Method and system for friction-aware collision avoidance

Abstract

A method of controlling a vehicle includes detecting an object along a path of the vehicle and within a predetermined distance from the vehicle, in response to detecting the object along the path of the vehicle and within the predetermined distance from the vehicle, determining a coefficient of friction between a road and a tire of the vehicle in real time, and command the vehicle to perform a control action in response to determining the coefficient of friction between the road and the tires of the vehicle.

Description

Technical Field

[0001] The present disclosure relates to a method and system for controlling a vehicle. More specifically, the present disclosure relates to a method and system for friction-aware collision avoidance. Background Art

[0002] This introduction generally presents the context of the present disclosure. To the extent described in this introduction, the work of the presently named inventors and aspects of the description that may not qualify as prior art at the time of filing are neither expressly nor impliedly admitted to be prior art against the present disclosure.

[0003] The motion of a vehicle may be affected by the friction between the road and the vehicle's tires. Therefore, it is useful to know the coefficient of friction between the road surface and the vehicle's tires. In addition, the friction between the road and the vehicle's tires needs to be taken into account when controlling the motion of the vehicle. Summary of the invention

[0004] The present disclosure describes a method for friction-aware collision avoidance. In one aspect of the present disclosure, the method includes detecting an object along a path of a vehicle and within a predetermined distance from the vehicle, determining in real time a coefficient of friction between a road and a tire of the vehicle in response to detecting the object along the path of the vehicle and within a predetermined distance from the vehicle, and commanding the vehicle to perform a control action in response to determining the coefficient of friction between the road and the tires of the vehicle. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the method. The method described in this paragraph improves vehicle technology by utilizing the coefficient of friction between the road and the tires of the vehicle to avoid collision with objects.

[0005] Implementations may include one or more of the following features. The method may include applying a braking load to the wheels of the vehicle, monitoring the movement of the vehicle (e.g., longitudinal deceleration, vehicle speed, and / or GNSS speed) while applying the braking load to the wheels of the vehicle, and determining in real time a coefficient of friction between a road and tires of the vehicle based on the movement of the vehicle under the braking load. The control action may be to continuously apply a braking load to the wheels of the vehicle in response to determining that the coefficient of friction between the road and the tires of the vehicle is less than a predetermined friction threshold. Alternatively or additionally, the control action may be to steer the vehicle to avoid an object along a path of the vehicle in response to determining that the coefficient of friction between the road and the tires of the vehicle is equal to or greater than a predetermined friction threshold. The steering path has a radius of curvature. The method may include a radius of curvature of the steering path. The radius of curvature of the steering path may be based on the coefficient of friction between the tires and the road. The method may include determining a time of collision with an object along a path of the vehicle and within a predetermined distance from the vehicle; determining a last time to determine friction; determining a last time to steer the vehicle to avoid the object along the path of the vehicle; determining the sum of the last time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle; and comparing the time of collision with the object along the path of the vehicle to the sum of the last time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle to determine whether the time of collision with the object along the path of the vehicle is greater than the sum of the last time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle. The method may include determining a last time to brake to avoid the object along the path of the vehicle in response to determining that the time of collision with the object along the path of the vehicle is greater than the sum of the last time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle. The method may include determining a last time to brake to avoid the object along the path of the vehicle in response to determining that the time of collision with the object along the path of the vehicle is greater than the sum of the last time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle and the sum of the time to determine friction. Additionally, the method may include comparing a time to collision with an object along the path of the vehicle to a sum of a last time to brake to avoid the object along the path of the vehicle and a time to determine friction, and in response to determining that the time to collision with the object along the path of the vehicle is greater than a sum of a last time to determine friction and a last time to steer the vehicle to avoid the object along the path of the vehicle, determining whether the time to collision is less than a sum of a last time to brake to avoid the object along the path of the vehicle and a time to determine friction. The coefficient of friction between the road and the tires of the vehicle may be determined solely based on: (a) detecting an object along the path of the vehicle and within a predetermined distance from the vehicle; and (b) determining that the time to collision is less than a sum of a last time to brake to avoid the object along the path of the vehicle and a time to determine friction.The method may include, in response to determining that the coefficient of friction between the road and the tires of the vehicle is equal to or greater than a predetermined friction threshold, determining an updated last time to steer to avoid an object along the path of the vehicle based on the coefficient of friction between the road and the tires of the vehicle, and comparing the time of collision with the object along the path of the vehicle with the updated last time to steer to avoid the object along the path of the vehicle to determine whether the time of collision with the object along the path of the vehicle is greater than the updated last time to steer to avoid the object along the path of the vehicle. The vehicle may be commanded to perform a control action only in response to determining that the time of collision with the object along the path of the vehicle is greater than the updated last time to steer to avoid the object along the path of the vehicle. The control action may be to steer the vehicle to avoid the object along the path of the vehicle in response to determining that the coefficient of friction between the road and the tires of the vehicle is equal to or greater than the predetermined friction threshold. The control action may include commanding a display of the vehicle to display an alert, such as "hold brake" and / or "do not steer". For example, the display 29 may issue an alert (e.g., "hold brake" and / or "do not steer") to the driver. Insufficient road friction may be used as a condition to inhibit prompting or "nudging" to suggest that the driver attempt evasive steering (e.g., alarm, vibration, screen message, HUD alert, etc.). Insufficient road friction may be used as a condition to inhibit evasive steering assistance that is engaged after the driver initiates steering. Implementations of the described techniques may include hardware, methods or processes, or computer software on a computer-accessible medium.

