Brake-to-steer lateral stability management based on a stability indicator correlation

Abstract

Several variations are disclosed comprehensively of a system and a method for modifying, in real time, at least one braking or drive application with respect to individual road wheels of a vehicle to increase lateral maneuverability in a vehicle which has a functioning, partially functioning, failing, or malfunctioning electronic steering system. The system and the method may include modifying a braking and / or drive instruction (102) with respect to individual road wheels when instability is detected.

Description

Technical FieldThe field to which the disclosure generally relates relates to steering, braking, and drive systems.BackgroundVehicles may include steering systems including electric power steering systems and steer-by-wire systems.Overview of Illustrative VariationsSome variations may include a method including modifying, in real-time, at least one braking or driving operation with respect to one or more road wheels of a vehicle to increase lateral stability during brake-to-steer functionality.Some variations may include a method including increasing, decreasing, or scaling brake instructions of an electronic brake system and / or propulsion system instructions while a brake-to-steer functionality is active. This may prevent instability of the vehicle or unintended oversteering of the vehicle.Vehicle instability may result in a complete loss of vehicle control or create a safety risk. Some variations may include a method that reduces the potential for loss of vehicle control by modifying brake-to-steer brake commands and / or drive commands based on a number of calculated, measured, or observed stability indicators. This not only improves vehicle safety, but improves overall controllability of the vehicle with brake-to-steering functionality.Further illustrative variations within the scope of the invention will become apparent from the following detailed description. It should be understood that the detailed description and specific examples, while variations of the invention are disclosed, are intended for purposes of illustration only and are not intended to limit the scope of the invention.Brief Description of the FiguresFurther details, features and advantages of the invention are evident from the following description of exemplary embodiments with reference to the drawings. The following shows: FIG. 1 shows an illustrative variation of a block diagram of a system and method for brake-to-steer lateral stability management; FIG. 2 shows an illustrative variation of a block diagram of a system and method for brake-to-steer lateral stability management; FIG. 3 shows an illustrative variation of a block diagram of a system and method for brake-to-steer lateral stability management; FIG. 4 shows an illustrative variation of a block diagram of a vehicle with a steer-by-wire system, where the vehicle also has the ability to perform brake-to-steer, and where the brake-to-steer function also includes methods for lateral stability management; and FIG. 5 shows an illustrative variation of a block diagram of a vehicle with a connected power steering system, where the vehicle also has the capability to perform brake-to-steer, and where the brake-to-steer function includes methods for lateral stability management.The figures are not necessarily to scale, and certain features and particular views of the figures may be shown on an exaggerated scale or schematically for clarity and accuracy and should not be considered limiting.DETAILED DESCRIPTION OF ILLUSTRATIVE VARIATIONSThe following description of the variations is merely illustrative in nature and is in no way intended to limit the scope of the invention, its application, or uses.Vehicles typically include steering systems, braking systems, and propulsion systems. A steering system may be a connected steering system (a steering system having a mechanical connection between the hand wheel and the rack) with a power steering, or a steer-by-wire system (a steering system without a mechanical connection between the hand wheel and the rack). A braking system may include various means for counteracting movement of a vehicle including a friction brake and electric brakes. A propulsion system may have various means for propulsion, such as an internal combustion engine or an electric motor, and various means for providing torques, forces, or pressures from the propulsion system to individual wheels, including clutches, differentials, and torque distributed differentials. A set of instructions for a brake system or drive system may include a commanded torque, a force, a throttle, or a pedal position, a current, a voltage, a pressure, or similar instructions not mentioned above. A load may include moments, forces, pressures or similar entity not mentioned previously. A steering system, a braking system, or a propulsion system may include electronics that allow them to transmit or receive signals and instructions, and convert received instructions into forces within the system or generate them through the system, and that ultimately act on the wheels. A driver of a vehicle controls the movement of a vehicle, and may represent a human driver or an automated driver. A system such as a steering system may fail, which may include a complete or partial failure or degradation.In a broad range of maneuvers, a vehicle driver normally controls the hand wheel and an electric power steering assist motor provides assist to assist the driver in easily controlling the vehicle. A component of an electric power steering assist system, such as, but not limited to, a prime mover or an electric motor, may fail. In such a case, the driver may achieve very high hand wheel torques after a steering maneuver is applied and the driver may not be able to adequately control the vehicle due to the high hand wheel torque required for the steering inputs. This may increase the risk of a vehicle accident. Single wheel brake actuation and / or propulsion actuation may be employed to provide a specific, diverse assist method using a variant actuator which may help add lateral capacity by adding yaw moment through braking forces and / or propulsion forces. This approach may be used for operational or partially operational electric power steering systems or steer-by-wire systems that have been degraded or degraded to assist a driver or automatic control in a wide range of maneuvers. This may provide or improve vehicle lateral control capability and supplement the power steering system or steer-by-wire system when the driver or automatic control attempts to execute a lateral maneuver to avoid steering or an obstacle.When a power steering assist system or steer-by-wire system includes a component such as, but not limited to, a prime mover, an electric motor, or an actuator that has failed, has a fault, or is degraded, a brake-to-steer algorithm may be executed by an electronic processor and cause generation of at least one brake command or a drive command for one or more wheels as a function of vehicle state information. Alternatively, regenerative braking in individual wheels may be used to provide brake-to-steer functionality. The brake-for-steering may be a software function that provides a brake command and / or a drive command to one or more road wheels that may be used in a brake actuation system or a drive actuation system based on information regarding a driver intent, such as a hand wheel torque or a hand wheel angle. The vehicle state information may include, for