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), 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 circuit-wise 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). It is proposed that the short-circuit switching unit (20a; 20b) includes at least one uncontrolled, self-conducting semiconductor switch (22a, 24a, 26a; 22b, 24b).

Description

State of the art

[0001] The invention relates to 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.

[0002] 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 actuator in the form of a steering gear. To provide steering assistance, the wheel steering angle actuator in this case typically includes an actuator assembly in the form of a servo motor. Vehicles with steer-by-wire steering systems are also 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 a control 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 actuator mechanically separate from the control unit, with a second actuator assembly in the form of a steering actuator.

[0003] In certain fault conditions, it may be necessary for various reasons to apply a braking torque to one of the aforementioned actuator assemblies, whereby the braking torque is generally implemented via a phase short circuit. In this context, reference is made, for example, to DE 10 2015 108 691 A1, whereby, according to the embodiment described therein, an uninterrupted supply voltage is always required for the phase short circuit.

[0004] 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 installation space and simultaneously exhibit reduced reliability.

[0005] The object of the invention is, in particular, to provide an actuator assembly with improved efficiency properties. 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 dependent claims. Disclosure of the invention

[0006] 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 circuit-wise between the power electronics and the electric motor for short-circuiting at least one phase of the electric motor.

[0007] It is proposed that the short-circuit switching unit comprise at least one uncontrolled, self-conducting semiconductor switch. In particular, the short-circuit switching unit for short-circuiting the phases of the electric motor can also comprise several uncontrolled, self-conducting semiconductor switches. This design can improve efficiency, especially space efficiency, component efficiency, energy efficiency, and / or cost efficiency. Furthermore, it can increase reliability and thereby improve operational safety.

[0008] The actuator assembly is specifically designed for use in a vehicle's steering system, and advantageously in a motor vehicle. The steering system can be a conventional mechanical system, particularly an electric power steering system or a superimposed steering system / active steering system. Alternatively, the steering system can be a steer-by-wire system, in which steering input is advantageously transmitted to the vehicle wheels purely electrically. The electric motor is preferably a servo motor, advantageously a brushless motor, and particularly advantageously an asynchronous motor or a permanent magnet synchronous motor. The electric motor can, for example, be a three-phase, six-phase, nine-phase, or twelve-phase electric motor.Furthermore, the power electronics are configured as an inverter unit, specifically as a power stage and / or bridge circuit, and are intended for supplying power to and / or energizing the electric motor. For this purpose, the power electronics comprise, in particular, several power switches, preferably designed as field-effect transistors, for example in the form of MOSFETs. The normally closed, self-conducting semiconductor switch is configured as a normally open contact and, when appropriately activated, disconnects a corresponding electrical connection. The semiconductor switch is therefore normally closed in its resting state.Furthermore, the semiconductor switch has at least one control terminal, preferably a controllable one, advantageously a base terminal and / or a gate terminal; at least one first power terminal, preferably a switchable one, advantageously an emitter terminal and / or a source terminal; and at least one second power terminal, preferably a switchable one, preferably a collector terminal and / or a drain terminal. A switching state of the semiconductor switch is advantageously controllable by a control voltage, preferably between the control terminal and the first power terminal, for example, a gate-source voltage. Furthermore, the semiconductor switch is specifically designed to short-circuit at least one phase of the electric motor in at least one fault operating state. Preferably, the semiconductor switch can be configured as a MOSFET without a parasitic body diode.The semiconductor switch is preferably designed as a Si-MOSFET or GaN-MOSFET. "Intended" is understood to mean specifically programmed, designed, and / or equipped. The fact that an object is intended for a specific function is understood to mean, in particular, that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0009] 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 thus provides a ground short circuit. Furthermore, the short-circuit switching unit can, in this case, comprise several uncontrolled, self-conducting semiconductor switches, with a first terminal of each additional semiconductor switch being electrically connected to a phase line of the electric motor and a second terminal of each additional semiconductor switch being electrically connected to a ground terminal. These 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, self-conducting semiconductor switches, wherein a first terminal of the first semiconductor switch is electrically connected to a first phase conductor 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 the second semiconductor switch is electrically connected to a second phase conductor 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 the third semiconductor switch is electrically connected to a third phase conductor 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.This allows a corresponding short circuit to be created in a particularly advantageous and flexible manner.

