Fail-Operational Steering Angle Sensor

Abstract

This application describes a fail-operational steering angle sensor for a vehicle. The fail-operational steering angle sensor comprises a central gear (hub) and two outer gears (Gear 1 and Gear 2) mechanically connected to the hub. The two outer gears have magnetic properties and are located in the vicinity of a printed circuit board (PCB). The fail-operational SAS is connected to a steering wheel actuator shaft. The steering wheel actuator shaft imparts angular rotation to the above moving parts by mechanical connections of the central gear, the two outer gears, and a rotor located between the central gear and the PCB. The variations in magnetic field and magnetic flux resulting from the rotation of the mechanical parts are determined by the PCB.

Description

Detailed Description of the Invention

[0001] [Technical field] This application describes a fail-operational steering angle sensor for a vehicle. [Background technology]

[0002] Fail-operational behavior means that a system will continue to perform a defined set of functions to a defined extent, with a defined performance, for a defined time, in the presence of a certain amount of failures. This definition leads to the creation of a mechanical system that continues to operate for a certain period of time even if one mechanical component fails.

[0003] With the expansion of autonomous driving in the automotive market, new steering systems are becoming a reality, especially those that meet fail-operational standards and requirements, such as steer-by-wire systems. These steering systems remove the steering shaft that connects the steering wheel to the rack system. In this case, inside the passenger compartment of the vehicle, there is an upper system, the Steering Wheel Actuator (SWA), which consists, among other components, of a motor, several sensors, a steering wheel and a shaft (SWA shaft) that connects all the elements. The motor allows the driver to continue to exert a resistance while facilitating the rotation of the steering wheel. The sensors are in charge of measuring the angle of the driver's hands and the torque.

[0004] By aligning multiple sensors and actuators in the lower system (Steering Rack Actuator: SRA), the driver can feel the same traditional driving experience as in a normal car while operating the wheel, and the force from the road surface can be transmitted to the driver's hands. In addition, the steering wheel can be turned, allowing the driver to enjoy autonomous driving without turning the steering wheel.

[0005] In the new steer-by-wire systems, the consequences of one of these sensors failing are much greater when compared to current steering systems with a steering shaft, where in current technology there is always a mechanical connection between the steering elements, so a sensor failure does not directly affect driver safety.

[0006] From these technological developments, a need has arisen to have a fail-operational sensor that measures the exact angle of the steering wheel while ensuring full availability of the angle signal in the presence or absence of failures. The perception system must continue to operate accurately until the vehicle reaches a safe parking spot or a workshop where the system can be repaired. The perception system is a device that measures the angle and speed of the steering wheel. The information measured by the steering angle sensor is sent to the steering control system for analysis and is used, together with information provided by other existing sensors, to control various driver assistance systems such as electronic stability control.

[0007] Currently, if one mechanical component of the SAS fails, the entire sensor fails and stops working for safety reasons. For example, if one of two gears that work simultaneously fails, the sensor can only read the signal from one gear, and no valid output signal can be obtained because both gears need to provide a certain range of angles.

[0008] Apart from this known issue, to ensure accurate transmission of motion between the hub and the outer gear of the SAS, a minimum gap between the gear teeth is required to accommodate thermal expansion of the components over a wide temperature range. These gaps, along with other gaps that exist between moving parts (e.g. bearing gaps, actuation gaps, etc.), cause a physical phenomenon known as hysteresis. Hysteresis is a critical parameter for these types of sensors and is primarily observed with reversals of direction / rotation of the steering wheel.

[0009] An additional and major advantage of steer-by-wire systems is the possibility of having different steering ratios, i.e. possible number of turns of the steering wheel, apart from the possibility of a switched on / off mode. The driver can select the steering driver mode and switch from comfort to sport mode. This change in the configuration allows the number of turns of the steering wheel to be changed, for example from two and a half turns to the left and right from the center position (comfort mode) to one turn to the left and right from the center position (sport mode). This means that the range of the sensor can change from ±900° to ±360° depending on the driver's mode change. This possibility brings about the need to increase the accuracy of the sensor. For example, when activating the steering system to turn the wheel ±40°, a sensor with an angle error of 5° (partly due to hysteresis) will have an effect on the wheel of 0.22° (for comfort mode, steering ratio 1:22.5). In sport mode, the same sensor has an effect on the wheel of 0.55° (sport mode - steering ratio 1:9). This low accuracy can affect the trajectory of the vehicle, especially when activated in sport mode.

