Actuator assembly, in particular steering actuator, and method for operating an actuator assembly

Abstract

The invention relates to an actuator assembly (10a, 12a; 10b, 12b), in particular for a steering system (14a), comprising a multiphase electric motor (16; 16b), power electronics (18a; 18b) electrically connected to the electric motor (16a; 16b) in order to actuate the electric motor (16a; 16b), and a short-circuit switching unit (20a; 20b) which is arranged between the power electronics (18a; 18b) and the electric motor (16a; 16b) in a circuit, said short-circuit switching unit being designed to short-circuit at least one phase of the electric motor (16a; 16b). According to the invention, the short-circuit switching unit (20a; 20b) comprises at least one semiconductor switch (22a, 24a, 26a; 22b, 24b) which is self-conducting in a non-active state.

Description

[0001] Description

[0002] Title Special steering actuator and method for operating

[0003] State of the art

[0004] The invention is based on an actuator assembly according to the preamble of claim 1. Furthermore, the invention relates to a steering system with at least one such actuator assembly, a vehicle with such a steering system, a first method for operating such an actuator assembly and a second method for operating such an actuator assembly.

[0005] Vehicles with conventional steering systems are known from the prior art, in which a steering handle, for example in the form of a steering wheel, is mechanically connected via a steering column to a wheel steering angle adjuster in the form of a steering gear. To provide steering assistance, the wheel steering angle adjuster in this case usually includes an actuator assembly in the form of a servomotor. Furthermore, vehicles with steer-by-wire steering systems are known, which do not require a direct mechanical connection between a steering handle and the steered vehicle wheels and in which steering input is transmitted electrically. Such a steer-by-wire steering system generally comprises an operating unit with a steering handle and a first actuator assembly in the form of a feedback actuator, as well as at least one wheel steering angle adjuster, mechanically separated from the operating unit, with a second actuator assembly in the form of a steering actuator.

[0006] In certain fault situations, it may be necessary for various reasons to apply a braking torque to one of the aforementioned actuator assemblies. This braking torque is usually achieved via a phase short circuit. In this context, reference is made, for example, to DE 10 2015 108 691 A1, where, according to the embodiment described therein, an uninterrupted supply voltage is always required for the phase short circuit.

[0007] To overcome this disadvantage, DE 10 2017 201 207 A1 discloses the use of relay switching elements to short-circuit an electric motor even in the event of a supply voltage drop. However, such relay switching elements require a lot of space and exhibit reduced reliability.

[0008] The object of the invention is, in particular, to provide an actuator assembly with improved properties in terms of efficiency. This object is achieved by the features of claims 1, 8, 11, 12, and 13, while advantageous embodiments and further developments of the invention can be found in the subclaims.

[0009] Disclosure of the invention

[0010] The invention is based on an actuator assembly with a multi-phase electric motor, with power electronics electrically connected to the electric motor for controlling the electric motor and with a short-circuit switching unit arranged between the power electronics and the electric motor for short-circuiting at least one phase of the electric motor.