[0006] The present disclosure also describes a system including a sensor and a controller in communication with the sensor. The controller is programmed to perform the above method. The present disclosure also describes a tangible, non-transitory machine-readable medium including machine-readable instructions that, when executed by a processor, cause the processor to perform the above method.

[0007] Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter.It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

[0008] The above features and advantages and other features and advantages of the presently disclosed systems and methods will become apparent from the detailed description, including the claims and exemplary embodiments, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure will be more fully understood from the detailed description and accompanying drawings, in which:

[0010] Figure 1 is a block diagram of the vehicle;

[0011] Figure 2 is a flow chart of a method for friction-aware collision avoidance; and

[0012] Figure 3 is a schematic diagram of a vehicle approaching an object. DETAILED DESCRIPTION

[0013] Reference will now be made in detail to several examples of the present disclosure, which are illustrated in the accompanying drawings. Whenever possible, the same or similar reference numerals are used in the drawings and the description to represent the same or similar components or steps.

[0014] refer to Figure 1 , the vehicle 10 is configured to travel on a road 39 and generally includes a chassis 12, a body 14, wheels 15, front tires and rear tires 17 and may be referred to as a vehicle system. In the depicted embodiment, the vehicle 10 includes two front tires 17a and two rear tires 17b. The body 14 is arranged on the chassis 12 and substantially surrounds the components of the vehicle 10. The body 14 and the chassis 12 may together form a frame. The wheels 15 are each rotationally coupled to the chassis 12 near the respective corners of the body 14. Each tire 17 is coupled to one of the wheels 15. The vehicle 10 includes a front axle 19 coupled to the front tires 17a and a rear axle 25 coupled to the rear tires 17b.

[0015] The vehicle 10 may be an autonomous vehicle, and the control system 98 is incorporated into the vehicle 10. The vehicle 10 is, for example, a vehicle that is automatically controlled to transport passengers from one location to another. The vehicle 10 is depicted as a pickup truck in the illustrated embodiment, but it should be understood that other vehicles such as trucks, sedans, coupes, sport utility vehicles (SUVs), recreational vehicles (RVs), etc. may also be used. In an embodiment, the vehicle 10 may include a so-called Level 2, Level 3, Level 4, or Level 5 driving automation system. Level 4 systems represent "high automation" and refer to the specific driving mode performance of the autonomous driving system for various aspects of dynamic driving tasks, even if the human driver does not respond appropriately to the intervention request. Level 5 systems represent "full automation" and refer to the full-time performance of the autonomous driving system for various aspects of dynamic driving tasks under multiple road and environmental conditions that can be managed by human drivers. In Level 3 vehicles, the system 98 performs the entire dynamic driving task (DDT) in the area it is designed to perform. In Level 2 vehicles, the system provides steering, braking / acceleration support, lane centering, and adaptive cruise control. However, even when these systems are activated, the vehicle operator at the steering wheel must steer and constantly supervise the automated features.

