Mechanically decoupled steering system for vehicle and method for operating mechanically decoupled steering system
By setting up sensors and control equipment in the mechanical decoupled steering system and using characteristic curves to perform dynamic driving intervention, the problem of vehicle instability caused by insufficient steering is solved, and stability guarantee is achieved when driving in corners.
Patent Information
- Application Number
- CN202380077252.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-11-11
- Filing Date
- 2023-11-10
- Publication Date
- 2025-06-20
AI Technical Summary
The existing mechanical decoupled steering system is difficult to effectively conduct dynamic driving intervention in the case of insufficient steering, resulting in unstable vehicle driving when turning.
By setting sensors and control devices in the steering system, detecting steering wheel angles and hand torques, setting the reference steering angle according to the actual steering angle using the characteristic curve, and matching the theoretical steering angle higher than the reference steering angle by changing the steering wheel angle, thereby performing driving dynamic intervention.
Effective driving dynamic intervention in the case of insufficient steering is achieved, ensuring the stability of the vehicle when turning, without braking intervention and slowing down the vehicle speed.
Smart Images
Figure CN120187624A_ABST
Abstract
Description
Field of the Invention
[0001] The present invention relates to a mechanical decoupling steering system for a vehicle and a method for operating a mechanical decoupling steering system for a vehicle. Background Art
[0002] Understeer is a term from driving dynamics that is used to describe the inherent steering behavior. This term describes the situation where, when cornering, the faster the radius is traversed, the greater the steering wheel angle. In modern electronic stability programs, the actual motion variables are compared with the driver's expectations derived from the steering wheel angle and the driving speed according to an internal single-track model. If the driver expects to "corner more" than what is actually measured, understeer is recognized. In the case of excessive deviation, the rear wheels inside the curve are automatically braked and the engine power is reduced. Another clear explanation for understeer is that there is a point at which the available lateral force decreases despite an increasing steering angle.
[0003] In a mechanical decoupling steering system, the movement of the steering handle can be decoupled from the movement of the wheels. A mechanical decoupling steer-by-wire system is characterized in that there is no longer a mechanical connection or coupling between the steering handle and the steering transmission mechanism. Typically, at least one sensor is arranged at the steering handle for detecting the steering angle or torque, and its sensor signal is transmitted to a control device, which then realizes the steering requirement by means of the steering transmission mechanism. For this purpose, the steering transmission mechanism is driven by at least one electric servo motor. For redundancy reasons, usually at least two servo motors with their respective power electronics are used. The servo motors work on a common rotor, which is connected to the steering transmission mechanism, which in turn is connected to the rack. It is also known here to use a servo motor with two half machines, which are preferably constructed symmetrically, i.e., each applies 50% of the total power. It is also known to provide an actuator at the steering handle, which generates a defined counter torque at the steering handle in order to give the vehicle driver a better tactile feeling through feedback. Such an actuator is also called a force feedback actuator. In a mechanical decoupling superimposed steering gear, an angle is superimposed on the steering wheel angle. Then, the steering angle at the input of the steering transmission mechanism no longer corresponds to the angle of the steering wheel. On the one hand, this enables a stepless adaptation of the steering ratio. On the other hand, the superimposition also allows for rapid intervention in the driving dynamics by changing the steering angle at the wheels while keeping the steering wheel angle the same during driving. Summary of the Invention
[0004] The object of the present invention is to create a mechanical decoupling steering system for a vehicle that in particular has improved stability performance, and to provide a corresponding method for operating a mechanical decoupling steering system.
[0005] According to the present invention, this task is solved by a mechanical decoupling steering system with the features of claim 1 and a method with the features of claim 10. Advantageous designs of the present invention result from the dependent claims.
[0006] In particular, a mechanical decoupling steering system for a vehicle is created, which steering system includes a steering handle, a steering transmission mechanism, and a control device, wherein at least one sensor is arranged at the steering handle for detecting the steering wheel angle and / or the hand torque at the steering handle, wherein the steering transmission mechanism has at least one electric motor, which is coupled to a rack, wherein the control device is configured to determine a theoretical steering angle depending on the actual steering wheel angle and / or the actual hand torque detected by means of the at least one sensor and to control the steering transmission mechanism, and wherein the control device is furthermore configured to identify an understeering situation starting from at least one understeering index, to set the actual steering angle present at the time of identification as a reference steering angle, and to match the theoretical steering angle requested by changing the actual steering wheel angle and being higher than this reference steering angle according to a predefined characteristic curve, in particular depending on the reference steering angle.