[0011] It is proposed that the short-circuit switching unit comprise at least one uncontrolled, normally-conducting semiconductor switch. In particular, the short-circuit switching unit for short-circuiting the phases of the electric motor can also comprise a plurality of uncontrolled, normally-conducting semiconductor switches. This configuration can improve efficiency, in particular space efficiency, component efficiency, energy efficiency, and / or cost efficiency. Furthermore, reliability can be increased and, as a result, operational safety can be improved. The actuator assembly is intended in particular for use in a steering system of a vehicle, and advantageously of a motor vehicle. The steering system can be designed as a conventional, mechanical steering system, in particular as an electric power steering system or superimposed steering system or active steering system.Alternatively, the steering system can be designed as a steer-by-wire steering system, in which a steering command is advantageously transmitted purely electrically to the vehicle wheels. The electric motor is designed in particular as a servomotor, advantageously as a brushless motor and particularly advantageously as an asynchronous motor or as a permanently excited synchronous motor. The electric motor can be designed, for example, as a three-phase, six-phase, nine-phase, or twelve-phase electric motor. Furthermore, the power electronics are designed as an inverter unit, in particular as an output stage and / or as a bridge circuit, and are provided for supplying power and / or energizing the electric motor. For this purpose, the power electronics comprise, in particular, a plurality of power switches, preferably designed as field-effect transistors, for example in the form of MOSFETs.The uncontrolled, normally-conducting semiconductor switch is designed as an opener and disconnects an associated electrical connection when appropriately controlled. The semiconductor switch is therefore normally closed. Furthermore, the semiconductor switch has at least one, in particular controllable, control terminal, advantageously a base terminal and / or a gate terminal, at least one, in particular switchable, first power terminal, advantageously an emitter terminal and / or a source terminal, and at least one, in particular switchable, second power terminal, in particular a collector terminal and / or a drain terminal. A switching state of the semiconductor switch can advantageously be controlled by a control voltage, in particular between the control terminal and the first power terminal, for example a gate-source voltage.Furthermore, the semiconductor switch is particularly intended to short-circuit at least one phase of the electric motor in at least one fault operating state. The semiconductor switch can preferably be designed as a MOSFET without a parasitic body diode. The semiconductor switch is particularly preferably designed as a Si-MOSFET or GaN-MOSFET. "Intended" is to be understood in particular as being specially programmed, designed, and / or equipped. The fact that an object is intended for a specific function is to be understood in particular as meaning that the object fulfills and / or executes this specific function in at least one application and / or operating state.

[0012] According to one embodiment, it is proposed that a first terminal of the semiconductor switch is electrically connected to a phase line of the electric motor and a second terminal of the semiconductor switch is electrically connected to a ground terminal. In this case, the semiconductor switch accordingly provides a ground short circuit. Furthermore, in this case, the short-circuit switching unit can comprise a plurality of uncontrolled, self-conducting additional semiconductor switches, wherein a respective first additional terminal of the respective additional semiconductor switch is electrically connected to a respective additional phase line of the electric motor and a respective second additional terminal of the respective additional semiconductor switch is electrically connected to a further ground terminal. Accordingly, the additional semiconductor switches also provide a ground short circuit.If the electric motor is three-phase, the short-circuit switching unit can, for example, comprise three uncontrolled, normally-conducting semiconductor switches, wherein a first terminal of a first semiconductor switch is electrically connected to a first phase line of the electric motor and a second terminal of the first semiconductor switch is electrically connected to a first ground terminal, a first terminal of a second semiconductor switch is electrically connected to a second phase line of the electric motor and a second terminal of the second semiconductor switch is electrically connected to a second ground terminal, and a first terminal of a third semiconductor switch is electrically connected to a third phase line of the electric motor and a second terminal of the third semiconductor switch is electrically connected to a third ground terminal. The ground terminals can be different or identical to one another.In this way, a corresponding short circuit can be generated in a particularly advantageous and flexible manner.

[0013] According to a further embodiment, it is proposed that a first terminal of the semiconductor switch be electrically connected to a first phase line of the electric motor, and a second terminal of the semiconductor switch be electrically connected to a second phase line of the electric motor. In this case, the semiconductor switch is accordingly arranged between two phases of the electric motor and conductively connects them to one another in the idle state. Furthermore, in this case, the short-circuit switching unit can comprise at least one further uncontrolled, normally-conductive semiconductor switch, wherein a first further terminal of the further semiconductor switch is electrically connected to the second phase line of the electric motor, and a second further terminal of the further semiconductor switch is electrically connected to a third phase line of the electric motor.Accordingly, the additional semiconductor switch is also arranged between two phases of the electric motor and connects them conductively in the idle state. This allows a corresponding short circuit to be generated in a particularly simple and space-efficient manner.

