Driver torque and steering angle measurement in a Torque Overlay Steering (TOS) system

Abstract

Method for determining a driver torque of a power steering assembly for an electro-hydraulic power steering system of motor vehicles, wherein the power steering assembly comprises an input shaft (2) for introducing a driver torque, an output shaft (1) for driving a steering linkage and a torsion bar (5) between the input shaft (2) and the output shaft (1) for actuating a rotary valve, an electric drive (10) for electric power steering assistance, and a control unit (9) for controlling the electric drive (10), and wherein a sensor arrangement (6) of the power steering assembly determines an actual torque using the torsion bar (5) for actuating the rotary valve, characterized in that the control unit (9) determines a driver torque based on the actual torque.

Description

[0001] The invention relates to a method for determining a driver torque of a power steering assembly for an electro-hydraulic power steering system of motor vehicles according to the preamble of claim 1, a low-floor vehicle for carrying out such a method, and a power steering assembly for an electro-hydraulic power steering system of motor vehicles according to the preamble of claim 20.

[0002] Hydraulically, electrically, or electro-hydraulically assisted power steering systems are known for providing steering assistance to motor vehicles. Such power steering systems are used, among other things, in light and heavy commercial vehicles, whereby the rotational movement of a steering wheel is transmitted, depending on the design, either directly or indirectly via linkages to tie rods.

[0003] Such power steering systems have been known for a long time and are available in many versions. For example, documents DE 10 2014 106 488 A1 and DE 10 2014 106 493 A1 describe power steering systems in which the steering assistance is obtained through the use of hydraulics.

[0004] Prior art DE 10 2017 219 161 A1 discloses a steering device for a vehicle comprising a controller configured to transmit steering control signals based on a first input signal from a torque sensor configured to detect the torque of a steering shaft, and a second input signal from any location sensor, camera sensor, distance sensor, vehicle speed sensor, and vehicle height sensor; a first steering force assist configured to generate steering force by rotating the steering shaft or to supplement the steering force of the forward or backward rotating steering shaft, using electrical energy in response to the steering control signal from the controller;and a second power steering assist configured to switch working fluid channels depending on the forward or reverse rotation of the steering shaft and to steer wheels by actuating a tie rod or steering knuckle using hydraulic pressure of the working fluid.

[0005] The prior art patent DE 11 2009 002 028 B4, which discloses the preamble, shows a method for controlling a steering device of a vehicle, the method comprising the following steps: (i) supplying a steering signal that indicates a steering maneuver to be performed; (ii) calculating a first desired parameter of the steering device during the steering maneuver when no external force is applied to a handwheel of the vehicle; (iii) measuring a second parameter with a sensor during the steering maneuver; (iv) generating a mode signal by comparing the first desired parameter with the second parameter; (v) switching the vehicle into an autonomous driving mode or a manual driving mode based on the mode signal, characterized by the steps (vi) calculating a desired handwheel position based on the steering signal after the steering maneuver has been performed;(vii) Determining the current handwheel position before the steering maneuver is performed; (viii) Rotating the handwheel (14) to the desired handwheel position by means of an electric motor when the vehicle is in autonomous driving mode.;

[0006] Electro-hydraulic power steering systems are equipped with various sensor combinations, such as a torque and angle sensor (TAS sensor), to differentiate between the torque applied by the driver via the steering wheel and the torque originating from, for example, the electric power steering system. A TAS sensor typically includes angle sensors to determine the angle difference between the steering wheel (or its input shaft to the power steering system) and a shaft of the electric power steering actuator. The electric actuator is connected to the input shaft via a torsion bar, allowing for relative rotation between the input shaft and the electric actuator. Using the characteristic curve of the torsion bar and the angle difference, the torque applied by the driver to the power steering system can be determined.