[0016] As shown, the vehicle 10 generally includes a propulsion system 20, a transmission system 22, a steering system 24, a braking system 26, a sensor system 28, an actuator system 30, at least one data storage device 32, at least one controller 34, and a communication system 36. The steering system 24 is a wire control steering system or an electronic power steering system. In various embodiments, the propulsion system 20 may include an electric motor such as a traction motor and / or a fuel cell propulsion system. The vehicle 10 may also include a battery (or battery pack) 21 electrically connected to the propulsion system 20. Therefore, the battery 21 is configured to store electrical energy and provide electrical energy to the propulsion system 20. In certain embodiments, the propulsion system 20 may include an internal combustion engine. The transmission system 22 is configured to transmit power from the propulsion system 20 to the vehicle tires 17 according to a selectable speed ratio. According to various embodiments, the transmission system 22 may include a stepped automatic transmission, a continuously variable transmission, or other suitable transmission. The braking system 26 is configured to provide braking torque to the vehicle tires 17. In various embodiments, the braking system 26 may include a friction brake, a wire control brake, a regenerative braking system (such as a motor), and / or other suitable braking systems. The steering system 24 affects the position of the vehicle tires 17 and may include a steering wheel 33. Although depicted as including a steering wheel 33 for purposes of illustration, in some embodiments contemplated within the scope of the present disclosure, the steering system 24 may not include a steering wheel 33.

[0017] The sensor system 28 includes one or more sensors 40 (i.e., sensing devices) that sense observable conditions of the external environment and / or the internal environment of the vehicle 10. The sensors 40 communicate with the controller 34 and may include, but are not limited to, one or more steering wheel sensors 45, one or more radars, one or more light detection and ranging (lidar) sensors, one or more proximity sensors, one or more odometers, one or more ground penetrating radar (GPR) sensors, one or more steering angle sensors, global navigation satellite system (GNSS) transceivers (e.g., one or more global positioning system (GPS) transceivers), one or more tire pressure sensors, one or more cameras 41 (e.g., eye trackers), one or more gyroscopes, one or more accelerometers, one or more inclinometers, one or more speed sensors, one or more ultrasonic sensors, one or more inertial measurement units (IMUs), one or more night vision devices, thermal imaging sensors, and / or other sensors. Each sensor 40 is configured to generate a signal indicative of a sensed observable condition of the external environment and / or the internal environment of the vehicle 10. Because the sensor system 28 provides data to the controller 34, the sensor system 28 and its sensors 40 are considered to be information sources (or simply sources). The vehicle 10 and / or the system 98 do not include a light sensor capable of detecting light inside the vehicle 10 .

[0018] The actuator system 30 includes one or more actuators 42 that control one or more vehicle features, such as, but not limited to, the propulsion system 20, the transmission system 22, the steering system 24, and the braking system 26. The steering system 24 may include a front steering device and possibly a rear steering device. The rear steering control may be controlled by a separate controller. In various embodiments, the vehicle features may also include interior and / or exterior vehicle features, such as, but not limited to, doors, trunk, and cab features, such as, air, music, lighting, etc. The actuator 42 may be part of the steering system 24 and include one or more road wheel actuators (RWA) and hand wheel actuators (HWA).

[0019] The data storage device 32 stores data for automatically controlling the vehicle 10. In various embodiments, the data storage device 32 stores a defined map of a navigable environment. In various embodiments, the defined map may be predefined by a remote system and obtained from the remote system. For example, the defined map may be assembled by a remote system and transmitted to the vehicle 10 (wirelessly and / or in a wired manner) and stored in the data storage device 32. The data storage device 32 may be part of the controller 34, separate from the controller 34, or part of the controller 34 and part of a separate system.

