METHOD AND SYSTEMS FOR CONTROLLING A STEER-BY-WIRE STEERING SYSTEM OF A VEHICLE

Abstract

A method for controlling a steer-by-wire (SbW) steering system of a vehicle includes, using one or more processors, receiving one or more inputs specifying respective operating characteristics of the vehicle, determining a baseline C-factor based on the vehicle speed, wherein the baseline C-factor corresponds to a linear distance traveled by a rack of the SbW steering system relative to the rotation of a handwheel of the vehicle, determining a scaling factor based on the vehicle speed and the vehicle lateral acceleration, determining a scaled C-factor using the baseline C-factor and the scaling factor, determining a rack position reference based on the scaled C-factor, and controlling at least one function of the vehicle using the rack position reference.

Description

TECHNICAL AREA

[0001] This disclosure relates to a method and systems for controlling a steer-by-wire steering system of a vehicle and in particular the determination of a C-factor in steer-by-wire steering systems (SbW steering systems). BACKGROUND OF THE INVENTION

[0002] A vehicle, such as a car, truck, off-road vehicle, crossover, minivan, personal watercraft, aircraft, SUV, recreational vehicle, or other suitable means of transport, typically includes a steering system, such as an electronic power steering (EPS) system, a steer-by-wire (SbW) system, a hydraulic steering system, or another suitable steering system. The steering system of such a vehicle typically controls various aspects of the vehicle's steering, including providing steering assistance to an operator, controlling the vehicle's steerable wheels, and the like.

[0003] DE 10 2008 012 007 B4 describes a steer-by-wire steering system in which, to reduce a tendency of a vehicle to roll over, a variable steering ratio is set depending on a vehicle speed and a vehicle lateral acceleration such that the greater the value of the speed of the motor vehicle, the greater the degree of steering ratio is set.

[0004] Further state of the art is described in DE 10 2023 113 044 B3, US 2024 / 0 375 706 A1, DE 10 2021 202 343 A1 and DE 10 2014 017 127 A1.

[0005] The object of the invention is to minimize the probability of tires reaching a limit of adhesion in a steer-by-wire steering system of a vehicle.

[0006] This problem is solved by a method for controlling a steer-by-wire steering system of a vehicle according to claim 1 and by systems for controlling a steer-by-wire steering system of a vehicle according to claims 8 and 15. Advantageous further developments are set forth in the dependent claims. BRIEF SUMMARY OF THE INVENTION

[0007] This disclosure generally relates to the control of SbW steering systems.

[0008] An exemplary aspect of the disclosed embodiments includes a method for controlling a steer-by-wire (SbW) steering system of a vehicle.The method includes, using one or more processors, receiving one or more inputs specifying the respective operating characteristics of the vehicle, determining a baseline C-factor based on the vehicle speed, wherein the baseline C-factor corresponds to a linear distance traveled by a rack of the SbW steering system relative to the rotation of a handwheel of the vehicle, determining a scaling factor based on the vehicle speed and the vehicle lateral acceleration, determining a scaled C-factor using the baseline C-factor and the scaling factor, determining a rack position reference based on the scaled C-factor, and controlling at least one function of the vehicle using the rack position reference.

[0009] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples serve only for illustration and are not intended to limit the scope of protection of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The revelation is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to scale. On the contrary, the dimensions of the various features are arbitrarily enlarged or reduced for the sake of clarity. Fig. 1A generally illustrates a vehicle according to the principles of the present disclosure. Fig. 1B generally illustrates control according to the principles of the present disclosure. Fig. Figure 2A illustrates in general an example rack and pinion or road wheel actuator control (RWA control) and a column or handwheel actuator control (HWA control) of a steering system configured according to the principles of the present disclosure. Fig. Figure 2B illustrates in general an example implementation of dynamic C-factor control according to the principles of the present disclosure. Fig. Figure 3 is a flowchart that generally illustrates a procedure for controlling an SbW steering system according to the principles of the present disclosure. DETAILED DESCRIPTION

[0011] The following discussion relates to various embodiments of the disclosure. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be interpreted or otherwise used as limiting the scope of protection of the disclosure, including the claims. Furthermore, a person skilled in the art will understand that the following description has a broad scope and that the discussion of one embodiment is intended only as an example of that embodiment and does not imply that the scope of protection of the disclosure, including the claims, is limited to that embodiment.

[0012] As described, a vehicle, such as a passenger car, truck, off-road vehicle, crossover, minivan, personal watercraft, aircraft, SUV, recreational vehicle, or other suitable means of transport, typically includes a steering system, such as an electronic power steering (EPS) system, a steer-by-wire (SbW) system, a hydraulic steering system, or another suitable steering system. The steering system of such a vehicle typically controls various aspects of the vehicle's steering, including providing steering assistance to an operator, controlling the vehicle's steerable wheels, and the like.

[0013] A SbW steering system can include at least one handwheel actuator (HWA), such as a steering wheel used by a driver to steer the vehicle laterally, and at least one road wheel actuator (RWA), which is used to control a steered axle of the vehicle and generate lateral movement of the vehicle in response to the movement of the HWA. An SbW system can further include a controller, such as a domain controller, configured to store and execute control logic.