example, a lateral acceleration and / or yaw rate, and / or, if available, steering sensor measurements including, for example, a hand wheel torque and / or hand wheel angle. According to some variations, a brake-to-steer system may be controlled by a range controller constructed and arranged to employ brake-to-steer functionality when a lateral maneuver is being performed.The braking-to-steering may receive driver intent inputs and output specific braking instructions to individual wheels, which may be used to assist the driver in turning the vehicle operated by the driver. Brake-to-steer instructions may be calculated in such a way that sufficient braking force is provided to at least one road wheel to generate a yaw moment, which in turn generates a lateral force that supplements the lateral force induced by the driver's manual steering, in a vehicle with a connected steering system with a power steering. In a steer-by-wire system, if the rack is degraded, the driver may lose full lateral control of the vehicle. Brake-to-steer brake instructions may be calculated in such a way as to provide sufficient braking force to at least one road wheel to generate a yaw moment, which in turn generates a lateral force that enables driver-limited lateral control of the vehicle initiated by the driver's steering. In a system controlled by an automated driver, if a steering error is present that reduces the ability of the electronic steering system to maneuver a vehicle laterally, the automated driver (an autonomous or semi-autonomous driving system) may apply brake-to-steering to generate a yaw moment that in turn generates a lateral force that supplements the lateral force requested by the automated driver. Brake-to-steer may also apply propulsion instructions in response to driver or automated driver inputs to help the vehicle maintain the intended longitudinal speed and to generate more yaw moments relative to the vehicle to improve brake-to-steer lateral capability increases. Braking-to-steering may allow the vehicle to achieve higher yaw rates during a wide range of maneuvers than would be achievable with a degraded steering system without braking-to-steering. Braking-to-steering may help improve yaw rates, reduce driver effort, and improve vehicle lateral control. This may be done for a range of speeds and maneuvers. For example, when maneuvers are performed at low speeds in parking spaces, braking to steer may provide significant effort reduction to the driver.In some driving scenarios, braking to steer may cause unintended oversteer or excessive vehicle yaw rate. An example of when such a scenario may occur would be when the driver crosses the surface friction limit in steering. Existing systems and methods developed to alleviate vehicle stability issues may not operate efficiently during a brake-to-steer operation for a number of reasons.Electronic stability control systems typically require a steering wheel angle signal to operate, which is important because, in the case of using some brake-to-steer implementations, the steering wheel angle signal may not be available, meaning that brake-to-steer may not be able to rely on existing vehicle stability control systems to maintain stability. If the hand wheel angle information is available, existing vehicle stability control systems may not be sufficient to prevent brake-to-steer from oversteering the vehicle because they do not alter the brake-to-steer brake command and / or the drive commands. An advantage of some variations of the disclosed system and method is ensuring stability in scenarios involving brake-to-steering and loss of power steering systems, as some of the variations of the disclosed system and method may rely on multiple stability indicators without the need to use a hand wheel angle. However, if hand wheel angle data or steering angle data is available, they may be used.An electronic brake force distribution lacks the possibility of controlling drive torque commands and is only effective when negative tire slip is taken into account. An advantage of some embodiments of the disclosed system and method of stability indicator-based brake-to-steering control, and in particular wheel speed-based brake-to-steering control, is more robust instability detection when a drive torque is applied, provided it has the capability of controlling drive torque instructions. Moreover, an advantage of some embodiments of the disclosed system is that the disclosed system may respond to positive and negative tire slips, in addition to some other stability indicators.Anti-lock brake systems (ABS) are unable to monitor or account for wheel speeds and wheel slip ratios for all corners of the vehicle because they primarily modulate based on wheel slip of one tire and not based on wheel slip relative to different tires. The ABS lacks the ability to control drive torque commands. Brake-to-steer with stability indicator scaling may be responsive to positive and negative tire slips. An advantage of some variations of the disclosed system or method, such as stability indicator-based brake-to-steer control, is a more robust instability detection when applying at least one brake command or drive command to individual wheels, as it may take into account positive and negative tire slips and some other stability indicators. Moreover, stability indicator-based brake-to-steering control, unlike typical ABS functions, has the ability to control drive torque instructions.Traction control systems lack the ability to control brake-to-steer brake commands. Traction control systems also lack the ability to respond to negative tire slip. An advantage of some embodiments of the disclosed system and method is that stability indicator-based brake-to-steering control may monitor wheel speeds or wheel slip ratios of all corners of the vehicle and their relationships to each other, in addition to other stability indicators. Therefore, the brake-to-steer stability method, system, or computer product, which may include an algorithm described herein, is more robust with respect to detecting instabilities when at least one brake command or drive command is applied to individual wheels.Stability indicator-based brake-to-steer control may continuously monitor vehicle stability under all driving conditions and prevent the vehicle from losing stability in situations where a brake-to-steer application causes oversteering of the vehicle. The system and method may be tuned to respond when override characteristics are detected based on single or a plurality of stability indicators.The stability indicators may include a number of stability detection metrics, such as, but not limited to, yaw rate error, differential wheel slip, outputs from an electric power steering (EPS), electronic stability control (ESC), traction control (TCS) systems, or anti-lock braking (ABS) systems, or measured or observed road surface friction (mu) indicators. Some variations may include, but are not limited to, a method, system, or computer medium having executable instructions to scale, reduce, or increase at least one of a brake-to-steer brake instruction and a brake-to-steer drive instruction in a case where the brake-to-steer instructions cause vehicle instability or unintended oversteering of the vehicle, particularly in the context of driving scenarios where low surface friction is present.Some variations may include a brake-to-steer stability method, system, or computer product including a medium with instructions executable by an electronic processor to modify, in real-time, a brake