BE1030678A1 - Steer-by-wire steering system and method for operating a feedback actuator comprising an electric machine in a steering system of a motor vehicle - Google Patents

Abstract

The present invention relates to a method for operating a feedback actuator (10) comprising an electric machine (11) in a steering system (1) of a motor vehicle, wherein the feedback actuator (10) is operated in motor operation and in generator operation, and wherein the electric machine (11) is designed to provide a speed-dependent maximum operating torque in the engine operation, wherein in the engine operation the torque provided by the electric machine (11) is limited so that the torque provided is smaller than the maximum operating torque. The invention further relates to a steer-by-wire steering system (1) comprising a steering shaft (2), a steering handle (7) arranged in rotation on the steering shaft (2), and a feedback actuator (10) with an electric machine (11). , which is designed to provide a speed-dependent maximum operating torque during engine operation of the feedback actuator (10), wherein the steer-by-wire steering system (1) is designed to operate the feedback actuator (10) according to a method mentioned above .

Description

! BE2022/5523

Steer-by-wire steering system and method for operating a feedback actuator comprising an electric machine in a steering system of a motor vehicle

The invention relates to a method for operating a feedback actuator comprising an electric machine in a steering system of a motor vehicle, wherein the

Feedback actuator is operated in a motor operation and in a generator operation, and wherein the electric machine is designed to provide a speed-dependent maximum operating torque in the engine operation.

The invention further relates to a steer-by-wire steering system for a motor vehicle comprising a steering shaft, a steering handle arranged in a rotationally fixed manner on the steering shaft and a feedback actuator having an electric machine, which is designed in one

Motor operation and in a generator operation to be operated and thereby to exert a torque or a steering resistance torque on the steering shaft. The electric machine is designed to provide a speed-dependent maximum operating torque during engine operation.

In a classic steering system for a motor vehicle, a steering command is given by a

Driver is introduced to a steering line via a steering input means, transmitted by means of a mechanical coupling to a steering gear, where a rotation corresponding to the steering command is caused at least one steerable wheel. From the prior art it is known, for example from the publication EP 2 353 968 B1, that a classic steering system can be expanded in such a way that an electric motor receives the steering command entered via the steering input means by means of an active connection to the

Steering system supported. This reduces the torque required by a driver

Motor vehicle must be applied to the steering input means in order to achieve a specific

To achieve rotation of the at least one steerable wheel. Nevertheless, even if the electric motor fails, there is a mechanical connection between the steering input means and the at least one steerable wheel, so that the motor vehicle can still be steered even in the event of electronic problems.

From the prior art, such electromechanical ones are a further development

Steer-by-wire steering systems for motor vehicles are known. At least in normal operation there is no mechanical coupling between the steering input means and the

Steering gear. Instead, the steering command is recorded using sensors and converted into an electrical one

Signal converted, which is then forwarded to an electric motor, which is operatively connected to the steering gear, in order to rotate the steering gear corresponding to the steering command

2 BE2022/5523 to effect at least one steerable wheel. Such a steer-by-wire steering system is disclosed, for example, in publication DE 10 2018 115 329 A1. Steer-by-wire steering systems have various advantages. For example, steer-by-wire steering systems require less installation space. In addition, the required components are subject to less mechanical stress than the components required in classic steering systems.

In addition to the advantages of such steer-by-wire steering systems, they are mechanical

Decoupling between steering input means and steering gear creates new problems that require a reliable solution to ensure safe driving. There is no direct one

Feedback about the road condition reaches the driver via the steering system, such feedback is simulated, for example, by means of an actuator which is operatively connected to the steering input means. Such actuators are also known as feedback actuators and include an electric machine to generate feedback for the driver. At the

When operating a motor vehicle, the electric machine can be operated in a generator mode in order to generate a steering resistance torque that is perceptible to the driver, and can be operated in a motor mode. During engine operation, for example, a signal that can be perceived by a driver can be applied to the steering handle, for example when it is detected that the motor vehicle is leaving a lane. Even with autonomous or semi-autonomous driving, for example with automated parking

Motor vehicle, the electric machine of the feedback actuator can be operated in engine mode.

