DRIVE UNIT FOR A WHEEL ACTUATOR OF A STEER-BY-WIRE SYSTEM FOR A VEHICLE, AND METHOD FOR DETERMINING THE POSITION OF THE CONTROL ROD OF A WHEEL ACTUATOR

Abstract

A drive unit for a steer-by-wire system for a vehicle having a motor for providing a drive power to a control rod of the wheel actuator. A sensor device determines the position of the control rod, wherein the sensor device has a first sensor unit and at least one second sensor unit. The first sensor unit is designed to detect an angle of a rotor shaft of the motor, and the second sensor unit is designed to detect an angle of an auxiliary shaft which is mechanically operatively connected to the rotor shaft. A transmission device provides the mechanical operative connection between the rotor shaft and the auxiliary shaft. A controller actuates the sensor device and/or determines the position of the control rod of the wheel actuator. The first sensor unit and second sensor unit use different measuring principles.

Claims

1. A drive unit for a wheel actuator of a steer-by-wire system for a vehicle, the drive unit comprising: a motor to provide drive power to a control rod of the wheel actuator; a sensor to determine a position of the control rod, the sensor having a first sensor unit and at least one second sensor unit, the first sensor unit designed to detect an angle of a rotor shaft of the motor, and the second sensor unit designed to detect an angle of an auxiliary shaft that is arranged in a mechanical operative connection to the rotor shaft; a transmission to provide a mechanical operative connection between the rotor shaft and the auxiliary shaft; and a controller to actuate the sensor and/or to determine a position of the control rod of the wheel actuator, wherein the first sensor unit and the second sensor unit use different measuring principles.

2. The drive unit according to claim 1, wherein the first sensor unit has a first signal generator that is connected to the rotor shaft in a rotationally fixed manner, and has a first sensor that, when viewed axially, is arranged on a face end in front of the rotor shaft and opposite the first signal generator, and/or wherein the second sensor unit has a second signal generator that is connected to the auxiliary shaft in a rotationally fixed manner, and has a second sensor that, when viewed axially, is arranged on the face end in front of the auxiliary shaft and opposite the second signal generator, and/or wherein the first sensor and/or the second sensor are arranged on the controller.

3. The drive unit according to claim 1, wherein the first sensor unit has a higher resolution and/or signal quality than the second sensor unit, and/or wherein the first sensor unit and the second sensor unit each have at least one of the following sensors: an inductive sensor; a magnetoresistive sensor; a Hall sensor; and/or a rotation angle sensor, and/or wherein the first sensor unit and the second sensor unit each use at least one of the following measuring principles: electromechanical; magnetic; inductive; and/or optical.

4. The drive unit according to claim 1, wherein the transmission has a main transmission element in the form of a gear, which is connected to the rotor shaft in a rotationally fixed manner and to which the first signal generator is attached, and/or wherein the transmission has at least one auxiliary transmission element in the form of a gear, which is connected to the auxiliary shaft in a rotationally fixed manner and to which the second signal generator is attached.

5. The drive unit according to claim 1, wherein the controller has a first control unit and a second control unit, and/or wherein the first sensor unit has at least one channel to a first control unit and at least one channel to a second control unit, and/or wherein the second sensor unit has at least one channel to a first control unit and potentially a channel to a second control unit.

6. A wheel actuator for a steer-by-wire system of a vehicle, comprising: a control rod to implement a steering command; and the drive unit according to claim 1 to provide drive power to the control rod in order to implement the steering command.

7. A steer-by-wire system for a vehicle with a wheel actuator according to claim 6.

8. A vehicle, in particular a highly automated and/or autonomously driven vehicle, with a steer-by-wire system according to claim 7.

9. A method to determine a position of a control rod of a wheel actuator via a drive unit according to claim 1, the method comprising: detecting, via the first sensor unit, the angle of the rotor shaft of the motor; detecting, via the second sensor unit, the angle of the auxiliary shaft; and determining a position of the control rod of the wheel actuator via measured values from the first sensor unit and/or with via measured values from the second sensor unit.

10. The method according to claim 9, wherein the measured values from the first sensor unit are used to validate the measured values from the second sensor unit.