[0010] According to a further embodiment, it is proposed that a first terminal of the semiconductor switch is electrically connected to a first phase conductor of the electric motor, and a second terminal of the semiconductor switch is electrically connected to a second phase conductor of the electric motor. In this case, the semiconductor switch is thus arranged between two phases of the electric motor and connects them conductively in the rest state. Furthermore, the short-circuit switching unit in this case can comprise at least one further uncontrolled, self-conducting semiconductor switch, wherein a first further terminal of the further semiconductor switch is electrically connected to the second phase conductor of the electric motor, and a second further terminal of the further semiconductor switch is electrically connected to a third phase conductor 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 resting state. This allows a corresponding short circuit to be created in a particularly advantageously simple and space-saving manner.

[0011] Furthermore, a steering system with the aforementioned actuator assembly is proposed, wherein the steering system is designed as a steer-by-wire system, and wherein the actuator assembly is integrated into a control unit and / or a wheel steering angle actuator. In this case, the steering system particularly comprises at least one wheel steering angle actuator for changing the steering angle of at least one vehicle wheel and advantageously a control unit that is mechanically separate from the at least one wheel steering angle actuator and can be operated by a driver. A "wheel steering angle actuator" is understood to be an actuating unit operatively connected to at least one vehicle wheel, which is designed to transmit a steering input to the vehicle wheel by changing the steering angle of at least one vehicle wheel and thereby advantageously control at least one orientation of the vehicle wheel and / or influence the vehicle's direction of travel.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, particularly in the form of a steering actuator, which is 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 as a single-wheel adjuster and assigned to exactly one, in particular steerable, vehicle wheel. Particularly 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.

[0012] Steering the vehicle can then be accomplished, for example, via another vehicle system, such as a drive and / or braking system. Furthermore, an "operating unit" is understood to be an input unit operable by a driver for controlling the at least one wheel steering angle actuator. The operating unit can, in particular, comprise a steering handle, for example, designed as a steering wheel, and at least one actuator assembly, especially in the form of a feedback actuator, for generating steering resistance and / or a restoring torque on the steering handle. Particularly 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, thereby enabling damping of the steering handle 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 control unit and / or the wheel steering angle adjuster(s). This allows a high level of operational reliability to be achieved, particularly in safety-critical cases.

[0013] 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 to short-circuit at least one phase of the electric motor, in particular by means of a control voltage and advantageously a negative gate-source voltage, such that the semiconductor switch is in a non-conducting state, and wherein in at least one fault operating state, the control of the semiconductor switch is omitted 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 preferred is the use of a system in which, during normal operation, all uncontrolled, self-conducting semiconductor switches of the short-circuit switching unit are controlled such that the semiconductor switches are in a non-conducting state, while in fault operation, control of all semiconductor switches is omitted. The fault operation can, in particular, correspond to a power supply failure. This allows the aforementioned advantages to be achieved.

[0014] 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 to short-circuit 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 preferred is the configuration in normal operation where all uncontrolled, self-conducting semiconductor switches of the short-circuit switching unit are controlled such that the semiconductor switches are in a non-conducting state, while in fault operation, one, at least two, or at least three, or all semiconductor switches are actively controlled. This further fault operation state can correspond, in particular, to a fault in the actuator assembly and / or a control signal, where a power supply is present. Furthermore, "increased braking torque" is understood to mean, in particular, a braking torque that is higher than the braking torque that would occur if the semiconductor switch were not controlled. This allows the advantages already mentioned to be achieved.

[0015] The actuator assembly, the steering system, and the methods for operating the actuator assembly are not 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, to achieve a functionality described herein, comprise a different number of individual elements, components, and units than specified herein. Drawings

[0016] Further advantages become apparent from the following description of the drawings. The drawings illustrate several embodiments of the invention.

