Surface estimation for vehicles

Abstract

A method for estimating a property of a surface of a road (11) on which a vehicle (12) is traveling, the method comprising: Exerting a torque of a specific magnitude to one or more wheels of the vehicle (12); Determining a first wheel slip for the one or more wheels prior to applying the torque; Determining a second wheel slip for the one or more wheels after applying the torque; Determining a wheel slip difference between the second wheel slip and the first wheel slip; and Estimating the property of the surface of the road (11) based at least in part on the wheel slip difference and the magnitude of the applied torque.

Description

TECHNICAL FIELDThe present disclosure relates generally to the field of vehicles, and more particularly to methods and systems for estimating surface characteristics for vehicles.BACKGROUNDCertain vehicles today use techniques to determine the characteristics of a road on which the vehicle is travelling, such as a coefficient of friction for the road. Often, such determinations are made during a braking or stabilization event. However, such techniques may not be optimal in all situations. For example, in certain situations, road property determinations may be desirable when a braking or stabilization event may not yet have occurred, e.g., in setting desired distances between vehicles driven with cruise control or without cruise control.Accordingly, it is desirable to provide improved methods and systems for estimating road surface characteristics for vehicles. Moreover, other desirable features and characteristics of the present invention will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the above technical field and background.US 2010 / 0 131 165 A1 relates to a method for estimating the maximum coefficient of friction between tire and road surface for a vehicle.US 2011 / 0 209 521 A1 relates to a device (or method) for estimating a grip characteristic of a vehicle wheel of a vehicle on a ground contact surface.EP 2 899 086 A1 relates to a slip ratio estimating apparatus, a slip ratio estimating method, a slip ratio estimating program, and a recording medium on which such a slip ratio estimating program is recorded.US 2004 / 0 263 099 A1 relates to drive systems for electric cars and other electric vehicles.SUMMARYAccording to an exemplary embodiment, a method is provided for estimating a characteristic of a surface of a road on which a vehicle is travelling. The method includes applying torque to one or more wheels of the vehicle, determining wheel slip for the one or more wheels, and estimating the surface property of the road based at least in part on the wheel slip and the torque.According to another exemplary embodiment, a system for estimating a property of the surface of a road on which a vehicle is traveling is provided. The system includes one or more sensors and a processor. The sensor is configured to measure information related to wheel slip of one or more wheels of the vehicle after applying a torque. The processor is coupled to the sensor and is configured to at least facilitate application of the torque to the one or more wheels of the vehicle and estimate the surface property of the road based at least in part on wheel slip after the application of the torque.According to another exemplary embodiment, a vehicle is provided. The vehicle includes a plurality of wheels, a sensor, and a processor. The sensor is configured to measure information related to wheel slip of one or more of the plurality of wheels after applying a torque. The processor is coupled to the sensor and is configured to at least facilitate the application of the torque to the one or more wheels and estimate a characteristic of the surface of a road on which the vehicle is travelling based at least in part on wheel slip after the application of the torque and the torque.BRIEF DESCRIPTION OF THE DRAWINGSThe present disclosure will now be described together with the following figures, wherein like reference numerals indicate like elements, and wherein: FIG. 1 is a functional block diagram of a system including a vehicle with a control system for determining the characteristics of the surface of a road on which the vehicle is being driven, presented along with other vehicles on or near the roadway, a remote server, and wireless networks coupling the vehicle, the other vehicles, and the remote server, according to an exemplary embodiment; FIG. 2 is a functional block diagram of a vehicle that may be used in connection with the system of FIG. 1, according to an exemplary embodiment; FIG. 3 is a functional block diagram of a control system that may be used in connection with the vehicle of FIGS. 1 and 2, according to an exemplary embodiment; and FIG. 4 is a flow diagram of a process for determining the characteristics of the surface of a road on which the vehicle is being driven, and which may be used in connection with the system of FIG. 1, the vehicle of FIGS. 1 and 2, and the control system of FIGS. 1-3, according to an exemplary embodiment.DETAILED DESCRIPTIONThe following detailed description is merely