Operating unit, method for testing functionality of magnetorheological brake, computer program product and steering-by-wire system

Abstract

The invention relates to an operating unit (1) for influencing the direction of travel of a motor vehicle (2) by means of a user, comprising: a rotatably mounted steering shaft (3) which can be coupled to a steering device (4); a force feedback actuator (5) connected to the steering shaft (3) for transmitting torque; a magnetorheological brake (6) likewise connected to the steering shaft (3) in order to transmit torque; and a control unit (7) for controlling the operating unit (1), the control unit (7) being designed to retrieve a program (9) for a functional test of the magneto-rheological brake (6) as a function of the trigger signal (8) and to run the program, the control unit (7) providing an error signal (10) when it is confirmed that the magneto-rheological brake (6) falls below a specified braking effect, the program (9) is configured such that the force feedback actuator (5) provides a motor torque (MEM), the magnetorheological brake (6) is provided with a test torque (MR), and the actual parameter (11) representative of the braking effect is the angular position of the magnetorheological brake (6) when the test torque (MR) is applied.

Description

Technical Field

[0001] This invention relates to an operating unit for influencing the direction of travel of a motor vehicle by a user. The operating unit includes: a rotatably mounted steering shaft connectable to a steering mechanism; a force feedback actuator connected to the steering shaft in a torque-transmitting manner; a magnetorheological brake also connected to the steering shaft in a torque-transmitting manner; and a control unit for controlling the operating unit. The invention also relates to a method for testing the functionality of a magnetorheological brake, a computer program product, and a steer-by-wire system. Background Technology

[0002] In applications such as motor vehicles, electric steering systems are used to receive directional requests from the driver and convert those requests into corresponding movements of one or more road-end wheels. Compared to purely mechanical steering systems, electric steering systems can be further categorized into electric assisted steering systems and fully electric steering systems, i.e., steer-by-wire systems. In particular, these steer-by-wire systems offer the following advantages: the operating unit can be positioned relatively freely within the vehicle, independent of mechanical connecting parts. This not only saves costs when distinguishing between right-hand and left-hand driving vehicles, for example, but also improves accidental behavior due to the absence of a steering column. Furthermore, the operating unit can be housed in a stowed position, which can also be used, for example, in fully automatic steering systems.

[0003] The steer-by-wire system within the scope of this invention should be understood to refer to a steering system that essentially includes a handwheel actuator (HWA), such as an actuator system around a command vehicle steering wheel, and a road wheel actuator (RWA), i.e., an actuator acting on a steering mechanism connected to the vehicle wheels. In this case, the steering signal is transmitted from the HWA to the RWA via wiring.

[0004] To create a realistic driving experience, existing technologies also know to record parameters such as vehicle speed, steering angle, lateral acceleration, and lever force from actual current driving conditions, or to calculate these parameters in a simulation and generate a feedback signal based on them, which is then fed into a force feedback actuator. The force feedback actuator is integrated into an input unit and has an actuator unit that includes an actuator that functions as a manual torque or steering wheel actuator and, based on the feedback signal, couples a feedback torque, at least partially corresponding to the actual reaction torque, to the steering wheel via the steering shaft. Partial feedback torque is particularly useful when other potentially controllable components, such as springs or brakes, provide additional feedback torque. The term feedback torque refers to two directions of action, meaning the feedback actuator can be rotated by the driver as an adjustable load. This force feedback system provides the driver with a feel for the actual driving situation, much like conventional steering, which aids in intuitive responses.

[0005] A steer-by-wire system with an input unit is known from DE 102008036730 A1, which includes an actuator unit driven by an electric motor. The electric motor is controlled by an electronic control unit that adjusts the motor current based on measurements characterizing the corresponding driving conditions. The motor shaft is directly coupled to the steering shaft such that the motor torque is the same as the manual torque coupled to the steering shaft. The electric motor is axially flanged to a housing unit relative to its longitudinal axis, and the motor shaft is connected via a coupling to the steering shaft mounted in the housing unit. An actuator unit with a similar structure is shown in EP 2414211 B1. In the embodiment described therein, the steering shaft itself forms the motor shaft of the electric motor, allowing for a more compact design.

[0006] In this context, force feedback actuators driven by electric motors with adaptive transmissions for improved speed and torque are also known. For example, electric motors with a worm gear drive at the end of the steering column, connected to the steering wheel by means of a shaft, are known. Examples of this implementation can be found in DE102018101528B4. With these transmissions, relatively high gear ratios and therefore high torque can be achieved or maintained, but the relatively large installation space requirements and angled designs are generally disadvantageous. Furthermore, such force feedback actuators coupled with worm gear drives typically require considerable effort to optimize in terms of precision and material selection regarding friction (often too high) and friction uniformity (often too uneven).

[0007] Besides worm gear drives, it is also known to connect an electric motor of a force feedback actuator to a planetary transmission at the end of the steering column, as described, for example, in CN215706606U. However, with planetary transmissions, only a moderate gear ratio and therefore only a moderate torque can typically be achieved in one stage. Force feedback using friction or loss torque requires additional effort and friction devices.

[0008] In principle, direct-drive force feedback actuators are also known, sometimes referred to as direct-drive. Examples of such designs can be found, for example, in CN112644580B or DE102018101528B4. In principle, such direct-drive force feedback actuators require a telescopic steering shaft at the distal end of the steering column, which is associated with cost and space requirements. For example, steering columns with direct-drive force feedback actuators near the steering wheel are disclosed in EP3960583A1 and EP3476692B1. EP3960583A1 and EP3476692B1 also disclose the option of a fixed steering column component positioned radially inward and a rotating steering wheel component positioned radially outward, which then also applies to force feedback actuators as motors (outer rotors) and / or magnetorheological brakes (outer rotors).