[0007] Furthermore, in particular, a method for operating a mechanical decoupling steering system for a vehicle is provided, wherein the steering system includes a steering handle, a steering transmission mechanism, and a control device, wherein the steering handle has at least one sensor for detecting the steering wheel angle and / or the hand torque at the steering handle, wherein the steering transmission mechanism has at least one electric motor, which is coupled to a rack, wherein a theoretical steering angle is determined depending on the actual steering wheel angle and / or the actual hand torque detected by means of the at least one sensor and the steering transmission mechanism is controlled by means of the control device, and wherein an understeering situation is identified starting from at least one understeering index, wherein the actual steering angle present at the time of identification is set as a reference steering angle, and the theoretical steering angle requested by changing the actual steering wheel angle and being higher than the reference steering angle is matched according to a predefined characteristic curve, in particular depending on the reference steering angle.
[0008] The steering system and the method can achieve effective driving dynamic intervention in the case of understeering in order to ensure the stability of the vehicle during cornering. The basic idea here is that if the vehicle driver continues to steer in the case of understeering, then it is corrected above the reference steering angle according to the characteristic curve, and thereby in particular the theoretical steering angle transmitted to the steering transmission mechanism is reduced depending on the steering wheel angle. In this way, understeering can be limited, which is pleasant for the vehicle driver in terms of driving comfort, since for this purpose in particular no braking intervention and / or reduction of the vehicle speed is required.
[0009] For example, the control device receives an understeer indicator from an electrical stability program or another control device (e.g., from a vehicle controller). Alternatively, the steering system itself may also have suitable sensing means that provide suitable sensor data in order to determine the understeer indicator and detect an understeer situation.
[0010] In particular, the characteristic curve depicts the relationship between the steering wheel angle at the steering handle (in particular at the steering wheel) and the steering angle at at least one steerable wheel. For example, if such a characteristic curve is linear, any change in the steering wheel angle is directly converted proportionally into a change in the steering angle. In this example, by changing the linear slope of the characteristic curve, such a relationship can be adjusted in terms of the intensity with which the steering wheel angle is converted into the steering angle. In particular, the characteristic curve is not continuously linearly configured, but can have a varying slope at least in some sections. For example, the characteristic curve can be described at least in some sections by means of a polynomial function. The characteristic curve profile and / or the characteristic curve parameters are determined in particular on the basis of an empirical series of tests and / or by simulation.
[0011] The components of the steering system, in particular the control device, can be configured individually or jointly as a combination of hardware and software, for example as program code implemented on a microcontroller or a microprocessor. However, it can also be provided that the components are configured individually or jointly as an application-specific integrated circuit (ASIC) and / or a field-programmable gate array (FPGA).
[0012] In one embodiment, it is provided that the characteristic curve has at least one transition range and a limit range, where the transition range lies between a reference steering angle and the limit range. Thereby, different ranges of the characteristic curve can be defined, where upon recognition of oversteer, the steering behavior changes from the normal range through the transition range into the limit range. In particular, thereby, a sudden change in the steering behavior of the steering system can be prevented, and instead it provides a transition that feels soft or smooth to the vehicle driver. In particular, it can be provided that the relationship between the steering wheel angle and the steering angle is linear in the normal range. Then in the transition range, that is, starting from the reference steering angle in an oversteer situation, the relationship changes across the transition range into a linear relationship with a smaller slope, such that in the limit range, compared to the normal range, a change in the steering wheel angle results in a smaller change in the steering angle. In particular in the transition range, the characteristic curve can be configured as a polynomial function and / or described as a polynomial function. In principle, however, other characteristic curve profiles are also applicable.
[0013] In an improved embodiment, it is provided that the characteristic curve can be parameterized at least for a transition range. Thereby, personal preferences can be taken into account. In addition, this also enables the use of situation-dependent characteristic curves. For example, the following preference can be achieved thereby: when converting the (actual) steering wheel angle into the (theoretical) steering wheel angle, the matching or compensation is made to vary smoothly within a range of 2° of the steering wheel angle from 0% to 90%.