11. The method according to claim 9, wherein available measured values from the first sensor unit and/or available measured values from the second sensor unit are combined in order to determine the position of the control rod of the wheel actuator, and/or wherein an offset between measured values of the first sensor unit and the measured values of the second sensor unit are determined at a startup of the vehicle in order to be able to continue to carry out a determination of the position of the control rod with only one sensor unit in the case of a failure of one of the first or second sensor unit, and/or wherein the determination of the position of the control rod is carried out via an offset between measured values of the first sensor unit and the measured values of the second sensor unit parallel to the primary determining of the position of the control rod in order to provide a determination of the position of the control rod with only one sensor unit in the case of a failure of one of the first or second sensor units.

12. The method according to claim 9, wherein a control method for control of the motor is adapted when the first sensor unit and/or the second sensor unit fails, wherein at least one of the following actions is carried out when the first sensor unit fails: reduction of a dynamic response for a higher-level control or a control of the position of the control rod; adding a damping component or a low-pass filter to a signal of the second sensor unit; limiting gradients and/or amplitudes of a signal for a target position of the control rod; and/or adapting control parameters for control of the motor and/or for control of the position of the control rod.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0045] FIG. 1 shows an exemplary depiction of a vehicle having a steer-by-wire system,

[0046] FIG. 2 shows an end view of a motor of a drive unit for a wheel actuator,

[0047] FIG. 3 shows an exemplary depiction of a sensor device of a drive unit for a wheel actuator, and

[0048] FIG. 4 shows an exemplary depiction of a sensor device of a drive unit for a wheel actuator.

DETAILED DESCRIPTION

[0049] FIGS. 1 to 4 serve to explain the inventive concept. FIG. 1 shows an exemplary steering system of the steer-by-wire type or, for short, a steer-by-wire system S for a vehicle F. Such a steer-by-wire system S does not require an intermediate steering shaft between a steering wheel L and a tie rod or a control rod 101, since the mechanical connection to the steering wheel L is dispensed with. In such a steer-by-wire system S, the steering feel at the steering wheel L can be provided by a force feedback actuator 120 that is connected to the steering wheel L directly or through a transmission. On account of the lack of mechanical connection to the steering wheel L, the position of the tie rod must be adjusted with high precision and taking into account the most stringent safety requirements.

[0050] In order to be able to unambiguously ascertain the position of the tie rod or the control rod 101 at any point in time, the invention proposes (see FIGS. 2 to 4): a drive unit 100 (so-called powerpack, e.g., including a motor and a controller) for a wheel actuator 110 of a steer-by-wire system S for a vehicle F. The drive unit 100 in this case has: a motor 10 for providing drive power to a control rod 101 of the wheel actuator 110, wherein, in particular, the control rod 101 can have different designs depending on the design of the wheel actuator 110, and can comprise, e.g., a steering rack, a lifting rod, or the like, wherein FIG. 1 shows the wheel actuator 110 only on the control rod 101, for example, wherein the wheel actuator 110 can, alternatively to FIG. 1, be arranged apart from the control rod 101, wherein preferably the wheel actuator 110 can be connected to the control rod 101 through a transmission; a sensor device 20 for determining a position of the control rod 101, wherein the sensor device 20 has a first sensor unit 21 and at least one second sensor unit(s) 22 (one or more second or secondary sensor units are possible), wherein the first sensor unit 21 is designed to detect an angle of a rotor shaft 11 of the motor 10, and wherein the second sensor unit 22 is designed to detect an angle of an auxiliary shaft 12 that is arranged in a mechanical operative connection to the rotor shaft 11; a transmission 30 for providing the mechanical operative connection between the rotor shaft 11 and the auxiliary shaft 12, wherein, in particular, the operative connection between the rotor shaft 11 and the auxiliary shaft 12 is provided in such a manner that the angle of rotation of the rotor shaft 11 and the angle of rotation of the auxiliary shaft 12 preferably have a specific angle ratio over the stroke of the control rod 101; and a controller 40 for actuating the sensor device 20 and/or for determining a position of the control rod 101 of the wheel actuator 110, wherein the first sensor unit 21 and the second sensor unit 22 use different measuring principles.

[0051] As FIGS. 3 and 4 illustrate, two sensor units 21, 22 are provided with the sensor device 20. The two sensor units 21, 22 can accordingly have two sensors S1, S2. The sensor units 21, 22 can advantageously be installed within the drive unit 100, in particular within a housing of the drive unit 100. The sensors S1, S2 serve to precisely determine the position of the control rod 101 at any point in time, wherein the rotor shaft 11 can execute multiple revolutions over a possible stroke or control travel of the control rod 101.