[0009] To achieve the most realistic steering feel possible in such steer-by-wire systems, it is also known to arrange magnetorheological brakes in the torque flow of the steering mechanism to increase the drag modulus. Combined, this allows for higher total restoring torque to be achieved with lower energy consumption in the same installation space.

[0010] For such magnetorheological brakes (whether internal or external rotors), immediate or gradual failure may occur, for example, due to seal failure or powder degradation. Summary of the Invention

[0011] In view of the prior art, the present invention aims to provide an operating unit for influencing the driving direction of a motor vehicle by a user, which can detect such loss of braking force of the magnetorheological brake and initiate countermeasures and / or warning measures. Another object of the invention is to realize an optimized method for testing the functionality of a magnetorheological brake, and to provide correspondingly improved computer program products and steer-by-wire systems.

[0012] This objective is achieved through an operating unit for influencing the driving direction of a motor vehicle by a user. The operating unit includes: a rotatably mounted steering shaft capable of being coupled to a steering mechanism; a force feedback actuator connected to the steering shaft in a torque-transmitting manner; a magnetorheological brake also connected to the steering shaft in a torque-transmitting manner; and a control unit for controlling the operating unit. The control unit is designed to invoke and execute a program for testing the functionality of the magnetorheological brake upon a trigger signal. If it is confirmed that the magnetorheological brake has degraded to a braking effect below a predefined level, the control unit provides a fault signal. The program is configured to cause the force feedback actuator to provide motor torque M. EM And test torque M R The actual parameter applied to the magnetorheological brake, and representing the braking effect, is the test torque M. R The angular position of the magnetorheological brake when it is applied.

[0013] This has the following advantages: a reduction in braking force or a failure of the magnetorheological brake can be detected at an early stage. The detected reduction in braking force can also be temporarily or partially compensated by means of the brake itself (e.g., by temporarily energizing the brake more forcefully) or by another feedback actuator (e.g., by a second brake or by an electric motor that is temporarily energized more forcefully).

[0014] Magnetorheological brakes can be designed as external rotors or internal rotors.

[0015] A magnetorheological brake can provide a magnetic field using an energized electromagnet and / or a permanent magnet, wherein the magnetic field acts on a magnetorheological medium. Preferably, the strength of the magnetic field acting on the magnetorheological medium can be adjusted.

[0016] Magnetorheological brakes can be designed as powder brakes based on the well-known effect of causing iron powder to agglomerate into clumps or form lines along field lines under the influence of a magnetic field. These lines or clumps generate braking force or braking torque through magnetic adhesion between the moving iron component and the stationary iron component. When the magnetic field is deactivated, the braking effect decreases as expected, partly because the small particles, typically 10 µm to 100 µm, subsequently begin to isolate, and partly because the particles migrate from the shear region to the adjacent stationary region. A magnetic field gradient exists in the stationary region, causing the particles to migrate back from the stationary region to the shear region when the brake is activated. The magnetorheological powder is surrounded by air or gas, which is easily compressible and has low viscosity.

[0017] Alternatively, the medium can be a liquid, and particularly preferably a magnetorheological fluid. Magnetorheological fluids have the property that their viscosity can change by several orders of magnitude depending on the magnetic field passing through them. The term "magnetorheological fluid" (MRF) refers to a liquid that responds to a magnetic field in a manner similar to that of a ferrofluid, but unlike a ferrofluid, a magnetorheological fluid solidifies. For example, a magnetorheological fluid comprises a suspension of micrometer-sized magnetic particles that are one to three orders of magnitude larger than the particles in a ferrofluid. When a magnetic field is applied, the relatively larger particles of the magnetorheological fluid form chains. These chains increase the viscosity of the MRF, and it can even solidify if the applied compressive force is not large enough to break the chains.

[0018] The operating unit is particularly preferred for use in the HWA (handwheel actuator) of a steering-by-wire system.

[0019] The steering shaft can be rotatably fixed to the steering mechanism. The steering mechanism can preferably be designed as a steering wheel. In principle, the steering mechanism can also be designed as a steering bracket.

[0020] The operating unit may also have a control unit. The control unit, as used in this invention, is particularly used for the electronic open-loop and / or closed-loop control of one or more technical systems of the operating unit, especially force feedback actuators and / or magnetorheological brakes.

[0021] Specifically, the control unit has wired or wireless signal inputs for receiving signals, particularly electrical signals such as trigger signals and / or sensor signals. Furthermore, the control unit also preferably has wired or wireless signal outputs for transmitting signals, particularly electrical signals, to, for example, force feedback actuators and / or magnetorheological brakes or other electrical devices of the operating unit.

[0022] Open-loop control operations and / or closed-loop control operations can be performed within the control unit. Particularly preferred is that the control unit includes hardware designed to run software. The control unit preferably includes at least one electronic processor for executing a sequence of programs defined in the software.

[0023] The control unit may also have one or more electronic memories, in which data contained in signals transmitted to the control unit can be stored and read again. Furthermore, the control unit may have one or more electronic memories in which data can be stored in a modifiable and / or immutable manner.

[0024] The control unit may include multiple controllers, which are particularly arranged spatially separated from each other in or on an operating unit or in a motor vehicle. The controllers are also referred to as electronic control units (ECUs) or electronic control modules (ECMs) and preferably have electronic microcontrollers for performing, particularly preferably using software, computational operations for processing data. The controllers may preferably be interconnected, enabling wired and / or wireless data exchange between the control units. In particular, the controllers may also be interconnected via a bus system present in the motor vehicle, such as a CAN bus or LIN bus.