[0014] In addition, a steering system with the aforementioned actuator assembly is proposed, wherein the steering system is designed as a steer-by-wire steering system, and wherein the actuator assembly is integrated into an operating unit and / or a wheel steering angle adjuster. In this case, the steering system comprises, in particular, at least one wheel steering angle adjuster for changing a wheel steering angle of at least one vehicle wheel and advantageously an operating unit that is mechanically separate from the at least one wheel steering angle adjuster and can be actuated by a driver. A "wheel steering angle adjuster" is to be understood as an actuating unit operatively connected to at least one vehicle wheel, which is provided to transmit a steering command to the vehicle wheel by changing a wheel steering angle of at least one vehicle wheel and thereby advantageously control at least one orientation of the vehicle wheel and / or influence a direction of travel of the vehicle.For this purpose, the wheel steering angle adjuster advantageously comprises at least one steering actuating element, for example in the form of a rack, and at least one actuator assembly, in particular in the form of a steering actuator, which is in particular operatively connected to the steering actuating element. Furthermore, the wheel steering angle adjuster can be designed in particular as a central adjuster and assigned to at least two, in particular steerable, vehicle wheels, or can be designed as an individual wheel adjuster and assigned to exactly one, in particular steerable, vehicle wheel. In particular when the actuator assembly according to the invention is integrated into a wheel steering angle adjuster, the phase short circuit advantageously stiffens and / or tensions a steering mechanism of the wheel steering angle adjuster. The vehicle can then be steered, for example, via another vehicle system, such as a drive and / or braking system.An "operating unit" should also be understood as an input unit operable by a driver for controlling the at least one wheel steering angle adjuster. The operating unit can, in particular, comprise a steering handle, for example designed as a steering wheel, and at least one actuator assembly, in particular in the form of a feedback actuator, for generating steering resistance and / or a restoring torque on the steering handle. In particular, when the actuator assembly according to the invention is integrated into an operating unit, the phase short circuit advantageously stiffens and / or tensions a feedback mechanism of the operating unit, whereby damping of the steering handle can be achieved even in the event of a fault. In principle, the steering system can, of course, also comprise several actuator assemblies according to the invention, wherein corresponding actuator assemblies can be integrated into the operating unit and / or the wheel steering angle adjuster(s).This enables a high level of operational reliability to be achieved, particularly in particularly safety-critical cases.

[0015] In addition, a method for operating an actuator assembly, in particular the actuator assembly already mentioned above, is proposed, wherein in a normal operating state a multi-phase electric motor is controlled by means of power electronics and at least one uncontrolled, self-conducting semiconductor switch, in particular a short-circuit switching unit, for short-circuiting at least one phase of the electric motor is controlled, in particular by means of a control voltage and advantageously a negative gate-source voltage, in such a way that the semiconductor switch is in a non-conducting state, and wherein in at least one fault operating state control of the semiconductor switch is dispensed with in order to short-circuit the at least one phase of the electric motor and to apply a defined braking torque to the electric motor.Particularly preferably, in the normal operating state, all uncontrolled, normally conducting semiconductor switches of the short-circuit switching unit are controlled such that the semiconductor switches are in a non-conductive state, while in the fault operating state, all semiconductor switches are not controlled. The fault operating state can, in particular, correspond to a power supply failure. This makes it possible, in particular, to achieve the advantages already mentioned.

[0016] Furthermore, a method for operating an actuator assembly, in particular the actuator assembly already mentioned above, is proposed, wherein in a normal operating state a multi-phase electric motor is controlled by means of power electronics and at least one uncontrolled, self-conducting semiconductor switch, in particular a short-circuit switching unit, is controlled for short-circuiting at least one phase of the electric motor, in particular by means of a first control voltage and advantageously a negative gate-source voltage, such that the semiconductor switch is in a non-conducting state, and wherein the semiconductor switch is actively controlled in at least one further fault operating state, in particular by means of a second control voltage and advantageously a positive gate-source voltage, in order to short-circuit the at least one phase of the electric motor and to apply an increased braking torque to the electric motor.Particularly preferably, in the normal operating state, all uncontrolled, normally conducting semiconductor switches of the short-circuit switching unit are controlled such that the semiconductor switches are in a non-conductive state, whereas in the fault operating state, one of the semiconductor switches or at least two of the semiconductor switches or at least three of the semiconductor switches or all of the semiconductor switches are actively controlled. The further fault operating state can in particular correspond to a fault in the actuator assembly and / or a control signal for which a power supply is present. Furthermore, an "increased braking torque" should be understood to mean in particular a braking torque that is higher than a braking torque when the semiconductor switch is not controlled. This makes it possible, in particular, to achieve the advantages already mentioned.