[0007] In addition to electric assistance, an electro-hydraulic power steering system includes hydraulic power steering. This is achieved by connecting a hydraulic power steering unit in series with the output of the electric power steering system. The hydraulic power steering unit also consists of two shafts connected by a torsion bar. Together with the torsion bar, these two shafts form a rotary valve, which controls the flow of hydraulic fluid. The greater the twist between the two shafts, the wider the rotary valve opens, and the stronger the hydraulic steering assistance.

[0008] However, such power steering systems comprise a large number of components and sensors, making them complex to manufacture and maintain. They also require more installation space compared to a purely hydraulic power steering system.

[0009] The object of the present invention is therefore to provide an improved electro-hydraulic power steering system for motor vehicles compared to the prior art, which has a significantly simplified design.

[0010] With regard to a method for determining a driver torque of a power steering assembly for an electro-hydraulic power steering system of motor vehicles according to the preamble of claim 1, the problem according to the invention is solved by the features of the characterizing part of claim 1. With regard to a low-floor vehicle for carrying out such a method, the problem according to the invention is solved by a low-floor vehicle with the features of claim 14. With regard to a power steering assembly for an electro-hydraulic power steering system of motor vehicles according to the preamble of claim 15, the problem according to the invention is solved by the features of the characterizing part of claim 20. Advantageous further embodiments are specified in the dependent claims.

[0011] The essential aspect of the invention is that the torsion bar for actuating the rotary valve is used to determine the driver's torque, which is already present due to the hydraulic steering assistance, and no additional torsion bar is necessary to determine the driver's torque.

[0012] This eliminates the need for numerous mechanical components such as an additional torsion bar, another shaft, bearings, etc. By utilizing other resources, such as a motor sensor, which is typically present on modern electric motors, and employing a specialized control system, the number of additional sensors required to determine the driver's torque can be minimized.

[0013] Furthermore, it has been shown that such an arrangement allows for the production of particularly compact electro-hydraulic power steering assemblies, which are of particular interest in confined spaces, such as in low-floor vehicles.

[0014] It should be noted that the features listed individually in the claims can be combined with one another in any technically meaningful way (even across category boundaries, for example between method and apparatus) and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0015] The method according to the invention serves to determine a driver torque of a power steering assembly for an electro-hydraulic power steering system of motor vehicles. According to the invention, the power steering assembly comprises an input shaft for introducing a driver torque, an output shaft for driving a steering linkage, a torsion bar between the input shaft and output shaft for actuating a rotary valve, an electric drive for electric power steering assistance, and a control unit for controlling the electric drive.

[0016] The method according to the invention provides that a sensor arrangement of the power steering assembly determines an actual torque using the torsion bar to actuate the rotary valve, and that the control unit determines a driver torque based on the actual torque.

[0017] The input shaft is connected to the vehicle's steering element. This steering element is typically a steering wheel and is connected to the input shaft via a steering column. By turning the steering wheel, the driver applies torque – the driver's torque – through the input shaft to the power steering assembly. Once the steering assistance is provided, the force is transmitted via the output shaft to a steering linkage to change the vehicle's direction.

[0018] The input shaft is connected to the output shaft via a torsion bar. This assembly is designed as a rotary valve for the hydraulic power steering system. This means that the input shaft can be rotated relative to the output shaft, with the rotation opening or closing a valve orifice through which the hydraulic fluid is regulated. The hydraulic fluid then provides the hydraulic power steering.

[0019] For additional electric power steering or steering assistance, an electric drive can be coupled to the input shaft. However, coupling to the output shaft or other shafts that are in friction with the steering linkage is also conceivable. To control the electric drive, the driver's torque is regularly determined, among other things. This is determined using the sensor array that monitors the torsion bar for actuating the rotary valve. When the driver turns the steering wheel, a differential angle is initially established between the input and output shafts. This angle, together with the characteristic curve of the torsion bar, can be converted into the actual torque. The actual torque is the torque actually applied to the steering linkage. The actual torque can be composed of several components.It typically comprises the driver's torque and the torques from the various power steering systems and opposes the vehicle's steering resistance. The actual torque can be converted into driver torque by considering the prevailing torques, and specifically the torque applied by the electric drive. This value is then used to control the electric drive.