[0014] Side-by-side (SbW) systems offer several advantages over other steering system types, such as EPS steering systems. For example, SbW systems are not limited by a mechanical linkage between the head-waving unit (HWA) and the rear-waving unit (RWA). Consequently, SbW systems can offer more efficient packaging, increased crash safety and cost savings, and improved interaction with automated driving and advanced driver assistance systems (and corresponding safety and performance benefits).

[0015] In SbW systems, a mechanical connection between the handwheel and the road wheel is removed, and a steering ratio between the handwheel and the road wheel is not fixed. The steering ratio between the handwheel and the road wheel is usually defined by a relationship between a pinion and a rack, which can be referred to as a C-factor. The C-factor is defined as a linear distance traveled by the rack for one complete revolution of the handwheel. The C-factor can be a virtual value that can be tuned based on various factors, including, but not limited to, rack position, vehicle speed, and vehicle lateral states (e.g., lateral acceleration and yaw rate).

[0016] As an example (e.g., for passenger vehicles with standard EPS), the handwheel can be steered from a center position to a rack end position by more than one (1) turn, and the C-factor is between 50-70 mm / revolution. Conversely, for passenger vehicles with SbW systems, the handwheel can be steered from the center position to the rack end position by less than half a turn, and the C-factor can be greater than 150 mm / revolution. Accordingly, vehicles with SbW systems react faster than non-SbW systems, thereby increasing the likelihood of reaching a tire grip limit. As used herein, the tire grip limit refers to the maximum lateral force a tire can generate before losing traction with a road surface.

[0017] Accordingly, SbW systems and methods according to the present disclosure are configured to implement dynamic C-factor control techniques to minimize the probability of reaching the tire grip limit. The C-factor is controlled / adjusted using a scaling factor or value that varies based on the lateral acceleration (the C-factor will be scaled down as the lateral acceleration increases to minimize the probability of reaching the tire grip limit). Furthermore, the C-factor can vary for different vehicle speeds or speed ranges, and different scaling can be applied for the different vehicle speeds.

[0018] Fig. Figure 1A generally illustrates a vehicle 10 according to the principles of this disclosure. The vehicle 10 may include any suitable vehicle, such as a passenger car, a truck, an off-road vehicle, a minivan, a crossover, any other passenger vehicle, any suitable commercial vehicle, or any other suitable vehicle. While the vehicle 10 is illustrated as a wheeled passenger vehicle for use on roads, the principles of this disclosure may be applied to other vehicles, such as airplanes, boats, trains, drones, or other suitable vehicles.

[0019] The vehicle 10 comprises a vehicle body 12 and a hood 14. A passenger compartment 18 is defined at least partially by the vehicle body 12. Another section of the vehicle body 12 defines an engine compartment 20. The hood 14 can be movably attached to a section of the vehicle body 12 such that the hood 14 provides access to the engine compartment 20 when the hood 14 is in a first or open position, and covers the engine compartment 20 when the hood 14 is in a second or closed position. In some embodiments, the engine compartment 20 can be located in the rear section of the vehicle 10, as is generally illustrated.

[0020] The passenger compartment 18 can be located behind the engine compartment 20, but in embodiments where the engine compartment 20 is located in the rear section of the vehicle 10, it can also be located in front of the engine compartment 20. The vehicle 10 can include any suitable propulsion system, including an internal combustion engine, one or more electric motors (e.g., an electric vehicle), one or more fuel cells, a hybrid (e.g., a hybrid vehicle) propulsion system comprising a combination of an internal combustion engine, one or more electric motors, and / or any other suitable propulsion system.

[0021] In some embodiments, the vehicle 10 may include a gasoline engine, such as a spark-ignition engine. In some embodiments, the vehicle 10 may include a diesel engine, such as a compression-ignition engine. The engine compartment 20 houses and / or encloses at least some components of the vehicle 10's propulsion system. Additionally or alternatively, propulsion controls such as an accelerator actuator (e.g., an accelerator pedal), a brake actuator (e.g., a brake pedal), a handwheel, and other such components are arranged in the passenger compartment 18 of the vehicle 10. The propulsion controls can be actuated or controlled by an operator of the vehicle 10 and can each be directly connected to corresponding components of the propulsion system, such as a throttle valve, a brake, a vehicle axle, a vehicle transmission, and the like. In some embodiments, the propulsion controls can communicate signals to a vehicle computer (e.g., a vehicle computer).Drive-by-wire), which in turn can control the corresponding drive component of the drive system. Accordingly, in some embodiments, vehicle 10 can be an autonomous vehicle.

[0022] In some embodiments, the vehicle 10 includes a transmission that communicates with a crankshaft via a flywheel, clutch, or fluid coupling. In some embodiments, the transmission includes a manual transmission. In some embodiments, the transmission includes an automatic transmission. In the case of an internal combustion engine or a hybrid vehicle, the vehicle 10 may include one or more pistons that cooperate with the crankshaft to generate a force that is transmitted via the transmission to one or more axles that rotate the wheels 22. If the vehicle 10 includes one or more electric motors, a vehicle battery and / or a fuel cell provides energy to the electric motors to rotate the wheels 22.