illustrative in nature and is not intended to limit the disclosure or the spirit and uses thereof. Moreover, there is no intention to be bound by any theory set forth in the foregoing background or the following detailed description.FIG. 1 is a functional block diagram of a system 10 including a vehicle 12. As shown in FIG. 1, the vehicle 12 includes a control system 13 that proactively determines the characteristics of the surface of a road 11 on which the vehicle 12 is driven, as described further below in connection with FIGS. 2-4. Also as shown in FIG. 1, the vehicle 12 communicates via one or more wireless networks 14 with a remote server 15 and a plurality of other vehicles 16 on or near the road 11.In one embodiment, the remote server 15 is located remotely from the vehicle 12 and the other vehicles 16 and includes a computer system having a processor 20, a communication system 22, and a memory 24. the processor 20 controls the operation of the remote server 15 and the components thereof. The communication system 22 communicates with the vehicle 12 and the other vehicles 16 included therein with respect to the information regarding the characteristics (including the coefficient of friction) of the road 11 In one embodiment, the processor 20, the communication system 22, and the memory 24 have features and a function similar to the description of the processor 220, the communication system 203, and the memory 222, respectively, of vehicle 12 as described further below in connection with FIG. 3. It is also seen that in certain embodiments, the other vehicles 16 of FIG. 1 may also include similar components and / or a control system similar to the control system 13 of vehicle 12 of FIG. 1.FIG. 2 provides a functional block diagram of vehicle 12 of FIG. 1, according to an example embodiment. As described in more detail below, the vehicle 12 includes a control system 13 that determines the characteristics of the surface of a road 11 on which the vehicle 12 is driven according to the steps of process 400, as described below in connection with FIG. 4.As shown in FIG. 2, the vehicle 12 includes a chassis 112, a body 114, four wheels 116, an electronic control system 118, a control system 150, a braking system 160, and the above-referenced control system 13. the body 114 is disposed on the chassis 112 and substantially encloses the other components of the vehicle 12. the body 114 and the chassis 112 may together form a frame. The wheels 116 are each rotatably coupled to the chassis 112 adjacent a corresponding corner of the body 114. As shown in FIG. 2, the wheels 116 include a front driver side wheel 181, a front passenger side wheel 182, a rear driver side wheel 183, and a rear passenger side wheel 184. It can be seen that the number of wheels 116 (including the number of front wheels 181, 182 and / or the number of rear wheels 183, 184) can vary in various embodiments.The vehicle 12 may be one or more of a number of different types of vehicles, such as a sedan, van, truck, or sport utility vehicle (SUV), and may include two-wheel drive (2WD) (i.e., rear-wheel drive or front-wheel drive), four-wheel drive (4WD), or all-wheel drive (AWD). The vehicle 12 may also include one or a combination of a number of different types of propulsion systems, such as a gasoline or diesel powered internal combustion engine, a "flexible fuel vehicle" (FFV) engine (i.e., using a mixture of gasoline and ethanol), a gaseous compound (e.g., hydrogen or natural gas) powered engine, a hybrid engine between an internal combustion / electric motor, and an electric motor.In the exemplary embodiment illustrated in FIG. 2, the vehicle 12 includes an actuator unit 120. In such an embodiment, the vehicle 12 may also include a radiator 128, as shown in FIG. 2 (although this may vary in other embodiments). The actuator unit 120 includes at least one drive system 129 mounted on the chassis 112 that drives the wheels 116. In the exemplary embodiment shown, the actuator unit 120 comprises a motor 130. In one embodiment, the engine 130 includes an internal combustion engine. In other embodiments, actuator unit 120 may include one or more other types of machines and / or motors, such as an electric motor / generator, instead of or in addition to the internal combustion engine.Still referring to FIG. 2, the machine 130 is coupled to at least some of the wheels 116. In one embodiment, this coupling is provided via one or more drive shafts 134, while in other embodiments, the vehicle may be a direct drive vehicle. As shown in FIG. 2, the drive shafts 134 include a front axle 170 and a rear axle 172.In some embodiments, the machine 130 is mechanically coupled to the transmission. In other embodiments, the engine 130 may instead be coupled to a generator used to power an electric motor mechanically coupled to the transmission.The control system 150 is mounted on the chassis 112 and controls the control of the wheels 116. In one embodiment, the control system 150 includes a steering wheel and a steering column (not shown) The steering wheel receives input from a driver of the vehicle. The steering column