The problem here is that until now it has to be ensured through suitable monitoring that the feedback actuator does not unintentionally come into contact with the electrical machine

Engine operation is operated to prevent an unsafe driving situation.

Against this background, it is an object of the present invention to provide an improved one

Method for operating a feedback actuator comprising an electric machine in a steering system of a motor vehicle and to provide an improved steer-by-wire steering system for a motor vehicle, thereby advantageously increasing safety for motor vehicle users.

To solve this problem, a method and a steer-by-wire steering system are proposed according to the independent claims. Further advantageous embodiments of the

Invention are described in the dependent claims and the description as well as in the

Figures shown.

The proposed solution provides a method for operating a feedback actuator comprising an electric machine in a steering system of a motor vehicle, wherein the

Feedback actuator is operated in a motor operation and in a generator operation, and wherein the electric machine is designed to provide a speed-dependent maximum operating torque in the engine operation, wherein in the engine operation the torque provided by the electric machine is limited, so that the provided

Torque is less than the maximum operating torque. The maximum

Operating torque is in particular a torque that the electric machine could provide due to its nature for operation in the motor mode, in particular also for continuous operation, in particular without being damaged by operation with the maximum operating torque. The limitation of the torque provided by the electric machine during engine operation is in particular not a limitation that would be due to the design or that would occur in order to keep the electric machine harmless. Rather, the invention is based on the idea of advantageously limiting the torque provided in the engine operation of the electric machine in such a way that a driver can always advantageously counteract the torque provided and overcome it if the driver applies a corresponding countertorque to the steering handle. Incorrect self-steering or incorrect torque applied to the steering shaft can thus advantageously be overcome by the driver, thereby advantageously increasing safety.

The torque provided is advantageously limited by control technology, in particular using a feedback actuator assigned to it

Control unit, wherein the control unit is in particular an appropriately equipped one

Microcontroller unit can be.

An advantageous embodiment of the method provides that for the engine operation of the

Feedback actuator a torque characteristic is specified, wherein the torque provided by the electric machine in the engine operation is advantageously limited such that the torque characteristic is not exceeded by the torque provided. Advantageously, the torque characteristic is a speed-dependent torque characteristic. In this case, a higher torque is advantageously permitted at low speeds of the electric machine than at higher speeds.

This advantageously makes it even easier for a driver to prevent an incorrectly generated signal

To overcome engine torque, which further improves safety. In particular, it is provided that from a predetermined speed value the torque that can be provided is limited to a constant value for all speeds above this.

This is advantageously provided in the engine operation of the electric machine

4 BE2022/5523

Torque limited in such a way that it is lower than a maximum steering resistance torque that can be provided in the generator operation of the electric machine.

According to a further advantageous embodiment, it is provided that the feedback actuator provided by the electric machine in the motor operation

Torque is limited, in particular additionally limited if a predetermined

Acceleration of a rotation of a steering shaft of the steering system is exceeded in the engine operation. Advantageously, this further increases security.

A further advantageous embodiment provides that the electrical machine in which

Motor operation of the feedback actuator provided torque is limited, in particular additionally limited when a predetermined rotational speed of a steering shaft of the

Steering system in engine operation is exceeded. This advantageously results in the

Security further increased.

It is further advantageous at a rotational speed of a steering shaft of the steering system in one

Interval between 100 deg/sec (deg: degree (degree); sec: second (second)) and 150 deg/sec provided by the electric machine in the motor operation of the feedback actuator

Torque limited to a value, in particular limited to a value in an interval between 3 Nm (Nm: Newton meter) and 5 Nm. The limitation advantageously takes place according to a predetermined characteristic curve, the limitation advantageously increasing as the rotational speed increases. In particular, it can be provided that

Torque is limited to 5 Nm at a rotational speed of the steering shaft of 100 deg/sec and is advantageously limited to 3Nm at a rotational speed of the steering shaft of 150 deg/sec. The limitation of the torque between a rotational speed of 100 deg/sec and 150 deg/sec is advantageously carried out continuously from 5 Nm to 3 Nm.

In particular, if a rotational speed of a steering shaft is exceeded

Steering system of 150 deg/sec from the electric machine in the engine operation of the

The torque provided by the feedback actuator is further limited, in particular limited to a value of 0 Nm. This means that at a rotational speed of the steering shaft that is more than 150 deg/sec, the engine is advantageously no longer operated. Advantageously, this further increases security.