[0023] Vehicle 10 may include automatic vehicle propulsion systems, such as cruise control, adaptive cruise control, automatic braking control, other automatic vehicle propulsion systems, or a combination thereof. Vehicle 10 may be an autonomous or semi-autonomous vehicle, or another suitable vehicle type. Vehicle 10 may include additional or fewer features than those generally illustrated and / or disclosed herein.

[0024] In some embodiments, the vehicle 10 may include an Ethernet component 24, a Controller Area Network (CAN) bus 26, a Media-Oriented Systems Transport (MOST) component 28, a FlexRay component 30 (e.g., a brake-by-wire system and the like), and a Local Interconnect Network (LIN) component 32. The vehicle 10 may use the CAN bus 26, the MOST 28, the FlexRay component 30, the LIN 32, other suitable networks or communication systems, or a combination thereof, to communicate various information from, for example, sensors inside or outside the vehicle to, for example, various processors or controllers inside or outside the vehicle. The vehicle 10 may include additional or fewer features than those generally illustrated and / or disclosed herein.

[0025] In some embodiments, the vehicle 10 may include a steering system, such as an EPS system, a steering-by-wire steering system (which may, for example, include or communicate with one or more control units that control, control, or communicate with components of the steering system without the use of a mechanical connection between the handwheel and the wheels 22 of the vehicle 10), a hydraulic steering system (which may, for example, include a magnetic actuator incorporated into a valve assembly of the hydraulic steering system), or another suitable steering system.

[0026] The steering system may include a control system or mechanism without feedback, a closed-loop control system or mechanism, or a combination thereof. The steering system may be configured to receive various inputs, including but not limited to a handwheel position, an input torque, one or more road wheel positions, other suitable inputs or information, or a combination thereof.

[0027] Additionally or alternatively, the inputs may include a handwheel torque, a handwheel angle, an engine speed, a vehicle speed, an estimated engine torque command, another suitable input, or a combination thereof. The steering system may be configured to provide a steering function and / or control of the vehicle 10. For example, the steering system may generate an auxiliary torque based on the various inputs. The steering system may be configured to selectively control a motor of the steering system using the auxiliary torque to provide steering assistance to the operator of the vehicle 10. The steering system of this disclosure is configured to implement the SbW control techniques described in more detail below.

[0028] In some embodiments, the vehicle 10 includes one or more controllers, such as the controller 100, as is generally the case in Fig. Figure 1B illustrates this. The controller 100 can correspond to a steering system controller. The controller 100 can include any suitable controller, such as an electronic control unit or other suitable controller. The controller 100 can be configured to control, for example, the various functions of the steering system and / or various functions of the vehicle 10. The controller 100 can include a processor 102 and a memory 104. The processor 102 can include any suitable processor, such as those described herein. Additionally or alternatively, the controller 100 can include any number of processors, in addition to or besides the processor 102. The memory 104 can comprise a single disk or a plurality of disks (e.g., hard disks) and includes a memory management module that manages one or more partitions within the memory 104.In some embodiments, the memory 104 may include flash memory, semiconductor memory (solid-state memory), or the like. The memory 104 may include random-access memory (RAM), read-only memory (ROM), or a combination thereof. The memory 104 may include instructions which, when executed by the processor 102, cause the processor 102 to control at least various aspects of the vehicle 10. Additionally or alternatively, the memory 104 may include instructions which, when executed by the processor 102, cause the processor 102 to perform functions associated with the systems and procedures described herein.

[0029] The controller 100 can receive one or more signals from various measuring devices or sensors 106 indicating detected or measured characteristics of the vehicle 10. The sensors 106 can include any suitable sensors, measuring devices, and / or other suitable mechanisms. For example, the sensors 106 can include one or more torque sensors or devices, one or more handwheel position sensors or devices, one or more engine position sensors or devices, one or more position sensors or devices, other suitable sensors or devices, or a combination thereof. The one or more signals can indicate handwheel torque, handwheel angle, engine speed, vehicle speed, other suitable information, or a combination thereof.

[0030] As used herein, the term "controller" can refer to a hardware module or assembly that includes one or more processors or microcontrollers, memory, sensors, one or more actuators, a communication interface, etc., any sections of which may be collectively referred to as "control logic." As described herein, the respective functions and steps performed by a given controller, control logic, etc., may be performed collectively by multiple controllers, processors, etc. For example, a processor, processing device, controller, control logic, etc., that is "configured to perform" may refer to a single processor, processing device, controller, etc.This can refer to a first processor, processing device, controller, etc., configured to perform both A and B, or it can refer to a first processor, processing device, controller, etc., configured to perform A, and a second processor, processing device, controller, etc., configured to perform B. For simplicity, a "control switching logic configured to perform A and B" can refer to one or more processors, processing devices, controllers, etc., configured together to perform A and B.

