Steering ratio synchronization for steer-by-wire systems

Abstract

A method for a steer-by-wire system. The method includes: determining a difference between a commanded steering ratio and an achieved steering ratio; and determining whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold. The method also includes: in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjusting the commanded steering ratio to be equal to the achieved steering ratio. The method also includes: in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold: selectively adjusting a bandwidth of a filter based on at least one vehicle characteristic of an associated vehicle; and using the filter, adjusting the commanded steering ratio to be equal to a desired steering ratio.

Description

Background Art

[0001] Electric power steering (EPS) generally includes components such as a steering wheel (or, for example, a hand-held steering wheel), a column, a rack and pinion, an electric motor actuator, etc. EPS assists the driver in steering the vehicle by providing an assist torque. The assist torque is based on the torque applied by the driver (applied torque). In a steady-state sense, the applied torque and the assist torque offset the rack force generated by the interaction between the vehicle's tires and the road surface.

[0002] A typical steer-by-wire (SbW) system includes a road wheel actuator (RWA) unit and a hand-held steering wheel (or steering wheel) actuator (HWA) unit. The RWA unit and the HWA unit in the SbW are mechanically disconnected and communicate through a controller area network (CAN) interface (or other similar digital communication protocol). The HWA unit receives the rack force signal from the RWA unit to generate the appropriate torque feel for the driver. Alternatively, the hand-held steering wheel angle and vehicle speed can also be used to generate the desired torque feel for the driver. The angle from the HWA unit is sent to the RWA unit, which controls the rack travel. Summary of the invention

[0003] One aspect of the disclosed embodiment includes a steer-by-wire system. The system includes a processor and a memory. The memory includes instructions that, when executed by the processor, cause the processor to: determine a difference between a commanded steering ratio and an achieved steering ratio; determine whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold; in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjust the commanded steering ratio to be equal to the achieved steering ratio; and in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than the threshold, selectively adjust a bandwidth of a filter based on at least one vehicle characteristic of an associated vehicle, and use the filter to adjust the commanded steering ratio to be equal to a desired steering ratio.

[0004] Another aspect of the disclosed embodiment includes a method for a steer-by-wire system. The method includes: determining a difference between a commanded steering ratio and an achieved steering ratio; and determining whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold. The method also includes: in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjusting the commanded steering ratio to be equal to the achieved steering ratio. The method also includes: in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than the threshold: selectively adjusting a bandwidth of a filter based on at least one vehicle characteristic of an associated vehicle; and using the filter, adjusting the commanded steering ratio to be equal to a desired steering ratio.

[0005] Another aspect of the disclosed embodiment includes a system. The system includes a processor and a memory. The memory includes instructions, which, when executed by the processor, cause the processor to: determine the difference between a commanded steering ratio and an achieved steering ratio; determine whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold; in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjust the commanded steering ratio to be equal to the achieved steering ratio; and in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than the threshold: determine whether a hand-held steering wheel position indicates that a hand-held steering wheel of a vehicle is in a center position; in response to determining that the hand-held steering wheel position indicates that the hand-held steering wheel of the vehicle is in the center position, selectively increase the bandwidth of a filter; and in response to determining that the hand-held steering wheel position indicates that the hand-held steering wheel of the vehicle is not in the center position, selectively reduce the bandwidth of the filter; and using the filter, adjust the commanded steering ratio to be equal to a desired steering ratio.

[0006] These and other advantages and features will become more apparent from the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A steer-by-wire system according to the principles of the present disclosure is generally shown.

[0008] Figure 2 is a flow chart generally illustrating steering ratio synchronization according to the principles of the present disclosure.

[0009] Figure 3 A continuation of a flow chart generally illustrating steering ratio synchronization according to the principles of the present disclosure.

[0010] Figure 4A steering ratio synchronization module according to the principles of the present disclosure is generally shown.

[0011] Figure 5 is a flow chart generally illustrating a steering ratio synchronization method according to the principles of the present disclosure. DETAILED DESCRIPTION

[0012] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification.The above and other features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0013] As described, electric power steering (EPS) generally includes components such as a steering wheel (or, for example, a hand-held steering wheel), a column, a rack and pinion, an electric motor actuator, etc. EPS assists the driver in steering the vehicle by providing an assist torque. The assist torque is based on the torque applied by the driver (applied torque). In a steady-state sense, the applied torque and the assist torque offset the rack force generated by the interaction between the vehicle's tires and the road surface.

[0014] A typical steer-by-wire (SbW) system includes a road wheel actuator (RWA) unit and a hand-held steering wheel (or steering wheel) actuator (HWA) unit. The RWA unit and the HWA unit in the SbW are mechanically disconnected and communicate through a controller area network (CAN) interface (or other similar digital communication protocol). The HWA unit receives the rack force signal from the RWA unit to generate the appropriate torque feel for the driver. Alternatively, the hand-held steering wheel angle and vehicle speed can also be used to generate the desired torque feel for the driver. The angle from the HWA unit is sent to the RWA unit, which controls the rack travel.

[0015] In some SbW systems, the desired steering ratio may not always be maintained during vehicle operation. This may occur, for example, in response to exceeding the slew rate capability of the road wheel actuators during rapid driver input, in response to hand-held steering wheel angle inputs requiring road wheel braking past travel stops, in response to excessive loads on the road wheel actuators, and in response to initialization problems.