[0025] Very particularly preferably, the control unit has at least one processor and at least one memory, the at least one memory specifically containing computer program code, wherein the memory and the computer program code are configured to enable the control unit to execute the computer program code using the processor.

[0026] The control unit may particularly preferably include a power electronic module for energizing the force feedback actuator and / or magnetorheological brake. The power electronic module is preferably a combination of different components providing open-loop or closed-loop control of the current to the motor, said different components preferably including peripheral components required for this purpose, such as cooling elements or power supply units. In particular, the power electronic module includes a power electronic system or one or more power electronic components configured to provide open-loop or closed-loop control of the current. These are particularly preferably one or more power switches, such as power transistors.

[0027] Preferably, the control unit is designed such that, upon receiving a trigger signal, it invokes and executes a program for testing the functionality of the magnetorheological brake. In principle, it is also conceivable to use electronic circuitry to partially or completely test the functionality of the magnetorheological brake.

[0028] The object of the present invention can also be achieved by a method for testing the functionality of a magnetorheological brake operating unit for influencing the direction of travel of a motor vehicle by a user, wherein the operating unit has: • A rotatable steering shaft that can be connected to the steering mechanism; and • A force feedback actuator, which is connected to the steering shaft in a torque-transmitting manner; and • A magnetorheological brake, which is also connected to the steering shaft via torque transmission; and • Control unit, which controls the operating unit. The method includes the following steps: • Receives a trigger signal used to initialize functional tests. • Determine the actual parameters representing the braking effect of the magnetorheological brake, and • Compare the determined actual parameters with the predefined target parameters, and • If a predefined deviation exists between the actual parameters and the target parameters, a fault signal will be provided. • In order to determine the braking effect of the magnetorheological brake, the control unit is configured to cause the force feedback actuator to provide motor torque M. EM And test torque M R The actual parameter representing the braking effect, applied to the magnetorheological brake, is the test torque M. R The angular position of the magnetorheological brake when it is applied.

[0029] Therefore, in a first embodiment of the method for testing the functionality of the magnetorheological brake of the operating unit, the angular position of the magnetorheological brake is used as the actual parameter. Thus, the control unit is configured such that the force feedback actuator provides the motor torque M. EM And test torque M R The actual parameter representing the braking effect, applied to the magnetorheological brake, is the test torque M. R The angular position of the magnetorheological brake when it is applied.

[0030] In terms of constructive implementation, for example, an electric motor can be used as a force feedback actuator, whereby it is then observed whether a slightly larger torque applied by the force feedback actuator for a short period of time, under the expected braking torque or energization of the magnetorheological brake, will cause the steering shaft to rotate initially.

[0031] Preferably, when the operating unit or control unit is turned on / off, for example when a door is opened, a trigger signal can also be sent to the control unit, which then, for example, calls and executes a program for testing the functionality of the magnetorheological brake in the control unit, such that, in chronological / causal order, a (low) test torque M is applied. R (Including basic friction) control magnetorheological brake and preferably with test torque M R Similar motor torque M EM A brief (0.1 s to 1 s) control force feedback actuator is employed. Particularly preferred is that the motor torque M of the electric motor... EM Slightly greater than the test torque M of the magnetorheological brake R This allows for the expectation of an initial slow rotational motion of the steering shaft and, consequently, an initial slow rotational motion of the rotor of the magnetorheological brake.

[0032] Preferably, the motor torque M of the force feedback actuator EM Between 0.1 Nm and 1.0 Nm. Furthermore, the test torque M of the magnetorheological brake...R The torque M of an electric motor is between 0.1 Nm and 1.0 Nm. EM Preferably, the torque M is slightly greater than that of the magnetorheological brake. R .

[0033] For example, during and at the end of energizing the motor, the rotation angle of the motor's rotor can then be determined, which can preferably be achieved via commutation of the motor. This makes it possible to obtain the change in angle W compared to the initial state.

[0034] In a preferred embodiment of the invention, if the angle change during functionality testing exceeds a predefined threshold, the motor power is interrupted prematurely to avoid excessive angle changes that the user may perceive unpleasantly via the steering mechanism during functionality testing of the magnetorheological brake. If an interruption occurs during functionality testing due to the angle being exceeded, the time prior to the interruption can also be used as an actual parameter for determining the braking effect of the magnetorheological brake.

[0035] In this context, an angle threshold between 1° and 5° is preferred because it provides a good trade-off between test accuracy and limiting steering shaft deflection when testing the functionality of a magnetorheological brake.

[0036] The method used to test the functionality of a magnetorheological brake by means of changes in angular position is also applicable to permanent magnet assisted magnetorheological brakes or magnetorheological brakes with mechanically constant basic friction. It is also conceivable to test multiple torque levels, such as basic friction and actuation friction.

[0037] A significant advantage of the method for testing the functionality of a magnetorheological brake by means of monitoring the angular position is that it can be performed using components of an operating unit that is already available and commonly used, making it particularly attractive from an economic standpoint.

[0038] Furthermore, the present invention can be further developed as follows: the force feedback actuator includes an electric motor, which can be energized by a control unit, enabling the application of a motor torque M to the steering shaft via the electric motor. EM .

[0039] The motor torque M of the force feedback actuator EM Preferably, the test torque M corresponds to the magnetorheological brake. RThe value is 1.0001 to 1.2000 times, particularly preferably 1.0010 to 1.1000 times. This ensures that the steering shaft or the steering mechanism fixed to the steering shaft does not make any excessive angular movement when testing the functionality of the brakes, which could annoy the user—especially when testing functionality while the vehicle is in motion.