[0052] Advantageously, the two sensor units 21, 22 can be designed according to the vernier principle. The vernier principle can, for example, be realized through two sensor values that change during rotation of the motor 10 such that the position of the control rod 101 can be unambiguously determined over its full travel via two sensor values. In this context, a magnet (as the first signal generator M1), for example, can be attached in a rotationally fixed manner to the rotor shaft 11 of the motor 10, and a toothed wheel, for example, for an inductive sensor (as the second signal generator M2) can be attached in a rotationally fixed manner to an auxiliary shaft 12. The operative connection, for example in the form of a rotation-angle relationship or an angle ratio, between the two signal generators M1, M2 can be realized through two intermeshing transmission elements 31, 32, for example in the form of spur gears, as part of the transmission device 30, which elements accordingly are attached to the rotor shaft 11 and the auxiliary shaft 12 in a rotationally fixed manner and which each carry a signal generator M1, M2. The spur gear on the auxiliary shaft 12 can, for example, have a smaller tooth count than the spur gear on the rotor shaft 11 so that a gear ratio can be provided and the angle of the rotor shaft 11 and the angle of the auxiliary shaft 12 have an unambiguous relationship or an unambiguous ratio to one another.

[0053] The transmission elements 31, 32 of the transmission 30 can be mounted with the rotor shaft 11 in a housing of the drive unit 100 in advantageous fashion. The sensors S1, S2 (as signal detectors) can be arranged directly on a printed circuit board of the controller 40 in advantageous fashion.

[0054] In accordance with the invention, the sensor units 21, 22 use different measuring principles or sensor principles: electromechanical, magnetic, inductive, optical, etc.

[0055] The sensor units 21, 22 can have the following sensors S1, S2 that are different in each case: an inductive sensor (e.g., for the first sensor S1), a magnetoresistive sensor (e.g., for the second sensor S2), a Hall sensor, a rotation angle sensor, etc.

[0056] Safety-related advantages can be achieved with the aid of different measuring principles so that a simultaneous failure of both sensor units 21, 22 is avoided in the case of an external influence (e.g., by electromagnetic waves), which could occur with an identical sensor principle. In addition, a mutual interference of the sensors S1, S2 (e.g., crosstalk of the signals) can be avoided.

[0057] The first sensor unit 21 can provide a primary function for motor control, and to this end have a higher resolution than the second sensor unit 22.

[0058] The second sensor unit 22 can provide a secondary and/or redundant function for motor control and potentially have a lower resolution then the first sensor unit 21. The resolution of the second sensor 22 in this case can be chosen such that the motor control can also take place on the basis of its signal. In the latter case, the motor control need not satisfy the highest requirements on acoustics and haptics. The purpose of the second sensor unit 22 can be maintaining the function/availability of the motor control.

[0059] An advantage of two sensor units 21, 22 can furthermore reside in that mutual monitoring and/or validation of the sensor units 21, 22 in normal operation of the wheel actuator 110 is made possible, for example: validation of angle signals from the first sensor unit 21 to the second sensor unit 22 and vice versa, for example with the aid of a ratio between the angle signals; and/or validation of the control rod position calculated according to the vernier principle versus other signals present in the vehicle F from which the steering angle can be calculated (e.g., yaw rate, individual wheel speeds, external sensors, etc.). Further, If the sensors S1, S2 are multichannel in design (see FIG. 3), the validation can also individually consider the respective individual channels K11, K12, K21, K22 of the sensors S1, S2.

[0060] If a failure of the primary sensor S1 should occur, then the second sensor S2 can take over the position determination of the control rod 101.

[0061] When the second sensor S2 has a lower resolution or signal quality than the first sensor S1, it can be advantageous to adapt the control behavior of the motor control. This can be accomplished in multiple ways, including: reducing the dynamic response of the higher-level control loop (steering rack position control); adding a damping component to the signal (e.g., low-pass filter); limiting of gradients and amplitudes of the signal (target steering rack position); switching to different control parameterization that has been adapted for operation with this sensor.

[0062] It can be advantageous for high-precision calculation of the steering rack position when the position of the control rod 101 is known from both sensors S1, S2 at system start. After a subsequent possible partial failure in one of the sensor units 21, 22, the further calculation of the position of the control rod 101 can also take place only with that signal. A counting of the shaft rotations can additionally enter into the further calculation in this case, for example.

[0063] The calculation of the angle on the basis of the offset value from the start advantageously can normally run in the background so that the value is always available in normal operation and can also be validated against the other available signals in accordance with the above-described methods.

