Steer-by-wire road wheel actuator jitter for improved rack force estimation

Abstract

The invention relates to steer-by-wire road wheel actuator jitter for improved rack force estimation. A method for controlling a motor of a road wheel actuator (RWA) in a steer-by-wire (SbW) steering system of a vehicle includes: providing a motor torque command signal to the motor; providing a dither signal to the motor such that the dither signal is applied to the motor torque command signal, the dither signal configured to allow road interference to cause movement of a rack bar of the SbW steering system; sensing the road interference; and generating a simulation signal based on the sensed road interference.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 534,148, filed on August 23, 2023. The entire disclosures of the above-referenced applications are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the control of components in a steer-by-wire (SbW) steering system. Background Art

[0004] Vehicles (such as cars, trucks, sport utility vehicles, crossovers, minivans, boats, aircraft, all-terrain vehicles, recreational vehicles, or other suitable forms of transportation) typically include a steering system, such as an electronic power steering (EPS) system, a steer-by-wire (SbW) steering system, a hydraulic steering system, or other suitable steering system. The steering system of such a vehicle typically controls various aspects of the vehicle's steering, including providing steering assistance to the operator of the vehicle, controlling the vehicle's steerable wheels, etc. Summary of the invention

[0005] The present disclosure generally relates to control of steer-by-wire (SbW) steering systems.

[0006] One aspect of the disclosed embodiment includes a method for controlling a motor of a road wheel actuator (RWA) in a steer-by-wire (SbW) steering system of a vehicle. The method includes: providing a motor torque command signal to the motor; providing a dither signal to the motor so that the dither signal is applied to the motor torque command signal, the dither signal being configured to allow a road disturbance to cause movement of a rack bar of the SbW steering system; sensing a road disturbance; and generating an emulation signal based on the sensed road disturbance.

[0007] Other areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with conventional practice, the various features of the drawings are not drawn to scale. Instead, the sizes of the various features are arbitrarily enlarged or reduced for clarity.

[0009] Figure 1A A vehicle in accordance with the principles of the present disclosure is generally illustrated.

[0010] Figure 1B A controller according to the principles of the present disclosure is generally illustrated.

[0011] Figure 2 An example system configured to control a road wheel actuator according to the principles of the present disclosure is shown.

[0012] Figure 3 is a flow chart generally illustrating a method for controlling a road wheel actuator according to the principles of the present disclosure. DETAILED DESCRIPTION

[0013] The following discussion is directed to various embodiments of the present disclosure. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be interpreted or otherwise used to limit the scope of the present disclosure (including the claims). In addition, it will be understood by those skilled in the art that the following description has a wide range of applications, and the discussion of any embodiment is only meant to illustrate the embodiment, and is not intended to imply that the scope of the present disclosure (including the claims) is limited to the embodiment.

[0014] As described, a vehicle (such as a car, truck, sport utility vehicle, crossover, minivan, boat, aircraft, all-terrain vehicle, recreational vehicle, or other suitable form of transportation) typically includes a steering system, such as an electronic power steering (EPS) system, a steer-by-wire (SbW) steering system, a hydraulic steering system, or other suitable steering system. The steering system of such a vehicle typically controls various aspects of the vehicle's steering, including providing steering assistance to the operator of the vehicle, controlling the vehicle's steerable wheels, etc.

[0015] In a steer-by-wire (SbW) steering system, many functions rely on accurate measurement or estimation of the forces at the steering rack. Systems that rely on estimates typically use a model-based observer (e.g., sensors and other circuits) to predict the rack force. The observer relies on signals from the motor and the controller. Friction interferes with this rack force estimation method. Since both the rack force and the friction force must be overcome by the motor, the observer has no way of knowing the difference between the rack force and the friction force, which the observer uses to calculate the rack force. Even if the observer can determine the difference between the rack force and the friction force, the road feedback input to the road wheel actuator (RWA) must overcome the system friction and move the motor before it can be measured / determined by the motor and transmitted to the steering wheel actuator for emulation.

