Methods for identifying and removing load biases correlated with a vehicle braking system

Abstract

Method for identifying and removing load biases correlated with a vehicle braking system, the method comprising the following: Provision of a vehicle steering system (16); Provision of a vehicle braking arrangement (17); Providing a first vehicle sensor (26) configured to measure vehicle brake pressure of the vehicle brake assembly (17); Providing a second vehicle sensor (26) configured to measure a vehicle property; Providing a control system (22) in conjunction with the first and second vehicle sensors (26), the vehicle brake assembly (17) and the vehicle steering system (16); Receiving first sensor data indicating the vehicle brake pressure by the controller (22) and receiving second sensor data from the second vehicle sensor (26); Calculating a total steering load by the control unit (22) from the second sensor data; Determine, by means of the control (22), whether a first condition is satisfied; if the first condition is met, generate a characterization table based on the first and second sensor data and determine a brake-induced steering load by the controller (22) from the first and second sensor data; Determining a data signal indicating a filtered steering load by comparing the total steering load with the brake-induced steering load; Generating, by means of the control (22), a control signal based on the filtered steering load data signal; and Transmission of the control signal to the vehicle steering system by the control unit (22); wherein the vehicle steering system (16) is a steer-by-wire system which includes a steering feel emulator (162) and comprises the transmission of the control signal to the vehicle steering system (16), including the transmission of the control signal to the steering feel emulator (162).

Description

[0001] The present invention relates generally to the field of vehicles, and more particularly to a method for identifying and removing load biases correlated with a vehicle braking system for steer-by-wire vehicles.

[0002] A steer-by-wire system allows the vehicle to be steered electronically, meaning without a direct mechanical connection between the steering wheel and the vehicle wheels. Steer-by-wire systems allow freedom in the design of the vehicle interior that would otherwise not be possible with a conventional steering system with a mechanical connection. Furthermore, steer-by-wire systems generally have fewer mechanical parts than conventional steering systems.

[0003] In a steer-by-wire system, measured or estimated tie rod loads can be used as a basis for simulating road feedback to the driver. The steer-by-wire system has no natural means of distinguishing between desired and undesired loads. Brake-induced steering pull is a consequence of this property.

[0004] JP 2007-38 766 A describes a vehicle control system that provides steering assistance. The steering assistance force varies depending on whether an accelerator or brake pedal is depressed. When the accelerator pedal is depressed, the steering assistance force is reduced. When the brake pedal is depressed, the steering assistance force is increased.

[0005] US 2003 / 0 019 687 A1 describes a braking system for a vehicle. An electric motor is provided between a steering wheel and a rack to dampen vibrations in the steering system and thereby reduce vibrations caused by uneven brake wear.

[0006] The object of the present invention is to gradually eliminate load distortions correlated with the brake-induced steering pull before the emulation of the operator feedback in the context of steer-by-wire systems.

[0007] According to the invention, a method for identifying and removing load biases correlated with a vehicle braking system includes the steps of providing a vehicle steering system, providing a vehicle braking assembly, providing a first vehicle sensor configured to measure a vehicle braking pressure of the vehicle braking assembly, providing a second vehicle sensor configured to measure a vehicle characteristic, and providing a controller in communication with the first and second vehicle sensors, the vehicle braking assembly, and the vehicle steering system.The method further includes receiving first sensor data indicative of vehicle brake pressure and receiving second sensor data and calculating a total steering load from the second sensor data, determining whether a first condition is met, and if the first condition is met, generating a characterization table based on the first and second sensor data, and determining a brake-induced steering load from the first and second sensor data. The method further includes determining a data signal indicative of a filtered steering load by comparing the total steering load to the brake-induced steering load, generating a control signal based on the filtered steering load data signal, and transmitting the control signal to the vehicle steering system.

[0008] According to the invention, the vehicle steering system is a steer-by-wire system with a steering feel emulator, and transmitting the control signal to the vehicle steering system includes transmitting the control signal to the steering feel emulator.

[0009] In one embodiment, the second sensor data includes one or more of a steering wheel angle, a yaw rate, and a vehicle speed.

[0010] In one embodiment, the first condition is a threshold of one or more of the steering wheel angle, the yaw rate, and the vehicle speed.