[0031] In some embodiments, the controller 100 can perform the methods described herein. However, the methods described herein, as performed by the controller 100, are not intended to be restrictive, and any type of software running on a controller, processor, or other switching logic can implement the SbW control techniques described herein without infringing upon the scope of protection of this disclosure. For example, a controller, such as a processor, that executes software within a computing device can implement the systems and methods described herein.

[0032] Fig. Figure 2A illustrates an example rack and pinion or RWA controller 200 and a controller 204 for a column or handwheel actuator (HWA) of a steering system configured to implement the SbW control techniques (e.g., SbW C-factor control techniques) according to the present disclosure. For example, the HWA controller 204 is configured to generate an engine torque command for the handwheel actuator (HWA) based on an estimated rack force (e.g., a signal of the estimated rack force) received by the RWA controller 200 and one or more other input signals (e.g., vehicle speed, handwheel position, and handwheel speed). The RWA controller 200 is configured to determine the estimated rack force based on the engine torque required to achieve or maintain an actual rack position.The controls 200 and 204 can correspond to one or more controls for the steering system, be implemented by them, etc.

[0033] As an example, the HWA controller 204 includes a reference torque computer 208, which is configured to provide a reference torque (T Ref) based on the estimated rack force and one or more other input signals. For example, the reference torque corresponds to a sum of various inputs / measurements such as force application, hysteresis, return correction, damping, detent, etc. A closed-loop torque controller 212 (e.g., a closed-loop PID controller) is configured to generate and output the motor torque command, which is based at least in part on a force or torque applied by the operator (e.g., "Tbar torque") and the reference torque. The motor torque command is provided as a control signal to control a handwheel actuator motor.

[0034] The estimated rack force corresponds to the measured or estimated torque of the road wheel actuator motor. Accordingly, the estimated rack force (and any estimated offset or error in the rack force) is a crucial factor in determining the force provided by the handwheel actuator motor.

[0035] In some examples, the HWA controller 204 may also include a C-factor lookup module 216 and a rack position reference calculator 220. The rack position reference calculator 220 is configured, for example, to generate the rack position reference based on a column or handwheel position and a C-factor received from the C-factor lookup module 216. In some examples, the C-factor provided by the C-factor lookup module is a ratio, multiplier value, percentage, etc., which is multiplied by the column position to obtain the rack position reference. The C-factor can be determined based on vehicle inputs, including but not limited to a handwheel angle (“HwAg”) corresponding to a driver input (e.g., a handwheel angle indicating the driver’s intention transmitted via the handwheel), a rack position, a vehicle speed, etc.Example systems and procedures for obtaining the rack position reference and the C-factor are described in more detail in US2024 / 0375706 A1.

[0036] The C-factor obtained and provided by the C-factor lookup module 216 is partly derived from the vehicle speed (e.g., using a 2D lookup table). For example, a variety of C-factors may be associated with specific vehicle speed ranges (e.g., 0–5 km / h, 5–20 km / h, 20–30 km / h, etc.). As an example, C-factors associated with lower vehicle speed ranges may be higher than C-factors associated with higher vehicle speed ranges (e.g., the C-factor obtained from the C-factor lookup module 216 may be inversely proportional to the vehicle speed). For example, at lower vehicle speeds, a higher C-factor may be used to reduce the number of handwheel turns required to achieve the desired lateral movement, thereby improving ride comfort and agility.Conversely, at higher vehicle speeds a lower C-factor can be used to improve the stability of the vehicle's lateral dynamics and driving safety.

[0037] The RWA controller 200 includes a rack position controller 224 (e.g., a PID rack position controller) configured to generate one or more rack position control signals based on the actual rack position and the rack position reference (e.g., based on a difference between the actual rack position and the rack position reference). The rack position control signals can include, but are not limited to, signals for the speed of the rack motor and the motor torque command (e.g., for the torque applied by the driver). In this way, the rack position is controlled to follow the driver's intention (as specified by the rack position reference).

[0038] A rack force predictor 228 generates the estimated rack force based on the outputs of the rack position controller 224 (e.g., based on a function of the rack motor speed, the rack motor torque command, etc.). In various examples, the estimated rack force can be calculated based on the torque applied to the handwheel by the operator (as specified by the rack motor torque command, various sensor signals, etc.). As shown, the rack force predictor 228 can output the estimated rack force, and the reference torque calculator 208 (and / or another component of the RWA controller 200, the HWA controller 204, etc.) can obtain an estimated rack load based on the estimated rack force. In other examples, the rack force predictor 228 can output the estimated rack load.In some contexts, the terms "estimated rack force" and "estimated rack load" can be used interchangeably.

[0039] For example, in RWA position control, the rack position reference signal (“RackPosRef’”) can be calculated based on a position error (“PosErr”) between an ADAS rack position reference value or signal (“ADASRackPosRef’”) and an HWA rack position reference value or signal (“HWARackPosRef”). Conversely, HWA position control is based on a position error between the HWA position and the RWA position, so that the handwheel can be controlled to rotate in a manner consistent with the rotation of the road wheel during hands-free operation.