[0016] Typically, if the SbW system does not achieve the desired steering ratio, the vehicle may suffer some adverse effects. For example, a typical algorithm executed by the controller of the SbW system may continue to attempt to achieve the desired steering ratio after the driver stops actuating the steering wheel. This may cause a noticeable lag in the vehicle's response, and it may appear to the driver as if the vehicle continues to steer autonomously (e.g., without driver input).

[0017] Therefore, systems and methods configured to synchronize the steering ratio of an SbW system, such as those described herein, may be desirable. The systems and methods described herein may be configured to detect when synchronization is lost and, after a given error level, adjust the commanded steering ratio to be equal to the achieved steering ratio. The systems and methods described herein may be configured to adjust the commanded steering ratio relatively quickly so that at any given time, the commanded steering ratio is not significantly different than the achieved steering ratio, but not sufficiently quickly to respond to noise conditions.

[0018] In some embodiments, the systems and methods described herein can be configured to adjust the commanded steering ratio using a nonlinear filter so that the commanded steering ratio is equal to the desired steering ratio. The systems and methods described herein can be configured to adjust the bandwidth of the nonlinear filter to control the rate of change of the commanded steering ratio to minimize driver perception.

[0019] In some embodiments, the bandwidth of the filter can be a function of several variables, such as hand-held steering wheel position, vehicle speed, throttle lever position, other suitable variables, or combinations thereof. The systems and methods described herein can be configured to increase the bandwidth of the filter when the vehicle is more "stationary" and less "active." For example, regardless of vehicle speed or throttle lever position, if the hand-held steering wheel position indicates that the hand-held steering wheel is centered, then the vehicle is relatively "stationary" and, in theory, the rate of change has no effect on the vehicle trajectory. The systems and methods described herein can be configured to increase the bandwidth to a relatively high value in response to the hand-held steering wheel position indicating that the hand-held steering wheel is centered.

[0020] Conversely, if the hand-held steering wheel position indicates that the hand-held steering wheel is at a certain angle relative to the center, then a relatively small rate of change may also affect the vehicle trajectory. The systems and methods described herein can be configured to reduce the bandwidth in response to the hand-held steering wheel position indicating that the hand-held steering wheel is at a certain angle relative to the center. The systems and methods described herein can be configured to further reduce the bandwidth in response to high vehicle speeds or high throttle lever positions, which can increase sensitivity and response.

[0021] In some embodiments, the systems and methods described herein may be configured to determine a difference between a commanded steering ratio and an achieved steering ratio. The systems and methods described herein may be configured to determine whether the difference between a commanded steering ratio and an achieved steering ratio is greater than a threshold. The systems and methods described herein may be configured to, in response to determining that the difference between a commanded steering ratio and an achieved steering ratio is greater than a threshold, adjust the commanded steering ratio to be equal to the achieved steering ratio.

[0022] In some embodiments, the systems and methods described herein may be configured to selectively adjust the bandwidth of a filter based on at least one vehicle characteristic of the associated vehicle in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than a threshold. In some embodiments, the filter comprises a nonlinear filter, such as a first-order digital filter. In some embodiments, at least one vehicle characteristic comprises a road wheel angle of a road wheel of the vehicle. In some embodiments, at least one vehicle characteristic comprises a vehicle speed of the vehicle. In some embodiments, at least one vehicle characteristic comprises a throttle lever position of a throttle lever of the vehicle. In some embodiments, at least one vehicle characteristic comprises a hand-held steering wheel position of a hand-held steering wheel of the vehicle.

[0023] In some embodiments, the systems and methods described herein may be configured to use a filter to adjust the commanded steering ratio to be equal to the desired steering ratio. The systems and methods described herein may be configured to selectively adjust the bandwidth of the filter by increasing the bandwidth in response to determining that the steering wheel position indicates that the steering wheel is in a center position. The systems and methods described herein may be configured to selectively adjust the bandwidth of the filter by decreasing the bandwidth in response to determining that the steering wheel position indicates that the steering wheel has an angle relative to the center position.

[0024] Figure 1 A steer-by-wire (SbW) system 40 of a vehicle 100 is generally illustrated. It will be appreciated that the SbW system 40 shown and described may be used in an autonomous or semi-autonomous vehicle, or in a more conventional vehicle. Additionally or alternatively, the vehicle 100 may include any suitable vehicle, including but not limited to an automobile, truck, agricultural vehicle, boat, airplane, helicopter, or any other suitable vehicle. The SbW system 40 includes a hand wheel actuator (HWA) 10 and a road wheel actuator (RWA) 20.

[0025] The HWA 10 includes one or more mechanical components 12, such as a hand-held steering wheel (steering wheel), a steering column, and a motor / inverter connected to the steering column through a gear mechanism or a direct drive system. The HWA 10 also includes a microcontroller 14 that controls the operation of the mechanical components 12. The microcontroller 14 receives and / or generates torque through the one or more mechanical components 12.

[0026] The RWA includes one or more mechanical components 24, such as a steering rack and / or pinion coupled to a motor / inverter via a ball nut / ball screw (gear) arrangement, and the rack is connected to a vehicle road wheel (e.g., tire) via a tie rod. The RWA 20 includes a microcontroller 22 that controls the operation of the mechanical components 24. The microcontroller 22 receives and / or generates torque via the one or more mechanical components 24.