[0016] Therefore, the systems and methods according to the present disclosure are configured to reduce the static friction of the RWA by maintaining the system in a dynamic state. For example, a dither signal is applied to the RWA (e.g., superimposed with the motor torque command signal) to overcome the static friction. This allows lower friction to be observed, resulting in improved rack force estimation, and provides improved road feedback by allowing the RWA to respond to road disturbances.

[0017] Some systems may apply a dither signal to a steering wheel actuator (HWA). For example, it may be undesirable that certain types of road or vehicle disturbances are transmitted to the steering wheel and perceived by the driver. Such disturbances may include, but are not limited to, road shock, vibration, or other repetitive periodic disturbances caused by vehicle mechanical defects or failures, misalignment, etc. The dither signal applied to the HWA may be configured to reduce or eliminate the effects of these disturbances so that they are not communicated to the driver via the steering wheel. For example, periodic or repetitive disturbances (such as those caused by road shock) may be sensed / measured, and the frequency and amplitude of the dither signal applied to the HWA may be dynamically adjusted based on the sensed disturbance to eliminate any detectable disturbance at the steering wheel. In contrast, the systems and methods according to the present disclosure apply a dither signal with a predetermined or calibrated frequency and amplitude to the RWA to overcome static friction forces associated with the RWA and related components of the steering system. In this way, "desired" road disturbances (i.e., road features that can improve driving "perception" when communicated to the driver) can be measured and simulated, and then communicated to the driver.

[0018] Figure 1A A vehicle 10 in accordance with the principles of the present disclosure is generally illustrated. The vehicle 10 may include any suitable vehicle, such as a car, a truck, a sport utility vehicle, a minivan, a crossover, any other passenger vehicle, any suitable commercial vehicle, or any other suitable vehicle. Although the vehicle 10 is illustrated as a passenger vehicle having wheels and for use on roads, the principles of the present disclosure may be applied to other vehicles, such as airplanes, boats, trains, drones, or other suitable vehicles.

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

[0020] The passenger compartment 18 may be disposed rearward of the engine compartment 20, but in embodiments where the engine compartment 20 is disposed at the rear of the vehicle 10, the passenger compartment 18 may be disposed forward of the engine compartment 20. The vehicle 10 may include any suitable propulsion system, including: an internal combustion engine; one or more electric motors (e.g., for an electric vehicle); one or more fuel cells; a hybrid (e.g., for a hybrid vehicle) propulsion system including a combination of an internal combustion engine and one or more electric motors; and / or any other suitable propulsion system.

[0021] In some embodiments, the vehicle 10 may include a petrol or gasoline fuel engine, such as a spark ignition engine. In some embodiments, the vehicle 10 may include a diesel fuel engine, such as a compression ignition engine. The engine compartment 20 accommodates and / or encloses at least some components of the propulsion system of the vehicle 10. Additionally or alternatively, propulsion controls (such as accelerator actuators (e.g., accelerator pedals), brake actuators (e.g., brake pedals), steering wheels, and other such components) are disposed in the passenger compartment 18 of the vehicle 10. The propulsion controls may be actuated or controlled by an operator of the vehicle 10, and the propulsion controls may be directly connected to corresponding components of the propulsion system, such as throttles, brakes, vehicle axles, vehicle transmissions, etc., respectively. In some embodiments, the propulsion controls may transmit signals to a vehicle computer (e.g., drive-by-wire), which in turn may control corresponding propulsion components of the propulsion system. Therefore, in some embodiments, the vehicle 10 may be an autonomous vehicle.

[0022] In some embodiments, the vehicle 10 includes a transmission that is connected to the crankshaft via a flywheel or a clutch or a 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 operate in conjunction with the crankshaft to generate a force that is transmitted through the transmission to rotate one or more axles of the wheels 22. When the vehicle 10 includes one or more electric motors, the vehicle battery and / or fuel cell provides energy to the electric motors to rotate the wheels 22.

