, it is intended to estimate the flow resistance of the vehicle 1 by positioning at least one aerodynamic element A1 to An and a resulting influence on the vehicle 1.

[0028] Conventional approaches that determine wind power by deriving it from a vehicle dynamics equation often have comparatively high inaccuracies because they contain a relatively large number of unknown variables, for example vehicle weight, gradient, rolling resistance of vehicle tires, especially after a tire change, losses in the drive train, etc. Errors in determining these unknown variables can potentially add up, so that the accuracy of a wind power determined in this way is low.

[0029] In the following, a formula is given for the wind speed vx_Wind hitting vehicle 1 in the direction of travel.

[0030] In a constant state of driving operation of vehicle 1, wherein the at least one aerodynamic element A1 to An is in its non-use position, i.e., does not influence flow resistance, M_p is considered a constant torque balance consisting of the torque of an electric drive unit of vehicle 1, the recuperation torque, and, if applicable, the braking torque. This results in a constant driving speed vx_vehicle of vehicle 1, provided the same transmission gear remains engaged, a constant gradient prevails, and wind conditions are approximately constant.

[0031] In contrast to the prior art, an energy balance is evaluated once for the at least one aerodynamic element A1 to An in a non-use position and again for the at least one aerodynamic element A1 to An in a use position. This results in two energy balances that can be inserted into each other, with the equation being rearranged for the wind speed vx_Wind: vx_Wind=sqrt{[(abs((M_a−M_p)) / r_dyn−0.5*ρ*vx_Vehicle2*(cw_a*A_a−cw_p*A_p)] / (0.5*ρ*(cw_a*A_a−cw_p*A_p))} with: vx_Wind: a wind speed acting on vehicle 1 in the direction of travel, M_a = first torque of the drive unit of vehicle 1 with the aerodynamic element A1 positioned in the use position to An, M_p = second torque of the drive unit of vehicle 1 with the aerodynamic element A1 positioned in the non-use position to An, r_dyn = dynamic rolling radius, ρ = air density, cw_a = drag coefficient with the aerodynamic element A1 to An positioned in the use position, cw_p = drag coefficient with the aerodynamic element A1 to An positioned in the non-use position, A_a = reference surface of vehicle 1 with aerodynamic element A1 positioned in the use position to An and A_p = reference surface of vehicle 1 with aerodynamic element A1 to An positioned in the non-use position.

[0032] In particular, the second torque M_p is set such that the vehicle speed vx_vehicle remains constant.

[0033] An essential parameter for determining the wind speed vx_Wind is a difference between the products of the drag coefficient cw_a, cw_p and the reference areas A_a, A_p, according to the formula: Delta[cw*A]=cw_a*A_a−cw_p*A_p.

[0034] Assuming that vehicle 1 is traveling from a driving situation with wind acting on it to a driving situation shaded by the wind, or vice versa, the following relationship applies: in order to keep the driving speed vx_vehicle constant, a torque M_W of the drive unit with acting wind must be adjusted to a torque M_WaF in a driving situation shaded by the wind, or vice versa. For example, the driving speed vx_vehicle is controlled by a speed-dependent distance control device of vehicle 1. In the wind-shaded driving situation, the driving speed vx_vehicle is assumed to be 0 m / s, with the drag coefficient cw and the area A remaining constant in the formula. Thus, a wind force F_constant and the driving speed vx_vehicle are unknown. The following applies: M_W=(F_constant+0.5*cw_p*A_p*ρ*(vx_vehicle+vx_wind)2)*r_dyn M_WaF=(F_constant+0.5*cw_p*A_p*ρ*(vx_vehicle+vx_wind=0)2)*r_dyn F_constant=M_WaF / r_dyn−0.5*cw_p*A_p*ρ*vx_vehicle2

[0035] Inserted into formula (3) the following applies: M_W=(M_WaF / r_dyn−0.5*cw_p*A_p*ρ*vx_vehicle2+0.5*cw_p*A_p*ρ*vx_vehicle2+0.5*cw_p*A_p*rho*vx_wind2)*r_dyn=(M_WaF / r_dyn+0.5*cw_p*A_p*ρ*vx_wind2)*r_dyn vx_wind=sqrt{[(abs(M_W−M_WaF)) / r_dyn] / (0.5*cw_p*A_p*ρ)

[0036] A method for determining a wind speed vx_Wind acting on the vehicle 1 in the direction of travel during operation of the vehicle 1 provides, as described above, that the vehicle 1 has at least one aerodynamic element A1 to An that can be electrically positioned from a non-use position to a use position.

[0037] The reference area A_a, A_p of the vehicle 1 and the drag coefficient cw_a, cw_p are determined and stored for different position(s) of the aerodynamic element A1 to An, for example in a wind tunnel, and are thus available on the vehicle side.

[0038] The Fig. The process sequence V1 shown in Fig. 1 begins with start S, and in a first process step S1 a vector for a constant state of driving operation of the vehicle 1 is determined.