[0011] In one embodiment, generating the characterization table includes generating a matrix of the first sensor data versus the second sensor data and determining a relationship between the first sensor data and the second sensor data.

[0012] In one embodiment, the relationship between the first sensor data and the second sensor data indicates a magnitude of the brake-induced steering load.

[0013] In one embodiment, generating the characterization table further includes recording a response delay between the vehicle brake pressure and the controller receiving the second sensor data.

[0014] In one embodiment, determining the data signal indicative of the filtered steering load includes removing the brake-induced steering load from the total steering load.

[0015] The present disclosure is described herein in conjunction with the following figures, wherein like reference numerals represent like elements. Fig. 1 is a functional block diagram of a vehicle that includes, among other features, a steering system and a vehicle braking system. Fig. 2 is a functional block diagram of a control system for a vehicle steering system. Fig. 3 is a flowchart of a method for controlling a vehicle, in particular for determining a component of a steering load due to brake drag according to an embodiment. Fig. 4 is a flowchart of a method for controlling a vehicle, in particular a method for mitigating the brake pull, according to an embodiment.

[0016] It is understood that the disclosed embodiments are merely examples. The figures are not necessarily to scale; some features may be shown larger or smaller to illustrate the details of specific components. The illustrated combinations of features provide representative embodiments for typical applications.

[0017] Certain terminology may also be used in the following description for reference purposes only and is therefore not intended to be limiting. For example, terms such as "above" and "below" refer to directions in the drawings to which reference is made. Terms such as "front", "rear", "left", "right", "stern", and "side" describe the orientation and / or location of parts of components or elements within a consistent but arbitrary framework, which will be clarified by reference to the text and the associated drawings in describing the components or elements being discussed. In addition, terms such as "first", "second", "third", and so on, may be used to describe separate components. This terminology may include the words expressly mentioned above, as well as derivatives thereof and words of comparable meaning.

[0018] Brake-induced forces that affect a vehicle driver's steering feel can be caused by both random and consistent effects. Consistency effects include, but are not limited to, uneven braking characteristics on the left and driving sides of the vehicle due to brake wear or contamination, uneven brake pressure from side to side, uneven vehicle suspension and / or steering geometry, friction coefficient differences from side to side, and suspension compliance differences from side to side of the vehicle.To prevent these consistent and detectable effects from being communicated to the vehicle operator as haptic feedback via a steer-by-wire system's steering feel emulator, the embodiments described herein analyze sensor data from one or more vehicle sensors and characterize the data to determine the tie rod loads associated with these undesirable braking effects. These undesirable effects are removed from the tie rod load signal, which is then used as the basis for the feedback provided to the operator, thereby transmitting a "selectively filtered" or true cornering load signal to the operator, independent of braking effects from the suspension system, steering system, braking system, or other consistent, detectable effects.

[0019] Fig. 1 schematically illustrates a motor vehicle 10 according to the present disclosure. Although the figures shown herein represent exemplary arrangements of elements, additional (intermediate) elements, devices, functions, or components may also be present in an actual embodiment. It should be noted that Fig. 1 is merely illustrative and may not be to scale.

[0020] The vehicle 10 generally includes a body 11, a chassis 12, and wheels 15. The body 11 is disposed on the chassis 12 and substantially encloses the other components of the vehicle 10. The body 11 and the chassis 12 may together form a frame. The wheels 15 are each rotationally coupled to the chassis 12 proximate a corresponding corner of the body 11 via one or more suspension components (not shown). In some embodiments, the suspension system includes one or more linkages, shock absorbers, or other components that connect the wheels 15 to the chassis 12 and allow relative movement therebetween. The vehicle 10 is shown as a passenger car in the illustrated embodiment, however, it should be understood that any other vehicle, including motorcycles, trucks, sport utility vehicles (SUVs), or recreational vehicles (RVs), etc., may be used.

[0021] The vehicle 10 includes a propulsion system 13, which in various embodiments may include an internal combustion engine, an electric machine such as a traction motor, and / or a fuel cell propulsion system. The vehicle 10 also includes a transmission 14 configured to transfer power from the propulsion system 13 to the plurality of vehicle wheels 15 according to selectable speed ratios. According to various embodiments, the transmission 14 may include a stepped-ratio automatic transmission, a continuously variable transmission, or other suitable transmission. The vehicle 10 additionally includes a brake assembly 17 configured to provide braking torque to the vehicle wheels 15. The brake assembly 17 may, in various embodiments, include friction brakes, a regenerative braking system such as an electric machine, and / or other suitable braking systems.In some embodiments, the brake assembly 17 is an electromechanical brake assembly that includes at least a brake pad, a brake caliper, a brake rotor, and a drive unit.

