Method for reducing load in a steering system

Abstract

A method is proposed for reducing loads in a steering system (10) during operation, particularly in a vehicle (12), in which loads induced in the steering system (10) by external force actions are determined and at least partially compensated for in at least one operating state by controlling an actuator unit (14), which is controlled to drive such that in the operating state, inertial effects of the steering system (10) correlated with the external force actions are reduced.

Description

Technical Field

[0001] Prior Art The present invention relates to a method for reducing the load on a steering system. Furthermore, the present invention relates to a control device having a computing unit for implementing such a method, and a vehicle having a computing unit for implementing such a method.

Background Art

[0002] Vehicles, particularly the steering systems of vehicles, need to be designed to have a high load capacity in order to maintain functionality over their entire lifespan. Especially when driving through rough road sections, here, very large loads act on the steering system. In this case, this load depends particularly on the size and arrangement of the masses and inertia within the steering system, and further on the stiffness of the steering system. Therefore, in order to prevent damage, it is usually necessary to use oversized mechanical components, but this increases the weight of the steering system and also raises the cost.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The problem of the present invention is, in particular, to provide a method for reducing the load in a steering system having characteristics improved with respect to efficiency. This problem is solved by the features of claim 1, claim 11 and claim 12, and in contrast, preferred configurations and developments of the present invention can be derived from the dependent claims.

Means for Solving the Problems

[0004] Disclosure of the Invention A method for reducing the load in an operating steering system, particularly in a vehicle, preferably an automobile, has been proposed, where the load occurring in the steering system due to external force action, particularly mechanical load, especially the mechanical load of the steering system, is determined, and in at least one operating state, at least partially, preferably at least mostly, is compensated by drive control of the actuator unit, where the actuator unit is drive-controlled in the operating state such that the inertial effect of the steering system correlated with the external force action is reduced, particularly for at least partial load compensation. Preferably, particularly, the load occurring in the steering system due to external force action here includes force actions from the ground and / or the vehicle surroundings. Particularly, the external force action leading to the load of the steering system can in this case be caused, for example, by road surface irregularities, potholes, running over obstacles, driving on rough road sections, and / or other such special events of this kind. 。 The external force action is different from the steering movement of the steering system and / or the direct force action on the steering wheel, particularly by the driver. Further, in the operating state, at least partially compensating the load of components such as tie rods and / or chassis, which are operatively connected to the steering system, can also be achieved by drive control of the actuator unit, whereby preferably the load of the entire vehicle axle, particularly the front axle, can be compensated. With this configuration, particularly efficiency, particularly weight efficiency, component efficiency, and / or cost efficiency can be improved. Further, preferably, the fatigue strength and / or service life of the vehicle, particularly the steering system, can be increased.

[0005] The "actuator unit" is to be understood in particular as meaning a unit which is at least partially electrically and / or electronically configured and which is provided to provide torque and / or force and to transmit it to at least one steering component. For this purpose, the actuator unit preferably includes at least one electric motor which is operatively connected to at least one, in particular, steering component. Furthermore, preferably, the actuator unit is part of a steering system. Furthermore, "the inertial effect of the steering system correlated with the external force action is reduced" is to be understood in particular as meaning that the inertia of the steering system resulting from the external force action and / or the resistance of the steering system against the external force action is reduced.

[0006] Furthermore, the vehicle and / or the steering system may in particular comprise at least one computing unit, in which case the computing unit is in particular provided to execute a method for reducing the load in the steering system. The "computing unit" should in particular be understood to mean an electrical and / or electronic unit that is responsible for information input, information processing, and information output. Furthermore, preferably, the computing unit comprises at least one processor, at least one operating memory, at least one input and / or output means, at least one operating program, at least one control routine, at least one calculation routine, at least one monitoring routine, and / or at least one evaluation routine. In particular, the computing unit is provided to determine at least the load generated in the steering system by an external force acting thereon. Furthermore, the computing unit is in particular provided to drive and control the actuator unit. In this aspect, the computing unit is furthermore in particular provided to drive and control the actuator unit in at least one operating state such that the inertial effect of the steering system correlated with the external force acting thereon is reduced and at least partially, preferably at least mostly, the load generated in the steering system by the external force acting thereon is compensated. Preferably, the computing unit is integrated into the control device of the vehicle and / or the steering system. The expression "at least mostly" should in this case in particular be understood to mean at least 55%, preferably at least 75%, particularly preferably at least 95%. The expression "is provided" should in particular be understood to mean being specially programmed, designed, and / or equipped. That an object is provided for a specific function should in particular be understood to mean that the object satisfies and / or executes this specific function in at least one application state and / or operating state.

