Method for force feedback system for a steering device

Abstract

The invention relates to a method (1) for a force feedback system for a steering device, in particular a steer-by-wire steering device, of a vehicle, wherein the force feedback system comprises at least one brake unit and one drive unit, wherein the method (1) comprises the following steps: receiving a steering angle (LW) and at least one vehicle operating parameter (P_FZ); determining a target total torque (M_Soll) for the force feedback system based on the received steering angle (LW) and the at least one received vehicle operating parameter (P_FZ); determining a first target partial torque (TM1_Soll) for a brake unit and the drive unit, based on a characteristic map (KF_TM1);and determining a second target partial torque (TM2_target) for the other from the brake unit and the drive unit, such that a sum of the first target partial torque (TM1_target) and the second target partial torque (TM2_target) substantially corresponds to the target total torque (M_target).

Description

[0001] The present invention relates to a method for a force feedback system for a steering device, in particular a steer-by-wire steering device of a vehicle. State of the art

[0002] Nowadays, both mechanical steering systems and steer-by-wire systems are common. These systems can be divided into two subsystems: the steering shaft system with a steering element, such as a steering wheel, also known as a "Hand Wheel Actuator" (HWA) system, and the steering actuator system for steering the wheels, also known as a "Road Wheel Actuator" (RWA) system. In mechanical steering systems, these two subsystems are mechanically connected via the steering column and, if applicable, a steering gear. Thus, the two subsystems are directly, physically, connected in mechanical steering systems. With these mechanical steering systems, a user or operator always experiences a perceptible response, known as force feedback, in the form of noticeable resistance at the steering element, especially when cornering, encountering curbs, etc.

[0003] In steer-by-wire systems, the mechanical connection between the two subsystems via the steering column is eliminated. Instead, the steering of the wheels, corresponding to a movement of the steering element, is controlled by the transmission of corresponding signals between the two subsystems, HWA (heading and rear steering). In other words, steer-by-wire systems replace the physical steering column, which transmits the "input signals" or driver inputs from the steering wheel directly to the wheel via the steering gear, tie rod, and wheel carrier, with an electrically redundant "by-wire" system, i.e., signal transmission via cable. Conversely, just as the signals are transmitted from the driver to the wheels, the driver also needs information or feedback, the so-called force feedback, from the wheels to the steering wheel. Force feedback actuators are currently commonly used for this purpose, to make the (steering) return torques perceptible to the driver via the steering element on a mechatronic basis.

[0004] The force feedback actuators are integrated into the steering shaft subsystem, i.e., the HWA system, whereby the actuators currently typically comprise a drive unit, in particular an electric motor, and a brake unit, which are electronically controlled according to the desired force feedback, see e.g.

[0005] EP 1 211 159 A. WO 2021 / 048254 A1 discloses a control of the force feedback actuator depending on predetermined vehicle states, such as speed, acceleration, wheel steering angle, etc. Alternatively, as disclosed, for example, by WO 2022 / 170050 A1, the functions requesting feedback are rigidly linked to one or the other implementing component, i.e., the drive unit or the brake unit. This means that, for example, a return function to the neutral position of the steering element and / or warning functions are only linked to or implemented by the drive unit, and, for example, a basic friction function and / or an end-stop function are only linked to or implemented by the brake unit.

[0006] Furthermore, it is known to control the drive unit and the brake unit of the force feedback actuator depending on the current operating point of the force feedback actuator, i.e., depending on a rotational speed and a torque. The following operating ranges are distinguished: a motor operating range, in which the actuator is in the operating range of the drive unit, for example, when the current direction of rotation of the steering element and the desired force feedback torque are in the same direction; and a generator operating range, in which the actuator is in the operating range of the brake unit, for example, when the desired force feedback torque opposes the current direction of rotation of the steering element. That is, in the motor operating range, the desired force feedback torque is generated solely by the drive unit, and in the generator operating range, the desired force feedback torque is generated solely by the brake unit.

[0007] It has now become apparent that there is a further need to improve a known method for a force feedback system for a steering device, in particular a steer-by-wire steering device, of a vehicle. Specifically, there is a further need to provide a method for a force feedback system that allows for a variable, especially situational, distribution of the desired force feedback torque between the drive unit and the brake unit.

[0008] Against this background, it is an object of the present invention to provide an improved method for a force feedback system for a steering device, in particular a steer-by-wire steering device, of a vehicle, which in particular enables a variable, especially situational, distribution for generating the desired force feedback moment between the drive unit and the brake unit. Disclosure of the invention

[0009] These and other problems, which will be mentioned in the following description or which can be recognized by a person skilled in the art, are solved by the subject matter of the independent claim. Advantageous embodiments and further developments can be found in the dependent claims and the following description.

[0010] The inventive method for a force feedback system for a steering device, in particular a steer-by-wire steering device, of a vehicle, wherein the force feedback system comprises at least one brake unit, in particular a controllable brake unit, and a drive unit, has the following steps: Receiving a steering angle and at least one vehicle operating parameter, in particular several vehicle operating parameters; Determining a target total torque for the force feedback system based on the received steering angle and at least one received vehicle operating parameter; Determining a first target partial torque for a brake unit and a drive unit, based on a characteristic map; and Determining a second target partial torque for the other of the brake unit and the drive unit, such that the sum of the first target partial torque and the second target partial torque essentially corresponds to the target total torque.

[0011] The target total torque for the force feedback system corresponds to the total feedback torque that the system is intended to provide. This total feedback torque, and therefore the target total torque, is signed and dependent on the steering angle as well as at least one other vehicle operating parameter or variable, such as vehicle speed, temperature (especially ambient temperature), acceleration, etc. The steering angle is defined here as the rotation angle of a steering element, such as a steering wheel. Thus, the target total torque can be said to be generated as a weighted sum of several contributions resulting from the steering angle or the at least one vehicle operating parameter. The steering angle of the steering element can also be referred to as the steering element angle or steering wheel angle and is typically measured using a sensor, particularly a rotation sensor.