[0010] Currently, in existing steering systems, there is no delay in the movement of the wheel because the steering wheel and the wheels are physically connected. When the driver operates the steering wheel, the force is transmitted to the wheel through the steering shaft. So, in the conventional system, the SAS reads the driver's intention and sends a signal of the driver's intention. Ultimately, there will be some deviation in the angle, but it will not have a significant impact on the driver's intention. However, when the steering shaft is removed, there is no physical connection between the steering wheel and the wheels.

[0011] Applying the current SAS to new steer-by-wire systems, in the absence of the aforementioned sensor accuracy limitations, could directly affect the position of the vehicle's wheels, resulting in poor driving experience and performance, and in the worst case scenario, posing a potential safety risk to the driver, passengers and bystanders.

[0012] Therefore, the currently existing SAS configuration has two major problems for direct application to steer-by-wire systems: the first is the fact that if one component fails, the whole system will not work, and the second is related to the very limited overall accuracy of the SAS. 〔summary〕

[0013] The present invention describes a fail-operational steering angle sensor for a vehicle, comprising: a disc-shaped hub with a central circular opening; at least two disc-shaped outer gears, gear A and gear B, mechanically connected to the disc-shaped hub by protruding teeth on the outer edge of the disc-shaped hub (130) and the outer edges of the at least two disc-shaped outer gears; and a printed circuit board arranged on the disc-shaped hub and the at least two disc-shaped outer gears, the disc-shaped hub comprising a drive key located in the central circular opening, the drive key mechanically engaging a SWA shaft through the central circular opening and mechanically engaging a disc-shaped rotor between the printed circuit board and the disc-shaped hub.

[0014] In a proposed embodiment of the invention, the SWA shaft facilitates direct rotational movement of the disc-shaped hub and the disc-shaped rotor, and indirect counter-rotational movement of the at least two disc-shaped outer gears through their inherent contact points with the disc-shaped hub.

[0015] In yet another potential embodiment of the present invention, the printed circuit board is configured to determine rotational variations of the disk-shaped hub, the disk-shaped rotor, and the at least two disk-shaped outer gears, wherein the at least two disk-shaped outer gears have different diameters and different numbers of protruding teeth.

[0016] Furthermore, in another proposed embodiment of the present invention, the at least two outer disc-shaped gears have different material properties.

[0017] In yet another proposed embodiment of the present invention, the disk-shaped rotor comprises a disk-shaped surface having a set of openings.

[0018] Furthermore, in another proposed embodiment of the present invention, a disk-shaped rotor has a central circular opening that extends along and above an inner wall of the central circular opening of the hub, and the disk-shaped rotor has a rotor gap that ensures mechanical alignment with the hub drive key located on the inner wall of the circular opening of the hub.

[0019] Additionally, in another proposed embodiment of the present invention, the rotor gap mechanically aligns a steering shaft keyway and a drive key provided on the SWA shaft.

[0020] Furthermore, in another proposed embodiment of the present invention, the printed circuit board includes a set of induction coils evenly spaced in a circular arrangement on its surface and precisely aligned with a set of openings in the disk-shaped rotor. 〔overview〕

[0021] This application describes a fail-operational steering angle sensor. The proposed configuration of this disclosure allows to solve both the state-of-the-art problems mentioned above, i.e. system freezing in case of failure of one of the components, and the overall accuracy of the developed system. It not only improves the signal quality by reducing the hysteresis, but also ensures a mechanical fail-operational sensor, which is the best solution for steer-by-wire systems.

[0022] The mechanical configuration of a current steering angle sensor (SAS) comprises one central gear (hub) and two outer gears (Gear 1 and Gear 2) mechanically connected to the hub. The two outer gears have magnetic properties and are constructed and placed under a printed circuit board (PCB). An IC (Integrated Circuit) is placed on the PCB and above the two outer gears to detect the variations in the magnetic field emanating from the two outer gears. The hub is connected to a steering shaft by a drive key / keyway system. When a driver turns the steering wheel of the vehicle, the steering wheel rotates the hub, which in turn moves the two outer gears. Thus, the IC placed on the PCB can detect the angular position of the gears.