[0064] In addition, it can be advantageous that one or more of the items of calculated angle or position information, including an associated signal on the status of the validation, is/are sent on one or more vehicle bus systems for use by other control units in the vehicle F.

[0065] As FIGS. 2 to 4 show, the first sensor unit 21 can have a first signal generator M1 that is connected to the rotor shaft 11 in a rotationally fixed manner, and have a first sensor S1 that, in particular when viewed axially, is arranged on the face end in front of the rotor shaft 11 and opposite the first signal generator M1. Moreover, the second sensor unit 22 can have a second signal generator M2 that is connected to the auxiliary shaft 12 in a rotationally fixed manner, and have a second sensor S2 that, in particular when viewed axially, is arranged on the face end in front of the auxiliary shaft 12 and opposite the second signal generator M2.

[0066] As FIGS. 3 and 4 show, the first sensor S1 and/or the second sensor S2 can be arranged on the controller 40, in particular directly on the control circuit board.

[0067] As FIG. 2 shows, the transmission device 30 can have a main transmission element 31, in particular in the form of a gear, preferably a spur gear, which is connected to the rotor shaft 11 in a rotationally fixed manner and to which the first signal generator M1 is attached. Moreover, the transmission device 30 can have at least one auxiliary transmission element 32, in particular in the form of a gear, preferably a spur gear, which is connected to the auxiliary shaft 12 in a rotationally fixed manner and to which the second signal generator M2 is attached.

[0068] As FIGS. 3 and 4 illustrate, the controller 40 can have a first control unit 41 and a second control unit 42. In addition, the first sensor unit 21 can have at least one channel K11 to a first control unit 41 and at least one channel K12 to a second control unit 42. Also, the second sensor unit 22 can have at least one channel K21 to a first control unit 41 (see FIGS. 3 and 4) and potentially a channel K22 to a second control unit 42 (see FIG. 3).

[0069] In FIG. 3, a possible interconnection of the sensors S1, S2 is shown in combination with a two-channel and/or two-part controller 40. This has the advantage that both sensors S1, S2 are still available in the event of a shutdown of one control unit 41 or 42. If, moreover, a fault should occur in one of the sensors S1, S2 in this case, then the remaining sensor S1 or S2 can maintain further operation in connection with the remaining control unit 41 or 42. If, for example, a channel K11, K12, K21, K22 supplies an ASIL B relative angle signal, then the control units 41 and/or 42 can determine two ASIL D relative angles from the respective two ASIL B relative angle signals. An ASIL D absolute angle can then be determined from the two ASIL D relative angles.

[0070] In an example, the second sensor S2, whose task it is to maintain the availability of the position signal together with the first sensor S1, can be designed with only one channel (see FIG. 4). In this case, the position calculation in normal operation can be accomplished as in the example from FIG. 3, since all signals are available at the first control unit 41. If a fault-related failure or a shutdown of the second control unit 42 occurs, this situation does not change. If a shutdown of the first control unit 41 occurs, the system is capable of ensuring operation, albeit with limited availability, on the basis of the still-available angle information from the first sensor S1. In other words, measures may be required such as, e.g., driver warnings and/or a prevention of operation after a specific operating time or distance traveled. When these solutions can be implemented within the scope of the safety requirements to be met, this example represents a simpler, and thus cost-reduced, variant of the system. This example takes into account the property that a highly precise calculation of the control rod position from both sensors S1, S2 can be accomplished at system startup. Further calculation can be accomplished even with only the signal from the first sensor S1 on the basis of the knowledge of the position at startup. A counting of the sensor revolutions can also enter into the determination.

[0071] Advantages and special features within the scope of the present disclosure can be highlighted as follows, in particular: different measuring principles. In the event of external interference, e.g. by magnetic fields, it is thus significantly less probable that both sensor units 21, 22 will be interfered with at the same time; arrangement of the stationary sensor part (sensors S1, S2) in front of the rotating part (signal generator M1, M2) (see FIGS. 3 and 4); redundant construction of the sensor units 21, 22; redundant construction of the control units 41, 42; and/or validation of the sensor values from the sensor units 21, 22.

[0072] Furthermore, it is possible that the sensor device 20 can also include more than two sensor units 21, 22, which can then be geared differently from or identically to one another in order to increase the precision and/or robustness of the angle measurement/position determination.

[0073] The above explanation of the examples describes the present invention solely within the framework of examples. Individual features of the embodiments and examples can of course be combined freely with one another, insofar as is technically appropriate, without departing from the scope of the present invention.

[0074] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.