Redundant manual steering torque sensing in steer-by-wire steering systems

Abstract

The invention relates to a device for sensing a manual steering torque in a steer-by-wire steering system (10), in particular in the event of a failure of a primary steering detection device (90), comprising: a steering handle (60), a steering column (80) which is mechanically coupled to the steering handle (60) and which is rotatably movable by means of the steering handle (60), and a force feedback motor (100) coupled to the steering column (80) for generating force feedback at the steering handle (60) and resetting the steering handle (60) during normal driving operation, wherein a steering input determination device (110) is coupled to the force feedback motor (100), which is designed to determine a steering direction and a To determine and provide steering torque.Furthermore, the invention relates to a method for determining the manual steering torque of a steer-by-wire steering system (10), in particular in the event of a failure of a primary steering detection device (90).

Description

The invention relates generally to steering systems for motor vehicles in which no mechanical coupling is present between a steering handle, for example a steering wheel, and the steered wheels, which is also referred to as a steer-by-wire steering system, since the steering information input at the steering handle is transmitted via a cable to a steering mechanism. In particular, the invention relates to the redundant determination of the manual steering torque with which a steering input takes place at the steering handle and, if appropriate, further variables which influence the steering.In principle, assistance systems are known which assist a vehicle driver who operates a steering system via a steering handle to apply the required torques for steering the wheels. DE 10 2018 200 995 A1 describes a method for operating a steering system, wherein the steering system has at least one electric three-phase machine for electric steering assistance, at least one control loop for controlling the electric three-phase machine and at least one compensation device operatively connected to the control loop for reducing a torque ripple of the electric three-phase machine, wherein at least one compensation parameter of the compensation device is determined. It is proposed that at least one operating parameter correlated with a pre-commutation angle of the three-phase electric machine and / or with a supply voltage of the three-phase electric machine is taken into account in the determination of the at least one compensation parameter. The method described is intended to reduce the three-phase ripple, which can lead, inter alia, to disadvantageous noise emissions.DE 10 2020 133 576 A1 describes a steering arrangement, in particular for a drive-by-wire steering system of a vehicle, for transmitting a steering torque, having an input means for inputting a steering command, a steering shaft having a first region and a second region spaced apart from the first region in a longitudinal direction of the steering shaft, and a sensor system for detecting a steering angle and / or a steering torque at the steering shaft, wherein the sensor system has a first angle sensor and a second angle sensor, wherein the first angle sensor is assigned to the first region and the second angle sensor is assigned to the second region, so that a determination of the steering torque at the steering shaft twisted by the steering torque is made possible by means of a difference between a first angle signal of the first angle sensor and a second angle signal of the second angle sensor. Furthermore, a method for determining a steering torque of a steering system is described.Since it is required, in particular for automated driving, that the vehicle can still be reliably transferred into a safe state even in the event of failure of one of the sensors, redundancy is necessary for sensors of the steering system.DE 102020 116 863 A1 is concerned with reducing the cabling outlay and describes a sensor arrangement for an electromechanical steering system of a motor vehicle, comprising a measuring device and a control device, wherein the measuring device comprises a torque sensor unit and an index sensor unit, wherein the torque sensor unit is connected to the control device via a supply line for the purpose of supplying said torque sensor unit with electrical energy, characterized in that the sensor arrangement is designed to transmit an index signal of the index sensor unit to the control device by modulation of a signal which can be transmitted via the supply line.The invention is based on the object of improving a redundant measurement of parameters important for steering, in particular to provide a device and a method for redundantly measuring a manual steering torque in a steer-by-wire steering system.The object is achieved according to the invention by a device having the features of patent claim 1 and by a method having the features of patent claim 8. Advantageous embodiments are evident from the dependent claims.The invention is based on the concept of using this force feedback motor in a steering arrangement of a steer-by-wire steering system which has a steering handle which is operatively connected to a force feedback motor via a steering column, such that the force feedback motor, during normal driving operation, generates or can generate a feedback force on the steering handle in the event of a steering input and moves it back or can move it into an initial position without the acting manual steering torque, in order to determine at least one steering direction and one manual steering torque in a generator operation. For this purpose, variables occurring on the force feedback motor on the basis of a rotational movement of a rotor occurring during the steering input are ascertained and evaluated.DefinitionsA steer-by-wire steering system is considered to be a steering system in a vehicle in which there is no operatively mechanical connection or coupling between a steering arrangement, via which steering inputs of a vehicle driver are detected, and the steered wheels. Rather, steering information is transmitted via a wire or cable (wire) from the steering arrangement to a steering mechanism which turns the wheels of the vehicle.A steering arrangement is understood to mean an arrangement by means of which steering inputs of a vehicle driver are detected. The steering arrangement here comprises a steering handle which represents an element which the vehicle driver moves in order to perform a steering input. As a rule, the steering handle is designed as a steering wheel. The steering arrangement further comprises a steering shaft, also referred to as a steering column, which performs a rotational movement about its own axis during a movement of the steering handle. The steering column is mechanically coupled to a rotor of the force feedback motor such that rotational movement of the steering column causes rotational movement of a rotor of the force feedback machine. Conversely, during motor operation of the force feedback motor, a torque acts on the steering column, which