[0023] These two outer gears have different number of teeth, which, combined with the number of teeth on the hub, allows the sensor to measure and obtain an angular range. This allows the vehicle to know the actual position of the steering wheel, regardless of any power cycle, which is true power on. The true power on property allows the system to know exactly the correct position of the steering wheel when powering on the vehicle, for example, every time the driver switches off the vehicle with the steering wheel in a defined position. This is true even if for some reason the steering wheel is not in the same position before and after a power cycle.

[0024] These four components (two outer gears, hub, PCB) are usually structurally supported by a housing, ensuring correct alignment and positioning of all the components. Finally, a cover closes the interior of said housing with all the components.

[0025] In the novel concept of the present invention disclosed herein, i.e. the fail-operational SAS, the two outer gears have magnetic properties but are made of different materials. Gear A is made of one magnetic material (material A) and gear B is made of a different magnetic material (material B). Both of the outer gears are placed under an integrated circuit (IC) containing a sensor mounted on a printed circuit board (PCB).

[0026] In addition to this configuration, the fail-operational steering angle sensor adds an additional metallic rotor located near the PCB. The rotor is composed of a number of wing-like protrusions located near the PCB. The rotor also includes a cylindrical element rigidly connected to the steering wheel actuator (SWA) shaft. On the printed circuit board, near the rotor wing-like protrusions are a number of Cooper coils connected to a specific IC configured to detect the change in magnetic flux when the metallic rotor rotates.

[0027] Thus, in the proposed mechanical arrangement, there is signal redundancy, with two magnetic signals provided by the action of the two outer gears and one inductive signal provided by the metallic rotor.

[0028] These different kinds of information signals imply new hardware configurations. Both mechanical and hardware configurations create "heterogeneous redundancy" of both signals.

[0029] The invention proposed herein presents a new mechanical configuration for a fail-operational sensor, which provides improved overall sensor accuracy by reducing the sensor hysteresis.

[0030] Another advantage of the fail-operational sensor principle is ensured through redundancy of all machine components. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] For a better understanding of the present application, figures illustrating preferred embodiments are attached herewith, which are not intended to limit the technology disclosed in this specification.

[0032] FIG. 1 illustrates a new proposal and embodiment of a fail-operational steering angle sensor. Reference numbers refer to the following: 10 - fail-operational steering angle sensor; 100 - cover; 110 - Printed Circuit Boards (PCB); 120 - rotor; 130 - Hub; 140 - Gear B; 150 - Gear A; 160 - Housing.

[0033] 2 illustrates a possible embodiment of the proposed fail-operational steering angle sensor, in which new mechanical and electrical relationships between the components of the sensor are depicted. 10 - fail-operational steering angle sensor; 111 - PCB induction coil; 120 - rotor; 130 - Hub; 140 - Gear B.

[0034] Figure 3 illustrates the main mechanical elements of the proposed fail-operational steering angle sensor. Reference numbers refer to the following: 10 - fail-operational steering angle sensor; 120 - rotor; 130 - Hub; 140 - Gear B (made of material B); 150 - Gear A (made of material A).

[0035] 4 shows the actuator sensor of the fail-operational steering angle sensor 10. Reference numbers refer to the following: 120 - rotor; 121 - rotor gap; 130 - Hub; 131 - Hub drive key.

[0036] 5 illustrates the rotor (120) connection of the fail-operational steering angle sensor (10) to the steering wheel actuator shaft (125). 121 - rotor gap; 122 - rotor punch area; 123 - steering shaft keyway; 125 - SWA shaft.

[0037] 6 illustrates the connection of the housing (160) of the fail-operational steering angle sensor (10) to an external system. 160 - housing; 161 - Connector A; 162 - Connector B. Description of the Preferred Embodiments

[0038] Next, several embodiments will be described in more detail with reference to the figures, which are not intended to limit the scope of the present application. According to the example shown in Figure 1, an exploded view of the developed sensor (10) is shown. 1, the precise positioning and mechanical connections between all components can be seen. A set of internal mechanical and electrical components are arranged to interact with each other within the housing (160), which is further closed by the cover (100).