[0007] Preferably, in the operating state, a compensation torque acting against the inertia of the steering system and / or a compensation force acting against the inertia of the steering system is generated using an actuator unit and is applied to the steering system, in particular for at least partial compensation of the load. In particular, the compensation torque generated using the actuator unit and / or the compensation force generated using the actuator unit is, in particular here, oriented in the same direction as the external force action, so that the steering system preferably, together with the external force action, in particular, is interlocked in the direction of the external force action and / or the resistance of the steering system against the external force action is reduced. Particularly preferably, the compensation torque generated using the actuator unit and / or the compensation force generated using the actuator unit is further introduced into the steering shaft of the steering system and / or the steering gear of the steering system. Thereby, the inertia effect of the steering system and thus the load on the steering system can be particularly preferably and simply reduced.

[0008] Furthermore, in the operating state, a load reduction function is used for the drive control of the actuator unit, where it is proposed that this load reduction function is specialized for the driving situation and is activated and / or deactivated in particular depending on the current driving situation. In particular, the load reduction function preferably corresponds to a software algorithm stored in the operating memory of the computing unit. In particular, the computing unit is provided to drive-control the actuator unit in the operating state using the load reduction function such that a compensation torque counteracting the inertia of the steering system and / or a compensation force counteracting the inertia of the steering system is generated using the actuator unit. Preferably, in this case, a load characteristic value is determined for the activation and / or deactivation of the load reduction function and is in particular compared with at least one limit value. The "load characteristic value" is to be understood in this context as meaning a characteristic value that at least correlates with the mechanical load on the steering system in particular caused by an external force action. In particular, based on at least the load characteristic value, the mechanical load and / or stress of the steering system and / or at least one steering component can be inferred and / or determined. Preferably, the load characteristic value further correlates with the current driving situation. Thus, preferably, based on at least the load characteristic value, the current driving situation can be inferred and / or determined. Preferably, the load characteristic value is further determined continuously or monitored during a total monitoring time interval, and the temporal change of the load characteristic value is evaluated for the determination of the load and / or the current driving situation. This enables, in particular, a flexible reaction to the load in the steering system. In particular, it can be ensured here that in the normal driving situation where the load in the steering system is below the limit value, no change in the steering characteristics and / or steering feel is perceived.

[0009] Furthermore, a load characteristic value correlated with the load, particularly the load characteristic value already described above, is determined. In this case, it is proposed that the load reduction function is activated when the load characteristic value exceeds a first limit value that is particularly defined and / or definable, and is deactivated when the load characteristic value falls below a second limit value that is particularly defined and / or definable. In particular, the first limit value and the second limit value may be different, and in this case, the second limit value preferably falls below the first limit value. Thereby, in particular, a suitable hysteresis characteristic can be realized. Furthermore, preferably, the load reduction function can be guaranteed to continue to be activated even when the load fluctuates. However, alternatively, the first limit value and the second limit value may be the same, and thereby, in particular, a predetermined reaction to an external load can be achieved.

[0010] Particularly unobtrusive activation and / or deactivation of the load reduction function can be achieved when the load reduction function, particularly the compensation torque and / or the compensation force, is faded in when activated and / or faded out when deactivated. Preferably, the activation and / or deactivation of the load reduction function is, in this case, carried out gradually or sequentially and is not carried out suddenly in particular. Particularly preferably, the activation and / or deactivation of the load reduction function is carried out using a continuous and preferably differentiable function at every point, particularly an asymptotic function, a sigmoid function, or preferably a ramp function.