results in desired steering angles for the wheels 116 via the drive shafts 134 based on input from the driver.The brake system 160 is mounted on the chassis 112 and provides braking to the vehicle 12. The brake system 160 receives input from the driver via a brake pedal (not shown) and provides appropriate braking via brake units (also not shown). The driver also provides inputs via an accelerator pedal (not shown) regarding a desired speed or acceleration of the vehicle, as well as various other inputs to various vehicle devices and / or systems, such as one or more vehicle radios, other entertainment systems, environmental coast systems, lighting units, navigation systems, and the like (also not shown).The control system 13 is mounted on the chassis 112. The control system 13 determines the characteristics of the surface of a road 11 according to the steps of process 400, as described below in connection with FIG. 4. In certain embodiments, the control system 13 may include and / or be coupled to all or part of various other vehicle systems, such as, but not limited to, the brake system 160, the control system 150, the actuator unit 120, and / or the electronic control system 118. For example, in certain embodiments, the control system 13 may also control certain aspects of such systems, e.g., the brake system 160, the control system 150, and / or the actuator unit 120.FIG. 3 is a functional block diagram of the control system 13 of FIGS. 1 and 2 according to an exemplary embodiment. As shown in FIG. 3, the control system 13 comprises a sensor arrangement 202, a communication system 203 and a control device 204.The sensor assembly 202 measures and receives information for use by the controller 204 in determining the characteristics of the surface of a road 11. In one embodiment, the sensor assembly 202 provides information regarding the wheel speeds of the various wheels 116, as well as a speed for the vehicle 12 for use in determining wheel slip. In one embodiment, each of the sensors in the sensor assembly 202 is disposed within an on-board housing of the vehicle 12. As shown in FIG. 3, in one embodiment, the sensor assembly 202 includes one or more wheel speed sensors 206 (preferably, one wheel speed sensor 206 for each wheel 116 of FIG. 1 ), vehicle speed sensors 208, and / or accelerometers 210. However, this may vary in other embodiments. The specific types and / or number of sensors in the sensor arrangement 202 may / may vary in various embodiments.The communication system 203 provides the communications for the vehicle 12, in connection with the remote server 15 and the other vehicles 16 of FIG. 1. As shown in FIG. 3, in one embodiment, communication system 203 includes a communication interface 209 that facilitates communications between vehicle 12 and remote server 15 and other vehicles 16 of FIG. 1 using one or more wireless networks, such as wireless networks 14 shown in FIG. 1. In the embodiment shown, communication system 203 includes antenna 211, cell chipset / component 212, satellite chipset / component 213, transceiver 214, wireless modem 215, and vehicle bus 216. The number and types of components of communication system 203 and communication interface 209 may vary in other embodiments.In one embodiment, antenna 211 powers various components of communication interface 209, including cell chipset / component 212, satellite chipset / component 213, and transceiver 214. In one embodiment, a single antenna 211 includes a multimode antenna that powers these various components. In other embodiments, numerous antennas 211 may be used.Also in one embodiment, cell chipset / component 212 facilitates communications with one or more cell networks using antenna 211, and satellite chipset / component 213 facilitates communications with one or more satellite networks using antenna 211. Cell chipset / component 212 and / or satellite chipset / component 213 may similarly be used to access the Internet (and / or other networks), e.g. using such cell and / or satellite networks. Also in one embodiment, the transceiver 214 facilitates communications with other vehicles 16 of FIG. 1 using one or more vehicle-to-vehicle networks (e.g., using radio frequencies).Additionally, in one embodiment, the wireless bus modem 215 facilitates the flow of data within the control system 13 (e.g., from and to the control device 204). Also in one embodiment, the vehicle bus 216 includes a wired communication bus (e.g., a CAN bus) for communications with the control device 204 (e.g., between the sensor assembly 202 and the control device 204); however, in other embodiments, this may vary (e.g., since wireless networks may also be used).In certain embodiments, communication system 203 (and / or control system 13 generally) may be part of and / or coupled to a telematics unit of vehicle 12, which may be in communication with, e.g., a call center, and / or may provide information and / or services, such as detailed directions and other navigation-related services, airbag deployment display, and other emergency or road assist related services, infotainment-related services regarding