Steering system and release method for use in test driving of autonomous vehicles

Abstract

The invention relates to a steering system for use in test drives of an autonomous vehicle, the steering system comprising: manual steering means arranged for manually steering the vehicle, a steering axle (30) attached to the manual steering means, and a direct drive motor (35) controllably exerting a torque on the steering axle (30), the direct drive motor (35) having an axis of rotation (37) coaxial with the steering axle (30). The steering system is characterized in that: the steering system has at least two predefined states characterizing different driving conditions, each predefined state having at least one predefined release limit, and the steering system further comprises a controller assembly operable based on a control parameter, the controller assembly being arranged to detect an actual predefined state of the vehicle, the controller assembly initiating release of the direct drive motor (35) when the at least one predefined release limit corresponding to the actual predefined state is reached based on a difference value between a defined value of the control parameter and an actual value of the control parameter. The invention further relates to a deactivation method, as well as a data processing system, a computer program product and a computer readable medium for carrying out the method.

Description

[Technical field]

[0001] The present invention relates to a steering system for use in test driving an autonomous vehicle. The present invention also relates to a release method, and a data processing system, a computer program product, and a computer readable medium for carrying out the method. [Background technology]

[0002] People want an easier and more comfortable driving experience, and therefore various solutions are known in the art to assist drivers in steering a vehicle. Vehicles with autonomous self-driving capabilities are also known, i.e. vehicles that can drive themselves without or with minimal user intervention.

[0003] US Patent Application Publication No. 2003 / 0221898A1 discloses a motor-driven steering controller adapted to reduce steering torque during counter-steer operations. An EPS motor is provided to steer the front wheels via a reduction gear and rack and pinion, thereby reducing the operator's effort to operate the steering wheel, thereby assisting the operator in steering the vehicle. The motor is mounted through gears rather than directly on the steering wheel shaft, requiring additional moving parts that are subject to wear and failure.

[0004] The steering torque required for counter-steer assist is calculated and implemented, but if the calculation is incorrect the operator can override the steering action. The document does not disclose a method to ensure a safe override.

[0005] US Patent Application Publication No. 2006 / 0015228 A1 discloses a method and system for steering deadband in a mobile machine, such as an agricultural vehicle. The method includes an operator manually measuring a deadband value and using the deadband value in a controller to compensate for the deadband and mitigate undesirable effects associated with the deadband. The system includes a reversible electric motor that can turn the steering wheel in either a clockwise or counterclockwise direction. The electric motor current is adjusted to turn the steering wheel without generating excessive torque, thereby allowing for user override. The motor is again not a direct drive motor, and therefore additional gearing is required to transfer the motor torque to the steering wheel.

[0006] US Patent Application Publication No. 2006 / 0195238 A1 discloses a method and system for implementing automatic vehicle control with parameter driven release, where the vehicle is an agricultural vehicle such as a tractor or harvester. The vehicle is automatically guided along a predefined route and if a predefined parameter is exceeded, steering commands for automatic driving are suspended until a new actuation signal is received. The predefined parameters for the system can be minimum vehicle speed, maximum vehicle speed, approach angle between the vehicle and the route vector, cross track error limit, vehicle braking, seat switch or time out sensor signal, excessive vehicle lean or roll, excessive acceleration, etc., or manual override by the user. The vehicle preferably utilizes a non-geared electric motor.

[0007] EP1972482A2 discloses a steering drive system, preferably for industrial trucks. The steering drive system comprises a steering drive unit with a motor, which, when activated, drives an adjusting wheel via a drive shaft. The document discloses a steer-by-wire solution, in which a brushless electric motor is connected to the steering system. When the adjusting wheel is driven by the motor, the driver or operator can feel a direct connection between the steering device and the adjusting wheel.

[0008] US 2012 / 0130596 A1 discloses a vehicle guidance system, where the vehicle is an agricultural vehicle and is guided along a predetermined path to ensure efficient use of fuel or agricultural materials. The vehicle includes a steering wheel assembly having a steering wheel and a hub, the hub being connected to a steering shaft, and a drive assembly that directly drives the steering wheel assembly. The axis of the drive assembly is coaxial with the steering wheel assembly. The document does not disclose a torque limit that the drive assembly cannot exceed, so there is no guarantee that the driver will be able to take over control of the vehicle at any time when it seems necessary to avoid an accident, for example.

[0009] US Patent Application Publication No. 2014 / 0214275(A1) discloses a steering controller for precision agriculture. The steering controller can rotate a steering shaft of a vehicle to steer the vehicle along a desired path. A hub can be coupled to the steering shaft of the vehicle, and a motor can rotate the steering shaft by rotating the hub. The vehicle is preferably an agricultural vehicle, and its steering system is typically a hydraulic-based system. An operator can take over control of the vehicle by rotating the steering wheel, but the document does not disclose how this is possible.

[0010] US Patent Application Publication No. 2016 / 0334790(A1) discloses an autonomous vehicle retrofit system. A steering motor is utilized to apply torque to a steering column, the steering motor can be an electric motor, such as a brushed or brushless motor, and the steering motor interacts with the steering column via pulleys or gears. The presence of a user can be detected, the user can take over control of the vehicle, and the system can further derive the direction of the torque applied by the user.

[0011] In view of known approaches, there is a need for a steering system that can be used to test autonomous vehicles under a variety of traffic and driving conditions and that allows for user or driver intervention in the event of possible unforeseen or unsafe situations during testing. There is also a need for a steering system that allows for user disengagement or override during testing, particularly in the event of a malfunction or problem with the autonomous steering of the vehicle. Summary of the Invention [Problem to be solved by the invention]

[0012] The main objective of the present invention is to provide a steering system for use in testing autonomous vehicles that eliminates as far as possible the drawbacks of the prior art approaches. [Means for solving the problem]

[0013] The term "autonomous vehicle" refers to any vehicle capable of at least partially operating without the intervention of a human driver, such as a self-driving automobile, a semi-automated vehicle with self-driving or autonomous driving capabilities that may be limited to certain road or environmental conditions or driving situations (such as automated parking), or any conventional vehicle equipped with means to enable autonomous driving of the vehicle (such as a vehicle with a driving robot).

[0014] It is envisaged that in the near future, transportation will be fully automated through the use of autonomous vehicles that can operate without any human intervention. However, such vehicles must be tested to ensure the safety of the user, passengers, transported goods, the vehicle itself, and any other person, vehicle, or object on the route of the autonomous vehicle. For example, redundant hardware and software solutions are required to meet the necessary safety requirements. The software responsible for the autonomous operation of the vehicle must be safe and be prepared to safely operate the vehicle in all possible environmental, vehicle, and traffic conditions, including rare and unexpected events.

[0015] Some vehicles are designed to have semi-automated solutions, i.e. the vehicle is able to drive itself autonomously under certain conditions, but requires a human driver to intervene if a dangerous or unexpected situation arises.

[0016] To ensure safe operation and compliance with safety regulations, autonomous vehicles and the software responsible for driving them must be thoroughly tested. Such testing must include a variety of driving scenarios that may occur during real-world use of the vehicle, including driving on busy public roads.

[0017] The object of the invention is to provide a steering system which allows safe testing of autonomous vehicles in traffic conditions and various driving scenarios and also allows testing of vehicles with different automation levels, even fully automated vehicles.

[0018] A major problem with autonomous vehicles is that most of the autonomous features are intended to be used only under certain conditions (e.g., on highways, in urban areas, under certain weather conditions, in darkness or at night, etc.), and therefore suffer from "vulnerabilities". Vulnerabilities refer to the phenomenon where a vehicle's automated features work well under the conditions for which they are intended to be used, but the system requires human intervention to deal with situations that the software is not designed to handle. This therefore poses a challenge to the human driver, who needs to realize that the automation is not functioning properly and needs to understand why it is not functioning properly. Human factors studies have shown that humans are slow to detect that there is a problem with the automation and slow to understand the problem even after it is detected. When automation fails, there may be a sudden, unexpected transition that requires the driver to take over or resume manual control of the vehicle, and the driver may not be ready to take over control of the vehicle. It is therefore a further object of the present invention to provide a steering system that allows safe disengagement and override, even in a variety of driving situations and traffic conditions.

[0019] It is a further object of the present invention to provide a release method that allows a driver or user to take over control of the vehicle.

[0020] It is further an object of the present invention to provide a data processing system comprising means for performing the steps of the method, a non-transitory computer program product for implementing the steps of the method according to the present invention on one or more computers, and a non-transitory computer readable medium comprising instructions for performing the steps of the method on one or more computers.

[0021] The object of the invention is achieved by a steering system according to claim 1. The object of the invention is further achieved by a method according to claim 10, by a data processing system according to claim 12, by a non-transitory computer program product according to claim 13 and by a non-transitory computer readable medium according to claim 14. Preferred embodiments of the invention are defined in the dependent claims.

[0022] The main advantage of the steering system according to the invention compared to prior art approaches comes from the fact that it allows testing of autonomous vehicles with different automation levels in various driving situations, thus contributing to safer autonomous vehicles that are less prone to malfunctions and accidents.

[0023] A further advantage of the steering system according to the invention is that it can be used by any driver, not just trained safety drivers, since the steering system can be operated like any conventional steering system, and therefore no special skills are required to drive the test vehicle. Optionally, the steering system according to the invention can also function without a driver, for example for testing vehicles of a robot taxi company on public roads, or preferably in closed areas where the entry of other vehicles is not allowed during testing.