[0023] The vehicle 10 may include an automatic vehicle propulsion system, such as cruise control, adaptive cruise control, automatic braking control, other automatic vehicle propulsion systems, or combinations thereof. The vehicle 10 may be an autonomous or semi-autonomous vehicle, or other suitable type of vehicle. The vehicle 10 may include more 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 system transport component (MOST) 28, a FlexRay component 30 (e.g., a wire control brake system, etc.), and a local interconnect network component (LIN) 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 transmit various information from sensors, such as those inside or outside the vehicle, to various processors or controllers, such as those inside or outside the vehicle. The vehicle 10 may include more 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 steer-by-wire steering system (e.g., which may include or communicate with one or more controllers that control components of the steering system without using a mechanical connection between a steering wheel of the vehicle 10 and the wheel 22), a hydraulic steering system (e.g., which may include a magnetic actuator incorporated into a valve assembly of the hydraulic steering system), or other suitable steering systems.

[0026] The steering system may include an open-loop feedback control system or mechanism, a closed-loop feedback control system or mechanism, or a combination thereof. The steering system may be configured to receive various inputs, including, but not limited to, steering wheel position, input torque, one or more road wheel positions, other suitable inputs or information, or a combination thereof.

[0027] Additionally or alternatively, the input may include steering wheel torque, steering wheel angle, motor speed, vehicle speed, estimated motor torque command, other suitable inputs, or combinations thereof. The steering system may be configured to provide steering functionality and / or control to the vehicle 10. For example, the steering system may generate an assist torque based on various inputs. The steering system may be configured to use the assist torque to selectively control a motor of the steering system to provide steering assistance to an operator of the vehicle 10. The steering system of the present disclosure is configured to implement RWA dithering, as described in more detail below.

[0028] In some embodiments, vehicle 10 includes one or more controllers, such as Figure 1B 1. The controller 100 is generally illustrated in FIG. 1. The controller 100 may correspond to a steering system controller. The controller 100 may include any suitable controller, such as an electronic control unit or other suitable controller. The controller 100 may be configured to control various functions of, for example, a steering system and / or various functions of the vehicle 10. The controller 100 may include a processor 102 and a memory 104. The processor 102 may include any suitable processor, such as the processor described herein. Additionally or alternatively, the controller 100 may include any suitable number of processors as a supplement or replacement to the processor 102. The memory 104 may include a single disk or multiple disks (e.g., a hard disk drive), and include a storage management module that manages one or more partitions within the memory 104. In some embodiments, the memory 104 may include a flash memory, a semiconductor (solid-state) memory, etc. The memory 104 may include a random access memory (RAM), a read-only memory (ROM), or a combination thereof. The memory 104 may include instructions that, 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 that, when executed by the processor 102, cause the processor 102 to perform functions associated with the systems and methods described herein.

[0029] The controller 100 may receive one or more signals indicating sensed or measured characteristics of the vehicle 10 from various measurement devices or sensors 106. The sensors 106 may include any suitable sensors, measurement devices, and / or other suitable mechanisms. For example, the sensors 106 may include one or more torque sensors or devices, one or more steering wheel position sensors or devices, one or more motor position sensors or devices, one or more position sensors or devices, other suitable sensors or devices, or combinations thereof. The one or more signals may indicate steering wheel torque, steering wheel angle, motor speed, vehicle speed, other suitable information, or combinations thereof.