[0017] The actuator assembly, the steering system, and the methods for operating the actuator assembly are not intended to be limited to the application and embodiment described above. In particular, the actuator assembly, the steering system, and the methods for operating the actuator assembly may comprise a number of individual elements, components, and units that differs from the number stated herein in order to fulfill a functionality described herein.

[0018] Drawings

[0019] Further advantages will become apparent from the following description of the drawings. Several embodiments of the invention are illustrated in the drawings.

[0020] They show:

[0021] Fig. 1 shows a vehicle with a steering system designed as a steer-by-wire steering system comprising at least one actuator assembly in a simplified representation

[0022] Fig. 2 shows a control circuit of the actuator assembly in a simplified representation,

[0023] Fig. 3 is an exemplary flow chart with main method steps of a method for operating the actuator assembly and Fig. 4 is a further embodiment of a control circuit of an actuator assembly in a simplified representation.

[0024] Description of the embodiments

[0025] Figures 1a and 1b show a simplified representation of a vehicle 44a, embodied by way of example as a passenger vehicle, with a plurality of vehicle wheels 46a and with a steering system 14a. The steering system 14a has an operative connection with the vehicle wheels 46a and is provided for influencing a direction of travel of the vehicle 44a. Furthermore, the steering system 14a is embodied here as a steer-by-wire steering system, in which a steering command is electrically transmitted to the vehicle wheels 46a in at least one operating state. In principle, however, a steering system could also be embodied as a conventional steering system, in particular as an electric power steering system. The steering system 14a has a wheel steering angle adjuster 40a. The wheel steering angle adjuster 40a is embodied, by way of example, as a central adjuster.The wheel steering angle adjuster 40a has an operative connection with at least two of the vehicle wheels 46a, in particular two front wheels, and is provided for converting a steering command into a steering movement of the vehicle wheels 46a. For this purpose, the wheel steering angle adjuster 40a comprises a steering actuating element 48a, exemplified by a rack, and an actuator assembly 10a in the form of a steering actuator that interacts with the steering actuating element 48a. The actuator assembly 10a is provided for providing a steering torque for adjusting the steerable vehicle wheels 46a. In principle, a steering system could, of course, also comprise several wheel steering angle adjusters, in particular designed as individual wheel adjusters, in which case each wheel steering angle adjuster can have an actuator assembly.

[0026] Furthermore, the steering system 14a has an operating unit 42a, which can be operated in particular by a driver and / or passenger. The operating unit 42a is mechanically separate from the wheel steering angle adjuster 40a. The operating unit 42a is connected purely electrically to the wheel steering angle adjuster 40a. The operating unit 42a comprises a steering handle 50a for applying a steering command, for example in the form of a steering wheel, as well as a further actuator assembly 12a in the form of a feedback actuator, which is particularly mechanically coupled to the steering handle 50a. In the present case, the further actuator assembly 12a is provided for providing a feedback torque and thereby generating a steering feel, in particular in the form of steering resistance and / or a restoring torque on the steering handle 50a. Alternatively, a steering handle could also be designed as a joystick, a steering lever and / or a steering ball or the like.Furthermore, it is fundamentally conceivable to do without a control unit entirely, as is the case, for example, with a purely autonomous vehicle.