[0020] The vehicle 10 may also include one or more airbags 35 in communication with the controller 34 or another controller of the vehicle 10. The airbag 35 includes an inflatable bag and is configured to transition between a stowed configuration and a deployed configuration to cushion the effects of external forces applied to the vehicle 10. The sensor 40 may include an airbag sensor (such as an IMU) configured to detect external forces and generate a signal indicating the magnitude of such external forces. The controller 34 is configured to command the airbag 35 to deploy based on signals from one or more sensors 40 (such as airbag sensors). Therefore, the controller 34 is configured to determine when the airbag 35 has been deployed.

[0021] The controller 34 includes at least one processor 44 and a non-transitory computer readable storage device or medium 46. The processor 44 can be a custom or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor of several processors associated with the controller 34, a semiconductor-based microprocessor (in the form of a microchip or chipset), a macroprocessor, a combination thereof, or generally a device for executing instructions. The computer readable storage device or medium 46 can include volatile and non-volatile storage devices such as read-only memory (ROM), random access memory (RAM), and keep alive memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operating variables when the processor 44 is powered off. The vehicle readable storage device or medium 46 can be implemented using a variety of memory devices, such as PROM (programmable read-only memory), EPROM (electrical PROM), EEPROM (electrically erasable PROM), flash memory, or other electrical, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable instructions used by the controller 34 when controlling the vehicle 10. The controller 34 of the vehicle 10 may be referred to as a vehicle controller and may be programmed to perform the method 100 described in detail below. Figure 2 ).

[0022] The instructions may include one or more separate programs, each of which includes an ordered list of executable instructions for implementing logical functions. When executed by the processor 44, the instructions receive and process signals from the sensor system 28, execute logic, calculations, methods and / or algorithms for automatically controlling components of the vehicle 10, and generate control signals to the actuator system 30 to automatically control components of the vehicle 10 based on the logic, calculations, methods and / or algorithms. Although Figure 1 , embodiments of the vehicle 10 may include multiple controllers 34 that communicate via a suitable communication medium or combination of communication mediums and cooperate to process sensor signals, execute logic, calculations, methods and / or algorithms, and generate control signals to automatically control characteristics of the vehicle 10. In various embodiments, one or more instructions of the controller 34 are included in the control system 98.

[0023] The vehicle 10 includes a user interface 23, which may be a touch screen in the dashboard. The user interface 23 may include, but is not limited to, an alarm, such as one or more speakers 27 for providing audible sounds, tactile feedback in a vehicle seat or other object, one or more displays 29, one or more microphones 31, and / or other devices suitable for providing notifications to a vehicle user of the vehicle 10. The user interface 23 is in electronic communication with a controller 34 and is configured to receive input from a vehicle occupant 11 (e.g., a vehicle driver or a vehicle passenger). For example, the user interface 23 may include a touch screen and / or buttons configured to receive input from a vehicle occupant 11. Thus, the controller 34 is configured to receive input from a user via the user interface 23. The vehicle 10 may include one or more displays 29, which are configured to display information to a vehicle occupant 11 (e.g., a vehicle operator or a passenger), and may be a head-up display (HUD).

[0024] The communication system 36 communicates with the controller 34 and is configured to wirelessly transmit information to and from other remote vehicles 48, such as, but not limited to, other vehicles ("V2V" communication), infrastructure ("V2I" communication), remote systems of a remote call center (e.g., General Motors' ON-STAR), and / or personal electronic devices, such as mobile phones. In the present disclosure, the term "remote vehicle" refers to a vehicle, such as an automobile, that is configured to send one or more signals to the vehicle 10 while not physically connected to the vehicle 10. In some embodiments, the communication system 36 is a wireless communication system configured to communicate via a wireless local area network (WLAN) using the IEEE 802.11 standard or by using cellular data communications. However, additional or alternative communication methods such as dedicated short-range communication (DSRC) channels are also considered within the scope of the present disclosure. DSRC channels refer to a one-way or two-way short-range to medium-range wireless communication channel designed specifically for automotive use and a set of corresponding protocols and standards. Thus, the communication system 36 may include one or more antennas and / or communication transceivers 37 for receiving and / or transmitting signals, such as collaborative sensing messages (CSM). The communication transceivers 37 may be considered sensors 40. The communication system 36 is configured to wirelessly transmit information between the vehicle 10 and another vehicle. In addition, the communication system 36 is configured to wirelessly transmit information between the vehicle 10 and infrastructure or other vehicles.

