Hybrides Steer-by-Wire-System

Abstract

The invention relates to a steer-by-wire system 1 for steering a motor vehicle. The steer-by-wire system 1 comprises two steering actuators 3, 5 for adjusting at least one steering angle of at least one wheel and / or at least one rigid axle of the motor vehicle. If one of the steering actuators 3, 5 fails, the motor vehicle can still be steered by the other steering actuator 3, 5. The steer-by-wire system 1 further comprises a control unit 7 for processing steering signals LS and controlling the steering actuators 3, 5 based on the steering signals LS. One of the steering actuators 3, 5 is of a first type, and the other of the steering actuators 3, 5 is of a second type, which differs from the first type.

Description

[0001] The invention relates to a steer-by-wire system according to the preamble of claim 1, a control device for a steer-by-wire system according to claim 12, and a method for adjusting at least one steering angle of at least one wheel of a motor vehicle by means of a steer-by-wire system according to claim 13.

[0002] Conventional steering systems for motor vehicles have a direct mechanical connection between the steering wheel and at least one wheel of the vehicle via the steering column and steering gear. For some time now, so-called "power steering" systems have also been used to assist the driver. These systems use a hydraulic or electric drive to reduce the effort required by the driver for steering. In the event of a power steering failure, the driver can still steer the vehicle, albeit with significantly more effort.

[0003] Steer-by-wire systems are steering systems for vehicles that lack a direct mechanical linkage. Steering inputs are detected and transmitted to a control unit in the form of (typically electrical) steering signals. Based on these signals, the control unit generates (typically electrical) control signals for a steering actuator, which performs a mechanical movement to adjust the steering angle.

[0004] Steer-by-wire systems offer several advantages over conventional steering systems. They allow for the implementation of dynamic steering, meaning steering systems where the relationship between the position of a steering input element—such as a steering wheel—and the steering angle is non-linear. Furthermore, the absence of a steering column reduces the risk of injury to the driver in the event of an accident. Additionally, the flexibility in the arrangement of steering input elements is increased. Steer-by-wire systems are particularly important for autonomous driving. Steering signals do not necessarily have to originate from a steering input element, but can be generated partially or even completely (i.e., no steering input element is required—Level 5 according to SAE J3016) by a computing unit for autonomous control.However, if a steer-by-wire system fails, the vehicle can no longer be steered due to the lack of mechanical coupling. To ensure safe operation, steer-by-wire systems are therefore designed with redundancy. Important components of a steer-by-wire system are duplicated or even multiplied, so that if one component fails, another component takes over its function.

[0005] For example, a steer-by-wire system can include two steering actuators or actuator systems, so that if one steering actuator or part of its actuator system (for example, a hydraulic pump) fails, the vehicle remains steerable.

[0006] A steer-by-wire system for a motor vehicle is disclosed, for example, in the generic WO 2017 / 198565 A1. The steer-by-wire system described therein has two steering actuators, each configured to adjust the steering angle of a steerable wheel. Steering electronics are configured to detect whether one of the steering actuators has failed. In this case, the steering electronics switch to emergency operation, in which the motor vehicle remains partially controllable by the second (functioning) steering actuator.

[0007] The steering actuators of the steer-by-wire system described in WO 2017 / 198565 A1 are electric actuators.

[0008] However, the applications of electric steering actuators are limited. Especially in larger vehicles, the required power output is so high that suitable electric steering actuators are very rarely used.

[0009] As an alternative, steer-by-wire systems are known from the state of the art, in which hydraulic steering actuators are used instead of electric steering actuators.

[0010] However, hydraulic systems, despite their advantages, have limited applicability. They are larger, exhibit higher latency, and are more complex. Furthermore, their efficiency is lower. Especially when using two independent hydraulic systems, the design requirements are very extensive, as all components, including the hydraulic pump, must be duplicated.

[0011] DE 10 2021 205 875 A1 describes a steering gear device with at least two actuators for transmitting torque to a steering gear of the steering gear device. The steering gear device can be designed as a redundant steer-by-wire system. The actuators of the respective actuators can differ in their dimensions.

[0012] In contrast, the object of the invention is to provide an improved steer-by-wire system that expands the handling of the system.