brings about feedback and moves the steering handle back into an initial position if no hand steering torque or a lower hand steering torque acts on the steering handle than the motor torque.A steering angle refers to an angular position of the steering column due to a steering movement of the steering handle relative to the initial angular position of the steering column, which coincides with an initial position of the steering handle and a straight-ahead position of the steered reeds of the vehicle.The steering torque is the torque acting on the steering column by a user by means of the steering handle, with which a change in the steering angle can be effected.Preferred EmbodimentsIn particular, a device for sensing a manual steering torque in a steer-by-wire steering system, in particular in the event of a failure of a primary steering detection device, is provided, which comprises:a steering handle,a steering column mechanically coupled to the steering handle, which steering column is rotationally movable by means of the steering handle,a force feedback motor coupled to the steering column for generating a force feedback on the steering handle and resetting the steering handle during normal driving operation,wherein a steering input detecting means is coupled to said force feedback motor,The invention is configured to ascertain and provide a steering direction and a steering torque during generator operation of the force feedback motor, in which a rotor of the force feedback motor is rotated due to a movement of the steering handle.Furthermore, a method for determining the manual steering torque of a steer-by-wire steering system is provided, which comprises a steering handle, a steering column mechanically coupled to the steering handle, which steering column is rotationally movable by means of the steering handle, and a force feedback motor coupled to the steering column for generating a force feedback at the steering handle and restoring the steering handle during normal driving operation, wherein the method comprises the steps:Operating the force feedback motor as a generator, in which a rotor of the force feedback motor is rotated due to a movement of the steering handle, and ascertaining a steering direction and a steering torque on the basis of the rotational movement of the rotor by means of a steering input detection device, and providing the steering direction and the steering torque from the steering input detection device.These embodiments provide the advantage that the most important information required to be able to transfer a vehicle into a safe state can be determined or is determined with the aid of the force feedback motor and the variables generated during its generator operation. No additional sensors are required as a result, material, costs and weight and installation space, in particular directly adjacent to the steering column, can be saved.During normal driving operation, the steering inputs of a vehicle driver detected at the steering arrangement are determined using a primary steering detection device and are provided for further processing. The steering detection device can comprise one or more sensors in order to detect a steering angle and a steering torque and optionally further parameters. If the steering detection device fails or components thereof fail, so that the steering angle and the steering torque can no longer be reliably determined, the determination of the necessary variables, at least one steering direction and one steering torque is carried out via the generator operation of the force feedback motor.A steering direction can be determined on the basis of an induced current change direction. The induced current direction depends on a rotation direction of the rotor in the force feedback motor.The steering torque acting on the rotor via the steering handle causes a slip in generator operation, which slip is linked to the acting torque, i.e. the manual steering torque. it is therefore provided in one embodiment that the steering torque is determined in generator operation on the basis of a specific slip.In one development, the steering input detection device is designed to plausibilize the steering angle determined by the primary steering detection device and / or the steering torque determined by the primary steering detection device and to switch the force feedback motor into a generator mode, provided that the steering angle determined by the primary steering detection device and / or the steering torque determined by the primary steering detection device are recognized as not plausible. The variables ascertained in normal operation are thus continuously checked for plausibility. If they are not plausible, the system switches to the determination by means of the force feedback motor.Thus, in one embodiment, in a normal driving mode, a steering angle input via an actuation of the steering handle and an input steering torque are ascertained by a primary steering detection device which is coupled to the steering column, and the steering angle ascertained by the primary steering detection device and / or the steering torque ascertained by the primary steering detection device are checked by the steering input detection device for plausibility, wherein the force feedback motor is operated by motor as long as the steering angle ascertained by the primary steering detection device and / or the steering torque ascertained by the primary steering detection device are ascertained as plausible and otherwise the force feedback motor is operated by generator in order to ascertain the steering direction and the steering torque.The change can also be triggered by other control units in the vehicle.In addition to the steering direction and the steering torque, it is desirable to also determine the steering angle. In one embodiment, it is therefore provided that the steering input detection device is designed to derive and provide the steering angle on the basis of signals from a rotor position sensor of the force feedback motor. A steering angle is determined and provided on the basis of the measurement signals of a rotor position sensor of the force feedback motor. This allows reliable steering.It can furthermore be provided that signals of a rotor position sensor of the force feedback motor are evaluated for plausibility checking the steering angle determined by the primary steering detection device.One specific embodiment provides that, for plausibility checking of the steering torque ascertained by the primary steering detection device, a rotational speed of the force feedback motor and the power consumed are evaluated for generating the force feedback. This allows simple and reliable plausibility checking using variables which are determined anyway during normal operation and / or which can be determined easily without great effort.The invention is explained in more detail below with reference to a drawing. The following shows: FIG. 1 shows a motor vehicle with a steer-by-wire steering system.FIG. 1 schematically illustrates a motor vehicle 10. This comprises a steer-by-wire steering system 10. The steer-by-wire steering system 10 comprises a steering arrangement 