[0030] As used herein, a "controller" may refer to a hardware module or component including one or more processors or microcontrollers, memory, sensors, one or more actuators, communication interfaces, etc., any portion of which may be collectively referred to as a "circuit". As described herein, the corresponding functions and steps performed by a given controller, control circuit, etc. may be performed by multiple controllers, processors, etc. in common. For example, a processor, processing device, controller, control circuit, etc. that is "configured to execute" may refer to a single processor, processing device, controller, etc. that is configured to execute both A and B, or may refer to a first processor, processing device, controller, etc. that is configured to execute A and a second processor, processing device, controller, etc. that is configured to execute B. For simplicity, a "control circuit configured to execute A and B" may refer to a single or multiple processors, processing devices, controllers, etc. that are collectively configured to execute A and B.

[0031] In some embodiments, the controller 100 may perform the methods described herein. However, the fact that the methods described herein are performed by the controller 100 is not meant to be limiting, and any type of software executed on a controller, processor, or other circuit may implement the RWA dithering functionality as described herein without departing from the scope of the present disclosure. For example, a controller (such as a processor executing software within a computing device) may implement the systems and methods described herein.

[0032] The RWA shaking system and method according to the present disclosure is configured to continuously and dynamically shake the RWA (e.g., the motor of the RWA, referred to herein as the RWA motor, which may be used interchangeably with "RWA" herein) at a calibrable frequency and amplitude (e.g., using an excitation waveform). The frequency is selected to be as high as possible without generating audible noise. The amplitude is selected to be as high as possible while causing little movement of the rack bar. The excitation waveform may be any periodic shape, such as a square wave, a triangle wave, a sine wave, etc.

[0033] As an example, a dither (tremble) command or signal according to the present disclosure is simply a superposition of the actual motor torque command provided to the RWA motor. By dithering the RWA motor, the static friction of the system no longer exists. Therefore, in order to cause the system to move, only dynamic friction must be overcome. This allows for more accurate rack force estimation and improved road feel, as road disturbances will cause the rack bar to move more easily. The motor must then be controlled to counteract this movement to maintain the desired position. An observer (e.g., one or more sensors, a controller or processor executing instructions, etc.) will be able to measure these disturbances and transmit a signal indicative of the disturbance to the steering wheel actuator for emulation.

[0034] In this way, dithering the RWA motor causes the EPS system to dither and eliminate low-frequency friction properties (such as static friction). Eliminating or minimizing lower-frequency friction properties improves two key characteristics: (i) rack force estimation, because friction becomes a smaller disturbance to the total rack force observation of the motor; and (ii) road feel, by reducing the amount of friction of the road disturbance used to overcome to move the rack bar. This in turn requires adjustment of the motor torque to maintain the desired position. Therefore, the required motor torque will be transmitted to the observer and measured as a disturbance force. Information indicative of the disturbance force can then be transmitted to the steering wheel actuator for simulation. In other words, the dithering technology described herein is configured to allow road disturbances to move the rack bar and thereby improve road feel, rather than eliminating vibrations caused by road disturbances.

[0035] Figure 2 An example system 200 is shown as described above and configured to control an RWA 204 (eg, an RWA of a SbW system, an RWA motor, etc.) according to the present disclosure. For example, a controller 208 (eg, in the form of a Figure 1B The controller (implemented in the manner described) is configured to provide a dither command or signal to dither the RWA 204 (e.g., by applying the dither signal described above to the motor torque command provided to the RWA 204) and minimize / eliminate static friction of the steering system 212. Controlling the RWA 204 (e.g., rotating the RWA motor) causes linear motion to be transmitted to the steering system 212, thereby steering the road wheels of the vehicle.

[0036] For example, the controller 208 is configured to provide a dither signal at a calibrable frequency (e.g., a frequency selected as high as possible without generating audible noise or other interference that is perceptible to the driver) and amplitude (e.g., an amplitude selected as high as possible while causing little movement of the rack rod of the steering system 212). The dither signal corresponds to a periodic excitation waveform (such as a square wave, a triangle wave, a sinusoidal signal, etc.).

