EP3746746A1

EP3746746A1 - Inductive angle sensor for a motor vehicle steering system

Info

Publication number: EP3746746A1
Application number: EP19702397.1A
Authority: EP
Inventors: Gergely RACZ; Zoltán BARANYAI; Gergely DZSUDZSÁK
Original assignee: ThyssenKrupp AG; ThyssenKrupp Presta AG
Current assignee: ThyssenKrupp AG; ThyssenKrupp Presta AG
Priority date: 2018-01-31
Filing date: 2019-01-29
Publication date: 2020-12-09
Also published as: DE102018102094A1; WO2019149669A1

Abstract

The invention relates to an angle sensor (2) for measuring an angle of rotation of the rotational position of a steering shaft (1, 11) of a motor vehicle in relation to a predefined starting rotational position, wherein the angle sensor (2) is an inductive sensor having a carrier plate (4) that can be connected to the steering shaft (1, 11) for conjoint rotation and an attachable printed circuit board (6, 60) which is spatially fixed manner with respect to the carrier plate (4), wherein at least one electrically conductive track (7, 70, 71) is arranged on the carrier plate (4) and a scanning device (5) is arranged on the printed circuit board (6, 60) and has two coils (80, 81, 82, 83) that are part of a resonant circuit, and wherein the scanning device (5) is designed to scan the at least one electrically conductive track (7, 70, 71) to generate an angle-dependent sensor signal when the steering shaft (1, 11) is rotated.

Description

Inductive angle sensor for a motor vehicle steering

The present invention relates to an angle sensor having the features of the preamble of claim 1, an electromechanical power steering system and a steer-by-wire steering system for a motor vehicle having the angle sensor and a method for determining a rotational angle of the rotational position of a rotatably mounted steering shaft of a motor vehicle the features of the preamble of claim 15.

Angle sensors are used in a motor vehicle, among other things, to measure the steering angle of the steering wheel. Currently used angle sensors are magnetic sensors whose measurement can easily be disturbed by external magnetic fields. Motor vehicles will be operated in the future, and in part already, fully or partially electrically, which can lead to high external field influence measurements by high-current cables, which are often in the vicinity of the steering system. Furthermore, currently used magnetic sensors have a low accuracy. However, steer-by-wire steering systems require higher resolution angle sensors than conventional electromechanical steering systems to replace torque-based steering control.

It is therefore an object of the present invention to provide an angle sensor which has an increased accuracy and a reduced influence of an existing magnetic interference field on the determination of the rotational angle value.

This task is performed by an angle sensor with the characteristics of

Claim 1 and a method for determining a rotational angle of the rotational position of a rotatably mounted steering shaft of a motor vehicle with the features of claim 15.

Accordingly, an angle sensor for measuring a rotational angle of the rotational position of a steering shaft of a motor vehicle in comparison to a predefined Starting rotational position provided. The angle sensor is an inductive sensor having a rotatably connected to the steering shaft carrier plate and a relation to the support plate fixed circuit board, wherein on the support plate at least one electrically conductive track and on the circuit board a scanning device with two coils that are part of a resonant circuit are arranged, and wherein the scanning device for scanning the at least one electrically conductive track for generating an angle-dependent sensor signal is formed during rotational movement of the steering shaft.

The inductive sensor system on which the angle sensor is based is one

Non-contact, short-range sensor technology that allows low-cost, high-resolution detection of conductive objects in the presence of dust, dirt, oil and moisture, making them highly reliable.

It is preferred that the at least one electrically conductive track is self-contained and extends around the center of the carrier plate.

Preferably, the at least one electrically conductive track has a wave pattern that allows an absolute angle determination via a steering shaft rotation.

In one embodiment, a single electrically conductive trace is provided, which is scanned by the two coils, the two coils being arranged at an angle of 90 degrees to each other. In this case, the scanning device preferably has an electronic control unit, which is set up by means of a Cordic algorithm, the rotation angle of

Steering shaft to determine.

It is advantageous if the circuit board is arranged asymmetrically to the center of the steering shaft, since this configuration allows a particularly compact design.