[0027] The microcontrollers 12 and 22 are coupled together by electrical connections that can transmit and / or receive signals. As described herein, the controller may include a combination of the HWA controller 12 and the RWA controller 22, or any one specific microcontroller.

[0028] In one or more examples, controllers 12 and 22 of SbW system 40 communicate with each other via a CAN interface (or other similar digital communication protocol). Vehicle 100 with SbW system 40 installed is steered using a steering gear having an input shaft rotated by RWA 20 (eg, a servo actuator).

[0029] The RWA 20 receives electronic communication signals from the driver rotating the steering wheel. The driver controls the steering wheel to steer the vehicle 100 in a certain direction. The angle from the HWA 10 is sent to the RWA 20, which performs position control to control the rack travel to guide the road wheels. However, since there is no mechanical connection between the steering wheel and the road wheels, there is no way for the driver to feel the road without torque feedback (unlike the situation in the described EPS).

[0030] In some embodiments, the HWA 10 coupled to the steering column and steering wheel simulates the feel of the road as experienced by the driver. The HWA 10 can apply tactile feedback to the steering wheel in the form of torque. The HWA 10 receives the rack force signal from the RWA 20 to generate the appropriate torque feel for the driver. Alternatively, the hand-held steering wheel angle and vehicle speed can also be used to generate the desired torque feel for the driver.

[0031] The HWA 10 and RWA 20 typically have a steering ratio that determines how much the position of the road wheels changes when the position of the hand steering wheel of the SbW system 40 changes accordingly. In a steering system with a mechanical linkage between the hand steering wheel and the road wheels, gears maintain this ratio. In the SbW system 40, the steering ratio is a predetermined value. However, in the SbW system 40, the desired steering ratio may not always be maintained. There are several common situations that may cause this to occur. These examples include exceeding the slew rate capabilities of the RWA 20 during rapid driver input, hand steering wheel angle input requiring road wheel actuation past travel stops, excessive load on the RWA 20 (exceeding a predetermined maximum threshold), initialization problems, etc.

[0032] The SbW system 40 may include a steering ratio synchronization module 200 configured to adjust at least a commanded steering ratio. The commanded steering ratio may include a steering ratio value that is set (e.g., a command sent to the EPS) to adjust the steering ratio. Based on the maneuver being performed by the driver, the SbW system 40 attempts to use the commanded steering ratio to position the road wheels according to the hand-held steering wheel position. However, the road wheels may be restricted due to, for example, being stuck on a sidewalk, stuck in a muddy road, or any other such reason. Therefore, the achieved steering ratio, i.e., the actual steering ratio between the hand-held steering wheel position and the actual position of the road wheels, may be different from the commanded steering ratio. Further, the desired steering ratio may represent a ratio between the hand-held steering wheel position desired by the driver and the position of the road wheels. It should be noted that although Figure 1 The steering ratio synchronization module 200 is generally shown as a separate block, but the steering ratio synchronization module 200 may also be part of the controller 14 / 22 of the HWA 10 and / or the RWA 20 .

[0033] The steering ratio synchronization module 200 may include one or more electronic circuits. Figure 4 As shown, the steering ratio synchronization module 200 may include a controller 300 and a memory 302. The controller 300 may include a processor. The processor may include any suitable processor, such as those described herein. Additionally or alternatively, the controller 300 may include any suitable number of processors. The memory 302 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 302. In some embodiments, the memory 302 may include a flash memory, a semiconductor (solid-state) memory, etc. The memory 302 may include a random access memory (RAM), a read-only memory (ROM), or a combination thereof. The memory 302 may include instructions that, when executed by the controller 300, cause the controller 300 to at least perform the functions described herein.

[0034] In some embodiments, the steering ratio synchronization module 200 may be configured to determine the difference between the commanded steering ratio and the steering ratio achieved by the SbW system 40. For example, typically, Figure 3 As shown, the steering ratio synchronization module 200 receives one or more steering signals, including a hand-held steering wheel angle 205, a road wheel angle 207, and a commanded steering ratio 210. It should be understood that the steering ratio synchronization module 200 may receive any suitable signals indicating any suitable measurements other than those described herein.

[0035] The steering ratio synchronization module 200 may determine the roadwheel angle command 215 by multiplying the commanded steering ratio 210 by the hand-held steering wheel angle (220). The steering ratio synchronization module 200 may determine the error angle 217 by determining the difference between the roadwheel angle command 215 and the roadwheel angle 207. In some embodiments, an absolute value of the error angle 217 is determined (230).

[0036] In some embodiments, generally, Figure 2 As shown, the steering ratio synchronization module 200 can determine whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a predetermined threshold (e.g., a predetermined maximum error angle value or other suitable value). The steering ratio synchronization module 200 can be configured to adjust the commanded steering ratio to be equal to the achieved steering ratio in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the predetermined threshold.

[0037] The steering ratio 255 is shown, where the road wheel error angle 217 exceeds (or is equal to) a predetermined threshold (e.g., the position closed loop is saturated). As generally shown, the achieved steering ratio (new ratio 255) is not equal to the commanded steering ratio 210, and the hand-held steering wheel angle does not correspond (is not synchronized) with the road wheel angle. The steering ratio synchronization module 200 can adjust the commanded steering ratio 210 toward the achieved steering ratio 225.