music, Internet web pages, movies, television programs, video games and / or other content, and the like.The control device 204 is coupled to the sensor arrangement 202 and the communication system 203. Additionally, in several embodiments, the control device 204 is also coupled to various other systems and / or components of vehicle 12 including, e.g., the wheels 116 and the brake system 160. The controller 204 determines the characteristics of the surface of a road 11 of FIG. 1 according to the steps of process 400, as described further below in connection with FIG. 4.As shown in FIG. 3, the control device 204 comprises a computer system. In certain embodiments, the control device 204 may also include one or more of the sensors of the sensor device 202 and / or one or more components of the communication system 203, among other possible vehicle components. It can also be seen that the control device 204 can deviate in another way from the exemplary embodiment shown in FIG. 3. 3. for example, the control device 204 may be coupled to or otherwise utilize one or more remote computer systems and / or other control systems.In the illustrated embodiment, the computer system of the control device 204 includes a processor 220, a memory 222, an interface 224, a storage device 226, and a bus 228. Processor 220 performs the computing and control functions of control device 204 and may include any type of processor or multiprocessors, single integrated circuits such as a microprocessor, or any suitable number of devices with integrated circuits and / or circuit boards that cooperate to perform the functions of a processing unit. During operation, processor 220 executes one or more programs 230 contained in memory 222, and thus controls the general operation of controller 204 and the computer system of controller 204, preferably by executing the steps of the processes described herein, such as the steps of process 400 (and all sub-processes thereof) in connection with FIG. 4.The memory 222 may be any type of suitable memory. In various embodiments, this may include the various types of dynamic random access memory (DRAM) such as SDRAM, the various types of static RAM (SRAM), and the various types of nonvolatile memory (PROM, EPROM, and flash). In certain examples, the memory 222 is located on and / or adjacent to the same computer chip as the processor 220. In the embodiment shown, the memory 222 stores the above-referenced program 230 along with one or more stored values 232 (e.g., equations, look-up tables, and / or thresholds) for use in implementing the steps of the process 400 (and all sub-processes thereof) of FIG. 4.Bus 228 is used to transfer programs, data, states, and other information or signals between the various components of the computer system of controller 204. The interface 224 enables communication to the computer system of the control device 204, e.g., from a system driver and / or other computer system, and may be implemented using any suitable method and apparatus. It may include one or more network interfaces to communicate with other systems or components. The interface 224 may also include one or more network interfaces to communicate with technicians and / or one or more memory interfaces to connect to storage devices such as the storage device 226.The storage device 226 may be any suitable type of storage device, including direct access storage devices such as hard disk drives, flash systems, floppy disk drives, and optical disk drives. In an exemplary embodiment, the storage device 226 includes a program product from which the memory 222 may receive a program 230 that performs one or more embodiments of one or more processes of the present disclosure, such as the steps of process 400 (and all sub-processes thereof) of FIG. 4, as described further below. In another exemplary embodiment, the program product may be directly stored in and / or otherwise accessed by memory 222 and / or a disk (e.g., disk 234) such as that referred to below.Bus 228 may be any suitable physical or logical means for interconnecting the computer systems and components. This includes, but is not limited to, direct hardwired connections, fiber optics, infrared, and wireless bus technologies. During operation, the program 230 is stored in the memory 222 and executed by the processor 220.It will be appreciated that while this exemplary embodiment is described in the context of a fully functioning computer system, those skilled in the art will recognize that the mechanisms of the present disclosure may be distributed as a program product with one or more types of non-transitory computer readable signal bearing media used to store the program and instructions thereof and to perform the distribution thereof, such as a non-transitory computer readable medium bearing the program and including computer instructions stored therein to cause a computer processor (such as processor 220) to perform and execute the program. Such a program product may take a variety of forms, and the present disclosure also applies regardless of the particular type of computer readable signal bearing media