[0012] The sum of the first target torque and the second target torque essentially equals the total target torque. It is possible that either the first or the second target torque is essentially zero or approximately zero.

[0013] The first target torque component is generated or applied by either the brake unit or the drive unit. The second target torque component is then generated or applied by the other unit. This means that if the first target torque component is intended to be applied by the brake unit, the second target torque component is intended to be applied by the drive unit, and vice versa. The target torque component to be generated by the brake unit can also be referred to as the target braking torque. The target torque component to be generated by the drive unit can also be referred to as the target drive torque.

[0014] The advantage of the solution according to the invention lies particularly in the fact that the method makes it possible to provide variability for the force feedback depending on the respective, especially current, driving situation of the vehicle. This variability not only allows for the coverage of a maximum torque range, but also enables driving situation-dependent and / or vehicle-situation-dependent characteristics, such as the generation of force feedback that conveys a sticky feeling or a force feedback that conveys an elastic feeling. It can therefore be said that the method enables the generation of "live" force feedback, particularly without the integration of additional components. Furthermore, the method allows the integration of additional functions, such as a run-flat and / or backup function, if the brake unit and / or the drive unit of the force feedback system fails, at least partially.

[0015] In other words, the inventive method does not involve a rigid allocation to the drive unit or brake unit based on the demand source or operating range, but rather enables a flexible allocation to the brake unit and the drive unit that is dependent on the driving situation and / or the vehicle situation, thus also allowing mutual support between the brake unit and the drive unit. The method therefore enables a situational distribution of the total feedback torque or the target total torque between the brake unit and the drive unit. This distribution can be fixed or variable, depending on the specific driving situation.

[0016] A "living" force feedback describes force feedback that the driver can feel and that comes as close as possible to the force feedback generated by the conventional, mechanical connection between the steering element and the wheels being steered. This is achieved by implementing a gradual transition, via a transition range, between a generator-based operating range, in which the target total torque is generated predominantly or essentially exclusively by the brake unit, and a motor-based operating range, in which the target total torque is generated predominantly or essentially exclusively by the drive unit.

[0017] For example, if the total target torque is applied solely by the brake unit, the force feedback is often perceived by the driver as frictional or dull. Additionally, abrupt transitions between the regenerative and motor operating ranges are frequently noticeable to the driver, partly due to differing response times between the brake and drive units in generating the corresponding feedback torque. For instance, during an abrupt transition from the regenerative to the motor operating range, the driver may experience an undesirable tendency to stick before the drive unit has built up the desired feedback torque. The degree to which these phenomena are more or less pronounced depends on the available control quality of the brake and drive units.The method according to the invention enables a less abrupt transition between the operating ranges, thereby making the steering feel resulting from the force feedback more dynamic for the driver.

[0018] The braking unit, which is particularly controllable, is designed as a magnetorheological brake, such as a brake using magnetorheological powder (MRP brake) and / or a brake using magnetorheological fluid (MRF brake). Magnetorheological brakes enable a very smooth torque without ripple, meaning essentially without fluctuations. Furthermore, a certain degree of friction in the steering feel, which is desirable to improve or make the steering feel more authentic for the driver, can be particularly well implemented with such brakes. The drive unit is designed as a motor-driven drive unit, for example, an electric motor. Thus, unlike the braking unit, the drive unit can cover both the generator and motor operating ranges.

[0019] It can therefore be said that the method according to the invention makes it possible to improve the steering feel for the driver. Furthermore, the method allows the drive unit and the brake unit to be used in such a way that the respective advantages and disadvantages of the drive unit and the brake unit are combined and balanced for generating force feedback. This is particularly relevant for small steering movements, i.e., small steering angles, since the driver is especially sensitive to force feedback in these situations. Moreover, switching between the generator and motor operating ranges occurs particularly frequently during small steering movements.

[0020] According to one embodiment, the characteristic map of the first target partial torque is defined as the first characteristic map dimension as a function of the target total torque and as the second characteristic map dimension as a function of a steering-related intermediate parameter.

[0021] The steering-related intermediate parameter can, for example, be a signed steering speed. Using the characteristic map, it is possible to implement logic that takes into account that the brake unit cannot generate motor torques. Motor torques are those torques whose direction coincides with the direction of rotational speed. The motor torques thus lie within the motor operating range. Furthermore, the use of a characteristic map particularly enables the implementation of continuous transitions and / or limits between the motor operating range and the generator operating range.

[0022] According to one embodiment, determining a first target partial torque for a brake unit and a drive unit, based on a characteristic map, further includes: Updating the first target partial torque based on a received malfunction test signal.

[0023] The fault test signal contains information about the functional status of at least one of the brake unit and one of the drive unit. In other words, updating the first target partial torque based on the received fault test signal allows the operational readiness of at least one of the brake unit and one of the drive unit to be taken into account. This makes it possible, for example, to compensate for the failure of one of the brake unit and one of the drive unit by the other, thus ensuring that the target total torque can be achieved as far as possible even during the failure of one of the units (e.g., the brake unit cannot generate any motor torque in the event of a drive unit failure).

[0024] According to one embodiment, the malfunction test signal has at least a first value indicating a malfunction of the drive unit, and / or a second value indicating a malfunction of the brake unit, and / or a third value indicating normal function of the brake unit and the drive unit.

[0025] When the fault test signal displays the first value, indicating a malfunction of the drive unit, the drive torque (the partial torque to be applied by the drive unit) is set to zero. Therefore, the brake torque (the partial torque to be applied by the brake unit) is equal to the target total torque when the fault test signal displays the first value. This means that when the fault test signal displays the first value, the target total torque is applied almost exclusively by the brake unit. It is important to note that the brake torque can only compensate for the regenerative torques generated by the drive unit, not the motor torques.