[0024] Additionally, the steering system according to the invention can be used for training test drivers, which can involve driving a test vehicle equipped with the steering system according to the invention, or the steering system according to the invention can be mounted on a test bench or any other simulated environment that provides realistic training for the test driver in a safe and secure testing environment.

[0025] The steering system according to the invention can be implemented both in fully automated vehicles without means of manual steering such as a steering wheel or joystick, and in vehicles with means for manual steering, i.e. semi-automated vehicles or vehicles with automatic driving functions under certain conditions. In the first case, the addition of means for manual steering allows more complex testing of the autonomous vehicle in a safe manner, i.e. a human driver can intervene if an unexpected or erroneous behavior of the vehicle is detected, thus allowing the vehicle to be tested not only on closed tracks but also on open roads in real traffic conditions. In the latter case, the steering system can be integrated into the existing steering axle of the vehicle.

[0026] The steering system according to the present invention can be used for professional and thorough testing of the quality of an autonomous vehicle or one or more autonomous or automated driving functions or features of a vehicle.

[0027] The steering system according to the invention is designed to test technologies with different automation levels, preferably from level 1 to level 5 of automation. Although level 5 automation does not require a human driver, for the purpose of developing and fine-tuning the autonomous driving software, it may be preferable to have a test vehicle with an interface for manual steering, e.g., a steering wheel, joystick, or any mechanism that can provide safe manual driving input during testing. Such manual driver intervention can ensure the safety of the vehicle and its environment in case any malfunction or bug occurs in the software responsible for the automated driving, or an unforeseen situation occurs during the test drive.

[0028] For example, level 1 automation requires the driver to physically operate the vehicle with hands and / or feet (not necessarily both) at all times. An example of level 1 automation is adaptive cruise control, which helps the driver maintain a safe distance from other vehicles. Level 2 automation requires the driver to monitor the road and preferably be available at all times to take over control at short notice. An example of level 2 automation is automated parking. For level 3 automation, the driver is assumed to be available to take control occasionally, but with ample transition time. An example of level 3 is a vehicle that can travel on its own without any driver intervention on a highway, preferably including maneuvering on-ramps and off-ramps. At level 4, the driver must provide destination or navigation input, but the driver is not assumed to be available to take over control at any time during the trip. Currently, there are no level 4 vehicles on the market, but a level 4 vehicle should be able to complete the entire journey from origin to destination without any driver input or intervention. Automation levels 1 to 4 all require a human driver to monitor the automated vehicle to ensure it is functioning as expected, and to intervene (assume control) in situations the automated vehicle cannot handle.

[0029] It is recognized that by implementing the drive motor directly on the steering axle of the vehicle, excellent dynamic performance and a comfortable driving experience can be achieved, since the direct drive motor adds only a very small inertia to the steering, which the driver does not notice, and therefore a normal driving experience can be provided. Furthermore, since the direct drive motor can directly drive the vehicle, precise control of the steering position and speed can be achieved, eliminating the need for additional transmission systems or gears, pulleys, gearing, etc. Without additional transmission systems or gears, no backlash or wear is expected, which improves the reliability of the steering system according to the invention, and further reduces the number of moving parts in the steering system, which also contributes to a more reliable operation of the steering system. The reduced number of moving parts improves the energy efficiency of the steering system by eliminating losses in intermediate mechanical parts, and the fewer parts means that less weight is added to the steering column, which allows easier and more precise driving. All this combines to reduce the environmental impact of the steering system.

[0030] A further advantage of the steering system according to the present invention is that it has a compact size with small axial dimension and large bore, which allows the steering system to be mounted on a wide variety of vehicles for testing purposes.

[0031] A steering system according to the present invention with a direct drive motor has a high torque-to-inertia ratio and a high torque-to-mass ratio, has low torque ripple or cogging, and has high torque even at low speeds.

[0032] The steering system according to the present invention also has low noise and low levels of self-excited vibration due to the direct drive and fewer parts in the steering system, which reduces the need and frequency of maintenance.

[0033] In certain embodiments, the steering system is implemented with a relatively large air gap between components of the steering system, which reduces cooling requirements and also provides relatively high impact resistance and resilience in dirty environments.

[0034] The steering system according to the invention can therefore be used for testing any autonomous vehicle.

[0035] Preferred embodiments of the invention will now be described, by way of example only, with reference to the following drawings, in which: [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a schematic cross-sectional view of a conventional electric steering drive device. [Diagram 2] 1 is a schematic diagram of a cross-section of a preferred steering system according to the present invention having a direct drive motor. [Diagram 3] FIG. 1 is a side view of a preferred embodiment of a steering system according to the present invention. [Figure 4] FIG. 4 is a cross-sectional view of a preferred embodiment of the steering system according to FIG. [Diagram 5] FIG. 1 is a schematic diagram of a preferred steering system according to the present invention, the steering system being connected to other vehicle components. [Figure 6] 1 is an exemplary architecture of a steering system according to the present invention; [Figure 7] 1 is an exemplary architecture of a steering system according to the present invention included in a simulation environment. [Figure 8] FIG. 1 is a schematic diagram illustrating a presumptive release event. [Figure 9] 4 is a graph illustrating possible release events based on a direct drive motor current signal. [Figure 10] FIG. 13 illustrates the effect of a change of state without a bridge state between the states. [Figure 11]FIG. 13 illustrates the effect of a change of state with a bridge state between states. [Figure 12] FIG. 13 is a diagram of two different predefined states with a bridge state in between and typical release limits for each state with respect to torque. [Figure 13] FIG. 13 is a diagram of three different predefined states with a bridge state between them and typical release limits for each state with respect to torque. [Figure 14] FIG. 13 is a diagram of four different predefined states with a bridge state between them and an exemplary release limit for each state with respect to torque. [Figure 15] Figure 14. The effect of a speed bump on the vertical acceleration signal. [Figure 16] 1 is a graph showing the relationship between direct drive motor torque and EPAS assist torque for different predefined conditions. [Figure 17] 1A to 1C are diagrams illustrating various uses of the steering system according to the present invention and the relationships between those uses. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The present invention relates to a steering system for use in testing autonomous vehicles. The steering system according to the invention comprises manual steering means configured to manually steer the vehicle such that a driver or user can override the steering system or take over control of the vehicle in order to avoid accidents or dangerous situations and ensure the safety of the vehicle's environment, including the vehicle under test as well as other vehicles, objects, occupants, etc. The manual steering means is preferably a steering wheel, a joystick, or any other handle that can be used to manually steer the vehicle.

[0038] The steering system according to the invention further comprises a steering axle attached to the manual steering means and a direct drive motor controllably exerting a torque on the steering axle, the direct drive motor having an axis of rotation coaxial with the steering axle, the direct drive motor being preferably a permanent magnet synchronous motor such as a brushless DC motor.

[0039] The steering system according to the present invention has at least two predefined states characterizing different driving conditions, the driving conditions preferably including at least one of parking maneuver, traffic jam, urban driving, suburban driving, low speed driving, high speed driving, emergency maneuver, and closed track driving. Preferably, the predefined state is determined based on at least one state parameter, the at least one state parameter being vehicle speed, lateral acceleration, yaw rate, and / or longitudinal acceleration.

[0040] Each predefined state has at least one predefined release limit, exceeding the predefined release limit preferably initiates release of the direct drive motor, and preferably in the event of a release, the driver or user of the vehicle is notified and requested to take over control of the vehicle.

[0041] The steering system according to the present invention further comprises a controller assembly operable based on a control parameter, preferably a position of the manual steering means, a torque on the manual steering means, a force on the manual steering means, a speed of the manual steering means or a direct drive motor current.

[0042] The controller assembly is configured to detect an actual predefined state of the vehicle, the controller assembly including a motion controller, a motor drive unit, and a feedback device. The motion controller is configured to generate commands including a prescribed value of the control parameter to be reached. The motor drive unit is configured to power the direct drive motor based on the command received from the motion controller, and the feedback device is configured to monitor the actual value of the control parameter and determine a difference value between the prescribed value of the control parameter according to the command and the actual value of the control parameter. The feedback device is further configured to initiate a release of the direct drive motor when at least one predefined release limit corresponding to the actual predefined state is reached based on the difference value.

[0043] The motion controller preferably comprises an upper controller and a lower controller, the upper controller preferably generating a motion profile including specified values ​​of control parameters for the direct drive motor, and the lower controller receiving the motion profile and generating commands including specified values ​​of the control parameters to be reached.

[0044] The controller assembly preferably further comprises a drive-by-wire unit disposed between the upper controller and the lower controller for converting a movement profile generated by the upper controller into a signal receivable by the lower controller.

[0045] The steering system according to the invention preferably has an intermediate bridge state between the two predefined states, which provides a smooth transition between the release limits of the two predefined states.

[0046] A preferred embodiment of a steering system according to the invention will now be described in more detail with reference to FIGS.

[0047] FIG. 1 is a schematic cross-sectional view of a conventional motorized steering drive with a steering axle 10 driven by a motor 15, which is attached to the steering axle 10 through a drive gear 12 and a reduction gearbox 14. At least one bearing 11 is preferably arranged around the steering axle 10. The steering axle 10 is rotatable around a first axis 17 and the motor 15 is rotatable around a second axis 18. In conventional motor drives such as FIG. 1, the first axis 17 and the second axis 18 are not coincident or coaxial, thus creating the need for the drive gear 12. Preferably, an angle sensor 13 is attached to the motor 15 to measure the rotation of the motor 15, which can be used to indicate the position of a steering wheel attached to the steering axle 10, as a means of manual steering. The angle sensor 13 also typically rotates around the second axis 18. If the motor 15 is a brushless DC motor (BLDC motor), the motor is preferably equipped with a commutation encoder 16 that generates a commutation signal for commutating the brushless DC motor. The commutation encoder 16 is also preferably arranged to rotate about a second axis 18, i.e. the axis of the motor 15.