used to perform the distribution. Examples of signal bearing media include: recordable media such as floppy disks, magnetic disk drives, memory cards and optical disks; and transmission media such as digital and analog communication links. It will also be appreciated that the computer system of the control device 204 may also otherwise differ from the embodiment shown in FIG. 3, e.g., in that the computer system of the control device 204 may be coupled to or otherwise use one or more remote computer systems and / or other control systems.FIG. 4 is a flowchart of a process 400 for determining the characteristics of the surface of a road on which a vehicle is traveling, according to an exemplary embodiment. The process 400 may be implemented in connection with the system 10 of FIG. 1, the vehicle 12 of FIGS. 1 and 2, and the control system 13 of FIGS. 1-3, according to an exemplary embodiment. In one embodiment, the various steps of processes 400 are continuously performed on a proactive basis (e.g., before automatic braking, stabilization, and / or an emergency event has occurred) during an entire ignition cycle or vehicle trip for the vehicle 12.As shown in FIG. 4, process 400 includes obtaining a position of the vehicle (step 402). In one embodiment, a geographic position (e.g., latitude / longitude values, a particular road, and / or a particular block or section of the road, or the like) for the vehicle 12 of FIGS. 1 and 2 is obtained via a global positioning system (GPS) device, such as via the communication system 203 of FIG. 3.Wheel speed values are determined (step 404). In one embodiment, the wheel speeds are determined for each of the wheels 116 of FIG. 2. In one embodiment, the wheel speeds are measured by the corresponding wheel speed sensors 206 of FIG. 3 for each wheel 116 and provided to the processor 220 of FIG. 3.A vehicle speed is determined (step 406). In one embodiment, the vehicle speed is calculated via the processor 220 of FIG. 3 based on a grouping of the wheel speeds of step 404. In other embodiments, the vehicle speed may be determined and / or measured using data from one or more vehicle speed sensors 208 and / or accelerometers 210 of FIG. 3 (e.g., as direct measurements and / or via calculations performed by the processor 220 of FIG. 3 ), among other possible techniques.Wheel slip values are determined (step 408). In one embodiment, the wheel slip values for each of the wheels 116 of FIG. 2 are determined by the processor 220 of FIG. 3 using the wheel speed values of step 404 and the vehicle speed values of step 406, e.g., by comparing each wheel slip value individually with the vehicle speed value. In one embodiment, wheel slip is calculated as a percentage by calculating a difference between wheel speed (e.g., average speed) and vehicle speed and dividing this difference by vehicle speed as follows:Torque is applied (or supplied, or removed) to one or more of the wheels 116 (step 410). In one embodiment, the processor 220 of FIG. 3 provides instructions for the torque to be provided to one or more wheels 116, but not others, and / or in various amounts to various wheels 116 to generate a small torque imbalance. In an exemplary embodiment, approximately 10 NM of torque is used, however, in other embodiments, this may vary. Also in one embodiment, torque is provided to different wheels 116 in different amounts such that a total net torque about a center of the vehicle 12 from the applied torque is equal to zero. Accordingly, in one embodiment, there is no net change in the direction or velocity of the vehicle 12 as a whole as a result of the applied torque, and there is no perceptible feel of effects of the applied torque on the part of the driver.In such an embodiment, different amounts of torque are applied to respective different wheels 116 of the vehicle 12 in a manner that is diagonally balanced across the vehicle 12. For example, in such an embodiment (e.g., in an electric vehicle with all-wheel engine control), diagonal alignment may be achieved by providing (i) a relatively large first amount of torque to both the front driver side wheel 181 and the rear passenger side wheel 184 of FIG. 2 and (ii) a relatively smaller second amount of torque to both the front passenger side wheel 182 and the rear driver side wheel 183 (or vice versa).In another embodiment, the torque may be balanced in a similar manner by applying different amounts of torque to respective different wheels of the vehicle via torque vectoring, in particular by a torque vectoring differential.In yet another embodiment, a small amount of braking deceleration is applied to a front wheel 181 or 182, and a compensating amount of positive torque is provided to one of the rear wheels 183, 184 disposed directly behind the front wheel 181, 182 to which the braking deceleration has been applied (e.g., when the braking deceleration is applied to the front ras of the passenger side 182, the compensating positive torque is applied to the rear wheel 184 of the passenger side). In one embodiment, the amount of brake deceleration is equal to the amount of compensating positive