[0027] With reference to Figure 2, the actuator assembly 10a of the wheel steering angle adjuster 40a is described below as an example. However, the following description also applies to the additional actuator assembly 12a of the control unit 42a. Furthermore, the actuator assembly 10a of the wheel steering angle adjuster 40a and the additional actuator assembly 12a can, in principle, also be constructed identically.

[0028] The actuator assembly 10a comprises a known electric motor 16a. The electric motor 16a is multi-phase, in this case, for example, three-phase, and thus comprises a first phase line 28a, a second phase line 30a, and a third phase line 32a. The electric motor 16a can be designed, for example, as a permanent magnet synchronous motor.

[0029] In addition, the actuator assembly 10a comprises a known power electronics unit 18a for controlling the electric motor 16a. The power electronics unit 18a is designed as an inverter unit, in particular as a B6 bridge circuit, and comprises a plurality of half-bridges 52a, 54a, 56a, in the present case, for example, three half-bridges 52a, 54a, 56a, wherein each phase of the electric motor 16a is assigned one of the half-bridges 52a, 54a, 56a.

[0030] In addition, the actuator assembly 10a comprises a short-circuit switching unit 20a, arranged between the power electronics 18a and the electric motor 16a, for short-circuiting at least one phase of the electric motor 16a. The short-circuit switching unit 20a comprises at least one semiconductor switch 22a, 24a, 26a. In the present case, the short-circuit switching unit 20a comprises, for example, three semiconductor switches 22a, 24a, 26a, with each phase line 28a, 30a, 32a being assigned one of the semiconductor switches 22a, 24a, 26a. The semiconductor switches 22a, 24a, 26a are structurally identical. The semiconductor switches 22a, 24a, 26a are each designed as MOSFETs without a parasitic body diode and without a cascode circuit, in the present case in particular as GaN MOSFETs. Alternatively, at least one semiconductor switch could also be designed as a Si-MOSFET.Furthermore, the semiconductor switches 22a, 24a, 26a are designed as uncontrolled, normally-on semiconductor switches 22a, 24a, 26a. The semiconductor switches 22a, 24a, 26a are accordingly designed as normally closed contacts and, when appropriately controlled, in particular by means of a control voltage, disconnect an associated electrical connection. In this context, the semiconductor switches 22a, 24a, 26a are each provided to short-circuit a phase of the electric motor 16a in at least one fault operating state. In this case, each of the semiconductor switches 22a, 24a, 26a provides a ground short circuit. A first terminal of a first semiconductor switch 22a is electrically connected to the first phase line 28a of the electric motor 16a, while a second terminal of the first semiconductor switch 22a is electrically connected to a first ground terminal 34a.In addition, a first terminal of a second semiconductor switch 24a is electrically connected to the second phase line 30a of the electric motor 16a, while a second terminal of the second semiconductor switch 24a is electrically connected to a second ground terminal 36a. Furthermore, a first terminal of a third semiconductor switch 26a is electrically connected to the third phase line 32a of the electric motor 16a, while a second terminal of the third semiconductor switch 26a is electrically connected to a third ground terminal 38a. The ground terminals 34a, 36a, 38a can be different or identical to one another.

[0031] Finally, Figure 3 shows an exemplary method for operating the actuator assembly 10a.

[0032] A method step 60a corresponds to a normal operating state. In this case, the electric motor 16a is controlled in a conventional manner by means of the power electronics 18a. Furthermore, the semiconductor switches 22a, 24a, 26a are controlled by a control voltage, in particular a negative gate-source voltage, such that the semiconductor switches 22a, 24a, 26a are in a non-conductive state.

[0033] In a method step 62a, an error or malfunction occurs. The error or malfunction can occur in a power supply of the actuator assembly 10a, a control of the actuator assembly 10a, and / or the actuator assembly 10a itself.