[0040] According to another preferred embodiment of the invention, the actual parameters representing the angular position of the magnetorheological brake can be determined by means of a rotor position sensor configured to commutate the electric motor. This means that a rotor position sensor that is already present and available can be used to determine the angular position, which can reduce the corresponding manufacturing cost of the system. Since both the commutating electric motor and the magnetorheological brake are located on a common steering shaft or are rotatably connected to a common steering shaft, the angular position can also be determined in the electric motor, and does not necessarily need to be determined on or within the magnetorheological brake.

[0041] Preferably, the magnetorheological brake can be energized to generate the test torque M. R However, in principle, magnetorheological brakes can also have a current-free base braking torque, which can also be used as a test torque M. R .

[0042] In another embodiment of the method for testing the functionality of a magnetorheological actuator for an operating unit, in addition to angular position, magnetic reluctance and / or inductance can be used as actual parameters. This enables the use of additional actual parameters to check or verify the functionality of the magnetorheological actuator based on angular position, which can facilitate testing for improvements in the functionality of the operating unit's safety-related functions due to the added redundancy.

[0043] In this context, supplementary diagnostics of the functionality of magnetorheological actuators can also be performed based on the presence of the magnetorheological medium, leveraging its influence on magnetorheological chain formation in terms of reluctance or inductance. Magnetorheological media, such as magnetorheological powders, possess higher reluctance before being affected by a magnetic field than the magnetorheological chains formed after the magnetic field influences the medium.

[0044] For example, in a magnetorheological brake, a powdered magnetorheological medium can be prepared in a "valley" such that when a magnetic field is applied, the powdered magnetorheological medium only needs to "climb" the mountain to form the corresponding magnetorheological chain, which then generates a braking torque between the fixed and movable braking components. In this example, the "mountain" is a region on either the fixed or movable braking component where the gap between the fixed and movable components of the brake is particularly small. The term "valley" refers, for example, to a region created as a rotational groove, where the distance between the fixed and movable braking components is locally larger and therefore less traversed by field lines.

[0045] If a corresponding trigger signal exists, for example, indicating system shutdown (ignition) or system stillness (constant steering angle, e.g., straight driving), the magnetorheological brake is controlled in a pulse-like manner in a time-sequential / causal sequence for 0.1 s to 1 s, preferably, where U = const after the stillness period, where U is a predetermined voltage, and functionality is further tested by means of angular position. The current I(t) flowing through the excitation coil of the magnetorheological brake is measured, for example, inductively, or as a voltage drop across a measuring resistor. Then, the existence of a process deviating from the target process, for example at time points t1…t2 within a predetermined time window, can be considered. m There is no minimum value I at that location. m The current curve I(t) is analyzed. The minimum value indicates the decrease in magnetorheological reluctance due to the formation of chains of powder particles in the magnetorheological medium. If the minimum value I... m Missing and / or if there are time points t other than t1...t2 m And / or if I m If the value is too high, a fault signal can be output. This fault may indicate, for example, the loss of magnetorheological particles due to seal failure, and / or the loss of the magnetic properties of the magnetorheological particles due to oxidation, and / or the loss of the mobility of the magnetorheological particles due to agglomeration.

[0046] In an advantageous further development of the invention, if the value I m Too low (in absolute value and / or compared to the initial value I at t=0) and / or if the time point t m If it occurs too early, a fault signal can also be generated and provided. This type of fault indicates metal wear in the magnetorheological shear gap between the rotor and stator of the brake, or indicates accidental contact on the shear gap surface.

[0047] A low measuring voltage or measuring current can also be applied to the magnetorheological brake for a limited time, and the resistance R0 of the brake's excitation coil can be determined. Preferably, a fault signal can be output if the value of R0 is too low (indicating a short circuit in the circuit) or too high (indicating a broken cable).

[0048] The method used to test the functionality of magnetorheological brakes for operating units—where reluctance and / or inductance are used as actual parameters—can also be applied to permanent magnet assisted brakes and is selectively sensitive to the presence of a magnetorheological medium. When control is achieved using a constant current, the time progression of the voltage, similar to the current curve described above, must be measured and analyzed.

[0049] One advantage of this variation is that it provides a purely electric method without the need for mechanically moving parts.

[0050] In an alternative embodiment of the method for testing the functionality of a magnetorheological brake for an operating unit, the resistance between the rotor and stator of the magnetorheological brake can be used as an actual parameter in addition to the angular position. This allows for the inspection or verification of the functionality of the magnetorheological brake based on the angular position and the additional actual parameter, which can facilitate testing for improved functionality of the operating unit's safety-related functions due to the added redundancy. Alternatively, the functionality of the magnetorheological brake can be verified using both the angular position, the resistance between the rotor and stator, and the magnetic reluctance and / or inductance, which can further improve the verification of the magnetorheological brake's functionality.

[0051] In this context, this allows for supplementary diagnostics of the presence of magnetorheological media to be based on the influence of the magnetorheological media on the resistance between the rotor and stator of the magnetorheological brake.

[0052] In this further preferred embodiment of the subject matter of the invention, the actual parameters representing the braking effect can correspond to the current curve when the excitation coil of the magnetorheological brake is energized.

[0053] In this preferred embodiment of the invention, the actual parameter representing the braking effect can also correspond to the resistance between the rotor and stator of the magnetorheological brake.

[0054] In terms of structural implementation, the rotor and stator of the magnetorheological brake can be electrically insulated, for example, using plastic sleeves on bearing housings and / or an elastomeric coupling between the rotor and the steering shaft. A test voltage can then be applied to the rotor, for example, via sliding contacts, where, in this case, no current or only a low current flows to the stator because the conductive particles of the magnetorheological medium form only loose aggregates. If the flowing current is too high, i.e., exceeding a predefined target value, a fault is inferred, for example, due to agglomeration of the magnetorheological medium.