[0038] In some embodiments, the steering ratio synchronization module 200 may compare the absolute value of the hand-held steering wheel angle (268) with the hand-held steering wheel filter start value (305). If the steering ratio synchronization module 200 determines that the hand-held steering wheel angle value is less than the filter start value, then the steering ratio synchronization module 200 determines that the achieved steering ratio is not located at the center. The steering ratio synchronization module 200 may use a predetermined value of the achieved ratio filter coefficient as a gain coefficient (275). Additionally or alternatively, the steering ratio synchronization module 200 may calculate the achieved steering angle (310) by dividing the road wheel angle 207 by the hand-held steering wheel angle 205.

[0039] In some embodiments, the steering ratio synchronization module 200 may subtract the commanded steering ratio 210 (312) from the calculated achieved steering ratio. The steering ratio synchronization module 200 may multiply the difference (315) by the gain factor (275). The steering ratio synchronization module 200 may generate a new steering ratio 255 by adding the result (e.g., the product of the difference (315) and the gain factor (275)) to the current commanded steering ratio 210. In this way, the steering ratio synchronization module 200 adjusts the commanded steering ratio 210 to the achieved steering ratio value (e.g., the command itself changes based on the value that the SbW system 40 is capable of achieving and / or has achieved).

[0040] In some embodiments, the steering ratio synchronization module 200 can determine whether the achieved steering ratio is centered based on the hand-held steering wheel position of the hand-held steering wheel of the vehicle 100. If the steering ratio synchronization module 200 determines that the achieved steering ratio is centered based on the hand-held steering wheel angle value being greater than (or equal to) the filter start value (305), the steering ratio synchronization module 200 does not calculate the difference (315) between the achieved steering ratio and the commanded steering ratio (210).

[0041] The steering ratio synchronization module 200 sets the difference value (315) to zero (0). Accordingly, the multiplication of the difference value (315) and the gain factor (275) is zero, which, when added (277) to the commanded steering ratio (210), does not change the current steering ratio value (e.g., it sets the new steering ratio (255) to the current value). The steering ratio synchronization module 200 calculates the gain factor by filtering the steering wheel angle (205) based on the achieved steering ratio (315).

[0042] Conversely, if the steering ratio synchronization module 200 determines that the achieved steering ratio is not centered, the steering ratio synchronization module 200 detects when synchronization is lost between the achieved steering ratio and the commanded steering ratio 210. The steering ratio synchronization module 200 may determine whether a difference between the achieved steering ratio and the commanded steering ratio 210 is greater than a predetermined threshold. The steering ratio synchronization module 200 may adjust the commanded steering ratio 210 to be equal to the achieved steering ratio in response to the difference being greater than the predetermined threshold. This adjustment may occur relatively quickly so that the commanded steering ratio 210 is substantially equal to the achieved steering ratio, but not quickly enough to respond to noise conditions.

[0043] The steering ratio synchronization module 200 uses a ratio calculator module 250 that performs nonlinear filtering to adjust the commanded steering ratio 210 to be equal to the achieved steering ratio. The nonlinear filtering of the commanded steering ratio 210 is performed by a subtraction unit 232, a multiplier 275, and an addition unit 277. The steering ratio synchronization module 200 can adjust the bandwidth of the nonlinear filtering of the ratio calculator module 250 to control the rate of change of the commanded steering ratio 210 to minimize driver distraction or minimize driver perception.

[0044] In some embodiments, as described, the steering ratio synchronization module 200 can selectively adjust the bandwidth of the filter based on at least one vehicle characteristic of the vehicle 100. The steering ratio synchronization module 200 can increase the bandwidth of the filter in response to the vehicle 100 being more "stationary" and less "active." For example, regardless of vehicle speed or throttle lever position, if the steering ratio synchronization module 200 determines that the hand-held steering wheel angle (205) (e.g., using the hand-held steering wheel position) is at the center (e.g., the vehicle 100 is relatively "stationary" and changes in the steering ratio have relatively little effect on the vehicle's trajectory), then the steering ratio synchronization module 200 can increase the bandwidth to a relatively large value.

[0045] Conversely, if the steering ratio synchronization module 200 determines that the hand-held steering wheel angle (205) (e.g., using the hand-held steering wheel position) is greater than a predetermined value (e.g., the hand-held steering wheel angle is not centered), and relatively small changes in the steering ratio may also affect the vehicle trajectory), the steering ratio synchronization module 200 may reduce the bandwidth of the filter. Additionally or alternatively, the steering ratio synchronization module 200 may determine whether the vehicle speed of the vehicle 100 is above a threshold and / or the throttle lever position of the throttle lever of the vehicle 100 is above a threshold. If the steering ratio synchronization module 200 determines that at least one of the vehicle speed of the vehicle 100 is above the threshold and / or the throttle lever position of the throttle lever of the vehicle 100 is above the threshold, the steering ratio synchronization module 200 further reduces the bandwidth of the filter.