[0013] This problem is solved by a steer-by-wire system for steering a motor vehicle with the features of claim 1, by a control device for a steer-by-wire system according to claim 12 and by a method for adjusting at least one steering angle of at least one wheel of a motor vehicle by means of a steer-by-wire system according to claim 13.

[0014] The motor vehicle can be, for example, a passenger car, a truck, a tractor, or a combine harvester. In particular, the motor vehicle can be an agricultural machine. The motor vehicle can have, for example, two, three, four, or six wheels, some of which may be steerable. Optionally, the motor vehicle can also be designed so that all wheels are steerable.

[0015] Steering actuators are used to adjust the steering angle of a wheel. An actuator is a technical element that generates a mechanical movement in response to a control signal.

[0016] For the purposes of this application, two actuators belong to the same category if they utilize the same form of energy and are based on the same physical effect. Based on their category, one can, for example, distinguish between electrical, hydraulic, and pneumatic actuators.

[0017] Actuators of different types have different advantages and disadvantages. By combining actuators of different types, a complementary relationship exists between the steering actuators. In normal operation, i.e., as long as none of the steering actuators of different types has failed, the advantages of the different types can be combined and the disadvantages compensated for. This requires no additional effort, since two redundant systems are already provided for increased safety.

[0018] Since the steer-by-wire system has two or more steering actuators for adjusting at least one steering angle, if one steering actuator (or several, provided at least one continues to function correctly) fails, the affected actuator can be deactivated, and the steer-by-wire system remains functional with the correctly functioning actuator(s). The steer-by-wire system is therefore "fail-operational." This also applies in the event of a failure of an actuator system associated with a steering actuator (for example, a hydraulic system for a hydraulic steering actuator, which includes, in particular, a hydraulic pump and a hydraulic valve).

[0019] The steer-by-wire system can, in particular, comprise exactly one control unit. The at least one control unit is preferably an Electronic Control Unit (ECU). The control unit can, in particular, be programmable. It can include memory elements and a processor and / or a microcontroller. The control unit can also optionally include other electronic components, for example, a programmable logic module. The at least one control unit is preferably designed to be fail-safe, in particular, it can have a redundant design.

[0020] The steer-by-wire system can also include two or more control units. In this case, the control units are preferably designed to communicate with each other. In particular, the first type of steering actuator and the second type of steering actuator can each have a dedicated control unit.

[0021] Preferably, the steer-by-wire system comprises at least one steering input element for detecting steering inputs and generating corresponding steering signals. Preferably, the at least one steering input element is exactly one steering input element. In this case, the steering input element is intended for operation by the driver. However, the steer-by-wire system can also have, for example, two steering input elements, with the second steering input element being operable by a driving instructor. The at least one steering input element can be, for example, at least one steering wheel, at least one mini-steering wheel, and / or at least one joystick. In the case of multiple steering input elements, these can also be of different types. For example, the steer-by-wire system can comprise a first steering input element in the form of a joystick and a second steering input element in the form of a steering wheel.The at least one steering input element is preferably connected to the at least one control unit via redundant channels (digital and / or analog), so that the steer-by-wire system remains functional even if one of the channels fails.

[0022] The steering signals do not necessarily have to originate from a steering input device, but can be generated partially or even completely by a computing unit for autonomous control. Therefore, the vehicle itself does not need to have a steering input device.

[0023] Preferably, the steer-by-wire system can include a force feedback unit connected to the at least one steering input element. The haptic feedback (force feedback) allows the driver to feel the road conditions and the vehicle's response. Preferably, the force feedback incorporates state parameters from both the at least one steering actuator of the first type or its associated actuator system, and state parameters from the at least one steering actuator of the second type or its associated actuator system. For example, if the at least one steering actuator of the first type is a hydraulic steering actuator and the at least one steering actuator of the second type is an electric steering actuator, the force feedback can be generated based on both the pressure of the hydraulic system and the motor current. The combination of both sources can provide a more direct steering feel.

[0024] Signal transmission between the at least one steering input element and the at least one control unit, as well as between the at least one control unit and the steering actuators or an associated actuator system, preferably takes place using standardized communication protocols. One example is the CAN bus. Alternatively, communication can also be carried out via modulated PWM signals (with feedback).