[0055] The test magnetic field can then be activated, particularly by energizing the excitation coil of the magnetorheological brake, and the increase in test current can be measured as the magnetic field causes conductive chains to form in the magnetorheological particles. If the test current does not increase or does not increase sufficiently, a fault is inferred, such as a lack of magnetorheological medium.

[0056] This method can be used for both permanent magnet assisted brakes and magnetorheological brakes with constant mechanical base friction. Where applicable, multiple torque levels can also be tested, such as reduced friction under base friction and magnetic field cancellation conditions.

[0057] Here, the following advantages also exist: additional all-electric methods can be provided without mechanical moving parts.

[0058] In principle, the functionality of the magnetorheological brake can be tested by means of angular position as an actual parameter, with time delay, time overlap, or simultaneous testing of additional functionality based on the resistance or magnetic reluctance and / or inductance between the rotor and stator of the magnetorheological brake.

[0059] According to another preferred further development of the invention, the trigger signal can indicate the opening of the driver's side door of the motor vehicle, or the starting of the motor vehicle, or the coming to a stop of the motor vehicle, or the stopping of the motor vehicle, or the user leaving the motor vehicle, or a command from the workshop testing device. In this regard, it is advantageous to generate the trigger signal in each case before using the operating unit. In principle, it is also conceivable to generate the trigger signal after using the operating unit, for example, when leaving the vehicle. Furthermore, the trigger signal may also occur while the operating unit is in use, for example, while driving straight. In particular, it is conceivable that the trigger signal is sent from a higher-level control unit of the motor vehicle to the control unit of the operating unit.

[0060] Furthermore, according to equally advantageous embodiments of the invention, the fault signal can result in a fault memory entry and / or can generate an optical warning signal and / or an acoustic warning signal and / or can result in a speed limit on the motor vehicle. It is also conceivable that the fault signal initiates a temporary higher energization of a force feedback actuator with an electric motor to fully or at least partially compensate for the loss of braking torque with higher motor torque.

[0061] It is also advantageous to further develop the invention by designing the magnetorheological brake as a permanently excited magnetorheological brake. This has the advantage of requiring a lower current to achieve the braking torque and providing basic friction suitable for emergency operation in the event of a fault.

[0062] Furthermore, the object of the present invention can be achieved by the following: a computer program product stored on a machine-readable medium or a computer data signal embodied by electromagnetic waves, having computer program code suitable for performing the method according to any one of claims 2 to 8.

[0063] Finally, the object of the present invention can also be achieved by a steer-by-wire system for motor vehicles, the steer-by-wire system comprising an operating unit according to any one of the preceding claims and / or a control unit designed to perform the method according to any one of claims 1 to 8. Attached Figure Description

[0064] The invention will now be described in more detail with reference to the accompanying drawings without limiting the overall concept of the invention.

[0065] In the attached diagram: Figure 1 A schematic block diagram illustrates a motor vehicle with a steer-by-wire system. Figure 2 A schematic axial cross-sectional view illustrates a first embodiment of the operating unit. Figure 3 A schematic axial cross-sectional view illustrates a second embodiment of the operating unit. Figure 4 The time-series current curves are shown when testing the functionality of the magnetorheological brake, using reluctance and / or inductance as actual parameters. Figure 5 A schematic axial cross-sectional view illustrates a third embodiment of the operating unit. Figure 6 The time-series signal curves are shown when testing the functionality of the magnetorheological brake, using mechanical braking torque or initial motion as the actual parameters. Figure 7 The signal curves in time sequence are shown when testing the functionality of the magnetorheological brake, where mechanical braking torque or initial motion is used as the actual parameter, and in each case, a first process and a second process are shown in a separate graph. Detailed Implementation

[0066] Figure 1 An operating unit 1 is shown for influencing the driving direction of a motor vehicle 2 by a user. The operating unit 1 is integrated into the online steering system 20, such that the steering motion of the steering device 4 is electrically transmitted from the operating unit 1 to the RWA 33 (road wheel actuator), and then the RWA adjusts the corresponding steering angle on the vehicle wheels of the vehicle axle.

[0067] As from Figure 2As can be clearly seen, the operating unit 1 has a rotatably mounted steering shaft 3 (which can also be designed as a hollow shaft or an external rotor), which can be connected to the steering device 4 and the force feedback actuator 5, which is also connected to the steering shaft 3 in a torque-transmitting manner. Furthermore, the operating unit 1 has a magnetorheological brake 6, which is also connected to the steering shaft 3 in a torque-transmitting manner. Therefore, the force feedback actuator 5, the magnetorheological brake 6, and the steering device 4 are located on a common torque path.

[0068] In addition, the operating unit 1 has a control unit 7 for controlling the operating unit 1, wherein the control unit 7 is designed to call and execute a program 9 for testing the functionality of the magnetorheological brake 6 after the trigger signal 8, wherein the control unit 7 provides a fault signal 10 when it determines that the magnetorheological brake 6 has deteriorated to below a predefined braking effect.

[0069] therefore, Figure 2 The operation unit 1 shown can be used to perform a method for testing the functionality of the magnetorheological brake 6, wherein the operation unit 1 has: • A rotatable steering shaft 3, which can be connected to the steering device 4; and • Force feedback actuator 5, which is connected to steering shaft 3 in a torque transmission manner; and • Magnetorheological brake 6, which is also connected to steering shaft 3 via torque transmission; and • Control unit 7 for controlling operation unit 1, Furthermore, the method includes the following steps: • Receive trigger signal 8 used to initialize functional testing. • Determine the actual parameter 11 representing the braking effect of the magnetorheological brake 6, and • Compare the determined actual parameter 11 with the predefined target parameter 12, and • If a predefined deviation exists between the actual parameter 11 and the target parameter 12, a fault signal 10 is provided. • In order to determine the braking effect of the magnetorheological brake 6, the control unit 7 is configured to cause the force feedback actuator 5 to provide motor torque M. EM And test torque M R The actual parameter 11, which is applied to the magnetorheological brake 6 and represents the braking effect, represents the test torque M. R The angular position of the magnetorheological brake 6 when it is applied.