In a second embodiment, two electrically conductive tracks are preferably provided, each of which is scanned by one of the two coils. The two electrically conductive tracks do not overlap. there It is advantageous if the two coils are stretched coils with an inhomogeneous magnetic field. Preferably, the stretched coils along the radius are arranged one behind the other on the circuit board and formed stretched in the direction of the radius. A displacement of the part of the electrically conductive track located above the track along the radius thus leads to a change in the resonant frequency of the resonant circuit, which can be detected.

Preferably, the two electrically conductive tracks in their wave pattern on an equal number of wave crests and wave troughs, which are arranged circumferentially offset from each other on the support plate. Thus, the measured signal can be clearly assigned to a rotation angle within a revolution of the steering shaft.

It is preferable that the above-described electrically conductive traces are formed of copper.

It may also be envisaged that the two coils are arranged to be used independently of each other. This allows, for example, the counting of the revolutions of the steering shaft or the detection of a sector.

Furthermore, an electromechanical power steering system is provided for a motor vehicle, comprising a steering shaft which is rotatably mounted about a steering shaft axis and can assume different rotational positions, a

Electric motor to assist a steering movement and a previously described inductive angle sensor.

The inductive angle sensor may also be part of a steer-by-Wi steering system for motor vehicles, comprising a steering actuator acting on the steered wheels, electronically controlled as a function of a driver's steering request, a reaction of the road to a control-transmitting feedback actuator, and a control unit that the feedback actuator and the

Steering wheel controls.

Furthermore, a method for determining a rotational angle of the rotational position of a rotatably mounted steering shaft of a motor vehicle is provided, wherein in the method, the rotational position of the rotation of the steering shaft is measured with an inductive angle sensor having two spatially fixed coils which are part of a resonant circuit, wherein the coils at least one rotating with the steering shaft, electrically conductive, extending around the steering shaft and in to scan closed track, in which a change of a resonant frequency of the resonant circuit is detected.

Preferred embodiments of the invention are explained below with reference to the drawings. The same or functionally identical components are cross-figured with the same reference numerals. Show it :

Fig. 1: a schematic representation of a steering system of a

Motor vehicle with an inductive steering angle sensor,

2 shows a schematic representation of a steering system of a

Motor vehicle with an inductive steering angle sensor with two elongated sensor coils,

Fig. 3 is a simplified representation of an inductive sensor with

stretched coil,

Fig. 4 is a plan view of two electrically conductive tracks, which are each scanned by a stretched coil, as well as

Fig. 5: a schematic representation of an electromechanical

Steering system of a motor vehicle with an inductive

Steering angle sensor.

FIG. 1 shows a rotating steering shaft 1 of a steer-by-wire motor vehicle steering system with an angle sensor 2 and an associated electronic control unit (ECU) 3. The angle sensor 2 has a carrier plate 4 connected to the rotating shaft 1 and a stationary scanning device 5 which is arranged on a printed circuit board 6 connected to the electronic control unit 3. The carrier plate 4 has a track 7 made of an electrically conductive material, preferably copper. The track 7 is self-contained and has no beginning and no end. The pattern of the track 7 is preferably a wave pattern that is curved

Has triangular shapes that extend around the center of the support plate 4. The wave pattern has peaks and troughs and repeats periodically. The pattern of the track 7 is not formed concentrically with the steering shaft. It is designed in such a way that an absolute angle determination is possible via a shaft rotation.

On the circuit board 6, two coils 80,81 of the scanning device 5 are arranged. The printed circuit board 6 is preferably formed as a PCB (printed circuit board) and carries all electronic components of the sensor 2, in particular an evaluation circuit and the coils 80,81. The circuit board 6 with the coils 80,81 is located immediately below the copper track 7. The circuit board is not arranged concentrically to the central axis of the steering shaft 1.