[0020] The electric drive preferably comprises an electric motor and a gearbox. The electric motor is preferably equipped with an internal motor sensor that measures and outputs motor characteristics. These motor characteristics can include the motor current, the angle of the motor shaft, the voltage, or similar values. The gearbox is not limited to a specific design and can be implemented as a spur gear, planetary gear, worm gear, or helical gear. Other gearbox types may also be suitable.

[0021] According to one embodiment of the method, it is characterized in that the driver torque is also determined based on an assistance torque supplied by the electric drive. For electric power steering in certain operating conditions, the driver torque must be known in order to control the assisting electric motor. Therefore, the torque of, for example, the electric motor – i.e., the assistance torque – is usually known or can be estimated, so that this torque can be used to calculate the driver torque.

[0022] In a preferred embodiment, the method is characterized in that the sensor arrangement for determining the driver torque uses a TAS system. A TAS system is a sensor arrangement called a "Torque and Angle Sensor" and typically comprises several angle sensors with which torque and steering angle are measured. A TAS system is mounted at the interface of two shafts and monitors them. Here, the TAS system is mounted at the interface of the input and output shafts and, as is usually the case, does not require an additional intermediate shaft with an additional torsion bar. Using the sensors of the TAS system, the torque, the differential angle, and the absolute angle of the two shafts can be measured.Preferably, the TAS system is configured to measure the differential angle between the input and output shafts and the resulting torque on the torsion bar, as well as the absolute angle of the input shaft and / or the absolute angle of the output shaft. The number of sensors is not limited to those mentioned above. Rather, the number and type of sensors used are selected to enable the measurement of both angles and torque. Therefore, the sensor arrangement of the TAS system preferably comprises several sensors, such as torque sensors, angle sensors, and / or sensors for detecting the number of revolutions of the input shaft, with the aim of reliably and precisely measuring the torque and angles required for the application.It is therefore preferred that the sensor arrangement uses several sensors to determine the actual torque, in particular torque sensors and / or angle sensors and / or sensors for the input shaft's rotational speed. The input shaft's rotational speed is of interest because it usually corresponds to the steering wheel's rotational speed. Preferably, the TAS system includes a torque sensor for determining the actual torque and / or an absolute angle sensor.

[0023] According to a further preferred embodiment, the method is characterized in that the sensor arrangement uses only one sensor for determining the driver torque, which is configured as an angle sensor. The determination of the driver torque is based on the data from the angle sensor and the data from a motor sensor included in the electric drive for monitoring an electric motor of the electric drive. With a suitable calculation of the driver torque, it is possible to limit the sensor arrangement to a single angle sensor. Preferably, the angle sensor is configured to determine a differential angle between the input shaft and the output shaft. For such a calculation of the driver torque, the differential angle between the input shaft and the output shaft is detected by the sensor arrangement and combined with the measurement data from the motor sensor. Preferably, the motor sensor is also an angle sensor.This can be referred to as a motor angle sensor. In this way, both the driver torque can be determined from the differential angle and the characteristic curve of the torsion bar for actuating the rotary valve, and the rotational position of a motor shaft of the electric motor can be determined from the angle sensor of the motor sensor of the electric motor.

[0024] According to a further preferred embodiment, the method is characterized in that the sensor arrangement redundantly detects the actual torque. Redundant detection of the actual torque means that the actual torque is detected based on two different measured values. Preferably, this is achieved through redundant sensor design. Since intervention in the steering of a motor vehicle is safety-relevant, it is advantageous to design the sensor arrangement redundantly. In the simplest case, this can be done by providing duplicate sensors in the sensor arrangement. However, it can also be advantageous to provide different sensor types for the same measured value. This allows a measurement error that would occur with a particular type of sensor due to external circumstances to be detected. It can be provided that the electric drive is switched to passive mode or put into a safe mode in the case of ambiguous measured values.