[0046] In some embodiments, generally Figure 3As shown, if the steering ratio synchronization module 200 determines that the error angle is less than a predetermined threshold (e.g., a maximum error angle) when compared to a predetermined threshold (235), then the ratio calculator module 250 uses one or more steering system signals to calculate a new steering ratio 255. In some embodiments, the steering ratio synchronization module 200 can be configured to selectively adjust the bandwidth of the filter based on at least one vehicle characteristic of the associated vehicle in response to determining that the error angle is less than a predetermined threshold when compared to a predetermined threshold (235). The filter can be a nonlinear filter, such as a first order digital filter or any suitable filter. The at least one vehicle characteristic can include a road wheel angle of a road wheel of the vehicle 100, a vehicle speed of the vehicle 100, a throttle lever position of a throttle lever of the vehicle 100, a hand steering wheel position of a hand steering wheel of the vehicle 100, any other suitable vehicle characteristic, or a combination thereof.

[0047] The ratio calculator 250 may calculate the desired steering ratio error 213 by determining the difference (232) between the desired steering ratio 212 and the commanded steering ratio 210. The desired steering ratio 212 may include a predetermined value or may include a proportional factor calculated by filtering the hand-held steering wheel angle 205 using a filter start, a filter end, and a maximum filter coefficient. The filter start value and the filter end value may include hand-held steering wheel position values ​​at the beginning and end of the steering wheel manipulation. The maximum filter coefficient may include a calibrable predetermined value.

[0048] In some embodiments, the steering ratio synchronization module 200 divides the difference (262) between the filter end value and the filter start value by (264) the maximum filter coefficient to generate a first scale factor. The steering ratio synchronization module 200 can generate an adjusted first scale factor by multiplying (270) the difference (266) between the filter end value and the absolute value (268) of the current hand-held steering wheel angle 205. The steering ratio synchronization module 200 can further limit the adjusted first scale factor within a predetermined range (272), such as between 0 and the maximum filter coefficient, and provide the result as a scale factor or gain factor to generate a new steering ratio 255.

[0049] In some embodiments, the steering ratio synchronization module 200 may multiply (275) the gain factor by the desired steering ratio error 213. The steering ratio synchronization module 200 may add (277) the result to the currently commanded steering ratio 210 to generate a new steering ratio 255. The steering ratio synchronization module 200 may calculate the gain factor for multiplying (275) the desired steering ratio error (213) by filtering the hand-held steering wheel angle (205) based on the desired steering ratio error (213). As generally shown, the error angle 217 of the load wheel is less than the predetermined threshold (235), the achieved steering ratio (new ratio 255) is substantially equal to the commanded steering ratio 210, and the load wheel angle corresponds to the hand-held steering wheel angle. The steering ratio synchronization module 200 may not adjust the commanded steering ratio in response to the achieved steering ratio (new ratio 255) being substantially equal to the commanded steering ratio.

[0050] In some embodiments, the steering ratio synchronization module 200 and / or the controller 300 can perform the methods described herein. However, the methods described herein performed by the steering ratio synchronization module 200 and / or the controller 300 are not meant to be limiting, but any type of software executed on a controller can perform the methods 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, can perform the methods described herein.

[0051] Figure 5 4 is a flow chart generally illustrating a steering ratio synchronization method 400 according to the principles of the present disclosure. At 402, the method 400 determines the difference between the commanded steering ratio and the achieved steering ratio. For example, the controller 300 determines the difference between the commanded steering ratio and the achieved steering ratio.

[0052] At 404, the method 400 determines whether the difference is greater than a threshold. For example, the controller 300 determines whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a predetermined threshold. If the controller 300 determines that the difference is less than the predetermined threshold, the method 400 proceeds to 408. If the controller 300 determines that the difference is greater than the predetermined threshold, the method 400 proceeds to 406.

[0053] At 406, the method 400 adjusts the commanded steering ratio to be equal to the achieved steering ratio. For example, the controller 300 adjusts the commanded steering ratio to be equal to the achieved steering ratio. The method 400 may continue at 402, or the method 400 may end. Additionally or alternatively, the method 400 may include performing additional operations before continuing at 402 or before ending.

[0054] At 408, the method 400 selectively adjusts the bandwidth of the filter based on at least one vehicle characteristic. For example, the controller 300 adjusts the bandwidth of the filter based on at least one vehicle characteristic. As described, the controller 300 can increase the bandwidth of the filter in response to the hand-held steering wheel position indicating that the hand-held steering wheel angle of the hand-held steering wheel of the vehicle 100 is located at the center. Conversely, the controller 300 can reduce the bandwidth of the filter in response to the hand-held steering wheel position indicating that the hand-held steering wheel angle of the hand-held steering wheel of the vehicle 100 is not located at the center. Additionally or alternatively, the controller 300 can also reduce the bandwidth of the filter based on the vehicle speed of the vehicle 100 and / or the throttle lever position of the throttle lever of the vehicle 100.

[0055] At 410, the method 400 uses the filter to adjust the commanded steering ratio to be equal to the desired steering ratio. For example, the controller 300 uses the filter to adjust the commanded steering ratio to be equal to the desired steering ratio. The method 400 may continue at 402, or the method 400 may end. Additionally or alternatively, the method 400 may include performing additional operations before continuing at 402 or before ending.

[0056] Accordingly, the technical scheme described herein facilitates the SbW system to dynamically adjust the steering ratio between the HWA and the RWA, and also adjusts the rate of adjustment of the steering ratio based on the hand-held steering wheel angle. The adjustment rate may also be adjusted based on other parameters such as vehicle speed, throttle lever position, etc. The technical scheme improves the operation of the steering system by preventing the steering system from continuing to attempt to achieve the desired steering ratio (predetermined value) after the driver stops driving the hand-held steering wheel. If the steering system is not prevented, the vehicle response will be delayed and it may appear as if the vehicle continues to drive itself.