[0025] refer to Figure 1 and Figure 3, the system 98 is configured to avoid a collision with an object 200 along a path 202 by taking into account the friction between the tires 18 and the road 39. When a collision with the object 200 is imminent, the collision can be avoided by automatic emergency braking or automatic evasive steering. At high speeds, avoiding a collision by steering provides the driver or automated system with more reaction time margin, but such maneuvers may present other challenges if the road surface friction is low. When a collision is imminent, the system 98 estimates the surface friction and then uses the estimate to take appropriate action to avoid a collision given the road conditions. When a collision is imminent, just before a braking and steering decision is required, the surface friction can be estimated by applying a short braking pulse. The longitudinal response of the vehicle is used to estimate the friction. If the friction is low, the braking pulse is maintained and the system 98 transitions to automatic emergency braking. If the friction is sufficient, automatic evasive steering can be engaged and the system 98 can use the friction estimate as a control parameter.

[0026] refer to Figure 2 and Figure 3 , the method 100 is configured to avoid a friction-aware collision with another object 200 along a path 202 of the vehicle 10. As a non-limiting example, the object 200 may be another vehicle, a stationary building, a pedestrian, etc. The method 100 begins at box 102. At box 102, the controller 34 receives sensor data from a sensor 40 (e.g., a camera 41). The sensor data may indicate, among other things, the location and movement of objects around the vehicle 10. At box 102, the vehicle controller 34 uses the sensor data to detect an object 200 along the path 202 of the vehicle 10 and within a predetermined distance from the vehicle 10. Alternatively or additionally, the vehicle 10 may use V2V or V2I communications to detect an object 200 along the path 202 of the vehicle 10 and within a predetermined distance from the vehicle 10. Then, the method 100 continues to box 104.

[0027] At box 104, the vehicle controller 34 uses the vehicle speed and the distance from the vehicle 10 to the object 200, etc. to determine the time to collision with the object 200 (TTI). The vehicle speed of the vehicle 10 and the distance from the vehicle 10 to the object 200 can be collected by the sensor 40. The vehicle controller 34 also determines the last turn time (LTTS). LTTS is the shortest possible time that the vehicle 10 can turn and avoid collision with the object 200 before the collision. The controller 34 can also determine the time to determine friction (TTDF), which can be a predetermined amount. TTDF is the time taken to determine the coefficient of friction between the road 39 and the tire 17. As a non-limiting example, TTDF can be between 300 and 500 microseconds. Then, at box 104, the controller 34 determines the sum of LTTS plus TTDF. Next, the controller 34 compares TTI with the sum of LTTS and TTDF. If TTI is equal to or less than the sum of LTTS and TTDF, the method 100 proceeds to box 106. At box 106, the controller 34 commands the vehicle 10 to brake completely immediately and autonomously. In other words, at box 106 , the controller 34 commands the braking system 26 to immediately brake the vehicle 10 . If TTI is greater than the sum of LTTS and TTDF, the method 100 proceeds to box 108 .