[0011] In a particularly preferred configuration, it is proposed that in the operating state, at least one load dominant in the servo system is at least partially, preferably at least mostly, compensated by driving and controlling the actuator unit. The servo system is particularly defined by the steering gear of the steering system in this case. Thereby, in particular, the load in the servo system of the steering system can be preferably reduced.

[0012] Alternatively or additionally, it is proposed that, in the operating state, at least one load prevailing in the steering system is at least partially, preferably at least largely, compensated for by drive control of the actuator unit. The steering system is here in particular defined by the steering shaft of the steering system. Thereby, it is possible to preferably reduce the load in particular in the steering system of the steering system.

[0013] Particularly preferably, the load prevailing in the servo system and the load prevailing in the steering system are corrected, and the cumulative load in that case corresponds in particular to the cumulative force of the rack and pinion. Thereby, it is possible to preferably reduce the load in particular in the entire steering system.

[0014] The actuator unit may be configured, for example, as an additional actuator and may be provided specifically for reducing the load in the steering system. Further, particularly in an aspect where the steering system is a steer-by-wire steering system, a feedback actuator that provides a restoring torque to the steering wheel may be used as the actuator unit. However, a particularly simple and / or low-cost structure can be achieved especially when an electric steering actuator that supplies a steering torque is used as the actuator unit. In this context, it should be understood that the "steering actuator" means an actuator unit that provides a steering torque and thereby is provided to preferably affect the driving direction of the vehicle. Preferably, the steering actuator is provided to provide a steering torque for assisting the driver manual torque applied to the steering wheel and / or to provide a steering torque for automatic and / or autonomous control of the driving direction of the vehicle. The steering actuator may be arranged particularly in the area of the steering system and may be coupled particularly to the steering shaft of the steering system. However, preferably, the steering actuator is arranged in the area of the servo system and is coupled particularly to the steering gear of the steering system.

[0015] Furthermore, in order to determine the load occurring in the steering system, in particular due to an external force acting thereon, it is proposed to monitor and in particular evaluate at least one operating variable of the actuator unit and / or the movement of the steering wheel of the steering system. This operating variable is preferably here, in particular, the acceleration of the actuator unit caused by an external force acting thereon, and / or an operating variable correlated with the acceleration, such as the operating voltage and / or operating current of the actuator unit. Preferably, furthermore, at least one motion sensor is used to monitor the movement of the steering wheel, and this motion sensor is provided in particular to capture a motion signal correlated with the movement of the steering wheel. Furthermore, preferably, in order to determine the load occurring in the steering system, in particular due to an external force acting thereon, at least one inertia and preferably the inertia torque of the actuator unit and / or the steering wheel and / or a peripheral assembly having a particularly predominant inertia of the steering wheel can be taken into account. In particular, this enables the load to be determined particularly flexibly and / or accurately.

[0016] The method for reducing the load in the steering system should not be limited here to the uses and embodiments described above. In particular, the method for reducing the load in the steering system can have a number different from the number of the individual elements, parts, and units mentioned herein in order to meet the functional modes described herein.

[0017] Further advantages will become apparent from the following description of the drawings. These drawings show embodiments of the invention.

Brief Description of the Drawings

[0018]

Figure 1a

Figure 1b

Figure 2

Best Mode for Carrying Out the Invention

[0019] Description of Embodiment Figures 1a and 1b schematically show an exemplary vehicle 12 configured as a passenger vehicle having a plurality of vehicle wheels 28 and a steering system 10. The steering system 10, in this aspect, has an operative connection, particularly with the wheels 28 configured as front wheels, and is provided to affect the driving direction of the vehicle 12. Further, the steering system 10, in this aspect, is configured as an electrically assisted steering system and accordingly comprises an electrical auxiliary force assistance in the form of power steering. However, in principle, it is also conceivable to configure the steering system as a hydraulically assisted steering system, particularly a steering system with hydraulic auxiliary force assistance. Further, the steering system may, in principle, be configured as a steer-by-wire steering system.