[0026] If the malfunction test signal shows the second value, indicating a malfunction of the brake unit, the brake component torque is set to a predetermined substitute value. This predetermined substitute value corresponds approximately to the basic drag torque of the brake unit, which is generated, for example, by bearings, seals, and possibly preset by additional devices such as the basic clamping force. It is typically between approximately 0 Nm and 4 Nm, and furthermore specifically between approximately 0.5 Nm and 3 Nm. Thus, the drive component torque corresponds approximately to the target total torque minus the substitute value. This means that if the malfunction test signal shows the second value, the target total torque is applied predominantly, and in particular almost exclusively, by the drive unit.

[0027] If the malfunction test signal shows the third value, no malfunction of the brake unit or the drive unit has been detected, and the target partial torque can be divided between the first target partial torque and the second target partial torque according to the characteristic map.

[0028] Furthermore, it is conceivable to consider the nature and consequences of the detected malfunction, such as a partial failure, etc., by allowing the malfunction test signal to assume additional values. For this purpose, methods for detecting cable breaks, short circuits, implausible or missing data messages, error filtering (i.e., multiple occurrences of the error), and / or a delayed return to normal operation can be used.

[0029] Furthermore, it is conceivable to use symmetrical or asymmetrical redundancies, for example, in sensors, actuators, storage units, and / or processing units, whereby the method can be executed at least partially, and in particular completely, using these redundancies. This can increase or improve the functional reliability of the force feedback system.

[0030] According to one embodiment, the first target partial torque is set essentially equal to the total target torque when the malfunction test signal is set to the first value, and / or the first target partial torque is set essentially equal to a substitute value when the malfunction test signal is set to the second value, and / or the first target partial torque remains essentially unchanged when the malfunction test signal is set to the third value. Thus, the first target partial torque here corresponds to the braking partial torque, i.e., the partial torque applied by the brake unit.

[0031] Alternatively, if the first target partial torque corresponds to the drive partial torque, i.e., the partial torque applied by the drive unit, the first target partial torque is set to zero when the fault test signal has the first value. If the fault test signal is set to the second value, the first target partial torque is set to the target total torque less the substitute value, particularly a predetermined one. If the fault test signal has the third value, the first target partial torque essentially corresponds to the predetermined value. This means that the first target partial torque remains essentially unchanged in this case.

[0032] According to one embodiment, the characteristic map is a, in particular predetermined or predefined, torque characteristic map or a, in particular predetermined or predefined, torque factor characteristic map.

[0033] In the torque map, the values ​​of the first target partial torque can be determined as a function of the first and second map dimensions. The torque factor map contains torque factors, e.g., in percent (%), which can be determined as a function of the first and second map dimensions. Based on the torque factor determined in this way, the value of the torque, in particular the first target partial torque, is then determined in the subsequent part of the process. For this purpose, at least one multiplication block can be provided.

[0034] In particular, the characteristic map is predefined and therefore customizable. This allows the logic and / or quantitative values ​​implemented in the map to be individually adjusted, enabling the map to be defined for different driving modes, such as Eco mode, Sport mode, etc., and / or for different vehicle types, such as sports cars, commercial vehicles, and so-called "family cars." Furthermore, the logic that prevents the brake unit from generating motor torque can be implemented during the map definition. Motor torque refers to torque that generates positive power. The direction of motor torque corresponds to the direction of the steering element's rotational speed. Generator torque refers to torque that generates negative power. The direction of generator torque is opposite to the direction of the steering element's rotational speed.Regenerative moments can be generated by both the brake unit and the drive unit.

[0035] According to one embodiment, the method further comprises: Synchronizing transient curves (e.g., curves during step changes) of the first target partial torque and the second target partial torque.

[0036] Synchronizing transient responses, such as those occurring during abrupt changes, allows the two target torque values ​​to be adjusted so that the corresponding actual torque values ​​applied by the brake unit and the drive unit are applied essentially simultaneously, even if the drive unit and brake unit have different "reaction times." This means, for example, that the target torque value of the "slower" unit is deliberately increased during changes, for instance, by adding a so-called derivative (D) component. This accelerates the behavior of the slower unit so that the actual torque values ​​of both units are applied at similar speeds. Alternatively, or additionally, it is conceivable to deliberately slow down the "faster" unit, for example, by low-pass filtering a command signal. This synchronization of transient responses...This transient adjustment is particularly important to prevent temporary over-torques or under-torques from occurring during a change, i.e., a change of operation, especially an abrupt change; from one unit to another, i.e., when switching from the brake unit to the drive unit or vice versa, which distort or worsen the driving feel perceived by the driver.

[0037] According to one embodiment, the intermediate parameter is a steering speed, particularly one with a sign. Alternatively, other intermediate parameters, such as a steering wheel angle, are also conceivable. The steering speed, in particular, allows for a simple determination of the operating range of the brake unit, since this is defined as a function of the steering speed.

[0038] According to one embodiment, the intermediate parameter is determined based on a second characteristic map, which is configured to further determine the intermediate parameter as a function of driving dynamics parameters, e.g., a steering angle dependency of static friction, a speed dependency, etc. This allows the intermediate parameter to be adapted to different driving modes, such as Eco mode, Sport mode, etc., and / or different vehicle types, such as commercial vehicles, sports cars, etc. For example, a value of the steering angle used as an intermediate parameter can be specified as a function of static friction and / or speed.

[0039] According to one embodiment, the method further comprises: Outputting an initial control signal to the brake unit, and Outputting a second control signal to the control unit, wherein the first control signal corresponds to one of the first target partial torque and the second target partial torque for the brake unit, and the second control signal corresponds to the other of the first target partial torque and the second target partial torque for the drive unit.

[0040] According to one embodiment, the method further comprises: Generating / applying, by the brake unit, a target braking torque based on the first control signal, and Generating / applying, by the drive unit, a target drive torque based on the second control signal.