[0028] At box 108, the controller 34 determines whether the last time to brake (LTTB) is to avoid the object 200 along the path of the vehicle 10. The LTTB is the shortest possible time before the collision that the vehicle 10 can brake and avoid colliding with the object 200. The LTTB can be determined using sensor data from the sensor 40, etc. For example, the LTTB can be determined using the vehicle speed of the vehicle 10, the distance from the vehicle 10 to the object 200, and / or the speed of the object 200. The controller 34 then determines the sum of the LTTB plus the TTDF. Next, the controller 34 compares the TTI with the sum of the LTTB and the TTDF. If the TTI is less than the sum of the LTTB and the TTDF, the method 100 proceeds to box 110. If the TTI is equal to or greater than the sum of the LTTB and the TTDF, the method 100 returns to box 102. At box 110, the vehicle controller 34 commands the braking system 26 to apply a braking load to the wheel 15 to determine the friction coefficient between the road 39 and the tire 17. Therefore, the initiation of the braking pulse at box 110 depends on the estimated TTI. The braking pulse can only be initiated in a time window that is less than LTTB plus buffer (i.e., TTDF) and greater than LTTS. Specifically, at box 110, the vehicle controller 34 can command the braking system 26 to apply a braking pulse (e.g., friction or regeneration) to one or more wheels 15 for a predetermined amount of time (e.g., 300 to 500 microseconds) to achieve the purpose of road friction estimation. The braking pulse can alert the driver that a potential collision is about to occur. Such braking may be accompanied by other alerts issued to the driver. For example, at this time, the controller 34 can command the user interface 23 to provide a visual and / or audible notification indicating that a collision is about to occur. For example, the display 29 can issue an alert to the driver (e.g., "hold the brake" and / or "don't turn"). Insufficient road friction can be used as a condition to prohibit prompting or "nudging" to suggest that the driver attempt to evade steering (e.g., alarm, vibration, screen message, HUD alert, etc.). Insufficient road friction can be used as a condition to prohibit engaging evasive steering assistance after the driver initiates steering. In this case, the system 98 can continue to apply braking and use automatic steering commands to stabilize the vehicle 10 instead of avoiding the object 200.

[0029] In one embodiment, evasive steering is engaged only after the driver initiates steering and assists the driver in avoiding a collision. In this embodiment, the friction force estimate can be used as a disabling prompt to advise the driver of the condition to attempt evasive steering. For example, if the estimated friction coefficient is less than a predetermined coefficient threshold, the controller 34 can command the vehicle 10 to disabling evasive steering assistance that is engaged after the driver initiates steering.

[0030] To determine the coefficient of friction between the road 39 and the tire 17, the controller 34 uses sensor data from the sensor 40 to monitor the longitudinal response (e.g., longitudinal deceleration) of the vehicle 10 while applying a braking load to the wheels 15 of the vehicle 10. Using this longitudinal response (e.g., longitudinal deceleration), the controller 34 determines (i.e., estimates) the coefficient of friction between the road 39 and the tire 17 in real time. The method 100 then continues to box 112. This friction estimate is used to decide the best collision avoidance control action (e.g., braking and / or steering). The control action can be a fully autonomous action of the vehicle 10 or an assisted action. After executing box 110, the method 100 continues to box 112.

[0031] At frame 112, the controller 34 compares the coefficient of friction between the road 39 and the tires 17 of the vehicle 10 with a predetermined friction threshold. If the coefficient of friction between the road 39 and the tires 17 of the vehicle 10 is less than the predetermined friction threshold, the method 100 continues to frame 114. At frame 113, the controller 34 commands the braking system 26 to continue to apply a braking load to the wheels 15 to avoid or mitigate a collision with the object 200. In other words, if the road friction is insufficient to perform an evasive steering maneuver, the controller 34 commands the braking system 26 to continue to apply a braking load to the wheels 15 to avoid or mitigate a collision with the object 200. The magnitude of the braking may be different from the magnitude of the braking used to detect the coefficient of friction. The term "braking load" includes braking load and / or regenerative torque. If the coefficient of friction between the road 39 and the tires 17 of the vehicle 10 is equal to or greater than the predetermined friction threshold, the method 100 proceeds to frame 116.

[0032] At box 116, the controller 34 determines an updated last turn time (ULLTS) based on the friction coefficient between the road 39 and the tires 17 of the vehicle 10 to avoid the object 200 along the path 202 of the vehicle 10. In other words, the controller 34 recalculates the LTTS. The method 100 then continues to box 118.

[0033] At block 118, the controller 34 compares the TTI to the ULTTS. If the TTI is equal to or less than the ULTTS, the method 100 proceeds to block 120. If the TTI is greater than the ULTTS, the method 100 returns to block 112.