[0057] In some embodiments, a steer-by-wire system includes a processor and a memory. The memory includes instructions that, when executed by the processor, cause the processor to: determine a difference between a commanded steering ratio and an achieved steering ratio; determine whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold; in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjust the commanded steering ratio to be equal to the achieved steering ratio; in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold: selectively adjust a bandwidth of a filter based on at least one vehicle characteristic of an associated vehicle; and adjust the commanded steering ratio to be equal to a desired steering ratio using the filter.

[0058] In some embodiments, at least one vehicle characteristic comprises a road wheel angle of a road wheel of the vehicle. In some embodiments, at least one vehicle characteristic comprises a vehicle speed of the vehicle. In some embodiments, at least one vehicle characteristic comprises a throttle lever position of a throttle lever of the vehicle. In some embodiments, at least one vehicle characteristic comprises a hand-held steering wheel position of a hand-held steering wheel of the vehicle. In some embodiments, the instructions further cause the processor to selectively adjust the bandwidth of the filter by increasing the bandwidth in response to determining that the hand-held steering wheel position indicates that the hand-held steering wheel is in a center position. In some embodiments, the instructions further cause the processor to selectively adjust the bandwidth of the filter by decreasing the bandwidth in response to determining that the hand-held steering wheel position indicates that the hand-held steering wheel has a certain angle relative to the center position. In some embodiments, the filter comprises a nonlinear filter.

[0059] In some embodiments, a method for a steer-by-wire system includes: determining a difference between a commanded steering ratio and an achieved steering ratio; and determining whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold. The method also includes: in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjusting the commanded steering ratio to be equal to the achieved steering ratio. The method also includes: in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than the threshold, selectively adjusting a bandwidth of a filter based on at least one vehicle characteristic of an associated vehicle; and adjusting the commanded steering ratio to be equal to a desired steering ratio using the filter.

[0060] In some embodiments, at least one vehicle characteristic comprises a road wheel angle of a road wheel of the vehicle. In some embodiments, at least one vehicle characteristic comprises a vehicle speed of the vehicle. In some embodiments, at least one vehicle characteristic comprises a throttle lever position of a throttle lever of the vehicle. In some embodiments, at least one vehicle characteristic comprises a hand-held steering wheel position of a hand-held steering wheel of the vehicle. In some embodiments, the method further comprises: selectively adjusting the bandwidth of the filter by increasing the bandwidth in response to determining that the hand-held steering wheel position indicates that the hand-held steering wheel is in a center position. In some embodiments, the method further comprises: selectively adjusting the bandwidth of the filter by reducing the bandwidth in response to determining that the hand-held steering wheel position indicates that the hand-held steering wheel has a certain angle relative to the center position. In some embodiments, the filter comprises a nonlinear filter.

[0061] In some embodiments, the system includes a processor and a memory. The memory includes instructions that, when executed by the processor, cause the processor to: determine a difference between a commanded steering ratio and an achieved steering ratio; determine whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold; in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjust the commanded steering ratio to be equal to the achieved steering ratio; and in response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than the threshold: determine whether the hand-held steering wheel position indicates that the hand-held steering wheel of the vehicle is in a center position; in response to determining that the hand-held steering wheel position indicates that the hand-held steering wheel of the vehicle is in a center position, selectively increase the bandwidth of the filter; in response to determining that the hand-held steering wheel position indicates that the hand-held steering wheel of the vehicle is not in a center position, selectively reduce the bandwidth of the filter; and use the filter to adjust the commanded steering ratio to be equal to the desired steering ratio.

[0062] In some embodiments, the instructions further cause the processor to: determine at least one of a vehicle speed of the vehicle and a throttle lever position of a throttle lever of the vehicle in response to reducing the bandwidth of the filter. In some embodiments, the instructions further cause the processor to: further reduce the bandwidth of the filter based on at least one of the vehicle speed of the vehicle and the throttle lever position of the throttle lever of the vehicle. In some embodiments, the filter comprises a nonlinear filter.

[0063] In some embodiments, the steer-by-wire system includes a hand-held steering wheel actuator, a road wheel actuator, and a steering ratio synchronization module. The steering ratio synchronization module is used to dynamically adjust the steering ratio between the road wheel actuator and the hand-held steering wheel actuator, and the dynamic adjustment includes: detecting that the difference between the commanded steering ratio and the achieved steering ratio exceeds a predetermined error threshold; calculating a gain coefficient using the hand-held steering wheel angle; calculating an adjustment factor by multiplying the gain coefficient by the difference between the commanded steering ratio and the desired steering ratio; and calculating the adjusted steering ratio by adding the adjustment factor to the commanded steering ratio to change the commanded steering ratio.