[0039] The interior of the housing (160) includes internal components, such as a flat circular hub (130) with a set of outer teeth and a centrally located circular opening, which is aligned with an existing circular opening in the housing (160) that is also centrally located with respect to the overall location of the housing (160). Both aligned central circular openings allow for mechanical traversal and contact with the SWA shaft (125) connected to the steering wheel, as suggested in the illustrated FIG. 5. A set of circular outer gears are mechanically connected with the outer teeth of the hub (130), which are located on a set of circular outer gears. The set of circular outer gears also includes a set of outer teeth and a centrally located circular opening, which are gear A (150) and gear B (140). Both gears (140, 150) have a smaller diameter relative to the hub (130) and have teeth located on their outer edges to perfectly match the teeth of the hub (130).

[0040] Gear A (150) and Gear B (140) are made of two different materials and have different magnetic properties. Gear A (150) is made of magnetic material A and Gear B (140) is made of magnetic material B. By using two different substrates for the gears (140, 150), the system ensures two different failure mechanisms. For example, material A of Gear A (150) has better mechanical performance and material B of Gear B (140) has better thermal performance.

[0041] That is, if the sensor is exposed to very severe thermal conditions, i.e. thermal swings, gear A (150) may fail, but the sensor will continue to work with gear B (140) since gear B has better thermal performance. The same happens with mechanical loads, if gear B (140) fails due to extreme loads, gear A (150) will survive the failure and continue to work since gear A has better mechanical performance. The key feature to ensure this behavior to withstand extreme external factors is the selection of the most high performance and suitable materials for each gear.

[0042] In one proposed embodiment of the present invention, in a non-limiting manner, gear A (150) is made of a polymeric wrist with at least a magnet pill therein, obtained via an overmolding process, and gear B (140) is made of a magnetic material inside. In the proposed embodiment, the materials used for both gears (140, 150) are not completely equal in terms of physical properties, but by using a combination of two completely different materials, it is possible to significantly reduce the chance of failure of both gears (140, 150) at the same time.

[0043] The proposed material combination used for Gear A (150) offers increased performance in terms of toughness and wear resistance, despite lower performance in terms of low operating temperatures, mechanical resistance, creep effects and thermal expansion, whereas the proposed material combination used for Gear B (140) withstands high operating temperatures, has higher mechanical resistance, overcomes creep effects and has lower thermal expansion, despite having lower toughness and lower wear resistance.

[0044] In one possible embodiment of the invention, hub 130 rotates on a dedicated bearing arrangement. Gear A 150 and gear B 140 also rotate on dedicated bearing arrangements. The bearing arrangements of hub 130, gear A 150 and gear B 140 are independent of each other and are defined by housing 160.

[0045] In another preferred embodiment of the present invention, in a non-limiting arrangement, the hub (130) and both gears A (150) and B (140) are preferably arranged on the same rotational plane, on which the circular rotor (120) with a set of projections is arranged. The rotor (120) has a circular opening similar to that described above and a diameter similar to that described above, and the center of rotation of the rotor (120) coincides with the center of rotation of the hub (130). The rotor (120) is rigidly connected to the SWA shaft (125) and is mechanically aligned with the hub (130) and mechanically designed to rotate with the hub (130). This is accomplished through an existing rotor gap (121) along a circular opening that runs along the top of the inner wall of the circular opening of the rotor (120). The rotor gap (121) coincides with an existing hub drive key (131) located on the inner wall of the circular opening of the hub (130).

[0046] Since the hub (130) is the critical element for actuating the gears (140, 150), in existing state-of-the-art steering angle sensors, if a particular part of the hub (130) fails, the entire sensor will fail. In the mechanical arrangement of the fail-operational SAS (10) proposed herein, even if the hub (130) fails during operation, the rotor (120) will maintain its movement / rotation activity in an independent manner, ensuring that there is still a signal supply from the steering.

[0047] In this particular case, if the hub (130) fails, the gears (140, 150) will no longer operate and the angle range of true power on will no longer exist. However, the rotor (120) will still move / rotate and provide a rotation angle signal. Also, the internal software is configured to process and determine the number of rotations of the rotor (120) to ensure the provision of a signal of the steering wheel position. Even if a back-off / downgrade of the signal from the sensor (10) occurs and true power on is lost, it is still possible to safely park the vehicle or drive it to the nearest workshop in perfect safety. The failure of the hub (130) does not compromise the operational safety of the vehicle.