[0034] A method step 64a corresponds to a faulty operating state. In this case, either, for example in the event of a power failure, control of the semiconductor switches 22a, 24a, 26a can be dispensed with in order to short-circuit the phases of the electric motor 16a and apply a defined braking torque to the electric motor 16a, or, for example in the event of a faulty control signal, at least one of the semiconductor switches 22a, 24a, 26a can be actively controlled by means of a second control voltage, in particular a positive gate-source voltage, in order to short-circuit the phases of the electric motor 16a and apply an increased braking torque to the electric motor 16a. Within the scope of integration into the wheel steering angle actuator 40a, the phase short-circuit can, for example, stiffen and / or tension a steering mechanism of the wheel steering angle actuator 40a.Steering of the vehicle 44a can then be carried out via another vehicle system (not shown), such as a drive and / or braking system.

[0035] The exemplary flowchart in Figure 3 is intended merely to describe a method for operating the actuator assembly 10a. In particular, individual method steps can also be varied, or additional method steps can be added. The method can also be applied analogously to the further actuator assembly 12a. In this case, the phase short circuit can, for example, stiffen and / or tension a feedback mechanism of the control unit 42a, which can dampen the steering handle 50a in the event of a fault.

[0036] Figure 4 shows a further embodiment of the invention. The following description and the drawings are essentially limited to the differences between the embodiments, whereby with regard to components with the same designation, in particular with regard to components with the same reference numerals, reference can in principle also be made to the drawings and / or the description of the other embodiment, in particular Figures 1 to 3. To distinguish the embodiments, the letter a is placed after the reference numerals of the embodiment in Figures 1 to 3. In the embodiment in Figure 4, the letter a is replaced by the letter b.

[0037] The further exemplary embodiment of Figure 4 differs from the previous exemplary embodiment at least substantially by a configuration of a short-circuit switching unit 20b of an actuator assembly 10b, 12b. The short-circuit switching unit 20b is again arranged in terms of circuitry between a power electronics unit 18b and a, in particular three-phase, electric motor 16b of the actuator assembly 10b, 12b. In this case, however, the short-circuit switching unit 20b comprises only two uncontrolled, normally-conductive semiconductor switches 22b, 24b and thus fundamentally one semiconductor switch 22b, 24b less than the existing phase lines 28b, 30b, 32b of the electric motor 16b. The semiconductor switches 22b, 24b are each arranged between two phases of the electric motor 16b and conductively connect them to one another in the idle state.Accordingly, a first terminal of a first semiconductor switch 22b is electrically connected to a first phase line 28b of the electric motor 16b, while a second terminal of the first semiconductor switch 22b is electrically connected to a second phase line 30b of the electric motor 16b. Furthermore, a first terminal of a second semiconductor switch 24b is electrically connected to the second phase line 30b of the electric motor 16b, while a second terminal of the second semiconductor switch 24b is electrically connected to a third phase line 32b of the electric motor 16b. This has the advantage that a corresponding short circuit can be generated in an advantageously simple and space-efficient manner.

Claims

Claims 1. Actuator assembly (10a, 12a; 10b, 12b), in particular for a steering system (14a), with a multi-phase electric motor (16a; 16b), with power electronics (18a; 18b) electrically connected to the electric motor (16a; 16b) for controlling the electric motor (16a; 16b), and with a short-circuit switching unit (20a; 20b) arranged between the power electronics (18a; 18b) and the electric motor (16a; 16b) for short-circuiting at least one phase of the electric motor (16a; 16b), characterized in that the short-circuit switching unit (20a; 20b) comprises at least one uncontrolled, normally-on semiconductor switch (22a, 24a, 26a; 22b, 24b).

2. Actuator assembly (10a, 12a; 10b, 12b) according to claim 1, characterized in that the semiconductor switch (22a, 24a, 26a; 22b, 24b) is designed as a MOSFET without a parasitic body diode.

3. Actuator assembly (10a, 12a; 10b, 12b) according to claim 1 or 2, characterized in that the semiconductor switch (22a, 24a, 26a; 22b, 24b) is designed as a Si-MOSFET or GaN-MOSFET.

