Method and device for determining an angle of rotation and/or a rotational speed of a steering shaft

Abstract

A method of determining an angle of rotation and/or a rotational speed of a motor shaft (110) of a motor (105) which is designed to produce a translational movement of a control element (115, 115a) relative to the motor (105). The method includes a step of reading in a movement signal via an interface with at least one sensor element (120) arranged outside the motor (105) such that the movement signal represents a translational movement of the control element (115) relative to the motor. In addition, the method further includes a step in which, using the movement signal, the angle of rotation and/or the rotational speed of the motor shaft (110) is/are determined.

Claims

1. A method (400) of determining at least one of an angle of rotation () and a rotational speed (n) of a motor shaft (110) of a motor (105), the motor (105) being designed to produce a translational movement of a control element (115) relative to the motor (105), the method (400) comprises: moving the control element axially along a rotational axis of the motor shaft by rotationally driving the motor shaft with the motor; arranging at least one sensor element outside the motor and adjacent the rotational axis of the motor shaft to detect the translational movement of the control element relative to the motor; reading (405) a movement signal, via an interface with the at least one sensor element (120, 120a) that is arranged outside the motor (105), and the movement signal representing the translational movement of the control element (115) relative to the motor; and determining (410), with a control unit, at least one of the angle of rotation () and the rotational speed (n) of the motor shaft (110) from the movement signal utilizing at least one of a linear conversion, an observer structure and a Kalman filter.

2. The method (400) according to claim 1, further comprising determining a speed of the translational movement, from the movement signal, to determine the rotational speed (n) of the motor shaft in the determination step (410).

3. The method (400) according to claim 1, further comprising, during the determination step (410), at least one of using a movement equation and taking into account a transmission ratio of a mechanical transmission chain, between the motor (105) and the control element (115, 115a), for determining at least one of the angle of rotation () and the rotational speed (n).

4. The method (400) according to claim 1, further comprising determining a motor shaft position, when the motor shaft (110) is at rest, and further, during the determination step (410), determining the angle of rotation () using the motor shaft position.

5. The method (400) according to claim 4, further comprising acting upon the motor (105) by a test signal for determining the motor shaft position during the determination step.

6. The method (400) according to claim 4, further comprising, during the determination step, at least temporarily blocking the control element (115, 115a).

7. The method according to claim 4, further comprising receiving a position signal, via the interface with the at least one sensor element (120), and the position signal represents an absolute position of the control element (115, 115a) such that, during the determination step, a position of the motor shaft is checked using the position signal.

8. A device (500) for determining at least one of an angle of rotation () and a rotational speed (n) of a motor shaft (110) of a motor (105), such that the motor (105) being designed to move a control element (115, 115a) in translation relative to the motor (105), the device (500) comprising: the motor shaft being rotationally driven by the motor to axially move the control element along a rotational axis of the motor shaft; at least one sensor element being arranged outside the motor and adjacent the rotational axis of the motor shaft to detect translational movement of the control element relative to the motor; a read-in unit (506) for reading in a movement signal via an interface with the at least one sensor element (120) arranged outside the motor (105), and the movement signal represents the translational movement of the control element (115, 115a) relative to the motor; and a determination unit (510) for determining at least one of the angle of rotation () and the rotational speed (n) of the motor shaft (110), from the movement signal, utilizing at least one of a linear conversion, an observer structure and a Kalman filter.

9. A steering mechanism of a vehicle for steering either a front axle or a rear axle of the vehicle, the steering mechanism comprises: a motor having a motor shaft that extends along a longitudinal axis, the motor driving the motor shaft to rotate about the longitudinal axis; a control element being connected to the motor shaft such that rotation of the motor shaft about the longitudinal axis moves the control element in translation along the longitudinal axis relative to the motor, and a steering angle of the vehicle being adjusted by translational movement of the control element relative to the motor; at least one sensor element being arranged outside the motor and adjacent the longitudinal axis for detecting the translational movement of the control element relative to the motor, the at least one sensor element emitting a movement signal, and the movement signal representing the translational movement of the control element relative to the motor; and a control unit being connected to the at least one sensor element and having a read-in unit for reading in the movement signal emitted by the at least one sensor element, and the control unit having a determination unit for determining at least one of an angle of rotation of the motor shaft and a rotational speed of the motor shaft based on the movement signal utilizing at least one of a linear conversion, an observer structure and a Kalman filter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An example of the invention is described in greater detail with reference to the attached drawings, which show:

(2) FIG. 1: A schematic representation of a control device for use with a device according to an embodiment of the present invention;

(3) FIG. 2: A schematic representation of a control device for use with a device according to an embodiment of the present invention;

(4) FIG. 3: A schematic representation of a vehicle with steering mechanisms according to example embodiments of the present invention;

(5) FIG. 4: A sequence diagram for an example embodiment of a method for determining an angle of rotation and/or a rotational speed of a motor shaft of a motor; and

(6) FIG. 5: A block circuit diagram of an example embodiment of a device for determining an angle of rotation and/or a rotational speed of a motor shaft of a motor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) In the following description of preferred example embodiments of the present invention, the same or similar indexes are used for similarly acting elements shown in the various figures, so that repeated descriptions of those elements are unnecessary.