[0048] Similar to what happens if the hub (130) fails, the same happens if the rotor (120) fails. If for the same reason the rotor (120) or the induction system consisting of ICs and coils fails, the hub (130) and gears (140, 150) still work. The only reversal detected is related to a decrease in accuracy of the output signal of the sensor (10) resulting from an increase in hysteresis. However, it is still possible to drive the vehicle and park it safely or drive it to the nearest workshop in perfect safety.

[0049] As shown in the representative images of the present invention, particularly in Figures 1, 3 and 4, both the rotor (120) and the hub (130) exhibit a shape similar to that of a disk. The rotor (120), whose disk-like surface rests on the hub (130), also includes a set of apertures disposed along its surface.

[0050] A set of electrical components is disposed on the set of mechanical components described above. The set of electrical components may include, for example, a printed circuit board (110).

[0051] In Fig. 2 it is possible to observe one of the possible positions of the PCB (110) which is centrally placed on the plane formed by the hub (130), the outer gears (140, 150) and the rotor (120). The proposed PCB (110) comprises a set of induction coils (111) evenly distributed on its surface. The PCB (110) is highlighted above the rotor (120) and conforms to and covers the surface formed by the two overlapping disc-shaped hubs (130) and the rotor (120) in order to determine these rotational process variations caused by a set of existing openings in the rotor (120) surface as previously described. These coils (111) are adapted to measure the variations in magnetic flux promoted by the movement of the rotor (120) together with an additional IC precisely adapted and configured to work with the PCB (110).

[0052] The housing (160) is responsible for the location and alignment of all the parts and internal components, while the cover (100) is responsible for ensuring the closure of the device.

[0053] In this newly developed mechanical configuration, the hub (130) is provided with a drive key (131). When the fail-operational steering angle sensor (10) is assembled, the hub's drive key (131) is also assembled to the keyway (123) of the SWA shaft (125). When the driver turns the steering wheel of the vehicle, it is mechanically connected to the fail-operational steering angle sensor (10) via the SWA shaft (125), not shown in the figure. It actuates the hub which further facilitates the movement of the outer gears (140, 150) and the rotor (120). To ensure this mechanical connection, there is a gap (121) in the central circular opening of the rotor (120) that is larger than the hub's drive key (131).

[0054] In addition to the current mechanical actuation of the sensor (10) provided by the interaction between the steering shaft keyway (123) and the hub drive key (131), the rotor (120) is rigidly connected to the SWA shaft (125) by a set of punches at three specific points (122) simultaneously. The SWA shaft (125) has three recesses (122) located on the same plane and spaced apart at an angle of 120° from each other. The recesses (122) are made by a specific tool during the assembly of the sensor. This assembly deforms the outside of the circular opening of the rotor (120), which runs along the inner wall of the circular opening of the hub (130) and above said circular opening, against the recesses of the SWA shaft (125). This assembly creates a localized deformation of the rotor (120) and ensures a perfect fit of the rotor (120) to the SWA shaft (125). This feature ensures precise fit between the parts minimizing the presence of gaps between the rotor (120) and the SWA shaft (125).

[0055] The use of a punched (122) rotor (120) against the SWA shaft (125) and the placement of the PCB (110) under the Cooper coil makes it possible to obtain a backlash-free induction system. This kind of punched (122) connection is particularly important to reduce the hysteresis of the sensor as previously mentioned. In the proposed configuration, the gear play is preserved, but there is no slack between the rotor (120) and the SWA shaft (125). As a result, mechanical hysteresis does not affect the induction signal.

[0056] By using different types of connections between the sensor (10) and the SWA shaft (125), it is possible to separate the failure modes of the transmission. The hub (130) is connected by a drive key / keyway system (131) and the rotor (120) is connected to the SWA shaft (125) by a punch (122). To operate the rotor (120) or the hub (130), it is sufficient to simply overmold a part of the rotor / hub, but only have one connection to the shaft. If this connection fails, the whole sensor fails. With the proposed mechanical arrangement of the present invention, this failure is suppressed and by having two different types of connections, it is always possible to have a communication between the SWA shaft (125) and the sensor (10).