The angle of rotation is estimated by the inductive sensor 1, in which the copper track 7 is queried on the support plate 4. The coils 80,81 are parts of a resonant circuit. They 80,81 produce a high-frequency magnetic field. As the track 7 moves in the magnetic field, an induction current begins to flow due to the electromagnetic induction. Based on the mutual inductance coupling, the resonant frequency of the resonant circuit changes. When a non-ferrous metal object such as the copper trace approaches, the resonant frequency of the electrical resonant circuit increases. The mutual inductance coupling thus changes as the copper trace rotates across the coils 80,81. The sensor monitors the

Movement of the conductive track with the support plate or the rotating shaft and thereby calculates its absolute angular position. Two coils 80, 81 are sufficient to calculate the angle when placed at 90 degrees to each other. The output of the two coils 80, 81 is a sine signal and a cosine signal in the case of the previously described triangular pattern. The angle calculation is based on the industry standard Coordinate Rotation Digital Computer (Cordic) algorithm. This algorithm makes it possible to efficiently compute elementary trigonometric and hyperbolic functions using almost exclusive use of fast operations such as additions and multiplications with powers of two. Multiple printed circuit boards with two coils each can be used to provide high redundancy and electronic error compensation capability (misalignment, mechanical errors). The coil pairs may be arranged in pairs on separate PCBs or on a common PCB.

Figure 2 shows an embodiment in which two coils 82,83 along the radius of the circuit board 60 are aligned one behind the other. The

Support plate 4 has two tracks 70,71 of an electrically conductive

Material, preferably copper, on. The tracks 70, 71 are self-contained, without beginning and end, and extend around the steering shaft 1. A track 70, 71 is in each case interrogated by one of the two coils 82, 83 by measuring mutual induction. The circuit board 60 is fixed in space and the support plate 4 with the two tracks rotates with the steering shaft 1. The steering shaft 1 is in the example shown part of a steer-by-wire steering, which has no mechanical connection to the steering gear. The coils 82, 83 are elongated coils.

The operation of the stretched coils 82, 83 is shown in FIG. The stretched coils 82,83 have a non-homogeneous magnetic field, i. H. on one side of the coil, the magnetic field is stronger than on the other side. This is achieved in the case shown by the rectangular

Windings 800 of the coil 82, 83 lie inside one another and become longer as viewed from the inside to the outside. On the one short side of the coil 82,83, therefore, the turns are very close to each other, while on the other short side of the coil 82,83 the turns have a wide, uniform distance from each other. The magnetic field is therefore to the right of the

geometric center of the coil on the largest. Moves a thin conductor 100 from one end of the coil to the other end can be a linear

Inductance change can be measured. In the example of FIG. 2, the thin conductor 100 is formed by the track 70, 71 applied to the carrier plate. The rotating shaft rotating track 70,71 moves over the stretched coil 82,83 along the radius of the circuit board, wherein the position of the located above the coil track portion is detected relative to the coil ends. FIG. 4 shows an example of an arrangement of two tracks 70, 71 and two elongate coils 82, 83. The coils 82,83 extend in the radial direction and are placed one behind the other in the radial direction. They are each arranged directly below the corresponding track 70,71. The patterns of the tracks are preferably wave patterns that have curved, rounded triangular shapes that extend around the center 40 of the carrier plate 4.

Both tracks 70, 71 preferably have the same number of wave crests 90 and wave troughs 91, which are distributed uniformly over the circumference. The wave crests 90 and wave troughs 91 of the two tracks 70, 71 are arranged with an angular offset in the circumferential direction relative to one another. The tracks 70,71 are thus designed so that an absolute angle determination is possible over a shaft rotation. The two tracks and the respective readout of a stretched coil allow a determination of the absolute position also immediately after a wake-up of the sensor. A renewed calibration can thus be dispensed with.

The illustrated arrangement of the elongated coils 82,83 is only exemplary. It may also be provided to place the coils on opposite sides of the carrier plate center 40.

FIG. 5 shows a steering shaft 11 of an electromechanical steering system. The angle sensor 2 corresponds to the sensor of Figure 1. Die

Support plate 4 of the sensor with the track 7 rotates with the steering shaft 11 and the circuit board 6 with the coils 80,81 is disposed adjacent to the steering shaft 11 below the track 7. In contrast to steer-by-wire steering systems is in electromechanical steering systems significantly less space for the circuit board 6 and the electronic control unit 3 available because the steering shaft 11 via mechanical components with the steering gear

connected is. The two coils 80,81 can be used independently of each other, for example, to count the revolutions of the steering shaft or to detect a sector. But they can also be used together, for example in a steering angle sensor with a reduction gear that works on the vernier scale. It may also be provided to use the angle sensor of Figures 2 to 4 for measuring the steering angle of an electromechanical steering system.