[0048] Contrary to Fig. 1, Fig. 2 shows a cross section of a steering system according to the invention, which comprises a steering axle 20 rotatable about a first axis 27 and a direct drive motor 25 also rotatable about the first axis 27 of the steering axle 20. The steering system preferably further comprises at least one bearing 21 around the steering axle 20. The steering system preferably further comprises an angle sensor 23 attached to the steering axle 20 via a gear 22, the angle sensor 23 being preferably rotatable about a second axis 28 arranged parallel to the first axis 27 of the steering axle 20 and of the direct drive motor 25.

[0049] An example of an implementation form of the steering system according to the present invention is shown below. The steering system according to this example includes the following hardware components: - a brushless DC motor (BLDC motor) as direct drive motor 25 with passive cooling and an aluminium alloy housing, the aluminium alloy being preferably 7075 aluminium alloy (AA7075); - as angle sensor 23, an absolute multi-turn encoder with optical scanning capability enabling precise position measurements over an angle of more than 360°; - High performance servo drives, preferably with 18A continuous RMS current and 36A peak RMS current; - a winding temperature sensor for monitoring the temperature of the windings of the rotor of the direct drive motor 25, - A boost converter (preferably with a specification of 12V / 48V and 50A) to power the direct drive motor 25; and - A steering axle 20, preferably the original (OEM) steering column of the vehicle being tested.

[0050] 3 and 4 are diagrams showing a preferred embodiment of a steering system according to the present invention, where FIG. 3 is a side view of the steering system and FIG. 4 is a cross-sectional view of the steering system.

[0051] The steering system according to figures 3 and 4 comprises a direct drive motor 35 with a stator 35a, a rotor 35b and a motor shaft 35c, which is rotatable around an axis 37. The motor shaft 35c is arranged around the steering axle 30 such that the axis 37 of the motor shaft 35c is coaxial with the axis of the steering axle 30, i.e. both the steering axle 30 and the motor shaft 35c are rotatable around the axis 37. Preferably, the steering axle 30 is the original steering column of the vehicle used for the test drive.

[0052] The direct drive motor 35 is preferably arranged in a motor housing 36. A joining method in the form of a special adhesive is preferably used to provide a sufficiently strong contact between the stator 35a of the direct drive motor 35 and the motor housing 36. A similar joining method can be applied between the rotor 35b and the motor shaft 35c. The motor housing 36 of the direct drive motor 35 preferably uses the original bolt holes of the steering axle 30 to fasten the motor housing 36 to the steering axle 30.

[0053] Preferably, one or more first bearings 31 are arranged around the motor shaft 35c, and in the preferred embodiment according to Figures 3 and 4, the direct drive motor 35 has two first bearings 31 arranged in respective bearing housings 38, 48.

[0054] The direct drive motor 35 has low inertia due to its compact size and therefore can turn the steering wheel attached to the steering axle 30 exactly to the required position when the controller assembly controlling the steering wheel is fine-tuned or adjusted. As an additional advantage, the compact size of the direct drive motor 35 does not add undue extra weight to the steering axle 30. As a result, the steering system according to the present invention is very responsive and maintains sufficient power. Preferably, a temperature sensor is located within the steering system to monitor the winding temperature of the rotor 35b.

[0055] The steering system preferably uses 48V DC current and therefore requires a motor drive unit to directly power the drive motor 35. The motor drive unit is preferably integrated into the vehicle, for example in the trunk of the vehicle, and may include a battery and / or a boost converter.

[0056] The motor shaft 35c is preferably connected to the steering axle 30 via a clutch 40, and the clutch 40 is preferably connected to the motor shaft 35c via a first bracket 41.

[0057] As an extension of the steering axle 30, the steering system according to the invention may include an inner column 32 and an outer column 34 arranged coaxially with respect to the axis 37 of the steering axle 30. A second bearing 49a may be arranged between the inner column 32 and the outer column 34. Further bearings, such as a third bearing 49b, may be arranged around the steering axle 30.

[0058] An angle sensor 33, preferably an absolute rotary encoder, is mounted directly on the steering axle 30. With the angle sensor 33 according to this preferred embodiment, the steering system according to the invention can obtain the actual steering angle position even after a power loss, thanks to the design capabilities of the angle sensor 33. For diagnostic reasons, it is possible to add two angle sensors 33 to measure the difference between the steering axle 30 and the rotor 35b. The use of a double winding on the direct drive motor 35 can also increase the redundancy of the steering system according to the invention.

[0059] According to the preferred embodiment of FIGS. 3 and 4, the steering axle 30 and the angle sensor 33 are connected via pulleys 42, 44 and a timing belt 43.

[0060] The steering system may further include means for fixing the steering system components to each other or to vehicle components. For example, a connector 39 may be used to fix the position of the outer column 34 relative to the direct drive motor 35. A second bracket 45 may be used to fix the position of the motor housing 36 of the direct drive motor 35 relative to the steering axle 30. Additionally, a third bracket 46 may be used to connect the direct drive motor 35 to the vehicle, i.e., the vehicle chassis. A fourth bracket 47 may be used to mount the entire steering system to the vehicle chassis.

[0061] Figure 5 is a schematic diagram of a preferred steering system according to the present invention showing the steering system connected to other vehicle components. The preferred embodiment of the steering system according to Figure 5 comprises a steering axle 50 attached to a steering wheel 52 to enable manual steering of the vehicle by a human driver 54. A direct drive motor 55 is arranged on the steering axle 50 without gears, the rotation axis of the direct drive motor 55 being coaxial with the rotation axis of the steering axle 50. The steering system according to Figure 5 further comprises an angle sensor 53 for determining the exact position of the steering wheel 52.

[0062] Both the direct drive motor 55 and the angle sensor 53 are connected to a controller assembly 56 which receives a feedback position signal from the angle sensor 53 and provides commands to the direct drive motor 55 to steer the vehicle, preferably the commands including a target current value for the direct drive motor 55 to reach. The controller assembly 56 can be connected to an external network 57 such as the internet, a cloud or a database to receive further information regarding the steering of the vehicle.

[0063] In order to steer a vehicle, the steering axle 50 has to be connected with the wheels 60 of the vehicle. According to FIG. 5, the steering axle 50 and the wheels 60 are connected via an intermediate shaft 51 which has a torque sensor 59. The torque sensor 59 can for example be implemented as a torsion bar. The wheels 60 and the torque sensor 59 are preferably mounted on a rack and pinion 61 which transmits the steering torque applied to the steering axle 50 to the wheels 60.

[0064] Furthermore, means for electric power assisted steering (EPAS) 63 may also be connected to the rack and pinion 61 via gears 62 to further assist steering of the wheels 60. The means for electric power assisted steering 63 preferably receives a signal from an electronic control unit (ECU) 58.

[0065] 6 shows a preferred architecture 600 of a steering system according to the present invention. The boxes with dashed borders indicate various locations within a vehicle where the steering system components and associated parts may be located. Possible locations are the vehicle driver's seat 610, the vehicle passenger seat 620, the vehicle trunk 630, the vehicle center console 640, and the vehicle steering column 650.

[0066] At the driver's seat 610, means for manually steering the vehicle are arranged, preferably a steering wheel 611 connected to the steering axle 601. The steering wheel 611 can apply a torque to the steering axle 601 in order to steer the vehicle.

[0067] A controller assembly is arranged on, preferably below, the passenger seat 620, and is connected to elements of the steering column 650 and to a power source 632, preferably arranged in the trunk 630 of the vehicle, in which is also arranged a main battery 631. Preferably, both the main battery 631 and the power source 632 are connected to a means 641 for emergency stopping, which is preferably implemented in the form of a button arranged in the central console 640 for easy access.

[0068] Disposed in the steering column 650 is a direct drive motor 655 connected to the steering axle 601 via a clutch 651, preferably an anti-skid clutch. In this arrangement, the direct drive motor 655 can apply torque to the steering axle 601 to steer the vehicle. The direct drive motor 655 is preferably thermally coupled to a temperature sensor 652. The steering column 650 also includes a steering angle sensor 653 in mechanical contact with the steering axle 601.

[0069] The direct drive motor 655 is preferably connected to a controller assembly 621 to receive a control signal, which is further connected to a temperature sensor 652 to monitor the temperature of the direct drive motor 655 and to a steering angle sensor 653 to receive information regarding the rotational position of the steering axle 601.

[0070] The steering axle 601 may further be connected to a vehicle servo motor 602, preferably the vehicle's own servo motor 602. The servo motor 602 may also apply torque to the steering axle 601, as well as a direct drive motor 655 and a steering wheel 611.

[0071] 7 shows an exemplary architecture of the steering system according to the invention included in a simulation environment, since testing of autonomous vehicles is not necessarily limited to road tests. The steering system according to the invention can also be used for simulation tests, in which the steering system is mounted on a test bench, preferably a Hardware in the Loop (HIL) test bench, and the driver can interact with the steering system in a similar manner as during a test drive.

[0072] Test benches, especially HIL test benches, can enable the testing of the following: - Testing the robustness of the steering system controller assembly; - testing the robustness of the mechanical structure of the direct drive motor 75; - testing the override function and the possible intervention of the driver by using means for manual steering such as a steering wheel 71 and actuators such as pedals 76, - Testing the complete steering system before installing it in a real vehicle, - Testing new firmware, i.e. hardware or software components, prior to their planned updates.