[0057] Inductive measurements, by design, can only measure a portion of the rotation of the SWA shaft (125). For example, if the rotor (120) has a set of four prongs / wings, it can only measure 4 times 360° / 4=90°. This means that to have true power-on between both measurement systems, the number of wings on the rotor (120) must be aligned to the number of teeth on the hub (130), gear A (150), and gear B (140). Both systems must have gear A (150) inductive, gear B (140) inductive, and gear A (150) aligned with gear B (140). This provides redundancy of three combinations with three respective vernier signals for how to measure the angle, all of which are true power-on.

[0058] The vernier signal acts as a secondary auxiliary scale for the measuring instrument, improving the accuracy of the measurement. For example, for a simple angle measuring instrument with one hub and one gear, if the hub has 50 teeth and the gear has 25 teeth, one revolution of the hub means two revolutions of the gear. For example, if the system can read the gear with an accuracy of 1°, it means that the instrument can read the hub with an accuracy of 0.5°. As a result of this improvement, the measurement range is reduced: the system only reads 180° instead of the conventional 360°.

[0059] In the disclosed invention, the aim is to read not only the exact position of the steering wheel, but also the number of revolutions. This means that only one gear cannot be applied, but two gears with different numbers of teeth must be applied to allow for misalignment in the gear rotation. This difference in the number of teeth allows to have a long angular range, since the final angle of the sensor is given by an unambiguous position equation. For example, a system with 70 teeth on the hub, 20 teeth on gear A and 21 teeth on gear B will have a sensor range of 2160°. After only six revolutions, gear A and gear B will be in the exact same angular position, and the system will read the same value as at the start of the rotation.

[0060] In the disclosed arrangement of the fail-operational SAS (10), redundancy of angle information is ensured by three types of signal information (two magnetic and one inductive), resulting in three vernier signals: Vernier signal A is obtained by the combination of the magnetic angles resulting from gear A (150) and gear B (140), Vernier signal B is obtained through the combination of the magnetic angle resulting from gear A (150) and the inductive angle resulting from rotor (120), and Vernier signal C is obtained through the combination of the magnetic angle resulting from gear B (140) and the inductive angle resulting from rotor (120).

[0061] These three final angle information are all true power-on, guarding against possible sensor (10) failure. If an electrical or mechanical component fails, redundancy occurs via elimination, resulting in a downgrade of the signal, but ensuring the system continues to operate, even if only for a short period of time. If the system fails, the driver is not put at risk.

[0062] The redundant signal of the sensor output is a highly accurate inductive measurement ensured by the interaction of the protrusions of the rotor (120) with the inductive coil (111) configured on the PCB (110). This inductive measurement must be combined with a magnetic measurement provided by an IC installed on the PCB (110) arranged to detect the variations in the magnetic field originating from the two outer gears A (150) and outer gear B (140). These two precise readings of the inductive and magnetic signals generated through the rotational movement of all the mechanically interconnected parts of the fail-operational SAS (10) cause them to have different weights for the angle calculation; one inductive for fine angle measurements and the other magnetic for high range measurements. These configurations must be set through software adjustment of the inputs and outputs of both aforementioned signals to accommodate two different hysteresis levels.

[0063] In addition to the critical mechanical systems already mentioned above, the connection to the higher level decision system is ensured by two existing connectors (161, 162) in the sensor (10). These two connectors, connector A (161) and connector B (162), originate from the sensor (10) and ensure redundancy of information and signals through the sensor (10).

[0064] By using a dual connection system to a higher-level determination system via two different connectors (161, 162), it is possible to ensure the functionality of the sensor (10) even if something fails inside the sensor, i.e. if a connector pin in the PCB fails, or outside the sensor, i.e. if the male connector falls or the communication cable is cut. To achieve this level of redundancy, the signal emerging from connector A (161) must be the same as the signal emerging from connector B (162). The higher-level system then receives dual information.

[0065] By isolating both the mechanical and electrical connections to external devices, i.e. the hub / rotor (130, 120) connected to the SWA shaft (125) via two different punch areas (122) and drive keys (131), and the PCB (110) to a set of two independent connectors (161, 162) providing independent interfaces for communication and power supply, it is possible to reduce the impact of failure of the sensor housing (160).