[0034] At box 120, the controller 34 commands the steering system 24 to initiate an automatic steering maneuver to avoid the object 200 along the path 202. The classification of road friction (e.g., medium vs. high or wet vs. dry asphalt) can be used to modify the timing or shape of the evasive steering maneuver. When the road friction is lower, the evasive steering maneuver can be initiated earlier to adapt to the lower curvature path. Therefore, at box 120, the controller 34 can determine the steering path and the radius of curvature of the steering path. The radius of curvature of the steering path can be based on the friction coefficient between the tire 17 and the road 39. Continuous estimation of road friction can be used for path planning or control. For example, the estimated friction or the maximum lateral and longitudinal acceleration derived therefrom can be used as a constraint in path planning to shape the desired trajectory according to the tire limitations. In addition, the estimated friction coefficient can be used as a model parameter in model predictive control or other model / parameter-based control methods, and / or as a variable for calculating the gain of any feedback controller. In addition, the maximum lateral acceleration derived from the estimated friction coefficient can be used as a constraint in control.

[0035] Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms included in the claims. The words used in the specification are descriptive rather than restrictive, and it is understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously mentioned, the features of the various embodiments can be combined to form further embodiments of the currently disclosed system and method that may not be explicitly described or illustrated. Although various embodiments can be described as providing advantages or being superior to other embodiments or prior art implementations relative to one or more desired features, a person of ordinary skill in the art recognizes that one or more characteristics or features can be compromised to achieve the desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, applicability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described as less ideal than other embodiments or prior art implementations relative to one or more features are not outside the scope of the present disclosure and may be ideal for specific applications.

[0036] The drawings are in simplified form and are not drawn to exact scale. Directional terms such as top, bottom, left, right, up, above, above, below, below, rear, and front may be used with respect to the drawings for the purpose of convenience and clarity of description only. These directional terms and similar directional terms should not be construed as limiting the scope of the present disclosure in any way.

[0037] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments in various alternative forms may be adopted. The drawings are not necessarily drawn to scale; certain features may be magnified or minimized to show the details of specific components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but only as a representative basis for teaching those skilled in the art to adopt the currently disclosed systems and methods in different ways. As will be understood by those of ordinary skill in the art, the various features illustrated and described with reference to any of the accompanying drawings may be combined with the features illustrated in one or more other figures to produce embodiments that are not explicitly described or described. The combination of the features shown provides representative embodiments of typical applications. However, various combinations and modifications of features consistent with the teachings of the present disclosure may be required for specific applications or implementations.

[0038] Embodiments of the present disclosure may be described herein in terms of functional and / or logical block components and various processing steps. It should be understood that such block components may be implemented by multiple hardware, software and / or firmware components configured to perform specified functions. For example, embodiments of the present disclosure may employ various integrated circuit components, such as memory elements, digital signal processing elements, logic elements, lookup tables, etc., which may perform multiple functions under the control of one or more microprocessors or other control devices. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with a variety of systems, and the systems described herein are merely exemplary embodiments of the present disclosure.

[0039] For the sake of brevity, technologies related to signal processing, data fusion, signaling, control and other functional aspects of the system (as well as the various operating components of the system) may not be described in detail herein. In addition, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and / or physical connections between the various elements. It should be noted that alternative or additional functional relationships or physical connections may exist in the embodiments of the present disclosure.

[0040] This description is merely illustrative in nature and is in no way intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in many forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, as other modifications will become apparent after studying the drawings, description and appended claims.

Claims

1. A method for controlling a vehicle, comprising: detecting an object along a path of the vehicle and within a predetermined distance from the vehicle; determining, in real time, a coefficient of friction between a road and a tire of the vehicle in response to detecting the object along a path of the vehicle and within a predetermined distance from the vehicle; as well as In response to determining the coefficient of friction between the road and the tires of the vehicle, the vehicle is commanded to perform a control action.

2. The method according to claim 1, wherein: Determining in real time the coefficient of friction between the road and the tires of the vehicle comprises: applying a braking load to wheels of the vehicle; monitoring movement of the vehicle while applying the braking load to the wheels of the vehicle; and Based on the movement of the vehicle under the braking load, the coefficient of friction between the road and tires of the vehicle is determined in real time.