[0020] In this embodiment, the steering system 10 includes a steering wheel 22 for applying a driver manual torque, which is exemplarily configured as a steering wheel, a steering gear 30 which is exemplarily configured as a rack and pinion steering gear, includes a steering adjustment element 32, and is provided for converting a steering setting at the steering wheel 22 into a steering movement of the wheels 28, and a steering shaft 34 for mechanically connecting the steering wheel 22 to the steering gear 30 in particular. The steering gear 30 defines a servo system 18 of the steering system 10, and the steering shaft 34 defines a steering system 20 of the steering system 10. Alternatively, the steering wheel may be configured as a steering lever or a steering ball, etc. Furthermore, it is also conceivable to completely omit the steering wheel. Even further, the steering shaft may temporarily connect the steering wheel to the steering gear only, and / or may have a mechanical separation, such as a steer-by-wire steering system, for example.

[0021] Furthermore, the steering system 10 includes an actuator unit 14. This actuator unit 14 is at least partially electrically and / or electronically configured. In this embodiment, the actuator unit 14 is configured as a steering actuator. The actuator unit 14 has an operative connection to the steering gear 30. The actuator unit 14 is coupled to the steering gear 30, particularly to the steering adjustment element 32. The actuator unit 14 is provided to provide a steering torque for assisting the driver manual torque applied to the steering wheel 22 and to transmit it to the steering adjustment element 32. For this purpose, the actuator unit 14 includes at least one electric motor. In this embodiment, this electric motor is particularly configured as a permanent magnet synchronous motor and is provided for the generation of the steering torque. However, basically, the actuator unit may include a plurality of electric motors. Furthermore, the actuator unit may be configured as a feedback actuator or as an additional actuator different from the steering actuator and the feedback actuator. Furthermore, the actuator unit may include a plurality of actuators, such as, for example, a steering actuator and a feedback actuator.

[0022] Furthermore, the steering system 10 includes at least one steering sensor 36, which is known per se and is arranged on the steering shaft 34. This steering sensor 36 is configured as a rotational torque sensor. The steering sensor 36 is provided for capturing steering information correlated with the operation of the steering wheel 22, in particular the driver manual torque and / or rotational torque applied to the steering wheel 22. In this embodiment, the steering sensor 36 is provided for capturing a torsion bar signal. Alternatively, the steering sensor may be configured as a sensor different from the rotational torque sensor, for example a rotational angle sensor, and / or as a sensor in which the rotational torque sensor and the rotational angle sensor are combined. Furthermore, the steering sensor may be omitted.

[0023] Furthermore, the steering system 10 includes at least one operation sensor 38 assigned to the actuator unit 14. This operation sensor 38 is configured as a rotor position sensor and is provided for capturing at least one operation variable of the actuator unit 14, in this embodiment, in particular the rotor position signal of the electric motor. However, alternatively or additionally, the operation sensor may be configured as a sensor different from the rotor position sensor, for example an acceleration sensor, an acoustic body sensor, a voltage sensor, a current sensor, and / or a temperature sensor. However, basically, the operation sensor may be omitted.

[0024] Furthermore, the steering system 10 includes at least one motion sensor 40. This motion sensor 40 is different from the steering sensor 36 and the operation sensor 38. The motion sensor 40 is configured as a speed sensor. The motion sensor 40 is configured as a handle sensor and is arranged in the region of the steering handle 22. The motion sensor 40 is provided to capture a motion signal correlated with the motion of the steering handle 22, in this embodiment, particularly a speed signal. However, alternatively, the motion sensor may be configured as a sensor different from the speed sensor, for example, a position sensor, a distance sensor, an acceleration sensor, and / or an acoustic body sensor, and particularly may be provided to capture a motion signal different from the speed signal.

[0025] Furthermore, the motion sensor may basically be arranged in the region of the steering shaft, preferably above the intermediate steering shaft. Furthermore, the motion sensor may be omitted.

[0026] Furthermore, the vehicle 12 has a control device 24. This control device 24 is exemplarily configured as a steering control device and is thus part of the steering system 10. The control device 24 has an electrical connection to the actuator unit 14. Furthermore, the control device 24 has electrical connections to the steering sensor 36, the operation sensor 38, and the motion sensor 40. The control device 24 is provided to receive the torsion bar signal from the steering sensor 36, the operation variable from the operation sensor 38, and the motion signal from the motion sensor 40. Furthermore, the control device 24 is provided to drive and control the actuator unit 14.