[0066] Failure of the housing (160) may affect the magnetic behavior of the gears (140, 150), but the induction rotor (120) remains operational. This also holds true for the reverse analysis and operation. This redundancy of physical features to ensure the operational state of the sensor (10) leads to improved performance and reduced chance of overall failure.

[0067] The proposed arrangement allows the fail-operation SAS sensor (10) to have two types of measurements, inductive and magnetic, a so-called heterogeneous redundancy, which allows to reduce the possibility of a complete failure in the system. Apart from the heterogeneous redundancy, the elimination of gaps and backlash in the inductive measurement allows to significantly improve the overall accuracy of the sensor (10) since there is no mechanical hysteresis between the SWA shaft (125) and the rotor (120).

[0068] It also increases the chance of reducing the non-linearity of the sensor. To increase the overall accuracy of the sensor (10), the software needs to provide different heights when calculating the final output angle. The "fine" or "zoom" kind of angle is provided by the guidance system, and the overall angle is provided by a combination of the guidance system and the magnetic system (gears). [Brief description of the drawings]

[0069] [Figure 1] A new proposal and embodiment of a fail-operational steering angle sensor is described. [Diagram 2] A possible embodiment of the proposed fail-operational steering angle sensor is described, in which new mechanical and electrical relationships between the components of the sensor are depicted. [Diagram 3] The main mechanical elements of the proposed fail-operational steering angle sensor are described. [Figure 4] 1 shows the actuator sensor of the fail-operational steering angle sensor (10). [Diagram 5] The rotor (120) connection of the fail-operational steering angle sensor (10) to the steering wheel actuator shaft (125) is now described. Reference numbers refer to the following: [Figure 6] The connection of the housing (160) of the fail-operational steering angle sensor (10) to an external system is described.

Claims

1. a disk-shaped hub (130) with a central circular opening; at least two outer disk-shaped gears, Gear A (150) and Gear B (140), mechanically connected to the disk-shaped hub (130) by projecting teeth on the outer periphery of the disk-shaped hub (130) and the outer periphery of the at least two outer disk-shaped gears; a printed circuit board (110) disposed on the disk-shaped hub (130) and the at least two disk-shaped outer gears; The disk-shaped hub (130) has a drive key (131) located in the central circular opening, the drive key (131) mechanically engaging a SWA shaft (125) through the central circular opening and mechanically engaging a disk-shaped rotor (120) between the printed circuit board (110) and the disk-shaped hub (130).

2. 2. The fail-operational steering angle sensor (10) for a vehicle of claim 1, wherein the SWA shaft (125) facilitates direct rotational variation of the disc-shaped hub (130) and disc-shaped rotor (120) and indirect opposing rotational variation of the at least two disc-shaped outer gears due to their inherent contact points with the disc-shaped hub (130).

3. 3. The fail-operational steering angle sensor for a vehicle according to claim 1, wherein the printed circuit board is configured to determine rotational variations of the disk-shaped hub, the disk-shaped rotor, and the at least two disk-shaped outer gears.

4. 4. The fail-operational steering angle sensor (10) for a vehicle according to claim 1, wherein the at least two outer disc-shaped gears have different diameters and different numbers of protruding teeth.

5. 5. The fail-operational steering angle sensor (10) for a vehicle according to claim 1, wherein the at least two outer disc-shaped gears have different material properties.

6. The fail-operational steering angle sensor (10) for a vehicle according to any one of claims 1 to 5, wherein the disc-shaped rotor (120) comprises a disc-shaped surface having a set of openings.

7. The disk-shaped rotor (120) has a central circular opening extending along an inner wall of the central circular opening of the hub (130) and above the central circular opening; 7. The fail-operational steering angle sensor for a vehicle according to claim 1, wherein the disk-shaped rotor (120) has a rotor gap (121) that ensures mechanical alignment with the hub drive key (131) disposed on an inner wall of the circular opening of the hub (130).

8. 8. The fail-operational steering angle sensor for a vehicle according to claim 1, wherein the rotor gap mechanically aligns a steering shaft keyway and a drive key on the SWA shaft.

9. 9. The fail-operational steering angle sensor (10) for a vehicle as recited in claim 1, wherein the printed circuit board (110) is provided with a set of induction coils (111) evenly spaced in a circular arrangement on a surface thereof and precisely aligned with a set of openings in the disk-shaped rotor (120).

Images