Method for controlling a steering actuator and steering system
By controlling the steering actuator, by calculating the wheel steering angle change and reduction factors, reducing the steering angle or torque theoretical value, the thermal load and wear problems of the steering system at low driving speeds are solved, ensuring the stability of the system. and other electrical equipment for proper functioning.
Patent Information
- Application Number
- CN202380047021.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-29
- Filing Date
- 2023-06-28
- Publication Date
- 2025-01-24
AI Technical Summary
When fast and persistent steering movements are performed at low driving speeds or stops, the energy demand of the electrically actuated steering device increases, resulting in high heat and load on the vehicle's on-board power grid, thereby accelerating wear of the steering device and affecting other electrical consumers and actuators Functions of the device.
Through a method to control the steering promoter, determine the steering angle change of the wheels, and calculate the accumulated steering angle change. Based on this, the reduction factor is required to reduce the theoretical value of the steering angle or the torque, and avoid heat load and premature wear.
It effectively prevents thermal overload and premature wear of the steering system, ensures the functional integrity of the steering actuator and sufficient on-board voltage, and reduces the impact on other electrical consumers and actuators.
Smart Images
Figure CN119365378A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for controlling a steering actuator. The invention also relates to a steering system. Background Art
[0002] It has been found that the increased energy demand of an electrically actuated steering system of a motor vehicle due to rapid and prolonged steering movements at low driving speeds or when stationary can lead to undesirably high heating and loading of the vehicle's onboard electrical system.
[0003] This undesirably high heating can lead to accelerated wear of certain components of the steering device, thereby causing additional costs. Loading of the vehicle's onboard electrical system can lead to a drop in the onboard voltage and thus affect the functionality of other electrical consumers and actuators. Summary of the invention
[0004] It is therefore an object of the present invention to provide a method for controlling a steering actuator and a steering system which prevent premature wear of the steering system due to thermal loading and influence on other electrical loads and actuators.
[0005] The object is achieved according to the invention by a method for controlling a steering actuator. The steering actuator is designed to adjust at least one wheel of a motor vehicle or to assist the adjustment of the at least one wheel by means of a steering torque. The method comprises the following steps:
[0006] - determining a change in the steering angle of the at least one wheel;
[0007] - ascertaining a cumulative steering angle change based on the steering angle change, wherein the steering angle changes or weighted steering angle changes are added up according to a quantity in order to ascertain the cumulative steering angle change;
[0008] - determining a reduction factor based on the accumulated steering angle change;
[0009] - ascertaining a temporary steering angle target value or a temporary steering torque target value for the steering actuator; and
[0010] - reducing a temporary steering angle target value or a temporary steering torque target value based on the ascertained reduction factor, thereby obtaining a scaled steering angle target value or a scaled steering torque target value for the steering actuator.
[0011] The method according to the invention is based on the basic idea of preventively preventing a thermal overload of the steering system, in particular of the steering actuator and / or the cabling of the steering actuator, as well as an influence on other electrical consumers and actuators.
[0012] In the case of fast and / or long-lasting steering movements, the value of the accumulated steering angle change increases. Correspondingly, the value of the reduction factor decreases, whereby the temporary steering angle target value or the temporary steering torque target value is reduced even more in order to obtain a scaled steering angle target value or a scaled steering torque target value for the steering actuator.
[0013] In other words, the steering movement of the at least one wheel or the steering assistance for the at least one wheel of the motor vehicle is preventively reduced, thereby reducing the thermal load on the steering system and preventing premature wear. The functional integrity of the steering actuator and a sufficient onboard voltage are thereby ensured. In addition, an influence on other electrical consumers and actuators is reliably prevented.
[0014] The method according to the invention is implemented here without additional sensor systems, since all parameters used, such as steering angle target value, steering angle actual value, vehicle speed, current electrical utilization, which is formed by the ratio of current current consumption to permissible current consumption, are actually required for controlling the steering actuator and are therefore already available.
[0015] The method according to the invention therefore offers a cost-effective way of preventing premature wear of the steering system and the effects on other electrical loads and actuators.
[0016] Preferably, the at least one wheel is a rear wheel of the motor vehicle. That is, the steering actuator is designed to adjust at least one rear wheel of the motor vehicle, in particular each rear wheel of the motor vehicle.
[0017] In this case, a temporary steering angle target value is ascertained and reduced for the steering actuator.
[0018] However, it is also conceivable that the at least one wheel is a front wheel or each front wheel of the motor vehicle.
[0019] In this case, a temporary steering torque target value is ascertained and reduced for the steering actuator.