[0073] As can be seen from the above list, the test bench allows testing and fine-tuning of the hardware components of the steering system according to the invention, including testing their reliability and durability before the steering system is integrated into the vehicle. Furthermore, the test bench equipped with the steering system can also be used for testing and validating subsystems or the entire steering system. Also, the test bench equipped with the steering system according to the invention can be used for training test drivers before they participate in real-world testing of the vehicle. Various driving scenarios can also be simulated by loop testing.

[0074] A driver or user may interact with an interface such as a steering wheel 71 or any other means for manual steering, and one or more actuators such as pedals 76. The steering wheel 71 is connected to a steering axle 70 equipped with a direct drive motor 75. The direct drive motor 75 is controlled by a controller assembly including a drive-by-wire unit 74. The drive-by-wire unit 74 is preferably connected to the pedals 76.

[0075] To provide realistic conditions, the test architecture includes a vehicle Electronic Control Unit (ECU) emulator 77 and an Electric Power Assisted Steering (EPAS) emulator 73. The EPAS emulator 73 is used to create an emulated assisted steering 72 for the steering axle 70.

[0076] A simulation computer 78 having simulation software 79a and virtual sensors 79b is used to generate input parameters to the controller assembly. The simulation computer 78 preferably provides virtual sensor data, traffic scenarios, and vehicle models to the controller assembly. The controller assembly can run in this simulated environment and receive signals and data from the simulation computer 78 and the vehicle ECU emulator 77 and provide commands to the direct drive motor 75 and pedals 76. The commands are preferably converted by the drive-by-wire unit 74 for the direct drive motor 75 and pedals 76. The EPAS emulator 73 preferably also uses the simulation data and inputs from the simulation computer 78.

[0077] The release features are explained in more detail below.

[0078] As already mentioned above, the steering system according to the invention has at least two predefined states characterizing different driving situations, e.g. parking, city driving, etc. Each predefined state has at least one predefined release limit in order to maintain a safe operation of the vehicle under test.

[0079] Overriding refers to an action where autonomous driving should be stopped for safety reasons and a manual override of the vehicle is required. The predetermined overriding limit can be a hardware limit or other predefined threshold that may indicate that the vehicle's behavior is becoming unstable or that autonomous driving is becoming unsafe, for example due to an error.

[0080] When the release limit is reached or exceeded, a manual override of autonomous driving is preferred to ensure the safety of the tester, the occupants of the vehicle being tested, the vehicle itself, and any other people, vehicles, or objects on the test vehicle's planned route.

[0081] It is recognized that different driving situations require different release limits to ensure safe testing and also to reduce the possibility of unnecessary manual intervention. Different driving situations serve as the basis for predefined conditions.

[0082] The predefined state is preferably determined based on at least one state parameter, such as the speed of the vehicle (see point a) below), lateral acceleration, yaw rate and / or longitudinal acceleration. Besides the state parameters, the parameters listed in points b) to f) below can also serve as a basis for determining which predefined state characterizes the vehicle at a given time, i.e. what the actual predefined state of the vehicle is. a) Vehicle speed. Vehicle speed should preferably be monitored, since it was found to be a key factor characterizing the need for a disengagement action. Monitoring the vehicle speed also enables steering control based on the vehicle speed (i.e. speed-dependent vehicle control). The vehicle speed can be derived by an indicated vehicle speed originating from the ABS block and transmitted via the CAN bus. Other methods can also be used to determine the vehicle speed, such as probing Hall effect sensors attached to the wheels of the vehicle and receiving the sensor's analog signal corresponding to the wheel tick. Auxiliary speedometers are also known and available on the market to determine the vehicle speed. Preferably, multiple methods can be used simultaneously to perform redundant speed measurements. The safety level of the speed signal preferably corresponds to the ASIL-D level in order to achieve the highest possible safety, and therefore redundant speed signal recognition is desired. b) Reference position or torque. In a steering system with a higher-level controller and a lower-level controller, the higher-level controller transmits a movement profile, i.e. a reference signal, to the lower-level controller, which contains defined values ​​of control parameters, such as a target position or a target torque to be achieved. The higher-level controller calculates the acceleration required to reach the target value and warns the driver to take over control from the autonomous driving system if the calculated acceleration exceeds a safety limit, indicating an unexpected or erroneous behavior of the vehicle or the autonomous driving software. The warning can be transmitted in the form of a visual and / or audio sign. In case of such a warning, the lower-level controller preferably continues to control the vehicle within the lower limiters that ensure the safety of the vehicle. In this way, a sudden increase in the target value can be avoided. c) Steering wheel or steering axle speed. The steering wheel or steering axle speed can preferably be calculated using either the vehicle's steering position sensor or the direct drive motor's position sensor. The vehicle's steering position sensor or the direct drive motor's position sensor is preferably an angle sensor. For safety and redundancy, it is possible to use both the steering position sensor and the direct drive motor's position sensor. The maximum steering wheel speed preferably defines a release limit, which cannot be exceeded and in case of this the subordinate controller immediately issues a warning to the driver and releases the automated steering function. Preferably, at least one steering angle sensor is mounted on the steering axle. Even more preferably, at least two steering angle sensors are mounted on the steering axle, one on the direct drive motor and one originally installed in the vehicle (integrated steering wheel position sensor). As explained above, for safety reasons the use of redundant signals is preferred. d) Target position of the steering wheel or steering axle. Preferably, the target position of the steering wheel or steering axle is also primarily monitored by a position sensor of the direct drive motor, preferably with high accuracy (±0.05-0.1°). Secondarily, an integrated steering wheel position sensor can also be used to monitor the target position of the steering wheel, but it will usually have lower accuracy and therefore the use of an integrated steering wheel position sensor is preferably only a fall-back option. e) Estimation of steering possibility. The autonomous software preferably calculates and transmits target position or torque values ​​directly to the drive motor, preferably via a higher-level controller and a lower-level controller. If the request of the higher-level controller is ignored by the lower-level controller, reaching a target position or torque value that is estimated to exceed the release limit, the steering system according to the invention preferably informs the driver before the release occurs, thus allowing the driver time to take the necessary safety actions. Figure 8 shows an example where the release limit is assumed to be exceeded on a curve. f) Direct drive motor current. The lower controller converts the output current of the direct drive motor into torque. More than one release limit can be defined in relation to the direct drive motor current. For example, a hardware limit can be defined, which cannot be exceeded since exceeding the hardware limit will result in release. In addition to a hard limit (i.e., a limit that cannot be exceeded), a soft limit can also be defined as a release limit. A soft limit can preferably be exceeded, for example, for a given time. In the case of a software limit, release occurs only if the time the limit is exceeded exceeds a certain limit or if the accumulated value of a parameter exceeds a certain limit. Figure 9 shows an example effect of reaching and / or exceeding different release limits in relation to the direct drive motor current.

[0083] One or more of the above parameters can be used to determine which predefined state the vehicle is in at a given time. For example, the vehicle's speed alone can be the determining factor, and in some cases a combination of other parameters can also be used.

[0084] As mentioned above, FIG. 8 shows a release action based on an estimation of steering feasibility, i.e., whether safe steering is possible with the specified target parameters or whether a future release is envisaged.

[0085] The autonomous driving software of the vehicle 80 typically comprises a route planning unit, which has a road model 84 within a perception distance. Based on the road model 84, an absolute steering torque 83 can be calculated that would be required to keep the vehicle 80 on the road 85, even if the road 85 is curved. As the vehicle 80 approaches the curve 86, the torque required to drive the vehicle 80 along the road 85 increases. The assumed future torque can be calculated by the estimation unit 81, preferably by a steerability estimation device, and compared with the release limit 82 in relation to the steering torque. If the estimation of the torque results in the release limit 82 being exceeded at a later time, i.e. when the vehicle 80 enters the curve 86, a warning 87 can be sent to the driver of the vehicle 80, who can resume manual control before entering the curve 86. Besides the torque acting on the steering wheel, other parameters can also be calculated with respect to the predefined release limits.

[0086] FIG. 9 is a graph showing a release event based on a current signal 90 of the direct drive motor. The current signal 90 constitutes the output current value of the direct drive motor and is shown as a function of time. In the lower controller, the output current of the direct drive motor is converted into a torque acting on the steering axle. Similar to the torque described in relation to FIG. 8, a predefined release limit can also be associated to the output current of the direct drive motor. For the output current, the predefined release limit can be a hardware limit 91 (a hard limit that cannot be exceeded) and / or a current threshold 92 (a soft limit that can be exceeded under certain conditions). The hardware limit 91 is preferably defined by the hardware of the direct drive motor and, since the hardware limit 91 is a hard limit, release occurs when the hardware limit 91 is reached (see release point 93 in FIG. 9). According to the example of FIG. 9, the hardware limit 91 of the output current is set to 30 A and therefore release occurs as soon as the actual value of the output current reaches 30 A, which is the hard limit 91 at the release point 93. When the output current falls below a predetermined release limit, ie, hardware limit 91, and also below current threshold 92, autonomous operation can be re-activated (see re-activation point 94).

[0087] Current threshold 92 is a soft limit and thus can be exceeded, for example, for a predefined time interval. When current signal 90 exceeds current threshold 92, a timer is preferably started, which runs as long as current signal 90 exceeds current threshold 92. If the time interval measured by the timer is less than the predefined time interval, no release occurs (see no release point 95). Figure 9 also illustrates the case where current signal 90 exceeds current threshold 92 for a longer time interval, and thus release occurs at release point 96.