[0037] By dithering the RWA 204 (e.g., the motor of the RWA 204) in this manner, the effects of static friction of the steering system 212 are reduced or eliminated, and only dynamic friction (i.e., by road disturbances) must be overcome in order to cause movement of the various components of the steering system 212 (e.g., the rack bar). As a result, road disturbances will more easily cause the rack bar to move. The controller 208 controls the RWA 204 to counteract (e.g., eliminate) any movement caused by movement of the rack bar to maintain the desired RWA position.

[0038] The system 200 (e.g., one or more sensors, controller 208, etc.) is configured to measure road disturbances that cause rack bar movement and transmit a signal (e.g., a simulated signal) indicative of the disturbance to a steering wheel actuator (HWA) 216. Because the dither signal affects the rack force estimate, the dither signal may be removed from the observed rack force before being transmitted to the HWA 216 for simulation.

[0039] The HWA 216 is configured to simulate a road disturbance as indicated by the simulation signal. Movement of the HWA 216 is transferred to the steering wheel 220 (and thus communicated to the driver). In other words, the HWA 216 is configured to actuate the steering wheel 220 in a manner that simulates the road disturbance, while the controller 208 controls the RWA 204 to prevent the road disturbance from actually affecting the movement of the road wheels. Thus, the system 200 according to the principles of the present disclosure is configured to communicate to the driver road disturbances and other road "feel" components that are not typically communicated in SbW systems.

[0040] In some examples, the controller 208 may be further configured to apply a dither signal to the HWA 216 and / or other actuators or motors of the system 200. For example, it may be undesirable for certain types of road or vehicle disturbances to be transmitted to the steering wheel 220 and felt by the driver. In contrast to the dither signal applied to the RWA 204, the dither signal applied to the HWA 216 may be configured to reduce or eliminate the effects of these disturbances so that they are not communicated to the driver via the steering wheel 220. For example, the system 200 may be configured to sense / measure periodic or repetitive disturbances (such as those caused by road vibrations), and the frequency and amplitude of the dither signal applied to the HWA 216 may be dynamically adjusted based on the sensed disturbances. In some examples, such a dither signal may be applied to the HWA 216 in addition to the simulated signal described above. In this way, the effects of certain road and / or mechanical disturbances may be reduced or eliminated while other road disturbances or characteristics (“desired” road feel characteristics) are communicated to the driver by (i) applying a dither signal to the RWA 204 to overcome static friction, (ii) sensing or measuring the road disturbance via movement of the road wheels transmitted to the RWA 204, and (iii) generating a simulated signal based on the measured road disturbance and providing the simulated signal to the HWA 216.

[0041] Figure 3300 for controlling an RWA according to the principles of the present 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 processors of the processors of the system described herein (e.g., a computing device or processor of a vehicle configured to implement the controller 100, the controller 208, etc.). In some examples, one or more of the steps of the method 300 described below may be skipped or omitted, and / or one or more of the steps may be performed in an order different from the order described.

[0042] At 304, method 300 includes determining a characteristic of a dither signal to be applied to the RWA. For example, determining the characteristic may include obtaining a frequency value and an amplitude value of the dither signal. The frequency value and the amplitude value may be obtained by determining a static friction force associated with the RWA and / or other components of the steering system (including any components mechanically coupled to the road wheel and the RWA and / or mechanically coupled between the road wheel and the RWA). As an example, the static friction force corresponds at least in part to a static friction force associated with movement of the rack bar. As an example, during the calibration process, the frequency is selected to be as high as possible without generating audible noise (e.g., a noise level below a threshold, which may be selected based on human hearing ability), and the amplitude is selected to be as high as possible when the rack bar is barely moving.

[0043] At 308, method 300 includes generating a dither signal based on the obtained frequency and amplitude during operation of the vehicle and applying the dither signal to the RWA. In one example, the dither signal is continuously applied to the RWA. The dither signal is applied together with (e.g., superimposed on) a motor torque command signal for controlling the RWA.