application and / or a propulsion application on individual road wheels of a vehicle to increase lateral stability during brake-to-steer functionality. Some variations may include a computer product that may include instructions such as an algorithm stored on a medium and executable by an electronic processor to perform various functions described herein. A brake-to-steer stability module or controller, which may include instructions such as an algorithm stored on a medium and executable by an electronic processor, receives signals from the vehicle, which may include, but are not limited to, yaw rate and / or vehicle speed and / or vehicle accelerations and / or steering wheel angle and / or hand wheel torque and / or wheel speeds or tire slips. The brake-to-steer stability module or controller uses these inputs to calculate one or more stability indicators. The brake-to-steer stability module or controller may also receive externally calculated stability indicators, which may include, but are not limited to, road surface friction or activation flags, from an external system such as an electronic stability control (ESC), an anti-lock brake system (ABS), a traction control system (TCS), or an electronic braking force distribution (EBD).A stability indicator calculated by the brake-to-steer stability module or controller may include a yaw rate error. The yaw rate error may be calculated by comparing an estimated or predicted yaw rate to the measured or calculated vehicle yaw rate. An estimated yaw rate may be calculated using a lateral acceleration and / or a vehicle speed and / or a steering wheel angle and / or a hand wheel torque and / or individual wheel speeds.A stability indicator calculated by the brake-to-steer stability module or controller may include differential wheel slip. In order to calculate the differential wheel slip, first individual wheel longitudinal slips can be calculated. The wheel speed signals and the estimated reference vehicle longitudinal speed may be used to calculate the longitudinal wheel slip at each corner of the vehicle. An iteration of this may also use the yaw rate and vehicle gauge to better estimate slip at each corner. Individual tire slips may also be calculated externally and communicated to the brake-to-steer stability module or controller.On the basis of the individual longitudinal tire slip, a plurality of types of differential wheel slip can be calculated. For example, the absolute value of the difference between the left and right wheel slip for each axle (associated with the yaw moment acting on each axle by the longitudinal wheel forces), or the sum of the absolute value of the difference between the left and right wheel slip for each axle (associated with the yaw moment acting on the entire vehicle by the longitudinal wheel forces), or (for rear wheel drive), the difference between the outer rear and outer front wheel slip, or (for front wheel drive), the difference between the outer front and outer rear wheel slip.Each stability indicator may be compared to its stability indicator threshold. A stability indicator threshold may include, but is not limited to, a threshold, a tolerance, or an expected value. These stability indicators and stability indicator thresholds may be used alone or in combination. When the stability indicators are within their thresholds, the brake-to-steer brake instructions and / or the brake-to-steer drive instructions are allowed to be sent to the vehicle unchanged to assist in lateral control for normal brake-to-steer operation. If the stability indicators are outside their thresholds, the brake-to-steer stability module or controller modulates the brake instructions and / or the drive instructions to prevent excessive vehicle instability. This modulation may be accomplished by various means including, but not limited to: calculating new instructions by multiplying or dividing original instructions by a scalar, or calculating new instructions by adding or subtracting an offset value to or from the original instructions. These scalars or offset values may be predefined or dynamically calculated based on the difference between the stability indicators and their thresholds. The brake-to-steer stability module or controller may also output its / her internal computations and / or status for downstream use. Further details and other variations include methods, systems, a computing medium including instructions therein executable by an electronic processor, and functionalities are described below.As a non-limiting example, a stability indicator-based brake-to-steer control may include a yaw rate error-based brake-to-steer control to improve brake-to-steer performance and vehicle safety. The estimated yaw rate may be calculated using a lateral acceleration and a vehicle speed. The estimated yaw rate may be calculated using wheel speeds. The estimated yaw rate may be calculated using the vehicle speed and the steering wheel angle. The estimated yaw rate may be calculated using any combination of the methods defined above. An estimated yaw rate may be compared to a measured or calculated vehicle yaw rate to calculate a yaw rate error. By using this error calculation and depending on the magnitude and direction of the yaw rate error, the system and method may adjust, modify, update, regulate, or generate at least one new drive command to prevent further oversteering of the vehicle. If the yaw rate error stability indicator is within an acceptable threshold range, it is permitted to send brake-to-steer brake commands and / or brake-to-steer drive commands to the vehicle without a stability modification to assist in lateral control for normal brake-to-steer operation.As a non-limiting example, stability indicator-based brake-to-steer control may include wheel speed-based brake-to-steer control to increase brake-to-steer performance and vehicle safety. The system, method, or product may use measured wheel speed signals and vehicle longitudinal speed to calculate a longitudinal tire slip for each corner of the vehicle. A plurality of stability indicators can be calculated on the basis of the slip conditions. For example, the absolute value of the difference between the left and right tire slippages for each axle, or the sum of the absolute value of the difference between the left and right tire slippages for each axle, or in the case of rear wheel drive vehicles, the difference between the outer rear tire slippage and the outer front tire slippage, or in the case of front wheel drive vehicles, the difference between the outer front tire slippage and the outer rear tire slippage. These slip ratio-based stability indicators may be used singly or in combination. According to the disclosed system and method for stability indicator-based brake-to-steer control, the brake-to-steer brake commands and / or the brake-to-steer drive commands may be modulated to prevent excessive vehicle instability when these stability indicators are outside their acceptable threshold range. If the slip ratio-based stability indicators are within an acceptable threshold range, it is permitted that the brake-to-steer brake commands or the brake-to-steer drive commands are sent to the vehicle without a change to assist in lateral control.In the case of a steer-by-wire vehicle, it is assumed that a steering wheel-based steering angle sensor (SAS) or other form of SAS is capable of interpreting driver intentions. This steering angle may be used to predict an intended vehicle yaw rate. The yaw rate error is calculated by comparing the predicted