[0039] When decisions need to be made, a yes is marked with a J and a no with an N.

[0040] The existence of a constant state of driving operation, i.e. whether the vehicle 1 is driving in a so-called stationary state, is determined on the basis of a constant driving speed vx_vehicle, a constant road gradient, one and the same transmission gear, a tire pressure, a temperature, a steering angle, a yaw rate, a lateral and longitudinal acceleration and the torque balance of drive, recuperation and braking torque.

[0041] In a second method step S2, it is determined whether vehicle 1 is in a constant state. A constant state means that the driving conditions of vehicle 1 do not change within a specified period of time. For this purpose, for example, the vehicle's surroundings are checked for upcoming curves, tunnels, or bridges, a constant road gradient, and the like. This can be done, for example, based on signals detected by sensors or cameras located on vehicle 1, and / or based on map data from a navigation device, and / or by evaluating previously collected environmental data.

[0042] In a third method step S3, it is determined whether the constant state of the driving operation changes by more than a predetermined amount within the specified time period. If the change in the constant state is greater than the predetermined amount, the method is aborted and begins again with the first method step S1.

[0043] If, however, it is determined that the change in the constant state of driving operation within the specified time window falls below the specified amount, a fourth method step S4 determines whether a value of a yaw rate, a steering angle, and a lateral acceleration is smaller than a further specified amount. In particular, a prediction / forecast of the route is performed based on an inertial sensor system of vehicle 1.

[0044] If the magnitude of the yaw rate, steering angle, and lateral acceleration is less than the specified additional magnitude, a fifth method step S5 determines whether a prediction of a constant or stationary route is possible based on digital map data from the navigation device within a further time window. The prediction is made with respect to a curvature, whether curves exist or whether turning maneuvers must be performed on a route.

[0045] In a sixth method step S6, it is determined whether historical data from other vehicles of a vehicle fleet to which vehicle 1 belongs are available for successful wind measurement for a current route section or not.

[0046] In a seventh method step S7, it is determined whether any change in the wind influence on vehicle 1 can be predicted / foreseen based on signals detected by sensors of vehicle 1, in particular an environmental sensor system. In particular, it is determined whether changes in wind conditions, for example due to tunnel entrances, bridges, or driving in a built-up area, are occurring, and whether changes in the gradient of the roadway can be recorded within the further time window of, for example, 10 seconds. Based on signals detected by the environmental sensors, it is also detected, in particular within a predetermined detection range, whether vehicle 1 is being shaded by other vehicles and where a guardrail begins and ends.

[0047] If it can be determined in an eighth method step S8 that at least one of the determinations carried out in the fifth method step S5, in the sixth method step S6 and in the seventh method step S7 could be answered with “Yes”, it is determined in a ninth method step S9 whether a Fig. 2, the method described in the further process sequence V2 is started to determine the wind speed vx_Wind acting on the vehicle 1 in the direction of travel during the driving operation of the vehicle 1. If none of the determinations can be answered with "yes", the method jumps back to the first process step S1.

[0048] The further procedure V2 also begins with Start and when decisions have to be made, a “Yes” is marked with a “J” and a “No” with an “N”.

[0049] In a first method step S1, a signal is transmitted in the first method step S1 of the Fig. 1, the vector determined in relation to the constant state of the driving operation of the vehicle 1 and a first torque M_p of the drive unit of the vehicle 1 is stored. The vector of the constant driving state and the instantaneous torque M_p of the drive unit, in particular the electric drive unit, can be stored, for example, in a memory unit 2 of a control unit 3 of the vehicle 1. The control unit 3 can be designed as an electronic control unit, which is responsible for regulating and / or controlling processes.

[0050] In a second method step S2, the at least one aerodynamic element A1 to An is positioned by means of its electric drive unit from a passive state, i.e., from a non-use position, to an active state, i.e., a use position. The respective position reached by the at least one aerodynamic element A1 to An can be determined, for example, based on signals detected by a correspondingly designed sensor.

[0051] In a third method step S3, a second torque M_a of the drive unit with the at least one aerodynamic element A1 to An positioned in the use position is adjusted such that a driving speed vx_vehicle of the vehicle 1, i.e., after changing the reference area A and the drag coefficient cw, is maintained compared to a driving speed vx_vehicle when the first torque M_p is detected. A change from the first torque M_p to the second torque M_a is detected.

[0052] In a fourth method step S4, another vector of the constant state of the driving operation of the vehicle 1 is detected. If it is determined that a difference, a so-called distance measure, between the vector and the further vector of the constant state of the driving operation exceeds a predetermined threshold value, the third method step S3 must be repeated. This requires a renewed adjustment of the second torque M_a. In other words, the second torque M_a is adjusted until the difference between the two vectors of the constant state of the driving operation is smaller than the predetermined threshold value, which can be 3%, for example.

[0053] If, however, it is determined in the fourth method step S4 that the difference falls below the predetermined threshold value, in a fifth method step S5 the at least one aerodynamic element A1 to An is positioned from its use position to the non-use position.