According to a further advantageous embodiment of the method it is provided that a

Motor operation of the feedback actuator is limited to the following operating situations:

Returning a steering handle of the steering system to a starting position and/or

> BE2022/5523

Introducing a vibration into a steering handle of the steering system as an indication function. The

Returning the steering handle to the starting position means in particular returning the steering handle to a central position in which a motor vehicle can drive straight ahead.

The introduction of a vibration into a steering handle of the steering system as an indication function can be initiated in particular by assistance systems of the motor vehicle, for example by a lane keeping assistant when a possible lane departure is detected.

Advantageously, there are no high torques for the operating situations mentioned

Operation of the electric machine of the feedback actuator in motor operation is required. The

Security through this further restriction is thus advantageously further increased.

A further advantageous embodiment of the method provides that in the generator operation of the feedback actuator a device that can be provided by the electrical machine

Steering resistance generating = speed-dependent maximum steering resistance

Operating torque is allowed. The maximum steering resistance operating torque is in particular a steering resistance torque that the electric machine could provide due to its nature for operation in the generator mode, in particular also for continuous operation, in particular without being damaged by operation with the maximum steering resistance operating torque. In particular, it is provided that higher torques are permitted for the generator operation of the electric machine than for the motor operation of the electric machine of the feedback actuator.

In particular, it is provided that in generator operation the maximum steering resistance

Operating torque has a value in an interval between 15 Nm and 30 Nm.

Advantageously, the maximum steering resistance operating torque increases

Speed continuously reduced from 30Nm to 15Nm, in particular according to a specified characteristic curve. This advantageously improves the steering feel for the driver.

The steer-by-wire steering system for a motor vehicle further proposed by the present invention comprises a steering shaft, which is arranged in a rotationally fixed manner on the steering shaft

Steering handle and a feedback actuator having an electric machine, which is designed to be operated in a motor mode and in a generator mode and thereby exert a torque or a steering resistance torque on the steering shaft. The electric machine is designed to provide a speed-dependent maximum operating torque during engine operation, with the steer-by-wire

Steering system is designed, the feedback actuator according to an inventive

To operate a process, in particular according to a process which has the above

6 BE2022/5523 has the features mentioned individually or in combination. In particular, the steer-by

Wire steering system is designed to limit the torque provided by the electric machine during engine operation, so that the torque provided is smaller than the maximum operating torque. The electric machine is in particular a

Synchronous motor, especially a permanent magnet synchronous motor. The proposed steer-by-wire steering system will ensure safety for motor vehicle users

Motor vehicles with such a steer-by-wire steering system are advantageously increased.

According to an advantageous embodiment, the steer-by-wire steering system comprises an electronic circuit that is designed to supply a current or a voltage

Operating the electric machine in motor mode when operating the feedback

Limit the actuator in terms of circuitry. By limiting the current or voltage in motor operation, the torque provided by the electric machine is advantageously also limited, so that the torque provided

Torque is less than the maximum operating torque. In particular, it can be provided that the components of the electronic circuit are dimensioned in such a way that there is a permanent, fixed limitation of the current or voltage caused by the components. This advantageously results in a constant

Limitation of the torque provided by the electric machine, so that the torque provided is smaller than the maximum operating torque, is guaranteed and thus further increases safety.

A further advantageous embodiment provides that the steer-by-wire steering system alternatively or additionally comprises a control unit for controlling the feedback actuator, wherein the

Control unit is advantageously set up by controlling the electrical

Machine in the engine operation of the electric machine in the engine operation of the

To limit the torque provided by the feedback actuator when operating the feedback actuator. In particular, it is provided that the control unit has an ECU (ECU: Electronic

Control unit), further in particular a correspondingly configured microcontroller unit.

According to one embodiment variant, the control unit is advantageously set up in such a way that the torque provided by the electric machine is limited during engine operation, so that the torque provided is smaller than the maximum

Operating torque is when a diagnostic device has identified a possible problem with the functionality of the feedback actuator. This is advantageous

Security further increased.