[0027] For this purpose, the control device 24 includes a calculation unit 26. This calculation unit 26 includes at least one processor (not shown), for example in the form of a microprocessor, and at least one operating memory (not shown). Furthermore, the calculation unit 26 includes at least one operating program having at least one control routine, at least one calculation routine, at least one monitoring routine, and at least one evaluation routine stored in the operating memory. However, in principle, it is also conceivable to configure the control device separately from the steering system. In this case, the vehicle may have, for example, a single central control device with a central calculation unit.

[0028] Particularly when driving through a rough road section, a very large load acts on the steering system 10. In this case, this load depends on the mass and inertia magnitude and arrangement within the steering system 10, and in particular on the rigidity of the steering system 10, especially the servo system 18 and the steering system 20. These loads here result substantially from the support of the steering system 10 against the ground or the road surface.

[0029] Therefore, in order to reduce the load on the steering system 10, a corresponding method has been proposed. In this case, in this embodiment, the calculation unit 26 is provided for executing this method. For this purpose, in particular, it has a computer program with corresponding program code means.

[0030] In this embodiment, the load on the steering system 10 caused by external force action is determined and compensated by driving control of the actuator unit 14 in at least one operating state. This load here includes force actions from the ground and / or the surroundings of the vehicle 12 and can result, for example, from the unevenness of the road surface and / or driving through a rough road section.

[0031] To compensate for the load, the actuator unit 14 is driven and controlled in the operating state such that the inertial effect of the steering system 10 correlated with the external force action is reduced. For this purpose, using the actuator unit 14, a compensation torque that reacts against the inertia of the steering system 10 and is oriented in the same direction as the external force action is generated and applied to the steering system 10, so that the steering system 10, together with the external force action, particularly interlocks in the direction of the external force action, and the resistance of the steering system 10 against the external force action is reduced. Therefore, in this aspect, the influence of the inertia of the steering system 10 is minimized, thereby reducing the load on the corresponding neural system part of the steering system 10.

[0032] To drive and control the actuator unit 14, the calculation unit 26 has a load reduction function 16 stored particularly in the operating memory of the calculation unit 26 and used in the operating state. Using this load reduction function 16, the actuator unit 14 is driven and controlled here such that a compensation torque is generated. The load reduction function 16 is further specialized for the driving situation and is activated and deactivated particularly depending on the current driving situation. In a normal driving situation where the load in the steering system 10 is slight, the load reduction function 16 is deactivated, whereby the driver does not perceive a change in the steering characteristics and / or steering feeling. In contrast, in a load situation, for example, when driving through a rough road section, the load reduction function 16 is activated to reduce the load on the steering system 10. Therefore, the load reduction function 16 is preferably not permanently activated but switched on only when necessary.

[0033] To activate and deactivate the load reduction function 16, a load characteristic value correlated with the load generated in the steering system 10 by an external force action and / or the current driving situation is determined. This load characteristic value is determined continuously here or monitored during the total monitoring time interval. Furthermore, the load reduction function 16 is activated when the load characteristic value exceeds a first limit value and deactivated when the load characteristic falls below a second limit value different from the first limit value, thereby enabling, in particular, the realization of a corresponding hysteresis characteristic.

[0034] Furthermore, the load reduction function 16 and in this embodiment in particular the compensation torque can fade in during activation and fade out during deactivation, thereby enabling, in particular, unobtrusive activation and / or deactivation. Preferably, for this purpose, a ramp function is used. However, alternatively, fading in and / or out may be performed by a function different from the ramp function, for example, an asymptotic function. Furthermore, fading in and / or out may be omitted.

[0035] Basically, the load consists of at least substantially two main components, specifically, the load in the steering gear 30 and / or the servo system 18, and the load in the steering shaft 34 and / or the steering system 20.

[0036] Accordingly, according to the first embodiment, it is conceivable to reduce only the load in the servo system 18. In this aspect, the actuator unit 14 is driven and controlled in the operating state so that the dominant load in the servo system 18 is compensated.