[0022] The vehicle 10 also includes a steering system 16. According to the invention, the steering system 16 is a steer-by-wire system that uses electric motors to turn the wheels, sensors to determine how much steering effort to apply, and steering feel emulators to provide haptic feedback to the driver via a steering wheel (not shown) or a rack and pinion steering system.

[0023] With further reference to Fig. 1, the vehicle 10 also includes a sensing system having a plurality of sensors 26 configured to measure and collect data about one or more vehicle characteristics, including, but not limited to, vehicle speed, drawbar load, brake pressure, steering wheel angle, yaw rate, lateral acceleration, etc. In the illustrated embodiment, the sensors 26 include, but are not limited to, an accelerometer, a speed sensor, a pressure sensor, or other sensors that detect observable conditions of the vehicle or the surroundings of the vehicle and the environment, and may include RADAR, LIDAR, optical cameras, thermal cameras, ultrasonic sensors, and / or additional sensors.One or more of the sensors 26 are included in each of the steering systems 16 and the braking assembly 17; however, one or more sensors 26 are located throughout the vehicle 10 and, in some embodiments, are included in an inertial measurement unit (IMU; not shown) of the vehicle 10. The vehicle 10 also includes a plurality of actuators 30 configured to receive control commands to control steering, shifting, throttle, braking, or other aspects of the vehicle 10, as discussed in more detail below.

[0024] As shown, the vehicle 10 includes at least one controller 22. Although depicted as a single unit for illustrative purposes, the controller 22 may additionally include one or more other "control units." The controller 22 may include a microprocessor, or a central processing unit (CPU), or a graphics processing unit (GPU) that may communicate with various types of computer-readable storage devices or media 72 (see Fig. 2). Computer-readable storage devices or media 72 may include volatile and non-volatile memory in read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). KAM is persistent or non-volatile memory that can be used to store various operating variables while the CPU is powered off.Computer-readable storage devices or media 72 may be implemented using any of a number of known storage devices, such as PROMs (programmable read-only memories), EPROMs (electrical PROMs), EEPROMs (electrically erasable PROMs), flash memory, or any other electrical, magnetic, optical, or combination storage devices capable of storing data, some of which represent executable instructions used by the controller 22 in controlling the vehicle, including the brake assembly 17 and the steering system 16.

[0025] In some embodiments, the controller 22 includes a brake load mitigation system 24. The brake load mitigation system 24 receives data from the steering system 16 and the brake assembly 17 and processes and synthesizes the data to remove the brake-induced steering pull from the simulated road feedback information before the feedback is transmitted to the vehicle operator.

[0026] As in Fig. 2, the steering system 16, the braking system 17, the plurality of sensors 26, and the plurality of actuators 30 are in electronic communication with the controller 22. The brake load mitigation system 24 of the controller 22 receives data, including sensor data, from the steering system 16, the braking system 17, and the plurality of sensors 26 and, using the sensor data, generates one or more control signals for controlling vehicle braking and / or vehicle steering via the plurality of actuators 30. According to the invention, one or more control signals are received from a steering feel emulator 162 of the steering system 16. The computer-readable storage devices or media 72 are in electronic communication with the controller 22 and are capable of storing data, such as a characterization table, as well as executable instructions used by the tire performance monitoring system 24 of the controller 22.

[0027] Fig. 3 illustrates a method 300 for characterizing a braking load effect. The method 300 may be used in conjunction with components of the vehicle 10, including the steering system 16, the braking system 17, the sensors 26, and the braking load mitigation system 24 of the controller 22. The method 300 may be used in conjunction with the controller 22 and the computer-readable storage devices or media 72 described herein, or by other systems connected to or separate from the vehicle. The sequence of operations of the method 300 is not limited to the Fig. 3, but may be performed in one or more different orders, or steps may be performed concurrently, as appropriate and consistent with the present disclosure.