[0014] In one embodiment, it is provided that the characteristic curve is selected or parameterized taking into account the speed of the vehicle and / or the friction value and / or the value of the at least one understeer indicator, or is selected or parameterized. This enables the characteristic curve to be matched to a certain driving situation of the vehicle.
[0015] In one embodiment, it is provided that the threshold value (from which understeer is confirmed) is defined or is defined taking into account the speed of the vehicle and / or the friction value. This enables the range to be defined depending on the current driving condition of the vehicle, from which range understeer is recognized. For example, different weather conditions (such as dry road surface, wet road surface, snow, ice, etc.) can be taken into account thereby.
[0016] In one embodiment, it is provided that the at least one understeer indicator is a continuous indicator proportional to the intensity of understeer. On the one hand, this makes it possible to quickly recognize understeer. In addition, the understeer indicator can thereby be used as a continuous variable for describing the current driving dynamic state of the vehicle, and based on this variable, intervention in the driving dynamics can be carried out at any time and in any situation with sufficient resolution. In particular, the characteristic curve can be selected and / or parameterized at any time by means of the at least one continuous understeer indicator.
[0017] In one embodiment, it is provided that the at least one understeer indicator is determined or is determined based on a comparison between the theoretical yaw rate and the actual yaw rate of the vehicle. For example, the at least one understeer indicator can be or include the difference determined from the theoretical yaw rate and the actual yaw rate. If the difference exceeds a preset threshold value, understeer is recognized. The characteristic curve can also be selected and / or parameterized taking into account such a difference.
[0018] In one embodiment, it is provided that the at least one understeer indicator is determined or is determined starting from the lateral force acting on the front wheels of the vehicle. For example, a lateral force sensor detects the lateral force caused by the adjusted actual steering wheel angle. Then, if the (actual) steering angle at the wheels increases but the lateral force does not increase, there is an understeer situation.
[0019] In one embodiment, it is provided that the at least one understeer indicator is determined or is to be determined starting from the lateral acceleration. For example, an acceleration sensor detects the lateral acceleration caused by the adjusted actual steering wheel angle. Then, if the (actual) steering angle at the wheels increases but the lateral acceleration does not increase, an understeer situation exists.
[0020] In one embodiment, it is provided that the steering system is a rear-wheel steering system or additionally includes a rear-wheel steering system configured in the same way. In particular, the rear-wheel steering system can be configured, additionally or alternatively, according to the steering system described in the present disclosure.
[0021] Other features of the design of the method result from the description of the design of the steering system. Here, the advantages of the method are the same, respectively, as in the design of the steering system. Description of the Drawings
[0022] Hereinafter, the present invention will be explained in more detail with reference to the preferred embodiments and the accompanying drawings. Among them:
[0023] Figure 1 A schematic diagram showing an embodiment of a mechanical decoupled steering system for a vehicle is shown;
[0024] Figure 2 A schematic diagram showing characteristic curves for elucidating the embodiments of the steering system and the method is shown. Detailed Description of the Embodiments
[0025] Figure 1 A schematic diagram showing an embodiment of a mechanical decoupled steering system 1 for a vehicle is shown. In this example, the steering system 1 is a steer-by-wire system. In principle, however, the steering system 1 can also be an overlay steering gear.
[0026] The steering system 1 includes a steering wheel module 2 and a steering module 3. A steering wheel grip 4 (steering wheel) is connected to the steering wheel module 2 and the steering wheel module 2 has sensors 5 for detecting the steering wheel angle 6 and / or the hand torque at the steering wheel grip 4. The detected steering wheel angle 6 is fed to the steering module 3. The steering module 3 has a steering transmission mechanism 7 and a control device 8. The steering transmission mechanism 7 has at least one electric motor 9 (for example, at least one servo motor), which is coupled to a rack 10. The rack 10 is coupled to at least one steerable wheel (not shown).
[0027] The control device 8 is configured to determine a theoretical steering angle 11 depending on the actual steering wheel angle 6 and / or the actual hand torque detected by means of the sensors 5 and to control (or regulate) the steering transmission mechanism 7 corresponding to the theoretical steering angle 11.
[0028] The control device 8 is furthermore set up to recognize an understeer situation starting from at least one understeer indicator 30, set the actual steering angle 12 present at the time of recognition as the reference steering angle 13, and match the theoretical steering angle 11 requested by changing the actual steering wheel angle 6 and higher than the reference steering angle 13 according to a preset characteristic curve 14 that depends in particular on the reference steering angle. The understeer indicator 30 is provided to the control device 8 by the vehicle controller, for example.