[0041] The target braking torque essentially corresponds to either the first target partial torque or the second target partial torque. The target driving torque essentially corresponds to the other half of the first target partial torque and the second target partial torque. This means, for example, if the first target partial torque corresponds to the target braking torque, then the second target partial torque corresponds to the target driving torque, and vice versa. Consequently, since the sum of the first target partial torque and the second target partial torque equals the target total torque, the sum of the target braking torque and the target driving torque also equals the target total torque.

[0042] According to one embodiment, particularly in a full steering lock range, i.e., a steering angle range greater than +90° or less than -90°, the target drive torque is less than or equal to 20% of the target total torque, and the target braking torque is equal to or greater than 80% of the target total torque. According to another embodiment, the target drive torque is approximately 6% of the target total torque, and the target braking torque is approximately 94% of the target total torque.

[0043] According to one embodiment, particularly in the case of a one-sided steering lock, e.g., in a steering angle range of approximately ±600°, and especially in a steering angle range of approximately ±500°, the target drive torque is approximately 50% of the target total torque, and the target braking torque is approximately 50% of the target total torque. Furthermore, this distribution of the target total torque also applies regardless of the steering angle range in the event of steering lock-up, e.g., when steering against a curb.

[0044] Simulating a one-sided steering stop is particularly advantageous for driving scenarios such as variable end stops or curb stops. With a one-sided stop, the steering element should lock or resist rotation in one direction, while remaining freely rotatable in the other. To achieve this, the target braking torque and the target drive torque are increased equally. In the direction of the stop, i.e., the direction of rotation to be blocked, both the drive unit and the brake unit generate a torque that acts as a resistance torque against the steering element's rotation in that direction. In the opposite direction, i.e., the direction of rotation not to be blocked, the torques of the drive unit and the brake unit essentially cancel each other out, allowing the steering element to rotate in that direction.Implementing a one-sided stop with essentially constant target partial torques for the drive unit and the brake unit, which can also be kept constant when the direction of rotation is reversed, makes it possible to reduce the requirements for control performance and / or sensors to simulate the one-sided stop. This allows for the use of simpler, and therefore less expensive, control and / or sensor components, thus reducing costs.

[0045] According to one embodiment, the target drive torque in a central steering range, i.e., in a steering angle range of approximately -20° to approximately +20°, particularly in a steering angle range of approximately -10° to approximately +10°, is equal to or greater than 50% of the target total torque, and the target braking torque is less than or equal to 50% of the target total torque, and the target total torque is approximately 0 Nm to approximately 1 Nm, particularly approximately 0 Nm to approximately 0.5 Nm, for a steering angle of approximately 0°. This can improve the steering feel, especially when driving straight ahead.

[0046] According to one embodiment, the target drive torque in a central steering range, i.e., in a steering angle range of approximately -20° to approximately +20°, particularly in a steering angle range of approximately -10° to approximately +10°, is equal to or greater than 50% of the target total torque, and the target braking torque is equal to or less than 50% of the target total torque, and the target total torque is greater than zero, particularly approximately 0 Nm to approximately 1 Nm, for a steering angle of approximately 0°. When the target total torque is greater than zero for a steering angle of approximately 0°, a slight braking torque is always applied to the steering element. This slight braking torque can reduce or even eliminate oscillations of the steering element during driving. This can improve the positional accuracy of the steering element, particularly its ability to hold the steering element in a specific position, such as when driving straight ahead. Detailed description based on drawing

[0047] Further measures improving the invention are described in more detail below, together with a description of preferred embodiments of the invention, with reference to the figures. The figures show: Fig. 1 a schematic functional representation of a method for a force feedback system according to an embodiment of the invention, Fig. 2 a schematic representation of a characteristic map for determining the first target partial torque according to an embodiment of the invention, Fig. 3 a schematic diagram for the target partial torque distribution for the realization of a one-sided stop according to an embodiment of the invention, Fig. 4 schematic representations of a target partial torque distribution for realizing on-steer behavior according to two embodiments of the invention, Fig. 5 schematic representations of a target partial torque distribution for realizing on-steer behavior according to two embodiments of the invention, Fig. 6 a schematic functional representation of a method for a force feedback system according to an embodiment of the invention, and Fig. 7 A schematic detail view of a characteristic curve as described in Fig. The procedure shown in section 6 is used.

[0048] The figures are purely schematic and serve only to illustrate the invention. The same elements are identified by the same reference symbols.

[0049] Fig. Figure 1 schematically and exemplarily shows a functional representation of a method 1 for a force feedback system for a steering device of a vehicle according to an embodiment of the invention. The force feedback system (not shown) comprises at least one brake unit (not shown) and one drive unit (not shown). The method 1 is here exemplarily divided into several sub-areas I to VI, which can also be referred to as functional blocks I to VI, and which are described in more detail below.

[0050] Subsection I essentially serves to determine a value W_M_Soll for a target total torque M_Soll, which can also be referred to as the target feedback torque. The target total torque M_Soll corresponds to the total torque to be applied by the force feedback system, which is perceived by a driver at the steering mechanism as "steering feel." The value W_M_Soll of the target total torque M_Soll is determined based on a received steering angle LW and at least one, and in particular several, received vehicle operating parameters P_FZ. After the value W_M_Soll of the target total torque M_Soll has been determined, a first value W_TM1_Soll_KF for a first target partial torque TM1_Soll is determined in a subsequent step (subsection II) based on a characteristic map KF_TM1. The in Fig. Method 1 shown illustrates the operation of method 1 when the first target partial torque TM1_target corresponds to a target braking torque BM_target to be generated by the braking unit of the force feedback system.