[0025] Preferably, the at least one control unit can receive information from a variety of input sources via interfaces (especially of the type mentioned), in particular from radio remote controls and systems for teleoperated control as well as from environmental sensor kits.

[0026] The steer-by-wire system can in particular be designed in such a way that it is retrofittable, i.e., that a conventional steering system and / or a steer-by-wire system of a previously known type can be replaced by a steer-by-wire system according to the invention.

[0027] The at least one steering actuator of the first type and the at least one steering actuator of the second type preferably cause a change in the steering angle of the same wheel of the motor vehicle. The at least one steering actuator of the first type and the at least one steering actuator of the second type can, in particular, be active simultaneously, i.e., cause a change in the steering angle at the same time. However, the use of only one type at a given time is also possible. A combination of these approaches is also possible, i.e., a steering system in which, at some times, the at least one steering actuator of the first type and the at least one steering actuator of the second type are active simultaneously, while at other times only the at least one steering actuator of the first type or only the at least one steering actuator of the second type is active.

[0028] If steering actuators of both types are active simultaneously, they can be controlled in such a way that they affect the steering angle to varying degrees. Which type of steering actuator is active (or which is primarily controlled when both types are active) can depend on a number of factors, in particular the driving situation, the steering signals, the state of the steering actuators, the magnitude of deviations in the control loop, and / or the type of vehicle.

[0029] Preferably, steering actuators of one type are faster and / or more precise, while those of the other type provide higher actuating force. Higher actuating force, in particular, allows for greater changes in the steering angle within a given time. By combining steering actuators of both types, the steer-by-wire system offers the advantages of both; that is, it is not only fast and / or precise, but also provides high actuating force for setting at least one steering angle.

[0030] The steer-by-wire system preferably comprises at least one steering angle sensor connected to the at least one control unit, thus forming a control loop. Particularly preferably, it includes multiple steering angle sensors and / or at least one redundant sensor. This improves steering precision and makes the feedback to the at least one control unit more reliable. The at least one steering angle sensor is preferably integrated into the outer pivot joint or, in the case of an electric steering actuator, into the actuator itself. The pivot joint is the wheel's pivot point. This pivot joint connects the steering knuckle to the axle.

[0031] Finally, the at least one control device is preferably configured such that the pressure in a hydraulic system of a hydraulic steering actuator of the steer-by-wire system is limited, with the limit decreasing as the vehicle speed increases. The pressure is intended to decrease with increasing vehicle speed because higher steering angles must be implemented at higher speeds.

[0032] In one embodiment, at least one of the steering actuators is an electric steering actuator. Electric steering actuators, for example in the form of electric servo motors, are characterized by low latency and high precision. In particular, when using an electric steering actuator, the latency of the steer-by-wire system in the steering response can be low. This high accuracy is especially relevant for autonomous driving.

[0033] In one embodiment, at least one of the steering actuators is a hydraulic steering actuator. Hydraulic steering actuators are characterized by their high actuating force. High loads on the front axle (e.g., front loader operations in agriculture) necessitate high steering power. This can be provided by the hydraulic system. In the event of a defect in the hydraulic steering actuator or the associated hydraulic system, the hydraulic system can preferably be depressurized (for example, by means of the at least one control device), which prevents the steering mechanism from locking up.

[0034] In one embodiment, at least one of the steering actuators is a pneumatic steering actuator. Pneumatic steering actuators also have a relatively high actuating force. However, this is typically lower than that of hydraulic steering actuators. Pneumatic steering actuators are vibration-resistant, durable, maintenance-free, and, unlike electric drives, are made up of few components and are therefore hardly susceptible to malfunctions.

[0035] In one embodiment, at least one steering actuator is a hydraulic steering actuator and at least one other steering actuator is an electric steering actuator.

[0036] In one embodiment, at least one steering actuator is a pneumatic steering actuator and at least one other steering actuator is an electric steering actuator.