[0088] For soft limiting, the cumulative excess signal can alternatively be measured based on the time interval measured by the timer and the output current value exceeding the current threshold 92. The cumulative excess signal can be calculated as the integral of the current signal 90 exceeding the current threshold 92, i.e., the area shown by the stripes. Instead of the integral, other methods of approximating the area shown can be used. For example, the sum of the output current values ​​can be multiplied by the time interval measured by the timer.

[0089] When a release action is initiated, for example due to a release limit exceeded or a critical unrecoverable error, a signal is sent to the human driver to assume control of the vehicle and a driver handover window begins. During the driver handover window, the steering system and autonomous software continue to drive the vehicle until the human driver assumes control of the vehicle or the driver handover window times out. The human driver may assume control by manually steering the vehicle, by using an actuation lever, or by any other means indicating a driver override. If the driver handover window times out without the human driver assuming control of the vehicle, a safety maneuver begins.

[0090] If a critical error occurs and the steering system and autonomous software can no longer reliably control the vehicle, a safety maneuver will begin immediately, without initiating a driver handover window. In this case, a signal will still be sent to the human driver to take over control of the vehicle as soon as possible. The signal in this case is preferably a stronger and more noticeable signal.

[0091] The safety maneuver is preferably implemented as a low level safety function in the drive-by-wire controller. During the safety maneuver, if steering was actuated by an advanced driver-assistance system (ADAS), the last received steering request is held and no acceleration request is accepted. However, if a braking request was actuated at the time of the error, the braking request is held. If braking was not actuated at the time of the error but the ADAS was controlling braking, a small deceleration is requested to slow the vehicle down during the safety maneuver.

[0092] If at any time the human driver initiates a driver override or presses an actuation lever, the safety operations are terminated and the human driver gains manual control over the vehicle.

[0093] As an example, when a safety maneuver is initiated, the last steering angle position is held and the vehicle's longitudinal speed is reduced until the vehicle is stopped.

[0094] In a further example, when a safety maneuver is initiated, the vehicle is requested to find a parking position, slow down, and stop the vehicle, preferably with the vehicle's hazard lights activated.

[0095] The predefined states may be based on various operating environments encountered during operation of the vehicle. Such predefined states may include, for example, highway driving, city driving, suburban driving, parking, closed track driving, etc. Different predefined states may require different release limits to be set depending on the characteristics of each driving situation. The decision to determine the actual predefined state of the vehicle may be based on one or more of the above parameters a)-f). The decision may be based on only one parameter, such as the speed of the vehicle, or on a combination of the above parameters.

[0096] For example, a decision regarding the actual predefined state of the vehicle may be made by a decision-making unit, which preferably has inputs such as information from an external inertial measurement unit (IMU) such as vehicle speed, vehicle lateral acceleration, yaw rate, and / or longitudinal acceleration.

[0097] Preferably, the decision-making unit receives map data of the vehicle's environment (e.g. SD or HD map data), which is preferably fused with high-precision position data of the vehicle (e.g. real-time kinematic (RTK) or GPS data) and / or visual data. The visual data is preferably derived from a camera and may include information based on traffic signs (e.g. speed limits) to improve the reliability of the decision. The decision-making unit may implement a specific neural network or any other machine learning algorithm trained to determine the actual state of the vehicle and thus also detect changes in the state of the vehicle.

[0098] By including additional parameters in the decision, the accuracy and reliability of the decision can be improved, thus reducing the possibility of misclassifying the predefined state of the vehicle. Optionally, the following parameters and measurements can be further included in the decision and can also serve as the basis for determining the release limit:

[0099] Most vehicles are equipped with torque sensors (TSU sensors), such as torsion bars, that measure the torque of the vehicle. By monitoring the torque sensor signal, the decision-making unit gets feedback from the torque applied by the human driver. During test drives, both the human driver and the direct drive motor can apply torque to the steering axle, and in fully autonomous driving, the vehicle would normally detect the torque applied by the direct drive motor as a driver input, even if the human driver does not apply any force to the steering wheel or any other manual steering means. In the case of a possible release, it is preferable to know whether the human driver, the direct drive motor, or both applied torque to the steering axle. An additional logic layer can be added to determine whether the human driver, the direct drive motor, or both applied torque to the steering axle. The additional logic layer can get input from the torque sensor that helps with the decision.

[0100] Information about the speed of the steering axle (also known as rack speed) introduced by the vehicle's servo drive can increase the robustness of the decision-making unit. The maximum allowable speed limit of the servo drive can also serve as a disengagement limit, where the controller alerts the human driver and disengages the direct drive motor from the steering system.

[0101] Any kind of mechanical, acoustic and / or optical sensor (i.e. strain sensor) can be mounted on or around the steering wheel. Based on the signal of the strain sensor, the release can be initiated. For example, a loud cry (e.g. "Please stop") above a certain decibel limit can be detected by the steering system and the lateral control is immediately released. This can ensure the safety of the vehicle occupants, for example, by initiating emergency braking and a safe stop of the vehicle, and can be used for fully autonomous vehicles without a steering wheel or other means for manual driving.

[0102] Preferably, each test vehicle is equipped with an external IMU sensor to enable autonomous driving. The IMU sensor can monitor the pitch, roll, and / or yaw of the vehicle and can therefore also be useful to determine external noises, speed bumps, rocks that on the one hand momentarily increase the required torque from the direct drive motors, but on the other hand do not pose any danger. Events like hitting a rock or a speed bump should not be a reason for disengagement and therefore the signal of one or more IMU sensors can be input to the decision making unit to reduce the risk of unnecessary disengagement. The effect of a speed bump on the torque signal is shown in Figure 15.

[0103] The steering system according to the invention has at least two different predefined states. In the following some examples of typical predefined states are explained in more detail. Figures 12, 13 and 14 also show preferred embodiments of the steering system with two, three and four predefined states respectively.

[0104] A possible driving scenario for an autonomous vehicle is driving on a closed track. Closed tracks are usually used for testing autonomous vehicles because there is no public traffic on closed tracks and the tests can be carried out in a safe and secure environment. In the state of closed track driving, it is possible to turn off all the release restrictions and test the true autonomous driving capability of the vehicle. Such tests can be carried out even if there is no human driver in the vehicle. Even if the release restrictions are turned off or set to values ​​that cannot be reached, a human driver can be in the vehicle and override the autonomous operation of the vehicle via the means for manual steering (e.g., steering wheel) of the steering system according to the invention in order to preserve the safety of the vehicle itself in case of an unforeseen software error.

[0105] The condition of closed-track driving allows vehicle manufacturers or vehicle testers to equip their own test vehicles (even fully automated vehicles without a driver) with the steering system according to the invention for the vehicle test day. In this way, functions such as lane keeping assistance, emergency overtaking, accident avoidance and other automated driving functions can be tested. A human driver can supervise the tests from inside the vehicle and intervene in case of an emergency to prevent accidents and possible damage to the vehicle.

[0106] Another predefined state may be a parking state, which may include driving in a parking lot. When parking, or when the vehicle is operating in a parking lot, the speed of the vehicle is relatively low, typically in the range of 0-15 km / h, but a higher torque may be required to move the vehicle. In this state, due in part to the lower speed, the danger level is relatively low and the human driver must easily override the steering system and manually steer the vehicle. The peak torque may be within the range of ±10 Nm, preferably within the range of ±8 Nm, or ±6 Nm. The peak torque may depend on various factors such as longitudinal force, lateral force, linear damping, inertial effects, front lift, friction, etc. The required average torque from the direct drive motor is typically higher than 4 Nm.

[0107] Further predefined conditions can be conditions of urban driving, which may also include driving in traffic jams. In urban areas, such as cities and towns, the maximum speed is typically limited to 50 km / h, but the exact speed limit is regulated by national laws and regulations. Driving in urban areas therefore corresponds to travel at moderate speeds, but unexpected situations due to pedestrians etc. may occur more frequently than in a parking lot. Urban environments may also include various road conditions and routes, such as steep hills, roundabouts, roads with sharp turns or curves. Even in urban environments, emergency braking should be possible, and therefore the speed range for urban driving conditions should be 0 km / h to 50 km / h. In urban environments, the vehicle travels at moderate speeds, so the power assist can provide sufficient torque to the direct drive motor for smooth operation. The reaction time of a human driver, especially a trained test driver, is sufficient to override the operation without straying from the lane. Hands-on operation is not a required use case, but is recommended: during autonomous emergency braking (AEB) operations, the self-driving software must keep the vehicle in its lane, and the steering system must handle situations at intersections and roundabouts.

[0108] Further conditions can be defined for travel in suburban areas. In suburban areas, speed limits usually allow higher speeds than in urban areas, therefore in suburban areas the speed of the vehicle is typically in the range of about 50-70 km / h. In the speed range of 50-70 km / h, existing steering assists usually have the best performance, i.e. if no limitations are applied, the steering wheel can be turned at the maximum possible speed. In this speed range, such a fast movement of the steering wheel would result in lane departure, therefore a high level of attention and ability to quickly intervene is assumed for the human driver controlling the vehicle. Therefore, if no limitations are applied to the steering system, the human driver must be ready to take over control of the vehicle at any time. For this reason, it is assumed that the human driver keeps his hands constantly on the steering wheel or any other means for manual steering. In the case of hands-on driving, the reaction speed of the human driver is significantly reduced.