[0051] The KF_TM1 characteristic map is a three-dimensional characteristic map (see Fig. 2), which defines the first value W_TM1_Soll_KF of the first target partial torque TM1_Soll as a function of two further characteristic map dimensions. The first of the two characteristic map dimensions can, for example, be the value W_M_Soll of the target total torque M_Soll, and the second of the two characteristic map dimensions can, for example, be a value W_P_Lenkung of a steering-related intermediate parameter P_Lenkung. This in Fig. The characteristic map shown, KF_TM1, is an example of a characteristic map KF_BM for determining the target braking torque BM_Soll. Alternatively, the characteristic map KF_TM1 can also be a characteristic map KF_AM for determining a target drive torque AM_Soll to be generated by the drive unit of the force feedback system, if the first target partial torque TM1_Soll is defined as the target drive torque AM_Soll to be generated by the drive unit.

[0052] With reference back to Fig. 1. Subsection III serves to update the first value W_TM1_Soll_KF of the first target partial torque TM1_Soll if a malfunction is detected in the drive unit or the brake unit. Therefore, subsection III can also be referred to as "emergency running logic". The emergency running logic is in Fig. 1. This is exemplified by a 3-way switch 2, where a middle position NO corresponds to normal operation in which no malfunction was detected. This means that no malfunction was detected for either the brake unit or the drive unit of the force feedback system. In normal operation, the predefined first value W_TM1_Soll_KF of the first target partial torque TM1_Soll does not need to be adjusted. This means that the value of the first target partial torque TM1_Soll remains unchanged. Thus, an updated second value W_TM1_Soll of the first target partial torque TM1_Soll after the 3-way switch 2 essentially corresponds to the first value W_TM1_Soll_KF of the first target partial torque TM1_Soll.

[0053] In the event that a malfunction, such as a broken cable, is detected in the drive unit, the 3-way switch 2 is switched to a first position F_AE, which corresponds to an initial emergency running mode in which a malfunction has been detected in the drive unit. In this initial emergency running mode, the drive unit does not accept any target partial torque due to the detected malfunction, which is why the target total torque M_Soll must be essentially entirely taken over by the brake unit. This means that in this initial emergency running mode, the first value W_TM1_Soll_KF of the first target partial torque TM1_Soll must be updated.The first value W_TM1_Soll_KF of the first target partial torque TM1_Soll is adjusted depending on whether the first target partial torque TM1_Soll is defined in procedure 1 as a target braking torque BM_Soll, i.e., a torque to be generated by the braking unit, or as a target drive torque AM_Soll, i.e., a torque to be generated by the drive unit. In the section... Fig. In the exemplary procedure shown in Figure 1, the first target partial torque TM1_target is assigned to the target braking torque BM_target. This means that the target braking torque BM_target, or an actual braking torque BM_actual, is determined based on the first target partial torque TM1_target. Thus, according to the procedure shown in Figure 1, the target braking torque BM_target is determined based on the target braking torque BM_target. Fig. In the exemplary embodiment of method 1 shown, the second value W_TM1_target of the first target partial torque TM1_target after the 3-way switch 2 in the event that a malfunction of the drive unit has been detected, is essentially the target total torque M_target.

[0054] In the event that a malfunction, such as a broken cable, is detected in the brake unit, the 3-way switch 2 is switched to a second position F_BE, which corresponds to a second emergency running mode in which a malfunction has been detected in the brake unit. In this second emergency running mode, the brake unit only applies a minimal target partial torque due to the detected malfunction. This corresponds to a substitute value W_BM_Ersatz, which is predefined. This means that in this second emergency running mode, the first value W_TM1_Soll_KF of the first target partial torque TM1_Soll must be updated. The first value W_TM1_Soll_KF of the first target partial torque TM1_Soll is adjusted depending on whether the first target partial torque TM1_Soll is defined in procedure 1 as the target braking torque BM_Soll or as the target drive torque AM_Soll.

[0055] The substitute value W_BM_substitute essentially corresponds to the natural or preset basic drag torque generated by the brake unit in the disengaged state. Specifically, the substitute value W_BM_substitute is approximately 0 Nm to approximately 4 Nm, and further specifically approximately 1 Nm to approximately 3 Nm.

[0056] In the event that the first target partial torque TM1_target is defined as the target braking torque BM_target, as exemplified in Fig. As shown in Figure 1, the second value W_TM1_Soll of the first target partial torque TM1_Soll after the 3-way switch 2 essentially corresponds to the substitute value W_BM_Ersatz.

[0057] The switching of the 3-way switch 2, or emergency running logic, is carried out by procedure 1, for example, based on a received malfunction test signal S_Prüf. The malfunction test signal S_Prüf can have, in particular, three different values ​​W_S_Prüf, of which a first value W1_S_Prüf indicates a malfunction of the drive unit, a second value W2_S_Prüf indicates a malfunction of the brake unit, and a third value W3_S_Prüf indicates normal operation, i.e., normal functioning of both the brake unit and the drive unit. The value W_S_Prüf of the malfunction test signal S_Prüf is initially set to the third value W3_S_Prüf and is changed accordingly, for example, after a detected fault has been "filtered." This means, for example, if...If a fault in the drive unit or brake unit is detected several times in succession, and it is not just a single measurement point, the value W_S_Prüf is set to either the first value W1_S_Prüf or the second value W2_S_Prüf, depending on the detected fault. Switching back to normal operation, i.e., a change in the value W_S_Prüf of the malfunction test signal from one of the values ​​W1_S_Prüf or W2_S_Prüf to the value W3_S_Prüf, is not only contingent on the absence of the fault, particularly after multiple occurrences, but also on the condition that the vehicle is in a safe situation, e.g., stationary and / or in the "P" (Park) position, and / or switched off, i.e., with the ignition switched off or deactivated.