intended vehicle yaw rate and the measured vehicle yaw rate. Similar instability mitigation strategies to those described in the above paragraphs may be implemented in a steer-by-wire system. Changing the at least one brake-to-steer brake command or the one brake-to-steer drive command may vary for a steer-by-wire vehicle application case.FIG. 1 shows an illustrative variation of a block diagram of a system and method for stability indicator-based brake-to-steer lateral stability management 100. FIG. 1 illustrates only one illustrative way in which the method may be performed. The system and method may include receiving vehicle data such as a vehicle speed 104, a lateral acceleration 106, and a vehicle yaw rate 108 from in-vehicle systems and sensors. A stability indicator-based instruction scaling algorithm 110 may include estimating a yaw rate 118 based on the vehicle speed 104 and the lateral acceleration 106. The yaw rate error 120 may be calculated based on the estimated yaw rate 118 and the measured vehicle yaw rate 108. The calculated yaw rate error 120 may be used in a yaw rate error-based scalar calculation 122 based on the measured vehicle speed 104. The yaw rate error-based scalar calculation 122 may communicate a scalar value 124 to at least one braking or drive command modifier 114. Alternatively, the yaw rate error-based scalar calculation 122 may communicate a reduction value to the brake-to-steer brake command modifier and / or the brake-to-steer drive command modifier 114. The system and method may include communicating brake-to-steer brake instructions and / or brake-to-steer drive instructions 102 in a pre-scaled state 112 to the brake-to-steer brake instruction modifier and / or the brake-to-steer drive instruction modifier 114. The brake-to-steer brake command modifier and / or the brake-to-steer drive command modifier 114 may determine the modified brake-to-steer brake commands and / or the brake-to-steer drive commands 126, based on the pre-scaled brake commands and / or the drive commands 102, 112 and the yaw rate error-based scalar calculation 122, and the scalar value or the reduction value 124. The modified brake-to-steer brake instructions and / or the brake-to-steer drive instructions 126 may be communicated to a range controller (not shown) to send the modified brake instructions and / or drive instructions to a brake actuator and / or a drive actuator to reduce lateral instability of a vehicle during brake-to-steer. In some variations, a modifier value may be based on, but is not limited to, a two-dimensional yaw rate error versus a speed table and / or a one-dimensional yaw rate error table and / or a single yaw rate error value and / or a two-dimensional yaw rate error versus a wheel speed table and / or a two-dimensional yaw rate error versus a yaw rate table and / or a three-dimensional table of a yaw rate error, a yaw rate and wheel speeds, and / or other numerical computations.FIG. 2 shows an illustrative variation of a block diagram of a system and method for stability indicator-based brake-to-steer lateral stability management 100. The system may use measured wheel speed signals 202 and vehicle speed 104 to calculate longitudinal tire slip ratios 204 for each corner of the vehicle. Based on the longitudinal tire slip ratios 204, stability indicators 206 a, 206 b, or 206 cmay be calculated that serve as an indication of vehicle stability. The stability indicator-based calculation 208 above may receive stability indicators 206 a, 206 b, and 206 c, and may use these alone or in combination to calculate a wheel speed-based scalar 210. The system and method may include communicating brake-to-steer brake instructions and / or brake-to-steer drive instructions 102 to the brake instruction modifier and / or the drive instruction modifier 114 in a pre-scaled state 112. A brake-to-steer brake command modifier and / or a brake-to-steer drive command modifier 114 may receive a wheel speed-based scalar 210 based on the stability indicators 206 a, 206 b, or 206 cand the stability indicator-based scalar calculation 208 determined via a stability indicator command scaling algorithm 110. The brake-to-steer brake command modifier or the brake-to-steer drive command modifier 114 may determine the modified brake-to-steer brake commands and / or the brake-to-steer drive commands 126, based on the pre-scaled brake commands and / or drive commands 102, 112 and a scalar calculation 208 and the scalar value or the reduction value 210. The modified brake-to-steer brake instructions and / or the brake-to-steer drive instructions 126 may be communicated to a range controller (not shown) to send the modified brake instructions and / or drive instructions to a brake actuator and / or a drive actuator to reduce lateral instability of a vehicle during a brake-to-steer operation.FIG. 3 illustrates a method and system 300 that may include original brake-to-steer instructions 302 received by the decision module 304 that outputs 320 the brake-to-steer instructions or modified brake-to-steer instructions to a brake system and / or a propulsion system. A plurality of vehicle signals 306 may be received by module 308, which may calculate or receive stability indicators and output 310 these, and the vehicle signals may also be received by module 312, which compares at least one stability indicator to a stability indicator threshold. Module 312 may receive stability indicators calculated or received by module 308. The module 312 may compare the stability indicator to a stability indicator threshold, and if the stability indicator is outside the limit of the stability indicator threshold range, the module 312 may output 314 data regarding the stability indicator and the stability indicator threshold that may be received by the module 316. The module 316 may calculate a brake command modulation or a drive command modulation and may output 318 the calculated modulation to the module 304. The module 304 may receive the calculated modulation and modifies at least one received brake or drive command using the calculated modulations to provide at least one modified brake or drive command and outputs 320 at least one modified brake or drive command to at least one brake system or drive system.Some variations may include a computer readable medium that may be non-transitory having written instructions stored thereon and executable by an electronic processor to provide functionality including: calculating or receiving a vehicle stability indicator, comparing the stability indicator to a stability indicator threshold, and if the stability indicator is beyond / outside the limit of the stability indicator threshold range, calculating a modulation of at least one brake-to-steer brake instruction and / or brake-to-steer drive instruction to provide at least one modified brake instruction or drive instruction and to output at least one brake instruction or drive instruction. The modified brake instructions and / or drive instructions may be received by at least one brake system or drive system.FIG. 4 illustrates a vehicle having steer-by-wire functionality and a system for carrying out a method therein. FIG. 5 illustrates a vehicle having a mechanical steering link and a system for carrying out the method described herein. The components and systems of FIGS. 4 and 5 may be interchanged provided that the vehicle in FIG. 4 maintains steer-by-wire functionality and the vehicle in FIG. 5 maintains the mechanical steering connection.FIG. 4 shows an illustrative variation of various portions of a