[0020] According to one aspect of the invention, the accumulated steering angle change is reduced based on a decay constant. In other words, the value of the accumulated steering angle change decreases again over time, so that the value of the reduction factor increases again. That is, if no more rapid steering movements and / or no more long-lasting steering movements are performed within a certain period of time, the steering angle target value or the steering torque target value decreases less, or no longer decreases from a certain point in time.
[0021] In one embodiment of the invention, a reduction factor is determined from the accumulated steering angle change based on a predetermined characteristic curve. The predetermined characteristic curve can be predetermined, for example, by a manufacturer of the steering system or the motor vehicle. The desired driving characteristics of the motor vehicle can be adjusted accordingly via the predetermined characteristic curve. Alternatively or additionally, the material properties of the steering system, in particular the steering actuator and / or the cable routing of the steering actuator, can be taken into account in the predetermined characteristic curve so that the steering system or the steering actuator is not thermally overloaded.
[0022] Preferably, the steering angle change is weighted based on a speed-dependent characteristic curve in order to determine the cumulative steering angle change. More precisely, the characteristic curve is dependent on the speed of the motor vehicle. The heat input caused by the steering angle change is mapped as a function of the speed of the motor vehicle via the speed-dependent characteristic curve.
[0023] In particular at low speeds, the accumulated steering angle change is weighted more heavily than at high speeds.
[0024] According to another aspect of the invention, the steering angle change is weighted based on the electromechanical utilization of the steering actuator in order to determine the accumulated steering angle change. The electromechanical utilization is used to map the heat input caused by the steering angle change as a function of the load state of the steering actuator.
[0025] For example, the electromechanical utilization rate may be formed from the ratio of the current power consumption to the permissible power consumption, so that at a high utilization rate the accumulated steering angle change may be weighted more heavily than at a lower utilization rate.
[0026] The steering angle change can be weighted based on the actual steering angle of the at least one wheel, for example based on a steering angle-dependent characteristic curve. Thus, the heat input caused by the steering angle change is mapped as a function of the actual steering angle.
[0027] That is, individual influencing variables, in particular the speed of the motor vehicle, the electromechanical utilization and / or the actual steering angle, can be represented (separately) by a characteristic curve.
[0028] However, it is also conceivable to represent two, more or all of these influencing variables in combination in at least one characteristic diagram, in particular also in a plurality of characteristic diagrams.
[0029] In particular, the steering angle change is accumulated only when the amount of the steering angle change is greater than a predetermined limit value. That is, if the amount of the steering angle change is less than a predetermined limit value, the value of the accumulated steering angle change does not increase. That is, an adjustable "dead zone" is set around the steering angle change of 0.
[0030] A predetermined minimum value for the reduction factor can be set. This ensures that the scaled steering angle target value or the scaled steering torque target value for the steering actuator does not decrease to zero, which would result in no steering movement or steering assistance. Instead, the steering movement or steering assistance is reduced at most to a limit value predetermined by the predetermined minimum value.
[0031] Preferably, the reduction factor is updated only when the steering angle passes through zero. That is, the reduction factor is not updated during a bend, but only between two different bends or between two steering turns in different directions. As a result, the steering characteristics of the motor vehicle do not change during a bend.
[0032] In another embodiment of the invention, the temporary steering angle target value or the temporary steering torque target value is reduced only below a predetermined critical speed of the motor vehicle. It has been found that the thermal load of typical operating conditions of a motor vehicle above a certain critical speed is so low that it is not necessary to reduce the temporary steering angle target value or the temporary steering torque target value, since less force is required to adjust the wheels.
[0033] The method described above is therefore used, in particular, when the motor vehicle is stationary or at a speed of the motor vehicle up to a predetermined limit speed both when driving forward and when driving in reverse.
[0034] Furthermore, the object is achieved according to the invention by a steering system having at least one electromechanical steering actuator and a control unit for the steering actuator. The steering system is designed to carry out the above-described method.
[0035] With regard to the advantages and further properties of the steering system, reference is made to the above explanations regarding the method, which also apply to the steering system and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Further advantages and features of the invention emerge from the following description and from the referenced drawings.
[0037] The single FIGURE shows a block diagram of a control circuit for implementing the method according to the invention for controlling a steering actuator. DETAILED DESCRIPTION
[0038] exist Figure 1 Schematically, a block diagram of a control loop 10 is shown in FIG. 1 , which is executed in a control unit for a steering actuator of a motor vehicle.
[0039] More precisely, Figure 1 A portion of a complete control circuit for a steering actuator of a motor vehicle is shown.