[0058] Next, a second target partial moment TM2_target is determined (sub-area IV) such that the sum of the first target partial moment TM1_target and the second target partial moment TM2_target essentially corresponds to the target total moment M_target. More precisely, a value W_TM2_target for the second target partial moment TM2_target is determined such that the sum of the second value W_TM1_target of the first target partial moment TM1_target and the value W_TM2_target of the second target partial moment TM2_target essentially corresponds to a value W_M_target of the target total moment M_target. In the Fig. In the exemplary embodiment of method 1 shown in Figure 1, the second target partial torque TM2_target is defined as the target drive torque AM_target and is calculated in particular such that the sum of the two target partial torques TM1_target and TM2_target (also using the values ​​determined in the emergency running logic) corresponds to the target total torque M_target. This is shown in Figure 1. Fig. 1. This is implemented by way of example by determining the value W_TM2_Soll of the second target partial moment TM2_Soll as the difference between the value W_M_Soll of the target total moment M_Soll and the second value W_TM1_Soll of the first target partial moment TM1_Soll.

[0059] In the case or variant of procedure 1, in which the first target partial torque TM1_target is assigned to the target drive torque AM_target in procedure 1, i.e., the target drive torque AM_target or an actual drive torque AM_actual is determined based on the first target partial torque TM1_target, the paths in sub-areas III and IV would "swap places". This means that if the target drive torque AM_target is determined based on the characteristic map KF_TM1, the 3-way switch 2 is located in the Fig. The lower path, which according to this variation serves to determine the target braking torque BM_target, and the sum calculation performed in sub-area IV are located in such a variation in the one in Fig. 1 upper path and serves to determine the target drive torque AM_target.

[0060] In other words, regardless of whether the target braking torque BM_Soll or the target driving torque AM_Soll is determined based on the characteristic map FK_TM1, the 3-way switch 2 is always in the path for determining the target braking torque BM_Soll or the actual braking torque BM_Ist, and the target driving torque AM_Soll or the actual driving torque AM_Ist is always determined based on the sum calculation located in sub-area IV.

[0061] Subsection V serves to synchronize the different control times of the brake unit and the drive unit in order to achieve the most simultaneous application of the target braking torque BM_target and the target drive torque AM_target. Therefore, this section can also be referred to as the transient synchronization block. The synchronization of the two aforementioned torques is carried out in the Fig. The exemplary embodiment of method 1 shown in Figure 1 is implemented in the control path of the brake unit and serves to reduce, and in particular even substantially eliminate, hysteresis of the brake control, which can occur especially in magnetic brake units such as magnetorheological brake units. This can be achieved, for example, by superimposing a derivative component, i.e., a so-called targeted overshoot, on the control of the brake unit. According to the Fig. In the embodiment shown in Figure 1, assuming that the first target partial torque TM1_target is to be implemented by the brake unit, the target braking torque BM_target is calculated as the sum of a product of the first target partial torque TM1_target with a first constant K1 and a product of the first time derivative d / dt, a signal corresponding to the first target partial torque TM1_target, and a second constant K2, and is adjusted in time to the second target partial torque TM2_target, i.e., here the target drive torque AM_target, such that the two torques BM_target and AM_target are implemented essentially simultaneously.

[0062] Alternatively, it is also conceivable to consider the hysteresis of the brake unit in a model-based feedforward control system. Furthermore, it is also conceivable to connect control elements and / or regulators downstream of sub-section V, possibly using pulse width modulation (in Fig. 1 not shown), in particular to improve the control of inductive loads and / or to reduce deviations, so-called I-components.

[0063] Sub-section VI in Fig. Procedure 1 presents the possibility of determining the value W_P_Lenkung of the intermediate parameter P_Lenkung using a second characteristic map KF_P_Lenkung. Determining the value W_P_Lenkung of the intermediate parameter P_Lenkung as a function of a characteristic map makes it possible to consider further, additional dependencies, hereinafter also referred to as supplementary dependencies, in the further course of Procedure 1. For example, the value W_P_Lenkung can be determined as a function of vehicle dynamics parameters (not shown here) in order to generate, in particular when determining the value W_TM1_Soll_KF of the first target partial torque TM1_Soll, for example, a steering angle dependency of static friction, a speed dependency, etc.

[0064] Such additional dependencies in Method 1 are desirable, or even necessary, depending on the vehicle type. For example, by generating a steering angle dependency of the static friction, the so-called "on-center behavior"—that is, the behavior of the steering system when driving straight ahead—can be perceived by the driver as elastic rather than sliding. The speed dependency can, for instance, make steering the wheels when the vehicle is stationary feel more like the tires rubbing against the road surface than "just" like a counterforce. Furthermore, such a modified intermediate parameter P_steering can represent an increased or decreased steering speed when the vehicle is stationary or reversing, which, when evaluating the characteristic map KF_TM1 to determine the first target partial torque TM1_target, can, for example,a higher or a lower value W_TM1_Soll_KF results.

[0065] Method 1 thus enables the realization of a target total torque M_target through two separately controllable target partial torques TM1_target and TM2_target. Furthermore, Method 1 allows the target total torque M_target to be distributed proportionally and / or absolutely between the brake unit and the drive unit. In other words, Method 1 enables a variable, and in particular situation-dependent, distribution of the target total torque M_target between the two target partial torques TM1_target and TM2_target.

[0066] In particular, the target total torque M_target is distributed such that the drive unit typically handles at least approximately 6% of the target total torque M_target, and the brake unit typically handles a maximum of approximately 94% of the target total torque M_target, provided the direction of rotation of the target total torque M_target is correct. In other words, the target drive torque AM_target is typically at least 6% of the target total torque M_target, and the target brake torque BM_target is typically a maximum of approximately 94% of the target total torque M_target. This results in a more dynamic steering feel perceived by the driver. Additionally, a transition between the operating ranges, i.e., a regenerative operating range 4 (see Fig. 2) and a motor operating range 3 (see Fig. 2) less abruptly, since both the drive unit and the brake unit are capable of providing torque in the regenerative operating range. This also makes it possible to utilize the different operating mechanisms of the drive unit and the brake unit, especially with realistic control quality, for the steering feel, i.e., to generate an "elastic steering feel" or a "frictiony steering feel".