[0109] In suburban areas where the roads are more than one lane and the vehicle is driven at a speed of 50-70 km / h, the human driver has more time to successfully perform an override or, in case of disengagement, to take over control of the vehicle. In suburban driving conditions, the average torque required from the direct drive motor during the tests is within a range of about ±3-6 Nm.

[0110] Driving on a highway can also be the basis for a predefined state. Contrary to the previously mentioned predefined states, on a highway, a vehicle is allowed to travel at a higher speed than on other types of roads, and the maximum allowed speed usually depends on the traffic regulations of the country. A typical maximum speed is 130 km / h, but in some countries, such as Germany, there are highways with no speed limit. For this reason, it is assumed that the vehicle will be driven at high speeds in an environment where other vehicles are also moving at high speeds. The coverage range of possible speeds is 0 km / h to 130 km / h. Since an automated vehicle must be able to perform automatic emergency braking (AEB) even on highways, the speed range for driving on a highway must also include lower speeds and, in extreme cases, 0 km / h. This means that the steering system must be active and be able to react when the vehicle in front of the test vehicle comes to a complete halt. The steering system according to the invention can also cope with sharp curves, for example at interchanges or junctions. The steering system can also guide the vehicle on inclined curves on a highway.

[0111] In normal operation, a vehicle is supposed to keep its lane on the highway, even if an emergency braking situation occurs. Based on artificial intelligence or sensor data, e.g. radar, visual sensors, lidar, and by using predictive models, the test vehicle can change lanes in emergency situations to avoid accidents. Lane changes can be made autonomously or with an override from the human driver. Before making a lane change maneuver, the target lane must be confirmed by the sensors and also by the driver.

[0112] When tests are performed to analyze a vehicle's lane-keeping ability, a single lane change requires light steering (approximately ±15°) to the left or right with fast and precise positioning to achieve maximum comfort for the human driver and vehicle occupants. A two-lane change requires more dynamic movements.

[0113] In highway driving conditions, the peak torque of the steering system's direct drive motor is not very high, typically around 7 Nm. Such torque resistance can be easily overcome by a human driver. If the human driver wants to take over control of the test vehicle in highway driving conditions, he must turn the steering wheel very carefully and smoothly to avoid veering into another lane. Due to the high speeds encountered on highways, great care must be taken not to apply excessive force or torque to the steering wheel to avoid any unwanted lane changes.

[0114] If the steering system is not functioning properly and does not want the human driver to steer the vehicle, the human driver must overcome the torque of the steering system. If the driver needs to use a torque greater than 10 Nm to override and disengage the steering system, the test vehicle may change lanes in the process.

[0115] A direct drive motor can use a maximum average torque of 2-3 Nm for lane keeping and one lane change. In such a case, insufficient torque, for example less than 1.1 Nm, will not turn the vehicle. This, together with friction in the steering system, can result in angular and lateral errors, which can be avoided by providing a torque above the average torque value. This phenomenon can also come into play for other predefined conditions.

[0116] In the exemplary state of highway driving, the following restrictions apply: If the speed of the vehicle is between 25 m / s and 37.5 m / s for more than 100 ms, the vehicle is considered to be in a state of highway driving. The release restrictions associated with the state of highway driving may be as follows: - The vehicle's yaw rate must not exceed ±0.11rad / s for more than 100ms; - The lateral acceleration of the vehicle is ±4.2m / s for more than 100ms. 2Must not exceed - The steering wheel position must not exceed ±0.262rad for more than 100ms, - The steering wheel torque must not exceed ±5Nm for more than 100ms, and - Steering wheel torque manually applied to the steering wheel for more than 100 ms must not exceed ±2.5 Nm.

[0117] Exceeding any one of the above limits will result in a disengagement and require a human driver to take over control of the vehicle.

[0118] A possible further predefined state may be that of an emergency maneuver. This state must cover the speed range from 0 km / h to the highest possible speed that is typically acceptable on a highway, e.g. 130 km / h or 200 km / h. The emergency state corresponds to an emergency situation, in which further fast and sharp turns of the vehicle are envisaged, i.e. to avoid an accident. The torque applied by the direct drive motor of the steering system may be within the range of ±10 Nm.

[0119] Different predefined states typically have different release limits, and therefore, when the vehicle state changes, the release limits may also change significantly, potentially leading to erratic vehicle operation or abrupt release actions due to exceeding the release limits of the new state.

[0120] To avoid problems with state changes, intermediate bridge states can be introduced between different predefined states that allow smooth transition of lift restrictions between the predefined states.

[0121] The controller assembly may use a decision-making unit, e.g., a neural network, to detect and determine the appropriate actual predefined stage of the vehicle based on available data, e.g., actual values ​​of the control parameters. If a change in the actual predefined stage is detected, a bridge command may be generated to apply a bridge function that allows for a smooth transition of the release limits between the predefined states. If a fault exists in the control of the vehicle or the bridge command cannot be delivered within a certain time, the steering system preferably alerts and returns control to the human driver.

[0122] The decision-making unit of the steering system must identify possible predefined states and their changes and must apply intermediate bridge states between the predefined states. Preferably, the decision-making unit must be able to recognize situations such as a traffic jam on a highway. If the decision-making unit defines the situation as urgent, the situation can instantly switch from a predefined stage of highway driving to a state of city driving including a traffic jam. In such situations, preferably a maximum possible speed limit is available for the controller assembly to steer the vehicle.

[0123] For example, bridge conditions can be applied between parked and city driving conditions, between city and suburban driving conditions, and between suburban and highway driving conditions. Figures 10 and 11 show the effect of changing vehicle conditions with and without bridge conditions.

[0124] Figure 10 is an example of not using bridge states for the steering system. According to this example, first the vehicle is driving at a lower, e.g. urban or suburban speed (e.g. 40 km / h, as indicated by a first road sign 108), whereby the applied torque 100 is higher, and then the vehicle enters a road with a higher speed limit, along a curve 107 (e.g. 110 km / h, as indicated by a second road sign 109). Due to the change in the speed of the vehicle, the actual predefined state of the vehicle also changes, e.g. t 1 10, the vehicle changes from a first state corresponding to urban or suburban driving to a second state corresponding to highway driving. With the change in the actual predefined state, the applicable release limits also change, i.e. from a first release limit 101 corresponding to the first state to a second release limit 102 corresponding to the second state. According to the example shown in FIG. 12, the first release limit 101 in the first state is higher than the second release limit 102 in the second state, since it is shown that on highways, high torque application can lead to undesirable lane changes, which should therefore be avoided. As can be seen from FIG. 10, the change in state occurs after the curve 107, and therefore the torque 100 applied to the steering system has already been reduced to a level below both the release limit 101 and the release limit 102. Therefore, in this case, no release occurs at points 103, 104, regardless of the presence or absence of a bridge state.

[0125] Conversely, FIG. 11 shows a vehicle moving through a curve 117 during which a change of state occurs (t 3An example is shown in Fig. 1. In this example, the speed limit in a first part of the curve 117 is lower (e.g., 40 km / h, as indicated by the first road sign 118) than in a second part of the curve 117 (e.g., 90 km / h, as indicated by the second road sign 119). In this case, the torque 110 applied to the steering system will be higher than the second release limit 112 of the second state when the vehicle enters the second state. This will lead to an immediate release in the middle of the curve 117, i.e., at the release point 114, which may be a dangerous situation if the human driver does not take immediate action to take over control of the vehicle. Such a situation may even lead to a deviation from the road or lane. Such an abrupt release can be avoided by a bridge state that allows a smooth transition of the release limits. The bridge state preferably includes a bridge function 115 that defines the transition between the release limit 111 and the release limit 112 of the state by connecting the bridge start point 113 and the bridge end point 116 with the bridge function 115. As can be seen, the bridge function 115 defines a smooth transition between the first release limit 111 and the second release limit 112 by extending the transition time. Thus, the torque 110 is allowed to remain below the bridge function 115, so that no release occurs.

[0126] The bridge function can be any monotonic function that connects the release limits 111, 112 of the states, for example the bridge function 115 can be a linear or non-linear function.

[0127] FIG. 12 shows an example of a steering system according to the invention with two predefined states corresponding to different driving situations. The driving situations according to FIG. 12 include a first state 120 corresponding to low speed driving, which preferably includes parking situations and driving in an urban environment. Typical speeds of vehicles are in the range of about 0-50 km / h due to the usual speed limit of 50 km / h in urban areas. The torque to be applied to the steering axle is usually in the range of ±8-10 Nm, since low speeds are typical especially for parking, but the vehicle is also expected to make sharp turns requiring higher torques on the steering axle. The release limit on the applied torque can preferably be set to ±10 Nm. In other embodiments of the steering system according to the invention, the first state 120 can be divided into further states, i.e. separate states corresponding to parking on the one hand and to urban driving on the other hand, similar to FIG. 14.

[0128] The second state 122 of Fig. 12 corresponds to another driving situation such as high speed driving, covering the scenarios of driving in suburban areas with a typical driving speed of about 50-70 km / h, driving on main roads with a typical driving speed of about 70-90 km / h, and also driving on highways or motorways where the typical driving speed is in the range of about 90-200 km / h. Preferably, in the second state 122, the vehicle typically travels at a speed in the range of about 50-200 km / h. In other embodiments of the steering system according to the present invention, the second state 122 can be divided into further states, similar to Figs. 13 and 14.

[0129] In the second state 122, the vehicle speed is relatively high and a smaller torque is expected to be applied to the steering axle compared to the first state 120. Too high a torque at high speed should be avoided as it may lead to unintended lane changes. In the second state 122, a torque range of ±3-6 Nm is expected and therefore the release limit can preferably be set to ±4 Nm or ±6 Nm.