7 BE2022/5523

Further advantageous details, features and design details of the invention are described in

Connection with the exemplary embodiments shown in the figures (Fig.: Figure) explained in more detail. This shows:

1 shows a simplified perspective view of an exemplary embodiment of a steer-by-wire steering system designed according to the invention; and

Fig. 2 is a diagrammatic representation of an exemplary embodiment of a method for operating an electrical machine when executing a method

Feedback actuator in a steering system according to the invention limits the torque provided by the electric machine.

1 shows an exemplary embodiment of a steer-by-wire system designed according to the invention.

Steering system 1 for a motor vehicle shown. The steer-by-wire steering system 1 includes one

Steering column with a steering shaft 2, a steering handle 7 designed as a steering wheel being arranged in a rotationally fixed manner at one end of the steering shaft 2. You can use the steering handle 7

Give the driver a steering command. The steering handle can be rotated in a known manner in order to introduce a torque as a steering command into the steering shaft 2, which is detected by sensors, in particular sensor signals S1 relating to an applied

Angle of rotation, an applied torque and a rotational speed of the steering shaft 2 are recorded.

Furthermore, the steer-by-wire steering system includes 1 in this exemplary embodiment

Steering gear 3 with a steering actuator 5 designed as a steering pinion and a coupling element 6 designed as a rack. The steering actuator 5 includes an electric motor 9, which can in particular be designed as a three-phase permanent magnet synchronous motor. With the electric motor 9, the steering actuator 5 can be used to act on the coupling element 6 and to trigger a steering movement of steerable wheels 4, which in particular

Tie rods 8 are connected to the coupling element 6, drive. The tie rods 8 themselves are each connected to a steered wheel 4 in a known manner via steering knuckles.

In a normal operating mode of the steer-by-wire steering system 1, the detected

Sensor signals S1 as a detected steering command to a control unit 12 of the steer-by-wire

Steering system 1, in particular an ECU (ECU: Electronic Control Unit), sent. The

Control unit 12 generates a control signal C2, in particular based on the received sensor signals S1. The control signal C2 is used to convert the detected steering command into the

Steering movement of the steerable wheels 4 is sent to the electric motor 9 of the steering actuator 5. The

Electric motor 9 then converts the received control signal C2 into a rotational movement of the steering actuator 5, with the steering actuator 5 converting this rotational movement into a corresponding translational movement of the coupling element 6, which leads to the adjustment of the steering angle of the steerable wheels 4. 5

The steer-by-wire steering system 1 further comprises a feedback actuator 10 having an electric machine 11, which is designed to be operated in a motor operation M1, M2 and in a generator operation G1, G2 and thereby generate a torque or a steering resistance -To exert torque on the steering shaft 2, as will be explained further below with reference to FIG. 2. The electric machine 11 is designed to have a speed-dependent maximum in engine operation M1, M2

To provide operating torque BD_max, wherein in the engine operation M1, M2 the torque provided by the electric machine 11 is limited, so that the provided

Torque is smaller than the maximum operating torque BD_max.

In Fig. 2 is a Cartesian coordinate system with an abscissa axis and a

The ordinate axis is shown, with a speed w of the steering shaft 2 on the abscissa axis

Steer-by-wire steering system 1 and a torque NM, which is generated by the electric machine 11 of the steer-by-wire steering system 1, is plotted on the ordinate axis. In this exemplary embodiment, the positive section of the abscissa axis describes a

Clockwise rotation of the steering shaft 2 and the negative section of the abscissa axis one

Left rotation of the steering shaft 2. In the first quadrant and the third quadrant of the

Coordinate system shows a motor operation M1, M2 of the electric machine 11 and in the second quadrant and the fourth quadrant a generator operation G2, G1 of the electric machine 11.

The maximum operating torque BD_max, which could in principle be provided by the electric machine 11 in engine operation M1, M2, is shown in dashed lines in the first and third quadrants of the coordinate system. However, the torque provided by the electric machine 11 in the engine operation M1, M2 is limited in such a way that the predetermined torque characteristic DK is different from that provided

Torque is not exceeded. The torque characteristic DK is in this

Embodiment a speed w-dependent torque characteristic. The

The torque characteristic curve drops steeply up to a predetermined speed w1, in particular to a value of 3.5 Nm, and is then kept constant at this value up to a speed w2, and then drops to 0 Nm up to a speed w_max.