[0029] The steering wheel module 2 furthermore has in particular an actuator 15, wherein the control device 8 is furthermore set up to determine a feedback torque 16 at the steering handle 4 starting from the actual steering angle 12 and to control the actuator 15 thereby.
[0030] Figure 2 A schematic view of an exemplary characteristic curve 14 is shown. The (actual) steering wheel angle 6 is shown on the x-axis in a linear scale in each case, and the (theoretical) steering angle 11 is shown on the y-axis. In particular, it is set up that the control device 8 determines the (theoretical) steering angle 11 starting from the (actual) steering wheel angle 6 with the aid of the characteristic curve 14. The characteristic curve 14 has in particular three ranges: a normal range 20, a transition range 21, and a limit range 22. In the normal range 20, the (theoretical) steering angle 11 is determined starting from the (actual) steering wheel angle 6 according to a linear relationship. The transition range 21 is located between the normal range 20 and the limit range 22. The transition range 21 starts at the reference steering angle 13, that is to say starting from the following (actual) steering angle from which oversteer is confirmed. In the transition range 21, for example with the aid of a suitable polynomial function, the slope depending on the (actual) steering wheel angle 6 is matched to the slope in the limit range 22. In the limit range 22, the relationship between the (actual) steering wheel angle 6 and the (theoretical) steering angle 11 is again linear, wherein the slope is much smaller than in the normal range. Once an understeer situation is recognized, that is to say starting from the reference steering angle 13 set then, all (theoretical) steering angles 11 higher than the reference steering angle 13 are matched to the characteristic curve 14. In particular, it is set up here that if there are different reference steering angles 13, the characteristic curve 14 above the reference steering angle 13 is shifted accordingly.
[0031] If understeer is no longer recognized, the relationship between the (actual) steering wheel angle 6 and the (theoretical) steering angle 11 again follows the characteristic curve 14 in the normal range 20, wherein the transition from the limit range 22 back to the normal range 21 is again carried out according to the characteristic curve 14 in the transition range 21.
[0032] It can be set such that the characteristic curve 14 can be parameterized at least for the transition range 21. For example, the width of the transition range 21 and / or the shape of the characteristic curve 14 in the transition range 21, such as the curvature, can be adjusted. For example, a polynomial function or other suitable function can be used here. Additionally, it can be set such that the characteristic curve 14 can also be parameterized in the limit range 22. For example, it can be set that the slope of the characteristic curve 14 in the limit range 22 can be adjusted.
[0033] It can be set that the characteristic curve 14 is selected or parameterized taking into account the speed of the vehicle and / or the friction value and / or the value of the at least one understeer indicator 30 ( Figure 1 ), or is selected or parameterized. For example, the slope and / or the curvature can be selected or parameterized.
[0034] It can be set that the threshold value (from which understeer is confirmed) is determined or is determined taking into account the speed of the vehicle and / or the friction value. This is achieved, for example, by means of the control device 8, which obtains the variables mentioned above, for example, in a manner transmitted from the vehicle controller.
[0035] It can be set that the at least one understeer indicator 30 is a continuous indicator proportional to the intensity of understeer.
[0036] It can be set that the at least one understeer indicator 30 is determined or is determined by comparing the theoretical yaw rate and the actual yaw rate of the vehicle. For this purpose, for example, the vehicle controller forms the difference between the theoretical yaw rate and the actual yaw rate and transmits this difference as the understeer indicator 30 to the control device 8. Then, the control device 8 compares this difference with a preset threshold value, and if it is higher than this threshold value, an understeer situation is confirmed. However, the difference can also be determined by the control device 8.
[0037] It can be set that the at least one understeer indicator 30 is determined starting from the lateral force acting on the front wheels of the vehicle. For this purpose, for example, the change in the lateral force is determined depending on the change in the (actual) steering angle 12. If the (actual) steering angle 12 changes, but the lateral force remains constant, an understeer situation is confirmed. For example, this can be done by means of the control device 8.
[0038] It can be set that the at least one understeer indicator 30 is determined starting from the actual lateral acceleration. For this purpose, for example, the change in the lateral acceleration is determined depending on the change in the (actual) steering angle 12. If the (actual) steering angle 12 changes, but the lateral acceleration remains constant, an understeer situation is confirmed. For example, this can be done by means of the control device 8.