[0040] The steering actuator is an electromechanical actuator which is designed to adjust at least one wheel of the motor vehicle or to assist in the adjustment of the at least one wheel by means of a steering torque.
[0041] Preferably, the at least one wheel is a rear wheel of the motor vehicle. That is, the steering actuator is designed to adjust at least one rear wheel of the motor vehicle, in particular each rear wheel of the motor vehicle.
[0042] Yet also can imagine, described at least one wheel is a front wheel or each front wheel of motor vehicle.In this case, described steering actuator is designed to assist the adjustment of described at least one wheel by steering torque.
[0043] Unless otherwise stated, the following explanations apply to both cases, namely to the rear wheels and to the front wheels.
[0044] A steering system of a motor vehicle, in particular a control unit, is designed to carry out a method for controlling a steering actuator, followed by a method for controlling a steering actuator. Figure 1 The control circuit 10 shown in FIG. 1 illustrates the steering system.
[0045] Obtaining the actual steering angle of the at least one wheel And it is differentiated over time by means of a differentiator 12, thereby obtaining a steering angle change.
[0046] In block 14, the steering angle change is determined and feeds it to the multiplication block 16.
[0047] Alternatively, the steering angle can be varied with a predetermined characteristic curve 18. The quantity weighting is particularly such that the predetermined characteristic curve 18 has a dead band around 0.
[0048] That is, when the steering angle changes When the amount is greater than a predetermined limit value, the steering angle supplied to the multiplication block 16 changes The value of the quantity is different from 0.
[0049] In addition, the speed v of the vehicle is obtained x Variables, in particular those involving the longitudinal speed of the motor vehicle or those involving the speed of the center of gravity of the motor vehicle.
[0050] Based on the obtained speed v of the motor vehicle x The speed-dependent weighting factor G is obtained from the speed-dependent characteristic curve 20. v And it is sent to the multiplication block 16.
[0051] Here, the weighting factor G for smaller values of the speed is v Greater than or equal to for speed vx The larger value of the weighting factor G v .
[0052] That is, the weighting factor G v is the speed v x A monotonically decreasing function of the amount.
[0053] Furthermore, an electromechanical utilization F of the steering actuator is determined, in particular wherein the electromechanical utilization F is provided by the steering actuator itself.
[0054] In this case, the electromechanical utilization F can assume values between 0% (no utilization) and 100% (full utilization).
[0055] Based on the predetermined characteristic curve 22, the weighting factor G is determined from the obtained utilization F. F And it is sent to the multiplication block 16.
[0056] Here, the weighting factor G for smaller values of the utilization factor F is F Less than the larger value used for utilization F.
[0057] Furthermore, the actual steering angle of the at least one wheel may be Find the weighting factor And it is sent to the multiplication block 16.
[0058] In particular, the weighting factor is determined based on a predetermined steering angle-dependent characteristic curve.
[0059] Multiplication block 16 is changed by the steering angle The amount and weighting factor G v , G F , Forming a weighted steering angle change The steering angle change is supplied to an integrator 24 .
[0060] That is, the influencing parameters, in particular the speed v of the vehicle x , electromechanical utilization F and / or actual steering angle Can be represented (alone) by a characteristic curve.
[0061] However, it is also conceivable to represent two, more or all of these influencing variables in combination in a characteristic diagram in the mechanical actuator model.
[0062] Integrator 24 calculates the weighted steering angle change Integrate over time to obtain the cumulative steering angle change
[0063] Optionally, an upper limit for the value of the accumulated steering angle change can be set The output variable of the integrator 24, namely the accumulated steering angle change You cannot exceed this upper limit at this time
[0064] Furthermore, a feedback loop 26 is provided in which the accumulated steering angle change Multiply by the decay constant c and change from the weighted steering angle Minus.
[0065] The accumulated steering angle changes are realized by the feedback loop 26. The value of decreases over time based on the decay constant c.
[0066] The reduction factor R is ascertained from the accumulated steering angle change on the basis of a predetermined characteristic curve 28 .
[0067] The values of the reduction factor R are between 0 and 1, wherein a smaller value of the reduction factor R in the case of the rear wheels means that the steering angle theoretical value for the steering actuator is reduced more and in the case of the front wheels means that the steering torque theoretical value for the steering actuator is reduced more, as explained in more detail below.
[0068] Predetermined characteristic curve 28 can be predetermined, for example, by a manufacturer of the steering system or of the motor vehicle and thus be adapted to different given conditions of the respective vehicle.
[0069] By means of predetermined characteristic curve 28 , for example, a desired driving characteristic of the motor vehicle can be set.