[0064] In some embodiments, calculating the gain factor includes: determining the error angle by calculating the difference between the multiplication result of the hand-held steering wheel angle and the commanded steering ratio and the road wheel angle. In some embodiments, calculating the gain factor also includes: determining that the error angle is greater than or equal to a predetermined maximum error angle; in response, calculating a first proportional factor using a filter end value and a filter start value; calculating the difference between the filter end value and the hand-held steering wheel angle; and calculating the product of the first proportional factor and the difference as the gain factor. In some embodiments, the gain factor is normalized within a predetermined range. In some embodiments, calculating the gain factor also includes: determining that the error angle is less than a predetermined maximum error angle; and in response, calculating the gain factor based on the achieved steering ratio. In some embodiments, calculating the gain factor also includes: if the hand-held steering wheel angle is less than the filter start value, then calculating the achieved steering ratio; and calculating the adjustment factor by multiplying the gain factor by the difference between the achieved steering ratio and the commanded steering ratio. In some embodiments, if the hand-held steering wheel angle is not less than the filter start value, then setting the achieved steering ratio to zero.

[0065] In some embodiments, a method for adjusting a steering ratio in a steer-by-wire system includes: detecting that a difference between a commanded steering ratio and an achieved steering ratio exceeds a predetermined error threshold; and calculating a gain factor using a hand-held steering wheel angle. The method also includes: calculating an adjustment factor by multiplying the gain factor by the difference between the commanded steering ratio and a desired steering ratio value; and calculating an adjusted steering ratio by adding the adjustment factor to the commanded steering ratio to change the commanded steering ratio.

[0066] In some embodiments, calculating the gain factor includes: determining the error angle by calculating the difference between the multiplication result of the hand-held steering wheel angle and the commanded steering ratio and the road wheel angle. In some embodiments, calculating the gain factor also includes: determining that the error angle is greater than or equal to a predetermined maximum error angle; in response, calculating a first proportional factor using a filter end value and a filter start value; calculating the difference between the filter end value and the hand-held steering wheel angle; and calculating the product of the first proportional factor and the difference as the gain factor. In some embodiments, the gain factor is normalized within a predetermined range. In some embodiments, calculating the gain factor also includes: determining that the error angle is less than a predetermined maximum error angle; and in response, calculating the gain factor based on the achieved steering ratio. In some embodiments, calculating the gain factor also includes: if the hand-held steering wheel angle is less than the filter start value, calculating the achieved steering ratio; and calculating the adjustment factor by multiplying the difference between the achieved steering ratio and the commanded steering ratio by the gain factor. In some embodiments, if the hand-held steering wheel angle is not less than the filter start value, the achieved steering ratio is set to zero.

[0067] In some embodiments, the computer program product includes a memory storage device having computer executable instructions stored therein. The computer executable instructions, when executed by a processing unit, cause the processing unit to adjust a steering ratio in a steer-by-wire system. The adjustment includes: detecting that a difference between a commanded steering ratio and an achieved steering ratio exceeds a predetermined error threshold; calculating a gain factor using a hand-held steering wheel angle; calculating an adjustment factor by multiplying the gain factor by a difference between a commanded steering ratio and a desired steering ratio; and calculating an adjusted steering ratio by changing the commanded steering ratio by adding the adjustment factor to the commanded steering ratio.

[0068] In some embodiments, calculating the gain coefficient includes: determining the error angle by calculating the difference between the multiplication result of the hand-held steering wheel angle and the commanded steering ratio and the road wheel angle. In some embodiments, calculating the gain coefficient also includes: determining that the error angle is greater than or equal to a predetermined maximum error angle; in response, calculating a first proportional factor using a filter end value and a filter start value; calculating the difference between the filter end value and the hand-held steering wheel angle; and calculating the product of the first proportional factor and the difference as the gain coefficient. In some embodiments, the gain coefficient is normalized within a predetermined range. In some embodiments, calculating the gain coefficient also includes: determining that the error angle is less than a predetermined maximum error angle; and in response, calculating the gain coefficient based on the achieved steering ratio. In some embodiments, calculating the gain coefficient also includes: calculating the achieved steering ratio if the hand-held steering wheel angle is less than the filter start value; calculating the adjustment factor by multiplying the gain coefficient by the difference between the achieved steering ratio and the commanded steering ratio; and setting the achieved steering ratio to zero if the hand-held steering wheel angle is not less than the filter start value.

[0069] The above discussion is intended to illustrate the principles and various embodiments of the present invention. Once the above disclosure is fully understood, various variations and modifications will readily occur to those skilled in the art. It is intended that the following claims be interpreted as including all such variations and modifications.

[0070] The word "example" is used in this article to mean to be used as an example, instance or diagram. Any aspect or design described as "example" herein is not necessarily interpreted as being preferred or advantageous over other aspects or designs. Rather, the use of the word "example" is intended to present concepts in a specific form. As used in this application, the term "or" is intended to express an inclusive "or" rather than an exclusive "or". That is, unless specifically stated, or clear from the context, "X includes A or B" is intended to express any common inclusive arrangement. That is, if X includes A, X includes B, or X includes A and B, "X includes A or B" is satisfied in any of the above cases. In addition, unless specifically stated or it is clear from the context that it refers to a singular form, the articles "one" and "an" used in this application and the appended claims should generally be interpreted as meaning "one or more". In addition, unless so described, the terms "an embodiment" or "an embodiment" used throughout the text are not intended to mean the same embodiment or embodiment.

[0071] The embodiments 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.

[0072] 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 a self-contained 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), 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 may be executed by a controller to implement the features of the module.

[0073] 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, performs 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 executing any method, algorithm or instruction described herein.