[0028] In some embodiments, during moderate to hard braking from straight-ahead travel, the controller 22 incrementally builds a matrix of brake pressure data and tie rod load data characterized by specific vehicle threshold conditions such as steering wheel angle, lateral acceleration, yaw rate, vehicle speed, and braking deceleration, and stores this data in a vehicle characterization table accessible to the brake load mitigation system 24 for calculations to mitigate the brake pull-induced steering loads transmitted to the operator. Method 300 begins at 302 and continues at 304. At 304, the controller 22 receives sensor data signals from one or more sensors 26. The sensor data includes, for example and without limitation, data on one or more of steering wheel angle, yaw rate, vehicle speed, and brake pressure.The sensor data indicates a total steering load of the vehicle 10, which in some embodiments is due to the drawbar load. In some embodiments, the controller 22 continuously receives and monitors the data received from the sensors 26.

[0029] The controller 22 then analyzes the sensor data at 306 and compares the sensor data with enable criteria, such as threshold values ​​for steering wheel angle, yaw rate, vehicle speed, and brake pressure, to determine whether a first condition is met. To ensure that the collected sensor data truly reflects the vehicle-specific linear braking behavior, the activation criteria for steering wheel angle, yaw rate, vehicle speed, lateral acceleration, and braking deceleration are scalable and adjustable, depending, for example, on vehicle type, geometry, environmental conditions, etc., and without limitation.

[0030] If the comparison performed at 306 is negative, ie, one or more of the sensor data signals for steering wheel angle, yaw rate, vehicle speed, and brake pressure do not meet the activation criteria, method 300 returns to 304 and proceeds as described herein.

[0031] If the comparison performed at 306 is positive, meaning the sensor data signals meet or exceed the activation criteria, method 300 proceeds to 308. At 308, controller 22 starts a timer and continues receiving sensor data. In some embodiments, controller 22 records the sensor data when controller 22 receives at least two (2) seconds of continuous sensor data that meets the activation criteria. In some embodiments, controller 22 records the sensor data when the duration of receiving continuous sensor data is less than or greater than two seconds. Additionally, controller 22 supplements the steering load determined from the sensor data with each feature torque applied during the recorded time interval to determine a total steering load.

[0032] Method 300 then proceeds to 310. Due to the dynamic response of brake assembly 17, a time delay occurs between the braking event and the resulting brake-induced steering load. At 310, controller 22 shifts the steering load data relative to the measured brake pressure based on a calculated response delay. The response delay is the gross time delay between the applied brake pressure and the resulting steering load. This delay is taken into account both in generating a vehicle characterization table and in subsequently removing the brake-induced loads from a total steering load data signal transmitted to steering feel emulator 162.The response delay can be calculated using classical engineering techniques of time delay analysis, such as, for example and without limitation, cross-correlation calculates the regression coefficient between two signals for a series of proposed time delays to find the delay time that maximizes the regression coefficient.

[0033] At 312, the controller 22 adds the new data point to the vehicle characterization table created from the continuous recording of the steering load data and the measured brake pressure data. The characterization table represents the steering load compensation and the response delay shift. In some embodiments, the characterization table is stored on storage media electronically connected to or integrated with the controller 22. As discussed above, the characterization table includes data related to the first-order time constant resulting from the correlation of previously recorded brake pressure and steering load response data. In some embodiments, the characterization data includes a characterization scatter plot of steering load versus master cylinder pressure. The controller 22 applies data analysis techniques to fit a line to the recorded data.The gradient and strength of the line are used to determine the strength of a brake-induced steering load or train. In some embodiments, the last 200 calibratable braking applications are used to generate the characterization table. In other embodiments, more or fewer braking applications are used to generate the characterization data. Method 300 then proceeds to 314 and ends.

[0034] In some embodiments, method 300 runs continuously such that the steering load compensation and response delay data are continuously added to the characterization table stored in the computer-readable storage devices or medium 72.

[0035] Fig. 4 illustrates a method 400 for controlling a vehicle steering system according to one embodiment. The method 400 may be used in conjunction with components of the vehicle 10, including the steering system 16, the braking system 17, the sensors 26, and the brake-coupling system 24 of the controller 22. The method 400 may be used in conjunction with the controller 22 and the computer-readable storage devices or media 72 described herein, or by other systems connected to or disconnected from the vehicle, according to exemplary embodiments. The sequence of operations of the method 400 is not limited to the Fig. 4, but may be performed in one or more different orders, or steps may be performed concurrently, as appropriate and consistent with the present disclosure.