[0040] The reference torque can correspond to a desired, ideal, or target torque that the driver should feel (e.g., at the handwheel / steering wheel). As described above, the reference torque is calculated based on the driver's inputs (e.g., an input torque corresponding to the steering handwheel angle), road conditions, damping, hysteresis, etc. The torque at the handwheel is controlled (e.g., via the HWA) to match the reference torque. For example, the outputs of one or more sensors measuring the actual torque at the wheel are used to minimize the difference between the reference torque and the actual torque.

[0041] An effort function (e.g., an effort function implemented by the Reference Torque Calculator 208) defines a relationship between the driver's input (e.g., the force or torque applied by the driver to the handwheel, which can be referred to as "effort") and a response (i.e., movement) of the steering system. The effort function can, for example, output an effort value based on a lookup table or another function (e.g., using an estimated rack load as input). The estimated rack load can be modified before being entered into the lookup table by adding a calculated return load value to the estimated rack load. The effort function indicates the amount of effort required from the driver to produce a desired response.

[0042] The HWA controller 204 according to the present disclosure further includes a C-factor scaling module 230. The C-factor scaling module 230 is configured to adjust / scale the C-factor provided by the C-factor lookup module 216 based on one or more inputs, including, but not limited to, the vehicle's lateral acceleration, vehicle speed, etc., as described in more detail below. The rack position reference computer 220 is configured to generate the rack position reference based on a scaled C-factor provided by the C-factor scaling module 230. As used herein, the C-factor provided by the C-factor lookup module may be referred to as a "baseline" C-factor relative to the scaled C-factor.

[0043] For example, the baseline C-factor, as described above, may be higher / larger at lower vehicle speeds and lower at higher vehicle speeds. However, increased lateral acceleration, even at lower vehicle speeds, can increase the likelihood of reaching the tire grip limits. Accordingly, the C-factor scaling module 230 is configured to scale the baseline C-factor downwards as lateral acceleration increases. In some examples, the rate at which the C-factor is scaled downwards may vary based on vehicle speed, and / or the lateral acceleration at which the C-factor begins to scale downwards may vary based on vehicle speed. The C-factor can be scaled downwards in a linear or non-linear manner.

[0044] As an example, the C-factor is scaled downwards in accordance with one or more scaling factors. For instance, in response to the lateral acceleration being below a certain threshold, the scaling factor for a given vehicle speed may be set to a fixed value such as one (1). Upon reaching the threshold, the scaling factor may decrease (i.e., downwards from one) as the lateral acceleration increases. Furthermore, for a given speed, multiple thresholds with corresponding downward scaling rates may be used. Accordingly, the scaled C-factor decreases as the lateral acceleration increases (e.g., by multiplying the scaling factor by the baseline C-factor).

[0045] As an example, the scaling factor can decrease to a minimum value (e.g., a non-zero value). This minimum value can vary for different vehicle speeds / ranges. The minimum value can be chosen to be no less than a value at which a corresponding final steering ratio would no longer affect the vehicle's handling. For example, the minimum value can be a minimum percentage of the baseline C-factor, such as 50% of the baseline C-factor (i.e., a scaling factor of 0.5), 33% of the baseline C-factor (i.e., a scaling factor of 0.33), and so on.

[0046] In some examples, the dynamic C-factor control described herein can be implemented for different steering / performance modes of the vehicle. For instance, the calibration of the C-factor scaling (e.g., scaling rates, thresholds, etc.) can differ for different steering modes. As an example, the C-factor scaling for a Comfort mode can be calibrated with a more aggressive scaling rate (e.g., a steeper decrease in the scaling rate) relative to other modes. Conversely, the C-factor scaling for Performance or other active driving modes can be calibrated with a less aggressive scaling rate (e.g., a more gradual decrease in the scaling rate).

[0047] Fig. Figure 2B shows an example implementation of a dynamic C-factor control according to the principles of the present disclosure, including the C-factor lookup module 216, the C-factor scaling module 230 and the rack position reference computer 220.

[0048] The C-factor lookup module 216 receives inputs, including but not limited to a rack position and vehicle speed, and determines the C-factor (e.g., a baseline C-factor) based on the rack position and vehicle speed. As described above, the C-factor can be obtained from a lookup table that correlates vehicle speed with the respective C-factors. As an example, different vehicle speed ranges are indexed with their respective C-factors. The different speed ranges can correspond to regular, uniform ranges (e.g., 0–5 km / h, 5–10 km / h, 10–15 km / h, etc.), irregular, non-uniform ranges (e.g., 0–5 km / h, 5–15 km / h, 15–30 km / h), and / or combinations thereof. In general, the baseline C-factors can decrease as the vehicle speed increases.