[0067] In motor operation, the total target torque M_target is fully delivered by the drive unit. While cogging torque, sensor resolution, and commutation can cause ripple in the torque generated by the drive unit, unlike the brake unit, the drive unit, which is typically an electric motor, does not suffer from static friction or sticking (the so-called "stick-in position"). Therefore, any ripple in the torque generated by the drive unit is negligible.

[0068] Fig. Figure 3 shows an example of the distribution of the two target partial torques TM1_target and TM2_target to simulate a one-sided stop in the steering feel for the driver. The one-sided stop is relevant for driving scenarios such as a variable end stop and / or a curb stop, i.e., when the wheels hit the curb. With the one-sided stop, the steering movement of the steering system should be blocked or encounter resistance in one direction of rotation, while steering movement should be freely possible in the other direction. To achieve this, the target drive torque AM_target and the target braking torque BM_target are... Fig. The torque is increased by 3 equal parts. In the direction of the one-sided stop, both the drive unit and the brake unit then generate a resistive torque against the direction of rotation to be blocked. In the opposite direction, the target drive torque AM_target and the target brake torque BM_target cancel each other out, thus allowing the direction of rotation opposite to the direction to be blocked. In other words, the one-sided stop blocks rotation of a steering element of the steering system in one direction and allows rotation in the opposite direction.

[0069] In particular, as in Fig. As shown in Figure 3, the target total torque for the one-sided stop, which can also be referred to as the target stop torque M_Endstop, is divided equally between the drive unit and the brake unit, so that the target drive torque AM_Target and the target brake torque BM_Target each amount to 50% of the target stop torque M_Endstop and are kept essentially constant for the simulation of the one-sided stop, particularly for both directions of rotation. This allows the requirements for control performance and sensors to be reduced, especially significantly.

[0070] Fig. 4 and Fig. Figure 5 shows schematic representations of a target partial torque distribution for realizing on-steer behavior according to various embodiments of the invention, wherein the in Fig. The embodiments shown in 4 exhibit a target total torque M_target of approximately zero for a steering angle LW of approximately 0°, and the ones in Fig. The embodiments shown in Figure 5 have a target total torque M_target of greater than zero for a steering angle LW of approximately 0°.

[0071] As explained above, the on-steer behavior serves in particular to improve the position of the steering element during straight-ahead driving and, in particular, to reduce vibrations or oscillations of the steering element in the straight-ahead position. For this purpose, it is conceivable that the target total torque M_target near the center position, i.e., in a steering angle range LW of approximately -20° to approximately +20°, is predominantly implemented by the drive unit, i.e., the target drive torque AM_target. In particular, it is conceivable that the target braking torque BM_target is significantly reduced in this range (see Fig. 4(a)) or even omit it entirely, i.e., switch off the brake unit completely (see Fig. 4(b)).

[0072] The in Fig. The exemplary embodiment shown in 5(a) is essentially the same as that shown in Fig. 4(a) shown, exemplary embodiment, and the embodiment shown in Fig. The exemplary embodiment shown in 5(b) corresponds to that shown in Fig. 4(b) shown. Exemplary embodiment, wherein according to the Fig. 5(a) and Fig. In the embodiments shown in 5(b), the target total torque M_target is always greater than zero. This makes it possible to always apply a low or slight feedback torque to the steering device, which makes it possible to further reduce or even eliminate the oscillations of the steering element and thereby improve the positional stability of the steering element, especially for straight-line driving.

[0073] Fig. 6 and Fig. Figure 7 shows an embodiment of method 1 which, instead of the characteristic map KF_TM1, uses a torque characteristic curve KL_AM. Taking into account the current operating range, which is defined as a function of the target total torque M_Soll and the current speed DZ, this curve determines the proportion of the target total torque M_Soll to be generated by the drive unit, i.e., the target drive torque AM_Soll. The characteristic curve KL_AM further smooths the transition between the motor operating range 3 and the generator operating range 4 by means of a blending effect.

[0074] During a transition 5 from the generator operating range 4 to the motor operating range 3, the target braking torque BM_Soll is controlled and continuously reduced before the generator operating range 4 is exited. Likewise, the target braking torque BM_Soll can be controlled and continuously increased once the generator operating range has been entered. These controlled, continuous transitions can also be implemented in the characteristic maps KF_TM1 and KF_P_Lenkung, respectively. According to the in Fig.In the exemplary embodiment of method 1 shown in Figure 6, the target drive torque AM_target is calculated as the product of the two input signals S_M_target and S_KL_AM, i.e., the target total torque M_target and the characteristic curve output, which can have a numerical value between 0 and 1. The target braking torque BM_target is calculated as the product of the two input signals S_M_target and S_Delta_KL_AM, i.e., the target total torque M_target and the difference between the numerical value 1 and the numerical value at the characteristic curve output.

[0075] Furthermore, although not explicitly shown in the figures, method 1 can also be used to divide the target total torque M_target into subfunctions. Individual generator-based subfunctions can be implemented, for example, by a combination of drive unit and brake unit. For instance, damping can be implemented partly by the brake unit and partly by the drive unit. Such a division can improve steering feel. Reference symbol list 1 Procedure 2 3-way switches 3 motor operating range 4 generator operating range 5 Transition M_Scope Target total moment TM1_Target first target partial torque TM2_Target second target partial torque BM_Spot Target braking torque BM_Ist Actual braking torque AM_Scope Target drive torque AM_Ist Actual Drive Torque M_Endstop Target stop torque LW steering angle DZ speed P_steering steering-related intermediate parameters P_FZ Vehicle operating parameters S_Test Malfunction Test Signal S_M_Soll signal regarding target total torque S_KL_AM signal at characteristic curve output S_Delta_KL_AM Differential signal KF map KF_TM1 Characteristic map of the first target partial torque KF_P_Steering Characteristic map of the steering-related intermediate parameter KF_BM characteristic map of the target braking torque KF_AM characteristic map of the target drive torque KL_AM_ Characteristic curve of the target drive torque W_M_Soll value of the target total moment W_TM1_Soll_KF first value of the first target partial torque W_TM1_Soll second value of the first setpoint partial torque W_TM2_Spot value of the second target partial torque W_BM_Ersatz Substitute value for the target braking torque W_S_Test Value of the malfunction test signal W_P_Steering Value of the steering-related intermediate parameter NO middle position F_AE first side position F_BE second side position I to VI Sub-area / Functional Block QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 1 211 159 A