[0037] Alternatively, at least one of the steering actuators can be a hydraulic steering actuator and at least one other steering actuator can be a pneumatic steering actuator. In one embodiment, the steer-by-wire system additionally comprises at least one sensor for monitoring at least one of the steering actuators and / or an associated actuator system and providing a resulting sensor signal.

[0038] The at least one sensor can be used, in particular, to monitor the pressure and / or temperature of a hydraulic system of a hydraulic steering actuator. Alternatively or additionally, the at least one sensor can be used to monitor the power electronics of an electric steering actuator or the electric steering actuator itself (for example, it would then be a current or temperature sensor).

[0039] The sensor signal can then be used by the at least one control unit to deactivate the affected steering actuator or to preferentially use another steering actuator.

[0040] In one embodiment, the at least one control unit is configured to control the steering actuators in such a way that the ratio of the proportion in which the at least one steering actuator of the first type acts on the steering angle to the proportion in which the at least one steering actuator of the second type acts on the steering angle depends on the driving situation.

[0041] The driving situation is determined in particular by the speed and / or the road surface (which can be determined by a navigation system and / or suitable sensors) and / or by whether the vehicle is driving through a curve and its radius (which can also be determined, for example, by means of a navigation system and / or sensors, such as acceleration sensors).

[0042] Preferably, the first type of actuator is characterized by a higher actuating force, and the second type by a lower latency and / or higher precision. Preferably, at low speeds, the steering angle is adjusted predominantly or entirely by means of the at least one steering actuator of the first type, while at low speeds, steering is performed predominantly or entirely by means of the at least one steering actuator of the second type.

[0043] The speed limit typically depends on the type of motor vehicle. For agricultural machinery, this is preferably set at 40 km / h or 50 km / h.

[0044] The first type of actuator is preferably hydraulic, while the second type is electric. Hydraulic power is primarily used at low speeds, as steering precision is less critical at slower speeds.

[0045] Hydraulic power steering enables higher steering forces and larger angle changes, especially during maneuvering. At higher speeds, electric power steering is generally more dominant, as it typically reacts faster and allows for more precise adjustments, which is advantageous at higher speeds. Large steering angles and rapid changes in steering angle (as hydraulic power steering would allow) are typically undesirable at high speeds for safety reasons.

[0046] In one embodiment, the at least one control unit is configured to control the steering actuators in such a way that the ratio of the proportion in which the at least one steering actuator of the first type acts on the steering angle to the proportion in which the at least one steering actuator of the second type acts on the steering angle depends on the steering signals.

[0047] This embodiment can be combined with the aforementioned embodiment, i.e., the ratio of the proportion to which the at least one steering actuator of the first type acts on the steering angle to the proportion to which the at least one steering actuator of the second type acts on the steering angle can depend on both the driving situation and the steering signals. Preferably, the first type is characterized by a higher actuating force (for example, hydraulic steering actuators), and the second type by a lower latency and / or higher precision (for example, electric steering actuators).Preferably, in the case of steering signals representing a large change in the steering angle, the steering angle is adjusted predominantly or completely by the at least one steering actuator of the first type, whereas in the case of steering signals representing a small change in the steering angle, it is adjusted predominantly or completely by the at least one steering actuator of the second type.

[0048] For fine or minor steering maneuvers, electric power is particularly preferred, as it offers more precise control and faster response times. For significant steering movements or when rapid adjustments are required, hydraulic power is preferred.

[0049] In one embodiment, the steer-by-wire system additionally comprises at least one sensor for detecting at least one state parameter of the at least one steering actuator of the first type and / or an associated actuator system, wherein the at least one control unit is configured to control the steering actuators in such a way that the ratio of the proportion in which the at least one steering actuator of the first type acts on the steering angle to the proportion in which the at least one steering actuator of the second type acts on the steering angle depends on the detected value of the at least one state parameter.

[0050] The control unit can be designed, in particular, for load-dependent control. Specifically, steering actuators of the first type can have a higher actuating force than steering actuators of the second type. Preferably, under a low load, the steering angle is adjusted predominantly or entirely by the at least one steering actuator of the second type, while under a high load, the steering angle is adjusted predominantly or entirely by the at least one steering actuator of the first type. The state parameter can, in particular, be the motor current of an electric steering actuator. The motor current of the electric steering actuator (which responds first due to its low latency) is an indicator of the load.