[0049] The C-factor scaling module 230 receives the C-factor (e.g., the baseline C-factor) from the C-factor lookup module 216. The C-factor scaling module 230 is configured to selectively scale (e.g., scale down) the C-factor provided by the C-factor lookup module 216 based on inputs, including but not limited to the vehicle's lateral acceleration and vehicle speed. Figure 240 shows an example scaling factor control technique implemented by the C-factor scaling module 230. As shown, a variety of scaling factors 242, 244, and 246 correspond to different example vehicle speeds or speed ranges, such as 60 km / h, 30 km / h, and 10 km / h, respectively. Although for specific vehicle speeds (e.g.,As shown (60, 30, and 10 km / h), the scaling factors for different speeds can be obtained using linear interpolation. For example, a scaling factor for a speed of 50 km / h can be obtained by applying linear interpolation for the range between 30 km / h and 60 km / h (e.g., a scaling factor value between the respective scaling factors for 30 km / h and 60 km / h). As another example, the scaling factors can correspond to different vehicle speed ranges, and the example vehicle speeds lie within the respective ranges. For example, a vehicle speed of 60 km / h can correspond to a range of 50–70 km / h, a vehicle speed of 30 km / h can correspond to a range of 25–35 km / h, and a vehicle speed of 10 km / h can correspond to a range of 0–10 km / h.

[0050] In one example, the C-factor scaling module 230 is configured to select or determine a specific scaling factor based on the vehicle speed (e.g., using a lookup table, a formula, etc.).For example, the C-factor scaling module 230 selects the scaling factor 242 in response to determining that the vehicle speed is 60 km / h (or within a vehicle speed range corresponding to scaling factor 242, such as 50-70 km / h), selects the scaling factor 244 in response to determining that the vehicle speed is 30 km / h (or within a vehicle speed range corresponding to scaling factor 244, such as 25-35 km / h), selects the scaling factor 246 in response to determining that the vehicle speed is 10 km / h (or within a vehicle speed range corresponding to scaling factor 246, such as 0-10 km / h), and so on. The scaling factor for a vehicle speed within a given range can be obtained using linear interpolation as described above.

[0051] In this example, the scaling factor 242 can remain constant (e.g., 1) and not decrease as the vehicle's lateral acceleration increases. For instance, the baseline C-factor may be sufficiently low for higher speeds (e.g., 50 km / h and above) that decreasing the C-factor as the vehicle's lateral acceleration increases is neither necessary nor desirable. Accordingly, the C-factor is not scaled down for some vehicle speeds.

[0052] Conversely, scaling factors 244 and 246 decrease as the vehicle's lateral acceleration increases. As shown, scaling factors 244 and 246 decrease at different rates in response to the vehicle's lateral acceleration reaching different thresholds. For example, scaling factor 244 begins to decrease at a first rate when the vehicle's lateral acceleration reaches a first threshold, as shown at 250. Scaling factor 246 begins to decrease at a second rate when the vehicle's lateral acceleration reaches a second threshold, as shown at 252. In this example, the second rate is greater (i.e., more aggressive) than the first rate. Although reactive to only one threshold, each of the scaling factors can respond to multiple thresholds and decrease at different rates in response to reaching different thresholds.For example, a given scaling factor can decrease at a first rate when a threshold is reached, and then decrease at a second rate when the vehicle's lateral acceleration increases upon reaching another threshold. In other words, the scaling factors can decrease piecewise at different rates.

[0053] The scaling factors can have an associated minimum value. In other words, the scaling factors cannot decrease below the associated minimum value. Different minimum values ​​can be assigned to the respective scaling factors. For example, as shown, a first minimum value of 256 can be assigned to scaling factor 244, while a second minimum value of 258, which is less than the first minimum value, can be assigned to scaling factor 246. Furthermore, as shown, the corresponding vehicle lateral acceleration at which the respective minimum values ​​are reached can differ for different scaling factors.

[0054] The C-factor scaling module 230 applies the selected / determined scaling factor to the baseline C-factor received from the C-factor lookup module 216. For example, the C-factor scaling module 230 determines a specific value of the scaling factor to apply to the baseline C-factor (e.g., by selecting the scaling factor based on the vehicle speed and determining the value to apply based on the vehicle lateral acceleration, such as using a formula, a lookup table, etc.) and multiplies the determined value by the baseline C-factor. In this way, the C-factor scaling module 230 determines the scaled C-factor based on the baseline C-factor, the vehicle speed, and the vehicle lateral acceleration.

[0055] The rack position reference calculator 220 is configured to generate the rack position reference based on the scaled C-factor and one or more other inputs, such as the column or handwheel position, as described above.

[0056] Fig.Figure 3 is a flowchart that generally illustrates a Method 300 for controlling a SbW steering system (e.g., for generating a rack position reference or a reference signal for an SbW steering system) according to the principles of this disclosure. For example, one or more computing devices, processors, or processing devices, etc., are configured to execute instructions to implement the Method 300, such as one or more of the processors of the systems described herein (e.g., a computing device or processor of a vehicle configured to implement the Controller 100, the HWA Controller 204, etc.). One or more of the steps of the Method 300 described below may be skipped or omitted in some examples, and / or one or more of the steps may be performed in a different order than described.