[0039] It can be set that the steering system 1 is a rear-wheel steering system 23, or additionally includes a rear-wheel steering system established in the same way.
[0040] The implementation of the method results from the implementation of the described steering system.
[0041] List of reference numerals
[0042] 1 Steering system
[0043] 2 Steering wheel module
[0044] 3 Steering module
[0045] 4 Steering handle
[0046] 5 Sensor
[0047] 6 (Actual) steering wheel angle
[0048] 7 Steering linkage
[0049] 8 Control device
[0050] 9 Motor
[0051] 10 Rack
[0052] 11 (Theoretical) steering angle
[0053] 12 (Actual) steering angle
[0054] 13 Reference steering angle
[0055] 14 Characteristic curve
[0056] 15 Actuator
[0057] 16 Feedback torque
[0058] 20 Normal range
[0059] 21 Transition range
[0060] 22 Limit range
[0061] 23 Rear-wheel steering system
[0062] 30 Understeer indicator
Claims
1. A mechanical decoupling steering system (1) for a vehicle, comprising: Steering handle (4), Steering transmission mechanism (7), and Control device (8), wherein at least one sensor (5) is arranged at the steering handle (4) for detecting the steering wheel angle (6) and / or the hand torque at the steering handle (4), wherein the steering transmission mechanism (7) has at least one electric motor (9) which is coupled to a rack (10), wherein the control device (8) is configured to determine a theoretical steering angle (11) depending on the actual steering wheel angle (6) and / or the actual hand torque detected by means of the at least one sensor (5) and to control the steering transmission mechanism (7), and wherein the control device (8) is furthermore configured to identify an understeer situation starting from at least one understeer index (30), to set the actual steering angle (12) present at the time of identification as a reference steering angle (13), and to adapt the theoretical steering angle (11) requested by changing the actual steering wheel angle (6) and being higher than the reference steering angle (13) according to a preset characteristic curve (14).
2. The steering system (1) according to claim 1, characterized in that The characteristic curve (14) has at least one transition range (21) and a limit range (22), wherein the transition range (21) is located between the reference steering angle (13) and the limit range (22).
3. The steering system (1) according to claim 2, characterized in that The characteristic curve (14) can be parameterized at least for the transition range (21).
4. The steering system (1) according to any one of the preceding claims, characterized in that The characteristic curve (14) is selected or parameterized taking into account the speed of the vehicle and / or the friction value and / or the value of the at least one understeer index (30).
5. The steering system (1) according to any one of the preceding claims, characterized in that A threshold value is defined taking into account the speed of the vehicle and / or the friction value, starting from which understeer is confirmed.
6. The steering system (1) according to any one of the preceding claims, characterized in that The at least one understeer index (30) is a continuous index proportional to the intensity of understeer.
7. The steering system (1) according to any one of the preceding claims, characterized in that The at least one understeer index (30) is determined starting from a comparison between the theoretical yaw rate and the actual yaw rate of the vehicle.
8. The steering system (1) according to any one of the preceding claims, characterized in that The at least one understeer index (30) is determined starting from the lateral force acting on the front wheels of the vehicle and / or starting from the actual lateral acceleration.
9. The steering system (1) according to any one of the preceding claims, characterized in that The steering system (1) is a rear-wheel steering system (23), or additionally includes a rear-wheel steering system (23) configured in the same way.
10. A method for operating a mechanical decoupling steering system (1) for a vehicle, wherein the steering system comprises a steering handle (4), a steering transmission mechanism (7) and a control device (8), wherein the steering handle (4) has at least one sensor (5) for detecting a steering wheel angle (6) and / or a hand torque at the steering handle (4), and wherein the steering transmission mechanism (7) has at least one electric motor (8) which is coupled to a rack (10). Wherein, The theoretical steering angle (11) is determined depending on the actual steering wheel angle (6) and / or the actual hand torque detected by means of the at least one sensor (5), and the steering transmission mechanism (7) is controlled by means of the control device (8), and an understeer situation is identified starting from at least one understeer index (30), wherein the actual steering angle (12) present at the time of identification is set as the reference steering angle (13), and the theoretical steering angle (11) requested by changing the actual steering wheel angle (6) and being higher than the reference steering angle (13) is adapted according to a preset characteristic curve (14).