[0051] In particular, low hydraulic assistance is possible under low load. Under high load (rapid and significant increases in motor current), however, high hydraulic assistance is preferred (since a high power demand is assumed).

[0052] In one embodiment, the steer-by-wire system additionally comprises at least one sensor for detecting at least one actual value of the at least one steering angle, wherein the at least one control unit is configured such that the ratio of the proportion in which the at least one steering actuator of the first type acts on the steering angle to the proportion in which the at least one steering actuator of the second type acts on the steering angle depends on a deviation of the actual value of the at least one steering angle from a corresponding setpoint.

[0053] In particular, steering actuators of the first type can exhibit a higher actuating force than steering actuators of the second type. In the case of strong or significant deviations of the actual value from the target value of the steering angle, at least one steering actuator of the first type (for example, at least one hydraulic steering actuator) is preferably used partially, particularly preferably predominantly, and most preferably completely, in order to achieve faster adaptation to the target value.

[0054] Preferably, the aforementioned embodiments can be combined. The ratio of the proportion in which the at least one steering actuator of the first type acts on the steering angle to the proportion in which the at least one steering actuator of the second type acts on the steering angle can therefore depend on the driving situation and / or on the steering signals and / or on the detected value of the at least one state parameter and / or on a deviation of the actual value of the at least one steering angle from a corresponding target value.

[0055] Another aspect of the invention relates to a control device for a steer-by-wire system, which is configured to receive steering signals and, on the basis of these steering signals, to control at least one steering actuator of a first type and at least one steering actuator of a second type, wherein the second type differs from the first type.

[0056] Preferably, the control device can be designed as described above in connection with the steer-by-wire system.

[0057] Another aspect of the invention relates to a method for adjusting at least one steering angle of at least one wheel of a motor vehicle by means of a steer-by-wire system, comprising the steps of: providing steering signals and controlling at least one steering actuator of a first type and at least one steering actuator of a second type based on the steering signals, wherein the second type differs from the first type.

[0058] Preferably, the method can be designed as described above in connection with the steer-by-wire system.

[0059] Further advantages of the invention will become apparent from the description and the drawing. Likewise, the features mentioned above and those listed below can be used individually or in any combination. The embodiments shown and described are not to be understood as an exhaustive list, but rather serve as examples to illustrate the invention.

[0060] The invention can also be implemented in conjunction with an articulated steering system. It requires that a two- or multi-axle vehicle consists of at least two parts connected by a joint. The wheel axles are rigidly mounted in the vehicle sections. A change of direction is achieved by pivoting the vehicle sections horizontally.

[0061] They show: Fig. 1 a schematic representation of a steer-by-wire system according to the invention; Fig. 2 an illustration of the control loop underlying the steer-by-wire system according to the invention; Fig. Figures 3a - 3n show detailed representations of the arrangement of the steering actuators of a steer-by-wire system according to the invention.

[0062] In the following description of the drawing, identical reference symbols are used for identical or functionally equivalent components.

[0063] In Fig. Figure 1 shows a steer-by-wire system for steering a motor vehicle.

[0064] The steer-by-wire system 1 comprises two steering actuators 3, 5 for adjusting at least one steering angle of at least one wheel of the vehicle. If one of the steering actuators 3, 5 fails, the vehicle can still be steered by the remaining steering actuator 3, 5. For the sake of clarity, only one axle 6 of the vehicle is shown here. The wheels themselves are not shown. The steer-by-wire system 1 can also comprise more than two steering actuators.

[0065] The steer-by-wire system 1 also includes a control unit 7 for processing steering signals LS and controlling the steering actuators 3, 5 based on the steering signals LS.

[0066] One of the steering actuators 3, 5 is from a first type, and the other of the steering actuators 3, 5 is from a second type, which differs from the first type. Specifically, by way of example, but not necessarily, steering actuators 3, 5 are an electric steering actuator 3 and a hydraulic steering actuator 5.

[0067] The electric steering actuator 3 has an associated actuator system that includes power electronics 8.