[0057] In procedure 304, method 300 involves receiving one or more vehicle inputs (e.g., from respective sensors, models, or calculations, etc.) that indicate operating characteristics of a vehicle. In this example, the vehicle inputs may include, but are not limited to, the rack position, vehicle speed, vehicle lateral acceleration, and / or column position.

[0058] In 308, procedure 300 includes determining a baseline C-factor (e.g., based on at least the vehicle speed). As an example, the baseline C-factor is obtained from a lookup table. In 312, procedure 300 includes determining a scaling factor. For example, the scaling factor is determined based on the vehicle speed and the vehicle lateral acceleration. In 316, procedure 300 includes determining a scaled C-factor. For example, the scaled C-factor is determined by multiplying the scaling factor by the baseline C-factor.

[0059] In procedure 300, part 320 includes determining a rack position reference using the scaled C-factor. For example, the rack position reference can be determined by applying the scaled C-factor to one or more other vehicle inputs, such as a handwheel or column position.

[0060] In 324, method 300 includes controlling at least one vehicle function based on the rack position reference. For example, controlling the at least one vehicle function may include, but is not limited to, one or more of the following: controlling the lateral movement / steering of the vehicle by controlling a rack position based on the rack position reference and an actual rack position.

[0061] The above explanation is intended to illustrate the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to the person skilled in the art once the above disclosure is fully understood. It is intended that the following claims be interpreted as encompassing all such variations and modifications.

[0062] The word "example" is used herein to mean serving as an example, case, or illustration. Any aspect or design described herein as an "example" is not necessarily to be construed as preferential or advantageous over other aspects or designs. Rather, the use of the word "example" is intended to illustrate concepts in a concrete way. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is to say, unless otherwise specified or clearly evident from the context, "X includes A or B" is intended to mean one of the natural inclusive permutations. That is to say, if X includes A, includes B, or X includes both A and B, then "X includes A or B" is satisfied in each of the foregoing cases.In addition, the articles “a” and “an” as used in this application and the attached claims should generally be interpreted as meaning “one or more”, unless otherwise specified or it is clear from the context that they refer to a singular form. Furthermore, the use of the term “implementation” or “an implementation” should not imply the same embodiment or implementation unless described as such.

[0063] Implementations of the systems, algorithms, procedures, instructions, etc., described herein may be realized in hardware, software, or any combination thereof. The hardware may include, for example, computers, intellectual property (IP) cores, application-specific integrated circuits (ASICs), programmable logic arrays, optical processors, programmable logic controllers, microcode, microcontrollers, servers, microprocessors, digital signal processors, or any other suitable circuitry. In the claims, the term "processor" is to be understood as encompassing any of the foregoing hardware, either individually or in combination. The terms "signal" and "data" are used interchangeably.

[0064] As used herein, the term module can include a packaged functional hardware unit designed for use with other components, a set of instructions executable by a controller (such as a processor running software or firmware), processing switching logic configured to perform a particular function, and a self-contained hardware or software component that provides an interface to a larger system. For example, a module might include an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a circuit, a digital logic circuit, an analog circuit, a combination of discrete circuits, gates, and other types of hardware, or a combination thereof.In other embodiments, a module may include a memory that stores instructions that can be executed by a controller to implement a feature of the module.

[0065] Furthermore, the systems described herein can be implemented, for example, using a general-purpose computer or a general-purpose processor with a computer program that, when executed, performs any of the procedures, algorithms, and / or instructions described herein. Additionally or alternatively, a dedicated computer / processor can be used, which may contain other hardware for performing any of the procedures, algorithms, or instructions described herein.

[0066] Furthermore, all or part of the implementations of the present disclosure may take the form of a computer program product accessible, for example, from a computer-usable or computer-readable medium. A computer-usable or computer-readable medium may be any device capable of containing, storing, communicating, or transporting the program for use by or in conjunction with any processor. The medium may be, for example, an electronic, magnetic, optical, electromagnetic, or semiconductor device. Other suitable media are also available.

[0067] The embodiments, implementations, and aspects described above have been provided for the purpose of facilitating a simple understanding of the present invention and do not limit it. Rather, the invention is intended to cover various modifications and equivalent arrangements included within the scope of protection of the appended claims, the scope of protection being interpreted as broadly as legally permissible to encompass all modifications and equivalent structurings.