[0017] They show: Fig. 1a-b a vehicle with a steering system designed as a steer-by-wire system comprising at least one actuator assembly in a simplified representation Fig. 2 a simplified representation of the control circuit of the actuator assembly, Fig. 3. An exemplary flowchart showing the main process steps of a procedure for operating the actuator assembly and Fig. 4 Another embodiment of a control circuit of an actuator assembly in a simplified representation. Description of the embodiments

[0018] The Fig. 1a and Fig. Figure 1b shows a simplified representation of a vehicle 44a, designed as a passenger car, with several wheels 46a and a steering system 14a. The steering system 14a has a functional connection with the wheels 46a and is intended to influence the direction of travel of the vehicle 44a. Furthermore, the steering system 14a is designed as a steer-by-wire system, in which a steering input is transmitted electrically to the wheels 46a in at least one operating state. However, a steering system could also be designed as a conventional steering system, in particular as an electric power steering system.

[0019] The steering system 14a includes a wheel steering angle actuator 40a. The wheel steering angle actuator 40a is designed, by way of example, as a central actuator. The wheel steering angle actuator 40a has an operative connection with at least two of the vehicle wheels 46a, in particular two front wheels, and is designed to convert a steering input into a steering movement of the vehicle wheels 46a. For this purpose, the wheel steering angle actuator 40a comprises a steering actuating element 48a, designed, for example, as 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 designed to provide a steering torque for adjusting the steerable vehicle wheels 46a. In principle, a steering system could, of course, also include several wheel steering angle actuators, in particular designed as individual wheel actuators, in which case each wheel steering angle actuator can have an actuator assembly.

[0020] Furthermore, the steering system 14a includes a control unit 42a, which can be operated, in particular, by a driver and / or occupants. The control unit 42a is mechanically separate from the wheel steering angle actuator 40a. The control unit 42a is connected to the wheel steering angle actuator 40a purely electrically. The control unit 42a comprises a steering handle 50a for applying a steering input, for example, in the form of a steering wheel, and a further actuator assembly 12a in the form of a feedback actuator, which is mechanically coupled to the steering handle 50a. In this case, the further actuator assembly 12a is designed to provide feedback torque and thereby generate 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 completely dispense with a control unit, as for example in a purely autonomous vehicle.

[0021] With reference to Fig. In the following, the actuator assembly 10a of the wheel steering angle adjuster 40a is described as an example. However, the following description also applies to the further actuator assembly 12a of the control unit 42a. Furthermore, the actuator assembly 10a of the wheel steering angle adjuster 40a and the further actuator assembly 12a can, in principle, be of identical construction.

[0022] The actuator assembly 10a comprises a known electric motor 16a. The electric motor 16a is multiphase, in this case by way of example three-phase, and therefore comprises a first phase line 28a, a second phase line 30a and a third phase line 32a. The electric motor 16a can, for example, be designed as a permanent magnet synchronous motor.

[0023] Furthermore, the actuator assembly 10a includes a power electronics unit 18a, known per se, 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 several half-bridges 52a, 54a, 56a, in the present case by way of 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.

[0024] Furthermore, the actuator assembly 10a includes a short-circuit switching unit 20a, arranged circuit-wise 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, by way of example, three semiconductor switches 22a, 24a, 26a, wherein each phase line 28a, 30a, 32a is assigned one of the semiconductor switches 22a, 24a, 26a. The semiconductor switches 22a, 24a, 26a are identical in construction. 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 specifically 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 normally open, self-conducting semiconductor switches 22a, 24a, 26a. The semiconductor switches 22a, 24a, 26a are therefore configured as normally closed contacts and, when appropriately controlled, in particular by means of a control voltage, disconnect a corresponding electrical connection. In this context, the semiconductor switches 22a, 24a, 26a are each designed to short-circuit a phase of the electric motor 16a in at least one fault operating condition.

[0025] In this case, each of the semiconductor switches 22a, 24a, and 26a provides a ground short circuit. The first terminal of the first semiconductor switch 22a is electrically connected to the first phase line 28a of the electric motor 16a, while the second terminal of the first semiconductor switch 22a is electrically connected to a first ground terminal 34a. Furthermore, the first terminal of the second semiconductor switch 24a is electrically connected to the second phase line 30a of the electric motor 16a, while the second terminal of the second semiconductor switch 24a is electrically connected to a second ground terminal 36a. Finally, the first terminal of the third semiconductor switch 26a is electrically connected to the third phase line 32a of the electric motor 16a, while the second terminal of the third semiconductor switch 26a is electrically connected to a third ground terminal 38a.The ground connections 34a, 36a, 38a can be different or identical to each other.