9 BE2022/5523

In contrast, in the generator operation G1, G2 of the feedback actuator 10, a speed-dependent maximum steering resistance operating torque LD max that can be provided by the electric machine 11 and generates a steering resistance is permitted.

In particular, the maximum steering resistance operating torque LD max can be 30 Nm at low speeds and can still drop to up to 15 Nm at high speeds. Beyond the speed w_max, the maximum steering resistance also falls

Operating torque drops to 0 Nm.

In particular, the feedback actuator in generator operation G1, G2 can have a steering resistance

Providing torque to give a driver a natural steering feel. In addition, the steering handle 7 can be adjusted using the electric machine 11 of the feedback actuator 10

Motor operation M1, M2 move back to the starting position after a steering movement, in which the steerable wheels 4 of a motor vehicle are aligned in the straight-ahead direction. Furthermore, by means of the electrical machine 11 of the feedback

Actuator 10 in engine operation M1, M2 causes a vibration in the steering handle 7 of the steer-by-wire

Steering system 1 can be introduced as an indication function. Preferably the engine operation is M1,

M2 of the feedback actuator is limited to these aforementioned operating situations.

In the exemplary embodiment shown in FIG. 1 it is provided that the control unit 12 of the steer-by-wire steering system 1 is also designed to control the feedback actuator 10. The control unit 12 is additionally set up to control the torque provided by the electric machine 11 in the motor operation M1, M2 of the feedback actuator 10 by controlling the electric machine 11 in the motor operation M1, M2

Limit operation of the feedback actuator 10, in particular as shown in Fig. 2. To do this, the control unit sends a control signal C1 to the electric machine 11. In particular, it can also be provided that the steer-by-wire steering system 1 comprises an electronic circuit that is designed to provide a current and/or a voltage for operating the electric machine 11 in the motor operation M1, M2 when operating the feedback actuator 10 in order to limit the torque that can be provided by the electric machine 11 in this way.

In the exemplary embodiment shown in FIG. 1, the control unit 12 is designed to evaluate the received sensor signals S1 and to limit the torque provided by the electric machine 11 in the motor operation M1, M2 depending on the situation. The torque provided by the electric machine 11 in the motor operation M1, M2 of the feedback actuator 10 is also limited by the control signal C1 when the control unit 12 has recognized that a predetermined acceleration of a rotation of the steering shaft 2 of the

10 BE2022/5523

Steer-by-wire steering system 1 is exceeded in the engine operation M1, M2. Furthermore, that provided by the electric machine 11 in the engine operation M1, M2

Torque limited by adjusting the control signal C1 when the control unit 12 has recognized that a predetermined rotational speed of the steering shaft 2 of the steer-by-wire

Steering system 1 is exceeded in the engine operation M1, M2. In particular, it is provided that the torque provided by the electric machine 11 in motor operation M1, M2 is provided by the control unit 12 at a rotational speed of

Steering shaft 2 steer-by-wire steering system 1 is limited in an interval between 100 deg/sec and 150 deg/sec to a value in an interval between 3 Nm and 5 Nm. At a

If the rotational speed of the steering shaft 2 of the steer-by-wire steering system 1 exceeds 150 deg/sec, the control signal C1 is further adjusted by the control unit 12 in such a way that no more torque is provided by the electric machine 11 in the motor operation M1, M2. The torque is therefore limited to a value of 0 Nm.

Those shown in the figures and explained in connection with them

Exemplary embodiments serve to explain the invention and are not limiting for it.