Claims

[1] Method for controlling a steer-by-wire (SbW) steering system of a vehicle (10), the method comprising using one or more processors (102): Receiving one or more inputs specifying the respective operating characteristics of the vehicle (10); Determining a baseline C-factor based on the vehicle speed, wherein the baseline C-factor corresponds to a linear distance traveled by a rack of the SbW steering system relative to a rotation of a handwheel of the vehicle (10); Determining a scaling factor based on the vehicle speed and the vehicle lateral acceleration, where the scaling factor decreases as the vehicle lateral acceleration increases; Determining a scaled C-factor using the baseline C-factor and the scaling factor; Determining a rack position reference based on the scaled C-factor; and Control at least one function of the vehicle (10) using the rack position reference. [2] Method according to claim 1, characterized by , that controlling at least one function of the vehicle (10) includes controlling the steering of the vehicle (10). [3] Method according to claim 1, characterized by , that determining the baseline C-factor involves selecting the baseline C-factor from a variety of C-factors indexed according to vehicle speed. [4] Method according to claim 1, characterized by , that determining the scaling factor involves selecting the scaling factor from among a multitude of scaling factors (242, 244, 246) and wherein each of the multitude of scaling factors (242, 244, 246) is associated with a different vehicle speed. [5] Method according to claim 4, characterized by , that two or more of the multitude of scaling factors (242, 244, 246) decrease relative to each other at different rates. [6] Method according to claim 4, characterized by , that a first scaling factor of the plurality of scaling factors (242, 244, 246) is associated with a first vehicle speed and decreases with a first rate, and wherein a second scaling factor of the plurality of scaling factors (242, 244, 246) is associated with a second vehicle speed which is less than the first vehicle speed and decreases with a second rate which is greater than the first rate. [7] Method according to claim 4, characterized by, that a first scaling factor of the plurality of scaling factors (242, 244, 246) has a first minimum value and wherein a second scaling factor of the plurality of scaling factors (242, 244, 246) has a second minimum value which is less than the first minimum value. [8] System for controlling a steer-by-wire (SbW) steering system of a vehicle (10), wherein the system comprises: one or more sensors configured to determine one or more operating characteristics of a vehicle (10); and a processor (102) configured to execute instructions stored in memory, the execution of which causes the processor (102) to: Receiving one or more inputs specifying the respective operating characteristics of the vehicle (10), Determining a baseline C-factor based on the vehicle speed, wherein the baseline C-factor corresponds to a linear distance traveled by a rack of the SbW steering system relative to a rotation of a handwheel of the vehicle (10), Determining a scaling factor based on the vehicle speed and the vehicle lateral acceleration, where the scaling factor decreases as the vehicle lateral acceleration increases. Determining a scaled C-factor using the baseline C-factor and the scaling factor, Determining a rack position reference based on the scaled C-factor and Control at least one function of the vehicle (10) using the rack position reference. [9] System according to claim 8, characterized by, that controlling at least one function of the vehicle (10) includes controlling the steering of the vehicle (10). [10] System according to claim 8, characterized by , that determining the baseline C-factor involves selecting the baseline C-factor from among a variety of C-factors (242, 244, 246) indexed according to vehicle speed. [11] System according to claim 8, characterized by , that determining the scaling factor involves selecting the scaling factor from among a multitude of scaling factors (242, 244, 246) and wherein each of the multitude of scaling factors (242, 244, 246) is associated with a different vehicle speed. [12] System according to claim 11, characterized by , that two or more of the multitude of scaling factors (242, 244, 246) decrease relative to each other at different rates. [13] System according to claim 11, characterized by, that a first scaling factor of the plurality of scaling factors (242, 244, 246) is associated with a first vehicle speed and decreases with a first rate, and wherein a second scaling factor of the plurality of scaling factors (242, 244, 246) is associated with a second vehicle speed which is less than the first vehicle speed and decreases with a second rate which is greater than the first rate. [14] System according to claim 11, characterized by , that a first scaling factor of the plurality of scaling factors (242, 244, 246) has a first minimum value and wherein a second scaling factor of the plurality of scaling factors (242, 244, 246) has a second minimum value which is less than the first minimum value. [15] System for controlling a steer-by-wire (SbW) steering system of a vehicle (10), wherein the system comprises: a handwheel actuator control (HWA control) (204) configured to Receiving one or more input signals that specify the respective operating characteristics of the vehicle (10), Determining a baseline C-factor based on the vehicle speed, wherein the baseline C-factor corresponds to a linear distance traveled by a rack of the SbW steering system relative to a rotation of a handwheel of the vehicle (10), Determining a scaling factor based on the vehicle speed and the vehicle lateral acceleration, where the scaling factor decreases as the vehicle lateral acceleration increases. Determining a scaled C-factor using the baseline C-factor and the scaling factor and Determining a rack position reference based on the scaled C-factor; and a road wheel actuator control (RWA control) (200) configured to control the steering of the vehicle (10) based on the rack position reference. [16] System according to claim 15, characterized by , that determining the baseline C-factor involves selecting the baseline C-factor from a plurality of C-factors indexed by vehicle speed, wherein determining the scaling factor involves selecting the scaling factor from a plurality of scaling factors (242, 244, 246) and wherein each of the plurality of scaling factors (242, 244, 246) is associated with a different vehicle speed. [17] System according to claim 16, characterized by , that at least one of the following is true: A first scaling factor of the plurality of scaling factors (242, 244, 246) is associated with a first vehicle speed and decreases with a first rate, and a second scaling factor of the plurality of scaling factors (242, 244, 246) is associated with a second vehicle speed that is less than the first vehicle speed and decreases with a second rate that is greater than the first rate; and The first scaling factor of the multitude of scaling factors (242, 244, 246) has a first minimum value, and the second scaling factor of the multitude of scaling factors (242, 244, 246) has a second minimum value that is less than the first minimum value.

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