[0026] Fig. Figure 3 shows an exemplary procedure for operating the actuator assembly 10a.

[0027] A process step 60a corresponds to a normal operating state. In this case, the electric motor 16a is controlled in a manner known per se by means of the power electronics 18a. In addition, the semiconductor switches 22a, 24a, 26a are controlled by means of a control voltage, in particular a negative gate-source voltage, such that the semiconductor switches 22a, 24a, 26a are in a non-conducting state.

[0028] In process step 62a, an error or malfunction occurs. The error or malfunction can occur in the power supply of the actuator assembly 10a, the control of the actuator assembly 10a, and / or the actuator assembly 10a itself.

[0029] A process step 64a corresponds to a fault operating state. In this case, either, for example in the event of a power supply failure, the semiconductor switches 22a, 24a, 26a can be omitted 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, to short-circuit the phases of the electric motor 16a and apply an increased braking torque to the electric motor 16a. Within the context of integration into the wheel steering angle actuator 40a, the phase short circuit can, for example, stiffen and / or preload a steering mechanism of the wheel steering angle actuator 40a.Steering of the vehicle 44a can then be accomplished via another vehicle system (not shown), such as a drive and / or braking system.

[0030] The example flowchart in Fig. Section 3 merely describes an exemplary method for operating the actuator assembly 10a. In particular, individual process steps may vary or additional process steps may be added. The method can also be applied analogously to the further actuator assembly 12a. In this case, for example, the phase short circuit can stiffen and / or tension a feedback mechanism of the control unit 42a, thereby damping the steering handle 50a in the event of a fault.

[0031] In Fig. Figure 4 shows a further embodiment of the invention. The following description and the drawing are essentially limited to the differences between the embodiments, whereby with regard to identically designated components, in particular with regard to components with the same reference numerals, reference is also generally made to the drawings and / or the description of the other embodiment, in particular the Fig. 1 to 3, reference can be made. To distinguish the embodiments, the letter a is the reference numeral of the embodiment in the Fig. 1 to 3 followed. In the exemplary embodiment of the Fig. In 4, the letter a is replaced by the letter b.

[0032] The further embodiment of the Fig. 4 differs from the previous embodiment at least substantially in a design of a short-circuit switching unit 20b of an actuator assembly 10b, 12b.

[0033] The short-circuit switching unit 20b is, in turn, arranged circuit-wise between a power electronics unit 18b and an electric motor 16b, in particular a three-phase motor, of the actuator assembly 10b, 12b. In this case, however, the short-circuit switching unit 20b comprises only two uncontrolled, self-conducting semiconductor switches 22b, 24b, and thus, in principle, one fewer semiconductor switch 22b, 24b than the number of 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 connect them conductively to each other in the rest 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, the first terminal of a second semiconductor switch 24b is electrically connected to the second phase line 30b of the electric motor 16b, while the 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 a conveniently simple and space-efficient manner. 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] DE 10 2015 108 691 A1

[0003] DE 10 2017 201 207 A1

[0004]

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 by that the short-circuit switching unit (20a; 20b) comprises at least one uncontrolled, self-conducting semiconductor switch (22a, 24a, 26a; 22b, 24b). [2] Actuator assembly (10a, 12a; 10b, 12b) according to claim 1, characterized by 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 bythat 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 by 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 byin 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 connection 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 connection of the respective further semiconductor switch (22a, 24a, 26a) is electrically connected to a further ground connection (34a, 36a, 38a). [6] Actuator assembly (10b, 12b) according to one of claims 1 to 3, characterized by 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 byin that the short-circuit switching unit (20b) comprises at least one further uncontrolled, self-conducting semiconductor switch (22b, 24b), wherein a first further connection 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 connection 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 by 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 bythat 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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