torque. Further, it will be appreciated that in one embodiment, no torque is physically added to the other wheel other than that transmitted by the differential.In yet another embodiment, torque is applied to one of the wheels 116, and the torque is compensated by providing steering angle adjustment via instructions provided by the processor 220 of FIG. 3, thereby compensating the applied torque (i.e., in a wire-function controlled vehicle). For example, in such an embodiment, the processor 220 of FIG. 3 determines a rotational angle for the vehicle 12 that would otherwise be caused by the applied torque on one of the wheels 12, and the processor 220 provides steering wheel adjustment instructions in an amount equal to and / or equal to the rotation (i.e., such that the net rotation of the vehicle 12 is equal to zero). In one embodiment, the steering angle may be expressed or considered as applying a lateral force such that the induced vehicle torque opposes the torque applied by the wheel torque.In certain embodiments, the applied torque of step 410 is varied over time. In such an embodiment, the applied torque is varied in a sinusoidal manner via instructions provided by the processor 220, e.g., to receive various values over time that help reduce any noise. Applicant notes that a sinusoid is only one example according to an exemplary embodiment. In other exemplary embodiments, a triangle, saw tooth, and / or one or more other types may also be used. In addition, by comparing the input torque and analyzing the calculated slip and performing regression, some noise in the data could be eliminated.Updated wheel slip values are determined (step 412). In one embodiment, the wheel slip values are determined in step 412 using the same technique(s) of step 408, but are executed after the torque is applied in step 410. The wheel slip differences are then calculated in step 414 (e.g., by subtracting the wheel slip values of step 408 from the updated wheel slip values of step 412) to determine the changes to the wheel (e.g., the inclination of wheel slip) that may be assigned to the applied torque of step 410. In one embodiment, these determinations are made by the processor 220 of FIG. 3.The characteristic of the road is determined (step 416). In one embodiment, a coefficient of friction for the surface of the road is determined using the slip difference values (e.g., slope) of step 412 and the amount of torque applied in step 410. In one embodiment, the slip difference values and torque are compared to known values of road surface friction coefficients for various combinations of torque and slip slope values, e.g., using one or more equations and / or look-up tables stored in memory 222 of FIG. 3 as stored values 232 thereof.In one embodiment, information regarding the road surface property is transmitted by the vehicle 12 (step 418). In one embodiment, the coefficient of friction is transmitted via the communication system 203 of FIG. 3 via one or more wireless networks 14 of FIG. 1 and the remote server 15 and / or other vehicles 16 of FIG. 1. The information may then be stored in the memory 24 of the remote server 15 and / or used by other vehicles 16 in implementing one or more actions and / or controls of the vehicle (step 420).In one embodiment, information regarding the characteristics of the road surface is received from the vehicle 12 (step 422) In one embodiment, the vehicle 12 receives the information of the road surface coefficient from other vehicles 16 of FIG. 1 that are being driven on the same road 11 as the vehicle 12 or on an adjacent road or have been being driven recently. Also in one embodiment, this information may be obtained directly from the vehicle 12 via the communication system 203 of FIG. 3 and the wireless network(s) 14 of FIG. 1. In another embodiment, this information may be obtained from the vehicle 12 via the communication system 203 of FIG. 3 and the wireless network(s) 14 of FIG. 1 from the remote server 15 of FIG. 1 (e.g., which may recently obtain such information from other vehicles 16 of FIG. 1 and may have stored the information in the memory 24 of FIG. 1 ). This may be done, for example, to distribute the responsibility of exerting torque imbalance and calculating the characteristics of the road surfaces between the vehicles, for example, to provide improved accuracy and redundancy and further limit any potential difficulty for the drivers of the vehicles.In one embodiment, the values obtained from the other vehicles 16 (directly or indirectly) in step 422 are combined with the information determined by vehicle 12 in step 416 (step 424). In one example, the coefficient values are averaged (e.g., using an arithmetic mean) by the processor 220 of FIG. 3; however, in other embodiments, this may vary.The road surface property (e.g., coefficient of friction) is then implemented (step 426). In various embodiments, the coefficient of friction is used as an input to various vehicle control algorithms, including, for example, for anti-lock braking systems, active safety, stability control, path planning, cruise control, and for adjusting