[0005] WO 2021 / 048254 A1

[0005] WO 2022 / 170050 A1

[0005]

Claims

[1] Method (1) for a force feedback system for a steering device, in particular a steer-by-wire steering device, of a vehicle, wherein the force feedback system comprises at least one brake unit and one drive unit, wherein the method (1) comprises the following steps: Receiving a steering angle (LW) and at least one vehicle operating parameter (P_FZ); Determining a target total torque (M_Soll) for the force feedback system based on the received steering angle (LW) and the at least one received vehicle operating parameter (P_FZ); Determining a first target partial torque (TM1_Soll) for one of the brake unit and the drive unit, based on a characteristic map (KF_TM1); and Determining a second target partial torque (TM2_Soll) for the other of the brake unit and the drive unit, such that a sum of the first target partial torque (TM1_Soll) and the second target partial torque (TM2_Soll) substantially corresponds to the target total torque (M_Soll). [2] Method (1) according to claim 1, wherein the characteristic map (KF_TM1) of the first desired partial torque (Tm1_Soll) is defined as a function of the desired total torque (M_Soll) as a first characteristic map dimension and as a function of a steering-related intermediate parameter (P_Steering) as a second characteristic map dimension. [3] Method (1) according to claim 1 or 2, wherein determining a first target partial torque (TM1_Soll) for one of the brake unit and the drive unit based on a characteristic map (KF_TM1) further comprises: Updating the first target partial torque (TM1_Target) based on a received malfunction check signal (S_Check). [4] Method (1) according to claim 3, wherein the malfunction test signal (S_Prüf) has at least a first value (W1_S_Prüf) indicating a malfunction of the drive unit, and / or a second value (W2_S_Prüf) indicating a malfunction of the brake unit, and / or a third value (W3_S_Prüf) indicating a normal function of the brake unit and the drive unit. [5] Method (1) according to claim 4, wherein the first target partial torque (TM1_Soll) is set substantially equal to the target total torque (M_Soll) when the malfunction test signal (S_Prüf) is set to the first value (W1_S_Prüf), and / or wherein the first target partial torque (TM1_Soll) is set substantially equal to a substitute value (W_BM_Ersatz) when the malfunction test signal (S_Prüf) is set to the second value (W2_S_Prüf), and / or wherein the first target partial torque (TM1_Soll) is substantially unchanged when the malfunction test signal is set to the third value (W3_S_Prüf). [6] Method (1) according to one of claims 1 to 5, wherein the characteristic map (KF_TM1) is a torque characteristic map, or wherein the characteristic map (KF_TM1) is a torque factor characteristic map. [7] Method (1) according to one of claims 1 to 6, further comprising: Synchronizing transients of the first target partial torque and the second target partial torque. [8] Method (1) according to one of claims 2 to 7, wherein the steering-related intermediate parameter (P_Steering) is a steering speed. [9] Method (1) according to one of claims 2 to 7, wherein the steering-related intermediate parameter (P_Steering) is determined based on a second characteristic map (KF_P_Steering), wherein the second characteristic map (KF_P_Steering) is configured to further determine the intermediate parameter (P_Steering) as a function of driving dynamics parameters. [10] Method (1) according to one of claims 1 to 9, further comprising: Outputting a first control signal to the brake unit, and Outputting a second control signal to the control unit, wherein the first control signal corresponds to one of the first target partial torque (TM1_Soll) and the second target partial torque (TM2_Soll) for the brake unit, and the second control signal corresponds to the other of the first target partial torque (TM1_Soll) and the second target partial torque (TM2_Soll) for the drive unit. [11] Method (1) according to claim 10, further comprising: Generating, by the braking unit, a target braking torque (BM_Soll) based on the first control signal, and Generating, by the drive unit, a target drive torque (AM_Soll) based on the second control signal. [12] Method (1) according to claim 11, wherein for a steering angle (LW) of less than - 90° and / or greater than +90°, the desired drive torque (AM_Soll) is less than or equal to 20% of the desired total torque (M_Soll) and the desired braking torque (BM_Soll) is equal to or greater than ≥ 80% of the desired total torque (M_Soll). [13] Method (1) according to claim 12, wherein the desired drive torque (AM_Soll) is approximately 6% of the desired total torque, and the desired braking torque (BM_Soll) is approximately 94% of the desired total torque. [14] Method (1) according to one of claims 1 to 11, wherein, to represent a one-sided stop, the desired drive torque (AM_Soll) is approximately 50% of the desired total torque (M_Soll) and the desired braking torque (BM_Soll) is approximately 50% of the desired total torque (M_Soll). [15] Method (1) according to one of claims 1 to 14, wherein in a range of a steering angle (LW) of approximately -20° to approximately +20°, the desired drive torque (AM_Soll) is equal to or greater than 50% of the desired total torque (M_Soll) and the desired braking torque (BM_Soll) is equal to or less than 50% of the desired total torque (M_Soll), and wherein the desired total torque (M_Soll) for a steering angle (LW) of approximately 0° is approximately zero. [16] Method (1) according to one of claims 1 to 14, wherein in a range of a steering angle (LW) of approximately -20° to approximately +20°, the desired drive torque (AM_Soll) is equal to or greater than 50% of the desired total torque (M_Soll) and the desired braking torque (BM_Soll) is equal to or less than 50% of the desired total torque (M_Soll), and wherein the desired total torque (M_Soll) for a steering angle (LW) of approximately 0° is greater than zero.

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