[0025] In a preferred embodiment, the method is characterized in that the sensor arrangement is configured such that the actual torque is determined via a differential angle. Determining the actual torque via a differential angle is advantageous because the actual torque can then be calculated using the characteristic curve of the torsion bar.

[0026] In a further preferred embodiment, the method is characterized in that the sensor arrangement detects a difference angle between the input shaft and the output shaft to calculate the actual torque.

[0027] According to a preferred embodiment, the method is characterized in that the sensor arrangement detects a differential angle between a motor shaft of an electric motor of the electric drive and the output shaft for calculating the driver torque. This differential angle is suitable for calculation because the angle of the motor shaft is already known from the motor sensor, and only the angle of the output shaft needs to be additionally detected.

[0028] According to a further preferred embodiment, the method is characterized in that the sensor arrangement detects a differential angle between a shaft of an electric drive gearbox and the output shaft for calculating the driver torque. Alternatively, the sensor arrangement can be configured to detect a differential angle between a shaft of an electric drive gearbox and the input shaft for calculating the driver torque. Depending on the application, it may be necessary to connect a gearbox upstream of the output shaft to either increase the force or the speed. Since a gearbox essentially does not allow differential angles between the individual gearbox shafts, it is also possible to determine the differential angle for calculating the driver torque using a shaft within the gearbox and not necessarily directly at the input or output shaft of the power steering assembly. Preferably, the gearbox comprises a worm gear.

[0029] In a preferred embodiment, the method is characterized in that the sensor arrangement detects a differential angle between a motor shaft of an electric motor of the electric drive and the input shaft for calculating the driver torque. A gearbox or at least a friction-fit connection is typically located between the motor shaft and the input shaft. This connection allows essentially no play between the motor shaft and the input shaft, so that the differential angle for determining the driver torque can be calculated using the gear ratio of the gearbox or the friction-fit connection.

[0030] A preferred embodiment of the method is characterized in that the electric drive for steering assistance exerts a motor torque on the input shaft. Preferably, the electric drive is engaged with the input shaft. In this case, the transmission of the motor torque thus occurs directly from the electric drive to the input shaft.

[0031] This engine torque can also be used to determine the driver torque. Another preferred embodiment of the method is characterized in that the control unit also determines the driver torque based on the engine torque.

[0032] In principle, the motor torque can be determined in any way. According to a preferred embodiment of the method, the control unit determines the motor torque based on a measurement of the motor current used to operate the electric drive. Specifically, the measured motor current can be the current used to operate the electric motor. However, other parameters, and in particular other measured parameters, can also be used to determine the motor torque.

[0033] In a further preferred embodiment, the method is characterized in that the sensor arrangement detects a multi-turn-capable steering angle from the angle of a motor shaft of an electric motor of the electric drive and the angle of the output shaft. A multi-turn-capable steering angle is a steering angle that clearly defines the position of the steering wheel even after more than one full rotation. This can be, for example, an angle reading from 0 to 360° combined with an indication of the number of full rotations already completed, or an angle reading that does not restart at 0° beyond 360° but continues to increment. Such angle sensors usually comprise several sensors capable of outputting the desired multi-turn-capable steering angle. To eliminate the need for additional sensors, the motor sensor of the electric motor can be used to determine the required information.Preferably, the multi-turn steering angle is determined using the vernier scale principle. The vernier scale principle is known from, for example, calipers and other measuring devices. In the case of the power steering assembly, this principle can be used by comparing the angle of the motor sensor, which ranges from 0 to 360°, in combination with the gear ratio, to the angle of the input shaft, which also ranges from 0 to 360°. Thus, depending on the gear ratio, for example, with a motor angle of 73° and an input shaft angle of 169°, the steering wheel must be in its first rotation, while with a motor angle of 17° and an input shaft angle of 169°, the steering wheel must be in its second rotation.