[0044] At 312, method 300 includes determining (e.g., measuring, sensing, etc.) the effects of "expected" road disturbances or features experienced by the RWA. For example, various road features may cause movement of the RWA and / or associated components (such as a rack bar), which may be sensed or measured by various sensors, with the static friction of the RWA being reduced or eliminated by the dither signal.

[0045] At 316, method 300 includes generating a simulation signal based on the determined impact of the road disturbance or feature. At 320, method 300 includes applying the simulation signal to the HWA (e.g., superimposed on the motor command signal applied to the HWA). In this way, the "desired" road feature is communicated to the driver via the HWA and the steering wheel, as described herein.

[0046] The above discussion is intended to illustrate the principles and various embodiments of the present invention. Once the above disclosure is fully understood, many changes and modifications will become apparent to those skilled in the art. The appended claims are intended to be interpreted as covering all such changes and modifications.

[0047] The word "example" is used herein to indicate use as an example, instance or illustration. Any aspect or design described herein as an "example" is not necessarily to be interpreted as being preferred or advantageous over other aspects or designs. On the contrary, the use of the word "example" is intended to present the concept in a concrete way. As used in this application, the term "or" is intended to represent an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or clear from the context, "X includes A or B" is intended to represent any one of the natural inclusive arrangements. That is, if X includes A; X includes B; or X includes both A and B, "X includes A or B" is satisfied under any of the aforementioned examples. In addition, the article "a / an" as used in this application and the appended claims should generally be interpreted as meaning "one or more", unless otherwise specified or clear from the context to refer to the singular form. In addition, the use of the term "a specific implementation" or "a specific implementation" throughout the text is not intended to represent the same embodiment or specific implementation, unless described as such.

[0048] The specific implementation of the systems, algorithms, methods, instructions, etc. described herein may be implemented in hardware, software, or any combination thereof. The hardware may include, for example, a computer, an intellectual property (IP) core, an application specific integrated circuit (ASIC), a programmable logic array, an optical processor, a programmable logic controller, microcode, a microcontroller, a server, a microprocessor, a digital signal processor, or any other suitable circuit. In the claims, the term "processor" should be understood to include any of the foregoing hardware, either alone or in combination. The terms "signal" and "data" are used interchangeably.

[0049] As used herein, the term module may include: a packaged functional hardware unit designed for use with other components; a set of instructions executable by a controller (e.g., a processor executing software or firmware); a processing circuit configured to perform a specific function; and an independent hardware or software component that interfaces with a larger system. For example, a module may include an application specific integrated circuit (ASIC); a field programmable gate array (FPGA); an electrical circuit; a digital logic circuit; an analog circuit; a combination of discrete circuits; a gate; and other types of hardware; or a combination thereof. In other embodiments, a module may include a memory that stores instructions that are executable by a controller to implement the features of the module.

[0050] Furthermore, in one aspect, for example, a general purpose computer or general purpose processor with a computer program can be used to implement the system described herein, which when executed implements any of the corresponding methods, algorithms and / or instructions described herein. Additionally or alternatively, for example, a special purpose computer / processor can be utilized, which may include other hardware for implementing any of the methods, algorithms or instructions described herein.

[0051] In addition, all or part of the specific implementation of the present disclosure may take the form of a computer program product accessible from, for example, a computer usable medium or a computer readable medium. A computer usable medium or a computer readable medium may be any device capable of, for example, tangibly containing, storing, transmitting or transporting a 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.

[0052] The above embodiments, specific implementations and aspects have been described to allow easy understanding of the present invention and do not limit the present invention. On the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, and its scope should be given the broadest interpretation to cover all such modifications and equivalent structures permitted under the law.