[0068] The hydraulic steering actuator 5 has an associated actuator system in the form of a hydraulic system 9, which includes a hydraulic pump 11, a hydraulic valve 13, and an oil tank 15. The hydraulic system 9 can be powered, in particular, by the motor vehicle's engine 17 via a transmission 19. The illustrated steer-by-wire system 1 also includes a steering input element 21, which, however, is not a necessary component. In the example shown, the steering input element 21 comprises a steering wheel 23, a force feedback unit 25 (which is controlled via the power electronics 8), and an encoder 27. Steering signals LS from the steering input element 21 are transmitted to the control unit 7.

[0069] The control unit 7 generates corresponding control signals SE, SH for controlling the steering actuators 3, 5, which are forwarded to the power electronics 8 and the hydraulic valve 13, respectively. The control unit also generates force feedback control signals SF for controlling the force feedback unit 25.

[0070] In the example shown, the steering actuators 3 and 5 are located on opposite sides of the axle 6, i.e., each at a wheel of the axle 6, and have short connecting rods 29 for adjusting the steering angle. Furthermore, both sides are connected by another connecting rod 31, so that both steering actuators 3 and 5 each influence the steering angles of both wheels.

[0071] The steer-by-wire system 1 also includes a sensor (not shown here) for monitoring the hydraulic steering actuator 5 by measuring the pressure MD. The corresponding sensor signal is forwarded to the control unit 7.

[0072] Furthermore, the steer-by-wire system 1 includes a steering angle sensor (not shown here) for recording the actual value MW of at least one steering angle, which is forwarded to the control unit 7.

[0073] Finally, the steer-by-wire system 1 includes a sensor (not shown here) for detecting the value MS of a state parameter in the form of the motor current of the electric steering actuator 3, which is forwarded to the control unit 7.

[0074] The control unit 7 is configured, by way of example, to control the steering actuators 3 and 5 such that the ratio of the proportion of the steering angle influenced by steering actuator 5 of the first type to the proportion of the steering angle influenced by steering actuator 3 of the second type depends on the driving situation. Alternatively or additionally, the control unit 7 can be configured to control the steering actuators 3 and 5 such that the ratio of the proportion of the steering angle influenced by steering actuator 5 of the first type to the proportion of the steering angle influenced by steering actuator 3 of the second type depends on the steering signals LS and / or the detected value of the state parameter MS and / or on the deviation of the actual value MW of at least one steering angle from a corresponding target value.

[0075] In Fig. Figure 2 illustrates the control loop underlying the steer-by-wire system 1 according to the invention.

[0076] Unlike Fig. 1 The steer-by-wire system 1 has a computing unit 33 for autonomous control, so that the steering signals LS (here steering angle specifications) also originate from this and not only from the steering input element 21.

[0077] Also shown are the motor controller 35 of the electric steering actuator 3, and the motor controller 37 of the force feedback unit 25.

[0078] The actual values ​​of the controlled quantity in the example shown are the measured pressure MD of the hydraulic steering actuator 5. Additionally, the measured value MW of the steering angle and the measured value MS of the motor current of the electric steering actuator 3 are transmitted. The control signals SE and SH correspond here to current specifications for the motor current and opening specifications for the hydraulic valve 13, respectively. The steering angle is controlled. The steering angle is set by the two manipulated variables: motor current and valve opening specification.

[0079] Also shown are a force feedback controller 39 and a guide angle controller 41 as part of the control unit 7.

[0080] Both Fig. Figures 3a-3n are detailed illustrations depicting variations in the mounting of the steering actuators of the steer-by-wire system according to the invention, the other components of which are not shown here. An axle 6 of the motor vehicle is shown, at both ends of which wheels (not shown here) are arranged.

[0081] In Fig. Figure 3a shows that the steer-by-wire system comprises an electric steering actuator 3 and a hydraulic steering actuator 5. In the example shown, the steering actuators 3 and 5 are arranged on the same side of the axle 6 and have short connecting rods 29 for adjusting the steering angle. Furthermore, both sides are connected by another connecting rod 31, so that both steering actuators 3 and 5 act on the steering angles of both wheels. The configuration is compact and enables efficient control.