[0037] The load in the servo system 18 is based on the following relational expression,

Equation

[0038] Here, M Sdescribes the total rotational torque on the motor shaft of the electric motor of the actuator unit 14 that characterizes the load in the servo system 18, this total rotational torque being the first or regenerative component M S,G , i.e., the acceleration of the servo system 18, and the second or motor component M S,M , i.e., the motor torque acting on the motor shaft of the electric motor of the actuator unit 14, and for which J S characterizes the inertia of the actuator unit 14, [Number] characterizes the acceleration of the actuator unit 14, in particular the rotor acceleration.

[0039] Thus, in this aspect, at least one operating variable of the actuator unit 14, in this aspect in particular the acceleration of the actuator unit 14, is monitored and evaluated in order to determine the load, in particular in the form of the regenerative component M S,G . Furthermore, at least one inertia of the actuator unit 14 is taken into account in order to determine the load. Furthermore, the motor component M S,M can be determined based on further operating variables of the actuator unit 14, in this aspect in particular the operating current and / or the phase current of the electric motor. Moreover, it is conceivable to take into account at least one essential inertia of further steering components in order to determine the load in the servo system 18.

[0040] The compensation torque is M K1 and in this aspect the following relationship, M K1 = -M S (2) applies.

[0041] However, alternatively, only the load resulting from the regenerative component M S,G , or only the motor component M S,MIt is also basically conceivable to compensate only the loads resulting from the torque transfer by means of a drive control of the actuator unit 14, so that the loads on the steering system 10, in particular on the servo system 18, can at least be reduced.

[0042] According to a second embodiment, it is conceivable to only reduce the loads in the steering system 20. In this manner, the actuator unit 14 is driven in such a way that in the operating state, the loads prevailing in the steering system 20 are compensated.

[0043] The load in the steering system 20 is expressed by the following relationship:

number

[0044] Here, M L describes the total rotational torque in the area of ​​the steering wheel 22 that characterizes the load in the steering system 20, which is a function of the additional rotational component M L,G and the driver's manual torque M L,F In contrast, J L characterizes the inertia of the steering wheel 22,

number

[0045] In this embodiment, the load is in particular a further cycle component M L,GIn order to determine in this form, at least one movement of the steering handle 22 captured using the motion sensor 40 is monitored and evaluated. For this purpose, using the motion sensor 40, a motion signal that is correlated with the movement speed of the steering handle 22 and is different from the acceleration signal is captured, and subsequently an acceleration signal correlated with the movement of the steering handle 22 is calculated therefrom. The calculation of this acceleration signal is preferably performed using gradient formation, in particular using the differential quotient. However, alternatively, another type of differential calculation may be used, or an acceleration signal correlated with the movement of the steering handle may be captured directly. Furthermore, in order to determine the load, at least one inertia of the steering handle 22 is taken into account. Furthermore, the driver manual torque M L,F can be determined based on the torsion bar signal from the steering sensor 36 and / or based on the motion signal from the motion sensor 40. Additionally, it is conceivable to take into account at least one essential inertia of further steering components in order to determine the load in the steering system 20.

[0046] For the compensation torque M K2 in this aspect, the following relational expression, M K2 = -M L ·i·η (4) applies.

[0047] Here, i describes the gear ratio of the actuator unit 14, and η defines the corresponding efficiency.

[0048] However, alternatively, it is basically also conceivable to compensate only for the load resulting from the additional regenerative component M L,G or only for the load resulting from the driver manual torque M L,F using the drive control of the actuator unit 14, whereby the load in the steering system 10, in particular in the steering system 20, can at least be reduced.

[0049] According to the third embodiment, it is further conceivable to reduce the load in the servo system 18 and the load in the steering system 20. In this aspect, the actuator unit 14 is driven and controlled in the operating state so that the dominant load in the servo system 18 and the dominant load in the steering system 20 are compensated.

[0050] In particular, the cumulative load corresponding to the rack and pinion cumulative force, in this aspect, is based on the following relational expression M = M S ·i S ·η S +M L ·i L ·η L (5) and is obtained based on this.

[0051] Here, M describes the cumulative load, and i S and i L are the corresponding gear ratios in the servo system 18 and the steering system 20, and η S and η L are the corresponding efficiencies in the servo system 18 and the steering system 20.