[0130] As described in relation to Fig. 11, a bridge state 121 can be introduced to smooth the transition of the lift restriction between state 120 and state 122. According to Fig. 12, the bridge state 121 is introduced between the first state 120 and the second state 122.

[0131] Preferably, the steering system according to Figure 12 also includes an emergency state (not shown) for dealing with emergency situations. The emergency state preferably covers a speed range of 0-200 km / h and has a torque range equivalent to the first state 120, preferably with a release limit of ±10 Nm.

[0132] Figure 13 shows an example of a steering system according to the invention with three predefined states corresponding to different driving situations. The driving situations according to figure 13 include a first state 130 corresponding to a parking situation (parked state), where a typical speed of the vehicle is in the range of about 0-5 km / h, and since low speeds are typical for parking, the torque applied to the steering axle is usually within the range of ±10 Nm, although it is assumed that the vehicle also performs sharp turns requiring higher torques on the steering axle. The release limit on the applied torque can preferably be set to ±10 Nm.

[0133] A second state 132 of FIG. 13 corresponds to another driving situation, such as driving in an urban environment (urban driving state). In an urban environment, a vehicle typically travels at a speed within a range of about 5-50 km / h, since urban areas typically have a speed limit of about 50 km / h. In an urban driving state, a smaller torque is expected on the steering axle compared to a parking state, but sharp turns may also be expected, and in an urban driving state, a torque range of ±8 Nm is expected, and therefore the release limit may be set to ±8 Nm.

[0134] The third state 134 shown in Fig. 13 corresponds to high speed driving, such as driving in suburban areas where the typical driving speed is about 50-70 km / h, driving on main roads where the typical driving speed is about 70-90 km / h, and also driving on highways or motorways where the typical driving speed is in the range of about 90-200 km / h. In other embodiments of the steering system according to the present invention, the third state 134 can be divided into further states, similar to Fig. 14.

[0135] Considering the traffic regulations of different countries, different speed limits are applied in the third state 134. In some countries, for example Germany, there are also highways without speed limits. Preferably, the upper speed limit in the state of high speed driving corresponds to the maximum permitted or possible speed of a road vehicle in a particular country. For high speed driving, highways tend to have fewer curves and sharp turns, so that a lower torque is assumed in normal operation. For this reason, the release limit in the state of high speed driving with respect to torque is lower than that in the state of city driving or in the state of parking. As an example, the release limit in the third state 134 can be set to ±4 Nm.

[0136] As explained in relation to Fig. 11, bridge states 131, 133 may be introduced to smooth the transition of the release restriction between adjacent states 130, 132, 134. According to Fig. 13, a first bridge state 131 is introduced between the first state 130 and the second state 132, and a second bridge state 133 is introduced between the second state 132 and the third state 134.

[0137] Preferably, the steering system according to Figure 13 also includes an emergency state (not shown) for dealing with emergency situations. The emergency state preferably covers a speed range of 0-200km / h and has a torque range comparable to the first state 130 (i.e. the parked state) with a similar release limit of ±10Nm.

[0138] Figure 14 shows an example of a steering system with more predefined states than the steering systems of Figures 12 and 13. Figure 14 shows four different predefined states (states 140, 142, 144, 146) and three bridge states 141, 143, 145 between them.

[0139] The steering system according to FIG. 14 includes a state for parking as a first state 140, the characteristics of which are similar to those of first state 130 of FIG. 13 with a release limit of approximately ±9-10 Nm.

[0140] The second state 142 of Figure 14 preferably corresponds to city driving conditions, with a speed range of approximately 5-50 km / h. The characteristics of the second state 142 of Figure 14 correspond to the characteristics of the second state 132 of Figure 13, which has a release limit of approximately ±7-8 Nm.

[0141] Above 50 km / h the steering system according to Fig. 14 comprises two further predefined states, namely a third state 144 corresponding to suburban driving and a fourth state 146 corresponding to driving on a highway. The third state 144 (suburban driving state) preferably covers a speed range of about 50-70 km / h and the maximum torque allowed is preferably within the range of 3-6 Nm, therefore the third state 144 has a release limit of about ±6 Nm.

[0142] The fourth state 146 (state of highway driving) preferably corresponds to a speed range of approximately 70-200 km / h. If the speed limit for highway driving is higher than 200 km / h, the fourth state 146 preferably covers that higher speed range as well. However, for safety reasons it is reasonable to limit the maximum possible speed of the vehicle, i.e. to disengage if the vehicle attempts to drive faster than the pre-set maximum speed limit. As mentioned above, in the case of high speed driving, even a relatively small torque applied to the steering axle can lead to dangerous situations, including lane departure. For this reason, the maximum torque allowed is preferably in the range of 2-4 Nm, and therefore the fourth state 146 preferably has a disengagement limit of approximately ±4 Nm.

[0143] Between the different predefined states 140, 142, 144, 146, three bridge states 141, 143, 145 are arranged, and each bridge state 141, 143, 145 has a bridge function that defines a smooth and monotonic transition between the release limits of the different predefined states 140, 142, 144, 146. The bridge function can be a linear function or any other monotonic function, and different bridge states can have different bridge functions. In some cases, when the difference between the release limits of the predefined states 140, 142, 144, 146 is larger, the bridge function preferably corresponds to a longer time period, allowing a longer and less steep transition, thereby reducing the probability of occurrence of a release event.

[0144] Preferably, the steering system according to Figure 14 also includes an emergency state (not shown) for dealing with emergency situations. The emergency state preferably covers a speed range of 0-200 km / h (i.e. the full allowable speed range) and has a torque range comparable to the first state 140 (i.e. the parked state) with similar release limits, i.e. a release limit of ±9-10 Nm.

[0145] In another preferred embodiment of the steering system according to the present invention, the third state 144 and the fourth state 146 may correspond to different speed ranges. For example, the third state 144 may preferably correspond to a speed range of about 50-90 km / h with a release limit of about ±5-6 Nm, and the fourth state 146 may preferably correspond to a speed range of about 90-200 km / h with a release limit of about ±3-4 Nm.

[0146] Figure 15 shows a diagram of the effect of a vehicle driving over a speed bump. The speed bump 151, due to its height, results in a change in the vertical acceleration 150 (Z acceleration) of the vehicle, which, according to Figure 15, changes the acceleration in the direction of the Z axis. The speed bump 151 causes a characteristic change in the vertical acceleration 150 signal, as shown in the graph of Figure 15. When the decision-making unit receives the vertical acceleration 150 signal, it can easily identify that the change in vertical acceleration 150 is the effect of the speed bump 151. Going over the speed bump 151 also results in an increase in torque, but this shall not be a reason to initiate a release.

[0147] 16 shows a graph of a typical distribution of torque between the direct drive motor and the EPAS assist torque of a steering system according to the invention in different driving situations, where the X-axis shows the torque applied by the direct drive motor on the steering axle and the Y-axis shows the torque applied by the EPAS. The driving situations include a first state 161 corresponding to parking, a second state 162 corresponding to city or suburban driving, a third state 163 corresponding to highway driving, a fourth state 164 corresponding to city or suburban driving, and a fifth state 165 corresponding to parking.

[0148] It can be seen that in the third state 163, corresponding to highway driving, very little torque is required from the EPAS side, while the direct drive motor is able to provide all the torque required for highway driving, and the torque applied by the direct drive motor is also limited, i.e. it is within the range of ±5 Nm. Conversely, a parking situation (see states 161, 165) requires a higher level of torque (up to ±10 Nm) from both the direct drive motor and the EPAS.

[0149] 17 is a diagram of various uses of the steering system according to the present invention, namely uses 181, 182, 183, 184, 185. To enable a vehicle to perform fully automated autonomous driving on public roads, preferably the following steps will be taken to ensure the safety of the vehicle, its occupants, the goods being transported, and also any other vehicles, people, and objects on the route of the autonomous vehicle.

[0150] As a first step 171, a driver can be trained to test the autonomous vehicle, so that the driver becomes familiar with the task. This first step 171 can be performed using any training and / or simulation environment, preferably using a steering system according to the invention as an interface between the driver and the autonomous driving software, the steering system preferably being mounted on a test bench. Thus, a first use 181 of the steering system according to the invention can be the training of the driver. A first goal 191 of the first step is to have a trained driver who is familiar with the vehicle and the steering system and is therefore able to perform test drives in a safer manner than a normal driver.

[0151] As a second step 172 of the test, a vehicle can be equipped with a steering system according to the invention, and thus as a second use 182, the steering system according to the invention can be used for evaluation of the steering system and its components without any autonomous driving software. The second step 172 allows the steering system to be tested without the limiters that are usually introduced by the autonomous software, and thus the hardware limitations can be tested and estimated, and the steering system can be operated with variable inputs. Thus, a second goal 192 associated with the second step 172 is to determine the hardware limitations of the steering system according to the invention.

[0152] As a third step 173 of the test, the test can be performed with the help of an autonomous simulation software, and thus as a third use 183, the steering system according to the invention can be used in a simulated driving environment (see FIG. 7). In the simulated environment, the robustness of the autonomous software and hardware of the steering system can be tested. Furthermore, with the help of the steering system according to the invention, the influence of the driver override can also be tested. The third step 173 can also be used for further training of the test driver, since in the simulated environment, driving restrictions, release restrictions can also be simulated, and furthermore, faults can also be added to the simulation so that the test driver can learn how to react in such situations. Thus, a third goal 193 associated with the third step 173 is to test the robustness of the hardware, software and firmware, and to continue the training of the test driver in real-life situations, allowing also a thorough test of the driver override.