vehicle equipped with hardware sufficient to perform at least some of the systems and methods described herein. All sensors shown in the illustrative variation are illustrative, such that the sensed inputs may come from different other vehicle locations or vehicle sensors, provided they provide a similar sensing function. A vehicle 750 may include a controller 712 constructed and arranged to provide brake-to-steer functionality in the vehicle 750. The controller 712 may be in operable communication with a steer-by-wire system 715 and an electronic brake system 716. The steer-by-wire system 715 may be comprised of a hand wheel actuator 746 and a road wheel actuator 714. The steer-by-wire system 715 may be constructed and arranged to rotate at least one road wheel 742. The electronic brake system 716 may apply a braking force or torque 720 to certain suitable road wheels 742. A rider may employ a hand wheel 744 including at least one hand wheel actuator 746 to provide a rider input 734 for lateral movement and to send steering instructions to the steer-by-wire system 715 and a road wheel actuator 714. The electronic brake system 716 may be in operable communication with the controller 712 and a driver brake input system 752, such as a brake pedal system, to receive a driver brake input. According to some variations, the hand wheel actuator 746 may be in operable communication with the controller 712, the steer-by-wire road wheel actuator 714, or the electronic brake system 716. In some variations, the hand wheel actuator 746 may be separate from or in a fault condition 748 or may not be able to communicate with the steer-by-wire road wheel actuator 714. In such a variation, the hand wheel actuator 746 may communicate steering instructions to the controller 712, which may receive health status information of a steer-by-wire system 715. When the controller 712 has received steer-by-wire system 715 information indicative of a failure 748 of the steer-by-wire system 715 or a failure of a road wheel actuator 714, the controller 712 may convert steering instructions from the hand wheel actuator 746 into braking force instructions or braking torque instructions to be communicated to the electronic brake system 716. The electronic brake system 716 may apply a braking force or torque 720 to particular road wheels 742 to cause lateral movement of the vehicle as input 734 by the driver via the hand wheel 744. The controller 712 may also send drive instructions to a drive system 708. The controller 712 and any other controller, for example the controller 768, may be provided to perform one or more of the functions described herein and may include a processor 760 and a memory 762, wherein the instructions 764 stored in the memory 762 are executable by the processor 760.Referring now to FIG. 5, an illustrative variation of a vehicle equipped with hardware that enables the vehicle to perform at least some of the methods described herein is shown. All sensors shown in the illustrative variation are illustrative, such that the sensed inputs may come from different other vehicle locations or vehicle sensors, provided they provide a similar sensing function. A vehicle 801 may be equipped with road wheels 802 and a hand wheel 803 for rotating the road wheels 802 via a pinion 804 that meshes with a rack 805 that is constructed and arranged to rotate the road wheels 802. In the illustrative variation shown, the hand wheel 803 may be equipped with a hand wheel torque sensor 806 and a hand wheel angle sensor 807, such that any rotation of the hand wheel may generate sensor data that may be communicated to or invoked by a controller 808. The controller 808 may provide all other functionality described herein including brake-to-steer, brake-to-steer stability, steer-by-wire control, propulsion control, brake control, vehicle system control, or one or more other controllers may be provided to perform the same. Although the controller 808 is shown onboard the vehicle in this illustrative variation, the controller may also be located at a location remote from the vehicle with the sensors or vehicle wirelessly communicating therewith. The pinion 804 may be equipped with a pinion torque sensor 809 such that any rotation of the pinion may be monitored by or communicated to the controller 808 and used by the methods described herein. In the illustrative variation shown, the rack 805 may be equipped with a rack force sensor 810 such that any rack forces may be observed or communicated to the controller 808 during driving and used by the methods described herein. The vehicle may include a steering shaft 814 that connects the steering wheel or steering interface 803 to a pinion 804. An electric power steering assist device or hydraulic power steering device 836 may be connected to the shaft 814 to assist the driver in steering the road wheels of the vehicle to reduce the force or torque that the driver(s) would have to apply with respect to the steering wheel or steering interface 803 if the power steering device 836 were not present. As shown in this illustrative variation, the road wheels 802 may be equipped with road wheel sensors such that any road wheel data detected during driving may be observed by or communicated to the controller 808 and used by the methods described herein. Additionally, in the illustrative variation, brakes 812 are shown being located proximate the road wheels 802. The controller 808 and any other controller, for example the controller 818, may be provided to perform one or more functions described herein and may include a processor 820 and a memory 822, wherein the instructions 824 stored in the memory 822 are executable by the processor 820 to determine whether the hand wheel angle sensor 807 or the pinion 804, the rack 805, the pinion sensor 809, or the rack sensor 810 have failed. Moreover, instructions 824 stored in memory 822 are executable by processor 820 to perform any of the methods or achieve any functionality described herein.Modules and controllers described herein may include software, hardware, or a computing device having a non-transitory computer readable medium, such as, but not limited to, a memory having instructions stored therein and a processor for executing the instructions to implement the operations, steps, methods, and functionalities described herein. Multiple modules and controllers and their associated operations, steps, methods, and functionalities may be included in or achieved by one or more computing devices.The following description of variations is merely illustrative of components, elements, operations, products, and methods that are considered to be within the scope of the invention and is in no way intended to limit such scope by what is specifically disclosed or not expressly stated. The components, elements, operations, products, and methods described herein may be combined and rearranged other than what is expressly described herein, and are still considered to be within the scope of the invention.Variation 1 may include a computer readable medium comprising: a non-transitory memory having instructions stored thereon and executable by an electronic processor, the instructions, when executed by the electronic processor, implementing the functions of: receiving or calculating at least one stability indicator, wherein the received at least one stability indicator comprises a vehicle speed and / or a lateral acceleration and / or a vehicle yaw rate and / or a steering wheel angle and / or a steering wheel torque and / or a speed and / or a wheel speed