[0070] The magnetorheological brake 6 has an electromagnet with an energized excitation coil 14, the field lines 30 of which extend through the stator 16 and rotor 15 connected to the steering shaft 3.

[0071] A toroidal excitation coil 14 is housed in a coil carrier 18 having a U-shaped cross-section, which is radially outer closed by a coil enclosure 17. The coil carrier 18 is radially inner closed by a coil enclosure 19. The coil carrier 18 and the coil enclosure 17 are formed of a ferromagnetic material. The excitation coil 14, the coil carrier 18, and the coil enclosure 17 form the stator 16 of the brake 6. The stator 16 is mounted on a rotatable brake shaft 23, which is part of the rotor 15, via end covers 21, 22 and rolling bearings 24, 25. The rotor 15 is sealed relative to the end covers 21, 22 by seals 26, 27.

[0072] In the described method for testing the functionality of the magnetorheological brake 6 of the operating unit 1, angular position is used as the actual parameter 11. In this case, braking torque is first generated by energizing the excitation coil 14 of the magnetorheological brake 6, and then the electric motor 13 is energized for a short time, and vice versa. If this results in excessive rotational movement of the steering shaft 3 (which is stored in the control unit 7 as a target parameter 12), a fault is identified and a fault signal 10 is provided.

[0073] Therefore, the force feedback actuator 5 includes an electric motor 13, which can be energized by the control unit 7, so that a motor torque M can be applied to the steering shaft via the electric motor 13. EM This is in Figure 3 As shown in the figure. In itself, the electric motor 13 includes a stator 31 and a rotor 32 that can rotate relative to the stator, and is connected to the steering shaft 3.

[0074] In addition, program 9 is configured to make the test torque M R The actual parameter 11, which is applied to the magnetorheological brake 6 and represents the braking effect, is the test torque M. R The angular position of the magnetorheological brake 6 when it is applied.

[0075] Because the motor torque M EM Only slightly higher than the test torque M R Therefore, the steering shaft 3 only begins to rotate relatively slowly, which can be analyzed with the help of the rotor position sensor of the electric motor 13 that is already present and can be used for its commutation.

[0076] If the rotational movement of the steering shaft 3 is too weak, even with a high energization of the electric motor 13, it can be inferred that the steering shaft 3 has excessive friction or even jamming. If the rotational movement is too strong (which can be verified by repeated measurements and / or a fault counter), it can be inferred that the brake 6 has lost its function. Preferably, during the functionality test, the rotational movement of the steering shaft 3 is between 1° and 5°. Then, a larger rotational angle >5° indicates a loss of braking force in the magnetorheological brake 6, and a smaller rotational angle <1° indicates excessive friction.

[0077] If the magnetorheological brake 6 generates a current-free basic braking torque, the method can also be used with an adjusted threshold and a test torque.

[0078] Trigger signal 8 may indicate, for example, the opening of the driver's side door of motor vehicle 2, the starting of motor vehicle 2, the coming to a stop of motor vehicle 2, the shutdown of motor vehicle 2, a command from the workshop testing equipment, or the user leaving motor vehicle 2. Fault signal 10 may, for example, generate a fault memory entry and / or generate an optical warning signal and / or an acoustic warning signal and / or cause a speed limit on motor vehicle 2.

[0079] Quantitative and precise control of the magnetorheological brake 6 (e.g., using support points and interpolation) requires a reliable characteristic curve, torque = f (current). In friction-based control, adaptive functions are typically used to correct for individual differences (adaptation during production or line-end testing) and life variations (adaptation during vehicle operation in the shop or under selected conditions). The magnetorheological brake 6 is controlled using the characteristic curve f and at least one parameter, which is here “R” in the form M = R*f(I). The parameter R is adapted at least at the beginning of the vehicle operation phase or after the end of the vehicle operation phase.

[0080] During the adaptation process, a diagnostic method based on torque comparison is used, and the magnetorheological brake 6 and the electric motor 13 are energized together. As a result of the adaptation, the adaptation parameter R is limited, and reaching the limit can be used as a trigger for the fault signal 10 and corresponding fault entries, as well as / or warning / emergency operation functions. If particulate losses are present in the magnetorheological brake 6, the adaptation will continuously reduce the parameter R to compensate for this decrease in braking torque capability. Therefore, reaching the predetermined adaptation limit indicates a fault in the brake 6.

[0081] In addition to the multiplicative action parameter R described here (note: it could also be the coefficient of friction, hence R), one could also conceive of an additive adaptive parameter E of the form M = E + f(I), an adaptive parameter A of the form M = f(I+A) that adds to the independent variable of the characteristic curve, an adaptive parameter B of the form M = f(I*B) that multiplies the independent variable of the characteristic curve, or combinations thereof, as equivalents. These representations can be particularly useful, for example, if a shift in the characteristic curve is caused by a permanent magnet or specific magnetization remanence.

[0082] As in Figure 6 As can be seen in t 阶段1 With t 阶段2 In the first adaptive phase, the controlled actuator torque 43 of the electric motor 13 is lower than the controlled expected braking torque 42. Therefore, the steering shaft 3 is not expected to rotate.

[0083] In the second stage of adaptation, at >t 阶段2 At this point, the controlled actuator torque 43 is higher than the controlled expected braking torque 42, thus the expected rotation of the steering shaft 3 and the rotation angle 44 are.