[0070] Alternatively or additionally, material properties and geometrical installation conditions of the steering system, in particular of the steering actuator and / or of the cabling of the steering actuator, may be taken into account in the predetermined characteristic curve.
[0071] Set a predetermined minimum value for the reduction factor R min The comparator 30 compares the reduction factor R with the minimum value R min The larger of the two values is compared and output to the update block 32 .
[0072] The updating block 32 is only executed when the actual steering angle passes through zero, i.e., only when The reduction factor R is updated when the sign of a The output value of .
[0073] If no actual steering angle occurs The output reduction factor R is re-output through the delay element 33. a The previous value of .
[0074] The reduction factor R output by the update block 32 is a Sent to the output block 34.
[0075] The output block 34 outputs the reduction factor R only if two conditions are met. a .
[0076] On the one hand, the reduction function must be switched on, ie the parameter c obtained by the switching block 36 S It must be indicated that the reduction function is switched on.
[0077] On the other hand, the speed of the vehicle v x The amount must be less than the predetermined critical speed v of the vehicle max .
[0078] For this purpose, the comparator 38 compares the speed v of the motor vehicle x and the predetermined critical speed v of the vehicle max And the comparison result is output to the output block 34 .
[0079] Optionally, a smoothing block 40 may be provided after the output block 34, wherein the smoothing block is configured to smooth the output reduction factor R a .
[0080] In particular, the leveling block 40 leveling the reduction factor R at the output a And thus the sudden change in the scaled steering angle target value or the scaled steering torque target value described below.
[0081] In the case of the rear wheels, based on the output reduction factor R a A temporary steering angle target value ascertained by a control circuit for the steering actuator is reduced, thereby resulting in a scaled steering angle target value for the steering actuator.
[0082] In particular, the temporary steering angle theoretical value By comparing the output reduction factor R a Multiply, that is, according to Get the scaled theoretical steering angle
[0083] In the case of the front wheels, based on the output reduction factor R a A temporary steering torque target value ascertained by a control circuit for the steering actuator is reduced, thereby resulting in a scaled steering torque target value for the steering actuator.
[0084] In particular, the temporary steering torque target value T is obtained by combining the output reduction factor R a Multiply, that is, according to T soll=R a ·T obtains the scaled steering torque theoretical value T soll The method described above therefore prevents the steering movement of the at least one wheel of the motor vehicle or the steering assistance provided, thereby reducing the thermal load on the steering system and preventing premature wear. Furthermore, an influence on other electrical consumers and actuators is prevented.
Claims
1. A method for controlling a steering actuator, which is designed to adjust at least one wheel of a motor vehicle or to assist adjustment of the at least one wheel by means of a steering torque, wherein: The method comprises the following steps: - determining a change in the steering angle of the at least one wheel - Based on the steering angle change Calculate the cumulative steering angle change Wherein, the steering angle changes according to the amount accumulated or weighted steering angle change In order to obtain the cumulative steering angle change - Based on the accumulated steering angle change Find the reduction factor (R a ); - ascertaining a temporary steering angle target value or a temporary steering torque target value for the steering actuator: and - Based on the reduction factor (R a ) reduces the temporary steering angle target value or the temporary steering torque target value, thereby obtaining a scaled steering angle target value or a scaled steering torque target value for the steering actuator.
2. The method according to claim 1, wherein: The accumulated steering angle change is reduced based on the decay constant (c) 3. The method according to any one of the preceding claims, characterized in that Based on a predetermined characteristic curve (28), the accumulated steering angle is changed Obtain the reduction factor (R a ).
4. The method according to any one of the preceding claims, wherein: The steering angle is changed based on a speed-dependent characteristic curve (20) Weighted to obtain the accumulated steering angle change 5. The method according to any one of the preceding claims, wherein: The steering angle is changed based on the electromechanical utilization (F) of the steering actuator. Weighted to obtain the accumulated steering angle change 6. The method according to any one of the preceding claims, wherein: Only when the steering angle changes When the amount is greater than a predetermined limit value, the steering angle is changed Accumulation.
7. The method according to any one of the preceding claims, wherein: Setting the reduction factor (R a ) of the predetermined minimum value (R min ).
8. The method according to any one of the preceding claims, wherein: Only at the steering angle The reduction factor (R a ).
9. The method according to any one of the preceding claims, wherein: Only at a predetermined critical speed (v max ) under which the temporary steering angle theoretical value or the temporary steering torque theoretical value is reduced.
10. A steering system comprising at least one electromechanical steering actuator and a controller for the steering actuator, wherein: The steering system is designed to carry out a method according to one of the preceding claims.