3. The method according to claim 2, further comprising: comparing the friction coefficient between the road and the tires of the vehicle with a predetermined friction threshold to determine whether the friction coefficient between the road and the tires of the vehicle is less than the predetermined friction threshold; as well as Wherein the control action is to continuously apply the braking load to the wheels of the vehicle in response to determining that the friction coefficient between the road and the tires of the vehicle is less than the predetermined friction threshold.

4. The method according to claim 2, further comprising: comparing the friction coefficient between the road and the tires of the vehicle with a predetermined friction threshold to determine whether the friction coefficient between the road and the tires of the vehicle is equal to or greater than the predetermined friction threshold; as well as Wherein the control action is to steer the vehicle to avoid the object along the path of the vehicle in response to determining that the coefficient of friction between the road and the tires of the vehicle is equal to or greater than the predetermined friction threshold.

5. The method according to claim 4, further comprising: In response to determining that the coefficient of friction between the road and the tires of the vehicle is equal to or greater than the predetermined friction threshold, determining a steering path to avoid the object along a path of the vehicle, wherein the steering path has a radius of curvature; and wherein determining the steering path to avoid the object along the path of the vehicle comprises determining a radius of curvature of the steering path; and Wherein the radius of curvature of the turning path is based on the coefficient of friction between the tire and the road.

6. The method according to claim 2, further comprising: determining a time of collision with the object along a path of the vehicle and within a predetermined distance from the vehicle; Determine the time to determine friction; determining a final time to steer the vehicle to avoid the object along a path of the vehicle; determining a sum of the time for determining friction and the final time for steer the vehicle to avoid the object along a path of the vehicle; as well as The time of collision with the object along the path of the vehicle is compared to the sum of the time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle to determine whether the time of collision with the object along the path of the vehicle is less than the sum of the time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle.

7. The method according to claim 6, further comprising: determining the last time to brake to avoid the object along the path of the vehicle in response to determining that the time to collide with the object along the path of the vehicle is greater than the sum of the time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle; responsive to determining that the time to collision with the object along the path of the vehicle is less than the sum of the time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle, determining the last time to brake to avoid the object along the path of the vehicle and the sum of the time to determine friction; as well as In response to determining that the time to collision with the object along the path of the vehicle is less than the sum of the last time to determine friction and the last time to steer the vehicle to avoid the object along the path of the vehicle, the time to collision with the object along the path of the vehicle is compared to the sum of the last time to brake to avoid the object along the path of the vehicle and the time to determine friction to determine whether the time to collision is less than the sum of the last time to brake to avoid the object along the path of the vehicle and the time to determine friction.

8. The method according to claim 7, wherein: The coefficient of friction between the road and the tires of the vehicle is determined solely based on: (a) detection of the object along the path of the vehicle and within a predetermined distance from the vehicle; and (b) determining the time of collision is less than the last time of braking or less than the sum of the last time of steering to avoid the object along the path of the vehicle and the time to determine friction.

9. The method according to claim 8, further comprising: comparing the friction coefficient between the road and the tires of the vehicle with a predetermined friction threshold to determine whether the friction coefficient between the road and the tires of the vehicle is equal to or greater than the predetermined friction threshold; as well as wherein the control action is to steer the vehicle to avoid the object along a path of the vehicle in response to determining that the coefficient of friction between the road and the tires of the vehicle is equal to or greater than the predetermined friction threshold; In response to determining that the coefficient of friction between the road and the tires of the vehicle is equal to or greater than the predetermined friction threshold, determining an updated last time to steer to avoid the object along a path of the vehicle based on the coefficient of friction between the road and the tires of the vehicle; and The time of collision with the object along the path of the vehicle is compared to the updated last time of turning to avoid the object along the path of the vehicle to determine whether the time of collision with the object along the path of the vehicle is greater than the updated last time of turning to avoid the object along the path of the vehicle.

10. The method according to claim 9, wherein: Insufficient road friction is used as a condition to inhibit evasive steering assistance from being engaged after the vehicle driver initiates steering.

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