[0034] According to a preferred embodiment, the method is characterized in that the sensor arrangement uses a computer module for calculating the driver torque. Depending on the complexity of the sensor data to be managed, it can be advantageous if the data is managed by a dedicated computer module and determines the driver torque. A combination of electric drive control and sensor data processing can also be useful. Preferably, the computer module is configured to control the electric drive. Other combinations of control units or data processing modules may be advantageous.

[0035] According to a further preferred embodiment, the method is characterized in that the sensor arrangement forwards the measured values ​​from the sensors to a module present in the vehicle for calculating the driver torque. To avoid the need for an additional control unit, the processing of the sensor data can be handled by a module already located in the vehicle. This could, for example, be a module that controls autonomous driving or is already responsible for steering functions. However, any other module with available capacity can also be used.

[0036] The low-floor vehicle according to the invention is characterized in that it comprises a power steering assembly for carrying out the proposed method.

[0037] The power steering assembly according to the invention is for an electro-hydraulic power steering system of motor vehicles and comprises an input shaft for introducing a driver torque, an output shaft for driving a steering linkage and a torsion bar between the input shaft and output shaft for actuating a rotary valve, an electric drive for electric power steering assistance and a sensor arrangement which is configured to determine an actual torque using the torsion bar for actuating the rotary valve.

[0038] The power steering assembly according to the invention is characterized in that the control unit is configured to determine a driver torque based on the actual torque.

[0039] Further advantages and features of the inventive method, the inventive low-floor vehicle, and the inventive power steering assembly will become apparent from the dependent claims, which relate to advantageous embodiments of the present invention and are not to be understood as limiting. The invention also encompasses combinations of features from different dependent claims, insofar as these are technically possible, even if the dependent claims do not relate to each other or if they belong to different claim categories. This also applies to the individual features of the exemplary embodiments discussed below, insofar as these are not recognizable to a person skilled in the art as necessarily belonging together.

[0040] The exemplary embodiments shown below are intended to explain the invention in more detail to those skilled in the art. The exemplary embodiments are explained with reference to the accompanying drawing. This drawing shows: Fig. 1: A schematic representation of a first embodiment of a power steering assembly according to the invention for carrying out the method according to the invention, Fig. 2: a schematic representation of a second embodiment of the power steering assembly according to the invention for carrying out the method according to the invention.

[0041] Fig. Figure 1 shows a first embodiment of the power steering assembly according to the invention for transmitting a steering movement from a steering wheel (not shown) to a steering linkage (also not shown). This embodiment of the Fig. 1 can also carry out the method according to the invention.

[0042] The driver's torque is transmitted via the steering wheel through the input shaft 2 into the power steering assembly. The input shaft 2 is connected to the gearbox 7 of the electric drive 10, which is a worm gear. The electric drive 10 further comprises the electric motor 3 with motor shaft 4 and motor sensor 8. The torsion bar 5 connects the input shaft 2 to the output shaft 1 in such a way that it allows a certain degree of rotation between the two. This is necessary because the input shaft 2 and output shaft 1 form a rotary valve, which is used to control the hydraulic power steering (not shown here). By rotating the input shaft 2 relative to the output shaft 1, valves are actuated that control the hydraulic power steering.As soon as the input shaft 2 and the output shaft 1 have a differential angle of essentially 0°, the steering linkage is in the position desired by the driver and the hydraulic power steering no longer transmits any force to the power steering assembly. The sensor assembly 6 is located at the interface of input shaft 2 and output shaft 1. This sensor assembly detects the differential angle between input shaft 2 and output shaft 1, which is then used to determine the driver's torque.

[0043] The one in Fig. The illustrated embodiment 2 shows essentially the same power steering assembly as the Fig. 1, with the difference that the sensor arrangement now only includes one angle sensor, which - in contrast to the sensor arrangement 6 which detects the difference angle Fig. 1 - the absolute angle of output wave 1 is recorded.