and / or a yaw rate, and wherein the calculating at least one stability indicator comprises calculating a yaw rate; calculating an estimated yaw rate based on the vehicle speed and / or the wheel speed and / or the lateral acceleration; calculating a yaw rate error based on the estimated yaw rate and / or the measured vehicle yaw rate; determining a brake command modifier value based on the measured vehicle speed and / or the yaw rate error; modifying at least one brake command based on the brake command modifier value to provide a modified brake command; and communicating the modified brake command to a brake-to-steer system.Variation 2 may include a computer readable medium according to Variation 1, and may further include determining a modified drive modifier value based on a measured vehicle speed and / or the yaw rate error; and modifying at least one drive command based on the drive command modifier value.Variation 3 may include a computer readable medium according to variation 1, wherein the brake command modifier value is a scalar value.Variation 4 may include a computer readable medium according to Variation 2, wherein the drive instruction modifier value is a scalar value.Variation 5 may include a computer readable medium according to variation 1, wherein the brake command modifier value is a reducer value.Variation 6 may include a computer readable medium according to Variation 2, wherein the drive instruction modifier value is a reduction value.Variation 7 may include a computer readable medium according to Variation 1, wherein determining a braking instruction modifier value based on the measured vehicle speed and / or the yaw rate error comprises using: a two-dimensional yaw rate error versus a speed table and / or a one-dimensional yaw rate error table and / or a single yaw rate error value and / or a two-dimensional yaw rate error versus a wheel speed table and / or a two-dimensional yaw rate error versus a yaw rate table and / or a three-dimensional table of a yaw rate error, a yaw rate, and wheel speeds and / or other numerical computations.Variation 8 may include a computer readable medium according to Variation 1, and may further include communicating brake-to-steer instructions in a pre-scaled state to a brake-to-steer instruction modifier prior to modifying at least one brake instruction based on the brake instruction modifier value.Variation 9 may include a computer program product comprising instructions executable by an electronic processor to perform acts including: determining that a steering maneuver is being performed in a vehicle; receiving vehicle data including vehicle feedback information and / or actuator feedback information; calculating a stability indicator threshold; calculating a stability indicator; determining a difference between the stability indicator and the stability indicator threshold; comparing the stability indicator threshold and the stability indicator; and based on the comparison, generating at least one change in a brake-to-steering actuator instruction.Variation 10 may include a computer readable medium according to variation 9 and may further include determining a modified brake-to-steer instruction modifier value based on the comparison, and wherein generating at least one change of a brake-to-steer actuator instruction is based on the brake-to-steer instruction modifier.Variation 11 may include a computer readable medium according to variation 9 and may further include generating at least one change in a drive instruction based on the comparison.Variation 12 may include a computer readable medium according to Variation 11 and may further include determining a modified drive instruction modifier value based on the comparison, wherein the generating of at least one change with respect to a drive instruction is based on a drive instruction modifier value.Variation 13 may include a computer readable medium according to variation 10, wherein the brake command modifier value is a scalar value.Variation 14 may include a computer readable medium according to variation 12 wherein the drive instruction modifier value is a scalar value.Variation 15 may include a computer readable medium according to variation 10, wherein the brake command modifier value is a reducer value.Variation 16 may include a computer readable medium according to variation 12, wherein the drive instruction modifier value is a reducer value.Variation 17 may include a computer readable medium according to Variation 10, wherein determining a braking instruction modifier value based on the comparison includes using: a two-dimensional yaw rate error versus a speed table and / or a one-dimensional yaw rate error table and / or a single yaw rate error value and / or a two-dimensional yaw rate error versus a wheel speed table and / or a two-dimensional yaw rate error versus a yaw rate table and / or a three-dimensional table of a yaw rate error, a yaw rate, and wheel speeds; or other numerical computations.Variation 18 may include a computer readable medium according to variation 9, and may further include communicating brake-to-steer instructions in a pre-scaled state to a brake-to-steer instruction modifier prior to modifying at least one brake instruction based on the brake instruction modifier value.Variation 19 may include a computer readable medium, which may be non-transitory, having written instructions stored thereon and executable by an electronic processor to provide functionality including: determining whether a brake-to-steer system is steering the vehicle, and if so, calculating or receiving a vehicle stability indicator, comparing the stability indicator to a stability indicator threshold, and if the stability indicator is beyond the limit of the stability indicator threshold range, calculating a modulation of a brake command and / or a drive command to provide a modified brake-to-steer brake command or a brake-to-steer drive command, and outputting the modified brake-to-steer brake command or the brake-to-steer drive command.Variation 20 may include a computer readable medium according to variation 19, wherein the calculating a modulation of a brake command and / or drive command is based on a measured vehicle speed and / or yaw rate error; and wherein the modified brake-to-steer commands is based on a brake command modifier value or a drive command modifier value.Variation 21 may include a computer readable medium according to variation 20, wherein the brake command modifier value is a scalar value.Variation 22 may include a computer readable medium according to variation 20, wherein the drive instruction modifier value is a scalar value.Variation 23 may include a computer readable medium according to variation 20, wherein the brake command modifier value is a reducer value.Variation 24 may include a computer readable medium according to Variation 20, wherein the drive instruction modifier value is a reducer value.Variation 25 may include a computer readable medium according to variation 20, wherein the braking instruction modifier value based on the measured vehicle speed and / or the yaw rate error includes using: a two-dimensional yaw rate error versus a speed table and / or a one-dimensional yaw rate error table and / or a single yaw rate error value and / or a two-dimensional yaw rate error versus a wheel speed table and / or a two-dimensional yaw rate error versus a yaw rate table and / or a three-dimensional table of a yaw rate error, a yaw rate, and wheel speeds and / or other numerical computations.Variation 26 may include a computer