brake gain in trailer / truck examples, among other possible systems and features. In one embodiment, the implementation is by the processor 220 of FIG. 3.Accordingly, methods and systems for determining characteristics of a surface of a road on which a vehicle is traveling are determined. As discussed above, smaller torque imbalance is applied and the resulting slip differences are used to estimate a coefficient of friction for the road. Also in certain embodiments, data may be captured from other vehicles that have recently traveled on or near the same roadway. The disclosed methods and systems enable the road surface coefficient to be estimated proactively and in situations where estimates may be otherwise difficult, e.g., during cruise control and / or otherwise, where an appropriate distance between vehicles is desirable, among other possible implementations.It can be seen that the system 10 of FIG. 1 and / or the vehicle 12 and / or the control system of FIGS. 1-3 and / or components thereof may vary in various embodiments. It will be appreciated that various steps of the process 400 and all sub-processes thereof described herein in connection with FIG. 4 may vary in certain embodiments. It is also seen that various steps of process 400 and all sub-processes thereof described herein in connection with FIG. 4 may occur simultaneously with each other and / or in a different order, as illustrated in FIG. 4 and / or as described above.ExamplesExample 1. a method for estimating a property of the surface of a road on which a vehicle is traveling, the method comprising:applying a torque to one or more wheels of the vehicle;determining wheel slip for the one or more wheels; andestimating the property of the surface of the road based at least in part on the wheel slip and the torque.Example 2. the method of example 1, further comprising: determining wheel slip for the one or more wheels according to the torque; wherein the step of estimating the characteristic comprises estimating a coefficient of friction for the surface based at least in part on the change in wheel slip and the torque.Example 3. The method of example 1 or example 2, wherein the step of applying the torque comprises applying different amounts of torque to respective different wheels of the vehicle such that a total net torque about a center of the vehicle of the applied torque is equal to zero.Example 4. the method of any one of Examples 1 to 3, wherein the step of applying the torque comprises applying different amounts of torque to respective different wheels of the vehicle in a manner that is diagonally balanced across the vehicle.Example 5. the method of any one of Examples 1 to 4, wherein the step of applying the torque comprises applying different amounts of torque to respective different wheels of the vehicle via torque vectoring.Example 6. the method of any one of Examples 1 to 5, wherein the step of applying the torque comprises applying a brake deceleration to a first of the wheels of the vehicle and applying a compensating positive torque to a second of the wheels of the vehicle.Example 7. the method of any one of Examples 1 to 6, further comprising:changing the applied torque in a sinusoidal manner.Example 8 The method of any one of Examples 1 to 7, further comprising:providing a steering angle adjustment that compensates for the applied torque.Example 9. the method of any one of Examples 1 to 8, further comprising:receiving information from one or more remote sources relating to the property of the surface.Example 10. a system for estimating a property of the surface of a road on which a vehicle is travelling, the system comprising:a sensor configured to measure information related to wheel slip of one or more wheels of the vehicle after applying a torque; anda processor coupled to the sensor and configured to at least facilitate:applying a torque to the one or more of the wheels of the vehicle; andestimating the property of the surface of the road based at least in part on the wheel slip after applying the torque and the torque.Example 11. the system of example 10, wherein the processor is configured to at least facilitate:determining wheel slip for the one or more wheels according to the torque; andestimating a coefficient of friction for the surface based at least in part on the wheel slip and the torque.Example 12. The system of example 10 or example 11, wherein the processor is configured to at least facilitate applying different amounts of torque to respective different wheels of the vehicle such that a total net torque about a center of the vehicle of the applied torque is equal to zero.Example 13. the system of any of Examples 10-12, wherein the processor is configured to at least facilitate the application of different amounts of torque to respective different wheels of the vehicle in a manner that is diagonally balanced across the vehicle 12.Example 14. The system of any of Examples 10-13, wherein the processor is configured to at least facilitate the application of different amounts of torque to respective different wheels of the vehicle via torque vectoring.Example 15. The