[0153] A fourth step 174 of the tests can preferably be a fine-tuning of the steering system by closed orbit operation. Thus, as a fourth use 184, the steering system according to the invention can be used in closed orbit operation and for fine-tuning the steering system hardware and software. A fourth goal 194 associated with the fourth step 174 of the tests is to define release limits for each predefined state.

[0154] The fifth step 175 of the test can be a test on a public road, where the steering system according to the invention is preferably integrated into a test vehicle provided by any manufacturer, serving as a fifth use 185 of the steering system according to the invention. As a fifth goal 195 associated with the fifth step 175 is to test the fully autonomous operation of the vehicle. In this case, a human driver is preferably present in the vehicle, alert and ready to take over control if necessary. Although the focus of the fifth step 175 of the test can be on the autonomous software, the steering system according to the invention ensures that even in emergency situations, the human driver is able to intervene and avoid any possible accident.

[0155] The invention also relates to a method for disengaging a direct drive motor of a steering system according to the invention from a manual steering means, the method comprising the step of commanding the direct drive motor of the steering system to achieve a defined value of a control parameter, the control parameter being preferably the position of the manual steering means, the torque of the manual steering means, the force of the manual steering means, the speed of the manual steering means or the drive motor current.

[0156] The method further includes the steps of monitoring an actual value of the control parameter and generating a difference value between a prescribed value of the control parameter and the actual value of the control parameter.

[0157] The method also includes initiating the release when at least one predefined release limit corresponding to an actual predefined condition is reached based on the difference value.

[0158] The invention also relates to a data processing system comprising means for carrying out the steps of the method according to the invention.

[0159] The invention further relates to a computer program product comprising instructions which, when executed by a computer, cause the computer to carry out an embodiment of the method according to the invention.

[0160] The computer program product may be executable by one or more computers.

[0161] The invention also relates to a computer readable medium comprising instructions which, when executed by a computer, cause the computer to carry out an embodiment of the method according to the invention.

[0162] The computer readable medium may be a unitary entity, or may comprise more distinct parts.

[0163] Of course, the present invention is not limited to the preferred embodiments described in detail above, but further variations, modifications and developments are possible within the scope of protection determined by the claims. Moreover, all embodiments that can be defined by any combination of dependent claims belong to the present invention. [Explanation of symbols]

[0164] 10 Steering axle 11 Bearings 12 Drive gear 13 Angle Sensor 14 Reduction gearbox 15 Motor 16 Commutation Encoder 17 First axis 18 Second Axis 20 Steering axle 21 Bearings 22 Gear 23 Angle Sensor 25 Direct Drive Motor 27 First Axis 28 Second Axis 30 Steering axle 31 Bearings 32 Inner column 33 Angle Sensor 34 Outer Column 35 Direct Drive Motor 35a Stator 35b rotor 35c motor shaft 36 Motor housing 37 Axis 38 Bearing housing 39 Connectors 40 Clutch 41 First Bracket 42 Pulley 43 Timing Belt 44 Pulley 45 Second Bracket 46 Third Bracket 47 Fourth Bracket 48 Bearing housing 49a Second bearing 49b Third bearing 50 Steering axle 51 Intermediate shaft 52 Steering Wheel 53 Angle Sensor 54 Human Driver 55 Direct Drive Motor 56 Controller Assembly 57 External Network 58 Electrical Control Unit (ECU) 59 Torque Sensor 60 Wheels 61 Rack and Pinion 62 Gear 63 Electric Power Assisted Steering (EPAS) 600 Architecture 601 Steering axle 602 Servo motor 610 Driver's seat 611 Steering Wheel 620 passenger seat 621 Controller Assembly 630 Trunk 631 Main Battery 632 Power supply 640 Center Console 641 Emergency stop measures 650 Steering column 651 Clutch 652 Temperature Sensor 653 Steering Angle Sensor 655 Direct Drive Motor 70 Steering axle 71 Steering Wheel 72 Emulated Assisted Steering 73 Electric Power Assisted Steering (EPAS) Emulator 74 Drive-by-wire unit 75 Direct Drive Motor 76 Pedals 77 Electronic Control Unit (ECU) Emulator 78 Simulation Computer 79a Simulation Software 79b Virtual Sensor 80 vehicles 81 Estimated Units 82 Release Restrictions 83 Absolute steering torque 84 Road Model 85 Road 86 Curve 87 Warning 90 Current Signal 91 Hardware Limitations 92 Current Threshold 93 Release point 94 Reactivation point 95 points 96 Release points 100 Torque 101 First Release Restriction 102 Second Release Restriction 103 points 104 points 107 Curve 108 First Road Sign 109 Second Road Sign 110 Torque 111 First Release Restriction 112 Second Release Restriction 113 Bridge start point 114 Release point 115 Bridge Functions 116 Bridge End Point 117 Curve 118 First Road Sign 119 Second Road Sign 120 First State 121 First bridge state 122 Second State 130 First State 131 First Bridge State 132 Second State 133 Second Bridge State 134 The Third State 140 First State 141 First bridge state 142 Second State 143 Second Bridge State 144 The Third State 145 Third Bridge State 146 The Fourth State 150 vertical acceleration 151 Speed ​​Bump 160 Torque 161 First State 162 Second State 163 The Third State 164 The Fourth State 165 The Fifth State 171 First Step 172 Second Step 173 Third Step 174 Fourth Step 175 The Fifth Step 181 First Use 182 Second Use 183 Third Use 184 Fourth Use 185 Fifth Use 191 First Goal 192 Second Goal 193 Third Goal 194 Fourth Goal 195 Fifth Goal

Claims

1. A steering system for use in a test drive of an autonomous vehicle, comprising: manual steering means configured to manually steer the autonomous vehicle; a steering axle (20, 30, 50, 601, 70) attached to the manual steering means; a direct drive motor (25, 35, 55, 655, 75) that controllably acts on the torque applied to the steering axle (20, 30, 50, 601, 70), the direct drive motor (25, 35, 55, 655, 75) having a rotational axis (27, 37) coaxial with the steering axle (20, 30, 50, 601, 70); the steering system having at least two predefined states characterizing different driving conditions, each predefined state having at least one predefined release limit (82, 101, 102, 111, 112), and the steering system further comprising a controller assembly (56) operable based on control parameters, the controller assembly (56) being configured to detect the actual predefined state of the autonomous vehicle, the controller assembly (56) comprising: a motion controller that generates a command including a specified value of the control parameter to be achieved; a motor drive unit for supplying power to the direct drive motor (25, 35, 55, 655, 75) based on the command received from the motion controller; a feedback device that monitors the actual value of the control parameter, determines a difference value between the specified value and the actual value of the control parameter, and initiates release of the direct drive motor (25, 35, 55, 655, 75) when the at least one predefined release limit (82, 101, 102, 111, 112) corresponding to the actual predefined state is reached based on the difference value. A steering system characterized by the above.

2. The steering system according to claim 1, wherein the predefined state is determined based on at least one state parameter.

3. The steering system according to claim 2, wherein the at least one state parameter is the speed, lateral acceleration, yaw rate, and / or longitudinal acceleration of the autonomous vehicle.

4. The steering system according to any one of claims 1 to 3, wherein the predefined state is further determined based on a driving situation including at least one of a parking operation, traffic jam, urban driving, suburban driving, low-speed driving, high-speed driving, emergency operation, and closed-loop driving.

5. The steering system according to any one of claims 1 to 3, wherein the steering system has an intermediate bridge state (121, 131, 133, 141, 143, 145) that provides a smooth transition between the two predefined states and between the release restrictions (82, 101, 102, 111, 112) of the two predefined states.

6. The steering system according to any one of claims 1 to 3, wherein the control parameter is the position of the manual steering means, the torque on the manual steering means, the force on the manual steering means, the speed of the manual steering means, or the current of the direct drive motor (25, 35, 55, 655, 75).

7. The movement controller is a host controller that generates a movement profile including a specified value of the control parameter for the direct drive motor (25, 35, 55, 655, 75), and a slave controller that receives the movement profile and generates the command including the specified value of the control parameter to be reached. The steering system according to any one of claims 1 to 3 is characterized by this.

8. The steering system according to claim 7, wherein the controller assembly includes a drive-by-wire unit (74) disposed between the host controller and the slave controller to convert the movement profile generated by the host controller into a signal receivable by the slave controller.

9. The steering system according to any one of claims 1 to 3, wherein the direct drive motor (25, 35, 55, 655, 75) is a permanent magnet synchronous motor.

10. A method of releasing a direct drive motor (25, 35, 55, 655, 75) of a steering system according to claim 1 from manual steering means, the method comprising: commanding the direct drive motor (25, 35, 55, 655, 75) of the steering system to achieve a defined value of a control parameter; monitoring an actual value of the control parameter; generating a difference value between the defined value of the control parameter and the actual value of the control parameter; starting the release when at least one predefined release limit (82, 101, 102, 111, 112) corresponding to an actual predefined state is reached based on the difference value.

11. The method according to claim 10, characterized in that the control parameter is the position of the manual steering means, the torque on the manual steering means, the force on the manual steering means, the speed of the manual steering means, or the current of the direct drive motor (25, 35, 55, 655, 75).

12. A data processing system comprising means for performing the steps of the method according to any one of claims 10 to 11.

13. A non-transitory computer program product comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of claims 10 to 11.

14. A non-transitory computer-readable medium comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of claims 10 to 11.

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