20 via which a steering input of a vehicle driver (not shown) is detected.The steering arrangement 20 further comprises a steering mechanism 30, which is coupled to wheels 40, for example a front axle, of the motor vehicle 1 in such a way that it can steer the wheels 40. The steering arrangement 20 and the steering mechanism 30 are coupled to one another by means of information technology via a steering control device 50. The information of the steering input is thus transmitted to the steering control device by information technology and there converted into control commands for the steering mechanism 30, which in turn are then transmitted to the steering mechanism by information technology. The information-related coupling between the various components can be effected, for example, via electrical and / or optical cables 140, 150 of a cable harness or else by means of wireless radio communication.For steering the motor vehicle 1, a driver or vehicle driver actuates a steering handle 60, which is preferably designed as a steering wheel 70. As a rule, there is an excellent position of the steering handle 60, i.e. preferably of the steering wheel 70, which is correlated with straight-ahead travel of the motor vehicle 1. If the steering handle 60 of the steering arrangement 30 is in this excellent position, the steering mechanism 30 and the steerable wheels 40 of the motor vehicle 1 mechanically coupled thereto are likewise in a straight-ahead travel position. In the straight-ahead position, the steerable wheels 40 are not steered in.Upon actuation, a manual steering torque acts on the steering handle 60 The steering handle 60 is mechanically coupled to a steering column 80 such that actuation of the steering handle 60 causes rotational movement of the steering column 80 about its own longitudinal axis 81.A primary steering detection device 90 senses the rotation of the steering column and measures, on the one hand, the wrist moment, which is also referred to as steering moment for short. Further, a steering angle is measured or determined by the primary steering detector 90. The steering angle indicates the angle by which the steering column 80 or the steering handle 60 is rotated with respect to the excellent position correlated with straight ahead travel. The steering angle can assume positive and negative values depending on the direction in which the vehicle is to be steered.The steering torque and the steering angle obtained are transmitted to the steering control device 50 via the cable 140. The steering control device 50 calculates from this the control commands which are transmitted via the cable 150 to the steering mechanism 30, which then correspondingly turns in the steerable wheels 40. It will be understood by those skilled in the art that the steering angle detected by the steering assembly 20 is different from the angle by which the angles are adjusted from their straight position.The steering column 80 is, in turn, mechanically coupled to a force feedback motor 100 such that rotation of the steering column 80 about its longitudinal axis 81 causes rotation of a rotor (not shown) of the force feedback motor 100. In the same way, analogously to the force feedback motor 100, a torque can be coupled into the steering column 80 in a motor-driven operation in order to generate a counter-torque for a driver to the manual steering torque applied by the driver and acting on the steering handle 60 as feedback of the steer-by-wire steering system 10. This simulates the behavior of a classic mechanical steering system of a motor vehicle. Further, the force feedback motor 100 is also used to move the steering handle back to the initial position when the manual steering torque decreases and is less than the counter torque generated by the force feedback motor 100.In the illustrated embodiment, a steering input determination device 110 is additionally formed in the steering control device 50. In other embodiments, this can also be formed separately from the steering control device 50. During normal driving operation, in which the steering angle and the steering torque are detected by the primary steering detection device 90, a plausibility checking device 130 of the steering input determination device 110 preferably plausibility checks this steering angle and this steering torque. The steering angle can be checked for plausibility, for example, on the basis of a signal from a rotor position sensor 120 of the force feedback motor 100.The steering torque can be checked for plausibility, for example, on the basis of the electrical power consumed for generating the counter torque for the force feedback and a rotational speed of the rotor derived from the signals of the rotor position sensor 120.If it is determined by the plausibility checking device 130 or in another way that the steering angle or the steering torque cannot be provided or cannot be provided correctly by the primary steering detection device 90, then the force feedback motor 100 is put into a generator mode. On the basis of the current direction or current change, which is induced in the force feedback motor 100 during a steering movement of the steering handle on account of the rotation of the rotor coupled thereto, it is possible to determine a steering direction which is then provided by the steering input determination device 110 in order to bring the motor vehicle 1 into a safe state.For example, on the basis of the slip of the force feedback motor 100 determined during generator operation, it is possible to infer the steering torque applied when the steering handle is moved. This is then likewise provided by the steering input determination device 110 in order to be able to bring the motor vehicle 1 into a safe state.In some embodiments, a steering angle can additionally be determined and provided from the evaluation of signals of the rotor position sensor 120.In order to still be able to provide a dynamic counterforce for the steering input, in one embodiment it can be provided that an electrical load is connected to the force feedback motor 100 in the generator mode.In this embodiment, it is thus possible to bring the vehicle into a safe state even in the event of failure of the primary steering detection device 90 which determines the steering angle and the steering torque of the steering input, and to determine and provide the steering information necessary for this purpose by means of the force feedback motor 100 from the variables detected during its generator operation.It will be understood by those skilled in the art that only one exemplary embodiment is described herein. The individual features can be used in any combination to implement the invention.List of reference characters1 Motor vehicle 10 steer-by-wire steering system 20 steering arrangement 30 steering mechanism 40 wheels 50 steering control device 60 steering handle 70 steering wheel 80 steering column 81 longitudinal axis 90 primary steering detection device 100 force feedback motor 110 steering input determination device 120 rotor position sensor 130 plausibility checking device 140 cable 150 cableReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2018 200 995 A1