[0054] Subsequently, in a sixth method step S6, a further torque M_p of the drive unit that has now been detected is adjusted again, and in a seventh method step S7, it is checked whether a difference between a current torque M_p and the torque M_p at the start S of the further method sequence V2 is smaller than a further threshold value.

[0055] If it is determined that the difference exceeds the additional threshold value, the additional torque M_p is adjusted again. However, if it is determined that the difference falls below the specified additional threshold value, an eighth process step S8 is performed.

[0056] In the eighth method step S8, it is determined whether a difference between a current constant state of the driving operation of the vehicle 1 and the constant state of the driving operation of the vehicle 1 determined in the method sequence V1 falls below a predetermined limit value. If it is determined that the difference exceeds the predetermined limit value, the method jumps to Start S in a ninth method step S9. However, if it is determined that the difference falls below the predetermined limit value, the wind speed vx_Wind can be determined in a tenth method step S10. In addition, a wind direction can be determined. The determined, in particular estimated, wind information can be averaged and transmitted to a central computer unit 4 that is data-linked to the vehicle 1.Alternatively or additionally, the wind information can be output in the vehicle 1, in particular displayed in a display area of an instrument panel. In particular, the wind information can be used to optimize range and for navigation calculations.

[0057] Wind information from a successful or unsuccessful implementation of an invasive measurement can also be aggregated in a wind map and made available to third parties, for example via the central computer unit 4.

[0058] Fig. 3 shows a vehicle 1 in a side view with a plurality of aerodynamic elements A1 to An.

[0059] A first aerodynamic element A1 is, for example, a rear diffuser, a second aerodynamic element A2 is a spoiler, third aerodynamic elements A3 can be vehicle windows, and a fourth aerodynamic element A4 is designed as a roof window. A fifth aerodynamic element A5 can be designed as an exterior mirror, a sixth aerodynamic element A6 can be designed as closable louvers, for example, of a radiator grille, and a seventh aerodynamic element A7 can be designed as a front diffuser. List of reference symbols 1 vehicle 2 storage units 3 Control unit 4 central computer unit A1 to an aerodynamic element S1 to S10 process step V1 Procedure V2 further procedure

Claims

[1] Method for determining a wind speed (vx_Wind) acting on the vehicle (1) in the direction of travel during operation of the vehicle (1), wherein the vehicle (1) has at least one wind speed sensor which can be positioned from a non-use position into at least one use position aerodynamic element (A1 to An), wherein a reference surface (A_a, A_p) of the vehicle (1) and a drag coefficient (cw_a, cw_p) of the vehicle (1) are determined in the non-use position and the at least one use position of the at least one aerodynamic element (A1 to An), characterized by , that - a first torque (M_p) of a drive unit of the vehicle (1) provided for generating a movement of the vehicle (1) is detected, wherein the at least one aerodynamic element (A1 to An) has the non-use position, - a second torque (M_a) of the drive unit is adjusted when the aerodynamic element (A1 to An) is positioned in the at least one use position such that a driving speed (vx_vehicle) of the vehicle (1) is maintained after changing the reference area (A_a) and the flow resistance coefficient (cw_a) compared to a driving speed (vx_vehicle) when the first torque (M_p) is detected, and - the wind speed (vx_Wind) is determined based on the first torque (M_p), the second torque (M_a) and a change in the drag coefficient (cw_p, cw_a) multiplied by the reference area (A_p, A_a). [2] Method according to claim 1, characterized by that the first torque (M_p) of the drive unit is detected in a constant state of driving operation of the vehicle (1). [3] Method according to claim 2, characterized bythat the constant state of driving operation exists when the vehicle (1) travels at least for a predetermined time window at least at a constant driving speed (vx_vehicle), a road gradient is constant and one and the same transmission gear is engaged. [4] Method according to claim 2 or 3, characterized by that, based on signals detected by an environmental sensor system and / or on map data available on the vehicle and / or on existing historical experience values, it is predicted for which section of the route and / or for which period of time the constant state of the driving operation of the vehicle (1) can be maintained. [5] Method according to claim 3 or 4, characterized by that parameters representing the constant state are stored in a vector on the vehicle side. [6] Method according to one of the preceding claims, characterized bythat an average speed is determined based on several wind speeds (vx_Wind) determined spatially and / or temporally in immediate succession. [7] Method according to claim 6, characterized by that the respectively determined wind speed (vx_Wind) and / or the determined average speed in the vehicle (1) is displayed. [8] Method according to claim 6 or 7, characterized by that the determined wind speeds (vx_Wind) and / or the determined average speeds are transmitted to a central computer unit (4) which is connected to the vehicle (1) by data technology. [9] Method according to claim 8, characterized by that a spatial and / or temporal wind map is created on the vehicle side and / or by means of the central computer unit (4) on the basis of the determined wind speeds (vx_Wind) and / or the determined average speeds.

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