[0044] In both embodiments, the driver operates the steering in manual mode. To do this, they turn the steering wheel to indicate the desired direction of travel. This rotational movement of the steering wheel is transmitted to the input shaft 2. This causes the electric drive 10 to rotate simultaneously. By moving the electric drive 10, the angle of the motor shaft 4, and thus, taking into account the gear ratio of the transmission 7, the angle of the input shaft 2, can be determined by the motor sensor 8. Therefore, the position of the steering wheel and the direction in which the driver intends to steer the vehicle are known.

[0045] The electric drive 10 can apply motor torque in addition to the torque applied by the driver. This can be directed in such a way as to assist the driver's turning motion, or it can be directed in the opposite direction, requiring the driver to apply increased torque. In this way, the driver's steering feel can be influenced.

[0046] Rotating the input shaft 2 initially creates a differential angle between input shaft 2 and output shaft 1, since the torsion bar 5 elastically connects the input shaft 2 to the output shaft 1, and the output shaft 1 typically resists rotation due to, for example, frictional forces from the wheels. The differential angle is determined by the steering resistance of the wheels or the steering mechanism, which is directly connected to the output shaft 1.

[0047] In the exemplary embodiment of the Fig. 1. The difference angle is directly detected by the sensor arrangement 6. In the exemplary embodiment of the Fig. 2. The difference angle is determined by knowing not only the absolute angle of the output shaft 1 via the sensor arrangement 6, but also the angle of the input shaft 2 via the motor sensor 8. Since in both embodiments the input shaft 2 and output shaft 1 are connected by means of the torsion bar 5, the actual torque can be determined in both cases.

[0048] The greater the driver's torque in conjunction with the torque of the electric drive – i.e., the motor torque – the greater this differential angle. The rotation of the input shaft relative to the output shaft causes the hydraulic valves to open, so that hydraulic power steering introduces additional torque into the power steering assembly, assisting the driver in their steering movement. The hydraulic power steering acts at a point downstream of the torsion bar 5, such as the output shaft 1. The magnitude of the hydraulically introduced torque depends primarily on the size of the differential angle. As soon as the hydraulic power steering has rotated the output shaft 1 sufficiently to reduce the differential angle, the hydraulic valves close again, and the hydraulic torque decreases.If the differential angle approaches zero, the valves are essentially closed and the hydraulic power steering is no longer available.

[0049] The magnitude of the electrically applied motor torque can initially be controlled independently by the electric drive 10. However, in manual operation, it is recommended to use a control system that takes into account the differential angle and the measured values ​​from the motor sensor 8. The motor sensor 8 can determine the magnitude of the motor torque by measuring the motor voltages or currents used to operate the electric motor 3. This motor torque can be combined with the measured actual torque from the sensor arrangement 6 to determine the driver torque. With these known torque values, it is then possible to determine the appropriate level of electric power steering assistance.

[0050] In autonomous driving mode, the hydraulic power steering system functions and provides support in the same way as in manual mode. The required differential angle for controlling the hydraulics is again achieved by rotating the input shaft 2 relative to the output shaft 1; however, only the electrically applied torque – i.e., the motor torque – acts on the input shaft 2 and results in a differential angle. The driver's torque is not present, and the electric drive 10 can operate the steering without driver input, its movements being supported by the hydraulic power steering system. Reference symbol list 1 Output shaft 2 Input wave 3 Electric motor 4 Motor shaft 5 Torsion bar 6 Sensor arrangement 7 gearboxes 8 Motor sensor 9 Control unit 10 Electric drive