system of any of Examples 10-14, wherein the processor is configured to at least facilitate applying a brake deceleration to a first of the wheels of the vehicle and applying a compensating positive torque to a second of the wheels of the vehicle.Example 16. The system of any of Examples 10-15, wherein the processor is configured to at least facilitate the change in applied torque in a sinusoidal manner.Example 17. the system of any of Examples 10-16, wherein the processor is configured to at least facilitate providing a steering angle adjustment that compensates for the applied torque.Example 18. The system of any one of Examples 10 to 17, further comprising:a receiver configured to at least facilitate receiving information from one or more remote sources related to the surface property.Example 19. A vehicle comprising:a plurality of wheels;a sensor configured to measure information related to wheel slip of one or more of the plurality of wheels after applying a torque; anda processor coupled to the sensor and configured to at least facilitate:applying a torque to the one or more of the wheels; andestimating the characteristic of the surface of a road on which the vehicle is travelling based at least in part on wheel slip after applying the torque and the torque.Example 20, the vehicle of example 20, wherein the processor is configured to at least facilitate applying different amounts of torque to respective different wheels of the vehicle such that a total net torque about a center of the vehicle of the applied torque is equal to zero.While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that there are a very great number of variations. It should also be appreciated that the exemplary embodiment or exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the detailed description provided above provides those skilled in the art with a suitable road map for implementing the exemplary embodiment or embodiments. It should be understood that various changes may be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.

Claims

A method of estimating a characteristic of a surface of a road (11) on which a vehicle (12) is travelling, the method comprising: applying a torque having a determined magnitude to one or more wheels of the vehicle (12); determining a first wheel slip for the one or more wheels prior to applying the torque; determining a second wheel slip for the one or more wheels after applying the torque; determining a wheel slip difference between the second wheel slip and the first wheel slip; and estimating the characteristic of the surface of the road (11) based at least in part on the wheel slip difference and the magnitude of the applied torque.The method of claim 1, further comprising: determining wheel slip for the one or more wheels corresponding to the torque; wherein the step of estimating the characteristic comprises estimating a coefficient of friction for the surface based at least in part on the wheel slip after applying the torque and the torque.The method of claim 1 or claim 2, wherein the step of applying the torque comprises applying different amounts of torque to respective different wheels of the vehicle (12) such that a total net torque of the applied torque about a center of the vehicle (12) is equal to zero.The method of claim 1 or claim 2, wherein the step of applying the torque comprises applying different amounts of torque to respective different wheels of the vehicle (12) in a manner that is diagonally balanced across the vehicle (12).The method of claim 1 or claim 2, wherein the step of applying the torque comprises applying different amounts of torque to respective different wheels of the vehicle (12) via torque vectoring.The method of claim 1 or claim 2, wherein the step of applying the torque comprises applying a brake deceleration to a first of the wheels of the vehicle (12) and applying a compensating positive torque to a second of the wheels of the vehicle (12).The method of any of claims 1 to 6, further comprising: changing the applied torque in a sinusoidal manner.The method of any of claims 1 to 7, further comprising: providing a steering angle adjustment that compensates for the applied torque.The method of any one of claims 1 to 8, further comprising: receiving information from one or more remote sources relating to the property of the surface.A system for estimating a characteristic of the surface of a road (11) on which a vehicle (12) is travelling, the system comprising: a sensor configured to measure information relating to a first wheel slip of one or more wheels of the vehicle (12) before a torque of a particular magnitude is applied and a second wheel slip of one or more wheels after the application of a torque; and a processor coupled to the sensor and configured to at least facilitate: applying a torque to the one or more of the wheels of the vehicle (12); determining a wheel slip difference between the second wheel slip and the first wheel slip; and estimating the characteristic of the surface of the road (11) based at least in part on the wheel slip difference and the magnitude of the applied torque.

Images