4. Actuator assembly (10a, 12a) according to one of the preceding claims, characterized in that a first terminal of the semiconductor switch (22a, 24a, 26a) is electrically connected to a phase line (28a, 30a, 32a) of the electric motor (16a) and a second terminal of the semiconductor switch (22a, 24a, 26a) is electrically connected to a ground terminal (34a, 36a, 38a).

5. Actuator assembly (10a, 12a) according to claim 4, characterized in that the short-circuit switching unit (20a) comprises a plurality of uncontrolled, self-conducting further semiconductor switches (22a, 24a, 26a), wherein in each case a first further terminal of the respective further semiconductor switch (22a, 24a, 26a) is electrically connected to a respective further phase line (28a, 30a, 32a) of the electric motor (16a) and a respective second further terminal of the respective further semiconductor switch (22a, 24a, 26a) is electrically connected to a further ground terminal (34a, 36a, 38a).

6. Actuator assembly (10b, 12b) according to one of claims 1 to 3, characterized in that a first terminal of the semiconductor switch (22b, 24b) is electrically connected to a first phase line (28b, 30b, 32b) of the electric motor (16b) and a second terminal of the semiconductor switch (22b, 24b) is electrically connected to a second phase line (28b, 30b, 32b) of the electric motor (16b).

7. Actuator assembly (10b, 12b) according to claim 6, characterized in that the short-circuit switching unit (20b) comprises at least one further uncontrolled, normally-conducting semiconductor switch (22b, 24b), wherein a first further terminal of the further semiconductor switch (22b, 24b) is electrically connected to the second phase line (28b, 30b, 32b) of the electric motor (16b) and a second further terminal of the further semiconductor switch (22b, 24b) is electrically connected to a third phase line (28b, 30b, 32b) of the electric motor (16b).

8. Steering system (14a) with at least one actuator assembly (10a, 12a; 10b, 12b) according to one of the preceding claims.

9. Steering system (14a) according to claim 8, characterized in that the steering system (14a) is designed as a steer-by-wire steering system and comprises at least one wheel steering angle adjuster (40a), wherein the actuator assembly (10a; 10b) is integrated into the wheel steering angle adjuster (40a).

10. Steering system (14a) according to claim 8 or 9, characterized in that the steering system (14a) is designed as a steer-by-wire steering system and comprises at least one operating unit (42a), wherein the actuator assembly (12a; 12b) is integrated into the operating unit (42a) 11. Vehicle (44a), in particular a motor vehicle, with a steering system (14a) according to one of claims 8 to 10.

12. Method for operating an actuator assembly (10a, 12a; 10b, 12b), in particular according to one of claims 1 to 7, wherein in a normal operating state, a multi-phase electric motor (16a; 16b) is controlled by means of power electronics (18a; 18b) and at least one uncontrolled, self-conducting semiconductor switch (22a, 24a, 26a; 22b, 24b) is controlled to short-circuit at least one phase of the electric motor (16a; 16b) in such a way that the semiconductor switch (22a, 24a, 26a; 22b, 24b) is in a non-conducting state, and wherein in at least one fault operating state, control of the semiconductor switch (22a, 24a, 26a; 22b, 24b) is dispensed with in order to short-circuit the at least one phase of the electric motor (16a; 16b) and to apply a defined braking torque to the electric motor (16a; 16b).

13. Method for operating an actuator assembly (10a, 12a; 10b, 12b), in particular according to one of claims 1 to 7, wherein in a normal operating state a multi-phase electric motor (16a; 16b) is controlled by means of power electronics (18a; 18b) and at least one uncontrolled, normally-conductive semiconductor switch (22a, 24a, 26a; 22b, 24b) is controlled to short-circuit at least one phase of the electric motor (16a; 16b) in such a way that the semiconductor switch (22a, 24a, 26a; 22b, 24b) is in a non-conductive state, and wherein the semiconductor switch (22a, 24a, 26a; 22b, 24b) is actively controlled in at least one fault operating state in order to short-circuit the at least one phase of the electric motor (16a; 16b) and apply an increased braking torque to the electric motor (16a; 16b).

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