Claims

1. A method for controlling an electric motor of a road wheel actuator in a steer-by-wire steering system of a vehicle, the method comprising: providing a motor torque command signal to the motor; providing a dither signal to the electric motor, wherein the dither signal is applied to the electric motor torque command signal, and wherein the dither signal is configured to allow a road disturbance to cause movement of a rack bar of the steer-by-wire steering system; sensing the road disturbance; as well as A simulated signal is generated based on the sensed road disturbance. 2 . The method of claim 1 , further comprising providing the simulation signal to an electric motor of a steering wheel actuator. 3 . The method of claim 2 , wherein the simulated signal is generated to cause the steering wheel actuator to move a steering wheel of the vehicle in accordance with the sensed road disturbance. 4 . The method of claim 1 , further comprising adjusting the motor torque command signal based on a sensed road disturbance. 5 . The method of claim 1 , wherein providing the dither signal comprises determining a frequency and an amplitude of the dither signal based on static friction associated with the steer-by-wire steering system. 6 . The method of claim 5 , further comprising determining the frequency and the amplitude such that the frequency does not cause audible noise and the amplitude does not cause movement of the rack bar. 7 . The method of claim 1 , further comprising providing a second dither signal to a motor of a steering wheel actuator. 8 . The method of claim 1 , wherein the dithering signal comprises at least one of a periodic waveform, a square wave, a triangle wave, and a sine wave. 9 . The method of claim 1 , wherein the dither signal is configured to minimize static friction associated with the steer-by-wire steering system without causing audible noise or causing movement of the rack bar.

10. A system for controlling an electric motor of a road wheel actuator in a steer-by-wire steering system of a vehicle, the system comprising: a sensor configured to sense a plurality of values ​​corresponding to operation of the steer-by-wire steering system; and A steering system controller configured, based on the sensed plurality of values, to: providing a motor torque command signal to the motor, providing a dither signal to the electric motor, wherein the dither signal is applied to the electric motor torque command signal, and wherein the dither signal is configured to allow a road disturbance to cause movement of a rack bar of the steer-by-wire steering system, sensing the road disturbance, and A simulated signal is generated based on the sensed road disturbance.

11. The system of claim 10, wherein the steering system controller is further configured to provide the simulation signal to an electric motor of a steering wheel actuator.

12. The system of claim 11, wherein the simulated signal is configured to cause the steering wheel actuator to move a steering wheel of the vehicle based on the sensed road disturbance. 13 . The system of claim 10 , wherein the steering system controller is further configured to adjust the motor torque command signal based on a sensed road disturbance.

14. The system of claim 10, wherein providing the dither signal comprises determining a frequency and an amplitude of the dither signal based on a static friction force associated with the steer-by-wire steering system.

15. The system of claim 14, wherein the steering system controller is further configured to determine the frequency and the amplitude such that the frequency does not cause audible noise and the amplitude does not cause movement of the rack bar.

16. The system of claim 10, wherein the steering system controller is further configured to provide a second dither signal to a motor of a steering wheel actuator.

17. The system of claim 10, wherein the dithering signal comprises at least one of a periodic waveform, a square wave, a triangle wave, and a sine wave.

18. A processor, the processor being configured to execute instructions stored in a memory, wherein executing the instructions causes the processor to control a motor of a road wheel actuator in a steer-by-wire steering system of a vehicle, the instructions comprising: providing a motor torque command signal to the motor; providing a dither signal to the electric motor, wherein the dither signal is applied to the electric motor torque command signal, and wherein the dither signal is configured to allow a road disturbance to cause movement of a rack bar of the steer-by-wire steering system; sensing the road disturbance; as well as A simulated signal is generated based on the sensed road disturbance.

19. The processor of claim 18, wherein the instructions further comprise providing the simulation signal to a motor of a steering wheel actuator, wherein the simulation signal is generated to cause the steering wheel actuator to move a steering wheel of the vehicle in accordance with the sensed road disturbance.

20. The processor of claim 18, wherein the instructions further comprise adjusting the motor torque command signal based on a sensed road disturbance.

21. The processor of claim 18, wherein providing the dither signal comprises determining a frequency and an amplitude of the dither signal based on static friction associated with the steer-by-wire steering system.

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