[0082] In Fig. 3b comprises the steer-by-wire system, an electric steering actuator 3, and a hydraulic steering actuator 5. In Fig. 3a The steer-by-wire system comprises an electric steering actuator 3 and a hydraulic steering actuator 5. In the example shown, the steering actuators 3 and 5 are arranged on the same side of the axle 6 and have short connecting rods 29 for adjusting the steering angle. Furthermore, both sides are connected by another connecting rod 31, so that both steering actuators 3 and 5 each act on the steering angles of both wheels.

[0083] In Fig. 3c comprises the steer-by-wire system with two electric steering actuators 3 and two hydraulic steering actuators 5. One electric steering actuator 3 and one hydraulic steering actuator are arranged on each side of the axle 6, each with short connecting rods 29 for adjusting the steering angle. Furthermore, both sides are connected by an additional connecting rod 31, so that each pair of steering actuators 3, 5 acts on the steering angles of both wheels. The redundancy of the system is increased in this configuration.

[0084] In Fig. 3d comprises the steer-by-wire system with two electric steering actuators 3 and two hydraulic steering actuators 5. On each side of the axle 6, one electric steering actuator 3 and one hydraulic steering actuator are arranged, which have short connecting rods 29 for adjusting the steering angle. Furthermore, both sides are connected by another connecting rod 31, so that each pair of steering actuators 3, 5 acts on the steering angles of both wheels. Unlike in Fig. 3c is the arrangement mirror-symmetrical with respect to axis 6, with the genus being interchanged.

[0085] To utilize the available space, the components of the invention can also be arranged opposite each other.

[0086] In Fig. 3e The steer-by-wire system comprises an electric steering actuator 3 and a hydraulic steering actuator 5. In the example shown, the electric steering actuator 3 is arranged on one side of the axle 6 and has a short connecting rod 29 for adjusting the steering angle. The hydraulic steering actuator 5 is connected to both sides via connecting rods 29.

[0087] The arrangement in Fig. 3f corresponds to the arrangement in Fig. 3e, wherein an additional electric steering actuator 3 is provided, which is located on the opposite side.

[0088] In Fig. The steer-by-wire system 3g comprises a hydraulic steering actuator 5, which is connected to both sides via connecting rods 29. The hydraulic steering actuator 5 additionally features a worm gear driven by another actuator and / or an integrated spindle drive.

[0089] In Fig. The steer-by-wire system comprises a hybrid actuator 4 in the form of a hydraulic cylinder with an integrated electric motor. A hybrid actuator, such as the one shown here, thus comprises two actuators of different types. For adjusting the steering angle, the hybrid actuator 4 has a short connecting rod 29 on each side.

[0090] In Fig. The steer-by-wire system in section 3i comprises a hydraulic steering actuator 5, which is connected to both sides via connecting rods 29. An electric motor can also be mechanically attached to a further connecting rod 31 as an additional steering actuator in various ways. This configuration allows for flexible adaptation of the electric drive to the specific requirements of the steering system, including integration with rack and pinion or recirculating ball couplings for precise transmission of steering movements.

[0091] In Fig. 3j The steer-by-wire system comprises a hydraulic steering actuator 5, which is connected to both sides via connecting rods 29. An electric motor 3' is connected as an actuator in the steering knuckle or via a gear and turntable. This configuration enables precise and direct control of the wheel position, which improves the steering precision and responsiveness of the vehicle. In the Fig. 3k - 3n uses a steer-by-wire system designed as individual wheel steering.

[0092] In Fig. The steer-by-wire system 3k comprises two electric steering actuators 3 and two hydraulic steering actuators 5. One electric steering actuator and one hydraulic steering actuator are arranged on each side of the axle 6.

[0093] In Fig. The steer-by-wire system in 3l comprises two hybrid actuators 4, with one hybrid actuator 4 arranged on each side. Fig. 3m is a variant of the in Fig. The arrangement shown in 3k is for the individual wheel steering.

[0094] In Fig. The steer-by-wire system 3n has two hydraulic steering actuators 5, one of which is arranged on each side. Two further drive units 3' are also arranged in the steering knuckles.

[0095] In the Fig. 3a - 3n can refer to steering actuators from a first category or steering actuators from a second category, instead of hydraulic steering actuators and electric steering actuators.