(8) FIG. 1 shows a schematic representation of a control device 100 for use with a device according to an example embodiment of the present invention. The control device 100 comprises a motor 105 with a motor shaft 110, a control element 115 and a sensor 120. The motor 105 is arranged coaxially around the control element 115. The control element 115 is arranged within the motor shaft 110 and can be moved in translation along a longitudinal axis 122 of the motor shaft 110. The sensor 120 is, for example, attached to an end area of the control element 115 located outside the motor 105. Alternatively, the sensor 120 can be attached to a housing of the motor 105 or to a structure of the control device 100 that surrounds the control element 115, such as a housing of the control device.

(9) The motor 105 is designed to cause the motor shaft 110 to rotate about the longitudinal axis 122. For example, the motor 105 is an electric motor and the motor shaft 110 is the rotor shaft of a rotor of the electric motor. The control element 115 is in the form of a threaded spindle, so that by virtue of the rotational movement of the motor shaft 110 it will be moved in translation along the longitudinal axis 122. The motor shaft 110 comprises or drives a spindle nut 111 which meshes with the thread of the threaded spindle 115. The sensor 120 is designed to detect the translational movement of the control element 115 within a control range 125 of the control element 115, and to emit a corresponding movement signal to an interface with a device (not shown in FIG. 1) for determining an angle of rotation and/or a rotational speed of the motor shaft 110.

(10) FIG. 2 shows a schematic representation of a control device 100 for use with a device according to an example embodiment of the present invention. In contrast to FIG. 1, FIG. 2 shows a cross-section transverse to the longitudinal axis 122. When the motor 105 is operated, the motor shaft 110 rotates with a speed that depends on the rotational speed n of the motor 105 through an angle of rotation a about the longitudinal axis 122. The rotational speed n and the angle of rotation a can be determined by means of a method described below with reference to FIG. 4, without using a motor-internal sensor.

(11) FIG. 3 shows a schematic representation of a vehicle 300 with two steering mechanisms 305, 305a according to example embodiments A and B of the present invention. The vehicle 300 is a two-track vehicle. In the vehicle 300 the control device 100, 100a pictured in FIGS. 1 and 2 is incorporated in two different versions. In this case an end area of the control element 115, 115a is fitted movably onto an articulated axle arm 310 of the vehicle 300.

(12) On the side of the vehicle opposite the axle arm 310 is arranged a further axle arm 315. This axle arm 315 is connected movably to the axle arm 310 by way of a transverse link 320. The transverse link 320 is designed such that a steering angle change of the wheel carrier 312 caused by displacing the control element 115 is transmitted to the further axle arm 315 and hence to the other wheel carrier 312a.

(13) The control device 100, 100a comprises a control unit 325, 325a which is connected to the sensor 120 and the motor 105 by way of corresponding interfaces in the vehicle 300. The control unit 325 is designed such that it reads in the movement signal emitted by the sensor 120, 120a, which represents the translational movement of the control element 115, 115a, and, using the movement signal, determines the angle of rotation and/or the rotational speed of the motor shaft of the motor 105.

(14) According to the example embodiments of the present invention, in rear-axle steering applications sensor-free motor control is enabled by replicating a motor rotational speed in the absence of a motor position sensor. In this case a steering mechanism 305 in the form of a rear axle steering control element 306, 306a comprises an absolute position sensor 120, 120a which cooperates with a control element 115. The control element is designed to produce a steering movement at a rear axle of the vehicle 300. The control element 115 is connected to the motor shaft by an interlocking machine element such as a spindle nut 111. As control elements, for example ball screw or ball ramp spindles or trapeze spindles can be used. Alternatively, belt drives or gear drives that serve as coupling elements between the motor shaft and the control element can also be used. In FIG. 3, in version A steering by means of a single control element, the central control element 305 is shown. Version B shows two individual control elements 305a, each with a control unit 325a of its own.