[0074] In addition, all or part of the embodiments 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 that may, for example, tangibly contain, store, communicate, or transmit a program used by or in conjunction with any processor. The medium may be, for example, an electrical, magnetic, optical, electromagnetic, or semiconductor device. Other suitable media are also available.

[0075] The above embodiments, implementations and aspects have been described to make the present disclosure easy to understand without limiting the present disclosure. On the contrary, the present disclosure is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is consistent with the broadest interpretation to include all such modifications and equivalent structures permitted by law.

Claims

1. A steer-by-wire system, comprising: processor; as well as a memory comprising instructions that, when executed by the processor, cause the processor to: determining a difference between a commanded steering ratio and an achieved steering ratio; determining whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold; In response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjusting the commanded steering ratio to be equal to the achieved steering ratio; as well as In response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than the threshold: selectively adjusting a bandwidth of the nonlinear filter based on at least one vehicle characteristic of an associated vehicle; as well as The commanded steering ratio is adjusted to be equal to a desired steering ratio using the non-linear filter, wherein the bandwidth is selectively adjusted to control a rate of change of the commanded steering ratio.

2. The steer-by-wire system according to claim 1, wherein: The at least one vehicle characteristic includes a road wheel angle of a road wheel of the vehicle.

3. The steer-by-wire system according to claim 1, wherein: The at least one vehicle characteristic comprises a vehicle speed of the vehicle.

4. The steer-by-wire system according to claim 1, wherein: The at least one vehicle characteristic includes a throttle lever position of a throttle lever of the vehicle.

5. The steer-by-wire system according to claim 1, wherein: The at least one vehicle characteristic includes a hands-on steering wheel position of a hands-on steering wheel of the vehicle.

6. The steer-by-wire system according to claim 5, wherein: The instructions further cause the processor to selectively adjust the bandwidth by increasing a bandwidth of the nonlinear filter in response to determining that the steering wheel position indicates that the steering wheel is in a center position.

7. The steer-by-wire system according to claim 5, wherein: The instructions further cause the processor to selectively adjust the bandwidth by reducing a bandwidth of the nonlinear filter in response to determining that the steering wheel position indicates that the steering wheel has an angle relative to a center position.

8. The steer-by-wire system according to claim 7, wherein: The nonlinear filter comprises a first order digital filter.

9. A method for a steer-by-wire system, the method comprising: determining a difference between a commanded steering ratio and an achieved steering ratio; determining whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold; In response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjusting the commanded steering ratio to be equal to the achieved steering ratio; as well as In response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than the threshold: selectively adjusting a bandwidth of the nonlinear filter based on at least one vehicle characteristic of an associated vehicle; as well as The commanded steering ratio is adjusted to be equal to a desired steering ratio using the non-linear filter, wherein the bandwidth is selectively adjusted to control a rate of change of the commanded steering ratio.

10. The method according to claim 9, wherein: The at least one vehicle characteristic includes a road wheel angle of a road wheel of the vehicle.

11. The method according to claim 9, wherein: The at least one vehicle characteristic comprises a vehicle speed of the vehicle.

12. The method according to claim 9, wherein: The at least one vehicle characteristic includes a throttle lever position of a throttle lever of the vehicle.

13. The method according to claim 9, wherein: The at least one vehicle characteristic includes a hands-on steering wheel position of a hands-on steering wheel of the vehicle.

14. The method according to claim 13, further comprising: The bandwidth is selectively adjusted by increasing a bandwidth of the non-linear filter in response to determining that the steering wheel position indicates that the steering wheel is in a center position.

15. The method according to claim 13, further comprising: The bandwidth is selectively adjusted by reducing a bandwidth of the non-linear filter in response to determining that the steering wheel position indicates that the steering wheel has an angle relative to a center position.

16. The method according to claim 15, wherein: The nonlinear filter comprises a first order digital filter.

17. A system comprising: processor; as well as a memory comprising instructions that, when executed by the processor, cause the processor to: determining a difference between a commanded steering ratio and an achieved steering ratio; determining whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold; In response to determining that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjusting the commanded steering ratio to be equal to the achieved steering ratio; as well as In response to determining that the difference between the commanded steering ratio and the achieved steering ratio is not greater than the threshold: determining whether the hand steering wheel position indicates that the hand steering wheel of the vehicle is in a center position; selectively increasing a bandwidth of a nonlinear filter in response to determining that the steering wheel position indicates that the steering wheel of the vehicle is in the center position; selectively reducing a bandwidth of the nonlinear filter in response to determining that the manual steering wheel position indicates that the manual steering wheel of the vehicle is not in the center position; as well as The commanded steering ratio is adjusted to be equal to a desired steering ratio using the non-linear filter, wherein the bandwidth is selectively adjusted to control a rate of change of the commanded steering ratio.

18. The system of claim 17, wherein: The instructions further cause the processor to determine at least one of a vehicle speed of the vehicle and a throttle lever position of a throttle lever of the vehicle in response to reducing a bandwidth of the non-linear filter.

19. The system of claim 18, wherein: The instructions further cause the processor to further reduce a bandwidth of the non-linear filter based on at least one of a vehicle speed of the vehicle and a throttle lever position of a throttle lever of the vehicle.

20. The system of claim 17, wherein: The nonlinear filter comprises a first order digital filter.

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