[0084] After a given time or when the movement exceeds the safety detection threshold (in Figure 6 t in Chinese 结束 (This indicates that) the actuator torque 43 is rapidly reduced to stop, or even reverse, the rotation of the steering shaft 3.

[0085] As long as there are two stages, "<brake torque 42" and ">brake torque 42", the adaptive process can be executed using either the ramp-shaped process of actuator torque 43 (as shown) or other processes (steps, etc.). Similarly, as long as there are two stages, "<brake torque 42" and ">brake torque 42", the brake torque 42 can be controlled either constantly (as shown) or using a decreasing ramp or other methods. The control can also be varied before the start of stage 1, for example, by first applying actuator torque 43 or brake torque 42.

[0086] For example, if—as in Figure 7 As seen in part a, the rotation angle 47 is less than the expected rotation angle 44 and does not exceed the threshold 45, thus it can be inferred that the braking torque 46 is actually quite large. This is in the control formula M = R*f(I) or I = f -1 The adaptive parameter R used in (M / R) is increased for correction. Here, f -1This represents the inverse interpolation or mathematical inverse function of the corresponding lookup table. Increases can be made incrementally or based on the actual rotational motion achieved, but are limited to minimum and maximum values. If the rotation angle 47 is greater than expected (or, as shown, the threshold is reached earlier and the EM torque decreases), it is inferred that the braking torque 42 is actually large, and the adaptive parameter R decreases, thus making future control more precise.

[0087] Figure 5 An embodiment of the operating unit 1 is shown, wherein, in addition to the actual parameter of the angular position, the additional actual parameter 11 representing the braking effect corresponds to the resistance between the rotor 15 and the stator 16 of the magnetorheological brake 6.

[0088] This creates an additional contact with the coil enclosure 17 and a sliding contact 38 with the steering shaft 3, through which the test current 41, provided by the control unit 7, can flow between the additional contact and the sliding contact of the magnetorheological brake 6. Here, the test resistor 37 limits the test current to the sliding contact 38. For example, the switch 40 can be used to selectively turn the test current 41 on and off to isolate the test current from leakage current. The rolling bearings 24, 25 provide electrical insulation between the rotor 15 and stator 16 of the magnetorheological brake 6, for example by means of a sheath, coating, ceramic balls, etc. This ensures that the test current 41 cannot flow through the magnetorheological chain of the magnetorheological medium 29 in the gap 28 to reach the sliding contact 38.

[0089] Therefore, the rotor 15 and stator 16 are electrically insulated, for example, by plastic sleeves on rolling bearings 24, 25. A test voltage is applied to the rotor 15 via the sliding contact 38, wherein no test current 41 or only a low test current flows to the stator 16 because the conductive magnetorheological particles of the magnetorheological medium 29 form only a loose mass.

[0090] If the flowing test current 41 is too high, i.e. exceeds the predetermined target value, a fault is inferred, such as agglomerated magnetorheological medium 29.

[0091] Then, the test magnetic field is activated by energizing the excitation coil 14, and the increase in the test current 41 is measured because the magnetic field causes conductive chains of magnetorheological particles to form in the gap 28 between the rotor 15 and the stator 16 of the magnetorheological brake 6.

[0092] If the test current 41 does not increase or does not increase sufficiently, a fault is inferred, such as a lack of magnetorheological medium 29, and a corresponding fault signal 10 is generated.

[0093] The energization of the excitation coil 14 can be controlled via switch 39.

[0094] based on Figure 2 and Figure 4The summary provides a more detailed explanation of diagnostic methods other than those based on angular position, wherein the additional practical parameter 11 representing the braking effect corresponds to the current curve when the excitation coil 14 of the magnetorheological brake 6 is energized.

[0095] This allows for additional diagnostics of the presence of the magnetorheological medium 29 based on its effect on magnetorheological resistance or inductance as the magnetorheological medium 29 forms chains. The magnetorheological medium 29, such as magnetorheological powder, has a higher magnetorheological resistance before being affected by a magnetic field than the magnetorheological chains formed after the magnetic field is applied to the magnetorheological medium 29.

[0096] If a corresponding trigger signal 8 exists, for example, indicating system shutdown (ignition) or system standstill (constant steering angle, e.g., straight driving), the magnetorheological brake 6 is controlled in a pulse-like manner in a time-sequential / causal sequence for 0.1 s to 1 s, preferably, where, after the standstill period, U = const, where U is a predetermined voltage. The current I(t) flowing through the excitation coil 14 of the magnetorheological brake 6 is measured, for example, inductively, or as a voltage drop across a measuring resistor.

[0097] like Figure 4 As shown, current curve 34 is plotted for the case of excitation coil 14 without magnetorheological medium 29. In contrast, in current curve 35, which shows the case of excitation coil 14 with magnetorheological medium 29, the mechanical dynamics of the chain formation of magnetorheological particles result in a minimum current 36 between t1 and t2.

[0098] Then, regarding the time point t in the predetermined time window t1...t2 m The minimum value at point 36 I m The existence of also Figure 4 The current curve I(t) plotted in the figure is analyzed. The minimum value 36 indicates the fact that the magnetorheological reluctance decreases due to the formation of chains of powder particles in the magnetorheological medium 29. If the minimum value 36 is missing and / or if there are time points t other than t1...t2... m And / or if I m If the value is too high, a fault signal 10 can be output. This fault may indicate, for example, the loss of magnetorheological particles due to seal failure, and / or the loss of the magnetic properties of the magnetorheological particles due to oxidation, and / or the loss of the mobility of the magnetorheological particles due to agglomeration.