Claims

[1] Method for determining a driver torque of a power steering assembly for an electro-hydraulic power steering system of motor vehicles, wherein the power steering assembly comprises an input shaft (2) for introducing a driver torque, an output shaft (1) for driving a steering linkage and a torsion bar (5) between the input shaft (2) and the output shaft (1) for actuating a rotary valve, an electric drive (10) for electric power steering assistance, and a control unit (9) for controlling the electric drive (10), and wherein a sensor arrangement (6) of the power steering assembly determines an actual torque using the torsion bar (5) for actuating the rotary valve. characterized by , that the control unit (9) determines a driver torque based on the actual torque. [2] Method according to claim 1, characterized by, that the driver torque is also determined based on an assistance torque delivered by the electric drive (10). [3] Method according to any of the preceding claims, characterized by , that the sensor arrangement (6) uses a TAS system to determine the actual torque, preferably that the sensor arrangement (6) uses several sensors, in particular torque sensors, and / or angle sensors, and / or sensors for detecting the number of revolutions of the input shaft (2), to determine the actual torque. [4] Method according to claim 3, characterized by that the TAS system includes a torque sensor to determine the actual torque and / or an absolute angle sensor. [5] Method according to any one of claims 1 to 4, , characterized by, that the sensor arrangement (6) uses only one sensor for determining the actual torque, which is designed as an angle sensor, wherein the determination of the driver torque is determined from the data of the angle sensor and the data of a motor sensor (8) encompassed by the electric drive (10) for monitoring an electric motor (3) of the electric drive (10). [6] Method according to one of claims 1 or 4, characterized by , that the sensor arrangement (6) redundantly detects the actual torque, preferably by redundant sensor design. [7] Method according to any of the preceding claims, characterized by , that the sensor arrangement (6) is set up such that the actual torque is determined via a differential angle. [8] Method according to any of the preceding claims, characterized by , that the sensor arrangement (6) detects a difference angle between input shaft (2) and output shaft (1) to calculate the actual torque. [9] Method according to any of the preceding claims, characterized by , that the sensor arrangement (6) detects a difference angle between a motor shaft (4) of an electric motor (3) of the electric drive (10) and the output shaft (1) for calculating the driver torque. [10] Method according to any of the preceding claims, characterized by , that the sensor arrangement (6) detects a differential angle between a shaft of a gearbox (7) of the electric drive (10) and the output shaft (1) for calculating the driver torque. [11] Method according to claim 10, characterized by , that the transmission (7) comprises a worm gear. [12] Method according to any of the preceding claims, characterized by , that the sensor arrangement (6) detects a difference angle between a motor shaft (4) of an electric motor (3) of the electric drive (10) and the input shaft (2) for calculating the driver torque. [13] Method according to any one of the preceding claims, characterized by , that the electric drive (10) exerts a motor torque on the input shaft (2) for steering assistance, preferably that the electric drive (10) engages with the input shaft (2). [14] Method according to claim 13, characterized by , that the control unit (9) also determines the driver torque based on the engine torque. [15] Method according to claim 13 or 14, characterized by , that the control unit (9) determines the motor torque based on a measurement of a motor current for the operation of the electric drive (10). [16] Method according to any of the preceding claims, characterized by, that the sensor arrangement (6) detects a multiturn-capable steering angle from the angle of a motor shaft (4) of an electric motor (3) of the electric drive (10) and the angle of the output shaft (1), preferably detecting the multiturn-capable steering angle using the vernier principle. [17] Method according to any of the preceding claims, characterized by , that the sensor arrangement (6) uses a computer module to calculate the driver torque. [18] Method according to any of the preceding claims, characterized by , that the sensor arrangement (6) forwards the measured values ​​from the sensors to a module present in the motor vehicle for calculating the driver torque. [19] Low-floor vehicle, characterized by that the low-floor vehicle comprises a power steering assembly for carrying out a method according to one of claims 1 to 18. [20] Power steering assembly for an electro-hydraulic power steering system for motor vehicles, comprising an input shaft (2) for introducing a driver torque, an output shaft (1) for driving a steering linkage and a torsion bar (5) between the input shaft (2) and the output shaft (1) for actuating a rotary valve, an electric drive (10) for electric power steering, a control unit (9) for controlling the electric drive (10) and a sensor arrangement (6) which is configured to determine an actual torque using the torsion bar (5) for actuating the rotary valve, characterized by , that the control unit (9) is configured to determine a driver torque based on the actual torque.

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