[0052] Regarding the total compensation torque M K in this aspect, the following relational expression M K = -M·i·η (6) applies.

[0053] Here, i describes the gear ratio of the actuator unit 14, and η defines the corresponding efficiency.

[0054] Finally, FIG. 2 shows an exemplary flowchart using the main method steps of a method for reducing the load in the steering system 10.

[0055] In method step 50, the load on the steering system 10 caused by an external force acting thereon is determined. For this purpose, at least one operating variable of the actuator unit 14 and / or the movement of the steering wheel 22 is monitored and evaluated. The load can in this case correspond to the load prevailing in the servo system 18 and / or the load prevailing in the steering system 20. Furthermore, the load caused by the external force acting on the steering system 10 and / or a load characteristic value correlated with the current driving situation is continuously determined and compared with a first limit value. If the load characteristic value exceeds the first limit value, method step 52 follows.

[0056] In method step 52, the load reduction function 16 is activated, in which case the load reduction function 16 is preferably faded in.

[0057] In method step 54, the actuator unit 14 is drive-controlled using the load reduction function 16 so as to generate a compensation torque that counteracts the inertia of the steering system 10 and is oriented in the same direction as the external force acting thereon. Since this compensation torque is applied to the steering system 10, the steering system 10 moves in conjunction with the external force, in particular in the direction of the external force, and the resistance of the steering system 10 against the external force is reduced. Thereby, the inertia effect of the steering system 10 correlated with the external force can be reduced and the load on the steering system 10 can be at least partially compensated. Furthermore, the load characteristic value is determined again and compared with a second limit value. If this load characteristic value falls below the second limit value, method step 56 follows.

[0058] In method step 56, the load reduction function 16 is deactivated, in which case the load reduction function 16 is preferably faded out.

[0059] The exemplary flowchart of FIG. 2 is herein intended to illustrate only by way of example a method for reducing the load in the steering system 10. In particular, it is also possible to change the individual method steps or to add additional method steps.

Claims

1. A method for reducing the load in an operating steering system (10) in a vehicle (12), comprising: determining a load generated in the steering system (10) by an external force action, and at least partially compensating, by drive control of an actuator unit (14), in at least one operating state; wherein the actuator unit (14) is drive-controlled in the operating state such that an inertia effect of the steering system (10) correlated with the external force action is reduced.

2. The method according to claim 1, wherein in the operating state, a compensation torque acting against the inertia of the steering system (10) and / or a compensation force acting against the inertia of the steering system (10) are generated using the actuator unit (14) and applied to the steering system (10).

3. The method according to claim 1 or 2, wherein in the operating state, a load reduction function (16) is used for drive control of the actuator unit (14), and the load reduction function (16) is activated and / or deactivated in a driving situation-specific manner.

4. A load characteristic value correlated with the load is determined, and the load reduction function (16) is activated when the load characteristic value exceeds a first limit value and deactivated when the load characteristic value is below a second limit value. The method according to claim 3.

5. The method according to claim 3 or 4, wherein the load reduction function (16) is faded in upon activation and / or faded out upon deactivation.

6. The method according to any one of claims 1 to 5, wherein in the operating state, at least one load in a servo system (18) of the steering system (10) is compensated by drive control of the actuator unit (14).

7. The method according to any one of claims 1 to 6, wherein in the operating state, at least one load in a steering system (20) is compensated by drive control of the actuator unit (14).

8. The method according to any one of claims 1 to 7, wherein an electric steering actuator providing a steering torque is used as the actuator unit (14).

9. The method according to any one of claims 1 to 8, wherein at least one operating variable of the actuator unit (14) and / or the movement of the steering wheel (22) is monitored in order to determine the load.

10. The method according to any one of claims 1 to 9, wherein the load includes the action of a force from the ground.

11. A control device (24), comprising a calculation unit (26) for implementing the method according to any one of claims 1 to 10.

12. A vehicle (12), comprising a steering system (10) including at least one actuator unit (14) and a calculation unit (26) for implementing the method according to any one of claims 1 to 10.

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