[0099] In an advantageous further development of the invention, if the value I m Too low (in absolute value and / or compared to the initial value I at t=0) and / or if the time point t mIf it occurs too early, a fault signal 10 can also be generated and provided. This type of fault indicates metal wear in the magnetorheological gap 28 between the rotor 15 and stator 16 of the brake 6, or indicates accidental contact of the shear gap surface.

[0100] A low measuring voltage or measuring current can also be applied to the magnetorheological brake 6 for a limited time, and the resistance R0 of the excitation coil 14 of the brake 6 can be determined. Preferably, if the value R0 is too low (indicating a short circuit in the circuit) or too high (indicating a broken cable), a fault signal 10 can be output.

[0101] This invention is not limited to the embodiments shown in the accompanying drawings. Therefore, the above description should not be considered limiting but rather illustrative. The following claims should be understood to indicate the presence of the stated features in at least one embodiment of the invention. This does not exclude the presence of other features. Where the claims and the above description define "first" and "second" features, this designation is used to distinguish between two features of the same type, without limiting the order of priority.

[0102] List of reference numerals 1. Operation Unit 2 Motor vehicles 3. Steering Axle 4. Steering mechanism 5 Force Feedback Actuator 6. Brakes 7 Control Unit 8 Trigger Signal 9. Program 10 Fault Signals 11 Actual Parameters 12 Target Parameters 13 Electric motors 14 Excitation Coil 15 Rotors 16 stators 17. Coil enclosure 18. Coil carrier 19 Coil Enclosure 20. Steer-by-wire system 21 End caps 22 End caps 23 Brake shaft 24 Rolling bearings 25 Rolling bearings 26. Seals 27. Seals 28 gaps 29. Medium 30-game line 31 Stator 32 rotors 33 RWA 34 Current Curve 35 Current Curve 36 Minimum value 37. Testing Resistors 38 Sliding contact part 39 Switch 40 Switches 41 Test Current 42 Braking Torque 43 Actuator Torque 44 Rotation Angle 45 threshold 46 Braking Torque 47 Rotation Angle

Claims

1. An operating unit (1) for influencing the driving direction of a motor vehicle (2) by a user, the operating unit comprising: • A rotatable steering shaft (3) that can be connected to a steering device (4); as well as • Force feedback actuator (5), which is connected to the steering shaft (3) in a torque transmission manner; and • A magnetorheological brake (6), which is also connected to the steering shaft (3) in a torque transmission manner; and • Control unit (7), which controls the operating unit (1). Its features are, The control unit (7) is designed to invoke and execute a program (9) for testing the functionality of the magnetorheological brake (6) after a trigger signal (8), wherein, when it is confirmed that the magnetorheological brake (6) has deteriorated below a predefined braking effect, the control unit (7) provides a fault signal (10), wherein the program (9) is configured to cause the force feedback actuator (5) to provide motor torque M. EM And test torque M R The actual parameter (11) applied to the magnetorheological brake (6) and representing the braking effect is the test torque M. R The angular position of the magnetorheological brake (6) when it is applied.

2. A method for testing the functionality of a magnetorheological brake (6) in an operating unit (1), said operating unit being used to influence the direction of travel of a motor vehicle (2) by a user, wherein, The operation unit (1) has: • A rotatable steering shaft (3) that can be connected to a steering device (4); and • Force feedback actuator (5), which is connected to the steering shaft (3) in a torque transmission manner; and • A magnetorheological brake (6), which is also connected to the steering shaft (3) in a torque transmission manner; and • Control unit (7), which controls the operating unit (1). The method includes the following steps: • Receive a trigger signal (8) for initializing the test of the aforementioned functionality. • Determine the actual parameters (11) representing the braking effect of the magnetorheological brake (6), and • Compare the determined actual parameters (11) with the predefined target parameters (12), and • If there is a predefined deviation between the actual parameter (11) and the target parameter (12), a fault signal (10) is provided. • In order to determine the braking effect of the magnetorheological brake (6), the control unit (7) is configured to cause the force feedback actuator (5) to provide motor torque M. EM And test torque M R The actual parameter (11) applied to the magnetorheological brake (6) and representing the braking effect represents the test torque M. R The angular position of the magnetorheological brake (6) when it is applied.

3. The method according to claim 2, Its features are, The trigger signal (8) indicates the opening of the driver's side door of the motor vehicle (2), or the starting of the motor vehicle (2), or the stopping of the motor vehicle (2), the turning off of the motor vehicle (2), the user leaving the motor vehicle (2), or the command of the workshop testing device.

4. The method according to any one of claims 2 to 3, Its features are, The fault signal (10) causes a fault memory entry and / or generates an optical warning signal and / or an acoustic warning signal and / or causes a speed limit on the motor vehicle (2).

5. The method according to any one of claims 2 to 4, Its features are, The force feedback actuator (5) includes an electric motor (13), which can be energized by the control unit (7) to apply a motor torque M to the steering shaft (3) via the electric motor (13). EM .

6. The method according to any one of claims 2 to 5, Its features are, The motor torque M EM Corresponding to the test torque M R The ratio is 1.0001 to 1.2000 times, preferably 1.0010 to 1.1000 times.

7. The method according to any one of claims 5 to 6, Its features are, The actual parameter (11) representing the angular position of the magnetorheological brake (6) is determined by means of a rotor position sensor, which is configured to commutate the electric motor (13).

8. The method according to any one of claims 2 to 7, Its features are, The magnetorheological brake (6) is energized to generate the test torque M. R .

9. A computer program product stored on a machine-readable medium or a computer data signal embodied by electromagnetic waves, having computer program code suitable for performing the method according to any one of claims 2 to 8.

10. A steer-by-wire system (20) for a motor vehicle (2), the steer-by-wire system comprising an operating unit (1) according to claim 1 and / or a control unit (7) designed to perform the method according to any one of claims 2 to 8.

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