N BE2022/5523

List of reference symbols 1 steering system 2 steering shaft 3 steering gear 4 steerable wheel 5 steering actuator 6 coupling element 7 steering handle 8 tie rod 9 electric motor of the steering gear (3) 10 feedback actuator 11 electric machine of the feedback actuator (10) 12 control unit

M1,M2 motor operation

G1,G2 generator operation

BD_max maximum operating torque

DK torque characteristic

LD max maximum steering resistance operating torque u abscissa (speed)

NM ordinate (torque) s1 sensor signals

C1 Control signals for the feedback actuator

C2 control signals for the steering actuator

Claims (13)

12 BE2022/5523 claims 1. Method for operating a feedback actuator (10) comprising an electric machine (11) in a steering system (1) of a motor vehicle, the feedback actuator (10) being in motor operation (M1, M2) and in generator operation (G1 , G2) is operated, and wherein the electric machine (11) is designed to provide a speed-dependent maximum operating torque (BD_max) in the engine operation (M1, M2), characterized in that in the engine operation (M1, M2) that of the electrical The torque provided to the machine (11) is limited so that the torque provided is smaller than the maximum operating torque (BD_max). 2. The method according to claim 1, characterized in that a torque characteristic (DK) is specified for the motor operation (M1, M2) of the feedback actuator (10), the electric machine (11) being used in the motor operation (M1, M2 ) provided torque is limited in such a way that the torque characteristic (DK) is not exceeded by the provided torque. 3. The method according to claim 2, characterized in that the torque characteristic (DK) is a speed (w)-dependent torque characteristic. 4. Method according to one of the preceding claims, characterized in that the torque provided by the electric machine (11) in the motor operation (M1, M2) of the feedback actuator (10) is limited when a predetermined acceleration of a rotation of a steering shaft ( 2) of the steering system (1) is exceeded in engine operation (M1, M2). 5. Method according to one of the preceding claims, characterized in that the torque provided by the electric machine (11) in the motor operation (M1, M2) of the feedback actuator (10) is limited when a predetermined rotational speed of a steering shaft (2) of the steering system (1) is exceeded in engine operation (M1, M2). 6. The method according to any one of the preceding claims, characterized in that at a rotational speed of a steering shaft (2) of the steering system (1) in an interval between 100 deg/sec and 150 deg/sec that of the electric machine (11) in which 13 BE2022/5523 engine operation (M1, M2) of the feedback actuator (10) is limited to a value in an interval between 3 Nm and 5 Nm. 7. The method according to any one of the preceding claims, characterized in that when a rotational speed of a steering shaft (2) of the steering system (1) of 150 deg/sec is exceeded, that of the electric machine (11) in the motor operation (M1, M2). Feedback actuator (10) provided torque is limited to a value of 0 Nm. 8 Method according to one of the preceding claims, characterized in that motor operation (M1, M2) of the feedback actuator is limited to the following operating situations: returning a steering handle (7) of the steering system (1) to a starting position and / or introducing a vibration in a steering handle (7) of the steering system (1) as an indication function. 9. The method according to any one of the preceding claims, characterized in that in the generator operation (G1, G2) of the feedback actuator (10), a speed-dependent maximum steering resistance operating torque (LD_max) which can be provided by the electric machine (11) and generates a steering resistance is permitted . 10. The method according to claim 9, characterized in that the maximum steering resistance operating torque (LD_max) has a value in an interval between 15 Nm and 30 Nm. 11. Steer-by-wire steering system (1) for a motor vehicle comprising a steering shaft (2), a steering handle (7) arranged in a rotationally fixed manner on the steering shaft (2) and a feedback actuator (10) having an electric machine (11). , which is designed to be operated in a motor mode (M1, M2) and in a generator mode (G1, G2) and thereby exert a torque or a steering resistance torque on the steering shaft (2), and wherein the electric machine (11) is designed to provide a speed-dependent maximum operating torque in the engine operation (M1, M2), characterized in that the steer-by-wire steering system (1) is designed to use the feedback actuator (10) according to a method according to one of the preceding claims to operate. 12. Steer-by-wire steering system (1) according to claim 11, characterized by an electronic circuit which is designed to provide a current or a 14 BE2022/5523 voltage for operating the electrical machine (11) in the motor operation (M1, M2) when operating the feedback actuator (10) to limit circuitry. 13. Steer-by-wire steering system (1) according to claim 11 or claim 12, characterized by a control unit (12) for controlling the feedback actuator (10), the control unit (12) being set up by controlling the electrical Machine (11) in the motor operation (M1, M2) to limit the torque provided by the electric machine (11) in the motor operation (M1, M2) of the feedback actuator (10) when operating the feedback actuator (10).