[0036] The steps of method 400 illustrate how the controller 22 applies the steering load compensation and response delay adjustment data collected and stored during performance of method 300 to remove the brake-induced steering load or extract it from the overall steering load road feedback information before providing the feedback to the vehicle operator. In some embodiments, one or more steps of method 400 are performed concurrently with one or more of the steps of method 300. In some embodiments, one or more steps of method 400 are performed subsequent to one or more of the steps of method 300.

[0037] Method 400 begins at 402 and continues at 404. At 404, controller 22 determines whether the activation criteria for the sensor data relating to steering wheel angle, vehicle speed, brake pressure, and yaw rate are met, as in step 308 in method 300. If the determination made at 404 is negative, ie, the activation criteria are not met, method 400 returns to 402 and proceeds as described herein.

[0038] If the determination made at 404 is positive, ie, the activation criteria for the sensor data are met, method 400 proceeds to 406. At 406, controller 22 determines the steering load associated with the current braking application. Controller 22 accesses and analyzes the steering load compensation and response delay offset data stored in the characterization table (as explained above with respect to method 300) to determine the component of the total steering load expected due to the brake pressure, ie, a brake-induced steering load.

[0039] Next, at 408, the controller 22 removes the brake-induced steering load component obtained from the characterization table and determined at 406 from the total steering load to obtain a filtered steering load data signal. In some embodiments, the controller 22 also applies a phase delay to the filtered steering load data signal based on the learned response delay determined at step 310 of the method 300. At 408, the controller 22 also generates a control signal based on the filtered steering load data signal. The control signal is transmitted to the steering feel emulator 162 of the steering system 16 so that the emulator 162 provides the driver with a more accurate steering feel, or "selectively filtered," road load signal. The method 400 then proceeds to step 410 and ends.

[0040] In some embodiments, both methods 300 and 400 run continuously and concurrently. In other embodiments, one or more steps of method 300 are performed before one or more steps of method 400.

Claims

[1] A method for identifying and removing load biases correlated with a vehicle braking system, the method comprising: Providing a vehicle steering system (16); Providing a vehicle brake assembly (17); Providing a first vehicle sensor (26) configured to measure a vehicle brake pressure of the vehicle brake assembly (17); Providing a second vehicle sensor (26) configured to measure a vehicle characteristic; Providing a controller (22) in communication with the first and second vehicle sensors (26), the vehicle brake assembly (17) and the vehicle steering system (16); Receiving first sensor data indicative of the vehicle brake pressure by the controller (22) and receiving second sensor data from the second vehicle sensor (26); Calculating a total steering load by the controller (22) from the second sensor data; Determining, by the controller (22), whether a first condition is met; if the first condition is met, generating a characterization table based on the first and second sensor data and determining a brake-induced steering load by the controller (22) from the first and second sensor data; Determining a data signal indicative of a filtered steering load by comparing the total steering load with the brake-induced steering load; generating, by the controller (22), a control signal based on the filtered steering load data signal; and Transmitting the control signal to the vehicle steering system by the controller (22); wherein the vehicle steering system (16) is a steer-by-wire system including a steering feel emulator (162) and comprising transmitting the control signal to the vehicle steering system (16), comprising transmitting the control signal to the steering feel emulator (162). [2] The method of claim 1, wherein the second sensor data includes one or more of a steering wheel angle, a yaw rate, and a vehicle speed. [3] The method of claim 2, wherein the first condition is a threshold of one or more of the steering wheel angle, the yaw rate, and the vehicle speed. [4] The method of claim 1, wherein generating the characterization table includes generating a matrix of the first sensor data versus the second sensor data and determining a relationship between the first sensor data and the second sensor data. [5] The method of claim 4, wherein the relationship between the first sensor data and the second sensor data indicates a magnitude of the brake-induced steering load. [6] The method of claim 4, wherein generating the characterization table further includes recording a response delay between the vehicle brake pressure and the controller (22) receiving the second sensor data. [7] The method of claim 1, wherein determining the data signal indicative of the filtered steering load includes removing the brake-induced steering load from the total steering load.

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