Claims

[1] Steer-by-wire system (1) for steering a motor vehicle, comprising two or more steering actuators (3, 5) for adjusting at least one steering angle of at least one wheel and / or at least one rigid axle of the motor vehicle, wherein in the event of failure of one of the steering actuators (3, 5) the motor vehicle can still be steered by another of the steering actuators (3, 5), and at least one control unit (7) for processing steering signals (LS) and controlling the steering actuators (3, 5) based on the steering signals (LS), characterized by , that at least one of the steering actuators (3, 5) is from a first genus and at least one further of the steering actuators (3, 5) is from a second genus that differs from the first genus. [2] Steer-by-wire system (1) according to claim 1, characterized by , that at least one of the steering actuators (3, 5) is an electric steering actuator (3, 5). [3] Steer-by-wire system (1) according to claim 1 or 2, characterized by , that at least one of the steering actuators (3, 5) is a hydraulic steering actuator (3, 5). [4] Steer-by-wire system (1) according to any one of claims 1 to 3, characterized by , that at least one of the steering actuators (3, 5) is a pneumatic steering actuator (3, 5). [5] Steer-by-wire system (1) according to claim 1, characterized by , that at least one of the steering actuators (3, 5) is a hydraulic steering actuator (3, 5) and at least one other of the steering actuators (3, 5) is an electric steering actuator (3, 5). [6] Steer-by-wire system (1) according to claim 1, characterized by , that at least one of the steering actuators (3, 5) is a pneumatic steering actuator (3, 5) and at least one other of the steering actuators (3, 5) is an electric steering actuator (3, 5). [7] Steer-by-wire system (1) according to any one of claims 1 to 6, further comprising at least one sensor for monitoring at least one of the steering actuators (3, 5) and / or an actuator system associated therewith and providing a resulting sensor signal. [8] Steer-by-wire system (1) according to any one of claims 1 to 7, characterized by , that the at least one control device (7) is configured to control the steering actuators (3, 5) in such a way that the ratio of the proportion in which the at least one steering actuator (3, 5) of the first type acts on the steering angle to the proportion in which the at least one steering actuator (3, 5) of the second type acts on the steering angle depends on the driving situation. [9] Steer-by-wire system (1) according to any one of claims 1 to 8, characterized by, that the at least one control device (7) is configured to control the steering actuators (3, 5) such that the ratio of the proportion in which the at least one steering actuator (3, 5) of the first type acts on the steering angle to the proportion in which the at least one steering actuator of the second type acts on the steering angle depends on the steering signals (LS). [10] Steer-by-wire system (1) according to any one of claims 1 to 9, further comprising at least one sensor for detecting at least one state parameter (MS) of the at least steering actuator (3, 5) of the first type and / or of an actuator system associated therewith, wherein the at least one control unit (7) is configured to control the steering actuators (3, 5) such that the ratio of the proportion in which the at least one steering actuator (3, 5) of the first type acts on the steering angle to the proportion in which the at least one steering actuator (3, 5) of the second type acts on the steering angle depends on the detected value of the at least one state parameter (MS). [11] Steer-by-wire system (1) according to one of claims 1 to 10, further comprising at least one sensor for detecting at least one actual value (MW) of the at least one steering angle, wherein the at least one control unit (7) is configured such that the ratio of the proportion in which the at least one steering actuator (3, 5) of the first type acts on the steering angle to the proportion in which the at least one steering actuator (3, 5) of the second type acts on the steering angle depends on a deviation of the actual value (MW) of the at least one steering angle from a corresponding setpoint value. [12] Control device (7) for a steer-by-wire system (1) configured to receive steering signals (LS) and, based on these steering signals (LS), to control at least one steering actuator (3, 5) of a first type and at least one steering actuator (3, 5) of a second type, wherein the second type differs from the first type. [13] Method for adjusting at least one steering angle of at least one wheel of a motor vehicle using a steer-by-wire system (1), comprising the steps: Providing steering signals (LS) Controlling at least one steering actuator (3, 5) of a first type and at least one steering actuator (3, 5) of a second type based on the steering signals (LS), wherein the second type differs from the first type.

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