Claims

claims

1. angle sensor (2) for measuring a rotational angle of the rotational position of a steering shaft (1,11) of a motor vehicle compared to a

predefined output rotational position, characterized in that the angle sensor (2) is an inductive sensor which has a support plate (4) which can be connected in a rotationally fixed manner to the steering shaft (1, 1) and a printed circuit board (6, 60) which is fixed in space relative to the carrier plate (4), wherein on the support plate (4) at least one electrically conductive track (7,70,71) and on the circuit board (6,60) has a scanning device (5) with two coils (80,81,82,83), the part of a resonant circuit are, are arranged, and wherein the scanning device (5) for scanning the at least one electrically conductive track (7,70,71) for generating an angle-dependent sensor signal upon rotation of the steering shaft (1,11) is formed.

Second angle sensor according to claim 1, characterized in that the at least one electrically conductive track (7,70,71) is closed in itself and extends around the center of the carrier plate (40).

3. angle sensor according to claim 1 or 2, characterized in that the at least one electrically conductive track (7,70,71) has a wave pattern that over a steering shaft rotation an absolute

Angle determination allows.

4. Angle sensor according to one of the preceding claims, characterized

characterized in that a single electrically conductive track (7) is provided, which is scanned by the two coils (80, 81), the two coils (80, 81) being arranged at an angle of 90 degrees to one another.

5. An angle sensor according to claim 4, characterized in that the scanning device (5) has an electronic control unit (3), which is adapted to the rotation angle by means of a Cordic algorithm to determine the steering shaft (1,11).

6. Angle sensor according to claim 4 or 5, characterized in that the circuit board (6,60) is arranged asymmetrically to the center of the steering shaft (1,11).

7. Angle sensor according to one of claims 1 to 3, characterized in that two electrically conductive tracks (70,71) are provided which are each scanned by one of the two coils (82,83).

8. Angle sensor according to claim 7, characterized in that the

both coils (82,83) stretched coils with an inhomogeneous

Magnetic field.

9. angle sensor according to claim 8, characterized in that the

elongated coils (82,83) are arranged along the radius one behind the other on the circuit board (60) and are stretched in the direction of the radius.

10. Angle sensor according to one of claims 7 to 9, characterized in that the two electrically conductive tracks (70,71) have an equal number of wave crests (90) and troughs (91) circumferentially offset from each other on the support plate (4th ) are arranged.

11. Angle sensor according to one of the preceding claims, characterized

in that the at least one electrically conductive track (7, 70, 71) is formed from copper.

12. Angle sensor according to one of the preceding claims, characterized

characterized in that the two coils (80, 81) are arranged to be used independently of each other.

13. Electromechanical power steering system for a motor vehicle, comprising a steering shaft (11) which is rotatably mounted about a steering shaft rotation axis and can assume different rotational positions, an electric motor for assisting a steering movement and an angle sensor (2) according to one of claims 1 to 12.

14. Steer-by-wire steering system for motor vehicles having a force acting on the steered wheels, in response to a driver's wish electronically controlled steering actuator, a reaction of the road on a control transmitting feedback actuator, a control unit, the feedback actuator and the steering actuator controls, and one

Angle sensor (2) according to one of claims 1 to 12.

15. A method for determining a rotational angle of the rotational position of a rotatably mounted steering shaft (1,11) of a motor vehicle, wherein in the

Method the rotational position of the rotation of the steering shaft (1,11) with an inductive angle sensor (2) is measured, the two spatially arranged coils (80,81,82,83), which are part of a resonant circuit, wherein the coils (80,81,82,83) at least one, with the steering shaft (1,11) rotating, electrically conductive to the steering shaft (1,11) extending and self-tracking track (7,70,71) scan, in the a change of a resonant frequency of the resonant circuit is detected.