[0002] DE 10 2020 133 576 A1

[0003] DE 102020 116 863 A1

[0005]

Claims

Device for sensing a manual steering torque in a steer-by-wire steering system (10) comprising a steering handle (60), a steering column (80) which is mechanically coupled to the steering handle (60) and can be moved in a rotational manner by means of the steering handle (60), and a force feedback motor (100) which is coupled to the steering column (80) for generating a force feedback at the steering handle (60) and resetting the steering handle (60) during normal driving operation, characterized in that a steering input determination device (110) is coupled to the force feedback motor (100) and is designed to determine and provide a steering direction and a steering torque during the generator operation of the force feedback motor (100), in which a rotor of the force feedback motor (100) is moved in a rotational manner on the basis of a movement of the steering handle (60).Device according to Claim 1, characterized in that a primary steering detection device is coupled to the steering column (80), which steering detection device is designed to ascertain and provide a steering angle and a steering torque during a normal driving operation.Device according to Claim 2, characterized in that the steering torque is determined in generator operation on the basis of a specific slip.Device according to one of the preceding claims, characterized in that the steering input determination device (110) is designed to plausibly check the steering angle determined by the primary steering detection device (90) and / or the steering torque determined by the primary steering detection device (90) and to switch the force feedback motor (100) into a generator mode, provided that the steering angle determined by the primary steering detection device (90) and / or the steering torque determined by the primary steering detection device (90) are recognized as not plausible.Device according to Claim 4, characterized in that the steering input detection device (110) is designed to derive and provide the steering angle on the basis of signals from a rotor position sensor (120) of the force feedback motor (100).Device according to one of Claims 4 or 5, characterized in that signals of a rotor position sensor (120) of the force feedback motor (100) are evaluated in order to plausibilise the steering angle determined by the primary steering detection device (90).Device according to one of Claims 3 to 6, characterized in that, in order to plausibilize the steering torque determined by the primary steering detection device (90), a rotational speed of the force feedback motor (100) and the power consumed for generating the force feedback are evaluated.Method for determining the manual steering torque of a steer-by-wire steering system (10), which comprises a steering handle (60), a steering column (80) which is mechanically coupled to the steering handle (60) and can be moved in a rotational manner by means of the one steering handle (60), and a force feedback motor (100) coupled to the steering column (80) for generating a force feedback on the steering handle (60) and resetting the steering handle (60) during normal driving operation, comprising the steps: operating the force feedback motor (100) as a generator, in which a rotor of the force feedback motor (100) is rotationally moved on the basis of a movement of the steering handle (60), and a steering direction and a steering torque are ascertained on the basis of the rotational movement of the rotor by means of a steering input detection device (110), and the steering direction and the steering torque are provided by the steering input detection device (110).Method according to Claim 8, characterized in that a steering angle is determined and provided on the basis of the measurement signals of a rotor position sensor (120) of the force feedback motor (100).Method according to Claim 8 or 9, characterized in that, in a normal driving mode, a steering angle which is input via actuation of the steering handle and an input steering torque are determined by a primary steering detection device (90) which is coupled to the steering column (80), and the steering angle which is determined by the primary steering detection device (90) and / or the steering torque which is determined by the primary steering detection device (90) are checked for plausibility by the steering input detection device (110), and the force feedback motor (100) is operated by motor as long as the steering angle which is determined by the primary steering detection device (90) and / or the steering torque which is determined by the primary steering detection device (90) are determined as plausible and otherwise the force feedback motor (100) is operated by generator in order to determine the steering direction and the steering torque.

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