(15) FIG. 4 shows a sequence diagram of an example embodiment of a method 400 for determining an angle of rotation and/or a rotational speed of a motor shaft of a motor. The method comprises a step 405 in which a movement signal is read in via an interface with at least one sensor arranged outside the motor, such that the movement signal represents a translational movement of the control element relative to the motor. In addition, the method comprises a step 410 in which the angle of rotation and/or the rotational speed of the motor shaft is/are determined using the movement signal.

(16) The sensor 120, 120a shown in FIGS. 1 and 3 is designed, for example, to work or detect over the entire control range 125. In this, an absolute position detection is not absolutely necessary. For example, a relative detection is sufficient for a speed determination. From the translational movement detected, a linear travel speed is determined, for example by derivation. As shown in FIG. 2, this is converted into an equivalent motor rotational speed by taking into account a movement equation and the characteristics of a mechanical transmission chain. A calculation can be done by way of a linear conversion, an observer structure or a Kalman filter. Alternatively to the rear axle steering, the detection of the linear control movement by a control element can also be used in a vehicle transmission. For example, in an automatic transmission the control element can engage a gear or actuate a selector lever. In the case of the transmission control the position of the control element is supplied.

(17) According to a further example embodiment of the present invention, the sensor-free motor control can also take place by means of position replication. In this case an estimate of the motor rotational speed n is combined with an estimate of a motor rotation angle .

(18) If a control device 100, 100a has been initialized, then by an injection method a position of a rotor of an electric motor 105 is determined. Injection methods are methods with active current imposition. In this, the motor 105 is acted upon with a test signal in order to determine the position of the rotor at rest.

(19) This takes place optionally in a condition in which the control device 100 is blocked by a locking device so that no control movement can take place.

(20) To determine the motor shaft position, in addition the position determined by the injection method is compared with and checked against position information from the absolute translational position sensor 120.

(21) In this case the absolute position sensor 120 detects a translational movement or an absolute linear position. From that movement or position, taking into account the movement equation and the characteristics of the mechanical transmission chain an equivalent rotational motor position is calculated.

(22) As in the case of the rotational speed replication, the calculation can be done by way of a linear conversion, an observer structure or a Kalman filter.

(23) The method described here can be applied in general with electric control devices 100, 100a which comprise a translational movement device 115 with a sensor 120, 120a for detecting a position of the movement device 115, wherein the movement device 115 is connected to a motor 105 by means of a transmission, a mechanical coupling or otherwise.

(24) FIG. 5 shows a block diagram of an example embodiment of a device 500 for determining an angle of rotation and/or a rotational speed of a motor shaft of a motor. The device 500 is, for example, the control unit 325, 325a shown in FIG. 3. The device 500 comprises a read-in unit 505 for reading in a movement signal via an interface to at least one sensor arranged outside the motor, such that the movement signal represents a translational movement of the control element 115 relative to the motor. To the read-in unit is connected a determination unit 510. The determination unit 510 is designed to determine the angle of rotation and/or the rotational speed of the motor shaft using the movement signal.

(25) The determination unit 510 can be connected to an optional control unit of the device 500. The control unit can be designed, using the angle of rotation and/or the rotational speed of the motor shaft, to emit to an interface with the motor a control signal for controlling the motor.

(26) The example embodiments described and illustrated in the figures have been chosen only as examples. Different example embodiments can be combined with one another completely or in relation to individual features. In addition one example embodiment can be supplemented by features of another example embodiment.

(27) Furthermore, process steps according to the invention can be repeated, or carried out in a sequence other than that described.

(28) If an example embodiment comprises an and/or link between a first feature and a second feature, this can be read in such manner that the example embodiment according to one version comprises both the first and the second feature, whereas according to another version it comprises either only the first feature or only the second feature.

INDEXES

(29) 100, 100a Control device 105 Motor 110 Motor shaft 111 Spindle nut 115, 115a Control element, threaded spindle, translational movement device 116 Link 120, 120a Sensor element 122 Longitudinal axis 125 Control range 300 Vehicle 305, 305a Steering mechanism 306, 306a Control element, individual control element, central control element 310 Axle arm 312 Wheel carrier 315 Further axle arm 320 Transverse control arm 325, 325a Control unit 400 Method for determining an angle of rotation and/or a rotational speed 405 Reading in of a movement signal 410 Determination of the angle of rotation and/or the rotational speed 500 Device for determining an angle of rotation and/or a rotational speed 505 Read-in unit 510 Determination unit Rotation angle n Rotational speed A, B Example embodiments of the steering mechanism