readable medium according to variation 20, and may further include communicating brake-to-steer instructions in a pre-scaled state to a brake-to-steer instruction modifier prior to providing a modified brake instruction based on the brake instruction modifier value.Variation 27 may include a method comprising: receiving or calculating at least one stability indicator, wherein the received at least one stability indicator comprises a vehicle speed and / or a lateral acceleration and / or a vehicle yaw rate and / or a steering wheel angle and / or a steering wheel torque and / or a speed and / or a wheel speed and / or a yaw rate, and wherein the calculating at least one stability indicator comprises calculating a yaw rate; calculating an estimated yaw rate based on the vehicle speed and / or the wheel speed and / or the lateral acceleration; calculating a yaw rate error based on the estimated yaw rate and / or the measured vehicle yaw rate; determining a braking instruction modifier value based on the measured vehicle speed and / or the yaw rate error; modifying at least one brake command based on the brake command modifier value to provide a modified brake command; and communicating the modified brake command to a brake-to-steer system.Variation 28 may include a method according to variation 27 and may further include determining a modified drive command modifier value based on a measured vehicle speed and / or yaw rate error; and modifying at least one drive command based on the drive command modifier value.Variation 29 may include a method according to variation 27, wherein the brake command modifier value is a scalar value.Variation 30 may include a method as set forth in variation 28, wherein the drive instruction modifier value is a scalar value.Variation 31 may include a method as set forth in variation 27, wherein the brake command modifier value is a reduction value.Variation 32 may include a method as set forth in variation 28, wherein the drive command modifier value is a reducer value.Variation 33 may include a method according to variation 27, wherein determining a braking instruction modifier value based on the measured vehicle speed and / or the yaw rate error includes using: a two-dimensional yaw rate error versus a speed table and / or a one-dimensional yaw rate error table and / or a single yaw rate error value and / or a two-dimensional yaw rate error versus a wheel speed table and / or a two-dimensional yaw rate error versus a yaw rate table and / or a three-dimensional table of a yaw rate error, a yaw rate, and wheel speeds and / or other numerical computations.Variation 34 may include a method according to variation 27 and may further include communicating brake-to-steer instructions in a pre-scaled state to a brake-to-steer instruction modifier prior to modifying at least one brake instruction based on the brake instruction modifier value.Variation 35 may include a method comprising: determining whether a brake-to-steer system is steering a vehicle, and if so, calculating or receiving a vehicle stability indicator, comparing the stability indicator to a stability indicator threshold, and if the stability indicator is beyond the limit of the stability indicator threshold range, calculating a modulation of brake commands and / or drive commands to provide a modified brake-to-steer brake command and / or brake-to-steer drive command, and outputting the modified brake-to-steer brake command or the brake-to-steer drive command.Variation 36 may include a method according to variation 35 and may further include receiving the output modified brake command by a brake system or the output modified drive command by a drive system.Variation 37 may include a method according to variation 35, wherein calculating a modulation of a braking command and / or drive command is based on a measured vehicle speed and / or yaw rate error; and wherein the modified braking command and / or drive command is based on a braking command modifier value or a drive command modifier value.Variation 38 may include a method as set forth in variation 37, wherein the brake command modifier value is a scalar value.Variation 39 may include a method as set forth in variation 37, wherein the drive instruction modifier value is a scalar value.Variation 40 may include a method as set forth in variation 37, wherein the brake command modifier value is a reduction value.Variation 41 may include a method as set forth in Variation 37, wherein the drive instruction modifier value is a reduction value.Variation 42 may include a method according to variation 37, wherein the braking instruction modifier value based on the measured vehicle speed and / or the yaw rate error includes using: a two-dimensional yaw rate error versus a speed table and / or a one-dimensional yaw rate error table and / or a single yaw rate error value and / or a two-dimensional yaw rate error versus a speed table and / or a two-dimensional yaw rate error versus a yaw rate table and / or a three-dimensional table of a yaw rate error, a yaw rate, and wheel speeds and / or other numerical computations.Variation 43 may include a method according to variation 37 and may further include communicating brake-to-steer instructions in a pre-scaled state to a brake-to-steer instruction modifier prior to providing a modified brake instruction based on the brake instruction modifier value.Variation 44 may include a method as set forth in variation 35, wherein the calculated modulation is a scalar value.Variation 45 may include a method including reducing the potential for loss of vehicle control by modifying a brake-to-steer drive command and / or a brake-to-steer drive command based on a number of calculated, measured, or observed stability indicators.Variation 46 may include a method according to variation 45 and may further include comparing the stability indicator to a stability indicator threshold, and if the stability indicator is beyond the limit of the stability indicator threshold range, calculating a modulation of brake commands and / or drive commands to provide a modified brake-to-steer brake command and / or brake-to-steer drive command, and outputting the modified brake-to-steer brake command and / or brake-to-steer drive command.Variation 47 may include a method according to variation 46, and may further include receiving the output modified brake command by a brake system or the output modified drive command by a drive system.Variation 48 may include a method according to variation 46, wherein calculating a modulation of a braking command and / or drive command is based on a measured vehicle speed and / or yaw rate error; and wherein the modified braking command and / or drive command is based on a braking command modifier value or a drive command modifier value.Variation 49 may include a method as set forth in variation 48, wherein the brake command modifier value is a scalar value.Variation 50 may include a method as set forth in variation 48, wherein the drive instruction modifier value is a scalar value.Variation 51 may include a method as set forth in variation 48, wherein the brake command modifier value is a reduction value.Variation 52 may include a method as set forth in variation 48, wherein the drive command modifier value is a reducer value.Variation 53 may include a method according to variation 48, wherein the braking instruction modifier value based on the measured vehicle speed and / or the yaw rate error includes using: a two-dimensional yaw rate error versus a speed table and / or a one-dimensional yaw rate error table and / or a single yaw rate error value and / or a two-dimensional yaw rate error versus a speed table and / or a two-dimensional yaw rate error versus a yaw rate table and / or a three-dimensional table of a yaw rate error, a yaw rate, and wheel speeds and / or other numerical computations.Variation 54 may include a method according to variation 48 and may further include communicating brake-to-steer instructions in a pre-scaled state to a brake-to-steer instruction modifier prior to providing a modified brake instruction based on the brake instruction modifier value.Variation 55 may include a method as set forth in variation 46, wherein the calculated modulation is a scalar value.Variation 56 may include a non-transitory computer readable medium having written instructions stored thereon and executable by an electronic processor to provide functionality comprising: receiving wheel speed data and vehicle speed data and calculating stability indicators using the wheel speed data and the speed data; calculating a stability indicator-based scalar using at least one of the stability indicators; communicating a brake-to-steer brake instruction or a brake-to-steer drive instruction in a pre-scaled state to a brake instruction modifier and / or a drive instruction modifier; communicating the stability indicator-based scalar to a brake-to-steer brake command modifier and / or a brake-to-steer drive command modifier and generating a modified brake-to-steer brake command or a modified brake-to-steer drive command.Variation 57 may include a non-transitory computer readable medium according to variation 56 and may further include calculating wheel slip ratios for each wheel at the corners of a vehicle using the wheel speed data and vehicle speed data; wherein calculating the stability indicators includes using the wheel slip ratios.Variation 58 may include a non-transitory computer readable medium as recited in variation 56, wherein the functionality further includes communicating the brake-to-steer brake command and / or a drive command in a pre-scaled state or communicating a modified brake-to-steer brake command and / or a modified drive command to a range controller to reduce lateral instability of a vehicle during a brake-to-steer operation.Variation 59 may include a non-transitory computer readable medium according to variation 56, wherein the brake command modifier value is a scalar value.Variation 60 may include a non-transitory computer readable medium according to variation 56, wherein the instruction modifier generates a drive instruction modifier value that is a scalar value.Variation 61 may include a non-transitory computer readable medium according to variation 56, wherein the instruction modifier generates a brake instruction modifier value that is a reduction value.Variation 62 may include a non-transitory computer readable medium according to variation 56, wherein the instruction modifier generates a drive instruction modifier value that is a reduction value.The above-described selected variations within the scope of the invention are merely illustrative in nature, so variations or variations thereof are not to be regarded as a departure from the spirit and scope of the invention.List of reference characters100 Stability indicator-based brake-to-steering lateral stability management 102 Brake-to-steering brake instructions, brake-to-steering drive instructions 104 Vehicle speed 106 Lateral acceleration 108 Vehicle yaw rate 110 Stability indicator-based instruction scaling algorithm 112 Prescaled state 114 Brake instruction modifier, drive instruction modifier 118 Yaw rate 120 Yaw rate error 122 Yaw rate error-based scalar calculation 124 Scalar value 126 Modified brake-to-steering brake instruction, Brake-to-steer drive instruction 202 Wheel speed signal 204 Longitudinal tire slip ratio 206 a Stability indicator 206 b Stability indicator 206 c Stability indicator 208 Stability indicator-based calculation 210 Wheel speed-based scalar 300 System 302 Original brake-to-steer instruction 304 Decision module 306 Vehicle signal 308 Module 310 Output 312 Module 314 Output 316 Module 318 Output 320 Output 708 Drive system 712 Controller 714 Road wheel actuator 715 Steer-by-wire system 716 Electronic brake system 720 Braking force, Brake torque 734 Input 742 Road wheel 744 Hand wheel 746 Hand wheel actuator 748 Fault condition 750 Vehicle 752 Driver brake input system 760 Processor 762 Memory 764 Instructions 768 Controller 801 Vehicle 802 Road wheel 803 Hand wheel 804 Pinion 805 Rack 806 Hand wheel torque sensor 807 Hand wheel angle sensor 808 Controller 809 Pinion torque sensor 810 Rack force sensor 812 Brake 814 Steering shaft 818 Controller 820 Processor 822 Memory 824 Instructions 836 Power steering apparatus

Claims

A method comprising reducing the potential for loss of vehicle control by modifying a brake-to-steer brake command and / or a brake-to-steer drive command (102) based on a number of calculated, measured, or observed stability indicators (104, 106, 108, 206a, 206b, 206c).The method of claim 1, further comprising: comparing the stability indicator (104, 106, 108, 206a, 206b, 206c) to a stability indicator threshold, and if the stability indicator (104, 106, 108, 206a, 206b, 206c) is beyond the limit of the stability indicator threshold range, then calculating a modulation of brake and / or drive instructions (102) to provide a modified brake-to-steer brake instruction and / or a modified brake-to-steer drive instruction (126), and outputting the modified brake-to-steer brake and / or the modified brake-to-steer drive instruction (126).The method of claim 2, further comprising: receiving, by a brake system (716), the output modified brake command (126) or the output modified drive command (126) by a drive system (708).The method of claim 2 or 3, wherein the calculating a modulation of a braking and / or a driving instruction (102) is based on the measured vehicle speed (104) and / or the yaw rate error (120), and wherein the modified braking or driving instruction (126) is based on a braking instruction modifier value or a driving instruction modifier value.The method of claim 4, wherein the brake command modifier value is a scalar value (124, 210).The method of claim 4 or 5, wherein the drive instruction modifier value is a scalar value (124, 210).The method according to claim 4 or 5, wherein the brake command modifier value is a reduction value.The method according to claim 4, 5 or 6, wherein the drive instruction modifier value is a reduction value.The method of any one of claims 4 to 8, wherein the braking instruction modifier value based on the measured vehicle speed (104) and / or the yaw rate error (120) comprises using: a two-dimensional yaw rate error (120) over a speed table and / or a one-dimensional yaw rate error table and / or a single yaw rate error value and / or a two-dimensional yaw rate error (120) over a wheel speed table and / or a two-dimensional yaw rate error (120) over a yaw rate table and / or a three-dimensional table of a yaw rate error (120), a yaw rate (118), and wheel speeds (202) and / or other numerical computations.The method of any of claims 4 to 9, further comprising: communicating brake-to-steer instructions (102) in a prescaled state (112) to a brake-to-steer instruction modifier prior to providing a modified brake instruction (126) based on the brake instruction modifier value.The method of any of claims 2 to 10, wherein the calculated modulation is a scalar value.

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